Activation of the Nrf2-ARE Pathway Attenuates Hyperglycemia-Mediated Injuries in Mouse Podocytes

Abstract

Background: Damage to podocytes caused by excessive reactive oxygen species (ROS) contributes to onset and progression of diabetic kidney disease (DKD). Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a redox-sensing transcription factor that can induce the expression of antioxidant enzymes. We explored whether activation of Nrf2 pathway attenuated hyperglycemia-induced injuries in mouse podocytes. Methods: Tert-Butylhydroquinone (tBHQ) and small interfering RNAs (siRNAs) were used to regulate Nrf2 expression. Apoptosis and intracellular superoxide anion production were measured by flow cytometry. The activity of the Nrf2 antioxidant pathway was measured by an antioxidant response element (ARE)-driven luciferase reporter gene assay, and Nrf2 expression was assessed by real-time PCR and western blot analyses. Results: Podocytes incubated with high-glucose (HG) medium had higher intracellular superoxide anion and hydrogen peroxide production, higher apoptosis rate, higher bovine serum albumin (BSA) permeability and lower synaptopodin expression compared with podocytes exposed normal glucose (NG) (p<0.05). tBHQ increased the activity of the Nrf2 antioxidant pathway and enhanced nuclear Nrf2 expression, reduced intracellular superoxide anion and hydrogen peroxide production, apoptosis rate and BSA permeability, and restored synaptopodin expression in podocytes exposed to HG (p<O.05). Podocytes with Nrf2 siRNAs showed higher intracellular superoxide anion and hydrogen peroxide production, apoptosis and BSA permeability as well as lower synaptopodin expression compared with podocytes exposed to HG (p<0.05). Conclusions: Our findings suggest that protection against activation of the Nrf2-ARE pathway in podocytes exposed to hyperglycemia. Thus, regulation of the Nrf2-ARE pathway could be a therapeutic option to combat oxidative stress and inhibit the development of DKD.