Identification of CD163 as an antiinflammatory receptor for HMGB1-haptoglobin complexes

CD163+ macrophages attenuate pressure overload-induced left ventricular systolic dysfunction and cardiac mitochondrial dysfunction via interleukin-10

Macrophage depletion exacerbates pressure overload-induced heart failure, but therapeutic translation is hindered by macrophage subset heterogeneity. The functional role of CD163+ macrophages in heart failure remains unclear. Transverse aortic constriction (TAC) was employed to induce pressure overload. Cd163-/- mice exhibited significantly aggravated TAC-induced left ventricular systolic dysfunction, as demonstrated by reduced ejection fraction, fractional shortening, and global longitudinal strain, compared to wild-type (WT) controls. RNA sequencing of cardiac tissues revealed significant differential gene expression between TAC-treated WT and Cd163-/- mice, especially in pathways governing mitochondrial bioenergetics and homeostasis. Transmission electron microscopy confirmed greater accumulation of dysfunctional mitochondria in cardiomyocytes of Cd163-/- mice relative to WT following TAC. Additionally, the proportion of CD163+ macrophages among cardiac macrophages increased post-TAC. Serum IL-10 levels and cardiac macrophage IL-10 expression were significantly diminished in Cd163-/- mice compared to WT after TAC. IL-10 supplementation effectively reversed the TAC-induced impairment in left ventricular systolic function in both WT and Cd163-/- mice, and reduced NADH/NAD+ ratios, reduced mitochondrial dysfunction, and improved mitochondrial membrane potential in Cd163-/- mice. Cross-sectional clinical data supported these findings, showing decreased IL-10 levels as a significant risk factor for heart failure in hypertensive patients (odds ratio: 0.397; 95% CI 0.203-0.775; p = 0.007). Collectively, these results highlight the protective role of CD163+ macrophages against pressure overload-induced left ventricular dysfunction and mitochondrial dysfunction through IL-10-dependent pathways.

Cell type mapping reveals tissue niches and interactions in subcortical multiple sclerosis lesions

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system. Inflammation is gradually compartmentalized and restricted to specific tissue niches such as the lesion rim. However, the precise cell type composition of such niches, their interactions and changes between chronic active and inactive stages are incompletely understood. We used single-nucleus and spatial transcriptomics from subcortical MS and corresponding control tissues to map cell types and associated pathways to lesion and nonlesion areas. We identified niches such as perivascular spaces, the inflamed lesion rim or the lesion core that are associated with the glial scar and a cilia-forming astrocyte subtype. Focusing on the inflamed rim of chronic active lesions, we uncovered cell-cell communication events between myeloid, endothelial and glial cell types. Our results provide insight into the cellular composition, multicellular programs and intercellular communication in tissue niches along the conversion from a homeostatic to a dysfunctional state underlying lesion progression in MS.

Proteome profiling, biochemical and histological analysis of diclofenac-induced liver toxicity in Yersinia enterocolitica and Lactobacillus fermentum fed rat model: a comparative analysis

Diclofenac is a hepatotoxic non-steroidal anti-inflammatory drug (NSAID) that affects liver histology and its protein expression levels. Here, we studied the effect of diclofenac on rat liver when co-administrated with either Yersinia enterocolitica strain 8081 serotype O:8 biovar 1B (D*Y) or Lactobacillus fermentum strain 9338 (D*L). Spectroscopic analysis of stool samples showed biotransformation of diclofenac. When compared with each other, D*Y rats lack peaks at 1709 and 1198 cm-1, while D*L rats lack peaks at 1411 cm-1. However, when compared to control, both groups lack peaks at 1379 and 1170 cm-1. Assessment of serum biomarkers of hepatotoxicity indicated significantly altered activities of AST (D*Y: 185.65 ± 8.575 vs Control: 61.9 ± 2.607, D*L: 247.5 ± 5.717 vs Control: 61.9 ± 2.607), ALT (D*Y: 229.8 ± 6.920 vs Control: 70.7 ± 3.109, D*L: 123.75 ± 6.068 vs Control: 70.7 ± 3.109), and ALP (D*Y: 276.4 ± 18.154 vs Control: 320.6 ± 9.829, D*L: 298.5 ± 12.336 vs Control: 320.6 ± 9.829) in IU/L. The analysis of histological alterations showed hepatic sinusoidal dilation with vein congestion and cell infiltration exclusively in D*Y rats along with other histological changes that are common to both test groups, thereby suggesting more pronounced alterations in D*Y rats. Further, LC-MS/MS based label-free quantitation of proteins from liver tissues revealed 74.75% up-regulated, 25.25% down-regulated in D*Y rats and 51.16% up-regulated, 48.84% down-regulated in D*L experiments. The proteomics-identified proteins majorly belonged to metabolism, apoptosis, stress response and redox homeostasis, and detoxification and antioxidant defence that demonstrated the potential damage of rat liver, more pronounced in D*Y rats. Altogether the results are in favor that the administration of lactobacilli somewhat protected the rat hepatic cells against the diclofenac-induced toxicity.

Wilson's Disease-Crossroads of Genetics, Inflammation and Immunity/Autoimmunity: Clinical and Molecular Issues

Wilson's disease (WD) is a rare, autosomal recessive disorder of copper metabolism caused by pathogenic mutations in the ATP7B gene. Cellular copper overload is associated with impaired iron metabolism. Oxidative stress, cuproptosis, and ferroptosis are involved in cell death in WD. The clinical picture of WD is variable. Hepatic/neuropsychiatric/other symptoms may manifest in childhood/adulthood and even old age. It has been shown that phenotypic variability may be determined by the type of ATP7B genetic variants as well as the influence of various genetic/epigenetic, environmental, and lifestyle modifiers. In 1976, immunological abnormalities were first described in patients with WD. These included an increase in IgG and IgM levels and a decrease in the percentage of T lymphocytes, as well as a weakening of their bactericidal effect. Over the following years, it was shown that there is a bidirectional relationship between copper and inflammation. Changes in serum cytokine concentrations and the relationship between cytokine gene variants and the clinical course of the disease have been described in WD patients, as well as in animal models of this disease. Data have also been published on the occurrence of antinuclear antibodies (ANAs), antineutrophil cytoplasmic antibodies (ANCAs), anti-muscle-specific tyrosine kinase antibodies, and anti-acetylcholine receptor antibodies, as well as various autoimmune diseases, including systemic lupus erythematosus (SLE), myasthenic syndrome, ulcerative colitis, multiple sclerosis (MS), polyarthritis, and psoriasis after treatment with d-penicillamine (DPA). The occurrence of autoantibodies was also described, the presence of which was not related to the type of treatment or the form of the disease (hepatic vs. neuropsychiatric). The mechanisms responsible for the occurrence of autoantibodies in patients with WD are not known. It has also not been clarified whether they have clinical significance. In some patients, WD was differentiated or coexisted with an autoimmune disease, including autoimmune hepatitis or multiple sclerosis. Various molecular mechanisms may be responsible for immunological abnormalities and/or the inflammatory processes in WD. Their better understanding may be important for explaining the reasons for the diversity of symptoms and the varied course and response to therapy, as well as for the development of new treatment regimens for WD.

Quantitative proteomic analysis and replacement therapy identifies haptoglobin as a therapeutic target in a murine model of SLE-associated diffuse alveolar hemorrhage

Background

Diffuse alveolar hemorrhage (DAH) is a catastrophic clinical syndrome and one of the manifestations of pulmonary involvement in systemic lupus erythematosus (SLE), which is characterized by hemoptysis, diffuse pulmonary infiltrates, and respiratory failure. However, the treatment options for DAH remain limited, and DAH-related studies are needed to explore more effective therapeutic directions for better disease management and improved prognosis.

Methods

This study utilized the pristane-induced DAH murine model to mimic the pathological process of DAH in patients with SLE. Proteomic analysis was conducted to detect differentially expressed proteins (DEPs) in the plasma of surviving and non-surviving mice, followed by an analysis of biological functions and pathways. The most significant DEP was then confirmed in the plasma of SLE patients with or without DAH and DAH murine model with or without fatal outcomes. Finally, the therapeutic value of haptoglobin (Hp) replacement was validated in a DAH murine model through lung histopathology, RT-qPCR, and survival analysis.

Results

This study identified 178 DEPs, with 118 upregulated and 60 downregulated DEPs in the non-survival group. Within a set of notable Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, complement and coagulation cascades emerged as the most prominent pathway associated with the process of DAH. Later, the most significant DEP, haptoglobin (Hp), was confirmed to exhibit a significant decrease in the plasma of individuals with SLE-DAH and DAH murine model with poor outcomes by the ELISA test. Finally, compared with the control group, the severity of DAH in the Hp treatment group was alleviated significantly, as manifested by the decreased levels of pro-inflammatory cytokines (IL-6 and TNF-α), increased levels of anti-inflammatory cytokines (IL-10 and TGF-β), and decreased mortality.

Conclusion

A reduction in plasma Hp levels was observed in SLE-DAH, and the replacement therapy with Hp could alleviate pulmonary hemorrhage and reduce mortality in DAH mice. This study identified Hp as a potential biomarker for its clinical diagnosis and a direction for treatment.

Hemoglobin scavenger receptor CD163 as a potential biomarker of hemolysis-induced hepatobiliary injury in sickle cell disease

Sickle cell disease (SCD)-associated chronic hemolysis promotes oxidative stress, inflammation, and thrombosis leading to organ damage, including liver damage. Hemoglobin scavenger receptor CD163 plays a protective role in SCD by scavenging both hemoglobin-haptoglobin complexes and cell-free hemoglobin. A limited number of studies in the past have shown a positive correlation of CD163 expression with poor disease outcomes in patients with SCD. However, the role and regulation of CD163 in SCD-related hepatobiliary injury have not been fully elucidated yet. Here we show that chronic liver injury in SCD patients is associated with elevated levels of hepatic membrane-bound CD163. Hemolysis and increase in hepatic heme, hemoglobin, and iron levels elevate CD163 expression in the SCD mouse liver. Mechanistically we show that heme oxygenase-1 (HO-1) positively regulates membrane-bound CD163 expression independent of nuclear factor erythroid 2-related factor 2 (NRF2) signaling in SCD liver. We further demonstrate that the interaction between CD163 and HO-1 is not dependent on CD163-hemoglobin binding. These findings indicate that CD163 is a potential biomarker of SCD-associated hepatobiliary injury. Understanding the role of HO-1 in membrane-bound CD163 regulation may help identify novel therapeutic targets for hemolysis-induced chronic liver injury.

ISL1-overexpressing BMSCs attenuate renal ischemia-reperfusion injury by suppressing apoptosis and oxidative stress through the paracrine action

Ischemia-reperfusion injury (IRI) is a major event in renal transplantation, leading to adverse outcomes. Bone marrow mesenchymal stem cells (BMSCs) are novel promising therapeutics for repairing kidney injuries. The therapeutic efficacy of BMSCs with ISL1 overexpression in renal IRI and its underlying mechanism need to be investigated. The unilateral renal IRI rat model was established to mimic clinical acute kidney injury. Rats were injected with PBS, BMSCs-Scrambled or BMSCs-ISL1 via the tail vein at the timepoint of reperfusion, and then sacrificed after 24 h of reperfusion. The administration of BMSCs-ISL1 significantly improved renal function, inhibited tubular cells apoptosis, inflammation, oxidative stress in rats. In vitro, HKC cells subjected to H2O2 stimulation were pretreated with the conditioned medium (CM) of BMSCs-Scrambled or BMSCs-ISL1. The pretreatment of ISL1-CM attenuated apoptosis and oxidative stress induced by H2O2 in HKC cells. Our proteomic data suggested that haptoglobin (Hp) was one of the secretory proteins in ISL1-CM. Subsequent experiments confirmed that Hp was the important paracrine factor from BMSCs-ISL1 that exerted anti-apoptotic and antioxidant functions. Mechanistically, Hp played a cytoprotective role via the inhibition of ERK signaling pathway, which could be abrogated by Ro 67-7476, the ERK phosphorylation agonist. The results suggested that paracrine action may be the main mechanism for BMSCs-ISL1 to exert protective effects. As an important anti-apoptotic and antioxidant factor in ISL1-CM, Hp may serve as a new therapeutic agent for treating IRI, providing new insights for overcoming the long-term adverse effects of stem cell therapy.

Inflammatory liver diseases and susceptibility to sepsis

Patients with inflammatory liver diseases, particularly alcohol-associated liver disease and metabolic dysfunction-associated fatty liver disease (MAFLD), have higher incidence of infections and mortality rate due to sepsis. The current focus in the development of drugs for MAFLD is the resolution of non-alcoholic steatohepatitis and prevention of progression to cirrhosis. In patients with cirrhosis or alcoholic hepatitis, sepsis is a major cause of death. As the metabolic center and a key immune tissue, liver is the guardian, modifier, and target of sepsis. Septic patients with liver dysfunction have the highest mortality rate compared with other organ dysfunctions. In addition to maintaining metabolic homeostasis, the liver produces and secretes hepatokines and acute phase proteins (APPs) essential in tissue protection, immunomodulation, and coagulation. Inflammatory liver diseases cause profound metabolic disorder and impairment of energy metabolism, liver regeneration, and production/secretion of APPs and hepatokines. Herein, the author reviews the roles of (1) disorders in the metabolism of glucose, fatty acids, ketone bodies, and amino acids as well as the clearance of ammonia and lactate in the pathogenesis of inflammatory liver diseases and sepsis; (2) cytokines/chemokines in inflammatory liver diseases and sepsis; (3) APPs and hepatokines in the protection against tissue injury and infections; and (4) major nuclear receptors/signaling pathways underlying the metabolic disorders and tissue injuries as well as the major drug targets for inflammatory liver diseases and sepsis. Approaches that focus on the liver dysfunction and regeneration will not only treat inflammatory liver diseases but also prevent the development of severe infections and sepsis.

CD163 protein inhibits lipopolysaccharide-induced macrophage transformation from M2 to M1 involved in disruption of the TWEAK-Fn14 interaction

Macrophages play a crucial role in regulating inflammation and innate immune responses, and their polarization into distinct phenotypes, such as M1 and M2, is involved in various diseases. However, the specific role of CD163, a scavenger receptor expressed by macrophages, in the transformation of M2 to M1 macrophages remains unclear. Here, dexamethasone-induced M2 macrophages were treated with lipopolysaccharide (LPS) to induce the transformation of M2 to M1 macrophages. We found that treatment with lipopolysaccharide (LPS) induced the transformation of M2-like macrophages to an M1-like phenotype, as evidenced by increased mRNA levels of Il1b and Tnf, decreased mRNA levels of Cd206 and Il10, and increased TNF-α secretion. Knockdown of CD163 enhanced the phenotypic features of M1 macrophages, while treatment with recombinant CD163 protein (rmCD163) inhibited the LPS-induced M2-to-M1 transformation. Furthermore, LPS stimulation resulted in the activation of P38, ERK, JNK, and NF-κB P65 signaling pathways, and this activation was increased after CD163 knockdown and suppressed after rmCD163 treatment during macrophage transformation. Additionally, we observed that LPS treatment reduced the expression of CD163 in dexamethasone-induced M2 macrophages, leading to a decrease in the CD163-TWEAK complex and an increase in the interaction between TWEAK and Fn14. Overall, our findings suggest that rmCD163 can inhibit the LPS-induced transformation of M2 macrophages to M1 by disrupting the TWEAK-Fn14 interaction and modulating the MAPK-NF-κB pathway.

The multifunctional protein HMGB1: 50 years of discovery

Fifty years since the initial discovery of HMGB1 in 1973 as a structural protein of chromatin, HMGB1 is now known to regulate diverse biological processes depending on its subcellular or extracellular localization. These functions include promoting DNA damage repair in the nucleus, sensing nucleic acids and inducing innate immune responses and autophagy in the cytosol and binding protein partners in the extracellular environment and stimulating immunoreceptors. In addition, HMGB1 is a broad sensor of cellular stress that balances cell death and survival responses essential for cellular homeostasis and tissue maintenance. HMGB1 is also an important mediator secreted by immune cells that is involved in a range of pathological conditions, including infectious diseases, ischaemia-reperfusion injury, autoimmunity, cardiovascular and neurodegenerative diseases, metabolic disorders and cancer. In this Review, we discuss the signalling mechanisms, cellular functions and clinical relevance of HMGB1 and describe strategies to modify its release and biological activities in the setting of various diseases.

Porcine Macrophage Markers and Populations: An Update

Besides its importance as a livestock species, pig is increasingly being used as an animal model for biomedical research. Macrophages play critical roles in immunity to pathogens, tissue development, homeostasis and tissue repair. These cells are also primary targets for replication of viruses such as African swine fever virus, classical swine fever virus, and porcine respiratory and reproductive syndrome virus, which can cause huge economic losses to the pig industry. In this article, we review the current status of knowledge on porcine macrophages, starting by reviewing the markers available for their phenotypical characterization and following with the characteristics of the main macrophage populations described in different organs, as well as the effect of polarization conditions on their phenotype and function. We will also review available cell lines suitable for studies on the biology of porcine macrophages and their interaction with pathogens.

Single-cell transcriptomics reveal a hyperacute cytokine and immune checkpoint axis after cardiac arrest in patients with poor neurological outcome

BACKGROUND

Most patients hospitalized after cardiac arrest (CA) die because of neurological injury. The systemic inflammatory response after CA is associated with neurological injury and mortality but remains poorly defined.

METHODS

We determine the innate immune network induced by clinical CA at single-cell resolution.

FINDINGS

Immune cell states diverge as early as 6 h post-CA between patients with good or poor neurological outcomes 30 days after CA. Nectin-2+ monocyte and Tim-3+ natural killer (NK) cell subpopulations are associated with poor outcomes, and interactome analysis highlights their crosstalk via cytokines and immune checkpoints. Ex vivo studies of peripheral blood cells from CA patients demonstrate that immune checkpoints are a compensatory mechanism against inflammation after CA. Interferon γ (IFNγ)/interleukin-10 (IL-10) induced Nectin-2 on monocytes; in a negative feedback loop, Nectin-2 suppresses IFNγ production by NK cells.

CONCLUSIONS

The initial hours after CA may represent a window for therapeutic intervention in the resolution of inflammation via immune checkpoints.

FUNDING

This work was supported by funding from the American Heart Association, Brigham and Women's Hospital Department of Medicine, the Evergreen Innovation Fund, and the National Institutes of Health.

A two-decade journey in identifying high mobility group box 1 (HMGB1) and procathepsin L (pCTS-L) as potential therapeutic targets for sepsis

INTRODUCTION

Microbial infections and resultant sepsis are leading causes of death in hospitals, representing approximately 20% of total deaths worldwide. Despite the difficulties in translating experimental insights into effective therapies for often heterogenous patient populations, an improved understanding of the pathogenic mechanisms underlying experimental sepsis is still urgently needed. Sepsis is partly attributable to dysregulated innate immune responses manifested by hyperinflammation and immunosuppression at different stages of microbial infections.

AREAS COVERED

Here we review our recent progress in searching for late-acting mediators of experimental sepsis and propose high mobility group box 1 (HMGB1) and procathepsin-L (pCTS-L) as potential therapeutic targets for improving outcomes of lethal sepsis and other infectious diseases.

EXPERT OPINION

It will be important to evaluate the efficacy of HMGB1- or pCTS-L-targeting agents for the clinical management of human sepsis and other infectious diseases in future studies.

UVA1 radiation attenuates pro-inflammatory functions in human monocytes

UVA1 therapy is effective in the treatment of inflammatory and autoimmune skin diseases. The mode of action of UVA1 therapy is not completely understood and especially data on cells of the innate immune system like monocytes, which are critically involved in many inflammatory processes, are sparse. We wanted to answer the question whether UVA1 irradiation alters functional properties of human monocytes. We treated human peripheral blood monocytes in vitro with 2 J/cm² UVA1 light, incubated the cells for 48 h and examined both functional properties and alterations in the gene and protein expression profile. While UVA1 did not alter cell viability or susceptibility to apoptosis inducing agents, it decreased the capacity of monocytes for phagocytosis and to eliminate infectious agents like Leishmania major. Moreover, we measured a significantly reduced production of interleukin (IL)-1β mRNA in lipopolysaccharide activated monocytes after UVA1 treatment. Importantly, UVA1-treated monocytes not only produce less IL-1β, but also upregulate expression of the anti-inflammatory IL-1β decoy receptor. Our data provide evidence that UVA1 radiation not only interferes with fundamental monocyte properties like phagocytosis, pathogen killing and activation, but could also specifically attenuate pro-inflammatory IL-1 effects. This might constitute a hitherto unknown anti-inflammatory mechanism of UVA1 in human monocytes.

In Schizophrenia, Chronic Fatigue Syndrome- and Fibromyalgia-Like Symptoms are Driven by Breakdown of the Paracellular Pathway with Increased Zonulin and Immune Activation-Associated Neurotoxicity

BACKGROUND

A meaningful part of schizophrenia patients suffer from physiosomatic symptoms (formerly named psychosomatic), which are reminiscent of chronic fatigue syndrome and fibromyalgia (FF) and are associated with signs of immune activation and increased levels of tryptophan catabolites (TRYCATs).

AIMS

The study aims to examine whether FF symptoms in schizophrenia are associated with the breakdown of the paracellular pathway, zonulin, lowered natural IgM responses to oxidative specific epitopes (OSEs); and whether FF symptoms belong to the behavioral-cognitive-physical-psychosocial- (BCPS)-worsening index consisting of indices of a general cognitive decline (G-CoDe), symptomatome of schizophrenia, and quality of life (QoL)-phenomenome.

METHODS

FF symptoms were assessed using the Fibromyalgia and Chronic Fatigue Rating scale in 80 schizophrenia patients and 40 healthy controls and serum cytokines/chemokines, IgA levels to TRYCATs, IgM to OSEs, zonulin and transcellular/paracellular (TRANS/PARA) molecules were assayed using ELISA methods.

RESULTS

A large part (42.3%) of the variance in the total FF score was explained by the regression on the PARA/TRANS ratio, pro-inflammatory cytokines, IgM to zonulin, IgA to TRYCATs (all positively), and IgM to OSEs (inversely). There were highly significant correlations between the total FF score and G-CoDe, symtopmatome, QoL phenomenome, and BCPS-worsening score. FF symptoms belong to a common core shared by G-CoDe, symtopmatome, and QoL phenomenome.

CONCLUSION

The physio-somatic symptoms of schizophrenia are driven by various pathways, including increased zonulin, breakdown of the paracellular tight-junctions pathway, immune activation with induction of the TRYCAT pathway, and consequent neurotoxicity. It is concluded that FF symptoms are part of the phenome of schizophrenia and BCPS-worsening as well.

Treatment of Marmoset Intracerebral Hemorrhage with Humanized Anti-HMGB1 mAb

Intracerebral hemorrhage (ICH) is recognized as a severe clinical problem lacking effective treatment. High mobility group box-1 (HMGB1) exhibits inflammatory cytokine-like activity once released into the extracellular space from the nuclei. We previously demonstrated that intravenous injection of rat anti-HMGB1 monoclonal antibody (mAb) remarkably ameliorated brain injury in a rat ICH model. Therefore, we developed a humanized anti-HMGB1 mAb (OKY001) for clinical use. The present study examined whether and how the humanized anti-HMGB1 mAb ameliorates ICH injury in common marmosets. The results show that administration of humanized anti-HMGB1 mAb inhibited HMGB1 release from the brain into plasma, in association with a decrease of 4-hydroxynonenal (4-HNE) accumulation and a decrease in cerebral iron deposition. In addition, humanized anti-HMGB1 mAb treatment resulted in a reduction in brain injury volume at 12 d after ICH induction. Our in vitro experiment showed that recombinant HMGB1 inhibited hemoglobin uptake by macrophages through CD163 in the presence of haptoglobin, suggesting that the release of excess HMGB1 from the brain may induce a delay in hemoglobin scavenging, thereby allowing the toxic effects of hemoglobin, heme, and Fe2+ to persist. Finally, humanized anti-HMGB1 mAb reduced body weight loss and improved behavioral performance after ICH. Taken together, these results suggest that intravenous injection of humanized anti-HMGB1 mAb has potential as a novel therapeutic strategy for ICH.

Chromatin-Associated Molecular Patterns (CAMPs) in sepsis

Several molecular patterns have been identified that recognize pattern recognition receptors. Pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) are commonly used terminologies to classify molecules originating from pathogen and endogenous molecules, respectively, to heighten the immune response in sepsis. Herein, we focus on a subgroup of endogenous molecules that may be detected as foreign and similarly trigger immune signaling pathways. These chromatin-associated molecules, i.e., chromatin containing nuclear DNA and histones, extracellular RNA, mitochondrial DNA, telomeric repeat-containing RNA, DNA- or RNA-binding proteins, and extracellular traps, may be newly classified as chromatin-associated molecular patterns (CAMPs). Herein, we review the release of CAMPs from cells, their mechanism of action and downstream immune signaling pathways, and targeted therapeutic approaches to mitigate inflammation and tissue injury in inflammation and sepsis.

Reappraising host cellular factors involved in attachment and entry to develop antiviral strategies against porcine reproductive and respiratory syndrome virus

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRS virus (PRRSV), is a highly contagious disease that brings tremendous economic losses to the global swine industry. As an intracellular obligate pathogen, PRRSV infects specific host cells to complete its replication cycle. PRRSV attachment to and entry into host cells are the first steps to initiate the replication cycle and involve multiple host cellular factors. In this review, we recapitulated recent advances on host cellular factors involved in PRRSV attachment and entry, and reappraised their functions in these two stages, which will deepen the understanding of PRRSV infection and provide insights to develop promising antiviral strategies against the virus.

The Role of HMGB1 in Rheumatic Diseases

HMGB1, a highly conserved non-histone nuclear protein, is widely expressed in mammalian cells. HMGB1 in the nucleus binds to the deoxyribonucleic acid (DNA) to regulate the structure of chromosomes and maintain the transcription, replication, DNA repair, and nucleosome assembly. HMGB1 is actively or passively released into the extracellular region during cells activation or necrosis. Extracellular HMGB1 as an alarmin can initiate immune response alone or combined with other substances such as nucleic acid to participate in multiple biological processes. It has been reported that HMGB1 is involved in various inflammatory responses and autoimmunity. This review article summarizes the physiological function of HMGB1, the post-translational modification of HMGB1, its interaction with different receptors, and its recent advances in rheumatic diseases and strategies for targeted therapy.

Haptoglobin Regulates Macrophage/Microglia-Induced Inflammation and Prevents Ischemic Brain Damage Via Binding to HMGB1

Background HMGB1 (high-mobility group box 1) is known to worsen the functional prognosis after cerebral ischemia. Hp (haptoglobin) binds and sequesters HMGB1. Furthermore, Hp-HMGB1 complexes are rapidly cleared by scavenger receptors on macrophages/microglia and modulate polarization of macrophages/microglia toward the M2 phenotype. Therefore, Hp may prevent aggravation by HMGB1 after cerebral ischemia and promote tissue repair by M2 macrophages/microglia. The aim of this study was to investigate the effects of Hp on ischemic brain damage induced by a high systemic HMGB1 level in mice subjected to 4 hours of middle cerebral artery occlusion (MCAO). Methods and Results One day after MCAO, Hp was administered intraperitoneally at a dose of 20 or 200 U/kg once daily for 7 days. Neurological scores, motor coordination, and plasma HMGB1 levels were measured 1, 3, and 7 days after MCAO. Expression of M1 and M2 macrophage/microglia markers, such as CD16/32 and CD206, were evaluated by immunostaining 7 days after MCAO. Treatment with Hp for 7 days improved the neurological score, motor coordination, and survival and prevented brain damage after MCAO. The systemic HMGB1 level increased 1 to 7 days after MCAO and was higher at 7 days than at day 1. Hp significantly decreased the systemic HMGB1 level and increased the M2 phenotype when compared with the M1 phenotype after MCAO. Conclusions Hp improved functional outcomes, including survival, motor function, and brain damage by binding to HMGB1 and modulating the polarization of macrophages/microglia. Hp may be an effective option in the treatment of cerebral ischemia.

Mortality at 180-days is affected by serum haptoglobin levels in septic patients with high magnitude serum high mobility group box-1 levels

Aim

High mobility group box‐1 (HMGB1) is a lethal mediator of sepsis that binds to haptoglobin (Hp) and is associated with its prognosis. We investigated the effect of the combination of HMGB1 and Hp on sepsis prognosis.

Methods

This single‐center, retrospective study registered 78 patients with sepsis according to Sepsis‐3 criteria on day 1 of diagnosis from July 2016 to November 2018. We divided the patients into four groups according to the serum concentration of 6.2 ng/mL HMGB1 and the median value of Hp. The 180‐day mortality rates and cytokine concentrations of the low and high HMGB1 groups were compared.

Results

There was no difference in the 180‐day mortality rate between the low Hp group and the high Hp group in the low HMGB1 group (P = 0.691). In the high HMGB1 group, a statistically significant difference was found between the low Hp group and the high Hp group (P = 0.002). In the high HMGB1 group, high Hp was associated with a better prognosis in univariate analysis (odds ratio, 0.131; 95% confidence interval [CI], 0.027–0.629; P = 0.011), and multivariate analysis (adjusted odds ratio, 0.086; 95% CI, 0.013–0.582; P = 0.009). In addition, in the high HMGB1 group, interleukin‐8 levels were significantly higher in the low Hp group than in the high Hp group (P = 0.004).

Conclusion

Patients with sepsis‐induced high serum HMGB1 levels and low serum Hp levels could have a poor long‐term prognosis.

Divergent roles of haptoglobin and hemopexin deficiency for disease progression of Shiga-toxin-induced hemolytic-uremic syndrome in mice

Thrombotic microangiopathy, hemolysis and acute kidney injury are typical clinical characteristics of hemolytic-uremic syndrome (HUS), which is predominantly caused by Shiga-toxin-producing Escherichia coli. Free heme aggravates organ damage in life-threatening infections, even with a low degree of systemic hemolysis. Therefore, we hypothesized that the presence of the hemoglobin- and the heme-scavenging proteins, haptoglobin and hemopexin, respectively impacts outcome and kidney pathology in HUS. Here, we investigated the effect of haptoglobin and hemopexin deficiency (haptoglobin^-/-, hemopexin^-/-) and haptoglobin treatment in a murine model of HUS-like disease. Seven-day survival was decreased in haptoglobin^-/- (25%) compared to wild type mice (71.4%), whereas all hemopexin^-/- mice survived. Shiga-toxin-challenged hemopexin^-/- mice showed decreased kidney inflammation and attenuated thrombotic microangiopathy, indicated by reduced neutrophil recruitment and platelet deposition. These observations were associated with supranormal haptoglobin plasma levels in hemopexin^-/- mice. Low dose haptoglobin administration to Shiga-toxin-challenged wild type mice attenuated kidney platelet deposition and neutrophil recruitment, suggesting that haptoglobin at least partially contributes to the beneficial effects. Surrogate parameters of hemolysis were elevated in Shiga-toxin-challenged wild type and haptoglobin^-/- mice, while signs for hepatic hemoglobin degradation like heme oxygenase-1, ferritin and CD163 expression were only increased in Shiga-toxin-challenged wild type mice. In line with this observation, haptoglobin^-/- mice displayed tubular iron deposition as an indicator for kidney hemoglobin degradation. Thus, haptoglobin and hemopexin deficiency play divergent roles in Shiga-toxin-mediated HUS, suggesting haptoglobin is involved, and hemopexin is redundant for the resolution of HUS pathology.

Increased circulating levels of High Mobility Group Box 1 (HMGB1) in acute-phase Chikungunya virus infection: Potential disease biomarker

BACKGROUND

Chikungunya virus (CHIKV) causes a febrile syndrome with intense and debilitating arthralgia that can persist for several months or years after complete virus clearance. As there is no specific antiviral treatment or vaccine against CHIKV, identification of serological markers that help clinical management of CHIKV patients is urgent. The High Mobility Group Box 1 (HMGB1) protein is secreted to extracellular milieu and triggers an intense inflammatory process by inducing the overexpression of pro-inflammatory cytokines. HMGB1 plays an important role in several virus diseases as well as in rheumatoid arthritis.

OBJECTIVES

This study focus on the investigation of HMGB1 serum levels in a sera panel from CHIKV-infected patients in an attempt to assess its potential as a biomarker for chikungunya clinical management.

STUDY DESIGN

Eighty CHIKV-positive samples and 32 samples from healthy donors were subjected to a quantitative HMGB1 ELISA assay to assess the HMGB1 circulating levels.

RESULTS

HMGB1 levels were significantly higher in CHIKV-positive samples (516.12 ng/mL, SEM ± 48.83 ng/mL) compared to negative control (31.20 ng/mL, SEM ± 3.24 ng/mL, p < 0.0001). Circulating levels of HMGB1 persisted elevated during the whole acute-phase of disease and correlated with virus titer (p < 0.05).

CONCLUSIONS

The present study is the first to describe increased serum levels of HMGB1 in CHIKV infection and its positive correlation with virus titer, suggesting its potential use as a biomarker for diagnosis and treatment of chikungunya fever.

From Anti-SARS-CoV-2 Immune Response to the Cytokine Storm via Molecular Mimicry

The aim of this study was to investigate the role of molecular mimicry in the cytokine storms associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Human proteins endowed with anti-inflammatory activity were assembled and analyzed for peptide sharing with the SARS-CoV-2 spike glycoprotein (gp) using public databases. It was found that the SARS-CoV-2 spike gp shares numerous pentapeptides with anti-inflammatory proteins that, when altered, can lead to cytokine storms characterized by diverse disorders such as systemic multiorgan hyperinflammation, macrophage activation syndrome, ferritinemia, endothelial dysfunction, and acute respiratory syndrome. Immunologically, many shared peptides are part of experimentally validated epitopes and are also present in pathogens to which individuals may have been exposed following infections or vaccinal routes and of which the immune system has stored memory. Such an immunologic imprint might trigger powerful anamnestic secondary cross-reactive responses, thus explaining the raging of the cytokine storm that can occur following exposure to SARS-CoV-2. In conclusion, the results support molecular mimicry and the consequent cross-reactivity as a potential mechanism in SARS-CoV-2-induced cytokine storms, and highlight the role of immunological imprinting in determining high-affinity, high-avidity, autoimmune cross-reactions as a pathogenic sequela associated with anti-SARS-CoV-2 vaccines.

A search for predictive biomarkers of ovine pre-partum vaginal prolapse

Ovine pre-partum vaginal prolapse (known as bearings in sheep) occurs within a few weeks prior to lambing and unless treated both ewes and unborn lambs will die. It is a worldwide problem with no clear aetiology. Rates of prolapse in New Zealand typically vary from 0.1 to 2% per annum, varying between seasons and farms. In order to determine preclinical changes leading to prolapse, blood samples were collected prior to prolapse occurring and analysed for changes in both protein and specific hormone and vitamin levels. 650 ewes were ear tagged and blood samples were taken one month prior to the beginning of lambing; 28 of these ewes subsequently prolapsed. Using an improved proteomic method plasma samples were subjected to 2D DIGE (two dimensional differential in gel electrophoresis) to determine if there were differences between the pre-prolapse and non-prolapsing ewes. Acidic isoforms of haptoglobin, a major acute phase protein in ruminants, increased approximately 3-fold in ewes prior to prolapse occurring. Total haptoglobin quantitation was confirmed with an independent assay. Although another plasma protein, α-1B-glycoprotein, was down regulated close to prolapse, the biological significance of this is unknown. While vitamin D levels were not associated with subsequent prolapse there was, however, a negative correlation between cortisol and days to prolapse from sampling (r² = 0.36); i.e. ewes sampled closest to prolapse had higher plasma cortisol concentrations than controls. This raises the possibility that the ewes which prolapsed may have been suffering from chronic stress. Further research is needed.

Does iron overload in metabolic syndrome affect macrophage profile? A case control study

AIMS

Dysmetabolic iron overload syndrome (DIOS) is common but the clinical relevance of iron overload is not understood. Macrophages are central cells in iron homeostasis and inflammation. We hypothesized that iron overload in DIOS could affect the phenotype of monocytes and impair macrophage gene expression.

METHODS

This study compared 20 subjects with DIOS to 20 subjects with metabolic syndrome (MetS) without iron overload, and 20 healthy controls. Monocytes were phenotyped by Fluorescence-Activated Cell Sorting (FACS) and differentiated into anti-inflammatory M2 macrophages in the presence of IL-4. The expression of 38 genes related to inflammation, iron metabolism and M2 phenotype was assessed by real-time PCR.

RESULTS

FACS showed no difference between monocytes across the three groups. The macrophagic response to IL-4-driven differentiation was altered in four of the five genes of M2 phenotype (MRC1, F13A1, ABCA1, TGM2 but not FABP4), in DIOS vs Mets and controls demonstrating an impaired M2 polarization. The expression profile of inflammatory genes was not different in DIOS vs MetS. Several genes of iron metabolism presented a higher expression in DIOS vs MetS: SCL11A2 (a free iron transporter, +76 %, p = 0.04), SOD1 (an antioxidant enzyme, +27 %, p = 0.02), and TFRC (the receptor 1 of transferrin, +59 %, p = 0.003).

CONCLUSIONS

In DIOS, macrophage polarization toward the M2 alternative phenotype is impaired but not associated with a pro-inflammatory profile. The up regulation of transferrin receptor 1 (TFRC) in DIOS macrophages suggests an adaptive role that may limit iron toxicity in DIOS.

Sample Preparation Strategies for Antibody-Free Quantitative Analysis of High Mobility Group Box 1 Protein

Sickness behavior and fatigue are induced by cerebral mechanisms involving inflammatory cytokines. High mobility group box 1 (HMGB1) is an alarmin, and a potential key player in this process. Reliable quantification methods for total HMGB1 and its redox variants must be established in order to clearly understand how it functions. Current methods pose significant challenges due to interference from other plasma proteins and autoantibodies. We aimed to develop an antibody-free sample preparation method followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) to measure HMGB1 in human plasma. Different methods were applied for the removal of interfering proteins and the enrichment of HMGB1 from spiked human plasma samples. A comparison of methods showed an overall low extraction recovery (<40%), probably due to the stickiness of HMGB1. Reversed-phase liquid chromatography separation of intact proteins in diluted plasma yielded the most promising results. The method produced an even higher degree of HMGB1 purification than that observed with immunoaffinity extraction. Detection sensitivity needs to be further improved for the measurement of HMGB1 in patient samples. Nevertheless, it has been demonstrated that a versatile and fully antibody-free sample preparation method is possible, which could be of great use in further investigations.

Mechanistic insights into cell-free hemoglobin-induced injury during septic shock

Cell-free hemoglobin (CFH) levels are elevated in septic shock and are higher in nonsurvivors. Whether CFH is only a marker of sepsis severity or is involved in pathogenesis is unknown. This study aimed to investigate whether CFH worsens sepsis-associated injuries and to determine potential mechanisms of harm. Fifty-one, 10-12 kg purpose-bred beagles were randomized to receive Staphylococcus aureus intrapulmonary challenges or saline followed by CFH infusions (oxyhemoglobin >80%) or placebo. Animals received antibiotics and intensive care support for 96 h. CFH significantly increased mean pulmonary arterial pressures and right ventricular afterload in both septic and nonseptic animals, effects that were significantly greater in nonsurvivors. These findings are consistent with CFH-associated nitric oxide (NO) scavenging and were associated with significantly depressed cardiac function, and worsened shock, lactate levels, metabolic acidosis, and multiorgan failure. In septic animals only, CFH administration significantly increased mean alveolar-arterial oxygenation gradients, also to a significantly greater degree in nonsurvivors. CFH-associated iron levels were significantly suppressed in infected animals, suggesting that bacterial iron uptake worsened pneumonia. Notably, cytokine levels were similar in survivors and nonsurvivors and were not predictive of outcome. In the absence and presence of infection, CFH infusions resulted in pulmonary hypertension, cardiogenic shock, and multiorgan failure, likely through NO scavenging. In the presence of infection alone, CFH infusions worsened oxygen exchange and lung injury, presumably by supplying iron that promoted bacterial growth. CFH elevation, a known consequence of clinical septic shock, adversely impacts sepsis outcomes through more than one mechanism, and is a biologically plausible, nonantibiotic, noncytokine target for therapeutic intervention.NEW & NOTEWORTHY Cell-free hemoglobin (CFH) elevations are a known consequence of clinical sepsis. Using a two-by-two factorial design and extensive physiological and biochemical evidence, we found a direct mechanism of injury related to nitric oxide scavenging leading to pulmonary hypertension increasing right heart afterload, depressed cardiac function, worsening circulatory failure, and death, as well as an indirect mechanism related to iron toxicity. These discoveries alter conventional thinking about septic shock pathogenesis and provide novel therapeutic approaches.

Increased Urinary CD163 Levels in Systemic Vasculitis with Renal Involvement

Objectives

Systemic vasculitis includes a group of disorders characterized by inflammation of the vessel wall, involving multiple systems, and can cause malignant hypertension. CD163 is a specific marker of anti-inflammatory macrophages. This study is aimed at evaluating the CD163 levels in relation to systemic vasculitis and renal involvements.

Methods

Urinary CD163 levels were retrospectively measured by enzyme-linked immunosorbent assay (ELISA) in 51 patients with systemic vasculitis, 42 essential hypertensions, and 36 healthy volunteers. The associations between urinary CD163 levels and clinical indicators were analyzed.

Results

Urinary CD163 levels were significantly higher in patients with systemic vasculitis [68.20 (38.25~158.78) (pg/ml)] compared to essential hypertension [43.86 (23.30-60.71) (pg/ml)] (p = 0.003) and the healthy volunteers [30.76 (9.30-54.16) (pg/ml)] (p < 0.001). Furthermore, systemic vasculitis patients with renal involvement had significantly higher urinary CD163 levels relative to patients without renal involvement [86.95 (47.61 and 192.38) pg/ml] vs. [41.99 (17.70 and 71.95) pg/ml, p = 0.005]. After control factors age, sex, and BMI, urinary CD163 levels in systemic vasculitis patients were positively correlated with serum creatinine, blood urea nitrogen, and β-2 microglobulin (r = 0.45, 0.48, and 0.46; p = 0.001, 0.001, and 0.002, respectively). In addition, we found the level of urinary CD163 in granulomatous vasculitis (including TA, GPA, and EGPA) was significantly higher than that in necrotizing vasculitis (including PAN) [86.95 (41.99 and 184.82) pg/ml] vs. [45.73 (21.43 and 74.43) pg/ml, p = 0.016].

Conclusion

Urinary CD163 levels were significantly higher in patients with systemic vasculitis, especially in patients with renal involvement. Thus, urinary CD163 has the potential to be a biomarker for systemic vasculitis with renal involvement.

Progress on haptoglobin and metabolic diseases

Haptoglobin (Hp) is an acidic glycoprotein, existing in the serum and other body fluids of human beings and a variety of mammals. Hp is produced in the liver, white adipose tissue, and the kidney. The genetic polymorphisms and different phenotypes of Hp have different biological functions. Hp has antibacterial, antioxidant, and angiogenic effects and is associated with multiple diseases including simple obesity, vascular complications of diabetes mellitus, nonalcoholic fatty liver disease, hypertension, blood diseases, autoimmune diseases, and malignant tumors. Hp also participates in many life activities, indicating the importance of Hp in further studies. Previously, we found that the expression of serum Hp changed after treatment of simple obesity patients in clinical trials. However, the specific mechanism of Hp in patients with simple obesity is still unclear. The purpose of this article is to introduce recent research progress on Hp, emphasizing the relationship between Hp and the development of metabolic disease, which will improve the understanding of the functions of Hp underlying metabolic diseases and discuss future research directions.

Sialoglycan recognition is a common connection linking acidosis, zinc, and HMGB1 in sepsis

Blood pH is tightly maintained between 7.35 and 7.45, and acidosis (pH <7.3) indicates poor prognosis in sepsis, wherein lactic acid from anoxic tissues overwhelms the buffering capacity of blood. Poor sepsis prognosis is also associated with low zinc levels and the release of High mobility group box 1 (HMGB1) from activated and/or necrotic cells. HMGB1 added to whole blood at physiological pH did not bind leukocyte receptors, but lowering pH with lactic acid to mimic sepsis conditions allowed binding, implying the presence of natural inhibitor(s) preventing binding at normal pH. Testing micromolar concentrations of divalent cations showed that zinc supported the robust binding of sialylated glycoproteins with HMGB1. Further characterizing HMGB1 as a sialic acid-binding lectin, we found that optimal binding takes place at normal blood pH and is markedly reduced when pH is adjusted with lactic acid to levels found in sepsis. Glycan array studies confirmed the binding of HMGB1 to sialylated glycan sequences typically found on plasma glycoproteins, with binding again being dependent on zinc and normal blood pH. Thus, HMGB1-mediated hyperactivation of innate immunity in sepsis requires acidosis, and micromolar zinc concentrations are protective. We suggest that the potent inflammatory effects of HMGB1 are kept in check via sequestration by plasma sialoglycoproteins at physiological pH and triggered when pH and zinc levels fall in late stages of sepsis. Current clinical trials independently studying zinc supplementation, HMGB1 inhibition, or pH normalization may be more successful if these approaches are combined and perhaps supplemented by infusions of heavily sialylated molecules.

The Immune Tolerance Role of the HMGB1-RAGE Axis

The disruption of the immune tolerance induces autoimmunity such as systemic lupus erythematosus and vasculitis. A chromatin-binding non-histone protein, high mobility group box 1 (HMGB1), is released from the nucleus to the extracellular milieu in particular environments such as autoimmunity, sepsis and hypoxia. Extracellular HMGB1 engages pattern recognition receptors, including Toll-like receptors (TLRs) and the receptor for advanced glycation endproducts (RAGE). While the HMGB1-RAGE axis drives inflammation in various diseases, recent studies also focus on the anti-inflammatory effects of HMGB1 and RAGE. This review discusses current perspectives on HMGB1 and RAGE's roles in controlling inflammation and immune tolerance. We also suggest how RAGE heterodimers responding microenvironments functions in immune responses.

Spinal macrophages resolve nociceptive hypersensitivity after peripheral injury

Peripheral nerve injury induces long-term pro-inflammatory responses in spinal cord glial cells that facilitate neuropathic pain, but the identity of endogenous cells that resolve spinal inflammation has not been determined. Guided by single-cell RNA sequencing (scRNA-seq), we found that MRC1⁺ spinal cord macrophages proliferated and upregulated the anti-inflammatory mediator Cd163 in mice following superficial injury (SI; nerve intact), but this response was blunted in nerve-injured animals. Depleting spinal macrophages in SI animals promoted microgliosis and caused mechanical hypersensitivity to persist. Conversely, expressing Cd163 in spinal macrophages increased Interleukin 10 expression, attenuated micro- and astrogliosis, and enduringly alleviated mechanical and thermal hypersensitivity in nerve-injured animals. Our data indicate that MRC1⁺ spinal macrophages actively restrain glia to limit neuroinflammation and resolve mechanical pain following a superficial injury. Moreover, we show that spinal macrophages from nerve-injured animals mount a dampened anti-inflammatory response but can be therapeutically coaxed to promote long-lasting recovery of neuropathic pain.

Sex-dependent role of microglia in disulfide high mobility group box 1 protein-mediated mechanical hypersensitivity

ABSTRACT

High mobility group box 1 protein (HMGB1) is increasingly regarded as an important player in the spinal regulation of chronic pain. Although it has been reported that HMGB1 induces spinal glial activation in a Toll-like receptor (TLR)4-dependent fashion, the aspect of sexual dimorphisms has not been thoroughly addressed. Here, we examined whether the action of TLR4-activating, partially reduced disulfide HMGB1 on microglia induces nociceptive behaviors in a sex-dependent manner. We found disulfide HMGB1 to equally increase microglial Iba1 immunoreactivity in lumbar spinal dorsal horn in male and female mice, but evoke higher cytokine and chemokine expression in primary microglial culture derived from males compared to females. Interestingly, TLR4 ablation in myeloid-derived cells, which include microglia, only protected male mice from developing HMGB1-induced mechanical hypersensitivity. Spinal administration of the glial inhibitor, minocycline, with disulfide HMGB1 also prevented pain-like behavior in male mice. To further explore sex difference, we examined the global spinal protein expression using liquid chromatography-mass spectrometry and found several antinociceptive and anti-inflammatory proteins to be upregulated in only male mice subjected to minocycline. One of the proteins elevated, alpha-1-antitrypsin, partially protected males but not females from developing HMGB1-induced pain. Targeting downstream proteins of alpha-1-antitrypsin failed to produce robust sex differences in pain-like behavior, suggesting that several proteins identified by liquid chromatography-mass spectrometry are required to modulate the effects. Taken together, the current study highlights the importance of mapping sex dimorphisms in pain mechanisms and point to processes potentially involved in the spinal antinociceptive effect of microglial inhibition in male mice.

Detection of fucosylated haptoglobin using the 10-7G antibody as a biomarker for evaluating endoscopic remission in ulcerative colitis

BACKGROUND

Inflammatory bowel disease (IBD) is a chronic, relapsing inflammation of the digestive tract. Although fecal and serum biomarkers have been extremely important and supportive for monitoring of IBD, their low sensitivity and high variability characteristics limit clinical efficacy. Thus, the establishment of better biomarkers is expected. Fucosylation is one of the most important glycosylation modifications of proteins. Fucosylated haptoglobin (Fuc-Hpt) is used as a biomarker for several cancers and inflammation-related diseases. We recently established a novel glycan monoclonal antibody (mAb), designated 10-7G, which recognizes Fuc-Hpt. We developed an enzyme-linked immunosorbent assay (ELISA) to measure serum levels of Fuc-Hpt (10-7G values).

AIM

To investigate the usefulness of the serum 10-7G values as a potential biomarker for monitoring disease activity in IBD.

METHODS

This was a case control study. Intestinal tissues of IBD patients (n = 10) were examined immunohistochemically using the 10-7G mAb. We determined 10-7G values using serum from patients with ulcerative colitis (UC, n = 110), Crohn's disease (n = 45), acute enteritis (AE, n = 11), and healthy volunteers (HVs) who exhibited normal (n = 20) or high (n = 79) C-reactive protein (CRP) levels at medical check-up. We investigated the correlation between the 10-7G value and various clinical parameters of IBD patients by correlation analysis. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the usefulness of the 10-7G values as a biomarker for clinical and endoscopic remission of UC compared to conventional serum biomarkers.

RESULTS

In the immunohistochemical analysis, positive 10-7G mAb staining was observed in lymphocytes infiltrating into inflammatory sites of the mucosal layer and lymphoid follicles. The 10-7G values were significantly higher in patients with IBD (P < 0.001) and AE (P < 0.05) compared with HVs. In addition, 10-7G values were correlated with clinical examination parameters related to inflammation in patients with UC, particularly the CRP level (rs = 0.525, P = 0.003) and clinical activity index score (rs = 0.435, P = 0.038). However, there was no correlation between 10-7G values and CRP in HVs with high CRP levels, suggesting that the 10-7G values is not the same as a general inflammation biomarker. ROC curve analysis showed that area under the curve (AUC) value of 10-7G values for the diagnosis of endoscopic remission was higher than other biomarkers (AUC value = 0.699).

CONCLUSION

The serum 10-7G value is a novel biomarker for evaluating intestinal inflammation and endoscopic mucosal healing in UC.

HMGB1 as a therapeutic target in disease

High-mobility group box 1 (HMGB1) was initially recognized as a ubiquitous nuclear protein involved in maintaining the nucleosome integrity and facilitating gene transcription. HMGB1 has since been reevaluated to be a prototypical damage-associated molecular pattern (DAMP) protein, and together with its exogenous counterpart, pathogen-associated molecular pattern (PAMP), completes the body's alarmin system against disturbances in homeostasis. HMGB1 can be released into the extracellular matrix (ECM) by either granulocytes or necrotic cells to serve as a chemotaxis/cytokine during infection, endotoxemia, hypoxia, ischemia-reperfusion events, and cancer. Different isoforms of HMGB1 present with distinctive physiological functions in ECM-fully-reduced HMGB1 (all thiol) acts as the initial damage signal to recruit circulating myeloid cells, disulfide HMGB1 behaves as a cytokine to activate macrophages and neutrophils, and both signals are turned off when HMGB1 is terminally oxidized into the final sulfonate form. Targeting HMGB1 constitutes a favorable therapeutic strategy for inflammation and inflammatory diseases. Antagonists such as ethyl pyruvate inhibit HMGB1 by interfering with its cytoplasmic exportation, while others such as glycyrrhizin directly bind to HMGB1 and render it unavailable for its receptors. The fact that a mixture of different HMGB1 isoforms is present in the ECM poses a challenge in pinpointing the exact role of an individual antagonist. A more discriminative probe for HMGB1 may be necessary to advance our knowledge of HMGB1, HMGB1 antagonists, and inflammatory-related diseases.

High Mobility Group Protein 1 and Dickkopf-Related Protein 1 in Schizophrenia and Treatment-Resistant Schizophrenia: Associations With Interleukin-6, Symptom Domains, and Neurocognitive Impairments

BACKGROUND

Schizophrenia (SCZ) and treatment-resistant schizophrenia (TRS) are associated with aberrations in immune-inflammatory pathways. Increased high mobility group protein 1 (HMGB1), an inflammatory mediator, and Dickkopf-related protein (DKK1), a Wnt/β-catenin signaling antagonist, affect the blood-brain barrier and induce neurotoxic effects and neurocognitive deficits.

AIM

The present study aims to examine HMGB1 and DDK1 in nonresponders to treatments (NRTT) with antipsychotics (n = 60), partial RTT (PRTT, n = 55), and healthy controls (n = 43) in relation to established markers of SCZ, including interleukin (IL)-6, IL-10, and CCL11 (eotaxin), and to delineate whether these proteins are associated with the SCZ symptom subdomains and neurocognitive impairments.

RESULTS

HMGB1, DKK1, IL-6, and CCL11 were significantly higher in SCZ patients than in controls. DKK1 and IL-6 were significantly higher in NRTT than in PRTT and controls, while IL-10 was higher in NRTT than in controls. Binary logistic regression analysis showed that SCZ was best predicted by increased DDK1 and HMGB1, while NRTT (vs PRTT) was best predicted by increased IL-6 and CCL11 levels. A large part of the variance in psychosis, hostility, excitation, mannerism, and negative (PHEMN) symptoms and formal thought disorders was explained by HMGB1, IL-6, and CCL11, while most neurocognitive functions were predicted by HMGB1, DDK1, and CCL11.

CONCLUSIONS

The neurotoxic effects of HMGB1, DKK1, IL-6, and CCL11 including the effects on the blood-brain barrier and the Wnt/β-catenin signaling pathway may cause impairments in executive functions and working, episodic, and semantic memory and explain, in part, PHEMN symptoms and a nonresponse to treatment with antipsychotic drugs.

Exploring the therapeutic promise of targeting HMGB1 in rheumatoid arthritis

High mobility group box-1 (HMGB1) protein is a diverse, single polypeptide moiety, present in mammalian eukaryotic cells. In response to stimuli, this nuclear protein is actively secreted in to the extracellular compartment or passively released by the necrotic cells, in order to mediate inflammatory responses, by forming complexes with IL-1α, IL-1β, LPS and other moieties, and binding to RAGE, TLR and other receptor ligands, initiating downstream, signaling processes. This molecule acts as a proinflammatory cytokine and contributes to the progression of diseases like, acute lung injury, autoimmune liver damage, graft rejection immune response and arthritis. Small concentrations of HMGB1 are released during apoptosis, which facilitates oxidative regulation on Cys106, and propagates immune inactivating tolerogenic signals in the body. The review portrays the role of HMGB1 in rheumatoid arthritis, evidently supported by pre-clinical and clinical investigations, demonstrating extensive HMGB1 expression in synovial tissue and fluid as well as serum, excessive expression of transduction receptor signaling molecules, bone remodeling and uncontrolled expression of bone destroying osteoclastogenesis, resulting in destruction of articular cartilage, bone deformation and synovial proliferation, alleviating the pathogenesis in RA disease. Moreover, the review highlights the therapeutic regime targeting HMGB1, facilitating inhibition of its actions and release into the extracellular compartment, to ameliorate the destructive events that prevail in rheumatoid arthritis.

Mouse CD163 deficiency strongly enhances experimental collagen-induced arthritis

The scavenger receptor CD163 is highly expressed in macrophages in sites of chronic inflammation where it has a not yet defined role. Here we have investigated development of collagen-induced arthritis (CIA) and collagen antibody-induced arthritis (CAIA) in CD163-deficient C57BL/6 mice. Compared to wild-type mice, the CIA in CD163-deficient mice had a several-fold higher arthritis score with early onset, prolonged disease and strongly enhanced progression. Further, the serum anti-collagen antibody isotypes as well as the cytokine profiles and T cell markers in the inflamed joints revealed that CD163-deficient mice after 52 days had a predominant Th2 response in opposition to a predominant Th1 response in CD163+/+ mice. Less difference in disease severity between the CD163+/+ and CD163-/- mice was seen in the CAIA model that to a large extent induces arthritis independently of T-cell response and endogenous Th1/Th2 balance. In conclusion, the present set of data points on a novel strong anti-inflammatory role of CD163.

Anti-inflammatory effects of haptoglobin on LPS-stimulated macrophages: Role of HMGB1 signaling and implications in chronic wound healing

Nonhealing wounds possess elevated numbers of pro-inflammatory M1 macrophages, which fail to transition to anti-inflammatory M2 phenotypes that promote healing. Hemoglobin (Hb) and haptoglobin (Hp) proteins, when complexed (Hb-Hp), can elicit M2-like macrophages through the heme oxygenase-1 (HO-1) pathway. Despite the fact that nonhealing wounds are chronically inflamed, previous studies have focused on non-inflammatory systems, and do not thoroughly compare the effects of complexed vs individual proteins. We aimed to investigate the effect of Hb/Hp treatments on macrophage phenotype in an inflammatory, lipopolysaccharide (LPS)-stimulated environment, similar to chronic wounds. Human M1 macrophages were cultured in vitro and stimulated with LPS. Concurrently, Hp, Hb, or Hb-Hp complexes were delivered. The next day, 27 proteins related to inflammation were measured in the supernatants. Hp treatment decreased a majority of inflammatory factors, Hb increased many, and Hb-Hp had intermediate trends, indicating that Hp attenuated overall inflammation to the greatest extent. From this data, Ingenuity Pathway Analysis software identified high motility group box 1 (HMGB1) as a key canonical pathway-strongly down-regulated from Hp, strongly up-regulated from Hb, and slightly activated from Hb-Hp. HMGB1 measurements in macrophage supernatants confirmed this trend. In vivo results in diabetic mice with biopsy punch wounds demonstrated accelerated wound closure with Hp treatment, and delayed wound closure with Hb treatment. This work specifically studied Hb/Hp effects on macrophages in a highly inflammatory environment relevant to chronic wound healing. Results show that Hp-and not Hb-Hp, which is known to be superior in noninflammatory conditions-reduces inflammation in LPS-stimulated macrophages, and HMGB1 signaling is also implicated. Overall, Hp treatment on M1 macrophages in vitro reduced the inflammatory secretion profile, and also exhibited benefits in in silico and in vivo wound-healing models.

Extracellular HMGB1: a therapeutic target in severe pulmonary inflammation including COVID-19?

BACKGROUND

The 2019 novel coronavirus disease (COVID-19) causes for unresolved reasons acute respiratory distress syndrome in vulnerable individuals. There is a need to identify key pathogenic molecules in COVID-19-associated inflammation attainable to target with existing therapeutic compounds. The endogenous damage-associated molecular pattern (DAMP) molecule HMGB1 initiates inflammation via two separate pathways. Disulfide-HMGB1 triggers TLR4 receptors generating pro-inflammatory cytokine release. Extracellular HMGB1, released from dying cells or secreted by activated innate immunity cells, forms complexes with extracellular DNA, RNA and other DAMP or pathogen-associated molecular (DAMP) molecules released after lytic cell death. These complexes are endocytosed via RAGE, constitutively expressed at high levels in the lungs only, and transported to the endolysosomal system, which is disrupted by HMGB1 at high concentrations. Danger molecules thus get access to cytosolic proinflammatory receptors instigating inflammasome activation. It is conceivable that extracellular SARS-CoV-2 RNA may reach the cellular cytosol via HMGB1-assisted transfer combined with lysosome leakage. Extracellular HMGB1 generally exists in vivo bound to other molecules, including PAMPs and DAMPs. It is plausible that these complexes are specifically removed in the lungs revealed by a 40% reduction of HMGB1 plasma levels in arterial versus venous blood. Abundant pulmonary RAGE expression enables endocytosis of danger molecules to be destroyed in the lysosomes at physiological HMGB1 levels, but causing detrimental inflammasome activation at high levels. Stress induces apoptosis in pulmonary endothelial cells from females but necrosis in cells from males.

CONCLUSION

Based on these observations we propose extracellular HMGB1 to be considered as a therapeutic target for COVID-19.

Identification of tetranectin-targeting monoclonal antibodies to treat potentially lethal sepsis

For the clinical management of sepsis, antibody-based strategies have only been attempted to antagonize proinflammatory cytokines but not yet been tried to target harmless proteins that may interact with these pathogenic mediators. Here, we report an antibody strategy to intervene in the harmful interaction between tetranectin (TN) and a late-acting sepsis mediator, high-mobility group box 1 (HMGB1), in preclinical settings. We found that TN could bind HMGB1 to reciprocally enhance their endocytosis, thereby inducing macrophage pyroptosis and consequent release of lactate dehydrogenase and apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain. The genetic depletion of TN expression or supplementation of exogenous TN protein at subphysiological doses distinctly affected the outcomes of potentially lethal sepsis, revealing a previously underappreciated beneficial role of TN in sepsis. Furthermore, the administration of domain-specific polyclonal and monoclonal antibodies effectively inhibited TN/HMGB1 interaction and endocytosis and attenuated the sepsis-induced TN depletion and tissue injury, thereby rescuing animals from lethal sepsis. Our findings point to a possibility of developing antibody strategies to prevent harmful interactions between harmless proteins and pathogenic mediators of human diseases.

Targeting Inflammation Driven by HMGB1

High mobility group box 1 (HMGB1) is a highly conserved, nuclear protein present in all cell types. It is a multi-facet protein exerting functions both inside and outside of cells. Extracellular HMGB1 has been extensively studied for its prototypical alarmin functions activating innate immunity, after being actively released from cells or passively released upon cell death. TLR4 and RAGE operate as the main HMGB1 receptors. Disulfide HMGB1 activates the TLR4 complex by binding to MD-2. The binding site is separate from that of LPS and it is now feasible to specifically interrupt HMGB1/TLR4 activation without compromising protective LPS/TLR4-dependent functions. Another important therapeutic strategy is established on the administration of HMGB1 antagonists precluding RAGE-mediated endocytosis of HMGB1 and HMGB1-bound molecules capable of activating intracellular cognate receptors. Here we summarize the role of HMGB1 in inflammation, with a focus on recent findings on its mission as a damage-associated molecular pattern molecule and as a therapeutic target in inflammatory diseases. Recently generated HMGB1-specific inhibitors for treatment of inflammatory conditions are discussed.

Extracellular CIRP induces macrophage endotoxin tolerance through IL-6R-mediated STAT3 activation

Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern, whose effect on macrophages is not entirely elucidated. Here we identified that eCIRP promotes macrophage endotoxin tolerance. Septic mice had higher serum levels of eCIRP; this was associated with a reduced ex vivo immune response of their splenocytes to LPS. Pretreatment of macrophages with recombinant murine CIRP (rmCIRP) resulted in a tolerance to LPS stimulation as demonstrated by a reduction of TNF-α production. We found that eCIRP increased phosphorylated STAT3 (p-STAT3) in macrophages. A STAT3 inhibitor, Stattic, rescued macrophages from rmCIRP-induced tolerance by restoring the release of TNF-α in response to LPS stimulation. We discovered strong binding affinity between eCIRP and IL-6 receptor (IL-6R) as revealed by Biacore, fluorescence resonance energy transfer (FRET), and their colocalization in macrophages by immunostaining assays. Blockade of IL-6R with its neutralizing Ab inhibited eCIRP-induced p-STAT3 and restored LPS-stimulated TNF-α release in macrophages. Incubation of macrophages with rmCIRP skewed them toward an M2 phenotype, while treatment with anti-IL-6R Ab prevented rmCIRP-induced M2 polarization. Thus, we have demonstrated that eCIRP activates p-STAT3 via a novel receptor, IL-6R, to promote macrophage endotoxin tolerance. Targeting eCIRP appears to be a new therapeutic option to correct immune tolerance in sepsis.

Extracellular CIRP as an endogenous TREM-1 ligand to fuel inflammation in sepsis

Extracellular cold-inducible RNA-binding protein (eCIRP) is a recently discovered damage-associated molecular pattern. Understanding the precise mechanism by which it exacerbates inflammation is essential. Here we identified that eCIRP is a new biologically active endogenous ligand of triggering receptor expressed on myeloid cells-1 (TREM-1), fueling inflammation in sepsis. Surface plasmon resonance revealed a strong binding affinity between eCIRP and TREM-1, and fluorescence resonance energy transfer assay confirmed eCIRP's interaction with TREM-1 in macrophages. Targeting TREM-1 by its siRNA or a decoy peptide, LP17, or by using TREM-1-/- mice dramatically reduced eCIRP-induced inflammation. We developed a potentially novel 7-aa peptide derived from human eCIRP, M3, which blocked the interaction of TREM-1 and eCIRP. M3 suppressed inflammation induced by eCIRP or agonist TREM-1 antibody cross-linking in murine macrophages or human peripheral blood monocytes. M3 also inhibited eCIRP-induced systemic inflammation and tissue injury. Treatment with M3 further protected mice from sepsis, improved acute lung injury, and increased survival. Thus, we have discovered a potentially novel TREM-1 ligand and developed a new peptide, M3, to block eCIRP-TREM-1 interaction and improve outcomes in sepsis.

Integration Analysis of m6A-SNPs and eQTLs Associated With Sepsis Reveals Platelet Degranulation and Staphylococcus aureus Infection are Mediated by m6A mRNA Methylation

Sepsis is a major threat with high mortality rate for critically ill patients. Response to pathogen infection by the host immune system is a key biological process involved in the onset and development of sepsis. Heterogeneous host genome variation, especially single nucleotide polymorphisms (SNPs), has long been suggested to contribute to differences in disease progression. However, the function of SNPs located in non-coding regions remains to be elucidated. Recently, m⁶A mRNA modification levels were revealed to differ at SNPs. As m⁶A is a crucial regulator of gene expression, these SNPs might control genes by changing the m⁶A level on mRNA. To investigate the potential role of m⁶A SNPs in sepsis, we integrated m⁶A-SNP and expression quantitative trait loci (eQTLs) data. Analysis revealed 15,720 m⁶A-cis-eQTLs and 381 m⁶A-trans-eQTLs associated with sepsis. We identified 1321 genes as locations of m⁶A-cis-eQTLs. These were enriched in platelet degranulation and Staphylococcus aureus infection pathways, which are vital for the pathophysiological process of sepsis. We conclude that m⁶A modification of mRNA plays a very important role in sepsis, with m⁶A-cis-eQTLs potentially having the most effect on individual variation in sepsis progression.

The Generation and Identity of Human Myeloid-Derived Suppressor Cells

Myeloid-derived suppressor cells (MDSCs) are cells of myeloid lineage with a potent immunosuppressive capacity. They are present in cancer patients as well as in patients with severe inflammatory conditions and infections. MDSCs exist as two main subtypes, the granulocytic (G-MDSCs) and the monocytic (Mo-MDSCs) type, as defined by their surface phenotype and functions. While the functions of MDSCs have been investigated in depth, the origin of human MDSCs is less characterized and even controversial. In this review, we recapitulate theories on how MDSCs are generated in mice, and whether this knowledge is translatable into human MDSC biology, as well as on problems of defining MDSCs by their immature cell surface phenotype in relation to the plasticity of myeloid cells. Finally, the challenge of pharmacological targeting of MDSCs in the future is envisioned.

Role of High-Mobility Group Box-1 in Liver Pathogenesis

High-mobility group box 1 (HMGB1) is a highly abundant DNA-binding protein that can relocate to the cytosol or undergo extracellular release during cellular stress or death. HMGB1 has a functional versatility depending on its cellular location. While intracellular HMGB1 is important for DNA structure maintenance, gene expression, and autophagy induction, extracellular HMGB1 acts as a damage-associated molecular pattern (DAMP) molecule to alert the host of damage by triggering immune responses. The biological function of HMGB1 is mediated by multiple receptors, including the receptor for advanced glycation end products (RAGE) and Toll-like receptors (TLRs), which are expressed in different hepatic cells. Activation of HMGB1 and downstream signaling pathways are contributing factors in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), and drug-induced liver injury (DILI), each of which involves sterile inflammation, liver fibrosis, ductular reaction, and hepatic tumorigenesis. In this review, we will discuss the critical role of HMGB1 in these pathogenic contexts and propose HMGB1 as a bona fide and targetable DAMP in the setting of common liver diseases.

Macrophage spatial heterogeneity in gastric cancer defined by multiplex immunohistochemistry

Tumor-associated macrophages (TAMs), one of the most abundant immune components in gastric cancer (GC), are difficult to characterize due to their heterogeneity. Multiple approaches have been used to elucidate the issue, however, due to the tissue-destructive nature of most of these methods, the spatial distribution of TAMs in situ remains unclear. Here we probe the relationship between tumor context and TAM heterogeneity by multiplex immunohistochemistry of 56 human GC cases. Using distinct expression marker profiles on TAMs, we report seven predominant populations distributed between tumor and non-tumor tissue. TAM population-associated gene signatures reflect their heterogeneity and polarization in situ. Increased density of CD163+ (CD206-) TAMs with concurrent high CD68 expression is associated with upregulated immune-signaling and improved patient survival by univariate, but not multivariate analysis. CD68-only and CD206+ TAMs are correlated with high PDL1 expression.