Immature Intestine Research Articles

Effect of an α-Tocopherol-Containing Antioxidant Parenteral Emulsion upon Gut Microbiota in Preterm Infants

Preterm babies are born with an immature intestine and are at higher risk for intestinal failure and needing for parenteral nutrition than full-term newborns. These babies show an altered intestinal microbiota, which may results of key importance for later health. However, there is a lack of information on effect of parenteral formulas upon the establishing infant microbiota. Moreover, the microbiota alterations present in preterm newborns have been related with an altered redox-potential which hinders the establishment of strict anaerobes. Thus, interventions aimed at reducing the oxidative stress in these infants, including those under parenteral nutrition, could also affect the intestinal microbiota composition. We assessed the effect upon the gut microbiota of the administration during 30 days of a lipid emulsion, containing ω3 polyunsaturated fatty acids and α-tocopherol, or a control emulsion containing soybean-bases lipids to parenterally-fed preterm newborns. In spite of its high antioxidant potential, the infants receiving the experimental fat emulsion showed a trend to increase of facultative anaerobes such as enterobacteria and specifically of Klebsiella. This study stresses the need of further work monitoring the impact of early-life parenteral nutrition on the establishment of the intestinal microbiota.

Transcriptional modulation of intestinal innate defense/inflammation genes by preterm infant microbiota in a humanized gnotobiotic mouse model.

Background and AimsIt is known that postnatal functional maturation of the small intestine is facilitated by microbial colonization of the gut. Preterm infants exhibit defects in gut maturation, weak innate immunity against intestinal infection and increased susceptibility to inflammatory disorders, all of which may be related to the inappropriate microbial colonization of their immature intestines. The earliest microbes to colonize the preterm infant gut encounter a naïve, immature intestine. Thus this earliest microbiota potentially has the greatest opportunity to fundamentally influence intestinal development and immune function. The aim of this study was to characterize the effect of early microbial colonization on global gene expression in the distal small intestine during postnatal gut development.MethodsGnotobiotic mouse models with experimental colonization by early (prior to two weeks of life) intestinal microbiota from preterm human infants were utilized. Microarray analysis was used to assess global gene expression in the intestinal epithelium.Results and ConclusionMultiple intestinal genes involved in metabolism, cell cycle regulation, cell-cell or cell-extracellular matrix communication, and immune function are developmental- and intestinal microbiota- regulated. Using a humanized gnotobiotic mouse model, we demonstrate that certain early preterm infant microbiota from prior to 2 weeks of life specifically induce increased NF-κB activation and a phenotype of increased inflammation whereas other preterm microbiota specifically induce decreased NF-κB activation. These fundamental differences correlate with altered clinical outcomes and suggest the existence of optimal early microbial communities to improve health outcomes.

Human milk oligosaccharides and galactosyloligosaccharides attenuate inflammation in human intestine

The immature intestinal mucosa is hyperresponsive to exogenous and endogenous inflammatory insults. Human milk provides immune protection to infants, and its oligosaccharides (HMOS) are putative immunomodulators. Of these, galactosyloligosaccharides (GOS) are high in colostrum, but not mature milk. The objective is to determine the ability of GOS to directly attenuate inflammation, and potential mechanisms investigated. Human models of immature and mature intestine were used to investigate the ability of a mixture of HMOS or synthetic GOS to attenuate inflammation induced by proinflammatory stimuli and enteric pathogens. These results were confirmed in the ex vivo immature human intestinal organ cultures. The ability of TNFα and of pathogens to elicit pro‐inflammatory neutrophil chemoattractants IL‐8, MIP‐3α and MCP1 and their mRNA levels was significantly attenuated by HMOS and GOS. TNFα‐induced nuclear translocation of NF‐κB was mitigated by HMOS and GOS. Consistent with previous indications of bioactivity of galactosyllactose from human colostrum, trimeric galactosyloligosaccharides interact with cell receptors to inhibit inflammatory response. HMOS and GOS suppress NF‐κB activation, thereby directly attenuating TNFα‐ and pathogen‐induced inflammation in human intestine. This provides a novel mechanism whereby specific galactosyloligosaccharides found in human milk may prove a novel therapeutic agent against gut inflammation.

Tu2007 Prenatal Microbial Exposure Induces Epigenetic Changes and Modulates TLR-Signaling Pathway Associated Gene Expression in the Immature Intestine

Tu2007 Prenatal Microbial Exposure Induces Epigenetic Changes and Modulates TLR-Signaling Pathway Associated Gene Expression in the Immature Intestine

Necrotizing enterocolitis: a clinical review on diagnostic biomarkers and the role of the intestinal microbiota.

Necrotizing enterocolitis (NEC) remains one of the most frequent gastrointestinal diseases in the neonatal intensive care unit, with a continuing unacceptable high mortality and morbidity rates. Up to 20% to 40% of infants with NEC will need surgical intervention at some point. Although the exact pathophysiology is not yet elucidated, prematurity, use of formula feeding, and an altered intestinal microbiota are supposed to induce an inflammatory response of the immature intestine. The clinical picture of NEC has been well described. However, an early diagnosis and differentiation against sepsis is challenging. Besides, it is difficult to timely identify NEC cases that will deteriorate and need surgical intervention. This may interfere with the most optimal treatment of infants with NEC. In this review, we discuss the pathogenesis, diagnosis, and treatment of NEC with a focus on the role of microbiota in the development of NEC. An overview of different clinical prediction models and biomarkers is given. Some of these are promising tools for accurate diagnosis of NEC and selection of appropriate therapy.

Marked methylation changes in intestinal genes during the perinatal period of preterm neonates.

BackgroundThe serious feeding- and microbiota-associated intestinal disease, necrotizing enterocolitis (NEC), occurs mainly in infants born prematurely (5-10% of all newborns) and most frequently after formula-feeding. We hypothesized that changes in gene methylation is involved in the prenatal maturation of the intestine and its response to the first days of formula feeding, potentially leading to NEC in preterm pigs used as models for preterm infants.ResultsReduced Representation Bisulfite Sequencing (RRBS) was used to assess if changes in intestinal DNA methylation are associated with formula-induced NEC outbreak and advancing age from 10 days before birth to 4 days after birth. Selected key genes with differentially methylated gene regions (DMRs) between groups were further validated by HiSeq-based bisulfite sequencing PCR and RT-qPCR to assess methylation and expression levels. Consistent with the maturation of many intestinal functions in the perinatal period, methylation level of most genes decreased with advancing pre- and postnatal age. The highest number of DMRs was identified between the newborn and 4 d-old preterm pigs. There were few intestinal DMR differences between unaffected pigs and pigs with initial evidence of NEC. In the 4 d-old formula-fed preterm pigs, four genes associated with intestinal metabolism (CYP2W1, GPR146, TOP1MT, CEND1) showed significant hyper-methylation in their promoter CGIs, and thus, down-regulated transcription. Methylation-driven down-regulation of such genes may predispose the immature intestine to later metabolic dysfunctions and severe NEC lesions.ConclusionsPre- and postnatal changes in intestinal DNA methylation may contribute to high NEC sensitivity in preterm neonates. Optimizing gene methylation changes via environmental stimuli (e.g. diet, nutrition, gut microbiota), may help to make immature newborn infants more resistant to gut dysfunctions, both short and long term.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-716) contains supplementary material, which is available to authorized users.

Transforming growth factor-β2 and endotoxin interact to regulate homeostasis via interleukin-8 levels in the immature intestine.

A balance between pro- and anti-inflammatory signals from milk and microbiota controls intestinal homeostasis just after birth, and an optimal balance is particularly important for preterm neonates that are sensitive to necrotizing enterocolitis (NEC). We suggest that the intestinal cytokine IL-8 plays an important role and hypothesize that transforming growth factor-β2 (TGF-β2) acts in synergy with bacterial lipopolysaccharide (LPS) to control IL-8 levels, thereby supporting intestinal homeostasis. Preterm pigs were fed colostrum (containing TGF-β2) or infant formula (IF) with or without antibiotics (COLOS, n = 27; ANTI, n = 11; IF, n = 40). Intestinal IL-8 levels and NEC incidence were much higher in IF than in COLOS and ANTI pigs (P < 0.001), but IL-8 levels did not correlate with NEC severity. Intestinal TGF-β2 levels were high in COLOS but low in IF and ANTI pigs. Based on these observations, the interplay among IL-8, TGF-β2, and LPS was investigated in a porcine intestinal epithelial cell line. TGF-β2 attenuated LPS-induced IL-6, IL-1β, and TNF-α release by reducing early ERK activation, whereas IL-8 secretion was synergistically induced by LPS and TGF-β2 via NF-κB. The TGF-β2/LPS-induced IL-8 levels stimulated cell proliferation and migration following epithelial injury, without continuous NF-κB activation and cyclooxygenase-2 expression. We suggest that a combined TGF-β2-LPS induction of IL-8 stimulates epithelial repair just after birth when the intestine is first exposed to colonizing bacteria and TGF-β2-containing milk. Moderate IL-8 levels may act to control intestinal inflammation, whereas excessive IL-8 production may enhance the damaging proinflammatory cascade leading to NEC.

Molecular epidemiology of infant botulism in California and elsewhere, 1976-2010.

Infant botulism (IB), first identified in California in 1976, results from Clostridium botulinum spores that germinate, multiply, and produce botulinum neurotoxin (BoNT) in the immature intestine. From 1976 to 2010 we created an archive of 1090 BoNT-producing isolates consisting of 1012 IB patient (10 outpatient, 985 hospitalized, 17 sudden death), 25 food, 18 dust/soils, and 35 other strains. The mouse neutralization assay determined isolate toxin type (56% BoNT/A, 32% BoNT/B). Amplified fragment-length polymorphism (AFLP) analysis of the isolates was combined with epidemiologic information. The AFLP dendrogram, the largest to date, contained 154 clades; 52% of isolates clustered in just 2 clades, 1 BoNT/A (n=418) and 1 BoNT/B (n=145). These clades constituted an endemic C. botulinum population that produced the entire clinical spectrum of IB. Isolates from the patient's home environment (dust/soil, honey) usually located to the same AFLP clade as the patient's isolate, thereby identifying the likely source of infective spores. C. botulinum A(B) strains were identified in California for the first time. Combining molecular methods and epidemiological data created an effective tool that yielded novel insights into the genetic diversity of C. botulinum and the clinical spectrum, occurrence, and distribution of IB in California.

Tumor necrosis factor induces developmental stage-dependent structural changes in the immature small intestine.

Background. Premature infants are commonly subject to intestinal inflammation. Since the human small intestine does not reach maturity until term gestation, premature infants have a unique challenge, as either acute or chronic inflammation may alter the normal development of the intestinal tract. Tumor necrosis factor (TNF) has been shown to acutely alter goblet cell numbers and villus length in adult mice. In this study we tested the effects of TNF on villus architecture and epithelial cells at different stages of development of the immature small intestine. Methods. To examine the effects of TNF-induced inflammation, we injected acute, brief, or chronic exposures of TNF in neonatal and juvenile mice. Results. TNF induced significant villus blunting through a TNF receptor-1 (TNFR1) mediated mechanism, leading to loss of villus area. This response to TNFR1 signaling was altered during intestinal development, despite constant TNFR1 protein expression. Acute TNF-mediated signaling also significantly decreased Paneth cells. Conclusions. Taken together, the morphologic changes caused by TNF provide insight as to the effects of inflammation on the developing intestinal tract. Additionally, they suggest a mechanism which, coupled with an immature immune system, may help to explain the unique susceptibility of the immature intestine to inflammatory diseases such as NEC.

Raw bovine milk improves gut responses to feeding relative to infant formula in preterm piglets

For preterm neonates, the quality of the first milk is crucial for intestinal maturation and resistance to necrotizing enterocolitis (NEC). Among other factors, milk quality is determined by the stage of lactation and processing. We hypothesized that unprocessed mature bovine milk (BM; raw bovine milk) would have less bioactivity than corresponding bovine colostrum (BC) in a preterm pig model, but have improved bioactivity relative to its homogenized, pasteurized, spray-dried equivalent, whole milk powder (WMP), or a bovine milk protein-based infant formula (IF). For 5 days, newborn preterm pigs received parenteral and enteral nutrition consisting of IF (n = 13), BM (n = 13), or BC (n = 14). In a second study, WMP (n = 15) was compared with IF (n = 10) and BM (n = 9). Compared with pigs fed IF, pigs that were fed BM had significantly improved intestinal structure (mucosal weight, villus height) and function (increased nutrient absorption and enzyme activities, decreased gut permeability, nutrient fermentation, and NEC severity). BC further improved these effects relative to BM (lactase activity, lactose absorption, plasma citrulline, and tissue interleukin-8). WMP induced similar effects as BM, except for lactase activity and lactose absorption. In conclusion, the maturational and protective effects on the immature intestine decreased in the order BC>BM>WMP, but all three intact bovine milk diets were markedly better than IF. The stage of lactation (colostrum vs. mature milk) and milk processing (e.g., homogenization, fractionation, pasteurization, spray-drying) are important factors in determining milk quality during the early postnatal period of preterm neonates.

Laminin receptor 37/67LR regulates adhesion and proliferation of normal human intestinal epithelial cells.

Interactions between the cell basal membrane domain and the basement membrane are involved in several cell functions including proliferation, migration and differentiation. Intestinal epithelial cells can interact with laminin, a major intestinal basement membrane glycoprotein, via several cell-surface laminin-binding proteins including integrin and non-integrin receptors. The 37/67kDa laminin receptor (37/67LR) is one of these but its role in normal epithelial cells is still unknown. The aim of this study was to characterise the expression pattern and determine the main function of 37/67LR in the normal human small intestinal epithelium. Immunolocalization studies revealed that 37/67LR was predominantly present in the undifferentiated/proliferative region of the human intestinal crypt in both the immature and adult intestine. Using a human intestinal epithelial crypt (HIEC) cell line as experimental model, we determined that 37/67LR was expressed in proliferative cells in both the cytoplasmic and membrane compartments. Small-interfering RNA-mediated reduction of 37/67LR expression led to HIEC cell-cycle reduction and loss of the ability to adhere to laminin-related peptides under conditions not altering ribosomal function. Taken together, these findings indicate that 37/67LR regulates proliferation and adhesion in normal intestinal epithelial cells independently of its known association with ribosomal function.

Progresses of the risk factors in neonatal necrotizing enterocolitis

Neonatal necrotizing enterocolitis is a common gastrointestinal disease in neonate.Recently,with the establishment of the NICU and the all-round development of perinatal medicine and pediatrics,survival rate of premature especially very low birth weight neonates have obviously increased and the incidence of the disease is rising year by year.It is generally considered that multiple risk factors such as premature birth,low birth weight,infections,asphyxia,irrational use of drugs and so on,acting on the immature intestine,but the pathogenesis is still unknown.Therefore,it is significant to clearify the pathogenesis of the risk factors of NEC for studying the pathogenesis of the disease and providing prevention and control strategy. Key words: Necrotizing enterocolitis; Newborn; Risk factor

Sa2011 Adverse Metabolic Effects of Indomethacin on the Immature Human Intestine

Background: Indomethacin (INDO) is a non-steroidal anti-inflammatory drug (NSAID) used for the treatment of patent ductus arteriosus in preterm infants and as a tocolytic agent in pregnant women. The exposure of preterm infants to INDO is associated with an increased risk of developing enteropathies such as necrotizing enterocolitis. Despite increasing progress in establishing the pathways involved in NSAID-induced damage, understanding the pathogenesis of gastrointestinal injury by NSAIDs in neonates relies on a limited number of studies carried out in animal models. Aims: In the present study, we combined our method for maintaining the mid-gestation human intestine in serum-free organ culture with highthroughput genomic studies and bioinformatic pathway analysis to investigate the specific intestinal effects of INDO on the overall physiology of both the small and large intestine at mid-gestation. Methods: After determining the optimal concentration of INDO to be 1μM (.90% inhibition of intestinal prostaglandin E2 production), a dose that corresponds to the range of circulating levels in treated preterm babies, we used Illumina microarrays to establish global gene expression profiles in human intestinal explants (ileums and colons) in response to an INDO treatment of 48 h. Differentially expressed genes between control and INDO-treated explants were determined using the Mann-Whitney test (p , 0.05), and further analyzed with Ingenuity Pathway Analysis software (IPA 8.8) to identify biological functions and canonical pathways modulated by INDO. Results: The gene expression profiles identified revealed that a large proportion of statistically significant biological, physiological and metabolic functions were modulated by INDO in the immature intestine. As expected, a number of these significantly modulated functions were inflammation-related such as Inflammatory diseases, Inflammatory response, and Acute phase response. Noteworthily, we have identified a series of metabolic-related gene clusters that were found to be significantly modulated, namely Glycolysis/gluconeogenesis, Oxidative phosphorylation and Free radical scavenging/oxidoreductase activity. Further analysis by qPCR confirmed that the expression of representative genes involved in these metabolic functions, such as ALDOA, LDHA, NDUFA9, DUOX2, SOD2, and TFF1, was inhibited by INDO in both intestinal segments, indicating that this adverse metabolic effect could be a component of the pathogenesis of intestinal damage induced by INDO. Conclusion: This study identified several different metabolic pathways that are modulated by INDO in the immature human intestine and suggests a mechanistic basis for better understanding the contributing effects of INDO and other NSAIDs on neonatal intestinal pathologies.

Sa2012 Risk Factors and Temporal Trends for Complicated Diverticulitis: A Population-Based Study

Background: Indomethacin (INDO) is a non-steroidal anti-inflammatory drug (NSAID) used for the treatment of patent ductus arteriosus in preterm infants and as a tocolytic agent in pregnant women. The exposure of preterm infants to INDO is associated with an increased risk of developing enteropathies such as necrotizing enterocolitis. Despite increasing progress in establishing the pathways involved in NSAID-induced damage, understanding the pathogenesis of gastrointestinal injury by NSAIDs in neonates relies on a limited number of studies carried out in animal models. Aims: In the present study, we combined our method for maintaining the mid-gestation human intestine in serum-free organ culture with highthroughput genomic studies and bioinformatic pathway analysis to investigate the specific intestinal effects of INDO on the overall physiology of both the small and large intestine at mid-gestation. Methods: After determining the optimal concentration of INDO to be 1μM (.90% inhibition of intestinal prostaglandin E2 production), a dose that corresponds to the range of circulating levels in treated preterm babies, we used Illumina microarrays to establish global gene expression profiles in human intestinal explants (ileums and colons) in response to an INDO treatment of 48 h. Differentially expressed genes between control and INDO-treated explants were determined using the Mann-Whitney test (p , 0.05), and further analyzed with Ingenuity Pathway Analysis software (IPA 8.8) to identify biological functions and canonical pathways modulated by INDO. Results: The gene expression profiles identified revealed that a large proportion of statistically significant biological, physiological and metabolic functions were modulated by INDO in the immature intestine. As expected, a number of these significantly modulated functions were inflammation-related such as Inflammatory diseases, Inflammatory response, and Acute phase response. Noteworthily, we have identified a series of metabolic-related gene clusters that were found to be significantly modulated, namely Glycolysis/gluconeogenesis, Oxidative phosphorylation and Free radical scavenging/oxidoreductase activity. Further analysis by qPCR confirmed that the expression of representative genes involved in these metabolic functions, such as ALDOA, LDHA, NDUFA9, DUOX2, SOD2, and TFF1, was inhibited by INDO in both intestinal segments, indicating that this adverse metabolic effect could be a component of the pathogenesis of intestinal damage induced by INDO. Conclusion: This study identified several different metabolic pathways that are modulated by INDO in the immature human intestine and suggests a mechanistic basis for better understanding the contributing effects of INDO and other NSAIDs on neonatal intestinal pathologies.

Probiotics and the mechanism of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a severe intestinal inflammatory disorder in newborns. Although the pathogenesis of NEC is not completely understood, we reviewed the literature and our previous studies to explore the mechanism of NEC and to evaluate the role for probiotics in this disease. NEC may be associated with an inappropriate innate immune and excessive inflammatory response of the immature intestine. Probiotics are widely used in promoting human health and adjunctive therapy of human disease. There are growing clinical trials and research studies that support a beneficial role for probiotics for NEC. We have reviewed the literature associated with the use of probiotics in NEC.

A Critical Role for TLR4 Induction of Autophagy in the Regulation of Enterocyte Migration and the Pathogenesis of Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) develops in response to elevated TLR4 signaling in the newborn intestinal epithelium and is characterized by TLR4-mediated inhibition of enterocyte migration and reduced mucosal healing. The downstream processes by which TLR4 impairs mucosal healing remain incompletely understood. In other systems, TLR4 induces autophagy, an adaptive response to cellular stress. We now hypothesize that TLR4 induces autophagy in enterocytes and that TLR4-induced autophagy plays a critical role in NEC development. Using mice selectively lacking TLR4 in enterocytes (TLR4(ΔIEC)) and in TLR4-deficient cultured enterocytes, we now show that TLR4 activation induces autophagy in enterocytes. Immature mouse and human intestine showed increased expression of autophagy genes compared with full-term controls, and NEC development in both mouse and human was associated with increased enterocyte autophagy. Importantly, using mice in which we selectively deleted the autophagy gene ATG7 from the intestinal epithelium (ATG7(ΔIEC)), the induction of autophagy was determined to be required for and not merely a consequence of NEC, because ATG7(ΔIEC) mice were protected from NEC development. In defining the mechanisms involved, TLR4-induced autophagy led to impaired enterocyte migration both in vitro and in vivo, which in cultured enterocytes required the induction of RhoA-mediated stress fibers. These findings depart from current dogma in the field by identifying a unique effect of TLR4-induced autophagy within the intestinal epithelium in the pathogenesis of NEC and identify that the negative consequences of autophagy on enterocyte migration play an essential role in its development.

Deleterious effects of indomethacin in the mid-gestation human intestine

The use of the anti-inflammatory drug indomethacin (INDO) in preterm infants has been associated with an increased risk of developing enteropathies. In this study, we have investigated the direct impact of INDO on the human mid-gestation intestinal transcriptome using serum-free organ culture. After determining the optimal dose of 1μM of INDO (90% inhibition of intestinal prostaglandin E2 production and range of circulating levels in treated preterm babies), global gene expression profiles were determined using Illumina bead chip microarrays in both small and large intestines after 48h of INDO treatment. Using Ingenuity Pathway Analysis software, we identified critical metabolic pathways that were significantly altered by INDO in both intestinal segments including inflammation and also glycolysis, oxidative phosphorylation and free radical scavenging/oxidoreductase activity, which were confirmed by qPCR at the level of individual genes. Taken together, these data revealed that INDO directly exerts multiple detrimental effects on the immature human intestine.

Lactobacillus rhamnosus (LGG) Regulates IL-10 Signaling in the Developing Murine Colon through Upregulation of the IL-10R2 Receptor Subunit

The intestinal microflora is critical for normal development, with aberrant colonization increasing the risk for necrotizing enterocolitis (NEC). In contrast, probiotic bacteria have been shown to decrease its incidence. Multiple pro- and anti-inflammatory cytokines have been identified as markers of intestinal inflammation, both in human patients with NEC and in models of immature intestine. Specifically, IL-10 signaling attenuates intestinal responses to gut dysbiosis, and disruption of this pathway exacerbates inflammation in murine models of NEC. However, the effects of probiotics on IL-10 and its signaling pathway, remain poorly defined. Real-time PCR profiling revealed developmental regulation of MIP-2, TNF-α, IL-12, IL-10 and the IL-10R2 subunit of the IL-10 receptor in immature murine colon, while the expression of IL-6 and IL-18 was independent of postnatal age. Enteral administration of the probiotic Lactobacillus rhamnosus GG (LGG) down-regulated the expression of TNF-α and MIP-2 and yet failed to alter IL-10 mRNA and protein expression. LGG did however induce mRNA expression of the IL-10R2 subunit of the IL-10 receptor. IL-10 receptor activation has been associated with signal transducer and activator of transcription (STAT) 3-dependent induction of members of the suppressors of cytokine signaling (SOCS) family. In 2 week-old mice, LGG also induced STAT3 phosphorylation, increased colonic expression of SOCS-3, and attenuated colonic production of MIP-2 and TNF-α. These LGG-dependent changes in phosphoSTAT3, SOCS3, MIP-2 and TNF-α were all inhibited by antibody-mediated blockade of the IL-10 receptor. Thus LGG decreased baseline proinflammatory cytokine expression in the developing colon through upregulation of IL-10 receptor-mediated signaling, most likely due to the combined induction of phospho-STAT3 and SOCS3. Furthermore, LGG-dependent increases in IL-10R2 were associated with reductions in TNF-α, MIP-2 and disease severity in a murine model of intestinal injury in the immature colon.

Contribution of FcRn binding to intestinal uptake of IgG in suckling rat pups and human FcRn-transgenic mice

Immunoglobulin G (IgG) is transcytosed across intestinal epithelial cells of suckling mammals by the neonatal Fc receptor (FcRn); however, the contribution of FcRn vs. FcRn-independent uptake to serum IgG levels had not been determined in either rat pups or human (h)FcRn-expressing mice (Tg276 and Tg32). In isoflurane-anesthetized rodents, serum levels were determined after regional intestinal delivery of human monoclonal antibodies (hIgG) with either wild-type (WT) Fc sequences or variants engineered for different FcRn binding affinities. Detection of full-length hIgG was by immunoassay; intestinal hFcRn and hIgG localization was by immunocytochemistry. High (μg/ml) serum levels of hIgG were detected after proximal intestinal delivery (0.1-10 mg/kg) in 2-wk-old rats. Human FcRn was visualized in epithelial cells of Tg276 mice, but low serum hIgG levels (<10 ng/ml) were obtained. In rat pups, intraintestinal hIgG1 WT administration resulted in dose-related and saturable uptake, whereas uptake of a low FcRn-binding affinity variant was nonsaturable. There were no differences in hIgG levels from systemic and hepatic portal vein serum samples, and intense hIgG immunostaining was noted in villi enterocytes and within lymphatic lacteal-like vessels. This study demonstrated that FcRn-mediated uptake in rat pups accounted for ~80% of serum hIgG levels and that IgG enters the circulation via the lymph and not the hepatic portal vein. The remaining uptake though the immature intestine is nonreceptor mediated. Intestinal epithelial cell hFcRn expression occurred in Tg276 mice, but receptor-mediated transport of IgG was not observed. The suckling rat pup intestine is a mechanistic model of FcRn-IgG-mediated transcytosis.

Modulation of the Inflammatory Response by Epidermal Growth Factor in the Immature Human Intestine

Modulation of the Inflammatory Response by Epidermal Growth Factor in the Immature Human Intestine