Inhibitor of growth 2 regulates the high glucose-induced cell cycle arrest and epithelial-to-mesenchymal transition in renal proximal tubular cells

The epithelial-to-mesenchymal transition (EMT)-based tubulointerstitial fibrosis is the major pathological feature of diabetic kidney disease (DKD). While several studies have linked cell cycle dysregulation to various kidney injuries in recent years, its involvement in fibrosis of DKD is far from being clarified. ING2 (inhibitor of growth 2) is the second member of the inhibitor of growth family and participates in the regulation of many cellular processes. So far the role of ING2 in DKD remains largely unknown. In the present study, ING2 expression was detected by western blotting and immunofluorescent staining both in vitro high glucose-stimulated human proximal tubular epithelial cells (HK-2) and in vivo streptozotocin-induced diabetic mice. Cell proliferation was analyzed by CCK-8 and EdU assay, and cell cycle arrest was measured by flow cytometry. Quantitative polymerase chain reaction (qPCR) and western blotting were used to detect the EMT markers, and the p53 signaling activation was evaluated by chromatin immunoprecipitation (ChIP), qPCR, and western blotting. We found that the proliferation of the cells was reduced upon high glucose stimulation, which was accompanied by cell cycle arrest. The expression of ING2 was increased in hyperglycemia conditions both in vivo and in vitro. ING2 suppression ameliorated the reduced proliferation and cell cycle arrest induced by high glucose in HK-2 cells. Moreover, ING2 knockdown suppressed p21 expression by reducing p53 acetylation and finally alleviated the EMT progress in the high glucose-stimulated HK-2 cells. Our study demonstrated that cell cycle regulation is bound up with the kidney fibrosis in DKD, suggesting a novel function of ING2 as a potential therapeutic strategy targeting cell cycle arrest for DKD.