Immunometabolism in microbial sepsis

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Project Summary/Abstract Sepsis is the most common cause of mortality in many intensive care units and is responsible for more than 250,000 deaths in the United States annually. Microbial infection and trauma are the most common causes of sepsis. Sepsis is characterized by an exaggerated innate immune response leading to a cytokine storm. Recent studies suggest that activation of the innate immune cells causes vigorous metabolic changes towards increased glucose utilization. Elevated glucose metabolism is also a common feature in the initial state of sepsis. However, the role of glucose metabolism reprogramming in the regulation of innate immune function and its relevance to sepsis is poorly understood. In this Proposal, we aim to study the role of two individual glucose metabolism pathways in microbial sepsis, the hexosamine biosynthesis pathway (HBP) and the pentose phosphate pathway (PPP). Our preliminary studies revealed essential roles of HBP-associated O- GlcNAc (O-linked β-N-acetylglucosamine) signaling and PPP in antagonizing inflammatory response and bacterial spreading, respectively. We further identified nuclear factor E2-related factor-2 (Nrf2) as a critical mediator of both HBP and PPP pathways. Therefore, promoting the activities of HBP and PPP pathways through pharmacological activation of Nrf2 may represent a promising therapeutic regimen for treating microbial sepsis. We hypothesize that 1) HBP-associated O-GlcNAc signaling inhibits the innate immune activation through O-GlcNAcylation of RIPK3 (receptor-interacting serine/threonine kinase 3); 2) PPP is required for macrophage bacterial killing and host survival in sepsis by mediating caspase-1 activation; 3) Genetic and pharmacological activation of these glucose metabolism pathways is effective in the treatment of microbial sepsis. Cecal ligation and puncture-induced polymicrobial sepsis model will be employed to examine the role and functions of glucose metabolism pathways. We will test whether dimethyl fumarate (DMF) treatment plays a protective role in sepsis-induced mortality. The goal of the proposal is to examine the function and mechanism of two glucose metabolism pathways on macrophage bacterial killing and inflammation, both of which are key determinants of host survival. Results of these studies will provide novel insights into the regulation and function of glucose metabolism signaling, which can potentially lead to the identification of new therapeutic targets in the treatment of microbial sepsis.