Denopamine, a beta1-adrenergic agonist, prolongs survival in a murine model of congestive heart failure induced by viral myocarditis: suppression of tumor necrosis factor-alpha production in the heart

2-Phenethylamines in Medicinal Chemistry: A Review

A concise review covering updated presence and role of 2-phenethylamines in medicinal chemistry is presented. Open-chain, flexible alicyclic amine derivatives of this motif are enumerated in key therapeutic targets, listing medicinal chemistry hits and appealing screening compounds. Latest reports in discovering new bioactive 2-phenethylamines by research groups are covered too.

Cardioprotective effect of NO-metoprolol in murine coxsackievirus B3-induced myocarditis

The effect of NO-metoprolol, that is, 3-nitrooxypivaloyl metoprolol-amide, a novel NO-releasing derivative of the β1-blocking drug metoprolol was investigated in A.CA/SnJ mice infected with coxsackievirus B3 (CVB3) and compared to metoprolol and placebo. Daily treatment of mice with the respective drug started immediately (experiment A) or 3 days after virus infection (experiment B) and was continued until day 13 post-infection (p.i.). Two doses of NO-metoprolol were administered. Body mass differences, viral load, and histopathological signs of myocarditis were compared between the several groups. As a result, NO-metoprolol diminished significantly the body weight loss, the viral load and the histopathology, whereas metoprolol treatment led solely to a significant attenuation of myocardial damage. In experiment A, low dose NO-metoprolol decreased significantly enteroviral copy numbers. Both doses of NO-metoprolol had a significant effect on reduction of myocardial infiltrates and fibrosis. The data suggest that delayed drug administration might more advantageous. Both doses of NO-metoprolol reduced significantly the scores of four tested parameters compared to placebo. Body weight loss, virus titers, plus-strand as well as minus-strand enteroviral RNA levels, infiltration and fibrosis scores were diminished significantly when NO-metoprolol was given 3 days p.i. In addition, a significant difference regarding the enteroviral copy numbers was observed between low dose NO-metoprolol- and metoprolol-treated mice. Treatment with metoprolol reduced insignificantly the viral load and body weight loss (experiment A and B) but led to a significant reduction of myocardial histopathology in experiment A. The results indicate that NO-metoprolol treatment has a greater therapeutic benefit than metoprolol.

Acute heart failure: inotropic agents and their clinical uses

Inotropic agents are indispensable for the improvement of cardiac contractile dysfunction in acute or decompensated heart failure. Clinically available agents, including sympathomimetic amines (dopamine, dobutamine, noradrenaline) and selective phosphodiesterase-3 inhibitors (amrinone, milrinone, olprinone and enoximone) act via cAMP/protein kinase A (PKA)-mediated facilitation of intracellular Ca2+ mobilisation. Phosphodiesterase-3 inhibitors also have a vasodilatory action, which plays a role in improving haemodynamic parameters in certain patients, and are termed inodilators. The available inotropic agents suffer from risks of Ca2+ overload leading to arrhythmias, myocardial cell injury and ultimately, cell death. In addition, they are energetically disadvantageous because of an increase in activation energy and cellular metabolism. Furthermore, they lose their effectiveness under pathophysiological conditions, such as acidosis, stunned myocardium and heart failure. Pimobendan and levosimendan (that act by a combination of an increase in Ca2+ sensitivity and phosphodiesterase-3 inhibition) appear to be more beneficial among existing agents. Novel Ca2+ sensitisers that are under basic research warrant clinical trials to replace available inotropic agents.

Beta2-Adrenergic agonists suppress rat autoimmune myocarditis: potential role of beta2-adrenergic stimulants as new therapeutic agents for myocarditis

BACKGROUND

The therapeutic potential of beta2-adrenergic receptor (AR) agonists in the treatment of autoimmune diseases has been reported. However, the role of these drugs in the myocardial structure-induced autoimmune process, which is thought to play a crucial role in the progression of myocarditis to subsequent complications, has not been elucidated.

METHODS AND RESULTS

Experimental autoimmune myocarditis (EAM) was induced in rats by immunization with cardiac myosin. On daily administration from day 0 after immunization, the beta2-selective AR agonists formoterol or salbutamol ameliorated EAM on day 21 and increased myocardial interleukin-10/interferon-gamma mRNA levels. Propranolol, a nonselective beta-AR antagonist, aggravated EAM on day 21 and decreased mRNA levels, whereas metoprolol, a beta1-selective AR antagonist, showed no effect. These results were reflected in vivo by the proliferation of cardiac myosin-primed lymph node cells from drug-treated rats. In vitro addition of beta2-selective AR agonists inhibited the activation of cardiac myosin fragment-specific myocarditogenic T lymphocytes, and this effect was reversed by ICI118,551, a beta2-selective AR antagonist. Furthermore, treatment with 2 different beta2-selective AR agonists starting on day 14 also ameliorated EAM on day 21.

CONCLUSIONS

beta2-AR stimulation suppressed the development of EAM by inhibiting cardiac myosin-specific T-lymphocyte activation in lymphoid organs and by shifting the imbalance in Th1/Th2 cytokine toward Th2 cytokine. Furthermore, it also ameliorated established myocardial inflammation. beta2-AR-stimulating agents may represent important immunomodulators of the cardiac myosin-induced autoimmune process and have potential as a new therapy for myocarditis.

The therapeutic potential of novel cardiotonic agents

During the course of treatment of heart failure patients, cardiotonic agents are inevitable for improvement of myocardial dysfunction. Clinically available agents, such as beta-adrenoceptor agonists and selective phosphodiesterase 3 inhibitors, act mainly via cyclic AMP/protein kinase A-mediated facilitation of Ca(2+) mobilisation (upstream mechanism). These agents are associated with the risk of Ca(2+) overload leading to arrhythmias, myocardial cell injury and premature cell death. In addition, they are energetically disadvantageous because of an increase in activation energy and metabolic effects. Cardiac glycosides act also via an upstream mechanism and readily elicit Ca(2+) overload with a narrow safety margin. No currently available agents act primarily via an increase in the myofilament sensitivity to Ca(2+) ions (central and/or downstream mechanisms). Novel Ca(2+) sensitisers under basic research may deserve clinical trials to examine the therapeutic potential to replace currently employed agents in acute and chronic heart failure patients. Molecular mechanisms of action of Ca(2+) sensitisers are divergent. In addition, they show a wide range of discrete pharmacological profiles due to additional actions associated with individual compounds. Therefore, the outcome of clinical trials has to be explained carefully based on these mechanisms of actions.

Left ventricular pressure-volume relationship in a murine model of congestive heart failure due to acute viral myocarditis

OBJECTIVES

This study, performed in a murine model of encephalomyocarditis virus myocarditis, used a new Millar 1.4F conductance-micromanometer system for the in vivo determination of the left ventricular (LV) pressure-volume relationship (PVR).

BACKGROUND

Viral myocarditis is an important cause of congestive heart failure and may lead to dilated cardiomyopathy. However, the hemodynamic changes associated with its acute phase have not been analyzed in detail.

METHODS

Four-week-old DBA/2 mice were inoculated with EMCV (day 0). Serial hemodynamic measurements, compared with uninfected control mice were made on days 0, 1, 3, 4, 5, 7, 9, 12, and 14.

RESULTS

On day 1, the hearts of infected mice manifested enhanced contractile function, decreased LV compliance, and abnormal diastolic function with increased LV end-diastolic pressure (EDP). Mean stroke index, ejection fraction (EF), and cardiac index (CI) were significantly higher than in uninfected control mice (p < 0.05). Contractile function decreased from days 4 to 14. On day 7, when hemodynamic abnormalities consistent with heart failure culminated, end-diastolic volume (EDV), EDP, and EDPVR were significantly higher, and CI, EF, end-systolic pressure (ESP), and ESPVR significantly lower in the infected than in control mice. Heart rate remained comparable in both groups. Although heart failure receded between day 9 and day 14, ESPVR, ESP, and EF remained significantly depressed up to day 14, and EDV and EDP remained significantly higher.

CONCLUSIONS

These hemodynamic data provide new insights into the pathophysiology of acute viral myocarditis and may be useful in the development of therapeutic interventions.

Mechanisms of action of novel cardiotonic agents

Regulation of myocardial contractility by cardiotonic agents is achieved by an increase in intracellular Ca2+ mobilization (upstream mechanism), an increase in Ca2+ binding affinity to troponin C (central mechanism), or facilitation of the process subsequent to Ca2+ binding to troponin C (downstream mechanism). cAMP mediates the regulation induced by Ca2+ mobilizers such as beta-adrenoceptor agonists and selective phosphodiesterase III inhibitors acting through the upstream mechanism. These agents act likewise on the central mechanism to decrease Ca2+ sensitivity of troponin C in association with the cAMP-mediated phosphorylation of troponin I. In addition to such a well-known action of cAMP, recent experimental findings have revealed that Ca2+ sensitizers, such as levosimendan, OR-1896, and UD-CG 212 Cl, require the cAMP-mediated signaling for induction of Ca2+ sensitizing effect. These agents shift the [Ca2+] -force relationship to the left, but their positive inotropic effect (PIE) is inhibited by carbachol, which suppresses selectively the cAMP-mediated PIE. These findings imply that cAMP may play a crucial role in increasing the myofilament Ca2+ sensitivity by cross-talk with the action of individual cardiotonic agents. No clinically available cardiotonic agents act primarily via Ca2+ sensitization, but the PIE of pimobendan and levosimendan is partly mediated by an increase in myofilament Ca2+ sensitivity. Evidence is accumulating that cardiotonic agents with Ca2+ sensitizing action are more effective than agents that act purely via the upstream mechanism in clinical settings. Further clinical trials are required to establish the effectiveness of Ca2+ sensitizers in long-term therapy for congestive heart failure patients.

Innovative drug treatments for viral and autoimmune myocarditis

Myocarditis is a common cause of cardiomyopathy and is thought to account for 25% of all cases in humans. Unfortunately, the disease is difficult to detect clinically before a myopathic process ensues. Management of myocarditis-induced heart failure includes the standard regimen of diuretics, digoxin, angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, and beta-adrenergic blockers. The management of myocarditis itself is dependent on the etiology of the illness. Treatments that are currently under investigation include immunosuppressants, nonsteroidal antiinflammatory agents, immunoglobulins, immunomodulation, antiadrenergics, calcium-channel blockers, angiotensin-converting enzyme inhibitors, nitric oxide inhibitors (e.g., aminoguanidine), and antivirals. Despite advances in treatment, more work needs to be done in the early detection of myocarditis. Additionally, better means need to be established for distinguishing between viral and noninfectious autoimmune forms of the disease, so that appropriate treatment can be instituted.

Immune and neurohormonal pathways in chronic heart failure

Chronic heart failure is a complex disorder with interactions among the cardiovascular, immune, and neurohormonal systems. The concept that the progression of heart failure is due to neurohormonal abnormalities has received the greatest attention to date, leading to substantial therapeutic benefits. Although many current therapies are also thought to exert a variety of immunologic effects, this has been much less studied. In this review, the authors discuss a number of interactions among immune pathways and neurohormonal abnormalities relevant to heart failure. Cytokines, in particular tumor necrosis factor-alpha, have tremendous interactive opportunities within a regulatory network of energy metabolism, immune function, and neuroendocrine and hormonal function. Inflammatory cytokines are known to contribute to the progression of heart failure, and have been related to patients' prognosis. Advanced heart failure can be considered a state of chronic (low-grade) inflammation, and there are many reasons to suggest that anticytokine therapy could be successful in these patients. These novel approaches are certainly not without some risk, and many of them are very expensive, which may limit their application to certain subgroups of patients. In the future, it may not be enough to monitor cardiac function alone. Rather, the immune and neurohormonal status of patients may also need to be included in the performance of a complete assessment.

The role of inflammatory mediators in the failing heart: immunomodulation of cytokines in experimental models of heart failure

Congestive heart failure may be produced by a variety of disorders, including dilated cardiomyopathy, hypertension, and ischemic heart disease. We have developed experimental models of these diseases, and found gene expressions of proinflammatory cytokines increased in the hearts of these animals. Various drugs for heart failure modulate the production of cytokines in experimental models of heart failure. Pimobendan, an inhibitor of phosphodiesterase III prolonged survival, attenuated inflammatory lesions, and decreased the production of cytokines and nitric oxide. Recent studies have shown that these inhibitory effects are due to inhibition of activation of NF-kappaB. In contrast, digitalis increased the production of cytokines and exacerbated myocarditis. Interleukin-10 prolonged survival, attenuated myocardial injury, and appears promising as a treatment of heart failure due to viral myocarditis. Endothelin-1 plays an important pathophysiological role in heart failure, and treatment with an endothelin antagonist had a cardioprotective effect in experimental models of heart failure.

Effects of the phosphodiesterase inhibitor rolipram on streptococcal cell wall-induced arthritis in rats

The phosphodiesterase-IV (PDE-IV) inhibitor, rolipram, is antiinflammatory in a number of animal models and inhibits the release of a variety of cytokines, including TNFalpha. Arthritis induced in rats by systemic reactivation with streptococcal cell walls (SCW) following intraarticular sensitization is a TNFalpha-dependent, delayed-type hypersensitivity (DTH) reaction. Rolipram administered during the reactivation phase dose-dependently inhibited hind paw edema through day 24, the day of peak swelling. PMN and T-cell recruitment to the arthritic joint were also attenuated in rolipram-treated rats. Histologic examination of ankle sections from rolipram-treated animals showed a marked attenuation of synovial inflammation. Mechanistic studies to determine the role of glucocorticoids in mediating rolipram action showed that the inhibitory effect of rolipram on swelling was not reversed by RU 486, a glucocorticoid antagonist. In contrast, RU 486 reversed the inhibitory effects of rolipram on TNFalpha secretion. To further evaluate the role of cAMP in the model, the beta-adrenergic receptor (betaAR) agonist isoproterenol was tested, and found to inhibit swelling but not the release of TNFalpha. These results are consistent with the view that the inhibitory effects of rolipram may be partially mediated by cAMP-dependent, but TNFalpha-independent, mechanisms. The betaAR antagonists propranolol and nadolol had no appreciable affect on the antiinflammatory effect of rolipram. However, rolipram reversed the lethal effects of the antagonists observed when either was administered alone. Apparently, beta-adrenergic mechanisms moderate the response to challenge, and rolipram treatment, presumably as a result of its effects on cAMP levels, reverses the toxic effect of the antagonists.

Treatment of experimental viral myocarditis with interleukin-10

BACKGROUND

The T helper cell type 2-associated cytokine interleukin (IL)-10 has a variety of immunomodulatory properties. However, the effects of the cytokine on viral myocarditis remain unclear.

METHODS AND RESULTS

We studied the effects of recombinant human IL-10 (rhIL-10) fully active on mouse cells in a murine experimental model of acute viral myocarditis caused by the encephalomyocarditis virus (EMCV). Four-week-old DBA/2 mice were inoculated with EMCV (day 0). rhIL-10 (10 microg/mouse) was administered once daily, starting on day 0, and control mice received vehicle only. Survival rates were determined on day 14. Myocardial histopathology, cytokine levels in the heart by ELISA assay, and myocardial virus concentration were examined on day 6, and the expression levels of myocardial inducible nitric oxide synthase (iNOS) mRNA were measured by competitive polymerase chain reaction. The 14-day survival in mice treated with rhIL-10 was significantly higher (80%) than in the control group (30%, n=10 in each, P<0.05). rhIL-10 treatment significantly attenuated myocardial lesions and suppressed tumor necrosis factor-alpha and IL-2 in the heart. rhIL-10 treatment had little effect on myocardial virus concentration. The expression levels of myocardial iNOS mRNA were significantly decreased in the group treated with rhIL-10 (8.6+/-4.7 amol/mg total RNA in treated versus 26.5+/-7.1 amol/mg total RNA in control mice, P<0.05).

CONCLUSIONS

These findings provide new insights into the in vivo effects of IL-10 on viral infection and suggest a therapeutic effect of IL-10 on viral myocarditis.