Towards the development of ecosystem-based indicators of mangroves functioning state in the context of the EU water framework directive

European Water Framework Directive is enforced in five tropical French Oversea Territories where mangroves are present. Developing bioindication tools to support the ecosystem-based management approach of the Directive is needed. A series of expert workshops was organized and led to the proposal of a strategy and of an applied research program to develop bioindication tools. The proceedings of the workshops are presented as a case study, as this is the first time such an integrative ecosystem-based approach is proposed in mangroves, combining structural and functional aspects, from forest structure to benthic community functioning

Major regression of Posidonia oceanica meadows in relation with recreational boat anchoring: A case study from Sant'Amanza bay

The anchoring of large recreational craft constitutes one of the main threats in shallow marine habitats. In the Mediterranean, this activity has seen constant development during the last decades, causing major physical disturbances in Posidonia oceanica meadows and associated ecosystem services. In this context, the main aims of the present study are to estimate the impact of this anchoring on P. oceanica meadows surface areas and carbon fixation and sequestration capacities, in a particularly highly-frequented area (Sant'Amanza bay, Corsica Island). Accurate benthic marine habitats mapping was performed yearly (2019–2021) using a drone coupled with ground-truthing data. The evaluation of carbon fixation and sequestration by the plant was measured at 12 stations within the bay (−5 m to −30 m). The maps of the marine habitats reveal an extensive regression of P. oceanica meadows (7.5 ha) between 2019 and 2020. This destruction represents a 9% decline in the total carbon fixation and sequestration performed each year by P. oceanica meadows within the bay. The related ecosystem services loss is estimated at 4.72 million € yr−1. Although an overall decline of boat anchoring in the seagrass meadow has been observed (e.g. recent enforcement of anchoring regulations), other solutions should be experimented to manage this major carbon sink

Long-term dynamics of a cladocora caespitosa bank as recorded by a posidonia oceanica millenary archive

Along most Mediterranean coasts, the endemic seagrass species Posidonia oceanica builds extensive meadows and complex peat-like bioconstruction known as ‘mattes’. These belowground deposits are recognized as a valuable long-term archive allowing the reconstruction and the study of palaeo-climatic and palaeo-ecological changes in the coastal environment over the Holocene period. One of the P. oceanica matte cores sampled during a coring survey along the eastern continental shelf of Corsica Island (France, NW Mediterranean) revealed the unprecedented finding of a dead bank of the scleractinian coral Cladocora caespitosa embedded in the matte. Measurement of the morphological and biometrical features of corallite fragments coupled to biogeosedimentological analysis and radiocarbon dating contributed to provide a basis for the reconstruction of the stratigraphic sequence since the mid-Holocene (last 4750 years). The study of the sediment core enabled identification of three major phases: (i) the settlement of the C. caespitosa colonies (~4750-3930 cal yr BP), (ii) the coexistence of the C. caespitosa bank and the P. oceanica meadow (~3930-1410 cal yr BP), followed by (iii) the death of the coral bank and the development of only the P. oceanica meadow (~1410 cal yr BP-present). The sclerochronological analysis completed on the well-preserved corallite fragments revealed that the mean annual growth rate of the coral ranged between 1.9 and 3.1 mm yr−1 with a mean value estimated at 2.3 ± 0.8 mm yr−1. Trend analysis showed semi-millennial to millennial oscillations in annual growth rates which are probably related to environmental climatic changes since the Cold Phase of the Subatlantic period (2925-2200 cal yr BP). During the Roman Warm Period (2200-1500 cal yr BP), the decline and the death of the bank (~1410 cal yr BP) was probably due to the combined effect of a prolonged increase in summer temperatures and an increase in the competition with the P. oceanica meadow

Coelomocytes regulate starvation-induced fat catabolism and lifespan extension through the lipase LIPL-5 in Caenorhabditis elegans

International audienceDietary restriction is known to extend the lifespan and reduce fat stores in most species tested to date, but the molecular mechanisms linking these events remain unclear. Here, we found that bacterial deprivation of Caenorhabditis elegans leads to lifespan extension with concomitant mobilization of fat stores. We find that LIPL-5 expression is induced by starvation and that the LIPL-5 lipase is present in coelomocyte cells and regulates fat catabolism and longevity during the bacterial deprivation response. Either LIPL-5 or coelomocyte deficiency prevents the rapid mobilization of intestinal triacylglycerol and enhanced lifespan extension in response to bacterial deprivation, whereas the combination of both defects has no additional or synergistic effect. Thus, the capacity to mobilize fat via LIPL-5 is directly linked to an animal's capacity to withstand long-term nutrient deprivation. Our data establish a role for LIPL-5 and coelomocytes in regulating fat consumption and lifespan extension upon DR

Two phases of aging separated by the Smurf transition as a public path to death.

International audienceAging's most obvious characteristic is the time dependent increase of an individual's probability to die. This lifelong process is accompanied by a large number of molecular and physiological changes. Although numerous genes involved in aging have been identified in the past decades its leading factors have yet to be determined. To identify the very processes driving aging we have developed in the past years an assay to identify physiologically old individuals in a synchronized population of Drosophila melanogaster. Those individuals show an age-dependent increase of intestinal permeability followed by a high risk of death. Here we show that this physiological marker of aging is conserved in 3 invertebrate species Drosophila mojavensis, Drosophila virilis, Caenorhabditis elegans as well as in 1 vertebrate species Danio rerio. Our findings suggest that intestinal barrier dysfunction may be an important event in the aging process conserved across a broad range of species, thus raising the possibility that it may also be the case in Homo sapiens

Unveiling novel phases: CO2 assisted co crystallization of proxyphylline with 4 hydroxybenzoic acid

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Optogenetically controlled inflammasome activation demonstrates two phases of cell swelling during pyroptosis

International audienceInflammasomes are multiprotein platforms that control caspase-1 activation, which process the inactive precursor forms of the inflammatory cytokines IL-1β and IL-18, leading to an inflammatory type of programmed cell death called pyroptosis. Studying inflammasome-driven processes, such as pyroptosis-induced cell swelling, under controlled conditions remains challenging because the signals that activate pyroptosis also stimulate other signaling pathways. We designed an optogenetic approach using a photo-oligomerizable inflammasome core adapter protein, apoptosis-associated speck–like containing a caspase recruitment domain (ASC), to temporally and quantitatively manipulate inflammasome activation. We demonstrated that inducing the light-sensitive oligomerization of ASC was sufficient to recapitulate the classical features of inflammasomes within minutes. This system showed that there were two phases of cell swelling during pyroptosis. This approach offers avenues for biophysical investigations into the intricate nature of cellular volume control and plasma membrane rupture during cell death

Regulation of Mitochondria-Associated Membranes (MAMs) by NO/sGC/PKG Participates in the Control of Hepatic Insulin Response

International audienceUnder physiological conditions, nitric oxide (NO) produced by the endothelial NO synthase (eNOS) upregulates hepatic insulin sensitivity. Recently, contact sites between the endoplasmic reticulum and mitochondria named mitochondria-associated membranes (MAMs) emerged as a crucial hub for insulin signaling in the liver. As mitochondria are targets of NO, we explored whether NO regulates hepatic insulin sensitivity by targeting MAMs. In Huh7 cells, primary rat hepatocytes and mouse livers, enhancing NO concentration increased MAMs, whereas inhibiting eNOS decreased them. In vitro, those effects were prevented by inhibiting protein kinase G (PKG) and mimicked by activating soluble guanylate cyclase (sGC) and PKG. In agreement with the regulation of MAMs, increasing NO concentration improved insulin signaling, both in vitro and in vivo, while eNOS inhibition disrupted this response. Finally, inhibition of insulin signaling by wortmannin did not affect the impact of NO on MAMs, while experimental MAM disruption, using either targeted silencing of cyclophilin D or the overexpression of the organelle spacer fetal and adult testis-expressed 1 (FATE-1), significantly blunted the effects of NO on both MAMs and insulin response. Therefore, under physiological conditions, NO participates to the regulation of MAM integrity through the sGC/PKG pathway and concomitantly improves hepatic insulin sensitivity. Altogether, our data suggest that the induction of MAMs participate in the impact of NO on hepatocyte insulin response

Participatory Qualitative Modeling to Assess the Sustainability of a Coastal Socio-Ecological System

International audienceAssessing the sustainability of socio-ecological systems requires understanding the interactions between numerous ecological, economic and social components. Models are often used to investigate how interactions shape system feedbacks and drive the complex dynamics at play in such systems. However, building these models is a non-trivial exercise, which often neglects stakeholder knowledge and perceptions. We adopted a participatory approach that relies on conducting workshops to engage stakeholders into the development of qualitative models of system feedback. This type of participatory qualitative modeling is well suited to address the complexity of socio-ecological systems in a holistic manner, identify key stakes and feedbacks, and predict responses to perturbations. We use this approach to investigate the factors that condition sustainability of the socio-ecological system associated with shellfish aquaculture in the Normand-Breton Gulf in France. Six region-specific workshops were organized with shellfish producers, managers and other stakeholders to identify and describe key components, interactions and pressures that contribute to overall socio-ecological dynamics. Differences and commonalities in system perceptions were identified across the different regions and focus groups. We reconciled stakeholder-specific discrepancies in model structure into a synthetic representation that conciliates alternative views of the system. Next, we predicted how the system might respond to alternative scenarios of change. Overall, our participatory qualitative modeling exercise identified key drivers of the system under study that constitute effective management levers to maintain system sustainability. For instance, low social acceptability of the aquaculture industry generally appears to be a major constraint on the sustainability of shellfish aquaculture in the Normand-Breton Gulf, while reducing rearing density appears to be a key driver of sustainability

Clusterin Neutralizes the Inflammatory and Cytotoxic Properties of Extracellular Histones in Sepsis

Rationale: Extracellular histones, released into the surrounding environment during extensive cell death, promote inflammation and cell death, and these deleterious roles have been well documented in sepsis. Clusterin (CLU) is a ubiquitous extracellular protein that chaperones misfolded proteins and promotes their removal. Objectives: We investigated whether CLU could protect against the deleterious properties of histones. Methods: We assessed CLU and histone expression in patients with sepsis and evaluated the protective role of CLU against histones in in vitro assays and in vivo models of experimental sepsis. Measurements and Main Results: We show that CLU binds to circulating histones and reduces their inflammatory, thrombotic, and cytotoxic properties. We observed that plasma CLU levels decreased in patients with sepsis and that the decrease was greater and more durable in nonsurvivors than in survivors. Accordingly, CLU deficiency was associated with increased mortality in mouse models of sepsis and endotoxemia. Finally, CLU supplementation improved mouse survival in a sepsis model. Conclusions: This study identifies CLU as a central endogenous histone-neutralizing molecule and suggests that, in pathologies with extensive cell death, CLU supplementation may improve disease tolerance and host survival