Alveolar Mitochondrial Quality Control During Acute Respiratory Distress Syndrome

Area of Science:

• Pulmonary Medicine
• Cell Biology
• Pathology

Background:

• Acute respiratory distress syndrome (ARDS) is a critical condition causing respiratory failure and mortality in intensive care units.
• Resolution of acute lung injury experimentally relies on mitochondrial quality control (MQC) pathways, including mitochondrial biogenesis and mitophagy.
• The role of MQC in human ARDS lungs remains uncharacterized.

Purpose of the Study:

• To investigate the status of MQC pathways, mitochondrial oxidant damage, biogenesis, and mitophagy in human lungs affected by ARDS.
• To compare these findings with control subjects who died from non-pulmonary causes.

Main Methods:

• A case-control autopsy study comparing ARDS lungs (n=8) with control lungs (n=7).
• Analysis using light microscopy and immunofluorescence confocal microscopy to detect co-localization of citrate synthase with markers of oxidant stress, DNA damage, mitophagy, and biogenesis.
• Specific markers included 8-hydroxydeoxyguanosine, malondialdehyde, heme oxygenase-1, Ogg1, LC3, Pink1, and Nuclear respiratory factor-1.

Main Results:

• ARDS lungs exhibited diffuse alveolar damage, edema, hyaline membranes, and neutrophils.
• Significant mitochondrial oxidant damage was observed in alveolar type 2 (AT2) cells and alveolar macrophages in ARDS lungs compared to controls.
• Mitophagy and mitochondrial biogenesis markers were largely absent in AT2 cells of ARDS lungs, indicating MQC pathway failure.
• Antioxidant and DNA repair proteins were present in macrophages but not AT2 cells in ARDS lungs.

Conclusions:

• Human ARDS lungs display substantial mitochondrial oxidant DNA damage, particularly in AT2 cells.
• There is a notable lack of MQC activity, including mitophagy and mitochondrial biogenesis, in the AT2 epithelium of ARDS lungs.
• These findings highlight MQC pathways as a potential novel therapeutic target for promoting ARDS resolution.