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Lead (Pb) is one of the most important heavy metals that possess many applications in different kinds of industrial procedures and consumer products. The adverse effects of Pb on different parts of the immune system have been reported in various studies. Although it has been shown that high concentrations of Pb have low cytotoxicity on human lymphocytes, the effects of non-cytotoxic concentrations of Pb (detected in human blood) on cellular organelles and oxidative stress factors of human lymphocytes have yet to be determined. In this study, human lymphocytes were obtained from the blood of healthy male volunteers through the use of the Ficoll standard method. The intention of this paper was to determine the effects of non-cytotoxic concentrations of Pb on human lymphocytes using the accelerated cytotoxicity mechanism screening technique. For determination of cell viability, lymphocytes were treated with 0–1 mm Pb for 12 h. Subsequently, we assayed the effects of non-cytotoxic concentrations of Pb which are detected in human blood on human lymphocytes and investigated if Pb can affect oxidative stress and cellular organelles at these concentrations. So, in concentrations which have no cytotoxic effects, Pb is shown to induce oxidative stress in addition to inflicting damage on mitochondria and lysosomes in human blood lymphocytes.

Addition of cationic lipids to plasmid DNA considerably increases the efficiency of transfection. The mechanism has not yet been elucidated. A possibility is that these compounds destabilize biological membranes (plasma, endosomal, lysosomal), facilitating tile transfer of nucleic molecules through these membranes. We have investigated the problem by determining if a cationic lipid N-(1-(2,3-dioleoxy)propyl)-N,N,N,-trimethylammonium methyl-sulfate (DOTAP, Boehringer, Mannheim, Germany) affects the integrity of rat liver lysosomal membrane. We have measured the latency of β-galactosidase, a lysosomal enzyme, and found that incubation of lysosomes with low concentrations of DOTAP causes a striking increase in free activity of thee hydrolase and even a release of the enzyme into the medium. This indicates that lysosomal membrane is deeply destabilized by the lipid. The phenomenon depends on pH, it is less pronounced at pH 5 than at pH 7.4. Anionic compounds, particularly anionic amphipathic lipids, can to some extent prevent this phenomenon. It can be observed with various cationic lipids. A possible explanation is that cationic liposomes interact with anionic lipids of lysosomal membrane, allowing a fusion between the lipid bilayers which results in a destabilization of the organelle membrane.