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Leukocyte-endothelial cell interactions, which are mediated by various adhesion molecules, are a crucial event in inflammatory reactions including atherosclerosis. alpha-tocopherol (alpha-Toc) has been used for therapy of vascular diseases because of its antioxidant activity. However, the effect of alpha-Toc on inflammatory reactions has not been investigated very well. In the present study, we examined the effect of alpha-Toc on expression of adhesion molecules on human neutrophils and human umbilical vein endothelial cells (HUVEC). Expression of CD11a, CD11b and CD18 on neutrophils was assessed by immunofluorescence flow cytometry 30 min after the stimulation of neutrophils with 10(-7) M platelet-activating factor (PAF). Surface expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on HUVEC was evaluated by enzyme immunoassay 8 h after the incubation of HUVEC with IL-1 beta (20 U/ml). PAF induced upregulation of CD11b and CD18 on neutrophils and IL-1 beta increased surface expression of ICAM-1 and VCAM-1 on HUVEC. Coincubation of neutrophils with alpha-Toc and pretreatment of HUVEC with alpha-Toc significantly reduced PAF-induced CD11b/CD18 expression and IL-1 beta-induced upregulation of ICAM-1 and VCAM-1, respectively. These findings indicate that alpha-Toc may work as an anti-inflammatory agent through inhibiting neutrophil-endothelial cell adhesive reactions.

We evaluated the effects of ␣-Toc on surface expression of CD11b/CD18 on polymorphonuclear leukocytes (PMN) stimulated with N-formylmethionyl-leucyl-phenylalanine (fMLP) and oxidized low-density lipoprotein (oxLDL). Incubation of PMN with fMLP (1 M) or oxLDL (100 g/mL) increased CD11b/CD18 expression; pretreatment with ␣-Toc reduced in a dose-dependent manner. PMN obtained from healthy adults ingesting 600 mg ␣-Toc per day for 10 days were similarly incubated with fMLP or oxLDL; the surface level of CD11b/CD18 was inversely correlated with serum ␣-Toc concentrations. Adherence of PMN to human umbilical vein endothelial cells was increased by fMLP or oxLDL stimulation but reduced by ␣-Toc pretreatment or anti-CD18 monoclonal antibodies. cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) activity in PMN was also assayed. A PKC inhibitor, but not a PKA inhibitor, suppressed CD11b/CD18 up-regulation, and ␣-Toc slightly decreased fMLP-and oxLDL-induced activation of PKC. These results suggest that ␣-Toc may prevent inflammation by both reducing CD11b/ CD18 up-regulation and decreasing PMN-dependent adherence to EC. J. Leukoc. Biol. 65: 757-763; 1999.

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Leukocyte-endothelial cell interactions, which are mediated by various adhesion molecules, are a crucial event in inflammatory reactions including atherosclerosis. Alpha-tocopherol (alpha-Toc) has been used for protection and therapy of vascular diseases because of its antioxidant activity. The objective of the present study was to determine effect of alpha-Toc on endothelial-dependent adhesive interactions with leukocytes elicited by oxidized low density lipoprotein (oxLDL). Incubation of HUVEC with oxLDL (100 microg/mL) increased expression of proteins and messenger RNA of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on enzyme immunoassay and northern blotting assay; pretreatment with alpha-Toc reduced in a dose dependent manner. Adherence of polymorphonuclear leukocytes (PMN) or mononuclear leukocytes (MNC) to oxLDL-activated HUVEC was much increased compared with that to unstimulated HUVEC. Treatment of HUVEC with alpha-Toc, monoclonal antibody to ICAM-1 or VCAM-1 inhibited adherence of PMN or MNC in a dose dependent manner. These results suggest that alpha-Toc works as anti-atherogenic agent through inhibiting endothelial-dependent adhesive interactions with leukocytes induced by oxLDL.

Cardiovascular tissue injury in ischemia/reperfusion has been shown to be prevented by angiotensin-converting enzyme (ACE) inhibitors. However, the mechanism on endothelial cells has not been assessed in detail. Cultured human aortic endothelial cells (HAEC) were exposed to hypoxia with or without reoxygenation. Hypoxia enhanced apoptosis along with the activation of caspase-3. Reoxygenation increased lactate dehydrogenase release time-dependently, along with an increase of intracellular oxygen radicals. ACE inhibitor quinaprilat and bradykinin significantly lessened apoptosis and lactate dehydrogenase release with these effects being diminished by a kinin B2 receptor antagonist and a nitric oxide synthase inhibitor. In conclusion, hypoxia activated the suicide pathway leading to apoptosis of HAEC by enhancing caspase-3 activity, while subsequent reoxygenation induced necrosis by enhancing oxygen radical production. Quinaprilat could ameliorate both apoptosis and necrosis through the upregulation of constitutive endothelial nitric oxide synthase via an increase of bradykinin, with the resulting increase of nitric oxide.

The protective effects and roles of AT1-receptor antagonists (AT1-RA) or angiotensin-converting enzyme inhibitors (ACEI) on vascular endothelial cell (EC) injury during hypoxia are not entirely known. Therefore, we investigated these effects and mechanisms in human aortic (HA) EC. DNA fragmentation, Lactate dehydrogenase (LDH) release, and caspase-3 activity were measured in cultured HAEC after exposure to hypoxia in the presence or absence of an AT1-RA (candesartan, CS) and/or an ACEI (temocaprilat, TC). Next, we investigated endothelial cell nitric oxide synthase (ecNOS) and inducible (i) NOS to determine the role of the bradykinin(BK)-NO pathway in the protective effect on ACEI and AT1-RA in the setting of hypoxia-induced apoptosis. Exposure to hypoxia increased DNA fragmentation in HAEC associated with the activation of caspase-3, but did not affect LDH release. In addition, hypoxia induced ecNOS mRNA but not mRNA iNOS. CS and/or TC reduced apoptosis induced by hypoxia in a dose-dependent manner, and significantly increased BK and ecNOS expression. This effect was attenuated by the kinin B2 receptor antagonist, HOE 140, and the NOS inhibitor, N-nitro-L-arginine methylester (L-NMMA). Hypoxia activates the pathway leading to apoptosis by enhancing caspase-3 activity. Both CS and TC can ameliorate hypoxia-induced apoptosis in HAEC through inhibiting caspase-3 activation by enhancing ecNOS activity, via the accumulation of BK.