Quercetin-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) increases Nrf2 expression via miR-27a mediation to prevent memory dysfunction in diabetic rats.

Oxidative stress is one of the earliest defects involved in the development of diabetes-induced cognitive impairment. Nrf2 is the master regulator of the cellular antioxidant system can be regulated by some microRNAs. The study aimed to evaluate the effects of quercetin (QC) and quercetin-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) on Nrf2-controlled antioxidant genes through the redox-sensitive miR-27a. Expression levels of miR-27a, Nrf2, SOD1, GPX1, and CAT were measured by quantitative real-time PCR. Moreover, the oxidative stress parameters including total antioxidant capacity (TAC) and histological alterations were investigated. The expression level of miR-27a was significantly up-regulated in diabetic rats. While expression levels of Nrf2, SOD1, GPX1, and CAT were significantly down-regulated under diabetic condition. Interestingly, QCSPIONs decreased expression level of miR-27a and subsequently enhanced the expression levels of Nrf2, SOD1, and CAT to the control level. No significant difference was observed in the expression level of GPX1. Besides, QC in pure and especially conjugated form was able to normalize TAC and regenerate pathological lesions in STZ-diabetic rats. Our result demonstrates that QCSPIONs as an effective combined therapy can decrease miR-27a expression, which in turn increases the Nrf2 expression and responsive antioxidant genes, resulting in improvement of memory dysfunction in diabetic rats.