References of "Fontaine-Aupart, Marie-Pierre"
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See detailEvidence of oxidative stress and mitochondrial respiratory chain dysfunction in an in vitro model of sepsis-induced kidney injury
Quoilin, Caroline ULg; Mouithys-Mickalad, Ange ULg; Lécart, Sandrine et al

in Biochimica et Biophysica Acta-Bioenergetics (2014), 1837(10), 1790-1800

To investigate the role of oxidative stress and/or mitochondrial impairment in the occurrence of acute kidney injury (AKI) during sepsis, we developed a sepsis-induced in vitro model using proximal ... [more ▼]

To investigate the role of oxidative stress and/or mitochondrial impairment in the occurrence of acute kidney injury (AKI) during sepsis, we developed a sepsis-induced in vitro model using proximal tubular epithelial cells exposed to a bacterial endotoxin (lipopolysaccharide, LPS). This investigation has provided key features on the relationship between oxidative stress and mitochondrial respiratory chain activity defects. LPS treatment resulted in an increase in the expression of inducible nitric oxide synthase (iNOS) and NADPH oxidase 4 (NOX-4), suggesting the cytosolic overexpression of nitric oxide and superoxide anion, the primary reactive nitrogen species (RNS) and reactive oxygen species (ROS). This oxidant state seemed to interrupt mitochondrial oxidative phosphorylation by reducing cytochrome c oxidase activity. As a consequence, disruptions in the electron transport and the proton pumping across the mitochondrial inner membrane occurred, leading to a decrease of the mitochondrial membrane potential, a release of apoptotic-inducing factors and a depletion of adenosine triphosphate. Interestingly, after being targeted by RNS and ROS, mitochondria became in turn producer of ROS, thus contributing to increase the mitochondrial dysfunction. The role of oxidants in mitochondrial dysfunction was further confirmed by the use of iNOS inhibitors or antioxidants that preserve cytochrome c oxidase activity and prevent mitochondrial membrane potential dissipation. These results suggest that sepsis-induced AKI should not only be regarded as failure of energy status but also as an integrated response, including transcriptional events, ROS signaling, mitochondrial activity and metabolic orientation such as apoptosis. [less ▲]

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See detailDisruption in energy metabolism and mitochondrial function in a cellular model of inflammation-induced acute kidney injury
Quoilin, Caroline ULg; Mouithys-Mickalad, Ange ULg; Lécart, Sandrine et al

Poster (2013, September)

Sepsis is a very complex clinical condition characterized by stimulation of a systemic inflammatory response due to an infection. It has a profound deleterious effect on kidney functions leading to sepsis ... [more ▼]

Sepsis is a very complex clinical condition characterized by stimulation of a systemic inflammatory response due to an infection. It has a profound deleterious effect on kidney functions leading to sepsis-induced acute kidney injury (AKI). This failure seems to occur through complex mechanisms involving the immune system response, inflammatory pathways, cellular dysfunction and hemodynamic instability. To study the role of cellular energetic metabolism dysfunction and mitochondrial impairment in the occurrence of AKI during sepsis, we developed an inflammation-induced in vitro model using proximal tubular epithelial cells (HK-2) exposed to a bacterial endotoxin (lipopolysaccharide, LPS). This investigation has provided key features on the relationship between endotoxic stress and mitochondrial respiratory chain assembly defects. Firstly, we have shown that renal cells subjected to LPS are no longer capable to use adequately the available oxygen to maintain their metabolic functions. One hypothesis of this down-regulation suggests that impairment in mitochondria oxidative phosphorylation could prevent cells from using oxygen for adenosine triphosphate (ATP) production and potentially could cause sepsis-induced organ failure. Our study has then investigated this possible mitochondrial impairment to explain the decreased O2 consumption rate observed in LPS-treated HK-2 cells. After exposure to LPS, functionality of mitochondria was affected without any disturbance in their spatial organization. LPS seemed rather to interrupt mitochondrial oxidative phosphorylation by blocking cytochrome c oxidase activity. As a consequence, disruptions in the electron transport and the proton pumping across the system occurred, leading to a decrease of the mitochondrial membrane potential, an electron leakage as the form of superoxide anion, a release of cytochrome c in the cytosol and a decrease in ATP production. This irreversible defect in the production of cellular energy would support the concept that kidney failure in sepsis may occur on the basis of cytopathic hypoxia. [less ▲]

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See detailA confocal microscopic study of mitochondrial alterations of renal HK-2 cells exposed to an endotoxic stress
Quoilin, Caroline ULg; Mouithys-Mickalad, Ange ULg; Fontaine-Aupart, Marie-Pierre et al

Poster (2012, September)

Sepsis has a profound deleterious effect on kidney functions through complex mechanisms, which involve the immune response, inflammatory pathways, intracellular dysfunction and hemodynamic instability ... [more ▼]

Sepsis has a profound deleterious effect on kidney functions through complex mechanisms, which involve the immune response, inflammatory pathways, intracellular dysfunction and hemodynamic instability. Those factors are difficult to discriminate in vivo. To get a better understanding of renal respiratory dysfunction, we developed an in vitro model of sepsis-induced acute kidney injury using proximal tubular epithelial cell lines (HK-2) exposed to a bacterial endotoxin (lipopolysaccharide, LPS). Using this model, our first work has demonstrated that the basal respiration of renal HK-2 cells subjected to endotoxins was altered and presented a strong decrease in the oxygen consumption rates. Our working hypothesis of the pathophysiology of sepsis-induced AKI is based on a change in mitochondrial function that has been termed cytopathic hypoxia. A consequence of mitochondrial function alterations is an inability of the cell to use molecular oxygen for ATP production. The oxidative phosphorylation within mitochondria is interrupted because of the inhibition of cytochrome oxidase. The present investigation was carried out to establish whether mitochondrial alterations might be a mechanism of renal tubular epithelial injury during sepsis. To reach this goal the mitochondrial alterations of renal HK-2 cells exposed to an endotoxic stress was studied by confocal laser-scanning microscope. Confocal microscope allowed observation of the evoked phenomena at the single cell level and in real time. More particulary, mitochondrial morphology, mitochondrial membrane potential (ΔΨm) and generation of reactive oxygen species were recorded using specific vital fluorescent probes and quantified by image processing and analysis. Mitochondrial membrane potential is generated by the mitochondrial electron transport chain. This gradient is critical for the formation of ATP, and a fall in membrane potential is an indicator of mitochondrial dysfunction. ΔΨm was measured using the lipophilic cationic probe TMRE and it was shown that LPS produced a decrease in ΔΨm. In parallel, superoxide generation was measured by using MitoSOX which is selectively targeted to the mitochondria. There was a significant increase in mitochondrial superoxide-specific oxidation of MitoSOX when HK-2 cells were submitted to LPS. Overall, the model of HK-2 cells exposed to LPS displays some key features of sepsis-induced acute kidney injury. The confocal microscopy study has suggested a mechanism of toxicity dependent on mitochondrial oxidant generation and mitochondrial dysfunction. Indeed, the exposure to LPS has resulted in an increased generation of superoxide and a loss of mitochondrial function probably initiated by a fall in mitochondrial potential. [less ▲]

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See detailAn ESR, Mass Spectrometry and Fluorescence microscopy approach to study the stearic acid derivatives anchoring in cells
Grammenos, Angeliki ULg; Fillet, Marianne ULg; Collodoro, Mike et al

in Applied Magnetic Resonance (2012)

Lateral phase separations in biological membranes are of great interest, making Electron Spin Resonance (ESR) spectroscopy combined with spin labelling a non destructive and sensitive technique for the ... [more ▼]

Lateral phase separations in biological membranes are of great interest, making Electron Spin Resonance (ESR) spectroscopy combined with spin labelling a non destructive and sensitive technique for the study of lipid rafts. This is currently accepted that spin probe localization is on the plasma membrane. However, no study confirms this hypothesis. Herein, we report, for the first time, an accurate multi spectral method for the quantification of lipid spin label presence in every sub-cellular fraction. Cells were incubated with 5-doxyl stearic acid derivative and then sub-fractionated. Results of our multimodal spectroscopy approach ubiquitously demonstrate that the presence of ESR spin label only sets in the plasma membranes. [less ▲]

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See detailMultiple spectroscopic study of in vitro photodynamic therapy induced by PPME
Guelluy, Pierre-Henri ULg; Quoilin, Caroline; Grammenos, Angeliki ULg et al

Conference (2010, June 01)

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See detailPyropheophorbide-a-methyl ester: DMPC liposome vectorization and biophysical properties for PDT
Guelluy, Pierre-Henri ULg; Fontaine-Aupart, Marie-Pierre; Grammenos, Angeliki ULg et al

Poster (2009, July)

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See detailPhotochemistry of 2,6-diisopropylphenol (propofol)
Heyne, B.; Tfibel, F.; Hoebeke, Maryse ULg et al

in Photochemical & Photobiological Sciences (2006), 5(11), 1059-1067

The photochemistry of the anaesthetic agent propofol (PPF) was investigated in three different solvents of quite different polarity (cyclohexane, methanol and phosphate buffer pH 7) by means of nanosecond ... [more ▼]

The photochemistry of the anaesthetic agent propofol (PPF) was investigated in three different solvents of quite different polarity (cyclohexane, methanol and phosphate buffer pH 7) by means of nanosecond laser flash photolysis and absorption spectroscopy. GC-MS spectrometry measurements of PPF in cyclohexane have revealed the formation of two major products upon low intensity UV continuous irradiation of PPF in aerated solution: the diphenol derivative of PPF and 2,6-diisopropyl-p-benzoquinone (PPFQ). Only the diphenol compound was obtained in anaerobic solution. PPF phenoxyl radical (PPF ) generation has been assigned as the original step leading to the formation of both the diphenol compound and PPFQ in cyclohexane as revealed by laser flash photolysis at 266 nm and by electron paramagnetic resonance spectroscopy as well. Investigation of PPF by nanosecond flash photolysis at 266 nm in the other solvents revealed the occurrence of different photochemical processes depending on the nature and the polarity of the solvent. A reaction scheme is proposed in order to discuss the mechanism of reaction of PPF in all media. [less ▲]

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See detailPhysical and chemical properties of pyropheophorbide)a-methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-a-phosphatidylcholine vesicles
Delanaye, Lisiane; Bahri, Mohamed Ali ULg; Tfibel, Francis et al

in Photochemical & Photobiological Sciences (2006), 5

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second generation hotosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the ... [more ▼]

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second generation hotosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-α-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS). [less ▲]

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See detailReactivity towards singlet oxygen of propofol inside liposomes and neuronal cells
Heyne, Belinda; Brault, Daniel; Fontaine-Aupart, Marie-Pierre et al

in Biochimica et Biophysica Acta - General Subjects (2005), 1724

Singlet oxygen (1O2), a reactive oxygen species, has been found to be implicated in many cellular events and pathological disorders.Herein, we investigated the reactivity of 1O2 towards the anaesthetic ... [more ▼]

Singlet oxygen (1O2), a reactive oxygen species, has been found to be implicated in many cellular events and pathological disorders.Herein, we investigated the reactivity of 1O2 towards the anaesthetic agent propofol (PPF) encapsulated within DMPC liposomes. By time resolved luminescence, the rate constant of 1O2 quenching by PPF was evaluated, depending on the location of the sensitizer. The nature of the oxidation product, resulting from the reaction of 1O2 with PPF, was determined using absorption and HPLC techniques. Finally, the in vitro protective effect of PPF towards the1O2-induced neuronal cell toxicity was evaluated in terms of cell viability. [less ▲]

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See detailInvestigation of singlet oxygen reactivity towards propofol
Heyne, Belinda; Kohnen, Stephan ULg; Brault, Daniel et al

in Photochemical & Photobiological Sciences (2003), 2(9), 939-945

The reaction between the anaesthetic agent 2,6-diisopropylphenol (propofol, PPF) and singlet oxygen (1O2) has been investigated in aqueous solution by means of HPLC, GC, absorption spectroscopy and laser ... [more ▼]

The reaction between the anaesthetic agent 2,6-diisopropylphenol (propofol, PPF) and singlet oxygen (1O2) has been investigated in aqueous solution by means of HPLC, GC, absorption spectroscopy and laser flash photolysis with infrared luminescence detection. The rate constants for the physical and chemical quenching of 1O2 by PPF (kPPF) are found to be 2.66 x 10(5) M(-1) s(-1) and approximately 3.2 x 10(6) M(-1) s(-1) in CD3OD and D2O-CD3OD (75:25 v/v), respectively. The reaction of propofol with singlet oxygen produced by light irradiation of Rose Bengal leads essentially to two reaction products, 2,6-diisopropyl-p-benzoquinone and 3,5,3',5'-tetraisopropyl-(4,4')-diphenoquinone that are unambiguously identified from comparison with authentic samples. [less ▲]

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See detailEffect of aggregation on bacteriochlorin a triplet-state formation: A laser flash photolysis study
Damoiseau, Xavier; Tfibel, Francis; Hoebeke, Maryse ULg et al

in Photochemistry & Photobiology (2002), 76(5), 480-485

Bacteriochlorin a (BCA) is a potential photosensitizer for photodynamic therapy of cancer. It has been shown previously that the photoefficiency of the dye is mainly dependent on singlet oxygen (O-1(2 ... [more ▼]

Bacteriochlorin a (BCA) is a potential photosensitizer for photodynamic therapy of cancer. It has been shown previously that the photoefficiency of the dye is mainly dependent on singlet oxygen (O-1(2)) generation. Nanosecond laser flash photolysis was used to produce and to investigate the excited triplet state of the dye in methanol, phosphate buffer and dimiristoyl-L-alpha-phosphatidylcholine (DMPC) liposomes. The transients were characterized in terms of their absorption spectra, decay kinetics, molar absorption coefficients and formation quantum yield of singlet-triplet intercrossing. The lifetime of the BCA triplet state was measured at room temperature. The triplet-state quantum yield is quite high in methanol (0.7) and in DMPC (0.4) but only 0.095 in phosphate buffer. In the last case, BCA is in a monomer-dimer equilibrium, and the low value of the quantum yield observed was ascribed to the fact the triplet state is only formed by the monomers. [less ▲]

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