Direct speciation analysis of arsenic in sub-cellular compartments using micro-X-ray absorption spectroscopy.
Identification of arsenic chemical species at a sub-cellular level is a key to understanding the mechanisms involved in arsenic toxicology and antitumor pharmacology. When performed with a microbeam, X-ray absorption near-edge structure (mu-XANES) enables the direct speciation analysis of arsenic in sub-cellular compartments avoiding cell fractionation and other preparation steps that might modify the chemical species. This methodology couples tracking of cellular organelles in a single cell by confocal or epifluorescence microscopy with local analysis of chemical species by mu-XANES. Here we report the results obtained with a mu-XANES experimental setup based on Kirkpatrick-Baez X-ray focusing optics that maintains high flux of incoming radiation (>10(11)ph/s) at micrometric spatial resolution (1.5 x 4.0 microm(2)). This original experimental setup enabled the direct speciation analysis of arsenic in sub-cellular organelles with a 10(-15) g detection limit. mu-XANES shows that inorganic arsenite, As(OH)3, is the main form of arsenic in the cytosol, nucleus, and mitochondrial network of cultured cancer cells exposed to As2O3. On the other hand, a predominance of As(III) species is observed in HepG2 cells exposed to As(OH)3 with, in some cases, oxidation to a pentavalent form in nuclear structures of HepG2 cells. The observation of intra-nuclear mixed redox states suggests an inter-individual variability in a cell population that can only be evidenced with direct sub-cellular speciation analysis.
Cellular Chemical Imaging and Speciation Group, CNAB, CNRS, University of Bordeaux, 33175 Gradignan, France.
Thomas
T
Bacquart
Guillaume
G
Devès
Richard
R
Ortega
D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D001151:Arsenic / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000737:chemistry / Q000378:metabolism*; D045744:Cell Line, Tumor; D056945:Hep G2 Cells; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism; D010087:Oxides / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D056928:X-Ray Absorption Spectroscopy
D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; D001151:Arsenic; D000077237:Arsenic Trioxide