SUN-254 Angiotensin II Stimulates Microglia Cell Inflammatory Responses

Abstract

Angiotensin II (AngII) is the principal effector molecule of the renin-angiotensin system (RAS). It’s effects on the cardiovascular and renal system are well-documented. AngII acts mainly via interaction with the AngII type-1 receptor (AT1R). Disordered levels of AngII lead to hypertension and cardiovascular disease. Increasing evidence suggests that AngII may also play a role in the pathophysiology of neurodegenerative diseases through unclear mechanisms. We investigated AngII, AT1R and AT2R levels in a mouse model of neurodegenerative disease, the experimentally induced autoimmune encephalomyelitis (EAE) mouse. In EAE mice, AngII and AT1R gene expression in brain tissue were significantly increased when compared to control mice (3.2 folds ±1.9, p<0.05, n=5; and 2.6 folds ±1.1, p<0.01, n=5 respectively). In addition, iNOS mRNA expression by qRT-PCR was likewise upregulated in EAE mice compared to control (3.4 ± 1.4 folds, p<0.01, n=5). We then studied the effects of AngII in human microglial cells (HMC3) -resident innate immune cells of the central nervous system (CNS). In HMC3 cells, treatment with AngII up-regulated the expression IL-6 (3.9 folds ± 1.2, p<0.01, n=4) and increased IL-6 concentration by 83% (p<0.05, n=4) by ELISA; effects that were blocked by the AT1R antagonist, Losartan. Also, AngII induced TNF-α production, increasing its concentration by 90% (p<0.05, n=4), an increase that was blocked by Losartan. We also quantified Nitric Oxide (NO) production by using Griess Reagent and reactive oxygen species (ROS) production by the MUSE Oxidative Stress assay. In these cells, NO and ROS production were significantly increased by AngII (p<0.05, n=4) and treatment with Losartan reduced their production (p<0.05, n=4). In addition, AngII treatment induced iNOS overexpression (2.5 folds ±0.8, p<0.05, n=4); results that are consistent with increases in the EAE mice. These data suggest that AngII can activate microglia cell inflammatory responses and as such may contribute to the pathophysiology of CNS inflammation and neurodegenerative diseases.