Colonic miRNA expression/secretion, regulated by intestinal epithelial PepT1, plays an important role in cell-to-cell communication during colitis

Extracellular Vesicles of the Probiotic Escherichia coli Nissle 1917 Reduce PepT1 Levels in IL-1β-Treated Caco-2 Cells via Upregulation of miR-193a-3p

PepT1, a proton-coupled oligopeptide transporter, is crucial for intestinal homeostasis. It is mainly expressed in small intestine enterocytes, facilitating the absorption of di/tri-peptides from dietary proteins. In the colon, PepT1 expression is minimal to prevent excessive responses to proinflammatory peptides from the gut microbiota. However, increased colonic PepT1 is linked to chronic inflammatory diseases and colitis-associated cancer. Despite promising results from animal studies on the benefits of extracellular vesicles (EVs) from beneficial gut commensals in treating IBD, applying probiotic EVs as a postbiotic strategy in humans requires a thorough understanding of their mechanisms. Here, we investigate the potential of EVs of the probiotic Nissle 1917 (EcN) and the commensal EcoR12 in preventing altered PepT1 expression under inflammatory conditions, using an interleukin (IL)-1-induced inflammation model in Caco-2 cells. The effects are evaluated by analyzing the expression of PepT1 (mRNA and protein) and miR-193a-3p and miR-92b, which regulate, respectively, PepT1 mRNA translation and degradation. The influence of microbiota EVs on PepT1 expression is also analyzed in the presence of bacterial peptides that are natural substrates of colonic PepT1 to clarify how the regulatory mechanisms function under both physiological and pathological conditions. The main finding is that EcN EVs significantly decreases PepT1 protein via upregulation of miR-193a-3p. Importantly, this regulatory effect is strain-specific and only activates in cells exposed to IL-1β, suggesting that EcN EVs does not control PepT1 expression under basal conditions but can play a pivotal role in response to inflammation as a stressor. By this mechanism, EcN EVs may reduce inflammation in response to microbiota in chronic intestinal disorders by limiting the uptake of bacterial proinflammatory peptides.

Molecular Insights to the Structure-Interaction Relationships of Human Proton-Coupled Oligopeptide Transporters (PepTs)

Human proton-coupled oligopeptide transporters (PepTs) are important membrane influx transporters that facilitate the cellular uptake of many drugs including ACE inhibitors and antibiotics. PepTs mediate the absorption of di- and tri-peptides from dietary proteins or gastrointestinal secretions, facilitate the reabsorption of peptide-bound amino acids in the kidney, and regulate neuropeptide homeostasis in extracellular fluids. PepT1 and PepT2 have been the most intensively investigated of all PepT isoforms. Modulating the interactions of PepTs and their drug substrates could influence treatment outcomes and adverse effects with certain therapies. In recent studies, topology models and protein structures of PepTs have been developed. The aim of this review was to summarise the current knowledge regarding structure-interaction relationships (SIRs) of PepTs and their substrates as well as the potential applications of this information in therapeutic optimisation and drug development. Such information may provide insights into the efficacy of PepT drug substrates in patients, mechanisms of drug-drug/food interactions and the potential role of PepTs targeting in drug design and development strategies.

Berberine represses Wnt/β-catenin pathway activation via modulating the microRNA-103a-3p/Bromodomain-containing protein 4 axis, thereby refraining pyroptosis and reducing the intestinal mucosal barrier defect induced via colitis

Intestinal barrier dysfunction is inflammatory bowel disease’s hallmark. Berberine (BBR) has manifested its anti-inflammatory properties in colitis. For exploring the molecular mechanism of BBR’s impacts on colitis, application of a dextran sodium sulfate-induced mouse colitis in vivo model was with recording the body weight, stool consistency, stool occult blood and general physical symptoms of all groups of mice every day. Behind assessment of intestinal permeability, detection of colon damage’s degree and apoptosis, and inflammatory factors for assessment of pyroptosis was conducted. Application of interleukin-6-stimulated Caco-2 cells was for construction of an in vitro model. Then detection of cell advancement with inflammation and measurement of the barrier’s integrity were put into effect. Verification of microRNA (miR)-103a-3p and Bromodomain-containing protein 4 (BRD4)’s targeting link was conducted. Experiments have clarified BBR, elevated miR-103a-3p or repressive BRD4 was available to alleviate colitis-stimulated pyroptosis and intestinal mucosal barrier defects. BBR elevated miR-103a-3p to target BRD4; Refraining miR-103a-3p or enhancive BRD4 turned around BBR’s therapeutic action on colitis injury. BBR depressed Wnt/β-catenin pathway activation via controlling the miR-103a-3p/BRD4 axis. All in all, BBR represses Wnt/β-catenin pathway activation via modulating the miR-103a-3p/BRD4 axis, thereby mitigating colitis-stimulated pyroptosis and the intestinal mucosal barrier defect. The research suggests BBR is supposed to take on potential in colitis cure.

Micro RNA-23b as a potential biomarker in rheumatoid arthritis disease activity and severity: clinical, laboratory, and radiological cross-sectional study

Background

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease. It is characterized by an inflammatory polyarthritis that preferentially affects the small joints leading to joint damage and eventual deformity and disability, and can also present with extra-articular manifestations. Micro RNA (miRNA) is a class of non-coding RNAs which negatively regulate messenger RNA (mRNA) expression. Several studies had shown that miRNA-23b has a close relationship with inflammation and autoimmune diseases. An increasing evidence has suggested that miRNA-23b is closely associated with many inflammatory and autoimmune diseases. The current study aimed to evaluate the plasma expression of miRNA-23b in rheumatoid arthritis (RA) patients and to explore its potential association with diseases activity.

Results

RA patients had a significantly higher plasma miRNA-23b expression than controls (P < 0.001). The miRNA-23b plasma expression was significantly associated with the clinical and laboratory indices of RA activity as well as with the DAS28-ESR score (P = 0.009) and grades (P < 0.001). The miRNA-23b plasma expression was significantly correlated with the radiological severity of RA (P = 0.002).

Conclusions

Plasma expression of miRNA-23b is significantly increased in patients with RA than controls. In RA patients, plasma expression of miRNA-23b was significantly correlated with the activity and radiological severity of RA. miRNA-23b may represent a potential therapeutic target that can retard progression of RA.

Fish c-Jun N-Terminal Kinase (JNK) Pathway Is Involved in Bacterial MDP-Induced Intestinal Inflammation

The c-Jun NH₂-terminal kinases (JNKs) are an evolutionarily conserved family of serine/threonine protein kinases that play critical roles in the pathological process in species ranging from insects to mammals. However, the function of JNKs in bacteria-induced intestinal inflammation is still poorly understood. In this study, a fish JNK (CiJNK) pathway was identified, and its potential roles in bacterial muramyl dipeptide (MDP)-induced intestinal inflammation were investigated in Ctenopharyngodon idella. The present CiJNK was found to possess a conserved dual phosphorylation motif (TPY) in a serine/threonine protein kinase (S_TKc) domain and to contain several potential immune-related transcription factor binding sites, including nuclear factor kappa B (NF-κB), activating protein 1 (AP-1), and signal transducer and activator of downstream transcription 3 (STAT3), in its 5′ flanking regions. Quantitative real-time PCR results revealed that the mRNA levels of the JNK pathway genes in the intestine were significantly upregulated after challenge with a bacterial pathogen (Aeromonas hydrophila) and MDP in a time-dependent manner. Additionally, the JNK pathway was found to be involved in regulating the MDP-induced expression levels of inflammatory cytokines (IL-6, IL-8, and TNF-α) in the intestine of grass carp. Moreover, the nutritional dipeptide carnosine and Ala–Gln could effectively alleviate MDP-induced intestinal inflammation by regulating the intestinal expression of JNK pathway genes and inflammatory cytokines in grass carp. Finally, fluorescence microscopy and dual-reporter assays indicated that CiJNK could associate with CiMKK4 and CiMKK7 involved in the regulation of the AP-1 signaling pathway. Overall, these results provide the first experimental demonstration that the JNK signaling pathway is involved in the intestinal immune response to MDP challenge in C. idella, which may provide new insight into the pathogenesis of inflammatory bowel disease.

Increased Expression of microRNA-141-3p Improves Necrotizing Enterocolitis of Neonates Through Targeting MNX1

Objective: MicroRNA-141-3p (miR-141-3p) has been investigated in various kinds of cancers. This research delves into the functions and regulatory mechanisms of miR-141-3p in necrotizing enterocolitis (NEC) of neonates. Methods: NEC tissues were obtained from neonatal mice, and subsequently, expression of miR-141-3p and motor neuron and pancreas homeobox 1 (MNX1) was assayed via RT-qPCR. Moreover, the intestinal histopathological changes and histiocytic apoptosis were observed via hematoxylin and eosin (H&E) and TUNEL staining. The correlative inflammatory factors and oxidative stress markers were evaluated to uncover the influence of miR-141-3p in NEC tissue damage. Further, the relation between MNX1 and miR-141-3p was predicated, and the functions of MNX1 in inflammatory response and cell growth of IEC-6 cells were investigated. Results: Downregulated miR-141-3p and upregulated MNX1 were discovered in NEC tissues. Moreover, miR-141-3p clearly alleviated inflammation response and oxidative stress damage in NEC, which was achieved through regulating inflammatory cytokines (IL-1β, IL-6, and TNF-α) and oxidative stress markers (MPO, MDA, and SOD) expression. MNX1 was forecasted as a target gene of miR-141-3p; meanwhile, MNX1 overexpression overturned the influence of miR-141-3p in the inflammatory response and cell growth process of IEC-6 cells. Conclusion: These explorations reveal that increased expression of miR-141-3p could improve the damage to intestinal tissues in NEC through targeting MNX1. The research might exhibit a neoteric therapeutic strategy for NEC.

Circulating microRNA-23b as a new biomarker for rheumatoid arthritis

MicroRNA-23b (miR-23b) is associated with inflammation and autoimmune diseases. This study evaluated miR-23b expression and assessed its potential as a biomarker of disease activity for rheumatoid arthritis (RA). Differential expression of microRNAs was determined by miRNA microarray analysis in fibroblast-like synoviocytes (FLSs) from four trauma patients as healthy controls (HCs) and eight RA patients. The microarray results showed elevated expression of miR-23b in FLSs from RA patients and this finding was corroborated by real-time quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization using synovial tissues (STs). Furthermore, we found miR-23b levels in plasma of RA patients were significantly higher than in HCs, and plasma miR-23b levels positively correlated with the erythrocyte sedimentation rate (ESR), hypersensitive C-reactive protein (hs-CRP), C-reactive protein (CRP), DAS28, and platelet (PLT) count (P < 0.05). MiR-23b levels in plasma inversely correlated with the levels of hemoglobin (Hb), total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) (P < 0.05), but not with rheumatoid factor (RF) or anti-cyclic citrullinated peptide antibodies (ACPA) (P > 0.05). Moreover, patients with anorexia showed higher levels of miR-23b in plasma than those without anorexia. Similar results were observed with fatigue. Appropriate treatment for RA not only ameliorated the disease condition but also reversed the elevated plasma miR-23b level remarkably. These results suggest that circulating miR-23b may be a promising biomarker for RA disease activity.

The pathways and mechanisms of muramyl dipeptide transcellular transport mediated by PepT1 in enterogenous infection

BACKGROUND

The transcellular transport of muramyl dipeptide (MDP) mediated by peptide transporter (PepT1) involves the translocation into intestinal epithelial cell (IEC) stage and the transport out of IEC stage. However, its mechanism has not been fully understood. This study aimed to investigate the pathways and mechanisms of MDP transcellular transport in enterogenous infection.

METHODS

Firstly, experimental rats were randomly divided into three groups: sham-operation (sham group), MDP perfusion (MDP group), and PepT1 competitive inhibition (MDP + Gly-Gly group). Then, the overall survival (OS) and intestinal weight were measured in MDP and MDP + Gly-Gly group. HE staining was performed to observe the pathological changes of the small intestine. The levels of IL-6, IL-1b, IL-8, IL-10, TNF-α, and nitric oxide (NO) in rat serum and small intestine were determined by ELISA. To further verify the pathways and mechanisms of MDP transcellular transport from IEC in intestinal inflammatory damage, the NFκB inhibitor, PDTC, was used to treated lamina propria macrophages in small intestinal mucosa in sham, MDP, and MDP + Gly-Gly groups. Finally, the expression of CD80/86 and the antigen presentation of dendritic cells (DCs) were measured by flow cytometry.

RESULTS

MDP infusion was able to induce death, weight loss, and intestinal pathological injury in rats. Competitive binding of Gly-Gly to PepT1 effectively inhibited these effects induced by MDP. As well, competitive of PepT1 by Gly-Gly inhibited inflammation-related cytokines induced by MDP in rat serum and small intestine. Furthermore, we also found that MDP transported by PepT1 contributes to activation of macrophages and antigen presentation of DCs.

CONCLUSIONS

PepT1-NFκB signal is pivotal for activation of intestinal inflammatory response and MDP transcellular transport.

Host-derived fecal microRNAs can indicate gut microbiota healthiness and ability to induce inflammation

Disruption of intestine-microbiota symbiosis can result in chronic gut inflammation. We hypothesize that assessing the initial inflammatory potential of the microbiota in patients is essential and that host-derived miRNAs, which can be found in feces, could fulfill this function. We investigated whether the gut microbiota composition impacts the fecal miRNA profile and thereby indicates its ability to influence intestinal inflammation.

Methods: We used high-throughput qPCR to compare fecal miRNA profile between germ-free and conventional mice. Conventionalization of germfree mice by various colitogenic and non-colitogenic microbiotas (IL10^-/- and TLR5^-/- associated microbiota) was performed.

Results: We identified 12 fecal miRNAs impacted by the presence of a microbiota. Conventionalization of germfree mice by various colitogenic and non-colitogenic microbiotas associated with the development of intestinal inflammation (IL10^-/- and TLR5^-/- associated microbiota) yielded distinctively altered fecal miRNA profiles compared to that of mice receiving a “healthy” microbiota. Correlation analysis revealed the existence of interactions between the 12 abovementioned miRNAs and specific microbiota members.

Conclusion: These results showed that fecal miRNA profile can be differentially and specifically impacted by microbiota composition, and that miRNA could importantly serve as markers of the colitogenic potential of the microbiota. This is particularly relevant to assess individual state of the microbiota in patients with dysbiosis-related disorders, such as IBD and potentially determine their ability to respond to therapeutics.

Comparison of Profiles of Extracellular MicroRNA Secreted by Caco-2 Cells from the Apical Side of the Membrane under Static and Microcirculation Conditions

Extracellular microRNA are one of the indicators of the functional state of cells. Culturing of Caco-2 cells under the conditions of microcirculation in a Homunculus microfluidic device allows better simulating natural environment of the body in comparison with static culturing. Impedance spectroscopy (BioClinicum Research Center) was used for non-invasive estimation of the monolayer quality and changes in the cell apical membrane due to the formation of microvilli. Under static conditions, Caco-2 cells release more microRNA from the apical membrane than under microcirculation conditions, while secretion of miR-320a, miR-24-3p, and miR-221-3p microRNA under static conditions can indicate stress of the cells and activation of inflammatory response. Under microcirculation conditions, the expression of laminin-α1 (LAMA1) was lower than under static conditions, which indicates deeper differentiation of cells.

Meat proteins in a high-fat diet have a substantial impact on intestinal barriers through mucus layer and tight junction protein suppression in C57BL/6J mice

Protein diets are well known for body maintenance and weight loss.

Overexpression of CD98 in intestinal epithelium dysregulates miRNAs and their targeted proteins along the ileal villus-crypt axis

CD98 has been implicated in the experimental model of inflammatory bowel disease. We have previously shown that IEC-specific overexpression of CD98 mediates intestinal inflammation and intestinal epithelial barrier dysfunction. Mice overexpressing CD98 exhibited severe colitis and a greater susceptibility to CAC. Here we demonstrated CD98 overexpression to dysregulate homeostatic gradient profile of miRNA and protein expression along the ileal villus-crypt axis. Using miRNA-target gene prediction module, we observed differentially expressed miRNAs to target proteins of villus and crypt profoundly affected by CD98 overexpression. We have utilized online bioinformatics as methods to further scrutinize the biological meanings of miRNA-target data. We identified significant interactions among the differentially regulated proteins targeted by altered miRNAs in Tg mice. The biological processes affected by the predicted targets of miRNAs deviate from the homeostatic functions of the miRNA-gene-protein axis of the wildtype mice. Our results emphasize a dynamic perturbation of miRNA and protein expression in villus-crypt axis contributing to potential biological consequences of altering CD98 expression. Our findings also suggest the need for a consideration of arrays of interacting biological entities (i.e. miRNAs-mRNAs, protein-protein interaction) or a combination comparison for a better understanding of the disease pathology which is necessary for an effective therapeutic target development.

Function, Regulation, and Pathophysiological Relevance of the POT Superfamily, Specifically PepT1 in Inflammatory Bowel Disease

Mammalian members of the proton-coupled oligopeptide transporter family are integral membrane proteins that mediate the cellular uptake of di/tripeptides and peptide-like drugs and couple substrate translocation to the movement of H⁺ , with the transmembrane electrochemical proton gradient providing the driving force. Peptide transporters are responsible for the (re)absorption of dietary and/or bacterial di- and tripeptides in the intestine and kidney and maintaining homeostasis of neuropeptides in the brain. These proteins additionally contribute to absorption of a number of pharmacologically important compounds. In this overview article, we have provided updated information on the structure, function, expression, localization, and activities of PepT1 (SLC15A1), PepT2 (SLC15A2), PhT1 (SLC15A4), and PhT2 (SLC15A3). Peptide transporters, in particular, PepT1 are discussed as drug-delivery systems in addition to their implications in health and disease. Particular emphasis has been placed on the involvement of PepT1 in the physiopathology of the gastrointestinal tract, specifically, its role in inflammatory bowel diseases. © 2018 American Physiological Society. Compr Physiol 8:731-760, 2018.

MicroRNAs in mucosal inflammation

Of the total human body's surface, the majority is internal surface, belonging to the lungs (100 m²) and intestinal tract (400 m²). In comparison, the external surface area, belonging to the skin, comprises less than 1% (2 m²). Continuous exposure of the mucosal surface to external factors (e.g., pathogens, food particles) requires tight regulation to maintain homeostasis. MicroRNAs (miRNAs) have gained noticeable attention as playing important roles in maintaining the steady-state of tissues by modulating immune functions and inflammatory responses. Accordingly, associations have been found between miRNA expression levels and human health conditions and diseases. These findings have important implications in inflammatory diseases involving pulmonary and intestinal mucosa, such as acute lung injury or inflammatory bowel disease. In this review, we highlight the known biology of miRNAs and discuss the role of miRNAs in modulating mucosal defense and homeostasis. Additionally, we discuss miRNAs serving as potential therapeutic targets to treat immunological conditions, particularly mucosal inflammation.

Role of MiRNAs in Inflammatory Bowel Disease

Inflammatory bowel diseases (IBD), mainly including Crohn's disease and ulcerative colitis, are characterized by chronic inflammation of the gastrointestinal tract. Despite improvements in detection, drug treatment and surgery, the pathogenesis of IBD has not been clarified. A number of miRNAs have been found to be involved in the initiation, development and progression of IBD, and they may have the potential to be used as biomarkers and therapeutic targets. Here, we have summarized the recent advances about the roles of miRNAs in IBD and analyzed the contribution of miRNAs to general diagnosis, differential diagnosis and activity judgment of IBD. Furthermore, we have also elaborated the promising role of miRNAs in IBD-related cancer prevention and prognosis prediction.

miR-23b improves cognitive impairments in traumatic brain injury by targeting ATG12-mediated neuronal autophagy

Dysregulated microRNAs (miRNAs) have been reported to involve in the pathophysiological process of traumatic brain injury (TBI), and modulate autophagy-related genes (ATGs) expression. Our previous studies showed that neuronal autophagy was activated in the injury hippocampus post- TBI and associated with neurological and cognitive impairments. The present study was designed to investigate the possible role of miR-23b in TBI-induced cognitive impairments. We found the overexpression of miR-23b conferred a better neuronprotective effects after TBI by decreasing lesion volume, alleviating brain edema, inhibiting neuron apoptosis and attenuating long-term neurological deficits, and most interestingly, improving cognitive impairments. To further explore the molecular underlying this neuronprotection, we evaluated autophagic activity and ATG12 expression in the injury hippocampus CA1 region. The results identified that miR-23b directly targeted to the 3'UTR region of ATG12 mRNA to suppress the activation of neuronal autophagy by a dual-luciferase reporter system. Notably, overexpression of ATG12 abrogated the neuronprotective effects of miR-23b on TBI-induced neurological and cognitive impairments. Taken together, these date revealed inhibition of ATG12-mediated autophagic activity by miR-23b overexpression might be involve in cognitive improvement after TBI, indicating that miR-23b might be a potential therapeutic target for TBI.

Meat proteins had different effects on oligopeptide transporter PEPT1 in the small intestine of young rats

The peptide transporter 1 (PEPT1) in the apical membrane of enterocytes is the central mechanism for regulating the absorption of di- and tripeptides. Dietary proteins may affect PEPT1 abundance and peptide absorption. The present study aimed to characterize changes in PEPT1 mRNA and PEPT1 protein levels in the duodenum and jejunum of young rats after 7-day diet intervention with casein (reference), soy, beef, pork, chicken and fish proteins and further evaluate the impact on the epithelial absorption capacity. RT-PCR and western blot analyses showed that: (1) PEPT1 protein level in duodenum was higher (p < 0.05) for soy protein group than that for casein group. However, no difference was observed in jejunal PEPT1 protein level between any two diet groups (p > 0.05). The soy protein group had lower crypt depth and higher V/C ratio in the jejunum (p < 0.05). (2) PEPT1 mRNA levels were lower (p < 0.05) in rat duodenum and jejunum in pork, chicken and fish protein groups, whose trend was contrary to the results of jejunual histological observation with lower crypt depth, greater villus height and higher V/C ratio. In conclusion, different meat proteins alter distinct PEPT1 expression level and absorption capacity as reflected by gut morphology in small intestine.

PepT1 Expression Helps Maintain Intestinal Homeostasis by Mediating the Differential Expression of miRNAs along the Crypt-Villus Axis

In the jejunum, PepT1 is particularly enriched in the well-differentiated absorptive epithelial cells in the villi. Studies of expression and function of PepT1 along the crypt-villus axis demonstrated that this protein is crucial to the process of di/tripeptide absorption. We recently exhibited that PepT1 plays an important role in multiple biological functions, including the ability to regulate the expression/secretion of specific microRNAs (miRNAs) and the expression levels of multiple proteins. In this study, we observed that PepT1 knockout (KO) mice exhibited reduced body weight and shorten intestinal microvilli. We then examined the expression levels of various miRNAs and their target proteins along the crypt-villi axis in the jejunum of PepT1 KO mice. We found that PepT1 KO altered the distribution of miRNAs along the crypt-villus axis and changed the miRNA profiles of both villi and crypts. Using miRNA-target prediction and 2D-DIGE/mass spectrometry on villi and crypts samples, we found that ablation of PepT1 further directly or indirectly altered expression levels of certain protein targets. Collectively, our results suggest that PepT1 contributes to maintain balance of homeostasis and proper functions in the small intestine, and dysregulated miRNAs and proteins along the crypt-villus axis are highly related to this process.

Mechanism(S) Involved in the Colon-Specific Expression of the Thiamine Pyrophosphate (Tpp) Transporter

Microbiota of the large intestine synthesizes considerable amount of vitamin B1 (thiamine) in the form of thiamine pyrophosphate (TPP). We have recently demonstrated the existence of an efficient and specific carrier-mediated uptake process for TPP in human colonocytes, identified the TPP transporter (TPPT) involved (product of the SLC44A4 gene), and shown that expression of TPPT along the gastrointestinal (GI) tract is restricted to the colon. Our aim in this study was to determine the molecular basis of the colon-specific expression of TPPT focusing on a possible epigenetic mechanism. Our results showed that the CpG island predicted in the SLC44A4 promoter is non-methylated in the human colonic epithelial NCM460 cells, but is hyper-methylated in the human duodenal epithelial HuTu80 cells (as well as in the human retinal pigment epithelial ARPE19 cells). In the mouse (where TPPT expression in the GI tract is also restricted to the colon), the CpG island predicted in the Slc44a4 promoter is non-methylated in both the jejunum and colon, thus arguing against possible contribution of DNA methylation in the colon-specific expression of TPPT. A role for histone modifications in the tissue-specific pattern of Slc44a4 expression, however, was suggested by the findings that in mouse colon, histone H3 in the 5’-regulatory region of Slc44a4 is tri-methylated at lysine 4 and acetylated at lysine 9, whereas the tri-methylation at lysine 27 modification was negligible. In contrast, in the mouse jejunum, histone H3 is hyper-trimethylated at lysine 27 (repressor mark). Similarly, possible involvement of miRNA(s) in the tissue-specific expression of TPPT was also suggested by the findings that the 3’-UTR of SLC44A4 is targeted by specific miRNAs/RNA binding proteins in non-colonic, but not in colonic, epithelial cells. These studies show, for the first time, epigenetic mechanisms (histone modifications) play a role in determining the tissue-specific pattern of expression of TPPT in the GI tract.

Critical role of PepT1 in promoting colitis-associated cancer and therapeutic benefits of the anti-inflammatory PepT1-mediated tripeptide KPV in a murine model

BACKGROUND AND AIMS

The human intestinal peptide transporter 1, hPepT1, is expressed in the small intestine at low levels in the healthy colon and upregulated during inflammatory bowel disease. hPepT1 plays a role in mouse colitis and human studies have demonstrated that chronic intestinal inflammation leads to colorectal cancer (colitis-associated cancer; CAC). Hence, we assessed here the role of PepT1 in CAC.

METHODS

Mice with hPepT1 overexpression in intestinal epithelial cells (TG) or PepT1 (PepT1-KO) deletion were used and CAC was induced by AOM/DSS.

RESULTS

TG mice had larger tumor sizes, increased tumor burdens, and increased intestinal inflammation compared to WT mice. Conversely, tumor number and size and intestinal inflammation were significantly decreased in PepT1-KO mice. Proliferating crypt cells were increased in TG mice and decreased in PepT1-KO mice. Analysis of human colonic biopsies revealed an increased expression of PepT1 in patients with colorectal cancer, suggesting that PepT1 might be targeted for the treatment of CAC. The use of an anti-inflammatory tripeptide KPV (Lys-Pro-Val) transported by PepT1 was able to prevent carcinogenesis in WT mice. When administered to PepT1-KO mice, KPV did not trigger any of the inhibitory effect on tumorigenesis observed in WT mice.

CONCLUSIONS

The observations that pepT1 was highly expressed in human colorectal tumor and that its overexpression and deletion in mice increased and decreased colitis associated tumorigenesis, respectively, suggest that PepT1 is a potential therapeutic target for the treatment of colitis associated tumorigenesis.

MicroRNA367 negatively regulates the inflammatory response of microglia by targeting IRAK4 in intracerebral hemorrhage

Background

Intracerebral hemorrhage (ICH) induces microglial activation and the release of inflammatory cytokines, leading to inflammation in the brain. IRAK4, an essential component of the MyD88-dependent pathway, activates subsets of divergent signaling pathways in inflammation.

Methods

In the experiment, microglia were stimulated with erythrocyte lysates, and then miR-367, IRAK4, NF-ĸB activation and downstream proinflammatory mediator production were analyzed. In addition, inflammation, brain edema, and neurological functions in ICH mice were also assessed.

Results

Here, we report that ICH downregulated miR-367 expression but upregulated IRAK4 expression in primary microglia. We also demonstrate that miR-367 suppressed IRAK4 expression by directly binding its 3′-untranslated region. MiR-367 inhibited NF-ĸB activation and downstream proinflammatory mediator production. Knocking down IRAK4 in microglia significantly decreased the IRAK4 expression and inhibited the NF-ĸB activation and the downstream production of proinflammatory mediators. In addition, our results indicate that miR-367 could inhibit expression of proinflammatory cytokines, reduce brain edema, and improve neurological functions in ICH mice.

Conclusions

In conclusion, our study demonstrates that miR-367/IRAK4 pathway plays an important role in microglial activation and neuroinflammation in ICH. Our finding also suggests that miR-367 might represent a potential therapeutic target for ICH.

Molecular regulation of miRNAs and potential biomarkers in the progression of hepatic steatosis to NASH

Increasing evidence suggests that microRNAs regulate diverse biological functions in the liver and play a very important function in metabolic-related disorders such as nonalcoholic fatty liver disease via regulating their target genes expression. In this review, we summarized the most recent progress in identification of miRNAs involving in the progression of liver steatosis and discussed the possible mechanisms by which miRNAs contribute to the diverse pathogenic liver injuries. We provide insights into the functional network of miRNAs by connecting miRNAs, their targets and biological pathways associated to hepatic steatosis and fibrosis, with important implications for our understanding of phenotypic-based disease pathogenesis. We also discuss the possible roles and challenges of miRNAs as biomarkers for drug-induced liver injury.

MicroRNA-193a-3p Reduces Intestinal Inflammation in Response to Microbiota via Down-regulation of Colonic PepT1

Intestinal inflammation is characterized by epithelial disruption, leading to the loss of barrier function, recruitment of immune cells, and host immune responses to gut microbiota. PepT1, a di/tripeptide transporter that uptakes bacterial products, is up-regulated in inflamed colon tissue, which implies its role in bacterium-associated intestinal inflammation. Although microRNA (miRNA)-mediated gene regulation has been found to be involved in various processes of inflammatory bowel disease (IBD), the biological function of miRNAs in the pathogenesis of IBD remains to be explored. In this study we detected miRNA expression patterns in colon tissues during colitis and investigated the mechanism underlying the regulation of colonic PepT1 by miRNAs. We observed an inverse correlation between PepT1 and miR-193a-3p in inflamed colon tissues with active ulcerative colitis, and we further demonstrated that miR-193a-3p reduced PepT1 expression and activity as a target gene and subsequently suppressed the NF-κB pathway. Intracolonic delivery of miR-193a-3p significantly ameliorated dextran sodium sulfate-induced colitis, whereas the overexpression of colonic PepT1 via PepT1 3'-untranslated region mutant lentivirus vector abolished the anti-inflammatory effect of miR-193a-3p. Furthermore, antibiotic treatment eliminated the difference in the dextran sodium sulfate-induced inflammation between the presence and absence of miR-193a-3p. These findings suggest that miR-193a-3p regulation of PepT1 mediates the uptake of bacterial products and is a potent mechanism during the colonic inflammation process. Overall, we believe miR-193a-3p may be a potent regulator of colonic PepT1 for maintaining intestinal homeostasis.