title: Intraplantar-injected ceramide in rats induces hyperalgesia through an NF-κB- and p38 kinase-dependent cyclooxygenase 2/prostaglandin E2 pathway.
abstract: Inflammatory pain represents an important unmet clinical need with important socioeconomic implications. Ceramide, a potent proinflammatory sphingolipid, has been shown to elicit mechanical hyperalgesia, but the mechanisms remain largely unknown. We now demonstrate that, in addition to mechanical hyperalgesia, intraplantar injection of ceramide (10 μg) led to the development of thermal hyperalgesia that was dependent on induction of the inducible cyclooxygenase (COX-2) and subsequent increase of prostaglandin E(2) (PGE(2)). The development of mechanical and thermal hyperalgesia and increased production of PGE(2) was blocked by NS-398 (15-150 ng), a selective COX-2 inhibitor. The importance of the COX-2 to PGE(2) pathway in ceramide signaling was underscored by the findings that intraplantar injection of a monoclonal PGE(2) antibody (4 μg) blocked the development of hyperalgesia. Our results further revealed that COX-2 induction is regulated by NF-κB and p38 kinase activation, since intraplantar injection of SC-514 (0.1-1 μg) or SB 203580 (1-10 μg), well-characterized inhibitors of NF-κB and p38 kinase activation, respectively, blocked COX-2 induction and increased formation of PGE(2) and thermal hyperalgesia in a dose-dependent manner. Moreover, activation of NF-κB was dependent on upstream activation of p38 MAPK, since SB 203580 (10 μg) blocked p65 phosphorylation, whereas p38 kinase phosphorylation was unaffected by NF-κB inhibition by SC-514 (1 μg). Our findings not only provide mechanistic insight into the signaling pathways engaged by ceramide in the development of hyperalgesia, but also provide a potential pharmacological basis for developing inhibitors targeting the ceramide metabolic-to-COX-2 pathway as novel analgesics.
authors.affiliation: Department of Pharmacological and Physiological Science, Saint Louis University School of Medicine, 1402 South Grand Blvd., St. Louis, MO 63104, USA.
authors.forename: Tim
authors.initials: T
authors.lastname: Doyle
authors.forename: Zhoumou
authors.initials: Z
authors.lastname: Chen
authors.forename: Carolina
authors.initials: C
authors.lastname: Muscoli
authors.forename: Lina M
authors.initials: LM
authors.lastname: Obeid
authors.forename: Daniela
authors.initials: D
authors.lastname: Salvemini
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D002518:Ceramides / Q000008:administration & dosage / Q000378:metabolism / Q000633:toxicity*; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000008:administration & dosage; D015232:Dinoprostone / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005121:Extremities; D006358:Hot Temperature; D006930:Hyperalgesia / Q000139:chemically induced* / Q000378:metabolism* / Q000517:prevention & control; D007093:Imidazoles / Q000008:administration & dosage; D007267:Injections; D008297:Male; D008954:Models, Biological; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D011725:Pyridines / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D013876:Thiophenes / Q000008:administration & dosage; D014110:Touch; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D002518:Ceramides; D052246:Cyclooxygenase 2 Inhibitors; D007093:Imidazoles; D016328:NF-kappa B; D011725:Pyridines; C477523:SC 514; D013876:Thiophenes; D051546:Cyclooxygenase 2; C489691:Ptgs2 protein, rat; D048051:p38 Mitogen-Activated Protein Kinases; D015232:Dinoprostone; C093642:SB 203580