help button home button Endocrine Society Endocrinology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology, doi:10.1210/en.2007-1469
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Veenema, A. H.
Right arrow Articles by Neumann, I. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Veenema, A. H.
Right arrow Articles by Neumann, I. D.
Endocrinology Vol. 149, No. 6 2727-2736
Copyright © 2008 by The Endocrine Society

Early Life Stress Enhances the Vulnerability to Chronic Psychosocial Stress and Experimental Colitis in Adult Mice

Alexa H. Veenema1, Stefan O. Reber1, Sandra Selch, Florian Obermeier and Inga D. Neumann

Department of Behavioral Neuroendocrinology (A.H.V., S.O.R., S.S., I.D.N.), Institute of Zoology, University of Regensburg, 93053 Regensburg, Germany; and Department of Internal Medicine I (F.O.), University Clinic Regensburg, 93042 Regensburg, Germany

Address all correspondence to: Dr. Stefan O. Reber, Department of Behavioral Neuroendocrinology, Institute of Zoology, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany. E-mail: stefan.reber{at}biologie.uni-regensburg.de; and requests for reprints to: Dr. Alexa H. Veenema, University of Regensburg, Universitaetsstrasse 31, 93053 Regensburg, Germany. E-mail: alexa.veenema{at}biologie.uni-regensburg.de.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Early life stress enhances the vulnerability to both mood and chronic inflammatory disorders, suggesting a link between these stress-related disorders. To study this, we exposed male C57BL/6 mice to early life stress [maternal separation (MS), 3 h/d, d 1–14] and to adult chronic psychosocial stress [chronic subordinate colony housing (CSC)] and measured changes in neuroendocrine parameters and in the severity of a chemically induced colitis. In both unseparated and MS mice, 19 d of CSC exposure resulted in a transient decrease in body weight gain, increased anxiety-related behavior, and decreased vasopressin mRNA expression in the hypothalamic paraventricular nucleus compared with respective nonstressed mice. However, only CSC-stressed MS mice showed elevated CRH mRNA expression in the paraventricular nucleus and reduced plasma corticosterone. Subsequent treatment with dextran sulfate sodium (1%, 7 d) resulted in a more severe colonic inflammation in MS compared with unseparated mice. This was indicated by an increased histological damage score and increased TNF secretion (nonstressed MS mice), more severe body weight loss and inflammatory reduction in colon length (CSC-stressed MS mice), and increased interferon-{gamma} secretion (nonstressed and CSC-stressed MS mice). In conclusion, early life stress and subsequent exposure to chronic psychosocial stress in adulthood induced neuroendocrine abnormalities, which likely contributed to enhanced vulnerability to chemically induced colitis. The combined use of MS and CSC represents a potential animal model providing novel (patho)physiological insights into the complex interactions between neuroendocrine and inflammatory actions upon chronic stress exposure. These findings may further help to reveal mechanisms of hypocortisolemic disorders.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
NEGATIVE EARLY CHILDHOOD experiences disrupt normal adaptive responses to subsequent stressors during life. Accordingly, child maltreatment is a well-known risk factor for the development of stress-related mood disorders, including e.g. anxiety- and depression-related diseases, in which a dysregulation of the hypothalamic-pituitary-adrenocortical (HPA) axis plays a key role (1, 2, 3). However, the consequences of early life stress on sensitivity to adult chronic stress exposure are unknown.

Child maltreatment may also enhance the risk for the development of inflammatory disorders. A recent study presents evidence that adults maltreated as children have increased levels of high-sensitivity C-reactive protein, fibrinogen, and white blood cells (4). This substantiates the well-acknowledged detrimental effects of chronic stress during adulthood on various immune functions (5, 6, 7, 8, 9). Because these effects of stress on immune function are likely to be due, in part, to disturbances in HPA axis function (10, 11, 12), it is not surprising that immune dysfunctions have been reported in stress-related mood disorders (13, 14, 15).

These findings suggest that exposure to early life stress and to chronic stress in adulthood further increases the risk for the development of both mood and chronic inflammatory disorders. To examine this and to investigate underlying mechanisms, we exposed male C57BL/6 mice to maternal separation (MS) as an animal model of early life stress and to chronic subordinate colony housing (CSC) as a model of adult chronic psychosocial stress (10, 12).

MS consists of the separation of pups from their mother for 3 h daily during postnatal d 1–14 and was shown to increase adult anxiety- and depression-like behaviors in rats (16, 17, 18) and mice (19, 20, 21). These behavioral changes are accompanied by alterations in HPA axis regulation, including higher CRH mRNA expression in the hypothalamic paraventricular nucleus (PVN) (16, 22), and elevated plasma ACTH and corticosterone responses to acute stressors (17, 18, 23, 24). Behavioral and neuroendocrine changes after MS are effectively reduced by antidepressant treatment (20, 25, 26, 27). To date, long-lasting effects of MS are mostly studied in response to exposure to an acute stressor in adulthood. However, stress-related psychopathologies in humans are likely instigated by long-lasting or chronic exposure to psychosocial stressors in adulthood (28). Therefore, we assessed the behavioral and neuroendocrine consequences of MS on subsequent exposure to CSC as a clinically relevant chronic stressor for mice (10, 12).

We further investigated the effects of MS and subsequent CSC exposure on the severity of a dextran sulfate sodium (DSS)-induced colitis, which is a frequently used experimental model of inflammatory bowel disease (IBD) (29, 30). IBD is a chronic relapsing inflammatory condition of the gastrointestinal tract that normally begins early in life and leads to decreased quality of life (31, 32). Importantly, IBD has been associated with both chronic stress and mood disorders (8, 33, 34, 35). For example, we could recently show that exposure to chronic psychosocial stress increases the severity of a subsequent DSS-induced colitis in male mice due to stress-induced dysregulation of the HPA axis (11, 12). Given the long-lasting MS-induced changes in HPA axis regulation, we hypothesize that MS potentiates the effects of chronic stress in adulthood on the severity of a DSS-induced colitis. To test this hypothesis, we first measured neuroendocrine changes at the end of CSC (as mentioned above) and then measured the severity of colonic inflammation induced by subsequent DSS treatment.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Mice
Adult male and female C57BL/6 mice (Charles River, Sulzfeld, Germany) were mated, and female mice were single-housed in standard polycarbonate mouse cages (22 x 16 x 14 cm) and maintained under standard laboratory conditions (12-h light, 12-h dark cycle, lights on at 0600 h, 22 C, 60% humidity, food and water ad libitum). All experimental protocols were approved by the Committee on Animal Health and Care of the local government of Bavaria and conformed to international guidelines on the ethical use of animals.

MS procedure
MS was performed as described before (17, 21). Briefly, pups were separated daily between 0900 and 1200 h from their dams for 3 h from postnatal d 1–14. First, dams were removed from the maternity cage and placed into separate individual cages. Pups were then removed as complete litters from the nest, transferred to an adjacent room, and put into a small box placed on a heating pad (30–33 C). After the 3-h separation period, the pups were returned to the home cage followed by reunion of the dam. Unseparated (US) litters served as controls and were left undisturbed, except for change of bedding once a week. Pups were taken from eight (experiment 1) or nine (experiment 2) US litters and six (experiment 1) or 10 (experiment 2) MS litters. Pups were weaned at postnatal d 21 and housed in groups of four to five of equal treatment until the start of the experiments. No more than two pups per litter were used for each experimental subgroup.

Elevated plus-maze
To measure long-lasting MS effects on anxiety-related behavior, mice (US, n = 48; MS, n = 41) were tested at 7 wk of age on the elevated plus-maze between 0800 and 1200 h as described before (21). Briefly, the maze consisted of two open (30 x 6 cm) and two closed (30 x 6 x 15 cm) arms radiating from a central square (6 x 6 cm) to form a plus-shaped figure elevated 130 cm above the floor. Each mouse was placed onto the central square facing a closed arm and allowed to explore the maze for 5 min. The maze was cleaned thoroughly before each test. The percentage of time spent on the open arms to total time spent on both open and closed arms and the percentage of open arm entries to total number of entries were taken as parameters of anxiety-related behavior. The number of closed arm entries was taken as measurement of locomotion.

CSC procedure
After plus-maze testing, mice were single-housed until they were randomly assigned to a nonstressed (US, n = 22; MS, n = 19) or a CSC-stressed (US, n = 26; MS, n = 22) group at 8 wk of age. As chronic psychosocial stressor, CSC exposure was used as described before (10). Briefly, four mice of the same treatment group were housed together with a larger C57BL/6 male in a polycarbonate cage (38 x 22 x 35 cm) for 19 d consecutively (i.e. from d 1 until d 20). All larger males were tested before CSC for their aggressive behavior. Males that injured their opponents by harmful bites were not used. To avoid habituation, each larger male was replaced by a novel larger male at d 8 and 15. During the first 30 min of colony formation on d 1, 8, and 15, the mice were videotaped to confirm the dominant status of the larger male (indicated by attacking and chasing all four experimental mice) and the subordinate status of the four US or MS mice (indicated by the display of defensive behavior, including flight, retreat, and submissive postures). Body weight was measured just before CSC exposure (d 1) and at d 3 and 20. Single-housed mice were considered appropriate controls in this set-up, because in group-housed controls, individual differences due to the establishment of a hierarchy cannot be excluded. Moreover, previous work from our lab showed that single-housing by itself poses no stressor for male mice in our set-up. This finding is in agreement with others showing that in the mouse, single-housing is less stressful than group-housing (36, 37, 38).

Experiment 1: MS effects on behavioral and neuroendocrine parameters after CSC exposure
After 19 d of CSC (see Fig. 1Go), nonstressed (US, n = 12; MS, n = 13) and CSC-stressed (US, n = 16; MS, n = 15) mice were exposed to an open field and to a novel object on d 20. These mice were also used in experiment 2 (see below). Another set of nonstressed (US, n = 10; MS, n = 6) and CSC-stressed (US, n = 10; MS, n = 7) mice was rapidly decapitated in a counterbalanced way under CO2 anesthesia between 0800 and 1000 h on d 20 of CSC. Trunk blood was collected on prechilled EDTA-coated tubes (Sarstedt Nümbrecht, Germany) containing 10 µl aprotinin (Trasylol; Bayer Corp. AG, Leverkusen, Germany) for subsequent analysis of plasma ACTH and corticosterone. Brains were rapidly removed, snap-frozen in isopentane, cooled on dry ice, and stored at –80 C for subsequent estimation of CRH, vasopressin, and oxytocin mRNA expression. Adrenal glands were removed, pruned of fat, and weighed.


Figure 1
View larger version (7K):
[in this window]
[in a new window]

  		FIG. 1. Experimental design. MS was carried out on postnatal d 1–14. US and MS mice were tested for anxiety-related behavior on the elevated plus maze (EPM) at 7 wk of age. After 1 wk of single-housing, US and MS mice were exposed to 19 d of chronic psychosocial stress (CSC, in which four US or MS males were housed together with a larger, dominant male, which was replaced by a novel dominant male at d 8 and 15). Single-housed US and MS mice served as respective controls (nonstressed). In experiment 1, US and MS mice were killed ({dagger}) at d 20 to assess the effects of MS and subsequent CSC exposure on neuroendocrine parameters. Separate groups of nonstressed and CSC-stressed US and MS mice were exposed to the open field (OF) to assess CSC-induced changes in anxiety-related behavior. These groups of mice were then used for experiment 2, in which all mice were treated with 1% DSS for 7 d to measure effects of MS and subsequent CSC exposure on the severity of a DSS-induced colitis.

 
Experiment 2: MS effects on DSS-induced colitis after CSC exposure
US (n = 16) and MS (n = 15) mice were exposed to CSC followed by single housing and treatment with 1% DSS (36–50 kDa; ICN, Eschwege, Germany) in the drinking water ad libitum for 7 d (i.e. d 1–8), as previously described (11, 39). Nonstressed US (n = 12) and MS (n = 13) mice also received 1% DSS treatment. DSS treatment started in all groups immediately after assessment of anxiety-related behavior in the open field (see Fig. 1Go). Body weight was measured on d 1 and 8 of DSS treatment. On d 8 of DSS treatment, all mice were rapidly killed in a counterbalanced way under CO2 anesthesia between 0800 and 1000 h for subsequent quantification of inflammation-induced reduction of colon length, histological assessment of the colon, and cytokine secretion from mesenteric lymph node cells.

Open field and novel object exploration
To measure possible differential effects of CSC in US and MS mice on anxiety-related behavior, mice (nonstressed US, n = 12; nonstressed MS, n = 13; CSC-stressed US, n = 16; CSC-stressed MS, n = 15) were exposed to the open field and novel object tests as described before (21). Briefly, the open field consisted of a square arena (80 x 80 cm) surrounded by a wall (30 cm) and divided into an inner (40 x 40 cm) and outer zone. The mouse was placed into the inner zone and was allowed to explore the arena for 10 min. The time spent in the inner zone and the number of inner zone entries were taken as parameters of anxiety-related behavior. After 10 min, a plastic ring-shaped object (diameter 9 cm, 4 cm high) was placed in the inner zone, and the mouse was allowed to explore the arena and the object for 5 min. The object exploration time and the number of object visits were taken as parameters of anxiety-related behavior. The test was performed between 0800 and 1200 h, under white light conditions. The open field was cleaned thoroughly before each test.

RIA
Blood samples were centrifuged at 4 C (5000 rpm, 10 min). Plasma aliquots (50 µl for ACTH, 10 µl for corticosterone) were stored at –20 C until assayed using commercially available RIA kits (ICN Biomedicals, Inc., Costa Mesa, CA) with a detection limit of 4 pg/ml for ACTH and 10 ng/ml for corticosterone and an intraassay variability of 4.1% for ACTH and 4.4% for corticosterone.

In situ hybridization for CRH, vasopressin, and oxytocin mRNA expression
The 16-µm coronal brain sections were thaw mounted onto poly-L-lysine-coated slides and stored at –80 C. The hybridization protocol was carried out as described before (10). Hybridization was performed using specific 48-mer, 35S-labeled oligonucleotide probes for CRH mRNA (5'-GGC CCG CGG CGC TCC AGA GAC GGA TCC CCT GCT CAG CAG GGC CCT GCA-3'), vasopressin mRNA (5'-GCA GAA GGC CCC GGC CGG CCC GTC CAG CTG CGT GGC GTT GCT CCG GTC-3'), and oxytocin mRNA (5'-CTC GGA GAA GGC AGA CTC AGG GTC GCA GGC GGG GTC GGT GCG GCA GCC-3') (40). Hybridized slices were exposed to BioMax MR film (Kodak, Rochester, NY). The mRNA expression of CRH, vasopressin, and oxytocin in the PVN was quantified as gray density minus background in digitized images using the NIH ImageJ 1.6 program (http://rsb.info.nih.gov/ij/). Bilateral measures were taken from two to four PVN sections for each mouse, which were pooled to provide individual means per mouse. For tissue background, the OD of a nonhybridized region outside the PVN was measured.

Determination of colonic length and histological damage score
The inflammatory reduction of colonic length was used as a parameter to assess the severity of colonic inflammation (11, 41). The colon was removed, measured to 0.1 cm precision, and mechanically cleaned. Afterward, 1 cm of the distal third of the colon was cut longitudinally, laid on a filter paper, fixed in 10% formalin overnight, embedded in paraffin, and cut longitudinally. Three 3-µm hematoxylin- and eosin-stained sections taken 100 µm apart were evaluated by histological scoring performed by an investigator blind to treatment. For statistics, each individual score represented the mean of the three sections. Histology was scored as follows based on reports published previously (11, 42). The histological score ranges from 0–8 and represents the sum of the epithelium score (0, normal morphology; 1, loss of goblet cells; 2, loss of goblet cells in large areas; 3, loss of crypts; 4, loss of crypts in large areas) and infiltration score (0, no infiltration; 1, infiltrate around crypt basis; 2, infiltrate reaching to lamina muscularis mucosae; 3, extensive infiltration reaching the lamina muscularis mucosae and thickening of the mucosa with abundant edema; 4, infiltration of the lamina submucosa).

Isolation and incubation of mesenteric lymph node cells
Mesenteric lymph nodes (pooled from each experimental group) were harvested under sterile conditions and collected on ice in cell culture medium [RPMI 1640 supplemented with 10% fetal calf serum (Biochrom, Germany), 100 U/ml penicillin and 100 µg/ml streptomycin (GIBCO-BRL, Eggenstein, Germany) and 3 x 10–5 M β-mercaptoethanol (Sigma, Deisenhofen, Germany)]. Lymph nodes were mechanically disrupted and filtered through a cell strainer (70 µm nylon, Falcon, Becton Dickinson, Heidelberg, Germany). Afterward, cells were washed three times in cell culture medium and adjusted to a concentration of 106 cells/ml, and 2 x 105 (200 µl) lymph node cells were transferred to wells of a 96-well plate and stimulated by precoating wells with 200 µl of 2.5 µg/ml anti-CD3 antibody in the presence of IL-2 (final concentration 100 U/ml). Eight wells were transferred with the respective number of cells of each experimental group. After incubation for 24 h (37 C, 5% CO2), cytokine concentrations were measured in the supernatants by ELISA (Endogen, Woburn, MA) using four wells per experimental group.

Statistics
The software package SPSS (version 12) was used. Plus-maze behavior was analyzed with the Student’s t test. Open field behavior, body and adrenal weights, plasma corticosterone, CRH, vasopressin, and oxytocin mRNA expression, and cytokines were analyzed with a two-way ANOVA (factor MS and factor CSC). When appropriate, ANOVA was followed by a Bonferroni post hoc test. Additionally, CRH mRNA expression and the percentage reduction in colon length were separately analyzed in mice exposed to CSC with a one-way ANOVA. Data are presented as means ± SEM. Significance was taken at P < 0.05.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
MS effects on anxiety-related behavior
Anxiety-related behavior was tested on the elevated plus-maze at 7 wk of age. MS mice showed increased levels of anxiety-related behavior as indicated by a decrease in the percentage of time spent on open arms (P < 0.005) and in the percentage of open arm entries (P < 0.005) (Fig. 2Go). MS had no effect on locomotion, as indicated by a similar number of closed arm entries between MS and US mice (Fig. 2Go).


Figure 2
View larger version (10K):
[in this window]
[in a new window]

  		FIG. 2. Effects of MS on anxiety-related behavior as measured on the elevated plus-maze (EPM). US and MS mice of both experiments 1 and 2 were exposed to the EPM at 7 wk of age. Anxiety-related behavior is indicated by the percentage of time spent on the open arms and the percentage of open arm entries. Locomotor activity is indicated by the number of entries into the closed arms. Data represent mean + SEM. *, P < 0.005 vs. US mice, Student’s t test.

 
Experiment 1: MS effects on physiological, behavioral, and neuroendocrine parameters in response to CSC exposure
Body weight after 3 d of CSC exposure.
Body weight was significantly decreased [factor CSC: F(1,85) = 26.6; P < 0.001] in both US and MS mice compared with respective nonstressed mice (P < 0.005) (Fig. 3Go).


Figure 3
View larger version (11K):
[in this window]
[in a new window]

  		FIG. 3. Effects of MS on body weight change during exposure to 19 d of CSC. Body weight was measured just before CSC (d 1) and at d 3 and 20 of CSC. Nonstressed US and nonstressed MS mice were single-housed, and body weight was measured on corresponding days. Numbers in parentheses indicate group sizes. Data represent mean + SEM. *, P < 0.005 vs. respective nonstressed mice, two-way ANOVA followed by Bonferroni post hoc test.

 
Body weight after 19 d of CSC exposure.
No interactive effect of MS and CSC was found on body weight (Fig. 3Go). Thus, irrespective of MS background, CSC resulted in a transient reduction in body weight.

Anxiety-related behavior.
CSC reduced the number of inner zone entries in the open field [factor CSC: F(1,52) = 4.27; P < 0.05] and the number of object visits during novel object exploration [factor CSC: F(1,52) = 6.51; P < 0.05], although post hoc testing revealed no further significance (Fig. 4Go). Furthermore, CSC reduced the object exploration time [factor CSC: F(1,52) = 12.1; P < 0.001] in both US and MS mice compared with respective nonstressed mice (P < 0.05) (Fig. 4Go). Thus, irrespective of MS background, CSC increased anxiety-related behavior in the open field and during novel object exploration.


Figure 4
View larger version (19K):
[in this window]
[in a new window]

  		FIG. 4. Effects of 19 d of CSC on anxiety-related behavior as measured in the open field (A) and during novel object exploration (B). US and MS mice were exposed to a 10-min open field test and subsequently to a novel object placed in the center of the open field for an additional 5-min period. Numbers in parentheses indicate group sizes. Data represent mean + SEM. *, P < 0.05 vs. respective nonstressed mice, two-way ANOVA followed by Bonferroni post hoc test.

 
Adrenal weights.
Exposure to 19 d of CSC resulted in an increase in relative adrenal weight [factor CSC: F(1,29) = 19.1; P < 0.001] in both CSC-stressed US (tendency, P = 0.056) and MS (P < 0.001) mice (Fig 5Go).


Figure 5
View larger version (50K):
[in this window]
[in a new window]

  		FIG. 5. A, Effects of MS on relative adrenal weights, plasma corticosterone concentrations, and OD of CRH and vasopressin mRNA expression within the PVN after exposure to 19 d of CSC. Numbers in parentheses indicate group sizes. Data represent mean + SEM. *, P < 0.05 vs. respective nonstressed mice; #, P < 0.05 vs. CSC-stressed US mice, two-way ANOVA followed by Bonferroni post hoc test. A–D, Images of coronal sections of the hypothalamic region representing CRH mRNA expression (B) vasopressin mRNA expression (C), and oxytocin mRNA (D) within the PVN of a nonstressed MS mouse (left) and a CSC-stressed MS mouse (right). E, Schematic drawing of the mouse brain at the level of the PVN (bregma –0.58 mm) (76 ); the rectangle encloses the PVN. Scale bar, 200 µm.

 
ACTH.
No MS or CSC effect was found for plasma ACTH (pg/ml: nonstressed US mice, 76.1 ± 16.6; nonstressed MS mice, 105.8 ± 34.0; CSC-stressed US mice, 150.7 ± 25.4; CSC-stressed MS mice, 129.3 ± 36.0) measured during the early light phase on d 20 of CSC exposure.

Corticosterone.
In contrast to ACTH, basal plasma corticosterone after 19 d of CSC was found to depend on MS and CSC [factor MS x CSC: F(1,29) = 5.75; P < 0.05]. CSC-stressed MS mice showed reduced plasma corticosterone concentrations compared with CSC-stressed US mice (P < 0.05) and nonstressed MS mice (P < 0.05) (Fig. 5Go) on d 20 of CSC exposure.

CRH mRNA.
Exposure to 19 d of CSC induced an increase in CRH mRNA expression in the PVN [factor CSC: F(1,27) = 4.50; P < 0.05] in MS mice only (P < 0.05) (Fig. 5Go). Separate statistics revealed that CSC-stressed MS mice had a higher CRH mRNA expression than CSC-stressed US mice (P < 0.05; one-way ANOVA).

Vasopressin mRNA.
Irrespective of MS background, 19 d of CSC exposure decreased vasopressin mRNA expression in the PVN [factor CSC: F(1,27) = 17.3; P < 0.001] in US and MS mice compared with respective nonstressed mice (P < 0.001) (Fig. 5Go).

Oxytocin mRNA.
No MS or CSC effect was found for oxytocin mRNA expression in the PVN (OD: nonstressed US mice, 78.7 ± 3.0; nonstressed MS mice, 79.1 ± 6.2; CSC-stressed US mice, 83.4 ± 3.9; CSC-stressed MS mice, 74.4 ± 5.3) after 19 d of CSC (Fig. 5DGo).

Experiment 2: MS effects on DSS-induced colitis after CSC exposure
All groups of mice were treated with 1% DSS for 7 d. Five CSC-stressed mice (US, n = 2; MS, n = 3) died before the end of the experiment.

Body weight after 7 d of DSS treatment.
The body weight change during DSS treatment was dependent on MS and CSC exposure [factor MS x CSC: F(1,47) = 9.86; P < 0.005]. US and MS mice exposed to CSC showed a more pronounced reduction in body weight than respective nonstressed mice (P < 0.005) (Fig. 6Go). Importantly, CSC-stressed MS mice showed an even stronger loss of body weight than CSC-stressed US mice (P < 0.001) (Fig. 6Go).


Figure 6
View larger version (110K):
[in this window]
[in a new window]

  		FIG. 6. A, Effects of MS on the severity of a DSS-induced colitis after 19 d of CSC, as indicated by body weight gain (d 8 to d 1 of DSS treatment), colon length (inset, colon length of CSC-stressed US and MS mice calculated as percentage of colon length of nonstressed US and MS mice, respectively), and histological damage scores. Numbers in parentheses indicate group sizes. Data represent mean + SEM. *, P < 0.05; **, P < 0.005 vs. respective nonstressed mice; #, P < 0.05 vs. nonstressed US mice, two-way ANOVA followed by Bonferroni post hoc test (except for inset, one-way ANOVA). B, Three images of colonic hematoxylin-eosin sections are shown representing the colon histology of a DSS-treated nonstressed US mouse (left, score 2: some loss of goblet cells, infiltration around crypt basis), a nonstressed MS mouse (middle, score 5: loss of mucosal crypts and goblet cells, infiltration of inflammatory cells reaching the lamina muscularis mucosa), and a CSC-stressed MS mouse (right, score 7: loss of mucosal crypts and goblet cells in large areas, thickening of the mucosa with abundant edema, infiltration of inflammatory cells reaching the lamina muscularis mucosa); a, lamina mucosa with crypts (tube-like glands, see asterisks) and goblet cells (see arrowheads); b, lamina muscularis mucosa; c, lamina submucosa; d, lamina muscularis external. Infiltration of inflammatory cells is indicated with arrows.

 
Colon length.
CSC exposure resulted in a more pronounced DSS-induced inflammatory reduction in colon length [factor CSC: F(1,47) = 24.6; P < 0.001] in both CSC-stressed US (P < 0.05) and MS (P < 0.001) mice compared with respective nonstressed mice (Fig. 6Go). The percentage reduction in colon length was, however, more severe in MS than US mice after CSC exposure (P < 0.05) (Fig. 6Go, inset).

Histological damage score.
The histological damage score of colonic tissue was dependent on MS and CSC exposure [factor MS x CSC: F(1,47) = 4.91; P < 0.05]. Nonstressed MS mice showed a higher histological damage score than nonstressed US mice (P < 0.001), reflecting higher intestinal inflammation in MS mice (indicated by a more pronounced loss of goblet cells and infiltration of inflammatory cells reaching the lamina muscularis mucosa) (Fig. 6Go). Furthermore, CSC exposure increased the histological damage score in both US mice (P < 0.001) and MS mice (P < 0.01) compared with respective nonstressed mice, reflecting severe intestinal inflammation after CSC exposure (indicated by loss of mucosal crypts and goblet cells in large areas, thickening of the mucosa with abundant edema, and infiltration of inflammatory cells reaching the lamina submucosa) (Fig. 6Go).

Secretion of cytokines from draining mesenteric lymph node cells.
Cytokine secretion was measured on d 8 of DSS treatment. A CSC effect was found for the secretion of the proinflammatory cytokines interferon (IFN)-{gamma}, TNF, and IL-6 and of the antiinflammatory cytokine IL-10 [factor CSC: IFN-{gamma}, F(1,12) = 26.6, P < 0.001; TNF, F(1,12) = 11.0, P < 0.01; IL-6, F(1,12) = 24.9, P < 0.001; IL-10, F(1,12) = 26.6, P < 0.001]. The secretion of these cytokines was significantly higher in CSC-stressed US mice compared with nonstressed US mice (IFN-{gamma}, P < 0.001; TNF, P < 0.005; IL-6, P < 0.001; IL-10, P < 0.05). CSC-stressed MS mice showed a higher secretion of IL-6 and IL-10 compared with respective nonstressed MS mice (IL-6, P < 0.05; IL-10, P < 0.005) (Fig. 7Go). Importantly, MS effects were found for IFN-{gamma} and TNF [factor MS: IFN-{gamma}, F(1,12) = 125, P < 0.001; TNF, F(1,12) = 12.0, P < 0.01]. The secretion of IFN-{gamma} was significantly higher in MS mice compared with US mice (nonstressed, P < 0.001; CSC-stressed, P < 0.005) (Fig. 7Go). The secretion of TNF was significantly higher in nonstressed MS mice (P < 0.05) but lower in CSC-stressed MS mice (P = 0.050) compared with respective US mice (Fig. 7Go).


Figure 7
View larger version (17K):
[in this window]
[in a new window]

  		FIG. 7. Effects of MS on the secretion of proinflammatory (IFN-{gamma}, TNF, and IL-6) and antiinflammatory (IL-10) cytokines by mesenteric lymph node cells on d 8 of 1% DSS treatment after 19 d of CSC. Numbers in parentheses indicate group sizes. Data represent mean + SEM. *, P < 0.05; **, P < 0.005 vs. respective nonstressed mice; #, P < 0.005; §, P = 0.050 vs. respective US mice, two-way ANOVA followed by Bonferroni post hoc test.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
This study reveals three major findings. 1) MS enhanced the vulnerability to CSC in adult male mice, because MS, but not US, mice showed elevated CRH mRNA expression in the PVN, reduced plasma corticosterone, and more pronounced adrenal hypertrophy after 19 d of CSC. 2) MS enhanced the vulnerability to DSS-induced colitis in adult male mice, as indicated by higher histological damage score and increased secretion of the proinflammatory cytokines IFN-{gamma} and TNF compared with US mice. 3) MS potentiated colitis-aggravating effects of CSC in adult male mice, because CSC-stressed MS mice had a more pronounced body weight loss, a higher inflammatory reduction of colon length, and increased IFN-{gamma} secretion compared with CSC-stressed US mice.

MS effects on anxiety and neuroendocrine parameters
MS increased anxiety-related behavior on the elevated plus-maze, which is in agreement with previous effects of MS in male mice (19, 21). The absence of the higher-anxiety phenotype of MS mice in the open field test, as was found previously (21), is likely explained by different housing conditions, i.e. single- vs. sibling-housing, respectively. No MS-induced changes were found in any of the neuroendocrine parameters. This is in line with other studies demonstrating foremost changes in neuroendocrine parameters in response to an additional acute stressor in adult MS mice and rats (16, 17, 18, 23, 43).

CSC effects on anxiety and neuroendocrine parameters
Exposure to CSC in adulthood reduced body weight gain and increased anxiety-related behavior and adrenal weight, confirming previous findings (10). CSC did not induce long-lasting changes in plasma corticosterone concentrations or in CRH mRNA expression in the PVN in US mice after 19 d of CSC. This is in line with the recent description of increased plasma corticosterone and CRH mRNA expression only during the first days of CSC (10). After 19 d of CSC, a diminished corticosterone response in vivo and in vitro were characteristic for CSC-stressed mice. The tendency of higher plasma ACTH levels in US mice at the end of CSC may give additional proof of CSC-induced long-lasting changes at the level of the adrenal glands.

Besides CRH, the neuropeptide vasopressin is an important regulator of pituitary ACTH secretion, especially during chronic stress (44, 45, 46). Vasopressin mRNA expression in the PVN was, however, significantly reduced after 19 d of CSC exposure, an effect described recently (47). Due to the inability to unambiguously separate the parvo- and magnocellular divisions of the PVN in mice, it remains unclear whether the decrease in vasopressin mRNA is due to changes in parvo- or magnocellular neurons. Others reported increases in vasopressin mRNA expression in the parvocellular PVN after exposure to chronic psychosocial stress (48, 49). Therefore, additional studies should address this issue, e.g. by quantification of plasma vasopressin or vasopressin immunoreactivity in the median eminence. Interestingly, vasopressin stimulates mitogenic processes within the pituitary (50), suggesting a putative role for hypothalamic vasopressin in preventing pituitary cellular damage under stress conditions. Furthermore, vasopressin was found to suppress proinflammatory cytokine production in the brain (51). Thus, after localizing the CSC-induced decrease in parvo- or magnocellular vasopressin, it is of interest to investigate in more detail the role of this neuropeptide in CSC effects on cell proliferation and inflammatory processes in the brain.

Combined MS and CSC effects on anxiety and neuroendocrine parameters
The CSC-induced increase in anxiety-related behavior, as measured in the open field, was not further increased by MS. However, MS mice exposed to CSC showed neuroendocrine abnormalities after 19 d of CSC, including increased CRH mRNA expression in the PVN, reduced plasma corticosterone levels and adrenal hypertrophy. We hypothesize that adrenal hypertrophy is the result of an initially enhanced HPA axis activity, whereas the reduced corticosterone levels seen after 19 d of CSC suggest a developing adrenal insufficiency in MS mice. In support, MS rats exposed to chronic variable stress in adulthood showed decreased HPA axis responsiveness (52). Thus, MS rodents exposed to chronic psychosocial stress in adulthood may show decreased HPA axis responsiveness. This is in contrast with the frequently reported exaggerated HPA axis response found in adult MS rodents exposed to an acute stressor (16, 17, 18, 23).

At the level of the hypothalamic PVN, corticosterone exerts a negative feedback on the synthesis and release of CRH (53). Accordingly, the reduced plasma corticosterone levels in CSC-stressed MS mice might be insufficient to ascertain this negative feedback regulation. This might indeed underlie the observed increase in hypothalamic CRH mRNA expression of CSC-stressed MS mice. CRH neurons in the PVN project to the median eminence but also to limbic and brainstem regions (54, 55). Hence, elevated CRH synthesis likely altered behavioral and emotional responses to stress in CSC-exposed MS mice, including increased anxiety.

Considering the neuroendocrine abnormalities seen in CSC-exposed MS mice, we propose that MS in combination with CSC might serve as an animal model to study the complex neuroendocrinology underlying hypercortisolemic disorders. These disorders include chronic fatigue syndrome, fibromyalgia, and posttraumatic stress disorder (56, 57). The latter might be of particular relevance because hypocortisolism in conjunction with CRH hyperactivity has been found in some patients suffering from posttraumatic stress disorders (58, 59), although contradictory findings are reported as well (60, 61, 62). On the other hand, hypocortisolism is also closely linked to alterations in immune system activation and inflammation (63). Especially fibromyalgia has been associated with gastrointestinal symptoms, including IBD (64).

MS effects on DSS-induced colitis
Chronic psychological stress in adulthood has been proposed to influence the onset, progression, and/or relapse of IBD (8, 65), but evidence for a causal role of early adverse life events in the pathogenesis of IBD and its underlying mechanisms is mostly lacking.

MS resulted in an increased vulnerability to DSS-induced intestinal inflammation as reflected by a higher histological damage score and increased secretion of the proinflammatory cytokines IFN-{gamma} and TNF from mesenteric lymph node cells. These findings are in line with two recent studies demonstrating that MS enhanced the inflammatory response to a chemically induced colitis in adult male mice (20) and rats (66). MS-induced long-term alterations in immune functions as well as in colonic epithelial barrier (67) likely underlie the increased susceptibility to inflammatory stimuli after MS. Moreover, MS-induced alterations in HPA axis responsiveness, bacterial-mucosal interactions, mucosal mast cells, and peripheral CRH (8) may contribute to the increased vulnerability to DSS, which needs to be elucidated.

Notably, a high percentage of children are suffering from IBD, but there is limited research to understand underlying mechanisms (32). IBD that begins in childhood results in growth failure, bone demineralization, and enhanced risk for mood disorders (32, 68). Besides genetic factors, negative early life events may play a role in facilitating the onset and pathogenesis of IBD (8). Our findings along with those of Varghese et al. (20) and Barreau et al. (66) indicate that MS is an important and promising animal model to study the link between early life stress, intestinal functions, and vulnerability to colitis in adulthood. Most importantly, MS can be used in future studies to assess its effects either on the vulnerability to DSS-induced colitis or on the development of spontaneous colonic inflammation at earlier (juvenile) ages. This is needed to understand the role of early life stress in the onset and course of IBD in children along with its link to the development of mood disorders.

CSC effects on DSS-induced colitis
In agreement with recent findings (11, 12), CSC-stressed US mice exposed to DSS treatment showed more severe body weight loss, higher inflammatory reduction in colon length, higher histological damage score, and higher secretion of proinflammatory (IFN-{gamma}, TNF, and IL-6) and antiinflammatory (IL-10) cytokines from mesenteric lymph node cells than nonstressed US mice treated with DSS. The increase in antiinflammatory IL-10 seems contradictory, but pro- and antiinflammatory processes are likely to occur simultaneously during inflammation. The balance is, however, biased toward proinflammatory cytokines at the beginning of an inflammation and toward antiinflammatory cytokines during the recovery phase.

Our findings demonstrate that exposure to a clinically relevant chronic psychosocial stressor makes rodents more prone to a chemically induced colonic inflammation. This is further in line with reports showing that chronic psychosocial stress worsens the outcome of a spontaneous colitis in human (69) and nonhuman primates (70, 71). In this respect, it is important to note that CSC exposure by itself induced a spontaneous colitis in mice (10). Thus, CSC could be a relevant animal model to study some pathological abnormalities seen in IBD.

Combined MS and CSC effects on DSS-induced colitis
Compared with respective US mice, MS mice exposed to CSC and subsequently treated with DSS showed a more pronounced body weight loss and inflammatory reduction in colon length (when expressed as percentage of colon length) and higher IFN-{gamma} but lower TNF secretion from mesenteric lymph node cells. This latter finding underscores the complex MS-induced regulation of cytokines during inflammatory processes.

We hypothesize that the neuroendocrine abnormalities seen in MS mice after 19 d of CSC have played an important role in the more severe inflammatory response to DSS treatment. First, CSC-exposed MS mice showed lower plasma corticosterone levels than CSC-exposed US mice. Under normal conditions, DSS treatment will induce a rise in cytokine secretion from mesenteric lymph node cells, which is then paralleled by an increase in plasma corticosterone, thereby restricting colonic inflammation. CSC-exposed MS mice most likely failed to show this adequate corticosterone response. Indeed, we previously demonstrated that a lack of an increase in corticosterone is associated with an increased severity of DSS-induced colitis (12). Second, CSC-exposed mice showed an increase in hypothalamic CRH mRNA expression. CRH within the gastrointestinal tract mediates proinflammatory actions (72, 73, 74). If this elevated hypothalamic CRH mRNA expression in CSC-stressed MS mice indicates a general increase in CRH activity, this might have contributed to the exaggerated intestinal immune functions. Third, other components, like the sympathetic nervous system (75), might have played an important additional role in the enhanced intestinal inflammation seen in CSC-stressed MS mice. The present findings thus emphasize the significant impact of early life stress on coping with stressful challenges later in life. We previously showed that exposure to adult chronic stressors (CSC and social defeat/overcrowding) induced alterations in HPA axis function and increased the vulnerability to colonic inflammation induced by DSS (10, 11, 12). We now demonstrate that MS further augmented CSC-induced HPA axis alterations, which likely underlie, at least in part, the higher vulnerability to colonic inflammation when treated with DSS. Further research is needed to confirm this link. We speculate that, e.g. corticosterone replacement at the end of CSC may reduce the high colonic inflammation seen in MS mice.

In conclusion, this study demonstrates that early life stress induced long-lasting changes in neuroendocrine and immune functions, thereby disrupting adaptive responsiveness to chronic psychosocial stress and immune challenge. In particular, the combined exposure to MS and CSC induced key abnormalities in neuroendocrine and immune parameters, including increased hypothalamic CRH expression, reduced plasma corticosterone, and increased IFN-{gamma} secretion. Therefore, future combined use of the MS and CSC paradigms may provide novel insights in the complex interactions between neuroendocrine and inflammatory systems under chronic stress conditions. This is likely to be relevant for understanding the suggested interplay between stress-related mood and inflammatory disorders in humans.


   Acknowledgments
 
We are grateful to R. Bredewold and G. Schindler (Department of Behavioral Neuroendocrinology) and N. Dunger and N. Grunwald (Department of Internal Medicine I) for excellent technical help and Dr. D. Slattery for critical reading of the manuscript.


   Footnotes
 
This study is supported by the Deutsche Forschungs-gemeinschaft (to I.D.N. and F.O.).

Disclosure Statement: The authors have nothing to disclose.

First Published Online February 28, 2008

1 A.H.V. and S.O.R. contributed equally to the manuscript. Back

Abbreviations: CSC, Chronic subordinate colony housing; DSS, dextran sulfate sodium; HPA, hypothalamic-pituitary-adrenocortical; IBD, inflammatory bowel disease; IFN, interferon; MS, maternal separation; PVN, paraventricular nucleus; US, unseparated.

Received October 25, 2007.

Accepted for publication February 19, 2008.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Heim C, Nemeroff CB 2001 The role of childhood trauma in the neurobiology of mood and anxiety disorders: preclinical and clinical studies. Biol Psychiatry 49:1023–1039[CrossRef][Medline]
  2. Kaufman J 1991 Depressive disorders in maltreated children. J Am Acad Child Adolesc Psychiatry 30:257–265[Medline]
  3. Van Voorhees E, Scarpa A 2004 The effects of child maltreatment on the hypothalamic-pituitary-adrenal axis. Trauma Violence Abuse 5:333–352[Abstract]
  4. Danese A, Pariante CM, Caspi A, Taylor A, Poulton R 2007 Childhood maltreatment predicts adult inflammation in a life-course study. Proc Natl Acad Sci USA 104:1319–1324[Abstract/Free Full Text]
  5. Silverman MN, Pearce BD, Biron CA, Miller AH 2005 Immune modulation of the hypothalamic-pituitary-adrenal (HPA) axis during viral infection. Viral Immunol 18:41–78[CrossRef][Medline]
  6. Bailey M, Engler H, Hunzeker J, Sheridan JF 2003 The hypothalamic-pituitary-adrenal axis and viral infection. Viral Immunol 16:141–157[CrossRef][Medline]
  7. McEwen BS, Biron CA, Brunson KW, Bulloch K, Chambers WH, Dhabhar FS, Goldfarb RH, Kitson RP, Miller AH, Spencer RL, Weiss JM 1997 The role of adrenocorticoids as modulators of immune function in health and disease: neural, endocrine and immune interactions. Brain Res Brain Res Rev 23:79–133[CrossRef][Medline]
  8. Mawdsley JE, Rampton DS 2005 Psychological stress in IBD: new insights into pathogenic and therapeutic implications. Gut 54:1481–1491[Free Full Text]
  9. Jessop DS, Richards LJ, Harbuz MS 2004 Effects of stress on inflammatory autoimmune disease: destructive or protective? Stress 7:261–266[Medline]
  10. Reber SO, Birkeneder L, Veenema AH, Obermeier F, Falk W, Straub RH, Neumann ID 2007 Adrenal insufficiency and colonic inflammation after a novel chronic psycho-social stress paradigm in mice: implications and mechanisms. Endocrinology 148:670–682[Abstract/Free Full Text]
  11. Reber SO, Obermeier F, Straub RH, Falk W, Neumann ID 2006 Chronic intermittent psychosocial stress (social defeat/overcrowding) in mice increases the severity of an acute DSS-induced colitis and impairs regeneration. Endocrinology 147:4968–4976[Abstract/Free Full Text]
  12. Reber SO, Obermeier F, Straub RH, Veenema AH, Neumann ID 2 November 2007 Aggravation of DSS-induced colitis after chronic subordinate colony (CSC) housing is partially mediated by adrenal mechanisms. Stress 10.1080/10253890701733351
  13. Kronfol Z 2002 Immune dysregulation in major depression: a critical review of existing evidence. Int J Neuropsychopharmacol 5:333–343[CrossRef][Medline]
  14. Irwin M 1999 Immune correlates of depression. Adv Exp Med Biol 461:1–24[Medline]
  15. Reiche EM, Nunes SO, Morimoto HK 2004 Stress, depression, the immune system, and cancer. Lancet Oncol 5:617–625[CrossRef][Medline]
  16. Plotsky PM, Meaney MJ 1993 Early, postnatal experience alters hypothalamic corticotropin-releasing factor (CRF) mRNA, median eminence CRF content and stress-induced release in adult rats. Brain Res Mol Brain Res 18:195–200[Medline]
  17. Veenema AH, Blume A, Niederle D, Buwalda B, Neumann ID 2006 Effects of early life stress on adult male aggression and hypothalamic vasopressin and serotonin. Eur J Neurosci 24:1711–1720[CrossRef][Medline]
  18. Wigger A, Neumann ID 1999 Periodic maternal deprivation induces gender-dependent alterations in behavioral and neuroendocrine responses to emotional stress in adult rats. Physiol Behav 66:293–302[CrossRef][Medline]
  19. Romeo RD, Mueller A, Sisti HM, Ogawa S, McEwen BS, Brake WG 2003 Anxiety and fear behaviors in adult male and female C57BL/6 mice are modulated by maternal separation. Horm Behav 43:561–567[CrossRef][Medline]
  20. Varghese AK, Verdu EF, Bercik P, Khan WI, Blennerhassett PA, Szechtman H, Collins SM 2006 Antidepressants attenuate increased susceptibility to colitis in a murine model of depression. Gastroenterology 130:1743–1753[Medline]
  21. Veenema AH, Bredewold R, Neumann ID 2007 Opposite effects of maternal separation on intermale and maternal aggression in C57BL/6 mice: link to vasopressin and oxytocin immunoreactivity. Psychoneuroendocrinology 32:437–450[CrossRef][Medline]
  22. Ladd CO, Huot RL, Thrivikraman KV, Nemeroff CB, Meaney MJ, Plotsky PM 2000 Long-term behavioral and neuroendocrine adaptations to adverse early experience. Prog Brain Res 122:81–103[Medline]
  23. Kalinichev M, Easterling KW, Plotsky PM, Holtzman SG 2002 Long-lasting changes in stress-induced corticosterone response and anxiety-like behaviors as a consequence of neonatal maternal separation in Long-Evans rats. Pharmacol Biochem Behav 73:131–140[CrossRef][Medline]
  24. Ladd CO, Owens MJ, Nemeroff CB 1996 Persistent changes in corticotropin-releasing factor neuronal systems induced by maternal deprivation. Endocrinology 137:1212–1218[Abstract]
  25. Huot RL, Thrivikraman KV, Meaney MJ, Plotsky PM 2001 Development of adult ethanol preference and anxiety as a consequence of neonatal maternal separation in Long Evans rats and reversal with antidepressant treatment. Psychopharmacology (Berl) 158:366–373[CrossRef][Medline]
  26. MacQueen GM, Ramakrishnan K, Ratnasingan R, Chen B, Young LT 2003 Desipramine treatment reduces the long-term behavioural and neurochemical sequelae of early-life maternal separation. Int J Neuropsychopharmacol 6:391–396[CrossRef][Medline]
  27. El Khoury A, Gruber SH, Mork A, Mathe AA 2006 Adult life behavioral consequences of early maternal separation are alleviated by escitalopram treatment in a rat model of depression. Prog Neuropsychopharmacol Biol Psychiatry 30:535–540[CrossRef][Medline]
  28. Kessler RC 1997 The effects of stressful life events on depression. Annu Rev Psychol 48:191–214[CrossRef][Medline]
  29. Hibi T, Ogata H, Sakuraba A 2002 Animal models of inflammatory bowel disease. J Gastroenterol 37:409–417[CrossRef][Medline]
  30. Steidler L, Hans W, Schotte L, Neirynck S, Obermeier F, Falk W, Fiers W, Remaut E 2000 Treatment of murine colitis by Lactococcus lactis secreting interleukin-10. Science 289:1352–1355[Abstract/Free Full Text]
  31. Blumberg RS, Strober W 2001 Prospects for research in inflammatory bowel disease. JAMA 285:643–647[Abstract/Free Full Text]
  32. Bousvaros A, Sylvester F, Kugathasan S, Szigethy E, Fiocchi C, Colletti R, Otley A, Amre D, Ferry G, Czinn SJ, Splawski JB, Oliva-Hemker M, Hyams JS, Faubion WA, Kirschner BS, Dubinsky MC 2006 Challenges in pediatric inflammatory bowel disease. Inflamm Bowel Dis 12:885–913[CrossRef][Medline]
  33. Maunder RG 2005 Evidence that stress contributes to inflammatory bowel disease: evaluation, synthesis, and future directions. Inflamm Bowel Dis 11:600–608[CrossRef][Medline]
  34. Kurina LM, Goldacre MJ, Yeates D, Gill LE 2001 Depression and anxiety in people with inflammatory bowel disease. J Epidemiol Community Health 55:716–720[Abstract/Free Full Text]
  35. Mikocka-Walus AA, Turnbull DA, Moulding NT, Wilson IG, Andrews JM, Holtmann GJ 2007 Controversies surrounding the comorbidity of depression and anxiety in inflammatory bowel disease patients: a literature review. Inflamm Bowel Dis 13:225–234[CrossRef][Medline]
  36. Bartolomucci A, Palanza P, Sacerdote P, Ceresini G, Chirieleison A, Panerai AE, Parmigiani S 2003 Individual housing induces altered immuno-endocrine responses to psychological stress in male mice. Psychoneuroendocrinology 28:540–558[CrossRef][Medline]
  37. Gasparotto OC, Lopes DM, Carobrez SG 2005 Pair housing affects anxiety-like behaviors induced by a social but not by a physiological stressor in male Swiss mice. Physiol Behav 85:603–612[CrossRef][Medline]
  38. Misslin R, Herzog F, Koch B, Ropartz P 1982 Effects of isolation, handling and novelty on the pituitary-adrenal response in the mouse. Psychoneuroendocrinology 7:217–221[CrossRef][Medline]
  39. Obermeier F, Kojouharoff G, Hans W, Scholmerich J, Gross V, Falk W 1999 Interferon-{gamma} (IFN-{gamma})- and tumour necrosis factor (TNF)-induced nitric oxide as toxic effector molecule in chronic dextran sulphate sodium (DSS)-induced colitis in mice. Clin Exp Immunol 116:238–245[CrossRef][Medline]
  40. Wigger A, Sanchez MM, Mathys KC, Ebner K, Frank E, Liu D, Kresse A, Neumann ID, Holsboer F, Plotsky PM, Landgraf R 2004 Alterations in central neuropeptide expression, release, and receptor binding in rats bred for high anxiety: critical role of vasopressin. Neuropsychopharmacology 29:1–14[CrossRef][Medline]
  41. Kojouharoff G, Hans W, Obermeier F, Mannel DN, Andus T, Scholmerich J, Gross V, Falk W 1997 Neutralization of tumour necrosis factor (TNF) but not of IL-1 reduces inflammation in chronic dextran sulphate sodium-induced colitis in mice. Clin Exp Immunol 107:353–358[CrossRef][Medline]
  42. Obermeier F, Dunger N, Strauch UG, Grunwald N, Herfarth H, Scholmerich J, Falk W 2003 Contrasting activity of cytosin-guanosin dinucleotide oligonucleotides in mice with experimental colitis. Clin Exp Immunol 134:217–224[CrossRef][Medline]
  43. Parfitt DB, Levin JK, Saltstein KP, Klayman AS, Greer LM, Helmreich DL 2004 Differential early rearing environments can accentuate or attenuate the responses to stress in male C57BL/6 mice. Brain Res 1016:111–118[CrossRef][Medline]
  44. Aguilera G 1994 Regulation of pituitary ACTH secretion during chronic stress. Front Neuroendocrinol 15:321–350[CrossRef][Medline]
  45. Lolait SJ, Stewart LQ, Jessop DS, Young 3rd WS, O'Carroll AM 2007 The hypothalamic-pituitary-adrenal axis response to stress in mice lacking functional vasopressin V1b receptors. Endocrinology 148:849–856[Abstract/Free Full Text]
  46. Engelmann M, Landgraf R, Wotjak CT 2004 The hypothalamic-neurohypophysial system regulates the hypothalamic-pituitary-adrenal axis under stress: an old concept revisited. Front Neuroendocrinol 25:132–149[CrossRef][Medline]
  47. Reber SO, Neumann ID, Chronic subordinate colony (CSC) housing enhances state anxiety and reduces hypothalamic arginine vasopressin, but not oxytocin, synthesis. Ann NY Acad Sci, in press
  48. Keeney A, Jessop DS, Harbuz MS, Marsden CA, Hogg S, Blackburn-Munro RE 2006 Differential effects of acute and chronic social defeat stress on hypothalamic-pituitary-adrenal axis function and hippocampal serotonin release in mice. J Neuroendocrinol 18:330–338[CrossRef][Medline]
  49. Aguilera G, Rabadan-Diehl C 2000 Vasopressinergic regulation of the hypothalamic-pituitary-adrenal axis: implications for stress adaptation. Regul Pept 96:23–29[CrossRef][Medline]
  50. Subburaju S, Aguilera G 2007 Vasopressin mediates mitogenic responses to adrenalectomy in the rat anterior pituitary. Endocrinology 148:3102–3110[Abstract/Free Full Text]
  51. Zhao L, Brinton RD 2004 Suppression of proinflammatory cytokines interleukin-1β and tumor necrosis factor-{alpha} in astrocytes by a V1 vasopressin receptor agonist: a cAMP response element-binding protein-dependent mechanism. J Neurosci 24:2226–2235[Abstract/Free Full Text]
  52. Ladd CO, Thrivikraman KV, Huot RL, Plotsky PM 2005 Differential neuroendocrine responses to chronic variable stress in adult Long Evans rats exposed to handling-maternal separation as neonates. Psychoneuroendocrinology 30:520–533[CrossRef][Medline]
  53. De Kloet ER, Reul JM 1987 Feedback action and tonic influence of corticosteroids on brain function: a concept arising from the heterogeneity of brain receptor systems. Psychoneuroendocrinology 12:83–105[CrossRef][Medline]
  54. Valentino RJ, Foote SL, Page ME 1993 The locus coeruleus as a site for integrating corticotropin-releasing factor and noradrenergic mediation of stress responses. Ann NY Acad Sci 697:173–188[Medline]
  55. Koob GF 1999 Corticotropin-releasing factor, norepinephrine, and stress. Biol Psychiatry 46:1167–1180[CrossRef][Medline]
  56. Heim C, Ehlert U, Hellhammer DH 2000 The potential role of hypocortisolism in the pathophysiology of stress-related bodily disorders. Psychoneuroendocrinology 25:1–35[CrossRef][Medline]
  57. Fries E, Hesse J, Hellhammer J, Hellhammer DH 2005 A new view on hypocortisolism. Psychoneuroendocrinology 30:1010–1016[CrossRef][Medline]
  58. Yehuda R 2001 Biology of posttraumatic stress disorder. J Clin Psychiatry 62(Suppl 17):41–46
  59. Kasckow JW, Baker D, Geracioti Jr TD 2001 Corticotropin-releasing hormone in depression and post-traumatic stress disorder. Peptides 22:845–851[CrossRef][Medline]
  60. Lemieux AM, Coe CL 1995 Abuse-related posttraumatic stress disorder: evidence for chronic neuroendocrine activation in women. Psychosom Med 57:105–115[Abstract/Free Full Text]
  61. Yehuda R 2002 Current status of cortisol findings in post-traumatic stress disorder. Psychiatr Clin North Am 25:341–368, vii[CrossRef][Medline]
  62. Carrion VG, Weems CF, Ray RD, Glaser B, Hessl D, Reiss AL 2002 Diurnal salivary cortisol in pediatric posttraumatic stress disorder. Biol Psychiatry 51:575–582[CrossRef][Medline]
  63. Raison CL, Miller AH 2003 When not enough is too much: the role of insufficient glucocorticoid signaling in the pathophysiology of stress-related disorders. Am J Psychiatry 160:1554–1565[Abstract/Free Full Text]
  64. Wallace DJ, Hallegua DS 2004 Fibromyalgia: the gastrointestinal link. Curr Pain Headache Rep 8:364–368[CrossRef][Medline]
  65. Levenstein S 2002 Psychosocial factors in peptic ulcer and inflammatory bowel disease. J Consult Clin Psychol 70:739–750[CrossRef][Medline]
  66. Barreau F, Ferrier L, Fioramonti J, Bueno L 2004 Neonatal maternal deprivation triggers long term alterations in colonic epithelial barrier and mucosal immunity in rats. Gut 53:501–506[Abstract/Free Full Text]
  67. Gareau MG, Jury J, Perdue MH 2007 Neonatal maternal separation of rat pups results in abnormal cholinergic regulation of epithelial permeability. Am J Physiol 293:G198–G203
  68. Mackner LM, Crandall WV, Szigethy EM 2006 Psychosocial functioning in pediatric inflammatory bowel disease. Inflamm Bowel Dis 12:239–244[CrossRef][Medline]
  69. Salem SN, Shubair KS 1967 Non-specific ulcerative colitis in Bedouin Arabs. Lancet 1:473–475[Medline]
  70. Wood JD, Peck OC, Tefend KS, Stonerook MJ, Caniano DA, Mutabagani KH, Lhotak S, Sharma HM 2000 Evidence that colitis is initiated by environmental stress and sustained by fecal factors in the cotton-top tamarin (Saguinus oedipus). Dig Dis Sci 45:385–393[CrossRef][Medline]
  71. Drossman DA 1985 Is the cotton-topped tamarin a model for behavioral research? Dig Dis Sci 30:24S–27S[CrossRef]
  72. Gravanis A, Margioris AN 2005 The corticotropin-releasing factor (CRF) family of neuropeptides in inflammation: potential therapeutic applications. Curr Med Chem 12:1503–1512[CrossRef][Medline]
  73. Tache Y, Bonaz B 2007 Corticotropin-releasing factor receptors and stress-related alterations of gut motor function. J Clin Invest 117:33–40[CrossRef][Medline]
  74. Bhatia V, Tandon RK 2005 Stress and the gastrointestinal tract. J Gastroenterol Hepatol 20:332–339[CrossRef][Medline]
  75. Straub RH, Wiest R, Strauch UG, Harle P, Scholmerich J 2006 The role of the sympathetic nervous system in intestinal inflammation. Gut 55:1640–1649[Free Full Text]
  76. Paxinos G, Franklin KBJ 2001 The mouse brain in stereotaxic coordinates. San Diego, CA: Academic Press



This article has been cited by other articles:


Home page
 EndocrinologyHome page
K. A. Spencer, N. P. Evans, and P. Monaghan
Postnatal Stress in Birds: A Novel Model of Glucocorticoid Programming of the Hypothalamic-Pituitary-Adrenal Axis
Endocrinology, April 1, 2009; 150(4): 1931 - 1934.
[Abstract] [Full Text] [PDF]

Home page
 EndocrinologyHome page
D. S. Jessop
The Fragile Mind: Early Life Stress and Inflammatory Disease
Endocrinology, June 1, 2008; 149(6): 2724 - 2726.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Veenema, A. H.
Right arrow Articles by Neumann, I. D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Veenema, A. H.
Right arrow Articles by Neumann, I. D.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals