Cigarette smoke and asbestos activate poly-ADP-ribose polymerase in alveolar epithelial cells.
BACKGROUND
Cigarette smoke augments asbestos-induced bronchogenic carcinoma in a synergistic manner by mechanisms that are not established. One important mechanism may involve alveolar epithelial cell (AEC) injury resulting from oxidant-induced DNA damage that subsequently activates poly (ADP-ribose) polymerase (PARP), an enzyme involved in DNA repair that can deplete cellular energy stores. We previously showed that whole aqueous cigarette smoke extracts (CSE) augment amosite asbestos-induced DNA damage and cytotoxicity to cultured AEC in part by generating iron-induced free radicals. We hypothesized that CSE increase asbestos-induced AEC injury by triggering PARP activation resulting from DNA damage caused by iron-induced free radicals.


METHODS
Aqueous CSE were prepared fresh on the day of each experiment. PARP activity in WI-26 (a type I-like cell line) and A549 (a type II-like cell line) cells was assessed by the uptake of labeled NAD over 4 hours and confirmed on the basis of the reduction of PARP levels in the presence of a PARP inhibitor, 3-aminobenzamide (3-ABA). Cell survival was assessed by trypan blue dye exclusion.


RESULTS
Hydrogen peroxide (H2O2; 1-250 microM), CSE (0.4-10 vol%), and amosite asbestos (5-250 micrograms/cm2) each caused PARP activation in WI-26 and A549 cells. The combination of asbestos (5 micrograms/cm2) and CSE (0.04-10%) induced WI-26 and A549 cell PARP activation without evidence of synergism. 3-ABA significantly attenuated WI-26 and A549 cell PARP activity and cell death after exposure to H2O2, CSE, and asbestos. Phytic acid, an iron chelator, catalase, and superoxide dismutase each decreased WI-26 cell PARP activation caused by asbestos and CSE.


CONCLUSIONS
CSE and asbestos induced PARP activation in cultured AEC in a nonsynergistic manner. These data provide further support that asbestos and cigarette smoke are genotoxic to relevant lung target cells and that iron-induced free radicals in part cause these effects.
Kamp
D W
DW
Department of Medicine, Divisions of Pulmonary and Critical Care Medicine and Hematology-Oncology, Veterans Affairs Chicago Health Care System-Lakeside Division and Northwestern University Medical School, Chicago, Ill., USA. d-kamp@nwu.edu
Srinivasan
M
M
Weitzman
S A
SA
D000975:Antioxidants / Q000494:pharmacology; D017639:Asbestos, Amosite / Q000633:toxicity*; D002283:Carcinoma, Bronchogenic / Q000209:etiology; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000201:enzymology*; D012907:Smoking / Q000009:adverse effects / Q000378:metabolism*
D000975:Antioxidants; D017639:Asbestos, Amosite; D006861:Hydrogen Peroxide; D011065:Poly(ADP-ribose) Polymerases