Quercetin protects rat dorsal root ganglion neurons against high glucose-induced injury in vitro through Nrf-2/HO-1 activation and NF-κB inhibition

Aim： To examine the effects of quercetin, a natural antioxidant, on high glucose （HG）-induced apoptosis of cultured dorsal root ganglion （DRG） neurons of rats. Methods： DRG neurons exposed to HG （45 mmol/L） for 24 h were employed as an in vitro model of diabetic neuropathy. Cell viability, reactive oxygen species （ROS） level and apoptosis were determined. The expression of NF-кB, IкBα, phosphorylated IкBα and Nrf2 was examined using RT PCR and Western blot assay. The expression of hemeoxygenase-1 （HO-1）, IL-6, TNF-α, iNOS, COX-2, and caspase-3 were also examined. Results： HG treatment markedly increased DRG neuron apoptosis via increasing intracellular ROS level and activating the NF-κB signaling pathway. Co-treatment with quercetin （2.5, 5, and 10 mmol/L） dose-dependently decreased HG-induced caspase-3 activation and apoptosis. Quercetin could directly scavenge ROS and significantly increased the expression of Nrf-2 and HO-1 in DRG neurons. Quercetin also dose-dependently inhibited the NF-κB signaling pathway and suppressed the expression of iNOS, COX-2, and proinflammatory cytokines IL-6 and TNF-α. Conclusion： Quercetin protects rat DRG neurons against HG-induced injury in vitro through Nrf-2/HO-1 activation and NF-κB inhibition, thus may be beneficial for the treatment of diabetic neuropathy.