Neuroprotective effects of quercetin in diabetic rat retina

Abstract

Diabetic retinopathy (DR) is a severe complication of diabetes and the leading cause of blindness among working adults worldwide. DR is being widely recognized as a neurodegenerative disease of the retina, since, retinal neurons are damaged soon after diabetes onset. Diabetes-induced oxidative stress is considered as central factor that dysregulates neurotrophic factors and activates apoptosis, thereby damages neurons in the diabetic retina. Flavonoids being a powerful antioxidant have been considered to protect neurons in diabetic retina. The purpose of this study was to analyze the beneficial effects of flavonoid, quercetin to protect neurons in the diabetic rat retina. We quantitated the expression levels of BDNF, NGF, TrkB, synaptophysin, Akt, Bcl-2, cytochrome c and caspase-3 using Western blotting techniques in the diabetic retina with and without quercetin treatments and compared with non-diabetic rats. In addition, we employed ELISA techniques to determine the level of BDNF. Caspase-3 activity and the level of glutathione were analyzed by biochemical methods. Our results indicate that quercetin treatment to diabetic rats caused a significant increase in the level of neurotrophic factors and inhibited the level of cytochrome c and caspase-3 activity in the diabetic retina. Furthermore, the level of an anti-apoptotic protein Bcl-2 was augmented in quercetin treated diabetic retina. Thus, quercetin, may protect the neuronal damage in diabetic retina by ameliorating the levels of neurotrophic factors and also by inhibiting the apoptosis of neurons. Therefore, this study suggests that quercetin can be a suitable therapeutic agent to prevent neurodegeneration in diabetic retinopathy.

Caffeic Acid Alkyl Amide Derivatives Ameliorate Oxidative Stress and Modulate ERK1/2 and AKT Signaling Pathways in a Rat Model of Diabetic Retinopathy

“…Similarly, some other studies have demonstrated obvious neurodegenerative histological changes of retinal tissue in the early stages of diabetes, and the underlying neuroprotective impacts of natural phenolic compounds have been reported to be correlated with activation of PI3 K/AKT signaling pathway …”

“…Overall, the reduction of AKT activation has an important role in the retinal neurodegeneration . Treatment with natural polyphenolic compounds has been shown to exert a significant neuroprotection possibly through enhancement of p‐AKT levels in animal model of diabetic retinopathy, and neuropathy …”

Protective effects of quercetin in a rodent model of anterior ischemic optic neuropathy (rAION)

“…Furthermore, Qcn preserved the visual function, prevented apoptosis of RGC, decreased the macrophage/microglial infiltration in the ONs, and impeded the secondary RGC death. Qcn was administered by intraperitoneal, oral, or intravitreal injection on the retina as described previously [17,22,23]. However, based on the pharmacodynamic maintenance and prolonged exposure of Qcn on the retina, we selected the intravitreal injection as the mode of Qcn administration.…”

Coupling Ultrasound with Heat-Reflux to Improve the Extraction of Quercetin, Kaempferol, Ginkgetin and Sciadopitysin from Mairei Yew Leaves

“…The chemical structural formulas of QU, KA, GI and SC are shown in Figure 1. These four flavonoids have many pharmacological activities, including anti-inflammatory, anti-tumor, anti-influenza virus, anti-platelet aggregation, cardiovascular protection and blood glucose regulation, improving depression associated with epilepsy and immunosuppressive activity [13][14][15][16][17][18][19][20][21][22]. The traditional method for extraction of flavonoids is mainly heating reflux extraction (HRE).…”