MiR-155 Plays an Essential Role in Anti-MHC-Induced Obliterative Airway Disease

Abstract

Purpose Previous studies in our lab demonstrated that development of Abs to HLA often precedes development of Abs to self-Antigens (SAgs), Collagen V (Col-V) and K-alpha1 Tubulin (Kα1T), increasing the risk of bronchiolitis obliterans syndrome as a significant risk factor for acute and chronic rejection (CR). Circulating exosomes expressing donor HLA, SAgs have been proposed to stimulate immune responses leading to lung allograft rejection. miR-155 was among the first miRNAs linked to inflammation, potent upregulation of Toll like receptors in multiple cell lineages leading to production of inflammatory cytokines including IL17 which has been proposed to play an important role in the development of CR following lung transplantation. In our present study, we elucidated the role of miR-155 in anti-MHC-induced obliterative airway disease (OAD) model and their role in inducing circulating exosomes with lung SAgs and contribution to OAD. Methods Wild-type C57BL/6 miR-155 knock-out (KO) B6.Cg-Mir155tm1Rsky/J mice (8-12 wks) were procured. Anti-H-2Kb (AF6-88.5.5.3, BioXcell,) Abs was administered intrabronchially. Mouse Abs to lung-SAgs, Col-V or Kα1T, was detected by ELISA. Circulating exosomes were isolated using total exosome isolation kit and analyzed for lung SAgs, CIITA and 20S proteosome by western blots. Results Anti-MHC class I Ab administration into the wild type mice developed Abs against lung SAgs, Col-V days 8, 16, 30, and K-α1T day 8. Anti-MHC class I Abs administrated to wild-type mice released exosomes with increased levels of SAgs, Col-V or K-α1T, CIITA and 20S proteasome on day 2; which increased by day 16. In contrast, miR-155KO mice demonstrated neither Abs to SAgs nor exosomes containing SAgs. Histopathological studies revealed that lungs from wild-type animals administered with anti-MHC class I Ab demonstrated significant inflammatory cells around the vessels and bronchiole with increase in fibrosis. miR-155KO mice did not show any significant lesions. Conclusion Our results demonstrate that Abs to lung SAgs and induction of circulating exosomes with lung SAgs occurs prior to development of OAD following anti-MHC administration into native lungs. Further, miR-155 plays an obligatory role in the pathogenesis of anti-MHC induced OAD since miR-55KO mice did not develop Abs to lung SAgs, induce circulating exosomes with lung SAgs, nor result in OAD.