Uranium Induces Apoptosis and Is Genotoxic to Normal Rat Kidney (NRK-52E) Proximal Cells

Abstract

Uranium (U) is a heavy metal used in the nuclear industry and for military applications. U compounds are toxic. Their toxicity is mediated either by their radioactivity or their chemical properties. Mammalian kidneys and bones are the main organs affected by U toxicity. Although the most characteristic response to U exposure is renal dysfunction, little information is available on the mechanisms of its toxicity at the molecular level. This report studied the genotoxicity of U. Apoptosis induction in normal rat kidney (NRK-52(E)) proximal cells was investigated as a function of exposure time or concentrations (0-800microM). In parallel, DNA damage was evaluated by several methods. In order to distinguish between the intrinsic and the extrinsic pathways of apoptosis, caspases-8, -9, -10 assays were conducted and the mitochondrial membrane potential was measured. Three methods were selected for their complementarities in the detection of genetic lesions. The comet assay was used for the detection of primary lesions of DNA. gamma-H2AX immunostaining was achieved to detect DNA double-strand breaks. The micronucleus assay was used to detect chromosomic breaks or losses. DNA damage and apoptosis were observed in a concentration-dependent manner. This study demonstrated that U is genotoxic from 300microM and induces caspase-dependent apoptosis cell death from 200microM mainly through the intrinsic pathway in NRK-52(E) cells. These results suggest that the DNA damage caused by U is reversible at low concentration (200-400microM) but becomes irreversible and leads to cell death for higher concentrations (500-800microM).

Données nouvelles sur la néphrotoxicité de l’uranium

“…Chez le rat, après exposition chronique (3 mois, 40 mg/kg) l'uranium induit une augmentation de marqueurs du stress oxydant (peroxydation lipidique et oxydation du glutathion (GSSG)) au niveau rénal (Linares et al, 2006). In vitro, sur des cellules rénales en culture, une augmentation de la production d'espèces réactives de l'oxygène est également observée et impliquerait une entrée des cellules en apoptose à partir de concentrations élevées (>600 µM) (Thiebault et al, 2007). Comme cela a été observé pour d'autres métaux, les perturbations de l'homéostasie redox sont donc susceptibles d'entraîner des phénomènes d'adaptation allant d'une induction de la réponse antioxydante à une mort cellulaire programmée (apoptose) afin de préserver le tissu environnant.…”

Cytogenetic biomonitoring of inhabitants of a large uranium mineralization area: the municipalities of Monte Alegre, Prainha, and Alenquer, in the State of Pará, Brazil

“…With high concentrations of DU, the cells underwent necrosis (Thiébault et al 2007). The MI of the populations of Monte Alegre, Prainha, and Alenquer did not present significant differences compared to the control population (P>0.05).…”

“…Thiébault et al (2007), using the comet assay, detected double-and single-strand breaks and/or labile sites on the DNA, after exposure of NRK-52 E cells to sublethal and lethal concentrations of DU. DNA lesions increased in direct proportion to the uranium concentration.…”

Apoptotic effects of satratoxin H is mediated through DNA double-stranded break in PC12 cells

“…That is, low concentrations of uranium induced small amount of DNA damage and cellular modifications, which can be efficiently repaired through adaptation responses, although some of these DNA damage might be misrepaired leading to apoptotic cell death (Thiebault et al, 2007). At higher concentrations, uranium induced strong cellular modifications and DNA damage producing apoptotic cell death (Thiebault et al, 2007). Previously we showed that satratoxin H induced ROS generation and the following phosphorylation of p38 MAPK (Nusuetrong et al, 2005(Nusuetrong et al, , 2008.…”

“…Our results are in accordance with a previous study about uranium. That is, low concentrations of uranium induced small amount of DNA damage and cellular modifications, which can be efficiently repaired through adaptation responses, although some of these DNA damage might be misrepaired leading to apoptotic cell death (Thiebault et al, 2007). At higher concentrations, uranium induced strong cellular modifications and DNA damage producing apoptotic cell death (Thiebault et al, 2007).…”