Initiation of Apoptosis by Actin Cytoskeletal Derangement in Human Airway Epithelial Cells

Changes in epithelial cell shape can lead to cell death and detachment. Actin filaments are cleaved during apoptosis, but whether disruption in the actin cytoskeletal network, as one manifestation of cell shape change, can itself induce apoptosis is not known. We tested this hypothesis in the airway epithelial cell line 1HAEo(-) and in primary airway epithelial cells by preventing actin filament elongation with cytochalasin D or by aggregating actin filaments with jasplakinolide. Disruption of actin filament integrity promptly induced apoptosis in adherent epithelial cells within 5 h. Jasplakinolide-induced apoptosis did not disrupt focal adhesions, whereas cytochalasin D-induced apoptosis decreased focal adhesion protein expression and occurred despite ligation of the fibronectin receptor. Death induction was abrogated by the caspase inhibitors z-VAD-fmk and Ac-DEVD-cho but not by blocking the Fas (CD95) receptor. Whereas cytochalasin D--induced apoptosis was associated with cleavage of pro-caspase-8, jasplakinolide-induced apoptosis was not. Both agents induced formation of a death-inducing signaling complex. These data demonstrate that disruption of actin filament integrity with either cytochalasin D or jasplakinolide induces apoptosis in airway epithelial cells but by different mechanisms, and suggest that actin may be an early modulator of apoptotic commitment.