Midazolam Ameliorates Hyperglycemia-Induced Glomerular Endothelial Dysfunction by Inhibiting Transglutaminase 2 in Diabetes

Midazolam is an anesthetic widely used for anxiolysis and sedation; however, to date, a possible role for midazolam in diabetic kidney disease remains unknown. Here, we investigated the effect of midazolam on hyperglycemia-induced glomerular endothelial dysfunction and elucidated its mechanism of action in kidneys of diabetic mice and human glomerular microvascular endothelial cells (HGECs). We found that, in diabetic mice, subcutaneous midazolam treatment for 6 weeks attenuated hyperglycemia-induced elevation in urine albumin/creatinine ratios. It also ameliorated hyperglycemia-induced adherens junction disruption and subsequent microvascular leakage in glomeruli of diabetic mice. In HGECs, midazolam suppressed high glucose-induced vascular endothelial-cadherin disruption and endothelial cell permeability via inhibition of intracellular Ca2+ elevation and subsequent generation of reactive oxygen species (ROS) and transglutaminase 2 (TGase2) activation. Notably, midazolam also suppressed hyperglycemia-induced ROS generation and TGase2 activation in glomeruli of diabetic mice and markedly improved pathological alterations in glomerular ultrastructure in these animals. Analysis of kidneys from diabetic Tgm2−/− mice further revealed that TGase2 played a critical role in microvascular leakage. Overall, our findings indicate that midazolam ameliorates hyperglycemia-induced glomerular endothelial dysfunction by inhibiting ROS-mediated activation of TGase2.

Loss of CLDN5 in podocytes deregulates WIF1 to activate WNT signaling and contributes to kidney disease

Although mature podocytes lack tight junctions (TJs) and form slit diaphragms between opposing foot processes, TJ integral membrane protein CLDN5 is predominantly expressed throughout the plasma membrane of podocytes under normal conditions. Here using podocyte specific Cldn5 knockout mice as a model, we identify CLDN5 as a crucial regulator of podocyte function and reveal Cldn5 deletion exacerbates podocyte injury and proteinuria in diabetic nephropathy (DN) mouse model. Mechanistically, CLDN5 absence reduces ZO1 expression and induces the nuclear translocation of ZONAB, followed by transcriptional downregulation of WIF1, which leads to activation of WNT signaling pathway. Knockout Wif1 in podocytes result in the development of proteinuria and typical glomerular ultrastructure change occurring in Cldn5 knockout mice, while targeted delivery of Wif1 to podocytes prevents the development of glomerular nephropathy in Cldn5 knockout diabetic mice. Podocyte-derived WIF1 also plays a paracrine role on tubular epithelial cells, evidenced by animals with podocyte deletion of Cldn5 or Wif1 have worse kidney fibrosis after unilateral ureteral obstruction when compared with littermate controls with intact podocyte WIF1 expression. These findings establish a novel function of podocyte CLDN5 in restricting WNT activity in the kidney.