Letteratura scientifica selezionata sul tema "Alarmin HMGB1"

Osteoarthritis (OA) is a multifactorial disease in which genetics, aging, obesity, and trauma are well-known risk factors. It is the most prevalent joint disease and the largest disability problem worldwide. Recent findings have described the role of damage-associated molecular patterns (DAMPs) in the course of the disease. In particular, alarmins such as HMGB1, IL-33, and S100B, appear implicated in enhancing articular inflammation and favouring a catabolic switch in OA chondrocytes. The aims of this review are to clarify the molecular signalling of these three molecules in OA pathogenesis, to identify their possible use as staging biomarkers, and, most importantly, to find out whether they could be possible therapeutic targets. Osteoarthritic cartilage expresses increased levels of all three alarmins. HMGB1, in particular, is the most studied alarmin with increased levels in cartilage, synovium, and synovial fluid of OA patients. High levels of HMGB1 in synovial fluid of OA joints are positively correlated with radiological and clinical severity. Counteracting HMGB1 strategies have revealed improving results in articular cells from OA patients and in OA animal models. Therefore, drugs against this alarmin, such as anti-HMGB1 antibodies, could be new treatment possibilities that can modify the disease course since available medications only alleviate symptoms.

Psoriasis is a multifactorial pathology linked to systemic inflammation. Enhanced keratinocytes proliferation and a minor maturation state of the cells are typical features. Perivascular T cells, dendritic cells, macrophages, and neutrophilic granulocytes are part of the scenario completed by apoptosis dysregulation. Several proinflammatory mediators, alarmins and growth factors are increased too, both in the skin and the patients’ blood. HMGB1 is important as an alarmin in several inflammatory conditions. Released after cellular damage, HMGB1 acts as a danger signal. Several studies have considered its role in psoriasis pathogenesis. We evaluated its level in psoriasis and the potential of the alarmin blockade through standard therapies, biological treatments and using monoclonal antibodies. PV patients were shown to have significantly increased levels of HMGB1 both in lesional skin and in serum, which were linked, in some cases, to other pro-inflammatory markers and alarmins. In most cases these parameters were correlated with PASI score. Data demonstrated that blocking HMGB1 is effective in ameliorating psoriasis. Focusing on this approach could be valuable in terms of a therapeutic option for counteracting immune-related diseases in a way unthinkable until few years ago.

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

Cellular senescence irreversibly arrests proliferation in response to potentially oncogenic stress. Senescent cells also secrete inflammatory cytokines such as IL-6, which promote age-associated inflammation and pathology. HMGB1 (high mobility group box 1) modulates gene expression in the nucleus, but certain immune cells secrete HMGB1 as an extracellular Alarmin to signal tissue damage. We show that nuclear HMGB1 relocalized to the extracellular milieu in senescent human and mouse cells in culture and in vivo. In contrast to cytokine secretion, HMGB1 redistribution required the p53 tumor suppressor, but not its activator ATM. Moreover, altered HMGB1 expression induced a p53-dependent senescent growth arrest. Senescent fibroblasts secreted oxidized HMGB1, which stimulated cytokine secretion through TLR-4 signaling. HMGB1 depletion, HMGB1 blocking antibody, or TLR-4 inhibition attenuated senescence-associated IL-6 secretion, and exogenous HMGB1 stimulated NF-κB activity and restored IL-6 secretion to HMGB1-depleted cells. Our findings identify senescence as a novel biological setting in which HMGB1 functions and link HMGB1 redistribution to p53 activity and senescence-associated inflammation.

Abstract Objectives Preterm birth remains the leading cause of perinatal morbidity and mortality worldwide. Preterm birth is preceded by spontaneous preterm labor, which is commonly associated with sterile intra-amniotic inflammation; yet, no approved treatment exists for this clinical condition. Corticosteroids are the standard of care to improve neonatal outcomes in women at risk of preterm birth. Herein, we first validated our model of alarmin-induced preterm birth. Next, we investigated whether treatment with betamethasone could prevent preterm birth resulting from sterile intra-amniotic inflammation in mice. Methods Under ultrasound guidance, the first cohort of dams received an intra-amniotic injection of the alarmin high-mobility group box-1 (HMGB1, n=10) or phosphate-buffered saline (PBS, n=9) as controls. A second cohort of dams received HMGB1 intra-amniotically and were subcutaneously treated with betamethasone (n=15) or vehicle (n=15). Dams were observed until delivery, and perinatal outcomes were observed. Results Intra-amniotic HMGB1 reduced gestational length (p=0.04), inducing preterm birth in 40% (4/10) of cases, of which 100% (4/4) were categorized as late preterm births. Importantly, treatment with betamethasone extended the gestational length (p=0.02), thereby reducing the rate of preterm birth by 26.6% (from 33.3% [5/15] to 6.7% [1/15]). Treatment with betamethasone did not worsen the rate of neonatal mortality induced by HMGB1 or alter weight gain in the first three weeks of life. Conclusions Treatment with betamethasone prevents preterm birth induced by the alarmin HMGB1. This study supports the potential utility of betamethasone for treating women with sterile intra-amniotic inflammation.

HMGB1 is an alarmin, a protein that warns and activates inflammation. Chronic obstructive pulmonary disease (COPD) is characterised by a progressive airflow obstruction and airway inflammation. Current anti-inflammatory therapies are poorly effective in maintaining lung function and symptoms of COPD. This underlines the need for finding new molecular targets involved in disease pathogenesis in order to block pathology progression. This review aims to analyse latest advances on HMGB1 role, utilisation, and potential application in COPD. To this purpose we reviewed experimental studies that investigated this alarmin as marker as well as a potential treatment in chronic obstructive pulmonary disease. This systematic review was conducted according to PRISMA guidelines. In almost all the studies, it emerged that HMGB1 levels are augmented in smokers and in patients affected by COPD. It emerged that cigarette smoking, the most well-known causative factor of COPD, induces neutrophils death and necrosis. The necrosis of neutrophil cells leads to HMGB1 release, which recruits other neutrophils in a self-maintaining process. According to the results reported in the paper both inhibiting HMGB1 and its receptor (RAGE) and blocking neutrophils necrosis (inducted by cigarette smoking) could be the aim for further studies.

Alarmins are endogenous mediators released by cells following insults or cell death to alert the host’s innate immune system of a situation of danger or harm. Many of these, such as high-mobility group box-1 and 2 (HMGB1, HMGB2) and S100 (calgranulin proteins), act through RAGE (receptor for advanced glycation end products), whereas the IL-1 and IL-33 cytokines bind the IL-1 receptors type I and II, and the cellular receptor ST2, respectively. The alarmin family and their signal pathways share many similarities of cellular and tissue localization, functions, and involvement in various physiological processes and inflammatory diseases including osteoporosis. The aim of the review was to evaluate the role of alarmins in osteoporosis. A bibliographic search of the published scientific literature regarding the role of alarmins in osteoporosis was organized independently by two researchers in the following scientific databases: Pubmed, Scopus, and Web of Science. The keywords used were combined as follows: “alarmins and osteoporosis”, “RAGE and osteoporosis”, “HMGB1 and osteoporosis”, “IL-1 and osteoporosis”, “IL 33 and osteopororsis”, “S100s protein and osteoporosis”. The information was summarized and organized in the present review. We highlight the emerging roles of alarmins in various bone remodeling processes involved in the onset and development of osteoporosis, as well as their potential role as biomarkers of osteoporosis severity and progression. Findings of the research suggest a potential use of alarmins as pharmacological targets in future therapeutic strategies aimed at preventing bone loss and fragility fractures induced by aging and inflammatory diseases.

Abstract The precise mechanism by which autophagy affects psoriasis is poorly understood. Here we show that keratinocytes (KCs) autophagy was activated in psoriatic lesions of patients and mice model, positively correlating with psoriatic severity, and could be inhibited by MAPK family (ERK, p38, JNK) inactivation, implying autophagy was associated with psoriatic inflammation. Indeed, impaired autophagy flux, caused by autophagy inhibitors or KC-specific deletion of Atg5, alleviated psoriasisform inflammation, demonstrating autophagy positively regulated psoriatic inflammation. We then found an autophagy-based unconventional secretory pathway (autosecretion), depended on Atg5 and GRASP55, promoted the psoriasiform KCs inflammation. Moreover, alarmin HMGB1 was more effective than other autosecretory proteins, IL-1β and IL-18, to regulate the psoriasiform cutaneous inflammation. HMGB1 neutralization in autophagy-efficient KCs vanished the psoriasiform inflammation differences between autophagy-efficient KCs and autophagy-deficient KCs. Conversely, recombinant HMGB1 almost completely restored the psoriasiform inflammation in autophagy-deficient KCs in vivo. These results suggested that HMGB1-associated autosecretion, not other intracellular autophagy pathways, played a pivotal role in cutaneous inflammation. Finally, we demonstrated that KC-specific HMGB1 deficient mice, but not DC- or myeloid cell-specific HMGB1 deficient mice, displayed attenuated psoriatic inflammation, due to the essential crosstalk between KC-specific HMGB1-associated autosecretion and γδT cells. Thus, we uncover a novel autophagy mechanism in psoriasis pathogenesis, and imply its clinical significance in psoriasis treatment.

La protéase C1s est un élément central dans l’initiation de la voie classique du système du complément. Elle était auparavant considérée comme ciblant exclusivement les protéines C2 et C4 dans cette cascade protéolytique. Des découvertes récentes ont cependant mis en lumière la présence de C1s libre constitutivement active dans certaines pathologies, suggérant un rôle plus large de cette protéase au-delà de l'activation du complément. Parmi les cibles non-canoniques identifiées de C1s figure la protéine HMGB1, initialement décrite comme une protéine nucléaire impliquéedans la condensation de la chromatine et l'expression des gènes. Des études récentes ont démontré que HMGB1 peut également être localisée dans différents compartiments cellulaires et qu'elle joue un rôle crucial dans l'inflammation lorsqu'elle est libérée dans le milieu extracellulaire. Ce projet de thèse avait pour objectif principal d'élucider le rôle du clivage de HMGB1 par C1s dans la modulation de la réponse inflammatoire. Nos travaux ont démontré que les fragments de digestion de HMGB1 possèdent des effets distincts de la protéine entière sur l'activation du complément et laréponse cytokinique des macrophages. Nous avons notamment confirmé que la protéine entière active la voie classique du complément lorsqu’elle est fixée à une surface et qu’elle favorise la polarisation M1 des macrophages en réponse aux LPS. En revanche, le fragment f2 est capable d'activer la voie classique du complément même lorsqu’il est en solution, tandis que le fragment f3 inhibe la sécrétion de cytokines pro-inflammatoires dans les études cellulaires. De plus, nous avons exploré l'impact de l'état d'oxydo-réduction des cystéines sur les effets de HMGB1 et de ses fragmentsen utilisant des mutants mimétiques. La digestion de HMGB1 est restreinte lorsque la protéine est sous forme disulfure, suggérant un rôle important du pont disulfure dans l’accès aux sites de digestion par C1s. Les formes redox de la protéine entière ne semblent pas affecter sa capacité à activer le complément, tandis que le fragment f2 oxydé pourrait perdre sa capacité d'activation en solution. Ces résultats révèlent que le clivage de HMGB1 par C1s agit comme un chronomètre de l’inflammation, orchestrant la réponse inflammatoire via la transition d’une phase d’amplification pro-inflammatoireà une phase de résolution. Ces découvertes ouvrent de nouvelles perspectives pour la compréhension des mécanismes complexes de l'inflammation et le développement de thérapies pour le traitement de pathologies inflammatoires<br>C1s protease is a central component in the initiation of the classical pathway of the complement system. It was originally believed to exclusively target proteins C2 and C4 in this proteolytic cascade. However, recent discoveries have highlighted the presence of constitutively active free C1s in certain pathologies, suggesting a broader role for this protease beyond complement activation. Among the non-canonical targets identified for C1s is the HMGB1 protein, initially described as a nuclear protein involved in chromatin condensation and gene expression.Recent studies have shown that HMGB1 can also be localized in different cellular compartments and plays a crucial role in inflammation when released into the extracellular environment. The main objective of this thesis project was to elucidate the role of C1s cleavage of HMGB1 in modulating the inflammatory response. Our work has shown that HMGB1 digestion fragments have distinct effects from the whole protein on complement activation and macrophage cytokine responses.In particular, we confirmed that the whole protein activates the classical complement pathway when bound to a surface and promotes M1 macrophage polarization in response to LPS. In contrast, fragment f2 is capable of activating the classical complement pathway, even when in solution, while fragment f3 inhibits the secretion of pro-inflammatory cytokines in cell studies. In addition, we explored the impact of cysteine redox state on the effects of HMGB1 and its fragments using mimetic mutants. HMGB1 digestion is restricted when the protein is in disulfide form, suggesting an important role of the disulfide bridge in access to the C1s digestion site. The redox forms of the whole protein do notappear to affect its ability to activate complement, while oxidized fragment f2 may lose its ability to activate it in solution. These results reveal that C1s cleavage of HMGB1 acts as an inflammation timer, orchestrating the inflammatory response through the transition from a pro-inflammatory amplification phase to a resolution phase. These findings open new perspectives for understanding the complex mechanisms of inflammation and the development of therapies for the treatment of inflammatory diseases

La neuro-inflammation induite par l'inflammation systémique ou générée en réponse à une lésion cérébrale aiguë a des conséquences cliniques néfastes : elle est mise en cause dans l'aggravation des lésions cérébrales aiguës chez l'homme, aussi bien chez l'adulte que chez l'enfant. La microglie est l'effecteur cérébral principal de cette réponse inflammatoire, et peut présenter selon les situations un profil neurotoxique ou, au contraire, anti-inflammatoire et régulateur. La compréhension des mécanismes d'activation microgliale et de leurs conséquences est capitale pour une meilleure prise en charge des malades. La première partie de ce travail de thèse s'intéresse aux conséquences de l'inflammation néonatale associée à la prématurité sur la réponse microgliale à l'âge adulte, face à de nouvelles agressions cérébrales que sont l'inflammation systémique et les lésions cérébrales aiguës. Dans un modèle murin d'inflammation néonatale, nous avons mis en évidence d'importantes modifications du transcriptome microglial une fois ces souris adultes. De plus, un stimulus inflammatoire à l'âge adulte modifie le profil d'activation microgliale, le pic des marqueurs pro-inflammatoires et immuno-régulateurs survenant plus précocement et intensément, démontrant l'existence d'une mémoire du système immunitaire inné cérébral. Ces modifications dans le profil d'activation microgliale s'accompagnent dans un modèle de lésion cérébrale excitotoxique d'une majoration de la taille des lésions de la substance blanche. Un traitement par mélatonine des souriceaux prévient cette aggravation. La deuxième partie de ce travail a consisté à caractériser in vitro le profil d'activation microgliale en réponse à une stimulation par HMGB1, une alarmine relarguée lors de la mort cellulaire et donc présente en cas de lésion cérébrale aiguë mais aussi de lésions extra-crâniennes associées. Nous avons montré que le profil d'activation microgliale dépend du type d'HMGB1 utilisé. Les microglies exposées à la forme recombinante de chez Sigma présentent un profil transcriptomique proinflammatoire mais une baisse des taux de cytokines sécrétées dans le milieu. Ces résultats mettent en évidence l'importance de l'inflammation et de l'activation microgliale dans le pronostic des lésions cérébrales et offrent la possibilité de mettre en place des stratégies neuroprotectrices innovantes<br>Neuroinflammation induced by systemic inflammation or generated in response to acute brain injury has adverse clinical consequences: it is implicated in exacerbation of acute brain injury in humans, for adults as well as for children. Microglia is the main effector of this cerebral inflammatory response, and may present, depending on the situation, a neurotoxic or - on the opposite - anti-inflammatory and regulating profile. To decipher the mechanisms of microglial activation and their consequences is essential for better management of patients.The first part of this thesis focuses on the consequences of neonatal inflammation associated with prematurity on the microglial response in adulthood, in case of new cerebral aggressions such as systemic inflammation or acute brain injury. Relying on a mouse model of inflammation of the preterm infant, we have demonstrated drastic modifications of the microglial transcriptome once these mice are adults. Moreover, when an inflammatory stimulus occurs in adulthood, the microglial activation profile is altered, the peak of pro-inflammatory and immuno-regulatory markers occurring earlier, demonstrating the existence of a memory of the cerebral innate immune system. These changes in the microglial activation profile are accompanied in a model of excitotoxic brain injury by an increase of the white matter lesion size. Melatonin treatment of mice prevents the happening of this worse outcome. In the second part of this thesis, we characterized the microglial activation profile in vitro, in response to stimulation by HMGB1, a damage associated molecular pattern released during cell death and therefore present in acute brain injuries but also in associated extra-cranial injuries. We have shown that the microglial activation profile depends of the kind of HMGB1 used. Microglia exposed to Sigma recombinant form have a proinflammatory transcriptomic profile but a lower release of cytokines in the culture medium. These results highlight the importance of inflammation and microglial activation in the prognosis of brain injuries and offer the opportunity to implement innovative neuroprotective strategies