Curcumin attenuates mechanical and thermal hyperalgesia in chronic constrictive injury model of neuropathic pain.

INTRODUCTION

The aim of this study was to observe the effect of stress caused by neuropathic pain on serum cortisol concentration and expression of 11β-hydroxysteroid dehydrogenase type I enzyme (11βHSD1) in spinal cord and dorsal root ganglions (DRG) and investigate the role and mechanism of curcumin in the neuropathic pain of stressful rats. Neuropathic pain is a prevalent disease that greatly impairs the patients' quality of life. A lack of the understanding of its etiology, inadequate relief, development of tolerance and potential toxicity of classical antinociceptives warrant the investigation of the newer agents to relieve this pain. The aim of the present study was to explore the antinociceptive effect of curcumin and its effect on expression of 11β-hydroxysteroid dehydrogenase type I enzyme (11βHSD1) in spinal dorsal horn and DRG in chronic constriction injury (CCI) mode of neuropathic pain of rats.

METHODS

Seventy-two male Sprague-Dawley rats were randomized into four groups with 18 rats in each: sham operation group (Sham), chronic constrictive injury group (CCI), solvent contrast group (SC), and curcumin-treated group (Cur100). Curcumin, 100 mg/kg/day intraperitoneal, was given for 14 days starting from the first day after operation in the Cur100 group. Paw thermal withdrawal latency (PTWL) and paw mechanical withdrawal threshold (PMWT) of rats were measured 2 days pre-operative, and 1, 3, 5, 7, 10, and 14 days post-operative. The animals were deeply anesthetized and blood was taken from the heart, the lumbar segment (L4, 5) of the spinal cord and DRG were dissected out and homogenized. The change of cortisol was measured by enzyme-linked immunosorbent assay and the change of 11βHSD1 expression was determined by immunochemistry and Western blot.

RESULTS

Compared with sham group, PTWL and PMWT significantly decrease after operation in the CCI group; serum cortisol concentration was significantly increased and the expression of 11βHSD1 was significantly increased in the CCI group. Comparing with CCI group, the PMWT and PTWL were increased and the serum cortisol concentration was decreased and the expression of 11βHSD1 was inhibited in Cur100 group.

CONCLUSION

Stress caused by neuropathic pain triggers release of cortisol to the blood and expression of 11βHSD1 would increase at the same time. Curcumin could alleviate thermal and mechanical hyperalgesia induced by CCI and inhibit the serum cortisol concentration and expression of 11βHSD1 in the spinal cord and DRG.