HMGB1/Advanced Glycation End Products (RAGE) does not aggravate inflammation but promote endogenous neural stem cells differentiation in spinal cord injury

NT-3 Combined with TGF-β Signaling Pathway Enhance the Repair of Spinal Cord Injury by Inhibiting Glial Scar Formation and Promoting Axonal Regeneration

This study investigated the mechanism of neurotrophin-3 (NT-3) in promoting spinal cord injury repair through the transforming growth factor-beta (TGF-β) signaling pathway. A mouse model of spinal cord injury was established. Forty C57BL/6J mice were randomized into model, NT-3, NT-3 + TGF-β1 and NT-3 + LY364947 groups. The Basso-Beattie-Bresnahan (BBB) scores of the NT-3 and NT-3 + LY364947 groups were significantly higher than the model group. The BBB score of the NT-3 + TGF-β1 group was significantly lower than NT-3 group. Hematoxylin-eosin staining and transmission electron microscopy showed reduction in myelin sheath injury, more myelinated nerve fibers in the middle section of the catheter, and relatively higher density and more neatly arranged regenerated axons in the NT-3 and NT-3 + LY364947 groups compared with the model and NT-3 + TGF-β1 groups. Immunofluorescence, TUNEL and Western blot analysis showed that compared with model group, the NEUN expression increased, and the apoptosis and Col IV, LN, CSPG, tenascin-C, Sema 3 A, EphB2 and Smad2/3 protein expression decreased significantly in the NT-3 and NT-3 + LY364947 groups; the condition was reversed in the NT-3 + TGF-β1 group compared with the NT-3 group. NT-3 combined with TGF-β signaling pathway promotes astrocyte differentiation, reduces axon regeneration inhibitory molecules, apoptosis and glial scar formation, promotes axon regeneration, and improves spinal cord injury.

Receptor for advanced glycation end-products: Biological significance and imaging applications

The receptor for advanced glycation end-products (RAGE or AGER) is a transmembrane, immunoglobulin-like receptor that, due to its multiple isoform structures, binds to a diverse range of endo- and exogenous ligands. RAGE activation caused by the ligand binding initiates a cascade of complex pathways associated with producing free radicals, such as reactive nitric oxide and oxygen species, cell proliferation, and immunoinflammatory processes. The involvement of RAGE in the pathogenesis of disorders such as diabetes, inflammation, tumor progression, and endothelial dysfunction is dictated by the accumulation of advanced glycation end-products (AGEs) at pathologic states leading to sustained RAGE upregulation. The involvement of RAGE and its ligands in numerous pathologies and diseases makes RAGE an interesting target for therapy focused on the modulation of both RAGE expression or activation and the production or exogenous administration of AGEs. Despite the known role that the RAGE/AGE axis plays in multiple disease states, there remains an urgent need to develop noninvasive, molecular imaging approaches that can accurately quantify RAGE levels in vivo that will aid in the validation of RAGE and its ligands as biomarkers and therapeutic targets. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Diagnostic Tools > Biosensing.

High-Mobility Group Box 1 in Spinal Cord Injury and Its Potential Role in Brain Functional Remodeling After Spinal Cord Injury

High-mobility group box 1 (HMGB1) is a nonhistone nuclear protein, the functions of which depend on its subcellular location. It is actively or passively secreted into the blood and/or cerebrospinal fluid (CSF) and can be used as a prognostic indicator of disease. HMGB1 released into the bloodstream can cause pathological reactions in distant organs, and entry into the CSF can destroy the blood-brain barrier and aggravate brain injuries. HMGB1 expression has been reported to be increased in the tissues of spinal cord injury (SCI) patients and involved in the regulation of neuroinflammation, neuronal apoptosis, and ferroptosis. SCI can lead to brain changes, resulting in neuropathic pain, depression, and cognitive dysfunction, but the specific mechanism is unknown. It remains unclear whether HMGB1 plays an important role in brain functional remodeling after SCI. Damaged cells at the site of SCI passively release HMGB1, which travels to the brain via the blood, CSF, and/or axonal transport, destroys the blood-brain barrier, and causes pathological changes in the brain. This may explain the remodeling of brain function that occurs after SCI. In this minireview, we introduce the structure and function of HMGB1 and its mechanism of action in SCI. Clarifying the functions of HMGB1 may provide insight into the links between SCI and various brain regions.

Review: The role of HMGB1 in spinal cord injury

High mobility group box 1 (HMGB1) has dual functions as a nonhistone nucleoprotein and an extracellular inflammatory cytokine. In the resting state, HMGB1 is mainly located in the nucleus and regulates key nuclear activities. After spinal cord injury, HMGB1 is rapidly expressed by neurons, microglia and ependymal cells, and it is either actively or passively released into the extracellular matrix and blood circulation; furthermore, it also participates in the pathophysiological process of spinal cord injury. HMGB1 can regulate the activation of M1 microglia, exacerbate the inflammatory response, and regulate the expression of inflammatory factors through Rage and TLR2/4, resulting in neuronal death. However, some studies have shown that HMGB1 is beneficial for the survival, regeneration and differentiation of neurons and that it promotes the recovery of motor function. This article reviews the specific timing of secretion and translocation, the release mechanism and the role of HMGB1 in spinal cord injury. Furthermore, the role and mechanism of HMGB1 in spinal cord injury and, the challenges that still need to be addressed are identified, and this work will provide a basis for future studies.

Role of RAGE in the Pathogenesis of Neurological Disorders

This review reflects upon our own as well as other investigators' studies on the role of receptor for advanced glycation end-products (RAGE), bringing up the latest information on RAGE in physiology and pathology of the nervous system. Over the last ten years, major progress has been made in uncovering many of RAGE-ligand interactions and signaling pathways in nervous tissue; however, the translation of these discoveries into clinical practice has not come to fruition yet. This is likely, in part to be the result of our incomplete understanding of this crucial signaling pathway. Clinical trials examining the therapeutic efficacy of blocking RAGE-external ligand interactions by genetically engineered soluble RAGE or an endogenous RAGE antagonist, has not stood up to its promise; however, other trials with different blocking agents are being considered with hope for therapeutic success in diseases of the nervous system.

Systematic analysis of critical genes and pathways identified a signature of neuropathic pain after spinal cord injury

Spinal cord injury (SCI) damages sensory systems, producing chronic neuropathic pain that is resistant to medical treatment. The specific mechanisms underlying SCI-induced neuropathic pain (SCI-NP) remain unclear, and protein biomarkers have not yet been integrated into diagnostic screening. To better understand the host molecular pathways involved in SCI-NP, we used the bioinformatics method, the PubMed database, and bioinformatics methods to identify target genes and their associated pathways. We reviewed 2504 articles on the regulation of SCI-NP and used the text mining of PubMed database abstracts to determine associations among 12 pathways and networks. Based on this method, we identified two central genes in SCI-NP: interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Adult male Sprague-Dawley rats were used to build the SCI-NP models. The threshold for paw withdrawal was significantly reduced in the SCI group and TLR4 was activated in microglia after SCI. ELISA analysis of TNF-α and IL-6 levels was significantly higher in the SCI group than in the sham group. Western blot showed that expressions of the TLR4/MyD88/NF-κB inflammatory pathway protein increased dramatically in the SCI group. Using the TLR4 inhibitor TAK-242, the pain threshold and expressions of inflammatory factors and proteins of the proteins of the inflammatory signal pathway were reversed, TLR4 in microglia was suppressed, suggesting that SCI-NP was related to neuroinflammation mediated by the TLR4 signaling pathway. In conclusion, we found TNF-α and IL-6 were the neuroinflammation-related genes involved in SCI-NP that can be alleviated by inhibiting the inflammatory pathway upstream of the TLR4/MyD88/NF-κB inflammatory pathway.

HMGB1 Promotes the Release of Sonic Hedgehog From Astrocytes

High mobility group box 1 protein (HMGB1) is known to be a trigger of inflammation in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS). However, it may play a different role in some way. Here we investigated the effect of HMGB1 on promoting sonic hedgehog (shh) release from astrocytes as well as the possible signal pathway involved in it. Firstly, shh increased in astrocytes after administration of recombinant HMGB1 or decreased after HMGB1 was blocked when stimulated by homogenate of the onset stage of EAE. Moreover, the expression of HMGB1 receptors, toll-like receptor (TLR) 2 and receptor for advanced glycation end products (RAGE) increased after HMGB1 administration in primary astrocytes. However, the enhancing effect of HMGB1 on shh release from astrocytes was suppressed only after RAGE was knocked out or blocked. Mechanistically, HMGB1 functioned by activating RAGE-mediated JNK, p38, stat3 phosphorylation. Moreover, HMGB1 could induce shh release in EAE. Additionally, intracerebroventricular injection of recombinant shh protein on the onset stage of EAE alleviated the progress of disease and decreased demylination, compared to the mice with normal saline treatment. Overall, HMGB1 promoted the release of shh from astrocytes through signal pathway JNK, p38 and stat3 mediated by receptor RAGE, which may provide new insights of HMGB1 function in EAE.

Transplantation of neural stem cells preconditioned with high‑mobility group box 1 facilitates functional recovery after spinal cord injury in rats

Spinal cord injury (SCI) is a devastating disorder that often results in temporary and/or permanent functional impairment below the injured level. To date, few satisfactory therapeutic strategies are available to treat SCI. Hence, exploring novel strategies for SCI is an essential public health concern. Cell transplantation therapy, which is associated with neuroprotection, immunomodulation, axon regeneration, neuronal relay formation and myelin regeneration, provides a promising therapeutic strategy for SCI. The neuronal stem cell (NSC) preconditioning method is an emerging approach, which facilitates NSC survival and neuronal differentiation after implantation. The aim of the present study was to develop a feasible candidate for cell-based therapy following SCI in rats and to investigate the role of high mobility group box-1 (HMGB1) in NSC activation. The results of the present study showed that transplantation of NSCs, preconditioned with 1 ng/ml HMGB1, facilitated functional improvement of injured spinal cords, as indicated by Basso, Beattie and Bresnahan mean scores, mechanical hypersensitivity and cold stimulation. Meanwhile, the histological examination of hematoxylin and eosin staining indicated that engraftment of HMGB1-preconditioned NSCs resulted in decreased atrophy of the injured spinal cord. Meanwhile, the transplantation of HMGB1-preconditioned NSCs resulted in an increased number of functional Nissl bodies in neurons, as detected by Nissl staining, and an increase in the number of βIII-tubulin⁺ cells in the epicenter of injured spinal cords in rats with SCI. In addition, the results also demonstrated that 1 ng/ml HMGB1 promoted the differentiation of NSCs into neurons, and that the ERK signaling pathway played an important role in this process. In conclusion, the present data indicated that the preconditioning strategy with 1 ng/ml HMGB1 may present a feasible candidate for cell-based therapy following SCI in rats, which may enlarge the scope of HMGB1 in NSC activation.

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

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.

Spinal cord injury can be relieved by the polysaccharides of Tricholoma matsutake by promoting axon regeneration and reducing neuroinflammation

With an increase in the number of spinal cord injuries (SCIs) in China, severe dysfunction of the limb below the injured segment is prominent. Among the studies centered on the factors inducing SCIs, inflammatory response has a dramatic input on the pathogenesis of SCIs.

The Receptor for Advanced Glycation End Products (RAGE) and DIAPH1: Implications for vascular and neuroinflammatory dysfunction in disorders of the central nervous system

The Receptor for Advanced Glycation End Products (RAGE) is expressed by multiple cell types in the brain and spinal cord that are linked to the pathogenesis of neurovascular and neurodegenerative disorders, including neurons, glia (microglia and astrocytes) and vascular cells (endothelial cells, smooth muscle cells and pericytes). Mounting structural and functional evidence implicates the interaction of the RAGE cytoplasmic domain with the formin, Diaphanous1 (DIAPH1), as the key cytoplasmic hub for RAGE ligand-mediated activation of cellular signaling. In aging and diabetes, the ligands of the receptor abound, both in the central nervous system (CNS) and in the periphery. Such accumulation of RAGE ligands triggers multiple downstream events, including upregulation of RAGE itself. Once set in motion, cell intrinsic and cell-cell communication mechanisms, at least in part via RAGE, trigger dysfunction in the CNS. A key outcome of endothelial dysfunction is reduction in cerebral blood flow and increased permeability of the blood brain barrier, conditions that facilitate entry of activated leukocytes into the CNS, thereby amplifying primary nodes of CNS cellular stress. This contribution details a review of the ligands of RAGE, the mechanisms and consequences of RAGE signal transduction, and cites multiple examples of published work in which RAGE contributes to the pathogenesis of neurovascular perturbation. Insights into potential therapeutic modalities targeting the RAGE signal transduction axis for disorders of CNS vascular dysfunction and neurodegeneration are also discussed.

HMGB1-modified mesenchymal stem cells attenuate radiation-induced vascular injury possibly via their high motility and facilitation of endothelial differentiation

Background

Vascular injury is one of the most common detrimental effects of cancer radiotherapy on healthy tissues. Since the efficacy of current preventive and therapeutic strategies remains limited, the exploration of new approaches to treat radiation-induced vascular injury (RIV) is on high demands. The use of mesenchymal stem cells (MSCs) to treat RIV holds great promise thanks to their well-documented function of mediating tissue regeneration after injury. Recently, we genetically modified MSCs with high mobility group box 1 (HMGB1) and demonstrated the high efficacy of these cells in treating graft atherosclerosis. The current study was to investigate the protective effect of HMGB1-modified MSCs (MSC-H) on RIV by using a rat model.

Methods

Female F344 rats received an intravenous injection of male F344 MSC-H cells or vehicle control at four doses of 2 × 10⁶ cells with a 15-day interval starting from 30 days after irradiation to the abdominal aorta. The aortas were procured for histological and biomedical analysis at 90 days after irradiation. Cell migration to irradiated aortas was traced by green fluorescent protein and sex determination region on the Y chromosome. In vitro cell migration and endothelial differentiation of MSC-H cells were analyzed by stromal-derived factor 1-induced transwell assay and RNA microarray, respectively. The contribution of extracellular HMGB1 to the bioactivity of MSC-H cells was investigated by inhibition experiments with HMGB1 antibody.

Result

MSC-H cell infusion alleviated neointimal formation, vascular inflammation, and fibrosis in irradiated aortas, which was associated with local migration and endothelial differentiation of MSC-H cells. The MSC-H cells showed high motility and potential of endothelial differentiation in vitro. Microarray analysis suggested multiple pathways like MAPK and p53 signaling were activated during endothelial differentiation. MSC-H cells highly expressed CXC chemokine receptor 4 and migrated progressively after stromal-derived factor 1 stimulation, which was blocked by the antagonist of CXC chemokine receptor 4. Finally, the migration and endothelial differentiation of MSC-H cells were inhibited by HMGB1 antibody.

Conclusion

MSC-H cell infusion significantly attenuated RIV, which was associated with their high motility and endothelial differentiation potential. Multiple pathways that possibly contributed to the efficacy of MSC-H cells were suggested and deserved further investigation.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1197-x) contains supplementary material, which is available to authorized users.

Blockade of receptor for advanced glycation end products promotes oligodendrocyte autophagy in spinal cord injury

Receptor for advanced glycation end product (RAGE) is involved in neuronal inflammation, cell cycle and differentiation. However, the role of RAGE in autophagy in the process of spinal cord injury (SCI) is yet unknown. The present study investigated the effect of RAGE blockade on autophagy in SCI. A rat Allen SCI model was established and the animals were micro-injected with rabbit RAGE neutralizing antibody or rabbit polyclonal Ig G immediately after the injury. The oligodendrocytes(OLs) marker, 2', 3'-cyclic nucleotide 3'-phosphodiesterase(CNPase) and autophagy-related marker microtubule associated protein light chain 3B(LC3B) were evaluated by Western blot. Furthermore, myelin basic protein (MBP) and LC3B double staining were observed in the SCI via immunofluorescence. The results showed that RAGE blockade reduced the expression of CNPase, promoted LC3B-II/I and p62 expression after SCI. In addition, the MBP/LC3B double positive oligodendrocytes-expressing LC3B was up-regulated by RAGE blockade. Moreover, RAGE blockade attenuated the neuronal survival at ventral horn after SCI. The present study revealed the role of RAGE in maintaining oligodendrocyte autophagy to promote neuronal regeneration post-SCI.

The effects of a maternal advanced glycation end product-rich diet on somatic features, reflex ontogeny and metabolic parameters of offspring mice

Maternal exposure to a Western type diet during pregnancy might predispose the offspring to manifestation of metabolic and behavioral disturbances in later life. The Western type diet contains large amounts of advanced glycation end products (AGEs). In humans and experimental rodents, the intake of an AGE-rich diet (AGE-RD) negatively affected glucose homeostasis, and initiated the production of reactive oxygen species. Rats consuming the AGE-RD presented changes in behavior. It remains unclear whether maternal intake of the AGE-RD might affect developmental plasticity in offspring. We examined early somatic (weight, incisor eruption, ear unfolding, and eye opening) and neuromotor development, oxidative status, insulin sensitivity (HOMA index) and locomotor activity assessed in PhenoTyper cages in the offspring of mice fed during pregnancy with either the AGE-RD (25% bread crusts/75% control chow) or control chow. Until weaning, the somatic development of offspring did not differ between the two dietary groups. The AGE-RD offspring manifested physiological reflexes (auditory startle, eye lid, ear twitch and righting reflexes) earlier. As young adults, the male offspring of the AGE-RD dams were heavier and less insulin sensitive compared with their control counterparts. The AGE-RD offspring showed higher locomotor activity during the active phase. Our data indicate that the maternal AGE-RD during pregnancy might accelerate the maturation of reflexes in offspring, predispose the male progeny to weight gain and affect their glucose homeostasis. These effects manifest without the direct consumption of the AGE-RD by offspring. Further work is needed to determine the mechanisms by which the maternal AGE-RD affects neurobehavioral pathways in offspring, as well as sex differences in adverse metabolic responses.

Receptor for Advanced Glycation End-Products (RAGE) Blockade Do Damage to Neuronal Survival via Disrupting Wnt/β-Catenin Signaling in Spinal Cord Injury

Wnt signaling are recognized key factors in neuronal development, cell proliferation and axonal guidance. However, RAGE effect on wnt signaling after spinal cord injury (SCI) are poorly understood. Our study aims to explore RAGE blockade effect on wnt signaling after SCI. We constructed Allen SCI model and micro-injected with RAGE neutralizing antibody or IgG after injury. We determined β-catenin, wnt3a and its receptor frizzled-5 via Western blot. We determined β-catenin/NeuN expression at 2 weeks after SCI via immunofluorescence (IF). We found that β-catenin, wnt3a and wnt receptor frizzled5 expression were activated after SCI at 3 days after injury. However, RAGE blockade inhibit β-catenin, wnt3a and frizzled5 expression. We found that β-catenin accumulation in NeuN cells were activated after SCI via IF, however, RAGE blockade reduced β-catenin and NeuN positive cells. RAGE blockade attenuated number of survived neurons and decreased area of spared white matter around the epicenter. RAGE signaling may involved in disrupting wnt signaling to aids neuronal recovery after SCI.

High-mobility group box 1 facilitates migration of neural stem cells via receptor for advanced glycation end products signaling pathway

High-mobility group box 1 (HMGB1) facilitates neural stem cells (NSCs) proliferation and differentiation into neuronal linage. However, the effect of HMGB1 on NSCs migration is still elusive. The present study is to investigate the corelation between HMGB1 and NSCs migration and the potential mechanism. The results indicated that 1 ng/ml HMGB1 promoted NSCs proliferation using CCK8 assays. Moreover, data showed that 1 ng/ml HMGB1 facilitated NSCs migration via filopodia formation using phase-contrast and transwell assays. Furthermore, 1 ng/ml HMGB1 upregulated the expression of RAGE, one of the HMGB1 receptor, using western blotting assays and immunofluorescence staining. In addition, 1 ng/ml HMGB1 increased the percentage of filopodia formation using phalloidin staining. Meanwhile, the enhanced migration effect could be abrogated by 50 nM FPS-ZM1, one of the RAGE antagonist, and RAGE-specific siRNA through immunofluorescence and phalloidin staining. Together, our data demonstrate that HMGB1/RAGE axis facilitates NSCs migration via promoting filopodia formation, which might serve as a candidate for central nervous system (CNS) injury treatment and/or a preconditioning method for NSCs implantation.