New Insights on Formyl Peptide Receptor Type 2 Involvement in Nociceptive Processes in the Spinal Cord.

Formyl peptide receptor type 2 (FPR2/ALX) belongs to the formyl peptide receptors (FPRs) family clustered on chromosome 19 and encodes a family of three Class A of G protein-coupled receptors (GPCRs). A short N-terminal region, an NPXXY motif in transmembrane (TM) region 7 and an E/DRY motif that bridges TM3 and TM6 stabilizing inactive receptor conformations characterize this class of receptors. In recognizing pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), FPRs play a crucial role in innate immune responses. FPR2/ALX is highly expressed in myeloid cells, as well as in chondrocytes, fibroblasts, endothelial, epithelial and smooth muscle cells. FPR2/ALX mRNA expression was recently reported in the rat brainstem, spinal cord, thalamus/hypothalamus, cerebral neocortex, hippocampus, cerebellum and striatum. The central nervous system (CNS) distribution of FPR2/ALX suggests important functions in nociception. Thus, the present study was carried out to investigate the possible role of FPR2/ALX in nociception in mice. Intrathecal administration of the formyl peptide receptor type 1 (FPR1) agonist fMLF and the FPR2/ALX agonist BML-111 relieved nociception and these effects were reduced by contemporary administration of the FPR2/ALX antagonist WRW. Furthermore, measurement of cytokines and brain-derived neurotrophic factor (BDNF) in the spinal cord of neuropathic mice demonstrated that the antinociceptive effects of BML-111 might depend on the reduction in cytokine release and BDNF in the spinal cord. These results suggest a possible role of FPR2/ALX for pain control in the spinal cord.