Régulation de l'apoptose mitochondriale par le facteur de survie FGF1 et l'inhibiteur de caspases zVAD-fmk

L apoptose est un processus physiologique de mort cellulaire essentiel à la survie des organismes pluricellulaires. L objectif de ce travail a été d étudier les effets de deux molécules : le facteur de survie FGF1 et l inhibiteur des caspases zVAD-fmk sur l apoptose dépendante de p53, un oncosuppresseur, régulateur clé de l apoptose. Dans un premier temps, nous nous sommes intéressés à l effet du FGF1 sur l apoptose dépendante de p53 dans un modèle de cellules neuronales : les cellules PC12. Les résultats obtenus lors de ma thèse montrent que : (1) les FGF1 exogène et endogène (intracellulaire et nucléaire) inhibent l apoptose dans les cellules PC12 en diminuant la phosphorylation et la stabilisation de p53, (2) la protéine FGF1 inhibe l activité transcriptionnelle de p53 vis-à-vis de ses gènes cibles pro-apoptotiques puma et noxa, (3) le FGF1 inhibe l activation de la caspase-3, effecteur de l apoptose (4) pour la majorité des activités du FGF1 endogène, la présence de sa séquence de nucléarisation est déterminante. Dans un second temps, nous avons étudié l effet de l inhibiteur de caspases zVAD-fmk sur la voie mitochondriale de l apoptose dans des fibroblastes embryonnaires de rongeurs. Les résultats obtenus montrent que : (1) le zVAD-fmk accélère l apoptose dépendante de p53 et du TNF dans ces cellules, (2) les protéines Bax et Bak et la dépolarisation des membranes mitochondriales sont nécessaires pour cette accélération, (3) le zVAD-fmk inhibe classiquement les caspases executrices-3/7 et (4) de façon surprenante, le zVAD-fmk induit une augmentation du clivage et de l activité de la caspase-9 et ne semble pas inhiber la caspase-8.Apoptosis is a physiological cell death in multicellular organisms that is required for embryogenesis, metamorphosis, homeostasis and elimination of cells that are potentially detrimental to organism. Deregulations of apoptosis have been implicated in many pathologies. The main aim of this work is the study of the Fibroblasts Growth Factor I (FGFI) and the caspase inhibitor zVAD-fmk effects in p53-dependent apoptosis. First, we study the effect of FGF1 in p53-dependent apoptosis. As both factors have been involved in neuronal apoptosis, we realized our study in PC12 cells, a neuronal cellular model. Our results show that: (1) exogenous and endogenous (intracellular and nuclear) FGF1 inhibit p53 phosphorylation and stabilization and thus p53-dependent apoptosis, (2) FGF1 inhibits puma and noxa trans-activation induced by p53, (3) FGF1 inhibits caspases-3 cleavage and (4) the nuclear localization of endogenous FGF1 is required for its anti-apoptotic activities. Second, we study the effect of pancaspase inhibitor zVAD-fmk in mitochondrial apoptosis in rodent embryonic fibroblasts. Our results show that: (1) zVAD-fmk increases p53- and TNF -dependent apoptosis, (2) this acceleration of apoptosis by zVAD-fmk involved mitochondrial events (3) Bax and/or Bak are required for p53- and TNF -dependent apoptosis and for zVAD-fmk induced apoptosis acceleration, (4) zVAD-fmk inhibits caspases-3/7 activity and (5) surprisingly, zVAD-fmk increases caspases-9 cleavage and activity and does not seems to inhibit caspases-8.VERSAILLES-BU Sciences et IUT (786462101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

Toxicities induced in cultured human hepatocarcinoma cells exposed to ochratoxin A: oxidative stress and apoptosis status

International audienc

FGF1 nuclear translocation is required for its neurotrophic activity and for its p53-dependent apoptosis protection

International audienc

Insulin a survival factor for olfactory mucosa

National audienc

Evidence for a mitochondrial localization of Rb protein

International audienc

Mitochondrial localization of the low level p53 protein in proliferative cells

International audienc

Insulin but not leptin protects olfactory mucosa from apoptosis

International audienceThe mammalian olfactory mucosa (OM) is continually renewed throughout life. Owing to their position in the nasal cavity, OM cells are exposed to multiple insults, including high levels of odourants that can induce their death. OM regeneration is therefore essential to maintain olfactory function, and requires the tight control of both cell death and proliferation. Apoptosis has been implicated in OM cell death. Olfaction is one of the senses involved in food intake and depends on individual nutritional status. We have previously reported the influence of hormones related to nutritional status on odour perception and have shown that the OM is a target of insulin and leptin, two hormones known for their anti-apoptotic properties. In the present study, we investigated the potential anti-apoptotic effect of these metabolic hormones on OM cells. Both Odora cells (an olfactive cell line) and OM cells treated with etoposide, a p53 activity inducer, exhibited mitochondrial-dependent apoptosis that was inhibited by the pan-caspase inhibitor zVAD-fmk. Insulin, but not leptin, impaired this apoptotic effect. Insulin addition to the culture medium reduced p53 phosphorylation, caspase-3 and caspase-9 cleavage, and caspase-3 enzymatic activity induced by etoposide. The apoptotic wave observed in the OM after interruption of the neuronal connections between the OM and the olfactory bulb by bulbectomy was impaired by intranasal insulin treatment. These findings suggest that insulin may be involved in OM cellular dynamics, through endocrine and/or paracrine-autocrine effects of circulating or local insulin, respectively

Assessing Liver Fibrosis Using the FIB4 Index in the Community Setting

Liver disease is frequently asymptomatic, challenging early identification in the primary care setting. The fibrosis 4 (FIB4) index is a liver fibrosis biomarker that is a potential alternative to liver biopsy for diagnosing and managing liver disease. This study aimed to calculate the FIB4 index for screening individuals at high risk of liver disease at the community level. This was a retrospective real-world study analyzing blood and serum test results from a central laboratory. The primary outcome was the number of individuals within each risk category for hepatic fibrosis: high risk (FIB4 ≥ 3.25) and low risk (FIB4 < 1.3). The analysis included samples from 31,753 patients, of which 18,102 were aged 40 to 75 years. In these patients, the FIB4 index had been explicitly requested in 1852 (10.2%) cases and estimated ad hoc in the rest. Of the 263 (1.5%) cases with FIB4 ≥ 3.25, the FIB4 index was requested in 46 (17.5%), and 52 (19.8%) showed evidence of liver fibrosis in their medical records, while the rest did not report any data regarding liver fibrosis. FIB4 is a simple score that can play a role as a "red flag" for early identification of patients at high risk of advanced liver fibrosis and their referral to specialized care