miR-155 influences cell-mediated immunity in Balb/c mice treated with aflatoxin M.

Aflatoxin M (AFM) is a 4-hydroxylated metabolite of aflatoxin B (AFB). It induces various toxicological effects including immunotoxicity. In the present study, we investigated the effects of AFM on immune system and its modulation by MicroRNA (miR)-155. AFM was administered intraperitoneally at doses of 25 and 50 µg/kg for 28 days to Balb/c mice and different immune system parameters were analyzed. The levels of miR-155 and targeted proteins were evaluated in isolated T cells from spleens of mice. Spleen weight was reduced in mice exposed to AFM compared to negative control. Proliferation of splenocytes in response to phytohemagglutinin-A was reduced in mice exposed to AFM. IFN-γ was decreased in mice exposed to AFM, whereas IL-10 was increased. Concentration of IL-4 did not change different in mice exposed to AFM compared to negative control. Exposure to AFM reduced the expression of miR-155. Significant upregulation of phosphatidylinositol-3, 4, 5-trisphosphate 5-phosphatase 1 (Ship1) and suppressor of cytokine signaling 1 (Socs1) was observed in isolated T cells from spleens of mice treated with AFM but the transcription factor Maf (c-MAF) was not affected. These results suggest that miR-155 and targeted proteins might be involved in the immunotoxicity observed in mice exposed to AFM.