Dynamic changes of cathepsins B and L expression in the monkey hippocampus after transient ischemia.

Enzymatic activities, expressions, and the immunohistochemical localization of lysosomal cystein proteases, cathepsins B and L, were analyzed in the monkey hippocampus after transient ischemia to clarify the mechanism of delayed cornu Ammonis (CA)-1 neuronal death. By enzymatic assay, the activity of cathepsin B increased in CA-1, 24 h after the ischemic insult, while that of cathepsin L decreased. On Western blotting, the protein contents of both cathepsins B and L increased immediately after ischemia. By immunohistochemistry, cathepsins B and L were stained as coarse granules in the perikarya of control CA-1 neurons, but in postischemic CA-1 neurons they were released from lysosome granules. In contrast, in CA-2 and the remaining sectors, enzymatic activities increased after ischemia, and immunoreactivities of cathepsins B and L increased only within lysosome granules. These results suggest that cathepsins B and L may play an important role in the breakdown of certain cell proteins in the postischemic CA-1 neurons.