Diverse biological functions of the renin-angiotensin system

The renin-angiotensin system (RAS) has been widely known as a circulating endocrine system involved in the control of blood pressure. However, components of RAS have been found to be localized in rather unexpected sites in the body including the kidneys, brain, bone marrow, immune cells, and reproductive system. These discoveries have led to steady, growing evidence of the existence of independent tissue RAS specific to several parts of the body. It is important to understand how RAS regulates these systems for a variety of reasons: It gives a better overall picture of human physiology, helps to understand and mitigate the unintended consequences of RAS-inhibiting or activating drugs, and sets the stage for potential new therapies for a variety of ailments. This review fulfills the need for an updated overview of knowledge about local tissue RAS in several bodily systems, including their components, functions, and medical implications.

Role of angiotensin II in ischemia/reperfusion‐induced leukocyte‐endothelium interactions in the colon

The aims of the present study were to determine the effects and mechanisms of angiotensin II (Ang II) on leukocyte-endothelium interactions and the role of Ang II in a novel model of ischemia/reperfusion (I/R) in the mouse colon. Ang II dose-dependently increased leukocyte rolling and adhesion in colonic venules. Importantly, Ang II-induced leukocyte rolling was completely inhibited by immunoneutralization of P-selectin, and leukocyte adhesion was abolished in lymphocyte function antigen-1 (LFA-1)-deficient mice. The P-selectin-dependent rolling was found to be a precondition for the subsequent LFA-1-dependent leukocyte adhesion. Moreover, Ang II-induced leukocyte responses involved generation of reactive oxygen species and up-regulation of CXC chemokines. Notably, CXC chemokines, but not Ang II, stimulated leukocyte chemotaxis in vitro. I/R increased gene expression of angiotensin converting enzyme (ACE) in the colon and plasma concentrations of Ang II. Inhibition of ACE and the type 1 angiotensin (AT1) receptor significantly decreased the I/R-induced leukocyte adhesion. Taken together, these novel findings demonstrate that Ang II exerts potent pro-inflammatory effects in the colonic microcirculation and that inhibition of Ang II expression or function protects against I/R-induced leukocyte responses in the colon. Thus, it is suggested that Ang II is a major target to control pathological inflammation in the colon.