Tehran University of Medical Sciences Acta Biochimica Iranica 0001-5261 2 3 2024 09 25 146 154 Kamal Yavari Nuclear Science and Technology Research Institute, (NSTRI), Tehran, Iran Maryam Ashofteh Faculty of biological science, Khwarizmi University, Tehran, Iran Zahra Ghorbani Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran 2025 05 23 Objectives:  In recent decades, deuterium-depleted water (DDW) has been discussed as a supplement to increase the longevity. In this study we aim to investigate the effects of DDW on the factors involved in the aging process including FOXO gene family and oxidative stress. We also aim to study the effect of DDW on cellular toxicity caused by heavy metal of manganese. Methods: We used HNNFPi8 cell line as an experimental model. HNNFPi8 cell line incubated with specific DDW media with deuterium concentration of 30ppm, 50ppm, 75ppm, 100ppm, 125ppm and 150ppm and 0.01 to 5mM MnCl2 up to 72 h. Cell proliferation, the activities of catalase and superoxide dismutase (SOD) antioxidant were determined by MTT and colorimetric methods, respectively.  RT-PCR was used to measure FOXO3A gene expression. Results: The increase in MnCl2 concentration resulted in dose-dependently reduction in the viability of the cells. However, the decrease in the cell viability in the treated groups with DDW was found to be significantly lower in concentrations of 50ppm to 125 ppm DDW. DDW at concentrations of 30, 50, 75, 100 and 125 ppm could significantly upregulate the expression of FOXO3A gene in the cells treated with different concentrations of MnCl2. In addition, DDW at concentrations of 75, 100 and 125 ppm were able to increase the activities of these two antioxidant enzymes in the cells treated with different concentrations of MnCl2 Conclusion: The results suggest that DDW, especially at concentrations of 100 and 125ppm, is effective in reducing the toxic effects of the MnCl2. https://abi.tums.ac.ir/index.php/abi/article/view/120 https://abi.tums.ac.ir/index.php/abi/article/download/120/68