Effect of platelet inhibitors on thrombus burden in patients with acute pulmonary embolism

Venous thromboembolism (VTE) whether provoked or not can be life-threatening due to an acute increase in load on the right ventricle (RV) from obstruction of the pulmonary artery (PA). Treatment for and prevention of VTE involves anti-thrombotic agents; more specifically, medications targeting the anticoagulation cascade. In spite of the widespread acceptance of anticoagulants in the treatment of VTE, there appears to be an ongoing belief that platelet reactivity contributes to thrombus burden in patients with acute pulmonary embolism (PE). This investigation of 398 patients presenting with acute PE evaluated whether anti-platelet medication use, which consisted mostly of aspirin therapy, at the time of presentation, affects PA thrombus burden, RV load, or short-term patient outcomes. We conclude that platelets may have been erroneously incriminated as direct thrombotic mediators in patients with acute PE since aspirin neither decreased PA thrombus burden, nor did aspirin improve short-term mortality following acute PE.

Effect of metabolic syndrome on mean pulmonary arterial pressures in patients with acute pulmonary embolism treated with catheter-directed thrombolysis

BACKGROUND

Metabolic syndrome (MetS) has been associated with a procoagulant and hypofibrinolytic state. Current data exploring the role of MetS in venous thromboembolism (VTE) are limited. The objective was to measure the prevalence of MetS in patients with acute PE receiving catheter-directed thrombolysis (CDT) and to investigate its effect on mean pulmonary arterial pressure and overall treatment success.

METHODS

We used a 3-year prospective registry of ED patients with acute PE with severity qualifying for activation of a PE response team (PERT). All patients had CDT with catheter-measured mPAP and angiography. The presence or absence of MetS components were extracted from chart review based on the following criteria: 1. body mass index (BMI) >30 kg/m²; 2. diagnosed hypertension; 3. diabetes mellitus (including HbA1c >6.5%) and; 4. dyslipidemia (including triglycerides >150 mg/dL or high-density lipoprotein <40 mg/dL).

RESULTS

Of the 134 patients, 85% met the criteria for at least one of four MetS components, with obesity being most common, present in 71%. Results demonstrated a positive concordance between the number of criteria for MetS and MPAP, both pre- and post-fibrinolysis, as pressures tended to increase with each additional MetS criterion. Multivariate regression analysis determined age (-), BMI (+) and hypertension (+) to be significant independent predictor variables for mPAP.

CONCLUSIONS

MetS was common in patients with more severe manifestations of PE and was associated with higher mPAP values both at diagnosis and following treatment with CDT.

Chronic thromboembolic pulmonary hypertension is a clot you cannot swat

A 49-year-old man with progressive dyspnea on exertion and a remote history of syncope presented with hypotension and acute right ventricular failure, and was ultimately diagnosed with acute pulmonary embolism. Laboratory data revealed a prolonged activated partial thromboplastin time, which confounded treatment options. He was ultimately diagnosed with anti-phospholipid syndrome and factor XII deficiency, and underwent a thromboendarterectomy procedure with resolution of right ventricular failure and symptoms. Careful attention to history, initial physical examination manifestations, and clinical data often permit a timely diagnosis of and treatment for chronic thromboembolic pulmonary hypertension.

Platelet-derived β2M regulates monocyte inflammatory responses

β-2 Microglobulin (β2M) is a molecular chaperone for the major histocompatibility class I (MHC I) complex, hemochromatosis factor protein (HFE), and the neonatal Fc receptor (FcRn), but β2M may also have less understood chaperone-independent functions. Elevated plasma β2M has a direct role in neurocognitive decline and is a risk factor for adverse cardiovascular events. β2M mRNA is present in platelets at very high levels, and β2M is part of the activated platelet releasate. In addition to their more well-studied thrombotic functions, platelets are important immune regulatory cells that release inflammatory molecules and contribute to leukocyte trafficking, activation, and differentiation. We have now found that platelet-derived β2M is a mediator of monocyte proinflammatory differentiation through noncanonical TGFβ receptor signaling. Circulating monocytes from mice lacking β2M only in platelets (Plt-β2M-/-) had a more proreparative monocyte phenotype, in part dependent on increased platelet-derived TGFβ signaling in the absence of β2M. Using a mouse myocardial infarction (MI) model, Plt-β2M-/- mice had limited post-MI proinflammatory monocyte responses and, instead, demonstrated early proreparative monocyte differentiation, profibrotic myofibroblast responses, and a rapid decline in heart function compared with WT mice. These data demonstrate a potentially novel chaperone-independent, monocyte phenotype-regulatory function for platelet β2M and that platelet-derived 2M and TGFβ have opposing roles in monocyte differentiation that may be important in tissue injury responses.

National trends and outcomes for extra-corporeal membrane oxygenation use in high-risk pulmonary embolism

Little is known about the temporal trends and outcomes for extra-corporeal membrane oxygenation (ECMO) in patients with high-risk pulmonary embolism (PE) in the United States. We queried the National Inpatient Sample (NIS) database from 2005 to 2013 to identify patients admitted with high-risk PE. Our objective was to determine trends for ECMO use in patients with high-risk PE. We also assessed in-hospital outcomes among patients with high-risk PE receiving ECMO. We evaluated 77,809 hospitalizations for high-risk PE. There was an upward trend in the utilization of ECMO from 0.07% in 2005 to 1.1% in 2013 ( p = 0.015). ECMO was utilized more in urban teaching hospitals and large hospitals. ECMO use was associated with lower mortality in patients with massive PE ( p < 0.001). In-hospital mortality for patients receiving ECMO was 61.6%, with no change over the observational period ( p = 0.68). Our investigation revealed several independent predictors of increased mortality in patients with high-risk PE using ECMO as hemodynamic support, including: age, female sex, obesity, congestive heart failure, and chronic pulmonary disease. ECMO, therefore, as a rescue strategy or bridge to definitive treatment, may be effective in the management of high-risk PE when selecting patients with favorable clinical characteristics.

Acetylcholine Inhibits Platelet Activation

Platelets are key mediators of thrombosis. Many agonists of platelet activation are known, but fewer endogenous inhibitors of platelets, such as prostacyclin and nitric oxide (NO), have been identified. Acetylcholinesterase inhibitors, such as donepezil, can cause bleeding in patients, but the underlying mechanisms are not well understood. We hypothesized that acetylcholine is an endogenous inhibitor of platelets. We measured the effect of acetylcholine or analogs of acetylcholine on human platelet activation ex vivo. Acetylcholine and analogs of acetylcholine inhibited platelet activation, as measured by P-selectin translocation and glycoprotein IIb IIIa conformational changes. Conversely, we found that antagonists of the acetylcholine receptor, such as pancuronium, enhance platelet activation. Furthermore, drugs inhibiting acetylcholinesterase, such as donepezil, also inhibit platelet activation, suggesting that platelets release acetylcholine. We found that NO mediates acetylcholine inhibition of platelets. Our data suggest that acetylcholine is an endogenous inhibitor of platelet activation. The cholinergic system may be a novel target for antithrombotic therapies.

Antithrombotic therapy in abdominal aortic aneurysm: beneficial or detrimental?

Abdominal aortic aneurysm (AAA) is a degenerative vascular pathology resulting in significant morbidity and mortality in older adults due to rupture and sudden death. Despite 150 000 new cases and nearly 15 000 deaths annually, the only approved treatment of AAA is surgical or endovascular intervention when the risk for aortic rupture is increased. The goal of the scientific community is to develop novel pharmaceutical treatment strategies to reduce the need for surgical intervention. Because most clinically relevant AAAs contain a complex structure of fibrin, inflammatory cells, platelets, and red blood cells in the aneurysmal sac known as an intraluminal thrombus (ILT), antithrombotic therapies have emerged as potential pharmaceutical agents for the treatment of AAA progression. However, the efficacy of these treatments has not been shown, and the effects of shrinking the ILT may be as detrimental as they are beneficial. This review discusses the prospect of anticoagulant and antiplatelet (termed collectively as antithrombotic) therapies in AAA. Herein, we discuss the role of the coagulation cascade and platelet activation in human and animal models of AAA, the composition of ILT in AAA, a possible role of the ILT in aneurysm stabilization, and the implications of antithrombotic drugs in AAA treatment.

Platelet factor 4 increases bone marrow B cell development and differentiation

Platelet factor 4 (PF4) is a megakaryocyte-/platelet-derived chemokine with diverse functions as a regulator of vascular and immune biology. PF4 has a central role in vessel injury responses, innate immune cell responses, and T-helper cell differentiation. We have now discovered that PF4 has a direct role in B cell differentiation in the bone marrow. Mice lacking PF4 (PF4^-/- mice) had fewer developing B cells in the bone marrow beginning after the pre-pro-B cell stage of differentiation. In vitro, PF4 increased the differentiation of hematopoietic progenitors to B cell lineage cells, indicating that PF4 has a direct effect on B cell differentiation. STAT5 activation is essential in early B cell development and PF4 increased the phosphorylation of STAT5. Taken together, these data demonstrate that PF4 has an important role in increasing B cell differentiation in the bone marrow environment.

The impact of a multi-specialty team for high risk pulmonary embolism on resident and fellow education

The impact of the Pulmonary Embolism Response Team (PERT) model on trainee physician education and autonomy over the management of high risk pulmonary embolism (PE) is unknown. A resident and fellow questionnaire was administered 1 year after PERT implementation. A total of 122 physicians were surveyed, and 73 responded. Even after 12 months of interacting with the PERT consultative service, and having formal instruction in high risk PE management, 51% and 49% of respondents underestimated the true 3-month mortality for sub-massive and massive PE, respectively, and 44% were unaware of a common physical exam finding in patients with PE. Comparing before and after PERT implementation, physicians perceived enhanced confidence in identifying ( p<0.001), and managing ( p=0.003) sub-massive/massive PE, enhanced confidence in treating patients appropriately with systemic thrombolysis ( p=0.04), and increased knowledge of indications for systemic thrombolysis and surgical embolectomy ( p=0.043 and p<0.001, respectively). Respondents self-reported an increased fund of knowledge of high risk PE pathophysiology (77%), and the perception that a multi-disciplinary team improves the care of patients with high risk PE (89%). Seventy-one percent of respondents favored broad implementation of a PERT similar to an acute myocardial infarction team. Overall, trainee physicians at a large institution perceived an enhanced educational experience while managing PE following PERT implementation, believing the team concept is better for patient care.

Hypoxia and Ischemia Promote a Maladaptive Platelet Phenotype

Supplemental Digital Content is available in the text.

Objective—

Reduced blood flow and tissue oxygen tension conditions result from thrombotic and vascular diseases such as myocardial infarction, stroke, and peripheral vascular disease. It is largely assumed that while platelet activation is increased by an acute vascular event, chronic vascular inflammation, and ischemia, the platelet activation pathways and responses are not themselves changed by the disease process. We, therefore, sought to determine whether the platelet phenotype is altered by hypoxic and ischemic conditions.

Approach and Results—

In a cohort of patients with metabolic and peripheral artery disease, platelet activity was enhanced, and inhibition with oral antiplatelet agents was impaired compared with platelets from control subjects, suggesting a difference in platelet phenotype caused by the disease. Isolated murine and human platelets exposed to reduced oxygen (hypoxia chamber, 5% O₂) had increased expression of some proteins that augment platelet activation compared with platelets in normoxic conditions (21% O₂). Using a murine model of critical limb ischemia, platelet activity was increased even 2 weeks postsurgery compared with sham surgery mice. This effect was partly inhibited in platelet-specific ERK5 (extracellular regulated protein kinase 5) knockout mice.

Conclusions—

These findings suggest that ischemic disease changes the platelet phenotype and alters platelet agonist responses because of changes in the expression of signal transduction pathway proteins. Platelet phenotype and function should, therefore, be better characterized in ischemic and hypoxic diseases to understand the benefits and limitations of antiplatelet therapy.

The platelet phenotype in patients with ST-segment elevation myocardial infarction is different from non-ST-segment elevation myocardial infarction

It is assumed that platelets in diseased conditions share similar properties to platelets in healthy conditions, although this has never been examined in detail for myocardial infarction (MI). We examined platelets from patients with ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation myocardial infarction (NSTEMI) compared with platelets from healthy volunteers to evaluate for differences in platelet phenotype and function. Platelet activation was examined and postreceptor signal transduction pathways were assessed. Platelet-derived plasma biomarkers were evaluated by receiver operator characteristic curve analysis. Maximum platelet activation through the thromboxane receptor was greater in STEMI than in NSTEMI but less through protease-activated receptor 1. Extracellular-signal related-kinase 5 activation, which can activate platelets, was increased in platelets from subjects with STEMI and especially in platelets from patients with NSTEMI. Matrix metalloproteinase 9 (MMP9) protein content and enzymatic activity were several-fold greater in platelets with MI than in control. Mean plasma MMP9 concentration in patients with MI distinguished between STEMI and NSTEMI (area under curve [AUC] 75% [confidence interval (CI) 60-91], P = 0.006) which was superior to troponin T (AUC 66% [CI 48-85, P = 0.08), predicting STEMI with 80% sensitivity (95% CI 56-94), 90% specificity (CI 68-99), 70% AUC (CI 54-86, P < 0.0001), and NSTEMI with 50% sensitivity (CI 27-70), 90% specificity (CI 68-99), 70% AUC (CI 54-86, P = 0.03). Platelets from patients with STEMI and NSTEMI show differences in platelet surface receptor activation and postreceptor signal transduction, suggesting the healthy platelet phenotype in which antiplatelet agents are often evaluated in preclinical studies is different from platelets in patients with MI.

Abstract 140: Real-time Modulation of Platelet Phenotype and Vein Wall Biology in Patients with Chronic Venous Insufficiency

Background: The role of antiplatelet agents in the modulation of arterial disease is well described, but a paucity of data exists regarding their role in chronic venous insufficiency (CVI). We hypothesize that platelet responses to various antiplatelet agents are altered when comparing platelet function within refluxing and non-refluxing vein segments. Additionally, changes in platelet phenotype may alter vein wall biology.

Methods: Isolated platelets were obtained simultaneously from the patient antecubital vein (ACV) and a refluxing greater saphenous vein (GSV) during surgical phlebectomy and compared to platelets from healthy individuals. Non-refluxing GSV was harvested for coronary bypass. Platelet surface receptor activation was assessed through P2Y12 (clopidogrel), PAR1 (vorapaxar), and thromboxane (aspirin) pathways by flow cytometry for p-selectin. Immunoblotting assessed CD41 (platelet) and CD45 (WBC) within the wall of vein samples.

Results: Platelets from refluxing GSV showed a significant increase in reactivity via all platelet signaling pathways, especially P2Y12 and thromboxane when compared to platelets from the ACV in the same patient. Conversely, platelets collected from the ACV in CVI patients showed a significant decrease in reactivity to all agonists compared to ACV in healthy individuals without CVI. Most notably, GSV from a patient with CVI had a reduction in CD41 content, but a seven-fold increase in the CD45:CD41 ratio, compared to GSV from healthy people (Figure).

Conclusions: Platelet activation by these clinically relevant pathways is enhanced locally in the refluxing GSV, yet systemic, circulating platelets isolated from CVI patients are 2-3-fold less active than systemic platelets from healthy people. Our data suggest that reflux may locally alter the circulating platelet phenotype and in turn also have a role in remodeling the vein wall.

Do elevated blood levels of omega-3 fatty acids modify effects of particulate air pollutants on fibrinogen?

Previously, we found short-term increases in ambient particulate matter (PM) air pollutant concentrations were associated with increased serum fibrinogen levels in patients with cardiac disease. We now studied whether high blood levels of omega-3 (ω-3) fatty acids blunted this fibrinogen response to increased PM concentrations in these same patients. Plasma fibrinogen and ω-3 fatty acid levels (% of total identified fatty acids) were measured in blood samples collected from 135 patients treated at the University of Rochester Medical Center for myocardial infarction or stable ischemic heart disease requiring cardiac catheterization. Using ambient measurements of ultrafine, accumulation mode, and fine particles (PM_2.5), Delta-C, and black carbon (BC), we regressed serum fibrinogen levels against pollutant concentrations over the previous 1-96 h, using interaction terms to estimate these associations separately for those with HIGH (> 5.12%) and LOWMED serum levels of ω-3 fatty acid (≤ 5.12%). Each 5.6 μg/m³ increase in PM_2.5 concentration in the previous hour was associated with a 3.1% increase in fibrinogen (95% CI = 1.5%, 4.7%) in those subjects with LOWMED total ω-3 fatty acid levels, but only a 0.9% increase (95% CI = - 1.5%, 3.2%) in patients with HIGH total ω-3 fatty acid levels. This same pattern was observed with fish oil-derived docosahexaenoic and eicosapentaenoic acids but not alpha-linolenic (from plant oil or seeds). A similar finding was observed with BC in the prior 24 h, but not other PM. Thus, increased blood levels of fish-based ω-3 fatty acids attenuated increases in fibrinogen associated with short-term increases in ambient PM.

Cancer and Thrombotic Risk: The Platelet Paradigm

Hematologic malignancies and solid tumors increase the risk of venous and arterial thrombosis and contribute greatly to patient morbidity and mortality. Thrombosis occurs when the intricate balance of circulating antithrombotic and prothrombotic blood elements are disrupted. In recent years, the interplay between paraneoplastic cells and platelets has become apparent, with a change in platelet phenotype causing dysregulated platelet activity. This review discusses mechanism of thrombosis in cancer, evidence for using drug therapy, and exciting research efforts to understand and hopefully control aberrant thrombotic events in patients with cancer.

Characterization of the Microbiome along the Gastrointestinal Tract of Growing Turkeys

The turkey microbiome is largely understudied, despite its relationship with bird health and growth, and the prevalence of human pathogens such as Campylobacter spp. In this study we investigated the microbiome within the small intestine (SI), caeca (C), large intestine (LI), and cloaca (CL) of turkeys at 6, 10, and 16 weeks of age. Eight turkeys were dissected within each age category and the contents of the SI, C, LI, and CL were harvested. 16S rDNA based QPCR was performed on all samples and samples for the four locations within three birds/age group were sequenced using ion torrent-based sequencing of the 16S rDNA. Sequencing data showed on a genus level, an abundance of Lactobacillus, Streptococcus, and Clostridium XI (38.2, 28.1, and 13.0% respectively) irrespective of location and age. The caeca exhibited the greatest microbiome diversity throughout the development of the turkey. PICRUSt data predicted an array of bacterial function, with most differences being apparent in the caeca of the turkeys as they matured. QPCR revealed that the caeca within 10 week old birds, contained the most Campylobacter spp. Understanding the microbial ecology of the turkey gastrointestinal tract is essential in terms of understanding production efficiency and in order to develop novel strategies for targeting Campylobacter spp.

Abstract 150: Hypoxia and Ischemia Promote a Maladaptive Platelet Phenotype

Background: An understudied area of platelet biology is that ischemic diseases such as peripheral vascular disease (PVD) can alter the platelet phenotype, and this may lead to unpredictable effects of anti-platelet agents.

Methods: Isolated murine and human platelets were exposed to a reduced oxygen environment (hypoxia chamber, 5% O 2 ). Platelet activation was assessed as mean fluorescence intensity (MFI) of surface p-selectin by flow cytometry, and morphologic changes by confocal microscopy. A murine model of critical limb ischemia (CLI) was used to assess changes in platelet activity in wild-type (WT) and in platelet ERK5 -/- mice. Limb blood flow was assessed by laser Doppler imaging. Hypoxia was additionally examined in mice by unilateral pneumonectomy. Western blotting was used to assess protein expression.

Results: In human platelets ex vivo at 5% O 2 , platelet activation increased to 5076 MFI±409 from 3548 MFI±187 at 20% O 2 (P=0.005). With the ERK5 inhibitor XMD892, platelet activation at 5% O 2 decreased from 5677 MFI±312 to 3175 MFI±247 (p=0.001). In a murine model of PVD, enhanced platelet activation was sustained for weeks vs. sham, and limb blood flow in platelet ERK5 -/- mice one week after ischemia was augmented by 26%: 0.61±0.03 vs 0.87±0.03 vs, WT mice (p=0.0002), with 50% less platelet activity. In mice with unilateral pneumonectomy vs. sham surgery, observed hypoxia was accompanied by increased platelet ERK5 activation coincident with enhanced platelet activation. In patients with CLI, augmented platelet activation in spite of aspirin treatment was observed via the thromboxane and the PAR1 receptors, and especially via P2Y 12 receptor.

Conclusions: Hypoxia and ischemic tissue injury, such as with critical limb ischemia, change the phenotype of the platelet, promoting a pro-thrombotic state that is partly dependent on platelet ERK5. Platelet phenotype and function should be better characterized in ischemic diseases.

Abstract 105: Association of Viscoelastic Material Properties and Extracellular Matrix Remodeling in Human Abdominal Aortic Aneurysmal Tissue

Objectives: Predicting rupture of abdominal aortic aneurysm (AAA) requires knowledge of both the rate of extracellular matrix (ECM) degradation and the pulsatile stress on the aortic tissue. The activity of matrix metallopeptidase 9 (MMP9) and its inhibitor, TIMP1, are associated with alterations in aortic ECM but it is unknown if these changes effect the dynamic viscoelastic properties. We hypothesize that increased levels of MMP9 within AAA tissue will be associated with a greater dynamic modulus (E*), as a surrogate of increased aortic wall stress.

Methods: Human aneurysmal aortic tissue was obtained at the time of open AAA repair (n=11) and age-matched non-aneurysmal cadavers (n=10). Uniaxial viscoelastic material properties were measured in the circumferential orientation under physiologic preload (110 mmHg) and cyclic strain (± 5%@1Hz). Quantitative histologic and immunohistochemistry were preformed using Fiji imaging software. Aortic MMP9 and TIMP1 content and activity were quantified using western blot and zymography.

Results: E* was greater (1862±464 vs 1362±405 kPa, p=0.02) in the AAA tissue as compared to non-aneurysmal tissue. AAA tissue contained less elastin (6.7±6.7 vs 23.4±8.7%, p=0.01) and a greater collagen/elastin ratio (19.9±20.6 vs 2.3±2.5%, p=0.05). Immunohistochemistry revealed 200% greater MMP9 content in the AAA tissue (Figure A & B, 0.61 vs 0.03%, p=0.03). Increased MMP9 content was confirmed using a western blot (0.43 vs 0.06 AU, p<0.01). No difference in relative MMP9 activity (4307 vs 2324 AU, p=0.25) or level of TIMP1 (0.03 vs 0.02, p=0.6) were observed. There was a positive linear correlation (Figure C, r 2 =0.47) between E* and MMP9 as determined by quantitative immunohistochemistry.

Conclusions: Our data suggests a positive relationship between E* and MMP9 content. Increased tissue stiffness may trigger MMP9 production resulting in a positive-feedback loop, progressively increasing aortic wall stress and rupture risk.

Associations between ambient wood smoke and other particulate pollutants and biomarkers of systemic inflammation, coagulation and thrombosis in cardiac patients

BACKGROUND

Increased particulate air pollution has been associated with both an increased risk of myocardial infarction (MI) and adverse changes in cardiac biomarkers. Up to 30% of ambient wintertime fine particles (PM_2.5) in Rochester, NY are from wood burning. Our study examined associations between ambient levels of a marker of wood smoke (Delta-C) and other particulate air pollutants and biomarkers of inflammation, coagulation and thrombosis.

METHODS

We measured blood concentrations of C-reactive protein (CRP), D-dimer, fibrinogen, P-selectin, platelet factor 4 (PF-4), von Willebrand factor (vWF), and myeloperoxidase (MPO) of 135 patients undergoing cardiac catheterization during the winters of 2011-2013. We coupled these data with hourly ambient concentrations of Delta-C, black carbon (BC; marker of traffic pollution), and ultrafine (10-100nm; UFP), accumulation mode (100-500nm; AMP), and fine particles (<2.5µm; PM_2.5). Using linear regression models, we estimated the change in each biomarker associated with increased pollutant concentrations at intervals between 1 and 96h preceding blood collection.

RESULTS

Each 0.13µg/m³ increase in Delta-C concentration in the prior 12h was associated with a 0.91% increase in fibrinogen levels (95% CI=0.23%, 1.59%), but unexpectedly in the prior 48h, each 0.17µg/m³ increase in Delta-C concentration was associated with a 2.75% decrease in MPO levels (95% CI=-5.13%,-0.37%). We did not see associations between Delta-C concentrations and any other biomarkers. Interquartile range (IQR) increases in PM_2.5, BC, UFP, and AMP concentrations were generally associated with increased CRP and fibrinogen, but not PF4, D-dimer, vWF, or P-selectin.

CONCLUSIONS

In a population of cardiac patients, we noted adverse changes in fibrinogen associated with increased concentrations of a marker of wood smoke. Increases in PM_2.5, BC, AMP, and UFP concentrations in the previous 96h were also associated with adverse changes in markers of systemic inflammation and coagulation, but not with markers of endothelial cell dysfunction or platelet activation.

Neprilysin inhibition: A brief review of past pharmacological strategies for heart failure treatment and future directions

Heart failure (HF) is a manifestation of aberrant vascular responses and remains a public health concern with a worldwide prevalence of around 23 million and a 5-year mortality numerically equivalent to many cancers. Over the last two decades, mortality from HF reached a plateau with current pharmaceutical agents and mechanical cardiac support. In the last several years, various "novel" pharmaceutical agents have been tested in clinical trials and ultimately met with disappointment, showing only incremental benefit in the treatment of HF. Designing a HF drug with enhanced efficacy over existing agents seemed like a Sisyphean task. Yet again, pharmaceutical chemists have demonstrated their prowess in lateral thinking by developing a vasoactive agent which is a co-crystallized compound of valsartan and sacubitril in a one-to-one molar ratio; the former molecule belongs to a family of agents that are the current standard of care for HF and the latter molecule is a novel agent which inhibits neprilysin - a neutral endopeptidase found in human plasma which alters neurohumoral responses. In July of 2015, a drug which is a combination of valsartan and sacubitril was formally licensed by the United States Food and Drug Administration for the treatment of HF. This review describes the evolution of HF medications focusing on rational drug design with the first HF medication, the beta-adrenergic receptor antagonist. We then discuss the biochemical and physiological properties of sacubitril/valsartan which likely lead to its dramatic ability to ameliorate HF mortality.

Glutamate Receptor Interacting Protein 1 Mediates Platelet Adhesion and Thrombus Formation

Thrombosis-associated pathologies, such as myocardial infarction and stroke, are major causes of morbidity and mortality worldwide. Because platelets are necessary for hemostasis and thrombosis, platelet directed therapies must balance inhibiting platelet function with bleeding risk. Glutamate receptor interacting protein 1 (GRIP1) is a large scaffolding protein that localizes and organizes interacting proteins in other cells, such as neurons. We have investigated the role of GRIP1 in platelet function to determine its role as a molecular scaffold in thrombus formation. Platelet-specific GRIP1^-/- mice were used to determine the role of GRIP1 in platelets. GRIP1^-/- mice had normal platelet counts, but a prolonged bleeding time and delayed thrombus formation in a FeCl₃-induced vessel injury model. In vitro stimulation of WT and GRIP1^-/- platelets with multiple agonists showed no difference in platelet activation. However, in vivo platelet rolling velocity after endothelial stimulation was significantly greater in GRIP1^-/- platelets compared to WT platelets, indicating a potential platelet adhesion defect. Mass spectrometry analysis of GRIP1 platelet immunoprecipitation revealed enrichment of GRIP1 binding to GPIb-IX complex proteins. Western blots confirmed the mass spectrometry findings that GRIP1 interacts with GPIbα, GPIbβ, and 14-3-3. Additionally, in resting GRIP1^-/- platelets, GPIbα and 14-3-3 have increased interaction compared to WT platelets. GRIP1 interactions with the GPIb-IX binding complex are necessary for normal platelet adhesion to a stimulated endothelium.

A Novel Anti-Inflammatory Effect for High Density Lipoprotein

High density lipoprotein has anti-inflammatory effects in addition to mediating reverse cholesterol transport. While many of the chronic anti-inflammatory effects of high density lipoprotein (HDL) are attributed to changes in cell adhesion molecules, little is known about acute signal transduction events elicited by HDL in endothelial cells. We now show that high density lipoprotein decreases endothelial cell exocytosis, the first step in leukocyte trafficking. ApoA-I, a major apolipoprotein of HDL, mediates inhibition of endothelial cell exocytosis by interacting with endothelial scavenger receptor-BI which triggers an intracellular protective signaling cascade involving protein kinase C (PKC). Other apolipoproteins within the HDL particle have only modest effects upon endothelial exocytosis. Using a human primary culture of endothelial cells and murine apo-AI knockout mice, we show that apo-AI prevents endothelial cell exocytosis which limits leukocyte recruitment. These data suggest that high density lipoprotein may inhibit diseases associated with vascular inflammation in part by blocking endothelial exocytosis.

Platelet Extracellular Regulated Protein Kinase 5 Is a Redox Switch and Triggers Maladaptive Platelet Responses and Myocardial Infarct Expansion

BACKGROUND

Platelets have a pathophysiologic role in the ischemic microvascular environment of acute coronary syndromes. In comparison with platelet activation in normal healthy conditions, less attention is given to mechanisms of platelet activation in diseased states. Platelet function and mechanisms of activation in ischemic and reactive oxygen species-rich environments may not be the same as in normal healthy conditions. Extracellular regulated protein kinase 5 (ERK5) is a mitogen-activated protein kinase family member activated in hypoxic, reactive oxygen species-rich environments and in response to receptor-signaling mechanisms. Prior studies suggest a protective effect of ERK5 in endothelial and myocardial cells after ischemia. We present evidence that platelets express ERK5 and that platelet ERK5 has an adverse effect on platelet activation via selective receptor-dependent and receptor-independent reactive oxygen species-mediated mechanisms in ischemic myocardium.

METHODS AND RESULTS

Using isolated human platelets and a mouse model of myocardial infarction (MI), we found that platelet ERK5 is activated post-MI and that platelet-specific ERK5(-/-) mice have less platelet activation, reduced MI size, and improved post-MI heart function. Furthermore, the expression of downstream ERK5-regulated proteins is reduced in ERK5(-/-) platelets post-MI.

CONCLUSIONS

ERK5 functions as a platelet activator in ischemic conditions, and platelet ERK5 maintains the expression of some platelet proteins after MI, leading to infarct expansion. This demonstrates that platelet function in normal healthy conditions is different from platelet function in chronic ischemic and inflammatory conditions. Platelet ERK5 may be a target for acute therapeutic intervention in the thrombotic and inflammatory post-MI environment.

Abstract 57: Platelet Extracellular-signal-regulated Kinase 5 is a Redox Switch which Regulates Myocardial Infarct Expansion via Matrix Metalloproteinases

Background: Dysregulated platelet activation in an ischemic microvascular environment may play a role in myocardial infarction (MI). Platelet receptor signaling is well-characterized, but mechanisms of receptor-independent activation, such as by reactive oxygen species (ROS) generated in ischemic conditions, are less well understood. We discovered that ERK5, a nuclear protein which is ROS-activated in others cells, is abundantly present in platelets. We investigated whether ERK5 could regulate platelet activation and thrombosis in healthy and diseased states.

Methods: Human and mouse platelets were stimulated with agonists including ADP, U46619, TRAP, convulxin, or ROS (H 2 O 2 or 5% O 2 ). ERK5 activity was assessed by immunoblotting. Platelet activation was assessed via fluorescent-activated cell sorting (FACS) for P-selectin or activated GPIIb/IIIa. Intravascular thrombus (pulmonary embolus) or mesenteric thrombus (oxidative injury) formation was assessed by ex vivo fluorescent imaging and in vivo intravital microscopy, respectively. MI was performed in wild-type (WT) and in platelet specific ERK5 deficient (ERK5 -/- ) mice by LAD coronary artery ligation. Left ventricular (LV) function was determined by echocardiography. Matrix metalloproteinase (MMP) activity was determined by in-gel zymography.

Results: Human and platelet ERK5 was activated by ROS and via the thrombin and thromboxane receptors, but not via the purinergic or collagen receptors. Murine in vivo thrombosis was regulated by platelet ERK5 only if the injury involved oxidative stress. MI in mice promoted sustained platelet activation over one week in an ERK5-dependent manner. Following MI, platelet ERK5 -/- mice had less reactive platelets, less platelet MMP activity and thromboxane production, attenuated MMP activity in the LV, less remodeling with smaller infarcts, and enhanced myocardial systolic performance.

Conclusions: ERK5 is an ischemic sensor in platelets which regulates ongoing platelet activation after MI as well as remodeling via myocardial microvasculature. These observations may explain ischemic microvascular aberrations like the no-reflow phenomenon following percutaneous coronary intervention, suggesting a novel pharmacologic target.

Ambient fine particulate air pollution triggers ST-elevation myocardial infarction, but not non-ST elevation myocardial infarction: a case-crossover study

Background

We and others have shown that increases in particulate air pollutant (PM) concentrations in the previous hours and days have been associated with increased risks of myocardial infarction, but little is known about the relationships between air pollution and specific subsets of myocardial infarction, such as ST-elevation myocardial infarction (STEMI) and non ST-elevation myocardial infarction (NSTEMI).

Methods

Using data from acute coronary syndrome patients with STEMI (n = 338) and NSTEMI (n = 339) and case-crossover methods, we estimated the risk of STEMI and NSTEMI associated with increased ambient fine particle (<2.5 um) concentrations, ultrafine particle (10-100 nm) number concentrations, and accumulation mode particle (100-500 nm) number concentrations in the previous few hours and days.

Results

We found a significant 18% increase in the risk of STEMI associated with each 7.1 μg/m³ increase in PM_2.5 concentration in the previous hour prior to acute coronary syndrome onset, with smaller, non-significantly increased risks associated with increased fine particle concentrations in the previous 3, 12, and 24 hours. We found no pattern with NSTEMI. Estimates of the risk of STEMI associated with interquartile range increases in ultrafine particle and accumulation mode particle number concentrations in the previous 1 to 96 hours were all greater than 1.0, but not statistically significant. Patients with pre-existing hypertension had a significantly greater risk of STEMI associated with increased fine particle concentration in the previous hour than patients without hypertension.

Conclusions

Increased fine particle concentrations in the hour prior to acute coronary syndrome onset were associated with an increased risk of STEMI, but not NSTEMI. Patients with pre-existing hypertension and other cardiovascular disease appeared particularly susceptible. Further investigation into mechanisms by which PM can preferentially trigger STEMI over NSTEMI within this rapid time scale is needed.

Regulation of blood flow by aspirin following muscle ischemia

BACKGROUND

The vascular endothelium secretes a balance of dilator and constrictor substances which regulate vascular tone. During ischemic stress, this balance changes. After a short period of ischemia, a protective mechanism known as reactive hyperemia (RH) contributes to a post-ischemic increase in blood flow. The agents regulating this phenomenon remain controversial.

AIM

The purpose of this study was to examine whether aspirin regulates vascular endothelial function following ischemia.

METHODS

Sixteen healthy volunteers presented for two visits, each serving as their own control, and randomized to receive 500 mg aspirin or placebo. Forearm blood flow (FBF) was measured at baseline and during reactive hyperemia (RH) which was induced by five minutes of arterial occlusion. Blood samples were analyzed for vWF and lipids.

RESULTS

After ischemia, RH was attenuated when subjects were pre-medicated with 500 mg aspirin compared to placebo: AUC[aspirin] = 1450 +/- 201 mL/100 mL tissue/min vs. AUC[pIacebo] = 2207 +/- 294 mL/100 mL tissue/min; (p < 0.05). Separation of the subjects with high HDL or low HDL levels resulted in a similar peak FBF response with placebo, but in the high-HDL group only, aspirin ingestion attenuated peak FBF after ischemia compared to the placebo condition (22.6 +/- 1.7 m/100 mL tissue/min vs. 33.5 +/- 3.2 mL/100 mL tissue/min, respectively) (p < 0.05).

CONCLUSIONS

Aspirin partially regulates the RH response following ischemia compared to placebo, and this effect appears to be more profound when adjusting for plasma HDL concentration in healthy individuals. This suggests that the post-ischemic RH response may be partially mediated by arachidonic acid-derived mediators such as the prostaglandins.

High-density lipoprotein metabolism and endothelial function

PURPOSE OF REVIEW

High-density lipoprotein (HDL) protects against atherosclerosis, transporting cholesterol from peripheral cells to the liver, where it is excreted into the bile. However, HDL also has prominent vascular protective effects.

RECENT FINDINGS

Recent studies have uncovered mechanisms through which HDL decreases vascular inflammation, boosts nitric oxide production, and inhibits thrombosis. The discovery that dysfunctional HDL can also have proinflammatory effects has uncovered a new aspect of HDL biology.

SUMMARY

Low-density lipoprotein is the primary target for drug therapy of dyslipidemias. Drugs that increase HDL also affect additional metabolic pathways. Development of selective drugs targeting key aspects of HDL metabolism may enable us to alter the composition of HDL and inhibit atherogenesis.

Interference in clinical chemistry assays by the hemoglobin-based oxygen carrier, Hemospan

OBJECTIVE

To evaluate interference by the hemoglobin-based oxygen carrier Hemospan on clinical laboratory assays.

DESIGN AND METHODS

Interfering Hemospan concentrations were determined for general chemistry and cardiac marker analytes in pooled serum and the corresponding hemolysis index was calculated.

RESULTS

Hemospan did not interfere with 20 of 35 analytes. Hemospan produced a negative interference in serum creatinine, amylase, alkaline phosphatase, uric acid, and GGT assays and a positive interference in serum phosphate, LDH, iron, triglycerides, total protein, AST, cholesterol, magnesium, and albumin assays, and appeared to positively bias the serum cardiac troponin I (cTnI) assay only when cTnI is present in the sample.

CONCLUSIONS

We present a report of assays affected by Hemospan and the threshold concentrations for interference. This study highlights the importance of interference studies in understanding the effects of hemoglobin-based oxygen carriers on results reported by the clinical laboratory.

Pseudohyponatremia in a patient with HIV and hepatitis C coinfection

Pseudohyponatremia refers to low serum sodium in the presence of normal plasma tonicity. Whereas pseudohyponatremia secondary to hyperlipidemia is a commonly recognized occurrence, falsely low sodium levels secondary to elevated protein are less frequently observed. We present in this paper the case of a man coinfected with HIV and hepatitis C who had pseudohyponatremia from hypergammaglobulinemia. As hypergammaglobulinemia is a frequent occurrence in both HIV and HCV, we suggest that pseudohyponatremia is an important and likely underdiagnosed phenomenon in this patient population. Clinicians need to be aware of the electrolyte exclusion effect and become familiar with the techniques used by their local laboratory in the measurement of serum electrolytes. Pseudohyponatremia should also be included in the differential diagnosis of an elevated osmolal gap, as the falsely lowered sodium level will lead to a falsely low calculated serum osmolality.

A multi-marker approach for the prediction of adverse events in patients with acute coronary syndromes

BACKGROUND

Cardiac troponin T (cTnT), high sensitivity C-reactive protein (hs-CRP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) have emerged as strong predictors of adverse events among patients presenting with acute coronary syndromes (ACS). We evaluated the prognostic performance of each of these markers, individually, and in combination in patients presenting to the emergency department (ED) with ACS symptoms.

METHODS

Serum samples were obtained from 422 consenting patients presenting to the ED with symptoms of acute coronary syndrome (ACS) and subsequently tested for cTnT, NT-proBNP, myoglobin, CK-MB, and hs-CRP. Adverse events (AEs) occurring within 30 days (death, myocardial infarction, unstable angina and the need for revascularization procedures) were recorded and ROC curves were constructed.

RESULTS

AEs occurred in 42 patients (10%). Relative risk, cut-off, and predictive values for each biomarker were determined statistically, with the exception of cTnT, where the concentration meeting the 99th percentile of a healthy population with a 10% coefficient of variation (0.03 ng/ml) was used. These cut-off values, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and relative risk (RR) were calculated. Sensitivity and RR for a panel of cTnT and NT-proBNP were 78.6% (66.2-91.0) and 4.7 (2.3-9.5), respectively.

CONCLUSIONS

If used alone, cTnT appeared to have greater prognostic value when compared to hs-CRP, NT-proBNP, myoglobin or CK-MB. The combination of cTnT and NT-proBNP performed better than the combination of cTnT and hs-CRP. When cTnT, NT-proBNP and hs-CRP were used as a panel, there was no significant improvement in prognostic performance over using cTnT and NT-proBNP together. Thus, in patients with suspected ACS, the measurement of both cTnT and NT-proBNP may have enhanced prognostic performance over using either marker in isolation.

Antibody to human leukocyte antigen triggers endothelial exocytosis

Although antibodies to HLA play a role in the pathogenesis of diseases processes such as rejection of transplanted organs, the precise mechanisms by which antibodies cause tissue injury are not completely understood. We hypothesized that antibodies to host tissues cause inflammation in part by activating endothelial exocytosis of granules that contain prothrombotic mediators such as von Willebrand Factor (VWF) and proinflammatory mediators such as P-selectin. To test this hypothesis, we treated human endothelial cells with murine monoclonal antibody W6/32 to HLA class I and then measured exocytosis by the release of VWF and the externalization of P-selectin. Antibody to HLA activates endothelial exocytosis in a dose-dependent manner over time. The biologically active complement split product, C5a, adds a slight but significant increase to antibody induction of exocytosis. Antibody to HLA alone or with C5a did not damage the cells. Cross-linking of HLA appears to play a role in the ability of antibody to activate exocytosis, because the W6/32 monovalent Fab fragment did not activate VWF release, but the bivalent Fab'2 was effective in triggering exocytosis. To explore the in vivo effects of antibody upon graft injury, we infused W6/32 Fab'2 antibody to human HLA into severe combined immunodeficient/beige mice that had been transplanted with human skin grafts. Antibody to HLA activated exocytosis and inflammation in human skin grafts. Our data show that antibody to host antigens can activate human endothelial cell exocytosis and leukocyte trafficking. By triggering vascular inflammation, antibody activation of exocytosis may play a role in transplant rejection.

Pre-Analytic Considerations for the Proper Assessment of Hormones of the Hypothalamic-Pituitary Axis in Epidemiological Research

There is growing epidemiological interest in hormones as predictors of chronic diseases. The correct handling and analysis of hormones can be cumbersome, and great care must be taken in these processes in order to gain the most information possible. Given differences in sampling, processing, and stability of the various hormonal assays, we sought to provide a comprehensive review to aid future epidemiological research. We have coupled a thorough literature search with our own analytical experience to outline common laboratory problems one must consider in analyzing the hormones of the hypothalamic-pituitary axis. In addition, we describe the benefits and limitations of using alternative media--including urine, saliva, and blood spots on filter paper--to measure endocrine hormones in epidemiological studies.

Assessment of BNP and NT-proBNP in emergency department patients presenting with suspected acute coronary syndromes

OBJECTIVES

The relationship between BNP and NT-proBNP among physiologically and clinically relevant demographic subgroups has never been clarified in the context of the emergency department (ED).

DESIGN AND METHODS

A blood sample taken from patients presenting to the E.D. with suspected acute coronary syndromes (ACS) was analyzed for BNP and NT-proBNP, and correlation between them was examined as an entire group then as subgroups according to gender, ethnicity, age, and comorbidity variables.

RESULTS

BNP and NT-proBNP correlate well (0.89, P < 0.0001) in a population of 420 patients and in patient subgroups with a history of various etiologies, including vascular disorders.

CONCLUSIONS

In general, BNP and NT-proBNP correlate very well in patients with suspected ACS and may aid in the risk stratification process in emergency departments.

HMG-CoA reductase inhibitors inhibit endothelial exocytosis and decrease myocardial infarct size

Three-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors protect the vasculature from inflammation and atherosclerosis by cholesterol dependent and cholesterol independent mechanisms. We hypothesized that HMG-CoA reductase inhibitors decrease exocytosis of Weibel-Palade bodies, endothelial cell granules whose contents promote thrombosis and vascular inflammation. We pretreated human aortic endothelial cells with simvastatin for 24 hours, then stimulated the cells with thrombin, and measured the amount of vWF released into the media. We then measured the effect of simvastatin on myocardial infarction in mice. Simvastatin decreased thrombin-stimulated Weibel-Palade body exocytosis by 89%. Simvastatin inhibited exocytosis in part by increasing synthesis of nitric oxide (NO), which S-nitrosylated N-ethylmaleimide sensitive factor (NSF), a critical regulator of exocytosis. Simvastatin treatment attenuated myocardial infarct size by 58% in wild-type but not eNOS knockout mice. Furthermore, simvastatin decreased endothelial exocytosis and neutrophil infiltration into ischemic-reperfused myocardium, which was mediated in part by P-selectin contained in Weibel-Palade bodies. However, simvastatin did not affect exocytosis and inflammation in myocardial infarcts of eNOS knockout mice. Inhibition of endothelial exocytosis is a novel mechanism by which HMG-CoA reductase inhibitors may reduce vascular inflammation, inhibit thrombosis, and protect the ischemic myocardium. These findings may explain part of the pleiotropic effects of statin therapy for patients with cardiovascular disease.

Dysprealbuminemic hyperthyroxinemia in a patient with hyperthyroid graves disease

Rare mutant forms of circulating albumin and prealbumin [transthyretin (TTR)] have increased binding affinity for thyroxine (T4). Patients with these variant plasma proteins, as a result of inherited mutations or as a paraneoplastic phenomenon, typically present with increased serum total T4 and, by some assay methodologies, an increased free T4 as well. Although these individuals are, in fact, euthyroid, nonspecific symptoms may lead to inappropriate treatment for hyperthyroidism. We present a 34-year-old woman in whom a mutant form of TTR with increased T4 binding affinity and coexisting Graves disease was present. Subsequent 131I therapy led to development of postablative hypothyroidism, which was obscured by her higher serum free T4 concentration. Circulating thyroid-binding globulin (TBG), albumin, and TTR concentrations were all within their respective reference limits. A T4-binding protein panel confirmed that TTR-bound T4 was significantly increased, whereas TBG- and albumin-bound T4 was normal, indicating that this patient had euthyroid dysprealbuminemic hyperthyroxinemia, which had been masked by the initial presentation of hyperthyroidism. These findings indicate that hypothyroidism can be masked by coexisting euthyroid dysprealbuminemic hyperthyroxinemia.

Evaluation of pregnancy-associated plasma protein A as a prognostic indicator in acute coronary syndrome patients

BACKGROUND

Higher circulating concentrations of pregnancy-associated plasma protein A (PAPP-A), a potential proatherosclerotic metalloproteinase, have been associated with increased risk for acute coronary syndrome (ACS). Our goal was to determine the ability of circulating concentrations of PAPP-A to predict adverse events in patients presenting to the Emergency Department (ED) with symptoms of ACS.

METHODS

A total of 346 patients with symptoms of ACS were included in the study. Serum samples obtained immediately after enrollment were analyzed for PAPP-A and cardiac troponin T (cTnT). The occurrence of adverse events during a 30-day follow-up period was recorded, and receiver-operating characteristic (ROC) curve analysis was performed to evaluate the prognostic characteristics of PAPP-A and cTnT.

RESULTS

A total of 33 (9.5 %) patients developed adverse events during the follow up period. At a cut-off concentration of 0.22 mIU/l, PAPP-A was a predictor of adverse events with a sensitivity and specificity (95% C.I.) of 66.7% (48.2-82.0) and 51.1% (45.4-56.8), respectively. The sensitivity and specificity of cTnT were 51.5% (33.6-69.2) and 82.1% (77.4-86.2), respectively, using a 0.01-ng/ml cut-off value, which was obtained using ROC analysis.

CONCLUSIONS

PAPP-A appears to be a modest predictor of adverse events in patients presenting to the ED with ACS symptoms, being inferior to cTnT in predicting adverse events in an ED setting. PAPP-A appears to be as sensitive as cTnT, but it is less specific.

Activation of big MAP kinase 1 (BMK1/ERK5) inhibits cardiac injury after myocardial ischemia and reperfusion

Big MAP kinase 1 (BMK1/ERK5) plays a critical role in pre-natal development of the cardiovascular system and post-natal eccentric hypertrophy of the heart. Of the two isoforms upstream of MAPK-kinase 5 (MEK5) known to exist, only the longer MEK5alpha isoform potently activates BMK1. We generated cardiac-specific constitutively active form of the MEK5alpha (CA-MEK5alpha transgenic (Tg) mice), and observed a 3 to 4-fold increase in endogenous BMK1 activation and hyperphosphorylation of connexin 43 in the ventricles of the Tg compared to wild-type mice. The CA-MEK5alpha-Tg-mice demonstrated a profoundly accelerated recovery of left ventricular developed pressure after ischemia/reperfusion. We propose a novel role for BMK1 in protecting the heart from ischemia/reperfusion-induced cardiac injury.

Differential role of MEK5alpha and MEK5beta in BMK1/ERK5 activation

Big mitogen-activated protein kinase 1/extracellular-regulated kinase 5 (BMK1/ERK5) is regulated sequentially by a series of upstream MAP kinase kinases (MEKs) in a signaling cascade. MEKs activate their downstream MAPK by phosphorylation of threonine and tyrosine in the T- X-Y motif. MEK5 is the upstream BMK1 kinase and exists as naturally occurring splice variants, MEK5alpha and MEK5beta. The full-length MEK5 (MEK5alpha) is 89 amino acids longer than MEK5beta at the N terminus, but the precise functional difference between the two splice variants is not known. Dual phosphorylation site mutation of MEK5alpha (Ser-311 --> Asp and Thr- 315 --> Asp; MEK5alpha(S311D/T315D)) activated BMK1, but the corresponding dual phosphorylation sites mutant of MEK5beta could not induce BMK1 kinase activation or nuclear translocation. Furthermore, MEK5beta inhibited epidermal growth factor-induced BMK1 activation and MEK5alpha(S311D/T315D)-induced MEF2 transcriptional activity. Both MEK5alpha and MEK5beta individually co-immunoprecipitated with BMK1, but the presence of MEK5beta prevented association of MEK5alpha with BMK1 suggesting a mechanistic basis for the dominant-negative behavior of MEK5beta on BMK1 activation. The ratio of MEK5alpha to MEK5beta expression was higher in cancer cell lines, and overexpression of MEK5beta-inhibited serum-induced DNA synthesis. These data suggest that alternative splicing of MEK5alpha and MEK5beta may play a critical role in BMK1 activation and subsequent cell proliferation.

Regulation of epidermal growth factor-induced connexin 43 gap junction communication by big mitogen-activated protein kinase1/ERK5 but not ERK1/2 kinase activation

The gap junction protein, Cx43, plays a pivotal role in coupling cells electrically and metabolically, and the putative phosphorylation sites that modulate its function are reflected as changes in gap junction communication. Growth factor stimulation has been correlated with a decrease in gap junction communication and a parallel activation of ERK1/2; the inhibition of epidermal growth factor (EGF)-induced Cx43 gap junction uncoupling was observed by using the MEK1/2 inhibitor, PD98059. Because 1) BMK1/ERK5, another MAPK family member also activated by growth factors, possesses a phosphorylation motif similar to ERK1/2, and 2) it has been reported that PD98059 can inhibit not only MEK1/2-ERK1/2 but also MEK5-BMK1 activation, we investigated whether BMK1 can regulate EGF-induced Cx43 gap junction uncoupling and phosphorylation, comparing this to the role of ERK1/2 on Cx43 function and phosphorylation induced by EGF. Selective activation or inactivation of ERK1/2 by using a constitutively active form or a dominant negative form of MEK1 did not regulate Cx43 gap junction coupling. In contrast, we found that BMK1, selectively activated by constitutively active MEK5alpha, induced gap junction uncoupling, and the inhibition of BMK1 activation by transfection of dominant negative BMK1 prevented EGF-induced gap junction uncoupling. Activated BMK1 selectively phosphorylates Cx43 on Ser-255 in vitro and in vivo, but not on S279/S282, which are reported as the consensus phosphorylation sites for MAPK. Furthermore, by co-immunoprecipitation, we found that BMK1 directly associates with Cx43 in vivo. These data indicate that BMK1 is more important than ERK1/2 in EGF-mediated Cx43 gap junction uncoupling by association and Cx43 Ser- 255 phosphorylation.

Downsizing-initiated job transfer of hospital nurses: how do the job transferees fare?

In this longitudinal panel study, the authors compared the reactions to hospital amalgamation of 66 nurses who had been transferred to a different unit for a downsizing-related reason (bumped/displaced, unit closed, redundancy) with the reactions of 181 nurses who remained on their same unit. Prior to any job transfers, the two groups perceived comparable levels of support and held similar attitudes towards their job and the hospital. Two years later, after job transfers had taken place, transferred nurses perceived significantly lower coworker support. They also reported a significantly greater decrease in organizational commitment than nurses who were not transferred. However, both groups reported a significant decrease between time a and time 2 in perceived organizational support, satisfaction with amount of work and career future, hospital identification, and organization trust. Overall, the results indicate that the downsizing associated with the amalgamation of the hospitals had a highly negative effects not only on those nurses who were transferred because of the downsizing but also on those nurses who remained on their original unit.

Developing a programme-review process for a baccalaureate nursing programme in Jordan

Programme review is one way of monitoring the quality of a programme of study and promoting the growth of nursing education. The Faculty of Nursing at the Jordan University of Science and Technology (JUST) demonstrated its professional maturity by participating in an international collaborative project with the University of Windsor in Canada, to review its baccalaureate programmes. This article outlines the rationale for undertaking a programme review and discusses key principles for inclusion in the development of such a process. It highlights some strategies for success, and suggests ways in which programmes can benefit from reviews and evaluations. This process has the potential to be used as a prototype for future reviews.

Advancing the Development of Human Resources in Nursing in Jordan

BACKGROUND

This article describes a collaborative international health and development program between a Jordanian and a Canadian university. It presents a human resource development model in Jordan that has been the basis for a variety of developmental activities for practicing nurses and nurse educators in academic and clinical settings.

METHOD

Reciprocal visits by leaders of the project, as well as continued collaboration between key members of the two universities were instrumental in ensuring success of this venture.

RESULTS

The activities implemented in this project culminated in the development of a pragmatic human resource development model that is sensitive to issues particularly relevant to the Jordanian culture.

CONCLUSION

The collaborative venture discussed in this article has enabled nurses and nurse educators to increase their academic and clinical skills and raised the profile of the nursing profession in Jordan.

An Arabic language version of the health promotion lifestyle profile

The purpose of this study was to assess the validity and reliability of an Arabic version of the Health-Promoting Lifestyle Profile instrument in Jordan, whose society and culture differ from that of North America, where the instrument was developed. The instrument was translated into Arabic, back-translated, and pilot tested to ascertain cultural sensitivity. The Arabic version was then evaluated using a convenience sample of 950 adults in the northern part of Jordan using a principal components factor analysis. The order of factors was not entirely identical to those isolated previously during the psychometric assessment of the English language version. Only the structure of three factors--self actualization, health responsibility--and exercise were the same as those obtained in the English version. The forced, six factor solution explained only 39.3% of the variance in the measure. The alpha reliability coefficients were 0.89 for the total scale and ranged from 0.85 to 0.60 for the subscales. It was concluded that the Arabic version of the Health-Promoting Lifestyle Profile has demonstrated initial reliability and validity. Further testing is recommended.

The impact of organizational downsizing on the job satisfaction of nurses

Professional nurses across Canada are being affected by health reform initiatives designed to deinstitutionalize the health care system. This panel study examined the impact this restructuring has had on nurses' overall job satisfaction as well as their satisfaction with various aspects of their job and work environment. The participants consisted of 345 nurses employed in 3 community hospitals in southwestern Ontario. Hospital downsizing had relatively little effect on overall job satisfaction, satisfaction with kind of work, amount of work, and physical work conditions. However, compared to before the downsizing, nurses reported a significant deterioration in satisfaction with their career future, hospital identification, supervision, and co-workers following the implementation of restructuring initiatives. We discuss the organizational and management implications of these findings and suggest ways that hospital administrators can minimize the negative effects of downsizing on nursing professionals.