Elevation of the Chemokine Pair CXCL10/CXCR3 Initiates Sequential Glial Activation and Crosstalk During the Development of Bimodal Inflammatory Pain after Spinal Cord Ischemia Reperfusion

Abstract

Background/Aims: Spinal microglia and astrocytes are the main responders to the inflammatory cascade and process pain through various neural interactions. CXCL10 is a late-phase protein that accelerates arteriogenesis during reperfusion through CXCR3. However, the early-phase expression (within 72 h postoperatively) of CXCL10 and CXCR3 during the development of ischemia-reperfusion (IR)-induced inflammatory pain remains unclear. We investigated whether this chemokine pair participates in glial interactions during early-phase IR injury. Methods: A rat model was induced by an 8-min occlusion of the aortic arch. Temporal assessments of mechanical and thermal allodynia and the protein levels of CXCL10 and CXCR3 were determined through measurements of paw withdrawal thresholds (PWTs) and paw withdrawal latencies (PWLs) and Western blotting assays. The co-localization of various cells with glial cells was detected by double immunofluorescence. The effects of CXCL10/CXCR3 on glial interactions were explored by intrathecal treatment with specific inhibitors (AMD487, minocycline and fluorocitrate) and recombinant CXCL10, and subsequent release of cytokines was assessed by ELISAs. Results: The IR injury initiated bimodal allodynia within 72 h of reperfusion, as illustrated by two W-shape trends in the PWTs and PWLs with two minima at 12 and 48 h post-IR. Allodynia was highly correlated with overexpression of CXCL10 and CXCR3, which were expressed in microglia at the early stage and in both microglia and astrocytes at the late stage, as shown by increased CXCL10 and CXCR3 immunoreactivities and double-labeled cells. AMD487 and minocycline injections exerted comparable inhibitory effects on CXCR3 and Iba-1 and on GFAP immunoreactivity at 12 and 48 h post-IR, and these inhibitory effects were only observed at 48 h following fluorocitrate injection. The levels of TNF-α and IL-6 showed variations in concert with the changes in Iba-1 and GFAP immunoreactivities. Recombinant CXCL10 injection reversed the abovementioned effects. Conclusion: The results showed that CXCL10/CXCR3 are involved in bimodal inflammatory pain during early-phase IR injury. The sequential activation of and crosstalk between microglia and astrocytes mediated through CXCR3 upregulation suggested that treatments targeting specific cell types are important in post-IR allodynia.

Identification of key microRNAs and the underlying molecular mechanism in spinal cord ischemia-reperfusion injury in rats

“…In the present study, cGMP-PKG and cAMP signaling pathways are involved in the target genes of the upregulated DEmiRNAs, while the Chemokine signaling pathway and MAPK signaling pathway are enrichment pathways of the downregulated DEmiRNAs target genes. The results are consistent with previous studies, which implicate the involvement of the above pathways in SCII ( Chen et al, 2020c ; Yu et al, 2018 ). Inhibition of reactive oxygen species reduced the MAPK pathway in the spinal cord following limb IRI in rats ( Choi et al, 2015 ).…”

“…CXCL13/CXCR5 axis promoted the development of SCII via ERK-mediated pathways ( Chen et al, 2020c ). During early-phase SCII, CXCL10/CXCR3 axis was related to inflammatory pain ( Yu et al, 2018 ).…”

“…CXCL13/CXCR5 axis promoted the development of SCII via ERK-mediated pathways (Chen et al, 2020c). During early-phase SCII, CXCL10/CXCR3 axis was related to inflammatory pain (Yu et al, 2018). Furthermore, the key DEmiRNAs target genes are strongly regulated by transcription factors such as SP1, GLI1, GLI2, and FOXO3.…”

Peer Review #1 of "Identification of key microRNAs and the underlying molecular mechanism in spinal cord ischemia-reperfusion injury in rats (v0.1)"

“…In the present study, cGMP-PKG and cAMP signaling pathways are involved in the target genes of the upregulated DEmiRNAs, while the Chemokine signaling pathway and MAPK signaling pathway are enrichment pathways of the downregulated DEmiRNAs target genes. The results are consistent with previous studies, which implicate the involvement of the above pathways in SCII (Chen et al 2020b;Yu et al 2018). Inhibition of reactive oxygen species reduced the MAPK pathway in the spinal cord following limb IRI in rats (Choi et al 2015).…”

TRPV1 Channel Contributes to the Behavioral Hypersensitivity in a Rat Model of Complex Regional Pain Syndrome Type 1

“…It is proposed that central sensitization may underlie this generalized bilateral hypersensitivity in CRPS-I (Terkelsen et al, 2014). Glial cells in the SCDH, such as microglia and astrocytes, are activated in response to peripheral painful stimuli and participate in spinal pain signal transmission and central sensitization (Milligan and Watkins, 2009; Yu et al, 2018). Astrocytes and microglia in both ipsilateral and contralateral SCDH are activated in CPIP model rats (Tang et al, 2018).…”