Uncovering the gastrointestinal passage, intestinal epithelial cellular uptake, and AGO2 loading of milk miRNAs in neonates using xenomiRs as tracers.

BACKGROUND: Human breast milk has a high microRNA (miRNA) content. It remains unknown whether and how milk miRNAs might affect intestinal gene regulation and homeostasis of the developing microbiome after initiating enteral nutrition. However, this requires that relevant milk miRNA amounts survive the gastrointestinal (GI) passage, are taken up by cells, and become available to the RNA interference machinery. It seems important to dissect the fate of these miRNAs after oral ingestion and GI passage. OBJECTIVES: Our goal was to analyze the potential transmissibility of milk miRNAs via the gastrointestinal system in neonate humans and a porcine model in vivo to contribute to the discussion of whether milk miRNAs could influence gene regulation in neonates and thus might vertically transmit developmental relevant signals. METHODS: We performed cross-species profiling of miRNAs via deep sequencing and utilized dietary xenobiotic taxon-specific milk miRNA (xenomiRs) as tracers in human and porcine neonates, followed by functional studies in primary human fetal intestinal epithelial cells using adenovirus-type 5-mediated miRNA gene transfer. RESULTS: Mammals share many milk miRNAs yet exhibit taxon-specific miRNA fingerprints. We traced bovine-specific miRNAs from formula nutrition in human preterm stool and 9 d after the onset of enteral feeding in intestinal cells (ICs) of preterm piglets. Thereafter, several xenomiRs accumulated in the ICs. Moreover, a few hours after introducing enteral feeding in preterm piglets with supplemented reporter miRNAs (cel-miR-39-5p/-3p), we observed their enrichment in blood serum and in argonaute RISC catalytic component 2 (AGO2)-immunocomplexes from intestinal biopsies. CONCLUSIONS: Milk-derived miRNAs survived GI passage in human and porcine neonates. Bovine-specific miRNAs accumulated in ICs of preterm piglets after enteral feeding with bovine colostrum/formula. In piglets, colostrum supplementation with cel-miR-39-5p/-3p resulted in increased blood concentrations of cel-miR-39-3p and argonaute RISC catalytic component 2 (AGO2) loading in ICs. This suggests the possibility of vertical transmission of miRNA signaling from milk through the neonatal digestive tract.

Reactive Oxygen Species Localization Programs Inflammation to Clear Microbes of Different Size.

How the number of immune cells recruited to sites of infection is determined and adjusted to differences in the cellular stoichiometry between host and pathogen is unknown. Here, we have uncovered a role for reactive oxygen species (ROS) as sensors of microbe size. By sensing the differential localization of ROS generated in response to microbes of different size, neutrophils tuned their interleukin (IL)-1ß expression via the selective oxidation of NF-κB, in order to implement distinct inflammatory programs. Small microbes triggered ROS intracellularly, suppressing IL-1ß expression to limit neutrophil recruitment as each phagocyte eliminated numerous pathogens. In contrast, large microbes triggered ROS extracellularly, amplifying IL-1ß expression to recruit numerous neutrophils forming cooperative clusters. Defects in ROS-mediated microbe size sensing resulted in large neutrophil infiltrates and clusters in response to small microbes that contribute to inflammatory disease. These findings highlight the impact of ROS localization on signal transduction.