Inhibition of TRPV1 by SHP-1 in nociceptive primary sensory neurons is critical in PD-L1 analgesia
Ben-Long Liu, Qi-Lai Cao, Xin Zhao, Hui-Zhu Liu, Yu-Qiu Zhang
Ben-Long Liu, Qi-Lai Cao, Xin Zhao, Hui-Zhu Liu, Yu-Qiu Zhang
View: Text | PDF
Research Article Neuroscience

Inhibition of TRPV1 by SHP-1 in nociceptive primary sensory neurons is critical in PD-L1 analgesia

Abstract

Recently programmed death-ligand 1 (PD-L1) receptor PD-1 was found in dorsal root ganglion (DRG) neurons, and PD-L1 activates PD-1 to inhibit inflammatory and neuropathic pain by modulating neuronal excitability. However, the downstream signaling of PD-1 in sensory neurons remains unclear. Here, we show that PD-L1 activated Src homology 2 domain-containing tyrosine phosphatase-1 (SHP-1) to downregulate transient receptor potential vanilloid 1 (TRPV1) in DRG neurons and inhibit bone cancer pain in mice. Local injection of PD-L1 produced analgesia. PD-1 in DRG neurons colocalized with TRPV1 and SHP-1. PD-L1 induced the phosphorylation of SHP-1 in DRG TRPV1 neurons and inhibited TRPV1 currents. Loss of TRPV1 in mice abolished bone cancer–induced thermal hyperalgesia and PD-L1 analgesia. Conditioned deletion of SHP-1 in NaV1.8+ neurons aggravated bone cancer pain and diminished the inhibition of PD-L1 on TRPV1 currents and pain. Together, our findings suggest that PD-L1/PD-1 signaling suppresses bone cancer pain via inhibition of TRPV1 activity. Our results also suggest that SHP-1 in sensory neurons is an endogenous pain inhibitor and delays the development of bone cancer pain via suppressing TRPV1 function.

Authors

Ben-Long Liu, Qi-Lai Cao, Xin Zhao, Hui-Zhu Liu, Yu-Qiu Zhang

×

Figure 4

Inhibition of SHP-1 sensitizes TRPV1 and facilitates pain-like behaviors.

Options: View larger image (or click on image) Download as PowerPoint
Inhibition of SHP-1 sensitizes TRPV1 and facilitates pain-like behaviors...
(A) Western blot analysis showing an increase in the level of phosphorylated SHP-1 (pSHP-1) in L3–L5 DRGs ipsilateral to the tumor-bearing bone after tumor inoculation. *P < 0.05, **P < 0.01 versus sham control; 1-way ANOVA followed by post hoc Student-Newman-Keuls test; n = 5 sham treatment day 7, 5 PTD 7, 6 PTD 14, 5 PTD 21, and 9 PTD 28 (mice). (B) Coimmunoprecipitation displays that PD-1 and SHP-1 are captured with anti–SHP-1 in L3–L5 DRGs. Normal rabbit IgG immunoprecipitation was performed as the negative control. Three individual trials were performed to repeat the result. (C) Double immunofluorescent staining detected colocalization of SHP-1 and PD-1 in the L4 DRG. Scale bar: 25 μm. (D) PD-L1 (50 ng/mL, 30 minutes) treatment increases tyrosine phosphorylation of SHP-1 in cultured DRG neurons. *P < 0.05 versus control; 2-tailed Student’s t test; n = 4 vehicle and 4 PD-L1 (mice). (E) Whole-cell patch clamp recording showing that specific SHP-1 inhibitor SSG (1 μM) or PTPiIII (25 nM) increases 1.5 μM capsaicin–evoked TRPV1 current density in DRG small-diameter neurons. Insert represents TRPV1 current traces in individual DRG neurons. *P < 0.05, **P < 0.01 versus vehicle control; 1-way ANOVA followed by post hoc Student-Newman-Keuls test; n = 30 vehicle, 18 SSG, and 11 PTPiIII (cells). (F) SHP-1 inhibitor PTPiIII attenuates the repeated capsaicin-induced desensitization, showing increased ratio of second trace peak amplitude to first trace peak amplitude. Insert represents TRPV1 current traces in vehicle- and PTPiIII-treated neurons. **P < 0.01 versus vehicle control; 2-tailed Student’s t test; n = 8 vehicle and 10 PTPiIII (cells). (G) Double immunofluorescent staining detected colocalization of SHP-1 and TRPV1 in the L4 DRG. Scale bar: 25 μm. (H and I) Immunocytochemistry double staining of TRPV1 and pSHP-1 in cultured DRG neurons treated by vehicle and PD-L1 (10 ng/mL, 30 minutes). After incubation in PD-L1 for 30 minutes, pSHP-1 was detected in most TRPV1-positive neurons; n = 4 vehicle and 4 PD-L1. Scale bar: 30 μm. (J and K) Intraplantar injection of SHP-1 inhibitor PTPiIII (30 and 150 μg) directly induces thermal hyperalgesia (J) and mechanical allodynia (K). *P < 0.05, **P < 0.01 versus vehicle control; ##P < 0.01 versus 30 μg PTPiIII, 2-way RM ANOVA followed by post hoc Student-Newman-Keuls test; n = 8 vehicle, 9 PTPiIII 30 μg, and 9 PTPiIII 150 μg (mice). (L) Intraplantar injection of SHP-1 inhibitor PTPiIII (150 μg) evokes spontaneous pain that manifested by licking and flinching within 3 minutes after the injection in naive WT mice and TRPV1–/– mice. *P < 0.05, **P < 0.01; 1-way ANOVA followed by post hoc Student-Newman-Keuls test; n = 7 vehicle and 8 PTPiIII (mice).