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Mitochondrial DNA mutations and respiratory chain dysfunction in idiopathic and connective tissue disease-related lung fibrosis.

ABSTRACT: Reactive oxygen species (ROS) are implicated in the aetiology of interstitial lung disease (ILD). We investigated the role of large-scale somatically acquired mutations in mitochondrial DNA (mtDNA) and consecutive respiratory chain dysfunction as a trigger of ROS-formation and lung fibrosis. Mitochondria were analysed in lung biopsies from 30 patients with idiopathic or connective tissue disease (CTD)-related ILD and 13 controls. In 17 patients we had paired biopsies from upper and lower lobes. Control samples were taken from lung cancer resections without interstitial fibrosis. Malondialdehyde, a marker of ROS-formation, was elevated in ILD-biopsies (p = 0.044). The activity of the mitochondrial respiratory chain (cytochrome c-oxidase/succinate dehydrogenase [COX/SDH]-ratio) was depressed in ILD (median = 0.10,) compared with controls (0.12, p < 0.001), as was the expression of mtDNA-encoded COX-subunit-2 protein normalized for the nucleus-encoded COX-subunit-4 (COX2/COX4-ratio; ILD-median = 0.6; controls = 2.2; p < 0.001). Wild-type mtDNA copies were slightly elevated in ILD (p = 0.088). The common mtDNA deletion was only present at low levels in controls (median = 0%) and at high levels in ILD (median = 17%; p < 0.001). In ILD-lungs with paired biopsies, lower lobes contained more malondialdehyde and mtDNA deletions than upper lobes and had lower COX2/COX4-ratios and COX/SDH-ratios (all p < 0.001). Acquired mtDNA-mutations and consecutive respiratory chain dysfunction may both trigger and perpetuate ROS-formation in ILD.

SUBMITTER: Jaeger VK

PROVIDER: S-EPMC6445113 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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Mitochondrial DNA mutations and respiratory chain dysfunction in idiopathic and connective tissue disease-related lung fibrosis.

Jaeger Veronika K VK Lebrecht Dirk D Nicholson Andrew G AG Wells Athol A Bhayani Harshil H Gazdhar Amiq A Tamm Michael M Venhoff Nils N Geiser Thomas T Walker Ulrich A UA

Scientific reports 20190402 1

Reactive oxygen species (ROS) are implicated in the aetiology of interstitial lung disease (ILD). We investigated the role of large-scale somatically acquired mutations in mitochondrial DNA (mtDNA) and consecutive respiratory chain dysfunction as a trigger of ROS-formation and lung fibrosis. Mitochondria were analysed in lung biopsies from 30 patients with idiopathic or connective tissue disease (CTD)-related ILD and 13 controls. In 17 patients we had paired biopsies from upper and lower lobes. ...[more]

PMID: 30940853

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Project description:Mitochondrial respiratory chain (RC) disease is a heterogeneous and highly morbid group of energy deficiency disorders for which no proven effective therapies exist. Robust vertebrate animal models of primary RC dysfunction are needed to explore the effects of variation in RC disease subtypes, tissue-specific manifestations, and major pathogenic factors contributing to each disorder, as well as their pre-clinical response to therapeutic candidates. We have developed a series of zebrafish (Danio rerio) models that inhibit, to variable degrees, distinct aspects of RC function, and enable quantification of animal development, survival, behaviors, and organ-level treatment effects as well as effects on mitochondrial biochemistry and physiology. Here, we characterize four pharmacologic inhibitor models of mitochondrial RC dysfunction in early larval zebrafish, including rotenone (complex I inhibitor), azide (complex IV inhibitor), oligomycin (complex V inhibitor), and chloramphenicol (mitochondrial translation inhibitor that leads to multiple RC complex dysfunction). A range of concentrations and exposure times of each RC inhibitor were systematically evaluated on early larval development, animal survival, integrated behaviors (touch and startle responses), organ physiology (brain death, neurologic tone, heart rate), and fluorescence-based analyses of mitochondrial physiology in zebrafish skeletal muscle. Pharmacologic RC inhibitor effects were validated by spectrophotometric analysis of Complex I, II and IV enzyme activities, or relative quantitation of ATP levels in larvae. Outcomes were prioritized that utilize in vivo animal imaging and quantitative behavioral assessments, as may optimally inform the translational potential of pre-clinical drug screens for future clinical study in human mitochondrial disease subjects. The RC complex inhibitors each delayed early embryo development, with short-term exposures of these three agents or chloramphenicol from 5 to 7 days post fertilization also causing reduced larval survival and organ-specific defects ranging from brain death, behavioral and neurologic alterations, reduced mitochondrial membrane potential in skeletal muscle (rotenone), and/or cardiac edema with visible blood pooling (oligomycin). Remarkably, we demonstrate that treating animals with probucol, a nutrient-sensing signaling network modulating drug that has been shown to yield therapeutic effects in a range of other RC disease cellular and animal models, both prevented acute rotenone-induced brain death in zebrafish larvae, and significantly rescued early embryo developmental delay from either rotenone or oligomycin exposure. Overall, these zebrafish pharmacologic RC function inhibition models offer a unique opportunity to gain novel insights into diverse developmental, survival, organ-level, and behavioral defects of varying severity, as well as their individual response to candidate therapies, in a highly tractable and cost-effective vertebrate animal model system.

Project description:BackgroundIdiopathic pulmonary fibrosis (IPF) is a progressive, eventually fatal disease. IPF is characterized by excessive accumulation of the extracellular matrix (ECM) in the alveolar parenchyma and progressive lung scarring. The pathogenesis of IPF and whether the ECM involved in the process remain unknown.MethodsTo identify potential treatment target and ECM associated proteins that may be involved in the development of IPF, we employed isobaric tag for relative and absolute quantitation (iTRAQ) combined liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach to examine protein expression in lung tissues from IPF patients.ResultsA total of 662 proteins with altered expression (455 upregulated proteins and 207 downregulated proteins) were identified in lung tissue of IPF patients compared with control. KEGG pathway enrichment analysis showed that the altered proteins in lung tissue mainly belonged to the PI3K-Akt signaling, focal adhesion, ECM-receptor interaction, and carbon metabolism pathways. According to the bioinformatic definition of the matrisome, 229 matrisome proteins were identified in lung tissue. These proteins comprised the ECM of lung, of which 104 were core matrisome proteins, and 125 were matrisome-associated proteins. Of the 229 ECM quantified proteins, 56 significantly differentially expressed proteins (19 upregulated proteins and 37 downregulated proteins) were detected in IPF lung tissue samples. In addition to proteins with well-known functions such as COL1A1, SCGB1A1, TAGLN, PSEN2, TSPAN1, CTSB, AGR2, CSPG2, and SERPINB3, we identified several novel ECM proteins with unknown function deposited in IPF lung tissue including LGALS7, ASPN, HSP90AA1 and HSP90AB1. Some of these differentially expressed proteins were further verified using Western blot analysis and immunohistochemical staining.ConclusionsThis study provides a list of proteomes that were detected in IPF lung tissue by iTRAQ technology combined with LC-MS/MS. The findings of this study will contribute better understanding to the pathogenesis of IPF and facilitate the development of therapeutic targets.

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Mitochondrial DNA mutations and respiratory chain dysfunction in idiopathic and connective tissue disease-related lung fibrosis.

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Mitochondrial DNA mutations and respiratory chain dysfunction in idiopathic and connective tissue disease-related lung fibrosis.

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