Apoptosis

Abstract

Cell death is an important process that regulates dynamic balances in living systems during development, growth, homeostasis, disease, and repair (see Chapter 1) (48). Three types of cell death are known: (i) apoptosis (programmed cell death), (ii) autophagy, and (iii) necrosis (69). Apoptosis is a highly regulated mechanism by which cells die in response to defined internal or external stimuli. Autophagy is characterized by bulk degradation of cellular components, principally proteins that are essential for maintaining cellular integrity when nutrients are scarce. Necrosis is a passive process characterized by disruption of cell membranes and a progressive breakdown of organelles in response to severe environmental perturbations such as hypoxia/ischemia, temperature variations, and mechanical trauma.