[The mechanism underlying Gingko biloba extract alleviating acrylamide-induced inflammatory response of mouse...

Objective To investigate the effect of Gingko biloba extract (GBE) on microglial inflammatory response due to long-term low-dose arylamide (ACR) exposure and its underlying mechanism. Methods Primary microglial cells were extracted from neonatal mouse brain cortex. Using CCK-8 assay to detect cell proliferation and immunofluorescence cytochemistry to detect cleaved-caspase 3, the optimal concentration of ACR (0.1 mmol/L) treatment was determined in order to minimize the apoptotic toxicity of ACR (0.01~10 mmol/L, for 48 hours). GBE (100 mg/L) pre-treatment was given 2 hours before ACR treatment. After 48 hours of ACR treatment, immunocytochemistry was used to detect the expression of ionized calcium-binding adaptor molecule-1 (IBA-1) and nuclear factor κB (NF-κB) for observing the morphological alteration of microglia and NF-κB nuclear translocation, respectively. The concentrations of nitric oxide (NO) and three inflammatory cytokines (IL-6, IL-1β, TNF-α) in the culture media were examined with Griess reaction and ELISA kits. Real-time PCR was applied to measure mRNA expression levels of IBA-1 and other inflammatory cytokine genes. Recruitments of p65, Nurr1 and CoREST onto the promoter regions of those inflammatory cytokine genes were examined by chromatin immunoprecipitation. Protein interaction between Nurr1 and CoREST was determined by protein immunoprecipitation. Results Long-term low-dose treatment of ACR transformed resting microglia towards activated morpholgy, activated the expression of inflammatory cytokine genes through NF-κB pathway, and resulted in extracellular release of those cytokines. Pre-treatment of GBE greatly prevented microglial activation and its adverse consequences. GBE decreased the recruitment of p65 on the promoter regions of inflammatory cytokine genes, while increased the recruitment of Nurr1-CoREST complex. Conclusion GBE can alleviate microglial inflammatory response induced by long-term low-dose ACR exposure by transrepression of inflammatory cytokine genes, which involves the expelling of p65 and the recruitment of Nurr1-CoREST complex onto NF-κB binding site in their promoters.