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CXCL12-mediated monocyte transmigration into brain perivascular space leads to neuroinflammation and memory deficit in neuropathic pain.

ABSTRACT: Emerging clinical and experimental evidence demonstrates that neuroinflammation plays an important role in cognitive impairment associated with neuropathic pain. However, how peripheral nerve challenge induces remote inflammation in the brain remains largely unknown. Methods: The circulating leukocytes and plasma C-X-C motif chemokine 12 (CXCL12) and brain perivascular macrophages (PVMs) were analyzed by flow cytometry, Western blotting, ELISA, and immunostaining in spared nerve injury (SNI) mice. The memory function was evaluated with a novel object recognition test (NORT) in mice and with Montreal Cognitive Assessment (MoCA) in chronic pain patients. Results: The classical monocytes and CXCL12 in the blood, PVMs in the perivascular space, and gliosis in the brain, particularly in the hippocampus, were persistently increased following SNI in mice. Using the transgenic CCR2^RFP/+ and CX3CR1^GFP/+ mice, we discovered that at least some of the PVMs were recruited from circulating monocytes. The SNI-induced increase in hippocampal PVMs, gliosis, and memory decline were substantially prevented by either depleting circulating monocytes via intravenous injection of clodronate liposomes or blockade of CXCL12-CXCR4 signaling. On the contrary, intravenous injection of CXCL12 at a pathological concentration in naïve mice mimicked SNI effects. Significantly, we found that circulating monocytes and plasma CXCL12 were elevated in chronic pain patients, and both of them were closely correlated with memory decline. Conclusion: CXCL12-mediated monocyte recruitment into the perivascular space is critical for neuroinflammation and the resultant cognitive impairment in neuropathic pain.

SUBMITTER: Mai CL

PROVIDER: S-EPMC7738876 | biostudies-literature | 2021

REPOSITORIES: biostudies-literature

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CXCL12-mediated monocyte transmigration into brain perivascular space leads to neuroinflammation and memory deficit in neuropathic pain.

Mai Chun-Lin CL Tan Zhi Z Xu Ya-Nan YN Zhang Jing-Jun JJ Huang Zhen-Hua ZH Wang Dong D Zhang Hui H Gui Wen-Shan WS Zhang Jun J Lin Zhen-Jia ZJ Meng Ying-Tong YT Wei Xiao X Jie Ying-Tao YT Grace Peter M PM Wu Long-Jun LJ Zhou Li-Jun LJ Liu Xian-Guo XG

Theranostics 20210101 3

Emerging clinical and experimental evidence demonstrates that neuroinflammation plays an important role in cognitive impairment associated with neuropathic pain. However, how peripheral nerve challenge induces remote inflammation in the brain remains largely unknown. <b>Methods:</b> The circulating leukocytes and plasma C-X-C motif chemokine 12 (CXCL12) and brain perivascular macrophages (PVMs) were analyzed by flow cytometry, Western blotting, ELISA, and immunostaining in spared nerve injury (S ...[more]

PMID: 33391521

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Project description:We investigated the hypothesis that transmigration drives monocyte transcriptional changes. Using Agilent Whole Human Genome Microarrays, we identified over 600 differentially expressed genes (2x, p<0.05) in freshly isolated human monocytes following 1.5 h of transmigration across IL1beta-stimulated ECs compared to untreated monocytes. Genes up-regulated by monocyte transmigration belong to a number of overrepresented functional groups including immune response, and inhibition of apoptosis. qRT-PCR confirmed increased expression of monocyte chemotactic proteins 1 and 3 and of NLR family apoptosis inhibitory protein (NAIP) following monocyte transmigration. In addition, quantification of annexin V binding revealed a reduction in apoptosis following monocyte transmigration. Comparison of gene expression in transmigrated monocytes to additional controls (monocytes which failed to transmigrate and monocytes incubated beneath stimulated ECs) revealed 89 differentially expressed genes which were controlled by the physical process of diapedesis. Functional annotation of these genes showed down-regulation of antimicrobial genes (e.g. alpha-defensin down 50x, cathelicidin down 9x, and cathepsin G down 3x). qRT-PCR confirmed down-regulation of these genes. Immunoblots confirmed that monocyte transmigration down-regulates alpha-defensin protein expression. Overall, these data indicate that exposure of monocytes to stimulated ECs promotes further monocyte recruitment and inhibits monocyte apoptosis. Unexpectedly, following transmigration monocytes displayed reduced anti-microbial expression. Monocytes were allowed to transmigrate across IL1b stimulated HUVEC. Monocytes which transmigrated and monocytes which failed to transmigrate were collected after 1.5 hours from 3 experimental replicates of different human donors. Untreated monocytes were collected as a control from 4 human donors. Monocytes incubated beneath stimulated HUVEC for 1.5 hours were also collected from four human donors as a control.

Dataset Information

CXCL12-mediated monocyte transmigration into brain perivascular space leads to neuroinflammation and memory deficit in neuropathic pain.

Publications

CXCL12-mediated monocyte transmigration into brain perivascular space leads to neuroinflammation and memory deficit in neuropathic pain.

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