Colonic miRNA Expression/Secretion, Regulated by Intestinal Epithelial PepT1, Plays an Important Role in Cell-to-Cell Communication during Colitis

PepT1 is a member of the proton-oligopeptide cotransporter family SLC15, which mediates the transport of di/tripeptides from intestinal lumen into epithelial cells. MicroRNAs (miRNAs), a small noncoding RNAs (21–23 nucleotides), posttranscriptionally regulate gene expression by binding to the 39-untranslated regions (UTRs) of their target mRNAs. Although the role of most miRNAs remains elusive, they have been implicated in vital cellular functions such as intestinal epithelial cells differentiation, proliferation, and apoptosis. In the present study, we investigated the effect of intestinal epithelial PepT1 expression on microRNA (miRNA) expression/secretion in the colons of control mice and in mice with experimentally induced colonic inflammation (colitis). The colonic miRNA expression was deregulated in both colitis and control mice but the deregulation of miRNA expression/secretion was specific to colonic tissue and did not affect other tissues such as spleen and liver. Intestinal epithelial PepT1-dependent deregulation of colonic miRNA expression not only affects epithelial cells but also other cell types, such as intestinal macrophages. Importantly, we found the miRNA 23b which was known to be involved in inflammatory bowel disease was secreted and transported between cells to impose a gene-silencing effect on recipient intestinal macrophages. Based on our data, we may conclude that the expression of a specific protein, PepT1, in the intestine affects local miRNA expression/secretion in the colon on a tissue specific manner and may play an important role during the induction and progression of colitis. Colonic miRNA expression/secretion, regulated by intestinal epithelial PepT1, could play a crucial role in cell-to-cell communication during colitis

Dextran Sodium Sulfate (DSS) Induces Colitis in Mice by Forming Nano-Lipocomplexes with Medium-Chain-Length Fatty Acids in the Colon

Inflammatory bowel diseases (IBDs), primarily ulcerative colitis and Crohn's disease, are inflammatory disorders caused by multiple factors. Research on IBD has often used the dextran sodium sulfate (DSS)-induced colitis mouse model. DSS induces in vivo but not in vitro intestinal inflammation. In addition, no DSS-associated molecule (free glucose, sodium sulfate solution, free dextran) induces in vitro or in vivo intestinal inflammation. We find that DSS but not dextran associated molecules established linkages with medium-chain-length fatty acids (MCFAs), such as dodecanoate, that are present in the colonic lumen. DSS complexed to MCFAs forms nanometer-sized vesicles ∼200 nm in diameter that can fuse with colonocyte membranes. The arrival of nanometer-sized DSS/MCFA vesicles in the cytoplasm may activate intestinal inflammatory signaling pathways. We also show that the inflammatory activity of DSS is mediated by the dextran moieties. The deleterious effect of DSS is localized principally in the distal colon, therefore it will be important to chemically modify DSS to develop materials beneficial to the colon without affecting colon-targeting specificity

Microbiota Modulate Host Gene Expression via MicroRNAs

Microbiota are known to modulate host gene expression, yet the underlying molecular mechanisms remain elusive. MicroRNAs (miRNAs) are importantly implicated in many cellular functions by post-transcriptionally regulating gene expression via binding to the 3′-untranslated regions (3′-UTRs) of the target mRNAs. However, a role for miRNAs in microbiota-host interactions remains unknown. Here we investigated if miRNAs are involved in microbiota-mediated regulation of host gene expression. Germ-free mice were colonized with the microbiota from pathogen-free mice. Comparative profiling of miRNA expression using miRNA arrays revealed one and eight miRNAs that were differently expressed in the ileum and the colon, respectively, of colonized mice relative to germ-free mice. A computational approach was then employed to predict genes that were potentially targeted by the dysregulated miRNAs during colonization. Overlapping the miRNA potential targets with the microbiota-induced dysregulated genes detected by a DNA microarray performed in parallel revealed several host genes that were regulated by miRNAs in response to colonization. Among them, Abcc3 was identified as a highly potential miRNA target during colonization. Using the murine macrophage RAW 264.7 cell line, we demonstrated that mmu-miR-665, which was dysregulated during colonization, down-regulated Abcc3 expression by directly targeting the Abcc3 3′-UTR. In conclusion, our study demonstrates that microbiota modulate host microRNA expression, which could in turn regulate host gene expression

ArcB1, a Homolog of Escherichia coli ArcB, Regulates Dimethyl Sulfoxide Reduction in Shewanella oneidensis MR-1▿ †

Shewanella oneidensis is a metal reducer that uses the cyclic AMP receptor protein, CRP, to regulate anaerobic respiration. In addition, ArcASo is required for anaerobic growth with dimethyl sulfoxide (DMSO) and plays a role in aerobic respiration. The sensor kinase that activates ArcASo in S. oneidensis is not known. ArcB1So, a homolog of the Escherichia coli sensor kinase ArcBEc, was identified and found to be required for DMSO reductase gene expression. In combination with HptA, ArcB1So complemented an E. coli arcBEc mutant. ArcASo, ArcB1So, and HptA appear to constitute a two-component signal transduction system that regulates DMSO reduction in S. oneidensis

Colonic miRNA expression levels are modulated in villin-hPepT1 and FVB WT mice with and without DSS.

<p>miRNAs expressed with the a <i>p</i>-value of <0.01 and signal >500 in microRNA microarray were analyzed by qRT-PCR (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087614#pone-0087614-g002" target="_blank">Fig. 2A</a>). miRNA 3077, miRNA 1934, miRNA 2145 were not associated with any target mRNAs so these three miRNAs were excluded from further analysis (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087614#pone-0087614-g002" target="_blank">Fig. 2B</a>) and the mature mmu-miR-1937a, mmu-miR-1937b, and mmu-miR-1937c are fragments of tRNA (<a href="http://www.mirbase.org" target="_blank">www.mirbase.org</a>) so we eliminated these from further analyses (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0087614#pone-0087614-g002" target="_blank">Fig. 2C</a>). Difference in miRNA expression noted as * <i>p</i><0.05, ** <i>p</i><0.001 and *** <i>p</i><0.0001. Values represent means ± SEM of n = 6/group.</p

DAVID functional annotation clustering of villin-hPepT1 and FVB WT at the basal level.

<p>The common proteins were clustered into 30 groups, but based on enrichment score >1.0. 11 groups were considered to be the potential targets with a total of 1100 genes.</p