Expression of cell death-associated proteins in neuronal apoptosis associated with pontosubicular neuron necrosis

Expression of apoptosis-associated proteins p53, bcl-2, bax, and caspase-3/CPP32, activation of caspase-3, and modification of proteins via poly(ADP-ribosyl)ation was studied in pontosubicular neuron necrosis (PSN), a form of perinatal brain damage revealing the morphological hallmarks of neuronal apoptosis. Immunoreactivity for p53 was completely absent. The majority of cells stained with the bax and procaspase-3 antibodies did not show morphological signs of apoptosis. In contrast, an antibody against activated caspase-3 almost exclusively stained cells with apoptotic morphology. Poly(ADP-ribosyl)ated proteins were only rarely detected in cells with apoptotic morphology. The expression patterns of bax, procaspase-3, bcl-2, and p53 in PSN were similar to that found in age-matched control brains. However, activated caspase-3 and poly-ADP-ribosylated proteins were exclusively found in apoptotic cells. These data indicate that detection of active caspase-3 is a reliable marker for apoptosis in formalin-fixed human tissue, and that neuronal apoptosis in pontosubicular neuron necrosis is accompanied by a pronounced activation of caspase-3.