Paraquat induces irreversible actin cytoskeleton disruption in cultured human lung cells

The herbicide paraquat (PQ) induces the selective necrosis of type I and type II alveolar pneumocytes. We investigated the effect of PQ on human lung A549 cells to determine the possible role of cytoskeleton in lung cytotoxicity. At 80 mumol/L PQ, a concentration that did not affect cell viability, the organization of actin cytoskeleton network depended on incubation time with the herbicide. Microfilaments appeared less numerous in 30% of the cells treated for 1 h. After 24 h, all the treated cells displayed only short filaments in the periphery. The effect of PQ on actin cytoskeleton was irreversible. Moreover, no modification of microtubule network was observed in PQ-treated cells. Next, we studied the effect of PQ on Chang Liver, an epithelial cell line from human liver. These cells appeared less sensitive to the herbicide than A549, and no cytoskeletal alteration was observed. To verify whether actin filament modifications in A549 cells were related to intracellular alterations of ATP concentrations, nucleotide levels during incubation with PQ were determined. The intracellular levels of ATP were not different in control and treated cells. Our results indicate that PQ induces specifically an irreversible actin filament disorganization on A549 cells and that the observed effect is independent of intracellular concentration of ATP.