title: EGCG protects endothelial cells against PCB 126-induced inflammation through inhibition of AhR and induction of Nrf2-regulated genes.
abstract: Tea flavonoids such as epigallocatechin gallate (EGCG) protect against vascular diseases such as atherosclerosis via their antioxidant and anti-inflammatory functions. Persistent and widespread environmental pollutants, including polychlorinated biphenyls (PCB), can induce oxidative stress and inflammation in vascular endothelial cells. Even though PCBs are no longer produced, they are still detected in human blood and tissues and thus considered a risk for vascular dysfunction. We hypothesized that EGCG can protect endothelial cells against PCB-induced cell damage via its antioxidant and anti-inflammatory properties. To test this hypothesis, primary vascular endothelial cells were pretreated with EGCG, followed by exposure to the coplanar PCB 126. Exposure to PCB 126 significantly increased cytochrome P450 1A1 (Cyp1A1) mRNA and protein expression and superoxide production, events which were significantly attenuated following pretreatment with EGCG. Similarly, EGCG also reduced DNA binding of NF-κB and downstream expression of inflammatory markers such as monocyte chemotactic protein-1 (MCP-1) and vascular cell adhesion protein-1 (VCAM-1) after PCB exposure. Furthermore, EGCG decreased endogenous or base-line levels of Cyp1A1, MCP-1 and VCAM-1 in endothelial cells. Most of all, treatment of EGCG upregulated expression of NF-E2-related factor 2 (Nrf2)-controlled antioxidant genes, including glutathione S transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), in a dose-dependent manner. In contrast, silencing of Nrf2 increased Cyp1A1, MCP-1 and VCAM-1 and decreased GST and NQO1 expression, respectively. These data suggest that EGCG can inhibit AhR regulated genes and induce Nrf2-regulated antioxidant enzymes, thus providing protection against PCB-induced inflammatory responses in endothelial cells.
authors.affiliation: Superfund Research Program, University of Kentucky, Lexington, KY 40536-0200, USA.
authors.forename: Sung Gu
authors.initials: SG
authors.lastname: Han
authors.forename: Seong-Su
authors.initials: SS
authors.lastname: Han
authors.forename: Michal
authors.initials: M
authors.lastname: Toborek
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hennig
mesh_terms: D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D019610:Cytoprotection; D042783:Endothelial Cells / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects*; D005982:Glutathione Transferase / Q000235:genetics; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013552:Swine; D019010:Vascular Cell Adhesion Molecule-1 / Q000235:genetics
chemical_list: D018932:Chemokine CCL2; D051267:NF-E2-Related Factor 2; D016328:NF-kappa B; D018336:Receptors, Aryl Hydrocarbon; D019010:Vascular Cell Adhesion Molecule-1; D002392:Catechin; C045651:epigallocatechin gallate; D011078:Polychlorinated Biphenyls; D019363:Cytochrome P-450 CYP1A1; D016660:NAD(P)H Dehydrogenase (Quinone); D005982:Glutathione Transferase; C023035:3,4,5,3',4'-pentachlorobiphenyl