Ex Vivo and In Vitro Studies Revealed Underlying Mechanisms of Immature Intestinal Inflammatory Responses Caused by Aflatoxin M1 Together with Ochratoxin A

Abstract

Aflatoxin M1 (AFM1) and ochratoxin A (OTA), which are occasionally detected in milk and commercial baby foods, could easily enter and reach the gastrointestinal tract, posing impairment to the first line of defense and causing dysfunction of the tissue. The objective of this study was to investigate the immunostimulatory roles of individual and combined AFM1 and OTA on the immature intestine. Thus, we used ELISA assays to evaluate the generation of cytokines from ex vivo CD-1 fetal mouse jejunum induced by AFM1 and OTA and explored the related regulatory pathways and pivot genes using RNA-seq analysis. It was found that OTA exhibited much stronger ability in stimulating pro-inflammatory cytokine IL-6 from jejunum tissues than AFM1 (OTA of 4 μM versus AFM1 of 50 μM), whereas the combination of the two toxins seemed to exert antagonistic actions. In addition, transcriptomics also showed that most gene members in the enriched pathway ‘cytokine–cytokine receptor interaction’ were more highly expressed in OTA than the AFM1 group. By means of PPI network analysis, NFKB1 and RelB were regarded as hub genes in response to OTA but not AFM1. In the human FHs 74 Int cell line, both AFM1 and OTA enhanced the content of reactive oxygen species, and the oxidative response was more apparent in OTA-treated cells in comparison with AFM1. Furthermore, OTA and AFM1 + OTA raised the protein abundance of p50/RelB, and triggered the translocation of the dimer from cytosol to nucleus. Therefore, the experimental data ex vivo and in vitro showed that OTA-induced inflammation was thought to be bound up with the up-regulation and translocation of NF-κB, though AFM1 seemed to have no obvious impact. Since it was the first attempt to uncover the appearances and inner mechanisms regarding inflammation provoked by AFM1 and OTA on immature intestinal models, further efforts are needed to understand the detailed metabolic steps of the toxin in cells and to clarify their causal relationship with the signals proposed from current research.

Luteolin and Chrysin Could Prevent E. coli Lipopolysaccharide-Ochratoxin A Combination-Caused Inflammation and Oxidative Stress in In Vitro Porcine Intestinal Model

“…OTA administration also promoted the mRNA expression and secretion of inflammatory cytokines, including IL-6 [ 43 ]. OTA was reported to increase the secretion of pro-inflammatory cytokines such as IL-6 in isolated jejunal tissue culture and affect immune function in the intestine [ 17 ]. The study of the combined effect of OTA and LPS, modelling the complexity of environmental factors and their effects on immunological parameters, has not been done before.…”

“…OTA could influence the cell viability of tumorigenic human colorectal adenocarcinoma CaCo-2/HT29-MTX cells [ 16 ]. A total of 48 h of treatment of cells with aflatoxin M1 or OTA (at 0.05 and 4 µg/mL) or with their combination caused significant cell death in human fetal FHs 74 intestinal cells [ 17 ]. OTA appeared to affect porcine intestinal jejunal epithelial cells (IPEC-J2) cell viability using both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) method, and it also caused barrier dysfunction such as damage to the integrity of IPEC-J2 monolayers [ 18 ].…”