We recently reported that cigarette sidestream smoke (CSS) induced inhibition of nucleotide excision repair (NER) and the cause was NER molecule degradation by aldehydes contained in CSS [Carcinogenesis 39, 56–65, 2018; Mutat. Res. 834, 42–50, 2018]. In this study, we examined the relationship between intracellular glutathione (GSH) levels and CSS-induced NER inhibition. CSS treatment decreased the intracellular GSH level in human keratinocytes HaCaT, in which the repair of pyrimidine (6−4) pyrimidone photoproducts (6-4PPs) after UVB irradiation was suppressed. We used l-buthionine-(S,R)-sulfoximine (BSO) to artificially deplete intracellular GSH level. BSO treatment remarkably accelerated the CSS-induced NER inhibition. The NER inhibition by CSS was attributed to the delay of accumulation of NER molecules (TFIIH and XPG) to DNA damaged sites, which was further enhanced by BSO treatment. CSS degraded TFIIH, and BSO promoted it as expected. Formaldehyde (FA), a major constituent of CSS, showed similar intracellular GSH reduction and NER inhibition, and BSO promoted its inhibitory effect. Five cultured cell lines showed considerable variability in intrinsic GSH levels, and CSS-induced NER inhibitory effect was significantly correlated with the GSH levels. Chemicals like aldehydes are known to react not only with proteins but also with DNA, causing DNA lesions targeted by NER. Our results suggest that the tissues and cells with low intrinsic GSH levels are susceptible to treatment with CSS and electrophilic compounds like aldehydes through NER inhibition, thus leading to higher genotoxicity and carcinogenicity.

我们最近报道，香烟侧流烟雾（CSS）诱导了核苷酸切除修复（NER）的抑制，其原因是CSS中所含醛类降解NER分子[ Carcinogenesis 39 , 56–65, 2018;变异。资源。 834，42-50，2018 ]。在这项研究中，我们研究了细胞内谷胱甘肽 (GSH) 水平与 CSS 诱导的 NER 抑制之间的关系。 CSS 处理降低了人角质形成细胞 HaCaT 的细胞内 GSH 水平，其中 UVB 照射后嘧啶 (6−4) 嘧啶酮光产物 (6-4PPs) 的修复受到抑制。我们使用l-丁硫氨酸-(S,R)-亚磺酰亚胺 (BSO) 人工消耗细胞内 GSH 水平。 BSO 处理显着加速了 CSS 诱导的 NER 抑制。 CSS对NER的抑制归因于NER分子（TFIIH和XPG）在DNA损伤位点的积累延迟，而BSO处理进一步增强了这种积累。 CSS 降低了 TFIIH，而 BSO 正如预期的那样提升了它。 CSS的主要成分甲醛（FA）表现出类似的细胞内GSH减少和NER抑制作用，而BSO则促进其抑制作用。五种培养细胞系的内在 GSH 水平表现出相当大的变异性，CSS 诱导的 NER 抑制作用与 GSH 水平显着相关。众所周知，醛等化学物质不仅会与蛋白质发生反应，还会与 DNA 发生反应，从而导致 NER 靶向的 DNA 损伤。我们的研究结果表明，内在 GSH 水平较低的组织和细胞容易通过 NER 抑制而受到 CSS 和醛等亲电化合物的处理，从而导致更高的遗传毒性和致癌性。