Cell damage (also known as cell injury) is a variety of changes of stress that a cell suffers due to external as well as internal environmental changes. Amongst other causes, this can be due to physical, chemical, infectious, biological, nutritional or immunological factors. Cell damage can be reversible or irreversible. Depending on the extent of injury, the cellular response may be adaptive and where possible, homeostasis is restored. Cell death occurs when the severity of the injury exceeds the cell's ability to repair itself. Cell death is relative to both the length of exposure to a harmful stimulus and the severity of the damage caused. Cell death may occur by necrosis or apoptosis.
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In this Dossier
Cell damage in the context of Injury
Injury is physiological damage to the living tissue of any organism, whether in humans, in other animals, or in plants.
Injuries can be caused in many ways, including mechanically with penetration by sharp objects such as teeth or with blunt objects, by heat or cold, or by venoms and biotoxins. Injury prompts an inflammatory response in many taxa of animals; this prompts wound healing. In both plants and animals, substances are often released to help to occlude the wound, limiting loss of fluids and the entry of pathogens such as bacteria. Many organisms secrete antimicrobial chemicals which limit wound infection; in addition, animals have a variety of immune responses for the same purpose. Both plants and animals have regrowth mechanisms which may result in complete or partial healing over the injury. Cells too can repair damage to a certain degree.
Cell damage in the context of Lipid peroxidation
Lipid peroxidation, or lipid oxidation, is a complex chemical process that leads to oxidative degradation of lipids, resulting in the formation of peroxide and hydroperoxide derivatives. It occurs when free radicals, specifically reactive oxygen species (ROS), interact with lipids within cell membranes, typically polyunsaturated fatty acids (PUFAs) as they have carbon–carbon double bonds. This reaction leads to the formation of lipid radicals, collectively referred to as lipid peroxides or lipid oxidation products (LOPs), which in turn react with other oxidizing agents, leading to a chain reaction that results in oxidative stress and cell damage.
In pathology and medicine, lipid peroxidation plays a role in cell damage which has broadly been implicated in the pathogenesis of various diseases and disease states, including ageing, whereas in food science lipid peroxidation is one of many pathways to rancidity.
Cell damage in the context of Superoxide dismutase
Superoxide dismutase (SOD, EC 1.15.1.1) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide (O
2) anion radical into normal molecular oxygen (O2) and hydrogen peroxide (H
2O
2). Superoxide is produced as a by-product of oxygen metabolism and, if not regulated, causes many types of cell damage. Hydrogen peroxide is also damaging and is degraded by other enzymes such as catalase. Thus, SOD is an important antioxidant defense in nearly all living cells exposed to oxygen. One exception is Lactobacillus plantarum and related lactobacilli, which use intracellular manganese to prevent damage from reactive O
2.