Ionic mechanisms of toluene cerebrovascular actions

甲苯（Tol）急性中毒是一个全球性的公共卫生问题。人类和动物数据 证明急性托尔中毒与脑灌注不足有关。血流量的减少是 Tol 引起的长期神经功能缺损和灾难性急性情况的重要决定因素，包括 死亡。值得注意的是，Tol 诱导的脑损伤减少的生物学靶点和机制 灌注情况未知。我们来自大鼠和小鼠的初步数据表明，与灌注不足一致， 急性暴露于中毒浓度的 Tol 会导致体外和活体脑动脉收缩 动物。因此，我们将通过偏离所有内容来弥补当前神经血管毒理学的知识空白 之前的工作重点关注 Tol 对中枢神经元离子通道的影响，以解决这一总体问题 假设：急性 Tol 暴露引起的脑动脉收缩主要是由于药物抑制 BK 型钾通道存在于动脉平滑肌 (SM) 本身中。这种药物的作用是 由产生 SM BK 表型的两个 BK 亚基对 Tol 的不同感应决定：通道- 形成 cbv1，其通过其胞质尾部结构域和 SM 丰富的调节性 β1 实现药物作用， 它下调 Tol 对通道和脑动脉功能的作用。我们将解决三个问题 概念上相关但可独立测试的具体目标 (SA)：SA1（现象学）将确定 急性中毒期间血液和脑中达到的 Tol 水平会收缩脑动脉，与其他因素无关 Tol 全身代谢、循环或内皮因子，但主要通过抑制 BK，这仅需要 两个 SM BK 亚基处于裸脂质环境中。 SA2（药物作用机制）将确定具体的 cbv1、β1 和变构门控过程的作用决定 Tol 对 BK 活性和脑动脉的作用 直径。 SA3（翻译方面）将证明β1水平自然发生的变化决定了 脑动脉分支对 Tol 诱导的收缩的不同脆弱性，而该亚基可用于 作为选择性小药物的治疗靶点来抵消 Tol 对脑血管的作用。测试建议的 目标，我们将使用多学科方法，包括 Tol 蒸气暴露范例和颅脑 体内窗口、体外肌源张力测定、新颖和选择性药理学工具， 工程小鼠、重组 DNA 和工程 BK 亚基、外源组织电穿孔 cDNA、生物素化和蛋白质印迹、脂质双层和膜片钳电生理学以及变构 门控分析。我们期望揭示介导 Tol- 的细胞靶点和分子机制 诱导脑血管收缩并为早期干预提供新的选择性药理学工具 Tol 会引起脑缺血，同时对其他器官有轻微的副作用。

Acute intoxication with toluene (Tol) constitutes a worldwide public health problem. Human and animal data demonstrate that acute Tol intoxication is associated with brain hypoperfusion. The decrease in blood flow is a significant determinant of Tol-induced long-term neurological deficits and catastrophic acute scenarios, including death. Remarkably, the biological targets and mechanisms underlying Tol-induced reduction in cerebral perfusion are unknown. Our preliminary data from rat and mouse show that, consistent with hypoperfusion, acute exposure to intoxicating concentrations of Tol leads to cerebral artery constriction both in vitro and in live animals. Thus, we will cover the current knowledge gap in neurovascular toxicology by departing from all previous work, which focused on Tol effects on central neuron ion channels, to address this overarching hypothesis: constriction of cerebral arteries by acute Tol exposure is primarily due to drug inhibition of potassium channels of the BK type present in the arterial smooth muscle (SM) itself. This drug action is determined by distinct sensing of Tol by the two BK subunits that give rise to the SM BK phenotype: channel- forming cbv1, which enables drug action through its cytosolic tail domain, and the SM-abundant, regulatory β1, which downregulates Tol actions on both channel and cerebral artery function. We will address three conceptually related, yet independently testable specific aims (SA): SA1 (phenomenology) will establish that Tol at levels reached in blood and brain during acute intoxication constricts cerebral arteries independently of Tol systemic metabolism, circulating or endothelial factors but by primarily inhibiting BK, which only requires the two SM BK subunits in a bare lipid environment. SA2 (mechanism of drug action) will identify the specific roles of cbv1, β1, and allosteric gating processes that determine Tol action on BK activity and cerebral artery diameter. SA3 (translational aspects) will prove that naturally occurring variations in β1 levels determine the differential vulnerability of brain arterial branches to Tol-induced constriction, whereas this subunit can be used as therapeutic target of selective small agents to counteract Tol action on brain vessels. To test the proposed aims, we will use a multidisciplinary approach that includes Tol vapor exposure paradigms and a cranial window in vivo, in vitro myogenic tone determinations, novel and selective pharmacological tools, engineered mice, recombinant DNA and engineered BK subunits, electroporation of tissues with foreign cDNAs, biotinylation and Western blotting, lipid bilayer and patch-clamp electrophysiology, and allosteric gating analysis. We expect to unveil the cellular targets and molecular mechanisms that mediate Tol- induced cerebrovascular constriction and to deliver new selective pharmacological tools for early intervention in Tol-induced brain ischemia, while having minor side effects in other organs.