PCB-induced endothelial cell dysfunction: role of poly(ADP-ribose) polymerase - PubMed (original) (raw)

PCB-induced endothelial cell dysfunction: role of poly(ADP-ribose) polymerase

Simon G Helyar et al. Biochem Pharmacol. 2009.

Abstract

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants implicated in the development of pro-inflammatory events critical in the pathology of atherosclerosis and cardiovascular disease. PCB exposure of endothelial cells results in increased cellular oxidative stress, activation of stress and inflammatory pathways leading to increased expression of cytokines and adhesion molecules and ultimately cell death, all of which can lead to development of atherosclerosis. To date no studies have been performed to examine the direct effects of PCB exposure on the vasculature relaxant response which if impaired may predispose individuals to hypertension, an additional risk factor for atherosclerosis. Overactivation of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP) following oxidative/nitrosative stress in endothelial cells and subsequent depletion of NADPH has been identified as a central mediator of cellular dysfunction. The aim therefore was to investigate whether 2,2',4,6,6'-pentachlorobiphenyl (PCB 104) directly causes endothelial cell dysfunction via increased oxidative stress and subsequent overactivation of PARP. Exposure of ex vivo rat aortic rings to PCB 104 impaired the acetylcholine-mediated relaxant response, an effect that was dependent on both concentration and exposure time. In vitro exposure of mouse endothelial cells to PCB 104 resulted in increased cellular oxidative stress through activation of the cytochrome p450 enzyme CYP1A1 with subsequent overactivation of PARP and NADPH depletion. Pharmacological inhibition of CYP1A1 or PARP protected against the PCB 104-mediated endothelial cell dysfunction. In conclusion, the environmental contaminants, PCBs, can activate PARP directly impairing endothelial cell function that may predispose exposed individuals to development of hypertension and cardiovascular disease.

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Figures

Fig. 1

Structure of 2,2′,4,6,6′-pentachlorobiphenyl (PCB 104), an example of a highly ortho-chlorinated nonplanar PCB.

Fig. 2

Exposure of ex vivo aortic rings to PCB 104 for 4 h (A) or 6 h (B) dose-dependently impairs the acetylcholine-relaxant response. Thoracic aortic rings obtained from male Sprague–Dawley rats were exposed to 1, 3, 10 or 20 μM PCB 104 for 2, 4 or 6 h. Following PCB exposure acetylcholine-induced endothelium-dependent relaxation was determined. Data is expressed as mean ± SEM from 6 animals; *p < 0.05 and **p < 0.01 vs. untreated rings.

Fig. 3

In vitro exposure of endothelial cells to PCB 104 dose- and time-dependently increased cellular levels of oxidative stress (A), CYP1A1 activity (B), and PARP activity (C) while depleting NADPH levels (D). Mouse endothelial cells were exposed to PCB 104 (1, 3, 10 or 20 μM) for 2, 4 or 6 h prior to the measurements being taken. Data is expressed as mean ± SEM from 4 separate experiments with 3–6 replicates per experiment; *p < 0.01 vs. untreated cells.

Fig. 4

PCB 104-mediated impairment of endothelium-dependent aortic ring relaxation is prevented by pharmacological inhibition of CYP1A1 or PARP. Exposure of thoracic aortic rings to 10 μM PCB 104 for 4 h significantly impaired acetylcholine-induced endothelium-dependent relaxation, an effect prevented by simultaneous incubation of the rings with the CYP 1A1 inhibitor α-naphthoflavone (NP, 0.3 μM) or the PARP inhibitor PJ-34 (3 μM). Data is expressed as mean ± SEM from 6 animals; **p < 0.01 vs. untreated rings and ††p < 0.01 vs. PCB 104 treated rings.

Fig. 5

Effect of CYP1A1 and PARP inhibition on the PCB 104-mediated increase in endothelial cell oxidative stress (A), CYP1A1 activity (B), PARP activity (C) and NADPH depletion (D). Inhibition of CYP1A1 with α-naphthoflavone (0.3 μM) prevents the increase in oxidative stress, CYP1A1 and PARP activity, plus the NADPH depletion observed following 4 h exposure to PCB 104 (10 μM). Inhibition of PARP either pharmacologically with PJ-34 (3 μM) or via gene knockout had no effect on PCB 104-mediated increase in oxidative stress or CYP1A1 activity but did inhibit the increase in PARP activity and NADPH depletion. Data is expressed as mean ± SEM from 4 separate experiments with 3–6 replicates per experiment; *p < 0.05, **p < 0.01 vs. untreated cells and †p < 0.01 vs. PCB 104 treated cells.

Fig. 6

Exposure of endothelial cells to PCB 104 dose-dependently reduced cell viability, an effect attenuated by inhibition of CYP1A1 and PARP either pharmacologically or through gene deletion. Data is expressed as mean ± SEM from 4 separate experiments with 3–6 replicates per experiment; *p < 0.05, **p < 0.01 vs. untreated cells and †p < 0.01 vs. PCB 104 treated cells.

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PCB-induced endothelial cell dysfunction: role of poly(ADP-ribose) polymerase - PubMed (original) (raw)