Subthreshold UV Radiation-induced Peroxide Formation in Cultured Corneal Epithelial Cells: The Protective Effects of Lactoferrin

• Published in: Experimental eye research 1996-11, Vol.63 (5), p.519-526
• Main Authors: SHIMMURA, SHIGETO, SUEMATSU, MAKOTO, SHIMOYAMA, MASARU, TSUBOTA, KAZUO, OGUCHI, YOSHIHISA, SHIMURAI, YUZURU
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; catalase; Cell Culture Techniques; corneal epithelium; deferoxamine; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Endothelium, Corneal - radiation effects; Eye and associated structures. Visual pathways and centers. Vision; Fundamental and applied biological sciences. Psychology; hydrogen peroxide; Hydrogen Peroxide - pharmacology; lactoferrin; Lactoferrin - pharmacology; Oxidation-Reduction - radiation effects; oxidative stress; Oxidative Stress - drug effects; Oxidative Stress - radiation effects; peroxidase; Peroxides - metabolism; Rabbits; superoxide dismutase; tears; ultraviolet radiation; Ultraviolet Rays; Vertebrates: nervous system and sense organs
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1006/exer.1996.0142

Acute exposure to suprathreshold ultraviolet B radiation (UV-B) is known to cause photokeratitis resulting from the necrosis and shedding of corneal epithelial cells. However, the corneal effects of low dose UV-B in the environmental range is less clear. In this study, subthreshold UV-B was demonstrated to cause non-necrotic peroxide formation in cultured corneal epithelial cells, which was attenuated by the major tear protein lactoferrin. Intracellular oxidative insults and cell viability of rabbit corneal epithelial cells (RCEC) were assessed by dual-color digital microfluorography using carboxydichlorofluorescin (CDCFH) diacetate bis (acetoxymethyl) ester, a hydroperoxide-sensitive fluoroprobe, and propidium iodide (PI), respectively. The magnitude of UV-induced oxidative insults was calibrated by concentrations of exogenously applied H 2O 2which evoke compatible levels of CDCFH oxidation. Exposure of RCEC to low-dose UV-B (2.0 mJ cm −2at 313 nm, 10.0 mJ cm −2total UV-B) caused intracellular oxidative changes which were equivalent to those elicited by 240 μ Mhydrogen peroxide under the conditions of the study. The changes were dose dependent, non-necrotic, and were partially inhibited by lactoferrin (1 mg ml −1) but not by iron-saturated lactoferrin. Pretreatment with deferoxamine (2 m M) or catalase (100 U ml −1) also attenuated the UV-induced oxidative stress. The results indicate that UV-B comparable to solar irradiation levels causes significant intracellular peroxide formation in corneal epithelial cells, and that lactoferrin in tears may have a physiological role in protecting the corneal epithelium from solar UV irradiation.