Immunohistochemical localization of lysosomal cysteine protease cathepsins B and L in monkey hippocampal neurons after transient ischemia

Abstract

The mechanism by which hippocampal neurons are selectively vulnerable to ischemic injury remains unclarified. Neuronal lysosomes are known to contain the cysteine protease cathepsins, which may be involved in the mechanism of delayed neuronal death. In this study, the expression and localization of cathepsins in the postischemic hippocampal neurons of the monkey were examined. Enzymatic activities and protein levels of cathepsins B and L were increased after ischemia in both the vulnerable CA1 sector and the remaining resistant sectors. Immunohistochemical analysis suggested that lysosomal enzymes of CA1 were localized mainly in the neuropil and not in the neuronal cell bodies, while the enzymes of CA2–4 sectors were located within the neurons and associated with the perinuclear lysosomal granules. Thus, it was concluded that distributional differences of cathepsins B and L after transient ischemia could be related to selective CA1 neuronal death in the hippocampus.