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Published on: February 10, 2023
Plasma Mitochondrial DNA--a Novel DAMP in Pediatric Sepsis
Valentina Di Caro1, Thomas D Walko, R Aaron Bola
1*Department of Critical Care Medicine, University of Pittsburgh School of Medicine and Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania †University at Buffalo, State University of New York at Buffalo, Buffalo, New York ‡Department of Chemistry, Carnegie Mellon University §Departments of Critical Care Medicine and Pediatrics, University of Pittsburgh School of Medicine and Children's Hospital of Pittsburgh, Pittsburgh ||Department of Pediatrics, Division of Pediatric Critical Care Medicine, Penn State Hershey Children's Hospital, Pennsylvania State University College of Medicine, Hershey, Pennsylvania.
Abstract:
Mitochondrial DNA (mtDNA) is a novel danger-associated molecular pattern that on its release into the extracellular milieu acts via toll-like receptor-9, a pattern recognition receptor of the immune system. We hypothesized that plasma mtDNA concentrations will be elevated in septic children, and these elevations are associated with an increase in the severity of illness. In a separate set of in vitro experiments, we test the hypothesis that exposing peripheral blood mononuclear cells (PBMC) to mtDNA activates the immune response and induces tumor necrosis factor (TNF) release. Children with sepsis/systemic inflammatory response syndrome or control groups were enrolled within 24 h of admission to the pediatric intensive care unit. Mitochondrial gene cytochrome c oxidase 1 (COX1) concentrations were measured by real-time quantitative PCR in the DNA extracted from plasma. PBMCs were treated with mtDNA (10 μg/mL) and supernatant TNF levels were measured. The median plasma mtDNA concentrations were significantly elevated in the septic patients as compared with the critically ill non-septic and healthy control patients [1.75E+05 (IQR 6.64E+04-3.67E+05) versus 5.73E+03 (IQR 3.90E+03-1.28E+04) and 6.64E+03 (IQR 5.22E+03-1.63E+04) copies/μL respectively]. The median concentrations of plasma mtDNA were significantly greater in patients with MOF as compared with patients without MOF (3.2E+05 (IQR 1.41E+05-1.08E+06) vs. 2.9E+04 (IQR 2.47E+04-5.43E+04) copies/μL). PBMCs treated with mtDNA demonstrated higher supernatant TNF levels as compared with control cells (6.5 ± 1.8 vs. 3.5 ± 0.5 pg/mL, P > 0.05). Our data suggest that plasma mtDNA is a novel danger-associated molecular pattern in pediatric sepsis and appears to be associated with MOF.
Insights
Elevated mitochondrial DNA (mtDNA) levels in septic children indicate a novel danger signal. Higher mtDNA concentrations correlate with increased illness severity and organ failure in pediatric sepsis.
Area of Science:
- Immunology
- Molecular Biology
- Pediatric Critical Care
Background:
- Mitochondrial DNA (mtDNA) functions as a danger-associated molecular pattern.
- Extracellular mtDNA signals through toll-like receptor-9 (TLR9), a key immune system receptor.
- Sepsis involves a dysregulated immune response, with potential roles for danger signals like mtDNA.
Purpose of the Study:
- To investigate if plasma mtDNA concentrations are elevated in children with sepsis.
- To determine the association between plasma mtDNA levels and sepsis severity, including organ failure.
- To examine the in vitro effect of mtDNA on immune cell activation and pro-inflammatory cytokine release.
Main Methods:
- Plasma samples from pediatric patients with sepsis/systemic inflammatory response syndrome and control groups were analyzed.
- Mitochondrial gene cytochrome c oxidase 1 (COX1) concentrations were quantified using real-time quantitative PCR.
- Peripheral blood mononuclear cells (PBMCs) were exposed to mtDNA in vitro, and supernatant tumor necrosis factor (TNF) levels were measured.
Main Results:
- Septic children exhibited significantly higher plasma mtDNA concentrations compared to critically ill non-septic and healthy controls.
- Plasma mtDNA levels were markedly elevated in patients with multiple organ failure (MOF) versus those without MOF.
- In vitro, mtDNA exposure led to increased TNF release from PBMCs, suggesting immune activation.
Conclusions:
- Plasma mtDNA serves as a novel danger-associated molecular pattern in pediatric sepsis.
- Elevated plasma mtDNA concentrations are associated with increased illness severity and MOF in pediatric sepsis.
- mtDNA can activate immune cells, contributing to the inflammatory response observed in sepsis.
