Protectin DX resolves fracture-induced postoperative pain in mice via neuronal signaling and GPR37-activated macrophage efferocytosis.

Summary

Protectin DX provided superior and resolution-promoting analgesia in a fracture-induced postoperative pain model, dependent on GPR37. It enhanced macrophage efferocytosis via calcium signaling and rapidly dampened nociceptor activity, outperforming PD1/DHA, steroids, and meloxicam and shortening pain duration.

Key Findings

• IV Protectin DX (100 ng/mouse) alleviates early and late phases of fracture-induced postoperative pain and shortens pain duration.
• PDX outperformed PD1/DHA, steroids, and meloxicam; dexamethasone and meloxicam prolonged pain, whereas PDX shortened it.
• Analgesic effects require GPR37: absent in Gpr37−/− mice; PDX binds GPR37 and induces macrophage calcium responses and efferocytosis.
• PDX rapidly suppresses nociceptor activity (C-fiber reflex, DRG calcium responses) and reduces TRPA1/TRPV1-induced acute pain/inflammation.

Clinical Implications

Supports development of specialized proresolving mediator–based analgesics to control postoperative pain while avoiding steroid/NSAID-related drawbacks (e.g., delayed resolution). Suggests patient stratification by GPR37 pathways in future trials.

Limitations

• Preclinical mouse data; human pharmacokinetics, dosing, and safety are unknown.
• Mechanism centered on GPR37 may not generalize across pain etiologies or species.

Future Directions

Evaluate PDX analogs with improved pharmacokinetics; test GPR37 pathway engagement and biomarkers in large animal models; conduct phase I safety and PK studies followed by efficacy trials in high-pain surgeries.