Cardiac Fractional Shortening Research Articles

Exercise Rehabilitation Preserves Cardiorespiratory Muscle Function Following Doxorubicin Treatment

Doxorubicin (DOX) is a highly effective chemotherapeutic agent. Unfortunately, cancer patients who have completed DOX treatment often experience exercise intolerance, reduced cardiac function, dyspnea and unfavorable changes to body composition, ultimately, leading to increased incidence of heart failure. Exercise has been shown to reduce the risk of developing chemotherapy-induced cardiorespiratory dysfunction; however, the ability of cancer patients to exercise during treatment can be limited by cancer type, stage and fatigue. Therefore, these experiments utilized a chronic DOX-induced cardiotoxicity model to determine the effects of rehabilitative exercise on cardiorespiratory muscle function. Female Sprague-Dawley rats were treated with DOX once every three weeks for four total cycles via intravenous infusion (i.e., cumulative dose of ~160mg/m2). One-week following the completion of DOX treatment, rats remained sedentary (Sed-DOX) or were prescribed 10-weeks of moderate intensity treadmill running at 30m/min, 0% grade, 1-hour/day, and 3x/week (Mod-DOX). Body composition, exercise tolerance and echocardiography were assessed at three timepoints: 1) pre-treatment; 2) post-treatment and; 3) post-rehabilitation. Diaphragm muscle specific force production was measured post-rehabilitation. From pre- to post-treatment each group gained weight and no differences existed between groups. However, from post-treatment to post-rehabilitation body weight of the DOX-treated groups did not change and was significantly reduced compared to sedentary saline-treated (Sed-Sal) rats from week 15 onwards. Although mean body weight did not differ between the DOX-treated groups, lean mass increased in Mod-DOX rats between each timepoint with no change in fat mass, while fat mass increased in Sed-DOX rats and an initial increase in lean mass was attenuated from post-treatment to post-rehabilitation. Exercise time to fatigue did not change between timepoints within each group; however, exercise run time from post-treatment to post-rehabilitation was significantly longer in Mod-DOX rats compared to Sed-DOX and Sed-Sal. Cardiac fractional shortening percentage (FS%) was reduced in Sed-DOX rats at post-treatment and post-rehabilitation compared to pre-treatment. Additionally, posterior wall shortening velocity (PWSV) was reduced in Sed-DOX rats at post-treatment compared to pre-treatment. No differences in FS% or PWSV were seen between any timepoint in the Mod-DOX group. Finally, ex vivo diaphragm muscle function showed significant diaphragm muscle weakness in Sed-DOX rats at 15-60Hz stimulations compared to Sed-Sal. Diaphragm force production did not differ in Mod-DOX rats compared to Sed-Sal at any stimulation frequency. These results demonstrate a beneficial effect of moderate intensity rehabilitation exercise for the maintenance of body composition, cardiac function and diaphragm muscle function following DOX treatment compared to sedentary rats. NIH R01 HL144858, NIH R01 HL146443, NIH HL134621. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Cardiac Troponin Activator CK-963 Increases Cardiac Contractility in Rats.

Novel cardiac troponin activators were identified using a high throughput cardiac myofibril ATPase assay and confirmed using a series of biochemical and biophysical assays. HTS hit 2 increased rat cardiomyocyte fractional shortening without increasing intracellular calcium concentrations, and the biological target of 1 and 2 was determined to be the cardiac thin filament. Subsequent optimization to increase solubility and remove PDE-3 inhibition led to the discovery of CK-963 and enabled pharmacological evaluation of cardiac troponin activation without the competing effects of PDE-3 inhibition. Rat echocardiography studies using CK-963 demonstrated concentration-dependent increases in cardiac fractional shortening up to 95%. Isothermal calorimetry studies confirmed a direct interaction between CK-963 and a cardiac troponin chimera with a dissociation constant of 11.5 ± 3.2 μM. These results provide evidence that direct activation of cardiac troponin without the confounding effects of PDE-3 inhibition may provide benefit for patients with cardiovascular conditions where contractility is reduced.

Preclinical characterization of CK-4021586, a new class of cardiac myosin inhibitors for the treatment of hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most common monogenetic heart disease, with an estimated carrier prevalence of ∼1 in 500. Hypercontractility of the cardiac sarcomere is a common driver of the pathological hypertrophic cardiac remodeling that is a hallmark of the disease. Clinical trials of the selective cardiac myosin inhibitors mavacamten and aficamten have demonstrated that inhibition of the biochemical activity of cardiac myosin can induce cardiac remodeling and improve both patient symptoms and exercise capacity in HCM with left ventricular outflow tract obstruction (oHCM). The diverse genetic underpinnings of HCM suggest that it is possible that additional classes of cardiac myosin inhibitors with distinct biochemical mechanisms-of-action may also have a salutary impact on disease expression. While both mavacamten and aficamten bind to the single-headed motor domain of myosin (subfragment-1) and inhibit its ATPase activity, CK-4021586 (CK-586) is a new class of cardiac myosin inhibitor that inhibits the ATPase activity of two-headed heavy meromyosin (HMM) but not single-headed subfragment-1. CK-586 is a partial inhibitor of cardiac myofibrillar ATPase activity (EC50 2.9 µM, maximal inhibition ∼50%) that requires the regulatory light chain. Notably, fractional shortening of electrically-paced adult rat ventricular cardiomyocytes was inhibited almost completely (>80% at 5 µM) without alterations in the calcium (Ca2+) transient. In normal Sprague Dawley rats, CK-586 reduced cardiac fractional shortening in a dose and concentration-dependent manner. In conclusion, CK-586 is a novel, small molecule, cardiac myosin inhibitor that reduces cardiac contractility in vitro and in vivo. CK-586 has a biochemical mechanism of action distinct from both mavacamten and aficamten, providing an additional tool to decrease the number of functionally-available myosin heads and treat the cardiac hypercontractility that forms the pathologic basis of HCM.

The Cardiac Dysfunction Caused by Metabolic Alterations in Alzheimer's Disease.

A progressive defect in the energy generation pathway is implicated in multiple aging-related diseases, including cardiovascular conditions and Alzheimer's Disease (AD). However, evidence of the pathogenesis of cardiac dysfunction in AD and the associations between the two organ diseases need further elucidation. This study aims to characterize cellular defects resulting in decreased cardiac function in AD-model. 5XFAD mice, a strain expressing five mutations in human APP and PS1 that shows robust Aβ production with visible plaques at 2 months and were used in this study as a model of AD. 5XFAD mice and wild-type (WT) counterparts were subjected to echocardiography at 2-, 4-, and 6-month, and 5XFAD had a significant reduction in cardiac fractional shortening and ejection fraction compared to WT. Additionally, 5XFAD mice had decreased observed electrical signals demonstrated as decreased R, P, T wave amplitudes. In isolated cardiomyocytes, 5XFAD mice showed decreased fraction shortening, rate of shortening, as well as the degree of transient calcium influx. To reveal the mechanism by which AD leads to cardiac systolic dysfunction, the immunoblotting analysis showed increased activation of AMP-activated protein kinase (AMPK) in 5XFAD left ventricular and brain tissue, indicating altered energy metabolism. Mito Stress Assays examining mitochondrial function revealed decreased basal and maximal oxygen consumption rate, as well as defective pyruvate dehydrogenase activity in the 5XFAD heart and brain. Cellular inflammation was provoked in the 5XFAD heart and brain marked by the increase of reactive oxygen species accumulation and upregulation of inflammatory mediator activities. Finally, AD pathological phenotype with increased deposition of Aβ and defective cognitive function was observed in 6-month 5XFAD mice. In addition, elevated fibrosis was observed in the 6-month 5XFAD heart. The results implicated that AD led to defective mitochondrial function, and increased inflammation which caused the decrease in contractility of the heart.

PHD Finger Protein 19 Promotes Cardiac Hypertrophy via Epigenetically Regulating SIRT2

Epigenetic regulations essentially participate in the development of cardiomyocyte hypertrophy. PHD finger protein 19 (PHF19) is a polycomb protein that controls H3K36me3 and H3K27me3. However, the roles of PHF19 in cardiac hypertrophy remain unknown. Here in this work, we observed that PHF19 promoted cardiac hypertrophy via epigenetically targeting SIRT2. In angiotensin II (Ang II)-induced cardiomyocyte hypertrophy, adenovirus-mediated knockdown of Phf19 reduced the increase in cardiomyocyte size, repressed the expression of hypertrophic marker genes Anp and Bnp, as well as inhibited protein synthesis. By contrast, Phf19 overexpression promoted Ang II-induced cardiomyocyte hypertrophy in vitro. We also knocked down Phf19 expression in mouse hearts in vivo. The results demonstrated that Phf19 knockdown reduced Ang II-induced decline in cardiac fraction shortening and ejection fraction. Phf19 knockdown also inhibited Ang II-mediated increase in heart weight, reduced cardiomyocyte size, and repressed the expression of hypertrophic marker genes in mouse hearts. Further mechanism studies showed that PHF19 suppressed the expression of SIRT2, which contributed to the function of PHF19 during cardiomyocyte hypertrophy. PHF19 bound the promoter of SIRT2 and regulated the balance between H3K27me3 and H3K36me3 to repress the expression of SIRT2 in vitro and in vivo. In human hypertrophic hearts, the overexpression of PHF19 and downregulation of SIRT2 were observed. Of importance, PHF19 expression was positively correlated with hypertrophic marker genes ANP and BNP but negatively correlated with SIRT2 in human hypertrophic hearts. Therefore, our findings demonstrated that PHF19 promoted the development of cardiac hypertrophy via epigenetically regulating SIRT2.

Chronic intermittent electronic cigarette exposure induces cardiac dysfunction and atherosclerosis in apolipoprotein-E knockout mice.

Electronic cigarettes (e-cigarettes), also known as electronic nicotine delivery systems, are a popular alternative to conventional nicotine cigarettes, both among smokers and those who have never smoked. In spite of the widespread use of e-cigarettes and the proposed detrimental cardiac and atherosclerotic effects of nicotine, the effects of e-cigarettes on these systems are not known. In this study, we investigated the cardiovascular and cardiac effects of e-cigarettes with and without nicotine in apolipoprotein-E knockout (ApoE-/-) mice. We developed an e-cigarette exposure model that delivers nicotine in a manner similar to that of human e-cigarettes users. Using commercially available e-cigarettes, bluCig PLUS, ApoE-/- mice were exposed to saline, e-cigarette without nicotine [e-cigarette (0%)], and e-cigarette with 2.4% nicotine [e-cigarette (2.4%)] aerosol for 12 wk. Echocardiographic data show that mice treated with e-cigarette (2.4%) had decreased left ventricular fractional shortening and ejection fraction compared with e-cigarette (0%) and saline. Ventricular transcriptomic analysis revealed changes in genes associated with metabolism, circadian rhythm, and inflammation in e-cigarette (2.4%)-treated ApoE-/- mice. Transmission electron microscopy revealed that cardiomyocytes of mice treated with e-cigarette (2.4%) exhibited ultrastructural abnormalities indicative of cardiomyopathy. Additionally, we observed increased oxidative stress and mitochondrial DNA mutations in mice treated with e-cigarette (2.4%). ApoE-/- mice on e-cigarette (2.4%) had also increased atherosclerotic lesions compared with saline aerosol-treated mice. These results demonstrate adverse effects of e-cigarettes on cardiac function in mice.NEW & NOTEWORTHY The present study is the first to show that mice exposed to nicotine electronic cigarettes (e-cigarettes) have decreased cardiac fractional shortening and ejection fraction in comparison with controls. RNA-seq analysis reveals a proinflammatory phenotype induced by e-cigarettes with nicotine. We also found increased atherosclerosis in the aortic root of mice treated with e-cigarettes with nicotine. Our results show that e-cigarettes with nicotine lead to detrimental effects on the heart that should serve as a warning to e-cigarette users and agencies that regulate them.

SUN-067 E-cigarettes and High Fat Diet Cause Alteration in Cardiac Structure and Function

Smoking is the major cause of cardiovascular diseases (CVD) and is the single largest cause of death in the USA. Smoking cessation can reduce the mortality from CVD. Electronic cigarettes, also known as electronic nicotine delivery systems (ENDS), have been marketed as a smoking cessation device. In spite of the widespread use of ENDS and the proposed detrimental cardiac and atherosclerotic effects of nicotine, the effects of ENDS on these systems are not well known. Recently, using Apolipoprotein E null mice, we demonstrated that mice exposed to e-cigarettes have decreased cardiac fractional shortening and ejection fraction together with ventricular ultrastructural abnormalities indicative of cardiomyopathy in comparison with controls. In this study, we investigated the detrimental effects of ENDS at doses similar to the clinically relevant concentrations found in habitual smokers and a high fat diet (HFD) on cardiac structure and function in a commonly used model of diet-induced obesity. C57 BL6 mice fed HFD were exposed to ENDS in the presence (2.4%) or absence (0%) of nicotine and saline aerosol for 12 weeks. Mice exposed to ENDS (2.4%) had increased serum free fatty acid levels in comparison with saline and ENDS (0%). Echocardiographic data show that mice treated with ENDS (2.4%) had decreased left ventricular fractional shortening and ejection fraction compared to ENDS (0%) and saline. Transmission electron microscopy revealed that cardiomyocytes of mice treated with ENDS (2.4%) exhibited ventricular abnormalities, including lipid accumulation (ventricular steatosis), myofibrillar derangement and destruction, and mitochondrial hypertrophy. Additionally, ENDS (2.4%) also caused increased cardiac oxidative stress and triggered cardiomyocyte apoptosis. These results demonstrate profound adverse effects of ENDS on ventricular structure and function in obese mice. We surmise that ENDS exposure may cause heart failure and other forms of cardiomyopathy in obese patients. This is important information for patients that use ENDS and regulatory agencies that regulate ENDS.

Cardiac gene expression and function in a mouse model of community-acquired methicillin-resistant Staphylococcus aureus sepsis: Role of inflammatory caspases 1 and 11

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is an important cause of invasive infections, including sepsis associated with myocardial dysfunction. Caspases 1 and 11, involved in activation of the inflammasome, have been shown to be critical in response to sepsis as well as myocardial dysfunction of numerous etiologies. We examined the survival, myocardial function, and production of inflammatory mediators in mice lacking caspases 1 and 11. Cas 1/11 KO mice demonstrated no significant difference in mortality or in cardiac shortening fraction relative to control mice. Cas 1/11 KO mice had significantly reduced upregulation of expression of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in the heart relative to control mice after CA-MRSA infection, as well as reduced serum production of IL-1β, TNF-α, and IL-6, with no difference in IL-10 production. Other inflammatory mediators beyond IL-1β, TNF-α, and IL-6 may be involved in myocardial dysfunction in CA-MRSA sepsis.

Is Prophylactic Parenteral Paracetamol Effective to Diminish Incidence of PDA in Preterm Neonates? A Randomized Trial

Background: Patent ductus arteriosus (PDA) is a common cause of morbidity and mortality among preterm infants. This study aimed to assess the efficacy of prophylactic parenteral paracetamol dosage to decrease rate of ductus patency in preterm infants. Methods: The study was a randomized double-masked clinical trial that was conducted at Afzalipour tertiary medical center (Kerman, Iran) between Novembers 2015 and 2016, recruiting 160 neonates with gestational age less than 34 weeks who were equally divided into case and control arms. The neonates of case group received parenteral paracetamol with the loading dose of 20 mg/kg and maintenance dose of 7.5 mg/kg every 6 hours during first three postnatal days and the neonates of control group received nothing. Thereafter, echocardiography was done at the day 4 to detect any ductus patency. Results: Among the included infants and after intervention, 12 (15%) in case group and 57 (71.25%) in control group had PDA. Ductus patency incidence among the neonates of case group was significantly lower than in control group. Means of assisted ventilation requirement, cardiac shortening fraction and mortality rate were not significantly different comparing the two groups. Conclusions: This study showed that the prophylactic dosage of parenteral paracetamol can prevent ductus patency and accounts as a trustworthy alternative to the traditional drugs e.g. Ibuprofen or Indomethacin.

P19.11: Novel technique to assess fetal fractional shortening by two‐dimensional tracking

To assess the usefulness of novel 2D tracking technique to measure fetal cardiac fractional shortening automatically (Auto FS) in normal singleton pregnancies. Two-dimensional tracking system to pursue wall motion of fetal heart, AutoFS, was constructed. In this study, temporal changes of AutoFS throughout gestation was studied in normal singleton pregnancies. At first, cardiac motion of the four chamber view was recorded in B-mode and then the AutoFS was calculated. The Region of interest (ROI) was set at a two-third of the wall from apex, in-to-in of the ventricular wall or septum, and tracking was performed. The values measured between the ventricular septum and at left side are defined as L-AutoFS. That at right side is R-AutoFS. We also obtained the value between each ventricular septum, which was defined as Combined-AutoFS. The equipment was Arietta70 (Hitachi). This study was approved by the ethics committee of this facility and was performed upon obtaining the written informed consent of the subject mother. This study was carried out from November 2016 to March 2017. The data was obtained from 68 of singleton fetuses. L-AutoFS decreased significantly with gestational weeks, and R-AutoFS showed the same tendency (Spearman correlation analysis: p=-0.33 and p=-0.64 respectively). Combined-AutoFS showed the same decline as gestational age (p=0.61). Two-dimensional and automatically calculation of fractional shortening was succeeded. This novel technique can assess fetal heart contractility by being combined with both longitudinal and short-axial dimensions. All L- R- and Combined AutoFS showed a trend towards a negative correlation with gestational weeks. Further examination would be needed for clinical usage.

Antecedent Hypoglycemia Does Not Attenuate the Acceleration of Gastric Emptying by Hypoglycemia.

Acute hypoglycemia accelerates gastric emptying and increases cardiac contractility. However, antecedent hypoglycemia attenuates counterregulatory hormonal responses to subsequent hypoglycemia. To determine the effect of antecedent hypoglycemia on gastric and cardiac responses to subsequent hypoglycemia in health. A prospective, single-blind, randomized, crossover study (performed at the Royal Adelaide Hospital, Adelaide, South Australia, Australia). Ten healthy young men 18 to 35 years of age were studied for 36 hours on two occasions. Participants were randomly assigned to either antecedent hypoglycemia [three 45-minute periods of strict hypoglycemia (2.8 mmol/L] or control [three 45-minute periods of strict euglycemia (6 mmol/L)] during the initial 12-hour period. Participants were monitored overnight, and the following morning blood glucose was clamped at 2.8 mmol/L for 60 minutes and then at 6 mmol/L for 120 minutes. At least 6 weeks later participants returned for the alternative intervention. Gastric emptying and cardiac fractional shortening were measured with scintigraphy and two-dimensional echocardiography, respectively, on the morning of all 4 study days. A single, acute episode of hypoglycemia accelerated gastric emptying (P = 0.01) and augmented fractional shortening (P < 0.01). Gastric emptying was unaffected by antecedent hypoglycemia (P = 0.74) whereas fractional shortening showed a trend to attenuation (P = 0.06). The adrenaline response was diminished (P < 0.05) by antecedent hypoglycemia. In health, the acceleration of gastric emptying during hypoglycemia is unaffected by antecedent hypoglycemia, whereas the increase in cardiac contractility may be attenuated.

Enhanced endothelin-1/Rho-kinase signalling and coronary microvascular dysfunction in hypertensive myocardial hypertrophy.

Hypertensive cardiac hypertrophy is associated with reduced coronary flow reserve, but its impact on coronary flow regulation and vasomotor function remains incompletely understood and requires further investigation. Left ventricular hypertrophy was induced in mice by transverse aortic coarctation (TAC) for 4 weeks. The left coronary artery blood velocity (LCABV) and myocardium lactate level were measured following the metabolic activation by isoproterenol. Septal coronary arterioles were isolated and pressurized for functional studies. In TAC mice, the heart-to-body weight ratio was increased by 45%, and cardiac fractional shortening and LCABV were decreased by 51 and 14%, respectively. The resting myocardial lactate level was 43% higher in TAC mice. Isoproterenol (5 µg/g, i.p.) increased heart rate by 20% in both groups of animals, but the corresponding increase in LCABV was not observed in TAC mice. The ventricular hypertrophy was associated with elevation of myocardial endothelin-1 (ET-1), increased vascular expression of rho-kinases (ROCKs), and increased superoxide production in the myocardium and vasculature. In coronary arterioles from TAC mice, the endothelial nitric oxide (NO)-mediated dilation to acetylcholine (ACh) was reversed to vasoconstriction and the vasoconstriction to ET-1 was augmented. Inhibition of ROCK by H-1152 alleviated oxidative stress and abolished enhanced vasoconstriction to ET-1. Both H-1152 and superoxide scavenger Tempol abolished coronary arteriolar constriction to ACh in a manner sensitive to NO synthase blocker NG-nitro-L-arginine methyl ester. Myocardial hypertrophy induced by pressure overload leads to cardiac and coronary microvascular dysfunction and ischaemia possibly due to oxidative stress, enhanced vasoconstriction to ET-1 and compromised endothelial NO function via elevated ROCK signalling.

The oxoglutarate receptor 1 (OXGR1) modulates pressure overload-induced cardiac hypertrophy in mice

The G-protein-coupled receptors (GPCRs) family of proteins play essential roles in the heart, including in the regulation of cardiac hypertrophy. One member of this family, the oxoglutarate receptor 1 (OXGR1), may have a crucial role in the heart because it acts as a receptor for α-ketoglutarate, a metabolite that is elevated in heart failure patients. OXGR1 is expressed in the heart but its precise function during cardiac pathophysiological process is unknown. Here we used both in vivo and in vitro approaches to investigate the role of OXGR1 in cardiac hypertrophy.Genetic ablation of Oxgr1 in mice (OXGR1−/−) resulted in a significant increase in hypertrophy following transverse aortic constriction (TAC). This was accompanied by reduction in contractile function as indicated by cardiac fractional shortening and ejection fraction. Conversely, adenoviral mediated overexpression of OXGR1 in neonatal rat cardiomyocytes significantly reduced phenylephrine-induced cardiomyocyte hypertrophy, a result that was consistent with the in vivo data. Using a combination of yeast two hybrid screening and phospho-antibody array analysis we identified novel interacting partner and downstream signalling pathway that might be regulated by the OXGR1. First, we found that OXGR1 forms a molecular complex with the COP9 signalosome complex subunit 5 (CSN5). Secondly, we observed that the STAT3 signalling pathway was upregulated in OXGR1−/− hearts. Since CSN5 interacts with TYK2, a major upstream regulator of STAT3, OXGR1 might regulate the pro-hypertrophic STAT3 pathway via interaction with the CSN5-TYK2 complex.In conclusion, our study has identified OXGR1 as a novel regulator of pathological hypertrophy via the regulation of the STAT3. Identification of molecules that can specifically activate or inhibit this receptor may be very useful in the development of novel therapeutic approach for pathological cardiac hypertrophy.

ESICM LIVES 2016: part two

Cardiac fractional shortening on day 1 and day 2 of control and antecedent hypoglycaemia study periods

CARD9 knockout ameliorates myocardial dysfunction associated with high fat diet-induced obesity

Obesity is associated with chronic inflammation which plays a critical role in the development of cardiovascular dysfunction. Because the adaptor protein caspase recruitment domain-containing protein 9 (CARD9) in macrophages regulates innate immune responses via activation of pro-inflammatory cytokines, we hypothesize that CARD9 mediates the pro-inflammatory signaling associated with obesity en route to myocardial dysfunction.C57BL/6 wild-type (WT) and CARD9−/− mice were fed normal diet (ND, 12% fat) or a high fat diet (HFD, 45% fat) for 5months. At the end of 5-month HFD feeding, cardiac function was evaluated using echocardiography. Cardiomyocytes were isolated and contractile properties were measured. Immunofluorescence was performed to detect macrophage infiltration in the heart. Heart tissue homogenates, plasma, and supernatants from isolated macrophages were collected to measure the concentrations of pro-inflammatory cytokines using ELISA kits. Western immunoblotting analyses were performed on heart tissue homogenates and isolated macrophages to explore the underlying signaling mechanism(s). CARD9 knockout alleviated HFD-induced insulin resistance and glucose intolerance, prevented myocardial dysfunction with preserved cardiac fractional shortening and cardiomyocyte contractile properties. CARD9 knockout also significantly decreased the number of infiltrated macrophages in the heart with reduced myocardium-, plasma-, and macrophage-derived cytokines including IL-6, IL-1β and TNFα. Finally, CARD9 knockout abrogated the increase of p38 MAPK phosphorylation, the decrease of LC3BII/LC3BI ratio and the up-regulation of p62 expression in the heart induced by HFD feeding and restored cardiac autophagy signaling.In conclusion, CARD9 knockout ameliorates myocardial dysfunction associated with HFD-induced obesity, potentially through reduction of macrophage infiltration, suppression of p38 MAPK phosphorylation, and preservation of autophagy in the heart.

Lysophosphatidic acid enhances survival of human CD34(+) cells in ischemic conditions.

Several clinical trials are exploring therapeutic effect of human CD34+ cells in ischemic diseases, including myocardial infarction. Unfortunately, most of the cells die few days after delivery. Herein we show that lysophosphatidic acid (LPA)-treated human umbilical cord blood-derived CD34+ cells cultured under hypoxic and serum-deprived conditions present 2.2-fold and 1.3-fold higher survival relatively to non-treated cells and prostaglandin E2-treated cells, respectively. The pro-survival effect of LPA is concentration- and time-dependent and it is mediated by the activation of peroxisome proliferator-activator receptor γ (PPARγ) and downstream, by the activation of pro-survival ERK and Akt signaling pathways and the inhibition of mitochondrial apoptotic pathway. In hypoxia and serum-deprived culture conditions, LPA induces CD34+ cell proliferation without maintaining the their undifferentiating state, and enhances IL-8, IL-6 and G-CSF secretion during the first 12 h compared to non-treated cells. LPA-treated CD34+ cells delivered in fibrin gels have enhanced survival and improved cardiac fractional shortening at 2 weeks on rat infarcted hearts as compared to hearts treated with placebo. We have developed a new platform to enhance the survival of CD34+ cells using a natural and cost-effective ligand and demonstrated its utility in the preservation of the functionality of the heart after infarction.

Abstract 17320: Inhibition of Ceramide Synthesis Preserves Cardiac Function and Increases Survival in Doxorubicin-induced Cardiomyopathy

Background: Previous studies have linked increased ceramide and dihydroceramide (DHC) synthesis to cardiotoxicity. However, the effects of ceramide synthesis inhibition on doxorubicin (DOX)-induced cardiomyopathy are unclear. Hypothesis: Inhibition of de novo ceramide synthesis by myriocin maintains heart function and survival rate. Methods: C57BL/6J mice (8 wks, n=52) were treated with DOX (3 mg/kg every other day for 2 wks) with or without myriocin (0.3 mg/kg). Cardiac function was assessed by echocardiography. AC16 cardiomyocyte-like cells were incubated with DOX in the presence or absence of myriocin (10 uM). Ceramides were analyzed by LC/MS lipidomics. Reactive oxygen species (ROS) were measured by FACS (CellROX) and mitochondrial function determined by Seahorse analyzer. Results: In DOX-treated mice, inhibition of ceramide synthesis by myriocin preserved cardiac fractional shortening (29.2±2.7 vs 36.9±1.4% in myriocin; p&lt;0.05), left ventricular systolic diameter dilation (3.2±0.1 vs 2.97±0.8 mm, p&lt;0.05), running endurance (8.5 vs 17.5 min; p&lt;0.05) and survival rates (35 vs 90% in myriocin, p&lt;0.001). DOX increased cardiac total ceramides (+70%; p&lt;0.001) and DHC (+73%; p&lt;0.05); these increases were prevented by myriocin. Cardiac apoptosis in these cells was increased 4.1 fold by DOX and reduced by 50% with myriocin (p&lt;0.05). In cells, DOX increased cellular ceramide content (+112.4%, p&lt;0.01), especially C14 (+69%; p&lt;0.05), C16 (+144%; p&lt;0.01), C18 (+53%; p&lt;0.05), C22 (+98%; p&lt;0.05), C24 (+83.5%; p&lt;0.01) and C24:1(+86%; p&lt;0.05). Interestingly, ceramide accumulation in mitochondria of DOX-treated cells (+125%; p&lt;0.05) was associated with decreased mitochondrial respiration (-76%; p&lt;0.05) and respiratory capacity (-88%; p&lt;0.05). Myriocin treatment decreased very long-chain ceramides (-52%; p&lt;0.05), reduced apoptosis (-23%; p&lt;0.01), and prevented proteolysis of actin protein ubiquitination (-31%; p&lt;0.05). Also, myriocin inhibited DOX-induced increase of ROS (+32%; p&lt;0.05). Conclusion: Cardiomyocyte ceramide accumulation, especially in mitochondria, is associated with mitochondrial dysfunction, cardiotoxicity and reduced survival. Pharmacological inhibition of ceramide synthesis may prevent lipotoxicity.

Novel Histone Deacetylase Inhibitor Modulates Cardiac Peroxisome Proliferator-Activated Receptors and Inflammatory Cytokines in Heart Failure

Background: Heart failure (HF) affects cardiac metabolism and inflammation. Histone deacetylases (HDACs) play a critical role in cardiac pathophysiology. This study investigated whether HDAC inhibition can regulate HF by modifying cardiac inflammation and peroxisome proliferator-activated receptor (PPAR) isoforms. Methods: Echocardiography, electrocardiography, ELISA and Western blot were performed in rats with isoproterenol-induced HF, with and without orally administered MPT0E014 (a novel HDAC inhibitor, 50 mg/kg for 7 consecutive days). Results: The left ventricles (LVs) of HF rats expressed significantly higher levels of HDAC1, HDAC2, HDAC3, HDAC4 and HDAC6 than the healthy LVs did. HF rats treated with MPT0E014 exhibited improved cardiac fraction shortening with reducing chamber size. The MPT0E014-treated HF LVs exhibited a smaller increase in the expression of interleukin (IL)-6, p22, SMAD2/3, extracellular signal-regulated kinase 1/2, PPAR isoforms and circulatory tumor growth factor-β1 than the untreated HF LVs did. Moreover, MPT0E014-treated HF LVs expressed less fibroblast growth factor receptor than untreated HF LVs did. Conclusions: HDAC inhibition can improve cardiac function and attenuate the effects of HF on cardiac metabolism and inflammation, which might contribute to the beneficial effects of HDAC inhibition in HF.

Abstract 72: Pka Is A Master Regulator Of Pathological Cardiac Hypertrophy

Aims: The role of PKA in pathological cardiac hypertrophy (PCH) is not clear. The literature suggests both prohypertrophic and antihypertrophic effects of PKA. Furthermore, there are endogenous PKA inhibitors, PKI, highly expressed in the heart to regulate PKA activity but their roles in PCH have not been studied. We aim to explore the role of PKI/PKA in PCH induced by isoproterenol, phenylephrine, angiotensin II and pressure overload. Methods and Results: 1. PKIα and PKIγ were highly expressed in the heart but only PKIα was reduced by transaortic banding (TAB); TAB induced a significant increase in cardiac PKA activity at 1 week post TAB. 2. Four transgenic mouse lines with high (HE), medium (ME), low (LE) and very low (VLE) expression of PKI-GFP were obtained with the inhibition of maximum PKA activity induced by 1μM cAMP by 95%, 57%, 20% and 10% in the cardiac homogenates; 3. In the VLE hearts, some myocytes were PKI-GFP+ and some were PKI-GFP-, GFP- LVMs had significantly larger surface area than GFP+ LVMs; 4. PKA inhibition by PKI-GFP abolished PCH induced by isoproterenol, phenylephrine, angiotensin II in HE mice; 5. TAB for 8 weeks did not change HW/BW, myocyte cross-sectional area and myocardial fibrosis in HE mice but induced significant increases in HW/BW, myocyte cross-sectional area, myocardial fibrosis and depressed cardiac fractional shortening in control mice. 6. In cultured neonatal rat ventricular myocytes, PKI-GFP prevented myocyte hypertrophy induced by isoproterenol (ISO), phenylephrine (PE) and angiotensin II, as evidenced by no significant increases in protein synthesis (protein/DNA ratio), myocyte surface area, sarcomere organization. 7. PKI-GFP in NRVMs prevented the translocation of NFAT3 and HDAC5 induced by ISO and PE and increased the secretion of antihypertrophic ANF at baseline; 8. TAB induced PKA-dependent phosphorylation of GSK-3α and GSK-3β, inactivating them to relieve their antihypertrophic effect and promote protein synthesis (increased phosphorylation of mTORC1, eIF-4EBP1, p70 S6K); PKA inhibition abolished these effects. Conclusions: PKA is regulated by PKI and is a master regulator of PCH induced by pressure overload.

Swimming training restores the cardiac microRNA‐1, and ‐214 levels and cardiac contractility in rat after myocardial infarction (LB43)

Myocardial infarction (MI) is accompanied by cardiac hypertrophy and fibrosis related to ventricular compliance reduction. MicroRNAs (miRNAs) are noncoding single stranded RNA molecules that regulate gene expression. The miRNA‐1, which target NCX and ‐214, which target Serca2a are involved in cardiac contractily. This study assessed the effects of swimming training (ST) on the cardiac miRNAs‐1 and ‐214 levels and ventricular function after MI. Male Wistar rats (n=6/group) were randomized into four groups: Control (CO), Training (TR), Control Infarcted (CI) Training Infarcted (TI). ST consisted of 60 min/days/5 days/week/10 week with 3% body overload began four weeks after the MI. Echocardiography was performed before and after the ST. MiRNAs analysis was performed by real‐time PCR in the Remote Myocardium (RM). The VO2max increased 38%in the TR compared with CO group and increased 14% in the TI compared with CI group. TI group decreased 15% the E/A ratio compared with CI group, showing improved ventricular compliance. Also, ST restored the cardiac shortening fraction in the TI group compared with CO group. MiRNA‐1 and ‐214 expression, respectively, were decreased (52%) and increased (54%) in the CI compared to the CO . However, ST increased (49%) and decreased (29%), respectively, the MiRNA‐1 and ‐214 expression in the TI compared to the CO . In this way, NCX and Serca2a were respectively decreased (36%) and increased (48%) in the TI compared to the CI. These results show that ST restored cardiac miRNA‐1 and ‐214 expression, which can be associate to the improved ventricular function, suggesting a mechanism for its potential therapeutic application in heart diseases.Grant Funding Source: Foundation for Research Support of the State of São Paulo ‐ FAPESP