The mechanism of N-acetylcysteine photoprotection is not related to dipyrimidine photoproducts

N-acetyl-l-cysteine prevents DNA damage induced by UVA, UVB and visible radiation in human fibroblasts

“…Given the pivotal role played by GSH in protecting cells from UV and visible light-induced DNA damage, NAC has been identified as a candidate antioxidant for this role partly because of its ability to both supply cysteine for the synthesis of GSH [7] but also because it is reputed to be an antioxidant (free radical scavenger) in its own right [20]. Although the efficacy of NAC in protecting human cells from UVA irradiation has been reported elsewhere [11], this study examines the photoprotective effects of NAC using a 150 W xenon-arc lamp light source with intensities analogous to early summer terrestrial solar radiation levels recorded in the southwest of England [16].…”

“…This is keeping with the results obtained by Emonet and co-workers [10,11] who found that adding 5 mM NAC to the medium of skin fibroblasts for 4 h gave protection against a physiological dose of UVA irradiation and maximised cellular GSH concentrations. NAC has been shown to be ineffective in preventing pyrimidine dimer formation induced directly by UVB irradiation [20] hence the action of NAC in protecting human fibroblasts against the effects of unfiltered xenon-arc lamp irradiation could be postulated as being due to the reduction of DNA damage caused by ROS. Investigations using filtered light (>320 nm) showed that an optimal 6 mM NAC supplement delayed an increase in tail DNA/% for up to 30 min irradiation and significantly reduced the level of tail DNA/% for more than an hour (Fig.…”

Quantitative measurement of hydroxyl radical induced DNA double‐strand breaks and the effect of N‐acetyl‐l‐cysteine

“…4. glutathione, which was an even more potent scavenger of free radicals than NAC itself [12]. On the other hand, NAC and other reducing agents were also shown to increase the oxidative DNA damages, depending on the experimental conditions, such as the presence or absence of transition metal ions [20,[33][34][35].…”

“…It has been proposed that the beneficial effect of NAC mainly comes from its capability of directly scavenging Å OH radicals as well as its function as a glutathione precursor [12][13][14][15][16][17]. However, there are still considerable controversies regarding the antioxidant efficacy of NAC.…”

“…NAC has been tested as a promising antigenotoxic and anticarcinogenic agent in a variety of experiments [9][10][11], and is sold in pharmacies as a food supplement for such purposes. It has been proposed that the beneficial effect of NAC mainly comes from its capability of directly scavenging Å OH radicals as well as its function as a glutathione precursor [12][13][14][15][16][17]. However, there are still considerable controversies regarding the antioxidant efficacy of NAC.…”