Strong Dietary Restrictions Protect Drosophila against Anoxia/Reoxygenation Injuries

Reoxygenation of ischemic tissues is a major factor that determines the severity of cardiovascular diseases. This paper describes the consequences of anoxia/reoxygenation (A/R) stresses on Drosophila, a useful, anoxia tolerant, model organism.Newly emerged adult male flies were exposed to anoxic conditions (<1% O2) for 1 to 6 hours, reoxygenated and their survival was monitored.A/R stresses induced a transient increase in mortality which peaked at the time of reoxygenation. Then flies recovered low mortality rates similar to those of control flies. A/R induced mortality was strongly dependent on dietary conditions during the 48 h that preceded anoxia. Well fed flies were anoxia sensitive. Strong dietary restrictions and starvation conditions protected flies against A/R injuries. The tolerance to anoxia was associated to large decreases in glycogen, protein, and ATP contents. During anoxia, anoxia tolerant flies produced more lactate, less phosphate and they maintained more stable ATP levels than anoxia sensitive flies. Moderate dietary restrictions, which increased the longevity of normoxic flies, did not promote resistance to A/R stresses. Diet dependent A/R injuries were still observed in sigma loss of function mutants and they were insensitive to dietary rapamycin or resveratrol. AICAR (5-aminoimidazole-4-carboxamide-1-beta-D-ribose-furanoside), an activator AMP kinase decreased A/R injuries. Mutants in the insulin signalling pathway were more anoxia tolerant in a fed state.Long A/R stresses induce a transient increase in mortality in Drosophila. This mortality is highly dependent on dietary conditions prior to the stress. Strong dietary restrictions and starvation conditions protect flies against A/R injuries, probably by inducing a major remodelling of energy metabolism. The results also indicate that mechanistically different responses develop in response to dietary restrictions of different strengths. AMP kinase and the insulin signalling pathway are possible mediators of diet dependent anoxic tolerance in Drosophila

Conditioning Medicine A new pharmacological preconditioning-based target: from drosophila to kidney transplantation

International audienceOne of the biggest challenges in medicine is to dampen the pathophysiological stress induced by an episode of ischemia. Such stress, due to various pathological or clinical situations, follows a restriction in blood and oxygen supply to tissue, causing a shortage of oxygen and nutrients that are required for cellular metabolism. Ischemia can cause irreversible damage to target tissue leading to a poor physiological recovery outcome for the patient. Contrariwise, preconditioning by brief periods of ischemia has been shown in multiple organs to confer tolerance against subsequent normally lethal ischemia. By definition, preconditioning of organs must be applied preemptively. This limits the applicability of preconditioning in clinical situations, which arise unpredictably, such as myocardial infarction and stroke. There are, however, clinical situations that arise as a result of ischemia-reperfusion injury, which can be anticipated, and are therefore adequate candidates for preconditioning. Organ and more particularly kidney transplantation, the optimal treatment for suitable patients with end stage renal disease (ESRD), is a predictable surgery that permits the use of preconditioning protocols to prepare the organ for subsequent ischemic/reperfusion stress. It therefore seems crucial to develop appropriate preconditioning protocols against ischemia that will occur under transplantation conditions, which up to now mainly referred to mechanical ischemic preconditioning that triggers innate responses. It is not known if preconditioning has to be applied to the donor, the recipient, or both. No drug/target pair has been envisioned and validated in the clinic. Options for identifying new target/drug pairs involve the use of model animals, such as drosophila, in which some physiological pathways, such as the management of oxygen, are highly conserved across evolution. Oxygen is the universal element of life existence on earth. In this review we focus on a very specific pathway of pharmacological preconditioning identified in drosophila that was successfully transferred to mammalian models that has potential application in human health. Very few mechanisms identified in these model animals have been translated to an upper evolutionary level. This review highlights the commonality between oxygen regulation between diverse animals

Role of TASK2 Potassium Channels Regarding Volume Regulation in Primary Cultures of Mouse Proximal Tubules

Several papers reported the role of TASK2 channels in cell volume regulation and regulatory volume decrease (RVD). To check the possibility that the TASK2 channel modulates the RVD process in kidney, we performed primary cultures of proximal convoluted tubules (PCT) and distal convoluted tubules (DCT) from wild-type and TASK2 knockout (KO) mice. In KO mice, the TASK2 coding sequence was in part replaced by the lac-Z gene. This allows for the precise localization of TASK2 in kidney sections using β-galactosidase staining. TASK2 was only localized in PCT cells. K+ currents were analyzed by the whole-cell clamp technique with 125 mM K-gluconate in the pipette and 140 mM Na-gluconate in the bath. In PCT cells from wild-type mice, hypotonicity induced swelling-activated K+ currents insensitive to 1 mM tetraethylammonium, 10 nM charybdotoxin, and 10 μM 293B, but blocked by 500 μM quinidine and 10 μM clofilium. These currents were increased in alkaline pH and decreased in acidic pH. In PCT cells from TASK2 KO, swelling-activated K+ currents were completely impaired. In conclusion, the TASK2 channel is expressed in kidney proximal cells and could be the swelling-activated K+ channel responsible for the cell volume regulation process during osmolyte absorptions in the proximal tubules

Knockout of Vdac1 activates hypoxia-inducible factor through reactive oxygen species generation and induces tumor growth by promoting metabolic reprogramming and inflammation

BACKGROUND: Mitochondria are more than just the powerhouse of cells; they dictate if a cell dies or survives. Mitochondria are dynamic organelles that constantly undergo fusion and fission in response to environmental conditions. We showed previously that mitochondria of cells in a low oxygen environment (hypoxia) hyperfuse to form enlarged or highly interconnected networks with enhanced metabolic efficacy and resistance to apoptosis. Modifications to the appearance and metabolic capacity of mitochondria have been reported in cancer. However, the precise mechanisms regulating mitochondrial dynamics and metabolism in cancer are unknown. Since hypoxia plays a role in the generation of these abnormal mitochondria, we questioned if it modulates mitochondrial function. The mitochondrial outer-membrane voltage-dependent anion channel 1 (VDAC1) is at center stage in regulating metabolism and apoptosis. We demonstrated previously that VDAC1 was post-translationally C-terminal cleaved not only in various hypoxic cancer cells but also in tumor tissues of patients with lung adenocarcinomas. Cells with enlarged mitochondria and cleaved VDAC1 were also more resistant to chemotherapy-stimulated cell death than normoxic cancer cells. RESULTS: Transcriptome analysis of mouse embryonic fibroblasts (MEF) knocked out for Vdac1 highlighted alterations in not only cancer and inflammatory pathways but also in the activation of the hypoxia-inducible factor-1 (HIF-1) signaling pathway in normoxia. HIF-1α was stable in normoxia due to accumulation of reactive oxygen species (ROS), which decreased respiration and glycolysis and maintained basal apoptosis. However, in hypoxia, activation of extracellular signal-regulated kinase (ERK) in combination with maintenance of respiration and increased glycolysis counterbalanced the deleterious effects of enhanced ROS, thereby allowing Vdac1 (-/-) MEF to proliferate better than wild-type MEF in hypoxia. Allografts of RAS-transformed Vdac1 (-/-) MEF exhibited stabilization of both HIF-1α and HIF-2α, blood vessel destabilization, and a strong inflammatory response. Moreover, expression of Cdkn2a, a HIF-1-target and tumor suppressor gene, was markedly decreased. Consequently, RAS-transformed Vdac1 (-/-) MEF tumors grew faster than wild-type MEF tumors. CONCLUSIONS: Metabolic reprogramming in cancer cells may be regulated by VDAC1 through vascular destabilization and inflammation. These findings provide new perspectives into the understanding of VDAC1 in the function of mitochondria not only in cancer but also in inflammatory diseases

Aneuploidy in intestinal stem cells promotes gut dysplasia in Drosophila

Aneuploidy is associated with different human diseases including cancer. However, different cell types appear to respond differently to aneuploidy, either by promoting tumorigenesis or causing cell death. We set out to study the behavior of adult Drosophila melanogaster intestinal stem cells (ISCs) after induction of chromosome missegregation either by abrogation of the spindle assembly checkpoint or through kinetochore disruption or centrosome amplification. These conditions induce moderate levels of aneuploidy in ISCs, and we find no evidence of apoptosis. Instead, we observe a significant accumulation of ISCs associated with increased stem cell proliferation and an excess of enteroendocrine cells. Moreover, aneuploidy causes up-regulation of the JNK pathway throughout the posterior midgut, and specific inhibition of JNK signaling in ISCs is sufficient to prevent dysplasia. Our findings highlight the importance of understanding the behavior of different stem cell populations to aneuploidy and how these can act as reservoirs for genomic alterations that can lead to tissue pathologies.This article is a result of the project Norte Portugal Regional Operational Program (NORTE 2020) Norte-01-0145-FEDER-000029 – Advancing Cancer Research: From basic knowledge to application, under the PORTUGAL 2020 Partnership Agreement through the European Regional Development Fund, and it is also funded by National Funds through Fundação para a Ciência e a Tecnologia under the project PTDC/BEX-BCM/1921/2014

Young children's understanding of disabilities: the influence of development, context and cognition

Throughout Europe, educational support for children with disabilities has moved towards a model of inclusive education. Such policy changes mean that for all children there will be an increased likelihood of working with and encountering children with differing disabilities and difficulties. Previous research had indicated that children had poorly differentiated views of developmental differences. The present study investigated children?s representations of different disabilities. Seventy-nine 8-9 and 10-11 year old Greek children from an urban school and a rural school completed an attitudes toward school inclusion rating scale and a semi-structured interview. Responses to the attitude scale provided generally positive views of educational inclusion. However, children were less positive about activities that might directly reflect upon themselves. Children?s responses in the interviews indicated that they were developing rich representations of differences and diversities. Children had the greatest understanding of sensory and physical disabilities, followed by learning disabilities. There was limited knowledge of dyslexia and hyperactivity and no child was familiar with the term autism. Both groups of children identified a range of developmental difficulties, with older children being more aware of specific learning disabilities, their origin and impact. Results are discussed in terms of children?s developing knowledge systems and the implications for educational practices

Un nouveau paradigme dans le traitement de l’ischémie

L’ischémie est une des préoccupations majeures des cliniciens qui y sont confrontés en permanence, que ce soit aussi bien d’un point de vue chirurgical que pathologique. Les conséquences des stress ischémiques sont dramatiques et peuvent conduire à des incapacités organiques, motrices ou cognitives. Actuellement il n’existe aucune cible moléculaire identifiée dont le ciblage pourrait être bénéfique dans ce domaine. La mouche Drosophila melanogaster, utilisée comme animal modèle, a conduit à une avancée majeure en permettant l’identification d’une toute nouvelle cible pharmacologique dont l’inhibition augmente de façon importante la tolérance à l’hypoxie. Appliqué à un modèle préclinique de transplantation rénale, cette nouvelle approche améliore nettement la reprise fonctionnelle du greffon à long terme. Cette revue retrace les étapes qui ont permis de transférer chez le mammifère supérieur une cible mise en évidence chez la drosophile, ce qui montre clairement, au-delà de la recherche fondamentale, l’apport que peut apporter un organisme modèle à la clinique

Calcium transport in rabbit distal cells

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Obtention de souris transgéniques exprimant la recombinase Cre sous le contrôle du promoteur du gène récepteur 2 à la vasopressine en vue d'inactiver CFTR dans le rein

Afin de déterminer le rôle exact de la protéine CFTR (considérée comme un canal Cl- activé par l AMPc) dans le rein, nous avons choisi de générer un modèle murin présentant une inactivation génique de CFTR spécifiquement dans le rein en utilisant le système Cre/LoxP. Pour diriger l expression de la recombinase Cre, nous avons choisi le promoteur du récepteur 2 à la vasopressine spécifique des canaux collecteurs, lieu d expression de la protéine CFTR dans le rein. Nous avons cloné ce promoteur chez la souris. Des souris transgéniques ont été obtenues par des techniques classiques de transgénèse. Le génotypage des souris transgéniques a permis de détecter six lignées transgéniques. Le phénotypage de ces lignées est réalisé par des techniques de biologie moléculaire et d immunohistochimie en croisant ces souris avec des souris transgéniques STOP/LacZ. Les résultats obtenus indiquent une expression fonctionnelle de la recombinase dans le rein mais aussi dans d autres organes tels que la rate, le cerveau, le poumon ou l intestin en fonction de la lignée étudiée. La lignée 5 présente la lignée la lus adéquate pour inactiver la protéine CFTR dans le rein.NICE-BU Sciences (060882101) / SudocSudocFranceF

Role of monocarboxylic acid transport in intracellular pH regulation of isolated proximal cells

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