The Role And Mechanism Of MDM2 In High Glucose-induced Glomerular Mesangial Cell Proliferation And Extracellular Matrix Accumulation

Diabetic kidney disease(DKD)is one of the major chronic microvascular complications of diabetes,and is a common cause of end stage renal disease(ESRD)and high mortality in diabetes.Glomerular mesangial cells(GMCs)abnormal proliferation and excessive extracellular matrix(ECM)deposition in mesangium are hallmark pathological features in the onset and progression of DKD,which gradually lead to glomerulosclerosis and deterioration of renal function.However,the mechanism mediating GMC proliferation and ECM accumulation under hyperglycemia condition has not been fully clarified yet.Murine double minute 2(MDM2)is an important E3 ubiquitin ligase which promotes cell proliferation and growth through modulating various kinds of signal transduction.It is previously reported that MDM2 is widely presented in kidney resident cells,and it is not only indispensable for physiologic cells homeostasis and renal function,but also participates in the pathological events of various kidney diseases.However,whether MDM2 contributes to the glomerular lesion of DKD,especially GMC proliferation and ECM accumulation is still unknown.In the present study,we take advantage of a rat GMC line as well as STZ-induced mouse type 1 DKD model to investigate the role of MDM2 in high glucose-induced GMC dysfunction and try to clarify the related molecular mechanism.In our current study,we confirmed that high glucose induces the upregulation of MDM2 protein level.Knocking down MDM2 attenuates high glucose-induced cell proliferation and ECM accumulation.However,MDM2-p53 interaction blocker Nutlin-3a,cannot protect diabetic mice from glomerular impairment,especially the mesangium lesion in vivo.In vitro,Nutlin-3a shows no benefit on ECM accumulation induced by high glucose in GMCs,which prompts a p53-independent manner of MDM2 in mediating the GMC dysfunction under diabetic status.Intriguingly.we found MDM2 forms interaction with Notch 1 intracellular domain(NICD1),and the ubiquitination status of NICD1 and Notch 1 signaling activation is obviously attenuated by MDM2 depletion in GMCs with high glucose exposure.However.Numb,another substrate of MDM2 which suppresses Notch 1 signaling,is not involved in the MDM2 and Notch 1 association.Collectively,our data propose a pivotal role of MDM2 in the high glucose-induced GMC proliferation and ECM accumulation,through modulating the activation of Notch 1 signaling pathway in an ubiquitination modification-dependent way,independent of p53 and Numb,which presents a novel mechanism of hyperglycemia-associated GMC dysfunction.