Nrf2 Activation Is Required for Ligustrazine to Inhibit Hepatic Steatosis in Alcohol-Preferring Mice and Hepatocytes

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Hepatic steatosis is the most distinctive feature of alcoholic liver disease (ALD). Our previous in vivo study showed that ligustrazine, a major active alkaloid isolated from Ligusticum chuanxiong Hort, attenuated alcohol-induced hepatic steatosis and in vitro study revealed that nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activation might be a prerequisite. This study was aimed to explore the in vivo function of Nrf2 in the protective effect of ligustrazine and illustrate downstream mechanisms. Nrf2 shRNA lentivirus was introduced to establish Nrf2-knockdown mice. Results showed that Nrf2 knockdown aggravated alcoholic liver injury and abolished the protective effect of ligustrazine, evidenced by elevated serum biomarkers and severe liver inflammation. Ligustrazine impressively ameliorated hepatic steatosis through inhibiting hepatic sterol regulatory element-binding protein-1c and inducing peroxisome proliferator-activated receptor-alpha, which was abrogated by Nrf2 knockdown. Noteworthily, Nrf2 knockdown apparently reinforced the inductive effect of alcohol on hypoxia-inducible factor 1-alpha (HIF-1α). Ligustrazine weakened the stimulation of alcohol on HIF-1α expression, which was abrogated by Nrf2 shRNA lentivirus. Consistent results were obtained from in vitro study, implying that Nrf2/HIF-1α pathway participated in the modulation of ligustrazine. Gain- or loss-of-function analyses further revealed that Nrf2 siRNA and dimethyloxalylglycine, a HIF-1α agonist, abolished the inhibitory effect of ligustrazine, whereas HIF-1α siRNA mimicked the role of ligustrazine and even rescued the inhibitory effect of ligustrazine on ethanol-induced lipid accumulation in Nrf2-knockdown hepatocytes. Taken together, we concluded that ligustrazine attenuated alcohol-induced hepatic steatosis via a Nrf2/HIF-1α pathway-dependent mechanism.

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