Decrease In Cardiac Function Research Articles

CirculatingPorphyromonas gingivalislipopolysaccharide resets cardiac homeostasis in mice through a matrix metalloproteinase-9-dependent mechanism

Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) circulates systemically in over 50% of periodontal disease (PD) patients and is associated with increased matrix metalloproteinase (MMP)-9. We hypothesized that low systemic Pg-LPS would stimulate an inflammatory response in the left ventricle (LV) through MMP-9, leading to a decrease in cardiac function. Wild-type (WT) and MMP-9 null mice (4–7 months old) were exposed for 1 or 28 days to low dose Pg-LPS or saline (n ≥ 6/group). MMP-9 significantly increased in WT mice LV at 1 and 28 days of exposure, compared to control (P < 0.05 for both). Fractional shortening decreased subtly yet significantly in WT mice by day 28 (31 ± 1%) compared to control (35 ± 1%; P < 0.05), and this decrease was attenuated in null (34 ± 1%) mice. Plasma cardiac troponin I levels were elevated in WT mice at day 28. Macrophage-related factors increased over twofold in WT plasma and LV after day 1 (monocyte chemoattractant protein-5, macrophage inflammatory protein (MIP)-1α, MIP-1γ, stem cell factor, Ccl12, Ccl9, Il8rb, Icam1, Itgb2, and Spp1; all P < 0.05), indicating a moderate inflammatory response. Levels returned to baseline by day 28, suggesting tolerance to Pg-LPS. In contrast, macrophage-related factors remained elevated in day 28 null mice, indicating a sustained defense against Pg-LPS stimulation. Consistent with these findings, LV macrophage numbers increased in both groups at day 1 and returned to baseline by day 28 in the WT mice only. Major histocompatibility complex (MCH) II remained elevated in the null group at day 28, confirming Pg-tolerance in the WT. Interestingly Il-1α, a regulator of macrophage immunosuppression, increased in the plasma of WT mice only on day 28, suggesting that Il-1α plays a role in tolerance in a MMP-9-dependent manner. In conclusion, circulating Pg-LPS induced tolerance in WT mice, resulting in significant LV changes and subtle cardiac dysfunction. MMP-9 played a major role in the regulation of chronic systemic inflammation and associated cardiac dysfunction.

Abstract 309: Two SoxD Family Transcription Factors Influence Heart Function at Baseline and After Cardiac Overload

Background: Sox6, a member of the SoxD family of transcription factors, has recently been established as a mediator of the actions of MyomiRs miR-208b and 499 in skeletal muscle. Sox6 suppresses the expression of slow skeletal muscle genes and its deletion promotes skeletal muscle fiber switching in mice. However, the role of Sox6 in the heart remains elusive. Given the importance of MyomiRs in regulating cardiac stress responses and the regulation of Sox6 by MyomiRs in the heart, we postulate that Sox6 is a central regulator of cardiac hypertrophy and heart failure. Results: Because of functional redundancy of Sox6 and Sox5 in multiple tissues, Sox6 fl/fl mice were crossbred with Sox5 fl/fl mice and mice expressing CRE recombinase under the control of the alphaMHC gene promoter to obtain Sox5 fl/fl / Sox6 fl/fl /CRE+ ( Sox5/6 cKO) animals or CRE- controls. Sox5/6 cKO animals were viable and born at expected Mendelian ratios. At baseline, Sox5/6 cKO mice did not show any signs of hypertrophy or cardiac failure as assessed by echocardiography at the age of 9 weeks. While cardiac size and heart function measured by echocardiography was unaltered in mice aged 4-5 months, cardiac catheterization revealed significant decreases in contractility in Sox5/6 cKO animals. In addition, qPCR analysis of hearts showed increased expression of slow myosin Myh7 and Nppa , a marker of cardiac stress, in Sox5/6 cKO animals compared to controls. Following cardiac pressure overload for 3 weeks by transverse aortic constriction (TAC), significant decreases in cardiac function, as measured by echocardiography, were apparent in Sox5/6 cKO compared to control mice. Sox5/6 cKO mice subjected to TAC also showed signs of cardiac failure such as increased wet lung weight. Conclusion: Cardiac-specific deletion of Sox6 and Sox5 lead to reduction of cardiac function at baseline and exacerbated susceptibility to the development of cardiac failure after cardiac pressure overload. The contribution of each individual transcription factor to the observed phenotypes is currently being investigated.

Cathepsin B inhibition attenuates cardiac dysfunction and remodeling following myocardial infarction by inhibiting the NLRP3 pathway

Recently, cathepsin B has been demonstrated to be involved in myocardial infarction (MI). This study aimed to elucidate the effects of a specific cathepsin B inhibitor, CA-074Me, on cardiac dysfunction, remodeling and fibrosis following MI in a rat model. Furthermore, the potential mechanisms of action of this inhibitor were investigated. In the present study, Sprague-Dawley rats were anesthetized and subjected to a sham operation or left anterior descending coronary artery ligation, followed by intraperitoneal injection of CA-074Me (10 mg/kg/day) or an equal volume of vehicle for 4 weeks. Activation of the cathepsin B and NLRP3 pathway was detected. Cardiac function was assessed by echocardiography, while hypertrophy and fibrosis were determined by Masson's trichrome, immunofluorescence and morphometry. The results demonstrated that cathepsin B-NLRP3 activation was inhibited by CA-074Me treatment. Following such treatment for 4 weeks, the rats demonstrated smaller decreases in cardiac function, and a decrease in cardiomyocyte hypertrophy and the level of fibrosis. Cathepsin B inhibition significantly attenuated cardiac dysfunction, and reduced cardiomyocyte size and cardiac fibrosis in the experimental MI model, by inhibiting NLRP3 activation. This suggested that targeting the cathepsin B-NLRP3 pathway may represent a novel therapeutic strategy to prevent heart failure and remodeling following MI.

Phase I dose escalation study of oral lapatinib in combination with docetaxel in patients with HER2-positive locally advanced or metastatic breast cancer (LAMBC): Initial safety and tolerability results.

e11529 Background: Previous studies evidenced that the combination docetaxel (D) (75 mg/m²) + lapatinib (L) (1,250 mg/d) is well tolerated in heavily pretreated HER2-positive metastatic breast cancer patients (pts) in association with systematic G-CSF. This phase I study was conducted to assess safety, optimal tolerated regimen (OTR) and clinical activity of D + L in naïve treatment pts with HER-2 positive LAMBC without primary use of growth factor. Methods: Women with HER2+ LAMBC, naïve of treatment for advanced or metastatic disease, ECOG PS 0-2, were eligible for this study. Pts received once daily oral dosing of L with intravenous D on day 1 of every 3 week cycle. Initial dose was D (75 mg/m²) + L (1,250 mg/d) escalating up to D 100 mg/m² and L 1,500 mg/d until the Maximal Tolerated Dose (MTD) was reached. An expansion cohort of 6 pts was treated at the OTR level. Primary use of G-CSF was not permitted. Results: From Aug 2008 to Nov 2011, 17 pts were enrolled: median age 54.4 years [34.6-77], 59% were PS 0. All patients have metastatic disease with lung (29,4%), bone (41,2%), liver (76.5%) and lymph nodes (35.3%) metastasis. 7 pts received previously chemotherapy in adjuvant setting, 5 pts hormonotherapy and 7 pts radiotherapy. All but two pts were evaluable for dose limiting toxicities (DLT). 1 DLT/6 pts (FN) was observed at dose level (DL) 1 (D 75 mg/m² + L 1,250 mg/d) and 2 DLT/3 pts (gr 3 diarrhoea; gr4 neutropenia &gt;7 d) at DL2 (D 75 mg/m² + L 1,500 mg/d). Only one DLT (FN) was observed in expansion cohort at OTR (D 75 mg/m² + L 1,250 mg/d; 6 pts). Over all C1, other significant toxicities (% pts) included gr4 neutropenia 53%, gr3 transaminase increase 6%, gr2 skin rash 36%, gr2 nausea/vomiting 18%, gr2 diarrhoea 12%, gr2 stomatitis 12%, gr2 hand-foot syndrome 6%; no decrease of cardiac function occurred. Conclusions: OTR for D and L was 75 mg/m² once every 3 weeks and 1,250 mg once daily respectively. This study demonstrates that this combination could be administered without systematic use of G-CSF in non pretreated pts with LAMBC. Additional safety data and preliminary evidence of activity are anticipated to be available at the time of presentation. Clinical trial information: NCT01044485.

Metabolic and Cardiac Responses of CunnerTautogolabrus adspersusto Seasonal and Acute Changes in Temperature

The cunner is a marine teleost that exhibits winter dormancy (i.e., becomes inactive and stops feeding) when seawater temperatures fall below 5°C. To examine whether this dormant state is also associated with active metabolic depression, the effect of season on routine metabolic rate (MR(rout)) was measured at five different times throughout the year: early spring (5°C), late spring (9°C), summer (14°C), late fall (5°C), and winter (0°C). In addition, cardiac function (cardiac output, heart rate, and stroke volume) was measured at the last three measurement time points, and the ability of fall- and winter-acclimated cunner to adjust MR(rout) and cardiac function when challenged with acute temperature changes was assessed. The cunner actively depressed MR(rout) between fall and winter as temperature fell from 5° to 0°C ([Formula: see text]). In addition, MR(rout) showed a substantial but smaller Q(10) (4.3) when the MR(rout) at 0°C (winter) was compared with the value recorded during the previous spring at ∼5°C. These seasonal changes were essentially mirrored by the response of MR(rout) to acute 5°C increases and decreases in temperature. Similar to MR(rout), cardiac output (Q) decreased dramatically as temperature fell from 5°C (fall) to 0°C (winter) in the seasonal study ([Formula: see text]) and increased substantially when temperature was acutely increased from 0° to 5°C ([Formula: see text]). However, when subjected to an acute temperature decrease (from 5° to 0°C), the Q(10) for Q was only approximately 2-3. These results show that (1) cunner actively depress their metabolism in the fall and winter and that this is associated with a large decrease in cardiac function and (2) there is a decoupling between Q and MR(rout) when 5°C seasonally acclimated cunner are exposed to an acute temperature decrease to 0°C.

Calorie restriction can reverse, as well as prevent, aging cardiomyopathy

Calorie restriction (CR) is the most widely studied intervention protecting from the adverse effects of aging. Almost all prior studies have examined the effects of CR initiated in young animals. Studies examining the effects of CR on development of aging cardiomyopathy found only partial prevention. The major goal of this study was to determine whether CR initiated after aging cardiomyopathy developed could reverse the cardiomyopathy. Aging cardiomyopathy in 2-year-old mice was characterized by reduced left ventricular (LV) function, cardiac hypertrophy, and increased cardiac apoptosis and fibrosis. When short-term (2 months) CR was initiated after aging cardiomyopathy developed in 20-month-old mice, the decrease in cardiac function, and increases in LV weight, myocardial fibrosis and apoptosis were reversed, such that the aging hearts in these mice were indistinguishable from those of young mice or mice where CR was initiated in young mice. If apoptosis was the mechanism for protecting against aging cardiomyopathy, then total myocyte numbers should have reverted to normal with CR, but did not. However, the alterations in cytoskeletal proteins, which contribute to aging cardiomyopathy, were no longer observed with CR. This is the first study to demonstrate complete prevention of aging cardiomyopathy by CR and, more importantly, that instituting this intervention even later in life can rapidly correct aging cardiomyopathy, which could have important therapeutic implications.

Carbonic anhydrase II promotes cardiomyocyte hypertrophy

Pathological cardiac hypertrophy, the maladaptive remodelling of the myocardium, often progresses to heart failure. The sodium-proton exchanger (NHE1) and chloride-bicarbonate exchanger (AE3) have been implicated as important in the hypertrophic cascade. Carbonic anhydrase II (CAII) provides substrates for these transporters (protons and bicarbonate, respectively). CAII physically interacts with NHE1 and AE3, enhancing their respective ion transport activities by increasing the concentration of substrate at their transport sites. Earlier studies found that a broad-spectrum carbonic anhydrase inhibitor prevented cardiomyocyte hypertrophy (CH), suggesting that carbonic anhydrase is important in the development of hypertrophy. Here we investigated whether cytosolic CAII was the CA isoform involved in hypertrophy. Neonatal rat ventricular myocytes (NRVMs) were transduced with recombinant adenoviral constructs to over-express wild-type or catalytically inactive CAII (CAII-V143Y). Over-expression of wild-type CAII in NRVMs did not affect CH development. In contrast, CAII-V143Y over-expression suppressed the response to hypertrophic stimuli, suggesting that CAII-V143Y behaves in a dominant negative fashion over endogenous CAII to suppress hypertrophy. We also examined CAII-deficient (Car2) mice, whose hearts exhibit physiological hypertrophy without any decrease in cardiac function. Moreover, cardiomyocytes from Car2 mice do not respond to prohypertrophic stimulation. Together, these findings support a role of CAII in promoting CH.

Abstract 19245: Time Trends of Echocardiography Measures of LV Function in a Cohort of Women with Breast Cancer Treated with Anthracyclines, Taxanes and Trastuzumab

Background: The cardiotoxicity that occurs during treatment by anthracyclines and trastuzumab used for cancer therapy is well recognized. However, the time trend of the decrease in cardiac function is unknown. In particular, the decrease in left ventricular ejection fraction (LVEF) seen with trastuzumab is thought to be transient although there is controversy on this reversibility. Aim: To determine the trends of LVEF, strain and strain rate after treatment by anthracyclines, taxanes and trastuzumab in a cohort of women with breast cancer that had been serially followed during their treatment. Methods: Follow up echocardiograms (TTEs) were performed in 25 women &gt;18 years of age with first time breast cancer treated with anthracyclines and trastuzumab, 26.4±11.1 months after the end of the cancer treatment. These women had undergone serial TTEs before and during the duration of the treatment (15 months). LVEF was calculated using a modified Simpson’s biplane method. Global peak systolic longitudinal strain and strain rate were calculated by averaging the values of peak systolic strain and strain rate in the basal, mid-wall and apical segments of the 4- and 2- chamber views. Results: LVEF, strain and strain rate decreased during the study period (p&lt;0.05 for all 3 parameters) and did not improve after 24 months of treatment completion. Of the three parameters, strain appeared to be most sensitive for the detection of cardiac dysfunction since it demonstrated a significant decrease within the 3 first months of treatment. Conclusion: Impairment in cardiac function from chemotherapy appears to be persistent even at 26.4±11.1 months post treatment suggestive of long term underlying cardiac damage. These results highlight the potential value of echocardiography in detecting sub-acute cardiac pathology and may help guide cardiac treatment in cancer survivors.

Obstructive sleep apnoea: longer respiratory event lengths in patients with heart failure

This study investigated the effect of heart failure on respiratory patterns in patients with obstructive sleep apnoea (OSA). 39 patients with established OSA (apnoea/hypopnoea index (AHI) >10 events·h(-1)) and either with heart failure (New York Heart Association (NYHA) class II and III, left ventricular-ejection fraction (LVEF) ≤40%; n=26, age mean ± SD 67 ± 9 years) or without heart failure (LVEF ≥50%, N-terminal pro-brain naturic peptide <400 pg·mL(-1); n=13, age 73 ± 6 years) underwent simultaneous right- and left-heart catheterisation within 12 h of cardiorespiratory polygraphy recording. Respiratory patterns of OSA were significantly longer in OSA patients with heart failure versus without heart failure, including mean ± SD cycle length (46.0 ± 10.0 versus 37.8 ± 10.6 s; p=0.024), ventilation length (25.4 ± 6.3 versus 21.3 ± 7.1 s; p=0.044), apnoea length (20.5 ± 4.9 versus 16.5 ± 3.9 s; p=0.013), time-to-peak ventilation (10.6 ± 3.0 versus 8.3 ± 2.5 sc; p=0.021) and circulatory delay (28.5 ± 7.5 versus 22.6 ± 3.7 s; p=0.005). Positive and robust correlations were found between some of these parameters and the degree of congestion in heart failure: cycle length (r=0.53; p=0.006), ventilation length (r=0.55; p=0.004) and time-to-peak ventilation (r=0.47; p=0.015) all increased with a rise in pulmonary capillary wedge pressure. Respiratory patterns in OSA appear to be dependent on cardiac function, with an increase in event lengths as cardiac function decreases. In patients with heart failure, some of these events correlate with the degree of pulmonary congestion.

Pressure Overload Induces Early Morphological Changes in the Heart

Cardiac hypertrophy, whether pathological or physiological, induces a variety of additional morphological and physiological changes in the heart, including altered contractility and hemodynamics. Events exacerbating these changes are documented during later stages of hypertrophy (usually termed pathological hypertrophy). Few studies document the morphological and physiological changes during early physiological hypertrophy. We define acute cardiac remodeling events in response to transverse aortic constriction (TAC), including temporal changes in hypertrophy, collagen deposition, capillary density, and the cell populations responsible for these changes. Cardiac hypertrophy induced by TAC in mice was detected 2 days after surgery (as measured by heart weight, myocyte width, and wall thickness) and peaked by day 7. Picrosirius staining revealed increased collagen deposition 7 days after TAC; immunostaining and flow cytometry indicated a concurrent increase in fibroblasts. The findings correlated with angiogenesis in TAC hearts; a decrease in capillary density was observed at day 2, with recovery to sham-surgery levels by day 7. Increased pericyte levels, which were observed 2 days after TAC, may mediate this angiogenic transition. Gene expression suggests a coordinated response in growth, extracellular matrix, and angiogenic factors to mediate the observed morphological changes. Our data demonstrate that morphological changes in response to cardiovascular injury occur rapidly, and the present findings allow correlation of specific events that facilitate these changes.

Cardioprotection of controlled and cardiac-specific over-expression of A(2A)-adenosine receptor in the pressure overload.

Adenosine binds to three G protein-coupled receptors (R) located on the cardiomyocyte (A1-R, A2A-R and A3-R) and provides cardiac protection during both ischemic and load-induced stress. While the role of adenosine receptor-subtypes has been well defined in the setting of ischemia-reperfusion, far less is known regarding their roles in protecting the heart during other forms of cardiac stress. Because of its ability to increase cardiac contractility and heart rate, we hypothesized that enhanced signaling through A2A-R would protect the heart during the stress of transverse aortic constriction (TAC). Using a cardiac-specific and inducible promoter, we selectively over-expressed A2A-R in FVB mice. Echocardiograms were obtained at baseline, 2, 4, 8, 12, 14 weeks and hearts were harvested at 14 weeks, when WT mice developed a significant decrease in cardiac function, an increase in end systolic and diastolic dimensions, a higher heart weight to body weight ratio (HW/BW), and marked fibrosis when compared with sham-operated WT. More importantly, these changes were significantly attenuated by over expression of the A2A-R. Furthermore, WT mice also demonstrated marked increases in the hypertrophic genes β-myosin heavy chain (β-MHC), and atrial natriuretic factor (ANF) – changes that are mediated by activation of the transcription factor GATA-4. Levels of the mRNAs encoding β-MHC, ANP, and GATA-4 were significantly lower in myocardium from A2A-R TG mice after TAC when compared with WT and sham-operated controls. In addition, three inflammatory factors genes encoding cysteine dioxygenase, complement component 3, and serine peptidase inhibitor, member 3N, were enhanced in WT TAC mice, but their expression was suppressed in A2A-R TG mice. A2A-R over-expression is protective against pressure-induced heart failure secondary to TAC. These cardioprotective effects are associated with attenuation of GATA-4 expression and inflammatory factors. The A2A-R may provide a novel new target for pharmacologic therapy in patients with cardiovascular disease.

Inhibition of vascular peroxidase alleviates cardiac dysfunction and apoptosis induced by ischemia–reperfusion

Myeloperoxidase (MPO) is involved in myocardial ischemia-reperfusion (IR) injury and vascular peroxidase (VPO) is a newly identified isoform of MPO. This study was conducted to explore whether VPO is involved in IR-induced cardiac dysfunction and apoptosis. In a rat Langendorff model of myocardial IR, the cardiac function parameters (left ventricular pressure and the maximum derivatives of left ventricular pressure and coronary flow), creatine kinase (CK) activity, apoptosis, VPO1 activity were measured. In a cell (rat-heart-derived H9c2 cells) model of hypoxia-reoxygenation (HR), apoptosis, VPO activity, and VPO1 mRNA expression were examined. In isolated heart, IR caused a marked decrease in cardiac function and a significant increase in apoptosis, CK, and VPO activity. These effects were attenuated by pharmacologic inhibition of VPO. In vitro, pharmacologic inhibition of VPO activity or silencing of VPO1 expression significantly suppressed HR-induced cellular apoptosis. Our results suggest that increased VPO activity contributes to IR-induced cardiac dysfunction and inhibition of VPO activity may have the potential clinical value in protecting the myocardium against IR injury.

Isolated Rabbit Working Heart Function During Progressive Inhibition of Myocardial SERCA Activity

The extent to which sarcoplasmic reticulum Ca(2+)ATPase (SERCA) activity alone determines left ventricular (LV) pump function is unknown. To correlate SERCA activity with hemodynamic function of rabbit LV during thapsigargin perfusion. Isolated rabbit hearts were perfused in working heart configuration, and LV pump function was assessed using a pressure-volume catheter. Rapid and complete (>95%) inhibition of SERCA was associated with a moderate decrease in cardiac function (to 70%-85% of control). Further decrease in cardiac function to 50%-75% of control occurred over the next ≈ 30 minutes despite no detectable further inhibition of SERCA activity. Analysis of the 20 seconds prior to pump failure revealed a rapid decrease in end diastolic volume. Intermediate levels of SERCA function (≈ 50% of control) had only minor hemodynamic effects. Parallel experiments in field-stimulated isolated ventricular cardiomyocytes monitored intracellular Ca(2+) and cell shortening. On perfusion with thapsigargin, Ca(2+) transient amplitude and cell shortening fell to ≈ 70% of control followed by increased diastolic Ca(2+) concentration and diastolic cell shortening to achieve a new steady state. The relationship between SERCA activity and LV function in the rabbit is highly nonlinear. In the short term, only moderate effects on LV pump function were observed despite almost complete (>95%) reduction in SERCA activity. The terminal decline of function was associated with sudden sustained increase in diastolic tone comparable to the sustained contraction observed in isolated cardiomyocytes. Secondary increases of intracellular Ca(2+) and Na(+) following complete SERCA inhibition eventually limit contractile function and precipitate LV pump failure.

MKP1 inhibits myocardial TNF‐alpha expression and improves cardiac function in endotoxemia

The objective of this study was to investigate the role of mitogen‐activated protein kinase phosphatase‐1 (MKP1) pathway in myocardial tumor necrosis factor (TNF)‐alpha expression and cardiac function during endotoxemia. Experiments were carried out in a mouse model of endotoxemia and in cultured neonatal cardiomyocytes. Lipopolysaccharide (LPS) increased MKP1 expression in the heart and in cultured neonatal cardiomyocytes. LPS‐induced ERK1/2 and p38 phosphorylation in the myocardium was prolonged in MKP1−/− mice. Myocardial TNF‐alpha mRNA and protein levels were enhanced in MKP1−/− compared to WT mice in endotoxemia, leading to a further decrease in cardiac function. Inhibition of Rac1 and PAK1 by a dominant negative Rac1 adenovirus (Ad‐Rac1N17) and PAK1 siRNA, respectively blocked LPS‐induced MKP1 expression in cardiomyocytes. PAK1 siRNA also decreased p38 and c‐Jun N‐terminal kinase (JNK) activation, and TNF‐alpha expression induced by LPS. Furthermore, deficiency in either Rac1 or JNK1 decreased myocardial MKP1 expression in endotoxemic mice. In conclusion, LPS increases myocardial MKP1 expression via JNK1. MKP1 attenuates ERK1/2 and p38 activation, inhibits myocardial TNF‐alpha expression and improves cardiac function in endotoxemia. Thus, MKP1 represents an important negative feedback mechanism limiting pro‐inflammatory response in the heart during sepsis.

AS-107 Effect of Remote Ischemic Preconditioning on Myocardial Injury during Hemodialysis: A Pilot Study

Recently, it has been known that hemodialysis (HD) itself may result in a myocardial regional wall motion abnormality, that is myocardial stunning, and this repeated insult may be associated with rapid decrease in cardiac function and high cardiovascular mortality in HD patients. Remote ischemic preconditioning (IPC) could attenuate cardiac injury during coronary artery bypass surgery or percutaneous coronary angioplasty. We made the hypothesis that remote IPC attenuates myocardial injury during HD and did a pilot study.

Mitogen-activated protein kinase phosphatase-1 inhibits myocardial TNF- expression and improves cardiac function during endotoxemia

Myocardial tumour necrosis factor-α (TNF-α) expression induces cardiac dysfunction in endotoxemia. The aim of this study was to investigate the role of mitogen-activated protein kinase phosphatase-1 (MKP1) pathway in myocardial TNF-α expression and cardiac function during endotoxemia. Lipopolysaccharide (LPS) increased MKP1 expression in the myocardium in vivo and in cultured neonatal cardiomyocytes in vitro. LPS-induced extracellular signal-regulated kinase (ERK) 1/2 and p38 phosphorylation in the myocardium was prolonged in MKP1(-/-) mice. Myocardial TNF-α mRNA and protein levels were enhanced in MKP1(-/-) compared with wild-type (WT) mice in endotoxemia, leading to a further decrease in cardiac function. To study if Rac1/p21-activated kinase 1 (PAK1) signalling regulates MKP1 expression, cardiomyocytes were treated with LPS. Inhibition of Rac1 and PAK1 by a dominant negative Rac1 adenovirus (Ad-Rac1N17) and PAK1 siRNA, respectively, blocked LPS-induced MKP1 expression in cardiomyocytes. PAK1 siRNA also decreased p38 and c-Jun N-terminal kinase (JNK) activation, and TNF-α expression induced by LPS. Furthermore, deficiency in either Rac1 or JNK1 decreased myocardial MKP1 expression in endotoxemic mice. LPS activates the Rac1/PAK1 pathway, which increases myocardial MKP1 expression via JNK1. MKP1 attenuates ERK1/2 and p38 activation, inhibits myocardial TNF-α expression, and improves cardiac function in endotoxemia. Thus, MKP1 represents an important negative feedback mechanism limiting pro-inflammatory response in the heart during sepsis.

Decreased cardiac L-type Ca2+ channel activity induces hypertrophy and heart failure in mice

Antagonists of L-type Ca²⁺ channels (LTCCs) have been used to treat human cardiovascular diseases for decades. However, these inhibitors can have untoward effects in patients with heart failure, and their overall therapeutic profile remains nebulous given differential effects in the vasculature when compared with those in cardiomyocytes. To investigate this issue, we examined mice heterozygous for the gene encoding the pore-forming subunit of LTCC (calcium channel, voltage-dependent, L type, α1C subunit [Cacna1c mice; referred to herein as α1C⁻/⁺ mice]) and mice in which this gene was loxP targeted to achieve graded heart-specific gene deletion (termed herein α1C-loxP mice). Adult cardiomyocytes from the hearts of α1C⁻/⁺ mice at 10 weeks of age showed a decrease in LTCC current and a modest decrease in cardiac function, which we initially hypothesized would be cardioprotective. However, α1C⁻/⁺ mice subjected to pressure overload stimulation, isoproterenol infusion, and swimming showed greater cardiac hypertrophy, greater reductions in ventricular performance, and greater ventricular dilation than α1C⁺/⁺ controls. The same detrimental effects were observed in α1C-loxP animals with a cardiomyocyte-specific deletion of one allele. More severe reductions in α1C protein levels with combinatorial deleted alleles produced spontaneous cardiac hypertrophy before 3 months of age, with early adulthood lethality. Mechanistically, our data suggest that a reduction in LTCC current leads to neuroendocrine stress, with sensitized and leaky sarcoplasmic reticulum Ca²⁺ release as a compensatory mechanism to preserve contractility. This state results in calcineurin/nuclear factor of activated T cells signaling that promotes hypertrophy and disease.

Serum troponin-I as an indicator of clinically significant myocardial injury in paediatric trauma patients

Myocardial injury is a cause of mortality in paediatric trauma, but it is often difficult to diagnose. The objectives of this pilot study were to (1) determine the prevalence of elevated cardiac troponin I (TnI) in paediatric trauma patients and (2) to determine whether elevated TnI correlates with clinically significant myocardial injury, defined as abnormalities on echocardiogram (ECHO) and/or electrocardiograms (ECG). To this end, we investigated a convenient sample size of 59 paediatric trauma patients with an Injury Severity Score (ISS)>12. TnI and creatine kinase-MB (CK-MB) were measured on admission, at then at regular intervals until TnI had normalized. Patients with elevated TnI levels had an ECHO performed within 24h of admission and underwent daily ECGs until TnI normalized. Elevated serum TnI was found in n=16/59 (27%; 95% CI: 18–40%) patients and was associated with elevated CK-MB in all cases. Abnormal ECHOs were seen in 4/16 patients with elevated TnI, but peak TnI values did not correlate with abnormalities on ECHO (p=0.23). Only 1 patient had a clinically significant, albeit mild, decrease in cardiac function. All ECGs were normal. Patients with elevated TnI were more likely to be intubated (p=0.04), to have higher Injury Severity Scores (p=0.02), required more resuscitation fluid (p=0.001), and to have thoracic injuries (p<0.001). Our data indicates that the prevalence of elevated TnI in paediatric trauma patients is 27%; and whilst elevated TnI reflects overall trauma severity, it is frequently elevated without a clinically significance myocardial injury. Hence, large scale studies are required to determine if an elevated threshold TnI value can be identified to accurately diagnose severe myocardial injury in paediatric trauma.

Risk Factors Affecting Cardiac Left Ventricular Systolic and Diastolic Function and Hypertrophy in the Chronic Phase Post-Allogeneic Hematopietic Cell Transplantation

Abstract 2000The long-term survival rate after allogeneic hematopoietic cell transplantation (HCT) has been significantly improved over recent decades due to improvements in the HCT procedure. However, chronic complications such as cardiovascular disease have become increasingly evident and constitute a serious problem among long-term survivors after HCT.It is well-known that high-dose cyclophosphamide (CY) used for conditioning is one of the major causes of acute cardiotoxicity after HCT; however, it is still unclear which factors contribute to chronic cardiotoxicity. Although there is a possibility that chronic GVHD (cGVHD) causes cardiac tissue damage via cytokines such as IL-2, or TNF-alpha, it is unclear whether or not cGVHD influences cardiac function.In the present retrospective cohort study, we investigated which factors affected cardiac function and left ventricular hypertrophy (LVH) in the chronic phase after HCT. We examined left ventricular systolic and diastolic functions and LVH in patients who received HCT between April 2000 and March 2011 and survived for more than one year post-HCT. Only the patients who had undergone an echocardiographic examination before HCT were eligible for the study. We assessed left ventricular ejection fraction (LVEF) as a surrogate marker of LV systolic function and the early peak flow velocity/atrial peak flow velocity (E/A) as a surrogate marker of LV diastolic function using echocardiography. LVH after HCT was identified when the interventricular septal wall (IVS) and/or the posterior wall (PW) became more than 12 mm thick after HCT. We examined the factors that could have had some influence on cardiac function after HCT including age, sex, cumulative dose of anthracycline, use of high-dose CY in the conditioning, total body irradiation (TBI), intensity of conditioning regimen (myeloablative vs. reduced intensity conditioning), a history of hypertension, hemoglobin and serum ferritin levels.A total of 58 patients (25 males and 33 females) were eligible for participation in the study. The median age of enrolled patients was 46 years (range: 21–73). The median cumulative dose of anthracycline was 90 mg/m2 (0–431mg/m2). Forty-nine patients received myeloablative conditioning and 20 of these patients received myeloabative conditioning with TBI 12 Gy. Twenty-four patients were treated for cGVHD and 7 had a history of hypertension and 2 had an LVEF of less than 55% before HCT. Six had an LVEF of less than 55% at more than 1 year after HCT. In the multiple regression analysis that assessed the relationship between LVEF or E/A and the factors, myeloablative conditioning with TBI 12Gy was significantly associated with a decrease in LVEF after HCT (coefficient= −7.57, P=.001). However, in a comparison of Ara-C/CY/TBI and CY/TBI conditioning, the degree of change in the LVEF before and after HCT was similar between the two groups (repeated measures of ANOVA analysis. P=.0972). Patients who had received myeloablative conditioning had a significant decrease in E/A after HCT(coefficient= -.31, P=.02). Furthermore, a history of hypertension was also slightly associated with a decrease in E/A after HCT(coefficient= -.30, P=.05). In addition, only age was identified as a significant risk factor of left ventricular hypertrophy after HCT in the multivariate logistic analysis. However, in the present study, we could not identify a significant impact of cGVHD on cardiac function and LVH post HCT.We concluded, based on our results, that the presence of cGVHD did not significantly contribute to a decrease in cardiac function in the chronic phase after HCT. Our results also suggest that the intensity of conditioning for HCT had a significant effect on chronic cardiac function after HCT. Disclosures:No relevant conflicts of interest to declare.

Decreased metalloprotease 9 induction, cardiac fibrosis, and higher autophagy after pressure overload in mice lacking the transcriptional regulator p8

Left ventricular remodeling, including the deposition of excess extracellular matrix, is key to the pathogenesis of heart failure. The stress-inducible transcriptional regulator p8 is increased in failing human hearts and is required both for agonist-stimulated cardiomyocyte hypertrophy and for cardiac fibroblasts matrix metalloprotease-9 (MMP9) induction. In the heart, upregulation of autophagy is an adaptive response to stress and plays a causative role in cardiomyopathies. We have recently shown that p8 ablation in cardiac cells upregulates autophagy and that, in vivo, loss of p8 results in a decrease of cardiac function. Here we investigated the effects of p8 genetic deletion in mediating adverse myocardial remodeling. Unstressed p8-/- mouse hearts manifested complex alterations in the expression of fibrosis markers. In addition, these mice displayed elevated autophagy and apoptosis compared with p8+/+ mice. Transverse aortic constriction (TAC) induced left ventricular p8 expression in p8+/+ mice. Pressure overload caused left ventricular remodeling in both genotypes, however, p8-/- mice showed less cardiac fibrosis induction. Consistent with this, although MMP9 induction was attenuated in the p8-/- mice, induction of MMP2 and MMP3 were strikingly upregulated while TIMP2 was downregulated. Left ventricular autophagy increased after TAC and was significantly higher in the p8-/- mice. Thus p8-deletion results in reduced collagen fibrosis after TAC, but in turn, is associated with a detrimental higher increase in autophagy. These findings suggest a role for p8 in regulating in vivo key signaling pathways involved in the pathogenesis of heart failure.