Apoptosis of peripheral blood lymphocytes is induced by catecholamines

We explored the mechanism through which patients sometimes show immunosuppr ession after cardiac surgery. To test the hypothesis that commonly used dru gs could cause apoptosis of immune cells, the proapoptotic effects of hepar in and catecholamines (dopamine and dobutamine) on peripheral blood lymphoc ytes were evaluated. Peripheral blood lymphocytes were purified from blood samples of normal healthy volunteers. These cells were cultured in the pres ence of heparin, dobutamine or dopamine. The apoptosis was quantified by An nexin V fluorescent assay, by DNA content and by morphological assessment. Lymphocytes did not show significant levels of apoptosis induction after 24 hours of incubation with heparin. Both dopamine and dobutamine demonstrate d a clear apoptosis inducing effect on lymphocytic population after 24 and 48 hours of culture, in concentrations comparable with the clinically used levels. Apoptosis was time and concentration dependent for both catecholami nes. The dopamine and dobutamine effect on lymphocyte viability was due, at least partially, to lymphocyte beta receptor engagement, as proved by bloc king the receptor with propranolol. These results suggest that catecholamin es could induce apoptosis of lymphocytes. This finding may be associated wi th immunosuppression observed in patients undergoing cardiac surgery.