Translocator Protein-Mediated Stabilization of Mitochondrial Architecture during Inflammation Stress in Colonic Cells.

International audienceChronic inflammation of the gastrointestinal tract increasing the risk of cancer has been described to be linked to the high expression of the mitochondrial translocator protein (18 kDa; TSPO). Accordingly, TSPO drug ligands have been shown to regulate cytokine production and to improve tissue reconstruction. We used HT-29 human colon carcinoma cells to evaluate the role of TSPO and its drug ligands in tumor necrosis factor (TNF)-induced inflammation. TNF-induced interleukin (IL)-8 expression, coupled to reactive oxygen species (ROS) production, was followed by TSPO overexpression. TNF also destabilized mitochondrial ultrastructure, inducing cell death by apoptosis. Treatment with the TSPO drug ligand PK 11195 maintained the mitochondrial ultrastructure, reducing IL-8 and ROS production and cell death. TSPO silencing and overexpression studies demonstrated that the presence of TSPO is essential to control IL-8 and ROS production, so as to maintain mitochondrial ultrastructure and to prevent cell death. Taken together, our data indicate that inflammation results in the disruption of mitochondrial complexes containing TSPO, leading to cell death and epithelia disruption. This work implicates TSPO in the maintenance of mitochondrial membrane integrity and in the control of mitochondrial ROS production, ultimately favoring tissue regeneration

Role physiologique et physiopathologique de la TSPO dans l'instestin

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Parmi les TSPO recombinantes, la BcTSPO

International audienceOverexpression of recombinant Bacillus cereus TSPO (BcTSPO) in E. coli bacteria leads to its recovery with a bound hemin both in bacterial membrane (MB) and inclusion bodies (IB). Unlike mouse TSPO, BcTSPO purified in SDS detergent from IB is well structured and can bind various ligands such as high-affinity PK 11195, protoporphyrin IX (PPIX) and d-aminolevulinic acid (ALA). For each of the three ligands, 1H-15N HSQC titration NMR experiments suggest that different amino acids of BcTSPO binding cavity are involved in the interaction. PPIX, an intermediate of heme biosynthesis, binds to the cavity of BcTSPO and its fluorescence can be significantly reduced in the presence of light and oxygen. The light irradiation leads to two products that have been isolated and characterized as photoporphyrins. They result from the addition of singlet oxygen to the two vinyl groups hence leading to the formation of hydroxyaldehydes. The involvement of water molecules, recently observed along with the binding heme in Rhodobacter sphaeroides (RsTSPO) is highly probable. Altogether, these results raise the question of the role of TSPO in heme biosynthesis regulation as a possible scavenger of reactive intermediates

Effects of TSPO and STAR inhibitors on cell death in a cardiomyocyte model of hypoxia-reoxygenation

International audienceHypoxia-reoxygenation TSPO-STAR Introduction We previously demonstrated that reperfusion of an ischemic myocardium induces an increase in mitochondrial cholesterol (CL) content accompanied by a generation of oxysterols. The translocator protein (TSPO) and the steroid acute regulatory protein (STAR) are involved in CL transport at the mitochondrial membrane in steroidogenic tissues but in the heart their role remain uncertain. The TSPO ligand 4'-chlorodiazepam (4'CDZ) has been demonstrated to inhibit STAR and sterols mitochondrial accumulations and to reduce infarct size. These data suggest that targeting mitochondrial sterol accumulation could participate to the protective effects of TSPO ligands. Objective To analyze the mechanisms and the role of the mitochondrial CL transport in cell death with a cardiomyocyte model of hypoxiareoxygenation (HR). Method AC16 human cardiomyocytes were submitted to different durations of hypoxia (1% O2) followed by reoxygenation (21% O2) to achieve 50% mortality. Cells were then treated at reoxygenation with 4'CDZ and novel TSPO and STAR inhibitors, known to delay steroidogenesis in vitro by targeting CL specific binding sites of these proteins (CRAC and START, respectively). Cell mortality was assessed with MTT and crystal violet assay and CL was identified by means of fluorescent probes. Results HR induced 41±3% mortality and modified membrane CL pattern in the cells. In this model, 4'-CDZ (10 µM) did not display cardioprotective effect (44±3% mortality). Similar results were observed with the TSPO inhibitors (CRAC benzamide 100 µM, CRAC triol 100 µM) and the STAR inhibitor (START triol 100 µM) (46±1% 43±3% and 54±3% mortality, respectively). Conclusion This preliminary study suggests that TSPO ligands do not exert cardioprotection through a direct action on cardiomyocytes. This conclusion needs to be confirmed with the use of adult primary cardiomyocytes

Origanum majorana Extracts: A Preliminary Comparative Study on Phytochemical Profiles and Bioactive Properties of Valuable Fraction and By-Product

Origanum majorana L. (O. majorana) (Lamiaceae) is an aromatic Mediterranean plant widely used in food, cosmetics, and traditional medicine due to its aroma and rich content of bioactive compounds. While its leaves and flowers are commonly utilized, lignified stems are often discarded. This study compared hydroalcoholic extracts from the leaves and flowers (valuable fraction, VF) and stems (by-product, BP). Phytochemical analysis revealed qualitatively similar profiles, identifying 20 phenolic compounds, with Rosmarinic acid and Salvianolic acid B as the most and second most abundant, respectively. Antioxidant activity was evaluated in vitro using DPPH (IC50 [µg/mL]: VF 30.11 ± 3.46; BP 31.72 ± 1.46), H2O2 (IC50 [µg/mL]: VF 103.09 ± 4.97; BP 119.55 ± 10.58), and O2•− (IC50 [µg/mL]: VF 0.71 ± 0.062; BP 0.79 ± 0.070). Both extracts (20 µg/mL) fully restored oxidative balance in hemin-stressed AC16 cardiomyocytes, without altering the expression of catalase, heme-oxygenase 1, superoxide dismutase 2, or ferritin. Anti-inflammatory activity in LPS-stimulated RAW 264.7 macrophages showed that VF (IC50 400 µg/mL) reduced •NO release to control levels, while BP achieved a ~60% reduction. Cytotoxicity was assessed on cancer cell lines: CaCo-2 (IC50 [µg/mL]: VF 154.1 ± 6.22; BP 305.2 ± 15.94), MCF-7 (IC50 [µg/mL]: VF 624.6 ± 10.27; BP 917.9 ± 9.87), and A549 (IC50 [µg/mL]: VF 720.8 ± 13.66; BP 920.2 ± 16.79), with no cytotoxicity on normal fibroblasts HFF-1 (IC50 > 1000 µg/mL for both extracts). Finally, both extracts slightly inhibited only CYP1A2 (IC50 [µg/mL]: VF 497.45 ± 9.64; BP 719.72 ± 11.37) and CYP2D6 (IC50 [µg/mL]: VF 637.15 ± 14.78, BP 588.70 ± 11.01). These results support the potential reuse of O. majorana stems as a sustainable source of bioactive compounds for nutraceutical and health-related applications

Dynamic Remodeling of Membranes and Their Lipids during Acute Hormone-Induced Steroidogenesis in MA-10 Mouse Leydig Tumor Cells

Lipids play essential roles in numerous cellular processes, including membrane remodeling, signal transduction, the modulation of hormone activity, and steroidogenesis. We chose steroidogenic MA-10 mouse tumor Leydig cells to investigate subcellular lipid localization during steroidogenesis. Electron microscopy showed that cAMP stimulation increased associations between the plasma membrane (PM) and the endoplasmic reticulum (ER) and between the ER and mitochondria. cAMP stimulation also increased the movement of cholesterol from the PM compared to untreated cells, which was partially inhibited when ATPase family AAA-domain containing protein 3 A (ATAD3A), which functions in ER and mitochondria interactions, was knocked down. Mitochondria, ER, cytoplasm, PM, PM-associated membranes (PAMs), and mitochondria-associated membranes (MAMs) were isolated from control and hormone-stimulated cells. Lipidomic analyses revealed that each isolated compartment had a unique lipid composition, and the induction of steroidogenesis caused the significant remodeling of its lipidome. cAMP-induced changes in lipid composition included an increase in phosphatidylserine and cardiolipin levels in PAM and PM compartments, respectively; an increase in phosphatidylinositol in the ER, mitochondria, and MAMs; and a reorganization of phosphatidic acid, cholesterol ester, ceramide, and phosphatidylethanolamine. Abundant lipids, such as phosphatidylcholine, were not affected by hormone treatment. Our data suggested that PM–ER–mitochondria tethering may be involved in lipid trafficking between organelles and indicated that hormone-induced acute steroid production involves extensive organelle remodeling.</jats:p