Author/Editor     Rozman, Branka; Gašperlin, Mirjana; Kristl, Julijana
Title     Preventivno delovanje naravnih antioksidantov na nastanek kožnega raka pod vplivom ultravijoličnih žarkov
Translated title     Preventive effects of natural antioxidants on ultraviolet-induced skin cancer
Type     članek
Source     Med Razgl
Vol. and No.     Letnik 45, št. 2
Publication year     2006
Volume     str. 141-53
Language     slo
Abstract     The incidence of non-melanoma skin cancer is rising and primary prevention, including the use of sunscreens, has been proven inadequate. Skin cancer strongly correlates with chronic sun exposure. Here we first describe the effects of ultraviolet light on skin: ultraviolet B light can initiate skin tumor development through direct DNA damage and mutation in tumor suppressor and prooncogenes whereas ultraviolet A light is particulary important in causing oxidative stress by inducing reactive oxygen and nitrogen species such as superoxide anion, hydroxyl radical, hydrogen peroxide and nitric oxide. Ultraviolet radiation also causes inflammation and immunosuppression in the skin. The possibilities for photoprotection of the skin are rewieved. A preventive strategy to support the endogenous antioxidant system by topical delivery of various enzymes or non-enzymatic antioxidants is described. The most important enzymatic antioxidants are glutathione peroxidase, catalase, superoxide dismutase and haem-oxygenase. The representatives of non-enzymatic skin antioxidants are glutathione, alfa-tocopherol, ascorbate, beta-carotene, ubiquinon and melanins. Numerous substances, particulary polyphenols, flavonoids and acyclic carotenids, derived from nutrient plants demonstrate strong antioxidant activity, too. Some substances of the natural orign such as curcumin, capsaicin and gingerol have also been shown to reduce photocarcinogenesis, not only because of their antioxidant activity but also due to their capacity to prevent inflammation, gene mutation or immunosuppression. Although the results of preclinical studies are very promising, clinical evidence that natural antioxidants prevent skin cancer is not always convincing.
Summary     Pogostost nemelanomskega kožnega raka narašča in primarna preventiva, vključno z uporabo varovalnih izdelkov za sončenje, se je pokazala kot neustrezna. Kožni rak je močno povezan s kronično izpostavljenostjo soncu. Ultravijolični B-žarki lahko sprožijo nastanek kožnih tumorjev z neposrednimi poškodbami DNA, mutacijami tumorsupresorskih genov in protoonkogenov, medtem ko ultravijolični A-žarki povzročajo kožnega raka predvsem posredno, preko nastanka reaktivnih kisikovih in dušikovih spojin, kot so superoksidni anion, hidroksilni radikal, vodikov peroksid, dušikov oksid in drugi. Ultravijolično sevanje povzroča tudi vnetje in imunosupresijo v koži. Članek podaja pregled možnosti preventive kožnega raka s spojinami biogenega in naravnega izvora. Zanimiva možnost zaščite je krepitev endogenega sistema antioksidantov z nanosom na kožo bodisi encimskih bodisi neencimskih antioksidantov. Med pomembnejše encimske antioksidante sodijo glutation peroksidaza, katalaza, superoksid dismutaza in hem oksigenaza, med neencimske pa glutation, vitamina C in E, beta-karoten, ubikinon in melanini. Močno antioksidativno delovanje izkazujejo tudi številne spojine, ki se nahajajo v užitnih rastlinah. V slednjo skupino uvrščamo mnoge polifenole, flavonoide in aciklične karotenoide. Nekatere naravne spojine, kot so na primer kurkumin, gingerol ali kapsaicin, sicer niso antioksidanti, vendar dokazano delujejo preventivno pri kožnem raku, saj zavirajo vnetje, mutacije genov in imunosupresijo. Rezultati predkliničnih testiranj naravnih antioksidantov v preventivi kožnega raka so sicer zelo obetajujoči, podatki o klinični učinkovitosti pa niso vedno prepričljivi.
Descriptors     SKIN NEOPLASMS
ULTRAVIOLET RAYS
OXIDATIVE STRESS
ANTIOXIDANTS
REACTIVE OXYGEN SPECIES
FREE RADICALS
CAROTENOIDS