RESUMO
Receptors are important pharmacological targets on cells. The Triggering Receptor Expressed on Myeloid Cells (TREM) - Like Transcript - 1 is an abundant, yet little understood, platelet receptor. It is a single Ig domain containing receptor isolated in the α-granules of resting platelets and brought to the platelet surface upon activation. On platelets, the integrin αIIbß3 is the major receptor having roughly 80,000 copies. αIIbß3 is a heterodimeric multidomain structure that mediates platelet aggregation through its interaction with the plasma protein fibrinogen. Anti-platelet drugs have successfully targeted αIIbß3 to control thrombosis. Like αIIbß3, TLT-1 also binds fibrinogen, making its role in platelet function somewhat obscure. In this review, we highlight the known structural features of TLT-1 and present the challenges of understanding TLT-1 function. In our analysis of the dynamics of the platelet surface after activation we propose a model in which TLT-1 supports αIIbß3 function as a mechanoreceptor that may direct platelets toward immune function.
Assuntos
Plaquetas/metabolismo , Células Mieloides/metabolismo , Animais , Modelos Animais de Doenças , Humanos , Camundongos , Modelos MolecularesRESUMO
Although multiple efforts have been initiated to increase students' science proficiency scores, most of the schools in the United States do not reach the expected student academic performance. This study addresses the impact of a one-week summer scientific learning experience on students that worked with experimental procedures and students that did not. We describe and evaluate these two different interventions to explore what components influence high school students' perception of their scientific competence, performance, and recognition, using science identity as an analytical lens. Science identity score was increased at the end of both interventions. Interestingly, science identity change index was higher for the group that did not work with experimental procedures. Although this group did not perform any hands-on experiments, they report, through reflexive diaries and interviews that working with CRISPR-Cas9 models, being in a research laboratory, and seeing the instrumentation made them feel like scientists. Regarding science competence, both groups report exponential learning gains, although the group that performed the experiments reports more difficulties. Both groups report that mentorship was key in their competence and performance development. These findings suggest that our one-week scientific learning programs influence participants' perception of scientific competence and performance and create an opportunity to develop further studies on short scientific learning experiences using models and active learning activities.
Assuntos
Aprendizagem Baseada em Problemas , Pesquisa/educação , Ciência/educação , Estações do Ano , Adolescente , Feminino , Humanos , Masculino , EstudantesRESUMO
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) affect >200 000 individuals yearly with a 40% mortality rate. Although platelets are implicated in the progression of ALI/ARDS, their exact role remains undefined. Triggering receptor expressed in myeloid cells (TREM)-like transcript 1 (TLT-1) is found on platelets, binds fibrinogen, and mediates clot formation. We hypothesized that platelets use TLT-1 to manage the progression of ALI/ARDS. Here we retrospectively measure plasma levels of soluble TLT-1 (sTLT-1) from the ARDS Network clinical trial and show that patients whose sTLT-1 levels were >1200 pg/mL had nearly twice the mortality risk as those with <1200 pg/mL (P < .001). After correcting for confounding factors such as creatinine levels, Acute Physiology And Chronic Health Evaluation III scores, age, platelet counts, and ventilation volume, sTLT-1 remains significant, suggesting that sTLT-1 is an independent prognostic factor (P < .0001). These data point to a role for TLT-1 during the progression of ALI/ARDS. We use a murine lipopolysaccharide-induced ALI model and demonstrate increased alveolar bleeding, aberrant neutrophil transmigration and accumulation associated with decreased fibrinogen deposition, and increased pulmonary tissue damage in the absence of TLT-1. The loss of TLT-1 resulted in an increased proportion of platelet-neutrophil conjugates (43.73 ± 24.75% vs 8.92 ± 2.4% in wild-type mice), which correlated with increased neutrophil death. Infusion of sTLT-1 restores normal fibrinogen deposition and reduces pulmonary hemorrhage by 40% (P ≤ .001) and tissue damage by 25% (P ≤ .001) in vivo. Our findings suggest that TLT-1 uses fibrinogen to govern the transition between inflammation and hemostasis and facilitate controlled leukocyte transmigration during the progression of ARDS.
Assuntos
Lesão Pulmonar Aguda/sangue , Plaquetas/metabolismo , Receptores Imunológicos/sangue , Síndrome do Desconforto Respiratório/sangue , Lesão Pulmonar Aguda/patologia , Animais , Plaquetas/patologia , Modelos Animais de Doenças , Humanos , Camundongos , Camundongos Knockout , Infiltração de Neutrófilos , Neutrófilos/metabolismo , Neutrófilos/patologia , Valor Preditivo dos Testes , Síndrome do Desconforto Respiratório/patologia , Migração Transendotelial e TransepitelialRESUMO
OBJECTIVE: The 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. METHODS: An 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. RESULTS: Patients 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. CONCLUSION: Compared 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.
RESUMO
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.
Assuntos
Anticorpos Monoclonais/farmacologia , Queimaduras/imunologia , Agregação Plaquetária/efeitos dos fármacos , Receptores Imunológicos/imunologia , Pele/efeitos dos fármacos , Cicatrização/efeitos dos fármacos , Administração Cutânea , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/biossíntese , Anticorpos Monoclonais/isolamento & purificação , Plaquetas/química , Plaquetas/metabolismo , Western Blotting , Queimaduras/patologia , Células Clonais , Grânulos Citoplasmáticos/química , Grânulos Citoplasmáticos/metabolismo , Expressão Gênica , Imunização , Imunoprecipitação , Masculino , Camundongos , Peptídeos/administração & dosagem , Peptídeos/química , Peptídeos/imunologia , Coelhos , Receptores Imunológicos/química , Pele/imunologia , Pele/patologia , Cicatrização/imunologiaRESUMO
We have previously demonstrated that elevated levels of soluble triggering receptor expressed on myeloid cells-like transcript 1 (sTLT-1) modulate sepsis-induced inflammation and positively correlate with disseminated intravascular coagulation (DIC). Here, we evaluate the clinical implications of plasma sTLT-1 in acute respiratory distress syndrome (ARDS), which is common in sepsis patients. Soluble TLT-1 levels in the plasma of ARDS patients (n = 20) were determined by slot blot analysis and were compared with clinical parameters to identify significant associations. For comparisons to ARDS, we also measured sTLT-1 levels in matched healthy controls (n = 20). Of the 20 plasma samples evaluated from patients with ARDS, 60% were diagnosed with sepsis and 40% were diagnosed with septic shock. The white blood cells (WBCs) of patients with ARDS were found to be significantly elevated over healthy controls with a mean of 13 k/µL over 6.2 k/µL, respectively. The mean plasma levels of sTLT-1 were 148.4 pg/mL ± 16.52 in the patient cohort and 92.45 pg/mL ± 17.12 in the control group ( P = .02). No statistically significant correlations were found between plasma levels of sTLT-1 and WBCs, sepsis, septic shock or acute physiologic, and chronic health evaluation II scores. A statistically significant inverse correlation (r2 = .25, P < .05) was found between plasma sTLT-1 and peripheral platelet counts in patients with ARDS. Increased levels of sTLT-1 in ARDS patients suggest that TLT-1 may mediate the pathobiology of ARDS. Moreover, our data are the first to demonstrate a specific platelet marker in the development of ARDS due to sepsis.
Assuntos
Inflamação/complicações , Células Mieloides/metabolismo , Síndrome do Desconforto Respiratório/sangue , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Síndrome do Desconforto Respiratório/patologiaRESUMO
Triggering receptor expressed on myeloid cells (TREM) like transcript-1 (TLT-1) is a membrane protein receptor found in alpha-granules of platelets and megakaryocytes. Upon platelet activation TLT-1 is rapidly brought to the surface of platelets. Recently, we demonstrated that activated platelets release a soluble form of TLT-1 (sTLT-1) that is found in serum but not in the plasma of healthy individuals and can enhance platelet aggregation in vitro. Furthermore, evaluation of patients diagnosed with inflammatory diseases, such as sepsis, show that these patients have significantly elevated levels of sTLT-1 in their blood. Accordingly, mice deficient in TLT-1 are predisposed to bleeding in response to an inflammatory challenge; however, the mechanism of TLT-1 function remains unknown. In this investigation, we demonstrate an increase in the amount of platelets that adhere to endothelial cell monolayers in the presence of recombinant sTLT-1 (rsTLT-1). Additionally, we present evidence that rsTLT-1 increases platelet adherence to glass slides by stimulating actin polymerization in platelets, as determined by increased staining of rodamine phalloidin. These results suggest that during inflammation, sTLT-1 may mediate hemostasis by enhancing actin polymerization, resulting in increased platelet aggregation and adherence to the endothelium.
Assuntos
Actinas/metabolismo , Plaquetas/citologia , Células Endoteliais/citologia , Receptores Imunológicos/metabolismo , Animais , Bovinos , Adesão Celular , Humanos , Camundongos , Receptores Imunológicos/genéticaRESUMO
Sepsis is a multi-factorial disease that kills an estimated 1,400 people a day worldwide. The Triggering Receptor Expressed in Myeloid (TREM) cells Like Transcript (TLT)-1 is a platelet receptor expressed on activated platelets. Translational studies of TLT-1 suggest that TLT-1 affects hemostatic and immunological parameters that lead to the formation of disseminated intravascular coagulation (DIC). Evaluation of mice suffering from endotoxic shock shows a dramatic increase of soluble TLT-1 (sTLT-1) in their blood. Accordingly, when we evaluated the blood of septic patients we find increased levels of sTLT-1 that correlate with the presence of DIC in humans. Based on current data we hypothesize that TLT-1 plays an important role in maintaining vascular integrity during sepsis; perhaps by modulation of both the immune and hemostatic systems, and that TLT-1 makes an attractive target not only for better understanding of sepsis, but also as a point of therapeutic intervention as well.