Transforming growth factor-beta and the protection from cardiovascular injury hypothesis

Relationship between bone disorders and stroke

Bone disorders are among the most uncommon causes of stroke, but they should be considered as stroke cause in particular clinical scenarios. On the other hand, osteoporosis/osteopenia and increased fracture risk are well documented post stroke complications. The relationship between stroke and bone health is complex. The current facts suggest that these two conditions share same risk factors, but also are risk factors for each other. However, the evidence shows more clear effect of stroke on the bone health, than in the opposite direction. This extensive review is aiming to fill the huge gap of evidence about this topic, and since bone pathology is extremely rare cause of cerebrovascular accident, although a complex connection between these two conditions definitely exists.

Patients with unrecognized peripheral arterial disease (PAD) assessed by ankle-brachial index (ABI) present a defined profile of proinflammatory markers compared to healthy subjects

BACKGROUND

Many studies have postulated that atherosclerosis should be considered as an inflammatory disease. In addition, some studies have focused on the relationship between inflammation and peripheral arterial disease (PAD).

OBJECTIVE

Define the plasma levels of soluble markers, including the proinflammatory cytokine interleukin-6 (IL-6), the anti-inflammatory cytokine transforming growth factor-β1 (TGF-β1), the endothelial-specific adhesion factor (E-selectin) and two proteinases involved in extracellular matrix degradation (matrix metalloproteinases-2 and -9, MMP-2, and MMP-9) in previously unrecognized patients with peripheral artery disease (PAD) and non-PAD controls.

RESULTS

Significantly higher levels of IL-6, E-selectin and MMP-2/MMP-9 and significantly reduced levels of TGF-β1 were found in PAD patients (ankle-brachial index, ABI⩽0.9) compared to non-PAD control subjects (1.4>ABI>0.9).

CONCLUSION

The results demonstrated the subjects with unrecognized PAD (ABI⩽0.9) show a characteristic phlogistic pattern differently from healthy subjects and it strongly supports the pivotal role played by inflammatory and immunological mechanisms in the initiation and progression of the atherosclerotic process in peripheral arteries. These biomarkers could be helpful to screen the susceptibility for the diseases in peripheral arteries.

Transforming growth factor β1 T868C gene polymorphism is associated with cerebral infarction in Japanese patients with type 2 diabetes

It is likely that the C allele of the polymorphism at position 29 of the translated sequence of transforming growth factor (TGF)-β1 gene, which codes a pleiotropic cytokine expressed in a variety of cells, is a susceptibility allele for cerebral infarction in Japanese type 2 diabetic patients.

Transforming growth factor beta expression by human vascular cells inhibits interferon gamma production and arterial media injury by alloreactive memory T cells

Arteriosclerosis is characterized by the local activation of effector T cells leading to production of proinflammatory cytokines, such as IFN (interferon)-γ and IL-17, within the vessel wall. Conversely, the production of antiinflammatory cytokines, for example, TGF-β, by regulatory lymphocytes is known to inhibit both the differentiation of naïve T cells into effector T cells and the development of arteriosclerosis in murine models. We investigated the role of TGF-β on the alloreactivity of human effector memory T cells (Tem). Quiescent vascular cells, but not Tem, expressed TGF-β. Blockade of TGF-β activity in cocultures of CD4(+) Tem with allogeneic endothelial cells significantly increased IFN-γ, but not IL-17, secretion. Additionally, serologic neutralization of TGF-β in immunodeficient mouse hosts of human coronary artery grafts into which allogeneic human T cells were adoptively transferred resulted in heavier medial infiltration by Tem, greater loss of medial smooth muscle cells and increased IFN-γ production within the grafts without significantly reducing either intimal injury or IL-17 production. Protective effects of TGF-β may be limited by fewer TGF-β-expressing vascular cells within the intimal compartment, by a reduction in the expression of TGF-β by vascular cells in rejecting grafts, or possibly to less effective suppression of Tem than naïve T cells.

Activation of human vascular cells decreases their expression of transforming growth factor-beta

OBJECTIVE

Despite pro-fibrotic effects, transforming growth factor (TGF)-β prevents arteriosclerosis by suppressing effector leukocytes and promoting smooth muscle differentiation. However, previous observations of increased TGF-β expression in arteriosclerotic plaques are not consistent with that of an effective protective factor. We investigated the expression, regulation, and responses of TGF-β in human arterial tissues and cells.

METHODS AND RESULTS

The expression of TGF-β by intrinsic vascular cells was lower in arteriosclerotic than non-diseased coronary arteries. Activation of resident and infiltrating leukocytes did not elicit TGF-β production from coronary artery segments in organ culture. Instead, the basal expression of TGF-β by coronary arteries decreased after vessel procurement and ex vivo culture. Activation of cultured smooth muscle cells and endothelial cells with phorbol ester and ionophore also decreased TGF-β expression. Isolated cell types representing those found in the artery wall were all capable of signaling in response to TGF-β, however production of the cytoprotective molecule, interleukin-11 was cell type-dependent and restricted to smooth muscle cells and fibroblasts. Interleukin-11 reduced smooth muscle cell apoptosis to T cell effectors.

CONCLUSIONS

Inflammation and cellular activation diminish the basal expression of TGF-β by quiescent human vascular cells. Induction of interleukin-11 may contribute to the anti-arteriosclerotic actions of TGF-β.

A mechanism by which dietary trans fats cause atherosclerosis

Dietary trans fats (TFs) have been causally linked to atherosclerosis, but the mechanism by which they cause the disease remains elusive. Suppressed transforming growth factor (TGF)-β responsiveness in aortic endothelium has been shown to play an important role in the pathogenesis of atherosclerosis in animals with hypercholesterolemia. We investigated the effects of a high TF diet on TGF-β responsiveness in aortic endothelium and integration of cholesterol in tissues. Here, we show that normal mice fed a high TF diet for 24 weeks exhibit atherosclerotic lesions and suppressed TGF-β responsiveness in aortic endothelium. The suppressed TGF-β responsiveness is evidenced by markedly reduced expression of TGF-β type I and II receptors and profoundly decreased levels of phosphorylated Smad2, an important TGF-β response indicator, in aortic endothelium. These mice exhibit greatly increased integration of cholesterol into tissue plasma membranes. These results suggest that dietary TFs cause atherosclerosis, at least in part, by suppressing TGF-β responsiveness. This effect is presumably mediated by the increased deposition of cholesterol into cellular plasma membranes in vascular tissue, as in hypercholesterolemia.

Genetic determinants of osteoporosis: common bases to cardiovascular diseases?

Osteoporosis is the most common and serious age-related skeletal disorder, characterized by a low bone mass and bone microarchitectural deterioration, with a consequent increase in bone fragility and susceptibility to spontaneous fractures, and it represents a major worldwide health care problem with important implications for health care costs, morbidity and mortality. Today is well accepted that osteoporosis is a multifactorial disorder caused by the interaction between environment and genes that singularly exert modest effects on bone mass and other aspects of bone strength and fracture risk. The individuation of genetic factors responsible for osteoporosis predisposition and development is fundamental for the disease prevention and for the setting of novel therapies, before fracture occurrence. In the last decades the interest of the Scientific Community has been concentrated in the understanding the genetic bases of this disease but with controversial and/or inconclusive results. This review tries to summarize data on the most representative osteoporosis candidate genes. Moreover, since recently osteoporosis and cardiovascular diseases have shown to share common physiopathological mechanisms, this review also provides information on the current understanding of osteoporosis and cardiovascular diseases common genetic bases.

Inhibitors of clathrin-dependent endocytosis enhance TGFbeta signaling and responses

Clathrin-dependent endocytosis is believed to be involved in TGFbeta-stimulated cellular responses, but the subcellular locus at which TGFbeta induces signaling remains unclear. Here, we demonstrate that inhibitors of clathrin-dependent endocytosis, which are known to arrest the progression of endocytosis at coated-pit stages, inhibit internalization of cell-surface-bound TGFbeta and promote colocalization and accumulation of TbetaR-I and SARA at the plasma membrane. These inhibitors enhance TGFbeta-induced signaling and cellular responses (Smad2 phosphorylation/nuclear localization and expression of PAI-1). Dynasore, a newly identified inhibitor of dynamin GTPase activity, is one of the most potent inhibitors among those tested and, furthermore, is a potent enhancer of TGFbeta. Dynasore ameliorates atherosclerosis in the aortic endothelium of hypercholesterolemic ApoE-null mice by counteracting the suppressed TGFbeta responsiveness caused by the hypercholesterolemia, presumably acting through its effect on TGFbeta endocytosis and signaling in vascular cells.

An overview of cytokine interactions in atherosclerosis and implications for peripheral arterial disease

Over the last three decades, a surge in research into the inflammatory pathophysiology of atherosclerosis has highlighted an array of cytokines and other inflammatory mediators associated with underlying inflammatory burden. The ability to identify and simultaneously measure multiple cytokines in peripheral blood highlights their potential as biomarkers of atherosclerosis. This has prompted much research in vascular medicine to identify the ;at-risk' groups for atherostenotic or atheroaneurysmal disease. This review is compiled with similar intentions and aims to discern the relevant evidence for cytokine profiling in peripheral arterial disease (PAD), where such information is lacking, while providing a holistic overview of cytokine interactions in atherosclerosis. This is pertinent given that cytokine profiles from coronary artery disease and aortic aneurysm studies cannot be directly extrapolated to PAD due to differences in inflammatory environments that exist in these conditions. Whilst plaque morphology and blood rheology play an important role in the cardiac manifestations of atherosclerosis, tissue thrombogenecity is very important in PAD. Further, cytokines act in concert rather than in isolation in a disease process, and no single cytokine in a cross-sectional model is able to serve as an absolute screening marker. Thus, it is essential to understand the regulation of cytokine production in atherosclerosis prior to evaluating the viability and merits of a multimarker approach for clinical risk stratification in PAD.

Cholesterol suppresses cellular TGF-beta responsiveness: implications in atherogenesis

Hypercholesterolemia is a major causative factor for atherosclerotic cardiovascular disease. The molecular mechanisms by which cholesterol initiates and facilitates the process of atherosclerosis are not well understood. Here, we demonstrate that cholesterol treatment suppresses or attenuates TGF-beta responsiveness in all cell types studied as determined by measuring TGF-beta-induced Smad2 phosphorylation and nuclear translocation, TGF-beta-induced PAI-1 expression, TGF-beta-induced luciferase reporter gene expression and TGF-beta-induced growth inhibition. Cholesterol, alone or complexed in lipoproteins (LDL, VLDL), suppresses TGF-beta responsiveness by increasing lipid raft and/or caveolae accumulation of TGF-beta receptors and facilitating rapid degradation of TGF-beta and thus suppressing TGF-beta-induced signaling. Conversely, cholesterol-lowering agents (fluvastatin and lovastatin) and cholesterol-depleting agents (beta-cyclodextrin and nystatin) enhance TGF-beta responsiveness by increasing non-lipid raft microdomain accumulation of TGF-beta receptors and facilitating TGF-beta-induced signaling. Furthermore, the effects of cholesterol on the cultured cells are also found in the aortic endothelium of ApoE-null mice fed a high-cholesterol diet. These results suggest that high cholesterol contributes to atherogenesis, at least in part, by suppressing TGF-beta responsiveness in vascular cells.

TGF-beta 1 polymorphisms and risk of myocardial infarction and stroke: the Rotterdam Study

BACKGROUND AND PURPOSE

Inflammation plays a pivotal role in the pathogenesis of atherosclerosis and of cardiovascular and cerebrovascular complications. Transforming growth factor-beta1 (TGF-beta1) is a pleiotropic cytokine with a central role in inflammation. Little is known of the relation of variations within the gene and risk of cardiovascular and cerebrovascular disease. We therefore investigated 5 polymorphisms in the TGF-beta1 gene (-800 G/A, -509 C/T, codon 10 Leu/Pro, codon 25 Arg/Pro, and codon 263 Thr/Ile) in relation to the risk of myocardial infarction and stroke in a population-based study.

METHODS

Participants (N=6456) of the Rotterdam Study were included in the current study. Analyses of the relations of genotypes with the risk of myocardial infarction and stroke were performed according to Cox proportional-hazards methods. All analyses were adjusted for age, sex, conventional cardiovascular risk factors, and medical history.

RESULTS

We found no association with the risk of myocardial infarction. A significantly increased risk of stroke was found, associated with the T allele of the -509 C/T polymorphism (relative risk, 1.26; (95% CI, 1.06 to 1.49) and the Pro variant of the codon 10 polymorphism (relative risk, 1.24; 95% CI, 1.04 to 1.48).

CONCLUSIONS

No association between the TGF-beta1 polymorphisms and myocardial infarction was observed; however, the -509 C/T and codon 10 Leu/Pro polymorphisms were associated with the risk of stroke.

c-Src and hydrogen peroxide mediate transforming growth factor-beta1-induced smooth muscle cell-gene expression in 10T1/2 cells

OBJECTIVE

Transforming growth factor-beta1 (TGF-beta1) controls the expression of numerous genes, including smooth muscle cell (SMC)-specific genes and extracellular matrix protein genes. Here we investigated whether c-Src plays a role in TGF-beta1 signaling in mouse embryonic fibroblast C3H10T1/2 cells.

METHODS AND RESULTS

TGF-beta1 induction of the SMC contractile protein SM22alpha gene expression was inhibited by PP1 (an inhibitor of Src family kinases) or by C-terminal Src kinase (a negative regulator of c-Src). Induction of SM22alpha by TGF-beta1 was markedly attenuated in SYF cells (c-Src(-), Yes(-), and Fyn(-)) compared with Src(++) cells (c-Src(++), Yes(-), and Fyn(-)). PP1 also inhibited the TGF-beta1-induced expression of serum response factor (SRF), a transcription factor regulating the SMC marker gene expression. Confocal immunofluorescence analysis showed that TGF-beta1 stimulates production of hydrogen peroxide. Antioxidants such as catalase or NAD(P)H oxidase inhibitors such as apocynin inhibited the TGF-beta1-induced expression of SM22alpha. Furthermore, we demonstrate that TGF-beta1 induction of the plasminogen activator inhibitor-1 (PAI-1) gene, which is known to be dependent on Smad but not on SRF, is inhibited by PP1 and apocynin.

CONCLUSIONS

Our results suggest that TGF-beta1 activates c-Src and generates hydrogen peroxide through NAD(P)H oxidase, and these signaling pathways lead to the activation of specific sets of genes, including SM22alpha and PAI-1. TGF-beta1 controls the expression of numerous genes, including SM22alpha and PAI-1. We investigated whether c-Src plays a role in TGF-beta1 signaling. TGF-beta1 induction of such genes was significantly reduced in Src family tyrosine kinase-deficient cells, and Csk and pharmacological inhibitors for Src family kinases or antioxidants inhibit the effects of TGF-beta1. These results indicate that c-Src and hydrogen peroxide are required for TGF-beta1 signaling.

Cytokine gene polymorphisms in ischaemic heart disease: investigation using family-based tests of association

Atherosclerosis has an inflammatory basis, with cytokines, cellular adhesion molecules and pro-inflammatory cells having important roles in the initiation and progression of this process. Interleukin (IL) 6, IL-10 and transforming growth factor (TGF) beta1 have been proposed as important modulators of the atherosclerotic process, with IL-6 having a pro-inflammatory, atherogenic effect and IL-10 and TGF-beta1 having anti-inflammatory, protective roles. The possible role of functional polymorphisms in the promoter regions of the IL-6, IL-10 and TGF-beta1 genes in the susceptibility to ischaemic heart disease (IHD) was investigated in a well-defined Irish population using two recently described family-based tests of association. We genotyped 1,012 individuals from 386 families with at least one member prematurely affected with IHD. Using the combined transmission disequilibrium test (TDT)/sib-TDT and the pedigree disequilibrium test, no association between any of the IL-6 -174G/C, IL-10 -1082G/A and TGF-beta1 -509C/T polymorphisms and IHD was found. Our data demonstrate that, in an Irish population, these polymorphisms are not associated with IHD.

Concerted effect of transforming growth factor-β, cyclin inhibitor p21, and c-mycon smooth muscle cell proliferation

Increased aortic smooth muscle cell (SMC) proliferation is a key event in the pathogenesis of atherosclerosis. Transforming growth factor-β (TGF-β) is one of the potent inhibitors of SMC proliferation. The purpose of this study was 1) to explore the effect of TGF-β inhibition on proliferation of SMC and expression of growth regulatory molecules like p21 and c- myc and 2) to determine whether restoration of cell cycle regulatory molecules normalizes the altered proliferation. To test the role of TGF-β in SMC proliferation, using antisense plasmid DNA, we inhibited TGF-β gene from aortic SMC, which resulted in a significant increase ( P < 0.03) in proliferation (studied by quantifying new DNA synthesis with [3H]thymidine uptake assay). In TGF-β-altered SMC (TASMC), the mRNA expression (studied by RT-PCR) of c- myc was increased whereas that of the cyclin inhibitor p21 was completely inhibited. Using p21 sense plasmid DNA, we transfected p21 gene in TASMC, which restored p21 mRNA and protein expression and decreased proliferation ( P < 0.002) in TASMC. Similar treatment with c- myc antisense oligonucleotides significantly ( P < 0.001) decreased the proliferation of TASMC. TASMC also exhibited alteration in morphological changes in SMC but returned to normal with treatment of p21 and TGF-β sense plasmid DNA. Two-dimensional gel electrophoresis analysis of SMC and TASMC demonstrated differential expression of proteins relevant to cellular proliferation and atherosclerosis. This study uniquely analyzes the effect of TGF-β at the molecular level on proliferation of SMC and on cell cycle regulatory molecules, implicating their potential role in the pathogenesis of atherosclerosis.

Transforming growth factor beta and atherosclerosis: so far, so good for the protective cytokine hypothesis

The role of the anti-inflammatory cytokine transforming growth factor beta (TGF-beta) in atherosclerosis has been the subject of considerable debate for a decade. In the early 1990s, we postulated that TGF-beta played an important role in maintaining normal vessel wall structure and that loss of this protective effect contributed to the development of atherosclerosis. We termed this the protective cytokine hypothesis. This proposal was slow to gain broad acceptance, however, because at that time there were little data available on the role of TGF-beta during the development of atherosclerosis but much information about its role during trauma-induced neointima formation. Because TGF-beta apparently aggravates neointima formation, both by inhibiting endothelial regeneration and by promoting fibrosis, it was difficult to accept that its presence might ameliorate the superficially similar atherogenesis process. But several recent studies revealed beyond doubt the fact that TGF-beta protects against lipid lesion formation, at least in mouse models of atherosclerosis. Therefore, two important questions remain. First, is the role of TGF-beta in vascular biology similar in humans and in mice? Secondly, how important, compared with defects in thrombosis or lipoprotein metabolism, is the protective role of TGF-beta during atherogenesis?

Transforming growth factor (TGF)-beta1 inversely related to vascular cell adhesion molecule-1 in postmenopausal women with coronary artery disease. A possible mechanism for the putative cardioprotective role of TGF-beta1?

OBJECTIVE AND DESIGN

Transforming growth factor beta (TGF-beta1) is involved in a variety of physiological processes as well as in many diseases. Both in vitro and in vivo evidence suggest that TGF-beta1 may influence atherogenesis and a dominant protective role of TGF-beta1 on coronary arteries has been proposed. On the other hand, increased levels of soluble adhesion molecules have been found in patients with atherosclerosis, and adhesion of monocytes to the endothelium followed by migration to the intima, has been proved to be an early event in atherosclerosis. The purpose of the present investigation was to look at a possible relationship between circulating active TGF-beta1 and adhesion molecules in postmenopausal women with angiographically verified coronary heart disease (CHD) (n=118).

RESULTS

Serum levels of the active form of TGF-beta1 showed a tendency to be lower in patients with increasing number of vessels with more than 50% stenosis (P=0.058), and there was higher TGF-beta1 in the group with one vessel disease compared with those with two or more vessels affected (P=0.041). Additionally, negative association between TGF-beta1 and VCAM-1 was found (r=-0.26, P=0.023). However, no associations were observed between TGF-beta1 and intercellular adhesion molecule-1 (ICAM-1) or E-selectin in the present study.

CONCLUSION

We observed an inverse correlation between the active form of TGF-beta1 and VCAM-1 in postmenopausal women with verified CHD. These results may suggest a role of TGF-beta1 in CHD.

TGF-beta1 gene polymorphisms in patients with end-stage heart failure

BACKGROUND

The regulatory cytokine transforming growth factor (TGF)-beta1 is thought to play a role in atherosclerotic heart disease as well as in idiopathic cardiomyopathy. The production of TGF-beta1 is genetically controlled as polymorphisms in the signaling sequence of the TGF-beta1 gene leucine(10)-->proline and arginine(25)-->proline are involved in the regulation of the protein production level. We investigated whether these polymorphisms are associated with end-stage heart failure caused by dilated cardiomyopathy (CMP) or ischemic heart disease (IHD).

METHODS

We determined polymorphisms using sequence specific oligonucleotide probing (SSOP) in genomic DNA samples from heart transplant recipients (n = 253) and controls (n = 94). Indications for transplantation were dilated CMP (n = 109) and IHD (n = 144).

RESULTS

We found a difference in TGF-beta1 codon 10 genotype distribution among patients with IHD, dilated CMP, and controls (p = 0.034; chi(2) test). Patients with dilated CMP differed from patients with IHD (p = 0.044) and healthy controls (0.017). The genotype distribution between patients with IHD and controls was comparable. For codon 25, we found no difference in genotype distribution.

CONCLUSIONS

The Leu(10)-->Pro (codon 10) polymorphism in the TGF-beta1 gene is associated with end-stage heart failure caused by dilated CMP and not with IHD. This observation suggests that TGF-beta1 is involved in the pathogenesis of CMP.

Increased plasma concentrations of TGF-beta1 after hormone replacement therapy

OBJECTIVES AND DESIGN

Hormone replacement therapy (HRT) in postmenopausal women may reduce the cardiovascular risk. A dominant protective role of transforming growth factor beta (TGF-beta1) on coronary arteries has been proposed. Lp(a) lipoprotein may block the activation of latent TGF-beta1. Given this background, we examined the effects of HRT on TGF-beta1 and Lp(a) lipoprotein in 99 postmenopausal women. The women had angiographically documented coronary heart disease (CHD) and were randomized to either sequential transdermal 17beta-oestradiol for 14 weeks and then medroxyprogesterone (MPA) for 14 days (HRT) or to a control group (C).

RESULTS

Serum levels of TGF-beta1 were increased in the HRT group compared with the C group after 3 months' treatment and this effect was sustained after 12 months. There was a significant reduction in Lp(a) lipoprotein serum levels after 3 months' treatment in the HRT group compared with the C group. However, after 12 months, no significant difference in changes in Lp(a) lipoprotein serum levels was detected between the two groups.

CONCLUSION

The novel observation that transdermal 17beta-oestradiol in postmenopausal women increases levels of TGF-beta1 and lowers the concentration of Lp(a) lipoprotein suggests yet another possible mechanism for the cardioprotective effect of HRT. Whereas combination therapy of oestradiol and MPA preserves the beneficial effect on TGF-beta1, it reduces the unopposed oestradiol effects on Lp(a) lipoprotein.