P53 Impairs Endothelium-Dependent Vasomotor Function Through Transcriptional Upregulation of P66shc

Activated factor X stimulates atrial endothelial cells and tissues to promote remodelling responses through AT1R/NADPH oxidases/SGLT1/2

AIMS

Atrial fibrillation (AF), the most common cardiac arrhythmia favouring ischemic stroke and heart failure involves left atrial remodelling, fibrosis and a complex interplay between cardiovascular risk factors. This study examined whether activated factor X (FXa) induces pro-remodelling and pro-fibrotic responses in atrial endothelial cells (AECs) and human atrial tissues and determined the underlying mechanisms.

METHODS AND RESULTS

AECs collected from porcine hearts and human right atrial appendages (RAA) from patients undergoing heart surgery. Protein expression levels were assessed by Western blot and immunofluorescence staining, mRNA levels by RT-qPCR, formation of reactive oxygen species (ROS) and NO using fluorescent probes, thrombin and angiotensin II generation by specific assays, fibrosis by Sirius red staining and senescence by senescence-associated beta-galactosidase (SA-β-gal) activity. In AECs, FXa increased ROS formation, senescence (SA-β-gal activity, p53, p21), angiotensin II generation and the expression of pro-inflammatory (VCAM-1, MCP-1), pro-thrombotic (tissue factor), pro-fibrotic (TGF-β and collagen-1/3a) and pro-remodelling (MMP-2/9) markers whereas eNOS levels and NO formation were reduced. These effects were prevented by inhibitors of FXa but not thrombin, protease-activated receptors antagonists (PAR-1/2) and inhibitors of NADPH oxidases, ACE, AT1R, SGLT1/SGLT2. FXa also increased expression levels of ACE1, AT1R, SGLT1/2 proteins which were prevented by SGLT1/2 inhibitors. Human RAA showed tissue factor mRNA levels that correlated with markers of endothelial activation, pro-remodelling and pro-fibrotic responses and SGLT1/2 mRNA levels. They also showed protein expression levels of ACE1, AT1R, p22phox, SGLT1/2, and immunofluorescence signals of nitrotyrosine and SGLT1/2 colocalized with those of CD31. FXa increased oxidative stress levels which were prevented by inhibitors of the AT1R/NADPH oxidases/SGLT1/2 pathway.

CONCLUSION

FXa promotes oxidative stress triggering premature endothelial senescence and dysfunction associated with pro-thrombotic, pro-remodelling and pro-fibrotic responses in AECs and human RAA involving the AT1R/NADPH oxidases/SGLT1/2 pro-oxidant pathway. Targeting this pathway may be of interest to prevent atrial remodelling and the progression of atrial fibrillation substrate.

C-peptide in diabetes: A player in a dual hormone disorder?

C-peptide, a byproduct of insulin synthesis believed to be biologically inert, is emerging as a multifunctional molecule. C-peptide serves an anti-inflammatory and anti-atherogenic role in type 1 diabetes mellitus (T1DM) and early T2DM. C-peptide protects endothelial cells by activating AMP-activated protein kinase α, thus suppressing the activity of NAD(P)H oxidase activity and reducing reactive oxygen species (ROS) generation. It also prevents apoptosis by regulating hyperglycemia-induced p53 upregulation and mitochondrial adaptor p66shc overactivation, as well as reducing caspase-3 activity and promoting expression of B-cell lymphoma-2. Additionally, C-peptide suppresses platelet-derived growth factor (PDGF)-beta receptor and p44/p42 mitogen-activated protein (MAP) kinase phosphorylation to inhibit vascular smooth muscle cells (VSMC) proliferation. It also diminishes leukocyte adhesion by virtue of its capacity to abolish nuclear factor kappa B (NF-kB) signaling, a major pro-inflammatory cascade. Consequently, it is envisaged that supplementation of C-peptide in T1DM might ameliorate or even prevent end-organ damage. In marked contrast, C-peptide increases monocyte recruitment and migration through phosphoinositide 3-kinase (PI-3 kinase)-mediated pathways, induces lipid accumulation via peroxisome proliferator-activated receptor γ upregulation, and stimulates VSMC proliferation and CD4+ lymphocyte migration through Src-kinase and PI-3K dependent pathways. Thus, it promotes atherosclerosis and microvascular damage in late T2DM. Indeed, C-peptide is now contemplated as a potential biomarker for insulin resistance in T2DM and linked to increased coronary artery disease risk. This shift in the understanding of the pathophysiology of diabetes from being a single hormone deficiency to a dual hormone disorder warrants a careful consideration of the role of C-peptide as a unique molecule with promising diagnostic, prognostic, and therapeutic applications.

Mitochondria in health, disease, and aging

Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.

Mitochondria in endothelial cells angiogenesis and function: current understanding and future perspectives

Endothelial cells (ECs) angiogenesis is the process of sprouting new vessels from the existing ones, playing critical roles in physiological and pathological processes such as wound healing, placentation, ischemia/reperfusion, cardiovascular diseases and cancer metastasis. Although mitochondria are not the major sites of energy source in ECs, they function as important biosynthetic and signaling hubs to regulate ECs metabolism and adaptations to local environment, thus affecting ECs migration, proliferation and angiogenic process. The understanding of the importance and potential mechanisms of mitochondria in regulating ECs metabolism, function and the process of angiogenesis has developed in the past decades. Thus, in this review, we discuss the current understanding of mitochondrial proteins and signaling molecules in ECs metabolism, function and angiogeneic signaling, to provide new and therapeutic targets for treatment of diverse cardiovascular and angiogenesis-dependent diseases.

Epigenetic Signatures in Arterial Hypertension: Focus on the Microvasculature

Systemic arterial hypertension (AH) is a multifaceted disease characterized by accelerated vascular aging and high cardiometabolic morbidity and mortality. Despite extensive work in the field, the pathogenesis of AH is still incompletely understood, and its treatment remains challenging. Recent evidence has shown a deep involvement of epigenetic signals in the regulation of transcriptional programs underpinning maladaptive vascular remodeling, sympathetic activation and cardiometabolic alterations, all factors predisposing to AH. After occurring, these epigenetic changes have a long-lasting effect on gene dysregulation and do not seem to be reversible upon intensive treatment or the control of cardiovascular risk factors. Among the factors involved in arterial hypertension, microvascular dysfunction plays a central role. This review will focus on the emerging role of epigenetic changes in hypertensive-related microvascular disease, including the different cell types and tissues (endothelial cells, vascular smooth muscle cells and perivascular adipose tissue) as well as the involvement of mechanical/hemodynamic factors, namely, shear stress.

The role of p53 in the alternation of vascular functions

Ageing is a risk factor for many degenerative diseases. Cardiovascular diseases (CVDs) are usually big burdens for elderly, caregivers and the health system. During the aging process, normal functions of vascular cells and tissue progressively lost and eventually develop vascular diseases. Endothelial dysfunction, reduced bioavailability of endothelium-derived nitric oxide are usual phenomena observed in patients with cardiovascular diseases. Myriad of studies have been done to investigate to delay the vascular dysfunction or improve the vascular function to prolong the aging process. Tumor suppressor gene p53, also a transcription factor, act as a gatekeeper to regulate a number of genes to maintain normal cell function including but not limited to cell proliferation, cell apoptosis. p53 also crosstalk with other key transcription factors like hypoxia-inducible factor 1 alpha that contribute to the progression of cardiovascular diseases. Therefore, in recent three decades, p53 has drawn scientists’ attention on its effects in vascular function. Though the role of tumor suppressor gene p53 is still not clear in vascular function, it is found to play regulatory roles and may involve in vascular remodeling, atherosclerosis or pulmonary hypertension. p53 may have a divergent role in endothelial and vascular muscle cells in those conditions. In this review, we describe the different effects of p53 in cardiovascular physiology. Further studies on the effects of endothelial cell-specific p53 deficiency on atherosclerotic plaque formation in common animal models are required before the therapeutic potential can be realized.

p66Shc in Cardiovascular Pathology

p66Shc is a widely expressed protein that governs a variety of cardiovascular pathologies by generating, and exacerbating, pro-apoptotic ROS signals. Here, we review p66Shc’s connections to reactive oxygen species, expression, localization, and discuss p66Shc signaling and mitochondrial functions. Emphasis is placed on recent p66Shc mitochondrial function discoveries including structure/function relationships, ROS identity and regulation, mechanistic insights, and how p66Shc-cyt c interactions can influence p66Shc mitochondrial function. Based on recent findings, a new p66Shc mitochondrial function model is also put forth wherein p66Shc acts as a rheostat that can promote or antagonize apoptosis. A discussion of how the revised p66Shc model fits previous findings in p66Shc-mediated cardiovascular pathology follows.

Signaling pathways associated with structural changes in varicose veins: a case-control study

INTRODUCTION AND OBJECTIVES

In varicose veins, blood pressure increases in the veins of the lower extremities due to mechanical stimulation and function remodeling. The aim of this study is assessment of Signaling pathways associated with structural changes in varicose veins.

MATERIALS AND METHODS

This pilot study was performed on patients with varicose veins, which had undergone surgery. The healthy tissues from trauma patients or vascular bypass without underlying diseases were used for control samples. Hematoxylin-eosin, trichrome, and elastin staining were used for histopathological examination. The levels of MDA (malondialdehyde), total thiol, SOD (Superoxide dismutase) and NO (nitric oxide) level were measured using Elisa kits to evaluate the oxidative stress level. Gene expression levels of MMP2, MMP9, FOXO3a, APOE and p53 genes were determined using Real-time PCR.

RESULTS

This study showed, the vascular Vein wall changes are visible in vascular collagen staining. Although these changes are observed in the structure of vascular wall collagen fibers, the accumulation of collagen and elastin was increased in the walls of varicose veins compared to the control group. The amount of nitric oxide and thiol were increased in the varicose group (P < 0.0001). The expression of metalloproteinase2 gene associated with extracellular matrix change was increased in varicose veins. However, the amount of metalloproteinase 9 was decreased in this group compared to control group. FOXO3a, APOE Genes were down-regulated in the varicose veins compared to control group, while p53 gene expression was significantly increased in the varicose group (P < 0.0001).

CONCLUSION

This study demonstrated changes in oxidative stress, morphological structure, and aging pathways in varicose when compared to non-varicose veins. The changes in oxidative stress may be associated with the variations in morphological structure and aging pathways which contribute to the pathogenesis of varicose veins.

Mitochondrial contributions to vascular endothelial dysfunction, arterial stiffness, and cardiovascular diseases

Cardiovascular disease (CVD) affects one in three adults and remains the leading cause of death in America. Advancing age is a major risk factor for CVD. Recent plateaus in CVD-related mortality rates in high-income countries after decades of decline highlight a critical need to identify novel therapeutic targets and strategies to mitigate and manage the risk of CVD development and progression. Vascular dysfunction, characterized by endothelial dysfunction and large elastic artery stiffening, is independently associated with an increased CVD risk and incidence and is therefore an attractive target for CVD prevention and management. Vascular mitochondria have emerged as an important player in maintaining vascular homeostasis. As such, age- and disease-related impairments in mitochondrial function contribute to vascular dysfunction and consequent increases in CVD risk. This review outlines the role of mitochondria in vascular function and discusses the ramifications of mitochondrial dysfunction on vascular health in the setting of age and disease. The adverse vascular consequences of increased mitochondrial-derived reactive oxygen species, impaired mitochondrial quality control, and defective mitochondrial calcium cycling are emphasized, in particular. Current evidence for both lifestyle and pharmaceutical mitochondrial-targeted strategies to improve vascular function is also presented.

Fluorescent nanocarriers targeting VCAM-1 for early detection of senescent endothelial cells

Endothelial senescence has been identified as an early event in the development of endothelial dysfunction, a hallmark of cardiovascular disease. This study developed theranostic nanocarriers (NC) decorated with VCAM-1 antibodies (NC-VCAM-1) in order to target cell surface VCAM-1, which is overexpressed in senescent endothelial cells (ECs) for diagnostic and therapeutic purposes. Incubation of Ang II-induced premature senescent ECs or replicative senescent ECs with NC-VCAM-1 loaded with lipophilic fluorescent dyes showed higher fluorescence signals than healthy EC, which was dependent on the NC size and VCAM-1 antibodies concentration, and not observed following masking of VCAM-1. NC loaded with omega 3 polyunsaturated fatty acid (NC-EPA:DHA6:1) were more effective than native EPA:DHA 6:1 to prevent Ang II-induced VCAM-1 and p53 upregulation, and SA-β-galactosidase activity in coronary artery segments. These theranostic NC might be of interest to evaluate the extent and localization of endothelial senescence and to prevent pro-senescent endothelial responses.

Overexpression of p53 due to excess protein O-GlcNAcylation is associated with coronary microvascular disease in type 2 diabetes

AIMS

We previously reported that increased protein O-GlcNAcylation in diabetic mice led to vascular rarefaction in the heart. In this study, we aimed to investigate whether and how coronary endothelial cell (EC) apoptosis is enhanced by protein O-GlcNAcylation and thus induces coronary microvascular disease (CMD) and subsequent cardiac dysfunction in diabetes. We hypothesize that excessive protein O-GlcNAcylation increases p53 that leads to CMD and reduced cardiac contractility.

METHODS AND RESULTS

We conducted in vivo functional experiments in control mice, TALLYHO/Jng (TH) mice, a polygenic type 2 diabetic (T2D) model, and EC-specific O-GlcNAcase (OGA, an enzyme that catalyzes the removal of O-GlcNAc from proteins)-overexpressing TH mice, as well as in vitro experiments in isolated ECs from these mice. TH mice exhibited a significant increase in coronary EC apoptosis and reduction of coronary flow velocity reserve (CFVR), an assessment of coronary microvascular function, in comparison to wild-type mice. The decreased CFVR, due at least partially to EC apoptosis, was associated with decreased cardiac contractility in TH mice. Western blot experiments showed that p53 protein level was significantly higher in coronary ECs from TH mice and T2D patients than in control ECs. High glucose treatment also increased p53 protein level in control ECs. Furthermore, overexpression of OGA decreased protein O-GlcNAcylation and down-regulated p53 in coronary ECs, and conferred a protective effect on cardiac function in TH mice. Inhibition of p53 with pifithrin-α attenuated coronary EC apoptosis and restored CFVR and cardiac contractility in TH mice.

CONCLUSIONS

The data from this study indicate that inhibition of p53 or down-regulation of p53 by OGA overexpression attenuates coronary EC apoptosis and improves CFVR and cardiac function in diabetes. Lowering coronary endothelial p53 levels via OGA overexpression could be a potential therapeutic approach for CMD in diabetes.

Cadmium Chloride Induces Memory Deficits and Hippocampal Damage by Activating the JNK/p66Shc/NADPH Oxidase Axis

This study investigated whether the mechanism underlying the neurotoxic effects of cadmium chloride (CdCl₂) in rats involves p⁶⁶Shc. This study comprised an initial in vivo experiment followed by an in vitro experiment. For the in vivo experiment, male rats were orally administered saline (vehicle) or CdCl₂ (0.05 mg/kg) for 30 days. Thereafter, spatial and retention memory of rats were tested and their hippocampi were used for biochemical and molecular analyses. For the in vitro experiment, control or p⁶⁶Shc-deficient hippocampal cells were treated with CdCl₂ (25 µM) in the presence or absence of SP600125, a c-Jun N-terminal kinase (JNK) inhibitor. Cadmium chloride impaired the spatial learning and retention memory of rats; depleted levels of glutathione and manganese superoxide dismutase; increased reactive oxygen species (ROS), tumor necrosis factor α, and interleukin 6; and induced nuclear factor kappa B activation. Cadmium chloride also decreased the number of pyramidal cells in the CA1 region and induced severe damage to the mitochondria and endoplasmic reticulum of cells in the hippocampi of rats. Moreover, CdCl₂ increased the total unphosphorylated p66Shc, phosphorylated (Ser³⁶) p⁶⁶Shc, phosphorylated JNK, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, cytochrome c, and cleaved caspase-3. A dose-response increase in cell death, ROS, DNA damage, p⁶⁶Shc, and NADPH oxidase was also observed in cultured hippocampal cells treated with CdCl₂. Of note, all of these biochemical changes were attenuated by silencing p⁶⁶Shc or inhibiting JNK with SP600125. In conclusion, CdCl₂ induces hippocampal ROS generation and apoptosis by promoting the JNK-mediated activation of p⁶⁶Shc.

Functional Role of p53 in the Regulation of Chemical-Induced Oxidative Stress

The nuclear transcription factor p53, discovered in 1979, has a broad range of biological functions, primarily the regulation of apoptosis, the cell cycle, and DNA repair. In addition to these canonical functions, a growing body of evidence suggests that p53 plays an important role in regulating intracellular redox homeostasis through transcriptional and nontranscriptional mechanisms. Oxidative stress induction and p53 activation are common responses to chemical exposure and are suggested to play critical roles in chemical-induced toxicity. The activation of p53 can exert either prooxidant or antioxidant activity, depending on the context. In this review, we discuss the functional role of p53 in regulating chemical-induced oxidative stress, summarize the potential signaling pathways involved in p53's regulation of chemically mediated oxidative stress, and propose issues that should be addressed in future studies to improve understanding of the relationship between p53 and chemical-induced oxidative stress.

Suppression of p66Shc prevents hyperandrogenism-induced ovarian oxidative stress and fibrosis

Background

Rats with hyperandrogen-induced polycystic ovary syndrome (PCOS) have been shown to develop ovarian oxidative stress (OS) and fibrosis. The Sirt1 agonist, resveratrol, can reduce OS through inhibiting p66Shc in other models of OS.

Methods

We created a rat PCOS model with increased OS levels following treatment with one of the two androgens, dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT). The PCOS related features were determined by measurement of malondialdehyde (MDA) and superoxide dismutase (SOD) levels or by examining the reactive oxygen species (ROS) levels using the DCF-DA probe. The potential mechanisms by which p66Shc/Sirt1 mediates ovarian fibrosis were explored by western blotting, quantitative reverse transcription-PCR, immunofluorescence staining, and immunohistochemistry.

Results

Hyperandrogen dramatically augmented OS and activation of fibrotic factors in the ovary. Our data demonstrated that treatment with resveratrol enhanced Sirt1 and decreased ovarian OS as well as inhibited phosphorylation of p66Shc both in vivo and in vitro. The treatment suppressed fibrotic factor activation and improved ovarian morphology. Lentivirus- or siRNA-mediated p66Shc knockdown resulted in a dramatic enhancement of Sirt1 expression, down-regulation of ROS and suppression of fibrotic factors in granulosa cells. Moreover, p66Shc overexpression markedly increased the expression of fibrotic factors. Additionally, silencing Sirt1 induced a dramatic increase in p66Shc and enhanced activation of fibrotic factors.

Conclusions

p66Shc may be a direct target of Sirt1 for inducing ROS and thus promoting fibrosis. Further exploration of the mechanisms of p66Shc in both fibrosis and OS may provide novel therapeutic strategies that will facilitate the improvement in PCOS symptoms and reproductive functions.

Multiple Cell Signalling Pathways of Human Proinsulin C-Peptide in Vasculopathy Protection

A major hallmark of diabetes is a constant high blood glucose level (hyperglycaemia), resulting in endothelial dysfunction. Transient or prolonged hyperglycemia can cause diabetic vasculopathy, a secondary systemic damage. C-Peptide is a product of cleavage of proinsulin by a serine protease that occurs within the pancreatic β-cells, being secreted in similar amounts as insulin. The biological activity of human C-peptide is instrumental in the prevention of diabetic neuropathy, nephropathy and other vascular complications. The main feature of type 1 diabetes mellitus is the lack of insulin and of C-peptide, but the progressive β-cell loss is also observed in later stage of type 2 diabetes mellitus. C-peptide has multifaceted effects in animals and diabetic patients due to the activation of multiple cell signalling pathways, highlighting p38 mitogen-activated protein kinase and extracellular signal-regulated kinase ½, Akt, as well as endothelial nitric oxide production. Recent works highlight the role of C-peptide in the prevention and amelioration of diabetes and also in organ-specific complications. Benefits of C-peptide in microangiopathy and vasculopathy have been shown through conservation of vascular function, and also in the prevention of endothelial cell death, microvascular permeability, neointima formation, and in vascular inflammation. Improvement of microvascular blood flow by replacing a physiological amount of C-peptide, in several tissues of diabetic animals and humans, mainly in nerve tissue, myocardium, skeletal muscle, and kidney has been described. A review of the multiple cell signalling pathways of human proinsulin C-peptide in vasculopathy protection is proposed, where the approaches to move beyond the state of the art in the development of innovative and effective therapeutic options of diabetic neuropathy and nephropathy are discussed.

Intake of omega-3 formulation EPA:DHA 6:1 by old rats for 2 weeks improved endothelium-dependent relaxations and normalized the expression level of ACE/AT1R/NADPH oxidase and the formation of ROS in the mesenteric artery

Omega-3 polyunsaturated fatty acids (PUFAs) including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been shown to protect the cardiovascular system, in part, by stimulating the endothelial formation of nitric oxide (NO). EPA:DHA 6:1 has been identified as a potent omega 3 PUFA formulation to induce endothelium-dependent vasorelaxation and activation of endothelial NO synthase (eNOS). This study examined whether intake of EPA:DHA 6:1 (500 mg/kg/day) for 2 weeks improves an established endothelial dysfunction in old rats (20 months old), and, if so, the underlying mechanism was subsequently determined. In the main mesenteric artery rings, an endothelial dysfunction characterized by a blunted NO component, an abolished endothelium-dependent hyperpolarization component, and increased endothelium-dependent contractile responses (EDCFs) are observed in old rats compared to young rats. Age-related endothelial dysfunction was associated with increased vascular formation of reactive oxygen species (ROS) and expression of eNOS, components of the local angiotensin system, senescence markers, and cyclooxygenase-2 (COX-2), and the downregulation of COX-1. The EPA:DHA 6:1 treatment improved the NO-mediated relaxation, reduced the EDCF-dependent contractile response and the vascular formation of ROS, and normalized the expression level of all target proteins in the old arterial wall. Thus, the present findings indicate that a 2-week intake of EPA:DHA 6:1 by old rats restored endothelium-dependent NO-mediated relaxations, most likely, by preventing the upregulation of the local angiotensin system and the subsequent formation of ROS.

Isosteviol Protects Free Fatty Acid- and High Fat Diet-Induced Hepatic Injury via Modulating PKC-β/p66Shc/ROS and Endoplasmic Reticulum Stress Pathways

Aims: Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver diseases. However, there are no approved pharmacotherapies for the treatment of NAFLD other than managing life style and controlling diets. Extensive studies have demonstrated that multiple mechanisms are involved in free fatty acid (FFA)- and high fat diet (HFD)-induced hepatic injury, including mitochondrial dysfunction, activation of oxidative stress and endoplasmic reticulum (ER) stress, and lysosome dysfunction. A previous study reported that Isosteviol (ISV), a derivative of stevioside, prevents HFD-induced hepatic injury. However, the underlying mechanisms remain unclear. Results: In this study, we examined the potential cellular/molecular mechanisms underlying ISV-mediated protective effect against FFA-/HFD-induced hepatic lipotoxicity by using both in vitro primary rat hepatocytes and the in vivo rat NAFLD model. The results indicated that ISV inhibits FFA-/HFD-induced hepatic injury via reducing oxidative and ER stress. Specifically, ISV inhibited the expression, activation, and mitochondrial translocation of Src-homology-2-domain-containing transforming protein 1 (p66Shc), an adapter protein that mediates oxidative stress-induced injury and is a substrate of protein kinase C-β (PKC-β), via inhibition of PKC-β activity. However, ISV had no effect on the expression and activity of peptidyl-prolyl cis-trans isomerase and serine/threonine protein phosphatase 2A, isomerase and phosphorylase of p66Shc. In addition, ISV also inhibited FFA-induced ER stress and decreased ER-mitochondrial interaction. Innovation and Conclusion: We first identified that ISV prevents FFA-/HFD-induced hepatic injury through modulating PKC-β/p66Shc/oxidative and ER stress pathways. ISV represents a promising therapeutic agent for NAFLD in the future. Antioxid. Redox Signal. 30, 1949-1968.

Adaptor Protein p66Shc: A Link Between Cytosolic and Mitochondrial Dysfunction in the Development of Diabetic Retinopathy

AIMS

Diabetes increases oxidative stress in the retina and dysfunctions their mitochondria, accelerating capillary cell apoptosis. A 66 kDa adaptor protein, p66Shc, is considered as a sensor of oxidative stress-induced apoptosis. In the pathogenesis of diabetic retinopathy, a progressive disease, reactive oxygen species (ROS) production by activation of a small molecular weight G-protein (Ras-related C3 botulinum toxin substrate 1 [Rac1])-Nox2 signaling precedes mitochondrial damage. Rac1 activation is facilitated by guanine exchange factors (GEFs), and p66Shc increases Rac1-specific GEF activity of Son of Sevenless 1 (Sos1). p66Shc also possesses oxidoreductase activity and can directly stimulate mitochondrial ROS generation. Our aim was to investigate the role of p66Shc in the development of diabetic retinopathy and mechanism of its transcription.

RESULTS

High glucose increased p66Shc expression in human retinal endothelial cells, and elevated acetylated histone 3 lysine 9 (H3K9) levels and transcriptional factor p53 binding at its promoter. Glucose also augmented interactions between Rac1 and Sos1 and activated Rac1-Nox2. Phosphorylation of p66Shc was increased, allowing it to interact with peptidyl prolyl isomerase to facilitate its localization inside the mitochondria, culminating in mitochondrial damage. P66shc-small interfering RNA (siRNA) inhibited glucose-induced Rac1 activation and mitochondrial damage. Similar results are observed in retinal microvessels from diabetic rats.

INNOVATION

This is the first report identifying the role of p66Shc in the development of diabetic retinopathy and implicating increased histone acetylation in its transcriptional regulation.

CONCLUSION

Thus, p66Shc has dual role in the development of diabetic retinopathy; its regulation in the early stages of the disease should impede Rac1-ROS production and, in the later stages, prevent mitochondrial damage and initiation of a futile cycle of free radicals.

P66Shc and vascular endothelial function

Dysfunctional endothelium is an early change in vasculature known to be associated with atherosclerosis. Among many regulators of vascular endothelial function, p66Shc has consistently been shown to mediate endothelial dysfunction. Over more than three decades of active research in the field of the physiological function of p66Shc, regulation of vascular endothelial functions has emerged as one of the most robust effects in a broad range of pathological conditions including hyperlipidemia, diabetes, and aging. A significant understanding has been developed with respect to the molecular signaling regulating the oxidative function of p66Shc in endothelial cells and its targets and regulators. In addition, novel regulatory modifications of p66Shc controlling its oxidative function, subcellular distribution, and stability have also been reported. This review will focus on summarizing the molecular signaling regulating the oxidative function of p66Shc and its role in vascular endothelium.

Modulation of Obesity and Insulin Resistance by the Redox Enzyme and Adaptor Protein p66Shc

Initially reported as a longevity-related protein, the 66 kDa isoform of the mammalian Shc1 locus has been implicated in several metabolic pathways, being able to act both as an adaptor protein and as a redox enzyme capable of generating reactive oxygen species (ROS) when it localizes to the mitochondrion. Ablation of p66^Shc has been shown to be protective against obesity and the insurgence of insulin resistance, but not all the studies available in the literature agree on these points. This review will focus in particular on the role of p66^Shc in the modulation of glucose homeostasis, obesity, body temperature, and respiration/energy expenditure. In view of the obesity and diabetes epidemic, p66^Shc may represent a promising therapeutic target with enormous implications for human health.

p53 plays a crucial role in endothelial dysfunction associated with hyperglycemia and ischemia

p53 is a guardian of the genome that protects against carcinogenesis. There is accumulating evidence that p53 is activated with aging. Such activation has been reported to contribute to various age-associated pathologies, but its role in vascular dysfunction is largely unknown. The aim of this study was to investigate whether activation of endothelial p53 has a pathological effect in relation to endothelial function. We established endothelial p53 loss-of-function and gain-of-function models by breeding endothelial-cell specific Cre mice with floxed Trp53 or floxed Mdm2/Mdm4 mice, respectively. Then we induced diabetes by injection of streptozotocin. In the diabetic state, endothelial p53 expression was markedly up-regulated and endothelium-dependent vasodilatation was significantly impaired. Impairment of vasodilatation was significantly ameliorated in endothelial p53 knockout (EC-p53 KO) mice, and deletion of endothelial p53 also significantly enhanced the induction of angiogenesis by ischemia. Conversely, activation of endothelial p53 by deleting Mdm2/Mdm4 reduced both endothelium-dependent vasodilatation and ischemia-induced angiogenesis. Introduction of p53 into human endothelial cells up-regulated the expression of phosphatase and tensin homolog (PTEN), thereby reducing phospho-eNOS levels. Consistent with these results, the beneficial impact of endothelial p53 deletion on endothelial function was attenuated in EC-p53 KO mice with an eNOS-deficient background. These results show that endothelial p53 negatively regulates endothelium-dependent vasodilatation and ischemia-induced angiogenesis, suggesting that inhibition of endothelial p53 could be a novel therapeutic target in patients with metabolic disorders.

The Src homology and collagen A (ShcA) adaptor protein may participate in the pathogenesis of membranous lupus nephritis

The Src homology and collagen A (ShcA) adaptor protein that binds to tyrosine kinase receptors. ShcA plays a role in insulin signaling, stress resistance and energy metabolism. The 66-kDa Src homology 2 domain-containing protein (p66shc) belongs to the ShcA family and has been associated with reactive oxygen species (ROS); increased ROS is involved in the pathology of lupus nephritis (LN). However, whether ShcA can act as a biomarker for oxidative injury in LN is unknown. This study is aimed to investigate the ShcA expression in kidney tissues from patients presenting with LN and the association between ShcA expression and clinical parameters. Renal biopsy tissues were obtained from 62 LN, 20 primary membranous nephropathy (MN) and 10 other secondary MN patients. ShcA was measured by immunofluorescence. The expression of ShcA in the membranous lupus nephritis (class V) group showed a higher trend but there were no significant differences compared with pure mesangial disease (class II) and proliferative (Class III/IV) lupus nephritis. ShcA deposits were negative in primary and other secondary MN. ShcA might act as a new biomarker and a diagnostic tool to identify membranous lupus nephritis with other MN.

Potential mechanisms underlying cardiovascular protection by polyphenols: Role of the endothelium

Epidemiological studies have indicated that regular intake of polyphenol-rich diets such as red wine and tea, are associated with a reduced risk of cardiovascular diseases. The beneficial effect of polyphenol-rich products has been attributable, at least in part, to their direct action on the endothelial function. Indeed, polyphenols from tea, grapes, cacao, berries, and plants have been shown to activate endothelial cells to increase the formation of potent vasoprotective factors including nitric oxide (NO) and to delay endothelial ageing. Moreover, intake of such polyphenol-rich products has been associated with the prevention and/or the improvement of an established endothelial dysfunction in several experimental models of cardiovascular diseases and in Humans with cardiovascular diseases. This review will discuss both experimental and clinical evidences indicating that polyphenols are able to promote endothelial and vascular health, as well as the underlying mechanisms.

Antiphospholipid antibodies induce thrombosis by PP2A activation via apoER2-Dab2-SHC1 complex formation in endothelium

In the antiphospholipid syndrome (APS), antiphospholipid antibody (aPL) recognition of β2 glycoprotein I promotes thrombosis, and preclinical studies indicate that this is due to endothelial nitric oxide synthase (eNOS) antagonism via apolipoprotein E receptor 2 (apoER2)-dependent processes. How apoER2 molecularly links these events is unknown. Here, we show that, in endothelial cells, the apoER2 cytoplasmic tail serves as a scaffold for aPL-induced assembly and activation of the heterotrimeric protein phosphatase 2A (PP2A). Disabled-2 (Dab2) recruitment to the apoER2 NPXY motif promotes the activating L309 methylation of the PP2A catalytic subunit by leucine methyl transferase-1. Concurrently, Src homology domain-containing transforming protein 1 (SHC1) recruits the PP2A scaffolding subunit to the proline-rich apoER2 C terminus along with 2 distinct regulatory PP2A subunits that mediate inhibitory dephosphorylation of Akt and eNOS. In mice, the coupling of these processes in endothelium is demonstrated to underlie aPL-invoked thrombosis. By elucidating these intricacies in the pathogenesis of APS-related thrombosis, numerous potential new therapeutic targets have been identified.

Endothelial Cell Metabolism

Endothelial cells (ECs) are more than inert blood vessel lining material. Instead, they are active players in the formation of new blood vessels (angiogenesis) both in health and (life-threatening) diseases. Recently, a new concept arose by which EC metabolism drives angiogenesis in parallel to well-established angiogenic growth factors (e.g., vascular endothelial growth factor). 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3-driven glycolysis generates energy to sustain competitive behavior of the ECs at the tip of a growing vessel sprout, whereas carnitine palmitoyltransferase 1a-controlled fatty acid oxidation regulates nucleotide synthesis and proliferation of ECs in the stalk of the sprout. To maintain vascular homeostasis, ECs rely on an intricate metabolic wiring characterized by intracellular compartmentalization, use metabolites for epigenetic regulation of EC subtype differentiation, crosstalk through metabolite release with other cell types, and exhibit EC subtype-specific metabolic traits. Importantly, maladaptation of EC metabolism contributes to vascular disorders, through EC dysfunction or excess angiogenesis, and presents new opportunities for anti-angiogenic strategies. Here we provide a comprehensive overview of established as well as newly uncovered aspects of EC metabolism.

Allopurinol protects human glomerular endothelial cells from high glucose-induced reactive oxygen species generation, p53 overexpression and endothelial dysfunction

PURPOSE

Mitochondrial reactive oxygen species (ROS) overproduction in capillary endothelial cells is a prerequisite for the development of diabetic nephropathy. Inhibition of xanthine oxidase, another ROS generator, ameliorates experimental diabetic nephropathy. To test the hypothesis that the initial high glucose-induced ROS production by the mitochondria activates xanthine oxidase, which afterward remains as the major source of ROS, we cultured primary human glomerular endothelial cells (GEnC) under normal or high-glucose conditions, with or without the xanthine oxidase inhibitor allopurinol.

METHODS

ROS generation and nitric oxide synthase (NOS) activity were assessed by chemiluminescence or colorimetrically. Levels of intercellular adhesion molecule 1 (ICAM-1), p53 and phosphorylated p53 (p-p53) were assessed by western blotting.

RESULTS

Allopurinol prevented high glucose-induced ROS generation indicating that xanthine oxidase is the major source of ROS. Allopurinol protected GEnC from endothelial dysfunction since it prevented the high glucose-induced decrease in NOS activity and increase in ICAM-1 expression. Allopurinol reduced p53 and p-p53 levels induced by high glucose suggesting an axis of xanthine oxidase-derived ROS, DNA damage, p53 stabilization and endothelial dysfunction that may contribute to the pathogenesis of diabetic nephropathy.

CONCLUSIONS

Allopurinol protects GEnC from high glucose-induced ROS generation, p53 overexpression and endothelial dysfunction. These data provide a pathogenetic mechanism that supports the results of experimental and clinical studies about the beneficial effect of xanthine oxidase inhibitors on the development of diabetic nephropathy.

Shc and the mechanotransduction of cellular anchorage and metastasis

Tissue cells continually monitor anchorage conditions by gauging the physical properties of their underlying matrix and surrounding environment. The Rho and Ras GTPases are essential components of these mechanosensory pathways. These molecular switches control both cytoskeletal as well as cell fate responses to anchorage conditions and are thus critical to our understanding of how cells respond to their physical environment and, by extension, how malignant cells gainsay these regulatory pathways. Recent studies indicate that 2 proteins produced by the SHC1 gene, thought for the most part to functionally oppose each other, collaborate in their ability to respond to mechanical force by initiating respective Rho and Ras signals. In this review, we focus on the coupling of Shc and GTPases in the cellular response to mechanical anchorage signals, with emphasis on its relevance for cancer.

P66Shc-Induced MicroRNA-34a Causes Diabetic Endothelial Dysfunction by Downregulating Sirtuin1

OBJECTIVE

Diabetes mellitus causes vascular endothelial dysfunction and alters vascular microRNA expression. We investigated whether endothelial microRNA-34a (miR-34a) leads to diabetic vascular dysfunction by targeting endothelial sirtuin1 (Sirt1) and asked whether the oxidative stress protein p66Shc governs miR-34a expression in the diabetic endothelium.

APPROACH AND RESULTS

MiR-34a is upregulated, and Sirt1 downregulated, in aortic endothelium of db/db and streptozotocin-induced diabetic mice. Systemic administration of miR-34a inhibitor, or endothelium-specific knockout of miR-34a, prevents downregulation of aortic Sirt1 and rescues impaired endothelium-dependent aortic vasorelaxation induced by diabetes mellitus. Moreover, overexpression of Sirt1 mitigates impaired endothelium-dependent vasorelaxation caused by miR-34a mimic ex vivo. Systemic infusion of miR-34a inhibitor or genetic ablation of endothelial miR-34a prevents downregulation of endothelial Sirt1 by high glucose. MiR-34a is upregulated, Sirt1 is downregulated, and oxidative stress (hydrogen peroxide) is induced in endothelial cells incubated with high glucose or the free fatty acid palmitate in vitro. Increase of hydrogen peroxide and induction of endothelial miR-34a by high glucose or palmitate in vitro is suppressed by knockdown of p66shc. In addition, overexpression of wild-type but not redox-deficient p66Shc upregulates miR-34a in endothelial cells. P66Shc-stimulated upregulation of endothelial miR-34a is suppressed by cell-permeable antioxidants. Finally, mice with global knockdown of p66Shc are protected from diabetes mellitus-induced upregulation of miR-34a and downregulation of Sirt1 in the endothelium.

CONCLUSIONS

These data show that hyperglycemia and elevated free fatty acids in the diabetic milieu recruit p66Shc to upregulate endothelial miR-34a via an oxidant-sensitive mechanism, which leads to endothelial dysfunction by targeting Sirt1.

C-peptide protects against hyperglycemic memory and vascular endothelial cell apoptosis

C-peptide exerts protective effects against diabetic complications; however, its role in inhibiting hyperglycemic memory (HGM) has not been elucidated. We investigated the beneficial effect of C-peptide on HGM-induced vascular damage in vitro and in vivo using human umbilical vein endothelial cells and diabetic mice. HGM induced apoptosis by persistent generation of intracellular ROS and sustained formation of ONOO(-) and nitrotyrosine. These HGM-induced intracellular events were normalized by treatment with C-peptide, but not insulin, in endothelial cells. C-peptide also inhibited persistent upregulation of p53 and activation of mitochondrial adaptor p66(shc) after glucose normalization. Further, C-peptide replacement therapy prevented persistent generation of ROS and ONOO(-) in the aorta of diabetic mice whose glucose levels were normalized by the administration of insulin. C-peptide, but not insulin, also prevented HGM-induced endothelial apoptosis in the murine diabetic aorta. This study highlights a promising role for C-peptide in preventing HGM-induced intracellular events and diabetic vascular damage.

The pro-oxidant gene p66shc increases nicotine exposure-induced lipotoxic oxidative stress in renal proximal tubule cells

Nicotine (NIC) exposure augments free fatty acid (FFA) deposition and oxidative stress, with a concomitant increase in the expression of the pro-oxidant p66shc. In addition, a decrease in the antioxidant manganese superoxide dismutase (MnSOD) has been observed in the kidneys of mice fed a high‑fat diet. The present study aimed to determine whether the pro‑oxidant p66shc mediates NIC‑dependent increases in renal oxidative stress by augmenting the production of reactive oxygen species (ROS) and suppressing the FFA‑induced antioxidant response in cultured NRK52E renal proximal tubule cells. Briefly, NRK52E renal proximal tubule cells were treated with 200 µM NIC, 100 µM oleic acid (OA), or a combination of NIC and OA. The expression levels of p66shc and MnSOD were modulated according to genetic methods. ROS production and cell injury, in the form of lactate dehydrogenase release, were subsequently detected. Promoter activity of p66shc and MnSOD, as well as forkhead box (FOXO)‑dependent transcription, was investigated using reporter luciferase assays. The results demonstrated that NIC exacerbated OA‑mediated intracellular ROS production and cell injury through the transcriptional activation of p66shc. NIC also suppressed OA‑mediated induction of the antioxidant MnSOD promoter activity through p66shc‑dependent inactivation of FOXO activity. Overexpression of p66shc and knockdown of MnSOD had the same effect as treatment with NIC on OA‑mediated lipotoxicity. These data may be used to generate a therapeutic means to ameliorate renal lipotoxicity in obese smokers.

p66Shc: A novel biomarker of tubular oxidative injury in patients with diabetic nephropathy

Increased p66Shc expression has been associated with diabetic nephropathy (DN). However, whether p66Shc can serve as a potential biomarker for tubular oxidative injury in DN is unknown. We measured the expression of p66Shc in peripheral blood monocytes (PBMs) and renal biopsy tissues from DN patients and then analysed the relationship between p66Shc expression and the clinical characteristics of patients with DN. Patients were divided into 4 groups (class IIa, class IIb, class III and the control group). qPCR, Western blotting and immunohistochemistry were performed. The results showed that both p66Shc and p-p66Shc expression significantly increased in PBMs and kidney tissues of DN patients. Moreover, Spearman’s correlation and multiple regression analyses were carried out. A positive relationship between the p66Shc expression and oxidative stress was found. p66Shc and oxidative stress were significant predictors of the degree of tubular damage. In addition, p66Shc expression was positively correlated with the concentrations of β-NAG, UACR and 8-OHdG, low-density lipoprotein and blood glucose levels, and duration of diabetes in patients with DN from class IIa to class III. These data indicated that increased expression of p66Shc may serve as a therapeutic target and a novel biomarker of DN.

Cardiovascular Outcome Studies in Diabetes: How Do We Make Sense of These New Data?

Poorly controlled diabetes is characterized by premature cardiovascular mortality and morbidity. The mechanisms linking hyperglycemia with accelerated atherosclerotic disease have not been fully elucidated; however, are thought to be mediated through vascular inflammation, oxidative stress and endothelial dysfunction. The advent of incretin-based therapy, whether by increasing endogenous glucagon-like peptide (GLP)-1 and glucose-dependent inhibitory polypeptide by inhibition of their breakdown using di-peptidyl peptidase 4 inhibitors, or augmenting GLP-1 activity using either exendin-4-based drugs or synthetic GLP-1 analogs promised not just improvements in glycemic control, but improvements in endothelial function, lipid profiles and markers of vascular inflammation. As such, it was anticipated they would demonstrate cardiovascular benefit in those with diabetes, indeed early meta-analyses suggested cardiovascular events would be reduced. To date, however, this benefit has failed to materialize, indeed the cardiovascular outcome trials, whilst meeting their primary endpoint of cardiovascular safety, have failed to demonstrate any improvements in stroke or myocardial infarction. This review will explore the data and attempt to answer the question: what went wrong?

Cigarette smoke induces mucin hypersecretion and inflammatory response through the p66shc adaptor protein-mediated mechanism in human bronchial epithelial cells

The p66Shc adaptor protein is a newly recognized mediator of mitochondrial dysfunction and might play a role in cigarette smoke (CS)-induced airway epithelial cell injury. CS can induce an excessive amount of reactive oxygen species (ROS) generation, which can cause mitochondrial depolarization and injury through the oxidative stress-mediated Serine36 phosphorylation of p66Shc. The excessive production of ROS can trigger an inflammatory response and mucin hypersecretion by enhancing the transcriptional activity of pro-inflammatory cytokines and mucin genes. Therefore, we speculate that p66Shc plays an essential role in airway epithelial cell injury and the process of mucin generation in CS-induced chronic inflammatory airway diseases. Our present study focuses on the role of p66Shc in ROS generation, and on the resulting mitochondrial dysfunction, inflammatory response and mucus hypersecretion in CS-stimulated human bronchial epithelial cells (16HBE). We found that CS disturbed the mitochondrial function by increasing the level of phosphorylated p66Shc in these cells and that the effects were significantly reduced by silencing p66Shc. Conversely, the ectopic overexpression of wild-type p66Shc enhanced these effects. We also found that high levels of ROS inhibited FOXO3a transcriptional activity, which led to NF-κB activation. Subsequently, activated NF-κB promoted pro-inflammatory cytokine production and mucin hypersecretion. Thus, manipulating p66Shc might offer a new therapeutic modality with which to treat chronic inflammatory airway diseases.

The Redox-sensitive Induction of the Local Angiotensin System Promotes Both Premature and Replicative Endothelial Senescence: Preventive Effect of a Standardized Crataegus Extract

Endothelial senescence, characterized by an irreversible cell cycle arrest, oxidative stress, and downregulation of endothelial nitric oxide synthase (eNOS), has been shown to promote endothelial dysfunction leading to the development of age-related vascular disorders. This study has assessed the possibility that the local angiotensin system promotes endothelial senescence in coronary artery endothelial cells and also the protective effect of the Crataegus extract WS1442, a quantified hawthorn extract. Serial passaging from P1 to P4 (replicative senescence) and treatment of P1 endothelial cells with the eNOS inhibitor L-NAME (premature senescence) promoted acquisition of markers of senescence, enhanced ROS formation, decreased eNOS expression, and upregulation of angiotensin-converting enzyme (ACE) and AT1 receptors. Increased SA-β-gal activity and the upregulation of ACE and AT1R in senescent cells were prevented by antioxidants, an ACE inhibitor, and by an AT1 receptor blocker. WS1442 prevented SA-β-gal activity, the downregulation of eNOS, and oxidative stress in P3 cells. These findings indicate that the impairment of eNOS-derived nitric oxide formation favors a pro-oxidant response triggering the local angiotensin system, which, in turn, promotes endothelial senescence. Such a sequence of events can be effectively inhibited by a standardized polyphenol-rich extract mainly by targeting the oxidative stress.

Trichostatin A Modulates Angiotensin II-induced Vasoconstriction and Blood Pressure Via Inhibition of p66shc Activation

Histone deacetylase (HDAC) has been recognized as a potentially useful therapeutic target for cardiovascular disorders. However, the effect of the HDAC inhibitor, trichostatin A (TSA), on vasoreactivity and hypertension remains unknown. We performed aortic coarctation at the inter-renal level in rats in order to create a hypertensive rat model. Hypertension induced by abdominal aortic coarctation was significantly suppressed by chronic treatment with TSA (0.5 mg/kg/day for 7 days). Nicotinamide adenine dinucleotide phosphate-driven reactive oxygen species production was also reduced in the aortas of TSA-treated aortic coarctation rats. The vasoconstriction induced by angiotensin II (Ang II, 100 nM) was inhibited by TSA in both endothelium-intact and endothelium-denuded rat aortas, suggesting that TSA has mainly acted in vascular smooth muscle cells (VSMCs). In cultured rat aortic VSMCs, Ang II increased p66shc phosphorylation, which was inhibited by the Ang II receptor type I (AT1R) inhibitor, valsartan (10 µM), but not by the AT2R inhibitor, PD123319. TSA (1~10 µM) inhibited Ang II-induced p66shc phosphorylation in VSMCs and in HEK293T cells expressing AT1R. Taken together, these results suggest that TSA treatment inhibited vasoconstriction and hypertension via inhibition of Ang II-induced phosphorylation of p66shc through AT1R.

Palmitic acid increases pro-oxidant adaptor protein p66Shc expression and affects vascularization factors in angiogenic mononuclear cells: Action of resveratrol

A defect in neo-vascularization process involving circulating angiogenic mononuclear cells (CACs) dysfunction is associated with diabetes. We showed that oxidative stress was elevated in CACs cultured from blood of individuals with metabolic syndrome (MetS) and diabetes. We then assessed the action of palmitic acid (PA), a deregulated and increased NEFA in metabolic disorders, focusing on its oxidant potential. We observed that the phyto-polyphenol resveratrol normalized oxidative stress both in CACs isolated from MetS patients or treated with PA. Resveratrol further decreased the deleterious action of PA on gene expression of vascularization factors (TNFα, VEGF-A, SDF1α, PECAM-1, VEGFR2, Tie2 and CXCR4) and improved CAC motility. Particularly, resveratrol abolished the PA-induced over-expression of the pro-oxidant protein p66Shc. Neither KLF2 nor SIRT1, previously shown in resveratrol and p66Shc action, was directly involved. Silencing p66Shc normalized PA action on VEGF-A and TNFα specifically, without abolishing the PA-induced oxidative stress, which suggests a deleterious role of p66Shc independently of any major modulation of the cellular oxidative status in a high NEFA levels context. Besides showing that resveratrol reverses PA-induced harmful effects on human CAC function, certainly through profound cellular modifications, we establish p66Shc as a major therapeutic target in metabolic disorders, independent from glycemic control.

The p66(Shc) redox adaptor protein is induced by saturated fatty acids and mediates lipotoxicity-induced apoptosis in pancreatic beta cells

AIMS/HYPOTHESIS

The role of the redox adaptor protein p66(Shc) as a potential mediator of saturated fatty acid (FA)-induced beta cell death was investigated.

METHODS

The effects of the FA palmitate on p66(Shc) expression were evaluated in human and murine islets and in rat insulin-secreting INS-1E cells. p66(Shc) expression was also measured in islets from mice fed a high-fat diet (HFD) and from human donors with different BMIs. Cell apoptosis was quantified by two independent assays. The role of p66(Shc) was investigated using pancreatic islets from p66 (Shc-/-) mice and in INS-1E cells with knockdown of p66(Shc) or overexpression of wild-type and phosphorylation-defective p66(Shc). Production of reactive oxygen species (ROS) was evaluated by the dihydroethidium oxidation method.

RESULTS

Palmitate induced a selective increase in p66(Shc) protein expression and phosphorylation on Ser(36) and augmented apoptosis in human and mouse islets and in INS-1E cells. Inhibiting the tumour suppressor protein p53 prevented both the palmitate-induced increase in p66(Shc) expression and beta cell apoptosis. Palmitate-induced apoptosis was abrogated in islets from p66 (Shc-/-) mice and following p66 (Shc) knockdown in INS-1E cells; by contrast, overexpression of p66(Shc), but not that of the phosphorylation-defective p66(Shc) mutant, enhanced palmitate-induced apoptosis. The pro-apoptotic effects of p66(Shc) were dependent upon its c-Jun N-terminal kinase-mediated phosphorylation on Ser(36) and associated with generation of ROS. p66(Shc) protein expression and function were also elevated in islets from HFD-fed mice and from obese/overweight cadaveric human donors.

CONCLUSIONS/INTERPRETATION

p53-dependent augmentation of p66(Shc) expression and function represents a key signalling response contributing to beta cell apoptosis under conditions of lipotoxicity.

Mitochondria-associated membranes: composition, molecular mechanisms, and physiopathological implications

SIGNIFICANCE

In all cells, the endoplasmic reticulum (ER) and mitochondria are physically connected to form junctions termed mitochondria-associated membranes (MAMs). This subcellular compartment is under intense investigation because it represents a "hot spot" for the intracellular signaling of important pathways, including the synthesis of cholesterol and phospholipids, calcium homeostasis, and reactive oxygen species (ROS) generation and activity.

RECENT ADVANCES

The advanced methods currently used to study this fascinating intracellular microdomain in detail have enabled the identification of the molecular composition of MAMs and their involvement within different physiopathological contexts.

CRITICAL ISSUES

Here, we review the knowledge regarding (i) MAMs composition in terms of protein composition, (ii) the relationship between MAMs and ROS, (iii) the involvement of MAMs in cell death programs with particular emphasis within the tumor context, (iv) the emerging role of MAMs during inflammation, and (v) the key role of MAMs alterations in selected neurological disorders.

FUTURE DIRECTIONS

Whether alterations in MAMs represent a response to the disease pathogenesis or directly contribute to the disease has not yet been unequivocally established. In any case, the signaling at the MAMs represents a promising pharmacological target for several important human diseases.

Skewed Epigenetics: An Alternative Therapeutic Option for Diabetes Complications

Vascular complications are major causes of morbidity and mortality in type 2 diabetes patients. Mitochondrial reactive oxygen species (ROS) generation and a lack of efficient antioxidant machinery, a result of hyperglycaemia, mainly contribute to this problem. Although advances in therapy have significantly reduced both morbidity and mortality in diabetic individuals, diabetes-associated vascular complications are still one of the most challenging health problems worldwide. New healing options are urgently needed as current therapeutics are failing to improve long-term outcomes. Particular effort has recently been devoted to understanding the functional relationship between chromatin structure regulation and the persistent change in gene expression which is driven by hyperglycaemia and which accounts for long-lasting diabetic complications. A detailed investigation into epigenetic chromatin modifications in type 2 diabetes is underway. This will be particularly useful in the design of mechanism-based therapeutics which interfere with long-lasting activating epigenetics and improve patient outcomes. We herein provide an overview of the most relevant mechanisms that account for hyperglycaemia-induced changes in chromatin structure; the most relevant mechanism is called "metabolic memory."

Molecular pathways of arterial aging

The incidence of stroke and myocardial infarction increases in aged patients and it is associated with an adverse outcome. Considering the aging population and the increasing incidence of cardiovascular disease, the prediction for population well-being and health economics is daunting. Accordingly, there is an unmet need to focus on fundamental processes underlying vascular aging. A better understanding of the pathways leading to arterial aging may contribute to design mechanism-based therapeutic approaches to prevent or attenuate features of vascular senescence. In the present review, we discuss advances in the pathophysiology of age-related vascular dysfunction including nitric oxide signalling, dysregulation of oxidant/inflammatory genes, epigenetic modifications and mechanisms of vascular calcification as well as insights into vascular repair. Such an overview highlights attractive molecular targets for the prevention of age-driven vascular disease.

Dual role of endothelial nitric oxide synthase in oxidized LDL-induced, p66Shc-mediated oxidative stress in cultured human endothelial cells

BACKGROUND

The aging gene p66Shc, is an important mediator of oxidative stress-induced vascular dysfunction and disease. In cultured human aortic endothelial cells (HAEC), p66Shc deletion increases endothelial nitric oxide synthase (eNOS) expression and nitric oxide (NO) bioavailability via protein kinase B. However, the putative role of the NO pathway on p66Shc activation remains unclear. This study was designed to elucidate the regulatory role of the eNOS/NO pathway on p66Shc activation.

METHODS AND RESULTS

Incubation of HAEC with oxidized low density lipoprotein (oxLDL) led to phosphorylation of p66Shc at Ser-36, resulting in an enhanced production of superoxide anion (O2-). In the absence of oxLDL, inhibition of eNOS by small interfering RNA or L-NAME, induced p66Shc phosphorylation, suggesting that basal NO production inhibits O2- production. oxLDL-induced, p66Shc-mediated O2- was prevented by eNOS inhibition, suggesting that when cells are stimulated with oxLDL eNOS is a source of reactive oxygen species. Endogenous or exogenous NO donors, prevented p66Shc activation and reduced O2- production. Treatment with tetrahydrobiopterin, an eNOS cofactor, restored eNOS uncoupling, prevented p66Shc activation, and reduced O2- generation. However, late treatment with tetrahydropterin did not yield the same result suggesting that eNOS uncoupling is the primary source of reactive oxygen species.

CONCLUSIONS

The present study reports that in primary cultured HAEC treated with oxLDL, p66Shc-mediated oxidative stress is derived from eNOS uncoupling. This finding contributes novel information on the mechanisms of p66Shc activation and its dual interaction with eNOS underscoring the importance eNOS uncoupling as a putative antioxidant therapeutical target in endothelial dysfunction as observed in cardiovascular disease.

Canonical Wnt signaling induces vascular endothelial dysfunction via p66Shc-regulated reactive oxygen species

OBJECTIVE

Reactive oxygen species regulate canonical Wnt signaling. However, the role of the redox regulatory protein p66(Shc) in the canonical Wnt pathway is not known. We investigated whether p66(Shc) is essential for canonical Wnt signaling in the endothelium and determined whether the canonical Wnt pathway induces vascular endothelial dysfunction via p66(Shc)-mediated oxidative stress.

APPROACH AND RESULTS

The canonical Wnt ligand Wnt3a induced phosphorylation (activation) of p66(Shc) in endothelial cells. Wnt3a-stimulated dephosphorylation of β-catenin, and β-catenin-dependent transcription, was inhibited by knockdown of p66(Shc). Exogenous H2O2-induced β-catenin dephosphorylation was also mediated by p66(Shc). Moreover, p66(Shc) overexpression dephosphorylated β-catenin and increased β-catenin-dependent transcription, independent of Wnt3a ligand. P66(Shc)-induced β-catenin dephosphorylation was inhibited by antioxidants N-acetyl cysteine and catalase. Wnt3a upregulated endothelial NADPH oxidase-4, and β-catenin dephosphorylation was suppressed by knocking down NADPH oxidase-4 and by antioxidants. Wnt3a increased H2O2 levels in endothelial cells and impaired endothelium-dependent vasorelaxation in mouse aortas, both of which were rescued by p66(Shc) knockdown. P66(Shc) knockdown also inhibited adhesion of monocytes to Wnt3a-stimulated endothelial cells. Furthermore, constitutively active β-catenin expression in the endothelium increased vascular reactive oxygen species and impaired endothelium-dependent vasorelaxation. In vivo, high-fat diet feeding-induced endothelial dysfunction in mice was associated with increased endothelial Wnt3a, dephosphorylated β-catenin, and phosphorylated p66(Shc). High-fat diet-induced dephosphorylation of endothelial β-catenin was diminished in mice in which p66(Shc) was knocked down.

CONCLUSIONS

p66(Shc) plays a vital part in canonical Wnt signaling in the endothelium and mediates Wnt3a-stimulated endothelial oxidative stress and dysfunction.

Adaptor protein p66(Shc) mediates hypertension-associated, cyclic stretch-dependent, endothelial damage

Increased cyclic stretch to the vessel wall, as observed in hypertension, leads to endothelial dysfunction through increased free radical production and reduced nitric oxide bioavailability. Genetic deletion of the adaptor protein p66(Shc) protects mice against age-related and hyperglycemia-induced endothelial dysfunction, as well as atherosclerosis and stroke. Furthermore, p66(Shc) mediates vascular dysfunction in hypertensive mice. However, the direct role of p66(Shc) in mediating mechanical force-induced free radical production is unknown; thus, we studied the effect of cyclic stretch on p66(Shc) activation in primary human aortic endothelial cells and aortic endothelial cells isolated from normotensive and hypertensive rats. Exposure of human aortic endothelial cells to cyclic stretch led to a stretch- and time-dependent p66(Shc) phosphorylation at Ser36 downstream of integrin α5β1 and c-Jun N-terminal kinase. In parallel, nicotinamide adenine dinucleotide phosphate oxidase activation, as well as production of reactive oxygen species, increased, whereas nitric oxide bioavailability decreased. Silencing of p66(Shc) blunted stretch-increased superoxide anion production and nicotinamide adenine dinucleotide phosphate oxidase activation and restored nitric oxide bioavailability. In line with the above, activation of p66(Shc) increased in isolated aortic endothelial cells of spontaneously hypertensive rats compared with normotensive ones. Pathological stretch by activating integrin α5β1 and c-Jun N-terminal kinase phosphorylates p66(Shc) at Ser36, augments reactive oxygen species production via nicotinamide adenine dinucleotide phosphate oxidase, and in turn reduces nitric oxide bioavailability. This novel molecular pathway may be relevant for endothelial dysfunction and vascular disease in hypertension.

P66Shc mediates increased platelet activation and aggregation in hypercholesterolemia

BACKGROUND AND HYPOTHESIS

Hypercholesterolemia leads to a prothrombotic phenotype. Platelet hyperactivity associated with hypercholesterolemia has been attributed, in part, to oxidative stress. P66Shc is a well-known determinant of cellular and organismal oxidative stress. However, its role in platelet biology is not known. We hypothesized that p66Shc mediates platelet hyperactivation and hyperaggregation in hypercholesterolemia.

METHODS AND RESULTS

P66Shc was expressed in both human and mouse platelets, as determined by qRT-PCR and immunoblotting. Mouse platelet p66Shc expression was upregulated by hypercholesterolemia induced by high-fat diet feeding. Compared to wild-type mice, high-fat diet-induced p66Shc expression in platelets was suppressed in transgenic mice expressing a short hairpin RNA targeting p66Shc (p66ShcRNAi). High-fat diet feeding of wild-type mice amplified surface P-selectin expression on platelets stimulated by the thrombin receptor agonist protease-activated receptor-4 (PAR4), and increased aggregation of platelets induced by thrombin. These exaggerated platelet responses induced by high-fat diet feeding were significantly blunted in p66ShcRNAi mice. Finally, thrombin-stimulated platelet reactive oxygen species were suppressed in p66ShcRNAi mice.

CONCLUSIONS

Hypercholesterolemia stimulates p66Shc expression in platelets, promoting platelet oxidative stress, hyperreactivity and hyperaggregation via p66Shc.

The anti-hypercholesterolemic effect of low p53 expression protects vascular endothelial function in mice

Aims

To demonstrate that p53 modulates endothelial function and the stress response to a high-fat western diet (WD).

Methods and Results

Three-month old p53^+/+ wild type (WT) and p53^+/− male mice were fed a regular or WD for 3 months. Plasma levels of total cholesterol (TC) and LDL-cholesterol were significantly elevated (p<0.05) in WD-fed WT (from 2.1±0.2 mmol/L to 3.1±0.2, and from 0.64±0.09 mmol/L to 1.25±0.11, respectively) but not in p53^+/− mice. The lack of cholesterol accumulation in WD-fed p53^+/− mice was ass–ociated with high bile acid plasma concentrations (p53^+/− =  4.7±0.9 vs. WT =  3.3±0.2 μmol/L, p<0.05) concomitant with an increased hepatic 7-alpha-hydroxylase mRNA expression. While the WD did not affect aortic endothelial relaxant function in p53^+/− mice (WD =  83±5 and RD =  82±4% relaxation), it increased the maximal response to acetylcholine in WT mice (WD =  87±2 vs. RD =  62±5% relaxation, p<0.05) to levels of p53^+/−. In WT mice, the rise in TC associated with higher (p<0.05) plasma levels of pro-inflammatory keratinocyte-derived chemokine, and an over-activation (p<0.05) of the relaxant non-nitric oxide/non-prostacyclin endothelial pathway. It is likely that in WT mice, activations of these pathways are adaptive and contributed to maintain endothelial function, while the WD neither promoted inflammation nor affected endothelial function in p53^+/− mice.

Conclusions

Our data demonstrate that low endogenous p53 expression prevents the rise in circulating levels of cholesterol when fed a WD. Consequently, the endothelial stress of hypercholesterolemia is absent in young p53^+/− mice as evidenced by the absence of endothelial adaptive pathway over-activation to minimize stress-related damage.

p53 and mitochondrial function in neurons

The p53 tumor suppressor plays a central role in dictating cell survival and death as a cellular sensor for a myriad of stresses including DNA damage, oxidative and nutritional stress, ischemia and disruption of nucleolar function. Activation of p53-dependent apoptosis leads to mitochondrial apoptotic changes via the intrinsic and extrinsic pathways triggering cell death execution most notably by release of cytochrome c and activation of the caspase cascade. Although it was previously believed that p53 induces apoptotic mitochondrial changes exclusively through transcription-dependent mechanisms, recent studies suggest that p53 also regulates apoptosis via a transcription-independent action at the mitochondria. Recent evidence further suggests that p53 can regulate necrotic cell death and autophagic activity including mitophagy. An increasing number of cytosolic and mitochondrial proteins involved in mitochondrial metabolism and respiration are regulated by p53, which influences mitochondrial ROS production as well. Cellular redox homeostasis is also directly regulated by p53 through modified expression of pro- and anti-oxidant proteins. Proper regulation of mitochondrial size and shape through fission and fusion assures optimal mitochondrial bioenergetic function while enabling adequate mitochondrial transport to accommodate local energy demands unique to neuronal architecture. Abnormal regulation of mitochondrial dynamics has been increasingly implicated in neurodegeneration, where elevated levels of p53 may have a direct contribution as the expression of some fission/fusion proteins are directly regulated by p53. Thus, p53 may have a much wider influence on mitochondrial integrity and function than one would expect from its well-established ability to transcriptionally induce mitochondrial apoptosis. However, much of the evidence demonstrating that p53 can influence mitochondria through nuclear, cytosolic or intra-mitochondrial sites of action has yet to be confirmed in neurons. Nonetheless, as mitochondria are essential for supporting normal neuronal functions and in initiating/propagating cell death signaling, it appears certain that the mitochondria-related functions of p53 will have broader implications than previously thought in acute and progressive neurological conditions, providing new therapeutic targets for treatment.