Dobutamine protects lymphocyctes against staurosporin-induced apoptosis via a receptor-independent and p38-independent pathway
© BioMed Central Ltd. 2007
Published: 22 March 2007
Since catecholamines have been shown to modulate various immunological functions, the goal of this work was to investigate their effects on staurosporin-induced apoptosis of Jurkat T cells, a well-established model for human T lymphocytes.
Jurkat T cells passages 1–12 were used. Apoptosis was measured with a caspase-activity assay and with FACS analysis of annexin–propidium iodide double-stained cells.
Exposure of Jurkat T cells for 2 hours to staurosporin (2 μM) induced apoptosis: the number of apoptotic cells increased to 14.0 ± 0.8% versus 2.3 ± 0.4% in the control group. Pre-treatment (4 hours) with dobutamine 100 and 500 μM decreased the staurosporin-induced apoptosis to 11.6 ± 0.6% and 8.7 ± 0.7%, respectively (P < 0.01, mean ± SEM, n = 44). Other catecholamines like epinephrine and norepinephrine (both up to 500 μM) had no effect on staurosporin-induced apoptosis. To investigate whether this protective effect of dobutamine was mediated via β-receptors, specific β-blockers were used: neither atenolol (β1) (100 mM), nor ICI 118,551 (β2) (10 mM) blocked the protective effect of dobutamine. Furthermore, dobutamine (1–500 μM) did not increase cAMP production in these cells. Therefore, the protective effect of dobutamine is not β-receptor-mediated. Since it was previously demonstrated that MAPKs p38 and JNK, but not ERK, are activated by dobutamine in Jurkat T cells, we investigated whether the activation of these MAPKs are involved in the protection by dobutamine: inhibition of JNK activation with SP 600125 (1 μM) did not influence the protective effect of dobutamine. Inhibition of p38 activation with SBI 202190 (5 μM) even seemed to reinforce the protection afforded by dobutamine.
These experiments demonstrate that dobutamine pretreatment protects T cells from staurosporin-induced apoptosis. This protective effect is not β-receptor-mediated. Also, activation of MAPKs p38 or JNK by dobutamine is not responsible for the protective effect. The molecular mechanisms by which dobutamine exerts this protective effect remain to be elucidated.