BIX激活内质网应激促进大鼠小体积肝移植物中脂肪代谢稳定并减轻移植物的脂毒性损伤

We constructed differentiated protein profiles of rat small-for-size liver grafts (SFSGs) in the previous studies. BIP/Grp78 expression was significantly increased from 6h to 24h after reperfusion, with highest expression at 48h post-reperfusion. BIP is an important marker for ERS and UPR activation, suggesting that the ERS and UPR activation occurred in SFSGs. Through Western blot, RT-PCR, Chip and IP et al, we are going to explore molecular mechanisms of SFSGs injury, related to IRE1α－XBP1, PERK－eIF2α and ATF6 pathways, associated to ERS and UPR; On the other hand, result of HE , triglycerides content detection and Oil Red staining, showed that disorders of lipid metabolism happened in rat SFSGs, especially during 24h and 48h after reperfusion. Downstream transcription factors of three ERS and UPR associated pathways are an important regulators of lipid metabolism by regulating transcription of lipid metabolic genes. we hypothesized that in SFSGs, ERS and UPR activated IRE1α－XBP1, PERK－eIF2α and ATF6 pathways, which regulated expression of lipid metabolism related transcription factors, further lipid metabolic genes, resulting in lipid metabolism homeostasis imbalance. BIX was a small molecule drug recently discovered as BIP specific inducer and could reduce a variety of tissues and cell injury by hypoxia through activation of the ERS and the UPR. In this project, our team intend to explore whether BIX could activate ERS and UPR pathways, further attenuate SFSGs injury and favor maintaining lipid metabolic homeostasis of SFSGs.

前期构建的大鼠小体积肝移植物差异蛋白表达谱提示BIP/Grp78在再灌注后24h、48h的小肝移植物中高表达，BIP是ERS及UPR激活的分子标志，提示ERS及UPR在小体积肝移植物中激活，通过免疫印迹及RT-PCR探讨ERS及UPR的三条途径在小体积肝移植物早期损伤中的作用及分子机制；另一方面HE及甘油三酯的检测提示大鼠小体积肝移植物中出现脂肪代谢的紊乱，而ERS及UPR的三条途径及其下游的多个转录因子都是脂肪代谢的重要调节因子；我们推测小肝移植物中ERS及UPR的激活引起脂肪代谢相关转录因子的表达异常，并进一步引起脂肪代谢相关基因表达改变，从而导致脂肪代谢内稳态的失衡；BIX是BIP的特异性诱导小分子，能通过ERS及UPR的激活减轻多种组织和细胞的缺血缺氧损伤，本课题拟将BIX作为ERS及UPR的激活剂，探讨BIX激活ERS及UPR对小体积肝移植损伤的保护作用及维持脂肪代谢内稳态的作用

本项目已初步阐明ERs及UPR三条途径的激活是小肝移植物早期损伤的重要机制，证明小肝移植物中发生脂肪代谢内稳态的失衡的现象，脂肪代谢相关基因受到ERs及UPR通路中重要转录因子GADD34,PPARγ,C/EBPα和C/EBPβ等的调控，这条通路是小肝移植物中发生脂肪代谢内稳态失衡的重要分子机制；脂毒性凋亡是ERs引起小肝移植物损伤的重要机制，而BIX可以通过调控ERs维持小体积肝移植物脂肪代谢的内稳态，减轻ERs引起的脂毒性凋亡对小肝移植物的损伤，从而达到保护小肝移植物的作用。本项目的顺利完成为预防小肝综合症，更为常规使用小体积供肝，缓解移植供体匮乏提供新的切入点和实验依据。