RESUMO
BACKGROUND: According to target cells, apoptosis-inducing agents, and NO concentration, NO concentration, NO shows both pro- and antiapoptotic effects. OBJECTS: Our study was perfermed to verify the role of NO in UVB-induced apoptosis in HaCaT cells. METHODS: After UVB irradiation, FACS using propidium iodide, LDH cytotoxicity assay, and nitrite assay based on Griess reaction were done in HaCaT cells. These procedures were repeated after UVB irradiation and NG-monomethyl-arginine (L-NMMA), a NO synthase (NOS) inhibitor, addition. RESULTS: 1) UVB irradiation (5-80mJ/cm2) induced apoptosis in HaCaT cells dose-dependently. 2) UVB irradiation (80mJ/cm2) stimulated NO production 30-50% more over baseline level, and this was inhibited by 500 micrometer L-NMMA. 3) 500 micrometer L-NMMA did not inhibit UVB-induced apoptosis. CONCLUSION: UVB irradiation evokes apoptosis in HaCaT keratinocytes through NO-independent mechanism.