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Biomedical subjects

E Fontaine

Publications and source records attributed to E Fontaine.

At least 19 recordsLinked to original sources
PubMed2006

Effects of permeability transition inhibition and decrease in cytochrome c content on doxorubicin toxicity in K562 cells.

As mitochondria play a key role in the commitment to cell death, we have investigated the mitochondrial consequences of resistance to doxorubicin (DOX) in K562 cells. We found that the permeability transition pore (PTP) inhibitor cyclosporine A (CsA) failed to inhibit PTP opening in the resistant clone. Moreover, the Ca2+ loading capacity in the resistant clone was identical to that observed in the parent cells in the presence of CsA, suggesting that the PTP was already inhibited in a CsA-like manner in the resistant cells. In agreement with this proposal, the mitochondrial target of CsA cyclophilin D (CyD) decreased by half in the resistant cells. The levels of adenine nucleotide translocator, voltage anion-dependent channel, Bax, Bcl-2, Bcl-xL, AIF and Smac/Diablo, were similar in both cell lines, whereas cytochrome c content was divided by three in the resistant cells. Since P-glycoprotein inhibition did not restore DOX toxicity in the resistant cells, while DOX-induced cell death in the parent cells was prevented by either PTP inhibition or siRNA-induced decrease in cytochrome c content, we conclude that the inhibition of PTP opening and the decrease in cytochrome c content participate in the mechanism that makes K562 cells resistant to DOX.

Antibiotics, Antineoplastic↗
PubMed2003

Mitochondrial metabolism and type-2 diabetes: a specific target of metformin.

Several links relate mitochondrial metabolism and type 2 diabetes or chronic hyperglycaemia. Among them, ATP synthesis by oxidative phosphorylation and cellular energy metabolism (ATP/ADP ratio), redox status and reactive oxygen species (ROS) production, membrane potential and substrate transport across the mitochondrial membrane are involved at various steps of the very complex network of glucose metabolism. Recently, the following findings (1) mitochondrial ROS production is central in the signalling pathway of harmful effects of hyperglycaemia, (2) AMPK activation is a major regulator of both glucose and lipid metabolism connected with cellular energy status, (3) hyperglycaemia by inhibiting glucose-6-phosphate dehydrogenase (G6PDH) by a cAMP mechanism plays a crucial role in NADPH/NADP ratio and thus in the pro-oxidant/anti-oxidant cellular status, have deeply changed our view of diabetes and related complications. It has been reported that metformin has many different cellular effects according to the experimental models and/or conditions. However, recent important findings may explain its unique efficacy in the treatment of hyperglycaemia- or insulin-resistance related complications. Metformin is a mild inhibitor of respiratory chain complex 1; it activates AMPK in several models, apparently independently of changes in the AMP-to-ATP ratio; it activates G6PDH in a model of high-fat related insulin resistance; and it has antioxidant properties by a mechanism (s), which is (are) not completely elucidated as yet. Although it is clear that metformin has non-mitochondrial effects, since it affects erythrocyte metabolism, the mitochondrial effects of metformin are probably crucial in explaining the various properties of this drug.

Adenosine Triphosphate↗
PubMed2002

Initiation of HAART in drug-naive HIV type 1 patients prevents viral breakthrough for a median period of 35.5 months in 60% of the patients.

The introduction of potent combinations of antiviral drugs is a major breakthrough in the treatment of HIV. We investigated the long-term virologic outcome and the development of resistance after initiating highly active antiretroviral therapy (HAART) in drug-naive patients in daily clinical practice. Twenty-five treatment-naive HIV-1 patients were started on HAART. Fifteen patients responded with a drop in viral load below the limit of detection during 35.5 (interquartile range: 7) months of therapy. In 6 of 10 patients with virologic failure, virus with resistance-related mutations against the received drugs emerged. Compared with responders (R), nonresponding (NR) patients were in a later disease stage at therapy start (p = 0.0089) with lower CD4 cell counts at baseline (p = 0.040), and a lower proportion of nonresponders showed protease inhibitor (PI) levels above C(min) (p = 0.049). More NR patients showed secondary PI mutations at baseline (p = 0.079), and the CCR2-64I coreceptor polymorphism was absent among NR patients, compared with 38.5% of R patients displaying CCR2-64I (p = 0.053), although the differences were not significant. In conclusion, starting HAART in antiretroviral drug-naive HIV-infected patients followed in daily clinical practice prevented viral breakthrough for up to 44 months in 60% of the patients. Virologic failure was associated with the development of resistance-related mutations, a later stage of disease at start of therapy and lower PI drug levels.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Effect of nonsteroidal anti-inflammatory agents and finasteride on prostate cancer risk.

PURPOSE: We examine the relationship of nonsteroidal anti-inflammatory drugs and finasteride on the risk of prostate cancer. MATERIALS AND METHODS: Participants in this case control study using a prospective collection of data were drawn from consecutive patients who underwent prostate biopsy at 12 different departments of urology from January 1999 to June 2000. Medication use was assessed by self-questionnaire as well as questions about dietary and lifestyle factors that might be relevant for prostate cancer risk. RESULTS: The study included 639 patients with prostate cancer and 659 cancer-free controls. Univariate analysis showed no significant impact of aspirin and finasteride on prostate cancer risk while the nonaspirin nonsteroidal anti-inflammatory drug users had a lower risk (OR 0.80, 95% CI 0.64-0.99). After adjusting for potential confounders, the protective effect of nonaspirin nonsteroidal anti-inflammatory drugs was no longer significant (OR, 0.84, 95% CI 0.66-1.07), while finasteride showed a significant protective effect (OR 0.58, 95% CI 0.37-0.92). CONCLUSIONS: The results suggest that finasteride could have a chemopreventive role in prostate cancer. While aspirin did not show any impact on prostate cancer risk, the role of nonaspirin nonsteroidal anti-inflammatory drugs warrants further studies.

Aged↗
PubMed2002

[Standards, options, and recommendation for external radiotherapy of prostatic cancer: evaluation of the effect of dosage].

CONTEXT: The "Standards, Options and Recommendations" (SOR) collaborative project was initiated in 1993 by the Federation of the French Cancer Centres (FNCLCC), with the 20 French Regional Cancer Centres, several French public university and general hospitals, as well as private clinics and medical speciality societies. Its main objective is the development of serviceable clinical practice guidelines in order to improve the quality of health care and the outcome of cancer patients. The methodology is based on a literature review, followed by critical appraisal by a multidisciplinary group of experts. Draft guidelines are produced, then validated by specialists in cancer care delivery. OBJECTIVES: Produce clinical practice guidelines for the radiotherapy of prostate cancer using the methodology developed by the Standards, Options and Recommendations project. METHODS: The FNCLCC and the French Urology Association (AFU) designated the multidisciplinary group of experts. Available data were collected by a search of Medline and lists selected by experts in the group. A first draft of the guidelines was written, they validated by independent reviewers. RESULTS: The main recommendations are: 1/ a minimal dose of 70 Gy must be used, whatever the prognostic factors; 2/ it appeared that patients with favourable prognostic indicators (stage T1-2, PSA < or = 10 micrograms/L and Gleason score < or = 6) do not benefit from a dose escalation effect for doses over 70-74 Gy; 3/ patients with intermediate prognosis are the ones who benefit most from the dose escalation effect over 74 Gy, provided they receive exclusive radiation therapy; 4/ whenever possible, patients should be included in controlled trials designed to assess the effects of dose escalation and hormonotherapy.

Humans↗
PubMed2001

Evaluation of two commercial kits for the detection of genotypic drug resistance on a panel of HIV type 1 subtypes A through J.

We compared the two commercially available sequencing kits for HIV-1 drug resistance testing, the ViroSeq Genotyping System (Applied Biosystems, Foster City, CA, U.S.A.) and the TRUGENE HIV-1 Genotyping Kit (Visible Genetics, Inc., Toronto, Ontario, Canada), with our in-house genotyping system. Fifteen viral isolates from African patients (6 treated and 9 untreated) covering a panel of HIV-1 subtypes A through J and 7 plasma samples from Belgian and African patients (2 treated and 5 untreated) were tested. All the samples could be amplified and sequenced by the three systems; however, for all systems, alternative amplification/sequencing primers had to be used for some samples belonging to subtype B as well as to other subtypes. The consensus sequence was partially derived from only one strand for the in-house system and for the ViroSeq Genotyping System. The TRUGENE HIV-1 Genotyping Kit scored the highest number of ambiguities, followed by the ViroSeq Genotyping System and the in-house system. For 11 samples, these differences in reporting mixtures affected 14 resistance-related positions, which altered the interpretation toward protease inhibitors for 2 samples when using version 1.2 RetroGram software (Virology Networks, Utrecht, The Netherlands). All three systems were able to sequence diluted samples with a viral load down to 10 3 or 10 4 RNA copies/ml. Our data therefore suggest that the performance of amplification and sequencing primers must be improved to allow fast and reliable resistance testing for all HIV-1 subtypes.

Drug Industry↗
PubMed2001

Mitochondrial respiratory chain adjustment to cellular energy demand.

Because adaptation to physiological changes in cellular energy demand is a crucial imperative for life, mitochondrial oxidative phosphorylation is tightly controlled by ATP consumption. Nevertheless, the mechanisms permitting such large variations in ATP synthesis capacity, as well as the consequence on the overall efficiency of oxidative phosphorylation, are not known. By investigating several physiological models in vivo in rats (hyper- and hypothyroidism, polyunsaturated fatty acid deficiency, and chronic ethanol intoxication) we found that the increase in hepatocyte respiration (from 9.8 to 22.7 nmol of O(2)/min/mg dry cells) was tightly correlated with total mitochondrial cytochrome content, expressed both per mg dry cells or per mg mitochondrial protein. Moreover, this increase in total cytochrome content was accompanied by an increase in the respective proportion of cytochrome oxidase; while total cytochrome content increased 2-fold (from 0.341 +/- 0.021 to 0.821 +/- 0.024 nmol/mg protein), cytochrome oxidase increased 10-fold (from 0.020 +/- 0.002 to 0.224 +/- 0.006 nmol/mg protein). This modification was associated with a decrease in the overall efficiency of the respiratory chain. Since cytochrome oxidase is well recognized for slippage between redox reactions and proton pumping, we suggest that this dramatic increase in cytochrome oxidase is responsible for the decrease in the overall efficiency of respiratory chain and, in turn, of ATP synthesis yield, linked to the adaptive increase in oxidative phosphorylation capacity.

Adenosine Triphosphate↗
PubMed2001

Rotenone inhibits the mitochondrial permeability transition-induced cell death in U937 and KB cells.

The permeability transition pore (PTP) is a mitochondrial inner membrane Ca(2+)-sensitive channel that plays a key role in different models of cell death. Because functional links between the PTP and the respiratory chain complex I have been reported, we have investigated the effects of rotenone on PTP regulation in U937 and KB cells. We show that rotenone was more potent than cyclosporin A at inhibiting Ca(2+)-induced PTP opening in digitonin-permeabilized cells energized with succinate. Consistent with PTP regulation by electron flux through complex I, the effect of rotenone persisted after oxidation of pyridine nucleotides by duroquinone. tert-butyl hydroperoxide induced PTP opening in intact cells (as shown by mitochondrial permeabilization to calcein and cobalt), as well as cytochrome c release and cell death. All these events were prevented by rotenone or cyclosporin A. These data demonstrate that respiratory chain complex I plays a key role in PTP regulation in vivo and confirm the importance of PTP opening in the commitment to cell death.

Cell Death↗
PubMed2001

Glucose 6-phosphate hydrolysis is activated by glucagon in a low temperature-sensitive manner.

Glucagon affects liver glucose metabolism mainly by activating glycogen breakdown and by inhibiting pyruvate kinase, whereas a possible effect on glucose-6-phosphatase has also been suggested. Although such a target is of physiological importance for liver glucose production it was never proven. By using a model of liver cells, perifused with dihydroxyacetone, we show here that the acute stimulation of gluconeogenesis by glucagon (10(-7) m) was not related to the significant inhibition of pyruvate kinase but to a dramatic activation of the hydrolysis of glucose 6-phosphate. We failed to find an acute change in glucose-6-phosphatase activity by glucagon, but the increase in glucose 6-phosphate hydrolysis was abolished at 21 degrees C; conversely the effect on pyruvate kinase was not affected by temperature. The activation of glucose 6-phosphate hydrolysis by glucagon was confirmed in vivo, in postabsorptive rats receiving a constant infusion of glucagon, by the combination of a 2-fold increase in hepatic glucose production and a 60% decrease in liver glucose 6-phosphate concentration. Besides the description of a novel effect of glucagon on glucose 6-phosphate hydrolysis by a temperature-sensitive mechanism, this finding could represent an important breakthrough in the understanding of type II diabetes, because glucose 6-phosphate is proposed to be a key molecule in the transcriptional effect of glucose.

Allosteric Site↗
PubMed2001

The mitochondrial consequences of uncoupling intact cells depend on the nature of the exogenous substrate.

In isolated mitochondria the consequences of oxidative phosphorylation uncoupling are well defined, whereas in intact cells various effects have been described. Uncoupling liver cells with 2,4-dinitrophenol (DNP) in the presence of dihydroxyacetone (DHA) and ethanol results in a marked decrease in mitochondrial transmembrane electrical potential (DeltaPsi), ATP/ADP ratios and gluconeogenesis (as an ATP-utilizing process), whereas the increased oxidation rate is limited and transient. Conversely, when DHA is associated with octanoate or proline, DNP addition results in a very large and sustained increase in oxidation rate, whereas the decreases in DeltaPsi, ATP/ADP ratios and gluconeogenesis are significantly less when compared with DHA and ethanol. Hence significant energy wastage (high oxidation rate) by uncoupling is achieved only with substrates that are directly oxidized in the mitochondrial matrix. Conversely in the presence of substrates that are first oxidized in the cytosol, uncoupling results in a profound decrease in mitochondrial DeltaPsi and ATP synthesis, whereas energy wastage is very limited.

Adenosine Diphosphate↗
PubMed2001

[Standards, Options, and Recommendations for brachytherapy in patients with prostate cancer: efficacy and toxicity].

CONTEXT: The "Standards, Options and Recommendations" (SOR) collaborative project was initiated in 1993 by the Federation of the French Cancer Centres (FNCLCC), with the 20 French Regional Cancer Centres, several French public university and general hospitals, as well as private clinics and medical specialty societies. Its main objective is the development of serviceable clinical practice guidelines in order to improve the quality of health care and the outcome of cancer patients. The methodology is based on a literature review, followed by a critical appraisal by a multidisciplinary group of experts. Draft guidelines are produced, then validated by specialists in cancer care delivery. OBJECTIVES: Produce clinical practice guidelines for the brachytherapy of prostate cancer using the methodology developed by the Standards, Options and Recommendations project. METHODS: The FNCLCC and the French Urology Association (AFU) first designated the multidisciplinary group of experts. Available data were collected by a search of Medline and lists selected by experts in the group. A first draft of the guidelines was written, they validated by independent reviewers. RESULTS: The main recommendations are: 1/Brachytherapy with permanent seeds alone is a possible curative treatment for prostate cancer patients with the following prognosis factors: tumour stage T1 or T2a (TNM 1992), Gleason score < or = 6 and PSA < 10 micrograms/L. 2/Combined treatment with brachytherapy and hormonal therapy could be more efficient than brachytherapy alone for prostate cancer patients with Gleason score > 7 and/or PSA > 10.3/Combination of brachytherapy and external beam radiation therapy can be proposed to prostate cancer patients with intermediate prognosis. 4/Before and after seed implantation, risks of infection must be prevented by appropriate antibiotic therapy (recommendation). 5/Brachytherapy must not be performed within 2 months of transurethral prostate resection. 6/The height of the urethra receiving more than 200% of the prescribed dose must be reported. The portion of the rectum receiving 100 and 120% of the prescribed dose must be limited to 10 and 5 mm length, respectively.

Antineoplastic Agents, Hormonal↗
PubMed2001

Mitochondrial adaptation to in vivo polyunsaturated fatty acid deficiency: increase in phosphorylation efficiency.

Polyunsaturated fatty acid (PUFA) deficiency affects respiratory rate both in isolated mitochondria and in hepatocytes, an effect that is normally ascribed to major changes in membrane composition causing, in turn, protonophoriclike effects. In this study, we have compared the properties of hepatocytes isolated from PUFA-deficient rats with those from control animals treated with concentrations of the protonophoric uncoupler 2,4-dinitrophenol (DNP). Despite identical respiratory rate and in situ mitochondrial membrane potential (delta psi), mitochondrial and cytosolic ATP/ADP-Pi ratios were significantly higher in PUFA-deficient cells than in control cells treated with DNP. We show that PUFA-deficient cells display an increase of phosphorylation efficiency, a higher mitochondrial ATP/ADP-Pi ratio being maintained despite the lower delta psi. This is achieved by (1) decreasing mitochondrial Pi accumulation, (2) increasing ATP synthase activity, and (3) by increasing the flux control coefficient of adenine nucleotide translocation. As a consequence, oxidative phosphorylation efficiency was only slightly affected in PUFA-deficient animals as compared to protonophoric uncoupling (DNP). Thus, the energy waste induced by PUFA deficiency on the processes that generate the proton motive force (pmf) is compensated in vivo by powerful adaptive mechanisms that act on the processes that use the pmf to synthesize ATP.

2,4-Dinitrophenol↗
PubMed2001

Variant human immunodeficiency virus type 1 proteases and response to combination therapy including a protease inhibitor.

The objective of this observational study was to assess the genetic variability in the human immunodeficiency virus (HIV) protease gene from HIV type 1 (HIV-1)-positive (clade B), protease inhibitor-naïve patients and to evaluate its association with the subsequent effectiveness of a protease inhibitor-containing triple-drug regimen. The protease gene was sequenced from plasma-derived virus from 116 protease inhibitor-naïve patients. The virological response to a triple-drug regimen containing indinavir, ritonavir, or saquinavir was evaluated every 3 months for as long as 2 years (n = 40). A total of 36 different amino acid substitutions compared to the reference sequence (HIV-1 HXB2) were detected. No substitutions at the active site similar to the primary resistance mutations were found. The most frequent substitutions (prevalence, >10%) at baseline were located at codons 15, 13, 12, 62, 36, 64, 41, 35, 3, 93, 77, 63, and 37 (in ascending order of frequency). The mean number of polymorphisms was 4.2. A relatively poorer response to therapy was associated with a high number of baseline polymorphisms and, to a lesser extent, with the presence of I93L at baseline in comparison with the wild-type virus. A71V/T was slightly associated with a poorer response to first-line ritonavir-based therapy. In summary, within clade B viruses, protease gene natural polymorphisms are common. There is evidence suggesting that treatment response is associated with this genetic background, but most of the specific contributors could not be firmly identified. I93L, occurring in about 30% of untreated patients, may play a role, as A71V/T possibly does in ritonavir-treated patients.

Adult↗
PubMed2001

Comparison of DNA sequencing and a line probe assay for detection of human immunodeficiency virus type 1 drug resistance mutations in patients failing highly active antiretroviral therapy.

The resistance of human immunodeficiency virus type 1 (HIV-1) to drugs is a major cause of antiretroviral treatment failure. We have compared direct sequencing to a line probe assay (LiPA) for the detection of drug resistance-related mutations in 197 clinical samples, and we have investigated the sequential appearance of mutations under drug pressure. For 26 patients with virological failure despite the use of two nucleoside analogues and one protease inhibitor (indinavir [n = 6], ritonavir [n = 10], and saquinavir [n = 10]), genotypic resistance assays were carried out retrospectively every 3 months for up to 2 years by using direct sequencing (TruGene; Visible Genetics) and a LiPA for detection of mutations in the reverse transcriptase (INNO-LiPA HIV-1 RT; Innogenetics) and the protease (INNO-LiPA HIV Protease, prototype version; Innogenetics) genes. Comparison of the results from both assays found rare major discrepancies (<1% of codons analyzed). INNO-LiPA detected more wild-type-mutant mixtures than sequencing but suffered from a high rate of codon hybridization failures for the reverse transcriptase. LiPA detected earlier and more frequently than sequencing the transient mixed virus population that contained I84V, which appears before V82A in the protease sequence. Mutations M461, G48V, and L90M were often transient and drug pressure related. In conclusion, direct sequencing and LiPAs give concordant results for most clinical isolates. LiPAs are more sensitive for the detection of mixed virus populations. Mutation I84V appears in minor populations in the early steps of the pathways of resistance to indinavir and ritonavir. The fact that some mutations can be found only transiently and in minor virus populations highlights the importance of a low detection limit for resistance assays.

Acquired Immunodeficiency Syndrome↗
PubMed2001

[Systematic conservative surgery for kidney cancer smaller than 4 cm: multicenter study].

OBJECTIVE: To evaluate tumour control and morbidity of systematic conservative surgery for patients with a renal cancer < or = 4 cm. MATERIALS AND METHODS: A retrospective multicentre study was performed in 73 patients undergoing systematic conservative surgery for renal cancer < or = 4 cm. The mean age of the patients was 55.8 years (range: 19-82). The mean diameter of the tumour was 2.8 cm +/- 0.9. Tumour stage was pT1 in 97% of cases and pT3a in 3% of cases. The mean follow-up was 46.2 months (range: 12-138). RESULTS: The postoperative morbidity was 11%, including urinary fistulas in 5 cases and haemorrhage in 3 cases. No patient has developed local recurrence. One patient died from metastases. The 5-year recurrence-free survival was 97.4%. CONCLUSION: Systematic partial nephrectomy has a low morbidity in patients with a renal cancer less than 4 cm. It ensures satisfactory medium-term tumour control. However, only long-term follow-up can establish the place of systematic partial nephrectomy in the treatment of renal cancer.

Adult↗