P5441Ventricular dysfunction and fibrosis precedes atrial conduction defects in JDP2 overexpression mice

Introduction

JDP2 (Jun Dimerization Protein 2) was recently characterized as potential prognostic marker for progression of heart failure after myocardial infarction. Furthermore, persistent cardiac-specific JDP2 overexpression provokes ventricular dysfunction, atrial dilatation and atrial fibrillation.

Purpose

In this study we investigated, if ventricular dysfunction is predisposed to atrial fibrillation. Therefore, we analyzed ventricular function in mice with 1 and 5 weeks of JDP2 overexpression and compared gene expression in ventricular and atrial tissues at these time points.

Methods

JDP2 expression was under control of a Tet-off system. Therefore, JDP2 overexpression was started by withdrawal of doxycycline diet in 4-week-old mice. After 1 or 5 weeks, cardiac function was determined by echocardiography and ECG. mRNA expression was analyzed by real-time RT-PCR and protein expression in western blots.

Results

After 1 or 5 weeks, JDP2 mRNA levels were increased in ventricular and atrial tissues of JDP2 mice. Already after 1 week ventricular dysfunction emerged in JDP2 mice: Ejection fraction decreased from 64.6±10.4% in WT to 58.8±9.3% in JDP2 mice, fractional shortening from 38.3±7.9% in WT to 27.4±4.8% in JDP -mice, and cardiac output from 23.0±4.7 ml/min in WT to 19.4±3.3 ml/min in JDP2 mice (n=11–16, p<0.05). In ventricular tissues, elastin mRNA expression increased, and the calcium handling protein SERCA decreased within one week of JDP2 overexpression (n=6, p<0.05 vs. WT). After 5 weeks of JDP2 overexpression ventricular dysfunction became even stronger with a cardiac output of 13.6±2.5 ml/min (n=11, p<0.05 vs. WT). Still reduction in SERCA protein was observed, and increased mRNA levels of fibrotic marker genes were detected, as well as contractile function of isolated cardiomyocytes of JDP2 mice continued to decline. In atrial tissue, besides the 3.6 times increase of JDP2 mRNA, no changes could be detected within one week. In addition, ECG recordings over 30 minutes on awake mice did not show any abnormalities after one week of JDP2-overexpression. Atrial dilatation became evident only after 5 weeks of JDP2 overexpression. ECG-recordings revealed prolonged PR-intervals (34.6±3.9 ms in JDP2-mice vs. 30.2±7.0 ms in WT) and broadened QRS-complexes (15.8±2.8 ms in JDP2 mice vs. 13.9±1.7 ms in WT, n=10–12, p<0.05). At the same time point, mRNA of the calcium-handling proteins PLB, NCX and SERCA, and of the fibrotic marker genes collagen I, fibronectin and elastin were dramatically reduced in atrial tissue of JDP2 compared to WT mice (n=6, p<0.05), and may be functionally involved in atrial conduction defects.

Conclusion

Enhanced expression of JDP2 provokes ventricular dysfunction and fibrosis within one week, whereas changes in the atrial tissue and conduction defects occur later and seem to be a secondary effect that is provoked by the pre-existing ventricular dysfunction.

Molecular switches under TGFβ signalling during progression from cardiac hypertrophy to heart failure

Cardiac hypertrophy is a mechanism to compensate for increased cardiac work load, that is, after myocardial infarction or upon pressure overload. However, in the long run cardiac hypertrophy is a prevailing risk factor for the development of heart failure. During pathological remodelling processes leading to heart failure, decompensated hypertrophy, death of cardiomyocytes by apoptosis or necroptosis and fibrosis as well as a progressive dysfunction of cardiomyocytes are apparent. Interestingly, the induction of hypertrophy, cell death or fibrosis is mediated by similar signalling pathways. Therefore, tiny changes in the signalling cascade are able to switch physiological cardiac remodelling to the development of heart failure. In the present review, we will describe examples of these molecular switches that change compensated hypertrophy to the development of heart failure and will focus on the importance of the signalling cascades of the TGFβ superfamily in this process. In this context, potential therapeutic targets for pharmacological interventions that could attenuate the progression of heart failure will be discussed.

Self-report compared to electronic medical record across eight adult vaccines: do results vary by demographic factors?

Immunizations are crucial to the prevention of disease, thus, having an accurate measure of vaccination status for a population is an important guide in targeting prevention efforts. In order to comprehensively assess the validity of self-reported adult vaccination status for the eight most common adult vaccines we conducted a survey of vaccination receipt and compared it to the electronic medical record (EMR), which was used as the criterion standard, in a population of community-dwelling patients in a large healthcare system. In addition, we assessed whether validity varied by demographic factors. The vaccines included: pneumococcal (PPSV), influenza (Flu), tetanus diphtheria (Td), tetanus diphtheria pertussis (Tdap), Human Papilloma Virus (HPV), hepatitis A (HepA), hepatitis B (HepB) and herpes zoster (shingles). Telephone surveys were conducted with 11,760 individuals, ≥18, half with documented receipt of vaccination and half without. We measured sensitivity, specificity, positive and negative predictive value, net bias and over- and under-reporting of vaccination. Variation was found across vaccines, however, sensitivity and specificity did not vary substantially by either age or race/ethnicity. Sensitivity ranged between 63% for HepA to over 90% (tetanus, HPV, shingles and Flu). Hispanics were 2.7 times more likely to claim receipt of vaccination compared to whites. For PPSV and Flu those 65+ had low specificity compared to patients of younger ages while those in the youngest age group had lowest specificity for HepA and HepB. In addition to racial/ethnic differences, over-reporting was more frequent in those retired and those with household income less than $75,000. Accurate information for vaccination surveillance is important to estimate progress toward vaccination coverage goals and ensure appropriate policy decisions and allocation of resources for public health. It was clear from our findings that EMR and self-report do not always agree. Finding approaches to improve both EMR data capture and patient awareness would be beneficial.

Self-report compared to electronic medical record across eight adult vaccines: do results vary by demographic factors?

Immunizations are crucial to the prevention of disease, thus, having an accurate measure of vaccination status for a population is an important guide in targeting prevention efforts. In order to comprehensively assess the validity of self-reported adult vaccination status for the eight most common adult vaccines we conducted a survey of vaccination receipt and compared it to the electronic medical record (EMR), which was used as the criterion standard, in a population of community-dwelling patients in a large healthcare system. In addition, we assessed whether validity varied by demographic factors. The vaccines included: pneumococcal (PPSV), influenza (Flu), tetanus diphtheria (Td), tetanus diphtheria pertussis (Tdap), Human Papilloma Virus (HPV), hepatitis A (HepA), hepatitis B (HepB) and herpes zoster (shingles). Telephone surveys were conducted with 11,760 individuals, ≥18, half with documented receipt of vaccination and half without. We measured sensitivity, specificity, positive and negative predictive value, net bias and over- and under-reporting of vaccination. Variation was found across vaccines, however, sensitivity and specificity did not vary substantially by either age or race/ethnicity. Sensitivity ranged between 63% for HepA to over 90% (tetanus, HPV, shingles and Flu). Hispanics were 2.7 times more likely to claim receipt of vaccination compared to whites. For PPSV and Flu those 65+ had low specificity compared to patients of younger ages while those in the youngest age group had lowest specificity for HepA and HepB. In addition to racial/ethnic differences, over-reporting was more frequent in those retired and those with household income less than $75,000. Accurate information for vaccination surveillance is important to estimate progress toward vaccination coverage goals and ensure appropriate policy decisions and allocation of resources for public health. It was clear from our findings that EMR and self-report do not always agree. Finding approaches to improve both EMR data capture and patient awareness would be beneficial.

Growth differentiation factor 15 acts anti-apoptotic and pro-hypertrophic in adult cardiomyocytes

Growth differentiation factor 15 (GDF15) is induced during heart failure development, and may influence different processes in cardiac remodeling. While its anti-apoptotic action under conditions of ischemia-reperfusion have been shown, it remained unclear if this is a broadly protective effect applicable to other apoptotic stimuli. Furthermore, effects on cardiac hypertrophy remained obscure. Therefore, we investigated the effects of GDF15 on induction of hypertrophy and apoptosis in ventricular cardiomyocytes. GDF15 (3 ng/ml) enhanced hypertrophic growth of cardiomyocytes as determined by an increase in cell size by 27 +/- 5% and rate of protein synthesis by 47 +/- 15%. In addition, a time and dose-dependent increase in SMAD-binding affinity was found, as well as enhanced phosphorylation of R-SMAD1. Inhibition of SMADs by transformation of cardiomyocytes with SMAD-decoy oligonucleotides abolished the hypertrophic growth effect. Specific inhibitors of PI3K (10 microM LY290042 or 10 nM wortmannin) or ERK (10 microM PD98059) also blocked GDF15-induced hypertrophy and SMAD activation. Apoptosis induction by three different agents, 100 nM angiotensin II, 1 ng/ml TGFbeta(1), or the NO-donor SNAP (100 microM) was blocked by addition of GDF15 (3 ng/ml). Scavenging of SMADs by transformation of cardiomyocytes with SMAD-decoy oligonucleotides abolished the anti-apoptotic effect of GDF15. In conclusion, GDF15 protects ventricular cardiomyocytes against different apoptotic stimuli and enhances hypertrophic growth. Hypertrophic signaling is thereby mediated via the kinases PI3K and ERK and the transcription factor R-SMAD1. Thus, GDF15 may influence cardiac remodeling via two different mechanisms, apoptosis protection and induction of hypertrophy.

Direct effects of the angiotensin-converting enzyme inhibitor ramiprilat on adult rat ventricular cardiomyocytes

AIM

Angiotensin-converting enzyme (ACE) inhibitors like ramiprilat bind to ACE expressed on the cell surface of endothelial cells and induce cell-specific signalling including the activation of activator protein (AP)-1. The present study addressed the question whether ramiprilat exerts a similar effect on adult ventricular cardiomyocytes, i.e. activates the AP-1 or modifies contractile performance. It was further aimed to decide whether such effects depend on bradykinin receptors or whether they are directly mediated via ACE.

METHODS

Adult rat ventricular cardiomyocytes were isolated and cultured. mRNA expression of ACE was investigated by RT-PCR, AP-1 activation by gel mobility shift assays, and cardiac contractile performance by electrical pacing of isolated cells and analysis of cell shortening via a line-camera.

RESULTS

Cardiomyocytes stably express ACE. Ramiprilat increased maximal contraction velocity and shortened the time-to-peak of contraction. In contrast to effects evoked by bradykinin, such effects caused by ramiprilat were not attenuated by HOE 140, a bradykinin-receptor antagonist. These effects were also not attenuated in the presence of l-nitro-arginine, used to mimic bradykinin-dependent signalling. In cardiomyocytes, bradykinin but not ramiprilat activated AP-1. Ramiprilat activates AP-1 in endothelial cells that are known to respond to ramiprilat in this way.

CONCLUSION

Ramiprilat exerts direct, bradykinin-receptor independent effects on cardiomyocytes that improve cellular function without a corresponding effect on AP-1 activation or induction of AP-1 dependent effects. This newly described effect of ramiprilat may contribute to the protective effects seen by application of ACE inhibitors.

Repression of anti-apoptotic genes via AP-1 as a mechanism of apoptosis induction in ventricular cardiomyocytes

Nitric oxide (NO) is increased under several pathophysiological, mainly inflammatory processes in the heart and has been characterized as an inducer of apoptosis in cardiomyocytes. The transcription factor activating protein-1 (AP-1) has been identified as a mediator of NO-induced apoptosis. Genes that are regulated by AP-1 under apoptotic conditions have not been identified yet. Therefore, we performed a microarray analysis with subsequent real-time polymerase chain reaction (PCR) to identify genes regulated by AP-1 in NO-induced ventricular cardiomyocytes of rats and tested the functional role of these genes in apoptosis. Cardiomyocytes were transformed with AP-1 decoy oligonucleotides for inhibition of AP-1 activity. These, as well as non-transformed control cells, were stimulated with the NO donor (+/-)-S-nitroso-N-acetylpenicillamine (SNAP, 100 microM) for 2 h. Some of the genes with differential gene expression on microarrays were further analysed by real-time PCR. Genes that are induced by SNAP were not identified. However, four genes, pyridoxal kinase, heat shock protein 10 (Hsp10), antigen identified by monoclonal antibodies 4F2 (4F2) and myosin light chain 2, were downregulated by SNAP in presence of AP-1. Pyridoxal kinase, Hsp10 and 4F2 have anti-apoptotic effects in unstimulated cells because downregulation of their expression by antisense oligos induced apoptosis in cardiomyocytes. An involvement of these genes in NO-induced apoptosis could only be proven for pyridoxal kinase. In conclusion, using microarray technology, we identified three anti-apoptotic genes (Hsp10, 4F2 and pyridoxal kinase) in ventricular cardiomyocytes, which may help the cells to resist some apoptotic stimuli. The downregulation of these genes results in cardiomyocyte apoptosis. Prevention of their downregulation may protect cardiomyocytes against apoptotic stimuli, and this may be of therapeutic benefit.

Angiotensin II stimulates apoptosis via TGF-beta1 signaling in ventricular cardiomyocytes of rat

Elevations in angiotensin II (AngII) and transforming growth factor (TGF-beta1) levels are often found under conditions leading to progression of heart failure. From several studies, it is evident that AngII enhances TGF-beta1 expression via activator protein 1 (AP-1) activation, and that this pathway is involved in hypertrophic growth of the heart muscle and in the development of cardiac fibrosis. We now continued characterization of the signaling pathway stimulated by AngII in ventricular cardiomyocytes of rat and analyzed if the enhancement of TGF-beta1 expression by AngII may also contribute to apoptosis induction, which is another predictor of heart failure progression. Stimulation of cardiomyocytes with 100 nM AngII for 2 h activated the transcription factors AP-1 and GATA by 68.6+/-23.9 or 70.7+/-9.8%. Induction of both factors was mediated by p38 mitogen-activated protein kinase (MAPK) because it was totally blocked using a specific inhibitor of the kinase (SB202190). When GATA was inhibited by transformation of cardiomyocytes with decoy oligonucleotides, AngII could not enhance TGF-beta1 expression. This inhibition was observed on the mRNA level in real-time polymerase chain reaction and on the protein level in Western blots. As a consequence, upon AngII stimulation for 24 h, release of TGF-beta1 from cardiomyocytes was also reduced from 240.5+/-50.4 to 130.5+/-22.1% (p<0.05). In contrast to the early induction of GATA and AP-1, the transcription factor similar to mothers against decapentaplegic homolog (SMAD) was induced by AngII after 24 h. This stimulation was dependent on TGF-beta1 because it was blocked by antibodies specific for TGF-beta1. Twenty-four hours after AngII addition, the number of apoptotic cardiomyocytes increased by 6.5+/-1.2%, and this apoptosis induction was blocked when SMAD activity was inhibited by transformation of cardiomyocytes with SMAD decoy oligonucleotides. In conclusion, the transcription factors AP-1 and GATA are activated by p38 MAPK upon AngII stimulation, and both are needed to enhance TGF-beta1 expression in ventricular cardiomyocytes. TGF-beta1 acts in an autocrine loop on the cells to induce apoptosis via SMAD signaling. Thus, the often-found correlation between AngII, TGF-beta1, AP-1, and SMAD in pathogenesis of heart disease reflects the proapoptotic signaling pathway induced by AngII in cardiomyocytes.