Oxidized low-density lipoproteins facilitate leukocyte adhesion to aortic intima without affecting endothelium-dependent relaxation. Role of P-selectin

Comprehensive Review of Cardiovascular Disease Risk in Nonalcoholic Fatty Liver Disease

Nonalcoholic Fatty Liver Disease (NAFLD) is a growing global phenomenon, and its damaging effects in terms of cardiovascular disease (CVD) risk are becoming more apparent. NAFLD is estimated to affect around one quarter of the world population and is often comorbid with other metabolic disorders including diabetes mellitus, hypertension, coronary artery disease, and metabolic syndrome. In this review, we examine the current evidence describing the many ways that NAFLD itself increases CVD risk. We also discuss the emerging and complex biochemical relationship between NAFLD and its common comorbid conditions, and how they coalesce to increase CVD risk. With NAFLD's rising prevalence and deleterious effects on the cardiovascular system, a complete understanding of the disease must be undertaken, as well as effective strategies to prevent and treat its common comorbid conditions.

Radiofrequency ablation reduces expression of SELF by upregulating the expression of microRNA-26a/b in the treatment of atrial fibrillation

BACKGROUND

In this study, we aimed to investigate the role of miR-26a and miR-26b in the management of AF.

METHODS

Real-time PCR was carried out to determine plasma microRNA expression in AF patients pre- and post-radiofrequency ablation. The correlation between the expression of SELP and miR-26a/miR-26b was also studied using luciferase assays to establish a miR-26a/miR-26b/SELP signaling pathway.

RESULTS

The relative expression of SELP reached its peak in pre-ablation AF ( +) patients, while ablation treatment reduced the expression of SELP in AF ( +) patients. Similarly, AF pigs showed dysregulation of miR-26a/b and SELP, thus verifying the involvement of miR-26a/b and SELP in AF. Meanwhile, the regulatory association between SELP and miR-26a/b was also investigated, and the results showed that the presence of pre-miR-26a/b increased the levels of miR-26a/b and inhibited the mRNA/protein expression of SELP. Finally, using bioinformatic tools and luciferase assays, SELP mRNA was confirmed as the target of miR-26a/b, which affected the effect of AF ablation treatment.

CONCLUSIONS

RFA helped to restore circulating levels of miR-26, which were reduced in atrial fibrillation. Meanwhile, miR-26 is a potential cause for the elevated plasma levels of pro-thrombogenic SELP in that disease.

Exosomal lncRNA GAS5 regulates the apoptosis of macrophages and vascular endothelial cells in atherosclerosis

Atherosclerosis is universally recognized as a chronic lipid-induced inflammation of the vessel wall. Oxidized low density lipoprotein (oxLDL) drives the onset of atherogenesis involving macrophages and endothelial cells (ECs). Our earlier work showed that expression of long noncoding RNA-growth arrest-specific 5 (lncRNA GAS5) was significantly increased in the plaque of atherosclerosis collected from patients and animal models. In this study, we found that knockdown of lncRNA GAS5 reduced the apoptosis of THP-1 cells treated with oxLDL. On the contrary, overexpression of lncRNA GAS5 significantly elevated the apoptosis of THP-1 cells after oxLDL stimulation. The expressions of apoptotic factors including Caspases were changed with lncRNA GAS5 levels. Moreover, lncRNA GAS5 was found in THP-1 derived-exosomes after oxLDL stimulation. Exosomes derived from lncRNA GAS5-overexpressing THP-1 cells enhanced the apoptosis of vascular endothelial cells after taking up these exosomes. However, exosomes shed by lncRNA GAS5 knocked-down THP-1 cells inhibited the apoptosis of endothelial cells. These findings reveal the function of lncRNA GAS5 in atherogenesis which regulates the apoptosis of macrophages and endothelial cells via exosomes and suggest that suppressing the lncRNA GAS5 might be an effective way for the therapy of atherosclerosis.

Pathophysiology of coronary vascular remodeling: relationship with traditional risk factors for coronary artery disease

The relationship between cardiovascular risk factors and vascular remodeling is a relatively new area of investigation. We discuss the various mechanisms by which cardiovascular risk factors cause vascular remodeling. Endothelial dysfunction, lipoprotein alterations, inflammation, and platelet activation are the mechanisms by which remodeling occurs. Plaque composition also plays an important role in directing remodeling. Plaque with extensive calcification is more likely to undergo constrictive remodeling. Positive and negative remodeling is based on how these factors coordinate and determine the direction of remodeling. Matrix metalloproteinases perform a crucial role in vascular remodeling. Advanced glycation end-products are key substances involved in the negative remodeling associated with diabetes. Remodeling in hypertension can be either eutrophic or hypertrophic. Endothelial dysfunction and low-grade inflammation lead to negative remodeling in hypertension. Dyslipidemia can be associated with either positive or negative remodeling. High high-density lipoprotein is associated with positive remodeling and high low-density lipoprotein with negative remodeling. Smoking causes endothelial dysfunction, increased oxidative stress, and decreased nitric oxide synthesis leading to inward remodeling. Aging also causes endothelial dysfunction and predisposes to negative remodeling. Knowledge of these associations can elucidate various clinical presentations and guide therapeutic choices in the future.

Atherogenic dyslipidemia

Atherogenic dyslipidemia (AD) refers to elevated levels of triglycerides (TG) and small-dense low-density lipoprotein and low levels of high-density lipoprotein cholesterol (HDL-C). In addition, elevated levels of large TG rich very low-density lipoproteins, apolipoprotein B and oxidised low-density lipoprotein (LDL), and reduced levels of small high-density lipoproteins plays a critical role in AD. All three elements of AD per se have been recognised as independent risk factor for cardiovascular disease. LDL-C/HDL-C ratio has shown excellent risk prediction of coronary heart disease than either of the two risk markers. Asian Indians have a higher prevalence of AD than western population due to higher physical inactivity, low exercise and diet deficient in polyunsaturated fatty acids (PUFA). The AD can be well managed by therapeutic lifestyle changes with increased physical activities, regular exercise, and diets low in carbohydrates and high in PUFA such as omega-3-fatty acids, as the primary intervention. This can be supplemented drug therapies such as statin monotherapy or combination therapy with niacin/fibrates. Rosuvastatin is the only statin, presently available, to effectively treat AD in diabetes and MS patients.

Nitric oxide function in atherosclerosis

Atherosclerosis is a chronic inflammatory process in the intima of conduit arteries, which disturbs the endothelium-dependent regulation of the vascular tone by the labile liposoluble radical nitric oxide (NO) formed by the constitutive endothelial nitric oxide synthase (eNOS). This defect predisposes to coronary vasospasm and cardiac ischaemia, with anginal pain as the typical clinical manifestation. It is now appreciated that endothelial dysfunction is an early event in atherogenesis and that it may also involve the microcirculation, in which atherosclerotic lesions do not develop. On the other hand, the inflammatory environment in atherosclerotic plaques may result in the expression of the inducible NO synthase (iNOS) isozyme. Whether the dysfunction in endothelial NO production is causal to, or the result of, atherosclerotic lesion formation is still highly debated. Most evidence supports the hypothesis that constitutive endothelial NO release protects against atherogenesis e.g. by preventing smooth muscle cell proliferation and leukocyte adhesion. Nitric oxide generated by the inducible isozyme may be beneficial by replacing the failing endothelial production but excessive release may damage the vascular wall cells, especially in combination with reactive oxygen intermediates.

Circulating soluble lectin-like oxidized low-density lipoprotein receptor-1 levels are associated with proximal/middle segment of the LAD lesions in patients with stable coronary artery disease

BACKGROUND/OBJECTIVES

Atherosclerosis is the main underlying pathology of coronary artery disease (CAD), which is the leading cause of mortality worldwide. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is involved in multiple phases of vascular dysfunction, including endothelial dysfunction, atherosclerotic plaque formation, and destabilization. The purpose of the current study was to determine whether soluble LOX-1 is associated with proximal/mid and distal segment of the left anterior descending (LAD) artery lesion in patients with stable CAD.

METHODS

Sixty-four patients with proximal/mid segment of the LAD lesions and 51 patients with distal segments of the LAD lesions were included in this study. Soluble LOX-1 levels were measured in all study subjects.

RESULTS

Baseline characteristics of the two groups were similar. In stable CAD, patients with proximal/middle segment of the LAD lesions had significantly higher circulating soluble LOX-1 levels than patients with distal segments of the LAD lesions (1.07 ± 0.33 vs. 0.70 ± 0.17 ng/ml, p < 0.001). No correlation was found between plasma-soluble LOX-1 levels and fasting glucose, lipid profile. For predicting proximal/middle LAD lesions, the highest specificity (95,2%) and sensitivity (53,8%) levels were obtained at the cut-off value of 0.68.

CONCLUSION

Our study demonstrated that serum-soluble LOX-1 levels were associated with proximal/mid segment of the LAD lesions. Furthermore, this study suggested soluble LOX-1 might be a useful biomarker of coronary plaque vulnerability in patients with stable CAD. Soluble LOX-1, the novel biochemical marker, may provide new insights into not only risk stratification but also therapeutic strategy for CAD.

Molecular imaging of the initial inflammatory response in atherosclerosis: implications for early detection of disease

Background- We hypothesized that molecular imaging of endothelial cell adhesion molecule expression could noninvasively evaluate prelesion atherogenic phenotype.

METHODS AND RESULTS

Mice deficient for the LDL-receptor and the Apobec-1 editing peptide (DKO mice) were studied as an age-dependent model of atherosclerosis. At 10, 20, and 40 weeks of age, ultrasound molecular imaging of the proximal thoracic aorta was performed with contrast agents targeted to P-selectin and VCAM-1. Atherosclerotic lesion severity and content were assessed by ultrahigh frequency ultrasound, histology, and immunohistochemistry. In wild-type mice at all ages, there was neither aortic thickening nor targeted tracer signal enhancement. In DKO mice, lesions progressed from sparse mild intimal thickening at 10 weeks to widespread severe lesions with luminal encroachment at 40 weeks. Molecular imaging for P-selectin and VCAM-1 demonstrated selective signal enhancement (P<0.01 versus nontargeted agent) at all ages for DKO mice. P-selectin and VCAM-1 signal in DKO mice were greater by 3-fold at 10 weeks, 4- to 6-fold at 20 weeks, and 9- to 10-fold at 40 weeks compared to wild-type mice. En face microscopy demonstrated preferential attachment of targeted microbubbles to regions of lesion formation.

CONCLUSIONS

Noninvasive ultrasound molecular imaging of endothelial activation can detect lesion-prone vascular phenotype before the appearance of obstructive atherosclerotic lesions.

LOX-1 and inflammation: a new mechanism for renal injury in obesity and diabetes

The early nephropathy in obese, diabetic, dyslipidemic (ZS) rats is characterized by tubular lipid accumulation and pervasive inflammation, two critically interrelated events. We now tested the hypothesis that proximal tubules from ZS obese diabetic rats in vivo, and proximal tubule cells (NRK52E) exposed to oxidized LDL (oxLDL) in vitro, change their normally quiescent epithelial phenotype into a proinflammatory phenotype. Urine of obese diabetic rats contained more lipid peroxides, and LOX-1, a membrane receptor that internalizes oxidized lipids, was mobilized to luminal sites. Levels of ICAM-1 and focal adhesion kinase, which participate in leukocyte migration and epithelial dedifferentiation, respectively, were also upregulated in tubules. NRK52E cells exposed to oxLDL showed similar modifications, plus suppression of anti-inflammatory transcription factor peroxisome proliferator-activated receptor-delta. In addition, oxLDL impaired epithelial barrier function. These alterations were prevented by an anti-LOX-1 antibody. The data support the concept that tubular LOX-1 activation driven by lipid oxidants in the preurine fluid is critical in the inflammatory changes. We suggest that luminal lipid oxidants and abnormal tubular permeability may be partly responsible for the renal tubulointerstitial injury of obesity, diabetes, and dyslipidemia.

Reduction of soluble P-selectin by statins is inversely correlated with the progression of coronary artery disease

BACKGROUND

Cell adhesion molecules (CAM) play an important role in the pathogenesis of atherosclerosis by mediating the binding of leukocytes to the endothelium. Soluble CAM isoforms are known to be elevated in the sera of patients suffering from coronary artery disease (CAD).

METHODS

We measured the concentrations of soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, P-selectin, platelet endothelial cell adhesion molecule-1, and highly sensitive C-reactive protein (hs-CRP) in the blood of 47 CAD patients before and 6 months after starting statin therapy and in 16 untreated CAD patients. The progression of CAD was monitored by calculating the coronary calcium score using electron beam computed tomography.

RESULTS

Soluble P-selectin (92+/-11 ng/ml vs. 59 +/- 4 ng/ml, p < 0.0001) and hs-CRP (0.92 +/- 0.14 mg/dl vs. 0.42 +/- 0.11 mg/dl, p < 0.001) decreased significantly in the statin-treated group compared to baseline levels. None of the other proteins studied showed significant changes. In contrast to hs-CRP, the reduction of soluble P-selectin concentrations correlated directly with the lowering of total cholesterol (r(2) = 0.236, p < 0.005) and inversely with the progression of CAD (r(2) = 0.393, p < 0.0001).

CONCLUSIONS

Our results suggest P-selectin as an additional marker for the beneficial action of statins in patients with CAD.

LDL-cholesterol predicts negative coronary artery remodelling in diabetic patients: an intravascular ultrasound study

AIMS

To investigate the relationship between coronary artery remodelling and glycaemic and lipid profiles in diabetic patients.

METHODS AND RESULTS

Intravascular ultrasound analyses of 131 angiographically non-significant coronary stenoses in 80 diabetic patients were performed. The remodelling index (RI) was calculated as the ratio between total vessel area at target site and total vessel area at proximal reference, and was assessed in two ways: as a continuous variable, and as a binary categorical variable: RI<1 namely, negative remodelling (group I), or RI> or =1 (group II). Percentage cross-sectional narrowing was 57+/-13%. On average, RI was 0.93+/-0.13. Coronary shrinkage was found in 94 (71.7%) lesions. Significant inverse correlations were demonstrated between RI and total cholesterol (r=-0.26, P=0.003), apolipoprotein-B (r=-0.23, P=0.01) and LDL-cholesterol (r=-0.3, P=0.001) levels. Multivariable lineal regression analysis identified LDL-cholesterol as the only independent predictor of RI (P=0.001).

CONCLUSION

Negative remodelling is a frequent finding in diabetics and it is associated with LDL-cholesterol levels. This may contribute to the diffuse coronary artery disease observed in diabetic patients.

Statins prevent oxidized LDL-induced injury of glomerular podocytes by activating the phosphatidylinositol 3-kinase/AKT-signaling pathway

The injury of podocytes is associated with alterations of the glomerular size-selective barrier to proteins. In this study, oxidized LDL (oxLDL) but not native LDL induced apoptosis in human cultured podocytes and reduced Akt activity and P-Akt/Akt ratio. Moreover, oxLDL-induced redistribution and loss of nephrin, an adhesion molecule specific for the glomerular slit diaphragm. Nephrin reduction was preceded by inhibition of nephrin tyrosine phosphorylation and of its association with p85 phosphatidylinositol 3-kinase (PI3K). Moreover, three different statins, mevastatin, pravastatin, and simvastatin, inhibited in a dose-dependent manner apoptosis and loss of nephrin induced by oxLDL by stimulating Akt activity. In addition, simvastatin significantly increased the expression of nephrin protein and mRNA by podocytes. The protective effects of statins were blocked by treatment of podocytes with two unrelated pharmacologic inhibitors of PI3K, LY294002 and wortmannin, suggesting a role for PI3K, and by mevalonate, indicating dependency on HMG-CoA reductase activity. Statins directly stimulated Akt phosphorylation ad activity. Finally, oxLDL induced a retraction of cultured podocytes and an increase in the albumin diffusion across their monolayer that was inhibited by treatment with statins. In conclusion, statins reduced the oxLDL-induced apoptosis and loss of nephrin in glomerular podocytes. The statin-induced Akt activation may protect from the loss of nephrin by an inhibition of its redistribution and shedding and by a stimulation of its synthesis. These data provide a rationale for the anti-proteinuric effect of statins.

Cilostazol Prevents Remnant Lipoprotein Particle-Induced Monocyte Adhesion to Endothelial Cells by Suppression of Adhesion Molecules and Monocyte Chemoattractant Protein-1 Expression via Lectin-Like Receptor for Oxidized Low-Density Lipoprotein Receptor Activation

This study shows cilostazol effect to prevent remnant lipoprotein particle (RLP)-induced monocyte adhesion to human umbilical vein endothelial cells (HUVECs). Upon incubation of HUVECs with RLP (50 microg/ml), adherent monocytes significantly increased by 3.3-fold with increased cell surface expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1, E-selectin, and monocyte chemoattractant protein-1 (MCP-1). Cilostazol ( approximately 1-100 microM) concentration dependently repressed these variables as did (E)3-[(4-t-butylphenyl)sulfonyl]-2-propenenitrile (BAY 11-7085) (10 microM), a specific nuclear factor-kappaB (NF-kappaB) inhibitor. Cilostazol effects were significantly antagonized by iberiotoxin (1 microM), a maxi-K channel blocker. RLP significantly increased expression of lectin-like receptor for oxidized low-density lipoprotein (LDL) (LOX-1) receptor protein. Upon transfection with antisense LOX-1 oligodeoxynucleotide (As-LOX-1), LOX-1 receptor expression was reduced, whereas HUVECs with sense LOX-1 oligodeoxynucleotide did express high LOX-1 receptor. RLP-stimulated superoxide and tumor necrosis factor-alpha levels were significantly lowered with decreased expression of VCAM-1 and MCP-1 by transfection with As-LOX-1 as did polyinosinic acid (10 microg/ml, a LOX-1 receptor inhibitor). RLP significantly degraded inhibitory kappaBalpha in the cytoplasm and activated nuclear factor-kappaB (NF-kappaB) p65 in the nucleus of HUVECs with increased luciferase activity of NF-kappaB, all of which were reversed by cilostazol (10 microM), BAY 11-7085, and polyinosinic acid. Together, cilostazol suppresses RLP-stimulated increased monocyte adhesion to HUVECs by suppression of LOX-1 receptor-coupled NF-kappaB-dependent nuclear transcription via mediation of the maxi-K channel opening.

Effects of oxidized low-density lipoprotein on leukocyte-endothelial interactions in the rat mesenteric microcirculation during pregnancy

OBJECTIVE

The accumulation of evidence implicates oxidized lipoproteins in atherosclerosis. Treatment of endothelial cells with these lipoproteins stimulates monocyte binding and the production of chemotactic factors that contribute to inflammation and endothelial injury and dysfunction. In preeclampsia, circulating low-density lipoprotein particles, which are susceptible to oxidation, are increased. We studied leukocyte-endothelial interactions that were related to oxidized lipoproteins in pregnant rats.

STUDY DESIGN

We examined oxidized low-density lipoprotein-induced leukocyte behavior and uptake of fluorescent-labeled oxidized low-density lipoprotein in rat mesenteric venules during pregnancy, with the use of intravital microscopy with a video imager.

RESULTS

The administration of oxidized low-density lipoprotein significantly reduced rolling velocities of leukocytes in venules and increased the numbers of leukocytes that adhered to endothelium in both nonpregnant and pregnant rats. These interactions were attenuated in pregnancy, when uptake of labeled oxidized low-density lipoprotein into leukocytes and endothelial cells also was decreased.

CONCLUSION

Pregnancy may be associated with antioxidant effects.

Adhesion molecules, catecholamines and leucocyte redistribution during and following exercise

The circulating blood normally contains no more than 1-2% of the body's population of leucocytes. The numbers and phenotypes of circulating leucocyte subsets can change dramatically during and immediately following exercise. The surface expression of adhesion molecules makes an important contribution to such responses by changing patterns of cell trafficking. Alterations in the surface expression of adhesion molecules could reflect a shedding of molecules, selective apoptosis or differential trafficking of cells with a particular phenotype, effects from mechanical deformation of the cytoplasm, active biochemical processes involving cytokines, catecholamines, glucocorticoids or other hormones, or changes in the induction of adhesion molecules. The expression of adhesion molecules changes with maturation and activation of leucocytes. Typically, mature cells express lower densities of L-selectin (CD62L), the homing receptor for secondary lymphoid organs, and higher densities of LFA-1 (CD11a), the molecule associated with trafficking to non-lymphoid reservoir sites. The neutrophils and natural killer cells that are mobilised during exercise also express high levels of Mac-1 (CD11b), a marker associated with cellular activation. Possibly, exercise demarginates older cells that are awaiting destruction in the spleen. Plasma concentrations of catecholamines rise dramatically with exercise, and there is growing evidence that catecholamines, acting through a cyclic adenosine monophosphate second messenger system, play an important role in modifying the surface expression of adhesion molecules. Analogous changes can be induced by other forms of stress that release catecholamines or by catecholamine infusion, and responses are blocked by beta(2)-blocking agents. Catecholamines also modify adherence and expression of adhesion molecules in vitro. Cell trafficking is modified by genetic deficiencies in the expression of adhesion molecules, but leucocyte responses to exercise and catecholamines are generally unaffected by splenectomy. A number of clinical conditions including atherogenesis and metaplasia are marked by an altered expression of adhesion molecules. The effects of exercise on these molecules could thus have important health implications.

Benefits of gliclazide in the atherosclerotic process: decrease in monocyte adhesion to endothelial cells

Atherosclerotic cardiovascular disease is the leading cause of premature death in patients with diabetes. Atherosclerosis is a chronic immune-mediated disease, the initiation, progression, and destabilization of which is driven and regulated by inflammatory cells. One critical event in the initiation of this vascular inflammatory disease is the adhesion of leukocytes to the activated endothelium and their migration into the vessel wall. These processes are mediated by the upregulation of adhesion molecules on endothelial cells (ECs) and an increased expression in the vascular wall of chemotactic factors to leukocytes. Monocyte binding to ECs is increased in diabetes. One major determinant of this alteration could be oxidative stress. Given the free-radical scavenging activity of gliclazide, we determined the ex vivo and in vitro effects of this drug on human monocyte binding to ECs and the molecular mechanisms involved in this effect. Our results demonstrate that short-term administration of gliclazide to patients with type 2 diabetes normalizes the levels of plasma lipid peroxides and monocyte adhesion in these subjects. Gliclazide (10 microg/mL) also reduces oxidized low-density lipoprotein (oxLDL)- and advanced glycation end product (AGE)-induced monocyte adhesion to ECs in vitro. The inhibitory effect of this drug on AGE-induced monocyte adhesion involves a reduction in EC adhesion molecule expression and inhibition of nuclear factor kappaB (NF-kappaB) activation. In addition, gliclazide inhibits oxLDL-induced monocyte adhesion to cultured human aortic vascular smooth muscle cells (HASMCs) in vitro and reduces the production of monocyte chemotactic protein-1 (MCP-1) by these cells. Taken collectively, these results show that gliclazide, at concentrations in the therapeutic range, inhibits ex vivo and in vitro monocyte adhesiveness to vascular cells. By doing so, this drug could reduce monocyte recruitment into the vessel wall and thereby contribute to attenuating the sustained inflammatory process that occurs in the atherosclerotic plaque. These findings suggest that treatment of diabetic patients with this drug may prevent or retard the development of vasculopathies associated with diabetes.

Monocyte adhesion in diabetic angiopathy: effects of free-radical scavenging

Increased interaction of monocytes with vascular cells is linked to the development and progression of atherosclerosis in patients with diabetes. One major determinant of increased monocyte binding to vascular cells could be oxidative stress. Given the free-radical scavenging properties of gliclazide, we evaluated the ex vivo and in vitro effects of this drug on human monocyte binding to endothelial cells and smooth muscle cells (SMCs). Short-term administration of gliclazide to patients with type 2 diabetes decreases plasma lipid peroxides and lowers the enhanced adhesion of diabetic monocytes to cultured endothelial cells observed before gliclazide treatment. Gliclazide (10 microg/ml) also reduces oxidized low-density lipoprotein (oxLDL)- and advanced glycation end product (AGE)-induced monocyte adhesion to cultured endothelial cells. The suppressive effect of gliclazide on AGE-induced monocyte adhesion to endothelium involves a reduction of cell adhesion molecule mRNA and protein expression and an inhibition of NF-kappaB activation. Gliclazide also inhibits oxLDL-induced monocyte adhesion to cultured human aortic smooth muscle cells (HASMCs). Furthermore, treatment of HASMCs with gliclazide results in a marked decrease in oxLDL-induced monocyte chemoattractant protein-1 expression, both at the gene and protein levels. These results suggest that gliclazide, at concentrations in the therapeutic range (5-10 microg/ml), by its ability to decrease monocyte-vascular cell interactions could reduce monocyte accumulation in the atherosclerotic plaque and thereby contribute to attenuate the sustained inflammatory process that occurs in the vessel wall. These findings suggest that treatment of diabetic patients with gliclazide may prevent or retard the development of vascular disturbances associated with diabetes.

LOX-1 inhibition in myocardial ischemia-reperfusion injury: modulation of MMP-1 and inflammation

A recently identified lectin-like oxidized low-density lipoprotein receptor (LOX-1) mediates endothelial cell injury and facilitates inflammatory cell adhesion. We studied the role of LOX-1 in myocardial ischemia-reperfusion (I/R) injury. Anesthetized Sprague-Dawley rats were subjected to 60 min of left coronary artery (LCA) ligation, followed by 60 min of reperfusion. Rats were treated with saline, LOX-1 blocking antibody JXT21 (10 mg/kg), or nonspecific anti-goat IgG (10 mg/kg) before I/R. Ten other rats underwent surgery without LCA ligation and served as a sham control group. LOX-1 expression was markedly increased during I/R (P < 0.01 vs. sham control group). Simultaneously, the expression of matrix metalloproteinase-1 (MMP-1) and adhesion molecules (P-selectin, VCAM-1, and ICAM-1) was also increased in the I/R area (P < 0.01 vs. sham control group). There was intense leukocyte accumulation in the I/R area in the saline-treated group. Treatment of rats with the LOX-1 antibody prevented I/R-induced upregulation of LOX-1 and reduced MMP-1 and adhesion molecule expression as well as leukocyte recruitment. LOX-1 antibody, but not nonspecific IgG, also reduced myocardial infarct size (P < 0.01 vs. saline-treated I/R group). To explore the link between LOX-1 and adhesion molecule expression, we measured expression of oxidative stress-sensitive p38 mitogen-activated protein kinase (p38 MAPK). The activity of p38 MAPK was increased during I/R (P < 0.01 vs. sham control), and use of LOX-1 antibody inhibited p38 MAPK activation (P < 0.01). These findings indicate that myocardial I/R upregulates LOX-1 expression, which through p38 MAPK activation increases the expression of MMP-1 and adhesion molecules. Inhibition of LOX-1 exerts an important protective effect against myocardial I/R injury.

Statins modulate oxidized low-density lipoprotein-mediated adhesion molecule expression in human coronary artery endothelial cells: role of LOX-1

LOX-1, a receptor for oxidized low-density lipoprotein (ox-LDL), plays a critical role in endothelial dysfunction and atherosclerosis. LOX-1 activation also plays an important role in monocyte adhesion to endothelial cells. A number of studies show that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) reduce total LDL cholesterol and exert a cardioprotective effect. We examined the modulation of LOX-1 expression and its function by two different statins, simvastatin and atorvastatin, in human coronary artery endothelial cells (HCAECs). We observed that ox-LDL (40 microg/ml) treatment up-regulated the expression of E- and P-selectins, VCAM-1 and ICAM-1 in HCAECs. Ox-LDL mediated these effects via LOX-1, since antisense to LOX-1 mRNA decreased LOX-1 expression and subsequent adhesion molecule expression. Pretreatment of HCAECs with simvastatin or atorvastatin (1 and 10 microM) reduced ox-LDL-induced expression of LOX-1 as well as adhesion molecules (all P < 0.05). A high concentration of statins (10 microM) was more potent than the low concentration (1 microM) (P < 0.05). Both statins reduced ox-LDL-mediated activation of the redox-sensitive nuclear factor-kappaB (NF-kappaB) but not AP-1. These observations indicate that LOX-1 activation plays an important role in ox-LDL-induced expression of adhesion molecules. Inhibition of expression of LOX-1 and adhesion molecules and activation of NF-kappaB may be another mechanism of beneficial effects of statins in vascular diseases.

Inhibition of LOX-1 by statins may relate to upregulation of eNOS

LOX-1, a receptor for oxidized low-density lipoprotein (ox-LDL), plays a critical role in endothelial dysfunction and atherosclerosis; both of these conditions are associated with diminished expression of constitutive endothelial nitric oxide synthase (eNOS). Recent studies show that HMG CoA reductase inhibitors (statins) exert cardioprotective effect. We examined the role of LOX-1 in eNOS expression and modulation of this relationship by two different statins, simvastatin and atorvastatin in human coronary artery endothelial cells (HCAECs). Ox-LDL (40 microg/ml) upregulated the expression of LOX-1; simultaneously, there was a reduction in eNOS expression. Pretreatment of HCAECs with simvastatin or atorvastatin (1 and 10 microM) reduced ox-LDL-induced upregulation of LOX-1 and downregulation of eNOS (both P < 0.05). High concentration of statins (10 microM) was more potent than the low concentration (1 microM) (P < 0.05). Both statins also attenuated ox-LDL-mediated activation of MAP kinase. These observations indicate that statins attenuate the effect of ox-LDL on eNOS expression. Inhibitory effect on LOX-1 and subsequently MAP kinase activity provides a potential mechanism of beneficial effects of statins beyond lowering cholesterol.

Coronary atherosclerosis and oxidative stress as reflected by autoantibodies against oxidized low-density lipoprotein and oxysterols

Clinical studies and animal experiments have demonstrated that oxidized low-density lipoprotein (oxLDL) and oxysterols play important roles in atherogenesis. OxLDL is immunogenic, and autoantibodies (Ab) against oxLDL are detectable in serum. We investigated the relevance of oxysterols and Ab against-oxLDL to coronary artery disease (CAD) in 183 patients undergoing coronary angiography. Patient groups included angiographically normal subjects (< 75% stenosis), others with spasm (> 75% narrowing in response to acetylcholine), and some others with fixed stenosis (> 75%). The group with stenosis was subdivided into patients with stable and unstable angina. Serum concentrations of autoantibodies and 25-, 27-, and 7-beta-hydroxycholesterols were significantly higher in the stenotic group than in the normal group (P < 0.01, P < 0.05, P < 0.05, and P < 0.05, respectively). Antibodies, but not oxysterol concentrations, were significantly greater in subjects with unstable than with stable angina (P < 0.01). We conclude that anti-oxLDL antibody and oxysterol concentrations are associated with coronary artery stenosis, and that oxidative stress may be greatly increased in unstable angina.

The smooth muscle cell membrane during atherogenesis: a potential target for amlodipine in atheroprotection

BACKGROUND

Atherosclerotic disease has been present in the human population apparently from the beginning of time. However, it has only been in the 20th century that improvements in the control of infectious diseases have allowed the average life span to increase to the point where atherosclerosis has been able to affect the general population. By the middle of the 20th century, atherosclerosis had reached epidemic levels, and it is currently pandemic and increasing worldwide. Despite its growing significance to health care, we still know relatively little about the cellular basis for plaque genesis in the vessel wall. Current thinking holds that atherosclerosis is caused by an unchecked chronic inflammatory process involving the cells of the arterial wall and their interaction with LDL and various inflammatory cells. Considerable evidence suggests that the principal insults underlying atherogenesis are serum dyslipidemias and oxidative stress mediated primarily by oxidized LDL. However, just how these insults alter the cell biology of vascular cells and lead to the atherosclerotic phenotype is still under intense investigation. Moreover, recent clinical trials have provided evidence that certain classes of drugs, including newer calcium channel blockers (CCBs), can remodel the arterial smooth muscle cell (SMC) membrane and inhibit the progression of atherosclerotic disease.

METHODS

This review summarizes our current thinking on atherogenesis in the arterial SMC and considers recent developments regarding alterations in the SMC membrane during the very early period of atherogenesis. We also discuss how certain CCBs might operate to produce atheroprotection.

RESULTS

The SMC membrane becomes enriched in unesterified cholesterol soon after the development of serum hypercholesterolemia. With excess membrane cholesterol, the membrane becomes thicker and develops distinct cholesterol domains. These alterations in the membrane increase the permeability of SMC to calcium and induce a variety of alterations in SMC function that contribute to cellular atherogenic processes during plaque genesis. Amlodipine, a third-generation CCB, markedly inhibits the progression of lesions. The explanation of this novel action may lie in the effects of this drug on various potential cellular targets.

CONCLUSIONS

Evidence is accumulating that excess membrane cholesterol may contribute to the cellular defects responsible for the transformation of the SMC to the atherosclerotic phenotype. Amlodipine, which has membrane-remodeling properties, is emerging as an important atheroprotective drug.

Effect of gliclazide on monocyte-endothelium interactions in diabetes

Enhanced monocyte-endothelial cell interactions have been documented in diabetes. Because adherence of monocytes to the endothelium is one of the earliest events in the development of atherosclerosis, its alteration may represent one of the mechanisms leading to accelerated atherosclerosis in diabetic patients. Previous studies have suggested that lipoprotein oxidation and protein glycation may contribute to the increased monocyte binding to the diabetic vasculature. Based on the recent finding that gliclazide has free-radical scavenging activity, we examined the ex vivo and in vitro effects of this drug on human monocyte binding to endothelial cells. Our results demonstrate that short-term administration of gliclazide to patients with type 2 diabetes lowers the enhanced adhesion of diabetic monocytes observed before gliclazide treatment (163+/-24% over control values, p<0.005) to levels similar to those observed in controls. They also show that gliclazide (10 microg/ml) reduces in vitro by approximately 35% both oxidized low-density lipoprotein (LDL)- and glycated albumin-induced monocyte adhesion to endothelial cells. Based on these results, we next investigated the molecular mechanisms responsible for the inhibitory effect of gliclazide on glycated albumin-induced monocyte adhesion to endothelium. In glycated albumin-treated endothelial cells, we observed induction of cell-associated expression of E-selectin (ELAM-1; 170+/-10% over control values, p<0.005), intercellular cell adhesion molecule-1 (ICAM-1; 131+/-8% over control values, p<0.005) and vascular cell adhesion molecule-1 (VCAM-1; 134+/-8% over control values, p<0.005), augmentation in the levels of the transcripts of these molecules, and an increase in the DNA binding of NF-kappaB in the promoters of these antigens. Gliclazide markedly inhibited the induction of all these parameters. Because the oxidative stress-sensitive transcription factor NF-kappaB is implicated in endothelial cell activation, the observed inhibitory effect of gliclazide on NF-kappaB activation and glycated albumin-induced expression of DNA binding activity for the NF-kappaB site in the ELAM-1, ICAM-1 and VCAM-1 promoters seems to be due to its antioxidant properties. These results suggest that gliclazide, by its ability to reduce endothelial activation, may exert potential beneficial effects in the prevention of atherosclerosis associated with type 2 diabetes.

Endothelial dysfunction in Type 1 diabetes mellitus: relationship with LDL oxidation and the effects of vitamin E

AIMS

To examine the hypothesis that increased susceptibility of low density lipoproteins (LDL) to oxidation predisposes to endothelial dysfunction in patients with Type 1 diabetes mellitus.

METHODS

A cross-sectional study of 46 non-nephropathic diabetic and 39 control subjects and in the diabetic patients, a 3-month duration, randomized, placebo-controlled double-blind trial of vitamin E 500 U/day. Flow-mediated vasodilatation (FMD) was measured in the forearm by high resolution ultrasound. LDL oxidation by Cu2+ was measured in vitro.

RESULTS

Diabetic patients had greater basal and reactive forearm blood flow (geometric mean (SD%) flow (ml/min) 110.15 (19.19%) vs. 74.99 (23.17%); P=0.045, and 344.35 (20.84%) vs. 205.17 (21.48%); P=0.007), compared with controls, but there was no difference in FMD (median (interquartile range) 0.00 (-0.01-0.02) vs. 0.02 (-0.01-0.02) cm2; P=0.78). Diabetic LDL oxidation lag time correlated with postdilatation brachial artery area (r= 0.32; P=0.05) but not with FMD. Lag-times and total LDL oxidation by Cu2+, lipoprotein and vitamin E concentrations were similar in diabetic and control groups. Antibody titres to oxidized LDL (oxLDL) were higher in non-diabetic than diabetic subjects, and were unrelated to FMD. In diabetic patients, vitamin E increased mean (SD) plasma vitamin E levels (24.0 (6.5) to 47.5 (7.5) gmol/l; P=0.0006) and resulted in increased FMD (delta 0.00 (-0.02-0.01) vs. 0.01 (0.01-0.02)) cm2; P=0.0036), but no changes in LDL Cu2+ oxidation profiles were observed.

CONCLUSIONS

FMD is no different in Type 1 diabetic and non-diabetic subjects and nor are indices of lipid peroxidation and in vitro LDL oxidation although levels of antibody to oxLDL are lower in diabetes. Vitamin E supplementation increases plasma vitamin E levels and may enhance FMD in diabetes but, in the absence of changes in LDL oxidation, this may not be mediated by reduced oxidation of LDL.

Probucol inhibits oxidized-low density lipoprotein-induced adhesion of monocytes to endothelial cells by reducing P-selectin synthesis in vitro

Probucol (PBC) is an unique antiatherogenic drug producing its effect by antioxidant action rather than hypolipidaemic effect. However, the exact mechanism of its antiatherogenic effect is unclear. Therefore we investigated the PBC effects on the adhesion of monocytes to endothelial cells, an early event in atherogenesis. Monocyte adhesion to cultured pig aortic endothelial cells (EC) was induced by oxidized low density lipoprotein (Ox-LDL). To elucidate the mechanisms of the inhibition on adhesion, PBC effects on the Ox-LDL-induced expression of P-selectin, on the synthesis of von Willebrand factor (vWF) and prostacyclin (PGI2) were examined. The results showed that Ox-LDL enhanced the adhesion of monocytes to EC in a concentration-dependent and time-related manner. PBC 25, 50 and 75 micromol/L inhibited the Ox-LDL-induced adhesion index from 37.3% to 19.7, 16.6 and 14.6% respectively (p all < 0.05), and inhibited the Ox-LDL-induced expression of P-selectin from 293.0 ng/ml to 180.0, 132.9 and 132.6 ng/ml respectively. Furthermore, PBC significantly attenuated the Ox-LDL-impaired synthesis of PGI2 and vWF. These results indicate that PBC may provide a new approach in the prevention of atherosclerosis (AS) by intervention of monocyte adhesion to EC. In conclusion, PBC inhibits the Ox-LDL-induced adhesion of monocytes to EC. This effect is associated with the inhibition of the Ox-LDL-induced expression of P-selectin and the protection on the synthesis of PGI2.

Leukocyte-endothelium adhesion molecules in atherosclerosis

The genetic manipulation of mice has provided an invaluable tool for studying the molecular mechanism(s) involved in atherosclerotic lesion development and maturation. The use of these new animal models has demonstrated that leukocyte-endothelium adhesion receptors play a significant part in promoting monocyte recruitment and consequently lesion growth. The next phase of investigation should test whether the inhibition of these adhesion receptors can reproduce the powerful anti-atherosclerotic effects seen in the adhesion receptor-deficient mice.

Identification and autoregulation of receptor for OX-LDL in cultured human coronary artery endothelial cells

Although macrophages scavenge oxidatively modified low density lipoprotein (ox-LDL) via specific receptors, the uptake of ox-LDL by endothelial cells is thought to be mediated by a different receptor (LOX-1). We examined the presence of LOX-1 on cultured human coronary artery endothelial cells (HCAECs) by RT-PCR, radioligand blot, and binding assays. LOX-1 mRNA and protein were consistently identified in HCAECs. [125I]-ox-LDL binding assay also identified high affinity binding sites for LOX-1 on HCAECs (KD: 1.71 x 10(-8) M: Bmax: 29.7 ng/mg protein). There was no change in LOX-1 expression in HCAECs treated with native-LDL. In contrast, incubation of HCAECs with ox-LDL (10-40 micrograms/ml) increased LOX-1 expression (mRNA and protein). The upregulation of LOX-1 expression appeared to be dependent on ox-LDL concentration. Higher concentration (100 micrograms/ml) however, decreased LOX-1 expression, perhaps related to its cytotoxic effect. These observations indicate that ox-LDL upregulates its own receptor on HCAECs. This phenomenon may explain enhanced uptake of ox-LDL by HCAECs in hyperlipidemia resulting in cellular dysfunction.

Native low density lipoprotein-induced calcium transients trigger VCAM-1 and E-selectin expression in cultured human vascular endothelial cells

Low density lipoprotein (LDL) interactions with the endothelium are thought to play a major role in the development of atherosclerosis. The mechanism(s) involved are not fully understood, although several lines of evidence support the idea that oxidation of LDL increases its atherogenicity. In this study we report for the first time that native LDL (n-LDL) binding to the LDL receptor (100-700 mug/ml) triggers a rise in intracellular calcium which acts as a second messenger to induce vascular cell adhesion molecule-1 (VCAM-1) expression in human coronary artery (HCAEC) and pig aortic endothelial cells (PAEC) and VCAM-1 and E-selectin expression in human aortic (HAEC) endothelial cells. Preincubation of HCAEC with a monoclonal antibody (IgGC7) to the classical LDL receptor or pretreatment with pertussis toxin blocked the n-LDL-induced calcium transients. Preincubation of each of the endothelial cell lines with the calcium chelator 1,-2-bis(o-aminophenoxy)ethane-N,N,N', N'-tetraacetic acetomethyl ester (BAPTA/AM) prevented the expression of VCAM-1 and E-selectin. The increase in VCAM-1 by n-LDL results in increased monocyte binding to HCAEC which can be attenuated by inhibiting the intracellular calcium rise or by blocking the VCAM-1 binding sites. These studies in human and pig endothelial cells link calcium signaling conferred by n-LDL to mechanisms controlling the expression of endothelial cell adhesion molecules involved in atherogenesis.

Localization of distinct F2-isoprostanes in human atherosclerotic lesions

F2-Isoprostanes are prostaglandin (PG) isomers formed in situ in cell membranes by peroxidation of arachidonic acid. 8-epi PGF2alpha and IPF2alpha-I are F2-isoprostanes produced in humans which circulate in plasma and are excreted in urine. Measurement of F2-isoprostanes may offer a sensitive, specific, and noninvasive method for measuring oxidant stress in clinical settings where reactive oxygen species are putatively involved. We determined whether isoprostanes were present in human atherosclerotic lesions, where lipid peroxidation is thought to occur in vivo. 8-epi PGF2alpha ranged from 1.310-3.450 pmol/micromol phospholipid in atherectomy specimens compared with 0.045-0.115 pmol/micromol phospholipid (P < 0.001) in vascular tissue devoid of atherosclerosis. Corresponding values of IPF2alpha-I were 5.6-13.8 vs. 0.16-0.44 pmol/micromol phospholipid (P < 0.001). Levels of the two isoprostanes in vascular tissue were highly correlated (r = 0.80, P < 0.0001). Immunohistochemical studies confirmed that foam cells adjacent to the lipid necrotic core of the plaque were markedly positive for 8-epi PGF2alpha. These cells were also reactive with anti-CD68, an epitope specific for human monocyte/macrophages. 8-epi PGF2alpha immunoreactivity was also detected in cells positive for anti-alpha-smooth muscle actin antibody, which specifically recognizes vascular smooth muscle cells. Our results indicate that 8-epi PGF2alpha and IPF2alpha-I, two distinct F2-isoprostanes and markers of oxidative stress in vivo, are present in human atherosclerotic plaque. Quantitation of these chemically stable products of lipid peroxidation in target tissues, as well as in biological fluids, may aid in the rational development of antioxidant drugs in humans.

Native and gamma radiolysis-oxidized lipoprotein(a) increase the adhesiveness of rabbit aortic endothelium

Accumulation of monocyte-derived foam cells in the arterial intima is a major event in the development of atherogenesis. We have examined whether native and oxidized lipoprotein(a) (Lp(a)) can induce adhesion of monocytic cells to aortic endothelium. The extensive oxidation of paired samples of Lp(a) and low-density lipoprotein (LDL) was achieved by O2.-/OH. free radicals produced by gamma radiolysis of water, leading to similar values for the formation of peroxidation markers (conjugated dienes, TBARS, 8-epi-PGF2alpha) for both Lp(a) and LDL. Rabbit aortic segments were incubated for 5 h in the presence of equimolar concentrations of native and oxidized preparations of Lp(a) and LDL (125 micromol cholesterol/l, corresponding to 40 and 30 mg protein/l for Lp(a) and LDL, respectively). The aortic segments were incubated with rhodamin-isothiocyanate labeled U937 monocytic cells for 30 min and cell adhesion was quantified by fluorescent microscopy. Native Lp(a), and to a larger extent oxidized Lp(a), significantly increased U937 cell adhesion by 2.3 and 2.7 fold compared to controls (P < 0.005 and P < 0.001, respectively). Monocytic cell adhesion was also increased by native LDL (1.6 fold, P < 0.005), and to a greater extent by oxidized LDL (2.3 fold, P < 0.001). Thus native Lp(a) enhances the adhesive properties of the arterial endothelium which may account for its proatherogenic action. Furthermore, our results show that oxidized Lp(a), as well as oxidized LDL, are potent stimuli of monocyte adhesion to endothelial cells.

Nitric Oxide Synthesis Inhibition and Role of P-selectin in Leukocyte Adhesion to Vascular Tissues

BACKGROUND: This study was designed to examine the role of P-selectin expression in leukocyte adhesion to endothelium caused by inhibition of nitric oxide synthesis. METHODS AND RESULTS: Rat aortic rings were treated with the nitric oxide synthesis inhibitor N(omicron)-nitro-l-arginine methyl ester (l-NAME) for 2 hours. Parallel sets of aortic rings were pretreated with the nitric oxide precursor l-arginine or posttreated with a specific monoclonal antibody against P-selectin. Some rings were used for determination of vasoreactivity in response to norepinephrine and acetylcholine, while other rings were incubated with autologous unlabeled leukocytes or Biotin-FITC labeled leukocytes for 30 minutes. Leukocyte adhesion to vascular endothelium was determined by scanning electron microscopy. l-NAME enhanced the contractile response in response to norepinephrine, suppressed the relaxant response to acetyleholine, promoted leukocyte adherence to the endothelium and resulted in P-selectin expression on the aortic endothelium. Pretreatment of aortic rings with l-arginine reversed the l-NAME-mediated changes in vasoreactivity in response to norepinephrine and acetyleholine and attenuated the l-NAME-enhanced leukocyte adhesion to endothelial intima. P-selectin treatment, on the other hand, had no effect on l-NAME-mediated changes. Intraperitoneal administration of l-NAME resulted in a significant decrease in plasma nitrite level, a small, but significant, increase in lung and spleen myeloperoxidase activity, and a significant increase in leukocyte deposition in lung and spleen. The l-NAME-mediated increase in myeloperoxidase activity and leukocyte deposition in the spleen, but not in the lungs, was abolished by treatment of rats with the P-selectin antagonist CY1503 administered 30 minutes prior to l-NAME. CONCLUSIONS: These observations indicate that a reduction in nitric oxide synthesis enhances leukocyte adhesion to aortic endothelium and in visceral tissues. While P-selectin expression is evident in some of the experimental models of leukocyte adhesion to endothelium under conditions of nitric oxide inhibition, the role of P-selectin expression remains unclear.

Absence of P-selectin delays fatty streak formation in mice

P-selectin is expressed on activated endothelium and platelets where it can bind monocytes, neutrophils, stimulated T cells, and platelets. Because recruitment of these cells is critical for atherosclerotic lesion development, we examined whether P-selectin might play a role in atherosclerosis. We intercrossed P-selectin-deficient mice with mice lacking the low density lipoprotein receptor (LDLR) because these mice readily develop atherosclerotic lesions on diets rich in saturated fat and cholesterol. The atherogenic diet stimulated leukocyte rolling in the mesenteric venules of LDLR-deficient mice, and the increase in adhesiveness of the vessels was P-selectin-dependent. Most likely due to the reduced leukocyte interaction with the vessel wall, P-selectin-deficient mice on diet for 8-20 wk formed significantly smaller fatty streaks in the cusp region of the aortae than did P-selectin-positive mice. This difference was more prominent in males. At 37 wk on diet, the lesions in the LDLR-deficient animals progressed to the fibrous plaque stage and were distributed throughout the entire aorta; their size or distribution was no longer dependent on P-selectin. Our results show that P-selectin-mediated adhesion is an important factor in the development of early atherosclerotic lesions, and that adhesion molecules such as P-selectin are involved in the complex process of atherosclerosis.

Nitric oxide and atherosclerosis: possible implications for therapy

Atherosclerosis and hypercholesterolaemia disturb the endothelium-dependent regulation of the vascular tone by the labile liposoluble radical nitric oxide. This defect predisposes to vasospasm and ischaemia, with anginal pain as a clinical manifestation. It is now appreciated that endothelial dysfunction is an early event in atherogenesis, possibly also involving the microcirculation, in which atherosclerosis does not develop. Furthermore, it is becoming clear that nitric oxide, in addition to regulating vasomotion, might also modulate the progression of the disease process. The latter notion could have therapeutic implications.

Cytotoxic and chemotactic potencies of several aldehydic components of oxidised low density lipoprotein for human monocyte-macrophages

We have investigated the cytotoxic and chemotactic potencies of malondialdehyde (MDA), hexanal, 4-hydroxyhexenal (HHE), 4-hydroxynonenal (HNE) and 4-hydroxyoctenal (HOE), which are aldehydes found in oxidised low density lipoprotein (LDL), for human monocyte-macrophages. They were toxic in the following order: hexanal<HHE= HOE< HNE. HNE was toxic at 20 microM and chemotactic at 2.5 microM. The other aldehydes tested had no chemoattractant activity. Our results suggest that HNE arising from LDL oxidation could attract monocytes into the human atherosclerotic lesion. A direct cytotoxic role of aldehydes in foam cell death in the lesion is less likely.