I am an Associate Professor in the Division of Anesthesiology Critical Care Medicine at Vanderbilt University Medical Center. As a critical care physician, I manage surgical patients with sequelae from surgical and anesthetic inflammation, immune suppression, and infection. My earlier work focused on rapid detection of infection and microbial resistance to aid in facilitating proper antimicrobial treatment. However, the increase in antibiotic resistance has rendered management of infection a greater challenge, thus a need for alternative infection control strategies. This award will allow me to explore the impact of a synthetic form of the TLR4 ligand MPLA termed phosphorylated hexaacyl disaccharide (PHAD) to enhance antimicrobial innate immunity and alter endothelial dysfunction. Furthermore, I plan to engage in an intensive training program to develop my career as a physician-scientist through mentored oversight and a structured curriculum leading to successful research independence in the field of innate immunity and organ projection. Antimicrobial resistant hospital-acquired infections continue to increase leading to morbidity to include inflammation, organ injury, and death. Using hydrolysis derived MPLA, our laboratory has demonstrated enhanced bacterial clearance and survival in murine models of infection; however the mechanisms by which sustained antimicrobial protection develops is not well understood. Our work shows that macrophages and endothelia cells primed by MPLA may strongly contribute to sustained antimicrobial function and alteration of endothelial dysfunction.
Aim 1 : We hypothesize that PHADs will induce re-programming of the human macrophage phenotype leading to predominance of phosphoinositide-3-kinase (PI3K)/Akt/mTOR/HIF-1? signaling, a metabolic profile characterized by aerobic glycolysis and augmented phagocytosis and bacterial killing.
Aim 2 : We hypothesize that PHADs will induce an endothelial phenotype that will facilitate antimicrobial functions and maintenance of barrier function. We will investigate the ability of PHAD to impact endothelial cell metabolism, expression of adhesion molecules (VCAM-1, ICAM-1, E-selectin), production of cytokines (IL-6, IP-10, G-CSF), and maintenance of barrier function using human endothelial cells and clinically relevant murine model of CLP. In the ex-vivo studies, the functional importance of specific signaling pathways in PHAD-induced alterations in endothelial cell metabolism and barrier function will be assessed using specific inhibitors. These studies will examine the impact of PHAD on the immunobiology of human macrophages and endothelial cells, and identify dependence on the TRL4 derived MyD88 and TRIF signaling pathways. This work could possibly lead to a novel immunotherapeutic agent for clinical use in perioperative and critical care medicine.

Public Health Relevance

Antimicrobial resistant infections have become a critical source of morbidity and mortality in critically ill patients. The purpose of this study is to investigate the properties of a synthetic TLR4 agonist towards enhancing innate immunity and protecting against organ injury by characterizing the cellular and molecular mechanisms involved in providing antimicrobial protection and preserving endothelial function.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Clinical Investigator Award (CIA) (K08)
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Surgery, Anesthesiology and Trauma Study Section (SAT)
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Zhao, Xiaoli
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Vanderbilt University Medical Center
United States
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Fensterheim, Benjamin A; Young, Jamey D; Luan, Liming et al. (2018) The TLR4 Agonist Monophosphoryl Lipid A Drives Broad Resistance to Infection via Dynamic Reprogramming of Macrophage Metabolism. J Immunol 200:3777-3789
Patil, Naeem K; Luan, Liming; Bohannon, Julia K et al. (2018) Frontline Science: Anti-PD-L1 protects against infection with common bacterial pathogens after burn injury. J Leukoc Biol 103:23-33