【罂粟摘要】瞬态受体电位通道6的分子修饰调节小鼠恶性高热模型中的钙动态异常
瞬态受体电位通道6的分子修饰调节
小鼠恶性高热模型中的钙动态异常
药理学调制已表明，瞬时受体电位（TRPC）通道在恶性高热的发病机理中起重要作用。这项研究验证了以下假设：在小鼠恶性高热的模型中，基因上抑制TRPC6的功能可以部分改善肌肉阳离子动态平衡和对氟烷的反应。
本研究使用20只 RYR1-p.R163C小鼠和20只野生型小鼠以及20只非表达小鼠作为对照组，采用选择性的钙和钠微电极和Western blot技术检测了各组中过表达肌肉特异性非传导性显性负性TRPC6通道的作用。
与野生型小鼠肌肉相比，RYR1-p.R163C小鼠肌肉的细胞内钙和钠水平长期升高。非传导性TRPC6通道的转基因表达将小鼠肌肉细胞内钙从331±34nM（均数±标准差）降低至190±27nM（P<0.0001），将钠从15±1mM降低至11±1mM（P<0.0001）。它的表达将RYR1-p.R163C肌肉纤维中，TRPC6特异性激活剂hyperforin处理的细胞内Ca2+的增加从52％（348±37nM降至537±70nM）降低至14％（185±11nM至210±44nM）。对TRPC3和TRPC6表达的Western blot结果分析表明，预期的TRPC6增加是由于其显性负转基因的过表达和TRPC3表达的补偿性增加。尽管肌肉特异性显性负性TRPC6的表达能够调节氟烷暴露和延长细胞寿命（35±5分钟vs.15±3分钟；P<0.0001）期间细胞内钙的增加，但氟烷暴露20分钟后，钙开始缓慢且稳定地增加，最终导致细胞死亡。
这些数据支持以往的研究发现，即TRPC通道在引起与恶性高热致病的RYR1变体相关的细胞内钙和钠动态失调中起重要作用。然而，数据也表明，仅调节TRPC通道不足以防止暴露于恶性高热触发剂挥发性麻醉药的致死作用。
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文献来源：
Lopez J R, Uryash A, Adams J, et al. Molecular Modification of Transient Receptor Potential Canonical 6 Channels Modulates Calcium Dyshomeostasis in a Mouse Model Relevant to Malignant Hyperthermia.[J]. Anesthesiology, 2020.DOI:10.1097/ALN.0000000000003635.
BACKGROUND: Pharmacologic modulation has previously shown that transient receptor potential canonical (TRPC) channels play an important role in the pathogenesis of malignant hyperthermia. This study tested the hypothesis that genetically suppressing the function of TRPC6 can partially ameliorate muscle cation dyshomeostasis and the response to halothane in a mouse model relevant to malignant hyperthermia.
METHODS: This study examined the effect of overexpressing a muscle-specific nonconducting dominant-negative TRPC6 channel in 20 RYR1-p.R163C and 20 wild-type mice and an equal number of nonexpressing controls, using calcium- and sodium-selective microelectrodes and Western blots. RESULTS: RYR1-p.R163C mouse muscles have chronically elevated intracellular calcium and sodium levels compared to wild-type muscles. Transgenic expression of the nonconducting TRPC6 channel reduced intracellular calcium from 331 ± 34 nM (mean ± SD) to 190 ± 27 nM (P < 0.0001) and sodium from 15 ± 1 mM to 11 ± 1 mM (P < 0.0001). Its expression lowered the increase in intracellular Ca2+ of the TRPC6-specific activator hyperforin in RYR1-p.R163C muscle fibers from 52% (348 ± 37 nM to 537 ± 70 nM) to 14% (185 ± 11 nM to 210 ± 44 nM). Western blot analysis of TRPC3 and TRPC6 expression showed the expected increase in TRPC6 caused by overexpression of its dominant-negative transgene and a compensatory increase in expression of TRPC3. Although expression of the muscle-specific dominant-negative TRPC6 was able to modulate the increase in intracellular calcium during halothane exposure and prolonged life (35 ± 5 min vs. 15 ± 3 min; P < 0.0001), a slow, steady increase in calcium began after 20 min of halothane exposure, which eventually led to death.
CONCLUSIONS: These data support previous findings that TRPC channels play an important role in causing the intracellular calcium and sodium dyshomeostasis associated with RYR1 variants that are pathogenic for malignant hyperthermia. However, they also show that modulating TRPC channels alone is not sufficient to prevent the lethal effect of exposure to volatile anesthetic malignant hyperthermia-triggering agents.
翻译：易菁 编辑：佟睿 审校：曹莹