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Arachidonic acid release mediated by OX 1 orexin receptors
Author(s) -
Turunen Pauli M,
Ekholm Marie E,
Somerharju Pentti,
Kukkonen Jyrki P
Publication year - 2010
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2009.00535.x
Subject(s) - arachidonic acid , receptor , orexin receptor , orexin , chemistry , endocrinology , biochemistry , biology , neuroscience , microbiology and biotechnology , neuropeptide , enzyme
Background and purpose: We have previously shown that lipid mediators, produced by phospholipase D and C, are generated in OX 1 orexin receptor signalling with high potency, and presumably mediate some of the physiological responses to orexin. In this study, we investigated whether the ubiquitous phospholipase A 2 (PLA 2 ) signalling system is also involved in orexin receptor signalling. Experimental approach: Recombinant Chinese hamster ovary‐K1 cells, expressing human OX 1 receptors, were used as a model system. Arachidonic acid (AA) release was measured from 3 H‐AA‐labelled cells. Ca 2+ signalling was assessed using single‐cell imaging. Key results: Orexins strongly stimulated [ 3 H]‐AA release (maximally 4.4‐fold). Orexin‐A was somewhat more potent than orexin‐B (pEC 50 = 8.90 and 8.38 respectively). The concentration–response curves appeared biphasic. The release was fully inhibited by the potent cPLA 2 and iPLA 2 inhibitor, methyl arachidonyl fluorophosphonate, whereas the iPLA 2 inhibitors, R‐ and S‐bromoenol lactone, caused only a partial inhibition. The response was also fully dependent on Ca 2+ influx, and the inhibitor studies suggested involvement of the receptor‐operated influx pathway. The receptor‐operated pathway, on the other hand, was partially dependent on PLA 2 activity. The extracellular signal‐regulated kinase, but not protein kinase C, were involved in the PLA 2 activation at low orexin concentrations. Conclusions and implications: Activation of OX 1 orexin receptors induced a strong, high‐potency AA release, possibly via multiple PLA 2 species, and this response may be important for the receptor‐operated Ca 2+ influx. The response coincided with other high‐potency lipid messenger responses, and may interact with these signals.