MECHANISM OF CHRONIC ALCOHOL INDUCED CARDIOMYOPATHY

该基金将通过纵向评估左心室（LV）和分离心肌细胞对慢性酒精摄入的结构和功能反应，研究慢性酒精诱导的扩张型心肌病（ADCM）的机制。此外，还将确定肾素-血管紧张素系统（RAS）及其细胞内信号的改变在ADCM产生中的作用。我们将检验以下具体假设：[H1]慢性酒精摄入会直接抑制心肌细胞收缩、舒张、[Ca2+]i短暂性和肌层Ca2+通道活性（ICa，L），从而导致[H2]左室收缩、舒张功能的进行性损害，并导致充血性心力衰竭，[H3]促进向ADCM过渡的最重要因素是酒精诱导的循环和心脏RAS的持续激活。这导致AT1受体偶联蛋白激酶C和/或抑制G蛋白（Gi）介导的左室和肌细胞对血管紧张素II （ANG II）的反应发生改变。因此，[H4]用慢性ACE抑制剂或ANG II AT1受体阻滞剂阻断RAS可减弱或阻止慢性酒精诱导的功能和结构变化。研究将在三个对照组和四个实验组中进行，研究时间为八个月：1)无仪器酒精喂养（每天一次22%的酒精，提供每日总热量摄入的33%）；2)仪器酒精饲养；3)灌喂酒精拉米普利（ACE抑制剂，0.1 mg/kg/天）；4)灌胃酒精-厄贝沙坦（angii AT1阻滞剂，5mg /kg/d）。对照组将由年龄匹配的狗在相同的条件下组成，除了对照组的狗不喝酒精。在这些有意识的狗中，心脏收缩和舒张功能以及RAS激活的一系列变化将被量化，长期测量左室压力和容积。细胞收缩功能，[Ca2+]i瞬态和ICa，L将连续测量从同一动物的左室活检获得的新鲜分离的心肌细胞。肌细胞将在以下条件下进行研究：1)钙，2)异丙肾上腺素，3)匹莫苯丹，4)酒精，5)ANG II。此外，在ADCM发生之前、期间和之后，用AT1受体阻滞剂、蛋白激酶C抑制剂或Gi蛋白抑制剂进行预孵育后，将重复研究肌细胞对ANG II的反应。这些研究将是慢性酒精摄入期间心脏和心肌细胞结构、功能、[Ca2+]i瞬态、ICa和L的首次详细纵向研究。此外，这些研究将为RAS的作用和ADCM的机制提供独特的信息。这些研究有助于我们进一步了解ADCM的发病机制，并有助于ADCM的靶向治疗。

This grant will investigate the mechanism of chronic alcohol- induced dilated cardiomyopathy (ADCM), by longitudinally assessing the structural and functional responses of the left ventricle (LV) and isolated cardiomyocytes to chronic alcohol intake. In addition, the role of the renin-angiotensin system (RAS) and the alterations in its intracellular signaling in producing ADCM will be determined. We will test the following specific Hypotheses: [H1] Chronic alcohol intake produces direct depressions in cardiomyocyte contraction, relaxation, [Ca2+]i transient and sarcolemmal Ca2+ channel activity (ICa,L), and thus causes [H2] a progressive impairment of LV systolic, diastolic function, and leads to congestive heart failure, and [H3] the most important factor in promoting the transition to ADCM is the alcohol-induced, sustained activation of circulating and cardiac RAS. This results in alterations in the AT1 receptor-coupled, protein kinase C and/or inhibitory G protein (Gi)-mediated responses of the LV and myocytes to angiotensin II (ANG II). Thus, [H4] blocking the RAS with chronic ACE inhibition or ANG II AT1 receptor blocker will blunt or prevent the chronic alcohol- induced functional and structural changes. The studies will be conducted in three control and four experimental groups studied over eight months: 1) uninstrumented alcohol-fed (22 percent alcohol once per day, providing 33 percent of total daily caloric intake); 2) instrumented alcohol-fed; 3) instrumented alcohol- ramipril (ACE inhibitor, 0.1 mg/kg/day)-fed; 4) instrumented alcohol-irbesartan (ANG II AT1 blocker, 5 mg/kg/day)-fed. The control groups will consist of age-matched dogs under identical conditions except dogs in the control groups will not receive alcohol. Serial changes of cardiac systolic and diastolic function and RAS activation will be quantitated in these conscious dogs, chronically instrumented to measure LV pressures and volume. Cell contractile function, [Ca2+]i transient and ICa,L will be serially measured in freshly isolated cardiomyocytes from the LV obtained by biopsy from the same animals. Myocytes will be studied under conditions with superfusion of: 1) calcium, 2) isoproterenol, 3) pimobendan, 4) alcohol, and 5) ANG II. In addition, the studies of myocytes response to ANG II will be repeated after preincubation with an AT1 receptor blocker, a protein kinase C inhibitor, or a Gi protein inhibitor, before, during and after the development of ADCM. These studies will be the first detailed longitudinal studies of cardiac and myocyte structure, function, [Ca2+]i transient, ICa,L during chronic alcohol intake. In addition, these studies will provide unique information on the role of the RAS and the mechanism of ADCM. These studies are necessary to extend our knowledge about the mechanism in the development of ADCM and help target therapy for ADCM.