Astragaloside IV improves high glucose-induced podocyte adhesion dysfunction via alpha3beta1 integrin upregulation and integrin-linked kinase inhibition.

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 12h in media containing 30 mM glucose (HG) with 10, 50 and 100 microg/ml of AS-IV. The cells were also exposed to HG media with 100 microg/ml of AS-IV for 3, 6, 12 and 24h. 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 alpha(3)beta(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 microg/ml of AS-IV and from 6h of incubation of AS-IV with 100 microg/ml. This was accompanied by significant increases in alpha(3)beta(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 alpha(3)beta(1) integrin upregulation and ILK inhibition.