Lp(a) and LDL induce apoptosis in human endothelial cells and in rabbit aorta: role of oxidative stress

Lipoprotein (a)-Related Inflammatory Imbalance: A Novel Horizon for the Development of Atherosclerosis

PURPOSE OF REVIEW

The primary objective of this review is to explore the pathophysiological roles and clinical implications of lipoprotein(a) [Lp(a)] in the context of atherosclerotic cardiovascular disease (ASCVD). We seek to understand how Lp(a) contributes to inflammation and arteriosclerosis, aiming to provide new insights into the mechanisms of ASCVD progression.

RECENT FINDINGS

Recent research highlights Lp(a) as an independent risk factor for ASCVD. Studies show that Lp(a) not only promotes the inflammatory processes but also interacts with various cellular components, leading to endothelial dysfunction and smooth muscle cell proliferation. The dual role of Lp(a) in both instigating and, under certain conditions, mitigating inflammation is particularly noteworthy. This review finds that Lp(a) plays a complex role in the development of ASCVD through its involvement in inflammatory pathways. The interplay between Lp(a) levels and inflammatory responses highlights its potential as a target for therapeutic intervention. These insights could pave the way for novel approaches in managing and preventing ASCVD, urging further investigation into Lp(a) as a therapeutic target.

Association between lipoprotein(a) plasma levels and diabetic nephropathy in Han Chinese patients with type 2 diabetes mellitus

The goal of this study was to evaluate the relationship between serum lipoprotein(a) [Lp(a)] levels and diabetic nephropathy (DN) among Han Chinese individuals with type 2 diabetes mellitus (T2DM). This retrospective analysis comprised a consecutive case series of 767 grown-up patients with T2DM (199 among them with DN) hospitalized in the Department of Endocrinology at the The First Affiliated Hospital of Anhui Medical University from February 20220 to February 2021. Clinical data and other laboratory measurements, such as glycated hemoglobin (HbA1c), were extracted from medical records and compared among groups. Clinical characteristics according to Lp(a) quartiles were also studied. Univariate and multivariate regression analysis were used to examine the relationship between serum Lp(a) and DN. Patients with DN had a longer disease duration, higher HbA1c, higher level of Lp(a), and were more likely to have diabetic retinopathy (DR) than those without DN (P < 0.005 for each). With regard to the Lp(a) quartile group, patients with a higher Lp(a) concentration were more likely to have DN and have higher level of HbA1c during the study (P for trend < 0.005 for each). After adjusting for several confounding factors, the development of DN was significantly associated with the serum Lp(a) level (P = 0.026, comparing the 4th vs 1st quartile of Lp(a)) according to multivariate regression analysis. The receiver operating characteristic (ROC) curves for DN development using serum Lp(a) showed that the area under the receiver operating characteristic curves (AUC) was 0.590 (P < 0.001). Findings from this study demonstrated that the DN was independently associated with the serum Lp(a) level in patients with T2DM in this retrospective study.

The effects of IGF-1 and IGFBP-2 treatments on the atherosclerosis in the aorta and the coronary arteries of the high cholesterol diet-fed rabbits

Several studies have demonstrated suppression of aortic atherosclerosis by insulin like growth factor-1 (IGF-1) in hypercholesterolemic rabbits. Though a recent study has reported that IGF-1 exerts anti-atherogenic effects in coronary arteries, the mechanisms of IGF-1 in coronary arteries need to be further verified. Studies about insulin like growth factor binding protein-2 (IGFBP-2) in atherosclerosis are rarely. The objective of this study is to examine the effects of IGF-1 and IGFBP-2 on the atherosclerosis development in the aorta and coronary arteries of the high-cholesterol diet (HCD)-fed rabbits. New Zealand white rabbits were fed either normal chow (n = 5) or a diet containing 1.0 % cholesterol (n = 18) for 12 weeks. Cholesterol-fed rabbits were given IGF-1 or IGFBP-2 or saline intravenously (each n = 6) for 10 weeks. The results revealed that IGF-1 decreased total cholesterol (TC) and low-density lipoprotein (LDL) levels (p < 0.05), whereas IGFBP-2 did not. IGF-1 significantly attenuated atherosclerotic lesions and reduced accumulated macrophages within the coronary artery plaques, whereas IGFBP-2 deteriorated these changes. Moreover, IGF-1 reduced serum platelet-activating factor acetylhydrolase levels, C reactive protein (CRP), and inhibited the protein expression levels of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6). IGFBP-2 elevated serum 8-hydroxy-2'-deoxyguanosine levels, CRP, and promoted the protein expression levels of TNF-α and IL-6. In conclusion, IGF-1 can substantially suppress plaque formation in coronary arteries with a marked inhibition of macrophage accumulation likely via its anti-inflammatory properties, whereas IGFBP-2 plays an opposite effect on atherosclerosis. The present study highlighted a theoretical basis for pharmacological treatment of atherosclerosis.

Differences in Structural Changes and Pathophysiological Effects of Low-Density Lipoprotein Particles upon Accumulation of Acylhydroperoxy Derivatives in Their Outer Phospholipid Monolayer or upon Modification of Apoprotein B-100 by Natural Dicarbonyls

Nanoparticles of the lipid-transporting system of the organism, low-density lipoproteins (LDL) of blood plasma, are prone to free radical peroxidation with formation of their main modified forms - oxidized LDL itself (containing hydroperoxy-acyls in phospholipids of the outer layer of particles) and dicarbonyl-modified LDL (apoprotein B-100 in which chemically modified via the Maillard reaction). Based on the study of free radical oxidation kinetics of LDLs, it was found that the existing in the literature designation of "oxidized lipoproteins" is incorrect because it does not reveal the nature of oxidative modification of LDLs. It was shown in this study that the "atherogenic" LDLs (particles of which are actively captured by the cultured macrophages) are not the oxidized LDL (in which LOOH-derivatives of phospholipids are formed by enzymatic oxidation by C-15 lipoxygenase of rabbit reticulocytes), but dicarbonyl-modified LDLs. Important role of the dicarbonyl-modified LDLs in the molecular mechanisms of atherogenesis and endothelial dysfunction is discussed.

Malondialdehyde as an Important Key Factor of Molecular Mechanisms of Vascular Wall Damage under Heart Diseases Development

This mini review is devoted to a specific issue: the role of malondialdehyde (MDA)-a secondary product of free radical lipid peroxidation-in the molecular mechanisms of the formation of primary atherosclerotic vascular wall lesions. The principal difference between this review and the available literature is that it discusses in detail the important role in atherogenesis not of "oxidized" LDL (i.e., LDL particles containing lipohydroperoxides), but of LDL particles chemically modified by the natural low-molecular weight dicarbonyl MDA. To confirm this, we consider the data obtained by us earlier, indicating that "atherogenic" are not LDL oxidized as a result of free radical lipoperoxidation and containing lipohydroperoxy derivatives of phospholipids in the outer layer of particles, but LDL whose apoprotein B-100 has been modified due to the chemical reaction of terminal lysine residue amino groups of the apoB-100 with the aldehyde groups of the MDA (Maillard reaction). In addition, we present our original data proving that MDA injures endothelial glycocalyx that suppress the ability of the endothelium to control arterial tone according to changes in wall shear stress. In summary, this mini review for the first time exhaustively discloses the key role of MDA in atherogenesis.

TetraSOD®, a Unique Marine Microalgae Ingredient, Promotes an Antioxidant and Anti-Inflammatory Status in a Metabolic Syndrome-Induced Model in Rats

Increased oxidative stress has been linked to the pathogenic process of obesity and can trigger inflammation, which is often linked with the risk factors that make up metabolic syndrome (MetS), including obesity, insulin resistance, dyslipidaemia and hypertension. TetraSOD^®, a natural marine vegan ingredient derived from the microalgae Tetraselmis chuii that is high in the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) has recently demonstrated in vitro increased activity of these key antioxidant enzymes. In the present study, the potential bioactive effects of three dietary dosages of TetraSOD^® in enhancing antioxidant and anti-inflammatory mechanisms to combat the metabolic disturbances that compose MetS were assessed in rats given a cafeteria (CAF) diet. Chronic supplementation with 0.17, 1.7, and 17 mg kg⁻¹ day⁻¹ of TetraSOD^® for 8 weeks ameliorated the abnormalities associated with MetS, including oxidative stress and inflammation, promoting endogenous antioxidant defence mechanisms in the liver (GPx and GSH), modulating oxidative stress and inflammatory markers in plasma (NOx, oxLDL and IL-10), and regulating genes involved in antioxidant, anti-inflammatory and immunomodulatory pathways in the liver, mesenteric white adipose tissue (MWAT), thymus, and spleen. Overall, TetraSOD^® appears to be a potential therapeutic option for the management of MetS.

Dicarbonyl-Dependent Modification of LDL as a Key Factor of Endothelial Dysfunction and Atherosclerotic Vascular Wall Damage

The review presents evidence that the main damage to the vascular wall occurs not from the action of “oxidized” LDL, which contain hydroperoxy acyls in the phospholipids located in their outer layer, but from the action of LDL particles whose apoprotein B-100 is chemically modified with low molecular weight dicarbonyls, such as malondialdehyde, glyoxal, and methylglyoxal. It has been argued that dicarbonyl-modified LDL, which have the highest cholesterol content, are particularly “atherogenic”. High levels of dicarbonyl-modified LDL have been found to be characteristic of some mutations of apoprotein B-100. Based on the reviewed data, we hypothesized a common molecular mechanism underlying vascular wall damage in atherosclerosis and diabetes mellitus. The important role of oxidatively modified LDL in endothelial dysfunction is discussed in detail. In particular, the role of the interaction of the endothelial receptor LOX-1 with oxidatively modified LDL, which leads to the expression of NADPH oxidase, which in turn generates superoxide anion radical, is discussed. Such hyperproduction of ROS can cause destruction of the glycocalyx, a protective layer of endotheliocytes, and stimulation of apoptosis in these cells. On the whole, the accumulated evidence suggests that carbonyl modification of apoprotein B-100 of LDL is a key factor responsible for vascular wall damage leading to atherogenesis and endothelial dysfunction. Possible ways of pharmacological correction of free radical processes in atherogenesis and diabetogenesis are also discussed.

The pathological growth of the prostate gland in atherogenic contexts

The human prostate is an androgen-dependent gland where an imbalance in cell proliferation can lead to benign prostatic hyperplasia (BPH), which results in voiding lower urinary tract symptoms in the elderly. In the last decades, novel evidence has suggested that BPH might represent an element into the wide spectrum of disorders conforming the Metabolic Syndrome (MS). The dyslipidemic state and the other atherogenic factors of the MS have been shown to induce, maintain and/or aggravate the pathological growth of different organs, with data regarding the prostate being still limited. We here review the available epidemiological and experimental studies about the association of BPH with dyslipidemias. In particular, we have focused on Oxidized Low-Density Lipoproteins (OxLDL) as a potential trigger for vascular disease and cellular proliferation in atherogenic contexts, analyzing their putative molecular mechanisms, including the induction of specific extracellular vesicles (EVs)-derived miRNAs. In addition to the epidemiological evidence, OxLDL is proposed to play a fundamental role in the upregulation of prostatic cell proliferation by activating the Rho/Akt/p27^Kip1 pathway in atherogenic contexts. miR-21, miR-141, miR-143, miR-145, miR-155, and miR-221 would be involved in the transcription of genes related to the proliferative process. Although much remains to be investigated regarding the impact of OxLDL, its receptors, and molecular mechanisms on the prostate, it is clear that EVs and miRNAs represent a promising target for proliferative pathologies of the prostate gland.

Circulating low density lipoprotein (LDL)

Low-density lipoprotein (LDL) particles are known as atherogenic agents in coronary artery diseases. They modify to other electronegative forms and may be the subject for improvement of inflammatory events in vessel subendothelial spaces. The circulating LDL value is associated with the plasma PCSK-9 level. They internalize into macrophages using the lysosomal receptor-mediated pathways. LDL uptake is related to the membrane scavenger receptors, modifications of lipid and protein components of LDL particles, vesicular maturation and lipid stores of cells. Furthermore, LDL vesicular trafficking is involved with the function of some proteins such as Rab and Lamp families. These proteins also help in the transportation of free cholesterol from lysosome into the cytosol. The aggregation of lipids in the cytosol is a starting point for the formation of foam cells so that they may participate in the primary core of atherosclerosis plaques. The effects of macrophage subclasses are different in the formation and remodeling of plaques. This review is focused on the cellular and molecular events involved in cholesterol homeostasis.

Endothelial glycocalyx, apoptosis and inflammation in an atherosclerotic mouse model

BACKGROUND AND AIMS

Previous experiments suggest that both increased endothelial cell apoptosis and endothelial surface glycocalyx shedding could play a role in the endothelial dysfunction and inflammation of athero-prone regions of the vasculature. We sought to elucidate the possibly synergistic mechanisms by which endothelial cell apoptosis and glycocalyx shedding promote atherogenesis.

METHODS

4- to 6-week old male C57Bl/6 apolipoprotein E knockout (ApoE(-/-)) mice were fed a Western diet for 10 weeks and developed plaques in their brachiocephalic arteries.

RESULTS

Glycocalyx coverage and thickness were significantly reduced over the plaque region compared to the non-plaque region (coverage plaque: 71 ± 23%, non-plaque: 97 ± 3%, p = 0.02; thickness plaque: 0.85 ± 0.15 μm, non-plaque: 1.2 ± 0.21 μm, p = 0.006). Values in the non-plaque region were not different from those found in wild type mice fed a normal diet (coverage WT: 92 ± 3%, p = 0.7 vs. non-plaque ApoE(-/-), thickness WT: 1.1 ± 0.06 μm, p = 0.2 vs. non-plaque ApoE(-/-)). Endothelial cell apoptosis was significantly increased in ApoE(-/-) mice compared to wild type mice (ApoE(-/-):64.3 ± 33.0, WT: 1.1 ± 0.5 TUNEL-pos/cm, p = 2 × 10(-7)). The number of apoptotic endothelial cells per unit length was 2 times higher in the plaque region than in the non-plaque region of the same vessel (p = 3 × 10(-5)). Increased expression of matrix metalloproteinase 9 co-localized with glycocalyx shedding and plaque buildup.

CONCLUSIONS

Our results suggest that, in concert with endothelial apoptosis that increases lipid permeability, glycocalyx shedding initiated by inflammation facilitates monocyte adhesion and macrophage infiltration that promote lipid retention and the development of atherosclerotic plaques.

Serum lipoprotein(a) levels and diabetic nephropathy among Japanese patients with type 2 diabetes mellitus

AIMS

We aimed to evaluate the association between serum lipoprotein(a) [Lp(a)] levels and diabetic nephropathy among Japanese patients with type 2 diabetes mellitus.

METHODS

This study included 581 patients with type 2 diabetes mellitus. Serum Lp(a) levels were divided into four groups; the cut-off points were at the 30th, 60th, and 90th percentile values on the basis of the distribution for all subjects. Diabetic nephropathy was defined as present when the urinary albumin-creatinine ratio was ≥33.9mg/mmol creatinine and/or the estimated glomerular filtration rate was <30ml/min/1.72m(2). Adjustment was made for age, sex, body mass index, hemoglobin A1c, duration of diabetes mellitus, current drinking, current smoking, hypertension, dyslipidemia, coronary heart disease, and stroke.

RESULTS

Higher serum Lp(a) levels were significantly associated with a higher prevalence of diabetic nephropathy: the adjusted odds ratios (95% confidence intervals) for diabetic nephropathy in relation to serum Lp(a) levels of ≤6, 7-15, 16-38, and ≥39mg/dl were 1.00 (reference), 2.74 (1.08-7.00), 3.31 (1.28-8.54), and 4.80 (1.57-14.60), respectively (P for trend=0.004).

CONCLUSIONS

The results suggest that serum Lp(a) levels may be positively associated with diabetic nephropathy among Japanese patients with type 2 diabetes mellitus.

Long-term therapeutic efficacy of lipoprotein apheresis on circulating oxidative stress parameters--A comparison of two different apheresis techniques

BACKGROUND

A chronic lipoprotein apheresis therapy leads to an expressed reduction in the incidence of cardiovascular events in high-risk patients. In addition to the elimination of atherogenic lipoproteins such as LDL and lipoprotein(a), an antioxidative effect of lipoprotein apheresis has been suspected.

OBJECTIVES AND METHODS

We investigated long-term biochemical effects in sixteen patients undergoing lipoprotein apheresis - lipid filtration (LF, n = 7) or dextran sulfate adsorption (DSA, n = 9). Systemic oxidative stress markers (blood phagocyte chemiluminescence, levels of oxidized LDL and antioxLDL antibodies) were examined at the 1st, 40th and 80th apheresis sessions.

RESULTS

In DSA patients, the 80th apheresis session was associated with significantly higher LDL cholesterol removal and lower HDL cholesterol deprivation as compared to LF patients. In contrast to LF patients, DSA patients showed a long-term progressive decrease in circulating oxidant generating activity as evaluated by whole blood chemiluminescence (p < 0.05). Moreover, a single LF apheresis session was associated with higher systemic generation of reactive oxygen species over time.

CONCLUSION

Compared to LF, long-term DSA apheresis is associated with a gradual reduction of circulating oxidative burden and may be considered a beneficial molecular mechanism of this technique.

Protective effect of vitamin E against diabetes-induced oxidized LDL and aorta cell wall proliferation in rat

Hyperlipidemia and oxidized-low-density lipoproteins (Ox-LDL) are important independent cardiovascular risk factors that have been shown to stimulate vascular smooth muscle cell (VSMC) proliferation. The purpose of the present study was to investigate the effect of vitamin E on Ox-LDL, lipid profile, C-reactive protein (CRP), and VSMC proliferation of rat aorta.

METHODS

Male Wistar rats (n = 32) were divided into four groups namely: sham (SH), control (C), non-treated diabetic, and vitamin E-treated diabetic (VETD) groups. Ox-LDL, lipid profile, CRP and VSMC proliferation of aorta were measured after 42 days.

RESULTS

The results revealed that along with a significant increase in VSMC proliferation, the amount of CRP, Ox-LDL, and lipid profiles in diabetic rats. VSMC proliferation was significantly ameliorated, and elevated CRP, Ox-LDL, and lipid profiles were also restored to those of shams in VETD.

CONCLUSIONS

These findings strongly support the idea that diabetes induces Ox-LDL-mediated oxidative stress and VSMC proliferation in aorta of rat and imply that vitamin E has a strong protective effect as an antioxidant.

Anthocyanins and their physiologically relevant metabolites alter the expression of IL-6 and VCAM-1 in CD40L and oxidized LDL challenged vascular endothelial cells

SCOPE

In vitro and in vivo studies suggest that dietary anthocyanins modulate cardiovascular disease risk; however, given anthocyanins extensive metabolism, it is likely that their degradation products and conjugated metabolites are responsible for this reported bioactivity.

METHODS AND RESULTS

Human vascular endothelial cells were stimulated with either oxidized LDL (oxLDL) or cluster of differentiation 40 ligand (CD40L) and cotreated with cyanidin-3-glucoside and 11 of its recently identified metabolites, at 0.1, 1, and 10 μM concentrations. Protein and gene expression of IL-6 and VCAM-1 was quantified by ELISA and RT-qPCR. In oxLDL-stimulated cells the parent anthocyanin had no effect on IL-6 production, whereas numerous anthocyanin metabolites significantly reduced IL-6 protein levels; phase II conjugates of protocatechuic acid produced the greatest effects (>75% reduction, p ≤ 0.05). In CD40L-stimulated cells the anthocyanin and its phase II metabolites reduced IL-6 protein production, where protocatechuic acid-4-sulfate induced the greatest reduction (>96% reduction, p ≤ 0.03). Similarly, the anthocyanin and its metabolites reduced VCAM-1 protein production, with ferulic acid producing the greatest effect (>65% reduction, p ≤ 0.04).

CONCLUSION

These novel data provide evidence to suggest that anthocyanin metabolites are bioactive at physiologically relevant concentrations and have the potential to modulate cardiovascular disease progression by altering the expression of inflammatory mediators.

Nox family NADPH oxidases: Molecular mechanisms of activation

NADPH oxidases of the Nox family are important enzymatic sources of reactive oxygen species (ROS). Numerous homologue-specific mechanisms control the activity of this enzyme family involving calcium, free fatty acids, protein-protein interactions, intracellular trafficking, and posttranslational modifications such as phosphorylation, acetylation, or sumoylation. After a brief review on the classic pathways of Nox activation, this article will focus on novel mechanisms of homologue-specific activity control and on cell-specific aspects which govern Nox activity. From these findings of the recent years it must be concluded that the activity control of Nox enzymes is much more complex than anticipated. Moreover, depending on the cellular activity state, Nox enzymes are selectively activated or inactivated. The complex upstream signaling aspects of these events make the development of "intelligent" Nox inhibitors plausible, which selectively attenuate disease-related Nox-mediated ROS formation without altering physiological signaling ROS. This approach might be of relevance for Nox-mediated tissue injury in ischemia-reperfusion and inflammation and also for chronic Nox overactivation as present in cancer initiation and cardiovascular disease.

Ethanol promotes rat aortic vascular smooth muscle cell proliferation via increase of homocysteine and oxidized-low-density lipoprotein

BACKGROUND

Increased levels of homocysteine and oxidized low-density lipoprotein (Ox-LDL) are considered independent risk factors for atherosclerosis. However, no previous study has examined the effects of ethanol-induced increase of homocysteine and Ox-LD on aortic vascular smooth muscle cell (VSMC) proliferation. The aim of the present study was to investigate the relationship between ethanol consumption, increase in homocysteine, Ox-LDL, and aortic VSMC proliferation in rats.

METHODS AND RESULTS

To address this issue, 24 male Wistar rats were randomly divided into three groups: control, sham, and ethanol-treated. Homocysteine, Ox-LDL, lipid profile, and aortic VSMC proliferation were assessed after 42 days. The results revealed a concurrent, significant increase in homocysteine and Ox-LDL levels, lipid profile levels, and aortic VSMC proliferation in the ethanol-treated group compared with the control and sham groups.

CONCLUSION

Based on these results, we conclude that ethanol apparently exerts aortic VSMC proliferation through increase in homocysteine and Ox-LDL-mediated oxidative stress, which in turn trigger proatherogenic changes in the aortic wall.

Lipoprotein(a): Cellular Effects and Molecular Mechanisms

Lipoprotein(a) (Lp(a)) is an independent risk factor for the development of cardiovascular disease (CVD). Indeed, individuals with plasma concentrations >20 mg/dL carry a 2-fold increased risk of developing CVD, accounting for ~25% of the population. Circulating levels of Lp(a) are remarkably resistant to common lipid lowering therapies, and there are currently no robust treatments available for reduction of Lp(a) apart from plasma apheresis, which is costly and labour intensive. The Lp(a) molecule is composed of two parts, an LDL/apoB-100 core and a unique glycoprotein, apolipoprotein(a) (apo(a)), both of which can interact with components of the coagulation cascade, inflammatory pathways, and cells of the blood vessel wall (smooth muscle cells (SMC) and endothelial cells (EC)). Therefore, it is of key importance to determine the molecular pathways by which Lp(a) exerts its influence on the vascular system in order to design therapeutics to target its cellular effects. This paper will summarise the role of Lp(a) in modulating cell behaviour in all aspects of the vascular system including platelets, monocytes, SMC, and EC.

Inhibition of Lp(a)-induced functional impairment of endothelial cells and endothelial progenitor cells by hepatocyte growth factor

BACKGROUND

Lipoprotein (a) (Lp(a)) is one of the risk factors for peripheral artery disease (PAD). Our previous report demonstrated that hepatocyte growth factor (HGF) gene therapy attenuated the impairment of collateral formation in Lp(a) transgenic mice. Since risk factors for atherosclerosis accelerate endothelial senescence and impair angiogenesis, we examined the role of Lp(a) in dysfunction and senescence of endothelial progenitor cells (EPC) and endothelial cells.

METHODS

In vitro and in vivo incorporation assays were performed using ex-vivo expanded DiI-labeled human EPC. Senescence of cultured endothelial cells, production of oxidative stress and angiogenesis function were evaluated by SA-β-galactosidase staining, dihydroethidium (DHE) staining and Matrigel assay, respectively.

RESULTS

EPC transplantation significantly stimulated recovery of ischemic limb perfusion, while EPC pre-treated with Lp(a) did not increase ischemic limb perfusion. Impairment of angiogenesis by EPC with Lp(a) was associated with a significant decrease in CD31-positive capillaries and DiI-labeled EPC. Importantly, Lp(a) significantly accelerated the onset of senescence and production of reactive oxygen species (ROS) in human aortic endothelial cells, accompanied by a significant increase in the protein expression of p53 and p21. On the other hand, HGF significantly attenuated EPC dysfunction, senescence, ROS production, and p53 and p21 expression induced by Lp(a).

CONCLUSION

Lp(a) might affect atherosclerosis via acceleration of senescence, ROS production, and functional impairment of the endothelial cell lineage. HGF might have inhibitory effects on these atherogenic actions of Lp(a).

Carbamylated LDL

Nonenzymatic modification of protein by cyanate, that is, carbamylation, has received new attention due to its apparent relevance in atherosclerosis. For example, carbamylation of low-density lipoprotein (LDL) is an important mechanism that potentially impacts high-risk atherosclerotic individuals with increased urea (renal insufficiency) or thiocyanate (tobacco smoking). Carbamylated LDL (cLDL) is increased in patients with end-stage kidney disease, especially those with atherosclerosis. In addition, cLDL exhibits distinct cytotoxic effects when tested in vitro on endothelial cells, induces the expression of adhesion molecules, and aggravates the monocyte adhesion to endothelial cells. It also facilitates the proliferation of vascular smooth-muscle cell (VSMC). Studies of potential pharmacological interruption of these processes in vivo may lead to discoveries of novel therapies for atherosclerosis.

Oxidized low-density lipoprotein and ankle-brachial pressure index in patients with clinically evident peripheral arterial disease

OBJECTIVES

To investigate whether oxidized low-density lipoprotein is a suitable predictor of peripheral arterial disease severity. The role of oxidized low-density lipoprotein in the pathogenesis of atherosclerosis has already been investigated. Its relevance as a predictor of the appearance and worsening of coronary arterial disease is also well known. However, the same is not true regarding peripheral arterial disease.

METHOD

Eighty-five consecutive patients with an ankle-brachial pressure index (ABPI) < 0.9 and the presence of either intermittent claudication or critical lower leg ischemia were included. The plasma level of IgG autoantibodies against oxidized low-density lipoprotein was evaluated through an enzyme-linked immunosorbent assay. The results were categorized into quartiles according to the ankle-brachial pressure index (a marker of peripheral arterial disease severity), and significant differences were investigated with the Kruskal-Wallis test.

RESULTS

There was no significant difference between the quartiles for this population (p = 0.33). No correlation was found between the ankle-brachial pressure index and oxidized low-density lipoprotein levels in subjects with clinically evident peripheral arterial disease with a wide range of clinical manifestations.

CONCLUSIONS

Oxidized low-density lipoprotein is not a good predictor of peripheral arterial disease severity.

Atorvastatin attenuates homocysteine-induced apoptosis in human umbilical vein endothelial cells via inhibiting NADPH oxidase-related oxidative stress-triggered p38MAPK signaling

AIM

To examine the effect of atorvastatin on homocysteine (Hcy)-induced reactive oxygen species (ROS) production and apoptosis in human umbilical vein endothelial cells (HUVECs).

METHODS

HUVECs were cultured with Hcy (0.1-5 mmol/L) in the presence or absence of atorvastatin (1-100 micromol//L) or various stress signaling inhibitors, including the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (DPI, 10 micromol/L), the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580 (10 micromol/L) and antioxidants N-acetyl cysteine (NAC, 1 mmol/L). Cell apoptosis was evaluated by Annexin V/propidium iodide staining and flow cytometry. ROS were detected by 2',7'-dichlorodihydrofluorescein diacetate (H(2)DCFH-DA). NADPH oxidases were evaluated with lucigenin-enhanced chemiluminescence. Hcy-induced expression of p38MAPK protein was measured by Western blotting analysis.

RESULTS

Atorvastatin inhibited endothelial cell apoptosis induced by 1 mmol/L Hcy in a dose-dependent manner and the maximal inhibitory effect was reached at 100 micromol/L. Atorvastatin (10 micromol/L) significantly suppressed Hcy (1 mmol/L for 30 min) induced ROS accumulation (3.17+/-0.33 vs 4.34+/-0.31, P<0.05). Atorvastatin (10 micromol/L) also antagonized Hcy (1 mmol/L for 30 min) induced activation of NADPH oxidase (2.57+/-0.49 vs 3.33+/-0.6, P<0.05). Furthermore, atorvastatin inhibited Hcy-induced phosphorylation of p38 MAPK (1.7+/-0.1 vs 2.22+/-0.25, P<0.05), similar effects occurred with DPI, NAC and SB203580.

CONCLUSION

Atorvastatin may inhibit Hcy-induced ROS accumulation and endothelium cell apoptosis through an NADPH oxidase and/or p38MAPK-dependent mechanisms, all of which may contribute to atorvastatin-induced beneficial effect on endothelial function.

Crude extracts of Solanum lyratum protect endothelial cells against oxidized low-density lipoprotein-induced injury by direct antioxidant action

BACKGROUND

Oxidized low-density lipoprotein (oxLDL) is a proatherogenic molecule that accumulates in the vascular wall and contributes to the pathogenesis of vascular dysfunction early in the development of atherosclerosis. The whole plant of Solanum lyratum is a traditional Chinese medicine that has been used for centuries to treat cancer, tumors, and herpes. However, the cellular and molecular mechanisms of its antioxidant effects are still largely unknown. This study tested the hypothesis that Solanum lyratum Thunberg extract (SLE) could block oxLDL-induced endothelial dysfunction in cultured human umbilical vein endothelial cells (HUVECs). Possible mechanisms were explored.

METHODS

Antioxidative activities of SLE were assayed by measuring the scavenging of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical and the inhibition of copper-mediated or cell-mediated LDL oxidation. Production of reactive oxygen species (ROS) and the expression of adhesion molecules were evaluated in HUVECs after exposure to oxLDL and treatment with SLE. Several apoptotic signaling pathways were investigated.

RESULTS

SLE scavenged DPPH and also delayed the kinetics of LDL oxidation in a dose-dependent manner. SLE attenuated the level of oxLDL-induced ROS generation, diminished the expression of endothelial NO synthase (eNOS), and enhanced the expression of adhesion molecules (vascular cellular adhesion molecule-1, E-selectin, and monocyte chemotactic protein-1) and the adherence of monocytic THP-1 cells to HUVECs. OxLDL increased the concentration of intracellular calcium, disturbed the balance of the Bcl-2 protein family, destabilized the mitochondrial membrane potential, increased the amount of cytochrome c released into the cytosol, and increased the activation of caspase 3. These detrimental effects were ameliorated dose-dependently by SLE (P < .05).

CONCLUSION

Crude extracts of Solanum lyratum protect against oxLDL-induced injury in endothelial cells by direct antioxidant action.

CLINICAL RELEVANCE

Atherosclerosis is a chronic inflammatory disease characterized by lipid-laden lesions within arterialblood vessel walls. Inhibiting the oxidation of low-density lipoprotein may be an effective way to prevent or delay theprogression of atherosclerosis. This study underscores the potential clinical benefits and application of Solanum lyratumextract in controlling oxidized low-density lipoprotein-associated vascular injury and cardiovascular disease.

Levels of oxidized low-density lipoproteins are increased in patients with severe sepsis

BACKGROUND

It was hypothesized that the inflammatory response of patients with severe sepsis may result in changes of plasma levels of oxidized low-density lipoproteins (ox-LDLs) and that drotrecogin alpha (activated) (DAA) (Xigris, Eli Lilly and Company [Indiana 46285, USA]) may influence ox-LDL levels.

MATERIALS AND METHODS

The ox-LDL levels were measured in severe septic patients on day 1, 4, and 7 of severe sepsis. Patients were treated either with or without DAA.

RESULTS

The ox-LDL levels increased significantly (P < .05) from day 1 to day 7 (day 1, mean +/- SEM, 25.4 +/- 1.8 U/L; day 4, mean +/- SEM, 34.3 +/- 2.1 U/L; day 7, mean +/- SEM, 38.3 +/- 2.1 U/L) in all patients (n = 68). The ox-LDL levels increased significantly from day 1 to day 7 both in patients treated with (n = 31) and without DAA (n = 37) (P < .001) (DAA-group: day 1, mean +/- SEM, 24.4 +/- 2.8 U/L; day 4, mean +/- SEM, 35.5 +/- 2.9 U/L; day 7, mean +/- SEM, 40.7 +/- 3.2 U/L) (control group: day 1, mean +/- SEM, 26.3 +/- 2.8 U/L; day 4, mean +/- SEM, 33.2 +/- 2.9 U/L; day 7, mean +/- SEM, 36.4 +/- 2.9 U/L). No significant differences of ox-LDL levels were observed between both groups at any point of time (P > .05).

CONCLUSIONS

The ox-LDL concentrations increase significantly during the first week of severe sepsis and are not affected by administration of drotrecogin alpha (activated) (Xigris).

Differential dyslipidemia associated with albuminuria in type 2 diabetic patients in Taiwan

BACKGROUND

This study evaluated the lipid abnormalities associated with different stages of albuminuria in type 2 diabetic patients.

METHODS AND RESULTS

A total of 549 patients (245 men and 304 women) with mean age of 63.4 were studied. Normoalbuminuria (n=251), microalbuminuria (n=242) and macroalbuminuria (n=56) were defined as albumin-to-creatinine ratio of < 30, 30-299 and > or = 300 microg/mg, respectively. Lipid parameters included total cholesterol, triglyceride (TG), high- and low-density lipoprotein (LDL) cholesterol, apolipoproteins A1 and B (ApoB), and lipoprotein(a) [Lp(a)]. Results showed that ApoB differed significantly (p<0.05) between normoalbuminuria and microalbuminuria/macroalbuminuria and Ln[Lp(a)] differed between normoalbuminuria/microalbuminuria and macroalbuminuria. Ln(TG) increased progressively with increasing albuminuria. In multivariate logistic regression analyses, only ApoB showed significant odds ratio (95% confidence interval) for microalbuminuria: 1.013 (1.004-1.022); and both ln(TG) and ln[Lp(a)] were significant for macroalbuminuria [respective odds ratios: 1.995 (1.010-3.938) and 1.708 (1.200-2.430)].

CONCLUSIONS

A differential dyslipidemia is observed for microalbuminuria and macroalbuminuria. Apo(B) and Lp(a) increase at the stages of microalbuminuria and macroalbuminuria, respectively. However, TG increases significantly throughout the three stages of albuminuria.

Aspects of immune dysfunction in end-stage renal disease

End-stage renal disease (ESRD) is associated with significantly increased morbidity and mortality resulting from cardiovascular disease (CVD) and infections, accounting for 50% and 20%, respectively, of the total mortality in ESRD patients. It is possible that these two complications are linked to alterations in the immune system in ESRD, as uremia is associated with a state of immune dysfunction characterized by immunodepression that contributes to the high prevalence of infections among these patients, as well as by immunoactivation resulting in inflammation that may contribute to CVD. This review describes disorders of the innate and adaptive immune systems in ESRD, underlining the specific role of ESRD-associated disturbances of Toll-like receptors. Finally, based on the emerging links between the alterations of immune system, CVD, and infections in ESRD patients, it emphasizes the potential role of the immune dysfunction in ESRD as an underlying cause for the high mortality in this patient population and the need for more studies in this area.

Estrogen decreases TNF-alpha and oxidized LDL induced apoptosis in endothelial cells

Apoptosis induced by oxidized low-density lipoproteins (oxLDL) and tumor necrosis factor-alpha (TNF-alpha) is believed to contribute to atherosclerosis and vascular dysfunction. Estrogen treatment reduces apoptosis due to TNF-alpha and we hypothesized that it would also reduce apoptosis due to oxLDL. We also explored the anti-apoptotic mechanisms. We used early passage human umbilical vein endothelial cells (HUVEC) grown in steroid-depleted, red phenol-free medium. Cells were synchronized by starvation for 6h and then treated with oxLDL (75microg/ml) or TNF-alpha (20ng/ml) in the presence of 17-beta-estradiol (E2) (20nM). Apoptosis was analyzed by flow cytometry and caspase-3 cleavage. We also assessed expression of Bcl-2 and Bcl-xL and phosphorylation of BAD. At 6h TNF-alpha induced apoptosis but oxLDL did not; E2 did not affect this TNF-alpha induced apoptosis and there was no change in Bcl-2 or Bcl-xL expression. At 24h both TNF-alpha and oxLDL increased apoptosis and E2 reduced the increase. E2 also increased expression of the anti-apoptotic Bcl-2 and Bcl-xL and increased phosphorylation of proapoptotic BAD which reduces its proapoptotic activity at 1h. However at 24h there was also an increase in total BAD so that the proportion of phosphorylation of BAD decreased. oxLDL induced apoptosis occurs later than that of TNF-alpha. E2 decreased this late phase apoptosis and this likely requires the production of anti-apoptotic proteins.

Protective effects of ginsenoside Rb1 on human umbilical vein endothelial cells in vitro

Ginseng has beneficial effects on the cardiovascular system, but its underlying mechanism is unclear. This study investigated the effects of ginsenoside Rb1, a major constituent of ginseng, on the changes of lactate dehydrogenase (LDH) activity, nitric oxide (NO), tissue-type plasminogen activator (t-PA), and plasminogen activator inhibitor-1 (PAI-1) in oxidized low-density lipoprotein (oxLDL)-injuring endothelial cells. Human umbilical vein endothelial cells were cultured and divided into 6 groups (n = 6): control group, oxLDL alone group (100 mg/L), ginsenoside Rb1 alone group (10 microg/mL), oxLDL plus ginsenoside Rb1 groups (0.1, 1.0, and 10 microg/mL, respectively.). Twenty-four hours after treatment, LDH activity and concentrations of NO, t-PA, and PAI-1 in culture medium were measured while the expressions of endothelial nitric oxide synthase (eNOS), t-PA, and PAI-1 mRNA in endothelial cells were detected by reverse-transcriptase polymerase chain reaction. Compared with control group, oxLDL (100 mg/L) caused LDH activity, the expressions of eNOS and t-PA mRNA, and concentrations of NO and t-PA to significantly decrease (P < 0.05, respectively), and it also led to dramatic increase of PAI-1 mRNA and concentration (P < 0.05, respectively). Ginsenoside Rb1 alone did not demonstrate this ability. High-dose Rb1 (10 microg/mL) could block the effects of oxLDL on LDH activity, mRNA of eNOS, t-PA, and PAI-1, and concentrations of NO, t-PA, and PAI-1 (P < 0.05, respectively), and neither low-dose Rb1 (0.1 microg/mL) nor medium-dose Rb1 (1.0 microg/mL) demonstrated this ability. We conclude that ginsenoside Rb1 has protective effects on oxLDL-injuring human vascular endothelial cells and can reverse the effects of oxLDL on NO, t-PA, and PAI-1.

Magnesium tanshinoate B protects endothelial cells against oxidized lipoprotein-induced apoptosisThis article is one of a selection of papers published in this special issue (part 2 of 2) on the Safety and Efficacy of Natural Health Products

The activation of c-Jun N-terminal kinase (JNK) signaling pathway plays an important role in the induction of cell apoptosis. We previously reported that magnesium tanshinoate B (MTB), a compound purified from a Chinese herb danshen ( Salvia miltiorrhiza ), could inhibit ischemia/reperfusion-induced myocyte apoptosis in the heart. The objective of the present study was to investigate whether MTB can prevent oxidized lipoprotein-induced apoptosis in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were incubated with copper-oxidized very low density lipoprotein (Cu-OxVLDL) or copper-oxidized low density lipoprotein (Cu-OxLDL). Treatment of cells with Cu-OxVLDL or Cu-OxLDL resulted in a 3-fold increase in the JNK activity. The amount of cytochrome c released and the activity of caspase-3 in cells treated with Cu-OxVLDL or Cu-OxLDL were significantly elevated, indicating the occurrence of apoptosis. The presence of MTB was able to abolish the JNK activation, cytochrome c release, and caspase-3 activation induced by Cu-OxVLDL or Cu-OxLDL, resulting in a marked reduction in apoptosis in endothelial cells. The data from this study indicate that oxidized lipoproteins induce apoptosis in endothelial cells. We postulate that the inhibition of the JNK signaling pathway by MTB is a key mechanism that protects these cells from oxidized lipoprotein-induced apoptosis.

Lipoprotein[a] and cancer: Anti-neoplastic effect besides its cardiovascular potency

While the death rate from cancer has substantially decreased over the past decade, the search for effective and tolerable therapies is a great challenge as yet. The evidence that malignant cells cannot grow to a clinically detectable tumor mass and spread in the absence of an adequate vascular support, has opened a new area of research towards the selective inhibition or even destruction of tumor vessels. Angiostatin and angiostatin-related proteins are a family of specific angiogenesis inhibitors produced by tumors from a family of naturally occurring proteins, which also includes plasminogen and lipoprotein[a]. The anti-angiogenic activity of these proteins resides in cryptic and highly-repetitive molecular domains hidden within the protein moiety, called kringles. Lipoprotein[a] is an intriguing molecule consisting of a low-density lipoprotein core in addition to the covalently bound apolipoprotein[a]. Apolipoprotein[a] is characterized by an inactive protease domain, a single copy of the plasminogen kringle V and multiple repeats of domains homologous to the plasminogen kringle IV. Reliable studies on animal models indicate that the proteolytic break-down products of apolipoprotein[a] would posses anti-angiogenic and anti-tumoral properties both in vitro and in vivo, a premise to develop novel therapeutic modalities which may efficiently suppress tumor growth and metastasis. This review is focused on the biochemical structure, metabolism and the anti-angiogenic activity of this unique and elusive kringle-containing lipoprotein.

Apoptosis induced by oxidized lipids is associated with up-regulation of p66Shc in intestinal Caco-2 cells: protective effects of phenolic compounds

In this study, we investigated the alterations of the redox balance induced by the lipid fraction of oxLDL in Caco-2 intestinal cells, and the effects of tyrosol and protocatechuic acid, two dietary phenolic compounds. We found that oxidized lipids extracted from oxLDL (LipE) induced oxidative stress by determining, 6 h after treatment, ROS overproduction (about a 100% and a 43% increase of O*2 and H2O2 production, respectively, P<.05: LipE vs. control) and, 12 h after treatment, GSH depletion (about a 26% decrease, P<.05: LipE vs. control), and by impairing the activities of superoxide dismutase, catalase and glutathione peroxidase. In response to the induced oxidative stress, we observed significant overexpression of glutathione peroxidase (6 h after treatment: P<.05), glutathione reductase and gamma-glutamylcysteine synthetase (12 h after treatment: P<.05). Notably, when GSH depletion occurred, p66Shc protein expression increased by about 300% with respect to control (P<.001; LipE vs. control). These effects were fully counteracted by dietary phenolics which inhibited ROS overproduction and GSH consumption, rendered the reactive transcription of glutathione-associated enzymes unnecessary and blocked the intracellular signals leading to the overexpression and rearrangement of p66Shc signalling molecule. Altogether, these results suggest that the impairment of the antioxidant system hijacks intestinal cells towards an apoptotic-prone phenotype via the activation of p66Shc molecule. They also propose a reappraisal of dietary polyphenols as intestinal protecting agents, indicating the antiapoptotic effect as a further mechanism of action of these antioxidant compounds.

Oxidative Stress in Uremia: The Role of Anemia Correction: Table 1

Patients with chronic kidney disease (CKD) are prone to develop cardiovascular disorders. Numerous reports have shown the association between uremia and oxidative stress, which increases patients' risk for cumulative injury to multiple organs. Anemia is a common and disabling feature of CKD and seems to be a main cause of oxidative stress; correction of anemia represents an effective approach to reduce oxidative stress and, consequently, cardiovascular risk. There is increasing evidence that correction of anemia with erythropoiesis-stimulating agents could protect from oxidative stress in patients with CKD and ESRD. However, iron deficiency frequently complicates anemia in patients with CKD, and ferrous iron cation is a co-factor that is needed for hydroxyl radical production, which can promote cytotoxicity and tissue injury. This has raised a justifiable concern that prescription of intravenous iron may exacerbate oxidative stress and, hence, endothelial dysfunction, inflammation, and progression of cardiovascular disease, which are widely known consequences of CKD. Correction of anemia represents an effective approach to reduce oxidative stress and, consequently, cardiovascular risk. Iron deficiency is a common cause of resistance to erythropoiesis-stimulating agents, and the overall risk-benefit ratio favors use of intravenous iron to treat iron deficiency in patients with CKD. Consecutive or combined treatment with intravenous iron and erythropoiesis-stimulating agents clearly is beneficial for patients with CKD and iron deficiency, and anemia and could contribute to prevent the risk for cardiovascular events in these patients.

Increased Ratio of CD31 + /CD42 − Microparticles to Endothelial Progenitors as a Novel Marker of Atherosclerosis in Hypercholesterolemia

Objectives— Atherosclerosis may be caused by increased endothelial damage and by a consumptive loss of endothelial repair capacity by endothelial progenitors. Arterial stiffness is a reliable marker of atherosclerosis and a positive correlate of endothelial damage. We investigated whether an increased ratio of CD31 + /CD42 − microparticles to endothelial progenitors, a possible indicator of endothelial damage and impaired endothelium reparation, may contribute to aortic stiffness in hypercholesterolemia. We also studied the in vitro effect of microparticles from hypercholesterolemic patients on endothelial progenitor survival.

Methods and Results— Circulating CD31 + /CD42 − microparticles, endothelial progenitors, and aortic pulse wave velocity (aPWV), a measure of aortic stiffness, were measured in 50 patients with never-treated hypercholesterolemia and 50 normocholesterolemic controls. Hypercholesterolemic patients had more circulating CD31 + /CD42 − microparticles, less endothelial progenitors, and a stiffer aorta than controls. aPWV was associated with CD31 + /CD42 − microparticles ( r =0.61; P <0.001), endothelial progenitors ( r =−0.45, P <0.001), and with cholesterol levels ( r =0.51; P <0.001). High plasma cholesterol and a high ratio of CD31 + /CD42 − microparticles to endothelial progenitors independently predicted an increased aPWV. Microparticles from hypercholesterolemic patients caused a significant endothelial progenitor loss in vitro.

Conclusions— Hypercholesterolemia-related aortic stiffness is promoted by plasma cholesterol directly, increased endothelial damage, and reduced endothelium repair capacity by endothelial progenitors.

Priming of polymorphonuclear leukocytes: a culprit in the initiation of endothelial cell injury

Peripheral polymorphonuclear leukocytes (PMNL) in hemodialysis (HD) patients are primed, continually releasing and exposing the vascular endothelium to soluble factors such as reactive oxygen species and inflammatory mediators. To mimic the close proximity between PMNL and the endothelial monolayer and to monitor and characterize the influence of soluble mediators released from PMNL, we developed a novel cocultivation system using primary human umbilical vein endothelial cell (HUVEC) cultures and PMNL, with a sieve separating the two cell types to prevent direct adhesive effects. PMNL (106) from HD patients or from healthy normal controls were cocultivated with HUVEC (105) for 15 min, and endothelial cell injury was assessed by HUVEC morphology, cell detachment, and apoptosis. Proinflammatory changes were estimated by expression of HUVEC adhesion molecule P-selectin and by endothelial IL-8 and endothelial nitric oxide synthase mRNA. The levels of intracellular tissue factor reflected the procoagulant state, whereas NADPH oxidase activity served as an indicator for prooxidative changes in HUVEC. Mediators released from the primed PMNL triggered activation/dysfunction of endothelial cells, causing 1) an increase in endothelial cell detachment and apoptosis, 2) a proinflammatory state manifested by increased IL-8 mRNA expression and P-selectin on the endothelial surface, 3) activation of endothelial NADPH oxidase, 4) an increase in endothelial cell tissue factor that directly correlated with PMNL priming index, and 5) a decrease in endothelial nitric oxide synthase mRNA. Our data support a pathogenic link between PMNL priming and endothelial dysfunction, suggesting that PMNL priming is a potential new nontraditional risk factor for the development of atherosclerosis.

NADPH oxidases in cardiovascular health and disease

Increased oxidative stress plays an important role in the pathophysiology of cardiovascular diseases such as hypertension, atherosclerosis, diabetes, cardiac hypertrophy, heart failure, and ischemia-reperfusion. Although several sources of reactive oxygen species (ROS) may be involved, a family of NADPH oxidases appears to be especially important for redox signaling and may be amenable to specific therapeutic targeting. These include the prototypic Nox2 isoform-based NADPH oxidase, which was first characterized in neutrophils, as well as other NADPH oxidases such as Nox1 and Nox4. These Nox isoforms are expressed in a cell- and tissue-specific fashion, are subject to independent activation and regulation, and may subserve distinct functions. This article reviews the potential roles of NADPH oxidases in both cardiovascular physiological processes (such as the regulation of vascular tone and oxygen sensing) and pathophysiological processes such as endothelial dysfunction, inflammation, hypertrophy, apoptosis, migration, angiogenesis, and vascular and cardiac remodeling. The complexity of regulation of NADPH oxidases in these conditions may provide the possibility of targeted therapeutic manipulation in a cell-, tissue- and/or pathway-specific manner at appropriate points in the disease process.

Impaired angiogenesis in glutathione peroxidase-1-deficient mice is associated with endothelial progenitor cell dysfunction

Several vascular disease are characterized by elevated levels of reactive oxygen species (ROS). Vascular endothelium is protected from oxidant stress by expressing enzymes such as glutathione peroxidase type 1 (GPx-1). In this study, we investigated the effect of vascular oxidant stress on ischemia-induced neovascularization in a murine model of homozygous deficiency of GPx-1. GPx-1-deficient mice showed impaired revascularization following hindlimb ischemic surgery based on laser Doppler measurements of blood flow and capillary density in adductor muscle. GPx-1-deficient mice also showed an impaired ability to increase endothelial progenitor cell (EPC) levels in response to ischemic injury or subcutaneous administration of vascular endothelial growth factor protein. EPCs isolated from GPx-1-deficient mice showed a reduced ability to neutralize oxidative stress in vitro, which was associated with impaired migration toward vascular endothelial growth factor and increased sensitivity to ROS-induced apoptosis. EPCs isolated from GPx-1-deficient mice were impaired in their ability to promote angiogenesis in wild-type mice, whereas wild-type EPCs were effective in stimulating angiogenesis in GPx-1-deficient mice. These data suggest that EPC dysfunction is a mechanism by which elevated levels of ROS can contribute to vascular disease.

OxLDL increases endothelial stiffness, force generation, and network formation

This study investigates the effect of oxidatively modified low density lipoprotein (OxLDL) on the biomechanical properties of human aortic endothelial cells (HAECs). We show that treatment with OxLDL results in a 90% decrease in the membrane deformability of HAECs, as determined by micropipette aspiration. Furthermore, aortic endothelial cells freshly isolated from hypercholesterolemic pigs were significantly stiffer than cells isolated from healthy animals. Interestingly, OxLDL had no effect on membrane cholesterol of HAECs but caused the disappearance of a lipid raft marker, GM1, from the plasma membrane. Both an increase in membrane stiffness and a disappearance of GM1 were also observed in cells that were cholesterol-depleted by methyl-beta-cyclodextrin. Additionally, OxLDL treatment of HAECs embedded within collagen gels resulted in increased gel contraction, indicating an increase in force generation by the cells. This increase in force generation correlated with an increased ability of HAECs to elongate and form networks in a three-dimensional environment. Increased force generation, elongation, and network formation were also observed in cholesterol-depleted cells. We suggest, therefore, that exposure to OxLDL results in the disruption or redistribution of lipid rafts, which in turn induces stiffening of the endothelium, an increase in endothelial force generation, and the potential for network formation.

Apolipoprotein A-IV predicts progression of chronic kidney disease: the mild to moderate kidney disease study

It has not been established firmly whether dyslipidemia contributes independently to the progression of kidney disease. Lipid and lipoprotein parameters, including levels of total, HDL, and LDL cholesterol; triglycerides; lipoprotein(a); apolipoprotein A-IV; and the apolipoprotein E and A-IV polymorphisms, were assessed in 177 patients who had mostly mild to moderate renal insufficiency and were followed prospectively for up to 7 yr. Progression of kidney disease was defined as doubling of baseline serum creatinine and/or terminal renal failure necessitating renal replacement therapy. In univariate analysis, patients who reached a progression end point (n = 65) were significantly older and had higher serum creatinine and proteinuria as well as lower GFR and hemoglobin levels. In addition, baseline apolipoprotein A-IV and triglyceride concentrations were higher and HDL cholesterol levels were lower. Multivariate Cox regression analysis revealed that baseline GFR (hazard ratio 0.714; 95% confidence interval [CI] 0.627 to 0.814 for an increment of 10 ml/min per 1.73 m(2); P < 0.0001) and serum apolipoprotein A-IV concentrations (hazard ratio 1.062; 95% CI 1.018 to 1.108 for an increment of 1 mg/dl; P = 0.006) were significant predictors of disease progression. Patients with apolipoprotein A-IV levels above the median had a significantly faster progression (P < 0.0001), and their mean follow-up time to a progression end point was 53.7 mo (95% CI 47.6 to 59.8) as compared with 70.0 mo (95% CI 64.6 to 75.4) in patients with apolipoprotein A-IV levels below the median. For the apolipoprotein E polymorphism, only the genotype epsilon2/epsilon4 was associated with an increased risk for progression. In summary, this prospective study in patients with nondiabetic primary kidney disease demonstrated that apolipoprotein A-IV concentration is a novel independent predictor of progression.

Impact of oxidized low density lipoprotein on vascular cells

Oxidized LDL (OxLDL) is a proatherogenic lipoprotein, accumulating in the vascular wall and contributing to the pathogenesis of vascular dysfunction early in the development of atherosclerosis. Enhanced serum levels of OxLDL, as well as antibodies against its epitopes, are predictive for endothelial dysfunction and coronary heart disease. While enhanced oxidative stress is one factor triggering formation of OxLDL, OxLDL itself has been identified as a potent stimulus for vascular oxygen radical formation, causing a vicious circle. OxLDL-induced O(2)(-) formation, largely through activation of NADPH oxidase, but also through uncoupling of endothelial NO-synthase and through direct O(2)(-) release, leads to endothelial dysfunction. Furthermore, OxLDL-induced O(2)(-) formation has a strong impact on tissue remodeling, resulting in either cell growth - proliferation or hyperplasia - or apoptotic cell death. The effect of OxLDL on cell cycle regulation is mediated by activation of the small GTPase RhoA and consequent regulation of p27(KIP1), a key enzyme of the cell cycle. In addition, OxLDL-induced activation of RhoA sensitizes the contractile apparatus of the vessel wall, enhancing the contractile tonus and favoring vasospasm. Thus, through a variety of mechanisms, OxLDL importantly contributes to vascular dysfunction and remodeling.

Exogenous superoxide mediates pro-oxidative, proinflammatory, and procoagulatory changes in primary endothelial cell cultures

Endothelial dysfunction/activation underlies the development of long-term cardiovascular complications and atherosclerosis. The aim of this study was to examine a direct role for exogenous sublethal flux of superoxide on endothelial cell dysfunction. Human umbilical vein endothelial cells (HUVEC) were exposed to superoxide generated by 0.1 mM xanthine and 4 mU/ml xanthine oxidase for 15 min and essential endothelial functions were examined. Superoxide dismutase and/or catalase was used as scavenger for O(2)(-)/H(2)O(2) to determine the key culprit. HUVEC detachment was determined by neutral red uptake and apoptosis by annexin V binding. Inflammation was estimated by IL-8 mRNA expression and cellular adhesion molecules (CAM). eNOS and iNOS message and eNOS protein served as an indirect measure for NO. Procoagulable state was evaluated by estimating the intracellular tissue factor. Activation of endothelial NADPH oxidase was determined by lucigenin chemiluminescence. Sublethal superoxide dose evoked: (1) proinflammatory state manifested by increased IL-8 mRNA expression and CAM on the endothelial surface, (2) HUVEC apoptosis and activated endothelial NADPH oxidase, (3) increase in intracellular tissue factor, and (4) decrease in eNOS mRNA and protein and up-regulation of iNOS mRNA. We conclude that extracellular low flux of superoxide exhibits pleiotropic characteristics, triggering activation/dysfunction of endothelial cells.

Effects of ethanol on lipids and atherosclerosis

Moderate alcohol consumption is associated with an increase in plasma high density lipoprotein (HDL) cholesterol concentration and a decrease in low density lipoprotein (LDL) cholesterol concentration. Changes in the concentration and composition of lipoproteins are estimated to account for more than half of alcohol's protective effect for coronary heart disease. Alcohol intake also affects plasma proteins involved in lipoprotein metabolism: cholesteryl ester transfer protein, phospholipid transfer protein, lecithin:cholesterol acyltransferase, lipoprotein lipase, hepatic lipase, and phospholipases. In addition, alcohol intake may result in acetaldehyde modification of apolipoproteins. Furthermore, "abnormal" lipids, phosphatidylethanol and fatty acid ethyl esters are formed in the presence of ethanol and are associated with lipoproteins in plasma. Ethanol and ethanol-induced modifications of lipids may modulate the effects of lipoproteins on the cells in the arterial wall. The molecular mechanisms involved in these processes are complex, requiring further study to better understand the specific effects of ethanol in the pathogenesis of atherosclerosis. This review discusses the effects of ethanol on lipoproteins and lipoprotein metabolism, as well as the novel effects of lipoproteins on vascular wall cells.

Functional modulation of antioxidant enzymes in vascular endothelial cells by glycated LDL

Reactive oxygen species (ROS) have been implicated in atherogenesis. Previous studies demonstrated that oxidized LDL (oxLDL) or glycated LDL (gly-LDL) increased the generation of superoxide from vascular endothelial cells (EC). The present study examined the effects of gly-LDL on the activation of antioxidant enzymes for the metabolism of ROS in cultured human vascular endothelial cells in comparison to oxLDL and LDL without chemical modification. Treatment with LDL, oxLDL or gly-LDL significantly increased the release of hydrogen peroxide (H(2)O(2)) from EC following 2h of incubation and the release of superoxide after 24 h of treatment. The increased release of H(2)O(2), but not superoxide, was normalized in EC treated with LDL or its modified forms. Elevated activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase in EC were detected following a 24 h-treatment with the LDLs. The levels of GR activity and reduced/oxidized glutathione (GSH/GSSG) in EC treated with the lipoproteins were increased after 2 h, but were reduced after > or =24 h of incubation. Gly-LDL caused less increases in SOD, GPx or catalase activity, but more evident changes in GR activity and H(2)O(2) release compared to oxLDL or LDL. The findings suggest that exposure to glucose-modified LDL altered the activities of multiple antioxidant enzymes in cultured EC, which partially normalizes the excess generation of ROS, but reduced the intracellular reservoir of GSH.