Mouse Large Intestine Research Articles

Distribution of the active components from Xianglian Pill in tissues of healthy and antibiotic-associated diarrhea model mice and the mechanism study

Antibiotic-associated diarrhea (AAD) is a common side effect of antibiotic therapy, characterized by intestinal inflammation which reduces the quality of life of patients. Xianglian Pill (XLP) has long been used to treat abdominal pain, diarrhea, bacillary dysentery and enteritis. Studies found that XLP has curative effect on AAD; however, the chemical constituents and mechanism of XLP have not been fully elucidated because of the lack of in vitro and in vivo studies. In this study, ultra-high performance liquid chromatography mass spectrometry method (UPLC-Q-Exactive-Orbitrap-HRMS) was used to examine the components of the XLP. Then, the binding between active compounds and the key targets was studied using network pharmacology and molecular docking. A comparative tissue distribution study was established for the simultaneous determination of the 10 active components in healthy and AAD mouse models. Forty-six components were characterized from XLP. According to the network pharmacology degree value, a prediction was made that encompassed 42 components and 14 core targets, which were intricately involved in crucial biological pathways, such as the AGE-RAGE signaling, cellular senescence, and MAPK signaling. Tissue distribution analysis showed that the 10 components were widely distributed in the heart, liver, spleen, lungs, kidneys, small intestine, and large intestine of mice, with varying concentrations in healthy and AAD mice. Molecular docking analysis also indicated that the active compounds in the tissue distribution could bind tightly to key targets of network pharmacological studies. This study provides a reference for further investigations of the relationships between the chemical components and pharmacological activities of XLP.

Supplementation of a High-Fat Diet with Pentadecylresorcinol Increases the Representation of Akkermansia muciniphila in the Mouse Small and Large Intestines and May Protect against Complications Caused by Imbalanced Nutrition.

Imbalanced nutrition, such as a high-fat/high-carbohydrate diet, is associated with negative effects on human health. The composition and metabolic activity of the human gut microbiota are closely related to the type of diet and have been shown to change significantly in response to changes in food content and food supplement administration. Alkylresorcinols (ARs) are lipophilic molecules that have been found to improve lipid metabolism and glycemic control and decrease systemic inflammation. Furthermore, alkylresorcinol intake is associated with changes in intestinal microbiota metabolic activity. However, the exact mechanism through which alkylresorcinols modulate microbiota activity and host metabolism has not been determined. In this study, alterations in the small intestinal microbiota (SIM) and the large intestinal microbiota (LIM) were investigated in mice fed a high-fat diet with or without pentadecylresorcinol (C15) supplementation. High-throughput sequencing was applied for jejunal and colonic microbiota analysis. The results revealed that C15 supplementation in combination with a high-fat diet could decrease blood glucose levels. High-throughput sequencing analysis indicated that C15 intake significantly increased (p < 0.0001) the abundance of the probiotic bacteria Akkermansia muciniphila and Bifidobacterium pseudolongum in both the small and large intestines and increased the alpha diversity of LIM (p < 0.05), but not SIM. The preliminary results suggested that one of the mechanisms of the protective effects of alkylresorcinol on a high-fat diet is the modulation of the content of SIM and LIM and metabolic activity to increase the probiotic bacteria that alleviate unhealthy metabolic changes in the host.

Z3495, a LysR-Type Transcriptional Regulator Encoded in O Island 97, Regulates Virulence Gene Expression in Enterohemorrhagic Escherichia coli O157:H7.

Enterohemorrhagic Escherichia coli (EHEC) is an important foodborne pathogen that infects humans by colonizing the large intestine. The genome of EHEC O157:H7 contains 177 unique O islands (OIs). Certain OIs significantly contribute to the heightened virulence and pathogenicity exhibited by EHEC O157:H7. However, the function of most OI genes remains unknown. We demonstrated here that EHEC O157:H7 adherence to and colonization of the mouse large intestine are both dependent on OI-97. Z3495, which is annotated as a LysR-type transcriptional regulator and encoded in OI-97, contributes to this phenotype. Z3495 activated the locus of enterocyte effacement (LEE) gene expression, promoting bacterial adherence. Deletion of z3495 significantly decreased the transcription of ler and other LEE genes, the ability to adhere to the host cells, and colonization in the mouse large intestine. Furthermore, the ChIP-seq results confirmed that Z3495 can directly bind to the promoter region of rcsF, which is a well-known activator of Ler, and increase LEE gene expression. Finally, phylogenetic analysis revealed that Z3495 is a widespread transcriptional regulator in enterohemorrhagic and enteropathogenic Escherichia coli. As a result of this study, we have gained a deeper understanding of how bacteria control their virulence and provide another example of a laterally acquired regulator that regulates LEE gene expression in bacteria.

Regulation of chlamydial spreading from the small intestine to the large intestine by IL-22-producing CD4+ T cells.

Following an oral inoculation, Chlamydia muridarum descends to the mouse large intestine for long-lasting colonization. However, a mutant C. muridarum that lacks the plasmid-encoded protein pGP3 due to an engineered premature stop codon (designated as CMpGP3S) failed to do so even following an intrajejunal inoculation. This was because a CD4+ T cell-dependent immunity prevented the spread of CMpGP3S from the small intestine to the large intestine. In the current study, we found that mice deficient in IL-22 (IL-22-/-) allowed CMpGP3S to spread from the small intestine to the large intestine on day 3 after intrajejunal inoculation, indicating a critical role of IL-22 in regulating the chlamydial spread. The responsible IL-22 is produced by CD4+ T cells since IL-22-/- mice were rescued to block the CMpGP3S spread by donor CD4+ T cells from C57BL/6J mice. Consistently, CD4+ T cells lacking IL-22 failed to block the spread of CMpGP3S in Rag2-/- mice, while IL-22-competent CD4+ T cells did block. Furthermore, mice deficient in cathelicidin-related antimicrobial peptide (CRAMP) permitted the CMpGP3S spread, but donor CD4+ T cells from CRAMP-/- mice were still sufficient for preventing the CMpGP3S spread in Rag2-/- mice, indicating a critical role of CRAMP in regulating chlamydial spreading, and the responsible CRAMP is not produced by CD4+ T cells. Thus, the IL-22-producing CD4+ T cell-dependent regulation of chlamydial spreading correlated with CRAMP produced by non-CD4+ T cells. These findings provide a platform for further characterizing the subset(s) of CD4+ T cells responsible for regulating bacterial spreading in the intestine.

Vaccination with an HIV T-Cell Immunogen (HTI) Using DNA Primes Followed by a ChAdOx1-MVA Boost Is Immunogenic in Gut Microbiota-Depleted Mice despite Low IL-22 Serum Levels.

Despite the important role of gut microbiota in the maturation of the immune system, little is known about its impact on the development of T-cell responses to vaccination. Here, we immunized C57BL/6 mice with a prime-boost regimen using DNA plasmid, the Chimpanzee Adenovirus, and the modified Vaccinia Ankara virus expressing a candidate HIV T-cell immunogen and compared the T-cell responses between individuals with an intact or antibiotic-depleted microbiota. Overall, the depletion of the gut microbiota did not result in significant differences in the magnitude or breadth of the immunogen-specific IFNγ T-cell response after vaccination. However, we observed marked changes in the serum levels of four cytokines after vaccinating microbiota-depleted animals, particularly a significant reduction in IL-22 levels. Interestingly, the level of IL-22 in serum correlated with the abundance of Roseburia in the large intestine of mice in the mock and vaccinated groups with intact microbiota. This short-chain fatty acid (SCFA)-producing bacterium was significantly reduced in the vaccinated, microbiota-depleted group. Therefore, our results indicate that, although microbiota depletion reduces serum levels of IL-22, the powerful vaccine regime used could have overcome the impact of microbiota depletion on IFNγ-producing T-cell responses.

Microbiota-Dependent Upregulation of Bitter Taste Receptor Subtypes in the Mouse Large Intestine in High-Fat Diet-Induced Obesity.

Bitter taste receptors (Tas2rs in mice) detect bitterness, a warning signal for toxins and poisons, and are expressed in enteroendocrine cells. We tested the hypothesis that Tas2r138 and Tas2r116 mRNAs are modulated by microbiota alterations induced by a long-term high-fat diet (HFD) and antibiotics (ABX) (ampicillin and neomycin) administered in drinking water. Cecum and colon specimens and luminal contents were collected from C57BL/6 female and male mice for qRT-PCR and microbial luminal 16S sequencing. HFD with/without ABX significantly increased body weight and fat mass at 4, 6, and 8 weeks. Tas2r138 and Tas2r116 mRNAs were significantly increased in mice fed HFD for 8 weeks vs. normal diet, and this increase was prevented by ABX. There was a distinct microbiota separation in each experimental group and significant changes in the composition and diversity of microbiome in mice fed a HFD with/without ABX. Tas2r mRNA expression in HFD was associated with several genera, particularly with Akkermansia, a Gram-negative mucus-resident bacterium. These studies indicate that luminal bacterial composition is affected by sex, diet, and ABX and support a microbial dependent upregulation of Tas2rs in HFD-induced obesity, suggesting an adaptive host response to specific diet-induced dysbiosis.

Mucous non-goblet cells in the small intestine of guinea pigs (Cavia porcellus): a histological and histochemical study.

The covering and glandular epithelium of the small intestine in guinea pigs (Cavia porcellus) include some mucus-secreting cells. Goblet cells are specific cells for mucus secretion with a distinctive cup-like appearance due to the accumulation of mucin in the apical pole. The deep crypt secretory (DCS) cells were identified in a limited array of species and only recently were noticed in the large intestine in mice, guinea pigs, humans, monkeys, and pigs. Our study focuses on the microscopical and histochemical features of the DCS cells in the small intestine of guinea pigs. The samples from the small intestine were collected from five fully grown guinea pigs that were presented to the Hospital of the Faculty of Veterinary Medicine Cluj-Napoca (Romania) with severe lesions resulted from domestic activities. The collected tissue samples underwent fixation in 10% buffered formalin and were later processed by standard paraffin technique. Mucous substances were detected using the Periodic Acid-Schiff and Alcian-Blue histochemical stain methods. The intestinal samples of the guinea pigs assessed had a standard microanatomical structure. As regards the mucous-secreting cells from the small intestine, two cell types were identified, i.e. the goblet cells and DCS cells. DCS cells were only detected in the deep parts of the Lieberkühn glands from the jejunum and ileum, and were different morphologically and histochemically from the regular goblet cells. Our study managed to describe for the first time in guinea pigs, the existence of DCS cells in the jejunum and ileum of the small intestine, but not in the duodenum.

Paracrine relationship between incretin hormones and endogenous 5-hydroxytryptamine in the small and large intestine.

Enterochromaffin (EC) cell-derived 5-hydroxytryptamine (5-HT) is a mediator of toxin-induced reflexes, initiating emesis via vagal and central 5-HT3 receptors. The amine is also involved in gastrointestinal (GI) reflexes that are prosecretory and promotile, and recently 5-HT's roles in chemosensation in the distal bowel have been described. We set out to establish the efficacy of 5-HT signaling, local 5-HT levels and pharmacology in discrete regions of the mouse small and large intestine. We also investigated the inter-relationships between incretin hormones, glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP) and endogenous 5-HT in mucosal and motility assays. Adult mouse GI mucosae were mounted in Ussing chambers and area-specific studies were performed to establish the 5-HT3 and 5-HT4 pharmacology, the sidedness of responses, and the inter-relationships between incretins and endogenous 5-HT. Natural fecal pellet transit in vitro and full-length GI transit in vivo were also measured. We observed the greatest level of tonic and exogenous 5-HT-induced ion transport and highest levels of 5-HT in ascending colon mucosa. Here both 5-HT3 and 5-HT4 receptors were involved but elsewhere in the GI tract epithelial basolateral 5-HT4 receptors mediate 5-HT's prosecretory effect. Exendin-4 and GIP induced 5-HT release in the ascending colon, while L cell-derived PYY also contributed to GIP mucosal effects in the descending colon. Both peptides slowed colonic transit. We provide functional evidence for paracrine interplay between 5-HT, GLP-1 and GIP, particularly in the colonic mucosal region. Basolateral epithelial 5-HT4 receptors mediated both 5-HT and incretin mucosal responses in healthy colon.

The Effects of Tribulus Terrestris on Aquaporin-1 (AQP1) Immunolocalization in Small and Large Intestines of Mice

This study aimed to examine the effects of Tribulus Terrestris on Aquaporin-1 (AQP1) immunolocalization in the small and large intestines of mice. A total of 16 male BALB/c mice were used in the study. The control and experiment groups consisted of randomly selected mice, with each group containing eight animals. Small and large intestine tissues of mice were taken under deep anesthesia at the end of the study. Routine histological and immunohistochemical methods were applied on the intestinal tissues obtained at the end of the study. The analyses indicated that the intestinal tissues of all groups had a normal histology, and there was a statistically significant difference between the numbers of goblet cells of the control and Tribulus Terrestris (TT) groups in the ileum, cecum, colon and rectum. AQP1immunoreactivity was detected in the small and large intestines of both groups. AQP1immunoreactivity increased in the apical cytoplasm of the intestinal villus and crypt epithelium cells in the small intestine of the TT group. Application of TT increased AQP1immunoreactivity and might have a role in absorption activities in the intestines.

A hemicyanidin-based NIR fluorescent probe for detection of H2S and imaging study in cells and mice.

The selective detection of hydrogen sulfide in physiological and pathological processes has gained substantial attention in recent years. However, the real-time detection of hydrogen sulfide remains an elusive goal. In this work, a new type of hemicyanidin-based fluorescent "turn-on" probe NTR-HS (Ex = 680nm, Em = 760nm) was developed to detected H2S in a very short time (3min).Thefluorescence quantum yield is 0.15 and accompanied with a noticeable color change from violet to bluethatcan be used to detect H2S in the range 1.04 × 10-7-4 × 10-5Mwith a limit of detection of 1.04 x 10-7 M. TheNTR-HS probewas also used for imaging of endogenous hydrogen sulfide and mitochondrial localization in HCT116 and HeLa cells. The detection mechanism was studied through fluorescence, UV-Vis, NMR, and mass analysis. Notably, the probe was successfully used to imaging H2S in mice and locating hydrogen sulfide in the large intestine of mice.

Characterization of transit rates in the large intestine of mice following treatment with a CGRP antibody, CGRP receptor antibody, and small molecule CGRP receptor antagonists.

ObjectiveTo characterize the effects of blocking calcitonin gene‐related peptide (CGRP) activity in a mouse model of gastrointestinal transport.BackgroundMigraine management using CGRP modulating therapies can cause constipation of varying frequency and severity. This variation might be due to the different mechanisms through which therapies block CGRP activity (e.g., blocking CGRP, or the CGRP receptor) with antibodies or receptor antagonists. The charcoal meal gastrointestinal transit assay was used to characterize constipation produced by these modes of therapy in transgenic mice expressing the human receptor activity–modifying protein 1 (hRAMP1) subunit of the CGRP receptor complex.MethodsMale and female hRAMP1 mice were dosed with compound or vehicle and challenged with a charcoal meal suspension via oral gavage. The mice were then humanely euthanized and the proportion of the length of the large intestine that the charcoal meal had traveled indicated gastrointestinal transit.ResultsAntibody to the CGRP receptor produced % distance traveled (mean ± standard deviation) of 31.8 ± 8.2 (4 mg/kg; p = 0.001) and 33.2 ± 6.0 (30 mg/kg; p < 0.001) compared to 49.7 ± 8.3 (control) in female mice (n = 6–8), and 35.6 ± 13.5 (30 mg/kg, p = 0.019) compared to 50.2 ± 14.0 (control) in male mice (n = 10). Telcagepant (5 mg/kg, n = 8) resulted in % travel of 30.6 ± 14.7 versus 41.2 ± 8.3 (vehicle; p = 0.013) in male mice. Atogepant (3 mg/kg, n = 9) resulted in % travel of 30.6 ± 12.0, versus 41.2 ± 3.7 (control; p = 0.030) in female mice. The CGRP antibody galcanezumab (n = 7–10; p = 0.958 and p = 0.929) did not have a statistically significant effect.ConclusionsThese results are consistent with reported clinical data. Selectively blocking the CGRP receptor may have a greater impact on gastrointestinal transit than attenuating the activity of the ligand CGRP. This differential effect may be related to physiologically opposing mechanisms between the CGRP and AMY1 receptors, as the CGRP ligand antibody could inhibit the effects of CGRP at both the CGRP and AMY1 receptors.

A new therapy against ulcerative colitis via the intestine and brain using the Si-based agent

Ulcerative colitis (UC) is a non-specific inflammatory bowel disease that causes ulcers and erosions in the colonic mucosa and becomes chronic with cycles of amelioration and exacerbation. Because its exact etiology remains largely unclear, and the primary therapy is limited to symptomatic treatment, the development of new therapeutic agent for UC is highly desired. Because one of the disease pathogenesis is involvement of oxidative stress, it is likely that an appropriate antioxidant will be an effective therapeutic agent for UC. Our silicon (Si)-based agent, when ingested, allowed for stable and persistent generation of massive amounts of hydrogen in the gastrointestinal tract. We demonstrated the Si-based agent alleviated the mental symptom as well as the gastrointestinal symptoms, inflammation, and oxidation associated with dextran sodium sulfate-induced UC model through Hydrogen and antioxidant sulfur compounds. As the Si-based agent was effective in treating UC in the brain and large intestine of mice, it was considered to be capable of suppressing exacerbations and sustaining remission of UC.

Expression of the relaxin family peptide 4 receptor by enterochromaffin cells of the mouse large intestine

The gastrointestinal hormone, insulin-like peptide 5 (INSL5), is found in large intestinal enteroendocrine cells (EEC). One of its functions is to stimulate nerve circuits that increase propulsive activity of the colon through its receptor, the relaxin family peptide 4 receptor (RXFP4). To investigate the mechanisms that link INSL5 to stimulation of propulsion, we have determined the localisation of cells expressing Rxfp4 in the mouse colon, using a reporter mouse to locate cells expressing the gene. The fluorescent signal indicating the location of Rxfp4 expression was in EEC, the greatest overlap of Rxfp4-dependent labelling being with cells containing 5-HT. In fact, > 90% of 5-HT cells were positive for Rxfp4 labelling. A small proportion of cells with Rxfp4-dependent labelling was 5-HT-negative, 11–15% in the distal colon and rectum, and 35% in the proximal colon. Of these, some were identified as L-cells by immunoreactivity for oxyntomodulin. Rxfp4-dependent fluorescence was also found in a sparse population of nerve endings, where it was colocalised with CGRP. We used the RXFP4 agonist, INSL5-A13, to activate the receptor and probe the role of the 5-HT cells in which it is expressed. INSL5-A13 administered by i.p. injection to conscious mice caused an increase in colorectal propulsion that was antagonised by the 5-HT3 receptor blocker, alosetron, also given i.p. We conclude that stimuli that excite INSL5-containing colonic L-cells release INSL5 that, through RXFP4, excites 5-HT release from neighbouring endocrine cells, which in turn acts on 5-HT3 receptors of enteric sensory neurons to elicit propulsive reflexes.

Goat milk fermented with combined lactic acid bacterium alter microbial community structures and levels of the targeted short-chain fatty acids in the large intestine of mice

The present study investigated effects of the fermented goat milk (FGM) produced with a combination of Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (SL) and with another one of SL as well as Bifidobacterium animalis subsp. lactis (SLB) on the internal environment in the large intestine of mice. Both the richness and the diversity of microbiota was the most abundant in SL group. SL, SLB and the control groups were clustered into three independent groups. At the phylum level, Firmicutes was the most abundant in all the groups, and Deferribacteres in SLB group was more abundant than in SL group. SL and SLB increased the proportions of 6 and 5 genera, respectively. Firmicutes was positively correlated with all the significantly different species but negative to Actinobacteria at the phylum level. SL and SLB both significantly decreased the levels of butyric and valeric acids. Either SL or SLB can significantly improve the structures of microbiota, and both of them significantly decreased the levels of butyric and valeric acids in the large intestine of mice. Certain microbiota negatively related to the levels of butyric and valeric acids. FGM produced with SL or SLB can effectively alter the microbialflora and the levels of SCFA in the large intestine of mice.

Effect of luxS encoding a synthase of quorum-sensing signal molecule AI-2 of Vibrio vulnificus on mouse gut microbiome.

Autoinducer-2 (AI-2), a quorum-sensing signal molecule from the human pathogen Vibrio vulnificus, was assessed for its effect on the gut microbiome of mice. For this, we employed 16S rRNA sequencing to compare the gut microbiome of mice infected with either wild-type V. vulnificus or with the isotype ΔluxS that has a deletion in luxS which encodes the biosynthetic function of AI-2. The relative ratio of wild-type Vibrio species in the jejunum and ileum of mice infected with the wild type was significantly higher than that in mice infected with ΔluxS, suggesting that AI-2 plays an important role in the colonization of V. vulnificus in the small intestine. The bacterial composition in the gut of mice infected with ΔluxS comprises a higher proportion of Firmicutes, composed mainly of Lactobacillus, compared to the mice infected with wild-type cells. In the large intestine, Vibrio species were barely detected regardless of genetic background. Three Lactobacillus spp. isolated from fecal samples from mice infected with ΔluxS manifested significant antibacterial activities against V. vulnificus. Culture supernatants from these three species were dissolved by HPLC, and a substance in fractions showing inhibitory activity against V. vulnificus was determined to be lactic acid. Our results suggest that luxS in V. vulnificus affects not only the ability of the species to colonize the host gut but also its susceptibility to the growth-inhibiting activity of commensal bacteria including Lactobacillus. KEY POINTS: • Gut microbiomes of ΔluxS-infected and WT Vibrio-infected mice differed greatly. • Difference was most prominent in the jejunum and ileum compared to the duodenum or large intestine. • In the small and large intestines of mice, the relative proportions of Vibrio and Lactobacillus species showed a negative relationship. • Effector molecules produced by Lactobacillus in mouse gut inhibit Vibrio growth.

Pre-clinical safety and therapeutic efficacy of a plant-based alkaloid in a human colon cancer xenograft model

A high-throughput drug screen revealed that veratridine (VTD), a natural plant alkaloid, induces expression of the anti-cancer protein UBXN2A in colon cancer cells. UBXN2A suppresses mortalin, a heat shock protein, with dominant roles in cancer development including epithelial–mesenchymal transition (EMT), cancer cell stemness, drug resistance, and apoptosis. VTD-dependent expression of UBXN2A leads to the deactivation of mortalin in colon cancer cells, making VTD a potential targeted therapy in malignant tumors with high levels of mortalin. VTD was used clinically for the treatment of hypertension in decades past. However, the discovery of newer antihypertensive drugs and concerns over potential neuro- and cardiotoxicity ended the use of VTD for this purpose. The current study aims to determine the safety and efficacy of VTD at doses sufficient to induce UBXN2A expression in a mouse model. A set of flow-cytometry experiments confirmed that VTD induces both early and late apoptosis in a dose-dependent manner. In vivo intraperitoneal (IP) administration of VTD at 0.1 mg/kg every other day (QOD) for 4 weeks effectively induced expression of UBXN2A in the small and large intestines of mice. Liquid chromatography–tandem mass spectrometry (LC–MS/MS) assays on tissues collected from VTD-treated animals demonstrated VTD concentrations in the low pg/mg range. To address concerns regarding neuro- and cardiotoxicity, a comprehensive set of behavioral and cardiovascular assessments performed on C57BL/6NHsd mice revealed that VTD generates no detectable neurotoxicity or cardiotoxicity in animals receiving 0.1 mg/kg VTD QOD for 30 days. Finally, mouse xenograft experiments in athymic nude mice showed that VTD can suppress tumor growth. The main causes for the failure of experimental oncologic drug candidates are lack of sufficient safety and efficacy. The results achieved in this study support the potential utility of VTD as a safe and efficacious anti-cancer molecule.

Rhythmicity in the Enteric Nervous System of Mice.

The enteric nervous system (ENS) is required for many cyclical patterns of motor activity along different regions of the gastrointestinal (GI) tract. What has remained mysterious is precisely how many thousands of neurons within the ENS are temporally activated to generate cyclical neurogenic contractions of GI-smooth muscle layers. This has been an especially puzzling conundrum, since the ENS consists of an extensive network of small ganglia, with each ganglion consisting of a heterogeneous population of neurons, with diverse cell soma morphologies, neurochemical and biophysical characteristics, and neural connectivity. Neuronal imaging studies of the mouse large intestine have provided major new insights into how the different classes of myenteric neurons are activated during cyclical neurogenic motor patterns, such as the colonic motor complex (CMC). It has been revealed that during CMCs (in the isolated mouse whole colon), large populations of myenteric neurons, across large spatial fields, coordinate their firing, via bursts of fast synaptic inputs at ~2 Hz. This coordinated firing of many thousands of myenteric neurons synchronously over many rows of interconnected ganglia occurs irrespective of the functional class of neuron. Aborally directed propulsion of content along the mouse colon is due, in large part, to polarity of the enteric circuits including the projections of the intrinsic excitatory and inhibitory motor neurons but still involves the fundamental ~2 Hz rhythmic activity of specific classes of enteric neurons. What remains to be determined are the mechanisms that initiate and terminate the patterned firing of large ensembles of enteric neurons during cyclic activity. This remains an exciting challenge for future studies.

Long range synchronization within the enteric nervous system underlies propulsion along the large intestine in mice

How the Enteric Nervous System (ENS) coordinates propulsion of content along the gastrointestinal (GI)-tract has been a major unresolved issue. We reveal a mechanism that explains how ENS activity underlies propulsion of content along the colon. We used a recently developed high-resolution video imaging approach with concurrent electrophysiological recordings from smooth muscle, during fluid propulsion. Recordings showed pulsatile firing of excitatory and inhibitory neuromuscular inputs not only in proximal colon, but also distal colon, long before the propagating contraction invades the distal region. During propulsion, wavelet analysis revealed increased coherence at ~2 Hz over large distances between the proximal and distal regions. Therefore, during propulsion, synchronous firing of descending inhibitory nerve pathways over long ranges aborally acts to suppress smooth muscle from contracting, counteracting the excitatory nerve pathways over this same region of colon. This delays muscle contraction downstream, ahead of the advancing contraction. The mechanism identified is more complex than expected and vastly different from fluid propulsion along other hollow smooth muscle organs; like lymphatic vessels, portal vein, or ureters, that evolved without intrinsic neurons.

Motor behavior of mouse large intestine: A Minireview.

Mice with a recessive gene which reduces the number of ganglion cells of the distal colon and rectum and produces megacolon, imitating Hirschsprung disease, are discussed as a model for integrative control of the large intestinal smooth musculature by the enteric division of the autonomic nervous system (ie, the brain-in-the-gut). Investigative approaches, such as propulsion of artificial pellets in preparations of whole colon in organ baths in vitro and innovative approaches capitalizing on neurogenetic technologies (eg, optogenetics), are considered in view of potential application in the development of novel therapeutic mechanisms to selectively evoke and control gastrointestinal motility patterns, such as the small intestinal digestive motility pattern, interdigestive pattern, and reversed direction of powerful propulsive motility during emesis. This minireview relates to the paper titled: "Motor patterns in the proximal and distal mouse colon which underlie formation and propulsion of feces," appearing in this issue of Neurogastroenterology and Motility.

Consequences of maternal breast milk antibodies on neonatal mucosal immunity and intestinal microbe composition

Abstract Breastfeeding is associated with decreased risk of acquiring inflammatory bowel disorders later in life. As breastfeeding is not possible for all mothers and children, having a mechanistic understanding of this process can lead to the development of early-life interventions to foster beneficial host-microbiota relationships, particularly in neonates who are not breastfed. We have shown that mice lacking breast milk antibodies (bmAbs) exhibit dysregulated intestinal homeostasis. These mice harbor increased numbers of live bacteria in the mesenteric lymph nodes and exhibit perturbations in mucosal immunity, including elevated T follicular helper (Tfh) cell and germinal center (GC) B cell responses in the gut-associated lymphoid tissues. Antibodies are key regulators of host-microbiome interactions, and T-dependent (TD) GC derived B cells can persist up to the lifetime of the host. We hypothesize that the TD antibodies generated by the neonate in the absence of bmAbs target resident gut bacteria and lead to long-term alterations in the composition of the microbiota. We performed RT-PCR of the bacterial 16s rRNA gene to quantify the amount of wall-associated microbes in the small and large intestine of mice that received or did not receive bmAbs. To probe the effects of Tfh cells and TD antibodies, we treated half of the mice from each group with anti-ICOS ligand antibody, which blocks Tfh and GC cell formation. We found no significant difference in bacterial burden across all four groups in the small or large intestine. These data suggest that Tfh-cell dependent, bmAb-dependent antibodies do not alter the abundance of wall-associated microbes. Studies are ongoing to determine if bmAbs affect intestinal microbe composition later in life.