Hypolipidaemic Effects of (24R)-4α-methyl-5α-stigmasta-7,22-dien-3β-ol Derived from Aurantiochytrium mangrovei BT3 in the HEPG2 Cell Line

Applied Biochemistry and Microbiology - Aurantiochytrium mangrovei BT3, a heterotrophic marine microalga, has the ability to produce high amounts of polyunsaturated fatty acids and bioactive...     

Antiproliferative effects of two hydrosoluble derivatives of oxysterols on cultured lymphoma cells.

The antitumor effects of two new hydrosoluble derivatives of oxygenated sterols: JB69 and JC40 have been evaluated in vitro on a panel of lymphoma and leukemia cells from human and murine origins. These compounds result from the combination of a nucleotide with 7 beta-hydroxycholesterol (JB69) or 7 beta,25-dihydroxycholesterol (JC40). Both derivatives exhibit a significant cytotoxic activity against the different tumor cell lines tested, with some degree of difference between them. On the whole, the concentrations needed to inhibit the cell growth were found to be higher than those required for their parent compounds. However, two interesting features appeared in our experiments. (1) In a serum-free culture medium, cell lysis occurred within the first hours of incubation and seemed to result from the detergent-like properties possessed by this type of compounds. (2) In a culture medium supplemented with serum, we noted, that at high concentrations of JB69 (40 microM or 20 microM) and only with this oxysterol derivative, an important increase of incorporation of tritiated thymidine and uridine into DNA and RNA by viable cells. The origin of this effect is as yet unknown, but it strongly suggests a possible action on nucleic acids synthesis and metabolism. Taken together, these results emphasize the diversity and the complexity of the mechanisms involved in the cytotoxicity of these derivatives of oxysterols.     

Metabolism of cytotoxic hydroxysterols in cultured cells. Chemical characterization of metabolites

The metabolism of labelled 7 alpha- and 7 beta-hydroxycholesterol was investigated in two lymphoma cell lines (YAC-1, RDM-4), in murine splenocytes and in HTC hepatoma cells. The structures of the metabolites in lymphoma cells were determined as 3 beta-esters of C14-C20 fatty acids by nuclear magnetic resonance and mass spectrometric studies. In hepatoma cells, more polar metabolites of 7 alpha- and 7 beta-hydroxycholesterol were detected whereas, in non-dividing lymphocyte cells, no metabolic transformation occurs. Therefore, metabolic transformation of the hydroxycholesterol is not required for the expression of their activity and the question of the physiological role of the metabolic products is raised.     

The importance of serum lipoproteins in the cytolytic action of 7 beta-hydroxycholesterol on cultured hepatoma cells

A soluble cytochrome P-450-dependent fatty acid monooxygenase activity obtained from Bacillus megaterium ATCC 14581 can be induced by at least 13 different barbiturates. In general, the potency of these compounds as inducers increases with their increasing lipophilicity. We have now shown that at least 4 of these barbiturates (phenobarbital, secobarbital, pentobarbital and methohexital) seem to induce the same active cytochrome P-450-containing enzyme by a non-substrate type mechanism. The partially purified enzymes obtained from cultures induced with each of the 4 barbiturates tested were all of similar molecular size (Mr = 130,000 +/- 10,000) and had similar turnover numbers (1400-1800 +/- 300) with either palmitoleate or myristate as substrates. None of the tested barbiturates served as substrates, activators or inhibitors of any of the monooxygenase preparations, nor did they appear to interact in any way with the monooxygenase enzyme or the P-450 component.     

Characterization of GABAA receptor-mediated 36chloride uptake in rat brain synaptoneurosomes

gamma-Aminobutyric acid (GABA) receptor-mediated 36chloride (36Cl-) uptake was measured in synaptoneurosomes from rat brain. GABA and GABA agonists stimulated 36Cl- uptake in a concentration-dependent manner with the following order of potency: Muscimol greater than GABA greater than piperidine-4-sulfonic acid (P4S)greater than 4,5,6,7-tetrahydroisoxazolo-[5,4-c]pyridin-3-ol (THIP) = 3-aminopropanesulfonic acid (3APS) much greater than taurine. Both P4S and 3APS behaved as partial agonists, while the GABAB agonist, baclofen, was ineffective. The response to muscimol was inhibited by bicuculline and picrotoxin in a mixed competitive/non-competitive manner. Other inhibitors of GABA receptor-opened channels or non-neuronal anion channels such as penicillin, picrate, furosemide and disulfonic acid stilbenes also inhibited the response to muscimol. A regional variation in muscimol-stimulated 36Cl- uptake was observed; the largest responses were observed in the cerebral cortex, cerebellum and hippocampus, moderate responses were obtained in the striatum and hypothalamus and the smallest response was observed in the pons-medulla. GABA receptor-mediated 36Cl- uptake was also dependent on the anion present in the media. The muscimol response varied in media containing the following anions: Br- greater than Cl- greater than or equal to NO3- greater than I- greater than or equal to SCN- much greater than C3H5OO- greater than or equal to ClO4- greater than F-, consistent with the relative anion permeability through GABA receptor-gated anion channels and the enhancement of convulsant binding to the GABA receptor-gated Cl- channel.     

Differential sensitivity of astrocyte primary cultures and derived spontaneous transformed cell lines to 70-hydroxycholesterol: effect on plasma membrane lipid composition and fluidity,and on cell surface protein expression

Summary The cytotoxicity of 7-hydroxycholesterol (7-OHC) was investigated on rat astrocyte primary cultures and spontaneously transformed cell lines derived from them. Confluent astrocyte primary cultures (normal cells) were unaffected by 20 µM 7(3-OHC over a period of 72 h whereas 30 µM markedly affected the viability of the transformed cells within the first 72 h. Both cell types incorporated 18% of the total amount of 7-OHC added to the cultures at concentrations of 20 µM or 30 µM. Cellular fractionation after incubation with 20 µM or 30 µM 7-OHC indicated that the plasma membrane incorporated 2 or 6 fold more 7-OHC than the intracellular one's respectively. Plasma membrane cholesterol (CH) and phospholipid (PL) analysis showed that 20 µM 7-OHC did not affect CH/PL in normal cells; in contrast, plasma membranes of transformed cells displayed a significant CH/PL decrease, which was more pronounced with 30 µM 7-OHC treatment. Fluorescence anisotropy measurements indicated that 20 µM 7-OHC slightly fluidified the plasma membrane of normal cells whereas it has not effect on that of the transformed cells one; however, an increase in plasma membrane fluidity was observed when the transformed cells were treated with 30 µM 7-OHC. Lactoperoxidase catalyzed radioiodination of cell surface proteins and subsequent autoradioelectrophoretic analysis demonstrated that the labelled protein pattern was unchanged when both cell types were incubated with 30 µM 7-OHC.     

Laser-raman spectra of d-fructose in aqueous solution

Laser-Raman spectra of d-fructose in water at different concentrations were recorded, and assignments of the frequencies were proposed, based on earlier work on the Raman spectra of other sugars, and determination by other techniques of the composition of aqueous solutions of d-fructose as regards different isomers. It was found that the frequencies of vibration of the furanoid are higher than those of the pyranoid ring. The proportions of the furanoses and pyranoses, found from the ratio of the Raman intensities for the same modes of vibration, were similar to those found by other techniques. Shifts of intensities and frequencies were observed in the region of OH and CH bands, and were assigned to probable association between molecules of d-fructose and water.