Study on neuronal protection of Gualou Guizhi decoction via inhibiting M1 microglia polarization
Objective To explore the molecular mechanism of Gualou Guizhi decoction which regulates the interferon regulator factor 5(IRF5)signaling pathway to inhibit M1 type microglia activation and reduce the inflammatory response to protect damaged nerve cells.Methods Microglia(BV2)cells were randomly divided into BV2-control,BV2-model,BV2-experimental-L,-M,-H groups.The BV2-control group was given routine culture;the BV2-model group used 100 ng·mL-1 lipopolysaccharide(LPS)to stimulate BV2 which establish an inflammatory model;the BV2-experimental-L,-M,-H groups were cultured in 50,100,200 μg·mL-1 GLGZD and 100 ng·mL-1 LPS.The HT22 cells were divided into the HT-22-blank group,HT-22-model group,HT-22-control group and HT-22 experimental group.HT-22-blank group were conventional culture;HT-22-model group were oxygen glucose deprivation was performed for 2 h,then the complete medium was replaced for 24 h;HT-22-control group were after 2 h of oxygen glucose deprivation,the 100 ng·mL-1 LPS conditioned medium was replaced and incubated for 24 h;HT-22-experimental group were after 2 h of oxygen glucose deprivation,the 200 μg·mL-1 GLGZD conditioned medium was added for 24 h.Interleukin-12(IL-12)and IL-23 were detected by enzyme-linked immunosorbent assay(ELISA);the protein of IRF5,cluster differentiation 16(CD1 6)and MHC class Ⅱ(MHC-Ⅱ)was detected by Western blot;the expression of the synaptic marker protein class Ⅲ β-Tubulin(Tuj-1)was observed by immunofluorescence.Results IL-12 contents in the BV2-control,BV2-model and BV2-experimental-L,-M,-H groups were(2.62±1.02),(10.67±3.22),(6.87±1.61),(3.96±1.22)and(3.36±1.04)pg·mL-1;IL-23 contents were(20.40±2.04),(77.08±3.25),(76.28±3.75),(63.96±4.94)and(54.48±3.34)pg·mL-1;relative expression levels of IRF5 protein were 0.80±0.41,2.22±0.69,1.11±0.11,0.92±0.39 and 0.65±0.29;relative expression levels of CD16 protein were 0.69±0.45,1.91±0.52,1.42±0.22,1.04±0.15 and 0.67±0.30;relative expression levels of MHC-Ⅱ protein were 0.89±0.27,1.96±0.19,1.34±0.38,1.15±0.19 and 0.68±0.24.BV2-experimental-M,-H groups were compared with the BV2-model group,the differences were statistically significant(all P<0.05).The Tuj-1 protein expression levels were 28.85±6.69,14.44±1.98,7.75±1.12 and 20.05±3.54,determined in the HT22-blank,HT22-model,HT22-control and HT22-experimental groups.The HT22-experimental group was compared with the HT22-control group,the difference was statistically significant(P<0.05).Conclusion GLGZD may reduces the activation of microglia M1 phenotype through IRF5 signaling pathway,and then inhibits inflammatory response to protect damaged nerve cells.