Silencing miR-21-5p in sensory neurons reverses neuropathic allodynia via activation of TGF-β–related pathway in macrophages
Lynda Zeboudj, George Sideris-Lampretsas, Rita Silva, Sabeha Al-Mudaris, Francesca Picco, Sarah Fox, David Chambers, Marzia Malcangio
Lynda Zeboudj, George Sideris-Lampretsas, Rita Silva, Sabeha Al-Mudaris, Francesca Picco, Sarah Fox, David Chambers, Marzia Malcangio
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Research Article Immunology Neuroscience

Silencing miR-21-5p in sensory neurons reverses neuropathic allodynia via activation of TGF-β–related pathway in macrophages

Abstract

Neuropathic pain remains poorly managed by current therapies, highlighting the need to improve our knowledge of chronic pain mechanisms. In neuropathic pain models, dorsal root ganglia (DRG) nociceptive neurons transfer miR-21 packaged in extracellular vesicles to macrophages that promote a proinflammatory phenotype and contribute to allodynia. Here we show that miR-21 conditional deletion in DRG neurons was coupled with lack of upregulation of chemokine CCL2 after nerve injury and reduced accumulation of CCR2-expressing macrophages, which showed TGF-β–related pathway activation and acquired an M2-like antinociceptive phenotype. Indeed, neuropathic allodynia was attenuated after conditional knockout of miR-21 and restored by TGF-βR inhibitor (SB431542) administration. Since TGF-βR2 and TGF-β1 are known miR-21 targets, we suggest that miR-21 transfer from injured neurons to macrophages maintains a proinflammatory phenotype via suppression of such an antiinflammatory pathway. These data support miR-21 inhibition as a possible approach to maintain polarization of DRG macrophages at an M2-like state and attenuate neuropathic pain.

Authors

Lynda Zeboudj, George Sideris-Lampretsas, Rita Silva, Sabeha Al-Mudaris, Francesca Picco, Sarah Fox, David Chambers, Marzia Malcangio

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Figure 7

Intrathecal injection of M2-like macrophages alleviates neuropathic allodynia via the polarization of sNAMs toward an antiinflammatory phenotype.

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Intrathecal injection of M2-like macrophages alleviates neuropathic allo...
(A) Schematic representation of the experimental design for intrathecal (i.t.) delivery of macrophages in WT mice, and the behavioral tests. (B) Effect of macrophage control (MΦ-control) and M2-like macrophages on the development of mechanical hypersensitivity in SNI (n = 5–6). Data are presented as 50% paw withdrawal thresholds (PWT); mean ± SEM. +P < 0.05, ++P < 0.01, +++P < 0.001 compared with M2-like contralateral thresholds; **P < 0.01, ***P < 0.001 compared with MΦ-control contralateral thresholds, #P < 0.05, ##P < 0.01 compared with MΦ-control ipsilateral thresholds; by 2-way ANOVA followed by Tukey’s multiple-comparison test. (C) Absolute number of GFP+F4/80+ cells in DRGs 2 hours after i.t. delivery of MΦ-control and M2-like macrophages (n = 6–8). (D) Representative scatterplots of CD206 and MHCII expression in CD11b+F4/80+ macrophages in DRGs 2 hours after i.t. delivery of MΦ-control and M2-like macrophages. (E) MHCII+CD206– (M1-like), and (F) CD206+MHCII– (M2-like) absolute cell number in DRGs 2 hours after i.t. delivery of MΦ-control and M2-like macrophages (n = 6–7). (G) Representative scatterplots of CD206 and MHCII expression in CD11b+F4/80+ macrophages in DRGs 48 hours after i.t. delivery of MΦ-control and M2-like macrophages. (H) MHCII+CD206– (M1-like) and (I) CD206+MHCII– (M2-like) absolute cell number in DRGs 48 hours after i.t. delivery of MΦ-control and M2-like macrophages (n = 6–8). Data are presented as mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001 by 1-way ANOVA followed by Tukey’s multiple-comparison test (C, E, F, H and I).