PATTERNS OF 8-HYDROXYDEOXYGUANOSINE FORMATION IN DNA AND INDICATIONS OF OXIDATIVE STRESS IN RAT AND HUMAN PLEURAL MESOTHELIAL CELLS AFTER EXPOSURE TO CROCIDOLITE ASBESTOS

Oxidative damage is a proposed mechanism of asbestos-induced carcinoge nesis, but the detection of oxidative DNA lesions in target cells of a sbestos-induced mesothelioma has not been examined. In studies here, D NA was isolated from both rat pleural mesothelial (RPM) cells and a hu man mesothelial cell line (MET5A) after exposure in vitro to crocidoli te asbestos at various concentrations, DNA was then examined for forma tion of 8-hydroxydeoxyguanosine (8-OHdG) at 24, 48 and 72 h using HPLC with electrochemical detection, In addition, steady-state mRNA levels of manganese-containing superoxide dismutase (MnSOD) were assessed as an indication of oxidative stress, Whereas RPM cells showed dose-depe ndent and significant increases in 8-OHdG formation in response to cro cidolite asbestos or iron-chelated crocidolite fibers (but not after e xposure to glass beads), MET5A cells showed decreases in 8-OHdG, Both cell types exhibited elevations in message levels of MnSOD. In compari son with human MET5A cells, RPM cells exhibited increased cytotoxicity and apoptosis in response to asbestos, as documented by cell viabilit y assays and flow cytometry analysis using propidium iodide, Results i n RPM cells indicate that asbestos causes oxidative damage that may re sult in potentially mutagenic lesions in DNA and/or apoptosis, despite compensatory increases in expression of an antioxidant enzyme.