Ginsenoside Rb1 Pretreatment Attenuates Myocardial Ischemia by Reducing Calcium/Calmodulin-Dependent Protein Kinase Ⅱ-Medicated Calcium Release

Objective:The aim of this study was to investigate the protective effects of ginsenoside Rb1 and assess whether these protective effects are related to calcium/calmodulin-dependent protein kinaseⅡ(Ca MKⅡ).Methods:A myocardial ischemia(IS)rat.model and a myocardial H9 C2 cell hypoxia model were established.MI was induced by occluding the left anterior descending artery for 120 min.Ginsenoside Rb1(10 mg/kg)was administered 30 min before ischemia induction,and the treatment continued for 7 days.Results:In the rat IS injury model,ginsenoside Rb1 reduced myocardial infarct size,mean left ventricular diastolic pressure,incidence of arrhythmia,and levels of serum creatine kinase,lactate dehydrogenase,and malondialdehyde.However,the mean left ventricular systolic pressure,and maximal rising and falling rates of ventricular pressure(±dp/dtmax)increased.In the myocardial H9 C2 cell hypoxia model,ginsenoside Rb1 reduced intracellular calcium concentrations([Ca2+]i)during hypoxia,and markedly reversed the hypoxia-induced decrease in cell survival.Ginsenoside Rb1 was involved in the downregulation of CaMKⅡand the ryanodine receptor,as well as hypoxia-induced H9 C2 cell survival.Conclusion:The findings of the present study suggest that ginsenoside Rb1 attenuates MI injury in rats,partially through the downregulation of CaMKⅡexpression.

Decorin Induces Cardiac Hypertrophy by Regulating the CaMKⅡ/MEF-2 Signaling Pathway In Vivo

Objective:Cardiac hypertrophy is an adaptive reaction of the heart against cardiac overloading,but continuous cardiac hypertrophy can lead to cardiac remodeling and heart failure.Cardiac hypertrophy is mostly considered reversible,and recent studies have indicated that decorin not only prevents cardiac fibrosis associated with hypertension,but also achieves therapeutic effects by blocking fibrosis-related signaling pathways.However,the mechanism of action of decorin remains unknown and unconfirmed.Methods:We determined the degree of myocardial hypertrophy by measuring the ratios of the heart weight/body weight and left ventricular weight/body weight,histological analysis and immunohistochemistry.Western blotting was performed to detect the expression levels of CaMKⅡ,p-CaMKⅡ and MEF-2 in the heart.Results:Our results confirmed that decorin can regulate the CaMKⅡ/MEF-2 signaling pathway,with inhibition thereof being similar to that of decorin in reducing cardiac hypertrophy.Conclusion:Taken together,the results of the present study showed that decorin induced cardiac hypertrophy by regulating the CaMKⅡ/MEF-2 signaling pathway in vivo,revealing a new therapeutic approach for the prevention of cardiac hypertrophy.

Changes of learning, memory and levels of CaMKII, CaM mRNA, CREB mRNA in the hippocampus of chronic multiple-stressed rats

Background The effect of chronic stress on cognitive functions has been one of the hot topic in neuroscience. But there has been much controversy over its mechanism. Such single stressor applied in the past could not simulate complicated living circumstances that people confronted with. The aim of this study was to investigate the effects of chronic multiple-stress on learning and memory as well as on the levels of calcium/calmodulin-dependent protein kinase Ⅱ（CaMKⅡ）, calmodulin （CAM） mRNA, and cAMP-response element binding protein （CREB） mRNA in the hippocampus of rats. Methods The rats were divided randomly into stressed and control groups. The stressed group was given chronic multiple-stress for 6 weeks to set up a chronic multiple-stressed model. The rats＇ performance of spatial learning and memory was tested using Morris Water Maze （MWM） and Y-maze. Meanwhile, the expressions of CAMKII, CAM mRNA and CREB mRNA of rats＇ hippocampus were detected by immunohistochemistry, Western blot and reverse transcription-polymerase chain reaction （RT-PCR）, respectively. In addition, the width of synaptic cleft and the thickness of post-synaptic densities （PSD） were observed in the hippocampal CA3 region of rats by electron microscopy. Results After exposure to chronic multiple-stress for 6 weeks, the ability of learning and memory of the stressed group was higher than that of the control group （P〈0.05, P〈0.01）. The width of synaptic cleft was smaller and the thickness of PSD was larger in the hippocampal CA3 region of the stressed group than in that of the control group （P〈0.01）. The CAMKII immunostaining of the stressed group was stronger than that of the control group in the stratum radiatum and oriens of the hippocampal CA1 and CA3, especially in the stratum oriens. Quantitative analysis indicated that the expression of CAMKII, CAM mRNA, and CREB mRNA in the hippocampus of the stressed group was higher than that of the control group （P〈0.05, P〈0.01）. Conclusions The capacity of learning and memory can be enhanced after chronic multiple-stress. The increased levels of CAMKⅡ, CAM mRNA, and CREB mRNA may contribute to the enhancing effect of chronic multiple-stress on learning and memory.