School of Clinical Medicine, Weifang Medical University, Weifang 266003, China.
Department of Chinese Medicine, Zhucheng Shiqiaozi Hospital, Weifang 262208, China; Department of Chinese Medicine, The Affiliated Hospital of Qingdao University, Qingdao 260153, China.
Int Immunopharmacol. 2020 Dec;89(Pt A):107005. doi: 10.1016/j.intimp.2020.107005. Epub 2020 Oct 9.
Myricitrin has been reported to exert protective effects on liver diseases, but the protective effects of myricitrin against liver ischemia reperfusion (I/R) injury and the underlying mechanisms remain unexplored. This study aimed to investigate the effects of myricitrin on liver I/R injury and elucidate the underlying mechanisms.
Mice were pretreated with myricitrin before liver I/R injury modeling. The mice were pretreated with either myricitrin or vehicle prior to liver ischemia. Some mice were further pretreated with the PI3K inhibitor LY294002. Liver tissues and blood samples were collected after 6 h of reperfusion. The degree of liver damage was determined by the serum levels of alanine aminotransferase (ALT), aspartate transaminase (AST), and lactic dehydrogenase (LDH) and histological examinations. The tumour necrosis factor-α (TNF-α), interleukin--1β (IL-1β), IL-4 and IL-10 expression levels were assessed by qRT-PCR and enzyme-linked immunosorbent assays (ELISAs). Serum superoxide dismutase (SOD) activity, catalase (CAT) activity, and contents of malondialdehyde (MDA), glutathione (GSH) and nitric oxide (NO) contents were measured. Western blotting and caspase-3 activity were conducted to determine the effect of myricitrin on apoptosis. The expression levels of proliferation related genes (Cyclin D1 and Cyclin E1) were determined by qRT-PCR and western-blotting. The expression of p-Akt, p-mTOR and p-eNOS in liver tissue were investigated by western-blotting.
Myricitrin not only significantly decreased the ALT, AST and LDH levels but also reduced the necrotic areas in the liver tissue compared with liver I/R injury group. In addition, myricitrin pretreatment alleviated liver injury by inhibiting the inflammatory response and suppressing oxidative stress. Western blotting and caspase-3 activity revealed that myricitrin inhibited liver I/R induced-apoptosis. Myricitrin promoted hepatocyte proliferation following liver I/R injury by upregulating the expression levels of Cyclin D1 and Cyclin E1. Further experiments indicated that the myricitrin pretreatment increased nitric oxide (NO) production by activating the PI3K/Akt signaling pathway. However, myricitrin triggered the hepatocyte proliferation and NO synthase activation was blocked by LY294002.
These results demonstrate that myricitrin alleviates liver I/R injury by suppressing oxidative stress, the inflammatory response, and apoptosis, improving liver proliferation and upregulating p-eNOS expression.
杨梅素已被报道对肝脏疾病具有保护作用，但杨梅素对肝缺血再灌注（I/R）损伤的保护作用及其机制尚不清楚。本研究旨在探讨杨梅素对肝 I/R 损伤的作用及其机制。
在肝 I/R 损伤模型建立前，用杨梅素预处理小鼠。在肝缺血前，用杨梅素或载体预处理部分小鼠。一些小鼠进一步用 PI3K 抑制剂 LY294002 预处理。再灌注 6 小时后采集肝组织和血样。通过血清丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）和乳酸脱氢酶（LDH）水平和组织学检查来确定肝损伤程度。通过 qRT-PCR 和酶联免疫吸附试验（ELISA）评估肿瘤坏死因子-α（TNF-α）、白细胞介素-1β（IL-1β）、IL-4 和 IL-10 的表达水平。测定血清超氧化物歧化酶（SOD）活性、过氧化氢酶（CAT）活性以及丙二醛（MDA）、谷胱甘肽（GSH）和一氧化氮（NO）含量。通过 Western blot 和 caspase-3 活性测定来确定杨梅素对细胞凋亡的影响。通过 qRT-PCR 和 Western blot 测定增殖相关基因（Cyclin D1 和 Cyclin E1）的表达水平。通过 Western blot 研究肝组织中 p-Akt、p-mTOR 和 p-eNOS 的表达。
与肝 I/R 损伤组相比，杨梅素不仅显著降低 ALT、AST 和 LDH 水平，还减少了肝组织中的坏死区域。此外，杨梅素预处理通过抑制炎症反应和抑制氧化应激来减轻肝损伤。Western blot 和 caspase-3 活性表明，杨梅素抑制了肝 I/R 诱导的细胞凋亡。杨梅素通过上调 Cyclin D1 和 Cyclin E1 的表达水平，促进肝 I/R 损伤后的肝细胞增殖。进一步的实验表明，杨梅素预处理通过激活 PI3K/Akt 信号通路增加一氧化氮（NO）的产生。然而，用 LY294002 阻断杨梅素触发的肝细胞增殖和一氧化氮合酶激活。
这些结果表明，杨梅素通过抑制氧化应激、炎症反应和细胞凋亡，改善肝增殖并上调 p-eNOS 表达，从而减轻肝 I/R 损伤。
