Vitamin E inhibits low-density lipoprotein-induced adhesion of monocytes to human aortic endothelial cells in vitro

Monocyte adhesion to human aortic endothelial cells (ECs) is one of the early events in the development of atherogenesis. ECs were used to investigate the role of vitamin E in human monocyte adhesion to ECs in vitro. ECs incubated with 40 to 193 mg/dL of low-density lipoprotein cholesterol (LDL) for 22 hours exhibited increasing dose-dependent adherence for untreated, isolated human monocytes (P<.05). ECs exposed to the highest dose of LDL (193 mg/dL) but pretreated with 19 mu mol/L alpha-tocopherol for 24 hours showed a trend to lower adherence for monocytes compared with nontreated ECs (4.4+/-1.2% versus 7.6+/-1.9%; P=.09). This effect of vitamin E became more significant (P<.05) when ECs were exposed to a lower level of LDL (40 mg/dL) or were pretreated with a higher level of alpha-tocopherol (42 mu mol/L) and then exposed to 80 mg/dL LDL. Presupplementation of ECs with 15, 19, and 37 mu mol/L alpha-tocopherol significantly (P<.05) reduced monocyte adhesion by 6+/-1%, 37+/-6%, and 69+/-17%, respectively. Levels of soluble intercellular adhesion molecule-1 (sICAM-1), one of the adhesion molecules for monocytes, increased after incubation of ECs with LDL 80 mg/dL (4.7+/-0.7 versus 6.4+/-1.2 ng/mL, respectively; P<.05). Treatment of ECs with alpha-tocopherol (42 mu mol/L) significantly reduced induction of sICAM-1 by LDL to 2.2+/-2.3 ng/mL. After exposure to LDL, prostaglandin I-2 production by ECs was diminished, whereas presupplementation of ECs with alpha-tocopherol partially reversed the LDL effect. Production of interleukin-1 beta was not detectable when ECs were treated with alpha-tocopherol, LDL, or alpha-tocopherol followed by LDL. Our findings indicate that vitamin E has an inhibitory effect on LDL-induced production of adhesion molecules and adhesion of monocytes to ECs via its antioxidant function and/or its direct regulatory effect on sICAM-1 expression.