Introduction:
Cerebral mitochondrial dysfunction is thought to play a role in the post-cardiac arrest syndrome, propagating secondary morbidity and mortality after return of spontaneous circulation (ROSC).
Hypothesis:
Based on our previous studies showing a persistent decrease in oxidative phosphorylation (particularly Complex I) and increased mitochondrial fission in a swine model of in-hospital cardiac arrest, we hypothesized that nuclear and mitochondrial genes related to respiratory function would be downregulated and genes promoting mitochondrial fission would be upregulated four hours post-ROSC.
Methods:
One-month old piglets were subjected to sham anesthesia (n=5) or asphyxial cardiac arrest (n=6; 7 minutes of asphyxia followed by induction of ventricular fibrillation) and treated with 10-20 minutes of AHA guideline-based CPR followed by four hours of standardized post-arrest management and humane euthanasia. RNA was extracted from flash-frozen sections of cerebral cortex using a QIAsymphony robot and sequenced on an Illumina HiSeq. Reads were aligned to the reference (SusScrofa11.1 and NC_012095) using STAR and quantified using subreads. Normalization and differential expression analysis were performed using DESeq2 with RNA quality, intra-arrest and post-ROSC physiologic variables as covariates. All p values were adjusted for multiple comparisons (Benjamini-Hochberg) with a significance cutoff of 0.05.
Results:
Compared to sham, cardiac arrest animals demonstrated reduced expression of multiple components of the respiratory chain, including NDUFA5 (2.4-fold, p<0.001) and NDUFC1 (2.0-fold, p=0.02), key components of Complex I. Components of Complex III (UQCRB, UQCRH) and Complex IV (COX1, COX7C, COX7A2, COX7B) were also downregulated. Dynamin-2 (DNM2), which increases mitochondrial fission, was upregulated (2.3-fold, p=0.005). There was also differential expression of inner membrane solute channel expression (SLC44A1, SLC25A48 and SLC25A16).
Conclusions:
Multiple components of the mitochondrial respiratory chain are downregulated 4 hours post-ROSC in the brain, including key components of Complex I with concurrent upregulation of the mitochondrial fission protein dynamin-2.
Global ischaemia induces a biphasic response of the mitochondrial respiratory chain. Anoxic pre-perfusion protects against ischaemic damage
