Astragaloside IV improves high glucose-induced podocyte adhesion dysfunction via α 3β 1 integrin upregulation and integrin-linked kinase inhibition

Abstract

Impaired podocyte adhesion to glomerular basement membrane (GBM) may contribute to podocyte detachment from GBM, which represents a novel early mechanism leading to diabetic nephropathy (DN). Here, we examined the effects of Astragaloside IV (AS-IV), a saponin purified from Astragalus membranaceus (Fisch) Bge, on high glucose-induced cell adhesion dysfunction in cultured mouse podocytes. Cells were seeded into 96-well plates coated with basement membrane protein complex (BMC). The cells were incubated for 12 h in media containing 30 mM glucose (HG) with 10, 50 and 100 μg/ml of AS-IV. The cells were also exposed to HG media with 100 μg/ml of AS-IV for 3, 6, 12 and 24 h. Cell adhesion assays were performed by fluorescence and centrifugation methods, respectively. Levels of mRNA were determined by quantitative reverse transcriptase real-time PCR and protein expression was analyzed by immunoblotting. HG strongly inhibited adhesion of podocytes to BMC, accompanied by reduction in α 3β 1 integrin mRNA and protein expression, as well as increase in integrin-linked kinase (ILK) activity and expression. When podocytes under HG stimulation were treated with AS-IV, a dose- and time-dependent increase in cell–matrix adhesion was observed, which was significant from 10 μg/ml of AS-IV and from 6 h of incubation of AS-IV with 100 μg/ml. This was accompanied by significant increases in α 3β 1 integrin mRNA and protein expression, as well as inhibition of ILK activation and overexpression. These results suggest that AS-IV improve HG-induced podocyte adhesion dysfunction, which is partly attributed to α 3β 1 integrin upregulation and ILK inhibition.