Involvement of Toll-like Receptors 2 and 4 in Cellular Activation by High Mobility Group Box 1 Protein

Identification of High-Mobility Group Box 1 (HMGB1) Expression as a Potential Predictor of Rejection and Poor Prognosis After Liver Transplantation

BACKGROUND Acute cellular rejection (ACR) frequently occurs after liver transplantation (LT) and can result in permanent damage of the liver allograft. Specific and sensitive biomarkers for predicting and monitoring ACR are vital for guiding post-transplantation care. In the present study, we aimed to investigate the function of high-mobility group box 1 (HMGB1) in predicting ACR and prognosis after LT. MATERIAL AND METHODS A total of 113 LT recipients were enrolled in the study, including 62 patients in an ACR group and 51 patients in a non-rejection group. Using tissues from the 113 patients, HMGB1 expression was examined by immunohistochemistry, and the total score for HMGB1 expression was calculated by multiplying the percentage of immunoreactive cells score and the staining intensity score. We then analyzed the association between HMGB1 expression and clinical features. Finally, the function of HMGB1 in predicting the prognosis of LT was determined using Kaplan-Meier (K-M) survival and Cox multivariate analyses. RESULTS Immunohistochemical staining results demonstrated that the expression of HMGB1 was significantly increased in the ACR group, compared with that in the non-rejection group (P<0.05). Clinical characteristic analysis revealed that high HMGB1 levels were related to ACR (P<0.05). Moreover, K-M survival analysis showed that patients with high HMGB1 expression displayed poorer prognosis (P<0.05). Cox multivariate analysis demonstrated that HMGB1 was an independent prognostic predictor for post-LT survival (odds ratio, 3.283; P=0.008). CONCLUSIONS LT recipients' HMGB1 levels may be a useful and noninvasive biomarker for the prediction of ACR and prognosis after LT.

CLEC14A protects against podocyte injury in mice with adriamycin nephropathy

Podocyte injury is a major determinant of focal segmental glomerular sclerosis (FSGS) and the identification of potential therapeutic targets for preventing podocyte injury has clinical importance for the treatment of FSGS. CLEC14A is a single-pass transmembrane glycoprotein belonging to the vascular expressed C-type lectin family. CLEC14A is found to be expressed in vascular endothelial cells during embryogenesis and is also implicated in tumor angiogenesis. However, the current understanding of the biological functions of CLEC14A in podocyte is very limited. In this study, we found that CLEC14A was expressed in podocyte and protected against podocyte injury in mice with Adriamycin (ADR)-induced FSGS. First, we observed that CLEC14A was downregulated in mice with ADR nephropathy and renal biopsies from individuals with FSGS and other forms of podocytopathies. Moreover, CLEC14A deficiency exacerbated podocyte injury and proteinuria in mice with ADR nephropathy accompanied by enhanced inflammatory cell infiltration and inflammatory responses. In vitro, overexpression of CLEC14A in podocyte had pleiotropic protective actions, including anti-inflammatory and anti-apoptosis effects. Mechanistically, CLEC14A inhibited high-mobility group box 1 protein (HMGB1) release, at least in part by directly binding HMGB1, and suppressed HMGB1-mediated signaling, including NF-κB signaling and early growth response protein 1 (EGR1) signaling. Taken together, our findings provide new insights into the pivotal role of CLEC14A in maintaining podocyte function, indicating that CLEC14A may be an innovative therapeutic target in FSGS.

The interplay of DAMPs, TLR4, and proinflammatory cytokines in pulmonary fibrosis

Pulmonary fibrosis is a chronic debilitating condition characterized by progressive deposition of connective tissue, leading to a steady restriction of lung elasticity, a decline in lung function, and a median survival of 4.5 years. The leading causes of pulmonary fibrosis are inhalation of foreign particles (such as silicosis and pneumoconiosis), infections (such as post COVID-19), autoimmune diseases (such as systemic autoimmune diseases of the connective tissue), and idiopathic pulmonary fibrosis. The therapeutics currently available for pulmonary fibrosis only modestly slow the progression of the disease. This review is centered on the interplay of damage-associated molecular pattern (DAMP) molecules, Toll-like receptor 4 (TLR4), and inflammatory cytokines (such as TNF-α, IL-1β, and IL-17) as they contribute to the pathogenesis of pulmonary fibrosis, and the possible avenues to develop effective therapeutics that disrupt this interplay.

Decellularization protocol-dependent damage-associated molecular patterns in rat uterus scaffolds differentially affect the immune response after transplantation

Scaffolds derived from decellularized tissue possess many advantages for bioengineering applications, including for novel infertility treatments. However, the decellularization process results in allogenic-independent damage-associated molecular patterns (DAMPs). This field is poorly studied, in particular for uterus bioengineering applications. An increased knowledge concerning the immune system activation after transplantation of decellularized tissue will enable safer construct development and thereby accelerate translation from research to clinic. We therefore transplanted rat uterus scaffolds produced by three different decellularization protocols based on Triton X-100 (P1 and P2) or sodium deoxycholate (P3) in a syngeneic animal model and assessed the immune response towards DAMPs exposed by the decellularization process. Biopsies were retrieved on day 5, 15, and 30 post transplantation and immunohistochemistry-stained CD45+ (leucocytes), CD4+ (T-cells), CD8a+ (cytotoxic T-cells), CD22+ (B-cells), NCR1+ (NK-cells), CD68+ (pan-macrophages), and CD163+ (M2 macrophages) cells within the grafts were quantified. The gene expression for interferon γ, interleukin (IL)-1β, IL-2, IL-6, and tumor necrosis factor (TNF) eotaxin-2, RANTES, MCP-1, MIP-1α, MIP-3α, IL-8 were also measured. Scaffolds from P1 induced a rapid cell infiltration after transplantation, presumably induced by DNA-based DAMPs. However, this response was only transient. Protocol 3 derived scaffolds induced an early pro-inflammatory cytokine response at the transcript level which remained high throughout the study. This response may be caused by the stronger decellularization detergent that could expose more extracellular matrix-related DAMPs. However, earlier proteomics analysis also identified significantly more abundant heat shook proteins-related DAMPs in this scaffold type. Protocol 2 caused the least immunogenic scaffolds and should thus be the future focus for in vivo uterus bioengineering applications.

Immune receptor toll-like receptor 4 contributes to stress-induced affective responses in a sex-specific manner

Stress activates innate immune Toll-like receptors (TLRs) and enhances susceptibility to depression, a condition that is more prevalent in females. The TLR4 receptor type is involved in inflammatory responses and its expression levels associate with depressive symptoms and their successful treatment. Yet, little preclinical research has examined the role of TLR4 in stress-induced affective responses to determine if these are sex-specific. One group per genotype of male and female Tlr4 knockout (KO) and wild type (WT) rats were exposed to predator odor in a place conditioning apparatus with others exposed to saline. Affective behaviors evaluated included distance traveled and center time in an open-field apparatus, sucrose preference and fluid intake in a two-bottle test, and conditioned place aversion to the odor-paired compartment. Predator odor exposed rats showed conditioned place aversion to the odor-paired compartment, demonstrating predator odor was aversive. Such exposure led to anhedonia (decreased sucrose preference) across genotypes and sex. Predator odor exposure decreased distance traveled, an effect that was greater in KO rats, especially in females. Tlr4 deletion also resulted in sex-specific effects on anxiety-like behavior. Compared to WTs, female KO rats showed lower center time after predator odor exposure whereas genotype did not affect this response in male rats. Across litters, fewer male KO and heterozygous rats and more WT rats were born whereas female rats showed the typical genotype distribution. Results suggest predator odor alters affective behaviors, consistent with the preclinical literature, and deletion of Tlr4 enhances some stress-induced affective responses, often in a sex-specific manner.

HMGB1 regulates lipopolysaccharide-induced cellular dysfunction in HTR8/SVneo cells: Implications for the role of HMGB1 in unexplained spontaneous miscarriage

INTRODUCTION

Approximately half of miscarriages are of an unknown aetiology and are likely characterized by aberrant inflammation at the uteroplacental interface. High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein that participates in the pathological inflammatory response. The present study investigated the role of HMGB1 in inflammation-induced damage in trophoblasts and elucidated the underlying mechanism.

METHODS

Immunohistochemistry, qRT-PCR and Western blotting were used to detect the expression of HMGB1 in early unexplained miscarriage and normal placentas. Lipopolysaccharide (LPS)-induced HTR8/SVneo cells were used as an in vitro model to mimic the aberrant inflammation at the uteroplacental interface of miscarriage. The expression of HMGB1 and the autophagy-related proteins LC3 and Beclin1 was detected using Western blotting. Autophagy was studied in villous tissues using immunofluorescence and Western blotting. Cell proliferation and migration were analysed.

RESULTS

The expression level of HMGB1 in villous tissues with early unexplained miscarriage was significantly higher than the normal pregnancy group. The inhibition of HMGB1 in LPS-treated HTR8/SVneo cells decreased the expression of Beclin 1 and LC3, which promoted cell proliferation and migration. We found a high level of autophagy in miscarriage placentas. HMGB1 and autophagy inhibition reversed the proliferation and migration of LPS-induced HTR-8/SVneo cells.

DISCUSSION

Our results demonstrated that HMGB1 participated in LPS-induced inflammation via autophagy and regulated trophoblast functions, such as cell proliferation and migration, to potentially participate in the pathogenesis of miscarriage.

MMP2 and TLRs modulate immune responses in the tumor microenvironment

The presence of an immunosuppressive tumor microenvironment is a major obstacle in the success of cancer immunotherapies. Because extracellular matrix components can shape the microenvironment, we investigated the role of matrix metalloproteinase 2 (MMP2) in melanoma tumorigenesis. We found that MMP2 signals proinflammatory pathways on antigen presenting cells, and this requires both TLR2 and TLR4. B16 melanoma cells that express MMP2 at baseline have slower kinetics in Tlr2^–/–Tlr4^–/– mice, implicating MMP2 in promoting tumor growth. Indeed, Mmp2 overexpression in B16 cells potentiated rapid tumor growth, which was accompanied by reduced intratumoral cytolytic cells and increased M2 macrophages. In contrast, knockdown of Mmp2 slowed tumor growth and enhanced T cell proliferation and NK cell recruitment. Finally, we found that these effects of MMP2 are mediated through dysfunctional DC–T cell cross-talk as they are lost in Batf3^–/– and Rag2^–/– mice. These findings provide insights into the detrimental role of endogenous alarmins like MMP2 in modulating immune responses in the tumor microenvironment.

HMGB1 Activates Myeloid Dendritic Cells by Up-Regulating mTOR Pathway in Systemic Lupus Erythematosus

Research has shown that HMGB1 can activate dendritic cells (DCs), but its molecular mechanisms are not clear. In this study, we reported that the myeloid dendritic cells (mDCs) were activated in the peripheral blood of SLE patients, and the activation of mDCs was associated with the up-regulation of HMGB1 and mTOR. After stimulated by HMGB1, expression of mTOR and its substrates P70S6K and 4EBP1 in dendritic cells increased considerably (P < 0.01). The expression of HLA-DR, CD40, and CD86 on dendritic cells also significantly increased following these stimuli (P < 0.01). In addition, stimulation with HMGB1 enhanced cytokine (IL-1β, IL-6, and TNF-a) production in dendritic cells. In contrast, the HMGB1-mediated expression of HLA-DR, CD40, and CD86 on dendritic cells and production of IL-1β, IL-6, and TNF-α were reduced by rapamycin. Rapamycin can inhibit HMGB1-induced activation of mDCs and secretion of pro-inflammatory cytokines. These findings indicated that HMGB1activates mDCs by up-regulating the mTOR pathway in SLE.

Restoring the Immunity in the Tumor Microenvironment: Insights into Immunogenic Cell Death in Onco-Therapies

Immunogenic cell death (ICD) elicited by cancer therapy reshapes the tumor immune microenvironment. A long-term adaptative immune response can be initiated by modulating cell death by therapeutic approaches. Here, the major hallmarks of ICD, endoplasmic reticulum (ER) stress, and damage-associated molecular patterns (DAMPs) are correlated with ICD inducers used in clinical practice to enhance antitumoral activity by suppressing tumor immune evasion. Approaches to monitoring the ICD triggered by antitumoral therapeutics in the tumor microenvironment (TME) and novel perspective in this immune system strategy are also reviewed to give an overview of the relevance of ICD in cancer treatment.

Transferring Plasmon Effect on a Biological System: Expression of Biological Polymers in Chronic Rejection and Inflammatory Rat Model

The plasmon-activated water (PAW) that reduces hydrogen bonds is made of deionized reverse osmosis water (ROW). However, compared with ROW, PAW has a significantly higher diffusion coefficient and electron transfer rate constant in electrochemical reactions. PAW has a boiling point of 97 °C and specific heat of0.94; the energy of PAW is also 1121 J/mol higher than ordinary water. The greater the force of hydrogen bonds between H₂O, the larger the volume of the H₂O cluster, and the easier it is to lose the original characteristics. The hydrogen bonding force of PAW is weak, so the volume of its cluster is small, and it exists in a state very close to a single H₂O. PAW has a high permeability and diffusion rate, which can improve the needs of biological applications and meet the dependence of biological organisms on H₂O when performing physiological functions. PAW can successfully remove free radicals, and efficiently reduce lipopolysaccharide (LPS)-induced monocytes to release nitric oxide. PAW can induce expression of the antioxidant gene Nrf2 in human gingival fibroblasts, lower amyloid burden in mice with Alzheimer’s disease, and decrease metastasis in mice grafted with Lewis lung carcinoma cells. Because the transferring plasmon effect may improve the abnormality of physiological activity in a biological system, we aimed to evaluate the influence of PAW on orthotopic allograft transplantation (OAT)-induced vasculopathy in this study. Here, we demonstrated that daily intake of PAW lowered the progression of vasculopathy in OAT-recipient ACI/NKyo rats by inhibiting collagen accumulation, proliferation of smooth muscle cells and fibroblasts, and T lymphocyte infiltration in the vessel wall. The results showed reduced T and B lymphocytes, plasma cells, and macrophage activation in the spleen of the OAT-recipient ACI/NKyo rats that were administered PAW. In contrast to the control group, the OAT-recipient ACI/NKyo rats that were administered PAW exhibited higher mobilization and levels of circulating endothelial progenitor cells associated with vessel repair. We use the transferring plasmon effect to adjust and maintain the biochemical properties of water, and to meet the biochemical demand of organisms. Therefore, this study highlights the therapeutic roles of PAW and provides more biomedical applicability for the transferring plasmon effect.

Dynamic role of LMW-hyaluronan fragments and Toll-like receptors 2,4 in progression of bleomycin induced lung parenchymal injury to fibrosis

Background

Pulmonary fibrosis (PF) is a progressive and lethal lung disease of elderly whose incidence has been increasing following the Covid-19 pandemic caused by severe acute respiratory syndrome corona virus 2 (SARS-CoV-2). PF immunopathogenesis involves progressive alveolar epithelial cell damage, release of damage-associated molecular patterns (DAMPs), and extracellular matrix (ECM) injury. We assessed the dynamic role of LMW-hyaluronan (LMW-HA) as DAMP in initiation of host immune TLR-2,4 responses and as determinant in progression of ECM injury to fibrosis. Male Wistar rats were divided into Group I (saline control, n = 24) and Group II (intratracheal bleomycin, 7 U/kg/animal, n = 24). Animals were euthanized on 0, 7, 14, and 28 days. The time course of release of LMW-HA, TLR-2,4 mRNA and protein levels, and NF-κB-p65 levels after bleomycin injury were correlated with the development of parenchymal inflammation, remodelling, and fibrosis.

Results

Acute lung injury caused by bleomycin significantly increases the pro-inflammatory LMW-HA levels and elevates TLR-2,4 levels on day 7. Subsequently, TLR-2 upregulation, TLR-4 downregulation, and NF-κB signalling follow on days 14 and 28. This results in progressive tissue inflammation, alveolar and interstitial macrophage accumulation, and fibrosis.

Conclusions

LMW-HA significantly increases in PF caused by non-infectious and infectious (Covid-19) etiologies. The accumulating HA fragments function as endogenous DAMPs and trigger inflammatory responses, through differential TLR2 and TLR4 signalling, thus promoting inflammation and macrophage influx. LMW-HA are reflective of the state of ongoing tissue inflammation and may be considered as a natural biosensor for fibrotic lung diseases and as potential therapeutic targets.

Tectorigenin attenuates cognitive impairments in mice with chronic cerebral ischemia by inhibiting the TLR4/NF-κB signaling pathway

This study aims to explore the effect of Tectorigenin in chronic cerebral ischemia (CCI)-induced cognitive impairment mice model. Cognitive impairment, hippocampal tissue histopathology, and myelin density in CCI mice were detected. HT22 cells were used to induce oxygen-glucose deprivation/reperfusion (OGD/R) injury. Cell viability and apoptosis of transfected HT22 cells and toll-like receptor-4 (TLR4)/nuclear factor-kappaB (NF-κB) pathway-related factor levels in hippocampal tissue and OGD/R models were detected. CCI caused cognitive impairment, hippocampal damage, and decreased myelin density in mice while promoting interleukin-1β, tumor necrosis factor-alpha, TLR4, myeloid differentiation primary response gene 88, p-p65, NLRP3, and ASC levels. Tectorigenin reversed the effects of CCI in mice and reversed the promoting effects of OGD/R on apoptosis and TLR4/NF-κB pathway-related factors levels, while overexpressed TLR4 reversed the effects of Tectorigenin in OGD/R-induced HT-22 cells. Tectorigenin alleviated cognitive impairment in CCI mice by inhibiting the TLR4/NF-κB signaling pathway.

When the Blood Hits Your Brain: The Neurotoxicity of Extravasated Blood

Hemorrhage in the central nervous system (CNS), including intracerebral hemorrhage (ICH), intraventricular hemorrhage (IVH), and aneurysmal subarachnoid hemorrhage (aSAH), remains highly morbid. Trials of medical management for these conditions over recent decades have been largely unsuccessful in improving outcome and reducing mortality. Beyond its role in creating mass effect, the presence of extravasated blood in patients with CNS hemorrhage is generally overlooked. Since trials of surgical intervention to remove CNS hemorrhage have been generally unsuccessful, the potent neurotoxicity of blood is generally viewed as a basic scientific curiosity rather than a clinically meaningful factor. In this review, we evaluate the direct role of blood as a neurotoxin and its subsequent clinical relevance. We first describe the molecular mechanisms of blood neurotoxicity. We then evaluate the clinical literature that directly relates to the evacuation of CNS hemorrhage. We posit that the efficacy of clot removal is a critical factor in outcome following surgical intervention. Future interventions for CNS hemorrhage should be guided by the principle that blood is exquisitely toxic to the brain.

Danger-associated molecular pattern molecules and the receptor for advanced glycation end products enhance ANCA-induced responses

Objectives

The pro-inflammatory activities of the calgranulins and HMGB1 can be counteracted by sRAGE, the soluble form of their shared receptor. To understand the role of these molecules in AAV and their potential as therapeutic targets we have studied (i) the relationship between these DAMPS and disease activity; (ii) the expression of RAGE and sRAGE in biopsy tissue and peripheral blood; and (iii) the effect of these molecules on ANCA-mediated cytokine production.

Methods

We examined circulating levels of calgranulins (S100A8/A9 and S100A12), HMGB1 and sRAGE by ELISA. RAGE was examined in AAV kidney and lung biopsies by immunohistochemistry and RAGE expression was monitored in peripheral blood by qPCR. In vitro, the effect of co-stimulating PBMC with ANCA and S100A8/A9 on cytokine production was studied by ELISA.

Results

We found significantly raised levels of calgranulins and HMGB1 in active AAV regardless of clinical phenotype (PR3+/MPO+ AAV). Levels of calgranulins showed significant correlations with each other. RAGE protein and message was raised in peripheral blood and in cells infiltrating kidney and lung biopsy tissue, while sRAGE was lowered. Furthermore, ANCA-mediated production of IL-8 from PBMC was significantly enhanced by the presence of S100A8/A9 in a RAGE/TLR4-dependent manner.

Conclusions

Raised circulating calgranulins provide a good marker of disease activity in AAV and are unlikely to be counteracted by sRAGE. Increased RAGE expression in AAV indicates receptor stimulation in active disease that may exacerbate ANCA-induced cytokine production. Targeting the RAGE pathway may provide a useful therapeutic approach in AAV.

Toll-like receptor 2 activation and up-regulation by high mobility group box-1 contribute to post-operative neuroinflammation and cognitive dysfunction in mice

Post-operative cognitive dysfunction (POCD) is common and is associated with poor clinical outcome. Toll-like receptor (TLR) 3 and 4 have been implied in the development of POCD. The role of TLR2, a major brain TLR, in POCD is not clear. High mobility group box-1 (HMGB1) is a delayed inflammatory mediator and may play a role in POCD. The interaction between HMGB1 and TLRs in the perioperative period is not known. We hypothesize that TLR2 contributes to the development of POCD and that HMGB1 regulates TLR2 for this effect. To test these hypotheses, 6- to 8-week old male mice were subjected to right carotid artery exposure under isoflurane anesthesia. CU-CPT22, a TLR1/TLR2 inhibitor, at 3 mg/kg was injected intraperitoneally 30 min before surgery and 1 day after surgery. Glycyrrhizin, a HMGB1 antagonist, at 200 mg/kg was injected intraperitoneally 30 min before surgery. Mice were subjected to Barnes maze and fear conditioning tests from 1 week after surgery. Hippocampus and cerebral cortex were harvested 6 hr or 12 hr after the surgery for Western blotting, ELISA, immunofluorescent staining, and chromatin immunoprecipitation. There were neuroinflammation and impairment of learning and memory in mice with surgery. Surgery increased the expression of TLR2 and TLR4 but not TLR9 in the brain of CD-1 male mice. CU-CPT22 attenuated surgery-induced neuroinflammation and cognitive impairment. Similarly, surgery induced neuroinflammation and cognitive dysfunction in C57BL/6J mice but not in TLR2^-/- mice. TLR2 staining appeared in neurons and microglia. Surgery increased HMGB1 in the cell nuclei of the cerebral cortex and hippocampus. Glycyrrhizin ameliorated this increase and the increase of TLR2 in the hippocampus after surgery. Surgery also increased the amount of tlr2 DNA precipitated by an anti-HMGB1 antibody in the hippocampus. Our results suggest that TLR2 contributes to surgery-induced neuroinflammation and cognitive impairment. HMGB1 up-regulates TLR2 expression in the hippocampus after surgery to facilitate this contribution. Thus, TLR2 and HMGB1 are potential targets for reducing POCD.

Anti-HMGB1 auto-Abs influence fatigue in patients with Crohn's disease

Fatigue is common in all chronic inflammatory and autoimmune diseases. A conceptual model for understanding the biological basis of fatigue describes it as being a part of the sickness behaviour response generated by pro-inflammatory cytokines and other mediators. We hypothesised that the pro-inflammatory high mobility group box 1 (HMGB1) protein is a fatigue-inducing molecule and that auto-Abs against HMGB1 reduce fatigue. We measured Abs against disulphide (ds) HMGB1 and fully reduced (fr) HMGB1 in plasma from 57 patients with Crohn’s disease. Fatigue was rated using the fatigue visual analogue scale (fVAS) and disease activity with faecal calprotectin, C-reactive protein and the Simple Endoscopic Score for Crohn’s disease. Multivariable regression models identified anti-dsHMGB1 and anti-frHMGB1 Abs as the strongest contributing factors for fVAS scores (B = −29.10 (P = 0.01), R² = 0.17, and B = −17.77 (P = 0.01), R² = 0.17, respectively). Results indicate that anti-HMGB1 auto-Abs alleviate fatigue possibly by down-regulating HMGB1-induced sickness behaviour.

Metabolic Syndrome and Autophagy: Focus on HMGB1 Protein

Metabolic syndrome (MetS) affects the population worldwide and results from several factors such as genetic background, environment and lifestyle. In recent years, an interplay among autophagy, metabolism, and metabolic disorders has become apparent. Defects in the autophagy machinery are associated with the dysfunction of many tissues/organs regulating metabolism. Metabolic hormones and nutrients regulate, in turn, the autophagy mechanism. Autophagy is a housekeeping stress-induced degradation process that ensures cellular homeostasis. High mobility group box 1 (HMGB1) is a highly conserved nuclear protein with a nuclear and extracellular role that functions as an extracellular signaling molecule under specific conditions. Several studies have shown that HMGB1 is a critical regulator of autophagy. This mini-review focuses on the involvement of HMGB1 protein in the interplay between autophagy and MetS, emphasizing its potential role as a promising biomarker candidate for the early stage of MetS or disease's therapeutic target.

Ellagitannins from Rosa roxburghii suppress poly(I:C)-induced IL-8 production in human keratinocytes

The anti-inflammatory effects of a 50% aqueous extract of Rosa roxburghii fruit (RRFE) and two ellagitannins (strictinin and casuarictin) isolated from the RRFE were evaluated in a cell model of skin inflammation induced by self-RNA released from epidermal cells damaged by UV ray (UVR) irradiation. The RRFE inhibited interleukin-8 (IL-8) mRNA expression in normal human epidermal keratinocytes (NHEKs) stimulated with polyinosinic:polycytidylic acid (poly(I:C)), a ligand of toll-like receptor-3 (TLR-3). The plant-derived anti-inflammatory agents, dipotassium glycyrrhizinate (GK2) and allantoin, had no influence on the IL-8 expression. The purified compounds, strictinin and casuarictin, inhibited the IL-8 mRNA expression and IL-8 release induced in NHEKs by poly(I:C). These ellagitannins were thus found to be responsible for the biological activity exhibited by the RRFE. This study demonstrates that RRFE and isolated RRFE compounds show promise as ingredients for products formulated to improve skin disorders induced by UVR irradiation.

The second phase of brain trauma can be controlled by nutraceuticals that suppress DAMP-mediated microglial activation

INTRODUCTION

A delayed second wave of brain trauma is mediated in large part by microglia that are activated to a pro-inflammatory M1 phenotype by DAMP proteins released by dying neurons. These microglia can promote apoptosis or necrosis in neighboring neurons by producing a range of pro-inflammatory cytokines and the deadly oxidant peroxynitrite. This second wave could therefore be mitigated with agents that blunt the post-traumatic M1 activation of microglia and that preferentially promote a pro-healing M2 phenotype.

AREAS COVERED

The literature on nutraceuticals that might have clinical potential in this regard.

EXPERT OPINION

The chief signaling pathway whereby DAMPs promote M1 microglial activation involves activation of toll-like receptor 4 (TLR4), NADPH oxidase, NF-kappaB, and the stress activated kinases JNK and p38. The green tea catechin EGCG can suppress TLR4 expression. Phycocyanobilin can inhibit NOX2-dependent NADPH oxidase, ferulate and melatonin can oppose pro-inflammatory signal modulation by NADPH oxidase-derived oxidants. Long-chain omega-3 fatty acids, the soy isoflavone genistein, the AMPK activator berberine, glucosamine, and ketone bodies can down-regulate NF-kappaB activation. Vitamin D activity can oppose JNK/p38 activation. A sophisticated program of nutraceutical supplementation may have important potential for mitigating the second phase of neuronal death and aiding subsequent healing.

Preventing or controlling periodontitis reduces the occurrence of osteonecrosis of the jaw (ONJ) in rice rats (Oryzomys palustris)

INTRODUCTION

Osteonecrosis of the jaw (ONJ) is an adverse event that requires association of both systemic risk factors, such as powerful anti-resorptives (pARs; e.g. zoledronic acid [ZOL]), and local oral risk factors (e.g. tooth extraction, periodontitis). Whereas optimal oral health prior to initiate pARs is recognized as critically important for minimizing ONJ risk, the efficacy of preventive/maintenance measures in patients who are taking pARs is understudied. Rice rats fed a standard diet (STD), rich in insoluble fiber, develop localized periodontitis. STD-rats with localized periodontitis treated with ZOL for 18-24 wk develop ONJ. Hence, we hypothesized that controlling/preventing localized periodontitis in the ZOL-treated rats, reduces ONJ occurrence.

METHODS

We used two approaches to attempt reducing periodontitis prevalence: 1) periodontal cleaning (PC); and 2) replacing the STD-diet with a nutritionally-equivalent diet high in soluble fiber (SF). 75 four-week-old male rats were weight-randomized into five groups (n = 15) in a 24-week experiment. Three groups ate the STD-diet and two the high SF-diet. STD-diet groups received intravenous (IV) vehicle (VEH) q4wks (STD + VEH), 80 μg/kg ZOL q4wks IV (STD + ZOL), or ZOL plus PC q2wks (STD + ZOL + PC). The SF-diet groups received VEH (SF + VEH) or ZOL (SF + ZOL). Jaws were processed for histopathology and evaluated for ONJ prevalence and tissue-level periodontitis.

RESULTS

1) 40% of STD + VEH rats developed maxillary localized periodontitis with no ONJ; 2) 50% of STD + ZOL rats developed ONJ; 3) 7% of STD + ZOL + PC rats developed ONJ (p < 0.01 vs. STD + ZOL); and 4) one SF + ZOL rat developed localized periodontitis, and no SF + VEH or SF + ZOL rats developed ONJ (p < 0.001 vs. STD + ZOL).

CONCLUSIONS

1) Periodontal cleaning in ZOL-treated rats decreases localized periodontitis severity and reduces ONJ prevalence; and 2) feeding a SF-diet to ZOL-treated rats reduces both incidence of localized periodontitis and ONJ. Our data indicates strong oral microbial community shifts according to oral health condition and trends in the shifts associated with diet.

Therapeutic Efficacy of Excretory-Secretory Products of Trichinella spiralis Adult Worms on Sepsis-Induced Acute Lung Injury in a Mouse Model

Acute lung injury (ALI) is a common complication of systemic inflammation or sepsis with high morbidity and mortality. Although many studies have confirmed that helminth-derived proteins had strong immunomodulatory functions and could be used to treat inflammatory diseases, there is no report on the therapeutic effect of excretory-secretory products of Trichinella spiralis adult worms (Ts-AES) on sepsis-induced ALI. In this study, the therapeutic efficacy of Ts-AES on sepsis-induced ALI and the underlying immunological mechanism and the signaling pathway were investigated. The results indicated that after being treated with Ts-AES, the survival rate of mice with CLP-induced sepsis was significantly increased to 50% for 72 hours after CLP surgery compared to PBS control group with all mice died. The sepsis-induced ALI was largely mitigated characterized by reduced inflammation cell infiltration and pathological changes in lung tissue, with decreased lung injury scores and lung wet/dry weight ratio. The therapeutic efficacy of Ts-AES is associated with stimulated Tregs response with increased regulatory cytokines IL-10 and TGF-β and downregulated pro-inflammatory cytokines (TNF-α, IL-6, IL-1β). The expression of HMGB1, TLR2 and MyD88 in lung tissue was inhibited after treatment of Ts-AES. Our results demonstrated that Ts-AES play an important role in immunomodulation and confer a therapeutic effect on sepsis-induced ALI through inhibiting pro-inflammatory cytokines. The activation of Tregs and increased level of regulatory cytokines IL-10 and TGF-β are possibly involved in the immunomodulatory functions of Ts-AES through HMGB1/TLR2/MyD88 signal pathway. The findings suggest Ts-AES is a potential therapeutic agent for prevention and treatment of sepsis-induced ALI and other inflammatory diseases.

Protective effect of glycyrrhizin on osteoarthritis cartilage degeneration and inflammation response in a rat model

This study was conducted to investigate the protective effects of glycyrrhizin on a rat model of osteoarthritis and elucidate the underlying mechanism. Rat osteoarthritis was established by using medial meniscectomy (MMx) and an anterior cruciate ligament transaction (ACLT). Glycyrrhizin (2, 4, and 10 mg/kg) was administered by intra-articular knee injection for 12 weeks. Incapacitance test was performed to determine mechanical hyperalgesia. Enzyme-linked immunosorbent assay (ELISA) was performed to measure cartilage degradation and inflammation-related markers. Quantitative reverse transcription PCR (RT-qPCR) and Western blot were performed to determine the mRNA and protein levels of genes, respectively. The results demonstrated that treatment with glycyrrhizin ameliorated mechanical hyperalgesia and bilateral joints oedema in a rat model of osteoarthritis. Treatment with 10 mg/kg glycyrrhizin also suppressed serum enzymes including matrix metalloproteinase (MMP)-1, MMP-3, prostaglandin E2, and C-telopeptide of type II collagen (CTX-II). In addition to inhibition of cartilage matrix catabolic related markers, treatment with glycyrrhizin also decreased the levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and iNOS in serum and cartilage. The underlying mechanism study demonstrated that treatment with glycyrrhizin inhibited HMGB1 and the TLR4/NF-κB signaling pathway. In summary, treatment with glycyrrhizin ameliorated cartilage degeneration and inflammation in osteoarthritis rats by the regulation of HMGB1 and the TLR4/NF-κB signaling pathway.

Glycyrrhizin ameliorates melanoma cell extravasation into mouse lungs by regulating signal transduction through HMGB1 and its receptors

Metastasis, which accounts for the majority of all cancer-related deaths, occurs through several steps, namely, local invasion, intravasation, transport, extravasation, and colonization. Glycyrrhizin has been reported to inhibit pulmonary metastasis in mice inoculated with B16 melanoma. This study aimed to identify the mechanism through which glycyrrhizin ameliorates the extravasation of melanoma cells into mouse lungs. Following B16 melanoma cell injection, mice were orally administered glycyrrhizin once every two days over 2 weeks; lung samples were then obtained and analyzed. Blood samples were collected on the final day, and cytokine plasma levels were determined. We found that glycyrrhizin ameliorated the extravasation of melanoma cells into the lungs and suppressed the plasma levels of interleukin-6, tumor necrosis factor-α, and transforming growth factor-β. Furthermore, glycyrrhizin ameliorated the lung tissue expression of high mobility group box-1 protein (HMGB1), receptor for advanced glycation end products (RAGE), Toll-like receptor (TLR)-4, RAS, extracellular signal-related kinase, NF-κB, myeloid differentiation primary response 88, IκB kinase complex, epithelial-mesenchymal transition markers, and vascular endothelial growth factor-A. Our study demonstrates that glycyrrhizin ameliorates melanoma metastasis by regulating the HMGB1/RAGE and HMGB1/TLR-4 signal transduction pathways.

Guidelines for Regulated Cell Death Assays: A Systematic Summary, A Categorical Comparison, A Prospective

Over the past few years, the field of regulated cell death continues to expand and novel mechanisms that orchestrate multiple regulated cell death pathways are being unveiled. Meanwhile, researchers are focused on targeting these regulated pathways which are closely associated with various diseases for diagnosis, treatment, and prognosis. However, the complexity of the mechanisms and the difficulties of distinguishing among various regulated types of cell death make it harder to carry out the work and delay its progression. Here, we provide a systematic guideline for the fundamental detection and distinction of the major regulated cell death pathways following morphological, biochemical, and functional perspectives. Moreover, a comprehensive evaluation of different assay methods is critically reviewed, helping researchers to make a reliable selection from among the cell death assays. Also, we highlight the recent events that have demonstrated some novel regulated cell death processes, including newly reported biomarkers (e.g., non-coding RNA, exosomes, and proteins) and detection techniques.

Myeloid-Derived Suppressor Cells: Facilitators of Cancer and Obesity-Induced Cancer

Immature myeloid cells at varied stages of differentiation, known as myeloid-derived suppressor cells (MDSC), are present in virtually all cancer patients. MDSC are profoundly immune-suppressive cells that impair adaptive and innate antitumor immunity and promote tumor progression through nonimmune mechanisms. Their widespread presence combined with their multitude of protumor activities makes MDSC a major obstacle to cancer immunotherapies. MDSC are derived from progenitor cells in the bone marrow and traffic through the blood to infiltrate solid tumors. Their accumulation and suppressive potency are driven by multiple tumor- and host-secreted proinflammatory factors and adrenergic signals that act via diverse but sometimes overlapping transcriptional pathways. MDSC also accumulate in response to the chronic inflammation and lipid deposition characteristic of obesity and contribute to the more rapid progression of cancers in obese individuals. This article summarizes the key aspects of tumor-induced MDSC with a focus on recent progress in the MDSC field.

Rs41291957 polymorphism in the promoter region of microRNA‑143 serves as a prognostic biomarker for patients with intracranial hemorrhage

The present study aimed to investigate the function of the single nucleotide polymorphism (SNP) rs41291957 in the prognosis of intracerebral hemorrhage (ICH). In addition, the molecular mechanisms underlying the role of microRNA (miR)‑143, Toll‑like receptor 2 (TLR2) and interleukin‑16 (IL‑16) were studied in patients with ICH that carried different alleles in the locus of the rs41291957 SNP. Kaplan‑Meier survival curves were calculated for 182 patients with ICH, genotyped as CC, presenting a cytosine in both chromosome, CT, presenting both variants, and TT, presents a thymine in both chromosomes. In addition, the possible regulatory relationships between miR‑143 and TLR2/IL‑16 were studied using computational analysis, luciferase assays and western blot assay. In addition, the inflammatory profiles of cerebrospinal fluid (CSF) and serum samples collected from the subjects were compared. The patients genotyped as TT presented the lowest survival rate, while patients genotyped as CC presented the highest survival rate. TLR2 mRNA was identified as a potential target of miR‑143, while IL‑16 showed no direct interaction with miR‑143. The above regulatory relationships were further investigated using cells transfected with miR‑143 precursor or TLR2 small interfering RNA. In addition, the expression levels of inflammatory factors, such as tumor necrosis factor α, interferon, IL‑6, IL‑10 and NF‑L‑6, were highest in the CSF/serum samples collected from patients genotyped as TT and lowest in patients genotyped as CC. By contrast, the expression levels of miR‑143 showed an opposite trend in the expression of the above inflammatory factors. The rs41291957 SNP, located in the promoter region of miR‑143, reduced the expression of miR‑143 and upregulated the expression of the pro‑inflammatory factor TLR2, eventually leading to a poorer prognosis in patients with ICH.

Extracellular HMGB1 blockade inhibits tumor growth through profoundly remodeling immune microenvironment and enhances checkpoint inhibitor-based immunotherapy

BACKGROUND

High-mobility group box 1 (HMGB1) is a multifunctional redox-sensitive protein involved in various intracellular (eg, chromatin remodeling, transcription, autophagy) and extracellular (inflammation, autoimmunity) processes. Regarding its role in cancer development/progression, paradoxical results exist in the literature and it is still unclear whether HMGB1 mainly acts as an oncogene or a tumor suppressor.

METHODS

HMGB1 expression was first assessed in tissue specimens (n=359) of invasive breast, lung and cervical cancer and the two distinct staining patterns detected (nuclear vs cytoplasmic) were correlated to the secretion profile of malignant cells, patient outcomes and the presence of infiltrating immune cells within tumor microenvironment. Using several orthotopic, syngeneic mouse models of basal-like breast (4T1, 67NR and EpRas) or non-small cell lung (TC-1) cancer, the efficacy of several HMGB1 inhibitors alone and in combination with immune checkpoint blockade antibodies (anti-PD-1/PD-L1) was then investigated. Isolated from retrieved tumors, 14 immune cell (sub)populations as well as the activation status of antigen-presenting cells were extensively analyzed in each condition. Finally, the redox state of HMGB1 in tumor-extruded fluids and the influence of different forms (oxidized, reduced or disulfide) on both dendritic cell (DC) and plasmacytoid DC (pDC) activation were determined.

RESULTS

Associated with an unfavorable prognosis in human patients, we clearly demonstrated that targeting extracellular HMGB1 elicits a profound remodeling of tumor immune microenvironment for efficient cancer therapy. Indeed, without affecting the global number of (CD45+) immune cells, drastic reductions of monocytic/granulocytic myeloid-derived suppressor cells (MDSC) and regulatory T lymphocytes, a higher M1/M2 ratio of macrophages as well as an increased activation of both DC and pDC were continually observed following HMGB1 inhibition. Moreover, blocking HMGB1 improved the efficacy of anti-PD-1 cancer monoimmunotherapy. We also reported that a significant fraction of HMGB1 encountered within cancer microenvironment (interstitial fluids) is oxidized and, in opposite to its reduced isoform, oxidized HMGB1 acts as a tolerogenic signal in a receptor for advanced glycation endproducts-dependent manner.

CONCLUSION

Collectively, we present evidence that extracellular HMGB1 blockade may complement first-generation cancer immunotherapies by remobilizing antitumor immune response.

Multiple Disruptions of Glial-Neuronal Networks in Epileptogenesis That Follows Prolonged Febrile Seizures

Background and Rationale: Bi-directional neuronal-glial communication is a critical mediator of normal brain function and is disrupted in the epileptic brain. The potential role of aberrant microglia and astrocyte function during epileptogenesis is important because the mediators involved provide tangible targets for intervention and prevention of epilepsy. Glial activation is intrinsically involved in the generation of childhood febrile seizures (FS), and prolonged FS (febrile status epilepticus, FSE) antecede a proportion of adult temporal lobe epilepsy (TLE). Because TLE is often refractory to treatment and accompanied by significant memory and emotional difficulties, we probed the role of disruptions of glial-neuronal networks in the epileptogenesis that follows experimental FSE (eFSE).

Methods: We performed a multi-pronged examination of neuronal-glia communication and the resulting activation of molecular signaling cascades in these cell types following eFSE in immature mice and rats. Specifically, we examined pathways involving cytokines, microRNAs, high mobility group B-1 (HMGB1) and the prostaglandin E2 signaling. We aimed to block epileptogenesis using network-specific interventions as well as via a global anti-inflammatory approach using dexamethasone.

Results: (A) eFSE elicited a strong inflammatory response with rapid and sustained upregulation of pro-inflammatory cytokines. (B) Within minutes of the end of the eFSE, HMGB1 translocated from neuronal nuclei to dendrites, en route to the extracellular space and glial Toll-like receptors. Administration of an HMGB1 blocker to eFSE rat pups did not decrease expression of downstream inflammatory cascades and led to unacceptable side effects. (C) Prolonged seizure-like activity caused overall microRNA-124 (miR-124) levels to plunge in hippocampus and release of this microRNA from neurons via extra-cellular vesicles. (D) Within hours of eFSE, structural astrocyte and microglia activation was associated not only with cytokine production, but also with activation of the PGE₂ cascade. However, administration of TG6-10-1, a blocker of the PGE₂ receptor EP2 had little effect on spike-series provoked by eFSE. (E) In contrast to the failure of selective interventions, a 3-day treatment of eFSE–experiencing rat pups with the broad anti-inflammatory drug dexamethasone attenuated eFSE-provoked pro-epileptogenic EEG changes.

Conclusions: eFSE, a provoker of TLE-like epilepsy in rodents leads to multiple and rapid disruptions of interconnected glial-neuronal networks, with a likely important role in epileptogenesis. The intricate, cell-specific and homeostatic interplays among these networks constitute a serious challenge to effective selective interventions that aim to prevent epilepsy. In contrast, a broad suppression of glial-neuronal dysfunction holds promise for mitigating FSE-induced hyperexcitability and epileptogenesis in experimental models and in humans.

Progesterone and vitamin D downregulate the activation of the NLRP1/NLRP3 inflammasomes and TLR4-MyD88-NF-κB pathway in monocytes from pregnant women with preeclampsia

This study evaluated the in vitro modulatory effect of progesterone (PG) and vitamin D (VD) on NLRP1/NLRP3 inflammasomes and TLR4/NF-κB pathway in monocytes from pregnant women with preeclampsia (PE). Monocytes from 20 preeclamptic and 20 normotensive (NT) pregnant women, and THP-1 cells were cultured with/without hyaluronan (HA), PG, or VD to determine gene and protein expression of TLR4 receptor, phosphorylated NF-κB, IκBα, TLR4, MYD88, NF-κB, NLRP1, NLRP3, caspase-1, IL-1β, IL-18, TNF-α, and IL-10. Higher endogenous activation of inflammatory genes and higher protein expression of TLR4 and NF-κB was detected in monocytes of PE group and decreased after PG or VD treatment. Monocyte from PE stimulated with HA increased while treatment with PG or VD decreased the expression of genes and proteins related to the inflammasomes. THP-1 cells showed a similar immune response profile as monocytes from PE. These results demonstrate that PG and VD play an immunomodulatory role in monocyte activation.

SARS-CoV-2 spike protein S1 subunit induces pro-inflammatory responses via toll-like receptor 4 signaling in murine and human macrophages

Coronavirus disease 2019 (COVID-19), an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has now spread globally. Some patients develop severe complications including multiple organ failure. It has been suggested that excessive inflammation associated with the disease plays major role in the severity and mortality of COVID-19. To elucidate the inflammatory mechanisms involved in COVID-19, we examined the effects of SARS-CoV-2 spike protein S1 subunit (hereafter S1) on the pro-inflammatory responses in murine and human macrophages. Murine peritoneal exudate macrophages produced pro-inflammatory mediators in response to S1 exposure. Exposure to S1 also activated nuclear factor-κB (NF-κB) and c-Jun N-terminal kinase (JNK) signaling pathways. Pro-inflammatory cytokine induction by S1 was suppressed by selective inhibitors of NF-κB and JNK pathways. Treatment of murine peritoneal exudate macrophages and human THP-1 cell-derived macrophages with a toll-like receptor 4 (TLR4) antagonist attenuated pro-inflammatory cytokine induction and the activation of intracellular signaling by S1 and lipopolysaccharide. Similar results were obtained in experiments using TLR4 siRNA-transfected murine RAW264.7 macrophages. In contrast, TLR2 neutralizing antibodies could not abrogate the S1-induced pro-inflammatory cytokine induction in either RAW264.7 or THP-1 cell-derived macrophages. These results suggest that SARS-CoV-2 spike protein S1 subunit activates TLR4 signaling to induce pro-inflammatory responses in murine and human macrophages. Therefore, TLR4 signaling in macrophages may be a potential target for regulating excessive inflammation in COVID-19 patients.

The Taming of Nuclear Factor Erythroid-2-Related Factor-2 (Nrf2) Deglycation by Fructosamine-3-Kinase (FN3K)-Inhibitors-A Novel Strategy to Combat Cancers

Simple Summary

Aim of this review is to provide an overview on (a) Fructosamine-3-Kinase (FN3K) and its role in regulating Nuclear Factor Erythorid-2-Related Factor-2 (Nrf2); (b) the role of glycation and deglycation mechanisms in modulating the functional properties of proteins, in particular, the Nrf2; (c) the dual role of Nrf2 in the prevention and treatment of cancers. Since controlling the glycation of Nrf2 is one of the key mechanisms determining the fate of a cell; whether to get transformed into a cancerous one or to stay as a normal one, it is important to regulate Nrf2 and deglycating FN3K using pharmacological agents. Inhibitors of FN3K are being explored currently to modulate Nrf2 activity thereby control the cancers.

Abstract

Glycated stress is mediated by the advanced glycation end products (AGE) and the binding of AGEs to the receptors for advanced glycation end products (RAGEs) in cancer cells. RAGEs are involved in mediating tumorigenesis of multiple cancers through the modulation of several downstream signaling cascades. Glycated stress modulates various signaling pathways that include p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor kappa–B (NF-κB), tumor necrosis factor (TNF)-α, etc., which further foster the uncontrolled proliferation, growth, metastasis, angiogenesis, drug resistance, and evasion of apoptosis in several cancers. In this review, a balanced overview on the role of glycation and deglycation in modulating several signaling cascades that are involved in the progression of cancers was discussed. Further, we have highlighted the functional role of deglycating enzyme fructosamine-3-kinase (FN3K) on Nrf2-driven cancers. The activity of FN3K is attributed to its ability to deglycate Nrf2, a master regulator of oxidative stress in cells. FN3K is a unique protein that mediates deglycation by phosphorylating basic amino acids lysine and arginine in various proteins such as Nrf2. Deglycated Nrf2 is stable and binds to small musculoaponeurotic fibrosarcoma (sMAF) proteins, thereby activating cellular antioxidant mechanisms to protect cells from oxidative stress. This cellular protection offered by Nrf2 activation, in one way, prevents the transformation of a normal cell into a cancer cell; however, in the other way, it helps a cancer cell not only to survive under hypoxic conditions but also, to stay protected from various chemo- and radio-therapeutic treatments. Therefore, the activation of Nrf2 is similar to a double-edged sword and, if not controlled properly, can lead to the development of many solid tumors. Hence, there is a need to develop novel small molecule modulators/phytochemicals that can regulate FN3K activity, thereby maintaining Nrf2 in a controlled activation state.

Role of cannabinoids in alcohol-induced neuroinflammation

Alcohol is a psychoactive substance highly used worldwide, whose harmful use might cause a broad range of mental and behavioural disorders. Underlying brain impact, the neuroinflammatory response induced by alcohol is recognised as a key contributing factor in the progression of other neuropathological processes, such as neurodegeneration. These sequels are determined by multiple factors, including age of exposure. Strikingly, it seems that the endocannabinoid system modulation could regulate the alcohol-induced neuroinflammation. Although direct CB1 activation can worsen alcohol consequences, targeting other components of the expanded endocannabinoid system may counterbalance the pro-inflammatory response. Indeed, specific modulations of the expanded endocannabinoid system have been proved to exert anti-inflammatory effects, primarily through the CB2 and PPARγ signalling. Among them, some endo- and exogeneous cannabinoids can block certain pro-inflammatory mediators, such as NF-κB, thereby neutralizing the neuroinflammatory intracellular cascades. Furthermore, a number of cannabinoids are able to activate complementary anti-inflammatory pathways, which are necessary for the transition from chronically overactivated microglia to a regenerative microglial phenotype. Thus, cannabinoid modulation provides cooperative anti-inflammatory mechanisms that may be advantageous to resolve a pathological neuroinflammation in an alcohol-dependent context.

High mobility group box 1 mediates inflammatory response of astrocytes via cyclooxygenase 2/prostaglandin E2 signaling following spinal cord injury

High mobility group box 1 (HMGB1) interacts with pattern-recognition receptors of immune cells to activate the inflammatory response. Astrocytes play a positive role in the inflammatory response of the central nervous system by expressing a broad range of pattern-recognition receptors. However, the underlying relationship between HMGB1 and the inflammatory reaction of astrocytes remains unclear. In this study, we established rat models of spinal cord injury via laminectomy at the T8–10 level, and the injured spinal cord was subjected to transcriptome sequencing. Our results showed that the HMGB1/Toll-like receptor 4 (TLR4) axis was involved in the activation of astrocyte inflammatory response through regulation of cyclooxygenase 2 (COX2)/prostaglandin E2 (PGE2) signaling. Both TLR4 and COX2 were distributed in astrocytes and showed elevated protein levels following spinal cord injury. Stimulation of primary astrocytes with recombinant HMGB1 showed that COX2 and microsomal PGE synthase (mPGES)-1, rather than COX1, mPGES-2, or cytosolic PGE synthase, were significantly upregulated. Accordingly, PGE2 production in astrocytes was remarkably increased in response to recombinant HMGB1 challenges. Pharmacologic blockade of TLR2/4 attenuated HMGB1-mediated activation of the COX2/PGE2 pathway. Interestingly, HMGB1 did not impact the production of tumor necrosis factor-α or interleukin-1β in astrocytes. Our results suggest that HMGB1 mediates the astrocyte inflammatory response through regulating the COX2/PGE2 signaling pathway. The study was approved by the Laboratory Animal Ethics Committee of Nantong University, China (approval No. 20181204-001) on December 4, 2018.

Regulation of the NLRP3 inflammasome with natural products against chemical-induced liver injury

The past decades have witnessed significant progress in understanding the process of sterile inflammation, which is dependent on a cytosolic complex termed the nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome. Activation of NLRP3 inflammasome requires two steps, including the activation of Toll-like receptor (TLR) by its ligands, resulting in transcriptional procytokine and inflammasome component activation, and the assembly and activation of NLRP3 inflammasome triggered by various danger signals, leading to caspase-1 activation, which could subsequently cleave procytokines into their active forms. Metabolic disorders, ischemia and reperfusion, viral infection and chemical insults are common pathogenic factors of liver-related diseases that usually cause tissue damage and cell death, providing numerous danger signals for the activation of NLRP3 inflammasome. Currently, natural products have attracted much attention as potential agents for the prevention and treatment of liver diseases due to their multitargets and nontoxic natures. A great number of natural products have been shown to exhibit beneficial effects on liver injury induced by various chemicals through regulating NLRP3 inflammasome pathways. In this review, the roles of the NLRP3 inflammasome in chemical-induced liver injury (CILI) and natural products that exhibit beneficial effects in CILI through the regulation of inflammasomes were systematically summarized.

Damage-Associated Molecular Patterns in Myocardial Infarction and Heart Transplantation: The Road to Translational Success

In the setting of myocardial infarction (MI), ischemia reperfusion injury (IRI) occurs due to occlusion (ischemia) and subsequent re-establishment of blood flow (reperfusion) of a coronary artery. A similar phenomenon is observed in heart transplantation (HTx) when, after cold storage, the donor heart is connected to the recipient's circulation. Although reperfusion is essential for the survival of cardiomyocytes, it paradoxically leads to additional myocardial damage in experimental MI and HTx models. Damage (or danger)-associated molecular patterns (DAMPs) are endogenous molecules released after cellular damage or stress such as myocardial IRI. DAMPs activate pattern recognition receptors (PRRs), and set in motion a complex signaling cascade resulting in the release of cytokines and a profound inflammatory reaction. This inflammatory response is thought to function as a double-edged sword. Although it enables removal of cell debris and promotes wound healing, DAMP mediated signalling can also exacerbate the inflammatory state in a disproportional matter, thereby leading to additional tissue damage. Upon MI, this leads to expansion of the infarcted area and deterioration of cardiac function in preclinical models. Eventually this culminates in adverse myocardial remodeling; a process that leads to increased myocardial fibrosis, gradual further loss of cardiomyocytes, left ventricular dilation and heart failure. Upon HTx, DAMPs aggravate ischemic damage, which results in more pronounced reperfusion injury that impacts cardiac function and increases the occurrence of primary graft dysfunction and graft rejection via cytokine release, cardiac edema, enhanced myocardial/endothelial damage and allograft fibrosis. Therapies targeting DAMPs or PRRs have predominantly been investigated in experimental models and are potentially cardioprotective. To date, however, none of these interventions have reached the clinical arena. In this review we summarize the current evidence of involvement of DAMPs and PRRs in the inflammatory response after MI and HTx. Furthermore, we will discuss various current therapeutic approaches targeting this complex interplay and provide possible reasons why clinical translation still fails.

Nuclear Alarmin Cytokines in Inflammation

Pathogen-associated molecular patterns (PAMPs) are some nonspecific and highly conserved molecular structures of exogenous specific microbial pathogens, whose products can be recognized by pattern recognition receptor (PRR) on innate immune cells and induce an inflammatory response. Under physiological stress, activated or damaged cells might release some endogenous proteins that can also bind to PRR and cause a harmful aseptic inflammatory response. These endogenous proteins were named damage-associated molecular patterns (DAMPs) or alarmins. Indeed, alarmins can also play a beneficial role in the tissue repair in certain environments. Besides, some alarmin cytokines have been reported to have both nuclear and extracellular effects. This group of proteins includes high-mobility group box-1 protein (HMGB1), interleukin (IL)-33, IL-1α, IL-1F7b, and IL-16. In this article, we review the involvement of nuclear alarmins such as HMGB1, IL-33, and IL-1α under physiological state or stress state and suggest a novel activity of these molecules as central initiators in the development of sterile inflammation.

Neurogenesis after traumatic brain injury - The complex role of HMGB1 and neuroinflammation

INTRODUCTION

Traumatic brain injury (TBI) is amongst the leading causes of morbidity and mortality worldwide. Despite evidence of neurogenesis post-TBI, survival and integration of newborn neurons remains impaired. High Mobility Group Box protein 1 (HMGB1) is an 'alarmin' released hyper-acutely following TBI and implicated in hosting the neuro-inflammatory response to injury. It is also instrumental in mediating neurogenesis under physiological conditions. Given its dual role in mediating neuro-inflammation and neurogenesis, it serves as a promising putative target for therapeutic modulation. In this review, we discuss neurogenesis post-TBI, neuro-pharmacological aspects of HMGB1, and its potential as a therapeutic target.

METHODS

PubMed database was searched with varying combinations of the following search terms: HMGB1, isoforms, neurogenesis, traumatic brain injury, Toll-like receptor (TLR), receptor for advanced glycation end-products (RAGE).

RESULTS

Several in vitro and in vivo studies demonstrate evidence of neurogenesis post-injury. The HMGB1-RAGE axis mediates neurogenesis throughout development, whilst interaction with TLR-4 promotes the innate immune response. Studies in the context of injury demonstrate that these receptor effects are not mutually exclusive. Despite recognition of different HMGB1 isoforms based on redox/acetylation status, effects on neurogenesis post-injury remain unexplored. Recent animal in vivo studies examining HMGB1 antagonism post-TBI demonstrate predominantly positive results, but specific effects on neurogenesis and longer-term outcomes remain unclear.

CONCLUSION

HMGB1 is a promising therapeutic target but its effects on neurogenesis post-TBI remains unclear. Given the failure of several pharmacological strategies to improve outcomes following TBI, accurate delineation of HMGB1 signalling pathways and effects on post-injury neurogenesis are vital.

Upregulation of HMGB1 secretion in lungs of pigs infected by highly pathogenic porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS) remains a major driver for substantial economic losses to the swine industry across the world. Pulmonary inflammatory injury is a common manifestation in infected pigs. Previous studies reported that PRRS virus (PRRSV) induces secretion of high mobility group box 1 (HMGB1), a proinflammatory factor, in cultured cells. The objective of this study was to evaluate whether HMGB1 secretion is associated with PRRSV-induced pulmonary inflammatory responses in the early stage of infection in vivo. Three-week-old piglets were inoculated with either HuN4, a highly pathogenic PRRSV (HP-PRRSV) strain, or CH1R, an avirulent PRRSV vaccine strain. Necropsy was performed at 7 days post-infection. The results showed that HuN4 significantly induced the secretion of HMGB1 and inflammatory cytokines (IL-1β, IL-6) into the bronchoalveolar lavage fluid (BALF). HuN4 infection induced severe interstitial pneumonia in the pigs. In contrast, pigs infected by CH1R had mild lung inflammation with minimal HMGB1 secretion. In addition, high viral load of HuN4 was detected in both pulmonary alveolar macrophages (PAMs) and lung tissue, whereas viral RNA of CH1R was confined to PAMs. In consistent with the pneumonia development, HuN4 induced inflammatory cytokines in both PAMs and lung tissue, while their expression in CH1R-infected pigs confined only to PAMs. These results indicate that the HuN4-induced HMGB1 secretion into BALF may enhance the pulmonary inflammatory response and exacerbate the lung injury. This finding provides insights to the inflammatory response and pathogenesis of the HP-PRRSV infection.

The role of RAGE in host pathology and crosstalk between RAGE and TLR4 in innate immune signal transduction pathways

Although the innate immune receptor protein, Receptor for Advanced Glycation End products (RAGE), has been extensively studied, there has been renewed interest in RAGE for its potential role in sepsis, along with a host of other inflammatory diseases of chronic, noninfectious origin. In contrast to other innate immune receptors, for example, Toll-like receptors (TLRs), that recognize ligands derived from pathogenic organisms that are collectively known as "pathogen-associated molecular patterns" (PAMPs) or host-derived "damage-associated molecular patterns" (DAMPs), RAGE has been shown to recognize a broad collection of DAMPs exclusively. Historically, these DAMPs have been shown to be pro-inflammatory in nature. Early studies indicated that the adaptor molecule, MyD88, might be important for this change. More recent studies have explored further the mechanisms underlying this inflammatory change. Overall, the newer results have shown that there is extensive crosstalk between RAGE and TLRs. The three canonical RAGE ligands, Advanced Glycation End products (AGEs), HMGB1, and S100 proteins, have all been shown to activate both TLRs and RAGE to varying degrees in order to induce inflammation in in vitro models. As with any field that delves deeply into innate signaling, obstacles of reagent purity may be a cause of some of the discrepancies in the literature, and we have found that commercial antibodies that have been widely used exhibit a high degree of nonspecificity. Nonetheless, the weight of published evidence has led us to speculate that RAGE may be physically interacting with TLRs on the cell surface to elicit inflammation via MyD88-dependent signaling.

Liver Ischemia Reperfusion Injury, Enhanced by Trained Immunity, Is Attenuated in Caspase 1/Caspase 11 Double Gene Knockout Mice

Ischemia reperfusion injury (IRI) during liver transplantation increases morbidity and contributes to allograft dysfunction. There are no therapeutic strategies to mitigate IRI. We examined a novel hypothesis: caspase 1 and caspase 11 serve as danger-associated molecular pattern (DAMPs) sensors in IRI. By performing microarray analysis and using caspase 1/caspase 11 double-knockout (Casp DKO) mice, we show that the canonical and non-canonical inflammasome regulators are upregulated in mouse liver IRI. Ischemic pre (IPC)- and post-conditioning (IPO) induce upregulation of the canonical and non-canonical inflammasome regulators. Trained immunity (TI) regulators are upregulated in IPC and IPO. Furthermore, caspase 1 is activated during liver IRI, and Casp DKO attenuates liver IRI. Casp DKO maintained normal liver histology via decreased DNA damage. Finally, the decreased TUNEL assay-detected DNA damage is the underlying histopathological and molecular mechanisms of attenuated liver pyroptosis and IRI. In summary, liver IRI induces the upregulation of canonical and non-canonical inflammasomes and TI enzyme pathways. Casp DKO attenuate liver IRI. Development of novel therapeutics targeting caspase 1/caspase 11 and TI may help mitigate injury secondary to IRI. Our findings have provided novel insights on the roles of caspase 1, caspase 11, and inflammasome in sensing IRI derived DAMPs and TI-promoted IRI-induced liver injury.

The rapid endocytic uptake of fetuin-A by adherent tumor cells is mediated by Toll-like receptor 4 (TLR4)

Fetuin‐A is a serum glycoprotein synthesized and secreted into blood by the liver and whose main physiological function is the inhibition of ectopic calcification. However, a number of studies have demonstrated that it is a multifunctional protein. For example, endocytic uptake of fetuin‐A by tumor cells resulting in rapid cellular adhesion and spreading has been reported. The precise uptake mechanism, however, has been elusive. The present studies were done to determine whether Toll‐like receptor‐4 (TLR4), which has been previously shown to be a receptor for fetuin‐A and is commonly expressed in immune cells, could take part in the rapid uptake (< 3 min) of fetuin‐A by tumor cells. Rapid uptake of fetuin‐A was inhibited by the specific TLR4 inhibitor CLI‐095 and also attenuated in TLR4 knockdown prostate tumor cells. Inhibition of TLR4 by CLI‐095 also attenuated the rapid adhesion of tumor cells as well as invasion through a bed of Matrigel. The data suggest mechanisms by which TLR4 modulates the adhesion and growth of tumor cells.

Time to Develop Therapeutic Antibodies Against Harmless Proteins Colluding with Sepsis Mediators?

Sepsis refers to a systemic inflammatory response syndrome resulting from microbial infections, and is partly attributable to dysregulated inflammation and associated immunosuppression. A ubiquitous nuclear protein, HMGB1, is secreted by activated leukocytes to orchestrate inflammatory responses during early stages of sepsis. When it is released by injured somatic cells at overwhelmingly higher quantities, HMGB1 may induce macrophage pyroptosis and immunosuppression, thereby impairing the host's ability to eradicate microbial infections. A number of endogenous proteins have been shown to bind HMGB1 to modulate its extracellular functions. Here, we discuss an emerging possibility to develop therapeutic antibodies against harmless proteins that collude with pathogenic mediators for the clinical management of human sepsis and other inflammatory diseases.

Toxic effects of perinatal maternal exposure to nonylphenol on lung inflammation in male offspring rats

The incidence of asthma and its related allergic diseases has increased dramatically over the last decade. Asthma is a complex disease caused by genetic and environmental factors. Nonylphenol (NP), a typical endocrine disrupting chemical (EDC), is a major current focus in asthma research. Pregnant Sprague-Dawley rats (n = 8-10 per group) were given a consecutive daily dose of NP (25, 50, or 100 mg/kg/day) or an equivalent volume of vehicle by gavage from gestational day 7 until postnatal day (PND) 21. Exposure to 100 mg/kg NP increased the body mass of the offspring on PND 43. Perinatal exposure to NP in maternal rats led to a dose-dependent increase of NP level in the lung tissue of the offspring. The numbers of lymphocytes and neutrophils in bronchoalveolar lavage fluid were significantly higher in the 100 mg/kg NP group than those in the control. Histopathological examination of the lung showed that exposure to high dose NP resulted in a slightly thickened bronchiolar smooth muscles with inflammatory cell infiltration. In the cytoplasm of type II epithelial cells, osmiophilic lamellar bodies were observed, with emptied lamellar bodies. NP significantly increased the expressions of high mobility group box 1 protein (HMGB1) mRNA and nuclear factor κB (NF-κB) mRNA in the lung tissue of the offspring in a dose dependent manner. Similarly, the expressions of HMGB1, NF-κBp65 and estrogen receptor-β (ER-β) proteins increased with an increase of NP dose. NP content was positively correlated with the expressions of HMGB1 and NF-κB mRNA as well as HMGB1, NF-κBp65, and ER-β proteins in the lung tissue of offspring. Perinatal exposure to NP from the maternal rats might induce airway inflammation in the offspring, which may be due to NP-induced infiltration of inflammatory cells into the airway, and pathological alterations in airway structure as well as abnormal expression patterns of inflammation-related genes, proteins (including HMGB1 and NF-κB) and estrogen receptor β.

Evaluation of the Biomarkers HMGB1 and IL-6 as Predictors of Mortality in Cirrhotic Patients with Acute Kidney Injury

Background

Acute kidney injury (AKI) affects from 20% to 50% of cirrhotic patients, and the one-month mortality rate is 60%. The main cause of AKI is bacterial infection, which worsens circulatory dysfunction through the release of HMGB1 and IL-6.

Objectives

To evaluate HMGB1 and IL-6 as biomarkers of morbidity/mortality.

Methods

Prospective, observational study of 25 hospitalised cirrhotic patients with AKI. Clinical and laboratory data were collected at the time of diagnosis of AKI, including serum HMGB1 and IL-6.

Results

The mean age was 55 years; 70% were male. Infections accounted for 13 cases. The 30-day and three-month mortality rates were 17.4% and 30.4%, respectively. HMGB1 levels were lower in survivors than in nonsurvivors at 30 days (1174.2 pg/mL versus 3338.5 pg/mL, p = 0.035), but not at three months (1540 pg/mL versus 2352 pg/mL, p = 0.243). Serum IL-6 levels were 43.3 pg/mL versus 153.3 pg/mL (p = 0.061) at 30 days and 35.8 pg/mL versus 87.9 pg/mL (p = 0.071) at three months, respectively. The area under the ROC curve for HMGB1 was 0.842 and 0.657, and that for IL-6 was 0.803 and 0.743 for discriminating nonsurvivors at 30 days and three months, respectively. In multivariate analysis, no biomarker was independently associated with mortality.

Conclusion

HMGB1 levels were associated with decreased survival in cirrhotics. Larger studies are needed to confirm our results.

Nutrition Regulates Innate Immunity in Health and Disease

Nutrient content and nutrient timing are considered key regulators of human health and a variety of diseases and involve complex interactions with the mucosal immune system. In particular, the innate immune system is emerging as an important signaling hub that modulates the response to nutritional signals, in part via signaling through the gut microbiota. In this review we elucidate emerging evidence that interactions between innate immunity and diet affect human metabolic health and disease, including cardiometabolic disorders, allergic diseases, autoimmune disorders, infections, and cancers. Furthermore, we discuss the potential modulatory effects of the gut microbiota on interactions between the immune system and nutrition in health and disease, namely how it relays nutritional signals to the innate immune system under specific physiological contexts. Finally, we identify key open questions and challenges to comprehensively understanding the intersection between nutrition and innate immunity and how potential nutritional, immune, and microbial therapeutics may be developed into promising future avenues of precision treatment.

Volatile Anesthetic Sevoflurane Attenuates Toll-Like Receptor 1/2 Activation

BACKGROUND

Although immunomodulatory effects of anesthetics have been increasingly recognized, their underlying molecular mechanisms are not completely understood. Toll-like receptors (TLRs) are one of the major receptors to recognize invading pathogens and danger signals from damaged host tissues to initiate immune responses. Among the TLR family, TLR2 and TLR4 recognize a wide range of ligands and are considered to be important players in perioperative pathophysiology. Based on our recent finding that volatile anesthetics modulate TLR4 function, we tested our hypothesis that they would also modulate TLR2 function.

METHODS

The effect of anesthetics isoflurane, sevoflurane, propofol, and dexmedetomidine on TLR2 activation was examined by reporter assays. An anesthetic that affected the activation was subjected to in silico rigid docking simulation on TLR2. To test our prediction that sevoflurane and a TLR1/TLR2 ligand Pam3CSK4 would compete for the same pocket of TLR2, we performed Pam3CSK4 competitive binding assay to TLR2 using HEK cells stably transfected with TLR2 (HEK-TLR2) with or without sevoflurane. We examined the effect of different anesthetics on the functions of human neutrophils stimulated with TLR2 ligands. Kruskal-Wallis test and Mann-Whitney U test were used for statistical analysis.

RESULTS

We observed that the attenuation of TLR1/TLR2 activation was seen on sevoflurane exposure but not on isoflurane, propofol, or dexmedetomidine exposure. The attenuation of TLR2/TLR6 activation was not seen in any of the anesthetics tested. The rigid docking simulation predicted that sevoflurane and Pam3CSK4 bound to the same pocket of TLR1/TLR2 complex. The binding of Pam3CSK4 to HEK-TLR2 cells was impaired in the presence of sevoflurane, indicating that sevoflurane and Pam3CSK4 competed for the pocket, as predicted in silico. The stimulation of neutrophils with Pam3CSK4 induced L-selection shedding but did not affect phagocytosis and reactive oxygen species production. L-selectin shedding from neutrophils was attenuated only by sevoflurane, consistent with the result of our reporter assays.

CONCLUSIONS

We found that TLR1/TLR2 activation was attenuated by sevoflurane, but we found no evidence for attenuation by isoflurane, propofol, or dexmedetomidine at clinically relevant concentrations. Our structural analysis and competition assay supported that sevoflurane directly bound to TLR2 at the interphase of the TLR1/TLR2 complex. Sevoflurane attenuated neutrophil L-selectin shedding, an important step for neutrophil migration.

Frontline Science: Anthrax lethal toxin-induced, NLRP1-mediated IL-1β release is a neutrophil and PAD4-dependent event

Anthrax lethal toxin (LT) is a protease that activates the NLRP1b inflammasome sensor in certain rodent strains. Unlike better-studied sensors, relatively little is known about the priming requirements for NLRP1b. In this study, we investigate the rapid and striking priming-independent LT-induced release of IL-1β in mice within hours of toxin challenge. We find IL-1β release to be a NLRP1b- and caspase-1-dependent, NLRP3 and caspase-11-independent event that requires both neutrophils and peptidyl arginine deiminiase-4 (PAD4) activity. The simultaneous LT-induced IL-18 response is neutrophil-independent. Bone marrow reconstitution experiments in mice show toxin-induced IL-1β originates from hematopoietic cells. LT treatment of neutrophils in vitro did not induce IL-1β, neutrophil extracellular traps (NETs), or pyroptosis. Although platelets interact closely with neutrophils and are also a potential source of IL-1β, they were unable to bind or endocytose LT and did not secrete IL-1β in response to the toxin. LT-treated mice had higher levels of cell-free DNA and HMGB1 in circulation than PBS-treated controls, and treatment of mice with recombinant DNase reduced the neutrophil- and NLRP1-dependent IL-1β release. DNA sensor AIM2 deficiency, however, did not impact IL-1β release. These data, in combination with the findings on PAD4, suggest a possible role for in vivo NETs or cell-free DNA in cytokine induction in response to LT challenge. Our findings suggest a complex interaction of events and/or mediators in LT-treated mice with the neutrophil as a central player in induction of a profound and rapid inflammatory response to toxin.