Atherosclerosis regression and high-density lipoproteins

Adsorption of Acylhydroperoxy-Derivatives of Phospholipids from Biomembranes by Blood Plasma Lipoproteins

It has been established that acylhydroperoxy derivatives of phospholipids from oxidized rat liver mitochondria are captured predominantly by LDL particles but not by HDL during co-incubation with blood plasma lipoproteins, which refutes the previously suggested hypothesis about the involvement of HDL in the reverse transport of oxidized phospholipids and confirms the possibility of different mechanisms of lipohydroperoxide accumulation in LDL during oxidative stress.

Comparative Susceptibility to Oxidation of Different Classes of Blood Plasma Lipoproteins

The kinetics of free radical peroxidation of different classes of blood plasma lipoproteins (nanoparticles involved in lipid transport in the body) was studied. The susceptibility of atherogenic low-density lipoproteins (LDLs) to the Cu2+-initiated free radical peroxidation in vitro was found to be more than ten times higher than that of antiatherogenic high density lipoproteins (HDLs). The baseline content of acyl hydroperoxy derivatives of phospholipids (primary products of free radical peroxidation) in the outer layer of LDL particles in vivo measured per particle exceeded the baseline content of these compounds in HDL particles by more than an order of magnitude. The susceptibility to oxidation of the HDL₂ subfraction of HDLs was higher than the susceptibility of total HDL fraction and HDL₃ subfraction. The data obtained confirm an important role of free radical peroxidation of LDLs in the molecular mechanisms of vascular wall damage in atherosclerosis.

Translating the effects of statins: from redox regulation to suppression of vascular wall inflammation

Vascular oxidative stress is a key feature of atherogenesis, and targeting vascular redox signalling is a rational therapeutic goal in vascular disease pathogenesis. 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors or statins are potent lipid-lowering drugs that improve cardiovascular outcomes. It is now widely accepted that cardiovascular disease prevention by statins is dependent not only on their lipid lowering effects, but also on their beneficial effects on vascular redox signalling. Cell culture and animal models have provided important findings on the effects of statins on vascular redox and nitric oxide bioavailability. Recent evidence from studies on human vessels has further enhanced our understanding of the "pleiotropic" effects of statins on vascular wall. Reversal of endothelial dysfunction in human vessels by statins is dependent on the mevalonate pathway and Rac1 inhibition. These critical steps are responsible for reducing NADPH-oxidase activity and improving tetrahydrobiopterin bioavailability and nitric oxide synthase (NOS) coupling in human vessels. However, mevalonate pathway inhibition has been also held responsible for some of the side effects observed after statin treatment. In this review we summarise the existing knowledge on the effects of statins on vascular biology by discussing key findings from basic science as well as recent evidence from translational studies in humans. Finally, we discuss emerging aspects of statin pleiotropy, such as their effects on adipose tissue biology and adipokine synthesis that may light additional mechanistic links between statin treatment and improvement of clinical outcome in primary and secondary prevention.

I4, a synthetic anti-diabetes agent, attenuates atherosclerosis through its lipid-lowering, anti-inflammatory and anti-apoptosis properties

Here, we investigated whether I₄, which was initially developed as a hypoglycemic agent, possesses anti-atherosclerotic activity and attempted to elucidate the probable mechanism of action underlying this activity. ApoE^-/- mice were fed a Western diet and simultaneously administered I₄, glimepiride, or pioglitazone once daily for 12 weeks, and the atherosclerotic vascular lesions, lipid content, and expression levels of LOX-1, ICAM-1, VCAM-1 and Bax/Bcl-2 in mouse aortas were assessed. RAW264.7 macrophage-derived foam cells were obtained via ox-LDL stimulation to investigate the lipid-lowering, anti-atherosclerotic inflammation and anti-apoptotic effect of I₄. The data indicated that I₄ significantly decreased the lipid accumulation in the circulation and tissue, especially for TG and FFA levels (p < 0.05 vs model group), alleviating the arterial and liver lesions induced by lipotoxicity. Its lipid-reducing effects may due to LOX-1and CD36 expression suppression. I₄, at doses of 20 mg/kg and 10 mg/kg, significantly decreased serum IL-6, IL-1β, and TNF-α production and suppressed the expression of p-ERK, p-p38, VCAM-1 and ICAM-1 protein. I₄ attenuated atherosclerotic inflammation by blocking NF-κB nuclear translocation, suppressing MAPK/NF-κB signaling pathway and diminishing NF-κB-VCAM-1 promoter region binding. Additionally, I₄ suppressed p-p53 and cleaved-caspase-3 expression to inhibit foam cell apoptosis induced by ox-LDL uptake. Overall, I₄ exerts potent inhibitory effects on atherosclerosis onset and development.

Research advances in the relationship between nonalcoholic fatty liver disease and atherosclerosis

Nonalcoholic fatty liver disease (NAFLD) is a metabolic stress-induced liver disease that is closely related not only to genetic susceptibility but also to insulin resistance and highly linked with metabolic syndrome. In recent years, the prevalence of NAFLD has increased rapidly, paralleling the epidemic of type 2 diabetes mellitus and obesity leading to cardiovascular disease. It has been demonstrated that NAFLD is highly associated with atherosclerosis. With recently gained knowledge, it appears that NAFLD may induce insulin resistance, dyslipidemia, oxidative stress, inflammation, and fluctuation of adipokines associated with atherosclerosis. In this review, we aimed to summarize recent discoveries related to both NAFLD and atherosclerosis, and to identify possible mechanisms linking them.

HDL and CER-001 Inverse-Dose Dependent Inhibition of Atherosclerotic Plaque Formation in apoE-/- Mice: Evidence of ABCA1 Down-Regulation

OBJECTIVE

CER-001 is a novel engineered HDL-mimetic comprised of recombinant human apoA-I and charged phospholipids that was designed to mimic the beneficial properties of nascent pre-ß HDL. In this study, we have evaluated the dose-dependent regulation of ABCA1 expression in vitro and in vivo in the presence of CER-001 and native HDL (HDL3).

METHODS AND RESULTS

CER-001 induced cholesterol efflux from J774 macrophages in a dose-dependent manner similar to natural HDL. A strong down-regulation of the ATP-binding cassette A1 (ABCA1) transporter mRNA (- 50%) as well as the ABCA1 membrane protein expression (- 50%) was observed at higher doses of CER-001 and HDL3 compared to non-lipidated apoA-I. In vivo, in an apoE-/- mouse "flow cessation model," in which the left carotid artery was ligatured to induce local inflammation, the inhibition of atherosclerotic plaque burden progression in response to a dose-range of every-other-day CER-001 or HDL in the presence of a high-fat diet for two weeks was assessed. We observed a U-shaped dose-response curve: inhibition of the plaque total cholesterol content increased with increasing doses of CER-001 or HDL3 up to a maximum inhibition (- 51%) at 5 mg/kg; however, as the dose was increased above this threshold, a progressively less pronounced inhibition of progression was observed, reaching a complete absence of inhibition of progression at doses of 20 mg/kg and over. ABCA1 protein expression in the same atherosclerotic plaque was decreased by-45% and-68% at 50 mg/kg for CER-001 and HDL respectively. Conversely, a-12% and 0% decrease in ABCA1 protein expression was observed at the 5 mg/kg dose for CER-001 and HDL respectively.

CONCLUSIONS

These data demonstrate that high doses of HDL and CER-001 are less effective at slowing progression of atherosclerotic plaque in apoE-/- mice compared to lower doses, following a U-shaped dose-response curve. A potential mechanism for this phenomenon is supported by the observation that high doses of HDL and CER-001 induce a rapid and strong down-regulation of ABCA1 both in vitro and in vivo. In conclusion, maximally efficient HDL- or CER-001-mediated cholesterol removal from atherosclerotic plaque is achieved by maximizing macrophage-mediated efflux from the plaque while minimizing dose-dependent down-regulation of ABCA1 expression. These observations may help define the optimal dose of HDL mimetics for testing in clinical trials of atherosclerotic burden regression.

Correlation of VEGF genetic polymorphisms and lipid profile to aortic calcification

BACKGROUND

Aortic calcification is developed due to accumulation of a large amount of calcium in the aorta of the heart and it is the leading cause of aortic valve replacement and third leading cause of cardiovascular disease. The purpose of this study was to investigate the relation between aortic calcification and VEGF SNPs (-2578C>A, -1154G>A and +936C>T) and to evaluate the association of these SNPs with biochemical parameter in relation to aortic calcification.

METHODS

Aortic calcification was diagnosed by examining the posteroanterior chest X-rays by a radiologist and graded into four groups. The real-time polymerase chain reaction with melting curve analysis in LightCycler was used to genotype the VEGF SNPs.

RESULTS

Among the VEGF SNPs, a significant genetic difference was found only between the aortic calcification and control group with VEGF SNP -2578C>A but haplotypes T-A-A of (+936/-1154/-2578) were significantly different in control and aortic calcification and could enhance the aortic calcification development. By regression analysis, it was found that age, hypertension, diabetes, dyslipidemia, and hyperhomocysteinemia were found significantly different with the different genotypes of VEGF SNPs which may induce aortic calcification development.

CONCLUSION

Age, hypertension, diabetes, dyslipidemia, and hyperhomocysteinemia were established as aggravating factors for the aortic calcification in association with different VEGF genotypes.

P2Y13 receptor regulates HDL metabolism and atherosclerosis in vivo

High-density lipoprotein (HDL) is known to protect against atherosclerosis by promoting the reverse cholesterol transport. A new pathway for the regulation of HDL-cholesterol (HDL-c) removal involving F1-ATPase and P2Y13 receptor (P2Y13R) was described in vitro, and recently in mice. However, the physiological role of F1-ATPase/P2Y13R pathway in the modulation of vascular pathology i.e. in the development of atherosclerotic plaques is still unknown. We designed a specific novel agonist (CT1007900) of the P2Y13R that caused stimulation of bile acid secretion associated with an increased uptake of HDL-c in the liver after single dosing in mice. Repeated dose administration in mice, for 2 weeks, stimulated the apoA-I synthesis and formation of small HDL particles. Plasma samples from the agonist-treated mice had high efflux capacity for mobilization of cholesterol in vitro compared to placebo group. In apoE^−/− mice this agonist induced a decrease of atherosclerotic plaques in aortas and carotids. The specificity of P2Y13R pathway in those mice was assessed using adenovirus encoding P2Y13R-shRNA. These results demonstrate that P2Y13R plays a pivotal role in the HDL metabolism and could also be a useful therapeutic agent to decrease atherosclerosis. In this study, the up-regulation of HDL-c metabolism via activation of the P2Y13R using agonists could promote reverse cholesterol transport and promote inhibition of atherosclerosis progression in mice.

Genetic Loci for Coronary Calcification and Serum Lipids Relate to Aortic and Carotid Calcification

Background—

Atherosclerosis in different vessel beds shares lifestyle and environmental risk factors. It is unclear whether this holds for genetic risk factors. Hence, for the current study genetic loci for coronary artery calcification and serum lipid levels, one of the strongest risk factors for atherosclerosis, were used to assess their relation with atherosclerosis in different vessel beds.

Methods and Results—

From 1987 persons of the population-based Rotterdam Study, 3 single-nucleotide polymorphisms (SNPs) for coronary artery calcification and 132 SNPs for total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol or triglycerides were used. To quantify atherosclerotic calcification as a marker of atherosclerosis, all participants underwent nonenhanced computed tomography of the aortic arch and carotid arteries. Associations between genetic risk scores of the joint effect of the SNPs and of all calcification were investigated. The joint effect of coronary artery calcification–SNPs was associated with larger calcification volumes in all vessel beds (difference in calcification volume per SD increase in genetic risk score: 0.15 [95% confidence interval, 0.11–0.20] in aorta, 0.14 [95% confidence interval, 0.10–0.18] in extracranial carotids, and 0.11 [95% confidence interval, 0.07–0.16] in intracranial carotids). The joint effect of total cholesterol SNPs, low-density lipoprotein SNPs, and of all lipid SNPs together was associated with larger calcification volumes in both the aortic arch and the carotid arteries but attenuated after adjusting for the lipid fraction and lipid-lowering medication.

Conclusions—

The genetic basis for aortic arch and carotid artery calcification overlaps with the most important loci of coronary artery calcification. Furthermore, serum lipids share a genetic predisposition with both calcification in the aortic arch and the carotid arteries, providing novel insights into the cause of atherosclerosis.

Paraoxonase 1 in chronic kidney failure

In this review we summarize the findings from the literature and our own laboratory on the decreased PON1 activity in renal failure, the mechanisms proposed and the effect of interventions. In addition to profound alterations in lipoproteins, reduced serum PON1 activity has been clearly established in the past decade and could contribute to accelerated development of atherosclerosis in ESRD and in HD. PON1 lactonase activity is lower in ESRD patients. Hemodialysis partially restores PON1 lactonase and the other activities. PON1 activity recovery after dialysis suggests that uremic toxins may play a mechanistic role in PON1 inactivation. Lower PON1 activity in CRF patients is associated with low thiol concentration, high CRP, and is beneficially enhanced with vitamin C and flavonoids. Changes in HDL subclasses, namely lower HDL₃ in these patients may also play a role in PON1 lower activity. Future research should focus on: (1) mechanistic studies on causes for low PON1 activity and mass; (2) prospective studies focusing on whether there is an added predictive value in measuring PON1 activity (and PON1 activity in HDL₃) in this patient population; (3) intervention studies attempting to increase PON1 activity.

High-density lipoprotein loses its anti-inflammatory capacity by accumulation of pro-inflammatory-serum amyloid A

AIMS

High-density lipoprotein (HDL) is known to have potent anti-inflammatory properties. Monocyte chemoattractant protein-1 is an important pro-inflammatory cytokine in early atherogenesis. There is evidence that HDL can lose its protective function during inflammatory disease. In patients with end-stage renal disease (ESRD), epidemiological studies have documented that the inverse correlation between HDL-cholesterol and cardiovascular risk is lost. Many structural modifications leading to reduced HDL function have been characterized, but the functional consequences are not fully understood.

METHODS AND RESULTS

We showed that HDL from patients with ESRD has a lower anti-inflammatory potential by reduced inhibition of monocyte chemoattractant protein-1 formation in vascular smooth muscle cells. Via a proteomic approach, we identified proteins in HDL from ESRD patients exerting pro-inflammatory actions. By chromatographic separation of proteins and mass-spectrometric analysis, we found serum amyloid A (SAA) to be one molecule acting as a potent pro-inflammatory protein. SAA is enriched in HDL from ESRD patients, correlating with reduced anti-inflammatory capacity. In SAA signal transduction, activation of formyl-peptide receptor 2 is involved. SAA enrichment in HDL of healthy subjects reduced the anti-inflammatory capacity of HDL and correlated with its decreased function.

CONCLUSION

These results suggest that SAA enrichment of HDL during disease conditions contributes to the decreased protective function. It is a novel finding that SAA acts as a pro-inflammatory molecule to reduce the anti-inflammatory properties of HDL.

Long-term curcumin administration protects against atherosclerosis via hepatic regulation of lipoprotein cholesterol metabolism

SCOPE

Atherosclerosis is a major cause of cardiovascular disease caused by high cholesterol. Stains are widely prescribed to lower cholesterol levels, but natural dietary compounds may also be effective. Therefore, we studied the effect of the natural dietary compound curcumin on atherosclerosis and its underlying mechanisms based on plasma and hepatic lipid metabolism.

METHODS AND RESULTS

LDLR(-/-) mice were fed a high-cholesterol diet and treated with curcumin, lovastatin or control (n=10 per group) for 18 wk. Aortic arch sections revealed curcumin ameliorated early atherosclerotic lesions, lipid infiltration, ICAM-1 and VCAM-1 localization, similar to lovastatin treatment. Furthermore, curcumin lowered plasma cholesterol, triglycerides, LDL cholesterol and Apo B levels as well as CETP activity, while curcumin increased plasma HDL cholesterol and liver Apo A-I expression, similar to lovastatin treatment. Curcumin caused transcriptional inhibition of HMG-CoA reductase, independent of ACAT1 and ACAT2 expression. Hepatic PPARα and LXRα expression was upregulated by curcumin treatment. Hepatic complement factor D (Cfd) and systemic CRP levels, markers of immune complement pathway activation, were significantly reduced by curcumin treatment.

CONCLUSION

Long-term curcumin treatment lowers plasma and hepatic cholesterol and suppresses early atherosclerotic lesions comparable to the protective effects of lovastatin. The anti-atherogenic effect of curcumin is mediated via multiple mechanisms including altered lipid, cholesterol and immune gene expression.