Role of Ca 2+ in the effects of shear stress and TNF-α on caveolin-1 expression

The aim of this work was to study the influences of Ca²⁺ (medium free calcium, with BAPTA, with 100 mM Ca²⁺, 100 mM Ca²⁺+10 μM ionomycin) on the expression of caveolin-1 (structural protein of caveolae) of endothelial cells (ECs) submitted to mechanical forces (shear stress) or biochemical stimulation (TNF-α). We found that shear stress enhanced the caveolin-1 expression. Simultaneously, the caveolin-1 expression is dependant on [Ca²⁺]i: [Ca²⁺]_{free medium+100 μM BAPTA}<[Ca²⁺]_{free medium}<[Ca²⁺]_{100 mM}<[Ca²⁺]_{100 mM+10 μM ionomycin}. In contrast, TNF-α induced a decrease of caveolin-1 in the cells, whatever the [Ca²⁺]i. These results suggest that there could be a synergistic effect between shear stress and Ca²⁺ on caveolin-1 expression but an inflammatory stimulation (TNF-α) induces a down regulation of caveolin-1 expression.