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 β-Amyrin, a naturally occurring pentacyclic triterpenoid compound, on inflammation induced by lipopolysaccharide (LPS) and interferone-γ (IFN-γ) in rat microglial cells.

Cytotoxicity of β-Amyrin (3–100) μM on microglial cells was evaluated using the MTT assay. Also, the protective effect of various β-Amyrin (2–16 μM) concentrations with LPS/IFN-γ-induced mice microglial cells was studied. The concentrations of TNF-α (Tumor Necrosis Factor-α), IL-1β (Interleukin-1β), IL-6 (Interleukin-6) and PGE-2 (Prostaglandin E2) were evaluated using ELISA. Gene expressions of TNF-α, IL-1β, 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.

The studied concentrations ​​of β-Amyrin had no significant effects on the viability of microglial cells. Interestingly, β-Amyrin concentration dependently and significantly increased the reduced cell proliferation concerning to LPS/IFN-γ exposure (p < 0.001). The concentrations and expression levels of pro-inflammatory factors including TNF-α, IL-1β, IL-6, PGE-2, COX-2 were significantly reduced after β-Amyrin treatment in LPS/IFN-γ-induced microglial cells (p < 0.05–0.001). β-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/IFN-g group (p < 0.001).

β-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.