Persistence of DNA damage following exposure of human bladder cells to chronic monomethylarsonous acid

Abstract

Malignant transformation was demonstrated in UROtsa cells following 52 wk exposure to 50 nM monomethylarsonous acid (MMA III ); the result was the malignantly transformed cell line, URO-MSC. URO-MSC cells were used to study the induction of DNA damage and the alteration of DNA repair enzymes in both the presence of MMA III [URO-MSC(+)] and after subsequent removal of MMA III [URO-MSC(-)] following chronic, low-level exposure. In the presence of MMA III , URO-MSC(+) cells demonstrated a sustained increase in DNA damage following 12 wk exposure; in particular, a significant increase in DNA single strand breaks at 12 wk exposure consistently elevated through 52 wk. The persistence of DNA damage in URO-MSC cells was assessed after a 2 wk removal of MMA III . URO-MSC(-) cells demonstrated a decrease in DNA damage compared to URO-MSC(+); however, DNA damage in URO-MSC(-) remained significantly elevated when compared to untreated UROtsa and increased in a time-dependent manner. Reactive oxygen species (ROS) were demonstrated to be a critical component in the generation of DNA damage determined through the incubation of ROS scavengers with URO-MSC cells. Poly (ADP-ribose) polymerase (PARP) is a key repair enzyme in DNA single strand break repair. URO-MSC(+) resulted in a slight increase in PARP activity after 36 wk MMA III exposure, suggesting the presence of MMA III is inhibiting the increase in PARP activity. In support, PARP activity in URO-MSC(-) increased significantly, coinciding with a subsequent decrease in DNA damage demonstrated in URO-MSC(-) compared to URO-MSC(+). These data demonstrate that chronic, low-level exposure of UROtsa cells to 50 nM MMA III results in: the induction of DNA damage that remains elevated upon removal of MMA III ; increased levels of ROS that play a role in MMA III induced-DNA damage; and decreased PARP activity in the presence of MMA III .

Evaluation of gene expression changes in human primary uroepithelial cells following 24‐Hr exposures to inorganic arsenic and its methylated metabolites

“…Activation of NRF2 protects these cells from toxicity due to As III and MMA III exposure [Wang et al, 2007a]. DNA strand breaks persisted up to 52 weeks in transformed UROTsa cells in the presence of a single dose of 50 nM MMA III ; PARP-1 activity increased significantly in the absence of MMA III [Wnek et al, 2009]. More recently, in transformed UROTsa cells exposed at 50 nM As III and MMA III , sustained production of inflammatory cytokines IL-1, IL-6, IL-8, and TNF was observed as well as an increase in NF-jB, c-jun, p38MAPK protein, and ERK [Escudero-Lourdes et al, 2010].…”

Intracellular Arsenic Speciation and Quantification in Human Urothelial and Hepatic Cells

“…is needed, as the genotoxic effect of arsenic metabolites is not only dependent on its oxidative state but also on the state of methylation Dopp et al, 2010b). Wnek et al (2009) reported that in UROtsa cells DNA damage caused by MMA(III) is not only a phenomenon of acute treatment but also an important effect in chronic, low-level exposure for 12 -52 weeks.…”

“…While ROS physiologically occur during cellular respiration or aerobic metabolism they also can result from exposure to oxidants. Already low levels of As(III) and MMA(III) are reported to generate ROS and therefore cause oxidative stress (Eblin et al, 2008;Wnek et al, 2009). These highly reactive radicals are discussed to exhibit their toxicity via induction of DNA damage, formation of DNA adducts, or alteration of DNA methylation and histone modifications , and finally leading to carcinogenesis (Kitchin & Ahmad, 2003;Huang et al, 2004).…”

“…One key mechanism is the inactivation of poly (ADP-ribose) polymerase (PARP) already at extremely low, environmentally relevant concentrations (Hartwig et al, 2002;Hartwig et al, 2003). Wnek et al (2009) reported that the relative PARP activity was significantly reduced during chronic exposure of immortalised human urothelial cells (UROtsa) to 50 nM MMA(III). After removal of MMA(III) PARP activity increased again.…”

Association of glutathione S-transferase Ω 1-1 polymorphisms (A140D and E208K) with the expression of interleukin-8 (IL-8), transforming growth factor beta (TGF-β), and apoptotic protease-activating factor 1 (Apaf-1) in humans chronically exposed to arsenic in drinking water

“…The mechanisms associated with these diseases have not been fully elucidated; however, it is a fact that exposure to iAs induces cellular oxidative stress in the cell through the generation of reactive oxygen species (ROS; Kumagai and Sumi 2007;Wnek et al 2009). These ROS in turn interact directly with biomolecules, causing modiWcations in gene expression by means of activating cell signaling pathways that involve activator protein-1 (AP-1), the nuclear factorkappa betta (NF-k ), the p53 protein, and mitogen-activated kinase proteins (MAPKs; Shi et al 2004), which play an important role in the proliferation, cell diVerentiation, and maintenance of genome integrity (Huang et al 2004), as well as in the inXammatory response and the regulation of cellular apoptosis.…”