Apoptosis is an active form of cell death, induced both by endogenous and exogenous stimuli, which occurs under physiological conditions (1, 2). Morphologically, it is characterized by cellular features such as membrane blebbing, cell shrinkage, and chromatin condensation (3). Intracellular events include various types of DNA fragmentation (4), cytoskeletal alterations, and protease activation (reviewed in ref. 5).

Oxidative stress is believed to play a key role in the process of apoptosis. Indeed, accumulation of oxidized proteins and lipids (6), rapid production of reactive oxygen intermediates (ROI), and alterations of the cellular redox (7, 8), as well as disruption of the transmembrane potential (Ai|/m) (9), have all been reported to be common metabolic alterations during the apoptosis of a variety of cell types. Oxidative stress is also seen in a number of pathological conditions (reviewed in ref. 10). The degeneration of neural cells observed during the progression of Alzheimer's, Parkinson's, and other neurodegenerative diseases have been linked to the cumulative damage caused by oxidative stress. The levels of glutathione (GSH), a major component of the intracellular antioxidant defence, have been shown to be decreased in HIV-infected cells (11). In addition, in vitro studies on cells from HIV patients have shown the decrease of several other antioxidant enzymes (12). Moreover, tumour promotion during oncogenesis is favoured under pro-oxidant conditions and several antineoplastic drugs have been demonstrated to be potent antioxidants (13).

This chapter describes some current procedures used to analyse common intracellular metabolic alterations which are of importance in apoptosis, namely the disruption of Ai|im, generation of ROI (e.g. peroxide and superoxide anion), alteration of glutathione levels and its oxidative state, and catalase levels.

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