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

Area of Science:

• Pulmonary Medicine
• Mitochondrial Biology
• Cellular Pathology

Background:

• Reactive oxygen species (ROS) are linked to interstitial lung disease (ILD) pathogenesis.
• Investigating somatic mutations in mitochondrial DNA (mtDNA) and respiratory chain dysfunction offers insight into ILD.
• Understanding these mechanisms is crucial for developing targeted therapies for lung fibrosis.

Purpose of the Study:

• To explore the role of large-scale somatic mtDNA mutations and respiratory chain dysfunction in ROS production and lung fibrosis in ILD.
• To analyze mitochondrial alterations in lung biopsies from ILD patients and controls.
• To compare mitochondrial parameters between upper and lower lung lobes in ILD.

Main Methods:

• Analysis of lung biopsies from 30 ILD patients (idiopathic or CTD-related) and 13 controls.
• Measurement of malondialdehyde (ROS marker) and mitochondrial respiratory chain activity (COX/SDH ratio).
• Assessment of mtDNA-encoded COX-subunit-2 and nucleus-encoded COX-subunit-4 (COX2/COX4 ratio), and quantification of common mtDNA deletions.

Main Results:

• Malondialdehyde levels were elevated in ILD biopsies compared to controls.
• Mitochondrial respiratory chain activity (COX/SDH and COX2/COX4 ratios) was significantly depressed in ILD lungs.
• ILD lungs exhibited high levels of common mtDNA deletions, particularly in lower lobes, which also showed increased ROS markers and reduced respiratory chain function.

Conclusions:

• Acquired mtDNA mutations and subsequent respiratory chain dysfunction are implicated in triggering and perpetuating ROS formation in ILD.
• These mitochondrial defects contribute to the pathophysiology of lung fibrosis in ILD.
• The findings highlight mitochondria as a potential therapeutic target for ILD.