STUDY ON THE MECHANISM OF TREM2/NF-ΚB INFLAMMATORY SIGNAL PATHWAY INVOLVED IN SPINAL CORD INJURY

Feng Mao, Dehua Zhang, Shaobo Wang, Yi Liao^*

Department of Orthopaedics, Xin Jiang Karamay Central Hospital, Karamay, PR China

Methods: Microglia cells were cultured in vitro and treated with 0, 1, 5, and 10 μg/ml of LPS to construct a spinal-cord injury cell model. The expression of TREM2 protein in LPS-treated cells was detected using western-blot assay. TREM2 interference and over-expression lentivirus were constructed and transfected into microglia. The expression of TREM2 mRNA in interfering and over-expressed cells was detected by real-time quantitative PCR and western-blot assay. The inhibitory effect of siTREM2 on the activation of inflammatory cytokines induced by LPS was analysed. The cells were divided into a control group, LPS group, LPS + NC group, and LPS + siTREM2 group. The expression of TREM2, p-NF-κB, IL-6, and TNF-α protein in each group was detected by the western-blot method. The effect of NF-κB inhibitor on the inflammatory factors induced by over-expression of TREM2 was analysed, and the level of inflammatory factors in the cells with TREM2 overexpression – treated with NF-κB inhibitor – was detected by ELISA.

Results: After microglia cells were treated with different concentrations of LPS for 24 h, the content of TREM2 protein increased significantly as the concentration of LBS increased. In this study, the spinal-cord injury model was constructed using 5 µg/ml LPS-treated cells. The expression of TREM2 mRNA and protein levels decreased significantly after microglia cells were infected with siTREM2 lentivirus. The expression level of TREM2 mRNA and protein increased markedly after microglia cells were infected with TREM2 over-expressed lentivirus. Compared with the control group, LPS could significantly promote the expression of TREM2, p-NF-κB, IL-6, and TNF-α, and the difference was statistically significant (P<0.05). Down-regulation of TREM2 could significantly inhibit the expression of p-NF-κB, IL-6, and TNF-α induced by LPS. It was found that treatment with NF-κB inhibitor PTDC can significantly inhibit the content of IL-6 and TNF-α in cells infected with TREM2 over-expressed lentivirus.

Conclusion: The level of TREM2, IL-6, and TNF-α increased in microglia cells induced by LPS. Down-regulation of TREM2 could significantly inhibit the release of inflammatory factors from microglia, while NF-κB inhibitor could significantly inhibit the production of inflammatory factors induced by TREM2 over-expression. The TREM2/NF-κB inflammatory signalling pathway was very important in the pathological process of spinal-cord injury.