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Abstract：
Sphingosine-1-phosphate (S1P), a bioactive lysophospholipid, is generated and released at sites of tissue injury in the heart and can act on S1P1, S1P2, and S1P3 receptor subtypes to affect cardiovascular responses. We established that S1P causes little phosphoinositide hydrolysis and does not induce hypertrophy indicating that it does not cause receptor coupling to Gq. We previously demonstrated that S1P confers cardioprotection against ischemia/reperfusion by activating RhoA and its downstream effector PKD. The S1P receptor subtypes and G proteins that regulate RhoA activation and downstream responses in the heart have not been determined. Using siRNA or pertussis toxin to inhibit different G proteins in NRVMs we established that S1P regulates RhoA activation through Gα13 but not Gα12, Gαq, or Gαi. Knockdown of the three major S1P receptors using siRNA demonstrated a requirement for S1P3 in RhoA activation and subsequent phosphorylation of PKD, and this was confirmed in studies using isolated hearts from S1P3 knockout (KO) mice. S1P treatment reduced infarct size induced by ischemia/reperfusion in Langendorff perfused wild-type (WT) hearts and this protection was abolished in the S1P3 KO mouse heart. CYM-51736, an S1P3-specific agonist, also decreased infarct size after ischemia/reperfusion to a degree similar to that achieved by S1P. The finding that S1P3 receptor- and Gα13-mediated RhoA activation is responsible for protection against ischemia/reperfusion suggests that selective targeting of S1P3 receptors could provide therapeutic benefits in ischemic heart disease.
摘要：
1-磷酸鞘氨醇(S1P),一种生物活性溶血磷脂,在心脏组织损伤部位产生和释放，并可作用于S1P1，S1P2和S1P3受体亚型以影响心血管反应。我们确定S1P几乎不会引起磷酸肌醇水解，并且不会诱导肥大，表明它不会导致受体与Gq偶联。我们先前证明了S1P通过激活RhoA及其下游效应物PKD赋予针对缺血/再灌注的心脏保护作用。尚未确定调节心脏中RhoA激活和下游反应的S1P受体亚型和G蛋白。使用siRNA或百日咳毒素抑制NRVM中的不同G蛋白，我们确定S1P通过Gα13而不是Gα12，Gαq，或者Gαi.使用siRNA敲除三种主要的S1P受体证明了在RhoA激活和随后的PKD磷酸化中需要S1P3,这在使用S1P3敲除（KO）小鼠的离体心脏的研究中得到了证实。S1P处理减少了Langendorff灌注野生型（WT）心脏中缺血/再灌注引起的梗塞面积，并且在S1P3KO小鼠心脏中这种保护被废除。CYM-51736，一种S1P3特异性激动剂，缺血/再灌注后梗死面积也减少到与S1P相似的程度。S1P3受体和Gα13介导的RhoA激活负责保护免受缺血/再灌注的发现表明S1P3受体的选择性靶向可以在缺血性心脏病中提供治疗益处。
