Forkhead transcription factors and cardiovascular biology

Aging and cardiovascular diseases: the role of gene-diet interactions

In the study of longevity, increasing importance is being placed on the concept of healthy aging rather than considering the total number of years lived. Although the concept of healthy lifespan needs to be defined better, we know that cardiovascular diseases (CVDs) are the main age-related diseases. Thus, controlling risk factors will contribute to reducing their incidence, leading to healthy lifespan. CVDs are complex diseases influenced by numerous genetic and environmental factors. Numerous gene variants that are associated with a greater or lesser risk of the different types of CVD and of intermediate phenotypes (i.e., hypercholesterolemia, hypertension, diabetes) have been successfully identified. However, despite the close link between aging and CVD, studies analyzing the genes related to human longevity have not obtained consistent results and there has been little coincidence in the genes identified in both fields. The APOE gene stands out as an exception, given that it has been identified as being relevant in CVD and longevity. This review analyzes the genomic and epigenomic factors that may contribute to this, ranging from identifying longevity genes in model organisms to the importance of gene-diet interactions (outstanding among which is the case of the TCF7L2 gene).

SIRT3 interactions with FOXO3 acetylation, phosphorylation and ubiquitinylation mediate endothelial cell responses to hypoxia

This article reports that hypoxia elicits SIRT3 to deacetylate FOXO3 in endothelial cells. This drives an increase in the expression of mitochondrial antioxidant enzymes, reduces accumulation of reactive oxygen species in mitochondria and thereby confers cellular capacity to adapt to hypoxia.

Acetylated FoxO1 mediates high-glucose induced autophagy in H9c2 cardiomyoblasts: regulation by a polyphenol -(-)-epigallocatechin-3-gallate

OBJECTIVE

FoxO1 acts as a pivotal transcription factor in insulin signaling. However, in hyperglycemia induced cardiac complications, whether FoxO1 is involved remains unclear. The goal of this study was to delineate the potential role of FoxO1 under high-glucose condition.

MATERIALS/METHODS

We investigated insulin resistance and reactive oxygen species (ROS) generation in H9c2 cardiomyoblasts after high-glucose exposure. A series of autophagy biomarkers were measured and further confirmed by LC3 turnover assay. Using gene silencing and overexpression experiments we dissected the molecular mechanisms of FoxO1 regulated autophagy. We also tested the protective effect of (-)-epigallocatechin-3-gallate (EGCG, a green tea-derived polyphenol) in high-glucose treated H9c2 cardiomyoblasts.

RESULTS

High-glucose elicited elevated ROS, autophagy and FoxO1 abundance in cultured H9c2 cardiomyoblasts. Specifically, high-glucose significantly augmented the acetylated FoxO1 in cytosol. In line, compared with 3A-FoxO1 (majorly localized in nuclei with a strong transcriptional activity), overexpression of WT-FoxO1 led to more intense elevated autophagy with enhanced acetylation of FoxO1. In addition, FoxO1 RNAi brought down autophagy induced by high-glucose. Intriguingly, EGCG successfully reversed ROS, autophagy and acetylated FoxO1 in high-glucose treated H9c2 cells.

CONCLUSION

Our findings suggest that FoxO1, especially the acetylated form, regulates high-glucose induced autophagy in H9c2 cardiomyoblasts, which can be prevented by EGCG via a possible ROS-FoxO1 pathway.

AMPK and FoxO1 regulate catalase expression in hypoxic pulmonary arterial smooth muscle

BACKGROUND

Hypoxia and reactive oxygen species (ROS) including H(2)O(2) play major roles in triggering and progression of pulmonary vascular remodeling in persistent pulmonary hypertension. Catalase (CAT), the major endogenous enzyme scavenging H(2)O(2), is regulated in a tissue- and context-specific manner.

OBJECTIVE

To investigate mechanisms by which hypoxia and H(2)O(2) regulate catalase expression, and the role of AMPK-FoxO pathway, in neonatal porcine pulmonary artery smooth muscle (PASMC).

DESIGN/METHODS

PASMC were grown in hypoxia (10% O(2)) or normoxia (21% O(2)) for 72 hr. We measured catalase activity and lipid peroxidation; CAT, FoxO1, and FoxO3a expression by qPCR; protein contents of CAT, FoxOs, p-AMPK, p-AKT, p-JNK, p-ERK1/2 in whole lysates, and FoxOs in nuclear extracts, by immunoblot; and FoxO-1 nuclear localization by immunocytochemistry, quantified by laser scanning cytometry.

RESULTS

Hypoxia upregulated CAT transcription, content and activity, by increasing CAT transcription factors FoxO1 and FoxO3a mRNA, and promoting nuclear translocation of FoxO1. However, lipid peroxidation increased in hypoxic PASMC. Among candidate FoxO regulatory kinases, hypoxia activated AMPK, and decreased p-Akt and ERK1/2. AMPK activation increased FoxO1 (total and nuclear) and CAT, while AMPK inhibition inhibited FoxO1 and CAT, but not FoxO3a. Exogenous H(2)O(2) decreased p-AMPK and increased p-AKT in hypoxic PASMC. This decreased active FoxO1, and reduced mRNA and protein content of CAT. Hypoxic induction of CAT, AKT inhibition (LY294002), or addition of PEG-catalase partly ameliorated the H(2)O(2) -mediated loss of nuclear FoxO1.

CONCLUSIONS

Hypoxia induces catalase expression, though this adaptation is insufficient to protect PASMC from hypoxia-induced lipid peroxidation. This occurs via hypoxic activation of AMPK, which promotes nuclear FoxO1 and thus catalase expression. Exogenous ROS may downregulate cellular antioxidant defenses; H(2)O(2) activates survival factor Akt, decreasing nuclear FoxO1 and thus catalase.

Metformin modulates hyperglycaemia-induced endothelial senescence and apoptosis through SIRT1

Background and Purpose: Endothelial dysfunction can be detected at an early stage in the development of diabetes-related microvascular disease and is associated with accelerated endothelial senescence and ageing. Hyperglycaemia-induced oxidative stress is a major contributing factor to the development of endothelial dysfunction. Clinical data indicate that the hypoglycaemic agent, metformin, has an endothelial protective action; however, its molecular and cellular mechanisms remain elusive. In the present study, we have investigated the protective effect of metformin during hyperglycaemia-induced senescence in mouse microvascular endothelial cells (MMECs).

Experimental Approach: MMECs were cultured in normal glucose (11 mM) and high glucose (HG; 40 mM) in the presence and absence of metformin (50 μM) for 72 h. The expression of sirtuin-1 (SIRT1) and senescence/apoptosis-associated markers was determined by immunoblotting and immunocyto techniques. SIRT1 expression was inhibited with appropriate siRNA.

Key Results: Exposure of MMECs to HG significantly reduced SIRT1 protein expression, increased forkhead box O1 (FoxO-1) and p53 acetylation, increased p21 and decreased Bcl2 expression. In addition, senescence-associated β-galactosidase activity in MMECs was increased in HG. Treatment with metformin attenuated the HG-induced reduction of SIRT1 expression, modulated the SIRT1 downstream targets FoxO-1 and p53/p21, and protected endothelial cells from HG-induced premature senescence. However, following gene knockdown of SIRT1 the effects of metformin were lost.

Conclusions and Implications: HG-induced down-regulation of SIRT1 played a crucial role in diabetes-induced endothelial senescence. Furthermore, the protective effect of metformin against HG-induced endothelial dysfunction was partly due to its effects on SIRT1 expression and/or activity.

Novel mechanism of blood pressure regulation by forkhead box class O1-mediated transcriptional control of hepatic angiotensinogen

The renin-angiotensin system is a major determinant of blood pressure regulation. It consists of a cascade of enzymatic reactions involving 3 components: angiotensinogen, renin, and angiotensin-converting enzyme, which generate angiotensin II as a biologically active product. Angiotensinogen is largely produced in the liver, acting as a major determinant of the circulating renin-angiotensin system, which exerts acute hemodynamic effects on blood pressure regulation. How the expression of angiotensinogen is regulated is not completely understood. Here, we hypothesize that angiotensinogen is regulated by forkhead transcription factor forkhead box class O1 (Foxo1), an insulin-suppressed transcription factor, and thereby controls blood pressure in mice. We generated liver-specific Foxo1 knockout mice, which exhibited a reduction in plasma angiotensinogen and angiotensin II levels and a significant decrease in blood pressure. Using hepatocyte cultures, we demonstrated that overexpression of Foxo1 increased angiotensinogen expression, whereas hepatocytes lacking Foxo1 demonstrated a reduction of angiotensinogen gene expression and partially impaired insulin inhibition on angiotensinogen gene expression. Furthermore, mouse angiotensinogen prompter analysis demonstrated that the angiotensinogen promoter region contains a functional Foxo1-binding site, which is responsible for both Foxo1 stimulation and insulin suppression on the promoter activity. Together, these data demonstrate that Foxo1 regulates hepatic angiotensinogen gene expression and controls plasma angiotensinogen and angiotensin II levels, modulating blood pressure control in mice.

Forkhead BoxO transcription factors restrain exercise-induced angiogenesis

The physiological process of exercise-induced angiogenesis involves the orchestrated upregulation of angiogenic factors together with repression of angiostatic factors. The Forkhead Box 'O' (FoxO) transcription factors promote an angiostatic environment in pathological contexts. We hypothesized that endothelial FoxO1 and FoxO3a also play an integral role in restricting the angiogenic response to aerobic exercise training. A single exercise bout significantly increased levels of FoxO1 and FoxO3a mRNA (5.5- and 1.7-fold, respectively) and protein (1.7- and 2.2-fold, respectively) within the muscles of mice 2 h post-exercise compared to sedentary. Training abolished the exercise-induced increases in both FoxO1 and FoxO3a mRNA and proteins, and resulted in significantly lower nuclear levels of FoxO1 and FoxO3a protein (0.5- and 0.4-fold, respectively, relative to sedentary). Thrombospondin 1 (THBS1) protein level closely mirrored the expression pattern of FoxO proteins. The 1.7-fold increase in THBS1 protein following acute exercise no longer occurred after 10 days of repeated exercise. Endothelial cell-directed conditional deletion of FoxO1/3a/4 in mice prevented the increase in THBS1 mRNA following a single exercise bout. Mice harbouring the endothelial FoxO deletion also demonstrated a significant 20% increase in capillary to muscle fibre ratio after only 7 days of training while 14 days of training was required to elicit a similar increase in wildtype littermates. Our results demonstrate that the downregulation of FoxO1 and FoxO3a proteins facilitates angiogenesis in response to repeated exercise. In conclusion, FoxO proteins can delay exercise-induced angiogenesis, and thus are critical regulators of the physiological angiogenic response in skeletal muscle.

Endurance exercise training inhibits neointimal formation via enhancement of FOXOs expression in balloon-induced atherosclerosis rat model

[Purpose]

This study investigated the effect of endurance exercise on neointimal formation, endothelial-dependant relaxation and FOXO expression in balloon-induced carotid arteries of rats.

[Methods]

Male SD(Sprague-Dawley) rats of 8 weeks ages were randomly divided into 3 groups; Sham-operated control (SO, n=10), Balloon-induced control (BIC, n=10), and Balloon-induced exercise (BIE, n=10). Endurance exercise training was performed on treadmill (18 m/min, 0% grade, 60 min/day, 5 days/week, 4 weeks).

[Results]

Body weight is significantly reduced in BIE compared with BIC. Neointiaml formation in BIC was significantly higher than SO, but it was significantly recovered in BIE compared with BIC. Endothelial-dependent relaxation in BIC was significantly lower than SO, but it was significantly recovered in BIE compared with BIC and expression of FOXO1 and FOXO3a also were significantly increased BIE compared with BIC.

[Conclusion]

These data suggest that endurance exercise inhibits neointimal formation and endothelial-dependent relaxation via FOXO expression in balloon-induce atherosclerosis rat model.

Transcriptional regulation of endothelial cell and vascular development

The establishment and maintenance of the vascular system is critical for embryonic development and postnatal life. Defects in endothelial cell development and vessel formation and function lead to embryonic lethality and are important in the pathogenesis of vascular diseases. Here, we review the underlying molecular mechanisms of endothelial cell differentiation, plasticity, and the development of the vasculature. This review focuses on the interplay among transcription factors and signaling molecules that specify the differentiation of vascular endothelial cells. We also discuss recent progress on reprogramming of somatic cells toward distinct endothelial cell lineages and its promise in regenerative vascular medicine.

Activation of FoxO3a/Bim axis in patients with Primary Biliary Cirrhosis

BACKGROUND/AIMS

Impaired regulation of apoptosis has been suggested to play a role in the pathogenesis of Primary Biliary Cirrhosis (PBC). In this study, we analysed a signalling pathway that comprises the transcription factor FoxO3a and its downstream target Bim, a Bcl-2 interacting mediator of apoptosis.

MATERIALS & METHODS

The tissues examined included livers explanted from patients with cirrhotic PBC, primary sclerosing cholangitis (PSC), alcoholic liver disease (ALD) and liver biopsies from patients with non-cirrhotic PBC. Large margin resections of hepatocellular carcinoma were used as controls.

RESULTS

Expression of FoxO3a and Bim mRNA was significantly enhanced in both non-cirrhotic and end-stage PBC (2.2-fold and 4.3-fold increases, respectively), but not in the other disorders. Similarly, FOXO3a protein level was increased in end-stage PBC (P < 0.05 vs. control). A significant increase in Bim mRNA in non-cirrhotic and cirrhotic PBC was observed (2.2-fold and 8.2-fold respectively). In addition, the most pro-apoptotic isoform of Bim dominated in livers of PBC patients (2.5- fold increase vs. control; P < 0.05). Enhanced FoxO3a and Bim expression was associated with a substantial activation of caspase-3 in PBC (2-fold increase vs. controls; P < 0.0001), whereas it was decreased in both ALD and PSC (46% and 67% reductions respectively). The relationship between FoxO3a and Bim was further investigated in the livers of FoxO-deficient mice. The somatic deletion of FoxO3a caused a significant decrease in Bim, but not caspase-3 protein expression confirming the crucial role of FoxO3a in induction of Bim gene transcription.

CONCLUSIONS

Our results imply that the FoxO3/Bim signalling pathway can be of importance in the livers of patients with PBC.

Parecoxib suppresses CHOP and Foxo1 nuclear translocation, but increases GRP78 levels in a rat model of focal ischemia

Parecoxib, a novel COX-2 inhibitor, functions as a neuroprotective agent and rescues neurons from cerebral ischemic reperfusion injury-induced apoptosis. However, the molecular mechanisms underlying parecoxib neuroprotection remain to be elucidated. There is growing evidence that endoplasmic reticulum (ER) stress plays an important role in neuronal death caused by brain ischemia. However, very little is known about the role of parecoxib in mediating pathophysiological reactions to ER stress induced by ischemic reperfusion injury. Therefore, in the present study, we investigated whether delayed administration of parecoxib attenuates brain damage via suppressing ER stress-induced cell death. Adult male Sprague-Dawley rats were administered parecoxib (10 or 30 mg kg(-1), IP) or isotonic saline twice a day starting 24 h after middle cerebral artery occlusion (MCAO) for three consecutive days. The expressions of glucose-regulated protein 78 (GRP78) and oxygen-regulated protein 150 (ORP150) and C/EBP-homologous protein (CHOP) and forkhead box protein O 1 (Foxo1) in cytoplasmic and nuclear fraction were determined by Western blotting. The levels of caspase-12 expression were checked by immunohistochemistry analysis, served as a marker for ER stress-induced apoptosis. Parecoxib significantly suppressed cerebral ischemic injury-induced nuclear translocation of CHOP and Foxo1 and attenuated the immunoreactivity of caspase-12 in ischemic penumbra. Furthermore, the protective effect of delayed administration of parecoxib was accompanied by an increased GRP78 and ORP150 expression. Therefore, our study suggested that elevation of GRP78 and ORP150, and suppression of CHOP and Foxo1 nuclear translocation may contribute to parecoxib-mediated neuroprotection during ER stress responses.

FoxC1-dependent regulation of vascular endothelial growth factor signaling in corneal avascularity

Angiogenesis is a crucial process whereby new blood vessels are formed from pre-existing vessels, and it occurs under both normal and pathophysiological conditions. The process is precisely regulated through the balance between proangiogenic and anti-angiogenic mechanisms, and many of these mechanisms have been well-characterized through extensive research. However, little is known about how angiogenesis is regulated at the transcriptional level. We have recently shown that deletion of the Forkhead box (Fox) transcription factor Foxc1 in cells of neural crest (NC) lineage leads to aberrant vessel growth in the normally avascular corneas of mice, and that the effect is cell type-specific because the corneas of mice lacking Foxc1 expression in vascular endothelial cells remained avascular. The NC-specific Foxc1 deletion was also associated with elevated levels of both proangiogenic factors, such as the matrix metalloproteases (MMPs) MMP-3, MMP-9, and MMP-19 and the angiogenic inhibitor soluble vascular endothelial growth factor receptor 1 (sVEGFR-1). Thus, FoxC1 appears to control angiogenesis by regulating two distinct and opposing mechanisms; if so, vascular development could be determined, at least in part, by a competitive balance between proangiogenic and anti-angiogenic FoxC1-regulated pathways. In this review, we describe the mechanisms by which FoxC1 regulates vessel growth and discuss how these observations could contribute to a more complete understanding of the role of FoxC1 in pathological angiogenesis.

Back to your heart: ubiquitin proteasome system-regulated signal transduction

Awareness of the regulation of cell signaling by post-translational ubiquitination has emerged over the past 2 decades. Like phosphorylation, post-translational modification of proteins with ubiquitin can result in the regulation of numerous cellular functions, for example, the DNA damage response, apoptosis, cell growth, and the innate immune response. In this review, we discuss recently published mechanisms by which the ubiquitin proteasome system regulates key signal transduction pathways in the heart, including MAPK JNK, calcineurin, FOXO, p53, and estrogen receptors α and β. We then explore how ubiquitin proteasome system-specific regulation of these signal transduction pathways plays a role in the pathophysiology of common cardiac diseases, such as cardiac hypertrophy, heart failure, ischemia reperfusion injury, and diabetes. This article is part of a Special Section entitled "Post-translational Modification."

Life is a pattern: vascular assembly within the embryo

The formation of the vascular system is one of the earliest and most important events during organogenesis in the developing embryo because the growing organism needs a transportation system to supply oxygen and nutrients and to remove waste products. Two distinct processes termed vasculogenesis and angiogenesis lead to a complex vasculature covering the entire body. Several cellular mechanisms including migration, proliferation, differentiation and maturation are involved in generating this hierarchical vascular tree. To achieve this aim, a multitude of signaling pathways need to be activated and coordinated in spatio-temporal patterns. Understanding embryonic molecular mechanism in angiogenesis further provides insight for therapeutic approaches in pathological conditions like cancer or ischemic diseases in the adult. In this review, we describe the current understanding of major signaling pathways that are necessary and active during vascular development.

Forkhead box transcription factor FoxC1 preserves corneal transparency by regulating vascular growth

Normal vision requires the precise control of vascular growth to maintain corneal transparency. Here we provide evidence for a unique mechanism by which the Forkhead box transcription factor FoxC1 regulates corneal vascular development. Murine Foxc1 is essential for development of the ocular anterior segment, and in humans, mutations have been identified in Axenfeld-Rieger syndrome, a disorder characterized by anterior segment dysgenesis. We show that FOXC1 mutations also lead to corneal angiogenesis, and that mice homozygous for either a global (Foxc1(-/-)) or neural crest (NC)-specific (NC-Foxc1(-/-)) null mutation display excessive growth of corneal blood and lymphatic vessels. This is associated with disorganization of the extracellular matrix and increased expression of multiple matrix metalloproteinases. Heterozygous mutants (Foxc1(+/-) and NC-Foxc1(+/-)) exhibit milder phenotypes, such as disrupted limbal vasculature. Moreover, environmental exposure to corneal injury significantly increases growth of both blood and lymphatic vessels in both Foxc1(+/-) and NC-Foxc1(+/-) mice compared with controls. Notably, this amplification of the angiogenic response is abolished by inhibition of VEGF receptor 2. Collectively, these findings identify a role for FoxC1 in inhibiting corneal angiogenesis, thereby maintaining corneal transparency by regulating VEGF signaling.

The Role of FoxC2 Transcription Factor in Tumor Angiogenesis

Much has been learned about the mechanisms underlying tumor angiogenesis, and therapies that target vascular endothelial growth factor (VEGF) to limit tumor angiogenesis and subsequent disease progression have recently been approved. However, the transcriptional mechanisms that regulate pathological angiogenesis remain largely unknown. FoxC2, a member of the Forkhead box (Fox) transcription factor family, is critical for vascular formation during development, and recent studies have shown that FoxC2 is expressed in the endothelium of tumors in both humans and mice. In a B16 mouse melanoma model, Foxc2 deficiency reduced tumor growth and neovascularization and was associated with impairments in mural-cell coverage and increases in endothelial-cell apoptosis in tumor blood vessels. FoxC2 is also expressed by tumor cells in human breast, colonic, and esophageal cancer and participates in the epithelial-mesenchymal transition (EMT), a key process that leads to the invasion and metastasis of aggressive tumors. Collectively, these observations suggest that FoxC2 is essential for tumor angiogenesis and disease progression and that FoxC2 may be a viable target for cancer therapy.

Opposing roles of FoxP1 and Nfat3 in transcriptional control of cardiomyocyte hypertrophy

Cardiac homeostasis is maintained by a balance of growth-promoting and growth-modulating factors. Sustained elevation of calcium signaling can induce cardiac hypertrophy through activation of Nfat family transcription factors. FoxP family transcription factors are known to interact with Nfat proteins and to modulate their transcriptional activities in lymphocytes. We investigated FoxP1 interaction with Nfat3 (Nfatc4) and their effects on transcription of hypertrophy-associated genes in neonatal rat cardiomyocytes. FoxP1-Nfat3 complexes were visualized using bimolecular fluorescence complementation (BiFC) analysis. Calcineurin activation induced FoxP1-Nfat3 BiFC complex formation. Amino acid substitutions in the predicted interaction interface inhibited it. FoxP1 repressed hypertrophy-associated genes (Myh7, Rcan1, Cx43, Anf, and Bnp) and counteracted their activation by constitutively nuclear Nfat3 (cnNfat3). In contrast, FoxP1 activated genes that maintain normal heart functions (Myh6 and p57Kip2) and cnNfat3 counteracted their activation by FoxP1. Amino acid substitutions in FoxP1 or cnNfat3 that inhibited their interaction abrogated the activation of hypertrophy-associated gene transcription by cnNfat3 and the repression of these genes by FoxP1. FoxP1 and Nfat3 co-occupied the promoter regions of hypertrophy-associated genes in neonatal and adult heart tissue. FoxP1 counteracted hypertrophic cardiomyocyte growth, and connexin 43 mislocalization caused by cnNfat3 expression. These data suggest that the opposing transcriptional activities of FoxP1 and Nfat3 maintain cardiomyocyte homeostasis.

Identification of a mechanism underlying regulation of the anti-angiogenic forkhead transcription factor FoxO1 in cultured endothelial cells and ischemic muscle

Chronic limb ischemia, a complication commonly observed in conjunction with cardiovascular disease, is characterized by insufficient neovascularization despite the up-regulation of pro-angiogenic mediators. One hypothesis is that ischemia induces inhibitory signals that circumvent the normal capillary growth response. FoxO transcription factors exert anti-proliferative and pro-apoptotic effects on many cell types. We studied the regulation of FoxO1 protein in ischemic rat skeletal muscle following iliac artery ligation and in cultured endothelial cells. We found that FoxO1 expression was increased in capillaries within ischemic muscles compared with those from rats that underwent a sham operation. This finding correlated with increased expression of p27(Kip1) and reduced expression of Cyclin D1. Phosphorylated Akt was reduced concurrently with the increase in FoxO1 protein. In skeletal muscle endothelial cells, nutrient stress as well as lack of shear stress stabilized FoxO1 protein, whereas shear stress induced FoxO1 degradation. Endogenous FoxO1 co-precipitated with the E3 ubiquitin ligase murine double minute-2 (Mdm2) in endothelial cells, and this interaction varied in direct relation to the extent of Akt and Mdm2 phosphorylation. Moreover, ischemic muscles had a decreased level of Mdm2 phosphorylation and a reduced interaction between Mdm2 and FoxO1. Our results provide novel evidence that the Akt-Mdm2 pathway acts to regulate endothelial cell FoxO1 expression and illustrate a potential mechanism underlying the pathophysiological up-regulation of FoxO1 under ischemic conditions.

Salicylate treatment improves age-associated vascular endothelial dysfunction: potential role of nuclear factor kappaB and forkhead Box O phosphorylation

We hypothesized that I kappa B kinase (IKK)-mediated nuclear factor kappa B and forkhead BoxO3a phosphorylation will be associated with age-related endothelial dysfunction. Endothelium-dependent dilation and aortic protein expression/phosphorylation were determined in young and old male B6D2F1 mice and old mice treated with the IKK inhibitor, salicylate. IKK activation was greater in old mice and was associated with greater nitrotyrosine and cytokines. Endothelium-dependent dilation, nitric oxide (NO), and endothelial NO synthase phosphorylation were lower in old mice. Endothelium-dependent dilation and NO bioavailability were restored by a superoxide dismutase mimetic. Nuclear factor kappa B and forkhead BoxO3a phosphorylation were greater in old and were associated with increased expression/activity of nicotinamide adenine dinucleotide phosphate oxidase and lower manganese superoxide dismutase expression. Salicylate lowered IKK phosphorylation and reversed age-associated changes in nitrotyrosine, endothelium-dependent dilation, NO bioavailability, endothelial NO synthase, nuclear factor kappa B and forkhead BoxO3a phosphorylation, nicotinamide adenine dinucleotide phosphate oxidase, and manganese superoxide dismutase. Increased activation of IKK with advancing age stimulates nuclear factor kappa B and inactivates forkhead BoxO3a. This altered transcription factor activation contributes to a pro-inflammatory/pro-oxidative arterial phenotype that is characterized by increased cytokines and nicotinamide adenine dinucleotide phosphate oxidase and decreased manganese superoxide dismutase leading to oxidative stress-mediated endothelial dysfunction.

Cellular FLICE-inhibitory protein protects against cardiac remodeling induced by angiotensin II in mice

The development of cardiac hypertrophy in response to increased hemodynamic load and neurohormonal stress is initially a compensatory response that may eventually lead to ventricular dilatation and heart failure. Cellular FLICE-inhibitory protein (cFLIP) is a homologue of caspase 8 without caspase activity that inhibits apoptosis initiated by death receptor signaling. Previous studies showed that cFLIP expression was markedly decreased in the ventricular myocardium of patients with end-stage heart failure. However, the critical role of cFLIP on cardiac remodeling remains unclear. To specifically determine the role of cFLIP in pathological cardiac remodeling, we used heterozygote cFLIP(+/-) mice and transgenic mice with cardiac-specific overexpression of the human cFLIP(L) gene. Our results demonstrated that the cFLIP(+/-) mice were susceptible to cardiac hypertrophy and fibrosis through inhibition of mitogen-activated protein kinase kinase-extracellular signal-regulated kinase 1/2 signaling, whereas the transgenic mice displayed the opposite phenotype in response to angiotensin II stimulation. These studies indicate that cFLIP protein is a crucial component of the signaling pathway involved in cardiac remodeling and heart failure.

Regulation of the Pulmonary Circulation in the Fetus and Newborn

During the development of the pulmonary vasculature in the fetus, many structural and functional changes occur to prepare the lung for the transition to air breathing. The development of the pulmonary circulation is genetically controlled by an array of mitogenic factors in a temporo-spatial order. With advancing gestation, pulmonary vessels acquire increased vasoreactivity. The fetal pulmonary vasculature is exposed to a low oxygen tension environment that promotes high intrinsic myogenic tone and high vasocontractility. At birth, a dramatic reduction in pulmonary arterial pressure and resistance occurs with an increase in oxygen tension and blood flow. The striking hemodynamic differences in the pulmonary circulation of the fetus and newborn are regulated by various factors and vasoactive agents. Among them, nitric oxide, endothelin-1, and prostaglandin I2 are mainly derived from endothelial cells and exert their effects via cGMP, cAMP, and Rho kinase signaling pathways. Alterations in these signaling pathways may lead to vascular remodeling, high vasocontractility, and persistent pulmonary hypertension of the newborn.

Haploinsufficiencies of FOXF1 and FOXC2 genes associated with lethal alveolar capillary dysplasia and congenital heart disease

Neonatal deaths account for about 67% of all deaths during the first year of life in the USA. Genetic defects are important factors contributing to neonatal deaths and congenital anomalies. Here we report on the identification of a 1.37 Mb de novo deletion of chromosome 16q24.1-q24.2 by microarray-based comparative genomic hybridization (aCGH) technique in a newborn boy with lethal severe alveolar capillary dysplasia and multiple congenital anomalies who died of irreversible pulmonary hypertension, respiratory failure and cor pulmonale at three days of age. The phenotypic findings and causal genes (FOXF1 and FOXC2) involved in producing this unusual syndrome are detailed. Our findings independently confirm the results in a previous publication describing multiple patients with similar clinical and genetic observations, and highlight the importance of scanning human genomes at high resolution for identifications of micro-imbalances as pathogenic causes in neonates with unexplained congenital anomalies. (c) 2010 Wiley-Liss, Inc.

Specification of arterial, venous, and lymphatic endothelial cells during embryonic development

The groundbreaking discovery about arterial and venous expression of ephrinB2 and EphB4, respectively, in early embryonic development has led to a new paradigm for vascular research, providing compelling evidence that arterial and venous endothelial cells are established by genetic mechanisms before circulation begins. For arterial specification, vascular endothelial growth factor (VEGF) induces expression of Notch signaling genes, including Notch1 and its ligand, Delta-like 4 (Dll4), and Foxc1 and Foxc2 transcription factors directly regulate Dll4 expression. Upon activation of Notch signaling, the Notch downstream genes, Hey1/2 in mice or gridlock in zebrafish, further promote arterial differentiation. On the other hand, the orphan nuclear receptor COUP-TFII is a determinant factor for venous specification by inhibiting expression of arterial specific genes, including Nrp1 and Notch. After arterial and venous endothelial cells differentiate, a subpopulation of venous endothelial cells is thought to become competent to acquire lymphatic endothelial cell fate by progressively expressing the transcription factors Sox18 and Prox1 to differentiate into lymphatic endothelial cells. Therefore, it has now evident that arterial-venous cell fate determination and subsequent lymphatic development are regulated by the multi-step regulatory system associated with the key signaling pathways and transcription factors. Furthermore, new signaling molecules as additional regulators in these processes have recently been identified. As the mechanistic basis for a link between signaling pathways and transcriptional networks in arterial, venous and lymphatic endothelial cells begins to be uncovered, it is now time to summarize the literature on this exciting topic and provide perspectives for future research in the field.

The FoxO family in cardiac function and dysfunction

The Forkhead family of transcription factors mediates many aspects of physiology, including stress response, metabolism, commitment to apoptosis, and development. The Forkhead box subfamily O (FoxO) proteins have garnered particular interest due to their involvement in the modulation of cardiovascular biology. In this review, we discuss the mechanisms of FoxO regulation and outcomes of FoxO signaling under normal and pathological cardiovascular contexts.

FoxO proteins mediate hypoxic induction of connective tissue growth factor in endothelial cells

Hypoxia, a driving force in neovascularization, promotes alterations in gene expression mediated by hypoxia-inducible factor (HIF)-1alpha. Connective tissue growth factor (CTGF, CCN2) is a modulator of endothelial cell growth and migration, but its regulation by hypoxia is poorly understood. Therefore, we analyzed signaling pathways involved in the regulation of CTGF by hypoxia in endothelial cells. Exposure to low oxygen tension or treatment with the hypoxia-mimetic dimethyloxalyl glycine (DMOG) stabilized HIF-1alpha and up-regulated CTGF in human umbilical vein endothelial cells and in a murine microvascular endothelial cell line. Induction of CTGF correlated with a HIF-dependent increase in protein and mRNA levels, and nuclear accumulation of the transcription factor FoxO3a. By contrast, gene expression and cellular localization of FoxO1 were not significantly altered by hypoxia. Expression of CTGF was strongly reduced by siRNA silencing of FoxO1 or FoxO3a. Furthermore, nuclear exclusion of FoxO1/3a transcription factors by inhibition of serine/threonine protein phosphatases by okadaic acid inhibited CTGF expression, providing evidence for both FoxO proteins as regulators of CTGF expression. The DMOG-stimulated induction of CTGF was further increased when endothelial cells were co-incubated with transforming growth factor-beta, an activator of Smad signaling. Activation of RhoA-Rho kinase signaling by the microtubule-disrupting drug combretastatin A4 also enhanced the DMOG-induced CTGF expression, thus placing CTGF induction by hypoxia in a network of interacting signaling pathways. Our findings provide evidence that FoxO1, hypoxia-stimulated expression of FoxO3a and its nuclear accumulation are required for the induction of CTGF by hypoxia in endothelial cells.

Isl1 is a direct transcriptional target of Forkhead transcription factors in second-heart-field-derived mesoderm

The cells of the second heart field (SHF) contribute to the outflow tract and right ventricle, as well as to parts of the left ventricle and atria. Isl1, a member of the LIM-homeodomain transcription factor family, is expressed early in this cardiac progenitor population and functions near the top of a transcriptional pathway essential for heart development. Isl1 is required for the survival and migration of SHF-derived cells into the early developing heart at the inflow and outflow poles. Despite this important role for Isl1 in early heart formation, the transcriptional regulation of Isl1 has remained largely undefined. Therefore, to identify transcription factors that regulate Isl1 expression in vivo, we screened the conserved noncoding sequences from the mouse Isl1 locus for enhancer activity in transgenic mouse embryos. Here, we report the identification of an enhancer from the mouse Isl1 gene that is sufficient to direct expression to the SHF and its derivatives. The Isl1 SHF enhancer contains three consensus Forkhead transcription factor binding sites that are efficiently and specifically bound by Forkhead transcription factors. Importantly, the activity of the enhancer is dependent on these three Forkhead binding sites in transgenic mouse embryos. Thus, these studies demonstrate that Isl1 is a direct transcriptional target of Forkhead transcription factors in the SHF and establish a transcriptional pathway upstream of Isl1 in the SHF.

Krüppel-like factor 4 inhibits proliferation by platelet-derived growth factor receptor beta-mediated, not by retinoic acid receptor alpha-mediated, phosphatidylinositol 3-kinase and ERK signaling in vascular smooth muscle cells

Proliferation inhibition of vascular smooth muscle cells (VSMCs) is governed by the activity of a transcription factor network. Krüppel-like factor 4 (Klf4), retinoic acid receptor (RAR alpha), and platelet-derived growth factor receptor (PDGFR) are expressed in VSMCs and are components of such a network. However, the relationship among them in the regulation of VSMC proliferation remains unknown. Here, we investigated the mechanisms whereby Klf4 mediates the growth inhibitory effects in VSMCs through RAR alpha and PDGFR beta. We demonstrated that Klf4 directly binds to the 5' regulatory region of RAR alpha, down-regulates RAR alpha expression, and specifically inhibits RAR alpha-mediated phosphatidylinositol 3-kinase (PI3K) and ERK signaling in cultured VSMCs induced by the synthetic retinoid Am80. Of particular interest, Klf4 inhibits RAR alpha and PDGFR beta expression while blocking PI3K and ERK signaling induced by Am80 and PDGF-BB, respectively. The anti-proliferative effects of Klf4 on neointimal formation depend largely on PDGFR-mediated PI3K signaling without involvement of the RAR alpha-activated signaling pathways. These findings provide a novel mechanism for signal suppression and growth inhibitory effects of Klf4 in VSMCs. Moreover, the results of this study suggest that Klf4 is one of the key mediators of retinoid actions in VSMCs.

The FOX transcription factors regulate vascular pathology, diabetes and Tregs

A small number of upstream master genes in "higher hierarchy" controls the expression of a large number of downstream genes and integrates the signaling pathways underlying the pathogenesis of cardiovascular diseases with or without autoimmune inflammatory mechanisms. In this brief review, we organize our analysis of recent progress in characterization of forkhead (FOX) transcription factor family members in vascular pathology, diabetes and regulatory T cells into the following sections: (1) Overview of the FOX transcription factor superfamily; (2) Vascular pathology of mice deficient in FOX transcription factors; (3) Roles of FOX transcription factors in endothelial cell pathology; (4) Roles of FOX transcription factors in vascular smooth muscle cells; (5) Roles of FOX transcription factors in the pathogenesis of diabetes; and (6) Immune system phenotypes of mice deficient in FOX transcription factors. Advances in these areas suggest that the FOX transcription factor family plays important roles in vascular development and in the pathogenesis of autoimmune inflammatory cardiovascular diseases.

Cardioprotection by vanadium compounds targeting Akt-mediated signaling

Treatment with inorganic and organic compounds of vanadium has been shown to exert a wide range of cardioprotective effects in myocardial ischemia/reperfusion-induced injury, myocardial hypertrophy, hypertension, and vascular diseases. Furthermore, administration of vanadium compounds improves cardiac performance and smooth muscle cell contractility and modulates blood pressure in various models of hypertension. Like other vanadium compounds, we documented bis(1-oxy-2-pyridinethiolato) oxovanadium (IV) [VO(OPT)] as a potent cardioprotective agent to elicit cardiac functional recovery in myocardial infarction and pressure overload-induced hypertrophy. Vanadium compounds activate Akt signaling through inhibition of protein tyrosine phosphatases, thereby eliciting cardioprotection in myocardial ischemia/reperfusion-induced injury and myocardial hypertrophy. Vanadium compounds also promote cardiac functional recovery by stimulation of glucose transport in diabetic heart. We here discuss the current understanding of mechanisms underlying vanadium compound-induced cardioprotection and propose a novel therapeutic strategy targeting for Akt signaling to rescue cardiomyocytes from heart failure.

Foxc2 transcription factor: a newly described regulator of angiogenesis

Angiogenesis is a critical process to form new blood vessels from preexisting vessels under physiologic and pathologic conditions and involves cellular and morphologic changes such as endothelial cell proliferation, migration, and vascular tube formation. Despite evidence that angiogenic factors, including vascular endothelial growth factor and Notch, control various aspects of angiogenesis, the molecular mechanisms underlying gene regulation in blood vessels and surrounding tissues are not fully understood. Importantly, recent studies demonstrate that Forkhead transcription factor Foxc2 directly regulates expression of various genes involved in angiogenesis, CXCR4, integrin beta3, Delta-like 4 (Dll4), and angiopoietin 2, thereby controlling angiogenic processes. Thus, Foxc2 is now recognized as a novel regulator of vascular formation and remodeling. This review summarizes current knowledge about the function of Foxc2 in angiogenesis and discusses prospects for future research in Foxc2-mediated pathologic angiogenesis in cardiovascular disease.

Transcriptional control of endothelial cell development

The transcription factors that regulate endothelial cell development have been a focus of active research for several years, and many players in the endothelial transcriptional program have been identified. This review discusses the function of several major regulators of endothelial transcription, including members of the Sox, Ets, Forkhead, GATA, and Kruppel-like families. This review also highlights recent developments aimed at unraveling the combinatorial mechanisms and transcription factor interactions that regulate endothelial cell specification and differentiation during vasculogenesis and angiogenesis.

The forkhead transcription factors play important roles in vascular pathology and immunology

Transcription factor families are a small number of upstream master genes in "higher hierarchy" that control the expression of a large number of downstream genes. These transcription factors have been found to integrate the signaling pathways underlying the pathogenesis of cardiovascular diseases with or without autoimmune inflammatory mechanisms. In this chapter, we organize our analysis of recent progress in characterization of forkhead (Fox) transcription factor family members in vascular pathology and immune regulation into the following sections: (1) Introduction of the FOX transcription factor superfamily; (2) FOX transcription factors and endotheial cell pathology; (3) FOX transcription factors and vascular smooth muscle cells; and (4) FOX transcription factors, inflammation and immune system. Advances in these areas suggest that the FOX transcription factor family is important in regulating vascular development and the pathogenesis of autoimmune inflammatory cardiovascular diseases.

Targeting protein kinase B/Akt signaling with vanadium compounds for cardioprotection

BACKGROUND

Akt is an important signaling molecule that modulates many cellular processes such as cell growth, survival and metabolism. Akt activation has been proposed as a potential strategy for increasing cardiomyocyte survival following ischemia.

OBJECTIVES

Vanadium compounds activate Akt signaling through inhibition of protein tyrosine phosphatases, thereby eliciting cardioprotection in myocardial ischemia/reperfusion-induced injury along with cardiac functional recovery. Like other vanadium compounds, we documented bis(1-oxy-2-pyridinethiolato) oxovanadium (IV) as a potent cytoprotective agent on myocardial infarction and elicited cardiac functional recovery through activation of Akt signaling pathway.

RESULTS/CONCLUSION

The ability of vanadium compounds to activate Akt signaling pathways are responsible for their ability to modulate cardiovascular functions and is probably beneficial as a cardioprotective drug in subjects undergoing reperfusion therapy following myocardial infarction.