Soluble (Pro)Renin Receptor Levels Are Regulated by Plasma Renin Activity and Correlated with Edema in Mice and Humans with HFrEF

Symptomatic heart failure with reduced ejection fraction (HFrEF) is characterized by edema and chronic pathological activation of the classical renin–angiotensin–aldosterone system (RAAS). The soluble (pro)renin receptor (s(P)RR) is released into circulation by proteolytic cleavage of tissue expressed (P)RR and is a candidate biomarker of RAAS activation. However, previous studies linked elevated levels of s(P)RR in patients with HFrEF to renal dysfunction. Utilizing prospectively enrolled patients with comparable rEF, we show that increased plasma levels of s(P)RR are associated with symptomatic HF (characterized by edema), independent of chronic renal dysfunction. We also found that s(P)RR levels were positively correlated with patient plasma renin activity (PRA). Normotensive mice with dilated cardiomyopathy (DCM) and HFrEF, without renal dysfunction, showed plasma s(P)RR and PRA patterns similar to human HFrEF patients. Plasma s(P)RR levels positively correlated with PRA and systemic edema, but not with EF, resembling findings in patients with HFrEF without chronic kidney dysfunction. In female DCM mice with elevated PRA levels and plasma s(P)RR levels, a randomized, blinded trial comparing the direct renin inhibitor, aliskiren vs. vehicle control, showed that direct renin inhibition normalized PRA, lowered s(P)RR, and prevented symptomatic HFrEF. Considered in light of previous findings, these data suggest that, in HFrEF, in the absence of renal dysfunction, elevation of plasma s(P)RR levels is caused by increased PRA and associated with the development of systemic edema.

Predictors of Adherence Among Vulnerable Populations of Adults Assigned to Smoke Very Low Nicotine Content Cigarettes

INTRODUCTION

Regulators are considering reducing the nicotine content in cigarettes to a minimally addictive level. This could particularly benefit smokers from populations vulnerable to heavy smoking and difficulties quitting. We assessed predictors of adherence among adults from vulnerable populations assigned to use very low nicotine content cigarettes (VLNCs) in randomized clinical trials, to identify characteristics of those who require additional assistance if a nicotine reduction policy were implemented.

AIMS AND METHODS

Data came from three populations of vulnerable adult smokers assigned to use VLNC cigarettes (0.4 mg/g nicotine) during 12-week randomized controlled trials (n = 286): Socioeconomically disadvantaged women of reproductive age, opioid-maintained adults, and adults with affective disorders. Logistic and linear regressions modeled predictors of adherence based on changes in cotinine at week-6 and week-12 assessments relative to baseline, and as a 90% reduction in cotinine relative to baseline (full adherence: yes/no). Predictors included satisfaction with study cigarettes, craving, nicotine dependence severity, withdrawal, population membership, baseline affective-disorder symptoms, and sociodemographic characteristics.

RESULTS

Dependence severity was negatively associated with both adherence measures at week 6 (p < .01), whereas increased satisfaction with study cigarettes and age were positively associated with both measures at weeks 6 and 12 (p < .01). Opioid-maintained adults exhibited reduced adherence and were less likely to reach full adherence at week 12 compared to disadvantaged women (p = .02).

CONCLUSIONS

Factors associated with VLNC adherence in vulnerable populations are similar to those in the general population of smokers. Furthermore, studies are indicated investigating nicotine supplements (e.g., e-cigarettes, NRT) to support highly dependent adults faced with using VLNCs.

IMPLICATIONS

This study identified factors predicting difficulty maintaining adherence to a regimen of very low nicotine content cigarettes (VLNC) among adults from vulnerable populations. Findings suggested that factors predicting difficulty maintaining adherence (greater nicotine dependence and low satisfaction with study-provided VLNC) were common across vulnerable smokers and the general population of adults who smoke. Furthermore, research should investigate alternatives to support highly dependent adults, such as pairing VLNC with supplemental, noncombusted nicotine. Some vulnerable populations (e.g., opioid-maintained adults) may be especially in need of supplemental, noncombusted nicotine.

Sodium-Glucose Cotransporter-2 Inhibitors Improve Heart Failure with Reduced Ejection Fraction Outcomes by Reducing Edema and Congestion

Pathological sodium-water retention or edema/congestion is a primary cause of heart failure (HF) decompensation, clinical symptoms, hospitalization, reduced quality of life, and premature mortality. Sodium-glucose cotransporter-2 inhibitors (SGLT-2i) based therapies reduce hospitalization due to HF, improve functional status, quality, and duration of life in patients with HF with reduced ejection fraction (HFrEF) independently of their glycemic status. The pathophysiologic mechanisms and molecular pathways responsible for the benefits of SGLT-2i in HFrEF remain inconclusive, but SGLT-2i may help HFrEF by normalizing salt-water homeostasis to prevent clinical edema/congestion. In HFrEF, edema and congestion are related to compromised cardiac function. Edema and congestion are further aggravated by renal and pulmonary abnormalities. Treatment of HFrEF patients with SGLT-2i enhances natriuresis/diuresis, improves cardiac function, and reduces natriuretic peptide plasma levels. In this review, we summarize current clinical research studies related to outcomes of SGLT-2i treatment in HFrEF with a specific focus on their contribution to relieving or preventing edema and congestion, slowing HF progression, and decreasing the rate of rehospitalization and cardiovascular mortality.

A Low-Sodium Diet Boosts Ang (1-7) Production and NO-cGMP Bioavailability to Reduce Edema and Enhance Survival in Experimental Heart Failure

Sodium restriction is often recommended in heart failure (HF) to block symptomatic edema, despite limited evidence for benefit. However, a low-sodium diet (LSD) activates the classical renin-angiotensin-aldosterone system (RAAS), which may adversely affect HF progression and mortality in patients with dilated cardiomyopathy (DCM). We performed a randomized, blinded pre-clinical trial to compare the effects of a normal (human-equivalent) sodium diet and a LSD on HF progression in a normotensive model of DCM in mice that has translational relevance to human HF. The LSD reduced HF progression by suppressing the development of pleural effusions (p < 0.01), blocking pathological increases in systemic extracellular water (p < 0.001) and prolonging median survival (15%, p < 0.01). The LSD activated the classical RAAS by increasing plasma renin activity, angiotensin II and aldosterone levels. However, the LSD also significantly up-elevated the counter-regulatory RAAS by boosting plasma angiotensin converting enzyme 2 (ACE2) and angiotensin (1-7) levels, promoting nitric oxide bioavailability and stimulating 3'-5'-cyclic guanosine monophosphate (cGMP) production. Plasma HF biomarkers associated with poor outcomes, such as B-type natriuretic peptide and neprilysin were decreased by a LSD. Cardiac systolic function, blood pressure and renal function were not affected. Although a LSD activates the classical RAAS system, we conclude that the LSD delayed HF progression and mortality in experimental DCM, in part through protective stimulation of the counter-regulatory RAAS to increase plasma ACE2 and angiotensin (1-7) levels, nitric oxide bioavailability and cGMP production.

Time-Restricted Salutary Effects of Blood Flow Restoration on Venous Thrombosis and Vein Wall Injury in Mouse and Human Subjects

BACKGROUND

Up to 50% of patients with proximal deep vein thrombosis (DVT) will develop the postthrombotic syndrome characterized by limb swelling and discomfort, hyperpigmentation, skin ulcers, and impaired quality of life. Although catheter-based interventions enabling the restoration of blood flow (RBF) have demonstrated little benefit on postthrombotic syndrome, the impact on the acuity of the thrombus and mechanisms underlying this finding remain obscure. In experimental and clinical studies, we examined whether RBF has a restricted time window for improving DVT resolution.

METHODS

First, experimental stasis DVT was generated in C57/BL6 mice (n=291) by inferior vena cava ligation. To promote RBF, mice underwent mechanical deligation with or without intravenous recombinant tissue plasminogen activator administered 2 days after deligation. RBF was assessed over time by ultrasonography and intravital microscopy. Resected thrombosed inferior vena cava specimens underwent thrombus and vein wall histological and gene expression assays. Next, in a clinical study, we conducted a post hoc analysis of the ATTRACT (Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis) pharmacomechanical catheter-directed thrombolysis (PCDT) trial (NCT00790335) to assess the effects of PCDT on Venous Insufficiency Epidemiological and Economic Study quality-of-life and Villalta scores for specific symptom-onset-to-randomization timeframes.

RESULTS

Mice that developed RBF by day 4, but not later, exhibited reduced day 8 thrombus burden parameters and reduced day 8 vein wall fibrosis and inflammation, compared with controls. In mice without RBF, recombinant tissue plasminogen activator administered at day 4, but not later, reduced day 8 thrombus burden and vein wall fibrosis. It is notable that, in mice already exhibiting RBF by day 4, recombinant tissue plasminogen activator administration did not further reduce thrombus burden or vein wall fibrosis. In the ATTRACT trial, patients receiving PCDT in an intermediate symptom-onset-to-randomization timeframe of 4 to 8 days demonstrated maximal benefits in Venous Insufficiency Epidemiological and Economic Study quality-of-life and Villalta scores (between-group difference=8.41 and 1.68, respectively, P<0.001 versus patients not receiving PCDT). PCDT did not improve postthrombotic syndrome scores for patients having a symptom-onset-to-randomization time of <4 days or >8 days.

CONCLUSIONS

Taken together, these data illustrate that, within a restricted therapeutic window, RBF improves DVT resolution, and PCDT may improve clinical outcomes. Further studies are warranted to examine the value of time-restricted RBF strategies to reduce postthrombotic syndrome in patients with DVT.

Alpha2-Antiplasmin: The Devil You Don't Know in Cerebrovascular and Cardiovascular Disease

Alpha2-antiplasmin (α2AP), the fast-reacting, serine protease inhibitor (serpin) of plasmin, was originally thought to play a key role in protection against uncontrolled, plasmin-mediated proteolysis of coagulation factors and other molecules. However, studies of humans and mice with genetic deficiency of α2AP have expanded our understanding of this serpin, particularly in disease states. Epidemiology studies have shown an association between high α2AP levels and increased risk or poor outcome in cardiovascular diseases. Mechanistic studies in disease models indicate that α2AP stops the body's own fibrinolytic system from dissolving pathologic thrombi that cause venous thrombosis, pulmonary embolism, arterial thrombosis, and ischemic stroke. In addition, α2AP fosters the development of microvascular thrombosis and enhances matrix metalloproteinase-9 expression. Through these mechanisms and others, α2AP contributes to brain injury, hemorrhage and swelling in experimental ischemic stroke. Recent studies also show that α2AP is required for the development of stasis thrombosis by inhibiting the early activation of effective fibrinolysis. In this review, we will discuss the key role played by α2AP in controlling thrombosis and fibrinolysis and, we will consider its potential value as a therapeutic target in cardiovascular diseases and ischemic stroke.

Abstract WMP99: Alpha2-Antiplasmin Inactivation Reduces Hemorrhagic Transformation and Ischemic Brain Injury After Tissue Plasminogen Activator Therapy and Mechanical Reperfusion

Tissue plasminogen activator (r-tPA) therapy followed by thrombectomy-mediated, mechanical reperfusion profoundly reduces neurologic disability in appropriately selected patients. Nevertheless, a high proportion of these patients (20-37%) develop brain hemorrhage. We examined the contribution of α2-antiplasmin, a fast-acting plasmin inhibitor, to brain hemorrhage and ischemic injury following r-tPA treatment and mechanical reperfusion.

Methods: Mice (C57Bl6) underwent 1 to 4 h of middle cerebral artery occlusion followed by treatment with r-tPA alone (10 mg/kg), r-tPA (10 mg/kg) plus an α2AP inhibitor (α2AP-I, 10 mg/kg) antibody or saline, followed by reperfusion. Mice were assessed by neurobehavioral measures (Bederson score and corner test) and histology 24 h post-ischemic stroke. Analyses were performed in a blinded fashion. Time course studies in r-tPA-treated mice showed that intracerebral hemorrhage (p<0.05), brain infarct volume (p<0.001) and brain swelling (p<0.01) increased progressively with ischemic time, with a plateau at 3 h of ischemia, as compared to saline treated controls. Mice treated at 3 h with r r-tPA + α2AP-I showed significantly (p<0.05) reduced brain hemorrhage, brain infarct volume (p<0.01) and brain swelling (p<0.05). Treatment with r-tPA + α2AP-I also significantly improved neurobehavioral deficits (p<0.01) and sensory motor dysfunction (p<0.01) at 24h of reperfusion.

Conclusion: α2AP contributes to the increased brain hemorrhage and ischemic brain injury associated with r-tPA treatment followed by mechanical reperfusion. Targeting a2AP appears beneficial, because specific, monoclonal antibody-mediated inhibition of α2AP markedly reduced brain hemorrhage, infarction, swelling and neurobehavioral disability.

Association of history of heart failure with hospital outcomes of hyperglycemic crises: Analysis from a University hospital and national cohort

AIMS

The impact of a history of heart failure (HF) on the outcomes of hospitalization for hyperglycemic crises (diabetic ketoacidosis and hyperosmolar hyperglycemic syndrome) is unknown. We aimed to test the hypothesis that a history of HF has a deleterious impact on the outcomes of hospitalization for hyperglycemic crises.

METHODS

We used two different datasets: National Inpatient Sample database 2003-2014 and a single University hospital cohort 2007-2017, to identify all adult hospitalizations with a primary diagnosis of hyperglycemic crises. Multivariable regression models were used to analyze the outcomes of in-hospital mortality, length of hospital stay and transfer to nursing home or similar short-term facility between HF and no-HF hospitalizations.

RESULTS

Of the 1, 570,726 hyperglycemic crises related hospitalizations, a history of HF was present in 57, 520 (3.6%) hospitalizations. After multivariable risk-adjustment, HF group had a higher observed in-hospital mortality [0.4% vs. 0.2%; adjusted odds ratio (AOR) = 1.7, 95% CI 1.4 to 2.0, P < .001] and transfer to nursing home or similar short-term facility (3.9 vs. 2.8%, AOR = 1.4, 95% CI 1.3 to 1.5, P < .001) compared with no-HF group. Mean length of hospital stay [6.5 vs. 3.5 days; P < .001] was also higher for HF group than no-HF group. Data from the smaller University hospital cohort showed similar findings.

CONCLUSIONS

Patients with a history of HF may be an under-recognized high-risk group among patients hospitalized for hyperglycemic crisis. Additional studies are warranted to clarify risk elements and optimize the inpatient care of individuals with hyperglycemic crises.

Cocaine Positivity in ST-Elevation Myocardial Infarction: A True or False Association

INTRODUCTION

Every year, more than 500,000 US Emergency Department visits are associated with cocaine use. People who use cocaine tend to have a lower incidence of true ST-elevation myocardial infarction (STEMI).

OBJECTIVE

To identify the factors associated with true STEMI in patients with cocaine-positive (CPos) findings.

METHODS

We retrospectively analyzed 1144 consecutive patients with STEMI between 2008 and 2013. True STEMI was defined as having a culprit lesion on coronary angiogram. Multivariate and univariate analyses were used to identify risk factors and create a predictive model.

RESULTS

A total of 64 patients with suspected STEMI were CPos (mean age 53.1 ± 11.2 years; male = 80%). True STEMI was diagnosed in 34 patients. Patients with CPos true STEMI were more likely to be uninsured than those with false STEMI (61.8% vs 34.5%, p = 0.03) and have higher peak troponin levels (21.1 ng/mL vs 2.12 ng/mL, p = < 0.01) with no difference in mean age between the 2 groups (p = 0.24). In multivariate analyses, independent predictors of true STEMI in patients with CPos findings included age older than 65 years (odds ratio [OR] = 19.3, 95% confidence iterval [CI] = 1.2-318.3), lack of health insurance (OR = 4.9, 95% CI = 1.2-19.6), and troponin level higher than 0.05 (OR = 24.0, 95% CI = 2.6-216.8) (all p < 0.05). A multivariate risk score created with a C-statistic of 82% (95% CI = 71-93) significantly improved the identification of patients with true STEMI.

CONCLUSION

Among those with suspected STEMI, patients with CPos findings had a higher incidence of false STEMI. Older age, lack of health insurance, and troponin levels outside of defined limits were associated with true STEMI in this group.

Termination of bleeding by a specific, anticatalytic antibody against plasmin

BACKGROUND

Excessive, plasmin-mediated fibrinolysis augments bleeding and contributes to death in some patients. Current therapies for fibrinolytic bleeding are limited by modest efficacy, low potency, and off-target effects.

OBJECTIVES

To determine whether an antibody directed against unique loop structures of the plasmin protease domain may have enhanced specificity and potency for blocking plasmin activity, fibrinolysis, and experimental hemorrhage.

METHODS

The binding specificity, affinity, protease cross-reactivity and antifibrinolytic properties of a monoclonal plasmin inhibitor antibody (Pi) were examined and compared with those of epsilon aminocaproic acid (EACA), which is a clinically used fibrinolysis inhibitor.

RESULTS

Pi specifically recognized loop 5 of the protease domain, and did not bind to other serine proteases or nine other non-primate plasminogens. Pi was ~7 logs more potent in neutralizing plasmin cleavage of small-molecule substrates and >3 logs more potent in quenching fibrinolysis than EACA. Pi was similarly effective in blocking catalysis of a small-molecule substrate as α2 -antiplasmin, which is the most potent covalent inhibitor of plasmin, and was a more potent fibrinolysis inhibitor. Fab or chimerized Fab fragments of Pi were equivalently effective. In vivo, in a humanized model of fibrinolytic surgical bleeding, Pi significantly reduced bleeding to a greater extent than a clinical dose of EACA.

CONCLUSIONS

A mAb directed against unique loop sequences in the protease domain is a highly specific, potent, competitive plasmin inhibitor that significantly reduces experimental surgical bleeding in vivo.

Relation of Obesity to Outcomes of Hospitalizations for Atrial Fibrillation

Obesity has been linked with increased incidence of atrial fibrillation (AF), but impact of presence of obesity on outcomes of hospitalizations for AF has not been investigated. We used the National Inpatient Sample database 2010 to 2014 to identify all adult hospitalizations aged ≥18years with a primary diagnosis of AF. Obese patients were identified using the co-morbidity variable for obesity, as defined in National Inpatient Sample databases. Multivariable logistic regression was used to compare in-hospital outcomes (mortality, acute stroke events) between obese and non-obese patients with AF. Of 431, 734 hospitalizations for AF, 66,138 (15.3%) were obese. Obese patients were younger and more likely to be African-Americans compared with non-obese patients. Despite being younger, obese patients had significantly higher prevalence of cardiovascular co-morbidities such as hypertension, diabetes mellitus, dyslipidemia, smoking, heart failure, and chronic renal failure (p <0.001 for all). After multivariate risk-adjustment, obese patients had a lower observed in-hospital mortality (0.5% vs 1.0%; unadjusted odds ratio = 0.52, 95% confidence interval [CI] 0.46 to 0.58, p <0.001; adjusted odds ratio = 0.83, 95% CI 0.73 to 0.94, p <0.001) and acute stroke events (0.4% vs 0.7%, unadjusted odds ratio = 0. 65, 95% CI 0.57 to 0.73, p < 0.001; adjusted odds ratio = 0.82, 95% CI 0.72 to 0.94) compared with non-obese patients. In conclusion, in this large retrospective analysis of an unselected nationwide cohort of patients hospitalized for AF, obese patients demonstrated lower risk-adjusted odds of in-hospital mortality and stroke events, consistent with an "obesity paradox."

Increases in plasma corin levels following experimental myocardial infarction reflect the severity of ischemic injury

Following acute myocardial infarction, clinical studies show alterations in the blood levels of corin, a cardiac-selective activator of the natriuretic peptides pro-atrial natriuretic peptide (pro-ANP) and pro-B-type natriuretic peptide (pro-BNP). However, the temporal changes in circulating and cardiac corin levels and their relationships to the severity of myocardial infarction have not been studied. The main objective of this study was to examine the relationship between cardiac and circulating corin levels and their association with cardiac systolic function and infarct size during the early phase of acute myocardial infarction (<72 h) in a translationally relevant induced coronary ligation mouse model. This acute phase timeline was chosen to correlate with the clinical practice within which blood samples are collected from myocardial infarction patients. Heart and plasma samples were examined at 3, 24, and 72 hours post acute myocardial infarction. Plasma corin levels were examined by enzyme-linked immunosorbent assay, transcripts of cardiac corin, pro-ANP and pro-BNP by quantitative real-time polymerase chain reaction, cardiac corin expression by immunohistology, infarct size by histology and heart function by echocardiography. Plasma corin levels were significantly increased at 3 (P<0.05), 24 (P<0.001), and 72 hours (P<0.01) post-acute myocardial infarction. In contrast, cardiac corin transcript levels dropped by 5% (P>0.05), 69% (P<0.001) and 65% (P<0.001) and immunoreactive cardiac corin protein levels dropped by 30% (P<0.05), 76% (P<0.001) and 75% (P<0.001), while cardiac pro-ANP and pro-BNP transcript levels showed an opposite pattern. Plasma corin levels were negatively correlated with immunoreactive cardiac corin (P<0.01), ejection fraction (P<0.05) and fractional shortening (P<0.05), but positively correlated with infarct size (P<0.01). In conclusion, acute myocardial infarction induces rapid increases in plasma corin and decreases in cardiac corin levels. In the early phase of acute myocardial infarction, plasma corin levels are inversely correlated with heart function and may reflect the severity of myocardial damage.

Generation and Mechanism of Action of a Potent Inhibitor of Factor XIII Function

Although known to play a critical role in thrombosis, the precise role of factor XIII in other processes like wound healing and gestation remains to be elucidated. Because a specific, potent inhibitor could help define the function of factor XIII in these processes, or determine the potential benefits of factor XIII suppression in thrombotic disease, we have derived and characterized a monoclonal antibody inhibitor of factor XIII activation. This immunoinhibitor, 9C11, reacts specifically with both plasma and platelet forms of factor XIII. When added to human plasma, either as whole immunoglobulin or as Fab fragments, 9C11 completely prevented thrombin-activated factor XIII activity with small molecular weight substrates like 14C-putrescine. In addition, when clotted with plasma, 9C11 ablated the gamma chain crosslinking of fibrin catalyzed by factor XIII and markedly accelerated the fibrinolysis of plasma clots by urokinase. Studies of the mechanism of action showed that 9C11 inhibited the cleavage and activation of factor XIII by thrombin, but did not affect the catalytic function of previously activated factor XIII. Although it inhibited thrombin activation, experiments indicated that it bound comparably to both factor XIII zymogen and the thrombin-cleaved zymogen, and did not bind to the thrombin cleavage site of the molecule. Taken together these experiments indicated that 9C11 acted as an inhibitor of the thrombin cleavage and activation of the factor XIII A-subunit. Its potency and specificity make it a useful agent for studying thrombin-activatable factor XIII function in biological systems.

Single Step Purification of Platelet Factor XIII Using an Immobilized Factor XIII A-Subunit Monoclonal Antibody

To facilitate the analysis of the catalytic subunit of factor XIII we have developed a method for the immunoaffinity purification of this protein from platelets. This method employs a monoclonal antibody that binds to the a-subunit of factor XIII. The anti-factor XIII antibody was immobilized on agarose and then incubated with platelet lysate. Subsequently factor XIII was isolated from the platelet lysate in a single step with a 41% yield as measured by enzyme assay. The purified platelet factor XIII appeared nearly homogeneous when analyzed by polyacrylamide electrophoresis and by immunoblotting with another factor XIII monoclonal antibody.

Platelet Factor XIII Increases the Fibrinolytic Resistance of Platelet-Rich Clots by Accelerating the Crosslinking of α2-Antiplasmin to Fibrin

Platelet clots resist fibrinolysis by plasminogen activators. We hypothesized that platelet factor XIII may enhance the fibrinolytic resistance of platelet-rich clots by catalyzing the crosslinking of α2-antiplasmin (α2AP) to fibrin. Analysis of plasma clot structure by polyacrylamide gel electrophoresis and immunoblotting revealed accelerated α2AP-fibrin crosslinking in platelet-rich compared with platelet-depleted plasma clots. A similar study of clots formed with purified fibrinogen (depleted of factor XIII activity), isolated platelets, and specific factor XIII inhibitors indicated that this accelerated crosslinking was due to the catalytic activity of platelet factor XIII. Moreover, when washed platelets were aggregated by thrombin, there was evidence of platelet factor XIII-mediated crosslinking between platelet α2AP and platelet fibrin(ogen). Specific inhibition (by a monoclonal antibody) of the α2AP associated with washed platelet aggregates accelerated the fibrinolysis of the platelet aggregate. Thus in platelet-rich plasma clots, and in thrombin-induced platelet aggregates, platelet factor XIII actively formed α2AP-fibrin crosslinks, which appeared to enhance the resistance of platelet-rich clots to fibrinolysis.

Impact of smoking in patients undergoing transcatheter aortic valve replacement

Background

The paradox that smokers have better clinical outcomes in cardiovascular diseases remains controversial. No literature exists studying impact of smoking on outcomes following transcatheter aortic valve replacement (TAVR).

Methods

We performed an electronic search of the 2011-2012 National Inpatient Sample (NIS) database to identify all TAVR hospitalizations. Outcomes were measured comparing smokers to non-smokers.

Results

A total of 8,345 TAVR hospitalizations were identified with 24% being smokers. Compared to non-smokers, smokers were younger (80.4±8.8 vs. 81.4±9.2 years, P<0.001), were more often men (63.6% vs. 47.8%, P<0.001), and had a higher disease burden. Despite a higher disease burden, smokers had lower post procedure stroke (2.8% vs. 3.1%), hemorrhage events (28.2% vs. 32.0%, P<0.05) and lower all cause in-hospital mortality (1.2% vs. 5.7%, adjusted odds ratio 0.21, 95% CI: 0.13-0.32, P<0.001) compared to non-smokers.

Conclusions

Despite having a higher cardiovascular disease burden, smokers had better outcomes compared to non-smokers. Therefore the smoker's paradox is applicable in the TAVR cohort.

Impact of family history of coronary artery disease on in-hospital clinical outcomes in ST-segment myocardial infarction

Background

Patients with a family history of coronary artery disease (FHxCAD) are at increased risk for development of myocardial infarction (MI). However, the data on the influence of FHxCAD on in-hospital clinical outcomes post ST-segment myocardial infarction (STEMI) is limited. Hence, we evaluated the impact of FHxCAD on in-hospital clinical outcomes post STEMI in an unselected nationwide cohort.

Methods

Nationwide Inpatient Sample (NIS) database [2003-2011] was used to compare differences in all-cause in-hospital mortality and adverse clinical events (cardiogenic shock, acute cerebrovascular events and use of intra-aortic balloon pump) between patients with and without FHxCAD.

Results

A total of 2,123,492 STEMI admissions were identified, of which 7.4% (n=158,079) patients were with FHxCAD and 92.6% (n=1,965,413) were without FHxCAD. The FHxCAD group had lower in-hospital mortality [1.4% vs. 8.1%; adjusted odds ratio (OR): 0.42, 95% confidence interval (CI): 0.41-0.44; P<0.001] when compared with no-FHxCAD group. They underwent a significantly higher number of coronary interventions, and were less likely to develop cardiogenic shock, acute cerebrovascular events and to require intra-aortic balloon pump during hospitalization.

Conclusions

This large sample size study demonstrates that STEMI patients with FHxCAD had lower in-hospital mortality and adverse clinical events in comparison to patients with no-FHxCAD. Further research is warranted to determine whether the superior outcomes in FHxCAD patients with STEMI are related to differences in strategies related to diet, exercise, use of medications or coronary interventions.

Matrix Metalloproteinase-9 Mediates the Deleterious Effects of α2-Antiplasmin on Blood-Brain Barrier Breakdown and Ischemic Brain Injury in Experimental Stroke

During acute brain ischemia, α2-antiplasmin markedly enhances brain injury, blood-brain barrier breakdown and matrix metalloproteinase-9 (MMP-9) expression. Although α2-antiplasmin inhibits fibrin thrombus-degradation, and MMP-9 is a collagen-degrading enzyme altering blood-brain barrier, both have similar deleterious effects on the ischemic brain. We examined the hypothesis that MMP-9 is an essential downstream mediator of α2-antiplasmin's deleterious effects during brain ischemia. Middle cerebral artery thromboembolic stroke was induced in a randomized, blinded fashion in mice with increased blood levels of α2-antiplasmin. There was a robust increase in MMP-9 expression (immunofluorescence) in the ischemic vs. the non-ischemic hemisphere of MMP-9^+/+ but not MMP-9^-/- mice, 24 h after stroke. Brain swelling and hemorrhage were significantly increased in the ischemic vs. the non-ischemic hemisphere of MMP-9^+/+ mice. By comparison to MMP-9^+/+ mice, the ischemic hemispheres of MMP-9^-/- mice showed a ∼6-fold reduction in brain swelling (p < 0.001) and a ∼9-fold reduction in brain hemorrhage. Brain infarction (p < 0.0001) and TUNEL-positive cell death (p < 0.001) were significantly diminished in the ischemic hemisphere of MMP-9^-/- mice vs. MMP-9^+/+ mice. Ischemic breakdown of the blood-brain barrier and fibrin deposition were also significantly reduced in MMP-9^-/- mice vs. MMP-9^+/+ mice (p < 0.05), as measured by quantitative immunofluorescence. We conclude that MMP-9 deficiency ablates many of the deleterious effects of high α2-antiplasmin levels, significantly reducing blood-brain barrier breakdown, TUNEL-positive cell death, brain hemorrhage, swelling and infarction. This suggests that the two molecules may be in a shared pathway in which MMP-9 is essential downstream for the deleterious effects of α2-antiplasmin in ischemic stroke.

Abstract P349: Plasma Corin Levels Reflect Dynamic Changes in Cardiac Expression Induced by Experimental Acute Myocardial Infarction

Introduction: Corin is a cardiac membrane protease that activates pro-ANP and pro-BNP. Changes in circulating corin levels have been linked to poor clinical outcomes following acute myocardial infarction (AMI) in some, but not all studies and the pathophysiologic mechanisms responsible for these changes are not understood.

Hypothesis: We examined the hypothesis that plasma corin levels are closely correlated with alterations in cardiac corin expression related to acute ischemic injury.

Methods: AMI was induced by left anterior descending coronary artery ligation. Hearts and plasma were assessed at 3 hrs, 24 hrs and 3 days post AMI. We measured plasma corin, troponin T levels, cardiac corin, infarct size, ANP and BNP expression by ELISA, qRT-PCR and histology staining. Cardiac function was assessed by echocardiography. Data represent means ± SE of n = 7-9 mice per group.

Results: Plasma corin levels were significantly increased at 3 hrs (1090±237.50 pg/ml, P<0.05), 24 hrs (1666±214.50 pg/ml, P<0.001), and 3 days (1221±185.90 pg/ml, P<0.01P<0.01) post-AMI with a “rise-and-fall” pattern similar as troponin T when compared to non-MI group (553.9±96.13 pg/ml). In contrast, at the same time-points, cardiac corin expression dropped by 5% (P>0.05), 69% (P<0.001) and 65% (P<0.001) as measured by real time PCR and 30% (P<0.05), 76% (P<0.001) and 75% (P<0.001) by immunohistology. Transcript levels of pro-ANP increased at 24 hrs (20%) and 3 days (3.8-fold, P<0.001) vs. non-MI mice. Transcript levels of pro-BNP also increased 3.2-fold at 24 hrs (P<0.001) and 1.8-fold at 3 days (P<0.01) post MI. EF% and FS% consistently dropped by 36% (P<0.01), 60% (P<0.001) and 68% (P<0.001) and 42% (P<0.01), 63% (P<0.001) and 72% (P<0.001) respectively. Plasma corin levels were negatively correlated with cardiac corin (P<0.01), EF% and FS% (P<0.05) and positively correlated with infarct sizes (P<0.01).

Conclusions: Plasma corin levels markedly increase and then decline following AMI, reflecting dynamic changes of cardiac corin expression related to acute cardiomyocyte injury. As such, plasma corin levels may serve as a valuable marker to indicate the severity of acute myocardial injury and, over a longer term, expression by the remaining viable cardiomyocyte mass.

Meta-Analysis of the Relative Efficacy and Safety of Oral P2Y12 Inhibitors in Patients With Acute Coronary Syndrome

A cornerstone of medical therapy for patients with acute coronary syndrome (ACS) is dual antiplatelet therapy, which includes aspirin and a P2Y12 inhibitor. Randomized controlled trials (RCTs) have shown that prasugrel and ticagrelor are superior to clopidogrel, but none directly compared these 3 commonly used oral P2Y12 inhibitors for safety and efficacy. Therefore, we performed a Bayesian network meta-analysis of RCTs to compare the efficacies and safeties of 3 commonly used oral P2Y12 inhibitors in patients with ACS. Scientific databases and websites were searched for relevant RCTs. We included data from 9 RCTs that enrolled 106,288 patients. Clopidogrel decreased the rates of major adverse cardiac event, recurrent myocardial infarction, and all-cause mortality compared with placebo. Both ticagrelor and prasugrel decreased the rates for major adverse cardiac event and recurrent myocardial infarction compared with clopidogrel, but there was no difference between the 2. Both also decreased the stent thrombosis rate compared with clopidogrel, but prasugrel was more effective than ticagrelor. Ticagrelor use was also associated with improved all-cause and CV mortalities compared with clopidogrel. There was no difference in CV mortality or all-cause mortality between clopidogrel and prasugrel. Prasugrel use was also associated with significantly increased risk of major bleeding compared with clopidogrel but showed a nonsignificant trend toward increasing the risk of bleeding compared with ticagrelor. In treatment ranking, ticagrelor was the most efficacious, and prasugrel was the least safe. In conclusion, this meta-analysis shows that in patients with ACS, adding P2Y12 inhibitors to aspirin and other standard treatments reduces ischemic events and all-cause mortality. Among the commonly used oral P2Y12 inhibitors, ticagrelor has the best net efficacy and safety profile.

Releasing the Brakes on the Fibrinolytic System in Pulmonary Emboli: Unique Effects of Plasminogen Activation and α2-Antiplasmin Inactivation

BACKGROUND

In patients with hemodynamically significant pulmonary embolism, physiological fibrinolysis fails to dissolve thrombi acutely and r-tPA (recombinant tissue-type plasminogen activator) therapy may be required, despite its bleeding risk. To examine potential mechanisms, we analyzed the expression of key fibrinolytic molecules in experimental pulmonary emboli, assessed the contribution of α2-antiplasmin to fibrinolytic failure, and compared the effects of plasminogen activation and α2-antiplasmin inactivation on experimental thrombus dissolution and bleeding.

METHODS

Pulmonary embolism was induced by jugular vein infusion of ¹²⁵I-fibrin or fluorescein isothiocyanate-fibrin labeled emboli in anesthetized mice. Thrombus site expression of key fibrinolytic molecules was determined by immunofluorescence staining. The effects of r-tPA and α2-antiplasmin inactivation on fibrinolysis and bleeding were examined in a humanized model of pulmonary embolism.

RESULTS

The plasminogen activation and plasmin inhibition system assembled at the site of acute pulmonary emboli in vivo. Thrombus dissolution was markedly accelerated in mice with normal α2-antiplasmin levels treated with an α2-antiplasmin-inactivating antibody (P<0.0001). Dissolution of pulmonary emboli by α2-antiplasmin inactivation alone was comparable to 3 mg/kg r-tPA. Low-dose r-tPA alone did not dissolve emboli, but was synergistic with α2-antiplasmin inactivation, causing more embolus dissolution than clinical-dose r-tPA alone (P<0.001) or α2-antiplasmin inactivation alone (P<0.001). Despite greater thrombus dissolution, α2-antiplasmin inactivation alone, or in combination with low-dose r-tPA, did not lead to fibrinogen degradation, did not cause bleeding (versus controls), and caused less bleeding than clinical-dose r-tPA (P<0.001).

CONCLUSIONS

Although the fibrinolytic system assembles at the site of pulmonary emboli, thrombus dissolution is halted by α2-antiplasmin. Inactivation of α2-antiplasmin was comparable to pharmacological r-tPA for dissolving thrombi. However, α2-antiplasmin inactivation showed a unique pattern of thrombus specificity, because unlike r-tPA, it did not degrade fibrinogen or enhance experimental bleeding. This suggests that modifying the activity of a key regulator of the fibrinolytic system, like α2-antiplasmin, may have unique therapeutic value in pulmonary embolism.

High-sensitivity C-reactive protein in stroke patients - The importance in consideration of influence of multiple factors in the predictability for disease severity and death

High sensitivity C-reactive protein (hsCRP) has been evaluated as a biomarker in stroke and relevant pathological diseases. While its predictive values in several pathological phenotypes have been confirmed, controversy exists among different studies. This review summarizes reports of the predictive values of hsCRP for the diagnosis, etiology, prognosis and mortality of stroke diseases. The current literature suggests that CRP expression is influenced by multiple factors, such as polymorphisms, the genomic backgrounds and gender. However, few reported studies analyzed data based on all these multiple factors. Future studies should focus on comprehensive analysis based on multiple factors.

Racial Difference in Symptom Onset to Door Time in ST Elevation Myocardial Infarction

BACKGROUND

There are poorer outcomes following ST elevation myocardial infarction in blacks compared to white patients despite comparable door-to-reperfusion time. We hypothesized that delays to hospital presentation may be contributory.

METHODS AND RESULTS

We conducted a retrospective analysis of the 1144 patients admitted for STEMI in our institution from 2008 to 2013. The door-to-balloon time (D2BT) and symptom-onset-to-door time (SODT) were compared by race. Bivariate analysis was done comparing the median D2BT and SODT. Stratified analyses were done to evaluate the effect of race on D2BT and SODT, accounting for insurance status, age, sex and comorbidities. The mean age was 59±13 years; 56% of this population was black and 41% was white. Males accounted for 66% of this population. The median D2BT was 60 minutes (interquartile range [IQR] 42-82), and median SODT was 120 minutes (IQR 60-720). There was no significant difference in D2BT by race (P=0.86). Black patients presented to the emergency room (ER) later than whites (SODT=180 [IQR 60-1400] vs 120 [IQR 60-560] minutes, P<0.01) and were more likely to be uninsured (P<0.01). After controlling for comorbidities, insurance, and socioeconomic status, blacks were 60% more likely to present late after a STEMI (OR 1.6, P<0.01). A subset analysis excluding transferred patients showed similar results.

CONCLUSIONS

Black patients present later to the ER after STEMI with no difference in D2BT compared to whites. This difference in time to presentation may be one of the factors accounting for poor outcomes in this population.

Physiologic variations in blood plasminogen levels affect outcomes after acute cerebral thromboembolism in mice: a pathophysiologic role for microvascular thrombosis

Essentials Physiologic variations in blood plasminogen (Pg) levels may affect ischemic stroke outcomes. We tested Pg effects in a model with translational relevance to human thromboembolic stroke. A dose-response exists between Pg levels and brain injury, fibrinolysis, barrier breakdown. Higher Pg levels reduce microvascular thrombosis and improve outcomes in ischemic stroke.

SUMMARY

Background and Objectives Plasminogen appears to affect brain inflammation, cell movement, fibrinolysis, neuronal excitotoxicity, and cell death. However, brain tissue and circulating blood plasminogen may have different roles, and there is wide individual variation in blood plasminogen levels. The aim of this study was to determine the integrated effect of blood plasminogen levels on ischemic brain injury. Methods We examined thromboembolic stroke in mice with varying, experimentally determined, blood plasminogen levels. Ischemic brain injury, blood-brain barrier breakdown, matrix metalloproteinase-9 expression and microvascular thrombosis were determined. Results Within the range of normal variation, plasminogen levels were strongly associated with ischemic brain injury; higher blood plasminogen levels had dose-related, protective effects. Higher plasminogen levels were associated with increased dissolution of the middle cerebral artery thrombus. Higher plasminogen levels decreased blood-brain barrier breakdown, matrix metalloproteinase-9 expression and microvascular thrombosis in the ischemic brain. In plasminogen-deficient mice, selective restoration of blood plasminogen levels reversed the harmful effects of plasminogen deficiency on ischemic brain injury. Specific inhibition of thrombin also reversed the effect of plasminogen deficiency on ischemic injury by decreasing microvascular thrombosis, blood-brain barrier breakdown, and matrix metalloproteinase-9 expression. Conclusions Variation in blood plasminogen levels, within the range seen in normal individuals, had marked effects on experimental ischemic brain injury. Higher plasminogen levels protected against ischemic brain injury, and decreased blood-brain barrier breakdown, matrix metalloproteinase-9 expression, and microvascular thrombosis. The protective effects of blood plasminogen appear to be mediated largely through a decrease in microvascular thrombosis in the ischemic territory.

α2-Antiplasmin: New Insights and Opportunities for Ischemic Stroke

Thrombotic vascular occlusion is the leading cause of ischemic stroke. High blood levels of α₂-antiplasmin (a2AP), an ultrafast, covalent inhibitor of plasmin, have been linked in humans to increased risk of ischemic stroke and failure of tissue plasminogen activator (tPA) therapy. Consistent with these observations, a2AP neutralizes the therapeutic benefit of tPA therapy in experimental stroke. In addition, a2AP has deleterious, dose-related effects on ischemic brain injury in the absence of therapy. Experimental therapeutic inactivation of a2AP markedly reduces microvascular thrombosis, ischemic brain injury, brain swelling, brain hemorrhage, and death after thromboembolic stroke. These data provide new insights into the critical importance of a2AP in the pathogenesis of ischemic brain injury and suggest that transiently inactivating a2AP may have therapeutic value in ischemic stroke.

Abstract 36: Alpha 2-antiplasmin Prevents the Resolution of Deep Vein Thrombosis

Introduction: Deep venous thrombosis is a major cause of death and disability. Despite anticoagulation treatment, venous thrombi persist for months, causing chronic venous obstruction, inflammatory remodeling and post-thrombotic syndrome. The mechanisms responsible for impaired clearance of venous thrombi are poorly understood. Alpha 2-antiplasmin (a2AP) is the primary physiological inhibitor of plasmin and a key regulator of the fibrinolytic pathway. The role of a2AP in the resolution of venous thrombosis has not been determined.

Hypothesis: We tested the hypothesis that a2AP prevents the resolution of experimental deep venous thrombi.

Methods and Results: Thrombus resolution and content were examined in a2AP +/+ and a2AP -/- mice using a well-established, fibrinolytic-resistant, stasis model induced by ligation of the inferior vena cava (IVC). Thrombus weight and composition were determined after 7 days. Data was analyzed by one-way ANOVA with Neumann-Keul’s correction. Thrombus weight was reduced in a2AP -/- mice by >90% when compared to a2AP +/+ mice (p<0.001); there was no significant difference between a2AP -/- mice and shams. Histochemical and immunofluorescence staining showed significant reductions in IVC fibrin content, neutrophil recruitment and matrix metalloproteinase-9 expression in a2AP -/- mice (p<0.001) vs. a2AP +/+ mice. The relative effect of plasminogen activation and a2AP on resolution of preformed venous thrombi was examined in wild-type a2AP +/+ mice treated 24 h after IVC ligation with tissue plasminogen activator (TPA) (1.2 or 5 mg/kg) or a monoclonal antibody inactivating a2AP (10 mg/Kg). By comparison to 7 day old venous thrombi in untreated mice, treatment with TPA at 1.2 mg/kg or 5 mg/kg did not decrease thrombus size after 7 days. In contrast, a2AP inactivation significantly reduced thrombus weight vs. untreated and TPA-treated mice (p<0.01 to p<0.001).

Conclusions: In experimental venous thrombosis, a2AP was required for the persistence of venous thrombi 7 days after formation. Venous thrombi resisted TPA, but were sensitive to resolution after a2AP inactivation. This suggests that a2AP may be responsible for the persistence of clinical venous thrombosis in humans.

Depressed Corin Levels Indicate Early Systolic Dysfunction Before Increases of Atrial Natriuretic Peptide/B-Type Natriuretic Peptide and Heart Failure Development

Dilated cardiomyopathy is a major cause of heart failure (HF) that affects millions. Corin cleaves and biologically activates pro-atrial natriuretic peptide (pro-ANP) and pro-B-type natriuretic peptide (pro-BNP). High corin levels reduce the development of systolic dysfunction and HF in experimental dilated cardiomyopathy. Yet, patients with significant HF unexpectedly show low corin levels with high plasma ANP/BNP levels. Therefore, we examined the relationship between cardiac corin expression, ANP/BNP levels, and the stages of HF. We used a well-established, dilated cardiomyopathy model to evaluate gene and protein expression as mice longitudinally developed Stages A-D HF. Cardiac systolic function (ejection fraction) continuously declined over time (P<0.001). Cardiac corin transcripts were decreased at early Stage B HF and remained low through Stages C and D (P<0.001). Cardiac corin levels were positively correlated with systolic function (r=0.96, P=0.003) and inversely with lung water (r=-0.92, P=0.001). In contrast, cardiac pro-ANP/BNP transcripts increased later (Stages C and D) and plasma levels rose only with terminal HF (Stage D, P<0.001). Immunoreactive plasma ANP and BNP levels were positively associated with plasma cyclic guanosine monophosphate levels (r=0.82, P=0.01 and r=0.8, P=0.02, respectively). In experimental dilated cardiomyopathy, corin levels declined early with progressive systolic dysfunction before the development of HF, whereas significant increases in plasma ANP, BNP, and cyclic guanosine monophosphate levels were found only in later stage (C and D) HF. This dyssynchrony in expression of corin versus ANP/BNP may impair cleavage activation of pro-natriuretic peptides, and thereby promote the transition from earlier to later stage HF.

Blood Accessibility to Fibrin in Venous Thrombosis is Thrombus Age-Dependent and Predicts Fibrinolytic Efficacy: An In Vivo Fibrin Molecular Imaging Study

Fibrinolytic therapy of venous thromboembolism (VTE) is increasingly utilized, yet limited knowledge is available regarding in vivo mechanisms that govern fibrinolytic efficacy. In particular, it is unknown how age-dependent thrombus organization limits direct blood contact with fibrin, the target of blood-based fibrinolytic agents. Utilizing high-resolution in vivo optical molecular imaging with FTP11, a near-infrared fluorescence (NIRF) fibrin-specific reporter, here we investigated the in vivo interrelationships of blood accessibility to fibrin, thrombus age, thrombus neoendothelialization, and fibrinolysis in murine venous thrombosis (VT). In both stasis VT and non-stasis VT, NIRF microscopy showed that FTP11 fibrin binding was thrombus age-dependent. FTP11 localized to the luminal surface of early-stage VT, but only minimally to subacute VT (p<0.001). Transmission electron microscopy of early stage VT revealed direct blood cell contact with luminal fibrin-rich surfaces. In contrast, subacute VT exhibited an encasing CD31+ neoendothelial layer that limited blood cell contact with thrombus fibrin in both VT models. Next we developed a theranostic strategy to predict fibrinolytic efficacy based on the in vivo fibrin accessibility to blood NIRF signal. Mice with variably aged VT underwent FTP11 injection and intravital microscopy (IVM), followed by tissue plasminogen activator infusion to induce VT fibrinolysis. Fibrin molecular IVM revealed that early stage VT, but not subacute VT, bound FTP11 (p<0.05), and experienced higher rates of fibrinolysis and total fibrinolysis (p<0.05 vs. subacute VT). Before fibrinolysis, the baseline FTP11 NIRF signal predicted the net fibrinolysis at 60 minutes (p<0.001). Taken together, these data provide novel insights into the temporal evolution of VT and its susceptibility to therapeutic fibrinolysis. Fibrin molecular imaging may provide a theranostic strategy to identify venous thrombi amenable to fibrinolytic therapies.

Microvascular thrombosis, fibrinolysis, ischemic injury, and death after cerebral thromboembolism are affected by levels of circulating α2-antiplasmin

OBJECTIVE

Ischemic stroke is primarily attributable to thrombotic vascular occlusion. Elevated α2-antiplasmin (a2AP) levels correlate with increased stroke risk, but whether a2AP contributes to the pathogenesis of stroke is unknown. We examined how a2AP affects thrombosis, ischemic brain injury, and survival after experimental cerebral thromboembolism.

APPROACH AND RESULTS

We evaluated the effects of a2AP on stroke outcomes in mice with increased, normal, or no circulating a2AP, as well as in mice given an a2AP-inactivating antibody. Higher a2AP levels were correlated with greater ischemic brain injury (rs=0.88, P<0.001), brain swelling (rs=0.82, P<0.001), and reduced middle cerebral artery thrombus dissolution (rs=-0.93, P<0.001). In contrast, a2AP deficiency enhanced thrombus dissolution, increased cerebral blood flow, reduced brain infarction, and decreased brain swelling. By comparison to tissue plasminogen activator (TPA), a2AP inactivation hours after thromboembolism still reduced brain infarction (P<0.001) and hemorrhage (P<0.05). Microvascular thrombosis, a process that enhances brain ischemia, was markedly reduced in a2AP-deficient or a2AP-inactivated mice compared with TPA-treated mice or mice with increased a2AP levels (all P<0.001). Matrix metalloproteinase-9 expression, which contributes to acute brain injury, was profoundly decreased in a2AP-deficient or a2AP-inactivated mice versus TPA-treated mice or mice with increased a2AP levels (all P<0.001). a2AP inactivation markedly reduced stroke mortality versus TPA (P<0.0001).

CONCLUSIONS

a2AP has profound, dose-related effects on ischemic brain injury, swelling, hemorrhage, and survival after cerebral thromboembolism. By comparison to TPA, the protective effects of a2AP deficiency or inactivation seem to be mediated through reductions in microvascular thrombosis and matrix metalloproteinase-9 expression.

Abstract 504: Circulating Alpha-2-Antiplasmin Affects Microvascular Thrombosis, Ischemic Neurodegeneration and Mortality in Mice Following Cerebral Thromboembolism

Introduction: For unknown reasons, clinical studies suggest that high circulating levels of human alpha2-antiplasmin may increase the risk of thrombotic vascular diseases such as stroke and contribute to the failure of tissue plasminogen activator therapy.

Hypothesis: We tested the hypothesis that circulating alpha2-antiplasmin affects thrombosis, tissue injury and fibrinolysis in a translational model of middle cerebral artery thromboembolism.

Methods and Results: Elevated alpha2-antiplasmin levels significantly decreased thrombus dissolution (p<0.001), enhanced matrix metalloproteinase-9 (MMP-9) expression (p<0.001) and worsened brain injury (p<0.001) and swelling (p<0.001). Conversely, genetic deficiency of circulating alpha2-antiplasmin, enhanced dissolution of thromboemboli (p<0.001) and reduced brain injury (p<0.001). Circulating alpha2-antiplasmin had dynamic effects on stroke outcomes because specific alpha2-antiplasmin inactivation after thromboembolism saved lives (p<0.001), prevented disability, decreased brain infarction (p<0.001), reduced hemorrhage (p<0.05) and brain swelling (p<0.001). Inactivation of alpha2-antiplasmin led to reductions in MMP-9 (p<0.001), microvascular thrombosis (p<0.001), blood brain barrier breakdown and apoptosis (p<0.01).

Conclusions: These data suggest that alpha2-antiplasmin has deleterious effects in experimental stroke, which are mediated through the fibrinolytic pathway to alter culprit thrombus dissolution, as well as through other mechanisms that contribute to downstream microvascular thrombosis, hemorrhage, MMP-9 expression, apoptosis and blood brain barrier leakage.

Abstract 310: Do Biologic Variations in Plasminogen Levels Affect Endogenous Fibrinolysis and Outcomes in Acute Thrombotic Disease Such as Ischemic Stroke?

Introduction: After activation of plasminogen (Pg), plasmin is the key enzyme that acutely dissolves thrombi. Yet, despite significant biologic variation in Pg levels between humans, there is no clear link between Pg levels (or Pg deficiency) and the development or resolution of acute thrombotic vascular diseases such as stroke.

Hypothesis: We tested the hypothesis that plasma levels of Pg affect endogenous fibrinolysis, brain injury, hemorrhage and swelling after thromboembolic stroke.

Methods and results: We examined male and female Pg +/+ ([Pg] =84±4.8 μg/ml), Pg +/- ([Pg] =37±5.2 μg/ml) and Pg -/- ([Pg] =1.3±3 μg/ml) mice, n= 10-13 per group. Ischemic stroke was induced by endovascular placement of an autologous 125 I-fibrin plasma clot at the origin of middle cerebral artery (MCA) that reduced hemispheric blood flow by ≥80%. After 6 hours of stroke, the dissolution of the culprit MCA thrombus was determined and the effects on brain injury were assessed. Data was analyzed by a two-way ANOVA with Neumann-Keul’s correction. There was a dose-dependent relationship between Pg levels and endogenous dissolution of the MCA thrombus (p=0.0019) with Pg +/+ mice showing greater lysis (20.7±6.6%) than Pg +/- mice (19.0±3.8%) and Pg -/- mice (12.6±6.4%). There was a significant, inverse dose-response effect on brain infarction with higher Pg levels associated with less severe infarction: Pg +/+ (24.8±4.3%) <Pg +/- (27.3±9.4%) <Pg -/- (37.4±8.9%) mice. No significant sex based differences were found in fibrinolysis and brain injury. Brain swelling showed a significant, but non-linear dose-dependence on Pg levels (p<0.01) which was affected by sex (p<0.01). There was no significant association between brain hemorrhage and Pg levels.

Conclusions: In vivo, Pg levels have concentration-dependent effects on endogenous fibrinolysis, brain infarction and swelling after thromboembolic stroke. Further studies should be done to assess how Pg levels may affect outcomes in human thrombotic diseases.

Atrial natriuretic peptide affects cardiac remodeling, function, heart failure, and survival in a mouse model of dilated cardiomyopathy

Dilated cardiomyopathy is a frequent cause of heart failure and death. Atrial natriuretic peptide (ANP) is a biomarker of dilated cardiomyopathy, but there is controversy whether ANP modulates the development of heart failure. Therefore, we examined whether ANP affects heart failure, cardiac remodeling, function, and survival in a well-characterized, transgenic model of dilated cardiomyopathy. Mice with dilated cardiomyopathy with normal ANP levels survived longer than mice with partial ANP (P<0.01) or full ANP deficiency (P<0.001). In dilated cardiomyopathy mice, ANP protected against the development of heart failure as indicated by reduced lung water, alveolar congestion, pleural effusions, etc. ANP improved systolic function and reduced cardiomegaly. Pathological cardiac remodeling was diminished in mice with normal ANP as indicated by decreased ventricular interstitial and perivascular fibrosis. Mice with dilated cardiomyopathy and normal ANP levels had better systolic function (P<0.001) than mice with dilated cardiomyopathy and ANP deficiency. Dilated cardiomyopathy was associated with diminished cardiac transcripts for NP receptors A and B in mice with normal ANP and ANP deficiency, but transcripts for NP receptor C and C-type natriuretic peptide were selectively altered in mice with dilated cardiomyopathy and ANP deficiency. Taken together, these data indicate that ANP has potent effects in experimental dilated cardiomyopathy that reduce the development of heart failure, prevent pathological remodeling, preserve systolic function, and reduce mortality. Despite the apparent overlap in physiological function between the NPs, these data suggest that the role of ANP in dilated cardiomyopathy and heart failure is not compensated physiologically by other NPs.

Corin overexpression improves cardiac function, heart failure, and survival in mice with dilated cardiomyopathy

Heart failure, caused by dilated cardiomyopathy and other cardiac disorders such as hypertension, is a major public health problem with high morbidity and mortality. Corin, a cardiac enzyme that cleaves natriuretic peptides, is a promising biomarker of cardiomyopathy and heart failure, but its functional role in these processes is not understood. We evaluated the potential effects of corin in mice with a well-characterized model of dilated cardiomyopathy. Mice with dilated cardiomyopathy developed heart failure, reduced contractile function, cardiac fibrosis, and accelerated mortality in the setting of low corin expression. In wild-type mice, transgenic, cardiac-targeted, overexpression of corin enhanced cyclic guanosine monophosphate and blood pressure responses to pro-atrial natriuretic peptide, but did not affect heart size, contractility, body weights, survival, and blood pressure. In mice with dilated cardiomyopathy, corin overexpression significantly reduced the development of myocardial fibrosis (P<0.05). Corin overexpression also enhanced heart contractile function (fractional shortening and ejection fraction; P<0.01) and it significantly reduced heart failure as assessed by lung water (P<0.05) and alveolar congestion (P<0.001). Consistent with these observations, corin overexpression significantly prolonged life in mice with dilated cardiomyopathy (P<0.0001). These results provide the first experimental evidence that corin expression plays a role in cardiomyopathy by modulating myocardial fibrosis, cardiac function, heart failure, and survival.

Streptococcus uberis plasminogen activator (SUPA) activates human plasminogen through novel species-specific and fibrin-targeted mechanisms

Bacterial plasminogen (Pg) activators generate plasmin to degrade fibrin blood clots and other proteins that modulate the pathogenesis of infection, yet despite strong homology between mammalian Pgs, the activity of bacterial Pg activators is thought to be restricted to the Pg of their host mammalian species. Thus, we found that Streptococcus uberis Pg activator (SUPA), isolated from a Streptococcus species that infects cows but not humans, robustly activated bovine but not human Pg in purified systems and in plasma. Consistent with this, SUPA formed a higher avidity complex (118-fold) with bovine Pg than with human Pg and non-proteolytically activated bovine but not human Pg. Surprisingly, however, the presence of human fibrin overrides the species-restricted action of SUPA. First, human fibrin enhanced the binding avidity of SUPA for human Pg by 4-8-fold in the presence and absence of chloride ion (a negative regulator). Second, although SUPA did not protect plasmin from inactivation by α(2)-antiplasmin, fibrin did protect human plasmin, which formed a 31-fold higher avidity complex with SUPA than Pg. Third, fibrin significantly enhanced Pg activation by reducing the K(m) (4-fold) and improving the catalytic efficiency of the SUPA complex (6-fold). Taken together, these data suggest that indirect molecular interactions may override the species-restricted activity of bacterial Pg activators; this may affect the pathogenesis of infections or may be exploited to facilitate the design of new blood clot-dissolving drugs.

Multifunctional nanoagent for thrombus-targeted fibrinolytic therapy

BACKGROUND

Current thrombolytic therapies utilize exogenous plasminogen activators (PAs) to effectively lyse clots, restoring blood flow, and preventing tissue and organ death. These PAs may also impair normal hemostasis, leading to life-threatening bleeding, including intracerebral hemorrhage.

AIMS

This study aims to develop new thrombus-targeted fibrinolytic agents that harness the multifunctional theranostic capabilities of nanomaterials, potentially allowing for the generation of efficacious thrombolytics while minimizing deleterious side effects.

MATERIALS & METHODS

A thrombus-targeted nano-fibrinolytic agent was synthesized using a magnetofluorescent crosslinked dextran-coated iron oxide nanoparticle platform that was conjugated to recombinant tissue PA (tPA). Thrombus-targeting was achieved by derivatizing the nanoparticle with an activated factor XIII (FXIIIa)-sensitive peptide. Human plasma clot binding ability of the targeted and control agents was assessed by fluorescence reflectance imaging. Next, the in vitro enzymatic activity of the agents was assessed by S2288-based amidolytic activity, and an ELISA D-dimer assay for fibrinolysis. In vivo targeting of the nanoagent was next examined by intravital fluorescence microscopy of murine arterial and venous thrombosis. The fibrinolytic activity of the targeted nanoagent compared to free tPA was then evaluated in vivo in murine pulmonary embolism.

RESULTS

In vitro, the targeted thrombolytic nanoagent demonstrated superior binding to fresh-frozen plasma clots compared to control nanoagents (analysis of variance, p < 0.05). When normalized by S2288-based amidolytic activity, targeted, control and free tPA samples demonstrated equivalent in vitro fibrinolytic activity against human plasma clots, as determined by ELISA D-dimer assays. The FXIIIa targeted fibrinolytic nanoagent efficiently bound the margin of intravascular thrombi as detected by intravital fluorescence microscopy. In in vivo fibrinolysis studies the FXIIIa-targeted agent lysed pulmonary emboli with similar efficacy as free tPA (p > 0.05).

CONCLUSION

The applicability of a FXIIIa-targeted thrombolytic nanoagent in the treatment of thromboembolism was demonstrated in vitro and in vivo. Future studies are planned to investigate the safety profile and overall efficacy of this class of nanoagents.

Decompensated heart failure is associated with reduced corin levels and decreased cleavage of pro-atrial natriuretic peptide

BACKGROUND

By promoting salt and water excretion, the corin and the atrial natriuretic peptide (ANP) system should help to maintain fluid balance in heart failure. Yet, the development of fluid retention despite high levels of ANP-related peptides suggests that this compensatory system is limited.

METHODS AND RESULTS

Levels of circulating corin (the pro-ANP-converting enzyme) and pro-ANP were measured in hospitalized patients with heart failure, using novel immunoassays. Patients (n=14) had severe heart failure (New York Heart Association class III-IV) with a median ejection fraction of 18% and median brain natriuretic peptide levels of 1940 pg/mL. In heart failure, median plasma corin levels were 7.6-fold lower than measured in plasma from 16 normal control subjects (180 versus 1368 pg/mL, P<0.01). In contrast, in patients with heart failure, levels of plasma N-terminal ANP peptides (N-ANP and pro-ANP) levels were markedly elevated (42.0 versus 7.5 ng/mL, P<0.01). Levels of uncleaved pro-ANP, measured by novel immunoassays, were significantly higher in patients with heart failure (P<0.01), suggesting that corin cleavage of pro-ANP was impaired. Median plasma levels of cyclic guanosine monophosphate were elevated in patients with heart failure (150.0 versus 7.6 pmol/mL, P<0.01), and plasma cyclic guanosine monophosphate levels positively correlated with the fractional amount of cleaved pro-ANP (r(s)=0.59, P<0.03) but not with levels of uncleaved pro-ANP, implying that the cellular response to ANP remained intact.

CONCLUSIONS

Taken together, these data suggest that there may be patients for whom low corin levels and impaired pro-ANP cleavage contribute to acute decompensation.

African-American women have a higher risk for developing peripartum cardiomyopathy

OBJECTIVES

The purpose of this study was to assess whether African-American women are at increased risk of having peripartum cardiomyopathy.

BACKGROUND

Peripartum cardiomyopathy is a heart disease of unknown cause that affects young women, often with devastating consequences. The frequency of peripartum cardiomyopathy varies markedly between African and non-African regions.

METHODS

A case-control study was performed at a regional center that provides medical care to a racially heterogeneous population. For each case, 3 healthy control patients were randomly selected who delivered babies within the same month.

RESULTS

African-American women had a 15.7-fold higher relative risk of peripartum cardiomyopathy than non-African Americans (odds ratio [OR]: 15.7, 95% confidence interval [CI]: 3.5 to 70.6). Other significant univariate risk factors were hypertension (OR: 10.8, 95% CI: 2.6 to 44.4), being unmarried (OR: 4.2, 95% CI: 1.4 to 12.3), and having had >2 previous pregnancies (OR: 2.9, 95% CI: 1.1 to 7.4). African-American ethnicity remained a significant risk factor for peripartum cardiomyopathy when other risk factors were considered in multivariable (OR: 31.5, 95% CI: 3.6 to 277.6) and stratified analyses (OR: 12.9 to 29.1, p < 0.001). Although the frequency of peripartum cardiomyopathy (185 of 100,000 deliveries) at this center was higher than in previous U.S. reports, it was comparable to the frequency in countries with more women of African descent (100 to 980 of 100,000). Analysis of other U.S. studies confirmed that the frequency of peripartum cardiomyopathy was significantly higher among African-American women.

CONCLUSIONS

African-American women have significantly higher odds of having peripartum cardiomyopathy that could not be explained by several other factors. Further research will be necessary to determine the potential environmental and/or genetic factors associated with African descent that confer this risk.

Platelet dense-granule secretion plays a critical role in thrombosis and subsequent vascular remodeling in atherosclerotic mice

BACKGROUND

Platelet aggregation plays a critical role in myocardial infarction and stroke; however, the role of platelet secretion in atherosclerotic vascular disease is poorly understood. Therefore, we examined the hypothesis that platelet dense-granule secretion modulates thrombosis, inflammation, and atherosclerotic vascular remodeling after injury.

METHODS AND RESULTS

Functional deletion of the Hermansky-Pudlak syndrome 3 gene (HPS3(-/-)) markedly reduces platelet dense-granule secretion. HPS3(-/-) mice have normal platelet counts, platelet morphology, and alpha-granule number, as well as maximal secretion of the alpha-granule marker P-selectin; however, their capacity to form platelet-leukocyte aggregates is significantly reduced (P<0.05). To examine the role of platelet dense-granule secretion in these processes, atherosclerosis-prone mice with combined genetic deficiency of apolipoprotein E and HPS3 (ApoE(-/-), HPS3(-/-)) were compared with congenic, atherosclerosis-prone mice with normal platelet secretion (ApoE(-/-), HPS3(+/+)). After 16 to 18 weeks on a high-fat diet, both groups of mice had similar fasting cholesterol levels and body weight. Carotid arteries of ApoE(-/-), HPS3(+/+) mice thrombosed rapidly after FeCl(3) injury, but ApoE(-/-), HPS3(-/-) mice were completely resistant to thrombotic arterial occlusion (P<0.01). Three weeks after injury, neointimal hyperplasia (from alpha-smooth muscle actin-positive cells) was significantly less (P<0.001) in arteries from ApoE(-/-), HPS3(-/-) mice. In ApoE(-/-), HPS3(-/-) mice, there were also pronounced reductions in arterial inflammation, as indicated by a 74% decrease in CD45-positive leukocytes (P<0.01) and a 73% decrease in Mac-3-positive macrophages (P<0.05).

CONCLUSIONS

In atherosclerotic mice, reduced platelet dense-granule secretion is associated with marked protection against the development of arterial thrombosis, inflammation, and neointimal hyperplasia after vascular injury.

Reprogrammed streptokinases develop fibrin-targeting and dissolve blood clots with more potency than tissue plasminogen activator

BACKGROUND

Given the worldwide epidemic of cardiovascular diseases, a more effective means of dissolving thrombi that cause heart attacks, could markedly reduce death, disability and healthcare costs. Plasminogen activators (PAs) such as streptokinase (SK) and tissue plasminogen activator (TPA) are currently used to dissolve fibrin thrombi. SK is cheaper and more widely available, but it appears less effective because it lacks TPA's fibrin-targeted properties that focus plasminogen activation on the fibrin surface.

OBJECTIVE

We examined whether re-programming SK's mechanism of action would create PAs with greater fibrin-targeting and potency than TPA.

METHODS AND RESULTS

When fibrinogen consumption was measured in human plasma, reprogrammed molecules SKDelta1 and SKDelta59 were 5-fold and > 119-fold more fibrin-dependent than SK (P < 0.0001), and 2-fold and > 50-fold more fibrin-dependent than TPA (P < 0.001). The marked fibrin-targeting of SKDelta59 was due to the fact that: (i) it did not generate plasmin in plasma, (ii) it was rapidly inhibited by alpha2-antiplasmin, and (iii) it only processed fibrin-bound plasminogen. To assess the fibrin-targeting and therapeutic potential of these PAs in vivo, a novel 'humanized' fibrinolysis model was created by reconstituting plasminogen-deficient mice with human plasminogen. When compared with TPA, SKDelta1 and SKDelta59 were 4-fold (P < 0.0001) and 2-fold (P < 0.003) more potent at dissolving blood clots in vivo, respectively, on a mass-dose basis and 2-3 logs more potent than TPA (P < 0.0001) when doses were calibrated by standard activity assays.

CONCLUSION

These experiments suggest that reprogramming SK's mechanism of action markedly enhances fibrin-targeting and creates, in comparison with TPA, activators with greater fibrinolytic potency.

Atrial natriuretic peptide increases inflammation, infarct size, and mortality after experimental coronary occlusion

Acute coronary artery occlusion triggers the release of atrial natriuretic peptide (ANP) from the heart. ANP affects vasodilation, natriuresis, and inflammation, but the integrated biological effects of ANP on myocardial infarction are unknown. To elucidate these effects, the left anterior coronary artery was ligated in anesthetized, ANP-deficient (ANP(-/-)) and congenic wild-type (ANP(+/+)) mice. The survival of ANP(-/-) mice was markedly better (56%) at 30 days postinfarction than the survival of ANP(+/+) mice (20%, P < 0.01). Surviving mice were comparable initially, but ANP(-/-) mice developed more cardiac hypertrophy (P < 0.001) and had lower contractility indexes 30 days after infarction (P < 0.05). An analysis 24 h after coronary occlusion showed that ANP(-/-) mice had smaller infarcts than ANP(+/+) mice (62.6 +/- 12.1 vs. 100.8 +/- 3.8%, P < 0.001) adjusted for comparable areas at risk for ischemia. The administration of ANP to ANP(-/-) mice via osmotic minipumps significantly enlarged infarct size to levels comparable with those observed in ANP(+/+) mice (P < 0.05). There was no difference in neutrophil migration into the noninfarcted myocardium of ANP(-/-) mice undergoing actual versus sham-operated coronary occlusion. By comparison, after coronary occlusion, the neutrophil infiltration into the myocardium was enhanced in ANP(+/+) (P < 0.0005) and ANP(-/-) mice administered ANP (P < 0.0005). The expression of P-selectin, a molecule that mediates neutrophil adhesion, was significantly greater after coronary occlusion in the vasculature of ANP(+/+) or ANP(-/-) mice treated with ANP than in ANP(-/-) mice (P < 0.002). Taken together, these results indicate that ANP increases P-selectin, neutrophil infiltration, infarct size, and mortality following experimental coronary occlusion.

An unusual case of peripartum cardiomyopathy manifesting with multiple thrombo-embolic phenomena

Peripartum cardiomyopathy (PPCM) is a rare form of heart failure with a reported incidence of 1 per 3000 to 1 per 4000 live births and a fatality rate of 20%–50%. Onset is usually between the last month of pregnancy and up to 5 months postpartum in previously healthy women. Although viral, autoimmune and idiopathic factors may be contributory, its etiology remains unknown. PPCM initially presents with signs and symptoms of congestive heart failure and rarely with thrombo-embolic complications. We report an unusual case of PPCM in a previously healthy postpartum woman who presented with an acute abdomen due to unrecognized thromboemboli of the abdominal organs. This case illustrates that abdominal pain in PPCM may not always result from hepatic congestion as previously reported, but may occur as a result of thromboemboli to abdominal organs. Further research is needed to determine the true incidence of thromboemboli in PPCM.

Fibrinolysis is amplified by converting alpha-antiplasmin from a plasmin inhibitor to a substrate

alpha(2)-Antiplasmin (alpha(2)-AP) is the fast serpin inhibitor of plasmin and appears to limit the success of treatment for thrombosis. We examined the mechanisms through which monoclonal antibodies (mAbs) against alpha(2)-AP amplify fibrinolysis. The mAbs RWR, 49 and 77 interfered with the ability of alpha(2)-AP to inhibit plasmin, microplasmin and trypsin. In solution, mAbs 49 and 77 bound to alpha(2)-AP with 5-fold to 10-fold higher relative affinity than mAb-RWR, while mAb-RWR bound with greater avidity to immobilized or denatured alpha(2)-AP. Binding studies with chimeric alpha(2)-APs revealed that none of the mAbs bound to sites in alpha(2)-AP that form putative contacts with plasmin, namely the carboxy terminal lysines of alpha(2)-AP, or the reactive center loop in the serpin domain of alpha(2)-AP. Rather, mAb-RWR recognized an epitope in the amino-terminus of alpha(2)-AP (L(13)GNQEPGGQTALKSPPGVCS(32)) near the site at which alpha(2)-AP cross-links to fibrin. mAbs 49 and 77 bound to another conformational epitope in the serpin domain of alpha(2)-AP. mAbs 49 and 77 markedly increased the stoichiometry of plasmin inhibition by alpha(2)-AP (from 1.1 +/- 0.1 to 51 +/- 4 and 67 +/- 7) indicating that they convert alpha(2)-AP from an inhibitor to a substrate of plasmin. This was confirmed by sodium dodecylsulfate polyacrylamide gel electrophoresis analysis showing cleavage of alpha(2)-AP by plasmin in the presence of these mAbs. In summary, these mAbs appear to act at sites distinct from known alpha(2)-AP-plasmin contacts to enhance fibrinolysis by converting alpha(2)-AP from an inhibitor to a plasmin substrate.

Regulation of Nonproteolytic Active Site Formation in Plasminogen

Streptokinase may be less effective at saving lives in patients with heart attacks because it explosively generates plasmin in the bloodstream at sites distant from fibrin clots. We hypothesized that this rapid plasmin generation is due to SK's singular capacity to nonproteolytically generate the active protease SK x Pg*, and we examined whether the kringle domains regulate this process. An SK mutant lacking Ile-1 (deltaIle1-SK) does not form SK x Pg*, although it will form complexes with plasmin that can activate plasminogen. When compared to SK, deltaIle1-SK diminished the generation of plasmin in plasma by more than 30-fold, demonstrating that the formation of SK x Pg* plays an important role in SK activity in the blood. The rate of SK x Pg* formation (measured by an active site titrant) was much slower in Glu-Pg, which contains five kringle domains, than in Pg forms containing one kringle (mini-Pg) or no kringles (micro-Pg). In a similar manner, Streptococcus uberis Pg activator (SUPA), an SK-like molecule, generated SUPA x Pg* much slower with bovine Pg than bovine micro-Pg. The velocity of SK x Pg* formation was regulated by agents that influence the conformation of Pg through interactions with the kringle domains. Chloride ions, which maintain the compact Pg conformation, hindered SK x Pg* formation. In contrast, epsilon-aminocaproic acid, fibrin, and fibrinogen, which induce an extended Pg conformation, accelerated the formation of SK x Pg*. In summary, the explosive generation of plasmin in blood or plasma, which diminishes SK's therapeutic effects, is attributable to the formation of SK x Pg*, and this process is governed by kringle domains.

The CREB leucine zipper regulates CREB phosphorylation, cardiomyopathy, and lethality in a transgenic model of heart failure

Signaling through cAMP plays an important role in heart failure. Phosphorylation of cAMP response element binding protein (CREB) at serine-133 regulates gene expression in the heart. We examined the functional significance of CREB-S133 phosphorylation by comparing transgenic models in which a phosphorylation resistant CREB-S133A mutant containing either an intact or a mutated leucine zipper domain (CREB-S133A-LZ) was expressed in the heart. In vitro, CREB-S133A retained the ability to interact with wild-type CREB, whereas CREB-S133A-LZ did not. In vivo, CREB-S133A and CREB-S133A-LZ were expressed at comparable levels in the heart; however, CREB-S133A markedly suppressed the phosphorylation of endogenous CREB, whereas CREB-S133A-LZ had no effect. The one-year survival of mice from two CREB-S133A-LZ transgenic lines was equivalent to nontransgenic littermate control mice (NTG), whereas transgenic CREB-S133A mice died with heart failure at a median 30 wk of age (P < 0.0001). CREB-S133A mice had an altered gene expression characteristic of the failing heart, whereas CREB-S133A-LZ mice did not. Left ventricular contractile function was substantially reduced in CREB-S133A mice versus NTG mice and only modestly reduced in CREB-S133A-LZ mice (P < 0.02). When considered in light of other studies, these findings indicate that overexpression of the CREB leucine zipper is required for both inhibition of endogenous CREB phosphorylation and cardiomyopathy in this murine model of heart failure.