Abstract
p38 mitogen-activated protein kinase (MAPK) is activated by norepinephrine (NE) in the vasculature and is implicated in vascular smooth muscle hypertrophy, contraction, and cell migration. NE promotes influx of Ca2+ and activates cytosolic phospholipase A2 (cPLA2) in vascular smooth muscle cells (VSMC). The purpose of this study was to determine the contribution of cPLA2-generated arachidonic acid (AA) and its metabolites to the activation of p38 MAPK measured by its phosphorylation, in response to NE in rabbit VSMC. NE-induced p38 MAPK activation was found to be mediated through the stimulation of α-1 and α-2 adrenergic receptors, was dependent on extracellular Ca2+, and was attenuated by an inhibitor of cPLA2 (pyrrolidine-1). Moreover, the cPLA2 product, AA, activated p38 MAPK in VSMC. p38 MAPK activation elicited by NE was decreased significantly by the lipoxygenase (LO) inhibitor baicalein, and to a lesser extent by the cytochrome P450 inhibitor 17-octadecynoic acid, but was not affected by the cyclooxygenase inhibitor indomethacin. The LO metabolites of AA, namely 5(S)-hydroxyeicosatetraenoic acid (HETE), 12(S)-HETE, and 15(S)-HETE and the cytochrome P450 metabolite 20-HETE, activated p38 MAPK. NE-induced p38 MAPK stimulation was found to be independent of phospholipase D (PLD) activation in rabbit VSMC. Transactivation of the epidermal growth factor receptor (EGFR) by NE also did not contribute to p38 MAPK activation. These data suggest that cPLA2-generated AA and its LO metabolites mediate NE-induced p38 MAPK stimulation in rabbit VSMC by a mechanism that is independent of PLD and EGFR activation.
Footnotes
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This study was supported by National Institutes of Health (National Heart, Lung, and Blood Institute) Grant 19134-27 and by grants from the Centers for Vascular Biology and Connective Tissue Diseases, University of Tennessee Health Science Center. Portions of this manuscript were presented at Experimental Biology 2002 and have been published in the meeting abstracts.
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DOI: 10.1124/jpet.102.040949
- Abbreviations:
- NE
- norepinephrine
- AR
- adrenergic receptor
- VSMC
- vascular smooth muscle cells
- cPLA2
- cytosolic phospholipase A2
- PLD
- phospholipase D
- AA
- arachidonic acid
- COX
- cyclooxygenase
- HETE
- hydroxy-eicosatetraenoic acid
- LO
- lipoxygenase
- P450
- cytochrome P450
- ERK
- extracellular signal-regulated kinase
- MAPK
- mitogen-activated protein kinase
- EGFR
- epidermal growth factor receptor
- EGF
- epidermal growth factor
- 17-ODYA
- 17-octadecynoic acid
- M199
- medium 199
- HBSS
- Hanks' balanced salt solution
- PBS
- phosphate-buffered saline
- RIPA
- radioimmunoprecipitation assay
- TBST
- Tris-buffered saline with Tween 20
- DMSO
- dimethyl sulfoxide
- GPCR
- G protein-coupled receptor
- Received June 28, 2002.
- Accepted October 8, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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