gamma-sitosterol and Hemolysis

Cholesterol suppresses the hemolysis and the detachment of cytoskeletal proteins from bilayer in the human erythrocyte membrane under stress conditions. However, there is little information on how cholesterol functions. So, examining the role of a short side chain of cholesterol, we used the plant sterols such as β-sitosterol and stigmasterol. Incorporation of sterols into the membrane using a sterol/methyl-β-cyclodextrin complex was confirmed by the mass spectrometry. Hemolysis of human erythrocytes under high hydrostatic pressure (200 MPa) or hypotonic conditions was suppressed by cholesterol, but not by β-sitosterol and stigmasterol. Moreover, the bilayer-cytoskeleton interaction was also strengthened by cholesterol, but not by β-sitosterol and stigmasterol. Taken together, we suggest that the short side chain of cholesterol plays an important role in the membrane stability of human erythrocytes.

Topics: beta-Cyclodextrins; Cell Membrane; Cells, Cultured; Cholesterol; Cytoskeletal Proteins; Cytoskeleton; Erythrocytes; Hemolysis; Humans; Sitosterols; Stigmasterol

The eryptotic and hemolytic effects of a phytosterol (PS) mixture (β-sitosterol, campesterol, stigmasterol) or β-cryptoxanthin (β-Cx) at physiological serum concentration and their effect against oxidative stress induced by tert-butylhydroperoxide (tBOOH) (75 and 300 μM) were evaluated. β-Cryptoxanthin produced an increase in eryptotic cells, cell volume, hemolysis, and glutathione depletion (GSH) without ROS overproduction and intracellular Ca

Topics: Beta-Cryptoxanthin; Cells, Cultured; Cholesterol; Eryptosis; Erythrocytes; Glutathione; Hemolysis; Humans; Oxidative Stress; Phytosterols; Sitosterols; Stigmasterol; tert-Butylhydroperoxide

Pneumolysin is one of the major virulence factors elaborated by Streptococcus pneumoniae; this toxin is a member of the cholesterol-dependent cytolysins. Engagement of cholesterol induces the formation of a multi-subunit complex by pneumolysin that lyses host cells by forming pores on the membrane. Because pneumolysin released by bacteria which have been killed by conventional antibiotics is still active, agents capable of directly attacking the toxin are considered advantageous against antimicrobials in the treatment of S. pneumoniae infections. Here we found that the phytosterol, β-sitosterol, effectively protects against cell lysis caused by pneumolysin. This compound interacts with the toxin at Thr459 and Leu460, two sites important for being recognized by its natural ligand, cholesterol. Similar to cholesterol, β-sitosterol induces pneumolysin oligomerization. This compound also protects cells from damage by other cholesterol-dependent toxins. Finally, this compound protects mice against S. pneumoniae infection. Thus, β-sitosterol is a candidate for the development of anti-virulence agents against pathogens that rely on cholesterol-dependent toxins for successful infections.

Topics: Animals; Anti-Bacterial Agents; Bacterial Proteins; Binding Sites; Cholesterol; Hemolysis; Humans; Lung; Male; Mice, Inbred C57BL; Models, Molecular; Pneumococcal Infections; Sitosterols; Streptococcus pneumoniae; Streptolysins; Surface Plasmon Resonance

Clionasterol (1a), clionasterol monoacetate (1b) and 5alpha,8alpha-epidioxy-24alpha-ethylcholest-6-en-3-ol (2), isolated from the marine sponge Xestospongia exigua, and beta-sitosterol (3) were tested for their influence on the classical (CP) and alternative (AP) pathways of activation of the human complement system in vitro. All the sterols inhibited the CP in a dose-dependent manner but no detectable effect was observed in the AP even at concentrations of 400 microM. Clionasterol was found to be a potent inhibitor of CP (IC50 = 4.1 microM) being ten-fold more active than beta-sitosterol. The presence of the epidioxy group on C-5 and C-8 of compound 2 caused a pronounced decrease of the inhibitory effect. Mechanistic studies on the anticomplementary effect of clionasterol revealed that it interferes with the complement component C1.

Topics: Animals; Complement Inactivator Proteins; Complement Pathway, Alternative; Complement Pathway, Classical; Dose-Response Relationship, Drug; Hemolysis; Humans; Inhibitory Concentration 50; Porifera; Sitosterols

In experiments with male Wistar rats the influence of the non-saponifiable constituents of dietary fats: dl-alpha-tocopherol (60 ppm), dl-gamma-tocopherol (480 ppm), ubiquinone (96 ppm) and beta-sitosterol (3035 ppm) on the tocopherol status was investigated, considering the fatty acid composition of the tested fats. For a test period of eight weeks the animals were fed isoenergetic diets containing three types of dietary fats: corn oil (60% PUFA), a kind of "stripped corn oil" (60% PUFA) and butter (nearly 5% PUFA). Independent of the PUFA-content of the diet, the tocopherol supplementations were able to stabilize the erythrocyte membrane; the calculated hemolysis rates were about 2%. The absence of tocopherols in the diets ("stripped corn oil", butter) caused an increase of the hemolysis rate up to 70% after two weeks. The original amounts of tocopherols in corn oil tended to minimize the hemolysis. Ubiquinone and beta-sitosterol did not reduce the hemolysis rates when they were applied without tocopherols. With respect to creatine-phosphokinase activity, creatine and creatinine excretion the results were similar. Plasma and erythrocyte levels of alpha- and gamma-tocopherol were determined in all groups and discussed in connection with the other examined parameters of tocopherol status. The ultimate result of this experiment is that the content of tocopherols in dietary fats is not always adequate to keep vitamin E status normal, especially if polyunsaturated fatty acid content is high in the diet. Reflecting the vitamin E adequacy of dietary fats, not only alpha-tocopherol but also gamma-tocopherol should be much more considered than previously.

Topics: Animals; Butter; Dietary Fats; Dose-Response Relationship, Drug; Fatty Acids, Unsaturated; Hemolysis; Male; Rats; Rats, Inbred Strains; Sitosterols; Structure-Activity Relationship; Triglycerides; Ubiquinone; Vitamin E; Zea mays

The in vitro uptake of radioactively labeled cholesterol and the plant sterol beta-sitosterol has been examined in rat erythrocytes. From mixed micellar solutions containing egg yolk phospholipid and sodium taurocholate, the erythrocytes showed a nonlinear uptake of the two sterols. The uptake leveled off after about 45 min with the attainment of a 1:1 total sterol-to-phospholipid ratio within the cell membrane, as determined on a mass basis. From solutions containing egg yolk phospholipid, or purified egg yolk phosphatidylcholine, a preference for cholesterol over the plant sterol was observed, increasing with time from a cholesterol/beta-sitosterol uptake ratio of unity (the media ratio) to a maximum of 2 after a 60-min incubation. Correction of the data for nonspecifically bound sterol increased the ratio to a maximum of 5 at the 30-min time point. The increase in the cholesterol/beta-sitosterol uptake ratio with time, following an initial nonspecific association, showed that penetration of the plasma membrane by the sterol was required for the selectivity to be expressed. The presence of lysophosphatidylcholine or bovine serum albumin did not exert any noticeable influence over the extent or selectivity of absorption. Replacement of the egg yolk phospholipid with synthetic dipalmitoyl-phosphatidylcholine led to a loss of the sterol selectivity. No evidence was found to support a selective extraction of sterol from the erythrocyte membrane to account for the observed effects, nor was there any sign of a mass accumulation of phospholipid during the incubation. It is suggested that the media phospholipid influences the membrane permeability toward cholesterol and beta-sitosterol.

Topics: Animals; Biological Transport; Cholesterol; Erythrocytes; Hemolysis; Kinetics; Male; Micelles; Plants; Rats; Rats, Inbred Strains; Sitosterols