title: Hypoxia-induced HIF-1 alpha accumulation is augmented in a co-culture of keloid fibroblasts and human mast cells: involvement of ERK1/2 and PI-3K/Akt.
abstract: Keloids represent a prolonged inflammatory fibrotic state with areas that display distinctive histological features characterized by an abundant extracellular matrix stroma, a local infiltration of inflammatory cells including mast cells, and a milieu of enriched cytokines. Previous studies from our laboratory demonstrated an intrinsic higher level of HIF-1alpha and VEGF protein expression in keloid tissues compared with their adjacent unremarkable skins. To further investigate the mechanisms underlying the elevated expression of HIF-1alpha and VEGF in keloids, we exposed a co-culture of keloid fibroblasts and mast cells (HMC-1) to hypoxic conditions and studied the expression of HIF-1alpha and its target gene, VEGF. Our results showed that hypoxia-dependent HIF-1alpha protein accumulation and VEGF expression is augmented in keloid fibroblasts when co-cultured with HMC-1 cells under the condition where direct cell-cell contact is allowed. But such augmentation is not observed in the transwell co-culture system whereas fibroblasts and HMC-1 cells were separated by a porous membrane. Our results also indicated that the enhancement of hypoxia-mediated activation of ERK1/2 and Akt requires direct cell-cell interaction between mast cells and keloid fibroblasts, and activation of both ERK1/2 and Akt is involved in the hypoxia-dependent HIF-1alpha protein accumulation and VEGF expression in the co-culture system. These findings suggest that under hypoxic conditions mast cells may contribute, at least in part, to an elevated expression of HIF-1alpha and VEGF protein in keloids via direct cell-cell interaction with fibroblasts.
authors.affiliation: Center for Craniofacial Molecular Biology, University of Southern California, School of Dentistry, Los Angeles, CA 90089, USA.
authors.forename: Qunzhou
authors.initials: Q
authors.lastname: Zhang
authors.forename: Chad K
authors.initials: CK
authors.lastname: Oh
authors.forename: Diana V
authors.initials: DV
authors.lastname: Messadi
authors.forename: Hai S
authors.initials: HS
authors.lastname: Duong
authors.forename: A Paul
authors.initials: AP
authors.lastname: Kelly
authors.forename: Chia
authors.initials: C
authors.lastname: Soo
authors.forename: Lina
authors.initials: L
authors.lastname: Wang
authors.forename: Anh D
authors.initials: AD
authors.lastname: Le
mesh_terms: D002450:Cell Communication / Q000502:physiology; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D018920:Coculture Techniques; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D007627:Keloid / Q000473:pathology; D008407:Mast Cells / Q000166:cytology / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3