title: Angiotensin II stimulates canonical TGF-β signaling pathway through angiotensin type 1 receptor to induce granulation tissue contraction.
abstract: Hypertrophic scar contraction (HSc) is caused by granulation tissue contraction propagated by myofibroblast and fibroblast migration and contractility. Identifying the stimulants that promote migration and contractility is key to mitigating HSc. Angiotensin II (AngII) promotes migration and contractility of heart, liver, and lung fibroblasts; thus, we investigated the mechanisms of AngII in HSc. Human scar and unwounded dermis were immunostained for AngII receptors angiotensin type 1 receptor (AT1 receptor) and angiotensin type 2 receptor (AT2 receptor) and analyzed for AT1 receptor expression using Western blot. In vitro assays of fibroblast contraction and migration under AngII stimulation were conducted with AT1 receptor, AT2 receptor, p38, Jun N-terminal kinase (JNK), MEK, and activin receptor-like kinase 5 (ALK5) antagonism. Excisional wounds were created on AT1 receptor KO and wild-type (WT) mice treated with AngII ± losartan and ALK5 and JNK inhibitors SB-431542 and SP-600125, respectively. Granulation tissue contraction was quantified, and wounds were analyzed by immunohistochemistry. AT1 receptor expression was increased in scar, but not unwounded tissue. AngII induced fibroblast contraction and migration through AT1 receptor. Cell migration was inhibited by ALK5 and JNK, but not p38 or MEK blockade. In vivo experiments determined that absence of AT1 receptor and chemical AT1 receptor antagonism diminished granulation tissue contraction while AngII stimulated wound contraction. AngII granulation tissue contraction was diminished by ALK5 inhibition, but not JNK. AngII promotes granulation tissue contraction through AT1 receptor and downstream canonical transforming growth factor (TGF)-β signaling pathway, ALK5. Further understanding the pathogenesis of HSc as an integrated signaling mechanism could improve our approach to establishing effective therapeutic interventions.
  
  
  CONCLUSIONS
  AT1 receptor expression is increased in scar tissue compared to unwounded tissue. AngII stimulates expression of proteins that confer cell migration and contraction. AngII stimulates fibroblast migration and contraction through AT1 receptor, ALK5, and JNK. AngII-stimulated in vivo granulation tissue contraction is AT1 receptor and ALK5 dependent.
authors.affiliation: Duke University School of Medicine, Duke University Medical Center (DUMC), Durham, NC, USA.
authors.forename: Tosan
authors.initials: T
authors.lastname: Ehanire
authors.forename: Licheng
authors.initials: L
authors.lastname: Ren
authors.forename: Jennifer
authors.initials: J
authors.lastname: Bond
authors.forename: Manuel
authors.initials: M
authors.lastname: Medina
authors.forename: George
authors.initials: G
authors.lastname: Li
authors.forename: Latif
authors.initials: L
authors.lastname: Bashirov
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: George
authors.initials: G
authors.lastname: Kokosis
authors.forename: Mohamed
authors.initials: M
authors.lastname: Ibrahim
authors.forename: Angelica
authors.initials: A
authors.lastname: Selim
authors.forename: Gerard C
authors.initials: GC
authors.lastname: Blobe
authors.forename: Howard
authors.initials: H
authors.lastname: Levinson
mesh_terms: D016475:3T3 Cells; D000328:Adult; D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D002465:Cell Movement; D017439:Cicatrix, Hypertrophic / Q000378:metabolism*; D003094:Collagen / Q000378:metabolism; D004817:Epidermis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D005260:Female; D006801:Humans; D008264:Macrophages / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008875:Middle Aged; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology*; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction; D055411:TGF-beta Superfamily Proteins / Q000502:physiology; D014945:Wound Healing; D055815:Young Adult
chemical_list: D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D018125:Receptors, Transforming Growth Factor beta; D055411:TGF-beta Superfamily Proteins; D000804:Angiotensin II; D003094:Collagen; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse