| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Department of Medicine (T.H., F.Y., Y.K.) and Research Institute (T.T., T.M., S.S., K.K.), National Cardiovascular Center, Suita, Osaka 565-8565, Japan; Department of Hypertension and Cardiorenal Medicine, Dokkyo University School of Medicine (T.N.), Tochigi 321-0293, Japan; and Institute of Life Sciences, Kurume University (M.K.), Kurume, Fukuoka 839-0861, Japan
Address all correspondence and requests for reprints to: Takeshi Horio, M.D., Division of Hypertension and Nephrology, Department of Medicine, National Cardiovascular Center, 5-7-1, Fujishirodai, Suita, Osaka 565-8565, Japan. E-mail: thorio{at}ri.ncvc.go.jp.
| Abstract |
|---|
|
|
|---|
| Introduction |
|---|
|
|
|---|
Subsequent studies have revealed the existence of two biological [guanylyl cyclase (GC)-containing] natriuretic peptide receptors, called GC-A and GC-B, in cardiac cells (3). In addition to acting as a circulating hormone, therefore, ANP and BNP may have some function as autocrine and/or paracrine factors. In fact, some studies, including our in vitro study, showed that endogenous ANP and BNP suppress the development of cardiac myocyte hypertrophy and interstitial fibrosis (4, 5, 6). With regard to CNP, however, its production in cardiac cells and the local effect on the heart itself have remained to be elucidated. Therefore, we conducted this study to investigate the production of CNP and the expression of GC-B, a specific receptor for CNP, in cultured ventricular cells and to examine the effects of CNP on DNA and collagen syntheses by fibroblast cells.
| Materials and Methods |
|---|
|
|
|---|
Neonatal ventricular myocytes and fibroblasts were prepared as described previously (8). From cardiac ventricles of 1- to 2-d-old Wistar rats, myocytes and fibroblasts were separately collected by the discontinuous Percoll gradient method. Primary cultures of neonatal rat cardiac myocytes and neonatal cardiac fibroblasts at the second passage were used for the gene expression study.
Measurement of immunoreactive (ir-) ANP, BNP, and CNP
After adult cardiac fibroblasts were incubated for 1272 h in 10-cm dishes with serum-free DMEM, the culture medium was collected. In the study examining the effect of various agents on ir-CNP secretion, cells were incubated for 24 h under treatment with IL-1ß (Genzyme Techne, Minneapolis, MN), TNF-
(Sigma, St. Louis, MO), TGF-ß1 (R Systems, Minneapolis, MN), basic fibroblast growth factor (bFGF; Sigma), IGF-1 (Sigma), insulin (Sigma), angiotensin II (Peptide Institute, Osaka, Japan), endothelin-1 (Peptide Institute), phenylephrine (Research Biochemicals International, Natick, MA), isoproterenol (Sigma), or norepinephrine (Research Biochemicals International). The collected medium (10 ml) was condensed with a Sep-Pak C18 cartridge (Waters, Milford, MA) and lyophilized. The RIA for rat ANP, BNP, and CNP was performed as previously reported (6, 9).
Characterization of ir-CNP
The conditioned medium (80 ml) from adult cardiac fibroblasts was condensed and separated by reverse-phase HPLC on a µ-Bondasphere C18 column (300 Å, 3.9 x 150 mm; Waters), as described previously (8). A linear gradient elution of acetonitrile for 1060% in 0.1% trifluoroacetic acid was made at a flow rate of 1 ml/min, and each collected fraction (1 ml) was submitted for RIA for CNP.
Northern blot analysis
After incubation in DMEM with FCS, the cultured cells were rinsed with PBS and submitted for RNA extraction. Total RNA was extracted with TRIzol reagent (Life Technologies, Inc.) and poly(A)+ RNA was prepared using Oligotex-dT30 Super (Takara Biomedicals, Shiga, Japan). Poly(A)+ RNA (10 µg/lane) was electrophoresed on 1% agarose gel and then transferred to a nylon membrane. Hybridization and washing of the membrane were carried out with cDNA probes for rat CNP, ANP, GC-A, GC-B, and glyceraldehyde-3-phosphate dehydrogenase genes, according to the method previously reported (8, 9).
Measurement of cellular cGMP
After preincubation, adult cardiac fibroblasts grown in 24-well plates were treated for 10 min with various concentrations of synthetic ANP, BNP, or CNP (Peptide Institute) in the presence of 5 x 10-4 mol/liter 3-isobutyl-1-methylxanthine (Nacalai Tesque, Kyoto, Japan). The intracellular cGMP levels were determined by a RIA performed with a cGMP assay kit (Yamasa Shoyu, Chiba, Japan), as previously reported (6).
DNA and collagen syntheses
The effects of natriuretic peptides and a cGMP analog on DNA synthesis and collagen synthesis in adult rat cardiac fibroblasts were evaluated by the incorporation of [3H]thymidine and [3H]proline into cells, respectively, as described previously (10). Fibroblasts at the second or third passage were seeded at a density of 2.5 x 104 cells/well on 24-well plates. After incubation in DMEM with 10% FCS, subconfluent fibroblast cells (approximately 7.5 x 104 cells/well) were maintained in serum-free DMEM for 48 h. After the preconditioning period, the culture medium was replaced with fresh DMEM with 1% FCS. Then, ANP, BNP, CNP, or 8-bromo cGMP (Sigma) was added, and 0.5 µCi of [3H]thymidine or [3H]proline was also added. After the cells were incubated for 24 h, the radioactivity of aliquots of the trichloroacetic acid-insoluble material was determined using a liquid scintillation counter.
Statistical analysis
The significance of differences among groups was estimated by an unpaired ANOVA, and probability values were calculated by the Fisher method. A value of P < 0.05 was accepted as statistically significant.
| Results |
|---|
|
|
|---|
|
We further examined which humoral factor stimulates CNP release from adult cardiac fibroblasts. The secretion levels of ir-CNP were slightly but significantly increased by TGF-ß1 (10-9 mol/liter) and bFGF (10-8 mol/liter) among several cytokines and growth factors (Table 1
). Among vasoactive peptides and catecholamines, only endothelin-1 (10-7 mol/liter) stimulated the ir-CNP release from cardiac fibroblasts.
|
|
Effects of natriuretic peptides on cellular cGMP production and on DNA and collagen syntheses in adult cardiac fibroblasts
CNP markedly increased the cellular level of cGMP in adult cardiac fibroblasts and its increase was concentration dependent (Fig. 3
). Although ANP and BNP also increased the cGMP levels concentration dependently, the stimulation of cGMP formation by ANP or BNP was weaker than by CNP.
|
|
| Discussion |
|---|
|
|
|---|
In the present study, TGF-ß1, bFGF, and endothelin-1 among various humoral factors elicited a weak but significant stimulatory effect on CNP secretion. TGF-ß and bFGF have been shown to increase CNP secretion in cultured vascular endothelial cells and/or chondrocytes (2, 13). In addition, it has been shown that CNP production is enhanced by activation of protein kinase C (21), of which endothelin-1 is one of the activators. Therefore, the present findings concerning stimulation factors of CNP secretion are consistent with previous observations. Because TGF-ß1, bFGF, and endothelin-1 all increase collagen or DNA synthesis in cardiac fibroblasts, CNP induced by these factors may display a counter-action against cardiac fibrosis.
Previous studies showed that ANP and BNP inhibited collagen production and proliferation of cultured cardiac fibroblasts (22, 23, 24). However, little is known about the effect of CNP on those cells, except for one study reported that CNP as well as ANP and BNP decreased bFGF-induced DNA synthesis in neonatal cardiac fibroblasts (23). The present study has clearly demonstrated that CNP inhibits both DNA and collagen syntheses in adult cardiac fibroblasts, and that these suppressive effects by CNP are more potent than those by ANP or BNP. Furthermore, CNP increased the intracellular cGMP levels more markedly compared with ANP or BNP, and a cGMP analog reproduced the suppression of DNA and collagen syntheses. Three receptor subtypes for natriuretic peptides are presently known. Two of these receptors have GC activity (i.e. induce cGMP accumulation) and are called GC-A and GC-B. ANP and BNP bind specifically to GC-A rather than GC-B (25). In contrast, CNP binds to GC-B with a very high affinity but almost lacks the binding ability to GC-A (26). Because our study showed that cultured adult rat cardiac fibroblasts predominantly expressed the GC-B by Northern hybridization, the inhibitory effects of CNP on the proliferation and collagen production of cardiac fibroblasts are probably through a GC-B-mediated cGMP-dependent pathway. The present observations concerning the gene expression of the GC-B- and CNP-stimulated cGMP accumulation in fibroblasts were broadly consistent with the findings previously reported by Lin et al. (3). In their study, however, expression levels of the GC-A receptor in cultured cardiac fibroblasts were comparable to those of the GC-B, and ANP stimulated cGMP production as potently as CNP. The exact reason for such discrepant findings is unclear, but it may be partly due to the difference in the methods of preparation of cardiac fibroblasts and the conditions of the fibroblast cell culture used, including their purity and passages.
A previous study showed that GC-B mRNA levels were markedly increased in the hypertrophied left ventricle induced by volume overload (27). Furthermore, Doyle et al. (28) recently revealed that the distribution of the GC-B receptor in adult rat ventricles was confined to the nonmyocytes such as interstitial and vascular fibroblasts. These findings suggest that CNP released from cardiac fibroblasts may function effectively on themselves as an autocrine negative regulator against excessive cardiac fibrosis in pathological states. However, further investigations are necessary to clarify the physiological and pathophysiological roles of endogenous CNP in the heart.
In conclusion, the present study demonstrated that CNP was synthesized in and secreted from cultured adult cardiac fibroblasts and that CNP inhibited DNA and collagen syntheses in these cells more potently than ANP and BNP. Cardiac CNP produced by fibroblasts may function as a local modulator of cardiac fibrosis, defined as a proliferation of interstitial fibroblasts and the biosynthesis of extracellular matrix components.
| Acknowledgments |
|---|
| Footnotes |
|---|
Abbreviations: ANP, Atrial natriuretic peptide; bFGF, basic fibroblast growth factor; BNP, brain natriuretic peptide; CNP, C-type natriuretic peptide; FCS, fetal calf serum; GC, guanylyl cyclase; ir, immunoreactive.
Received January 27, 2003.
Accepted for publication March 4, 2003.
| References |
|---|
|
|
|---|
. Endocrinology 139:45764580This article has been cited by other articles:
![]() |
D. J. Glenn, D. Rahmutula, M. Nishimoto, F. Liang, and D. G. Gardner Atrial natriuretic peptide suppresses endothelin gene expression and proliferation in cardiac fibroblasts through a GATA4-dependent mechanism Cardiovasc Res, November 1, 2009; 84(2): 209 - 217. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. C. Palmer, T. C.R. Prickett, E. A. Espiner, T. G. Yandle, and A. M. Richards Regional Release and Clearance of C-Type Natriuretic Peptides in the Human Circulation and Relation to Cardiac Function Hypertension, September 1, 2009; 54(3): 612 - 618. [Abstract] [Full Text] [PDF] |
||||
![]() |
O. Lisy, B. K. Huntley, D. J. McCormick, P. A. Kurlansky, and J. C. Burnett Jr Design, Synthesis, and Actions of a Novel Chimeric Natriuretic Peptide: CD-NP. J. Am. Coll. Cardiol., July 1, 2008; 52(1): 60 - 68. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. A. Rose and W. R. Giles Natriuretic peptide C receptor signalling in the heart and vasculature J. Physiol., January 15, 2008; 586(2): 353 - 366. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. S. Hu, L. K. Landeen, N. Aroonsakool, and W. R. Giles An analysis of the effects of stretch on IGF-I secretion from rat ventricular fibroblasts Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H677 - H683. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Wang, M. C. de Waard, A. Sterner-Kock, H. Stepan, H.-P. Schultheiss, D. J. Duncker, and T. Walther Cardiomyocyte-restricted over-expression of C-type natriuretic peptide prevents cardiac hypertrophy induced by myocardial infarction in mice Eur J Heart Fail, June 1, 2007; 9(6-7): 548 - 557. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. A. Rose, N. Hatano, S. Ohya, Y. Imaizumi, and W. R. Giles C-type natriuretic peptide activates a non-selective cation current in acutely isolated rat cardiac fibroblasts via natriuretic peptide C receptor-mediated signalling J. Physiol., April 1, 2007; 580(1): 255 - 274. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Wakeno, T. Minamino, O. Seguchi, H. Okazaki, O. Tsukamoto, K.-i. Okada, A. Hirata, M. Fujita, H. Asanuma, J. Kim, et al. Long-Term Stimulation of Adenosine A2b Receptors Begun After Myocardial Infarction Prevents Cardiac Remodeling in Rats Circulation, October 31, 2006; 114(18): 1923 - 1932. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. D. Jarvis, M. T. Rademaker, L. J. Ellmers, M. J. Currie, J. L. McKenzie, B. R. Palmer, C. M. Frampton, A. M. Richards, and V. A. Cameron Comparison of infarct-derived and control ovine cardiac myofibroblasts in culture: response to cytokines and natriuretic peptide receptor expression profiles. Am J Physiol Heart Circ Physiol, October 1, 2006; 291(4): H1952 - H1958. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. E. H. Christoffersen, M. Aplin, C. C. Strom, S. P. Sheikh, O. Skott, P. K. Busk, S. Haunso, and L. B. Nielsen Increased natriuretic peptide receptor A and C gene expression in rats with pressure-overload cardiac hypertrophy Am J Physiol Heart Circ Physiol, April 1, 2006; 290(4): H1635 - H1641. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. H. Langenickel, J. Buttgereit, I. Pagel-Langenickel, M. Lindner, J. Monti, K. Beuerlein, N. Al-Saadi, R. Plehm, E. Popova, J. Tank, et al. Cardiac hypertrophy in transgenic rats expressing a dominant-negative mutant of the natriuretic peptide receptor B PNAS, March 21, 2006; 103(12): 4735 - 4740. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Nishikimi, N. Maeda, and H. Matsuoka The role of natriuretic peptides in cardioprotection Cardiovasc Res, February 1, 2006; 69(2): 318 - 328. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Rahmutula and D. G. Gardner C-Type Natriuretic Peptide Down-Regulates Expression of Its Cognate Receptor in Rat Aortic Smooth Muscle Cells Endocrinology, November 1, 2005; 146(11): 4968 - 4974. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Tokudome, T. Horio, I. Kishimoto, T. Soeki, K. Mori, Y. Kawano, M. Kohno, D. L. Garbers, K. Nakao, and K. Kangawa Calcineurin-Nuclear Factor of Activated T Cells Pathway-Dependent Cardiac Remodeling in Mice Deficient in Guanylyl Cyclase A, a Receptor for Atrial and Brain Natriuretic Peptides Circulation, June 14, 2005; 111(23): 3095 - 3104. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Soeki, I. Kishimoto, H. Okumura, T. Tokudome, T. Horio, K. Mori, and K. Kangawa C-type natriuretic peptide, a novel antifibrotic and antihypertrophic agent, prevents cardiac remodeling after myocardial infarction J. Am. Coll. Cardiol., February 15, 2005; 45(4): 608 - 616. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Murakami, N. Nagaya, T. Itoh, T. Fujii, T. Iwase, K. Hamada, H. Kimura, and K. Kangawa C-type natriuretic peptide attenuates bleomycin-induced pulmonary fibrosis in mice Am J Physiol Lung Cell Mol Physiol, December 1, 2004; 287(6): L1172 - L1177. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Tokudome, T. Horio, T. Soeki, K. Mori, I. Kishimoto, S.-i. Suga, F. Yoshihara, Y. Kawano, M. Kohno, and K. Kangawa Inhibitory Effect of C-Type Natriuretic Peptide (CNP) on Cultured Cardiac Myocyte Hypertrophy: Interference between CNP and Endothelin-1 Signaling Pathways Endocrinology, May 1, 2004; 145(5): 2131 - 2140. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| 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 |