The Lipophilic Vitamin C Derivative, 6-O-Palmitoylascorbate Protects Human Keratinocytes and 3D-Human Skin Equivalents Against X-Ray-Induced Oxidative Stress and Apoptosis More Markedly Than L-Ascorbic Acid

The aim of this study was to investigate preventive effects of the lipophilic vitamin C derivative, 6-O-palmitoylascorbate (PlmtVC) against X-ray radiation-induced harmful events. Free radical scavenging activity tests showed that both fresh and old (being kept at 37°C for 72 h) solutions of PlmtVC showed significantly higher abilities for scavenging both DPPH and peroxyl radical (ROO·) radicals than L-ascorbic acid (L-AA) under the same conditions, suggesting that PlmtVC is an antioxidant more efficient and stable than L-AA. Irradiation with X-ray (15 Gy) increased intracellular ROS production, lipid peroxidation and protein carbonylation, in human keratinocytes HaCaT, all of which were repressed, especially for intracellular ROS more markedly, by PlmtVC than by L-AA. After X-ray (15 Gy)-irradiation, caspase 3/7 activation and TUNEL-detected DNA-strand-breakages characteristic of apoptosis obviously increased in HaCaT cells or 3D-skin tissue equivalents, respectively, both of which were prevented more appreciably by PlmtVC than by L-AA. PlmtVC also noticeably prevented cumene hydroperoxide-induced generation of cellular ROS in epidermis parts of 3D-skin equivalents. Thus, PlmtVC prevents X-ray-induced diverse harmful effects, through its antioxidant activity and the palmitoyl moiety-based lipophilicity, more efficiently than L-AA. J. Cell. Biochem. 118: 318-329, 2017.