Levels Of Damage-associated Molecular Patterns Research Articles

Exosomes in Sepsis.

Sepsis is a severe state of infection with high mortality. Pathogen-associated molecular patterns and damage-associated molecular patterns (DAMPs) initiate dysregulated systemic inflammation upon binding to pattern recognition receptors. Exosomes are endosome-derived vesicles, which carry proteins, lipids and nucleic acids, and facilitate intercellular communications. Studies have shown altered contents and function of exosomes during sepsis. In sepsis, exosomes carry increased levels of cytokines and DAMPs to induce inflammation. Exosomal DAMPs include, but are not limited to, high mobility group box 1, heat shock proteins, histones, adenosine triphosphate, and extracellular RNA. Exosomes released during sepsis have impact on multiple organs, including the lungs, kidneys, liver, cardiovascular system, and central nervous system. Here, we review the mechanisms of inflammation caused by exosomes, and their contribution to multiple organ dysfunction in sepsis.

Abstract 5596: Dynamic monitoring of plasma DAMP proteins during multimodal anticancer treatment in advanced lung cancer patients

Abstract Immunogenic cell death characterized by the release of damage-associated molecular patterns (DAMPs) from dying cancer cells is a potential contributor to the synergistic antitumor effects of the combination of cytotoxic chemotherapy with immune checkpoint blockade. However, little information on the kinetics of circulating DAMP levels in cancer patients has been available. We evaluated the possible effects of various anticancer treatment modalities on the kinetics of plasma DAMP proteins in lung cancer patients. In a prospective observational study, plasma concentrations of three representative DAMP proteins–high-mobility group box 1 (HMGB1), calreticulin (CRT), and histone H3–in 50 patients with advanced lung cancer were measured at five time points during the first cycle of anticancer therapy by ELISA assay. The plasma levels of HMGB1 and CRT increased during the first treatment cycle in 42 (84%) and 35 (70%) patients, respectively, with these increases being detectable as early as day 3. The maximum fold changes in HMGB1 and CRT concentrations was associated with clinical response. Among the various treatment modalities, cytotoxic chemotherapy induced the greatest increases in the concentrations of these DAMPs. There was no correlation between the maximum fold changes in the plasma levels of HMGB1 and CRT. Meanwhile, histone H3 was essentially undetectable in most patients. In conclusion, serial monitoring of plasma revealed that anticancer treatment modalities increased the circulating levels of DAMPs with their association with clinical response, suggesting that agents capable of increasing the release of DAMPs into plasma might induce immunogenic cell death in advanced lung cancer patients. Citation Format: Hiroyuki Inoue, Hirono Tsutsumi, Yoshimasa Shiraishi, Koji Okamura, Yoichi Nakanishi, Isamu Okamoto. Dynamic monitoring of plasma DAMP proteins during multimodal anticancer treatment in advanced lung cancer patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5596.

Damage-associated molecular patterns (DAMPs) related to immunogenic cell death are differentially triggered by clinically relevant chemotherapeutics in lung adenocarcinoma cells

BackgroundChemotherapeutics can stimulate immune antitumor response by inducing immunogenic cell death (ICD), which is activated by Damage-Associated Molecular Patterns (DAMPs) like the exposure of calreticulin (CRT) on the cell surface, the release of ATP and the secretion of High Mobility Group Box 1 (HMGB1).MethodsHere, we investigated the levels of ICD-associated DAMPs induced by chemotherapeutics commonly used in the clinical practice of non-small cell lung cancer (NSCLC) and the association of these DAMPs with apoptosis and autophagy. A549 human lung adenocarcinoma cells were treated with clinically relevant doses of cisplatin, carboplatin, etoposide, paclitaxel and gemcitabine. We assessed ICD-associated DAMPs, cell viability, apoptosis and autophagy in an integrated way.ResultsCisplatin and its combination with etoposide induced the highest levels of apoptosis, while etoposide was the less pro-apoptotic treatment. Cisplatin also induced the highest levels of ICD-associated DAMPs, which was not incremented by co-treatments. Etoposide induced the lower levels of ICD and the highest levels of autophagy, suggesting that the cytoprotective role of autophagy is dominant in relation to its pro-ICD role. High levels of CRT were associated with better prognosis in TCGA databank. In an integrative analysis we found a strong positive correlation between DAMPs and apoptosis, and a negative correlation between cell number and ICD-associated DAMPs as well as between autophagy and apoptosis markers. We also purpose a mathematical integration of ICD-associated DAMPs in an index (IndImunnog) that may represent with greater biological relevance this process. Cisplatin-treated cells showed the highest IndImmunog, while etoposide was the less immunogenic and the more pro-autophagic treatment.ConclusionsCisplatin alone induced the highest levels of ICD-associated DAMPs, so that its combination with immunotherapy may be a promising therapeutic strategy in NSCLC.

Soft Textured Implants: Roughness, Friction, and the Complications

Friction and shear between soft medical implants and the contacting cells and tissues can lead to the production and secretion of pro-inflammatory proteins and small molecules: cytokines, chemokines, and damage-associated molecular patterns (DAMPs). Biotribological considerations should be included in biocompatibility studies and the design of soft medical implants. Clinical experience with textured breast implants has revealed a number of complications linked to chronic inflammation. Long-term exposure to elevated levels of pro-inflammatory cytokines, proteins, and DAMPs may lead to chronic inflammation, which can have numerous negative biological consequences: pain, swelling, seromas, DNA damage, and even cancer. Contact pressure, surface roughness, surface elastic modulus, and friction all contribute to the dynamics and shear stresses reacted across these interfaces during use; in many soft implant applications, controlled mobility (without migration) is desirable, and slip is essentially unavoidable. Depending on the magnitude of shear stress, cells will undergo a wide range of responses from proliferation and remodeling, to cytokine and chemokine production, and even cell death (apoptosis or necrosis). In soft medical implants, friction coefficients and shear stresses increase with increasing roughness. Models of breast implant contact pressure as a function of geometry and relative size reveal that the shear stresses of the aggressively textured implants may exceed 100 Pa, while the smooth implants are likely well below 100 Pa. At shear stresses of around 100 Pa, epithelial cells have been shown to produce pro-inflammatory cytokines and undergo programmed cell death (apoptosis). Increasing roughness and texturing of soft medical implants should be considered a risk factor for implant biocompatibility, particularly for larger, high-projection designs.

Donor Leukocyte Trafficking and Damage-associated Molecular Pattern Expression During Ex Vivo Lung Perfusion.

Background.While ex vivo lung perfusion (EVLP) has become established in lung transplantation, the cellular processes occurring during this period are not yet fully understood. Prior studies demonstrated that donor leukocytes (DLs) migrate from the graft into the perfusate during EVLP, but the distribution of DLs in graft and perfusate compartments has not been characterized. Moreover, cell death of DLs has been implicated in mediating graft injury during EVLP, but the underlying mechanisms have not been elucidated. We hypothesized the following: (1) there is a nonspecific migration of DLs from the graft into perfusate and (2) cell death of DLs releases damage-associated molecular patterns (DAMPs) that contribute to the inflammatory milieu during EVLP.Methods.EVLP was performed on rat lungs for 3 hours (N = 6). At the end of EVLP, flow cytometry was used to quantify the distribution of different DL cell types in both the graft and perfusate compartments. During EVLP, the perfusate was also sampled hourly to measure levels of DAMPs and downstream inflammatory cytokines generated during EVLP.Results.At the conclusion of EVLP, there was a significantly higher proportion of T and B cells present in the perfusate compartment compared with the graft compartment. There was a time-dependent increase in extracellular DNA and tumor necrosis factor α in the perfusate during EVLP.Conclusions.T cells and B cells are enriched in the perfusate compartment during EVLP. Cell death of DLs contributes to an accumulation of DAMPs during EVLP.

Tumor-related HSP70 released after cryo-thermal therapy targeted innate immune initiation in the antitumor immune response

Purpose In our previous study, a novel cryo-thermal therapy that could stimulate the maturation of innate immune cells to subsequently activate the CD4+Th1 cell-dominated antitumor response was developed. However, why cryo-thermal therapy can induce the maturation of innate immunity remains unknown. Methods In this study, western blot and ELISA were used to analyze the levels of damage-associated molecular patterns (DAMPs, including heat shock protein 70 (HSP70), calreticulin and high-mobility group box protein 1) in situ and in the peripheral blood at different times after cryo-thermal therapy or traditional radiofrequency ablation. The effects of these three DAMPs on myeloid-derived suppressor cells (MDSCs), dendritic cells (DCs) and macrophages were investigated by antibody neutralization in vitro. The phenotypic and functional changes in MDSCs, DCs and macrophages were analyzed using FACS and qRT-PCR. An anti-HSP70 antibody was injected intravenously at 6 h after cryo-thermal therapy on days 1 and 2 and mouse survival was monitored. Results Cryo-thermal therapy could trigger the release of DAMPs in situ and in the peripheral circulation, which could downregulate the proportion and suppressive signature of MDSCs, and promote the M1 macrophages polarization and DCs maturation. Among three DAMPs, HSP70 played the most evident role in M1 macrophage polarization. In vivo neutralization of HSP70 in the early stage of treatment could significantly decrease the survival rate of cryo-thermal therapy treated mice. Conclusions Local cryo-thermal therapy not only destroyed solid tumors thermally and mechanically but also induced the release of a large amount of DAMPs to effectively trigger a systemic antitumor response.

Elevated Plasma Levels of Mitochondria-Derived Damage-Associated Molecular Patterns during Liver Transplantation: Predictors for Postoperative Multi-Organ Dysfunction Syndrome.

The systemic cytokine response during surgery has been reported to be stimulated by the molecules released from damaged cells, called damage-associated molecular patterns (DAMPs). The relationship between DAMPs and liver transplantation has not been reported. We aimed to clarify the relationship between the plasma levels of DAMPs and the short-term post-transplant outcomes, including mortality and postoperative multi-organ dysfunction syndrome (MODS). This retrospective cohort study enrolled 61 patients who underwent liver transplantation. Mitochondrial DNA fragments, as mitochondria-derived DAMPs (mtDAMPs), were isolated from frozen plasma obtained at the start and the end of transplantation and were quantified by polymerase chain reaction. The short-term post-transplant outcomes were compared among the groups categorized based on the median value of the intraoperative fluctuation of mtDAMPs levels. The mtDAMPs levels were increased from the start to the end of transplantation in 52 recipients (85.2%, n = 61). Regarding mortality, no significant differences were noted between the high group (n = 30) and the low group (n = 31). The higher plasma levels of mtDAMPs were correlated with the longer duration of postoperative vasopressor support (P < 0.05). Importantly, the rate of MODS on post-operative day 1 was significantly higher in the high group (high vs. low group: 21 patients [70%] vs. 11 patients [35.1%], P < 0.01). In conclusion, mtDAMPs were increased in plasma during liver transplantation in most recipients. This elevation was not associated with mortality, but associated with the post-transplant recovery. Measuring plasma mtDAMPs may be helpful for predicting posttransplant recovery among liver-transplant recipients.

Differential DAMP release was observed in the sputum of COPD, asthma and asthma-COPD overlap (ACO) patients

Asthma-COPD overlap (ACO) has been under intensive focus; however, the levels of damage-associated molecular patterns (DAMPs) that can activate the innate and adaptive immune responses of ACO are unknown. The present study aimed to examine the levels of some DAMPs in asthma, COPD, and ACO and to identify the associations between clinical characteristics and DAMPs in ACO. Sputum from subjects with asthma (n = 87) or COPD (n = 73) and ACO (n = 68) or from smokers (n = 62) and never-smokers (n = 62) was analyzed for high mobility group protein B1 (HMGB1), heat shock protein 70 (HSP70), LL-37, S100A8, and galectin-3 (Gal-3). The concentration of HMGB1, HSP70, LL-37, and S100A8 proteins in sputum from ACO patients was significantly elevated, whereas that of Gal-3 was reduced, compared to that of smokers and never-smokers. The levels of HMGB1 and Gal-3 proteins in ACO patients were elevated compared to those in asthma patients. The sputum from ACO patients showed an increase in the levels of LL-37 and S100A8 proteins compared to that of asthma patients, whereas the levels decreased compared to those of COPD patients. The concentrations of HMGB1, HSP70, LL-37, and S100A8 proteins in the sputum of 352 participants were negatively correlated, whereas the levels of Gal-3 were positively correlated, with FEV1, FEV1%pred, and FEV1/FVC. Sputum HMGB1 had a high AUC of the ROC curve while distinguishing ACO patients from asthma patients. Meanwhile, sputum LL-37 had a high AUC of the ROC curve in differentiating asthma and COPD. The release of sputum DAMPs in ACO may be involved in chronic airway inflammation in ACO; the sputum HMGB1 level might serve as a valuable biomarker for distinguishing ACO from asthma, and the sputum LL-37 level might be a biomarker for differentiating asthma and COPD.

EP2/4 Receptors Promote the Synthesis of PGE2 Increasing Tissue Damage in Bovine Endometrial Explants Induced by Escherichia coli.

The bovine uterine is easily contaminated with bacteria during coitus or parturition. A previous study suggested that prostaglandin E2 (PGE2) promoted Escherichia coli-infected bovine endometrial tissue inflammatory damage via cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1). However, it remains unclear which PGE2 receptors regulate the proinflammatory effect of PGE2 In this study, we evaluated the effect of PGE2 and its mediated receptors on E. coli-infected endometrium explants isolated from the bovine uterus. The E. coli-infected bovine endometrial explants were cultured in vitro, and the study used EP2/4 receptor agonists to investigate the responses of COX-2, mPGES-1, PGE2, proinflammatory factors, and damage-associated molecular patterns (DAMPs). The expression of COX-2, mPGES-1, PGE2, proinflammatory factors, and DAMPs was significantly increased after infection with E. coli; however, the high expression levels caused by E. coli were reduced following treatment with COX-2 and mPGES-1 inhibitors. In addition, the expression levels of COX-2, mPGES-1, PGE2, proinflammatory factors, and DAMPs were higher in treatment with EP2/4 receptor agonists in E. coli-infected endometrium explants, and their promotable effects were effectively blocked by EP2/4 receptor antagonists. These findings provide evidence that PGE2 may promote the progress of inflammation in endometrial explants infected with E. coli in bovines. Furthermore, EP2/4 may be involved in a positive feedback loop for COX-2 and mPGES-1 expression, and this may be responsible for the proinflammatory reaction of PGE2 in E. coli-infected uteri of bovines. SIGNIFICANCE STATEMENT: PGE2 promoted E. coli-infected bovine endometrial tissue damage via COX-2 and mPGES-1. However, this proinflammatory effect of PGE2 depends on which receptors are affected by PGE2, and this remains unclear. In this study, it was investigated that EP2 and EP4 may be involved in a positive feedback loop for COX-2 and mPGES-1 expression, and this may be responsible for the proinflammatory reaction of PGE2 in E. coli-infected uteri of bovines.

Damage-Associated Molecular Patterns Induce Inflammatory Injury During Machine Preservation of the Liver: Potential Targets to Enhance a Promising Technology.

Machine preservation (MP) has emerged as a promising technology in liver transplantation, but the cellular processes occurring during MP have not been characterized. Recent studies have noted the presence of inflammatory molecules generated during MP. We hypothesized that there is a metabolism‐dependent accumulation of damage‐associated molecular patterns (DAMPs) and inflammatory cytokines during MP and that these molecules provoke inflammation in the graft. To stratify groups by metabolic rate, MP was performed on rat livers from standard donors at 3 different temperatures: room temperature (RT), subnormothermic (30°C), and normothermic (37°C). Static cold storage at 4°C was included as a reference group. Following a 4‐hour preservation period, graft reperfusion was performed ex vivo at 37°C (n = 6 for all groups). Levels of DAMPs and inflammatory cytokines were measured, and their biological activity was assessed by determining toll‐like receptor (TLR) stimulation, inflammatory gene expression, and activation of cell death pathways. There was a time‐dependent increase in levels of DAMPs during MP with high‐mobility group box 1 and extracellular DNA levels increasing for all groups (P < 0.05, 30 versus 240 minutes). Tumor necrosis factor α levels in the perfusate also increased during MP for all groups (P < 0.05, 30 minutes versus 240 minutes). Levels of inflammatory molecules correlated with increased activation of TLRs (TLR3, P = 0.02, normothermic machine preservation [MP37] versus machine preservation at room temperature [MPRT]; TLR9, P = 0.02, MP37 versus MPRT). Priming of the NLRP3 inflammasome and activation of cell death pathways were reduced in grafts preserved by MP at room temperature. In conclusion, inflammatory molecules produced during MP have a biological impact on the graft. Therapies to attenuate DAMP‐mediated inflammation during MP may further enhance this promising technology.

Effects of Changes in the Levels of Damage-Associated Molecular Patterns Following Continuous Veno-Venous Hemofiltration Therapy on Outcomes in Acute Kidney Injury Patients With Sepsis.

Background: We investigated the association of damage-associated molecular pattern (DAMP) removal with mortality in sepsis patients undergoing continuous veno–venous hemofiltration (CVVH).Methods: Circulating levels of DAMPs [mitochondrial DNA (mtDNA); nuclear DNA (nDNA); heat shock protein 70 (HSP70); and high mobility group box 1 (HMGB1)] and cytokines were measured at baseline, 6 and 12 h after initiation of CVVH. Urinary DNA levels were analyzed at baseline and end of CVVH. The expression of human leukocyte antigen (HLA)-DR was assayed at 0, 3, and 7 days after initiation of CVVH. Moreover, the effects of HSP70 and HMGB1 clearance on survival were analyzed.Results: We evaluated 43 patients with acute kidney injury (AKI) (33 sepsis patients). Twenty-two sepsis patients (67%) and three non-sepsis patients (30%) expired (P = 0.046). Significant reductions in the levels of circulating interleukin-6 (P = 0.046) and tumor necrosis factor-α (P = 0.008) were found in the sepsis group. The levels of mtDNA were increased (ND2, P = 0.035; D-loop, P = 0.003), whereas that of HSP70 was reduced (P = 0.000) in all patients during the first 12 h. The levels of DAMPs in the plasma were markedly increased after blood passage from the inlet through the dialyzer in survivor sepsis patients. The clearance rates of HSP70 and HMGB1 were good predictors of mortality [area under the curve (AUC) = 0.937, P = 0.000; AUC = 0.90, P = 0.001, respectively]. The level of HLA-DR was increased in response to higher HSP70 clearance (P = 0.006). Survival was significantly worse in groups with higher clearance rates of HSP70 and HMGB1 than the cut-off value (log-rank test: P = 0.000 for both). Higher HSP70 clearance was a significant independent predictor of mortality (odds ratio = 1.025, 95% confidence interval [CI]: 1.012–1.039, P = 0.000). The urinary nDNA (β-globin) level before CVVH was an independent risk factor for the duration of CVVH in patients with sepsis (sRE = 0.460, 95% CI: 1.720–8.857, P = 0.005).Conclusion: CVVH removes inflammatory factors, reduces urinary DAMPs, and removes plasma DAMPs. However, survival decreases in response to higher HSP70 clearance.

DAMPs and sterile inflammation in drug hepatotoxicity.

Drug hepatotoxicity is the leading cause of acute liver failure (ALF) in the developed countries. The early diagnosis and treatment are still problematic, and one important reason is the lack of reliable mechanistic biomarkers and therapeutic targets; therefore, searching for new biomarkers and therapeutic targets is urgent. Drug hepatotoxicity induces severe liver cells damage and death. Dead and damaged cells release endogenous damage-associated molecular patterns (DAMPs). Increased circulating levels of DAMPs (HMGB1, histones and DNA) can reflect the severity of drug hepatotoxicity. Elevated plasma HMGB1 concentrations can serve as early and sensitive mechanistic biomarker for clinical acetaminophen hepatotoxicity. DAMPS significantly contribute to liver injury and inhibiting the release of DAMPs ameliorates experimental hepatotoxicity. In addition, HMGB1 mediates 80% of gut bacterial translocation (BT) during acetaminophen toxicity. Gut BT triggers systemic inflammation, leading to multiple organ injury and mortality. Moreover, DAMPs can trigger and extend sterile inflammation, which contributes to early phase liver injury but improves liver regeneration at the late phase of acetaminophen overdose, because anti-inflammatory treatment reduces liver injury at early phase but impairs liver regeneration at late phase of acetaminophen toxicity, whereas pro-inflammatory therapy improves late phase liver regeneration. DAMPs are promising mechanistic biomarkers and could also be the potential therapeutic targets for drug hepatotoxicity. DAMPs-triggered sterile inflammation contributes to liver injury at early phase but improves liver regeneration at later phase of acetaminophen hepatotoxicity; therefore, anti-inflammatory therapy would be beneficial at early phase but should be avoided at the late phase of acetaminophen overdose.

Long-Term Cognitive Outcomes After Sepsis: a Translational Systematic Review.

Sepsis is systemic inflammatory response syndrome with a life-threatening organ dysfunction that is caused by an unbalanced host immune response in an attempt to eliminate invasive microorganisms. We posed questions, "Does sepsis survivor patients have increased risk of neuropsychiatric manifestations?" and "What is the mechanism by which sepsis induces long-term neurological sequelae, particularly substantial cognitive function decline in survivor patients and in pre-clinical sepsis models?" The studies were identified by searching PubMed/MEDLINE (National Library of Medicine), PsycINFO, EMBASE (Ovid), LILACS (Latin American and Caribbean Health Sciences Literature), IBECS (Bibliographical Index in Spanish in Health Sciences), and Web of Science databases for peer-reviewed journals that were published until January 2018. A total of 3555 papers were included in the primary screening. After that, 130 articles were selected for the study. A number of pre-clinical studies have shown an auto amplification of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, and IL-6 in the first few hours after sepsis induction, also increased blood-brain barrier permeability, elevated levels of matrix metalloproteinases, increased levels of damage-associated molecular patterns were demonstrated. In addition, the rodents presented long-term cognitive impairment in different behavioral tasks that were prevented by blocking the mechanism of action of these inflammatory mediators. Clinical studies have showed that sepsis survivors presented increased bodily symptoms such as fatigue, pain, visual disturbances, gastrointestinal problems, and neuropsychiatric problems compared to before sepsis. Sepsis leaves the survivors with an aftermath of physiological, neuropsychiatric, and functional impairment. Systematic review registration: CRD42017071755.

Immunothrombotic Activity of Damage-Associated Molecular Patterns and Extracellular Vesicles in Secondary Organ Failure Induced by Trauma and Sterile Insults.

Despite significant improvements in injury prevention and emergency response, injury-related death and morbidity continues to increase in the US and worldwide. Patients with trauma, invasive operations, anti-cancer treatment, and organ transplantation produce a host of danger signals and high levels of pro-inflammatory and pro-thrombotic mediators, such as damage-associated molecular patterns (DAMPs) and extracellular vesicles (EVs). DAMPs (e.g., nucleic acids, histone, high-mobility group box 1 protein, and S100) are molecules released from injured, stressed, or activated cells that act as endogenous ligands of innate immune receptors, whereas EVs (e.g., microparticle and exosome) are membranous vesicles budding off from plasma membranes and act as messengers between cells. DAMPs and EVs can stimulate multiple innate immune signaling pathways and coagulation cascades, and uncontrolled DAMP and EV production causes systemic inflammatory and thrombotic complications and secondary organ failure (SOF). Thus, DAMPs and EVs represent potential therapeutic targets and diagnostic biomarkers for SOF. High plasma levels of DAMPs and EVs have been positively correlated with mortality and morbidity of patients or animals with trauma or surgical insults. Blocking or neutralizing DAMPs using antibodies or small molecules has been demonstrated to ameliorate sepsis and SOF in animal models. Furthermore, a membrane immobilized with nucleic acid-binding polymers captured and removed multiple DAMPs and EVs from extracellular fluids, thereby preventing the onset of DAMP- and EV-induced inflammatory and thrombotic complications in vitro and in vivo. In this review, we will summarize the current state of knowledge of DAMPs, EVs, and SOF and discuss potential therapeutics and preventive intervention for organ failure secondary to trauma, surgery, anti-cancer therapy, and allogeneic transplantation.

Role of pattern recognition receptors of the neurovascular unit in inflamm-aging.

Aging is associated with chronic inflammation partly mediated by increased levels of damage-associated molecular patterns, which activate pattern recognition receptors (PRRs) of the innate immune system. Furthermore, many aging-related disorders are associated with inflammation. PRRs, such as Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain-like receptors (NLRs), are expressed not only in cells of the innate immune system but also in other cells, including cells of the neurovascular unit and cerebral vasculature forming the blood-brain barrier. In this review, we summarize our present knowledge about the relationship between activation of PRRs expressed by cells of the neurovascular unit-blood-brain barrier, chronic inflammation, and aging-related pathologies of the brain. The most important damage-associated molecular pattern-sensing PRRs in the brain are TLR2, TLR4, and NLR family pyrin domain-containing protein-1 and pyrin domain-containing protein-3, which are activated during physiological and pathological aging in microglia, neurons, astrocytes, and possibly endothelial cells and pericytes.

Nucleic acid scavenging microfiber mesh inhibits trauma-induced inflammation and thrombosis.

Trauma patients produce a host of danger signals and high levels of damage-associated molecular patterns (DAMPs) after cellular injury and tissue damage. These DAMPs are directly and indirectly involved in the pathogenesis of various inflammatory and thrombotic complications in patients with severe injuries. No effective therapeutic agents for the removal of DAMPs from blood or tissue fluid have been developed. Herein, we demonstrated that nucleic acid binding polymers, e.g., polyethylenimine (PEI) and polyamidoamine dendrimers, immobilized onto electrospun microfiber mesh can effectively capture various DAMPs, such as extracellular DNAs and high mobility group box 1 (HMGB1). Furthermore, treatment with PEI-immobilized microfiber mesh abrogated the ability of DAMPs, released from dead and dying cells in culture or found in patients following traumatic injury, to activate innate immune responses and coagulation invitro and invivo. Nucleic acid scavenging microfiber meshes represent an effective strategy to combat inflammation and thrombosis in trauma.

Histones link inflammation and thrombosis through the induction of Weibel–Palade body exocytosis

Background Damage-associated molecular patterns (DAMPs), including molecules such as DNA and histones, are released into the blood following cell death. DAMPs promote a procoagulant phenotype through enhancement of thrombin generation and platelet activation, thereby contributing to immunothrombosis. Weibel-Palade bodies (WPBs) are dynamic endothelial cell organelles that contain procoagulant and proinflammatory mediators, such as von Willebrand factor (VWF), and are released in response to cell stresses. VWF mediates platelet adhesion and aggregation, and has been implicated as a procoagulant component of the innate immune response. Objective To determine the influence of histones and DNA on WPB release, and characterize their association in models of inflammation. Methods We treated C57BL/6J mice and cultured endothelial cells with histones (unfractionated, lysine-rich or arginine-rich) and DNA, and measured WPB exocytosis. We used inhibitors to determine a mechanism of histone-induced WPB release invitro. We characterized the release of DAMPs and WPBs in response to acute and chronic inflammation in human and murine models. Results and conclusions Histones, but not DNA, induced the release of VWF (1.46-fold) from WBPs and caused thrombocytopenia (0.74-fold), which impaired arterial thrombus formation in mice. Histones induced WPB release from endothelial cells in a caspase-dependent, calcium-dependent and charge-dependent manner, and promoted platelet capture in a flow chamber model of VWF-platelet string formation. The levels of DAMPs and WPB-released proteins were elevated during inflammation, and were positively correlated in chronic inflammation. These studies showed that DAMPs can regulate the function and level of VWF by inducing its release from endothelial WPBs. This DAMP-WPB axis may propagate immunothrombosis associated with inflammation.

Damage-associated molecular patterns (DAMPs) released after burn are associated with inflammation and monocyte activation

Burns are associated with activation of the innate immunity that can contribute to complications. Damage-associated molecular patterns (DAMPs) released after tissue injury play a critical role in the activation of the innate immunity, which appears to be mediated via toll-like receptors (TLRs). Previous findings have shown that TLRs and TLR-mediated responses are up-regulated after burn. Nonetheless, it is unclear what impact burn has on circulating levels of DAMPs. To study this, male C57BL/6 mice were subjected to a major burn or sham procedure. Three hours to 7days thereafter, plasma was collected and assayed for the representative DAMPs (i.e., HMGB1, cytochrome C, DNA and S100A) and extracellular cleavage products (fibronectin and hyaluronan). HMGB1, cytochrome C, fibronectin and hyaluronan levels were elevated in a time-dependent manner after burn as compared to sham levels. A significant elevation in TNF-α, IL-6 and IL-10 cytokine plasma levels was also found after burn. All cytokine levels were increased as early as 3h and remained elevated up to 24h. Circulating CD11b+ monocytes were increased at 24h after burn and showed increased expression of TLR-2. In conclusion, these findings support the concept that burn-induced elevations in circulating DAMPs are in part responsible for monocyte activation and the development of inflammatory complications under such conditions and warrants further investigation.

Gut mucosal DAMPs in IBD: from mechanisms to therapeutic implications.

Endogenous damage-associated molecular patterns (DAMPs) are released during tissue damage and have increasingly recognized roles in the etiology of many human diseases. The inflammatory bowel diseases (IBD), ulcerative colitis (UC) and Crohn's disease (CD), are immune-mediated conditions where high levels of DAMPs are observed. DAMPs such as calprotectin (S100A8/9) have an established clinical role as a biomarker in IBD. In this review, we use IBD as an archetypal common chronic inflammatory disease to focus on the conceptual and evidential importance of DAMPs in pathogenesis and why DAMPs represent an entirely new class of targets for clinical translation.

Cigarette smoke-induced necroptosis and DAMP release trigger neutrophilic airway inflammation in mice.

Recent data indicate a role for airway epithelial necroptosis, a regulated form of necrosis, and the associated release of damage-associated molecular patterns (DAMPs) in the development of chronic obstructive pulmonary disease (COPD). DAMPs can activate pattern recognition receptors (PRRs), triggering innate immune responses. We hypothesized that cigarette smoke (CS)-induced epithelial necroptosis and DAMP release initiate airway inflammation in COPD. Human bronchial epithelial BEAS-2B cells were exposed to cigarette smoke extract (CSE), and necrotic cell death (membrane integrity by propidium iodide staining) and DAMP release (i.e., double-stranded DNA, high-mobility group box 1, heat shock protein 70, mitochondrial DNA, ATP) were analyzed. Subsequently, BEAS-2B cells were exposed to DAMP-containing supernatant of CS-induced necrotic cells, and the release of proinflammatory mediators [C-X-C motif ligand 8 (CXCL-8), IL-6] was evaluated. Furthermore, mice were exposed to CS in the presence and absence of the necroptosis inhibitor necrostatin-1, and levels of DAMPs and inflammatory cell numbers were determined in bronchoalveolar lavage fluid. CSE induced a significant increase in the percentage of necrotic cells and DAMP release in BEAS-2B cells. Stimulation of BEAS-2B cells with supernatant of CS-induced necrotic cells induced a significant increase in the release of CXCL8 and IL-6, in a myeloid differentiation primary response gene 88-dependent fashion. In mice, exposure of CS increased the levels of DAMPs and numbers of neutrophils in bronchoalveolar lavage fluid, which was statistically reduced upon treatment with necrostatin-1. Together, we showed that CS exposure induces necrosis of bronchial epithelial cells and subsequent DAMP release in vitro, inducing the production of proinflammatory cytokines. In vivo, CS exposure induces neutrophilic airway inflammation that is sensitive to necroptosis inhibition.