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Int J Biol Sci 2008; 4(2):63-70. doi:10.7150/ijbs.4.63 This issue Cite

Short Research Communication

Effect of UVA Fluence Rate on Indicators of Oxidative Stress in Human Dermal Fibroblasts

James D. Hoerter^1,2, Christopher S. Ward^1,3,*, Kyle D. Bale^1,4,*, Admasu N. Gizachew^1,*, Rachelle Graham^1,5, Jaclyn Reynolds¹, Melanie E. Ward¹, Chesca Choi¹, Jean-Leonard Kagabo¹, Michael Sauer¹, Tara Kuipers¹, Timothy Hotchkiss¹, Nate Banner¹, Renee A. Chellson¹, Theresa Ohaeri¹, Langston Gant⁶, Leah Vanderhill⁶

1. Ferris State University, Department of Biological Sciences, Big Rapids, MI 49307 USA
2. Dublin Institute of Technology, Radiation and Environmental Science Centre, Focas Institute, Dublin-8, Ireland (U.S. Fulbright Scholar, January-August, 2008)
3. Current address: Baylor College of Medicine, Department of Molecular and Human Genetics, Houston, TX 77030 USA
4. Current address: Cayman Chemical Company, Antibody Group, Ann Arbor, MI 48108 USA
5. Current address: National Cancer Institute, Center for Cancer Research, Pediatric Oncology Branch, Bethesda, MD 20892 USA
6. Mecosta-Osceola Intermediate School District, Math Science Technology Center, Big Rapids, MI 49307 USA
^* Equal contribution

Abstract

During the course of a day human skin is exposed to solar UV radiation that fluctuates in fluence rate within the UVA (290-315 nm) and UVB (315-400 nm) spectrum. Variables affecting the fluence rate reaching skin cells include differences in UVA and UVB penetrating ability, presence or absence of sunscreens, atmospheric conditions, and season and geographical location where the exposure occurs. Our study determined the effect of UVA fluence rate in solar-simulated (SSR) and tanning-bed radiation (TBR) on four indicators of oxidative stress---protein oxidation, glutathione, heme oxygenase-1, and reactive oxygen species--in human dermal fibroblasts after receiving equivalent UVA and UVB doses. Our results show that the higher UVA fluence rate in TBR increases the level of all four indicators of oxidative stress. In sequential exposures when cells are exposed first to SSR, the lower UVA fluence rate in SSR induces a protective response that protects against oxidative stress following a second exposure to a higher UVA fluence rate. Our studies underscore the important role of UVA fluence rate in determining how human skin cells respond to a given dose of radiation containing both UVA and UVB radiation.

Keywords: UVA, UVB, tanning bed, solar simulated radiation, fluence rate, sunbed

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