[show abstract][hide abstract] ABSTRACT: Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP), now known as G6PC2, is a major target of autoreactive T cells implicated in the pathogenesis of type 1 diabetes in both mice and humans. This study aimed to determine whether suppression of G6p2 gene expression might therefore prevent or delay disease progression.
G6pc2(-/-) mice were generated on the NOD/ShiLtJ genetic background, and glycemia was monitored weekly up to 35 weeks of age to determine the onset and incidence of diabetes. The antigen specificity of CD8(+) T cells infiltrating islets from NOD/ShiLtJ G6pc2(+/+) and G6pc2(-/-) mice at 12 weeks was determined in parallel.
The absence of G6pc2 did not affect the time of onset, incidence, or sex bias of type 1 diabetes in NOD/ShiLtJ mice. Insulitis was prominent in both groups, but whereas NOD/ShiLtJ G6pc2(+/+) islets contained CD8(+) T cells reactive to the G6pc2 NRP peptide, G6pc2 NRP-reactive T cells were absent in NOD/ShiLtJ G6pc2(-/-) islets.
These results demonstrate that G6pc2 is an important driver for the selection and expansion of islet-reactive CD8(+) T cells infiltrating NOD/ShiLtJ islets. However, autoreactivity to G6pc2 is not essential for the emergence of autoimmune diabetes. The results remain consistent with previous studies indicating that insulin may be the primary autoimmune target, at least in NOD/ShiLtJ mice.
[show abstract][hide abstract] ABSTRACT: Methods are presented for the separation of dense core secretory vesicles from insulin-secreting tissues (insulin granules) based on a combination of differential and density gradient centrifugation on various media. Emphasis is given to the use of transplantable tumors, tissue culture cell lines, and pancreatic islets as a tissue source.
Current protocols in cell biology / editorial board, Juan S. Bonifacino ... [et al.] 04/2009; Chapter 3:Unit 3.32.
[show abstract][hide abstract] ABSTRACT: We have recently demonstrated that upregulation of the innate immune system plays a key role in KRV-induced autoimmune diabetes in the BBDR rat, but the nature of this proinflammatory reaction has not yet been addressed. Using a DNA microarray approach, we identified 569 genes upregulated in pancreatic lymph nodes following virus infection. Among the most highly activated are IL-1 pathways, IFN-gamma-induced chemokines, and genes associated with interferon production and signaling. Ex vivo and in vitro studies indicate that KRV upregulates proinflammatory cytokines and chemokines in B lymphocytes and Flt-3L-induced plasmacytoid DCs (pDCs). Finally, in contrast to KRV, infection of BBDR rats with the non-diabetogenic KRV homologue H-1 parvovirus fails to induce a robust proinflammatory response in pancreatic lymph nodes. Our findings provide new insights into KRV-induced innate immune pathways that may play a role in early mechanisms leading to islet inflammation and diabetes.
[show abstract][hide abstract] ABSTRACT: To document the transcriptome of the pancreatic islet during the early and late development of the mouse pancreas and highlight the qualitative and quantitative features of gene expression that contribute to the specification, growth, and differentiation of the major endocrine cell types. A further objective was to identify endocrine cell biomarkers, targets of diabetic autoimmunity, and regulatory pathways underlying islet responses to physiological and pathological stimuli.
mRNA expression profiling was performed by microarray analysis of e12.5-18.5 embryonic pancreas from neurogenin 3 (Ngn3)-null mice, a background that abrogates endocrine pancreatic differentiation. The intersection of this data with mRNA expression in isolated adult pancreatic islets and pancreatic endocrine tumor cell lines was determined to compile lists of genes that are specifically expressed in endocrine cells.
The data provided insight into the transcriptional and morphogenetic factors that may play major roles in patterning and differentiation of the endocrine lineage before and during the secondary transition of endocrine development, as well as genes that control the glucose responsiveness of the beta-cells and candidate diabetes autoantigens, such as insulin, IA-2 and Slc30a8 (ZnT8). The results are presented as downloadable gene lists, available at https://www.cbil.upenn.edu/RADQuerier/php/displayStudy.php?study_id=1330, stratified by predictive scores of relative cell-type specificity.
The deposited data provide a rich resource that can be used to address diverse questions related to islet developmental and cell biology and the pathogenesis of type 1 and 2 diabetes.
[show abstract][hide abstract] ABSTRACT: Indoleamine 2,3-dioxygenase (IDO) catalyzes the initial, rate-limiting step of tryptophan (Trp) catabolism along the kynurenine (KYN) pathway, and its induction in cells of the immune system in response to cytokines has been implicated in the regulation of antigen presentation and responses to cell-mediated immune attack. Microarray and quantitative PCR analyses of isolated human islets incubated with interferon (IFN)-gamma for 24 h revealed increased expression of IDO mRNA (>139-fold) and Trp-tRNA synthase (WARS) (>17-fold) along with 975 other transcripts more than threefold, notably the downstream effectors janus kinase (JAK)2, signal transducer and activator of transcription (STAT)1, IFN-gamma regulatory factor-1, and several chemokines (CXCL9/MIG, CXCL10/IP10, CXCL11/1-TAC, CCL2, and CCL5/RANTES) and their receptors. IDO protein expression was upregulated in IFN-gamma-treated islets and accompanied by increased intracellular IDO enzyme activity and the release of KYN into the media. The response to IFN-gamma was countered by interleukin-4 and 1alpha-methyl Trp. Immunohistochemical localization showed IDO to be induced in cells of both endocrine, including pancreatic duodenal homeobox 1-positive beta-cells, and nonendocrine origin. We postulate that in the short term, IDO activation may protect islets from cytotoxic damage, although chronic exposure to various Trp metabolites could equally lead to beta-cell attrition.