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Biomedical subjects

L Corcos

Publications and source records attributed to L Corcos.

At least 19 recordsLinked to original sources
PubMed2005

Identification of a functional DNA binding site for the SREBP-1c transcription factor in the first intron of the human caspase-2 gene.

Sterol Regulatory Element Binding Proteins (SREBP) are transcription factors that regulate lipid synthesis. We have shown recently that the human CASP-2 gene, encoding procaspase-2, was under the positive control of SREBP-2 that transactivates several responsive elements in the promoter region. We describe here the function of an additional SREBP-responsive element located in the first intron. Remarkably, this site is uniquely responsive to SREBP-1c that is mainly involved in fatty acids synthesis. This observation, together with our recent findings, strengthens the notion that the CASP-2 gene belongs to the SREBP-responsive gene battery in human cells.

Binding Sites↗
PubMed2005

Comparison of the cytotoxic, pro-oxidant and pro-inflammatory characteristics of different oxysterols.

Oxidized low-density lipoproteins play important roles in the development of atherosclerosis and contain several lipid-derived, bioactive molecules which are believed to contribute to atherogenesis. Of these, some cholesterol oxidation products, referred to as oxysterols, are suspected to favor the formation of atherosclerotic plaques involving cytotoxic, pro-oxidant and pro-inflammatory processes. Ten commonly occurring oxysterols (7alpha-, 7beta-hydroxycholesterol, 7-ketocholesterol, 19-hydroxycholesterol, cholesterol-5alpha,6alpha-epoxide, cholesterol-5beta,6beta-epoxide, 22R-, 22S-, 25-, and 27-hydroxycholesterol) were studied for both their cytotoxicity and their ability to induce superoxide anion production (O2*-) and IL-8 secretion in U937 human promonocytic leukemia cells. Cytotoxic effects (phosphatidylserine externalization, loss of mitochondrial potential, increased permeability to propidium iodide, and occurrence of cells with swollen, fragmented and/or condensed nuclei) were only identified with 7beta-hydroxycholesterol, 7-ketocholesterol and cholesterol-5beta,6beta-epoxide, which also induce lysosomal destabilization associated or not associated with the formation of monodansylcadaverine-positive cytoplasmic structures. No relationship between oxysterol-induced cytotoxicity and HMG-CoA reductase activity was found. In addition, the highest O2*- overproduction quantified with hydroethidine was identified with 7beta-hydroxycholesterol, 7-ketocholesterol and cholesterol-5beta,6beta-epoxide, with cholesterol-5alpha, 6alpha-epoxide and 25-hydroxycholesterol. The highest capacity to simultaneously stimulate IL-8 secretion (quantified by ELISA and by using a multiplexed, particle-based flow cytometric assay) and enhance IL-8 mRNA levels (determined by RT-PCR) was observed with 7beta-hydroxycholesterol and 25-hydroxycholesterol. None of the effects observed for the oxysterols were detected for cholesterol. Therefore, oxysterols may have cytotoxic, oxidative, and/or inflammatory effects, or none whatsoever.

Acyl Coenzyme A↗
PubMed2005

Caspase-2, a novel lipid sensor under the control of sterol regulatory element binding protein 2.

Caspases play important roles in apoptotic cell death and in some other functions, such as cytokine maturation, inflammation, or differentiation. We show here that the 5'-flanking region of the human CASP-2 gene contains three functional response elements for sterol regulatory element binding proteins (SREBPs), proteins that mediate the transcriptional activation of genes involved in cholesterol, triacylglycerol, and fatty acid synthesis. Exposure of several human cell lines to statins, lipid-lowering drugs that drive SREBP proteolytic activation, induced the CASP-2 gene to an extent similar to that for known targets of SREBP proteins. Adenoviral vector-mediated transfer of active SREBP-2 also induced expression of the CASP-2 gene and the caspase-2 protein and increased the cholesterol and triacylglycerol cellular content. These rises in lipids were strongly impaired following small interfering RNA-mediated silencing of the CASP-2 gene. Taken together, our results identify the human CASP-2 gene as a member of the SREBP-responsive gene battery that senses lipid levels in cells and raise the possibility that caspase-2 participates in the control of cholesterol and triacylglycerol levels.

5' Flanking Region↗
PubMed2003

A new autologous venous valve by intimal flap. One case report.

Various surgical techniques have been proposed for the treatment of chronic venous insufficiency of post-thrombotic recanalized deep veins of the lower limbs. The preferable method seems to be represented by intravenous valvuloplasty except for the cases affected by extensive valvular damage. For this reason some experimental autologous, heterologous and prosthetic venous valves have been proposed. Such a problem emerged for 1 patient (male, aged 78 years, right limb, leg dystrophy, multiple ulcerations at the ankle) which was selected by duplex, Doppler venous pressure index, photoplethysmography and ascending phlebography. An iliac-femoral and popliteal post-thrombotic, recanalized, decompensated venous insufficiency and one Cockett's perforator incompetence were diagnosed (CEAP classification: C6s Es As2d14 Pr). A bicuspid apparently repairable popliteal valve was detected by phlebography. A traditional intravenous valvuloplasty was planned but the valve was not found at surgical exploration. A monocuspid valve reconstruction by intimal flap vein was performed. The following results were obtained and controlled after one year: stable ulceration healing, dystrophy reduction, improvement in the quality of life, normalization of the hemodynamic parameters and of the radiological morphology of the new valve. It can be concluded that monocuspid valvular repair by intimal flap can be successfully performed in cases affected by secondary valveless deep venous insufficiency of the lower limbs.

Aged↗
PubMed2001

Mitochondria-targeting drugs arsenic trioxide and lonidamine bypass the resistance of TPA-differentiated leukemic cells to apoptosis.

Exposure of U937 human leukemic cells to the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) induces their differentiation into monocyte/macrophage-like cells. This terminal differentiation is associated with a resistant phenotype to apoptosis induced by the topoisomerase II inhibitor etoposide. The inhibition occurs upstream of the mitochondrial release of cytochrome c and the activation of procaspase-2, -3, -6, -7, -8, and -9. By using cell-free systems, it was demonstrated that the mitochondrial pathway to cell death that involves mitochondrial membrane depolarization, cytochrome c release and cytosolic activation of procaspases by cytochrome c/dATP remains functional in TPA-differentiated U937 cells. Accordingly, 2 drugs recently shown to target the mitochondria, namely lonidamine and arsenic trioxide, bypass the resistance of TPA-differentiated U937 cells to classical anticancer drugs. Cell death induced by the 2 compounds is associated with mitochondrial membrane depolarization, release of cytochrome c and Smac/Diablo from the mitochondria, activation of caspases, poly(ADP-ribose) polymerase cleavage and internucleosomal DNA fragmentation. Moreover, the decreased glutathione content associated with the differentiation process amplifies the ability of arsenic trioxide to activate the mitochondrial pathway to cell death. Similar results were obtained by comparing undifferentiated and TPA-differentiated human HL60 leukemic cells. These data demonstrate that mitochondria-targeting agents bypass the resistance to classical anticancer drugs induced by TPA-mediated leukemic cell differentiation. (Blood. 2001;97:3931-3940)

Antineoplastic Agents↗
PubMed2001

Anticancer agents sensitize tumor cells to tumor necrosis factor-related apoptosis-inducing ligand-mediated caspase-8 activation and apoptosis.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a new cytokine that was proposed to specifically induce apoptosis of cancer cells. In tumor cells that are resistant to the cytokine, subtoxic concentrations of chemotherapeutic drugs can restore the response to TRAIL. The present study further explores the mechanisms that determine tumor cell sensitivity to TRAIL by comparing four human colon carcinoma cell lines We show that colon cancer cell sensitivity to TRAIL-induced apoptosis and cytotoxicity correlates with the expression of the death receptors TRAIL-R1 and TRAIL-R2 at the cell surface, as determined by now cytometry, whereas the two decoy receptors TRAIL-R3 and TRAIL-R4 can be detected only in permeabilized cells. Clinically relevant concentrations of cisplatin and doxorubicin sensitize the most resistant colon cancer cell lines to TRAIL-induced cell death without modifying the expression nor the localization of TRAIL receptors in these cells. TRAIL induces the activation of procaspase-8 and triggers caspase-dependent apoptosis off colon cancer cells. Cytotoxic drugs lower the signaling threshold required for TRAIL-induced procaspase-8 activation. In turn, caspase-8 cleaves Bid, a BH3 domain-containing proapoptotic molecule of the Bcl-2 family and activates effector caspases. Together, these data indicate that chemotherapeutic drugs sensitize colon tumor cells to TRAIL-mediated caspase-8 activation and apoptosis.

Antibiotics, Antineoplastic↗
PubMed2001

Early increase in DcR2 expression and late activation of caspases in the platelet storage lesion.

Platelet transfusion is widely used to prevent bleeding in patients with severe thrombocytopenia. The maximal storage duration of platelet concentrates is usually 5 days, due to the platelet storage lesion that impairs their functions when stored for longer times. Some of the morphological and biochemical changes that characterize this storage lesion are reminiscent of cell death by apoptosis. The present study analyzed whether proteins involved in nucleated cell apoptosis could play a role in the platelet storage lesion. Storage of leukocyte-depleted platelets obtained by apheresis is associated with a late and limited activation of caspases, mainly caspase-3. This event correlates with an increased expression of the pro-apoptotic BH3-only protein Bim in the particulate fraction and a slight and late release of the pro-apoptotic mitochondrial protein Diablo/Smac in the cytosol. Platelets do not express the death receptors Fas, DR4 and DR5 on their plasma membrane, while the expression of the decoy receptor DcR2 increases progressively during platelet storage. Addition of low concentrations of the cryoprotector dimethylsulfoxide accelerates platelet caspase activation during storage, an effect that is partially prevented by the caspase inhibitor z-VAD-fmk. Altogether, DcR2 expression on the plasma membrane is an early event while caspase activation is a late event during platelet storage. These observations suggest that caspases are unlikely to account for the platelet storage lesion. As a consequence, addition of caspase inhibitors may not improve the quality of platelet concentrates stored in standard conditions.

Apoptosis↗
PubMed2001

Carbamazepine: a 'blind' assessment of CVP-associated metabolism and interactions in human liver-derived in vitro systems.

1. The ability of various in vitro systems for CYP enzymes (computer modelling, human liver microsomes, precision-cut liver slices, hepatocytes in culture, recombinant enzymes) to predict various aspects of in vivo metabolism and kinetics of carbamazepine (CBZ) was investigated. 2. The study was part of the EUROCYP project that aimed to evaluate relevant human in vitro systems to study drug metabolism. 3. CBZ was given to the participating laboratories without disclosing its chemical nature. 4. The most important enzyme (CYP3A4) and metabolic route (10,11-epoxidation) were predicted by all the systems studied. 5. Minor enzymes and routes were predicted to a different extent by various systems. 6. Prediction of a clearance class, i.e. slow clearance, was correctly predicted by microsomes, slices, hepatocytes and recombinant enzymes (CYP3A4). 7. The 10,11-epoxidation of CBZ by the recombinant CYP3A4 was enhanced by the addition of exogenous cytochrome-b5, leading to a considerable over-prediction. 8. Induction potency of CBZ was predicted in cultured hepatocytes in which 7-ethoxycoumarin O-deethylase was used as an index activity. 9. It seems that for a principally CYP-metabolized substance such as CBZ, all liver-derived systems provide useful information for prediction of metabolic routes, rates and interactions.

Anticonvulsants↗
PubMed2001

Gene induction by Phenobarbital: an update on an old question that receives key novel answers.

Phenobarbital has long been used as a sedative and antiepileptic drug. The drug is the representative of a myriad of lipophilic molecules able to evoke a pleiotropic response in the liver and also in prokaryotes and flies. A great deal of novel information has been obtained in recent years regarding the mechanism of cytochrome P450 (CYP) gene induction by phenobarbital. Most importantly, a nuclear orphan receptor, the constitutive androstane receptor has been identified as a primary determinant of the transcriptional activation of CYP genes in response to phenobarbital-like inducers in mammals. Another nuclear receptor, the pregnane X receptor can also mediate some of the phenobarbital response, but the functional overlap of the two inductive pathways is only partial. The response of mammalian CYP2B genes to phenobarbital was abolished in the liver of mice carrying a null allele of the constitutive androstane receptor gene, whereas that of CYP3A genes was lost in pregnane X receptor knock-out mice.

Androstanes↗
PubMed2001

An assessment of human liver-derived in vitro systems to predict the in vivo metabolism and clearance of almokalant.

The ability of various human derived in vitro systems to predict various aspects of the in vivo metabolism and kinetics of almokalant have been investigated in a multicenter collaborative study. Although almokalant has been withdrawn from further clinical development, its metabolic and pharmacokinetic properties have been well characterized. Studies with precision-cut liver slices, primary hepatocyte cultures, and hepatic microsomal fractions fortified with UDP-glucuronic acid all suggested that almokalant is mainly glucuronidated to the stereoisomers M18a and M18b, which is in good agreement with the results in vivo. Both in vivo and in vitro studies indicate that the formation of M18b dominates over that of M18a, although the difference is more pronounced with the in vitro systems. Molecular modeling, cDNA-expressed enzyme analysis, correlation analysis, and inhibition studies did not clearly indicate which P450 enzymes catalyze the oxidative pathways, which may indicate a problem in identifying responsible enzymes for minor metabolic routes by in vitro methods. All of the in vitro systems underpredicted the metabolic clearance of almokalant, which has previously been reported to be a general problem for drugs that are cleared by P450-dependent metabolism. Although few studies on in vivo prediction of primarily glucuronidated drugs have appeared, in vitro models may consistently underpredict in vivo metabolic clearance. We conclude that in vitro systems, which monitor phase II metabolism, would be beneficial for prediction of the in vivo metabolism, although all of the candidate liver-derived systems studied here, within their intrinsic limitations, provided useful information for predicting metabolic routes and rates.

Anti-Arrhythmia Agents↗
PubMed2000

Inhalation of toluene diisocyanate affects cytochrome P450 2B1 expression in rat lung.

In the lung the expression of xenobiotic-metabolizing enzymes such as cytochromes P450 (CYP) and glutathione S-transferases (GST) may be affected by inhaled pollutants. Toluene diisocyanate (TDI) is a highly volatile chemical compound known to induce a wide array of diseases in workers exposed to vapors or sprays, including respiratory allergy and asthma. We investigated the effect of inhaled TDI on expression of CYP 1A1, 2B1, 2E1, and 3A1 and of alpha-, mu-, and pi-GST in rat lung. Animals were exposed to targeted concentrations of 0.01, 0.1, or 1 ppm TDI vapors or to cleaned filtered air for 8 h. Expression of CYP and GST was analyzed 18 24 h after the end of exposure using western blotting, northern blotting, and immunohistochemistry. Constitutive levels of CYP 2B1 and 3A1 proteins were found in lung tissue from control rats, whereas CYP 1A1 and 2E1 proteins were not detectable. Animal exposure to TDI vapors neither modified CYP 3A1 protein expression, nor led to any detectable expression of CYP 1A1 or 2E1. In contrast, exposure to 1 ppm TDI induced a 40% reduction in CYP 2B1 protein levels. This decrease was associated with a 33% decrease in CYP 2B1 mRNA levels. Additionally, CYP 2B1 immunolabeling localized to ciliated epithelial cells, Clara cells, and type II alveolar cells in the lung tissue of control rats was markedly decreased in animals exposed to 1 ppm TDI. Constitutive levels of alpha-, mu-, and pi-GST proteins were found in lung tissue from control rats. Exposure to TDI had no effect on lung expression of either of the GST. In conclusion, this study clearly shows a selective decrease in CYP 2B1 expression by TDI vapors in rat lung. The contribution of CYP 2B1 to metabolize further xenobiotics is therefore altered.

Administration, Inhalation↗
PubMed2000

Phenobarbital induction of aldehyde dehydrogenase type 2 mRNA in mouse liver: a candidate region on chromosome 7 for a putative regulatory gene.

Phenobarbital (PB) strongly induces in the liver the expression of many genes encoding detoxication enzymes, such as the aldehyde dehydrogenase type 2 in the mouse (Aldh2). With the aim of identifying genes involved in this response, we have undertaken an approach based on a genetic analysis in mice. In a previous report, the genetic analysis of both the C57BL/6J (B6) x DBA/2J (D2) F1 and the (F1 x F1) F2 led us to the hypothesis that Aldh2 responsiveness to PB was under the control of one major locus independent of the structural gene. In the present study, the genetic analysis of the inducibility by PB of Aldh2 in the backcross population B6D2F1 x D2 has allowed us to confirm the involvement of a major regulatory gene in this mechanism. By searching for genetic linkage between this locus and a series of microsatellites DNA markers, we obtained indicative evidence for a region on chromosome 7, which may carry this gene.

Aldehyde Dehydrogenase↗
PubMed2000

The induction of the human hepatic CYP2E1 gene by interleukin 4 is transcriptional and regulated by protein kinase C.

Cytochrome P4502E1 (CYP2E1) plays a key role in the metabolism of numerous drug substrates, mostly in mammalian liver. Both the apoprotein and mRNA levels are increased in response to interleukin 4 (IL-4) in primary human hepatocyte cultures. We developed a human hepatoma cell model that faithfully reproduces the responsiveness of the CYP2E1 gene to IL-4 at least in part through transcriptional activation, upon treatment with 150 U/ml of IL-4. As expected, IL-4 induced tyrosine phosphorylation of the STAT6 transcription factor, an effect prevented by the tyrosine kinase inhibitor tyrphostin A25. However, this inhibitor as well as genistein (another inhibitor of tyrosine kinases) had no effect on the IL-4 induction of CYP2E1. Similarly, protein kinase A activators (forskolin and dibutyryl-cAMP) and inhibitor (H89) did not influence the response to IL-4. However, PKC inhibitors (H7 and calphostin C) strongly blocked any induction of the gene, as well as the IL-4-dependent translocation of PKCS. Taken together, our results show that IL-4 coordinately induces CYP2E1 transcription, mRNA and apoprotein levels in human hepatoma cells in a PKC-dependent manner, potentially through the activity of the PKCzeta isoform.

1-Methyl-3-isobutylxanthine↗
PubMed2000

Regulation of phenobarbital-induction of CYP2B and CYP3A genes in rat cultured hepatocytes: involvement of several serine/threonine protein kinases and phosphatases.

We investigated the involvement of diverse protein kinases and phosphatases in the transduction pathways elicited by phenobarbital (PB), a well-known inducer of some hepatic cytochromes P450 (CYP). Different inhibitors or activators of protein kinases or phosphatases were assessed for their ability to modulate PB-induction of CYP2B and CYP3A mRNA expression. Rat hepatocytes in primary culture were treated with the test compounds one hour prior to, and then continuously, in the absence or presence of 1 mmol/L PB for 24 h. By northern blot analysis of CYP2B1/2 and 3A1/2 gene expression, we first confirmed the negative role of the adenosine 3':5' cyclic monophosphate (cAMP)/protein kinase A pathway and the positive role of some serine/threonine protein phosphatases in the mechanism of PB-induction. The present data further suggested that Ca2+/calmodulin-dependent protein kinases II (independently of Ca2+) and extracellular signal-regulated kinases 1/2 (ERK1/2) might function respectively as positive and negative regulator in the PB-induction of CYP2B and CYP3A. In contrast, protein kinases C and phosphatidylinositol-3-kinase did not appear to be involved, while the role of tyrosine kinases remained unclear. We conclude that a complex network of phosphorylation/dephosphorylation events might be crucial for PB-induction of rat CYP2B and CYP3A.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed2000

Positive and negative regulation of apoptotic pathways by cytotoxic agents in hematological malignancies.

Most chemotherapeutic drugs can induce tumor cell death by apoptosis. Analysis of the molecular mechanisms that regulate apoptosis has indicated that anticancer agents simultaneously activate several pathways that either positively or negatively regulate the death process. The main pathway from specific damage induced by the drug to apoptosis involves activation of caspases in the cytosol by pro-apoptotic molecules such as cytochrome c released from the mitochondrial intermembrane space. At least in some cell types, anticancer drugs also upregulate the expression of death receptors and sensitize tumor cells to their cognate ligands. The Fas-mediated pathway could contribute to the early steps of drug-induced apoptosis while sensitization to the cytokine TRAIL could be used to amplify the response to cytotoxic drugs. The Bcl-2 family of proteins, that includes anti- and pro-apoptotic molecules, regulates cell sensitivity mainly at the mitochondrial level. Anticancer drugs modulate their expression (eg through p53-dependent gene transcription), their activity (eg by phosphorylating Bcl-2) and their subcellular localization (eg by inducing the translocation of specific BH3-only pro-apoptotic proteins). Very early after interacting with tumor cells, anticancer drugs also activate lipid-dependent signaling pathways that either increase or decrease cell ability to die by apoptosis. In addition, cytotoxic agents can activate protective pathways that involve activation of NFkappaB transcription factor, accumulation of heat shock proteins such as Hsp27 and activation of proteins involved in cell cycle regulation. This review discusses how modulation of the balance between noxious and protective signals that regulate drug-induced apoptosis could be used to improve the efficacy of current therapeutic regimens in hematological malignancies.

Antineoplastic Agents↗
PubMed2000

Regulation of phenobarbital induction of the cytochrome P450 2b9/10 genes in primary mouse hepatocyte culture. Involvement of calcium- and cAMP-dependent pathways.

Phenobarbital (PB) has long been known as an inducer of drug-metabolizing enzymes in liver, but the molecular mechanism underlying this induction is still poorly understood. Using primary mouse hepatocyte culture, we have investigated the possible involvement of different regulatory pathways in PB action, by exposing PB-treated cells to various protein kinase/phosphatase modulators. Our results showed a negative role of the cAMP-dependent pathway, as treatment with cAMP-dependent protein kinase (PKA) activators (10 microM dibutyryl-cAMP and 50 microM forskolin) dramatically inhibited PB-induced Cyp2b9/10 mRNA accumulation, whereas PKA inhibitor potentiated the PB responsiveness of this gene. The cGMP-dependent protein kinase (PKG) seems to play a positive role as PKG inhibitor reduced the PB-induced level of Cyp2b9/10 mRNA. We also obtained two lines of evidence for the involvement of Ca2+ in modulating PB action. Firstly, measurements of intracellular Fura-2 fluorescence ratio in murine hepatocytes showed that long-term PB incubation (24 and 48 h) led to a significant increase of [Ca2+]i. Secondly, treatment with an intracellular Ca2+ chelator (BAPTA-AM) nearly completely abolished PB-induced Cyp2b9/10 expression. Ca2+ thus appeared to mediate PB action likely via Ca2+/calmodulin-dependent protein kinase II, as KN62, a specific inhibitor of this enzyme, also dramatically inhibited PB induction of the Cyp2b9/10 genes.

Animals↗
PubMed2000

Proximal long saphenous vein valves in primary venous insufficiency.

OBJECTIVE: To verify some of the previous findings of venous valves described in the literature, their pathophysiological significance and clinical implications. MATERIALS AND METHODS: The elementary components of 65 proximal valves of the long saphenous vein and their interrelationships were subjected to histopathological examination. Valves were taken from patients subjected to long saphenous vein surgical removal for varicose veins of the lower limbs. Measurements and morphological evaluations were performed by optical microscopy. RESULTS: The valvular sinus, agger and proximal portion of the cusp underwent parallel variations of thickness. Thickening of the proximal portion of cusp was related to increase in smooth muscle cells in the agger and to elastic layer dissociation. Thickening of the distal portion of cusp depended on the collagen component; sometimes it was shortened, crumpled and led to the formation of a thickened border. The vein wall in a commissural aneurysm was usually thinner than in the valvular sinus. Alterations in the intima, in the elastic membrane and in the media were found in the 98% of the valvular annulus. Ectasis and asymmetry of the venous wall were mainly related to the muscular hypoplasia of the media. CONCLUSIONS: The development of primary venous insufficiency seems to be due to the following tissue alterations: dilatation of the valvular annulus and hypotrophy of the cusp. The hemodynamic mechanical injury increases the tissue damages of both annulus and cusps. This pathophysiologic interpretation of venous insufficiency suggests the need for detailed diagnostic procedures before reparative surgery of valves.

Humans↗