School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, 505A, Lo Kwee-Seong Integrated Biomedical Sciences Building, Area 39, Hong Kong SAR, China.
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, 505A, Lo Kwee-Seong Integrated Biomedical Sciences Building, Area 39, Hong Kong SAR, China; School of Traditional Chinese Medicine, Guangdong Pharmaceutical University, Guangzhou, China.
Phytomedicine. 2022 Jul 20;102:154162. doi: 10.1016/j.phymed.2022.154162. Epub 2022 May 13.
Misusage of pyrrolizidine alkaloid (PA)-containing plants or unaware intake of PA-contaminated foodstuffs causes thousands of PA poisoning cases in humans. PA intoxication is accompanied by oxidative stress and subsequent extensive hepatocellular damage. Our previous study has demonstrated that 18β-glycyrrhetinic acid (GA), a bioactive constituent of liquorice, prevented PA-induced hepatotoxicity in rats, however the underlying mechanisms remain unclear.
This study aims to explore the mechanisms underlying the hepato-protective effect of GA in combating retrorsine (RTS, a representative toxic PA)-induced liver injury.
Histological and biochemical assessments were employed to evaluate the protective effect of GA on RTS-induced hepatotoxicity in rats. Sulforhodamine B assay, real-time PCR, western blotting, and immunostaining were used to explore the underlying mechanisms in human hepatocytes and rats.
Our findings demonstrated that GA alleviated RTS-induced elevation of serum ALT and bilirubin levels, as well as hepatocytes necrosis and sinusoidal endothelial cells (SECs) damage in rats. GA also enhanced the activities and expressions of several antioxidant enzymes through upregulating nuclear factor-erythroid 2-related factor2 (Nrf2). Moreover, inhibition of Nrf2 blocked the hepatoprotective effect of GA against RTS intoxication. Mechanistically, GA increased the phosphorylation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and enhanced glycogen synthase kinase 3 beta (GSK3β) inhibitory phosphorylation at serine 9, thus promoting the nuclear accumulation of Nrf2 and activating its downstream targets.
This study for the first time demonstrated that GA exerted protective effects against RTS-induced liver injury by potentiating the Nrf2-mediated antioxidant system through PI3K/Akt/GSK3β pathway. The findings indicated that GA may serve as a potential candidate drug for the treatment of PA intoxication.
吡咯里西啶生物碱（PA）含量植物的误用或未意识到的摄入 PA 污染的食物会导致数千例人类 PA 中毒病例。PA 中毒伴有氧化应激和随后广泛的肝细胞损伤。我们之前的研究表明，甘草中的生物活性成分 18β-甘草酸（GA）可预防大鼠 PA 诱导的肝毒性，但其潜在机制尚不清楚。
本研究旨在探讨 GA 对抗 retrorsine（RTS，一种代表性的有毒 PA）诱导的肝损伤的肝保护作用的机制。
采用组织学和生化评估来评估 GA 对 RTS 诱导的大鼠肝毒性的保护作用。采用磺酰罗丹明 B 测定法、实时 PCR、western blot 和免疫染色法在人肝细胞和大鼠中探讨潜在机制。
我们的研究结果表明，GA 减轻了 RTS 诱导的大鼠血清 ALT 和胆红素水平升高，以及肝细胞坏死和窦内皮细胞（SECs）损伤。GA 还通过上调核因子-红细胞 2 相关因子 2（Nrf2）来增强几种抗氧化酶的活性和表达。此外，抑制 Nrf2 阻断了 GA 对 RTS 中毒的肝保护作用。机制上，GA 增加了磷脂酰肌醇 3-激酶（PI3K）/蛋白激酶 B（AKT）的磷酸化，并增强了丝氨酸 9 处糖原合酶激酶 3β（GSK3β）的抑制性磷酸化，从而促进了 Nrf2 的核积累并激活了其下游靶点。
本研究首次表明，GA 通过增强 Nrf2 介导的抗氧化系统来发挥对 RTS 诱导的肝损伤的保护作用，通过 PI3K/Akt/GSK3β 途径。研究结果表明，GA 可能成为治疗 PA 中毒的潜在候选药物。
