Inflammatory Forms of Cardiomyocyte Cell Death in the Rat Model of Isoprenaline-Induced Takotsubo Syndrome

Takotsubo syndrome (TTS) is associated with inflammatory response, therefore the aim of the study was to evaluate the presence and dynamics of inflammatory-associated forms of cell death, necroptosis, and pyroptosis in the female rat model of isoprenaline (ISO)-induced TTS. TTS was induced in female Sprague Dawley rats (n = 36) by ISO 150 mg/kg intraperitoneally. Animals were divided into four groups: TTSO (TTS+ovariectomy; n = 10), TTSP (TTS+sham operation; n = 10), CO (0.9% NaCl+ovariectomy; n = 8), CP (0.9% NaCl+sham operation; n = 8). Histopathological analysis, evaluation of plasma concentration, and myocardial expression of pyroptosis- and necroptosis-associated proteins were performed. TTSO and TTSP groups had higher plasma concentrations of interleukin-1β in comparison with the controls. Low myocardial protein expression of mixed lineage kinase domain-like pseudokinase (MLKL), caspase-1 (Casp-1), and calcium/calmodulin-dependent kinase type II isoform delta (CAMKIIδ) was visible 6 and/or 12 h post-ISO. Twenty-four hours post-ISO, high myocardial and vascular protein expression of CAMKIIδ was visible in TTSO but not TTSP rats, while high myocardial expression of MLKL and Casp-1 was visible both in TTSO and TTSP rats. The course of TTS is associated with activation of inflammatory-associated programmed cell death, necroptosis, and pyroptosis, therefore inflammation may be a primary response occurring simultaneously with cardiomyocyte death in TTS.

Protein Alterations in Cardiac Ischemia/Reperfusion Revealed by Spatial-Omics

Myocardial infarction is the most common cause of death worldwide. An understanding of the alterations in protein pathways is needed in order to develop strategies that minimize myocardial damage. To identify the protein signature of cardiac ischemia/reperfusion (I/R) injury in rats, we combined, for the first time, protein matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) and label-free proteomics on the same tissue section placed on a conductive slide. Wistar rats were subjected to I/R surgery and sacrificed after 24 h. Protein MALDI-MSI data revealed ischemia specific regions, and distinct profiles for the infarct core and border. Firstly, the infarct core, compared to histologically unaffected tissue, showed a significant downregulation of cardiac biomarkers, while an upregulation was seen for coagulation and immune response proteins. Interestingly, within the infarct tissue, alterations in the cytoskeleton reorganization and inflammation were found. This work demonstrates that a single tissue section can be used for protein-based spatial-omics, combining MALDI-MSI and label-free proteomics. Our workflow offers a new methodology to investigate the mechanisms of cardiac I/R injury at the protein level for new strategies to minimize damage after MI.

Are we any WISER yet? Progress and contemporary need for smart trials to include women in coronary artery disease trials

Despite calls to ensure proportionate representation of both sexes in biomedical research, women continue to be underrepresented in cardiovascular disease (CVD) clinical trials. A comprehensive analysis of seven large suspected ischemic heart disease/coronary artery disease (HD/CAD) clinical trials (PROMISE, ISCHEMIA, CIAO-ISCHEMIA, ORBITA, FAME, FAME 2 and COURAGE trial) provides understanding of contributions to barriers to enrollment of women and leads to strategies to address these barriers. Specifically, in the seven trials, enrollment of women did not exceed 27%, while numerous barriers are evident. Proposed strategies to improve women´s inclusion in clinical trials, include adding reproductive stage/estrogen status, attention to study design inclusion/exclusion criteria using female thresholds, consideration of diagnostic and intervention study design to be inclusive, increasing women and minorities in leadership positions, including sex as a biological variable (SABV) in study design and statistical analysis, and addressing social and race/ethnicity barriers. Dedicated action to actualizing these steps are needed at this time to developing diagnostic and therapeutic strategies resulting in better care and improved outcomes for CVD in women.

Research-Relevant Clinical Pathology Resources: Emphasis on Mice, Rats, Rabbits, Dogs, Minipigs, and Non-Human Primates

Clinical pathology testing for investigative or biomedical research and for preclinical toxicity and safety assessment in laboratory animals is a distinct specialty requiring an understanding of species specific and other influential variables on results and interpretation. This review of clinical pathology principles and testing recommendations in laboratory animal species aims to provide a useful resource for researchers, veterinary specialists, toxicologists, and clinical or anatomic pathologists.

Modeling trauma in rats: similarities to humans and potential pitfalls to consider

Trauma is the leading cause of mortality in humans below the age of 40. Patients injured by accidents frequently suffer severe multiple trauma, which is life-threatening and leads to death in many cases. In multiply injured patients, thoracic trauma constitutes the third most common cause of mortality after abdominal injury and head trauma. Furthermore, 40-50% of all trauma-related deaths within the first 48 h after hospital admission result from uncontrolled hemorrhage. Physical trauma and hemorrhage are frequently associated with complex pathophysiological and immunological responses. To develop a greater understanding of the mechanisms of single and/or multiple trauma, reliable and reproducible animal models, fulfilling the ethical 3 R's criteria (Replacement, Reduction and Refinement), established by Russell and Burch in 'The Principles of Human Experimental Technique' (published 1959), are required. These should reflect both the complex pathophysiological and the immunological alterations induced by trauma, with the objective to translate the findings to the human situation, providing new clinical treatment approaches for patients affected by severe trauma. Small animal models are the most frequently used in trauma research. Rattus norvegicus was the first mammalian species domesticated for scientific research, dating back to 1830. To date, there exist numerous well-established procedures to mimic different forms of injury patterns in rats, animals that are uncomplicated in handling and housing. Nevertheless, there are some physiological and genetic differences between humans and rats, which should be carefully considered when rats are chosen as a model organism. The aim of this review is to illustrate the advantages as well as the disadvantages of rat models, which should be considered in trauma research when selecting an appropriate in vivo model. Being the most common and important models in trauma research, this review focuses on hemorrhagic shock, blunt chest trauma, bone fracture, skin and soft-tissue trauma, burns, traumatic brain injury and polytrauma.

Sex differences in ischemic heart disease and heart failure biomarkers

Since 1984, each year, more women than men die of ischemic heart disease (IHD) and heart failure (HF), yet more men are diagnosed. Because biomarker assessment is often the first diagnostic employed in such patients, understanding biomarker differences in men vs. women may improve female morbidity and mortality rates.

Some key examples of cardiac biomarker utility based on sex include contemporary use of “unisex” troponin reference intervals under-diagnosing myocardial necrosis in women; greater use of hsCRP in the setting of acute coronary syndrome (ACS) could lead to better stratification in women; and greater use of BNP with sex-specific thresholds in ACS could also lead to more timely risk stratification in women.

Accurate diagnosis, appropriate risk management, and monitoring are key in the prevention and treatment of cardiovascular diseases; however, the assessment tools used must also be useful or at least assessed for utility in both sexes. In other words, going forward, we need to evaluate sex-specific reference intervals or cutoffs for laboratory tests used to assess cardiovascular disease to help close the diagnostic gap between men and women.

Technological Advances in Cardiovascular Safety Assessment Decrease Preclinical Animal Use and Improve Clinical Relevance

Cardiovascular (CV) safety liabilities are significant concerns for drug developers and preclinical animal studies are predominately where those liabilities are characterized before patient exposures. Steady progress in technology and laboratory capabilities is enabling a more refined and informative use of animals in those studies. The application of surgically implantable and telemetered instrumentation in the acute assessment of drug effects on CV function has significantly improved historical approaches that involved anesthetized or restrained animals. More chronically instrumented animals and application of common clinical imaging assessments like echocardiography and MRI extend functional and in-life structural assessments into the repeat-dose setting. A growing portfolio of circulating CV biomarkers is allowing longitudinal and repeated measures of cardiac and vascular injury and dysfunction better informing an understanding of temporal pathogenesis and allowing earlier detection of undesirable effects. In vitro modeling systems of the past were limited by their lack of biological relevance to the in vivo human condition. Advances in stem cell technology and more complex in vitro modeling platforms are quickly creating more opportunity to supplant animals in our earliest assessments for liabilities. Continuing improvement in our capabilities in both animal and nonanimal modeling should support a steady decrease in animal use for primary liability identification and optimize the translational relevance of the animal studies we continue to do.

Age-related remodeling of the JAK/STAT/SOCS signaling pathway and associated myocardial changes: From histological to molecular level

BACKGROUND

The cellular and molecular mechanisms implicated in age-associated changes in myocardial structure are of paramount importance since they cause profound alterations in the functional response and represent targets for alleviating age-related pathologies. One of these mechanisms is the JAK/STAT/SOCS signaling pathway.

AIM OF THE STUDY

The present study is designed to elucidate age-dependent changes of the myocardium to provide morphological basis displaying the pathogenesis of myocardial hypertrophy, fibrosis and inflammation with aging.

MATERIAL AND METHODS

Thirty male Sprague Dawley rats aged; 6, 30 and 36 months were used in this study. The animals were divided into three age groups, young adult, senile and very senile rats, respectively. The heart weight/body weight ratio was determined. The heart was subjected to gross morphologic examination, microscopic examination using H&E and Masson's trichrome stains and immunohistochemical examination for detection of JAK, pSTAT3, α-SMA, β-MHC and CD45. Western blotting was also carried out to detect SOCS genes. Real-time PCR was used to detect the inflammatory markers TNFα and IL1β and the hypertrophy marker α-SKA. Biochemical analysis of cardiac troponin I and creatine kinase-MB was done. Quantitative histomorphometric estimations included estimation of cardiac myocyte cross sectional area, estimation of the area percent of collagen fibers in Masson's trichrome stained sections and determination of optical density in immunostained sections. Electron microscopic examination was done to determine capillary density.

RESULTS

Jak and pSTAT3 were predominantly localized to the nuclei and exhibited progressive decline with aging, while SOCS3 activity displayed an age-related increase. The aged myocardium displayed profound age associated structural changes as well as myocardial hypertrophy, fibrosis and inflammation in senile and very senile rats.

CONCLUSION

The age-related modifications in the JAK/STAT/SOCS signaling as well as the age-associated pathological changes in myocardial structure are of particular interest as they provide further insight in age-associated heart pathologies and represent potential targets for cardioprotective and therapeutic approaches.

Experimental determination of diagnostic window of cardiac troponins in the development of chronic anthracycline cardiotoxicity and estimation of its predictive value

BACKGROUND

Cardiac troponins (cTns) seem to be more sensitive for the detection of anthracycline cardiotoxicity than the currently recommended method of monitoring LV systolic function. However, the optimal timing of blood sampling remains unknown. Hence, the aims of the present study were to determine the precise diagnostic window for cTns during the development of chronic anthracycline cardiotoxicity and to evaluate their predictive value.

METHODS

Cardiotoxicity was induced in rabbits with daunorubicin (3mg/kg, weekly, for 8 weeks). Blood samples were collected 2-168 h after the 1st, 5th and 8th drug administrations, and concentrations of cTns were determined using highly sensitive assays: hs cTnT (Roche) and hs cTnI (Abbott).

RESULTS

The plasma levels of cTns progressively increased with the rising number of chemotherapy cycles. While only a mild non-significant increase in both cTn levels occurred after the first daunorubicin dose, a significant rise was observed after the 5th and 8th administrations. Two hours after these administrations, a significant increase occurred with a peak between 4-6h and a decline until 24h. Discrete cTn release continued even after cessation of the therapy. While greater variability of cTn levels was observed around the peak concentrations, the values did not correspond well with the severity of LV systolic dysfunction. Unlike AMI in cardiotoxicity, cTn elevations may be better associated with cumulative dose and concentrations at steady state than cmax.

CONCLUSIONS

To the best of our knowledge, this is the first study to precisely describe the diagnostic window and predictive value of cTns in anthracycline cardiotoxicity.

Differential analysis of transient increases of serum cTnI in response to handling in rats

Serum cardiac troponins are the key biomarkers of myocardial necrosis in humans and in preclinical species. The use of ultrasensitive assays for serum cardiac troponin I (cTnI) as a biomarker in safety studies is hampered by interindividual differences. In this study, we investigated the effect of handling procedures on serum cTnI and explored modeling and simulation approaches to mitigate the impact of these interindividual differences. Femoral-catheterized male Crl:WI(Han) rats (n = 16/group) were left undisturbed in their cages with no handling; subjected to 5 min of isoflurane/O₂ anesthesia (A); or placed into a rodent restrainer followed by simulated tail vein injection (RR). Serum cTnI concentrations were assessed over a 24-h period using an ultrasensitive assay, and the study was repeated for confirmation. The mean serum cTnI concentration pre-procedure was 4.2 pg/mL, and remained stable throughout the duration of the study in the rats submitted to the A procedure. Serum cTnI concentrations increased transiently after the RR procedure with a median time to maximum concentration (T_max), of 1 and 2 h and a mean maximum value concentration (C_max), of 53.0 and 7.2 pg/mL in the initial and repeat studies, respectively. A population pharmacodynamic model identified interindividual, procedure- and study-specific effects on serum cTnI concentrations in rats. It is concluded that a modeling and simulation approach more appropriately describes and statistically analyzes the data obtained with this ultrasensitive assays.

The influence of age on serum concentrations of cardiac troponin I: results in rats, monkeys, and commercial sera

Cardiac troponins serve as serum biomarkers of myocardial injury. The current study examined the influence of age on serum concentrations of cardiac troponin I (cTnI). An ultrasensitive immunoassay was used to monitor cTnI concentrations in Sprague-Dawley (SD) rats and Erythrocebus patas monkeys of different ages. The mean cTnI concentrations were highest in 10-day-old rats compared to 25-, 40-, and 80-day-old SD rats. Cardiomyocyte remodeling was apparent in hearts from 10-day-old SD rats as evident by hypercellularity, irregularly shaped nuclei, and moderate numbers of myocytes undergoing mitosis and apoptosis. The mean concentration of cTnI in 5 newborn monkeys was considerably higher than that of three 1-year-old monkeys. Evidence of cardiomyocyte remodeling was also observed in these newborn hearts (loss of myofibrils and cytoplasmic vacuolation). Commercial animal serum samples were also analyzed. The concentrations of cTnI detected in fetal equine and porcine serum were considerably higher than that found in adult equine and porcine serum samples Likewise, fetal bovine serum had higher cTnI concentrations (>2,400 pg/ml) than did adult caprine and laprine samples (2.5-2.7 pg/ml). The present study found age-related differences in cTnI concentrations, with higher levels occurring at younger ages. This effect was consistent across several animal species.

Cardiac biomarkers in HIV-exposed uninfected children

OBJECTIVES

To evaluate associations of cardiac biomarkers with in-utero antiretroviral drug exposures and cardiac function/structure measured by echocardiograms in HIV-exposed but uninfected (HEU) children.

DESIGN AND METHODS

We analyzed the association of three cardiac biomarkers (cardiac troponin T, cTnT; high sensitivity C-reactive protein, hsCRP; and N-terminal pro-brain natriuretic peptide, NT-proBNP) with prenatal antiretroviral drug exposures, maternal-child characteristics, and echocardiographic parameters.

RESULTS

Among 338 HEU children (mean age 4.3 years), 51% had at least one elevated cardiac biomarker. Maternal tobacco use was associated with elevated NT-proBNP [adjusted odds ratio (aOR) 2.28, P=0.02]. Maternal alcohol and abacavir use were associated with elevated cTnT levels (aOR 3.56, P=0.01 and aOR 2.33, P=0.04, respectively). Among 94 children with paired echocardiogram-biomarker measurements, cTnT measurements were correlated with increased left-ventricular thickness-to-dimension ratio (r=0.21, P=0.04); and elevated cTnT was associated with higher mean left-ventricular end-diastolic (LVED) posterior wall thickness (P=0.04). hsCRP measurements were negatively correlated with septal thickness (r=-0.22, P=0.03) and elevated hsCRP was associated with lower mean left-ventricular contractility Z-scores (P=0.04). NT-proBNP measurements were correlated with increased LVED dimension (r=0.20, P=0.05) and elevated NT-proBNP was associated with lower mean end-systolic septal thickness (P=0.03).

CONCLUSION

Our findings suggest that cardiac biomarkers may help identify HEU children who require further cardiac evaluation including echocardiography. Potential cardiac effects of prenatal abacavir exposure in this population need further investigation.

Spontaneous cardiomyopathy in young Sprague-Dawley rats: evaluation of biological and environmental variability

Cardiovascular safety signals in nonclinical studies remain among the main reasons for drug attrition during pharmaceutical research and development. Drug-induced changes can be functional and/or associated with morphological alterations in the normal heart histology. It is therefore crucial to understand the normal variations in histology to discriminate test article-related changes from background lesions. Rodent progressive cardiomyopathy is probably the most commonly encountered change in control animals of nonclinical toxicity studies. A multisite study mimicking standard short-term toxicity studies using young male Sprague-Dawley rats was performed to better characterize this finding. Using an enhanced sectioning method for this research study, it was observed that the incidence of background cardiomyopathy was 100%. The vast majority of the microscopic findings were inflammatory in nature, with associated necrotic changes (defined as necrosis/inflammatory cell infiltrate) and these changes were mainly located in the myocardium of the mid region of the ventricles (the left side being predominantly affected). The monitored environmental factors in this study (multiple facilities, study duration, handling) did not have an effect on the incidence or severity of the spontaneous cardiomyopathy. In addition, cardiac-specific serum troponin levels were measured and were within the published control range.

The PPARα agonists fenofibrate and CP-778875 cause increased β-oxidation, leading to oxidative injury in skeletal and cardiac muscle in the rat

Weak peroxisome proliferator-activated receptor (PPAR) α agonists (fibrates) are used to treat dyslipidemia. This study compared the effects of the potent and selective PPARα agonist CP-778875 on peroxisomal β-oxidation and cardiac and/or skeletal muscle injury with those of the weak PPARα agonist fenofibrate. We hypothesized that these muscle effects are mediated through the PPARα receptor, leading to increased β-oxidation and consequent oxidative stress. CP-778875 (5 or 500 mg/kg) and fenofibrate (600 or 2,000→1,200 mg/kg, dose lowered because of intolerance) were administered to rats for six weeks. Standard end points, serum troponin I, heart and skeletal muscle β-oxidation of palmitoyl-CoA, and acyl co-oxidase (AOX) mRNA were assessed. Both compounds dose-dependently increased the incidence and/or severity of cardiomyocyte degeneration and necrosis, heart weight, troponin I, and skeletal muscle degeneration. Mean heart β-oxidation (3.4- to 5.1-fold control) and AOX mRNA (2.4- to 3.2-fold control) were increased with CP-778875 500 mg/kg and both doses of fenofibrate. β-Oxidation of skeletal muscle was not affected by either compound; however, a significant increase in AOX mRNA (1.6- to 2.1-fold control) was observed with CP-778875 500 mg/kg and both doses of fenofibrate. Taken together, these findings were consistent with PPARα agonism and support the link between increased cardiac and skeletal muscle β-oxidation and resultant muscle injury in the rat.