Regional differences in the ultrastructure of mucosal macrophages in the rat large intestine

We previously clarified the histological characteristics of macrophages in the rat small intestine using serial block-face scanning electron microscopy (SBF-SEM). However, the regional differences in the characteristics of macrophages throughout the large intestine remain unknown. Here, we performed a pilot study to explore the regional differences in the ultrastructure of mucosal macrophages in the large intestine by using SBF-SEM analysis. SBF-SEM analysis conducted on the luminal side of the cecum and descending colon revealed macrophages as amorphous cells possessing abundant lysosomes and vacuoles. Macrophages in the cecum exhibited a higher abundance of lysosomes and a lower abundance of vacuoles than those in the descending colon. Macrophages with many intraepithelial cellular processes were observed beneath the intestinal superficial epithelium in the descending colon. Moreover, macrophages in contact with nerve fibers were more prevalent in the cecum than in the descending colon, and a subset of them surrounded a nerve bundle only in the cecum. In conclusion, the present pilot study suggested that the quantity of some organelles (lysosomes and vacuoles) in macrophages differed between the cecum and the descending colon and that there were some region-specific subsets of macrophages like nerve-associated macrophages in the cecum.

Molecular mechanism of the TGF‑β/Smad7 signaling pathway in ulcerative colitis

Aberrant TGF‑β/Smad7 signaling has been reported to be an important mechanism underlying the pathogenesis of ulcerative colitis. Therefore, the present study aimed to investigate the effects of a number of potential anti‑colitis agents on intestinal epithelial permeability and the TGF‑β/Smad7 signaling pathway in an experimental model of colitis. A mouse model of colitis was first established before anti‑TNF‑α and 5‑aminosalicyclic acid (5‑ASA) were administered intraperitoneally and orally, respectively. Myeloperoxidase (MPO) activity, histological index (HI) of the colon and the disease activity index (DAI) scores were then detected in each mouse. Transmission electron microscopy (TEM), immunohistochemical and functional tests, including Evans blue (EB) and FITC‑dextran (FD‑4) staining, were used to evaluate intestinal mucosal permeability. The expression of epithelial phenotype markers E‑cadherin, occludin, zona occludens (ZO‑1), TGF‑β and Smad7 were measured. In addition, epithelial myosin light chain kinase (MLCK) expression and activity were measured. Anti‑TNF‑α and 5‑ASA treatments was both found to effectively reduce the DAI score and HI, whilst decreasing colonic MPO activity, plasma levels of FD‑4 and EB permeation of the intestine. Furthermore, anti‑TNF‑α and 5‑ASA treatments decreased MLCK expression and activity, reduced the expression of Smad7 in the small intestine epithelium, but increased the expression of TGF‑β. In mice with colitis, TEM revealed partial epithelial injury in the ileum, where the number of intercellular tight junctions and the expression levels of E‑cadherin, ZO‑1 and occludin were decreased, all of which were alleviated by anti‑TNF‑α and 5‑ASA treatment. In conclusion, anti‑TNF‑α and 5‑ASA both exerted protective effects on intestinal epithelial permeability in an experimental mouse model of colitis. The underlying mechanism may be mediated at least in part by the increase in TGF‑β expression and/or the reduction in Smad7 expression, which can inhibit epithelial MLCK activity and in turn reduce mucosal permeability during the pathogenesis of ulcerative colitis.

Mitochondrial complex II in intestinal epithelial cells regulates T cell-mediated immunopathology

Intestinal epithelial cell (IEC) damage by T cells contributes to graft-versus-host disease, inflammatory bowel disease and immune checkpoint blockade-mediated colitis. But little is known about the target cell-intrinsic features that affect disease severity. Here we identified disruption of oxidative phosphorylation and an increase in succinate levels in the IECs from several distinct in vivo models of T cell-mediated colitis. Metabolic flux studies, complemented by imaging and protein analyses, identified disruption of IEC-intrinsic succinate dehydrogenase A (SDHA), a component of mitochondrial complex II, in causing these metabolic alterations. The relevance of IEC-intrinsic SDHA in mediating disease severity was confirmed by complementary chemical and genetic experimental approaches and validated in human clinical samples. These data identify a critical role for the alteration of the IEC-specific mitochondrial complex II component SDHA in the regulation of the severity of T cell-mediated intestinal diseases.

Ultrastructural intestinal mucosa change after prolonged inhibition of gastric acid secretion by omeprazole in male rats

Omeprazole is a potent inhibitor of gastric acid secretion. It was reported that omeprazole induced dramatic gastric mucosa morphologic changes from the resting state to the stimulated state. However, the effect of omeprazole administration on the ultrastructure and absorptive function of small intestines was largely unknown. Here, male Sprague-Dawley rats were daily treated with a single dose of omeprazole for 12 or 24 weeks. Ultrastructure intestinal mucosal change in duodenum, jejunum, and ileum was observed. We also determined small intestine inflammation, using intraepithelial lymphocytes activation. Finally, magnesium levels were measured in plasma, urine, feces, muscle, and bone to determine systemic magnesium balance. Omeprazole-treated rats had significantly decreased the width of tight junction, villous length, and absorptive area of duodenum, jejunum, and ileum compared to control rats. The small intestine of the omeprazole-treated group showed significantly higher intraepithelial lymphocytes activation levels compared with the control group. Lower secretory granules of Paneth cells at the base of the crypts were showed in omeprazole-treated rats. They also had significantly lower plasma, urinary, bone, and muscle Mg2+ contents indicating hypomagnesemia with systemic magnesium deficiency. In conclusion, prolonged omeprazole treatment-induced small intestinal inflammation and villous atrophy, which led to decrease small intestinal magnesium absorption in the condition of proton pump inhibitor-induced hypomagnesemia.

Intestinal Barrier Breakdown and Mucosal Microbiota Disturbance in Neuromyelitis Optical Spectrum Disorders

Background and Purpose

The mechanism underlying the pathology of neuromyelitis optica spectrum disorders (NMOSD) remains unclear even though antibodies to the water channel protein aquaporin-4 (AQP4) on astrocytes play important roles. Our previous study showed that dysbiosis occurred in the fecal microbiota of NMOSD patients. In this study, we further investigated whether the intestinal barrier and mucosal flora balance are also interrupted in NMOSD patients.

Methods

Sigmoid mucosal biopsies were collected by endoscopy from six patients with NMOSD and compared with samples from five healthy control (HC) individuals. These samples were processed for electron microscopy and immunohistochemistry to investigate changes in ultrastructure and in the number and size of intestinal inflammatory cells. Changes in mucosal flora were also analyzed by high-throughput 16S ribosomal RNA gene amplicon sequencing.

Results

The results from bacterial rRNA gene sequencing showed that bacterial diversity was decreased, but Streptococcus and Granulicatella were abundant in the colonic mucosa specimens of NMOSD patients compared to the HC individuals. The intercellular space between epithelia of the colonic mucosa was wider in NMOSD patients compared to the HC subjects (p < 0.01), and the expression of tight junction proteins [occludin, claudin-1 and zonula occludens-1 (ZO-1)] in NMOSD patients significantly decreased compared to that in the HC subjects. We also found numerous activated macrophages with many inclusions within the cytoplasm, mast cells with many particles in their cytoplasm, and enlarged plasma cells with rich developed rough endoplasmic reticulum in the lamina propria of the mucosa of the patients with NMOSD. Quantitative analysis showed that the percentages of small CD38+ and CD138+ cells (plasma cells) were lower, but the percentage of larger plasma cells was higher in NMOSD patients.

Conclusion

The present study demonstrated that the intestinal barrier was disrupted in the patients with NMOSD, accompanied by dysbiosis and inflammatory activation of the gut. The mucosal microbiota imbalance and inflammatory responses might allow pathogens to cross the damaged intestinal barrier and participate in pathological process in NMOSD. However, further study on the pathological mechanism of NMOSD underlying gut dysbiosis is warranted in the future.

Role of interleukin 1 beta in the regulation of rat intestinal multidrug resistance-associated protein 2 under conditions of experimental endotoxemia

Multidrug resistance-associated protein 2 (Mrp2), expressed at the brush border membrane (BBM) of the enterocyte, is an ABC transporter with relevant intestinal barrier function. Its toxicological relevance lies in preventing absorption and tissue accumulation of dietary contaminants, drugs, and potentially harmful endogenous metabolites. Expression and activity of intestinal Mrp2 is downregulated in LPS-induced endotoxemia. In addition, confocal microscopy studies demonstrated internalization of the transporter to endocytic vesicles. Since IL-1β plays an important role as early mediator of LPS-inflammatory responses, we evaluated whether IL-1β mediates LPS-induced impairment of Mrp2 function. Two protocols were used: I) In vivo administration of LPS (5 mg/kg b.wt., i.p., single dose) to rats in simultaneous with administration of anti-IL-1β (25 μg/kg b.wt., i.p., 4 doses), followed by studies of Mrp2 expression, localization and activity, 24 h after LPS administration; II) In vitro incubation of isolated intestinal sacs with IL-1β (10 ng/mL) for 30 min, followed by analysis of Mrp2 activity and localization. We found that in vivo immunoneutralization of IL-1β partially prevented the decrease of Mrp2 protein expression and activity as well as its internalization to intracellular domains induced by LPS. Involvement of IL-1β in the alteration of Mrp2 localization and activity was more directly demonstrated in isolated intestinal sacs, as incubation with IL-1β resulted in detection of Mrp2 in intracellular regions of the enterocyte in simultaneous with alteration of transport activity. In conclusion, IL-1β induces early internalization of intestinal Mrp2, which could partially explain loss of expression at the BBM under conditions of experimental endotoxemia. Concomitant impairment of Mrp2-dependent barrier function may have pathophysiological relevance since IL-1β mediates the effect of many local and systemic inflammatory processes.

Altered organization of collagen fibers in the uninvolved human colon mucosa 10 cm and 20 cm away from the malignant tumor

Remodelling of collagen fibers has been described during every phase of cancer genesis and progression. Changes in morphology and organization of collagen fibers contribute to the formation of microenvironment that favors cancer progression and development of metastasis. However, there are only few data about remodelling of collagen fibers in healthy looking mucosa distant from the cancer. Using SHG imaging, electron microscopy and specialized softwares (CT-FIRE, CurveAlign and FiberFit), we objectively visualized and quantified changes in morphology and organization of collagen fibers and investigated possible causes of collagen remodelling (change in syntheses, degradation and collagen cross-linking) in the colon mucosa 10 cm and 20 cm away from the cancer in comparison with healthy mucosa. We showed that in the lamina propria this far from the colon cancer, there were changes in collagen architecture (width, straightness, alignment of collagen fibers and collagen molecules inside fibers), increased representation of myofibroblasts and increase expression of collagen-remodelling enzymes (LOX and MMP2). Thus, the changes in organization of collagen fibers, which were already described in the cancer microenvironment, also exist in the mucosa far from the cancer, but smaller in magnitude.

Viable bacterial colonization is highly limited in the human intestine in utero

Mucosal immunity develops in the human fetal intestine by 11-14 weeks of gestation, yet whether viable microbes exist in utero and interact with the intestinal immune system is unknown. Bacteria-like morphology was identified in pockets of human fetal meconium at mid-gestation by scanning electron microscopy (n = 4), and a sparse bacterial signal was detected by 16S rRNA sequencing (n = 40 of 50) compared to environmental controls (n = 87). Eighteen taxa were enriched in fetal meconium, with Micrococcaceae (n = 9) and Lactobacillus (n = 6) the most abundant. Fetal intestines dominated by Micrococcaceae exhibited distinct patterns of T cell composition and epithelial transcription. Fetal Micrococcus luteus, isolated only in the presence of monocytes, grew on placental hormones, remained viable within antigen presenting cells, limited inflammation ex vivo and possessed genomic features linked with survival in the fetus. Thus, viable bacteria are highly limited in the fetal intestine at mid-gestation, although strains with immunomodulatory capacity are detected in subsets of specimens.

If host is refractory, insistent parasite goes berserk: Trypanosomatid Blastocrithidia raabei in the dock bug Coreus marginatus

Here we characterized the development of the trypanosomatid Blastocrithidia raabei in the dock bug Coreus marginatus using light and electron microscopy. This parasite has been previously reported to occur in the host hemolymph, which is rather typical for dixenous trypanosomatids transmitted to a plant or vertebrate with insect's saliva. In addition, C. marginatus has an unusual organization of the intestine, which makes it refractory to microbial infections: two impassable segments isolate the anterior midgut portion responsible for digestion and absorption from the posterior one containing symbiotic bacteria. Our results refuted the possibility of hemolymph infection, but revealed that the refractory nature of the host provokes very aggressive behavior of the parasite and makes its life cycle more complex, reminiscent of that in some dixenous trypanosomatids. In the pre-barrier midgut portion, the epimastigotes of B. raabei attach to the epithelium and multiply similarly to regular insect trypanosomatids. However, when facing the impassable constricted region, the parasites rampage and either fiercely break through the isolating segments or attack the intestinal epithelium in front of the barrier. The cells of the latter group pass to the basal lamina and accumulate there, causing degradation of the epitheliocytes and thus helping the epimastigotes of the former group to advance posteriorly. In the symbiont-containing post-barrier midgut segment, the parasites either attach to bacterial cells and produce cyst-like amastigotes (CLAs) or infect enterocytes. In the rectum, all epimastigotes attach either to the cuticular lining or to each other and form CLAs. We argue that in addition to the specialized life cycle B. raabei possesses functional cell enhancements important either for the successful passage through the intestinal barriers (enlarged rostrum and well-developed Golgi complex) or as food reserves (vacuoles in the posterior end).

Quercetin Exposure Suppresses the Inflammatory Pathway in Intestinal Organoids from Winnie Mice

Inflammatory bowel diseases (IBDs) are chronic and relapsing immune disorders that result, or possibly originate, from epithelial barrier defects. Intestinal organoids are a new reliable tool to investigate epithelial response in models of chronic inflammation. We produced organoids from the ulcerative colitis murine model Winnie to explore if the chronic inflammatory features observed in the parental intestine were preserved by the organoids. Furthermore, we investigated if quercetin administration to in vitro cultured organoids could suppress LPS-induced inflammation in wild-type organoids (WT-organoids) and spontaneous inflammation in ulcerative colitis organoids (UC-organoids). Our data demonstrate that small intestinal organoids obtained from Winnie mice retain the chronic intestinal inflammatory features characteristic of the parental tissue. Quercetin administration was able to suppress inflammation both in UC-organoids and in LPS-treated WT-organoids. Altogether, our data demonstrate that UC-organoids are a reliable experimental system for investigating chronic intestinal inflammation and pharmacological responses.

[STRUCTURAL FORM OF THE FOLLICLE-ASSOCIATED EPITHELIUM OF PEYERS' PATCHES OF THE ALBINO RATS' SMALL INTESTINE]

The paper was aimed at detailed specification of microscopic structure of the intestinal epithelium, associated with lymphoid nodules of the Peyer's patches of the albino rats' small intestine. 30 mature albino male rats weighted 200,0±20,0 g were involved into the study. Slices of the small intestine with Peyer's patches have been analyzed. Serial paraffin sections have been studied using the "Konus' light microscope. Morphometric characteristics of the tissue structures have been obtained using the Sigeta X 1 mm/100 Div.x0.01mm object-micrometer. The findings of the study of serial paraffin sections have discovered a hitherto unknown form of association of the intestinal epithelium with lymphoid nodules, which was called column-inline lymphoepithelial fractals. Between them, wide intercellular fissures were found; they separated both the limbic enterocytes, and columns of lymphocytic elements, located beneath them.

From 2-dimensional to 3-dimensional: Overcoming dilemmas in intestinal mucosal interpretation

The purpose of this review is to provide a definitive account of small intestinal mucosal structure and interpretation. The coeliac lesion has been well known, but not well described to date and this review aims to identify the interpretative difficulties which have arisen over time with the histological assessment of coeliac disease. In early coeliac interpretation, there were significant inaccuracies, particularly surrounding intraepithelial lymphocyte counts and the degree of villous flattening which occurred in the tissue. Many of these interpretive pitfalls are still encountered today, increasing the potential for diagnostic errors. These difficulties are mostly due to the fact that stained 2-dimensional sections can never truly represent the 3-dimensional framework of the intestinal tissue under investigation. Therefore, this review offers a critical account occasioned by these 2-dimensional interpretative errors and which, in our opinion, should in general be jettisoned. As a result, we leave a framework regarding the true 3-dimensional knowledge of mucosal structure accrued over the 70-year period of study, and one which is available for future reference.

Persistence and safety assessment of novel probiotic strain Lactobacillus plantarum 1 strain Lp86 and Lp36 in Salmonella typhi infected mice

The species of Lactic acid bacteria are known to confer beneficial effects on the host by inhabiting in their gastrointestinal tract (GIT). They succeed in surviving the harsh conditions of the GIT by exhibiting strong tolerance against gastric acids, digestive enzymes and bile simultaneously antagonizing the pathogens by production of antimicrobials. This study has been conducted to elaborate these probiotic characteristics in vivo for which mice were intragastrically given a probiotic approved dose of 1011cfu/ml for 4 days to assess the persistence of two probiotic candidates Lactobacillus plantarum Lp36 and Lactobacillus plantarum Lp86. The fecal count of the test probiotic candidates were seen to persist well in the GIT for 15 days with a count ranging between 104-108cfu/ mg of feces (p>0.01). The safety assessment of L. plantarum Lp36 in healthy and S. typhi in infected mice showed an increase in cell count from (day zero of inoculation) 106cfu/100mg of feces to108cfu/100mg (p>0.01) which was maintained till day six, suggesting the persistence in the GIT. The sections of the mice intestinal lining under scanning electron microscope revealed the adherence of Lp36 and Lp86 to the intestinal epithelia. The mice did not show any adverse effect on its health. These findings make our strains promising probiotic candidates to be used to promote health benefits after further assessments.

Redox modulatory protective effects of ω-3 fatty acids rich fish oil against experimental colitis

Ulcerative colitis (UC), a form of inflammatory bowel disease (IBD), is an immune-modulated disorder characterized by chronic and recurring inflammatory episodes. Oxidative stress and COX pathway of prostaglandin (PG) biosynthesis are indispensable to pathogenesis of UC. Any imbalance between PGs can compromise the mucosal homeostasis, leading to mucosal damage and chronic inflammation. However, blocking these PGs using classical Cox inhibitors such as non-steroidal anti-inflammatory drugs (NSAIDs) can instead aggravate signs of IBD. Therefore, realizing the need for safer and well tolerable alterative treatment approaches, currently, we evaluated the efficacy of n-3 fatty acids rich fish oil (FO) in the resolution of UC. Using a dextran sodium sulfate (DSS) model of experimental colitis, we have demonstrated that supplementation of FO containing 180 mg EPA and 120 mg DHA for 1 month relieved the signs (diarrhea, bloody stools, weight loss) of colitis-associated inflammation. To understand the biophysical changes associated with FO mediated inflammatory regulation, impedance measurement and Fourier transform infrared spectroscopy (FTIR) were done. These changes were also correlated with oxidative stress through markers such as GST, glutathione peroxidase (GPx), LPO, catalase, protein carbonyl content, GR, etc. in colonic mucosa. The modulation of COX mediated pathways in UC-associated inflammation was observed by protein expressions of various pro-inflammatory cytokines such as TNF-α and enzymes of PG synthesis such as COX-2, PGES, TXAS, and anti-inflammatory PGDS. Refuting the earlier reports that suggested the contradictory effects of FO, in the current study, we evidently demonstrated that the protective effects of FO are mediated through molecular mechanisms involving the redox-regulation of metabolism of key lipid metabolites.

The microstructure of buccal cavity and alimentary canal of Siganus rivulatus: Scanning electron microscope study

The microstructure of the oral cavity and alimentary canal of herbivorous fish Siganus rivulatus collected from the Red Sea were investigated by using scanning electron microscope (SEM). The results showed that S. rivulatus has three types of teeth, tri-cusped, bi-cusped, and papilliform. A taste bud (Type I) was recorded in the oropharyngeal cavity. Characteristic styles of microridges on the cell's surface inside the buccal cavity were recorded. Also, the distribution of the mucous cells in the lining of the mouth cavity, alimentary canal was observed. Mucosal folds along the distinct parts of alimentary canal, showed characteristic pattern which was complex in the intestinal mucosa. The results concluded that there are characteristic microstructures according to feeding habitat compared with other bony fishes.

KCa3.1 Transgene Induction in Murine Intestinal Epithelium Causes Duodenal Chyme Accumulation and Impairs Duodenal Contractility

The epithelial intermediate-conductance calcium/calmodulin-regulated KCa3.1 channel is considered to be a regulator of intestine function by controlling chloride secretion and water/salt balance. Yet, little is known about the functional importance of KCa3.1 in the intestinal epithelium in vivo. Our objective was to determine the impact of epithelial-specific inducible overexpression of a KCa3.1 transgene (KCa3.1+) and of inducible suppression (KCa3.1−) on intestinal homeostasis and function in mice. KCa3.1 overexpression in the duodenal epithelium of doxycycline (DOX)-treated KCa3.1+ mice was 40-fold above the control levels. Overexpression caused an inflated duodenum and doubling of the chyme content. Histology showed conserved architecture of crypts, villi, and smooth muscle. Unaltered proliferating cell nuclear antigen (PCNA) immune reactivity and reduced amounts of terminal deoxynucleotide transferase mediated X-dUTP nick end labeling (TUNEL)-positive apoptotic cells in villi indicated lower epithelial turnover. Myography showed a reduction in the frequency of spontaneous propulsive muscle contractions with no change in amplitude. The amount of stool in the colon was increased and the frequency of colonic contractions was reduced in KCa3.1+ animals. Senicapoc treatment prevented the phenotype. Suppression of KCa3.1 in DOX-treated KCa3.1− mice caused no overt intestinal phenotype. In conclusion, inducible KCa3.1 overexpression alters intestinal functions by increasing the chyme content and reducing spontaneous contractions and epithelial apoptosis. Induction of epithelial KCa3.1 can play a mechanistic role in the process of adaptation of the intestine.

Shen-ling-bai-zhu-san, a spleen-tonifying Chinese herbal formula, alleviates lactose-induced chronic diarrhea in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Shen-ling-bai-zhu-san (SLBZS) was firstly documented in ancient Chinese medical works "Tai Ping Hui Min He Ji Ju Fang" in Song-dynasty. It has been widely used for treating gastrointestinal disorders such as diarrhea with poor appetite for about 900 years. The present study is to observe the effects of SLBZS on high lactose diet-induced chronic diarrhea.

MATERIALS AND METHODS

Rats were subjected to a high lactose diet to induce chronic diarrhea, which were then administrated with SLBZS or smecta. General symptom, body weight, food consumption, water intake and fecal fluid content were recorded every day. The intestinal absorption function was determined by d-xylose uptake assay. The ultrastructures of intestine segments including jejunum, ileum, proximal and distal colon were observed by transmission electron microscopy. Additionally, sodium transport proteins including γ-epithelial sodium channel (ENAC-γ) and sodium/potassium-transporting ATPase subunit alpha-1 (ATP1A1) in distal colon were detected by immunohistochemistry and western blotting.

RESULTS

Diarrheal rats produced watery or loose, sticky feces, and presented inactiveness and grouping. A high lactose diet caused a significant decline in body weight, serum d-xylose level as well as food consumption rather than water intake. In contrast, general symptoms were improved to a certain extent and body weight loss was alleviated in the rats treated by SLBZS for one week. Fecal fluid content in diarrheal rats treated by SLBZS presented a gradual decrease trend with about 55% in the end, which was significantly less than the model group with about 81%. Meanwhile, SLBZS significantly improved the serum d-xylose level and reversed abnormal changes of tight junctions and microvilli in intestine. Additionally, SLBZS significantly modulated the abnormal expressions of ENAC-γ and ATP1A1 in distal colon of diarrheal rats.

CONCLUSIONS

These findings suggested that SLBZS exhibited ameliorating effects against lactose-induced diarrhea, which might be attributed to its modulations on intestinal absorption function as well as mucosal ultrastructure.

Localization of the 1,25-dihydroxyvitamin d-mediated response in the intestines of mice

1,25-Dihydroxyvitamin D₃ (1,25(OH)₂D) elicits a transcriptional response in the intestines. Assessments of this response are often derived from crude tissue homogenates and eliminate the ability to discriminate among different cell types. Here, we used an RNA in situ hybridization assay, RNAScope (Advanced Cell Diagnostics, Newark, CA), to identify the cells in the intestine that respond to 1,25(OH)₂D with expression of cytochrome P450 family 24 subfamily A member 1 (Cyp24a1) mRNA. Mice were gavaged with a single bolus dose of 1,25(OH)₂D to target the duodenum or a glucuronic acid conjugate of 1,25(OH)₂D, β-G-1,25(OH)₂D, to target the colon. QRT-PCR analysis of Cyp24a1 mRNA verified that the 1,25(OH)₂D-induced responses were present. RNAScope revealed that the mRNA response present after six hours is limited to mature enterocytes exposed to the intestinal lumen in both the duodenum and colon. No detectable expression was observed in goblet cells, lamina propria, muscularis mucosa muscle, submucosa and submucosal lymphoid follicles, or tunica muscularis. Our findings have identified epithelial enterocytes to be the intestinal targets for 1,25(OH)₂D in both the duodenum and colon.

Protective Effect of Low Molecular Weight Seleno-Aminopolysaccharide on the Intestinal Mucosal Oxidative Damage

Low molecular weight seleno-aminopolysaccharide (LSA) is an organic selenium compound comprising selenium and low molecular weight aminopolysaccharide (LA), a low molecular weight natural linear polysaccharide derived from chitosan. LSA has been found to exert strong pharmacological activity. In this study, we aimed to investigate the protective effect of LSA on intestinal mucosal oxidative stress in a weaning piglet model by detecting the growth performance, intestinal mucosal structure, antioxidant indices, and expression level of intracellular transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and its related factors. Our results indicated that LSA significantly increased the average daily gain and feed/gain (p < 0.05), suggesting that LSA can effectively promote the growth of weaning piglets. The results of scanning electron microscope (SEM) microscopy showed that LSA effectively reduced intestinal damage, indicating that LSA improved the intestinal stress response and protected the intestinal structure integrity. In addition, diamine oxidase (DAO) and d-lactic acid (d-LA) levels remarkably decreased in LSA group compared with control group (p < 0.05), suggesting that LSA alleviated the damage and permeability of weaning piglets. LSA significantly increased superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and total antioxidant capacity (T-AOC) levels, but decreased malondialdehyde (MDA) level, indicating that LSA significantly enhanced the antioxidant capacity and reduced oxidative stress in weaning piglets. RT-PCR results showed that LSA significantly increased GSH-Px1, GSH-Px2, SOD-1, SOD-2, CAT, Nrf2, HO-1, and NQO1 gene expression (p < 0.05). Western blot analysis revealed that LSA activated the Nrf2 signaling pathway by downregulating the expression of Keap1 and upregulating the expression of Nrf2 to protect intestinal mucosa against oxidative stress. Collectively, LSA reduced intestinal mucosal damage induced by oxidative stress via Nrf2-Keap1 pathway in weaning stress of infants.

Micro-patterned endogenous stroma equivalent induces polarized crypt-villus architecture of human small intestinal epithelium

The small intestine is the major site for digestion, drug and nutrient absorption, as well as a primary site for many diseases. Current in vitro gut models fail in reproducing the complex intestinal extracellular matrix (ECM) network of the lamina propria and the peculiar architecture of the crypt-villus axis. Here we proposed a novel in vitro human intestine model that mimics the intestinal stromal topography and composition and strictly reproduces the tissue polarity with the crypt-villus architecture. First we developed a 3D human intestinal stromal equivalent (3D-ISE) composed of human intestinal subepithelial myofibroblasts (ISEMFs) embedded in their own extracellular matrix. Then, we seeded human colon carcinoma-derived cells (Caco-2) onto flat or patterned cell-synthetized stromal equivalent structure and cultured them until the formation of a well-oriented epithelium. We demonstrated that the patterned stroma increases the absorbing surface area, the epithelial proliferation rate, and the density of microvilli. In addition it induces changes in the biological functions of the epithelial cells such as enzymes and mucus production, polarization and tightness showing a physiological cell-lineage compartmentalization along the crypt/villi axes with the undifferentiated phenotypes at the base. At last, we reproduced an inflamed intestinal tissue model in which we identified the contribution of the stromal microenvironment by molecular (cytokines release and MMPs production) and immunofluorescence analyses and the effects of the epithelial-stromal cross-talk in the intestinal innate immunity by multiphoton investigation that revealed differences in the collagen network architecture. STATEMENT OF SIGNIFICANCE: The intestinal stroma morphology and composition has a fundamental role in crypt-villus development and appropriate epithelial cell-lineage compartmentalization. On this base, here we develop an engineered organotypic model of human intestine equivalent in which a functional epithelial/ECM crosstalk is recapitulated. Due to its accessible luminal surface it provides a new platform for preclinical studies of mucosal immunology and bowel inflammation as well as the assessment of pharmaco-toxicity studies.

Postnatal maturation of the intestinal epithelial barrier in prairie voles

Intestinal epithelium develops during gestation and continues to mature post-natally into a selective barrier that will protect the individual while still allowing passage of nutrients. Until fully mature, the risk of translocation of microorganisms, toxins or antigens into the sub-epithelial tissue is high and could result in pathologies with life-altering consequences, or even premature death. Because of their monogamous mating system, prairie voles are an emerging model for studying the role of the intestinal microbiota in modulating social behavior via the microbiota-gut-brain-behavior axis. However, knowledge about the voles' intestinal barrier maturation is lacking. Understanding the maturation of the intestine epithelial barrier can complement the extensive behavioral literature for future studies involving the vole gut-brain axis. In this study, we characterized intestinal barrier function by demonstrating that two-week-old prairie voles have high paracellular absorption of FITC-dextran molecules prior to markedly decreased permeability at three weeks of age. In light of the fundamental role of tight junctions in maintaining epithelial integrity regulating intestinal permeability, we examined tight junction gene expression profiles. Transmission electron microscopy was used to visualize tight junction structure. Our results provide a timeline for intestinal barrier maturation and point to tight junction proteins involved in this process in prairie voles.

Nano-delivery of trace minerals for marine fish larvae: influence on skeletal ossification, and the expression of genes involved in intestinal transport of minerals, osteoblast differentiation, and oxidative stress response

Currently, the larviculture of many marine fish species with small-sized larvae depends for a short time after hatching, on the supply of high-quality live zooplankton to ensure high survival and growth rates. During the last few decades, the research community has made great efforts to develop artificial diets, which can completely substitute live prey. However, studies aimed at determining optimal levels of minerals in marine larvae compound feeds and the potential of novel delivery vectors for mineral acquisition has only very recently begun. Recently, the agro-food industry has developed several nano-delivery systems, which could be used for animal feed, too. Delivery through nano-encapsulation of minerals and feed additives would protect the bioactive molecules during feed manufacturing and fish feeding and allow an efficient acquisition of active substances into biological system. The idea is that dietary minerals in the form of nanoparticles may enter cells more easily than their larger counterparts enter and thus speed up their assimilation in fish. Accordingly, we evaluated the efficacy of early weaning diets fortified with organic, inorganic, or nanoparticle forms of trace minerals (Se, Zn, and Mn) in gilthead seabream (Sparus aurata) larvae. We tested four experimental diets: a trace mineral-deficient control diet, and three diets supplemented with different forms of trace minerals. At the end of the feeding trial, larvae growth performance and ossification, and the level of expression of six target genes (SLC11A2β, dmt1, BMP2, OC, SOD, GPX), were evaluated. Our data demonstrated that weaning diets supplemented with Mn, Se, and Zn in amino acid-chelated (organic) or nanoparticle form were more effective than diets supplemented with inorganic form of minerals to promote bone mineralization, and prevent skeletal anomalies in seabream larvae. Furthermore, nanometals markedly improved larval stress resistance in comparison to inorganic minerals and upregulated mRNA copy number of OC gene. The expression of this gene was strongly correlated with mineralization degree, thus confirming its potency as a good marker of bone mineralization in gilthead seabream larvae.

Acute Exposure to Commonly Ingested Emulsifiers Alters Intestinal Mucus Structure and Transport Properties

The consumption of generally regarded as safe emulsifiers has increased, and has been associated with an increased prevalence of inflammatory bowel and metabolic diseases, as well as an altered microbiome. The mucus barrier, which selectively controls the transport of particulates and microorganisms to the underlying epithelial layer, has been previously shown to be altered by dietary salts and lipids. However, the potential impact of emulsifiers on the protective mucus barrier, its permeability, and associated structural changes are not clear. In this study, we analyzed changes in the mucus barrier to both passively diffusing nanoparticles and actively swimming E. coli upon exposure to two emulsifiers, carboxymethylcellulose (CMC) and polysorbate 80 (Tween). When exposed to CMC, mucus pore size decreased, which resulted in significantly slower E. coli speed and particle diffusion rates through mucus. Tween exposure minimally impacted mucus microstructure and particle diffusion, but increased E. coli speed in mucus. Moreover, both emulsifiers appeared to alter mucus amount and thickness in rat intestinal tissue and mucus-producing cell cultures. These results indicate that acute exposure to emulsifiers impacts barrier and structural properties of intestinal mucus, modulating interactions between intestinal lumen contents, microbes, and underlying tissue, which may contribute to development of intestinal inflammation.

Cytochemical features of the digestive tract mucosa of Hemisorubim platyrhynchos (Siluriformes: Pimelodidae)

Membranous organelles, acid glycoconjugates and lipids were characterized in the digestive tract mucosa of Hemisorubim platyrhynchos by cytochemistry techniques. Two types of mucous-secreting cells were observed in the digestive tract epithelium: goblet cells in the oesophagus and intestine and epithelial cells in the stomach. These cells had a Golgi apparatus more developed than the other cell types. The cytochemical analysis revealed that secretory granules are reactive to acid glycoconjugates, varying in reaction intensity according to the region of the digestive tract. Acid glycoconjugate reactions were also observed in oesophageal epithelial cell microridges and in enterocyte microvilli. In the digestive tract, acid glycoconjugates act to protect the epithelial surface, increasing mucous viscosity, which facilitates the passage of food, prevents the binding of parasites and facilitates their removal. Through lipid staining, a coated membrane was observed around each secretory granule of the oesophageal and intestinal goblet cells, while gastric epithelial cells granules were fully reactive. Oxynticopeptic cells of the gastric glands showed lipid droplets in the cytoplasm and also in the mitochondrial matrix, which act as an energy reserve for these cells that have a high energy demand. Enterocytes showed a well-developed smooth endoplasmic reticulum, especially in the apical region of the cell, being related to absorption and resynthesis of lipids.

Protective Effect of Aplysin Supplementation on Intestinal Permeability and Microbiota in Rats Treated with Ethanol and Iron

Aplysin, a kind of phytochemicals or phytonutrients, is purified from red alga Laurencia tristicha. The present study aims to investigate the influence of aplysin on changes of intestinal permeability and microbiota induced by excessive ethanol and iron. Thirty male rats were randomly divided into three groups (10/group): control group (normal saline); ethanol + iron group as EI treated with ethanol (8–12 mL/kg/day) and iron (1000 mg/kg) in diet; EI supplemented with aplysin (150 mg/kg/day) group as AEI; the trial lasts for 12 weeks. The result showed that levels of plasma endotoxin, fatty acid-binding protein 2, D-lactic acid, diamine oxidase were increased in rats in the EI group; and significantly decreased by 14%, 17%, 26%, 16%, respectively (p < 0.05) in the AEI group after the 12-week aplysin treatment. Moreover, in the AEI group the amount of Escherichia coli and Bacteroides fragilis were higher, while the amount of Lactobacillus, Bifidobacterium and Clostridium were lower than those in the EI group. The expressions of iron transporters divalent-metal transporter 1(DMT1) and ferroportin 1(FPN1) were significantly upregulated in the EI group compared to those in the control group. In conclusion, aplysin could effectively improve intestinal permeability and intestinal flora disorder induced with excessive ethanol and iron.

Dietary sodium butyrate improves intestinal development and function by modulating the microbial community in broilers

This study investigated the effects of dietary sodium butyrate (SB) supplementation, provided as a specially coated product, on growth performance, intestinal development, morphological structure and function in broilers. In total, 720 one-day-old Arbor Acres male broilers were randomly allocated into six treatment groups with six replicates each and then fed basal diets (control) supplemented with 0, 200, 400, 800 or 1000 mg/kg of SB or with antibiotics (100 mg/kg aureomycin and 20 mg/kg colistin sulfate). The growth trial lasted for 42 days. No differences (P>0.05) in growth performance were detected between groups during the grower period (1–21 d) or over the total (1–42 d) trial period, whereas the addition of SB improved the intestinal structure by stimulating (P<0.05) goblet cells on jejunal and ileal villi accompanied by a trend towards increased (P_diets<0.10) ileal villus height. In addition, more inerratic leaf-shaped villi and mucus secretion and significantly fewer erosions were demonstrated by scanning electron microscopy. Apart from decreased (P<0.05) malondialdehyde (MDA) in the ileal mucosa at 21 d of age, supplemental SB at higher doses (800 mg/kg) led to greater (P<0.05) total antioxidant capacity and depressed (P<0.05) MDA concentrations in the jejunal mucosa. Birds fed with 400 mg/kg and 800 mg/kg SB had higher (P<0.05) acetic acid concentrations at 42 d and higher butyric acid at 21 d in the jejunum chyme. Morever, chicks fed SB diet were found to have higher concentrations of butyric acid (P<0.05) in the ileal chyme. SB additions at 400 mg/kg displayed higher Firmicutes and Proteobacteria levels, while a higher (P<0.05) relative abundance of Bacteroidetes was observed at 800 mg/kg. Furthermore, we found a striking decrease in Enterobacteriaceae and increases in Lachnospiraceae and Rikenellaceae in the cecal lumen of birds fed 800 mg/kg SB as well as a higher proportion of Ruminococcaceae and a noticeable reduction (P<0.05) of Lactobacillaceae in birds treated with 400 mg/kg SB. Taken together, our results support the importance of SB in improving the intestinal development, morphological structure and biological functions of broilers through modulation of the microbial community, which seems to be optimized for gut health at higher doses (800 mg/kg) of SB.

Ischemia/reperfusion injury in porcine intestine - Viability assessment

AIM

To investigate viability assessment of segmental small bowel ischemia/reperfusion in a porcine model.

METHODS

In 15 pigs, five or six 30-cm segments of jejunum were simultaneously made ischemic by clamping the mesenteric arteries and veins for 1 to 16 h. Reperfusion was initiated after different intervals of ischemia (1-8 h) and subsequently monitored for 5-15 h. The intestinal segments were regularly photographed and assessed visually and by palpation. Intraluminal lactate and glycerol concentrations were measured by microdialysis, and samples were collected for light microscopy and transmission electron microscopy. The histological changes were described and graded.

RESULTS

Using light microscopy, the jejunum was considered as viable until 6 h of ischemia, while with transmission electron microscopy the ischemic muscularis propria was considered viable until 5 h of ischemia. However, following ≥ 1 h of reperfusion, only segments that had been ischemic for ≤ 3 h appeared viable, suggesting a possible upper limit for viability in the porcine mesenteric occlusion model. Although intraluminal microdialysis allowed us to closely monitor the onset and duration of ischemia and the onset of reperfusion, we were unable to find sufficient level of association between tissue viability and metabolic markers to conclude that microdialysis is clinically relevant for viability assessment. Evaluation of color and motility appears to be poor indicators of intestinal viability.

CONCLUSION

Three hours of total ischemia of the small bowel followed by reperfusion appears to be the upper limit for viability in this porcine mesenteric ischemia model.

A 3D intestinal tissue model supports Clostridioides difficile germination, colonization, toxin production and epithelial damage

Endospore-forming Clostridioides difficile is a causative agent of antibiotic-induced diarrhea, a major nosocomial infection. Studies of its interactions with mammalian tissues have been hampered by the fact that C. difficile requires anaerobic conditions to survive after spore germination. We recently developed a bioengineered 3D human intestinal tissue model and found that low O2 conditions are produced in the lumen of these tissues. Here, we compared the ability of C. difficile spores to germinate, produce toxin and cause tissue damage in our bioengineered 3D tissue model versus in a 2D transwell model in which human cells form a polarized monolayer. 3D tissue models or 2D polarized monolayers on transwell filters were challenged with the non-toxin producing C. difficile CCUG 37787 serotype X (ATCC 43603) and the toxin producing UK1 C. difficile spores in the presence of the germinant, taurocholate. Spores germinated in both the 3D tissue model as well as the 2D transwell system, however toxin activity was significantly higher in the 3D tissue models compared to the 2D transwells. Moreover, the epithelium damage in the 3D tissue model was significantly more severe than in 2D transwells and damage correlated significantly with the level of toxin activity detected but not with the amount of germinated spores. Combined, these results show that the bioengineered 3D tissue model provides a powerful system with which to study early events leading to toxin production and tissue damage of C. difficile with mammalian cells under anaerobic conditions. Furthermore, these systems may be useful for examining the effects of microbiota, novel drugs and other potential therapeutics directed towards C. difficile infections.

Ultrastructural Alterations of Midgut Epithelium, But Not Greater Wing Fluctuating Asymmetry, in Paper Wasps (Polistes dominula) from Urban Environments

Polistes paper wasps can be used to monitor trace metal contaminants, but the effects of pollution on the health of these insects are still unknown. We evaluated, in a south-eastern area of Spain, whether workers of Polistes dominula collected at urban and rural sites differ in health of midgut tissue and in fluctuating asymmetry, an estimate of developmental noise. We found that wasps collected at the urban sites had abundant lead (Pb)-containing spherites, which were less visible in wasps from the rural sites. Evident ultrastructural alterations in the epithelium of the midgut of the wasps collected at the urban sites included broken and disorganized microvilli, a high amount and density of heterochromatin in the nucleus of epithelial cells, cytoplasmic vacuolization and mitochondrial disruptions. Altogether, these findings suggest a negative effect on the transmembrane transport and a less efficient transcription. On the contrary, a healthy epithelium was observed in wasps from the rural sites. These differences may be preliminarily linked with levels of lead pollution, given that wasps from urban sites had double the Pb concentrations of wasps from rural sites. Level of fluctuating asymmetry was unrelated to wasp origin, thus suggesting no link between developmental noise and Pb-driven pollution.

Marked differences in tight junction composition and macromolecular permeability among different intestinal cell types

BACKGROUND

Mammalian small intestinal tight junctions (TJ) link epithelial cells to one another and function as a permselective barrier, strictly modulating the passage of ions and macromolecules through the pore and leak pathways, respectively, thereby preventing the absorption of harmful compounds and microbes while allowing regulated transport of nutrients and electrolytes. Small intestinal epithelial permeability is ascribed primarily to the properties of TJs between adjoining enterocytes (ENTs), because there is almost no information on TJ composition and the paracellular permeability of nonenterocyte cell types that constitute a small but significant fraction of the intestinal epithelia.

RESULTS

Here we directed murine intestinal crypts to form specialized organoids highly enriched in intestinal stem cells (ISCs), absorptive ENTs, secretory goblet cells, or Paneth cells. The morphological and morphometric characteristics of these cells in organoids were similar to those in vivo. The expression of certain TJ proteins varied with cell type: occludin and tricellulin levels were high in both ISCs and Paneth cells, while claudin-1, -2, and -7 expression was greatest in Paneth cells, ISCs, and ENTs, respectively. In contrast, the distribution of claudin-15, zonula occludens 1 (ZO-1), and E-cadherin was relatively homogeneous. E-cadherin and claudin-7 marked mainly the basolateral membrane, while claudin-2, ZO-1, and occludin resided in the apical membrane. Remarkably, organoids enriched in ENTs or goblet cells were over threefold more permeable to 4 and 10 kDa dextran compared to those containing stem and Paneth cells. The TJ-regulator larazotide prevented the approximately tenfold increases in dextran flux induced by the TJ-disrupter AT1002 into organoids of different cell types, indicating that this ZO toxin nonselectively increases permeability. Forced dedifferentiation of mature ENTs results in the reacquisition of ISC-like characteristics in TJ composition and dextran permeability, suggesting that the post-differentiation properties of TJs are not hardwired.

CONCLUSIONS

Differentiation of adult intestinal stem cells into mature secretory and absorptive cell types causes marked, but potentially reversible, changes in TJ composition, resulting in enhanced macromolecular permeability of the TJ leak pathway between ENTs and between goblet cells. This work advances our understanding of how cell differentiation affects the paracellular pathway of epithelia.

Human small intestine is capable of restoring barrier function after short ischemic periods

AIM

To assess intestinal barrier function during human intestinal ischemia and reperfusion (IR).

METHODS

In a human experimental model, 6 cm of jejunum was selectively exposed to 30 min of ischemia (I) followed by 30 and 120 min of reperfusion (R). A sham procedure was also performed. Blood and tissue was sampled at all-time points. Functional barrier function was assessed using dual-sugar absorption tests with lactulose (L) and rhamnose (R). Plasma concentrations of citrulline, an amino acid described as marker for enterocyte function were measured as marker of metabolic enterocytes restoration. Damage to the epithelial lining was assessed by immunohistochemistry for tight junctions (TJs), by plasma marker for enterocytes damage (I-FABP) and analyzed by electron microscopy (EM) using lanthanum nitrate as an electrondense marker.

RESULTS

Plasma L/R ratio’s were significantly increased after 30 min of ischemia (30I) followed by 30 min of reperfusion (30R) compared to control (0.75 ± 0.10 vs 0.20 ± 0.09, P < 0.05). At 120 min of reperfusion (120R), ratio’s normalized (0.17 ± 0.06) and were not significantly different from control. Plasma levels of I-FABP correlated with plasma L/R ratios measured at the same time points (correlation: 0.467, P < 0.01). TJs staining shows distortion of staining at 30I. An intact lining of TJs was again observed at 30I120R. Electron microscopy analysis revealed disrupted TJs after 30I with paracellular leakage of lanthanum nitrate, which restored after 30I120R. Furthermore, citrulline concentrations closely paralleled the histological perturbations during intestinal IR.

CONCLUSION

This study directly correlates histological data with intestinal permeability tests, revealing that the human gut has the ability of to withstand short episodes of ischemia, with morphological and functional recovery of the intestinal barrier within 120 min of reperfusion.

Intestinal epithelium, intraepithelial lymphocytes and the gut microbiota - Key players in the pathogenesis of celiac disease

Celiac disease (CD) is a chronic immune-mediated disorder triggered by the ingestion of gluten in genetically predisposed individuals. Before activating the immune system, gluten peptides are transferred by the epithelial barrier to the mucosal lamina propria, where they are deamidated by intestinal tissue transglutaminase 2. As a result, they strongly bind to human leucocyte antigens (HLAs), especially HLA-DQ2 and HLA-DQ8, expressed on antigen-presenting cells. This induces an inflammatory response, which results in small bowel enteropathy. Although gluten is the main external trigger activating both innate and adaptive (specific) immunity, its presence in the intestinal lumen does not fully explain CD pathogenesis. It has been hypothesized that an early disruption of the gut barrier in genetically susceptible individuals, which would result in an increased intestinal permeability, could precede the onset of gluten-induced immune events. The intestinal barrier is a complex functional structure, whose functioning is dependent on intestinal microbiota homeostasis, epithelial layer integrity, and the gut-associated lymphoid tissue with its intraepithelial lymphocytes (IELs). The aim of this paper was to review the current literature and summarize the role of the gut microbiota, epithelial cells and their intercellular junctions, and IELs in CD development.

Combustion-derived nanoparticles, the neuroenteric system, cervical vagus, hyperphosphorylated alpha synuclein and tau in young Mexico City residents

Mexico City (MC) young residents are exposed to high levels of fine particulate matter (PM_2.5), have high frontal concentrations of combustion-derived nanoparticles (CDNPs), accumulation of hyperphosphorylated aggregated α-synuclein (α-Syn) and early Parkinson's disease (PD). Swallowed CDNPs have easy access to epithelium and submucosa, damaging gastrointestinal (GI) barrier integrity and accessing the enteric nervous system (ENS). This study is focused on the ENS, vagus nerves and GI barrier in young MC v clean air controls. Electron microscopy of epithelial, endothelial and neural cells and immunoreactivity of stomach and vagus to phosphorylated ɑ-synuclein Ser129 and Hyperphosphorylated-Tau (Htau) were evaluated and CDNPs measured in ENS. CDNPs were abundant in erythrocytes, unmyelinated submucosal, perivascular and intramuscular nerve fibers, ganglionic neurons and vagus nerves and associated with organelle pathology. ɑSyn and Htau were present in 25/27 MC gastric,15/26 vagus and 18/27 gastric and 2/26 vagus samples respectively. We strongly suggest CDNPs are penetrating and damaging the GI barrier and reaching preganglionic parasympathetic fibers and the vagus nerve. This work highlights the potential role of CDNPs in the neuroenteric hyperphosphorylated ɑ-Syn and tau pathology as seen in Parkinson and Alzheimer's diseases. Highly oxidative, ubiquitous CDNPs constitute a biologically plausible path into Parkinson's and Alzheimer's pathogenesis.

Vasoactive Intestinal Polypeptide and Mast Cells Regulate Increased Passage of Colonic Bacteria in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Irritable bowel syndrome (IBS) is associated with intestinal dysbiosis and symptoms of IBS develop following gastroenteritis. We aimed to study the passage of live bacteria through the colonic epithelium, and determine the role of mast cells (MCs) and vasoactive intestinal polypeptide (VIP) in barrier regulation in IBS and healthy individuals.

METHODS

Colon biopsies from 32 women with IBS and 15 age-matched healthy women (controls) were mounted in Ussing chambers; we measured numbers of fluorescently labeled Escherichia coli HS and Salmonella typhimurium that passed through from the mucosal side to the serosal side of the tissue. Some biopsies were exposed to agents that block the VIP receptors (VPAC1 and VPAC2) or MCs. Levels of VIP and tryptase were measured in plasma and biopsy lysates. Number of MCs and MCs that express VIP or VIP receptors were quantified by immunofluorescence. Biopsies from an additional 5 patients with IBS and 4 controls were mounted in chambers and Salmonella were added; we studied passage routes through the epithelium by transmission electron microscopy and expression of tight junctions by confocal microscopy.

RESULTS

In colon biopsies from patients with IBS, larger numbers of E coli HS and S typhimurium passed through the epithelium than in biopsies from controls (P < .0005). In transmission electron microscopy analyses, bacteria were found to cross the epithelium via only the transcellular route. Bacterial passage was reduced in biopsies from patients with IBS and controls after addition of antibodies against VPACs or ketotifen, which inhibits MCs. Plasma samples from patients with IBS had higher levels of VIP than plasma samples from controls. Biopsies from patients with IBS had higher levels of tryptase, larger numbers of MCs, and a higher percentage of MCs that express VPAC1 than biopsies from controls. In biopsies from patients with IBS, addition of Salmonella significantly reduced levels of occludin; subsequent addition of ketotifen significantly reversed this effect.

CONCLUSIONS

We found that colonic epithelium tissues from patients with IBS have increased translocation of commensal and pathogenic live bacteria compared with controls. The mechanisms of increased translocation include MCs and VIP.

Protective responses of intestinal mucous cells in a range of fish-helminth systems

Histopathological, immunofluorescence and ultrastructural studies were conducted on the intestines of four fish species infected with different taxa of enteric helminths. Brown trout (Salmo trutta trutta), eel (Anguilla anguilla) and tench (Tinca tinca) obtained from Lake Piediluco (central Italy) were examined. Brown trout and eel were infected with two species of acanthocephalans, and tench was parasitized with a tapeworm species. In addition to the above site, specimens of chub (Squalius cephalus) and brown trout infected with an acanthocephalan were examined from the River Brenta (north Italy). Moreover, eels were examined from a brackish water, Comacchio lagoons (north Italy), where one digenean species was the predominant enteric worm. All the helminths species induced a similar response, the hyperplasia of the intestinal mucous cells, particularly of those secreting acid mucins. Local endocrine signals seemed to affect the production and secretion of mucus in the parasitized fish, as worms often were surrounded by an adherent mucus layer or blanket. This is the first quantitative report of enteric worm effects on the density of various mucous cell types and on the mucus composition in intestine of infected/uninfected conspecifics. We provide a global comparison between the several fish-helminth systems examined.

Lactobacillus plantarum culture supernatants improve intestinal tissue exposed to deoxynivalenol

In the present study, histological, morphometrical and ultrastructural analysis were performed to investigate intestinal mucosa changes in piglets exposed to deoxynivalenol alone or associated with two strains of Lactobacillus plantarum and the respective culture supernatants. Jejunal explants were incubated for 4h in culture medium with a) only culture medium (DMEM, control group), b) deoxynivalenol (DON, 10μM), c) heat-inactivated Lactobacillus plantarum strain1 - LP1 (1.1×10⁸ CFU/ml) plus DON, d) heat-inactivated Lactobacillus plantarum strain2-LP2 (2.0×10⁹ CFU/ml) plus DON, e) heat-inactivated Lactobacillus plantarum strain1 culture supernatant (CS1) plus DON, and f) heat-inactivated Lactobacillus plantarum strain1 culture supernatant (CS1) plus DON. Explants exposed to DON and DON plus LP1 and LP2 showed a significant increase in histological changes (mainly villi atrophy and apical necrosis) and a significant decrease in villi height when compared to unexposed explants. However, explants treated with CS1+DON and CS2+DON remained similar to the control group both in histological and morphometrical aspects. DON also induced a significant decrease in goblet cell density compared to control whereas CS1+DON treatment induced an increase in the number of goblet cells in comparison to DON explants. In addition, ultrastructural assessment showed control, CS1+DON and CS2+DON explants with well delineated finger shape villi, meanwhile DON-treated, LP1+DON and LP2+DON explants showed a severe villi atrophy with leukocytes exudation on the intestinal surface. Taken together, our results indicate that the culture supernatant treatment reduced the toxic effects induced by DON on intestinal tissue and may contribute as an alternative strategy to reduce mycotoxin toxicity.

An unusual cause of severe, persistent diarrhoea

We present two cases of patients with severe persistent diarrhoea, in whom duodenal biopsies revealed villous atrophy that could be attributed to the use of olmesartan. The differential diagnosis of villous atrophy without serological markers of celiac disease should include drugs as possible cause, with olmesartan as a recently discovered culprit. Gastroenterologist should be aware of this entity.

Intestinal anti-inflammatory activity of Ground Cherry (Physalis angulata L.) standardized CO2 phytopharmaceutical preparation

AIM

To investigate the effects of Ground Cherry (Physalis angulata L.) standardized supercritical CO₂ extract in trinitrobenzenesulphonic acid (TNBS) model of rat intestinal inflammation.

METHODS

The animals were divided into groups that received vehicle or P. angulata extract (PACO₂) orally at the doses 25, 50 and 100 mg/kg daily by 5 d before TNBS damage. Protective effects of PACO₂ were assessed by macroscopic analysis, biochemical determinations of the levels of myeloperoxidase (MPO), alkaline phosphatase (ALP), glutathione and cytokines (such as INF-γ, IL-1β, IL-6, IL-10 and TNF-α), gene expression evaluation (including Hsp70, heparanase, NF-κB, mitogen-activated protein kinases (Mapk) 1, 3, 6 and 9, and the mucins genes Muc 1, 2, 3 and 4) and histopathological studies using optical, and electronic (transmission and scanning) microscopy.

RESULTS

PACO₂ extract promoted a significant reduction in MPO and ALP activities, reducing oxidative stress and neutrophil infiltration. These effects were accompanied by significant reduction of colonic levels of IFN-γ and IL-6 and down-regulation of heparanase, Hsp70, Mapk3, Mapk9, Muc1 and Muc2 genes expression when compared with TNBS-control animals. In addition, protective effects were also evidenced by reduced neutrophil infiltration, recovery of cell architecture and replacement of mucin by histopathological and ultrastructural analysis.

CONCLUSION

Physalis angulata supercritical CO₂ extract is an intestinal anti-inflammatory product that modulates oxidative stress, immune response and expression of inflammatory mediators, with potentially utility for treating inflammatory bowel disease.

Uptake of label-free graphene oxide by Caco-2 cells is dependent on the cell differentiation status

BACKGROUND

Understanding the interaction of graphene-related materials (GRM) with human cells is a key to the assessment of their potential risks for human health. There is a knowledge gap regarding the potential uptake of GRM by human intestinal cells after unintended ingestion. Therefore the aim of our study was to investigate the interaction of label-free graphene oxide (GO) with the intestinal cell line Caco-2 in vitro and to shed light on the influence of the cell phenotype given by the differentiation status on cellular uptake behaviour.

RESULTS

Internalisation of two label-free GOs with different lateral size and thickness by undifferentiated and differentiated Caco-2 cells was analysed by scanning electron microscopy and transmission electron microscopy. Semi-quantification of cells associated with GRM was performed by flow cytometry. Undifferentiated Caco-2 cells showed significant amounts of cell-associated GRM, whereas differentiated Caco-2 cells exhibited low adhesion of GO sheets. Transmission electron microscopy analysis revealed internalisation of both applied GO (small and large) by undifferentiated Caco-2 cells. Even large GO sheets with lateral dimensions up to 10 µm, were found internalised by undifferentiated cells, presumably by macropinocytosis. In contrast, no GO uptake could be found for differentiated Caco-2 cells exhibiting an enterocyte-like morphology with apical brush border.

CONCLUSIONS

Our results show that the internalisation of GO is highly dependent on the cell differentiation status of human intestinal cells. During differentiation Caco-2 cells undergo intense phenotypic changes which lead to a dramatic decrease in GRM internalisation. The results support the hypothesis that the cell surface topography of differentiated Caco-2 cells given by the brush border leads to low adhesion of GO sheets and sterical hindrance for material uptake. In addition, the mechanical properties of GRM, especially flexibility of the sheets, seem to be an important factor for internalisation of large GO sheets by epithelial cells. Our results highlight the importance of the choice of the in vitro model to enable better in vitro-in vivo translation.

Three-dimensional mechanisms of macro-to-micro-scale transport and absorption enhancement by gut villi motions

We evaluate the potential for physiological control of intestinal absorption by the generation of "micromixing layers" (MMLs) induced by coordinated motions of mucosal villi coupled with lumen-scale "macro" eddying motions generated by gut motility. To this end, we apply a three-dimensional (3D) multigrid lattice-Boltzmann model of a lid-driven macroscale cavity flow with microscale fingerlike protuberances at the lower surface. Integrated with a previous 2D study of leaflike villi, we generalize to 3D the 2D mechanisms found there to enhance nutrient absorption by controlled villi motility. In three dimensions, increased lateral spacing within villi within groups that move axially with the macroeddy reduces MML strength and absorptive enhancement relative to two dimensions. However, lateral villi motions create helical 3D particle trajectories that enhance absorption rate to the level of axially moving 2D leaflike villi. The 3D enhancements are associated with interesting fundamental adjustments to 2D micro-macro-motility coordination mechanisms and imply a refined potential for physiological or pharmaceutical control of intestinal absorption.

Effect of toll-like receptor 3 agonist poly I:C on intestinal mucosa and epithelial barrier function in mouse models of acute colitis

AIM

To investigate potential effects of poly I:C on mucosal injury and epithelial barrier disruption in dextran sulfate sodium (DSS)-induced acute colitis.

METHODS

Thirty C57BL/6 mice were given either regular drinking water (control group) or 2% (w/v) DSS drinking water (model and poly I:C groups) ad libitum for 7 d. Poly I:C was administrated subcutaneously (20 μg/mouse) 2 h prior to DSS induction in mice of the poly I:C group. Severity of colitis was evaluated by disease activity index, body weight, colon length, histology and myeloperoxidase (MPO) activity, as well as the production of proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin 17 (IL-17) and interferon-γ (IFN-γ). Intestinal permeability was analyzed by the fluorescein isothiocyanate labeled-dextran (FITC-D) method. Ultrastructural features of the colon tissue were observed under electron microscopy. Expressions of tight junction (TJ) proteins, including zo-1, occludin and claudin-1, were measured by immunohistochemistry/immunofluorescence, Western blot and real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

DSS caused significant damage to the colon tissue in the model group. Administration of poly I:C dramatically protected against DSS-induced colitis, as demonstrated by less body weight loss, lower disease activity index score, longer colon length, colonic MPO activity, and improved macroscopic and histological scores. It also ameliorated DSS-induced ultrastructural changes of the colon epithelium, as observed under scanning electron microscopy, as well as FITC-D permeability. The mRNA and protein expressions of TJ protein, zo-1, occludin and claudin-1 were also found to be significantly enhanced in the poly I:C group, as determined by immunohistochemistry/immunofluorescence, Western blot and RT-qPCR. By contrast, poly I:C pretreatment markedly reversed the DSS-induced up-regulated expressions of the inflammatory cytokines TNF-α, IL-17 and IFN-γ.

CONCLUSION

Our study suggested that poly I:C may protect against DSS-induced colitis through maintaining integrity of the epithelial barrier and regulating innate immune responses, which may shed light on the therapeutic potential of poly I:C in human colitis.

Surface architecture of the oropharyngeal cavity and the digestive tract of Mulloidichthys flavolineatus from the red sea, Egypt: A scanning electron microscope study

Surface architecture of the buccal cavity and the surface organization of the luminal mucosa of the oesophagus, stomach, and intestine of the carnivorous fish M. flavolineatus from the Red Sea were studied by using SEM. The results revealed that M. flavolineatus has four kinds of teeth; curved-blunt, wedge-shaped, flattened crowns, molariform and papilliform. Three types of taste buds (type I, II and III) were recorded in the oropharyngeal cavity. It was observed that taste buds and teeth are co-located in the pharyngeal region. Characteristic patterns of microridges of the surface cells in the oral cavity and oesophagus were observed. Mucous cells are distributed in the lining of the mouth cavity, oesophagus, stomach, and intestine. Characteristic patterns of mucosal folds throughout the alimentary canal, concerning oesophagus, stomach, and intestine were revealed. Numerous gastric pits, which represents the emergence of the gastric glands, were recorded in the anterior and middle regions of the stomach. Complex patterns of the folds and mucous cells were recorded in the intestinal mucosa. These results were discussed with other teleost fishes.

Coordination of signaling and tissue mechanics during morphogenesis of murine intestinal villi: a role for mitotic cell rounding

Efficient digestion and absorption of nutrients by the intestine requires a very large apical surface area, a feature that is enhanced by the presence of villi, fingerlike epithelial projections that extend into the lumen. Prior to villus formation, the epithelium is a thick pseudostratified layer. In mice, villus formation begins at embryonic day (E)14.5, when clusters of mesenchymal cells form just beneath the thick epithelium. At this time, analysis of the flat lumenal surface reveals a regular pattern of short apical membrane invaginations that form in regions of the epithelium that lie in between the mesenchymal clusters. Apical invaginations begin in the proximal intestine and spread distally, deepening with time. Interestingly, mitotically rounded cells are frequently associated with these invaginations. These mitotic cells are located at the tips of the invaginating membrane (internalized within the epithelium), rather than adjacent to the apical surface. Further investigation of epithelial changes during membrane invagination reveals that epithelial cells located between mesenchymal clusters experience a circumferential compression, as epithelial cells above each cluster shorten and widen. Using a computational model, we examined whether such forces are sufficient to cause apical invaginations. Simulations and in vivo data reveal that proper apical membrane invagination involves intraepithelial compressive forces, mitotic cell rounding in the compressed regions and apico-basal contraction of the dividing cell. Together, these data establish a new model that explains how signaling events intersect with tissue forces to pattern apical membrane invaginations that define the villus boundaries.

GYY4137 ameliorates intestinal barrier injury in a mouse model of endotoxemia

Intestinal barrier injury has been reported to play a vital role in the pathogenesis of endotoxemia. This study aimed to investigate the protective effect of GYY4137, a newly synthesized H₂S donor, on the intestinal barrier function in the context of endotoxemia both in vitro and in vivo. Caco-2 (a widely used human colon cancer cell line in the study of intestinal epithelial barrier function) monolayers incubated with lipopolysaccharide (LPS) or TNF-α/IFN-γ and a mouse model of endotoxemia were used in this study. The results suggested that GYY4137 significantly attenuated LPS or TNF-α/IFN-γ induced increased Caco-2 monolayer permeability. The decreased expression of TJ (tight junction) proteins induced by LPS and the altered localization of TJs induced by TNF-α/IFN-γ was significantly inhibited by GYY4137; similar results were obtained in vivo. Besides, GYY4137 promoted the clinical score and histological score of mice with endotoxemia. Increased level of TNF-α/IFN-γ in the plasma and increased apoptosis in colon epithelial cells was also attenuated by GYY4137 in mice with endotoxemia. This study indicates that GYY4137 preserves the intestinal barrier function in the context of endotoxemia via multipathways and throws light on the development of potential therapeutic approaches for endotoxemia.

Role of soluble zinc in ZnO nanoparticle cytotoxicity in Daphnia magna: A morphological approach

The role of soluble zinc has been determined in Daphnia magna by a morphological approach, integrating a previous paper in which the ultrastructural damages to gut epithelial cells have been studied after ZnO nanoparticles exposure. In the present paper, the toxicity and morphological effects of soluble zinc from ZnSO4 have been determined in a 48-h acute exposure test. Daphnids have been exposed to six nominal zinc concentrations (0.075, 0.15, 0.3, 0.6, 1.2, and 2.4mg Zn/L) and then fixed for microscopic analyses. Data from the acute toxicity tests gave an EC50 value of 0.99mg/L and showed that no immobilization appeared up to 0.3mg Zn/L. Ultrastructural analyses of samples from the two highest concentrations showed large vacuolar structures, swelling of mitochondria, multilamellar bodies, and a great number of autophagy vacuoles. These findings have been compared to those from our previous study, and similarities and/or differences discussed. Based on the overall results it can be concluded that dissolved zinc ions played a key role in ZnO nanoparticle toxicity and that the morphological approach is an extremely useful tool for comparing toxicological effects as well. A possible common toxic mechanism of soluble zinc and ZnO nanoparticles was also proposed.

Histopathological Effects of Dietary Fusarium Graminearum on Rat Duodenum

Microscopic pathology of duodenum in rats exposed to Fusarium graminearum, a fungus infecting small-grain cereals, was investigated. Intestinal haemorrhage was observed macroscopically in one of the rats. Light microscopy demonstrated detachments between the surface epithelium and the lamina propria and severe interstitial oedema in the lamina propria in the test group. Electron microscopy identified epithelial absorptive cells with highly expanded endoplasmic reticulum tubules, abundant cytoplasmic vesicles containing electron-lucent materials, swollen mitochondria with spongiform appearance, and prominent cellular swelling. Other observations included opening of junctional complexes between epithelial cells lining the duodenum, highly enlarged intercellular spaces in duodenal epithelium, and numerous eosinophilic granulocytes and mast cells in the lamina propria. These findings indicate that dietary F. graminearum causes epithelial cell and connective tissue damage in rat duodenum. This is the first histopathological study showing that F. graminearum ingestion is associated with duodenal damage.

A prospective observational study of the effect of critical illness on ultrastructural and microscopic morphology of duodenal mucosa

OBJECTIVE

Disturbed intestinal barrier function due to 'leaky' tight junctions may cause secondary sepsis via paracellular translocation across the gut wall. Our objective was to describe the effects of critical illness on duodenal morphology and ultrastructure.

DESIGN, SETTING AND PARTICIPANTS

Prospective observational study of 12 mechanically ventilated critically ill patients in an intensive care unit and 15 control participants in an outpatient endoscopy suite.

INTERVENTION

We took six endoscopic biopsy samples of the duodenum from each participant for analysis by electron and light microscopy.

MAIN OUTCOME MEASURES

Our primary outcome was tight junction morphology, examined with electron microscopy. Secondary outcomes were microvillus length and density, vascular endothelium morphology and mitochondrial density and morphology, examined with electron microscopy, and morphology examined with light microscopy.

RESULTS

We observed no abnormalities of tight junction ultrastructure in either group. There was a tendency towards shorter microvilli in the critically ill group: mean length in critically ill patients, 1.17 µm (interquartile range [IQR], 1.05-1.60 µm) v mean length in control patients, 1.58 µm (IQR, 1.30-1.72 µm); P = 0.07. There was a tendency towards less dense microvilli in the critically ill group: mean density in critically ill patients, 7.29 microvilli/µm (IQR, 6.83-8.05 microvilli/µm) v mean density in control patients, 8.23 microvilli/µm (IQR, 7.34-9.11 microvilli/µm); P = 0.07. Vascular endothelium appeared normal in all critically ill patients and abnormal in one control participant. Abnormal mitochondrial morphology was noted in one critically ill patient and one control participant, and no differences were seen in mitochondrial density. Using light microscopy, we saw more apoptotic cells in the critically ill patients (P = 0.018), but villus height, crypt depth and lymphocyte density were normal.

CONCLUSIONS

We did not detect any morphological abnormalities of duodenal tight junctions in critically ill patients. Our results should be interpreted with caution because of the small sample population, but our observations challenge the concept that paracellular translocation facilitates secondary sepsis.

Neurotensin Is Coexpressed, Coreleased, and Acts Together With GLP-1 and PYY in Enteroendocrine Control of Metabolism

The 2 gut hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are well known to be coexpressed, costored, and released together to coact in the control of key metabolic target organs. However, recently, it became clear that several other gut hormones can be coexpressed in the intestinal-specific lineage of enteroendocrine cells. Here, we focus on the anatomical and functional consequences of the coexpression of neurotensin with GLP-1 and PYY in the distal small intestine. Fluorescence-activated cell sorting analysis, laser capture, and triple staining demonstrated that GLP-1 cells in the crypts become increasingly multihormonal, ie, coexpressing PYY and neurotensin as they move up the villus. Proglucagon promoter and pertussis toxin receptor-driven cell ablation and reappearance studies indicated that although all the cells die, the GLP-1 cells reappear more quickly than PYY- and neurotensin-positive cells. High-resolution confocal fluorescence microscopy demonstrated that neurotensin is stored in secretory granules distinct from GLP-1 and PYY storing granules. Nevertheless, the 3 peptides were cosecreted from both perfused small intestines and colonic crypt cultures in response to a series of metabolite, neuropeptide, and hormonal stimuli. Importantly, neurotensin acts synergistically, ie, more than additively together with GLP-1 and PYY to decrease palatable food intake and inhibit gastric emptying, but affects glucose homeostasis in a more complex manner. Thus, neurotensin is a major gut hormone deeply integrated with GLP-1 and PYY, which should be taken into account when exploiting the enteroendocrine regulation of metabolism pharmacologically.

Carbon Monoxide-Releasing Molecule-2 Reduces Intestinal Epithelial Tight-Junction Damage and Mortality in Septic Rats

Objective

Damage to intestinal epithelial tight junctions plays an important role in sepsis. Recently we found that Carbon Monoxide-Releasing Molecule-2 (CORM-2) is able to protect LPS-induced intestinal epithelial tight junction damage and in this study we will investigate if CORM-2 could protect intestinal epithelial tight junctions in the rat cecal ligation and puncture (CLP) model.

Materials and Methods

The CLP model was generated using male Sprague-Dawley (SD) rats according to standard procedure and treated with CORM-2 or inactive CORM-2 (iCORM-2), 8 mg/kg, i.v. immediately after CLP induction and euthanized after 24h or 72h (for mortality rate only). Morphological changes were investigated using both transmission electron and confocal microscopy. The levels of important TJ proteins and phosphorylation of myosin light chain (MLC) were examined using Western blotting. Cytokines, IL-1β and TNF-α were measured using ELISA kits. The overall intestinal epithelial permeability was evaluated using FD-4 as a marker.

Results

CORM-2, but not iCORM-2, significantly reduced sepsis-induced damage of intestinal mucosa (including TJ disruption), TJ protein reduction (including zonula occludens-l (ZO-1), claudin-1 and occludin), MLC phosphorylation and proinflammatory cytokine release. The overall outcomes showed that CORM-2 suppressed sepsis-induced intestinal epithelial permeability changes and reduced mortality rate of those septic rats.

Conclusions

Our data strongly suggest that CORM-2 could be a potential therapeutic reagent for sepsis by suppressing inflammation, restoring intestinal epithelial barrier and reducing mortality.

The effects of low doses of two Fusarium toxins, zearalenone and deoxynivalenol, on the pig jejunum. A light and electron microscopic study

Immature gilts were administered per os with zearalenone (ZEN) at 40 μg/kg BW (group Z, n = 9), deoxynivalenol (DON) at 12 μg/kg BW (group D, n = 9), a mixture of ZEN and DON (group M, n = 9) or a placebo (group C, n = 9) over a period of six weeks. The pigs were sacrificed after one, three, or six weeks of the treatment (12 pigs per each time-point). Histological investigations revealed an increase in the mucosal thickness and the crypt depth as well as a decrease in the ratio of the villus height to the crypt depth in groups D and M after six weeks of exposure to the mycotoxins. The number of goblet cells in the villus epithelium was elevated in groups Z and M after one week and in group D after three weeks. The administration of ZEN increased the lymphocyte number in the villus epithelium after 1 week and the plasma cell quantity in the lamina propria after one, three, and six weeks of the experiment. DON treatment resulted in an increase in the lymphocyte number in the villus epithelium and the lamina propria after six weeks, and in the plasma cell quantity in the lamina propria after one, three, and six weeks of exposure. In group M, lymphocyte counts in the epithelium and the lamina propria increased significantly after six weeks. Neither mycotoxin induced significant adverse changes in the ultrastructure of the mucosal epithelium and the lamina propria or in the intestinal barrier permeability. Our results indicate that immune cells are the principal target of low doses of ZEN and DON.