TIM3 attenuates morphine antinociceptive tolerance and microglial neuroinflammation by suppressing the TRAF6/NF-κB pathway in male mice.

Chronic morphine administration often leads to the development of antinociceptive tolerance, presenting a significant challenge in the chronic pain management. Although microglia are known to mediate the neuroinflammation associated with morphine-induced antinociceptive tolerance, the molecular mechanisms underlying this process remain incompletely understood. Recent evidence indicates that T cell immunoglobulin domain and mucin domain-3 (TIM3) acts as an important regulator in inflammation-related diseases. In this study, we investigated the role of TIM3 in morphine antinociceptive tolerance. Pharmacological blockade of TIM3 exacerbated morphine antinociceptive tolerance and associated hyperalgesia, whereas upregulation of TIM3 in the spinal cord significantly reduced both the development and maintenance of antinociceptive tolerance. We found that TIM3 negatively regulated microglia-mediated neuroinflammation and neuronal apoptosis following chronic morphine exposure. Mechanistically, TIM3 promoted the degradation of tumor necrosis factor receptor-associated factor 6 (TRAF6) and inhibited the activation of nuclear factor κB (NF-κB) signaling pathways. Furthermore, we identified TRAF6 as a key mediator through which TIM3 attenuated morphine-induced antinociceptive tolerance and suppressed the secretion of proinflammatory factors. Notably, TIM3 interacted with tumor necrosis factor α-induced protein 3 (TNFAIP3) to enhance K48-linked ubiquitination of TRAF6 in morphine-stimulated microglia, thereby mitigating inflammatory responses. Together, these findings suggest that spinal TIM3 negatively modulates morphine antinociceptive tolerance by regulating microglial inflammatory responses through a TNFAIP3/TRAF6/NF-κB-dependent mechanism. This study highlights TIM3 as a promising therapeutic target for preventing morphine antinociceptive tolerance in chronic pain management. Schematic diagram for the proposed mechanisms of TIM3 regulates morphine antinociceptive tolerance. TIM3 may alleviate morphine antinociceptive tolerance by suppressing microglia-mediated neuroinflammation and neuronal apoptosis, which is associated with the TRAF6/NF-κB pathway.