Objective To investigate the therapeutic effect and underlying mechanism of piceatannol against hepatic ischemia-reperfusion injury (HIRI) in fatty liver.

Methods A mouse model of fatty liver combined with HIRI was established, and experimental animals were assigned into four groups: sham operation group, fatty liver HIRI group, fatty liver HIRI + piceatannol group, and fatty liver HIRI + piceatannol + ML385 group (n=5). Serum levels of alanine transaminase (ALT), aspartate transaminase (AST) and lactate dehydrogenase (LDH) were detected in each group. Hepatic tissue injury was evaluated by hematoxylin-eosin staining. Biochemical assays were performed to measure the contents of malondialdehyde (MDA), glutathione (GSH) and superoxide dismutase (SOD). Reactive oxygen species (ROS) were quantified using the DHE fluorescent probe method, while the expression of 4-hydroxynonenal (4-HNE) was determined via immunohistochemical staining. Western blot was adopted to detect the protein expression of glutathione peroxidase 4 (GPX4), acyl-CoA synthetase long-chain family member 4 (ACSL4), heme oxygenase-1 (HO-1) and nuclear factor E2-related factor 2 (Nrf2). Primary mouse hepatocytes were isolated and cultured in vitro. After treatment with palmitic acid, an hypoxia/reoxygenation (H/R) model was established. Cellular experiments were divided into control group, steatosis H/R group, steatosis H/R + piceatannol group, and steatosis H/R + piceatannol + ML385 group. Calcein-AM/PI dual staining was used to observe cell viability, C11 BODIPY staining was used to determin lipid peroxidation levels, and DCFH-DA fluorescent probe was utilized to test intracellular ROS levels. Western blot was used to detect the protein abundances of GPX4, ACSL4, HO-1 and Nrf2, and real-time fluorescence quantitative polymerase chain reaction was applied to quantify their corresponding messenger RNA (mRNA) expression levels.

Results Compared with the sham operation group, the levels of ALT, AST and LDH, liver injury score, DHE positive rate, MDA level and 4-HNE level increased, the levels of GSH and SOD decreased, the relative expression level of ACSL4 protein increased, and the relative expression levels of GPX4, Nrf2 and HO-1 proteins decreased in the fatty liver HIRI group; compared with the fatty liver HIRI group, the levels of ALT, AST and LDH, liver injury score, DHE positive rate, MDA level and 4-HNE level decreased, the levels of GSH and SOD increased, the relative expression level of ACSL4 protein decreased, and the relative expression levels of GPX4, Nrf2 and HO-1 proteins increased in the fatty liver HIRI + piceatannol group; compared with the fatty liver HIRI + piceatannol group, the levels of ALT, AST and LDH, liver injury score, DHE positive rate, MDA level and 4-HNE level increased, the levels of GSH and SOD decreased, the relative expression level of ACSL4 protein increased, and the relative expression levels of Nrf2 and HO-1 proteins decreased in the fatty liver HIRI + piceatannol + ML385 group (all P<0.05). Compared with the control group, the mean fluorescence intensity of DCFH-DA and MDA level increased, the levels of GSH and SOD decreased, the proportion of oxidized lipids increased, the protein and mRNA expression levels of ACSL4 increased, and the protein and mRNA expression levels of GPX4, HO-1 and Nrf2 decreased in the steatosis H/R group; compared with the steatosis H/R group, the mean fluorescence intensity of DCFH-DA and MDA level decreased, the levels of GSH and SOD increased, the proportion of oxidized lipids decreased, the relative protein and mRNA expression levels of ACSL4 decreased, and the relative protein and mRNA expression levels of GPX4, HO-1 and Nrf2 increased in the steatosis H/R + piceatannol group; compared with the steatosis H/R + piceatannol group, the mean fluorescence intensity of DCFH-DA and MDA level increased, the levels of GSH and SOD decreased, the proportion of oxidized lipids increased, the relative protein and mRNA expression levels of ACSL4 increased, and the relative protein and mRNA expression levels of GPX4, HO-1 and Nrf2 decreased in the steatosis H/R + piceatannol + ML385 group (all P<0.05).

Conclusions Piceatannol relieves HIRI in fatty liver by activating the Nrf2/HO-1 signaling pathway to suppress ferroptosis in hepatocytes.