CCL2/CCR2 signaling elicits itch- and pain-like behavior in a murine model of allergic contact dermatitis

• Published in: Brain, behavior, and immunity behavior, and immunity, 2019-08, Vol.80, p.464-473
• Main Authors: Jiang, Haowu, Cui, Huan, Wang, Tao, Shimada, Steven G., Sun, Rui, Tan, Zhiyong, Ma, Chao, LaMotte, Robert H.
• Format: Article
• Language: English
• Subjects: Allergic contact dermatitis; Animals; Chemokine; Chemokine CCL2 - metabolism; Chemokine CCL2 - physiology; Cyclobutanes - pharmacology; Dermatitis, Allergic Contact - metabolism; Dermatitis, Allergic Contact - physiopathology; Disease Models, Animal; Dorsal root ganglion; Ganglia, Spinal - metabolism; Itch; Male; Mice; Mice, Inbred C57BL; Pain; Pain - metabolism; Patch-Clamp Techniques; Pruritus - metabolism; Receptors, CCR2 - metabolism; Receptors, CCR2 - physiology; Sensory Receptor Cells - metabolism; Signal Transduction; Skin - metabolism
• ISSN: 0889-1591; 1090-2139
• DOI: 10.1016/j.bbi.2019.04.026

•Contact hypersensitivity (CHS) upregulated CCL2/MCP-1 and CCR2 in nociceptors.•CCL2 injected into CHS site evoked site-directed itch- and pain-like behaviors.•CCL2 activated nociceptive dorsal root ganglion neurons innervating CHS site.•A CCR2 antagonist decreased these behavioral and neuronal responses.•Targeting CCL2/CCR2 signaling might treat allergic itch and pain in humans. Spontaneous itch and pain are the most common symptoms in various skin diseases, including allergic contact dermatitis (ACD). The chemokine (C-C motif) ligand 2 (CCL2, also referred to as monocyte chemoattractant protein 1 (MCP-1)) and its receptor CCR2 are involved in the pathophysiology of ACD, but little is known of the role of CCL2/CCR2 for the itch- and pain-behaviors accompanying the murine model of this disorder, termed contact hypersensitivity (CHS). C57BL/6 mice previously sensitized to the hapten, squaric acid dibutyl ester, applied to the abdomen were subsequently challenged twice with the hapten delivered to either the cheek or to the hairy skin of the hind paw resulting in CHS at that site. By 24 h after the 2nd challenge to the hind paw CCL2 and CCR2 mRNA, protein, and signaling activity were upregulated in the dorsal root ganglion (DRG). Calcium imaging and whole-cell current-clamp recordings revealed that CCL2 directly acted on its neuronal receptor, CCR2 to activate a subset of small-diameter, nociceptive-like DRG neurons retrogradely labeled from the CHS site. Intradermal injection of CCL2 into the site of CHS on the cheek evoked site-directed itch- and pain-like behaviors which could be attenuated by prior delivery of an antagonist of CCR2. In contrast, CCL2 failed to elicit either type of behavior in control mice. Results are consistent with the hypothesis that CHS upregulates CCL2/CCR2 signaling in a subpopulation of cutaneous small diameter DRG neurons and that CCL2 can activate these neurons through neuronal CCR2 to elicit itch- and pain-behavior. Targeting the CCL2/CCR2 signaling might be beneficial for the treatment of the itch and pain sensations accompanying ACD in humans.