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Angiotensin II AT₁ Receptor Blockade Decreases Lipopolysaccharide-Induced Inflammation in the Rat Adrenal Gland

Section on Pharmacology, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland 20892

Address all correspondence and requests for reprints to: Enrique Sanchez-Lemus, Section on Pharmacology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Department of Health and Human Services, 10 Center Drive, MSC 1514, Building, 10, Room 2D57, Bethesda, Maryland 20892. E-mail: sancheze{at}mail.nih.gov.

Peripheral administration of bacterial endotoxin [lipopolysaccharide (LPS)] to rodents produces an innate immune response and hypothalamic-pituitary-adrenal axis stimulation. Renin-angiotensin-aldosterone system inhibition by angiotensin II AT₁ receptor blockade has antiinflammatory effects in the vasculature. We studied whether angiotensin II receptor blockers (ARBs) prevent the LPS response. We focused on the adrenal gland, one organ responsive to LPS and expressing a local renin-angiotensin-aldosterone system. LPS (50 µg/kg, ip) produced a generalized inflammatory response with increased release of TNF- and IL-6 to the circulation, enhanced adrenal aldosterone synthesis and release, and enhanced adrenal cyclooxygenase-2, IL-6, and TNF- gene expression. ACTH and corticosterone release were also increased by LPS. Pretreatment with the ARB candesartan (1 mg/kg·d, sc for 3 d before the LPS administration) decreased LPS-induced cytokine release to the circulation, adrenal aldosterone synthesis and release, and cyclooxygenase-2 and IL-6 gene expression. Candesartan did not prevent the LPS-induced ACTH and corticosterone release. Our results suggest that AT₁ receptors are essential for the development of the full innate immune and stress responses to bacterial endotoxin. The ARB decreased the general peripheral inflammatory response to LPS, partially decreased the inflammatory response in the adrenal gland, prevented the release of the pro-inflammatory hormone aldosterone, and protected the antiinflammatory effects of glucocorticoid release. An unrestricted innate immune response to the bacterial endotoxin may have deleterious effects for the organism and may lead to development of chronic inflammatory disease. We postulate that the ARBs may have therapeutic effects on inflammatory conditions.

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