Similarity in the distribution of F(2)-isoprostanes in the lipid subfractions of atherosclerotic plaque and in vitro oxidised low density lipoprotein

Relationship between subclasses low-density lipoprotein and carotid plaque

Backgound

Low-density lipoprotein (LDL) cholesterol can lead to the occurrence of atherosclerotic plaques, but patients with normal LDL still have atherosclerotic plaques in clinical practice. With the proposal of LDL subclass, this experiment investigated the relationship between the LDL content of different subclasses and the stability of carotid plaques.

Methods

Plaque stability was suggested by carotid ultrasound results. 37 patients with stable plaques were classified into one group and 41 patients with unstable plaques were classified into another group. The data of age, glycosylated hemoglobin (Ghb), and homocysteine (Hcy) were collected. The contents of LDL subclasses were measured by LIPOPRINT system. The data of total cholesterol (TC), LDL cholesterol, and triglyceride (TG) were collected. The plaque stability was assessed by carotid artery color Doppler ultrasound and the intima-media thickness (IMT) was measured.

Results

The levels of LDL-1 subclass 19.00 (13.00, 27.50) and LDL-2 subclass (21.62 ± 7.24) in the stable plaque group were higher than those in the unstable plaque group (p < 0.05). The levels of LDL-3 subclass (12.24 ± 4.58), LDL-4 subclass 5.00 (2.00, 9.00), and sd-LDL 0 (0.00, 3.00) in the unstable plaque group were higher than those in the stable plaque group (p < 0.05). LDL-1 subclass (adjusted OR = 0.923 and p < 0.05), and LDL-3 subclass (adjusted OR = 1.176 and p < 0.05) were independent risk factors for plaque stability.

Conclusion

Elevated LDL1 is associated with stable plaques whereas LDL3 was found associated with unstable plaques.

Lipid Peroxidation in Atherosclerotic Cardiovascular Diseases

Significance: Atherosclerotic cardiovascular diseases (ACVDs) continue to be a primary cause of mortality worldwide in adults aged 35-70 years, occurring more often in countries with lower economic development, and they constitute an ever-growing global burden that has a considerable socioeconomic impact on society. The ACVDs encompass diverse pathologies such as coronary artery disease and heart failure (HF), among others. Recent Advances: It is known that oxidative stress plays a relevant role in ACVDs and some of its effects are mediated by lipid oxidation. In particular, lipid peroxidation (LPO) is a process under which oxidants such as reactive oxygen species attack unsaturated lipids, generating a wide array of oxidation products. These molecules can interact with circulating lipoproteins, to diffuse inside the cell and even to cross biological membranes, modifying target nucleophilic sites within biomolecules such as DNA, lipids, and proteins, and resulting in a plethora of biological effects. Critical Issues: This review summarizes the evidence of the effect of LPO in the development and progression of atherosclerosis-based diseases, HF, and other cardiovascular diseases, highlighting the role of protein adduct formation. Moreover, potential therapeutic strategies targeted at lipoxidation in ACVDs are also discussed. Future Directions: The identification of valid biomarkers for the detection of lipoxidation products and adducts may provide insights into the improvement of the cardiovascular risk stratification of patients and the development of therapeutic strategies against the oxidative effects that can then be applied within a clinical setting.

Polar head groups are important for barrier-protective effects of oxidized phospholipids on pulmonary endothelium

We have previously described protective effects of oxidized 1-palmitoyl-2-arachidonoyl- sn-glycero-3-phosphocholine (OxPAPC) on pulmonary endothelial cell (EC) barrier function and demonstrated the critical role of cyclopentenone-containing modifications of arachidonoyl moiety in OxPAPC protective effects. In this study we used oxidized phosphocholine (OxPAPC), phosphoserine (OxPAPS), and glycerophosphate (OxPAPA) to investigate the role of polar head groups in EC barrier-protective responses to oxidized phospholipids (OxPLs). OxPAPC and OxPAPS induced sustained barrier enhancement in pulmonary EC, whereas OxPAPA caused a transient protective response as judged by measurements of transendothelial electrical resistance (TER). Non-OxPLs showed no effects on TER levels. All three OxPLs caused enhancement of peripheral EC actin cytoskeleton. OxPAPC and OxPAPS completely abolished LPS-induced EC hyperpermeability in vitro, whereas OxPAPA showed only a partial protective effect. In vivo, intravenous injection of OxPAPS or OxPAPC (1.5 mg/kg) markedly attenuated increases in the protein content, cell counts, and myeloperoxidase activities detected in bronchoalveolar lavage fluid upon intratracheal LPS instillation in mice, although OxPAPC showed less potency. All three OxPLs partially attenuated EC barrier dysfunction induced by IL-6 and thrombin. Their protective effects against thrombin-induced EC barrier dysfunction were linked to the attenuation of the thrombin-induced Rho pathway of EC hyperpermeability and stimulation of Rac-mediated mechanisms of EC barrier recovery. These results demonstrate for the first time the essential role of polar OxPL groups in blunting the LPS-induced EC dysfunction in vitro and in vivo and suggest the mechanism of agonist-induced hyperpermeability attenuation by OxPLs via reduction of Rho and stimulation of Rac signaling.

Application of gas chromatography-mass spectrometry for analysis of isoprostanes: their role in cardiovascular disease

Cardiovascular disease (CVD) is the major cause of death in the Western hemisphere. Oxidative stress is involved in the pathophysiology of cancer, neurodegenerative conditions and CVD. Lipid peroxidation is one of the oxidative modifications possible in biological systems. The isoprostanes are derivatives of one specific lipid, i.e., arachidonic acid, after lipid peroxidation. Several isoprostanes have been identified in biological tissues and fluids, among them 8-iso prostaglandin F2alpha (8-iso-PGF2alpha, 8-epi-PGF2alpha, iPF2alpha-III, 15-F2t-IsoP) and its metabolite, 2,3-dinor-4,5-dihydro-8-iso-PGF2alpha. The isoprostanes are reliable in vivo markers of lipid peroxidation in humans: they are endogenously formed, characteristic in structure, ubiquitous in nature, stable in- and ex vivo and reliably quantitatable. In this Review, different analytical approaches will be discussed including immunologic, chromatographic and spectrometric techniques with the main emphasis on mass spectrometry. Analysis of isoprostanes applying radio immunoassay (RIA), enzyme immunoassay (EIA), high performance-liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-tandem MS), gas chromatography-mass spectrometry (GC-MS) and GC-tandem MS will be exemplified in the field of cardiovascular research. Results from several clinical studies are included indicating the validity of isoprostanes as surrogate parameters of oxidative stress in cardiovascular disease.

8-isoprostane increases scavenger receptor A and matrix metalloproteinase activity in THP-1 macrophages, resulting in long-lived foam cells

BACKGROUND

Oxidative stress is a key factor in atherogenesis, in which it is closely associated with the inflammation and formation of bioactive lipids. Although 8-isoprostane is regarded as a reliable marker of oxidative stress in vivo, the pathogenic role of this F(2)-isoprostane in atherogenesis is far from clear. Based on the important role of foam cells in the initiation and progression of atherosclerosis we hereby examined the ability of 8-isoprostane to modulate oxidized (ox)LDL-induced foam cell formation and the function of these cells, particularly focusing on the effect on matrix degradation.

METHODS AND RESULTS

8-isoprostane (10 micro M) augmented the oxLDL-induced (20 micro g mL(-1)) lipid accumulation of THP-1 macrophages evaluated by Oil-Red-O staining and lipid mass quantification (colourimetric assay). Additionally, 8-isoprostane induced the expression of the scavenger receptor A type 1 (MSR-1) [mRNA and protein level], assessed by RT-PCR and Western blotting, respectively. Moreover, 8-isoprostane counteracted the oxLDL-induced apoptosis of these cells, involving both mitochondrial-protective and caspase-suppressive mechanisms. Along with these changes, 8-isoprostane increased the oxLDL-induced gene expression of matrix metalloproteinase (MMP)-9 and its endogenous inhibitor [i.e. tissue inhibitor of MMP (TIMP)-1] accompanied by enhanced total MMP activity.

CONCLUSIONS

We show that 8-isoprostane increases foam cell formation at least partly by enhancing MSR-1 expression and by inhibiting apoptosis of these cells, inducing long-lived foam cells with enhanced matrix degrading capacity. Our findings further support a role for 8-isoprostane not only as a marker of oxidative stress in patients with atherosclerotic disorders, but also as a mediator in atherogenesis and plaque destabilization.

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.

Exchange of unsaturated fatty acids between adipose tissue and atherosclerotic plaque studied with artificial neural networks

The linoleic C18:2 (n-6) and linolenic C18:3 (n-3) are recognized as essential components of the diet. Free radical peroxidation of essential fatty acids (EFAs) present in lipoproteins produces oxidized low-density lipoproteins which play a critical role in the development of atherosclerosis. The accumulation of EFAs in the vascular wall and correlations between their content in the adipose tissue and atherosclerotic plaque have been confirmed. The present study was undertaken to determine the usefulness of a neural network for studying the exchange between tissues of linoleic, alpha-linolenic, and arachidonic acids-three fatty acids with a well-understood metabolism. Atheromatous plaques, adipose tissue, and serum were obtained from 31 patients who underwent surgery due to atherosclerotic stenosis of the abdominal aorta, iliac or femoral arteries. Fatty acids were extracted and separated as methyl esters using gas chromatography. Statistical analysis was done with STATISTICA neural networks package. Several correlations reported previously were corroborated and factors modifying the content of individual EFAs in adipose tissue and atherosclerotic plaque were revealed. Artificial neural networks (ANNs) were used to determine factors modifying the content of linoleic, alpha-linolenic, and arachidonic acids in human atheromatous plaques. The mechanism of exchange of some fatty acids between the adipose tissue, atheromatous plaque, and plasma is discussed. The results provide evidence for an effective mechanism of tissue uptake and turnover of linoleic acid. Reduced plasma levels of this acid are compensated by release from adipose tissue and atheromatous plaque. While alpha-linolenic acid is continuously taken up by the plaque, adipose tissue absorbs this acid to a certain level only. The dynamics of exchange of arachidonic acid between adipose tissue and atheromatous plaque reflects a minor role for adipose tissue in determining plaque content of this acid, suggesting that "de novo" synthesis is the chief source of arachidonic acid in plaques.