Differential inhibition by α- and β-tocopherol of human erythroleukemia cell adhesion: role of integrins

The effect of α- and β-tocopherol on human erythroleukemia cell (HEL) adhesion induced by phorbol 12-myristate 13-acetate (PMA) has been studied. Adhesion induced by PMA stimulation was prevented by 44.5% by physiological concentrations of α-tocopherol. Under the same experimental conditions, β-tocopherol, an analogue of α-tocopherol, produced 11% inhibition of adhesion. Cell response gradually increased from 0 to 24 h of α-tocopherol treatment. Only a slight time dependency of β-tocopherol inhibition was observed. Another human erythroleukemia cell line (K562) and the human monocyte tumor cell line U937 showed 5.0 and 11.2% inhibition, respectively. Similar to α-tocopherol, the protein kinase C inhibitor, Calphostin C, and the MAPK inhibitor, PD98059, prevented PMA-induced cell adhesion. An inhibition of ERK-1 phosphorylation was observed for α-tocopherol only in HEL, implying that MAP kinase pathway is involved in this cell line. Fluorescence-activated cell sorting (FACS), by using various integrin-specific monoclonal antibodies, has shown that α (1–6), β1, and αv integrins are less expressed at the cell surface after α-tocopherol treatment. Beta-tocopherol treatment was less effective.