Modulation Of Homeostasis Research Articles

Cryo-electron microscopy structure of CLHM1 ion channel from Caenorhabditis elegans.

Calcium homeostasis modulators (CALHMs/CLHMs) comprise a family of pore‐forming protein complexes assembling into voltage‐gated, Ca2+‐sensitive, nonselective channels. These complexes contain an ion‐conduction pore sufficiently wide to permit the passing of ATP molecules serving as neurotransmitters. While their function and structure information is accumulating, the precise mechanisms of these channel complexes remain to be full understood. Here, we present the structure of the Caenorhabditis elegans CLHM1 channel in its open state solved through single‐particle cryo‐electron microscopy at 3.7‐Å resolution. The transmembrane region of the channel structure of the dominant class shows an assembly of 10‐fold rotational symmetry in one layer, and its cytoplasmic region is involved in additional twofold symmetrical packing in a tail‐to‐tail manner. Furthermore, we identified a series of amino acid residues critical for the regulation of CeCLHM1 channel using functional assays, electrophysiological analyses as well as structural‐based analysis. Our structure and function analyses provide new insights into the mechanisms of CALHM channels.

Altering Plant Architecture to Improve Performance and Resistance.

High-stress resistance and yield are major goals in crop cultivation, which can be addressed by modifying plant architecture. Significant progress has been made in recent years to understand how plant architecture is controlled under various growth conditions, recognizing the central role phytohormones play in response to environmental stresses. miRNAs, transcription factors, and other associated proteins regulate plant architecture, mainly via the modulation of hormone homeostasis and signaling. To generate crop plants of ideal architecture, we propose simultaneous editing of multiple genes involved in the regulatory networks associated with plant architecture as a feasible strategy. This strategy can help to address the need to increase grain yield and/or stress resistance under the pressures of the ever-increasing world population and climate change.

Serum untargeted metabolomic changes in response to diet intervention in dogs with preclinical myxomatous mitral valve disease.

Myocardial energy deprivation plays a causal role in the development of heart failure. A cardiac protection blend (CPB) of nutrients including medium chain triglycerides, fish oil and other key nutrients was developed to slow the progression of canine myxomatous mitral valve disease (MMVD). A six-month dietary intervention demonstrated efficacy of CPB in slowing MMVD progression. Untargeted metabolomic analysis of serum from these dogs identified 102 differential metabolites (adjusted P < 0.05). The ratios of omega-6 to omega-3 fatty acid (FA) changed from 2.41 and 1.46 in control and CPB groups at baseline to 4.30 and 0.46 at 6 months respectively. A 2.7-fold increase of α-aminobutyrate, a myocardial modulator of glutathione homeostasis, was found in CPB dogs compared to 1.3-fold increase in control dogs. Arginine and citrulline, precursors of nitric oxide biosynthesis, were both increased 2-fold; caprate, a medium chain FA, was increased 3-fold; and deoxycarnitine, precursor of carnitine biosynthesis, was increased 2.5-fold in CPB dogs. Margarate and methylpalmitate decreased in response to CPB, a potential benefit in MMVD dogs as positive correlations were found between changes in both these FAs and left atrial diameter (r = 0.69, r = 0.87 respectively, adjusted P < 0.05). Sphingomyelins with very long chain saturated FAs associated with decreased risk of heart failure in humans were increased in MMVD dogs fed the CPB diet. Our data supports the hypothesis that CPB improves FA utilization and energetics, reduces oxidative stress and inflammation in MMVD dogs. More studies are needed to understand the roles of specific metabolites in MMVD.

Targeting the Hippo pathway in cancer, fibrosis, wound healing and regenerative medicine.

The Hippo pathway is an evolutionarily conserved signalling pathway with key roles in organ development, epithelial homeostasis, tissue regeneration, wound healing and immune modulation. Many of these roles are mediated by the transcriptional effectors YAP and TAZ, which direct gene expression via control of the TEAD family of transcription factors. Dysregulated Hippo pathway and YAP/TAZ-TEAD activity is associated with various diseases, most notably cancer, making this pathway an attractive target for therapeutic intervention. This Review highlights the key findings from studies of Hippo pathway signalling across biological processes and diseases, and discusses new strategies and therapeutic implications of targeting this pathway.

Interplay Between Lipid Metabolism and Autophagy.

Autophagy is a self-eating process of using lysosomes to degrade macromolecular substances (e.g., proteins and organelles) that are damaged, degenerated, or aging. Lipid metabolism is the synthesis and degradation of lipids (e.g., triglycerides, steroids, and phospholipids) to generate energy or produce the structural components of cell membranes. There is a complex interplay between lipid metabolism (e.g., digestion, absorption, catabolism, biosynthesis, and peroxidation) and autophagy machinery, leading to the modulation of cell homeostasis, including cell survival and death. In particular, lipid metabolism is involved in the formation of autophagic membrane structures (e.g., phagophores and autophagosomes) during stress. Moreover, autophagy, especially selective autophagy (e.g., lipophagy, ferritinophagy, clockophagy, and mitophagy), promotes lipid catabolism or lipid peroxidation-induced ferroptosis through the degradation of various substances within the cell. A better understanding of the mechanisms of autophagy and possible links to lipid metabolism will undoubtedly promote potential treatments for a variety of diseases.

Intense Sweeteners, Taste Receptors and the Gut Microbiome: A Metabolic Health Perspective.

Intense sweeteners (IS) are often marketed as a healthier alternative to sugars, with the potential to aid in combating the worldwide rise of diabetes and obesity. However, their use has been counterintuitively associated with impaired glucose homeostasis, weight gain and altered gut microbiota. The nature of these associations, and the mechanisms responsible, are yet to be fully elucidated. Differences in their interaction with taste receptors may be a potential explanatory factor. Like sugars, IS stimulate sweet taste receptors, but due to their diverse structures, some are also able to stimulate bitter taste receptors. These receptors are expressed in the oral cavity and extra-orally, including throughout the gastrointestinal tract. They are involved in the modulation of appetite, glucose homeostasis and gut motility. Therefore, taste genotypes resulting in functional receptor changes and altered receptor expression levels may be associated with metabolic conditions. IS and taste receptors may both interact with the gastrointestinal microbiome, and their interactions may potentially explain the relationship between IS use, obesity and metabolic outcomes. While these elements are often studied in isolation, the potential interactions remain unexplored. Here, the current evidence of the relationship between IS use, obesity and metabolic outcomes is presented, and the potential roles for interactions with taste receptors and the gastrointestinal microbiota in modulating these relationships are explored.

1498-P: A Feedback Loop between miRNA Processing Complex and miR-3975 in Western Diet–Induced Brown Adipose Tissue Dysfunction

Brown adipose tissue (BAT) is considered as promising therapeutic targets for obesity and metabolic disorder through modulation of energy homeostasis. microRNAs (miRNAs) are established as essential modulators of biological processes in many tissues, including the differentiation and function of BAT. Here we demonstrated that high-fat/high fructose associated dysfunction of BAT coincides with impaired miRNA-processing pathway in a feedback loop with miR-3975 activation. Eight-week-old male C57BL/6 mice were fed a low-fat diet (10% fat and 17% sucrose; LFD) and high fat-high fructose (45% fat, 17% sucrose, and 17% fructose; HFHFD) for 4, 12, and 20 weeks (n=6-9 per group). We evaluated expression levels of apoptosis markers, thermogenesis markers, miRNA biogenesis regulators, and miRNAs in BAT. Mice fed an HFHFD showed a gradually significance increased body weight and brown adipose tissue weight when compared to the mice fed with LFD. BAT of HFHFD fed mice has a pale appearance versus feeding period matched LFD fed mice. The protein expression of thermogenesis markers, UCP1 (P &amp;lt;0.05), and PGC1α (P &amp;lt;0.05) were shown to decrease after 12 weeks of HFHFD diet feeding. The apoptosis marker, the Bax/Bcl-2 ratio, was upregulated at 12 weeks (P &amp;lt; 0.01). Mice fed HFHFD for 12 and 20 weeks showed a significant decrease in Dicer (P &amp;lt; 0.01 for 12 and 20 weeks) and TRBP2 (P &amp;lt; 0.01 for 12 weeks and P &amp;lt; 0.0001 for 20 weeks). miR-3975, which is predicted miRNA to regulate both Dicer and TRBP2 by IPA was activated at 12 weeks (P &amp;lt; 0.01), while inactivated at 20 weeks (P &amp;lt; 0.001). Our results suggest that miR-3975 acts as a component of a negative feedback loop that blocks miRNA biogenesis machinery through the inhibition of Dicer and TRBP2 expression. Therefore, long-term HFHFD may disturb miRNA processing and contribute to brown adipose tissue dysfunction and apoptosis by modulation of miRNA expression. We are currently investigating the novel feedback loop in brown adipocyte primary cells. Disclosure M. Park: None. S. Meruvu: None. J. Zhang: None. M. Choudhury: None.

The immune function of a novel crustin with an atypical WAP domain in regulating intestinal microbiota homeostasis in Litopenaeus vannamei

Crustins are a family of antimicrobial peptides (AMP) with multiple functions, including antimicrobial activity, capability of protease inhibition, phagocytosis promotion, and wound healing in crustaceans. Till present, several members of crustins have been identified and their activities were studied. However, there are still less investigations on how they play functions in vivo. Here, we identified a novel crustin with an atypical WAP domain, LvCrustin Ⅰ-1, which is mainly distributed in tissues, including intestine, gill, epidermis and stomach of the shrimp Litopenaeus vannamei. The expression level of LvCrustin Ⅰ-1 was significantly up-regulated at 3 h, 6 h, 12 h, and 24 h after Vibrio parahaemolyticus infection. Knockdown of LvCrustin Ⅰ-1 with dsRNA resulted in a significant increase of the bacteria number in hepatopancreas of shrimp upon V. parahaemolyticus infection, showing that LvCrustin Ⅰ-1 participated in pathogen infection process. Recombinant LvCrustin Ⅰ-1 protein showed microorganism-binding activity rather than antibacterial activity against tested bacteria. Furthermore, significant difference existed between the intestinal microbiota in shrimp before and after LvCrustin Ⅰ-1 knockdown based on the result of alpha and NMDS analyses. Knockdown of LvCrustin Ⅰ-1 increased the proportion of Demequina, Nautella, Propionibacterium, Anaerospora and decreased the proportion of Bacteroidia and Vibrio. These data suggest that LvCrustin Ⅰ-1 might perform its immunological function through modulation of the intestinal microbiota homeostasis rather than direct inhibition of bacterial growth in shrimp.

Proteomic analysis revealed ROS-mediated growth inhibition of Aspergillus terreus by shikonin

Aspergillus terreus is an emerging fungal pathogen in immunocompromised patients. Due to the intrinsic resistance of AmB against A. terreus and acquiring resistance to azoles, an alternative antifungal strategy needs investigation. Thus, we explored the activity of phytochemicals such as shikonin, gallic acid, coumaric acid and quercetin against A. terreus. Among these, shikonin showed significant inhibition at MIC50; 2 μg/ml. SEM analyses revealed delayed swelling and distorted cell wall organization in shikonin treated A. terreus conidia. Further, we performed differential proteome profiling using nLC-ESI-MS/MS, qRT-PCR and catalase assay with and without shikonin treated A. terreus. Protein data generated using Proteome Discoverer showed 882 differentially expressed proteins (680 up- and 202 down-regulated). GO analysis showed proteins from signaling pathways, oxidative stress, energy metabolism, and cytoskeleton organization. qRT-PCR of selected genes from ROS detoxification (catalase-peroxidase, superoxide dismutase), respiration (succinate-dehydrogenase, NADH-ubiquinone oxidoreductase), signaling (protein kinase C, Mitogen-activated protein kinase, cAMP-dependent protein kinase, ras-1), and 1, 3-β-glucanosyltransferase, rho-1, β-hexosaminidase showed correlation with expressed proteins. We also observed elevated reactive oxygen species using fluorescence ROS assay correlating with low catalase-peroxidase activity in shikonin treated A. terreus. Modulation of ROS homeostasis and the metabolic shift could be instrumental in shikonin- mediated growth inhibition of A. terreus. SignificanceAspergillosis caused by A. terreus requires more attention due to the development of drug resistance. In this report, we employed nLC-ESI-MS/MS to identify the differential proteome in A. terreus in response to shikonin. The identified proteins involved in pathways influenced by shikonin could be helpful to understand the molecular mechanism on how shikonin/ phytochemicals or other antifungal agents inhibit fungal growth and may enable the discovery of novel or synergistic drug targets.

Exogenous jasmonic acid enhances oxidative protection of Lemna valdiviana subjected to arsenic

Oxidative damage is one of the most harmful effects arising from arsenic (As) toxicity in plants. Herein, the role of exogenous jasmonic acid (JA) in the modulation of As-induced oxidative stress in Lemna valdiviana was investigated. Plants were grown for 24 h in Clark’s nutritive solution containing As (4.0 mg L−1) or As + JA (50, 100, 250 and 500 µM). Chlorophyll a and b content decreased under As stress, either in isolation or associated with JA. The decreased chlorophyll a/b ratio in As-exposed plants was recovered by JA treatment at 100 µM. The carotenoid content was higher in plants exposed to As compared to controls and lower when it was associated with JA. Arsenic triggered the accumulation of O2•− and H2O2, in addition to severely increasing lipid peroxidation. Application of JA in As-grown plants resulted in lower O2•− content and lipid peroxidation than in those grown under As alone, as a result of enhanced SOD activity. On the other hand, H2O2 accumulation was increased by JA in As-stressed plants, associated with higher CAT, POX and GPX activity. The As content and bioaccumulation factor (BF) were improved by application of JA in the nutritive solution at 250 and 500 µM. Our findings indicate that JA modulates the pigment balance, thereby fine-tuning energy dissipation as well as alleviating As-induced oxidative damage in L. valdiviana through modulation of ROS homeostasis and improvement of the antioxidant enzymatic system, allowing increased accumulation of As without showing major damage.

Zinc and the modulation of Nrf2 in human neuroblastoma cells

Zinc plays a key role in the modulation of neuronal redox homeostasis. A decreased zinc availability is associated with neuronal NADPH oxidase and nitric oxide synthase activation, deregulation of redox signaling, and impaired glutathione synthesis. The present work tested the hypothesis that zinc is necessary in the neuronal defense response against dopamine (DA)-induced oxidative stress, in particular through heme oxygenase-1 (HO-1) upregulation. DA showed higher cytotoxicity when zinc availability was low. Human IMR-32 neuroblastoma cells responded to high DA concentrations (100 μM) by upregulating HO-1. This upregulation involved Nrf2 translocation to the nucleus, degradation of the Bach-1 repressor, and Nrf2-DNA binding, but it was independent of ERK1/2 activation. DA-mediated induction of HO-1 expression was dependent on the concentration of zinc in the medium. IMR-32 cells incubated in zinc deficient medium showed an impaired response to DA, with lower HO-1 mRNA and protein levels than control DA-challenged cells. This altered HO-1 upregulation was reversed by zinc supplementation. In the presence of DA, Nrf2 nuclear translocation and Bach-1 degradation were lower in zinc deficient cells. The mechanisms involved include: i) impaired Nrf2-tubulin interactions and ii) alterations in the proteasome-mediated degradation of Bach-1 secondary to a decreased ubiquitylation. Results suggest that zinc is crucial in the neuronal response to DA-induced oxidative stress in part through its role in the modulation of the Nrf2-and Bach-1-driven upregulation of HO-1 expression.

Hepatic Lipidomics Analysis Reveals the Antiobesity and Cholesterol-Lowering Effects of Tangeretin in High-Fat Diet-Fed Rats.

Tangeretin (TAN) exhibited antilipogenic, antidiabetic, and lipid-lowering effects. However, the lipid biomarkers and the underlying mechanisms for antiobesity and cholesterol-lowering effects of TAN have not been sufficiently investigated. Herein, we integrated biochemical analysis with lipidomics to elucidate its efficacy and mechanisms in high-fat diet-fed rats. TAN at supplementation levels of 0.04 and 0.08% not only significantly decreased body weight gain, serum total cholesterol, and low-density lipoprotein cholesterol levels but also ameliorated hepatic steatosis. These beneficial effects were associated with the declining levels of fatty acids, diacylglycerols (DGs), triacylglycerols, ceramides, and cholesteryl esters by hepatic lipidomics analysis, which were attributed to downregulating lipogenesis-related genes and upregulating lipid oxidation- and bile acid biosynthesis-related genes. Additionally, 21 lipids were identified as potential lipid biomarkers, such as DGs and phosphatidylethanolamines. These findings indicated that the modulation of lipid homeostasis might be the key pathways for the mechanisms of TAN in the antiobesity and cholesterol-lowering effects.

Stress Management: Death Receptor Signalling and Cross-Talks with the Unfolded Protein Response in Cancer.

Throughout tumour progression, tumour cells are exposed to various intense cellular stress conditions owing to intrinsic and extrinsic cues, to which some cells are remarkably able to adapt. Death Receptor (DR) signalling and the Unfolded Protein Response (UPR) are two stress responses that both regulate a plethora of outcomes, ranging from proliferation, differentiation, migration, cytokine production to the induction of cell death. Both signallings are major modulators of physiological tissue homeostasis and their dysregulation is involved in tumorigenesis and the metastastic process. The molecular determinants of the control between the different cellular outcomes induced by DR signalling and the UPR in tumour cells and their stroma and their consequences on tumorigenesis are starting to be unravelled. Herein, I summarize the main steps of DR signalling in relation to its cellular and pathophysiological roles in cancer. I then highlight how the UPR and DR signalling control common cellular outcomes and also cross-talk, providing potential opportunities to further understand the development of malignancies.

Integrated miRNAome and Transcriptome Analysis Reveals Argonaute 2-Mediated Defense Responses Against the Devastating Phytopathogen Sclerotinia sclerotiorum.

Argonaute 2 (AGO2)-mediated role in plant defense against fungal pathogens remains largely unknown. In this study, integrated miRNAome and transcriptome analysis employing ago2 mutant was performed to reveal AGO2-associated miRNAs and defense responses against the devastating necrotrophic phytopathogen Sclerotinia sclerotiorum. Both miRNAome and transcriptomes of S. sclerotiorum-inoculated ago2-1 mutant (ago2-Ss) and wild-type (WT-Ss) as well as mock-inoculated ago2-1 mutant (ago2) and wild-type (WT) Arabidopsis plants, were analyzed by sRNA and mRNA deep sequencing. Differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) of the comparisons WT-Ss/WT, ago2/WT, ago2-Ss/WT-Ss, and ago2-Ss/ago2 were identified. Furthermore, integration analysis for the DEMs and DEGs identified over 40 potential AGO2-dependent Sclerotinia sclerotiorum-responsive (ATSR) DEM-DEG pairs involving modulation of immune recognition, calcium flux, redox homeostasis, hormone accumulation and signaling, cell wall modification and metal ion homeostasis. Data-mining result indicated that most of the DEMs were bound with AGO2. Moreover, Arabidopsis mutant analysis demonstrated that three ROS and redox homeostatasis related DEGs of identified DEM-DEG pairs, GSTU2, GSTU5, and RBOHF contributed to the AGO2-mediated defense against S. sclerotiorum. This work provides genome-wide prediction of miRNA–target gene pairs that are potentially associated with the AGO2-dependent resistance against S. sclerotiorum.

The pivotal role of ubiquitin-activating enzyme E1 (UBA1) in neuronal health and neurodegeneration.

Ubiquitin-activating enzyme E1, UBA1, functions at the apex of the enzymatic ubiquitylation cascade, catalysing ubiquitin activation. UBA1 is thus of fundamental importance to the modulation of ubiquitin homeostasis and to all downstream ubiquitylation-dependent cellular processes, including proteolysis through the ubiquitin-proteasome system and selective autophagy. The proteasome-dependent and -independent functions of UBA1 contribute significantly to a range of processes crucial to neuronal health. The significance of UBA1 activity to neuronal health is clear in light of accumulating evidence implicating impaired UBA1 activity in a range of neurodegenerative conditions, including Parkinson's disease, Alzheimer's disease, Huntington's disease and spinal muscular atrophy. Moreover, ubiquitylation-independent functions of UBA1 of importance to neuronal functioning have been proposed. Here, we summarise findings supporting the significant role of UBA1 in regulating neuronal functioning, and discuss the detrimental consequences of UBA1 impairment that contribute to neuronal dysfunction and degeneration.

Lack of Syndecan-1 produces significant alterations in whole-body composition, metabolism and glucose homeostasis in mice.

BACKGROUNDObesity is a disease state with serious adverse metabolic complications, including glucose intolerance and type 2 diabetes that currently has no cure. Identifying and understanding roles of various modulators of body composition and glucose homeostasis is required for developing effective cures. Syndecan-1 (Sdc1) is a member of the heparan sulfate proteoglycan family that has mainly been investigated for its role in regulating proliferation and survival of epithelia and tumor cells, but little is known about its roles in regulating obesity and glucose homeostasis.AIMTo examine the role of Sdc1 in regulating body fat and glucose metabolism.METHODSWe used female wild type and Sdc1 knockout (Sdc1 KO) mice on BALB/c background and multiple methods. Metabolic measurements (rates of oxygen consumption, carbon dioxide production, respiratory exchange ratio and energy expenditure) were performed using an open-flow indirect calorimeter with additional features to measure food intake and physical activity. Glucose intolerance and insulin resistance were measured by established tolerance test methods.RESULTSAlthough our primary goal was to investigate the effects of Sdc1 deficiency on body fat and glucose homeostasis, we uncovered that Sdc1 regulates multiple metabolic parameters. Sdc1KO mice have reduced body weight due to significant decreases in fat and lean masses under both chow and high fat diet conditions. The reduced body weight was not due to changes in food intakes, but Sdc1 KO mice exhibited altered feeding behavior as they ate more during the dark phase and less during the light phase than wild type mice. In addition, Sdc1 KO mice suffered from high rate of energy expenditure, glucose intolerance and insulin resistance.CONCLUSIONThese results reveal critical multisystem and opposing roles for Sdc1 in regulating normal energy balance and glucose homeostasis. The results will have important implications for targeting Sdc1 to modulate metabolic parameters. Finally, we offer a novel hypothesis that could reconcile the opposing roles associated with Sdc1 deficiency.

Exogenous NO Therapy for the Treatment and Prevention of Atherosclerosis.

Amyl nitrite was introduced in 1867 as the first molecule of a new class of agents for the treatment of angina pectoris. In the following 150 years, the nitric oxide pathway has been the subject of a number of pharmacological approaches, particularly since when this elusive mediator was identified as one of the most important modulators of vascular homeostasis beyond vasomotion, including platelet function, inflammation, and atherogenesis. While having potent antianginal and antiischemic properties, however, nitric oxide donors are also not devoid of side effects, including the induction of tolerance, and, as shown in the last decade, of oxidative stress and endothelial dysfunction. In turn, endothelial dysfunction is itself felt to be involved in all stages of atherogenesis, from the development of fatty streaks to plaque rupture and thrombosis. In the present review, we summarize the agents that act on the nitric oxide pathway, with a particular focus on their potentially beneficial antiatherosclerotic and unwanted pro-atherosclerotic effects.

Frequent non‐nutritive sweetener intake alters the expression of endocannabinoid receptors in liver and pancreas in mice

The endocannabinoid system plays a major role in the regulation of systemic energy balance, including the modulation of hepatic and pancreatic homeostasis, which is relevant for energy metabolism. Nutritional alterations such as consumption of hypercaloric diets associated with development of obesity promote alterations in hepatic and pancreatic functions and also affect endocannabinoid‐dependent signaling. Non‐nutritive sweeteners have been extensively used to decrease calorie intake from diet and inhibit development of chronic non‐transmissible diseases like obesity and type II diabetes; nonetheless, there is accumulating evidence that these compounds may have additional metabolic effects of clinical significance. The objective of this study is to determine alterations in the expression of CB1 and CB2 endocannabinoid receptors in liver and pancreas of adult mice supplemented with the commercially available non‐nutritive sweeteners sucralose and steviol glycosides, daily, for 6 weeks. After supplementation, hepatic and pancreatic expression of CB1 and CB2 receptors is evaluated by western blot and immunofluorescence. Preliminary results show increased expression of CB1 receptors in male animals supplemented with sucralose, whereas a similar effect is observed in female mice supplemented with sucrose, compared to non‐supplemented controls. In contrast, CB2 expression is increased in male animals supplemented with steviol glycosides and no significant changes have been observed for CB2 expression in females. So far, our results suggest that frequent consumption of non‐nutritive sweeteners alter the expression of endocannabinoid receptors in liver and pancreas in vivo, which may affect the activity of metabolic routes involved in the regulation of systemic energy balance.

The Echinodermata PPAR: Functional characterization and exploitation by the model lipid homeostasis regulator tributyltin

The wide ecological relevance of lipid homeostasis modulators in the environment has been increasingly acknowledged. Tributyltin (TBT), for instance, was shown to cause lipid modulation, not only in mammals, but also in fish, molluscs, arthropods and rotifers. In vertebrates, TBT is known to interact with a nuclear receptor heterodimer module, formed by the retinoid X receptor (RXR) and the peroxisome proliferator-activated receptor (PPAR). These modulate the expression of genes involved in lipid homeostasis. In the present work, we isolated for the first time the complete coding region of the Echinodermata (Paracentrotus lividus) gene orthologues of PPAR and RXR and evaluated the ability of a model lipid homeostasis modulator, TBT, to interfere with the lipid metabolism in this species. Our results demonstrate that TBT alters the gonadal fatty acid composition and gene expression patterns: yielding sex-specific responses in fatty acid levels, including the decrease of eicosapentaenoic acid (C20:5 n-3, EPA) in males, and increase of arachidonic acid (20:4n-6, ARA) in females, and upregulation of long-chain acyl-CoA synthetase (acsl), ppar and rxr. Furthermore, an in vitro test using COS-1 cells as host and chimeric receptors with the ligand binding domain (LBD) of P. lividus PPAR and RXR shows that organotins (TBT and TPT (Triphenyltin)) suppressed activity of the heterodimer PPAR/RXR in a concentration-dependent manner. Together, these results suggest that TBT acts as a lipid homeostasis modulator at environmentally relevant concentrations in Echinodermata and highlight a possible conserved mode of action via the PPAR/RXR heterodimer.

Novel Control Mechanism of the Neurovascular Coupling in an Alzheimer’s Disease Model

Alzheimer’s disease (AD) is a type of dementia related to age characterized by a progressive and irreversible deterioration of memory and general cognitive abilities. There is a consensus that the production of β‐amyloid protein (Aβ) aggregates correlates with neuronal alterations, triggering the characteristic neurodegeneration process of this disease. Furthermore, disease progression has been closely associated with cerebral vascular alterations, such as reduction in cerebral blood flow observed in patients and animal models of AD.It has been documented that Aβ not only has harmful effects at neuronal level but has also been associated with the alteration of astrocytes normal activity. One of the events modulated by astrocytes at cerebral level is its key role in the neurovascular coupling (NVC), mechanism that ensures nutrients and oxygen supply in proportion to the increase in neuronal activity. The NVC functions controlled by the astrocytes is mediated by vasodilator signals, a process that is dependent of intracellular calcium increase in astrocytes, which is propagated and coordinated by the release of paracrine and autocrine adenosine triphosphate (ATP).There is no consensus about the way of ATP release from astrocytes during NVC, but the description of a new channel, Calcium Homeostasis Modulator 1 (CALHM1) which permit the ATP release in some type of neurons, could be an important element in astrocyte signaling during this mechanism. In previous results we observed that ATP is released through CALHM1 in an astrocyte primary culture model stimulated with glutamate (a stimulus validated in NVC studies) and also was dependent of the CALHM1 activation by S‐nitrosylation through nitric oxide (NO) produced by the astrocytes.Considering that it has been reported that NVC is altered in AD, which contribute to the pathophysiological mechanisms of this disease, our main aim was to evaluate the ATP release in astrocytes primary cultures from a validated murine model of AD: B6C3‐Tg(APPswe,PSEN1dE9)85Dbo/Mmjax.Our results show that ATP release, and CALHM1 relative levels and expression are significatively reduced in astrocytes primary cultures from AD animals in comparing with cultures from wild type animals. These results suggest that calcium signaling could be diminished in the astrocytes in AD and could explicate the relation between the alteration of NVC in AD.Support or Funding InformationUniversidad del Desarrollo Intern Proyect 23.400.163