Investigating the effect of the heavy metals cadmium, chromium and lead, alone and in combination on an endothelial cell line

Heavy metals are natural elements characterized by their relatively large atomic mass as well as high density. It can be introduced into the ecosystem by the mining of heavy metals from deep within the earth's crust, thereby exposing the metals into air and water systems. Cigarette smoke is another source of heavy metal exposure and has been shown to have carcinogenic, toxic and genotoxic properties. Cadmium, lead, and chromium are the most abundant metals found in cigarette smoke. In response to tobacco smoke exposure, endothelial cells release inflammatory and pro-atherogenic cytokines that are linked to endothelial dysfunction. Endothelial dysfunction is directly related to the production of reactive oxygen species, leading to endothelial cell loss through necrosis and/or apoptosis. The current study aimed to investigate the effect of cadmium, lead, and chromium, alone and as part of metal mixtures, on endothelial cells. The EA.hy926 endothelial cell line was exposed to different concentrations of each of these metals and their combinations and analyzed using flow cytometric analyses with Annexin V. A clear trend was seen with the Pb + Cr as well as the triple combination group with the significant increase of early apoptotic cells. Scanning electron microscopy was used to study possible ultrastructural effects. Morphological changes observed with scanning electron microscopy included cell membrane damage and membrane blebbing at certain metal concentrations. In conclusion, the exposure of endothelial cells to cadmium, lead, and chromium, caused a disruption in cellular processes and morphology, possibly diminishing the protective ability of endothelial cells.