Abstract Body (Do not enter title and authors here): Background: Heart failure (HF) with reduced ejection fraction (HFrEF) is associated with increased inflammatory response that contributes to progressive worsening of the HF state. Potential endogenous triggers of this process include damage-associated molecular patterns (DAMPs). DAMPs originate from within cells following tissue stress or injury and activate pattern recognition receptors of the immune system, triggering an inflammatory response. Mitochondria are the major cell organelles that release DAMPs into the circulation. Chronic HF is associated with multi-organ mitochondrial dysfunction and cell injury and death.
Purpose: The present study sought to quantify differences in mitochondrial DNA (mtDNA) DAMPs in the setting of HFrEF in humans and dogs compared to normal humans and dogs.
Methods: Plasma samples were obtained from 9 HFrEF patients with left ventricular ejection fraction (LVEF) ≤35% and 9 age-matched healthy subjects, and from 6 dogs with coronary microembolization-induced HF (LVEF ≤35%) and 6 normal dogs. DNA fragments were isolated from 1 ml of plasma using a commercially available kit. Quantitative PCR and specifically designed primers were used to measure the amount of DNA in plasma from COX1 (cytochrome c oxidase subunit 1), ND1 (NADH dehydrogenase subunit 1) and ND6 (NADH dehydrogenase subunit 6) using an Applied Biosystems 7500 Fast-PCR unit. The relative abundances of plasma mtDNA DAMPs were expressed as threshold cycles (C_T).
Results: Compared to normal human subjects, mtDNA DAMPs levels of COX1, ND1 and ND6 in plasma of HFrEF patients was 4-fold, 9-fold and 8-fold greater, respectively. Similarly, compared to normal dogs, mtDNA DAMPs levels of COX1, ND1 and ND6 in plasma of HFrEF dogs was increased 48-fold, 12-fold and 4-fold, respectively.
Conclusions: These findings indicate a marked increase of mtDNA DAMPs in plasma of humans and dogs with HFrEF. The increase of mtDNA DAMPs is consistent with the elevated systemic inflammatory state of HFrEF. The results underscore mitochondrial abnormalities as integral players in the progressive worsening of HFrEF.