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G Lepage

Publications and source records attributed to G Lepage.

At least 19 recordsLinked to original sources

Epidermal growth factor-induced neuroendocrine differentiation and apoptotic resistance of androgen-independent human prostate cancer cells.

Neuroendocrine differentiation (NED) has been implicated in prostate cancer progression and hormone-therapy failure. Neuroendocrine cells are non-proliferating and escape apoptotic cell death, although their origin and the causes of their apoptotic resistance have as yet been poorly elucidated. This study demonstrates a new mechanism involved in controlling NED. We report that epidermal growth factor (5-50 ng/ml) promotes neuroendocrine-like differentiation of androgen-independent DU145 prostate cancer cells. This differentiation is associated with an increase in the expression of Neuron Specific Enolase (NSE) and a reduction in cell proliferation and is blocked by inhibiting tyrosine kinase activity with genistein and with compound 56 (C56). An increase in the cAMP level, using dibutryl cAMP (db-cAMP) (1 mM) and isobutylmethylxanthine (100 microM), does not promote NED by itself, but does increase the effect of EGF on NED. In addition, EGF-induced NED protects cells from apoptosis induced with thapsigargin (1 microM) by reducing the thapsigargin-induced cytosolic calcium overload. In order to describe how EGF-induced NED protects cells against thapigargin-induced calcium overload we investigated the spatiotemporal calcium signalling linked to apoptosis. By using thapsigargin in various conditions on DU145 cells and using micro-fluorimetric calcium measurements, we show that depletion of intracellular calcium store induces apoptosis and that the amplitude and duration of the capacitive calcium entry are two apoptosis-modulating parameters. We show that protection against thapsigargin-induced apoptosis conferred by NED is achieved by reducing the amount and the speed of calcium that can be released from calcium pools, as well as modulating the amplitude of the subsequent calcium entry.

Androgens↗

Alterations in the regulatory volume decrease (RVD) and swelling-activated Cl- current associated with neuroendocrine differentiation of prostate cancer epithelial cells.

Neuroendocrine (NE) differentiation of prostate epithelial/basal cells is a hallmark of advanced, androgen-independent prostate cancer, for which there is no successful therapy. Here we report for the first time on alterations in regulatory volume decrease (RVD) and its key determinant, swelling-activated Cl- current (I(Cl,swell)), associated with NE differentiation of androgen-dependent LNCaP prostate cancer epithelial cells. NE-differentiating regimens, namely, chronic cAMP elevation or androgen deprivation, resulted in generally augmented I(Cl,swell) and enhanced RVD. This occurred as a result of both the increased endogenous expression of ClC-3, which is a volume-sensitive Cl- channel involved, as we show, in I(Cl,swell) in LNCaP (lymph-node carcinoma of the prostate) cells and the weaker negative I(Cl,swell) control from Ca2+ entering via store-dependent pathways. The changes in the RVD of NE-differentiated cells generally mimicked those reported for Bcl-2-conferred apoptotic resistance. Our results suggest that strengthening the mechanism that helps to maintain volume constancy may contribute to better survival rates of apoptosis-resistant NE cells.

Androgens↗

Ca2+ homeostasis and apoptotic resistance of neuroendocrine-differentiated prostate cancer cells.

Neuroendocrine (NE) differentiation is a hallmark of advanced, androgen-independent prostate cancer, for which there is no successful therapy. NE tumor cells are nonproliferating and escape apoptotic cell death; therefore, an understanding of the apoptotic status of the NE phenotype is imperative for the development of new therapies for prostate cancer. Here, we report for the first time on alterations in intracellular Ca(2+) homeostasis, which is a key factor in apoptosis, caused by NE differentiation of androgen-dependent prostate cancer epithelial cells. NE-differentiating regimens, either cAMP elevation or androgen deprivation, resulted in a reduced endoplasmic reticulum Ca(2+)-store content due to both SERCA 2b Ca(2+) ATPase and luminal Ca(2+) binding/storage chaperone calreticulin underexpression, and to a downregulated store-operated Ca(2+) current. NE-differentiated cells showed enhanced resistance to thapsigargin- and TNF-alpha-induced apoptosis, unrelated to antiapoptotic Bcl-2 protein overexpression. Our results suggest that targeting the key players determining Ca(2+) homeostasis in an attempt to enhance the proapoptotic potential of malignant cells may prove to be a useful strategy in the treatment of advanced prostate cancer.

Apoptosis↗

Receptor-coupled, DAG-gated Ca2+-permeable cationic channels in LNCaP human prostate cancer epithelial cells.

Although the prostate gland is a rich source of alpha1-adreno- (alpha1-AR) and m1-cholino receptors (m1-AChR), the membrane processes associated with their activation in glandular epithelial cells is poorly understood. We used the whole-cell patch-clamp technique to show that the agonists of the respective receptors, phenylephrine (PHE) and carbachol (CCh), activate cationic membrane currents in lymph node carcinoma of the prostate (LNCaP) human prostate cancer epithelial cells, which are not dependent on the filling status of intracellular IP3-sensitive Ca2+ stores, but directly gated by diacylglycerol (DAG), as evidenced by the ability of its membrane permeable analogue, OAG, to mimic the effects of the agonists. The underlying cationic channels are characterized by the weak field-strength Eisenman IV permeability sequence for monovalent cations (PK(25) > PCs(4.6) > PLi(1.4) > PNa(1.0)), and the following permeability sequence for divalent cations: PCa(1.0) > PMg(0.74) > PBa(0.6) > PSr(0.36) > PMn(0.3). They are 4.3 times more permeable to Ca2+ than Na+ and more sensitive to the inhibitor 2-APB than SK&F 96365. RT-PCR analysis shows that DAG-gated members of the transient receptor potential (TRP) channel family, including TRPC1 and TRPC3, are present in LNCaP cells. We conclude that, in prostate cancer epithelial cells, alpha1-ARs and m1-AChRs are functionally coupled to Ca2+-permeable DAG-gated cationic channels, for which TRPC1 and TRPC3 are the most likely candidates.

Base Sequence↗

A randomized trial of two levels of iron supplementation and developmental outcome in low birth weight infants.

OBJECTIVES: To investigate the effect of increased iron intakes on hematologic status and cognition in low birth weight infants. STUDY DESIGN: We randomly assigned 58 infants to receive formula with 13.4 mg iron/L (normal iron) or 20.7 mg iron/L (high iron). At baseline, discharge, and at 3, 6, 9, and 12 months' corrected age, we assessed anthropometry; infections; red blood cell hemoglobin, catalase, glutathione peroxidase, red blood cell fragility (hydrogen peroxide test), and superoxide dismutase values; plasma malondialdehyde, ferritin, iron, transferrin, zinc and copper levels; and diet intake. Griffiths' Development Assessment was done at 3, 6, 9, and 12 months only. RESULTS: No statistical differences (P <.05) were noted for weight, catalase or malondialdehyde levels, red blood cell fragility, or Griffith's Development Assessment. Iron intakes were greater in the high iron group except at 12 months. Hemoglobin (high iron, 123 +/- 9; normal iron, 118 +/- 8) was not different at 3 months (P =.07). Plasma zinc levels (high iron, 70 +/- 14; normal iron, 89 +/- 27) and copper levels (high iron, 115 +/- 26; normal iron, 132 +/- 27; P =.06) at 12 months suggested inhibition of absorption by high iron formula. Glutathione peroxidase levels were higher in the high iron group. The total number of respiratory tract infections was greater in the high iron group (3.3 +/- 0.9) than in the normal iron group (2.5 +/- 0.9). CONCLUSION: In terms of cognitive outcome, there is no advantage associated with elevated iron intake for low birth weight infants.

Analysis of Variance↗

2,3-Dinor-5,6-dihydro-15-F(2t)-isoprostane: a bioactive prostanoid metabolite.

15-F(2t)-isoprostane (15-F(2t)-IsoP), also termed 8-isoprostaglandin F(2alpha), is one of a series of prostanoids formed by free radical-mediated peroxidation of arachidonic acid and exerts potent biological actions such as vasoconstriction. We recently demonstrated that 15-F(2t)-IsoP is metabolized in humans to a major metabolite, 2,3-dinor-5,6-dihydro-15-F(2t)-IsoP (15-F(2t)-IsoP-M). 15-F(2t)-IsoP-M can also potentially be formed as a product of free radical-induced oxidation of the low abundance fatty acid gamma-linolenic acid. We confirmed that 15-F(2t)-IsoP-M is generated during oxidation of gamma-linolenic acid and explored whether it may exhibit biological activity. 15-F(2t)-IsoP-M caused marked constriction of porcine surface retinal and intraparenchymal brain microvessels, comparable to that observed with 15-F(2t)-IsoP. These effects were associated with increased thromboxane A(2) (TXA(2)) formation and were virtually abolished by TXA(2)-synthase and -receptor inhibitors (CGS-12970 and L-670596). Vasoconstriction induced by either 15-F(2t)-IsoP or 15-F(2t)-IsoP-M on perfused ocular choroid was also abrogated by TXA(2)-synthase inhibition as well as by removal of endothelium. Similar to 15-F(2t)-IsoP, 15-F(2t)-IsoP-M evoked vasoconstriction and TXA(2) generation by activating Ca(2+) influx from nonvoltage-gated channels (SK&F96365 sensitive) in the retina and from both nonvoltage- and N-type voltage-gated Ca(2+) channels (omega-conotoxin MVIIA sensitive), respectively, in brain endothelial and astroglial cells; smooth muscle cells were unresponsive to both agents. Cross-desensitization experiments further suggest that 15-F(2t)-IsoP and 15-F(2t)-IsoP-M act on the same receptor mechanism. Findings reveal a novel concept by which a beta-oxidation metabolite of 15-F(2t)-IsoP that can also be formed by nonenzymatic oxidation of gamma-linolenic acid is equivalently bioactive to 15-F(2t)-IsoP and may prolong the vascular actions of F(2)-IsoPs.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

Molecular cloning, expression analysis and iron metal cofactor characterisation of a superoxide dismutase from Toxoplasma gondii.

A genomic region of 12 kb encompassing the gene encoding the superoxide dismutase (SOD) of Toxoplasma gondii has been cloned. The gene contains four exons of 121, 42, 381 and 59 bp which are separated by three introns of 321, 202, and 577 bp, respectively. The open reading frame can be translated into a protein of 201 amino acids with a molecular mass of 22.6 kDa. Alignment indicated that it is a FeSOD, a type only found in bacteria, protozoa and chloroplast of higher plants. Recombinant SOD was expressed in a Escherichia coli double mutant lacking both MnFeSOD and FeSODs. The presence of iron as metal cofactor was confirmed by measurements of iron by absorption mass spectrometry and electron paramagnetic resonance studies. Semi-quantitative reverse transcribed polymerase chain reaction experiments showed a similar amount of SOD transcripts in two developmental stages of T. gondii. Antibodies raised against the purified recombinant protein detected SOD protein in both bradyzoite and tachyzoite forms suggesting this SOD might be essential for the intracellular growth of both developmental stages. Southern blot analysis indicated that SOD occured as a single copy gene in T. gondii genome.

Amino Acid Sequence↗

Modulation of endoplasmic reticulum-bound cholesterol regulatory enzymes by iron/ascorbate-mediated lipid peroxidation.

Mammalian sterol regulatory enzymes are integral membrane proteins of the endoplasmic reticulum. They play a critical role in liver cholesterol homeostasis and the maintenance of overall cholesterol balance in different species. Because lipid peroxidation has been implicated in hepatic dysfunction and atherosclerosis, we hypothesized that its occurrence could alter the composition and properties of the bilayer lipid environment, and thereby affect the functions of these membrane proteins. Preincubation of rat liver microsomes with iron (Fe)/ascorbate (50 microM/200 microM), known to induce peroxidation, resulted in a significant inhibition of (i) the rate-limiting enzyme in cholesterol biosynthesis, HMG-CoA reductase (46%, p < .01), (ii) the crucial enzyme controlling the conversion of cholesterol in bile acids, cholesterol 7alpha-hydroxylase (48%, p < .001), and (iii) the central enzyme for cholesterol esterification: Acyl-CoA:cholesterol acyltransferase (ACAT, 80%, p < .0001). The disturbances of these key enzymes took place concomitantly with the high production of malondialdehyde (350%, p < .007) and the loss of polyunsaturated fatty acids (36.19 +/- 1.06% vs. 44.24 +/- 0.41 in controls, p < .0008). While alpha-tocopherol simultaneously neutralized lipid peroxidation, preserved microsomal fatty acid status, and restored ACAT activity, it was not effective in preventing Fe/ascorbate-induced inactivation of both HMG-CoA reductase (44%, p < .01) and cholesterol 7alpha-hydroxylase (71%, p < .0001). These results indicate that Fe/ascorbate alters the activity of the rate-determining steps in liver cholesterol metabolism, either directly or via lipid peroxidation, capable of modifying their membrane environment. The present data also suggest that the three regulatory enzymes respond differently when exposed to Fe/ascorbate or antioxidants, which may be due to dissimilar mechanisms.

Animals↗

Altered lipid profile, lipoprotein composition, and oxidant and antioxidant status in pediatric Crohn disease.

BACKGROUND: Growing evidence supports a role for peroxidation in the pathogenesis of Crohn disease (CD). The activation of inflammatory cells, the release of their mediators, and the excessive production of free radicals may affect circulating lipids. OBJECTIVE: We examined the lipid profile, lipoprotein composition, and oxidant-antioxidant status of children with CD. DESIGN: We studied 22 pediatric CD patients and 10 healthy control subjects. RESULTS: The proportion of saturated and monounsaturated fatty acids in plasma of CD patients was higher but that of polyunsaturated fatty acids was lower than in control subjects. This resulted in higher ratios in CD patients of palmitoleic acid to linoleic acid (P < 0. 05) and of eicosatrienoic acid to arachidonic acid (P < 0.04), 2 established indexes of essential fatty acid deficiency. Hypocholesterolemia was noted in CD patients as a result of lower LDL-cholesterol concentrations than in control subjects (P < 0.02). Plasma apolipoproteins B (P < 0.02) and A-I (P < 0.02) were also lower in CD patients, whereas plasma triacylglycerols were higher (P < 0.005). Lipoprotein composition was altered in CD patients, with relative triacylglycerol depletion and protein enrichment in VLDL. In contrast, intermediate-density lipoprotein of CD patients was characterized by an increased percentage of triacylglycerol and protein (P < 0.005) and a reduced proportion of phospholipids (P < 0. 01). Additional abnormalities were observed in the chemical distribution of HDL(2) and HDL(3) moieties. Lipid peroxidation was documented by higher plasma malondialdehyde concentrations in CD patients (P < 0.05), accompanied by lower retinol concentrations (P < 0.02). CONCLUSION: Disturbances in the lipid profile, in lipoprotein concentrations and composition, and in oxidant-antioxidant status occur in CD patients.

Adolescent↗

N-acetylcysteine in pig liver transplantation from non-heart-beating donors.

Lipid peroxidation due to oxygen free radicals (OFR) seems to play a major role in loss of liver graft viability after warm ischemia, preservation, and transplantation. N-acetylcysteine (NAC) is an antioxidant that has a direct effect on OFR, and is also a glutathione precursor, another antioxidant. This study was designed to evaluate the efficacy of NAC in preventing ischemia-reperfusion damage of liver grafts harvested from non-heart-beating donors. Liver transplantation was performed on pigs divided into five groups: group 1 (control group; n=5) received livers from heart-beating donors; livers were subjected to 30 min of warm ischemia in groups 2 (n=3, no NAC) and group 3 (n=3; NAC treatment); warm ischemia time lasted 60 min in groups 4 (n=4; no NAC) and 5 (n=5; NAC treatment). Studied parameters included graft survival for more than 3 days, aspartate aminotransferase plasma levels, liver histology, and hepatic total glutathione concentrations. Graft survival was 100% in groups 1, 2, and 3, 0% in group 4, and 20% in group 5. NAC treatment did not influence initial mean aspartate aminotransferase release which was greater in warm ischemic livers than in controls. NAC treatment had no effect on liver hepatic total glutathione after reperfusion of animals receiving warm ischemic grants. Finally, no effect on liver histology was observed with NAC treatment. Our study suggests that in liver transplantation from non-heart-beating donors, NAC has no effect in both graft viability and lipid peroxidation. The role of OFR in primary dysfunction of transplanted warm ischemic livers remains controversial.

Acetylcysteine↗

Uptake and metabolism of structured triglyceride by Caco-2 cells: reversal of essential fatty acid deficiency.

Structured lipids have been proposed as efficient vehicles for the supplementation of essential fatty acids (EFA) to patients with malabsorption. We investigated how a novel structured triglyceride (STG), containing purely octanoic acid in the sn-1/sn-3 and [14C]linoleic acid in the sn-2 positions, was incorporated into different lipid classes in Caco-2 cells. We also evaluated the contribution of gastric lipase in the uptake and metabolism of [14C]linoleic acid from the STG. We furthermore determined the potential of the STG to correct EFA deficiency induced in Caco-2 cells. The absorption of STG by Caco-2 cells was significantly greater compared with that of triolein. The addition of human gastric lipase significantly enhanced cellular uptake of the labeled substrate, reflecting the stereoselectivity of gastric lipase to hydrolyze medium chain FA. Analysis of the intracellular lipids synthesized revealed a predominance of phospholipids-monoglycerides. Most of the radioactivity in the lipoproteins isolated from Caco-2 cells was recovered in TG-rich lipoproteins (45%) and to a lesser extent in the high-density lipoprotein (36%) and low-density lipoprotein (17%) fractions. The administration of STG to Caco-2 cells rendered EFA deficient produced a marked increase of the cellular level of linoleic and arachidonic acids. This resulted in a lower ratio of 20:3(n-9) to 20:4(n-6), reflecting the correction of EFA deficiency in Caco-2 cells. Our data demonstrate that STG, in the presence of gastric lipase, have beneficial effects on lipid incorporation, lipoprotein production, and EFA status, utilizing Caco-2 cells as a model of EFA deficiency.

Biological Transport↗

Definitive chemical evidence for the constitutive ability of Candida albicans serotype A strains to synthesize beta-1,2 linked oligomannosides containing up to 14 mannose residues.

We have previously reported the presence of phosphate bound beta-1,2 linked oligomannosides with unusually high degrees of polymerization (DP > 7) in the mannan of Candida albicans strain VW32. To confirm this observation, we have prepared these oligomannosides from the mannan of C. albicans strain NIH A 207. Gel filtration chromatography and TLC analysis revealed DP up to 14. For both strains, NMR analysis confirmed the exclusive presence of beta-1,2 linkages in the pools of oligomannosides with a DP higher than 6 which presented an average DP of 10.6 (VW32) and 10.4 (NIH A 207). These results are important to consider in relation with the ability of these C. albicans derived oligomannosides to trigger TNFalpha synthesis according to their DP.

Candida albicans↗

Clearances of Candida albicans-derived alpha- and beta-linked mannose residues in sera from patients with candidiasis.

Two monoclonal antibodies (MAbs) reacting with different Candida albicans mannan oligomannosidic epitopes were used to detect antigens in human sera. The first MAb reacted with alpha-linked mannose residues shared by mannoproteins, and the second displayed reactivity against beta-1,2-linked oligomannosides shared by phospholipomannan. Two latex agglutination tests performed after dissociation of serum immune complexes were 100% specific. In a retrospective analysis of 39 sera from 20 patients with candidiasis, each test detected seven patients; in combination, they detected ten. More than 60% of positive samples were positive with only one test. These results demonstrate that the clearance of Candida albicans antigens from the blood differs according to the type of oligomannoside and glycoconjugate. Antigen detection kits with MAbs to different Candida albicans mannan epitopes could provide a logical rationale to compensate for the transitory character of mannanemia detection during candidal infections.

Antibodies, Monoclonal↗

Ursodeoxycholic acid improves the hepatic metabolism of essential fatty acids and retinol in children with cystic fibrosis.

OBJECTIVE: Several clinical trials of ursodeoxycholic acid (UDCA) have shown improvement of liver-function test results in cystic fibrosis (CF) with liver disease; however, there is no evidence that the long-term course will be affected. In view of the observations that UDCA can change the lipid profile and that patients with CF and liver disease are more likely to have essential fatty acid (EFA) deficiency, we elected to examine changes in the lipid profile and in the status of fat-soluble vitamins in response to UDCA. METHODS: Nineteen children with CF and liver dysfunction were recruited for a double-blind, crossover study of 1 year's duration, followed by treatment of the entire group. UDCA was administered at a dosage of 15 mg/kg per day, which, in the absence of a 50% decrease of alanine transaminase or aspartate transaminase or both within 2 months, was increased to 30 mg/kg per day. RESULTS: At entry, all patients had biochemical evidence of EFA deficiency. The lipid profiles during an average period of 25 months of follow-up showed a significant decrease in triglycerides (p <0.002), cholesterol (p <0.02), and total fatty acids (p <0.006). In addition, UDCA therapy led to an improvement in EFA status, as indicated by an increase (p <0.05) in the n-6 fatty acid concentration and a reduction (p <0.04) in the 20:3n-9/20:4n-6 fatty acid ratio. Although no change in vitamin E levels was observed, retinol metabolism was altered. There was an increase (p <0.02) in the unesterified retinol/retinol binding protein molar ratio in the absence of a difference in retinol binding protein concentration. Furthermore, retinyl esters, which normally account for less than 3% of circulating retinol, decreased (p <0.05) from 13.7% +/- 3.6% to 8.1% +/- 1.7%. CONCLUSIONS: This study confirms that UDCA alters lipoprotein metabolism and shows that it improves the EFA and retinol status of patients with CF and liver disease.

Adolescent↗

[Intrahepatic glutathione and oxidative stress in liver transplantation in the pig].

OBJECT: To determine the loss of endogenous GSH from livers cold-stored and reperfused, using a model of liver transplantation in the pig. MATERIAL AND METHODS: Four female Yorkshire pigs weighing 19 to 40 kg received a liver allograft. Donor livers were cold-stored in the UW solution. Mean cold ischemic time was 6.5 hours. Malondialdehyde (MDA) levels were used as an index of oxidative stress. MDA plasma levels were measured following recipient laparotomy (H0), immediately (H1), and 90 minutes after liver reperfusion (H2). MDA and GSH levels in liver were measured following donor laparotomy (T0), at the end of cold ischemic period (T1), and at 90 minutes following liver reperfusion (T2). RESULTS: Three animals survived. MDA liver levels decreased of 44% between T0 and T1, then increased to 92% at T2. In contrast, in plasma, graft reperfusion was associated with an increase of MDA to 140% of the baseline values which reached 188% at H2. Intrahepatic GSH levels decreased of 49% at T1, then to 72% at T2. CONCLUSION: our study suggests that in liver transplantation: (1) Hepatic GSH is depleted to 49% during cold-storage, and an additional 23% is lost after reperfusion; (2) GSH contained in the UW solution does not prevent the loss of hepatocellular glutathione during preservation and reperfusion; (3) after short periods of cold ichemia, endogenous hepatic GSH may protect against oxydative stress in the transplanted liver.

Animals↗

Supplementation with carotenoids corrects increased lipid peroxidation in children with cystic fibrosis.

Evidence of lipid peroxidation previously documented in cystic fibrosis (CF) implies an imbalance between free radical generation and antioxidant defense mechanisms. The aim of the present study was to examine the relation between plasma concentrations of malondialdehyde, a marker of lipid peroxidation, and the exogenous antioxidant line of defense. Malondialdehyde concentrations (90.2 +/- 4.7 nmol/L) in 25 children with CF aged 9.6 +/- 0.8 y were higher (P < 0.001) than concentrations (69.1 +/- 2.6 nmol/L) in 17 children used as control subjects and were not correlated with any marker of disease severity. In contrast with their all-rac-alpha-tocopherol status, which was normal as a result of routine supplementation with a 200-mg dose of all-rac-alpha-tocopheryl acetate/d, beta-carotene was very low. A 2-mo open trial in which 12 children with CF aged 11.5 +/- 0.8 y were given 4.42 mg (8.23 mumol) beta-carotene three times per day led to normalization of the malondialdehyde concentration in all but 1 patient, in conjunction with an increase of plasma beta-carotene from 0.08 +/- 0.03 to 3.99 +/- 0.92 mumol/L. Their plasma concentrations were inversely correlated (r = -0.54, P = 0.006) [corrected] with malondialdehyde when the values measured pre- and posttreatment were pooled. We conclude that beta-carotene deficiency contributes to lipid peroxidation in CF and that supplementation may eventually prove to be a useful adjunct for the management of the disease.

Adolescent↗