S100A4 a classical DAMP as a therapeutic target in fibrosis

Fibrosis regardless of aetiology is characterised by persistently activated myofibroblasts that are contractile and secrete excessive amounts of extracellular matrix molecules that leads to loss of organ function. Damage-Associated Molecular Patterns (DAMPs) are endogenous host-derived molecules that are released from cells dying or under stress that can be triggered by a variety of insults, either chemical or physical, leading to an inflammatory response. Among these DAMPs is S100A4, part of the S100 family of calcium binding proteins that participate in a variety of cellular processes. S100A4 was first described in context of cancer as a pro-metastatic factor. It is now appreciated that aside from its role in cancer promotion, S100A4 is intimately involved in tissue fibrosis. The extracellular form of S100A4 exerts its effects through multiple receptors including Toll-Like Receptor 4 and RAGE to evoke signalling cascades involving downstream mediators facilitating extracellular matrix deposition and myofibroblast generation and can play a role in persistent activation of myofibroblasts. S100A4 may be best understood as an amplifier of inflammatory and fibrotic processes. S100A4 appears critical in systemic sclerosis pathogenesis and blocking the extracellular form of S100A4 in vivo in various animal models of disease mitigates fibrosis and may even reverse established disease. This review appraises S100A4's position as a DAMP and its role in fibrotic conditions and highlight therapeutically targeting this protein to halt fibrosis, suggesting that it is a tractable target.

Blockade of IL-6R prevents preterm birth and adverse neonatal outcomes

BACKGROUND

Preterm birth preceded by spontaneous preterm labour often occurs in the clinical setting of sterile intra-amniotic inflammation (SIAI), a condition that currently lacks treatment.

METHODS

Proteomic and scRNA-seq human data were analysed to evaluate the role of IL-6 and IL-1α in SIAI. A C57BL/6 murine model of SIAI-induced preterm birth was developed by the ultrasound-guided intra-amniotic injection of IL-1α. The blockade of IL-6R by using an aIL-6R was tested as prenatal treatment for preterm birth and adverse neonatal outcomes. QUEST-MRI evaluated brain oxidative stress in utero. Targeted transcriptomic profiling assessed maternal, foetal, and neonatal inflammation. Neonatal biometrics and neurodevelopment were tested. The neonatal gut immune-microbiome was evaluated using metagenomic sequencing and immunophenotyping.

FINDINGS

IL-6 plays a critical role in the human intra-amniotic inflammatory response, which is associated with elevated concentrations of the alarmin IL-1α. Intra-amniotic injection of IL-1α resembles SIAI, inducing preterm birth (7% vs. 50%, p = 0.03, Fisher's exact test) and neonatal mortality (18% vs. 56%, p = 0.02, Mann-Whitney U-test). QUEST-MRI revealed no foetal brain oxidative stress upon in utero IL-1α exposure (p > 0.05, mixed linear model). Prenatal treatment with aIL-6R abrogated IL-1α-induced preterm birth (50% vs. 7%, p = 0.03, Fisher's exact test) by dampening inflammatory processes associated with the common pathway of labour. Importantly, aIL-6R reduces neonatal mortality (56% vs. 22%, p = 0.03, Mann-Whitney U-test) by crossing from the mother to the amniotic cavity, dampening foetal organ inflammation and improving growth. Beneficial effects of prenatal IL-6R blockade carried over to neonatal life, improving survival, growth, neurodevelopment, and gut immune homeostasis.

INTERPRETATION

IL-6R blockade can serve as a strategy to treat SIAI, preventing preterm birth and adverse neonatal outcomes.

FUNDING

NICHD/NIH/DHHS, Contract HHSN275201300006C. WSU Perinatal Initiative in Maternal, Perinatal and Child Health.

S100A alarmins and thymic stromal lymphopoietin (TSLP) regulation in severe asthma following bronchial thermoplasty

RATIONALE

Severe asthma affects a small proportion of asthmatics but represents a significant healthcare challenge. Bronchial thermoplasty (BT) is an interventional treatment approach preconized for uncontrolled severe asthma after considering biologics therapy. It was showed that BT long-lastingly improves asthma control. These improvements seem to be related to the ability of BT to reduce airway smooth muscle remodeling, reduce the number of nerve fibers and to modulate bronchial epithelium integrity and behavior. Current evidence suggest that BT downregulates epithelial mucins expression, cytokine production and metabolic profile. Despite these observations, biological mechanisms explaining asthma control improvement post-BT are still not well understood.

OBJECTIVES

To assess whether BT affects gene signatures in bronchial epithelial cells (BECs).

METHODS

In this study we evaluated the transcriptome of cultured bronchial epithelial cells (BECs) of severe asthmatics obtained pre- and post-BT treatment using microarrays. We further validated gene and protein expressions in BECs and in bronchial biopsies with immunohistochemistry pre- and post-BT treatment.

MEASUREMENTS AND MAIN RESULTS

Transcriptomics analysis revealed that a large portion of differentially expressed genes (DEG) was involved in anti-viral response, anti-microbial response and pathogen induced cytokine storm signaling pathway. S100A gene family stood out as five members of this family where consistently downregulated post-BT. Further validation revealed that S100A7, S100A8, S100A9 and their receptor (RAGE, TLR4, CD36) expressions were highly enriched in severe asthmatic BECs. Further, these S100A family members were downregulated at the gene and protein levels in BECs and in bronchial biopsies of severe asthmatics post-BT. TLR4 and CD36 protein expression were also reduced in BECs post-BT. Thymic stromal lymphopoietin (TSLP) and human β-defensin 2 (hBD2) were significantly decreased while no significant change was observed in IL-25 and IL-33.

CONCLUSIONS

These data suggest that BT might improve asthma control by downregulating epithelial derived S100A family expression and related downstream signaling pathways.

Development of a novel modified vaccine (TheraVacM) for curative treatment of mouse solid tumors

Monotherapy with immune checkpoint blockade (ICB) antibodies (anti-CTLA4 and anti-PD1/PDL-1) is only effective for 20% to 30% of patients with certain cancers. Patients with cancers harboring few effector T cells (Teffs) are insensitive to ICB therapy. The lack of tumor-specific Teffs is predominantly caused by the paralysis of tumor-infiltrating dendritic cells (TiDCs) resulting from immunosuppression in the tumor microenvironment. We have identified a potent combination of high mobility group nucleosome binding domain 1 (HMGN1, N1) and fibroblast stimulating lipopeptide-1 (FSL-1) that can synergistically trigger maturation of both mouse and human DCs. Accordingly, we designed a combinational anti-cancer immunotherapy with two arms: an immune-activating arm consisting of N1 and FSL-1 to stimulate the generation of Teffs by triggering full maturation of TiDCs, and an ICB arm using anti-PDL-1 or anti-CTLA4 to prevent Teffs from being silenced in the tumor tissue. This combinational immunotherapeutic vaccination regimen dubbed modified TheraVac (TheraVacM) has proved particularly effective as it cured 100% of mice bearing established ectopic CT26 colon and RENCA kidney tumors. The resultant tumor-free mice were resistant to subsequent re-challenge with the same tumors, indicating the generation of long-term tumor specific protective immunity. Since the immune-activating arm also induces full maturation of human DCs, and anti-PDL-1 or anti-CTLA4 have been FDA-approved, this combinational immunotherapy has the potential to be an effective clinical therapy for patients with solid tumors.

The HDM allergen orchestra and its cysteine protease maestro: Stimulators of kaleidoscopic innate immune responses

House dust mite (HDM) encloses an explosive cocktail of allergenic proteins sensitizing hundreds of millions of people worldwide. To date, the innate cellular and molecular mechanism(s) orchestrating the HDM-induced allergic inflammation remains partially deciphered. Understanding the kaleidoscope of HDM-induced innate immune responses is hampered by (1) the large complexity of the HDM allergome with very diverse functional bioreactivities, (2) the perpetual presence of microbial compounds (at least LPS, β-glucan, chitin) promoting as well pro-Th2 innate signaling pathways and (3) multiple cross-talks involving structural, neuronal and immune cells. The present review provides an update on the innate immune properties, identified so far, of multiple HDM allergen groups. Experimental evidence highlights the importance of HDM allergens displaying protease or lipid-binding activities on the initiation of the allergic responses. Specifically, group 1 HDM cysteine proteases are considered as the key initiators of the allergic response through their capacities to impair the epithelial barrier integrity, to stimulate the release of pro-Th2 danger-associated molecular patterns (DAMPs) in epithelial cells, to produce super-active forms of IL-33 alarmin and to mature thrombin leading to Toll-like receptor 4 (TLR4) activation. Remarkably, the recently evidenced primary sensing of cysteine protease allergens by nociceptive neurons confirms the critical role of this HDM allergen group in the early events leading to Th2 differentiation.

Pro- and anti-inflammatory roles of interleukin (IL)-33, IL-36, and IL-38 in inflammatory bowel disease

Interleukin-33 (IL-33), IL-36, and IL-38 are members of the IL-1 cytokine family. The expression of each cytokine has been reported to be increased in the inflamed mucosa of patients with inflammatory bowel disease (IBD). IL-33 and IL-36 have been studied for pro- and anti-inflammatory functions, and IL-38 has been characterized as an anti-inflammatory cytokine by antagonizing the IL-36 receptor (IL-36R). IL-33 is a nuclear cytokine constitutively expressed by certain cell types such as epithelial, endothelial, and fibroblast-like cells and released on necrotic cell death. IL-33 mainly induces type 2 immune response through its receptor suppression tumorigenicity 2 (ST2) from Th2 cells and type 2 innate lymphoid cells (ILC2s), but also by stimulating Th1 cells, regulatory T cells, and CD8⁺ T cells. IL-36 cytokines consist of three agonists: IL-36α, IL-36β, and IL-36γ, and two receptor antagonists: IL-36R antagonist (IL-36Ra) and IL-38. All IL-36 cytokines bind to the IL-36R complex and exert various functions through NF-κB and mitogen-activated protein kinase (MAPK) pathways in inflammatory settings. IL-33 and IL-36 also play a crucial role in intestinal fibrosis characteristic manifestation of CD. In this review, we focused on the current understanding of the pro- and anti-inflammatory roles of IL-33, IL-36, and IL38 in experimental colitis and IBD patients.

A potential role of human RNASET2 overexpression in the pathogenesis of Graves' disease

Genetic variation of the gene encoding for the only human enzyme of the T2 ribonucleases family (RNASET2) emerged in genome-wide association studies as a putative risk hotspot for Graves' disease (GD). T2 ribonucleases activities include immune regulation, induction of cell apoptosis and differentiation. Several reports supported the hypothesis that RNASET2 represents a "danger" message addressed to the innate immune system in peculiar conditions. This was a longitudinal, case-control study. RNASET2 protein levels were assessed in blood samples from 34 consecutive newly diagnosed GD patients and in healthy controls. At enrollment, RNASET2 levels were significantly higher in GD patients (98.5 ± 29.1 ng/ml) compared to healthy controls (72.5 ± 27.9 ng/ml, p = 0.001). After 6 months of methimazole treatment, RNASET2 levels significantly decrease and return to levels similar to healthy controls (62.4 ± 22 ng/ml, p = 0.69). These preliminary results suggest that RNASET2 is overexpressed in patients with GD and might represent an "alarm signal" generated by thyroid cells in response to endogenous or environmental stress to alert the immune system.

Role of alarmins in poststroke inflammation and neuronal repair

Severe loss of cerebral blood flow causes hypoxia and glucose deprivation in the brain tissue, resulting in necrotic cell death in the ischemic brain. Several endogenous molecules, called alarmins or damage-associated molecular patterns (DAMPs), are extracellularly released from the dead cells to activate pattern recognition receptors (PRRs) in immune cells that infiltrate into ischemic brain tissue following the disruption of the blood-brain barrier (BBB) after stroke onset. The activated immune cells produce various inflammatory cytokines and chemokines, triggering sterile cerebral inflammation in the ischemic brain that causes further neuronal cell death. Poststroke inflammation is resolved within several days after stroke onset, and neurological functions are restored to some extent as neural repair occurs around peri-infarct neurons. Clearance of DAMPs from the injured brain is necessary for the resolution of poststroke inflammation. Neurons and glial cells also express PRRs and receive DAMP signaling. Although the role of PRRs in neural cells in the ischemic brain has not yet been clarified, the signaling pathway is likely to be contribute to stroke pathology and neural repair after ischemic stroke. This review describes the molecular dynamics, signaling pathways, and functions of DAMPs in poststroke inflammation and its resolution.

IL-33 priming amplifies ATP-mediated mast cell cytokine production

Inflammatory responses are required to block pathogen infection but can also lead to hypersensitivity and chronic inflammation. Barrier tissues actively release IL-33, ATP, and other alarmins during cell stress, helping identify pathogenic stimuli. However, it is unclear how these signals are integrated. Mast cells are critical initiators of allergic inflammation and respond to IL-33 and ATP. We found that mouse mast cells had a 3-6-fold increase in ATP-induced cytokine production when pre-treated with IL-33. This effect was observed at ATP concentrations < 100 µM and required < 30-minute IL-33 exposure. ATP-induced degranulation was not enhanced by pretreatment nor was the response to several pathogen molecules. Mechanistic studies implicated the P2X7 receptor and calcineurin/NFAT pathway in the enhanced ATP response. Finally, we found that IL-33 + ATP co-stimulation enhanced peritoneal eosinophil and macrophage recruitment. These results support the hypothesis that alarmins collaborate to surpass a threshold necessary to initiate an inflammatory response.

Targeting the P2Y13 Receptor Suppresses IL-33 and HMGB1 Release and Ameliorates Experimental Asthma

RATIONALE

The alarmins IL-33 and HMGB1 (high mobility group box 1) contribute to type-2 inflammation and asthma pathogenesis.

OBJECTIVES

To determine whether P2Y13 receptor (P2Y13-R), a purinergic G protein-coupled receptor (GPCR) and risk allele for asthma, regulates the release of IL-33 and HMGB1.

METHODS

Bronchial biopsies were obtained from healthy and asthmatic subjects. Primary human airway epithelial cells (AECs), primary mouse (m)AECs, or C57Bl/6 mice were inoculated with various aeroallergens or respiratory viruses, and the nuclear-to-cytoplasmic translocation and release of alarmins measured by immunohistochemistry and ELISA. The role of P2Y13-R in AEC function and in the onset, progression, and an exacerbation of experimental asthma, was assessed using pharmacological antagonists and P2Y13-R gene-deleted mice.

MEASUREMENTS AND MAIN RESULTS

Aeroallergen-exposure induced the extracellular release of ADP and ATP, nucleotides that activate P2Y13-R. ATP, ADP, aeroallergen (house dust mite, cockroach or Alternaria) or virus exposure induced the nuclear-to-cytoplasmic translocation and subsequent release of IL-33 and HMGB1, and this response was ablated by genetic deletion or pharmacological antagonism of P2Y13. In mice, prophylactic or therapeutic P2Y13-R blockade attenuated asthma onset, and critically, ablated the severity of a rhinovirus-associated exacerbation in a high-fidelity experimental model of chronic asthma. Moreover, P2Y13-R antagonism derepressed antiviral immunity, increasing IFN-λ production and decreasing viral copies in the lung.

CONCLUSIONS

We identify P2Y13-R as a novel gatekeeper of the nuclear alarmins IL-33 and HMGB1, and demonstrate that the targeting of this GPCR via genetic deletion or treatment with a small-molecule antagonist protects against the onset and exacerbations of experimental asthma.

Alarmins/stressorins and immune dysregulation in intractable skin disorders

Unlike other barrier epithelia of internal organs, the stratified squamous epithelium of the skin is always exposed to the external environment. However, the robust barrier structure and function of the skin are highly resistant against external insults so as to not easily allow foreign invasions. Upon sensing danger signals, the innate immunity system is promptly activated. This process is mediated by alarmins, which are released passively from damaged cells. Nuclear alarmins or stressorins are actively released from intact cells in response to various cellular stresses. Alarmins/stressorins are deeply involved in the disease processes of chronic skin disorders of an unknown cause, such as rosacea, psoriasis, and atopic dermatitis. Furthermore, alarmins/stressorins are also induced in the congenital skin disorders of ichthyosis and keratoderma due to defective keratinization. Studies on alarmin activation and its downstream pathways may help develop novel therapeutic agents for intractable skin disorders.

Doxorubicin induces an alarmin-like TLR4-dependent autocrine/paracrine action of Nucleophosmin in human cardiac mesenchymal progenitor cells

Background

Doxorubicin (Dox) is an anti-cancer anthracycline drug that causes double-stranded DNA breaks. It is highly effective against several types of tumours; however, it also has adverse effects on regenerative populations of normal cells, such as human cardiac mesenchymal progenitor cells (hCmPCs), and its clinical use is limited by cardiotoxicity. Another known effect of Dox is nucleolar disruption, which triggers the ubiquitously expressed nucleolar phosphoprotein Nucleophosmin (NPM) to be released from the nucleolus into the cell, where it participates in the orchestration of cellular stress responses. NPM has also been observed in the extracellular space in response to different stress stimuli; however, the mechanism behind this and its functional implications are as yet largely unexplored. The aim of this study was to establish whether Dox could elicit NPM secretion in the extracellular space and to elucidate the mechanism of secretion and the effect of extracellular NPM on hCmPCs.

Results

We found that following the double-strand break formation in hCmPCs caused by Dox, NPM was rapidly secreted in the extracellular space by an active mechanism, in the absence of either apoptosis or necrosis. Extracellular release of NPM was similarly seen in response to ultraviolet radiation (UV). Furthermore, we observed an increase of NPM levels in the plasma of Dox-treated mice; thus, NPM release also occurred in vivo. The treatment of hCmPCs with extracellular recombinant NPM induced a decrease of cell proliferation and a response mediated through the Toll-like receptor (TLR)4. We demonstrated that NPM binds to TLR4, and via TLR4, and nuclear factor kappa B (NFkB) activation/nuclear translocation, exerts proinflammatory functions by inducing IL-6 and COX-2 gene expression. Finally, we found that in hCmPCs, NPM secretion could be driven by an autophagy-dependent unconventional mechanism that requires TLR4, since TLR4 inhibition dramatically reduced Dox-induced secretion.

Conclusions

We hypothesise that the extracellular release of NPM could be a general response to DNA damage since it can be elicited by either a chemical agent such as Dox or a physical genotoxic stressor such as UV radiation. Following genotoxic stress, NPM acts similarly to an alarmin in hCmPCs, being rapidly secreted and promoting cell cycle arrest and a TLR4/NFκB-dependent inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01058-5.

Sojadodamgangki-tang attenuates allergic lung inflammation by inhibiting T helper 2 cells and Augmenting alveolar macrophages

ETHNOPHARMACOLOGICAL RELEVANCE

Sojadodamgangki-tang (SDG) is a traditional East-Asian herbal medicine mainly composed of Pinellia ternate (Thunb.) Makino, Perilla frutescens (L.) Britt and 10 kinds of medicinal herbs. It has been used to treat asthma and mucus secretion including lung and bronchi.

AIM OF THE STUDY

The aim of this study was to investigate the anti-inflammatory effects of Sojadodamgangki-tang (SDG) on allergic lung inflammation in vitro and in vivo as well as the underlying mechanisms.

MATERIALS AND METHODS

We used an ovalbumin (OVA)-induced murine allergic airway inflammation model. Five groups of 8-week-old female BALB/C mice were divided into the following groups: saline control group, the vehicle (allergic) group that received OVA only, groups that received OVA and SDG (200 mg/kg or 400 mg/kg), and a positive control group that received OVA and Dexamethasone (5 mg/kg). In vitro experiments include T helper 2 (TH2) polarization system, murine macrophage cell culture, and human bronchial epithelial cell line (BEAS-2B) culture.

RESULTS

SDG administration reduced allergic airway inflammatory cell infiltration, especially of eosinophils, mucus production, Th2 cell activation, OVA-specific immunoglobulin E (IgE), and total IgE production. Moreover, the activation of alveolar macrophages, which leads to immune tolerance in the steady state, was promoted by SDG treatment. Interestingly, SDG treatment also reduced the production of alarmin cytokines by the human bronchial epithelial cell line BEAS-2B stimulated with urban particulate matter.

CONCLUSION

Our findings indicate that SDG has potential as a therapeutic drug to inhibit Th2 cell activation and promote alveolar macrophage activation.

SOURCE: a phase 3, multicentre, randomized, double-blind, placebo-controlled, parallel group trial to evaluate the efficacy and safety of tezepelumab in reducing oral corticosteroid use in adults with oral corticosteroid dependent asthma

BACKGROUND

Many patients with severe asthma continue to experience asthma symptoms and exacerbations despite standard-of-care treatment. A substantial proportion of these patients require long-term treatment with oral corticosteroids (OCS), often at high doses, which are associated with considerable multiorgan adverse effects, including metabolic disorders, osteoporosis and adrenal insufficiency. Tezepelumab is a human monoclonal antibody that blocks the activity of the epithelial cytokine thymic stromal lymphopoietin. In the PATHWAY phase 2b study (NCT02054130), tezepelumab significantly reduced exacerbations by up to 71% in adults with severe, uncontrolled asthma. Several ongoing phase 3 trials (SOURCE, NCT03406078; NAVIGATOR, NCT03347279; DESTINATION, NCT03706079) are assessing the efficacy and safety of tezepelumab in patients with severe, uncontrolled asthma. Here, we describe the design and objectives of SOURCE, a phase 3 OCS-sparing study.

METHODS

SOURCE is an ongoing phase 3, multicentre, randomized, double-blind, placebo-controlled study to evaluate the effect of tezepelumab 210 mg administered subcutaneously every 4 weeks on OCS dose reduction in adults with OCS-dependent asthma. The study comprises a 2-week screening and enrolment period, followed by an OCS optimization phase of up to 8 weeks and a 48-week treatment period, which consists of a 4-week induction phase, followed by a 36-week OCS reduction phase and an 8-week maintenance phase. The primary objective is to assess the effect of tezepelumab compared with placebo in reducing the prescribed OCS maintenance dose. The key secondary objective is to assess the effect of tezepelumab on asthma exacerbation rates. Other secondary objectives include the proportion of patients with a reduction in OCS dose (100% or 50% reduction or those receiving < 5 mg) and the effect of tezepelumab on lung function and patient-reported outcomes.

CONCLUSIONS

SOURCE is evaluating the OCS-sparing potential of tezepelumab in patients with OCS-dependent asthma. SOURCE also aims to demonstrate that treatment with tezepelumab in patients with severe asthma is associated with reductions in exacerbation rates and improvements in lung function, asthma control and health-related quality of life, while reducing OCS dose.

TRIAL REGISTRATION

NCT03406078 ( ClinicalTrials.gov ). Registered 23 January 2018. https://clinicaltrials.gov/ct2/show/NCT03406078.

Thymic stromal lymphopoietin: its role and potential as a therapeutic target in asthma

INTRODUCTION

Thymic stromal lymphopoietin (TSLP), an epithelial cytokine (alarmin), is a central regulator of the immune response to inhaled environmental insults such as allergens, viruses and pollutants, initiating a cascade of downstream inflammation. There is compelling evidence that TSLP plays a major role in the pathology of asthma, and therapies that aim to block its activity are in development.

AREAS COVERED

We review studies conducted in humans and human cells, largely published in PubMed January 2010-October 2019, that investigated the innate and adaptive immune mechanisms of TSLP in asthma relevant to type 2-driven (eosinophilic/allergic) inflammation and non-type 2-driven (non-eosinophilic/non-allergic) inflammation, and the role of TSLP as a mediator between immune cells and structural cells in the airway. Clinical data from studies evaluating TSLP blockade are also discussed.

EXPERT OPINION

The position of TSLP at the top of the inflammatory cascade makes it a promising therapeutic target in asthma. Systemic anti-TSLP monoclonal antibody therapy with tezepelumab has yielded positive results in clinical trials to date, reducing exacerbations and biomarkers of inflammation in patients across the spectrum of inflammatory endotypes. Inhaled anti-TSLP is an alternative route currently under evaluation. The long-term safety and efficacy of TSLP blockade need to be evaluated.

Activation of innate immunity by 14-3-3 ε, a new potential alarmin in osteoarthritis

OBJECTIVE

The innate immune system plays a central role in osteoarthritis (OA). We identified 14-3-3ε as a novel mediator that guides chondrocytes toward an inflammatory phenotype. 14-3-3ε shares common characteristics with alarmins. These endogenous molecules, released into extracellular media, are increasingly incriminated in sustaining OA inflammation. Alarmins bind mainly to toll-like receptor 2 (TLR2) and TLR4 receptors and polarize macrophages in the synovium. We investigated the effects of 14-3-3ε in joint cells and tissues and its interactions with TLRs to define it as a new alarmin involved in OA.

DESIGN

Chondrocyte, synoviocyte and macrophage cultures from murine or OA human samples were treated with 14-3-3ε. To inhibit TLR2/4 in chondrocytes, blocking antibodies were used. Moreover, chondrocytes and bone marrow macrophage (BMM) cultures from knockout (KO) TLRs mice were stimulated with 14-3-3ε. Gene expression and release of inflammatory mediators [interleukin 6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor alpha (TNFα)] were evaluated via reverse transcription quantitative polymerase chain reaction (RT-qPCR) and ELISA.

RESULTS

In vitro, 14-3-3ε induced gene expression and release of IL6 and MCP1 in the treated cells. The inflammatory effects of 14-3-3ε were significantly reduced following TLRs inhibition or in TLRs KO chondrocytes and BMM.

CONCLUSIONS

14-3-3ε is able to induce an inflammatory phenotype in synoviocytes, macrophages and chondrocytes in addition to polarizing macrophages. These effects seem to involve TLR2 or TLR4 to trigger innate immunity. Our results designate 14-3-3ε as a novel alarmin in OA and as a new target either for therapeutic and/or prognostic purposes.

Autophagy-based unconventional secretion of HMGB1 by keratinocytes plays a pivotal role in psoriatic skin inflammation

The precise mechanism through which macroautophagy/autophagy affects psoriasis is poorly understood. Here, we found that keratinocyte (KC) autophagy, which was positively correlated with psoriatic severity in patients and mouse models and could be inhibited by mitogen-activated protein kinase (MAPK) family inactivation. The impairment of autophagic flux alleviated psoriasisform inflammation. We also found that an autophagy-based unconventional secretory pathway (autosecretion) dependent on ATG5 (autophagy related 5) and GORASP2 (golgi reassembly stacking protein 2) promoted psoriasiform KC inflammation. Moreover, the alarmin HMGB1 (high mobility group box 1) was more effective than other autosecretory proteins in regulating psoriasiform cutaneous inflammation. HMGB1 neutralization in autophagy-efficient KCs eliminated the differences in psoriasiform inflammation between Krt14^+/+-Atg5^f/f KCs and Krt14^Cre/+-atg5^f/f KCs, and conversely, recombinant HMGB1 almost completely restored psoriasiform inflammation in Krt14^Cre/+-atg5^f/f KCs in vivo. These results suggest that HMGB1-associated autosecretion plays a pivotal role in cutaneous inflammation. Finally, we demonstrated that Krt14^Cre/+-hmgb1^f/f mice displayed attenuated psoriatic inflammation due to the essential crosstalk between KC-specific HMGB1-associated autosecretion and γδT cells. Thus, this study uncovered a novel autophagy mechanism in psoriasis pathogenesis, and the findings imply the clinical significance of investigating and treating psoriasis.Abbreviations: 3-MA: 3-methyladenine; ACTB: actin beta; AGER: advanced glycosylation end-product specific receptor; Anti-HMGB1: anti-HMGB1 neutralizing antibody; Anti-IL18: anti-IL18 neutralizing antibody; Anti-IL1B: anti-IL1B neutralizing antibody; ATG5: autophagy related 5; BAF: bafilomycin A₁; BECN1: beclin 1; CASP1: caspase 1; CCL: C-C motif chemokine ligand; CsA: cyclosporine A; ctrl shRNA: lentivirus harboring shRNA against control; CXCL: C-X-C motif chemokine ligand; DCs: dendritic cells; DMEM: dulbecco's modified Eagle's medium; ELISA: enzyme-linked immunosorbent assay; EM: electron microscopy; FBS: fetal bovine serum; GORASP2 shRNA: lentivirus harboring shRNA against GORASP2; GORASP2/GRASP55: golgi reassembly stacking protein 2; GR1: a composite epitope between LY6 (lymphocyte antigen 6 complex) locus C1 and LY6 locus G6D antigens; H&E: hematoxylin and eosin; HMGB1: high mobility group box 1; HMGB1 shRNA: lentivirus harboring shRNA against HMGB1; IFNG/IFN-γ: interferon gamma; IL17A: interleukin 17A; IL18: interleukin 18; IL1A/IL-1α: interleukin 1 alpha; IL1B/IL-1β: interleukin 1 beta; IL22/IL-22: interleukin 22; IL23A: interleukin 23 subunit alpha; IL23R: interleukin 23 receptor; IMQ: imiquimod; ITGAM/CD11B: integrin subunit alpha M; ITGAX/CD11C: integrin subunit alpha X; IVL: involucrin; KC: keratinocyte; KD: knockdown; KO: knockout; Krt14^+/+-Atg5^f/f mice: mice bearing an Atg5 flox allele, in which exon 3 of the Atg5 gene is flanked by two loxP sites; Krt14^+/+-Hmgb1^f/f: mice bearing an Hmgb1 flox allele, in which exon 2 to 4 of the Hmgb1 gene is flanked by two loxP sites; Krt14^Cre/+-atg5^f/f mice: keratinocyte-specific atg5 knockout mice generated by mating Atg5-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt4; Krt14^Cre/+-hmgb1^f/f mice: keratinocyte-specific hmgb1 knockout mice generated by mating Hmgb1-floxed mice with mice expressing Cre recombinase under the control of the promoter of Krt14; Krt14-Vegfa mice: mice expressing 164-amino acid Vegfa splice variant recombinase under the control of promoter of Krt14; LAMP1: lysosomal associated membrane protein 1; LDH: lactate dehydrogenase; LORICRIN: loricrin cornified envelope precursor protein; M5: TNF, IL1A, IL17A, IL22 and OSM in combination; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MAPK: mitogen-activated protein kinase; MKI67: marker of proliferation Ki-67; MTT: thiazolyl blue tetrazolium bromide; NFKB/NF-κB: nuclear factor kappa B; NHEKs: primary normal human epidermal keratinocytes; NS: not significant; OSM: oncostatin M; PASI: psoriasis area and severity index; PtdIns3K: class III phosphatidylinositol 3-kinase; qRT-PCR: quantitative RT-PCR; RELA/p65: RELA proto-oncogene, NF-kB subunit; rHMGB1: recombinant HMGB1; rIL18: recombinant interleukin 18; rIL1B: recombinant interleukin 1 beta; S100A: S100 calcium binding protein A; SQSTM1/p62: sequestosome 1; T17: IL17A-producing T; TCR: T-cell receptor; tcrd KO mice: tcrd (T cell receptor delta chain) knockout mice, which show deficient receptor expression in all adult lymphoid and epithelial organs; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor; WOR: wortmannin; WT: wild-type; γδT17 cells: IL17A-producing γδ T cells.

Interactions between rat cortico-striatal slice cultures and neutrophil-like HL60 cells under thrombin challenge: Toward elucidation of pathological events in intracerebral hemorrhage

Neutrophils constitute the major population of infiltrating leukocytes after stroke including intracerebral hemorrhage (ICH), and these cells may exhibit pro-inflammatory and anti-inflammatory phenotypes depending on the external stimuli. Here we constructed an experimental system to evaluate how the properties of neutrophils were influenced by the injured brain tissues. HL60 cells differentiated into neutrophils were added to the culture medium of neonatal rat cortico-striatal slices maintained at liquid-air interface. Thrombin was applied to the cultures to mimic the pathogenic events associated with ICH. HL60 cells responded to thrombin by increasing mRNA expression of pro-inflammatory IL-1β and anti-inflammatory IL-10 with a different time course. Co-presence of cortico-striatal slice cultures significantly enhanced IL-1β mRNA expression, whereas attenuated IL-10 mRNA expression, in HL60 cells. Toll-like receptor 4 (TLR4) agonist lipopolysaccharide synergistically enhanced IL-1β mRNA expression with thrombin, and TLR4 inhibitor TAK-242 abolished thrombin-induced IL-1β mRNA expression in the presence of slice cultures. On the other hand, thrombin-induced cell death in cortico-striatal cultures was attenuated by the presence of HL60 cells. This experimental system may provide a unique platform to elucidate complex cell-to-tissue interactions during ICH pathogenesis.

Correlations between Interleukin-33 and -1α Levels in Gingival Crevicular Fluid and Plasma in Patients with Chronic or Aggressive Periodontitis and Disease-free Subjects

Interleukin (IL)-33 is a dual-function protein that may play important roles as both a cytokine and intracellular nuclear factor. It may also function similarly to prototypical alarmin IL-1α, as an endogenous danger signal to alert innate immune system cells to tissue damage during trauma or infection, as it can be released in the extracellular space after endothelial cell damage or mechanical injury. The aim of this study was to determine possible correlations between concentrations of IL-33 and IL-1α in gingival crevicular fluid (GCF) and plasma obtained from healthy patients, those with chronic periodontitis (CP), and those with generalized aggressive periodontitis (GAP) patients. Forty-five patients with an age range of 20-60 years were enrolled and divided into 3 groups: Group H, 30 samples (15 GCF and 15 plasma) from 15 patients with healthy periodontium; Group CP, 30 samples from 15 patients with CP; and Group GAP, 30 samples from 15 patients with GAP. The clinical periodontal parameters investigated in all groups comprised the gingival index score, probing pocket depth, and clinical attachment level. The GCF and plasma levels of IL-33 and IL-1α were quantitated using enzyme linked immunosorbent assay. The mean IL-33 concentrations in GCF and plasma were highest in Group GAP, followed by Group CP, with the lowest in Group H; the difference among them was statistically significant (p<0.05). Concentration of IL-1α followed the same trend as that of IL-33 in GCF, but was lower than detection levels in plasma. The GCF and plasma concentrations of IL-33 correlated with IL-1α concentrations in GCF. Concentrations of IL-33 and IL-1α in GCF varied significantly between healthy patients and those with disease, allowing healthy patients to be distinguished from those with GAP or CP. The results of this study suggest that IL-33 offers a potential inflammatory marker of periodontal disease, similar to IL-1α.

Glucocorticoids mediate stress induction of the alarmin HMGB1 and reduction of the microglia checkpoint receptor CD200R1 in limbic brain structures

Exposure to stressors primes neuroinflammatory responses to subsequent immune challenges and stress-induced glucocorticoids (GCs) play a mediating role in this phenomenon of neuroinflammatory priming. Recent evidence also suggests that the alarmin high-mobility group box-1 (HMGB1) and the microglial checkpoint receptor CD200R1 serve as proximal mechanisms of stress-induced neuroinflammatory priming. However, it is unclear whether stress-induced GCs play a causal role in these proximal mechanisms of neuroinflammatory priming; this forms the focus of the present investigation. Here, we found that exposure to a severe acute stressor (inescapable tailshock) induced HMGB1 and reduced CD200R1 expression in limbic brain regions and pharmacological blockade of GC signaling (RU486) mitigated these effects of stress. To confirm these effects of RU486, adrenalectomy (ADX) with basal corticosterone (CORT) replacement was used to block the stress-induced increase in GCs as well as effects on HMGB1 and CD200R1. As with RU486, ADX mitigated the effects of stress on HMGB1 and CD200R1. Subsequently, exogenous CORT was administered to determine whether GCs are sufficient to recapitulate the effects of stress. Indeed, exogenous CORT induced expression of HMGB1 and reduced expression of CD200R1. In addition, exposure of primary microglia to CORT also recapitulated the effects of stress on CD200R1 suggesting that CORT acts directly on microglia to reduce expression of CD200R1. Taken together, these findings suggest that GCs mediate the effects of stress on these proximal mechanisms of neuroinflammatory priming.

IL-33 and its increased serum levels as an alarmin for imminent pulmonary complications in polytraumatized patients

Background

According to recently published findings, we hypothesized that serum interleukin-33 (IL-33) may qualify for predicting pulmonary complications in polytraumatized patients.

Methods

One hundred and thirty patients (age ≥ 18 years, ISS ≥ 16) were included in our prospective analysis after primary admission to our level I trauma center during the first post-traumatic hour. Serum samples immediately after admission and on day 2 after trauma were obtained and analyzed.

Results

Median initial IL-33 levels (in picograms per milliliter) were higher in polytrauma victims (1) with concomitant thoracic trauma [5.08 vs. 3.52; p = 0.036], (2) sustaining parenchymal lung injury (PLI) [5.37 vs. 3.71; p = 0.027], and (3) developing acute respiratory distress syndrome (ARDS) [6.19 vs. 4.48; p = 0.003], compared to the respective rest of the study group. The median initial IL-33 levels were higher in patients experiencing both PLI and ARDS compared to those sustaining PLI and not developing ARDS [6.99 vs. 4.69; p = 0.029]. ROC statistics provided an AUC of 0.666 (p = 0.003) and a cut-off value of 4.77 (sensitivity, 71.8%; specificity, 75.7%) for predicting ARDS. Moreover, a higher initial median IL-33 level was revealed in the deceased compared to the survivors [12.25 vs. 4.72; p = 0.021]. ROC statistics identified the initial level of IL-33 as a predictor of death with 11.19 as cut-off value (sensitivity, 80.0%; specificity, 80.0%; AUC = 0.805; p = 0.021).

Conclusions

Following tissue damage, IL-33 is abundantly released in the serum of polytraumatized patients immediately after their injuries occurred. As initial IL-33 levels were particularly high in individuals experiencing both PLI and ARDS, IL-33 release after trauma seems to be involved in the promotion of ARDS and might serve already at admission as a solid indicator of impending death in polytraumatized patients.

A Non-Peptidic S100A9 Specific Ligand for Optical Imaging of Phagocyte Activity In Vivo

PURPOSE

Non-invasive assessment of inflammatory activity in the course of various diseases is a largely unmet clinical challenge. An early feature of inflammation is local secretion of the alarmin S100A8/A9 by activated phagocytes. We here evaluate a novel S100A9-targeted small molecule tracer Cy5.5-CES271 for in vivo optical imaging of inflammatory activity in exemplary disease models.

PROCEDURES

Dynamics of Cy5.5-CES271 was characterized in a model of irritant contact dermatitis by sequential fluorescence reflectance imaging (FRI) up to 24 h postinjection (p.i.). Specificity of Cy5.5-CES271 binding to S100A9 in vivo was examined by blocking studies and by employing S100A9^-/- mice. Finally, S100A9 secretion in acute lung inflammation was assessed by Cy5.5-CES271 and FRI of explanted lungs.

RESULTS

In ear inflammation, we were able to non-invasively follow the time course of S100A9 expression using Cy5.5-CES271 and FRI over 24 h p.i. (peak activity at 3 h p.i.). Specificity of imaging could be shown by a significant signal reduction after predosing and using S100A9^-/- mice. In acute lung injury, local and systemic S100A8/A9 levels increased over time and correlated significantly with FRI signal levels in explanted lungs.

CONCLUSIONS

Cy5.5-CES271 shows significant accumulation in models of inflammatory diseases and specific binding to S100A9 in vivo. This study, for the first time, demonstrates the potential of a small molecule non-peptidic tracer enabling imaging of S100A9 as a marker of local phagocyte activity in inflammatory scenarios suggesting this compound class for translational attempts.

Alarmin Detection in Senescent Cells

Senescent cells secrete diverse array of proteins. One group of proteins, damage-associated molecular pattern (DAMP) proteins exhibit relocalization from inside to outside the cell. High Mobility Group Box 1 protein (HMGB1) is the founding DAMP member. HMGB1 relocalization from the nucleus provides a molecular signature during senescence. We provide distinct molecular techniques (immunofluorescence, immunohistochemistry, and Western blot assays) to assess HMGB1 relocalization during the initial stages of senescence.

The Janus face of HMGB1 in heart disease: a necessary update. Cell Mol Life Sci. 2019;76:211-229. [PMID: 30306212 PMCID: PMC6339675 DOI: 10.1007/s00018-018-2930-9]

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein involved in transcription regulation, DNA replication and repair and nucleosome assembly. HMGB1 is passively released by necrotic tissues or actively secreted by stressed cells. Extracellular HMGB1 acts as a damage-associated molecular pattern (DAMPs) molecule and gives rise to several redox forms that by binding to different receptors and interactors promote a variety of cellular responses, including tissue inflammation or regeneration. Inhibition of extracellular HMGB1 in experimental models of myocardial ischemia/reperfusion injury, myocarditis, cardiomyopathies induced by mechanical stress, diabetes, bacterial infection or chemotherapeutic drugs reduces inflammation and is protective. In contrast, administration of HMGB1 after myocardial infarction induced by permanent coronary artery ligation ameliorates cardiac performance by promoting tissue regeneration. HMGB1 decreases contractility and induces hypertrophy and apoptosis in cardiomyocytes, stimulates cardiac fibroblast activities, and promotes cardiac stem cell proliferation and differentiation. Interestingly, maintenance of appropriate nuclear HMGB1 levels protects cardiomyocytes from apoptosis by preventing DNA oxidative stress, and mice with HMGB1cardiomyocyte-specific overexpression are partially protected from cardiac damage. Finally, higher levels of circulating HMGB1 are associated to human heart diseases. Hence, during cardiac injury, HMGB1 elicits both harmful and beneficial responses that may in part depend on the generation and stability of the diverse redox forms, whose specific functions in this context remain mostly unexplored. This review summarizes recent findings on HMGB1 biology and heart dysfunctions and discusses the therapeutic potential of modulating its expression, localization, and oxidative-dependent activities.

Immunization with Mycobacterium vaccae induces an anti-inflammatory milieu in the CNS: Attenuation of stress-induced microglial priming, alarmins and anxiety-like behavior

Exposure to stressors induces anxiety- and depressive-like behaviors, which are mediated, in part, by neuroinflammatory processes. Recent findings demonstrate that treatment with the immunoregulatory and anti-inflammatory bacterium, Mycobacterium vaccae (M. vaccae), attenuates stress-induced exaggeration of peripheral inflammation and stress-induced anxiety-like behavioral responses. However, the effects of M. vaccae on neuroimmune processes have largely been unexplored. In the present study, we examined the effect of M. vaccae NCTC11659 on neuroimmune regulation, stress-induced neuroinflammatory processes and anxiety-like behavior. Adult male rats were immunized 3× with a heat-killed preparation of M. vaccae (0.1 mg, s.c.) or vehicle. M. vaccae induced an anti-inflammatory immunophenotype in hippocampus (increased interleukin (Il)4, Cd200r1, and Mrc1 mRNA expression) and increased IL4 protein 8 d after the last immunization. Central administration of recombinant IL4 recapitulated the effects of M. vaccae on Cd200r1 and Mrc1 mRNA expression. M. vaccae reduced basal levels of genes (Nlrp3 and Nfkbia) involved in microglial priming; thus, we explored the effects of M. vaccae on stress-induced hippocampal microglial priming and HMGB1, which mediates priming. We found that M. vaccae blocked stress-induced decreases in Cd200r1, increases in the alarmin HMGB1, and priming of the microglial response to immune challenge. Furthermore, M. vaccae prevented stress-induced increases in anxiety-like behavior. The present findings suggest that M. vaccae enhances immunomodulation in the CNS and mitigates the neuroinflammatory and behavioral effects of stress, which may underpin its capacity to impart a stress resilient phenotype.

The human RNASET2 protein affects the polarization pattern of human macrophages in vitro

Macrophages represent key inflammatory cellular effectors of the innate immune response. Despite being widely acknowledged as professional phagocytes, the functional roles played by these cells have been progressively widened over the years to encompass regulation of the adaptive immune system, stimulation or suppression of cancer cell growth and tissue remodeling. These diverse functional features have led to the concept of "macrophage plasticity", i.e. the ability of these cells to express a wide range of phenotypes endowed with different functional roles. Several activation programs have been described for mammalian macrophages, based mainly on their differential transcriptional profiles. Based on established in vitro experimental conditions, many researchers currently refer to the M1 (or M1-like) and M2 (or M2-like) terms to describe the two extremes of a rather broad spectrum of polarization states that macrophages can experience in vivo. In light of the widely recognized opposite roles of M1-like and M2-like macrophages on cancer growth, and our largely incomplete knowledge of the cellular and molecular mechanisms underlying the establishment of the M1-like versus M2-like balance within a tumor mass, we report here results from in vitro assays pointing at the human RNASET2 gene as a potential regulator of the balance between M1-like/M2-like macrophage polarization. Not only do our results confirm previous in vivo data, thus further supporting a role for this pleiotropic protein in the innate immune system, but they also define RNASET2 as a new molecular target with potential applications for in vivo reprogramming of macrophage polarization, an increasingly appraised anticancer strategy.

Alarmins of the extracellular space

The ability of the immune system to discriminate between healthy-self, abnormal-self, and non-self has been attributed mainly to alarmins signaling as "danger signals". It is now evident, however, that alarmins are much more complex and can perform specialized functions that can regulate a wide spectrum of processes ranging from propagation of disease to tissue homeostasis. As such, alarmins and their signaling mechanisms are now actively pursued as therapeutic targets. The clinical utility of alarmins requires an understanding of their specific localization. Specifically, many alarmins can function paradoxically depending upon their localization, intra or extracellular. The present review focuses upon alarmin presence and differential expression in the extracellular space versus within the cell and how variation of the localization of alarmins can reveal important mechanistic insights into alarmin functions and their efficacy as biomarkers of disease and therapeutic targets.

High-mobility group nucleosome binding domain 1 (HMGN1) functions as a Th1-polarizing alarmin

High-mobility group (HMG) nucleosome binding domain 1 (HMGN1), which previously was thought to function only as a nucleosome-binding protein that regulates chromatin structure, histone modifications, and gene expression, was recently discovered to be an alarmin that contributes extracellularly to the generation of innate and adaptive immune responses. HMGN1 promotes DC recruitment through interacting with a Gαi protein-coupled receptor (GiPCR) and activates DCs predominantly through triggering TLR4. HMGN1 preferentially promotes Th1-type immunity, which makes it relevant for the fields of vaccinology, autoimmunity, and oncoimmunology. Here, we discuss the alarmin properties of HMGN1 and update recent advances on its roles in immunity and potential applications for immunotherapy of tumors.

Recent advances in understanding the roles of blood platelets in the pathogenesis of allergic inflammation and bronchial asthma

Platelets play an essential role in hemostasis to minimize blood loss due to traumatic injury. In addition, they contain various immune-associated molecules and contribute to immunological barrier formation at sites of vascular injury, thereby protecting against invading pathogens. Platelets are also crucially involved in development of allergic diseases, including bronchial asthma. Platelets in asthmatics are more activated than those in healthy individuals. By using a murine asthma model, platelets were shown to be actively involved in progression of the disease, including in airway eosinophilia and airway remodeling. In the asthmatic airway, pathological microvascular angiogenesis, a component of airway remodeling, is commonly observed, and the degree of abnormality is significantly associated with disease severity. Therefore, in order to repair the newly formed and structurally fragile blood vessels under inflammatory conditions, platelets may be continuously activated in asthmatics. Importantly, platelets constitutively express IL-33 protein, an alarmin cytokine that is essential for development of bronchial asthma. Meanwhile, the concept of development of allergic diseases has recently changed dramatically, and allergy researchers now share a belief in the centrality of epithelial barrier functions. In particular, IL-33 released from epithelial barrier tissue at sites of eczema can activate the antigen-non-specific innate immune system as an alarmin that is believed to be necessary for subsequent antigen-specific acquired immunological responses. From this perspective, we propose in this review a possible mechanism for how activated platelets act as an alarmin in development of bronchial asthma.

New insights into hypoxia-related mechanisms involved in different microvascular patterns of bronchopulmonary carcinoids and poorly differentiated neuroendocrine carcinomas. Role of ribonuclease T2 (RNASET2) and HIF-1α

Ribonuclease T2 (RNASET2) is a pleiotropic and polyfunctional protein, which exerts several different activities in neoplastic cells since the early steps of tumor development. Besides having an antitumorigenic activity, RNASET2 inhibits both bFGF-induced and VEGF-induced angiogenesis and has a role as a stress-response, alarmin-like, protein. In this study, we investigated RNASET2 expression in well-differentiated and poorly differentiated neuroendocrine neoplasms of the lung (Lu-NENs), which are known to show clear-cut differences in morphology, biology and clinical behavior. In addition, we explored possible relationships between RNASET2 expression and a series of immunohistochemical markers related to hypoxic stress, apoptosis, proliferation and angiogenesis. Our results showed a significantly higher expression of RNASET2, HIF-1α, and its target CA IX in poorly differentiated than in well-differentiated Lu-NENs, the former also showing higher proliferation and apoptotic rates, as well as a lower microvessel density (MVD) than the latter. Moreover, we were able to demonstrate in vitro an overexpression of RNASET2 in consequence of the activation of HIF-1α. In conclusion, we suggest that in poorly differentiated Lu-NENs, RNASET2 expression may be induced by HIF-1α, behaving as an alarmin-like molecule. In this aggressive group of cancers, which have highly deregulated proliferation pathways, RNASET2 fails to exert the growth-inhibiting effects described in other types of neoplasms. Its increased expression, however, may contribute to the typical phenotypic alterations seen in poorly differentiated Lu-NENs, such as the high apoptotic rate and the extensive necrosis, and may also enhance the low MVD observed in these neoplasms.

Ligation of free HMGB1 to TLR2 in the absence of ligand is negatively regulated by the C-terminal tail domain

Background

High mobility group box 1 (HMGB1) protein is a central endogenous inflammatory mediator contributing to the pathogenesis of several inflammatory disorders. HMGB1 interacts with toll-like receptors (TLRs) but contradictory evidence regarding its identity as a TLR2 ligand persists. The aim of this study was to investigate if highly purified HMGB1 interacts with TLR2 and if so, to determine the functional outcome.

Methods

Full length or C-terminal truncated (Δ30) HMGB1 was purified from E.coli. Binding to TLR2-Fc was investigated by direct-ELISA. For the functional studies, proteins alone or in complex with peptidoglycan (PGN) were added to human embryonic kidney (HEK) cells transfected with functional TLR2, TLR 1/2 or TLR 2/6 dimers, macrophages, whole blood or peripheral blood mononuclear cells (PBMCs). Cytokine levels were determined by ELISA.

Results

In vitro binding experiments revealed that Δ30 HMGB1, lacking the acidic tail domain, but not full length HMGB1 binds dose dependently to TLR2. Control experiments confirmed that the interaction was specific to TLR2 and could be inhibited by enzymatic digestion. Δ30 HMGB1 alone was unable to induce cytokine production via TLR2. However, full length HMGB1 and Δ30 HMGB1 formed complexes with PGN, a known TLR2 ligand, and synergistically potentiated the inflammatory response in PBMCs.

Conclusions

We have demonstrated that TLR2 is a receptor for HMGB1 and this binding is negatively regulated by the C-terminal tail. HMGB1 did not induce functional activation of TLR2 while both full length HMGB1 and Δ30 HMGB1 potentiated the inflammatory activities of the TLR2 ligand PGN. We hypothesize that Δ30 HMGB1 generated in vivo by enzymatic cleavage could act as an enhancer of TLR2-mediated inflammatory activities.

Electronic supplementary material

The online version of this article (10.1186/s10020-018-0021-x) contains supplementary material, which is available to authorized users.

Stress disinhibits microglia via down-regulation of CD200R: A mechanism of neuroinflammatory priming

Exposure to stressors primes the neuroinflammatory and microglial proinflammatory response to subsequent immune challenges, suggesting that stress might attenuate immunoregulatory mechanisms in the CNS microenvironment. CD200:CD200R is a key immunoregulatory signaling dyad that constrains microglial activation, and disruption of CD200:CD200R signaling primes microglia to subsequent immune challenges. Therefore, the present study examined the mediating role of CD200:CD200R signaling in stress-induced microglial priming. Here, we found that exposure to an acute stressor reduced CD200R expression across sub-regions of the hippocampus, amygdala as well as in isolated hippocampal microglia. A transcriptional suppressor of CD200R, CAAT/Enhancer Binding Proteinβ, was induced by stress and inversely associated with CD200R expression. To examine whether disrupted CD200:CD200R signaling plays a mediating role in stress-induced microglial priming, a soluble fragment of CD200 (mCD200Fc) was administered intra-cisterna magna prior to stressor exposure and stress-induced microglia priming assessed ex vivo 24 h later. Treatment with mCD200Fc blocked the stress-induced priming of the microglial pro-inflammatory response. Further, treatment with mCD200R1Fc recapitulated the effects of stress on microglial priming. We previously found that stress increases the alarmin high mobility group box-1 (HMGB1) in hippocampus, and that HMGB1 mediates stress-induced priming of microglia. Thus, we examined whether stress-induced increases in hippocampal HMGB1 are a consequence of disrupted CD200:CD200R signaling. Indeed, treatment with mCD200Fc prior to stress exposure blocked the stress-induced increase in hippocampal HMGB1. The present study suggests that stress exposure disrupts immunoregulatory mechanisms in the brain, which typically constrain the immune response of CNS innate immune cells. This attenuation of immunoregulatory mechanisms may thus permit a primed activation state of microglia to manifest.

The Heart as a Psychoneuroendocrine and Immunoregulatory Organ

The heart can be viewed not just as muscle pump but also as an important checkpoint for a complex network of nervous, endocrine, and immune signals. The heart is able to process neurological signals independently from the brain and to crosstalk with the endocrine and immune systems. The heart communicates with the psyche through the neuro-endocrine-immune system in a highly integrated way, in order to maintain the homeostasis of the whole body with peculiarities specific to males and females.

Plasma levels of alarmin HNPs 1-3 associate with lung dysfunction after cardiac surgery in children

Background

Early onset of lung injury is considerable common after cardiac surgery and is associated with increasing in morbidity and mortality, but current clinical predictors for the occurrence of this complication always have limited positive warning value. This study aimed to evaluate whether elevated plasma levels of human neutrophil peptides (HNPs) 1–3 herald impaired lung function in infants and young children after cardiac surgery necessitating cardiopulmonary bypass (CPB).

Methods

Consecutive children younger than 3 years old who underwent cardiac surgery were prospectively enrolled. Plasma concentrations of HNPs 1–3 and inflammatory cytokines were measured before, and immediately after CPB, as well as at 1 h, 12 h, and 24 h after CPB.

Results

Thirty patients were enrolled, 18 (60%) of whom were infants. Plasma levels of HNPs 1–3 and the pro-inflammatory cytokine interleukin-6 (IL-6) significantly increased immediately after CPB (P < 0.001), while IL-8 increased 1 h after the CPB operation (P = 0.002). The anti-inflammatory cytokine IL-10 levels were also significantly elevated immediately after CPB compared with the baseline (P < 0.001). The stepwise multiple linear regression analysis showed that the plasma HNPs 1–3 levels immediately after CPB was independent correlated with the declined lung function, as reflected by the PaO₂/FiO₂ ratio on the first 2 days after operation (for the first day: OR, −1.067, 95% CI, −0.548 to −1.574; P < 0.001; for the second day: OR, −0.667, 95% CI, −0.183 to −1.148; P = 0.009) and prolonged mechanical ventilation time (OR, 0.039, 95% CI, 0.005 to 0.056; P = 0.011). Plasma levels of HNPs 1–3 and IL-10 returned to the baseline values, while IL-6 and IL-8 levels remained significantly higher than baseline 24 h after CPB (P ≤ 0.01).

Conclusions

Elevated HNPs 1–3 levels immediately after CPB correlate with impaired lung function, and HNPs 1–3 could serve as a quantifiable early alarmin biomarker for onset of lung injury in infants and young children undergoing cardiac surgery with CPB.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0558-4) contains supplementary material, which is available to authorized users.

HMGB1, an innate alarmin, plays a critical role in chronic inflammation of adipose tissue in obesity

Obesity has emerged as an imminent global public health concern over the past several decades. It has now become evident that obesity is characterized by the persistent and low-grade inflammation in the adipose tissue, and serves as an independent risk factor for many metabolic disorders such as diabetes and cardiovascular disease. Particularly, adipocytes originated from obese mice and humans likely predominate necrosis upon stressful insults, leading to passive release of cellular contents including the high mobility group box 1 (HMGB1) into the extracellular milieu. Extracellular HMGB1 acts as an innate alarmin to stimulate the activation of resident immune cells in the adipose tissue. Upon activation, those resident immune cells actively secrete additional HMGB1, which in turn activates/recruits additional immune cells, and induces adipocyte death. This review summarizes those novel discoveries in terms of HMGB1 in the initiation and maintenance of chronic inflammatory state in adipose tissue in obesity, and discusses its potential application in clinical settings.

Cytokine expression and barrier disruption in human corneal epithelial cells induced by alarmin released from necrotic cells

PURPOSE

Dying cells release endogenous molecules known as alarmins that signal danger to surrounding tissue. We investigated the effects of necrotic cell-derived alarmins on cytokine expression and barrier function in human corneal epithelial cells.

METHODS

The release of interleukin (IL)-6 and IL-8 from immortalized human corneal epithelial (HCE) cells in culture was measured with enzyme-linked immunosorbent assays. The abundance of IL-6 and 8 mRNAs was quantitated by reverse transcription and real-time polymerase chain reaction analysis. Barrier function of HCE cells was evaluated by measurement of transepithelial electrical resistance (TER). The subcellular localization of the p65 subunit of the transcription factor NF-κB was determined by immunofluorescence analysis, and phosphorylation of the endogenous NF-κB inhibitor IκBα was examined by immunoblot analysis.

RESULTS

A necrotic cell supernatant prepared from HCE cells induced the up-regulation of IL-6 and 8 expression at both mRNA and protein levels as well as reduced TER in intact HCE cells. Among alarmins tested, only IL-1α (not IL-33 or HMGB1) mimicked these effects of the necrotic cell supernatant. Furthermore, IL-1 receptor antagonist (IL-1RA) and neutralizing antibodies to IL-1α (but not those to IL-1β) each attenuated the effects of the necrotic cell supernatant. Exposure of HCE cells to the necrotic cell supernatant also induced the phosphorylation and degradation of IκBα as well as translocation of the p65 subunit of NF-κB to the nucleus.

CONCLUSION

IL-1α released from necrotic corneal epithelial cells may trigger inflammatory responses at the ocular surface, including cytokine production and barrier disruption.

Association between HMGB1 and asthma: a literature review

Background

Recently, some studies demonstrated that HMGB1, as proinflammatory mediator belonging to the alarmin family, has a key role in different acute and chronic immune disorders. Asthma is a complex disease characterised by recurrent and reversible airflow obstruction associated to airway hyper-responsiveness and airway inflammation.

Objective

This literature review aims to analyse advances on HMGB1 role, employment and potential diagnostic application in asthma.

Methods

We reviewed experimental studies that investigated the pathogenetic role of HMGB in bronchial airway hyper-responsiveness, inflammation and the correlation between HMGB1 level and asthma.

Results

A total of 19 studies assessing the association between HMGB1 and asthma were identified.

Conclusions

What emerged from this literature review was the confirmation of HMGB-1 involvement in diseases characterised by chronic inflammation, especially in pulmonary pathologies. Findings reported suggest a potential role of the alarmin in being a stadiation method and a marker of therapeutic efficacy; finally, inhibiting HMGB1 in humans in order to contrast inflammation should be the aim for future further studies.

Alarmin high mobility group box-1 in maternal serum as a potential biomarker of chorioamnionitis-associated preterm birth

Chorioamnionitis is associated with an increased risk of spontaneous preterm birth. The aim of this study was to investigate the serum levels of high mobility group box-1 (HMGB1) in pregnancies with histological chorioamnionitis (HCA)-associated preterm labor (PTL) with intact membranes or preterm premature rupture of membranes (PPROM), and to access the role of serum HMGB1 in HCA and HCA-associated PTL. A total of 190 pregnant women were enrolled in this study: PLT patients with (n = 28) or without HCA (n = 36), PPROM patients with (n = 26) or without HCA (n = 65), and non-HCA PTL controls (n = 35). Maternal serum levels of HMGB1 were measured by enzyme-linked immunosorbent assay. Serum HMGB1 levels were significantly higher in PTL or PPROM patients than in control group (p < 0.01, respectively). The PPROM patients also exhibited higher serum HMGB1 levels compared to PTL patients (p = 0.015). HCA patients were characterized by significantly increased levels of serum HMGB1 when compared with non-HCA patients (p < 0.01). Therefore, maternal serum HMGB1 may become a potential biomarker of HCA and HCA-associated PTL.

High-mobility group box 1 is associated with neurological outcome in patients with post-cardiac arrest syndrome after out-of-hospital cardiac arrest

BACKGROUND

Alarmins, including high-mobility group box 1 (HMGB-1), can be released from damaged tissues and activated cells as inflammatory mediators. We aimed to evaluate HMGB-1 and mitochondrial DNA dynamics and estimate the prognostic value for neurological outcome in patients with post-cardiac arrest syndrome after out-of-hospital cardiac arrest.

METHODS

We evaluated the dynamics of HMGB-1, mitochondrial DNA, and other variables in patients with return of spontaneous circulation after out-of-hospital cardiac arrest. Patients were divided into two groups according to the cerebral performance category at 30 days: the favourable outcome group (cerebral performance categories 1 and 2) and unfavourable group (≥3).

RESULTS

Twenty-one patients were included, and 11 demonstrated favourable outcomes. HMGB-1 levels and mitochondrial DNA on day 1 were significantly higher than on days 2, 3, 5, and 7. Plasma levels of HMGB-1 on day 1 correlated with prognostic parameters (estimated interval to return of spontaneous circulation, lactate, and NH3), tissue damage, systemic inflammation, and disease severity. HMGB-1 on day 1 in the unfavourable group was significantly higher than in the favourable group (median [interquartile range] 15.5 [6.65-18.7], 39.4 [17-69.5], P = 0.009). These findings were not observed regarding mitochondrial DNA. Regarding HMGB-1 prediction accuracy for a good neurological outcome, the area under the receiver operating characteristic curve was 0.864 (95 % confidence interval 0.702, 1.000).

CONCLUSIONS

HMGB-1 may be involved in acute-phase post-cardiac arrest syndrome pathophysiology, and an increase in plasma levels may be associated with a poor neurological outcome. The study was registered with the University Hospital Medical Information Network Clinical Trials Registry ID: UMIN000006714.

Alarmin human α defensin HNP1 activates plasmacytoid dendritic cells by triggering NF-κB and IRF1 signaling pathways

Human neutrophil peptide 1 (HNP1), a predominant α defensin in the azurophilic granules of human neutrophils, is an alarmin capable of inducing the migration and maturation of human myeloid/conventional dendritic cells. However, it is not determined whether it can activate plasmacytoid dendritic cells (pDCs). Herein, we found that both human pDCs and CAL-1 cells, a pDC-like cell line, produced IFNα upon treatment with HNP1. Additionally, HNP1 could promote CpG ODN-induced pDC production of proinflammatory cytokines including IFNα. HNP1 triggered activation of NF-κB and nuclear translocation of interferon regulatory factor 1 (IRF1) in CAL-1 cells. HNP1 upregulation of cytokine expression in pDCs was inhibited by blockade of NF-κB activation or knockdown of IRF1, demonstrating the importance of these two signaling events in HNP1-induced pDC activation. Using a human pDC-nude mouse model, HNP1 was shown to induce IFNα production by human pDCs in vivo. Thus, HNP1 can activate human pDCs using NF-κB and IRF signaling pathways, and HNP-induced IFN production may participate in the inflammatory pathogenesis in certain authoimmune diseases such as rheumatoid arthritis.

Hepatoma derived growth factor (HDGF) dynamics in ovarian cancer cells

As a leading cause of cancer death among women, identification of pathophysiologically-relevant biomarkers for ovarian cancer is important. The heparin binding, hepatoma-derived growth factor (HDGF) is overexpressed in ovarian cancer cell lines and may have prognostic value, but the mechanism by which this predominantly nuclear protein is secreted or functions is unknown. In this study, we focused on the circumstances under which HDGF is released by cells and the functional relevance of extracellular HDGF in the context of ovarian cancer. Immunofluorescence imaging showed nuclear localization of HDGF in ovarian cells, but unlike what is reported for other cell types, HDGF was minimally secreted into the media. However, HDGF was passively released by necrotic and late apoptotic cells. Extracellular HDGF was functionally relevant as it stimulated phosphorylation of ERK 1/2 and P38 in both non-cancer and ovarian cancer cells, and enhanced cellular migration. Overall, our study uncovers a novel function of HDGF as a messenger of cellular condition (alarmin) which in-turn modulates cellular function-aspects that could be used as a biomarker for ovarian cancer.

Leukocytes recruited by tumor-derived HMGB1 sustain peritoneal carcinomatosis

The factors that determine whether disseminated transformed cells in vivo yield neoplastic lesions have only been partially identified. We established an ad hoc model of peritoneal carcinomatosis by injecting colon carcinoma cells in mice. Tumor cells recruit inflammatory leukocytes, mostly macrophages, and generate neoplastic peritoneal lesions. Phagocyte depletion via clodronate treatment reduces neoplastic growth. Colon carcinoma cells release a prototypic damage-associated molecular pattern (DAMP)/alarmin, High Mobility Group Box1 (HMGB1), which attracts leukocytes. Exogenous HMGB1 accelerates leukocyte recruitment, macrophage infiltration, tumor growth and vascularization. Lentiviral-based HMGB1 knockdown or pharmacological interference with its extracellular impair macrophage recruitment and tumor growth. Our findings provide a preclinical proof of principle that strategies based on preventing HMGB1-driven recruitment of leukocytes could be used for treating peritoneal carcinomatosis.

Prothymosin Alpha and Immune Responses: Are We Close to Potential Clinical Applications?

The thymus gland produces soluble molecules, which mediate significant immune functions. The first biologically active thymic extract was thymosin fraction V, the fractionation of which led to the isolation of a series of immunoactive polypeptides, including prothymosin alpha (proTα). ProTα displays a dual role, intracellularly as a survival and proliferation mediator and extracellularly as a biological response modifier. Accordingly, inside the cell, proTα is implicated in crucial intracellular circuits and may serve as a surrogate tumor biomarker, but when found outside the cell, it could be used as a therapeutic agent for treating immune system deficiencies. In fact, proTα possesses pleiotropic adjuvant activity and a series of immunomodulatory effects (eg, anticancer, antiviral, neuroprotective, cardioprotective). Moreover, several reports suggest that the variable activity of proTα might be exerted through different parts of the molecule. We first reported that the main immunoactive region of proTα is the carboxy-terminal decapeptide proTα(100-109). In conjunction with data from others, we also revealed that proTα and proTα(100-109) signal through Toll-like receptor 4. Although their precise molecular mechanism of action is yet not fully elucidated, proTα and proTα(100-109) are viewed as candidate adjuvants for cancer immunotherapy. Here, we present a historical overview on the discovery and isolation of thymosins with emphasis on proTα and data on some immune-related new activities of the polypeptide and smaller immunostimulatory peptides thereof. Finally, we propose a compiled scenario on proTα's mode of action, which could eventually contribute to its clinical application.

Galectins: Double-edged Swords in the Cross-roads of Pregnancy Complications and Female Reproductive Tract Inflammation and Neoplasia

Galectins are an evolutionarily ancient and widely expressed family of lectins that have unique glycan-binding characteristics. They are pleiotropic regulators of key biological processes, such as cell growth, proliferation, differentiation, apoptosis, signal transduction, and pre-mRNA splicing, as well as homo- and heterotypic cell-cell and cell-extracellular matrix interactions. Galectins are also pivotal in immune responses since they regulate host-pathogen interactions, innate and adaptive immune responses, acute and chronic inflammation, and immune tolerance. Some galectins are also central to the regulation of angiogenesis, cell migration and invasion. Expression and functional data provide convincing evidence that, due to these functions, galectins play key roles in shared and unique pathways of normal embryonic and placental development as well as oncodevelopmental processes in tumorigenesis. Therefore, galectins may sometimes act as double-edged swords since they have beneficial but also harmful effects for the organism. Recent advances facilitate the use of galectins as biomarkers in obstetrical syndromes and in various malignancies, and their therapeutic applications are also under investigation. This review provides a general overview of galectins and a focused review of this lectin subfamily in the context of inflammation, infection and tumors of the female reproductive tract as well as in normal pregnancies and those complicated by the great obstetrical syndromes.

Identification of a functional interaction of HMGB1 with Receptor for Advanced Glycation End-products in a model of neuropathic pain

Recent studies indicate that the release of high mobility group box 1 (HMGB1) following nerve injury may play a central role in the pathogenesis of neuropathic pain. HMGB1 is known to influence cellular responses within the nervous system via two distinct receptor families; the Receptor for Advanced Glycation End-products (RAGE) and Toll-like receptors (TLRs). The degree to which HMGB1 activates a receptor is thought to be dependent upon the oxidative state of the ligand, resulting in the functional isoforms of all-thiol HMGB1 (at-HMGB1) acting through RAGE, and disufide HMGB1 (ds-HMGB1) interacting with TLR4. Though it is known that dorsal root ganglia (DRG) sensory neurons exposed to HMGB1 and TLR4 agonists can influence excitation, the degree to which at-HMGB1 signaling through neuronal RAGE contributes to neuropathic pain is unknown. Here we demonstrate that at-HMGB1 activation of nociceptive neurons is dependent on RAGE and not TLR4. To distinguish the possible role of RAGE on neuropathic pain, we characterized the changes in RAGE mRNA expression up to one month after tibial nerve injury (TNI). RAGE mRNA expression in lumbar dorsal root ganglion (DRG) is substantially increased by post-injury day (PID) 28 when compared with sham injured rodents. Protein expression at PID28 confirms this injury-induced event in the DRG. Moreover, a single exposure to monoclonal antibody to RAGE (RAGE Ab) failed to abrogate pain behavior at PID 7, 14 and 21. However, RAGE Ab administration produced reversal of mechanical hyperalgesia on PID28. Thus, at-HMGB1 activation through RAGE may be responsible for sensory neuron sensitization and mechanical hyperalgesia associated with chronic neuropathic pain states.

Neutrophil extracellular traps, damage-associated molecular patterns, and cell death during sepsis

In addition to pathogen-associated molecular patterns from invasive microorganisms, alarmins, which are major components of host defense mechanisms, are involved in the pathophysiology of sepsis. In fact, the magnitude of the insult is defined according to the damage-associated molecular pattern (DAMP), which is composed of alarmins as well as pathogen-associated molecular patterns, such as those involving nucleosomes, histones, and DNA. Regarding the antimicrobial mechanism of neutrophils, an alternative non-phagocytic mechanism was first recognized as "NETosis" in 2004. In this mechanism, microorganisms are trapped and eliminated by neutrophil extracellular traps (NETs). These NETs are composed of histones and DNA that have been expelled from the nucleus as well as antimicrobial proteases, including elastase and myeloperoxidase. NETosis, a cell death pathway reported to be distinct from apoptosis, is an active area of research. As NETs are composed of deleterious substances, they are extremely harmful to the host cells once they are released into the circulating blood. Therefore, the meanings and putative roles of these components in sepsis have attracted much attention.

Stress-induced glucocorticoids as a neuroendocrine alarm signal of danger

A considerable number of studies demonstrate that acute and chronic stressors prime CNS innate immune responses to subsequent pro-inflammatory challenges and that glucocorticoids mediate, in part, stress-induced sensitization of pro-inflammatory immune responses. Here, we explore the notion that GCs produce a persisting sensitization of CNS innate immune effectors (e.g. microglia) so that they will generate a potentiated pro-inflammatory response after the GC rise has dissipated, thereby enhancing the sickness response to infection or injury and maximizing the animal's ability to neutralize danger. The stress-induced GC response is conceptualized here as an neuroendocrine warning signal or alarmin to the innate immune system, which prepares or sensitizes the innate immune response to potential danger. Thus, a new understanding of the stress response and its function (priming CNS innate immune responses to infection or injury during a fight/flight emergency) would be suggested.