title: Arachidonic acid mediates non-capacitative calcium entry evoked by CB1-cannabinoid receptor activation in DDT1 MF-2 smooth muscle cells.
abstract: Cannabinoid CB1-receptor stimulation in DDT1 MF-2 smooth muscle cells induces a rise in [Ca2+]i, which is dependent on extracellular Ca2+ and modulated by thapsigargin-sensitive stores, suggesting capacitative Ca2+ entry (CCE), and by MAP kinase. Non-capacitative Ca2+ entry (NCCE) stimulated by arachidonic acid (AA) partly mediates histamine H1-receptor-evoked increases in [Ca2+]i in DDT1 MF-2 cells. In the current study, both Ca2+ entry mechanisms and a possible link between MAP kinase activation and increasing [Ca2+]i were investigated. In the whole-cell patch clamp configuration, the CB-receptor agonist CP 55, 940 evoked a transient, Ca2+-dependent K+ current, which was not blocked by the inhibitors of CCE, 2-APB, and SKF 96365. AA, but not its metabolites, evoked a transient outward current and inhibited the response to CP 55,940 in a concentration-dependent manner. CP 55,940 induced a concentration-dependent release of AA, which was inhibited by the CB1 antagonist SR 141716. The non-selective Ca2+ channel blockers La3+ and Gd3+ inhibited the CP 55,940-induced current at concentrations that had no effect on thapsigargin-evoked CCE. La3+ also inhibited the AA-induced current. CP 55,940-induced AA release was abolished by Gd3+ and by phospholipase A2 inhibition using quinacrine; this compound also inhibited the outward current. The CP 55,940-induced AA release was strongly reduced by the MAP kinase inhibitor PD 98059. The data suggest that in DDT1 MF-2 cells, AA is an integral component of the CB1 receptor signaling pathway, upstream of NCCE and, via PLA2, downstream of MAP kinase.
authors.affiliation: School of Life Sciences, Faculty of Health and Human Sciences, University of Hertfordshire, Hatfield, Hertfordshire, United Kingdom.
authors.forename: Dirk G
authors.initials: DG
authors.lastname: Demuth
authors.forename: Effimia
authors.initials: E
authors.lastname: Gkoumassi
authors.forename: Melloney J
authors.initials: MJ
authors.lastname: Dröge
authors.forename: Bart G J
authors.initials: BG
authors.lastname: Dekkers
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Esselink
authors.forename: Rutger M
authors.initials: RM
authors.lastname: van Ree
authors.forename: Mike E
authors.initials: ME
authors.lastname: Parsons
authors.forename: Johan
authors.initials: J
authors.lastname: Zaagsma
authors.forename: Areles
authors.initials: A
authors.lastname: Molleman
authors.forename: S Ad
authors.initials: SA
authors.lastname: Nelemans
mesh_terms: D016718:Arachidonic Acid / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D025802:Electric Capacitance; D005682:Gadolinium / Q000494:pharmacology; D006632:Histamine / Q000378:metabolism; D007811:Lanthanum / Q000494:pharmacology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists* / Q000378:metabolism*
chemical_list: D043884:Receptor, Cannabinoid, CB1; D016718:Arachidonic Acid; D007811:Lanthanum; D006632:Histamine; D005682:Gadolinium; D020928:Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D002118:Calcium