Difference in uptake and toxicity of trivalent and pentavalent inorganic arsenic in rat heart microvessel endothelial cells

Abstract

Intake of inorganic arsenic is known to cause vascular diseases as well as skin lesions and cancer in humans. We investigated the differences in cytotoxicity, uptake rate of arsenic, and gene expression of antioxidative enzymes between arsenite (As(3+))- and arsenate (As(5+))-exposed rat heart microvessel endothelial cells. As(3+) was more cytotoxic than As(5+), and LC(50) values were calculated to be 36 and 220 micro M, respectively. As(3+) (1-25 micro M) increased mRNA levels of antioxidant enzymes such as heme oxygenase-1 (HO-1), thioredoxin peroxidase 2, NADPH dehydrogenase, and glutathione S-transferase P subunit. HO-1 mRNA levels showed the most remarkable increase in response to As(3+). cDNA microarray analysis indicated that there was no prominent difference in arsenic-induced transcriptional changes between As(3+)- and As(5+)-exposed cells, when the cells were exposed to one-fourth the LC(50) concentration of arsenic (9 and 55 micro M for As(3+) and As(5+), respectively). N-acetyl- l-cysteine (NAC) reduced both the cytotoxicity of inorganic arsenic and the HO-1 mRNA level, and buthionine sulfoximine enhanced cytotoxicity of inorganic arsenic. As(3+) was taken up by the endothelial cells 6-7 times faster than As(5+), and the presence of NAC in the culture medium did not change the uptake rate of As(3+). These results suggest that the effects of NAC on arsenic-induced cytotoxicity and oxidative stress were due to the antioxidative role of non-protein thiols and not to chelation of arsenic in the culture medium. The difference in cellular uptake of arsenic between As(3+) and As(5+) appeared not to be due to the ionic charge on arsenic (at physiological pH, trivalent arsenic is neutral whereas pentavalent arsenic is negatively charged). These results suggest that the higher toxicity of As(3+) compared with that of As(5+) is probably due to the faster uptake of As(3+) by endothelial cells, and inorganic arsenic exerts its toxicity at least in part via intracellular oxidative stress.

Analysis of genomic dose‐response information on arsenic to inform key events in a mode of action for carcinogenicity

“…DOI 10.1002/em ment of NHEK cells with arsenate for 2 weeks [Rea et al, 2003]. Studies conducted with primary cell lines in animals, including rabbit renal cortical slices [Parrish et al, 1999], rat heart endothelial cells [Hirano et al, 2003;Sturlan et al, 2003], rat cardiomyocytes [Wang and Proud, 1997], rat lung epithelial cells [Wijeweera et al, 2001], rat myoblasts, [Shimizu et al, 1998], and rat neuronal cells [Namgung and Xia, 2001], provided results that were consistent with those observed in human cells. Although not all the same genes were measured in all studies, the number of genes representative of the same functional categories that were induced increased with increasing concentrations.…”

Cytotoxic and antiangiogenic activity of AW464 (NSC 706704), a novel thioredoxin inhibitor: an in vitro study

“…The sensitivity of microvessel endothelial cells, HUMMEC, was important as angiogenesis involves the proliferation of microvessel endothelial cells. Inorganic arsenic, another compound that can target the thioredoxin system, has also been shown to be toxic to rat heart microvessel endothelial cells in its trivalent form (Hirano et al, 2003) and inhibits endothelial cell proliferation in vitro and angiogenesis in vivo (Don et al, 2003). Both fibroblast cell lines, NHDF and MRCV, are resistant to the IC 50 dose of AW464.…”

Glutathione protects cells against arsenite-induced toxicity

“…To determine if other antioxidants could substitute for GSH, we rescued GCS-2 cells in the presence of thiol antioxidant NAC and examined arsenite-induced cytotoxicity. Because NAC is known not to complex with arsenite [27], we cultured GCS-2 cells in the presence of NAC for 48 h and divided them into two groups: one group was grown for an additional 24 h in NAC and treated with arsenite for 21 h. In a parallel experiment, NAC was withdrawn from GCS-2 cells for 24 h and treated with arsenite in the absence of NAC for 21 h. GCS-2 cells treated with arsenite in the absence of NAC showed decreased viability rates similar to GCS-2 cells deprived of GSH, while cells exposed to arsenite in the presence of NAC exhibited intermediate survival rates (Fig. 1).…”