Effect Of Cholesterol Content Research Articles

Effect of Surfactant Type, Cholesterol Content and Various Downsizing Methods on the Particle Size of Niosomes.

The present study was conducted to investigate the performance of different size reduction techniques including probe sonication, extrusion, and high pressure homogenization for nanosizing of niosomes. Also, the effects of cholesterol content and surfactant type on the size and poly dispersity index (PDI) of the formulations were evaluated. Various niosomal formulations composed of Brij 72, Span 60, or Tween 60 were prepared and then, to reduce vesicle size and minimize the PDI, the niosomes were treated by various post-processing procedures. Surfactant type showed a significant effect on the particle size of the niosomes. The particle size of Tween 60 niosomes was significantly larger than those of Span 60 and Brij 72 niosomes (P < 0.05), indicating that at the same cholesterol content, niosomes composed of a surfactant with a higher HLB value show larger particle size than those with a lower HLB value. The influences of cholesterol content as well as downsizing methods, on the particle size and distribution of niosomes were significantly dependent on the surfactant composition of the niosomes. Extrusion and probe sonication were found to be the most efficient methods for size reduction of the Tween 60 and Span 60 niosomes, while for downsizing of Brij 72 niosomes, all employed methods were efficient and resulted in the approximately similar size of about 200 nm. In conclusion, the selection of an efficient method for nanosizing of niosomes and also achievement of a desired size range, and homogeneity highly depends on the niosome composition, particularly on the employed surfactant type.

Solid lipid microparticles of lamotrigine: an injectable controlled release system for local delivery in nerve injuries

Designing an injectable controlled release system containing lamotrigine loaded solid lipid microparticles (SLMs) for repairing nerve injuries was considered. Lamotrigine was loaded in mixture of stearic acid and cholesterol by melt dispersion method in the presence of surfactant. The mixture was cooled under stirring and SLMs were freeze-dried. Effect of cholesterol content, surfactant percentage and duration of mixing on particle size was studied by Taguchi design. Morphology, stability, entrapment efficiency and release behavior of SLMs were also examined. Results showed that higher levels of surfactant provided smaller SLMs. Increasing amount of cholesterol resulted in decreasing size distribution. Formulation containing higher level of cholesterol released the drug faster than others. SLMs containing mannitol as cryoprotectant presented higher stability in freeze drying and showed lower change in size distribution. Drug release was controlled by this system and it seems that SLMs would be a promising system for local controlled delivery of lamotrigine.

Effect of Cholesterol Content on Gramicidin S-Induced Hemolysis of Erythrocytes

Gramicidin S (GS) is a cyclo-decapeptide antibiotic with wide Gram+ and Gram− antimicrobial spectrum. However, its therapeutic application is very limited due to hemolytic activity of GS. The presence of cholesterol defines one of the most significant differences between eukaryotic plasma membranes and bacterial inner membranes. To find out the cholesterol effect on the GS hemolytic efficiency we compared GS-induced hemolysis of erythrocytes extracted from the blood of healthy donors against donors with atherosclerosis, “naturally” enriched with cholesterol. Our results show that increased cholesterol levels significantly attenuates yet does not abolishes the GS hemolytic activity. High levels of cholesterol content in erythrocyte membranes results in a decrease in the membrane fluidity and deformability leading to a decrease in the rate of GS interaction with membranes. The results obtained confirm that hydrophobic as well as electrostatic interactions must be involved in the binding of GS to cell membranes. Lipid peroxidation occurring within atherosclerotic erythrocytes leads to considerable decrease in the degree of GS-induced erythrocyte hemolysis in vitro. These results can be applied to the rational design of GS analogs with increased antibacterial efficiency but reduced hemolytic activity.

Effect of cholesterol content on affinity and stability of factor VIII and annexin V binding to a liposomal bilayer membrane

To investigate the effect of cholesterol composition on the binding of factor VIII (FVIII) and annexin V (AV) to membranes, liposomal membranes with phospholipid bilayers of various compositions of phosphatidylcholine (PC), phosphatidylserine (PS), and cholesterol were constructed. A surface plasmon resonance (SPR) biosensor system was employed to measure the equilibrium and rate constants of the bindings. As expected, PS was found to play a dominant role in the binding of AV; its binding level was directly proportional to the PS composition in a liposome. The binding levels of FVIII and AV to liposome increased with an increase in cholesterol composition in liposome. It seemed to suggest that cholesterol in liposome acts as a 'phospholipid arrangement' factor by inducing the formation of PS-rich microdomains. However, in the absence of PS (20% on a mole basis), cholesterol could not exert the binding enhancement effect, which again confirmed the critical role of PS in the bindings. Stability of the AV binding was significantly improved by the increase in cholesterol content; for AV, the dissociation rate constant was decreased approximately fivefold, from 1.7 x 10(-3)s(-1) in the absence of cholesterol to 3.3 x 10(-4)s(-1) in the presence of only 10% cholesterol. But, for FVIII the binding stability was not so much influenced by the cholesterol addition (up to 50% on a mole basis). In summary, by using liposomes on an SPR system, we were able to demonstrate quantitatively the apparent effects of cholesterol on the binding affinity and stability of the membrane-binding proteins.

Evaluation of Ferulic Acid-Biomembrane Interaction by Liposome Electrokinetic Chromatography

A facile method for evaluating acidic drug-biomembrane interaction was established by liposome electrokinetic chromatography (LEKC). LEKC is a capillary electrophoresis technique, where liposome is incorporated into a buffer solution and acts as a pseudostationary phase using the structural similarity of liposome and biomembrane. Liposome–water partition coefficient ( K lw) of ferulic acid was determined within a few minutes. The effect of cholesterol content, buffer pH, and buffer composition on K lw was investigated, respectively. An increase in cholesterol content (0–30%) and pH values (4.00–12.00) resulted in a lower K lw . In different buffer systems, the greater the ionic strength, the larger K lw was. The difference of K lw revealed ferulic acid–biomembrane interaction.

Effect of cholesterol content in activation of the classical versus the alternative pathway of rat complement system induced by hydrogenated egg phosphatidylcholine-based liposomes

Liposomes composed of hydrogenated egg phosphatidylcholine (HEPC) and cholesterol (CHOL) were found to activate the rat complement (C) system in a CHOL content-dependent manner. Liposomes containing 22 or 33 mol% CHOL activated the C system in a Ca 2+-dependent manner, suggesting that C activation occurred via the classical pathway. Liposomes containing 44 mol% CHOL activated the C system in a Ca 2+ independent manner, suggesting that C activation occurred via the alternative pathway. The CHOL content appeared to dictate the pathway by which the C system was activated. This C activation was inhibited by removal of serum component(s), which adsorb to the liposomes. Activation of the alternative pathway, induced by the liposomes, was reduced by the depletion of IgG and IgM, whereas the classical pathway activation was reduced by the depletion of IgG, but not IgM. In addition, the removal of adsorbed serum component(s) by treatment with 44 mol% CHOL-containing liposomes decreased serum IgG and IgM levels that adsorb to the same liposomes, whereas the removal of adsorbed serum component(s) by treatment with 22 mol% CHOL-containing liposomes only slightly decreased serum IgG levels, which adsorbs to the same liposomes. Collectively, both IgG and IgM, which are specifically adsorbed to the liposomes in a CHOL-content dependent manner, were responsible for C activation via the alternative pathway induced by the 44 mol% CHOL containing liposomes. IgG alone would be partially responsible for C activation via the classical pathway induced by 22 or 33 mol% CHOL-containing liposomes. The discovery of this unique C-activating property of liposomes will be of value in attempts to decipher the underlying mechanism of C activation by providing a useful model membrane system.

リポソーム膜中のコレステロール含量が及ぼす補体第３成分（Ｃ３）の結合と体内動態への影響

In this study we analyzed the binding ability of complement component 3 (C3) associated with liposomes after incubation in rat serum in order to determine the effect of cholesterol content of liposomes on the complement system liposomes interactions and the fate of liposomes in vivo. Liposomes having different cholesterol content showed no difference in clearances from blood circulation, while in both hepatic and renal clearances the liposomes showed marked difference. The hepatic clearance increased with increasing cholesterol content and the renal clearance decreased with increasing cholesterol content. Further, it appeared that those liposomes had different C3 binding potentials : cholesterol-rich (44 mol%) liposomes had higher affinity for C3 than cholesterol-poor (22 mol%) liposomes. Interestingly, there was a good correlation between the C3 binding ability and hepatic clearance of liposomes, while there was an inverse correlation between the C3 binding ability and renal clearance of liposomes. These results suggested that the extent of interaction of liposomes with complement system directly related to the distribution of liposomes in liver, leading to a possibility that the liposomes having high affinity for C3 are phagocytosed by Kuppfer cells via complement receptors. Release of encapsulated carboxy fluorescein from liposomes was inhibited in heat-treated rat serum, less done in EDTA-treated one. This finding indicated that degradation of liposomes in in vivo or in vitro was attributed to a heat-labile serum component, but not complement system. We clarified in this study that the complement-liposome interactions play a critical role on the hepatic uptake of liposomes, but not on the degradation of liposomes in blood circulation.

Fracture strength of human gallstones

Extracorporeal shock-wave lithotripsy (ESWL) is currently being evaluated as a treatment for symptomatic gallstones in the USA. It was first used to treat kidney stones in humans approximately 10 years ago, and now 85% of all kidney stones can be treated with this method [1]. Although ESWL can efficiently fragment gallstones, rendering them more amenable to dissolution therapy with oral bile acid therapy [2], methyl-ten-butyl ether (MTBE) [3] or Monooctanoin [4], at present it is successfully used only in a select group of patients. Nevertheless, shock-wave therapy remains a viable treatment for gallstones, particularly for those patients who prefer non-surgical treatment or for those who are physically unfit for surgery. Cholesterol is the major component of most gallstones found in the USA and Europe, the remaining components being calcium bilirubinate, calcium carbonate and mixed bile pigments. Only patients who are suspected to have cholesterol gallstones (defined as 70% cholesterol by weight) [5] are being treated with ESWL in order that the remaining fragments be dissolved. It is estimated that 10-25% of all people suffering from cholelithiasis (gallstone disease) can be successfully treated by ESWL [6]. With this in mind, some lithotripter manufacturers are attempting to develop machines that may treat both kidney stones and gallstones. The mechanical properties of these stones, however, are very different. This work was aimed at determining the fracture strength of human gallstones and investigating the effect of cholesterol content on this fracture strength. There are very few published data on the mechanical properties of gallstones. In one study two gallstones were tested by diametral compression [7]. These stones had fracture strengths of 0.23 MPa (33 lb in.-2) and 0.31 MPa (44 lb in.-2). In comparison, similar tests performed on kidney stones yielded fracture strengths ranging from 0.45 to 1.54MPa (65 to 2241bin. -2) [8]. In testing both kidney stones and gallstones, completely brittle behaviour of the stones was observed. These stones had been dried and rehydrated before testing. The present work serves to extend the determination of fracture strength of gallstones by diametral compression testing and to determine any correlation of cholesterol content with this fracture strength. Gallstones cannot readily be formed into standard tensile test samples for use with normal tensile testing machines. However, one test, the diametral compression test (sometimes called the Brazilian

Effect of cholesterol content on some physical and functional properties of mitochondria isolated from adult rat liver, fetal liver, cholesterol-enriched liver and hepatomas AH-130, 3924A and 5123

The choleterol to phospholipid ratio in mitochodria from hepatomas AH-130, 3924A and 5123 is higher than in the particles isolated from adult or fetal rat livers. Nearly all the cholesterol of hepatoma mitochonda is located in membranes. As in liver mitochondria, in the particles isolated from hepatoma AH-130 there is more cholesterol in the outer than in the inner membrane. In mitochondria from cholesterol-enriched liver and hepatomas, there occur a decrease in extent of hypoosmotic and phosphate-induced sweeling and decrease of conformational linked energy states. The phenomenon is more marked in particles which exhibit higher cholesterol to phospholopid ratios. A statistically significant negative correlation exists between the cholesterol to phospholipid ratio and extent of volume or conformation changes. No significant modifications of these parameters were found in fetal liver mitochondria. Cholesterol content does not influence K + uptake by cholesterol-enriched or hepatoma mitochondria. Nor does cholesterol content affect the respiratory increment related to this uptake. As a consequence of K + uptake, total mitochodrial water exchangeable with tritiated water rises 20% while sucrose-impermeable water rises 42–48% in both adult rat liver and hepatoma AH-130 mitochondria. Absorbance changes linked to ion uptake do not correspond merely to variations in mitochobdrial water content. Water content. Water is apparently not influenced by the cholesterol to phospholipid ratio. However, the ratio is signifacantly correlated to both extent and initial rate of absorbance decrease of mitochondrial suspension during K + uptake. The higher the ratio, the lower the extent and and initial rate of absorbance decrease.