Sepsis, a clinical systemic inflammatory response syndrome occurring in patients following infection or injury, remains the leading cause of death in intensive care units worldwide, including the United States. Emerging evidence indicates that immunometabolism may play an important role in the pathogenesis of sepsis through its ability to regulate the expression and release of cytokines. In particular, we recently provided the first direct evidence that PKM2-mediated aerobic glycolysis promotes the release of HMGB1, a late mediator of lethal systemic inflammation with a wider therapeutic time window for clinical intervention. These exciting findings raise several important questions regarding the previously unknown role of PKM2 in the pathogenesis of sepsis, as well as the novel mechanisms underlying the regulation of PKM2 expression and HMGB1 release. We hypothesize that PKM2-mediated immunometabolism is an emerging hallmark of sepsis that contributes to cytokine (e.g., HMGB1) release and the subsequent systemic inflammatory response. We propose the following specific aims:
Aim 1. Define the mechanism underlying the regulation of PKM2 expression and activity in both immune and non-immune cells during sepsis. We will test the hypothesis that AMPK is a negative regulator of PKM2 expression and activity, and therefore suppresses aerobic glycolysis and HMGB1 release in activated macrophages, monocytes, and endothelial cells in vitro and in vivo.
Aim 2. Define the mechanism underlying the regulation of HMGB1 release by aerobic glycolysis in both immune and non-immune cells during sepsis. We will test the hypothesis that metabolites production (e.g., lactate) from PKM2-mediated aerobic glycolysis can inhibit the activity of histone deacetylases including SIRT1, which in turn enables HMGB1 hyperacetylation and subsequent release in activated macrophages, monocytes, and endothelial cells in vitro and in vivo.
Aim 3. Determine the efficacy of PKM2 inhibition in protecting against sepsis in two experimental animal models. We will test the hypothesis that mice with PKM2 ablation in myeloid cells are protected from lethal endotoxemia or cecal ligation and puncture-induced polymicrobial sepsis through altering lactate accumulation, HMGB1 release, inflammatory response, and organ dysfunction. The completion of these exciting studies will further improve our understanding of the emerging role of immunometabolism in inflammation and the mechanisms of HMGB1 release and guide future development of therapeutic strategies to treat sepsis and other lethal inflammatory diseases.
Despite recent advances in antibiotic therapy and intensive care, severe sepsis and septic shock remain the leading causes of death in intensive care units worldwide, including the United States. We postulate that the dysfunction of PKM2-mediated immunometabolism is an emerging hallmark of sepsis that can regulate HMGB1 release and the subsequent systemic inflammatory response. Our proposal will provide new insights into our understanding of the pathophysiology of sepsis and may lead to new therapeutic strategies to treat this lethal inflammatory disease.
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