Neuroprotection of quercetin on central neurons against chronic high glucose through enhancement of Nrf2/Glo-1 mediated by phosphorylation regulation

Meng-ya ZHANG,Xiao-li LIU,Yao-wu LIU,2

(Xuzhou Medical University,1.Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy,2.Department of Pharmacology,School of Pharmacy,Xuzhou 221004,China)

T2-15

Neuroprotection of quercetin on central neurons against chronic high glucose through enhancement of Nrf2/Glo-1 mediated by phosphorylation regulation

Meng-ya ZHANG1,Xiao-li LIU1,Yao-wu LIU1,2

(Xuzhou Medical University,1.Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy,2.Department of Pharmacology,School of Pharmacy,Xuzhou 221004,China)

OBJECTIVETo investigate the neuroprotective effects of quercetin on central neurons against chronic high glucose in central neurons,in relation to Nrf2/ARE/Glo-1 activation.METHODSSH-SY5Y cells were cultured with high glucose(HG,70 mmol·L-1),4-fold of the normal glucose(17.5 mmol· L-1).Quercetin was set three concentrations(5,10,20 μmol· L-1),with Nrf2 activator sulforaphane(SFN)as a positive group(2.5 μmol·L-1).After 72 h,cells were collected for glyoxalase 1(Glo-1)activity and GSH level were by spectrophotometry;advanced glycation end-products(AGEs)as well as nuclear Nrf2 and p-Nrf2 levels by immunofluorescence;Glo-1,γ-glutamycysteine synthase(γ-GCS),Nrf2 and p-Nrf2 protein levels by Western blotting,and Glo-1 and γ-GCS mRNA levels by real-time qPCR.RESULTSQuercetin increased the cell viability of SH-SY5Y cells,and upregulated the levels of Glo-1 activity,protein,and mRNA in SH-SY5Y cells cultured with HG,accompanied by the elevated levels of glutathione,a cofactor of Glo-1 activity,and the reduced levels of AGEs.Meanwhile,quercetin could increase p-Nrf2 and Nrf2 levels in nucleus as well as p-Nrf2 levels in cytosol of SH-SY5Y cells exposed to chronic HG,accompanied by the elevated protein expression and mRNA levels of γ-GCS,a known target gene of Nrf2/ARE signaling.Moreover,a PKC activator or a p38 MAPK inhibitor pretreatment could significantly increase the protein expression of γ-GCS in HGcondition,but an alkylating agent for sulfydryl of cysteine in Keap 1,a negative regulator of Nrf2,pretreatment only showed an increased tendency of γ-GCS protein,compared with without pretreatment;however,after pretreatment with those tool drugs,co-treatment with quercetin and HGhad similar results to those of single tool drug pretreatment followed by HGexposure.CONCLUSIONFirstly,quercetin can enhance Glo-1 function in central neurons,which is mediated by activation of Nrf2/ARE pathway,then exerts the neuroprotection against HGinduced damage;moreover,PKC and p38 MAPK pathways may be involved in Nrf2 inactivation in chronic HGcondition.

glyoxalase 1;quercetin;nuclear factor erythroid-2-related factor 2;high glucose;central neurons;protein kinases

The project supported by National Natural Science Foundation of China(81371210);Qing Lan Project of Jiangsu Province(2014);and Priority Academic Program Development of Jiangsu Higher Education Institutions

Yao-wu LIU,Tel:15996976630,E-mail：ywliu@xzhmu.edu.cn