The Kidney Protection Effect Of Nebivolol In Renovascular Hypertension Rats And Its Relationship With ADMA

Objective:This purpose of this study was to observe the renal protective effect of nebivolol in renovascular hypertension rats and explore the mechanisms underlying this potential effect.Methods:2K1C hypertension was induced by clipping the left renal artery with a silver clip(0.2 mm internal diameter).The sham-operated rats underwent the same laparotomy without clipping of the renal artery.Systolic blood pressure(SBP)was measured by the tail-cuff method.Rats with SBP ? 160 mm Hg were determined to be hypertensive rats at 4 weeks after surgery.Then 2K1 C rats were divided into four groups:(1)2K1C group: untreated hypertensive rats;(2)2K1C+nebivolol group: hypertensive rats treated with nebivolol(10 mg/kg,i.g);(3)2K1C+atenolol group: hypertensive rats treated with atenolol(80 mg/kg,i.g);(4)2K1C+captopril group: hypertensive rats treated with captopril(20 mg/kg,i.g).Treatments lasted for 8 weeks.SBP,water intake,food intake,body weight,urine volume were measured at different time point.At the end of the experimental period,blood and urine were separated,aliquoted,and stored at-80°C.Different biochemical parameters(serum creatinine(Scr),urine creatinine(Ucr),creatinine clearance rate(Ccr),urine total protein,microalbumin(MALB)and ?2-microglobulin(?2-MG)N-acetyl-?-glucosaminidase(NAG),serum ADMA,blood urea nitrogen(BUN),renin activity(PRA)and Ang ?,NO in plasma and kidney were measured.The left and right kidneys were removed quickly and weighted.One part of kidneys were used for hematoxylin and eosin(HE)stain,periodic acid-Schiff(PAS,mesangial expansion)stain,Masson's trichrome stain(kidney fibrosis),transmission electron microscopy(TEM)and immunofluorescence(?-SMA,nephrine,KIM-1).The other part of kidneys were frozen in liquid nitrogen for western blot(iNOS,eNOS,nNOS,DDAH1,DDAH2,PRMT1).Results:Compared to sham group,SBP increased at the first week after operation,and further reached to 176.40±3.73 mmHg at the fourth week and sustained elevation to the end of study.Nebivolol,atenolol and captopril decreased SBP gradually.Urine volume and water intake increased sharply and reached a peak at the second week.Ucr reduced significantly,especially at 2 weeks and then back to sham level gradually.Compared with the sham group,the urinary protein progressively increased and were significantly higher at as early as 4 weeks.Nebivolol and captopril reduced the increasing in urine protein.There were no differences in PRA and AngII in plasma and left kidney between 2K1 C and sham groups.But AngII level was increased in right kidney of 2K1 C rats which was reduced by the treatment of nebivolol,atenolol and captoril.Glomerular hypertrophy in right kidney from 2K1 C rats was observed by HE staining.Glomerular glycogen deposition in 2K1 C rats was shown by PAS staining and kidney fibrosis was shown by Masson staining and ?-SMA immunofluorescence.Transmission electron microscope showed rats in 2K1 C group had an increase in GBM thickening and foot process effacement.The expression of nephrin was decreased in 2K1 C rats,especially in the right kidney.These changes were ameliorated by treatment with nebivolol,atenolol and captopril,especially by nebivolol.The urine levels of ?2/Ucr,mALB/Ucr,NAG and the expression of KIM-1 increased significantly in 2K1 C rats.Nebivolol effectively improved these changes.Nebivolol also reduced the levels of Scr,BUN and improved the endogenous Ccr.Although there was no significant difference in serum NO level between 2K1 C and sham group,the plasma NO concentration was clearly elevated after the administration of nebivolol.Compared with Sham group,the expression of nNOS in left kidney and eNOS in both side kidneys were lower,while the expression of iNOS in the left kidney was higher in 2K1 C rats,which was reversed by nebivolol.On the other hand,the plasma level of ADMA was increased.The expression of PRMT1 increased,and the DDAH2 expression in left kidney decreased although there was no difference at the expression of DDAH1 between 2K1 C and Sham group.Although all the three drugs,nebivolol,atenolol and captopril,could ameliorate the expression of DDAH2 and PRMT1,only nebivolol reduced serum level of ADMA.Conclusion:Nebivolol significantly improved kidney structure and function in 2K1 C rats.This protective effect of nebivolol may be related to it's regulation of kidney PRMT/ADMA/DDAH axis.