Punicalagin induces Nrf2 translocation and HO-1 expression via PI3K/Akt, protecting rat intestinal epithelial cells from oxidative stress

Abstract

Purpose: Oxidative stress plays a central role in heat stress-induced gastrointestinal injury. Punicalagin (PUN), a major polyphenol abundant in pomegranate fruit, husk and juice, exhibits antioxidative effects. In this study we used a heat stress model to investigate the intestinal protection effect of PUN and the underlying mechanisms. Materials and methods: IEC-6 cells were pretreated with PUN for 6 h and exposed to 42 °C for 6 h. Intracellular reactive oxygen species levels, malondialdehyde, nitrogen oxide, and superoxide dismutase activity were measured. IEC-6 cells were treated with PUN at different times and doses, the protein levels of haeme oxygenase-1 (HO-1) were evaluated. The nuclear translocation of the transcription factor NF-erythroid 2-related factor (Nrf2) and the phosphorylation level of PI3K/Akt were also investigated. Results: PUN significantly decreased the heat stress-induced cell death and apoptosis. Heat stress increased reactive oxygen species, malondialdehyde and nitrogen oxide production, while it decreased superoxide dismutase activity. These effects were markedly inversed when the cells were pretreated with PUN. Furthermore, PUN treatment induced the expression of HO-1 and increased Nrf2 nuclear translocation in a time- and dose-dependent manner. The Nrf2-related cytoprotective effects of PUN were via the PI3K/Akt signalling pathway, as LY294002, a specific PI3K/Akt inhibitor, suppressed the PUN-induced nuclear translocation of Nrf2, the HO-1 up-regulation and the protective effect of PUN against oxidative stress. Conclusions: PUN protects IEC-6 cells against oxidative stress by up-regulating the expression of HO-1 via a mechanism that involves PI3K/Akt activation and Nrf2 translocation.

Keywords:

• Cytoprotection
• Nrf2
• oxidative stress
• punicalagin

Acknowledgements

We are thankful for the help from the members of CAU-BUA TCVM teaching and research team.

Disclosure statement

This work was supported by grants from the National Natural Science Foundation of China (No. 31272478), National Twelve-Five Technological Supported Plan of China (No. 2013BAD10B04), Ministry of Agriculture, public service sectors agriculture research projects (No. 201403051-07), Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions (CIT&TCD20130324). The authors declare that there is no conflict of interests regarding the publication of this article. The authors alone are responsible for the content and writing of the paper.