Blockade of the renin-angiotensin system prevents acute and immunologically relevant colitis in murine models.

BACKGROUND: Blockade of the renin-angiotensin system (RAS) has been shown to alleviate inflammatory processes in the gastrointestinal tract. The aim of this study was to determine if blockade of the RAS would be effective in an immunologically relevant colitis model, and to compare outcome with an acute colitis model. METHODS: A losartan analog, CCG-203025 (C23H26ClN3O5S) containing a highly polar sulfonic acid moiety that we expected would allow localized mucosal antagonism with minimal systemic absorption was selected as an angiotensin II type 1a receptor antagonist (AT1aR-A). Two colitis models were studied: (1) Acute colitis was induced in 8- to 10-week-old C57BL/6J mice by 2.5 % dextran sodium sulfate (DSS, in drinking water) for 7 days. (2) IL10-/-colitis Piroxicam (200 ppm) was administered orally in feed to 5-week-old IL-10-/-mice (C57BL/6J background) for 14 days followed by enalaprilat (ACE-I), CCG-203025 or PBS administered transanally for 14 days. RESULTS: In the DSS model, weight loss and histologic score for CCG-203025 were better than with placebo. In the IL10-/-model, ACE-I suppressed histologic damage better than CCG-203025. Both ACE-I and CCG-203025 reduced pro-inflammatory cytokines and chemokines. CONCLUSIONS: This study demonstrated the therapeutic efficacy of both ACE-I and AT1aR-A for preventing the development of both acute and immunologically relevant colitis.

Angiotensin receptor blockers suppress antigen-specific T cell responses and ameliorate collagen-induced arthritis in mice.

OBJECTIVE: The renin-angiotensin system plays an important role in the regulation of cardiovascular, renal, and endocrine functions. Recent studies have demonstrated that angiotensin II has proinflammatory effects that may contribute to the pathogenesis of immune-mediated diseases. We used the collagen-induced arthritis (CIA) model to investigate the influence of angiotensin II receptor blockers (ARBs) on antigen-specific immune responses and determine whether ARBs have preventive or therapeutic effects on the development of arthritis. METHODS: We administered ARBs (olmesartan, candesartan, and telmisartan) to mice and evaluated antigen-specific T cell proliferation and cytokine production following immunization with ovalbumin (OVA) or type II collagen in Freund's complete adjuvant (CFA) or aluminum hydroxide (alum). Next, we induced CIA in DBA/1 mice and administered olmesartan. The severity and incidence of arthritis were scored according to clinical manifestations, and joint tissue sections were examined histopathologically. RESULTS: ARBs severely suppressed lymphocyte proliferation and interferon-gamma production in mice immunized with OVA or type II collagen in CFA. Olmesartan also suppressed lymphocyte proliferation in mice immunized with ovalbumin in alum. In the CIA model, olmesartan reduced the mean arthritis score and the incidence of severe arthritis, even when it was administered only after disease onset. Histopathologic findings for joint destruction were improved in olmesartan-treated mice. CONCLUSION: ARBs suppressed antigen-specific immune responses for Th1 and Th2 in vivo. Furthermore, olmesartan suppressed the development of severe arthritis and joint destruction in the CIA model. These findings suggest that ARBs may have therapeutic potential in rheumatoid arthritis.