Stimulation of Angiotensin II Type 2 Receptor Modulates Pro-Inflammatory Response in Microglia and Macrophages: Therapeutic Implications for the Treatment of Stroke

Background: Sustained microglial activation contributes to the development of post-stroke cognitive impairment (PSCI). Compound 21 (C21), an angiotensin II type 2 receptor agonist, has shown some neurovascular protection after stroke. This study aimed to investigate the direct anti-inflammatory effects of C21 on macrophages, as well as brain innate immune cells. Methods: Murine microglial cell line (C8-B4) and RAW 264.7 macrophages were exposed to lipopolysaccharide (LPS) and co-treated with C21. Pro-inflammatory mediators were assessed via RT-qPCR and ELISA. Cellular reactive oxygen species (ROS) were evaluated via CellROXGreen staining, and nitrate production was assessed using Griess assay. Results: C21 suppressed LPS-induced inflammation and ROS generation in both cells. In microglia, C21 blunted LPS-induced mRNA expression of IL-1 & beta;, IL-12b, COX-1, iNOS, and IL-6. A similar pattern was observed in macrophages, where C21 suppressed LPS-induced IL-1 & beta;, TNF-& alpha;, and CXCL1 expression. These anti-inflammatory effects in microglia and macrophages were associated with increased neuroprotective gene expression, including GDNF and BDNF, in a dose-dependent manner. Conclusions: Our findings suggest a protective effect of C21 against the inflammatory response, in both macrophages and microglia, via suppression of the release of pro-inflammatory cytokines/chemokines and the generation of ROS while stimulating the production of neurotrophic factors.