Organochlorine pesticides (OCPs) are environmental pollutants that bioaccumulate and are known to produce oxidative stress via reactive oxygen species (ROS) generation in different experimental models1. Several epidemiological studies have revealed the association between exposure to OCPs and endothelial injury and consequent endothelial dysfunction in humans2. During OCPs detoxification process, expression of Phase I enzyme, cytochrome P450 1A1 (CYP1A1) is induced, that has been shown to be associated with increased ROS generation. Angiotensin converting enzyme (ACE) has been implicated in various cardiovascular disorders and its expression has been shown to be mediated via enhanced ROS production. Therefore the present study is designed to assess the effect on ACE gene expression mediated via increased ROS generation through CYP1A1 expression after exposure to OCPs in human umbilical vein endothelial cells (HUVECs). HUVECs were cultured in endothelial cell expansion medium, reduced serum supplemented with endothelial growth factors and 1% antibiotic-antimycotic solution in T-25 culture flask and were maintained at 37°C, 5% CO2 in a humidified atmosphere. Cells were treated with p,p-DDE (0.5 µM) and with aldrin (1µM) for 24 hours. ROS generation was measured as the fluorescence of the oxidation product of 2’,7’-dichlorodihydroflourescein diacetate (H2DCFDA). CYP1A1activity was measured using EROD assay. ACE and CYP1A1 mRNA expression was evaluated through real time PCR. Expression and activity of CYP1A1 was increased significantly (p<0.05) in HUVECs in response to treatment with OCPs for 24 hours. p,p-DDE induced 5.9 fold EROD activity as compared to controls whereas aldrin exposure induced 4.2 fold activity in HUVECs. p,p-DDE at a concentration of 0.5µM induced expression of CYP1A1 by 5.2 fold whereas induction of CYP1A1 by aldrin at a concentration of 1µM was 3.8 fold as compared to control which consequently resulted in a significantly (p<0.05) increased ROS production (79% and 37% in p,p-DDE and aldrin treated HUVECs respectively as compared to control) which in turn become the contributory factor for significant (p<0.05) increase in the expression ACE gene. Expression of ACE gene was increased by 3.9 and 2.4 fold in p,p-DDE (0.5µM) and aldrin (1µM) treated HUVECs respectively. Based on the findings, it may be concluded that OCPs (DDE;0.5µM & aldrin;1µM) mediated increased CYP1A1 expression in endothelial cells is associated with the increase in ROS production. In endothelial cells increase in ROS production might be associated with increase in ACE gene expression which represents a common pathway for several factors that are able to activate endothelial cells and hence caused endothelial dysfunction.
2 Sun Q, Hong X, Wold LE. Cardiovascular effects of ambient particulate air pollution exposure. Circulation. 2010;121:2755–2765.