Objective: To investigate the effects of hydroxyl radicals, low density lipoprotein and cholesterol on the response of vascular endothelial cells to the change in extracellular calcium ion concentration.
Methods: After treatment with the above mentioned atherogenic factors respectively, the cells were loaded with Fluo-3 and then the response of the cells to the increase in extracellular [Ca(2+)] was observed under a confocal laser scanning microscope.
Results: Normal vascular endothelial cells were sensitive to the increase in extracellular [Ca(2+)]. The free calcium ions in cytosol increased pulsively until a maximum was reached, and then was reduced to the initial level rapidly. Treatment with hydroxyl radicals produced by Fe(2+)-EDTA made the cells rather slow to the change in extracellular [Ca(2+)]. A morphological examination showed that some damage to the cells was caused. After cultivation with low density lipoprotein (0.10 g x L(-1)), the cells lost most of their capability to modulate intracellular calcium ion and thus the calcium level remained high at the end of the experiment. If a hydroxyl radical treatment preceded the incubation with low density lipoprotein, a more serious damage was observed. Some of the cells were caused to death while the extracellular [Ca(2+)] increased. Upon exposing to a higher level of extracellular calcium ion, the cytosol [Ca(2+)] did not increase; contrarily, it decreased gradually. The hydroxyl radical oxidation followed by cholesterol treatment made the cells respond disorderly to the increase in extracellular [Ca(2+)], indicating that rather serious damage had been caused to the cells.
Conclusion: These findings indicate that hydroxyl radicals, low density lipoprotein and cholesterol interfere with the response of vascular endothelial cells to extracellular calcium ions. This may be one of the ways these factors contribute to the initiation and development of atherosclerosis.