The Experimental Study Of Calycosin's Effect On Cardiac Hypertrophy In Mice

BackgroundCardiovascular disease currently is still a common disease in the world,which accounts for a predominant part of all-cause mortality.Heart failure is the final outcome of many cardiovascular diseases,incuding hypertension,and acute myocardial infarction.Previous researchs indicate that heart failure can not be reversed once occurred.The mortality rate of heart failure is high,and the outcome of heart failure is bad.It's said by the famous cardiologist Braunwald that heart failure is one of the most diseases in the 21st centery.Research focusing on heart failure has been performed for decades,however,we still did not found the new target for the preventation and treatment of heart failure.The underlying reason is that there is no big breakthrough of the mechanism of heart failure.The basic mechanism of heart failure is impaired systolic or diastolic function,which mainly caused by neurohormonal over-activation,and abnormal cardiac structure and function.The current drugs could be used to treat heart failure by anatagonize the overactivation of neuroendocrine.However,these drugs have been reaching a thereshold that the mortality rate of heart failure can not be further decreased.During heart failure,the hypertrophic stimuli induced the death or hypertrophy of cardiac myocytes,cardiac fibroblasts activated and transformed into myofibroblasts,and leading to the reconstructure of extracellular matrix.The pathological changes resulted in the impaired hemostasis of collagen synthesis and collagen degradation.Therefore,it is of great importance to inhibit the hypertrophy of cardiac hypertrophy and suppress the proliferation and transformation of cardiac fibroblasts during heart failure.Cardiac hYypertrophy is an adaptive change in response to a variety of extrinsic and intrinsic stimuli.The level of angiotensin II increased after pathological stimuli,which activated receptor of angiotensin,resulting in the increased cell area and increased protein synthesis.The hypertrophic cardiac myocoytes then secret a lot of growth factors including endothelin-1(ET-1),transforming growth factor ?(TGF-P)and connective tissue growth factor(CTGF),which activated endothelials,cardiac fibroblasts and inflammatory cells.These cell also secreted ET-1,TGF-? and CTGF,which function on cardiac myocytes and form a positive feedback,leading to a prolonged hypertrophic response and decreased cardiac function.Calycosin(CA),one of main bioactive compounds isolated from the root of Radix Astragali,has a number of biological properties including inhibiting oxiadative stress,promoteing angiogenesis,suppressing allergy and tumor,and reducing endothelial injuries.Calycosin has been demonstrated to have favorable efficacy on hepatoprotective properties against non-alcoholic steatohepatitis via activating famesoid X receptor.Calycosin attenuates diabetes-induced cognitive impairments in rats by suppressing oxidative injuries.Calycosin inhibits apoptosis of cardiomyocytes induced by oxidative stress activating estrogen receptor.However,there no report describing the effect of calycosin on cardiac hypertrophy and the underlying mechanism.MethodThe C57 mice were selected based on the age and body weight(Age:8?10 weeks;body weight:23.5-27.5g).Mice were subjected to the repeated intraperitoneal injection of isoprenaline(50mg/kg)for 14 days to induce cardiac hypertrophy,or were subjected to aortic banding(AB)to induce cardiac hypertrophy.The animals in the treatment group were orally given 50mg/kg CA for 14 days in iso group or for 4 weeks in AB group while the mice in the control group were given the same volume of vehicle at the same time.At the end point of the study,the mice were killed to detect the ratio of heart weight and body weight,the ratio of heart weight and tibal length.The cross-sectional areas were determined by HE staining.The mRNA levels of hypertrophic markers were detected by the real-time PCR.The signaling pathway including mitogen-activated protein kinase(MAPKs)and protein kinase B(PKB/AKT)were evaluated by western blot.Neonatal rat cardiac myocytes were isolated,and were divided into three groups:control group,phenylephrine(PE)group and CA+PE group.The hypertrophy of cardiomyocytes were induced by the treatment of PE(10 ?mol/L).To investigate the protective effect of CA,the cardiac myocytes were given a series of dose of CA.After treatment,the cells were harvested and the mRNA of hypertrophic markers were detected.a-Actinin staining were used to outline the area of myocytes.ResultAfter the repeated injection of ISO for 14 days,the ratio of heart weight and body weight(HW/BW),heart weight and tibal length(HW/TL),and the cross-sectional area significantly increased(P<0.05).As indicated by echocardiogram and hemodynamics analysis,the end systolic interventricular septum thickness(IVSs)and left ventricular end diastolic diameter(LVIE)d)increased,and the ejection fraction(EF)reduced(P<0.05).Mice with CA treatment had decreased ratios of heart weight and body weight,heart weight and tibal length,and cross-sectional area(P<0.05).Besides;after 4 weeks of AB surgery,the HW/BW,HW/TL,IVSs and LVIIDd were significantly increased,while CA treatment for 4w markedly decreased these parameters.Meanwhile,CA treatment also recoveried the decreased EF(P<0.05).Western blot analysis showed that CA treatment the activation of MAPKs and AKT pathway.Using neonatal rat cardiac myocytes,we found that CA could dose-dependently decrease the mRNA level of hypertrophic markers(P<0.05).Conclusions1.Calycosin could decrease isoprenaline or AB-induced cardiac hypertrophy,and improve cardiac function in mice.2.Calycosin could reduce the activation of MAPKs and AKT pathway induced by ISO.3.Calycosin could reduce the hypertrophy of cardiac myocytes induced by phenylephrine.