Antiproliferative property of sphingosine 1-phosphate in rat hepatocytes involves activation of Rho via Edg-5
Antiproliferative property of sphingosine 1-phosphate in rat hepatocytes involves activation of Rho via Edg-5
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DOI：
10.1053/gast.2003.50049
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发表时间：
2003-02-01
期刊：
影响因子：
29.4
通讯作者：
Fujiwara, K
中科院分区：
文献类型：
--
作者：
Ikeda, H;Satoh, H;Fujiwara, K
背景和目标：鞘氨醇1-磷酸（S1 P）是G蛋白偶联的内皮分化基因-1（Edg-1）、Edg-3、Edg-5、Edg-6和Edg-8的配体，引起细胞的多种反应。其中突出的是细胞增殖。S1 P大量储存在血小板中并在其活化时释放，表明S1 P在体内起病理生理作用。由于注射的S1 P的大部分分布在小鼠的肝脏中，我们想知道肝脏是否是其靶点之一。研究了S1 P对肝细胞（肝脏中的主要组成细胞）的影响。方法和结果：北方印迹分析显示，在培养的大鼠肝细胞中Edg-1和Edg-5信使RNA（mRNA）的表达，其中S1 P减少肝细胞生长因子（HGF）或表皮生长因子（EGF）诱导的DNA合成，而不影响总蛋白质合成。用C3外毒素灭活小G（i）Rho可减弱这种抑制作用，但用百日咳毒素灭活G（i）则不会减弱这种抑制作用。此外，在JTE-013，一个新开发的和特异性的结合拮抗剂Edg-5的存在下，抑制作用也被取消。最后，在大鼠70%部分肝切除术后给予S1 P降低了肝细胞中DNA合成的峰值，同时增加了Rho活性。此外，肝部分切除术后24-72小时，肝细胞中Edg-5而不是Edg-1 mRNA表达增强，这与肝细胞增殖减少一致。结论：S1 P通过Edg-5激活Rho，具有抗大鼠肝细胞增殖的特性。我们的研究结果提高了S1 P在肝再生中是负调节剂的可能性。
Background & Aims: Sphingosine 1-phosphate (S1P), a ligand for G protein-coupled endothelial differentiation gene-1 (Edg-1), Edg-3, Edg-5, Edg-6, and Edg-8, elicits a variety of responses by cells. Prominent among these is cell proliferation. S1P is abundantly stored in platelets and released upon their activation, suggesting that S1P plays a pathophysiologic role in vivo. Because the major part of injected S1P was distributed into the liver in mice, we wondered whether the liver would be one of its targets. The effects of S1P on hepatocytes, the major constituent cells in the liver, were examined. Methods & Results: Northern blot analysis revealed the expression of Edg-1 and Edg-5 messenger RNA (mRNA) in cultured rat hepatocytes, in which S1P decreased DNA synthesis induced by hepatocyte growth factor (HGF) or epidermal growth factor (EGF) without affecting total protein synthesis. This inhibitory effect was attenuated by inactivation of small GTPase Rho with C3 exotoxin but not by inactivation of G(i) with pertussis toxin. Moreover, in the presence of JTE-013, a newly developed and specific binding antagonist for Edg-5, the inhibitory effect was also cancelled. Finally, the administration of S1P after 70% partial hepatectomy in rats reduced the peak of DNA synthesis in hepatocytes with increased Rho activity. Furthermore, Edg-5 but not Edg-1 mRNA expression was enhanced in hepatocytes 24-72 hours after partial hepatectomy, which coincides with decreasing hepatocyte proliferation. Conclusions: S1P has an antiproliferative property in rat hepatocytes by activating Rho via Edg-5. Our results raise the possibility that S1P is a negative regulator in liver regeneration.