Neuropathic Pain: Characterization and Modulation of Macrophage/Microglial Activation
Abstract
Neuropathic pain is a common, debilitating disorder and effective treatments are limited. Persistent activation of macrophages/microglia along ascending somatosensory nerve pathways following peripheral nerve injury contributes to neuropathic pain, though the role of polarization of pro- and anti-inflammatory macrophage/microglial phenotypes in neuropathic pain is not well understood. Photobiomodulation treatment has been used to decrease neuropathic pain, has an anti-inflammatory effect in models of spinal cord injury and wound healing, and has modulated microglial polarization in vitro. The aim of this study was to characterize the activation and polarization of macrophages/microglia after peripheral nerve injury and modulate the response using photo biomodulation. Adult male Sprague-Dawley rats were assigned to Sham surgery (n=37), Spared Nerve Injury (SNI) (n=37) or SNI with photobiomodulation treatment groups (n=22). Mechanical allodynia was assessed with an electronic Von Frey. Photobiomodulation (980 nm wavelength light) was applied to affected hindpaw, dorsal root ganglia (DRG), and spinal cord regions every other day from day 7 to day 30 post-operatively. Macrophage/microglial activation was characterized with immunohistochemistry and gene expression. Injured groups demonstrated increased mechanical allodynia from day 1-30 postoperatively. Photobiomodulation-treated animals began to recover after two treatments; at day 26 mechanical allodynia reached baseline levels. Peripheral nerve injury caused significant, region-specific, general activation of macrophages/microglia along ascending somatosensory pathways. Pro-inflammatory microglial marker expression was increased in the spinal cord of SNI rats compared to photobiomodulation-treated and sham group. Photobiomodulation-treated DRG macrophages expressed increased anti-inflammatory markers.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 15, 2014
- Accession Number
- AD1127764
Entities
People
- Ann K. Ketz
Organizations
- Uniformed Services University of the Health Sciences