Protease-activated receptor 2 drives migration in a colon cancer cell line but not in noncancerous human epithelial cells

The inflamed mucosa contains a complex assortment of proteases that may participate in wound healing or the development of inflammation-associated colon cancer. We sought to determine the role of protease-activated receptor 2 (PAR2) in epithelial wound healing in both untransformed and transformed colonic epithelial cells. Monolayers of primary epithelial cells derived from organoids cultivated from patient colonic biopsies and of the T84 colon cancer cell line were grown to confluence, wounded in the presence of a selective PAR2-activating peptide, and healing was visualized by live cell microscopy. Inhibitors of various signaling molecules were used to assess the relevant pathways responsible for wound healing. Activation of PAR2 induced an enhanced wound-healing response in T84 cells but not primary cells. The PAR2-enhanced wound-healing response was associated with the development of lamellipodia in cells at the wound edge, consistent with sheet migration. The response to PAR2 activation in T84 cells was completely dependent on Src kinase activity and partially dependent on Rac1 activity. The Src-associated signaling molecules, focal adhesion kinase, and epidermal growth factor receptor, which typically mediate wound-healing responses, were not involved in the PAR2 response. Experiments repeated in the presence of the inflammatory cytokines TNF and IFNγ revealed a synergistically enhanced PAR2 wound-healing response in T84s but not primary cells. The epithelial response to proteases may be different between primary and cancer cells and is accentuated in the presence of inflammatory cytokines. Our findings have implications for understanding epithelial restitution in the context of inflammatory bowel disease (IBD) and inflammation-associated colon cancer.NEW & NOTEWORTHY Protease-activated receptor 2 enhances wound healing in the T84 colon cancer cell line, but not in primary cells derived from patient biopsies, an effect that is synergistically enhanced in the presence of the inflammatory cytokines TNF and IFNγ.

Microsporidia persistence in host impairs epithelial barriers and increases chances of inflammatory bowel disease

Microsporidia are intracellular fungus-like pathogens and the infection symptoms include recurrent diarrhea and systematic inflammations. The major infection route of microsporidia is the digestive tract. Since microsporidia are hard to fully eliminate, the interactions and persistence of the pathogen within epithelium may modulate host susceptibility to digestive disorders. In this study, both in vitro and in vivo infection models were applied. The alterations of epithelial barrier integrity, permeability, and tight junction proteins after microsporidia infection were assessed on MDCK/Caco-2 monolayers. The fecal intestinal microbiota and tissue alterations after microsporidia infection were assessed on C57BL/6 mice. Moreover, the susceptibility to develop dextran sulfate sodium (DSS)-induced inflammatory bowel diseases (IBDs) was also analyzed by the murine infection model. The results demonstrated that microsporidia infection increased epithelium permeability, weakened wound healing capability, and destructed tight junction protein zonula occludens-1. Microsporidia infection also dysregulates intestinal microbiota. These impairing effects of microsporidia increased host vulnerability to develop enteritis as shown by the murine model of DSS-induced IBD. Our study is the first to elucidate molecular mechanisms of the damaging effects of microsporidia on host epithelium and pointed out the cryptic threats of latent microsporidia infection to public health as reflected by the increased chances of developing more severe diseases.IMPORTANCEMicrosporidia are widely present in nature and usually cause latent and persistent infections in hosts. Given the fact that the digestive tract is the major infection route, it is of great importance to explore the consequences of microsporidia infection on the intestinal epithelial barrier and the risks to the host. In this study, we demonstrated the destructing effects of microsporidium infection on epithelial barriers manifested as increased epithelial permeability, weakened wound healing ability, and disrupted tight junctions. Moreover, microsporidia made the host more susceptible to dextran sulfate sodium-induced inflammatory bowel disease. These findings provide new evidence for us to better understand and develop novel strategies for microsporidia prevention and disease control.

Protease-activated receptor 2 attenuates doxorubicin-induced apoptosis in colon cancer cells

Drug resistance represents a major problem in cancer treatment. Doxorubicin (adriamycin) is an injectable DNA intercalating drug that halts cancer cell growth by inhibiting topoisomerase 2, but its long-term effectiveness is compromised by onset of resistance. This study demonstrates that expression of the PAR2 gene in human colon adenocarcinoma tissue samples was the highest among 32 different cancer types (n = 10,989), and higher in colon adenocarcinoma tissues (n = 331) than normal colon tissues (n = 308), revealing an association between PAR2 expression and human colon cancer. HT29 cells are a human colorectal adenocarcinoma cell line that is sensitive to the chemotherapeutic drug doxorubicin and also expresses PAR2. We find that PAR2 activation in HT29 cells, either by an endogenous protease agonist (trypsin) or an exogenous peptide agonist (2f-LIGRL-NH2), significantly reduces doxorubicin-induced cell death, reactive oxygen species production, caspase 3/7 activity and cleavage of caspase-8 and caspase-3. Moreover, PAR2-mediated MEK1/2-ERK1/2 pathway induced by 2f-LIGRL-NH2 leads to upregulated anti-apoptotic MCL-1 and Bcl-xL proteins that promote cellular survival. These findings suggest that activation of PAR2 compromises efficacy of doxorubicin in colon cancer. Further support for this conclusion came from experiments with human colon cancer HT29 cells, either with the PAR2 gene deleted or in the presence of a pharmacological antagonist of PAR2, which showed full restoration of all doxorubicin-mediated effects. Together, these findings reveal a strong link between PAR2 activation and signalling in human colon cancer cells and increased survival against doxorubicin-induced cell death. They support PAR2 antagonism as a possible new strategy for enhancing doxorubicin therapy.

Influence of food emulsifiers on cellular function and inflammation, a preliminary study

Emulsifiers are extensively used as food additives and their consumption is increasing in Western countries. However, so far only few studies examined their potential effects on intestinal cellular functions and gut inflammation. The aim of this preliminary analysis was to study the emulsifiers and their concentrations capable of causing cellular damage compared to extra virgin olive oil (EVOO). We tested two commonly used emulsifiers (EMI, EMII) and EVOO on Caco-2 cells, derived from a colon carcinoma and widely used as a model of the intestinal inflammation. The diphenyltetrazolium bromide test MTT and clonogenic assay were used to study the effect of emulsifiers on cell viability. Cell migration was determined by the wound-healing assay. The inflammation was studied by measuring the levels of interleukin 6 (IL-6) and monocyte chemoattractant protein-1/C-C motif chemokine ligand 2 (CCL2), multifunctional cytokines with a major role in the acute-phase response. Furthermore, we analyzed the effect of conditioned media of Caco-2 cells treated with EMs on macrophages activation. In conclusion, our preliminary data provide evidence that EMs increase the proliferation and migration rate of Caco-2 cells. Moreover, Caco-2 cells treated with EMs enhance the IL-6 and CCL2 release and activated macrophages, supporting their role as proinflammatory molecules.

Akkermansia muciniphila and its membrane protein ameliorates intestinal inflammatory stress and promotes epithelial wound healing via CREBH and miR-143/145

BACKGROUND

The intestinal epithelial barrier is the interface for interaction between gut microbiota and host metabolic systems. Akkermansia muciniphila (A. muciniphila) is a key player in the colonic microbiota that resides in the mucus layer, whose abundance is selectively decreased in the faecal microbiota of inflammatory bowel disease (IBD) patients. This study aims to investigate the regulatory mechanism among A. muciniphila, a transcription factor cAMP-responsive element-binding protein H (CREBH), and microRNA-143/145 (miR-143/145) in intestinal inflammatory stress, gut barrier integrity and epithelial regeneration.

METHODS

A novel mouse model with increased colonization of A muciniphila in the intestine of CREBH knockout mice, an epithelial wound healing assay and several molecular biological techniques were applied in this study. Results were analysed using a homoscedastic 2-tailed t-test.

RESULTS

Increased colonization of A. muciniphila in mouse gut enhanced expression of intestinal CREBH, which was associated with the mitigation of intestinal endoplasmic reticulum (ER) stress, gut barrier leakage and blood endotoxemia induced by dextran sulfate sodium (DSS). Genetic depletion of CREBH (CREBH-KO) significantly inhibited the expression of tight junction proteins that are associated with gut barrier integrity, including Claudin5 and Claudin8, but upregulated Claudin2, a tight junction protein that enhances gut permeability, resulting in intestinal hyperpermeability and inflammation. Upregulation of CREBH by A. muciniphila further coupled with miR-143/145 promoted intestinal epithelial cell (IEC) regeneration and wound repair via insulin-like growth factor (IGF) and IGFBP5 signalling. Moreover, the gene expressing an outer membrane protein of A. muciniphila, Amuc_1100, was cloned into a mammalian cell-expression vector and successfully expressed in porcine and human IECs. Expression of Amuc_1100 in IECs could recapitulate the health beneficial effect of A. muciniphila on the gut by activating CREBH, inhibiting ER stress and enhancing the expression of genes involved in gut barrier integrity and IEC's regeneration.

CONCLUSIONS

This study uncovers a novel mechanism that links A. muciniphila and its membrane protein with host CREBH, IGF signalling and miRNAs in mitigating intestinal inflammatory stress-gut barrier permeability and promoting intestinal wound healing. This novel finding may lend support to the development of therapeutic approaches for IBD by manipulating the interaction between host genes, gut bacteria and its bioactive components.

Characterization and bioactivity of extracellular vesicles isolated from pomegranate

In the current study, extracellular vesicles from pomegranate juice (PgEVs) were isolated for the first time using size exclusion chromatography (SEC). This method permitted us to obtain highly enriched EV samples without most of the non-EV co-isolated proteins. The characterization of PgEVs through nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) allowed the determination of vesicles' concentration/volume, size, and morphology. It was confirmed from the analytical data that PgEVs contain a homogeneous population of vesicles, with a dimension and structure comparable to plant-derived EVs. Proteomic analyses by LC-MS/MS led to the characterization of 131 proteins, and several of them were related commonly to the biogenesis and transport of EVs, and/or proposed as EV markers. PgEVs exerted anti-inflammatory, antioxidant and wound-healing effects when added to the in vitro cultures of monocytic (THP-1) and intestinal (Caco-2) cell lines, respectively.

A Genomics-Based Semirational Approach for Expanding the Postbiotic Potential of Collagen Peptides Using Lactobacillaceae

Food-derived bioactive peptides (BPs) have received considerable attention as postbiotics for human gut health. Here we used a genomics-based semirational approach to expand the postbiotic potential of collagen peptides (CPs) produced from probiotic fermentation. In silico digestion revealed distinct BPs embedded in fish collagen in a protease-dependent manner. Anaerobic digestion of collagen by representative Lactobacillaceae species revealed differential substrate utilization and collagen degradation patterns. Nanoliquid chromatography-mass spectrometry analysis of CPs showed that each species exhibited different cleavage patterns and unique peptide profiles. Remarkably, the 1-10 kDa CPs produced by Lacticaseibacillus paracasei showed agonistic activities toward G protein-coupled receptor 35 (GPR35). These CPs could repair intestinal epithelium through the GPR35-mediated extracellular signal-regulated protein kinase (ERK) 1/2 signaling pathway, suggesting that probiotic-aided collagen hydrolysates can serve as postbiotics for host-microbe interactions. Therefore, this study provides an effective strategy for the rapid screening of CPs for gut health in the gastrointestinal tract.

Mechanisms and modeling of wound repair in the intestinal epithelium

The intestinal epithelial barrier is susceptible to injury from insults, such as ischemia or infectious disease. The epithelium's ability to repair wounded regions is critical to maintaining barrier integrity. Mechanisms of intestinal epithelial repair can be studied with models that recapitulate the in vivo environment. This review focuses on in vitro injury models and intestinal cell lines utilized in such systems. The formation of artificial wounds in a controlled environment allows for the exploration of reparative physiology in cell lines modeling diverse aspects of intestinal physiology. Specifically, the use of intestinal cell lines, IPEC-J2, Caco-2, T-84, HT-29, and IEC-6, to model intestinal epithelium is discussed. Understanding the unique systems available for creating intestinal injury and the differences in monolayers used for in vitro work is essential for designing studies that properly capture relevant physiology for the study of intestinal wound repair.

Matrix Metalloproteinase MMP-12 Promotes Macrophage Transmigration Across Intestinal Epithelial Tight Junctions and Increases Severity of Experimental Colitis

BACKGROUND AND AIMS

Matrix metalloproteinases [MMPs] play an important role in extracellular matrix regulation during cell growth and wound healing. Increased expression of MMP-12 [human macrophage elastase] has been reported in inflammatory bowel disease [IBD] which is characterised by the loss of epithelial tight junction [TJ] barrier function and an excessive inflammatory response. The aim of this study was to investigate the role of MMP-12 in intestinal TJ barrier function and inflammation.

METHODS

Wild type [WT] and MMP-12-/- mice were subjected to experimental acute or chronic dextran sodium sulphate [DSS] colitis. The mouse colonic permeability was measured in vivo by recycling perfusion of the entire colon and ex vivo by Ussing chamber studies.

RESULTS

DSS administration increased colonic permeability through modulation of TJ proteins and also increased MMP-12 expression in the colonic mucosa of WT mice. The acute as well as chronic DSS-induced increase in colonic TJ permeability and the severity of DSS colitis was found to be markedly attenuated in MMP-12-/- mice. The resistance of MMP-12-/- mice to DSS colitis was characterised by reduced macrophage infiltration and transmigration, and reduced basement membrane laminin degradation. Further in vitro and in vivo studies show that macrophage transmigration across the epithelial layer is MMP-12 dependent and the epithelial TJ barrier is compromised during macrophage transmigration. Conclusions: Together, these data demonstrate that MMP-12 mediated degradation of basement membrane laminin, macrophage transmigration, and associated loss of intestinal TJ barrier are key pathogenic factors for intestinal inflammation.

Protease-activated receptor-2 activation enhances epithelial wound healing via epidermal growth factor receptor

The intestinal barrier function relies on the presence of a single layer of epithelial cells. Barrier dysfunction is associated with the inflammatory bowel diseases (IBD). Understanding the mechanisms involved in intestinal wound healing in order to sustain the barrier function has a great therapeutic potential. Activation of protease-activated receptor-2 (PAR2) induces COX-2 expression in intestinal epithelial cells via EGFR transactivation. COX-2 is well known for its protective effects in the gastrointestinal tract. Therefore, we hypothesized that PAR-2 activation induces a wound healing response in intestinal epithelial cells through COX-2-derived lipid mediators and EGFR transactivation. Immunofluorescence and calcium assay were used to characterize CMT-93 mouse colonic epithelial cell line for PAR2 expression and its activity, respectively. Treatment with PAR2 activating peptide 2-furoyl-LIGRLO-NH₂ (2fLI), but not by its inactive reverse-sequence peptide (2fO) enhanced wound closure in scratch wounded monolayers. The EGFR tyrosine kinase inhibitor (PD153035), broad-spectrum matrix metalloproteinase inhibitor (GM6001) and Src tyrosine kinase inhibitor (PP2) inhibited PAR2-induced wound healing. However, PAR2 activation did not induce COX-2 expression in CMT-93 cells and inhibition of COX-2 by COX-2 selective inhibitor (NS-398) did not alter PAR2-induced wound healing. In conclusion, PAR2 activation drives wound healing in CMT-93 cells via EGFR transactivation. Matrix metalloproteinases and Src tyrosine kinase activity may involve in EGFR transactivation and PAR2-induced wound healing is independent of COX-2 activity. These findings provide a mechanism whereby PAR2 can participate in the resolution of intestinal wounds in gastrointestinal inflammatory diseases.

Hypoxic Pretreatment of Adipose-Derived Stem Cells Accelerates Diabetic Wound Healing via circ-Gcap14 and HIF-1α/VEGF Mediated Angiopoiesis

Background and Objectives

Adipose-derived stem cell (ADSC) transplantation improves stem cell paracrine function and can enhance wound healing. However, in diabetic patients, glucose-associated effects on this function and cell survival lead to impaired wound closure, thereby limiting ADSC transplantation efficiency. The hypoxia-inducible factor HIF-1α has an important protective function during wound healing. Here, we aim to clarify the regulatory mechanism of ADSCs.

Methods and Results

ADSCs were isolated from BALB/C mice adipose samples. We then used high-throughput sequencing to assess abnormal expression of circular RNAs (circRNAs). We also used an in vivo full-thickness skin defect mouse model to assess the effects of transplanted ADSC on diabetic wound closure. Hypoxic pretreatment of ADSCs accelerated diabetic wound closure, which enhanced angiogenic growth factor expression in our mouse model. High-throughput sequencing and RT-qPCR indicated that circ-Gcap14 was upregulated in hypoxic pretreated ADSCs. Similarly, circ-Gcap14 downregulation also decreased the therapeutic effects of ADSCs; however, circ-Gcap14 overexpression increased the effects of ADSC by promoting angiopoiesis. We also used a luciferase reporter assay to confirm that miR-18a-5p and HIF-1α were downstream targets of circ-Gcap14. HIF-1α expression plays an important role in increased VEGF level.

Conclusions

Based on our data, we suggest that circ-Gcap14 plays an important role in accelerating hypoxic ADSC-mediated diabetic wound closure, by enhancing mouse angiogenic growth factor expression and regulating downstream miR-18a-5p/HIF-1α expression.

Immunosuppressive Drugs Alter α1-Antitrypsin Production in Hepatocytes: Implications for Epithelial Gap Repair

Immunosuppressive drugs are an inherent component of hematopoietic stem cell transplantation (HSCT) for the prevention of acute graft-versus-host disease (GVHD). Circulating α1-antitrypsin (AAT), a serine-protease inhibitor produced predominantly by hepatocytes that rises during acute phase responses, is lost in patient's stool due to gastrointestinal GVHD, and its augmentation has been found to attenuate GVHD. Here we explored the effect of immunosuppressive drugs on hepatocyte production of AAT and intestinal epithelial gap repair. The effect of commonly used immunosuppressants on AAT production was examined in vitro using HepG2 cells and primary mouse hepatocytes, and their impact on human intestinal epithelial cell line gap repair was evaluated. Sera from 12 allogeneic HSCT recipients, obtained at 14 days post-transplantation, predating the diagnosis of GVHD (n = 6), were examined for reepithelialization, with added clinical-grade AAT. Rapamycin compromised AAT production under inflammatory conditions. Mycophenolate mofetil and cyclosporine A (CSA) inhibited reepithelialization; AAT minimized the effect of CSA. Patient sera displayed superior gap repair with exogenous AAT. Functional insufficiency in circulating AAT may be the result of drug toxicities leading to ineffective gut reepithelization and compromised gut lining. Taken together, our data strengthen the rationale for incorporating AAT augmentation therapy into immunosuppressive treatment protocols.