Régulation des systèmes d'adhérence cellulaire par le CRF2 (un effecteur du stress dans le tube digestif)

Le stress est impliqué dans le développement et l'exacerbation de diverses pathologies notamment au niveau intestinal. Les effets du stress dépendent de l'expression de neuromédiateurs spécifiques (CRF) et de leurs récepteurs. Notre étude porte sur la régulation et la fonction du CRF2 au niveau des entérocytes et des cellules tumorales coliques humaines. In vivo, nous avons montré que le stress et l'inflammation conduisent à l'augmentation de l'expression du CRF2 dans les colonocytes chez le rat. Dans les tumeurs, l'expression du CRF2 augmente avec le grade tumoral. In vitro, dans les cellules HT-29, l'activation du CRF2 induit une altération des jonctions adhérentes et des adhérences focales par la voie Src/ERK/FAK. Ces mécanismes sont responsables de la régulation de la perméabilité épithéliale et de l'augmentation de la migration des cellules tumorales. Ces travaux contribuent à la compréhension des mécanismes impliquant le stress dans le développement des pathologies intestinales.Stress is involved in the initiation and the exacerbation of several diseases especially in the intestine. Stress effects depends on the expression of specific neuromediators (CRF) and there receptors. Our study is about regulation and function of the CRF2, a stress receptor expressed in human enterocytes and colorectal cancer cells. In vivo, we showed that stress and inflammation are responsible for the increased expression of the CRF2 in colon epithelial cells of rats. In tumors, the CRF2 expression is increased with the tumor. In vitro, in HT-29 cells, the CRF2 activation leads to the alteration of adherens junctions and focal adhesions by a Src/ERK/FAK pathway. These mechanisms are responsible for the regulation of epithelial cell permeability and the increased migration of tumor cells. This work contributes to the understanding of the pathways involved in the regulation of intestinal diseases by stress.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Exposure of monocytes to heat shock does not increase class II expression but modulates antigen-dependent T cell responses

Expression of heat shock (HS) proteins (HSP) increases after exposure to elevated temperatures or other types of injury, such as oxldative injury. Because of their function as ‘molecular chaperones', HSP are suggested to participate in antigen processing and presentation. We have previously reported that HS modulates antigen presentation in a human EBV-transformed B cell line. Here we investigated the effects of HS on MHC class II expression and on antigen processing and presentation by human monocytes. Monocytes were isolated from peripheral blood of normal human volunteers, purified by adherence, then exposed to temperatures ranging from 37 to 45°C for 20 min, allowed to recover for 2 h at 37°C and used for immunofluorescence or as antigen presenting cells in autologous and heterologous lymphocyte proliferation assays. No increase in class II expression was detected as assessed by flow cytometry. Monocytes (3 × 104) and lymphocytes (1 × 105) were co-cultured for 5 days in the presence of several antigens [diphtheria toxold, tetanus toxold or purified peptlde derivative (PPD)] and labeled with 1 μCI [3H]thymldlne for 16 h. Pre-exposure to HS (44°C) significantly (P < 0.001) increased T cell responses to diphtheria toxold, whereas the effect on the responses to other antigens (tetanus toxold or PPD) were not significant. HS did not increase heterologous T cell responses nor T cell proliferation induced by the non-processed superantigens such as staphylococcal enterotoxln B. The effect of HS was inhibited by actlnomycln B and thus appeared dependent upon HSP synthesis. HSP-mediated increases in antigen processing may potentiate the ongoing immune response at inflammatory site

A modularity based spectral method for simultaneous community and anti-community detection

In a graph or complex network, communities and anti-communities are node sets whose modularity attains extremely large values, positive and negative, respectively. We consider the simultaneous detection of communities and anti-communities, by looking at spectral methods based on various matrix-based definitions of the modularity of a vertex set. Invariant subspaces associated to extreme eigenvalues of these matrices provide indications on the presence of both kinds of modular structure in the network. The localization of the relevant invariant subspaces can be estimated by looking at particular matrix angles based on Frobenius inner products

Mise en place des jonctions adhérentes lors de la différenciation entérocytaire et rôles de p120ctn dans l'homéostasie intestinale

En utilisant la lignée cellulaire d'adénocarcinome colique humain HT-29, nous étudions la mise en place des jonctions adhérentes accompagnant la différenciation entérocytaire et nous soulignons l'importance de différents facteurs dans les étapes successives de maturation de ces jonctions. Ainsi, nous montrons que la laminine 5 est capable d'induire une augmentation d'expression de la E-cadhérine et permet d'initier la mise en place des jonctions adhérentes par un mécanisme dépendant de l'adhérence cellule-matrice extracellulaire: en activant les intégrines a[alpha ] 3b[Bêta ]1 et a[alpha ] 6b[Bêta ]4, la laminine 5 induit une augmentation transitoire de l'activité de la PI3 Kinase qui active à son tour la GTPase monomérique Rac1 et son variant Rac 1 b. Nous montrons que la maturation des jonctions adhérentes est ensuite favorisée par l'émergence de radeaux lipidiques au sein desquels la E-cadhérine et la p 120ctn interagissent de façon préférentielle. Le recrutement des protéines des jonctions adhérentes dans ces microdomaines est dépendant de l'activité de Rac1 et conduit à l'apparition de marqueurs de différenciation entérocytaire. Dans une seconde partie, nous étudions le rôle spécifique de la p120ctn dans la régulation de l'homéostasie des cellules intestinales. Nous montrons que l'augmentation du pool cytoplasmique de p120ctn induit une baisse de prolifération des cellules HT-29 suite à l'interaction de p120ctn avec le complexe cycline E /cdk2. Cette association se traduit par une augmentation de la stabilité de la cycline E et conduit à des défauts de duplication des centrosomes. Des effets similaires sont observés dans les cellules cancéreuses et pourraient être à l'origine du développement tumoral.During intestinal differentiation, epithelial cells modifY their shape and genes activities in response to environmental signais. ln particular, intestinal ce Ils modulate their cell-matrix and ce Il-ce Il adhesion through protein complexes associated with integrins and cadherins respectively.Using the human adenocarcinoma cell line HT-29, we study adherens junction's formation along enterocytic differentiation and we highlight key factors implicated in the successive steps that allow the maturation of these junctions. We show that laminine 5 induces an increase in E-cadherin expression and allows the initiation of adherent junction's assembly through cell -matrix adhesion: laminine 5 - dependent activation of a[alpha ] 3b[Bêta ]1 et a[alpha ] 6b[Bêta ]4 integrins induces a transitional activation of PB Kinase that activates monomeric GTP Ases Rac1 and its variant Rac 1 b. Then we show that adherens junction maturation is favoured by lipid rafts emergence. p 120ctn interacts preferentially with Ecadherin in lipid rafts and their recruitment into this fraction is Rac1-dependent. Furthermore this process is correlated with epithelial cell differentiation. ln a second part, we describe a new function of p 120ctn in intestinal ce Ils homeostasis. We show that the increase in p120ctn cytoplasmic level induces a downregulation of HT-29 cells proliferation. This effect results from the interaction ofp120ctn with the cyclin E / cdk2 complex in the centrosome which leads to cyclin E overexpression. This process leads to centrosome overduplication, a phenomenon often observed in tumor cells.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Stress neuromediators are key regulators of the intestinal barrier: Link to inflammation and cancer: Stress neuromediators regulate the intestinal barrier

ReviewInternational audienceIn the past year, the influence of psychosocial and environmental stressors in different pathogenesis received increased awareness. The brain is the master manager of the interpretation of what is stressful and of the physiological responses that are produced. Animals have developed conserved strategies to respond to stressful conditions, in particular, the secretion of stress-specific neuromediators which mediate protective and adaptative effects in the short run and yet can accelerate pathophysiology when they are over-produced or mis-managed. The Cortico-Releasing Factor (CRF) and their derived peptides are the majors stress neuromediators. Their localization has originally been described in the central nervous system where they play a pivotal role to activate the hypothalamic-pituitary-adrenal (HPA) axis and was recently extended to the periphery. While the peripheral effects of CRF signalling need to be more thoroughly investigated, it has been described to influence disease negatively, in particular in the intestine. The epithelial barrier is a crucial checkpoint to control body entrances. Prolonged exposure to stress can cause ultrastructural epithelial abnormalities and can increase barrier permeability, which favors luminal translocation, immune activation and thus induces inflammation. This review summarizes the present knowledge on the stress response and the effects of both acute and chronic stress to induce pathological damage to the intestine. We present the potential pathways involved, and the proposed mechanisms of action, mediating these effects. The CRF system is potentially useful as a diagnostic marker or a therapy target for inflammatory diseases and cancer

Nicotine-induced cellular stresses and autophagy in human cancer colon cells: A supportive effect on cell homeostasis via up-regulation of Cox-2 and PGE2 production

International audienc

Role of cholinergic receptors in colorectal cancer: potential therapeutic implications of vagus nerve stimulation?

International audiencelapsing intestinal inflammation that favours the development of colitis associated cancer (CAC). This inflammation is initiated by aberrant activations of the innate immune responses associated to intestinal barrier defects. The conven-tional medical therapies consist to decrease the inflammatory response, which also decrease the risk of colon carcinoma but lead to severe side-effects. Recently, a number of animal studies have demonstrated that innate immune responses are attenuated by stimulation of the efferent arm of vagus nerve (VN) through its neurotransmitter acetylcholine (ACh), that acts on resident macrophages α7 nicotinic receptor (α7 nAChR). ACh also acts as a signalling molecule in epithet- lial cells through cholinergic receptors such as nAChR or muscarinic (mAChR) receptors. In the current study, we aimed to extend these findings to CAC prevention by treating human adenocarcinoma cell lines through targeting cho- linergic receptors with nicotine (which binds nAChR) and ACh (which binds both cholinergic receptors). Using HT-29 and Caco-2 cell lines, we demonstrated that ACh-induced activation of mAChR results in cell dissociation together with changes in expression and localization of intestinal tight and adherens junction proteins. ACh-induced modulation of cell adhesion proprieties correlates with the acquisition of invasive potential. By contrast, nicotine-mediated activation of nAChR maintains epithelial cell organisation. ACh-released by VN stimulation (VNS) could effectively preserve epithelium integrity thus limiting inflammatory response and tumor development. However, attention should be paid on the nature of the cholinergic receptor solicited. Indeed, regarding to the protective effects of nAChR signalling on epithelial cells, activation of mAChR would worsen the disease and led to increase inflammation. These data have im- portant repercussions on the therapeutic potential of VNS in IBD and CAC, which may represent "the yin and yang" of the intestinal homeostasis

Effect of Alzheimer’s disease‐related β‐amyloid peptide conformations in transgenic mouse models of β‐amyloidosis

International audienceBackground: Alzheimer's disease (AD) brain dysfunctions are not exclusively related to amyloid plaques occurence, but are thought to start much earlier, presumably due to soluble pathological forms of b-amyloid peptide (Aβ). Indeed Aβ oligomers induce synaptic dysfunctions that cause cognitive decline, exacerbate tau pathology[1] and influence neuronal networks[2]. Although mutation-induced phenotypes are identified in AD patients, the in vivo effects of different Aβ variants are poorly understood. Here we characterized the effects of different Aβ variants in a transgenic mouse modelto provide deeper insight of transconformational processes and the subsequent alterations. Deciphering Ab profiles would help in developing new diagnostic and therapeutic approaches.References: (1) Delacourte et al., Experimental Gerontology, 2002. (2) Bero et al., Journal of Neuroscience, 2012

Astrocyte-neuron interplay is critical for Alzheimer's disease pathogenesis and is rescued by TRPA1 channel blockade

International audienceAbstract The sequence of cellular dysfunctions in preclinical Alzheimer’s disease must be understood if we are to plot new therapeutic routes. Hippocampal neuronal hyperactivity is one of the earliest events occurring during the preclinical stages of Alzheimer’s disease in both humans and mouse models. The most common hypothesis describes amyloid-β accumulation as the triggering factor of the disease but the effects of this accumulation and the cascade of events leading to cognitive decline remain unclear. In mice, we previously showed that amyloid-β-dependent TRPA1 channel activation triggers hippocampal astrocyte hyperactivity, subsequently inducing hyperactivity in nearby neurons. In this work, we investigated the potential protection against Alzheimer's disease progression provided by early chronic pharmacological inhibition of the TRPA1 channel. A specific inhibitor of TRPA1 channel (HC030031) was administered intraperitoneally from the onset of amyloid-β overproduction in the APP/PS1-21 mouse model of Alzheimer’s disease. Short-, medium- and long-term effects of this chronic pharmacological TRPA1 blockade were characterized on Alzheimer’s disease progression at functional (astrocytic and neuronal activity), structural, biochemical and behavioural levels. Our results revealed that the first observable disruptions in the Alzheimer’s disease transgenic mouse model used correspond to aberrant hippocampal astrocyte and neuron hyperactivity. We showed that chronic TRPA1 blockade normalizes astrocytic activity, avoids perisynaptic astrocytic process withdrawal, prevents neuronal dysfunction and preserves structural synaptic integrity. These protective effects preserved spatial working memory in this Alzheimer’s disease mouse model. The toxic effect of amyloid-β on astrocytes triggered by TRPA1 channel activation is pivotal to Alzheimer’s disease progression. TRPA1 blockade prevents irreversible neuronal dysfunction, making this channel a potential therapeutic target to promote neuroprotection