Targeting the innate immune system in pediatric inflammatory bowel disease

Investigating the infant gut microbiota in developing countries: worldwide metagenomic meta-analysis involving infants living in sub-urban areas of Côte d'Ivoire

In recent decades, infants' gut microbiota has aroused constant scientific interest, primarily due to early- and long-term repercussions on the host health. In this context, nutritional challenges such as those found in less developed countries can influence infants' gut microbiota development, thus generating potentially critical health outcomes. However, comprehensive investigations regarding species-level differences in the infant gut microbiota's composition between urbanized and rural countries are still missing. In this study, 16S rRNA and Shallow Shotgun metagenomics sequencing were exploited to dissect the microbial community's species-level composition of 11 faecal samples collected from infants living in a semi-urban area of Sub-Saharan Africa, i.e. Côte d'Ivoire. Moreover, the generated data were coupled with those retrieved from public available metagenomic repositories, including two rural communities and 13 urban communities of industrialized countries. The meta-analysis led to the identification of Infant Species Community States Type (ISCSTs) and microbial species covariances, which were exploited to reveal key signatures of infants living in rural and semi-urban societies. Remarkably, analysis of rural and semi-urban datasets revealed shifts from ISCSTs prevalent in urbanized populations with putative health implications. Thus, indicating the need for population-wide investigations aimed to define the factors determining such potentially harmful gut microbial communities' signatures.

The Human Milk Oligosaccharides 3-FL, Lacto-N-Neotetraose, and LDFT Attenuate Tumor Necrosis Factor-α Induced Inflammation in Fetal Intestinal Epithelial Cells In Vitro through Shedding or Interacting with Tumor Necrosis Factor Receptor 1

SCOPE

Human milk oligosaccharides (hMOs) can attenuate inflammation by modulating intestinal epithelial cells, but the mechanisms of action are not well-understood. Here, the effects of hMOs on tumor necrosis factor-α (TNF-α) induced inflammatory events in gut epithelial cells are studied.

METHODS AND RESULTS

The modulatory effects of 2'-fucosyllactose, 3-fucosyllactose (3-FL), 6'-sialyllactose, lacto-N-tetraose, lacto-N-neotetraose (LNnT), lactodifucotetraose (LDFT), and lacto-N-triaose (LNT2) on immature (FHs 74 Int) and adult (T84) intestinal epithelial cells with or without TNF-α are determined. Interleukin-8 (IL-8) secretion in FHs 74 Int and T84 are quantified to determine hMO induced attenuation of inflammatory events by ELISA. 3-FL, LNnT, and LDFT significantly attenuate TNF-α induced inflammation in FHs 74 Int, while LNT2 induces IL-8 secretion in T84. In addition, microscale thermophoresis assays and ELISA are used to study the possible mechanisms of interaction between effective hMOs and tumor necrosis factor receptor 1 (TNFR1). 3-FL, LNnT, and LDFT exert TNFR1 ectodomain shedding while LNnT also shows binding affinity to TNFR1 with a Kd of 900 ± 660 nM.

CONCLUSION

The findings indicate that specific hMO types attenuate TNF-α induced inflammation in fetal gut epithelial cells through TNFR1 in a hMO structure-dependent fashion suggest possibilities to apply hMOs in management of TNF-α dependent diseases.

The infant gut microbiome as a microbial organ influencing host well-being

Initial establishment of the human gut microbiota is generally believed to occur immediately following birth, involving key gut commensals such as bifidobacteria that are acquired from the mother. The subsequent development of this early gut microbiota is driven and modulated by specific dietary compounds present in human milk that support selective colonization. This represents a very intriguing example of host-microbe co-evolution, where both partners are believed to benefit. In recent years, various publications have focused on dissecting microbial infant gut communities and their interaction with their human host, being a determining factor in host physiology and metabolic activities. Such studies have highlighted a reduction of microbial diversity and/or an aberrant microbiota composition, sometimes referred to as dysbiosis, which may manifest itself during the early stage of life, i.e., in infants, or later stages of life. There are growing experimental data that may explain how the early human gut microbiota affects risk factors related to adult health conditions. This concept has fueled the development of various nutritional strategies, many of which are based on probiotics and/or prebiotics, to shape the infant microbiota. In this review, we will present the current state of the art regarding the infant gut microbiota and the role of key commensal microorganisms like bifidobacteria in the establishment of the first microbial communities in the human gut.

FGL2 regulates IKK/NF-κB signaling in intestinal epithelial cells and lamina propria dendritic cells to attenuate dextran sulfate sodium-induced colitis

Inflammatory bowel disease (IBD) is an autoimmune disease characterized by an abnormal immune response. Fibrinogen-like protein 2 (FGL2) is known to have immunoregulatory and anti-inflammatory activity. The level of FGL2 is elevated in patients with IBD; however, its comprehensive function in IBD is almost unknown. In our study, we explored the effect of FGL2 on dextran sulfate sodium (DSS)-induced colitis in mice and on NF-κB signaling in intestinal epithelial cells (IECs) and lamina propria dendritic cells (LPDCs). We founded that FGL2^-/- mice in the colitis model showed more severe colitis manifestations than WT mice did, including weight loss, disease activity index (DAI), and colon histological scores. FGL2^-/- mice treated with DSS produced more proinflammatory cytokines (IL-1β, IL-6, TNF-α) in serum than WT mice did and demonstrated upregulated expression of TNF-α and inflammatory marker enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (Cox-2) in the colon tissue. Our data suggested that DSS-treated FGL2^-/- mice showed stronger activation of NF-κB signaling, especially in IECs. Next, we demonstrated that recombinant FGL2 (rFGL2) inhibited the production of proinflammatory cytokines and the expression of inflammatory marker enzymes by downregulating the NF-κB signaling in HT-29 cells. Finally, we discovered that LPDCs from the colon of DSS-treated FGL2^-/- mice showed significantly upregulated expression of surface maturation co-stimulatory molecules, including CD80, CD86, CD40, and MHC class II molecules compared with that in WT mice. In addition, LPDCs in FGL2^-/- treated with DSS exhibited excessive NF-κB activity and the administration of rFGL2 to FGL2^-/- mice could rescue the aggravated results of FGL2^-/- mice. Taken together, our findings demonstrated that FGL2 might be a target for further therapy of IBD.

Health benefits conferred by the human gut microbiota during infancy

Development of the human gut throughout the entire life.

Intestinal Microbiota in Early Life and Its Implications on Childhood Health

Trillions of microbes reside in the human body and participate in multiple physiological and pathophysiological processes that affect host health throughout the life cycle. The microbiome is hallmarked by distinctive compositional and functional features across different life periods. Accumulating evidence has shown that microbes residing in the human body may play fundamental roles in infant development and the maturation of the immune system. Gut microbes are thought to be essential for the facilitation of infantile and childhood development and immunity by assisting in breaking down food substances to liberate nutrients, protecting against pathogens, stimulating or modulating the immune system, and exerting control over the hypothalamic-pituitary-adrenal axis. This review aims to summarize the current understanding of the colonization and development of the gut microbiota in early life, highlighting the recent findings regarding the role of intestinal microbes in pediatric diseases. Furthermore, we also discuss the microbiota-mediated therapeutics that can reconfigure bacterial communities to treat dysbiosis.

The First Microbial Colonizers of the Human Gut: Composition, Activities, and Health Implications of the Infant Gut Microbiota

The human gut microbiota is engaged in multiple interactions affecting host health during the host's entire life span. Microbes colonize the neonatal gut immediately following birth. The establishment and interactive development of this early gut microbiota are believed to be (at least partially) driven and modulated by specific compounds present in human milk. It has been shown that certain genomes of infant gut commensals, in particular those of bifidobacterial species, are genetically adapted to utilize specific glycans of this human secretory fluid, thus representing a very intriguing example of host-microbe coevolution, where both partners are believed to benefit. In recent years, various metagenomic studies have tried to dissect the composition and functionality of the infant gut microbiome and to explore the distribution across the different ecological niches of the infant gut biogeography of the corresponding microbial consortia, including those corresponding to bacteria and viruses, in healthy and ill subjects. Such analyses have linked certain features of the microbiota/microbiome, such as reduced diversity or aberrant composition, to intestinal illnesses in infants or disease states that are manifested at later stages of life, including asthma, inflammatory bowel disease, and metabolic disorders. Thus, a growing number of studies have reported on how the early human gut microbiota composition/development may affect risk factors related to adult health conditions. This concept has fueled the development of strategies to shape the infant microbiota composition based on various functional food products. In this review, we describe the infant microbiota, the mechanisms that drive its establishment and composition, and how microbial consortia may be molded by natural or artificial interventions. Finally, we discuss the relevance of key microbial players of the infant gut microbiota, in particular bifidobacteria, with respect to their role in health and disease.

Human colostrum oligosaccharides modulate major immunologic pathways of immature human intestine

The immature neonatal intestinal immune system hyperreacts to newly colonizing unfamiliar bacteria. The hypothesis that human milk oligosaccharides from colostrum (cHMOSs) can directly modulate the signaling pathways of the immature mucosa was tested. Modulation of cytokine immune signaling by HMOSs was measured ex vivo in intact immature (fetal) human intestinal mucosa. From the genes whose transcription was modulated by cHMOSs, Ingenuity Pathway Analysis identified networks controlling immune cell communication, intestinal mucosal immune system differentiation, and homeostasis. cHMOSs attenuate pathogen-associated molecular pattern-stimulated acute phase inflammatory cytokine protein levels (interleukin-8 (IL-8), IL-6, monocyte chemoattractant protein-1/2 and IL-1β), while elevating cytokines involved in tissue repair and homeostasis. In all, 3'-, 4-, and 6'-galactosyllactoses of cHMOSs account for specific immunomodulation of polyinosinic:polycytodylic acid-induced IL-8 levels. cHMOSs attenuate mucosal responses to surface inflammatory stimuli during early development, while enhancing signals that support maturation of the intestinal mucosal immune system.

Phenotype and disease course of early-onset pediatric inflammatory bowel disease

BACKGROUND

Early-onset (EO) pediatric inflammatory bowel diseases (IBD) seem to be more extensive than those with a later onset. To test this hypothesis, we examined the phenotype and disease course of patients with IBD diagnosis at 0 to 5 years, compared with the ranges 6 to 11 and 12 to 18 years.

METHODS

Anatomic locations and behaviors were assessed according to Paris classification in 506 consecutive patients: 224 Crohn's disease, 245 ulcerative colitis, and 37 IBD-unclassified.

RESULTS

Eleven percent of patients were in the range 0 to 5 years, 39% in 6 to 11 years, and 50% in 12 to 18 years. Ulcerative colitis was the most frequent diagnosis in EO-IBD and in 6- to 11-year-old group, whereas Crohn's disease was predominant in older children. A classification as IBD-unclassified was more common in the range 0 to 5 years compared with the other groups (P < 0.005). EO Crohn's disease showed a more frequent isolated colonic (P < 0.005) and upper gastrointestinal involvement than later-onset disease. Sixty-two percent of the patients in the 0 to 5 years range had pancolonic ulcerative colitis, compared with 38% of 6 to 11 years (P = 0.02) and 31% of 12-18 years (P = 0.002) range. No statistical difference for family history for IBD was found in the 3-year age groups. Therapies at the diagnosis were similar for all children. However, at latest follow-up, a significantly higher proportion of younger children were under steroids compared with older groups (P < 0.05). Surgical risk did not differ according to age.

CONCLUSIONS

EO-IBD exhibits an extensive phenotype and benefit from aggressive treatment strategies, although surgical risk is similar to later-onset disease. A family history for IBD is not common in EO disease.

Interactions between intestinal microbiota and innate immune system in pediatric inflammatory bowel disease

Inflammatory bowel disease (IBD) is the result of an altered immune homeostasis within the intestinal mucosa against the gut microbiota, leading to chronic inflammation in genetically predisposed individuals. Under normal conditions, the immune system defends against pathogens and prevents the passage of excessive intestinal bacteria; regulatory pathways must maintain a low-grade, controlled inflammation in a healthy gut, but also induce a protective response against pathogens. The innate immune system is the first-line defense from microbes; dendritic cells, macrophages, and epithelial cells produce an initial, immediate response. The immune system constantly controls commensal bacteria and utilizes constitutive antimicrobial mechanisms to sustain immune homeostasis. The discovery that several genes linked to IBD modulate microbial recognition and innate immune pathways, such as nucleotide oligomerization domain 2 (Nod2), and genes that mediate autophagy (ie, ATG16L1, IRGM), has highlighted the critical role of host-microbe interactions in controlling intestinal immune homeostasis. Commensal microorganisms actively interact with the intestinal mucosa and influence the activity of the immune system as well as the amplitude of the immune response. In contrast, host factors can influence microbes, which in turn modulate disease susceptibility. In this paper, we focus on the mechanisms that mediate host-microbe interactions and how the disruption of this balance leads to chronic intestinal inflammation in IBD.