Pirt promotes substance P release in cancer-induced bone pain

Introduction: Cancer-induced bone pain (CIBP) is a major clinical challenge due to its intricate, poorly understood pathogenesis. Sensitized tumor-innervating nerves interacting with cancer cells drive CIBP, and substance P (SP) released by these nerves is a key mediator of pathological processes. However, the mechanisms regulating SP release in CIBP remain unclear. Objectives: To explore Pirt's involvement in CIBP and its role in regulating SP release. Methods: Molecular and behavioral experiments were performed using Pirt knockout (Pirt-KO) and wild-type (WT) mice in a CIBP model. Pain-related behaviors and SP were assessed, with Pirt expression and localization analyzed in dorsal root ganglia (DRG) and spinal cord. Results: Pirt-KO mice exhibited attenuated heat allodynia, mechanical allodynia, and spontaneous pain vs WT mice. Substance P level in tissues and SP release from DRG neurons was significantly reduced in Pirt-KO mice. All DRG SP-positive neurons expressed Pirt, and Pirt – green fluorescent protein (GFP) terminals projected to spinal lamina I/II, colocalizing with SP-positive terminals. Conclusion: Pirt plays a crucial role in promoting SP release in CIBP, shedding light on the molecular mechanisms underlying CIBP and providing a potential therapeutic target.