An immunohistochemical study on cathepsin D in human hippocampus

Cathepsin D is a lysosomal enzyme involved in neuronal degeneration. In this study, the immunohistochemistry of cathepsin D was studied in hippocampal CA1 neurons that are vulnerable to ischemia, and parahippocampal glial cells. CA1 neurons from the majority of cases showed cathepsin D immunoreactivity in the cytoplasm, whereas shrunk neurons were unstained in only one case. There was no statistically significant correlation between the postmortem interval between death and autopsy, and cathepsin D immunoreactivity in CA1 neurons. These observations indicate that cathepsin D immunoreactivity is not a sensitive marker for neuronal degeneration or postmortem changes. On the other hand, there was a statistically significant correlation between age and cathepsin D immunoreactivity in the cytoplasm of parahippocampal glial cells. This shows that senescence is correlated with cathepsin D expression in humans as has been reported previously in an animal study.