The Primary Cytotoxicity in Ultraviolet-A-Irradiated Riboflavin Solution Is Derived from Hydrogen Peroxide

Abstract

The cytotoxic action of near-ultraviolet (UVA) radiation on cultured mammalian cells is dependent upon oxygen, suggesting that reactive oxygen species are involved in the cellular action of the radiation. Flavins are thought to be an important chromophore for photo-induced skin injury. Irradiation of riboflavin with UVA radiation is known to produce singlet oxygen, superoxide anions, and triplet-state riboflavin radicals, which, however, are immediately quenched by many constituents of the human skin. If the chemical produces a long-lived reactive oxygen species, hydrogen peroxide (H2O2), after UVA radiation, its deleterious effect is not limited to its generation site. Thus, we investigated whether H2O2, is produced in UVA-irradiated riboflavin solution and whether it plays an important role in the cytotoxic action of the solution. The solution showed a marked cytotoxic effect when placed on human fibroblasts, and cytotoxicity was retained in the solution for at least 40 min after radiation. Most of the toxicity appeared to be derived from H2O2 produced in the solution, because the solution lost its cytotoxicity as a result of catalase treatment, and the resultant restoration of survival was almost complete. Under our conditions, two molecules of riboflavin were calculated to produce one molecule of H2O2 after UVA radiation.

Riboflavin activated by ultraviolet A1 irradiation induces oxidative DNA damage-mediated mutations inhibited by vitamin C

“…However, in combination with UVA1 irradiation, riboflavin treatment could significantly impair cellular viability. It has been shown that UVA irradiation of riboflavin generates reactive intermediate species, such as singlet oxygen, superoxide anions, triplet state riboflavin radicals, and hydrogen peroxide (33)(34)(35). High-dose UVA irradiation alone has also been proven to produce reactive oxygen species with known cytotoxic properties (36).…”

Biocompatibility and antibacterial activity of nitrogen-doped titanium dioxide nanoparticles for use in dental resin formulations

“…17 Recent research has shown that the light absorption of TiO 2 can be shifted to the visible range by doping with a variety of atoms, including nitrogen, [18][19][20][21] fluorine, 22 copper, 23 and silver, 24 resulting in a new class of visible light active materials. This is of particular interest in the development of novel dental materials for two reasons: exposure of gum tissue to blue light is preferable to cytotoxic UV light 25 and most of the dental offices are already equipped with blue light sources used to cure photoactive composite dental resins. The incorporation of blue light-sensitive TiO 2 into a dental material could allow for long-term and repeatable release of antibacterial ROS.…”

3-Hydroxypyridine Chromophores Are Endogenous Sensitizers of Photooxidative Stress in Human Skin Cells

“…Photosensitization occurs as a consequence of initial formation of excited states of chromophores and their subsequent interaction with substrate molecules (type I photoreaction) or molecular oxygen (type II photoreaction) through energy and/or electron transfer (9). Various chromophores contained in human skin, such as urocanic acid (10), riboflavin (11), melanin precursors (12), and advanced glycation end products (13,14) have been proposed as endogenous UV sensitizers of photooxidative stress, but molecular identity and mechanism of action of relevant endogenous skin photosensitizers remain elusive (3,15,16). Recently, we have presented evidence that skin structural proteins such as collagen and elastin and specifically their UVA chromophores represent a novel class of potent endogenous photosensitizers in human skin (13,14,17).…”