Inflammatory cytokines enhance muscarinic-mediated arachidonic acid release through p38 mitogen-activated protein kinase in A2058 cells

The human melanoma cell line A2058 expresses the G(q)-coupled M5 subtype of muscarinic receptor. Stimulation with the cholinergic agonist, carbachol; induces a dose-dependent increase in arachidonic acid release. The carbacho l-induced arachidonate release is potentiated two- to threefold by pretreat ment of A2058 cells with either of the inflammatory cytokines, tumor necros is factor-alpha or interleukin-1 beta. Cytokine-induced enhancement of musc arinic-mediated arachidonic acid release peaks near 1 h. Western analysis s uggests that both cytokines are capable of activating the nuclear factor-ka ppa B (NF-kappa B) and p38 mitogen-activated protein kinase (MAPK) pathways . Anisomycin (1 mu M) treatment mimics the cytokine-induced enhancement of arachidonic acid production and activates the p38 MAPK pathway, but does no t activate the NF-kappa B pathway. Furthermore, pretreatment of A2058 cells with the putative p38 MAPK inhibitor, SB202190, ablates the cytokine-depen dent augmentation without interfering with the muscarinic-mediated arachido nic acid release in untreated cells. Moreover, cytokine treatment does not affect other M5-coupled pathways (e.g., phospholipase C activity or intrace llular Ca2+ mobilization), suggesting that p38 MAPK activation principally modulates muscarinic-mediated phospholipase A(2) activity. Finally, in prim ary cultures of cells taken from rat cerebellum, key aspects of this findin g are repeated in cultures enriched for glia, but not in cultures enriched for granule neurons.