Role of Militarine in PM2.5-Induced BV-2 Cell Damage

A growing number of studies have shown that air fine particulate matter (PM 2.5 ) pollution is closely associated with neuroinflammation in humans. Militarine, a glucosyloxybenzyl 2-isobutylmalate compound isolated from Bletilla striata , has been found to exert significant neuroprotective effects. However, the anti-inflammatory, antioxidant and antiapoptotic effects of militarine on PM 2.5 -stimulated BV-2 microglial cells have not been reported. This study aimed to investigate the protective effects of militarine against PM 2.5 -induced cytotoxicity and its mechanism in BV-2 microglial cells. Our results revealed that pretreatment with 0.31–1.25 μg/mL militarine reversed the morphological changes caused by PM 2.5 and decreased proinflammatory cytokine generation and gene expression in PM 2.5 -treated BV-2 cells. In particular, tumor necrosis factor-α and interleukin-6 expression was inhibited in a dose-dependent manner. Notably, militarine markedly inhibited the upregulation of Toll-like receptor 4, Toll-like receptor 2, and cyclo-oxygenase-2 expression at both the mRNA and protein levels and reduced NF-κB pathway-associated protein expression. Immunofluorescence analysis showed that militarine suppressed NF‐κB activity through inhibiting p65 nuclear translocation. Our data suggested that militarine alleviated neuroinflammation in BV-2 microglial cells, possibly by inhibiting the expression of neuroinflammatory cytokines through the TLR/NF-κB signaling pathway. Additionally, militarine significantly reduced PM 2.5 -mediated reactive oxygen species (ROS) generation and cell apoptosis and restored the mitochondrial membrane potential (MMP; ΔΨm). Collectively, these findings demonstrate that militarine played a protective role against PM 2.5 ‐induced damage in BV-2 cells by exerting anti-inflammatory, antioxidant, and antiapoptotic effects.