Dendritic cells: the host Achille's heel for mucosal pathogens?

Mucosal surfaces represent the main sites of interaction with environmental microorganisms and antigens. Sentinel cells, including epithelial cells and dendritic cells (DCs), continuously sense the environment and coordinate defenses for the protection of mucosal tissues. DCs play a central role in the control of adaptive immune responses owing to their capacity to internalize foreign materials, to migrate into lymph nodes and to present antigens to naive lymphocytes. Some pathogenic microorganisms trigger epithelial responses that result in the recruitment of DCs. These pathogens hijack the recruited DCs to enable them to infect the host, escape the host's defense mechanisms and establish niches at remote sites.

A critical role for the T cell receptor alpha-chain connecting peptide domain in positive selection of CD1-independent NKT cells.

Natural killer T (NKT) cells are a subset of mature alpha beta TCR(+) cells that co-express NK lineage markers. Whereas most NKT cells express a canonical Valpha14/Vbeta8.2 TCR and are selected by CD1d, a minority of NKT cells express a diverse TCR repertoire and develop independently of CD1d. Little is known about the selection requirements of CD1d-independent NKT cells. We show here that NKT cells develop in RAG-deficient mice expressing an MHC class II-restricted transgenic TCR (Valpha2/Vbeta8.1) but only under conditions that lead to negative selection of conventional T cells. Moreover development of NKT cells in these mice is absolutely dependent upon an intact TCR alpha-chain connecting peptide domain, which is required for positive selection of conventional T cells via recruitment of the ERK signaling pathway. Collectively our data demonstrate that NKT cells can develop as a result of high avidity TCR/MHC class II interactions and suggest that common signaling pathways are involved in the positive selection of CD1d-independent NKT cells and conventional T cells.

Physiological differences between cycling and running: lessons from triathletes

The purpose of this review was to provide a synopsis of the literature concerning the physiological differences between cycling and running. By comparing physiological variables such as maximal oxygen consumption (V O(2max)), anaerobic threshold (AT), heart rate, economy or delta efficiency measured in cycling and running in triathletes, runners or cyclists, this review aims to identify the effects of exercise modality on the underlying mechanisms (ventilatory responses, blood flow, muscle oxidative capacity, peripheral innervation and neuromuscular fatigue) of adaptation. The majority of studies indicate that runners achieve a higher V O(2max) on treadmill whereas cyclists can achieve a V O(2max) value in cycle ergometry similar to that in treadmill running. Hence, V O(2max) is specific to the exercise modality. In addition, the muscles adapt specifically to a given exercise task over a period of time, resulting in an improvement in submaximal physiological variables such as the ventilatory threshold, in some cases without a change in V O(2max). However, this effect is probably larger in cycling than in running. At the same time, skill influencing motor unit recruitment patterns is an important influence on the anaerobic threshold in cycling. Furthermore, it is likely that there is more physiological training transfer from running to cycling than vice versa. In triathletes, there is generally no difference in V O(2max) measured in cycle ergometry and treadmill running. The data concerning the anaerobic threshold in cycling and running in triathletes are conflicting. This is likely to be due to a combination of actual training load and prior training history in each discipline. The mechanisms surrounding the differences in the AT together with V O(2max) in cycling and running are not largely understood but are probably due to the relative adaptation of cardiac output influencing V O(2max) and also the recruitment of muscle mass in combination with the oxidative capacity of this mass influencing the AT. Several other physiological differences between cycling and running are addressed: heart rate is different between the two activities both for maximal and submaximal intensities. The delta efficiency is higher in running. Ventilation is more impaired in cycling than in running. It has also been shown that pedalling cadence affects the metabolic responses during cycling but also during a subsequent running bout. However, the optimal cadence is still debated. Central fatigue and decrease in maximal strength are more important after prolonged exercise in running than in cycling.

Interim analysis of the Reitan Catheter Pump (RCP) heart failure efficacy study: RCP improves cardiovascular and renal function in acute decompensated heart failure (ADHF)

Background: The RCP is a 14 French collapsable percutaneous cardiovascular support device positioned in the descending part of the thoracic aorta via the femoral artery. A 10 patient first in man study demonstrated device safety and significant improvement in renal function among high risk PCI patients. We now report haemodynamic and renal efficacy in patients with ADHF.Methods: Prospective non randomised study seeking to recruit 20 patients with ADHF with a need for inotropic or mechanical circulatory support with: i) EF < 30% ii)Cardiac index(CI) < 2.2 L / min / m2 Outcome measures included: 1) Cardiac index (CI) 2) Pulmonary Capillary Wedge Pressure (PCWP) 3) Urine output / serum creatinine 4) Vascular / device complications 5) 30 day mortalityResults: INTERIM ANALYSIS (n=12) The mean age of the study group was 64 years, with a mean baseline creatinine of 193 umol/L, eGFR 38 ml/min. The intended RCP treatment period was 24 hours. During RCP treatment there was a significant mean reduction of PCWP at 4 hours of 17% (25 to 21 mmHg p=0.04). Mean CI increased at 12 hours by 11%, though not reaching significance (1.78 to 1.96 L/min/m2 p=0.08). RCP insertion prompted substantial diuresis. Urine output tripled over the first 12 hours compared to baseline (55 ml/hr vs 213 ml/hr p=0.03). This was associated with significantly improved renal function, a 28% reduction in serum creatinine at 12 hours (193 to 151 umol/L p=0.003), and a increase in eGFR from 38 ml/min to 50 ml/min (p=0.0007). 2 patients previously refused cardiac transplantation were reassessed and successfully transplanted within 9 months of RCP treatment on the basis of demonstrable renal reversibility. There were no vascular or device complications. There were 2 deaths at 30 days, one from multi-organ failure and sepsis, and one from intractable heart failure - neither were device related.Conclusion: RCP support in ADHF patients was associated with improved haemodynamics, and an improvement in renal function. The Reitan Catheter Pump may have a role in providing percutaneous cardiovascular and renal support in the acutely decompensated cardiac patient, and may have a role in suggesting renal reversibility in potential cardiac transplant patients. Further data will be reported at recruitment completion.

Characteristic bimodal profiles of RNA polymerase II at thousands of active mammalian promoters.

BACKGROUND: In mammals, ChIP-seq studies of RNA polymerase II (PolII) occupancy have been performed to reveal how recruitment, initiation and pausing of PolII may control transcription rates, but the focus is rarely on obtaining finely resolved profiles that can portray the progression of PolII through sequential promoter states. RESULTS: Here, we analyze PolII binding profiles from high-coverage ChIP-seq on promoters of actively transcribed genes in mouse and humans. We show that the enrichment of PolII near transcription start sites exhibits a stereotypical bimodal structure, with one peak near active transcription start sites and a second peak 110 base pairs downstream from the first. Using an empirical model that reliably quantifies the spatial PolII signal, gene by gene, we show that the first PolII peak allows for refined positioning of transcription start sites, which is corroborated by mRNA sequencing. This bimodal signature is found both in mouse and humans. Analysis of the pausing-related factors NELF and DSIF suggests that the downstream peak reflects widespread pausing at the +1 nucleosome barrier. Several features of the bimodal pattern are correlated with sequence features such as CpG content and TATA boxes, as well as the histone mark H3K4me3. CONCLUSIONS: We thus show how high coverage DNA sequencing experiments can reveal as-yet unnoticed bimodal spatial features of PolII accumulation that are frequent at individual mammalian genes and reminiscent of transcription initiation and pausing. The initiation-pausing hypothesis is corroborated by evidence from run-on sequencing and immunoprecipitation in other cell types and species.

Preferential binding of the methyl-CpG binding domain protein 2 at methylated transcriptional start site regions.

Methyl-CpG Binding Domain (MBD) proteins are thought to be key molecules in the interpretation of DNA methylation signals leading to gene silencing through recruitment of chromatin remodeling complexes. In cancer, the MBD-family member, MBD2, may be primarily involved in the repression of genes exhibiting methylated CpG at their 5' end. Here we ask whether MBD2 randomly associates methylated sequences, producing chance effects on transcription, or exhibits a more specific recognition of some methylated regions. Using chromatin and DNA immunoprecipitation, we analyzed MBD2 and RNA polymerase II deposition and DNA methylation in HeLa cells on arrays representing 25,500 promoter regions. This first whole-genome mapping revealed the preferential localization of MBD2 near transcription start sites (TSSs), within the region analyzed, 7.5 kb upstream through 2.45 kb downstream of 5' transcription start sites. Probe by probe analysis correlated MBD2 deposition and DNA methylation. Motif analysis did not reveal specific sequence motifs; however, CCG and CGC sequences seem to be overrepresented. Nonrandom association (multiple correspondence analysis, p < 0.0001) between silent genes, DNA methylation and MBD2 binding was observed. The association between MBD2 binding and transcriptional repression weakened as the distance between binding site and TSS increased, suggesting that MBD2 represses transcriptional initiation. This hypothesis may represent a functional explanation for the preferential binding of MBD2 at methyl-CpG in TSS regions.

TRAIL receptors 1 (DR4) and 2 (DR5) signal FADD-dependent apoptosis and activate NF-kappaB.

TRAIL induces apoptosis through two closely related receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5). Here we show that TRAIL-R1 can associate with TRAIL-R2, suggesting that TRAIL may signal through heteroreceptor signaling complexes. Both TRAIL receptors bind the adaptor molecules FADD and TRADD, and both death signals are interrupted by a dominant negative form of FADD and by the FLICE-inhibitory protein FLIP. The recruitment of TRADD may explain the potent activation of NF-kappaB observed by TRAIL receptors. Thus, TRAIL receptors can signal both death and gene transcription, functions reminiscent of those of TNFR1 and TRAMP, two other members of the death receptor family.

Calpain hydrolysis of alpha- and beta2-adaptins decreases clathrin-dependent endocytosis and may promote neurodegeneration.

Clathrin-dependent endocytosis is mediated by a tightly regulated network of molecular interactions that provides essential protein-protein and protein-lipid binding activities. Here we report the hydrolysis of the alpha- and beta2-subunits of the tetrameric adaptor protein complex 2 by calpain. Calcium-dependent alpha- and beta2-adaptin hydrolysis was observed in several rat tissues, including brain and primary neuronal cultures. Neuronal alpha- and beta2-adaptin cleavage was inducible by glutamate stimulation and was accompanied by the decreased endocytosis of transferrin. Heterologous expression of truncated forms of the beta2-adaptin subunit significantly decreased the membrane recruitment of clathrin and inhibited clathrin-mediated receptor endocytosis. Moreover, the presence of truncated beta2-adaptin sensitized neurons to glutamate receptor-mediated excitotoxicity. Proteolysis of alpha- and beta2-adaptins, as well as the accessory clathrin adaptors epsin 1, adaptor protein 180, and the clathrin assembly lymphoid myeloid leukemia protein, was detected in brain tissues after experimentally induced ischemia and in cases of human Alzheimer disease. The present study further clarifies the central role of calpain in regulating clathrin-dependent endocytosis and provides evidence for a novel mechanism through which calpain activation may promote neurodegeneration: the sensitization of cells to glutamate-mediated excitotoxicity via the decreased internalization of surface receptors.

Octacalcium Phosphate (OCP) Crystals Induce Synovial Inflammation and Cartilage

Introduction: The presence of intra-articular basic calcium phosphate (BCP) crystals, including OCP, carbonated-apatite, hydroxyapatite and tricalcium phosphate crystals, is associated with severe osteoarthritis and destructive arthropathies such as Milwaukee shoulder. Although BCP crystals displayed, in vitro, mitogenic, anabolic and catabolic responses, their intra-articular effect was never assessed.Objective: To determine the effects of OCP crystals in joints in vivo.Methods: OCP crystals (200 ug in 20 ml PBS) were injected into the right knee joint (the contra-lateral knee joint injected with 20 ul of PBS serving as a control) of wild-type mice treated or not by the IL1R antagonist Anakinra or mice deficient for the inflammasome proteins ASC and NALP3. 4 days and 17 days after crystal injection, mice were sacrificed and knee joints dissected. Histological scoring for synovial inflammation and characterisation of macrophages, neutrophils and T cells were performed. Technetium (Tc) uptake was measured at 6h, 1 and 4 days after OCP injection. Cartilage degradation was evaluated by Safranin O staining and VDIPEN immunohistochemistry. Intra-articular localisation of injected OCP crystals was evidenced by Von Kossa staining.Results: The intra-articular localisation of injected OCP crystals was evidenced by Von Kossa staining performed on non-decalcified samples embedded in methyl-metacrylate. Injection of OCP crystals into knee joints led at day 4 to an inflammatory response with intense macrophage staining and also some neutrophil recruitment in the synovial membrane. This synovitis was not accompanied by increased Tc uptake into the knee joint, Tc uptake being similar in OCP crystal injected knee or control knee at all time points investigated (6h, 1 day, 4 days). The histological modifications persisted over 17 days, with an additional fibrosis evidenced at this later time-point. The OCP crystal-induced synovitis was totally IL-1a and IL-1 independent as shown by the absence of inhibitory effects of anakinra injected into wild-type mice. Accordingly, OCP crystal-induced synovitis was similar in ASC-/- and NALP3-/- mice as no alterations of inflammation were demonstrated between these mice groups. Concerning cartilage matrix degradation, OCP crystals induced a strong breakdown of proteoglycans 4 and 17 days after injection, as measured by loss of red staining from Safranin O-stained sections of cartilage surfaces. In addition, we also measured advanced cartilage matrix destruction mediated by MMPs, as evidenced by VDIPEN staining of cartilage. OCP-mediated cartilage degradation was similar in all experimental conditions tested (WT+Anakinra, or ASC or NALP3 deficient mice).Conclusion: These data indicate in vivo that the intra-articular presence of OCP crystals is associated with cartilage destruction along with synovial inflammation. This is an interesting and new model of destructive arthropathy related to BCP crystals which will allow to assess new therapies in this disease.

Binge drinking in 19 year old men.

QUESTION UNDER STUDY: To describe alcohol use, binge drinking and drinking consequences in 19 year old men. METHODS: During a one-day army recruitment process mandatory for all Swiss males, a convenience sample of 1,004 men completed the "Health and Lifestyle Questionnaire", assessing demographics, alcohol use, binge drinking, and drinking consequences over the last 12 months. Binge drinking was defined as having 5 or more drinks on a single occasion at least once over the last 12 months. Among the 1,004 subjects, binge drinking could not be defined in 123 (12.3%) due to "don't know" responses, leaving 881 subjects with complete data. RESULTS: Of the 881 subjects, 690 (78.3%) reported binge drinking at least once over the last 12 months, 269 (30.5%) with infrequent binge drinking (< or = 1x/month) and 421 (47.8%) with frequent binge drinking (> or = 2x/month). In addition, 379 (43.0%) of the subjects experienced 3 or more drinking consequences over the last 12 months and the number of these consequences increased as the frequency of binge drinking increased (trend analyses significant for 9 of the 12 consequences evaluated). Among the 687 subjects with moderate average alcohol intake (< 14 drinks per week), 252 (36.7%) reported infrequent binge drinking, of whom 82 (32.5%) experienced 3 or more adverse drinking consequences over the last 12 months, whereas 246 (35.8%) reported frequent binge drinking and 128 (52.0%) of these experienced 3 or more adverse drinking consequences. CONCLUSIONS: Binge drinking in this sample of young men is frequent and is associated with numerous consequences, even among those consuming moderate amounts of alcohol.

Contribution of NFI-C to TGF-β1 signalling and tissue regeneration

Summary : Platelet Derived Growth Factor (PDGF) and Transforming Growth Factor-ß (TGF-ß) are two crucial growth factors in tissue repair and regeneration. They control migration and proliferation of macrophages and fibroblasts, as well as myofibroblast differentiation and synthesis of the new connective tissue. The transcription factor Nuclear Factor I-C (NFI-C) has been implicated in the TGF-ß pathway and regulation of extracellular matrix proteins in vitro. This suggests a possible implication of NFI-C in tissue repair. In this study, our purpose was to identify the NFI-C target genes in TGF-ß1 pathway activation and define the relationship between these two factors in cutaneous wound healing process. High-throughput genomic analysis in wild-type and NFI-C knock-out embryonic fibroblasts indicated that NFI-C acts as a repressor of the expression of genes which transcriptional activity is enhanced by TGF-ß. Interestingly, we found an over representation of genes involved in connective tissue inflammation and repair. In accordance with the genomic analysis, NFI-C-/- mice showed an improvement of skin healing during the inflammatory stage. Analysis of this new phenotype indicated that the expression of PDGFA and PDGF-Ra genes were increased in the wounds of NFI-C-/- mice resulting in early recruitment of macrophages and fibroblasts in the granulation tissue. In correlation with the stimulation effect of TGF-ß on myofibroblast differentiation we found an increased differentiation of these cells in null mice, providing a rationale for rapid wound closure. Thus, in the absence of NFI-C, both TGF-ß and PDGF pathways may be activated, leading to enhanced healing process. Therefore, the inhibition of NFI-C expression could constitute a suitable therapy for healing improvement. In addition, we identified a delay of hair follicle cycle initiation in NFI-C-/- mice. This prompted us to investigate the role of NFI-C in skin appendage. The transition from a quiescent to a proliferative phase requires a perfect timing of signalling modulation, leading to stem cell activation. As a consequence of cycle initiation delay in null mice, the activation of signalling involved in cell proliferation was also retarded. Interestingly, at the crucial moment of cell fate determination, we identified a decrease of CD34 gene in mutant mice. Since CD34 protein is involved in migration of multipotent cells, we suggest that NFI-C may be involved in stem cell mobilisation required for hair follicle renewal. Further investigations of the role of NFI-C in progenitor cell activation will lead to a better understanding of tissue regeneration and raise the possibility of treating alopecia with NFI-C-targeting treatment. In summary, this study demonstrates new regenerative functions of NFI-C in adult mice, which regulates skin repair and hair follicle renewal. Résumé : PDGF et TGF-ß sont des facteurs important du mécanisme de défense immunitaire. Ils influencent la prolifération et migration des macrophages et des fibroblastes, ainsi que la différenciation des myofibroblastes et la formation du nouveau tissu conjonctif. Le facteur de transcription NFI-C a été impliqué dans la voie de signalisation de TGF-ß et dans 1a régulation de l'expression des protéines de la matrice extracellulaire in vitro. Ces études antérieures laissent supposer que NFI-C serait un facteur important du remodelage tissulaire. Cependant le rôle de NFI-C dans un tissu comme la peau n'a pas encore été étudié. Dans ce travail, le but a été de d'identifier la relation qu'il existe entre I~1FI-C et TGF-ßl à un niveau transcriptionnel et dans le processus de cicatrisation cutanée in vivo. Ainsi, une analyse génétique à grande échelle, a permis d'indiquer que NFI-C agit comme un répresseur sur l'expression des gènes dont l'activité transcriptionnelle est activée par TGF-ß. De plus nous avons identifié un groupe de gènes qui controlent le développement et l'inflammation du tissue conjonctif. En relation avec ce résultat, l'absence de NFI-C dans la peau induit une cicatrisation plus rapide pendant la phase inflammatoire. Durant cette période, nous avons montré que les expressions de PDGFA et PDGFRa seraient plus élevées en absence de NFI-C. En conséquence, l'activation de la voie de PDGF induit une infiltration plus importante des macrophages et fibroblastes dans le tissue granuleux des souris mutantes. De plus, en corrélation avec le rôle de TGF-ßl dans la différenciation des myofibroblasts, nous avons observé une différenciation plus importante de ces cellules chez les animaux knock-out, ce qui peut expliquer une contraction plus rapide de la plaie. De plus, nous avons découvert que NFI-C est impliqué dans l'initiation du cycle folliculaire. La caractérisation de ce nouveau phénotype a montré un ralentissement de la transition telogène-anagène des souris NFI-C-/-. Or, un événement clé de cette transition est la modulation de plusieurs signaux moléculaires aboutissant à' l'activation des cellules souches. En corrélation avec le decalage du cycle, l'activation de ces signaux est également décalée dans les souris NFI-C-/-. Ainsi, au commencement de l'anagène, la prolifération des keratinocytes,NFI-C-/- est retardée et corrèle avec une diminution de l'expression de CD34, une protéine responsable de la détermination du migration des cellules multipotentes. Ainsi, NFI-C semble être impliqué dans la mobilisation des cellules souches qui sont nécessaires au renouvellement folliculaire. En résumé, NFI-C est impliqué dans la régulation des signaux moléculaires nécessaires à la réparation tissulaire et son inhibition pourrait constituer un traitement de la cicatrisation. L'analyse de son rôle dans l'activation des cellules souches permettrait de mieux comprendre le renouvellement tissulaire et, à long terme, d'améliorer les techniques de greffe des cellules souches épithéliales ou consituter une cible pour le traitement de l'alopecie.

RNA-based gene duplication sheds new light on mammalian sex chromosome evolution

ABSTRACT : Gene duplication is a fundamental source of raw material for the origin of genetic novelty. It has been assumed for a long time that DNA-based gene duplication was the only source of new genes. Recently however, RNA-based gene duplication (retroposition) was shown in multiple organisms to contribute significantly to their genetic diversity. This mechanism produces intronless gene copies (retrocopies) that are inserted in random genomic position, independent of the position of the parental source genes. In human, mouse and fruit fly, it was demonstrated that the X-linked genes spawned an excess of functional retroposed gene copies (retrogenes). In human and mouse, the X chromosome also recruited an excess of retrogenes. Here we further characterized these interesting biases related to the X chromosome in mammals. Firstly, we have confirmed presence of the aforementioned biases in dog and opossum genome. Then based on the expression profile of retrogenes during various spermatogenetic stages, we have provided solid evidence that meiotic sex chromosome inactivation (MSCI) is responsible for an excess of retrogenes stemming from the X chromosome. Moreover, we showed that the X-linked genes started to export an excess of retrogenes just after the split of eutherian and marsupial mammalian lineages. This suggests that MSCI has originated around this time as well. More fundamentally, as MSCI reflects the spread of recombination barrier between the X and Y chromosomes during their evolution, our observation allowed us to re-estimate the age of mammalian sex chromosomes. Previous estimates suggested that they emerged in the common ancestor of all mammals (before the split of monotreme lineage); whereas, here we showed that they originated around the split of marsupial and eutherian lineages, after the divergence of monotremes. Thus, the therian (marsupial and eutherian) sex chromosomes are younger than previously thought. Thereafter, we have characterized the bias related to the recruitment of genes to the X chromosome. Sexually antagonistic forces are most likely driving this pattern. Using our limited retrogenes expression data, it is difficult to determine the exact nature of these forces but some conclusions have been made. Lastly, we looked at the history of this biased recruitment: it commenced around the split of marsupial and eutherian lineages (akin to the biased export of genes out of the X). In fact, the sexually antagonistic forces are predicted to appear just around that time as well. Thereby, the history of the recruitment of genes to the X, provides an indirect evidence that these forces are responsible for this bias.

Cardiac dysfunction and impaired compensatory response to pressure overload in mice deficient in stem cell antigen-1.

Stem cell antigen-1 (Sca-1) has been used to identify cardiac stem cells in the mouse heart. To investigate the function of Sca-1 in aging and during the cardiac adaptation to stress, we used Sca-1-deficient mice. These mice developed dilated cardiomyopathy [end-diastolic left ventricular diameter at 18 wk of age: wild-type (WT) mice, 4.2 mm ± 0.3; Sca-1-knockout (Sca-1-KO) mice, 4.6 mm ± 0.1; ejection fraction: WT mice, 51.1 ± 2.7%; Sca-1-KO mice, 42.9 ± 2.7%]. Furthermore, the hearts of mice lacking Sca-1 demonstrated exacerbated susceptibility to pressure overload [ejection fraction after transaortic constriction (TAC): WT mice, 43.5 ± 3.2%; Sca-1-KO mice, 30.8% ± 4.0] and increased apoptosis, as shown by the 2.5-fold increase in TUNEL(+) cells in Sca-1-deficient hearts under stress. Sca-1 deficiency affected primarily the nonmyocyte cell fraction. Indeed, the number of Nkx2.5(+) nonmyocyte cells, which represent a population of cardiac precursor cells (CPCs), was 2-fold smaller in Sca-1 deficient neonatal hearts. In vitro, the ability of CPCs to differentiate into cardiomyocytes was not affected by Sca-1 deletion. In contrast, these cells demonstrated unrestricted differentiation into cardiomyocytes. Interestingly, proliferation of cardiac nonmyocyte cells in response to stress, as judged by BrdU incorporation, was higher in mice lacking Sca-1 (percentages of BrdU(+) cells in the heart after TAC: WT mice, 4.4 ± 2.1%; Sca-1-KO mice, 19.3 ± 4.2%). These data demonstrate the crucial role of Sca-1 in the maintenance of cardiac integrity and suggest that Sca-1 restrains spontaneous differentiation in the precursor population. The absence of Sca-1 results in uncontrolled precursor recruitment, exhaustion of the precursor pool, and cardiac dysfunction.

Environment-dependent microevolution in a Mediterranean pine (Pinus pinaster Aiton).

BACKGROUND: A central question for understanding the evolutionary responses of plant species to rapidly changing environments is the assessment of their potential for short-term (in one or a few generations) genetic change. In our study, we consider the case of Pinus pinaster Aiton (maritime pine), a widespread Mediterranean tree, and (i) test, under different experimental conditions (growth chamber and semi-natural), whether higher recruitment in the wild from the most successful mothers is due to better performance of their offspring; and (ii) evaluate genetic change in quantitative traits across generations at two different life stages (mature trees and seedlings) that are known to be under strong selection pressure in forest trees. RESULTS: Genetic control was high for most traits (h2 = 0.137-0.876) under the milder conditions of the growth chamber, but only for ontogenetic change (0.276), total height (0.415) and survival (0.719) under the more stressful semi-natural conditions. Significant phenotypic selection gradients were found in mature trees for traits related to seed quality (germination rate and number of empty seeds). Moreover, female relative reproductive success was significantly correlated with offspring performance for specific leaf area (SLA) in the growth chamber experiment, and stem mass fraction (SMF) in the experiment under semi-natural conditions, two adaptive traits related to abiotic stress-response in pines. Selection gradients based on genetic covariance of seedling traits and responses to selection at this stage involved traits related to biomass allocation (SMF) and growth (as decomposed by a Gompertz model) or delayed ontogenetic change, depending also on the testing environment. CONCLUSIONS: Despite the evidence of microevolutionary change in adaptive traits in maritime pine, directional or disruptive changes are difficult to predict due to variable selection at different life stages and environments. At mature-tree stages, higher female effective reproductive success can be explained by differences in their production of offspring (due to seed quality) and, to a lesser extent, by seemingly better adapted seedlings. Selection gradients and responses to selection for seedlings also differed across experimental conditions. The distinct processes involved at the two life stages (mature trees or seedlings) together with environment-specific responses advice caution when predicting likely evolutionary responses to environmental change in Mediterranean forest trees.

Cytotoxins of the human pathogen Aeromonas hydrophila trigger, via the NLRP3 inflammasome, caspase-1 activation in macrophages.

Aeromonas hydrophila is a Gram-negative pathogen that causes serious infectious disease in humans. A. hydrophila induces apoptosis in infected macrophages, but the host proinflammatory responses triggered by macrophage death are largely unknown. Here, we demonstrate that the infection of mouse macrophages with A. hydrophila triggers the activation of caspase-1 and release of IL-1β. Caspase-1 activation was abrogated in macrophages deficient in Nod-like receptor family, pyrin domain containing 3 (NLRP3) and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), but not NLR family, CARD domain containing 4 (NLRC4). The activation of the NLRP3 inflammasome was mediated by three cytotoxins (aerolysin, hemolysin and multifunctional repeat-in-toxin) produced by A. hydrophila. Our results indicated that the NLRP3 inflammasome senses A. hydrophila infection through the action of bacterial cytotoxins.