MAXIK CHANNELS IN AGING CORONARY SMOOTH MUSCLE

这项建议的长期目标是确定导致冠状动脉平滑肌兴奋性增加的增龄相关机制，重点是K通道的作用。主要假说认为，KCA通道作为冠状动脉张力的关键参与者，受强大的血管活性物质的调节，其表达和/或调节可能随着年龄的增长而减弱。因此，KCA通道维持最佳动脉张力的能力在老年人中减弱。这一假说将通过研究青年-成人、成熟和衰老受试者冠状动脉中KCA通道的丰度、其分子组成(α+/β亚基)、对血管活性物质的反应和调节机制(S)来验证。Kca通道广泛存在于各种物种的血管平滑肌中。我们和其他人已经证明，KCA通道设定了大脑动脉和子宫肌层的平滑肌收缩水平。我们的初步数据表明：1)KCA通道在人和大鼠冠状动脉中含量丰富，并受一个β亚基的正向调节；2)它们受强大的血管活性代谢物如血栓素A2(TXA2)和一氧化氮(NO)的调节；3)冠状动脉平滑肌的衰老与KCA通道的表达和功能下调有关；4)它们在冠状动脉张力的控制中起着关键作用。我们想要回答的问题是：1)KCA通道对冠状动脉张力的调节是否受衰老的影响？2)KCA通道的功能表达和/或特征在衰老过程中是否发生变化？3)KCA通道的α和β亚基在不同年龄段是否同等表达或分布？4)KCA通道受强大的血管活性物质(如TXA2或NO)的调节是否受衰老的影响？我们将使用电生理、生化、免疫化学和机械相结合的方法。具体目的是比较年轻、成熟和衰老的受试者(大鼠和人)：1)对KCA通道阻滞剂和激动剂的收缩反应；2)通道的功能表达、生物物理性质和药理学；3)成孔α和调节β亚基的相对丰富；4)通道对血管活性物质(如TXA2、NO)的反应及其调节机制(S)。这项研究将有助于我们了解与年龄相关的冠状动脉血管反应性的变化，并可能在设计临床治疗方法以减少冠状动脉痉挛和心功能障碍方面有所帮助。

The long term goal of this proposal is to identify mechanisms responsible for the aging associated rise in coronary smooth muscle excitability, with emphasis on the role of K channels. The main hypothesis postulates that KCa channels, as key players of coronary arterial tone, are regulated by potent vasoactive substances and that their expression and/or modulation may decrease with aging. Thus, the capacity of KCa channels to maintain an optimal arterial tone is diminished in the elderly. This hypothesis will be tested by studying in coronary arteries of young-adult, mature and senescent subjects the abundance of KCa channels, their molecular constituents (alpha +/- beta subunits), response to vasoactive substances and mechanism(s) of regulation. KCa channels are abundant in vascular smooth muscle of various species. We and others have shown that KCa channels set the level of smooth muscle contractility in cerebral arteries and myometrium. Our preliminary data indicate that: 1) KCa channels are abundant in human and rat coronary arteries and are positively regulated by a beta subunit; 2) they are modulated by potent vasoactive metabolites like thromboxane A2 (TXA2) and nitric oxide (NO); 3) aging of coronary smooth muscle is associated with a downregulation of KCa channel expression and function; 4) they play a critical role in the control of coronary arterial tone. The questions that we want to answer are: 1) is regulation of coronary arterial tone by KCa channels affected by aging? 2) does the functional expression and/or characteristics of KCa channels change in the aging process? 3) are the alpha and beta subunits of KCa channels equally expressed or distributed at different ages? 4) is the modulation of KCa channels by potent vasoactive substances (e.g. TXA2 or NO) affected by aging? We will use a combined electrophysiological, biochemical, immunochemical, and mechanical approach. The specific aims are to compare in young, mature and senescent subjects (rats and humans): 1) the contractile responses to KCa channel blockers and agonists; 2) the channel functional expression, biophysical properties, and pharmacology; 3) the relative abundance of the pore-forming alpha and regulatory beta subunits; and 4) the channel response to vasoactive substances (e.g. TXA2, NO) and their mechanism(s) of modulation. This study will aid our understanding of age-related changes of coronary vasoreactivity, and possibly in the design of clinical treatments that reduce coronary spasm and heart dysfunction.