Caspases, proteolytic enzymes that play important roles in inflammation and cell death, are independently activated via either an intrinsic pathway involving caspase 9 or an extrinsic pathway through caspase 8 (Fuentes-Prior and Salvesen, 2004) . It is thus important to note that DON activated caspases 8 and 9, both of which can activate caspase 3, suggesting the involvement of both apoptotic pathways, respectively, in rRNA cleavage. Caspases mediate degradation of some ribosomalassociated proteins, including eukaryotic translation initiation factor (eIF)2a, eIF3/p35, eIF4B, and eIF4G family (Clemens et al., 2000) . This proteolytic action might expose ribosome- FIG. 7 . DON induces cleavage of caspases 3, 8, and 9 in RAW 264.7. Cells were treated with DON (1000 ng/ml) for 3 and 6 h. Western blotting was used to detect (A) caspase 9, cleaved caspase 9, and cleaved caspase 3 and (B) caspase 8 and cleaved caspase 8. b-Actin was used as loading control. Data are representative of three separate experiments.