Advanced glycation end products are independently associated with the development of atherosclerosis . Oxysterols, mainly 24(s),25 epoxycholesterol, 22(R)-hydroxycholesterol, o 24(S)-hydroxycholesterol and 25 hydroxycholesterol , modulate intracellular cholesterol exportation by increasing the LXR-mediated expression of ABCA-1 and ABCG-1 . On the other hand, 7-oxygenated cholesterol derivatives such as 7-ketocholesterol, are related to cell toxicity and death by inducing inflammation and endoplasmic reticulum stress . In fact, these oxysterols are prevalent in oxidized LDL and its accumulation in arterial wall macrophages is a hallmark of atherosclerosis and plaque instability [15, 16].
Oxidized LDL utilized to overload macrophages with lipids previously to the incubation with HDL and LXR agonist was in fact enriched in 7-ketocholesterol  due to the no enzymatic conversion of cholesterol into oxysterols. HDL on its turn presented very small amounts of oxysterols maybe related to the acquisition of these components from other lipoproteins before plasma ultracentrifugation .
In cells grown in the absence of oxidized LDL only a very small amount of oxysterols was detected by CG/MS in regard to the total amount of cell cholesterol (data not shown). Then, the majority of oxysterols that we found in oxidized LDL-overloaded macrophages was originated from the uptake of the modified LDL.
We found that advanced glycation in macrophages induced by the treatment with glycolaldehyde disturbs the exportation of 7-ketocholesterol, inducing its intracellular accumulation. Interestingly, GAD treatment mitigates the HDL ability to remove cell cholesterol and 7-ketocholesterol even in the presence of T0901317. In cholesterol-enriched macrophages, ABCA-1 contributes to a large amount of cholesterol net efflux to lipid-poor apolipoprotein A-I generating pre- betaHDL. In this present study a reduced amount of cellular ABCA-1 protein level was observed in GAD-macrophages with a small increment in its expression even after LXR agonist treatment.
We have recently demonstrated that advanced glycated albumin isolated from poorly controlled diabetes mellitus' serum reduces protein content of ABCA-1 and ABCG-1 in macrophages, impairing cholesterol efflux and inducing intracellular lipid accumulation . It has been previously shown that advanced glycation reduces ABCG-1 mRNA levels by impairing ABCG-1 gene transcriptional activity independently of LXR . On the other hand, advanced glycation induced both by oxoaldehyde or advanced glycated albumin treatment reduces ABCA-1 protein levels in macrophages which are not related to alterations in ABCA-1 mRNA levels [6, 20]. The mechanisms that regulate ABCA-1 final protein content in cells submitted to advanced glycation are not completely understood so far but may involve post-translational modifications of ABCA-1. Previous data from our group showed that advanced glycated albumin induces the expression of endoplasmic reticulum stress and unfolded protein response markers in macrophages. Interestingly, a chemical chaperone (4-phenylbutyric acid) that alleviates endoplasmic reticulum stress is able to recover ABCA-1 level and apo A-I- mediated cholesterol efflux in these cells . These events were also related to the elevated generation of reactive oxygen species in glycolaldehyde-modified albumin-treated macrophages, since treatment with aminoguanidine that reduced ROS generation was able to restore ABCA-1 protein content . AGE-albumin also primers macrophages to inflammation which is related to the diminished cholesterol exportation to apolipoprotein A-I . Although we were not able to detect by immunoblot CML derivatives in ABCA-1 and ABCG-1, at this point we cannot completely exclude that part of the changes observed in the content and activity of ABCA-1 and ABCG-1 relates to GAD modification of both transporters.
Oxidative stress and inflammation induced by AGE trigger endoplasmic reticulum stress that is also observed in instable atherosclerotic plaques enriched in 7-ketocholesterol. More recently, Yehuda et al  have demonstrated that a lipid extract obtained from carotid atherosclerotic lesion induces the expression of inflammatory markers in macrophages, which was mainly attributed to the cholesterol and oxysterol-enriched fraction (7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 7-ketocholesterol and 26-hydroxycholesterol) of the lipid extract.
ABCG-1 plays a major role in the efflux of 7-ketocholesterol to large HDL minimizing its apoptotic effects in macrophages. Nonetheless, in ABCG-1 knockout mice the development of atherosclerosis is still controversial. It is possible that in those animal models the compensatory expression of ABCA-1 may abrogates the absence of ABCG-1-mediated lipid efflux. In the setting of hyperglycemia, AGE formation is prevalent compromising both the expressions of ABCA-1 and ABCG-1. Then, the accumulation of 7-ketocholesterol together with total sterols may aggravate the development of atherosclerosis in diabetes mellitus.