Astragaloside IV attenuates indoxyl sulfate-induced injury of renal tubular epithelial cells by inhibiting the aryl hydrocarbon receptor pathway.

Abstract

Astragalus membranaceus Fisch. ex Bunge has long been used to treat chronic kidney disease (CKD) in China. However, the mechanism of action requires further study. Indoxyl sulfate accumulation is the key cause of CKD progression. The aryl hydrocarbon receptor (AhR) plays an essential role in the renal tubular injury induced by indoxyl sulfate (IS). We explored the effects of Astragaloside IV (AS-IV), a minor component of the flowering perennial Astragalus membranaceus Fisch. ex Bunge, on AhR activity during IS-induced injury of renal tubular epithelial cells. C57BL/6 mice fed a 0.2% adenine diet (adenine+IS) and intraperitoneally injected with IS were used to study the protective effects of AS-IV, and specifically the effect on the AhR. In addition, apoptosis (annexin/PI), oxidative stress and the AhR pathway were investigated in IS-stimulated HK-2cells treated with AS-IV. The binding of AS-IV to the AhR was assessed in a molecular docking analysis. AhR knockdown using AhR siRNA allowed determination of the effects of AS-IV in IS-stimulated HK-2cells. AS-IV inhibited tubulointerstitial injury in adenine+IS mice. While AS-IV did not reduce serum IS levels, it did inhibit AhR expression in the kidney. In IS-stimulated HK-2cells, AS-IV also dramatically reduced apoptosis, decreased oxidative stress responses and inhibited the expression of the AhR pathway. The molecular docking analysis showed surface binding of AS-IV to the AhR. Following AhR knockdown in HK-2cells, IS-induced apoptosis was reduced and could not be further reduced by AS-IV. By targeting the AhR, AS-IV may alleviate IS-induced renal tubular injury, thus offering a novel therapeutic approach to the treatment of chronic renal failure.