LY333531, a PKCβ inhibitor, attenuates glomerular endothelial cell apoptosis in the early stage of mouse diabetic nephropathy via down-regulating swiprosin-1

Glomerular endothelial cell （GEC） injury plays an important role in the early stage of diabetic nephropathy （DN）. Previous studies show that a PKCβ inhibitor is effective for treating DN. In the current study we further explored the effects and molecular mechanisms of PKCI3 inhibitors on GEC apoptosis in DN in streptozotocin-induced diabetic mice in vivo and high glucoseor PMA-treated human renal glomerular endothelial cells （HRGECs） in vitro. In the diabetic mice, hyperglycemia caused aggravated nephropathy and GEC apoptosis accompanied by significantly increased expression of swiprosin-1, a potentally pro-apoptotic protein. Administration of LY333531 （1 mg.kg-1.d-1 for 8 weeks） significantly attenuated both GEC apoptosis and swiprosin-1 upregulation in the diabetic mice. Similar results were observed in high glucoseor PMA-treated HRGECs in vitro. The pro-apoptotic role of swiprosin-1 was further examined using HRGECs treated with lentivirus mediating RNA interference or over-expression and swiprosin-1-knockout mice. Over-expression of swiprosin-1 in HRGECs resulted in increases in apoptosis and in caspase-9, caspase-3 and Bax expression. In contrast, knockdown of swiprosin-1 attenuated high glucoseor PMA-induced HRGECs apoptosis. Furthermore, over-expression of swiprosin-1 promoted interaction between swiprosin-1 and caspase-9 and increased the formation of apoptosomes. In diabetic swiprosin-1-/- mice, the kidney/body weight, urinary albumin, glomerular hypertrophy, mitochondrial apoptotic-associated proteins and GEC apoptosis were significantly attenuated as compared with those in diabetic swiprosin-1＋/＋ mice. These results demonstrate that swiprosin-1 is up-regulated by PKCβ in the early stage of DN, and that PKCβ facilitates GEC apoptosis through the mitochondrial-dependent pathway.