Objective. In a model of rat cardiac hypertrophy, the changes in the distribution of ET-1 receptors in two subcellular fractions, the sarcolemma and the light vesicles during myocardial hypertrophy were studied. Methods. Cardiac hypertrophy was produced by placing a constricting clip around the suprarenal abdominal aorta of rats, and ET-1 receptor was assayed with radioactive analysis method. Results. It was found that plasma and ventricular ET-1 levels increased significantly on week 2 and week 4 of pressure overload. ET-1 binding studies showed that during myocardial hypertrophy, the maximum binding capacity (Bmax) was increased by 41％ (P<0.01) and 65％ (P< 0.01) in sarcolemma in H-2 week and H-4 week groups, but was decreased by 24％ (P< 0.01) and 21％ (P< 0.01) in light vesicles. The sum of Bmax of sarcolemmal and light vesicle fractions was increased by 33％ (P< 0.01) and 57％ (P< 0.01) in group H-2 week and H-4 week, respectively. ? Conclusion. ET-1 receptors in rat heart were externalized from light vesicles to sarcolemma, which may contribute to the development of myocardial hypertrophy.

AIM:We investigated how AT 1-R stimulated by mechanical stresses induces cardiac fibrosis .METHODS:We produced in vivo cardiac pressure overload model in angiotensinogen knockout ( ATG-/-) mice and in vitro mechanically-stretched cell model in cultured neonatal cardiac cells of ATG-/-mice both lack the participation of Ang II .RESULTS: Pressure overload for 4 weeks in ATG-/-mice induced myocardial hypertrophy accompanied by the significant interstitial fibrosis , however , the TGF-β, a key regulatory factor of fibrosis, was not significantly increased in these ATG-/-mice.Meanwhile, the inhibitor for AT1-R significantly inhibited mechani-cal stress-induced cardiac fibrosis in these ATG-/-models whereas inhibition of TGF-βdid not.CONCLUSION:The results showed that mechanical stress-induced fibrotic responses through AT 1-R required the phosphorylation of Smad 2 but not the involvement of TGF-β.

AIM:To examine and compare the effects of several ARBs that are widely used in clinics , on the ACE-Ang II-AT1 receptor and the ACE2-Ang(1-7)-Mas axis during the development of cardiac remodeling after pressure overload .METHODS: All of the mice used in the study underwent transverse aortic constriction (TAC) or sham operation for 2 or 4 weeks.A solution of either ARBs or sa-line was administered through a stomach tube 3 days before the operation .Meanwhile , to eliminate the influence of Ang II , a recombi-nant adenovirus expressing small interfering RNAs targeting angiotensinogen ( Ad-ATG siRNA) was injected via the tail vein .The sur-gery was then performed and the drug was administered as mentioned above .Cardiac function and remodeling were evaluated by echo-cardiography , hemodynamic measurements and cardiac histology .Western blotting was used to determine the protein expression levels . Meanwhile , we performed similar experiments using ARBs with or without ATG siRNA in cardiomyocytes induced by mechanical stretch.RESULTS:Although all of the six ARBs , none of which repressed the elevation of left ventricular pressure after TAC , attenu-ated the development of cardiac hypertrophy and heart failure in the wild-type mice, the degree of attenuation by Olmesartan , Candesar-tan and Losartan tended to be larger than that of the other three drugs tested .Additionally , the degree of downregulation of the ACE-Ang II-AT1 axis and upregulation of the ACE2-Ang(1-7)-Mas axis was higher in response to Olmesartan, Candesartan and Losartan administration in vivo and in vitro.Additionally, Olmesartan had a larger influence when administered long term .However, the expres-sion of ACE was not influenced by the administration of ARBs in vivo and in vitro.Moreover, in angiotensinogen-knockdown mice, TAC-induced cardiac hypertrophy and heart failure were inhibited by Olmesartan , Candesartan and Losartan but not by Telmisartan , Valsartan and Irbesartan administration .Furthermore , only Olmesartan and Candesartan could downregulate the ACE-Ang II-AT1 axis and upregulate the ACE2-Ang(1-7)-Mas axis in vitro.CONCLUSION: Olmesartan, Candesartan and Losartan could effectively in-hibit pressure overload-induced cardiac remodeling even when with knockdown of Ang II , possibly through upregulation of the expres-sion of the ACE2-Ang(1-7)-Mas axis and downregulation of the expression of the ACE-Ang II-AT1 axis.In contrast, Telmisartan, Valsartan and Irbesartan only played a role in the presence of Ang II , and Losartan had no effect in the presence of Ang II in vitro.

Emerging evidence has indicated that BRCC 36-mediated K63-linked ubiquitination modification was involved in diverse cellular functions , including endocytosis , apoptosis and DNA damage repair .We previously showed that activation of cGMP/PKG pathway con-tributed to the binding of BRCC36 and the pro-fibrotic factor Smad3.The current study tested the hypothesis that BRCC 36 functions as a negative regulator of transforming growth factor-beta ( TGF-β)/Smad3 pathway and participates in cardiac remodeling .In isolated adult mouse cardiac fibroblasts , we have demonstrated that TGF-β1 treatment significantly increased the expression of BRCC 36.Over-expression BRCC36 suppressed TGF-β1-induced Smad3 phosphorylation, nuclear translocation, extracellular matrix molecular expres-sion and cell proliferation .On the contrary, silencing BRCC36 by transfection of adenovirus-carrying BRCC36 shRNA potentiated to
enhance the pro-fibrotic effect of TGF-β.In vivo, under chronic pressure overload condition-induced by transverse aortic constriction , myocardial pro-survival protein Bcl-2 and Mcl-1 expression were significantly decreased and the pro-apoptosis protein Puma was in-creased.However, the cardiac-specific over-expression of BRCC36 significantly increased myocardial Bcl-2 and Mcl-1 and inhibited Puma expression .Interestingly , we also found that sustained pressure overload resulted in a significant myocardial DNA injury in wild type mice, which was characterized by the increase of γH2AX level.However, cardiac-specific BRCC36 over-expression significantly decreased the level of γH2AX in the pressure overloaded heart in the transgenic mice , while effectively enhanced myocardial RAD 51 expression, a marker of DNA damage repair.Furthermore, BRCC36 over-expression effectively attenuated TAC-induced cardiac fibro-sis and remodeling in the transgenic mice , compared with the wild type mice .Collectively , the results have suggested that BRCC 36 ef-fectively protected heart against chronic pressure overload-induced cardiac remodeling though antagonizing TGF-β/Smad3 pathway and enhancing myocardial DNA injury repair response .