Dexamethasone Modulates the Cytokine Response but Not COVID-19-Induced Coagulopathy in Critically Ill.

Severe forms of coronavirus 2019 (COVID-19) disease are caused by an exaggerated systemic inflammatory response and subsequent inflammation-related coagulopathy. Anti-inflammatory treatment with low dose dexamethasone has been shown to reduce mortality in COVID-19 patients requiring oxygen therapy. However, the mechanisms of action of corticosteroids have not been extensively studied in critically ill patients in the context of COVID-19. Plasma biomarkers of inflammatory and immune responses, endothelial and platelet activation, neutrophil extracellular trap formation, and coagulopathy were compared between patients treated or not by systemic dexamethasone for severe forms of COVID-19. Dexamethasone treatment significantly reduced the inflammatory and lymphoid immune response in critical COVID-19 patients but had little effect on the myeloid immune response and no effect on endothelial activation, platelet activation, neutrophil extracellular trap formation, and coagulopathy. The benefits of low dose dexamethasone on outcome in critical COVID-19 can be partially explained by a modulation of the inflammatory response but not by reduction of coagulopathy. Future studies should explore the impact of combining dexamethasone with other immunomodulatory or anticoagulant drugs in severe COVID-19.

A first-in-man safety and pharmacokinetics study of nangibotide, a new modulator of innate immune response through TREM-1 receptor inhibition.

AIMS: The peptide nangibotide is the first clinical-stage agent targeting the immunoreceptor TREM-1 (triggering receptor expressed on myeloid cells-1) and is being investigated as a novel therapy for acute inflammatory disorders such as septic shock. This first-in-man, randomized, double-blind, ascending dose, placebo-controlled Phase I study evaluated the safety, tolerability and pharmacokinetics of nangibotide. METHODS: Twenty-seven healthy subjects (aged 18-45 years) were randomized into eight groups. Nangibotide was administered as a single continuous intravenous infusion. The first two groups received a single i.v. dose of 1 and 10 mg, respectively, over 15 min. Subsequent groups were randomized in a product : placebo ratio of 3:1 at doses ranging from 0.03 to 6 mg kg-1  h-1 over 7 h 45 min, preceded by a 15-minute loading dose of up to 5 mg kg-1 . RESULTS: Nangibotide was safe and well tolerated up to the highest dose tested. There were only few adverse events and they were mild in severity and considered unrelated to treatment. Nangibotide displayed dose-proportional PK properties, with a clearance of 6.6 l kg-1  h-1 for a subject of 70 kg and a 3 min effective half-life, which are compatible with extensive enzymatic metabolism in blood. Central and peripheral volumes of distribution were 16.7 l and 15.9 l respectively, indicating limited distribution of the drug mainly in blood and interstitial fluid. No circulating anti-drug antibodies were detectable up to 28 days after administration. CONCLUSIONS: The novel immunomodulator nangibotide displayed favourable safety and PK profiles at all doses, including expected pharmacologically active doses, and warrants further clinical development.

TREM-1 Mediates Inflammatory Injury and Cardiac Remodeling Following Myocardial Infarction.

RATIONALE: Optimal outcome after myocardial infarction (MI) depends on a coordinated healing response in which both debris removal and repair of the myocardial extracellular matrix play a major role. However, adverse remodeling and excessive inflammation can promote heart failure, positioning leucocytes as central protagonists and potential therapeutic targets in tissue repair and wound healing after MI. OBJECTIVE: In this study, we examined the role of triggering receptor expressed on myeloid cells-1(TREM-1) in orchestrating the inflammatory response that follows MI. TREM-1, expressed by neutrophils and mature monocytes, is an amplifier of the innate immune response. METHODS AND RESULTS: After infarction, TREM-1 expression is upregulated in ischemic myocardium in mice and humans. Trem-1 genetic invalidation or pharmacological inhibition using a synthetic peptide (LR12) dampens myocardial inflammation, limits neutrophils recruitment and monocyte chemoattractant protein-1 production, thus reducing classical monocytes mobilization to the heart. It also improves left ventricular function and survival in mice (n=20-22 per group). During both permanent and transient myocardial ischemia, Trem-1 blockade also ameliorates cardiac function and limits ventricular remodeling as assessed by fluorodeoxyglucose-positron emission tomographic imaging and conductance catheter studies (n=9-18 per group). The soluble form of TREM-1 (sTREM-1), a marker of TREM-1 activation, is detectable in the plasma of patients having an acute MI (n=1015), and its concentration is an independent predictor of death. CONCLUSIONS: These data suggest that TREM-1 could constitute a new therapeutic target during acute MI.

Attenuation of responses to endotoxin by the triggering receptor expressed on myeloid cells-1 inhibitor LR12 in nonhuman primate.

BACKGROUND: The triggering receptor expressed on myeloid cells-1 is an immunoreceptor that amplifies the inflammatory response mediated by toll-like receptors engagement. Triggering receptor expressed on myeloid cells-1 inhibitory peptides such LR12 have been shown to prevent hyperresponsiveness and death in several experimental models of septic shock. METHODS: Twelve adult male Cynomolgus (Macaca fascicularis) monkeys exposed to an intravenous bolus of endotoxin (10 µg/kg) were randomized to receive LR12 or placebo (n = 6 per group) as an initial intravenous bolus followed by an 8-h continuous intravenous infusion. An additional group of four only received vehicle infusion. Vital signs were monitored for 8 h. Blood was sampled at H0, 1, 2, 4, and 8 for analysis of clinical chemistries, leukocyte count, coagulation parameters, and cytokine plasma concentration. RESULTS: LR12 showed no effect on heart rate and body temperature. By contrast to the placebo group, which experienced a 25 to 40% blood pressure decrease after endotoxin administration, LR12-treated monkeys remained normotensive. Endotoxin induced leukopenia at 2 h (mean leukocyte count, 7.62 g/l vs. 21.1 at H0), which was attenuated by LR12. LR12 also attenuated cytokine production. CONCLUSIONS: The triggering receptor expressed on myeloid cells-1 inhibitor LR12 is able to mitigate endotoxin-associated clinical and biological alterations, with no obvious side effects. This study paves the way for future phases Ia and Ib trials in humans.

Soluble TREM-like transcript-1 regulates leukocyte activation and controls microbial sepsis.

The triggering receptor expressed on myeloid cells (TREM)-1 plays a crucial role during the onset of sepsis by amplifying the host immune response. The TREM-like transcript-1 (TLT-1) belongs to the TREM family, is selectively expressed on activated platelets, and is known to facilitate platelet aggregation through binding to fibrinogen. In this study, we show that a soluble form of TLT-1 is implicated in the regulation of inflammation during sepsis by dampening leukocyte activation and modulating platelet-neutrophil crosstalk. A 17-aa sequence of the TLT-1 extracellular domain (LR17) is responsible for this activity through competition with the TREM-1 ligand. Whereas early or late LR17 treatment of septic mice improves survival, treml-1(-/-) animals are highly susceptible to polymicrobial infection. The present findings identify platelet-derived soluble TLT-1 as a potent endogenous regulator of sepsis-associated inflammation and open new therapeutic perspectives. We anticipate soluble TLT-1 to be important in regulating leukocyte activation during other noninfectious inflammatory disorders.

THBS1+ myeloid cells expand in SLD hepatocellular carcinoma and contribute to immunosuppression and unfavorable prognosis through TREM1.

Hepatocellular carcinoma (HCC) is an inflammation-associated cancer arising from viral or non-viral etiologies including steatotic liver diseases (SLDs). Expansion of immunosuppressive myeloid cells is a hallmark of inflammation and cancer, but their heterogeneity in HCC is not fully resolved and might underlie immunotherapy resistance. Here, we present a high-resolution atlas of innate immune cells from patients with HCC that unravels an SLD-associated contexture characterized by influx of inflammatory and immunosuppressive myeloid cells, including a discrete population of THBS1+ regulatory myeloid (Mreg) cells expressing monocyte- and neutrophil-affiliated genes. THBS1+ Mreg cells expand in SLD-associated HCC, populate fibrotic lesions, and are associated with poor prognosis. THBS1+ Mreg cells are CD163+ but distinguished from macrophages by high expression of triggering receptor expressed on myeloid cells 1 (TREM1), which contributes to their immunosuppressive activity and promotes HCC tumor growth in vivo. Our data support myeloid subset-targeted immunotherapies to treat HCC.

Persistently Elevated Soluble Triggering Receptor Expressed on Myeloid Cells 1 and Decreased Monocyte Human Leucocyte Antigen DR Expression Are Associated With Nosocomial Infections in Septic Shock Patients.

Sepsis-acquired immunosuppression may play a major role in patients' prognosis through increased risk of secondary infections. Triggering receptor expressed on myeloid cells 1 (TREM-1) is an innate immune receptor involved in cellular activation. Its soluble form (sTREM-1) has been described as a robust marker of mortality in sepsis. The objective of this study was to evaluate its association with the occurrence of nosocomial infections alone or in combination with human leucocyte antigen-DR on monocytes (mHLA-DR). DESIGN: Observational study. SETTING: University Hospital in France. PATIENTS: One hundred sixteen adult septic shock patients as a post hoc study from the IMMUNOSEPSIS cohort (NCT04067674). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Plasma sTREM-1 and monocyte HLA-DR were measured at day 1 or 2 (D1/D2), D3/D4, and D6/D8 after admission. Associations with nosocomial infection were evaluated through multivariable analyses. At D6/D8, both markers were combined, and association with increased risk of nosocomial infection was evaluated in the subgroup of patients with most deregulated markers in a multivariable analysis with death as a competing risk. Significantly decreased mHLA-DR at D6/D8 and increased sTREM-1 concentrations were measured at all time points in nonsurvivors compared with survivors. Decreased mHLA-DR at D6/D8 was significantly associated with increased risk of secondary infections after adjustment for clinical parameters with a subdistribution hazard ratio of 3.61 (95% CI, 1.39-9.34; p = 0.008). At D6/D8, patients with persistently high sTREM-1 and decreased mHLA-DR presented with a significantly increased risk of infection (60%) compared with other patients (15.7%). This association remained significant in the multivariable model (subdistribution hazard ratio [95% CI], 4.65 [1.98-10.9]; p < 0.001). CONCLUSIONS: In addition to its prognostic interest on mortality, sTREM-1, when combined with mHLA-DR, may help to better identify immunosuppressed patients at risk of nosocomial infections.

Soluble TREM-1 plasma concentration predicts poor outcome in COVID-19 patients.

BACKGROUND: The immuno-receptor Triggering Expressed on Myeloid cells-1 (TREM-1) is activated during bacterial infectious diseases, where it amplifies the inflammatory response. Small studies suggest that TREM-1 could be involved in viral infections, including COVID-19. We here aim to decipher whether plasma concentration of the soluble form of TREM-1 (sTREM-1) could predict the outcome of hospitalized COVID-19 patients. METHODS: We conducted a multicentre prospective observational study in 3 university hospitals in France. Consecutive hospitalized patients with confirmed infection with SARS-CoV-2 were enrolled. Plasma concentration of sTREM-1 was measured on admission and then at days 4, 6, 8, 14, 21, and 28 in patients admitted into an ICU (ICU cohort: ICUC) or 3 times a week for patients hospitalized in a medical ward (Conventional Cohort: ConvC). Clinical and biological data were prospectively recorded and patients were followed-up for 90 days. For medical ward patients, the outcome was deemed complicated in case of requirement of increased oxygen supply > 5 L/min, transfer to an ICU, or death. For Intensive Care Unit (ICU) patients, complicated outcome was defined by death in the ICU. RESULTS: Plasma concentration of sTREM-1 at inclusion was higher in ICU patients (n = 269) than in medical ward patients (n = 562) (224 pg/mL (IQR 144-320) vs 147 pg/mL (76-249), p < 0.0001), and higher in patients with a complicated outcome in both cohorts: 178 (94-300) vs 135 pg/mL (70-220), p < 0.0001 in the ward patients, and 342 (288-532) vs 206 pg/mL (134-291), p < 0.0001 in the ICU patients. Elevated sTREM-1 baseline concentration was an independent predictor of complicated outcomes (Hazard Ratio (HR) = 1.5 (1.1-2.1), p = 0.02 in ward patients; HR = 3.8 (1.8-8.0), p = 0.0003 in ICU patients). An sTREM-1 plasma concentration of 224 pg/mL had a sensitivity of 42%, and a specificity of 76% in the ConvC for complicated outcome. In the ICUC, a 287 pg/mL cutoff had a sensitivity of 78%, and a specificity of 74% for death. The sTREM-1 concentrations increased over time in the ConvC patients with a complicated outcome (p = 0.017), but not in the ICUC patients. CONCLUSIONS: In COVID-19 patients, plasma concentration of sTREM-1 is an independent predictor of the outcome, although its positive and negative likelihood ratio are not good enough to guide clinical decision as a standalone marker.

Prospective evaluation of the efficacy, safety, and optimal biomarker enrichment strategy for nangibotide, a TREM-1 inhibitor, in patients with septic shock (ASTONISH): a double-blind, randomised, controlled, phase 2b trial.

BACKGROUND: Activation of the triggering receptor expressed on myeloid cells-1 (TREM-1) pathway is associated with septic shock outcomes. Data suggest that modulation of this pathway in patients with activated TREM-1 might improve survival. Soluble TREM-1 (sTREM-1), a potential mechanism-based biomarker, might facilitate enrichment of patient selection in clinical trials of nangibotide, a TREM-1 modulator. In this phase 2b trial, we aimed to confirm the hypothesis that TREM1 inhibition might improve outcomes in patients with septic shock. METHODS: This double-blind, randomised, placebo-controlled, phase 2b trial assessed the efficacy and safety of two different doses of nangibotide compared with placebo, and aimed to identify the optimum treatment population, in patients across 42 hospitals with medical, surgical, or mixed intensive care units (ICUs) in seven countries. Non-COVID-19 patients (18-85 years) meeting the standard definition of septic shock, with documented or suspected infection (lung, abdominal, or urinary [in patients ≥65 years]), were eligible within 24 h of vasopressor initiation for the treatment of septic shock. Patients were randomly assigned in a 1:1:1 ratio to intravenous nangibotide 0·3 mg/kg per h (low-dose group), nangibotide 1·0 mg/kg per h (high-dose group), or matched placebo, using a computer-generated block randomisation scheme (block size 3). Patients and investigators were masked to treatment allocation. Patients were grouped according to sTREM-1 concentrations at baseline (established from sepsis observational studies and from phase 2a change to data) into high sTREM-1 (≥ 400 pg/mL). The primary outcome was the mean difference in total Sequential Organ Failure Assessment (SOFA) score from baseline to day 5 in the low-dose and high-dose groups compared with placebo, measured in the predefined high sTREM-1 (≥ 400 pg/mL) population and in the overall modified intention-to-treat population. Secondary endpoints included all-cause 28-day mortality, safety, pharmacokinetics, and evaluation of the relationship between TREM-1 activation and treatment response. This study is registered with EudraCT, 2018-004827-36, and Clinicaltrials.gov, NCT04055909. FINDINGS: Between Nov 14, 2019, and April 11, 2022, of 402 patients screened, 355 were included in the main analysis (116 in the placebo group, 118 in the low-dose group, and 121 in the high-dose group). In the preliminary high sTREM-1 population (total 253 [71%] of 355; placebo 75 [65%] of 116; low-dose 90 [76%] of 118; high-dose 88 [73%] of 121), the mean difference in SOFA score from baseline to day 5 was 0·21 (95% CI -1·45 to 1·87, p=0·80) in the low-dose group and 1·39 (-0·28 to 3·06, p=0·104) in the high-dose group versus placebo. In the overall population, the difference in SOFA score from baseline to day 5 between the placebo group and low-dose group was 0·20 (-1·09 to 1·50; p=0·76),and between the placebo group and the high-dose group was 1·06 (-0·23 to 2·35, p=0·108). In the predefined high sTREM-1 cutoff population, 23 (31%) patients in the placebo group, 35 (39%) in the low-dose group, and 25 (28%) in the high-dose group had died by day 28. In the overall population, 29 (25%) patients in the placebo, 38 (32%) in the low-dose, and 30 (25%) in the high-dose group had died by day 28. The number of treatment-emergent adverse events (111 [96%] patients in the placebo group, 113 [96%] in the low-dose group, and 115 [95%] in the high-dose group) and serious treatment-emergent adverse events (28 [24%], 26 [22%], and 31 [26%]) was similar between all three groups. High-dose nangibotide led to a clinically relevant improvement in SOFA score (of two points or more) from baseline to day 5 over placebo in those with higher cutoff concentrations (≥532 pg/mL) of sTREM-1 at baseline. Low dose nangibotide displayed a similar pattern with lower magnitude of effect across all cutoff values. INTERPRETATION: This trial did not achieve the primary outcome of improvement in SOFA score at the predefined sTREM-1 value. Future studies are needed to confirm the benefit of nangibotide at higher concentrations of TREM-1 activation. FUNDING: Inotrem.

Evaluation of the efficacy and safety of TREM-1 inhibition with nangibotide in patients with COVID-19 receiving respiratory support: the ESSENTIAL randomised, double-blind trial.

Background: Activation of the TREM-1 pathway is associated with outcome in life threatening COVID-19. Data suggest that modulation of this pathway with nangibotide, a TREM-1 modulator may improve survival in TREM-1 activated patients (identified using the biomarker sTREM-1). Methods: Phase 2 double-blind randomized controlled trial assessing efficacy, safety, and optimum treatment population of nangibotide (1.0 mg/kg/h) compared to placebo. Patients aged 18-75 years were eligible within 7 days of SARS-CoV-2 documentation and within 48 h of the onset of invasive or non-invasive respiratory support because of COVID-19-related ARDS. Patients were included from September 2020 to April 2022, with a pause in recruitment between January and August 2021. Primary outcome was the improvement in clinical status defined by a seven-point ordinal scale in the overall population with a planned sensitivity analysis in the subgroup of patients with a sTREM-1 level above the median value at baseline (high sTREM-1 group). Secondary endpoints included safety and all-cause 28-day and day 60 mortality. The study was registered in EudraCT (2020-001504-42) and ClinicalTrials.gov (NCT04429334). Findings: The study was stopped after 220 patients had been recruited. Of them, 219 were included in the mITT analysis. Nangibotide therapy was associated with an improved clinical status at day 28. Fifty-two (52.0%) of patients had improved in the placebo group compared to 77 (64.7%) of the nangibotide treated population, an odds ratio (95% CI) for improvement of 1.79 (1.02-3.14), p = 0.043. In the high sTREM-1 population, 18 (32.7%) of placebo patients had improved by day 28 compared to 26 (48.1%) of treated patients, an odds ratio (95% CI) of 2.17 (0.96-4.90), p = 0.063 was observed. In the overall population, 28 (28.0%) of placebo treated patients were not alive at the day 28 visit compared to 19 (16.0%) of nangibotide treated patients, an absolute improvement (95% CI) in all-cause mortality at day 28, adjusted for baseline clinical status of 12.1% (1.18-23.05). In the high sTREM-1 population (n = 109), 23 (41.8%) of patients in the placebo group and 12 (22.2%) of patients in the nangibotide group were not alive at day 28, an adjusted absolute reduction in mortality of 19.9% (2.78-36.98). The rate of treatment emergent adverse events was similar in both placebo and nangibotide treated patients. Interpretation: Whilst the study was stopped early due to low recruitment rate, the ESSENTIAL study demonstrated that TREM-1 modulation with nangibotide is safe in COVID-19, and results in a consistent pattern of improved clinical status and mortality compared to placebo. The relationship between sTREM-1 and both risk of death and treatment response merits further evaluation of nangibotide using precision medicine approaches in life threatening viral pneumonitis. Funding: The study was sponsored by Inotrem SA.

Triggering Receptors Expressed on Myeloid Cells 1 : Our New Partner in Human Oncology?

Inflammation is recognized as one of the hallmarks of cancer. Indeed, strong evidence indicates that chronic inflammation plays a major role in oncogenesis, promoting genome instability, epigenetic alterations, proliferation and dissemination of cancer cells. Mononuclear phagocytes (MPs) have been identified as key contributors of the inflammatory infiltrate in several solid human neoplasia, promoting angiogenesis and cancer progression. One of the most described amplifiers of MPs pro-inflammatory innate immune response is the triggering receptors expressed on myeloid cells 1 (TREM-1). Growing evidence suggests TREM-1 involvement in oncogenesis through cancer related inflammation and the surrounding tumor microenvironment. In human oncology, high levels of TREM-1 and/or its soluble form have been associated with poorer survival data in several solid malignancies, especially in hepatocellular carcinoma and lung cancer. TREM-1 should be considered as a potential biomarker in human oncology and could be used as a new therapeutic target of interest in human oncology (TREM-1 inhibitors, TREM-1 agonists). More clinical studies are urgently needed to confirm TREM-1 (and TREM family) roles in the prognosis and the treatment of human solid cancers.

Triggering receptor expressed on myeloid cells-1 deletion in mice attenuates high-fat diet-induced obesity.

Introduction: The low-grade inflammatory state present in obesity leads to the development and perpetuation of comorbidities associated with obesity. Our laboratory has been working for several years on an amplification loop of the inflammatory response mediated by TREM-1 (Triggering Receptor of Expressed on Myeloid Cells-1). It is implicated in many acute (septic shock) and chronic (IBD) inflammatory diseases. Previously, TREM-1 has been shown to be overexpressed in adipose and liver tissue in obese and diabetic patients, but its impact has never been characterized in these pathologies. Methods: Our hypothesis is that TREM-1 plays a major role in the generation and perpetuation of inflammation during obesity and its associated complication (Insulin resistance and cardiac dysfunction). We assessed TREM-1 protein expression by western blot and immunofluorescence in omental and subcutaneous (pre-)adipocyte. Moreover, we submitted mice to a high-fat diet and investigated the effects of the genetic Trem1 deletion (trem1 KO mice). Results: We showed, for the first time, that TREM-1 is expressed and is functional in subcutaneous and omental (pre-)adipocytes. In the mouse model of high-fat diet-induced obesity, we found that Trem1 suppression limited weight gain, insulin resistance and inflammation in white adipose tissue and liver. Discussion/conclusion: Our results reveal the trem1 KO model can be viewed as a preventive model and that TREM-1 seems to play an important role in the development of obesity and its associated complication. It could therefore be a new therapeutic target in this context.

Oxidative stress-induced endothelial dysfunction and decreased vascular nitric oxide in COVID-19 patients.

BACKGROUND: SARS-CoV-2 targets endothelial cells through the angiotensin-converting enzyme 2 receptor. The resulting endothelial injury induces widespread thrombosis and microangiopathy. Nevertheless, early specific markers of endothelial dysfunction and vascular redox status in COVID-19 patients are currently missing. METHODS: Observational study including ICU and non-ICU adult COVID-19 patients admitted in hospital for acute respiratory failure, compared with control subjects matched for cardiovascular risk factors similar to ICU COVID-19 patients, and ICU septic shock patients unrelated to COVID-19. FINDINGS: Early SARS-CoV-2 infection was associated with an imbalance between an exacerbated oxidative stress (plasma peroxides levels in ICU patients vs. controls: 1456.0 ± 400.2 vs 436 ± 272.1 mmol/L; P < 0.05) and a reduced nitric oxide bioavailability proportional to disease severity (5-α-nitrosyl-hemoglobin, HbNO in ICU patients vs. controls: 116.1 ± 62.1 vs. 163.3 ± 46.7 nmol/L; P < 0.05). HbNO levels correlated with oxygenation parameters (PaO2/FiO2 ratio) in COVID-19 patients (R2 = 0.13; P < 0.05). Plasma levels of angiotensin II, aldosterone, renin or serum level of TREM-1 ruled out any hyper-activation of the renin-angiotensin-aldosterone system or leucocyte respiratory burst in ICU COVID-19 patients, contrary to septic patients. INTERPRETATION: Endothelial oxidative stress with ensuing decreased NO bioavailability appears as a likely pathogenic factor of endothelial dysfunction in ICU COVID-19 patients. A correlation between NO bioavailability and oxygenation parameters is observed in hospitalized COVID-19 patients. These results highlight an urgent need for oriented research leading to a better understanding of the specific endothelial oxidative stress that occurs during SARS-CoV-2. FUNDING: Stated in the acknowledgments section.

Urine sTREM-1 assessment in diagnosing sepsis and sepsis-related acute kidney injury.

The triggering receptor expressed on myeloid cells-1 (TREM-1) is an immunoreceptor whose role is to amplify the inflammatory response mediated by the engagement of Toll-like and NOD-like receptors. As the expression of TREM-1 is believed to be upregulated during infection, this protein has been studied as a sepsis biomarker. In the previous issue of Critical Care, Su and colleagues reported on the usefulness of urinary soluble TREM-1 in diagnosing sepsis and assessing its severity. Importantly, the authors describe, for the first time, that urinary soluble TREM-1 measurement is able to predict the development of sepsis-associated acute kidney injury (AKI). If these results were to be confirmed by larger studies, urinary soluble TREM-1 would possibly become a new biomarker for sepsis-associated AKI.

Potentiation of NETs release is novel characteristic of TREM-1 activation and the pharmacological inhibition of TREM-1 could prevent from the deleterious consequences of NETs release in sepsis.

During sepsis, neutrophil activation induces endothelial cell (EC) dysfunction partly through neutrophil extracellular trap (NET) release. The triggering receptor expressed on myeloid cell-1 (TREM-1) is an orphan immune receptor that amplifies the inflammatory response mediated by Toll-like receptor-4 (TLR4) engagement. Although the key role of TLR4 signaling in NETosis is known, the role of TREM-1 in this process has not yet been investigated. Here, we report that TREM-1 potentiates NET release by human and murine neutrophils and is a component of the NET structure. In contrast, pharmacologic inhibition or genetic ablation of TREM-1 decreased NETosis in vitro and during experimental septic shock in vivo. Moreover, isolated NETs were able to activate ECs and impair vascular reactivity, and these deleterious effects were dampened by TREM-1 inhibition. TREM-1 may, therefore, constitute a new therapeutic target to prevent NETosis and associated endothelial dysfunction.

Rationale and protocol for the efficacy, safety and tolerability of nangibotide in patients with septic shock (ASTONISH) phase IIb randomised controlled trial.

INTRODUCTION: Septic shock is the subgroup of patients with sepsis, which presents as vasopressor dependence, an elevated blood lactate concentration and is associated with a mortality of at least 30%. Expression of the triggering receptor expressed on myeloid cells 1 (TREM-1) pathway, measured using a serum biomarker of pathway activation (soluble TREM-1, sTREM-1) has been associated with outcome in septic shock. Preclinical and early phase patient data suggest that therapeutic modulation of this pathway may improve survival. METHODS AND ANALYSIS: Efficacy, Safety and Tolerability of Nangibotide in Patients with Septic Shock is a phase IIb randomised controlled trial that will take place in up to 50 centres in seven countries and recruit 450 patients with septic shock to receive either placebo or one of two doses of nangibotide, a novel regulator of the TREM-1 pathway. The primary outcome will be the impact of nangibotide therapy on the change in Sequential Organ Failure Assessment score from a baseline determined before initiation of study drug therapy. This will be assessed first in the patients with an elevated sTREM-1 level and then in the study population as a whole. In addition to safety, secondary outcomes of the study will include efficacy of nangibotide in relation to sTREM-1 levels in terms of organ function, mortality and long-term morbidity. This study will also facilitate the development of a novel platform for the measurement of sTREM-1 at the point of care. ETHICS AND DISSEMINATION: The study has been approved by the responsible ethics committees/institutional review boards in all study countries: Belgium: Universitair Ziekenhuis Antwerpen, France: CPP Ile de France II, Denmark: Region Hovedstaden, Spain: ethics committee from Valld'Hebron Hospital, Barcelona, Finland: Tukija, Ireland: St. James' Hospital (SJH) / Tallaght University Hospital (TUH) Joint Research Ethics Committee, USA: Lifespan, Providence TRIAL REGISTRATION NUMBERS: EudraCT Number: 2018-004827-36 and NCT04055909.

Plasma and genetic determinants of soluble TREM-1 and major adverse cardiovascular events in a prospective cohort of acute myocardial infarction patients. Results from the FAST-MI 2010 study.

INTRODUCTION: Triggering receptor expressing on myeloid cells (TREM)-1 is involved in the pathophysiology of ischemic heart disease. Plasma soluble TREM-1 levels (sTREM-1) has been associated with increased risk of major adverse cardiovascular events (MACE) in acute myocardial infarction (AMI) patients. However, the causative link between TREM-1 and MACE remains unknown and requires further investigation before developing potential therapeutic approaches. METHODS AND RESULTS: Using the serum and DNA data bank from the prospective, nationwide French registry of Acute ST-elevation and non-ST-elevation Myocardial Infarction (FAST-MI 2010, N = 1293), we studied the association of plasma levels of sTREM-1 with 9 common genetic variants at the TREM1 locus and their relationship with recurrent MACE over a 3-year follow up. Plasma levels of sTREM-1 were associated with an increased risk of MACEs (death, recurrent MI or stroke) (adjusted HR = 1.86, 95%CI = 1.06-3.26 and HR = 1.11, 95%CI = 0.61-2.02 respectively for tertiles 3 and 2 versus tertile 1, P < 0.001). The study of common variants identified two major genetic determinants of sTREM-1 (rs4714449: beta = -0.11, Padd = 7.85 × 10-5 and rs3804276: beta = 0.18, Padd = 2.65 × 10-11) with a potential role on maintenance and/or differentiation of hematopoietic stem cells. However, associated variants only explained 4% of sTREM-1 variance (P = 2.74 × 10-14). Moreover, the rs4714449 variant, individually and in haplotype, was not significantly associated with MACE (HR = 0.61, 95%CI: 0.35-1.05, P = 0.07). CONCLUSIONS: Despite its relationship with increased risk of death, recurrent MI and stroke, genetic determinants of plasma levels of sTREM-1 were not found to be causal prognostic factors in patients with acute myocardial infarction.

Increased sTREM-1 plasma concentrations are associated with poor clinical outcomes in patients with COVID-19.

Patients with sepsis display increased concentrations of sTREM-1 (soluble Triggering Receptor Expressed on Myeloid cells 1), and a phase II clinical trial focusing on TREM-1 modulation is ongoing. We investigated whether sTREM-1 circulating concentrations are associated with the outcome of patients with coronavirus disease 2019 (COVID-19) to assess the role of this pathway in COVID-19. This observational study was performed in two independent cohorts of patients with COVID-19. Plasma concentrations of sTREM-1 were assessed after ICU admission (pilot cohort) or after COVID-19 diagnosis (validation cohort). Routine laboratory and clinical parameters were collected from electronic patient files. Results showed sTREM-1 plasma concentrations were significantly elevated in patients with COVID-19 (161 [129-196] pg/ml) compared to healthy controls (104 [75-124] pg/ml; P<0.001). Patients with severe COVID-19 needing ICU admission displayed even higher sTREM-1 concentrations compared to less severely ill COVID-19 patients receiving clinical ward-based care (235 [176-319] pg/ml and 195 [139-283] pg/ml, respectively, P = 0.017). In addition, higher sTREM-1 plasma concentrations were observed in patients who did not survive the infection (326 [207-445] pg/ml) compared to survivors (199 [142-278] pg/ml, P<0.001). Survival analyses indicated that patients with higher sTREM-1 concentrations are at higher risk for death (hazard ratio = 3.3, 95%CI: 1.4-7.8). In conclusion, plasma sTREM-1 concentrations are elevated in patients with COVID-19, relate to disease severity, and discriminate between survivors and non-survivors. This suggests that the TREM-1 pathway is involved in the inflammatory reaction and the disease course of COVID-19, and therefore may be considered as a therapeutic target in severely ill patients with COVID-19.

Inflammation-Induced Coagulopathy Substantially Differs Between COVID-19 and Septic Shock: A Prospective Observational Study.

Critical COVID-19, like septic shock, is related to a dysregulated systemic inflammatory reaction and is associated with a high incidence of thrombosis and microthrombosis. Improving the understanding of the underlying pathophysiology of critical COVID-19 could help in finding new therapeutic targets already explored in the treatment of septic shock. The current study prospectively compared 48 patients with septic shock and 22 patients with critical COVID-19 regarding their clinical characteristics and outcomes, as well as key plasmatic soluble biomarkers of inflammation, coagulation, endothelial activation, platelet activation, and NETosis. Forty-eight patients with matched age, gender, and co-morbidities were used as controls. Critical COVID-19 patients exhibited less organ failure but a prolonged ICU length-of-stay due to a prolonged respiratory failure. Inflammatory reaction of critical COVID-19 was distinguished by very high levels of interleukin (IL)-1ß and T lymphocyte activation (including IL-7 and CD40L), whereas septic shock displays higher levels of IL-6, IL-8, and a more significant elevation of myeloid response biomarkers, including Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) and IL-1ra. Subsequent inflammation-induced coagulopathy of COVID-19 also differed from sepsis-induced coagulopathy (SIC) and was characterized by a marked increase in soluble tissue factor (TF) but less platelets, antithrombin, and fibrinogen consumption, and less fibrinolysis alteration. In conclusion, COVID-19 inflammation-induced coagulopathy substantially differs from SIC. Modulating TF release and activity should be evaluated in critical COVID-19 patients.

TREM-1 orchestrates angiotensin II-induced monocyte trafficking and promotes experimental abdominal aortic aneurysm.

The triggering receptor expressed on myeloid cells 1 (TREM-1) drives inflammatory responses in several cardiovascular diseases but its role in abdominal aortic aneurysm (AAA) remains unknown. Our objective was to explore the role of TREM-1 in a mouse model of angiotensin II-induced (AngII-induced) AAA. TREM-1 expression was detected in mouse aortic aneurysm and colocalized with macrophages. Trem1 gene deletion (Apoe-/-Trem1-/-), as well as TREM-1 pharmacological blockade with LR-12 peptide, limited both AAA development and severity. Trem1 gene deletion attenuated the inflammatory response in the aorta, with a reduction of Il1b, Tnfa, Mmp2, and Mmp9 mRNA expression, and led to a decreased macrophage content due to a reduction of Ly6Chi classical monocyte trafficking. Conversely, antibody-mediated TREM-1 stimulation exacerbated Ly6Chi monocyte aorta infiltration after AngII infusion through CD62L upregulation and promoted proinflammatory signature in the aorta, resulting in worsening AAA severity. AngII infusion stimulated TREM-1 expression and activation on Ly6Chi monocytes through AngII receptor type I (AT1R). In human AAA, TREM-1 was detected and TREM1 mRNA expression correlated with SELL mRNA expression. Finally, circulating levels of sTREM-1 were increased in patients with AAA when compared with patients without AAA. In conclusion, TREM-1 is involved in AAA pathophysiology and may represent a promising therapeutic target in humans.