Absence of prostate apoptosis response-4 protein in substantia nigra of Parkinson's disease autopsies

The morphological evidence for apoptosis of dopaminergic neurons in Parkinson's disease (PD) remains a conflicting issue. The present study examined autopsy material containing substantia nigra and putamen of PD (n=7) and control subjects (n=5) for the expression of prostate apoptosis response-4 (Par-4) protein, a protein expressed by apoptotic cells. Par-4 was not detected in the substantia nigra pars compacta. By contrast, duodenal enterocytes, which served as positive controls and are known to be apoptotic, profoundly expressed Par-4. The present study is in agreement with previous studies of the substantia nigra pars compacta in PD, which failed to detect molecules expressed by apoptotic cells. The absence of Par-4 immunoreactivity suggests that death of dopaminergic neurons in PD follows a degenerative pathway that circumvents the induction of Par-4.