Methylmercury Retards the Repair of Wounded Monolayer of Human Brain Microvascular Endothelial Cells by Inhibiting Their Proliferation without Nonspecific Cell Damage

Abstract

Methylmercury (MeHg) is an environmental pollutant that causes severe neuropathy in the brain of exposed humans and animals. It is possible that MeHg induces functional damage of the brain microvessels and neuropathy occurs secondarily. Thus, the effects of MeHg on the maintenance of vascular endothelial cell monolayer were investigated using a culture system of human brain microvascular endothelial cells. MeHg did not damage the morphology of the monolayer; however, it retarded the repair of the wounded monolayer. The proliferation of endothelial cells was observed to be inhibited by MeHg when assessed by the cell number, [3 H]thymidine incorporation, and lactate dehydrogenase (LDH) leakage in sparsely growing cells. Cadmium also decreased the [ 3 H]thymidine incorporation but failed to decrease the cell number; inorganic mercury and lead did not exhibit any inhibitory effect under the same conditions. Considering these results together, it is suggested that MeHg exhibits toxicity in the brain microvessels when the endothelial monolayer is damaged. MeHg specifically inhibits the proliferation of endothelial cells during the repair process of the damaged monolayers. The present data support the hypothesis that the mechanism of MeHg-induced neuropathy in the brain includes changes in the microenvironment of the neurons caused by functional damage to the microvessels.

MARCKS is involved in methylmercury-induced decrease in cell viability and nitric oxide production in EA.hy926 cells

“…Treatment of cells with MeHg significantly and dose-dependently inhibited EA.hy926 cell migration in the wound healing assay and tube formation on the Matrigel. These observations are in agreement with a previous report using primary human endothelial cells [11, 12, 20, 21]. In the wound healing assay, we observed significant inhibition of migration at 0.3 µ M MeHg, which is a lower concentration than that which induced significant decrease in the cell viability assay, suggesting that the inhibition of migration may be one of the principal toxic actions of MeHg on EA.hy926 cells.…”

“…Significant decrease in cell viability was observed at concentrations higher than 1 µ M MeHg. The concentration of MeHg that caused significant decrease in cell viability was in accordance with that reported previously in neuroblastoma SH-SY5Y cells and primary human endothelial cells, such as brain microvascular endothelial cells and umbilical vein endothelial cells [11, 21, 37]. MeHg has been reported to elicit cell growth inhibition by interfering with the cell cycle process [19].…”

Resistance of human brain microvascular endothelial cells in culture to methylmercury: cell-density-dependent defense mechanisms

“…The expression of LAT-1 appears to be higher in sparse cells, because such cells require higher amounts of amino acids for their growth. However, sparse and dense cultures of the endothelial cells were equally resistant to methylmercury cytotoxicity (Hirooka et al, 2007).…”

“…It was found that methylmercury retards the repair of wounded endothelial cell monolayers by inhibiting cell proliferation (Hirooka et al, 2007), which is due to reduced expression of the fibroblast growth factor-2 (Hirooka et al, 2009). On the other hand, pericytes at a high cell density are resistant, whereas those at a low cell density are susceptible to methylmercury cytotoxicity (Hirooka et al, 2010).…”

The Cytotoxicity of Methylmercury in Human Microvascular Endothelial Cells and Pericytes in Culture

“…In this review, we describe the toxic * To whom correspondence should be addressed. e-mail: thirooka@rs.noda.tus.ac.jp 14,15) First, the toxic effects of methylmercury on the maintenance of an endothelial cell monolayer were investigated. Methylmercury did not damage the cells at high or low cell densities, but the organometal retarded repair of the wounded cell monolayer.…”