Clinicopathological significance of lipid peroxidation in carotid plaques

Relationship of the Low-Density Lipoprotein Cholesterol/High-Density Lipoprotein Cholesterol Ratio with a Vulnerable Plaque in Patients with Severe Carotid Artery Stenosis: A Case-Control Study in the Han Chinese Population

BACKGROUND

Carotid plaque is often an important factor in ischemic stroke after it changes from stable to vulnerable, and low-density lipoprotein cholesterol (LDL-c) and high-density lipoprotein cholesterol (HDL-c) are associated with plaque vulnerability. We aimed to investigate whether the LDL-c/HDL-c ratio, an easily available and novel biomarker, is associated with vulnerable plaques and enhances the warning effect on vulnerability compared to LDL-c or HDL-c alone.

METHODS

We conducted a retrospective study of 187 patients with severe CAS admitted to the Department of Vascular Surgery at the Nanjing Drum Tower Hospital from January 2019 to July 2021. They were divided into a stable plaque group and a vulnerable plaque group according to carotid ultrasonography, carotid angiography (CTA), and plaque pathology. Baseline information was collected and compared between the two groups. Correlation analysis was used to determine the degree of correlation between clinical variables. Univariate and multifactor logistic regression analyses were used to examine independent risk factors for vulnerable plaque in patients with severe CAS. Receiver operating characteristic (ROC) curves were used to assess the capacity of LDL-c/HDL-c to predict the occurrence of vulnerable plaque.

RESULTS

The age of the vulnerable plaque group was 68.12 ± 8.90 years, with 85 males (89.91%); the age of the stable plaque group was 68.77 ± 8.43 years, with 70 males (89.74%). Multivariate logistic regression analysis showed that LDL-c/HDL-c, smoking and diabetes were independent risk factors for vulnerable plaque (all P <0.05). The risk of vulnerable plaque was 4.78-fold greater in the highest LDL-c/HDL-c quartile (≥ 2.63) than in the lowest quartile (≤ 1.31) (P-trend <0.001), and the area under the ROC curve for LDL-c/HDL-c (AUC=0.681, P <0.001) was higher than that for LDL-c and HDL-c.

CONCLUSION

LDL-c/HDL-c, smoking and diabetes were independent risk factors for vulnerable plaque in patients with severe CAS, and LDL-c/HDL-c had a higher predictive value for the presence of vulnerable plaque compared with other lipid parameters.

Association of Plasma Marker of Oxidized Lipid with Histologic Plaque Instability in Patients with Peripheral Artery Disease

BACKGROUND

The association between oxidized low-density lipoprotein (OxLDL) and plaque instability in coronary and carotid artery disease is well established. However, the association between OxLDL and the histologic changes of plaque in peripheral artery disease has not been clearly elucidated. This study aims to investigate the association between plasma OxLDL and histologic plaque instability in patients with peripheral artery disease.

METHODS

Prospectively obtained plaques from 48 patients who underwent endovascular atherectomy (n = 20), surgical endarterectomy (n = 9), or bypass surgery (n = 19) for treatment of atherosclerotic femoropopliteal artery disease were evaluated for histologic fibrosis, sclerosis, calcification, necrosis, cholesterol cleft, and foamy macrophages using hematoxylin and eosin, oil red O, and immunohistochemical staining. Unstable plaques were defined as plaques that were positive for foamy macrophages and with lipid content of more than 10% of the total plaque area. Plasma OxLDL levels were measured using an enzyme-linked immunosorbent assay (Mercodia AB, Uppsala, Sweden).

RESULTS

Of the 48 patients, 26 (54%) had unstable plaques. The unstable plaque group was younger, had fewer angiographic total occlusions, less calcification, and more CD68-positive and LOX-1-positive cells than the stable plaque group. Plasma OxLDL levels were significantly higher in the unstable plaque group than in the stable plaque group (57.4 ± 13.9 vs. 47.2 ± 13.6 U/L, P = 0.014). Multivariate analysis revealed that plasma OxLDL level, smoking, angiographic nontotal occlusion, and statin nonuse were independent predictors of unstable plaque.

CONCLUSIONS

Among patients with peripheral artery disease, the histologic instability of femoropopliteal plaque was independently associated with high plasma OxLDL, smoking, nontotal occlusion, and statin nonuse. Further large-scale studies are necessary to evaluate the role of noninvasive OxLDL measurement for predicting plaque instability and future adverse vascular event.

Neopterin and 7,8-dihydroneopterin are generated within atherosclerotic plaques

Plasma neopterin correlates with the level of cardiovascular disease. Neopterin is the oxidation product of 7,8-dihydroneopterin, which is released by γ-interferon-stimulated macrophages. 7,8-Dihydroneopterin is a potent antioxidant, which inhibits lipid oxidation, macrophage cell death and scavenger receptor CD36 expression. The concentration of neopterin within atherosclerotic plaques was measured in tissue removed from carotid and femoral arteries. The excised plaques were cut into 3-mm-thick sections, and each section was analysed for neopterin, total neopterin, cholesterol, lipid peroxides, α-tocopherol and protein-bound 3,4-dihydroxyphenylalanine. Selected plaques were placed in tissue culture, and the media was analysed for 7,8-dihydroneopterin and neopterin release. Total neopterin levels ranged from 14 to 18.8 nmol/g of tissue. Large ranges of values were seen both within the same plaque and between plaques. No correlation between neopterin and any of the other analytes was observed, nor was there any significant trend in levels along the length of the plaques. γ-Interferon stimulation of cultured plaque generated total neopterin concentrations from 1 to 4 nmol/(g 24 h). The level of 7,8-dihydroneopterin generated within the plaque was within the range that inhibits lipid oxidation. The data show that atherosclerotic plaques are extremely dynamic in biochemistry and are the likely source of the plasma 7,8-dihydroneopterin and neopterin.

Serum albumin and biomolecular oxidative damage of human atherosclerotic plaques

OBJECTIVES

To investigate the association of serum albumin (SA) with oxidative damage of human atherosclerotic plaques and the severity of atherosclerosis.

DESIGN AND METHODS

Correlation of the levels of SA with those of lipid and protein oxidation of endarterectomy-removed carotid atherosclerotic plaques; SA and plaque oxidative biomarkers comparison between 2 groups of patients with different severity of atherosclerotic carotid stenosis, i.e. <90% (group I) or ≥90% (group II).

RESULTS

SA was strongly inversely correlated with plaque oxidative damage; SA was lower and plaque oxidative damage higher in group II than group I.

CONCLUSIONS

Lowered SA is associated with oxidative damage of atherosclerotic plaques and the severity of atherosclerosis.

Inhaled diesel emissions alter atherosclerotic plaque composition in ApoE(-/-) mice

Recent epidemiological studies suggest that traffic-related air pollution may have detrimental effects on cardiovascular health. Previous studies reveal that gasoline emissions can induce several enzyme pathways involved in the formation and development of atherosclerotic plaques. As a direct comparison, the present study examined the impact of diesel engine emissions on these pathways, and further examined the effects on vascular lesion pathology. Apolipoprotein E-null mice were simultaneously placed on a high-fat chow diet and exposed to four concentrations, plus a high concentration exposure with particulates (PM) removed by filtration, of diesel emissions for 6 h/day for 50 days. Aortas were subsequently assayed for alterations in matrix metalloproteinase-9, endothelin-1, and several other biomarkers. Diesel induced dose-related alterations in gene markers of vascular remodeling and aortic lipid peroxidation; filtration of PM did not significantly alter these vascular responses, indicating that the gaseous portion of the exhaust was a principal driver. Immunohistochemical analysis of aortic leaflet sections revealed no net increase in lesion area, but a significant decrease in lipid-rich regions and increasing trends in macrophage accumulation and collagen content, suggesting that plaques were advanced to a more fragile, potentially more vulnerable state by diesel exhaust exposure. Combined with previous studies, these results indicate that whole emissions from mobile sources may have a significant role in promoting chronic vascular disease.

Gender differences in short-term effects of atorvastatin on lipid profile, fibrinolytic parameters, and endothelial function

BACKGROUND AND AIM

Little is known about the impact of gender on short-term effects of atorvastatin. We investigated the gender differences in the short-term lipid-lowering and pleiotropic effects of atorvastatin therapy.

METHODS AND RESULTS

Seventy-two consecutive patients including 48 women with primary hypercholesterolemia, were assigned prospectively to treatment with atorvastatin (10mg/day) for 3 months. We measured fasting lipid concentrations, thiobarbituric acid reactive substances (TBARS) as marker of lipid peroxide, fibrinolytic parameters, and endothelial function by flow-mediated vasodilation of the brachial artery (FMD), at baseline and after 3 months of therapy. We assessed the impact of gender on temporal differences in these parameters. In men, atorvastatin decreased total, low-density lipoprotein (LDL), and small, dense LDL-cholesterol concentrations, and increased FMD after 3 months. In women, atorvastatin decreased TBARS, triglyceride, and total, LDL, small, dense LDL, and remnant-like lipoprotein particle-cholesterol concentrations, and increased FMD after 3 months. Fibrinolytic parameters did not change significantly in either men or women. With respect to the percent change in those parameters after 3 months, TBARS (-17.6+/-12.4 vs. -0.4+/-18.8%, p<0.01) and small, dense LDL-cholesterol (-96.7+/-8.3 vs. -68.6+/-29.7%, p<0.01) decreased to a greater degree in women, although the relative changes in other parameters were similar between men and women.

CONCLUSIONS

We found gender differences in some of the lipid altering changes, including TBARS and small, dense LDL-cholesterol concentrations, after short-term atorvastatin therapy, which were greater in women. However, short-term atorvastatin therapy may be beneficial in improving endothelial function equally in both men and women.

Comparison between early and late carotid endarterectomy for symptomatic carotid stenosis in relation to oxidized low-density lipoprotein and plaque vulnerability

OBJECTIVE

Although carotid endarterectomy (CEA), the gold standard in stroke prevention, has been performed in the late stage after the insult, its optimal timing remains unclear. Using biomarkers in plaque and plasma, we evaluated oxidative stress and plaque vulnerability between early and late CEA in symptomatic patients.

METHODS

We compared symptomatic stroke patients who underwent early CEA within 4 weeks of the last insult (group A; n = 15) with those who received CEA in the late stage beyond 4 weeks from the last symptom (group B; n = 57). They were divided into vulnerable (group Av, n = 13; group Bv, n = 33) and stable (group As, n = 2; group Bs, n = 24) subgroups according to the pathologic findings on their plaques. We studied the relationships among their primary symptoms, clinical findings, oxidized low-density lipoprotein levels, and gelatinase A (matrix metalloproteinase [MMP]-9) activity in their plaques and plasma.

RESULTS

Group A had a variety of symptoms; there was no difference in the outcome of CEA between groups A and B. The plaque and plasma oxidized low-density lipoprotein levels were higher in group A than in group B (P < .05). The incidence of pathologically vulnerable plaque was higher in group A than in group B. Plaque oxidized low-density lipoprotein levels and MMP-9 activity were similar in group Av and group Bv and were higher in those groups than in group As and Bs.

CONCLUSIONS

We first demonstrated that vulnerable plaques in patients subjected to early CEA manifested a remarkable increase in oxidized low-density lipoprotein and MMP-9 activation. Our findings suggest that early CEA may be beneficial in the aspect of oxidative stress.

Effect of atorvastatin on type 2 diabetic dyslipidemia

Hyperlipidemia is commonly observed in patients with type 2 diabetes and is an independent risk factor for cardiovascular disease. The authors tested the effect of atorvastatin (10 mg/d) on 110 hyperlipidemic type 2 diabetes patients with low-density lipoprotein cholesterol (LDL-C) levels exceeding 130 mg/d. The primary efficacy end point was the percentage change in LDL-C and high-density lipoprotein cholesterol (HDL-C), and secondary efficacy included the percentage change in apolipoproteins at weeks 6, 12, and 24. The tertiary goal was percentage change in free radical scavenger enzymes and oxidative stress. LDL-C was reduced by 25%, 39.3%, and 49.2%. A similar trend was observed in total cholesterol, triglyceride, non-HDL-C, and apolipoprotein (apo) B-100. HDL-C was raised by 3.2%, 6%, and 8.2%. A similar trend was seen in apo A-1. Copper zinc-superoxide dismutase and glutathione were raised significantly (P < .001); however, changes in glutathione-S-transferase and glutathione peroxidase activities were nonsignificant. Malondialdehyde was decreased significantly (P < .001). Atorvastatin improves the lipoprotein profile and oxidative status in patients with type 2 diabetes.

Cytocidal effects of atheromatous plaque components: the death zone revisited

OBJECTIVE

Earlier we suggested that atheroma lesions constitute a "death zone" containing toxic materials that may cause dysfunction and demise of invading macrophages to prevent the removal of plaque materials. Here we have assessed the cytotoxic effects of nonfractionated gruel and insoluble (ceroid-like) material derived from advanced human atheroma.

METHODS AND RESULTS

The insoluble material within advanced atherosclerotic plaque was isolated following protease K digestion and extensive extraction with aqueous and organic solvents. FTIR, Raman, and atomic absorption spectroscopy suggested that, despite its fluorescent nature, this material closely resembled hydroxyapatite and dentin, but also contained a significant amount of iron and calcium. When added to J774 cells and human macrophages in culture, this insoluble substance was phagocytosed, and progressive cell death followed. However, an even more cytotoxic activity was found in the atheromatous "gruel" that contains abundant carbonyls/aldehydes. Cell death caused by both crude gruel and ceroid could be blocked by preincubating cells with the lipophilic iron chelator salicylaldehyde isonicotinoyl hydrazone, apoferritin, BAPTA/AM, or sodium borohydride, indicating that cellular iron, calcium, and reactive aldehyde(s) are responsible for the observed cytotoxicity.

CONCLUSIONS

Toxic materials within atheromatous lesions include both ceroid and even more cytotoxic lipidaceous materials. The cytotoxic effects of these plaque components may help explain the persistence of atherosclerotic lesions.

Lipid-altering changes and pleiotropic effects of atorvastatin in patients with hypercholesterolemia

In this prospective study, we found beneficial short-term effects from atorvastatin therapy, including effects on low-density lipoprotein subfractions and remnant-like lipoprotein particle cholesterol, antioxidant effects, and alterations in endothelial function that may be important in early benefit from statin therapy; some effects would support much earlier benefit than previously reported. We also found long-term effects of atorvastatin, including decreased plasminogen activator inhibitor type-1 and additional significant alterations in low-density lipoprotein subfractions and endothelial function, supporting benefits from continuous long-term atorvastatin therapy beyond early reversal of hypercholesterolemia.

Time course differences for statin-induced pleiotropic effects in hypercholesterolemic patients

BACKGROUND

It is unclear whether there are temporal differences for the pleiotropic effects for different members of the statin class. The present study investigated differences in the short- and intermediate-term pleiotropic effects of statins in hypercholesterolemic patients.

METHODS

Thirty-five hypercholesterolemic patients were randomly treated with either atorvastatin or cerivastatin for 3 months. We measured fasting lipid concentrations, thiobarbituric acid reactive substances (TBARS), fibrinolytic parameters, and flow-mediated dilation of the brachial artery (FMD) at baseline and after 2 weeks and 3 months of therapy.

RESULTS

After 2 weeks of therapy, atorvastatin decreased the low density lipoprotein (LDL) cholesterol, small, dense LDL cholesterol (34+/-22 vs. 18+/-20%, P<0.01), remnant-like particles (RLP) cholesterol (8.8+/-6.0 vs. 5.1+/-2.6 mg/ml, P<0.01), and TBARS (3.3+/-1.0 vs. 3.1+/-0.9 nmol/ml, P<0.05), and cerivastatin decreased LDL cholesterol. After 3 months of therapy, atorvastatin decreased small dense LDL cholesterol (8+/-13%, P<0.0001) additionally, and cerivastatin decreased small, dense LDL cholesterol (51+/-11 vs. 12+/-22%, P<0.0001) and plasminogen activator inhibitor type 1 (68+/-32 vs. 51+/-21 ng/ml, P<0.05). FMD increased significantly in both groups after 2 weeks, although the relative change in FMD was greater with cerivastatin therapy after 2 weeks than atorvastatin therapy (60+/-78 vs. 23+/-26%, P<0.05). However, FMD was the same for both groups after 3 months (58+/-65 vs. 66+/-61%, NS), because atorvastatin additionally increased FMD. There was no correlation between these pleiotropic effects and the improvement in the lipid profile for either group.

CONCLUSIONS

These findings suggest that the degree of pleiotropic effect as well as the time course for the effect are different among members of the statin class of drugs.

Phospholipids and oxophospholipids in atherosclerotic plaques at different stages of plaque development

We identified and quantified the hydroperoxides, hydroxides, epoxides, isoprostanes, and core aldehydes of the major phospholipids as the main components of the oxophospholipids (a total of 5-25 pmol/micromol phosphatidylcholine) in a comparative study of human atheroma from selected stages of lesion development. The developmental stages examined included fatty streak, fibrous plaque, necrotic core, and calcified tissue. The lipid analyses were performed by normal-phase HPLC with on-line electrospray MS using conventional total lipid extracts. There was great variability in the proportions of the various oxidation products and a lack of a general trend. Specifically, the early oxidation products (hydroperoxides and epoxides) of the glycerophosphocholines were found at the advanced stages of the plaques in nearly the same relative abundance as the more advanced oxidation products (core aldehydes and acids). The anticipated linear accumulation of the more stable oxidation products with progressive development of the atherosclerotic plaque was not apparent. It is therefore suggested that lipid infiltration and/or local peroxidation is a continuous process characterized by the formation and destruction of both early and advanced products of lipid oxidation at all times. The process of lipid deposition appears to have been subject to both enzymatic and chemical modification of the normal tissue lipids. Clearly, the appearance of new and disproportionate old lipid species excludes randomness in any accumulation of oxidized LDL lipids in atheroma.

Cholesteryl ester oxidation products in atherosclerosis

Lipid oxidation products are formed at sites of increased oxidant stress and have been shown to accumulate in atherosclerotic lesions. Although recent studies have focused on the formation and metabolism of oxidized lipids, very little is known about their biological activities and possible (patho)physiological functions. Oxidation of cholesteryl esters containing unsaturated fatty acids leads to the formation of hydroperoxides that are either reduced to alcohols or degrade into biologically active "core-aldehydes". In this review, the mechanisms of formation and metabolic fate of oxidized cholesteryl esters, their occurrence, as well as possible biological activities are discussed. Based on the current knowledge, cholesteryl ester oxidation leads to the formation of biologically active substances, which could actively contribute to the progression of atherosclerotic lesions and their resulting complications.

Does dietary sugar and fat influence longevity?

Simultaneous consideration of the influence of the different types of carbohydrates and fats in human diets on mortality rates (especially the diseases of aging), and the probable retardation of such diseases by caloric restriction (CR) leads to the hypothesis that restriction of foods with a high glycemic index and saturated or hydrogenated fats would avoid or delay many diseases of aging and might result in life extension. Many of the health benefits of CR might thereby be available to humans without the side effects or unacceptability of semi-starvation diets.

Fatty acid oxidation products in human atherosclerotic plaque: an analysis of clinical and histopathological correlates

Markers of lipid peroxidative damage have been shown to be elevated in individuals with risk factors for cardiovascular disease, and human atherosclerotic plaque contains products resulting from lipid peroxidation. In particular, the presence of fatty acid oxidation products such as hydroxyeicosatetraenoic acids (HETEs) has previously been suggested as a marker of plaque instability and symptomatic cerebrovascular disease. The aim of the present study was to quantitate the levels of various oxidation products of linoleic acid (HODEs) and arachidonic acid (HETEs), respectively, in human atherosclerotic plaque tissue and assess their level in relation to plaque histopathology, symptoms of cerebrovascular disease and preexisting atherosclerotic risk factors. We also assessed the correlation between the levels of the hydroxy fatty acid compounds and F(2)-isoprostanes, an established marker of in vivo free radical mediated oxidation. Hydroxy fatty acid oxidation products were identified in all histological subtypes of advanced plaque. However, there were no significant differences in levels between the histopathologically classified sub-groups or between patients symptomatic or asymptomatic for cerebrovascular disease. Arachidonic acid oxidation products were significantly higher in those subjects who also had symptomatic peripheral vascular disease. The level of linoleic acid oxidation products was significantly higher in individuals who consumed alcohol on a regular basis. While F(2)-isoprostanes and fatty acid oxidation products were highly correlated (P<0.01), levels of the hydroxy fatty acid compounds were 20-40-fold higher than F(2)-isoprostanes. Chiral analysis of the plaque extracts indicated that all HODEs and HETEs originated primarily from non-enzymatic lipid peroxidation. While our results do not support previous reports that fatty acid oxidation products such as the HETEs are associated with plaque instability and symptomatic cerebrovascular disease, further work is warranted to determine the potential of these compounds as circulating markers for underlying atherosclerotic disease and lipid peroxidative stress.

Effects of Atorvastatin Therapy on the Low-Density Lipoprotein Subfraction, Remnant-Like Particles Cholesterol, and Oxidized Low-Density Lipoprotein Within 2 Weeks in Hypercholesterolemic Patients

The short- and intermediate-term pleiotropic effects of atorvastatin were investigated in 18 hypercholesterolemic patients, as well as the temporal differences in these pleiotropic effects. Atorvastatin was given for 3 months and fasting lipid concentrations, thiobarbituric acid reactive substances (TBARS), fibrinolytic parameters, and flow-mediated dilation of the brachial artery (FMD) were measured at baseline and after 2 weeks and 3 months of therapy. Atorvastatin reduced the total cholesterol (273+/-34 vs 188+/-31 mg/dl, p<0.0001), low-density lipoprotein-cholesterol (LDL-C: 174+/-28 vs 111+/-23 mg/dl, p<0.0001), small, dense LDL-C (34+/-22 vs 18+/-20%, p<0.01), remnant-like particles cholesterol (RLP-C: 8.8+/-6.0 vs 5.1+/-2.6 mg/ml, p<0.01), and TBARS (3.3+/-1.0 vs 3.1+/-0.9 nmol/ml, p<0.05) after 2 weeks. Atorvastatin decreased the concentration of small, dense LDL-C again after 3 months (8+/-13%, p<0.0001). The plasma concentrations of the fibrinolytic parameters did not change significantly after 3 months of atorvastatin therapy. FMD increased significantly after 2 weeks (5.6+/-2.1 vs 6.3+/-2.0%, p<0.01) and additionally increased after 3 months of therapy (8.3+/-1.9%, p<0.0001). There were no correlations between the pleiotropic effects and the improvement in the lipid profile. The results indicate some short-term pleiotropic effects of atorvastatin therapy within 2 weeks, which may be important with respect to the early benefits of statin therapy.

Oxidized LDL in carotid plaques and plasma associates with plaque instability

OBJECTIVE

Oxidation of LDL plays a significant pathogenic role in atherosclerosis. In this study, we attempted to clarify the correlation between the morphology of human atherosclerotic plaques and the oxidized LDL (OxLDL) levels in plasma and carotid plaques.

METHODS AND RESULTS

OxLDL levels (ng/microg apolipoprotein B) in plasma and carotid plaques from 44 patients undergoing carotid endarterectomy and OxLDL levels in 17 control plasma and 9 normal intima samples were determined by a sandwich ELISA by using specific antibodies against OxLDL (DLH3) and apolipoprotein B. The plaques were immunohistochemically classified as macrophage (Mphi)-rich and Mphi-poor. In paired samples from individual patients, plaque OxLDL was nearly 70 times higher than plasma OxLDL (mean+/-SEM, 11.9+/-1.7 vs 0.18+/-0.01 ng/microg apoB, P<0.0001). The OxLDL level was significantly higher in Mphi-rich- than Mphi-poor plaques (19.6+/-2.8 vs 5.50+/-0.77 ng/microg apoB, P<0.0001) and corresponded with DLH3 antigen positivity of the plaques. In patients with Mphi-rich plaques, plasma OxLDL was significantly higher than in the controls (0.20+/-0.02 vs 0.13+/-0.01 ng/microg apoB, P=0.02).

CONCLUSIONS

Our results suggest that LDL undergoes further oxidation in plaques, and that high plasma and plaque levels of OxLDL are correlated with the vulnerability to rupture of atherosclerotic lesions.