[Effects of glucocorticoid receptor agonists on hyperalgesia of rats with neuropathic pain and its mechanisms].

Abstract

Objective: To investigate the effects of glucocorticoid receptor agonists on hyperalgesia in rats with neuropathic pain (NPP) by regulating nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3)/interleukin-1β (IL-1β) pathway and its mechanisms.

Methods: Forty SD rats were divided into control group, NPP model group, NPP treated with NLRP3 inhibitor group and dexamethasone treatment group with 10 rats in each group. The NPP rat model was induced by vincristine. The model group was established according to the above method, the NLRP3 inhibitor group was treated with NLRP3 inhibitor (MCC950) after the NPP model was established, and the treatment group was treated with glucocorticoid receptor agonist (dexamethasone) after the model was established according to the design. The rats of the control group were given the same amount of normal saline. After 7 days of intervention, the mechanical pain threshold, thermal pain threshold, morphological changes of spinal dorsal horn, pain factors (prostaglandin E2 (PGE2), substance P (SP), 5-hydroxytryptamine (5-HT)), inflammatory factors (interleukin-8 (IL-8), tumor necrosis factor α (TNF-α), interleukin-6 (IL-6)), and NLRP3/IL-1β protein expressions were determined and compared among the four groups.

Results: Compared with the model group, the pathological changes of spinal dorsal horn neurons in NLRP3 inhibitor group and treatment group were alleviated significantly, the arrangement of neurons was tended to be close, the number of neurons was gradually returned to normal, and the pyknosis of neurons was decreased. Compared with the control group, the mechanical pain threshold and thermal pain threshold of the model group were decreased significantly (P＜0.05), and the expressions of inflammatory factors, pain factors and NLRP3, IL-1β protein were increased significantly (P＜0.05); compared with the model group, the mechanical pain threshold and thermal pain threshold of the NLRP3 inhibitor group and the dexamethasone treatment group were increased significantly (P＜0.05), and the expressions of inflammatory factors, pain factors and NLRP3, IL-1β protein were decreased significantly (P＜ 0.05). The difference between NLRP3 inhibitor group and treatment group was not statistically significant (P＞0.05).

Conclusion: Glucocorticoid receptor agonists may reduce the hyperalgesia of neuropathic pain rat model by down regulating NLRP3/IL-1β pathway, which may be the mechanism of dexamethasone on antiinflammatory of analgesia in early stage of NPP.