Cationic ribosomal proteins can inhibit pro-inflammatory action stimulated by LPS+HMGB1 and are hindered by advanced glycation end products.

We previously found that ribosomal protein L9 (RPL9) is a novel advanced glycation end product (AGE)-binding protein that can decrease pro-inflammatory TNF-α expression stimulated by lipopolysaccharide (LPS) plus high-mobility group box 1 (HMGB1), suggesting that RPL9 has a role in regulating LPS+HMGB1-stimulated inflammatory reactions. Among the various ribosomal proteins, it was found that RPS5 reproduced the regulatory activity of RPL9 on LPS+HMGB1-stimulated TNF-α expression in macrophage-like RAW264.7 cells. RPL9 and RPS5 share a common feature as cationic proteins. Polylysine, a cationic polypeptide, and a synthetic peptide of the cationic region from RPL9 also exhibited reducing activity on LPS+HMGB1-induced TNF-α expression. By pull-down assay, RPL9 and RPS5 were confirmed to interact with AGEs. When AGEs coexisted with LPS, HMGB1, plus RPL9 or RPS5, the reducing effect of TNF-α expression by these cationic ribosomal proteins was shown to be abrogated. The results suggest that cationic ribosomal proteins have a regulatory role in the pro-inflammatory response induced by LPS+HMGB1, and in the pathophysiological condition of accumulating AGEs, this regulatory effect is abolished, which exacerbates inflammation.

Perineural Treatment with High Mobility Group Box-1 Monoclonal Antibody Prevents Initiation of Pain-Like Behaviors in Female Mice with Trigeminal Neuropathy.

Post-traumatic trigeminal neuropathy (PTTN) is a type of chronic pain caused by damage to the trigeminal nerve. A previous study reported that pretreatment with anti-high mobility group box-1 (HMGB1) neutralizing antibodies (nAb) prevented the onset of PTTN following distal infraorbital nerve chronic constriction injury (dIoN-CCI) in male mice. Clinical evidence indicates a high incidence of PTTN in females. Although our previous study found that perineural HMGB1 is crucial in initiation of PTTN in male mice, it is currently unknown whether HMGB1 is also involved in the pathogenesis of PTTN in female mice. Therefore, in the current study, we examined the effect of anti-HMGB1 nAb on pain-like behavior in female mice following dIoN-CCI surgery. We found that dIoN-CCI surgery enhanced reactivity to mechanical and cold stimuli in female mice, which was suppressed by treatment with anti-HMGB1 nAb. Moreover, the increase in macrophages after dIoN-CCI was significantly attenuated by pretreatment with anti-HMGB1 nAb. Furthermore, anti-HMGB1 nAb treatment inhibited microglial activation in the trigeminal spinal tract nucleus. These data suggest that HMGB1 also plays a crucial role in the onset of PTTN after nerve injury in female mice. Thus, anti-HMGB1 nAb could be a novel therapeutic agent for inhibiting the onset of PTTN in female and male mice.

Anti-HMGB1 mAb Therapy Reduces Epidural Hematoma Injury.

Epidural and subdural hematomas are commonly associated with traumatic brain injury. While surgical removal is the primary intervention for these hematomas, it is also critical to prevent and reduce complications such as post-traumatic epilepsy, which may result from inflammatory responses in the injured brain areas. In the present study, we observed that high mobility group box-1 (HMGB1) decreased in the injured brain area beneath the epidural hematoma (EDH) in rats, concurrent with elevated plasma levels of HMGB1. Anti-HMGB1 monoclonal antibody therapy strongly inhibited both HMGB1 release and the subsequent increase in plasma levels. Moreover, this treatment suppressed the up-regulation of inflammatory cytokines and related molecules such as interleukin-1-beta (IL-1ß), tumor necrosis factor-alpha (TNF-α), and inducible nitric oxide synthase (iNOS) in the injured areas. Our in vitro experiments using SH-SY5Y demonstrated that hematoma components-thrombin, heme, and ferrous ion- prompted HMGB1 translocation from the nuclei to the cytoplasm, a process inhibited by the addition of the anti-HMGB1 mAb. These findings suggest that anti-HMGB1 mAb treatment not only inhibits HMGB1 translocation but also curtails inflammation in injured areas, thereby protecting the neural tissue. Thus, anti-HMGB1 mAb therapy could serve as a complementary therapy for an EDH before/after surgery.

Different modulation of STING/TBK1/IRF3 signaling by advanced glycation end products.

Advanced glycation end products (AGEs) are a heterogeneous group of compounds that are non-enzymatically produced by reactions between carbonyl compounds and proteins. Many types of AGEs are produced according to the type or concentration of the reacting carbonyl compound. We have previously demonstrated that a glycolaldehyde-derived AGE suppresses stimulator of interferon gene (STING)/TANK-binding kinase 1 (TBK1)/interferon regulatory transcription factor 3 (IRF3), which is a component of the innate immune system. In this report, we investigated the effects of AGEs prepared by several carbonyl compounds on STING/TBK1/IRF3 signaling. AGEs used in the present study were numbered based on the carbonyl compound type: AGE1, derived from glucose; AGE2, derived from glyceraldehyde; AGE3, derived from glycolaldehyde; AGE4, derived from methylglyoxal; and AGE5, derived from glyoxal. AGEs derived from aldehyde (AGE2 and AGE3) and dicarbonyl compounds (AGE4 and AGE5) suppressed cyclic GMP-AMP (cGAMP)-induced activation of STING/TBK1/IRF3 signaling, with different suppression efficiencies observed. Lysine modification by carbonyl compounds was related to the efficiency of the suppressive effect on STING/TBK1/IRF3 signaling. Among the AGEs used, only AGE1 enhanced cGAMP-induced activation of STING/TBK1/IRF3 signaling. Enhancing the modulation of STING/TBK1/IRF3 signaling by AGE1 was mediated by toll-like receptor 4. These results indicated that modulation of STING/TBK1/IRF3 signaling by prepared AGEs is dependent on the type and concentration of the carbonyl compound present. Modulating STING/TBK1/IRF3 signaling by AGEs may involve modification of lysine residues in proteins.

Histamine promotes angiogenesis through a histamine H1 receptor-PKC-VEGF-mediated pathway in human endothelial cells.

Histamine is a well-known inflammatory mediator, but how histamine induces angiogenesis remains poorly understood. In the present study, we demonstrated a dose-dependent dynamic tube formation in the human endothelial cell line EA.hy926 in the presence of histamine that was completely blocked by histamine H1 receptor (H1R) and protein kinase C (PKC) inhibitors. However, histamine H2, H3, and H4 receptor inhibitors did not inhibit tube formation, suggesting that H1R-PKC signaling is involved in histamine-induced tube formation. Moreover, we found an H1-specific induction of vascular endothelial growth factor (VEGF) expression. Inhibition of VEGF receptor 2 (VEGFR2) suppressed the histamine-induced tube formation, indicating that VEGF is downstream of histamine signaling. Additionally, we demonstrated that histamine stimulation induces the expression of critical regulators of angiogenesis such as matrix metalloproteinase (MMP)-9 and MMP-14 metalloproteases, as histamine-induced tube formation is blocked by MMP inhibitors. In summary, our study indicates that histamine can activate the H1R in human endothelial cells and thereby promote tube formation through the PKC, MMP, and VEGF signaling pathways.

Histidine-Rich Glycoprotein Stimulates Human Neutrophil Phagocytosis and Prolongs Survival through CLEC1A.

Histidine-rich glycoprotein (HRG) is a multifunctional plasma protein and maintains the homeostasis of blood cells and vascular endothelial cells. In the current study, we demonstrate that HRG and recombinant HRG concentration dependently induced the phagocytic activity of isolated human neutrophils against fluorescence-labeled Escherichia coli and Staphylococcus aureus through the stimulation of CLEC1A receptors, maintaining their spherical round shape. The phagocytosis-inducing effects of HRG were inhibited by a specific anti-HRG Ab and enhanced by opsonization of bacteria with diluted serum. HRG and C5a prolonged the survival time of isolated human neutrophils, in association with a reduction in the spontaneous production of extracellular ROS. In contrast, HRG maintained the responsiveness of neutrophils to TNF-α, zymosan, and E. coli with regard to reactive oxygen species production. The blocking Ab for CLEC1A and recombinant CLEC1A-Fc fusion protein significantly inhibited the HRG-induced neutrophil rounding, phagocytic activity, and prolongation of survival time, suggesting the involvement of the CLEC1A receptor in the action of HRG on human neutrophils. These results as a whole indicated that HRG facilitated the clearance of E. coli and S. aureus by maintaining the neutrophil morphology and phagocytosis, contributing to the antiseptic effects of HRG in vivo.

Glycolaldehyde-derived advanced glycation end products promote macrophage proliferation via the JAK-STAT signaling pathway.

BACKGROUND: Advanced glycation end products (AGEs) are heterogeneous proinflammatory molecules produced by a non-enzymatic glycation reaction between reducing sugars (and their metabolites) and biomolecules with amino groups, such as proteins. Although increases in and the accumulation of AGEs have been implicated in the onset and exacerbation of lifestyle- or age-related diseases, including diabetes, their physiological functions have not yet been elucidated in detail. METHODS AND RESULTS: The present study investigated the cellular responses of the macrophage cell line RAW264.7 stimulated by glycolaldehyde-derived AGEs (Glycol-AGEs) known as representative toxic AGEs. The results obtained showed that Glycol-AGEs significantly promoted the proliferation of RAW264.7 cells at a low concentration range (1-10 µg/mL) in a concentration-dependent manner. On the other hand, neither TNF-α production nor cytotoxicity were induced by the same concentrations of Glycol-AGEs. The increases observed in cell proliferation by low concentrations of Glycol-AGEs were also detected in receptor triple knockout (RAGE-TLR4-TLR2 KO) cells as well as in wild-type cells. Increases in cell proliferation were not affected by various kinase inhibitors, including MAP kinase inhibitors, but were significantly suppressed by JAK2 and STAT5 inhibitors. In addition, the expression of some cell cycle-related genes was up-regulated by the stimulation with Glycol-AGEs. CONCLUSIONS: These results suggest a novel physiological role for AGEs in the promotion of cell proliferation via the JAK-STAT pathway.

Inflachromene attenuates seizure severity in mouse epilepsy models via inhibiting HMGB1 translocation.

Epilepsy is not well controlled by current anti-seizure drugs (ASDs). High mobility group box 1 (HMGB1) is a DNA-binding protein in the nucleus regulating transcriptional activity and maintaining chromatin structure and DNA repair. In epileptic brains, HMGB1 is released by activated glia and neurons, interacting with various receptors like Toll-like receptor 4 (TLR4) and downstream glutamatergic NMDA receptor, thus enhancing neural excitability. But there is a lack of small-molecule drugs targeting the HMGB1-related pathways. In this study we evaluated the therapeutic potential of inflachromene (ICM), an HMGB-targeting small-molecule inhibitor, in mouse epilepsy models. Pentylenetetrazol-, kainic acid- and kindling-induced epilepsy models were established in mice. The mice were pre-treated with ICM (3, 10 mg/kg, i.p.). We showed that ICM pretreatment significantly reduced the severity of epileptic seizures in all the three epilepsy models. ICM (10 mg/kg) exerted the most apparent anti-seizure effect in kainic acid-induced epileptic status (SE) model. By immunohistochemical analysis of brain sections from kainic acid-induced SE mice, we found that kainic acid greatly enhanced HMGB1 translocation in the hippocampus, which was attenuated by ICM pretreatment in subregion- and cell type-dependent manners. Notably, in CA1 region, the seizure focus, ICM pretreatment mainly inhibited HMGB1 translocation in microglia. Furthermore, the anti-seizure effect of ICM was related to HMGB1 targeting, as pre-injection of anti-HMGB1 monoclonal antibody (5 mg/kg, i.p.) blocked the seizure-suppressing effect of ICM in kainic acid-induced SE model. In addition, ICM pretreatment significantly alleviated pyramidal neuronal loss and granule cell dispersion in kainic acid-induced SE model. These results demonstrate that ICM is an HMGB-targeting small molecule with anti-seizure potential, which may help develop a potential drug for treating epilepsy.

Decreased levels of histidine-rich glycoprotein and increased levels of high-mobility group box 1 are risk factors for refractory Kawasaki disease.

OBJECTIVES: Histidine-rich glycoprotein (HRG) and high-mobility group box 1 (HMGB1) regulate the activation of neutrophils and vascular endothelium. The aim of this study was to quantify HRG and HMGB1 levels in patients with Kawasaki disease (KD) and evaluate their use in the clinical management of KD. METHODS: This study was prospectively performed. Patients were divided into two groups and analysed depending on whether KD symptoms improved by Day 10 of illness. HRG, HMGB1, and other laboratory variables were measured before the first treatment in all cases and, in most cases, afterwards for assessing trends. RESULTS: In this prospective study, we enrolled 60 patients with KD and 48 healthy controls. The HRG level in the KD group was significantly lower than that in the healthy control group; HMGB1 levels showed no obvious differences. In the KD group, HRG levels were negatively correlated with white blood cell and neutrophil counts. In the poor responders and responders groups, a tendency for a decrease in HRG and HMGB1 levels, respectively, was observed from pretreatment to post-treatment. CONCLUSIONS: HRG and HMGB1 are related to the pathogenesis of KD; low HRG and high HMGB1 levels cause resistance against KD treatment.

Toll-like receptor 4 promotes bladder cancer progression upon S100A8/A9 binding, which requires TIRAP-mediated TPL2 activation.

Bladder cancer is an often widely disseminated and deadly cancer. To block the malignant outgrowth of bladder cancer, we must elucidate the molecular-level characteristics of not only bladder cancer cells but also their surrounding milieu. As part of this effort, we have long been studying extracellular S100A8/A9, which is elevated by the inflammation associated with certain cancers. Extracellularly enriched S100A8/A9 can hasten a shift to metastatic transition in multiple types of cancer cells. Intriguingly, high-level S100A8/A9 has been detected in the urine of bladder-cancer patients, and the level increases with the stage of malignancy. Nonetheless, S100A8/A9 has been investigated mainly as a potential biomarker of bladder cancers, and there have been no investigations of its role in bladder-cancer growth and metastasis. We herein report that extracellular S100A8/A9 induces upregulation of growth, migration and invasion in bladder cancer cells through its binding with cell-surface Toll-like receptor 4 (TLR4). Our molecular analysis revealed the TLR4 downstream signal that accelerates such cancer cell events. Tumor progression locus 2 (TPL2) was a key factor facilitating the aggressiveness of cancer cells. Upon binding of S100A8/A9 with TLR4, TPL2 activation was enhanced by an action with a TLR4 adaptor molecule, TIR domain-containing adaptor protein (TIRAP), which in turn led to activation of the mitogen-activated protein kinase (MAPK) cascade of TPL2. Finally, we showed that sustained inhibition of TLR4 in cancer cells effectively dampened cancer survival in vivo. Collectively, our results indicate that the S100A8/A9-TLR4-TPL2 axis influences the growth, survival, and invasive motility of bladder cancer cells.

High-mobility group box-1 and inter-alpha inhibitor proteins: In vitro binding and co-localization in cerebral cortex after hypoxic-ischemic injury.

The high-mobility group box-1 (HMGB1) protein is a transcription-regulating protein located in the nucleus. However, it serves as a damage-associated molecular pattern protein that activates immune cells and stimulates inflammatory cytokines to accentuate neuroinflammation after release from damaged cells. In contrast, Inter-alpha Inhibitor Proteins (IAIPs) are proteins with immunomodulatory effects including inhibition of pro-inflammatory cytokines. We have demonstrated that IAIPs exhibit neuroprotective properties in neonatal rats exposed to hypoxic-ischemic (HI) brain injury. In addition, previous studies have suggested that the light chain of IAIPs, bikunin, may exert its anti-inflammatory effects by inhibiting HMGB1 in a variety of different injury models in adult subjects. The objectives of the current study were to confirm whether HMGB1 is a target of IAIPs by investigating the potential binding characteristics of HMGB1 and IAIPs in vitro, and co-localization in vivo in cerebral cortices after exposure to HI injury. Solid-phase binding assays and surface plasmon resonance (SPR) were used to determine the physical binding characteristics between IAIPs and HMGB1. Cellular localizations of IAIPs-HMGB1 in neonatal rat cortex were visualized by double labeling with anti-IAIPs and anti-HMGB1 antibodies. Solid-phase binding and SPR demonstrated specific binding between IAIPs and HMGB1 in vitro. Cortical cytoplasmic and nuclear co-localization of IAIPs and HMGB1 were detected by immunofluorescent staining in control and rats immediately and 3 hours after HI. In conclusion, HMGB1 and IAIPs exhibit direct binding in vitro and co-localization in vivo in neonatal rats exposed to HI brain injury suggesting HMGB1 could be a target of IAIPs.

Role of neuron-derived ATP in paclitaxel-induced HMGB1 release from macrophages and peripheral neuropathy.

We examined the role of ATP and high mobility group box 1 (HMGB1) in paclitaxel-induced peripheral neuropathy (PIPN). PIPN in mice was prevented by HMGB1 neutralization, macrophage depletion, and P2X7 or P2X4 blockade. Paclitaxel and ATP synergistically released HMGB1 from macrophage-like RAW264.7 cells, but not neuron-like NG108-15 cells. The paclitaxel-induced HMGB1 release from RAW264.7 cells was accelerated by co-culture with NG108-15 cells in a manner dependent on P2X7 or P2X4. Paclitaxel released ATP from NG108-15 cells, but not RAW264.7 cells. Thus, PIPN is considered to involve acceleration of HMGB1 release from macrophages through P2X7 and P2X4 activation by neuron-derived ATP.

Development of hepatic impairment aggravates chemotherapy-induced peripheral neuropathy following oxaliplatin treatment: Evidence from clinical and preclinical studies.

Oxaliplatin often induces peripheral neuropathy, a dose-limiting adverse reaction, and in rare cases leads to sinusoidal obstruction syndrome. We thus conducted a retrospective cohort study to examine the relationship between oxaliplatin-induced peripheral neuropathy (OIPN) and hepatic impairment, and then perform a fundamental study to analyze the underlying mechanisms. Analysis of medical records in cancer patients treated with oxaliplatin indicated that laboratory test parameters of hepatic impairment including AST, ALT and APRI (AST to platelet ratio index) moderately increased during oxaliplatin treatment, which was positively correlated with the severity of OIPN (grades 1-4), and associated with later incidence of survivors with OIPN grades ≥2. In mice, hepatic injury induced by CCl4 or ethanol accelerated OIPN in mice, an effect prevented by inactivation of high mobility group box 1 (HMGB1), known to participate in OIPN, by the neutralizing antibody or thrombomodulin alfa capable of promoting its thrombin-dependent degradation. Oxaliplatin also aggravated the hepatic injury in mice. CCl4 released HMGB1 from cultured hepatic parenchymal cells, and oxaliplatin at clinically achievable concentrations released HMGB1 from hepatic parenchymal and non-parenchymal cells. Our clinical and preclinical data suggest that the development of mild hepatic impairment during oxaliplatin treatment is associated with later aggravation of OIPN.

Identification of ribosomal protein L9 as a novel regulator of proinflammatory damage-associated molecular pattern molecules.

BACKGROUND: We previously reported that advanced glycation endproducts (AGEs) increase the proinflammatory activity of high mobility group box-1 (HMGB1), a representative damage-associated molecular pattern molecule (DAMP), through their direct interaction. This suggested that AGEs activate other DAMPs and led us to search for novel DAMPs capable of interacting with AGEs. METHODS AND RESULTS: The chromatographic analysis using AGE-immobilized gel revealed the ribosomal protein family to be a factor with binding activity to AGEs. Ribosomal protein L9 (RPL9), a member of the ribosomal protein family, was found in the centrifugal supernatant of ruptured cells and in the serum of lipopolysaccharide (LPS)-stimulated sepsis model mice, exhibiting similar characteristic properties to HMGB1. Although HMGB1 potentiated LPS-stimulated TNF-α expression in macrophage-like RAW264.7 cells, RPL9 hardly exhibited this activity. Of note, RPL9 significantly suppressed the potentiated mRNA expression and protein production of TNF-α by HMGB1 plus LPS stimulation, suggesting its regulatory roles in DAMP-induced proinflammatory activity. Based on the differential scanning fluorimetric analysis, the direct interaction between RPL9 and HMGB1 may play a role in the suppressive effects of RPL9. CONCLUSIONS: This study suggested that RPL9 is a novel type of DAMP with a regulatory role in the proinflammatory response and provided insight into the pathophysiology of inflammatory diseases.

Nordihydroguaiaretic acid inhibits glyoxalase I, and causes the accumulation of methylglyoxal followed by cell-growth inhibition.

BACKGROUND: Methylglyoxal (MGO) is a known toxic byproduct of glycolysis, with MGO-induced cytotoxicity believed to contribute to the pathogenesis of several diseases. Glyoxalase I (GLO1) is a key enzyme for eliminating MGO in mammalian cells, therefore, compounds affecting GLO1 activity are potential therapeutic agents for MGO-induced disorders. Previously, we found nordihydroguaiaretic acid (NDGA) as a potent GLO1 inhibitor. METHODS: The inhibitory characteristics of NDGA were determined spectrophotometrically with recombinant GLO1. NDGA-induced growth-inhibition and accumulation of MGO-derived advanced glycation end products (AGEs) were examined in EA.hy926 cells. RESULTS: NDGA showed significant inhibition of GLO1 enzymatic activity in a dose-dependent manner. Its Ki value was estimated to be 146-fold lower than that of myricetin, a known GLO1 inhibitor. The co-addition of MGO with NDGA to the cells resulted in significant growth inhibition, suggesting that MGO accumulation, sufficient to affect cell growth, was caused by NDGA inhibiting GLO1. These findings were supported by the observations that the addition of aminoguanidine, a typical MGO scavenger, significantly reversed cell-growth inhibition by co-addition of MGO with NDGA, and that an increase in intracellular MGO-derived AGEs was observed during incubation with the co-addition of MGO with NDGA. CONCLUSION: NDGA was found to be a novel and potent inhibitor of GLO1. The co-addition of NDGA with MGO to the cells resulted in increased intracellular MGO accumulation followed by enhanced cell-growth inhibition.

Involvement of multiple scavenger receptors in advanced glycation end product-induced vessel tube formation in endothelial cells.

Toxic advanced glycation end products (toxic AGEs) derived from glycolaldehyde (AGE3) have been implicated in the development of diabetic vascular complications such as retinopathy characterised by excessive angiogenesis. Different receptor types, such as receptor for AGEs (RAGE), Toll like receptor-4 and scavenger receptors, are expressed in endothelial cells and contribute to AGE-elicited alteration of cell function. In the present study, we examined the involvement of AGE-related receptors on AGE-induced angiogenesis in endothelial cells. The effects of pharmacological inhibitors or receptor neutralizing antibodies on AGE3-induced tube formation were investigated using the in vitro Matrigel tube formation assay in b.End5 cells (mouse endothelial cells). AGE3-induced signalling pathways and receptor expression changes were analysed by Western blot analysis and flow cytometry, respectively. Both FPS-ZM1, a RAGE inhibitor, and fucoidan, a ligand for scavenger receptors, suppressed AGE3-induced tube formation. Cocktails of neutralizing antibodies against the scavenger receptors CD36, CD163 and LOX-1 prevented AGE3-induced tube formation. AGE3 activated mTOR signalling, resulting in facilitation of tube formation. Activation of the AGE-RAGE pathway also led to the upregulation of scavenger receptors. Taken together, our findings suggest that the scavenger receptors CD36, CD163 and LOX-1 in conjunction with the RAGE receptor work together to mediate toxic AGE-induced facilitation of angiogenesis.

Histidine-Rich Glycoprotein Suppresses the S100A8/A9-Mediated Organotropic Metastasis of Melanoma Cells.

The dissection of the complex multistep process of metastasis exposes vulnerabilities that could be exploited to prevent metastasis. To search for possible factors that favor metastatic outgrowth, we have been focusing on secretory S100A8/A9. A heterodimer complex of the S100A8 and S100A9 proteins, S100A8/A9 functions as a strong chemoattractant, growth factor, and immune suppressor, both promoting the cancer milieu at the cancer-onset site and cultivating remote, premetastatic cancer sites. We previously reported that melanoma cells show lung-tropic metastasis owing to the abundant expression of S100A8/A9 in the lung. In the present study, we addressed the question of why melanoma cells are not metastasized into the brain at significant levels in mice despite the marked induction of S100A8/A9 in the brain. We discovered the presence of plasma histidine-rich glycoprotein (HRG), a brain-metastasis suppression factor against S100A8/A9. Using S100A8/A9 as an affinity ligand, we searched for and purified the binding plasma proteins of S100A8/A9 and identified HRG as the major protein on mass spectrometric analysis. HRG prevents the binding of S100A8/A9 to the B16-BL6 melanoma cell surface via the formation of the S100A8/A9 complex. HRG also inhibited the S100A8/A9-induced migration and invasion of A375 melanoma cells. When we knocked down HRG in mice bearing skin melanoma, metastasis to both the brain and lungs was significantly enhanced. The clinical examination of plasma S100A8/A9 and HRG levels showed that lung cancer patients with brain metastasis had higher S100A8/A9 and lower HRG levels than nonmetastatic patients. These results suggest that the plasma protein HRG strongly protects the brain and lungs from the threat of melanoma metastasis.

HMGB1 in the mPFC governs comorbid anxiety in neuropathic pain.

BACKGROUND: Whether neuroinflammation causes comorbid mood disorders in neuropathic pain remains elusive. Here we investigated the role of high mobility group box 1 protein (HMGB1), a proinflammatory cytokine, in the medial prefrontal cortex (mPFC) in anxiety comorbidity of neuropathic pain. METHODS: Neuropathic pain was induced by partial transection of the infraorbital nerve (p-IONX) or partial sciatic nerve ligation (PSL) in mice and evaluated by measuring nociceptive thresholds to mechanical and heat stimulation. Anxiety-like behaviors were assessed by elevated plus maze, light dark box and open field tests. Aversive or anti-aversive effect was detected by conditioned place preference test. Neuronal activity was evaluated by single-unit and patch clamp recordings. The contribution of mPFC pyramidal neurons to anxiety was further examined by selectively inhibiting them by optogenetics. HMGB1 expression was measured by immunohistochemistry and western blotting. Antagonism of HMGB1 was achieved by injecting anti-HMGB1 monoclonal antibody (mAb) intracerebrally or intraperitoneally. RESULTS: Anxiety-like behaviors were presented earlier after p-IONX than after PSL. HMGB1 expression was upregulated in the mPFC temporally in parallel to anxiety onset, rather than in other regions associated with anxiety. The upregulation of HMGB1 expression and its translocation from the nucleus to cytoplasm in the mPFC occurred predominantly in neurons and were accompanied with activation of microglia and astrocytes. Infusion of anti-HMGB1 mAb into the mPFC during the early and late phases after either p-IONX or PSL alleviated anxiety-like behaviors and aversion without changing pain sensitization, while local infusion of exogenous ds-HMGB1, the proinflammatory form of HMGB1, into the mPFC induced anxiety and aversion but not pain sensitization in naïve mice. In addition to reversing established pain sensitization and anxiety simultaneously, intraperitoneal injection of anti-HMGB1 mAb reduced HMGB1 upregulation and suppressed the hyperexcitability of layer 2/3 pyramidal neurons in the mPFC after p-IONX. Moreover, optogenetic inhibition of mPFC pyramidal neurons alleviated anxiety in p-IONX mice. CONCLUSION: These results demonstrate that HMGB1 in the mPFC drives and maintains anxiety comorbidity in neuropathic pain by increasing the excitability of layer 2/3 pyramidal neurons, and justify antagonism of HMGB1, e.g., neutralization by mAb, as a promising therapeutic strategy for neuropathic pain with anxiety comorbidity.

Protective effects of anti-HMGB1 monoclonal antibody on lung ischemia reperfusion injury in mice.

During ischemia reperfusion (IR) injury, high mobility group box 1 (HMGB1), a chromatin binding protein, is released from necrotic cells and triggers inflammatory responses. We assessed the therapeutic effect of a neutralizing anti-HMGB1 monoclonal antibody (mAb) on lung IR injury. A murine hilar clamp model of IR was used, where mice were divided into sham and IR groups with intravenous administration of anti-HMGB 1 mAb or control mAb. We analyzed the effect of anti-HMGB1 mAb against IR injury by assessing lung oxygenation, lung injury score, neutrophil infiltration, expression of proinflammatory cytokines and chemokines, levels of mitogen-activated protein kinase (MAPK) signaling, and measurement of apoptotic cells. Anti-HMGB1 mAb significantly decreased the plasma level of HMGB1 elevated by IR. The severity of IR injury represented by oxygenation capacity, lung injury score, and neutrophil infiltration was significantly improved by anti-HMGB1 mAb treatment. The expression of proinflammatory factors, including IL-1ß, IL-6, IL-12, TNF-α, CXCL-1, and CXCL-2, and phosphorylation of p38 MAPK were both significantly reduced by anti-HMGB1 mAb treatment. Furthermore, anti-HMGB1 mAb treatment suppressed apoptosis, as determined through TUNEL assays. Overall, anti-HMGB1 mAb ameliorated lung IR injury by reducing inflammatory responses and apoptosis. Our findings indicate that anti-HMGB1 mAb has potential for use as a therapeutic to improve IR injury symptoms during lung transplantation.

Anti-high mobility group box 1 monoclonal antibody suppressed hyper-permeability and cytokine production in human pulmonary endothelial cells infected with influenza A virus.

OBJECTIVE: High mobility group box-1 (HMGB1) has been reported to be involved in influenza A virus-induced acute respiratory distress syndrome (ARDS). We studied the efficacy of an anti-HMGB1 mAb using an in vitro model of TNF-α stimulation or influenza A virus infection in human pulmonary microvascular endothelial cells (HMVECs). METHODS: Vascular permeability of HMVECs was quantified using the Boyden chamber assay under tumor necrosis factor-α (TNF-α) stimulation or influenza A virus infection in the presence of anti-HMGB1 mAb or control mAb. The intracellular localization of HMGB1 was assessed by immunostaining. Extracellular cytokine concentrations and intracellular viral mRNA expression were quantified by the enzyme-linked immunosorbent assay and quantitative reverse transcription PCR, respectively. RESULTS: Vascular permeability was increased by TNF-α stimulation or influenza A infection; HMVECs became elongated and the intercellular gaps were extended. Anti-HMGB1 mAb suppressed both the increase in permeability and the cell morphology changes. Translocation of HMGB1 to the cytoplasm was observed in the non-infected cells. Although anti-HMGB1 mAb did not suppress viral replication, it did suppress cytokine production in HMVECs. CONCLUSION: Anti-HMGB1 mAb might be an effective therapy for severe influenza ARDS.