MDM2 is implicated in high-glucose-induced podocyte mitotic catastrophe via Notch1 signalling.

Hui Tang,Yu‐Mei Wang,Chun‐Tao Lei,Chun Zhang,Hua Su,Pan Gao,Cheng Wan,Chen Ye,Shan Chen,Fang‐Fang He

doi:10.1111/jcmm.13253

Abstract

Podocyte injury and depletion are essential events involved in the pathogenesis of diabetic nephropathy (DN). As a terminally differentiated cell, podocyte is restricted in ‘post‐mitosis’ state and unable to regenerate. Re‐entering mitotic phase will cause podocyte disastrous death which is defined as mitotic catastrophe (MC). Murine double minute 2 (MDM2), a cell cycle regulator, is widely expressed in renal resident cells including podocytes. Here, we explore whether MDM2 is involved in podocyte MC during hyperglycaemia. We found aberrant mitotic podocytes with multi‐nucleation in DN patients. In vitro, cultured podocytes treated by high glucose (HG) also showed an up‐regulation of mitotic markers and abnormal mitotic status, accompanied by elevated expression of MDM2. HG exposure forced podocytes to enter into S phase and bypass G2/M checkpoint with enhanced expression of Ki67, cyclin B1, Aurora B and p‐H3. Genetic deletion of MDM2 partly reversed HG‐induced mitotic phase re‐entering of podocytes. Moreover, HG‐induced podocyte injury was alleviated by MDM2 knocking down but not by nutlin‐3a, an inhibitor of MDM2‐p53 interaction. Interestingly, knocking down MDM2 or MDM2 overexpression showed inhibition or activation of Notch1 signalling, respectively. In addition, genetic silencing of Notch1 prevented HG‐mediated podocyte MC. In conclusion, high glucose up‐regulates MDM2 expression and leads to podocyte MC. Notch1 signalling is an essential downstream pathway of MDM2 in mediating HG‐induced MC in podocytes.

Highlights

Due to the growing prevalence of diabetes mellitus (DM) in worldwide, the most common microvascular complication of DM–diabetic nephropathy (DN) has become a dominant cause of end-stage renal disease (ESRD) [1]
We investigated the ultrastructure of podocytes in DN patients, and the role of Murine double minute 2 (MDM2) in cell cycle control in high-glucose-treated human podocytes
To further explore whether podocyte could reenter into cell cycle and endure subsequent mitosis in diabetic status, we examined the protein level of mitotic marker Aurora B and p-H3

Summary

Introduction

Due to the growing prevalence of diabetes mellitus (DM) in worldwide, the most common microvascular complication of DM–diabetic nephropathy (DN) has become a dominant cause of end-stage renal disease (ESRD) [1]. DN is characterized by aggravating albuminuria and gradually loss of renal function [2]. Histological alternations of DN include the hyperplasia of the mesangial cells, deposition of extracellular matrix (ECM) in glomerular mesangium, thickness of basement membrane in glomeruli and tubules and injury of the endothelial cells and podocytes [3]. The pathophysiology of DN changes from a ‘mesangial cell-central theory’ to a ‘podocytecentral theory’[4]. Podocyte injury and loss are considered as the early and critical event in DN development [5]. Podocytes are highly specialized cells lining the outer surface of the glomerular basement membrane and interdigitate with neighbouring podocytes to form the slit diaphragm.

Methods

Results

Conclusion