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Spinal phospholipase A 2 in inflammatory hyperalgesia: role of Group IVA cPLA 2
Author(s) -
Lucas Karin Killermann,
Svensson Camilla I,
Hua XiaoYing,
Yaksh Tony L,
Dennis Edward A
Publication year - 2005
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 - 10.1038/sj.bjp.0706116
Subject(s) - hyperalgesia , group (periodic table) , phospholipase a , neuroscience , medicine , chemistry , phospholipase a2 , psychology , biochemistry , nociception , enzyme , receptor , organic chemistry
1 Current work has shown the importance of spinal cyclooxygenase (COX) products in facilitatory processes leading to tissue injury induced hyperalgesia. This cascade must originate with free arachidonic acid (AA) released by the activity of spinal phospholipase A 2 's (PLA 2 ). In the present work, we studied the role of PLA 2 's in spinal sensitization. 2 We first demonstrate the presence of constitutive mRNA in the spinal cord for PLA 2 Groups IB, IIA, IIC, IVA, V and VI by reverse transcription–polymerase chain reaction (RT–PCR) and sequencing. Using quantitative‐PCR, we found that Group IVA cPLA 2 and Group VI iPLA 2 are the predominant PLA 2 messages in the spinal cord. Western blotting and activity assays specific for Group IVA cPLA 2 and Group VI iPLA 2 verified the presence of these enzymes. PLA 2 activity in spinal cord homogenates was suppressed by methyl arachidonyl fluorophosphonate (MAFP) and arachidonyl trifluoromethylketone (AACOCF 3 ), mixed inhibitors of Group IVA cPLA 2 and Group VI iPLA 2 as well as by bromoenol lactone (BEL), a Group VI iPLA 2 inhibitor. The spinal expression of PLA 2 mRNA or protein was not altered in the face of peripheral inflammation. Secondly, we showed that intrathecal (i.t.) administration of MAFP and AACOCF 3 , but not BEL, dose‐dependently prevented thermal hyperalgesia induced by intraplantar carrageenan as well as formalin‐induced flinching. Finally, i.t. injection of AACOCF 3 , at antihyperalgesic doses, decreased the release of prostaglandin E 2 (PGE 2 ) into spinal dialysate evoked by i.t. NMDA, while i.t. injection of BEL had no effect. 3 Taken together, this work points to a role for constitutive Group IVA cPLA 2 in spinal nociceptive processing.British Journal of Pharmacology (2005) 144 , 940–952. doi: 10.1038/sj.bjp.0706116