Sphingosine kinase-1 inhibition protects primary rat hepatocytes against bile salt-induced apoptosis

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• 作者：Golnar Karimian ; Manon Buist-Homan ; Martina Schmidt ; Uwe J.F. Tietge ; Jan Freark de Boer ; Karin Klappe ; Jan Willem Kok ; Laurent Combettes ; Thierry Tordjmann ; Klaas Nico Faber ; Han Moshage
• 关键词：Glycochenodeoxycholic acid ; Sphingosine kinase ; Calcium oscillation ; Cholestatic liver disease ; Sphingosine-1 phosphate ; Sphingosine-1 phosphate receptor
• 刊名：Biochimica et Biophysica Acta (BBA)/Molecular Basis of Disease
• 出版年：December, 2013
• 年：2013
• 卷：1832
• 期：12
• 页码：1922-1929
• 全文大小：773 K

文摘

Sphingosine kinases (SphKs) and their product sphingosine-1-phosphate (S1P) have been reported to regulate apoptosis and survival of liver cells. Cholestatic liver diseases are characterized by cytotoxic levels of bile salts inducing liver injury. It is unknown whether SphKs and/or S1P play a role in this pathogenic process. Here, we investigated the putative involvement of SphK1 and S1P in bile salt-induced cell death in hepatocytes. Primary rat hepatocytes were exposed to glycochenodeoxycholic acid (GCDCA) to induce apoptosis. GCDCA-exposed hepatocytes were co-treated with S1P, the SphK1 inhibitor Ski-II and/or specific antagonists of S1P receptors (S1PR₁ and S1PR₂). Apoptosis and necrosis were quantified. Ski-II significantly reduced GCDCA-induced apoptosis in hepatocytes (鈭?#xA0;70%, P < 0.05) without inducing necrosis. GCDCA increased the S1P levels in hepatocytes (P < 0.05). GCDCA induced [Ca^2 +] oscillations in hepatocytes and co-treatment with the [Ca^2 +] chelator BAPTA repressed GCDCA-induced apoptosis. Ski-II inhibited the GCDCA-induced intracellular [Ca^2 +] oscillations. Transcripts of all five S1P receptors were detected in hepatocytes, of which S1PR₁ and S1PR₂ appear most dominant. Inhibition of S1PR₁, but not S1PR₂, reduced GCDCA-induced apoptosis by 20%. Exogenous S1P also significantly reduced GCDCA-induced apoptosis (鈭?#xA0;50%, P < 0.05), however, in contrast to the GCDCA-induced (intracellular) SphK1 pathway, this was dependent on S1PR₂ and not S1PR₁. Our results indicate that SphK1 plays a pivotal role in mediating bile salt-induced apoptosis in hepatocytes in part by interfering with intracellular [Ca^2 +] signaling and activation of S1PR₁.