Cardiac Mitochondrial Dysfunction Following Bleomycin-Induced Acute Lung Injury in Rats.

Area of Science:

• Cardiovascular Biology
• Pulmonary Medicine
• Mitochondrial Physiology

Background:

• Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are linked to cardiac complications like myocardial injury and right ventricular dysfunction.
• The precise mechanisms connecting lung injury to cardiac dysfunction are not fully understood.
• This study investigates ventricular mitochondrial respiratory function during the acute phase of bleomycin-induced ALI.

Purpose of the Study:

• To investigate ventricular mitochondrial respiratory function in the context of acute lung injury.
• To determine the sex-specific effects of ALI on cardiac mitochondrial bioenergetics.
• To explore the impact of pro-inflammatory cytokines and hypoxia on cardiac cell mitochondrial respiration.

Main Methods:

• Acute lung injury was induced in male and female rats using intratracheal bleomycin.
• Cardiac troponin I (cTnI) levels were measured to assess myocardial injury.
• High-resolution respirometry (HRR) was used to assess mitochondrial respiration in ventricular fibers and H9C2 cardiomyoblast cells.

Main Results:

• Bleomycin-induced ALI increased cTnI in male rats, indicating cardiac stress.
• Male rats showed impaired mitochondrial oxidative capacity in the right ventricle (RV), while the left ventricle (LV) had modest alterations.
• Female rats exhibited better mitochondrial function preservation, especially in the RV, with higher oxidative phosphorylation (OXPHOS) capacity.

Conclusions:

• Acute lung injury causes ventricle-specific and sex-dependent changes in cardiac mitochondrial bioenergetics, with males experiencing more impairment.
• Pro-inflammatory cytokines increase uncoupled mitochondrial respiration in H9C2 cells under normoxia.
• Hypoxia independently enhances maximal respiration and spare respiratory capacity in cardiac cells.