| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Molecular biology of reverse cholesterol transport system and impairment of the protection system against atherosclerosis Yamashita, S. and Y. Matsuzawa (1993), Nippon Rinsho 51(6): 1684-91. Abstract: High density lipoprotein (HDL) plays an important role in the protection system against atherosclerosis, designated as "reverse cholesterol transport". Cholesterol from peripheral tissues is taken up by HDL and is esterified by lecithin: cholesterol acyltransferase (LCAT). The cholesteryl ester is subsequently transported to apoprotein B-containing lipoproteins, such as VLDL, IDL or LDL by cholesteryl ester transfer protein (CETP). These lipoproteins are catabolized by the liver via the LDL receptor pathway. This review focuses on the recent molecular biological data on the enzymes and proteins involved in this system, with special reference to their genetic abnormalities. The molecular basis of HDL, LCAT, CETP or HTGL deficiency has recently been clarified. HDL deficiency is often accompanied by premature atherosclerosis. Deficiency of these enzymes causes marked alterations in the concentration and composition of HDL and apo B-containing lipoproteins. |
| Molecular biology of the human cytosolic sulfotransferase gene superfamily implicated in the bioactivation of minoxidil and cholesterol in skin Dooley, T. P. (1999), Exp Dermatol 8(4): 328-9. Abstract: Cytosolic sulfotransferases (ST) catalyze the sulfation of various phenolic agents, catecholamines, thyroid hormones, steroids, drugs, and procarcinogens, usually resulting in the inactivation and subsequent excretion of the compound. My laboratory's efforts have focused on the cloning of the human phenol-sulfating (PST) members of this gene superfamily, implicated in the bioactivation of the hair growth stimulant, minoxidil. At least two major forms of human PST enzymes have been characterized biochemically, the phenol-preferring PST (P-PST), and the catecholamine-preferring PST (M-PST). Various cDNAs have been cloned representing alleles of 3 gene loci termed as STP1, STP2, and STM, which were all mapped precisely to a small region on human chromosome 16p and to the homologous region of mouse chromosome 7. Human cosmid genomic clones have been sequenced to determine the genomic organization for each of the 3 highly-related genes. All contain 7 coding exons, with conserved intron-exon boundaries, and presumptive alternative tissue-specific promoters. At least one of the 3 PST-encoding genes is responsible for forming minoxidil sulfate in the lower outer root sheath of anagen hair follicles. The steroid sulfating genes, STD and STE, have been cloned by other laboratories. The isozyme products of these genes sulfate DHEA and estrogens, respectively. I hypothesize that either STE or STD is involved in the formation of cholesterol sulfate (CS) in epidermal keratinocytes. CS has been demonstrated by other groups to be an activator of keratinocyte Protein Kinase Ceta, which subsequently results in the activation of epidermal transglutaminase and formation of the cornified envelop. STE or STD might also be involved in bioinactivation of estrogens and androgens within skin. Our recent unpublished results have focused on elucidating the patterns of ST gene expression in cultured keratinocytes and fibroblasts derived from human skin using RT-PCR, to understand which of the 5 different ST genes in involved in the regulation of keratinocyte differentiation and minoxidil-induced hair growth. |
| Molecular characterization of the detergent-insoluble cholesterol-rich membrane microdomain (raft) of the central nervous system Maekawa, S., S. Iino, et al. (2003), Biochim Biophys Acta 1610(2): 261-70. Abstract: Many fundamental neurological issues such as neuronal polarity, the formation and remodeling of synapses, synaptic transmission, and the pathogenesis of the neuronal cell death are closely related to the membrane dynamics. The elucidation of functional roles of a detergent-insoluble cholesterol-rich domain (raft) could therefore provide good clues to the molecular understanding of these important phenomena, for the participation of the raft in the fundamental cell functions, such as signal transduction and selective transport of lipids and proteins, has been elucidated in nonneural cells. Interestingly, the brain is rich in raft and the brain-derived raft differs in its lipid and protein components from other tissue-derived rafts. Since many excellent reviews are written on the membrane lipid dynamics of this microdomain, signal transduction, and neuronal glycolipids, we review on the characterization of the raft proteins recovered in the detergent-insoluble low-density fraction from rat brain. Special focus is addressed on the biochemical characterization of a neuronal enriched protein, NAP-22, for the lipid organizing activity of this protein has become increasingly clear. |
| Molecular chlorine generated by the myeloperoxidase-hydrogen peroxide-chloride system of phagocytes converts low density lipoprotein cholesterol into a family of chlorinated sterols Hazen, S. L., F. F. Hsu, et al. (1996), J Biol Chem 271(38): 23080-8. Abstract: Oxidation of low density lipoprotein (LDL) may be of critical importance in triggering the pathological events of atherosclerosis. Myeloperoxidase, a heme protein secreted by phagocytes, is a potent catalyst for LDL oxidation in vitro, and active enzyme is present in human atherosclerotic lesions. We have explored the possibility that reactive intermediates generated by myeloperoxidase target LDL cholesterol for oxidation. LDL exposed to the myeloperoxidase-H2O2-Cl- system at acidic pH yielded a family of chlorinated sterols. The products were identified by mass spectrometry as a novel dichlorinated sterol, cholesterol alpha-chlorohydrin (6beta-chlorocholestane-(3beta,5alpha)-diol), cholesterol beta-chlorohydrin (5alpha-chlorocholestane-(3beta, 6beta)-diol), and a structurally related cholesterol chlorohydrin. Oxidation of LDL cholesterol by myeloperoxidase required H2O2 and Cl-, suggesting that hypochlorous acid (HOCl) was an intermediate in the reaction. However, HOCl failed to generate chlorinated sterols under chloride-free conditions. Since HOCl is in equilibrium with molecular chlorine (Cl2) through a reaction which requires Cl- and H+, this raised the possibility that Cl2 was the actual chlorinating intermediate. Consonant with this hypothesis, HOCl oxidized LDL cholesterol in the presence of Cl- and at acidic pH. Moreover, in the absence of Cl- and at neutral pH, Cl2 generated the same family of chlorinated sterols as the myeloperoxidase-H2O2-Cl- system. Finally, direct addition of Cl2 to the double bond of cholesterol accounts for dichlorinated sterol formation by myeloperoxidase. Collectively, these results indicate that Cl2 derived from HOCl is the chlorinating intermediate in the oxidation of cholesterol by myeloperoxidase. Our observations suggest that Cl2 generation in acidic compartments may constitute one pathway for oxidation of LDL cholesterol in the artery wall. |
| Molecular cloning of the promoter for rat hepatic neutral cholesterol ester hydrolase: evidence for transcriptional regulation by sterols Natarajan, R., S. Ghosh, et al. (1998), Biochem Biophys Res Commun 243(2): 349-55. Abstract: Neutral cholesterol ester hydrolase is a key enzyme in regulating hepatic free cholesterol. Using the CEH specific cDNA sequence in the 5'-untranslated region as a primer, we amplified and cloned 1.3 Kb of promoter sequence upstream of the ATG initiation codon. Analysis of the sequence revealed the presence of a consensus GC-box, which can bind the positive transcription factor Sp1, 35 bases upstream from the transcription start site. Transcriptional regulation by agents perturbing cholesterol metabolism was studied in HepG2 cells by transient transfection assays of the promoter activity in deletion constructs linked to the luciferase reporter gene. Three functional sterol response sequences were identified at positions-92, -160, and -280 of the CEH promoter. The sterol response sequence at position -92 was shown to bind SREBP-2. Therefore, the CEH gene is similar to other genes involved in regulation of cholesterol homeostasis, in that it appears to be transcriptionally regulated by sterols. |
| Molecular composition of biliary phosphatidylcholines, as related to cholesterol saturation, transport and nucleation in human gallbladder bile Angelico, M., S. Ginanni Corradini, et al. (1992), J Hepatol 15(1-2): 59-66. Abstract: It has been suggested that qualitative changes in bile phosphatidylcholine (lecithin) play a role in the pathogenesis of cholesterol gallstones. We investigated the possible relationship between the molecular composition and hydrophobicity of biliary lecithins and bile cholesterol saturation, nucleation time and the mode of cholesterol transport in human gallbladder bile. Nineteen patients (12 with and seven without gallstones) undergoing abdominal surgery were studied. Bile cholesterol saturation ranged from 77% to 186% (median: 123%) and nucleation time from 1 to 24 days (median: 3 days). Biliary lipid carriers (vesicles and mixed micelles) were separated using Superose-6 gel chromatography and their lipid content was quantitated. Biliary lecithin composition was analyzed by HPLC. Fourteen individual molecular species were detected in the bile: none were related to cholesterol saturation or nucleation time. An arbitrary cumulative index of lecithin hydrophobicity was computed for each bile sample, based on the HPLC capacity factor of the individual species and their percent mole fraction: this index ranged from 47.0 and 58.5 (median: 49) and was unrelated to cholesterol saturation and nucleation time. The biliary concentration of sn-1 palmitoyl:sn-2 arachidonoyl lecithin was significantly correlated (p less than 0.01) with the fraction of cholesterol carried by mixed micelles. This finding suggests that arachidonoyl lecithin may play a modulatory role in the partitioning of cholesterol among biliary carriers. We conclude that major abnormalities in the composition of biliary lecithins are unlikely to play a causative role in the pathogenesis of cholesterol gallstone, although the role of arachidonoyl species requires further investigation. |
| Molecular diagnosis of lecithin: cholesterol acyltransferase deficiency in a presymptomatic proband Cirera, S., J. Julve, et al. (1998), Clin Chem Lab Med 36(7): 443-8. Abstract: We report the molecular diagnosis of a lecithin: cholesterol acyltransferase deficiency in a 12-year old proband with a high-density lipoprotein deficiency. The increased percentage of free cholesterol in plasma and high-density lipoprotein indicated an inherited lecithin: cholesterol acyltransferase deficiency as the underlying cause. This diagnosis was confirmed by a low plasma lecithin: cholesterol acyltransferase activity and a combination of genetic analyses which demonstrated compound heterozygosity for two mutations in the lecithin: cholesterol acyltransferase gene of the proband. One was a previously unreported 2 bp deletion leading to a stop signal in codon 77 and the other a point mutation causing Arg 135-->Gln transition. To our knowledge, this is the first diagnosis of lecithin: cholesterol acyltransferase deficiency in a pre-symptomatic patient. Whether the proband will develop signs of complete lecithin: cholesterol acyltransferase deficiency or the milder form (Fish Eye Disease) is uncertain, although the former possibility is more likely. The risk of premature atherosclerosis conferred by lecithin: cholesterol acyltransferase deficiency is not well established. The proband will need to be carefully monitored in the future. |
| Molecular dynamics simulation of dipalmitoylphosphatidylcholine membrane with cholesterol sulfate Smondyrev, A. M. and M. L. Berkowitz (2000), Biophys J 78(4): 1672-80. Abstract: Using the molecular dynamics simulation technique, we studied the changes occurring in a dipalmitoylphosphatidylcholine (DPPC):cholesterol (CH) membrane at 50 mol% sterol when cholesterol is replaced with cholesterol sulfate (CS). Our simulations were performed at constant pressure and temperature on a nanosecond time scale. We found that 1) the area per DPPC:CS heterodimer is greater than the area of the DPPC:CH heterodimer; 2) CS increases ordering of DPPC acyl chains, but to a lesser extent than CH; 3) the number of hydrogen bonds between DPPC and water is decreased in a CS-containing membrane, but CS forms more water hydrogen bonds than CH; and 4) the membrane dipole potential reverses its sign for a DPPC-CS membrane compared to a DPPC-CH bilayer. We also studied the changes occurring in lipid headgroup conformations and determined the location of CS molecules in the membrane. Our results are in good agreement with the data available from experiments. |
| Molecular dynamics simulation of the structure of dimyristoylphosphatidylcholine bilayers with cholesterol, ergosterol, and lanosterol Smondyrev, A. M. and M. L. Berkowitz (2001), Biophys J 80(4): 1649-58. Abstract: Five molecular dynamics computer simulations were performed on different phospholipid:sterol membrane systems in order to study the influence of sterol structure on membrane properties. Three of these simulated bilayer systems were composed of a 1:8 sterol:phospholipid ratio, each of which employed one of the sterol molecules: cholesterol, ergosterol, and lanosterol. The two other simulations were of a bilayer with a 1:1 sterol:phospholipid ratio. These simulations employed cholesterol and lanosterol, respectively, as their sterol components. The observed differences in simulations with cholesterol and lanosterol may have their implication on the form of the phospholipid/sterol phase diagram. |
| Molecular dynamics simulations of phospholipid bilayers with cholesterol Hofsass, C., E. Lindahl, et al. (2003), Biophys J 84(4): 2192-206. Abstract: To investigate the microscopic interactions between cholesterol and lipids in biological membranes, we have performed a series of molecular dynamics simulations of large membranes with different levels of cholesterol content. The simulations extend to 10 ns, and were performed with hydrated dipalmitoylphosphatidylcholine (DPPC) bilayers. The bilayers contain 1024 lipids of which 0-40% were cholesterol and the rest DPPC. The effects of cholesterol on the structure and mesoscopic dynamics of the bilayer were monitored as a function of cholesterol concentration. The main effects observed are a significant ordering of the DPPC chains (as monitored by NMR type order parameters), a reduced fraction of gauche bonds, a reduced surface area per lipid, less undulations--corresponding to an increased bending modulus for the membrane, smaller area fluctuations, and a reduced lateral diffusion of DPPC-lipids as well as cholesterols. |
| Molecular dynamics simulations of stratum corneum lipid models: fatty acids and cholesterol Holtje, M., T. Forster, et al. (2001), Biochim Biophys Acta 1511(1): 156-67. Abstract: We report the results of an investigation on stratum corneum lipids, which present the main barrier of the skin. Molecular dynamics simulations, thermal analysis and FTIR measurements were applied. The primary objective of this work was to study the effect of cholesterol on skin structure and dynamics. Two molecular models were constructed, a free fatty acid bilayer (stearic acid, palmitic acid) and a fatty acid/cholesterol mixture at a 1:1 molar ratio. Our simulations were performed at constant pressure and temperature on a nanosecond time scale. The resulting model structures were characterized by calculating surface areas per headgroup, conformational properties, atom densities and order parameters of the fatty acids. Analysis of the simulations indicates that the free fatty acid fraction of stratum corneum lipids stays in a highly ordered crystalline state at skin temperatures. The phase behavior is strongly influenced when cholesterol is added. Cholesterol smoothes the rigid phases of the fatty acids: the order of the hydrocarbon tails (mainly of the last eight bonds) is reduced, the area per molecule becomes larger, the fraction of trans dihedrals is lower and the hydrophobic thickness is reduced. The simulation results are in good agreement with our experimental data from FTIR analysis and NIR-FT Raman spectroscopy. |
| Molecular genetic evidence of bacterial colonization of cholesterol gallstones Swidsinski, A., W. Ludwig, et al. (1995), Gastroenterology 108(3): 860-4. Abstract: BACKGROUND/AIMS: Cholesterol gallstone formation is believed to be unrelated to the presence of bacteria because attempts to culture potentially causative bacteria from surgically removed cholesterol stones have failed. However, the formation of gallbladder gallstones takes years. Embedded bacteria may be damaged or killed. The aim of this study was to search for bacterial DNA sequences in cholesterol stones with negative bacterial culture. METHODS: Bacterial gene fragments were amplified in vitro from DNA extracted from cholesterol gallbladder stones. Comparative 16S ribosomal RNA sequence analysis was used for identification. RESULTS: Gallstones with cholesterol content between 70% to 90% harbored bacterial DNA (16 of 17 patients). No bacterial DNA was found in the gallstones with cholesterol content of > 90% (3 patients). Three bacterial groups typical for gallstone colonization were identified. Propionibacteria-related DNA was found in the stones of 9 patients (45%). Enterobacterial type sequences were obtained in 5 patients (25%). A more heterogenous sequence collection was retrieved from 7 patients (35%) and could be assigned to the major bacterial line of gram-positive bacteria with a low DNA guanine and cytosine content. CONCLUSIONS: Most cholesterol gallstones harbor bacterial DNA. It is important to determine the actual role of these microorganisms in gallstone formation. |
| Molecular genetic study of Finns with hypoalphalipoproteinemia and hyperalphalipoproteinemia: a novel Gly230 Arg mutation (LCATFin) of lecithin:cholesterol acyltransferase (LCAT) accounts for 5% of cases with very low serum HDL cholesterol levels Miettinen, H. E., H. Gylling, et al. (1998), Arterioscler Thromb Vasc Biol 18(4): 591-8. Abstract: In an attempt to identify genetic factors underlying extreme alterations of serum HDL cholesterol (HDL-C) concentrations, we examined two probands with HDL-C levels <0.2 mmol/L and subsequently screened two large cohorts of smoking men, one with very low (0.2 to 0.7 mmol/L, n=156) and the other with elevated (1.9 to 3.6 mmol/L, n=160) HDL-C levels, for the newly detected mutations as well as some other mutations proposed to affect HDL-C levels. One of the probands had corneal opacities, microalbuminuria, hypertriglyceridemia, and reduced LDL apoprotein B concentration; the other had anemia and presented with stomatocytosis in his peripheral blood. The first proband was found to be homozygous for a novel LCAT Gly230Arg (LCATFin) mutation, and the second was homozygous for an Arg399Cys mutation we described previously. Transient expression of the mutant LCAT(Fin) cDNA in COS cells disclosed markedly diminished LCAT enzyme activity. In the low-HDL-C group of men (n=156), 8 carriers of LCAT(Fin) and 1 carrier of the LCAT Arg399Cys were identified. In addition, the frequency of the lipoprotein lipase (LPL) Asn291Ser mutation was significantly (P<.05) higher in the low-HDL-C group (4.8%) than in the high-HDL-C group (1.6%). In addition, we identified 1 carrier of the intron 14G-->A mutation of cholesterol ester transfer protein (CETP) in the high-HDL-C group and subsequently demonstrated cosegregation of the mutant allele with elevated HDL-C levels in the proband's family. In conclusion, we have identified a novel LCAT gene Gly230Arg mutation (LCATFin), which, together with the LPL Asn291Ser mutation, represents a relatively common genetic cause of diminishing HDL-C levels, at least among Finns. This article also reports occurrence of a CETP mutation in subjects having non-Japanese roots. |
| Molecular genetics of cholesterol cholelithiasis: identification of human and murine gallstone genes Figge, A., S. Matern, et al. (2002), Z Gastroenterol 40(6): 425-32. Abstract: Cholesterol cholelithiasis is one of the most common gastroenterological diseases in Western countries. It is a polygenic disease resulting from disturbed biliary cholesterol homeostasis. Association studies identified six human gallstone candidate genes. Polymorphisms in the genes encoding the apolipoproteins B and E, phospholipid flippase (ABCB4), cholesterol ester transfer protein (CETP), cholesterol-7alpha-hydroxylase (CYP7A1) and ileal bile acid transporter (SLC10A2) are correlated with gallstone prevalence. Quantitative Trait Locus (QTL) analysis localises additional unknown gallstone genes in inbred mice. Based on the natural variation of cholesterol gallstone susceptibility among different inbred strains, 5 lithogenic (Lith) loci have been identified. Hepatobiliary transporters (e. g. bile salt export pump Abcb11) and key proteins of the lipoprotein metabolism (e. g. hepatic lipase Lipc) could be established as creedal candidate genes for Lith loci. The rapid progress of mouse and human genome projects provides the basis for the analysis of orthologous human LITH genes in gallstone patients, which might offer new prospects for individual risk assessment and molecular targets for stone prevention. |
| Molecular genetics of cholesterol transport and cholesterol reverse transport disorders (familial hypercholesterolemia and CETP deficiency) and coronary heart disease Mabuchi, H., K. Yagi, et al. (1995), Ann N Y Acad Sci 748: 333-41. |
| Molecular genetics of cholesterol transport and cholesterol reverse transport disorders (familial hypercholesterolemia and CETP deficiency), and coronary heart disease Mabuchi, H. (1995), Rinsho Byori 43(4): 342-6. Abstract: Familial hypercholesterolemia (FH) is a disorder of LDL receptor abnormalities, and the resultant high-LDL-cholesterolemia produces atherosclerosis. More than 150 different mutations in the LDL receptor gene have been reported in the world. Seven variants of the LDL receptor gene have been identified in our laboratory. These seven mutants in 85 patients from 31 families accounted for only 15.5% of the FH cases. LDL receptor gene abnormalities are highly heterogenous in Japan, and the variation of the LDL receptor mutant may determine the severity of hypercholesterolemia and coronary heart disease in FH. A serum HDL above 60 mg/dl is a negative risk factor for coronary atherosclerosis. We found that familial hyperalphalipoproteinemia can be produced by CETP deficiency due to a CETP gene. Two common mutants of the CETP gene produce a CETP deficiency and resultant antiatherogenic lipoprotein pattern (i.e. hyper-HDL-cholesterolemia and hypo-LDL-cholesterolemia), and the frequency of the mutant allele is more than 1 in 10 subjects in Japan. Finally, we found unique patients with double heterozygotes of FH and CETP deficiency. We found 16 double heterozygotes of the LDL receptor gene and CETP gene. Four of the 16 patients showed myocardial infarction and 4 showed angina pectoris. These findings suggest that the atherogenicity of hyper-LDL-cholesterolemia in FH is more powerful than antiatherogenicity of hyper-HDL-cholesterolemia in CETP deficiency. |
| Molecular link between cholesterol, cytokines and atherosclerosis Kaul, D. (2001), Mol Cell Biochem 219(1-2): 65-71. Abstract: Current investigation on the origin of atherosclerosis has initiated an intense debate over whether atherosclerosis results from hypercholesterolemia or an inappropriate immune response to vascular injury. Although the role of the immune system has been questioned, the overwhelming body of evidence clearly indicates that atherogenesis is initiated by the interplay between cholesterol and cellular secretion of cytokines (especially IL-6) and apolipoprotein 'E' within the arterial wall. Recent studies have revealed that cells possess two cholesterol-sensors: (a) Receptor-Ck which senses the extracellular cholesterol and initiates signalling pathway responsible for the regulation of genes involved in the cell cycle, cell death, cellular cholesterol homeostasis and cytokines including IL-6; (b) LxR alpha which senses intracellular oxysterols and controls genes involved in cell death, cellular cholesterol homeostasis and cytokine IL-8. These cholesterol sensors define the molecular mechanism responsible for cholesterol-depended regulation of cellular synthesis and secretion of cytokines (IL-6, IL-8) within arterial wall. On the basis of this mechanism, presence of cholesterol and its oxy-derivative in the modified LDL will result in transient activation/deactivation of Receptor-Ck-dependent genes which will give rise to repeated cycles of growth coupled with apoptosis leading to a situation where apoptotic-deficient cells in the arterial wall, would be selected resulting in their accumulation and formation of oligoclonal atherosclerotic plaque. |
| Molecular link between membrane cholesterol and cyclic nucleotides in human platelets Kochhar, N. and D. Kaul (1992), Blood Coagul Fibrinolysis 3(2): 215-9. Abstract: Because of the unresolved complex role of membrane cholesterol content in platelet activity, the present study was addressed to understand two specific issues; firstly whether variation in membrane cholesterol content could influence cyclic nucleotide levels within platelets, and secondly whether the membrane cholesterol modulated cyclic nucleotide levels were mediated through phospholipase A2 activation. The results of this in vitro study revealed that membrane cholesterol not only had the inherent capacity to induce changes in the levels of cyclic nucleotides within human platelets but also that this effect was mediated through its ability to modulate phospholipase A2 activity. Based on these results we suggest that membrane cholesterol modulated phospholipase A2 activity may be the molecular link between the membrane cholesterol content and cyclic nucleotides within human platelets. |
| Molecular link between membrane cholesterol and Na+/H+ exchange within human platelets Kochhar, N. and D. Kaul (1992), FEBS Lett 299(1): 19-22. Abstract: Incubation of human platelets with cholesterol-poor, cholesterol-normal and cholesterol-rich liposomes revealed that: (i) acquisition or depletion of platelet membrane cholesterol was highly selective; (ii) variation in membrane cholesterol was highly selective. Variation in membrane cholesterol content (cholesterol-to-phospholipid molar ratio from 0.15-1.2) with respect to values found in unmodified normal platelets, was paralleled by the observed changes in amiloride-sensitive cytoplasmic pH, as well as phospholipase A2 activity. However, a decrease in cytoplasmic pH was accompanied by an increase in phospholipase A2 activity; (iii) membrane cholesterol-modulated changes in intra-platelet pH, as well as phospholipase A2 activity, was completely inhibited when platelets were pretreated with quinacrine (a specific phospholipase A2 inhibitor) before exposure to various types of liposomes. Although exposure of platelets (pretreated with amiloride) with various types of liposomes resulted in the inhibition of Na+/H+ exchange it had no noticeable effect upon the observed phospholipase A2 activity. Based upon these results we suggest that membrane cholesterol-modulated phospholipase A2 activity may be the basic mechanism responsible for the nature of Na+/H+ exchanger activity observed in cholesterol-enriched platelets, leading these platelets to a hypersensitized state. |
| Molecular mechanism investigation of phenobarbital-induced serum cholesterol elevation in rat livers by microarray analysis Kiyosawa, N., K. Tanaka, et al. (2004), Arch Toxicol 78(8): 435-42. Abstract: Phenobarbital (PB) increases serum total cholesterol levels in rodents and humans. To investigate the underlying molecular mechanisms, we performed a microarray analysis on liver of rats treated repeatedly with 100 mg/kg PB, and examined the serum blood chemistry. The serum concentration of non-esterified fatty acids was decreased from day 1 to day 14 except for day 7, and that of cholesterol was increased from day 4 to day 14. The serum concentration of total ketone bodies was increased on day 7, and that of triglycerides was decreased on day 14. Transcript content of glycolytic genes was decreased by PB treatments, while that of lipoprotein lipase was continuously increased, suggesting a notion that repetitive PB treatments impaired glycolysis and stimulated lipolysis in the liver. The hypothesis was examined by using a previously reported flux-balance model. The increase in mRNA content of malic enzyme after the PB treatment agreed well with the flux-balance model result, suggesting the validity of our hypothesis. The findings also suggested that there was an abundance of acetyl-CoA and shortage of glycolytic products after the repeated PB treatments. Although ketogenesis would normally occur under such cellular conditions, it was only weakly observed after the repeated PB treatments, presumably owing to a decrease in HMG-CoA synthase mRNA content. On the other hand, the mRNA content of several cholesterogenic genes was slightly induced by PB treatments. Thus, serum chemistry and microarray results suggested that repeated PB treatments induced cholesterogenesis in rat livers, which may have contributed to the elevation of the serum total cholesterol concentration. |