The effect of hypoxia on permeability and bacterial translocation in Caco-2 adult and I-407 fetal enterocyte cell culture models

Mechanisms and modeling of wound repair in the intestinal epithelium

The intestinal epithelial barrier is susceptible to injury from insults, such as ischemia or infectious disease. The epithelium's ability to repair wounded regions is critical to maintaining barrier integrity. Mechanisms of intestinal epithelial repair can be studied with models that recapitulate the in vivo environment. This review focuses on in vitro injury models and intestinal cell lines utilized in such systems. The formation of artificial wounds in a controlled environment allows for the exploration of reparative physiology in cell lines modeling diverse aspects of intestinal physiology. Specifically, the use of intestinal cell lines, IPEC-J2, Caco-2, T-84, HT-29, and IEC-6, to model intestinal epithelium is discussed. Understanding the unique systems available for creating intestinal injury and the differences in monolayers used for in vitro work is essential for designing studies that properly capture relevant physiology for the study of intestinal wound repair.

Stem Cells for Next Level Toxicity Testing in the 21st Century

The call for a paradigm change in toxicology from the United States National Research Council in 2007 initiates awareness for the invention and use of human-relevant alternative methods for toxicological hazard assessment. Simple 2D in vitro systems may serve as first screening tools, however, recent developments infer the need for more complex, multicellular organotypic models, which are superior in mimicking the complexity of human organs. In this review article most critical organs for toxicity assessment, i.e., skin, brain, thyroid system, lung, heart, liver, kidney, and intestine are discussed with regards to their functions in health and disease. Embracing the manifold modes-of-action how xenobiotic compounds can interfere with physiological organ functions and cause toxicity, the need for translation of such multifaceted organ features into the dish seems obvious. Currently used in vitro methods for toxicological applications and ongoing developments not yet arrived in toxicity testing are discussed, especially highlighting the potential of models based on embryonic stem cells and induced pluripotent stem cells of human origin. Finally, the application of innovative technologies like organs-on-a-chip and genome editing point toward a toxicological paradigm change moves into action.

Mathematical analysis of clinical data reveals a homunculus of bacterial mimotopes protecting from autoimmunity via oral tolerance in human

Oral tolerance (OT) means systemic immunological unresponsiveness to harmless antigens present in the gastrointestinal tract. We presumed that tolerance to these antigens may also protect self-proteins that show immunological similarity to the intestinal normal flora. To investigate the existence and in vivo relevance of such a tolerogenic molecular mimicry, we focused our attention to Autoimmune Polyendocrine Syndrome type 1 (APS1) and Hemolysis, Elevated Liver Enzymes, Low Platelet count (HELLP) syndrome. APS1 is a human form of Autoimmune Regulator (AIRE) dysfunction with severely impaired central immunotolerance to a specific set of autoantigens, allowing investigation of tolerogenic mimicry by itself, without a disturbing background. HELLP syndrome is a mediocre manifestation of thrombotic microangiopathy, complicating pregnancy, with platelet-fibrin deposits in small blood vessels and transient development of autoantibodies. Impaired microcirculation in the liver is well described, while intestinal ischemia is possible but has not yet been studied. As the harmless nature of an antigen is essential for OT, ischemia-induced bacterial microinvasion represses this process. In case that oral tolerance to a bacterial homunculus is an existing way of self-protection and has an in vivo relevance when central tolerance is intact, significant intestinal ischemia--if present--is expected to promote autoimmunity in HELLP syndrome. We used an experimentally validated, highly reliable mathematical algorithm to predict the extent of immunological similarity between a certain autoantigen and intestinal bacteria. We found a strong negative correlation between the similarity of autoantigens to intestinal bacteria and the production of specific autoantibodies in APS1 (R=-0.70, P=0.002), while a positive correlation was observed in patients with predominantly the severe/moderately severe form of HELLP syndrome according to Mississippi classification (R=0.94, P=0.005). Autoantigen length inversely correlated with the production of autoantibodies in APS1 (R=-0.68, P=0.004). As a longer chain with more epitopes associates with an increased possibility of mimicry to any proteome, molecular mimicry in general--regarding at least major tissue-specific autoantigens--seems to be rather protective. Our calculations support the hypothesis that OT to an intestinal "bacterial homunculus" is an in vivo relevant mechanism of self-protection in humans, furthermore, HELLP syndrome presumably associates with significant intestinal ischemia and leak, resulting in transient autoimmunity via loss of OT.

Modulation of early growth response gene 1 and interleukin-8 expression by ribotoxin deoxynivalenol (vomitoxin) via ERK1/2 in human epithelial intestine 407 cells

Epithelium senses external toxic insults transmit the sentinel signals into the cells to reprogram a broad range of mucosal responses like epithelial inflammatory diseases. The purpose of this study was to test the hypothesis that ribotoxin DON evokes the epithelial sentinel signals which contributes to the pro-inflammatory cytokine interleukin-8 in human epithelial cells. Treatment with DON elevated interleukin-8 production in the human epithelial intestine 407 cells. Particularly, ribotoxin DON markedly elevated the phosphorylated extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) mitogen-activated protein kinase (MAPK) which mediated DON-induced interleukin-8 (IL-8) production. DON-activated ERK1/2 also mediated the production of early growth response gene 1 (EGR-1) in the epithelial cell line and EGR-1 had the positive regulatory effect on the interleukin-8 production in the human epithelial cells. Taken all, DON-activated MAPK sentinel signals of the epithelial cells which promoted interleukin-8 production and its positive modulator EGR-1. These findings will provide insight into the possible mechanism associated with the early epithelial inflammation by ribotoxic insults.