The antioxidant peptide SS31 prevents oxidative stress, downregulates CD36 and improves renal function in diabetic nephropathy.

Background: Oxidative stress plays an independent role in the pathogenesis of diabetic nephropathy (DN). CD36, a class B scavenger receptor, mediates reactive oxygen species (ROS) production in DN. SS31 is a mitochondria-targeted antioxidant peptide that can scavenge mitochondrial ROS. The antioxidative effects of SS31 on DN and the interaction between SS31 and CD36 remain poorly understood. Herein, we examined the effects of SS31 and investigated whether SS31 treatment attenuates CD36 expression in db/db diabetic mice and high glucose (HG)-induced HK-2 cells. Methods: Eight-week-old db/m mice and db/db mice were administered with SS31 (3 mg/kg/day) for 12 weeks by intraperitoneal injection. For the in vitro studies, HG-cultured HK-2 cells were used. Biochemical parameters, body weight and histological changes in the mice were measured. The levels of oxidative stress, activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, Mn superoxide dismutase (MnSOD) and catalase (CAT), and the expression of CD36, nuclear factor-κB (NF-κB) p65 in mice and HK-2 cells were also analyzed. Results: The results showed that SS31 alleviated proteinuria, glomerular hypertrophy and tubular injury, and affected creatinine level in db/db mice. SS31 suppressed the levels of oxidative stress, NADPH oxidase subunits, CD36 and NF-κB p65, and activated MnSOD and CAT in db/db mice and HG-induced HK-2 cells. Conclusion: Taken together, these data demonstrated a renoprotective role of SS31 in DN by suppression of enhanced oxidative stress and CD36 expression.