PROJECT SUMMARY / ABSTRACT
Sepsis is a medical emergency of life-threatening organ dysfunction due to a dysregulated host response to
infection. In the United States, over one million people are hospitalized with sepsis or septic shock every year,
including >75,000 children. Multiple organ dysfunction syndrome (MODS) is the most common cause of death
for children with sepsis. Although most children who develop sepsis recover with appropriate conventional
care, ~20% develop MODS, and one in five of these children with sepsis-induced MODS still die. For this
high-risk subset, we have no cure and care is largely supportive. Widespread alterations in the ability of
mitochondria to supply sufficient energy for normal cellular activities has been implicated as a key pathologic
event leading to MODS in sepsis. Using a protocol optimized to measure mitochondrial respiration and content
in peripheral blood mononuclear cells (PBMC), our group discovered that children with prolonged sepsis-
induced MODS are more likely to have persistent mitochondrial dysfunction. This proposal builds on our prior
work to test the hypothesis that low mitochondrial respiration in PBMCs is caused by abnormal mitochondrial
quality control processes (biogenesis, fission, fusion, and mitophagy) that normally restore and maintain
mitochondrial health. The resulting mitochondrial dysfunction, through release of mitochondrial DNA (mtDNA)
into the cytosol, can then activate inflammatory pathways that sustain inflammation and organ dysfunction in
children with sepsis. In Aim 1, we will determine which changes in mitochondrial quality control are associated
with recovery versus persistence of low mitochondrial respiration in children with sepsis. We will enroll 106
children with sepsis-induced MODS and measure mitochondrial respiration, redox state, content, biogenesis,
fission, fusion, and mitophagy on days 1, 3, 5, and 7 of illness. In Aim 2, we will determine if the persistence of
PBMC mitochondrial dysfunction activates three inflammatory pathway (cGAS-STING, TLR-9, and
inflammasome) that sense release of mtDNA into the cytosol. In Aim 3, we will test whether mitochondrial
dysfunction, abnormal mitochondrial quality control, or activation of inflammatory pathways are associated with
the severity or duration of MODS in children with sepsis. As part of Aims 1 and 2, we will also conduct a
parallel set of in vitro experiments to test the utility of lipopolysaccharide- and lipoteichoic acid-stimulation of
EBV-transformed lymphoblasts as a potential translational platform for future therapeutic investigation and to
establish cytosolic mtDNA as one mechanism through which mitochondria can promote inflammation in sepsis.
These aims address the NICHD’s interest in “studies focused on mitochondrial dysfunction as a
pathophysiologic process of MODS…with potential to advance to translational and clinical projects.” By
understanding why mitochondrial dysfunction persists in some children and how this can lead to sustained
inflammation and MODS, we will identify new potential therapeutic targets for children with prolonged MODS,
the leading cause of death in sepsis for which we currently have no cure.
