Ameliorative Effect of Boric Acid Against Nicotine-Induced Cytotoxicity on Cultured Human Primary Alveolar Epithelial Cells

Abstract

Nearly six million people die from smoking due to addiction to nicotine. Because of high toxicity by nicotine, main alkaloid in tobacco, the action modes of nicotine have been analyzed comprehensively by scientists in different organisms and cell cultures. One of the main cytotoxicity mechanisms of nicotine is that activating lipid peroxidation by inducing production of reactive oxygen species (ROS). Recent investigations support that boric acid exhibits cyto-protective properties on different cell types via its antioxidant nature. Thus, in this study boric acid (BA) was assessed as a potential cyto-protective agent against nicotine-induced cytotoxicity. Therefore, toxic concentrations of nicotine were evaluated on human primary alveolar epithelial cells (HPAEpiC) and BA was applied against toxic dose of nicotine to analyze whether cytotoxicity could be attenuated or not. Wide spectrum nicotine hydrogen tartrate concentrations (0.312 mM to 20 mM) were used to investigate the cytotoxicity. 3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) release assays were used to analyze cytotoxicity after exposure to nicotine and boric acid, and their combinations. In addition, Hoechst 33258 (bis-Benzimide) dye was used to analyze genome integrity under fluorescent microscope. According to the results of MTT cell viability assay, IC50 concentration of nicotine was determined as 1.71 mM. Different concentration of BA (0.625 µg/ml to 20 µg/ml) were applied into cultured HPAEpiC cells with nicotine to prevent cellular damages by nicotine. MTT and LDH assays clearly showed that 5 µg/ml of BA supplementation increased cell viability against nicotine exposure. Again, Hoechst 33258 test revealed that chromosome structure was preserved significantly after BA exposure. As a conclusion, our results revealed for the first time that BA could be used as a protective agent against nicotine-induced toxicity on human lung alveolar cells