DIFFERENTIAL SUSCEPTIBILITY OF EPIDERMAL-KERATINOCYTES AND NEUROBLASTOMA-CELLS TO CYTOTOXICITY OF ULTRAVIOLET-B LIGHT IRRADIATION PREVENTEDBY THE OXYGEN RADICAL SCAVENGER ASCORBATE-2-PHOSPHATE BUT NOT BY ASCORBATE

Human or mouse epidermal keratinocytes NHEK or Pam212 was less suscept ible to ultraviolet (UV)-B irradiation than mouse neuroblastoma NAs1 c ells in culture, undergoing apoptosis-like cell death as shown by cell fragmentation and cell membrane integrity disruption. UV susceptibili ty was appreciably reduced by the reactive oxygen species (ROS)-scaven ger L-ascorbic acid-2-phosphate (Asc2P) endowed with long-lasting func tions but not by L-ascorbic acid (Asc) for each cell type. DehydroAsc reduced UV susceptibility of Pam212 or NAs1 established cell lines but not of normal diploid NHEK cells destined to be thereafter submitted to cellular senescence. The susceptibility reduction may not be ascrib ed to extracellular Asc2P or DehAsc, which was removed by aspirating a nd/or rinsing upon irradiation after the intracellular uptake. Asc2P p revented cell fragmentation and disruption of cell membrane integrity as demonstrated by channelyzer analysis and dead cell-specific DNA-int ercalator ethidium homodimer/fluorometry, respectively. Thus, the thre e cell types differed in UV susceptibility partly because of their dif ferent ROS-scavenging abilities, which may be potently promoted by Asc 2P or dehydroAsc but not Asc.