title: UVB radiation induces an increase in intracellular zinc in human epidermal keratinocytes.
abstract: Ultraviolet (UV) radiation is known to cause oxidative stress, inflammation, DNA damage and apoptotic cell death; however, many details of these malign mechanism have yet to be elucidated. In this study, the exposure of adult human epidermal keratinocytes (HEKa) with UVB (>100 mJ/cm(2)) resulted in the significant increase of intracellular zinc that was released from its storage and was detected by fluorescent zinc indicators. Toxicity testing revealed that UVB-induced zinc release in HEKa is associated with HEKa cell death. Cells that showed elevated intracellular zinc fluorescence upon UVB exposure were also stained by propidium iodide (PI), a traditional viability indicator whose fluorescent signal is as a result of its intercalating with DNA fragments and is unaffected by zinc concentration, showing significant colocalization [Pearson's correlation coefficients r=0.956 (n=6)]. The cytotoxicity of zinc was also determined by an MTT assay after applying the exogenous zinc (ZnCl2) along with its ionophore pyrithione (20 microM) into HEKa culture medium. A significant reduction in cell viability as a function of both zinc concentration and exposure time was observed. The treatments of 1, 10 and 100 microM ZnCl2 with pyrithione demonstrated 2.3, 60 and 84% cell deaths, respectively (control 0.5%) after 30 min. ZnCl2 (100 microM) was also found to induce complete HEKa death after 1 h. Thus, the present study demonstrates that UVB irradiation-induced increased zinc is detrimental to HEKa viability, and zinc may be a necessary step in UVB-induced cell death signaling pathways.
authors.affiliation: Molecular and Cellular Biology Program, Ohio University, Athens, OH 45701, USA.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Stork
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Martorano
authors.forename: Yang V
authors.initials: YV
authors.lastname: Li
mesh_terms: D000328:Adult; D016923:Cell Death / Q000528:radiation effects; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D000078404:Epidermal Cells; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D014466:Ultraviolet Rays; D015032:Zinc / Q000009:adverse effects / Q000032:analysis / Q000378:metabolism*
chemical_list: D015032:Zinc