Effect of cigarette smoking on cultured human endothelial cells

The aim was to investigate whether the morphological changes previously described in endothelium exposed to cigarette smoke are linked with the oxidative burden imposed on the cells.

Cultured human umbilical vein endothelial cells (HUVEC) were exposed to samples of plasma taken from volunteer smokers and to samples of plasma to which small doses of fresh cigarette smoke derived from a smoking machine had been added. Measurements of the pentose phosphate pathway and the extruded total glutathione (GSSG) were performed to assess the presence and degree of oxidative stress on cells. Angiotensin converting enzyme (ACE) release into the medium and the ATP content of the cells were used to assess early membrane damage and cytotoxicity.

Treatment of endothelial cells with plasma exposed to cigarette smoke in vitro resulted in activation of the pentose phosphate pathway of glucose metabolism, increased extrusion of glutathione from the cells into the medium, a decrease in the ATP pool, and release of ACE from the cells into the medium. Plasma taken from volunteers immediately after smoking showed, as might be expected, similar but less marked changes in the release of glutathione and ACE.

Plasma from human volunteer smokers or human plasma exposed to cigarette smoke in vitro produced injury in HUVEC as assessed by changes in the ATP pool and ACE release. The extrusion of glutathione from the cells and the activation of the hexose monophosphate shunt, which is necessary to keep glutathione in the reduced state, is indicative of oxidative stress. These findings support the view that cigarette smoke related endothelial injury is, at least in part, mediated by the oxidative burden imposed by the free radicals present in cigarette smoke.