Identificador: TDX:489
Autores: Mulero Abellán, Miquel
Resumen:
The oxidative stress is a direct consequence of the necessary consumption of oxygen by the living aerobic organisms, and its intensity and consequences depend on the capacity of specific defence systems to counteract the generated reactive oxygen species (ROS), among which the most relevant are the oxygen free radicals (OFR). Numerous circumstances, physiological or pathological, can increase the production of OFR and, therefore, increase the oxidative stress. Among them there is the UV radiation (UVR), to which we are all exposed with greater or smaller intensity and frequency. Exposition to UVR cause numerous cutaneous alterations, included the skin cancer. The progressive increase of this type of cancer in the last decades provoke a great social and sanitary concern; in consequence all the aspects related to photoprotection are object of investigation from different points of view: physical, chemical, biological and sanitary. In this sense, there is no doubt that at the present we have very valuable information about the risks of the exposition to the UVR and, at the same time, there are very efficient sunscreens, which are developed with advanced scientific criteria. Nevertheless, and in spite of the fact that the consumption of sunscreens increases day by day, the incidence of skin cancer increases continuously. With this work we intend to point out the false sensation of security that can be derived from the incorrect use of sunscreens and the need of a depth revision about some of the concepts which photoprotecction is based. Consequently, in the development of experimental protocols, we irradiated groups of animals (hairless rats) in the following way: acute radiations, chronic radiations and radiations with sunscreens. Different biochemical parameters related to OFR were determined in blood and in epidermis. The damage produced on the genetic material, and the number and functional capacity of the immune cells of the skin (Langerhans cells) were also evaluated. The main conclusions derived from this work are the following:1. UVR, from equivalent dose to 1 MED (minimal erithemal dose), induces systemic and cutaneous changes in the specific defence systems in front of oxidative stress, simultaneously to the loose of the cutaneous immunity. 2. Suberithemal and repeated doses of UVR, similar to the received by a person exposed to moderate sun exposure, also determine the lost of the cutaneous immunity and produce oxidative stress relative alterations.3. The number of epidermal Langerhans cells correlates with diverse blood and epidermal parameters related to oxidative stress. The fact that the eritrocytari activity of GPx and concentration of GSH can be predictors of the number of Langerhans cells, suggests the possibility that these parameters could constitute a valid alternative to indirectly evaluate the cutaneous immune capacity. 4. The evaluation of the sun protection factor (SPF), based exclusively in the capacity of prevention from erithema, does not offer the needed guarantees for a sure photoprotection against the UVR. It is necessary to adopt new criteria of photoprotection, based on premature and more sensitive indicators than the erithema. 5. The values of SPF of the sunscreens should be submitted to a critical judgment. In this sense, would be prudent the reduction of this values to the half or to the third part.Due to the fact that many of the effects of the UVR derive from the oxidative stress, is very recommendable to develop new photoprotective formulations that include capable active principles to restore the oxidative equilibrium and to neutralize the effects of free radicals.
Repositori URV