title: Activation of Dll4/Notch Signaling and Hypoxia-Inducible Factor-1 Alpha Facilitates Lymphangiogenesis in Lacrimal Glands in Dry Eye.
abstract: OBJECTIVE
  By using hypoxia-inducible factor-1 alpha conditional knockout (HIF-1α CKO) mice and a dry eye (DE) mouse model, we aimed to determine the role played by delta-like ligand 4 (Dll4)/Notch signaling and HIF-1α in the lymphangiogenesis of lacrimal glands (LGs).
  
  
  METHODS
  C57BL/6 mice were housed in a controlled-environment chamber for DE induction. During DE induction, the expression level of Dll4/Notch signaling and lymphangiogenesis in LGs was measured by quantitative RT-PCR, immunoblot, and immunofluorescence staining. Next, lymphangiogenesis was measured after Dll4/Notch signal inhibition by anti-Dll4 antibody or γ-secretase inhibitor. Using HIF-1α CKO mice, the expression of Dll4/Notch signaling and lymphangiogenesis in LGs of DE-induced HIF-1α CKO mice were assessed. Additionally, the infiltration of CD45+ cells in LGs was assessed by immunohistochemical (IHC) staining and flow cytometry for each condition.
  
  
  RESULTS
  DE significantly upregulated Dll4/Notch and lymphangiogenesis in LGs. Inhibition of Dll4/Notch significantly suppressed lymphangiogenesis in LGs. Compared to wild-type (WT) mice, DE induced HIF-1α CKO mice showed markedly low levels of Dll4/Notch and lymphangiogenesis. Inhibition of lymphangiogenesis by Dll4/Notch suppression resulted in increased CD45+ cell infiltration in LGs. Likewise, CD45+ cells infiltrated more in the LGs of HIF-1α CKO DE mice than in non-DE HIF-1α CKO mice.
  
  
  CONCLUSIONS
  Dll4/Notch signaling and HIF-1α are closely related to lymphangiogenesis in DE-induced LGs. Lymphangiogenesis stimulated by Dll4/Notch and HIF-1α may play a role in protecting LGs from DE-induced inflammation by aiding the clearance of immune cells from LGs.
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ji Hwan
authors.initials: JH
authors.lastname: Min
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Chul Hee
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.|Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yong Woo
authors.initials: YW
authors.lastname: Ji
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Areum
authors.initials: A
authors.lastname: Yeo
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Hyemi
authors.initials: H
authors.lastname: Noh
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Insil
authors.initials: I
authors.lastname: Song
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.|Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Eung Kweon
authors.initials: EK
authors.lastname: Kim
authors.affiliation: Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.|Corneal Dystrophy Research Institute, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea.|Severance Institute for Vascular and Metabolic Research, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Hyung Keun
authors.initials: HK
authors.lastname: Lee
mesh_terms: D000818:Animals; D015536:Down-Regulation; D015352:Dry Eye Syndromes / Q000378:metabolism* / Q000473:pathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D007765:Lacrimal Apparatus / Q000378:metabolism* / Q000473:pathology; D017493:Leukocyte Common Antigens / Q000378:metabolism; D042583:Lymphangiogenesis; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D015854:Up-Regulation
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch; C064045:delta protein; D017493:Leukocyte Common Antigens
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