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1 Diabetes Research Center, Division of Endocrinology
2 Division of Pediatric Informatics
3 Division of Developmental Biology
4 Divison of Molecular Immunology, Cincinnati Childrens Hospital Research Foundation and College of Medicine, University of Cincinnati, Cincinnati, Ohio
| ABSTRACT |
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, Reg3ß, and Reg3
. Our data indicate that progression to insulitis was connected to marked changes in islet antigen expression, ß-cell differentiation, and T cell activation and signaling, all associated with tumor necrosis factor-
and IL-6 expression. Overt diabetes saw a clear shift in cytokine, chemokine, and T cell differentiation factor expression, consistent with a focused Th1 response, as well as a significant upregulation in genes associated with cellular adhesion, homing, and apoptosis. Importantly, the temporal pattern of expression of key verified genes suggested that T1DM develops in a relapsing/remitting as opposed to a continuous fashion, with insulitis linked to hypoxia-regulated gene control and diabetes with C/EBP and Nkx2 gene control. type 1 diabetes; nonobese diabetic mouse; pancreas; microarray; gene expression profile
| INTRODUCTION |
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However, the close association between T1DM and MHC class II has inspired intense investigation into the role that MHC class II-restricted CD4+ T cells play in T1DM. It is now well established that CD4+ T cells play a prominent role, as 1) CD4+ T cells from NOD mice respond naturally to pancreatic ß-cell antigens (53), 2) bulk and cloned CD4+ T cells from diabetic NOD mice can transfer T1DM to young NOD and NOD.scid recipients (21, 31), 3) NOD mice lacking CD4+ T cells fail to develop T1DM (32, 47), and 4) T cell receptor (TCR) transgenic NOD mice harboring CD4+ T cells with islet antigen reactivity develop insulitis and diabetes (30). We and others have used one of these TCR transgenic mice, BDC2.5, to establish the presence of discrete checkpoints along the way to overt diabetes (4, 30).
To understand the complex autoimmune processes affecting the pathogenesis of T1DM, it is absolutely essential to identify, catalog, and investigate the major modulations in gene expression patterns that occur during the course of disease pathogenesis. In light of the rapid advances in genome-based research, it is now possible to undertake a comprehensive molecular study of complex diseases such as T1DM using cDNA microarray analysis. Complementary DNA microarrays provide us with a powerful tool for the simultaneous imaging of the expression of large numbers of genes (36) and are used to delineate the progression of cancer (12), type 2 diabetes (42), asthma (29), and other complex or multiorgan diseases. In the present study, we report the application of cDNA microarray technology to T1DM and the identification of subsets of genes the expression of which changes markedly during the initiation of insulitis, as well as others that are modulated during the progression to ß-cell destruction and overt diabetes in the NOD mouse.
| MATERIALS AND METHODS |
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Histology and immunohistochemistry of pancreas.
Pancreata from N.sc, N, BDC/N, and BDC/N.sc were removed and embedded in paraffin, sectioned, and stained with hematoxylin and eosin for the identification of mononuclear cells or stained with guinea pig anti-insulin antibody (Dako) followed by Alexa-568-conjugated goat anti-guinea pig IgG (H+L) antibody (Molecular Probes) as described in Ref. 33. 2-(2-Nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetamide (EF-5) was detected using ELK3-51, a monoclonal antibody conjugated to Alexa-488 (Dr. Cameron J. Koch, Dept. of Radiation Oncology, Univ. of Pennsylvania, Philadelphia, PA).
Imaging procedure.
Stained sections were imaged with a Zeiss Axioplan 2.0 fluorescence microscope (Zeiss) with a 100-W mercury lamp illumination, and image was analyzed with Axio Vision software (v.4.0, Zeiss).
Interleukin-17 determination.
Interleukin (IL)-17 was quantified, using the IL-17 Quantikine kit (R&D Systems).
EF-5 treatment of mice for the detection of hypoxia.
BDC/N and BDC/N.sc mice were given an intraperitoneal injection of 10 mM EF-5 (obtained from Dr. R. Vishnuvajjala, National Cancer Institute, Bethesda, MD), prepared in 0.9% saline. The mass of solution administered was 1% mouses mass; the equivalent whole body concentration was 100 µM.
Diabetes.
Diabetes was assessed by measurement of venous blood as described previously (33).
RNA isolation.
Total RNA was isolated from pancreas (3-wk-old mice, unless otherwise noted) by the guanidinium isothiocyanate method (10). RNA was isolated from 12 individual mice in each group, and 2 RNA pools were made from 6 animals each after verification of RNA quality to minimize expression biases. The integrity of isolated RNA was assessed by formaldehyde-agarose gel electrophoresis and Agilent bioanalyzer chips.
DNA microarrays and analysis of GeneChip data.
Analysis of mRNA expression was performed in duplicate, using the mouse U74Av2 microarray (GeneChip, Affymetrix, Santa Clara, CA). RNA labeling and microarray hybridizations were performed according to the manufacturers recommendations by the Cincinnati Childrens Hospital Research Foundation (CCHRF) genomics core. All the experiments were done in duplicate.
Data analysis.
Affymetrix MicroArray Suite version 5.0 was used to scan and quantify the GeneChips, using default scan settings. Intensity data were collected from each chip, scaled to a target intensity of 1,500. For subsequent analysis of gene expression, we used Robust MultiArray (RMA) (23). RMA files were made using RMA Express software (v.0.1, biolstat@stat.berkeley.edu) and analyzed with GeneSpring 6.0 software (Silicon Genetics, Redwood City, CA). All experiments were carried out in duplicate to maximize the statistical significance. Hybridization data were normalized in a two-step process to minimize variation at both chip and gene level. Initially, each chip data point was normalized to the distribution of all genes on the chip to control for variation between samples and then normalized to the specific sample, N.sc. Normalized data were filtered by data file restriction, expression percentage ratio, and statistical significance and clustered (based on expression profile or pattern) using K-means and hierarchical clustering. Subsets of genes such as chemokines, cytokines, cell cycle control, antigen processing, and so forth were made from the filtered gene lists, based on imported pathway schematics designed by our laboratory from published data as well as the simplified gene ontology at CCHRF. Raw and RMA experimental data for N.sc, N, BDC/N, and BDC/N.sc were deposited in the Gene Expression Omnibus database (http://www.ncbi.nlm.nih.gov/geo/) under the accession numbers GSM27453, GSM27454, GSM27456, GSM27457, GSM27446, GSM27447, GSM27451, GSM27452, and GSE1623, respectively.
Verification of gene expression data.
To verify the fidelity of microarray analysis, we selected, for further analysis, representative genes (
20) with a broad range of expression variations from our initial list of genes associated with insulitis and diabetes. Fresh total pancreatic RNA from BDC/N.sc, BDC/N, N, and N.sc was prepared, reverse transcribed, and subjected to semiquantitative PCR using an Eppendorf thermocycler, followed by real-time PCR on a Roche LightCycler with SYBR Green (Roche Diagnostics), according to the manufacturers recommendations. Expression of target genes was normalized to ß-actin. In the case of real-time PCR, the relationship between cycle threshold (CT) and gene copy number was determined by a regression equation (log copy no. = 0.283 CT + 11.309) as described in Ref. 13. Dynamic gene expression (kinetics analysis) was performed, as described above, from freshly isolated RNA samples from mice at 1, 2, 3, 4, 6, 8, 12, 16, and 20 wk of age.
Pathway and literature search analysis.
Biological function and associated regulatory pathway search analysis for the selected genes was performed using a mouse U74Av2 annotation database with system identifiers. Gene description, functional categories, and molecular function were identified using databases such as NetAffy (http://www.affymetrix.com) and BLAST (http://www.ncbi.nlm.nih.gov).
GenomeTraFaC analysis.
To identify conserved regulatory elements in mouse and human orthologs, TraFaC analysis was performed as described in Ref. 25, and the results were stored in the GenomeTraFaC database (http://genometrafac.cchmc.org). Briefly, complete genomic and cDNA sequences of mice and humans were downloaded from the UCSC Golden Path (28). With the use of the RepeatMasker program (http://ftp.genome.washington.edu/RM/RepeatMasker.html), repeat elements were masked before computational alignment using Advanced Pipmaker (http://bio.cse.psu.edu). The MatInspector Professional version 4.3 (http://www.genomatix.de) program was used to locate putative transcription factor binding sites in orthologous sequences utilizing the TRANSFAC database (63) (http://www.gene-regulation.com/) to identify matches in DNA sequences. The output consists of a table indicating a list of putative transcription factor binding sites. Exon annotations were based on the mRNAs of the Reference Sequence (RefSeq) database of the National Center for Biotechnology Information (NCBI).
CisMols analysis.
To identify putative consensus cis-acting regulatory sequences in genes that were coexpressed, putative cis-regulatory regions were identified and stored in GenomeTraFaC, using the CisMols server (http://cismols.cchmc.org). Cis-clusters with at least two binding sites and shared across at least five genes in each group were identified.
| RESULTS |
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Establishing a functional genomics approach.
For functional genomics to provide meaningful measurements of stage-specific gene expression, the specific disease stage must be well defined. BDC2.5 TCR transgenic NOD mice all manifest highly reproducible and distinct changes in phenotype during their progression toward T1DM (30, 33). We and others have previously shown that BDC/N and BDC/N.sc develop insulitis from 13 to 16 days of age, yet only the BDC/N.sc mice develop diabetes by 34 wk of age (Fig. 1A). BDC/N mice do not become diabetic until 4 mo of age, and then only with an
40% incidence (Fig. 1A), representing mice with accelerated acquisition of the checkpoint 1 (insulitis) phenotype. The BDC/N.sc mice, on the other hand, represent mice with an accelerated transition through checkpoint 1 to checkpoint 2, overt diabetes (Fig. 1A). Therefore, we examined the gene expression differences in pancreata from four distinct groups of 3-wk-old mice: BDC/N.sc mice with both severe insulitis and recent onset diabetes, BDC/N mice with severe insulitis without diabetes, and NOD and N.sc mice that served as controls for preclinical disease, adaptive immunity, and genetic background. NOD mice in our barrier colony have a very low incidence (
57%) of peri-insulitis lesions at 3 wk of age (Fig. 1B). To allow for statistical analysis, two independent pools of RNA (6 mice/pool) were isolated and hybridized to Affymetrix U74Av2 microarrays.
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0.05) by either log or simple normalized ratios corrected for false discovery, using the Benjamini-Hochberg algorithm (7). This master list is available as Supplemental Table S1 (supplemental materials are available at the Physiological Genomics web site)1
. By using whole pancreas analysis, we avoided the potential for artifact and bias due to differences in the enzymatic digestion and isolation of intact and infiltrated islets as disease progressed. Moreover, this technique proved highly reproducible, as can be seen in the comparison of hierarchical clustering of both individually isolated and hybridized samples with their replicate log averages (Supplemental Fig. S1). Mining these data, using K-means and hierarchical clustering with Pearson correlation, showed that our functional genomics approach provided clear sets of genes with tight statistical correlation to specific phenotypes and disease stages (Fig. 2).
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Islet cell autoantigens.
T1DM is an autoimmune disease, and islet cell autoantigens serve as targets for the T cells (52). Our GeneChip data show that most islet antigens, such as ICA-69, peripherin, and insulin, are lost with insulitis. Heat shock proteins (HSP) rose transiently with the onset of insulitis but declined with disease progression (Fig. 3). The 67-kDa isoform of glutamic acid decarboxylase (GAD67) was not detected at all. Expression of the 65-kDa isoform of GAD (GAD65) was only observed in NOD mice, and then only weakly. Islet destruction is an important pathological feature of T1DM, so it was not surprising that islet cell autoantigens were lost at this stage. This is most notable for the two insulin genes, where their levels of expression drop precipitously with the transition to late-stage insulitis and diabetes. In general, these data strongly suggest that known islet antigens are not markedly upregulated with insulitis, and the priming of autoimmunity via these antigens is before significant insulitis. In addition, they suggest that these antigens do not drive the late stages of the disease process.
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-induced antigen processing genes (MHCI + II, Lmp7, ctsS) and downregulation of ctsL, several peptidases, and H2Oa. Although it can be argued that these appreciable rises in IFN-
-induced genes can be accounted for by a generalized accumulation of host antigen presenting cells (APC) during late-stage insulitis and diabetes, we did not observe a global rise in generalized APC message levels but rather a specific rise in IFN-
-induced transcripts (Fig. 3). These data are consistent with a prominent role for IFN-
and activated APC at this critical stage of T1DM pathogenesis.
Leukocyte adhesion molecules.
Infiltration of islets with immune cells is thought to occur in T1DM in response to localized inflammation. As seen in Fig. 3, we observed increased expression of P-selectin ligand in diabetes. It has been reported that Th1 but not Th2 cells express this gene, thereby allowing migration in response to E- and P-selectins (6). We also observed increased expression of transcripts from genes encoding adhesion molecules such as thrombospondin (THBS)1.
Integrins and adhesion molecules.
The integrins and Ig superfamily adhesion molecules are important for stopping leukocyte rolling and mediating leukocyte aggregation and transendothelial migration (65). The migration of T cells during the pancreatic inflammatory response is integrin dependent; however, only vascular cell adhesion molecule (VCAM)1 gene (Vcam1) expression modulated significantly with progression to diabetes (Fig. 3).
Islet cell differentiation genes.
Elevated expression of the regenerating genes Reg3
, Reg3ß, and Reg3
was observed during insulitis in both BDC/N and BDC/N.sc (Fig. 3). These genes, first isolated from the rat (51), are IL-6 responsive and showed augmented expression upon inflammation (14). These genes are associated with protection from oxidative damage and may play a role in islet regeneration and islet cell homeostasis (44). Of particular note is a recent study suggesting that Reg3ß may act as a autoantigen in NOD mice and humans (20). Moreover, the prominence of the Reg gene family in the maintenance of islet homeostasis is underscored by the recent gene-targeted disruption of Reg3
, which exhibited a significant reduction in adult islet cell mass (58).
It is important to note that, with insulitis, Pax1, Pdx1, Neurog2, and other early ß-cell differentiation genes are either unaffected or are downmodulated (Fig. 3), suggesting that the differentiation of new ß-cells from pancreatic stem cells is highly unlikely or at least does not require alterations in these critical differentiation genes.
Cytokines and chemokines and their receptors.
Cytokines alter the local expression of chemokine and adhesion molecules to increase recruitment of specific lymphocyte populations. To our surprise, we could not detect the presence of the Th1-specific marker IFN-
in our analysis; however, IFN-
mRNA levels are generally quite low and therefore did not meet our expression cutoffs. Yet there is undeniable evidence that IFN-
is present, as established by IFN-
-responsive gene expression (Figs. 3 and 4 and Supplemental Table S1). Elevated IFN-
mRNA levels are readily observed, however, by real-time PCR (Fig. 5). Moreover, the IFN-
-driven expression of CXCL9 and CXCL10 are observed during the late stages of insulitis and diabetes seen in BDC/N.sc (Fig. 4A). Increased expression of CCL5 in BDC/N.sc (1.6-fold) is also observed. This is consistent with published data implicating CCL5 as a critical chemokine in T1DM (8).
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and TGF-ß3 and a number of inflammation-associated cytokine receptors, form the general cytokine mRNA expression pattern seen with late-stage insulitis and diabetes. The upregulation of the cytokine-related signaling molecule nuclear factor (NF)-IL-6 (Nfil6), also referred to as CCAAT/enhancer binding protein (C/EBP), in BDC/N.sc samples (2.4-fold) suggests that IL-6 plays an important role in T1DM pathogenesis. NF-IL-6 is a DNA binding protein and mediates IL-1-induced IL-6 transcription. Elevated levels of IL-6 have been reported in T1DM and are seen here (Fig. 4B). Downregulation of cytokines such as IL-1ß, IL-2, IL-3, IL-7, IL-11, and IL-13 was observed with the onset of late-stage insulitis (Fig. 4B). Taken as a whole, these data strongly suggest that the initial inflammatory response in T1DM is weakly polarized or represents a mixed Th1/Th2 response, which gradually morphs into a dominant Th1 response with late-stage insulitis.
Th1-specific genes in T1DM.
Where assessed in absolute terms or normalized to TCR levels, the Th1 differentiation genes such as Tbet, GADD45 members, Rac2, and Il12Rb2 are upregulated in BDC/N.sc mice but are largely absent in BDC/N mice, suggesting a molecular switch before onset of diabetes (Fig. 5 and Supplemental Table S1). T-bet is a transcription factor that plays a central role in the development of Th1 T cells (50). T-bet transactivates the IFN-
gene, induces IFN-
production when transduced into primary T cells, and redirects polarized Th2 cells into the Th1 pathway (50). GADD45ß is induced by TCR signaling in both naive and effector CD4+ T cells and required for the function and generation of Th1 cells (37). GADD45
(CR6/OIG37) is induced during T cell activation and is higher in Th1 cells than in Th2 effector cells (38). The small guanosine triphosphatase Rac2 is expressed selectively in mouse Th1 cells (34). The elevated expression of these Th1-specific genes in our mouse model clearly indicates a role for Th1 T cells in the spontaneous development of T1DM in the NOD mouse.
Complement components and inflammation.
Alternative complement pathway components such as C3 and C4 were upregulated (8.5- and 3.2-fold, respectively) during diabetes, in the absence of immunoglobulins, suggesting antibody-independent T cell-mediated inflammatory responses (Supplemental Table S2). Increased expression of Tnfr2 was observed during diabetes in BDC/N.sc. We also observed augmented transcripts for ceruloplasmin and metallothionein genes (2.6- and 2.7-fold, respectively) during diabetes. Ceruloplasmin or multicopper oxidase is an acute-phase responsive enzyme, and its increased expression here likely reflects greater oxidant stress (11).
High expression of Atf4, Atf5, and Hspa5 during insulitis in BDC2.5/N mice suggests ER stress. ER stress is known to occur in several pathophysiological states such as hypoxia. ATF4 is basally repressed in nonstressed cells. Under stress, ATF4 translation is derepressed through the phosphorylation of eIF2
. The role of ATF5 in islet function or maintenance is not known. ATF5 is expressed in the central nervous system, implicating its role in neuroendocrine as well as pancreatic endocrine development and function (5). The role for HSPA5 in T1DM is likewise unclear, although it is a stress response gene.
Kinetic analysis and gene expression validation via real-time PCR.
Independent verification of our microarray data is vital. Moreover, a dynamic study of these disease-associated genes is more likely to shed new mechanic insights into T1DM than simple static measures of expression. To these ends, we isolated high-quality pancreatic RNA from our mice, quantified mRNA expression using real-time PCR, and standardized expression to ß-actin. As shown in Fig. 5, we followed the expression of Tcrb, VCAM1, casp1, casp12, Gzmb, Il4, Ccl8, Tnfa, and a set of genes specific for Th1 population such as Ifng, Tbet, Cr6/Gadd45g, Il17, and Rac2. We observed a rapid increase in the expression levels for all of the above genes by 3 wk of age in BDC/N.sc mice. As for BDC/N and NOD mice, the expression levels were low at 3 wk compared with BDC/N.sc mice, thereby verifying our previous microarray data, but then underwent significant modulation with time. Although not all genes showed synchronicity in their modulation, there is a generalized trend of periodic expression modulation in these and other genes tested (Fig. 5 and data not shown). These data show that the insulitis in BDC/N and NOD mice is a dynamic waxing and waning process, suggesting that T1DM is a relapsing/remitting autoimmune disease much like multiple sclerosis.
In addition to real-time PCR analysis, we also analyzed the stage-specific expression of Reg genes, Reg3
, -ß, and -
, using semi-quantitative PCR, necessitated by the high homology in the Reg gene family that precluded real-time analysis (Fig. 6). The expression of Reg3
, Reg3ß, and Reg3
genes is clearly elevated in BDC2.5/N.sc and BDC/N pancreas as early as 12 wk of age, at the time coincident with the initiation of insulitis (33). Therefore, these genes appear to serve as excellent markers for insulitis. Expression of Reg3
above basal levels was not seen in NOD mice until 8 wk (Fig. 6A), at an age when insulitis begins in these animals. It remained at basal levels in N.sc mice throughout the entire assay period. Interestingly, these genes do not wax and wane, suggesting that the protection and repair response may be an ongoing event once infiltration ensues (Fig. 6B).
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-induced inflammation (55), as well as expression of superoxide dismutase and nitric oxide synthase genes (57). These findings are consistent with the observed changes in gene expression during insulitis, which showed marked increases in TNF-
- and IL-1/IL-6-induced inflammatory genes and increased levels of superoxide dismutase and synthase genes and hypoxia- and stress-induced genes. This suggests that the initial phase of insulitis is controlled to a great degree by the localized liberation of TNF-
and the recruitment of leukocytes via TNF-
and IL-1/IL-6-induced chemokines.
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To analyze whether the islet environment is hypoxic, as predicted by GenomeTraFaC and CisMols during insulitis, we conducted experiments using EF-5. EF-5 covalently binds to cells and tissues in a hypoxic state; this binding is easily revealed using an anti EF-5 monoclonal antibody (18). Both BDC/N and BDC/N.sc mice (3 wk old) were given intraperitoneal injections of EF-5 in saline; 1216 h later, the mice were killed and tissues were sampled and stained for evidence of localized hypoxia. We found clear evidence of a highly hypoxic local environment in and around infiltrated islets in BDC/N mice (Fig. 9). No hypoxia was observed in the liver and spleen tissue sections from BDC/N. Interestingly, pancreatic sections from BDC/N.sc showed little if any regions of localized hypoxia (data not shown); however, at this point in time, BDC/N.sc mice had little intact islet mass and markedly reduced inflammation associated with end-stage disease, consistent with our predicted analysis using CisMols.
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| DISCUSSION |
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-driven process; 2) insulitis caused the upregulation of a family of genes associated with end-stage ß-cell maturation and repair, the Reg gene family; 3) insulitis is a mixed Th1/Th2 infiltration; 4) late-stage insulitis and overt diabetes correlate with a focused Th1 T cell response with unregulated IL-17; 5) IFN-
-responsive genes play a critical role in diabetes pathogenesis; 6) insulitis correlates with the usage of the Ets family of transcription factors, whereas diabetes correlates with the usage of C/EBP and Nkx2 transcription factors; and 7) islet environment is highly hypoxic during rapid insulitis. THBS1, a glycoprotein released from platelet granules in response to thrombin stimulation (2), is a transient component of the extracellular matrix known to promote chemotaxis of leukocytes to inflammatory sites. It has been shown that THBS1 provides a costimulatory signal, necessary for the activation of autoreactive T cells (59). The specific expression of THBS1 in NOD T1DM is consistent with the observed upregulation of THBS1 in vessel walls of diabetic Zucker rats and is a direct response of vascular cells to glucose (48). In addition, we observed that high glucose levels upregulate THBS1-dependent TGF-ß activation by altering cGMP-dependent protein kinase activity, itself regulated by a decreased nitric oxide signaling (see Fig. 4B). A role for THBS1 has not been previously reported for NOD diabetes.
Consistent with our observation, the adoptive transfer of diabetes in the NOD mouse can be delayed by treatment with anti-VCAM-1 (24, 56). Therefore, the blockade of VCAM-1 may represent a potential therapeutic treatment for T1DM.
As for chemokines, CCL5 is known to have a number of profound consequences on T cells, including costimulation of cytokine release and T cell proliferation. Similar results were observed by Eaves et al. (15), using congenic strains and microarray gene expression analysis, in NOD mice. CCL5 levels are higher in a wide range of inflammatory disorders and pathologies (19) including pancreatic infiltrates that promote rapid destruction of the insulin-producing ß-cells in the NOD mouse (8). Interestingly, CCL5 maps to the known diabetes control locus, IDD4, which plays a role in modulating the tempo and severity of insulitis in the NOD mouse (61). It has been reported that a pancreatic Th1 cytokine environment greatly accelerates the recruitment of islet-specific CD4+ T cells to the pancreas, especially in the presence of IFN-
, suggesting that the rapid onset of diabetes in the BDC/N.sc mouse is in part due to enhanced levels of IFN-
-responsive chemokines (22).
IL-17 is a proinflammatory cytokine, originally cloned from herpes virus (66). It is produced by activated and memory CD4+ T cells, particularly Th1 cells (1). IL-17 has pleiotropic activities including induction of TNF-
, IL-1, and various other cytokines, chemokines, and adhesion molecules that play important roles in various inflammatory responses (27). In rheumatoid arthritis, IL-17 acts in association with TNF-
to destroy cartilage; in this respect, IL-17 acts as an effector cytokine (60). Its exact role in T1DM pathogenesis has not previously been explored. Our identification of it here is therefore intriguing. Its presence here is consistent with its action as an effector cytokine, perhaps under the control of IL-12 and IL-23, both of which are present during this period and are known to regulate IL-17 expression (3).
The low level and periodic modulation of Il17 observed in the BDC/N mice is consistent with a relapsing/remitting course of insulitis. Treatment of N.sc recipient mice of activated BDC2.5 T cells with anti-IL-17 antibody did not prevent the onset of diabetes significantly (data not shown), suggesting that activated effector T cells act in an IL-17-dependent manner. However, what is not yet clear is whether IL-17 inhibition can alter the de novo activation of diabetogenic T cells, but this seems unlikely given the phenotype of IL-17-deficient mice, as IL-17 was mainly seen as an effector cytokine (43). Further studies are required to establish the importance of this particular cytokine in T1DM. At present, IL-17 seems to represent an important new marker for progression toward ß-cell destruction and diabetes onset that is reliably detectable in peripheral blood of NOD mice (Fig. 7).
Metallothionein is associated with stress responses; its ectopic overexpression in pancreatic ß-cells protects islets from hypoxia, providing broad resistance to oxidative stress by scavenging most kinds of reactive oxygen species and by reduced nitric oxide-induced ß-cell death (35). The influence of metallothionein upregulation is observed in multiple sclerotic lesions as well (36) . Metallothionein is likewise modulated in experimental autoimmune encephalitis (EAE), where metallothioneine deficiency results in the development of more clinically severe EAE (46).
The recent observation that the Reg3ß serves as an autoantigen (20) suggests that the Reg gene family may drive the observed "antigenic spread" seen in T1DM by providing new antigenic substrates for autoreactive T cell recognition. We propose then that islet infiltration is initiated by Th2 or mixed T cell subsets; this retrograde inflammation induces ß-cell repair/protection response in the absence of additional de novo differentiation of ß-cells from pancreatic stem cells (as evidenced by the lack of expression of early ß-cell differentiation genes and by the lack of proapoptosis gene expression). This in turn produces a state of "reactive homeostasis," where ß-cell damage and repair are in equilibrium. However, once a dominant Th1 response results and the pace of ß-cell death quickens, cellular repair is insufficient to maintain ß-cell mass, and frank diabetes ensues.
To date, studies on differential expression of genes in T1DM using cDNA microarrays have taken advantage of pancreatic ß-cell lines, as they provide an attractive source of starting material for analysis and in vitro manipulation (9, 67). In addition, these cell lines are rather homogeneous, which provides yet another distinct advantage for expression studies. However, these cell lines cannot model the complexity of in vivo interactions among islets, exocrine pancreas, and the host immune response seen in T1DM. Other approaches include the use of NOD mice spleens to define key checkpoints for T1DM (16). Our data, on the other hand, provide a more global survey of gene modulation in vivo over a 20-wk period and indicate that insulitis is not a progressively increasing process but a relapsing and remitting one. Genes examined in our experiments should now afford the immunology community a "first pass" opportunity to link specific phenotypes with known genetic linkages and provide a framework within which to measure how known induced and spontaneous alterations in the NOD perturb specific genetic pathways implicated in the disease process. In conclusion, we have analyzed and verified the differential expression of genes during the evolution of T1DM pathogenesis in the NOD and in genetically altered BDC/N and BDC2.5/N.sc mice using cDNA microarrays. Microarray analysis of large-scale gene expression provides a versatile tool to open new avenues of research and simultaneously provides for the exciting possibilities for the identification of novel drug targets in T1DM that may facilitate the noninvasive staging and treatment of prediabetic individuals.
| GRANTS |
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| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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Address for reprint requests and other correspondence: J. D. Katz, Cincinnati Childrens Hospital Research Foundation and College of Medicine, Univ. of Cincinnati, 3333 Burnet Ave., Cincinnati, OH 45229-3039 (E-mail: jonathan.katz{at}cchmc.org).
10.1152/physiolgenomics.00173.2004.
1 The Supplemental Material for this article (Supplemental Tables S1 and S2 and Supplemental Fig. S1) is available online at http://physiolgenomics.physiology.org/cgi/content/full/00173.2004/DC1. ![]()
| REFERENCES |
|---|
|
|
|---|
B-dependent genes in primary rat pancreatic ß-cells. J Biol Chem 276: 4887948886, 2001.
(HIF-2
) and Ets-1 in the transcriptional activation of vascular endothelial growth factor receptor-2 (Flk-1). J Biol Chem 278: 75207530, 2003.
4-integrin receptors in vivo. Inhibition of autoimmune diabetes in an adoptive transfer model in nonobese diabetic mice. J Immunol 155: 938946, 1995.[Abstract]
, by human macrophages. J Immunol 160: 35133521, 1998.
mediates the activation of the p38 and JNK MAP kinase pathways and cytokine production in effector TH1 cells. Immunity 14: 583590, 2001.[CrossRef][Web of Science][Medline]
, RegIIIß, RegIII
. Gene 185: 159168, 1997.[CrossRef][Web of Science][Medline]
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R. Spolski, M. Kashyap, C. Robinson, Z. Yu, and W. J. Leonard IL-21 signaling is critical for the development of type I diabetes in the NOD mouse PNAS, September 16, 2008; 105(37): 14028 - 14033. [Abstract] [Full Text] [PDF] |
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K. Venkatachalam, S. Mummidi, D. M. Cortez, S. D. Prabhu, A. J. Valente, and B. Chandrasekar Resveratrol inhibits high glucose-induced PI3K/Akt/ERK-dependent interleukin-17 expression in primary mouse cardiac fibroblasts Am J Physiol Heart Circ Physiol, May 1, 2008; 294(5): H2078 - H2087. [Abstract] [Full Text] [PDF] |
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R. Geoffrey, S. Jia, A. E. Kwitek, J. Woodliff, S. Ghosh, A. Lernmark, X. Wang, and M. J. Hessner Evidence of a Functional Role for Mast Cells in the Development of Type 1 Diabetes Mellitus in the BioBreeding Rat J. Immunol., November 15, 2006; 177(10): 7275 - 7286. [Abstract] [Full Text] [PDF] |
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Y. Komiyama, S. Nakae, T. Matsuki, A. Nambu, H. Ishigame, S. Kakuta, K. Sudo, and Y. Iwakura IL-17 Plays an Important Role in the Development of Experimental Autoimmune Encephalomyelitis J. Immunol., July 1, 2006; 177(1): 566 - 573. [Abstract] [Full Text] [PDF] |
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M. Liang and B. Ventura Physiological genomics in PG and beyond: October to December 2005 Physiol Genomics, December 14, 2005; 24(1): 1 - 3. [Full Text] [PDF] |
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