Mas receptor deficiency exacerbates lipopolysaccharide-induced cerebral and systemic inflammation in mice

Beyond the classical actions of the renin-angiotensin system on the regulation of cardiovascular homeostasis, several studies have shown its involvement in acute and chronic inflammation. The G protein-coupled receptor Mas is a functional binding site for the angiotensin-(1-7); however, its role in the immune system has not been fully elucidated. In this study, we evaluated the effect of genetic deletion of Mas receptor in lipopolysaccharide (LPS)-induced systemic and cerebral inflammation in mice. Inflammatory response was triggered in Mas deficient (Mas(-/-)) and C57BL/6 wild-type (WT) mice (8-12 weeks-old) by intraperitoneal injection of LPS (5mg/kg). Mas(-/-) mice presented more intense hypothermia compared to WT mice 24h after LPS injection. Systemically, the bone marrow of Mas(-/-) mice contained a lower number of neutrophils and monocytes 3h and 24h after LPS injection, respectively. The plasma levels of inflammatory mediators KC, MCP-1 and IL-10 were higher in Mas(-/-) mice 24h after LPS injection in comparison to WT. In the brain, Mas(-/-) animals had a significant increase in the number of adherent leukocytes to the brain microvasculature compared to WT mice, as well as, increased number of monocytes and neutrophils recruited to the pia-mater. The elevated number of adherent leukocytes on brain microvasculature in Mas(-/-) mice was associated with increased expression of CD11b - the alpha-subunit of the Mac-1 integrin - in bone marrow neutrophils 3h after LPS injection, and with increased brain levels of chemoattractants KC, MIP-2 and MCP-1, 24h later. In conclusion, we demonstrated that Mas receptor deficiency results in exacerbated inflammation in LPS-challenged mice, which suggest a potential role for the Mas receptor as a regulator of systemic and brain inflammatory response induced by LPS.