In Vitro Immune Toxicity of Depleted Uranium: Effects on Murine Macrophages, CD4 ⁺ T Cells, and Gene Expression Profiles

Abstract

Depleted uranium (DU) is a by-product of the uranium enrichment process and shares chemical properties with natural and enriched uranium. To investigate the toxic effects of environmental DU exposure on the immune system, we examined the influences of DU (in the form of uranyl nitrate) on viability and immune function as well as cytokine gene expression in murine peritoneal macrophages and splenic CD4+ T cells. Macrophages and CD4+ T cells were exposed to various concentrations of DU, and cell death via apoptosis and necrosis was analyzed using annexin-V/propidium iodide assay. DU cytotoxicity in both cell types was concentration dependent, with macrophage apoptosis and necrosis occurring within 24 hr at 100 μM DU exposure, whereas CD4+ T cells underwent cell death at 500 μM DU exposure. Noncytotoxic concentrations for macrophages and CD4+ T cells were determined as 50 and 100 μM, respectively. Lymphoproliferation analysis indicated that macrophage accessory cell function was altered with 200 μM DU after exposure times as short as 2 hr. Microarray and real-time reverse-transcriptase polymerase chain reaction analyses revealed that DU alters gene expression patterns in both cell types. The most differentially expressed genes were related to signal transduction, such as c-jun, NF-κ Bp65, neurotrophic factors (e.g., Mdk), chemokine and chemokine receptors (e.g., TECK/CCL25), and interleukins such as IL-10 and IL-5, indicating a possible involvement of DU in cancer development, autoimmune diseases, and T helper 2 polarization of T cells. The results are a first step in identifying molecular targets for the toxicity of DU and the elucidation of the molecular mechanisms for the immune modulation ability of DU.

In vitro immune toxicity of polybrominated diphenyl ethers on murine peritoneal macrophages: Apoptosis and immune cell dysfunction

“…Mouse peritoneal elicited macrophages and splenic CD4 + T cells were prepared exactly according to the method described by Wan et al (2006). The resulting macrophage and T cell purities were all >95%, as determined by CD11b and CD4 staining analyses.…”

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

“…The cytotoxicity of DU in studies performed in vitro with different cell lines and types varies from doses of 200 to 800 µM (Mirto et al 1999;Carrière et al 2004;Wan et al 2006). NRK-52 E cells undergo death by apoptosis after exposure to low doses of DU.…”

“…In vivo studies, performed in rats and mice, demonstrated that DU alters gene expression, particularly of genes involved in apoptosis (Taulan et al 2004;Monleau et al 2006;Wan et al 2006). In human renal cells, the expression of genes related to apoptosis was also reported to be altered after exposure to DU (Prat et al 2005).…”

Medical Consequences of Depleted Uranium Use in Northern Kosovo

“…Epidemiological studies and toxicological tests on laboratory animals point to it as being immunotoxic [Wan et al, 2006], teratogenic [Arfsten et al, 2001], neurotoxic [Briner and Murray, 2005], with carcinogenic and leukemogenic potential [Miller et al, 2005]. A 2005 report by epidemiologists concluded: "the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU."…”