Impaired endocytosis in proximal tubule from subchronic exposure to cadmium involves angiotensin II type 1 and cubilin receptors

BACKGROUND: Chronic exposure to low cadmium (Cd) levels produces urinary excretion of low molecular weight proteins, which is considered the critical effect of Cd exposure. However, the mechanisms involved in Cd-induced proteinuria are not entirely clear. Therefore, the present study was designed to evaluate the possible role of megalin and cubilin (important endocytic receptors in proximal tubule cells) and angiotensin II type 1 (AT1) receptor on Cd-induced microalbuminuria. METHODS: Four groups of female Wistar rats were studied. Control (CT) group, vehicle-treated rats; LOS group, rats treated with losartan (an AT1 antagonist) from weeks 5 to 8 (10 mg/kg/day by gavage); Cd group, rats subchronically exposed to Cd (3 mg/kg/day by gavage) during 8 weeks, and Cd + LOS group, rats treated with Cd for 8 weeks and LOS from weeks 5–8. Kidney Cd content, glomerular function (evaluated by creatinine clearance and plasma creatinine), kidney injury and tubular function (evaluated by Kim-1 expression, urinary excretion of N-acetyl-β-D-glucosaminidase (NAG) and glucose, and microalbuminuria), oxidative stress (measured by lipid peroxidation and NAD(P)H oxidase activity), mRNA levels of megalin, expressions of megalin and cubilin (by confocal microscopy) and AT1 receptor (by Western blot), were measured in the different experimental groups. Data were analyzed by one-way ANOVA or Kruskal-Wallis test using GraphPad Prism 5 software (Version 5.00). P < 0.05 was considered statistically significant. RESULTS: Administration of Cd (Cd and Cd + LOS groups) increased renal Cd content. LOS-treatment decreased Cd-induced microalbuminuria without changes in: plasma creatinine, creatinine clearance, urinary NAG and glucose, oxidative stress, mRNA levels of megalin and cubilin, neither protein expression of megalin nor AT1 receptor, in the different experimental groups studied. However, Cd exposure did induce the expression of the tubular injury marker Kim-1 and decreased cubilin protein levels in proximal tubule cells whereas LOS-treatment restored cubilin levels and suppressed Kim-1 expression. CONCLUSION: LOS treatment decreased microalbuminuria induced by Cd apparently through a cubilin receptor-dependent mechanism but independent of megalin

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Peroxisome proliferator-activated receptors: regulation of transcriptional activities and roles in inflammation

International audiencePeroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear receptor superfamily. Three PPARs isoforms have been characterized: PPARα, β/δ and γ. As other nuclear receptors, the PPARs are organized in distinct functional domains: A/B, C or DNA binding domain (DBD), D, E or ligand binding domain (LBD) and F. The A/B domain contains the activation function 1 (AF-1) which is transcriptionally active in absence of ligands. The DBD and the LBD of the PPARs determine the specificity of promoter DNA sequence recognition and ligand recognition, respectively. An activation function 2 (AF-2) is contained in the E domain, which mediates the ligand-dependent activation of the receptor. The transcriptional activity of the PPARs is regulated by post-translational modifications, such as phosphorylation and ubiquitination. Phosphorylation of PPARs is controlled by environmental factors activating different kinase pathways leading to the modulation of their activities. PPARs degradation by the ubiquitin–proteasome system modulates the intensity of the ligand response by controlling the level of PPAR proteins in the cells. PPARs also control the expression of genes implicated in the inflammatory response via negative interference with different inflammatory pathways, such as NFκB, AP-1, C/EBP β, STAT-1 and NFAT. As such, PPARs influence inflammatory cytokine production and cell recruitment to the inflammatory sites. A better understanding of the mechanism of action of PPARs could improve the design of more specific and more efficient novel drugs. Molecules with dissociated effects could be useful for the treatment of lipid disorders or inflammation

Peroxisome Proliferator-activated Receptor α (PPARα) Turnover by the Ubiquitin-Proteasome System Controls the Ligand-induced Expression Level of Its Target Genes

International audiencePeroxisome proliferator activated-receptor α (PPARα) is a ligand-activated transcription factor belonging to the nuclear receptor family. PPARα is implicated in the regulation of lipid and glucose metabolism and in the control of inflammatory response. Recently, it has been demonstrated that a number of nuclear receptors are degraded by the ubiquitin-proteasome pathway. Since PPARα exhibits a circadian expression rhythm and since PPARα is rapidly regulated under certain pathophysiological conditions such as the acute phase inflammatory response, we hypothesized that PPARα protein levels must be under tight control. Here, we studied the mechanisms controlling PPARα protein levels and their consequences on the transcriptional control of PPARα target genes. Using pulse-chase experiments, it is shown that PPARα is a short-lived protein and that addition of its ligands stabilizes this nuclear receptor. By transient cotransfection experiments using expression vectors for PPARα and hemagglutinin-tagged ubiquitin, it is demonstrated that PPARα protein is ubiquitinated and that its ligands decrease the ubiquitination of this nuclear receptor, thus providing a mechanism for the ligand-dependent stabilization observed in pulse-chase experiments. In addition, treatment with MG132, a selective proteasome inhibitor, increases the level of ubiquitinated PPARα and inhibits its degradation in transfected cells. Furthermore, MG132 treatment enhances the level of endogenous PPARα in HepG2 cells. Finally, transient transfection and quantitative reverse transcription-PCR show that inhibition of PPARα degradation increases its transcriptional activation and expression of target genes such as apoA-II and fatty acid transport protein (FATP). Taken together, these data demonstrate that PPARα is degraded by the ubiquitin-proteasome system in a ligand-dependent manner. Regulation of its degradation provides a novel regulatory mechanism of transcriptional activity of this nuclear receptor

Estimation of the center of mass displacement in quiet standing by means of a 3D biomechanical model

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Fast pole figure acquisition using area detectors at the DiffAbs beamline – Synchrotron SOLEIL

Structural anisotropy, for example texture, may govern important physical properties of thin film, such as electrical, magnetic and/or mechanical ones. Texture (orientation information) is typically observed and quantified by the measurement of so-called pole figures. An optimized experimental approach implemented at the DiffAbs beamline (Synchrotron SOLEIL) is presented here. Using an X-ray pixel area detector and synchrotron radiation sources, a complete pole figure (with resolutions adapted for metallic textured thin films, typically of the order of a few degrees) can be measured in time intervals as short as one minute. The necessary corrections enabling complete pole figure retrieval from the experimental data using this optimized approach are provided and discussed. A gain in measuring time by up to two orders of magnitude is found with respect to the use of a point detector (classical approach) under the same experimental conditions. Data measured using these two approaches are shown, compared and discussed

Overview of Traditional and Environmental Factors Related to Bone Health

International audienceBone mass in adulthood depends on growth and mineralization acquired during childhood and adolescence. It is well knownthat these stages of life are crucial for bone development, where genetic, nutritional, hormonal, and lifestyle factors play asignificant role. Bone loss is normally a natural and slow process that begins years later after the peak bone mass is achievedand continues throughout the lifespan. Lifestyle choices in childhood and adolescence such as minimal physical activity,excessive caffeine or carbonated beverages intake, malnutrition, cigarette use, or high alcohol consumption and other factorslike environmental pollutants can also negatively affect bone health and accelerate the bone loss process. The aim of thiswork is an overview of risk factors associated with inadequate bone health in early life

Acquisition rapide de figures polaires à l'aide de détecteurs de zone sur la ligne DiffAbs - Synchrotron SOLEIL

International audienceL'anisotropie structurelle, par exemple la texture, peut régir d'importantes propriétés physiques d'un film mince, telles que les propriétés électriques, magnétiques et/ou mécaniques. La texture (information d'orientation) est typiquement observée et quantifiée par la mesure de ce que l'on appelle les figures polaires. Une approche expérimentale optimisée mise en œuvre sur la ligne DiffAbs (Synchrotron SOLEIL) est présentée ici. À l'aide d'un détecteur de zone de pixels à rayons X et de sources de rayonnement synchrotron, une figure de pôle complète (avec des résolutions adaptées aux films minces texturés métalliques, généralement de l'ordre de quelques degrés) peut être mesurée à des intervalles de temps aussi courts qu'une minute. Les corrections nécessaires permettant la récupération complète de la figure de pôle à partir des données expérimentales en utilisant cette approche optimisée sont fournies et discutées. On constate un gain de temps de mesure jusqu'à deux ordres de grandeur par rapport à l'utilisation d'un détecteur ponctuel (approche classique) dans les mêmes conditions expérimentales. Les données mesurées à l'aide de ces deux approches sont présentées, comparées et discutées

Identification of features regulating OST1 kinase activity and OST1 function in guard cells.

The phytohormone abscisic acid (ABA) mediates drought responses in plants and, in particular, triggers stomatal closure. Snf1-related kinase 2 (SnRK2) proteins from several plant species have been implicated in ABA-signaling pathways. In Arabidopsis (Arabidopsis thaliana) guard cells, OPEN STOMATA 1 (OST1)/SRK2E/SnRK2-6 is a critical positive regulator of ABA signal transduction. A better understanding of the mechanisms responsible for SnRK2 protein kinase activation is thus a major goal toward understanding ABA signal transduction. Here, we report successful purification of OST1 produced in Escherichia coli: The protein is active and autophosphorylates. Using mass spectrometry, we identified five target residues of autophosphorylation in recombinant OST1. Sequence analysis delineates two conserved boxes located in the carboxy-terminal moiety of OST1 after the catalytic domain: the SnRK2-specific box (glutamine-303 to proline-318) and the ABA-specific box (leucine-333 to methionine-362). Site-directed mutagenesis and serial deletions reveal that serine (Ser)-175 in the activation loop and the SnRK2-specific box are critical for the activity of recombinant OST1 kinase. Targeted expression of variants of OST1 kinase in guard cells uncovered additional features that are critical for OST1 function in ABA signaling, although not required for OST1 kinase activity: Ser-7, Ser-18, and Ser-29 and the ABA-specific box. Ser-7, Ser-18, Ser-29, and Ser-43 represent putative targets for regulatory phosphorylation and the ABA-specific box may be a target for the binding of signaling partners in guard cells