This is a genetically controlled type of cell death. There is an orchestrated collapse of a cell (see CELLS), typiﬁed by destruction of the cell’s membrane; shrinkage of the cell with condensation of CHROMATIN; and fragmentation of DNA. The dead cell is then engulfed by adjacent cells. This process occurs without evidence of the inﬂammation normally associated with a cell’s destruction by infection or disease.
Apoptosis, ﬁrst identiﬁed in 1972, is involved in biological activities including embryonic development, ageing and many diseases. Its importance to the body’s many physiological and pathological processes has only fairly recently been understood, and research into apoptosis is proceeding apace.
In adults, around 10 billion cells die each day
– a ﬁgure which balances the number of cells arising from the body’s stem-cell populations (see STEM CELL). Thus, the body’s normal HOMEOSTASIS is regulated by apoptosis. As a person ages, apoptopic responses to cell DNA damage may be less eﬀectively controlled and so result in more widespread cell destruction, which could be a factor in the onset of degenerative diseases. If, however, apoptopic responses become less sensitive, this might contribute to the uncontrolled multiplication of cells that is typical of cancers. Many diseases are now associated with changed cell survival: AIDS (see AIDS/HIV); ALZHEIMER’S DISEASE and PARKINSONISM; ischaemic damage after coronary thrombosis (see HEART, DISEASES OF) and STROKE; thyroid diseases (see THYROID GLAND, DISEASES OF); and AUTOIMMUNE DISORDERS. Some cancers, autoimmune disorders and viral infections are associated with reduced or inhibited apoptosis. Anticancer drugs, GAMMA RAYS and ULTRAVIOLET RAYS (UVR) initiate apoptosis. Other drugs – for example, NONSTEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS) – alter the process of apoptosis. Research is in train to harness new knowledge about apoptosis for the development of new treatments and modiﬁcations of existing ones for serious disorders such as cancer and degenerative nervous diseases.