CAPE-pNO(2) ameliorated diabetic nephropathy through regulating the Akt/NF-κB/ iNOS pathway in STZ-induced diabetic mice

Diabetic nephropathy (DN) is one of the most severe complications of diabetes mellitus. This study aimed to determine the effects and potential mechanism of caffeic acid para-nitro phenethyl ester (CAPE-pNO(2)), a derivative of caffeic acid phenethyl ester (CAPE), on DN; In vivo, intraperitoneal injections of streptozotocin (STZ) were used to induce diabetes in mice; then, the mice were intraperitoneally injected daily with CAPE or CAPE-pNO(2) for 8 weeks. The mice were sacrificed, and blood samples and kidney tissues were collected to measure biological indexes. The results showed that CAPE and CAPE-pNO(2) could lower serum creatinine, blood urea nitrogen, 24-h albumin excretion, malondialdehyde and myeloperoxidase levels and increase superoxide dismutase activity in diabetic mice. According to HE, PAS and Masson staining, these two compounds ameliorated structural changes and fibrosis in the kidneys. In addition, the immunohistochemical and western blot results showed that CAPE and CAPE-pNO(2) inhibited inflammation through the Akt/NF-κB pathway and prevented renal fibrosis through the TGF-β/Smad pathway. In vitro, CAPE and CAPE-pNO(2) inhibited glomerular mesangial cell (GMC) proliferation, arrested cell cycle progression and suppressed ROS generation. These compounds also inhibited ECM accumulation via regulating the TGF-β1, which was a similar effect to that of the NF-κB inhibitor PDTC. More importantly, CAPE and CAPE-pNO(2) could up-regulate nitric oxide synthase expression in STZ-induced diabetic mice and HG-induced GMCs. CAPE-pNO(2) had stronger effects than CAPE both in vivo and in vitro. These data suggest that CAPE-pNO(2) ameliorated DN by suppressing oxidative stress, inflammation, and fibrosis via the Akt/NF-κB/ iNOS pathway.