Expression profiling in pancreas during the acute phase of pancreatitis using cDNA microarrays

Factors released by the tumor far microenvironment are decisive for pancreatic adenocarcinoma development and progression

The REG3β protein was identified more than 2 decades ago, but its role in PDAC development was only recently reported. In Pancreatic Ductal Adenocarcinoma (PDAC), REG3β protein is expressed and released by the far microenvironment, which is situated out of the tumor, at the periphery of the tumor mass, and is part of the healthy peri-tumoral region. This compartment is completely unrelated to the classical microenvironment that corresponds to the intra-tumoral stoma. Clinically relevant, the far microenvironment, and the factors released by it, could be novel and original therapeutic targets for treating patients with a PDAC. In this way we recently demonstrated that REG3β is an essential soluble factor necessary for PDAC development which is able to stimulate several simultaneous pro-tumoral mechanisms. We also find that secreted REG3β boosts interactions between epithelial cells and immune cells by activating the CXCL12/CXCR4 signaling cascade, which facilitates tumor escape through evasion of immune surveillance, and promotes metastasis. In addition, REG3β interfere the intercellular communication inside the tumor mediated by extracellular vesicles, resulting in relevant changes in macrophage phenotype or tumor cell migration. Therefore, we are proposing to call as near microenvironment to the classical microenvironment that is constituted by fibroblasts, inflammatory cells and fibers and located into the tumor, and as far microenvironment, which is constituted by the parenchymal non transformed cells located at the periphery of the tumor mass.

Microarray analysis of pancreatic gene expression during biotin repletion in biotin-deficient rats

Biotin is a B vitamin involved in multiple metabolic pathways. In humans, biotin deficiency is relatively rare but can cause dermatitis, alopecia, and perosis. Low biotin levels occur in individuals with type-2 diabetes, and supplementation with biotin plus chromium may improve blood sugar control. The acute effect on pancreatic gene expression of biotin repletion following chronic deficiency is unclear, therefore we induced biotin deficiency in adult male rats by feeding them a 20% raw egg white diet for 6 weeks. Animals were then randomized into 2 groups: one group received a single biotin supplement and returned to normal chow lacking egg white, while the second group remained on the depletion diet. After 1 week, pancreata were removed from biotin-deficient (BD) and biotin-repleted (BR) animals and RNA was isolated for microarray analysis. Biotin depletion altered gene expression in a manner indicative of inflammation, fibrosis, and defective pancreatic function. Conversely, biotin repletion activated numerous repair and anti-inflammatory pathways, reduced fibrotic gene expression, and induced multiple genes involved in pancreatic endocrine and exocrine function. A subset of the results was confirmed by quantitative real-time PCR analysis, as well as by treatment of pancreatic AR42J cells with biotin. The results indicate that biotin repletion, even after lengthy deficiency, results in the rapid induction of repair processes in the pancreas.

Epigenetic reprogramming in Mist1(-/-) mice predicts the molecular response to cerulein-induced pancreatitis

Gene expression is affected by modifications to histone core proteins within chromatin. Changes in these modifications, or epigenetic reprogramming, can dictate cell fate and promote susceptibility to disease. The goal of this study was to determine the extent of epigenetic reprogramming in response to chronic stress that occurs following ablation of MIST1 (Mist1^−/−), which is repressed in pancreatic disease. Chromatin immunoprecipitation for trimethylation of lysine residue 4 on histone 3 (H3K4Me3) in purified acinar cells from wild type and Mist1^−/− mice was followed by Next Generation sequencing (ChIP-seq) or ChIP-qPCR. H3K4Me3-enriched genes were assessed for expression by qRT-PCR in pancreatic tissue before and after induction of cerulein-induced pancreatitis. While most of H3K4Me3-enrichment is restricted to transcriptional start sites, >25% of enrichment sites are found within, downstream or between annotated genes. Less than 10% of these sites were altered in Mist1^−/− acini, with most changes in H3K4Me3 enrichment not reflecting altered gene expression. Ingenuity Pathway Analysis of genes differentially-enriched for H3K4Me3 revealed an association with pancreatitis and pancreatic ductal adenocarcinoma in Mist1^−/− tissue. Most of these genes were not differentially expressed but several were readily induced by acute experimental pancreatitis, with significantly increased expression in Mist1^−/− tissue relative to wild type mice. We suggest that the chronic cell stress observed in the absence of MIST1 results in epigenetic reprogramming of genes involved in promoting pancreatitis to a poised state, thereby increasing the sensitivity to events that promote disease.

Systemic differential gene regulation of the inter-α-trypsin inhibitor family in acute necrotizing pancreatitis in mice

BACKGROUND

Therapy for systemic complications in severe necrotizing pancreatitis remains symptomatic owing to the unavailability of more specific therapeutic targets. We investigated the differential gene expression in typically affected organs in a mouse model of severe necrotizing pancreatitis.

METHODS

Acute necrotizing pancreatitis was induced in mice by retrograde infusion of taurocholate into the common bile duct. Microarray hybridization was subsequently performed with mRNA isolated from the spleen, liver, intestine, and lungs. Additionally, quantitative real-time polymerase chain reaction was performed to confirm the microarray results.

RESULTS

Severe necrotizing pancreatitis induced widespread changes in gene expression, affecting 27.20% of the genes tested in the spleen and 29.07% in the liver. Fewer genes were differentially regulated in the intestine (10.28%) and the lungs (10.75%). Only 10 genes were found to be upregulated in all 4 organs using microarray analysis. This upregulation in all organs was confirmed by quantitative real-time polymerase chain reaction for only 3 molecules. These molecules were lipocalin 2, insulin-like growth factor binding protein 1, and CD14. Additionally we observed significantly aberrant gene regulation of inter-α-trypsin inhibitor family members in several organs.

CONCLUSIONS

Differential gene regulation in severe necrotizing pancreatitis is far more organ specific than anticipated, with only 3 molecules uniformly regulated systemically. The inter-α-trypsin inhibitor family of molecules appears to play a crucial biologic role in the systemic inflammatory response in acute pancreatitis. Finally, owing to its regulation and function, α1-microglobulin (or bikunin) may be a suitable predictive marker of the systemic inflammatory response syndrome in acute pancreatitis.

Redox signaling and histone acetylation in acute pancreatitis

Histone acetylation via CBP/p300 coordinates the expression of proinflammatory cytokines in the activation phase of inflammation, particularly through mitogen-activated protein kinases (MAPKs), nuclear factor-κB (NF-κB), and signal transducers and activators of transcription (STAT) pathways. In contrast, histone deacetylases (HDACs) and protein phosphatases are mainly involved in the attenuation phase of inflammation. The role of reactive oxygen species (ROS) in the inflammatory cascade is much more important than expected. Mitochondrial ROS act as signal-transducing molecules that trigger proinflammatory cytokine production via inflammasome-independent and inflammasome-dependent pathways. The major source of ROS in acute inflammation seems to be NADPH oxidases, whereas NF-κB, protein phosphatases, and HDACs are the major targets of ROS and redox signaling in this process. There is a cross-talk between oxidative stress and proinflammatory cytokines through serine/threonine protein phosphatases, tyrosine protein phosphatases, and MAPKs that greatly contributes to amplification of the uncontrolled inflammatory cascade and tissue injury in acute pancreatitis. Chromatin remodeling during induction of proinflammatory genes would depend primarily on phosphorylation of transcription factors and their binding to gene promoters together with recruitment of histone acetyltransferases. PP2A should be considered a key modulator of the inflammatory cascade in acute pancreatitis through the ERK/NF-κB pathway and histone acetylation.

Proteomic analysis of a rat pancreatic stellate cell line using liquid chromatography tandem mass spectrometry (LC-MS/MS)

Pancreatic stellate cells (PaSC) are emerging as key mediators in chronic pancreatitis and pancreatic cancer pathogenesis. Proteins regulating the biomolecular pathways involved in the conversion of quiescent to activated PaSC may have a significant influence on the development of chronic pancreatitis. We aim to compare differentially expressed proteins in activated and serum-starved non-proliferating PaSC using a mass spectrometry-based proteomics strategy. We cultured an immortalized rat PaSC cell line in media supplemented with 10% fetal bovine serum and in serum-free media. Using gel-based mass spectrometry (GeLC-MS/MS), we identified nearly 1500 proteins. Qualitative and quantitative proteomic analysis revealed several hundred proteins as differentially abundant between the two cell states. Proteins of greater abundance in activated PaSC included isoforms of actin (e.g., smooth muscle actin) and ribosomal proteins. Conversely, proteins more abundant in non-proliferating PaSC than in activated PaSC included signaling proteins MAP kinase 3 and Ras-related proteins. In addition, we have determined the molecular functions and biological pathways for these proteins. We are confident that the application of mass spectrometry-based strategies, such as that described herein, to investigate specific proteins in PaSC may lead to a better understanding of the molecular mechanisms involved in pancreatic diseases, such as chronic pancreatitis.

Absence of tumor suppressor tumor protein 53-induced nuclear protein 1 (TP53INP1) sensitizes mouse thymocytes and embryonic fibroblasts to redox-driven apoptosis

The p53-transcriptional target TP53INP1 is a potent stress-response protein promoting p53 activity. We previously showed that ectopic overexpression of TP53INP1 facilitates cell cycle arrest as well as cell death. Here we report a study investigating cell death in mice deficient for TP53INP1. Surprisingly, we found enhanced stress-induced apoptosis in TP53INP1-deficient cells. This observation is underpinned in different cell types in vivo (thymocytes) and in vitro (thymocytes and MEFs), following different types of injury inducing either p53-dependent or -independent cell death. Nevertheless, absence of TP53INP1 is unable to overcome impaired cell death of p53-deficient thymocytes. Stress-induced ROS production is enhanced in the absence of TP53INP1, and antioxidant NAC complementation abolishes increased sensitivity to apoptosis of TP53INP1-deficient cells. Furthermore, antioxidant defenses are defective in TP53INP1-deficient mice in correlation with ROS dysregulation. Finally, we show that autophagy is reduced in TP53INP1-deficient cells both at the basal level and upon stress. Altogether, these data show that impaired ROS regulation in TP53INP1-deficient cells is responsible for their sensitivity to induced apoptosis. In addition, they suggest that this sensitivity could rely on a defect of autophagy. Therefore, these data emphasize the role of TP53INP1 in protection against cell injury.

Risk assessment in acute pancreatitis

BACKGROUND

Acute pancreatitis has a variable natural history and in a proportion of patients is associated with severe complications and a significant risk of death. The various tools available for risk assessment in acute pancreatitis are reviewed.

METHODS

Relevant medical literature from PubMed, Ovid, Embase, Web of Science and The Cochrane Library websites to May 2008 was reviewed.

RESULTS AND CONCLUSION

Over the past 30 years several scoring systems have been developed to predict the severity of acute pancreatitis in the first 48-72 h. Biochemical and immunological markers, imaging modalities and novel predictive models may help identify patients at high risk of complications or death. Recently, there has been a recognition of the importance of the systemic inflammatory response syndrome and organ dysfunction.

Clusterin is protective in pancreatitis through anti-apoptotic and anti-inflammatory properties

Clusterin is overexpressed in pancreas during the acute phase of pancreatitis. We intended to clarify the role of clusterin expression in stressed exocrine pancreas. We performed in vitro experiments in transfected AR4-2J cells with modified expression levels of clusterin and in vivo studies in clusterin-deficient mice. AR4-2J cells were exposed to agents mimicking cell-stress during pancreatitis (cerulein, hydrogen peroxide, staurosporine or lysophosphatidylcholine). Clusterin-overexpressing AR4-2J cells showed higher viability after cell stress and accordingly reduced rates of apoptosis and lessened caspase-3 activation. Blockage of endogenous clusterin expression reduced viability and enhanced apoptosis. Presence of clusterin reduced NF-kappaB activation and expression of the NF-kappaB target genes TNF-alpha and MOB-1 under cell stress. Clusterin-deficient mice showed a more severe course of acute experimental pancreatitis with enhanced rates of apoptosis and inflammatory cell infiltration. We concluded that clusterin was protective during inflammation of exocrine pancreas because of its anti-apoptotic and anti-inflammatory functions.

Colitis and colitis-associated cancer are exacerbated in mice deficient for tumor protein 53-induced nuclear protein 1

Tumor protein 53-induced nuclear protein 1 (TP53INP1) is an antiproliferative and proapoptotic protein involved in cell stress response. To address its physiological roles in colorectal cancer and colitis, we generated and tested the susceptibility of Trp53inp1-deficient mice to the development of colorectal tumors induced by injection of the carcinogen azoxymethane followed by dextran sulfate sodium (DSS)-induced chronic colitis. Trp53inp1-deficient mice showed an increased incidence and multiplicity of tumors compared to those of wild-type (WT) mice. Furthermore, acute colitis induced by DSS treatment was more severe in Trp53inp1-deficient mice than in WT mice. Treatment with the antioxidant N-acetylcysteine prevented colitis and colitis-associated tumorigenesis more efficiently in WT mice than in Trp53inp1-deficient mice, suggesting a higher oxidative load in the latter. Consistently, we demonstrated by electron spin resonance and spin trapping that colons derived from deficient mice produced more free radicals than those of the WT during colitis and that the basal blood level of the antioxidant ascorbate was decreased in Trp53inp1-deficient mice. Collectively, these results indicate that the oxidative load is higher in Trp53inp1-deficient mice than in WT mice, generating a more-severe DSS-induced colitis, which favors development of colorectal tumors in Trp53inp1-deficient mice. Therefore, TP53INP1 is a potential target for the prevention of colorectal cancer in patients with inflammatory bowel disease.

Caerulin-induced pancreatitis in rats: Histological and genetic expression changes from acute phase to recuperation

AIM: To study the histological and pancreatitis-associated protein mRNA accumulation changes of pancreas from acute phase of caerulin-induced pancreatitis to recuperation in rats.

METHODS: Acute pancreatitis was induced by caerulein in male Wistar rats and followed up for 90 d by histological and mRNA analyses of pancreas. Pancreases were dissected at 0, 9, 24 h and 3, 5, 15, 30, 60, 90 d post-induction. Edema (E), polymorphonuclear neutrophil (PMN) infiltration, cytoplasmic vacuolization (V), zymogen granule depletion (ZD) and acinar disorganization (AD) were microscopically evaluated. Accumulation of pancreatitis-associated protein (PAP) and L13A mRNAs were quantified by real-time PCR.

RESULTS: The main histological changes appeared at 9 h post-induction for PMN infiltration and cytoplasmic V, while at 24 h and 3 d for E and ZD, respectively. All the parameters were recovered after 5 d, except for ZD which delayed more than 30 d. The main AD was observed after 15 d and values returned to normal after 30 d. Similarly to histological changes, accumulation of the PAP mRNA was increased at 9 h with the highest accumulation at 24 h and differences disappeared after 5 d.

CONCLUSION: From the acute phase to recuperation of pancreatitis, regeneration and re-differentiation of pancreas occur and PAP expression is exclusively an acute response of pancreatitis.

TP53INP1 is a novel p73 target gene that induces cell cycle arrest and cell death by modulating p73 transcriptional activity

TP53INP1 is an alternatively spliced gene encoding two nuclear protein isoforms (TP53INP1alpha and TP53INP1beta), whose transcription is activated by p53. When overexpressed, both isoforms induce cell cycle arrest in G1 and enhance p53-mediated apoptosis. TP53INP1s also interact with the p53 gene and regulate p53 transcriptional activity. We report here that TP53INP1 expression is induced during experimental acute pancreatitis in p53-/- mice and in cisplatin-treated p53-/- mouse embryo fibroblasts (MEFs). We demonstrate that ectopic expression of p73, a p53 homologue, leads to TP53INP1 induction in p53-deficient cells. In turn, TP53INP1s alters the transactivation capacity of p73 on several p53-target genes, including TP53INP1 itself, demonstrating a functional association between p73 and TP53INP1s. Also, when overexpressed in p53-deficient cells, TP53INP1s inhibit cell growth and promote cell death as assessed by cell cycle analysis and colony formation assays. Finally, we show that TP53INP1s potentiate the capacity of p73 to inhibit cell growth, that effect being prevented when the p53 mutant R175H is expressed or when p73 expression is blocked by a siRNA. These results suggest that TP53INP1s are functionally associated with p73 to regulate cell cycle progression and apoptosis, independently from p53.

Modeling of SEB-induced host gene expression to correlate in vitro to in vivo responses

Detection of exposure to biological threat agents has relied on ever more sensitive methods for pathogen identification, but that usually requires pathogen proliferation to dangerous, near untreatable levels. Recent events have demonstrated that assessing exposure to a biological threat agent well in advance of onset of illness or at various stages post-exposure is invaluable among the diagnostic options. There is an urgent need for better diagnostic tools that will be sensitive, rapid, and unambiguous. Since human clinical cases of illness induced by biothreat agents are, fortunately, rare, use of animal models that closely mimic the human illness is the only in vivo option. Such studies can be very difficult and expensive; therefore, maximizing the information obtained from in vitro exposures to peripheral blood mononuclear cells (PBMCs) provide an opportunity to investigate dose/time variability in host responses. In our quest to study staphylococcal enterotoxin B (SEB) induced host gene expression patterns, we addressed two core issues using microarray analysis and predictive modeling. Our first objective was to determine gene expression patterns in human PBMCs exposed to SEB in vitro. Second, we compared the in vitro data with host responses gene expression patterns in vivo using PBMCs from an animal model of SEB intoxication that closely replicates the progression of illness in humans. We used cDNA microarrays to study global gene expression patterns in piglets intoxicated with SEB. We applied a supervised learning method for class prediction based on the k-nearest neighbor algorithm for the data obtained in piglets exposed to SEB in vivo against a training data set. This data set included gene expression profiles derived from in vitro exposures to eight different pathogens (Bacillus anthracis, Yersinia pestis, Brucella melitensis, SEB, cholera toxin, Clostridium botulinum toxin A, Venezuelan equine encephalitis, and Dengue-2) in PBMCs. We found that despite differences in gene expression profiles between in vitro and in vivo systems, there exists a subset of genes that show correlations between in vitro and in vivo exposures, which can be used as a predictor of exposure to SEB in vivo.

Genetic variations in peripheral blood mononuclear cells in piglets used as an animal model for staphylococcal enterotoxin exposures

We have used piglets as an animal model for studying the toxic effects of staphylococcal enterotoxins (SEs). Piglets are easy to handle, easy to carry out vital measurements, inexpensive, and more importantly, express remarkably similar pathological symptoms and responses to SE intoxication as humans at comparable doses. Microarray analyses are used to study the effect of many infections on gene expression profile in peripheral blood mononuclear cells. This high throughput application offers detailed depiction of alteration at the molecular levels. When using high throughput gene expression analysis, there is a high possibility of finding genes that vary normally in the tissues under study. It is necessary to verify genes that are normally differentially expressed between piglets. To evaluate the normal physiological variation in gene expression in vivo in piglets, we used cDNA microarray to measure gene expression levels in peripheral blood mononuclear cells from 10 normal Yorkshire piglets. We used analysis of variance to determine genes that showed statistically significant variations across piglets. Out of 1185 genes, 19 (1.6%) genes revealed statistically significant variance between RNA samples. Some of these varying genes are involved in stress response, immune response, and transcription. This study facilitates the characterization of gene expression base line needed for meaningful interpretation of microarray data.

Cloning of IP15, a pancreatitis-induced gene whose expression inhibits cell growth

We describe the cloning and expression of the mouse gene interferon-inducible-protein 15 (IP15), whose activation is related to the acute phase of experimental pancreatitis. Analysis of its structure indicates that it encodes a putative transmembrane protein of 137 amino acids. This gene contains a predicted IFN-stimulable-response element. In vivo studies showed that IP15 is strongly activated in pancreas early during caerulein-induced pancreatitis. In situ hybridization of IP15 mRNA showed that its expression is restricted to acinar cells. IP15 was also induced in pancreas under systemic-lipopolysaccharide treatment and in intestine under Salmonella infection. In vitro studies using NIH3T3 fibroblasts showed that IP15 is induced by IFN-alpha. Growth rate was significantly lower in cells transfected with pcDNA4/IP15 plasmid. In addition, cells expressing IP15 showed less capacity to develop colonies after antibiotic selection. In conclusion, we identified a new interferon-inducible gene that is activated early in pancreas with pancreatitis and whose expression inhibits cell growth.

Expression of the stress-associated protein p8 is a requisite for tumor development

We identified a new gene, called p8, because its expression was strongly induced during the acute phase of pancreatitis. Further experiments have shown that p8 mRNA is activated in response to several stresses and that its activation is not restricted to pancreatic cells. p8 is a nuclear protein and biochemical and biophysical studies have shown that p8 was very similar in many structural aspects to the HMG proteins, although sharing only low amino acid sequence homology. Also, p8 was found overexpressed in many human cancers. Therefore, we wondered whether the p8-mediated response to cellular stress was necessary for tumor establishment. Subcutaneous or intraperitoneal injections of transformed p8-expressing fibroblasts led to tumor formation in nude mice, but no tumor was observed with transformed p8-deficient cells. Restoring p8 expression in transformed p8-deficient fibroblasts led to tumor formation, demonstrating that p8 expression is crucial for tumor development and suggesting that the stress-response mechanisms governed by p8 are required for tumor establishment.

Pancreatic gene expression during the initiation of acute pancreatitis: identification of EGR-1 as a key regulator

We hypothesized that genes expressed in pancreatic acinar cells during the initiation of acute pancreatitis determine the severity of the disease. Therefore, we utilized microarrays to identify those genes commonly induced in rat pancreatic acinar cells within 1-4 h in two in vivo models, caerulein and taurocholate administration. This strategy yielded 51 known genes representing a complex array of molecules, including those that are likely to either reduce or increase the severity of the disease. Novel genes identified in the current study included ATF3, BRF1, C/EBPbeta, CGRP, EGR-1, ephrinA1, villin2, ferredoxin, latexin, lipocalin, MKP-1, NGFI-B, RhoA, tissue factor (TF), and syndecan. To validate these microarray results, the role of EGR-1 was further investigated using quantitative RT-PCR, Western blotting, and immunocytochemistry. EGR-1 expression occurred within acinar cells and correlated with the development of caerulein-induced acute pancreatitis in rats. Furthermore, the levels of the inflammation-related genes MCP-1, PAI, TF, IL-6, and ICAM-1 and the extent of lung inflammation were reduced during the initiation of caerulein-induced acute pancreatitis in EGR-1-deficient mice. Thus this study identified EGR-1 and several other novel genes likely to be important in the development and severity of acute pancreatitis.

Genetic factors in pancreatitis

A number of genetic mutations have recently been identified that appear to be important in the development of pancreatitis. Point mutations in the cationic trypsinogen gene are capable of initiating pancreatitis. These mutations also provide important insights into the pathophysiology of acute pancreatitis and into potential connections between acute and chronic pancreatitis. Mutations in the genes encoding for the pancreatic secretory trypsin inhibitor and the cystic fibrosis transmembrane conductance regulator more likely work in concert with other genes and environmental factors in affecting disease susceptibility. Although the subject so far has received only a limited amount of study, genetic polymorphisms in a wide range of genes relating to pancreatic function and to regulation of inflammation are likely to play major roles in determining each individual's susceptibility to developing pancreatitis, and its severity if it does develop.

The family of IL-10-related cytokines and their receptors: related, but to what extent?

Five novel cytokines (IL-19, IL-20, IL-22 (IL-TIF), IL-24 (human MDA-7, mouse FISP, rat C49A/Mob-5), and IL-26 (AK155)) demonstrating limited primary sequence identity and probable structural homology to IL-10 have been identified. These cellular cytokines, as well as several cytokines encoded in viral genomes (viral cytokines), form a family of IL-10-related cytokines or the IL-10 family. These cytokines share not only homology but also receptor subunits and perhaps activities. Receptors for these cytokines belong to the class II cytokine receptor family. The receptors are IL-10R2 (CRF2-4), IL-22R1 (CRF2-9), IL-22BP (CRF2-10), IL-20R1 (CRF2-8) and IL-20R2 (CRF2-11). Biological activities of these cytokines, receptor utilization and signaling, as well as expression patterns for cytokines and their receptors are summarized. Although data indicate that these cytokines are involved in regulation of inflammatory and immune responses, their major functions remain to be discovered.

Acinar cells of the pancreas are a target of interleukin-22

Interleukin-22 (IL-22) (also reported as IL-10-related T cell-derived inducible factor, IL-TIF) is a recently identified cytokine found to signal through a receptor comprising the class II cytokine receptor family members IL-10Rbeta/CRF2-4 and IL-22R. Previous work has established that IL-10Rbeta, also a component of the IL10R complex, exhibits a broad distribution of mRNA expression. Here, we observe that IL-22R exhibits a restricted expression pattern, with highest levels of mRNA expression in pancreas and detectable expression in multiple other tissues, particularly liver, small intestine, colon, and kidney. We find that isolated primary pancreatic acinar cells and the acinar cell line 266-6 respond to IL-22 with activation of Stat3 and changes in gene transcription. IL-22 mediates robust induction of mRNA for pancreatitis-associated protein (PAP1)/Reg2 and osteopontin (OPN). PAP1 is a secreted protein related to the Reg family of trophic factors and was initially characterized as a protein elevated in pancreatitis. In vivo injection of IL-22 resulted in rapid induction of PAP1 in pancreas, a response not observed in mice deficient in IL-10Rbeta. These results support the conclusion that IL-10Rbeta is a required common component of both the IL-10 and IL-22 receptors and suggest that IL-22 may play a role in the immune response in pancreas.

Molecular and functional characterization of the stress-induced protein (SIP) gene and its two transcripts generated by alternative splicing. SIP induced by stress and promotes cell death

We have used a quantitative fluorescent cDNA microarray hybridization approach to identify pancreatic genes induced by the cellular stress promoted by acute pancreatitis in the mouse. We report the cloning and characterization of one of them that encodes the stress-induced proteins (SIP). The mouse SIP gene is organized into five exons and expands over approximately 20 kilobase pairs. Exon 4 (38 base pairs) is alternatively spliced to generate two transcripts. Northern blot and in situ hybridization showed that both SIP mRNAs are rapidly and strongly induced in acinar cells of the pancreas with acute pancreatitis. They are also constitutively expressed in several other tissues, although with different ratios. They encode proteins of 18 and 27 kDa (SIP(18) and SIP(27)). SIP(27) is identical to the thymus-expressed acidic protein (TEAP) protein, formerly described as a thymus-specific protein. Expression of the SIP(18) and SIP(27)/EGFP or V5 fusion proteins showed that both are nuclear factors. We monitored SIP expression in NIH3T3 cells submitted to various stress agents. UV stress, base damaging, mutagenic stress, ethanol, heat shock, and oxidative stress induced the concomitant expression of SIP(18) and SIP(27) mRNAs. Finally, transient transfection of SIP(18) and SIP(27) expression plasmids induced death by apoptosis in COS7 cells as measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining. In conclusion, the SIP gene is an important element of cellular stress response. It is expressed in many tissues and induced by a variety of stress agents affecting many cellular pathways. SIP generates, by alternative splicing, two nuclear proteins that can promote cell death by apoptosis.

Project normal: defining normal variance in mouse gene expression

The mouse has become an indispensable and versatile model organism for the study of development, genetics, behavior, and disease. The application of comprehensive gene expression profiling technologies to compare normal and diseased tissues or to assess molecular alterations resulting from various experimental interventions has the potential to provide highly detailed qualitative and quantitative descriptions of these processes. Ideally, to interpret experimental data, the magnitude and diversity of gene expression for the system under study should be well characterized, yet little is known about the normal variation of mouse gene expression in vivo. To assess natural differences in murine gene expression, we used a 5406-clone spotted cDNA microarray to quantitate transcript levels in the kidney, liver, and testis from each of 6 normal male C57BL6 mice. We used ANOVA to compare the variance across the six mice to the variance among four replicate experiments performed for each mouse tissue. For the 6 kidney samples, 102 of 3,088 genes (3.3%) exhibited a statistically significant mouse variance at a level of 0.05. In the testis, 62 of 3,252 genes (1.9%) showed statistically significant variance, and in the liver, there were 21 of 2,514 (0.8%) genes with significantly variable expression. Immune-modulated, stress-induced, and hormonally regulated genes were highly represented among the transcripts that were most variable. The expression levels of several genes varied significantly in more than one tissue. These studies help to define the baseline level of variability in mouse gene expression and emphasize the importance of replicate microarray experiments.

Cloning and expression of the mouse PIP49 (Pancreatitis Induced Protein 49) mRNA which encodes a new putative transmembrane protein activated in the pancreas with acute pancreatitis

We have used a microarray-based strategy to characterize, at the molecular level, the pancreatic emergency program set up by the pancreatic cells in response to pancreatitis. In this strategy, the phenotype of the pancreatitis-affected pancreas is established by characterization of a large number of its transcripts using a high-density mouse cDNA microarray. This method allows identification of transcripts differentially expressed during pancreatitis. We describe here the cloning, sequencing, and expression analysis of a new gene, named PIP49 (Pancreatitis Induced Protein 49). Its very strong expression is specific of acinar cells and occurs rapidly after initiation of the acute phase of pancreatitis. Analysis of its primary and secondary structures strongly suggests that PIP49 encodes a putative transmembrane protein.