Astragaloside IV inhibits palmitate-mediated oxidative stress and fibrosis in human glomerular mesangial cells via downregulation of CD36 expression.

Abstract

The increased influx of free fatty acids (FFAs) into the kidney is a risk factor for diabetes nephropathy (DN). In the present study we investigated the effects of astragaloside IV (AS-IV) on FFA-induced lipid accumulation, oxidative stress, and activation of TGF-β1 signaling in human glomerular mesangial cells (HMCs). A DN model was induced in Sprague Dawley rats by the administration of a high-fat diet and streptozocin, and HMCs were stimulated with palmitate. Lipid accumulation and FFA uptake were detected using Oil Red O and BODIPY™ FL C16 staining, respectively. The expression levels of TGF-β1, p-Smad2/3, FN, Col4 A1, NOX4, p22phox, and CD36 were evaluated by western blotting or immunofluorescence/immunohistochemistry. The level of reactive oxygen species (ROS) was detected using 2',7'-dichlorofluorescein diacetate and dihydroethidium. Exposure to palmitate induced marked lipid accumulation in HMCs, whereas co-treatment with AS-IV significantly attenuated this phenomenon. Moreover, AS-IV suppressed palmitate-induced expression of TGF-β1, p-Smad2/3, FN, Col4 A1, NOX4, and p22phox, in addition to ROS production. Notably, AS-IV reduced the palmitate-induced expression of CD36 in HMCs and DN rats. Treatment of HMCs with the CD36 inhibitor, sulfo-N-succinimidyl oleate (SSO), significantly attenuated FFA uptake, oxidative stress, and fibrosis. Nevertheless, the combined use of SSO and AS-IV did not enhance the efficacy. AS-IV inhibited palmitate-induced HMCs oxidative stress and fibrosis via the downregulation of CD36 expression, mediating FFA uptake and lipid accumulation.