Volume 13, Issue 4 pp. 380-386

Effects of transgene-mediated endomorphin-2 in inflammatory pain

Shuanglin Hao

Shuanglin Hao

Department of Neurology and VA Ann Arbor Healthcare System, Ann Arbor, MI, United States

These authors contributed equally to this work.

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Darren Wolfe

Darren Wolfe

Department of Molecular Genetics and Biochemistry, University of Pittsburgh, Pittsburgh, PA, United States

These authors contributed equally to this work.

Current address: Diamyd, Inc. Pittsburgh, PA, United States.

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Joseph C. Glorioso

Joseph C. Glorioso

Department of Molecular Genetics and Biochemistry, University of Pittsburgh, Pittsburgh, PA, United States

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Marina Mata

Marina Mata

Department of Neurology and VA Ann Arbor Healthcare System, Ann Arbor, MI, United States

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David J. Fink

Corresponding Author

David J. Fink

Department of Neurology and VA Ann Arbor Healthcare System, Ann Arbor, MI, United States

Tel.: +1 734 936 9070; fax: +1 734 763 5059. [email protected]Search for more papers by this author
First published: 09 January 2012
Citations: 44

Current address: Diamyd, Inc. Pittsburgh, PA, United States.

ABSTRACT

We examined the analgesic properties of endomorphin-2 expressed in DRG neurons transduced with a non-replicating herpes simplex virus (HSV)-based vector containing a synthetic endomorphin-2 gene construct. HSV-mediated endomorphin-2 expression reduced nocisponsive behaviors in response to mechanical and thermal stimuli after injection of complete Freund's adjuvant (CFA) into the paw, and reduced peripheral inflammation measured by paw swelling after injection of CFA. The analgesic effect of the vector was blocked by either intraperitoneal or intrathecal administration of naloxone methiodide, blocking peripheral and central μ opioid receptors, respectively. Endomorphin-2 vector injection also reduced spontaneous pain-related behaviors in the delayed phase of the formalin test and in both CFA and formalin models suppressed spinal c-fos expression. The magnitude of the vector-mediated analgesic effect on the delayed phase of the formalin test was similar in naïve animals and in animals with opiate tolerance induced by twice daily treatment with morphine, suggesting that there was no cross-tolerance between vector-mediated endomorphin-2 and morphine. These results suggest that transgene-mediated expression of endomorphin-2 in transduced DRG neurons in vivo acts both peripherally and centrally through mu opioid receptors to reduce pain perception.

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