Mitochondrial DNA damage triggers mitochondrial dysfunction and apoptosis in oxidant-challenged lung endothelial...

Area of Science:

• Cellular and Molecular Biology
• Cardiovascular Research
• Pulmonary Medicine

Background:

• Oxidative stress contributes to acute lung injury by damaging pulmonary vascular cells.
• Mitochondrial DNA (mtDNA) damage is implicated in oxidant-induced cytotoxicity in pulmonary artery endothelial cells (PAECs).
• The precise mechanism linking mtDNA damage to cell death remains unclear.

Purpose of the Study:

• To investigate whether enhanced mtDNA repair can prevent mitochondrial dysfunction and apoptosis in PAECs subjected to oxidative stress.
• To test the hypothesis that increased activity of the DNA repair enzyme human Ogg1 (hOgg1) mitigates xanthine oxidase (XO)-induced cellular damage.

Main Methods:

• PAECs were transfected with an adenoviral vector encoding mitochondrially targeted human Ogg1 (hOgg1) or an empty vector.
• Cells were subsequently challenged with varying doses of xanthine oxidase (XO) and hypoxanthine to induce oxidative stress.
• Quantitative Southern blot analysis was used to assess mtDNA damage, mitochondrial membrane potential, and apoptosis markers (caspase-3 activation, DNA fragmentation).

Main Results:

• Overexpression of hOgg1 significantly suppressed XO-induced damage to mtDNA.
• Mitochondrial hOgg1 also prevented the loss of mitochondrial membrane potential caused by XO.
• hOgg1 overexpression attenuated XO-induced apoptosis, evidenced by reduced caspase-3 activation and DNA fragmentation.

Conclusions:

• mtDNA damage acts as a critical trigger for mitochondrial dysfunction and subsequent apoptosis in PAECs exposed to oxidants like XO.
• Enhancing mtDNA repair mechanisms, such as through hOgg1, offers a potential therapeutic strategy to protect pulmonary vascular cells from oxidative injury.
• These findings elucidate a key pathway in oxidant-induced cell death relevant to acute lung injury.