title: Persistent pain is dependent on spinal mitochondrial antioxidant levels.
abstract: Reactive oxygen species (ROS) scavengers have been shown to relieve persistent pain; however, the mechanism is not clearly understood. Superoxide produced from mitochondrial oxidative phosphorylation is considered the major source of ROS in neurons during excitation where mitochondrial superoxide levels are normally controlled by superoxide dismutase (SOD-2). The present study hypothesizes that capsaicin-induced secondary hyperalgesia is a consequence of superoxide build-up in spinal dorsal horn neurons and SOD-2 is a major determinant. To test this hypothesis, the spinal levels of SOD-2 activity, inactivated SOD-2 proteins, and mitochondrial superoxide were measured and correlated to the levels of capsaicin-induced secondary hyperalgesia in mice with and without SOD-2 manipulations. The data suggest that superoxide accumulation is a culprit in the abnormal sensory processing in the spinal cord in capsaicin-induced secondary hyperalgesia. Our studies also support the notion that SOD-2 nitration is a critical mechanism that maintains elevated superoxide levels in the spinal cord after capsaicin treatment. Finally, our findings suggest a therapeutic potential for the manipulation of spinal SOD-2 activity in pain conditions.
authors.affiliation: Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA.
authors.forename: Erica S
authors.initials: ES
authors.lastname: Schwartz
authors.forename: Hee Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Jigong
authors.initials: J
authors.lastname: Wang
authors.forename: Inhyung
authors.initials: I
authors.lastname: Lee
authors.forename: Eric
authors.initials: E
authors.lastname: Klann
authors.forename: Jin Mo
authors.initials: JM
authors.lastname: Chung
authors.forename: Kyungsoon
authors.initials: K
authors.lastname: Chung
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D002211:Capsaicin / Q000009:adverse effects; D004050:Ditiocarb / Q000008:administration & dosage / Q000031:analogs & derivatives; D004305:Dose-Response Relationship, Drug; D005528:Foot / Q000503:physiopathology; D016166:Free Radical Scavengers / Q000008:administration & dosage; D006930:Hyperalgesia / Q000139:chemically induced / Q000378:metabolism / Q000517:prevention & control; D008297:Male; D008665:Metalloporphyrins / Q000008:administration & dosage; D051379:Mice; D018345:Mice, Knockout; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D010146:Pain / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D013116:Spinal Cord / Q000473:pathology / Q000648:ultrastructure*; D013266:Stilbamidines; D013482:Superoxide Dismutase / Q000172:deficiency / Q000378:metabolism; D000099156:Superoxide Dismutase 2
chemical_list: D000975:Antioxidants; D002211:Capsaicin; D004050:Ditiocarb; D016166:Free Radical Scavengers; D008665:Metalloporphyrins; D017382:Reactive Oxygen Species; D013266:Stilbamidines; D013482:Superoxide Dismutase; D000099156:Superoxide Dismutase 2; C049774:2-hydroxy-4,4'-diamidinostilbene, methanesulfonate salt; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; C073220:S-methyl N,N-diethylthiolcarbamate sulfoxide