Spinal NLRP3 blockade reverses morphine-prolonged neuropathic pain and proinflammatory immune actions in prenatal alcohol-exposed male mice.

Prenatal alcohol exposure (PAE) exerts long-term alterations in the adult neuroimmune system. Previous work showed that PAE exacerbates morphine-mediated immune responses, prolonging nerve injury-induced allodynia and promoting aberrant NLRP3-driven inflammation in both the periphery and spinal cord. Whether the spinal actions of NLRP3, arising from aberrant TLR4 activation, are critical in driving allodynia remains unknown. With a 25+ day-long time course study, using another previously established PAE model in mice, we reproduced these adverse effects of PAE and further examined whether spinal blockade of TLR4 or the NLRP3 reverses this pathological pain state by dampening proinflammatory actions in the spinal cord and dorsal root ganglia (DRG), critical relay nociceptive signaling regions. We demonstrate that pharmacological inhibition of either the spinal TLR4 receptor (Tak-242) or the NLRP3 inflammasome (MCC950) reverses established morphine-induced prolonged allodynia in nerve-injured male PAE mice. In the spinal cord, increased IL-1β, caspase-1, HMGB1, IL-18, and astrocyte activation were detected in PAE mice, which were dampened by MCC950 treatment. DRGs from allodynic PAE mice exhibited heightened expression of IL-1β, TNF-α, NLRP3, and caspase-1, as well as satellite glial and neuronal activation (Panx1 and TRPV1), which were reduced by MCC950. Despite allodynia reversal, inflammatory mediators persisted at the peripheral injury site in PAE mice. Together, these findings elucidate the spinal TLR4-NLRP3 axis as a modulator of morphine-prolonged allodynia and provide mechanistic insights into neuroimmune dysfunction underlying PAE-associated vulnerability and altered responses to opioid therapeutics.