| Heart failure (HF) is the end-stage state of various cardiovascular diseases. Patients with HF are characterized by deteriorated cardiac function, impaired labor ability, and unacceptably high mortality, thus HF have made a serious health problem which threats the public society. Hypertension is a major pathogenic factor which leads to heart failure. According to the China prevention and treatment of hypertension guide in 2009, about 20 million residents in China are afflicted with hypertension, and the number is still rising. With persistent blood pressure over-load, cardiac function and structure usually carry out compensatory changes in the early stage, termed"cardiac remodeling", which enables the heart to meet the body's metabolism needs within a certain time. But in the long run, this compensation can not keep up with the body's needs. At this time, however, the heart turns to the decompensated stage and the patients begin to show symptoms of HF. During the process from myocardial compensated hypertrophy to decompensated heart failure, many questions need to be clarified, such as the changes taken place in the structure and function of heart, factors involved in this process, and the possible molecular mechanisms, et. In order to tackle with the above-mentioned questions, we adopted the following experiments: (1)First, we established hypertension-induced myocardial hypertrophy animal model with transverse aortic constriction (TAC) and tried to explore the potential mechanisms which regulate circulation aortic blood pressure in the combination rat model with the tenth thoracic spinal cord transaction and TAC; (2)We detected the structure changes of hypertrophied heart, and measured the contractile function of single left ventricular cardiomyocyte; (3)We explored the possible mechanisms of myocardial apoptosis by TUNEL, Western Blot, LSAB, and laser scanning confocal technologies. Main results are as follow :1. Femoral artery (FA) blood pressures of both SCT and CON rats were significantly lowered after abdominal aortic constriction. After one week, the FA blood pressure of CON rats raised to an equal level with normal rats and the carotid artery (CA) blood pressure raised to an even higher level compared with the initial elevation immediately after TAC, but the FA and CA blood pressure of SCT rats did not exhibit the same changes. The FA and CA blood pressures of SCT rats stayed at the same level as 1 w before. These results suggest that the hind-limbs may involved in the up-regulating of FA and CA blood pressure through the spinal nerve after TAC.2. Since TAC rats suffered higher stress, body weight had a slower growth rate compared with synchronous control rats. Therefore, the left ventricular to body weight ratio produced an experimental bias to evaluate the degree of cardiac hypertrophy. Length and width of isolated cardiomyocyte reflected the degree of cardiac hypertrophy. Besides, length, width, and calculated surface area of cardiomyocyte showed a progressive increase in 8-week, 16-week, and 20-week TAC rats. The increasing of width in cardiomyocytes was higher at the early stage of TAC and the increase of length was more significant at the later stage. 3. In order to measure the sarcomere length and calculate the sarcomere number, we stained the Z-line enrichment protein desmin by LSAB. The sarcomeric length of cardiomyocytes was unchanged, whereas the sarcomeric numbers in single cardiomyocyte were significantly increased in 8-week, 16-week, and 20-week TAC rats.4. Shortening amplitude of unloaded contraction in single cardiomyocyte was significantly enhanced in 1-week TAC rats, but not altered in 8-week TAC rats compared with the synchronous CON. On the contrary, shortening amplitude of single cardiomyocyte was significantly reduced in 16- and 20-week TAC rats. Collagen hyperplasia did not influence the contractile function in isolated cardiomyocyte. Although cardiomyocytes were widened in 16- and 20-week TAC rats, the diffusion of oxygen was sufficient in in vitro perfusion condition. The sarcomere length was not involved in regulating contractile function of hypertrophied cardiomyocytes. The above results suggest that the reduced shortening amplitude may be associated with intrinsic molecular alterations in hypertrophied cardiomyocytes.5. The apoptotic rate of hypertrophied cardiomyocytes increased. AngII-treated hearts exhibited a higher rate of TUNEL positive cells, while PKCδinhibitor Rottlerin prevented the increase in AngII-induced apoptosis. It indicates that PKCδmight mediate AngII-induced apoptosis of cardiomyocytes in TAC rats.6. The expression of PKCδincreased, but the expression of p-Akt and Bcl-2 decreased in the hypertrophied myocardium compared with the synchronous control. Treatment with AngⅡactivated PKCδand induced translocation of PKCδto mitochondrial outer membrane, where activated PKCδmight facilitate the phosphorylation of Bcl-2 at the Ser87 and Ser70. Multi-site phosphorylation of Bcl-2 might induce the release of mitochondrial cytochrome C, and then activate the caspase-3 apoptotic pathway. PKCδinhibitor Rottlerin inhibited these effects induced by AngⅡ. These results suggest that PKCδcan counteract the anti-apoptosis effect of Bcl-2 and may promote cardiomyocyte apoptosis through the multi-site phosphorylation of Bcl-2. |
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