Research On The Protective Role Of Renalase In Type 4 Cardiorenal Syndrome And Underlying Mechanisms

Background: In pathological circumstance,primary disorder of kidney or heart will casuse damage on the other organ,which in turn will also accelerate progression of primary disease.These bidirectional heart-kidney interactions can lead to a vicious cycle.The phenomenon that kidney and heart dysfunction are often concomitant is defined as cardiorenal syndrome,which has become hot and difficult issues in clinical practice.Clinical studies demonstrated that patients with primary chronic kidney disease(CKD)show higher incidence of cardiovascular diseases and cardiac death is the leading cause of death in patients with CKD.This phenomenon has been classified as chronic renocardiac syndrome or type 4 cardiorenal syndrome.Among many factors involved in the pathogensis of type 4 cardiorenal syndrome,it has been identified that deficiency of several hormones or cytokines secreted by kidney,such as erythropoietin,calcitriol or klotho may directly participate in the pathogenesis of worsening of renal function and cardiovascular complication.Therefore,the identification of novel hormones or cytokines secrected by kidney will help to elucidate the pathophysiology of cardiorenal syndrome and may represent as a novel therapeutic approach.Renalase,as a rencently discovered enzyme secreted by kidney into circulation,plays a crucial role in regulation of blood pressure and electrolyte metabolism through degrading catecholamines.It has been reported that renalase not only protects against various renal diseases but also exerts cardio-protective effects and renalase deficiency is present both in CKD patients and animal model.Thus,renalase deficiency may lead to elevation of circulatory catecholamines and subsequent activation of sympathetic nervous system,which will ultimately aggravate the progression of renal dysfunction and accelerate the occurrence of cardiovascular complication.Objectives: We tested whether tail vein injection of renalase adenovirus could restore renalase level in 5/6 subtotal nephrectomy rats and evaluated whether renalase supplementation could attenuate the progression of renal injury and cardiac remodelling.Furthermore,the underlying mechanisms of renalase’s protective effects on kidney and heart were also investigated.Methods:We first constructed a rat renalase recombinant adenovirus and obtained high titer virus particles from 293 cells through a large number of amplification and purification.Besides,the infection efficacy was assessed in vitro and in vivo.The CKD model was established by 5/6 subtotal nephrectomy.Renalase recombinant adenovirus was administered in rats with subtotal nephrectomy via tail vein injection and the effects of renalase adenovirus on renal injury and cardiac remodelling were determined.Results: 1.The rat renalase recombinant adenovirus was successfully constructed and high titer virus particles used for animal studies was also obtained through amplification and purification.Besides,the infection efficacy was assessed in renal tubular cells and primary neonatal cardiomyoctyes respectively,and was also evaluated in 5/6 subtotal nephrectomy after tail vein injection of adenovirus-renalase.All the results proved that renalase adenovirus could effectively infect cells and lead to overexpression in vitro and in vivo.2.In comparison to control-adenovirus administered subtotal nephrectomy rats,renalase recombinant adenovirus significantly reduced blood urea nitrogen,proteinuria and attenuated decline of creatinine clearance.Kidney sections from subtotal nephrectomy rats revealed remarkable glomerular hypertrophy and tubular enlargement while renalase adenovirus treatment significantly ameliorated glomerular hypertrophy,glomerularsclerosis and tubulointerstitial injury.In addition,Masson and Sirus Red staining showed that renalase supplementation attenuated renal interstitial fibrosis induced by subtotal nephrectomy.The reno-protective effects of renalase might be associated with inhibition of inflammatory response,downregulation of pro-fibrotic molecules and inhibiton of oxidative stress and apoptosis.3.Adenovirus-renalase administration significantly attenuated subtotal nephrectomy induced activation of sympathetic nervous system characterized by decline of serum norepinephrine levels and blood pressure.Rats underwent 5/6 subtotal nephrectomy exhibited left ventricular hypertrophy and diastolic dysfunction.The heart weight/body weight ratio and left ventricular weight/body weight ratio were significantly lower in adenovirus-renalase-treated rats than untreated 5/6 subtotal nephrectomy rats.Histological analysis demonstrated that adenovirus-renalase delivery significantly blunted elevation of cardiomyocytes cross-section area and cardiac fibrosis induced by subtotal nephrectomy.In addition,we also found that adenovirus-renalase administration significantly attenuated progression of cardiac remodelling by echocardiography examination,which was characterized by decreased LVPWd、LVPWs、LVAWd and LVAWs.Left ventricular catheterization showed that renalase treatment restored left ventricular diastolic function.It was also observed that renalase supplementation might prevent cardiac remodelling through inhibition of pro-fibrotic genes expression and phosphorylation of ERK-1/2.Conclusion: Renalase supplementation by systemic delivery of Ad-renalase restored renalase levels and attenuated hypertension,renal injury and cardiac remodelling in rats after subtotal nephrectomy in catecholamines-lowering-dependent/independent manners.The potential mechanism of its protective effects may be mediated by its anti-inflammatory,antioxidant function,inhibition of apoptosis and inhibition of ERK1/2 pathway.Therefore,renalase is a crucial modulator of CRS progression and renalase supplementation may be a promising approach for prevention and treatment of type 4 CRS in CKD patients.