ABSTRACT
Plasma membranes of animal cells are enriched for cholesterol. Cholesterol-dependent cytolysins (CDCs) are pore-forming toxins secreted by bacteria that target membrane cholesterol for their effector function. Phagocytes are essential for clearance of CDC-producing bacteria; however, the mechanisms by which these cells evade the deleterious effects of CDCs are largely unknown. Here, we report that interferon (IFN) signals convey resistance to CDC-induced pores on macrophages and neutrophils. We traced IFN-mediated resistance to CDCs to the rapid modulation of a specific pool of cholesterol in the plasma membrane of macrophages without changes to total cholesterol levels. Resistance to CDC-induced pore formation requires the production of the oxysterol 25-hydroxycholesterol (25HC), inhibition of cholesterol synthesis and redistribution of cholesterol to an esterified cholesterol pool. Accordingly, blocking the ability of IFN to reprogram cholesterol metabolism abrogates cellular protection and renders mice more susceptible to CDC-induced tissue damage. These studies illuminate targeted regulation of membrane cholesterol content as a host defense strategy.
Subject(s)
Bacterial Infections/immunology , Bacterial Toxins/immunology , Hydroxycholesterols/metabolism , Interferons/isolation & purification , Phagocytes/immunology , Streptolysins/immunology , Animals , Bacteria/immunology , Bacteria/metabolism , Bacterial Proteins/administration & dosage , Bacterial Proteins/immunology , Bacterial Proteins/metabolism , Bacterial Toxins/metabolism , Cell Membrane/metabolism , Cell Membrane Permeability/immunology , Cells, Cultured , Disease Models, Animal , Disease Susceptibility/immunology , Female , Host Microbial Interactions/immunology , Humans , Intravital Microscopy , Male , Mice , Mice, Transgenic , Phagocytes/cytology , Phagocytes/metabolism , Primary Cell Culture , Steroid Hydroxylases/genetics , Steroid Hydroxylases/metabolism , Streptolysins/administration & dosage , Streptolysins/metabolismABSTRACT
Macrophages reprogram their lipid metabolism in response to activation signals. However, a systems-level understanding of how different pro-inflammatory stimuli reshape the macrophage lipidome is lacking. Here, we use complementary "shotgun" and isotope tracer mass spectrometry approaches to define the changes in lipid biosynthesis, import, and composition of macrophages induced by various Toll-like receptors (TLRs) and inflammatory cytokines. "Shotgun" lipidomics data revealed that different TLRs and cytokines induce macrophages to acquire distinct lipidomes, indicating their specificity in reshaping lipid composition. Mechanistic studies showed that differential reprogramming of lipid composition is mediated by the opposing effects of MyD88- and TRIF-interferon-signaling pathways. Finally, we applied these insights to show that perturbing reprogramming of lipid composition can enhance inflammation and promote host defense to bacterial challenge. These studies provide a framework for understanding how inflammatory stimuli reprogram lipid composition of macrophages while providing a knowledge platform to exploit differential lipidomics to influence immunity.