Abstract-Oxidized low density lipoproteins (LDLs) play a central role in atherosclerosis, and their toxicity is due, at least in part, to the formation of oxysterols that have been shown to induce apoptosis in various cell types. As 7-hydroxycholesterol and 7-ketocholesterol are the major oxysterols found in oxidized LDLs, we have investigated and compared the mode of cell death, apoptosis versus necrosis, that they induce in the cells of the vascular wall, ie, endothelial cells, smooth muscle cells, and fibroblasts. To this end, human vascular endothelial cells from umbilical cord veins (HUVECs), human artery smooth muscle cells, A7R5 rat smooth muscle cells, MRC5 human fibroblasts, and human fibroblasts isolated from umbilical cord veins were taken at confluence and incubated for 48 hours with 7-hydroxycholesterol or 7-ketocholesterol (concentration range, 5 to 80 g/mL). In all cells, both 7-hydroxycholesterol and 7-ketocholesterol exhibited toxic effects characterized by a loss of cell adhesion and an increased permeability to propidium iodide. In oxysterol-treated endothelial and smooth muscle cells, typical features of apoptosis were revealed: condensed and/or fragmented nuclei were detected by fluorescence microscopy after staining with Hoechst 33342, oligonucleosomal DNA fragments were visualized in situ in the cell nuclei by the TdT-mediated dUTP-biotin nick-end labeling (TUNEL) method, and internucleosomal DNA fragmentation was found on agarose gel. In contrast, in oxysterol-treated fibroblasts, fragmented and/or condensed nuclei were never revealed, and no DNA fragmentation was observed either by the TUNEL method or by DNA analysis on agarose gel, indicating that these oxysterols induced necrosis in these cells but not apoptosis. In addition, acetylated Asp-Glu-Val-L-aspartic acid aldehyde (an inhibitor of Asp-Glu-Val-L-aspartic acid-sensitive caspases) prevented 7-hydroxycholesterol-and 7-ketocholesterol-induced cell death in HUVECs and smooth muscle cells but not in fibroblasts. Thus, 7-hydroxycholesterol and 7-ketocholesterol have dual cytotoxic effects on the cells of the vascular wall by their ability to induce apoptosis in endothelial and smooth muscle cells and necrosis in fibroblasts. (Arterioscler Thromb Vasc Biol.
The oxidised derivatives of phytosterols (oxyphytosterols) were identified in plasma samples from thirteen healthy human volunteers, using MS. All the samples contained noticeable quantities of (24R)-5beta,6beta-epoxy-24-ethylcholestan-3beta-ol (beta-epoxysitostanol) and (24R)-ethylcholestan-3beta,5alpha,6beta-triol (sitostanetriol) and also trace levels of (24R)-5alpha,6alpha-epoxy-24-ethylcholestan-3beta-ol (alpha-epoxysitostanol), (24R)-methylcholestan-3beta,5alpha,6beta-triol (campestanetriol) and (24R)-ethylch olest-5-en-3beta-ol-7-one(7-ketositosterol). The amounts of these oxyphytosterols in plasma varied from 4.8 to 57.2 ng/ml. There are two possibilities concerning the origin of these compounds. First, they could come from the small amounts of oxyphytosterols in food. Second, they could originate from the in vivo oxidation of phytosterols in plasma. Very few data actually exist concerning these compounds. Their identification in human samples suggests that further research is necessary in this field.
Washed bacterial suspensions obtained from the pig hindgut were incubated under 13CO2 in a buffer containing NaH13CO3 and carbohydrates. Incorporation of 13C into short chain fatty acids was assayed by quantitative nuclear magnetic resonance. The effects of different levels of H2 added to the gas phase (0, 20 and 80% v/v) and of the specific methanogenesis inhibitor 2-bromoethane-sulphonic acid (BES) were determined. In control incubations increasing the concentration of H2 markedly increased methane production. Single- and double-labelled acetate and butyrate were formed in all incubations. In the absence of BES, increasing H2 significantly increased the incorporation of 13CO2 into butyrate and the proportion of double-labelled acetate in total labelled acetate. The addition of BES proved to be very successful as a methane inhibitor and greatly enhanced the amount of mono- and double-labelled acetate, especially at the highest H2 partial pressure. The results suggest that methanogenesis inhibited both routes of reductive acetogenesis, i.e. the homoacetate fermentation of hexose (represented for the most part by single labelling) and the synthesis of acetate from external CO2 and H2 (represented mostly by double labelling). A highly significant interaction between BES and H2 concentration was observed. At the highest pH2 BES increased the proportion of labelled acetate in total acetate from 17.1% for the control to 50.9%. It was concluded that although acetogenesis and methanogenesis can occur simultaneously in the pig hindgut, reductive acetogenesis may become a significant pathway of acetate formation in the absence of methanogenesis.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.