The environmental pollutant 3-methyl-4-nitrophenol reduces the regulatory T cells in the intestine

Dysfunction of immune regulation plays a crucial role in the pathogenesis of many immune disorders in the body. The underlying mechanism is still not completely understood. Environmental pollution contributes to immune de-regulation. 3-methyl-4-nitrophenol (MNP) is one of the major environmental pollutants. This study aims to investigate the role of MNP in compromising immune regulatory functions in the intestine. A food allergy (FA) mouse model was established using ovalbumin (OVA) as the specific antigen. The activities of regulatory T cells in the mouse intestine were evaluated by flow cytometry and enzyme-linked immunosorbent assay. We found that MNP reduced the CD4(+) Foxp3(+) Treg frequency, increased Th17 cells, and converted Tregs to Th17 cells in the intestine. MNP induced the expression of IL-6 in regulatory T cells (Tregs). Estrogen receptor (ER) mediated the effects of MNP on promoting IL-6 expression in Tregs. The IL-6 in synergy with transforming growth factor (TGF)-beta to convert Tregs to Th17 cells. The concomitant exposure of MNP and OVA induced FA like response in mice. Modulation of the ER-STAT3-IL-6 signal pathway attenuated mouse FA response. In summary, MNP, an environmental pollutant, acts as an immunoadjuvant for developing FA. By activation of the estrogen receptor, MNP induces Tregs to express IL-6. IL-6 in synergy with TGF-beta converts Tregs to Th17 cells.