Ultrastructural and metabolic changes in osteoblasts exposed to uranyl nitrate.
Exposure to uranium is an occupational hazard to workers who continually handle uranium and an environmental risk to the population at large. Since the cellular and molecular pathways of uranium toxicity in osteoblast cells are still unknown, the aim of the present work was to evaluate the adverse effects of uranyl nitrate (UN) on osteoblasts both in vivo and in vitro. Herein we studied the osteoblastic ultrastructural changes induced by UN in vivo and analyzed cell proliferation, generation of reactive oxygen species (ROS), apoptosis, and alkaline phosphatase (APh) activity in osteoblasts exposed to various UN concentrations (0.1, 1, 10, and 100 microM) in vitro. Cell proliferation was quantified by means of the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, ROS was determined using the nitro blue tetrazolium test, apoptosis was morphologically determined using Hoechst 3332 and APh activity was assayed spectrophotometrically. Electron microscopy revealed that the ultrastructure of active and inactive osteoblasts exposed to uranium presented cytoplasmic and nuclear alterations. In vitro, 1-100 microM UN failed to modify cell proliferation ratio and to induce apoptosis. ROS generation increased in a dose-dependent manner in all tested doses. APh activity was found to decrease in 1-100 microM UN-treated cells vs. controls. Our results show that UN modifies osteoblast cell metabolism by increasing ROS generation and reducing APh activity, suggesting that ROS may play a more complex role in cell physiology than simply causing oxidative damage.
Tasat
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Escuela de Ciencia y Tecnología, Universidad Nacional de San Martín, M de Irygoyen 3100, San Martín (1650), Pcia de Bs As, Argentina. dtasat@gmail.com
Orona
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Mandalunis
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Cabrini
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Ubios
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D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D018870:Endoplasmic Reticulum, Rough / Q000648:ultrastructure; D005260:Female; D033042:Fetal Research; D006801:Humans; D007274:Injections, Intraperitoneal; D008297:Male; D008854:Microscopy, Electron; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000008:administration & dosage / Q000494:pharmacology / Q000633:toxicity; D013977:Tibia / Q000166:cytology / Q000378:metabolism / Q000648:ultrastructure; D013997:Time Factors; D014502:Uranyl Nitrate / Q000008:administration & dosage / Q000494:pharmacology* / Q000633:toxicity
D017382:Reactive Oxygen Species; D014502:Uranyl Nitrate; D000469:Alkaline Phosphatase; D013755:Tetradecanoylphorbol Acetate