White Pages: Free Radicals
Free radicals are a form of molecule that is damaging to skin cells and particularly to DNA, which can lead to skin cancer. Free radicals are created when sunlight contacts our skin. Free radicals are also created when sunlight contacts sunscreens on our skin. Both can be damaging.
But free radicals are also a molecular interaction essential to life. They are part of the process by which our body converts it’s “fuel” and nutrients to energy and tissue. They have many functions in the body including (simplistically) as “germ killers”.
The body is designed to use internally generated free radicals in specific ways and under normal conditions can control these interactions and repair any stray free radical damage. Free radicals become a problem when they are created in such large amount that the body is overwhelmed and they become destructive. Aging, hyperpigmentation, skin cancer, amongst other things, result.
The following will give you a general idea of what free radicals are and what they do. From our sun care perspective, free radical overload from UV light is common and destructive – something we cannot ignore.
What are free radicals
“Free radicals have long been associated with the aging process, but we cannot avoid them. They are “the price we pay for breathing, the inescapable byproducts of living in a world full of oxygen,” to quote New York Times science writer Natalie Anger. Free radicals are at the heart of our immune system’s ability to kill microbes, which is good, but they also attack the very DNA of our cells. Air pollution and cigarette smoking are major sources of free radicals, producing a phenomenon known as oxidative stress. A free radical is any molecule that possesses an unpaired electron, one which is therefore constantly seeking another electron to “complete” itself. Free radicals often activate chain reactions known as cascades, sometimes polymerizing into larger molecules, sometimes degrading longer ones into short pieces. The latter effect, especially when it involves free radicals containing oxygen (such as the hydroxyl radical) is the most damaging physiologically, leading to destruction of fatty membranes, cell collapse, or DNA mutation which occasionally leads to cancer. The body limits excess free radical formation in various ways, via the antioxidant Vitamins C and E, and via an enzyme called Superoxide Dismutase (SOD) which eliminates superoxide radicals.”
Molecular aspects of skin ageing – recent data [very technical]
A FREE RADICAL’S Half Life (Free radicals are fast workers…)
ns=nanosecond (1 billionth of a second) ms= millisecond (1 thousandth of a second)
Hydroxyl 0.3 ns
Superoxide 0.4 ns
Nitric oxide Seconds
Peroxynitrite 50 ms – second
Singlet oxygen s
Hydrogen peroxide Stable
“The first changes that occur in the skin after chronic or acute UV irradiation is the generation of reactive oxygen species, leading to the peroxidation of unsaturated lipids in the cell membrane. Low phototype [light skinned] individuals are more likely to produce large amounts of ROS after exposure to UVA, in particular singlet oxygen that can diffuse across the cell membrane.”
Free Radicals and Aging
“…Unrepaired accumulated cellular damage, caused by free radicals generated by on-going normal metabolism and contributed to by environmental sources, is the basis of aging…..
First proposed by Denham Harman (1956) and little recognized for some 40 years, this theory is now cited in every biological and medical journal and even in newspaper articles….. Many free radicals are highly reactive, owing to the tendency of electrons to pair–that is, to pair by the receipt of an electron from an appropriate donor or to donate an electron to an appropriate acceptor. Whenever a free radical reacts with a non-radical, a chain reaction is initiated ……
The free radicals of special interest in aging are the oxygen free radicals. These free radicals often take an electron away from a “target” molecule to pair with their single free electron. This is called “oxidation”. There are some closely related oxygen containing molecules that are not strictly free radicals but contribute to their production or are strong oxidants themselves, such as singlet oxygen and hydrogen peroxide. The term “reactive oxygen species” (ROS) is used to refer to these oxidants and the oxygen free radicals.
This has created the impression that all free radicals are highly damaging–in short, all bad. A more informed examination of free radicals reveals a range of unique functions in normal physiology and even in information processing in the brain…… It is calculated that endogenously generated oxygen free radicals make about 10,000 oxidative interactions with DNA per human cell per day (Ames et al, 1993). These modifications and damage to such vital molecules would be expected to ultimately lead to deficiencies in normal functions in a global way–AGING.”