Classifying class I and class II compounds by hydrophobicity and hydrogen bonding descriptors

The successful development of quantitative structure-activity relationships (QSARs) and the prediction of toxicity based on QSARs depend on the correct classification of the mechanism of toxic action of chemical compounds. The toxicity mechanism of a compound can be determined by a few existing methods, such as studying the chemical structure of the compound for certain substructures and assigning a mechanism accordingly. However, these methods are less reliable for compounds with complex structures and are usually complicated. A novel descriptor-based method employing a multivariate statistical technique--discriminant analysis--was developed in this study for the classification of class I and class II compounds. The discriminating variables used in discriminant analysis were the hydrophobicity descriptor log(K(ow)) and the hydrogen bonding descriptors E(LUMO), E(HOMO), Q(+), and Q(-). Because only numerical values of these descriptors are required for this method, which can be calculated, no additional experimental work was required for the toxicity mechanism classification of new compounds. A nonlinear discriminant function was generated that could not be expressed explicitly. Assessing the predicting ability of the discriminant function by the cross-validation method showed that a low total error rate, 4.2% was achieved.

Determining the mechanisms of toxic action of phenols to Tetrahymena pyriformis

Phenols are environmentally important compounds that are widely used in agriculture and industry. Thus, phenols are of interest to environmental toxicologists, which has led to the development of several quantitative structure-activity relationship (QSAR) models. The most successful QSARs have been established for compounds having a common mechanism of toxic action (MOA). However, correctly determining the MOA of a compound is not easy. Discriminant analysis was used in this study to separate phenols by their MOAs. The working hypothesis of this study was that phenols with different MOAs lie in different regions in the response surface described by the ionization-corrected hydrophobicity descriptor, log D, the electrophilicity descriptor, ELUMO, and the interaction between hydrophobicity and electrophilicity, D * ELUMO. Results of discriminant analysis showed a total error rate of 15%. In addition, it was difficult to separate phenols that had a polar narcosis MOA from phenols that had a proelectrophile MOA.

Killing effect and antitoxic activity of the Leptospira interrogans toxin-antitoxin system in Escherichia coli

We report the first evidence of a chromosome-encoded toxin-antitoxin locus in spirochetes. This locus has been found in the pathogenic spirochete Leptospira interrogans and exhibits homologies with the pem/chp loci. The L. interrogans chp locus consists of two genes: chpK (for "killer protein") and its upstream partner chpI (for "inhibitory protein"). Expression of ChpK in Escherichia coli results in the inhibition of bacterial growth. The coexpression of ChpI neutralizes ChpK toxicity. By Southern blot analysis, chp homologs were found in all representative pathogenic strains of L. interrogans.

Development of HIV protease inhibitors: a survey

In the treatment of infections caused by rapidly mutating viruses like human immunodeficiency virus (HIV), combination therapy with multiple drugs acting by different mechanisms offers several advantages over monotherapy. It may provide: synergistic effect, possible reduction of dosages and side-effects, and reduction of the chance of drug resistance. In the past few years, hundreds of HIV protease inhibitors have been synthesized and tested in order to overcome the limitations of reverse transcriptase inhibitors like zidovudine and others. In this review, emphasis is placed on the development of HIV protease inhibitors as antiviral agents against HIV, and structure-activity relationship analysis of saquinavir and related compounds. Limitations of some protease inhibitors and ways to overcome the shortcomings are presented. Among these many protease inhibitors five have been marketed during 1995-1999. They are saquinavir, ritonavir, indinavir, nelfinavir and amprenavir. Their different structural features, important physicochemical, pharmacokinetic and clinical profiles are presented in a table form for easy comparison. It is hoped that in the future new drugs based on additional mechanisms can be developed for the treatment of AIDS.

Inhibition of tumor cell growth by Schiff bases of hydroxysemicarbazide

The inhibitory activities of Schiff bases of hydroxysemicarbazide (HSC) against eight human and murine tumor cell lines and one non-cancer cell line were studied using MTS/PES microculture tetrazolium and methylene blue assays. Compounds 1 (1-[9-(10-methylanthryl)methylene]-4-HSC), 2 (1-[2-hydroxy-3,5-dibromobenzylidene]-4-HSC) and 3 (1-[2,3,4-trihydroxybenzylidene]-4-HSC), which have been shown to be active against murine leukemia L1210 cells in our laboratories, inhibited human leukemia CCRF-CEM cells with similar IC50s ranging from 2.7 to 7.0 microM. Of the compounds tested against attached tumor cell lines (B16, CHO, HT29, ZR75) at 50 microM concentration, compound 1 showed the strongest inhibition, followed by 4 (1-[2-(5-nitrothienyl)methylene]-4-HSC), 2 and 5 (1-[2-hydroxy-3,5-diiodobenzylidene]-4-HSC) with more than 50% inhibition. The IC50s of compound 1 were found to range from 2.7 to 12 microM against the attached tumor cell lines examined. As compared with hydroxyurea, compound 1 had more favorable selectivity against tumor cells. Further more, compound 1 was found to have IC50s of 2.8 and 6.5 microM against hydroxyurea-resistant and gemcitabine-resistant KB cells, respectively, but had no cross-resistance with hydroxyurea and gemcitabine (two known ribonucleotide reductase inhibitors acting at different sites of the same enzyme). In conclusion, several Schiff bases of HSC showed inhibition of tumor cell growth at micromolar concentration and had no cross-resistance with hydroxyurea-resistant KB cells.

The simultaneous determination of diazepam and its three metabolites in dog plasma by high-performance liquid chromatography with mass spectroscopy detection

A fast, sensitive and specific LC/MS/MS method for the simultaneous determination of diazepam and its three metabolites, oxazepam, temazepam and desmethyldiazepam, in dog plasma is described. The method consists of an automated 96-well solid phase extraction procedure and electrospray LC/MS/MS analysis. D(5)-Diazepam is used as the internal standard for all the compounds. Intra-day and inter-day assay coefficients of variations are less than 12.7%. The lower limit of quantitation (LLOQ) is 1 nM for each analyte, based on 0.1 ml aliquots of dog plasma. The analytical run time was 5 min. Linearity is observed over the range of 1--500 nM. This method has been used to support the discovery of pharmacokinetic studies.

Synthesis and in vitro antitumor activity of oligonucleotide-tethered and related platinum complexes

Three classes of hydroxy-tethered platinum(II) complexes have been synthesized from K(2)PtCl(4) and appropriate amino alcohols. A sequence of selective oxidation and hydrolysis has been developed to prepare hydroxy-tethered platinum(IV) complexes. A novel procedure for the synthesis of amminetrichloroplatinate(II) anion has been generated and used to synthesize a number of monohydroxy-tethered nonchelating platinum complexes. These tethered platinum complexes, including hydroxy-tethered, phosphoramidite-tethered, and monodeoxyribonucleotide-tethered platinum(II) and -(IV) complexes, have been examined in vitro for antitumor activity in both leukemia and ovarian cancer cell lines. Activity of some of these complexes was similar to cis-platin, and most of them showed much better potency than carboplatin. We observed an interesting structure-activity correlation for platinum(II) complexes for both PA-1 and SK-OV-3 ovarian cancer cell lines. However, platinum(IV) complexes showed much more diversified response among cancer cell lines studied. We observed enhanced selectivity among different cancer cell lines for some agents. The most promising is the monodeoxyribonucleotide-tethered platinum(IV) complex, which is the first analogue of the conjugates between a platinum fragment and monodeoxyribonucleotides, showing antitumor activity and selectivity among the cell lines. Finally, the p53 status of the cells appears to contribute to the effectiveness of these agents in that cells harboring wild-type p53 appear to be more sensitive to these agents.

Biotransformation of D-limonene to (+) trans-carveol by toluene-grown Rhodococcus opacus PWD4 cells

The toluene-degrading strain Rhodococcus opacus PWD4 was found to hydroxylate D-limonene exclusively in the 6-position, yielding enantiomerically pure (+) trans-carveol and traces of (+) carvone. This biotransformation was studied using cells cultivated in chemostat culture with toluene as a carbon and energy source. The maximal specific activity of (+) trans-carveol formation was 14.7 U (g of cells [dry weight])(-1), and the final yield was 94 to 97%. Toluene was found to be a strong competitive inhibitor of the D-limonene conversion. Glucose-grown cells did not form any trans-carveol from D-limonene. These results suggest that one of the enzymes involved in toluene degradation is responsible for this allylic monohydroxylation. Another toluene degrader (Rhodococcus globerulus PWD8) had a lower specific activity but was found to oxidize most of the formed trans-carveol to (+) carvone, allowing for the biocatalytic production of this flavor compound.

Purine analogs as CDK enzyme inhibitory agents: a survey and QSAR analysis

Characterization of the cell cycle has introduced CDKs and other proteins as possible targets for inhibition of cell proliferation, such as, CDK1 and CDK2, whose inhibition may be useful in the treatment of proliferative disorders. Structure-activity analyses have been instrumental in the design and discovery of potent CDK inhibitors, such as purine analogs, which have increased in potency from the micromolar to the nanomolar level. X-ray crystallography and molecular modeling have provided evidence that these compounds act on the CDK target enzyme. Selected CDK inhibitors have successfully entered clinical trials. Further characterization of the cell cycle to identify molecular targets to inhibit cell proliferation, QSAR and SAR studies, and clinical trials may expedite the development of CDK inhibitors for therapeutic use. The ultimate goal of these studies is to determine whether specific CDKs, CDK1 or CDK2, are enzymes essential to cell proliferation that can be targeted for treatment of proliferative disorders. CDK1 and CDK2 are viable molecular targets for cancer therapies based on isolated-enzyme inhibition by CDK inhibitors, successful clinical trials of CDK1 and CDK2 inhibitors, and x-ray crystallographic confirmation of CDK inhibitors binding to the putative target enzyme active site. It is now reported that CDK1 inhibitory activities of purine analogs correlate with the physiochemical parameters of purine analogs. Enzyme inhibition [1-5], clinical trials (see Tab. 1), x-ray crystallographic [4, 6, 7] and QSAR correlation studies are evidence that specific CDK1 and/or CDK2 inhibitors are potentially useful agents for various cell-proliferation disorders. A brief overview of the cell cycle precedes a literature review of clinical applications of CDK inhibitors, followed by a new QSAR study, and a SAR and molecular modeling discussion.

Caspase-dependent cytosolic release of cytochrome c and membrane translocation of Bax in p53-induced apoptosis

Activation of p53 induces apoptosis in various cell types. However, the mechanism by which p53 induces apoptosis is still unclear. We reported previously that the activation of a temperature-sensitive mutant p53 (p53(138Val)) induced activation of caspase 3 and apoptosis in Jurkat cells. To elucidate the pathway linking p53 and downstream caspases, we examined the activation of caspases 8 and 9 in apoptotic cells. The results showed that both caspases were activated during apoptosis as judged by the appearance of cleavage products from procaspases and the caspase activities to cleave specific fluorogenic substrates. The significant inhibition of apoptosis by a tetrapeptide inhibitor of caspase 8 and caspase 9 suggested that both caspases are required for apoptosis induction. In addition, the membrane translocation of Bax and cytosolic release of cytochrome c, but not loss of mitochondrial membrane potential, were detected at an early stage of apoptosis. Moreover, Bax translocation, cytochrome c release, and caspase 9 activation were blocked by the broad-spectrum caspase inhibitor, Z-VAD-fmk and the caspase 8-preferential inhibitor, Ac-IETD-CHO, suggesting that the mitochondria might participate in apoptosis by amplifying the upstream death signals. In conclusion, our results indicated that activation of caspase 8 or other caspase(s) by p53 triggered the membrane translocation of Bax and cytosolic release of cytochrome c, which might amplify the apoptotic signal by activating caspase 9 and its downstream caspases.

Transcellular signaling and pharmacological modulation of thrombin-induced production of plasminogen activator inhibitor-1 in vascular smooth muscle cells

Thrombin formation is increased at the sites of vascular injury. Previous studies by our group and other groups indicated that the generation of plasminogen activator inhibitor-1 (PAI-1), the major physiological inhibitor for plasminogen activators, from cultured vascular smooth muscle cells (SMC) is elicited by thrombin. The present study demonstrates that the thrombin receptor, pertussis toxin-sensitive G protein, genistein-sensitive tyrosine kinase, phospholipase C, and protein kinase C may be involved in thrombin-induced PAI-1 production in cultured baboon aortic SMC. Forskolin and 8-bromo-cyclic AMP inhibited thrombin-induced PAI-1 production in cultured SMC. Treatment with hirulog-1, a synthetic thrombin receptor inhibitor, suppressed thrombin-induced PAI-1 generation at mRNA and protein levels in SMC. The results of the present study suggest that transmembrane receptor and multiple signal transduction systems are involved in thrombin-induced increase in PAI-1 transcription in vascular SMC. The production of PAI-1 stimulated by thrombin in vascular SMC may be pharmacologically modulated by thrombin receptor inhibitor.

A simplified method to prepare PCR template DNA for screening of transgenic and knockout mice

Polymerase chain reaction (PCR) amplification of DNA is the most widely used technique for screening of large numbers of genetically engineered transgenic or knockout mice (Mus musculus). In this report, we present a new DNA preparation procedure for running diagnostic PCR. In this procedure, mouse ear tissue was used directly for PCR after the tissue underwent brief digestion in a solution containing only proteinase K. Using this method, we have successfully screened several lines of single, double, and triple transgenic and knockout mice. The results are reliable and reproducible. The advantage of this new method is that DNA purification by organic extraction or isolation kit was omitted. DNA purification is the limiting factor in terms of time and money when screening transgenic and knockout mice by PCR. In addition, using ear instead of tail tissue can reduce distress of animals because the samples can be obtained when the mice are labeled by ear punch.

[Construction of luciferase reporter plasmid which is under the control of dioxin-responsive enhancers]

To improve the bio-detection of dioxin-type chemicals, we constructed a plasmid containing reporter under the control of dioxin-responsive enhancer. After connected the enhancer from the plasmid pHAV with the MMTV promoter of the plasmid pCatM, the connected segment was linked with the luciferase vector. Then the recombinant plasmid was transfected to the HepG2 human hepatoma cell line, and the luciferase activity was induced by 2,3,7,8-TCDD. The result suggested that expression of the recombinant luciferase was controlled by the dioxin-responsive enhancer, and there were a linear relationship between the activity of luciferase and certain range of 2,3,7,8-TCDD concentration. It is promising that the transfected cell line could be used for rapid screen and semi quantitation of dioxin-type chemicals, and a standard and routine method for the detection of dioxin-type chemicals by this recombinant plasmid is being under way.

Hirulog-like peptide reduces balloon catheter injury induced neointima formation in rat carotid artery without increase in bleeding tendency

Vascular restenosis is one of the major concerns for the management of coronary artery disease using therapeutic vascular procedures. Treatments with thrombin-specific inhibitors, hirudin or hirulog-1, reduced ischemic events in coronary artery disease patients. Early started and prolonged infusions of these thrombin inhibitors partially prevented balloon catheter injury induced restenosis or neointima formation in experimental animal models, but increased the bleeding tendency. Hirulog-like peptide (HLP) was rationally designed to enhance the inhibition of the binding of thrombin to its receptor with less interruption of coagulation activity in comparison to hirulog-1. A single infusion of HLP for 4 h started 0.5 h before balloon catheter injury reduced neointima formation by 36% in rat carotid artery compared to vehicle controls. Tail bleeding time and activated partial thromboplastin time during HLP infusion were not significantly different from vehicle controls, but were significantly shorter than during heparin or hirulog-1 infusion. HLP treatment attenuated the expression of platelet-derived growth factor in the neointima of injured arteries. HLP also inhibited thrombin-induced thymidine incorporation in cultured baboon aortic smooth muscle cells. The findings suggest that HLP may substantially inhibit balloon catheter injury induced neointima formation without noticeable increase in bleeding tendency in rats. The inhibition by HLP of the expression of platelet-derived growth factor and of the smooth muscle cell proliferation in the vascular wall potentially contributes to the preventive effect of the new thrombin inhibitor on injury-induced neointima formation in the vascular wall.

Hepatitis B virus (HBV) virion and covalently closed circular DNA formation in primary tupaia hepatocytes and human hepatoma cell lines upon HBV genome transduction with replication-defective adenovirus vectors

Hepatitis B virus (HBV), the causative agent of B-type hepatitis in humans, is a hepatotropic DNA-containing virus that replicates via reverse transcription. Because of its narrow host range, there is as yet no practical small-animal system for HBV infection. The hosts of the few related animal viruses, including woodchuck hepatitis B virus and duck hepatitis B virus, are either difficult to keep or only distantly related to humans. Some evidence suggests that tree shrews (tupaias) may be susceptible to infection with human HBV, albeit with low efficiency. Infection efficiency depends on interactions of the virus with factors on the surface and inside the host cell. To bypass restrictions during the initial entry phase, we used recombinant replication-defective adenovirus vectors, either with or without a green fluorescent protein marker gene, to deliver complete HBV genomes into primary tupaia hepatocytes. Here we show that these cells, like the human hepatoma cell lines HepG2 and Huh7, are efficiently transduced by the vectors and produce all HBV gene products required to generate the secretory antigens HBsAg and HBeAg, replication-competent nucleocapsids, and enveloped virions. We further demonstrate that covalently closed circular HBV DNA is formed. Therefore, primary tupaia hepatocytes support all steps of HBV replication following deposition of the genome in the nucleus, including the intracellular amplification cycle. These data provide a rational basis for in vivo experiments aimed at developing tupaias into a useful experimental animal system for HBV infection.

Disialoganglioside GD3 is selectively expressed by developing and mature human mast cells

BACKGROUND

Disialoganglioside GD3 is expressed on the surface of selected cell types. Anti-GD3 mAb administered to human subjects with malignant melanoma produces signs and symptoms of immediate hypersensitivity reactions.

OBJECTIVE

The expression of GD3 by human mast cells was assessed during mast cell development in vitro and in samples of lung and skin.

METHODS

GD3 on tissue- and in vitro-derived mast cells was analyzed after double labeling of cells for tryptase (G3 mAb) or Kit (YB5.B8 mAb) and GD3 (R24 mAb). Glycolipids in extracts of fetal liver-derived mast cells were examined by using high-performance thin-layer chromatography.

RESULTS

Flow cytometry showed that the percentage of GD3+ cells increased in parallel to Kit+ cells during the recombinant human stem cell factor-dependent development of fetal liver-derived mast cells. Double-labeling experiments showed that GD3+ cells were also surface Kit+ and granule tryptase positive, identifying them as mast cells in preparations of lung-, skin-, fetal liver-, and cord blood-derived cells. The major acidic glycolipid detected was NeuAcalpha2-8NeuAcalpha2-3Galbeta1-4Glcbeta1-1'Cer (GD3). Among peripheral blood leukocytes, only basophils and about 10% of the T cells were labeled with anti-GD3 mAb. Anti-GD3 mAb-conjugated magnetic beads were used to purify mast cells to greater than 90% purity from dispersed skin cells enriched to approximately 12% purity by means of density-dependent sedimentation but were less proficient for dispersed human lung mast cells, most likely because of other cell types that express GD3.

CONCLUSION

GD3 is expressed on the surface of developing human mast cells in parallel to tryptase in secretory granules and, like Kit, can serve as a target for their enrichment by immunoaffinity techniques.

Neurological abnormalities in a knock-in mouse model of Huntington's disease

Mice representing precise genetic replicas of Huntington's disease (HD) were made using gene targeting to replace the short CAG repeat of the mouse Huntington's disease gene homolog (HDH:) with CAG repeats within the length range found to cause HD in humans. Mice with alleles of approximately 150 units in length exhibit late-onset behavioral and neuroanatomic abnormalities consistent with HD. These symptoms include a motor task deficit, gait abnormalities, reactive gliosis and the formation of neuronal intranuclear inclusions predominating in the striatum. This model differs from previously described HDH: knock-ins by its method of construction, longer repeat length and more severe phenotype. To our knowledge, this is the first knock-in mouse model of HD to show increased glial fibrillary acidic protein immunoreactivity in the striatum, suggesting that these mice have neuronal injury similar to that found early in the course of HD. These mice will serve as useful reagents in experiments designed to reveal the molecular nature of neuronal dysfunction underlying HD.

Efficacy and effect of SI17 therapy on pancreatic polypeptide in vascular and tension-type headache

BACKGROUND AND PURPOSE

Vascular and tension-type headache is most commonly encountered, and SI17 therapy has been tested to treat headache with good results. The efficacy of SI17 therapy for vascular and tension-type headache was compared and the effect of SI17 therapy on pancreatic polypeptide (PP) was studied.

MATERIALS AND METHODS

29 cases of vascular headache (20 cases in acute attack during the trial) and 27 cases of tension-type headache (19 cases in acute attack) were enrolled in the study. Plasma PP level before and 4th day after treatment was measured by radioimmunoassay.

RESULTS

SI17 therapy is better for the treatment of vascular headache. Vascular headache with higher PP level and tension-type headache with normal PP level had good therapeutic results.

CONCLUSION

The clinical efficacy is better for vascular headache with the increase of vagus tension and for tension-type headache with normal vagus tension.

Intracellular vitamin D binding proteins: novel facilitators of vitamin D-directed transactivation

Previously recognized intracellular proteins with an affinity for vitamin D metabolites include the vitamin D receptor and the cytochrome P-450-based vitamin D metabolizing mixed-function oxidases. We recently characterized a third set of high-capacity, intracellular vitamin D binding proteins (IDBPs) in the inducible heat shock protein-70 (hsp-70) family. Here we report the cloning and expression of cDNAs coding for two IDBPs. The full-length cDNAs for IDBP-1 and IDBP-2 demonstrated 95% and 94% nucleotide homology, respectively, with the cDNAs for human constitutively expressed heat shock protein 70 (hsc-70) and hsp-70. Transient expression of the IDBP cDNAs in a vitamin D-responsive primate cell line increased extractable 25-hydroxylated vitamin D metabolite-IDBP-binding 25-fold. Transfection experiments also demonstrated that the majority of the constitutively expressed 25-hydroxylated vitamin D metabolite binding activity was attributable to expression of the hsc-70-related IDBP-1 and that metabolite binding activity sublocalized to the highly conserved ATP-binding/ATPase domain of hsp-70s. Stable overexpression of IDBP-1 in wild-type cells enhanced vitamin D-directed responsiveness of endogenous vitamin D-24-hydroxylase, osteopontin, and osteocalcin genes by several-fold over that observed in cells transfected with an empty vector. These results suggest that IDBP-1 facilitates the intracellular localization of active vitamin D metabolites and vitamin D receptor-mediated transactivation.

Glycation amplifies lipoprotein(a)-induced alterations in the generation of fibrinolytic regulators from human vascular endothelial cells

Increased lipoprotein(a) [Lp(a)] in plasma is an independent risk factor for premature cardiovascular diseases. The levels of glycated Lp(a) are elevated in diabetic patients. The present study demonstrated that glycation enhanced Lp(a)-induced production of plasminogen activator inhibitor-1 (PAI-1), and further decreased the generation of tissue-type plasminogen activator (t-PA) from human umbilical vein endothelial cells (HUVEC) and human coronary artery EC. The levels of PAI-1 mRNA and its antigen in the media of HUVEC were significantly increased following treatments with 5 microgram/ml of glycated Lp(a) compared to equal amounts of native Lp(a). The secretion and de novo synthesis of t-PA, but not its mRNA level, in EC were reduced by glycated Lp(a) compared to native Lp(a). Treatment with aminoguanidine, an inhibitor for the formation of advanced glycation end products (AGEs), during glycation normalized the generation of PAI-1 and t-PA induced by glycated Lp(a). Butylated hydroxytoluene, a potent antioxidant, inhibited native and glycated Lp(a)-induced changes in PAI-1 and t-PA generation in EC. The results indicate that glycation amplifies Lp(a)-induced changes in the generation of PAI-1 and t-PA from venous and arterial EC. This may attenuate fibrinolytic activity in blood circulation and potentially contributes to the increased incidence of cardiovascular complications in diabetic patients with hyperlipoprotein(a). EC-mediated oxidative modification and the formation of AGEs may be implicated in glycated Lp(a)-induced alterations in the generation of fibrinolytic regulators from vascular EC.

Impact of antioxidants and HDL on glycated LDL-induced generation of fibrinolytic regulators from vascular endothelial cells

Hyperglycemia and dyslipoproteinemia are biochemical markers of diabetes mellitus (DM). Elevated levels of plasminogen activator inhibitor-1 (PAI-1) with and without reduction of tissue plasminogen activator (tPA) in plasma have been frequently found in patients with DM. Our previous studies indicated that glycation enhances low density lipoprotein (LDL)-induced production of PAI-1 and further decreases tPA generation in vascular endothelial cells (ECs). The present study demonstrated that treatment with antioxidants, butylated hydroxytoluene or vitamin E, blocked native LDL- and glycated LDL-induced changes in PAI-1 and tPA generation in ECs. Native or glycated high density lipoprotein (HDL) did not significantly alter tPA generation in ECs. Glycated but not native HDL (>/=100 microg/mL) moderately increased PAI-1 release from ECs. Cotreatment with native or glycated HDL inhibited LDL-induced or glycated LDL-induced changes in PAI-1 and tPA generation in ECs. The abundance of conjugated dienes was increased in glycated or EC-modified LDL. Treatment with butylated hydroxytoluene, vitamin E, or HDL reduced the abundance of conjugated dienes in glycated or EC-modified LDL. The effects of antioxidants and HDL on LDL-induced or its glycated LDL-induced changes in the generation of PAI-1 and tPA were also found in cultured human coronary artery ECs. The findings of the present study suggest that antioxidants and HDL may attenuate native LDL- or glycated LDL-induced changes in the generation of fibrinolytic regulators from vascular ECs, which possibly results from their inhibition on the lipid peroxidation of LDL particles. Treatment with antioxidants or hypolipidemic agents potentially improves fibrinolytic activity and reduces thrombotic tendencies in patients with DM.

Heme: a regulator of rat hepatic tryptophan 2,3-dioxygenase?

The hepatic cytosolic hemoprotein tryptophan 2,3-dioxygenase (TDO) is the rate-limiting enzyme in tryptophan catabolism and thus plays a key role in regulating the physiological flux of tryptophan into relevant metabolic pathways. The TDO protein is induced by corticosteroids such as dexamethasone (DEX) and is stabilized by its prosthetic heme. In rats, acute chemically induced hepatic heme depletion reduces the functional hepatic TDO levels to 25-30% of basal levels within 1 h, and this decrease persists beyond 28 h of heme depletion at which time only 25-30% of the protein is available for heme incorporation. Since this could stem from impaired de novo synthesis and/or instability of the newly synthesized apoTDO protein in the absence of heme, we examined the specific role of heme in these events in a previously validated rat model of acute hepatic heme depletion triggered by the P450 suicide substrate 3, 5-dicarbethoxy 2,6-dimethyl-4-ethyl-1,4-dihydropyridine. We now show that exogenous heme can reverse the functional impairment of the enzyme observed during hepatic heme depletion and fully restore the impaired DEX-mediated induction of the enzyme to normal. Furthermore, through Northern/slot blot analyses coupled with nuclear run-on studies, we now document that this heme regulation of TDO is exerted primarily at the transcriptional level. Immunoblotting analyses also reveal corresponding changes in the TDO protein, thereby establishing that heme is necessary for DEX-inducible TDO mRNA transcription and subsequent translation. Thus, the TDO gene may contain heme-regulatory elements in addition to the reported glucocorticoid-responsive elements. Together, these findings suggest that clinically, hepatic heme deficiency may enhance the tryptophan flux into synthetic (serotonergic) pathways, not only by depriving prosthetic heme for a functionally competent TDO hemoprotein, its primary catabolic enzyme, but also by impairing the de novo synthesis of this enzyme.

Locus-specific contig assembly in highly-duplicated genomes, using the BAC-RF method

Polyploidy, the presence of multiple sets of chromosomes that are similar but not identical, complicates both chromosome walking and assembly of sequence-ready contigs for many plant taxa including a large number of economically-significant crops. Traditional 'dot-blot hybridization' or PCR-based assays for identifying BAC clones corresponding to a mapped DNA landmark usually do not provide sufficient information to distinguish between allelic and non-allelic loci. A restriction fragment matching method using pools of BAC DNA in combination with dot-blots reveals the locus specificity of individual BACs that correspond to multi-locus DNA probes, in a manner that can efficiently be applied on a large scale. This approach also provides an alternative means of mapping DNA loci that exploits many advantages of 'radiation hybrid' mapping in taxa for which such hybrids are not available. The BAC-RF method is a practical and reliable approach for using high-density RFLP maps to anchor sequence-ready BAC contigs in highly-duplicated genomes, provides an alternative to high-density robotic gridding for screening BAC libraries when the necessary equipment is not available, and permits the expedient isolation of individual members of multigene or repetitive DNA families for a wide range of genetic and evolutionary investigations.