Expression Of Triggering Receptor Expressed On Myeloid Cells-1 mRNA Research Articles

Value of Triggering Receptor Expressed on Myeloid Cells-1 (TREM-1) as a Diagnostic Marker for Neonatal Sepsis

Introduction: Neonatal Sepsis (NS) is a serious clinical condition caused by a dysregulated immune response to an infection. Neonatal period is the most vulnerable time in the child’s life. Globally, approximately 7000 newborns die everyday. Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) is an important receptor for the inflammatory response regulated by neutrophils. Aim: To explore the role of TREM-1 as a potential early diagnostic marker of NS compared to the conventional blood culture technique. The prognostic utility and relation of TREM-1 expression level to the clinical disease severity in septic neonates were also evaluated. Materials and Methods: The study enrolled 75 neonates with NS admitted to the Neonatal Intensive Care Unit (NICU). The studied neonates were categorised into three groups; group I: 25 neonates with an Early Onset Sepsis (EOS), group II: 25 neonates with a Late Onset Sepsis (LOS), group III: 25 neonates with septic shock. In addition, 25 age and sex-matched healthy neonates with no evidence of sepsis or any other medical illness were studied as a control group. Blood samples for conventional blood cultures and estimation of TREM-1 gene expression level in Polymorph Nuclear Neutrophils (PMNs) using quantitative Real-Time Polymerase Chain Reaction (RT-PCR) assay were synchronously collected. Data regarding clinical and laboratory findings, and risk factors of NS were also analysed. Statistical Package for the Social Sciences (SPSS) software version 20 was used to analyse the data obtained from the study. Results: The total culture-proven cases represented 24% (18/75) of all the studied neonates with NS. Klebsiella spp. was the most frequently isolated Gram-negative bacteria (4/18; 22.2%) followed by Pseudomonas spp. (3/18; 16.7%) and Acinetobacter spp. (1/18; 5.5%). Coagulase- Negative Staphylococci (CoNs), S. aureus and Candida spp. accounted for 22.2% (4/18), 16.7% (3/18) and 16.7% (3/18) of the isolated organisms respectively. No statistically significant difference was detected between the three studied groups as regards blood culture results. Significant statistical differences were detected between groups I, II and III in relation to the control group (p=0.048, p=0.049 and p<0.001) regarding TREM-1 mRNA expression level. Low Birth Weight (LBW) and prematurity were the most significant risk factors for NS. At a cut-off point of ≥0.631 TREM-1 mRNA could be considered as a potential marker for diagnosis of NS with sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) of 65.33%, 96.0%, 98.0% and 48.0%, respectively. The prognostic utility of TREM-1 gene expression proved a sensitivity of 87.8% at a cut-off point >0.369. Conclusion: TREM-1 gene expression has a potential value in prognostic assessment of NS and could be considered as an early diagnostic marker.

Activation of TREM1 Signaling in Kupffer Cells Following HIV and HCV Stimulation Augments Hepatic Inflammatory Responses

Abstract In this study, we sought to examine inflammatory responses following HIV or HCV stimulation of macrophages or Kupffer cells (KCs), that may contribute to virus mediated inflammation and subsequent liver disease. KCs are liver-resident macrophages and reports have provided evidence that HIV can stimulate and infect them. In order to characterize HIV-intrinsic innate immune responses that may occur in the liver, we performed microarray analyses on KCs following HIV stimulation. Our data demonstrate that KCs upregulate several innate immune signaling pathways involved in inflammation, myeloid cell maturation, stellate cell activation, and Triggering Receptor Expressed on Myeloid cells 1 (TREM1) signaling. TREM1 is a member of the immunoglobulin superfamily of receptors and it is reported to be involved in systemic inflammatory responses due to its ability to amplify activation of host defense signaling pathways. Our data demonstrate that stimulation of KCs with HIV or HCV induces the upregulation of TREM1. Additionally, HIV viral proteins can upregulate expression of TREM1 mRNA through NF-κB signaling. Furthermore, activation of the TREM1 signaling pathway, with a targeted agonist, increased HIV or HCV-mediated inflammatory responses in macrophages due to enhanced activation of the ERK1/2 signaling cascade. Silencing TREM1 dampened inflammatory immune responses elicited by HIV or HCV stimulation. Finally, HIV and HCV infected patients exhibit higher expression and frequency of TREM1 and CD68 positive cells. Taken together, TREM1 induction by HIV contributes to chronic inflammation in the liver and targeting TREM1 signaling may be a therapeutic option to minimize HIV induced chronic inflammation.

HIV and HCV augments inflammatory responses through increased TREM-1 expression and signaling in Kupffer and Myeloid cells.

Chronic infection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) affects an estimated 35 million and 75 million individuals worldwide, respectively. These viruses induce persistent inflammation which often drives the development or progression of organ-specific diseases and even cancer including Hepatocellular Carcinoma (HCC). In this study, we sought to examine inflammatory responses following HIV or HCV stimulation of macrophages or Kupffer cells (KCs), that may contribute to virus mediated inflammation and subsequent liver disease. KCs are liver-resident macrophages and reports have provided evidence that HIV can stimulate and infect them. In order to characterize HIV-intrinsic innate immune responses that may occur in the liver, we performed microarray analyses on KCs following HIV stimulation. Our data demonstrate that KCs upregulate several innate immune signaling pathways involved in inflammation, myeloid cell maturation, stellate cell activation, and Triggering Receptor Expressed on Myeloid cells 1 (TREM1) signaling. TREM1 is a member of the immunoglobulin superfamily of receptors and it is reported to be involved in systemic inflammatory responses due to its ability to amplify activation of host defense signaling pathways. Our data demonstrate that stimulation of KCs with HIV or HCV induces the upregulation of TREM1. Additionally, HIV viral proteins can upregulate expression of TREM1 mRNA through NF-кB signaling. Furthermore, activation of the TREM1 signaling pathway, with a targeted agonist, increased HIV or HCV-mediated inflammatory responses in macrophages due to enhanced activation of the ERK1/2 signaling cascade. Silencing TREM1 dampened inflammatory immune responses elicited by HIV or HCV stimulation. Finally, HIV and HCV infected patients exhibit higher expression and frequency of TREM1 and CD68 positive cells. Taken together, TREM1 induction by HIV contributes to chronic inflammation in the liver and targeting TREM1 signaling may be a therapeutic option to minimize HIV induced chronic inflammation.

TGF-β1 Upregulates the Expression of Triggering Receptor Expressed on Myeloid Cells 1 in Murine Lungs.

Triggering receptor expressed on myeloid cells 1 (TREM-1) increases the expression of TGF-β family genes, which are known as profibrogenic cytokines in the pathogenesis of pulmonary fibrosis. In this study, we determined whether TGF-β1 regulated the expression of TREM-1 in a mouse model of pulmonary fibrosis. The expression of TGF-β1 and TREM-1 was increased on day 7, 14, and 21 after single intratracheal injection of bleomycin (BLM). And there was positive correlation between the expression of TGF-β1 and TREM-1. TGF-β1 increased expression of TREM-1 mRNA and protein in a time- and dose-dependent manner in mouse macrophages. The expression of the activator protein 1 (AP-1) was increased in lung tissues from mouse after BLM injection and in mouse macrophages after TGF-β1 treatment, respectively. TGF-β1 significantly increased the relative activity of luciferase in the cells transfected with plasmid contenting wild type-promoter of TREM-1. But TGF-β1 had no effect on the activity of luciferase in the cells transfected with a mutant-TREM1 plasmid carrying mutations in the AP-1 promoter binding site. In conclusion, we found the expression of TREM-1 was increased in lung tissues from mice with pulmonary fibrosis. TGF-β1 increased the expression of TREM-1 in mouse macrophages partly via the transcription factor AP-1.

Evaluation of the lipopolysaccharide-induced transcription of the human TREM-1 gene in vitamin D3-matured THP-1 macrophage-like cells

Triggering receptor expressed on myeloid cells-1 (TREM-1) plays a role in inflammation by augmenting inflammatory responses through the production of pro-inflammatory cytokines. TREM-1 is expressed in mature macrophages, and is upregulated by stimulation with bacterial components, such as lipopolysaccharide (LPS). In the present study, the regulatory mechanisms responsible for the transcription of the human TREM-1 gene were examined using a human monocytic cell line (THP-1 cells). Reverse transcription-polymerase chain reaction (RT-PCR) revealed that TREM-1 mRNA was constitutively expressed at a low level in resting cells, and that its expression was upregulated by treatment with vitamin D3 (VitD3), but not by LPS. Importantly, TREM-1 mRNA expression was further upregulated by stimulation of the VitD3‑treated THP-1 cells with LPS. In addition, a luciferase reporter assay revealed that the serum response element (SRE) was involved in VitD3-induced promoter activity, whereas the activator protein-1 (AP-1) sites participated in the VitD3- and LPS-induced promoter activity. Of note, the CCAAT-enhancer-binding protein (C/EBP) site contributed not only to basal, but also to VitD3- and LPS-induced promoter activity. Transfection with transcription factor oligodeoxynucleotide (ODN) decoys indicated that transcription factors of the C/EBP and AP-1 families are likely involved in the basal, as well as in the VitD3- and LPS-induced TREM-1 transcription. Western blot analysis indicated that, of the members of the C/EBP family, C/EBPα was constitutively expressed in resting cells; its expression was enhanced by treatment with VitD3 and was further increased by treatment with VitD3 and LPS. Moreover, the expression of c-Fos and c-Jun (members of the AP-1 family) was augmented by treatment with both VitD3 and LPS. These observations indicate that members of the C/EBP family participate not only in basal, but also in the VitD3- and LPS-induced promoter activity of the human TREM-1 gene, and that members of the AP-1 family are involved in the VitD3- and LPS-induced promoter activity.

Significance of triggering receptor expressed on myeloid cells-1 of cord blood leukocytes in neonates

Objective To investigate the triggering receptor expressed on myeloid cells-1(TREM-1) of cord blood leukocytes in neonates and the transcription level of mRNA, and analyze its promoting function of inflammatory cytokine secretion. Methods During the period from September 2013 to March 2014, cord blood was collected from 20 term neonates at the time of birth, and peripheral blood was collected from 20 healthy adults. The expression of TREM-1 and TREM-1 mRNA on leukocytes was observed using flow cytometry and real-time reverse transeription-polymerase chain reaction, respectively. After the whole cord blood was stimulated by lipopolysaccharide (LPS) or LP17 plus LPS, the contents of interleukin (IL)-6, tumor necrosis factor-α (TNF-α), IL-8 and soluble TREM-1 (sTREM-1) in the supernatant were analyzed by enzyme linked immunosorbent assay. The statistical significance was determined using the one-way ANOVA test, t test, q test and Pearson correlation coefficient. Results The mean fluorescence intensity of TREM-1 on leukocytes of newborns was not different compared with healthy adults (P>0.05), while the percentage of TREM-1 positive on polymorphonuclear cells was lower than that of healthy adults [(82.3±7.1)% vs (98.6±4.8)%, P<0.05]. The level of TREM-1 mRNA in newborns was lower than in healthy adults (1.16±0.13 vs 1.63±0.24, t=7.714, P<0.01). The LPS treatment significantly increased sTREM-1 in newborn whole blood compared with the control treatment [(156.7±36.3) vs (34.6±6.1) pg/ml, t=13.623, P<0.01]. The concentration of IL-6, TNF-α and IL-8 decreased significantly when TREM-1 was blocked by LP17. In addition, the concentration of sTREM-1 showed a positive correlation 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 healthy adults, and most PMNs express TREM-1 at the newborn stage. Blocking the TREM-1 signal transduction pathway may reduce inflammatory responses of neonate leukocytes. Key words: Receptors, immunologic; Leukocytes; Fetal blood; Sepsis; Infant, newborn

Expression and regulation of triggering receptor expressed on myeloid cells 1 in periodontal diseases.

Periodontitis is an inflammatory infectious disease that destroys the tooth-supporting tissues. It is caused by multi-species subgingival biofilms that colonize the tooth surface. Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia (i.e. 'red complex' bacteria) are characteristic subgingival biofilm species. The triggering receptor expressed on myeloid cells 1 (TREM-1) is a cell surface receptor of the immunoglobulin superfamily, with a role in the amplification of proinflammatory cytokine production during infection. This study aimed to investigate TREM-1 mRNA expression in gingival tissues from patients with chronic periodontitis, generalized aggressive periodontitis and healthy subjects and its correlation with the levels of periodontal pathogens in the tissue. A further aim was to investigate the regulation of TREM-1 in human monocytic cells (MM6) challenged with an in-vitro subgingival biofilm model. Gingival tissue TREM-1 expression was increased in both chronic and aggressive periodontitis, compared to health, and correlated with the levels of the 'red complex' species in the tissue. No significant differences were detected between the two forms of periodontitis. Biofilm-challenged MM6 cells exhibited higher TREM-1 expression and secretion compared to controls, with partial involvement of the 'red complex'. Engagement or inhibition of TREM-1 affected the capacity of the biofilms to stimulate interleukin (IL)-1β, but not IL-8, secretion by the cells. In conclusion, this study reveals that TREM-1 tissue expression is enhanced in periodontal disease, and correlates with the level of periodontal pathogens. It also provides a mechanistic insight into the regulation of TREM-1 expression and the associated IL-1β production in biofilm-challenged monocytes.

Regulation of TREM-1 expression by 1,25-dihydroxyvitamin D3 in human monocytes/macrophages

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a recently identified cell surface receptor that is expressed mainly on monocytes and neutrophils, and acts as an amplifier of immune responses. In this study, 1,25(OH)2D3 strongly upregulated the expression of TREM-1 in human monocytes and macrophages. 1,25(OH)2D3 stimulated TREM-1 mRNA expression by augmenting transcription, and not by inhibiting mRNA degradation. The upregulated expression of TREM-1 by 1,25(OH)2D3 was dependent on the NF-κB signaling pathway and required new protein synthesis in differentiated U937 macrophages. Our results show that 1,25(OH)2D3 can affect the innate and inflammatory responses by upregulating TREM-1 expression, and suggest that 1,25(OH)2D3 may function as an enhancer of the innate immune response by upregulating TREM-1 expression, in addition to inducing the antimicrobial peptide cathelicidin.

TREM-1 is a positive regulator of TNF-α and IL-8 production in U937 foam cells

The purpose of our study was to investigate the expression levels of TREM-1 (triggering receptor expressed on myeloid cells-1) in U937 foam cells and determine whether TREM-1 regulates the production of tumor necrosis factor-alpha and interleukin-8 in these cells. Human U937 cells were incubated with phorbol 12-myristate 13-acetate and then oxidized human low-density lipoprotein to induce foam cell formation. Oil red O staining was used to identify the foam cells. The production of IL-8 and TNF-α by U937 foam cells was assayed by enzyme-linked immunosorbent assay. The expression of TREM-1 mRNA in U937 foam cells was detected by reverse transcription-polymerase chain reaction. Moreover, U937 foam cells were transfected by small interfering RNA using Lipofectamine 2000 to knockdown TREM-1. Western blot was performed to assay protein expression of TREM-1 and ELISA was used to examine the effect of TREM-1 knockdown on IL-8 and TNF-α production. PMA and ox-LDL induced U937 cells to form foam cells. The production of TNF-α and IL-8 was found to be significantly elevated in U937 foam cells, concomitant with a significant up-regulation of TREM-1 mRNA. TREM-1 siRNA was able to partially silence the expression of TREM-1 protein and remarkably inhibited TNF-α and IL-8 production in U937 foam cells, suggesting that TREM-1 is a positive regulator of TNF-α and IL-8 production in U937 foam cells. Our finding that TREM-1 controls the production of IL-8 and TNF-α in U937 foam cells defines a potentially critical role of TREM-1 in the pathogenesis of atherosclerosis and implicates TREM-1 as a potential therapeutic target for the disease.

The diagnosis value of triggering receptor expressed on myeloid cells-1 in early liver damage of severe acute pancreatitis with secondary infection

Objective To explore the diagnosis value and the mechanism of triggering receptor expressed on myeloid cells-1 (TREM-1) in early liver damage of severe acute pancreatitis with secondary infection. Methods Twenty-four male SD rats were randomly divided into the control group, the severe acute pancreatitis (SAP) group and the secondary infection of SAP (SISAP) group.The animal model was established by intraperitoneal injection of L- arginine and E. coli. After 24 hours, the serum levels of amylase, glutamate aminotransferase (ALT), aspartate aminotransferase (AST), tumor necrosis factor (TNF)-α, C-reactive protein (CRP) and the variation of TREM-1 expression were tested. The blood and peritoneal fluid samples were collected for bacterial culture.Part of the pancreas and liver tissue were taken for histopathological score under microscope. The expression of TREM-1 at mRNA and protein level in liver tissue was detected through Real-time PCR and Western Blot. Results The histological score of pancreas and liver, serum amylase, ALT and AST were significantly higher in the SAP and SISAP groups than those in C group (P<0. 05), and higher in SISAP group than in SAP group (P<0. 05). The CRP and TNF-a expression in SAP and SISAP groups were higher then those in control group, while there was no significant difference between the two groups (P=0. 262 and 0. 359 , respectively). The positive ratio of bacterial culture in blood and peritoneal fluid was 0(0/8), 12. 5% (1/8), and 100% (8/8) in control group, SAP group and SISAP group respectively. The expression of TREM-lmRNA in liver was 2. 10 ± 0. 33 in SAP group and 4. 58+ 1. 00 in SISAP group, which were significantly higher than that in control group (1. 00,P<0. 05) , and the expression of TREM-1 mRNA in SISAP group was higher than that in SAP group (P < 0.05). The expression of TREM-1 at protein level was higher in SISAP group,significantly stronger than that in control and SAP group. Conclusions TREM-1 may play an important role in the early liver damage caused by severe acute pancreatitis. Key words: Pancreatitis, acute; Bacterial infections; Receptors, immunologic; Membranceglycoproteins; Liver diseases

Effect of calcitonin gene-related peptide on the expression of triggering receptor expressed on myeloid cells-1 in lipopolysaccharide-induced macrophages.

To determine the effect of calcitonin gene-related peptide (CGRP) on triggering receptor expressed on myeloid cells-1 (TREM-1) in the lipopolysaccharide (LPS)-induced macrophages and its signal transduction pathway. The levels of TREM-1 mRNA in the macrophages were observed by reverse transcription-polymerase chain reaction (RT-PCR), and flow cytometry was performed to detect TREM-1 protein expression levels in the macrophages. CGRP had no regulating effect on the expression of TREM-1 in the macrophages; LPS could up-regulate macrophages to express TREM-1; CGRP increased TREM-1 mRNA expression in LPS-induced macrophages in dose and time-dependent manner; CGRP increased TREM-1 protein expression in LPS-induced macrophages, which could be partially reversed by H-7 or H-89 (P<0.05). CGRP can regulate the LPS-induced macrophages synthesis and secretion of TREM-1, and the intracellular signal transduction pathway is related to PKA and PKC.

TREM-1 expression is increased in the synovium of rheumatoid arthritis patients and induces the expression of pro-inflammatory cytokines

To investigate the expression and function of triggering receptor expressed on myeloid cells-1 (TREM-1) in the synovium of human RA patients as well as the level of soluble TREM-1 in the plasma of RA patients. Twenty-four RA synovial samples were analysed by gene expression oligonucleotide microarrays. Expression levels of TREM-1 mRNA in murine CIA paws were determined by quantitative PCR (qPCR). TREM-1 protein expression was detected by immunohistochemistry in five RA synovial samples and two OA synovial samples. TREM-1-positive cells from five RA synovial tissues were analysed by FACS staining to determine the cell type. Activation of TREM-1 was tested in five RA synovial samples. Soluble TREM-1 was measured in serum from 32 RA patients. The expression of TREM-1 mRNA was found to increase 6.5-fold in RA synovial samples, whereas it was increased 132-fold in CIA paws. Increased numbers of TREM-1-positive cells were seen in RA synovium sections and these cells co-expressed CD14. Using a TREM-1-activating cross-linking antibody in RA synovial cultures, multiple pro-inflammatory cytokines were induced. The average amount of soluble TREM-1 in plasma from RA patients was found to be higher than that in plasma from healthy volunteers. These findings suggest that the presence of high levels of functionally active TREM-1 in RA synovium may contribute to the development or maintenance of RA, or both. Inhibiting TREM-1 activity may, therefore, have a therapeutic effect on RA. High levels of soluble TREM-1 in the plasma of RA patients compared with healthy volunteers may indicate disease activity.

Functional genomics of silencing TREM-1 on TLR4 signaling in macrophages

Triggering receptor expressed on myeloid cells 1 (TREM-1) is a recently discovered molecule that is expressed on the cell surface of monocytes and neutrophils. Engagement of TREM-1 triggers synthesis of proinflammatory cytokines in response to microbes, but the extent and mechanism by which TREM-1 modulates the inflammatory response is poorly defined. In the present study, we investigated the functional effects of blocking TREM-1 on the Toll-like receptor (TLR)4-mediated signaling pathway in macrophages. By transfecting cells with small hairpin interfering RNA molecules to TREM-1 (shRNA), we confirmed that TREM-1 mRNA and protein expression was greatly attenuated in RAW cells in response to treatment with LPS. PCR array for genes related to or activated by the TLR pathway revealed that although the expression of TLR4 itself was not significantly altered by silencing of TREM-1, expression of several genes, including MyD88, CD14, IkappaBalpha, IL-1beta, MCP-1, and IL-10 was significantly attenuated in the TREM-1 knockdown cells in response to treatment with LPS. These data indicate that expression of TREM-1 modulates the TLR signaling in macrophages by altering the expression of both adaptor and effector proteins that are critical to the endotoxin response.