RESUMO
As ultraviolet (UV) radiation is naturally and ubiquitously emitted by the sun, almost everyone is exposed to it on a daily basis, and it is necessary for normal physiological function. Human exposure to solar UV radiation thus has important health implications. The generation of reactive oxygen species (ROS) by UV radiation is one of the mechanisms through which UV light can manifest its possible detrimental effects on health. When an imbalance develops due to ROS generation exceeding the body's antioxidant defence mechanisms, oxidative stress can develop. Oxidative stress can lead to cellular damage (e.g. lipid peroxidation and DNA fragmentation), apoptosis and cell death. Broadly UV can induce ROS by affecting the cellular components directly or by means of photosensitization mechanisms. More specifically UV light can induce ROS by affecting the enzyme catalase and up-regulating nitric oxide synthase (NOS) synthesis. It may also cause a decrease in protein kinase C (PKC) expression leading to increased ROS production. UVR is capable of modifying DNA and other chromophores resulting in elevated ROS levels. The effects of raised ROS levels can vary based on the intracellular oxidant status of the cell. It is therefore important to protect yourself against the potentially harmful effects of UV light as it can lead to pathological UV-induced ROS production.
