INHIBITION OF SPINAL MICROGLIAL-NLRP3-IL1<EM>Β</EM> SIGNALLING PREVENTS CHRONIC STRESS-INDUCED PROLONGATION OF POST-SURGICAL PAIN-RELATED BEHAVIOUR

Chronic pre-surgical stress increases the risk of prolonged post-surgical pain^1,2, yet the underlying mechanisms remain unclear. Microglial activation and pro-inflammatory signalling in the spinal cord (SC) are key mediators of the transition from acute to chronic pain³ and chronic stress enhances glial activity and neuroinflammation, priming pain pathways and exacerbating post-surgical pain hypersensitivity¹. Here, we examined whether chronic repeated restraint stress (RRS) prolongs post-surgical pain behaviour via spinal microglia and NLRP3-IL1β signalling.
Male Sprague–Dawley rats were exposed to RRS (6 h/day/21days) or left undisturbed (NRRS), followed by hind paw incision (PI) or sham surgery. Ipsilateral dorsal horn SC was collected for bulk 3′ RNA-seq, RT-qPCR and immunofluorescence (IF). In mechanistic follow-up studies, RRS and NRRS-PI rats received intrathecal administration of a non-analgesic concentration of minocycline (50μg/10ul), IL-1RA (30μg/30μl) or the NLRP3 inhibitor MCC50 (20μg/30μl), followed by affective-pain responding (day-2) and mechanical hypersensitivity (day-5) testing.
RNA-seq identified 946 differentially expressed genes between RRS-PI and NRRS-PI groups. GSEA showed significant enrichment of the inflammasome-mediated signalling pathway. RRS increased microglial activity (increased IBA1 IF), (Iba1, Itgam) and inflammatory (Nlrp3, Il1b) gene expression in PI rats. Minocycline attenuated RRS-exacerbated mechanical hypersensitivity post PI and reduced Iba1, Il1b and Ccl2 expression. IL1-RA and MCC50 attenuated both the RRS-induced increase in affective pain responding and mechanical hypersensitivity post PI.
These findings suggest that chronic pre-surgical stress enhances spinal glial and neuroinflammatory signalling post-surgery, thereby exacerbating and prolonging post-surgical pain-related behaviour. Targeting spinal neuroinflammatory mechanisms may offer therapeutic potential for preventing stress-induced chronic post-surgical pain.