Transforming growth factor-β1 downregulates beating frequency and remodeling of cultured rat adult cardiomyocytes

The MEK/ERK Module Is Reprogrammed in Remodeling Adult Cardiomyocytes

Fetal and hypertrophic remodeling are hallmarks of cardiac restructuring leading chronically to heart failure. Since the Ras/Raf/MEK/ERK cascade (MAPK) is involved in the development of heart failure, we hypothesized, first, that fetal remodeling is different from hypertrophy and, second, that remodeling of the MAPK occurs. To test our hypothesis, we analyzed models of cultured adult rat cardiomyocytes as well as investigated myocytes in the failing human myocardium by western blot and confocal microscopy. Fetal remodeling was induced through endothelial morphogens and monitored by the reexpression of Acta2, Actn1, and Actb. Serum-induced hypertrophy was determined by increased surface size and protein content of cardiomyocytes. Serum and morphogens caused reprogramming of Ras/Raf/MEK/ERK. In both models H-Ras, N-Ras, Rap2, B- and C-Raf, MEK1/2 as well as ERK1/2 increased while K-Ras was downregulated. Atrophy, MAPK-dependent ischemic resistance, loss of A-Raf, and reexpression of Rap1 and Erk3 highlighted fetal remodeling, while A-Raf accumulation marked hypertrophy. The knock-down of B-Raf by siRNA reduced MAPK activation and fetal reprogramming. In conclusion, we demonstrate that fetal and hypertrophic remodeling are independent processes and involve reprogramming of the MAPK.

Radixin Relocalization and Nonmuscle α-Actinin Expression Are Features of Remodeling Cardiomyocytes in Adult Patients with Dilated Cardiomyopathy

Background

Pediatric patients show an impressive capacity of cardiac regeneration. In contrast, severely deteriorated adult hearts do usually not recover. Since cardiac remodeling—involving the expression of fetal genes—is regarded as an adaptation to stress, we compared hearts of adult patients suffering from dilated cardiomyopathy (DCM) with remodeling of cultured neonatal (NRC) as well as adult (ARC) rat cardiomyocytes and the developing postnatal myocardium.

Methods

NRC and ARC were stimulated with serum and cardiac morphogens derived from DCM hearts. Protein synthesis (PS) as well as protein accumulation (PA) was measured, and cell survival was determined under ischemic conditions. Fetal markers were investigated by Western blot. Biomarkers of remodeling were analyzed in controls, DCM, and 2- to 6-month-old children with tetralogy of Fallot as well as in neonatal and adult rats by immunofluorescence.

Results

In NRC, serum and morphogens strongly stimulated PS and PA and the reestablishment of cell-cell contacts (CCC). In ARC, both stimulants increased PS and CCC, but PA was only elevated after serum stimulation. In contrast to serum, morphogen treatment resulted in the expression of fetal genes in ARC as determined by nonmuscle α-actinin-1 and α-actinin-4 expression (NM-actinins) and was associated with increased survival under ischemia. NM-actinins were present in cardiomyocytes of DCM in a cross-striated pattern reminiscent of sarcomeres as well as in extensions of the area of the intercalated disc (ID). NM-actinins are expressed in NRC and in the developing heart. Radixin staining revealed remodeling of the area of the ID in DCM almost identical to stimulated cultured ARC.

Conclusions

Remodeling was similar in ARC and in cardiomyocytes of DCM suggesting evolutionary conserved mechanisms of regeneration. Despite activation of fetal genes, the atrophy of ARC indicates differences in their regenerative capacity from NRC. Cardiac-derived factors induced NM-actinin expression and increased survival of ischemic ARC while circulating molecules were less effective. Identification of these cardiac-derived factors and determination of their individual capacity to heal or damage are of particular importance for a biomarker-guided therapy in adult patients.

Therapeutic targeting of the oncostatin M receptor-β prevents inflammatory heart failure

Heart failure (HF) is a common and potentially deadly condition, which frequently develops as a consequence of various diseases of the heart. The incidence of heart failure continuously increases in aging societies illustrating the need for new therapeutic approaches. We recently discovered that continuous activation of oncostatin M (OSM), a cytokine of the interleukin-6 family that induces dedifferentiation of cardiomyocytes, promotes progression of heart failure in dilative cardiomyopathy. To evaluate whether inhibition of OSM signaling represents a meaningful therapeutic approach to prevent heart failure we attenuated OSM-receptor (Oβ) signaling in a mouse model of inflammatory dilative cardiomyopathy. We found that administration of an antibody directed against the extracellular domain of Oβ or genetic inactivation of a single allele of the Oβ gene reduced cardiomyocyte remodeling and dedifferentiation resulting in improved cardiac performance and increased survival. We conclude that pharmacological attenuation of long-lasting Oβ signaling is a promising strategy to treat different types and stages of HF that go along with infiltration by OSM-releasing inflammatory cells.

Small intestinal submucosa gel as a potential scaffolding material for cardiac tissue engineering

Cardiac tissue engineering typically utilizes protein-rich scaffolding materials and growth factors to improve cardiac tissue function in vitro and in vivo. The objectives of this preliminary study were (i) to investigate the potential of porcine small intestinal submucosa gel (SIS gel) in cardiac tissue engineering and (ii) to compare the function of tissues based on either SIS gel or Matrigel, a tumor-derived benchmark material. Neonatal rat cardiac cells were combined with either SIS gel or Matrigel and cultured on porous elastomeric scaffolds composed of poly(glycerol sebacate) for 13days. Tissue function was assessed by measuring contraction rates twice daily. Tissue morphology was compared qualitatively by hematoxylin and eosin staining. Normalized troponin T expression (troponin T:DNA) was compared using image analysis. SIS gel constructs contracted at significantly higher rates than Matrigel constructs on days 8-11. Normalized troponin T expression was significantly higher in SIS gel constructs compared with Matrigel constructs. In summary, this research demonstrated that: (i) SIS gel can be used to create contractile engineered cardiac tissue; (ii) SIS gel produced engineered cardiac tissues with a more physiological contraction rate and higher phenotypic protein expression based on the basic in vitro examinations performed in this study.

Role of TGF-beta on cardiac structural and electrical remodeling

The type β transforming growth factors (TGF-βs) are involved in a number of human diseases, including heart failure and myocardial arrhythmias. In fact, during the last 20 years numerous studies have demonstrated that TGF-β affects the architecture of the heart under both normal and pathological conditions. Moreover, TGF-β signaling is currently under investigation, with the aim of discovering potential therapeutic roles in human disease. In contrast, only few studies have investigated whether TGF-β affects electrophysiological properties of the heart. This fact is surprising since electrical remodeling represents an important substrate for cardiac disease. This review discusses the potential role of TGF-β on cardiac excitation-contraction (EC) coupling, action potentials, and ion channels. We also discuss the effects of TGF-β on cardiac development and disease from structural and electrophysiological points of view.

Clinical toxicology of citalopram after acute intoxication with the sole drug or in combination with other drugs: overview of 26 cases

There is discussion concerning the cardiac safety of citalopram in an overdose. The aim of this study was to investigate the toxic effects and toxicokinetic parameters of citalopram in an overdose as a single drug and in combination with other drugs. Cases observed between 1997 and 2006 were evaluated. Patient demographics, ingested doses, serum concentrations of citalopram, coingested drugs, and clinical parameters were acquired. Outcomes were observed symptoms of the gastrointestinal tract, respiratory tract, central nervous system, and cardiovascular system. Poisoning Severity Score was used to evaluate severity of every intoxicated patient. Individual toxicokinetic parameter values were calculated. Twenty-nine cases of citalopram overdose were observed; three cases had incomplete data so that 26 cases were evaluable. The ingested amount ranged from 200 to 4960 mg. Blood concentrations ranged from 0.21 to 7.5 mg/L with 20 minutes to 8 hours between suggested time of ingestion and blood sampling. Most frequently reported symptoms were drowsiness (seven cases), tachycardia (15 cases), QTc prolongation (eight cases), decrease of consciousness (eight cases), and seizures (four cases). Median length of hospital stay was 3 days (range, 1-8 days). Of the 26 evaluated cases, two fatalities occurred, one because of a cardiac arrest and one as a result of a respiratory arrest. According to Poisoning Severity Score, severity of intoxication was minor in three patients (11%), moderate in nine patients (35%), and severe in 14 patients (54%). Severity was mainly caused by neurologic and respiratory effects. Elimination half-life was prolonged but did not correlate with the amount of ingestion. Citalopram intoxications seem to proceed more severely than is known for other selective serotonin reuptake inhibitor intoxications, causing drowsiness, coma, and seizures in overdose. Cardiac toxicity is generally mild. Therefore, we recommend seizure precautions and intensive care unit admission with cardiac monitoring for citalopram-intoxicated patients. Because elimination half-life is prolonged, normal pharmacokinetics do not apply.