G protein-coupled receptor GPR151 is involved in trigeminal neuropathic pain via the induction of Gβγ/ERK-mediated neuroinflammation in the trigeminal ganglion.

Trigeminal nerve injury-induced neuropathic pain is a debilitating chronic orofacial pain syndrome but lack of effective treatment. G protein-coupled receptors (GPCRs), especially orphan GPCRs (oGPCRs) are important therapeutic targets in pain medicine. Here we screened upregulated oGPCRs in the trigeminal ganglia (TG) after partial infraorbital nerve transection (pIONT) and found that Gpr151 was the most significantly upregulated oGPCRs. Gpr151 mRNA was increased from pIONT Day 3 and maintained for more than 21 days. Furthermore, GPR151 was expressed in the neurons of the TG after pIONT. Global mutation or knockdown of Gpr151 in the TG attenuated pIONT-induced mechanical allodynia. In addition, the excitability of TG neurons was increased after pIONT in wild-type (WT) mice, but not in Gpr151 mice. Notably, GPR151 bound to Gαi protein, but not Gαq, Gα12, or Gα13, and activated ERK through Gβγ. ERK was also activated by pIONT in the TG of WT mice, but not in Gpr151 mice. Gene microarray showed that Gpr151 mutation reduced the expression of a large number of neuroinflammation-related genes that were upregulated in WT mice after pIONT, including chemokines CCL5, CCL7, CXCL9, and CXCL10. MEK inhibitor (PD98059) attenuated mechanical allodynia and reduced the upregulation of these chemokines after pIONT. Collectively, the present study not only revealed the involvement of GPR151 in the maintenance of trigeminal neuropathic pain but also identified GPR151 as a Gαi-coupled receptor to induce ERK-dependent neuroinflammation. Thus, GPR151 may be a potential drug target for the treatment of trigeminal neuropathic pain.