Neuronal FcγRI mediates acute and chronic joint pain
Li Wang, … , Michael J. Caterina, Lintao Qu
Li Wang, … , Michael J. Caterina, Lintao Qu
Published September 3, 2019; First published June 18, 2019
Citation Information: J Clin Invest. 2019;129(9):3754-3769. https://doi.org/10.1172/JCI128010.
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Research Article Neuroscience

Neuronal FcγRI mediates acute and chronic joint pain

Abstract

Although joint pain in rheumatoid arthritis (RA) is conventionally thought to result from inflammation, arthritis pain and joint inflammation are at least partially uncoupled. This suggests that additional pain mechanisms in RA remain to be explored. Here we show that FcγRI, an immune receptor for IgG immune complex (IgG-IC), is expressed in a subpopulation of joint sensory neurons and that, under naive conditions, FcγRI cross-linking by IgG-IC directly activates the somata and peripheral terminals of these neurons to evoke acute joint hypernociception without obvious concurrent joint inflammation. These effects were diminished in both global and sensory neuron–specific Fcgr1-knockout mice. In murine models of inflammatory arthritis, FcγRI signaling was upregulated in joint sensory neurons. Acute blockade or global genetic deletion of Fcgr1 significantly attenuated arthritis pain and hyperactivity of joint sensory neurons without measurably altering joint inflammation. Conditional deletion of Fcgr1 in sensory neurons produced similar analgesic effects in these models. We therefore suggest that FcγRI expressed in sensory neurons contributes to arthritis pain independently of its functions in inflammatory cells. These findings expand our understanding of the immunosensory capabilities of sensory neurons and imply that neuronal FcγRI merits consideration as a target for treating RA pain.

Authors

Li Wang, Xiaohua Jiang, Qin Zheng, Sang-Min Jeon, Tiane Chen, Yan Liu, Heather Kulaga, Randall Reed, Xinzhong Dong, Michael J. Caterina, Lintao Qu

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Figure 8

Neuronal FcγRI mediates arthritis pain in the AIA and CFA models.

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Neuronal FcγRI mediates arthritis pain in the AIA and CFA models. (A–E) ...
(A–E) Time course of ankle mechanical threshold (A), paw withdrawal frequency (PWF) to 0.07 g (B) and 0.4 g force (C), paw withdrawal latency to radiant heat (D), and ankle joint diameter (E) of male mice following AIA in PirtCre Fcgr1fl/fl mice and Fcgr1fl/fl control littermates. n = 10 mice per group; *P < 0.05 vs. Fcgr1fl/fl controls, #P < 0.05 vs. day 0; 2-way repeated-measures ANOVA followed by Bonferroni’s post hoc test. (F–J) Ankle mechanical threshold (F), PWF to 0.07 g (G) and 0.4 g force (H), paw withdrawal latency to radiant heat (I), and ankle joint diameter (J) in male Fcgr1fl/fl and PirtCre Fcgr1fl/fl mice after injection of CFA (5 μL) into the ankle joint. n = 10 mice per group; *P < 0.05 vs. Fcgr1fl/fl controls, #P < 0.05 vs. week 0; 2-way repeated-measures ANOVA followed by Bonferroni’s post hoc test. (K and L) Total duration of pain-related behavior during the first (1–10 minutes) and second phases (11–60 minutes) after intraplantar injection of formalin (5%; 20 μL) in Fcgr1fl/fl and PirtCre Fcgr1fl/fl mice (both sexes). n = 8 mice per group; P > 0.05 vs. Fcgr1fl/fl controls; 1-way repeated-measures ANOVA followed by Bonferroni’s post hoc test.