Circulating mitochondrial DNA is an early indicator of severe illness and mortality from COVID-19

Abstract

BackgroundMitochondrial DNA (MT-DNA) are intrinsically inflammatory nucleic acids released by damaged solid organs. Whether circulating cell-free MT-DNA quantitation could be used to predict the risk of poor COVID-19 outcomes remains undetermined.MethodsWe measured circulating MT-DNA levels in prospectively collected, cell-free plasma samples from 97 subjects with COVID-19 at hospital presentation. Our primary outcome was mortality. Intensive care unit (ICU) admission, intubation, vasopressor, and renal replacement therapy requirements were secondary outcomes. Multivariate regression analysis determined whether MT-DNA levels were independent of other reported COVID-19 risk factors. Receiver operating characteristic and area under the curve assessments were used to compare MT-DNA levels with established and emerging inflammatory markers of COVID-19.ResultsCirculating MT-DNA levels were highly elevated in patients who eventually died or required ICU admission, intubation, vasopressor use, or renal replacement therapy. Multivariate regression revealed that high circulating MT-DNA was an independent risk factor for these outcomes after adjusting for age, sex, and comorbidities. We also found that circulating MT-DNA levels had a similar or superior area under the curve when compared against clinically established measures of inflammation and emerging markers currently of interest as investigational targets for COVID-19 therapy.ConclusionThese results show that high circulating MT-DNA levels are a potential early indicator for poor COVID-19 outcomes.FundingWashington University Institute of Clinical Translational Sciences COVID-19 Research Program and Washington University Institute of Clinical Translational Sciences (ICTS) NIH grant UL1TR002345.

Keywords: COVID-19; Complement; Immunology; Mitochondria.

Figure 1. CONSORT flow diagram showing enrollment of patients, allocation, and outcomes.

RRT, renal replacement therapy.

Figure 2. High circulating MT-DNA levels predict a higher risk of mortality in COVID-19 patients.

Plasma for determination of circulating levels of MT-CYTB was obtained at time of hospital presentation. (A) Box-and-whisker plots of MT-CYB levels in relation to mortality status in COVID-19 patients. The box plots depict the minimum and maximum values (whiskers), the upper and lower quartiles, and the median. The length of the box represents the interquartile range. (B) Receiver operating characteristic (ROC) curves in predicting the outcome mortality based on MT-CYTB levels. Statistical significance was determined using Mann-Whitney U test (**P < 0.01).

Figure 3. High circulating MT-DNA levels predict a higher risk of ICU requirement and intubation in COVID-19 patients.

Plasma for determination of circulating levels of MT-CYTB was obtained at time of hospital presentation. Box-and-whisker plots of MT-CYB levels in relation to (A) ICU admission and (C) intubation in COVID-19 patients. The box plots depict the minimum and maximum values (whiskers), the upper and lower quartiles, and the median. The length of the box represents the interquartile range. Empty dots indicate alive patients and shaded dots indicate deceased patients. ROC curves in predicting the outcome (B) ICU and (D) intubation based on MT-CYTB levels. Statistical significance was determined using Mann-Whitney U test (****P <.0001).

Figure 4. High circulating MT-DNA levels predict a higher risk for end organ dysfunction requiring vasopressors and renal replacement in COVID-19 patients.

Plasma for determination of circulating levels of MT-CYTB was obtained at time of hospital presentation. Box-and-whisker plots of MT-CYB levels in relation to (A) requirement for vasopressors and (C) renal replacement in COVID-19 patients. The box plots depict the minimum and maximum values (whiskers), the upper and lower quartiles, and the median. The length of the box represents the interquartile range. ROC curves in predicting the outcomes (B) requirement for pressors and (D) renal replacement based on MT-CYTB levels. Statistical significance was determined using Mann-Whitney U test (****P < 0.0001).

Figure 5. Circulating MT-DNA levels have similar or improved accuracy over clinically utilized biomarkers for outcomes of severity in COVID-19.

Blood samples for determination of biomarkers levels were collected within 24 hours from hospital presentation. ROC curves in predicting the outcomes (A) mortality, (B) admission to ICU, and (C) intubation based on MT-CYTB (red), reactive C protein (CRP) (blue), ferritin (black), lactic acid dehydrogenase (LDH) (purple), and D-dimer (green) levels. AUC with 95% CI and P values for the different biomarkers are summarized in the corresponding tables.

Figure 6. Circulating MT-DNA levels correlate with other emerging markers of inflammation and cytokines in COVID-19 patients.

Scatter plots showing the correlation between MT-CYTB and (A) IL-6, (B) C5b-9 (terminal complement complex), and (C) neutrophil-to-lymphocyte ratio (NLR), (D) CXCL9, (E) CCL2, (F) CXCL10, (G) IL-1RA, (H) IL-2R, and (I) HGF. The degree of correlation was assessed using Spearman’s rank correlation coefficient test.