Lipopolysaccharides Impair Insulin Gene Expression in Isolated Islets of Langerhans via Toll-Like Receptor-4 and NF-κB Signalling

BACKGROUND:Type 2 diabetes is characterized by pancreatic β-cell dysfunction and is associated with low-grade inflammation. Recent observations suggest that the signalling cascade activated by lipopolysaccharides (LPS) binding to Toll-Like Receptor 4 (TLR4) exerts deleterious effects on pancreatic β-cell function; however, the molecular mechanisms of these effects are incompletely understood. In this study, we tested the hypothesis that LPS alters insulin gene expression via TLR4 and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in islets. METHODOLOGY/PRINCIPAL FINDINGS:A 24-h exposure of isolated human, rat and mouse islets of Langerhans to LPS dose-dependently reduced insulin gene expression. This was associated in mouse and rat islets with decreased mRNA expression of pancreas-duodenum homebox-1 (PDX-1) and mammalian homologue of avian MafA/l-Maf (MafA). Accordingly, LPS exposure also decreased glucose-induced insulin secretion. LPS repression of insulin, PDX-1 and MafA expression, as well as its inhibition of insulin secretion, were not observed in islets from TLR4-deficient mice. LPS inhibition of β-cell gene expression in rat islets was prevented by inhibition of the NF-κB pathway, but not the p38 mitogen-activated protein kinase (p38 MAPK) pathway. CONCLUSIONS/SIGNIFICANCE:Our findings demonstrate that LPS inhibit β-cell gene expression in a TLR4-dependent manner and via NF-κB signaling in pancreatic islets, suggesting a novel mechanism by which the gut microbiota might affect pancreatic β-cell function

PAX4 preserves endoplasmic reticulum integrity preventing beta cell degeneration in a mouse model of type 1 diabetes mellitus

Mellado-Gil, José Manuel et al.[Aims/hypothesis]: A strategy to enhance pancreatic islet functional beta cell mass (BCM) while restraining inflammation, through the manipulation of molecular and cellular targets, would provide a means to counteract the deteriorating glycaemic control associated with diabetes mellitus. The aims of the current study were to investigate the therapeutic potential of such a target, the islet-enriched and diabetes-linked transcription factor paired box 4 (PAX4), to restrain experimental autoimmune diabetes (EAD) in the RIP-B7.1 mouse model background and to characterise putative cellular mechanisms associated with preserved BCM. [Methods]: Two groups of RIP-B7.1 mice were genetically engineered to: (1) conditionally express either PAX4 (BPTL) or its diabetes-linked mutant variant R129W (mutBPTL) using doxycycline (DOX); and (2) constitutively express luciferase in beta cells through the use of RIP. Mice were treated or not with DOX, and EAD was induced by immunisation with a murine preproinsulin II cDNA expression plasmid. The development of hyperglycaemia was monitored for up to 4 weeks following immunisation and alterations in the BCM were assessed weekly by non-invasive in vivo bioluminescence intensity (BLI). In parallel, BCM, islet cell proliferation and apoptosis were evaluated by immunocytochemistry. Alterations in PAX4- and PAX4R129W-mediated islet gene expression were investigated by microarray profiling. PAX4 preservation of endoplasmic reticulum (ER) homeostasis was assessed using thapsigargin, electron microscopy and intracellular calcium measurements. [Results]: PAX4 overexpression blunted EAD, whereas the diabetes-linked mutant variant PAX4R129W did not convey protection. PAX4-expressing islets exhibited reduced insulitis and decreased beta cell apoptosis, correlating with diminished DNA damage and increased islet cell proliferation. Microarray profiling revealed that PAX4 but not PAX4R129W targeted expression of genes implicated in cell cycle and ER homeostasis. Consistent with the latter, islets overexpressing PAX4 were protected against thapsigargin-mediated ER-stress-related apoptosis. Luminal swelling associated with ER stress induced by thapsigargin was rescued in PAX4-overexpressing beta cells, correlating with preserved cytosolic calcium oscillations in response to glucose. In contrast, RNA interference mediated repression of PAX4-sensitised MIN6 cells to thapsigargin cell death. [Conclusions/interpretation]: The coordinated regulation of distinct cellular pathways particularly related to ER homeostasis by PAX4 not achieved by the mutant variant PAX4R129W alleviates beta cell degeneration and protects against diabetes mellitus. The raw data for the RNA microarray described herein are accessible in the Gene Expression Omnibus database under accession number GSE62846.This work was funded by grants from the Consejeria de Salud, Fundacion Publica Andaluza Progreso y Salud, Junta de Andalucia (PI-0727-2010 to BRG and PI-0085-2013 to PIL), Consejeria de Economia, Innovacion y Ciencia (P10.CTS.6359 to BRG), Ministerio de Ciencia e Innovacion (BFU2013-42789-P to IQ) and the Ministerio de Economia y Competidividad, Instituto de Salud Carlos III co-funded by Fondos FEDER (PI10/00871 and PI13/00593 to BRG). NC-V is supported by a JDRF subsidy (17-2013-372 to BRG.). AM-M is a recipient of a Miguel Servet grant (CP14/00105) from the Instituto de Salud Carlos III co-funded by Fondos FEDER and EF-M is a recipient of a Juan de la Cierva Fellowship. PM is supported by Swiss National Science Foundation grant 310030-141162, and the European Union grant IMIDIA, C2008-T7. BOB is supported by grants from the Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Republic of Singapore.Peer Reviewe

Structure-based discovery of cannabinoid-1 receptor agonists with reduced side effects

AbstractDocking tangible virtual libraries can reveal unexpected chemotypes that complement the structures of biological targets. Seeking new agonists for the cannabinoid-1 receptor (CB1R), we docked 74 million tangible molecules, prioritizing 46 high ranking ones forde novosynthesis and testing. Nine were active by radioligand competition, with &gt; 50% radioligand displacement, a 20% hit-rate. Structure-based optimization of one of the most potent of these (Ki= 731 nM) led to‘3234, a 1.9 nM binder and a full CB1 agonist. A cryo-EM structure of the‘3234-CB1-Gi1complex confirmed its docked pose, providing a template for further optimization. The new agonist was strongly analgesic especially against thermal pain, with a 10-fold therapeutic window over sedation and no observable catalepsy or conditioned place preference or aversion. These findings suggest that new cannabinoid chemotypes may be able to disentangle the characteristic “tetrad” side-effects from its desired analgesic effect, supporting the further development of cannabinoids as pain therapeutics.</jats:p

Diversity and intragroup conflict at work: an empirical study in Portugal

Facing a constantly changing environment, nowadays’ organizations are looking for innovative ways of organizing and managing work, in which workgroups represent a source of competitive advantage. In this context, group diversity has received increasingly attention by researchers. Jackson, May and Whitney (1995) define diversity in terms of characteristics classified as observable or underlying, as either task-related or relational-oriented. Although there are no conclusive results on this subject, researches relating diversity and the main types of conflict (affective and task-related) suggest that relational-oriented diversity (e.g., age, gender) influences the emergence of affective conflict, while task-oriented diversity (e.g., education, organizational tenure) contributes to task conflict (PELLED, 1996; JEHN; NORTHCRAFT; NEALE, 1999; PELLED; EISENHARDT; XIN, 1999). Following Jackson, May and Whitney (1995), we analyzed the effects of observable attributes of diversity (educational level, gender and age), on the emergence of intragroup conflict in 231 Portuguese workgroups, whose members perceived themselves as a group, and interacted with interdependence to achieve common goals. The Intragroup Conflict Assessment Scale (DIMAS; LOURENÇO; MIGUEZ, 2007) and a sociodemographic questionnaire were used. In contrast with the literature, but congruent with recent Portuguese researches (PASSOS, 2005; SILVESTRE, 2008), our results revealed no association between the studied diversity variables and intragroup conflict, indicating new directions in this field, and highlighting the importance of considering different contexts and variables in diversity’s studies