Norepinephrine-induced stimulation of p38 mitogen-activated protein kinase is mediated by arachidonic acid metabolites generated by activation of cytosolic phospholipase A(2) in vascular smooth muscle cells.
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 Ca(2+) and activates cytosolic phospholipase A(2) (cPLA(2)) in vascular smooth muscle cells (VSMC). The purpose of this study was to determine the contribution of cPLA(2)-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 alpha-1 and alpha-2 adrenergic receptors, was dependent on extracellular Ca(2+), and was attenuated by an inhibitor of cPLA(2) (pyrrolidine-1). Moreover, the cPLA(2) 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 cPLA(2)-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.
Kalyankrishna
Shailaja
S
Department of Pharmacology and Centers for Vascular Biology and Connective Tissue Diseases, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Malik
Kafait U
KU
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism* / Q000502:physiology; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D009638:Norepinephrine / Q000494:pharmacology*; D010741:Phospholipases A / Q000378:metabolism* / Q000502:physiology; D011817:Rabbits; D048051:p38 Mitogen-Activated Protein Kinases
D016718:Arachidonic Acid; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D009638:Norepinephrine