Role of apoptosis in acute neurodegenerative disorders

Many toxic factors are generated during stroke that contribute directly to the death of neurons. Several recent studies suggest that a suicide-like phenomena similar to apoptosis or programmed cell death also contributes to the loss of neurons in stroke. The evidence implicating apoptosis in stroke can be divided into three categories; biochemical, molecular and pharmacological. Biochemical evidence: One hallmark of apoptosis is the early activation of destructive enzymes, including endonucleases and proteases. Endonuclease-mediated DNA fragmentation can be observed within 4 h after focal cerebral ischemia and precedes morphological evidence of cell death. Cells with damaged DNA appear to concentrate in the salvageable tissue of the penumbra while necrosis predominates in areas where the sustained lack of blood flow may make tissue salvage impossible. Molecular evidence: Bcl-2 is an anti-apoptotic gene that confers the ability to block apoptosis from a wide variety of stimuli. The levels of bcl-2 can be enhanced by viral gene delivery or transgenic methodology. In cortical tissue where bcl-2 was elevated, neurons were protected from a subsequent ischemic attack. In contrast to bcl-