[Delta5-7-Ketosterols with modified side chain: the synthesis and the effects on viability and cholesterol biosynthesis in Hep G2 cells].

(22E)-3beta-Hydroxysitosta-5,22-dien-7-one, (22R, 23R)-3beta,22,23-trihydroxysitost-5-en-7-one, and (22R, 23R)-3beta-hydroxy-22,23-isopropylidenedioxysitost-5-en-7-one were synthesized. The cytotoxicity and effects on cholesterol biosynthesis of the resulting 7-ketosterols, 7-ketocholesterol, and (22S,23S)-3beta-hydroxy-22,23-oxidositost-5-en-7-one were studied in hepatoblastoma Hep G2 cells.

[22,23-epoxides of sitosterol and related 7-oxygenated delta5-sterols].

(22S,23S)-22,23-Epoxysitosterol, (22R,23R)-22,23-epoxysitosterol, (22S,23S)-22,23-epoxy-7-ketositosterol, (22R,23R)-22,23-epoxy-7-ketositosterol, (22S,23S)-22,23-epoxy-7alpha-hydroxysitosterol, (22R,23R)-22,23-epoxy-7alpha-hydroxysitosterol, (22S,23S)-22,23-epoxy-7beta-hydroxysitosterol, and (22R,23R)-22,23-epoxy-7beta-hydroxysitosterol were synthesized. Their 1H and 13C NMR and the mass spectra of their trimethylsilyl derivatives were studied.

[New delta8(14)-ketosterols with an oxygenated side chain].

New analogues of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one (15-ketosterol) with modified 17-chains [(22S,23S,24S)- and (22R,23R,24S)-3beta-hydroxy-24-methyl-22,23-oxido-5alpha-cholest-8(14)-en-15-ones and (22RS,23xi,24S)-24-methyl-5alpha-cholesta-3beta,22,23-triol-15-one] were synthesized from (22E,24S)-3beta-acetoxy-24-methyl-5alpha-cholesta-8(14),22-dien-15-one. The chiralities of their 22 and 23 centers were determined by NMR spectroscopy. The isomeric 22,23-epoxides effectively inhibited cholesterol biosynthesis in hepatoma Hep G2 cells (IC50 0.9 +/- 0.2 and 0.7 +/- 0.2 microM, respectively), and their activities significantly exceeded those of 15-ketosterol (IC50 4.0 +/- 0.5 microM), (22E,24S)-3beta-hydroxy-24-methyl-5alpha-cholesta-8(14),22-dien-15-one (IC50 3.1 +/- 0.4 microM), and the 3beta,22,23-triol synthesized (IC50 6.0 +/- 1.0 microM). The English version of the paper: Russian Journal of Bioorganic Chemistry, 2005, vol. 31, no. 3; see also http://www.maik.ru.

[The effect of 15-ketosterol analogues with a 5,6-dimethylhept-3-en-2-yl chain at C17 on cholesterol metabolism in Hep G2 hepatoma cells]. / Vliianie analogov 15-ketosterina, soderzhashchikh 5,6-dimetilgept-3-en-2-il'nuiu tsep' pri C17, na metabolizm kholesterina v kletkakh gepatomy HepG2.

The effect on cholesterol metabolism in Hep G2 hepatoma cells was studied for new analogues of 15-ketosterol [3beta-hydroxy-5alpha-cholest-8(14)-en-15-one] (I): (24S)-3beta-hydroxy-24-methyl-5alpha-cholesta-8(14),22-diene-15-one (II), (24S)-3alpha-hydroxy-24-methyl-5-alpha-cholesta-8(14),22-diene-15-one (III), and (24S)-24-methyl-5alpha-cholesta-8(14),22-diene-3,15-dione (IV). Analogues (I) and (II) were found to be equally effective inhibitors of cholesterol biosynthesis after a 3-h incubation with Hep G2 cells; however, (II) produced a stronger inhibitory effect after a 24-h incubation or after an incubation of cells preliminarily treated with the inhibitor in a medium containing no ketosterol. The ability of ketosterols to inhibit cholesterol biosynthesis decreased in the order (II) > (IV) > (III). Ketosterol (II) inhibited, whereas ketosterol (III) stimulated the biosynthesis of cholesteryl esters. (IV) stimulated the biosynthesis of cholesteryl esters at a concentration of 1-10 microM and exerted no marked effect at a concentration of 30 microM. These results indicate that delta8(14)-15-ketosterols containing a modified side chain are of interest as regulators of cholesterol metabolism in liver cells. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 5; see also http: // www.maik.ru.

[Interaction of acyl derivatives of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one and 3alpha-hydroxy-5alpha-cholest-8(14)-en-15-one with hepatoma hep G2 cells]. / Vzaimodeistvie atsil'nykh proizvodnykh 3beta-gidroksi-5alpha-kholest-8(14)-en-15-ona i 3alpha-gidroksi-5-alpha-kholest-8(14)-en-15-ona s kletkami gepatomy Hep G2.

Effects of 3beta-hydroxy-5alpha-cholest-8(14)-en-15-one (I), 3alpha-hydroxy-5alpha-cholest-8(14)-en-15 one (II), 3beta-hexadecanoyloxy-5alpha-cholest-8(14)-en-15-one (III), 3alpha-hehadeeanoyloxy-5alpha-cholest-8(14)-en-15-one (IV), 3beta-acetoxy-5alpha-cholest-8(14)-en-15-one (V), 3alpha-acetoxy-5alpha-cholest-8(14)-en-15-one (VI) on cholesterol metabolism in hepatoma Hep G2 cells were studied. Compound III slowly bind to Hep G2 cells followed by internalization and metabolic transformation (at a concentration of 30 microM the total binding of compound III was (3.9 +/- 0.4) nmol per 1 mg of cell protein for 24 h incubation). Compound I depressed and compound III stimulated the uptake of low density lipoproteins radiolabeled with oleyl cholesteryl ether [14C-CE]LDL (58% and 149% from control). Compounds I and II inhibited cholesterol biosynthesis from [14C]acetate (with IC50 values of 4.0 +/- 0.7 and 8.0 +/- 1.5 microM). Effects of compounds V and VI were less potent; compounds III and IV were inactive. Compound II activated cholesterol acylation, estimated by incorporation of [14C]-oleic acid into cholesteryl esters (170% from control at a concentration of 30 microM). The results indicate correlation between polarity of the compound and its ability to regulate cholesterol metabolism in Hep G2 cells.

[Transformation of 3beta-(2-hydroxyethoxy)-5alpha-cholest-8(14)-en-15-one in a polar metabolite in HepG2 hepatoma cells]. / Prevrashchnie 3beta-(2-gidroksiétoksi)5alpha-kholest-8(14)-en-15-ona v poliarnyi metabolit v kletkakh gepatomy HepG2.

Incubation of 3 beta-(2-hydroxy-2[3H]-ethoxy)-5 alpha-cholest-8(14)-en-15-one with Hep G2 cells led to the accumulation of a radioactive polar product in the culture medium, which was identified as 3 beta-(2-hydroxyethoxy)-15-keto-5 alpha-cholest-8(14)-ene-24-oic acid. Its structure was confirmed by a chemical counter synthesis. The labeled ketosterol was rapidly (tau 1/2 = 6 min) and reversibly bound by Hep G2 cells. The intracellular concentration of 15-ketosterol decreased during incubation mainly due to the formation of a polar metabolite, secreted to the medium. The level of cholesterol biosynthesis was 22 +/- 5% of the control value in Hep G2 cells at a 15-ketocholesterol concentration in the medium of 30 microM. However, further incubation for 3 h in the medium without the ketosterol led to restoration of the level of biosynthesis to 85 +/- 11% of the control value. These results suggest that inhibition of the cholesterol biosynthesis by 15-ketocholesterol in Hep G2 cells depends on the intracellular concentration of the inhibitor, which, in turn, is determined by the rate of its conversion into the polar metabolite. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2003, vol. 29, no. 6; see also http://www.maik.ru.