Pilot study identifying circulating miRNA signature specific to alcoholic chronic pancreatitis and its implication on alcohol-mediated pancreatic tissue injury.

BACKGROUND AND AIM: Alcohol exerts its effects on organs in multiple ways. Alcoholic chronic pancreatitis (ACP) is a disease in which alcohol triggers the pathological changes in pancreas, leading to chronic inflammation and fibrosis. The molecular mechanism behind these changes is not clear. Identification of key circulating miRNA changes in ACP patients and determination of the fraction that is secreted from diseased pancreas not only could serve as potential biomarker for assessing disease severity, but also could help identifying the molecular alterations prevailing in the organ precipitating the disease, to some extent. METHODS: We performed microRNA microarray using the Affymetrix miRNA 4.0 platform to identify differentially expressed miRNAs in serum of ACP patients as compared to alcoholic control individuals and then found out how many of them could be pancreas-specific and exosomally secreted. We further analyzed a pancreatitis-specific gene expression data set to find out the differentially expressed genes in diseased pancreas and explored the possible role of those selected miRNAs in regulation of gene expression in ACP. RESULTS: We identified 14 miRNAs differentially expressed in both serum and pancreas and also identified their experimentally validated targets. Transcription factors modulating the miRNA expression in an alcohol-dependent manner were also identified and characterized to derive the miRNA-gene-TF interaction network responsible for progression of the disease. CONCLUSIONS: Differentially expressed miRNA signature demonstrated significant changes in both pro- and anti-inflammatory pathways probably balancing the chronic inflammation in the pancreas. Our findings also suggested possible involvement of pancreatic stellate cells in disease progression.

Transcriptomic meta-analysis reveals up-regulation of gene expression functional in osteoclast differentiation in human septic shock.

Septic shock is a major medical problem with high morbidity and mortality and incompletely understood biology. Integration of multiple data sets into a single analysis framework empowers discovery of new knowledge about the condition that may have been missed by individual analysis of each of these datasets. Electronic search was performed on medical literature and gene expression databases for selection of transcriptomic studies done in circulating leukocytes from human subjects suffering from septic shock. Gene-level meta-analysis was conducted on the six selected studies to identify the genes consistently differentially expressed in septic shock. This was followed by pathway-level analysis using three different algorithms (ORA, GSEA, SPIA). The identified up-regulated pathway, Osteoclast differentiation pathway (hsa04380) was validated in two independent cohorts. Of the pathway, 25 key genes were selected that serve as an expression signature of Septic Shock.

Helicobacter pylori colonization ameliorates glucose homeostasis in mice through a PPAR γ-dependent mechanism.

BACKGROUND: There is an inverse secular trend between the incidence of obesity and gastric colonization with Helicobacter pylori, a bacterium that can affect the secretion of gastric hormones that relate to energy homeostasis. H. pylori strains that carry the cag pathogenicity island (PAI) interact more intimately with gastric epithelial cells and trigger more extensive host responses than cag(-) strains. We hypothesized that gastric colonization with H. pylori strains differing in cag PAI status exert distinct effects on metabolic and inflammatory phenotypes. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis, we examined metabolic and inflammatory markers in db/db mice and mice with diet-induced obesity experimentally infected with isogenic forms of H. pylori strain 26695: the cag PAI wild-type and its cag PAI mutant strain 99-305. H. pylori colonization decreased fasting blood glucose levels, increased levels of leptin, improved glucose tolerance, and suppressed weight gain. A response found in both wild-type and mutant H. pylori strain-infected mice included decreased white adipose tissue macrophages (ATM) and increased adipose tissue regulatory T cells (Treg) cells. Gene expression analyses demonstrated upregulation of gastric PPAR γ-responsive genes (i.e., CD36 and FABP4) in H. pylori-infected mice. The loss of PPAR γ in immune and epithelial cells in mice impaired the ability of H. pylori to favorably modulate glucose homeostasis and ATM infiltration during high fat feeding. CONCLUSIONS/SIGNIFICANCE: Gastric infection with some commensal strains of H. pylori ameliorates glucose homeostasis in mice through a PPAR γ-dependent mechanism and modulates macrophage and Treg cell infiltration into the abdominal white adipose tissue.

Microarray data analysis.

Gene expression profiling has revolutionized functional genomics research by providing a quick handle on all the transcriptional changes that occur in the cell in response to internal or external perturbations or developmental programs. Microarrays have become the most popular technology for recording gene expression profiles. This chapter describes all the necessary steps for analyzing Affymetrix microarray data using the open-source statistical tools (R and bioconductor). The reader is walked through all the basic steps of data analysis: reading raw data, assessing quality, preprocessing/normalization, discovery of differentially expressed genes, comparison of gene lists, functional enrichment analysis, and saving results to files for future reference. Some familiarity with computer is assumed. This chapter is self-contained with installation instructions for R and bioconductor packages along with links to downloadable data and code for reproducing the examples.

The role of T cell PPAR gamma in mice with experimental inflammatory bowel disease.

BACKGROUND: Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a nuclear receptor whose activation has been shown to modulate macrophage and T cell-mediated inflammation. The objective of this study was to investigate the mechanisms by which the deletion of PPAR gamma in T cells modulates immune cell distribution and colonic gene expression and the severity of experimental IBD. METHODS: PPAR gamma flfl; CD4 Cre+ (CD4cre) or Cre- (WT) mice were challenged with 2.5% dextran sodium sulfate in their drinking water for 0, 2, or 7 days. Mice were scored on disease severity both clinically and histopathologically. Flow cytometry was used to assess lymphocyte and macrophage populations in the blood, spleen, and mesenteric lymph nodes (MLN). Global gene expression in colonic mucosa was profiled using Affymetrix microarrays. RESULTS: The deficiency of PPAR gamma in T cells accelerated the onset of disease and body weight loss. Examination of colon histopathology revealed significantly greater epithelial erosion, leukocyte infiltration, and mucosal thickening in the CD4cre mice on day 7. CD4cre mice had more CD8+ T cells than WT mice and fewer CD4+ FoxP3+ regulatory T cells (Treg) and IL10+ CD4+ T cells in blood and MLN, respectively. Transcriptomic profiling revealed around 3000 genes being transcriptionally altered as a result of DSS challenge in CD4cre mice. These included up-regulated mRNA expression of adhesion molecules, proinflammatory cytokines interleukin-6 (IL-6) and IL-1beta, and suppressor of cytokine signaling 3 (SOCS-3) on day 7. Gene set enrichment analysis (GSEA) showed that the ribosome and Krebs cycle pathways were downregulated while the apoptosis pathway was upregulated in colons of mice lacking PPAR gamma in T cells. CONCLUSIONS: The expression of PPAR gamma in T cells is involved in preventing gut inflammation by regulating colonic expression of adhesion molecules and inflammatory mediators at later stages of disease while favoring the recruitment of Treg to the mucosal inductive sites.

Immunoregulatory actions of epithelial cell PPAR gamma at the colonic mucosa of mice with experimental inflammatory bowel disease.

BACKGROUND: Peroxisome proliferator-activated receptors are nuclear receptors highly expressed in intestinal epithelial cells (IEC) and immune cells within the gut mucosa and are implicated in modulating inflammation and immune responses. The objective of this study was to investigate the effect of targeted deletion of PPAR gamma in IEC on progression of experimental inflammatory bowel disease (IBD). METHODOLOGY/PRINCIPAL FINDINGS: In the first phase, PPAR gamma flfl; Villin Cre- (VC-) and PPAR gamma flfl; Villin Cre+ (VC+) mice in a mixed FVB/C57BL/6 background were challenged with 2.5% dextran sodium sulfate (DSS) in drinking water for 0, 2, or 7 days. VC+ mice express a transgenic recombinase under the control of the Villin-Cre promoter that causes an IEC-specific deletion of PPAR gamma. In the second phase, we generated VC- and VC+ mice in a C57BL/6 background that were challenged with 2.5% DSS. Mice were scored on disease severity both clinically and histopathologically. Flow cytometry was used to phenotypically characterize lymphocyte and macrophage populations in blood, spleen and mesenteric lymph nodes. Global gene expression analysis was profiled using Affymetrix microarrays. The IEC-specific deficiency of PPAR gamma in mice with a mixed background worsened colonic inflammatory lesions, but had no effect on disease activity (DAI) or weight loss. In contrast, the IEC-specific PPAR gamma null mice in C57BL/6 background exhibited more severe inflammatory lesions, DAI and weight loss in comparison to their littermates expressing PPAR gamma in IEC. Global gene expression profiling revealed significantly down-regulated expression of lysosomal pathway genes and flow cytometry results demonstrated suppressed production of IL-10 by CD4+ T cells in mesenteric lymph nodes (MLN) of IEC-specific PPAR gamma null mice. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that adequate expression of PPAR gamma in IEC is required for the regulation of mucosal immune responses and prevention of experimental IBD, possibly by modulation of lysosomal and antigen presentation pathways.

Modulation of hepatic PPAR expression during Ft LVS LPS-induced protection from Francisella tularensis LVS infection.

BACKGROUND: It has been shown previously that administration of Francisella tularensis (Ft) Live Vaccine Strain (LVS) lipopolysaccharide (LPS) protects mice against subsequent challenge with Ft LVS and blunts the pro-inflammatory cytokine response. METHODS: To further investigate the molecular mechanisms that underlie Ft LVS LPS-mediated protection, we profiled global hepatic gene expression following Ft LVS LPS or saline pre-treatment and subsequent Ft LVS challenge using Affymetrix arrays. RESULTS: A large number of genes (> 3,000) were differentially expressed at 48 hours post-infection. The degree of modulation of inflammatory genes by infection was clearly attenuated by pre-treatment with Ft LVS LPS in the surviving mice. However, Ft LVS LPS alone had a subtle effect on the gene expression profile of the uninfected mice. By employing gene set enrichment analysis, we discovered significant up-regulation of the fatty acid metabolism pathway, which is regulated by peroxisome proliferator activated receptors (PPARs). CONCLUSIONS: We hypothesize that the LPS-induced blunting of pro-inflammatory response in mouse is, in part, mediated by PPARs (alpha and gamma).

An essential role for the antiviral endoribonuclease, RNase-L, in antibacterial immunity.

Type I IFNs were discovered as the primary antiviral cytokines and are now known to serve critical functions in host defense against bacterial pathogens. Accordingly, established mediators of IFN antiviral activity may mediate previously unrecognized antibacterial functions. RNase-L is the terminal component of an RNA decay pathway that is an important mediator of IFN-induced antiviral activity. Here, we identify a role for RNase-L in the host antibacterial response. RNase-L(-/-) mice exhibited a dramatic increase in mortality after challenge with Bacillus anthracis and Escherichia coli; this increased susceptibility was due to a compromised immune response resulting in increased bacterial load. Investigation of the mechanisms of RNase-L antibacterial activity indicated that RNase-L is required for the optimal induction of proinflammatory cytokines that play essential roles in host defense from bacterial pathogens. RNase-L also regulated the expression of the endolysosomal protease, cathepsin-E, and endosome-associated activities, that function to eliminate internalized bacteria and may contribute to RNase-L antimicrobial action. Our results reveal a unique role for RNase-L in the antibacterial response that is mediated through multiple mechanisms. As a regulator of fundamental components of the innate immune response, RNase-L represents a viable therapeutic target to augment host defense against diverse microbial pathogens.