title: Combined activation of methyl paraben by light irradiation and esterase metabolism toward oxidative DNA damage.
abstract: Methyl paraben (MP) is often used as a preservative in foods, drugs, and cosmetics because of its high reliability in safety based on the rapid excretion and nonaccumulation following administration. Light irradiation sometimes produces unexpected activity from chemicals such as MP; furthermore, there is ample opportunity for MP to be exposed to sunlight. Here, we investigated whether MP shows DNA damage after sunlight irradiation. Two major photoproducts, p-hydroxybenzoic acid (PHBA) and 3-hydroxy methyl paraben (MP-3OH), were detected after sunlight irradiation to an aqueous MP solution. Both photoproducts were inactive in the in vitro DNA damage assay that measures oxidized guanine formed in calf thymus DNA in the presence of divalent copper ion, a known mediator of oxidative DNA damage. Simulated MP metabolism using dermal tissues after light irradiation produced these two photoproducts, which reacted with a microsomal fraction (S9) of the skin. A metabolite from MP-3OH, not PHBA, caused distinct DNA damage in the in vitro assay. This active metabolite was identified as protocatechuic acid, a hydrolyzed MP-3OH product. In addition, NADH, a cellular reductant, enhanced DNA damage by approximately five times. These results suggest that reactive oxygen species generated by the redox cycle via metal ion and catechol autoxidation are participating in oxidative DNA damage. This study reveals that MP might cause skin damage involving carcinogenesis through the combined activation of sunlight irradiation and skin esterases.
authors.affiliation: Faculty of Pharmacy, Meijo University, 150 Yagotoyama, Tempaku-ku, Nagoya 468-8503, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Okamoto
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hayashi
authors.forename: Shinpei
authors.initials: S
authors.lastname: Matsunami
authors.forename: Koji
authors.initials: K
authors.lastname: Ueda
authors.forename: Nakao
authors.initials: N
authors.lastname: Kojima
mesh_terms: D000818:Animals; D002417:Cattle; D004249:DNA Damage; D004950:Esterases / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D062385:Hydroxybenzoates / Q000737:chemistry; D008297:Male; D008861:Microsomes / Q000378:metabolism / Q000528:radiation effects; D010084:Oxidation-Reduction; D010226:Parabens / Q000737:chemistry / Q000528:radiation effects*; D010777:Photochemistry; D011310:Preservatives, Pharmaceutical / Q000737:chemistry / Q000528:radiation effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000737:chemistry; D012867:Skin / Q000737:chemistry / Q000201:enzymology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D062385:Hydroxybenzoates; D010226:Parabens; D011310:Preservatives, Pharmaceutical; D017382:Reactive Oxygen Species; C531013:protocatechuic acid methyl ester; C009091:protocatechuic acid; C015358:methylparaben; D004950:Esterases; C038193:4-hydroxybenzoic acid