UVB Light Stimulates Production of Reactive Oxygen Species

Abstract

In keratinocytes, UVB light stimulates the production of reactive oxygen species (ROS). Lysates of these cells were found to possess a non-dialyzable, trypsin- and heat-sensitive material capable of generating ROS in response to UVB light. Using ion exchange, metal affinity, and size exclusion chromatography, a 240-kDa protein was isolated with ROS generating activity. The protein exhibited strong absorption in the 320-360 nm range with additional soret peaks around 400-410 nm, suggesting the presence of heme. Sequencing using liquid chromatography-ion trap mass spectrometry identified the protein as catalase. Using purified catalases from a variety of species, the ROS generating activity was found to be temperature- and O2-dependent, stimulated by inhibitors of the catalatic activity of catalase, including 3-aminotriazole and azide, and inhibited by cyanide. A marked increase in the production of ROS was observed in UVB-treated cells overexpressing catalase and decreased generation of oxidants was found in UVB-treated keratinocytes with reduced levels of catalase. Our data indicate that catalase plays a direct role in generating oxidants in response to UVB light. The finding that catalase mediates the production of ROS following UVB treatment is both novel and highly divergent from the well known antioxidant functions of the enzyme. We hypothesize that, through the actions of catalase, high energy DNA damaging UVB light is absorbed by the enzyme and converted to reactive chemical intermediates that can be detoxified by cellular antioxidant enzymes. Accumulation of excessive ROS, generated through the action of catalase, may lead to oxidative stress, DNA damage, and the development of skin cancer.

Curcumin inhibits the expression of COX-2 in UVB-irradiated human keratinocytes (HaCaT) by inhibiting activation of AP-1: p38 MAP kinase and JNK as potential upstream targets

“…Ultraviolet B (UVB) is a well-known major risk factor for the development of acute inflammation as well as non-melanoma skin cancer in epidermis (De Fabo et al, 2004;Ramos et al, 2004). Accumulating data indicate that UVB exerts its detrimental effect mainly through the induction of direct DNA damage or the production of reactive oxygen species (ROS) (de Gruijl, 2002;Kulms et al, 2002;Heck et al, 2003). Direct DNA damage or ROS often triggers some signaling pathw ays such as m itogen-activated protein kinases (MAPKs) which are known to be involved in proliferation and survival of the cells (Rhee, 1999;Torres and Forman, 2003).…”

Ultraviolet B irradiation selectively increases the production of interleukin-8 in human cord blood-derived mast cells

“…There is strong evidence linking UVB with functional deficiencies in cellular immunity, resulting in changes in epidermal pro-and anti-inflammatory cytokine profiles, suppression of phagocytosis [6] and increased reactive oxygen species (ROS) production by keratinocytes [7], reduced antigen presentation by Langerhans cells [8] and induction of early lymphocyte depletion and late T cell proliferation [9]. UVB can also provoke apoptosis [10], immunosuppression [11], and ROS production can initiate cell damage and induce apoptosis [10,12] and cause direct DNA damage [13].…”

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).…”