title: Adventitial fibroblasts induce a distinct proinflammatory/profibrotic macrophage phenotype in pulmonary hypertension.
abstract: Macrophage accumulation is not only a characteristic hallmark but is also a critical component of pulmonary artery remodeling associated with pulmonary hypertension (PH). However, the cellular and molecular mechanisms that drive vascular macrophage activation and their functional phenotype remain poorly defined. Using multiple levels of in vivo (bovine and rat models of hypoxia-induced PH, together with human tissue samples) and in vitro (primary mouse, rat, and bovine macrophages, human monocytes, and primary human and bovine fibroblasts) approaches, we observed that adventitial fibroblasts derived from hypertensive pulmonary arteries (bovine and human) regulate macrophage activation. These fibroblasts activate macrophages through paracrine IL-6 and STAT3, HIF1, and C/EBPβ signaling to drive expression of genes previously implicated in chronic inflammation, tissue remodeling, and PH. This distinct fibroblast-activated macrophage phenotype was independent of IL-4/IL-13-STAT6 and TLR-MyD88 signaling. We found that genetic STAT3 haplodeficiency in macrophages attenuated macrophage activation, complete STAT3 deficiency increased macrophage activation through compensatory upregulation of STAT1 signaling, and deficiency in C/EBPβ or HIF1 attenuated fibroblast-driven macrophage activation. These findings challenge the current paradigm of IL-4/IL-13-STAT6-mediated alternative macrophage activation as the sole driver of vascular remodeling in PH, and uncover a cross-talk between adventitial fibroblasts and macrophages in which paracrine IL-6-activated STAT3, HIF1α, and C/EBPβ signaling are critical for macrophage activation and polarization. Thus, targeting IL-6 signaling in macrophages by completely inhibiting C/EBPβ or HIF1α or by partially inhibiting STAT3 may hold therapeutic value for treatment of PH and other inflammatory conditions characterized by increased IL-6 and absent IL-4/IL-13 signaling.
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, School of Medicine, University of Colorado Denver, Aurora, CO 80045; Karim.Elkasmi@UCDenver.edu Kurt.Stenmark@UCDenver.edu.
authors.forename: Karim C
authors.initials: KC
authors.lastname: El Kasmi
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Steven C
authors.initials: SC
authors.lastname: Pugliese
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Suzette R
authors.initials: SR
authors.lastname: Riddle
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Jens M
authors.initials: JM
authors.lastname: Poth
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Aimee L
authors.initials: AL
authors.lastname: Anderson
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Maria G
authors.initials: MG
authors.lastname: Frid
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Lung Development and Remodeling, Max-Planck Institute for Heart and Lung Research, University of Giessen and Marburg Lung Center, German Center for Lung Research, D-61231 Bad Nauheim, Germany;
authors.forename: Soni S
authors.initials: SS
authors.lastname: Pullamsetti
authors.affiliation: Department of Lung Development and Remodeling, Max-Planck Institute for Heart and Lung Research, University of Giessen and Marburg Lung Center, German Center for Lung Research, D-61231 Bad Nauheim, Germany;
authors.forename: Rajkumar
authors.initials: R
authors.lastname: Savai
authors.affiliation: Department of Neurology, University of Colorado Denver, School of Medicine, Aurora, CO 80045;
authors.forename: Maria A
authors.initials: MA
authors.lastname: Nagel
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Mehdi A
authors.initials: MA
authors.lastname: Fini
authors.affiliation: Program in Translational Lung Research, Department of Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Brian B
authors.initials: BB
authors.lastname: Graham
authors.affiliation: Program in Translational Lung Research, Department of Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Rubin M
authors.initials: RM
authors.lastname: Tuder
authors.affiliation: Division of Biochemistry and Molecular Genetics, Department of Pediatrics, School of Medicine, University of Colorado Denver, Aurora, CO 80045; and.
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Friedman
authors.affiliation: Department of Anesthesiology, School of Medicine, University of Colorado Denver, Aurora, CO 80045.
authors.forename: Holger K
authors.initials: HK
authors.lastname: Eltzschig
authors.affiliation: Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, School of Medicine, University of Colorado Denver, Aurora, CO 80045;
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Sokol
authors.affiliation: Division of Critical Care Medicine/Cardiovascular Pulmonary Research Laboratories, Department of Pediatrics and Medicine, School of Medicine, University of Colorado Denver, Aurora, CO 80045; Karim.Elkasmi@UCDenver.edu Kurt.Stenmark@UCDenver.edu.
authors.forename: Kurt R
authors.initials: KR
authors.lastname: Stenmark
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002417:Cattle; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism / Q000494:pharmacology; D005347:Fibroblasts / Q000276:immunology* / Q000378:metabolism; D005355:Fibrosis / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D006801:Humans; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015151:Immunoblotting; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects / Q000235:genetics / Q000276:immunology*; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010641:Phenotype; D011921:Rats, Inbred WKY; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000276:immunology / Q000378:metabolism
chemical_list: D022782:CCAAT-Enhancer-Binding Protein-beta; D017077:Culture Media, Conditioned; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015850:Interleukin-6; D050796:STAT3 Transcription Factor