Alpha-1A Adrenergic Receptor Stimulation with Phenylephrine Promotes Arachidonic Acid Release by Activation of Phospholipase D in Rat-1 Fibroblasts: Inhibition by Protein Kinase A

• Published in: The Journal of pharmacology and experimental therapeutics 1998-02, Vol.284 (2), p.576
• Main Authors: Ruan, Y, Kan, H, Parmentier, J H, Fatima, S, Allen, L F, Malik, K U
• Format: Article
• Language: English
• Subjects: Adenine - analogs & derivatives; Adenine - pharmacology; Adenylate Cyclase Toxin; Animals; Arachidonic Acid - metabolism; Calcimycin - pharmacology; Carbazoles; Cell Line; Cholera Toxin - pharmacology; Colforsin - pharmacology; Cyclic AMP - physiology; Cyclic AMP-Dependent Protein Kinases - antagonists & inhibitors; Cyclic AMP-Dependent Protein Kinases - physiology; Diglycerides - physiology; Enzyme Activation - drug effects; Enzyme Inhibitors - pharmacology; Glycerides - physiology; GTP-Binding Proteins - physiology; Indoles - pharmacology; Lipase - metabolism; Phenylephrine - pharmacology; Phospholipase D - metabolism; Phospholipases A - metabolism; Phospholipases A2; Prazosin - metabolism; Pyrroles - pharmacology; Radioligand Assay; Rats; Receptors, Adrenergic, alpha-1 - physiology; Transfection; Virulence Factors, Bordetella - pharmacology
• ISSN: 0022-3565; 1521-0103

This study was conducted to determine the mechanism of arachidonic acid (AA) release elicited by phenylephrine (PHE) stimulation of alpha adrenergic receptor (AR), and its modulation by cyclic adenosine 3′,5′-monophosphate (cAMP) in Rat-1 fibroblasts (R-1Fs) transfected with the alpha -1A, alpha -1B or alpha -1D AR. PHE increased AA release and also caused a marked accumulation of cAMP in R-1Fs expressing the alpha -1 AR subtypes, but not in those transfected with vector alone. PHE also enhanced phospholipase D (PLD), but not phospholipase A 2 (PLA 2 ) activity. The increase in PHE-induced AA release, PLD activity and cAMP accumulation differed among the various alpha AR subtypes with: alpha -1A > alpha -1B > alpha -1D AR. The effect of PHE to increase AA release was attenuated by C 2 -ceramide, an inhibitor of PLD; propranolol, a phosphatidate phosphohydrolase inhibitor; and RHC-80267, a diacylglycerol lipase inhibitor in R-1Fs expressing the alpha -1A AR. Forskolin, which activates adenylyl cyclase, increased cAMP accumulation and inhibited PHE-induced AA release and PLD activity in alpha -1A-AR–expressing R-1Fs. 8-(4-chlorophenyl-thio)-cAMP, a nonhydrolyzable analog of cAMP, also attenuated the rise in AA release and PLD activity elicited by PHE in these cells. In contrast, SQ 22536, an adenylyl cyclase inhibitor, and KT 5720, a protein kinase A inhibitor, increased PHE-induced AA release and PLD activity in R-1Fs expressing the alpha -1A AR. These data suggest that the alpha -1A, alpha -1B and alpha -1D ARs are coupled to PLD activation and cAMP accumulation. Moreover, PHE promotes AA release in R-1Fs expressing the alpha -1A AR through PLD activation. Furthermore, cAMP generated by alpha -1A AR stimulation acts as an inhibitory modulator of PLD activity and AA release via protein kinase A.