TREM-like Transcript-1 Research Articles

Interrogating a Compound Library in Search of an Inhibitor for TREM-like Transcript-1 to Fibrinogen Binding.

Cardiovascular disease (CVD) remains one of leading causes of death worldwide. Aberrant platelet function mediate fibrin(ogen) rich thrombi that lead to occlusive thrombi associated with mortality. The receptor, TREM-like transcript-1 (TLT-1), stored in the platelet a-granules and released upon platelet activation, binds fibrinogen and von Willebrand factor. Once it is released from platelets TLT-1 is a potential therapeutic target to prevent the thrombosis associated with CVD. Here we design an assay to screen a compound library of small molecules inhibitors. HEK-293 cells stably transfected with a full length human treml-1 construct were used to screen library of 800 compounds, for inhibition of TLT-1 to fibrinogen binding in an attachment assay using crystal violet staining. The possible cytotoxicity of the best compounds was determined via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide MTT and calcein AM staining assays. Here we demonstrate that the addition of TLT-1 to HEK-293 cells increases cell adhesion by more than 2-fold. We identified ~80 compounds that inhibit binding by more than 80%. We further tested the top compounds and confirmed that reduction of hTLT-1 to fibrinogen bound in the top compounds was not caused by cytotoxicity, as per colorimetric and fluorescent viability assays. Four compounds were identified as potential small molecule inhibitors one of which, BM-8372, demonstrated significant effect in platelet aggregation assays. Significance Statement TLT-1 is a key platelet receptor that binds fibrinogen and mediates clot formation The developed assay successfully screens 800 small molecules, pinpointing ~80 potent inhibitors that reduce TLT-1 binding by over 80%. Importantly, the study rigorously rules out cytotoxicity concerns, affirming the therapeutic potential of the identified compounds. By elucidating TLT-1's role and presenting promising inhibitors, this research offers a significant stride toward developing novel strategies to combat CVD-related thrombosis.

Identification of Novel Ways Disrupting Platelet-Fibrinogen Interactions

Background: Platelets play a central role in thrombosis and hemostasis and immunity through their interaction with fibrinogen. Fibrinogen is a plasma protein that facilitates thrombosis and inflammation. Fibrinogen is the ligand for the major platelet receptor aIIbb3 and TREM- Like Transcript-1 (TLT-1), which platelets release from their a-granules, upon platelet activation. TLT-1 binding fibrinogen was surprising since αIIbβ3, the most abundant platelet receptor, binds fibrinogen, facilitating platelet aggregation. Although TLT-1 may assist in clot formation and hemostasis with αIIbβ3, TLT-1's main association is with regulating inflammatory-derived bleeding. Little is known about the TLT-1-fibrinogen interaction. The goal of this study is to identify the binding sites for this interaction and determine whether it can regulate inflammatory hemostasis in an LPS inflammatory mouse model. Aims: Delineate the TLT-1-fibrinogen binding site and determine if, peptides representing the molecular interaction affect platelet function. Methods: Using an Octet Qke Bio-layer Interferometry (BLI), we confirmed a binding interaction between TLT-1 and fibrinogen. Subsequently we digested fibrinogen using either trypsin or chymotrypsin and immunoprecipitated the peptides with a TLT-1-fc chimera followed by -Mass Spectrometry (LC-MS/MS) to identify potential interacting peptides. As an alternative method, we used a peptide microarray, where fluorescently labeled TLT-1 was incubated with 8-mers of α, β, γ chain fibrinogen peptides attached to a chip to determine which peptides bound TLT-1. Additionally, competitive ELISAs using peptides representing the TLT-1 extracellular domain loops (CDR-1, CDR2, CDR3 and LP17) were incubated with soluble TLT-1 in fibrinogen coated wells to determine the region of TLT-1 responsible for binding fibrinogen. To determine whether any of the selected peptides had inhibitory activity, we used two in vitro competitive inhibitory assays, first, we quantified FITC-labelled fibrinogen binding to activated human platelets and second, human platelet aggregometry incubated in the presence of these peptides at different concentrations (varying from 4-40 μM) using different agonists (ADP, thrombin, collagen, thromboxane A2). Results: We obtained an equilibrium dissociation constant (KD) of 3.02 ± 0.20 nM for the TLT-1 Fibrinogen interaction, suggesting a high affinity interaction. We identified four peptides that had consistent interaction without nonspecific binding in all three trials (trypsin and chymotrypsin IP, as well as the peptide microarray). The competitive platelet aggregometry and flow cytometry assays show decreased aggregation and significantly decreased fluorescent intensity of FITC-labelled fibrinogen in the presence of these peptides, suggesting two of these peptides are our potential binding sites (decrease of FITC-fluorescence intensity when compared to control: p1=20% decrease, p2=44% decrease, p3=21% decrease and P4=39% decrease, p=0.023). A HEK-293 transfected cell line expressing TLT-1 YFP is currently being used to access the ability of the identified peptides to mediate adhesion. In competitive ELISAs, TLT-1 loops LP17 and CDR3 show decreased absorbance when TLT-1 is incubated with fibrinogen in the presence of these peptides. Conclusions: Our TLT-1 data suggests that fibrinogen interacts with TLT-1 in the CD3 loop and in the region designated as LP17. With the aggregometry and flowcytometry competitive assays we have identified p2 as our most promising candidate for the TLT-1 interaction sight on fibrinogen. Currently we are adding the isolated peptides to our HEK/TLT-1 binding assay to determine if our selected peptide yields the same level of inhibition as seen in our aggregation and flow cytometric assays. We will then use an inflammatory in vivo mouse model to determine the effects of administering the selected peptide on platelet neutrophil conjugate formation and mortality. Our poster will report the current state of these studies .

PB0909 TREM-Like Transcript-1, a Platelet Receptor, as a Potential Regulator of Hepatic Regeneration Post-Surgical Resection

PB0909 TREM-Like Transcript-1, a Platelet Receptor, as a Potential Regulator of Hepatic Regeneration Post-Surgical Resection

Decreased level of TREM like Transcript 1 (TLT-1) is associated with prematurity and promotes the in-utero inflammatory response to maternal lipopolysaccharide (LPS) exposure.

The occurrence of preterm birth is associated with multiple factors including bleeding, infection and inflammation. Platelets are mediators of hemostasis and can modulate inflammation through interactions with leukocytes. TREM like Transcript 1 (TLT-1) is a type 1 single Ig domain receptor on activated platelets. In adults, it plays a protective role by dampening the inflammatory response and facilitating platelet aggregation at sites of vascular injury. TLT-1 is expressed in human placenta and found in cord blood. We thus hypothesized that TLT-1 deficiency is associated with prematurity and fetal inflammation. To test this hypothesis, we examined cord blood levels of soluble TLT-1 (sTLT) in premature and term infants and compared the inflammatory response in C57BL/6 (WT) and TLT-1-/- (treml1-/- , KO) mice given intraperitoneal LPS mid-gestation RESULTS: The preterm infant cord blood level of sTLT was significantly lower than that found at term. On exposure to LPS, histology of KO (as compared to WT) placenta and decidua showed increased hemorrhage, and KO decidual RNA expression of IL-10 was significantly lower. KO fetal interface tissues (placenta, membranes, amniotic fluid) over time showed increased expression of inflammatory cytokines such as IL-6, IFN-γ,and TNF, but not MCP-1. However, fetal organs showed similar levels. There is a potential association between insufficient TLT-1 expression and increased fetal inflammatory responses in the setting of prematurity. The data support further study of TLT-1 in the mechanistic link between bleeding, inflammation and preterm birth, and perhaps as a biomarker in human pregnancy.

Soluble TREM-like Transcript-1 Acts as a Damage-Associated Molecular Pattern through the TLR4/MD2 Pathway Contributing to Immune Dysregulation during Sepsis.

Studies have shown that elevated plasma levels of platelet-derived soluble TREM-like transcript-1 (sTLT-1) are associated with an unfavorable outcome in patients with septic shock. However, the underlying molecular mechanisms are not well defined. This research aimed to study the role of sTLT-1 in mediating immune dysfunction during the development of sepsis. Our study demonstrated that patients with septic shock have significantly higher plasma concentrations of sTLT-1, whereas sTLT-1 is not detectable in healthy subjects. Plasma concentrations of sTLT-1 were correlated with the degree of immunosuppressive parameters in monocytes from patients with septic shock. sTLT-1 can first activate monocytes by binding to the TLR4/MD2 complex but subsequently induce immunosuppressive phenotypes in monocytes. Blocking Abs against TLR4 and MD2 led to a significant decrease in sTLT-1-induced activation. Treatment with an anti-TLT-1 Ab also significantly reduces sTLT-1 binding to monocytes and proinflammatory cytokine secretion in a mouse model of endotoxemia. sTLT-1 acts as an endogenous damage-associated molecular pattern molecule, triggering the activation of monocytes through the TLR4/MD2 complex followed by sustained immune suppression. This process plays a crucial role in the development of sepsis-associated pathophysiology. Our findings outline, to our knowledge, a novel pathway whereby platelets counteract immune dynamics against infection through sTLT-1.

Platelet-derived TLT-1 promotes tumor progression by suppressing CD8+ T cells.

Current understanding of tumor immunosuppressive mechanisms forms the basis for modern day immunotherapies. Immunoregulatory role of platelets in cancer remains largely elusive. Platelets from non-small cell lung cancer (NSCLC) patients revealed a distinct activation phenotype. TREM-like transcript 1 (TLT-1), a platelet protein, was increased along with enhanced extracellular release from NSCLC platelets. The increased platelet TLT-1 was also evident in humanized mice with patient-derived tumors. In immunocompetent mice with syngeneic tumors, TLT-1 binding to T cells, in vivo, led to suppression of CD8 T cells, promoting tumor growth. We identified direct interaction between TLT-1 and CD3ε on T cells, implicating the NF-κB pathway in CD8 T cell suppression. Anti-TLT-1 antibody rescued patients' T cells from platelet-induced suppression ex vivo and reduced tumors in mice in vivo. Clinically, higher TLT-1 correlated with reduced survival of NSCLC patients. Our findings thus identify TLT-1 as a platelet-derived immunosuppressor that suppresses CD8 T cells and demonstrate its therapeutic and prognostic significance in cancer.

Triggering receptor expressed on myeloid cells (TREM) like transcript-1 (TLT-1) reveals platelet activation in preeclampsia

Triggering receptor expressed on myeloid cells (TREM) like transcript-1 (TLT-1) is a membrane protein receptor found in α-granules of megakaryocytes and platelets. Upon platelet activation TLT-1 is rapidly relocated to the surface of platelets. In plasma, a soluble form of TLT-1 (sTLT-1) is present. Plasma levels of sTLT-1 are significantly elevated in thrombotic diseases. In the present study, we investigated to whether TLT-1 reflects platelet activation in pregnant women with preeclampsia. We studied 30 preeclamptic patients who were matched with 30 normotensive pregnant women and 30 non-pregnant controls. Basal TLT-1, P-selectin, and CD63 expressions on platelets were analyzed with the use of flow-cytometry (FCM). Platelet reactivity was induced by thrombin receptor activation peptide and determined by FCM. Plasma concentrations of sTLT-1 and soluble P-selectin (sP-selectin) were measured by an enzyme-linked immunosorbent assay. Results show that basal platelet expression of TLT-1, P-selectin and CD63 were increased in women with preeclampsia (PE) compared with normotensive pregnant women (NP). Platelets from PE women and NP women were more responsive compared to from nonpregnant women controls (NC), and which was demonstrated by increased expression of TLT-1, P-selectin, and CD63 upon stimulation in vitro. Plasma concentration of sTLT-1 was greater in PE women compared to NP women and NC women. Plasma sP-selectin level was higher in pregnant women than in nonpregnant women, but there were no significant differences between PE and NP women. In summary, our results revealed that platelet activation is prominent in preeclampsia, TLT-1 reflects platelet activation and may be a useful indicator for preeclampsia.

Deciphering the TLT-1 Fibrinogen Ligand Interaction

Background:Platelets, derived from megakaryocytes primarily play a central role in thrombosis and hemostasis, however, they extend beyond this role as immune cells that initiate and accelerate various vascular inflammatory conditions. Upon activation, platelets release TREM-Like Transcript-1 (TLT-1) from their a-granules onto their surface. Early studies by amino link columns preloaded with soluble TLT-1 followed by mass spectrometry and immunoblotting identified fibrinogen as a ligand for TLT-1. Fibrinogen is a plasma protein that is essential for clot formation, during inflammation and hypercoagulable states tissue deposition and plasma concentration of fibrinogen are increased, demonstrating a role of fibrinogen in both thrombosis and inflammation.TLT-1 binding fibrinogen was a surprising discovery since αIIbβ3, the most abundant platelet receptor, also binds fibrinogen and facilitates platelet aggregation. It is difficult to understand why there are two platelet specific receptors that have the same ligand, drawing us to question what the difference in function between the two is? Our studies suggest that although TLT-1 may assist in clot formation and hemostasis to arrest bleeding in a non-inflammatory setting like αIIbβ3, TLT-1's main association is with regulating inflammatory-derived bleeding. Very little is known about the TLT-1-Fibrinogen interaction, further studies would set the stage for a better understanding as to why two fibrinogen ligands exist on platelets and potentially outline a novel platelet therapeutic target during hypercoagulable and/or hyperinflammatory states. We set out to determine the binding affinity and localize the binding sites for the TLT-1 fibrinogen molecular interaction.Aims:Delineate the TLT-1 fibrinogen molecular interaction and elucidate the mechanism by which this interaction drives inflammation and thrombosis-hemostasis.Methods:To confirm the TLT-1 fibrinogen ligand interaction we carried out a kinetics assay using an Octet Qk e Bio-layer Interferometry (BLI) that measures biomolecular complex formation in real time. The TLT-1 Chimera was captured onto an Anti-Human Fc Capture (AHC) Biosensor, washed in kinetics buffer to limit nonspecific binding and submerged in a 96 well plate containing varying concentrations of Fibrinogen. To localize the exact binding sites for this molecular interaction, we digested fibrinogen using trypsin and carried out an immunoprecipitation (IP) followed by Liquid Chromatography-Mass Spectrometry (LC-MS/MS).Results:The curve (Figure 1) shows that the TLT-1 fibrinogen interaction has increasing bimolecular complex formation with increases in concentration of Fibrinogen (15.625nM - 250nM), with a concentration of 250nM showing the best bicomplex formation. In the control well with HIV01 4E10 capture, reference and sensor well, no bicomplex formation is shown, highlighting the specificity of the TLT-1 fibrinogen interaction. The curve illustrates a strong association with no dissociation, suggesting a strong interaction between the proteins. We isolated and identified four potential peptides (Alpha chain: GGSTSYGTGSETESPR, GSESGIFTNTK, Beta chain: QDGSVDFGR , QGFGNVATNTDGK) that bind TLT-1. We are currently performing BLI Competitive kinetics assays using biotinylated constructs of the peptides isolated from the Immunoprecipitation/ LC-MS/MS. The BLI competitive assays using the four peptides are suggestive of an interaction between TLT-1 and the four peptides as illustrated by increasing bimolecular complex formation with increasing concentration of soluble TLT-1 for all four peptides(data not shown).Conclusions:We obtained an equilibrium dissociation constant (KD) of 3.02 ± 0.20 nM for the TLT-1 fibrinogen interaction, suggesting a high affinity interaction between TLT-1 and fibrinogen. In our preliminary results from the BLI Competitive kinetics assays we obtained KD values within the nanomolar concentration range and are currently conducting experiments to optimize conditions to obtain our final bicomplex binding curve and KD values. We are currently assessing the identified peptides for potential of mediating the molecular interaction between TLT-1 and fibrinogen. Our poster will report the current state of these studies . [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Low-soluble TREM-like transcript-1 levels early after severe burn reflect increased coagulation disorders and predict 30-day mortality

BackgroundPatients with severe burns often show systemic coagulation changes in the early stage and even develop extensive coagulopathy. Previous studies have confirmed that soluble TREM-like transcript-1 (sTLT-1) mediates a novel mechanism of haemostasis and thrombosis in inflammatory vascular injury. At present, the role of sTLT-1 in patients with severe burns is not well known. ObjectiveTo investigate the early association between sTLT-1 levels and markers of burn severity, coagulation disorders, endothelial permeability, shock and prognosis in patients with severe burns. MethodsA prospective, observational study was conducted with 60 severe burn patients (divided into a death group and a survival group according to 30-day prognosis) admitted to our hospital. Twenty-eight healthy volunteers were recruited as the control group. Blood components at 48 h after burn were analysed for sTLT-1 and biomarkers reflecting platelet activation, shock, endothelial glycocalyx damage, capillary leakage, haemostasis, fibrinolytic activity, natural anticoagulation and blood cells. We compared the three groups, analysed the correlation between sTLT-1 and biomarkers, and investigated the predictive value of sTLT-1 for 30-day prognosis. ResultCompared with the surviving patients, the patients who died had a lower degree of platelet activation [lower sTLT-1, platelet factor 4 (PF-4) and platelet counts] and a higher degree of burn [higher abbreviated burn severity index score (ABSI score)], shock (higher lactate), endothelial glycocalyx damage [higher syndecan-1 and soluble thrombomodulin (sTM)] and capillary leakage [higher resuscitation fluid (0−48 h), lower albumin] as well as decreased haemostasis [higher activated partial prothrombin time (APTT), lower fibrinogen and thrombin-antithrombin III complex (TAT)], increased fibrinolytic activity [higher D-dimer and tissue-type plasminogen activator (tPA)] and decreased natural anticoagulation [lower protein C (PC) and protein S (PS)]. Higher D-dimer (P = 0.013) and lower PF-4 (P = 0.001) were significantly independently associated with lower sTLT-1. Low circulating sTLT-1 (a unit is 50 pg/mL) (odds ratio [OR] 2.08 [95% CI 1.11–3.92], P = 0.022) was an independent predictor of increased 30-day mortality. ConclusionLow sTLT-1 levels at 48 h after burn in patients with severe burns is associated with increased coagulation disorders. Low circulating sTLT-1 levels were an independent predictor of increased 30-day mortality.

P-selectin (CD62P) and soluble TREM-like transcript-1 (sTLT-1) are associated with coronary artery disease: a case control study

BackgroundPlatelet activation plays a crucial role in the pathogenesis of coronary artery disease (CAD). Platelet P-selectin (CD62P) is a classic platelet activation indicator on the platelet surface, and soluble TREM-like transcript-1 (sTLT-1) is a new indicator. However, the relationship between these two markers and CAD, especially in acute coronary syndrome (ACS), has not been elucidated. This study aimed to investigate CD62P expression on the platelet surface and sTLT-1 expression in serum, as well as to assess their relationship with CAD.MethodsWe measured the levels of CD62P and sTLT-1 in 83 patients with CAD compared to 49 controls. The association of these indicators with age, blood pressure, lipid profile, body mass index, and liver injury marker level were also examined.ResultsCD62P concentration was higher in CAD patients than in the control group (P < 0.01), especially in acute myocardial infarction (AMI) patients (P < 0.01). Serum sTLT-1 concentration was higher in the AMI and unstable angina pectoris (UAP) groups than in the normal control (NC) group (P < 0.01).ConclusionsThe consistency of sTLT-1 and CD62P expression levels in CAD patients indicates that sTLT-1 level, the same as CD62P, may be a new marker of platelet activation that is positively related to CAD.

A Candidate Regulatory Variant at the TREM Gene Cluster Confer Alzheimer's Disease Risk by Modulating Both Amyloid-β Pathology and Neuronal Degeneration.

Background: rs9357347 located at the triggering receptor expressed on myeloid cells (TREM) gene cluster could increase TREM2 and TREM-like transcript 1 (TREML1) brain gene expression, which is considered to play a protective role against Alzheimer’s disease (AD).Objectives: To investigate the role of rs9357347 in AD pathogenesis by exploring the effects of rs9357347 on AD specific biomarkers.Methods: This study analyzed the association of rs9357347 with AD-related cerebrospinal fluid (CSF) and neuroimaging markers from 201 cognitively normal (CN) older adults, 349 elders with mild cognitive impairment (MCI), and 172 elders with AD dementia from the Alzheimer’s Disease Neuroimaging Initiative (ADNI). We next analyzed the association in 259 amyloid-β positive (Aβ+) elders and 117 amyloid-β negative (Aβ-) elders (Aβ+: CSF Aβ1-42 ≤ 192 pg/ml; Aβ-: CSF Aβ1-42 > 192 pg/ml). Associations were tested using multiple linear regression models at baseline. Furthermore, multiple mixed-effects models were used in a longitudinal study which lasted 4 years.Results: At baseline, we found that rs9357347 had association with CSF Aβ1-42 in CN group (β = 0.357, P = 0.009). In AD group, rs9357347 was associated with total tau (T-tau) level (β = -0.436, P = 0.007). Moreover, the strong influence exerted by rs9357347 on T-tau was also seen in Aβ+ group (β = -0.202, P = 0.036). In the longitudinal study, rs9357347 was also found to be associated with Aβ1-42 in CN group (β = 0.329, P = 0.023). In AD group, the mutation of rs9357347 was associated with slower accumulation of T-tau (β = -0.472, P = 0.002) and tau phosphorylated at threonine 181 [P-tau 181 (β = -0.330, P = 0.019)]. Furthermore, the obvious influence exerted by rs9357347 on T-tau was also seen in Aβ+ group (β = -0.241, P = 0.013).Conclusion: This study suggested that rs9357347 reduced the risk of AD by modulating both amyloid-β pathology and neuronal degeneration.

Downregulation of TREM-like transcript-1 and collagen receptor α2 subunit, two novel RUNX1-targets, contributes to platelet dysfunction in familial platelet disorder with predisposition to acute myelogenous leukemia.

Germline RUNX1 mutations lead to thrombocytopenia and platelet dysfunction in familial platelet disorder with predisposition to acute myelogenous leukemia (AML). Multiple aspects of platelet function are impaired in these patients, associated with altered expression of genes regulated by RUNX1. We aimed to identify RUNX1-targets involved in platelet function by combining transcriptome analysis of patient and shRUNX1-transduced megakaryocytes (MK). Down-regulated genes included TREM-like transcript (TLT)-1 (TREML1) and the integrin subunit alpha (α)-2 (ITGA2) of collagen receptor α2-beta (β)-1, which are involved in platelet aggregation and adhesion, respectively. RUNX1 binding to regions enriched for H3K27Ac marks was demonstrated for both genes using chromatin immunoprecipitation. Cloning of these regions upstream of the respective promoters in lentivirus allowing mCherry reporter expression showed that RUNX1 positively regulates TREML1 and ITGA2, and this regulation was abrogated after deletion of RUNX1 sites. TLT-1 content was reduced in patient MK and platelets. A blocking anti-TLT-1 antibody was able to block aggregation of normal but not patient platelets, whereas recombinant soluble TLT-1 potentiated fibrinogen binding to patient platelets, pointing to a role for TLT-1 deficiency in the platelet function defect. Low levels of α2 integrin subunit were demonstrated in patient platelets and MK, coupled with reduced platelet and MK adhesion to collagen, both under static and flow conditions. In conclusion, we show that gene expression profiling of RUNX1 knock-down or mutated MK provides a suitable approach to identify novel RUNX1 targets, among which downregulation of TREML1 and ITGA2 clearly contribute to the platelet phenotype of familial platelet disorder with predisposition to AML.

Association of soluble TREM-like transcript-1 with clinical features and patient reported outcomes in systemic lupus erythematosus.

ObjectiveThe soluble triggering receptor expressed on myeloid cells (TREM-1)-like transcript 1 (sTLT-1) has a modulatory effect on the activation of TREM-1. We compared plasma sTLT-1 levels between patients with systemic lupus erythematosus (SLE) and healthy individuals and determined the association between sTLT-1 levels and clinical features and patient-reported outcomes (PROs) among patients with lupus.MethodsAn unmatched case-control study was conducted in 46 patients with SLE and 28 healthy subjects. sTLT-1 plasma levels were determined using enzyme-linked immunosorbent assay. Demographic factors, SLE manifestations, comorbidities, pharmacologic profile, disease activity (per SLAM-R), damage accrual, and PROs (as per Lupus Patient-Reported Outcome [LupusPRO]) were studied.ResultsPatients with SLE were found to have lower sTLT-1 levels compared with healthy individuals (9.0±7.2 vs. 18.6±22.3 pg/mL, p=0.008). Among patients with SLE, higher sTLT-1 levels were found in those taking corticosteroids (11.1±8.8 vs. 6.9±4.6 pg/mL, p=0.014). Significant correlations were found for the cognition (r=−0.442, p=0.027) and desires/goals (r=0.435, p=0.030) domains of LupusPRO. A tendency was observed between sTLT-1 levels and the SLAM-R (r=−0.278, p=0.064) and the lupus symptoms (r=−0.388, p=0.055) and physical health (r=−0.382, p=0.060) domains of LupusPRO.ConclusionCompared with healthy individuals, sTLT-1 levels were significantly lower in patients with SLE. Among patients with SLE, correlations were observed for some domains of LupusPRO. Given that sTLT-1 has anti-inflammatory properties, the deficiency of this protein could play an important role in the pathogenesis of SLE.

Serum STLT-1 and bilirubin levels in patients with acute coronary syndrome and correlation with prognosis.

The serum triggering receptor expressed on myeloid cell (TREM)-like transcription factor-1 [soluble TREM-like transcript-1 (STLT-1)] and bilirubin levels were investigated in patients with acute coronary syndrome and the correlation with prognosis. A total of 125 patients of acute coronary syndrome admitted to the Department of Cardiology in People's Hospital of Rizhao were selected, including 45 cases with ST-segment elevation myocardial infarction (STEMI), 36 cases with non-ST-elevation myocardial infarction (NSTEMI) and 44 cases with unstable angina pectoris (UAP), while 48 subjects were enrolled as the normal control. The serum STLT-1 and bilirubin levels on admission and on the 3rd, 7th and 10th day after admission of patients in each group were respectively determined, the level changes of these two indicators in serum during the initial stage of acute coronary syndrome were analyzed, and their effects on prognosis of patients were analyzed. STLT-1 levels in groups STEMI, NSTEMI and UAP were higher than those in the normal control group, and serum levels of STLT-1 in groups STEMI and NSTEMI were higher than those in group UAP. Bilirubin levels in groups STEMI, NSTEMI and UAP were lower than those in the normal control group, and serum levels of bilirubin in groups STEMI and NSTEMI were lower than those in group UAP. The proportions of complications in patients of groups STEMI and NSTEMI were significantly higher than those in group UAP (P<0.05). The results showed that the timely and effective treatment administered to patients with acute coronary syndrome during the initial stage to reduce the level of STLT-1 in serum and enhance bilirubin to a relatively high level is conducive in ameliorating the prognosis of patients, which is of clinical significance.

The Characterization of Monoclonal Antibodies to Mouse TLT-1 Suggests That TLT-1 Plays a Role in Wound Healing.

Platelets play a vital role in hemostasis and inflammation. The membrane receptor TREM-like transcript-1 (TLT-1) is involved in platelet aggregation, bleeding, and inflammation, and it is localized in the α-granules of platelets. Upon platelet activation, TLT-1 is released from α-granules both in its transmembrane form and as a soluble fragment (sTLT-1). Higher levels of sTLT-1 have been detected in the plasma of patients with acute inflammation or sepsis, suggesting an important role for TLT-1 during inflammation. However, the roles of TLT-1 in hemostasis and inflammation are not well understood. We are developing the mouse model of TLT-1 to mechanistically test clinical associations of TLT-1 in health and disease. To facilitate our studies, monoclonal murine TLT-1 (mTLT-1) antibodies were produced by the immunization of a rabbit using the negatively charged region of the mTLT-1 extracellular domain 122PPVPGPREGEEAEDEK139. In the present study, we demonstrate that two selected clones, 4.6 and 4.8, are suitable for the detection of mTLT-1 by western blot, immunoprecipitation, immunofluorescent staining, flow cytometry and inhibit platelet aggregation in aggregometry assays. In addition, we found that the topical administration of clone 4.8 delayed the wound healing process in an experimental burn model. These results suggest that TLT-1 plays an important role in wound healing and because both clones specifically detect mTLT-1, they are suitable to further develop TLT-1 based models of inflammation and hemostasis in vivo.

TLT-1 as a possible modulator of Systemic Lupus Erythematosus.

Abstract Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune system hyperactivity and autoantibody production that can affect almost any organ system. TREM like transcript-1 (TLT-1) is a membrane receptor found in platelet α-granules with a soluble form (sTLT-1) detected in serum but not plasma of healthy individuals. The evaluations of patients suffering from diseases, such as sepsis, show a significant increase of plasma sTLT-1 levels. It is not known if TLT-1 plays a role in auto immune diseases such as Lupus. In the present study we evaluate the potential that TLT-1 may play a role in the etiology of SLE. We assessed the plasma of 46 SLE patients and compared to 28 healthy controls by ELISA. Our results showed that SLE patients had a significant decrease in plasma sTLT-1 levels compared to healthy controls (9.0 [7.2] vs. 18.6 [22.3] ng/ml, p=0.008). A negative correlation was observed between TLT-1 levels and LupusPRO [lupus symptoms (r = −0.388, p = 0.055). Based on this data; we hypothesized that SLE patients produce autoantibodies against TLT-1 in serum which might correlate with clinical aspects of the disease. To address this question; TLT-1 antibodies levels in serum were measured by ELISA. Our data suggests that a sub-population of SLE patients have TLT-1 autoantibodies. This data was further confirmed by confocal microscopy. Using HEK cells stably transfected with TLT-1; we evaluated the serum of SLE patients for the presence of TLT-1 autoantibodies using immunofluorescence. Our data confirms that a sub-population of SLE patients with active disease expresses antibodies against TLT-1 suggesting a possible role for TLT-1 during the pathogenesis of SLE and targets new treatment possibilities for lupus patients.

Triggering receptor expressed on myeloid cells 1 (TREM-1) and cytokine gene variants in complicated and uncomplicated malaria.

Malaria elicits inflammatory responses, which, if not well regulated, may exert detrimental effects. When activated, triggering receptor expressed on myeloid cells 1 (TREM-1) enhances inflammatory responses by increasing secretion of IL-8 and other Th1 cytokines. In contrast, TREM-like transcript 1 (TREML-1) promotes anti-inflammatory responses by binding to TREM-1 ligands and competing with TREM-1, thus antagonizing TREM-1 activation to reduce inflammation. Endothelial protein C receptor (EPCR) also mediates anti-inflammatory responses by activating endothelial protein C (PC). Upon microbial stimulation, soluble forms of TREM-1 (sTREM-1) and soluble EPCR (sEPCR) are released. Their plasma levels reflect the degree of inflammation and the severity of infection. In a cross-sectional study comparing patients with severe with uncomplicated malaria, sTREM-1, soluble TREML-1 (sTREML-1) and sEPCR plasma levels as well as plasma levels of sEPCR derived from convalescent patients were quantified. Samples were collected on admittance of paediatric patients infected with Plasmodium falciparum to hospitals in Accra, Ghana. Distinct genetic regions of the genes encoding TREM-1, EPCR, interleukin (IL)-8 and IL-18 encompassing known genetic polymorphisms that influence plasma levels underwent DNA sequencing. Higher sTREM-1 levels were observed among children suffering from severe malaria compared to those with uncomplicated malaria (P = 0.049). Low TREM-1 to TREML-1 ratios were associated with uncomplicated malaria (P = 0.033). The TREM1 rs2234237T variant causing the amino acid exchange Thr25Ser, which has been associated with higher TREM-1 plasma levels, was significantly more frequent among patients with severe malaria than in those with uncomplicated malaria (P = 0.036). Low levels of sEPCR were observed in severe and uncomplicated malaria, while variant genotypes of IL8, IL18 and EPCR did not show any association. Higher plasma levels of sTREM-1 alone or relative to sTREML-1 during malaria predispose to the phenotype of severe malaria. Carriage of the TREM1 rs2234237T allele appears to be a risk factor for the development of severe malaria.

Abstract 606: Impaired Glucose Metabolism in the Triggering Receptor Expressed in Myeloid Cells Like Transcript- 1 Null Mice A Link to Obesity

Fat rich foods have been shown to produce increased body weight and diabetes in various strains of mice. When fed ad libitum with a high fat diet (HFD), apolipoprotein E deficient ( apoe -/- ) mice develop hypercholesterolemia, but are not known to be obese. Our laboratory demonstrated that the triggering receptor expressed in myeloid cells (TREM) like transcript-1 (TLT-1), as a potential target for intervention during atherosclerosis, diabetes, and obesity. Crossing the treml1 -/- mouse onto an apoe -/- background (DKO), we found DKO mice had smaller lesions than apoe -/- mice, yet had significantly higher triglycerides and weight gain over a 20-week period of HFD. Further investigation demonstrated treml1 -/- mice to have higher cholesterol than wild type mice (wt), suggesting the treml1 mutation contributes to the phenotype observed in DKO mice. Glucose evaluation of treml1 -/- , treml1 +/- and wt mice, showed a significant difference in basal glucose, and in plasma glucose clearance, as revealed by intraperitoneal (IP) glucose tolerance test. Analysis of serum insulin by ELISA showed no differences, while IP insulin tolerance test revealed treml1 -/- and treml1 +/- mice present apparent insulin hypersensitivity, as represented by the steady glucose decline 15 min post injection, with no recovery after two hours. Western blot performed in various tissues, demonstrated the presence of a TLT-1 splice variant that lacks the extracellular domain (TLT-1s), in the adipose tissue of treml1 -/- but not wt mice. Analysis of insulin response, in vivo by insulin sensitivity assay and in vitro using TSA 201 cells transfected with TLT-1s to determine the effect on AKT activation, revealed enhanced phosphorylation in the presence of TLT-1, with a similar response observed in vitro. This data support a model where TLT-1s modulation of AKT phosphorylation, increases adipocyte glucose uptake, leading to: low blood glucose levels, increased fatty acid production and storage, and the obese phenotype we observed in our mice.

Abstract 459: Differential Responses of Bone Marrow-Derived Macrophages to Lipopolysaccharide in the Treml1 Null Mouse

Atherosclerosis, the hardening and narrowing of the arteries, is a chronic inflammatory disease driven by a crosstalk of signaling molecules between circulating immune cells and the vessel wall. In the classic view of this cardiovascular disease, hyperlipidemia initiates an inflammatory cascade that promotes macrophage infiltration into the vessel wall leading to a feedback mechanism which exacerbates lesion growth and ultimately, atherothrombosis. Our laboratory has characterized a novel atherosclerotic mice model, in which deletion of the platelet receptor Triggering Receptor Expressed on Myeloid Cells (TREM)-Like Transcript-1 (TLT-1) on a apolipoprotein E ( apoe -/- /treml1 -/- ) background dampens early macrophage infiltration into the vessel wall. This leads to decreased lesion size, instability, and calcification of atherosclerotic lesions. We have demonstrated that one of the mechanisms for dampened lesion progression is decreased platelet activation and we hypothesize that the macrophage infiltration differences may also be due to fundamental differences in macrophage phenotypic functions. In order to further define the mechanism by which TLT-1 modulates macrophage infiltration, we analyzed macrophage function in vitro . Analysis of bone marrow-derived macrophages (BMDM) from apoe -/- /treml1 -/- and apoe -/- /treml1 -/+ mice revealed no significant differences in the phagocytic function of long chain fatty acids. However, analysis of basal levels of monocyte chemoattractant protein-1 (MCP1), a key chemokine regulating monocyte infiltration, were significantly decreased in the apoe -/- /treml1 -/- BMDM supernatants. Accordingly, levels of Interleukin 6 (IL6) and Interleukin 10 (IL10) were significantly decreased in the apoe -/- /treml1 -/- BMDM supernatants after two hours of lipopolysaccharide (LPS) stimulation (p&lt;0.05; n=5-8). These findings define an underlying difference in the BMDM secretory phenotype of the apoe -/- /treml1 -/- mice. However, it also opens the possibility of treml1 expression in macrophages, which may account for these differences. We will now investigate if an alternate isoform of treml1 is expressed in macrophages or at some period of their differentiation.

Abstract 548: TLT-1 as a Possible Modulator of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by immune system hyperactivity and autoantibody production that can affect almost any organ system. TREM like transcript-1 (TLT-1) is a membrane receptor found in platelets α-granules with activating properties. We have demonstrated that activated platelets release a soluble isoform of TLT-1 (sTLT-1) which is not found in the plasma of healthy individuals. Moreover, evaluation of patients suffering from inflammatory diseases, such as sepsis, reveals a significant increase of plasma sTLT-1 levels. It is not known if TLT-1 plays a role in auto immune diseases such as Lupus. In the present study we evaluate the potential that TLT-1 may play a role in the etiology of SLE. We assessed the plasma of 46 SLE patients and compared to 28 healthy controls by ELISA. Our results showed that SLE patients had a significant decrease in plasma sTLT-1 levels compared to healthy controls (9.0 [7.2] vs. 18.6 [22.3] ng/ml, p=0.008). A negative correlation was observed between TLT-1 levels and LupusPRO [lupus symptoms (r = -0.388, p = 0.055). Based on this data; we hypothesize that SLE patients produce autoantibodies against TLT-1 in serum which might correlate with clinical aspects of the disease . To address this question; TLT-1 antibodies levels in serum were measured by ELISA. Our data suggests that a sub-population of SLE patients have TLT-1 autoantibodies. This data was further confirmed by confocal microscopy. Using human embryonal kidney cells (HEKt) stably transfected with TLT-1, we evaluated the serum of SLE patients for the presence of TLT-1 autoantibodies using immunofluorescence. Our data confirms that a sub-population of SLE patients with active disease is expressing antibodies against TLT-1. These findings suggest a possible role for TLT-1 during the pathogenesis of SLE and targets new treatment possibilities for lupus patients.