REACTIVE OXYGEN SPECIES IN HUMANS SKIN
REACTIVE OXYGEN SPECIES IN HUMANS FREE

Human skin essentially consists of two layers: The epidermis on the outside and the dermis below, both are attached to each other via the basal lamina. However, there are many more environmental factors influencing skin aging, as discussed later. Extrinsic aging is synonymous with photoaging as UV-radiation has severe consequences for exposed skin. In contrast, focusing on extrinsic aging, it seems that the skin gets thicker and completely changes its composition.

In addition the skin gets dryer and gradually loses the function to serve as a first barrier against the environment. The skin also loses sensibility due to decreased production of sex hormones and a decreased number of nerve-endings. Aging leads to a thinning of epidermal as well as dermal skin layers. It was proposed that only three percent of all aging factors have a genetic background. Intrinsic aging is described as a result of genetic factors and corporal changes that occur/appear during the normal aging process, whereas extrinsic aging focuses on aging process accelerated by environmental influences. A characteristic of this organ is also the fact that extrinsic aging is at least as important as intrinsic aging. Not only is the ROS load in this organ higher than in any other organ, but in many cases a clear correlation between the ROS originating from external and internal insults and a pro-aging effect can be found.

REACTIVE OXYGEN SPECIES IN HUMANS FREE

However, if the free radical theory of aging holds true in any organ of the human body it is in the skin. In several cases it could be demonstrated that an increase in oxidative stress led to an increase in lifespan (summarized in more detail by Ristow and Schmeisser in ). For example it was shown that SOD +/− mice had a clear increase in the ROS load but a quite normal lifespan. Especially in the last decade, serious doubts arose that ROS are in fact the most important components that are fueling aging. This concept was broadened 16 years later by Harman himself by identifying mitochondria as the main source of ROS, forming the basis for the mitochondrial free radical theory of aging. In this year Denham Harman proposed that reactive oxygen species (ROS) accumulate over time and are a main contributor to the aging process. Introduction: The Skin as a Model for the “ROS-Aging” ConnectionĪging research has focused on a central finding that dates back to the year 1956. This modified cornified envelope also leads to an altered anti-oxidative capacity and a reduced barrier function of the epidermis.ġ. They include a disruption of the epidermal calcium gradient in old skin with an accompanying change in the composition of the cornified envelope. Finally age-related changes of the skin are also a topic of this review. In addition the oxidative stress induced modifications caused to proteins, lipids and DNA are discussed. Furthermore, the defense mechanisms against oxidative stress ranging from enzymes like superoxide dismutases, catalases, peroxiredoxins, and GSH peroxidases to organic compounds such as L-ascorbate, α-tocopherol, beta-carotene, uric acid, CoQ10, and glutathione are described in more detail. In this review the overall effects of oxidative stress are discussed as well as the sources of ROS including the mitochondrial ETC, peroxisomal and ER localized proteins, the Fenton reaction, and such enzymes as cyclooxygenases, lipoxygenases, xanthine oxidases, and NADPH oxidases. Although the results are quite different in dermis and epidermis, extrinsic aging is driven to a large extent by oxidative stress caused by UV irradiation. This is true for intrinsic aging and even more for extrinsic aging. Oxidative stress in skin plays a major role in the aging process.

Reactive oxygen species in humans