Luanda Grazette

Cardiotoxicity of the cancer therapeutic agent imatinib mesylate

Imatinib mesylate (Gleevec) is a small-molecule inhibitor of the fusion protein Bcr-Abl, the causal agent in chronic myelogenous leukemia. Here we report ten individuals who developed severe congestive heart failure while on imatinib and we show that imatinib-treated mice develop left ventricular contractile dysfunction. Transmission electron micrographs from humans and mice treated with imatinib show mitochondrial abnormalities and accumulation of membrane whorls in both vacuoles and the sarco- (endo-) plasmic reticulum, findings suggestive of a toxic myopathy. With imatinib treatment, cardiomyocytes in culture show activation of the endoplasmic reticulum (ER) stress response, collapse of the mitochondrial membrane potential, release of cytochrome c into the cytosol, reduction in cellular ATP content and cell death. Retroviral gene transfer of an imatinib-resistant mutant of c-Abl, alleviation of ER stress or inhibition of Jun amino-terminal kinases, which are activated as a consequence of ER stress, largely rescues cardiomyocytes from imatinib-induced death. Thus, cardiotoxicity is an unanticipated side effect of inhibition of c-Abl by imatinib.

Differential activation of signal transduction pathways in human hearts with hypertrophy versus advanced heart failure.

Background —Left ventricular failure is commonly preceded by a period of hypertrophy. Intriguingly, many of the signaling pathways that have been implicated in the regulation of hypertrophy, including the 3 mitogen-activated protein kinases (MAPKs: extracellular signal-regulated kinase, stress-activated protein kinase, and p38), protein phosphatase, calcineurin, and the protein kinase Akt and its target glycogen synthase kinase-3 (GSK-3), also regulate the apoptotic response. Methods and Results —To understand the mechanisms that might regulate the progression of heart failure, we analyzed the activity of these signaling pathways in the hearts of patients with advanced heart failure, patients with compensated cardiac hypertrophy, and normal subjects. In patients with hypertrophy, neither the MAPK nor the Akt/GSK-3 pathways were activated, and the dominant signaling pathway was calcineurin. In failing hearts, calcineurin activity was increased but less so than in the hypertrophied hearts, and all 3 MAPKs and Akt were activated (and, accordingly, GSK-3&bgr; was inhibited), irrespective of whether the underlying diagnosis was ischemic or idiopathic cardiomyopathy. Conclusions —In the failing heart, there is a clear prohypertrophic activity profile, likely occurring in response to increased systolic wall stress and neurohormonal mediators. However, with the activation of these hypertrophic pathways, potent proapoptotic and antiapoptotic signals may also be generated. Therapies directed at altering the balance of activity of these signaling pathways could potentially alter the progression of heart failure.

Magnetic resonance imaging of cardiomyocyte apoptosis with a novel magneto-optical nanoparticle

The ability to image cardiomyocyte apoptosis in vivo with high‐resolution MRI could facilitate the development of novel cardioprotective therapies. The sensitivity of the novel nanoparticle AnxCLIO‐Cy5.5 for cardiomyocyte apoptosis was thus compared in vitro to that of annexin V‐FITC and showed a high degree of colocalization. MRI was then performed, following transient coronary artery (LAD) occlusion, in five mice given AnxCLIO‐Cy5.5 and in four mice given an identical dose (2 mg Fe/kg) of CLIO‐Cy5.5. MR signal intensity and myocardial T2* were evaluated, in vivo, in hypokinetic regions of myocardium in the LAD distribution. Ex vivo fluorescence imaging was performed to confirm the in vivo findings. Myocardial T2* was significantly lower in the mice given AnxCLIO‐Cy5.5 (8.1 versus 13.2 ms, P < 0.01), and fluorescence target to background ratio was significantly higher (2.1 versus 1.1, P < 0.01). This study thus demonstrates the feasibility of obtaining high‐resolution MR images of cardiomyocyte apoptosis in vivo with the novel nanoparticle, AnxCLIO‐Cy5.5. Magn Reson Med, 2005.

Effects of Denosumab Treatment and Discontinuation on Bone Mineral Density and Bone Turnover Markers in Postmenopausal Women with Low Bone Mass

CONTEXT Denosumab treatment for 24 months increased bone mineral density (BMD) and reduced bone turnover markers (BTM) in postmenopausal women. OBJECTIVE The aim was to determine the effects of prior denosumab or placebo injections on BMD, BTM, and safety over 24 months after treatment discontinuation. DESIGN We conducted an off-treatment extension of a phase 3, randomized, double-blind, parallel-group study. PARTICIPANTS A total of 256 postmenopausal women with a mean age of 59 yr and a mean lumbar spine T-score of -1.61 at randomization participated in the study. INTERVENTIONS Participants received placebo or 60 mg denosumab every 6 months for 24 months, followed by 24 months off treatment. MAIN OUTCOME MEASURES We measured the percentage changes in BMD and BTM, and evaluated safety. RESULTS Of the 256 participants enrolled in the posttreatment phase, 87% completed the study. During 24 months of denosumab treatment, BMD increased (lumbar spine, 6.4%; total hip, 3.6%; 1/3 radius, 1.4%), and BTM decreased (serum C-terminal telopeptide of type 1 collagen, 63%; and N-terminal propeptide of type 1 procollagen, 47%), compared with placebo. After discontinuation, BMD declined, but the previously treated denosumab group maintained higher BMD than the previously treated placebo group at these sites (P ≤ 0.05). Final BMD at month 48 strongly correlated with month 0 BMD. After denosumab discontinuation, BTM increased above baseline within 3 months (serum C-terminal telopeptide of type 1 collagen) or 6 months (N-terminal propeptide of type 1 procollagen) and returned to baseline by month 48. Adverse event rates during the off-treatment phase were similar between groups. CONCLUSIONS In postmenopausal women with low BMD, the effects of 60 mg denosumab treatment for 24 months on BMD and BTM are reversible upon discontinuation, reflecting its biological mechanism of action. Residual BMD measurements remained above those of the group previously treated with placebo.

PI3K rescues the detrimental effects of chronic Akt activation in the heart during ischemia/reperfusion injury

Acute activation of the serine-threonine kinase Akt is cardioprotective and reduces both infarction and dysfunction after ischemia/reperfusion injury (IRI). However, less is known about the chronic effects of Akt activation in the heart, and, paradoxically, Akt is activated in samples from patients with chronic heart failure. We generated Tg mice with cardiac-specific expression of either activated (myristoylated [myr]) or dominant-negative (dn) Akt and assessed their response to IRI in an ex vivo model. While dn-Akt hearts demonstrated a moderate reduction in functional recovery after IRI, no function was restored in any of the myr-Akt-Tg hearts. Moreover, infarcts were dramatically larger in myr-Akt-Tg hearts. Biochemical analyses demonstrated that chronic Akt activation induces feedback inhibition of PI3K activity through both proteasome-dependent degradation of insulin receptor substrate-1 (IRS-1) and inhibition of transcription of IRS-1 as well as that of IRS-2. To test the functional significance of these signaling changes, we performed in vivo cardiac gene transfer with constitutively active PI3K in myr-Akt-Tg mice. Restoration of PI3K rescued function and reduced injury after IRI. These data demonstrate that PI3K-dependent but Akt-independent effectors are required for full cardioprotection and suggest a mechanism by which chronic Akt activation can become maladaptive.

RANKL Inhibition With Denosumab Does Not Influence 3-Year Progression of Aortic Calcification or Incidence of Adverse Cardiovascular Events in Postmenopausal Women With Osteoporosis and High Cardiovascular Risk

Atherosclerosis and osteoporosis are chronic diseases that progress with age, and studies suggest aortic calcification, an indicator of atherosclerosis, is inversely associated with bone mineral density (BMD). The osteoprotegerin (OPG)/receptor activator of NF‐κB (RANK)/RANK ligand (RANKL) system has been proposed as a shared regulatory system for bone and vasculature. Denosumab (DMAb), a monoclonal antibody against RANKL, improved BMD and reduced fracture risk in the Fracture Reduction Evaluation of Denosumab in Osteoporosis Every 6 Months (FREEDOM) trial. We evaluated whether or not treatment with DMAb influenced progression of aortic calcification (AC) and incidence of cardiovascular (CV) adverse events. We included 2363 postmenopausal women with osteoporosis (1142 placebo, 1221 DMAb), selected from 7808 participants in the FREEDOM trial (3906 placebo, 3902 DMAb), at high risk of CV events according to modified Raloxifene Use for the Heart (RUTH) criteria. CV adverse events were reported by participants. AC scores were assessed using a semiquantitative method from lateral spine X‐rays. Change in AC score from baseline to 12 (n = 1377), 24 (n = 1231), and 36 months (n = 1045) was calculated as AC score at follow‐up minus AC score at baseline. AC progression was defined as change in AC score >0. Baseline characteristics, CV risk factors, and AC scores were similar between treatment groups. Mean age of participants was 74 years (range, 60–90), 88% were white, and 77% had AC score >0 at baseline. Frequency of AC progression over 3 years did not differ between women in placebo (22%) and DMAb (22%) groups (p = 0.98). AC progression did not differ between treatment groups when analyzed by baseline estimated glomerular filtration rate or by baseline AC scores. Frequency of CV adverse events did not differ between placebo (40%) and DMAb (38%) groups (p = 0.26). In conclusion, DMAb treatment had no effect on progression of AC or incidence of CV adverse events compared to placebo.

Cardiac-Specific Gene Expression Facilitated by an Enhanced Myosin Light Chain Promoter

BACKGROUND Adenoviral gene transfer has been shown to be effective in cardiac myocytes in vitro and in vivo. A major limitation of myocardial gene therapy is the extracardiac transgene expression. METHODS To minimize extracardiac gene expression, we have constructed a tissue-specific promoter for cardiac gene transfer, namely, the 250-bp fragment of the myosin light chain-2v (MLC-2v) gene, which is known to be expressed in a tissue-specific manner in ventricular myocardium followed by a luciferase (luc) reporter gene (Ad.4 x MLC250.Luc). Rat cardiomyocytes, liver and kidney cells were infected with Ad.4 x MLC.Luc or control vectors. For in vivo testing, Ad.4 x MLC250.Luc was injected into the myocardium or in the liver of rats. Kinetics of promoter activity were monitored over 8 days using a cooled CCD camera. RESULTS In vitro: By infecting hepatic versus cardiomyocyte cells, we found that the promoter specificity ratio (luc activity in cardiomyocytes per liver cells) was 20.4 versus 0.9 (Ad.4 x MLC250.Luc vs. Ad.CMV). In vivo: Ad.4 x MLC250.Luc significantly reduced luc activity in liver (38.4-fold), lung (16.1-fold), and kidney (21.8-fold) versus Ad.CMV (p =.01); whereas activity in the heart was only 3.8-fold decreased. The gene expression rate of cardiomyocytes versus hepatocytes was 7:1 (Ad.4 x MLC.Luc) versus 1:1.4 (Ad.CMV.Luc). DISCUSSION This new vector may be useful to validate therapeutic approaches in animal disease models and offers the perspective for selective expression of therapeutic genes in the diseased heart.

Electrocardiographic patch devices and contemporary wireless cardiac monitoring

Cardiac electrophysiologic derangements often coexist with disorders of the circulatory system. Capturing and diagnosing arrhythmias and conduction system disease may lead to a change in diagnosis, clinical management and patient outcomes. Standard 12-lead electrocardiogram (ECG), Holter monitors and event recorders have served as useful diagnostic tools over the last few decades. However, their shortcomings are only recently being addressed by emerging technologies. With advances in device miniaturization and wireless technologies, and changing consumer expectations, wearable “on-body” ECG patch devices have evolved to meet contemporary needs. These devices are unobtrusive and easy to use, leading to increased device wear time and diagnostic yield. While becoming the standard for detecting arrhythmias and conduction system disorders in the outpatient setting where continuous ECG monitoring in the short to medium term (days to weeks) is indicated, these cardiac devices and related digital mobile health technologies are reshaping the clinician-patient interface with important implications for future healthcare delivery.

Higher frequency of high-grade rejections in cardiac allograft patients after Quilty B lesions or grade 2/4 rejections.

Background. To better understand how different histologic patterns of allograft inflammation found on biopsies of human cardiac allografts progress to high-grade rejection, we undertook a statistical analysis of our institutional database to detect statistical patterns among different types of myocardial allograft inflammations found on sequential biopsies. Methods. Biopsies were analyzed for statistical associations between high-grade rejections (International Society of Heart and Lung Transplantation [ISHLT] grade ≥3A/4) and the type of cardiac allograft inflammation found on prior biopsies. Case cross-over and case control designs were used to compare the antecedent patterns of inflammation on biopsies with high-grade rejection compared to biopsies with low-grade rejection, all within the same subject. Quilty lesions were correlated with cyclosporine levels. Results. Patients with Quilty B lesions or ISHLT grade 2/4 rejections show an increased risk for high-grade rejection on their next biopsies (Odds ratio 5.9 to 11.2). The presence of two pathological findings, especially Quilty B and grade 2/4 rejection, creates additional risk in excess of that found independently (Odds ratio >14). Quilty lesions are found only in cardiac allografts, and do not correlate with trough cyclosporine levels. Conclusions. The morphological patterns of several types of human cardiac allograft inflammation found on sequential protocol biopsies are not randomly associated. Patients with grade 2/4 rejections and Quilty B lesions show an increased risk for high-grade rejections on their next biopsies. Quilty B lesions, similar to ISHLT grade 2/4 rejections, may represent subclinical rejection. Both are more likely to progress to a high-grade rejection.

Point-of-Care Technologies for Precision Cardiovascular Care and Clinical Research

Summary Point-of-care technologies (POC or POCT) are enabling innovative cardiovascular diagnostics that promise to improve patient care across diverse clinical settings. The National Heart, Lung, and Blood Institute convened a working group to discuss POCT in cardiovascular medicine. The multidisciplinary working group, which included clinicians, scientists, engineers, device manufacturers, regulatory officials, and program staff, reviewed the state of the POCT field; discussed opportunities for POCT to improve cardiovascular care, realize the promise of precision medicine, and advance the clinical research enterprise; and identified barriers facing translation and integration of POCT with existing clinical systems. A POCT development roadmap emerged to guide multidisciplinary teams of biomarker scientists, technologists, health care providers, and clinical trialists as they: 1) formulate needs assessments; 2) define device design specifications; 3) develop component technologies and integrated systems; 4) perform iterative pilot testing; and 5) conduct rigorous prospective clinical testing to ensure that POCT solutions have substantial effects on cardiovascular care.