烟酰胺单核苷酸通过Sirt3减轻心脏死亡供肝诱导的缺血-再灌注损伤

目的  探讨烟酰胺单核苷酸（NMN）对大鼠心脏死亡供肝诱导的缺血-再灌注损伤（IRI）的作用及机制。方法  通过“磁环+双袖套”法建立大鼠原位肝移植模型。将SD大鼠随机分为假手术组（Sham组）、原位肝移植组（OLT组）、NMN处理+原位肝移植组（NMN组）、NMN+去乙酰化酶-3（Sirt3）抑制剂（3-TYP）+原位肝移植组（NMN+3-TYP组）。观察各组大鼠肝组织病理学改变及肝细胞凋亡情况，检测血清丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）水平，测定肝组织超氧化物歧化酶（SOD）和丙二醛（MDA）含量，检测肝组织Sirt3、微管相关蛋白1轻链3（LC3）Ⅱ、PTEN诱导假定激酶1（PINK1）、Parkin、线粒体外膜转位酶20（TOMM20）表达水平。分析各组大鼠术后生存情况。结果  与Sham组比较，OLT组ALT、AST水平升高；与OLT组比较，NMN组ALT、AST水平均下降；与NMN组比较，NMN+3-TYP组ALT、AST水平升高（均为P < 0.05）。
Sham组大鼠肝组织结构基本正常；OLT组大鼠肝组织可见明显的淤血、空泡变性和肝细胞坏死等病理改变。OLT组Suzuki评分、细胞凋亡率较Sham组升高；NMN组Suzuki评分、细胞凋亡率较OLT组降低；NMN+3-TYP组Suzuki评分、细胞凋亡率较NMN组升高（均为P < 0.05）。与Sham组比较，OLT组SOD含量下降，MDA含量升高；与OLT组比较，NMN组SOD含量升高，MDA含量下降；与NMN组比较，NMN+3-TYP组SOD含量下降，MDA含量升高（均为P < 0.05）。与Sham组比较，OLT组Sirt3、TOMM20蛋白相对表达量下降，PINK1、Parkin、LC3Ⅱ蛋白相对表达量升高；与OLT组比较，NMN组Sirt3、PINK1、Parkin、LC3Ⅱ蛋白相对表达量升高，TOMM20蛋白相对表达量下降；与NMN组比较，NMN+3-TYP组PINK1、Parkin、LC3Ⅱ蛋白相对表达量下降，TOMM20蛋白相对表达量升高（均为P < 0.05）。Sham组、OLT组、NMN组、NMN+3-TYP组大鼠术后7 d生存率分别为100%、50%、75%、58%。结论  NMN可通过上调Sirt3，增强肝脏抗氧化能力及诱导PINK1/Parkin介导的线粒体自噬，减轻肝IRI，从而对心脏死亡供肝发挥保护作用。

Nicotinamide mononucleotide attenuates ischemia-reperfusion injury induced by donor liver from cardiac death through Sirt3

Objective To evaluate the effect and mechanism of nicotinamide mononucleotide (NMN) on ischemia-reperfusion injury (IRI) induced by donor liver after cardiac death in rat models. Methods Rat models of orthotopic liver transplantation were established by "magnetic ring + double cuff" method. SD rats were randomly divided into the sham operation group (Sham group), orthotopic liver transplantation group (OLT group), NMN treatment + orthotopic liver transplantation group (NMN group), NMN+sirtuin-3 (Sirt3) inhibitor (3-TYP) + orthotopic liver transplantation group (NMN+3-TYP group), respectively. Pathological changes and hepatocyte apoptosis of the rats were observed in each group. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were determined. Superoxide dismutase (SOD) and malondialdehyde (MDA) contents in liver tissues were detected. The expression levels of Sirt3, microtubule-associated protein 1 light chain 3 (LC3)Ⅱ, PTEN-induced putative kinase 1 (PINK1), Parkin and translocase of the outer mitochondrial membrane 20 (TOMM20) in liver tissues were measured. Postoperative survival of the rats in each group was analyzed. Results Compared with the Sham group, serum ALT and AST levels were higher in the OLT group. Compared with the OLT group, the levels of ALT and AST were decreased in the NMN group. Compared with the NMN group, the levels of ALT and AST were increased in the NMN +3-TYP group (all P < 0.05). The liver tissue structure of rats in the Sham group was basically normal. In the OLT group, pathological changes, such as evident congestion, vacuolar degeneration and hepatocyte necrosis, were observed in the liver tissues.
Compared with the Sham group, Suzuki score and apoptosis rate were higher in the OLT group. Suzuki score and apoptosis rate in the NMN group were lower than those in the OLT group. Suzuki score and apoptosis rate in the NMN+3-TYP group were higher compared with those in the NMN group (all P < 0.05). Compared with the Sham group, the SOD content was decreased, whereas the MDA content was increased in the OLT group. Compared with the OLT group, the SOD content was increased, whereas the MDA content was decreased in the NMN group. Compared with the NMN group, the SOD content was decreased, whereas the MDA content was increased in the NMN+3-TYP group (all P < 0.05). Compared with the Sham group, the relative expression levels of Sirt3 and TOMM20 proteins were down-regulated, whereas those of PINK1, Parkin and LC3Ⅱproteins were up-regulated in the OLT group. Compared with the OLT group, the relative expression levels of Sirt3, PINK1, Parkin and LC3Ⅱproteins were up-regulated, whereas that of TOMM20 protein was down-regulated in the NMN group. Compared with the NMN group, the relative expression levels of PINK1, Parkin and LC3Ⅱproteins were down-regulated, whereas that of TOMM20 protein was up-regulated in the NMN+3-TYP group (all P < 0.05). In the Sham group, the 7 d survival rate of rats was 100%, 50% in the OLT group, 75% in the NMN group and 58% in the NMN+3-TYP group, respectively. Conclusions NMN may enhance the antioxidative capacity of the liver, induce PINK1/Parkin-mediated mitochondrial autophagy, and alleviate IRI of the liver by up-regulating Sirt3, thereby playing a protective role in the donor liver after cardiac death.