5α,6α-Epoxyphytosterols and 5α,6α-Epoxycholesterol Increase Oxidative Stress in Rats on Low-Cholesterol Diet.

OBJECTIVE: Cholesterol oxidation products have an established proatherogenic and cytotoxic effect. An increased exposure to these substances may be associated with the development of atherosclerosis and cancers. Relatively little, though, is known about the effect of phytosterol oxidation products, although phytosterols are present in commonly available and industrial food products. Thus, the aim of the research was to assess the effect of 5α,6α-epoxyphytosterols, which are important phytosterol oxidation products, on redox state in rats. MATERIAL AND METHODS: The animals were divided into 3 groups and exposed to nutritional sterols by receiving feed containing 5α,6α-epoxyphytosterols (ES group) and 5α,6α-epoxycholesterol (Ech group) or sterol-free feed (C group). The levels of malondialdehyde (MDA), conjugated dienes (CD), and ferric reducing antioxidant potential (FRAP) were assayed in the plasma; anti-7-ketocholesterol antibodies and activity of paraoxonase-1 (PON1) were determined in serum, whereas the activity of catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), S-glutathione transferase (GST), and superoxide dismutase (SOD) were assayed in RBCs. RESULTS: During the experiment, the levels of lipid peroxidation products increased, such as CD and anti-7-ketocholesterol antibodies. At the same time, the plasma levels of FRAP and serum activity of PON1 decreased alongside the reduced activity of GPx, GR, and SOD in RBCs. There was no effect of the studied compounds on the plasma MDA levels or on the activity of CAT and GST in RBCs. CONCLUSIONS: Both 5α,6α-epoxyphytosterols and 5α,6α-epoxycholesterols similarly dysregulate the redox state in experimental animal model and may significantly impact atherogenesis.

Concentration of anti-7-ketocholesterol antibodies in patient sera after heart transplantation.

Oxidized low-density lipoproteins (ox-LDL) have been shown to be strongly atherogenic and immunogenic in experimental animals and in humans. Autoantibodies against ox-LDL and its various epitopes have been detected in sera and in atherosclerotic lesions. LDL oxidation may also lead to generation of oxidized derivatives of cholesterol (eg, 7-ketocholesterol [7-ketoCh]), which are characterized by high levels of cytotoxicity, muta- and carcinogenicity, as well as immunosuppressive effects and probable immunogenic properties. The aim of this study was to quantify autoantibodies to 7-ketoCh in sera from patients after orthotopic heart transplantation (OHT). IgG antibodies were measured in sera from 81 patients after OHT and 73 healthy volunteers using and enzyme-linked immunosorbent assay (ELISA) method. For the antigen we used 7-ketoCh hemisuccinate conjugated to bovine serum albumin. Anti-7-ketoCh antibodies were detected in all examined sera. Their concentrations were significantly higher among OHT patients than the control group, namely, 109.0 +/- 109.7 vs 53.5 +/- 20.0 U/mL (P < .005). Also, we observed a direct relationship between antibody concentration and time after OHT. Our results showed that the low molecular product of LDL oxidation, 7-ketoCh, was immunogenic possibly playing a role in the progression of atherosclerosis among OHT patients.

New steroid haptens for radioimmunoassay: synthesis of steroids substituted with thioether or ester linkages at the 2 alpha-position.

Haptens with bridge at the 2-position have not yet been explored. Radioimmunoassays with antibodies directed against 2 alpha-alkyl bridged steroid haptens are expected to be highly specific due to greater topographical exposure and similarity in conformation to the native steroid. The 2 alpha-alkyl bridged haptens were synthesized by first adding a cyclopropane ring to 2-methylene-4-en-3-one. Selective opening of the three-membered ring with trimethyl silyl iodide and transformation of the iodo group gave a carbocyclic acid, the desired analog for conjugation with protein.