Elevated Levels of Plasma Mitochondrial DNA DAMPs Are Linked to Clinical Outcome in Severely Injured Human Subjects

Objective: Our objective was to execute a prospective cohort study to determine relationships between plasma mtDNA DAMP levels and the occurrence of systemic inflammatory response syndrome (SIRS), multiple organ dysfunction syndrome (MODS), and mortality. Background: Mitochondrial DNA damage-associated molecular patterns (DAMPs) accumulate in the circulation after severe injury. Observations in animal models demonstrate that mtDNA DAMPs contribute to organ dysfunction; however, the link between plasma mtDNA DAMPs and outcome in severely injured human subjects has not been established. Methods: DNA was isolated from plasma samples taken from severely injured patients at hospital days 0, 1, and 2. Real-time PCR was used to quantify selected approximate to 200 base pair sequences of mtDNA within the COX1, ND1, and ND6 genes, as well as from the D-Loop transcriptional regulatory region. MODS was defined as a Denver Multiple Organ Failure score of 4 or greater. Results: MtDNA DAMPs were quantified as PCR threshold cycle number. Lower threshold cycles indicate increased mtDNA DAMP content. Patients with SIRS had significantly increased mtDNA DAMP levels in all 4 sequences examined (32.14 +/- 0.90 vs 29.00 +/- 1.15 for COX1, 31.90 +/- 0.47 vs 30.16 +/- 1.42 for ND1, 32.40 +/- 0.61 vs 28.94 +/- 1.13 for ND6, and 33.12 +/- 0.83 vs 28.30 +/- 1.14 for D-Loop). Patients who developed MODS also had elevated mtDNA DAMP levels compared with those who did not (32.57 +/- 0.74 vs 27.12 +/- 0.66 for COX1, 32.45 +/- 0.65 vs 28.20 +/- 0.73 for ND1, 32.52 +/- 0.56 vs 27.60 +/- 0.79 for ND6, and 32.85 +/- 0.75 vs 27.86 +/- 1.27 for D-Loop). Patients with above-median mtDNA DAMP levels had a significantly elevated relative risk for mortality. Four patients died secondary to severe MODS. Conclusions: These findings comprise the first observational evidence that plasma mtDNA DAMPs is associated with the evolution of SIRS, MODS, and mortality in severely injured human subjects.