Peroxidative stress and in vitro ageing of endothelial cells increases the monocyte-endothelial cell adherence in a human in vitro system.

Adherence of monocytes to the endothelium is an early event in atherogenesis. Changes in the endothelium are probably involved in this process. We have investigated the influence of peroxidative stress and in vitro ageing of endothelial cells on the subsequent adherence of monocytes using an in vitro system. Treatment of young human umbilical vein endothelial cells (HUVEC) with 60 microM cumene hydroperoxide (Chp) resulted in a 2.1-fold increase in monocyte adherence. This increase was not dependent on de novo synthesis of membrane antigens. No such increase upon Chp treatment was observed using young human umbilical artery endothelial cells (HUAEC) and in vitro aged HUVEC and HUAEC. As compared with "young" HUVEC, a higher spontaneous adherence of monocytes to "young" HUAEC (1.8 times), "aged" HUVEC (2.5 times) and "aged" HUAEC (2.7 times) was observed. Furthermore, fibroblasts showed an about 3 times higher monocyte adherence, whereas an 8 times higher adherence was observed to endothelial extracellular matrix. These data suggest that the spontaneous monocyte adherence to "young", intact endothelium can be increased by peroxidative damaging and by ageing of the endothelial cells. A denudation and subsequent exposure of the extracellular matrix may further stimulate this process. The possible physiological vector for endothelial peroxidation is discussed.