Triggering receptor expressed on myeloid cells type 1 as a potential therapeutic target in sepsis

Shortened PGLYRP1 Peptides Regulate Antitumor Activity of Cytotoxic Lymphocytes via TREM-1 Receptor: From Biology to Bioinformatics

The pro-inflammatory immune response plays an important role in protecting the body from pathogens and tumors. In this study, we were able to identify three peptides of the innate immunity protein PGLYRP1 (Tag7) that could regulate the activity of the TREM-1 receptor. TREM-1 receptor activation on monocytes triggers the appearance of antitumor lymphocytes. All three peptides studied (17.0, N9, and N15) bind with the TREM-1 receptor with the Kds 1.32 ± 0.2 nM, 9.66 ± 0.5 nM, and 7.43 ± 0.4 nM, respectively. An N9 peptide inhibiting the activity of the receptor was identified in addition to two peptides (N9 and N15) that jointly trigger the activation of the receptor. The conducted molecular docking study revealed amino acid residues (Ile57, Ile58, Glu106, Ser108, Leu110, Tyr116, Pro118, Pro119, Arg130, and Val 132), necessary for various functions of peptides, providing important knowledge for understanding the mechanism of activation of this receptor that can also serve as a basis for the development of therapeutic drugs to regulate its activity in the treatment of autoimmune diseases and tumors.

Role of MLIP in burn-induced sepsis and insights into sepsis-associated cancer progression

Introduction

Burn-induced sepsis is a critical clinical challenge marked by systemic inflammation, immune dysregulation, and high mortality. Macrophage-driven inflammatory pathways are central to sepsis pathogenesis, while immune cell metabolic reprogramming plays a key role in both sepsis and cancer progression.

Methods

Bioinformatics analyses using GEO, TCGA, and GTEx datasets identified MLIP-modulated genes linked to immune responses and prognosis. In vitro, LPS-stimulated HUVEC cells were used to study MLIP's effects on inflammation and macrophage function through cell viability, ROS levels, cytokine expression, qRT-PCR, and immunofluorescence assays.

Results

MLIP-modulated genes were associated with immune-related metabolic pathways in both sepsis and cancer. Epigenetic analysis showed MLIP expression is regulated by promoter methylation and chromatin accessibility. Prognostic analyses revealed MLIP's impact on survival outcomes across cancer types. In vitro, MLIP reduced inflammation, oxidative stress, and macrophage hyperactivation.

Conclusions

MLIP regulates immune-metabolic dynamics in burn-induced sepsis, influencing macrophage activity and oxidative stress. Its role in metabolic reprogramming suggests MLIP as a potential therapeutic target linking immune modulation and cancer progression. Further research on MLIP's role in immune evasion and tumor metabolism may inform novel therapeutic strategies.

Huang-Lian-Jie-Du decoction ameliorates sepsis through dynamic regulation of immune response and gut microbiota-metabolite axis

Sepsis remains a life-threatening condition with high mortality rates despite current therapeutic approaches. While Huang-Lian-Jie-Du Decoction (HLJDD), a traditional Chinese medicine formula, has been historically used to treat inflammatory conditions, its therapeutic potential in sepsis and underlying mechanisms remain unexplored. This study investigated HLJDD's comprehensive effects on sepsis pathophysiology using a rat cecal ligation and puncture (CLP) model. HLJDD significantly improved survival rates and demonstrated sophisticated immunomodulatory effects through temporal regulation of the biphasic immune response characteristic of sepsis. In early sepsis, HLJDD suppressed pro-inflammatory cytokines (IL-1β, IL-6) while maintaining defensive inflammation. During late sepsis, it counteracted immunosuppression by reducing IL-10 levels and CD4+CD25+ T cell populations while protecting CD4+ and CD8+ T cells from apoptosis. Notably, HLJDD demonstrated dynamic regulation of the gut microbiota-metabolite axis. It enhanced beneficial bacterial populations (Firmicutes, Lactobacillus) while suppressing potentially pathogenic species (Bacteroides, Parabacteroides). Metabolomic analysis revealed time-dependent modulation of short-chain fatty acids, with elevated levels at 12 h followed by strategic reduction at 18-30 h, coordinating with changes in SCFA-producing bacteria. This temporal metabolic regulation corresponded with improved intestinal barrier function and balanced immune responses. The study unveils HLJDD's novel mechanism of action through synchronized modulation of immune responses, gut microbiota, and metabolite profiles, presenting a multi-target therapeutic approach that addresses the complex pathophysiology of sepsis. These findings provide a strong foundation for further clinical investigation of HLJDD as an innovative treatment strategy for sepsis.

Exploring novel protein biomarkers for early-stage diagnosis and prognosis of T-acute lymphoblastic leukemia (T-ALL)

BACKGROUND

Efficient classification of T-acute lymphoblastic leukemia (T-ALL) involves considering various factors, such as age, white blood cell count, and chromosomal alterations. However, studying protein markers are crucial to improving T-ALL patients' diagnosis and treatment. A study analyzing the expression of proteomes was conducted to identify promising early-stage biomarkers for T-ALL patients METHODS: Label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the blood proteins of both patients and healthy individuals to identify new biomarkers for T-ALL. The findings were validated by RT-PCR, ELISA and computational analysis RESULTS: The study identified 1467 proteins in the blood, of which nine were upregulated and 35 were downregulated by more than 2-fold. T-ALL patients showed a significant increase in specific disease-related proteins, such as eleven-nineteen lysine-rich leukemia protein, triggering receptor expressed on myeloid cells 1, cisplatin resistance-associated-overexpressed protein, X-ray radiation resistance-associated protein 1, tumor necrosis factor receptor superfamily member 10D, protein S100-A8, and copine-4, by more than 3-fold CONCLUSION: The findings of this study provide a valuable protein map of leukemic cells and identify potential biomarkers for leukemic aggressiveness. However, further studies using larger T-ALL patient samples must confirm these preliminary results.

TREM-1 Modulation Strategies for Sepsis

The triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor, which can be upregulated in inflammatory diseases as an amplifier of immune responses. Once activated, TREM-1 induces the production and release of pro-inflammatory cytokines and chemokines, in addition to increasing its own expression and circulating levels of the cleaved soluble extracellular portion of TREM-1 (sTREM-1). This amplification of the inflammatory response by TREM-1 has now been considered as a critical contributor to the dysregulated immune responses in sepsis. Studies have shown that in septic patients there is an elevated expression of TREM-1 on immune cells and increased circulating levels of sTREM-1, associated with increased mortality. As a result, a considerable effort has been made towards identifying endogenous ligands of TREM-1 and developing TREM-1 inhibitory peptides to attenuate the exacerbated inflammatory response in sepsis. TREM-1 modulation has proven a promising strategy for the development of therapeutic agents to treat sepsis. Therefore, this review encompasses the ligands investigated as activators of TREM-1 thus far and highlights the development and efficacy of novel inhibitors for the treatment of sepsis and septic shock.

N-Terminal Peptide of PGLYRP1/Tag7 Is a Novel Ligand for TREM-1 Receptor

An investigation of innate immunity receptors sheds light on the mechanisms of inflammation and associated immune reactions. One of the key immune regulators is the TREM-1 receptor, which is involved in both inflammation and antitumor immune response. In this article, we have obtained a new ligand for the TREM-1 receptor. The peptide, named N3, is a part of the innate immune protein PGLYRP1/Tag7. It is responsible for activating the TREM-1 signaling pathway. Here, we have demonstrated that the N3 peptide acts like other TREM-1 receptor ligands: its binding results in a mild inflammation response and appearance of cytotoxic lymphocytes. We have shown that cytotoxic populations of lymphocytes in N3 peptide-treated PBMCs are similar to those treated with Tag7 or Hsp70. We also determined the part of the N3 peptide responsible for binding to TREM-1. The resulting peptide (N9) consists of nine amino acids and can be considered as a potential peptide that blocks TREM-1 signaling.

Cutaneous leishmaniasis: multiomics approaches to unravel the role of immune cells checkpoints

INTRODUCTION

Cutaneous leishmaniasis (CL) is the most frequent form of leishmaniases, associated with skin inflammation and ulceration. Understanding the interaction of different phagocytic cells in the recognition and uptake of different Leishmania species is critical for controlling the infection. Phagocytic cells have a pivotal role as professional antigen-presenting cells that bridge the innate and adaptive immunity and shape the outcome of the disease.

AREAS COVERED

Here we reviewed new technologies with high-throughput data collection capabilities along with systems biology approaches which are recently being used to decode the paradox of CL immunology.

EXPERT OPINION

We emphasized on the crosstalk between DC and T-cells while focusing on the immune checkpoints interactions between the human immune system and the Leishmania species. Further, we discussed omics technologies including bulk RNA sequencing, reverse transcriptase-multiplex ligation dependent probe amplification (RT-MLPA), and proximity extension assay (PEA) in studies on human blood or tissue-driven samples from CL patients in which we have so far been involved.

Diagnostic and prognostic predictive values of triggering receptor expressed on myeloid cell-1 expression in neonatal sepsis: A meta-analysis and systematic review

OBJECTIVE

The purpose of this systematic review was to explore the value of the expression level of the triggering receptor expressed on myeloid cell-1 (TREM-1) in the diagnosis and prognosis of neonatal sepsis.

METHODS

A comprehensive search was performed to identify the diagnostic and prognostic predictive values of the TREM-1 expression level in neonatal sepsis. Based on the retrieval strategy, Cochrane Library, Embase, Ovid, ProQuest, PubMed, Scopus, and Web of Science databases were searched from inception to February 2022. Studies were included if they assessed the accuracy of TREM-1 expression in the diagnosis of neonatal sepsis and distinguished survival and death in neonatal sepsis. Two authors independently evaluated the study and extracted the data, including the first author of the literature, country, total study population, basic population characteristics of the study group and the control group, study design (observational studies), type of sample, sepsis onset, type of biomarker, assay method, cut-off, sensitivity, specificity, true positives (TP), false positives (FP), false negatives (FN), and true negatives (TN). A third party will be consulted if disputed. The accuracy of TREM-1 expression in the diagnosis and prognostic prediction of neonatal sepsis was evaluated by a bivariate mixed-effects model. The source of heterogeneity was explored through meta-regression analysis.

RESULTS

Thirteen articles that met the research criteria were included in qualitative analysis, and 11 of them were included in quantitative analysis. The pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and the area under the summary receiver operator characteristic (SROC) curve of soluble TREM-1 (sTREM-1) were 0.94 (95% CI: 0.82, 0.98), 0.87 (95% CI: 0.70, 0.95), 7.36 (95% CI: 2.75, 19.74), 0.07 (95% CI: 0.02, 0.24), 111.71 (95% CI: 13.24, 942.92), and 0.96 (95% CI: 0.94, 0.98), respectively. Meta-regression and subgroup analysis were used to investigate the heterogeneity, owing to non-threshold effects caused by types of test sample and research design. sTREM-1 as a biomarker for distinguishing survival and death in neonates with sepsis had pooled sensitivity, specificity, area under the SROC curve, PLR, NLR, and DOR of 0.95 (95% CI: 0.83, 0.99), 0.98 (95% CI: 0.68, 1.00), 0.99 (95% CI: 0.97, 0.99), 39.28 (95% CI: 2.13, 723.99), 0.05 (95% CI: 0.01, 0.19), and 789.61 (95% CI: 17.53, 35,560.72), respectively.

CONCLUSION

The study showed that TREM-1 was a potential biomarker for the diagnosis and prognosis of neonatal sepsis. The biggest advantage of this study is that it is the first to comprehensively explore the role of TREM-1 expression in the diagnosis and prognosis of neonatal sepsis. However, there are some limitations in this study, such as the reduced number of clinical studies on TREM-1 expression as a biomarker of neonatal sepsis, regional bias, and differences in detection methods. Hence, more large-scale and high-quality studies are needed to improve diagnostic accuracy.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022338041.

Diagnostic and prognostic predictive values of circulating sTREM-1 in sepsis: A meta-analysis

BACKGROUND

With the increasing studies regarding the diagnostic value of soluble triggering receptor expressed on myeloid cells (sTREM)-1 in sepsis in recent years, it is essential to make an updated meta-analysis to explore the sepsis differentiation value of circulating sTREM-1 from systemic inflammatory response syndrome (SIRS). Recently, no meta-analysis was made to explore the prognostic predictive value of circulating sTREM-1 in sepsis. Thus, the present aimed to make meta-analyses to explore the diagnostic and prognostic predictive values of circulating sTREM-1 in sepsis.

METHODS

Articles published before March 2021 were searched in databases: PubMed, Web of Science, EMBASE, Medline and Google Scholar. After a summary of sensitivity, specificity, positive likelihood ratios (PLR), negative likelihood ratios (NLR), and diagnostic odds ratio (DOR), the receive-operating characteristics (SROC) curve were performed to summarize true positive (TP) and false positive (FP) rates. Q test and I² were used to explore heterogeneity between studies.

RESULTS

Circulating sTREM-1 showed a high sensitivity (0.85 (95% confidence interval (CI): 0.76-0.91)) and moderate specificity (0.79 (95% CI: 0.70-0.86)) to differentiate sepsis from SIRS. The study showed a high sensitivity (0.80 (95% CI: 0.66-0.89)) and moderate specificity (0.75 (95% CI: 0.69-0.81)) to predict 28-day mortality in sepsis.

CONCLUSION

In conclusion, the present study suggested that circulating sTREM-1 showed diagnostic and prognostic predictive values in sepsis.

Tryptophanyl-tRNA Synthetase 1 Signals Activate TREM-1 via TLR2 and TLR4

Tryptophanyl-tRNA synthetase 1 (WARS1) is an endogenous ligand of mammalian Toll-like receptors (TLR) 2 and TLR4. Microarray data, using mRNA from WARS1-treated human peripheral blood mononuclear cells (PBMCs), had indicated WARS1 to mainly activate innate inflammatory responses. However, exact molecular mechanism remains to be understood. The triggering receptor expressed on myeloid cells (TREM)-1 is an amplifier of pro-inflammatory processes. We found WARS1 to significantly activate TREM-1 at both mRNA and protein levels, along with its cell surface expression and secretion in macrophages. WARS1 stimulated TREM-1 production via TLR2 and TLR4, mediated by both MyD88 and TRIF, since targeted deletion of TLR4, TLR2, MyD88, and TRIF mostly abrogated TREM-1 activation. Furthermore, WARS1 promoted TREM-1 downstream phosphorylation of DAP12, Syk, and AKT. Knockdown of TREM-1 and inhibition of Syk kinase significantly suppressed the activation of inflammatory signaling loop from MyD88 and TRIF, leading to p38 MAPK, ERK, and NF-κB inactivation. Finally, MyD88, TRIF, and TREM-1 signaling pathways were shown to be cooperatively involved in WARS1-triggered massive production of IL-6, TNF-α, IFN-β, MIP-1α, MCP-1, and CXCL2, where activation of Syk kinase was crucial. Taken together, our data provided a new insight into WARS1′s strategy to amplify innate inflammatory responses via TREM-1.

Diagnostic value of serum soluble triggering expressed receptor on myeloid cells 1 (sTREM-1) in suspected sepsis: a meta-analysis

Background

We aim to synthesize the up-to-date studies to investigate the diagnostic value of serum soluble triggering expressed receptor on myeloid cells 1 (sTREM-1) in suspected sepsis.

Results

A total of 19 studies with 2418 patients were finally enrolled in the meta-analysis. The pooled sensitivity was 0.82 (95% CI 0.73 to 0.89), specificity 0.81 (95% CI 0.75 to 0.86), positive likelihood ratio 4.3 (95% CI 3.02 to 6.12), negative likelihood ratio 0.22 (95% CI 0.24 to 0.35), diagnostic odds ratio 20 (95% CI 9 to 41) and AuROC 0.88 (95% CI 0.85 to 0.91). The meta-regression analysis revealed that the sample size, reference standard description, prevalence of sepsis in the trials and consecution of patient recruitment might be the source of heterogeneity.

Conclusions

The serum sTREM-1 had a moderate ability in diagnosis in suspected sepsis based on the current studies. However, more large-scale studies were needed to further evaluate the diagnostic accuracy of sTREM-1.

TREM-1 Attenuates RIPK3-mediated Necroptosis in Hyperoxia-induced Lung Injury in Neonatal Mice

Hyperoxia-induced injury to the developing lung, impaired alveolarization, and dysregulated vascularization are critical factors in the pathogenesis of bronchopulmonary dysplasia (BPD); however, mechanisms for hyperoxia-induced development of BPD are not fully known. In this study, we show that TREM-1 (triggering receptor expressed on myeloid cells 1) is upregulated in hyperoxia-exposed neonatal murine lungs as well as in tracheal aspirates and lungs of human neonates with respiratory distress syndrome and BPD as an adaptive response to survival in hyperoxia. Inhibition of TREM-1 function using an siRNA approach or deletion of the Trem1 gene in mice showed enhanced lung inflammation, alveolar damage, and mortality of hyperoxia-exposed neonatal mice. The treatment of hyperoxia-exposed neonatal mice with agonistic TREM-1 antibody decreased lung inflammation, improved alveolarization, and was associated with diminished necroptosis-regulating protein RIPK3 (receptor-interacting protein kinase 3). Mechanistically, we show that TREM-1 activation alleviates lung inflammation and improves alveolarization through downregulating RIPK3-mediated necroptosis and NLRP3 (nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3) inflammasome activation in hyperoxia-exposed neonatal mice. These data show that activating TREM-1, enhancing angiopoietin 1 signaling, or blocking the RIPK3-mediated necroptosis pathway may be used in new therapeutic interventions to control adverse effects of hyperoxia in the development of BPD.

The Leukocyte VCS Parameters Compared with Procalcitonin, Interleukin-6, and Soluble Hemoglobin Scavenger Receptor sCD163 for Prediction of Sepsis in Patients with Cirrhosis

Background

Patients with liver cirrhosis have a high risk of sepsis and a poor prognosis. Recently, a new standard for sepsis (Sepsis-3) has been proposed in the general population. The Coulter Lh 750 hematology analyzer can evaluate mean volume, conductivity, scatter, and distribution width of leukocyte. We tried to use Sepsis-3 criteria to study the diagnostic value of volume, conductivity, and scattering (VCS) parameters in sepsis and infection in patients with liver cirrhosis compared with traditional infection markers (PCT, IL-6, sCDl63).

Methods

A blinded, cohort study was conducted in three different ED populations within three affiliated hospitals. A total of 249 patients with liver cirrhosis were enrolled in the study. According to the “Sepsis-3” consensus criteria, clinical history, and laboratory examination, the subjects were divided into sepsis (n = 54), patients with infections (n = 95), and patients without systemic infections (n = 100). The blood samples of the patients were collected at the time of ED admission and were evaluated for the detection of sepsis.

Results

The differences of MNV, MNS, MMV, MMS, MLV, NDW, and MDW in the three groups were statistically significant. In the diagnosis of sepsis in patients with liver cirrhosis, the sensitivity of combined detection of MMV and MDW was 88.89%; the specificity was 74%. This sensitivity was significantly better than the 83.3% achieved using 0.97 mg/L as the cutoff for sCD163. In the diagnosis of infection in cirrhosis, the sensitivity of combination of MNV and MMS was increased to 86.32%; the specificity was 92%. The sensitivity was the same as that achieved by using 0.31 ng/mL as the cutoff value of PCT, but the specificity increased.

Conclusion

The leukocyte VCS parameter could be potential parameters for indicating sepsis and infection in patients with liver cirrhosis. The combined detection of MMV and MDW seemed to be helpful for the diagnosis of sepsis in these patients, and the combination of MNV and MMS could better indicate infection for them.

Rheumatoid arthritis synovial fibroblasts promote TREM-1 expression in monocytes via COX-2/PGE2 pathway

BACKGROUND

Triggering receptor expressed on myeloid cells-1 (TREM-1) is inducible on monocyte/macrophages and neutrophils and amplifies the inflammatory response. The aim of this study was to determine whether rheumatoid arthritis synovial fibroblasts (RASF) promote the expression of TREM-1 in monocytes and its potential regulatory mechanism.

METHODS

Synovial fluid and paired peripheral blood from rheumatoid arthritis (RA) patients were analyzed using flow cytometry. Expression of TREM-1 in monocytes was detected after co-culture with RASF, with or without pre-treatment with toll-like receptor (TLR) ligands. Whether RASF-regulated TREM-1 level in monocytes require direct cell contact or soluble factors was evaluated by transwell experiment. COX-2 expression and PGE₂ secretion in RASF were determined by quantitative PCR (qPCR) and ELISA. RASF, with and without TLR ligand stimulation, were treated with COX-2 inhibitors, COX-2 siRNA (siCOX-2) or EP1-4 antagonists, and the resulting TREM-1 level in CD14⁺ monocytes was measured using flow cytometry.

RESULTS

TREM-1 was highly expressed in CD14⁺ cells from peripheral blood and especially synovial fluid from RA patients. The expression of TREM-1 in monocytes was increased by co-culture with RASF. TLR-ligand-activated RASF further elevated TREM-1 level. Transwell assay indicated that soluble factors played a key role in RASF-promoted expression of TREM-1 in monocytes. RASF, with or without stimulation by TLR ligands, increased secretion of PGE₂ in a cyclooxygenase (COX)-2-dependent manner. PGE₂ enhanced the increase in TREM-1 level in monocytes. Finally, studies using COX-2 inhibitors, COX-2 siRNA (siCOX-2) and EP1-4 antagonists, showed that RASF promotion of TREM-1 expression in monocytes was mediated by COX-2/PGE₂/EP2,4 signaling.

CONCLUSIONS

Our data is the first report to reveal the critical role of RASF in upregulating TREM-1 expression in monocytes, which indicates that TREM-1 might be a novel target for RA therapy.

Soluble triggering receptor expressed on myeloid cells-1 as a useful biomarker for diagnosing ventilator-associated pneumonia after congenital cardiac surgery in children

The present study aimed to assess the usefulness of soluble triggering receptor expressed on myeloid cells 1 (sTREM-1) in the diagnosis of ventilator-associated pneumonia (VAP) in paediatric patients with congenital heart disease (CHD) following cardiac surgery. The current prospective study enrolled 48 patients with congenital heart diseases who were suspected of having VAP; these patients were undergoing cardiac surgery between August 2016 and October 2017 in the Cardiac Intensive Care Unit of Shanghai Children's Medical Center (Shanghai, China). A total of 31 patients were diagnosed with VAP using a polymerase chain reaction (PCR) assay, while 17 patients without VAP were designated as the Non-VAP group. A bronchoscopy was performed and samples were collected for measurement on the day that VAP was diagnosed. The sTREM-1 levels were measured in bronchoalveolar lavage fluid (BALF) and exhaled ventilator condensate (EVC). BALF specimens were also sent to the microbiology laboratory for PCR assays and quantitative culturing. The positive detection rate of bacteria using the PCR assay and traditional culture was 64.6% (31/48) and 39.6% (19/48). sTREM-1 was significantly higher in the BALF (146.21 pg/ml vs. 118.06 pg/ml) and EVC (125.29 pg/ml vs. 120.48 pg/ml) of patients with VAP demonstrated compared with the patients without VAP. The findings suggest that the detection of sTREM-1 in BALF and EVC samples may be useful for the diagnosis of VAP following heart surgery in children.

Expression level of 12-amino acid triggering receptor on myeloid cells-like transcript 1 derived peptide alleviates lipopolysaccharide-induced acute lung injury in mice

Acute lung injury (ALI) is a critical illness with a high morbidity and mortality rate due to severe inflammation in the lungs. The effects and underlying mechanism of the triggering receptor expressed on myeloid cells‑1 (TREM‑1)‑like transcript‑1‑derived peptide (LR12) on ALI remain unclear. The aim of the present study was to determine whether LR12 attenuates lipopolysaccharide (LPS)‑induced ALI and elucidate the mechanism underlying it. Male C57BL/6 mice were randomly assigned to three groups as follows: Sham group, LPS + scramble group and LPS + LR12 group. Normal saline (NS) or LPS was administrated by intratracheal instillation, and NS, LR12 or LR12 scramble was administered intraperitoneally 30 min later. The treatment was repeated every 3 h three times. Mice were sacrificed 24 h later. Pulmonary pathological changes, the lung wet/dry weight ratio, the macrophage and neutrophil counts in bronchoalveolar lavage fluid and myeloperoxidase (MPO) activity in the lung tissues were observed. The inflammatory cytokines were evaluated by enzyme‑linked immunosorbent assay and lung neutrophil infiltration was detected by immunohistochemistry. Nuclear factor (NF)‑κB p65 and TREM‑1 were analyzed by western blotting, and the activation of NF‑κB was detected by electrophoretic mobility shift assay. LPS‑induced pathohistological injury, edema and neutrophil infiltration were significantly alleviated by TREM‑1 inhibitor, LR12. The proinflammatory cytokines [interleukin (IL)‑6, IL‑1β, tumor necrosis factor‑α] and chemokines (keratinocyte chemokine and monocyte chemoattractant protein‑1) were significantly reduced, whereas the anti‑inflammatory cytokines, IL‑10 were significantly increased by LR12. LR12 was identified to significantly decrease p65 expression levels in the nucleus and inhibit the activity of NF‑κB. Furthermore, LR12 alleviated LPS‑induced ALI by reducing the expression of TREM‑1, increasing the release of soluble TREM‑1 and inhibiting activation of the NF-κB signaling pathway.

Soluble triggering receptor expressed on myeloid cell-1 (sTREM-1): a potential biomarker for the diagnosis of infectious diseases

Sensitive and useful biomarkers for the diagnosis and prognosis of infectious diseases have been widely developed. An example of these biomarkers is triggering receptor expressed on myeloid cell-1 (TREM-1), which is a cell surface receptor expressed on monocytes/macrophages and neutrophils. TREM-1 amplifies inflammation by activating the TREM-1/DAP12 pathway. This pathway is triggered by the interaction of TREM-1 with ligands or stimulation by bacterial lipopolysaccharide. Consequently, pro-inflammatory cytokines and chemokines are secreted. Soluble TREM-1 (sTREM-1) is a special form of TREM-1 that can be directly tested in human body fluids and well-known biomarker for infectious diseases. sTREM-1 level can be potentially used for the early diagnosis and prognosis prediction of some infectious diseases, including infectious pleural effusion, lung infections, sepsis, bacterial meningitis, viral infections (e.g., Crimean Congo hemorrhagic fever and dengue fever), fungal infections (e.g., Aspergillus infection), and burn-related infections. sTREM-1 is a more sensitive and specific biomarker than traditional indices, such as C-reactive protein and procalcitonin levels, for these infectious diseases. Therefore, sTREM-1 is a feasible biomarker for the targeted therapy and rapid and early diagnosis of infectious diseases.

Inhibition of triggering receptor expressed on myeloid cells-1 ameliorates experimental autoimmune neuritis

Experimental autoimmune neuritis (EAN) is a cluster of differentiation 4+ T helper 1 cell-mediated inflammatory demyelinating disease of the peripheral nervous system and serves as a useful animal model for Guillain‑Barré syndrome. Triggering receptor expressed on myeloid cells‑1 (TREM‑1) is an important receptor involved in sepsis and the innate inflammatory response. Linear plasmid 17 (LP 17) peptide is a competitive antagonist of TREM‑1. To investigate the role of TREM‑1 in EAN, 64 male Lewis rats were randomly divided into four groups: Normal saline, complete Freund's adjuvant, EAN and LP 17. The present study assessed the mRNA expression levels of TREM‑1, tumor necrosis factor‑α and interleukin‑1β in sciatic nerves and peripheral blood mononuclear cells. The results demonstrated that inhibiting TREM-1 by administering LP 17 ameliorated symptoms and reduced inflammation in EAN rats. The present study concluded that TREM‑1 may be involved in the pathogenesis of EAN, and that inhibition of TREM-1 may ameliorate EAN.

Predictive value of maternal serum NF-κB p65 and sTREM-1 for subclinical chorioamnionitis in premature rupture of membranes

PROBLEM

The aim of this study was to investigate the levels of nuclear factor kappa B-p65 (NF-κB p65) and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) in maternal blood with premature rupture of membranes (PROM) and to assess their values for prediction of subclinical chorioamnionitis.

METHOD

NF-κB p65 and sTREM-1 levels were measured in maternal blood and cord blood by fluorescence quantitative RT-PCR assay. According to the placental membranes pathological examination, pregnant women with PROM were divided into chorioamnionitis group (n=28) and non-chorioamnionitis group (n=22).

RESULTS

In the PROM group,the NF-κB p65 and sTREM-1 levels in maternal blood were significantly higher in women with chorioamnionitis than women without chorioamnionitis (P<.05). The cutoff value of maternal NF-κB p65, sTREM-1, C-reactive protein (CRP), and WBC level were 6.73, 2.93, 6.75 mg/L, and 10.8×10(9) /L, respectively, through analysis of the area under the ROC curve (AUC). The optimal combination test was detection of maternal blood NF-κB p65 and CRP levels, which resulted in a sensitivity of 89.3% and a specificity of 72.7% for the prediction of subclinical chorioamnionitis.

CONCLUSION

Combined measurements of maternal NF-κB p65 and CRP levels may be used as early biological indicators that predict subclinical chorioamnionitis in premature rupture of membranes.

Ameliorative effects of glycine in an experimental nonalcoholic steatohepatitis and its correlation between TREM-1 and TREM-2

Inflammation plays an important role in Nonalcoholic Steatohepatitis (NASH), triggering receptor expressed on myeloid cells-1 and 2 (TREM-1 and TREM-2) modulates inflammatory and innate immune, they have been investigated in various inflammatory diseases, but not in NASH. Meanwhile we added glycine in HFO (HFOG) to investigate if the liver pathologic relief is related with TREM-1 and TREM-2. Liver tissue staining and serum indexes showed that the NASH was successful from the 4(th) weekend and glycine can improved many features of NASH. Results from Q-PCR and ELISA study showed that compareaded with control, TREM-1 is upregulated and TREM-2 is downregulated respectively in 4 and 8-week NASH model (TREM-1: p < 0.001; TREM-2: p < 0.001).Compared with HFO group, HFOG group with an extra 5% Glycine into the diet of NASH, we found that all model liver pathologic and serum indexes ameliorated in this group. Furthermore, Results from Q-PCR and ELISA study showed that compareaded with HFO group, TREM-2 of this group is upregulated and TREM-1 is downregulated respectively from the 4(th) weekend, which is more significant at the 8(th) weekend (TREM-1: p <0.001; TREM-2: p =0.048). Pearson correlation showed that TREM-1 and TREM-2 were closely associated with serum ET, TNF-α, TLR-4 and PC III. Besides, using multiple-stepwise regression analysis, we found that the ameliorative effects of glycine in HFOG was mainly related to its counteraction of PC III, TREM-1 and upregulation of TREM-2. Furthermore, we detected the expression of TREM-1 and TREM-2 in gall stone patients without drinking excessively before undergoing cholecystectomy, and found that the rise of TREM-1 and reduction of TREM-2 was close associated with the severity of fatty liver. To conclude, our results support the concept that TREM-1 and TREM-2 were close strongly linked to NASH and NALFD. Glycine can relieve NASH by its anti-fibrosis effect, and this ameliorative effect is related to the expression change of TREM-1/2 to some extent.

Markers for sepsis diagnosis in the forensic setting: state of the art

Reliable diagnoses of sepsis remain challenging in forensic pathology routine despite improved methods of sample collection and extensive biochemical and immunohistochemical investigations. Macroscopic findings may be elusive and have an infectious or non-infectious origin. Blood culture results can be difficult to interpret due to postmortem contamination or bacterial translocation. Lastly, peripheral and cardiac blood may be unavailable during autopsy. Procalcitonin, C-reactive protein, and interleukin-6 can be measured in biological fluids collected during autopsy and may be used as in clinical practice for diagnostic purposes. However, concentrations of these parameters may be increased due to etiologies other than bacterial infections, indicating that a combination of biomarkers could more effectively discriminate non-infectious from infectious inflammations. In this article, we propose a review of the literature pertaining to the diagnostic performance of classical and novel biomarkers of inflammation and bacterial infection in the forensic setting.

TREM-1 as a potential therapeutic target in neonatal sepsis

OBJECTIVE

Bacterial sepsis in neonates is associated with elevated morbidity and mortality. A role for the pro-inflammatory Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) is suspected in the innate immune response to bacteria, but little is known about its activities in infants. To begin exploring the feasibility of treating neonatal sepsis by blocking leukocyte TREM-1, we compared TREM-1 membrane expression and mRNA in newborns without clinical or microbiological evidence of infection, to that of healthy adults. The functionality of pro-inflammatory reactions in leukocyte TREM-1 of newborns was also evaluated.

METHODS

Twenty term newborns were enrolled in this study and cord blood samples were collected at birth. For comparison, peripheral blood specimens were collected from 20 healthy adults (control adult, CA). The expression of TREM-1 protein and mRNA in leukocytes was detected with flow cytometry and real-time qPCR, respectively. Whole cord blood was also stimulated by Escherichia coli or blocked by the TREM-1-specific peptide LP17 to identify changes in the secretion of pro-inflammatory cytokines interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α, as well as soluble TREM-1 (sTREM-1) using enzyme linked immunosorbent assay (ELISA).

RESULTS

Mean fluorescence intensity (MFI) of TREM-1 on leukocytes of newborns appeared comparable to healthy adults [monocytes: 37.5 ± 6.7 vs. 37.6 ± 8.7; polymorphonuclear cells (PMNs): 32.9 ± 6.6 vs. 33.6 ± 5.8]. However, the percentage of PMNs positive for TREM-1 was lower in newborns than in healthy adults (82.3 ± 7.1 vs. 98.6 ± 4.8; P < 0.01); the percentage of TREM-1-positive CD14-positive monocytes was comparable to that of healthy adults (97.1 ± 8.3 vs. 97.5 ± 7.4). Exposure of cord blood to E. coli resulted in increased secretion of IL-6, IL-8, TNF-α, and sTREM-1. In contrast, the concentrations of IL-6, IL-8, and TNF-α decreased by a minimum of 15% when TREM-1 was blocked by LP17 then exposed to E. coli, versus E. coli alone. In addition, the concentration of sTREM-1 was positively correlated with the levels of TNF-α (r = 0.519, P < 0.05), IL-6 (r = 0.507, P < 0.05), and IL-8 (r = 0.538, P < 0.05).

CONCLUSIONS

Healthy newborns exhibit expression of TREM-1 on monocytes similar to that in healthy adults, and most PMNs express TREM-1 at the newborn stage. Detection of sTREM-1 in neonatal peripheral blood should be further investigated as a potential method for the diagnosis of neonatal infection. Finally, blocking the TREM-1 signal transduction pathway may reduce inflammatory responses of neonate leukocytes and thereby provide a new strategy for treatment of neonatal infection.

Diagnostic value of the soluble triggering receptor expressed on myeloid cells-1 in lower respiratory tract infections: a meta-analysis

The soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is a promising diagnostic marker for many types of infections. A bivariate meta-analysis was performed to evaluate its diagnostic value for lower respiratory tract infections (LRTI). We searched PubMed, Cochrane Library and Web of Science (from January 1966 to August 2013) for all trials assessing diagnostic value of sTREM-1 for LRTI. The pooled sensitivity, specificity, positive likelihood ratio(PLR), negative likelihood ratio(NLR), diagnostic odds ratio (DOR), the area under summary receiver operator characteristic (SROC) curve and the Q* were calculated. Thirteen studies with 1138 patients were included in our meta-analysis. The pooled sensitivity and specificity of sTREM-1 for diagnosis of LRTI was 0.84 and 0.77. The PLR, NLR and DOR were 3.6, 0.21 and 17. The area under SROC curve was 0.88 and the Q* was 0.82. The univariate meta-regression analysis demonstrated that the assay method for sTREM-1 significantly affected sensitivity for LRTI. The Q* of sTREM-1 for diagnosis of community-acquired LRTI was 0.82, and the area under SROC curve was 0.88. The Q* of sTREM-1 in diagnosis of hospital-acquired LRTI was 0.83, and the area under SROC curve was 0.90. The Q* of sTREM-1 for distinguishing culture-positive LRTI from culture-negative diseases was 0.79, and the area under SROC curve was 0.86. Current evidence suggests that sTREM-1 is an accurate marker of LRTI. The overall diagnostic value of sTREM-1 for LRTI, community-acquired LRTI and hospital-acquired LRTI is similar.

Triggering receptor expressed on myeloid cells-1 (Trem-1) on blood neutrophils is associated with cytokine inducibility in human E. coli sepsis

Background

Bacterial sepsis induced immunsuppression via antigen hyporesponsibility increases the risk of nosokomial infections and mortality. Pattern recognition receptors (PRR) might have a central role in the pathophysiology of hyporesponsibility.

Methods

In this study we evaluated in a human E. coli sepsis cohort, the role of PRR including TLR’s and Trem-1. Expression of Trem-1, TLR2, TLR4, CD14 and HLA-DR on blood monozytes and neutrophils were examined using flow cytometry from 22 patients with E. coli sepsis and 6 healthy controls. LPS and LTA stimulated TNF alpha, IL-10, IL-8 and IL-6 production was studied in a 24 h whole blood assay. Free cytokine serum concentration of TNF alpha, PCT and IP-10 were evaluated.

Results

We found a significant higher expression of Trem-1 and TLR-2 on monocytes and neutrophils in patients compared to healthy volunteers. TLR2 expression (p < 0.05) was higher and HLA-DR lower (p < 0.05) on monocytes of patients with severe sepsis compared to patients with simple sepsis. Trem-1 expression was tendentially higher (p = 0,07) on monocytes and lower on neutrophils of patients with severe sepsis. Trem-1 expression on neutrophils was associated with the IL-10 (LPS: r = 0,61, p < 0.02) and TNF-α inducibility (LPS: r = 0,78, p < 0,002). In addition Trem-1 expression on neutrophils shows a negative correlation to the serum levels of TNF alpha (r = −0,63; p < 0,005), IP-10 (r = −0,5; p < 0,035) and procalcitonin (r = −0,59; p < 0,007).

Conclusions

Patients with E. coli sepsis are characterized by an association of Trem-1 expression on blood neutrophils with cytokine inducibility. The TREM-1 pathway on neutrophils might play a role in producing an adequate inflammatory and bactericidal response in bacterial sepsis.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4441869398748313