Supraspinal inactivation of mitochondrial superoxide dismutase is a source of peroxynitrite in the development of morphine antinociceptive tolerance.

Published

Journal Article

Effective treatment of chronic pain with morphine is limited by decreases in the drug's analgesic action with chronic administration (antinociceptive tolerance). Because opioids are mainstays of pain management, restoring their efficacy has great clinical importance. We have recently reported that formation of peroxynitrite (ONOO(-), PN) in the dorsal horn of the spinal cord plays a critical role in the development of morphine antinociceptive tolerance and have further documented that nitration and enzymatic inactivation of mitochondrial superoxide dismutase (MnSOD) at that site provides a source for this nitroxidative species. We now report for the first time that antinociceptive tolerance in mice is also associated with the inactivation of MnSOD at supraspinal sites. Inactivation of MnSOD led to nitroxidative stress as evidenced by increased levels of products of oxidative DNA damage and activation of the nuclear factor poly (ADP-ribose) polymerase in whole brain homogenates. Co-administration of morphine with potent Mn porphyrin-based peroxynitrite scavengers, Mn(III) 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP5+) and Mn(III) 5,10,15,20-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin (MnTnHex-2-PyP5+) (1) restored the enzymatic activity of MnSOD, (2) attenuated PN-derived nitroxidative stress, and (3) blocked the development of morphine-induced antinociceptive tolerance. The more lipophilic analogue, MnTnHex-2-PyP5+ was able to cross the blood-brain barrier at higher levels than its lipophylic counterpart MnTE-2-PyP5+ and was about 30-fold more efficacious. Collectively, these data suggest that PN-mediated enzymatic inactivation of supraspinal MnSOD provides a source of nitroxidative stress, which in turn contributes to central sensitization associated with the development of morphine antinociceptive tolerance. These results support our general contention that PN-targeted therapeutics may have potential as adjuncts to opiates in pain management.

Full Text

Duke Authors

Cited Authors

  • Doyle, T; Bryant, L; Batinic-Haberle, I; Little, J; Cuzzocrea, S; Masini, E; Spasojevic, I; Salvemini, D

Published Date

  • December 2009

Published In

Volume / Issue

  • 164 / 2

Start / End Page

  • 702 - 710

PubMed ID

  • 19607887

Pubmed Central ID

  • 19607887

Electronic International Standard Serial Number (EISSN)

  • 1873-7544

International Standard Serial Number (ISSN)

  • 0306-4522

Digital Object Identifier (DOI)

  • 10.1016/j.neuroscience.2009.07.019

Language

  • eng