Effects And Mechanisms Of Quercetin On Neuroinflammation Induced By A Kind Of NRTI Drug AZT

Nucleoside reverse transcriptase inhibitors(NRTI)are important antiviral drugs to inhibite human immunodeficiency virus(HIV)and play a key role in highly active antiretroviral therapy(HAART).AZT is widely used in HAART which is recommended as the first choice for antiretroviral drugs.Although HIV can be effectively inhibited,long-term HAART can lead to HIV-related neurological disorders(HAND).Neuroinflammation is one of the adverse effects of HAART.Therefore,it is urgent to find a new treatment strategy as an adjunctive therapy for HAART to reduce neuroinflammation.It has been reported that flavonoids quercetin has good anti-inflammatory effect.However,the effect and mechanism of quercetin on NRTI-induced neuroinflammation has not been reported.Therefore,this study was aimed to explore some related question in this aspective.First,a series of experiments in vitro were carried out as follows.The expression of inflammatory cytokines in BV2 cells treated with different concentrations of AZT(15,25,50 μM)or AZT+ quercetin for 24 hours was detected by Western blotting.The results showed that AZT drugs significantly increased inflammatory cytokines(IL-1β,IL-6)release in BV2 cell.Compared with AZT group,the inhibition rates of different concentrations of quercetin(10,20,30 μM)on AZT-induced IL-1β were 35.02 ± 3.61%,16.59 ± 5.58% and 20.78 ± 6.15% and the inhibition rates of different concentrations of quercetin(10,20,30 μM)on IL-6 were 29.80±1.49%,66.11±5.65% and 68.63±14.27%,respectively.Therefore,quercetin can effectively reduce the release of inflammatory cytokines induced by AZT.The results in vitro studies showed that quercetin exerted a significant inhibition on the release of inflammatory mediators induced by NRTI.Next,a series of experiments in vivo were also performed as follows.Mice were treated with quercetin(100 mg / kg / day)and AZT(100 mg/kg/day).The central nervous tissues(CNS: cortex,hippocampus,spinal cord)were collected after 8 days.The expression of inflammatory cytokines(IL-1β,IL-6)in the central nervous system(CNS)was detected by Western blotting.The results showed that the inhibition rates of quercetin on AZT induced IL-1β in central nervous system(CNS: cortex,hippocampus,spinal cord)was 35.02 ± 3.61%,16.59 ±5.58%,20.78 ± 6.15%,respectively and the inhibition rates of quercetin on IL-6 were 39.43±14.21%,20.87±7.62%,17.67±1.17%,respectively.Therefore,quercetin can significantly reduce the inflammatory cytokine up-regulation induced by AZT in CNS of mice.The results showed that quercetin could effectively inhibit the neurotoxicity induced by NRTI in CNS.Activation of glial cell is the mark of neuroinflammation.GFAP and CD11 b were used to label astrocytes and microglia,respectively.Western blotting and immunohistochemical staining were used to investigate the effect of quercetin on neuroinflammation induced by NRTI.The result showed that quercetin could inhibit the activation of astrocyte induced by AZT in CNS and the activation of microglia in the spinal cord and hippocampus.These results suggested that quercetin alleviated NRTI-induced neuroinflammation mainly by inhibiting activation of astrocyte and microglia,which was further demonstrated that quercetin exerted an inhibitory effect on NRTI-induced neuroinflammation.These results suggested that quercetin inhibited NRTI-induced neuroinflammation,but its mechanism is still unclear.Wnt5 a signaling pathway is associated with many inflammatory diseases.Recent studies have found that Wnt5 a signaling pathway is involved in regulation of neuroinflammation,so we speculated the inhibitory effect of quercetin on neuroinflammation is associated with Wnt5 a signaling pathway.Therefore,we performed experiments to detect Wnt5 a expression by Western blotting in vivo and in vitro.The results showed that Wnt5 a was significantly up-regulated in AZT-treated group,while quercetin could inhibit the up-regulation of Wnt5 a,which indicated that Wnt5 a maybe involve in the regulation of NRTI-induced neuroinflammation by quercetin.In conclusion,quercetin can inhibit the activation of glial cells and reduce the neuroinflammation induced by NRTI.The mechanism underlying the regulation of NRTI-induced inflammatory cytokines by quercetin is via Wnt5 a signaling pathway.