Effect of cholesta-3,5-dien-7-one on human liver aldehyde dehydrogenase

Distinct features of bivalent direct thrombin inhibitors, hirudin and bivalirudin, revealed by clot waveform analysis and enzyme kinetics in coagulation assays

AIMS

Bivalent direct thrombin inhibitors (DTIs), hirudin and bivalirudin, bind to the active site and exosite 1 of thrombin irreversibly and reversibly, respectively. The present study aims to assess in vitro effects of hirudin and bivalirudin through clot waveform analysis (CWA) and enzyme kinetics in coagulation assays.

METHODS

The pooled normal plasma and its dilutions were spiked with hirudin or bivalirudin. The activated partial thromboplastin time (APTT) assay and the Clauss fibrinogen assay were performed using the CS-5100 (Sysmex). The APTT-CWA data were automatically gained by the CS-5100 programme.

RESULTS

In APTT-CWA, the maximum coagulation velocity, acceleration and deceleration were decreased dependently on the drug concentrations, demonstrating evidence for the blockade of thrombin-positive feedback by hirudin or bivalirudin. The Hill plot analysis was applied to the dose-dependent curves in bivalirudin. The Hill coefficients were greater than 1, showing positive anticoagulant cooperativity. Regarding the dose-dependent curves in hirudin, all the parameters dropped to almost zero without making an asymptotic line. In the Clauss fibrinogen assay, the Lineweaver-Burk plots demonstrated that both drugs exhibit mixed inhibition mimicking uncompetitive binding. The Dixon plots in bivalirudin were linear and supported the inhibition type described above. The Dixon plots in hirudin were non-linear and inappropriate to use for determination of the inhibition type. In addition, the inverse function of the clotting time appeared to drop to zero without making an asymptotic line, suggesting complete loss of thrombin activity by irreversible binding.

CONCLUSIONS

The results provide insights into anticoagulation with bivalent DTIs.

Biodegradation of cytotoxic 7-Ketocholesterol by Pseudomonas aeruginosa PseA

The present study aims to degrade 7-Ketocholesterol (7KC), a major oxysterol implicated in many age-related disorders, through microbial means and find candidate enzymes involved for further application in food systems and as a therapeutic. During initial screening of previously isolated bacteria from our laboratory, Pseudomonas aeruginosa PseA was found to be a potential degrader strain using 7KC as a sole carbon source. Under optimized conditions, it is able to degrade 88% of an initial concentration of 1000ppm (1g/l) 7KC. Preliminary in vitro studies with extra-cellular extract has shown degradation of the compound, thus reinforcing the occurrence of suitable enzymatic systems involved in the process. We have been able to identify cholesterol oxidase as one such potential enzyme. Some intermediate products of degradation have also been identified. This is the first detailed report of 7KC degradation by a P. aeruginosa strain.

Oxysterols: modulators of cholesterol metabolism and other processes

Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.

Review of progress in sterol oxidations: 1987-1995

Material dealing with the chemistry, biochemistry, and biological activities of oxysterols is reviewed for the period 1987-1995. Particular attention is paid to the presence of oxysterols in tissues and foods and to their physiological relevance.

Identification of cholesta-3,5-dien-7-one by gas chromatography-mass spectrometry in the erythrocyte membrane of alcoholic patients

Lipids and oxidized lipids were analyzed by gas chromatography-mass spectrometry in the erythrocyte membranes of alcoholic and control subjects. Cholesta-3,5-dien-7-one and cholesta-trienes were detected in alcoholic samples examined, but not in significant amounts in controls. Levels of polyunsaturated fatty acids (arachidonic acid, 20:4; docosahexaenoic acid, 22:6; and docosatetraenoic acid, 22:4) in alcoholic samples declined significantly, whereas cholesta-3,5-dien-7-one levels increased. A high level of total bilirubin was observed in most patients. A possible mechanism of the accumulation of cholesta-3,5-dien-7-one in the erythrocyte membrane of alcoholics is discussed.

Human prostatic aldehyde dehydrogenase of healthy controls and diseased prostates

Aldehyde dehydrogenase (ALDH, EC 1.2.1.3) of the human prostate was the subject of investigation in this study. The possible physiological role of aldehyde dehydrogenase in the human prostate might be to detoxify aldehydes arising from the oxidation of the polyamines via monoamine or diamine oxidases. The specific activity of the enzyme with 1 mM propionaldehyde as substrate and 0.5 mM NAD at pH 7.4 in the control normal prostates and prostates afflicted with the disease, benign prostatic hyperplasia (BPH), was 26.06 +/- 2.96 and 5.17 +/- 0.48 nmol/g prostate per min, respectively. When 100 microM gamma-aminobutyraldehyde was used as a substrate, the specific activity in the normal controls and prostates with benign prostatic hyperplasia was 19.80 +/- 1.33 and 2.95 +/- 2.46 nmol/g prostate per min, respectively. Upon isoelectric focusing of the extracts of the control prostates when the gels were developed for aldehyde dehydrogenase activity, there were three aldehyde dehydrogenase activity bands visible, pI 4.9 (mitochondrial), 5.4 (cytosolic) and about 6.0-6.5, on the IEF gels developed with gamma-aminobutyraldehyde as a substrate. With the extracts of prostates with benign prostatic hyperplasia the pI 4.9 band was significantly reduced, the pI 5.4 band enhanced and the approx. pI 6.0 band was not detectable on the IEF gels with propionaldehyde as a substrate. There was no detectable aldehyde dehydrogenase activity in the extract of the prostate with cancer on IEF gels nor in the activity assays with propionaldehyde or gamma-aminobutyraldehyde as substrates.