Nitrosation of Glutathione and Nitration of Tyrosine by N-Nitrosoproline with Ultraviolet Light

Abstract

N-Nitrosoproline was thought to be nonmutagenic and noncarcinogenic because of its stability. However, it has been reported that N-nitrosoproline releases nitric oxide and shows direct mutagenicity by UV light irradiation. In this study, nitrosation and nitration of glutathione and tyrosine by N-nitrosoproline with UV light are tested. When a neutral solution of N-nitrosoproline and glutathione was irradiated with UV light of 365 nm generated from an 8 W mercury lamp, S-nitrosoglutathione was formed. When a neutral solution of N-nitrosoproline and tyrosine was irradiated with the UV light, a small amount of 3-nitrotyrosine was generated. A similar intensity of UV light of 254 nm induced formation of S-nitrosoglutathione and 3-nitrotyrosine with lesser e‹ciencies. When UV light of 365 nm was irradiated to a neutral mixture of Nnitrosoproline, gluthathione and tyrosine, a similar amount of S-nitrosoglutathione was generated, while the yield of 3-nitrotyrosine greatly decreased. Similar results to the 365 nm UV light irradiation were observed by sunlight. These results suggest that N-nitrosoproline may induce nitrosation and nitration of cellular components in humans with sunlight.