Activation of transcription factors and gene expression by oxidized low-density lipoprotein

Low-density lipoprotein modified by myeloperoxidase in inflammatory pathways and clinical studies

Oxidation of low-density lipoprotein (LDL) has a key role in atherogenesis. Among the different models of oxidation that have been studied, the one using myeloperoxidase (MPO) is thought to be more physiopathologically relevant. Apolipoprotein B-100 is the unique protein of LDL and is the major target of MPO. Furthermore, MPO rapidly adsorbs at the surface of LDL, promoting oxidation of amino acid residues and formation of oxidized lipoproteins that are commonly named Mox-LDL. The latter is not recognized by the LDL receptor and is accumulated by macrophages. In the context of atherogenesis, Mox-LDL accumulates in macrophages leading to foam cell formation. Furthermore, Mox-LDL seems to have specific effects and triggers inflammation. Indeed, those oxidized lipoproteins activate endothelial cells and monocytes/macrophages and induce proinflammatory molecules such as TNFα and IL-8. Mox-LDL may also inhibit fibrinolysis mediated via endothelial cells and consecutively increase the risk of thrombus formation. Finally, Mox-LDL has been involved in the physiopathology of several diseases linked to atherosclerosis such as kidney failure and consequent hemodialysis therapy, erectile dysfunction, and sleep restriction. All these issues show that the investigations of MPO-dependent LDL oxidation are of importance to better understand the inflammatory context of atherosclerosis.

Multiple antioxidants improve cardiac complications and inhibit cardiac cell death in streptozotocin-induced diabetic rats

Diabetic cardiomyopathy, a disorder of the heart muscle in diabetic patients, is one of the major causes of heart failure. Since diabetic cardiomyopathy is now known to have a high prevalence in the asymptomatic diabetic patient, prevention at the earliest stage of development by existing molecules would be appropriate in order to prevent the progression of heart failure. In this study, we investigated the protective role of multiple antioxidants (MA), on cardiac dysfunction and cardiac cell apoptosis in streptozotocin (STZ)-induced diabetic rat. Diabetic cardiomyopathy in STZ-treated animals was characterized by declined systolic, diastolic myocardial performance, oxidative stress and apoptosis in cardiac cells. Diabetic rats on supplementation with MA showed decreased oxidative stress evaluated by the content of reduced levels of lipid per-oxidation and decreased activity of catalase with down-regulation of heme-oxygenase-1 mRNA. Supplementation with MA also resulted in a normalized lipid profile and decreased levels of pro-inflammatory transcription factor NF-kappaB as well as cytokines such as TNF-α, IFN-γ, TGF-β, and IL-10. MA was found to decrease the expression of ROS-generating enzymes like xanthine oxidase, monoamine oxidase-A along with 5-Lipoxygenase mRNA and/or protein expression. Further, left ventricular function, measured by a microtip pressure transducer, was re-established as evidenced by increase in ±dp/dtmax, heart rate, decreased blood pressure, systolic and diastolic pressure as well as decrease in the TUNEL positive cardiac cells with increased Bcl-2/Bax ratio. In addition, MA supplementation decreased cell death and activation of NF-kappaB in cardiac H9c2 cells. Based on our results, we conclude that MA supplementation significantly attenuated cardiac dysfunction in diabetic rats; hence MA supplementation may have important clinical implications in terms of prevention and management of diabetic cardiomyopathy.

Diabetes alters activation and repression of pro- and anti-inflammatory signaling pathways in the vasculature

A central mechanism driving vascular disease in diabetes is immune cell-mediated inflammation. In diabetes, enhanced oxidation and glycation of macromolecules, such as lipoproteins, insults the endothelium, and activates both innate and adaptive arms of the immune system by generating new antigens for presentation to adaptive immune cells. Chronic inflammation of the endothelium in diabetes leads to continuous infiltration and accumulation of leukocytes at sites of endothelial cell injury. We will describe the central role of the macrophage as a source of signaling molecules and damaging by-products which activate infiltrating lymphocytes in the tissue and contribute to the pro-oxidant and pro-inflammatory microenvironment. An important aspect to be considered is the diabetes-associated defects in the immune system, such as fewer or dysfunctional athero-protective leukocyte subsets in the diabetic lesion compared to non-diabetic lesions. This review will discuss the key pro-inflammatory signaling pathways responsible for leukocyte recruitment and activation in the injured vessel, with particular focus on pro- and anti-inflammatory pathways aberrantly activated or repressed in diabetes. We aim to describe the interaction between advanced glycation end products and their principle receptor RAGE, angiotensin II, and the Ang II type 1 receptor, in addition to reactive oxygen species (ROS) production by NADPH-oxidase enzymes that are relevant to vascular and immune cell function in the context of diabetic vasculopathy. Furthermore, we will touch on recent advances in epigenetic medicine that have revealed high glucose-mediated changes in the transcription of genes with known pro-inflammatory downstream targets. Finally, novel anti-atherosclerosis strategies that target the vascular immune interface will be explored; such as vaccination against modified low-density lipoprotein and pharmacological inhibition of ROS-producing enzymes.

High sensitivity C-reactive protein concentrations, birthweight and cardiovascular risk markers in Brazilian children

BACKGROUND/OBJECTIVES

High sensitivity C-reactive protein (hs-CRP) and low birthweight have emerged as predictors of cardiovascular diseases (CVDs). In studies involving adults, higher concentrations of hs-CRP have been associated with low birthweight. This study assessed the relationship between hs-CRP and birthweight, and other risk markers for CVDs in childhood.

SUBJECTS/METHODS

A total of 459 Brazilian children aged 5-8 years were included in the study. hs-CRP was measured by particle-enhanced immunonephelometry. The nutritional status of the children was assessed by BMI and waist circumference. Total cholesterol and fractions, triglycerides and glucose were measured by enzymatic methods. Insulin sensitivity was determined by the homeostasis model assessment (HOMA) method. Blood pressure was measured by the HDI/Pulse Wave CR-2000 equipment (Hypertension Diagnostics, Eagan, MN, USA). A multivariate linear regression analysis investigated the association between hs-CRP and birthweight, and risk markers for CVDs.

RESULTS

There were positive associations between hs-CRP and gender (P=0.001), waist circumference (P<0.001) and systolic blood pressure (SBP) (P=0.03), and negative associations between hs-CRP and age (P<0.001), and high-density lipoprotein cholesterol (HDL-c) (P=0.005) (R²=0.14). Abnormal values of hs-CRP, waist circumference, HDL-c and SBP, respectively, were observed in 27.7, 26.4, 14.4 and 34.7% of the children.

CONCLUSIONS

Opposite to studies involving adults, there was no association between hs-CRP and birthweight, implying that time may strengthen the relationship, considering that hs-CRP-concentration-associated metabolic changes increase from childhood to adulthood. The associations between hs-CRP and waist circumference, HDL-c and SBP in very young ages is a matter of concern, especially in females, in view of the large number of children with abnormal values of these measurements.

Interleukin-13 inhibits cytokines synthesis by blocking nuclear factor-κB and c-Jun N-terminal kinase in human mesangial cells

Objective

Monocytes/macrophages, proinflammatory cytokines and chemokines are important in the pathogenesis of glomerulonephritis. Interleukin (IL) -13 has been shown to exert potent anti-inflammatory properties. This study was designed to investigate the effect of IL-13 on the expression of proinflammatory cytokines, chemokines and profibrogenic cytokines and the involved molecular mechanism in cultured human mesangial cells (HMCs).

Methods

The expressions of proinflammatory cytokines, chemokines and profibrogenic cytokines were determined by ribonuclease protection assay (RPA). Activity of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1) was examined by electrophoretic mobility shift assay (EMSA). NF-κB subunit p65 nuclear transportation and c-Jun N-terminal kinase (JNK) activity were assayed by immunoblot.

Results

Recombinant IL-13 inhibited tumor necrosis factor-α (TNF-α), IL-1α, IL-1β, monocyte chemoattractant protein-1 (MCP-1), IL-8, and transforming growth factor-β1 (TGF-β1) mRNA expressions in a dose-dependent manner. Lipopolysacchorides (LPS) dramatically increased NF-κB DNA binding activity of HMCs, which was inhibited by IL-13 in a dose-dependent manner. LPS-activated NF-κB contained p50 and p65 dimers, but not c-Rel subunit. IL-13 blocked LPS-induced NF-κB subunit p65. LPS stimulated JNK/AP-1 activation, which was inhibited by IL-13 in a dose-dependent manner.

Conclusion

IL-13 inhibits proinflammatory cytokines, chemokines, and profibrogenic cytokines synthesis by blocking NF-κB and JNK/AP-1 activation. These observations point to the importance of IL-13 in the modulation of inflammatory processes in the renal glomerulus.

Ginseng Berry Extract Prevents Atherogenesis via Anti-Inflammatory Action by Upregulating Phase II Gene Expression

Ginseng berry possesses higher ginsenoside content than its root, which has been traditionally used in herbal medicine for many human diseases, including atherosclerosis. We here examined the antiatherogenic effects of the Korean ginseng berry extract (KGBE) and investigated its underlying mechanism of action in vitro and in vivo. Administration of KGBE decreased atherosclerotic lesions, which was inversely correlated with the expression levels of phase II genes to include heme oxygenase-1 (HO-1) and glutamine-cysteine ligase (GCL). Furthermore, KGBE administration suppressed NF-κB-mediated expression of atherogenic inflammatory genes (TNF-α, IL-1β, iNOS, COX-2, ICAM-1, and VCAM-1), without altering serum cholesterol levels, in ApoE^−/− mice fed a high fat-diet. Treatment with KGBE increased phase II gene expression and suppressed lipopolysaccharide-induced reactive oxygen species production, NF-κB activation, and inflammatory gene expression in primary macrophages. Importantly, these cellular events were blocked by selective inhibitors of HO-1 and GCL. In addition, these inhibitors reversed the suppressive effect of KGBE on TNF-α-mediated induction of ICAM-1 and VCAM-1, resulting in decreased interaction between endothelial cells and monocytes. These results suggest that KGBE ameliorates atherosclerosis by inhibiting NF-κB-mediated expression of atherogenic genes via upregulation of phase II enzymes and thus has therapeutic or preventive potential for atherosclerosis.

Exaggerated myocardial oxLDL amount and LOX-1 receptor over-expression associated with coronary microvessel inflammation in unstable angina

The pathophysiological relationship between coronary atherosclerosis and coronary microvessels remains undefined and the specific causative role of oxidatively modified low density lipoprotein (oxLDL) in human atherosclerosis is debated. The purposes of this study are to investigate whether coronary microvessels are involved in coronary atherosclerosis and whether increased myocardial oxLDL amount can be associated with coronary microvessel inflammation. A combination of immunohistochemical, RT-PCR and real-time PCR studies performed on myocardial biopsy specimens from patients with mitral stenosis (control hearts, CHs) and from unstable and stable angina patients (UAP and SAP), demonstrated that myocardial oxLDL was associated with a chronic low-grade inflammation in SAP and with a severe high grade inflammation in UAP. oxLDL amount was notably higher in UAP than in SAP and in UAP the high grade of inflammation was correlated with the increased amount of oxLDL in endothelial cells and macrophages. The exaggerated amount of oxLDL in UAP and the interaction of oxLDL with lectin-like oxLDL (LOX-1) receptor are amplified by the activation of transcriptional factor octamere 1 (OCT-1) with consequent activation of a series of inflammatory endothelial feed-back mechanisms resulting in LOX-1 gene over-expression, endothelial inflammation as well as uncontrolled nuclear factor kappa B (NFkB) activation. Moreover, in UAP genes for signal transducer and activator transcriptional factor 1α (STAT1α), angiotensin converting enzyme (ACE) and numerous pro-inflammatory cytokines were over-expressed. The present results may have clinical relevance because they show that coronary atherosclerosis is a disease not confined to the large arteries but involving the whole coronary tree. In UAP the exaggerated amount of myocardial oxLDL is associated with widespread high grade microvessel inflammation.

Synergistic effect of scavenger receptor A and low-density lipoprotein receptor on macrophage foam cell formation under inflammatory stress

To provide experimental evidence for the effect of inflammation on cholesterol accumulation in macrophages, we investigated the expression of low-density lipoprotein receptor (LDL-R) and scavenger receptor A (SR-A) genes and proteins in the lipopolysaccharide (LPS)-stimulated macrophage-like RAW264.7 cell line. RAW264.7 cells were incubated in serum-free medium in the absence or presence of LDL alone, LDL+LPS and LPS alone. Intracellular cholesterol content, tumor necrosis factor α levels in the supernatants, mRNA and protein expression of LDL-R and SR-A in the treated cells were assessed by Oil Red O staining cholesterol enzymatic assay, enzyme-linked immunosorbent assay, semi-quantitative polymerase chain reaction and western blot analysis, respectively. Our results demonstrated that LPS was able to upregulate SR-A mRNA and protein expression, override LDL-R suppression induced by a high dose of LDL and increase LDL uptake by enhancing receptor expression, leading to foam cell formation in RAW264.7 cells. These findings suggest that the synergy of the upregulation of SR-A and dysregulation of LDL-R under inflammatory stress may contribute to macrophage-derived foam cell formation.

Molecular signaling involved in oxysterol-induced β₁-integrin over-expression in human macrophages

The hypercholesterolemia-atherosclerosis association is now established; hypercholesterolemia may induce vascular-cell activation, subsequently increasing expression of adhesion molecules, cytokines, chemokines, growth factors, and other key inflammatory molecules. Among inflammatory molecules expressed by vascular cells, integrins play a critical role in regulating macrophage activation and migration to the site of inflammation, by mediating cell-cell and cell-extracellular matrix interactions. The main lipid oxidation products present in oxidized LDL that may be responsible for inflammatory processes in atherogenesis, are cholesterol oxidation products, known as oxysterols. This study demonstrates the effect of an oxysterol mixture, compatible with that detectable in human hypercholesterolemic plasma, on the expression and synthesis of β₁-integrin in cells of the macrophage lineage. The molecular signaling whereby oxysterols induce β₁-integrin up-regulation is also comprehensively investigated. Over-expression of β₁-integrin depends on activation of classic and novel members of protein kinase C and extracellular signal-regulated kinases 1 and 2, as well as of the up-stream G-protein (Gq and G13), c-Src, and phospholipase C. In addition, the localization of β₁-integrin in advanced human carotid plaques is highlighted, marking its importance in atherosclerotic plaque progression.

Serum lipids modify periodontal infection - C-reactive protein association

AIM

To investigate whether low-grade inflammation-related factors such as serum low-density (LDL-C) and high-density lipoprotein cholesterol (HDL-C) modify the association between periodontal infection and C-reactive protein.

MATERIAL AND METHODS

This study was based on a subpopulation of the Health 2000 Survey, which consisted of dentate, non-diabetic, non-rheumatic subjects who were 30-49 years old (n = 2710). The extent of periodontal infection was measured by means of the number of teeth with periodontal pocket ≥4 mm and teeth with periodontal pocket ≥6 mm and systemic inflammation using high sensitive C-reactive protein.

RESULTS

The extent of periodontal infection was associated with elevated levels of C-reactive protein among those subjects whose HDL-C value was below the median value of 1.3 mmol/l or LDL-C above the median value of 3.4 mmol/l. Among those with HDL-C ≥ 1.3 mmol/l or LDL-C ≤ 3.4 mmol/l, the association between periodontal infection and serum concentrations of C-reactive protein was practically non-existent.

CONCLUSION

This study suggests that the relation of periodontal infection to the systemic inflammatory condition is more complicated than previously presumed. The findings of this study suggest that the possible systemic effect of periodontal infection is dependent on serum lipid composition.

Hyperglycemia and endothelial dysfunction in atherosclerosis: lessons from type 1 diabetes

A clear relationship between diabetes and cardiovascular disease has been established for decades. Despite this, the mechanisms by which diabetes contributes to plaque formation remain in question. Some of this confusion derives from studies in type 2 diabetics where multiple components of metabolic syndrome show proatherosclerotic effects independent of underlying diabetes. However, the hyperglycemia that defines the diabetic condition independently affects atherogenesis in cell culture systems, animal models, and human patients. Endothelial cell biology plays a central role in atherosclerotic plaque formation regulating vessel permeability, inflammation, and thrombosis. The current paper highlights the mechanisms by which hyperglycemia affects endothelial cell biology to promote plaque formation.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.

Dietary total antioxidant capacity is inversely related to central adiposity as well as to metabolic and oxidative stress markers in healthy young adults

Background

Dietary total antioxidant capacity (TAC) has been assumed as a useful tool to assess the relationship between the cumulative antioxidant food capacity and several chronic disorders. The aim of this cross-sectional study was to investigate the potential relationships of dietary TAC with adiposity, metabolic and oxidative stress markers in healthy young adults.

Methods

This study enrolled 266 healthy subjects (105 men/ 161 women; 22 ± 3 years-old; 22.0 ± 2.7 kg/m²). Dietary intake, anthropometry, blood pressure, lifestyle features, and biochemical data were assessed with validated procedures.

Results

In linear regression analyses, dietary TAC values were inversely associated with glycemia, total cholesterol:HDL-c ratio, triglycerides and oxidized-LDL concentrations, and positively associated with HDL-c concentrations, independently of gender, age, smoking status, physical activity, vitamin use supplement, waist circumference, energy intake, fatty acid intake. In addition, plasma TAC was negatively correlated with ox-LDL concentrations (r= -0.20, P = 0.003), independently of the assessed confounding variables. Finally, dietary TAC values were inversely related to waist circumference values (r= -0.17, P = 0.005) as well as to lower mild central obesity occurrence (waist circumference ≥ 80/ 94 cm for women/ men, respectively).

Conclusion

Dietary TAC values are inversely associated with glucose and lipid biomarkers as well as with central adiposity measurements in healthy young adults, indicating dietary TAC as a useful tool to assess the health benefits of cumulative antioxidant capacity from food intake. In addition, the independent and inverse relationships of ox-LDL concentrations with dietary and plasma TAC respectively suggest a putative role of antioxidant rich-diet in the link between redox state and atherogenesis at early stage.

ATM protects against oxidative stress induced by oxidized low-density lipoprotein

Chronic oxidative stress is involved in the pathogenesis of multiple inflammatory diseases, including cardiovascular disease and atherosclerosis. The rare autosomal recessive disorder Ataxia-telangiectasia (A-T) is characterized by progressive cerebellar ataxia secondary to Purkinje cell death, immunodeficiency, and increased cancer incidence. ATM, the protein mutated in A-T, plays a key role in cellular DNA-damage responses. A-T cells show poor cellular anti-oxidant defences and increased oxidant sensitivity compared to normal cells, and ATM functions, in part, as an oxidative stress sensor. The oxidation of low-density lipoprotein (oxLDL) and its uptake by macrophages is an initiating step in the development of atherosclerosis. We demonstrate that oxLDL activates ATM and downstream p21 expression in normal fibroblasts and endothelial cells. In ATM-deficient fibroblasts oxLDL induces DNA double-strand breaks, micronuclei formation and causes chromosome breaks. Furthermore, oxLDL decreases cell viability and inhibits colony formation in A-T fibroblasts more effectively as compared to normal controls. Formation of oxLDL-induced reactive oxygen species is significantly higher in A-T, than normal fibroblasts. Last, pre-treatment of cells with ammonium pyrrolidine dithiocarbamate, a potent antioxidant and inhibitor of transcription factor nuclear factor κB, reduces oxLDL-induced reactive oxygen species formation. Our data indicates that ATM functions in the defence against oxLDL-mediated cytotoxicity.

Potential role of nuclear factor κB in diabetic cardiomyopathy

Diabetic cardiomyopathy entails the cardiac injury induced by diabetes independently of any vascular disease or hypertension. Some transcription factors have been proposed to control the gene program involved in the setting and development of related processes. Nuclear factor-kappa B is a pleiotropic transcription factor associated to the regulation of many heart diseases. However, the nuclear factor-kappa B role in diabetic cardiomyopathy is under investigation. In this paper, we review the nuclear factor-kappa B pathway and its role in several processes that have been linked to diabetic cardiomyopathy, such as oxidative stress, inflammation, endothelial dysfunction, fibrosis, hypertrophy and apoptosis.

OxLDL up-regulates microRNA-29b, leading to epigenetic modifications of MMP-2/MMP-9 genes: a novel mechanism for cardiovascular diseases

MicroRNAs (miRNAs), small noncoding RNAs, can control gene expression by binding to their target genes for degradation and/or translational repression. Epigenetic mechanisms are defined as heritable changes in gene expression that do not involve coding sequence modifications. Both mechanisms play an important role in maintaining physiological functions and are also related to disease development. However, few studies report that miRNA-mediated epigenetic regulations are involved in atherosclerosis. In the present study, oxidized low-density lipoprotein (oxLDL) significantly increased primary human aortic smooth muscle cell (HASMC) migration through MMP-2/MMP-9 up-regulation associated with decreased DNA methylation levels. Either mRNA or protein level of DNA methyltransferase 3b (DNMT3b) showed a dose-dependent down-regulation in oxLDL-mediated HASMCs. Knockdown DNMT3b expression enhanced oxLDL-induced DNA demethylation levels of MMP-2/MMP-9. The expression of miRNA-29b (miR-29b), directly targeting DNMT3b, was up-regulated by oxLDL treatment in a dose-dependent manner. OxLDL-mediated MMP-2/MMP-9 up-regulation, DNMT3b down-regulation, and DNA demethylation were all attenuated after knockdown miR-29b expression by antagomiR-29b. We find that oxLDL can up-regulate miR-29b expression, resulting in DNMT3b down-regulation in HASMCs and epigenetically regulated MMP-2/MMP-9 genes involved in cell migration. These results show that miRNA-mediated epigenetic regulation may be a novel mechanism in atherosclerosis.

The influence of sulforaphane on vascular health and its relevance to nutritional approaches to prevent cardiovascular disease

Oxidation of low-density lipoproteins (LDL) promotes atherosclerosis by enhancing vascular inflammation and foam cell formation. The corollary is that diets that stimulate endogenous anti-oxidants may protect against atherosclerosis. This review focuses on sulforaphane, an isothiocyanate derived from green vegetables, which induces multiple anti-oxidant enzymes via activation of a transcription factor called Nrf2. Although studies of cultured cells and experimental animals revealed that sulforaphane can suppress inflammatory activation of vascular cells, the potential beneficial effects of sulforaphane in atherosclerosis have not been studied directly. A deeper understanding of vascular responses to sulforaphane may inform nutritional approaches to prevent vascular inflammation and atherosclerosis.

Salvianolic acid B inhibits low-density lipoprotein oxidation and neointimal hyperplasia in endothelium-denuded hypercholesterolaemic rabbits

BACKGROUND

Atherosclerosis and restenosis are inflammatory responses involving free radicals and lipid peroxidation and may be prevented/cured by antioxidant-mediated lipid peroxidation inhibition. Salvianolic acid (Sal B), a water-soluble antioxidant obtained from a Chinese medicinal herb, is believed to have multiple preventive and therapeutic effects against human vascular diseases. In this study the in vitro and in vivo inhibitory effects of Sal B on oxidative stress were determined.

RESULTS

In human aortic endothelial cells (HAECs), Sal B reduced oxidative stress, inhibited low-density lipoprotein (LDL) oxidation and reduced oxidised LDL-induced cytotoxicity. Sal B inhibited Cu(2+) -induced LDL oxidation in vitro (with a potency 16.3 times that of probucol) and attenuated HAEC-mediated LDL oxidation as well as reactive oxygen species (ROS) production. In cholesterol-fed New Zealand White rabbits (with probucol as positive control), Sal B intake reduced Cu(2+) -induced LDL oxidation, lipid deposition in the thoracic aorta, intimal thickness of the aortic arch and thoracic aorta and neointimal formation in the abdominal aorta.

CONCLUSION

The data obtained in this study suggest that Sal B protects HAECs from oxidative injury-mediated cell death via inhibition of ROS production. The antioxidant activity of Sal B may help explain its efficacy in the treatment of vascular diseases.

Oxygenomics in environmental stress

Environmental stressors such as chemicals and physical agents induce various oxidative stresses and affect human health. To elucidate their underlying mechanisms, etiology and risk, analyses of gene expression signatures in environmental stress-induced human diseases, including neuronal disorders, cancer and diabetes, are crucially important. Recent studies have clarified oxidative stress-induced signaling pathways in human and experimental animals. These pathways are classifiable into several categories: reactive oxygen species (ROS) metabolism and antioxidant defenses, p53 pathway signaling, nitric oxide (NO) signaling pathway, hypoxia signaling, transforming growth factor (TGF)-beta bone morphogenetic protein (BMP) signaling, tumor necrosis factor (TNF) ligand-receptor signaling, and mitochondrial function. This review describes the gene expression signatures through which environmental stressors induce oxidative stress and regulate signal transduction pathways in rodent and human tissues.

Oxidized LDL: diversity, patterns of recognition, and pathophysiology

Oxidative modification of LDL is known to elicit an array of pro-atherogenic responses, but it is generally underappreciated that oxidized LDL (OxLDL) exists in multiple forms, characterized by different degrees of oxidation and different mixtures of bioactive components. The variable effects of OxLDL reported in the literature can be attributed in large part to the heterogeneous nature of the preparations employed. In this review, we first describe the various subclasses and molecular composition of OxLDL, including the variety of minimally modified LDL preparations. We then describe multiple receptors that recognize various species of OxLDL and discuss the mechanisms responsible for the recognition by specific receptors. Furthermore, we discuss the contentious issues such as the nature of OxLDL in vivo and the physiological oxidizing agents, whether oxidation of LDL is a prerequisite for atherogenesis, whether OxLDL is the major source of lipids in foam cells, whether in some cases it actually induces cholesterol depletion, and finally the Janus-like nature of OxLDL in having both pro- and anti-inflammatory effects. Lastly, we extend our review to discuss the role of LDL oxidation in diseases other than atherosclerosis, including diabetes mellitus, and several autoimmune diseases, such as lupus erythematosus, anti-phospholipid syndrome, and rheumatoid arthritis.

Activation of Janus kinase/signal transducer and activator of transcription 3 pathway by growth hormone-releasing hormone

Growth hormone-releasing hormone (GHRH) can act as a potent growth factor in various cancers. The mitogenic activity of this neuropeptide is exerted through binding to the pituitary type receptors (GHRH-R) or their splice variants (SV). In the present work, we studied whether this hormone can activate the JAK2/STAT3 pathway which plays a crucial role in cancer cell proliferation and is also linked to carcinogenesis. We transfected HeLa human cervical cancer cells, which are not sensitive to GHRH analogs with the pGHRH-R. Transfected cells responded to the GHRH or its antagonist with an increase or a decrease in proliferation, respectively. These results were confirmed by the expression of proliferating cell nuclear antigen. We then showed that these effects are linked to the activation of the JAK2/STAT3 pathway. Our work demonstrates the activation of JAK/STAT3 pathway by GHRH and sheds further light to the mechanisms of the antitumorogenic action of GHRH antagonists.

Induction of MIF expression by oxidized LDL via activation of NF-kappaB in vascular smooth muscle cells

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine playing important roles in atherosclerosis. MIF gene deficiency and neutralizing antibodies against MIF have been reported to exert anti-atherosclerotic effects in various animal models. However, the mechanism by which MIF is induced in atherosclerotic lesions remains unclear. In the present studies, we cloned a 540bp full-length rabbit MIF cDNA by screening a rabbit uterine library. The cDNA contains a 348bp open-reading frame which encodes a deduced 115-amino acid polypeptide with approximately 90% similarity to human and mouse homologs. Constitutive MIF mRNA expression was detected in most rabbit tissues including aortas. The expression of MIF obviously abounded in vascular smooth muscle cells (VSMCs) of the atherosclerotic plaques. In cultured VSMCs, MIF expression was significantly induced by a pro-atherogenic factor, oxidized low-density lipoprotein (oxLDL). Promoter analysis showed there were two NF-kappaB binding sites in the MIF proximal promoter region. Deletion or mutation of the two sites abolished oxLDL-enhanced MIF promoter activity. Moreover, the induction of MIF by oxLDL can be blocked by IkappaB-alpha overexpression. Taken together, our results revealed that MIF expression can be induced by oxLDL in VSMCs via a NF-kappaB dependent manner, which may contribute to the pathogenesis of atherosclerosis.