Abstract
The endogenous nucleoside adenosine is thought to play a role in the pathophysiology of asthma by stimulating mast cells. We previously showed that the human mast cell line HMC-1 expresses A2Aand A2B receptors, and that both receptors activate adenylate cyclase via Gs-protein but that only A2B receptors are also coupled to phospholipase C via Gq proteins. Stimulation of A2B but not A2A receptors induced production of interleukin-8 (IL-8) from HMC-1 cells. The mechanism by which adenosine promotes IL-8 synthesis has not been defined. In this study, we tested the hypothesis that mitogen-activated protein kinase (MAPK) signaling pathways are involved in this process. Stimulation of HMC-1 with the stable adenosine analog NECA (5′-N-ethylcarboxamidoadenosine) activated p21ras and both p42 and p44 isoforms of extracellular signal-regulated kinase (ERK). NECA (10 μM) induced a 1.9 ± 0.06-fold increase in ERK activity, whereas 10 μM of the selective A2A agonist CGS 21680 (4-((N-ethyl-5′-carbamoyladenos-2-yl)-aminoethyl)-phenylpropionic acid) had no effect. NECA, in parallel with the activation 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 98059 (2′-amino-3′-methoxyflavone), and p38 MAPK inhibitors SB 202190 (4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole) and SB 203580 (4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole) blocked A2B receptor-mediated production of IL-8. These results indicate that extracellular adenosine can regulate ERK, c-Jun N-terminal kinase, and p38 MAPK signaling cascades and that activation of ERK and p38 MAPK pathways are essential steps in adenosine A2B receptor-dependent stimulation of IL-8 production in HMC-1.
Footnotes
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Send reprint requests to: Igor Feoktistov, Ph.D., Departments of Pharmacology and Medicine, Room 315 MRB II, Vanderbilt University, Nashville, TN 37232-6300. E-mail:Igor.Feoktistov{at}mcmail.vanderbilt.edu
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Supported by National Institutes of Health Grants R29HL55596 and RR00095.
- Abbreviations:
- NECA
- 5′-N-ethylcarboxamidoadenosine
- CGS 21680
- 4-((N-ethyl-5′-carbamoyladenos-2-yl)-aminoethyl)-phenylpropionic acid
- IL-8
- interleukin-8
- MAPK
- mitogen-activated protein kinase
- ERK
- extracellular signal-regulated kinase
- JNK
- Jun N-terminal kinase
- SB 202190
- 4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole
- SB 203580
- 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole
- MEK
- MAPK/ERK kinase
- RBD
- minimal p21ras-binding domain of Raf-1
- GST
- glutathione S-transferase
- PD 98059
- 2′-amino-3′-methoxyflavone
- Ro 32-0432
- [2-{8-[(dimethylamino)methyl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-3-yl}-3-(1-methylindol-3-yl)maleimide, hydrochloride]
- PMA
- phorbol 12-myristate 13-acetate
- Received December 29, 1998.
- Accepted January 25, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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