Enhancement of lethality of near-ultraviolet by p-aminobenzoic acid in human skin fibroblasts deficient in dna repair

Abstract

Introduction Para-aminobenzoic acid (PABA) is widely used as a topical sunscreen to protect the skin from the harmful effects of ultraviolet (UV) light. PABA acts as a UV filter since its ultraviolet absorption extends beyond that of DNA down to about 320 nm. As such, PABA protects the DNA of skin cells from photolysis. However, synergetic side effects of near-UV photoexcited PABA in pyrimidine dimer-repair-deficient E. coli cells have been reported¹ and dimer formation of E. coli. DNA has been demonstrated by chemical analysis.² Similar sensitization has been observed with mammalian cells including mouse lymphoma cell line³ and human skin fibroblasts,4 and in the latter case the formation of pyrimidine dimers was demonstrated. In this study we confirm the involvement of DNA damage in PABA photosensitization of human cells through the extent of sensitization of cells killing by comparing a DNA-repair-deficient with a normal human skin fibroblast cell line.