title: Release of luminal exosomes contributes to TLR4-mediated epithelial antimicrobial defense.
abstract: Exosomes are membranous nanovesicles released by most cell types from multi-vesicular endosomes. They are speculated to transfer molecules to neighboring or distant cells and modulate many physiological and pathological procedures. Exosomes released from the gastrointestinal epithelium to the basolateral side have been implicated in antigen presentation. Here, we report that luminal release of exosomes from the biliary and intestinal epithelium is increased following infection by the protozoan parasite Cryptosporidium parvum. Release of exosomes involves activation of TLR4/IKK2 signaling through promoting the SNAP23-associated vesicular exocytotic process. Downregulation of let-7 family miRNAs by activation of TLR4 signaling increases SNAP23 expression, coordinating exosome release in response to C. parvum infection. Intriguingly, exosomes carry antimicrobial peptides of epithelial cell origin, including cathelicidin-37 and beta-defensin 2. Activation of TLR4 signaling enhances exosomal shuttle of epithelial antimicrobial peptides. Exposure of C. parvum sporozoites to released exosomes decreases their viability and infectivity both in vitro and ex vivo. Direct binding to the C. parvum sporozoite surface is required for the anti-C. parvum activity of released exosomes. Biliary epithelial cells also increase exosomal release and display exosome-associated anti-C. parvum activity following LPS stimulation. Our data indicate that TLR4 signaling regulates luminal exosome release and shuttling of antimicrobial peptides from the gastrointestinal epithelium, revealing a new arm of mucosal immunity relevant to antimicrobial defense.
authors.affiliation: Department of Medical Microbiology and Immunology, Creighton University School of Medicine, Omaha, Nebraska, United States of America.
authors.forename: Guoku
authors.initials: G
authors.lastname: Hu
authors.forename: Ai-Yu
authors.initials: AY
authors.lastname: Gong
authors.forename: Amanda L
authors.initials: AL
authors.lastname: Roth
authors.forename: Bing Q
authors.initials: BQ
authors.lastname: Huang
authors.forename: Honorine D
authors.initials: HD
authors.lastname: Ward
authors.forename: Guan
authors.initials: G
authors.lastname: Zhu
authors.forename: Nicholas F
authors.initials: NF
authors.lastname: Larusso
authors.forename: Nancy D
authors.initials: ND
authors.lastname: Hanson
authors.forename: Xian-Ming
authors.initials: XM
authors.lastname: Chen
mesh_terms: D017951:Antigen Presentation; D054804:Cathelicidins / Q000378:metabolism; D002460:Cell Line; D003457:Cryptosporidiosis / Q000276:immunology*; D016785:Cryptosporidium parvum / Q000276:immunology*; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism; D055354:Exosomes / Q000378:metabolism*; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D035683:MicroRNAs / Q000096:biosynthesis; D050766:Qb-SNARE Proteins / Q000378:metabolism; D050767:Qc-SNARE Proteins / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000276:immunology; D034101:Sporozoites / Q000276:immunology / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D023083:beta-Defensins / Q000378:metabolism
chemical_list: D054804:Cathelicidins; C106641:DEFB4A protein, human; D035683:MicroRNAs; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; C100493:SNAP23 protein, human; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D023083:beta-Defensins; C487931:mirnlet7 microRNA, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human