LCN2 inhibits lipopolysaccharide-mediated M1 polarization of mouse BV2 microglia through P38 MAPK-PGC1α-PPARγ pathway
AIM:To investigate the role of lipocalin 2(LCN2)in lipopolysaccharide(LPS)-induced microg-lia polarization in mice and to elucidate the potential mechanisms involving the P38 mitogen-activated protein kinase(MAPK)pathway.METHODS:BV2 microglia were treated with LPS to induce M1 polarization,and short hairpin RNA(shRNA)and exogenous LCN2 protein were used to silence or overexpress LCN2 in BV2 cells.BV2 microglia were cul-tured in vitro and divided into the following groups:control,LPS(100 µg/L),LPS+sh-NC,LPS+sh-LCN2,and LPS+LCN2(1 mg/L).Flow cytometry was used to detect the number of CD16/32+and CD206+T cells.Western blot and RT-qP-CR were employed to measure the protein and mRNA levels of P38 MAPK,PGC-1α,and PPARγ to assess the effects of LCN2 on LPS-induced BV2 cell polarization and the P38 MAPK pathway.Additionally,the P38 MAPK pathway inhibitor SB203580 was used to treat LPS or LCN2-induced cells.The cells were categorized into control,LPS,LPS+LCN2(1 mg/L),LPS+SB203580(50 nmol/L),and LPS+LCN2+SB203580 groups.ELISA was used to measure inflammatory factor levels,Western blot was used to detect M1/M2 marker proteins,and Western blot and RT-qPCR were used to analyze pro-tein and mRNA expressions in the P38 MAPK pathway.RESULTS:LPS significantly increased LCN2 expression in BV2 cells(P＜0.05)and induced M1 polarization(P＜0.01).Silencing LCN2 reduced LCN2 expression and M2 polarization in LPS-induced BV2 cells(P＜0.01),increased M1 polarization(P＜0.01),and inhibited activation of the P38 MAPK-PGC-1α-PPARγ pathway(P＜0.05).Conversely,exogenous addition of LCN2 promoted M2 polarization in LPS-induced BV2 cells and activated the P38 MAPK pathway(P＜0.05).The use of a P38 MAPK pathway inhibitor further confirmed that LCN2 modulates LPS-induced microglia polarization through the P38 MAPK pathway.CONCLUSION:LCN2 inhibits LPS-mediated M1 polarization of BV2 microglia by activating the P38 MAPK pathway,thereby playing a protective role in neuroinflammatory responses.
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