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Strong epidemiological evidence supports the association between increased air pollution and the risk of developing atherosclerotic cardiovascular diseases (CVDs). However, the mechanism remains unclear. As an environmental air pollutant and benzo-a-pyrene (BP) metabolite, BP-1,6-quinone (BP-1,6-Q) is present in the particulate phase of air pollution. This study was undertaken to examine the redox activity of BP-1,6-Q and mechanisms associated with it using EA.hy926 endothelial cells. BP-1,6-Q at 0.01–1 μM significantly stimulated the production of reactive oxygen species (ROS)·in intact cells and isolated mitochondria. Furthermore, BP-1,6-Q-induced ROS was altered by mitochondrial electron transport chain (METC) inhibitors of complex I (rotenone) and complex III (antimycin A), denoting the involvement of mitochondrial electron transport chain (METC) in BP-1,6-Q mediated ROS production. In METC deficient cells, interestingly, BP-1,6-Q-mediated ROS production was enhanced, suggesting that overproduction of ROS by BP-1,6-Q is not only produced from mitochondria but can also be from the cell outside of mitochondria (extramitochondrial). BP-1,6-Q also triggered endothelial-monocyte interaction and stimulated expression of vascular adhesion molecule-1 (VCAM-1). In conclusion, these results demonstrate that BP-1,6-Q can generate ROS within both mitochondria and outside of mitochondria, resulting in stimulation of adhesion of monocytes to endothelial cells, a key event in the pathogenesis of atherosclerosis.

Objective To investigate the potential compensatory effects of hOGG1 and hMTH1 in the repair of oxidative DNA damage. Methods The hOGG1 and hMTH1 gene knockdown human embryonic pulmonary fibroblast cell lines were established by lentivirus-mediated RNA interference. The messenger RNA (mRNA) levels of hOGG1 and hM1TH1 were analyzed by the real-time polymerase chain reaction, and 8-hydroxy-2′-deoxyguanosine (8-oxo-dG) formation was analyzed in a high-performance liquid chromatography-electrochemical detection system. Results The hOGG1 and hMTH1 knockdown cells were obtained through blasticidin selection. After transfection of hOGG1 and hMTH1 small interfering RNA, the expression levels of the mRNA of hOGG1 and hMTH1 genes were decreased by 97.2% and 96.2%, respectively. The cells then were exposed to 100 μmol/L of hydrogen peroxide (H2O2) for 12 h to induce oxidative DNA damage. After H2O2 exposure, hMTH1 mRNA levels were increased by 25% in hOGG1 gene knockdown cells, whereas hOGG1 mRNA levels were increased by 52% in hMTH1 gene knockdown cells. Following the treatment with H2O2, the 8-oxo-dG levels in the DNA of hOGG1 gene knockdown cells were 3.1-fold higher than those in untreated HFL cells, and 1.67-fold higher than those in H2O2-treated wild-type cells. The 8-oxo-dG levels in hMTH1 gene knockdown cells were 2.3-fold higher than those in untreated human embryonic pulmonary fibroblast cells, but did not differ significantly from those in H2O2-treated wild-type cells. Conclusion Our data suggested that hOGG1 could compensate for hMTH1 during oxidative DNA damage caused by H2O2, whereas hMTH1 could not compensate sufficiently for hOGG1 during the process.