Protective Effect of Borassus flabellifer Haustorium Extract against Alkoxyl Radical-Induced Cytotoxicity by Improving Glutathione Metabolism by Modulating Nrf2/Haeme Oxygenase-1 Expression

Abstract

Aim

The study was aimed to assess the ability of Borassus flabellifer haustorium methanolic extract (BHE) on de novo glutathione biosynthesis in normal and pro-oxidant exposed cells via Nuclear factor erythroid 2-related factor 2 (Nrf2) and haeme oxygenase-1 (HO1) signaling in 2,2′-Azobis(2-methylpropionamidine) di-hydrochloride (AAPH) induced cytotoxicity in normal intestinal epithelial cells (IEC-6 cells).

Methods

The in vitro antioxidant activity was determined in terms of radical scavenging and ex vivo hemolysis. The cytoprotective effect was studied using AAP H as the alkoxyl radical inducer in IEC-6 cell model. The mechanistic basis of protection is determined by Nrf2/HO1 expression using qPCR.

Results

In vitro screening observed DPPH, hydrogen peroxide and ABTS radical scavenging activity for the BHE; further, BHE also protected the oxidative hemolysis in the erythrocytes induced by AAPH. In IEC-6 cells, AAPH treatment significantly reduced the cell viability (p < 0.001) by inducing lipid peroxidation. Further, there observed a significant reduction in the activities of enzymes involved in the de novo glutathione biosynthesis (p < 0.01) and glutathione reductase in these cells. However, pretreatment with BHE (10, 25 and 50 µg/mL) dose-dependently protected from the cytotoxicity of AAPH-derived alkoxyl radicals (p < 0.05); besides, the de novo glutathione biosynthesis and regeneration of GSH from oxidized form was also increased in these cells. In corroboration with the biochemical parameters, the Nrf2/HO1 expression was upregulated by the BHE pretreatment concomitantly reducing the cellular lipid peroxidation products. The improvement glutathione biosynthesis was also observed in BHE alone treated cells.

Conclusion

The study indicated the potential of methanolic extract of Borassus flabellifer haustorium in enhancing the de novo glutathione biosynthesis in normal and pro-oxidant exposed cells by Nrf2/HO1 dependent manner, concomitantly mitigating the toxicity of AAPH-derived alkoxyl radicals in intestinal epithelial cells.

Keywords:

• Cytoprotection
• Borassus flabellifer
• Haustorium extract
• Glutathione metabolism
• Antioxidant activity
• Nrf2 signaling

Disclosure statement

No potential conflict of interest was reported by the author(s).

Availability of data and material

Available on genuine request by authorized persons.

Authors contributions

JTJ- Cytoprotective studies in cells exposed to AAPH, qPCR analysis and Manuscript draft preparation (along with AN); AA and RR- Phytochemical and nutritional analysis, In vitro antioxidant properties; YOK- Impact of BHE alone on the antioxidant status of IEC-6 cells; HJK- Study on the effect of BSO on the cytoprotective effect of BHE; AN designed the concept, analyzed data and prepared the manuscript. All authors approved the manuscript.

Additional information

Funding

The authors acknowledge King Saud University, Riyadh, Saudi Arabia for funding this research through Researchers Supporting Project No: RSP 2021/11. The study was also supported by Kerala State Council for Science, Technology and Environment (KSCSTE) under Student Project Scheme (Letter No. 01519/SPS64/2019/KSCSTE and 01476/SPS64/2019/KSCSTE).