Evidence that dendritic cells infiltrate atherosclerotic lesions in apolipoprotein E-deficient mice

Earlier we reported that atherosclerotic lesions of apoE-deficient mice contained cells which stained positively with anti-S-100 antibody and that cells exhibiting the ultrastructural features of dendritic cells were present in the aortic lesions. These observations suggested that dendritic cells might be involved in mouse atherosclerosis. By employing DEC-205 and MIDC-8 antibodies specific for dendritic cells, the present study has established that dendritic cells indeed accumulate in atherosclerotic lesions of apoE-deficient mice. Finding dendritic cells infiltrating atherosclerotic lesions in apoE-deficient mice offers the possibility of investigating the migratory routes of dendritic cells and their involvement in T-cell activation.     

The human ABCG4 gene is regulated by oxysterols and retinoids in monocyte-derived macrophages

The heptapeptide TT-232 is structurally related to the hypothalamic hormone somatostatin and shows promise as an anticancer drug because of its tumor-specific cytotoxic effects. Apart from the ability to induce apoptosis, the synthetic peptide can trigger an alternative pathway that leads to cell cycle arrest in certain tumor cell systems. We found that pulse treatment with TT-232 blocks the cell cycle G(1)/S transition irreversibly in A431 cells. Investigation of the TT-232 signaling pathway yielded results similar to those reported for somatostatin although its affinity to the somatostatin receptor 1 is significantly reduced. We show that functional protein kinase C (PKC) delta as well as c-Src are necessary mediators of the TT-232 cytostatic effect and we propose a signaling pathway that leads to cell cycle arrest.     

Increased aortic stiffness assessed by pulse wave velocity in apolipoprotein E-deficient mice

Atherosclerosis develops and progresses spontaneously in apolipoprotein E-knockout (apoE-KO) mice. A direct consequence of atherosclerosis is an increase in vascular stiffness. Pulse wave velocity (PWV) has been used to assess the stiffness of large vessels and was found to be increased in patients with atherosclerosis. In the present study, aortic stiffness was assessed by PWV in 4- and 13-mo-old apoE-KO mice and age-matched controls (C57BL/6J). In 13-mo-old apoE-KO mice with extensive atherosclerotic lesions in the aorta (61 +/- 4%), PWV increased significantly (3.8 +/- 0.2 m/s) compared with controls (2.9 +/- 0.2 m/s). Endothelial nitric oxide (EDNO)-mediated vasorelaxation in response to ACh was markedly diminished in the aortic rings isolated from 13-mo-old apoE-KO mice compared with age-matched controls. In contrast, in 4-mo-old apoE-KO mice with only moderate atherosclerotic lesions in the aorta (23 +/- 5%), there were no significant changes in PWV and EDNO-mediated relaxation compared with controls. Blood pressure was not different among the four groups of mice. There were no significant differences in endothelium-independent vascular responses to sodium nitroprusside among different groups investigated. Histological evaluation revealed focal fragmentation of the elastic laminae in the aortic walls of 13-mo-old apoE-KO mice. These results demonstrate for the first time that aortic stiffness determined by PWV increases in 13-mo-old apoE-KO mice. Endothelial dysfunction and elastic destruction in vascular wall caused by atherosclerosis may have contributed.     

Diet and atherosclerosis in apolipoprotein E-deficient mice

Atherosclerosis is a multifactorial, long-lasting process in humans. Accordingly, animal models in which more rapid changes occur can be useful for the study of this process. Among such models are apolipoprotein E-deficient (apoE-/-) mice, which give insight into the human process. ApoE-/- mice show impaired clearing of plasma lipoproteins and develop atherosclerosis in a short time, and hence they are an excellent model in which to assess the impact of dietary factors. This review considers lipid metabolism and inflammation as well as nutritional constituents affecting atherosclerosis, with reference to apoE-/- mice, and discusses the mechanisms through which they act.     

Expression of human apolipoprotein A-II in apolipoprotein E-deficient mice induces features of familial combined hyperlipidemia

Familial combined hyperlipidemia (FCHL) is a common inherited hyperlipidemia and a major risk factor for atherothrombotic cardiovascular disease. The cause(s) leading to FCHL are largely unknown, but the existence of unidentified "major" genes that would increase VLDL production and of "modifier" genes that would influence the phenotype of the disease has been proposed. Expression of apolipoprotein A-II (apoA-II), a high density lipoprotein (HDL) of unknown function, in transgenic mice produced increased concentration of apoB-containing lipoproteins and decreased HDL. Here we show that expression of human apoA-II in apoE-deficient mice induces a dose-dependent increase in VLDL, resulting in plasma triglyceride elevations of up to 24-fold in a mouse line that has 2-fold the concentration of human apoA-II of normolipidemic humans, as well as other well-known characteristics of FCHL: increased concentrations of cholesterol, triglyceride, and apoB in very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and low density lipoprotein (LDL), reduced HDL cholesterol, normal lipoprotein lipase and hepatic lipase activities, increased production of VLDL triglycerides, and increased susceptibility to atherosclerosis. However, FCHL patients do not have plasma concentrations of human apoA-II as high as those of apoE-deficient mice overexpressing human apoA-II, and the apoA-II gene has not been linked to FCHL in genome-wide scans. Therefore, the apoA-II gene could be a "modifier" FCHL gene influencing the phenotype of the disease in some individuals through unkown mechanisms including an action on a "major" FCHL gene. We conclude that apoE-deficient mice overexpressing human apoA-II constitute useful animal models with which to study the mechanisms leading to overproduction of VLDL, and that apoA-II may function to regulate VLDL production.     

Angiotensin II injures the arterial wall causing increased aortic stiffening in apolipoprotein E-deficient mice

Cardiovascular diseases, such as atherosclerosis and hypertension, are associated with arterial stiffening. Previous studies showed that ANG II exacerbated atherosclerosis and induced hypertension and aneurysm formation in apolipoprotein E-deficient (apoE-KO) mice. The aim of the present study was to examine the effects of chronic treatment of ANG II on the arterial elastic properties in apoE-KO mice. We hypothesized that ANG II will injure the arterial wall resulting in increased arterial stiffening. Male apoE-KO mice were infused with either ANG II (1.44 mg. kg(-1). day(-1)) or vehicle (PBS) for 30 days. ANG II treatment accelerated atherosclerosis in the carotid artery by sixfold (P < 0.001) and increased blood pressure by 30% (P < 0.05). Additionally, our data demonstrated that ANG II increased arterial stiffening using both in vivo and in vitro methods. ANG II significantly increased pulse wave velocity by 36% (P < 0.01) and decreased arterial elasticity as demonstrated by a more than 900% increase in maximal stiffening (high strain Young's modulus) compared with vehicle (P < 0.05). These functional changes were correlated with morphological and biochemical changes as demonstrated by an increase in collagen content (60%), a decrease in elastin content (74%), and breaks in the internal elastic lamina in the aortic wall. In addition, endothelium-independent vasorelaxation to sodium nitroprusside was impaired in the aortic rings of ANG II-treated mice compared with vehicle. Thus, the present data indicate that ANG II injures the artery wall in multiple ways and arterial stiffening may be a common outcome of ANG II-induced arterial damage.     

Participation of macrophages in atherosclerotic lesion morphology in LDLr-/- mice

Lystbeige (beige) mice crossed with LDL receptor-deficient (LDLr-/-) mice had a distinct atherosclerotic lesion morphology that was not observed in LDLr-/- mice. This morphology is often associated with a stable plaque phenotype. We hypothesized that macrophage expression of the beige mutation accounted for this distinct morphology. Cultured bone marrow-derived macrophages from LDLr-/- and beige,LDLr-/- mice were compared for their ability to accumulate cholesterol, efflux cholesterol, migrate in response to chemotactic stimuli through Matrigel-coated membranes, and express matrix metalloproteinase 9 (MMP9). No differences in cholesterol metabolism were identified. Beige,LDLr-/- macrophage invasion in vitro appeared to be less than LDLr-/- macrophage invasion but did not achieve significance. Nevertheless, tumor necrosis factor-alpha-induced MMP9 expression, secretion, and enzymatic activity of beige,LDLr-/- macrophages were all significantly decreased compared with those of LDLr-/- macrophages (P < 0.05). For in vivo analyses of macrophage function, bone marrow transplantation (BMT) studies were performed. LDLr-/- mice and beige,LDLr-/- mice were irradiated and reconstituted with wild-type or beige bone marrow from mice expressing green fluorescent protein (GFP). Identification of GFP cells provided for direct identification of donor-derived cells within lesions. Only expression of the beige mutation in the BMT recipients altered the macrophage location and collagen content of the lesions. These results suggested that impaired macrophage function by itself did not account for the stable lesion morphology of beige,LDLr-/- double-mutant mice.     

Differential effect of walnut oil and safflower oil on the serum cholesterol level and lesion area in the aortic root of apolipoprotein E-deficient mice

Walnut oil (WO) is a good source of alpha-linolenic acid. We compared the effects of WO and high-linoleic safflower oil (HLSO) on the serum lipid level and atherosclerosis development in male and female apolipoprotein (apo) E-deficient mice. The WO diet resulted in a higher level of serum cholesterol than with HLSO. Female mice fed on the WO diet had a greater lesion area in the aortic root than did those on the HLSO diet. There was no diet-dependent difference in the level of cholesterol and its oxidation products in the abdominal and thoracic aorta. These results suggest that the unpleasant effects of the WO diet on apo E-deficient mice may be attributable to alpha-linolenic acid.     

Macrophage-derived apolipoprotein E ameliorates dyslipidemia and atherosclerosis in obese apolipoprotein E-deficient mice

Previous studies have demonstrated that macrophage-derived apolipoprotein E (apoE) reduces atherosclerotic lesion formation in lean apoE-deficient ((-/-)) mice. apoE has also been demonstrated to play a role in adipocyte differentiation and lipid accumulation. Because the prevalence of obesity has grown to epidemic proportions, we sought to determine whether macrophage-derived apoE could impact atherosclerotic lesion formation or adipose tissue expansion and inflammation in obese apoE(-/-) mice. To this end, we transplanted obese leptin-deficient (ob/ob) apoE(-/-) mice with bone marrow from either ob/ob;apoE(-/-) or ob/ob;apoE(+/+) donors. There were no differences in body weight, total body adipose tissue, or visceral fat pad mass between recipient groups. The presence of macrophage-apoE had no impact on adipose tissue macrophage content or inflammatory cytokine expression. Recipients of apoE(+/+) marrow demonstrated 3.7-fold lower plasma cholesterol (P < 0.001) and 1.7-fold lower plasma triglyceride levels (P < 0.01) by 12 wk after transplantation even though apoE was present in plasma at concentrations <10% of wild-type levels. The reduced plasma lipids reflected a dramatic decrease in very low density lipoprotein and a mild increase in high-density lipoprotein levels. Atherosclerotic lesion area was >10-fold lower in recipients of ob/ob;apoE(+/+) marrow (P < 0.005). Similar results were seen in leptin receptor-deficient (db/db) apoE(-/-) mice. Finally, when bone marrow transplantation was performed in 4-mo-old ob/ob;apoE(-/-) and db/db;apoE(-/-) mice with preexisting lesions, recipients of apoE(+/+) marrow had a 2.8-fold lower lesion area than controls (P = 0.0002). These results demonstrate that macrophage-derived apoE does not impact adipose tissue expansion or inflammatory status; however, even very low levels of macrophage-derived apoE are capable of reducing plasma lipids and atherosclerotic lesion area in obese mice.     

Oxidized cholesterol metabolites found in human atherosclerotic lesions promote apolipoprotein C-II amyloid fibril formation

Apolipoprotein amyloid deposits and lipid oxidation products are colocalized in human atherosclerotic tissue. In this study we show that the primary ozonolysis product of cholesterol, 3beta-hydroxy-5-oxo-5,6-secocholestan-6-al (KA), rapidly promotes human apolipoprotein (apo) C-II amyloid fibril formation in vitro. Previous studies show that hydrophobic aldehydes, including KA, modify proteins by the formation of a Schiff base with the lysine epsilon-amino group or N-terminal amino group. High-performance liquid chromatography, mass spectrometry, and proteolysis of KA-modified apoC-II revealed that KA randomly modified six different lysine residues, with primarily one KA attached per apoC-II molecule. Competition experiments showed that an aldehyde scavenging compound partially inhibited the ability of KA to hasten apoC-II fibril formation. Conversely, the acid derivative of KA, lacking the ability to form a Schiff base, accelerated apoC-II fibril formation, albeit to a lesser extent, suggesting that amyloidogenesis triggered by KA involves both covalent and noncovalent mechanisms. The viability of a noncovalent mechanism mediated by KA has been observed previously with alpha-synuclein aggregation, implicated in Parkinson's disease. Electron microscopy demonstrated that fibrils formed in the presence of KA had a similar morphology to native fibrils; however, the isolated KA-apoC-II covalent adducts in the absence of unmodified apoC-II formed fibrillar structures with altered ropelike morphologies. KA-mediated fibril formation by apoC-II was inhibited by the addition of the amine-containing compound hydralazine and the lipid-binding protein apoA-I. These in vitro studies suggest that the oxidized small molecule pool could trigger or hasten the aggregation of apoC-II to form amyloid deposits.     

Resveratrol inhibits lipid accumulation in the intestine of atherosclerotic mice and macrophages

Disordered intestinal metabolism is highly correlated with atherosclerotic diseases. Resveratrol protects against atherosclerotic diseases. Accordingly, this study aims to discover novel intestinal proatherosclerotic metabolites and potential therapeutic targets related to the anti‐atherosclerotic effects of resveratrol. An untargeted metabolomics approach was employed to discover novel intestinal metabolic disturbances during atherosclerosis and resveratrol intervention. We found that multiple intestinal metabolic pathways were significantly disturbed during atherosclerosis and responsive to resveratrol intervention. Notably, resveratrol abolished intestinal fatty acid and monoglyceride accumulation in atherosclerotic mice. Meanwhile, oleate accumulation was one of the most prominent alterations in intestinal metabolism. Moreover, resveratrol attenuated oleate‐triggered accumulation of total cholesterol, esterified cholesterol and neutral lipids in mouse RAW 264.7 macrophages by activating ABC transporter A1/G1‐mediated cholesterol efflux through PPAR (peroxisome proliferator‐activated receptor) α/γ activation. Furthermore, we confirmed that PPARα and PPARγ activation by WY14643 and pioglitazone, respectively, alleviated oleate‐induced accumulation of total cholesterol, esterified cholesterol and neutral lipids by accelerating ABC transporter A1/G1‐mediated cholesterol efflux. This study provides the first evidence that resveratrol abolishes intestinal fatty acid and monoglyceride accumulation in atherosclerotic mice, and that resveratrol suppresses oleate‐induced accumulation of total cholesterol, esterified cholesterol and neutral lipids in macrophages by activating PPARα/γ signalling.     

Effects of high-fat,low-cholesterol diets on hepatic lipid peroxidation and antioxidants in apolipoprotein E-deficient mice

The present study describes the effects of several high-fat low-cholesterol antiatherogenic diets on the hepatic lipid peroxidation and hepatic antioxidant systems in apolipoprotein E-deficient mice. Eighty mice were distributed into five groups and fed with regular mouse chow or chow supplemented with coconut, palm, olive and sunflower seed oils. After ten weeks, they were sacrificed and the livers were removed so that lipid peroxidation and -tocopherol concentrations, and superoxide dismutase, glutathione peroxidase and glutathione reductase activities could be measured. The size of the atherosclerotic lesions in the aortas was also measured. Results showed that the diets supplemented with olive oil, palm oil or sunflower seed oil significantly decreased the size of the lesion. However, there was an association between those mice that were on diets supplemented with palm or coconut oils and a significant increase in hepatic lipid peroxidation. This association was not found in animals fed with olive or sunflower seed oils, the diets with the highest content of vitamin E. The dietary content of vitamin E was significantly correlated (r = 0.98; p < 0.05) with the hepatic concentration of this compound. Our study suggests that the high content of vitamin E in olive oil or sunflower seed oil may protect from the undesirable hepatotoxic effects of high-fat diets in apo E-deficient mice and that this should be taken into account when these diets are used to prevent atherosclerosis.     

ERK5/KLF2 activation is involved in the reducing effects of puerarin on monocyte adhesion to endothelial cells and atherosclerotic lesion in apolipoprotein E-deficient mice

Puerarin has properties of anti-oxidation and anti-inflammation, which has been demonstrated protective effects in atherosclerosis and other cardiovascular diseases. However, the detail molecular mechanism still remains unclear. Here, we determined whether the atheroprotective effect of puerarin was by reducing monocyte adhesion and explored the underlying mechanism. The results showed that puerarin dose- and time-dependently reduced oxLDL-induced monocyte THP-1 adhesion to HUVECs and the expression of adhesion-related genes such as VCAM-1, ICAM-1, MCP-1 and IL-8 in HUVECs. Puerarin activated ERK5 phosphorylation and up-regulated expressions of downstream KLF2 and its targeted genes endothelial nitric oxide synthase and thrombomodulin. However, the protective effects were reversed by ERK5/KLF2 pathway inhibitor XDM8-92, BIX02189 or KLF2 siRNA suggesting the pathway involved in the function. The ex vivo assay, in which THP-1 adhesion to endothelium isolated from apoE?/? mice received various treatments further confirmed the results from HUVECs. Finally, we found that the atherosclerotic lesions in both cross sections at aortic root and whole aorta were significantly reduced in high fat-diet (HFD) mice with puerarin treatment compared with the HFD-only mice, but were increased respectively by 76% and 71% in XMD8-92 group, and 82% and 73% in BIX02189 group. Altogether, the data revealed that puerarin inhibited the monocyte adhesion in vitro and in vivo and thus reduced atherosclerotic lesions in apoE?/? mice; the protective effects were mediated by activation of ERK5/KLF2 signaling pathway. Our findings advance the understanding of puerarin function in atherosclerosis and point out a way to prevent the disease.     

Angiotensin II-induced abdominal aortic aneurysm occurs independently of the 5-lipoxygenase pathway in apolipoprotein E-deficient mice

Genetic association studies and pathological analysis of cardiovascular disease specimens implicate a role for the 5-lipoxygenase (5-LO)/leukotriene (LT) pathway in human cardiovascular disease. Previously, we had detected a role for this pathway in the incidence and severity of hyperlipidemic, cholate-containing, diet-induced aortic aneurysm in mice. The goal of the present study was to assess the importance of the 5-LO/LT pathway in angiotensin II (Ang II)-induced murine abdominal aortic aneurysm (AAA) formation. Mice with either genetic (5-LO(-/-)) or pharmacological (MK-0591) inhibition of the 5-LO pathway on an apolipoprotein E-deficient (apoE(-/-)) background were subjected to a normal chow diet with infusion of Ang II (500 ng/kg/min) for 28 days for assessment of AAA incidence and severity. Ang II-induced marked aortic wall remodeling with an incidence of 32, 29 and 40% AAA formation in 5-LO(-/-) apoE(-/-), 5-LO(+/+)apoE(-/-) and 5-LO(+/+)apoE(-/-) mice treated with FLAP inhibitor MK-0591, respectively, with no statistically significant differences in incidence or severity between groups. Abrogation of the 5-LO pathway in mice indicates a lack of role of leukotrienes in Ang II-induced AAA pathogenesis stressing the need for additional non-rodent AAA pre-clinical models to be tested.     

Combined application of rapamycin and atorvastatin improves lipid metabolism in apolipoprotein E-deficient mice with chronic kidney disease

Atherosclerosis arising from the pro-inflammatory conditions associated with chronic kidney disease (CKD) increases major cardiovascular morbidity and mortality. Rapamycin (RAPA) is known to inhibit atherosclerosis under CKD and non-CKD conditions, but it can cause dyslipidemia; thus, the co-application of lipid-lowering agents is recommended. Atorvastatin (ATV) has been widely used to reduce serum lipids levels, but its synergistic effect with RAPA in CKD remains unclear. Here, we analyzed the effect of their combined treatment on atherosclerosis stimulated by CKD in apolipoprotein E-deficient (ApoE^−/−) mice. Oil Red O staining revealed that treatment with RAPA and RAPA＋ ATV, but not ATV alone, significantly decreased the atherosclerotic lesions in the aorta and aortic sinus, compared to those seen in the control (CKD) group. The co-administration of RAPA and ATV improved the serum lipid profile and raised the expression levels of proteins involved in reverse cholesterol transport (LXRα, CYP7A1, ABCG1, PPARγ, ApoA1) in the liver. The CKD group showed increased levels of various genes encoding atherosclerosis-promoting cytokines in the spleen (Tnf-α, Il-6 and Il-1β) and aorta (Tnf-α and Il-4), and these increases were attenuated by RAPA treatment. ATV and RAPA＋ATV decreased the levels of Tnf-α and Il-1β in the spleen, but not in the aorta. Together, these results indicate that, in CKD-induced ApoE^−/− mice, RAPA significantly reduces the development of atherosclerosis by regulating the expression of inflammatory cytokines and the co-application of ATV improves lipid metabolism.     

ATP binding cassette transporter ABCA1 modulates the secretion of apolipoprotein E from human monocyte-derived macrophages.

Apolipoprotein E (apoE) produced by macrophages in the arterial wall protects against atherosclerosis, but the regulation of its secretion by these cells is poorly understood. Here we investigated the contribution of the adenosine triphosphate binding cassette transporters ABCA1 and ABC8 to the secretion of apoE from either primary human monocyte-derived macrophages (HMDM) or human THP1 macrophages. During incubations of up to 6 h, apoE secretion from both THP1 macrophages and HMDM was stimulated by 8-Br-cAMP, which activates ABCA1 expression. The putative ABCA1 inhibitor glyburide and antisense oligonucleotides directed against ABCA1 mRNA significantly reduced apoE secretion from THP1 macrophages and HMDM. Antisense oligonucleotides directed against ABC8 mRNA also inhibited apoE secretion, although this inhibition was less pronounced and consistent than in the case of ABCA1. ApoE secretion from HMDM of ABCA1-deficient patients with Tangier disease was also decreased. ApoE mRNA expression was not affected by inhibition of ABCA1 or ABC8 in normal HMDM or the lack of functional ABCA1 in HMDM from Tangier disease patients. Inhibition of ABCA1 in HMDM prevented the occurrence of anti-apoE-immunoreactive granular structures in the plasma membrane. We conclude that ABCA1 and, to a lesser extent, ABC8 both promote secretion of apoE from human macrophages.     

Paraoxonase 1 protects macrophages from atherogenicity of a specific triglyceride isolated from human carotid lesion

Human atherosclerotic lesions contain oxidized lipids that facilitate further oxidation of macrophages, LDLs, and oxidative stress (OS)-sensitive markers and inhibit the antiatherogenic enzyme paraoxonase 1 (PON1). Our aim was to isolate and identify the oxidizing agent in a human atherosclerotic lesion lipid extract (LLE) and to explore the mechanisms of oxidation and of PON1's effect on the oxidizing agent. Of the five main fractions separated from the LLE, only fraction 2 (F2) promoted macrophage reactive oxygen species (ROS) production via a mechanism requiring mitochondrial involvement, whereas the NADPH oxidase system was not involved. Incubation of F2 with PON1 abridged the former's peroxide value and reduced its capacity to oxidize OS markers. The active agent was a triglyceride composed of palmitic, oleic, and linoleic acids, with 0.3% of its linoleic moiety in oxidized form. Incubation of either F2 or an identical synthetic triglyceride with PON1 reduced their ability to oxidize macrophages, without affecting cellular accumulation of triglycerides. We conclude that macrophage ROS production by LLE occurs in the presence of a specific triglyceride and requires mitochondrial involvement. Lipid peroxide in the triglyceride can also facilitate lipid autoxidation. Both atherogenic pathways are suppressed by PON1, which acts as an antiatherogenic element.     

Selective distribution of oxysterols in atherosclerotic lesions and human plasma lipoproteins

The presence of oxidized sterols (oxysterols) in human serum and lesions has been linked to the initiation and progression of atherosclerosis. Data concerning the origin, identity and quantity of oxysterols in biological samples are controversial and inconsistent. This inconsistency may arise from different analytical methods or handling conditions used by different investigators. In the present study, oxysterol levels and distribution were analyzed by an optimized GC-MS method, in human atherosclerotic coronary and carotid lesions, in atherosclerotic apolipoprotein E deficient mice (E° mice) and in native and in vitro oxidized human low and high density lipoproteins. Oxysterol levels were analyzed with a limit of detection of 0.06 – 0.24 ng, with 25-hydroxycholesterol (25-OH) being the least sensitive. In human coronary and carotid lesions, obtained from endatherectomic samples, 27-hydroxycholesterol (27-OH) was the major oxysterol, with about 85% as sterols esterified to fatty acids. While total cholesterol and oxysterols levels were similar in both kinds of human lesions, oxysterol distribution was significantly different. In coronary lesions the mean levels of 27-OH and 7β-hydroxycholesterol (7β-OH) were 38% and 20% of total oxysterols, whereas in carotid lesions their mean levels were 66% and 5%, respectively. Unlike in human aortic lesions, 27-OH was entirely absent in E° mice, whereas the level of 7α-hydroxycholesterol (7α-OH) was 28% of the total oxysterols, vs. 5% in human coronary lesions. As 27-OH is an enzymatic product of cholesterol oxidation, this finding may indicate that such an enzymatic process does not take place in E° mice.     

Concentration of serum lipids and aortic lesion size in female and male apo E-deficient mice fed docosahexaenoic acid

Apolipoprotein (apo) E-deficient mice were fed an atherogenic diet with either 1% ethyl ester docosahexaenoic acid (DHA) or safflower oil (SO) as a source of linoleic acid for 8 week. Both genders fed DHA had higher proportions of eicosapentaenoic acid and DHA, and lower proportions of linoleic and arachidonic acids in the liver and serum phospholipids than those fed SO. Males fed DHA had greater liver weight and tended to have higher concentrations of serum lipids and liver cholesterol than those fed SO, and there were opposite trends in females. Dietary fats and gender led to no significant effect on lesion sizes in aortic arch and thoracic plus abdominal aorta. These results indicate that the interactive action of sex-related factor(s) with dietary polyunsaturated fatty acids is involved in metabolic changes of serum lipids in apoE-deficient mice, and addition of DHA, compared with addition of SO, is not effective to abolish the atherosclerosis in this animal model.