Induction of mitochondria-mediated apoptosis and PI3K/Akt/mTOR-mediated autophagy by aflatoxin B2 in hepatocytes of broilers

Aflatoxins have been shown to induce hepatotoxicity in animal models, but the effects of aflatoxin B2 (AFB(2)) on broiler hepatocytes is unclear. This study aimed to investigate the effects of AFB(2) on apoptosis and autophagy to provide an experimental basis for understanding the mechanism of aflatoxin-induced hepatotoxicity. One hundred-twenty Cobb500 broilers were allocated to four groups and exposed to 0 mg/kg, 0.2 mg/kg, 0.4 mg/kg, and 0.8 mg/kg of AFB(2) per day for 21 d. AFB(2) exerted potent proapoptotic and proautophagic effects on hepatocytes, with increased numbers of apoptotic and autophagic hepatocytes. Poly ADP-ribose polymerase (PARP) was cleaved and caspase-3 was activated in experimental groups, showing that the apoptosis of hepatocytes was triggered by AFB2. Increased levels of the autophagy factors Beclin-1 and LC3-II/LC3-I, as well as down-regulation of p62, a marker of autophagic flux, provided additional evidence for AFB(2)-triggered autophagy. AFB(2) induced mitochondria-mediated apoptosis via the production of reactive oxygen species (ROS) and promotion of the translocation of Bax and cytochrome c (cyt c) between mitochondria and the cytosol, triggering the formation of apoptosomes. AFB(2) also inhibited the phosphoinositide 3-kinase/Akt/ mammalian target of rapamycin (PI3K/Akt/mTOR) pathway by activating PI3K, Akt, and mTOR and inhibiting their phosphorylation, contributing to the proautophagic activity of AFB(2). These findings provide new insights into the mechanisms involved in AFB(2)-induced hepatotoxicity in broilers.