Downregulation of TREM2/NF-кB signaling may damage the blood-brain barrier and aggravate neuronal apoptosis in experimental rats with surgically injured brain.

Surgical brain injury (SBI) is unavoidable in neurosurgery, and could aggravate secondary brain injury. Post-brain injury, multiple inflammatory factors are released, resulting in neuroinflammation and cell apoptosis, with subsequent brain edema and nerve function injury. TREM2, an immune protein mainly expressed in microglia, is an important link for nerve cells to participate in the inflammatory response. TREM2 and nuclear factor кB (NF-кB) are indeed closely associated with the release of inflammatory cytokines following brain injury. This work aimed to determine the inflammatory function of TREM2 in SBI, and to investigate whether TREM2 regulates interleukin-1 beta (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) release through the NF-кB p65 signaling pathway. We established a rat model of SBI, and performed Western blotting (WB), immunofluorescence (IF) and enzyme-linked immunosorbent assay (ELISA) for further analysis. Next, brain edema and neurological score analyses were performed. Finally, whether TREM2 regulating NF-кB p65 signaling affects blood-brain barrier (BBB) permeability and nerve cell apoptosis was examined. We found that post-SBI, TREM2 was upregulated, and inflammation and brain injury were aggravated. After TREM2 downregulation, NF-кB p65 production, inflammation and brain injury were enhanced, suggesting that TREM2 may play a protective role by inhibiting NF-кB p65 production after SBI. Overall, these findings suggest that TREM2 in SBI may have protective effects on postoperative nerve and BBB damage, possibly in part via the NF-κB p65 pathway.