The Role Of Caveolin-1 In Albumin Transcytosis Of Glomerular Endothelial Cell

Objective: Diabetic nephropathy(DN)is a major cause of end-stage kidney disease(ESRD),the early symptom is microalbuminuria,which gradually develop into a large amount of albuminuria.Albuminuria is an independent risk factor for the development of DN.It was previously believed that the formation of albuminuria was mainly caused by the damage of filtration barrier.Caveolin-1(Cav-1),as an endocytosis dependent protein,plays an important role in albumin transcytosis across vascular endothelial cells,which may be involved in the formation of albuminuria in DN.Losartan is commonly used to treat proteinuria,and the main mechanism is to reduce urinary protein by blocking renin angiotensin aldosterone system(RAAS).The purpose of this study is to investigate whether losartan could regulate the formation of early albuminuria in DN by regulating Cav1-mediated albumin transcytosis across glomerular endothelial cells.Methods:(1)Establish an in-vitro albumin transcytosis model: Human glomerular endothelial cells(HGECs)in good growth condition were digested and implanted in 24-well Transwell,then adding fluorescein isothiocyanate(FITC)labeled bovine serum albumin(BSA)into the upper chamber of the transwell to trace the process of albumin transcytosis,and monolayer integrity of HGECs were detected by measuring the transendothelial electrical resistance(TEER).(2)The transcytosis model established above was used to investigate the change of albumin transcytosis across HGECs under normal glucose(NG)and high glucose(HG)conditions.(3)Western blot was used to detect the expression of Cav-1 in HGECs in NG and HG environments to study the possible mechanism of albumin transcytosis.(4)In vitro,transcytosis model was used to detect the changes of albumin transcytosis after knockdown the expression of Cav-1 in the cells through Cav-1 si-RNA transfection under NG and HG conditions,respectively.(5)To explore the effects of losartan,we tested albumin transcytosis and Cav-1 expression with losartan intervention in NG and HG environment.Result:(1)The albumin transcytosis model in vitro was established successfully.(2)The expression of Cav-1 in HGECs was significantly increased and albumin transcytosis was also increased under HG,whileas,albumin transcytosis was significantly decreased by transfection of Cav-1 siRNA.(3)The expression of Cav-1 in HGEC in the HG group was downregulated by using losartan,meanwhile,albumin transcytosis was found decreased in the same group.Conclusion: The possible mechanism of early albuminuria reduction by losartan in diabetic nephropathy could be its regulation of Cav1-mediated albumin transcytosis across glomerular endothelial cells.This new finding may provide a new target for losartan in the treatment of albuminuria in DN patients.