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Systems wide analyses of lipids in the brainstem during inflammatory orofacial pain – Evidence of increased phospholipase A 2 activity
Author(s) -
Ma M.T.,
Yeo J.F.,
Shui G.,
Wenk M.R.,
Ong W.Y.
Publication year - 2012
Publication title -
european journal of pain
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.305
H-Index - 109
eISSN - 1532-2149
pISSN - 1090-3801
DOI - 10.1016/j.ejpain.2011.06.013
Subject(s) - medulla oblongata , chemistry , lysophosphatidylethanolamine , lipidomics , orofacial pain , phospholipase a2 , endocrinology , nociception , medulla , rostral ventromedial medulla , hyperalgesia , medicine , biochemistry , phospholipid , biology , central nervous system , enzyme , phosphatidylcholine , receptor , radiology , membrane
Recent studies suggest that CNS phospholipase A 2 ( PLA 2 ) isoforms play a role in nociception, but until now, direct evidence of increased brain PLA 2 activity during allodynia or hyperalgesia is lacking. The present study was carried out, using lipidomics or systems wide analyses of lipids using tandem mass spectrometry, to elucidate possible changes in rat brain lipids after inflammatory pain induced by facial carrageenan injection. The caudal medulla oblongata showed decreases in phospholipids including phosphatidylethanolamine and phosphatidylinositol species, but increases in lysophospholipids, including lysophosphatidylethanolamine, lysophosphatidylinositol and lysophosphatidylserine, indicating increased PLA 2 activity and release of arachidonic acid after facial carrageenan injection. These changes likely occur in the spinal trigeminal nucleus which relays nociceptive input from the orofacial region. High levels of sPLA 2 ‐III , sPLA 2 ‐XIIA , cPLA 2 and iPLA 2 mRNA expression were detected in the medulla oblongata. Increase in sPLA 2 ‐III mRNA expression was found in the caudal medulla of carrageenan‐injected rats, although no difference in sPLA 2 ‐III protein expression was detected. The changes in lipids as determined by lipidomics were therefore consistent with an increase in PLA 2 enzyme activity , but no change in enzyme protein expression. Together, these findings indicate enhanced PLA 2 activity in the caudal medulla oblongata after inflammatory orofacial pain.