Norepinephrine-mediated inhibition of antitumor cytotoxic T lymphocyte generation involves a beta-adrenergic receptor mechanism and decreased TNF-alpha gene expression

We have previously shown that norepinephrine (NE) inhibits the in vitro gen eration of anti-MOPC-315 CTL activity by spleen cells from BALB/c mice reje cting a large MOPC-315 tumor as a consequence of low-dose melphalan (L-phen ylalanine mustard (L-PAM)) treatment (L-PAM TuB spleen cells), Since TNF-cr plays a hey role in the generation of antitumor CTL activity in this syste m, we determined whether NE mediates this inhibition through inhibition of TNF-cu production. Here, we show that NE inhibits the production of TNF-alp ha protein and mRNA by L-PAM TuB spleen cells stimulated in vitro with mito mycin C-treated tumor cells, Flow cytometric analysis of intracellular expr ession of TNF-alpha revealed substantial NE-mediated decreases in the perce ntages of TNF-alpha(+) cells among CD4(+) and CD8(+) T cells and F4/80(+) a ctivated macrophages, NE inhibition of CTL generation was largely overcome by addition of TNF-alpha to the stimulation cultures, When the beta-adrener gic antagonist propranoIol was added to the stimulation cultures of L-PAM T uB spleen cells at a concentration that prevented NE-induced cAMP elevation , the NE-mediated decrease in TNF-alpha mRNA and NE-mediated inhibition of CTL generation were reversed. Collectively, these results suggest that NE i nhibits antitumor CTL generation, at least in part, by inhibiting TNF-alpha synthesis through a mechanism(S) involving beta-adrenergic receptor signal ing.