Rat PPARs: quantitative analysis in adult rat tissues and regulation in fasting and refeeding.

PPARs are members of the nuclear hormone receptor superfamily and are primarily involved in lipid metabolism. The expression patterns of all 3 PPAR isotypes in 22 adult rat organs were analyzed by a quantitative ribonuclease protection assay. The data obtained allowed comparison of the expression of each isotype to the others and provided new insight into the less studied PPAR beta (NR1C2) expression and function. This isotype shows a ubiquitous expression pattern and is the most abundant of the three PPARs in all analyzed tissues except adipose tissue. Its expression is especially high in the digestive tract, in addition to kidney, heart, diaphragm, and esophagus. After an overnight fast, PPAR beta mRNA levels are dramatically down-regulated in liver and kidney by up to 80% and are rapidly restored to control levels upon refeeding. This tight nutritional regulation is independent of the circulating glucocorticoid levels and the presence of PPAR alpha, whose activity is markedly up-regulated in the liver and small intestine during fasting. Finally, PPAR gamma 2 mRNA levels are decreased by 50% during fasting in both white and brown adipose tissue. In conclusion, fasting can strongly influence PPAR expression, but in only a few selected tissues.

IL-10 controls cystatin C synthesis and blood concentration in response to inflammation through regulation of IFN regulatory factor 8 expression.

Cystatin C (CstC) is a cysteine protease inhibitor of major clinical importance. Low concentration of serum CstC is linked to atherosclerosis. CstC can prevent formation of amyloid β associated with Alzheimer's disease and can itself form toxic aggregates. CstC regulates NO secretion by macrophages and is a TGF-β antagonist. Finally, the serum concentration of CstC is an indicator of kidney function. Yet, little is known about the regulation of CstC expression in vivo. In this study, we demonstrate that the transcription factor IFN regulatory factor 8 (IRF-8) is critical for CstC expression in primary dendritic cells. Only those cells with IRF-8 bound to the CstC gene promoter expressed high levels of the inhibitor. Secretion of IL-10 in response to inflammatory stimuli downregulated IRF-8 expression and consequently CstC synthesis in vivo. Furthermore, the serum concentration of CstC decreased in an IL-10-dependent manner in mice treated with the TLR9 agonist CpG. CstC synthesis is therefore more tightly regulated than hitherto recognized. The mechanisms involved in this regulation might be targeted to alter CstC production, with potential therapeutic value. Our results also indicate that caution should be exerted when using the concentration of serum CstC as an indicator of kidney function in conditions in which inflammation may alter CstC production.

Molecular and social regulation of worker division of labour in fire ants.

Reproductive and worker division of labour (DOL) is a hallmark of social insect societies. Despite a long-standing interest in worker DOL, the molecular mechanisms regulating this process have only been investigated in detail in honey bees, and little is known about the regulatory mechanisms operating in other social insects. In the fire ant Solenopsis invicta, one of the most studied ant species, workers are permanently sterile and the tasks performed are modulated by the worker's internal state (age and size) and the outside environment (social environment), which potentially includes the effect of the queen presence through chemical communication via pheromones. However, the molecular mechanisms underpinning these processes are unknown. Using a whole-genome microarray platform, we characterized the molecular basis for worker DOL and we explored how a drastic change in the social environment (i.e. the sudden loss of the queen) affects global gene expression patterns of worker ants. We identified numerous genes differentially expressed between foraging and nonforaging workers in queenright colonies. With a few exceptions, these genes appear to be distinct from those involved in DOL in bees and wasps. Interestingly, after the queen was removed, foraging workers were no longer distinct from nonforaging workers at the transcriptomic level. Furthermore, few expression differences were detected between queenright and queenless workers when we did not consider the task performed. Thus, the social condition of the colony (queenless vs. queenright) appears to impact the molecular pathways underlying worker task performance, providing strong evidence for social regulation of DOL in S. invicta.

Protracted treatment with MDMA induces heteromeric nicotinic receptor up-regulation in rat brain: an autoradiography study.

Previous studies indicate that 3,4-methylenedioxy-methamphetamine (MDMA, ecstasy) can induce heteromeric nicotinic acetylcholine receptor (nAChR, mainly of α4β2 subtype) up-regulation. In this study we treated Sprague-Dawley rats twice-daily for 10 days with either saline or MDMA (7 mg/kg) and killed them on day 11 to perform [125I]epibatidine binding autoradiograms on serial coronal slices. Results showed significant increases in nAChR density in the substantia nigra, ventral tegmental area, nucleus accumbens, olfactory tubercle, anterior caudate-putamen, somatosensory cortex, motor cortex, auditory cortex, retrosplenial cortex, laterodorsal thalamus nuclei, amygdala, postsubiculum and pontine nuclei. These increases ranged from 3% (retrosplenial cortex) to 30 and 33% (amygdala and substantia nigra). No increased α4 subunit immunoreactivity was found in up-regulated areas compared with saline-treated rats, suggesting a post-translational mechanism as occurs with nicotine. The percentage of up-regulation correlated positively with the density of serotonin transporters, according to the serotonergic profile of MDMA. The heteromeric nAChR increase in concrete areas could account, at least in part, for the reinforcing, sensitizing and psychiatric disorders observed after long-term treatment with MDMA.

Protracted treatment with MDMA induces heteromeric nicotinic receptor up-regulation in rat brain: an autoradiography study.

Previous studies indicate that 3,4-methylenedioxy-methamphetamine (MDMA, ecstasy) can induce heteromeric nicotinic acetylcholine receptor (nAChR, mainly of α4β2 subtype) up-regulation. In this study we treated Sprague-Dawley rats twice-daily for 10 days with either saline or MDMA (7 mg/kg) and killed them on day 11 to perform [125I]epibatidine binding autoradiograms on serial coronal slices. Results showed significant increases in nAChR density in the substantia nigra, ventral tegmental area, nucleus accumbens, olfactory tubercle, anterior caudate-putamen, somatosensory cortex, motor cortex, auditory cortex, retrosplenial cortex, laterodorsal thalamus nuclei, amygdala, postsubiculum and pontine nuclei. These increases ranged from 3% (retrosplenial cortex) to 30 and 33% (amygdala and substantia nigra). No increased α4 subunit immunoreactivity was found in up-regulated areas compared with saline-treated rats, suggesting a post-translational mechanism as occurs with nicotine. The percentage of up-regulation correlated positively with the density of serotonin transporters, according to the serotonergic profile of MDMA. The heteromeric nAChR increase in concrete areas could account, at least in part, for the reinforcing, sensitizing and psychiatric disorders observed after long-term treatment with MDMA.

Protracted treatment with MDMA induces heteromeric nicotinic receptor up-regulation in rat brain: an autoradiography study.

Previous studies indicate that 3,4-methylenedioxy-methamphetamine (MDMA, ecstasy) can induce heteromeric nicotinic acetylcholine receptor (nAChR, mainly of α4β2 subtype) up-regulation. In this study we treated Sprague-Dawley rats twice-daily for 10 days with either saline or MDMA (7 mg/kg) and killed them on day 11 to perform [125I]epibatidine binding autoradiograms on serial coronal slices. Results showed significant increases in nAChR density in the substantia nigra, ventral tegmental area, nucleus accumbens, olfactory tubercle, anterior caudate-putamen, somatosensory cortex, motor cortex, auditory cortex, retrosplenial cortex, laterodorsal thalamus nuclei, amygdala, postsubiculum and pontine nuclei. These increases ranged from 3% (retrosplenial cortex) to 30 and 33% (amygdala and substantia nigra). No increased α4 subunit immunoreactivity was found in up-regulated areas compared with saline-treated rats, suggesting a post-translational mechanism as occurs with nicotine. The percentage of up-regulation correlated positively with the density of serotonin transporters, according to the serotonergic profile of MDMA. The heteromeric nAChR increase in concrete areas could account, at least in part, for the reinforcing, sensitizing and psychiatric disorders observed after long-term treatment with MDMA.

Monocarboxylate transporters: new players in body weight regulation.

Over the last two decades, several genes have been identified that appear to play a role in the regulation of energy homeostasis and body weight. For a small subset of them, a reduction or an absence of expression confers a resistance to the development of obesity. Recently, a knockin mouse for a member of the monocarboxylate transporter (MCT) family, MCT1, was demonstrated to exhibit a typical phenotype of resistance to diet-induced obesity and a protection from its associated metabolic perturbations. Such findings point out at MCTs as putatively new therapeutic targets in the context of obesity. Here, we will review what is known about MCTs and their possible metabolic roles in different organs and tissues. Based on the description of the phenotype of the MCT1 knockin mouse, we will also provide some insights about their putative roles in weight gain regulation.

Atmung, Aufmerksamkeit und Ablenkung als Funktion emotionaler Stimuli: Ablenkung, Atmung, Aufmerksamkeit, Emotion, Erregung, Valenz

Mittels Bilder, Musikstücken und Geräuschen induzierten wir Emotionen und gingen einerseits der Frage nach, wie emotionale Bewertung und physiologische Vorgänge, insbesondere die Atmung, miteinander verknüpft sind. Andererseits untersuchten wir mit Geruchsexpositionen während einer Mehrfachverrichtung, welche Rolle die Geruchs-Valenz bei der Arbeitsablenkung spielt. Unsere Versuche zeigten, dass die Atmungsantworten auf induzierte Emotionen in einem gewissen Rahmen dem Dimensionsmodell von Valenz und Arousal folgten, insbesondere bildeten sie die induzierte Erregung konsistent ab. Auch das Aufmerksamkeits-Engagement hing von der emotionalen Bedeutung des Stimulus ab, da nur die negativ attribuierten Gerüche eine Leistungsminderung in der Mehrfachverrichtung auslösten. [Autoren]

Tissue-specific opposing functions of the inflammasome adaptor ASC in the regulation of epithelial skin carcinogenesis.

A chronic inflammatory microenvironment favors tumor progression through molecular mechanisms that are still incompletely defined. In inflammation-induced skin cancers, IL-1 receptor- or caspase-1-deficient mice, or mice specifically deficient for the inflammasome adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) in myeloid cells, had reduced tumor incidence, pointing to a role for IL-1 signaling and inflammasome activation in tumor development. However, mice fully deficient for ASC were not protected, and mice specifically deficient for ASC in keratinocytes developed more tumors than controls, suggesting that, in contrast to its proinflammatory role in myeloid cells, ASC acts as a tumor-suppressor in keratinocytes. Accordingly, ASC protein expression was lost in human cutaneous squamous cell carcinoma, but not in psoriatic skin lesions. Stimulation of primary mouse keratinocytes or the human keratinocyte cell line HaCaT with UVB induced an ASC-dependent phosphorylation of p53 and expression of p53 target genes. In HaCaT cells, ASC interacted with p53 at the endogenous level upon UVB irradiation. Thus, ASC in different tissues may influence tumor growth in opposite directions: it has a proinflammatory role in infiltrating cells that favors tumor development, but it also limits keratinocyte proliferation in response to noxious stimuli, possibly through p53 activation, which helps suppressing tumors.

Sustainability, certification, and regulation of biochar

Biochar has a relatively long half-life in soil and can fundamentally alter soil properties, processes, and ecosystem services. The prospect of global-scale biochar application to soils highlights the importance of a sophisticated and rigorous certification procedure. The objective of this work was to discuss the concept of integrating biochar properties with environmental and socioeconomic factors, in a sustainable biochar certification procedure that optimizes complementarity and compatibility between these factors over relevant time periods. Biochar effects and behavior should also be modelled at temporal scales similar to its expected functional lifetime in soils. Finally, when existing soil data are insufficient, soil sampling and analysis procedures need to be described as part of a biochar certification procedure.

Extracellular microvesicles from astrocytes contain functional glutamate transporters: regulation by protein kinase C and cell activation.

Glutamate transport through astrocytic excitatory amino-acid transporters (EAAT)-1 and EAAT-2 is paramount for neural homeostasis. EAAT-1 has been reported in secreted extracellular microvesicles (eMV, such as exosomes) and because the protein kinase C (PKC) family controls the sub-cellular distribution of EAATs, we have explored whether PKCs drive EAATs into eMV. Using rat primary astrocytes, confocal immunofluorescence and ultracentrifugation on sucrose gradient we here report that PKC activation by phorbol myristate acetate (PMA) reorganizes EAAT-1 distribution and reduces functional [(3)H]-aspartate reuptake. Western-blots show that EAAT-1 is present in eMV from astrocyte conditioned medium, together with NaK ATPase and glutamine synthetase all being further increased after PMA treatment. However, nanoparticle tracking analysis reveals that PKC activation did not change particle concentration. Functional analysis indicates that eMV have the capacity to reuptake [(3)H]-aspartate. In vivo, we demonstrate that spinal astrocytic reaction induced by peripheral nerve lesion (spared nerve injury, SNI) is associated with a phosphorylation of PKC δ together with a shift of EAAT distribution ipsilaterally. Ex vivo, spinal explants from SNI rats release eMV with an increased content of NaK ATPase, EAAT-1 and EAAT-2. These data indicate PKC and cell activation as important regulators of EAAT-1 incorporation in eMV, and raise the possibility that microvesicular EAAT-1 may exert extracellular functions. Beyond a putative role in neuropathic pain, this phenomenon may be important for understanding neural homeostasis and a wide range of neurological diseases associated with astrocytic reaction as well as non-neurological diseases linked to eMV release.

Regulation of mass and function of pancreatic β-cells: identification of anti-apoptotic peptides and role of GLP-1

Résumé La masse de cellules β sécrétrices d'insuline est un tissu dynamique qui s'adapte aux variations de la demande métabolique pour assurer une normoglycémie. Cette adaptation se fait par un changement de sécrétion d'insuline et de la masse totale des cellules β. Une perte complète ou partielle des cellules β conduit respectivement à un diabète de type 1 et de type 2. Les mécanismes qui régulent la masse de cellules β et maintiennent leur phénotype differencié sont encore peu connus. Leur identification est nécessaire pour comprendre le développement du diabète et développer des stratégies de traitement. La greffe d'îlots est une approche thérapeutique prometteuse pour le diabète de type 1, mais est limitée par une perte précoce des cellules β due à une apoptose induite par des cytokines. Afin d'améliorer la survie des cellules β lors de la greffe d'îlots, le premier but était de trouver des peptides pouvant bloquer l'apoptose induite par FasL et TNF-α. Pour ce faire, deux librairies de phages ont été criblées pour sélectionner des peptides se liant au Fas DD ou au TNFRl DD. Nous avons identifié six peptides différents. Cependant, aucun d'entre eux n'était capable de protéger les cellules de l'apoptose induite par FasL ou TNF-α. Deuxièmement, le GLP-1 est une hormone qui stimule la sécrétion d'insuline, et est impliquée dans la prolifération des cellules β, la différentiation, et inhibe l'apoptose. Nous avons fait l'hypothèse que le GLP-1 joue un rôle crucial dans le contrôle de la masse et de la fonction des cellules β. Afin de l'évaluer, une analyse par puce à ADN a été réalisée en comparant des cellules βTC-Tet traitées avec du GLP-1 à des cellules non-traitées. 376 gènes régulés ont été identifiés, dont RGS2, CREM, ICERI et DUSP14, augmentés significativement par le GLP-1. Nous avons confirmé que le GLP-1 augmente l'expression de ces gènes, aussi bien au niveau des transcripts que des protéines. De plus, nous avons montré que le GLP-1 induit leur expression par activation de la voie cAMP/PKA, et nécessite l'entrée de calcium extracellulaire. D'après leur fonction biologique, nous avons ensuite supposé que ces gènes pourraient agir comme régulateurs négatifs de la signalisation du GLP-l, et donc freiner son effet proliférateur. Pour vérifier notre hypothèse, des siRNAs contre ces gènes ont été développés, et leurs effets sur la prolifération des cellules β seront évalués ultérieurement. Abstract The pancreatic β-cell mass is a dynamic tissue which adapts to variations in metabolic demand in order to ensure normoglycemia. This adaptation occurs through a change in both insulin secretion and the total mass of ,β-cells. An absolute or relative loss of β-cells leads to type 1 and type 2 diabetes, respectively. The mechanisms that regulate the pancreatic β-cell mass and maintain the fully differentiated phenotype of the insulin-secreting β-cells are only poorly defined. Their identification is required to understand the progression of diabetes, but also to design strategies for the treatment of diabetes. Islet transplantation is a promising therapeutic approach for type 1 diabetes, but it is still limited by an early graft loss due to cytokine-induced apoptosis. In order to improve β-cell survival during islet transplantation, our first goal was to find novel blockers of FasL- and TNF-α-mediated cell death in the form of peptides. To that end, we screened two phage display libraries to select Fas DD- or TNFR1 DD-binding peptides. We identified six different small peptides. However, none of these peptides was able to prevent cells from FasL- or TNF-α-mediated apoptosis. Secondly, GLP-1 is a hormone that has been shown to stimulate insulin secretion and to be involved in β-cell proliferation, differentiation and inhibition of apoptosis. We hypothesized that GLP-1 plays a crucial role to control mass and function of β-cells. To evaluate this hypothesis, we performed a cDNA microarray analysis with GLP-1-treated βTC-Tet cells compared to untreated cells. We found 376 regulated genes, among these, RGS2, CREM, ICERI and DUSP14, which were significantly upregulated by GLP-1. We confirmed that both their mRNA and protein levels were strongly and rapidly increased after GLP-1 treatment. Moreover, we found that GLP-1 activates their expression mainly through the activation of the cAMP/PKA signaling pathway, and requires extracellular calcium entry. According to their biological function, we then hypothesized that these genes might act as negative regulators of the GLP-1 signaling. In particular, they might brake the effects of GLP-1 on β-cell proliferation. To verify this hypothesis, siRNAs against these genes were developed. The effect of these siRNAs on GLP-1-induced β-cell proliferation will be evaluated later.

Compensatory up-regulation of angiotensin II subtype 1 receptors in alpha ENaC knockout heterozygous mice.

BACKGROUND: In mice, a partial loss of function of the epithelial sodium channel (ENaC), which regulates sodium excretion in the distal nephron, causes pseudohypoaldosteronism, a salt-wasting syndrome. The purpose of the present experiments was to examine how alpha ENaC knockout heterozygous (+/-) mice, which have only one allele of the gene encoding for the alpha subunit of ENaC, control their blood pressure (BP) and sodium balance. METHODS: BP, urinary electrolyte excretion, plasma renin activity, and urinary adosterone were measured in wild-type (+/+) and heterozygous (+/-) mice on a low, regular, or high sodium diet. In addition, the BP response to angiotensin II (Ang II) and to Ang II receptor blockade, and the number and affinity of Ang II subtype 1 (AT1) receptors in renal tissue were analyzed in both mouse strains on the three diets. RESULTS: In comparison with wild-type mice (+/+), alpha ENaC heterozygous mutant mice (+/-) showed an intact capacity to maintain BP and sodium balance when studied on different sodium diets. However, no change in plasma renin activity was found in response to changes in sodium intake in alpha ENaC +/- mice. On a normal salt diet, heterozygous mice had an increased vascular responsiveness to exogenous Ang II (P < 0.01). Moreover, on a normal and low sodium intake, these mice exhibited an increase in the number of AT1 receptors in renal tissues; their BP lowered markedly during the Ang II receptor blockade (P < 0.01) and there was a clear tendency for an increase in urinary aldosterone excretion. CONCLUSIONS: alpha ENaC heterozygous mice have developed an unusual mechanism of compensation leading to an activation of the renin-angiotensin system, that is, the up-regulation of AT1 receptors. This up-regulation may be due to an increase in aldosterone production.