Neuropathic pain (NP) is a devastating consequence of peripheral nerve injury that most often affects younger people. NP is often chronic and resistant to current treatments leaving the patient with persistent disability. A key factor in the genesis of NP after nerve injury stems from activation of microglia in the spinal cord at the level of injury. This activation leads to the production of pro-inflammatory cytokines that hyperexcite neurons transmitting pain. Pro-inflammatory chemokines also draw in peripheral immune cells including macrophages and T cells which amplify and sustain the inflammatory milieu underlying NP. A common regulatory thread for pro-inflammatory mediators, including IL-1β, IL-6, TNF-α, iNOS, CXCL1, and CCL2, is at the mRNA level where adenine- and uridine--rich elements (ARE) in the 3’ untranslated region (UTR) modulate mRNA stability, translational efficiency, and ultimately protein expression. Our prior work has identified HuR as a major positive regulator of these mRNAs in glial cells by binding to the ARE, translocating to the cytoplasm, and augmenting translation. Our team has developed a novel class of small molecule inhibitors that block HuR dimerization, a process necessary for its nucleocytoplasmic translocation and positive regulatory effect. We have shown that the prototype, SRI-42127, potently suppresses microglial activation and the production of pro-inflammatory cytokines and chemokines. In a recently- published pilot study with the spared nerve injury (SNI) model of NP, we observed a significant attenuation of allodynic pain in male and female mice after administration of SRI-42127 (8). Using a microglial-selective HuR knockout mouse model developed in our laboratory, we found that the allodynia-mitigating effect could be recapitulated only in male mice, indicating a sex dimorphism. In this proposal we hypothesize that HuR drives NP after nerve injury through its positive regulation of pro-inflammatory cytokines and chemokines by resident microglia for male mice and macrophages for female mice. Furthermore, inhibiting HuR function chemically or by genetic deletion will attenuate this response and reduce NP. We propose 3 specific aims: (1) Investigate the required dosing schedule, longevity and applicability of HuR inhibition by SRI-42127 following SNI in male and female mice, (2) Assess the cellular and molecular mechanisms whereby SRI-42127 attenuates NP after SNI in male and female mice, and (3) Explore sex differences in immune cell-specific HuR inhibition following SNI using conditional knockout mouse models for microglia and macrophages. The long term objectives of this proposal are: (1) to advance our small molecule HuR inhibitors as a potential therapy for NP, and (2) to gain an understanding of how ARE- mediated RNA regulation impacts NP and the sex-dependent cell types that drive it. The innovation of this proposal is the investigation of a novel class of HuR inhibitors for targeting the acute infl...