Arhgap17, a RhoGTPase activating protein, regulates mucosal and epithelial barrier function in the mouse colon

Tff3 Deficiency Differentially Affects the Morphology of Male and Female Intestines in a Long-Term High-Fat-Diet-Fed Mouse Model

Trefoil factor family protein 3 (Tff3) protects the gastrointestinal mucosa and has a complex mode of action in different tissues. Here, we aimed to determine the effect of Tff3 deficiency on intestinal tissues in a long-term high-fat-diet (HFD)-fed model. A novel congenic strain without additional metabolically relevant mutations (Tff3-/-/C57Bl6NCrl strain, male and female) was used. Wild type (Wt) and Tff3-deficient mice of both sexes were fed a HFD for 36 weeks. Long-term feeding of a HFD induces different effects on the intestinal structure of Tff3-deficient male and female mice. For the first time, we found sex-specific differences in duodenal morphology. HFD feeding reduced microvilli height in Tff3-deficient females compared to that in Wt females, suggesting a possible effect on microvillar actin filament dynamics. These changes could not be attributed to genes involved in ER and oxidative stress, apoptosis, or inflammation. Tff3-deficient males exhibited a reduced cecal crypt depth compared to that of Wt males, but this was not the case in females. Microbiome-related short-chain fatty acid content was not affected by Tff3 deficiency in HFD-fed male or female mice. Sex-related differences due to Tff3 deficiency imply the need to consider both sexes in future studies on the role of Tff in intestinal function.

Evaluating Prophylactic Effect of Bovine Colostrum on Intestinal Barrier Function in Zonulin Transgenic Mice: A Transcriptomic Study

The intestinal barrier comprises a single layer of epithelial cells tightly joined to form a physical barrier. Disruption or compromise of the intestinal barrier can lead to the inadvertent activation of immune cells, potentially causing an increased risk of chronic inflammation in various tissues. Recent research has suggested that specific dietary components may influence the function of the intestinal barrier, potentially offering a means to prevent or mitigate inflammatory disorders. However, the precise mechanism underlying these effects remains unclear. Bovine colostrum (BC), the first milk from cows after calving, is a natural source of nutrients with immunomodulatory, anti-inflammatory, and gut-barrier fortifying properties. This novel study sought to investigate the transcriptome in BC-treated Zonulin transgenic mice (Ztm), characterized by dysbiotic microbiota, intestinal hyperpermeability, and mild hyperactivity, applying RNA sequencing. Seventy-five tissue samples from the duodenum, colon, and brain of Ztm and wild-type (WT) mice were dissected, processed, and RNA sequenced. The expression profiles were analyzed and integrated to identify differentially expressed genes (DEGs) and differentially expressed transcripts (DETs). These were then further examined using bioinformatics tools. RNA-seq analysis identified 1298 DEGs and 20,952 DETs in the paired (Ztm treatment vs. Ztm control) and reference (WT controls) groups. Of these, 733 DEGs and 10,476 DETs were upregulated, while 565 DEGs and 6097 DETs were downregulated. BC-treated Ztm female mice showed significant upregulation of cingulin (Cgn) and claudin 12 (Cldn12) duodenum and protein interactions, as well as molecular pathways and interactions pertaining to tight junctions, while BC-treated Ztm males displayed an upregulation of transcripts like occludin (Ocln) and Rho/Rac guanine nucleotide exchange factor 2 (Arhgf2) and cellular structures and interfaces, protein-protein interactions, and organization and response mechanisms. This comprehensive analysis reveals the influence of BC treatment on tight junctions (TJs) and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) signaling pathway gene expressions. The present study is the first to analyze intestinal and brain samples from BC-treated Ztm mice applying high-throughput RNA sequencing. This study revealed molecular interaction in intestinal barrier function and identified hub genes and their functional pathways and biological processes in response to BC treatment in Ztm mice. Further research is needed to validate these findings and explore their implications for dietary interventions aimed at improving intestinal barrier integrity and function. The MGH Institutional Animal Care and Use Committee authorized the animal study (2013N000013).

Transcriptomic Context of RUNX3 Expression in Monocytes: A Cross-Sectional Analysis

The runt-related transcription factor 3 (RUNX3) regulates the differentiation of monocytes and their response to inflammation. However, the transcriptomic context of RUNX3 expression in blood monocytes remains poorly understood. We aim to learn about RUNX3 from its relationships within transcriptomes of bulk CD14+ cells in adults. This study used immunomagnetically sorted CD14+ cell gene expression microarray data from the Multi-Ethnic Study of Atherosclerosis (MESA, n = 1202, GSE56047) and the Correlated Expression and Disease Association Research (CEDAR, n = 281, E-MTAB-6667) cohorts. The data were preprocessed, subjected to RUNX3-focused correlation analyses and random forest modeling, followed by the gene ontology analysis. Immunity-focused differential ratio analysis with intermediary inference (DRAIMI) was used to integrate the data with protein-protein interaction network. Correlation analysis of RUNX3 expression revealed the strongest positive association for EVL (r_mean = 0.75, p_FDR-MESA = 5.37 × 10^-140, p_FDR-CEDAR = 5.52 × 10^-80), ARHGAP17 (r_mean = 0.74, p_FDR-MESA = 1.13 × 10^-169, p_FDR-CEDAR = 9.20 × 10^-59), DNMT1 (r_mean = 0.74, p_FDR-MESA = 1.10 × 10^-169, p_FDR-CEDAR = 1.67 × 10^-58), and CLEC16A (r_mean = 0.72, p_FDR-MESA = 3.51 × 10^-154, p_FDR-CEDAR = 2.27 × 10^-55), while the top negative correlates were C2ORF76 (r_mean = -0.57, p_FDR-MESA = 8.70 × 10^-94, p_FDR-CEDAR = 1.31 × 10^-25) and TBC1D7 (r_mean = -0.55, p_FDR-MESA = 1.36 × 10^-69, p_FDR-CEDAR = 7.81 × 10^-30). The RUNX3-associated transcriptome signature was involved in mRNA metabolism, signal transduction, and the organization of cytoskeleton, chromosomes, and chromatin, which may all accompany mitosis. Transcriptomic context of RUNX3 expression in monocytes hints at its relationship with cell growth, shape maintenance, and aspects of the immune response, including tyrosine kinases.

Transcription analyses of differentially expressed mRNAs, lncRNAs, circRNAs, and miRNAs in the growth plate of rats with glucocorticoid-induced growth retardation

Background

Glucocorticoids (GCs) are commonly used to treat autoimmune diseases and malignancies in children and adolescents. Growth retardation is a common adverse effect of GC treatment in pediatric patients. Accumulating evidence indicates that non-coding RNAs (ncRNAs) are involved in the pathogenesis of glucocorticoid-induced growth retardation (GIGR), but the roles of specific ncRNAs in growth remain largely unknown.

Methods

In this study, 2-week-old male Sprague-Dawley rats had been treated with 2 mg/kg/d of dexamethasone for 7 or 14 days, after which the growth plate tissues were collected for high-throughput RNA sequencing to identify differentially expressed mRNAs, lncRNAs, circRNAs, and miRNAs in GIGR rats.

Results

Transcriptomic analysis identified 1,718 mRNAs, 896 lncRNAs, 60 circRNAs, and 72 miRNAs with different expression levels in the 7d group. In the 14d group, 1,515 mRNAs, 880 lncRNAs, 46 circRNAs, and 55 miRNAs with differential expression were identified. Four mRNAs and four miRNAs that may be closely associated with the development of GIGR were further validated by real-time quantitative fluorescence PCR. Function enrichment analysis indicated that the PI3K-Akt signaling pathway, NF-kappa B signaling pathway, and TGF-β signaling pathway participated in the development of the GIGR. Moreover, the constructed ceRNA networks suggested that several miRNAs (including miR-140-3p and miR-127-3p) might play an important role in the pathogenesis of GIGR.

Conclusions

These results provide new insights and important clues for exploring the molecular mechanisms underlying GIGR.

β-Arrestin2 Is Critically Involved in the Differential Regulation of Phosphosignaling Pathways by Thyrotropin-Releasing Hormone and Taltirelin

In recent years, thyrotropin-releasing hormone (TRH) and its analogs, including taltirelin (TAL), have demonstrated a range of effects on the central nervous system that represent potential therapeutic agents for the treatment of various neurological disorders, including neurodegenerative diseases. However, the molecular mechanisms of their actions remain poorly understood. In this study, we investigated phosphosignaling dynamics in pituitary GH1 cells affected by TRH and TAL and the putative role of β-arrestin2 in mediating these effects. Our results revealed widespread alterations in many phosphosignaling pathways involving signal transduction via small GTPases, MAP kinases, Ser/Thr- and Tyr-protein kinases, Wnt/β-catenin, and members of the Hippo pathway. The differential TRH- or TAL-induced phosphorylation of numerous proteins suggests that these ligands exhibit some degree of biased agonism at the TRH receptor. The different phosphorylation patterns induced by TRH or TAL in β-arrestin2-deficient cells suggest that the β-arrestin2 scaffold is a key factor determining phosphorylation events after TRH receptor activation. Our results suggest that compounds that modulate kinase and phosphatase activity can be considered as additional adjuvants to enhance the potential therapeutic value of TRH or TAL.

Rho GTPases as Key Molecular Players within Intestinal Mucosa and GI Diseases

Rho proteins operate as key regulators of the cytoskeleton, cell morphology and trafficking. Acting as molecular switches, the function of Rho GTPases is determined by guanosine triphosphate (GTP)/guanosine diphosphate (GDP) exchange and their lipidation via prenylation, allowing their binding to cellular membranes and the interaction with downstream effector proteins in close proximity to the membrane. A plethora of in vitro studies demonstrate the indispensable function of Rho proteins for cytoskeleton dynamics within different cell types. However, only in the last decades we have got access to genetically modified mouse models to decipher the intricate regulation between members of the Rho family within specific cell types in the complex in vivo situation. Translationally, alterations of the expression and/or function of Rho GTPases have been associated with several pathological conditions, such as inflammation and cancer. In the context of the GI tract, the continuous crosstalk between the host and the intestinal microbiota requires a tight regulation of the complex interaction between cellular components within the intestinal tissue. Recent studies demonstrate that Rho GTPases play important roles for the maintenance of tissue homeostasis in the gut. We will summarize the current knowledge on Rho protein function within individual cell types in the intestinal mucosa in vivo, with special focus on intestinal epithelial cells and T cells.

Immunolocalization of Keratan Sulfate in Rat Spinal Tissues Using the Keratanase Generated BKS-1(+) Neoepitope: Correlation of Expression Patterns with the Class II SLRPs, Lumican and Keratocan

This study has identified keratan sulfate in fetal and adult rat spinal cord and vertebral connective tissues using the antibody BKS-1(+) which recognizes a reducing terminal N-acetyl glucosamine-6-sulfate neo-epitope exposed by keratanase-I digestion. Labeling patterns were correlated with those of lumican and keratocan using core protein antibodies to these small leucine rich proteoglycan species. BKS-1(+) was not immunolocalized in fetal spinal cord but was apparent in adult cord and was also prominently immunolocalized to the nucleus pulposus and inner annulus fibrosus of the intervertebral disc. Interestingly, BKS-1(+) was also strongly associated with vertebral body ossification centers of the fetal spine. Immunolocalization of lumican and keratocan was faint within the vertebral body rudiments of the fetus and did not correlate with the BKS-1(+) localization indicating that this reactivity was due to another KS-proteoglycan, possibly osteoadherin (osteomodulin) which has known roles in endochondral ossification. Western blotting of adult rat spinal cord and intervertebral discs to identify proteoglycan core protein species decorated with the BKS-1(+) motif confirmed the identity of 37 and 51 kDa BKS-1(+) positive core protein species. Lumican and keratocan contain low sulfation KS-I glycoforms which have neuroregulatory and matrix organizational properties through their growth factor and morphogen interactive profiles and ability to influence neural cell migration. Furthermore, KS has interactive capability with a diverse range of neuroregulatory proteins that promote neural proliferation and direct neural pathway development, illustrating key roles for keratocan and lumican in spinal cord development.

Application quantitative proteomics approach to identify differentially expressed proteins associated with cardiac protection mediated by cycloastragenol in acute myocardial infarction rats

Acute myocardial infarction (AMI) is an acute heart disease. Cycloastragenol, as a natural product, inhibits inflammation and protects cardiomyocytes. Cycloastragenol (Y006) modulates inflammation in AMI is not known. To explore the function of Cycloastragenol in AMI, this study investigated the effect of Y006 and its mechanisms both in vitro and in vivo. Y006 influences the concentration of 11 proteins, as shown by a proteomics analysis, immunohistochemistry and western blotting. Among these 11 proteins, Erk1/2, PLCG1, IKBKG, and ZEB1 are related to inflammatory regulation. BAX, COX2, and GSK3β are involved in modulating cardiomyocyte apoptosis, and RhoA and DSC2 are directly associated with myocardial function. However, the functions of ARHGAP17 and Rit2 in heart are less well established. Additionally, Y006 suppressed TNF-α, IFN-γ and IL-17 production in PBMCs (peripheral blood monocytes) from patients with acute myocardial infarction and enhanced IL-10 and IL-4 expression. Similar results were obtained in a rat model of AMI by flow cytometry detection and ELISA. Our findings indicate that Y006 protects rats from AMI through direct or indirect inhibition of inflammation and cardiomyocyte apoptosis. However, the specific mechanism of Y006's protective function requires further study. Nonetheless, this research revealed a novel aspect for the treatment of myocardial infarction. SIGNIFICANCE: In the present study, we undertook the first proteomic evaluation of Cycloastragenol (Y006) function in acute myocardial infarction (AMI). Y006 significantly improved myocardial function in vivo by regulating multiple molecular expressions. Hypoxia is a direct reason for AMI. And our data support a role of Y006 in gene expression, cell apoptosis under hypoxia. The conclusions of this research assist to explain the potential molecular mechanism in Cycloastragenol treating AMI and supply a new method for ameliorating AMI.

Esrp1-Regulated Splicing of Arhgef11 Isoforms Is Required for Epithelial Tight Junction Integrity

The epithelial-specific splicing regulators Esrp1 and Esrp2 are required for mammalian development, including establishment of epidermal barrier functions. However, the mechanisms by which Esrp ablation causes defects in epithelial barriers remain undefined. We determined that the ablation of Esrp1 and Esrp2 impairs epithelial tight junction (TJ) integrity through loss of the epithelial isoform of Rho GTP exchange factor Arhgef11. Arhgef11 is required for the maintenance of TJs via RhoA activation and myosin light chain (MLC) phosphorylation. Ablation or depletion of Esrp1/2 or Arhgef11 inhibits MLC phosphorylation and only the epithelial Arhgef11 isoform rescues MLC phosphorylation in Arhgef11 KO epithelial cells. Mesenchymal Arhgef11 transcripts contain a C-terminal exon that binds to PAK4 and inhibits RhoA activation byArhgef11. Deletion of the mesenchymal-specific Arhgef11 exon in Esrp1/2 KO epithelial cells using CRISPR/Cas9 restored TJ function, illustrating how splicing alterations can be mechanistically linked to disease phenotypes that result from impaired functions of splicing regulators.

Kinase activity of ERBB3 contributes to intestinal organoids growth and intestinal tumorigenesis

As a member of the epidermal growth factor receptor (EGFR) family, ERBB3 plays an essential role in development and disease independent of inherently inactive kinase domain. Recently, ERBB3 has been found to bind to ATP and has catalytic activity in vitro. However, the biological function of ERBB3 kinase activity remains elusive in vivo. Here we have identified the physiological function of inactivated ERBB3 kinase activity by creating Erbb3‐K740M knockin mice in which ATP cannot bind to ERBB3. Unlike Erbb3 knockout mice, kinase‐inactive Erbb3^K740M homozygous mice were born in Mendelian ratios and showed normal development. After dextran sulfate sodium‐induced colitis, the kinase‐inactive Erbb3 mutant mice showed normal recovery. However, the outgrowth of ileal organoids by neuregulin‐1 treatment was more attenuated in Erbb3 mutant mice than in WT mice. Moreover, in combination with the Apc^Min mouse, the proportion of polyps less than 1 mm in diameter in mutant mice was higher than in control mice and an increase in the number of apoptotic cells was observed in polyps from mutant mice compared with polyps from control mice. Taken together, the ERBB3 kinase activity contributes to the outgrowth of ileal organoids and intestinal tumorigenesis, and the development of ERBB3 kinase inhibitors, including epidermal growth factor receptor family members, can be a potential way to target colorectal cancer.

ARHGAP17 suppresses tumor progression and up-regulates P21 and P27 expression via inhibiting PI3K/AKT signaling pathway in cervical cancer

ARHGAP17 has long been thought to be involved in the maintenance of tight junction and epithelial barrier. Recently, a few Rho GTPase activating proteins (RhoGAPs) have been identified as tumor suppressors in some human cancers. The present study aimed to explore ARHGAP17 expression in cervical cancer and the possible function in tumor progression. ARHGAP17 expression in cervical cancer cell lines was assessed by RT-PCR and Western blotting. ARHGAP17 expression in cervical cancer tissues and normal tissues was assessed by immunohistochemistry. The cell proliferation was determined using CCK-8 in vitro and subcutaneous xenograft model in vivo. Here, we showed lower expression of ARHGAP17 in cell lines and human cervical cancer samples. Manipulation of ARHGAP17 affected cell proliferation in vitro and tumor growth in vivo. Furthermore, the phosphorylation of AKT was enhanced in ARHGAP17 silencing cervical cancer cells. ARHGAP17 can elevate P21 and P27 expression level through inhibiting PI3K/AKT signaling pathway. Stepwise investigations demonstrated that ARHGAP17 suppressed malignant phenotype of cervical cancer cells via inhibiting PI3K/AKT signaling pathway. These results reveal that ARHGAP17 functions as a tumor suppressor in cervical cancer that suppresses tumor growth, at least partly, through inhibition of PI3K/AKT signaling and up-regulation of P21 and P27 expression.

Functional Consequences of Keratan Sulfate Sulfation in Electrosensory Tissues and in Neuronal Regulation

Keratan sulfate (KS) is a functional electrosensory and neuro-instructive molecule. Recent studies have identified novel low sulfation KS in auditory and sensory tissues such as the tectorial membrane of the organ of Corti and the Ampullae of Lorenzini in elasmobranch fish. These are extremely sensitive proton gradient detection systems that send signals to neural interfaces to facilitate audition and electrolocation. High and low sulfation KS have differential functional roles in song learning in the immature male zebra song-finch with high charge density KS in song nuclei promoting brain development and cognitive learning. The conductive properties of KS are relevant to the excitable neural phenotype. High sulfation KS interacts with a large number of guidance and neuroregulatory proteins. The KS proteoglycan microtubule associated protein-1B (MAP1B) stabilizes actin and tubulin cytoskeletal development during neuritogenesis. A second 12 span transmembrane synaptic vesicle associated KS proteoglycan (SV2) provides a smart gel storage matrix for the storage of neurotransmitters. MAP1B and SV2 have prominent roles to play in neuroregulation. Aggrecan and phosphacan have roles in perineuronal net formation and in neuroregulation. A greater understanding of the biology of KS may be insightful as to how neural repair might be improved.

Keratan sulfate (KS)-proteoglycans and neuronal regulation in health and disease: the importance of KS-glycodynamics and interactive capability with neuroregulatory ligands

Compared to the other classes of glycosaminoglycans (GAGs), that is, chondroitin/dermatan sulfate, heparin/heparan sulfate and hyaluronan, keratan sulfate (KS), have the least known of its interactive properties. In the human body, the cornea and the brain are the two most abundant tissue sources of KS. Embryonic KS is synthesized as a linear poly-N-acetyllactosamine chain of d-galactose-GlcNAc repeat disaccharides which become progressively sulfated with development, sulfation of GlcNAc is more predominant than galactose. KS contains multi-sulfated high-charge density, monosulfated and non-sulfated poly-N-acetyllactosamine regions and thus is a heterogeneous molecule in terms of chain length and charge distribution. A recent proteomics study on corneal KS demonstrated its interactivity with members of the Slit-Robbo and Ephrin-Ephrin receptor families and proteins which regulate Rho GTPase signaling and actin polymerization/depolymerization in neural development and differentiation. KS decorates a number of peripheral nervous system/CNS proteoglycan (PG) core proteins. The astrocyte KS-PG abakan defines functional margins of the brain and is up-regulated following trauma. The chondroitin sulfate/KS PG aggrecan forms perineuronal nets which are dynamic neuroprotective structures with anti-oxidant properties and roles in neural differentiation, development and synaptic plasticity. Brain phosphacan a chondroitin sulfate, KS, HNK-1 PG have roles in neural development and repair. The intracellular microtubule and synaptic vesicle KS-PGs MAP1B and SV2 have roles in metabolite transport, storage, and export of neurotransmitters and cytoskeletal assembly. MAP1B has binding sites for tubulin and actin through which it promotes cytoskeletal development in growth cones and is highly expressed during neurite extension. The interactive capability of KS with neuroregulatory ligands indicate varied roles for KS-PGs in development and regenerative neural processes.

Long isoform of VEGF stimulates cell migration of breast cancer by filopodia formation via NRP1/ARHGAP17/Cdc42 regulatory network

VEGF stimulates endothelial cells as a key molecule in angiogenesis. VEGF also works as a multifunction molecule, which targets a variety of cell members in the tumor microenvironment. We aimed to reveal VEGF-related molecular mechanisms on breast cancer cells. VEGF-knocked-out MDA-MB-231 cells (231 VEGFKOex3 ) showed rounded morphology and shorter perimeter (1.6-fold, p < 0.0001). The 231 VEGFKOex3 cells also showed impaired cell migration (2.6-fold, p = 0.002). Bevacizumab treatment did not induce any change in morphology and mobility. Soluble neuropilin-1 overexpressing MDA-MB-231 cells (231 sNRP1 ) exhibited rounded morphology and shorter perimeter (1.3-fold, p < 0.0001). The 231 sNRP1 cells also showed impaired cell migration (1.7-fold, p = 0.003). These changes were similar to that of 231 VEGFKOex3 cells. As MDA-MB-231 cells express almost no VEGFR, these results indicate that the interaction between NRP1 and long isoform of VEGF containing a NRP-binding domain regulates the morphology and migration ability of MDA-MB-231 cells. Genome-wide gene expression profiling identified ARHGAP17 as one of the target genes in the downstream of the VEGF/NRP1 signal. We also show that VEGF/NRP1 signal controls filopodia formation of the cells by modulating Cdc42 activity via ARHGAP17. Among 1,980 breast cancer cases from a public database, the ratio of VEGF and SEMA3A in primary tumors (n = 450) of hormone-receptor-negative breast cancer is associated with ARHGAP17 expression inversely, and with disease free survival. Altogether, the bevacizumab-independent VEGF/NRP1/ARHGAP17/Cdc42 regulatory network plays important roles in malignant behavior of breast cancer.

Peroxisome proliferator-activated receptor gamma activation promotes intestinal barrier function by improving mucus and tight junctions in a mouse colitis model

BACKGROUND AND AIMS

Defects in mucus and intestinal epithelia can lead to intestinal inflammation in colitis. Reduced peroxisome proliferator-activated receptor gamma (PPAR_γ) in the mucosa may contribute to inflammation. However, the roles of PPAR_γ in the intestinal barrier remain poorly understood.

METHODS

Chronic colitis was induced in C57BL/6 mice by administration of dextran sulfate sodium (DSS) for 27 days. Three days before DSS treatment, mice were treated with the PPAR_γ agonist rosiglitazone (Ro) orally at 20 mg kg^-1 day^-1.

RESULTS

The colitis based on disease activity index and colonic histopathology was significantly ameliorated in the DSS + Ro group. Additionally, mice in the DSS + Ro group had a thicker mucous layer than those in DSS + NS group, and muc2 mRNA expression was elevated significantly along with the mouse atonal homolog, SAM-pointed domain-containing Ets-like factor, and anterior gradient 2 genes. Moreover, tight junctions were up-regulated, whereas long myosin light chain kinase and phosphorylation of the myosin II light chain were lower in DSS + Ro mice. Similarly, after HT-29 and Caco-2 cells were treated by LPS or LPS + Ro, PPAR_γ activation by Ro could effectively improve the intestinal barrier, including intestinal mucus and tight junctions.

CONCLUSIONS

Our results demonstrate that activated PPAR_γ could effectively promote intestinal mucus integrity by increasing the number of goblet cells, the glycosylation of mucins, and tight junctions via an MLCK-dependent mechanism.

The effect of fucoidan on intestinal flora and intestinal barrier function in rats with breast cancer

Recent research studies have shown that the intestinal flora are related to the occurrence and progress of breast cancer. This study investigates the effect of fucoidan on intestinal flora and intestinal barrier function in rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced breast cancers. Sixty female Sprague-Dawley rats were randomly assigned to the control group, the model group, and the F1 and F2 groups, which were fed fucoidan at concentrations of 200 and 400 mg per kg bw (body weight), respectively. Intestinal histopathological analysis was performed and 16S rDNA high-throughput sequencing was used to provide an overview of the intestinal flora composition. The contents of d-lactic acid (d-LA), diamine oxidase (DAO) and endotoxin in plasma were detected by ELISA. Expression levels of the tight junction (TJ) proteins, phosphorylated p38 MAPK and ERK1/2 were measured using western blotting. Our results suggested that the intestinal wall of the model group was damaged. However, after fucoidan intervention, the villi were gradually restored. ELISA showed that the levels of plasma endotoxin, d-LA and DAO decreased in the F1 and F2 groups compared to those in the model group. Fucoidan treatment also increased the expressions of ZO-1, occludin, claudin-1 and claudin-8. Furthermore, the expression levels of phosphorylated p38 MAPK and ERK1/2 were upregulated in fucoidan treatment groups. The results of 16S rDNA high-throughput sequencing indicated that fucoidan increased the diversity of the intestinal microbiota and induced changes in microbial composition, with the increased Bacteroidetes/Firmicutes phylum ratio. In conclusion, the supplement of fucoidan could improve the fecal microbiota composition and repair the intestinal barrier function. The study suggested the use of fucoidan as an intestinal flora modulator for potential prevention of breast cancer.

BAR Domain Proteins Regulate Rho GTPase Signaling

The Bin-Amphiphysin-Rvs (BAR) domain is a membrane lipid binding domain present in a wide variety of proteins, often proteins with a role in Rho-regulated signaling pathways. BAR domains do not only confer binding to lipid bilayers, they also possess a membrane sculpturing ability and thereby directly control the topology of biomembranes. BAR domain-containing proteins participate in a plethora of physiological processes but the common denominator is their capacity to link membrane dynamics to actin dynamics and thereby integrate processes such as endocytosis, exocytosis, vesicle trafficking, cell morphogenesis and cell migration. The Rho family of small GTPases constitutes an important bridging theme for many BAR domain-containing proteins. This review article will focus predominantly on the role of BAR proteins as regulators or effectors of Rho GTPases and it will only briefly discuss the structural and biophysical function of the BAR domains.

Interplay of GTPases and Cytoskeleton in Cellular Barrier Defects during Gut Inflammation

An essential role of the intestine is to build and maintain a barrier preventing the luminal gut microbiota from invading the host. This involves two coordinated physical and immunological barriers formed by single layers of intestinal epithelial and endothelial cells, which avoid the activation of local immune responses or the systemic dissemination of microbial agents, and preserve tissue homeostasis. Accordingly, alterations of epithelial and endothelial barrier functions have been associated with gut inflammation, for example during inflammatory bowel disease (IBD). The discriminative control of nutriment uptake and sealing toward potentially pathological microorganisms requires a profound regulation of para- and transcellular permeability. On the subcellular level, the cytoskeleton exerts key regulatory functions in the maintenance of cellular barriers. Increased epithelial/endothelial permeability occurs primarily as a result of a reorganization of cytoskeletal–junctional complexes. Pro-inflammatory mediators such as cytokines can induce cytoskeletal rearrangements, causing inflammation-dependent defects in gut barrier function. In this context, small GTPases of the Rho family and large GTPases from the Dynamin superfamily appear as major cellular switches regulating the interaction between intercellular junctions and actomyosin complexes, and in turn cytoskeleton plasticity. Strikingly, some of these proteins, such as RhoA or guanylate-binding protein-1 (GBP-1) have been associated with gut inflammation and IBD. In this review, we will summarize the role of small and large GTPases for cytoskeleton plasticity and epithelial/endothelial barrier in the context of gut inflammation.

Disruption of the epithelial barrier during intestinal inflammation: Quest for new molecules and mechanisms

The intestinal epithelium forms a key protective barrier that separates internal organs from the harmful environment of the gut lumen. Increased permeability of the gut barrier is a common manifestation of different inflammatory disorders contributing to the severity of disease. Barrier permeability is controlled by epithelial adherens junctions and tight junctions. Junctional assembly and integrity depend on fundamental homeostatic processes such as cell differentiation, rearrangements of the cytoskeleton, and vesicle trafficking. Alterations of intestinal epithelial homeostasis during mucosal inflammation may impair structure and remodeling of apical junctions, resulting in increased permeability of the gut barrier. In this review, we summarize recent advances in our understanding of how altered epithelial homeostasis affects the structure and function of adherens junctions and tight junctions in the inflamed gut. Specifically, we focus on the transcription reprogramming of the cell, alterations in the actin cytoskeleton, and junctional endocytosis and exocytosis. We pay special attention to knockout mouse model studies and discuss the relevance of these mechanisms to human gastrointestinal disorders.