The biphasic effects of oxidized-low density lipoprotein on the vasculogenic function of endothelial progenitor cells

Nitric oxide and hormesis

This present paper provides an assessment of the occurrence of nitric oxide (NO)-induced hormetic-biphasic dose/concentration relationships in biomedical research. A substantial reporting of such NO-induced hormetic effects was identified with particular focus on wound healing, tumor promotion, and sperm biology, including mechanistic assessment and potential for translational applications. Numerous other NO-induced hormetic effects have been reported, but require more development prior to translational applications. The extensive documentation of NO-induced biphasic responses, across numerous organs (e.g., bone, cardiovascular, immune, intestine, and neuronal) and cell types, suggests that NO-induced biological activities are substantially mediated via hormetic processes. These observations are particularly important because broad areas of NO biology are constrained by the quantitative features of the hormetic response. This determines the amplitude and width of the low dose stimulation, affecting numerous biomedical implications, study design features (e.g., number of doses, dose spacing, sample sizes, statistical power), and the potential success of clinical trials.

Diabetic dyslipidemia impairs coronary collateral formation: An update

Coronary collateralization is substantially impaired in patients with type 2 diabetes and occlusive coronary artery disease, which leads to aggravated myocardial ischemia and a more dismal prognosis. In a diabetic setting, altered serum lipid profiles and profound glycoxidative modification of lipoprotein particles induce endothelial dysfunction, blunt endothelial progenitor cell response, and severely hamper growth and maturation of collateral vessels. The impact of dyslipidemia and lipid-lowering treatments on coronary collateral formation has become a topic of heightened interest. In this review, we summarized the association of triglyceride-based integrative indexes, hypercholesterolemia, increased Lp(a) with its glycoxidative modification, as well as quantity and quality abnormalities of high-density lipoprotein with impaired collateral formation. We also analyzed the influence of innovative lipid-modifying strategies on coronary collateral development. Therefore, clinical management of diabetic dyslipidemia should take into account of its effect on coronary collateralization in patients with occlusive coronary artery disease.

Endothelial Progenitor Cells Dysfunctions and Cardiometabolic Disorders: From Mechanisms to Therapeutic Approaches

Metabolic syndrome (MetS) is a cluster of several disorders, such as hypertension, central obesity, dyslipidemia, hyperglycemia, insulin resistance and non-alcoholic fatty liver disease. Despite health policies based on the promotion of physical exercise, the reduction of calorie intake and the consumption of healthy food, there is still a global rise in the incidence and prevalence of MetS in the world. This phenomenon can partly be explained by the fact that adverse events in the perinatal period can increase the susceptibility to develop cardiometabolic diseases in adulthood. Individuals born after intrauterine growth restriction (IUGR) are particularly at risk of developing cardiovascular diseases (CVD) and metabolic disorders later in life. It has been shown that alterations in the structural and functional integrity of the endothelium can lead to the development of cardiometabolic diseases. The endothelial progenitor cells (EPCs) are circulating components of the endothelium playing a major role in vascular homeostasis. An association has been found between the maintenance of endothelial structure and function by EPCs and their ability to differentiate and repair damaged endothelial tissue. In this narrative review, we explore the alterations of EPCs observed in individuals with cardiometabolic disorders, describe some mechanisms related to such dysfunction and propose some therapeutical approaches to reverse the EPCs dysfunction.

Oxidatively Modified LDL Suppresses Lymphangiogenesis via CD36 Signaling

Arterial accumulation of plasma-derived LDL and its subsequent oxidation contributes to atherosclerosis. Lymphatic vessel (LV)-mediated removal of arterial cholesterol has been shown to reduce atherosclerotic lesion formation. However, the precise mechanisms that regulate LV density and function in atherosclerotic vessels remain to be identified. The aim of this study was to investigate the role of native LDL (nLDL) and oxidized LDL (oxLDL) in modulating lymphangiogenesis and underlying molecular mechanisms. Western blotting and immunostaining experiments demonstrated increased oxLDL expression in human atherosclerotic arteries. Furthermore, elevated oxLDL levels were detected in the adventitial layer, where LV are primarily present. Treatment of human lymphatic endothelial cells (LEC) with oxLDL inhibited in vitro tube formation, while nLDL stimulated it. Similar results were observed with Matrigel plug assay in vivo. CD36 deletion in mice and its siRNA-mediated knockdown in LEC prevented oxLDL-induced inhibition of lymphangiogenesis. In addition, oxLDL via CD36 receptor suppressed cell cycle, downregulated AKT and eNOS expression, and increased levels of p27 in LEC. Collectively, these results indicate that oxLDL inhibits lymphangiogenesis via CD36-mediated regulation of AKT/eNOS pathway and cell cycle. These findings suggest that therapeutic blockade of LEC CD36 may promote arterial lymphangiogenesis, leading to increased cholesterol removal from the arterial wall and reduced atherosclerosis.

Exogenous endothelial progenitor cells reached the deficient region of acute cerebral ischemia rats to improve functional recovery via Bcl-2

Background

As discovered in our previous study, autologous endothelial progenitor cells (EPCs) protect against acute focal ischemia rat via the promotion of angiogenesis. However, it is unknown whether the EPCs that reached the deficient region were transplanted ones or the products of other auto-conversion cells they had promoted. This study aimed to gather direct evidence for determining if exogenous transplanted EPCs directly participate in angiogenesis in ischemic areas and attempted to clarify the related mechanism.

Methods

First, EPCs were extracted in vitro from male rats, which were characterized by uptake of fluorescently labeled acetylated low-density lipoprotein (ac-LDL) intake and Ulex europaeus agglutinin (UEA-1) and subsequently introduced to middle cerebral artery occlusion (MCAO) female rats for 7 days after ischemia surgery. The EPC-treated animals received approximately 1×10⁶ cells, while the control animals received phosphate buffered saline (PBS). The animals behavior function recovery were by a rotarod (TOR) test, while infarct volume was assessed by brain magnetic resonance imaging (MRI). CD31 antibody was used to determine the presence of EPCs in the ischemic zone, and sex-determining region Y (SRY) gene in-situ hybridization (ISH) traced the EPC process. In addition, immunohistochemistry and Western blot were used to assess B-cell lymphoma 2 (Bcl-2) expression in the ischemic brain.

Results

Behavior tests and MRI of all ischemic stroke groups on postoperative day 14 indicated that EPCs were more effective in behavior function recovery and reducing infarct volume and gliosis status than the control group. Cluster of differentiation (CD31) immunofluorescent staining and SRY gene ISH demonstrated that EPCs yielded a better outcome in both angiogenesis and exogenous cell homing status. We also observed increased Bcl-2 distribution and higher plasma Bcl-2 levels in the EPC-treated group compared to the control group.

Conclusions

Our results provide direct evidence that exogenous EPCs can participate in angiogenesis to improve neurological outcome and revascularization directly after stroke, with Bcl-2 playing an important role in this process.

Oxidized LDL Modify the Human Adipocyte Phenotype to an Insulin Resistant, Proinflamatory and Proapoptotic Profile

Little information exists in humans on the regulation that oxidized low-density lipoprotein (oxLDL) exerts on adipocyte metabolism, which is associated with obesity and type 2 diabetes. The aim was to analyze the oxLDL effects on adipocytokine secretion and scavenger receptors (SRs) and cell death markers in human visceral adipocytes. Human differentiated adipocytes from visceral adipose tissue from non-obese and morbidly obese subjects were incubated with increasing oxLDL concentrations. mRNA expression of SRs, markers of apoptosis and autophagy, secretion of adipocytokines, and glucose uptake were analyzed. In non-obese and in morbidly obese subjects, oxLDL produced a decrease in insulin-induced glucose uptake, a significant dose-dependent increase in tumor necrosis factor-α (TNF-α), IL-6, and adiponectin secretion, and a decrease in leptin secretion. OxLDL produced a significant increase of Lox-1 and a decrease in Cxcl16 and Cl-p1 expression. The expression of Bnip3 (marker of apoptosis, necrosis and autophagy) was significantly increased and Bcl2 (antiapoptotic marker) was decreased. OxLDL could sensitize adipocytes to a lower insulin-induced glucose uptake, a more proinflammatory phenotype, and could modify the gene expression involved in apoptosis, autophagy, necrosis, and mitophagy. OxLDL can upregulate Lox-1, and this could lead to a possible amplification of proinflammatory and proapoptotic effects of oxLDL.

Astragaloside IV protects endothelial progenitor cells from the damage of ox-LDL via the LOX-1/NLRP3 inflammasome pathway

Purpose: Functional impairment of endothelial progenitor cells (EPCs) is frequently observed in patients with diabetic vascular complications. Astragaloside IV (ASV) has a significant protective effect against vascular endothelial dysfunction. Thus, this study aimed to investigate the role of ASV on oxidized low-density lipoprotein (ox-LDL)-induced EPCs dysfunction and its potential mechanisms.

Methods: EPCs were isolated from the peripheral blood of mice and treated with different concentration of ASV (10, 20, 40, 60, 80, 100 and 200 µM). ox-LDL was served as a stimulus for cell model. The proliferation and migration, and improved tube formation ability of EPCs were determined. Reactive oxygen species (ROS) production and the levels of inflammatory cytokines, including interleukin 1β (IL-1β), IL-6, IL-10 and tumor necrosis factor (TNF-α) were measured. The expression oflectin-like oxidized LDL receptor (LOX-1) andNod-like receptor nucleotide-binding domain leucine rich repeat containing protein 3 (NLRP3) inflammasome were detected by Western blot analysis.

Results: We found ASV treatment alleviated ox-LDL-induced cellular dysfunction, as evidenced by promoted proliferation and migration, and improved tube formation ability. Besides, ASV treatment significantly suppressed ox-LDL-induced ROS production and the levels of inflammatory cytokines. ASV inhibited ox-LDL-induced expression of LOX-1 in a concentration-dependent manner. Overexpression of LOX-1 in EPCs triggered NLRP3inflammasome activation, while inhibition of LOX-1 or treatment with ASV suppressed ox-LDL-induced NLRP3 inflammasome activation. Furthermore, overexpression of LOX-1 in ox-LDL-induced EPCs furtherly impaired cellular function, which could be ameliorated by ASV treatment.

Conclusion: Our study showed that ASV may protect EPCs against ox-LDL-induced dysfunction via LOX-1/NLRP3 pathway.

Involvement of endothelial nitric oxide synthase pathway in IGF‑1 protects endothelial progenitor cells against injury from oxidized LDLs

A high level of oxidized low‑density lipoproteins (oxLDLs) is an independent risk factor for cardiovascular disease. The aim of the present study was to investigate whether insulin‑like growth factor‑1 (IGF‑1) protected endothelial progenitor cells (EPCs) from injury caused by ox‑LDLs, and whether the endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) pathway was involved in this process. EPCs were isolated from human peripheral blood and characterized. In order to evaluate the effect of IGF‑1 on EPCs, cells were incubated with ox‑LDLs (100 mg/ml) for 24 h to induce a model of EPC dysfunction in vitro, which demonstrated a decrease in the number of EPCs, concomitant with increased apoptosis and decreased proliferation rates. IGF‑1 dose‑dependently increased the number of EPCs. Concurrently, IGF‑1 decreased the levels of apoptosis of EPCs and improved EPCs proliferation following ox‑LDLs challenge. In addition, IGF‑1 significantly increased NO levels in ox‑LDLs‑treated EPCs, accompanied by an upregulation in eNOS expression. The protective effects of IGF‑1 on EPCs and NO production were abolished by L‑NAME, a specific eNOS inhibitor. These results suggested that IGF‑1 protects EPCs from dysfunction induced by oxLDLs through a mechanism involving the eNOS/NO pathway.

Endothelial Progenitor Cells and Cardiovascular Correlates

Cardiovascular disease is cited as the underlying cause of death in one out of every three deaths within the United States; this burden on the health care system percolates down to affect patients on an individual level. In part, the problem arises from the low regenerative capacity of cardiovascular system cells, for example, cardiac myocytes, and from oxidative stressors to the human body.

Endothelial progenitor cells (EPCs) are a type of stem cell, and various clinical conditions including hypertension and renal failure underlie their dysfunction. EPCs are classified as either early or late outgrowth endothelial progenitor cells depending on the time they appear in circulation and at the site of injury after an inciting event. Their function is paracrine through the release of cytokines, growth factors and chemokines such as interleukin-6 and vascular endothelial growth factor, and they are involved in transdifferentiation into vascular smooth muscle cells and potentially cardiac myocytes. They are beneficial to the modification of cardiovascular cell apoptosis, fibrosis, and contractility. In times of stress, the normal function of endothelial progenitor cells is altered; this creates a maladaptive cycle where stress and failed coping mechanisms enhance each other toward the culmination of cardiovascular disease.

The development of the cardiovascular system follows gastrulation in the embryonic period, and the cells that form the system are derived from the mesoderm; being mesoderm, the vascular cells exhibit heterogeneity in their origin and function. The need to understand the molecular and cellular regulatory pathways during development can amalgamate efforts of endothelial cell and cardiovascular system pathophysiology for the advancement of patient cardiovascular reserve and function.

Decreased Count and Dysfunction of Circulating EPCs in Postmenopausal Hypercholesterolemic Females via Reducing NO Production

Endothelial progenitor cells (EPCs) contribute to the endogenous endothelial repair program during hypercholesterolemia. EPC count and migratory and proliferative capacities remain unchanged in the premenopausal female with hypercholesterolemia. However, the changes of count and activity of circulating EPCs in the hypercholesterolemic postmenopausal females are unknown. Here, we find that the migratory and proliferative capacities of circulating EPCs were decreased in patients with hypercholesterolemia versus normocholesterolemia. No significant differences were found between postmenopausal females and age-matched males. NO production showed positive correlation with the activity and count of circulating EPCs in patients with hypercholesterolemia. Flow-mediated dilatation (FMD) is directly interrelated with EPC counts and function. Our findings reveal that decreased EPC count and endothelial dysfunction lead to less NO production in hypercholesterolemic postmenopausal females. Maintaining the EPC numbers and activity might be emerging as a potential therapeutic strategy to reduce the risk of cardiovascular injury in elder women.

Nitric oxide bioavailability dysfunction involves in atherosclerosis

The pathological characteristics of atherosclerosis (AS) include lipid accumulation, fibrosis formation and atherosclerotic plaque produced in artery intima, which leads to vascular sclerosis, lumen stenosis and irritates the ischemic changes of corresponding organs. Endothelial dysfunction was closely associated with AS. Nitric oxide (NO) is a multifunctional signaling molecule involved in the maintenance of metabolic and cardiovascular homeostasis. NO is also a potent endogenous vasodilator and enters for the key processes that suppresses the formation vascular lesion even AS. NO bioavailability indicates the production and utilization of endothelial NO in organisms, its decrease is related to oxidative stress, lipid infiltration, the expressions of some inflammatory factors and the alteration of vascular tone, which plays an important role in endothelial dysfunction. The enhancement of arginase activity and the increase in asymmetric dimethylarginine and hyperhomocysteinemia levels all contribute to AS by intervening NO bioavailability in human beings. Diabetes mellitus, obesity, chronic kidney disease and smoking, etc., also participate in AS by influencing NO bioavailability and NO level. Here, we reviewed the relationship between NO bioavailability and AS according the newest literatures.

Endothelial Progenitor Cell Biology and Vascular Recovery Following Transradial Cardiac Catheterization

BACKGROUND

Transradial catheterization is associated with radial artery injury and vasomotor dysfunction and represents an accessible model of acute vascular injury in humans. We characterized vascular injury and functional recovery to understand the role of circulating endothelial progenitor cells in vascular repair.

METHODS AND RESULTS

In 50 patients (aged 64±10 years, 70% male) undergoing transradial cardiac catheterization, radial artery injury was assessed by optical coherence tomography and examination of explanted vascular sheaths. Flow- and nitrate-mediated dilatation of the radial artery was assessed in both arms at baseline, at 24 hours, and at 1, 4, and 12 weeks. Circulating endothelial progenitor cell populations were quantified using flow cytometry. Late endothelial outgrowth colonies were isolated and examined in vitro. Optical coherence tomography identified macroscopic injury in 12 of 50 patients (24%), but endothelial cells (1.9±1.2×104 cells) were isolated from all arterial sheaths examined. Compared with the noncatheterized radial artery, flow-mediated vasodilatation was impaired in the catheterized artery at 24 hours (9.9±4.6% versus 4.1±3.1%, P<0.0001) and recovered by 12 weeks (8.1±4.9% versus 10.1±4.9%, P=0.09). Although the number of CD133+ cells increased 24 hours after catheterization (P=0.02), the numbers of CD34+ cells and endothelial outgrowth colonies were unchanged. Migration of endothelial cells derived from endothelial outgrowth colonies correlated with arterial function before catheterization but was not related to recovery of function following injury.

CONCLUSIONS

Transradial cardiac catheterization causes endothelial denudation, vascular injury, and vasomotor dysfunction that recover over 12 weeks. Recovery of vascular function does not appear to be dependent on the mobilization or function of endothelial progenitor cells.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02147119.

Oxidized low-density lipoprotein (oxLDL) affects load-free cell shortening of cardiomyocytes in a proprotein convertase subtilisin/kexin 9 (PCSK9)-dependent way

Recent studies have documented that oxidized low-density lipoprotein cholesterol (oxLDL) levels directly impact myocardial structure and function. However, the molecular mechanisms by which oxLDL affects cardiac myocytes are not well established. We addressed the question whether oxLDL modifies load-free cell shortening, a standardized readout of cardiac cellular function, and investigated whether proprotein convertase subtilisin/kexin-9 (PCSK9) is involved on oxLDL-dependent processes. Adult rat ventricular cardiomyocytes were isolated and incubated for 24 h with oxLDL. PCSK9 was silenced by administration of siRNA. Load-free cell shortening was analyzed via a line camera at a beating frequency of 2 Hz. RT-PCR and immunoblots were used to identify molecular pathways. We observed a concentration-dependent reduction of load-free cell shortening that was independent of cell damage (apoptosis, necrosis). The effect of oxLDL was attenuated by silencing of oxLDL receptors (LOX-1), blockade of p38 MAP kinase activation, and silencing of PCSK9. oxLDL increased the expression of PCSK9 and caused oxidative modification of tropomyosin. In conclusion, we found that oxLDL significantly impaired contractile function via induction of PCSK9. This is the first report about the expression of PCSK9 in adult terminal differentiated ventricular cardiomyocytes. The data are important in the light of recent development of PCSK9 inhibitory strategies.

Overexpression of LOXIN Protects Endothelial Progenitor Cells From Apoptosis Induced by Oxidized Low Density Lipoprotein

Human endothelial progenitor cells (hEPC) are adult stem cells located in the bone marrow and peripheral blood. Studies have indicated that hEPC play an important role in the recovery and repair of injured endothelium, however, their quantity and functional capacity is reduced in several diseases including hypercholesterolemia. Recently, it has been demonstrated that hEPC express lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) and its activation by oxidized low-density lipoprotein (ox-LDL) induces cellular dysfunction and apoptosis. This study aimed to investigate whether overexpression of LOXIN, a truncated isoform of LOX-1 that acts as a dominant negative, plays a protective role against ox-LDL-induced apoptosis in hEPC. Human endothelial progenitor cells exposed to ox-LDL showed a significant increase in LOX-1 expression, and apoptosis began at ox-LDL concentrations above 50 μg/mL. All hEPC apoptosed at 200 μg/mL ox-LDL. High LOXIN expression was generated using adenoviral systems in hEPC and SiHa cells transduced with 100 colony-forming units per cell. Transduced LOXIN localized to the plasma membrane and blocked ox-LDL uptake mediated by LOX-1. Overexpression of LOXIN protected hEPC from ox-LDL-induced apoptosis, and therefore maybe a novel way of improving hEPC function and quantity. These results suggest that adenoviral vectors of LOXIN may provide a possible treatment for diseases related to ox-LDL and vascular endothelium dysfunction, including atherosclerosis.

Store-operated calcium entry-activated autophagy protects EPC proliferation via the CAMKK2-MTOR pathway in ox-LDL exposure

Improving biological functions of endothelial progenitor cells (EPCs) is beneficial to maintaining endothelium homeostasis and promoting vascular re-endothelialization. Because macroautophagy/autophagy has been documented as a double-edged sword in cell functions, its effects on EPCs remain to be elucidated. This study was designed to explore the role and molecular mechanisms of store-operated calcium entry (SOCE)-activated autophagy in proliferation of EPCs under hypercholesterolemia. We employed oxidized low-density lipoprotein (ox-LDL) to mimic hypercholesterolemia in bone marrow-derived EPCs from rat. Ox-LDL dose-dependently activated autophagy flux, while inhibiting EPC proliferation. Importantly, inhibition of autophagy either by silencing Atg7 or by 3-methyladenine treatment, further aggravated proliferative inhibition by ox-LDL, suggesting the protective effects of autophagy against ox-LDL. Interestingly, ox-LDL increased STIM1 expression and intracellular Ca²⁺ concentration. Either Ca²⁺ chelators or deficiency in STIM1 attenuated ox-LDL-induced autophagy activation, confirming the involvement of SOCE in the process. Furthermore, CAMKK2 (calcium/calmodulin-dependent protein kinase kinase 2, β) activation and MTOR (mechanistic target of rapamycin [serine/threonine kinase]) deactivation were associated with autophagy modulation. Together, our results reveal a novel signaling pathway of SOCE-CAMKK2 in the regulation of autophagy and offer new insights into the important roles of autophagy in maintaining proliferation and promoting the survival capability of EPCs. This may be beneficial to improving EPC transplantation efficacy and enhancing vascular re-endothelialization in patients with hypercholesterolemia.

15-Lipoxygenase-1 Is Involved in the Effects of Atorvastatin on Endothelial Dysfunction

Statins exert pleiotropic effects on endothelial cells in addition to lowering cholesterol. 15-Lipoxygenase-1 (ALOX15) has been implicated in vascular inflammation and disease. The relationship between atorvastatin and ALOX15 was investigated using a rat carotid artery balloon-injury model. Hematoxylin and eosin (HE) staining showed that ALOX15 overexpression increased the thickness of the intima-media (IMT). Immunohistochemistry and western blotting showed that atorvastatin increased the expression of cellular adhesion molecules (CAMs) but decreased the expression of endothelial nitric oxide synthase (eNOS); these effects of atorvastatin were blocked by ALOX15 overexpression. In human umbilical venous endothelial cells (HUVECs), silencing of ALOX15 enhanced the effects of atorvastatin on endothelial function. Expression levels of CAMs and Akt/eNOS/NO under oxidized low-density lipoprotein (ox-LDL) stimulation were modulated by ALOX15 inhibitor and ALOX15 small interfering RNA (siRNA). Atorvastatin abolished the activation of nuclear factor-kappa B (NF-κB) induced by ox-LDL. Exposure to ox-LDL induced upregulation of ALOX15 in HUVECs, but this effect was partially abolished by atorvastatin or the NF-κB inhibitor pyrrolidine dithiocarbamate (PDTC). These results demonstrate that regulation of ALOX15 expression might be involved in the effects of atorvastatin on endothelial dysfunction.

Inhibition of p38 Mitogen-Activated Protein Kinase Enhances the Apoptosis Induced by Oxidized Low-Density Lipoprotein in Endothelial Progenitor Cells

Oxidized low-density lipoprotein (oxLDL) is an important risk factor in the development of atherosclerosis. oxLDL has been shown to decrease endothelial progenitor cell (EPC) number by inducing apoptosis. p38 mitogen-activated protein kinase (MAPK) was shown to be activated by oxLDL and participated in the regulation of EPC number and function. However, the role of p38 remains unknown. Here, we show that oxLDL-induced p38 phosphorylation in EPCs is time and dose dependent. Treatment with antioxidant N-acetyl cysteine restored oxLDL-induced p38 phosphorylation to basal levels. LOX-1-blocking antibody also significantly decreased oxLDL-induced p38 phosphorylation. Interestingly, TUNEL staining showed that pretreatment with the p38 inhibitor SB203580 further increased oxLDL-induced apoptosis in EPCs. In accordance with these findings, pretreatment with SB203580 further attenuated Akt phosphorylation in EPCs challenged with oxLDL, indicating an interaction between Akt and p38 MAPK pathways. In agreement, inhibition of p38 MAPK further attenuated Akt phosphorylation and increased apoptosis in EPCs isolated from hypercholesterolemic ApoE-/- mice. In conclusion, p38 MAPK serves as an anti-apoptotic pathway by supporting Akt activity when EPCs are challenged with oxLDL.

The relationship between oxidised LDL, endothelial progenitor cells and coronary endothelial function in patients with CHD

Objective

The balance between coronary endothelial dysfunction and repair is influenced by many protective and deleterious factors circulating in the blood. We studied the relationship between oxidised low-density lipoprotein (oxLDL), circulating endothelial progenitor cells (EPCs) and coronary endothelial function in patients with stable coronary heart disease (CHD).

Methods

33 patients with stable CHD were studied. Plasma oxLDL was measured using ELISA, coronary endothelial function was assessed using intracoronary acetylcholine infusion and EPCs were quantified using flow cytometry for CD34⁺/KDR⁺ cells.

Results

Plasma oxLDL correlated positively with the number of EPCs in the blood (r=0.46, p=0.02). There was a positive correlation between the number of circulating EPCs and coronary endothelial function (r=0.42, p=0.04). There was no significant correlation between oxLDL and coronary endothelial function.

Conclusions

Plasma levels of oxLDL are associated with increased circulating EPCs in the blood of patients with CHD, which may reflect a host-repair response to endothelial injury. Patients with stable CHD had a high prevalence of coronary endothelial dysfunction, which was associated with lower numbers of circulating EPCs, suggesting a mechanistic link between endothelial dysfunction and the pathogenesis of atherosclerosis.

Oxidative theory of atherosclerosis and antioxidants

Atherosclerosis is a multifactorial process that begins early in infancy and affects all the humans. Early steps of atherogenesis and the evolution towards complex atherosclerotic plaques are briefly described. After a brief history of the 'Lipid theory of atherosclerosis', we report the most prominent discoveries on lipoproteins, their receptors and metabolism, and their role in atherogenesis. The main focus is the 'oxidative theory of atherosclerosis', with emphasis on free radicals and reactive oxygen species, lipid peroxidation and LDL oxidation, biological properties of oxidized LDL and their potential role in atherogenesis. Then, we report the properties of antioxidants and antioxidant systems and their effects in vitro, on cultured cells, in animal models and in humans. The surprising discrepancy between the efficacy of antioxidants in vitro and in animal models of atherosclerosis and the lack of protective effect against cardiovascular events and death in epidemiological study and clinical trials are discussed. In contrast, epidemiological studies seem to indicate that the Mediterranean diet may protect (in part) against atherosclerosis complications (myocardial infarction and cardiovascular death).