Effects of air pollution and smoking on DNA damage of human lymphocytes.

The comet assay is a useful technique for the study of genetic damage in humans exposed to environmental mutagens and carcinogens. In this study the effects of hydrogen peroxide (H(2)O(2)) and ultraviolet (UV) irradiation on 80 healthy individuals living in urban and rural areas with different smoking habits were investigated. Endonuclease III (endo III) treatment was also used to reveal the level of oxidized pyrimidine formation in these groups. The extent of damage and subsequent repair appear to be influenced by the living conditions (urban or rural areas). Smoking, however, was shown to have the most significant effect on DNA damage on all groups studied.

Biomonitoring with the comet assay of Greek greenhouse workers exposed to pesticides.

The pesticides in use in Greek greenhouses include a number of agents known to be mutagens and carcinogens. In the present study, we evaluated whether occupational exposure of agricultural workers to a complex mixture of pesticides resulted in a significant increase in DNA damage in human peripheral blood lymphocytes (PBLs). A total of 116 healthy individuals were divided into groups based on exposure to pesticides, smoking status, and gender. Alkaline comet assays performed on PBLs from these individuals indicated no statistically significant differences in basal DNA damage between the study groups. In addition, exposure of PBLs to a dose of hydrogen peroxide led to a similar degree of DNA damage and subsequent repair for all the study populations. The results of the study indicate that the agricultural workers who participated in this study had no detectable increase in DNA damage or alteration in the cellular response to DNA damage.

Effects of pulsed electric fields on DNA of human lymphocytes.

The effects of pulsed electric fields of low frequency (50 Hz) on DNA of human lymphocytes were investigated. The influence of additional external factors, such as hydrogen peroxide (H2O2) and gamma-irradiation, as well as the repair efficiency in these lymphocytes, was also evaluated. The comet assay, a very sensitive and rapid method for detecting DNA damage at the single cells level was the method used. A significant amount of damage was observed after exposure to the electric fields, compared to the controls. After 2 h incubation at 37 degrees C, a proportion of damage was repaired. H2O2 and gamma-irradiation increased the damage to lymphocytes exposed to pulsed electric fields according to the dose used, while the amount of the repair was proportional to the damage.

Nicotinamide "protects" resting lymphocytes exposed to hydrogen peroxide from necrosis but not from apoptosis.

The aim of this work was to investigate the relationship between mechanisms of DNA repair and apoptosis induced by oxidative stress (H2O2) in human lymphocytes. Using the comet assay, fluorescent microscopy, and DNA electrophoresis, we studied the DNA damage induced by hydrogen peroxide (H2O2) treatment, the time and the amount of repair of strand breaks, the type of cell death, and the influence of inhibitors of repair (nicotinamide). When lymphocytes were treated with H2O2, we observed an increased in necrosis compared to apoptosis. However, when nicotinamide (which inhibits DNA repair) was added, the mode of death reversed to increased apoptosis. These results indicate that nicotinamide "protects" resting lymphocytes exposed to H2O2 from necrosis but not from apoptosis.