Differential remodeling of the left and right heart after norepinephrine treatment in rats: studies on cytokines and collagen

Randomized trial of phosphodiesterase inhibitors versus catecholamines in patients with acutely decompensated heart failure

Increased neurohormone and cytokine concentrations are associated with adverse outcome in patients with congestive heart failure, so minimizing these increases may improve outcome, even in the acute phase of decompensated heart failure. The present study was designed to test the hypothesis that phosphodiesterase inhibitors, but not catecholamines, could favorably affect neurohormone and cytokine profiles in patients with acutely decompensated heart failure. Twenty-nine patients underwent monitoring using a Swan-Ganz catheter and were randomly allocated to receive phosphodiesterase inhibitors (PDEI group, n=19) or catecholamines (CA group, n=10). Pulmonary capillary wedge pressure decreased significantly in both groups and cardiac output showed a slight, but not statistically significant increase, in both groups. There was a significant decrease in plasma brain natriuretic peptide concentration in the PDEI group, but not in the CA group, whereas plasma interleukin-6 concentration increased in the CA group, but not in the PDEI group. Phosphodiesterase inhibitors favorably affect neurohormone and cytokine concentrations in patients with acutely decompensated heart failure.

Catecholamines stimulate interleukin-6 synthesis in rat cardiac fibroblasts

Proinflammatory cytokines have been implicated in the pathophysiology of different heart diseases. Recent evidence suggests that interleukin-6 (IL--6) may play a role in mechanisms leading to cardiac hypertrophy. In addition, catecholamines are known to induce cardiac hypertrophy. In the present study, we examined whether cardiac fibroblasts may be a potential source of IL--6 production in the rat heart and whether catecholamines can modulate the IL--6 synthesis. Only a small amount of IL--6 mRNA was detected in unstimulated rat cardiac fibroblasts. However, a 50-fold increase of IL--6 mRNA was found after stimulation with norepinephrine (NE). Addition of carvedilol, a alpha- and beta-adrenergic receptor antagonist, prevented almost completely the NE-induced synthesis of IL--6 mRNA. Phenylephrine, an alpha-adrenergic agonist, and isoproterenol, a beta-adrenergic agonist, also induced an increase in IL--6. However, the stimulation via beta-receptors led to a more pronounced elevation. These data show that NE increases IL--6 expression in rat cardiac fibroblasts and that IL--6 may play an important autocrine/paracrine role in cardiac disease states associated with hypertrophy.

Changes in extracellular matrix and in transforming growth factor beta isoforms after coronary artery ligation in rats

Extensive myocardial remodeling occurs after transmural myocardial infarction (MI). The infarcted myocardium is being replaced by scar tissue after gradual resorption of the necrotic tissue. The remodeling process involves both synthesis and degradation of collagens as major components of the extracellular matrix (ECM). In the present study we have analyzed the time-dependent changes of the processes related to this fibrosis in the infarct area and in the non-infarcted left ventricle (LV) six hours to 82 days after occlusion of the left anterior descending coronary artery (LAD) in rats. We also examined whether changes occurred in the expression pattern of the transforming growth factor (TGF) beta isoforms, since this cytokine is known as powerful inductor of fibrosis. Elevation in colligin expression preceded the pronounced increase in mRNA expression of both type I and type III collagen after MI from day three onwards. The maximal increase in colligin protein in the infarct area coincided with the most pronounced expression of collagen I and collagen III mRNA expression. Also, the expression and activity of matrix metalloproteinases (MMPs) and of tissue inhibitor of matrix metalloproteinase (TIMP)-2 mRNA were increased predominantly in the infarct area. TGF beta(1)and TGF-beta(2)expression increased within the first days after MI, whereas TGF-beta(3)expression was elevated predominantly in the infarct area. This pronounced increase in TGF-beta(3)persisted up to 82 days and correlated positively with the parameters of ECM metabolism. Thus, the scar formation is an ongoing dynamic process in which TGF-beta(3)seems to play an active role in the complex ventricular remodeling.

Induction of cardiac fibrosis by transforming growth factor-beta(1)

The role of transforming growth factor-beta(1) (TGF-beta(1)) in the production and deposition of collagens and in the induction of gene expression in the myocardium in relation to the development of myocardial fibrosis will be discussed. Very low expression of TGF-beta(1) and collagen type I and III mRNA is seen in the normal rat heart. Both expressions are markedly increased in the infarcted heart and the levels of TGF-beta(1) mRNA precedes increases in mRNA levels for extracellular matrix (ECM) proteins, suggesting a possible role of TGF-beta(1) in remodeling processes in the myocardium. The TGF-beta(1) expression is normally only transient since continuous TGF-beta(1) overexpression seems to promote nonadaptive cardiac hypertrophy and myocardial fibrosis. In vitro, TGF-beta(1) induces an increase in collagen production and secretion and enhances the abundance of mRNA levels for collagen type I and III in rat cardiac fibroblasts in culture. TGF-beta(1) also stimulates in vivo the expression of ECM proteins and in vivo gene transfer of TGF-beta(1) can induce myocardial fibrosis. Increased myocardial TGF-beta(1) and ECM protein mRNA are found in myocardial fibrosis induced by angiotensin II infusion, by noradrenaline treatment, by isoprenaline infusion, and by long-term blockade of NO synthesis. In vivo antagonism of TGF-beta(1) by neutralizing anti-TGF-beta(1) antibodies or by proteoglycans prevents the increase in gene expression of ECM proteins and inhibits myocardial fibrosis, suggesting that the increases in matrix protein production and fibrosis are mediated by TGF-beta(1).