Short-chain fatty acids contribute to neuropathic pain via regulating microglia activation and polarization

Microglia activation and subsequent pro-inflammatory responses play a key role in the development of neuropathic pain. The process of microglia polarization towards pro-inflammatory phenotype often occurs during neuroinflammation. Recent studies have demonstrated an active role for the gut microbiota in promoting microglial full maturation and inflammatory capabilities via the production of Short-Chain Fatty Acids (SCFAs). However, it remains unclear whether SCFAs is involved in pro-inflammatory/anti-inflammatory phenotypes microglia polarization in the neuropathic pain. In the present study, chronic constriction injury (CCI) was used to induce neuropathic pain in mice, the mechanical withdrawal threshold, thermal hyperalgesia were accomplished. The levels of microglia markers including ionized calcium-binding adaptor molecule 1 (Iba1), cluster of differentiation 11b (CD11b), pro-inflammatory phenotype markers including CD68, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and anti-inflammatory phenotype markers including CD206, IL-4 in the hippocampus and spinal cord were determined on day 21 after CCI. The results showed that CCI produced mechanical allodynia and thermal hyperalgesia, and also increased the expressions of microglia markers (Iba1, CD11b) and pro-inflammatory phenotype markers (CD68, IL-1β, and TNF-α), but not anti-inflammatory phenotype marker (CD206, IL-4) in the hippocampus and spinal cord, accompanied by increased SCFAs in the gut. Notably, antibiotic administration reversed these abnormalities, and its effects was also bloked by SCFAs administration. In conclusion, data from our study suggest that CCI can lead to mechanical and thermal hyperalgesia, while SCFAs play a key role in the pathogenesis of neuropathic pain by regulating microglial activation and subsequent pro-inflammatory phenotype polarization. Antibiotic administration may be a new treatment for neuropathic pain by reducing the production of SCFAs and further inhibiting the process of microglia polarization.

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Reciprocal Regulatory Interaction between TRPV1 and Kinin B1 Receptor in a Rat Neuropathic Pain Model

International Journal of Molecular Sciences ◽

10.3390/ijms21030821 ◽

2020 ◽

Vol 21 (3) ◽

pp. 821 ◽

Cited By ~ 1

Author(s):

Veronica Cernit ◽

Jacques Sénécal ◽

Rahmeh Othman ◽

Réjean Couture

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Mrna Expression ◽

Thermal Hyperalgesia ◽

Mrna Levels ◽

Regulatory Interaction ◽

B1 Receptor ◽

Tnf Α ◽

Kinin B1 Receptor ◽

Sensory Fibers

Kinins are mediators of pain and inflammation and evidence suggests that the inducible kinin B1 receptor (B1R) is involved in neuropathic pain (NP). This study investigates whether B1R and TRPV1 are colocalized on nociceptors and/or astrocytes to enable regulatory interaction either directly or through the cytokine pathway (IL-1β, TNF-α) in NP. Sprague Dawley rats were subjected to unilateral partial sciatic nerve ligation (PSNL) and treated from 14 to 21 days post-PSNL with antagonists of B1R (SSR240612, 10 mg·kg−1, i.p.) or TRPV1 (SB366791, 1 mg·kg−1, i.p.). The impact of these treatments was assessed on nociceptive behavior and mRNA expression of B1R, TRPV1, TNF-α, and IL-1β. Localization on primary sensory fibers, astrocytes, and microglia was determined by immunofluorescence in the lumbar spinal cord and dorsal root ganglion (DRG). Both antagonists suppressed PSNL-induced thermal hyperalgesia, but only SB366791 blunted mechanical and cold allodynia. SSR240612 reversed PSNL-induced enhanced protein and mRNA expression of B1R and TRPV1 mRNA levels in spinal cord while SB366791 further increased B1R mRNA/protein expression. B1R and TRPV1 were found in non-peptide sensory fibers and astrocytes, and colocalized in the spinal dorsal horn and DRG, notably with IL-1β on astrocytes. IL-1β mRNA further increased under B1R or TRPV1 antagonism. Data suggest that B1R and TRPV1 contribute to thermal hyperalgesia and play a distinctive role in allodynia associated with NP. Close interaction and reciprocal regulatory mechanism are suggested between B1R and TRPV1 on astrocytes and nociceptors in NP.

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Gastrodia elata Blume Polysaccharides Attenuate Vincristine-Evoked Neuropathic Pain through the Inhibition of Neuroinflammation

Mediators of Inflammation ◽

10.1155/2021/9965081 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Hengtao Xie ◽

Yingying Chen ◽

Wei Wu ◽

Xiaobo Feng ◽

Kairong Du

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Sciatic Nerve ◽

Inflammatory Cytokines ◽

Thermal Hyperalgesia ◽

Mrna Levels ◽

Gastrodia Elata ◽

Neuroprotective Effects ◽

Gastrodia Elata Blume ◽

Tnf Α

Vincristine (Vin) is a well-known antitumor agent that frequently evokes neuropathic pain and decreases the quality of life of patients. Polysaccharides (GBP) extracted from Gastrodia elata Blume have been demonstrated to possess anti-inflammatory and neuroprotective effects in vivo; however, the effects of GBP on Vin-induced neuropathic pain remain unknown. The present study is aimed at exploring the alleviative potential of GBP against chemotherapy-evoked peripheral neuropathy to better understand and extend its pharmacological application. Vin was administered intraperitoneally to evoke neuropathic pain. GBP was orally administered for 21 days. The mechanical allodynia and thermal hyperalgesia were assessed using the Von Frey test and hot-plate test. Histopathological changes were assessed by hematoxylin and eosin staining. ELISA kits were used to measure the levels of inflammatory cytokines in the sciatic nerve, spinal cord, and dorsal root ganglion (DRG). qRT-PCR was employed to examine the expression of inflammatory cytokines and Sirtuin1 (SIRT1) in the sciatic nerve, spinal cord, and DRG. Our findings revealed that GBP treatment enhanced the paw withdrawal latency and paw withdrawal threshold and restored Vin-induced sciatic nerve damage in rats. GBP also attenuated the Vin-induced increase of proinflammatory cytokine levels, including IL-6, IL-8, TNF-α, IL-1β, and NF-κB. On the molecular level, treatment with GBP downregulated the mRNA levels of IL-6, IL-8, TNF-α, and IL-1β in the sciatic nerve, spinal cord, and DRG. Meanwhile, GBP increased SIRT1 activity and mRNA expression levels. Our data indicated that GBP exerted a potential protective effect against chemotherapy-induced neuropathic pain which might be mediated via the inhibition of neuroinflammation.

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Fumagillin Attenuates Spinal Angiogenesis, Neuroinflammation, and Pain in Neuropathic Rats After Chronic Constriction Injury

10.21203/rs.3.rs-741520/v1 ◽

2021 ◽

Author(s):

Zhi-Hong Wen ◽

Shi-Ying Huang ◽

Hsiao-Mei Kuo ◽

Chao-Ting Chen ◽

Nan-Fu Chen ◽

...

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Chronic Constriction Injury ◽

Angiogenesis Inhibitor ◽

Thermal Hyperalgesia ◽

Lumbar Spinal Cord ◽

Astrocyte Activation ◽

Anti Vegf ◽

Tnf Α ◽

The Impact

Abstract Background Angiogenesis in the central nervous system is visible in animal models of neuroinflammation and bone cancer pain. However, whether spinal angiogenesis exists and contributes to central sensitization in neuropathic pain remains unclear. This study analyzed the impact of angiogenesis on spinal neuroinflammation in neuropathic pain. Methods Rats with chronic constriction injury (CCI) to sciatic nerve underwent implantation of an intrathecal catheter. Fumagillin or vascular endothelial growth factor-A antibody (anti-VEGF-A) was administered intrathecally. Nociceptive behaviors, cytokine immunoassay, Western blot, and immunohistochemical analysis assessed the effect of angiogenesis inhibition on CCI-induced neuropathic pain. Results VEGF, cluster of differentiation 31 (CD31), and von Willebrand factor (vWF) expressions increased after CCI in the ipsilateral lumbar spinal cord compared to that in the contralateral side of CCI and control rats from postoperative day (POD) 7 to 28, with a peak at POD 14. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 concentrations, but not IL-10 levels, also increased in the ipsilateral spinal cord after CCI. Fumagillin and anti-VEGF-A reduced CCI-induced thermal hyperalgesia from POD 5 to 14 and mechanical allodynia from POD 3 to 14. Fumagillin reduced CCI-upregulated expressions of angiogenic factors and astrocytes. Furthermore, fumagillin decreased TNF-α and IL-6 amounts and increased IL-10 levels at POD 7 and 14, but not IL-1β concentrations. Conclusions Fumagillin significantly ameliorates CCI-induced nociceptive sensitization, spinal angiogenesis and astrocyte activation. Our results suggest that angiogenesis inhibitor treatment suppresses peripheral neuropathy-induced central angiogenesis, neuroinflammation, astrocyte activation, and neuropathic pain.

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Effect of Umbelliprenin on antinociceptive activity of morphine in a rat model of neuropathic pain induced by chronic constriction injury of the sciatic nerve

The Natural Products Journal ◽

10.2174/2210315510999200421201705 ◽

2020 ◽

Vol 10 ◽

Author(s):

Samad Nazemi ◽

Faranak Jafari ◽

Bahareh Amin ◽

Omid Gholami ◽

Marzieh Kafami ◽

...

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Sciatic Nerve ◽

Rat Model ◽

Chronic Constriction Injury ◽

Antinociceptive Activity ◽

Necrosis Factor Alpha ◽

Tnf Α ◽

Male Wistar Rats ◽

Anti Inflammatory

Objective: Although morphine is among of the first line medicines for treatment of neuropathic pain, evidence has shown that the morphine efficacy gradually decreases and a tolerance can occur. Rregarding the many reports concerning the antinociceptive and anti-inflammatory properties of umbelliprenin (UMB), this study aimed to investigate the effect of UMB on antinociceptive activity of morphine in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve. Methods: Twenty-four male Wistar rats were randomly divided into sham, CCI and CCI + UMB100 (100 μg UMB per rat) groups. UMB was intrathecally administered once daily for four consecutive days (from the day before surgery until the day 2 after surgery). All the animals received a single dose of morphine (5 mg/kg, s.c.) on day 14. To evaluate the effect of UMB on antinociceptive activity of morphine, allodynia and hyperalgesia were measured using the von-Frey and hot plate tests, before and 30 min after morphine injection, and the Percentage of Maximum Possible Effect (%MPE) was calculated. In addition, the expression and concentration of tumor necrosis factor-alpha (TNF-α), as a proinflammatory cytokine, was measured in the spinal cord using quantitative real-time PCR (RT-PCR) and ELISA, respectively. Key Findings: UMB significantly enhanced anti-allodynic and anti-hyperalgesic effects of morphine in the neuropathic animals. Moreover, UMB considerably downregulated TNF-α expression in the spinal cord of the animals. Conclusion: UMB can enhance antinociceptive effects of morphine, and this action may be due in part to its anti-inflammatory property.

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Fumagillin Attenuates Spinal Angiogenesis, Neuroinflammation, and Pain in Neuropathic Rats after Chronic Constriction Injury

Biomedicines ◽

10.3390/biomedicines9091187 ◽

2021 ◽

Vol 9 (9) ◽

pp. 1187

Author(s):

Zhi-Hong Wen ◽

Shi-Ying Huang ◽

Hsiao-Mei Kuo ◽

Chao-Ting Chen ◽

Nan-Fu Chen ◽

...

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Chronic Constriction Injury ◽

Angiogenesis Inhibitor ◽

Thermal Hyperalgesia ◽

Lumbar Spinal Cord ◽

Astrocyte Activation ◽

Anti Vegf ◽

Tnf Α ◽

The Impact

Introduction: Angiogenesis in the central nervous system is visible in animal models of neuroinflammation and bone cancer pain. However, whether spinal angiogenesis exists and contributes to central sensitization in neuropathic pain remains unclear. This study analyzes the impact of angiogenesis on spinal neuroinflammation in neuropathic pain. Methods: Rats with chronic constriction injury (CCI) to the sciatic nerve underwent the implantation of an intrathecal catheter. Fumagillin or vascular endothelial growth factor-A antibody (anti-VEGF-A) was administered intrathecally. Nociceptive behaviors, cytokine immunoassay, Western blot, and immunohistochemical analysis assessed the effect of angiogenesis inhibition on CCI-induced neuropathic pain. Results: VEGF, cluster of differentiation 31 (CD31), and von Willebrand factor (vWF) expressions increased after CCI in the ipsilateral lumbar spinal cord compared to that in the contralateral side of CCI and control rats from post-operative day (POD) 7 to 28, with a peak at POD 14. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 concentrations, but not IL-10 levels, also increased in the ipsilateral spinal cord after CCI. Fumagillin and anti-VEGF-A reduced CCI-induced thermal hyperalgesia from POD 5 to 14 and mechanical allodynia from POD 3 to 14. Fumagillin reduced CCI-upregulated expressions of angiogenic factors and astrocytes. Furthermore, fumagillin decreased TNF-α and IL-6 amounts and increased IL-10 levels at POD 7 and 14, but not IL-1β concentrations. Conclusions: Fumagillin significantly ameliorates CCI-induced nociceptive sensitization, spinal angiogenesis, and astrocyte activation. Our results suggest that angiogenesis inhibitor treatment suppresses peripheral neuropathy-induced central angiogenesis, neuroinflammation, astrocyte activation, and neuropathic pain.

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TRPV1 Blocker HCRG21 Suppresses TNF-α Production and Prevents the Development of Edema and Hypersensitivity in Carrageenan-Induced Acute Local Inflammation

Biomedicines ◽

10.3390/biomedicines9070716 ◽

2021 ◽

Vol 9 (7) ◽

pp. 716

Author(s):

Oksana Sintsova ◽

Irina Gladkikh ◽

Anna Klimovich ◽

Yulia Palikova ◽

Viktor Palikov ◽

...

Keyword(s):

Transient Receptor Potential ◽

Thermal Hyperalgesia ◽

Control Group ◽

Transient Receptor Potential Vanilloid ◽

Paw Edema ◽

Mice Model ◽

Edema Formation ◽

Sensitivity Experiment ◽

Tnf Α ◽

Anti Inflammatory

Currently the TRPV1 (transient receptor potential vanilloid type 1) channel is considered to be one of the main targets for pro-inflammatory mediators including TNF-α. Similarly, the inhibition of TRPV1 activity in the peripheral nervous system affects pro-inflammatory mediator production and enhances analgesia in total. In this study, the analgesic and anti-inflammatory effects of HCRG21, the first peptide blocker of TRPV1, were demonstrated in a mice model of carrageenan-induced paw edema. HCRG21 in doses of 0.1 and 1 mg/kg inhibited edema formation compared to the control, demonstrated complete edema disappearance in 24 h in a dose of 1 mg/kg, and effectively reduced the productionof TNF-α in both doses examined. ELISA analysis of blood taken 24 h after carrageenan administration showed a dramatic cytokine value decrease to 25 pg/mL by HCRG21 versus 100 pg/mL in the negative control group, which was less than the TNF-α level in the intact group (40 pg/mL). The HCRG21 demonstrated potent analgesic effects on the models of mechanical and thermal hyperalgesia in carrageenan-induced paw edema. The HCRG21 relief effect was comparable to that of indomethacin taken orally in a dose of 5 mg/kg, but was superior to this nonsteroidal anti-inflammatory drug (NSAID) in duration (which lasted 24 h) in the mechanical sensitivity experiment. The results confirm the existence of a close relationship between TRPV1 activity and TNF-α production once again, and prove the superior pharmacological potential of TRPV1 blockers and the HCRG21 peptide in particular.

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Comparative Phenotypic and Functional Analyses of the Effects of IL-10 or TGF-β on Porcine Macrophages

Animals ◽

10.3390/ani11041098 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1098

Author(s):

Tania Carta ◽

Elisabetta Razzuoli ◽

Floriana Fruscione ◽

Susanna Zinellu ◽

Dionigia Meloni ◽

...

Keyword(s):

Macrophage Polarization ◽

Phagocytic Cells ◽

Mhc Ii ◽

Tnf Α ◽

Regulated Expression ◽

Inflammatory Phenotype ◽

Anti Inflammatory ◽

Functional Analyses ◽

The Impact ◽

Immunosuppressive Cytokines

Macrophages are phagocytic cells involved in maintaining tissue homeostasis and defense against pathogens. Macrophages may be polarized into different functionally specialized subsets. M2c macrophages arise following stimulation with IL-10 or TGF-β and mediate anti-inflammatory and tissue repair functions. M2c macrophages remain poorly characterized in the pig, thus we investigated the impact of these regulatory cytokines on porcine monocyte-derived macrophages (moMΦ). The phenotype and functionality of these cells was characterized though confocal microscopy, flow cytometry, ELISA, and RT-qPCR. Both cytokines induced CD14 and MHC II DR down-regulation and reduced IL-6, TNF-α, and CD14 expression, suggestive of an anti-inflammatory phenotype. Interestingly, neither IL-10 or TGF-β were able to trigger IL-10 induction or release by moMΦ. Differences between these cytokines were observed: stimulation with IL-10, but not TGF-β, induced up-regulation of both CD16 and CD163 on moMΦ. In addition, IL-10 down-regulated expression of IL-1β and IL-12p40 4h post-stimulation and induced a stronger impairment of moMΦ ability to respond to either TLR2 or TLR4 agonists. Overall, our results provide an overview of porcine macrophage polarization by two immunosuppressive cytokines, revealing differences between IL-10 and TGF-β, and reporting some peculiarity of swine, which should be considered in translational studies.

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Effect of aerobic exercise on innate immune responses and inflammatory mediators in the spinal cord of diabetic rats

Comparative Exercise Physiology ◽

10.3920/cep190050 ◽

2020 ◽

Vol 16 (4) ◽

pp. 293-301

Author(s):

A. Kaki ◽

M. Nikbakht ◽

A.H. Habibi ◽

H.F. Moghadam

Keyword(s):

Spinal Cord ◽

Neuropathic Pain ◽

Immune Responses ◽

Diabetic Neuropathy ◽

Aerobic Exercise ◽

Inflammatory Mediators ◽

Innate Immune ◽

Moderate Intensity ◽

Innate Immune Responses ◽

Tnf Α

Neuronal inflammation is one of the pathophysiological causes of diabetes neuropathic pain. The purpose of this research was to determine the effect of aerobic exercise on innate immune responses and inflammatory mediators in the spinal dorsal horn in rats with diabetic neuropathic pain. 40 eight-week-old male Wistar rats (weight range 220±10.2 g) were randomly divided into four groups of (1) sedentary diabetic neuropathy (SDN), (2) training diabetic neuropathy (TDN), (3) training control (TC), and (4) sedentary control (SC). Diabetes was induced by injection of streptozocin (50 mg/kg). Following confirmation of behavioural tests for diabetes neuropathy, the training groups performed 6 weeks of moderate-intensity aerobic exercise on the treadmill. The expression of Toll like receptor (TLR)4, TLR2, tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-10 genes in L4-L6 spinal cord sensory neurons was measured by Real Time PCR. Two-way ANOVA and Bonferroni’s post hoc tests were used for statistical analysis. After performing aerobic exercise protocol, the TDN compared to the SDN showed a significant decrease in the mean score of pain in the formalin test and a significant increase in the latency in Tail-Flick test was observed. The expression of TLR4, TLR2, TNF-α and IL-1β genes was significantly higher in the SDN than in the SC group (P<0.05). The expression of the above genes in the TDN was significantly lower than the SDN group (P<0.05). Also, the expression level of IL-10 gene was significantly higher in the TDN than the SDN group (P<0.05). Aerobic exercise improved sensitivity of nociceptors to pain-inducing agents in diabetic neuropathy due to inhibition of inflammatory receptors and increased levels of anti-inflammatory agents in the nervous system. Thus, aerobic exercise should be used as a non-pharmacological intervention for diabetic patients to reduce neuropathic pain.

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Abstract 553: Siglec-1 (CD169) on Monocytes/Macrophages: A New Receptor For Extracellular Self-RNA in Triggering Inflammatory Responses via the Sheddase TACE/ADAM17

Arteriosclerosis Thrombosis and Vascular Biology ◽

10.1161/atvb.35.suppl_1.553 ◽

2015 ◽

Vol 35 (suppl_1) ◽

Author(s):

Hector A Cabrera-Fuentes ◽

Klaus T Preissner ◽

William A Boisvert

Keyword(s):

Inflammatory Cytokines ◽

Inflammatory Responses ◽

Transmembrane Protein ◽

Macrophage Polarization ◽

Extracellular Rna ◽

Tnf Α ◽

M1 Phenotype ◽

Phenotype Markers ◽

Anti Inflammatory

As an important component of atherosclerosis, monocytes/macrophages respond to external stimuli with rapid changes in their expression of many inflammation-related genes to undergo polarization towards the M1 (pro-inflammatory) or M2 (anti-inflammatory) phenotype. Although sialoadhesin (Sn), also known as SIGLEC-1 or CD169, is a transmembrane protein receptor expressed on monocytes and macrophages whether it has a role in macrophage polarization and ultimately, macrophage-driven atherogenesis, has not been investigated. We have previously shown that, independently of Toll-like receptor signaling, extracellular RNA (eRNA) could exert pro-thrombotic and pro-inflammatory properties in the cardiovascular system by inducing cytokine mobilization. In the current study, recombinant mouse macrophage CSF[[Unable to Display Character: –]]driven bone marrow-derived macrophage (BMDM) differentiation was found to be skewed towards the M1 phenotype by exposure of cells to eRNA. This resulted in up-regulation of inflammatory markers, whereas anti-inflammatory genes were significantly down-regulated by eRNA. Interestingly, eRNA was released from BMDM under hypoxia and induced TNF-α liberation by activating TNF-α converting enzyme (TACE) to provoke inflammation. Conversely, TNF-α promoted eRNA release, especially under hypoxia, feeding a vicious cycle of cell damage. Administration of RNase1 or TAPI (a TACE-inhibitor) prevented the production of inflammatory mediators. Murine BMDM isolated from mice deficient in sialoadhesin had the opposite reaction to eRNA treatment with a prominent down-regulation of pro-inflammatory cytokines/M1 phenotype markers, while anti-inflammatory cytokines/M2 phenotype markers were significantly raised. In keeping with the proposed role of eRNA as a pro-inflammatory “alarm signal”, these data further shed light on the role of eRNA in macrophage function in the context of chronic inflammatory diseases such as atherosclerosis. The identification of sialoadhesin as putative eRNA recognition site on macrophages may allow further investigation of the underlying mechanisms of eRNA-macrophage interaction and related signal transduction pathways. Siglec-1 thereby may provides a new target to treat eRNA-mediated vascular diseases.

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Inhibiting HMGB1-RAGE axis prevents pro-inflammatory macrophages/microglia polarization and affords neuroprotection after spinal cord injury

Journal of Neuroinflammation ◽

10.1186/s12974-020-01973-4 ◽

2020 ◽

Vol 17 (1) ◽

Author(s):

Hong Fan ◽

Hai-Bin Tang ◽

Zhe Chen ◽

Hu-Qing Wang ◽

Lei Zhang ◽

...

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Western Blot ◽

Functional Recovery ◽

Sterile Inflammation ◽

Qrt Pcr ◽

Cord Injury ◽

Microglia Polarization ◽

Anti Inflammatory ◽

Inflammatory Macrophages

Abstract Background Spinal cord injury (SCI) favors a persistent pro-inflammatory macrophages/microglia-mediated response with only a transient appearance of anti-inflammatory phenotype of immune cells. However, the mechanisms controlling this special sterile inflammation after SCI are still not fully elucidated. It is known that damage-associated molecular patterns (DAMPs) released from necrotic cells after injury can trigger severe inflammation. High mobility group box 1(HMGB1), a ubiquitously expressed DNA binding protein, is an identified DAMP, and our previous study demonstrated that reactive astrocytes could undergo necroptosis and release HMGB1 after SCI in mice. The present study aimed to explore the effects and the possible mechanism of HMGB1on macrophages/microglia polarization, as well as the neuroprotective effects by HMGB1 inhibition after SCI. Methods In this study, the expression and the concentration of HMGB1 was determined by qRT-PCR, ELISA, and immunohistochemistry. Glycyrrhizin was applied to inhibit HMGB1, while FPS-ZM1 to suppress receptor for advanced glycation end products (RAGE). The polarization of macrophages/microglia in vitro and in vivo was detected by qRT-PCR, immunostaining, and western blot. The lesion area was detected by GFAP staining, while neuronal survival was examined by Nissl staining. Luxol fast blue (LFB) staining, DAB staining, and western blot were adopted to evaluate the myelin loss. Basso-Beattie-Bresnahan (BBB) scoring and rump-height Index (RHI) assay was applied to evaluate locomotor functional recovery. Results Our data showed that HMGB1 can be elevated and released from necroptotic astrocytes and HMGB1 could induce pro-inflammatory microglia through the RAGE-nuclear factor-kappa B (NF-κB) pathway. We further demonstrated that inhibiting HMGB1 or RAGE effectively decreased the numbers of detrimental pro-inflammatory macrophages/microglia while increased anti-inflammatory cells after SCI. Furthermore, our data showed that inhibiting HMGB1 or RAGE significantly decreased neuronal loss and demyelination, and improved functional recovery after SCI. Conclusions The data implicated that HMGB1-RAGE axis contributed to the dominant pro-inflammatory macrophages/microglia-mediated pro-inflammatory response, and inhibiting this pathway afforded neuroprotection for SCI. Thus, therapies designed to modulate immune microenvironment based on this cascade might be a prospective treatment for SCI.

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