3,3'-Diindolylmethane induces immunotoxicity via splenocyte apoptosis in neonatal mice.

3,3'-Diindolylmethane (DIM), a major product of indole-3-carbinol derived from vegetables of the genus Brassica, exhibits chemotherapeutic activity and various immune modulatory effects in animal models and in vitro studies. Although extensive studies have only focused on DIM's beneficial effects, the toxic effects of DIM on the immune systems have not been clearly elucidated. The aim of this study was to explore the immunotoxic effects of DIM in a neonatal mouse and to further evaluate whether DIM administration affects rotavirus (RV)-induced gastroenteritis. Interestingly, multiple immunotoxic effects were observed in the DIM treated group, including decreases in various immune cells (F4/80(+), CD11c(+), CD19(+), and CD3(+) cells) in the spleen, induction of splenic white pulp atrophy, an increase in immune cell apoptosis, and decreased expression of various toll-like receptors (TLRs) in the spleen and small intestine. Apoptosis was notably promoted by up-regulating caspase-3 activity and by the change in the ratio of Bcl-2/Bax activities. Finally, oral administration of DIM led to deterioration of RV-induced intestinal disease and delayed viral clearance in the intestine and MLNs. Our results indicate that oral administration of DIM in neonatal mice induces immunotoxicity and hampers efficient RV clearance in the intestine. This new information about the immunotoxic roles of DIM in a newborn mouse model may provide valuable clues for the development of a safe supplement, especially one designed for human infants.

Prodomain processing of recombinant plasmepsin II and IV, the aspartic proteases of Plasmodium falciparum, is auto- and trans-catalytic.

Prodomain processing of the four food vacuole plasmepsins (PMs), the malarial aspartic proteases, is prerequisite for their activity on hemoglobin degradation of the parasite Plasmodium falciparum. Although previous studies have suggested the involvement of a calpain-like PM convertase in the processing of PMs, the underlying mechanism of their processing remains to be clarified. Here, to investigate the mechanism by which food vacuole PM II and IV are processed, we used their wild-type and mutant proteins in which the catalytic Asp residue in two active-site motifs was mutated, as well as protease inhibitors. Autocatalytic processing of wild-type PM II and IV was inhibited only by an aspartic protease inhibitor pepstatin A. Unexpectedly, their proteolytic activities were inhibited not only by pepstatin A but also by calpain inhibitor ALLN. The active-site mutants of both PM II and IV showed neither autocatalytic processing nor proteolytic activities. However, the mutants of both PMs were efficiently processed upon incubation with their respective wild type proteins. Furthermore, the mutants of both PMs were processed upon incubation with each other's wild-type PM in both pepstatin A- and ALLN-sensitive manners. These results suggest that the processing of PM II and IV occurs via an intra- and inter-molecular autocatalytic event as well as via a transcatalytic event between them.