Endothelial FoxO1 is an intrinsic regulator of thrombospondin 1 expression that restrains angiogenesis in ischemic muscle

A Novel tRNA-Derived Fragment, tRFGlnCTG, Regulates Angiogenesis by Targeting Antxr1 mRNA

As a novel non-coding RNA with important functions corresponding to various cellular stresses, the function of tRFs in angiogenesis remains unclear. Firstly, small RNA sequencing was performed on normal and post-muscle injury mouse tibialis anterior muscle to identify and analyse differentially expressed tRF/tiRNA. tRNA GlnCTG-derived fragments (tRFGlnCTG) were found to be overexpressed in high abundance in the damaged muscle. Subsequent in vitro experiments revealed that the overexpression of tRFGlnCTG suppressed the vascular endothelial cells' viability, cell cycle G1/S transition, proliferation, migration, and tube-formation capacity. Similarly, in vivo experiments showed that the tRFGlnCTG decreased the relative mRNA levels of vascular endothelial cell markers and pro-angiogenic factors and reduced the proportion of CD31-positive cells. Finally, luciferase activity analysis confirmed that the tRFGlnCTG directly targeted the 3'UTR of Antxr1, leading to a significant reduction in the mRNA expression of the target gene. These results suggest that tRFGlnCTG is a key regulator of vascular endothelial cell function. The results provide a new idea for further exploration of the molecular mechanisms that regulate angiogenesis.

Wildland fire, air pollution and cardiovascular health: is it time to focus on the microvasculature as a risk assessment tool?

Climate change favors weather conditions conducive to wildland fires. The intensity and frequency of forest fires are increasing, and fire seasons are lengthening. Exposure of human populations to smoke emitted by these fires increases, thereby contributing to airborne pollution through the emission of gas and particulate matter (PM). The adverse health outcomes associated with wildland fire exposure represent an important burden on the economies and health systems of societies. Even though cardiovascular diseases (CVDs) are the main of cause of the global burden of diseases attributable to PM exposure, it remains difficult to show reliable associations between exposure to wildland fire smoke and cardiovascular disease risk in population-based studies. Optimal health requires a resilient and adaptable network of small blood vessels, namely, the microvasculature. Often alterations of this microvasculature precede the occurrence of adverse health outcomes, including CVD. Biomarkers of microvascular health could then represent possible markers for the early detection of poor cardiovascular outcomes. This review aims to synthesize the current literature to gauge whether assessing the microvasculature can better estimate the cardiovascular impact of wildland fires.

Angiostatic freeze or angiogenic move? Acute cold stress prevents angiokine secretion from murine myotubes but primes primary endothelial cells for greater migratory capacity

The skeletal muscle tissue can adapt to exercise and environmental stressors with a remarkable plasticity. Prolonged cold stress exposure has been associated to increased skeletal muscle capillarization. Angioadaptation refers to the coordinated molecular and cellular processes that influence the remodeling of skeletal muscle microvasculature. Two cell types are central to angioadaptation: the myocytes, representing an important source of angiokines; and the skeletal muscle endothelial cell (SMECs), targets of these angiokines and main constituents of muscle capillaries. The influence of cold stress on skeletal muscle angioadaptation remains largely unknown, particularly with respect to myocyte-specific angiokines secretion or endothelial cell angioadaptive responses. Here, we use an in vitro model to investigate the impact of cold stress (28°C versus 37°C) on C2C12 myotubes and SMECs. Our main objectives were to evaluate: 1) the direct impact of cold stress on C2C12 cellular expression of angiokines and their release in the extracellular environment; 2) the indirect impact of cold stress on SMECs migration via these C2C12-derived angiokines; and 3) the direct effect of cold stress on SMECs angioadaptive responses, including migration, proliferation, and the activation of the vascular endothelial growth factor receptor-2 (VEGFR2). Cold stress reduced the secretion of angiokines in C2C12 myotubes culture media irrespective their pro-angiogenic or angiostatic nature. In SMECs, cold stress abrogated cell proliferation and reduced the activation of VEGFR2 despite a greater expression of this receptor. Finally, SMECs pre-conditioned to cold stress displayed an enhanced migratory response when migration was stimulated in rewarming conditions. Altogether our results suggest that cold stress may be overall angiostatic. However, cold stress accompanied by rewarming may be seen as a pro-angiogenic stressor for SMECs. This observation questions the potential for using pre-cooling in sport-performance or therapeutic exercise prescription to enhance skeletal muscle angioadaptive responses to exercise.

Phytochemical Analysis, Total Phenolic, Flavonoid Contents, and Anticancer Evaluations of Solvent Extracts and Saponins of H. digitata

Cancer is one of the most challenging diseases in the modern era for the researchers and investigators. Extensive research worldwide is underway to find novel therapeutics for prevention and treatment of diseases. The extracted natural sources have shown to be one of the best and effective treatments for cell proliferation and angiogenesis. Different approaches including disc potato model, brine shrimp, and chorioallantoic membrane (CAM) assay were adopted to analyze the anticancer effects. Habenaria digitata was also evaluated for MTT activity against NIH/3T3 cell line. The dexamethasone, etoposide, and vincristine sulfate were used as a positive control in these assays. All of the extracts including crude extracts (Hd.Cr), saponin (Hd.Sp), n-hexane (Hd.Hx), chloroform (Hd.Chf), ethyl acetate (Hd.EA), and aqueous fraction (Hd.Aq) were shown excellent results by using various assays. For example, saponin and chloroform have displayed decent antitumor and angiogenic activity by using potato tumor assay. The saponin fraction and chloroform were shown to be the most efficient in potato tumor experiment, demonstrating 87.5 and 93.7% tumor suppression at concentration of 1000 μg/ml, respectively, with IC50 values of 25.5 and 18.3 μg/ml. Additionally, the two samples, chloroform and saponins, outperformed the rest of the test samples in terms of antiangiogenic activity, with IC50 28.63 μg/ml and 16.20 μg/ml, respectively. In characterizing all solvent fractions, the chloroform (Hd.Chf) and saponin (Hd.Sp) appeared to display good effectiveness against tumor and angiogenesis but very minimal activity against A. tumefaciens. The Hd.Chf and Hd.Sp have been prospective candidates in the isolation of natural products with antineoplastic properties.

Time course of capillary regression and an expression balance between vascular endothelial growth factor-A and thrombospondin-1 in the soleus muscle of hindlimb unloaded rats

INTRODUCTION/AIMS

Skeletal muscle capillaries regress with disuse; however, information on time-dependent changes in the expression of pro- and anti-angiogenic factors in disused muscle is limited. This study aimed to clarify time-dependent changes in skeletal muscle capillarization, pro-angiogenic vascular endothelial growth factor-A (VEGF-A), and anti-angiogenic thrombospondin-1 (TSP-1) in the soleus muscle of hindlimb unloaded rat.

METHODS

Eight-week-old male Sprague Dawley rats were randomly divided into four groups corresponding to different hindlimb unloading (HU) duration at 0, 1, 2, and 3 weeks.

RESULTS

Muscle atrophy and capillary regression worsened in the soleus muscle with longer periods of HU. The VEGF-A protein expression level was lower at week 1 than at week 0. In addition, the value at week 3 was also lower than those at weeks 0, 1, and 2. The TSP-1 protein expression level was higher at week 1 than that at week 0 but was similar at weeks 2 and 3. Moreover, reactive oxygen species, assessed by dihydroethidium fluorescence intensity on cryosection, were higher at weeks 2 and 3 than that at week 0.

DISCUSSION

Depending on the HU period, VEGF-A and TSP-1 showed different expression patterns. In the early HU phase, TSP-1 may play an important role in capillary regression. However, when HU extends for a longer period, decreased VEGF-A, and/or increased oxidative stress may be more involved in capillary regression. This article is protected by copyright. All rights reserved.

Resveratrol Promotes Angiogenesis in a FoxO1-Dependent Manner in Hind Limb Ischemia in Mice

Critical limb ischemia (CLI) is a severe form of peripheral artery diseases (PAD) and seriously endangers the health of people. Therapeutic angiogenesis represents an important treatment strategy for CLI; various methods have been applied to enhance collateral circulation. However, the current development drug therapy to promote angiogenesis is limited. Resveratrol (RSV), a polyphenol compound extracted from plants, has various properties such as anti-oxidative, anti-inflammatory and anti-cancer effects. Whether RSV exerts protective effects on CLI remains elusive. In the current study, we demonstrated that oral intake of RSV significantly improved hind limb ischemia in mice, and increased the expression of phosphorylated Forkhead box class-O1 (FoxO1). RSV treatment in human umbilical vein endothelial cells (HUVECs) could increase the phosphorylation of FoxO1 and its cytoplasmic re-localization to promote angiogenesis. Then we manipulated FoxO1 in HUVECs to further verify that the effect of RSV on angiogenesis is in a FoxO1-dependent manner. Furthermore, we performed metabolomics to screen the metabolic pathways altered upon RSV intervention. We found that the pathways of pyrimidine metabolism, purine metabolism, as well as alanine, aspartate and glutamate metabolism, were highly correlated with the beneficial effects of RSV on the ischemic muscle. This study provides a novel direction for the medical therapy to CLI.

Antioxidative and Angiogenic Hyaluronic Acid-Based Hydrogel for the Treatment of Peripheral Artery Disease

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by blockages of the arteries supplying the lower extremities. Ischemia initiates oxidative damage and mitochondrial dysfunction in the legs of PAD patients, causing injury to the tissues of the leg, significant decline in walking performance, leg pain while walking, and in the most severe cases, nonhealing ulcers and gangrene. Current clinical trials based on cells/stem cells, the trophic factor, or gene therapy systems have shown some promising results for the treatment of PAD. Biomaterial matrices have been explored in animal models of PAD to enhance these therapies. However, current biomaterial approaches have not fully met the essential requirements for minimally invasive intramuscular delivery to the leg. Ideally, a biomaterial should present properties to ameliorate oxidative stress/damage and failure of angiogenesis. Recently, we have created a thermosensitive hyaluronic acid (HA) hydrogel with antioxidant capacity and skeletal muscle-matching stiffness. Here, we further optimized HA hydrogels with the cell adhesion peptide RGD to facilitate the development of vascular-like structures in vitro. The optimized HA hydrogel reduced intracellular reactive oxygen species levels and preserved vascular-like structures against H₂O₂-induced damage in vitro. HA hydrogels also provided prolonged release of the vascular endothelial growth factor (VEGF). After injection into rat ischemic hindlimb muscles, this VEGF-releasing hydrogel reduced lipid oxidation, regulated oxidative-related genes, enhanced local blood flow in the muscle, and improved running capacity of the treated rats. Our HA hydrogel system holds great potential for the treatment of the ischemic legs of patients with PAD.

Altitude, Exercise, and Skeletal Muscle Angio-Adaptive Responses to Hypoxia: A Complex Story

Hypoxia, defined as a reduced oxygen availability, can be observed in many tissues in response to various physiological and pathological conditions. As a hallmark of the altitude environment, ambient hypoxia results from a drop in the oxygen pressure in the atmosphere with elevation. A hypoxic stress can also occur at the cellular level when the oxygen supply through the local microcirculation cannot match the cells’ metabolic needs. This has been suggested in contracting skeletal myofibers during physical exercise. Regardless of its origin, ambient or exercise-induced, muscle hypoxia triggers complex angio-adaptive responses in the skeletal muscle tissue. These can result in the expression of a plethora of angio-adaptive molecules, ultimately leading to the growth, stabilization, or regression of muscle capillaries. This remarkable plasticity of the capillary network is referred to as angio-adaptation. It can alter the capillary-to-myofiber interface, which represent an important determinant of skeletal muscle function. These angio-adaptive molecules can also be released in the circulation as myokines to act on distant tissues. This review addresses the respective and combined potency of ambient hypoxia and exercise to generate a cellular hypoxic stress in skeletal muscle. The major skeletal muscle angio-adaptive responses to hypoxia so far described in this context will be discussed, including existing controversies in the field. Finally, this review will highlight the molecular complexity of the skeletal muscle angio-adaptive response to hypoxia and identify current gaps of knowledges in this field of exercise and environmental physiology.

Bioengineering strategies for the treatment of peripheral arterial disease

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by narrowing and occlusion of arteries supplying the lower extremities. Approximately 200 million people worldwide are affected by PAD. The current standard of operative care is open or endovascular revascularization in which blood flow restoration is the goal. However, many patients are not appropriate candidates for these treatments and are subject to continuous ischemia of their lower limbs. Current research in the therapy of PAD involves developing modalities that induce angiogenesis, but the results of simple cell transplantation or growth factor delivery have been found to be relatively poor mainly due to difficulties in stem cell retention and survival and rapid diffusion and enzymolysis of growth factors following injection of these agents in the affected tissues. Biomaterials, including hydrogels, have the capability to protect stem cells during injection and to support cell survival. Hydrogels can also provide a sustained release of growth factors at the injection site. This review will focus on biomaterial systems currently being investigated as carriers for cell and growth factor delivery, and will also discuss biomaterials as a potential stand-alone method for the treatment of PAD. Finally, the challenges of development and use of biomaterials systems for PAD treatment will be reviewed.

Murine double minute-2 mediates exercise-induced angiogenesis in adipose tissue of diet-induced obese mice

OBJECTIVE

This study aimed to determine the effects of physical exercise on the angio-adaptive response in adipose tissue following weight loss in a mouse model of diet-induced obesity. We hypothesized that physical exercise stimulates angiogenesis through the regulation of Vascular endothelial growth factor-A (VEGF-A) pro-/Thrombospondin-1 (TSP-1) anti-angiogenic signal under the control of the Murine double-minute 2/Forkhead box Os (Mdm2/FoxOs) axis, as reported in skeletal muscle.

METHODS

We studied the effects of 7 weeks-voluntary exercise (Ex) in C57Bl/6 control or diet-induced obese (HFS) mice on vascularization of white adipose tissue (AT).

RESULTS

Diet-induced obese sedentary (HFSsed) mice presented a powerful angiostatic control in all adipose tissues, under FoxOs protein regulation, leading to capillary rarefaction. Exercise increased expression of Mdm2, repressing the angiostatic control in favor of adipose vascular regrowth in normal chow (NCex) and HFSex mice. This phenomenon was associated with adipocytes microenvironment improvement, such as decreased adipocytes hypertrophy and adipose tissue inflammation. In addition, adipose angiogenesis stimulation by exercise through Mdm2 pro-angiogenic action, improved visceral adipose insulin sensitivity, activated browning process within subcutaneous adipose tissue (ScWAT) and decreased ectopic fat deposition (muscle, heart and liver) in obese HFSex mice. The overall result of this approach of therapy by physical exercise is an improvement of all systemic cardiometabolic parameters.

CONCLUSIONS

These data demonstrated the therapeutic efficacy of physical exercise against obesity-associated pathologies, and also offer new prospects for molecular therapies targeting the adipose angio-adaptation in obese humans.

Thrombospondin-1 in maladaptive aging responses: a concept whose time has come

Numerous age-dependent alterations at the molecular, cellular, tissue and organ systems levels underlie the pathophysiology of aging. Herein, the focus is upon the secreted protein thrombospondin-1 (TSP1) as a promoter of aging and age-related diseases. TSP1 has several physiological functions in youth, including promoting neural synapse formation, mediating responses to ischemic and genotoxic stress, minimizing hemorrhage, limiting angiogenesis, and supporting wound healing. These acute functions of TSP1 generally require only transient expression of the protein. However, accumulating basic and clinical data reinforce the view that chronic diseases of aging are associated with accumulation of TSP1 in the extracellular matrix, which is a significant maladaptive contributor to the aging process. Identification of the relevant cell types that chronically produce and respond to TSP1 and the molecular mechanisms that mediate the resulting maladaptive responses could direct the development of therapeutic agents to delay or revert age-associated maladies.

Considering the Role of Murine Double Minute 2 in the Cardiovascular System?

The E3 ubiquitin ligase Murine double minute 2 (MDM2) is the main negative regulator of the tumor protein p53 (TP53). Extensive studies over more than two decades have confirmed MDM2 oncogenic role through mechanisms both TP53-dependent and TP53-independent oncogenic function. These studies have contributed to designate MDM2 as a therapeutic target of choice for cancer treatment and the number of patents for MDM2 antagonists has increased immensely over the last years. However, the question of the physiological functions of MDM2 has not been fully resolved yet, particularly when expressed and regulated physiologically in healthy tissue. Cardiovascular complications are almost an inescapable side-effect of anti-cancer therapies. While several MDM2 antagonists are entering phase I, II and even III of clinical trials, this review proposes to bring awareness on the physiological role of MDM2 in the cardiovascular system.

Endothelial specific deletion of FOXO1 alters pericyte coverage in the developing retina

Pericytes are mural cells that cover small blood vessels. While defects in pericyte coverage are known to be involved in various vessel related pathologies, including diabetic retinopathy, the molecular mechanisms underlying pericyte coverage are not fully understood. In this study, we investigated the contribution of the forkhead transcription factor FOXO1 in endothelial cells to pericyte coverage in the developing retina. We observed retinal pericytes in tamoxifen-inducible endothelium-specific Foxo1 deletion mice. Tamoxifen was injected at postnatal day 1-3 and the retinas were harvested at P21. Our results demonstrated that Foxo1 deletion in the endothelium affected arteriole pericyte morphology without altering pericyte number, proliferation, and apoptosis. We hypothesized that abnormal pericyte morphogenesis in the knockout retina was caused by impaired pericyte differentiation. FOXO1 silencing by siRNA in the primary artery endothelium further revealed that THBS1 (thrombospondin 1), which promotes pericyte differentiation via TGFβ activation, was reduced in the FOXO1-deficient endothelium. Immunohistochemistry of FOXO1 knockout mice showed reduced numbers of phospho-Smad3⁺ arteriole pericytes compared with wild-type mice. In addition, endothelium-pericyte co-culture analysis revealed that pericytes cultured with FOXO1-deficient endothelial cells failed to differentiate sufficiently; this failure was partially rescued by the addition of recombinant THBS1 to the supernatant. The findings suggest that endothelial FOXO1 contributes to pericyte differentiation via regulation of THBS1 expression. This study provides new insights into the molecular mechanism of pericyte coverage in the context of endothelium-derived regulation and highlights a new therapeutic target for pericyte-related pathology.

Application of transcutaneous carbon dioxide improves capillary regression of skeletal muscle in hyperglycemia

The purpose of the present study was to determine the effects of transcutaneous CO2 application on the blood flow and capillary architecture of the soleus muscle in rats with streptozotocin (STZ)-induced hyperglycemia. Wistar rats were randomly divided into four groups: control, control + CO2-treated, STZ-induced hyperglycemia, and STZ-induced hyperglycemia + CO2-treated groups. Blood flow in soleus muscle increased during the transcutaneous CO2 exposure, and continued to increase for 30 min after the treatment. In addition, the transcutaneous CO2 attenuated a decrease in capillary and the expression level of eNOS and VEGF protein, and an increase in the expression level of MDM-2 and TSP-1 protein of soleus muscle due to STZ-induced hyperglycemia. These results indicate that the application of transcutaneous CO2 could improve capillary regression via the change of pro- and anti-angiogenesis factors, which might be induced by an increase in blood flow.

Hyperglycaemia correlates with skeletal muscle capillary regression and is associated with alterations in the murine double minute-2/forkhead box O1/thrombospondin-1 pathway in type 1 diabetic BioBreeding rats

Type 1 diabetes can have deleterious effects on skeletal muscle and its microvasculature. Our laboratory has recently identified murine double minute-2 as a master regulator of muscle microvasculature by controlling expression levels of two key molecular actors of the angio-adaptive process: the pro-angiogenic vascular endothelial growth factor-A and the anti-angiogenic thrombospondin-1. Here, we show for the first time that in the soleus and plantaris muscles of the diabetes-prone BioBreeding rats, a rodent model of autoimmune type 1 diabetes, murine double minute-2 protein levels are significantly decreased, coinciding with elevated protein levels of thrombospondin-1 and its transcription factor forkhead box O1. Significant capillary regression was observed to similar extent in soleus and plantaris muscles of type 1 diabetic rats. Elevated blood glucose levels were correlated with the loss of capillaries, the reduction in murine double minute-2 expression and with the elevations in thrombospondin-1. Vascular endothelial growth factor-A protein levels were unaltered or even increased in diabetic animals, yet type 1 diabetic animals had less vascular endothelial growth factor receptor-2 abundance. The vascular endothelial growth factor-A/thrombospondin-1 ratio, a good indicator of skeletal muscle angio-adaptive environment, was decreased in type 1 diabetic muscle. Our results suggest that the murine double minute-2-forkhead box O1-thrombospondin-1 pathway plays an important role in angio-regulation of the skeletal muscle in the pathophysiological context of type 1 diabetes.

Endothelial-specific FoxO1 depletion prevents obesity-related disorders by increasing vascular metabolism and growth

Impaired angiogenesis is a hallmark of metabolically dysfunctional adipose tissue in obesity. However, the underlying mechanisms restricting angiogenesis within this context remain ill-defined. Here, we demonstrate that induced endothelial-specific depletion of the transcription factor Forkhead Box O1 (FoxO1) in male mice led to increased vascular density in adipose tissue. Upon high-fat diet feeding, endothelial cell FoxO1-deficient mice exhibited even greater vascular remodeling in the visceral adipose depot, which was paralleled with a healthier adipose tissue expansion, higher glucose tolerance and lower fasting glycemia concomitant with enhanced lactate levels. Mechanistically, FoxO1 depletion increased endothelial proliferative and glycolytic capacities by upregulating the expression of glycolytic markers, which may account for the improvements at the tissue level ultimately impacting whole-body glucose metabolism. Altogether, these findings reveal the pivotal role of FoxO1 in controlling endothelial metabolic and angiogenic adaptations in response to high-fat diet and a contribution of the endothelium to whole-body energy homeostasis.

In the body, thread-like blood vessels called capillaries weave their way through our tissues to deliver oxygen and nutrients to every cell. When a tissue becomes bigger, existing vessels remodel to create new capillaries that can reach far away cells. However, in obesity, this process does not happen the way it should: when fat tissues expand, new blood vessels do not always grow to match. The starved fat cells can start to dysfunction, which causes a range of issues, from inflammation and scarring of the tissues to problems with how the body processes sugar and even diabetes. Yet, it is still unclear why exactly new capillaries fail to form in obesity.

What we know is that a protein called FoxO (short for Forkhead box O) is present in the cells that line the inside of blood vessels, and that it can stop the development of new capillaries. FoxO controls how cells spend their energy, and it can force them to go into a resting state. During obesity, the levels of FoxO actually increase in capillary cells. Therefore, it may be possible that FoxO prevents new blood vessels from growing in the fat tissues of obese individuals.

To find out, Rudnicki et al. created mice that lack the FoxO protein in the cells lining the capillaries, and then fed the animals a high-fat diet. These mutant mice had more blood vessels in their fat tissue, and their fat cells looked healthier. They also stored less fat than normal mice on the same diet, and their blood sugar levels were normal. This was because the FoxO-deprived cells inside capillaries were burning more energy, which they may have obtained by pulling sugar from the blood.

These results show that targeting the cells that line capillaries helps new blood vessels to grow, and that this could mitigate the health problems that arise with obesity, such as high levels of sugar (diabetes) and fat in the blood. However, more work is needed to confirm that the same cellular processes can be targeted to obtain positive health outcomes in humans.

Metabolic Regulation of Angiogenesis in Diabetes and Aging

Impaired angiogenesis and endothelial dysfunction are hallmarks of diabetes and aging. Clinical efforts at promoting angiogenesis have largely focused on growth factor pathways, with mixed results. Recently, a new repertoire of endothelial intracellular molecules critical to endothelial metabolism has emerged as playing an important role in regulating angiogenesis. This review thus focuses on the emerging importance and therapeutic potential of these proteins and of endothelial bioenergetics in diabetes and aging.

Increased skeletal muscle mitochondrial free radical production in peripheral arterial disease despite preserved mitochondrial respiratory capacity

NEW FINDINGS

What is the central question of this study? What is the degree to which skeletal muscle mitochondria-derived reactive oxygen species (ROS) production is linked to impaired skeletal muscle function in patients with early-stage peripheral arterial disease (PAD) and what is the impact on mitochondrial respiratory capacity? What is the main finding and its importance? This is the first study to document increased mitochondria-derived reactive oxygen species production associated with elevated intramuscular oxidative stress, despite preserved mitochondrial respiratory function, in patients with PAD. Furthermore, systemic inflammation, mitochondria-derived ROS production and skeletal muscle oxidative stress were strongly correlated to disease severity, as indicated by ankle-brachial index, in patients with PAD.

ABSTRACT

Skeletal muscle mitochondrial dysfunction, which is not fully explained by disease-related arterial occlusion, has been implicated in the pathophysiology of peripheral arterial disease (PAD). Therefore, this study comprehensively assessed mitochondrial respiratory function in biopsies from the gastrocnemius of 10 patients with PAD (Fontaine Stage II) and 12 healthy controls (HC). Intramuscular and systemic inflammation, mitochondria-derived reactive oxygen species (ROS) production, and oxidative stress were also assessed to better understand the mechanisms responsible for the proposed PAD-induced mitochondrial dysfunction. Interestingly, mitochondrial respiratory capacity, assessed as complex I (CI) and complex II (CII)-driven State 3 respiration, measured separately and in combination (State 3 CI+II), revealed no difference between the patients with PAD and the HC. However, mitochondria-derived ROS production was significantly elevated in PAD (HC: 1.0 ± 0.9; PAD: 4.3 ± 1.0 AU (mg tissue)^-1 ). Furthermore, patients with PAD exhibited significantly greater concentrations of the pro-inflammatory markers tumour necrosis factor α in plasma (HC: 0.9 ± 0.4; PAD: 2.0 ± 0.3 pg ml^-1 ) and interleukin 6 in both plasma (HC: 2.3 ± 0.4; PAD: 4.3 ± 0.5 pg ml^-1 ) and muscle (∼75% greater). Intramuscular oxidative stress, assessed by protein carbonyls and 4-hydroxynonenal, was significantly greater in PAD compared to HC. Ankle brachial index was significantly correlated with intramuscular inflammation, oxidative stress and mitochondria-derived ROS production. Thus, elevated intramuscular inflammation, oxidative stress and mitochondria-derived ROS production are likely to contribute to the pathophysiology of the skeletal muscle dysfunction associated with PAD, even in the presence of preserved mitochondrial respiratory function in this population.

FOXOs in cancer immunity: Knowns and unknowns

In the tumor microenvironment (TME), cancer cells, stromal cells, and immune cells, along with their extracellular factors, have profound effects on either promoting or repressing anti-cancer immunity. Accumulating evidence has shown the paradoxical intrinsic role of the Forkhead box O (FOXO) family of transcription factors in cancer, which can act as a tumor repressor while also maintaining cancer stem cells. FOXOs also regulate cancer immunity. FOXOs promote antitumor activity through negatively regulating the expression of immunosuppressive proteins, such as programmed death 1 ligand 1 (PD-L1), and vascular endothelial growth factor (VEGF) in tumor cells or stromal cells, which can shape an immunotolerant state in the TME. FOXOs also intrinsically control the anti-tumor immune response as well as the homeostasis and development of immune cells, including T cells, B cells, natural killer (NK) cells, macrophages, and dendritic cells. As a cancer repressor, reviving the activity of Foxo1 forces tumor-infiltrating activated regulatory T (T_reg) cells to egress from tumor tissues. As a promoter of cancer development, Foxo3 and Foxo1 negatively regulate cytotoxicity of both CD8⁺ T cells and NK cells against tumor cells. In this review, we focus on the complex role of FOXOs in regulating cancer immunity due to the various roles that they play in cancer cells, stromal cells, and immune cells. We also speculate on some possible additional roles of FOXOs in cancer immunity based on findings regarding FOXOs in non-cancer settings, such as infectious disease.

Regulation of Cellular Redox Signaling by Matricellular Proteins in Vascular Biology, Immunology, and Cancer

SIGNIFICANCE

In contrast to structural elements of the extracellular matrix, matricellular proteins appear transiently during development and injury responses, but their sustained expression can contribute to chronic disease. Through interactions with other matrix components and specific cell surface receptors, matricellular proteins regulate multiple signaling pathways, including those mediated by reactive oxygen and nitrogen species and H2S. Dysregulation of matricellular proteins contributes to the pathogenesis of vascular diseases and cancer. Defining the molecular mechanisms and receptors involved is revealing new therapeutic opportunities. Recent Advances: Thrombospondin-1 (TSP1) regulates NO, H2S, and superoxide production and signaling in several cell types. The TSP1 receptor CD47 plays a central role in inhibition of NO signaling, but other TSP1 receptors also modulate redox signaling. The matricellular protein CCN1 engages some of the same receptors to regulate redox signaling, and ADAMTS1 regulates NO signaling in Marfan syndrome. In addition to mediating matricellular protein signaling, redox signaling is emerging as an important pathway that controls the expression of several matricellular proteins.

CRITICAL ISSUES

Redox signaling remains unexplored for many matricellular proteins. Their interactions with multiple cellular receptors remains an obstacle to defining signaling mechanisms, but improved transgenic models could overcome this barrier.

FUTURE DIRECTIONS

Therapeutics targeting the TSP1 receptor CD47 may have beneficial effects for treating cardiovascular disease and cancer and have recently entered clinical trials. Biomarkers are needed to assess their effects on redox signaling in patients and to evaluate how these contribute to their therapeutic efficacy and potential side effects. Antioxid. Redox Signal. 27, 874-911.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

Multiple roles of RARRES1 in prostate cancer: Autophagy induction and angiogenesis inhibition

BACKGROUND

Prostate cancer (PCa) poses a major health concern in men worldwide. Retinoic Acid Receptor Responder (RARRES1)/ Tazarotene-induced gene-1 (TIG-1) is a putative tumor suppressor gene that exerts its tumor suppressor function via unknown mechanisms. Epigenetic silencing of RARRES1 leads to its loss in several types of cancer, including PCa. Determining the molecular mechanisms that mediate the tumor suppressor role of RARRES1 in PCa is the focus of our study.

FINDINGS

Our data indicates that RARRES1 over expression in PCa cell lines represses mitogen-activated protein kinase (MAPK) activation. RARRES1 expression induces the levels of autophagy-related genes, beclin, ATG3 and increases LC3B-II conversion. A significant induction of SIRT1 along with mTOR inhibition is noted on RARRES1 expression. Furthermore, RARRES1 over expression elevates the levels of the antioxidant enzyme, catalase. Our results also indicate that RARRES1 expression inhibits angiogenesis in endothelial cells.

CONCLUSIONS

In summary, the data presented here indicate that forced expression of RARRES1 in PCa cells (a) induces ER stress and autophagic response; (b) increases SIRT1 levels; and (c) higher levels of anti-oxidant enzymes. Our study also implicates the role of RARRES1 as a novel anti-angiogenic molecule. Overall this study reports the molecular players that RARRES1 modulates to serve as a tumor suppressor molecule. Future studies will help determine the in vivo mechanisms by which RARRES1 may serve as a target for therapeutic intervention both in cancer and in angiogenesis-related disorders.

Expression of tissue factor and forkhead box transcription factor O-1 in a rat model for chronic thromboembolic pulmonary hypertension

Few reports have examined tissue factor (TF) and forkhead box transcription factor O-1 (FoxO1) expression in chronic thromboembolic pulmonary hypertension (CTEPH) animal models. To investigate the role of TF and FoxO1 and their interactions during CTEPH pathogenesis in a rat model. Autologous blood clots were repeatedly injected into the pulmonary arteries through right jugular vein to induce a rat model of CTEPH. Hemodynamic parameters, histopathology, and TF and FoxO1expression levels were detected. The mean pulmonary arterial pressure (mPAP), pulmonary vascular resistance and vessel wall area/total area (WA/TA) ratio in the experiment group increased significantly than sham group (P < 0.05). The cardiac output in the 1-, 2-, and 4-week groups decreased significantly (P < 0.05) when compared to sham group. TF mRNA expression levels in the experiment group increased significantly than sham group (P < 0.05). FoxO1 mRNA and protein expression levels were lower in the experiment group than sham group (P < 0.05). The mPAP had a positive correlation with WA/TA ratio (r = 0.45, P = 0.01). TF mRNA expression had a positive correlation with WA/TA ratio (r = 0.374, P = 0.035) and a positive correlation with mPAP (r = 0.48, P= 0.005). FoxO1 mRNA expression had a negative correlation trend with the WA/TA ratio (r = -0.297, P = 0.099) and a negative correlation trend with mPAP (r = -0.34, P = 0.057). TF mRNA expression had a negative correlation with FoxO1 mRNA expression (r = -0.62, P < 0.001). A rat model of CTEPH can be successfully established by the injection of autologous blood clots into the pulmonary artery. TF and FoxO1 may play a key role in vascular remodeling during CTEPH pathogenesis.

Tissue Inhibitor of Metalloproteinase 1 Influences Vascular Adaptations to Chronic Alterations in Blood Flow

Remodeling of the skeletal muscle microvasculature involves the coordinated actions of matrix metalloproteinases (MMPs) and their endogenous inhibitors, tissue inhibitor of metalloproteinases (TIMPs). We hypothesized that the loss of TIMP1 would enhance both ischemia and flow-induced vascular remodeling by increasing MMP activity. TIMP1 deficient (Timp1^-/- ) and wild-type (WT) C57BL/6 mice underwent unilateral femoral artery (FA) ligation or were treated with prazosin, an alpha-1 adrenergic receptor antagonist, in order to investigate vascular remodeling to altered flow. Under basal conditions, Timp1^-/- mice had reduced microvascular content as compared to WT mice. Furthermore, vascular remodeling was impaired in Timp1^-/- mice. Timp1^-/- mice displayed reduced blood flow recovery in response to FA ligation and no arteriogenic response to prazosin treatment. Timp1^-/- mice failed to undergo angiogenesis in response to ischemia or prazosin, despite maintaining the capacity to increase VEGF-A and eNOS mRNA. Vascular permeability was increased in muscles of Timp1^-/- mice in response to both prazosin treatment and FA ligation, but this was not accompanied by greater MMP activity. This study highlights a previously undescribed integral role for TIMP1 in both vascular network maturation and adaptations to ischemia or alterations in flow. J. Cell. Physiol. 232: 831-841, 2017. © 2016 Wiley Periodicals, Inc.

Heat therapy promotes the expression of angiogenic regulators in human skeletal muscle

Heat therapy has been shown to promote capillary growth in skeletal muscle and in the heart in several animal models, but the effects of this therapy on angiogenic signaling in humans are unknown. We evaluated the acute effect of lower body heating (LBH) and unilateral thigh heating (TH) on the expression of angiogenic regulators and heat shock proteins (HSPs) in healthy young individuals. Exposure to LBH (n = 18) increased core temperature (Tc) from 36.9 ± 0.1 to 37.4 ± 0.1°C (P < 0.01) and average leg skin temperature (Tleg) from 33.1 ± 0.1 to 39.6 ± 0.1°C (P < 0.01), but did not alter the levels of circulating angiogenic cytokines and bone marrow-derived proangiogenic cells (CD34(+)CD133(+)). In skeletal muscle, the change in mRNA expression from baseline of vascular endothelial growth factor (VEGF), angiopoietin 2 (ANGPT2), chemokines CCL2 and CX3CL1, platelet factor-4 (PF4), and several members of the HSP family was higher 30 min after the intervention in the individuals exposed to LBH (n = 11) compared with the control group (n = 12). LBH also reduced the expression of transcription factor FOXO1 (P = 0.03). Exposure to TH (n = 14) increased Tleg from 32.8 ± 0.2 to 40.3 ± 0.1°C (P < 0.05) but Tc remained unaltered (36.8 ± 0.1°C at baseline and 36.9 ± 0.1°C at 90 min). This intervention upregulated the expression of VEGF, ANGPT1, ANGPT2, CCL2, and HSPs in skeletal muscle but did not affect the levels of CX3CL1, FOXO-1, and PF4. These findings suggest that both LBH and TH increase the expression of factors associated with capillary growth in human skeletal muscle.

Endothelial FoxO proteins impair insulin sensitivity and restrain muscle angiogenesis in response to a high-fat diet

Skeletal muscle microvascular dysfunction contributes to disease severity in type 2 diabetes. Recent studies indicate a role for Forkhead box O (FoxO) transcription factors in modulating endothelial cell phenotype. We hypothesized that a high-fat (HF) diet generates a dysfunctional vascular niche through an increased expression of endothelial FoxO. FoxO1 protein increased (+130%) in the skeletal muscle capillaries from HF compared to normal chow-fed mice. FoxO1 protein was significantly elevated in cultured endothelial cells exposed to the saturated fatty acid palmitate or the proinflammatory cytokine TNF-α. In HF-fed mice, endothelium-directed depletion of FoxO1/3/4 (FoxO(Δ)) improved insulin sensitivity (+110%) compared to that of the controls (FoxO(L/L)). The number of skeletal muscle capillaries increased significantly in the HF-FoxO(Δ) mice. Transcript profiling of skeletal muscle identified significant increases in genes associated with angiogenesis and lipid metabolism in HF-FoxO(Δ) vs. HF-FoxO(L/L) mice. HF-FoxO(Δ) muscle also was characterized by a decrease in inflammation-related genes and an enriched M2 macrophage signature. We conclude that endothelial FoxO proteins promote insulin resistance in HF diet, which may in part result from FoxO proteins establishing an antiangiogenic and proinflammatory microenvironment within skeletal muscle. These findings provide mechanistic insight into the development of microvascular dysfunction in the progression of type 2 diabetes.-Nwadozi, E., Roudier, E., Rullman, E., Tharmalingam, S., Liu, H.-Y., Gustafsson, T., Haas, T. L. Endothelial FoxO proteins impair insulin sensitivity and restrain muscle angiogenesis in response to a high-fat diet.

Physiological Capillary Regression is not Dependent on Reducing VEGF Expression

Investigations into physiologically controlled capillary regression report the provocative finding that microvessel regression occurs in the face of persistent elevation of skeletal muscle VEGF expression. TSP-1, a negative angiogenic regulator, is increasingly being observed to temporally correlate with capillary regression, suggesting that increased TSP-1 (and not reduction in VEGF per se) is needed to initiate, and likely regulate, capillary regression. Based on evidence being gleaned from physiologically mediated regression of capillaries, it needs to be recognized that capillary regression (and perhaps capillary rarefaction with disease) is not simply the reversal of factors used to stimulate angiogenesis. Rather, the conceptual understanding that angiogenesis and capillary regression each have specific and unique requirements that are biologically constrained to opposite sides of the balance between positive and negative angioregulatory factors may shed light on why anti-VEGF therapies have not lived up to the promise in reversing angiogenesis and providing the cure that many had hoped toward fighting cancer. Emerging evidence from physiological controlled angiogenesis suggest that cases involving excessive or uncontrolled capillary expansion may be best treated by therapies designed to increase expression of negative angiogenic regulators, whereas those involving capillary rarefaction may benefit from inhibiting negative regulators (like TSP-1).

(-)-Epicatechin Attenuates Degradation of Mouse Oxidative Muscle Following Hindlimb Suspension

The purpose of this study was to conduct a 14-day hindlimb suspension (HS) with and without (-)-epicatechin supplementation to determine whether (-)-epicatechin treatment can attenuate the loss in muscle degradation, angiogenesis, and mitochondrial signaling in oxidative skeletal muscle. Adult mice were randomized into 3 groups: (a) control (C); (b) HS with vehicle (HS-V); and (c) HS with (-)-epicatechin (HS-(-)-Epi). Animals in the HS-(-)-Epi group received (-)-epicatechin (1.0 mg · kg(-1) of body mass) twice daily through oral gavage. For markers related to muscle degradation, the HS-V group had significantly higher protein expression compared with the control and HS-(-)-Epi groups. Moreover, protein expression for myosin heavy chain type I was significantly reduced by approximately 45% in the HS-V group compared with the control and HS-(-)-Epi groups. In addition, capillarity contact and capillary-to-fiber ratio were significantly higher in the HS-(-)-Epi group compared with the HS-V group. Furthermore, protein expression for thrombospondin-1 was significantly higher in HS-V group compared with the control and HS-(-)-Epi groups. Hindlimb suspension also significantly reduced protein expression for mitochondrial signaling compared with the control and HS-(-)-Epi groups. These findings suggest that (-)-epicatechin supplementation attenuates degradation in oxidative muscles after HS.

Role of Growth Factors in Modulation of the Microvasculature in Adult Skeletal Muscle

Post-natal skeletal muscle is a highly plastic tissue that has the capacity to regenerate rapidly following injury, and to undergo significant modification in tissue mass (i.e. atrophy/hypertrophy) in response to global metabolic changes. These processes are reliant largely on soluble factors that directly modulate muscle regeneration and mass. However, skeletal muscle function also depends on an adequate blood supply. Thus muscle regeneration and changes in muscle mass, particularly hypertrophy, also demand rapid changes in the microvasculature. Recent evidence clearly demonstrates a critical role for soluble growth factors in the tight regulation of angiogenic expansion of the muscle microvasculature. Furthermore, exogenous modulation of these factors has the capacity to impact directly on angiogenesis and thus, indirectly, on muscle regeneration, growth and performance. This chapter reviews recent developments in understanding the role of growth factors in modulating the skeletal muscle microvasculature, and the potential therapeutic applications of exogenous angiogenic and anti-angiogenic mediators in promoting effective growth and regeneration, and ameliorating certain diseases, of skeletal muscle.

Advances and challenges in skeletal muscle angiogenesis

The role of capillaries is to serve as the interface for delivery of oxygen and removal of metabolites to/from tissues. During the past decade there has been a proliferation of studies that have advanced our understanding of angiogenesis, demonstrating that tissue capillary supply is under strict control during health but poorly controlled in disease, resulting in either excessive capillary growth (pathological angiogenesis) or losses in capillarity (rarefaction). Given that skeletal muscle comprises nearly 40% of body mass in humans, skeletal muscle capillary density has a significant impact on metabolism, endocrine function, and locomotion and is tightly regulated at many different levels. Skeletal muscle is also high adaptable and thus one of the few organ systems that can be experimentally manipulated (e.g., by exercise) to study physiological regulation of angiogenesis. This review will focus on the methodological concerns that have arisen in determining skeletal muscle capillarity and highlight the concepts that are reshaping our understanding of the angio-adaptation process. We also summarize selected new findings (physical influences, molecular changes, and ultrastructural rearrangement of capillaries) that identify areas of future research with the greatest potential to expand our understanding of how angiogenesis is normally regulated, and that may also help to better understand conditions of uncontrolled (pathological) angiogenesis.

Regulation of skeletal muscle capillary growth in exercise and disease

Capillaries, which are the smallest and most abundant type of blood vessel, form the primary site of gas, nutrient, and waste transfer between the vascular and tissue compartments. Skeletal muscle exhibits the capacity to generate new capillaries (angiogenesis) as an adaptation to exercise training, thus ensuring that the heightened metabolic demand of the active muscle is matched by an improved capacity for distribution of gases, nutrients, and waste products. This review summarizes the current understanding of the regulation of skeletal muscle capillary growth. The multi-step process of angiogenesis is coordinated through the integration of a diverse array of signals associated with hypoxic, metabolic, hemodynamic, and mechanical stresses within the active muscle. The contributions of metabolic and mechanical factors to the modulation of key pro- and anti-angiogenic molecules are discussed within the context of responses to a single aerobic exercise bout and short-term and long-term training. Finally, the paradoxical lack of angiogenesis in peripheral artery disease and diabetes and the implications for disease progression and muscle health are discussed. Future studies that emphasize an integrated analysis of the mechanisms that control skeletal muscle capillary growth will enable development of targeted exercise programs that effectively promote angiogenesis in healthy individuals and in patient populations.

Abnormalities in three-dimensional capillary architecture and imbalance between vascular endothelial growth factor-A and thrombospondin-1 in soleus muscle of ovariectomized rat

Reduced ovarian hormone levels associated with menopause or ovariectomy (OVX) not only result in vascular dysfunction but also lead to structural abnormalities in capillaries. Therefore, the effect of OVX on the three-dimensional (3-D) architecture of capillary networks and the underlying molecular mechanisms were investigated in rat soleus muscle. Seven-week-old female Wistar rats were divided into the OVX and sham-treated (Sham) groups. The OVX group exhibited lower endurance exercise capacity compared to the sham group and resulted in decreased capillary diameter, number of anastomoses and capillary/anastomosis volume in soleus muscle, indicating 3-D structural abnormalities of capillary networks. Furthermore, OVX led to increased concentrations of thrombospondin-1 (TSP-1) protein and a decreased VEGF-A/TSP-1 ratio, an indicator of angio-adaptations, in soleus muscle compared with the Sham group. These results indicate OVX may induce 3-D capillary regression in soleus muscle through an imbalance between VEGF-A and TSP-1 expression, possibly associated with decreased exercise tolerance in ovariectomized rats.

(-)-Epicatechin combined with 8 weeks of treadmill exercise is associated with increased angiogenic and mitochondrial signaling in mice

The purpose of this study was to conduct an 8 week endurance training program with and without (–)–epicatechin treatment and to determine whether there is a possible cumulative effect on protein markers of angiogenesis and mitochondrial biogenesis. Thirty-four 14-month old male mice (C57BL/6N) were randomized into four groups: control (C); (–)–epicatechin only ((–)–Epi); control with endurance training (CE); and (–)–epicatechin with endurance training ((–)–Epi-Ex). Mice in the training groups performed treadmill exercise for 8 weeks (5 × /week for 60 min/session), whereas mice in the (–)–epicatechin group received 1.0 mg/kg of body mass twice daily during the training period. At 8 weeks, distance ran on the treadmill increased by 46, 69, and 84% in the (–)–Epi, CE, and (–)–Epi-Ex groups, respectively compared to the control group (p < 0.001 for all comparisons). Furthermore, the (–)–Epi-Ex group had significantly higher exercise capacity than the (–)–Epi and CE group. For angiogenic regulators, the (–)–Epi-Ex group had significantly higher VEGF-R2 protein expression with a concomitant reduction in TSP-1 protein expression than the exercise group. Interestingly, FoxO1 protein expression was significantly reduced for all three experimental groups compared to the control group. Protein markers such as PGC-1β and TFAM were significantly higher in the (–)–Epi-Ex group compared to the three other groups. These findings suggest that (–)–epicatechin treatment combined with 8 weeks of endurance training provide a cumulative effect on a number of angiogenic and mitochondrial signaling which functionally translates to enhanced exercise tolerance.

Decreased astrocytic thrombospondin-1 secretion after chronic ammonia treatment reduces the level of synaptic proteins: in vitro and in vivo studies

Chronic hepatic encephalopathy (CHE) is a major complication in patients with severe liver disease. Elevated blood and brain ammonia levels have been implicated in its pathogenesis, and astrocytes are the principal neural cells involved in this disorder. Since defective synthesis and release of astrocytic factors have been shown to impair synaptic integrity in other neurological conditions, we examined whether thrombospondin-1 (TSP-1), an astrocytic factor involved in the maintenance of synaptic integrity, is also altered in CHE. Cultured astrocytes were exposed to ammonia (NH₄Cl, 0.5-2.5 mM) for 1-10 days, and TSP-1 content was measured in cell extracts and culture media. Astrocytes exposed to ammonia exhibited a reduction in intra- and extracellular TSP-1 levels. Exposure of cultured neurons to conditioned media from ammonia-treated astrocytes showed a decrease in synaptophysin, PSD95, and synaptotagmin levels. Conditioned media from TSP-1 over-expressing astrocytes that were treated with ammonia, when added to cultured neurons, reversed the decline in synaptic proteins. Recombinant TSP-1 similarly reversed the decrease in synaptic proteins. Metformin, an agent known to increase TSP-1 synthesis in other cell types, also reversed the ammonia-induced TSP-1 reduction. Likewise, we found a significant decline in TSP-1 level in cortical astrocytes, as well as a reduction in synaptophysin content in vivo in a rat model of CHE. These findings suggest that TSP-1 may represent an important therapeutic target for CHE. Defective release of astrocytic factors may impair synaptic integrity in chronic hepatic encephalopathy. We found a reduction in the release of the astrocytic matricellular proteins thrombospondin-1 (TSP-1) in ammonia-treated astrocytes; such reduction was associated with a decrease in synaptic proteins caused by conditioned media from ammonia-treated astrocytes. Exposure of neurons to CM from ammonia-treated astrocytes, in which TSP-1 is over-expressed, reversed (by approx 75%) the reduction in synaptic proteins. NF-kB = nuclear factor kappa B; PSD95 = post-synaptic density protein 95; ONS = oxidative/nitrative stress.

Resveratrol modulates the angiogenic response to exercise training in skeletal muscles of aged men

In animal studies, the polyphenol resveratrol has been shown to influence several pathways of importance for angiogenesis in skeletal muscle. The aim of the present study was to examine the angiogenic effect of resveratrol supplementation with parallel exercise training in aged men. Forty-three healthy physically inactive aged men (65 ± 1 yr) were divided into 1) a training group that conducted 8 wk of intense exercise training where half of the subjects received a daily intake of either 250 mg trans-resveratrol (n = 14) and the other half received placebo (n = 13) and 2) a nontraining group that received either 250 mg trans-resveratrol (n = 9) or placebo (n = 7). The group that trained with placebo showed a ~20% increase in the capillary-to-fiber ratio, an increase in muscle protein expression of VEGF, VEGF receptor-2, and tissue inhibitor of matrix metalloproteinase (TIMP-1) but unaltered thrombospodin-1 levels. Muscle interstitial VEGF and thrombospodin-1 protein levels were unchanged after the training period. The group that trained with resveratrol supplementation did not show an increase in the capillary-to-fiber ratio or an increase in muscle VEGF protein. Muscle TIMP-1 protein levels were lower in the training and resveratrol group than in the training and placebo group. Both training groups showed an increase in forkhead box O1 protein. In nontraining groups, TIMP-1 protein was lower in the resveratrol-treated group than the placebo-treated group after 8 wk. In conclusion, these data show that exercise training has a strong angiogenic effect, whereas resveratrol supplementation may limit basal and training-induced angiogenesis.

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.

Invoking the power of thrombospondins: regulation of thrombospondins expression

Increasing evidence suggests critical functions of thrombospondins (TSPs) in a variety of physiological and pathological processes. With the growing understanding of the importance of these matricellular proteins, the need to understand the mechanisms of regulation of their expression and potential approaches to modulate their levels is also increasing. The regulation of TSP expression is multi-leveled, cell- and tissue-specific, and very precise. However, the knowledge of mechanisms modulating the levels of TSPs is fragmented and incomplete. This review discusses the known mechanisms of regulation of TSP levels and the gaps in our knowledge that prevent us from developing strategies to modulate the expression of these physiologically important proteins.

Novel perspective: exercise training stimulus triggers the expression of the oncoprotein human double minute-2 in human skeletal muscle

High expression levels of human double minute-2 (Hdm2) are often associated with increased risk of cancer. Hdm2 is well established as an oncoprotein exerting various tumorigenic effects. Conversely, the physiological functions of Hdm2 in nontumor cells and healthy tissues remain largely unknown. We previously demonstrated that exercise training stimulates expression of murine double minute-2 (Mdm2), the murine analog of Hdm2, in rodent skeletal muscle and Mdm2 was required for exercise-induced muscle angiogenesis. Here we showed that exercise training stimulated the expression of Hdm2 protein in human skeletal muscle from +38% to +81%. This robust physiological response was observed in 60-70% of the subjects tested, in both young and senior populations. Similarly, exercise training stimulated the expression of platelet endothelial cell adhesion molecule-1, an indicator of the level of muscle capillarization. Interestingly, a concomitant decrease in the tumor suppressor forkhead box O-1 (FoxO1) transcription factor levels did not occur with training although Mdm2/Hdm2 is known to inhibit FoxO1 expression in diseased skeletal muscle. This could suggest that Hdm2 has different targets when stimulated in a physiological context and that exercise training could be considered therapeutically in the context of cancer in combination with anti-Hdm2 drug therapies in order to preserve Hdm2 physiological functions in healthy tissues.