Role of p38 mitogen-activated protein kinase and extracellular signal-regulated protein kinase kinase in adenosine A(2B) receptor-mediated interleukin-8 production in human mast cells

The endogenous nucleoside adenosine is thought to play a role in the pathop hysiology of asthma by stimulating mast cells. We previously showed that th e human mast cell line HMC-1 expresses A(2A) and A(2B) receptors, and that both receptors activate adenylate cyclase via G(s)-protein but that only A( 2B) receptors are also coupled to phospholipase C via G(q) proteins. Stimul ation of A(2B) but not A(2A) receptors induced production of interleukin-8 (IL-8) from HMC-1 cells. The mechanism by which adenosine promotes IL-8 syn thesis has not been defined. In this study, we tested the hypothesis that m itogen-activated protein kinase (MAPK) signaling pathways are involved in t his process. Stimulation of HMC-1 with the stable adenosine analog NECA (5' -N-ethylcarboxamidoadenosine) activated p21(ras) and both p42 and p44 isofo rms of extracellular signal-regulated kinase (ERK). NECA (10 mu M) induced a 1.9 +/- 0.06-fold increase in ERK activity, whereas 10 mu M of the select ive A(2A) agonist CGS 21680 (4-((N-ethyl-5'-carbamoyladenos-2-yl)-aminoethy l)- phenylpropionic acid) had no effect. NECA, in parallel with the activat ion of ERK, also stimulated the p46 isoform of c-Jun N-terminal kinase (MEK ) and p38 MAPK. Furthermore, the selective MAPK/ERK kinase 1 inhibitor PD 9 8059 (2'-amino-3'-methoxyflavone), and p38 MAPK inhibitors SB 202190 (4-(4- fluorophenyl)-2-(4- hydroxyphenyl)-5-(4-pyridyl) 1H-imidazole) and SE 20358 0 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl) 1H-imidazole ) blocked A(2B) receptor-mediated production of IL-8. These results indicat e that extracellular adenosine can regulate ERK, c-Jun N-terminal kinase,an d p38 MAPK signaling cascades and that activation of ERK and p38 MAPK pathw ays are essential steps in adenosine A(2B) receptor-dependent stimulation o f IL-8 production in HMC-1.