鞘氨醇激酶I在药物诱导的急性肝损伤和炎症中的分子机制研究

Drug induced liver injury is a major cause of acute liver failure, with limited therapeutic options. Sphingosine kinase (SphK) 1 and 2, which catalyse the formation of the bioactive lipid sphingosine 1-phosphate (S1P), are involved in many pathophysiological processes. The current study employed the use of SphK1 deficient mice to elucidate the critical role of this enzyme in the pathogenesis of APAP-induced liver injury. We first discovered that SphK1 deficient mice were protected from APAP toxicity. Tissue histology, leukocyte infiltration, serum AST and ALT levels exhibited significantly less liver injury and inflammation, compared to wild type mice. Further, we will check the role for SphK1 in the molecular mechanisms of hepatic cell death, including mitochondrial permeability transition, endoplasmic reticulum stress, the up-regulation of cell apoptotic related protein, such as, Bax and Caspase-3/9. S1P modulates HDAC activities either by direct binding or through activation of nuclear reactive oxygen species and regulates pro-inflammatory gene expression. We will also check whether the deficiency of SphK1 will lead to any impact on HDACs activities. Finally, we will examine systemically the activation of how many molecules or pathways will be affected by the deficiency of SphK1 in the APAP induced hepatocyte activation. Overall, if we can make real progress in the understanding of the role for SphK1in the pathogenesis of APAP-induced liver injury. Therefore, the blockade of Sphingosine kinase activities and its related signaling might represent potential treatment strategies for APAP-induced liver injury.

药物性肝损伤是引起急性肝功能衰竭的主要原因，临床治疗方法局限。鞘氨醇激酶（SphKs）包含两种亚型，SphK1和SphK2，可催化鞘氨醇形成1-磷酸-鞘氨醇（S1P），在多种生理病理过程中发挥重要作用。我们的前期研究发现，用对乙酰氨基酚（APAP）诱导小鼠肝损伤后，SphK1-/-小鼠的肝脏组织病理学、免疫细胞浸润、以及血清转氨酶水平较野生型小鼠均显著减轻。本课题将进一步从线粒体渗透性转变、内质网应激、细胞凋亡相关蛋白（包括Bax和Caspase-3/9）的上调、以及组蛋白去乙酰化酶（HDACs）的活性等机制方面探索SphK1影响肝细胞死亡的具体分子机制。本课题将为阐明SphK1在APAP诱导的肝损伤和炎症中的作用，以及通过阻断SphK1及其相关信号分子来治疗肝损伤提供一条崭新的线索。

研究背景：.过量服用对乙酰氨基酚（APAP）是引起药物性急性肝衰竭的主因。鞘氨醇-1-磷酸 (S1P)信号与人类健康和疾病密切相关、具有多种生物活性。..研究内容：.对8周龄雄性野生型C57BL/6J小鼠和SPHK1基因敲除小鼠腹腔注射高剂量APAP（250mg/kg体重），并与未处理组进行比较，探究SPHK1在APAP诱导的内质网应激以及肝细胞炎症中的重要作用。..研究结果：.与野生型小鼠相比，APAP处理后 SPHK1 敲除小鼠血清转氨酶水平显著低于野生型对照小鼠，也表现出更低程度的肝损伤和炎症。SPHK1缺失后通过影响IRE1α和PERK-eIF2α -ATF4的磷酸化以及激活转录因子4 (ATF4)和激活转录因子6 (ATF6)的激活，从而缓解了APAP诱导的内质网应激(ER stress)。同时，SPHK1缺乏影响了调节线粒体MPT的关键分子JNK、ASK1和GSK3β的激活。此外，SPHK1缺失降低组蛋白去乙酰化酶水平、促进p65和STAT1的乙酰化，导致炎症基因转录受损。补充外源性S1P可显著逆转内质网应激中PERK-eIF2α-ATF4通路和ATF6通路的激活，以及线粒体膜电位转换（MPT）的GSK3β、ASK1和JNK的激活。S1P受体拮抗剂FTY720和SPHK1抑制剂PF543均可显著改善APAP诱导的肝损伤，从而提高动物存活率。..科学意义：.我们的研究揭示了SPHK1通过促进内质网应激和MPT在APAP诱导的肝毒性中具有重要作用。