Early detection of doxorubicin myocardial injury by ultrasonic tissue characterization in an experimental animal model

In the clinical setting, the early detection of myocardial injury induced by doxorubicin (DXR) is still considered a challenge. To assess whether ultrasonic tissue characterization (UTC) can identify early DXR-related myocardial lesions and their correlation with collagen myocardial percentages, we studied 60 rats at basal status and prospectively after 2mg/Kg/week DXR endovenous infusion. Echocardiographic examinations were conducted at baseline and at 8,10,12,14 and 16 mg/Kg DXR cumulative dose. The left ventricle ejection fraction (LVEF), shortening fraction (SF), and the UTC indices: corrected coefficient of integrated backscatter (IBS) (tissue IBS intensity/phantom IBS intensity) (CC-IBS) and the cyclic variation magnitude of this intensity curve (MCV) were measured. The variation of each parameter of study through DXR dose was expressed by the average and standard error at specific DXR dosages and those at baseline. The collagen percent (%) was calculated in six control group animals and 24 DXR group animals. CC-IBS increased (1.29 +/- 0.27 x 1.1 +/- 0.26-basal; p=0.005) and MCV decreased (9.1 +/- 2.8 x 11.02 +/- 2.6-basal; p=0.006) from 8 mg/Kg to 16mg/Kg DXR. LVEF presented only a slight but significant decrease (80.4 +/- 6.9% x 85.3 +/- 6.9%-basal, p=0.005) from 8 mg/Kg to 16 mg/Kg DXR. CC-IBS was 72.2% sensitive and 83.3% specific to detect collagen deposition of 4.24%(AUC=0.76). LVEF was not accurate to detect initial collagen deposition (AUC=0.54). In conclusion: UTC was able to early identify the DXR myocardial lesion when compared to LVEF, showing good accuracy to detect the initial collagen deposition in this experimental animal model.

Effect of Colchicine on Myocardial Injury Induced by Trypanosoma cruzi in Experimental Chagas Disease

Background: The hallmark of Chagas disease (CD) is multifocal myocarditis and extensive fibrosis. We investigated the potential effect of colchicine on myocardial remodeling in experimental CD. Methods and Results: One hundred Syrian hamsters were randomly divided into noninfected untreated control (CG), noninfected control treated with colchicine (COLG 0.4 mg kg(-1) d(-1) by gavage), infected (IG), and infected treated with colchicine (ICOLG, 0.4 mg kg(-1) d(-1)) groups. The interstitial collagen volume fraction (ICVF) was evaluated by videomorphometry with picrosirius red staining. The gelatinolytic activities of matrix metalloproteinase (MMP) 2 were examined with the use of zymography. Myocarditis was described according to the Dallas criteria. Statistical comparisons were performed with parametric analysis of variance and Tukey test. ICVF (%) accumulation was attenuated in infected colchicine-treated animals in the left (CG 0.81 +/- 0.13, COLG 0.85 +/- 0.13, IG: 1.35 +/- 0.31,* ICOLG 1.06 +/- 0.19; *P < .05 compared with ICOLG) and right ventricles (CG 1.4 +/- 0.36, COLG 1.26 +/- 0.14, IG 1.97 +/- 0.058,* ICOLG: 1.52 +/- 0.23; *P < .05 compared with ICOLG). A significant increase in MMP-2 enzymatic activity (UA) was observed in ICOLG (17,432.8*) compared with GC (3731.6), COLG (2,792.6), and IG (4,286.3; *P < .001). In IG, 66% of animals had myocarditis compared with only 49% in ICOLG. Conclusions: Colchicine had a protective effect on myocardium, indicated by decreased interstitial myocardial fibrosis, increased intensity of MMP-2, and attenuated myocardial inflammation. (J Cardiac Fail 2012;18:654-659)

Opposite effects of nitric oxide and nitroxyl on postischemic myocardial injury

Recent experimental evidence suggests that reactive nitrogen oxide species can contribute significantly to postischemic myocardial injury. The aim of the present study was to evaluate the role of two reactive nitrogen oxide species, nitroxyl (NO−) and nitric oxide (NO⋅), in myocardial ischemia and reperfusion injury. Rabbits were subjected to 45 min of regional myocardial ischemia followed by 180 min of reperfusion. Vehicle (0.9% NaCl), 1 μmol/kg S-nitrosoglutathione (GSNO) (an NO⋅ donor), or 3 μmol/kg Angeli’s salt (AS) (a source of NO−) were given i.v. 5 min before reperfusion. Treatment with GSNO markedly attenuated reperfusion injury, as evidenced by improved cardiac function, decreased plasma creatine kinase activity, reduced necrotic size, and decreased myocardial myeloperoxidase activity. In contrast, the administration of AS at a hemodynamically equieffective dose not only failed to attenuate but, rather, aggravated reperfusion injury, indicated by an increased left ventricular end diastolic pressure, myocardial creatine kinase release and necrotic size. Decomposed AS was without effect. Co-administration of AS with ferricyanide, a one-electron oxidant that converts NO− to NO⋅, completely blocked the injurious effects of AS and exerted significant cardioprotective effects similar to those of GSNO. These results demonstrate that, although NO⋅ is protective, NO− increases the tissue damage that occurs during ischemia/reperfusion and suggest that formation of nitroxyl may contribute to postischemic myocardial injury.

Neurodegeneration, myocardial injury, and perinatal death in mitochondrial superoxide dismutase-deficient mice.

Manganese superoxide dismutase (SOD2) converts superoxide to oxygen plus hydrogen peroxide and serves as the primary defense against mitochondrial superoxide. Impaired SOD2 activity in humans has been associated with several chronic diseases, including ovarian cancer and type I diabetes, and SOD2 overexpression appears to suppress malignancy in cultured cells. We have produced a line of SOD2 knockout mice (SOD2m1BCM/SOD2m1BCM) that survive up to 3 weeks of age and exhibit several novel pathologic phenotypes including severe anemia, degeneration of neurons in the basal ganglia and brainstem, and progressive motor disturbances characterized by weakness, rapid fatigue, and circling behavior. In addition, SOD2m1BCM/SOD2m1BCM mice older than 7 days exhibit extensive mitochondrial injury within degenerating neurons and cardiac myocytes. Approximately 10% of SOD2m1BCM/SOD2m1BCM mice exhibit markedly enlarged and dilated hearts. These observations indicate that SOD2 deficiency causes increased susceptibility to oxidative mitochondrial injury in central nervous system neurons, cardiac myocytes, and other metabolically active tissues after postnatal exposure to ambient oxygen concentrations. Our SOD2-deficient mice differ from a recently described model in which homozygotes die within the first 5 days of life with severe cardiomyopathy and do not exhibit motor disturbances, central nervous system injury, or ultrastructural evidence of mitochondrial injury.

T1 mapping for assessment of myocardial injury and microvascular obstruction at one week post myocardial infarction

Acknowledgements This study was supported by a Medical Research Council UK grant (grant number G0800901), as a sub-study of Nitrites in Acute Myocardial Infarction. Thanks are due to Roger Staff, for invaluable advice regarding receiver operator characteristic analysis.

T1 mapping for assessment of myocardial injury and microvascular obstruction at one week post myocardial infarction

Acknowledgements This study was supported by a Medical Research Council UK grant (grant number G0800901), as a sub-study of Nitrites in Acute Myocardial Infarction. Thanks are due to Roger Staff, for invaluable advice regarding receiver operator characteristic analysis.

A role for GRK2 in myocardial ischemic injury: indicators of a potential future therapy and diagnostic

Morbidity and mortality of myocardial infarction remains significant with resulting left ventricular function presenting as a major determinant of clinical outcome. Protecting the myocardium against ischemia reperfusion injury has become a major therapeutic goal and the identification of key signaling pathways has paved the way for various interventions, but until now with disappointing results. This article describes the recently discovered new role of G-protein-coupled receptor kinase-2 (GRK2), which is known to critically influence the development and progression of heart failure, in acute myocardial injury. This article focuses on potential applications of the GRK2 peptide inhibitor βARKct in ischemic myocardial injury, the use of GRK2 as a biomarker in acute myocardial infarction and discusses the challenges of translating GRK2 inhibition as a cardioprotective strategy to a possible future clinical application.

Abnormal mitochondrial L-arginine transport contributes to the pathogenesis of heart failure and rexoygenation injury

Impaired mitochondrial function is fundamental feature of heart failure (HF) and myocardial ischemia. In addition to the effects of heightened oxidative stress, altered nitric oxide (NO) metabolism, generated by a mitochondrial NO synthase, has also been proposed to impact upon mitochondrial function. However, the mechanism responsible for arginine transport into mitochondria and the effect of HF on such a process is unknown. We therefore aimed to characterize mitochondrial L-arginine transport and to investigate the hypothesis that impaired mitochondrial L-arginine transport plays a key role in the pathogenesis of heart failure and myocardial injury.

Formyl-peptide receptor is not involved in the protection afforded by annexin 1 in murine acute myocardial infarct

Recent interest in the annexin 1 field has come from the notion that specific G-protein-coupled receptors, members of the formyl-peptide receptor (FPR) family, appear to mediate the anti-inflammatory actions of this endogenous mediator. Administration of the annexin 1 N-terminal derived peptide Ac2-26 to mice after 25 min ischemia significantly attenuated the extent of acute myocardial injury as assessed 60 min postreperfusion. Evident at the dose of 1 mg/kg (similar to9 nmol per animal), peptide Ac2-26 cardioprotection was intact in FPR null mice. Similarly, peptide Ac2-26 inhibition of specific markers of heart injury (specifically myeloperoxidase activity, CXC chemokine KC contents, and endogenous annexin 1 protein expression) was virtually identical in heart samples collected from wild-type and FPR null mice. Mouse myocardium expressed the mRNA for FPR and the structurally related lipoxin A(4) receptor, termed ALX; thus, comparable equimolar doses of two ALX agonists (W peptide and a stable lipoxin A4 analog) exerted cardioprotection in wild-type and FPR null mice to an equal extent. Curiously, marked (>95%) blood neutropenia produced by an anti-mouse neutrophil serum did not modify the extent of acute heart injury, whereas it prevented the protection afforded by peptide Ac2-26. Thus, this study sheds light on the receptor mechanism(s) mediating annexin 1-induced cardioprotection and shows a pivotal role for ALX and circulating neutrophil, whereas it excludes any functional involvement of mouse FPR. These mechanistic data can help in developing novel therapeutics for acute cardioprotection.

Hypotheses, rationale, design, and methods for prognostic evaluation of cardiac biomarker elevation after percutaneous and surgical revascularization in the absence of manifest myocardial infarction. A comparative analysis of biomarkers and cardiac magnetic resonance. The MASS-V Trial

Background: Although the release of cardiac biomarkers after percutaneous (PCI) or surgical revascularization (CABG) is common, its prognostic significance is not known. Questions remain about the mechanisms and degree of correlation between the release, the volume of myocardial tissue loss, and the long-term significance. Delayed-enhancement of cardiac magnetic resonance (CMR) consistently quantifies areas of irreversible myocardial injury. To investigate the quantitative relationship between irreversible injury and cardiac biomarkers, we will evaluate the extent of irreversible injury in patients undergoing PCI and CABG and relate it to postprocedural modifications in cardiac biomarkers and long-term prognosis. Methods/Design: The study will include 150 patients with multivessel coronary artery disease (CAD) with left ventricle ejection fraction (LVEF) and a formal indication for CABG; 50 patients will undergo CABG with cardiopulmonary bypass (CPB); 50 patients with the same arterial and ventricular condition indicated for myocardial revascularization will undergo CABG without CPB; and another 50 patients with CAD and preserved ventricular function will undergo PCI using stents. All patients will undergo CMR before and after surgery or PCI. We will also evaluate the release of cardiac markers of necrosis immediately before and after each procedure. Primary outcome considered is overall death in a 5-year follow-up. Secondary outcomes are levels of CK-MB isoenzyme and I-Troponin in association with presence of myocardial fibrosis and systolic left ventricle dysfunction assessed by CMR. Discussion: The MASS-V Trial aims to establish reliable values for parameters of enzyme markers of myocardial necrosis in the absence of manifest myocardial infarction after mechanical interventions. The establishments of these indices have diagnostic value and clinical prognosis and therefore require relevant and different therapeutic measures. In daily practice, the inappropriate use of these necrosis markers has led to misdiagnosis and therefore wrong treatment. The appearance of a more sensitive tool such as CMR provides an unprecedented diagnostic accuracy of myocardial damage when correlated with necrosis enzyme markers. We aim to correlate laboratory data with imaging, thereby establishing more refined data on the presence or absence of irreversible myocardial injury after the procedure, either percutaneous or surgical, and this, with or without the use of cardiopulmonary bypass.

Increased myocardial susceptibility to repetitive ischemia with high-fat diet-induced obesity.

Obesity and diabetes are frequently associated with cardiovascular disease. When a normal heart is subjected to brief/sublethal repetitive ischemia and reperfusion (I/R), adaptive responses are activated to preserve cardiac structure and function. These responses include but are not limited to alterations in cardiac metabolism, reduced calcium responsiveness, and induction of antioxidant enzymes. In a model of ischemic cardiomyopathy inducible by brief repetitive I/R, we hypothesized that dysregulation of these adaptive responses in diet-induced obese (DIO) mice would contribute to enhanced myocardial injury. DIO C57BL/6J mice were subjected to 15 min of daily repetitive I/R while under short-acting anesthesia, a protocol that results in the development of fibrotic cardiomyopathy. Cardiac lipids and candidate gene expression were analyzed at 3 days, and histology at 5 days of repetitive I/R. Total free fatty acids (FFAs) in the cardiac extracts of DIO mice were significantly elevated, reflecting primarily the dietary fatty acid (FA) composition. Compared with lean controls, cardiac FA oxidation (FAO) capacity of DIO mice was significantly higher, concurrent with increased expression of FA metabolism gene transcripts. Following 15 min of daily repetitive I/R for 3 or 5 days, DIO mice exhibited increased susceptibility to I/R and, in contrast to lean mice, developed microinfarction, which was associated with an exaggerated inflammatory response. Repetitive I/R in DIO mice was associated with more profound significant downregulation of FA metabolism gene transcripts and elevated FFAs and triglycerides. Maladaptive metabolic changes of FA metabolism contribute to enhanced myocardial injury in diet-induced obesity.

Inhibition of caspase 1 reduces human myocardial ischemic dysfunction via inhibition of IL-18 and IL-1β

The proinflammatory cytokine IL-18 was investigated for its role in human myocardial function. An ischemia/reperfusion (I/R) model of suprafused human atrial myocardium was used to assess myocardial contractile force. Addition of IL-18 binding protein (IL-18BP), the constitutive inhibitor of IL-18 activity, to the perifusate during and after I/R resulted in improved contractile function after I/R from 35% of control to 76% with IL-18BP. IL-18BP treatment also preserved intracellular tissue creatine kinase levels (by 420%). Steady-state mRNA levels for IL-18 were elevated after I/R, and the concentration of IL-18 in myocardial homogenates was increased (control, 5.8 pg/mg vs. I/R, 26 pg/mg; P < 0.01). Active IL-18 requires cleavage of its precursor form by the IL-1β-converting enzyme (caspase 1); inhibition of caspase 1 also attenuated the depression in contractile force after I/R (from 35% of control to 75.8% in treated atrial muscle; P < 0.01). Because caspase 1 also cleaves the precursor IL-1β, IL-1 receptor blockade was accomplished by using the IL-1 receptor antagonist. IL-1 receptor antagonist added to the perifusate also resulted in a reduction of ischemia-induced contractile dysfunction. These studies demonstrate that endogenous IL-18 and IL-1β play a significant role in I/R-induced human myocardial injury and that inhibition of caspase 1 reduces the processing of endogenous precursors of IL-18 and IL-1β and thereby prevents ischemia-induced myocardial dysfunction.

A locus on chromosome 7 determines myocardial cell necrosis and calcification (dystrophic cardiac calcinosis) in mice.

Dystrophic cardiac calcinosis, an age-related cardiomyopathy that occurs among certain inbred strains of mice, involves myocardial injury, necrosis, and calcification. Using a complete linkage map approach and quantitative trait locus analysis, we sought to identify genetic loci determining dystrophic cardiac calcinosis in an F2 intercross of resistant C57BL/6J and susceptible C3H/HeJ inbred strains. We identified a single major locus, designated Dyscalc, located on proximal chromosome 7 in a region syntenic with human chromosomes 19q13 and 11p15. The statistical significance of Dyscalc (logarithm of odds score 14.6) was tested by analysis of permuted trait data. Analysis of BxH recombinant inbred strains confirmed the mapping position. The inheritance pattern indicated that this locus influences susceptibility of cells both to enter necrosis and to subsequently undergo calcification.