Plasma levels of transforming growth factor-beta1 reflect left ventricular remodeling in aortic stenosis

Transforming growth factor beta signaling in adult cardiovascular diseases and repair

The majority of children with congenital heart disease now live into adulthood due to the remarkable surgical and medical advances that have taken place over the past half century. Because of this, adults now represent the largest age group with adult cardiovascular diseases. It includes patients with heart diseases that were not detected or not treated during childhood, those whose defects were surgically corrected but now need revision due to maladaptive responses to the procedure, those with exercise problems and those with age-related degenerative diseases. Because adult cardiovascular diseases in this population are relatively new, they are not well understood. It is therefore necessary to understand the molecular and physiological pathways involved if we are to improve treatments. Since there is a developmental basis to adult cardiovascular disease, transforming growth factor beta (TGFβ) signaling pathways that are essential for proper cardiovascular development may also play critical roles in the homeostatic, repair and stress response processes involved in adult cardiovascular diseases. Consequently, we have chosen to summarize the current information on a subset of TGFβ ligand and receptor genes and related effector genes that, when dysregulated, are known to lead to cardiovascular diseases and adult cardiovascular deficiencies and/or pathologies. A better understanding of the TGFβ signaling network in cardiovascular disease and repair will impact genetic and physiologic investigations of cardiovascular diseases in elderly patients and lead to an improvement in clinical interventions.

TNF-α increases cardiac fibroblast lysyl oxidase expression through TGF-β and PI3Kinase signaling pathways

TNF-α is a proinflammatory cytokine that is upregulated in many cardiac diseases. The increase of TNF-α expression affects both heart function and the structure of the extracellular matrix. Lysyl oxidase (LOX) is a key enzyme responsible for the maturation of extracellular matrix proteins, including collagens type I and III. In this study, we investigated the regulation of LOX expression and activity by TNF-α using adult rat cardiac fibroblasts. Our results indicate that TNF-α has a dichotomous effect on LOX expression by cardiac fibroblasts. Low dose TNF-α (1-5 ng/ml) decreased LOX expression, whereas higher doses (10-30 ng/ml) increased expression. The higher dose TNF-α effect on LOX expression was attenuated by the inhibition of PI3Kinase/Akt pathway. TGF-β1 signaling played a significant role in mediating the TNF-α effect. TNF-α increased the expression of TGF-β, and TGF-β receptors type I and II, and also stimulated Smad3 phosphorylation. Inhibition of TGF-β receptor I or Smad3 prevented increased LOX expression by TNF-α. These findings indicate that TNF-α stimulated LOX expression may play an important role in progressive cardiac fibrosis.

TGFB1 disrupts the angiogenic potential of microvascular endothelial cells of the corpus luteum

Cyclical formation and regression of the ovarian corpus luteum is required for reproduction. During luteal regression, the microvasculature of the corpus luteum is extensively disrupted. Prostaglandin F2α, a primary signal for luteal regression, induces the expression of transforming growth factor β1 (TGFB1) in the corpus luteum. This study determined the actions of TGFB1 on microvascular endothelial cells isolated from the bovine corpus luteum (CLENDO cells). We hypothesized that TGFB1 participates in the disruption of the microvasculature during luteal regression. TGFB1 activated the canonical SMAD signaling pathway in CLENDO cells. TGFB1 (1 ng/ml) significantly reduced both basal and fetal-calf-serum-stimulated DNA synthesis, without reducing cell viability. TGFB1 also significantly reduced CLENDO cell transwell migration and disrupted the formation of capillary-like structures when CLENDO cells were plated on Matrigel. By contrast, CLENDO cells plated on fibrillar collagen I gels did not form capillary-like structures and TGFB1 induced cell death. Additionally, TGFB1 caused loss of VE-cadherin from cellular junctions and loss of cell-cell contacts, and increased the permeability of confluent CLENDO cell monolayers. These studies demonstrate that TGFB1 acts directly on CLENDO cells to limit endothelial cell function and suggest that TGFB1 might act in the disassembly of capillaries observed during luteal regression.

Transforming growth factor (TGF)-β signaling in cardiac remodeling

Myocardial TGF-β expression is upregulated in experimental models of myocardial infarction and cardiac hypertrophy, and in patients with dilated or hypertrophic cardiomyopathy. Through its effects on cardiomyocytes, mesenchymal and immune cells, TGF-β plays an important role in the pathogenesis of cardiac remodeling and fibrosis. TGF-β overexpression in the mouse heart is associated with fibrosis and hypertrophy. Endogenous TGF-β plays an important role in the pathogenesis of cardiac fibrotic and hypertrophic remodeling, and modulates matrix metabolism in the pressure-overloaded heart. In the infarcted heart, TGF-β deactivates inflammatory macrophages, while promoting myofibroblast transdifferentiation and matrix synthesis through Smad3-dependent pathways. Thus, TGF-β may serve as the "master switchThis article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure". for the transition of the infarct from the inflammatory phase to formation of the scar. Because of its crucial role in cardiac remodeling, the TGF-β system may be a promising therapeutic target for patients with heart failure. However, efforts to translate these concepts into therapeutic strategies, in order to prevent cardiac hypertrophy and fibrosis, are hampered by the complex, pleiotropic and diverse effects of TGF-β signaling, by concerns regarding deleterious actions of TGF-β inhibition and by the possibility of limited benefit in patients receiving optimal treatment with ACE inhibitors and β-adrenergic blockers. Dissection of the pathways responsible for specific TGF-β-mediated actions and understanding of cell-specific actions of TGF-β are needed to design optimal therapeutic strategies. This article is part of a special issue entitled "Key Signaling Molecules in Hypertrophy and Heart Failure".