This study aimed to examine whether and how third-hand smoke (THS) exposure would influence serum melatonin level. 1083 participants with or without exposure to THS were enrolled. Serum ROS, SOD, GSH-Px, and melatonin were measured by ELISA. Methylation microarrays detection and WGCNA were performed to identify hub methylated-sites. The methylation levels of hub-sites were validated in addtional samples. Moreover, mice were exposed to THS for 6 months mimicking exposure of human and the serum, liver, and pineal were collected. Oxidative stress-related indicators in serum, pineal, and liver were measured by ELISA. The expressions of mRNA and protein and methylation levels of hub-gene discovered in human data were further explored by RT-PCR, western-blot, and TBS. The results showed the participants exposed to THS had lower melatonin-level. 820 differentially methylated sites associated with THS were identified. And the hub-site located on the CYP1A2 promoter was identified, which mediated the association between THS and decreased melatonin-level. Decreased peak of serum melatonin, increased ROS and reduced SOD and GSH-Px in pineal and liver, and elevated CYP1A2 expression in liver was also found in the THS-exposed mice. Hypo-methylation of 7 CPG sites on the CYP1A2 promoter was identified, which accelerated the catabolism of melatonin. Overall, THS exposure is associated with abnormal melatonin catabolism through hypo-methylation of CYP1A2-promoter.

本研究旨在检查三手烟 (THS) 暴露是否以及如何影响血清褪黑激素水平。招募了 1083 名有或没有接触过 THS 的参与者。通过ELISA测量血清ROS、SOD、GSH-Px和褪黑激素。进行甲基化微阵列检测和 WGCNA 以识别中心甲基化位点。在其他样本中验证了中枢位点的甲基化水平。此外，将小鼠暴露于 THS 6 个月，模拟人类的暴露，并收集血清、肝脏和松果体。通过ELISA测量血清、松果体和肝脏中的氧化应激相关指标。通过 RT-PCR、western-blot 和 TBS 进一步探索人类数据中发现的 mRNA 和蛋白质的表达以及 hub-gene 的甲基化水平。结果显示，暴露于 THS 的参与者褪黑激素水平较低。鉴定了 820 个与 THS 相关的差异甲基化位点。并且确定了位于 CYP1A2 启动子上的中心位点，它介导了 THS 与褪黑激素水平降低之间的关联。在 THS 暴露的小鼠中，还发现血清褪黑激素峰值降低，ROS 增加，松果体和肝脏中的 SOD 和 GSH-Px 降低，肝脏中 CYP1A2 表达升高。确定了 CYP1A2 启动子上 7 个 CPG 位点的低甲基化，这加速了褪黑激素的分解代谢。总体而言，THS 暴露与通过 CYP1A2 启动子的低甲基化导致的异常褪黑激素分解代谢有关。在暴露于 THS 的小鼠中，还发现松果体和肝脏中 ROS 增加，SOD 和 GSH-Px 减少，肝脏中 CYP1A2 表达升高。确定了 CYP1A2 启动子上 7 个 CPG 位点的低甲基化，这加速了褪黑激素的分解代谢。总体而言，THS 暴露与通过 CYP1A2 启动子的低甲基化导致的异常褪黑激素分解代谢有关。在暴露于 THS 的小鼠中，还发现松果体和肝脏中 ROS 增加，SOD 和 GSH-Px 减少，肝脏中 CYP1A2 表达升高。确定了 CYP1A2 启动子上 7 个 CPG 位点的低甲基化，这加速了褪黑激素的分解代谢。总体而言，THS 暴露与通过 CYP1A2 启动子的低甲基化导致的异常褪黑激素分解代谢有关。