Regulation of calcium-activated potassium channels by blood breakdown products

描述(由申请人提供)：我们中的许多人最终都会患上血管疾病，如高血压和脑出血。脑出血后常伴有迟发性脑血管痉挛，这本身就是一个重要的发病率和死亡率因素。脑血管痉挛的特征是血管平滑肌细胞持续的异常收缩。以前的研究表明，血液分解产物，如血红素、一氧化碳、胆红素和胆红素氧化终末产物(BOX)可能参与其中，但其潜在机制仍不清楚。在参与血管平滑肌调节的众多蛋白质中，大电导钙电压激活钾通道(Slo1BK)在血管松弛中起着关键作用。Slo1通道在调节血管张力中的重要性表明，许多血管松弛障碍，包括脑血管痉挛，可能与Slo1通道的调节失调有关。由于胆红素和胆红素氧化终末产物与血管痉挛有关，而Slo1通道在调节血管张力中起关键作用，我们推测血红素分解代谢产物可能通过调节Slo1通道而参与脑血管痉挛。为了验证这一假说，我们通过宏观和单通道离子电流以及宏观门控电流的测量，从电生理学和定量的角度研究了血红素分解产物(一氧化碳、胆红素和胆红素氧化终产物)对Slo1通道功能的影响。这些生物物理测量与生理等长力测量相补充，使用来自野生型和Slo1基因敲除小鼠的主动脉血管进行测量。所提出的研究计划的预期结果将建立Slo1感知CO的新范式，并将强调Slo1通道是脑出血和脑血管痉挛之间的重要因果联系。这些新的概念框架反过来又为包括迟发性脑血管痉挛在内的血管松弛障碍提出了新的治疗策略。

DESCRIPTION (provided by applicant): Many of us will be eventually afflicted with vascular disorders, such as hypertension and brain hemorrhage. Cerebral hemorrhage is often followed by delayed cerebral vasospasm, which itself represents a significant morbidity and mortality factor. Cerebral vasospasm is characterized by a long-lasting abnormal contraction of vascular smooth muscle cells. Previous studies have suggested that blood breakdown products, such as heme, CO, bilirubin and bilirubin oxidation end products (BOXes), may be involved but the underlying mechanism has remained elusive. Among the many proteins involved in regulation of vascular smooth muscles, large-conductance calcium- and voltage-activated (Slo1 BK) potassium channels play a critical role in vascular relaxation. The importance of Slo1 channels in regulation of vascular tone suggests that many disorders of vascular relaxation, including cerebral vasospasm, may involve dysregulation of Slo1 channels. Because bilirubin and bilirubin oxidation end products are implicated in vasospasm and Slo1 channels play a critical role in regulation of vascular tone, we hypothesize that heme catabolic products may contribute to cerebral vasospasm by modulating Slo1 channels. To test this hypothesis, effects of heme catabolic products (CO, bilirubin and bilirubin oxidation end products) on the Slo1 channel function are electrophysiologically and quantitatively investigated using macroscopic and single-channel ionic current and macroscopic gating current measurements. These biophysical measurements are complemented with physiological isometric force measurements using aortic blood vessels from wild-type and Slo1 knockout mice. The results expected from the research program proposed will establish a new paradigm of CO sensing by Slo1 and will highlight Slo1 channels as an important causal link between cerebral hemorrhage and cerebral vasospasm. These novel conceptual frameworks in turn suggest new therapeutic strategies for disorders of vascular relaxation including delayed cerebral vasospasm.