Oxidative stress and increased eNOS and NADPH oxidase expression in mouse microvessel endothelial cells

Targeting endothelial cells with golden spice curcumin: A promising therapy for cardiometabolic multimorbidity

Cardiometabolic multimorbidity (CMM) is an increasingly significant global public health concern. It encompasses the coexistence of multiple cardiometabolic diseases, including hypertension, stroke, heart disease, atherosclerosis, and T2DM. A crucial component to the development of CMM is the disruption of endothelial homeostasis. Therefore, therapies targeting endothelial cells through multi-targeted and multi-pathway approaches hold promise for preventing and treatment of CMM. Curcumin, a widely used dietary supplement derived from the golden spice Carcuma longa, has demonstrated remarkable potential in treatment of CMM through its interaction with endothelial cells. Numerous studies have identified various molecular targets of curcumin (such as NF-κB/PI3K/AKT, MAPK/NF-κB/IL-1β, HO-1, NOs, VEGF, ICAM-1 and ROS). These findings highlight the efficacy of curcumin as a therapeutic agent against CMM through the regulation of endothelial function. It is worth noting that there is a close relationship between the progression of CMM and endothelial damage, characterized by oxidative stress, inflammation, abnormal NO bioavailability and cell adhesion. This paper provides a comprehensive review of curcumin, including its availability, pharmacokinetics, pharmaceutics, and therapeutic application in treatment of CMM, as well as the challenges and future prospects for its clinical translation. In summary, curcumin shows promise as a potential treatment option for CMM, particularly due to its ability to target endothelial cells. It represents a novel and natural lead compound that may offer significant therapeutic benefits in the management of CMM.

Race and sex differences in ROS production and SOD activity in HUVECs

Black individuals and men are predisposed to an earlier onset and higher prevalence of hypertension, compared with White individuals and women, respectively. Therefore, the influence of race and sex on reactive oxygen species (ROS) production and superoxide dismutase (SOD) activity following induced inflammation was evaluated in female and male human umbilical vein endothelial cells (HUVECs) from Black and White individuals. It was hypothesized that HUVECs from Black individuals and male HUVECs would exhibit greater ROS production and impaired SOD activity. Inflammation was induced in HUVEC cell lines (n = 4/group) using tumor necrosis factor-alpha (TNF-α, 50ng/ml). There were no between group differences in ROS production or SOD activity in HUVECs from Black and White individuals, and HUVECs from Black individuals exhibited similar SOD activity at 24hr compared with 4hr of TNF-α treatment (p>0.05). However, HUVECs from White individuals exhibited significantly greater SOD Activity (p<0.05) at 24hr as compared to 4hr in the control condition but not with TNF-α treatment (p>0.05). Female HUVECs exhibited significantly lower ROS production than male HUVECs in the control condition and following TNF-α induced inflammation (p<0.05). Only female HUVECs exhibited significant increases in SOD activity with increased exposure time to TNF-α induced inflammation (p<0.05). HUVECs from White individuals alone exhibit blunted SOD activity when comparing control and TNF-α conditions. Further, compared to female HUVECs, male HUVECs exhibit a pro-inflammatory state.

Resveratrol alleviates high glucose-induced oxidative stress and apoptosis in rat cardiac microvascular endothelial cell through AMPK/Sirt1 activation

Diabetic cardiomyopathy (DCM) is a common complication of diabetes. DCM causes extensive lesions on cardiac microvasculature that is predominantly cardiac microvascular endothelial cells (CMECs). Reducing high glucose (HG)-induced damage such as oxidative damage and apoptosis could alleviate the development of DCM. The natural polyphenol resveratrol (RSV) is widely suggested as a cardioprotective agent that protect against DCM. However, limited evidence supports the protection of RSV against oxidative damage and apoptosis and study on the direct effects of RSV in CMEC is missing. Therefore, the current paper aimed to illustrate if RSV could attenuate oxidative stress and apoptosis in CMEC and to investigate the underlying mechanisms. Our data showed that HG elevated reactive oxygen species, malondialdehyde, decreased superoxide dismutase activity, increased apoptotic cell percentage in CMEC, which were reversed by RSV administration. In addition, RSV demonstrated antioxidative and anti-apoptotic effects in CMEC through AMPK/Sirt1 activation, further confirmed by AMPK inhibition or Sirt1 silencing. This study provides new evidence to support RSV as a potential cardioprotective alternative in treating DCM.

Interleukin-6 in retinal diseases: From pathogenesis to therapy

Interleukin-6 (IL-6) is a pleiotropic cytokine that participates in immunomodulation, inflammation, increases vascular permeability, hematopoiesis, and stimulates cell proliferation, among other biological processes. It exerts effects primarily through the classic and trans-signaling pathways. Many studies have demonstrated that IL-6 plays a critical role in the development of retinal diseases including diabetic retinopathy, uveitis, age-related macular degeneration, glaucoma, retinal vein occlusion, central serous chorioretinopathy and proliferative vitreoretinopathy. Thus, the progressive development of drugs targeting IL-6 and IL-6 receptor may play a role in the treatment of multiple retinal diseases. In this article, we comprehensively review the IL-6's biological functions of and its mechanisms in the pathogenesis of various retinal diseases. Furthermore, we summarize the drugs targeting IL-6 and its receptor and prospect their potential application in retinal diseases, hoping to provide new ideas for the treatment of retinal diseases.

Oxidative Regulation of Vascular Cav1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders

Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca²⁺ (Ca_v1.2) channel in small arteries and arterioles plays an essential role in regulating Ca²⁺ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Ca_v1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Ca_v1.2 and potential roles of ROS-mediated Ca_v1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.

Paracrine Shear-Stress-Dependent Signaling from Endothelial Cells Affects Downstream Endothelial Function and Inflammation

Cardiovascular diseases (CVDs), mainly ischemic heart disease (IHD) and stroke, are the leading cause of global mortality and major contributors to disability worldwide. Despite their heterogeneity, almost all CVDs share a common feature: the endothelial dysfunction. This is defined as a loss of functionality in terms of anti-inflammatory, anti-thrombotic and vasodilatory abilities of endothelial cells (ECs). Endothelial function is greatly ensured by the mechanotransduction of shear forces, namely, endothelial wall shear stress (WSS). Low WSS is associated with endothelial dysfunction, representing the primary cause of atherosclerotic plaque formation and an important factor in plaque progression and remodeling. In this work, the role of factors released by ECs subjected to different magnitudes of shear stress driving the functionality of downstream endothelium has been evaluated. By means of a microfluidic system, HUVEC monolayers have been subjected to shear stress and the conditioned media collected to be used for the subsequent static culture. The results demonstrate that conditioned media retrieved from low shear stress experimental conditions (LSS-CM) induce the downregulation of endothelial nitric oxide synthase (eNOS) expression while upregulating peripheral blood mononuclear cell (PBMC) adhesion by means of higher levels of adhesion molecules such as E-selectin and ICAM-1. Moreover, LSS-CM demonstrated a significant angiogenic ability comparable to the inflammatory control media (TNFα-CM); thus, it is likely related to tissue suffering. We can therefore suggest that ECs stimulated at low shear stress (LSS) magnitudes are possibly involved in the paracrine induction of peripheral endothelial dysfunction, opening interesting insights into the pathogenetic mechanisms of coronary microvascular dysfunction.

The Blood-Brain Barrier, Oxidative Stress, and Insulin Resistance

The blood–brain barrier (BBB) is a network of specialized endothelial cells that regulates substrate entry into the central nervous system (CNS). Acting as the interface between the periphery and the CNS, the BBB must be equipped to defend against oxidative stress and other free radicals generated in the periphery to protect the CNS. There are unique features of brain endothelial cells that increase the susceptibility of these cells to oxidative stress. Insulin signaling can be impacted by varying levels of oxidative stress, with low levels of oxidative stress being necessary for signaling and higher levels being detrimental. Insulin must cross the BBB in order to access the CNS, levels of which are important in peripheral metabolism as well as cognition. Any alterations in BBB transport due to oxidative stress at the BBB could have downstream disease implications. In this review, we cover the interactions of oxidative stress at the BBB, how insulin signaling is related to oxidative stress, and the impact of the BBB in two diseases greatly affected by oxidative stress and insulin resistance: diabetes mellitus and Alzheimer’s disease.

Vascular Health Triad in Humans With Hypertension-Not the Usual Suspects

Hypertension (HTN) affects more than one-third of the US population and remains the top risk factor for the development of cardiovascular disease (CVD). Identifying the underlying mechanisms for developing HTN are of critical importance because the risk of developing CVD doubles with ∼20 mmHg increase in systolic blood pressure (BP). Endothelial dysfunction, especially in the resistance arteries, is the primary site for initiation of sub-clinical HTN. Furthermore, inflammation and reactive oxygen and nitrogen species (ROS/RNS) not only influence the endothelium independently, but also have a synergistic influence on each other. Together, the interplay between inflammation, ROS and vascular dysfunction is referred to as the vascular health triad, and affects BP regulation in humans. While the interplay of the vascular health triad is well established, new underlying mechanistic targets are under investigation, including: Inducible nitric oxide synthase, hydrogen peroxide, hydrogen sulfide, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and nuclear factor activated T cells. This review outlines the role of these unusual suspects in vascular health and function in humans. This review connects the dots using these unusual suspects underlying inflammation, ROS and vascular dysfunction especially in individuals at risk of or with diagnosed HTN based on novel studies performed in humans.

Oxidative Stress Triggers Defective Autophagy in Endothelial Cells: Role in Atherothrombosis Development

Atherothrombosis, a multifactorial and multistep artery disorder, represents one of the main causes of morbidity and mortality worldwide. The development and progression of atherothrombosis is closely associated with age, gender and a complex relationship between unhealthy lifestyle habits and several genetic risk factors. The imbalance between oxidative stress and antioxidant defenses is the main biological event leading to the development of a pro-oxidant phenotype, triggering cellular and molecular mechanisms associated with the atherothrombotic process. The pathogenesis of atherosclerosis and its late thrombotic complications involve multiple cellular events such as inflammation, endothelial dysfunction, proliferation of vascular smooth muscle cells (SMCs), extracellular matrix (ECM) alterations, and platelet activation, contributing to chronic pathological remodeling of the vascular wall, atheromatous plague formation, vascular stenosis, and eventually, thrombus growth and propagation. Emerging studies suggest that clotting activation and endothelial cell (EC) dysfunction play key roles in the pathogenesis of atherothrombosis. Furthermore, a growing body of evidence indicates that defective autophagy is closely linked to the overproduction of reactive oxygen species (ROS) which, in turn, are involved in the development and progression of atherosclerotic disease. This topic represents a large field of study aimed at identifying new potential therapeutic targets. In this review, we focus on the major role played by the autophagic pathway induced by oxidative stress in the modulation of EC dysfunction as a background to understand its potential role in the development of atherothrombosis.

Porcine placenta extract improves high-glucose-induced angiogenesis impairment

Background

High glucose (HG)-induced reactive oxygen species (ROS) overproduction impairs angiogenesis that is one pivotal factor of wound healing process. Angiogenesis impairment induces delayed wound healing, whereby it eventually leads to amputation in cases of poorly controlled diabetes with diabetic ulceration. Porcine placenta extract (PPE) is a natural waste product that comprises plenty of bioactive agents including growth factors and antioxidants. It was reported as an effective compound that prevents ROS generation. The goal of this study was to investigate the in vitro effect of PPE on HG-induced ROS-mediated angiogenesis impairment.

Methods

Primary endothelial cells (HUVECs) and endothelial cell line (EA.hy926) were treated with HG in the presence of PPE. The endothelial cells (ECs) viability, intracellular ROS generation, migration, and angiogenesis were determined by MTT assay, DCFDA reagent, wound healing assay, and tube formation assay, respectively. Additionally, the molecular mechanism of PPE on HG-induced angiogenesis impairment was investigated by Western blot. The angiogenic growth factor secretion was also investigated by the sandwich ELISA technique.

Results

HG in the presence of PPE significantly decreased intracellular ROS overproduction compared to HG alone. HG in the presence of PPE significantly increased ECs viability, migration, and angiogenesis compared to HG alone by showing recovery of PI3K/Akt/ERK1/2 activation. HG in the presence of PPE also decreased ECs apoptosis compared to HG alone by decreasing p53/Bax/cleaved caspase 9/cleaved caspase 3 levels and increasing Bcl 2 level.

Conclusion

PPE attenuated HG-induced intracellular ROS overproduction that improved ECs viability, proliferation, migration, and angiogenesis by showing recovery of PI3K/Akt/ERK1/2 activation and inhibition of ECs apoptosis. This study suggests PPE ameliorated HG-induced ROS-mediated angiogenesis impairment, whereby it potentially provides an alternative treatment for diabetic wounds.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03243-z.

A Critical Review of the Evidence That Metformin Is a Putative Anti-Aging Drug That Enhances Healthspan and Extends Lifespan

The numerous beneficial health outcomes associated with the use of metformin to treat patients with type 2 diabetes (T2DM), together with data from pre-clinical studies in animals including the nematode, C. elegans, and mice have prompted investigations into whether metformin has therapeutic utility as an anti-aging drug that may also extend lifespan. Indeed, clinical trials, including the MILES (Metformin In Longevity Study) and TAME (Targeting Aging with Metformin), have been designed to assess the potential benefits of metformin as an anti-aging drug. Preliminary analysis of results from MILES indicate that metformin may induce anti-aging transcriptional changes; however it remains controversial as to whether metformin is protective in those subjects free of disease. Furthermore, despite clinical use for over 60 years as an anti-diabetic drug, the cellular mechanisms by which metformin exerts either its actions remain unclear. In this review, we have critically evaluated the literature that has investigated the effects of metformin on aging, healthspan and lifespan in humans as well as other species. In preparing this review, particular attention has been placed on the strength and reproducibility of data and quality of the study protocols with respect to the pharmacokinetic and pharmacodynamic properties of metformin. We conclude that despite data in support of anti-aging benefits, the evidence that metformin increases lifespan remains controversial. However, via its ability to reduce early mortality associated with various diseases, including diabetes, cardiovascular disease, cognitive decline and cancer, metformin can improve healthspan thereby extending the period of life spent in good health. Based on the available evidence we conclude that the beneficial effects of metformin on aging and healthspan are primarily indirect via its effects on cellular metabolism and result from its anti-hyperglycemic action, enhancing insulin sensitivity, reduction of oxidative stress and protective effects on the endothelium and vascular function.

Can Metformin Exert as an Active Drug on Endothelial Dysfunction in Diabetic Subjects?

Cardiovascular mortality is a major cause of death among in type 2 diabetes (T2DM). Endothelial dysfunction (ED) is a well-known important risk factor for the development of diabetes cardiovascular complications. Therefore, the prevention of diabetic macroangiopathies by preserving endothelial function represents a major therapeutic concern for all National Health Systems. Several complex mechanisms support ED in diabetic patients, frequently cross-talking each other: uncoupling of eNOS with impaired endothelium-dependent vascular response, increased ROS production, mitochondrial dysfunction, activation of polyol pathway, generation of advanced glycation end-products (AGEs), activation of protein kinase C (PKC), endothelial inflammation, endothelial apoptosis and senescence, and dysregulation of microRNAs (miRNAs). Metformin is a milestone in T2DM treatment. To date, according to most recent EASD/ADA guidelines, it still represents the first-choice drug in these patients. Intriguingly, several extraglycemic effects of metformin have been recently observed, among which large preclinical and clinical evidence support metformin’s efficacy against ED in T2DM. Metformin seems effective thanks to its favorable action on all the aforementioned pathophysiological ED mechanisms. AMPK pharmacological activation plays a key role, with metformin inhibiting inflammation and improving ED. Therefore, aim of this review is to assess metformin’s beneficial effects on endothelial dysfunction in T2DM, which could preempt development of atherosclerosis.

Cardioprotective effect of grape polyphenol extract against doxorubicin induced cardiotoxicity

Doxorubicin is a chemotherapeutic agent known to cause cardiotoxicity that is thought to be associated with oxidative stress. The aim of the current study is to investigate the role of grape polyphenols' antioxidant property as cardioprotective against doxorubicin-induced cardiotoxicity. Adult Wistar rats weighing 200 ± 20 g were divided into 3 different groups: a doxorubicin group that received a single intraperitoneal administration of doxorubicin (8.0 mg/kg body weight), an experimental group that received doxorubicin and grape polyphenol concentrate (25 mg/kg) via intragastric route, and the third group was a negative control group that received water only. On day 8, blood samples and tissues were harvested for analyses. The results indicated that grape polyphenol concentrate was able to reduce the signs of cardiotoxicity of doxorubicin through the reduction of aspartate aminotransferase activation, increasing the plasma antioxidant levels and decreasing the level of free radicals. The results also showed that grape polyphenol concentrate was able to reverse doxorubicin-induced microscopic myocardial damage. The myocardial protective effect of grape polyphenol might likely be due to the increase in the level and activity of the antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase. In conclusion, grape polyphenol concentrate displayed cardioprotective effect and was able to reverse doxorubicin-induced-cardiomyopathy in experimental rats.

Pharmacological management of vascular endothelial dysfunction in diabetes: TCM and western medicine compared based on biomarkers and biochemical parameters

Diabetes, a worldwide health concern while burdening significant populace of countries with time due to a hefty increase in both incidence and prevalence rates. Hyperglycemia has been buttressed both in clinical and experimental studies to modulate widespread molecular actions that effect macro and microvascular dysfunctions. Endothelial dysfunction, activation, inflammation, and endothelial barrier leakage are key factors contributing to vascular complications in diabetes, plus the development of diabetes-induced cardiovascular diseases. The recent increase in molecular, transcriptional, and clinical studies has brought a new scope to the understanding of molecular mechanisms and the therapeutic targets for endothelial dysfunction in diabetes. In this review, an attempt made to discuss up to date critical and emerging molecular signaling pathways involved in the pathophysiology of endothelial dysfunction and viable pharmacological management targets. Importantly, we exploit some Traditional Chinese Medicines (TCM)/TCM isolated bioactive compounds modulating effects on endothelial dysfunction in diabetes. Finally, clinical studies data on biomarkers and biochemical parameters involved in the assessment of the efficacy of treatment in vascular endothelial dysfunction in diabetes was compared between clinically used western hypoglycemic drugs and TCM formulas.

Interleukin-6 trans-signaling inhibition prevents oxidative stress in a mouse model of early diabetic retinopathy

Purpose

Diabetic retinopathy (DR), a microvascular complication of diabetes, is the leading cause of visual disability and blindness in diabetic patients. Chronic hyperglycemia leads to increased oxidative stress and inflammation in the retina, resulting in microvascular damage. Our recent in vitro studies have demonstrated that inhibition of interleukin-6 (IL-6) trans-signaling significantly reduces oxidative stress in retinal endothelial cells. The purpose of this study was to further explore the relationship between IL-6 trans-signaling and oxidative stress using a streptozotocin (STZ) induced mouse model of early diabetic retinopathy.

Methods

Diabetes was induced in eight week-old male C57BL/6J mice using STZ injections. sgp130Fc (mouse sgp130Fc protein) treatment was used for inhibition of IL-6 trans-signaling. Studies were conducted to evaluate the effects of IL-6 trans-signaling on oxidative balance at the systemic and retinal level.

Results

Decreased antioxidant capacity and increased oxidative stress was observed in diabetic mice, which returned to near-normal levels with sgp130Fc treatment. Similarly, superoxide levels, lipid peroxidation, and markers of oxidative DNA damage were increased in the diabetic retina, and these effects were abrogated by sgp130Fc treatment. Inhibition of IL-6 trans-signaling also restored normal expression of catalase and endothelial nitric oxide synthase in mouse retinas.

Conclusions

Inhibition of IL-6 trans-signaling significantly reduces diabetes-induced oxidative damage at the systemic level and in the retina. These findings provide further evidence for the role of IL-6 trans-signaling in diabetes-mediated oxidative stress.

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Decreased antioxidant capacity and increased oxidative stress in mice with DR.

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Inhibition of L-6 trans-signaling restores catalase and eNOS in the retina.

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Inhibition of IL-6 trans-signaling reduces retinal oxidative damage.

Why the endothelium? The endothelium as a target to reduce diabetes-associated vascular disease

Over the past 66 years, our knowledge of the role of the endothelium in the regulation of cardiovascular function and dysfunction has advanced from the assumption that it is a single layer of cells that serves as a barrier between the blood stream and vascular smooth muscle to an understanding of its role as an essential endocrine-like organ. In terms of historical contributions, we pay particular credit to (1) the Canadian scientist Dr. Rudolf Altschul who, based on pathological changes in the appearance of the endothelium, advanced the argument in 1954 that "one is only as old as one's endothelium" and (2) the American scientist Dr. Robert Furchgott, a 1998 Nobel Prize winner in Physiology or Medicine, who identified the importance of the endothelium in the regulation of blood flow. This review provides a brief history of how our knowledge of endothelial function has advanced and now recognize that the endothelium produces a plethora of signaling molecules possessing paracrine, autocrine, and, arguably, systemic hormone functions. In addition, the endothelium is a therapeutic target for the anti-diabetic drugs metformin, glucagon-like peptide I (GLP-1) receptor agonists, and inhibitors of the sodium-glucose cotransporter 2 (SGLT2) that offset the vascular disease associated with diabetes.

Redox Regulation of the Microcirculation

The microcirculation maintains tissue homeostasis through local regulation of blood flow and oxygen delivery. Perturbations in microvascular function are characteristic of several diseases and may be early indicators of pathological changes in the cardiovascular system and in parenchymal tissue function. These changes are often mediated by various reactive oxygen species and linked to disruptions in pathways such as vasodilation or angiogenesis. This overview compiles recent advances relating to redox regulation of the microcirculation by adopting both cellular and functional perspectives. Findings from a variety of vascular beds and models are integrated to describe common effects of different reactive species on microvascular function. Gaps in understanding and areas for further research are outlined. © 2020 American Physiological Society. Compr Physiol 10:229-260, 2020.

Minimizing Hyperglycemia-Induced Vascular Endothelial Dysfunction by Inhibiting Endothelial Sodium-Glucose Cotransporter 2 and Attenuating Oxidative Stress: Implications for Treating Individuals With Type 2 Diabetes

This overview deals with mechanisms whereby hyperglycemia-induced oxidative stress compromises vascular endothelial function and provides a background for a recently published study illustrating the beneficial impact of endothelial sodium-glucose cotransporter 2 (SGLT2) inhibitors in attenuating hyperglycemia-induced vascular dysfunction in vitro. The data provide new insight that can possibly lead to improved drug therapy for people with type 2 diabetes. The working hypotheses that underpinned the experiments performed are provided, along with the findings of the study. For the causes of hyperglycemia-induced vascular endothelial dysfunction, the findings point to the key roles of: 1) functional endothelial SGLT2; 2) oxidative stress-induced signalling pathways including mammalian sarcoma virus kinase, the EGF receptor-kinase and protein kinase C; and 3) mitochondrial dysfunction triggered by hyperglycemia was mitigated by an SGLT2 inhibitor in the hyperglycemic mouse aorta vascular organ cultures. The overview sums up the approaches implicated by the study that can potentially counteract the detrimental impact of hyperglycemia on vascular function in people with diabetes, including the clinical use of SGLT2 inhibitors for those with type 2 diabetes already being treated, for example, with metformin, along with dietary supplementation with broccoli-derived sulforaphane and tetrahydrobiopterin. The caveats associated with the study for extending the findings from mice to humans are summarized, pointing to the need to validate the work using vascular tissues from humans. Suggestions for future clinical studies are made, including the assessment of the impact of the therapeutic strategies proposed on measurements of blood flow in subjects with diabetes.

Anticancer activity of metformin: a systematic review of the literature

Background

The anticancer activity of metformin has been confirmed against several cancer types in vitro and in vivo. However, the underlying mechanisms of metformin in the treatment of cancer are not fully understood. This systematic review aims to discuss the possible anticancer mechanism of action of metformin.

Method

A search through different databases was conducted, including Medline and EMBASE.

Results

A total of 96 articles were identified of which 56 were removed for duplication and 24 were excluded after reviewing the title and abstract. A total of 12 research articles were included that describe different antiproliferative mechanisms that may contribute to the antineoplastic effects of metformin.

Conclusion

This analysis discussed the potential anticancer activity of metformin and highlighted the importance of AMPK as a potential target for anticancer therapy.

Endothelial Dysfunction: Is There a Hyperglycemia-Induced Imbalance of NOX and NOS?

NADPH oxidases (NOX) are enzyme complexes that have received much attention as key molecules in the development of vascular dysfunction. NOX have the primary function of generating reactive oxygen species (ROS), and are considered the main source of ROS production in endothelial cells. The endothelium is a thin monolayer that lines the inner surface of blood vessels, acting as a secretory organ to maintain homeostasis of blood flow. The enzymatic production of nitric oxide (NO) by endothelial NO synthase (eNOS) is critical in mediating endothelial function, and oxidative stress can cause dysregulation of eNOS and endothelial dysfunction. Insulin is a stimulus for increases in blood flow and endothelium-dependent vasodilation. However, cardiovascular disease and type 2 diabetes are characterized by poor control of the endothelial cell redox environment, with a shift toward overproduction of ROS by NOX. Studies in models of type 2 diabetes demonstrate that aberrant NOX activation contributes to uncoupling of eNOS and endothelial dysfunction. It is well-established that endothelial dysfunction precedes the onset of cardiovascular disease, therefore NOX are important molecular links between type 2 diabetes and vascular complications. The aim of the current review is to describe the normal, healthy physiological mechanisms involved in endothelial function, and highlight the central role of NOX in mediating endothelial dysfunction when glucose homeostasis is impaired.

Public knowledge, attitude and practice toward diabetes mellitus in Hail region, Saudi Arabia

Background: There is a rapid increase in the number of people with type II diabetes worldwide with many preventable cases. Diabetes control or prevention is partially influenced by the individual’s knowledge, attitude and practice toward the disease.

Objective: The aim of this study was to determine the general public knowledge, attitude and practice toward diabetes in the region of Hail, which is located northern of the Saudi capital.

Methodology: This is a cross-sectional study conducted during the period of March 2018 until September 2018. We randomly selected participants over the age of 18 years at different locations.

Results: A total of 738 participants (428 females and 310 males) with and an age range of 18–61 years and mean age of 35±12 were surveyed. The majority of the participants, regardless of education levels, residence and employment status showed high knowledge of diabetes (82%) and knew that physical activity can positively affect/prevent diabetes. Participant's age was found to have a significant association with participant's knowledge of diabetes with the ≥35 year old group knew the different types of diabetes (p<0.001) and knew that high carbohydrate consumption can increase the risk of diabetes (p<0.001), but only the younger group <18 year old's identified diabetes as a genetic disorder (p<0.001).

Conclusion: The high knowledge of the disease and its risk factors were not truly mirrored in the participant’s attitude and practice toward the disease. Therefore, it is quite essential for the local health authorities to implement awareness programs to improve public attitude and practice toward diabetes.

Biomarkers of Oxidative Stress in Metabolic Syndrome and Associated Diseases

Metabolic syndrome (MS) represents worldwide public health issue characterized by a set of cardiovascular risk factors including obesity, diabetes, dyslipidemia, hypertension, and impaired glucose tolerance. The link between the MS and the associated diseases is represented by oxidative stress (OS) and by the intracellular redox imbalance, both caused by the persistence of chronic inflammatory conditions that characterize MS. The increase in oxidizing species formation in MS has been accepted as a major underlying mechanism for mitochondrial dysfunction, accumulation of protein and lipid oxidation products, and impairment of the antioxidant systems. These oxidative modifications are recognized as relevant OS biomarkers potentially able to (i) clarify the role of reactive oxygen and nitrogen species in the etiology of the MS, (ii) contribute to the diagnosis/evaluation of the disease's severity, and (iii) evaluate the utility of possible therapeutic strategies based on natural antioxidants. The antioxidant therapies indeed could be able to (i) counteract systemic as well as mitochondrial-derived OS, (ii) enhance the endogenous antioxidant defenses, (iii) alleviate MS symptoms, and (iv) prevent the complications linked to MS-derived cardiovascular diseases. The focus of this review is to summarize the current knowledge about the role of OS in the development of metabolic alterations characterizing MS, with particular regard to the occurrence of OS-correlated biomarkers, as well as to the use of therapeutic strategies based on natural antioxidants.

A systematic review: the appraisal of the effects of metformin on lipoprotein modification and function

AIMS

Metformin is a commonly prescribed anti-hyperglycaemic pharmacological agent, and it remains a staple in the management of type II diabetes. In addition to metformin's glucose lowering effects, research has indicated that metformin inhibits glycation-mediated and oxidative modification of lipoprotein residues. The purpose was to discuss the effects of metformin as it relates to high-density lipoprotein (HDL) and low-density lipoprotein (LDL) modification.

MATERIALS AND METHODS

The purpose was to conduct a narrative and pragmatic review on the effects of metformin as it pertains to HDL and LDL modification.

RESULTS

High-density lipoprotein (HDL) concentration is a quantitative measure and therefore does not provide insight into its function, which is a qualitative property. Dysfunctional HDLs are unable to carry out functions normally associated with HDL because they can be modified by glycating agents. Metformin may counteract HDL dysfunction by abating HDL modification. Reductions in HDL modification may improve reverse cholesterol transport ability and thus possibly diminish cardiovascular risk. Similarly, metformin-mediated attenuations in LDL modification may reduce their atherogenic potency.

CONCLUSION

Metformin may partially ameliorate HDL dysfunction and reduce LDL modification by inhibiting alpha-dicarbonyl-mediated modification of apolipoprotein residues; consequently, the results are salient because cardiovascular disease incidence may be reduced given that reverse cholesterol transport activity predicts risk, and modified LDL are proatherogenic.

Hyperglycemia modulates redox, inflammatory and vasoactive markers through specific signaling pathways in cerebral endothelial cells: Insights on insulin protective action

Type 2 diabetes is associated with major vascular dysfunctions, leading to clinical complications such as stroke. It is also known that hyperglycemia dysregulates blood-brain barrier homeostasis by altering cerebral endothelial cell function. Oxidative stress may play a critical role. The aim of this study was to evaluate the effect of hyperglycemia and insulin on the production of redox, inflammatory and vasoactive markers by cerebral endothelial cells. Murine bEnd.3 cerebral endothelial cells were exposed to hyperglycemia in the presence or not of insulin. Results show that hyperglycemia altered the expression of genes encoding the ROS-producing enzyme Nox4, antioxidant enzymes Cu/ZnSOD, catalase and HO-1 as well as Cu/ZnSOD, MnSOD and catalase enzymatic activities, leading to a time-dependent modulation of ROS levels. Cell preconditioning with inhibitors targeting PI3K, JNK, ERK, p38 MAPK or NFĸB signaling molecules partly blocked hyperglycemia-induced oxidative stress. Conversely, AMPK inhibitor exacerbated ROS production, suggesting a protective role of AMPK on the antioxidant defense system. Hyperglycemia also modulated both gene expression and nuclear translocation of the redox-sensitive transcription factor Nrf2. Moreover, hyperglycemia caused a pro-inflammatory response by activating NFĸB-AP-1 pathway and IL-6 secretion. Hyperglycemia reduced eNOS gene expression and NO levels, while increasing ET-1 gene expression. Importantly, insulin counteracted all the deleterious effects of hyperglycemia. Collectively, these results demonstrate that hyperglycemia dysregulated redox, inflammatory and vasoactive markers in cerebral endothelial cells. Insulin exerted a protective action against hyperglycemia effects. Thus, it will be of high interest to evaluate the benefits of antioxidant and anti-inflammatory strategies against hyperglycemia-mediated vascular complications in type 2 diabetes.

Pulmonary vascular dysfunction in metabolic syndrome

Metabolic syndrome is a critically important precursor to the onset of many diseases, such as cardiovascular disease, and cardiovascular disease is the leading cause of death worldwide. The primary risk factors of metabolic syndrome include hyperglycaemia, abdominal obesity, dyslipidaemia, and high blood pressure. It has been well documented that metabolic syndrome alters vascular endothelial and smooth muscle cell functions in the heart, brain, kidney and peripheral vessels. However, there is less information available regarding how metabolic syndrome can affect pulmonary vascular function and ultimately increase an individual's risk of developing various pulmonary vascular diseases, such as pulmonary hypertension. Here, we review in detail how metabolic syndrome affects pulmonary vascular function.

Relation of Biochemical Parameters with Flow-mediated Dilatation in Patients with Metabolic Syndrome

BACKGROUND

Metabolic syndrome (MetS) is one of the high cardiovascular (CV) situations. Endothelial dysfunction, which is a common finding in patients with MetS, is related with increased CV risk. In patients with MetS, the effect of the major CV risk factors, not included in the MetS definition, on endothelial dysfunction is not well known. The aim of this study was to determine the effect of major CV risk factors such as gender, smoking, family history, and biochemical parameters on endothelial dysfunction in patients with MetS.

METHODS

The study was performed between December 2010 and August 2014. A total of 55 patients (15 females and 40 males) with MetS and 81 healthy controls (37 females and 44 males) with a body mass index <25 kg/m2 were enrolled in the study. Endothelial dysfunction was measured by flow-mediated dilatation (FMD), oxidative stress parameters; high-sensitivity C-reactive protein (hs-CRP), oxidized low-density lipoprotein (ox-LDL), endothelial nitric oxide synthase (e-NOS), nitric oxide, and cell adhesion markers; von Willebrand factor, and e-selectin. Platelet aggregation (endothelial adenosine diphosphate), total platelet count, and mean platelet volume were additionally analyzed and demographic parameters were explored. Student's t- test, Mann-Whitney U-test, and Chi-square test were used to analyze the results.

RESULTS

The fasting blood glucose (z= 3.52, P= 0.001), hs-CRP (z = 3.23, P= 0.004), ox-LDL (z = 2.62, P= 0.013), and e-NOS (z = 2.22, P= 0.026) levels and cardiac risk score (z = 5.23, P< 0.001) were significantly higher in patients with MetS compared with the control group. Smoking was correlated with decreased FMD (χ2 = 9.26, P= 0.002) in MetS patients but not in the control group.

CONCLUSIONS

Increased ox-LDL, hs-CRP, and e-NOS are likely to be a result of oxidative stress, a condition in which an imbalance occurs between the production and inactivation of reactive nitrogen and oxygen species. In addition, in patients with MetS, smoking is independently related to endothelial dysfunction.

Glucose dilates renal afferent arterioles via glucose transporter-1

Glomerular hyperfiltration occurs during the early stage of diabetes. An acute glucose infusion increases glomerular filtration rate. The involvement of tubuloglomerular feedback response and direct effect of glucose on the afferent arterioles (Af-Arts) have been suggested. However, the signaling pathways to trigger Af-Art dilatation have not been fully identified. Therefore, in the present study we tested our hypothesis that an increase in glucose concentration enhances endothelial nitric oxide synthesis activity and dilates the Af-Arts via glucose transporter-1 (GLUT1) using isolated mouse Af-Arts with perfusion. We isolated and microperfused the Af-Arts from nondiabetic C57BL/6 mice. The Af-Arts were preconstricted with norepinephrine (1 µM). When we switched the d-glucose concentration from low (5 mM) to high (30 mM) in the perfusate, the preconstricted Af-Arts significantly dilated by 37.8 ± 7.1%, but L-glucose did not trigger the dilation. GLUT1 mRNA was identified in microdisserted Af-Arts measured by RT-PCR. Changes in nitric oxide (NO) production in Af-Art were also measured using fluorescent probe when ambient glucose concentration was increased. When the d-glucose concentration was switched from 5 to 30 mM, NO generation in Af-Art was significantly increased by 19.2 ± 6.2% (84.7 ± 4.1 to 101.0 ± 9.3 U/min). l-Glucose had no effect on the NO generation. The GLUT1-selective antagonist 4-[({[4-(1,1-Dimethylethyl)phenyl]sulfonyl}amino)methyl]- N-3-pyridinylbenzamide and the nitric oxide synthase inhibitor N^G-nitro-l-arginine methyl ester blocked the high glucose-induced NO generation and vasodilation. In conclusion, we demonstrated that an increase in glucose concentration dilates the Af-Art by stimulation of the endothelium-derived NO production mediated by GLUT1.

Vitamin A deficiency induces endoplasmic reticulum stress and apoptosis in pancreatic islet cells: Implications of stearoyl-CoA desaturase 1-mediated oleic acid synthesis

Previously, we reported that vitamin A deficiency resulted in the reduction of stearoyl-CoA desaturase 1 (SCD1) and monounsaturated fatty acid (MUFA) levels, which corroborated with attenuation of high fructose-induced hepatic steatosis. Here, we aimed at assessing the effect of vitamin A deficiency on SCD1, MUFA levels and their impact on pancreas' structure and functions. Male weanling Wistar rats fed one of the four diets, namely control (Con), vitamin A-deficient (VAD), highfructose (HFr) and vitamin A-deficient diet with highfructose (VADHFr) for 16 weeks period. Compared to the control, feeding of VAD diet (alone or with HFr) resulted in pancreatic intra-islet vessel dilation and reduced plasma insulin, glucagon and C-peptide levels, however, glucose levels decreased only in VADHFr group. In line with plasma levels, VAD diet-fed animals displayed lower immunostaining for insulin and glucagon, which corroborated with increased apoptotic staining observed in the islet regions, possibly due to increased cellular stress, as indicated by high immunostaining for endothelial nitric oxide synthase (eNOS) and CCAAT/Enhancer-binding protein homologues protein (CHOP). On the other hand, it significantly decreased the SCD1 protein, which corroborated with reduced MUFA levels, particularly, oleic acid (C18:1), when compared to the control and HFr groups. In conclusion, chronic vitamin A deficiency altered the structure and functions of pancreas by diminishing the islet cells, possibly by inducing cellular stress-mediated apoptosis and decreasing SCD1-mediated oleic acid (C18:1) synthesis. Thus, the data suggest that unlike liver, the reduction in SCD1 and MUFA levels in the pancreas exerts deleterious effects on its functions and perturb the overall cellular metabolism.

Ingested capsaicinoids can prevent low-fat-high-carbohydrate diet and high-fat diet-induced obesity by regulating the NADPH oxidase and Nrf2 pathways

Objective

Capsaicinoids (CAPs), most commonly found in chili peppers, have a multitude of pharmacological and physiological effects, such as anti-inflammation, antioxidant, and anticancer effects. In the present study, we set out to investigate the hypothesis that CAPs mitigate obesity in rats and the possible mechanisms thereof.

Materials and methods

Rats were divided into six groups, including control (±10 mg CAPs/kg body weight [BW]), low-fat–high-sucrose diet (±10 mg CAPs/kg BW), and high-fat diet (±10 mg CAPs/kg BW). Blood samples and liver and aortic tissues were taken at the end of the study.

Results

CAPs supplementation significantly reduced hyperglycemia and hyperlipidemia (P<0.001) and ameliorated oxidative damage by reducing malondialdehyde concentrations in serum and liver and by increasing total antioxidant capacity in serum induced by the low-fat–high-sucrose and high-fat diets (P<0.001 for all). CAPs also depressed levels of NFκB p65, gp91^phox, and p22^phox, essential components of NADPH oxidase, in the aorta of rats. However, levels of Nrf2, Sirt1, and endothelial nitric oxide synthase were significantly increased in the aorta.

Conclusion

CAPs may at least partially reduce adverse effects due to high-fat diet and sucrose consumption through regulation of energy metabolism, oxidative stress, and proteins involved in vasoprotection.

HSP90 Inhibition and Cellular Stress Elicits Phenotypic Plasticity in Hematopoietic Differentiation

Cancer cells exist in a state of Darwinian selection using mechanisms that produce changes in gene expression through genetic and epigenetic alteration to facilitate their survival. Cellular plasticity, or the ability to alter cellular phenotype, can assist in survival of premalignant cells as they progress to full malignancy by providing another mechanism of adaptation. The connection between cellular stress and the progression of cancer has been established, although the details of the mechanisms have yet to be fully elucidated. The molecular chaperone HSP90 is often upregulated in cancers as they progress, presumably to allow cancer cells to deal with misfolded proteins and cellular stress associated with transformation. The objective of this work is to test the hypothesis that inhibition of HSP90 results in increased cell plasticity in mammalian systems that can confer a greater adaptability to selective pressures. The approach used is a murine in vitro model system of hematopoietic differentiation that utilizes a murine hematopoietic stem cell line, erythroid myeloid lymphoid (EML) clone 1, during their maturation from stem cells to granulocytic progenitors. During the differentiation protocol, 80%-90% of the cells die when placed in medium where the major growth factor is granulocyte-macrophage-colony stimulating factor. Using this selection point model, EML cells exhibit increases in cellular plasticity when they are better able to adapt to this medium and survive. Increases in cellular plasticity were found to occur upon exposure to geldanamycin to inhibit HSP90, when subjected to various forms of cellular stress, or inhibition of histone acetylation. Furthermore, we provide evidence that the cellular plasticity associated with inhibition of HSP90 in this model involves epigenetic mechanisms and is dependent upon high levels of stem cell factor signaling. This work provides evidence for a role of HSP90 and cellular stress in inducing phenotypic plasticity in mammalian systems that has new implications for cellular stress in progression and evolution of cancer.

Cardiovascular effects of gasotransmitter donors

Gasotransmitters represent a subfamily of the endogenous gaseous signaling molecules that include nitric oxide (NO), carbon monoxide (CO), and hydrogen sulphide (H(2)S). These particular gases share many common features in their production and function, but they fulfill their physiological tasks in unique ways that differ from those of classical signaling molecules found in tissues and organs. These gasotransmitters may antagonize or potentiate each other's cellular effects at the level of their production, their downstream molecular targets and their direct interactions. All three gasotransmitters induce vasodilatation, inhibit apoptosis directly or by increasing the expression of anti-apoptotic genes, and activate antioxidants while inhibiting inflammatory actions. NO and CO may concomitantly participate in vasorelaxation, anti-inflammation and angiogenesis. NO and H(2)S collaborate in the regulation of vascular tone. Finally, H(2)S may upregulate the heme oxygenase/carbon monoxide (HO/CO) pathway during hypoxic conditions. All three gasotransmitters are produced by specific enzymes in different cell types that include cardiomyocytes, endothelial cells and smooth muscle cells. As translational research on gasotransmitters has exploded over the past years, drugs that alter the production/levels of the gasotransmitters themselves or modulate their signaling pathways are now being developed. This review is focused on the cardiovascular effects of NO, CO, and H(2)S. Moreover, their donors as drug targeting the cardiovascular system are briefly described.

Oxidative Stress-Related Mechanisms and Antioxidant Therapy in Diabetic Retinopathy

Diabetic retinopathy (DR) is one of the most common microvascular complications of diabetes and is the leading cause of blindness in young adults. Oxidative stress has been implicated as a critical cause of DR. Metabolic abnormalities induced by high-glucose levels are involved in the development of DR and appear to be influenced by oxidative stress. The imbalance between reactive oxygen species (ROS) production and the antioxidant defense system activates several oxidative stress-related mechanisms that promote the pathogenesis of DR. The damage caused by oxidative stress persists for a considerable time, even after the blood glucose concentration has returned to a normal level. Animal experiments have proved that the use of antioxidants is a beneficial therapeutic strategy for the treatment of DR, but more data are required from clinical trials. The aims of this review are to highlight the improvements to our understanding of the oxidative stress-related mechanisms underlying the development of DR and provide a summary of the main antioxidant therapy strategies used to treat the disease.

Diabetes and Kidney Disease: Role of Oxidative Stress

Intrarenal oxidative stress plays a critical role in the initiation and progression of diabetic kidney disease (DKD). Enhanced oxidative stress results from overproduction of reactive oxygen species (ROS) in the context of concomitant, insufficient antioxidant pathways. Renal ROS production in diabetes is predominantly mediated by various NADPH oxidases (NOXs), but a defective antioxidant system as well as mitochondrial dysfunction may also contribute. Recent Advances: Effective agents targeting the source of ROS generation hold the promise to rescue the kidney from oxidative damage and prevent subsequent progression of DKD. Critical Issues and Future Directions: In the present review, we summarize and critically analyze molecular and cellular mechanisms that have been demonstrated to be involved in NOX-induced renal injury in diabetes, with particular focus on the role of increased glomerular injury, the development of albuminuria, and tubulointerstitial fibrosis, as well as mitochondrial dysfunction. Furthermore, novel agents targeting NOX isoforms are discussed. Antioxid. Redox Signal. 25, 657-684.

Metformin improves endothelial function in aortic tissue and microvascular endothelial cells subjected to diabetic hyperglycaemic conditions

The cellular mechanisms whereby metformin, the first line drug for type 2 diabetes (T2DM), mediates its antidiabetic effects remain elusive, particularly as to whether metformin has a direct protective action on the vasculature. This study was designed to determine if a brief 3-h exposure to metformin protects endothelial function against the effects of hyperglycaemia. We investigated the protective effects of metformin on endothelial-dependent vasodilatation (EDV) in thoracic aortae from T2DM db/db mice and on high glucose (HG, 40 mM) induced changes in endothelial nitric oxide synthase (eNOS) signaling in mouse microvascular endothelial cells (MMECs) in culture. Exposure of aortae from db+/? non-diabetic control mice to high glucose (HG, 40 mM) containing Krebs for 3-h significantly (P<0.05) reduced acetylcholine (ACh)-induced EDV compared to ACh-induced EDV in aortae maintained in normal glucose (NG, 11 mM) Krebs. The reduction of EDV was partially reversed following a 3-h exposure to 50 μM metformin; metformin also improved ACh-induced EDV in aortae from diabetic db/db mice. Immunoblot analysis of MMECs cultured in HG versus NG revealed a significant reduction of the ratio of phosphorylated (p-eNOS)/eNOS and p-Akt/Akt, but not the expression of total eNOS or Akt. The 3-h exposure of MMECs to metformin significantly (P<0.05) reversed the HG-induced reduction in phosphorylation of both eNOS and Akt; however, no changes were detected for phosphorylation of AMPK or the expression of SIRT1. Our data indicate that a 3-h exposure to metformin can reverse/reduce the impact of HG on endothelial function, via mechanisms linked to increased phosphorylation of eNOS and Akt.

Cardiac NO signalling in the metabolic syndrome

It is well documented that metabolic syndrome (i.e. a group of risk factors, such as abdominal obesity, elevated blood pressure, elevated fasting plasma glucose, high serum triglycerides and low cholesterol level in high-density lipoprotein), which raises the risk for heart disease and diabetes, is associated with increased reactive oxygen and nitrogen species (ROS/RNS) generation. ROS/RNS can modulate cardiac NO signalling and trigger various adaptive changes in NOS and antioxidant enzyme expressions/activities. While initially these changes may represent protective mechanisms in metabolic syndrome, later with more prolonged oxidative, nitrosative and nitrative stress, these are often exhausted, eventually favouring myocardial RNS generation and decreased NO bioavailability. The increased oxidative and nitrative stress also impairs the NO-soluble guanylate cyclase (sGC) signalling pathway, limiting the ability of NO to exert its fundamental signalling roles in the heart. Enhanced ROS/RNS generation in the presence of risk factors also facilitates activation of redox-dependent transcriptional factors such as NF-κB, promoting myocardial expression of various pro-inflammatory mediators, and eventually the development of cardiac dysfunction and remodelling. While the dysregulation of NO signalling may interfere with the therapeutic efficacy of conventional drugs used in the management of metabolic syndrome, the modulation of NO signalling may also be responsible for the therapeutic benefits of already proven or recently developed treatment approaches, such as ACE inhibitors, certain β-blockers, and sGC activators. Better understanding of the above-mentioned pathological processes may ultimately lead to more successful therapeutic approaches to overcome metabolic syndrome and its pathological consequences in cardiac NO signalling.

Association between the nicotinamide adenine dinucleotide phosphate oxidase p22phox gene -A930G polymorphism and intracerebral hemorrhage

The present study aimed to evaluate whether the ‑A930G polymorphism of the nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase p22phox gene is involved in intracerebral hemorrhage (ICH) in the Chinese Han population. In the present case‑control investigation, the subjects included 118 patients with ICH and 147 healthy controls. The ‑A930G polymorphism was determined using polymerase chain reaction and restriction fragment length polymorphism. Furthermore, the correlation between the ‑A930G gene polymorphism and ICH was evaluated using statistical analyses. The distribution of p22phox ‑A930G genotypes differed significantly between the two groups (P=0.003), with the AA, AG and GG genotype frequencies being 61.9, 29.3 and 8.8% in the control group and 40.7, 45.8 and 13.6% in the ICH group, respectively. The G allele frequency was significantly higher in patients with ICH compared with healthy controls (36.4 vs. 23.5%; P<0.05), however, the opposite was observed in the frequency of the A allele (63.6 vs. 76.5%; P<0.05). Binary logistic regression analysis revealed that genetic mutations of the p22phox ‑A930G gene were independent risk factors of ICH (odds ratio, 2.196; 95% confidence interval, 1.003‑4.586; P=0.009). In addition, certain conventional factors were associated with increased risk of ICH, including elevated blood pressure, increased levels of glucose and triglycerides in the blood, a history of hypertension and smoking. The ‑A930G polymorphism of the p22phox gene may affect the susceptibility to ICH and certain haplotypes of the gene may be associated with a higher susceptibility to ICH.

Metformin: An Old Drug for the Treatment of Diabetes but a New Drug for the Protection of the Endothelium

The anti-diabetic and oral hypoglycaemic agent metformin, first used clinically in 1958, is today the first choice or 'gold standard' drug for the treatment of type 2 diabetes and polycystic ovary disease. Of particular importance for the treatment of diabetes, metformin affords protection against diabetes-induced vascular disease. In addition, retrospective analyses suggest that treatment with metformin provides therapeutic benefits to patients with several forms of cancer. Despite almost 60 years of clinical use, the precise cellular mode(s) of action of metformin remains controversial. A direct or indirect role of adenosine monophosphate (AMP)-activated protein kinase (AMPK), the fuel gauge of the cell, has been inferred in many studies, with evidence that activation of AMPK may result from a mild inhibitory effect of metformin on mitochondrial complex 1, which in turn would raise AMP and activate AMPK. Discrepancies, however, between the concentrations of metformin used in in vitro studies versus therapeutic levels suggest that caution should be applied before extending inferences derived from cell-based studies to therapeutic benefits seen in patients. Conceivably, the effects, or some of them, may be at least partially independent of AMPK and/or mitochondrial respiration and reflect a direct effect of either metformin or a minor and, as yet, unidentified putative metabolite of metformin on a target protein(s)/signalling cascade. In this review, we critically evaluate the data from studies that have investigated the pharmacokinetic properties and the cellular and clinical basis for the oral hypoglycaemic, insulin-sensitising and vascular protective effects of metformin.

Features of endothelial dysfunction in umbilical cord vessels of women with gestational diabetes

BACKGROUND AND AIMS

Gestational diabetes (GDM) is associated with increased oxidative stress and overexpression of inflammatory cytokines, both of which might lead to endothelial dysfunction and vascular disease. As such, GDM could be viewed as a sort of ‘short lived’ metabolic syndrome. As umbilical cord vessels represent a suitable model for the study of vascular alterations brought about by GDM, the aim of the present work was to characterize the phenotype of human umbilical vein endothelial cells (HUVECs) chronically exposed to hyperglycaemia and to a pro-inflammatory environment during pregnancy so as to identify molecular modifications of cellular homoeostasis eventually impacting on endothelial dysfunction.

METHODS AND RESULT

Tissue specimens and HUVECs were obtained from umbilical cords of GDMand control women. As compared to controls, GD-HUVEC exhibited enhanced monocyte adhesion and vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1(ICAM-1) expression and exposure on plasma membrane after tumour necrosis factor-alpha(TNF-α) stimulation (Western blot, flow cytometer). As compared to control cells, GD-HUVEC in basal conditions exhibited enhanced monocyte adhesion, nitric oxide synthase (NOS) expression and activity (eNOS Real-Time polymerase chain reaction, Western Blot for eNOS total protein and monomers/dimers ratio, conversion of [3H]-L-arginine in [3H]-L-citrulline), increased O(-)(2)egeneration together with increased NT levels (immunofluorescence) and reduced NO bioavailability(guanosine 3',5'-monophosphate (cGMP) production, EIA). Furthermore, immunohistochemistry revealed increased eNOS and NT immunoreactivity in GD umbilical cords.

CONCLUSION

Endothelial cells exposed in vivo even transiently to hyperglycaemia, oxidative stress and inflammation exhibit durable pro-atherogenic modifications.

Type 2 diabetes: increased expression and contribution of IKCa channels to vasodilation in small mesenteric arteries of ZDF rats

Impaired endothelial function, which is dysregulated in diabetes, also precedes hypertension. We hypothesized that in Type 2 diabetes, the impaired endothelium-dependent relaxation is due to a loss of endothelium-derived hyperpolarization (EDH) that is regulated by impaired ion channel function. Zucker diabetic fatty (ZDF), Zucker heterozygote, and homozygote lean control rats were used as the experimental models in our study. Third-order mesenteric arteries were dissected and mounted on a pressure myograph; mRNA was quantified by RT-PCR and channel proteins by Western blotting. Under nitric oxide (NO) synthase and cyclooxygenase inhibition, endothelial stimulation with ACh fully relaxes control but not diabetic arteries. In contrast, when small-conductance calcium-activated potassium (KCa) channels and intermediate- and large-conductance KCa (I/BKCa) are inhibited with apamin and charybdotoxin, NO is able to compensate for ACh-induced relaxation in control but not in diabetic vessels. After replacement of charybdotoxin with 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34; IKCa inhibitor), ACh-induced relaxation in diabetic animals is attenuated. Specific inhibition with TRAM-34 or charybdotoxin attenuates ACh relaxation in diabetes. Stimulation with 1-ethyl-2-benzimidazolinone (IKCa activator) shows a reduced relaxation in diabetes. Activation of BKCa with 1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one NS619 leads to similar relaxations of control and diabetic arteries. RT-PCR and Western blot analysis demonstrate elevated mRNA and protein expression levels of IKCa in diabetes. Our results suggest that the compensatory effect of NO and EDH-associated, endothelium-dependent relaxation is reduced in ZDF rats. Specific blockade of IKCa with TRAM-34 reduces NO and EDH-type relaxation in diabetic rats, indicating an elevated contribution of IKCa in diabetic small mesenteric artery relaxation. This finding correlates with increased IKCa mRNA and protein expression in this vessel.

The effect of recombinant human growth hormone and insulin-like growth factor-1 on the mitochondrial function and viability of peripheral blood mononuclear cells in vitro

This study investigated whether the putative physiological benefits induced by growth hormone (GH) and insulin-like growth factor-1 (IGF-1) are countered at supra-physiological concentrations because of an augmentation in the production of mitochondrial-derived free radicals with a subsequent increase in oxidative damage, compromising mitochondrial function. To test this hypothesis, peripheral blood mononuclear cells were incubated for 4 h with either recombinant human GH (rhGH) (range = 0.25-100 μg/L) or recombinant IGF-1 (rIGF-1) (range = 100-600 μg/L) and along with control samples were subsequently analyzed by flow cytometry for the determination of cellular viability, mitochondrial membrane potential (Δψm), mitochondrial superoxide (O2(-)) generation, and mitochondrial permeability transition pore (mtPTP) activity. Results showed levels of mitochondrial O2(-) generation to be significantly reduced compared with control samples (lymphocytes: 21.5 ± 1.6 AU; monocytes: 230.2 ± 9.8 AU) following rhGH treatment at both concentrations of 5 μg/L (13.5 ± 1.3 AU, P ≤ 0.05) and 10 μg/L (12.3 ± 1.5 AU, P ≤ 0.05) in lymphocytes and at 10 μg/L (153.4 ± 11.4 AU, P ≤ 0.05) in monocytes. However, no significant effect was found at either higher rhGH concentrations or following treatment with any concentration of rIGF-1. In addition, neither of the 2 hormones had any significant effect on Δψm, mtPTP activity, or on cellular viability. In conclusion, physiological concentrations of rhGH elicited a protective cellular effect through the reduction of oxidative free radicals within mitochondria. This antioxidant effect was diminished at supra-physiological concentrations but not to a level that would elicit disruption of mitochondrial function.

Metformin modulates hyperglycaemia-induced endothelial senescence and apoptosis through SIRT1

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

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

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

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

Ca(2+) handling alterations and vascular dysfunction in diabetes

More than 65% of patients with diabetes mellitus die from cardiovascular disease or stroke. Hyperglycemia, due to either reduced insulin secretion or reduced insulin sensitivity, is the hallmark feature of diabetes mellitus. Vascular dysfunction is a distinctive phenotype found in both types of diabetes and could be responsible for the high incidence of stroke, heart attack, and organ damage in diabetic patients. In addition to well-documented endothelial dysfunction, Ca(2+) handling alterations in vascular smooth muscle cells (VSMCs) play a key role in the development and progression of vascular complications in diabetes. VSMCs provide not only structural integrity to the vessels but also control myogenic arterial tone and systemic blood pressure through global and local Ca(2+) signaling. The Ca(2+) signalosome of VSMCs is integrated by an extensive number of Ca(2+) handling proteins (i.e. channels, pumps, exchangers) and related signal transduction components, whose function is modulated by endothelial effectors. This review summarizes recent findings concerning alterations in endothelium and VSMC Ca(2+) signaling proteins that may contribute to the vascular dysfunction found in the diabetic condition.

NADPH oxidases in vascular pathology

SIGNIFICANCE

Reactive oxygen species (ROS) play a critical role in vascular disease. While there are many possible sources of ROS, nicotinamide adenine dinucleotide phosphate (NADPH) oxidases play a central role. They are a source of "kindling radicals," which affect other enzymes, such as nitric oxide synthase endothelial nitric oxide synthase or xanthine oxidase. This is important, as risk factors for atherosclerosis (hypertension, diabetes, hypercholesterolemia, and smoking) regulate the expression and activity of NADPH oxidases in the vessel wall.

RECENT ADVANCES

There are seven isoforms in mammals: Nox1, Nox2, Nox3, Nox4, Nox5, Duox1 and Duox2. Nox1, Nox2, Nox4, and Nox5 are expressed in endothelium, vascular smooth muscle cells, fibroblasts, or perivascular adipocytes. Other homologues have not been found or are expressed at very low levels; their roles have not been established. Nox1/Nox2 promote the development of endothelial dysfunction, hypertension, and inflammation. Nox4 may have a role in protecting the vasculature during stress; however, when its activity is increased, it may be detrimental. Calcium-dependent Nox5 has been implicated in oxidative damage in human atherosclerosis.

CRITICAL ISSUES

NADPH oxidase-derived ROS play a role in vascular pathology as well as in the maintenance of normal physiological vascular function. We also discuss recently elucidated mechanisms such as the role of NADPH oxidases in vascular protection, vascular inflammation, pulmonary hypertension, tumor angiogenesis, and central nervous system regulation of vascular function and hypertension.

FUTURE DIRECTIONS

Understanding the role of individual oxidases and interactions between homologues in vascular disease is critical for efficient pharmacological regulation of vascular NADPH oxidases in both the laboratory and clinical practice.

Tea polyphenols alleviate high fat and high glucose-induced endothelial hyperpermeability by attenuating ROS production via NADPH oxidase pathway

Background

Hyperglycemia-induced endothelial hyperpermeability is crucial to cardiovascular disorders and macro-vascular complications in diabetes mellitus. The objective of this study is to investigate the effects of green tea polyphenols (GTPs) on endothelial hyperpermeability and the role of nicotinamide adenine dinucleotide phosphate (NADPH) pathway.

Methods

Male Wistar rats fed on a high fat diet (HF) were treated with GTPs (0, 0.8, 1.6, 3.2 g/L in drinking water) for 26 weeks. Bovine aortic endothelial cells (BAECs) were treated with high glucose (HG, 33 mmol/L) and GTPs (0.0, 0.4, or 4 μg/mL) for 24 hours in vitro. The endothelial permeabilities in rat aorta and monolayer BAECs were measured by Evans blue injection method and efflux of fluorescein isothiocyanate (FITC)-dextran, respectively. The reactive oxygen species (ROS) levels in rat aorta and monolayer BAECs were measured by dihydroethidium (DHE) and 2′, 7′-dichloro-fluorescein diacetate (DCFH-DA) fluorescent probe, respectively. Protein levels of NADPH oxidase subunits were determined by Western-blot.

Results

HF diet-fed increased the endothelial permeability and ROS levels in rat aorta while HG treatments increased the endothelial permeability and ROS levels in cultured BAECs. Co-treatment with GTPs alleviated those changes both in vivo and in vitro. In in vitro studies, GTPs treatments protected against the HG-induced over-expressions of p22^phox and p67^phox. Diphenylene iodonium chloride (DPI), an inhibitor of NADPH oxidase, alleviated the hyperpermeability induced by HG.

Conclusions

GTPs could alleviate endothelial hyperpermeabilities in HF diet-fed rat aorta and in HG treated BAECs. The decrease of ROS production resulting from down-regulation of NADPH oxidase contributed to the alleviation of endothelial hyperpermeability.