H₂O₂inhibits alveolar epithelial wound repair in vitro by induction of apoptosis

Abstract

Reactive oxygen species (ROS) are released into the alveolar space and contribute to alveolar epithelial damage in patients with acute lung injury. However, the role of ROS in alveolar repair is not known. We studied the effect of ROS in our in vitro wound healing model using either human A549 alveolar epithelial cells or primary distal lung epithelial cells. We found that H(2)O(2) inhibited alveolar epithelial repair in a concentration-dependent manner. At similar concentrations, H(2)O(2) also induced apoptosis, an effect seen particularly at the edge of the wound, leading us to hypothesize that apoptosis contributes to H(2)O(2)-induced inhibition of wound repair. To learn the role of apoptosis, we blocked caspases with the pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp (zVAD). In the presence of H(2)O(2), zVAD inhibited apoptosis, particularly at the wound edge and, most importantly, maintained alveolar epithelial wound repair. In H(2)O(2)-exposed cells, zVAD also maintained cell viability as judged by improved cell spreading and/or migration at the wound edge and by a more normal mitochondrial potential difference compared with cells not treated with zVAD. In conclusion, H(2)O(2) inhibits alveolar epithelial wound repair in large part by induction of apoptosis. Inhibition of apoptosis can maintain wound repair and cell viability in the face of ROS. Inhibiting apoptosis may be a promising new approach to improve repair of the alveolar epithelium in patients with acute lung injury.

Pulmonary effects of keratinocyte growth factor in newborn rats exposed to hyperoxia

“…Reactive oxygen species (ROS) are released into the alveolar space and contribute to alveolar epithelial damage in patients with acute lung injury. It was shown that H 2 O 2 inhibits alveolar epithelial wound repair in large part by induction of apoptosis and that apoptosis inhibition can maintain wound repair and cell viability in the face of ROS (24). Consistent with this assumption, KGF inhibited H 2 O 2 -induced cleavage of both procaspase-3 and the substrate of caspase-3, the poly(ADP-ribose) polymerase protein, in murine lung cells (42).…”

Asthmatic Airway Epithelium Is Intrinsically Inflammatory and Mitotically Dyssynchronous

“…An in vitro epithelial injury model that allows for the study of epithelial repair processes in the lung was adapted for use in this study (16)(17)(18). Briefly, at 0 hours on the timeline in Figure 1, epithelia were scraped in two perpendicular lines with a p1000 pipette tip and placed in bromodeoxyuridine (BrdU)-containing (10 mM) medium.…”

Role of β-catenin-regulated CCN matricellular proteins in epithelial repair after inflammatory lung injury

“…may signal to more distant surviving cells via calcium waves or paracrine mediators, as has been previously demonstrated (4,58), responses that could effectuate repair. As the CCN proteins are known to regulate apoptosis (41,63), an additional mechanism by which they might regulate wound repair is via decreased apoptosis of epithelial cells at the wound edge, an established mechanism for differential wound repair (20). Although neutrophil transmigration induces epithelial cell death and denudation of the epithelium in our models, the stimuli used (1 M fMLP in vitro or 1 g KC in vivo) are relatively modest, and the injury induced is relatively mild and repairs rapidly.…”