Journal article
The Complement System Component C5a Produces Thermal Hyperalgesia via Macrophage-to-Nociceptor Signaling That Requires NGF and TRPV1
The Journal of neuroscience, Vol.36(18), pp.5055-5070
05/04/2016
DOI: 10.1523/JNEUROSCI.3249-15.2016
PMCID: PMC4854968
PMID: 27147658
Abstract
The complement cascade is a principal component of innate immunity. Recent studies have underscored the importance of C5a and other components of the complement system in inflammatory and neuropathic pain, although the underlying mechanisms are largely unknown. In particular, it is unclear how the complement system communicates with nociceptors and which ion channels and receptors are involved. Here we demonstrate that inflammatory thermal and mechanical hyperalgesia induced by complete Freund's adjuvant was accompanied by C5a upregulation and was markedly reduced by C5a receptor (C5aR1) knock-out or treatment with the C5aR1 antagonist PMX53. Direct administration of C5a into the mouse hindpaw produced strong thermal hyperalgesia, an effect that was absent in TRPV1 knock-out mice, and was blocked by the TRPV1 antagonist AMG9810. Immunohistochemistry of mouse plantar skin showed prominent expression of C5aR1 in macrophages. Additionally, C5a evoked strong Ca(2+) mobilization in macrophages. Macrophage depletion in transgenic macrophage Fas-induced apoptosis mice abolished C5a-dependent thermal hyperalgesia. Examination of inflammatory mediators following C5a injection revealed a rapid upregulation of NGF, a mediator known to sensitize TRPV1. Preinjection of an NGF-neutralizing antibody or Trk inhibitor GNF-5837 prevented C5a-induced thermal hyperalgesia. Notably, NGF-induced thermal hyperalgesia was unaffected by macrophage depletion. Collectively, these results suggest that complement fragment C5a induces thermal hyperalgesia by triggering macrophage-dependent signaling that involves mobilization of NGF and NGF-dependent sensitization of TRPV1. Our findings highlight the importance of macrophage-to-neuron signaling in pain processing and identify C5a, NGF, and TRPV1 as key players in this cross-cellular communication.
This study provides mechanistic insight into how the complement system, a key component of innate immunity, regulates the development of pain hypersensitivity. We demonstrate a crucial role of the C5a receptor, C5aR1, in the development of inflammatory thermal and mechanical sensitization. By focusing on the mechanisms of C5a-induced thermal hyperalgesia, we show that this process requires recruitment of macrophages and initiation of macrophage-to-nociceptor signaling. At the molecular level, we demonstrate that this signaling depends on NGF and is mediated by the heat-sensitive nociceptive channel TRPV1. This deeper understanding of how immune cells and neurons interact to regulate pain processing is expected to facilitate mechanism-based approaches in the development of new analgesics.
Details
- Title: Subtitle
- The Complement System Component C5a Produces Thermal Hyperalgesia via Macrophage-to-Nociceptor Signaling That Requires NGF and TRPV1
- Creators
- Leonid P Shutov - Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242Charles A Warwick - Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242Xiaoyu Shi - Department of Anesthesia, Veterans Administration Palo Alto Healthcare System and Stanford University, Palo Alto, California 94305Aswini Gnanasekaran - Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242Andrew J Shepherd - Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242, Department of Anesthesiology, Washington University Pain Center, Washington University School of Medicine, St. Louis, Missouri 63110, andDurga P Mohapatra - Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242, Department of Anesthesiology, Washington University Pain Center, Washington University School of Medicine, St. Louis, Missouri 63110, andTrent M Woodruff - School of Biomedical Sciences, University of Queensland, St. Lucia, Queensland 4072, AustraliaJ David Clark - Department of Anesthesia, Veterans Administration Palo Alto Healthcare System and Stanford University, Palo Alto, California 94305Yuriy M Usachev - Department of Pharmacology, University of Iowa, Iowa City, Iowa 52242, yuriy-usachev@uiowa.edu
- Resource Type
- Journal article
- Publication Details
- The Journal of neuroscience, Vol.36(18), pp.5055-5070
- Publisher
- United States
- DOI
- 10.1523/JNEUROSCI.3249-15.2016
- PMID
- 27147658
- PMCID
- PMC4854968
- ISSN
- 0270-6474
- eISSN
- 1529-2401
- Grant note
- T32 GM067795 / NIGMS NIH HHS R21 NS092851 / NINDS NIH HHS T32 NS045549 / NINDS NIH HHS R01 NS072432 / NINDS NIH HHS R01 GM079126 / NIGMS NIH HHS R01 NS087068 / NINDS NIH HHS R01 NS069898 / NINDS NIH HHS
- Language
- English
- Date published
- 05/04/2016
- Academic Unit
- Iowa Neuroscience Institute; Anesthesia; Neuroscience and Pharmacology
- Record Identifier
- 9984040338802771
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