Activation of p38 mitogen-activated protein kinase by norepinephrine in T-lineage cells

The catecholamine norepinephrine (NE) stimulates T lymphocytes through a beta-adrenergic receptor (βAR)/adenylyl cyclase (AC)/cyclic AMP (cAMP)/protein kinase A (PKA) pathway, leading to altered cell responsiveness and apoptosis. p38 Mitogen-activated protein kinase (MAPK), a major intracellular signalling mediator for cellular and environmental stressors, is involved in the production of immune modulators and in the regulation of T-cell development, survival and death. In these studies we investigated the relationship among NE signalling, p38 MAPK activity and T-cell death. We showed that NE stimulation of BALB/c mouse thymocytes and S49 thymoma cells selectively increases the dual phosphorylation and activity of p38α MAPK. p38 MAPK activation involves the βAR, Gs protein, AC, cAMP and PKA, as determined through the use of a βAR antagonist, activators of AC and cAMP, and S49 clonal mutants deficient in Gs and PKA. Dual phosphorylation of p38 MAPK is also dependent on its own catalytic activity. Inhibition of p38 MAPK activity revealed its involvement in cAMP-mediated activating transcription factor-2 (ATF-2) phosphorylation, Fas ligand messenger RNA (mRNA) up-regulation, and cell death. These results identify a mechanism through which NE stimulation of the βAR/Gs/PKA pathway activates p38 MAPK, which can be potentiated by autophosphorylation, and leads to changes in T-cell dynamics, in part through the regulation of Fas ligand mRNA expression.