Les espèces actives de l’oxygène : le yin et le yang de la mitochondrie

Il existe de nombreuses sources d’espèces actives de l’oxygène (EAO) dans la cellule ; malgré l’importance de chacune d’entre elles, la mitochondrie a été choisie comme sujet central de cet article en raison de son rôle primordial dans la bio-énergétique et du fait qu’elle constitue le site majeur de la production cellulaire d’EAO, 80 % de l’anion superoxyde provenant de la chaîne respiratoire. Cette production est indissociable du processus respiratoire et fortement modulée par les conditions environnementales : elle varie notamment selon l’intensité du métabolisme énergétique ou de la pression en oxygène, permettant aux cellules de s’adapter à ces changements environnementaux en activant des voies spécifiques de signalisation. Lorsque cette production d’EAO devient chronique, elle induit des effets délétères, le stress oxydant mitochondrial étant impliqué aussi bien en physiopathologie qu’au cours du vieillissement.Literature on reactive oxygen species (ROS) effects on cell biology and physiopathology is huge and appears to be controversial. This could be explained by the fact that very few studies take into account the real subcellular source of ROS production, their chemical nature and the intensity of their production. In spite of the importance of the other sites of ROS production in the cell, we decided to focus on mitochondrial ROS. Besides their key role in bioenergetics and ATP synthesis, mitochondria are one of the main sites of ROS generation within the cell. 80 % of intracellular superoxide anion is provided by the mitochondrial respiratory chain. Mitochondrial ROS production is closely associated with activity of the respiratory chain and is modulated by environmental factors which can induce constraints on respiratory chain components. Nutrient availability as well as oxygen pressure can both modulate mitochondrial ROS production. When moderately produced, ROS specifically regulate intracellular signalling pathways by reversible oxidation of proteins such as transcription factors or proteins kinases. In this way, they can trigger cell adaptation to environmental changes as modifications of energetic metabolism or hypoxia. Indeed, we demonstrated that mitochondrial ROS act as key elements in the control of white adipose tissue development by specific up-regulation of the anti-adipogenic transcription factor CHOP-10/GADD153. However, when they are produced at high level and in a chronic manner, mitochondrial ROS can also have deleterious effects by massive and irreversible oxidation of their principals targets i.e. lipids, DNA and proteins. In these conditions, mitochondrial ROS are involved in aging process and in pathological situations as metabolic disease

Sex-specific depressive symptoms as markers of pre-Alzheimer dementia: findings from the Three-City cohort study

International audienceLate-life depression, as a potential marker of pre-dementia, has seldom been explored by symptom dimension and sex, despite sexual dimorphic differences. This study aimed to examine whether specific depressive dimensions were associated with pre-Alzheimer's disease dementia (pre-AD), separately for women and men. Data were drawn from 5617 (58% women) community-dwellers aged 65+ recruited in 1999-2000 and followed at 2-year intervals for 12 years. We used Cox proportional hazard models to study associations between time-dependent Centre for Epidemiologic Studies-Depression Scale (CES-D) symptom dimensions (namely somatic, depressed, positive affect, and interpersonal challenge) and pre-AD, defined retrospectively from validated diagnoses established 3.5 (IQR: 3.2-4.0) years onwards. Analyses were performed according to overall depressive symptomatology (DS+: CES-D score ≥ 16) and antidepressant/anxiolytic medication use (AA). Results indicated that in DS+ women only, all four dimensions were significantly associated with pre-AD in the AA-group, in particular somatic item 'Mind' and depressed affect items 'Depressed' and 'Blues'. The most depression-specific dimension, depressed affect, was also significantly associated with pre-AD in the DS-AA-women (HR:1.28, 95%CI: 1.12;1.47). In both sexes, in the DS-groups somatic affect was the most robust pre-AD marker, irrespective of treatment (women: HR = 1.22, 95%CI: 1.08;1.38; men: HR = 1.30, 95%CI: 1.14;1.48). Our findings highlight sex-specific associations between depressive symptom dimensions and pre-AD, modulated by depressive symptomatology and treatment. Assessment of specific symptom dimensions taking into account overall symptomatology and treatment could help identify and target high-risk AD-dementia profiles for interventions

Lifetime exposure to ambient ultraviolet radiation and the risk for cataract extraction and age-related macular degeneration : the Alienor Study

While exposure to ultraviolet radiation (UVR) is a recognized risk factor for cataract, its association is more controversial with age-related macular degeneration (AMD). We report the associations of lifetime exposure to ambient UVR with cataract extraction and AMD. The Alienor Study is a population-based study of 963 residents of Bordeaux (France), aged 73 years or more. Lifetime exposure to ambient UVR was estimated from residential history and Eurosun satellite-based estimations of ground UVR. It was divided in three groups (lower quartile, intermediate quartiles, upper quartile), using the intermediate quartiles as the reference. Early and late AMD was classified from retinal color photographs. Cataract extraction was defined as absence of the natural lens at slit-lamp. After multivariate adjustment, subjects in the upper quartile of lifetime ambient UVR exposure were at increased risk for cataract extraction (odds ratio [OR] = 1.53; 95% confidence interval [CI], 1.04-2.26; P = 0.03) and for early AMD (OR = 1.59; 95% CI, 1.04-2.44; P = 0.03), by comparison with subjects in the intermediate quartiles. Subjects in the lower quartile of UVR exposure also were at increased risk for early AMD (OR = 1.69; 95% CI, 1.06-2.69; P = 0.03), by comparison with those with medium exposure. Associations of late AMD with UVR exposure was not statistically significant. This study further confirms the increased risk for cataract extraction in subjects exposed to high ambient UVR. Moreover, it suggests that risk for early AMD is increased in subjects exposed to high UVR, but also to low UVR, by comparison with medium exposures

3D analysis of the whole subcutaneous adipose tissue reveals a complex spatial network of interconnected lobules with heterogeneous browning ability

Adipose tissue, as the main energy storage organ and through its endocrine activity, is interconnected with all physiological functions. It plays a fundamental role in energy homeostasis and in the development of metabolic disorders. Up to now, this tissue has been analysed as a pool of different cell types with very little attention paid to the organization and putative partitioning of cells. Considering the absence of a complete picture of the intimate architecture of this large soft tissue, we developed a method that combines tissue clearing, acquisition of autofluorescence or lectin signals by confocal microscopy, segmentation procedures based on contrast enhancement, and a new semi-automatic image analysis process, allowing accurate and quantitative characterization of the whole 3D fat pad organization. This approach revealed the unexpected anatomic complexity of the murine subcutaneous fat pad. Although the classical picture of adipose tissue corresponds to a superposition of simple and small ellipsoidal lobules of adipose cells separated by mesenchymal spans, our results show that segmented lobules display complex 3D poly-lobular shapes. Despite differences in shape and size, the number of these poly-lobular subunits is similar from one fat pad to another. Finally, investigation of the relationships of these subunits between each other revealed a never-described organization in two clusters with distinct molecular signatures and specific vascular and sympathetic nerve densities correlating with different browning abilities. This innovative procedure reveals that subcutaneous adipose tissue exhibits a subtle functional heterogeneity with partitioned areas, and opens new perspectives towards understanding its functioning and plasticity

SUpporting well-being through PEeR-Befriending (SUPERB) trial: an exploration of fidelity in peer-befriending for people with aphasia

Assessing the evolution of severely brain-injured patients with disorders of consciousness (DOC) with current tools like the Glasgow Outcome Scale-Extended (GOS-E) remains a challenge. At the bedside, the most reliable diagnostic tool is currently the Coma Recovery Scale-Revised. The CRS-R distinguishes patients with unresponsive wakefulness syndrome (UWS) from patients in minimally conscious state (MCS) and patients who have emerged from MCS (EMCS). This international multi-centric study aims to validate a phone outcome questionnaire (POQ) based on the CRS-R and compare it to the CRS-R performed at the bedside and to the GOS-E which evaluates the level of disability and assigns patient’s in outcomes categories. The POQ will allow clinicians to probe the evolution of patient’s state of consciousness based on caregivers feedback. This research project is part of the International Brain Injury Association, Disorders of Consciousness-Special Interest Group (DOCSIG) and DOCMA consortium

Crop pests and predators exhibit inconsistent responses to surrounding landscape composition

The idea that noncrop habitat enhances pest control and represents a win–win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win–win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies

Le lactate, substrat énergétique majeur, mais aussi molécule de signalisation

International audienceLe lactate a pendant de trop nombreuses années été considéré comme un simple déchet du métabolisme glycolytique, potentiellement délétère pour les organes étant donné le lien entre sa production et l’acidification du microenvironnement. Cette vision a été remise en cause par des études récentes qui placent le métabolisme du lactate au centre de l'homéostasie énergétique de l’organisme, et qui participent à sa réhabilitation en tant que métabolite majeur situé au carrefour du métabolisme glycolytique et oxydatif. De plus, cette littérature très dynamique ne cesse de mettre en lumière de nouveaux mécanismes par lesquels le lactate régule la physiologie cellulaire et notamment les processus de plasticité , en réponse aux modifications environnementales et métaboliques. Ainsi, il apparait que le lactate assure une communication métabolique inter-cellulaire et inter-tissulaire, non seulement par le transport de carbones et d’électrons entre différents compartiments, mais aussi grâce à son rôle de molécule de signalisation

Low-tech approaches for sustainability: key principles from the literature and practice

Low-tech approaches have come to the fore in the last few years, mainly in opposition to the techno-optimistic model proposed to solve current and future environmental crises. However, low-tech thinking is multifaceted, making the concept potentially rich but also vague. This article develops a seven-principle framework to categorize low-tech concepts based on an abductive approach which included a literature review and interviews with low-tech actors. Principle occurrence was assessed among the authors and interviewees. The results demonstrate that the low-tech movement entails more than a shift to robust and less-consumptive technical artifacts. While resource efficiency and material reuse are important traits of low-tech approaches, technical appropriation is the most frequently cited key principle in the literature and by the actors. This delineation into several principles can help to differentiate low-tech from other sustainability concepts related to resource conservation such as frugal innovations and circular economy. We aim in this article to open a discussion about the ways low-tech proponents are seeking to introduce transformative development pathways to sustainability

Low-tech approaches for sustainability: key principles from the literature and practice

Low-tech approaches have come to the fore in the last few years, mainly in opposition to the techno-optimistic model proposed to solve current and future environmental crises. However, low-tech thinking is multifaceted, making the concept potentially rich but also vague. This article develops a seven-principle framework to categorize low-tech concepts based on an abductive approach which included a literature review and interviews with low-tech actors. Principle occurrence was assessed among the authors and interviewees. The results demonstrate that the low-tech movement entails more than a shift to robust and less-consumptive technical artifacts. While resource efficiency and material reuse are important traits of low-tech approaches, technical appropriation is the most frequently cited key principle in the literature and by the actors. This delineation into several principles can help to differentiate low-tech from other sustainability concepts related to resource conservation such as frugal innovations and circular economy. We aim in this article to open a discussion about the ways low-tech proponents are seeking to introduce transformative development pathways to sustainability

Low-tech approaches for sustainability: key principles from the literature and practice

Low-tech approaches have come to the fore in the last few years, mainly in opposition to the techno-optimistic model proposed to solve current and future environmental crises. However, low-tech thinking is multifaceted, making the concept potentially rich but also vague. This article develops a seven-principle framework to categorize low-tech concepts based on an abductive approach which included a literature review and interviews with low-tech actors. Principle occurrence was assessed among the authors and interviewees. The results demonstrate that the low-tech movement entails more than a shift to robust and less-consumptive technical artifacts. While resource efficiency and material reuse are important traits of low-tech approaches, technical appropriation is the most frequently cited key principle in the literature and by the actors. This delineation into several principles can help to differentiate low-tech from other sustainability concepts related to resource conservation such as frugal innovations and circular economy. We aim in this article to open a discussion about the ways low-tech proponents are seeking to introduce transformative development pathways to sustainability