[Epigenetics in atherosclerosis]. / Epigenética en la arteriosclerosis.

The association studies based on candidate genes carried on for decades have helped in visualizing the influence of the genetic component in complex diseases such as atherosclerosis, also showing the interaction between different genes and environmental factors. Even with all the knowledge accumulated, there is still some way to go to decipher the individual predisposition to disease, and if we consider the great influence that environmental factors play in the development and progression of atherosclerosis, epigenetics is presented as a key element in trying to expand our knowledge on individual predisposition to atherosclerosis and cardiovascular disease. Epigenetics can be described as the discipline that studies the mechanisms of transcriptional regulation, independent of changes in the sequence of DNA, and mostly induced by environmental factors. This review aims to describe what epigenetics is and how epigenetic mechanisms are involved in atherosclerosis.

Polymorphisms in LPL, CETP, and HL protect HIV-infected patients from atherogenic dyslipidemia in an allele-dose-dependent manner.

HIV-infected patients treated with highly active antiretroviral therapy (HAART) may be predisposed to a lipid profile, associated with increased cardiovascular risk, derived from having high triglycerides (TG) and low high-density lipoprotein cholesterol (HDLc) levels. We propose that genetic variability leaves some HIV-infected patients more predisposed to this lipid profile than others. We performed a cross-sectional, observational study including 321 antiretroviral-treated HIV-infected patients classified as normolipidemic (n=173) or presenting with high TG (≥1.7 mmol/liter) and low HDLc [<1.02 (men) or 1.28 mmol/liter (women)] (n=148) to investigate the impact of 13 polymorphisms of 9 genes affecting lipid metabolism (APOA5, APOC3, LPL, CETP, HL, MTP, APOE, LRP5, and VLDLR genes). The polymorphism rs328 in LPL was 40% significantly more frequent in normolipidemics (p=0.018), and in the same group, polymorphisms rs708272 in CETP and rs1800588 in HL were 10% significantly more frequent (p=0.037 for both polymorphisms). Patients who presented a combination of one to six alleles from these polymorphisms had 10% increased HDLc levels [1.13 (0.40) vs. 1.24 (0.23) mmol/liter, p=0.002] and a trend toward lower triglycerides [2.23 (2.34) vs. 1.89 (1.24) mmol/liter] and lower remnant-like particle cholesterol (RLPc) [16.41 (11.42) vs. 12.99 (11.69) mmol/liter]. This effect was dependent on the number of protective alleles and independent of the regimen administered. Polymorphisms in LPL, CETP, and HL protect HIV-infected patients from developing the dyslipidemia derived from high TG and low HDLc levels in a dose-dependent manner.

Cytotoxic effects of the lipid peroxidation product 2,4-decadienal in vascular smooth muscle cells.

It is well known that oxidized LDL can be cytotoxic to smooth muscle cells (SMC) and then contribute to the progression of atherosclerosis. Nevertheless, which oxidized compound and which mechanism are involved in cell death is still under study. In this work we have studied the role of two representative apolar aldehydes (hexanal and 2,4-decadienal (2,4-DDE)), derived from polyunsaturated fatty acids oxidation, on human SMC cytotoxicity. Cell cytotoxicity was assessed by means of lactate deshydrogenase (LDH) release, cell morphology and DNA fragmentation. Results showed that hexanal up to 50 microM for 24 h was not cytotoxic to cells. However, 2,4-DDE at 50 microM for 24 h induced a 48% LDH leakage. The observed cytotoxic effect of 2,4-DDE was not due to a programmed cell death as no DNA ladder was detected. After aldehydes exposition a decreased expression of p53 and c-myc mRNA, genes involved in cell death regulation, was also demonstrated by RT-PCR. These observations suggest that 2,4-DDE may be the molecular cause of lipid oxidation cytotoxicity to human vascular SMC. By inducing cell necrosis in advanced stages, lipid oxidation may contribute to the cell debris core which is growing in the atherosclerotic lesion leading to a weakened and unstable plaque.

Increased concentrations of circulating vitamin E in carriers of the apolipoprotein A5 gene - 1131T>C variant and associations with plasma lipids and lipid peroxidation.

The aim of this study was to investigate the effects of the apolipoprotein A5 (APOA5) 1131T>C gene variant on vitamin E status and lipid profile. The gene variant was determined in 297 healthy nonsmoking men aged 20-75 years and recruited in the VITAGE Project. Effects of the genotype on vitamin E in plasma, LDL, and buccal mucosa cells (BMC) as well as on cholesterol and triglyceride (TG) concentrations in plasma and apolipoprotein A-I (apoA-I), apoB, apoE, apoC-III, and plasma fatty acids were determined. Plasma malondialdehyde concentrations as a marker of in vivo lipid peroxidation were determined. C allele carriers showed significantly higher TG, VLDL, and LDL in plasma, higher cholesterol in VLDL and intermediate density lipoprotein, and higher plasma fatty acids. Plasma alpha-tocopherol (but not gamma-tocopherol, LDL alpha- and gamma-tocopherol, or BMC total vitamin E) was increased significantly in C allele carriers compared with homozygote T allele carriers (P = 0.02), but not after adjustment for cholesterol or TG. Plasma malondialdehyde concentrations did not differ between genotypes. In conclusion, higher plasma lipids in the TC+CC genotype are efficiently protected against lipid peroxidation by higher alpha-tocopherol concentrations. Lipid-standardized vitamin E should be used to reliably assess vitamin E status in genetic association studies.

Aldehydes mediate tissue factor induction: a possible mechanism linking lipid peroxidation to thrombotic events.

Tissue factor (TF), which is expressed in atherosclerotic plaques and colocalizes with oxidized lipids, initiates the thrombogenic process. We have analyzed the effect of aldehydes derived from peroxidation of polyunsaturated fatty acids on TF expression in human vascular smooth muscle cells (HVSMC). Our results demonstrate that hexanal and 2,4-decadienal (2,4-DDE), two apolar aldehydes, increase TF expression. Exposure of HVSMC to hexanal for 2 h led to TF protein levels up to seven times higher than untreated cells whereas 2,4-DDE for 30 min led to them being up to 2.2 times higher. This induction of TF antigen by aldehydes correlates with an increase in TF mRNA levels. Electrophoretic mobility shift assays (EMSAs) showed that the binding activity of the transcription factor AP-1 (c-Fos/c-Jun) to TF promoter was elevated in response to these oxidation products. This enhancement was associated to an increase of c-fos transcriptional activity, which was reversible by pretreatment with simvastatin. We conclude that the induction of TF by aldehydes might contribute to the severity of atherogenesis.