Growth promoting effect of thioredoxin on intestinal epithelial cells

Redox Active Antimicrobial Peptides in Controlling Growth of Microorganisms at Body Barriers

Epithelia in the skin, gut and other environmentally exposed organs display a variety of mechanisms to control microbial communities and limit potential pathogenic microbial invasion. Naturally occurring antimicrobial proteins/peptides and their synthetic derivatives (here collectively referred to as AMPs) reinforce the antimicrobial barrier function of epithelial cells. Understanding how these AMPs are functionally regulated may be important for new therapeutic approaches to combat microbial infections. Some AMPs are subject to redox-dependent regulation. This review aims to: (i) explore cysteine-based redox active AMPs in skin and intestine; (ii) discuss casual links between various redox environments of these barrier tissues and the ability of AMPs to control cutaneous and intestinal microbes; (iii) highlight how bacteria, through intrinsic mechanisms, can influence the bactericidal potential of redox-sensitive AMPs.

A Novel 3D in Vitro Tumor Model Based on Silk Fibroin/Chitosan Scaffolds To Mimic the Tumor Microenvironment

Drug development involves various evaluation processes to ascertain drug effects and rigorous analysis of biological indicators during in vitro preclinical studies. Two-dimensional (2D) cell cultures are commonly used in numerous in vitro studies, which are poor facsimiles of the in vivo conditions. Recently, three-dimensional (3D) tumor models mimicking the tumor microenvironment and reducing the use of experimental animals have been developed generating great interest to appraise tumor response to treatment strategies in cancer therapy. In this study, silk fibroin (SF) protein and chitosan (CS), two natural biomaterials, were chosen to construct the scaffolds of 3D cell models. Human non-small cell lung cancer A549 cells in the SF/CS scaffolds were found to have a great tendency to gather and form tumor spheres. A549 cell spheres in the 3D scaffolds showed biological and morphological characteristics much closer to the in vivo tumors. Besides, the cells in 3D models displayed better invasion ability and drug resistance than 2D models. Additionally, differences in drug-resistant and immune-related protein levels were found, which indicated that 3D models might resemble the real-life situation. These findings suggested that these 3D tumor models composed of SF/CS are promising to provide a valuable biomaterial platform in the evaluation of anticancer drugs.

Paneth cell α-defensin 6 (HD-6) is an antimicrobial peptide

Defensins protect human barriers from commensal and pathogenic microorganisms. Human α-defensin 6 (HD-6) is produced exclusively by small intestinal Paneth cells but, in contrast to other antimicrobial peptides (AMPs) for HD-6, no direct antibacterial killing activity has been detected so far. Herein, we systematically tested how environmental factors, like pH and reducing conditions, affect antimicrobial activity of different defensins against anaerobic bacteria of the human intestinal microbiota. Remarkably, by mimicking the intestinal milieu we detected for the first time antibacterial activity of HD-6. Activity was observed against anaerobic gut commensals but not against some pathogenic strains. Antibiotic activity was attributable to the reduced peptide and independent of free cysteines or a conserved histidine residue. Furthermore, the oxidoreductase thioredoxin, which is also expressed in Paneth cells, is able to reduce a truncated physiological variant of HD-6. Ultrastructural analyses revealed that reduced HD-6 causes disintegration of cytoplasmic structures and alterations in the bacterial cell envelope, while maintaining extracellular net-like structures. We conclude that HD-6 is an antimicrobial peptide. Our data suggest two distinct antimicrobial mechanisms by one peptide: HD-6 kills specific microbes depending on the local environmental conditions, whereas known microbial trapping by extracellular net structures is independent of the reducing milieu.

Role of thioredoxin 1 and thioredoxin 2 on proliferation of human adipose tissue-derived mesenchymal stem cells

Thioredoxin (TRX) is a ubiquitous redox protein that is involved in numerous biological functions, including the first unique step in DNA synthesis. TRX provides control over a number of transcription factors affecting cell proliferation and death through a mechanism referred to as redox regulation. In mammals, there are at least 3 members of the TRX family: TRX1, TRX2, and sperm TRX. To investigate the role of TRX1 and TRX2 in human adipose tissue-derived mesenchymal stem cells (hADSC), we modulated TRX1 and TRX2 expressions in hADSC using a lentiviral gene transfer system and small interfering RNA technique. Reverse transcription-polymerase chain reaction analysis confirmed the changes in expression of TRX1 and TRX2 in lentivirus-transduced or small interfering RNA-transfected cells. Although overexpression of TRX1 and TRX2 did not affect the differentiation of hADSC into adipogenic and osteogenic lineages, it increased the proliferation of hADSC compared with control lentivirus-transduced cells, decreased reactive oxygen species production, and inhibited oxidant-induced cell death. Downregulation of TRX1 and TRX2 inhibited cell proliferation. The treatment of U0126 blocked TRX-induced increase in cell proliferation. Overexpression of TRX1 and TRX2 increased ERK1/2 phosphorylation, nuclear factor-kappaB activation, and β-catenin/Tcf promoter activities and inhibited lucine zipper tumor suppressor 2 expression. On the contrary, downregulation of TRX1 and TRX2 expression induced inhibition of ERK1/2 phosphorylation, nuclear factor-kappaB activation, and β-catenin/Tcf promoter activities and increased lucine zipper tumor suppressor 2 expression. Activation of Wnt signal increased ERK1/2 activities in hADSC. These results indicated that TRX1 and TRX2 regulate the proliferation and survival of hADSC; these processes are mediated by the activation of ERK1/2.

Regulation of intestinal epithelial cells transcriptome by enteric glial cells: impact on intestinal epithelial barrier functions

BACKGROUND

Emerging evidences suggest that enteric glial cells (EGC), a major constituent of the enteric nervous system (ENS), are key regulators of intestinal epithelial barrier (IEB) functions. Indeed EGC inhibit intestinal epithelial cells (IEC) proliferation and increase IEB paracellular permeability. However, the role of EGC on other important barrier functions and the signalling pathways involved in their effects are currently unknown. To achieve this goal, we aimed at identifying the impact of EGC upon IEC transcriptome by performing microarray studies.

RESULTS

EGC induced significant changes in gene expression profiling of proliferating IEC after 24 hours of co-culture. 116 genes were identified as differentially expressed (70 up-regulated and 46 down-regulated) in IEC cultured with EGC compared to IEC cultured alone. By performing functional analysis of the 116 identified genes using Ingenuity Pathway Analysis, we showed that EGC induced a significant regulation of genes favoring both cell-to-cell and cell-to-matrix adhesion as well as cell differentiation. Consistently, functional studies showed that EGC induced a significant increase in cell adhesion. EGC also regulated genes involved in cell motility towards an enhancement of cell motility. In addition, EGC profoundly modulated expression of genes involved in cell proliferation and cell survival, although no clear functional trend could be identified. Finally, important genes involved in lipid and protein metabolism of epithelial cells were shown to be differentially regulated by EGC.

CONCLUSION

This study reinforces the emerging concept that EGC have major protective effects upon the IEB. EGC have a profound impact upon IEC transcriptome and induce a shift in IEC phenotype towards increased cell adhesion and cell differentiation. This concept needs to be further validated under both physiological and pathophysiological conditions.

H19 mRNA-like noncoding RNA promotes breast cancer cell proliferation through positive control by E2F1

The imprinted H19 gene has riboregulatory functions. We show here that H19 transcription is up-regulated during the S-phase of growth-stimulated cells and that the H19 promoter is activated by E2F1 in breast cancer cells. H19 repression by pRb and E2F6 confirms the E2F1-dependent control of the H19 promoter. Consistently, we demonstrate by chromatin immunoprecipitation assays that endogenous E2F1 is recruited to the H19 promoter in vivo. The functionality of E2F promoter sites was further confirmed by gel shift and mutagenesis experiments, revealing that these sites are required for binding and promoter response to E2F1 exogenous expression and serum stimulation. Furthermore, we show that H19 overexpression confers a growth advantage on breast cancer cells released from growth arrest as well as in asynchronously growing cells. The H19 knockdown by small interfering RNA duplexes impedes S-phase entry in both wild-type and stably H19-transfected cells. Based on these findings, we conclude that the H19 RNA is actively linked to E2F1 to promote cell cycle progression of breast cancer cells. This clearly supports the H19 oncogenic function in breast tumor genesis.

Identification of GM-CSF in Paneth cells using single-cell RT-PCR

Paneth cells, granule-containing cells located at the bottom of the intestinal crypts, have a role in innate mucosal immunity. We identified the exclusive expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) in Paneth cells using single-cell reverse transcription-polymerase chain reaction and cDNA array. Cytosolic total RNA was aspirated from single Paneth cells and other villous epithelial cells (non-Paneth cells) of rats using capillary micropipettes. In addition to lysozyme, secretory phospholipase A2, defensin, TNF-alpha, and xanthine dehydrogenase genes, cDNA array analysis revealed that the GM-CSF gene is specifically present in Paneth cells, whereas GM-CSF receptor beta-chain mRNA is expressed in Paneth cells and other epithelial cells. There was intense immunohistochemical staining of GM-CSF in Paneth cells but not in other epithelial cells. Treatment of IEC6 cells with GM-CSF enhanced expression of CD80 and CD86. Thus, GM-CSF in Paneth cells might have an important role in mucosal immunity through increasing the expression of costimulatory molecules in epithelial cells.