title: Peripheral sensitization increases opioid receptor expression and activation by crotalphine in rats.
abstract: Inflammation enhances the peripheral analgesic efficacy of opioid drugs, but the mechanisms involved in this phenomenon have not been fully elucidated. Crotalphine (CRP), a peptide that was first isolated from South American rattlesnake C.d. terrificus venom, induces a potent and long-lasting anti-nociceptive effect that is mediated by the activation of peripheral opioid receptors. Because the high efficacy of CRP is only observed in the presence of inflammation, we aimed to elucidate the mechanisms involved in the CRP anti-nociceptive effect induced by inflammation. Using real-time RT-PCR, western blot analysis and ELISA assays, we demonstrate that the intraplantar injection of prostaglandin E2 (PGE2) increases the mRNA and protein levels of the µ- and κ-opioid receptors in the dorsal root ganglia (DRG) and paw tissue of rats within 3 h of the injection. Using conformation state-sensitive antibodies that recognize activated opioid receptors, we show that PGE2, alone does not increase the activation of these opioid receptors but that in the presence of PGE2, the activation of specific opioid receptors by CRP and selective µ- and κ-opioid receptor agonists (positive controls) increases. Furthermore, PGE2 down-regulated the expression and activation of the δ-opioid receptor. CRP increased the level of activated mitogen-activated protein kinases in cultured DRG neurons, and this increase was dependent on the activation of protein kinase Cζ. This CRP effect was much more prominent when the cells were pretreated with PGE2. These results indicate that the expression and activation of peripheral opioid receptors by opioid-like drugs can be up- or down-regulated in the presence of an acute injury and that acute tissue injury enhances the efficacy of peripheral opioids.
authors.affiliation: Laboratório Especial de Dor e Sinalização, Instituto Butantan, São Paulo, SP, Brazil.
authors.forename: Vanessa Olzon
authors.initials: VO
authors.lastname: Zambelli
authors.affiliation: Laboratório Especial de Dor e Sinalização, Instituto Butantan, São Paulo, SP, Brazil.
authors.forename: Ana Carolina de Oliveira
authors.initials: AC
authors.lastname: Fernandes
authors.affiliation: Laboratório Especial de Dor e Sinalização, Instituto Butantan, São Paulo, SP, Brazil.
authors.forename: Vanessa Pacciari
authors.initials: VP
authors.lastname: Gutierrez
authors.affiliation: Departamento de Anatomia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil.
authors.forename: Julio Cesar Batista
authors.initials: JC
authors.lastname: Ferreira
authors.affiliation: Departamento de Fisiologia e Biofísica, Instituto de Biociências (UNICAMP) Rua Monteiro Lobato, Cidade Universitária, Campinas, SP, Brazil.
authors.forename: Carlos Amilcar
authors.initials: CA
authors.lastname: Parada
authors.affiliation: Department of Chemical and Systems Biology, Stanford University, School of Medicine, Stanford, California, United States of America.
authors.forename: Daria
authors.initials: D
authors.lastname: Mochly-Rosen
authors.affiliation: Laboratório Especial de Dor e Sinalização, Instituto Butantan, São Paulo, SP, Brazil.
authors.forename: Yara
authors.initials: Y
authors.lastname: Cury
mesh_terms: D000701:Analgesics, Opioid / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D017839:Crotalus / Q000378:metabolism; D015232:Dinoprostone; D005727:Ganglia, Spinal / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006930:Hyperalgesia / Q000139:chemically induced* / Q000188:drug therapy* / Q000235:genetics / Q000276:immunology; D008297:Male; D010455:Peptides / Q000302:isolation & purification / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000819:agonists / Q000235:genetics* / Q000276:immunology
chemical_list: D000701:Analgesics, Opioid; D010455:Peptides; D011957:Receptors, Opioid; C533006:crotalphine; D015232:Dinoprostone