Interferon regulatory factor 1–Rab27a regulated extracellular vesicles promote liver ischemia/reperfusion injury

The role and regulators of extracellular vesicle (EV) secretion in hepatic ischemia/reperfusion (IR) injury have not been defined. Rab27a is a guanosine triphosphatase known to control EV release. Interferon regulatory factor 1 (IRF‐1) is a transcription factor that plays an important role in liver IR and regulates certain guanosine triphosphatases. However, the relationships among IRF‐1, Rab27a, and EV secretion are largely unknown. Here, we show induction of IRF‐1 and Rab27a both in vitro in hypoxic hepatocytes and in vivo in warm IR and orthotopic liver transplantation livers. Interferon γ stimulation, IRF‐1 transduction, or IR promoted Rab27a expression and EV secretion. Meanwhile, silencing of IRF‐1 decreased Rab27a expression and EV secretion. Rab27a silencing decreased EV secretion and liver IR injury. Ten putative IRF‐1 binding motifs in the 1,692‐bp Rab27a promoter region were identified. Chromatin immunoprecipitation and electrophoretic mobility shift assay verified five functional IRF‐1 binding motifs, which were confirmed by a Rab27a promoter luciferase assay. IR‐induced EVs contained higher oxidized phospholipids (OxPL). OxPLs on the EV surface activated neutrophils through the toll‐like receptor 4 pathway. OxPL‐neutralizing E06 antibody blocked the effect of EVs and decreased liver IR injury. Conclusion: These findings provide a novel mechanism by which IRF‐1 regulates Rab27a transcription and EV secretion, leading to OxPL activation of neutrophils and subsequent hepatic IR injury. (H epatology 2018;67:1056–1070)