Clinical parameters, intestinal function, and IGF1 concentrations in colostrum-deprived and colostrum-fed newborn pony foals.

Colostrum (COL) contains cytokines and growth factors that may enhance intestinal development in neonates. The hypothesis of this study was that besides providing immunoglobulins, COL is important for intestinal function and meconium release in foals. Newborn foals were either fed COL (n = 5) or an equal amount of milk replacer (MR, n = 7) during the first 24 hours of life. To ensure passive immunity, all foals received 1 L plasma. Postnatal development, meconium release, intestinal motility, white blood cell count, insulin-like growth factor 1, and intestinal absorptive function (xylose absorption test) were evaluated. Clinical findings and meconium release were not affected by feeding of COL or MR. Ultrasonography revealed a slightly larger jejunum and stomach in group COL versus MR (P < 0.05). The percentage of polymorphonuclear leucocytes was higher in foals of group MR versus group COL (P < 0.05) and the percentage of lymphocytes was lower in MR compared with COL foals (P < 0.05). Plasma insulin-like growth factor 1 concentration increased during the first 14 days after birth in both groups. A xylose absorption test on Day 5 revealed similar increases in plasma xylose concentrations after oral intake. In conclusion, feeding of COL versus MR was without effect on meconium release and intestinal absorptive function. Differences between foals fed COL and MR with regard to intestinal function are apparently without clinical relevance. In foals that have not received maternal COL, there is no major risk of intestinal problems if they are fed MR and provided with immunoglobulins by transfusion of plasma.

Lack of Host Gut Microbiota Alters Immune Responses and Intestinal Granuloma Formation during Schistosomiasis

Fatalities from schistosome infections arise due to granulomatous, immune-mediated responses to eggs that become trapped in host tissues. Schistosome-specific immune responses are characterized by initial Th1 responses and our previous studies demonstrated that Myd88-deficient mice failed to initiate such responses in vivo. Paradoxically, schistosomal antigens fail to stimulate innate cells to release pro-inflammatory cytokines in vitro. Since S. mansoni infection is an intestinal disease, we hypothesized that commensal bacteria could act as bystander activators of the intestinal innate immune system to instigate Th1 responses. Using a broad spectrum of orally-administered antibiotics and antimycotics we analyzed schistosome-infected mice that were simultaneously depleted of gut bacteria. After depletion there was significantly less inflammation in the intestine which was accompanied by decreased intestinal granuloma development. In contrast, liver pathology remained unaltered. In addition, schistosome-specific immune responses were skewed and fecal egg excretion was diminished. This study demonstrates that host microbiota can act as a third partner in instigating helminth-specific immune responses.

Interferon-γ Induces Expression of MHC Class II on Intestinal Epithelial Cells and Protects Mice from Colitis

Immune responses against intestinal microbiota contribute to the pathogenesis of inflammatory bowel diseases (IBD) and involve CD4(+) T cells, which are activated by major histocompatibility complex class II (MHCII) molecules on antigen-presenting cells (APCs). However, it is largely unexplored how inflammation-induced MHCII expression by intestinal epithelial cells (IEC) affects CD4(+) T cell-mediated immunity or tolerance induction in vivo. Here, we investigated how epithelial MHCII expression is induced and how a deficiency in inducible epithelial MHCII expression alters susceptibility to colitis and the outcome of colon-specific immune responses. Colitis was induced in mice that lacked inducible expression of MHCII molecules on all nonhematopoietic cells, or specifically on IECs, by continuous infection with Helicobacter hepaticus and administration of interleukin (IL)-10 receptor-blocking antibodies (anti-IL10R mAb). To assess the role of interferon (IFN)-γ in inducing epithelial MHCII expression, the T cell adoptive transfer model of colitis was used. Abrogation of MHCII expression by nonhematopoietic cells or IECs induces colitis associated with increased colonic frequencies of innate immune cells and expression of proinflammatory cytokines. CD4(+) T-helper type (Th)1 cells - but not group 3 innate lymphoid cells (ILCs) or Th17 cells - are elevated, resulting in an unfavourably altered ratio between CD4(+) T cells and forkhead box P3 (FoxP3)(+) regulatory T (Treg) cells. IFN-γ produced mainly by CD4(+) T cells is required to upregulate MHCII expression by IECs. These results suggest that, in addition to its proinflammatory roles, IFN-γ exerts a critical anti-inflammatory function in the intestine which protects against colitis by inducing MHCII expression on IECs. This may explain the failure of anti-IFN-γ treatment to induce remission in IBD patients, despite the association of elevated IFN-γ and IBD.

Hydrostatic intestinal edema induced signaling pathways: potential role of mechanical forces.

BACKGROUND: Hydrostatic intestinal edema initiates a signal transduction cascade that results in smooth muscle contractile dysfunction. Given the rapid and concurrent alterations in the mechanical properties of edematous intestine observed with the development of edema, we hypothesize that mechanical forces may serve as a stimulus for the activation of certain signaling cascades. We sought to examine whether isolated similar magnitude mechanical forces induced the same signal transduction cascades associated with edema. METHODS: The distal intestine from adult male Sprague Dawley rats was stretched longitudinally for 2 h to 123% its original length, which correlates with the interstitial stress found with edema. We compared wet-to-dry ratios, myeloperoxidase activity, nuclear signal transduction and activator of transcription (STAT)-3 and nuclear factor (NF)-kappa B DNA binding, STAT-3 phosphorylation, myosin light chain phosphorylation, baseline and maximally stimulated intestinal contractile strength, and inducible nitric oxide synthase (iNOS) and sodium hydrogen exchanger 1-3 messenger RNA (mRNA) in stretched and adjacent control segments of intestine. RESULTS: Mechanical stretch did not induce intestinal edema or an increase in myeloperoxidase activity. Nuclear STAT-3 DNA binding, STAT-3 phosphorylation, and nuclear NF-kappa B DNA binding were significantly increased in stretched seromuscular samples. Increased expression of sodium hydrogen exchanger 1 was found but not an increase in iNOS expression. Myosin light chain phosphorylation was significantly decreased in stretched intestine as was baseline and maximally stimulated intestinal contractile strength. CONCLUSION: Intestinal stretch, in the absence of edema/inflammatory/ischemic changes, leads to the activation of signaling pathways known to be altered in intestinal edema. Edema may initiate a mechanotransductive cascade that is responsible for the subsequent activation of various signaling cascades known to induce contractile dysfunction.

Effect of indomethacin on bile acid-phospholipid interactions: implication for small intestinal injury induced by nonsteroidal anti-inflammatory drugs.

The injurious effect of nonsteroidal anti-inflammatory drugs (NSAIDs) in the small intestine was not appreciated until the widespread use of capsule endoscopy. Animal studies found that NSAID-induced small intestinal injury depends on the ability of these drugs to be secreted into the bile. Because the individual toxicity of amphiphilic bile acids and NSAIDs directly correlates with their interactions with phospholipid membranes, we propose that the presence of both NSAIDs and bile acids alters their individual physicochemical properties and enhances the disruptive effect on cell membranes and overall cytotoxicity. We utilized in vitro gastric AGS and intestinal IEC-6 cells and found that combinations of bile acid, deoxycholic acid (DC), taurodeoxycholic acid, glycodeoxycholic acid, and the NSAID indomethacin (Indo) significantly increased cell plasma membrane permeability and became more cytotoxic than these agents alone. We confirmed this finding by measuring liposome permeability and intramembrane packing in synthetic model membranes exposed to DC, Indo, or combinations of both agents. By measuring physicochemical parameters, such as fluorescence resonance energy transfer and membrane surface charge, we found that Indo associated with phosphatidylcholine and promoted the molecular aggregation of DC and potential formation of larger and isolated bile acid complexes within either biomembranes or bile acid-lipid mixed micelles, which leads to membrane disruption. In this study, we demonstrated increased cytotoxicity of combinations of bile acid and NSAID and provided a molecular mechanism for the observed toxicity. This mechanism potentially contributes to the NSAID-induced injury in the small bowel.

Regulation of hepatic cytochrome P450 expression in mice with intestinal or systemic infections of citrobacter rodentium.

We reported previously that infection of C3H/HeOuJ (HeOu) mice with the murine intestinal pathogen Citrobacter rodentium caused a selective modulation of hepatic cytochrome P450 (P450) gene expression in the liver that was independent of the Toll-like receptor 4. However, HeOu mice are much more sensitive to the pathogenic effects of C. rodentium infection, and the P450 down-regulation was associated with significant morbidity in the animals. Here, we report that oral infection of C57BL/6 mice with C. rodentium, which produced only mild clinical signs and symptoms, produced very similar effects on hepatic P450 expression in this strain. As in HeOu mice, CYP4A mRNAs and proteins were among the most sensitive to down-regulation, whereas CYP4F18 was induced. CYP2D9 mRNA was also induced 8- to 9-fold in the C57BL/6 mice. The time course of P450 regulation followed that of colonic inflammation and bacterial colonization, peaking at 7 to 10 days after infection and returning to normal at 15 to 24 days as the infection resolved. These changes also correlated with the time course of significant elevations in the serum of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor-alpha, as well as of interferon-gamma and IL-2, with serum levels of IL-6 being markedly higher than those of the other cytokines. Intraperitoneal administration of C. rodentium produced a rapid down-regulation of P450 enzymes that was quantitatively and qualitatively different from that of oral infection, although CYP2D9 was induced in both models, suggesting that the effects of oral infection on the liver are not due to bacterial translocation.

Type I hypersensitivity and its pharmacological modulation in {\it Trichinella\/}-induced intestinal fluid secretion and rapid rejection of the parasite in immunized rats

Studies were performed to test the hypothesis that type I hypersensitivity underlies worm induced intestinal fluid secretion and the rapid rejection of Trichinella spiralis from immunized rats, and the two events may be related in a cause-effect manner.^ Two approaches were taken. One was to determine whether inhibition of anaphylaxis-mediated Cl$\sp{-}$ and fluid secretion accompanying a secondary infection impedes worm rejection from immune hosts. The other was to determine whether induction of intestinal fluid secretion in nonimmune hosts interfered with worm establishment. In both studies, fluid secretion was measured volumetrically 30 min after a challenge infection and worms were counted.^ In immunized rats indomethacin did not affect the worm-induced fluid secretion when used alone, despite inhibiting mucosal prostaglandin synthesis. Fluid secretion was reduced by treatment with diphenhydramine and further reduced by the combination of diphenhydramine and indomethacin. The paradoxical effects of indomethacin when used alone compared with its coadministration with diphenhydramine is explained by the enhancing effect of indomethacin on histamine release. Abolishing net fluid secretion in these studies had no effect on rapid worm rejection in immune hosts.^ Worm establishment was reduced in recipients of immune serum containing IgE antibodies. Net intestinal fluid secretion induced in normal rats by PGE$\sb2$, cholera toxin, or hypertonic mannitol solution had no effect on worm establishment compared with untreated controls.^ In a related experiment, worm-induced intestinal fluid secretion and worm rejection in immune rats were partially blocked by concurrent injection with 5-HT$\sb2$ and 5-HT$\sb3$ blockers (Ketanserin and MDL-72222), suggesting that 5-HT is involved. This possible involvement was supported in that treatment of nonimmune rats with 5-HT significantly inhibited worm establishment in the intestine.^ Results indicate that anaphylaxis is the basis for both worm-induced intestinal fluid secretion and rapid rejection of T. spiralis in immune rats, but these events are independent of one another. 5-HT is a possible mediator of worm rejection, however, its mechanism of action is related to something other than fluid secretion. ^

High intestinal cholesterol absorption is associated with cardiovascular disease and risk alleles in ABCG8 and ABO: evidence from the LURIC and YFS cohorts and from a meta-analysis.

OBJECTIVES This study sought to determine whether high intestinal cholesterol absorption represents a cardiovascular risk factor and to link ABCG8 and ABO variants to cardiovascular disease (CVD). BACKGROUND Plant sterol-enriched functional foods are widely used for cholesterol lowering. Their regular intake yields a 2-fold increase in circulating plant sterol levels that equally represent markers of cholesterol absorption. Variants in ABCG8 and ABO have been associated with circulating plant sterol levels and CVD, thereby suggesting atherogenic effects of plant sterols or of cholesterol uptake. METHODS The cholestanol-to-cholesterol ratio (CR) was used as an estimate of cholesterol absorption because it is independent of plant sterols. First, we investigated the associations of 6 single nucleotide polymorphisms in ABCG8 and ABO with CR in the LURIC (LUdwisghafen RIsk and Cardiovascular health study) and the YFS (Young Finns Study) cohorts. Second, we conducted a systematic review and meta-analysis to investigate whether CR might be related to CVD. RESULTS In LURIC, the minor alleles of rs4245791 and rs4299376 and the major alleles of rs41360247, rs6576629, and rs4953023 of the ABCG8 gene and the minor allele of rs657152 of the ABO gene were significantly associated with higher CR. Consistent results were obtained for rs4245791, rs4299376, rs6576629, and rs4953023 in YFS. The meta-analysis, including 6 studies and 4,362 individuals, found that CR was significantly increased in individuals with CVD. CONCLUSIONS High cholesterol absorption is associated with risk alleles in ABCG8 and ABO and with CVD. Harm caused by elevated cholesterol absorption rather than by plant sterols may therefore mediate the relationships of ABCG8 and ABO variants with CVD.

Stratification and compartmentalisation of immunoglobulin responses to commensal intestinal microbes

The gastrointestinal tract is heavily colonized with commensal microbes with the concentration of bacteria increasing longitudinally down the length of the intestine. Bacteria are also spatially distributed transversely from the epithelial surface to the intestinal lumen with the inner mucus layer normally void of bacteria. Maintenance of this equilibrium is extremely important for human health and, as the dominant immunoglobulin at mucosal sites, IgA influences mutualism between the host and its normal microbiota. In this review we focus on the links between immune and microbial geography of the mammalian intestinal tract.

Intestinal Microbial Diversity during Early-Life Colonization Shapes Long-Term IgE Levels

Microbial exposure following birth profoundly impacts mammalian immune system development. Microbiota alterations are associated with increased incidence of allergic and autoimmune disorders with elevated serum IgE as a hallmark. The previously reported abnormally high serum IgE levels in germ-free mice suggests that immunoregulatory signals from microbiota are required to control basal IgE levels. We report that germ-free mice and those with low-diversity microbiota develop elevated serum IgE levels in early life. B cells in neonatal germ-free mice undergo isotype switching to IgE at mucosal sites in a CD4 T-cell- and IL-4-dependent manner. A critical level of microbial diversity following birth is required in order to inhibit IgE induction. Elevated IgE levels in germ-free mice lead to increased mast-cell-surface-bound IgE and exaggerated oral-induced systemic anaphylaxis. Thus, appropriate intestinal microbial stimuli during early life are critical for inducing an immunoregulatory network that protects from induction of IgE at mucosal sites.

Metabolites from intestinal microbes shape Treg

Intestinal bacterial metabolites are an important communication tool between the host immune system and the commensal microbiota to establish mutualism. In a recent paper published in Science, Wendy Garrett and her colleagues report an exciting role of the three most abundant microbial-derived short-chain fatty acids (SCFA), acetic acid, propionic acid and butyric acid, in colonic regulatory T cell (cTreg) homeostasis.

Intestinal bacteria induce TSLP to promote mutualistic T-cell responses

Thymic stromal lymphopoietin (TSLP) is constitutively expressed in the intestine and is known to regulate inflammation in models of colitis. We show that steady-state TSLP expression requires intestinal bacteria and has an important role in limiting the expansion of colonic T helper type 17 (Th17) cells. Inappropriate expansion of the colonic Th17 cells occurred in response to an entirely benign intestinal microbiota, as determined following the colonization of germ-free C57BL/6 or TSLPR(-/-) mice with the altered Schaedler flora (ASF). TSLP-TSLPR (TSLP receptor) interactions also promoted the expansion of colonic Helios(-)Foxp3(+) regulatory T cells, necessary for the control of inappropriate Th17 responses following ASF bacterial colonization. In summary, these data reveal an important role for TSLP-TSLPR signaling in promoting steady-state mutualistic T-cell responses following intestinal bacterial colonization.