[Show abstract][Hide abstract] ABSTRACT: Leukemia-inhibitory factor (LIF) is a member of the interleukin-6 family of cytokines that utilize gp130 as a common signaling component. In the present study, we examined the mechanisms that govern LIF expression and functional effects in the adult heart.
LIF mRNA and protein biosynthesis were examined in the adult feline heart after hemodynamic overloading ex vivo. Both LIF mRNA and protein expression were detected within 60 to 90 minutes after hemodynamic overloading. Studies in isolated adult cardiac myocytes showed that these cells synthesized both LIF mRNA and protein. The functional effects of LIF in the heart were demonstrated by studies that showed that LIF stimulation led to a significant increase in general protein synthesis and an increase in sarcomeric protein synthesis. Pretreatment with LIF also protected the cells against hypoxia/reoxygenation-induced cardiac myocyte apoptosis and cellular injury. Finally, LIF had no effect on isolated cardiac myocyte cell motion.
Hemodynamic overload is a sufficient stimulus for LIF expression in the adult mammalian heart. Given that LIF confers both hypertrophic and cytoprotective responses in adult cardiac myocytes, this study suggests that the expression of LIF within the heart may play an important role in mediating homeostatic responses within the myocardium.
[Show abstract][Hide abstract] ABSTRACT: Encephalomyocarditis virus causes viral myocarditis with myocyte necrosis and inflammatory cell infiltration in mice. Because previous studies have shown that some cytokines prevent the sequelae of myocarditis, we assessed the effect of a newly identified cytokine, interleukin-18 (IL-18), in preventing the sequelae of myocarditis. Murine IL-18 (10μ g/day/mouse) was given peritoneally for 10 days in C3H mice infected with EMC virus. Mice were divided into group IL-18 (infected-treated), saline group (infected-untreated), group IL-18-2 (treatment started on day 2), group IL-18-5 (treatment started on day 5). Although the 14-day survival rate in saline group was 20%, that in the group IL-18 increased to 80% (P<0.05). Either mice in group IL-18-2 or in group IL-18-5 did not survive longer than saline group. The viral titer of the heart on day 3 was lower in group IL-18 compared to the saline group (1.00±0.20 log10tissue culture infected dose (TCID)50/mg wet weight v 1.42±0.12 log10TCID50/mg,n =3 of each). Mice in group IL-18 had less myocardial necrosis and cellular infiltration than the saline group. The myocardial expression of interferon- γ (IFN- γ) mRNA in group IL-18 was significantly (P<0.05) greater than the saline group on days 1 and 3 after viral inoculation. Circulating IFN- γ was significantly elevated on days 1, 5, and 7, but significantly reduced on day 3. The natural killer cell activities in the spleen on days 1, 3, and 5 were significantly (P<0.05) greater in group IL-18 than in the saline group (41±9%v 10±6% on day 3, 4 of each). We conclude that IL-18 reduces the severity of EMC viral myocarditis by inducing cardiac expression of IFN- γ mRNA and increasing splenic natural killer cell activity.
No preview · Article · Dec 2000 · Journal of Molecular and Cellular Cardiology
[Show abstract][Hide abstract] ABSTRACT: The mechanism(s) responsible for the persistent coexpression of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) in the failing heart is unknown.
To determine whether NO was sufficient to provoke TNF-alpha biosynthesis, we examined the effects of an NO donor, S-nitroso-N-acetyl penicillamine (SNAP), in buffer-perfused Langendorff hearts. SNAP (1 micromol/L) treatment resulted in a time- and dose-dependent increase in myocardial TNF-alpha mRNA and protein biosynthesis in adult cat hearts. The effects of SNAP were completely abrogated by a NO quenching agent, 2-(4-carboxyphenyl)-4, 4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (C-PTIO), and mimicked by sodium nitroprusside. Electrophoretic mobility shift assays demonstrated that SNAP treatment led to the rapid induction of nuclear factor kappa-beta (NF-kappaB) but not AP-1. The importance of the cGMP pathway in terms of mediating NO-induced TNF-alpha biosynthesis was shown by studies that demonstrated that 8-bromo-cGMP mimicked the effects of SNAP and that the effects of SNAP could be completely abrogated using a cGMP antagonist, 1H-(1,2, 4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ), or protein kinase G antagonist (Rp-8-Br-cGMPS). SNAP and 8-Br-cGMP were both sufficient to lead to the site-specific phosphorylation (serine 32) and degradation of IkappaBalpha in isolated cardiac myocytes. Finally, protein kinase G was sufficient to directly phosphorylate IkappaBalpha on serine 32, a critical step in the activation of NF-kappaB.
These studies show that NO provokes TNF-alpha biosynthesis through a cGMP-dependent pathway, which suggests that the coincident expression of TNF-alpha and NO may foster self-sustaining positive autocrine/paracrine feedback inflammatory circuits within the failing heart.
[Show abstract][Hide abstract] ABSTRACT: Endothelin-1 (ET-1) is a potent vasoconstrictor. This peptide exerts numerous effects on the heart, including regulation of cardiomyocyte growth during hypertrophy. The effects of the structurally novel, nonpeptide, ET-1-selective, competitive antagonist (ETA) 97-139 were investigated in mice with congestive heart failure (CHF) and myocardial hypertrophy. Morphological and microscopical analyses were conducted on day 56 after viral inoculation following 28 day treatment with 99-139. Eight week-old DBA2 mice were intraperitoneally inoculated with encephalomyocarditis virus at a dose of 500 pfu/mouse. The 30 mice were divided into two groups--an ETA treated group and an untreated group. Heart weight (HW) in the infected group was significantly (p < 0.05) increased compared to that in the uninfected group. HW and the HW/body weight (BW) ratio were significantly (p < 0.05) reduced in the ETA treated group compared with the untreated group (HW; 127.7 +/- 6.2 mg vs 144.3 +/- 4.2 mg, HW/BW; 4.9 +/- 0.9 x 10(-3) vs 5.4 +/- 0.5 x 10(-3)). Myofiber diameter in the ETA treated group was significantly reduced compared with the untreated group (12.1 +/- 1.5 microm vs 14.3 +/- 1.9 microm). These results suggest the ET-1 receptor antagonist 97-139 has an effect on the reduction of cardiac mass and myofiber hypertrophy, and that 97-139 may be a useful agent for CHF due to viral myocarditis.
No preview · Article · Jan 2000 · Japanese Heart Journal
[Show abstract][Hide abstract] ABSTRACT: Activated inflammatory responses appear to play a role in the development of congestive heart failure (CHF). We investigated interleukin-18 (IL-18), which is a cytokine synthesized by activated macrophage, changes in patients with CHF. We evaluated 11 Japanese patients with angina pectoris (n=4) or CHF (n=7). Blood was sampled immediately after admission and at 1, 2, 3, 6, and 9 hours after admission and then every 12 hours until 5 days after admission. Plasma IL-18 concentrations were measured by an enzyme-linked immunosorbent assay. Expression of atrial natriuretic peptide (ANP) mRNA and protein synthesis was examined in cardiac myocyte by stimulation of IL-18. Plasma IL-18 concentration was significantly higher in patients with CHF than in 15 healthy volunteers (51+/-21 pg/mL, and 28+11 pg/mL, respectively, P<0.05). Increased expression of ANP mRNA was demonstrated in IL-18 treated myocytes. Protein synthesis in myocytes was increased by IL-18 in a dose-dependent manner. Increased secretion of IL-18 is induced in patients with CHF and correlates with the severity of myocardial damage and dysfunction.
No preview · Article · Jan 2000 · Research communications in molecular pathology and pharmacology
[Show abstract][Hide abstract] ABSTRACT: Recent studies have shown that patients with heart failure overexpress a class of biologically active molecules, generically referred to as pro-inflammatory cytokines. This article will review recent clinical and experimental material that suggests that pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6) may play a role in the pathogenesis of congestive heart failure. In addition, we will review recent studies that suggest that antagonizing cytokines may represent a novel target for heart failure therapy.
No preview · Article · Sep 1999 · Proceedings of the Association of American Physicians
[Show abstract][Hide abstract] ABSTRACT: Although previous studies suggested that TNF may contribute to heart failure progression, it is unclear whether antagonizing TNF is beneficial in heart failure patients.
Eighteen NYHA class III heart failure patients were randomized into a double-blind dose-escalation study to examine the safety and potential efficacy of etanercept, a specific TNF antagonist (Enbrel). Patients received placebo (6 patients) or an escalating dose (1, 4, or 10 mg/m2) of etanercept (12 patients) given as a single intravenous infusion. Safety parameters and patient functional status were assessed at baseline and at days 1, 2, 7, and 14. There were no significant side effects or clinically significant changes in laboratory indices. There was, however, a decrease in TNF bioactivity and a significant overall increase in quality-of-life scores, 6-minute walk distance, and ejection fraction in the cohort that received 4 or 10 mg/m2 of etanercept; there was no significant change in these parameters in the placebo group.
A single intravenous infusion of etanercept was safe and well tolerated in patients with NYHA class III heart failure. These studies provide provisional evidence that suggests that etanercept is sufficient to lower levels of biologically active TNF and may lead to improvement in the functional status of patients with heart failure.
[Show abstract][Hide abstract] ABSTRACT: Despite repeated attempts to develop a unifying hypothesis that explains the clinical syndrome of heart failure, no single conceptual paradigm has withstood the test of time. In this regard, recent studies have shown that a class of biologically active molecules, generically referred to as cytokines, are overexposed in heart failure. This article will review recent clinical and experimental material that suggest proinflammatory (stress activated) cytokines such as tumor necrosis factor-alpha (TFN-alpha), interleukin-1 (IL-1), and interleukin-6 (IL-6) may play a role in the pathogenesis of congestive heart failure. The scope of this article includes an overview of the biology of cytokines in the heart, as well as review of the clinical studies that have documented elevated levels of cytokines and cytokine receptors in patients with heart failure.
No preview · Article · Dec 1998 · Cardiology Clinics
[Show abstract][Hide abstract] ABSTRACT: Natural history studies in heart failure have shown that increases in left ventricular (LV) volume and LV mass are directly related to future deterioration in LV performance and a less favorable clinical course. Despite the recognized importance of remodeling in heart failure, very little is known about the basic mechanisms that lead to cardiac remodeling. In this review, we will summarize recent clinical and experimental studies that highlight the importance of the remodeling process during the progression of heart failure. The intent of this review is to provide an integrated view of the mechanisms that contribute to LV remodeling at the cellular level, the myocardial level, and the level of the chamber.
Full-text · Article · Dec 1998 · Clinical Cardiology
[Show abstract][Hide abstract] ABSTRACT: Although patients with heart failure express elevated circulating levels of tumor necrosis factor-alpha (TNF-alpha) in their peripheral circulation, the structural and functional effects of circulating levels of pathophysiologically relevant concentrations of TNF-alpha on the heart are not known.
Osmotic infusion pumps containing either diluent or TNF-alpha were implanted into the peritoneal cavity of rats. The rate of TNF-alpha infusion was titrated to obtain systemic levels of biologically active TNF-alpha comparable to those reported in patients with heart failure (approximately 80 to 100 U/mL), and the animals were examined serially for 15 days. Two-dimensional echocardiography was used to assess changes in left ventricular (LV) structure (remodeling) and LV function. Video edge detection was used to assess isolated cell mechanics, and standard histological techniques were used to assess changes in the volume composition of LV cardiac myocytes and the extracellular matrix. The reversibility of cytokine-induced effects was determined either by removal of the osmotic infusion pumps on day 15 or by treatment of the animals with a soluble TNF-alpha antagonist (TNFR:Fc). The results of this study show that a continuous infusion of TNF-alpha led to a time-dependent depression in LV function, cardiac myocyte shortening, and LV dilation that were at least partially reversible by removal of the osmotic infusion pumps or treatment of the animals with TNFR:Fc.
These studies suggest that pathophysiologically relevant concentrations of TNF-alpha are sufficient to mimic certain aspects of the phenotype observed in experimental and clinical models of heart failure.
[Show abstract][Hide abstract] ABSTRACT: The mechanism(s) by which mutations in sarcomeric proteins cause hypertrophic cardiomyopathy (HCM) remains unknown. A leading hypothesis proposes that mutant sarcomeric proteins impair cardiac myocyte contractility, providing an impetus for compensatory hypertrophy. To test this hypothesis, we determined the impact of expression of a mutant (Arg92Gln) human cardiac troponin T (cTnT), known to cause HCM in humans, on adult cardiac myocyte contractility. A full-length human cTnT cDNA was cloned, and the Arg92Gln mutation was induced. Recombinant adenoviruses Ad5/CMV/cTnT-N and Ad5/CMV/cTnT-Arg92Gln were generated through homologous recombination. Adult feline cardiac myocytes were infected with recombinant adenoviruses or a control viral vector (Ad5 delta E1) at a multiplicity of infection of 100. Expression levels of the full-length normal and mutant cTnT proteins were equal on Western blots. Expression of the exogenous cTnT proteins in cardiac myocytes was also shown by immunocytochemistry and immunofluorescence, and their incorporation into myofibrils was confirmed by Western blotting on myofibrillar extracts. Electron microscopy showed intact sarcomere structure in rod-shaped cardiac myocytes in all groups. Cell fractional shortening and the peak velocity of shortening were not significantly different among the groups 24 hours after transduction. However, 48 hours after transduction, both fractional shortening and the peak velocity of shortening were significantly reduced (24% [P < .001] and 26% [P < .001], respectively) in cardiac myocytes in the Ad5/CMV/cTnT-Arg92Gln compared with the Ad5/CMV/cTnT-N groups. The magnitude of the reductions was greater at 72 hours after transduction (45% and 39%, respectively; P < .001). Our results indicated that expression of the mutant (Arg92Gln) cTnT, known to cause HCM in humans, impaired intact adult cardiac myocyte contractility. Our data also show that both normal and mutant cTnT were incorporated into myofibrils. These results provide a potential mechanism by which mutations in sarcomeric proteins cause HCM.
No preview · Article · Aug 1997 · Circulation Research
[Show abstract][Hide abstract] ABSTRACT: Recent studies have identified the importance of biologically active molecules such as neurohormones as mediators of disease progression in heart failure. More recently it has become apparent that in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that the cytokines, much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.
No preview · Article · Jun 1997 · Current Opinion in Cardiology
[Show abstract][Hide abstract] ABSTRACT: Management of acute viral myocarditis is still controversial. Amrinone, a noncatecholamine nonglycoside bipyridine agent, produces sustained improvement of cardiac function and symptomatology in congestive heart failure (CHF). Amrinone demonstrates phosphodiesterase inhibitory activity that is relatively selective for the major phosphodiesterase isozyme in cardiac muscles, PDE III, which specifically hydrolyzes cyclic 3'5' adenosine monophosphate (cAMP). We investigated the effects of amrinone in an animal model of acute CHF related to myocarditis caused by the encephalomyocarditis virus (EMCV). Female C3H mice were inoculated intraperitoneally (i.p.) with 500 plaque-forming units of EMCV in 0.1 ml of saline. A total of 96 mice were randomly assigned to four groups. Each animal was administered 0.2 ml of phosphate-buffered saline (PBS) containing amrinone at a concentration of 1, 10, or 50 mg/kg, or PBS as an infected control, injected i.p. once daily for 21 days, starting on day 1 after viral inoculation. Each group contains 20 to 30 mice. Infected untreated mice survived at 80% (n = 16), however, only 13% (n = 16) of mice treated with amrinone (50 mg/kg) survived (p < 0.01). Downregulation of cardiac cAMP occurred 1 day after the viral infection. Although amrinone (10 and 50 mg/kg) treatment significantly (p < 0.05) increased the cardiac cAMP content and the dose of 10 mg/kg could potentially retard death from CHF due to viral myocarditis. The higher (50 mg/kg) doses of amrinone may produce unfavorable effects when used to treat mammals with viral myocarditis and CHF.
No preview · Article · Jan 1997 · Research communications in molecular pathology and pharmacology
[Show abstract][Hide abstract] ABSTRACT: The basic mechanisms that are responsible for the development and progression of congestive heart failure are not known. Although clinicians have traditionally viewed heart failure as a hemodynamic disorder related to left ventricular pump dysfunction, one of the more recent concepts that has emerged is that the development and progression of heart failure is attributable, at least in part, to the overexpression of biologically active molecules that can contribute both to patient symptomatology as well as to disease progression. In this regard, one of the more recent interesting and intriguing observations in clinical heart failure research is the finding that a proinflammatory cytokine, termed tumor necrosis factor- (TNF-), is expressed in patients with heart failure. Accordingly, the focus of the present brief review is to summarize recent clinical and experimental observations that implicate the elaboration of TNF- and TNF receptors in the progression of human heart failure.
No preview · Article · Oct 1996 · Heart Failure Reviews
[Show abstract][Hide abstract] ABSTRACT: Although the development and progression of heart failure have traditionally been viewed as hemodynamic disorders, there is now an increasing awareness that the syndrome of heart failure cannot be simply and/or precisely defined solely in hemodynamic terms. The inability of the so-called hemodynamic hypothesis to explain the progression of heart failure has given rise to the notion that heart failure may progress as a result of the overexpression of an ensemble of biologically active molecules referred to generically as neurohormones. More recently, it has become apparent that in addition to neurohormones, another portfolio of biologically active molecules, termed cytokines, are also expressed in the setting of heart failure. This article reviews recent clinical and experimental material that suggests that the cytokines, much like the neurohormones, may represent another class of biologically active molecules that are responsible for the development and progression of heart failure.
No preview · Article · Oct 1996 · Journal of Cardiac Failure