The Effect of Virus Mimetic Poli I:C-Primed Airway Exosomes on Microglial Energetic Metabolism

Abstract

Background and aim: Viral infections of upper respiratory tract can induce airway epithelial exosomes with inflammatory cargos including even viral particles. Exosomes are shown to easily cross blood brain barrier; thus, they might transmit inflammatory signal from periphery to the brain. Activated immune effector cells undergo immune-metabolic transition characterised by shift from mitochondrial to glycolytic ATP production and increase in reactive oxygen species (ROS). However, it is not known whether virus-primed airway exosomes might trigger similar changes in microglia. The aim of this study – to investigate the effect of virus mimetic polyinosinic polycytidylic acid (poly I:C)-primed airway exosomes on human microglial cell energetic metabolism. Materials and methods: Exosomes were isolated from poly I:C-primed human bronchial epithelial cell (HBEC- 3) culture medium by Total Exosome Isolation Reagent, and characterized by particle size (Zetasizer) and specific exosomes markers (ELISA). Poly I:C encapsulation in HBEC-3 exosomes was monitored by using dihydrorhodamine-conjugated poly I:C and fluorescent plate reader. Exosome internalisation by microglia (HMC-3) was identified by light and fluorescent microscopy. Mitochondrial and glycolytic activity of microglial cells was assessed by Seahorse XFp metabolic analyser. Intracellular ROS were determined by 2’,7’-dichlorofluorescein diacetate assay and mitochondrial superoxide – by MitoSOX™ Red followed by fluorescence imaging and analysis by Image J software. Statistical data analysis was performed by IBM SPSS Statistics 20 software. Results: HBEC-3 exosomes were internalized by microglial cells after 2 hours after treatment. Mitochondrial function of microglial cells was significantly inhibited and glycolysis activated after 24-hour treatment with virus-primed HBEC-3 exosomes. This was accompanied by increase in the production of intracellular and [...].