Combined effect of cadmium, lead, and UV rays on Bacillus cereus using comet assay and oxidative stress parameters

Exposure to environmental chemicals and oxidative stress particularly at low dose levels may produce additive or synergistic interactions not seen in single component exposure. Exposure to cadmium, lead, and ultraviolet rays occurs in many occupational settings, such as pigment and battery production, galvanization, and recycling of electric tools. However, little is known about interactions between heavy metals and ultraviolet rays. This study aimed to evaluate the interactions of ultraviolet rays of 254 nm (UV-B) with cadmium or lead on Bacillus cereus. B. cereus was treated with different concentrations of cadmium or lead followed by exposure to UV-B radiation as combined effect. Photoirradiation of B. cereus with UV-B with exposure to cadmium or lead results in DNA damage, cytotoxicity, depletion of glutathione, and formation of lipid peroxidation. UV-B rays alone enhanced glutathione production which was depleted with lead and high doses of cadmium. Lead alone does not increase DNA breaking. The mechanism behind these interactions might be repair inhibition of oxidative DNA damage, since a decrease in repair capacity will increase susceptibility to reactive oxygen species generated by cadmium or lead. Lipid peroxidation was increased with exposure to UV-B and cadmium or lead. DNA, glutathione, and lipid peroxidation can be used as biomarkers to identify possible environmental contamination in bacteria. One conclusion from this model is the existence of more than multiplicative effects for co-exposures of cadmium or lead and UV rays.