US EPA

2304911 

Journal Article 

Abstract 

Methylmercury (MeHg) cytotoxicity and effects on cellular distribution and protein expression of paraoxonase-2 (PON2), thioredoxin reductase-1 (TrxR1), and glutathione peroxidase-1 (GPx1) in human coronary artery endothelial cells (HCAEC) 

Coughlan, M; Kearns, N; Skof, J; Jin, X( 

2008 

Yes 

Free Radical Biology and Medicine
ISSN: 0891-5849
EISSN: 1873-4596 

45 

Suppl. 

S145-S146 

English 

WOS:000260867900411 

http://www.sciencedirect.com/science/article/pii/S0891584908006321
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is part of a larger document 3452652 SFRBM's 15th Annual Meeting: Program and Abstracts

Hypothesis: Epidemiological studies revealed that high MeHg body burdens were associated with increased risk of cardiovascular diseases. However, the underlying mechanisms remain unclear. We hypothesize that MeHg may contribute to the pathogenesis of cardiovascular disease by attacking antioxidant enzymes leading to endothelial dysfunction. This study examined the effects of MeHg on cell viability and morphology, and distribution and expression of PON2, TrxR1, and GPx1 in cultured HCAEC.

Methods: HCAEC were treated with 0-250 µM MeHg for 24 h. Cell viability was determined by MTT assay. Cellular distributions of PON2, TrxR1, and GPx1 were examined in cells treated with 7.5 µM MeHg (LD50) for 3 or 6 hours using immunofluorescent staining. Protein expressions were determined by Western blots.

Results: MeHg decreased cell viability in a dose-dependent fashion. MeHg at LD50 altered cell morphology even at 3 h after dosing, with loss of cell connection and attachment, and transformation from protruding to more round shapes. in the control cells, PON2 was visualized as microtubule-like filaments covering the whole cytoplasmic region, but diffused in the nuclei. TrxR1 was diffused in both the cytoplasm and nuclei, while GPx1 was associated with lysosome-like granular structures in the cytoplasm. MeHg increased the intensity and granularity of PON2 staining in the nuclei, and disrupted filamentous staining in the cytoplasm. MeHg induced a decreased and punctuated cytoplasmic staining and an increased nuclear staining of TrxR1, and decreased or abolished cytoplasmic staining of GPx1. These effects of MeHg intensified with duration of exposure. MeHg markedly increased PON2 protein expression in a time-dependent fashion, slightly increased GPx1 protein expression only at 3 h after treatment, but had not effects on TrxR1 protein expression.

Conclusions: These results suggest that cytoskeleton proteins are primary targets of MeHg, and GPx1 may be more sensitive than PON2 and TrxR1 to MeHg-induced structural damage. The compensatory increase in PON2 protein expression along with the nuclear translocation of TrxR1 in MeHg-treated cells implies an important role of these antioxidant enzymes in regulating stress response, protecting structural integrity and function, and repairing oxidative damage in HCAEC. 

Society for Free Radical Biology and Medicine 15th Annual Meeting 

Indianapolis, IN 

November 19-23, 2008