Mitochondrial-derived free radicals mediate asbestos-induced alveolar epithelial cell apoptosis

Vijayalakshmi Panduri, Sigmund A. Weitzman, Navdeep S. Chandel, David W. Kamp*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

95 Scopus citations

Abstract

Asbestos causes pulmonary toxicity by mechanisms that in part involve reactive oxygen species (ROS). However, the precise source of ROS is unclear. We showed that asbestos induces alveolar epithelial cell (AEC) apoptosis by a mitochondrial-regulated death pathway. To determine whether mitochondrial-derived ROS are necessary for causing asbestos-induced AEC apoptosis, we utilized A549-ρ° cells that lack mitochondrial DNA and a functional electron transport. As expected, antimycin, which induces an oxidative stress by blocking mitochondrial electron transport at complex III, increased dichlorofluoroscein (DCF) fluorescence in A549 cells but not in A549-ρ° cells. Compared with A549 cells, ρ° cells have less asbestos-induced ROS production, as assessed by DCF fluorescence, and reductions in total glutathione levels as well as less caspase-9 activation and apoptosis, as assessed by TdT-mediated dUTP nick end labeling staining and DNA fragmentation. A mitochondrial anion channel inhibitor that prevents ROS release from the mitochondria to the cytoplasm also blocked asbestos-induced A549 cell caspase-9 activation and apoptosis. Finally, a role for nonmitochondrial-derived ROS with exposure to high levels of asbestos (50 μg/cm2) was suggested by our findings that an iron chelator (phytic acid or deferoxamine) or a free radical scavenger (sodium benzoate) provided additional protection against asbestos-induced caspase-9 activation and DNA fragmentation in ρ° cells. We conclude that asbestos fibers affect mitochondrial DNA and functional electron transport, resulting in mitochondrial-derived ROS production that in turn mediates AEC apoptosis. Nonmitochondrial-associated ROS may also contribute to AEC apoptosis, particularly with high levels of asbestos exposure.

Original languageEnglish (US)
Pages (from-to)L1220-L1227
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume286
Issue number6 30-6
DOIs
StatePublished - Jun 2004

Keywords

  • DNA damage
  • Mitochondria
  • Oxidants
  • Pulmonary epithelium
  • ρ° cells

ASJC Scopus subject areas

  • Physiology
  • Pulmonary and Respiratory Medicine
  • Physiology (medical)
  • Cell Biology

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