The Effects And Mechanisms Of Apelin/APJ Signaling On Pressure Overload Mediated Aortic Remodeling And Fibrosis

Objective: Vascular remodeling is an adaptive change responded to pressure overload,and plays a key role in the development and progression of cardiovascular diseases.While irreversible vascular remodeling is the main important factor for target-organ damage mediated by pressure overload.As an important physiological regulatory peptide,Apelin involves in a variety of biological effects,including vasodilatation,enhanced myocardial contractility and regulation of fluid homeostasis.However,the roles of Apelin in pressure overload induced vascular remodeling and its progression remain be elucidated.In this study,we aimed to investigate the regulatory effects and molecular mechanisms of Apelin signaling in aortic remodeling and fibrosis under the pressure overload condition.Methods: The male Sprague-Dawley rats were subjected to pressure overload by transverse aortic constriction(TAC)and then randomized to daily deliver Apelin-13(50μg/kg)or angiotensin type 1 blocker Irbesartan(50 mg/kg)or placebo for 4 weeks.The in vitro cultured rat adventitial fibroblasts(AFs)were pretreated with Ang II(100 n M)in the presence and absence of Apelin-13(100 n M),Irbesartan(10 μM)and miRNA-122inhibitor(50 n M).Blood pressure levels were measured non-invasively by using tail-cuff method and cardiac function was evaluated by transthoracic echocardiography.The levels of Apelin,APJ receptor,leucine rich repeat containing G protein-coupled receptor 4(LGR4),tissue growth factor β1(TGFβ1),connective tissue growth factor(CTGF)and cell migration were examined in aorta tissue and AFs cells by Western blotting analysis,real-time PCR,immunofluorescence staining and wound-healing assay respectively.Results: Compared with sham-operated group,pressure overload resulted in increased myocardial hypertrophy,cardiac dysfunction,aggravetaed aortic remodeling and fibrosis in TAC rats,associated with increased TGFβ1 and CTGF levels in ascending aortas.These changes were associated with increases in levels of miRNA-122,LGR4 and β-catenin.Interestingly,treatment with Apelin-13 and Irbesartan promoted the aortic Apelin and APJ expression,along with decreases in levels of miRNA-122,LGR4,β-catenin,TGFβ1 and CTGF,contributing to attenuation of aortic remodeling and fibrosis mediated by pressure overload.In cultured rat adventitial fibroblasts,exposure to Ang II led to significant increases in cellular migration,linked with elevated levels of fibrosis-related cytokines,including TGFβ1,CTGF and NFAT5.These changes were significantly prevented by pre-treatment with Apelin-13 and miRNA-122 inhibitor.However,there were no significant differences in ANF levels among groups.Conclusions: Pressure overload mediated by TAC leads to cardiovascular hypertrophy,cardiac systolic dysfunction,exacerbated vascular remodeling and fibrotic injury,while Apelin-13 treatment alleviates TAC-mediated aortic remodeling and fibrosis by regulating LGR4-β-catenin and TGFβ1/CTGF/NFAT5 signaling.Our findings reveal that Apelin has the potential to provide the new insights for preventing and intervening hypertension and related vascular diseases.