Beta3-Adrenergic Receptor & Progression to Heart Failure

描述（由申请人提供）：我们实验室的初步数据显示，在CHF中，β -肾上腺素能受体（AR）刺激引起的正常心肌的心脏抑制被放大，这表明β -AR激活在CHF中有直接的不良功能后果。该资助的目的是：1)表征心房β 3- ar介导的左心室（LV）功能反应在CHF发生前和发生时的变化，并评估时间过程，以确定心脏β 3- ar在CHF患者儿茶酚胺（NE）异常反应中的因果作用；2)确定β - ar介导的改变的肌力反应的细胞和分子机制。我们将检验假设：[H1]心力衰竭后，由于(i) β - ar介导的正性肌力反应减弱和(ii) β - ar介导的左室抑制和心肌细胞收缩和舒张增强，外源性和内源性NE的心功能反应发生改变。（iii）在伴有CHF的运动期间，由于循环和心肌NE水平的增加，β 3-AR激活在CHF中的不良功能影响可能会加剧，[H2] (i)由于CHF肌细胞中β 3-AR表达增加，（ii）伴随着对[Ca2+]i调节的增强负调节。（iii）这些效应与Gi有关，（iv）涉及一氧化氮（NO）依赖和NO独立的信号转导途径。[H3]慢性a1-AR阻滞剂可减弱，而β - ar拮抗剂可预防左室和心肌细胞功能损害，限制CHF的进展。研究将在起搏诱导的CHF之前和之后，在休息和运动期间，以及在CHF之前和之后从这些动物的左室心肌中分离的肌细胞中进行。我们将比较心肌细胞β 3- ar mRNA和蛋白水平；在接受β 1和β 3-AR阻滞剂治疗三周后，CHF进展前和CHF进展时，LV和心肌细胞收缩，[ca2 +]是短暂的，ca2 +电流反应。NO和抑制性G蛋白参与受体激活的信号转导将通过L-NAME和PTX来评估。这些研究将是第一个详细的纵向研究心脏β 3- ar基因表达，以及在临床相关的高等哺乳动物CHF模型中，在CHF发生前和进展过程中休息和运动时的功能影响。这些研究是必要的，以扩大我们对心脏β - ar调节和这些受体在CHF中儿茶酚胺异常反应中的作用的认识。因此，为CHF功能损害进展的机制提供了有价值的新见解，并可能有助于CHF的特异性靶向治疗。

DESCRIPTION (provided by applicant): Preliminary data from our laboratory revealed that in CHF, beta3-adrenergic receptor (AR) stimulation-induced cardiac depression on the normal myocardium is amplified, thus suggesting a direct adverse functional consequence of beta3-ARs activation in CHF. The purpose of this grant is to 1) characterize alterations of a3-AR-mediated functional responses of left ventricle (LV) before and as CHF progresses and assess the time course to establish a contributing causal role of cardiac beta3-AR in the abnormal responsiveness of catecholamine (NE) with CHF; and 2) define the cellular and molecular mechanisms of the altered beta3-AR-mediated inotropic response. We will test Hypothesis: [H1] after CHF, cardiac functional responses to exogenous and endogenous NE are altered due to (i) attenuated beta1-AR-mediated positive inotropic responses and (ii) an enhanced beta3-AR-mediated depression in LV and myocyte contraction and relaxation. (iii) During exercise with CHF, the adverse functional effects of beta3 -AR activation in CHF may be accentuated, due to increases in circulating and myocardial levels of NE, which [H2] (i) results from an increased expression of beta3-AR in CHF myocytes, (ii) accompanied with an enhanced negative modulation on [Ca2+]i regulation. (iii) These effects are linked with Gi, (iv) involving both nitric oxide (NO)-dependent and NO-independent signal transduction pathways. [H3] Chronic a1-AR blocker may attenuate, while beta3-AR antagonist may prevent LV and myocyte functional impairment and limits the progression of CHF. Studies will be conducted in chronically instrumented conscious dogs before and after pacing-induced CHF at rest and during exercise and in myocytes isolated from LV myocardium obtained by biopsy from these same animals before and after CHF. We will compare myocyte beta3-AR mRNA and protein levels; and LV and myocyte contractile, [Ca 2+]i transient, and Ca 2+ current responses to beta3- AR agonist or beta3-AR antagonist before and as CHF progresses and CHF after received three weeks of treatment with beta1-and beta3-AR blockers. The involvement of NO, and inhibitory G proteins in receptor-activated signal transduction will be evaluated by using L-NAME, and PTX. These studies will be the first detailed longitudinal study of the cardiac beta3-AR gene expression, and its functional effects at rest and during exercise before and during the progression of CHF in a clinically relevant higher mammal model of CHF. These studies are necessary to extend our knowledge regarding the cardiac beta-AR regulation and the role of these receptors in the abnormal responsiveness of catecholamine in CHF. Thus, provide valuable new insight into the mechanism of the progression of functional impairment in CHF, and may assist in specifically targeting therapy for CHF.