Excitatory monocyte chemoattractant protein-1 signaling is up-regulated in sensory neurons after chronic compression of the dorsal root ganglion.
Neuronal hyperexcitability in both injured and adjacent uninjured neurons is associated with states of chronic injury and pain and is likely subject to neuroinflammatory processes. Chronic inflammatory responses are largely orchestrated by chemokines. One chemokine, monocyte chemoattractant protein-1 (MCP-1), in the presence of its cognate receptor, the beta chemokine receptor 2 (CCR2), produces neural activity in dissociated neuronal cultures of neonatal dorsal root ganglion (DRG) neurons. Using a neuropathic pain model, chronic compression of the DRG (CCD), we compared anatomically separate populations of noncompressed lumbar DRG (L3/L6) with compressed lumbar DRG (L4/L5) for changes in the gene expression of CCR2. In situ hybridization revealed that CCR2 mRNA was up-regulated in neurons and nonneuronal cells present in both compressed L4/L5 and ipsilateral noncompressed L3/L6 DRGs at postoperative day 5 (POD5). The total percentages of compressed and noncompressed neurons exhibiting CCR2 mRNA transcripts in L3, L5, and L6 DRG were 33 +/- 3.5%, 49 +/- 6.2%, and 41 +/- 5.6%, respectively, and included cell bodies of small, medium, and large size. In addition, the preferred CCR2 ligand, MCP-1, was up-regulated by POD5 in both compressed L4/L5 and noncompressed L3/L6 DRG neurons. Application of MCP-1 to the cell bodies of the intact formerly compressed DRG in vitro produced potent excitatory effects not observed in control ganglia. MCP-1/CCR2 signaling is directly involved with a chronic compression injury and may contribute to associated neuronal hyperexcitability and neuropathic pain.
White
Fletcher A
FA
Department of Cell Biology, Neurobiology, and Anatomy, and Anesthesiology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL 60153, USA. fwhite@lumc.edu
Sun
Jihu
J
Waters
Stephen M
SM
Ma
Chao
C
Ren
Dongjun
D
Ripsch
Matthew
M
Steflik
Jeremy
J
Cortright
Daniel N
DN
Lamotte
Robert H
RH
Miller
Richard J
RJ
D000818:Animals; D018932:Chemokine CCL2 / Q000032:analysis / Q000378:metabolism*; D005260:Female; D005727:Ganglia, Spinal / Q000378:metabolism / Q000473:pathology*; D015870:Gene Expression; D008161:Lumbosacral Region / Q000473:pathology; D008264:Macrophages / Q000378:metabolism; D009475:Neurons, Afferent / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D011843:Radiculopathy / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D054390:Receptors, CCR2; D019707:Receptors, Chemokine / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
C515336:Ccr2 protein, rat; D018932:Chemokine CCL2; D012333:RNA, Messenger; D054390:Receptors, CCR2; D019707:Receptors, Chemokine