Progesterone reduces the expression of spinal cyclooxygenase-2 and inducible nitric oxide synthase and prevents allodynia in a rat model of central neuropathic pain

Background Spinal cord injury (SCI) results in the development of chronic pain that is refractory to conventional treatment. Progesterone, a neuroprotective steroid, may offer a promising perspective in pain modulation after central injury. Here, we explore the impact of progesterone administration...

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Bibliographic Details
Published in:European journal of pain 2014-03, Vol.18 (3), p.348-359
Main Authors: Coronel, M.F., Labombarda, F., De Nicola, A.F., González, S.L.
Format: Article
Language:English
Subjects:
Animals
Cyclooxygenase 2 - metabolism
Disease Models, Animal
Hyperalgesia - drug therapy
Hyperalgesia - enzymology
Hyperalgesia - etiology
Male
Neuralgia - drug therapy
Neuralgia - enzymology
Neuralgia - etiology
Nitric Oxide Synthase Type II - metabolism
Pain Measurement
Progesterone - pharmacology
Progesterone - therapeutic use
Rats
Rats, Sprague-Dawley
Spinal Cord - drug effects
Spinal Cord - enzymology
Spinal Cord Injuries - complications
Spinal Cord Injuries - enzymology
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Summary:Background Spinal cord injury (SCI) results in the development of chronic pain that is refractory to conventional treatment. Progesterone, a neuroprotective steroid, may offer a promising perspective in pain modulation after central injury. Here, we explore the impact of progesterone administration on the post‐injury inflammatory cascade involving the enzymes cyclooxygenase‐2 (COX‐2) and inducible nitric oxide synthase (iNOS) at the spinal cord level. We also analyse pain behaviours, the profile of glial cell activation, and IκB‐α mRNA levels, as an index of NF‐κB transactivation. Methods We used biochemical, immunohistochemical and molecular techniques, as well as behavioural studies, to investigate the effects of progesterone in a well‐characterized model of central neuropathic pain. Results Injured animals receiving progesterone presented reduced mRNA levels of the proinflammatory enzymes, as well as decreased COX‐2 activity and nitrite levels, as compared to vehicle‐treated injured rats. Further, animals receiving the steroid exhibited lower levels of IκB‐α mRNA, suggesting decreased NF‐κB transactivation. Progesterone administration also attenuated the injury‐induced increase in the number of glial fibrillary acidic protein and OX‐42 positive cells both at early and late time points after injury, and prevented the development of mechanical and thermal allodynia. Further, when injured rats received early progesterone administration for a critical period of time after injury, they did not display allodynic behaviours even after the treatment had stopped. Conclusions Our results suggest that progesterone, by modulating early neuroinflammatory events triggered after SCI, may represent a useful strategy to prevent the development of central chronic pain.
ISSN:1090-3801
1532-2149
DOI:10.1002/j.1532-2149.2013.00376.x