ABSTRACT
The mechanism of cell death is usually determined by the insult causing it.
Apoptosis is the process of genetically programmed cell death. Expression of a particular ‘apoptosis gene’ leads to cytoplasmic and nuclear shrinking, and nucleic acid degradation by calcium- and magnesium-dependent endonucleases before cell digestion by lysozymes from adjacent cells. No inflammatory response occurs. Apoptosis may be triggered by genes such as p53 in damaged cells or may occur as part of normal development, as happens during the formation of the normal web spaces between digits.
Death by cell lysis commonly follows viral infection but may also follow osmotic shock.
Various drugs kill cells by disrupting metabolic pathways. Bacteriocidal antibiotics such as penicillins, which inhibit cell wall synthesis, and amino-glycosides, which are inhibitors of protein synthesis, act in this way as do many chemotherapeutic agents used in cancer treatment.
Other drugs kill cells by blocking respiratory pathways, leading to an inability to maintain metabolism. An example is cyanide: this blocks reduction of molecular oxygen by inhibiting cytochrome oxidase.
Essential nutrient supply may be interrupted. This occurs after central retinal artery occlusion where ischaemia leads to rapid death of the inner retinal areas.
