TREM2 inhibits inflammatory responses in mouse microglia by suppressing the PI3K/NF-κB signaling

This study aimed to investigate the effects of triggering receptor expressed on myeloid cell-2 (TREM2) on the production of pro-inflammatory mediators and cytokines induced by lipopolysaccharide (LPS) in BV2 microglia. TREM2 expression or TREM2-specific siRNA were used to induce TREM2 overexpression or silencing. The BV2 cells were pre-treated with the PI3 K inhibitor of LY294002 for 1 h and stimulated with LPS for 24 h. Then, the cell viability, apoptosis, phagocytosis, nitric oxide (NO), lactate dehydrogenase (LDH), and cytokine production, as well as the activation of AKT and NF-kB were determined, respectively. We found LPS stimulation significantly reduced BV2 cell viability, enhanced BV2 cell phagocytosis and apoptosis compared to the control groups. In addition, LPS stimulation significantly increased the production of NO, LDH, TNF-alpha, IL-1 beta, and the activation of AKT and NF-kB, while decreased the levels of IL-10 and TGF-beta 1. However, these pro-inflammatory effects were significantly attenuated by TREM2 overexpression or pre-treatment with LY294002, while enhanced by TREM2 silencing. Thus, we concluded that TREM2 inhibited neuroinflammation by down-regulating PI3 K/AKT and NF-kB signaling in BV2 microglia. Above all, therapeutic enhanced TREM2 expression may be a new strategy for intervention of neuroinflammatory diseases.