Role of CGRP in Neuroimmune Interaction via NF-κB Signaling Genes in Glial Cells of Trigeminal Ganglia.

Shaista Afroz,Arief Waskitho,Takuma Iwasa,Masamitsu Oshima,Rieko Arakaki,Yoshizo Matsuka

doi:10.3390/ijms21176005

Abstract

Activation of the trigeminal system causes the release of various neuropeptides, cytokines, and other immune mediators. Calcitonin gene-related peptide (CGRP), which is a potent algogenic mediator, is expressed in the peripheral sensory neurons of trigeminal ganglion (TG). It affects the inflammatory responses and pain sensitivity by modulating the activity of glial cells. The primary aim of this study was to use array analysis to investigate the effect of CGRP on the glial cells of TG in regulating nuclear factor kappa B (NF-κB) signaling genes and to further check if CGRP in the TG can affect neuron-glia activation in the spinal trigeminal nucleus caudalis. The glial cells of TG were stimulated with CGRP or Minocycline (Min) + CGRP. The effect on various genes involved in NF-κB signaling pathway was analyzed compared to no treatment control condition using a PCR array analysis. CGRP, Min + CGRP or saline was directly injected inside the TG and the effect on gene expression of Egr1, Myd88 and Akt1 and protein expression of cleaved Caspase3 (cleav Casp3) in the TG, and c-Fos and glial fibrillary acidic protein (GFAP) in the spinal section containing trigeminal nucleus caudalis was analyzed. Results showed that CGRP stimulation resulted in the modulation of several genes involved in the interleukin 1 signaling pathway and some genes of the tumor necrosis factor pathway. Minocycline pre-treatment resulted in the modulation of several genes in the glial cells, including anti-inflammatory genes, and neuronal activation markers. A mild increase in cleav Casp3 expression in TG and c-Fos and GFAP in the spinal trigeminal nucleus of CGRP injected animals was observed. These data provide evidence that glial cells can participate in neuroimmune interaction due to CGRP in the TG via NF-κB signaling pathway.

Highlights

IntroductionImmune activation and the subsequent release of immune mediators in the peripheral nervous system (PNS) contribute to pain [1,2]
Neuroimmune interaction causes the development of sensitization of pain
The genes which were included in the PCR array analysis were related to the various steps involved in NF-κB signaling pathway, namely various ligands and receptors regulating NF-κB signaling, genes related to the downstream signaling of NF-κB, cytoplasmic sequestering/releasing of NF-κB, transcription factors, NF-κB responsive genes, e.g., immune response and apoptosis, and other NF-κB signaling genes, e.g., kinases and transcription factors

Summary

Introduction

Immune activation and the subsequent release of immune mediators in the peripheral nervous system (PNS) contribute to pain [1,2]. The release of cytokines and inflammatory mediators from the peripheral glial cells (satellite glial cells (SGC) or Schwann cells) or blood derived immune cells (mast cells, macrophages, and lymphocytes) in response to some trauma or noxious stimuli to the PNS, has been shown by various researchers to be responsible for causing peripheral and central sensitization, thereby contributing to the development of allodynia and hyperalgesia, two hallmarks of neuropathic pain (NP) [1,2,3,4]. NF-κB plays an essential role in the gene expression of inflammatory mediators in different cell types, including neurons and glial cells. Transgenic inhibition of glial NF-κB has been shown to inhibit hyperalgesia and allodynia in mice, and these effects were related to a reduction in cytokine/chemokine production in DRGs [7]

Objectives

Methods

Results

Conclusion