Changes in energy metabolism of endotoxin tolerant peripheral blood mononuclear cells

• Grant number: 20/05077-5
• Support type: Scholarships in Brazil - Master
• Effective date (Start): September 01, 2020
• Effective date (End): March 31, 2022
• Field of knowledge: Health Sciences - Medicine - Medical Clinics
• Principal researcher: Reinaldo Salomão
• Grantee: Mônica Bragança Sousa
• Home Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil
• Associated research grant: 17/21052-0 - Sepsis: mechanisms, therapeutic targets and epidemiology, AP.TEM

Abstract

Endotoxin tolerance is a phenomenon in which pre-exposure to LPS modulates the biological response to a re-exposure to high doses of LPS. It may represent a protective cellular mechanism to limit the inflammatory damage, to control excessive LPS-induced activation of monocytes and macrophages, and inhibit cytokine production (particularly TNF-±). The cell reprogramming observed in the endotoxin tolerance model resembles the immunomodulation of leukocytes from septic patients. Studies conducted by our group demonstrated that LPS-tolerant monocytes present preserved phagocytosis and ROS production despite of an impaired production of IL-6 and TNF-±, similarly to what is observed in septic patients. The choice of metabolic pathway, e.g. glycolysis or oxidative phosphorylation, has a role in the immune cell regulation, acting not only as an energy source but also integrating signaling pathways to guide the cell function and fate. Different studies show that the protective effect of a pre-exposure to LPS is related to induction of metabolic alterations. However, there are few studies that demonstrate how the metabolic switch is related to the immunomodulation observed after a second stimulus or re-exposure to LPS. Hence, the aim of this project is to analyze how the metabolic alterations influence the function of tolerant cells and to understand the kinetics of metabolism in the tolerance model. LPS tolerance will be assessed by measuring pro-inflammatory cytokines production by flow cytometry. The energy state will be determined by the ATP production; glycolytic metabolism will be evaluated by measuring extracellular acidification rate, glucose uptake and lactate production; oxidative phosphorylation will be evaluated by the activity of TCA cycle enzymes, oxygen consumption and measurement of mitochondrial function. The contribution of different metabolic pathways to the tolerant-cell function will also be assessed. Understanding how metabolic alterations influence cellular function in the tolerance model might improve the comprehension of the leukocytes' immune response in sepsis. (AU)