β-Amyrin, the cannabinoid receptors agonist, abrogates mice brain microglial cells inflammationinduced by lipopolysaccharide/interferon-γ and regulates Mφ1/Mφ2 balances

Background: Inflammation is a primary response to infection that can pathologically lead to various diseases including neurodegenerative diseases. The purpose of this study was to evaluate the effect of beta-Amyrin, a naturally occurring pentacyclic triterpenoid compound, on inflammation induced by lipopolysaccharide (LPS) and interferone-gamma (IFN-gamma) in rat microglial cells. Materials and methods: Cytotoxicity of beta-Amyrin (3-100) mu M on microglial cells was evaluated using the MTT assay. Also, the protective effect of various beta-Amyrin (2-16 mu M) concentrations with LPS/IFN-gamma-induced mice microglial cells was studied. The concentrations of TNF-alpha (Tumor Necrosis Factor-alpha), IL-1 beta (Interleukin-1 beta), IL-6 (Interleukin-6) and PGE-2 (Prostaglandin E2) were evaluated using ELISA. Gene expressions of TNF-alpha, IL-1 beta, IL-6, COX-2 (Cyclooxygenase-2), iNOS and arginase-1 were also evaluated using the Real-Time PCR method. Nitrite oxide and urea were measured using biochemical methods. Results: The studied concentrations of beta-Amyrin had no significant effects on the viability of microglial cells. Interestingly, beta-Amyrin concentration dependently and significantly increased the reduced cell proliferation concerning to LPS/IFN-gamma exposure (p < 0.001). The concentrations and expression levels of pro-inflammatory factors including TNF-alpha, IL-1 beta, IL-6, PGE-2, COX-2 were significantly reduced after beta-Amyrin treatment in LPS/ IFN-gamma-induced microglial cells (p < 0.05-0.001). beta-Amyrin also decreased the levels of nitric oxide, increased urea and down regulated the expression of nitric oxide synthesis while arginase-1 expression was enhanced (p < 0.001). The ratio of NO/urea and iNOS/Arg1 were also markedly increased in comparison to the LPS/IFNg group (p < 0.001). Conclusion: beta-Amyrin reduces inflammation in microglial cells and can be used as a potential anti-inflammatory agent in central nervous system neurodegenerative diseases such as Alzheimer and multiple sclerosis, by affecting the inflammatory cytokine and differentiation of microglia as resident CNS macrophages.