Oxygen radical-induced mitochondrial DNA damage and repair in pulmonary vascular endothelial cell phenotypes

Area of Science:

• Pulmonary vascular biology
• Mitochondrial medicine
• Oxidative stress research

Background:

• Mitochondrial DNA (mtDNA) is susceptible to free radical damage.
• Cell type-specific differences in mtDNA repair capacity are increasingly recognized.
• Understanding these differences is crucial for pulmonary vascular health.

Purpose of the Study:

• To investigate the impact of xanthine oxidase (XO) and menadione on mtDNA in pulmonary arterial (PA), microvascular (MV), and pulmonary venous (PV) endothelial cells (ECs).
• To determine the differential susceptibility and repair capabilities of mtDNA across lung vascular EC phenotypes.
• To elucidate the role of iron-catalyzed hydroxyl radical formation in mtDNA damage.

Main Methods:

• Exposure of PAECs, MVECs, and PVECs to XO and menadione to induce oxidative stress.
• Assessment of mtDNA damage using nucleotide resolution analysis.
• Evaluation of mtDNA repair capacity in response to XO- and menadione-induced damage.
• Inhibition studies using dimethylthiourea and deferoxamine to investigate radical formation.

Main Results:

• Both XO and menadione induced mtDNA damage in all EC phenotypes, with varying sensitivity: PV > PA > MV for XO, and MV = PV > PA for menadione.
• Dimethylthiourea and deferoxamine mitigated damage, indicating a role for iron-catalyzed hydroxyl radical.
• Nuclear vascular endothelial growth factor gene remained undamaged.
• PAECs and MVECs rapidly repaired XO-induced mtDNA damage, while PVECs did not.
• MVECs and PVECs repaired menadione-induced mtDNA damage effectively, but PAECs showed slower repair.
• Specific nucleotide damage patterns differed between XO and menadione exposure.

Conclusions:

• Mitochondrial DNA in lung vascular ECs is vulnerable to free radical damage from XO and menadione.
• Significant disparities exist in both mtDNA damage susceptibility and repair capacity among PA, MV, and PV endothelial cells.
• These findings highlight cell type-specific mechanisms of mtDNA maintenance in the pulmonary vasculature.