Cholecystokinin B Receptor from Human Jurkat Lymphoblastic T Cells Is Involved in Activator Protein-1-Responsive Gene Activation

SUMMARY The aim of this study was to analyze the role of cholecystokinin (CCK B ) receptor in human lymphoblastic Jurkat T cells. We investigated the trophic effect resulting from activation of such a receptor by using the reporter gene strategy. For this purpose, we transiently transfected Jurkat T cells with the reporter plasmid p[(TRE)3-tk-Luc] and found that CCK-8 was able to dose-dependently induce luciferase expression related to activator protein-1 (AP-1) activation with a maximal response identical to that obtained with compounds known to activate AP-1 complex (quantitatively, the same level of induction was obtained with 1 nM 12-O-tetradecanoylphorbol-13-acetate, 100 M diacylglycerol, or 4 nM epidermal growth factor). The involvement of the CCK B receptor in such a stimulation was demonstrated by the inhibiting effect of the selective CCK B receptor antagonist 158. This effect was confirmed in COS-7 cells transfected with the cDNA of CCK B receptor cloned from Jurkat T cells. To better understand the AP-1-dependent luciferase expression in Jurkat T cells, we tested two specific inhibitors of serine/threonine phosphatases-1 and -2A: okadaic acid and calyculin A. These compounds strongly increased the phorbol-12-myristate-13-acetate response, whereas we have not observed a contribution of phosphatase inhibitors on a CCK-8-induced luciferase activity. To confirm that CCK B receptors are involved in AP-1 response, we investigated the CCK-8 effect on interleukin-2 expression, a natural endogenous gene regulated by several factors, including AP-1. In Jurkat T cells activated by phorbol-12-myristate-13-acetate and phytohemagglutinin, CCK-8 induced IL-2 expression. This induction was abolished by PD-135,158. Our results indicate that CCK-8 exerts a trophic effect in Jurkat T cells through stimulation of CCK B receptors by modulation of expression of AP-1-regulated genes. Several studies have shown that various gastrointestinal peptides may be involved in the control of proliferation of various tissues and neoplastic cells (1). For example, CCK was shown to increase growth of tumors in nude mice bearing transplanted pancreatic cancer tissues (2). CCK is also known to increase the number of animals developing nitrosamine-induced pancreatic cancers (3), and CCK was shown to increase the rate of growth of cultured pancreatic cancer cells (2). Similar observations were described for bombesin/ gastrin-releasing peptide in human glioblastoma in vitro and in vivo in small-cell lung carcinoma, prostatic, mammary, and pancreatic cancer cell lines (1). In addition, gastrointestinal peptides can function as autocrine growth factors in neoplastic tissues as shown for bombesin/gastrin-releasing peptide in small-cell lung carcinoma cells, for gastrin an

Effets insulino-sécrétoires et protecteurs de la quercétine au niveau de la cellule beta pancréatique (implication du calcium intracellulaire et de ERK1/2)

Dans le diabète de type 2 établi, l'hyperglycémie chronique, un taux élevé d'acides gras libres et l'inflammation induisent un stress oxydatif (SO) au niveau de la cellule beta. Le SO, qui apparaît dès le stade de pré-diabète, peut induire un dysfonctionnement précoce de cette cellule. Ainsi, la protection de la cellule b par des molécules anti-oxydantes pourrait ralentir la progression du pré-diabète au diabète.La quercétine, un flavonoïde, a présenté des propriétés antidiabétiques dans plusieurs études in vivo. Cependant, très peu de données traitent de son mécanisme d'action directement au niveau de la cellule beta. Dans ce contexte, nous avons étudié les effets de la quercétine au niveau de la cellule beta dans des conditions physiologiques et des conditions de SO.Nos résultats montrent qu'en présence de concentrations stimulantes de sécrétagogue, la quercétine potentialise la sécrétion d'insuline par un mécanisme impliquant l'augmentation de calcium intracellulaire et la potentialisation de ERK1/2 via l'activation des voies de la PKA et de la CaMK II. De plus, la quercétine protège la cellule beta du SO en sur-activant ERK1/2. Le resvératrol et la NAC, deux antioxydants de référence, sont inactifs dans ces conditions expérimentales.En absence de concentrations stimulantes de sécrétagogue, la quercétine induit une sécrétion d'insuline modérée en augmentant le calcium intracellulaire suite à une activation directe des CaV de type L. Dans ces conditions, l'activation de ERK1/2 induite par la quercétine, qui est indépendante de l'activation des voies de la PKA et de la CaMK II, ne serait pas impliquée dans le mécanisme sécrétoire. Nos résultats indiquent que le mécanisme d'action de la quercétine au niveau de la cellule b ne repose pas uniquement sur ses capacités anti-oxydantes mais fait intervenir des cibles pharmacologiques et la régulation de voies de signalisation intracellulaires.In type 2 diabetes, chronic hyperglycaemia, elevated free fatty acids and inflammation induce oxidative stress (OS) in pancreatic b cell. SO, which appears at the stage of pre-diabetes, may induce early dysfunction of this cell. Thus, the b cell protection by antioxidant molecules could slow the progression of pre-diabetes to diabetes.Quercetin, a flavonoid, has shown antidiabetic properties in several in vivo studies. However, very few data address its mechanism of action directly at the b cell. In this context, we studied the effects of quercetin at the b cell under physiological conditions and conditions of OS.Our results show that in the presence of stimulating concentrations of secretagogue, quercetin potentiates insulin secretion by a mechanism involving increased intracellular calcium and potentiation of ERK1 / 2 via activation of the PKA and the CaMK II pathways. In addition, quercetin protects beta cell from OS via a suractivation of ERK1/2. Resveratrol and NAC, two antioxidants of reference are inactive under these experimental conditions.In the absence of stimulating concentration of secretagogue, quercetin induced moderate insulin secretion by increasing the intracellular calcium via a direct activation of L-type CaV Under these conditions, the activation of ERK1/2 induced by quercetin, which is independent of the activation pathways of PKA and CaMK II to, would not be involved in the secretory mechanism.Our results indicate that the mechanism of action of quercetin at the b cell not only based on its antioxidant capacity but involves pharmacological targets and the regulation of intracellular signaling pathways.MONTPELLIER-BU Pharmacie (341722105) / SudocSudocFranceF

Un référentiel pour articuler les compétences stratégiques et individuelles

National audienceThe question of individual and strategic competencies articulation (competencies management) waits to receive both theoretical and operational responses. A major challenge lies in building a common framework relevant for all competencies levels analysis. Even if HRM has a large number of frameworks, they are ineffective for articulation: they were not designed for this purpose but for individual competencies assessment. The framework built here will be able to serve a dual purpose of competencies management and assessment. The comparative case study conducted here is specifically designed to provide original answers for this twofold purpose.La question de l'articulation des compétences individuelles et stratégiques (pilotage des compétences) attend de recevoir des réponses à la fois théoriques et opérationnelles. Un des enjeux majeurs consiste dans la construction d'un référentiel commun pour tous les niveaux de la compétence. En effet, même si la GRH bénéficie de très nombreux référentiels, ils sont inopérants pour l'articulation : ils n'ont pas été conçus pour cette finalité mais pour l'évaluation des compétences individuelles. Ainsi, le référentiel proposé devra être capable de servir une double finalité de pilotage et d'évaluation des compétences. L'étude de cas comparative réalisée ici vise précisément à proposer des éléments de réponse originaux à cette finalité

MAP Kinase cross talks in oxidative stress-induced impairment of insulin secretion. Involvement in the protective activity of quercetin

International audienceInsulin secretion preservation is a major issue for the prevention or treatment of type 2 diabetes. We previously showed on β-cells that quercetin (Q), but not resveratrol (R) or N-acetyl cysteine (NAC), amplified glucose-induced insulin secretion in a calcium- and ERK1/2-dependent manner. Quercetin, but not resveratrol or NAC, also protected β-cell function and hyperamplified ERK1/2 phosphorylation in oxidative stress conditions. As quercetin may interfere with other stress-activated protein kinases (JNK and p38 MAPK), we further explored MAPK cross talks and their relationships with the mechanism of the protective effect of quercetin against oxidative stress. In INS-1 insulin-secreting β-cells, using pharmacological inhibitors of MAPK pathways, we found that under oxidative stress (50 μm H2O2) and glucose-stimulating insulin secretion conditions: (i) p38 MAPK phosphorylation was increased and regulated by ERK1/2 (positively) and JNK (negatively), although p38 MAPK activation did not seem to play any significant role in oxidative stress-induced insulin secretion impairment; (ii) the JNK pathway appeared to inhibit both ERK1/2 activation and insulin secretion, although JNK phosphorylation was not significantly changed in our experimental conditions; (iii) the functionality of β-cell in the presence of oxidative stress was closely linked to the level of ERK1/2 activation, (iv) quercetin, resveratrol, or NAC inhibited H2O2 -induced p38 MAPK phosphorylation. The preservation of β-cell function against oxidative stress appears dependent on the balance between ERK1/2 and JNK activation. The protecting effect of quercetin appears due to ERK1/2 hyperactivation, possibly induced by L-type calcium channel opening as we recently showed

COMPOSITIONS COMPRISING UROLITHINS AND USES THEREOF FOR THE STIMULATION OF INSULIN SECRETION

The present invention relates to a composition comprising urolithin A, urolithin B, urolithin C, urolithin D, or a combination thereof, for the stimulation of insulin secretion, and to the use of a compound chosen among urolithin A, urolithin B, urolithin C, urolithin D, or a combination thereof, intended for the stimulation of insulin secretion. The present invention also relates to a composition comprising an effective amount of urolithin B, urolithin C, urolithin D, or a combination thereof, for the treatment or the prevention of diabetes mellitus, and in particular for the treatment or the prevention of type 2 diabetes, and to the use of a compound chosen among urolithin B, urolithin C, urolithin D, and a combination thereof, intended for the treatment or the prevention of diabetes mellitus, and in particular of type 2 diabetes

L’acide chicorique est une molécule antioxydante stimulant la voie AMP Kinase, l’expression de PGC1 α et l’activité mitochondriale dans un modèle de cellules musculaires striées

Poster présenté à la réunion scientifique de la SFD, de la SFD Paramédical et de l'AJD, 26-29/03/2013Introduction : Les antioxydants d’origine alimentaire pourraient prévenir la résistance à l’insuline ainsi que le développement du stress oxydant associé aux maladies métaboliques. Parmi ceux-ci, les polyphénols tels que l’acide caféique et ses dérivés (acide chlorogénique et acide chicorique) posséderaient des propriétés antidiabétiques. Nous avons étudié, sur la lignée de myoblastes L6, l’influence de l’acide chicorique (AC) sur le stress oxydant, l’activité mitochondriale, la voie de l’AMPK (protéine kinase activée par l’AMP) et celle de l’insuline.Matériels et méthodes: L’expression des protéines et des ARNm a été déterminée par Western Blot et qPCR. Les espèces réactives de l’oxygène (ROS) ont été quantifiées avec la sonde 2’,7-dichlorofluoresceine. La captation cellulaire de glucose a été mesurée par l’incorporation de 2-deoxy-D-glucose[3H].Résultats : Dans les myotubes L6, l’AC est un piégeur de ROS en condition basale et en condition de stress oxydant. L’AC augmente l’activité des systèmes de défenses enzymatiques anti-oxydantes glutathion peroxydase et superoxyde dismutase (SOD). Il protège la mitochondrie contre les dommages oxydatifs en augmentant l’expression de la MnSOD. L’AC augmente l’activité du complexe II ainsi que l’expression de PGC-1α impliqué dans la régulation de l’expression des enzymes anti-oxydantes et la biogénèse mitochondriales. L’AC stimule la voie AMPK/ACC et inhibe la voie Akt/mTOR en présence d’insuline, sans modification de la captation de glucose.Conclusion : L’AC possède des propriétés anti-oxydantes, à la fois par sa capacité à neutraliser les ROS et à augmenter les systèmes enzymatiques de défense anti-oxydante. L’AC stimule également la biogénèse mitochondriale et protège les mitochondries contre les dommages oxydatifs, tout en améliorant leur capacité à oxyder les acides gras en stimulant l’AMPK et en augmentant l’activité du complexe II. Ces résultats suggèrent que le potentiel de l’acide chicorique à prévenir ou traiter les pathologies associées au syndrome métabolique mérite d’être étudié de façon plus approfondie

Protection of pancreatic β-cell function by dietary polyphenols

Diabetes mellitus is a complex metabolic disorder and is considered a fast-growing global health problem. Type 2 diabetes (T2D) represents the majority of total diabetes prevalence and b-cell dysfunction has been described as a crucial point for this disease development and progression. To date, all of the common anti-hyperglycaemic drugs used for diabetes management cause undesirable side effects or problems with long-term efficacy or safety and the development of alternative approaches for the prevention as well as for the treatment of T2D might be a valuable solution to meet this rising demand. In this regards, numerous epidemiological studies indicate that exposure to certain polyphenol compounds is associated with the prevention of chronic diseases, including diabetes. Here, we review growing evidence suggesting that polyphenols can modulate the activity of various molecular targets, which are known to control b-cell function, involved in the development and the progression of this diabetes. The protective effects of polyphenols on b-cell function is reported with a particular focus on the mechanism of action behind polyphenol putative bioactivity. Animal and in vitro studies selected in this review, reporting about both flavonoid and non-flavonoid compounds, highlight the direct action of polyphenols on pancreatic b-cells, stimulating insulin secretion through the activation of specific cellular targets and protecting these cells from damages mediated by oxidative stress and inflammation, both typically elevated in diabetes. Some of the reviewed studies describe polyphenol effects comparable to those exerted by many drugs commonly used in diabetes treatment, and, in some occasions, synergistic polyphenol-drug interactions. Finally, future studies need to be addressed to the effects of specific polyphenol human and microbial metabolites, which are still poorly studied, in order to better define the preventive and therapeutic approach to contrast b-cell failure and diabetes progression

Short-term intravenous insulin infusion is associated with reduced expression of NADPH oxidase p47 phox subunit in monocytes from type 2 diabetes patients

International audienceHyperglycemia is a well-known inducing factor of oxidative stress through activation of NADPH oxidase. In addition to its plasma glucose lowering effect, insulin may also have antioxidant activity and was shown to downregulate NADPH oxidase expression in vitro. In this study, we show that a short-term (3-day) intravenous insulin infusion in patients with type 2 diabetes induces normalization of both glycemia and mRNA expression of circulating monocyte p47(phox) subunit