Laboratory of Experimental Medicine

Montigny le Tilleul, Belgium

Laboratory of Experimental Medicine

Montigny le Tilleul, Belgium
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Eizirik D.L.,Laboratory of Experimental Medicine | Cnop M.,Laboratory of Experimental Medicine | Cnop M.,Erasmus University College Brussels
Cell Metabolism | Year: 2012

Pancreatic β cell failure is central in the pathogenesis of type 2 diabetes (T2D), but the mechanisms involved remain unclear. Mahdi and colleagues (2012) couple global evaluation of gene expression with coexpression network analysis of human islets from T2D patients to identify SFRP4 as an early mediator of b cell dysfunction in T2D. © 2012 Elsevier Inc.


Boittin F.-X.,University of Geneva | Alonso F.,Laboratory of Experimental Medicine | Le Gal L.,Laboratory of Experimental Medicine | Allagnat F.,Laboratory of Experimental Medicine | And 2 more authors.
Cellular Physiology and Biochemistry | Year: 2013

Background/Aims: Smooth muscle tone is controlled by Ca2+ signaling in the endothelial layer. Mouse endothelial cells are interconnected by gap junctions made of Connexin40 (Cx40) and Cx37, which allow the exchange of signaling molecules to coordinate their activity. Here, we investigated the role of Cx40 in the endothelial Ca2+ signaling of the mouse aorta. Methods: Ca2+ imaging was performed on intact aortic endothelium from both wild type (Cx40+/+) and Connexin40-deficient (Cx40 -/-) mice. Results: Acetylcholine (ACh) induced early fast and high amplitude Ca2+ transients in a fraction of endothelial cells expressing the M3 muscarinic receptors. Inhibition of intercellular communication using carbenoxolone or octanol fully blocked the propagation of ACh-induced Ca2+ transients toward adjacent cells in WT and Cx40-/- mice. As compared to WT, Cx40-/- mice displayed a reduced propagation of ACh-induced Ca2+ waves, indicating that Cx40 contributes to the spreading of Ca2+ signals. The propagation of those Ca2+ responses was not blocked by suramin, a blocker of purinergic ATP receptors, indicating that there is no paracrine effect of ATP release on the Ca2+ waves. Conclusions: Altogether our data show that Cx40 and Cx37 contribute to the propagation and amplification of the Ca2+ signaling triggered by ACh in endothelial cells expressing the M3 muscarinic receptors. Copyright © 2013 S. Karger AG, Basel.


Roumeguer T.,Laboratory of Experimental Medicine | Roumeguer T.,University Clinics of Brussels | Delree P.,Institute of Pathology and Genetics IPG | Van Antwerpen P.,Laboratory of Pharmaceutical Chemistry and Analytical Platform | And 7 more authors.
Prostate | Year: 2012

Background: Myeloperoxidase (MPO) is a member of the peroxidase- cyclooxygenase superfamily, which is secreted from stimulated leucocytes at inflammatory sites. It is well known that MPO catalyses oxidation reactions via the release of reactive halogenating and nitrating species and thus induces tissue damage. Several studies have already implicated MPO in the development of neoplasia. Chronic or recurrent prostatic inflammation has long been recognized as having the potential to initiate and promote the development of prostate cancer. The objective was to investigate whether MPO is present in the prostate. METHODS Human prostate material was obtained from biopsies, transurethral resections of the prostate (TURP), prostatic adenomectomies, and retropubic radical prostatectomies. Twenty-nine slides of normal prostate tissue, benign prostatic hyperplasia (BPH), and prostate cancer were reviewed by a pathologist. Immunohistochemical analysis using MPO-specific human antibody was performed to detect MPO in the prostate tissue. Results: Immunocytohistochemistry showed cellular colocalization of MPO in the secretory epithelial cells of the prostate with staining varying from light to strong intensity. Staining in the glandular apical snouts was often reinforced although staining of basal as well as of luminal glandular cells was also present. Conclusions: We identified, for the first time, the presence of MPO at the surface of prostatic epithelial cells. In view of the pro-oxidant properties of this enzyme, further research is needed to define whether MPO contributes to the development of prostatic lesions. © 2011 Wiley Periodicals,Inc.


Martin D.,Ecole Polytechnique Federale de Lausanne | Kim Y.-H.,Copenhagen University | Sever D.,Copenhagen University | Mao C.-A.,University of Houston | And 3 more authors.
Developmental Biology | Year: 2015

To contribute to devise successful beta-cell differentiation strategies for the cure of Type 1 diabetes we sought to uncover barriers that restrict endocrine fate acquisition by studying the role of the transcriptional repressor REST in the developing pancreas. Rest expression is prevented in neurons and in endocrine cells, which is necessary for their normal function. During development, REST represses a subset of genes in the neuronal differentiation program and Rest is down-regulated as neurons differentiate. Here, we investigate the role of REST in the differentiation of pancreatic endocrine cells, which are molecularly close to neurons. We show that Rest is widely expressed in pancreas progenitors and that it is down-regulated in differentiated endocrine cells. Sustained expression of REST in Pdx1+ progenitors impairs the differentiation of endocrine-committed Neurog3+ progenitors, decreases beta and alpha cell mass by E18.5, and triggers diabetes in adulthood. Conditional inactivation of Rest in Pdx1+ progenitors is not sufficient to trigger endocrine differentiation but up-regulates a subset of differentiation genes. Our results show that the transcriptional repressor REST is active in pancreas progenitors where it gates the activation of part of the beta cell differentiation program. © 2015 Elsevier Inc.


Velloso L.A.,University of Campinas | Eizirik D.L.,Laboratory of Experimental Medicine | Cnop M.,Erasmus University College Brussels
Nature Reviews Endocrinology | Year: 2013

Inflammation-induced inhibition of the insulin signalling pathway can lead to insulin resistance and contribute to the development of type 2 diabetes mellitus (T2DM). Obesity and insulin resistance are associated with a chronic but subclinical inflammatory process that impairs insulin action in most tissues and could also hamper pancreatic β-cell function. The involvement of monocytic cells and the profiles of the chemokines and cytokines induced by this inflammation suggest an innate immune response. However, emerging data indicate that elements of the adaptive immune system could also be involved. As activation of an adaptive response requires antigen specificity, some researchers have hypothesized that T2DM evolves from an innate immune response to an autoimmune condition. In this Perspectives article, we present the arguments for and against this hypothesis and discuss which mechanisms could be involved in a putative switch from innate immunity to autoimmunity. © 2013 Macmillan Publishers Limited.


Horton J.S.,Laboratory of Experimental Medicine | Stokes A.J.,Laboratory of Experimental Medicine | Stokes A.J.,Chaminade University of Honolulu
OncoImmunology | Year: 2014

Epidermodysplasia verruciformis (EV) is a rare genodermatosis characterized by increased sensitivity to infection by the β-subtype of human papillomaviruses (β-HPVs), causing persistent, tinea versicolor-like dermal lesions. In a majority of affected individuals, these macular lesions progress to invasive cutaneous squamous cell carcinoma (CSCC) in sunexposed areas. While mutations in transmembrane channel-like 6 (TMC6 / EVER1) and 8 (TMC8 / EVER2) have been causally linked to EV, their molecular functions are unclear. It is likely that their protective effects involve regulation of the β-HPV life cycle, host keratinocyte apoptosis vs. survival balance and/or T-cell interaction with infected host cells. © 2014 Landes Bioscience.


Gal L.L.,University of Lausanne | Alonso F.,University of Lausanne | Wagner C.,University of Regensburg | Germain S.,Collège de France | And 4 more authors.
Hypertension | Year: 2014

Connexin 40 (Cx40) is expressed by the renin-producing cells (RSCs) of the kidneys and the endothelial cells of blood vessels. Cx40 null mice (Cx40 -/-) feature a much increased renin synthesis and secretion, which results in chronic hypertension, and also display an altered endothelium-dependent relaxation of the aorta because of reduced eNOS levels and nitric oxide production. To discriminate the effect of Cx40 in renin secretion and vascular signaling, we targeted Cx40 to either the RSCs or the endothelial cells of Cx40 null mice. When compared with Cx40-/- controls, the animals expressing Cx40 in RSCs were less hypertensive and featured reduced renin levels, still numerous RSCs outside the wall of the afferent arterioles. In contrast, mice expressing Cx40 in the endothelial cells were as hypertensive as Cx40-/- mice, in spite of control levels of Cx37 and eNOS. Our data show that blood pressure is improved by restoration of Cx40 expression in RSCs but not in endothelial cells, stressing the prominent role of renin in the mouse hypertension linked to loss of Cx40. © 2014 American Heart Association, Inc.


Roumeguere T.,Laboratory of Experimental Medicine | Roumeguere T.,University Clinics of Brussels | Zouaoui Boudjeltia K.,Laboratory of Experimental Medicine | Babar S.,Free University of Brussels | And 6 more authors.
European Urology | Year: 2010

Background: Sildenafil, vardenafil, and tadalafil are phosphodiesterase type 5 inhibitors (PDE5-Is) usually used in the treatment of erectile dysfunction (ED). Previously, we have shown the presence of myeloperoxidase-modified low-density lipoprotein (Mox-LDL) in the penises of patients with ED, and we have shown the impact of Mox-LDL on cyclic monophosphate (cGMP) level. In vitro, Mox-LDL triggered the inflammatory response by increasing the release of both interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-α) by endothelial cells (ECs) and monocytes respectively. Objective: To determine whether or not the three therapeutically PDE5-Is protect against the proinflammatory effects of Mox-LDL or TNF-α on ECs. Design, setting, and participants: ECs (EA.hy926) were incubated in the presence of either TNF-α (100 pg/ml) or Mox-LDL (200 μg/ml) with each of the three PDE5-Is (1 μM, 5 μM, and 10 μM) respectively. IL-8 production was measured in the supernatant after 48 h of incubation. Measurements: All experiments were repeated at least three times. Statistical analysis was performed with an ANOVA. Results and limitations: Two-way ANOVA analysis showed that TNF-α alone (p < 0.001) or Mox-LDL alone (p < 0.001) increased IL-8 production. Sildenafil, vardenafil, or tadalafil alone did not generate an increase of IL-8 production. Tadalafil in combination with Mox-LDL and TNF-α showed a decrease of IL-8 (p < 0.05) compared with sildenafil and vardenafil. Conclusions: Among the three available PDE5-Is, tadalafil showed an additional potentially anti-inflammatory effect on relaxation. Those data could be considered for the chronic use of PDE5-Is, but extrapolations of experimental evidence to the clinical setting should be made cautiously. © 2009 European Association of Urology.


Allagnat F.,Laboratory of Experimental Medicine | Klee P.,University of Geneva | Cardozo A.K.,Free University of Colombia | Meda P.,University of Geneva | Haefliger J.-A.,Laboratory of Experimental Medicine
Cell Death and Differentiation | Year: 2013

Cell-to-cell communication mediated by gap junctions made of Connexin36 (Cx36) contributes to pancreatic β-cell function. We have recently demonstrated that Cx36 also supports β-cell survival by a still unclear mechanism. Using specific Cx36 siRNAs or adenoviral vectors, we now show that Cx36 downregulation promotes apoptosis in INS-1E cells exposed to the pro-inflammatory cytokines (IL-1β, TNF- and IFN-γ) involved at the onset of type 1 diabetes, whereas Cx36 overexpression protects against this effect. Cx36 overexpression also protects INS-1E cells against endoplasmic reticulum (ER) stress-mediated apoptosis, and alleviates the cytokine-induced production of reactive oxygen species, the depletion of the ER Ca 2+ stores, the CHOP overexpression and the degradation of the anti-apoptotic protein Bcl-2 and Mcl-1. We further show that cytokines activate the AMP-dependent protein kinase (AMPK) in a NO-dependent and ER-stress-dependent manner and that AMPK inhibits Cx36 expression. Altogether, the data suggest that Cx36 is involved in Ca 2+ homeostasis within the ER and that Cx36 expression is downregulated following ER stress and subsequent AMPK activation. As a result, cytokine-induced Cx36 downregulation elicits a positive feedback loop that amplifies ER stress and AMPK activation, leading to further Cx36 downregulation. The data reveal that Cx36 plays a central role in the oxidative stress and ER stress induced by cytokines and the subsequent regulation of AMPK activity, which in turn controls Cx36 expression and mitochondria-dependent apoptosis of insulin-producing cells. © 2013 Macmillan Publishers Limited All rights reserved.


PubMed | Laboratory of Experimental Medicine
Type: Journal Article | Journal: The Prostate | Year: 2012

Myeloperoxidase (MPO) is a member of the peroxidase-cyclooxygenase superfamily, which is secreted from stimulated leucocytes at inflammatory sites. It is well known that MPO catalyses oxidation reactions via the release of reactive halogenating and nitrating species and thus induces tissue damage. Several studies have already implicated MPO in the development of neoplasia. Chronic or recurrent prostatic inflammation has long been recognized as having the potential to initiate and promote the development of prostate cancer. The objective was to investigate whether MPO is present in the prostate.Human prostate material was obtained from biopsies, transurethral resections of the prostate (TURP), prostatic adenomectomies, and retropubic radical prostatectomies. Twenty-nine slides of normal prostate tissue, benign prostatic hyperplasia (BPH), and prostate cancer were reviewed by a pathologist. Immunohistochemical analysis using MPO-specific human antibody was performed to detect MPO in the prostate tissue.Immunocytohistochemistry showed cellular colocalization of MPO in the secretory epithelial cells of the prostate with staining varying from light to strong intensity. Staining in the glandular apical snouts was often reinforced although staining of basal as well as of luminal glandular cells was also present.We identified, for the first time, the presence of MPO at the surface of prostatic epithelial cells. In view of the pro-oxidant properties of this enzyme, further research is needed to define whether MPO contributes to the development of prostatic lesions.

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