Lead exposure raises superoxide and hydrogen peroxide in human endothelial and vascular smooth muscle cells.
BACKGROUND
Chronic lead exposure causes hypertension and cardiovascular disease, which are associated with, and, in part, due to oxidative stress. While occurrence of oxidative stress in lead-exposed animals and cultured endothelial cells has been well-established, direct and specific evidence on the type of the reactive oxygen species (ROS) produced by lead-exposed vascular cells is lacking and was investigated.


METHODS
Human coronary endothelial (EC) and vascular smooth muscle cells (VSMC) were incubated in appropriate culture media in the presence of either 1 ppm or 10 ppm lead acetate or sodium acetate (control) for 1 to 30 minutes or 60 hours. Productions of superoxide and hydrogen peroxide in the cell populations were determined by flow cytometry using hydroethidine and dihydrorhodamine, respectively. Data from a minimum of 10,000 cells were collected and analyzed using Cell Quest software. In addition, Cu Zn superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), and NAD(P)H oxidase (gp91phox) were measured.


RESULTS
Short-term lead exposure resulted in a significant rise in both superoxide and hydrogen peroxide production by both EC and VSMC. After long-term exposure, detectable superoxide levels fell to near normal level, while hydrogen peroxide production remained high. This was associated with up-regulations of gp91phox, elevation of superoxide dismutase, reduction of VSMC catalase, and no change in GPX levels. Together, these events can account for the observed decline in superoxide and the rise in hydrogen peroxide following long-term lead exposure.


CONCLUSIONS
Lead exposure promotes generation of superoxide and hydrogen peroxide in human EC and VSMC. This phenomenon can potentially contribute to the pathogenesis of the lead-associated hypertension and cardiovascular disease, and points to the potential benefit of lowering lead burden in the exposed populations.
Ni
Zhenmin
Z
Division of Nephrology and Hypertension, University of California, Irvine, Irvine, California, USA.
Hou
Stephen
S
Barton
Cyril H
CH
Vaziri
Nosratola D
ND
D002374:Catalase / Q000378:metabolism; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007854:Lead / Q000633:toxicity*; D008562:Membrane Glycoproteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
D008562:Membrane Glycoproteins; D013481:Superoxides; D007854:Lead; D006861:Hydrogen Peroxide; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases