The role of melatonin as an antioxidant in human lens epithelial cells

Abstract

Oxidative stress plays a significant role in pathophysiology of cataracts and also known to affect the phosphatidylinositol-3-kinase/ protein kinase B (PI3K/Akt) signaling pathway. This well-documented pathway is involved in protecting against apoptosis-inducing insults, including oxidative stress. Melatonin (N-acetyl-5-methoxy-tryptamine), the major secretory product of the pineal gland, was identified as a powerful free radical scavenger and a broad-spectrum antioxidant that defends against various oxidative stress-associated diseases. This study was conducted to determine whether melatonin could prevent hydrogen peroxide (H₂O₂)-induced oxidative stress in human lens epithelial cells (HLECs) and to elucidate the molecular pathways involved in this protection. HLECs were subjected to various concentrations of H₂O₂ in the presence or absence of melatonin at different concentrations. Cell viability was monitored by a 3-(4, 5-dimethylthiazol-2yl)-2, 5-diphenyl-tetrazoliumbromide (MTT) assay, and the apoptosis rate and intracellular reactive oxygen species (ROS) levels were measured by flow cytometry using annexin V-FITC and propidium iodide (PI) staining. The expression levels of HO-1, Nrf-2, CAT, and MDA were measured using Western blot analysis. Akt activation was also evaluated by Western blot analysis. The data from our study showed that cells pretreated with melatonin can reduce H₂O₂-induced intracellular ROS generation and thus protect HLECs from cell apoptosis. Furthermore, we found that melatonin is a potent activator of Akt in HLECs. Our findings suggest that in addition to functioning as a direct free radical scavenger, melatonin can elicit cellular signaling pathways that are protective against oxidative stress-induced cataracts.

Keywords::

• antioxidant enzymes
• human lens epithelial cells
• hydrogen peroxide
• melatonin
• PI3K/Akt

Acknowledgments

We would like to thank Yonggang Liu and Yuming Li for excellent technical assistance. We are thankful to Dr. Peter M. Olley for insightful discussions of this paper.

Declaration of interest

The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.

This work was supported by a grant from the National Natural Science Foundation (30973275) and the Youngth Science Foundation of Heilongjiang Province of China (No: QC2010113).