Activation-induced changes in platelet surface receptor expression and the contribution of the large-platelet subpopulation to activation.

Objective:Platelet surface receptors are also present subcellularly in organelle membranes and can be expressed on the surface upon platelet activation. However, some receptors were reported to be decreased after activation. We analyzed the mechanism of activation-dependent expression for different receptors. Methods:Flow cytometry using platelet-rich plasma or washed platelets was used to analyze receptor-expression changes after platelet activation by glycoprotein (GP) VI-specific agonists, crosslinked collagen-related peptide (CRP-XL) and convulxin (Cvx), and thrombin. Platelets prelabeled with fluorescent antibody specific for a receptor were allowed to adhere on immobilized collagen or fibrinogen and post-stained with antibody against the same receptor labeled with another fluorophore, allowing us to differentiate preexisting receptors from newly expressed receptors. Results:Surface expression of αIIbβ3 increased in CRP-XL-, Cvx-, or thrombin-stimulated platelets, but GPIb decreased due to shedding and internalization. Both total and dimeric GPVI increased in thrombin-induced platelets, but decreased in platelets stimulated by Cvx, as a result of internalization. The larger platelets showed a greater increase in surface receptor (α2β1, αIIbβ3, GPVI, GPIb) expression upon activation compared to the smaller ones. Pre- and postlabeling with antibody specific for the same receptor, but conjugated with different fluorophores, allowed us to differentiate the receptors expressed on the surface of resting platelets from receptors newly exposed to the surface upon platelet activation. Conclusions:Increased receptor expressions after activation are mainly manifested in the larger platelets. On platelets adhered on fibrinogen, the newly expressed receptors, especially GPVI, are localized in the lamellipodia of the spread platelets

Beyond antiplatelets: The role of glycoprotein VI in ischemic stroke.

BACKGROUND: Platelets are essential to physiological hemostasis or pathological thrombus formation. Current antiplatelet agents inhibit platelet aggregation but leave patients at risk of systemic side-effects such as hemorrhage. Newer therapeutic strategies could involve targeting this cascade earlier during platelet adhesion or activation via inhibitory effects on specific glycoproteins, the thrombogenic collagen receptors found on the platelet surface. AIMS: Glycoprotein VI (GPVI) is increasingly being recognized as the main platelet-collagen receptor involved in arterial thrombosis. This review summarizes the crucial role GPVI plays in ischemic stroke as well as the current strategies used to attempt to inhibit its activity. SUMMARY OF REVIEW: In this review, we discuss the normal hemostatic process, and the role GPVI plays at sites of atherosclerotic plaque rupture. We discuss how the unique structure of GPVI allows for its interaction with collagen and creates downstream signaling that leads to thrombus formation. We summarize the current strategies used to inhibit GPVI activity and how this could translate to a clinically viable entity that may compete with current antiplatelet therapy. CONCLUSION: From animal models, it is clear that GPVI inhibition leads to an abolished platelet response to collagen and reduced platelet aggregation, culminating in smaller arterial thrombi. There is now an increasing body of evidence that these findings can be translated into the development of a bleeding free pharmacological entity specific to sites of plaque rupture in humans.British Heart FoundationThis is the final version of the article. It first appeared from SAGE via https://doi.org/ 10.1177/174749301665453

MMP-13 binds to platelet receptors αIIbβ3 and GPVI and impairs aggregation and thrombus formation.

BACKGROUND: Acute thrombotic syndromes lead to atherosclerotic plaque rupture with subsequent thrombus formation, myocardial infarction and stroke. Following rupture, flowing blood is exposed to plaque components, including collagen, which triggers platelet activation and aggregation. However, plaque rupture releases other components into the surrounding vessel which have the potential to influence platelet function and thrombus formation. OBJECTIVES: Here we sought to elucidate whether matrix metalloproteinase-13 (MMP-13), a collagenolytic metalloproteinase up-regulated in atherothrombotic and inflammatory conditions, affects platelet aggregation and thrombus formation. RESULTS: We demonstrate that MMP-13 is able to bind to platelet receptors alphaIIbbeta3 (αIIbβ3) and platelet glycoprotein (GP)VI. The interactions between MMP-13, GPVI and αIIbβ3 are sufficient to significantly inhibit washed platelet aggregation and decrease thrombus formation on fibrillar collagen. CONCLUSIONS: Our data demonstrate a role for MMP-13 in the inhibition of both platelet aggregation and thrombus formation in whole flowing blood, and may provide new avenues of research into the mechanisms underlying the subtle role of MMP-13 in atherothrombotic pathologies

The use of proactive risk management to reduce emergency service vehicle crashes among firefighters

Introduction: Emergency service vehicle crashes (ESVCs), including rollovers and collisions with other vehicles and fixed objects, are a leading cause of death among U.S. firefighters. Risk management (RM) is a proactive intervention to identifying and mitigating occupational risks and hazards. The goal of this study was to assess the effect of RM in reducing ESVCs. Methods: Three fire departments (A, B and C), representing urban and suburban geographies, and serving medium to large populations, participated in facilitated RM programs to reduce their ESVCs. Interventions were chosen by each department to address their department-specific circumstances and highest risks. Monthly crash rates per 10,000 calls were calculated for each department an average of 28 months before and 23 months after the start of the RM programs. Interrupted time series analysis was used to assess the effect of the RM programs on monthly crash rates. Poisson regression was used to estimate the number of crashes avoided. Economic data from Department A were analyzed to estimate cost savings. Results: Department A had a 15.4% (P = 0.30) reduction in the overall monthly crash rate immediately post-RM and a 1% (P = 0.18) decline per month thereafter. The estimated two-year average cost savings due to 167 crashes avoided was $253,100 (95$192,355 - $313,885). Department B had a 9.7% (P = 0.70) increase in the overall monthly crash rate immediately post-RM and showed no significant changes in their monthly crash rate. Department C had a 28.4% (P = 0.001) reduction in overall monthly crash rate immediately post-RM and a 1.2% (P = 0.09) increase per month thereafter, with an estimated 122 crashes avoided. Conclusions: RM programs have the potential to reduce ESVCs in the fire service and their associated costs; results may vary based on the interventions chosen and how they are implemented. Practical applications: Risk management may be an effective and broadly implemented intervention to reduce ESVCs in the US fire service. (C) 2019 The Author(s). National Safety Council and Elsevier Ltd.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Where Are You From? A Validation of the Foreigner Objectification Scale and the Psychological Correlates of Foreigner Objectification Among Asian Americans and Latinos

Many ethnic minorities in the United States consider themselves to be just as American as their European American counterparts. However, there is a persistent cultural stereotype of ethnic minorities as foreigners (i.e., the perpetual foreigner stereotype) that may be expressed during interpersonal interactions (i.e., foreigner objectification). The goal of the present study was to validate the Foreigner Objectification Scale, a brief self-report measure of perceived foreigner objectification, and to examine the psychological correlates of perceived foreigner objectification. Results indicated that the Foreigner Objectification Scale is structurally (i.e., factor structure) and metrically (i.e., factor loadings) invariant across foreign-born and U.S.-born Asian Americans and Latinos. Scalar (i.e., latent item intercepts) invariance was demonstrated for the two foreign-born groups and the two U.S.-born groups, but not across foreign-born and U.S.-born individuals. Multiple-group structural equation models indicated that, among U.S.-born individuals, perceived foreigner objectification was associated with less life satisfaction and more depressive symptoms, and was indirectly associated with lower self-esteem via identity denial, operationalized as the perception that one is not viewed by others as American. Among foreign-born individuals, perceived foreigner objectification was not significantly associated directly with self-esteem, life satisfaction, or depressive symptoms. However, perceived foreigner objectification was positively associated with identity denial, and identity denial was negatively associated with life satisfaction. This study illustrates the relevance of perceived foreigner objectification to the psychological well-being of U.S.-born Asian Americans and Latinos

Dietary Cholesterol Promotes Adipocyte Hypertrophy and Adipose Tissue Inflammation in Visceral, But Not Subcutaneous, Fat in Monkeys

Objective—Excessive caloric intake is associated with obesity and adipose tissue dysfunction. However, the role of dietary cholesterol in this process is unknown. The aim of this study was to determine whether increasing dietary cholesterol intake alters adipose tissue cholesterol content, adipocyte size, and endocrine function in nonhuman primates. Approach and Results—Age-matched, male African Green monkeys (n=5 per group) were assigned to one of three diets containing 0.002 (Lo), 0.2 (Med) or 0.4 (Hi) mg cholesterol/Kcal. After 10 weeks of diet feeding, animals were euthanized for adipose tissue, liver, and plasma collection. With increasing dietary cholesterol, free cholesterol (FC) content and adipocyte size increased in a step-wise manner in visceral, but not subcutaneous fat, with a significant association between visceral adipocyte size and FC content (r2=0.298; n=15; p=0.035). In visceral fat, dietary cholesterol intake was associated with: 1) increased pro-inflammatory gene expression and macrophage recruitment, 2) decreased expression of genes involved in cholesterol biosynthesis and lipoprotein uptake, and 3) increased expression of proteins involved in FC efflux. Conclusions—Increasing dietary cholesterol selectively increases visceral fat adipocyte size, FC and macrophage content, and proinflammatory gene expression in nonhuman primates

Constitutive dimerization of glycoprotein VI (GPVI) in resting platelets is essential for binding to collagen and activation in flowing blood

The platelet collagen receptor glycoprotein VI (GPVI) has been suggested to function as a dimer, with increased affinity for collagen. Dissociation constants (K(d)) obtained by measuring recombinant GPVI binding to collagenous substrates showed that GPVI dimers bind with high affinity to tandem GPO (Gly-Pro-Hyp) sequences in collagen, whereas the markedly lower affinity of the monomer for all substrates implies that it is not the collagen-binding form of GPVI. Dimer binding required a high density of immobilized triple-helical (GPO)(10)-containing peptide, suggesting that the dimer binds multiple, discrete peptide helices. Differential inhibition of dimer binding by dimer-specific antibodies, m-Fab-F and 204-11 Fab, suggests that m-Fab-F binds at the collagen-binding site of the dimer, and 204-11 Fab binds to a discrete site. Flow cytometric quantitation indicated that GPVI dimers account for ~29% of total GPVI in resting platelets, whereas activation by either collagen-related peptide or thrombin increases the number of dimers to ~39 and ~44%, respectively. m-Fab-F inhibits both GPVI-dependent static platelet adhesion to collagen and thrombus formation on collagen under low and high shear, indicating that pre-existing dimeric GPVI is required for the initial interaction with collagen because affinity of the monomer is too low to support binding and that interaction through the dimer is essential for platelet activation. These GPVI dimers in resting circulating platelets will enable them to bind injury-exposed subendothelial collagen to initiate platelet activation. The GPVI-specific agonist collagen-related peptide or thrombin further increases the number of dimers, thereby providing a feedback mechanism for reinforcing binding to collagen and platelet activation

Deficiency in the LIM-only protein Fhl2 impairs skin wound healing

After skin wounding, the repair process is initiated by the release of growth factors, cytokines, and bioactive lipids from injured vessels and coagulated platelets. These signal molecules induce synthesis and deposition of a provisional extracellular matrix, as well as fibroblast invasion into and contraction of the wounded area. We previously showed that sphingosine-1-phosphate (S1P) triggers a signal transduction cascade mediating nuclear translocation of the LIM-only protein Fhl2 in response to activation of the RhoA GTPase (Muller, J.M., U. Isele, E. Metzger, A. Rempel, M. Moser, A. Pscherer, T. Breyer, C. Holubarsch, R. Buettner, and R. Schule. 2000. EMBO J. 19:359–369; Muller, J.M., E. Metzger, H. Greschik, A.K. Bosserhoff, L. Mercep, R. Buettner, and R. Schule. 2002. EMBO J. 21:736–748.). We demonstrate impaired cutaneous wound healing in Fhl2-deficient mice rescued by transgenic expression of Fhl2. Furthermore, collagen contraction and cell migration are severely impaired in Fhl2-deficient cells. Consequently, we show that the expression of α-smooth muscle actin, which is regulated by Fhl2, is reduced and delayed in wounds of Fhl2-deficient mice and that the expression of p130Cas, which is essential for cell migration, is reduced in Fhl2-deficient cells. In summary, our data demonstrate a function of Fhl2 as a lipid-triggered signaling molecule in mesenchymal cells regulating their migration and contraction during cutaneous wound healing

DNA methylation among firefighters

Firefighters are exposed to carcinogens and have elevated cancer rates. We hypothesized that occupational exposures in firefighters would lead to DNA methylation changes associated with activation of cancer pathways and increased cancer risk. To address this hypothesis, we collected peripheral blood samples from 45 incumbent and 41 new recruit nonsmoking male firefighters and analyzed the samples for DNA methylation using an Illumina Methylation EPIC 850k chip. Adjusting for age and ethnicity, we performed: 1) genome-wide differential methylation analysis; 2) genome-wide prediction for firefighter status (incumbent or new recruit) and years of service; and 3) Ingenuity Pathway Analysis (IPA). Four CpGs, including three in the YIPF6, MPST, and PCED1B genes, demonstrated above 1.5-fold statistically significant differential methylation after Bonferroni correction. Genome-wide methylation predicted with high accuracy incumbent and new recruit status as well as years of service among incumbent firefighters. Using IPA, the top pathways with more than 5 gene members annotated from differentially methylated probes included Sirtuin signaling pathway, p53 signaling, and 5' AMP-activated protein kinase (AMPK) signaling. These DNA methylation findings suggest potential cellular mechanisms associated with increased cancer risk in firefighters.US Federal Emergency Management Agency Assistance to Firefighters Grant program [EMW-2014-FP-00200]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]