Arachidonic acid mediates non-capacitative calcium entry evoked by CB1-cannabinoid receptor activation in DDT1 MF-2 smooth muscle cells
✍ Scribed by Dirk G. Demuth; Effimia Gkoumassi; Melloney J. Dröge; Bart G.J. Dekkers; Henk J. Esselink; Rutger M. van Ree; Mike E. Parsons; Johan Zaagsma; Areles Molleman; S. Ad Nelemans
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 219 KB
- Volume
- 205
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
Cannabinoid CB~1~‐receptor stimulation in DDT~1~ MF‐2 smooth muscle cells induces a rise in [Ca^2+^]~i~, which is dependent on extracellular Ca^2+^ and modulated by thapsigargin‐sensitive stores, suggesting capacitative Ca^2+^ entry (CCE), and by MAP kinase. Non‐capacitative Ca^2+^ entry (NCCE) stimulated by arachidonic acid (AA) partly mediates histamine H~1~‐receptor‐evoked increases in [Ca^2+^]~i~ in DDT~1~ MF‐2 cells. In the current study, both Ca^2+^ entry mechanisms and a possible link between MAP kinase activation and increasing [Ca^2+^]~i~ were investigated. In the whole‐cell patch clamp configuration, the CB‐receptor agonist CP 55, 940 evoked a transient, Ca^2+^‐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 CB~1~ antagonist SR 141716. The non‐selective Ca^2+^ channel blockers La^3+^ and Gd^3+^ inhibited the CP 55,940‐induced current at concentrations that had no effect on thapsigargin‐evoked CCE. La^3+^ also inhibited the AA‐induced current. CP 55,940‐induced AA release was abolished by Gd^3+^ and by phospholipase A~2~ 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 DDT~1~ MF‐2 cells, AA is an integral component of the CB~1~ receptor signaling pathway, upstream of NCCE and, via PLA~2~, downstream of MAP kinase. © 2005 Wiley‐Liss, Inc.