Paeonia japonica ameliorates oxidative stress-induced liver injury through activation of AMPK-mediated GSK3β

Paeonia japonica root has been widely used in Korean traditional medicine for its anti-oxidative, anti-inflammatory, analgesic, and anti-spasmodic effects as well as anti-convulsant and anti-anxiety activities [1 – 4]. Arachidonic acid (AA) + iron induce apoptosis through excess production of reactive oxygen species and mitochondrial dysfunction [5]. In this study, we investigated the hepatoprotective effects of P. japonica root extract (PJE) and its molecular mechanisms involved. PJE protects HepG2 cells from AA + iron-induced hepatotoxicity in a dose-dependent manner. In addition, PJE attenuated H₂O₂ production and restored GSH depletion and mitochondrial dysfunction induced by AA + iron. Based on a previous study, it is known that AMPK and GSK3β are involved in hepatocytes protection from oxidative stress induced by AA + iron [6]. Results from immunoblot analysis showed that PJE significantly increased the phosphorylation of AMPK as well as GSK3β. Moreover, chemical inhibition of AMPK blocked the ability of PJE to increase inactive phosphorylation of GSK3β, indicating that AMPK is one of upstream kinase to regulate GSK3β. Furthermore, benzoic acid, albiflorin and paeoniflorin found in PJE contributed to cell protection through AMPK activation. To validate our knowledge that PJE protects cells from AA + iron in vitro, we used a phenylhydrazine-induced acute liver injury model. Oral administration of PJE showed remarkable hepatoprotective effects against phenylhydrazine-induced peripheral hepatic damage and alleviated nitrotyrosine and 4-HNE immunoreactivity in hepatic tissues. Thus, Paeonia japonica root might be a beneficial pharmaceutical material for the treatment of oxidative stress-mediated liver injuries.

Acknowledgements: This research was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIP) (No. 2012 R1A5A2A42671316).

Keywords: Paeonia japonica, oxidative stress, AMPK, GSK3β.

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