EGCG protects against oxidized LDL-induced endothelial dysfunction by inhibiting LOX-1-mediated signaling

(-)‑Epigallocatechin‑3‑O‑gallate upregulates the expression levels of miR‑6757‑3p, a suppressor of fibrosis‑related gene expression, in extracellular vesicles derived from human umbilical vein endothelial cells

As pulmonary fibrosis (PF), a severe interstitial pulmonary disease, has such a poor prognosis, the development of prevention and treatment methods is imperative. (-)-Epigallocatechin-3-O-gallate (EGCG), one of the major catechins in green tea, exerts an antifibrotic effect, although its mechanism remains unclear. Recently, it has been reported that microRNAs (miRNAs or miRs) transported by extracellular vesicles (EVs) from vascular endothelial cells (VECs) are involved in PF. In the present study, the effects of EGCG on the expression of miRNAs in EVs derived from human umbilical vein endothelial cells (HUVECs) were assessed and miRNAs with antifibrotic activity were identified. miRNA microarray analysis revealed that EGCG modulated the expression levels of 31 miRNAs (a total of 27 miRNAs were upregulated, and 4 miRNAs were downregulated.) in EVs from HUVECs. Furthermore, TargetScan analysis indicated that miR-6757-3p in particular, which exhibited the highest degree of change, may target transforming growth factor-β (TGF-β) receptor 1 (TGFBR1). To evaluate the effects of miR-6757-3p on TGFBR1 expression, human fetal lung fibroblasts (HFL-1) were transfected with an miR-6757-3p mimic. The results demonstrated that the miR-6757-3p mimic downregulated the expression of TGFBR1 as well the expression levels of fibrosis-related genes including fibronectin and α-smooth muscle actin in TGF-β-treated HFL-1 cells. In summary, EGCG upregulated the expression levels of miR-6757-3p, which may target TGFBR1 and downregulate fibrosis-related genes, in EVs derived from VECs.

Harnessing polyphenol power by targeting eNOS for vascular diseases

Vascular diseases arise due to vascular endothelium dysfunction in response to several pro-inflammatory stimuli and invading pathogens. Thickening of the vessel wall, formation of atherosclerotic plaques consisting of proliferating smooth muscle cells, macrophages and lymphocytes are the major consequences of impaired endothelium resulting in atherosclerosis, hypercholesterolemia, hypertension, type 2 diabetes mellitus, chronic renal failure and many others. Decreased nitric oxide (NO) bioavailability was found to be associated with anomalous endothelial function because of either its reduced production level by endothelial NO synthase (eNOS) which synthesize this potent endogenous vasodilator from L-arginine or its enhanced breakdown due to severe oxidative stress and eNOS uncoupling. Polyphenols are a group of bioactive compounds having more than 7000 chemical entities present in different cereals, fruits and vegetables. These natural compounds possess many OH groups which are largely responsible for their strong antioxidative, anti-inflammatory antithrombotic and anti-hypersensitive properties. Several flavonoid-derived polyphenols like flavones, isoflavones, flavanones, flavonols and anthocyanidins and non-flavonoid polyphenols like tannins, curcumins and resveratrol have attracted scientific interest for their beneficial effects in preventing endothelial dysfunction. This article will focus on in vitro as well as in vivo and clinical studies evidences of the polyphenols with eNOS modulating activity against vascular disease condition while their molecular mechanism will also be discussed.

PCSK9 Biology and Its Role in Atherothrombosis

It is now about 20 years since the first case of a gain-of-function mutation involving the as-yet-unknown actor in cholesterol homeostasis, proprotein convertase subtilisin/kexin type 9 (PCSK9), was described. It was soon clear that this protein would have been of huge scientific and clinical value as a therapeutic strategy for dyslipidemia and atherosclerosis-associated cardiovascular disease (CVD) management. Indeed, PCSK9 is a serine protease belonging to the proprotein convertase family, mainly produced by the liver, and essential for metabolism of LDL particles by inhibiting LDL receptor (LDLR) recirculation to the cell surface with the consequent upregulation of LDLR-dependent LDL-C levels. Beyond its effects on LDL metabolism, several studies revealed the existence of additional roles of PCSK9 in different stages of atherosclerosis, also for its ability to target other members of the LDLR family. PCSK9 from plasma and vascular cells can contribute to the development of atherosclerotic plaque and thrombosis by promoting platelet activation, leukocyte recruitment and clot formation, also through mechanisms not related to systemic lipid changes. These results further supported the value for the potential cardiovascular benefits of therapies based on PCSK9 inhibition. Actually, the passive immunization with anti-PCSK9 antibodies, evolocumab and alirocumab, is shown to be effective in dramatically reducing the LDL-C levels and attenuating CVD. While monoclonal antibodies sequester circulating PCSK9, inclisiran, a small interfering RNA, is a new drug that inhibits PCSK9 synthesis with the important advantage, compared with PCSK9 mAbs, to preserve its pharmacodynamic effects when administrated every 6 months. Here, we will focus on the major understandings related to PCSK9, from its discovery to its role in lipoprotein metabolism, involvement in atherothrombosis and a brief excursus on approved current therapies used to inhibit its action.

Parkinson's disease and mitophagy: an emerging role for LRRK2

Parkinson's disease (PD) is a progressive neurodegenerative disorder that affects around 2% of individuals over 60 years old. It is characterised by the loss of dopaminergic neurons in the substantia nigra pars compacta of the midbrain, which is thought to account for the major clinical symptoms such as tremor, slowness of movement and muscle stiffness. Its aetiology is poorly understood as the physiological and molecular mechanisms leading to this neuronal loss are currently unclear. However, mitochondrial and lysosomal dysfunction seem to play a central role in this disease. In recent years, defective mitochondrial elimination through autophagy, termed mitophagy, has emerged as a potential contributing factor to disease pathology. PINK1 and Parkin, two proteins mutated in familial PD, were found to eliminate mitochondria under distinct mitochondrial depolarisation-induced stress. However, PINK1 and Parkin are not essential for all types of mitophagy and such pathways occur in most cell types and tissues in vivo, even in the absence of overt mitochondrial stress - so-called basal mitophagy. The most common mutation in PD, that of glycine at position 2019 to serine in the protein kinase LRRK2, results in increased activity and this was recently shown to disrupt basal mitophagy in vivo. Thus, different modalities of mitophagy are affected by distinct proteins implicated in PD, suggesting impaired mitophagy may be a common denominator for the disease. In this short review, we discuss the current knowledge about the link between PD pathogenic mutations and mitophagy, with a particular focus on LRRK2.

Natural products: The role and mechanism in low-density lipoprotein oxidation and atherosclerosis

Atherosclerosis is a chronic inflammatory, metabolic, and epigenetic disease, which leads to the life-threatening coronary artery disease. Emerging studies from bench to bedside have demonstrated the pivotal role of low-density lipoprotein (LDL) oxidation in the initiation and progression of atherosclerosis. This article hereby reviews oxidation mechanism of LDL, and the pro-atherogenic and biomarker role of oxidized LDL in atherosclerosis. We also review the pharmacological effects of several representative natural products (vitamin E, resveratrol, quercetin, probucol, tanshinone IIA, epigallocatechin gallate, and Lycopene) in protecting against LDL oxidation and atherosclerosis. Clinical and basic research supports the beneficial effects of these natural products in inhibiting LDL oxidation and preventing atherosclerosis, but the data are still controversial. This may be related to factors such as the population and the dosage and time of taking natural products involved in different studies. Understanding the mechanism of LDL oxidation and effect of oxidized LDL help researchers to find novel therapies against atherosclerosis.

Epigallocatechin-3-gallate ameliorates LPS-induced inflammation by inhibiting the phosphorylation of Akt and ERK signaling molecules in rat H9c2 cells

The inflammatory response has been implicated in various cardiac and systemic diseases. Epigallocatechin-3-gallate (EGCG), the major polyphenol extracted from green tea, has various biological and pharmacological properties, such as anti-inflammation, anti-oxidative and anti-tumorigenesis. To some extent, the mechanism of EGCG in the inflammatory response that characterizes myocardial dysfunction is not fully understood. The present study aimed to investigate the inhibiting effect of EGCG on lipopolysaccharide (LPS)-induced inflammation in vitro. Treatment with LPS affected rat H9c2 cardiomyocytes and induced an inflammatory response. However, the LPS-induced effects were attenuated after treatment with EGCG. The present results demonstrated that EGCG treatment repressed several inflammatory mediators, such as vascular endothelial growth factor, chemokine ligand 5, chemokine ligand 2, intercellular adhesion molecule-1, matrix metalloproteinase-2, tumor necrosis factor-α and nitric oxide (induced by LPS), and the repressing effect of EGCG on inflammatory response was dose-dependent in the range of 6.25-100 µM. EGCG inhibited these marked inflammatory key signaling molecules by reducing the expression of phospho-nuclear factor-κB p65, -Akt, -ERK and -MAPK p38 while the total protein level of these signal proteins were not affected. In conclusion, the present findings suggested that EGCG possesses cardiomyocyte-protective action in reducing the LPS-induced inflammatory response due to the inhibition of the phosphorylation of Akt and ERK signaling molecules.

Influence of Cardiometabolic Risk Factors on Platelet Function

Platelets are key players in the thrombotic processes. The alterations of platelet function due to the occurrence of metabolic disorders contribute to an increased trend to thrombus formation and arterial occlusion, thus playing a major role in the increased risk of atherothrombotic events in patients with cardiometabolic risk factors. Several lines of evidence strongly correlate metabolic disorders such as obesity, a classical condition of insulin resistance, dyslipidemia, and impaired glucose homeostasis with cardiovascular diseases. The presence of these clinical features together with hypertension and disturbed microhemorrheology are responsible for the prothrombotic tendency due, at least partially, to platelet hyperaggregability and hyperactivation. A number of clinical platelet markers are elevated in obese and type 2 diabetes (T2DM) patients, including the mean platelet volume, circulating levels of platelet microparticles, oxidation products, platelet-derived soluble P-selectin and CD40L, thus contributing to an intersection between obesity, inflammation, and thrombosis. In subjects with insulin resistance and T2DM some defects depend on a reduced sensitivity to mediators—such as nitric oxide and prostacyclin—playing a physiological role in the control of platelet aggregability. Furthermore, other alterations occur only in relation to hyperglycemia. In this review, the main cardiometabolic risk factors, all components of metabolic syndrome involved in the prothrombotic tendency, will be taken into account considering some of the mechanisms involved in the alterations of platelet function resulting in platelet hyperactivation.

Depletion of CPEB1 protects against oxidized LDL-induced endothelial apoptosis and inflammation though SIRT1/LOX-1 signalling pathway

Atherosclerosis (AS) is a chronic inflammatory disease that results from Oxidized low-density lipoprotein (Ox-LDL) induced endothelial dysfunction. Cytoplasmic polyadenylation element binding protein 1 (CPEB1) is closely related to the development of epithelial cells, but the role of CPEB1 in AS remains unknown. The RNA and protein levels of CPEB1 expression are increased by Ox-LDL exposure, which is abrogated by c-Jun amino-terminal kinase (JNK) inhibitor SP600125. CPEB1 small interfering RNA (siRNA) suppressed the oxidative stress, inflammation, and apoptosis. Furthermore, CPEB1 siRNA enhanced the sirtuin 1 (SIRT1) transcription levels in Ox-LDL-treated HUVECs. Co-Immunoprecipitation (Co-IP) assay showed that CPEB1 siRNA declined the ubiquitination of SIRT1, and SIRT1 siRNA enhanced the Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), which were decreased by CPEB1 siRNA. In addition, LOX-1 and SIRT1 attenuated the protection of SIRT1 siRNA on Ox-LDL-induced oxidative stress. Therefore, our study revealed that CPEB1 depletion might play an anti-inflammatory and antiapoptotic role in Ox-LDL-induced apoptosis and inflammation though SIRT1/LOX-1 signalling pathway.

Modulation of Nitric Oxide Synthases by Oxidized LDLs: Role in Vascular Inflammation and Atherosclerosis Development

The maintenance of physiological levels of nitric oxide (NO) produced by eNOS represents a key element for vascular endothelial homeostasis. On the other hand, NO overproduction, due to the activation of iNOS under different stress conditions, leads to endothelial dysfunction and, in the late stages, to the development of atherosclerosis. Oxidized LDLs (oxLDLs) represent the major candidates to trigger biomolecular processes accompanying endothelial dysfunction and vascular inflammation leading to atherosclerosis, though the pathophysiological mechanism still remains to be elucidated. Here, we summarize recent evidence suggesting that oxLDLs produce significant impairment in the modulation of the eNOS/iNOS machinery, downregulating eNOS via the HMGB1-TLR4-Caveolin-1 pathway. On the other hand, increased oxLDLs lead to sustained activation of the scavenger receptor LOX-1 and, subsequently, to NFkB activation, which, in turn, increases iNOS, leading to EC oxidative stress. Finally, these events are associated with reduced protective autophagic response and accelerated apoptotic EC death, which activates atherosclerotic development. Taken together, this information sheds new light on the pathophysiological mechanisms of oxLDL-related impairment of EC functionality and opens new perspectives in atherothrombosis prevention.

Recent Advances in the Understanding of the Health Benefits and Molecular Mechanisms Associated with Green Tea Polyphenols

Tea, leaf, or bud from the plant Camellia sinensis, make up some of the beverages popularly consumed in different parts of the world as green tea, oolong tea, or black tea. More particularly, as a nonfermented tea, green tea has gained more renown because of the significant health benefits assigned to its rich content in polyphenols. As a main constituent, green tea polyphenols were documented for their antioxidant, anti-inflammation, anticancer, anticardiovascular, antimicrobial, antihyperglycemic, and antiobesity properties. Recent reports demonstrate that green tea may exert a positive effect on the reduction of medical chronic conditions such as cardiovascular disease, cancer, Alzheimer's disease, Parkinson's disease, and diabetes. The health benefits of green teas, in particular EGCG, are widely investigated, and these effects are known to be primarily associated with the structure and compositions of its polyphenols. This Review focuses on the diverse constituents of green tea polyphenols and their molecular mechanisms from the perspective of their potential therapeutic function. Recent advances of green tea polyphenols on their bioavailability, bioaccessibility, and microbiota were also summarized in this article. Dietary supplementation with green tea represents an attractive alternative toward promoting human health.

Tea polyphenols protect bovine mammary epithelial cells from hydrogen peroxide-induced oxidative damage in vitro

Periparturient dairy cows are subjected to altered intracellular reduction-oxidation (redox) balance due to the high metabolic rates and physiological adaptations characteristic of the transition into lactation. Such conditions could alter oxidative stress status. The objective of this study was to investigate the cytoprotective effects of tea polyphenols (TP) in cultured bovine mammary epithelial cells (BMEC) exposed to hydrogen peroxide (H2O2)-induced oxidative stress. To establish oxidative stress, isolated BMEC were exposed to increasing concentrations of H2O2 (0, 100, 200, 400, 600, 800, and 1,000 µM) for 0, 2, 4, 6, 8, 12, and 24 h. Doses of TP (0, 60, 80, and 100 µg/mL) were evaluated by pretreatment of BMEC for 0, 2, 4, 6, 8, 12 and 24 h, followed by an H2O2 (600 µM per culture well) challenge for 6 h. Bovine mammary epithelial cells were preincubated for 30 min with or without 2,4-dinitrochloro-benzene (DNCB), then cultured with or without TP (100 µg/mL) for another 12 h followed by H2O2 (600 µM per culture well) exposure. There were 5 replicate cultures for each treatment in each experiment. Treatment with 600 µM H2O2 per culture well for 6 h induced oxidative damage of BMEC, indicating this system could be used to establish an oxidative stress model. After H2O2 (600 µM per culture well) exposure, a concentration of TP of 100 µg/mL during a 12-h incubation increased cell viability, decreased intracellular reactive oxygen species accumulation, and increased the abundance of nuclear factor-erythroid 2-related factor 2 (NFE2L2). Furthermore, TP upregulated mRNA abundance of genes in the NFE2L2 and mitogen-activated protein kinase (MAPK) pathways of BMEC. The DNCB assay allowed further confirmation that the induction of NFE2L2 and HMOX-1 in response to TP was mediated through the sustained upregulation of the abundance of MAPK3/1 [formerly known as extracellular regulated kinases 1/2] and MAPK11/12/13/14 (formerly known as p38). Overall, results indicate that TP has beneficial effects on BMEC redox balance; it can reduce cellular oxidative stress-related injury and may potentially serve as an antioxidant against oxidative stress in dairy cows.

Epigallocatechin-3-gallate ameliorates erectile function in aged rats via regulation of PRMT1/DDAH/ADMA/NOS metabolism pathway

Aging-related ED is predominantly attributed to neurovascular dysfunction mediated by NO suppression and increased oxidative stress in penis. The alterations of protein arginine methyltransferases 1 (PRMT1)/dimethylarginine dimethylaminohydrolase (DDAH)/asymmetrical dimethylarginine (ADMA)/NO synthase (NOS) pathway regulate NO production in the vascular endothelium. Epigallocatechin-3-gallate (EGCG) is one of the most abundant and antioxidative ingredients isolated from green tea. In the present study, 40 Sprague-Dawley rats were randomly distributed into four groups: one young rat group and three aged rat groups treated with daily gavage feedings of EGCG at doses of 0, 10 mg kg⁻¹, and 100 mg kg⁻¹ for 12 weeks, respectively. Erectile function was assessed by electrical stimulation of the cavernous nerves with intracavernous pressure (ICP) measurement. After euthanasia, penile tissue was investigated using Western blot and ELISA to assess the PRMT1/DDAH/ADMA/NOS metabolism pathway. Superoxide dismutase (SOD) and malondialdehyde (MDA) levels were detected by colorimetry. We also evaluated smooth muscle contents. The ratio of maximal ICP and mean systemic arterial pressure (MAP) was markedly higher in EGCG-treated aged rats than in untreated aged rats. We found that DDAH1 and DDAH2 were expressed in cavernosal tissue, and they were downregulated in corpora of aged rats. The administration of EGCG upregulated the expression and activity of DDAH. In contrast, EGCG treatment downregulated the expression of PRMT1 and ADMA content. Moreover, EGCG-treated rats showed an improvement in smooth muscle expression, the ratio of smooth muscle cell/collagen fibril, SOD activity, and MDA levels when compared with untreated aged rats.

Oolong tea prevents cardiomyocyte loss against hypoxia by attenuating p-JNK mediated hypertrophy and enhancing P-IGF1R, p-akt, and p-Badser136 activity and by fortifying NRF2 antioxidation system

Tea, the most widely consumed natural beverage has been associated with reduced mortality risk from cardiovascular disease. Oolong tea is a partially fermented tea containing high levels of catechins, their degree of oxidation varies between 20%-80% causing differences in their active metabolites. In this study we examined the effect of oolong tea extract (OTE) obtained by oxidation at low-temperature for short-time against hypoxic injury and found that oolong tea provides cyto-protective effects by suppressing the JNK mediated hypertrophic effects and by enhancing the innate antioxidant mechanisms in neonatal cardiomyocytes and in H9c2 cells. OTE effectively attenuates 24 h hypoxia-triggered cardiomyocyte loss by suppressing caspase-3-cleavage and apoptosis in a dose-dependent manner. OTE also enhances the IGFIR/p-Akt associated survival-mechanism involving the elevation of p-Bad^ser136 in a dose-dependent manner to aid cellular adaptations against hypoxic challenge. The results show the effects and mechanism of Oolong tea to provide cardio-protective benefits during hypoxic conditions.

Epigallocatechin-3-gallate confers protection against corticosterone-induced neuron injuries via restoring extracellular signal-regulated kinase 1/2 and phosphatidylinositol-3 kinase/protein kinase B signaling pathways

Extensive studies suggested epigallocatechin-3-gallate (EGCG) has significant neuroprotection against multiple central neural injuries, but the underlying mechanisms still remain poorly elucidated. Here we provide evidence to support the possible involvement of extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphatidylinositol-3 kinase/ protein kinase B (PI3K/AKT) pathways in EGCG-mediated protection against corticosterone-induced neuron injuries. As an essential stress hormone, corticosterone could induce obvious neurotoxicity in primary hippocampal neurons. Pre-treatment with EGCG ameliorated the corticosterone-induced neuronal injuries; however, it was blocked by pharmacological inhibitors for ERK1/2 (U0126) and PI3K/AKT (LY294002). Furthermore, the results confirmed that EGCG restored the corticosterone-induced decrease of ERK1/2 and PI3K/AKT phosphorylation, and attenuated the corticosterone-induced reduction of peroxisome proliferators-activated receptor-γ coactivator-1α (PGC-1α) expression and ATP production. Taken together, these findings indicated that EGCG has significant neuroprotection against corticosterone-induced neuron injuries partly via restoring the ERK1/2 and PI3K/AKT signaling pathways as well as the PGC-1α-mediated ATP production.

Contribution of lectin-like oxidized low-density lipoprotein receptor-1 and LOX-1 modulating compounds to vascular diseases

The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the major receptor for binding and uptake of oxidized low-density lipoprotein (oxLDL) in endothelial cells. LOX-1 is also expressed in macrophages, smooth muscle cells and platelets. Following internalization of oxLDL, LOX-1 initiates a vicious cycle from activation of pro-inflammatory signaling pathways, thus promoting an increased reactive oxygen species formation and secretion of pro-inflammatory cytokines. LOX-1 plays a pivotal role in the development of endothelial dysfunction, foam cell and advanced lesions formation as well as in myocardial ischemia. Furthermore, it is known that LOX-1 plays a pivotal role in mitochondrial DNA damage, vascular cell apoptosis, and autophagy. A large number of studies provide evidence of a LOX-1's role in endothelial dysfunction, hypertension, diabetes, and obesity. In addition, novel insights into LOX-1 ligands and the activated signaling pathways have been gained. Recent studies have shown an interaction of LOX-1 with microRNA's, thus providing novel tools to regulate LOX-1 function. Because LOX-1 is increased in atherosclerotic plaques and contributes to endothelial dysfunction, several compounds were tested in vivo and in vitro to modulate the LOX-1 expression in therapeutic approaches.

Homocysteine‑induced oxidative stress through TLR4/NF‑κB/DNMT1‑mediated LOX‑1 DNA methylation in endothelial cells

Atherosclerosis (AS) is a progressive disease of multifactorial origin, which occurs in response to endothelial injury. Increased homocysteine (Hcy) is considered a major cause of endothelial dysfunction, oxidative stress and DNA methylation; however, the mechanisms remain to be fully elucidated. The aim of the present study was to investigate whether Hcy causes injury to endothelial cells (ECs) by the effect of lectin‑like oxidized‑low density lipoprotein receptor‑1 (LOX‑1) DNA methylation through toll‑like receptor 4(TLR4)/nuclear factor (NF)‑κB/DNA methyltransferase (DNMT)1. The ECs were treated with different concentrations of Hcy, and it was found that Hcy promoted the expression of TLR4, leading to EC injury. The effect of oxidative stress was analyzed by measuring superoxide dismutase, malondialdehyde and hydrogen peroxide in the ECs. In addition, the association between NF‑κB and DNMT1 was examined by treatment of the ECs with pyrrolidine dithiocarbamate (PDTC). The results suggested that Hcy induced LOX‑1 DNA hypomethyaltion to promote the expression levels of LOX‑1. Taken together, Hcy injured the ECs through the effect of methylation and trans‑sulfuration metabolism of LOX‑1 through TLR4/NF‑κB/DNMT1. Following injury to the ECs, lipids, particularly ox‑LDL, accumulated in the sub‑endothelial layer to promote the formation of AS.

Roselle supplementation prevents nicotine-induced vascular endothelial dysfunction and remodelling in rats

Vascular endothelial dysfunction (VED) plays an important role in the initiation of cardiovascular diseases. Roselle, enriched with antioxidants, demonstrates high potential in alleviating hypertension. This study was undertaken to investigate the effects of roselle supplementation of VED and remodelling in a rodent model with prolonged nicotine administration. Male Sprague–Dawley rats (n = 6 per group) were administered with 0.6 mg/kg nicotine for 28 days to induce VED. The rats were given either aqueous roselle (100 mg/kg) or normal saline orally 30 min prior to nicotine injection daily. One additional group of rats served as control. Thoracic aorta was isolated from rats to measure vascular reactivity, vascular remodelling and oxidative stress. Roselle significantly lowered aortic sensitivity to phenylephrine-induced vasoconstriction (Endo-(+) Cmax = 234.5 ± 3.9%, Endo-(–) Cmax = 247.6 ± 5.2%) compared with untreated nicotine group (Endo-(+) Cmax = 264.5 ± 6.9%, Endo-(–) Cmax = 276.5 ± 6.8%). Roselle also improved aortic response to endothelium-dependent vasodilator, acetylcholine (Endo-(+) Rmax = 73.2 ± 2.1%, Endo-(–) Rmax = 26.2 ± 0.8%) compared to nicotine group (Endo-(+) Rmax = 57.8 ± 1.7%, Endo-(–) Rmax = 20.9 ± 0.8%). In addition, roselle prevented an increase in intimal media thickness and elastic lamellae proliferation to preserve vascular architecture. Moreover, we also observed a significantly lowered degree of oxidative stress in parallel with increased antioxidant enzymes in aortic tissues of the roselle-treated group. This study demonstrated that roselle prevents VED and remodelling, and as such it has high nutraceutical value as supplement to prevent cardiovascular diseases.

The efficacy of Epigallocatechin-3-gallate (green tea) in the treatment of Alzheimer's disease: an overview of pre-clinical studies and translational perspectives in clinical practice

Alzheimer's disease (AD) is a neurodegenerative disorder and the most common form of dementia characterized by cognitive and memory impairment. One of the mechanism involved in the pathogenesis of AD, is the oxidative stress being involved in AD's development and progression. In addition, several studies proved that chronic viral infections, mainly induced by Human herpesvirus 1 (HHV-1), Cytomegalovirus (CMV), Human herpesvirus 2 (HHV-2), and Hepatitis C virus (HCV) could be responsible for AD's neuropathology. Despite the large amount of data regarding the pathogenesis of Alzheimer's disease (AD), a very limited number of therapeutic drugs and/or pharmacological approaches, have been developed so far. It is important to underline that, in recent years, natural compounds, due their antioxidants and anti-inflammatory properties have been largely studied and identified as promising agents for the prevention and treatment of neurodegenerative diseases, including AD. The ester of epigallocatechin and gallic acid, (-)-Epigallocatechin-3-Gallate (EGCG), is the main and most significantly bioactive polyphenol found in solid green tea extract. Several studies showed that this compound has important anti-inflammatory and antiatherogenic properties as well as protective effects against neuronal damage and brain edema. To date, many studies regarding the potential effects of EGCG in AD's treatment have been reported in literature. The purpose of this review is to summarize the in vitro and in vivo pre-clinical studies on the use of EGCG in the prevention and the treatment of AD as well as to offer new insights for translational perspectives into clinical practice.

Potential phytoestrogen alternatives exert cardio-protective mechanisms via estrogen receptors

The 17 beta-estradiol (E2) is a sex hormone that is most abundant and most active estrogen in premenopausal women. The importance of E2 in providing cardioprotection and reducing the occurrence of heart disease in women of reproductive age has been well recognized. There are three subtype of estrogen receptors (ERs), including ERα, ERβ and GPR30 have been identified and accumulating evidence reveal their roles on E2-mediated genomic and nongenomic pathway in cardiomyocytes against various cardiac insults. In this review, we focus on the estrogen and ERs mediated signaling pathways in cardiomyocytes that determines cardio-protection against various stresses and further discuss the clinical implication of ERs and phytoestrogens. Further we provide some insights on phytoeostrogens which may play as alternatives in estrogen replacement therapies.

Dyslipidemia Part 1--Review of Lipid Metabolism and Vascular Cell Physiology

Dyslipidemia, more specifically, high-serum low-density lipoproteins and low-serum high-density lipoproteins, are known risk factors for cardiovascular disease. The current clinical treatment of dyslipidemia represents the outcome of a large body of fundamental basic science research on lipids, lipid metabolism, and the effects of different lipids on cellular components of the artery, inflammatory cells, and platelets. In general, lower density lipids activate intracellular pathways to increase local and systemic inflammation, monocyte adhesion, endothelial cell dysfunction and apoptosis, and smooth muscle cell proliferation, resulting in foam cell formation and genesis of atherosclerotic plaque. In contrast, higher density lipids prevent or attenuate atherosclerosis. This article is part 1 of a 2-part review, with part 1 focusing on lipid metabolism and the downstream effects of lipids on the development of atherosclerosis, and part 2 on the clinical treatment of dyslipidemia and the role of these drugs for patients with arterial disease exclusive of the coronary arteries.

Neuroprotective Activity of (-)-Epigallocatechin Gallate against Lipopolysaccharide-Mediated Cytotoxicity

Lipopolysaccharide- (LPS-) mediated systemic inflammation plays a critical role in neurodegenerative diseases. The present study was conducted to evaluate the protective effects of epigallocatechin gallate (EGCG), the major component in green tea, on LPS-mediated inflammation and neurotoxicity. LPS treatment of macrophages induced expression of proinflammatory cytokines (TNF-α, IL-1β, and IL-6). However, EGCG pretreatment of macrophages significantly inhibited LPS-mediated induction of these cytokines. In addition, EGCG significantly diminished LPS-induced inflammatory cytokines in the peripheral mononuclear blood cells (PBMCs). Supernatant from EGCG-pretreated and LPS-activated macrophage cultures was found to be less cytotoxic to neurons than that from non-EGCG-pretreated and LPS-activated macrophage cultures. Furthermore, EGCG treatment of neurons could inhibit LPS-induced production of reactive oxygen species (ROS). Thus EGCG represents a potent and useful neuroprotective agent for inflammation-mediated neurological disorders.

Redox homeostasis, T cells and kidney diseases: three faces in the dark

The redox equilibrium is crucial for the maintenance of immune homeostasis. Here, we summarize recent data showing that oxidation regulates T-cell functions and that alterations of the redox equilibrium may play an important role in the pathogenesis of inflammatory conditions affecting the kidneys. We further discuss potential links between oxidation, T cells and renal diseases such as systemic lupus erythematosus, renal ischaemia/reperfusion injury, end-stage renal disease and hypertension. The basic understanding of oxidation as a means by which diseases are directly affected results in unexpected pathophysiological similarities. Finally, we describe potential therapeutic options targeting redox systems for the treatment of nephropathies affecting humans.

Cryptotanshinone inhibits oxidized LDL-induced adhesion molecule expression via ROS dependent NF-κB pathways

Adhesion molecules, such as intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin, play important roles in the initial stage of atherosclerosis. Cryptotanshinone (CPT), a natural compound isolated from Salvia miltiorrhiza Bunge, exhibits anti-atherosclerotic activity although the underlying mechanisms remain elusive. In this study, the protective effect of CPT against oxidized low-density lipoprotein (ox-LDL)-induced adhesion molecule expression was investigated in human umbilical vein endothelial cells. Ox-LDL significantly induced ICAM-1, VCAM-1, and E-selectin expression at the mRNA and protein levels but reduced eNOS phosphorylation and NO generation, which were reversed by CPT pretreatment. Sodium nitroprusside, a NO donor, N-acetyl-L-cysteine (NAC), a reactive oxygen species (ROS) scavenger, and BAY117082, a NF-κB inhibitor, inhibited ox-LDL-induced ICAM-1, VCAM-1, and E-selectin expression. Ox-LDL-induced ROS production was significantly inhibited by CPT and NAC. Furthermore, ox-LDL activated the NF-κB signaling pathway by inducing phosphorylation of IKKβ and IκBα, promoting the interaction of IKKβ and IκBα, and increasing p65 nuclear translocation, which were significantly inhibited by CPT. In addition, CPT, NAC, and BAY117082 inhibited ox-LDL-induced membrane expression of ICAM-1, VCAM-1, E-selectin, and endothelial-monocyte adhesion and restored eNOS phosphorylation and NO generation. Results suggested that CPT inhibited ox-LDL-induced adhesion molecule expression by decreasing ROS and inhibiting the NF-κB pathways, which provides new insight into the anti-atherosclerotic mechanism of CPT.

Systemic circulatory influences on retinal microvascular function in middle-age individuals with low to moderate cardiovascular risk

PURPOSE

To investigate the relationship between retinal microvascular reactivity, circulatory markers for CVD risk and systemic antioxidative defence capacity in healthy middle-aged individuals with low to moderate risk of CVD.

METHODS

Retinal vascular reactivity to flickering light was assessed in 102 healthy participants (46-60 years) by means of dynamic retinal vessel analysis (DVA). Other vascular assessments included carotid intima-media thickness (C-IMT) and blood pressure (BP) measurements. Total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglycerides (TG) and blood glutathione levels in its reduced (GSH) and oxidized (GSSG) forms were also determined for each participant, along with Framingham risk scores (FRS).

RESULTS

Retinal arterial baseline diameter fluctuation (BDF) was independently, significantly and negatively influenced by LDL-C levels (β = -0.53, p = 0.027). Moreover, the arterial dilation slope (SlopeAD ) was independently, significantly and positively associated with redox index (GSH: GSSG ratio, β = 0.28, p = 0.016), while the arterial constriction slope (SlopeAC ) was significantly and negatively influenced by blood GSH levels (β = -0.20, p = 0.042), and positively associated with FRS (β = 0.25, p = 0.009). Venous BDF and dilation amplitude (DA) were also negatively influenced by plasma LDL-C levels (β = -0.83, p = 0.013; and β = -0.22, p = 0.028, respectively).

CONCLUSIONS

In otherwise healthy individuals with low to moderate cardiovascular risk, retinal microvascular dilation and constriction responses to stress levels are influenced by systemic antioxidant capacity, and circulating markers for cardiovascular risk.

Epigallocatechin-3-gallate protects HUVECs from PM2.5-induced oxidative stress injury by activating critical antioxidant pathways

Endothelial dysfunction and oxidative stress likely play roles in PM_2.5-induced harmful effects. Epigallocatechin-3-gallate (EGCG), the major polyphenolic constituent of green tea, is a potent antioxidant that exerts protective effects on cardiovascular diseases (CVDs) in part by scavenging free radicals. The exposure to ambient fine particulate matter (PM_2.5) is responsible for certain CVDs. The aim of the present study was to investigate whether EGCG could also inhibit PM_2.5-induced oxidative stress by activating the nuclear factor E2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway in human umbilical vein endothelial cells (HUVECs). PM_2.5 (200 μg/mL) increased both cell death and intracellular ROS levels significantly, whereas EGCG (50–400 μM) inhibited these effects in a concentration-dependent manner. Western blotting and PCR demonstrated that EGCG increased Nrf2 and HO-1 expression in HUVECs that had been exposed to PM_2.5. PD98059 (a selective inhibitor of extracellular signal regulated kinase [ERK]-1/2) and SB203580 (a selective inhibitor of p38 MAPK), but not SP600125 (a selective inhibitor of c-jun N-terminal kinase [JNK]), attenuated the EGCG-induced Nrf2 and HO-1 expression. In addition, silencing Nrf2 abolished EGCG-induced Nrf2 and HO-1 upregulation and enhancement of cell viability. The present study suggests that EGCG protects HUVECs from PM_2.5-induced oxidative stress injury by upregulating Nrf2/HO-1 via activation of the p38 MAPK and the ERK1/2 signaling pathways.

Oxidized LDL attenuates protective autophagy and induces apoptotic cell death of endothelial cells: Role of oxidative stress and LOX-1 receptor expression

BACKGROUND

Overproduction of oxidized-low density lipoproteins (oxyLDLs) has been found to contribute in endothelial cell (EC) dysfunction thereby leading to atherosclerosis development and progression. In particular, oxyLDLs lead to apoptotic cell death of EC via oxidative stress production, mostly subsequent to the overexpression of the scavenger receptor LOX-1. Here, we hypothesize that LOX-1 expression in EC represents a crucial event which attenuates protective autophagic response, thereby enhancing programmed endothelial cell death.

METHODS AND RESULTS

Bovine aortic endothelial cells (BAECs) in culture were exposed to oxyLDL (1-100 μM). After 48 h incubation, oxyLDL produced pronounced malondialdehyde (MDA) elevation and apoptotic cell death of BAEC as detected by FACS analysis, an effect counteracted by antioxidant N-acetyl-cysteine (NAC) as well as by the NO-donor SNAP. OxyLDL-induced apoptotic cell death was also accompanied by reduced VEGF-dependent phosphorylation of constitutive NO synthase (cNOS) in BAEC and consistent attenuation of autophagic response as detected by the expression of Beclin-1 and LC3, two reliable biomarkers of autophagy. Moreover, silencing LOX-1 receptor significantly restored LC3 expression in oxyLDL-treated BAEC, thus suggesting a key role of LOX-1 overproduction in oxyLDL-induced endothelial dysfunction.

CONCLUSIONS

OxyLDL leads to impaired NO generation and apoptotic cell death in BAECs. This effect occurs via the overexpression of LOX-1 and subsequent attenuation of protective autophagic response thereby contributing to the pathophysiology of oxyLDL-induced endothelial dysfunction which characterizes early stages of atherosclerotic process.

Protective effects of let-7a and let-7b on oxidized low-density lipoprotein induced endothelial cell injuries

Lectin-like low-density lipoprotein receptor 1 (LOX-1) is a receptor for oxidized low density lipoprotein (oxLDL) in endothelial cells. The activation of LOX-1 by oxLDL stimulates the apoptosis and dysfunction of endothelial cells, and contributes to atherogenesis. However, the regulatory factors for LOX-1 are still unclear. MicroRNAs are small, endogenous, non-coding RNAs that regulate gene expressions at a post-transcriptional level. The let-7 family is the second microRNA been discovered, which plays important roles in cardiovascular diseases. Let-7a and let-7b were predicted to target LOX-1 3′-UTR and be highly expressed in endothelial cells. The present study demonstrated that LOX-1 was a target of let-7a and let-7b. They inhibited the expression of LOX-1 by targeting the positions of 310-316 in LOX-1 3′-UTR. Over-expression of let-7a and let-7b inhibited the oxLDL-induced endothelial cell apoptosis, NO deficiency, ROS over-production, LOX-1 upregulation and endothelial nitric oxide synthase (eNOS) downregulation. Moreover, we found that oxLDL treatment induced p38MAPK phosphorylation, NF-κB nuclear translocation, IκB degradation and PKB dephosphorylation. Let-7a or let-7b over-expression attenuated these alterations significantly. The present study may provide a new insight into the protective properties of let-7a and let-7b in preventing the endothelial dysfunction associated with cardiovascular disease, such as atherosclerosis.

Epigallocatechin-3-O-gallate, a green tea polyphenol, induces expression of pim-1 kinase via PPARγ in human vascular endothelial cells

Pim-1 is a serine/threonine kinase and involved in cell survival and proliferation. Recently, it has been shown that pim-1 signaling pathway plays an important role in cardiovascular protection and differentiation. In this study, we sought to explore the expression of pim-1 in human vascular endothelial cells (ECs) and its regulation by epigallocatechin-3-O-gallate (EGCG), a green tea polyphenol which has anti-oxidant, anti-inflammatory and vascular protective effects. By using quantitative reverse transcriptase PCR (qRT-PCR) and Western blotting, we showed that EGCG dose-dependently increased the expression of pim-1 in cultured umbilical vein endothelial cells. Next, we showed that EGCG activated a luciferase reporter driven by peroxisome proliferators-activated receptor (PPAR)-responsive elements. The induced expression of pim-1 was inhibited in ECs pretreated with GW9662, a specific antagonist of PPARγ. In addition, pim-1 was also up-regulated in endothelial cells treated with rosiglitazone, a specific agonist for PPARγ, or those infected with the adenovirus expressing a constitutively active PPARγ. Collectively, our results provided new evidence that pim-1 can be up-regulated by EGCG via a PPARγ-mediated mechanism and may mediate its vascular protective effects.

Palmitic acid-induced lipotoxicity and protection by (+)-catechin in rat cortical astrocytes

BACKGROUND

Astrocytes do not only maintain homeostasis of the extracellular milieu of the neurons, but also play an active role in modulating synaptic transmission. Palmitic acid (PA) is a saturated fatty acid which, when being excessive, is a significant risk factor for lipotoxicity. Activation of astrocytes by PA has been shown to cause neuronal inflammation and demyelination. However, direct damage by PA to astrocytes is relatively unexplored. The aim of this study was to identify the mechanism(s) of PA-induced cytotoxicity in rat cortical astrocytes and possible protection by (+)-catechin.

METHODS

Cytotoxicity and endoplasmic reticulum (ER) markers were assessed by MTT assay and Western blotting, respectively. Cytosolic Ca(2+) and mitochondrial membrane potential (MMP) were measured microfluorimetrically using fura-2 and rhodamine 123, respectively. Intracellular reactive oxygen species (ROS) production was assayed by the indicator 2'-7'-dichlorodihydrofluorescein diacetate.

RESULTS

Exposure of astrocytes to 100μM PA for 24h resulted in apoptotic cell death. Whilst PA-induced cell death appeared to be unrelated to ER stress and perturbation in cytosolic Ca(2+) signaling, it was likely a result of ROS production and subsequent MMP collapse, since ascorbic acid (anti-oxidant, 100μM) prevented PA-induced MMP collapse and cell death. Co-treatment of astrocytes with (+)-catechin (300μM), an anti-oxidant found abundantly in green tea, significantly prevented PA-induced ROS production, MMP collapse and cell death.

CONCLUSION

Our results suggest that PA-induced cytotoxicity in astrocytes may involve ROS generation and MMP collapse, which can be prevented by (+)-catechin.

LOX-1 and ROS, inseparable factors in the process of endothelial damage

Lectin-like oxidized low-density lipoprotein (LOX-1) has been identified in endothelial cells as the main receptor of oxidized low-density lipoprotein (OxLDL). LOX-1 is upregulated in the presence of pathological conditions including atherosclerosis, hypertension, and diabetes because it acts as a mediator of "endothelial dysfunction". It promotes the generation of superoxide anion (O2(-)), the inhibition of nitric oxide (NO) production and the increment of endothelial adhesiveness to monocytes. Recently, it was reported that OxLDL, binding to LOX-1, determined a significant increase in the generation of reactive oxygen species (ROS), suggesting the involvement of signaling pathways such as mitogen-activated protein kinases (MAPKs). It is now generally accepted that ROS act indirectly on the modulation of LOX-1 expression because ROS oxidize native LDL. Moreover, LOX-1 activation per se may stimulate ROS generation. Accordingly, our findings showed that high levels of ROS can directly increase LOX-1 production in microvascular endothelial cells (HMEC-1). It has been reported that OxLDL, usually > 20 μg protein/ml, induced apoptosis in a variety of cell types. At low concentrations (< 5 μg protein/ml) OxLDL appears to be associated with cell proliferation and low levels of ROS-induced capillary tube formation in endothelial cells. Our data and those of the literature indicate the existence of a direct control of LOX-1 by ROS. Although ROS in large amounts clearly have detrimental effects on cell biology, small amounts of ROS could have a beneficial effect, suggesting its therapeutic potential for reducing ischemic tissue.

Puerarin protects endothelial cells from oxidized low density lipoprotein induced injuries via the suppression of LOX-1 and induction of eNOS

Oxidized low density lipoprotein (oxLDL) induced injury of endothelial cells is considered to be the first step in the pathogenesis of atherosclerosis. This study aimed to investigate some of the effects and mechanisms of puerarin on oxLDL-induced endothelial injuries. We measured cell viability, and the release of lactate dehydrogenase (LDH), nitric oxide (NO), and interleukin-8 (IL-8) to evaluate the protective effects of puerarin. Intracellular reactive oxygen species (ROS) were detected using 2',7'-dichlorofluorescein diacetate (DCFH-DA). The expression of lectin-like low-density lipoprotein receptor-1 (LOX-1), endothelial nitric oxide synthase (eNOS), cyclooxygenase 2 (COX-2), p38MAPK, and protein kinase B (PKB) phosphorylation, nuclear factor-κB (NF-κB) nuclear translocation, and inhibitor of κB (IκB) degradation were detected using quantitative real-time PCR or Western blot. The results showed that oxLDL significantly decreased cell viability, increased LDH and IL-8 release, inhibited NO production, and induced COX-2 expression. Pretreatment with puerarin led to a strong inhibition of these effects. OxLDL stimulated the expression of LOX-1, the overproduction of ROS, the phosphorylation of p38MAPK, the dephosphorylation of PKB, activation of NF-κB, and the degradation of IκB. These oxLDL-induced effects were suppressed after puerarin pretreatment. These results suggest that puerarin inhibits oxLDL-induced endothelial cell injuries, at least in part, via inhibition of the LOX-1-mediated p38MAPK-NF-κB inflammatory and the PKB-eNOS signaling pathways.

Polyphenols: benefits to the cardiovascular system in health and in aging

Numerous studies have demonstrated the importance of naturally occurring dietary polyphenols in promoting cardiovascular health and emphasized the significant role these compounds play in limiting the effects of cellular aging. Polyphenols such as resveratrol, epigallocatechin gallate (EGCG), and curcumin have been acknowledged for having beneficial effects on cardiovascular health, while some have also been shown to be protective in aging. This review highlights the literature surrounding this topic on the prominently studied and documented polyphenols as pertaining to cardiovascular health and aging.

LOX-1, OxLDL, and atherosclerosis

Oxidized low-density lipoprotein (OxLDL) contributes to the atherosclerotic plaque formation and progression by several mechanisms, including the induction of endothelial cell activation and dysfunction, macrophage foam cell formation, and smooth muscle cell migration and proliferation. Vascular wall cells express on their surface several scavenger receptors that mediate the cellular effects of OxLDL. The lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is the main OxLDL receptor of endothelial cells, and it is expressed also in macrophages and smooth muscle cells. LOX-1 is almost undetectable under physiological conditions, but it is upregulated following the exposure to several proinflammatory and proatherogenic stimuli and can be detected in animal and human atherosclerotic lesions. The key contribution of LOX-1 to the atherogenic process has been confirmed in animal models; LOX-1 knockout mice exhibit reduced intima thickness and inflammation and increased expression of protective factors; on the contrary, LOX-1 overexpressing mice present an accelerated atherosclerotic lesion formation which is associated with increased inflammation. In humans, LOX-1 gene polymorphisms were associated with increased susceptibility to myocardial infarction. Inhibition of the LOX-1 receptor with chemicals or antisense nucleotides is currently being investigated and represents an emerging approach for controlling OxLDL-LOX-1 mediated proatherogenic effects.

Paeonol suppresses oxidized low-density lipoprotein induced endothelial cell apoptosis via activation of LOX-1/p38MAPK/NF-κB pathway

Paeonol is an active compound isolated from traditional Chinese medicine, and has been shown to have anti-atherosclerosis, anti-inflammatory, antioxidant effects. The present investigation was undertaken to determine the suppression effects of paeonol on oxidized low-density lipoprotein (ox-LDL) induced endothelial cell line HUVEC apoptosis and to uncover some of the underlying mechanisms of these effects. Cell viability and lactate dehydrogenase (LDH) were measured to evaluate the cell injuries. Apoptosis was evaluated by Hoechst 33342 staining and flow cytometry. Intracellular reactive oxygen species (ROS) generation was detected by 2',7'-dichlorofluorescein diacetate (DCFH-DA). Real-time PCR was used to confirm the expression of LOX-1 mRNA. Western blotting was used to evaluate the protein expression of LOX-1 and Bcl-2, as well as caspase-3 cleavage, p38-mitogen-activated protein kinase (p38MAPK) phosphorylation. NF-κB nuclear translocation was detected by Western blotting and immunofluorescence. Caspase-3 activity was measured using a colorimetric protease assay kit. The results showed that ox-LDL significantly decreased cell viability and increased the LDH release, as well as the apoptotic rate (P<0.01). Pre-treatment of paeonol resulted in remarkable increase of cell viability, decrease of LDH release and cell apoptosis in a concentration-dependent manner. Besides, ox-LDL caused the up-regulation of LOX-1, the down-regulation of Bcl-2, the phosphorylation of p38MAPK, the translocation of NF-κB and the activation of caspase-3. Paeonol pre-treatment reversed these effects introduced by ox-LDL. Moreover, paeonol also showed its inhibition effects on ox-LDL induced ROS overproduction. These results indicate the preventive effects of paeonol on ox-LDL induced endothelial cell apoptosis. The effects might, at least partly, be obtained via inhibition of LOX-1-ROS- p38MAPK-NF-κB signaling pathway.

LOX-1 in atherosclerosis: biological functions and pharmacological modifiers

Lectin-like oxidized LDL (oxLDL) receptor-1 (LOX-1, also known as OLR-1), is a class E scavenger receptor that mediates the uptake of oxLDL by vascular cells. LOX-1 is involved in endothelial dysfunction, monocyte adhesion, the proliferation, migration, and apoptosis of smooth muscle cells, foam cell formation, platelet activation, as well as plaque instability; all of these events are critical in the pathogenesis of atherosclerosis. These LOX-1-dependent biological processes contribute to plaque instability and the ultimate clinical sequelae of plaque rupture and life-threatening tissue ischemia. Administration of anti-LOX-1 antibodies inhibits atherosclerosis by decreasing these cellular events. Over the past decade, multiple drugs including naturally occurring antioxidants, statins, antiinflammatory agents, antihypertensive and antihyperglycemic drugs have been demonstrated to inhibit vascular LOX-1 expression and activity. Therefore, LOX-1 represents an attractive therapeutic target for the treatment of human atherosclerotic diseases. This review aims to integrate the current understanding of LOX-1 signaling, regulation of LOX-1 by vasculoprotective drugs, and the importance of LOX-1 in the pathogenesis of atherosclerosis.

Cardioprotective effects of a proanthocyanidin-rich fraction from Croton celtidifolius Baill: focus on atherosclerosis

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies have pointed to proanthocyanidins as promising molecules that could prevent the development of several coronary syndromes by inhibiting the atherogenic process. The present study was designed to investigate the antiatherogenic effects of a proanthocyanidin-rich fraction (PRF) obtained from Croton celtidifolius Baill (Euphorbiaceae) barks. In isolated human LDL, PRF caused a concentration-dependent inhibition of Cu2+-induced oxidative modifications, evidenced by the increasing of the lag phase of lipid peroxidation and decreasing in the oxidation rate (Vmax), moreover, the protein moieties from LDL were protected against Cu2+-induced oxidation. In human umbilical vein endothelial cells (HUVECs), PRF reduced the ROS production stimulated by oxidized LDL. Herein, we demonstrate that oral treatment with PRF improved endothelium-dependent vasorelaxation in hypercholesterolemic LDL receptor knockout mice (LDLr-/-), however, the fraction did not modify plasma lipids and atherosclerotic lesion size in this experimental model. Finally, our results showed for the first time that PRF prevent isolated LDL oxidation, decrease oxidative stress in endothelial cells and improve endothelial function in mice.

FOXO1 mediates the autocrine effect of endothelin-1 on endothelial cell survival

Chronic hyperglycemia exerts a deleterious effect on endothelium, contributing to endothelial dysfunction and microvascular complications in poorly controlled diabetes. To understand the underlying mechanism, we studied the effect of endothelin-1 (ET-1) on endothelial production of Forkhead box O1 (FOXO1), a forkhead transcription factor that plays an important role in cell survival. ET-1 is a 21-amino acid peptide that is secreted primarily from endothelium. Using adenovirus-mediated gene transfer approach, we delivered FOXO1 cDNA into cultured human aorta endothelial cells. FOXO1 was shown to stimulate B cell leukemia/lymphoma 2-associated death promoter (BAD) production and promote cellular apoptosis. This effect was counteracted by ET-1. In response to ET-1, FOXO1 was phosphorylated and translocated from the nucleus to cytoplasm, resulting in inhibition of BAD production and mitigation of FOXO1-mediated apoptosis. Hyperglycemia stimulated FOXO1 O-glycosylation and promoted its nuclear localization in human aorta endothelial cells. This effect accounted for unbridled FOXO1 activity in the nucleus, contributing to augmented BAD production and endothelial apoptosis under hyperglycemic conditions. FOXO1 expression became deregulated in the aorta of both streptozotocin-induced diabetic mice and diabetic db/db mice. This hyperglycemia-elicited FOXO1 deregulation and its ensuing effect on endothelial cell survival was corrected by ET-1. Likewise, FoxO1 deregulation in the aorta of diabetic mice was reversible after the reduction of hyperglycemia by insulin therapy. These data reveal a mechanism by which FOXO1 mediated the autocrine effect of ET-1 on endothelial cell survival. FOXO1 deregulation, resulting from an impaired ability of ET-1 to control FOXO1 activity in endothelium, may contribute to hyperglycemia-induced endothelial lesion in diabetes.

A novel mechanism of coenzyme Q10 protects against human endothelial cells from oxidative stress-induced injury by modulating NO-related pathways

BACKGROUND

Atherosclerosis is a chronic inflammatory disease of the vessel wall associated with oxidized low-density lipoprotein (oxLDL)-induced apoptosis of endothelial cells. Coenzyme Q10 (CoQ10), a potent antioxidant and a critical intermediate of the electron transport chain, has been reported to inhibit LDL oxidation and thus the progression of atherosclerosis. However, its molecular mechanisms on endothelial cells remain still unclarified.

METHODS

In this study, primary human umbilical vein endothelial cell cultures treated with oxLDL were used to explore the protective effects of CoQ10.

RESULTS

Our results showed that CoQ10 attenuated the oxLDL-induced generation of reactive oxygen species and improved the antioxidant capacity. CoQ10 also attenuated the oxLDL-mediated down-regulation of endothelial nitric oxide synthase (eNOS) and up-regulation of inducible nitric oxide synthase (iNOS). In addition, CoQ10 suppressed oxLDL-activated NF-κB and downstream inflammatory mediators, including expression of adhesion molecules, release of proinflammatory cytokines and the adherence of monocytic THP-1 cells. Moreover, CoQ10 attenuated oxLDL-altered proapoptotic responses. The inhibitor of eNOS (L-NIO 10 μM) and iNOS (1400W 10 μM) as well as NO enhancer (SNP 10 μM) were used to clean up the mechanism.

CONCLUSION

These results provide new insight into the possible molecular mechanisms by which CoQ10 protects against atherogenesis by NO-related pathways.

Proinflammatory effect of cholesterol and its oxidation products on CaCo-2 human enterocyte-like cells: effective protection by epigallocatechin-3-gallate

Cholesterol and its oxidation products, namely oxysterols, have very recently been shown to potentially interfere with homeostasis of the human digestive tract, by promoting and sustaining irreversible damage of the colonic epithelial layer. This report concerns the strong proinflammatory action that a dietary oxysterol mixture and, to a lesser extent, an identical concentration of unoxidized cholesterol exert on CaCo-2 colonic epithelial cells by up-regulating both expression and synthesis of interleukin 8. The oxysterol mixture and its most effective component, 7β-hydroxycholesterol, are also shown to markedly enhance the expression of key inflammatory and chemotactic cytokines in colonic epithelial cells, more efficiently than unoxidized cholesterol. The sterols' proinflammatory effect seems to be mediated by enhanced activation of NOX1, because it is prevented by pretreatment of the cells with DPI, a selective inhibitor of this oxidase. Importantly, NOX1 hyperactivation by the oxysterol mixture or cholesterol was fully prevented by CaCo-2 cell preincubation with epigallocatechin-3-gallate. Consistently, supplementation with this compound fully protected colonic epithelial cells against overexpression of inflammatory and chemotactic genes induced by the sterols investigated.