Activation of protein kinases A and C increase lymphocyte penetration through endothelial monolayers

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Abstract
A brief incubation of lymphocytes with either PMA, stimulating protein kinase C, or with dibutyryl‐cAMP, leading to protein kinase A activation, led to increased lymphocyte penetration through intact endothelial monolayers in vitro. The PMA‐induced penetration could be dose‐dependently down‐regulated with a protein kinase C inhibitor, H7. Similarly HA 1004, being mainly a protein kinase A inhibitor, decreased the dibutyryl‐cAMP induced penetration. Treatment of lymphocytes with PMA and cAMP did not alter the expression of CD44 homing receptors on lymphocytes. Stimulation of lymphocytes with dibutyryl‐cGMP or calcium ionophore had no effect on lymphocyte penetration. These results suggest that activation of both protein kinases A and C is important in the lymphocyte binding to endothelium.