Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0018801 (heart failure)
 72,216 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Troponin I is a subunit of the thin filament-associated troponin-tropomyosin complex involved in calcium regulation of skeletal and cardiac muscle contraction. We deleted the cardiac isoform of troponin I by using gene targeting in murine embryonic stem cells to determine the developmental and physiological effects of the absence of this regulatory protein. Mice lacking cardiac troponin I were born healthy, with normal heart and body weight, because a fetal troponin I isoform (identical to slow skeletal troponin I) compensated for the absence of cardiac troponin I. Compensation was only temporary, however, as 15 days after birth slow skeletal troponin I expression began a steady decline, giving rise to a troponin I deficiency. Mice died of acute heart failure on day 18, demonstrating that some form of troponin I is required for normal cardiac function and survival. Ventricular myocytes isolated from these troponin I-depleted hearts displayed shortened sarcomeres and elevated resting tension measured under relaxing conditions and had a reduced myofilament Ca sensitivity under activating conditions. The results show that (1) developmental downregulation of slow skeletal troponin I occurs even in the absence of cardiac troponin I and (2) the resultant troponin I depletion alters specific mechanical properties of myocardium and can lead to a lethal form of acute heart failure.
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PMID:Cardiac troponin I gene knockout: a mouse model of myocardial troponin I deficiency. 991 81

The tumor necrosis factor (TNF) alpha level is elevated in patients with advanced heart failure, and the phosphorylation of contractile regulatory proteins is reduced in the human heart. We hypothesized that TNFalpha affects the phosphorylation of proteins involved in regulating contraction; phospholamban (PLB), myosin light chain 2 (MLC2) and troponin I (TnI). Spontaneously beating rat neonatal cardiac myocytes, prelabelled with [32P]orthophosphate, were treated with TNFalpha for 30 min, and stimulated with isoproterenol for 5 min. 32P-labelled myofibrillar proteins were isolated by 15% SDS-PAGE. Baseline phosphorylation levels of PLB, TnI and an unknown 23kDa phosphoprotein were decreased by TNFalpha in a dose-dependent manner. Moreover, TNFalpha attenuated the phosphorylation levels of PLB and TnI increased by a concentration of 0.01 microM isoproterenol, but not by 1 microM of isoproterenol. Although TNFalpha had no effect on the cAMP content or cAMP-dependent protein kinase activity in the presence or absence of isoproterenol, an inverse relationship was observed between the concentration of TNFalpha and the cGMP content in cardiac myocytes, and treatment with TNFalpha resulted in a concentration-dependent increase in type 2A protein phosphatase activity. The observation that TNFalpha decreases phosphorylation levels of PLB and TnI in cardiac myocytes suggests that the reduction of these protein phosphorylation levels is partially responsible for alterations of intracellular Ca2+-cycling and the force of contraction in TNF alpha-treated cardiac myocytes. Furthermore, TNFalpha reduces myocyte contraction and protein phosphorylation states possibly via cAMP-independent mechanisms, at least in part, by the activation of type 2A protein phosphatase.
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PMID:Tumor necrosis factor-alpha decreases the phosphorylation levels of phospholamban and troponin I in spontaneously beating rat neonatal cardiac myocytes. 1007 33

Stunned myocardium is a syndrome of reversible contractile failure that frequently complicates coronary artery disease. Cardiac excitation is uncoupled from contraction at the level of the myofilaments. Selective proteolysis of the thin filament protein troponin I has been correlated with stunned myocardium. Here, transgenic mice expressing the major degradation product of troponin I (TnI1-193) in the heart were found to develop ventricular dilatation, diminished contractility, and reduced myofilament calcium responsiveness, recapitulating the phenotype of stunned myocardium. Proteolysis of troponin I also occurs in ischemic human cardiac muscle. Thus, troponin I proteolysis underlies the pathogenesis of a common acquired form of heart failure.
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PMID:Transgenic mouse model of stunned myocardium. 1064 51

Conventional positive inotropy with beta-adrenergic agonists or phosphodiesterase inhibitors increases the amplitude of the calcium transient and is associated with increases in myocardial oxygen consumption that may not be desirable when used in heart failure. Alternatively, agents that increase the sensitivity of the contractile apparatus without increasing the amplitude of the calcium transient have been shown to increase contractility without increasing energy consumption. Also, agents that result in negative inotropy while maintaining the amplitude of the calcium transient result in more energy-inefficient negative inotropy in comparison with agents that cause negative inotropy though a decrease in the amplitude of the calcium transient. These experiments suggest that calcium handling is responsible for a large proportion of the total energy expenditure associated with changes in inotropy. Problems that remain with the use of calcium-sensitizing agents include uncertainty regarding the site of action, adverse effects on systemic and coronary vasculature and diastolic function, and concomitant phosphodiesterase-inhibiting activity. One alternative is to use genetically engineered mouse models in which specific mutations selective to the myocyte can be produced. Potential molecular targets include the protein kinase A and C phosphorylation sites on troponin I, which, when phosphorylated, mediate a reduction in calcium sensitivity and a reduction in maximal actomyosin adenosinetriphosphatase activity, respectively. Mutations at these sites, by altering the relationship between force and calcium, may provide significant insights into the molecular mechanisms controlling the energetics of positive inotropy.
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PMID:Inotropic and energetic effects of altering the force-calcium relationship: mechanisms, experimental results, and potential molecular targets. 1090 89

Ca(2+) sensitizers may be advantageous for treatment in human heart failure by increasing cardiac force without increasing the Ca(2+) transient or energy consumption. To study the mode of action of the Ca(2+) sensitizers EMD 57033 (EMD) and CGP 48506 (CGP), their influence on butanedione monoxime (BDM)-mediated depression of cross-bridge cycling was analyzed in human myocardium (explanted hearts, dilated cardiomyopathy, n = 19). In Triton X (1%)-skinned fiber preparations of left ventricular myocardium from patients suffering from dilated cardiomyopathy, troponin I was extracted by vanadate (10 mM) treatment, resulting in a Ca(2+)-independent contraction. In troponin I-depleted fibers BDM (5-50 mM) was applied in the absence and presence of EMD (10 microM) or CGP (10 microM). To analyze the influence on cross-bridge kinetics, tension cost (ratio of ATPase activity and tension development) was studied. BDM exerted a dose-dependent force inhibition in troponin I-depleted fibers (IC(50) = 7.22 mM), which was antagonized by EMD (IC(50) of BDM + EMD = 19.97 mM) and CGP (IC(50) of BDM + CGP = 15.30 mM). EMD increased Ca(2+) sensitivity of force and maximal force in Triton X-skinned fibers. The Ca(2+)-sensitizing effect of CGP was accompanied by an increased Ca(2+) sensitivity of myosin-ATPase activity, an increased slope of the Ca(2+) force and Ca(2+) ATPase curve, as well as a reduced maximal myosin ATPase activity. CGP and EMD reduced tension cost. In conclusion, EMD and CGP antagonize the BDM-mediated relaxation in troponin I-depleted cardiac muscle fibers. The Ca(2+)-sensitizing effect of CGP seems to be dependent on an improvement of the myofilament cooperativity, whereas EMD seems to operate by increasing the force per cross-bridge.
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PMID:Different effect of the Ca(2+) sensitizers EMD 57033 and CGP 48506 on cross-bridge cycling in human myocardium. 1108 66

Two main troponin I genes, cardiac (cTnI) and slow skeletal (ssTnI), are expressed in the mammalian heart under the control of a developmentally regulated program. ssTnI is expressed first in embryonic and fetal heart, and is then downregulated by an unknown mechanism after birth. Unlike other contractile protein genes, ssTnI is not re-expressed during hypertrophy or end-stage heart failure in rats and humans. In the present study, we also show that ssTnI re-expression does not occur in hypertrophic mouse heart. To investigate ssTnI downregulation further, cTnI knockout mice were used to examine a possible role for thyroid hormone. Northern blot analysis of euthyroid animals showed a time-dependent loss of ssTnI mRNA that was similar for wild-type, heterozygous and homozygous cTnI mutant mice. In cTnI null mice made hyperthyroid by l -thyroxine, the duration of ssTnI expression assessed by both mRNA and protein content was abbreviated compared with the euthyroid group. Hyperthyroid cTnI null mice also died significantly earlier than euthyroids (postnatal day 14 v day 18). In cTnI null mice made hypothyroid by addition of phenylthiouracil to the drinking water, ssTnI expression was prolonged and mice survived until day 20 or 21. Overall, the results indicate that inactivation of the ssTnI gene occurs even in the absence of cTnI mRNA and protein indicating that these are not critical signals for ssTnI down regulation in the heart. In contrast, thyroid hormone influences the time course of ssTnI expression and the life span of cTnI null mice probably through a transcriptional regulation of ssTnI in the heart.
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PMID:Thyroid hormone regulates slow skeletal troponin I gene inactivation in cardiac troponin I null mouse hearts. 1111 97

In cardiovascular pharmacotherapy, the main focus is now on statins (HMG-CoA-reductase inhibitors) because of their antihyperlipidaemic and antiatherogenic effect. They are suggested to be beneficial also in senile dementia, stroke and osteoporosis and they can reduce incidence of ventricular arrhythmias in patients with cardioverter-defibrillator. In chronic heart failure, statins should be used with caution since reduced cholesterol levels relate to impaired survival. As an alternative to statins and fibrates, niacin therapy may be considered. ACE inhibitors are of proven benefit for patients with left ventricular dysfunction after acute myocardial infarction; however, in long-term treatment, their protective activity is not superior to that of beta-blockers, diuretics and clonidine. Ca-channel antagonists slightly increase the incidence of cardiovascular complications but reduce the incidence of stroke in high-risk patients. Biventricular pacing has been used with success in patients with severe heart failure and conduction disturbances, and the first permanent artificial ventricle was implanted to a patient with irreversible terminal heart failure in summer 2000. Cardiospecific troponin I may be an uninvasive marker of a procoagulant status indicating e.g. graft failure after cardiac transplantation; T-cadherin belongs to the cell-adhesion molecules and has a role in maintenance of cellular contacts which are critical for the vessel wall architecture. Etamoxir, originally developed for the treatment of diabetes II, has recently been shown to be a potential novel drug for heart failure. Routine use of nitric oxide after congenital heart surgery lessens the risk of pulmonary hypertensive crises.
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PMID:[Cardiology 2000]. 1137 23

Postoperative cardiac failure due to myocardial necrosis remains a major complication in cardiac surgical procedures and its diagnosis is still difficult. In fact, cardiac enzymes, electrocardiogram and echographic signs are often misleading. The prognostic valve of troponin I after coronary artery bypass or conventional value surgery has been evaluated in 500 adult patients. Postoperative troponin I concentrations after cardiac surgery represent an independent variable associated with mortality (in-hospital death) and morbidity (low cardiac output and acute renal failure).
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PMID:Utility of cardiac troponin measurement after cardiac surgery. 1155 51

Cardiac troponin I levels are frequently above normal values in several disease states in which myocardial necrosis is not a prominent aspect, particularly in pulmonary embolism, heart failure, liver cirrhosis, septic shock, renal failure and arterial hypertension. Sub-clinical myocardial necrosis has been postulated to be the cause of the phenomenon. Studies performed so far have not included pathological data to confirm this hypothesis. Increased troponin I plasma levels may be the result of myocardial strain, especially the type of strain that accompanies some forms of cardiac dilatation or hypertrophy. Troponin I may act as a marker of myocardial strain, either acute (in pulmonary embolism, septic shock and acute heart failure) or chronic (in chronic cardiac, renal and hepatic failure, as well as in arterial hypertension). The apparent paradox of elevated levels of troponin I without elevated levels of creatine kinase in several disease states might be solved if troponin I could be released from myocardial cells without the disruption of myocardial cell plasma membranes. Precise pathological studies are needed to elucidate whether increased troponin I with normal CK is associated with myocyte death, and, if so, with necrosis or with apoptosis.
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PMID:Cardiac troponin I in systemic diseases. A possible role for myocardial strain. 1158 28

Massive loss of cardiac myocytes after myocardial infarction (MI) is a common cause of heart failure. The present study was designed to investigate the improvement of cardiac function in MI rats after embryonic stem (ES) cell transplantation. MI in rats was induced by ligation of the left anterior descending coronary artery. Cultured ES cells used for cell transplantation were transfected with the marker green fluorescent protein (GFP). Animals in the treated group received intramyocardial injection of ES cells in injured myocardium. Compared with the MI control group injected with an equivalent volume of the cell-free medium, cardiac function in ES cell-implanted MI animals was significantly improved 6 wk after cell transplantation. The characteristic phenotype of engrafted ES cells was identified in implanted myocardium by strong positive staining to sarcomeric alpha-actin, cardiac alpha-myosin heavy chain, and troponin I. GFP-positive cells in myocardium sectioned from MI hearts confirmed the survival and differentiation of engrafted cells. In addition, single cells isolated from cell-transplanted MI hearts showed rod-shaped GFP-positive myocytes with typical striations. The present data demonstrate that ES cell transplantation is a feasible and novel approach to improve ventricular function in infarcted failing hearts.
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PMID:Transplantation of embryonic stem cells improves cardiac function in postinfarcted rats. 1174 72


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