Presenting Author:

Paul Cheresh, Ph.D.

Principal Investigator:

David Kamp

Department:

Medicine

Keywords:

Idiopathic Pulmonary Fibrosis, alveolar epithelial cell injury, fibrosis, mitochondrial DNA damage, asbestos, reactive o... [Read full text] Idiopathic Pulmonary Fibrosis, alveolar epithelial cell injury, fibrosis, mitochondrial DNA damage, asbestos, reactive oxygen species. [Shorten text]

Location:

Third Floor, Feinberg Pavilion, Northwestern Memorial Hospital

B33 - Basic Science

Mitochondrial DNA regulates lung fibrosis in IPF patients and mice.

Rationale: Alveolar epithelial cell (AEC) injury and repair are crucial determinants of the fibrogenic potential of asbestos and other noxious agents. We have previously shown that AEC mitochondrial reactive oxygen species (ROS) mediate asbestos-induced AEC mitochondrial DNA (mtDNA) damage and apoptosis by a mitochondria-regulated (intrinsic) death pathway. We showed that overexpression of mitochondrial human 8-oxoguanine DNA glycosylase (mtOGG1) preserves mtDNA and prevents asbestos-induced AEC mtDNA damage in vitro whereas mice deficient in Ogg1 have increased AEC mtDNA damage, apoptosis and lung fibrosis. We reasoned that transgenic mice with enforced expression of mitochondrial OGG1 (mt-Ogg1-EE) would have decreased asbestos-induced mtDNA damage and lung fibrosis compared to wild type (WT). Further, we hypothesized that patients with IPF have increased lung cell mtDNA damage as compared to normal controls. Objectives: To determine whether mtOGG1 is protective against lung fibrosis by assessing whether mt-Ogg1-EE mice are protected against asbestos-induced lung fibrosis and whether mtDNA levels are increased in the lungs of patients with IPF as compared to controls. Methods: Crocidolite asbestos (100 or 200 µg/100 µl) or TiO2 (200 µg/100 µl, negative control) was instilled intratracheally in male 8-10 week old WT (C57BL/6J) or mt-Ogg1-EE mice. The lungs were harvested at 21 days. Lung fibrosis was quantified via Sircol assay (lung collagen levels) or fibrosis score (trichrome staining, Cheresh et al. AJRCMB 2015). DNA was extracted from formalin-fixed, paraffin-embedded lungs from mice and IPF and normal human lung biopsies. Mitochondrial DNA damage was assessed by a quantitative PCR-based assay (Kim et al. JBC 2014). Results: Mt-Ogg1-EE mice, as compared to WT, were protected against crocidolite asbestos-induced pulmonary fibrosis as measured by Sircol lung collagen and fibrosis scoring (Figure). This was accompanied by reduced asbestos-induced lung cell mtDNA damage in Mt-Ogg1-EE mice as compared to controls. Furthermore, we show that mtDNA damage is increased in human IPF lung biopsies relative to those from normal lungs. Conclusions: We demonstrate that Mt-Ogg1-EE mice are protected against asbestos-induced mtDNA damage and lung fibrosis and that the lungs of IPF patients have increased mtDNA damage. These results extend our previous findings implicating an important role for OGG1 in the preservation of AEC mtDNA integrity following oxidative stress necessary for preventing lung fibrosis. We reason that mtDNA damage may be a crucial regulator of human lung fibrosis. Strategies designed to limit AEC mtDNA damage arising from excess mitochondrial ROS may be novel therapeutic approaches for preventing lung fibrosis.