Prediction of new-onset atrial fibrillation in patients with hypertrophic cardiomyopathy using proteomics profiling

Background

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac disorders and affects 1 in 200–500 individuals. HCM is known to be heterogeneous. Approximately 20–30% of patients with HCM develop atrial fibrillation (AF), which can lead to stroke and worsening of heart failure symptoms. As AF increases the risk of stroke by 8-fold, AF in HCM is a Class 1 indication for anticoagulation. Despite its high prevalence and clinical importance of early AF detection, there are no risk stratification tools available to predict new-onset AF in patients with HCM. Furthermore, it is still unknown which signaling pathways mediate AF in HCM. Proteomics profiling can determine concentrations of thousands of proteins and potentially reveal underlying molecular mechanisms of disease progression.

Purpose

To develop plasma proteomics-based model to predict new-onset AF in patients with HCM and to determine signaling pathways dysregulated in those who subsequently develop AF.

Methods

In this prospective, multi-center cohort study, we conducted plasma proteomics profiling of 5,032 proteins on 397 patients with HCM. We developed a proteomics-based random forest machine learning model to predict new-onset AF using samples from one institution (training set, n=278). We tested the predictive ability of the model using independent samples from the other institution (test set, n=119). We estimated the hazard ratio for new-onset AF using a Cox proportional hazards model comparing high- and low-risk groups as determined by the proteomics-based model. We also performed pathway analysis of proteins significantly (i.e., univariable P<0.05) associated with new-onset AF using a false discovery rate (FDR) threshold of 0.05.

Results

A total of 15 patients in the training set (5.4%) and 7 in the test set (5.9%) developed new-onset AF. Using the proteomics-based model developed in the training set, the area under the receiver-operating characteristic (ROC) curve to predict new-onset AF was 0.87 (95% confidence interval [CI] 0.77–0.98; Figure) in the test set. The sensitivity was 0.86 (95% CI 0.42–0.99) and the specificity was 0.77 (95% CI 0.68–0.84). In the test set, patients categorized as high-risk based on the proteomics model had a significantly higher rate of developing new-onset AF (hazard ratio 8.18; 95% CI 1.55–43.20; P=0.01). Pathway analysis revealed that the Ras-MAPK pathway was dysregulated in patients who subsequently developed AF (FDR=0.01; Table). Pathways involved in inflammation were also dysregulated.

Conclusions

This study serves as the first to demonstrate the ability of proteomics profiling to predict new-onset AF in patients with HCM, exhibiting dysregulation of both novel (e.g., Ras-MAPK) and known pathways in patients who subsequently experience AF. These results not only exhibit the utility of proteomics profiling for clinical risk stratification but also suggest mechanisms underlying the development of AF in HCM.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIH/NHLBI

Prediction of worsening heart failure in patients with hypertrophic cardiomyopathy using plasma proteomics profiling

Background

While hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease affecting 1 in 200–500 people, it is a heterogeneous disease. Only a subset of patients with HCM develop heart failure (HF; prevalence 35–50%). Prediction of worsening HF using clinical measures alone (e.g., cardiac imaging, genetic testing) remains limited. Furthermore, the underlying mechanism by which patients with HCM develop worsening HF has not been fully investigated. Proteomics profiling measures concentrations of thousands of proteins simultaneously and has been used to predict worsening of HF and to highlight which signaling pathways mediate worsening HF in non-HCM populations.

Purpose

In patients with HCM, we aimed to develop a plasma proteomics-based model to predict which patients with HCM would develop worsening HF and to identify signaling pathways that are differentially regulated in those who subsequently develop worsening HF.

Methods

We conducted a prospective cohort study in our multi-center biorepository of patients with HCM. We performed plasma proteomics profiling of 5032 proteins. We then developed a random forest model to predict worsening HF using proteomics profiling data from patients enrolled through one institution (training set). The outcome of worsening HF was defined as an increase in New York Heart Association functional class by at least 1 class. We externally validated this model in independent samples from patients enrolled through a different institution (test set). Further, we executed pathway analysis of proteins significantly dysregulated (i.e., univariable p<0.05) in patients who developed worsening HF compared to those who did not. Pathways with false discovery rate [FDR]<0.05 were considered to be dysregulated.

Results

There were 398 patients included in the study, with 278 in the training set and 120 in the test set. During a median follow-up of 1.8 years [interquartile range, 1.2–2.6], 60 (15%) patients developed worsening HF symptoms (45 patients in the training set and 15 patients in the test set). Using the proteomics-based model derived from the training set, the area under the receiver-operating-characteristic curve to predict worsening HF was 0.85 (95% confidence interval: 0.75–0.95) in the test set (Figure 1). Pathway analysis revealed that the Ras-MAPK pathway (FDR<0.00001) and its upstream PI3K-Akt pathway (FDR<0.00001) were dysregulated in patients who subsequently developed worsening HF (Figure 2).

Conclusions

Our study is the first to apply proteomics profiling to the prediction of worsening HF symptoms in patients with HCM, identifying patients who are at high risk of worsening HF and elucidating that the Ras-MAPK and related signaling pathways as potential underlying mechanisms. These findings support the potential application of proteomics profiling to clinical risk stratification and the investigation of signaling pathways underlying disease progression in HCM.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIH/NHLBI R01 grant

Proteomics profiling reveals signaling pathways associated with major adverse cardiovascular events in patients with hypertrophic cardiomyopathy

Background

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy affecting 1 in 200–500 people in the US. It is characterized by a diverse clinical course, and only a subset of patients with HCM experience major adverse cardiovascular events (MACE) such as arrhythmias (e.g., ventricular tachycardia/fibrillation [VT/VF], atrial fibrillation [AF]), stroke, and heart failure. However, the molecular mechanisms underlying the presence of MACE in HCM are still not well understood.

Purpose

Our aim was to reveal signaling pathways associated with prior MACE in patients with HCM by applying plasma proteomics profiling.

Methods

We conducted a multicenter case-control study of patients with HCM comparing those with and without a prior history of MACE. We performed plasma proteomics profiling of 5032 proteins. We defined prior MACE as a composite outcome of sustained VT/VF, AF, stroke/transient ischemic attack, left ventricular ejection fraction ≤50%, New York Heart Association functional class ≥2 symptoms, resuscitated cardiac arrest, or appropriate implantable cardioverter defibrillator therapy. We applied the random forest method to derive a proteomics-based discrimination model developed in patients enrolled at one institution (training set) and externally validated the model on patients enrolled at another institution (test set). We then performed pathway analysis of proteins differentially regulated in patients with prior MACE. Pathways with a false discovery rate (FDR) <0.05 with at least 5 associated proteins were declared positive.

Results

A total of 396 patients were included, with 278 in the training set and 118 in the test set. In this cohort, 251 (63%) patients had prior MACE (171 in the training set and 80 in the test set). Using the proteomics-based model derived from the training set, the area under the receiver operating characteristic curve was 0.81 (95% CI 0.73–0.88) in the test set (Figure 1). There were 632 differentially expressed proteins (univariable p<0.05). Pathway analysis identified significantly dysregulated pathways in patients with prior MACE (Figure 2). This included both pathways known to be associated with MACE (e.g., TGF-β [FDR=0.03]) and novel pathways (e.g., Ras-MAPK [FDR=0.01] and its upstream PI3K-Akt [FDR=7.7x10–7] pathways). Pathways involved in cellular metabolism/proliferation (e.g., HIF 1 [FDR=0.01] and Wnt [FDR=0.04] pathways) and inflammation (e.g., complement and coagulation cascades [FDR=2.7x10–21], cytokine-cytokine receptor interaction [FDR=8.1x10–16]) were also significantly dysregulated.

Conclusions

Our study in patients with HCM reveals that those with a prior history of MACE have a distinctive plasma proteomics profile. We further identified both previously known and novel pathways dysregulated in this subset with a more severe form of HCM. Our findings may aid in development of targeted therapies for the prevention of MACE in HCM.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): R01 HL157216

Prediction of major adverse cardiovascular events in patients with hypertrophic cardiomyopathy using proteomics profiling

Background

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac diseases, affecting 1 in 200–500 people in the US. HCM often causes major adverse cardiovascular events (MACE) – e.g., arrhythmias (atrial fibrillation, ventricular tachycardia/fibrillation), cerebrovascular accident, heart failure (HF), and sudden cardiac death (SCD). Although these HCM-related morbidities and mortality substantially affect the patients' quality and quantity of life, no systems are available to predict MACE. Furthermore, it remains unclear which signaling pathways mediate MACE.

Purpose

To prospectively determine protein biomarkers that predict MACE in patients with HCM and to identify signaling pathways differentially regulated in patients with HCM who subsequently develop MACE.

Methods

In this multi-center prospective cohort study of patients with HCM, we carried out plasma proteomics profiling of 4,979 proteins upon enrollment. We defined MACE as a composite of new-onset arrhythmias, cerebrovascular accident, increase in New York Heart Association class, HF death, SCD, and emergency department visit or non-elective hospitalization for HCM-related morbidities. We performed a sparse partial least squares discriminant analysis to develop a proteomics-based model to predict MACE using data from one institution (i.e., the training set). We tested the predictive ability in independent samples from the other institution (i.e., the test set) and performed time-to-event analysis. Additionally, we executed pathway analysis of the predictive proteins. A pathway was declared positive (i.e., dysregulated) if the false discovery rate (FDR) of the pathway was <0.01 and there were ≥5 proteins that map to the pathway.

Results

The study included 257 patients with HCM (n=186 in the training set; n=71 in the test set). The median follow-up duration was 2.5 years (interquartile range, 1.4–3.1 years). Each year, 11.7% of patients had MACE. Using the proteomics-based prediction model derived from the training set, the area under the receiver-operating-characteristic curve was 0.84 (95% confidence interval [CI] 0.72–0.96) in the test set (Figure 1). The sensitivity was 0.82 (95% CI, 0.72–0.91) and the specificity was 0.84 (95% CI, 0.79–0.89) in the test set. In the test set, high-risk group determined by the proteomics-based predictive model had significantly higher rate of developing MACE (hazard ratio 20.2; 95% CI 2.4–168; p=0.005; Figure 2). The Ras-MAPK and related pathways were upregulated in patients who subsequently developed MACE (FDR<0.001). Pathways involved in inflammation and fibrosis – e.g., the TGF-β pathway – were also upregulated.

Conclusions

This multi-center prospective cohort study with validation serves as the first to demonstrate the ability of proteomics profiling to predict MACE in HCM, exhibiting both novel (e.g., Ras-MAPK) and known (e.g., TGF-β) pathways that are differentially regulated in patients who subsequently experience MACE.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institute of Health, American Heart Association Figure 1Figure 2

The use of telemedicine in cardiogenetics clinical practice during the COVID-19 pandemic

Background

The coronavirus disease 2019 (COVID-19) pandemic has necessitated the widespread adoption of telemedicine, and while many clinics have now re-established in-person patient visits, telemedicine is likely to continue to play an important role in health care delivery. In particular, the embrace of telemedicine presents an unprecedented opportunity through which to expand the reach of genetic counseling, i.e., telegenetics.

Purpose

The aim of this study was to examine the impact of COVID-19 on genetic counseling practices within the cardiogenetics clinics at a large academic center in New York City.

Methods

We retrospectively analyzed clinical characteristics of patients who were seen for cardiovascular genetic counseling visits pre-pandemic between April 1, 2019 through December 23, 2019 and during the pandemic between April 1, 2020 through December 23, 2020 at Columbia University Irving Medical Center. Genetic testing results were recorded for each encounter when available.

Results

Overall, 104 patients had a cardiovascular genetic counseling visit in 2019 compared to 132 patients in 2020 (Table). Only 6% (n=6) of visits in 2019 were remote telemedicine encounters whereas 80% (n=106) of visits in 2020 were telemedicine encounters. There was a significant increase in the number of family members seen for genetic counseling in 2020; in 2019 only 15% (n=16) of the patients seen for genetic counseling were family members of probands whereas this percentage increased to 34% in 2020 (n=45; p=0.002). In addition, in 2020 the geographic reach of genetic counseling extended far beyond New York state, reaching a total of 11 states as well as one patient in Puerto Rico (Figure). Genetic testing results were similar between the two years with 29% of patients found to be genotype positive in 2019 and 29% of patients genotype positive in 2020 (p=0.91). Notably, of those patients who underwent telemedicine visits and were sent genetic testing kits (n=106), 14% (n=15) did not return a sample.

Conclusions

In this study we found that despite the health care delivery barriers created by the COVID-19 pandemic, the use of telemedicine allowed us to not only continue seeing patients for cardiovascular genetic counseling visits but also to expand the reach of genetic counseling and testing beyond the geographical boundaries of our previous catchment area. Telegenetics offers patients and clinicians convenience and flexibility and has likely earned its permanent place in clinical practice. Future efforts are warranted to study the longer-term clinical impacts of telegenetics as well as to continue to improve telemedicine technology, with the ultimate aim of increasing patient access to personalized genomic medicine.

Funding Acknowledgement

Type of funding sources: None.

Proteomics profiling reveals distinct molecular subtypes of hypertrophic cardiomyopathy with differential risks of major adverse cardiovascular events

Background

Hypertrophic cardiomyopathy (HCM) is a heterogeneous disease, and a subset (10–15%) of patients per year experience major adverse cardiovascular events (MACE). Current risk prediction models based solely on clinical data have yielded limited power in predicting MACE. Although the diagnosis of HCM is made based on clinical features, the heterogeneity of HCM suggests that “HCM” may actually encompass several subtypes of disease with distinct biological mechanisms that can only be elucidated via molecular-level investigation. Proteomics profiling measures concentrations of thousands of proteins simultaneously and has the potential to reveal underlying molecular mechanisms of disease and distinct subtypes of HCM.

Purpose

Our aim was to derive distinct subtypes of HCM in our multi-center biorepository of patients with HCM using proteomics profiling, and to examine their associations with MACE.

Methods

We applied unsupervised machine learning methods to derive HCM molecular subtypes using plasma proteomics profiling data from 258 patients in our multi-center HCM prospective cohort study. The primary outcome was MACE, defined as a composite of arrhythmias, progressive heart failure, stroke, and sudden cardiac death. We performed time-to-event analysis with a Cox proportional hazards model, using the subtype with the lowest risk as the reference group. We also performed pathway analysis of proteins differentially regulated in patients in the highest-risk subtype.

Results

We identified 4 distinct HCM subtypes. Patients in subtype D (n=74) were older on average compared to the other groups and more likely to be female. 50% of patients in subtype D had NYHA class II or greater heart failure symptoms compared to 37% in the rest of the groups combined. There were no significant differences in echocardiographic parameters or rates of genotype positivity between the four subtypes. Compared to the reference group (i.e., subtype A), patients in subtype D had a higher rate of MACE with a hazard ratio of 2.59 (95% CI 1.21–5.57, p=0.01 compared to subtype A; Figure). Pathway analysis identified significantly upregulated signaling pathways in the high-risk subtype D compared to the other subtypes (Table), with a number of upstream and downstream pathways associated with the Ras-MAPK pathway (FDR 0.0005).

Conclusions

Our study exhibits not only the presence of HCM molecular subtypes but also their distinct pathobiological mechanisms associated with different MACE risks. The four subtypes identified bore similar clinical characteristics and would not have been distinguishable based on the conventional analysis of clinical and echocardiographic parameters alone, but rather required deeper investigation at the molecular level. Furthermore, pathway analysis revealed an upregulation of Ras-MAPK pathways in the subtype with the highest risk of MACE, implicating this pathway as a potential underlying mechanism of more severe disease.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): NIH

Comprehensive proteomics profiling reveals molecular pathways that are differentially regulated in hypertrophic cardiomyopathy and correlate with clinical markers of disease severity

Background

Hypertrophic cardiomyopathy (HCM) is caused by mutations in the genes coding for proteins essential in normal myocardial contraction. However, it remains unclear through which molecular pathways gene mutations mediate the development and progression of HCM.

Purpose

To determine protein biomarkers and molecular pathways that are differentially regulated in HCM and correlated with disease severity.

Methods

We conducted a multicenter case-control study of cases with HCM and controls with hypertensive left ventricular hypertrophy. We carried out plasma proteomics profiling of 1681 proteins using the SOMAscan assay. We performed a sparse partial least squares discriminant analysis to develop a proteomics-based discrimination model with data from 1 institution (i.e., the training set). We tested the discriminative ability in independent samples from the other institutions (i.e., the test set). We executed pathway analysis using significantly dysregulated proteins with Bonferroni-corrected p<0.05. Pathways with false discovery rate (FDR) <0.05 and dysregulation of ≥5 member proteins were declared positive. In HCM, we also identified proteins with significant correlation with clinical markers of disease severity (e.g., New York Heart Association [NYHA] class, left atrial diameter) and performed pathway analysis.

Results

The study included 266 cases and 167 controls (n=308 in the training set; n=125 in the test set). Using the proteomics-based model derived from the training set, the area under the receiver-operating-characteristic curve was 0.89 (95% confidence interval [CI] 0.83–0.94, p<0.001) in the test set (Figure). The sensitivity was 0.84 (95% CI 0.76–0.92) and the specificity was 0.78 (95% CI 0.66–0.90). A total of 508 proteins were significantly associated with the disease status. As shown in the Table, pathway analysis revealed that the Ras-MAPK pathway, along with its upstream and downstream (e.g., Rap1, PI3K-Akt) pathways, was upregulated in HCM (FDR <0.001). Pathways involved in inflammation and fibrosis – e.g., the TGF-β pathway – were also found to be upregulated in HCM. In patients with HCM, 207 out of the 1681 proteins were significantly correlated with NYHA functional class. This number is more than twice as large as what would be expected by chance (i.e., 84 proteins at α=0.05 level). Pathway analysis of these 207 proteins showed upregulation of the Ras-MAPK and related pathways – e.g., PI3K-Akt, Rap1, and TNF. Similarly, 264 of the 1681 proteins were correlated with left atrial diameter in HCM. Pathway analysis of the 264 proteins revealed upregulation of the MAPK and the PI3K-Akt pathways.

Conclusions

This multicenter case-control study with independent validation serves as the largest-scale investigation with the most comprehensive proteomics profiling in HCM, exhibiting both novel (e.g., Ras-MAPK) and known (e.g., TGF-β) pathways that are differentially regulated in HCM and correlated with disease severity.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institute of Health and American Heart Association Figure 1. ROC curveTable 1. Differentially regulated pathways

Comprehensive proteomics profiling identifies patients with late gadolinium enhancement on cardiac magnetic resonance imaging in the hypertrophic cardiomyopathy population

Introduction

Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR) represents myocardial fibrosis. In patients with hypertrophic cardiomyopathy (HCM), LGE on CMR has been associated with an increased risk of sudden cardiac death (SCD), which can be prevented with implantable cardioverter-defibrillators. Yet, CMR is expensive, resource-intensive, and, in certain patients, contraindicated. Therefore, it is important to determine which patients with HCM have a high pre-test probability of LGE on CMR. Proteomics profiling is a recently developed technology that simultaneously measures thousands of protein concentrations in plasma with a single blood draw. To date, no studies have examined the ability of proteomics profiling to identify which patients with HCM are more likely to have LGE on CMR.

Purpose

To test the hypothesis that plasma proteomics profiling can distinguish patients with and without LGE on CMR in the HCM population.

Methods

We performed a multicenter case-control (i.e., LGE vs. no LGE) study of 147 patients with HCM who underwent CMR between July 2006 and October 2020. We carried out plasma proteomics profiling of 4979 proteins using the SOMAscan assay. Using the 17 most discriminant proteins, we performed logistic regression analysis with elastic net regularization to develop a discrimination model with data from 1 institution (the training set; n=111) and tested the discriminative ability in independent samples from the other institution (the test set; n=36). We calculated the area under the receiver-operating-characteristic curve (AUC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Furthermore, we performed pathway analysis of proteins that were differentially regulated between patients with and without LGE with p<0.05.

Results

The mean age was 57 years and 67% were male. Overall, 82 of the 147 patients (56%) had LGE on CMR. The AUC of the 17-protein model was 0.83 (95% CI, 0.75–0.90) in the training set and 0.71 in the independent test set for validation (95% CI, 0.54–0.88; Figure). The sensitivity, specificity, PPV, and NPV are shown in the Figure. The pathway analysis revealed that multiple signaling pathways were dysregulated in patients with LGE (Table). The list included signaling pathways that have been previously associated with myocardial fibrosis (e.g., pathways related to inflammation) and previously unrecognized pathways (e.g., glycolysis, amino acid metabolism).

Conclusions

In this multicenter study of 147 patients with HCM, comprehensive proteomics profiling identified a panel of 17 plasma protein biomarkers to specify patients with LGE on CMR and revealed associated signaling pathways. This 17-protein plasma protein biomarker panel would help physicians specify patients with LGE, in whom CMR is more likely to change the clinical management of HCM.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institute of Health, USA

Non-random sampling leads to biased estimates of transcriptome association

Integration of independent data resources across -omics platforms offers transformative opportunity for novel clinical and biological discoveries. However, application of emerging analytic methods in the context of selection bias represents a noteworthy and pervasive challenge. We hypothesize that combining differentially selected samples for integrated transcriptome analysis will lead to bias in the estimated association between predicted expression and the trait. Our results are based on in silico investigations and a case example focused on body mass index across four well-described cohorts apparently derived from markedly different populations. Our findings suggest that integrative analysis can lead to substantial relative bias in the estimate of association between predicted expression and the trait. The average estimate of association ranged from 51.3% less than to 96.7% greater than the true value for the biased sampling scenarios considered, while the average error was - 2.7% for the unbiased scenario. The corresponding 95% confidence interval coverage rate ranged from 46.4% to 69.5% under biased sampling, and was equal to 75% for the unbiased scenario. Inverse probability weighting with observed and estimated weights is applied as one corrective measure and appears to reduce the bias and improve coverage. These results highlight a critical need to address selection bias in integrative analysis and to use caution in interpreting findings in the presence of different sampling mechanisms between groups.

Psoriasis is associated with decreased plasma adiponectin levels independently of cardiometabolic risk factors

BACKGROUND

Psoriasis is an inflammatory skin disease that may be associated with an adverse cardiometabolic profile including modulated plasma adiponectin and leptin levels. Whether these levels are independent of cardiometabolic risk factors, which are also prevalent in psoriasis, is not known.

METHODS

A consecutive sample of 122 participants with varying degrees of psoriasis severity, and a random sample of 134 participants without psoriasis, were recruited for this case-control study. Cardiometabolic risk factors including traditional cardiovascular risk factors, waist circumference, insulin resistance, and total plasma adiponectin and leptin were measured. Total plasma adiponectin and leptin levels were compared in unadjusted and adjusted analyses by psoriasis status.

RESULTS

Participants with psoriasis had mostly mild disease and were mainly on topical therapies, but still had a more adverse cardiometabolic profile compared with those without psoriasis. Furthermore, plasma adiponectin levels were significantly lower in participants with psoriasis than those without {7.13 μg/mL [interquartile range (IQR) 4.9-11.3) vs. 14.5 μg/mL (IQR 8.4-24.1); P < 0.001]}. Plasma leptin (ng/mL) levels were higher in the psoriasis group but this did not reach statistical significance [11.3 (IQR 6.4-21.8) vs. 9.8 (IQR 4.9-20.5); P = 0.07]. In multivariable modelling, plasma adiponectin levels were still negatively associated with psoriasis status after adjusting for waist size (% difference = -41.2%, P < 0.001), insulin resistance (% difference = -39.5%, P < 0.001), and both waist size and insulin resistance (% difference = -38.5%, P < 0.001).

CONCLUSIONS

Plasma levels of adiponectin were lower in psoriasis, and this relationship persisted after adjusting for cardiometabolic risk factors known to decrease adiponectin levels. These findings suggest that inflammation present in psoriasis may be associated with adipose tissue dysfunction; however, direct studies of adipose tissue are needed to confirm this.

Dietary isoflavone intake is associated with evoked responses to inflammatory cardiometabolic stimuli and improved glucose homeostasis in healthy volunteers

BACKGROUND AND AIMS

Consumption of foods that modulate inflammatory stress in genetically-prone individuals may influence development of cardiometabolic diseases. Isoflavones in soy-derived foods function as phytoestrogens, have antioxidant and anti-inflammatory activity, inhibit protein-tyrosine kinase activity, and may be atheroprotective. We examined the relationship between soy food consumption and inflammatory responses to endotoxemia, postprandial responses to oral lipid tolerance test (OLTT), and insulin sensitivity from frequently sampled intravenous tolerance tests (FSIGTT).

METHODS AND RESULTS

We administered low-dose endotoxin (LPS 1 ng/kg) to induce transient endotoxemia in young, healthy volunteers (N = 215) of African (AA), and European (EA) ancestry as part of the GENE Study. We further supported these findings in two independent samples: the MECHE Study and NHANES. Soy food consumption was a significant predictor of peak cytokine response following LPS. Individuals with moderate-high (>1.48 mg/day, N = 65) vs. low-no (<1.48 mg/day, N = 150) isoflavone consumption had significantly higher tumor necrosis factor alpha (TNFα) post-LPS (AUC, P = 0.009). Further, high-isoflavone consumers were protected against inflammation-induced decline in insulin sensitivity (SI) in GENE. We observed significant differences by soy consumption in the interferon gamma (IFNγ) response to OLTT, and the insulin response to OGTT in MECHE, as well as significantly lower fasting insulin, and 2-hour glucose post-OGTT in EA NHANES subjects.

CONCLUSION

We demonstrate that soy consumption may influence inflammatory and metabolic responses. In research of nutritional exposures, measuring evoked phenotypes may be more informative than describing resting characteristics. The GENE Study was registered under NCT00953667 and the MECHE Study under NCT01172951, both at clinicaltrials.gov.

The renaissance of the experimental analysis of human behavior

Ten years ago, a number of authors commented on the dismal state of the basic research area known as the experimental analysis of human behavior (EAHB). At that time, data on the number of research articles using human subjects published in the Journal of the Experimental Analysis of Behavior (JEAB) indicated little progress since the early 1960s. However, updated publication data through 1991 reveal that EAHB research has accelerated in the last decade, reaching a peak of nearly half of all research articles published in JEAB, with an increasing trend evident. The increase in this percentage is not due solely to a long-term declining trend in the total number of experimental articles in JEAB using either human or nonhuman subjects, a trend that appears to have slowed or stabilized in the last 6 years. These data indicate that the EAHB has made dramatic progress in a decade and is healthy and growing.

Identification of craniofacial risk factors for obstructive sleep apnoea using three-dimensional MRI

The alteration of craniofacial structures has been associated with obstructive sleep apnoea (OSA). We hypothesised that: 1) a smaller mandible is a risk factor for OSA; and 2) the previously observed inferiorly positioned hyoid bone in apnoeics is associated with enlarged tongue volume. This is a case-control study using three-dimensional magnetic resonance imaging cephalometry. 55 apneics and 55 controls were matched for age, sex and race. The analysis was stratified by sex and controlled for age, race, height, neck visceral fat, skeletal type and tongue volume. We found that a 1-sd increase in mandibular length and depth were associated with decreased risk of sleep apnoea (OR 0.52, 95% CI 0.28-0.99 and OR 0.46, 95% CI 0.23-0.91, respectively) in males but not in females. Greater hyoid-to-nasion (OR 2.64, 95% CI 1.19-5.89 in males and OR 5.01, 95% CI 2.00-12.52 in females) and supramentale-to-hyoid (OR 2.39, 95% CI 1.12-5.14) in males and OR 3.38, 95% CI 1.49-7.68 in females) distances were associated with increased risk of OSA. The difference for hyoid position between apnoeics and controls was lost after controlling for tongue volume. Enlargement of tongue is likely to be the pathogenic factor for inferior-posterior positioning of hyoid. A small and shallow mandible is an independent risk factor for OSA in males but not in females.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Mean platelet volume as a predictor of cardiovascular risk: a systematic review and meta-analysis

AIM

To determine whether an association exists between mean platelet volume (MPV) and acute myocardial infarction (AMI) and other cardiovascular events. Platelet activity is a major culprit in atherothrombotic events. MPV, which is widely available in clinical practice, is a potentially useful biomarker of platelet activity in the setting of cardiovascular disease.

METHODS AND RESULTS

We performed a systematic review and meta-analysis investigating the association between MPV and AMI, all-cause mortality following myocardial infarction, and restenosis following coronary angioplasty. Results were pooled using random-effects modeling. Pooled results from 16 cross-sectional studies involving 2809 patients investigating the association of MPV and AMI indicated that MPV was significantly higher in those with AMI than those without AMI [mean difference 0.92 fL, 95% confidence interval (CI) 0.67-1.16, P < 0.001). In subgroup analyses, significant differences in MPV existed between subjects with AMI, subjects with stable coronary disease (P < 0.001), and stable controls (P < 0.001), but not vs. those with unstable angina (P = 0.24). Pooled results from three cohort studies involving 3184 patients evaluating the risk of death following AMI demonstrated that an elevated MPV increased the odds of death as compared with a normal MPV (11.5% vs. 7.1%, odds ratio 1.65, 95% CI 1.12-2.52, P = 0.012). Pooled results from five cohort studies involving 430 patients who underwent coronary angioplasty revealed that MPV was significantly higher in patients who developed restenosis than in those who did not develop restenosis (mean difference 0.98 fL, 95% CI 0.74-1.21, P < 0.001).

CONCLUSIONS

Elevated MPV is associated with AMI, mortality following myocardial infarction, and restenosis following coronary angioplasty. These data suggest that MPV is a potentially useful prognostic biomarker in patients with cardiovascular disease. Whether the relationship is causal, and whether MPV should influence practice or guide therapy, remains unknown.

Mixed modeling and multiple imputation for unobservable genotype clusters

Understanding the genetic contributions to complex diseases will require consideration of interaction across multiple genes and environmental factors. At the same time, capturing information on allelic phase, that is, whether alleles within a gene are in cis (on the same chromosome) or in trans (on different chromosomes), is critical when using haplotypic approaches in disease association studies. This paper proposes a combination of mixed modeling and multiple imputation for assessing high-order genotype-phenotype associations while accounting for the uncertainty in phase inherent in population-based association studies. This method provides a flexible statistical framework for controlling for potential confounders and assessing gene-environment and gene-gene interactions in studies of unrelated individuals where the haplotypic phase is generally unobservable. The proposed method is applied to a cohort of 626 subjects with human immunodeficiency virus (HIV) to assess the potential contribution of four genes, apolipoprotein-C-III, apolipoprotein-E, endothelial lipase and hepatic lipase in predicting lipid abnormalities. A simulation study is also presented to describe the method performance.

Prothrombotic factors enhance heparin-induced thrombocytopenia and thrombosis in vivo in a mouse model

BACKGROUND

Heparin-induced thrombocytopenia/thrombosis (HIT/T) is a common cause of life- and limb-threatening thrombosis. The development of antibodies that react with complexes of heparin and platelet factor 4 (PF4) is fundamental to the development of the disease. However, anti-PF4/heparin antibodies are far more common than is HIT/T and there is less understanding of the factors that contribute to thrombosis in only a subset of patients.

OBJECTIVES

Both qualitative and quantitative differences in multiple factors (e.g. antibodies, heparin and platelets) may influence the clinical course of patients who develop anti-PF4/heparin antibodies. We examined the hypothesis that host-specific factors, such as comorbid prothrombotic conditions, would exacerbate the pathologic effects of anti-PF4/heparin antibodies.

METHODS AND RESULTS

A mouse model transgenic for human Fcgamma RIIa and PF4 and null for mouse PF4 was used to study the influence of prothrombotic conditions on the effects of anti-PF4/heparin antibodies in vivo. To simulate a prothrombotic milieu, mice were fed a hypercholesterolemic diet (HD). HD-fed mice had elevated plasma cholesterol, increased platelet reactivity and increased endothelial activation relative to mice fed a standard diet (SD). Age- and sex-matched mice from each diet group were treated with an anti-PF4/heparin antibody and heparin. HD-fed mice developed more severe thrombocytopenia than similarly treated SD-fed mice. Mice with moderate to severe thrombocytopenia had elevated plasma levels of thrombin-antithrombin complexes, indicative of increased thrombin generation in vivo. Platelet-fibrin thrombi were observed in multiple organs of HD-fed mice that developed severe thrombocytopenia.

CONCLUSIONS

Host-specific factors, such as prothrombotic changes in platelet reactivity and/or endothelial activation, may influence the development of thrombosis in a subset of patients who develop anti-PF4/heparin antibodies.

A study of aspirin and clopidogrel in idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is characterised by in situ thrombosis and increased thromboxane (Tx) A2 synthesis; however, there are no studies of antiplatelet therapy in IPAH. The aim of the current study was to determine the biochemical effects of aspirin (ASA) and clopidogrel on platelet function and eicosanoid metabolism in patients with IPAH. A randomised, double-blind, placebo-controlled crossover study of ASA 81 mg once daily and clopidogrel 75 mg once daily was performed. Plasma P-selectin levels and aggregometry were measured after exposure to adenosine diphosphate, arachidonic acid and collagen. Serum levels of TxB2 and urinary metabolites of TxA2 and prostaglandin I2 (Tx-M and PGI-M, respectively) were assessed. A total of 19 IPAH patients were enrolled, of whom nine were being treated with continuous intravenous epoprostenol. ASA and clopidogrel significantly reduced platelet aggregation to arachidonic acid and adenosine diphosphate, respectively. ASA significantly decreased serum TxB2, urinary Tx-M levels and the Tx-M/PGI-M ratio, whereas clopidogrel had no effect on eicosanoid levels. Neither drug significantly lowered plasma P-selectin levels. Epoprostenol use did not affect the results. In conclusion, aspirin and clopidogrel inhibited platelet aggregation, and aspirin reduced thromboxane metabolite production without affecting prostaglandin I2 metabolite synthesis. Further clinical trials of aspirin in patients with idiopathic pulmonary arterial hypertension should be performed.

An evaluation of ultrasound imaging for identification of lumbar intervertebral level

The accuracy of ultrasound imaging to identify lumbar intervertebral level was assessed in 50 patients undergoing X-ray of the lumbar spine. Using an ultraviolet marker, an anaesthetist attempted to mark the L2/3, L3/4 and L4/5 intervertebral spaces. A radiologist unaware of these marks attempted to mark the same spaces with the aid of ultrasound imaging. X-ray-visible pellets were taped to the back at the various marks prior to lateral lumbar X-ray. Ultrasound imaging identified the correct level in up to 71% of cases, but palpation was successful in only 30% (p < 0.001). Up to 27% of marks using the palpation method were more than one spinal level above or below the assumed level using palpation, but none were more than one level high or low using ultrasound guidance.

No thanks, I'm good. Any more and I'll be sick: comment on Lynch and Carroll (2001)

W. J. Lynch and M. E. Carroll's (2001) excellent analyses of drug intake from a regulation perspective are formalized in terms of control systems. Satiation corresponds to the set point, deviations below which are called hunger or craving, deviations above which are called surfeit. Although simple, the model provides a unifying framework for many of the phenomena Lynch and Carroll describe.

Cyclooxygenase inhibitors and the antiplatelet effects of aspirin

BACKGROUND

Patients with arthritis and vascular disease may receive both low-dose aspirin and other nonsteroidal antiinflammatory drugs. We therefore investigated potential interactions between aspirin and commonly prescribed arthritis therapies

METHODS

We administered the following combinations of drugs for six days: aspirin (81 mg every morning) two hours before ibuprofen (400 mg every morning) and the same medications in the reverse order; aspirin two hours before acetaminophen (1000 mg every morning) and the same medications in the reverse order; aspirin two hours before the cyclooxygenase-2 inhibitor rofecoxib (25 mg every morning) and the same medications in the reverse order; enteric-coated aspirin two hours before ibuprofen (400 mg three times a day); and enteric-coated aspirin two hours before delayed-release diclofenac (75 mg twice daily)

RESULTS

Serum thromboxane B(2) levels (an index of cyclooxygenase-1 activity in platelets) and platelet aggregation were maximally inhibited 24 hours after the administration of aspirin on day 6 in the subjects who took aspirin before a single daily dose of any other drug, as well as in those who took rofecoxib or acetaminophen before taking aspirin. In contrast, inhibition of serum thromboxane B(2) formation and platelet aggregation by aspirin was blocked when a single daily dose of ibuprofen was given before aspirin, as well as when multiple daily doses of ibuprofen were given. The concomitant administration of rofecoxib, acetaminophen, or diclofenac did not affect the pharmacodynamics of aspirin

CONCLUSIONS

The concomitant administration of ibuprofen but not rofecoxib, acetaminophen, or diclofenac antagonizes the irreversible platelet inhibition induced by aspirin. Treatment with ibuprofen in patients with increased cardiovascular risk may limit the cardioprotective effects of aspirin.

Heparin-induced thrombocytopenia/thrombosis in a transgenic mouse model requires human platelet factor 4 and platelet activation through FcgammaRIIA

Heparin-induced thrombocytopenia/thrombosis (HIT/HITT) is a severe, life-threatening complication that occurs in 1% to 3% of patients exposed to heparin. Interactions between heparin, human platelet factor 4 (hPF4), antibodies to the hPF4/heparin complex, and the platelet Fc receptor (FcR) for immunoglobulin G, FcgammaRIIA, are the proposed primary determinants of the disease on the basis of in vitro studies. The goal of this study was to create a mouse model that recapitulates the disease process in humans in order to understand the factors that predispose some patients to develop thrombocytopenia and thrombosis and to investigate new therapeutic approaches. Mice that express both human platelet FcgammaRIIA and hPF4 were generated. The FcgammaRIIA/hPF4 mice and controls, transgenic for either FcgammaRIIA or hPF4, were injected with KKO, a mouse monoclonal antibody specific for hPF4/heparin complexes, and then received heparin (20 U/d). Nadir platelet counts for KKO/heparin-treated FcgammaRIIA/hPF4 mice were 80% below baseline values, significantly different (P <.001) from similarly treated controls. FcgammaRIIA/hPF4 mice injected with KKO and 50 U/d heparin developed shock and showed fibrin-rich thrombi in multiple organs, including thrombosis in the pulmonary vasculature. This is the first mouse model of HIT to recapitulate the salient features of the human disease and demonstrates that FcgammaRIIA and hPF4 are both necessary and sufficient to replicate HIT/HITT in an animal model. This model should facilitate the identification of factors that modulate disease expression and the testing of novel therapeutic interventions.

Localization of distal regulatory domains in the megakaryocyte-specific platelet basic protein/platelet factor 4 gene locus

The genes for the related human (h) chemokines, PBP (platelet basic protein) and PF4 (platelet factor 4), are within 5.3 kilobases (kb) of each other and form a megakaryocyte-specific gene locus. The hypothesis was considered that the PBP and PF4 genes share a common distal regulatory region(s) that leads to their high-level megakaryocyte-specific expression in vivo. This study examined PBP and PF4 expression in transgenic mice using 4 distinct human PBP/PF4 gene locus constructs. These studies showed that within the region studied there was sufficient information to regulate tissue-specific expression of both hPBP and hPF4. Indeed this region contained sufficient DNA information to lead to expression levels of PBP and PF4 comparable to the homologous mouse genes in a position-independent, copy number-dependent fashion. These studies also indicated that the DNA domains that led to this expression were distinct for the 2 genes; hPBP expression is regulated by a region that is 1.5 to 4.4 kb upstream of that gene. Expression of hPF4 is regulated by a region that is either intergenic between the 2 genes or immediately downstream of the hPF4 gene. Comparison of the available human and mouse sequences shows conserved flanking region domains containing potential megakaryocyte-related transcriptional factor DNA-binding sites. Further analysis of these regulatory regions may identify enhancer domains involved in megakaryopoiesis that may be useful in the selective expression of other genes in megakaryocytes and platelets as a strategy for regulating hemostasis, thrombosis, and inflammation. (Blood. 2001;98:610-617)

Hirudin therapy during thrombolysis for venous thrombosis in heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is the most common drug-related thrombocytopenia. Thromboembolic complications occur in approximately 50% of patients with HIT and result in limb amputation and death in up to 20% and 30% respectively. Because patients with a history of HIT may require future intravenous anticoagulation but have a high-risk of thromboembolism if re-challenged with heparin, alternative therapies are necessary when further anticoagulation is indicated. The use of direct thrombin inhibitors in HIT patients who also require thrombolytic therapy offers unique challenges to anticoagulant monitoring and safety. We present a case of progressive ileofemoral deep venous thrombosis in a patient with a history of HIT in order to review the combined use of hirudin and thrombolysis in this setting.

The influence of exchange delays on cigarette versus money choice: a laboratory analog of voucher-based reinforcement therapy

Contingency-management interventions that provide reinforcement in the form of exchangeable vouchers, contingent on drug abstinence, are among the most effective substance abuse treatment strategies available. Factors known to contribute to the efficacy of these interventions include voucher magnitude and the schedule with which vouchers are made available. Another potential factor may be the delay between earning a voucher and exchanging it for a desired good or service. The authors adapted a laboratory analog of a voucher program to examine the effects of immediacy of reinforcement and its interaction with reinforcer magnitude. Abstinent cigarette smokers made repeated choices between puffs on a cigarette and points worth a variety of monetary values (10 cents-2 dollars). The time at which these points could be exchanged for money varied from the end of the session to 1 or 3 weeks. Results indicated that longer exchange delays and tower magnitude reinforcers increased the number of choices for drug.

Cilostazol: treatment of intermittent claudication

OBJECTIVE

To review the pharmacology and clinical utility of cilostazol, an antiplatelet and vasodilator agent approved for the management of intermittent claudication.

DATA SOURCES

Primary literature on cilostazol was identified from a comprehensive MEDLINE literature search (1980-February 2000). Selected meeting abstracts and manufacturer literature were also used as source material. Indexing terms included cilostazol, intermittent claudication, platelet inhibitors, and restenosis.

STUDY SELECTION

Human clinical, pharmacokinetic and randomized comparative trials performed in the US and Asia were reviewed. Selected in vitro, ex vivo, and animal studies were evaluated when human data were not available.

DATA SYNTHESIS

Intermittent claudication, defined as reproducible discomfort of a muscle group induced by exercise and relieved by rest, is the most common clinical manifestation of peripheral arterial disease (PAD). Cilostazol, a specific inhibitor of cyclic adenosine monophosphate phosphodiesterase in platelets and vascular smooth-muscle cells, is a potent antiplatelet agent and vasodilator that reduces vascular proliferation and has lipid-lowering effects in vivo. Recent multicenter, randomized, placebo-controlled trials have led to approval of cilostazol by the Food and Drug Administration for relief of intermittent claudication in patients with stable PAD. Cilostazol doubled walking distances and improved quality of life compared with placebo in these studies. One trial found that cilostazol was more effective than pentoxifylline, the only alternative pharmacologic therapy for claudication. Although frequent (approximately 50%) minor adverse effects, including headache, diarrhea, and palpitations, may occur in clinical practice, cilostazol has not been associated with major adverse events or increased mortality. Small, nonblind studies suggest that cilostazol may prove useful in preventing thrombosis and restenosis following percutaneous coronary interventions, although these remain unlabeled uses.

CONCLUSIONS

The unique combination of antiplatelet, vasodilatory, and antiproliferative effects of cilostazol appear to make it an attractive agent for use in patients with PAD. Clinical trials demonstrating a significant improvement in walking distances with cilostazol therapy suggest that it will be an important tool in improving symptoms and quality of life in patients with intermittent claudication.

Thrombosis and shock induced by activating antiplatelet antibodies in human Fc gamma RIIA transgenic mice: the interplay among antibody, spleen, and Fc receptor

Transgenic mouse lines were created that express Fc gamma RIIA on platelets and macrophages at human physiologic levels, and they were used to explore the consequences in vivo of activating antiplatelet antibodies. Anti-CD9 antibody activated platelets of Fc gamma RIIA transgenic (tg) mice and, following injection in vivo, caused more rapid severe thrombocytopenia than nonactivating antiplatelet antibody. Anti-CD9 injected into Fc gamma RIIA tg crossed with FcR gamma-chain knockout (gamma-KO) mice caused thrombosis and shock in all mice, and death in 16 of 18 mice. The shock depended on platelet Fc receptor density and antibody dose. On histologic examination, the lung vasculature of anti-CD9-treated Fc gamma RIIA tg x gamma-KO mice contained extensive platelet-fibrin thrombi. Thrombosis and shock in Fc gamma RIIA tg mice in the context of the FcR gamma-chain knockout suggested the importance of the interplay of intravascular platelet activation and splenic clearance. Reduction of splenic clearance surgically (splenectomy) or functionally (monoclonal antibody treatment) also facilitated anti-CD9-mediated shock in Fc gamma RIIA tg mice. The spleen, which clears nonactivating antibody-coated platelets leading to thrombocytopenia, appears to play a protective role in the thrombosis and shock observed with activating antiplatelet antibody. The data indicate that antibodies, which activate platelets in an Fc gamma RIIA-dependent manner, can lead to thrombosis, shock, and death. Furthermore, antibody titer, platelet Fc receptor density, and splenic clearance are likely important determinants of the outcome. (Blood. 2000;96:4254-4260)

Frequency, risk factors, and clinical outcomes of left ventricular assist device-associated ventricular thrombus

A retrospective, transesophageal study of 51 consecutive patients receiving a left ventricular (LV) assist device (AD) over a 2-year period showed that LVAD-associated LV thrombosis (16%) was predicted by acute myocardial infarction, atrial cannulation, and postimplantation bleeding, and was associated with a fourfold increased risk of stroke compared with patients without thrombosis. LV cannulation, when using short-term LVADs, may decrease the incidence of LV thrombosis, and early transition to Heartmate-LVAD support may improve outcome.

Clinical applications of acupuncture in anesthesia practice

The most widely successful use of acupuncture in Western medicine has been in the treatment of chronic and intractable pain syndromes. Thus, it is especially important for the nurse anesthetist who is the practice of chronic pain management to be familiar with this treatment choice. This article provides the nurse anesthetist with basic information about the practice of acupuncture, the patient who may ask for acupuncture, application of segmental acupuncture techniques, and legislative and licensure issues.

Internalization and sequestration of the human prostacyclin receptor

Prostacyclin (PGI(2)), the major product of cyclooxygenase in macrovascular endothelium, mediates its biological effects through its cell surface G protein-coupled receptor, the IP. PKC-mediated phosphorylation of human (h) IP is a critical determinant of agonist-induced desensitization (Smyth, E. M., Hong Li, W., and FitzGerald, G. A. (1998) J. Biol. Chem. 273, 23258-23266). The regulatory events that follow desensitization are unclear. We have examined agonist-induced sequestration of hIP. Human IP, tagged at the N terminus with hemagglutinin (HA) and fused at the C terminus to the green fluorescent protein (GFP), was coupled to increased cAMP (EC(50) = 0.39 +/- 0.09 nm) and inositol phosphate (EC(50) = 86. 6 +/- 18.3 nm) generation when overexpressed in HEK 293 cells. Iloprost-induced sequestration of HAhIP-GFP, followed in real time by confocal microscopy, was partially colocalized to clathrin-coated vesicles. Iloprost induced a time- and concentration-dependent loss of cell surface HA, indicating receptor internalization, which was prevented by inhibitors of clathrin-mediated trafficking and partially reduced by cotransfection of cells with a dynamin dominant negative mutant. Sequestration (EC(50) = 27.6 +/- 5.7 nm) was evident at those concentrations of iloprost that induce PKC-dependent desensitization. Neither the PKC inhibitor GF109203X nor mutation of Ser-328, the site for PKC phosphorylation, altered receptor sequestration indicating that, unlike desensitization, internalization is PKC-independent. Deletion of the C terminus prevented iloprost-induced internalization, demonstrating the critical nature of this region for sequestration. Internalization was unaltered by cotransfection of cells with G protein-coupled receptor kinases (GRK)-2, -3, -5, -6, arrestin-2, or an arrestin-2 dominant negative mutant, indicating that GRKs and arrestins do not play a role in hIP trafficking. The hIP is sequestered in response to agonist activation via a PKC-independent pathway that is distinct from desensitization. Trafficking is dependent on determinants located in the C terminus, is GRK/arrestin-independent, and proceeds in part via a dynamin-dependent clathrin-coated vesicular endocytotic pathway although other dynamin-independent pathways may also be involved.

Impulsivity and voucher versus money preference in polydrug-dependent participants enrolled in a contingency-management-based substance abuse treatment program

Thirty-four polydrug-dependent participants enrolled in a voucher-based substance abuse treatment program were given choices between hypothetical amounts of money and hypothetical amounts of vouchers, which are traded for goods and services, to determine their preferences for the two payment modalities. It was hypothesized that the majority of participants would prefer money to voucher because under the circumstances of the treatment program, the delay associated with money exchange is shorter than the delay associated with voucher exchange. It was further hypothesized that those participants who selected money over voucher also would have greater levels of impulsivity as assessed by the Barratt Impulsiveness Rating Scale (BIS) (Barratt, 1965). The results show large individual differences in money/voucher preference with approximately half of the participants preferring money to voucher when the two amounts are equivalent. In addition, as the magnitude of the money/voucher comparisons increased from 0.50 dollars to 32.00 dollars, the percentage of participants that preferred money increased. No correlations were found between money/voucher preference and impulsivity scores.

The role of the human Fc receptor Fc gamma RIIA in the immune clearance of platelets: a transgenic mouse model

In humans, the Fc receptor for IgG, FcgammaRIIA, is expressed on macrophages and platelets and may play an important role in the pathophysiology of immune-mediated thrombocytopenia. Mice lack the genetic equivalent of human FcgammaRIIA. To better understand the role of FcgammaRIIA in vivo, FcgammaRIIA transgenic mice were generated and characterized. One transgenic mouse line expressed FcgammaRIIA on platelets and macrophages at levels equivalent to human cells, and cross-linking FcgammaRIIA on these platelets induced platelet aggregation. Immune-mediated thrombocytopenia in this transgenic line was studied using i.v. and i.p. administration of anti-mouse platelet Ab. In comparison with matched wild-type littermates that are negative for the FcgammaRIIA transgene, Ab-mediated thrombocytopenia was significantly more severe in the FcgammaRIIA transgenic mice. In contrast, FcR gamma-chain knockout mice that lack functional expression of the Fc receptors FcgammaRI and FcgammaRIII on splenic macrophages did not demonstrate Ab-mediated thrombocytopenia. We generated FcgammaRIIA transgenic x FcR gamma-chain knockout mice to examine the role of FcgammaRIIA in immune clearance in the absence of functional FcgammaRI and FcgammaRIII. In FcgammaRIIA transgenic x FcR gamma-chain knockout mice, severe immune thrombocytopenia mediated by FcgammaRIIA was observed. These results demonstrate that FcgammaRIIA does not require the FcR gamma-chain for expression or function in vivo. Furthermore, taken together, the data suggest that the human Fc receptor FcgammaRIIA plays a significant role in the immune clearance of platelets in vivo.

Feline adult beta-globin polymorphism reflected in restriction fragment length patterns

Adult domestic cats (Felis catus) appear to have the most polymorphic beta-globin system of any species. Reversed-phase high-performance liquid chromatography (RP-HPLC) revealed one alpha-chain and six different beta-globin chains. Each cat may have one to four different beta-globins, and a total of 17 different beta-globin patterns were identified. Based on family studies, a beta-globin gene region with two linked beta-globin gene loci and two to five alleles was proposed. In order to further define the molecular basis of this polymorphism we performed Southern blot analysis of the beta-globin gene region from 25 cats with 13 different HPLC patterns. Genomic DNA was digested with five restriction endonucleases (BamHI, BglII, EcoRI, HindIII, and PstI) and blots were hybridized with a human beta-globin probe. Restriction fragment length polymorphisms (RFLPs) with one to five fragments of 2.2-23 kb in size were found with BglII, EcoRI, HindIII, and PstI. Cats with specific HPLC beta-globin patterns had a unique DNA restriction pattern. The similarly sized BamHI and HindIII fragments of 4.6 kb suggest the presence of two closely linked genes. Furthermore, family studies suggest an autosomal codominant mode of inheritance of the beta-globin chains with seven haplotypes. Thus the RFLP data analyzed in the context of the HPLC haplotypes provide evidence at the DNA level for a feline beta-globin gene region with two closely linked gene loci and two to five alleles.

A randomized, placebo-controlled, crossover study of E5510 and aspirin in healthy volunteers

Platelet inhibition significantly reduces the risk of cardiovascular mortality and morbidity. However, current antiplatelet therapies have limitations, and more efficacious agents are needed. E5510 is a novel compound that has multiple platelet inhibitory effects in in vitro studies. We compared the in vivo, pharmacodynamic effects of maximal antiplatelet doses of E5510 (20 mg) with 300 mg aspirin in a placebo-controlled, triple crossover trial in nine healthy volunteers. Collagen-induced platelet aggregation and serum thromboxane B2 (TxB2) were similarly inhibited by both compounds in the first 12 h but showed recovery at 24 h in the E5510 group only (p < 0.05). Thrombin and U46619-induced platelet aggregation, as well as basal and prostaglandin E2 (PGE2)-stimulated platelet cyclic adenosine monophosphate (cAMP) levels were unchanged after ingestion of either agent. E5510 and aspirin reduced systemic thromboxane formation without affecting prostacyclin biosynthesis. Neither E5510 nor aspirin inhibited the excretion of 8-epi PGF2alpha and 5,6-DHET, two indices of cyclooxygenase-independent arachidonate metabolism. In conclusion, (a) E55 10 in vivo most likely induces a reversible inhibition of cyclooxygenase, without affecting thromboxane synthetase, phosphodiesterase, thrombin, or thromboxane receptor-mediated signaling; (b) single doses of aspirin or E5510 affect thromboxane/prostacyclin profiles favorably, supporting their use in acute coronary syndromes. This study outlines a comprehensive and minimally invasive approach for the assessment of the in vivo mechanism of action of novel antiplatelet agents.

Increased formation of distinct F2 isoprostanes in hypercholesterolemia

BACKGROUND

F2 isoprostanes are stable, free radical-catalyzed products of arachidonic acid that reflect lipid peroxidation in vivo.

METHODS AND RESULTS

Specific assays were developed by use of mass spectrometry for the F2 isoprostanes iPF2alpha-III and iPF2alpha-VI and arachidonic acid (AA). Urinary excretion of the 2 F2 isoprostanes was significantly increased in hypercholesterolemic patients, whereas substrate AA in urine did not differ between the groups. iPF2alpha-III (pmol/mmol creatinine) was elevated (P<0.0005) in homozygous familial hypercholesterolemic (HFH) patients (85+/-5. 5; n=38) compared with age- and sex-matched normocholesterolemic control subjects (58+/-4.2; n=38), as were levels of iPF2alpha-VI (281+/-22 versus 175+/-13; P<0.0005). Serum cholesterol correlated with urinary iPF2alpha-III (r=0.41; P<0.02) and iPF2alpha-VI (r=0. 39; P<0.03) in HFH patients. Urinary excretion of iPF2alpha-III (81+/-10 versus 59+/-4; P<0.05) and iPF2alpha-VI (195+/-18 versus 149+/-20; P<0.05) was also increased in moderately hypercholesterolemic subjects (n=24) compared with their controls. Urinary excretion of iPF2alpha-III and iPF2alpha-VI was correlated (r=0.57; P<0.0001; n=106). LDL iPF2alpha-III levels (ng/mg arachidonate) were elevated (P<0.01) in HFH patients (0.32+/-0.08) compared with controls (0.09+/-0.02). The concentrations of iPF2-III in LDL and urine were significantly correlated (r=0.42; P<0.05) in HFH patients.

CONCLUSIONS

Asymptomatic patients with moderate and severe hypercholesterolemia have evidence of oxidant stress in vivo.

Effect of an allosteric modifier of hemoglobin, RSR-4, on oxygen affinity and oxygen saturation of hemoglobin in rabbits

Theoretically, if the arterial partial oxygen pressure (PaO2) does not change, a right shift in the oxygen equilibrium curve (OEC) of hemoglobin should reduce arterial oxygen saturation. In this study we investigate whether a right shift in the OEC of hemoglobin decreases transcutaneous oxygen saturation (Tc-SO2) following the administration of an allosteric effector, 2-[4-(((3, 5-dichloroanilino)-carbonyl) methyl) phenoxy]-2-methylpropionic acid (RSR-4). The effect of RSR-4 on hemoglobin oxygen affinity was studied in four New Zealand white male rabbits. Following intraperitoneal administration of RSR-4, Tc-SO2 decreased in a dose-dependent manner. P50 (partial oxygen pressure at 50% hemoglobin oxygen saturation) in whole blood increased as the concentration of RSR-4 increased. Tc-SO2 decreased as whole-blood affinity (1/P50) decreased. There was no positive correlation between Tc-SO2 and PaO2. We concluded that a decrease in hemoglobin oxygen affinity following RSR-4 administration reduced arterial oxygen saturation. This decrease in the presence of an allosteric effector such as RSR-4 in vivo can be detected and monitored as a reduction in Tc-SO2.

Effect of erythrocytapheresis on arterial oxygen saturation and hemoglobin oxygen affinity in patients with sickle cell disease

An important purpose of blood transfusion in patients with sickle cell disease is to improve arterial oxygen saturation (SaO2) and thereby reduce red cell sickling. To investigate the degree of improvement in SaO2 by blood transfusion, we determined the hemoglobin oxygen affinity, transcutaneous oxygen saturation (Tc-SO2), and pulse rate before and after automated partial exchange transfusion (erythrocytapheresis). In 13 patients with sickle cell disease who underwent 24 erythrocytapheresis procedures, the mean oxygen tension at half saturation (P50) was significantly reduced from 30.4 +/- 2.2 to 26.0 +/- 1.6 mm Hg (P< 0.01) immediately after exchange transfusion. Mean Tc-SO2 values increased from 96.2 +/- 2.8 to 98.5 +/- 2.1% (P< 0.01). Approximately 50% of the increase in Tc-SO2 after erythrocytapheresis could be explained by the increase in hemoglobin oxygen affinity. An increase in arterial oxygen pressure (PaO2) following erythrocytapheresis, suggested by the calculated PaO2 in this study, may explain some of the increase in Tc-SO2. We conclude that improvement in Tc-SO2 in patients with sickle cell disease resulted from changes in hemoglobin oxygen affinity as well as blood oxygen pressure following erythrocytapheresis.

Polymorphism of feline beta-globins studied by reversed-phase high-performance liquid chromatography

OBJECTIVE

To characterize the feline beta-globin system with respect to the number and genetics of adult beta-globin chains.

ANIMALS

84 domestic and purebred cats (9 breeds), 14 cats were mildly to severely anemic. For genetic analyses, 12 litters with 1 to 5 offspring for a total of 29 kittens.

PROCEDURE

Feline globins from erythrocyte lysates were separated by reversed-phase high-performance liquid chromatography and analyzed on the basis of retention time and area of each beta-globin peak. Mixing studies with half the amount of hemoglobin (Hb) from 2 cats were performed to assign the beta-globin peaks in each cat. The Hb from 60 cats were also separated by standard isoelectric focusing methods.

RESULTS

Heme and alpha- and beta-globins were effectively separated by high-performance liquid chromatography. Although there was only 1 alpha-globin, a total of 6 beta-globins (I through VI) were identified, with each cat having 1 to 4 beta-globin chains. From analysis of the number of beta-globins, their relative amounts, and Hb mixing studies, 17 beta-globin patterns were observed. The beta-globin pattern in healthy and anemic cats was identical. Family studies documented an autosomal codominant mode of inheritance of the adult beta-globins and a linkage of 2 beta-chains forming haplotypes.

CONCLUSIONS

Biochemical and genetic evidence for the greatest polymorphism of adult beta-globins thus far described in any species is provided. A feline beta-globin gene region with 2 linked beta-globin gene loci and 2 and 5 alleles is proposed.

CLINICAL RELEVANCE

Better understanding of feline Hb will likely be helpful for diagnosis of hemoglobinopathies in anemic cats.

-245 bp of 5'-flanking region from the human platelet factor 4 gene is sufficient to drive megakaryocyte-specific expression in vivo

Platelet factor 4 (PF4) serves as a lineage-specific marker of megakaryocyte development. We previously identified two positively acting sequences in the human platelet factor 4 (hPF4) gene promoter that synergized to drive high-level luciferase reporter gene expression in vitro. Using portions of the hPF4 5'-flanking region linked to the lacZ reporter gene, we observed in this investigation that constructs with -245 bp of 5'-flanking region were more active than constructs with -2 kb of 5'-flanking region in vitro. We created two independent transgenic mouse lines with a -245-bp hPF4/lacZ construct. Cells from these mice were tested for beta-galactosidase (beta-gal) expression at the mRNA level by Northern blot and semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and at the protein level by immunohistochemistry assay. Mice from one line showed beta-gal expression specifically in all megakaryocytes of all ploidy classes from bone marrow and in platelets. Expression level was comparable to that driven by the 1.1-kb rat PF4 promoter in other transgenic mouse lines. Those in the second line showed no beta-gal expression in megakaryocytes, platelets, or any of the eight organs tested. The -245-bp hPF4 promoter is capable of driving reporter gene expression in a megakaryocyte-specific manner in transgenic mice. The small size of this megakaryocyte-specific promoter is compatible with that required in some viral vectors and may provide a model for targeting gene expression to megakaryocytes.

Cerebrovascular emboli related to pulmonary venous thrombosis after lung transplantation

We describe a case of cerebral emboli related to pulmonary venous thrombosis after bilateral lung transplantation in a young man with cystic fibrosis. The diagnosis was made by transesophageal echocardiography, leading to aggressive anticoagulation within 24 hours of surgery. Hemodynamic deterioration in the following hours was of concern for the development of obstructive thrombus but was found to be due to pericardial tamponade, which, remarkably, resolved during a repeat transesophageal echocardiography.

Mechanisms underlying the effects of unsignaled delayed reinforcement on key pecking of pigeons under variable-interval schedules

Three experiments were conducted to test an interpretation of the response-rate-reducing effects of unsignaled nonresetting delays to reinforcement in pigeons. According to this interpretation, rates of key pecking decrease under these conditions because key pecks alternate with hopper-observing behavior. In Experiment 1, 4 pigeons pecked a food key that raised the hopper provided that pecks on a different variable-interval-schedule key met the requirements of a variable-interval 60-s schedule. The stimuli associated with the availability of the hopper (i.e., houselight and keylight off, food key illuminated, feedback following food-key pecks) were gradually removed across phases while the dependent relation between hopper availability and variable-interval-schedule key pecks was maintained. Rates of pecking the variable-interval-schedule key decreased to low levels and rates of food-key pecks increased when variable-interval-schedule key pecks did not produce hopper-correlated stimuli. In Experiment 2, pigeons initially pecked a single key under a variable-interval 60-s schedule. Then the dependent relation between hopper presentation and key pecks was eliminated by arranging a variable-time 60-s schedule. When rates of pecking had decreased to low levels, conditions were changed so that pecks during the final 5 s of each interval changed the keylight color from green to amber. When pecking produced these hopper-correlated stimuli, pecking occurred at high rates, despite the absence of a peck-food dependency. When peck-produced changes in keylight color were uncorrelated with food, rates of pecking fell to low levels. In Experiment 3, details (obtained delays, interresponse-time distributions, eating times) of the transition from high to low response rates produced by the introduction of a 3-s unsignaled delay were tracked from session to session in 3 pigeons that had been initially trained to peck under a conventional variable-interval 60-s schedule. Decreases in response rates soon after the transition to delayed reinforcement were accompanied by decreases in eating times and alterations in interresponse-time distributions. As response rates decreased and became stable, eating times increased and their variability decreased. These findings support an interpretation of the effects of delayed reinforcement that emphasizes the importance of hopper-observing behavior.

Eicosanoids and isoeicosanoids: indices of cellular function and oxidant stress

Arachidonic acid (AA) is an unsaturated fatty acid constituent of the phospholipid domain of cell membranes. It is subject to release via mobilization of phospholipases, particularly a cytoplasmic phospholipase A2. Thereafter, it may be metabolized by at least two cyclooxygenase (COX) isoforms to prostaglandins and related compounds, via lipoxygenases to leukotrienes and via p450-catalyzed metabolism to epoxyeicosatrienoic acids. Collectively, these bioactive lipids are termed eicosanoids. All of these lipids express potent bioactivity in vitro. Clinical studies have already demonstrated the importance of COX and lipoxygenase (LOX) products in human disease. The generation of models of COX, LOX and prostaglandin receptor gene inactivation is likely to broaden our insight into the importance of these compounds in vivo. Crystallization of the biosynthetic enzymes is likely to facilitate the development of highly specific inhibitors, as is the case already for COX-2. AA possesses intrinsic biological properties. It is also subject to free radical attack, generating isomeric eicosanoid species, the isoeicosanoids. These compounds may also express biological activity in vitro, although their importance in vivo is unclear. Development of specific assays for these compounds in urine suggests their utility as noninvasive indices of oxidant stress in vivo.

Increased formation of the isoprostanes IPF2alpha-I and 8-epi-prostaglandin F2alpha in acute coronary angioplasty: evidence for oxidant stress during coronary reperfusion in humans

BACKGROUND

The role of oxidant stress in cardiac ischemia/reperfusion injury in humans remains controversial. This is due, in part, to the limitations of available indices of oxidant stress in vivo. Isoprostanes are stable, free radical-catalyzed products of arachidonic acid. We assessed their formation in patients undergoing coronary reperfusion via percutaneous transluminal coronary angioplasty (PTCA).

METHODS AND RESULTS

We developed specific, mass spectrometry assays for two structurally distinct F2 isoprostanes, 8-epi-PGF2alpha and IPF2alpha-I. Urine samples for isoprostane determination were collected in patients undergoing coronary arteriography (n=11), elective PTCA (n=15), and angiography after thrombolysis for acute myocardial infarction (MI) (n=10). Urinary levels (pmol/mmol creatinine) of both isoprostanes were markedly increased from baseline in the first 6 hours after PTCA for acute MI (105+/-17.8 versus 230+/-66 for 8-epi-PGF2alpha [P=.009] and 466+/-91 versus 833+/-153 for IPF2alpha-I [P=.001]) and returned toward preprocedural values by 24 hours (122+/-18 for 8-epi-PGF2alpha and 457+/-102 for IPF2alpha-I). There was a slight increase in urinary 8-epi-PGF2alpha levels (64.7+/-9.5 versus 84.9+/-10.6; P=.02) after diagnostic coronary arteriography and elective PTCA (88.7+/-7.5 versus 114.3+/-16.1; P=.01). A striking correlation was observed (r=.68, P<.0001; n=33) between urinary 8-epi-PGF2alpha and IPF2alpha-I levels in patients receiving thrombolytic agents for acute MI.

CONCLUSIONS

Urinary F2 isoprostane levels are elevated in patients after treatments resulting in reperfusion for acute MI. These findings provide evidence consistent with increased oxidant stress in vivo in this setting. Measurement of urinary isoprostanes may offer a noninvasive approach to the assessment of oxidant stress and the efficacy of antioxidant therapies in these syndromes.

The presurgical management with erythrocytapheresis of a patient with a high-oxygen-affinity, unstable Hb variant (Hb Bryn Mawr)

BACKGROUND

Hemoglobin (Hb) Bryn Mawr is an unstable Hb variant resulting in congenital hemolytic anemia. This variant Hb also has an increased affinity for oxygen. The perioperative transfusion management of this disorder is described, and the first genomic analysis of this Hb variant is given.

CASE REPORT

An 11-year-old boy, heterozygous for Hb Bryn Mawr, was referred for cholecystectomy. Sequence analysis of genomic DNA confirmed that the patients was heterozygous for a T-->C transition in the codon for amino acid 85, causing a substitution of serine for phenylalanine in the beta-globin chain. On the basis of whole-blood O2 dissociation studies, projected tissue O2 delivery would have been suboptimal during general anesthesia; therefore, a partial red cell exchange transfusion was performed to lower variant Hb and prevent tissue hypoxia during surgery. The red cell mass to be exchanged (50%) was determined from the calculated increase in O2 delivery capacity required to maintain an O2 extraction of 4 to 5 mL of O2 per dL of whole blood. The p50 of whole blood from the patients immediately after the exchange transfusion was 16.0 torr. At the time of surgery, the p50 was normal (25.9 torr). The patient's whole blood 2,3 DPG levels were 4.70 mmol per mL of red cells (before transfusion) (normal range = 4.8 +/- 0.3 mmol/mL red cells), 4.07 mmol per mL of red cells (immediately after transfusion), and 4.55 mmol per mL of red cells (48 hours after transfusion).

CONCLUSION

This patient with Hb Bryn Mawr was prepared for surgery with a partial exchange transfusion to prevent tissue hypoxia during anesthesia. Decreased 2,3 DPG levels immediately after transfusion resulted in increased O2 affinity of whole blood; however, 48 hours after exchange transfusion, a normal p50 (due to both removal of variant Hb and regeneration of 2,3, DPG) was observed. Partial exchange transfusion is useful in the preoperative management of patients with Hb variants characterized by increased O2 affinity.