title: Involvement of NOX1/NADPH oxidase in morphine-induced analgesia and tolerance.
abstract: The involvement of reactive oxygen species (ROS) in morphine-induced analgesia and tolerance has been suggested, yet how and where ROS take part in these processes remains largely unknown. Here, we report a novel role for the superoxide-generating enzyme NOX1/NADPH oxidase in the regulation of analgesia and acute analgesic tolerance. In mice lacking Nox1 (Nox1(-/Y)), the magnitude of the analgesia induced by morphine was significantly augmented. More importantly, analgesic tolerance induced by repeated administration of morphine was significantly suppressed compared with that in the littermates, wild-type Nox1(+/Y). In a membrane fraction obtained from the dorsal spinal cord, no difference was observed in morphine-induced [(35)S]GTPγS-binding between the genotypes, whereas morphine-stimulated GTPase activity was significantly attenuated in Nox1(-/Y). At 2 h after morphine administration, a significant decline in [(35)S]GTPγS-binding was observed in Nox1(+/Y) but not in Nox1(-/Y). No difference in the maximal binding and affinity of [(3)H]DAMGO was observed between the genotypes, but the translocation of protein kinase C isoforms to the membrane fraction following morphine administration was almost completely abolished in Nox1(-/Y). Finally, the phosphorylation of RGS9-2 and formation of a complex by Gαi2/RGS9-2 with 14-3-3 found in morphine-treated Nox1(+/Y) were significantly suppressed in Nox1(-/Y). Together, these results suggest that NOX1/NADPH oxidase attenuates the pharmacological effects of opioids by regulating GTPase activity and the phosphorylation of RGS9-2 by protein kinase C. NOX1/NADPH oxidase may thus be a novel target for the development of adjuvant therapy to retain the beneficial effects of morphine.
authors.affiliation: Department of Pharmacology, Kyoto Prefectural University of Medicine, Kyoto 602-8566, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Ibi
authors.forename: Kuniharu
authors.initials: K
authors.lastname: Matsuno
authors.forename: Misaki
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Mika
authors.initials: M
authors.lastname: Sasaki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Masato
authors.initials: M
authors.lastname: Katsuyama
authors.forename: Kazumi
authors.initials: K
authors.lastname: Iwata
authors.forename: Jia
authors.initials: J
authors.lastname: Zhang
authors.forename: Shuji
authors.initials: S
authors.lastname: Kaneko
authors.forename: Chihiro
authors.initials: C
authors.lastname: Yabe-Nishimura
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004361:Drug Tolerance / Q000235:genetics*; D004622:Embryo, Mammalian; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D005727:Ganglia, Spinal / Q000166:cytology; D005786:Gene Expression Regulation / Q000187:drug effects; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006930:Hyperalgesia / Q000188:drug therapy* / Q000235:genetics; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009020:Morphine / Q000627:therapeutic use*; D009247:NADH, NADPH Oxidoreductases / Q000172:deficiency / Q000378:metabolism*; D000074624:NADPH Oxidase 1; D009294:Narcotics / Q000627:therapeutic use*; D009457:Neuroglia / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D010147:Pain Measurement; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism; D020710:RGS Proteins / Q000378:metabolism; D012333:RNA, Messenger; D013116:Spinal Cord / Q000166:cytology; D013460:Sulfur Isotopes / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014316:Tritium / Q000378:metabolism
chemical_list: D009294:Narcotics; D020710:RGS Proteins; D012333:RNA, Messenger; D013460:Sulfur Isotopes; C116925:regulator of g-protein signaling 9; D014316:Tritium; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D013481:Superoxides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009020:Morphine; D006160:Guanosine Triphosphate; D009247:NADH, NADPH Oxidoreductases; D000074624:NADPH Oxidase 1; C000614711:NOX1 protein, mouse; D011493:Protein Kinase C; D020558:GTP Phosphohydrolases