title: Increased fibroblast chymase production mediates procollagen autophagic digestion in volume overload.
abstract: BACKGROUND
  Previous work has identified mast cells as the major source of chymase largely associated with a profibrotic phenotype. We recently reported increased fibroblast autophagic procollagen degradation in a rat model of pure volume overload (VO). Here we demonstrate a connection between increased fibroblast chymase production and autophagic digestion of procollagen in the pure VO of aortocaval fistula (ACF) in the rat.
  
  
  RESULTS
  Isolated LV fibroblasts taken from 4 and 12week ACF Sprague-Dawley rats have significant increases in chymase mRNA and chymase activity. Increased intracellular chymase protein is documented by immunocytochemistry in the ACF fibroblasts compared to cells obtained from age-matched sham rats. To implicate VO as a stimulus for chymase production, we show that isolated adult rat LV fibroblasts subjected to 24h of 20% cyclical stretch induces chymase mRNA and protein production. Exogenous chymase treatment of control isolated adult cardiac fibroblasts demonstrates that chymase is internalized through a dynamin-dependent mechanism. Chymase treatment leads to an increased formation of autophagic vacuoles, LC3-II production, autophagic flux, resulting in increased procollagen degradation. Chymase inhibitor treatment reduces cyclical stretch-induced autophagy in isolated cardiac fibroblasts, demonstrating chymase's role in autophagy induction.
  
  
  CONCLUSIONS
  In a pure VO model, chymase produced in adult cardiac fibroblasts leads to autophagic degradation of newly synthesized intracellular procollagen I, suggesting a new role of chymase in extracellular matrix degradation.
authors.affiliation: Birmingham Veteran Affairs Medical Center, University of Alabama at Birmingham, Birmingham, AL, United States; Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States.
authors.forename: Lianwu
authors.initials: L
authors.lastname: Fu
authors.affiliation: Birmingham Veteran Affairs Medical Center, University of Alabama at Birmingham, Birmingham, AL, United States; Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States.
authors.forename: Chih-Chang
authors.initials: CC
authors.lastname: Wei
authors.affiliation: Birmingham Veteran Affairs Medical Center, University of Alabama at Birmingham, Birmingham, AL, United States.
authors.forename: Pamela C
authors.initials: PC
authors.lastname: Powell
authors.affiliation: Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States.
authors.forename: Wayne E
authors.initials: WE
authors.lastname: Bradley
authors.affiliation: Division of Surgical Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, United States.
authors.forename: Sarfaraz
authors.initials: S
authors.lastname: Ahmad
authors.affiliation: Division of Surgical Sciences, Wake Forest University School of Medicine, Winston-Salem, NC, United States.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Ferrario
authors.affiliation: Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States.
authors.forename: James F
authors.initials: JF
authors.lastname: Collawn
authors.affiliation: Birmingham Veteran Affairs Medical Center, University of Alabama at Birmingham, Birmingham, AL, United States; Division of Cardiovascular Disease, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States; Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, AL, United States. Electronic address: louis.dellitalia@va.gov.
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Dell'Italia
mesh_terms: D000818:Animals; D001011:Aorta / Q000378:metabolism* / Q000473:pathology; D001159:Arterio-Arterial Fistula; D001343:Autophagy / Q000235:genetics; D053818:Chymases / Q000096:biosynthesis* / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D006333:Heart Failure / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008407:Mast Cells / Q000378:metabolism / Q000473:pathology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D010588:Phagosomes / Q000378:metabolism; D011347:Procollagen / Q000378:metabolism*; D059748:Proteolysis; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats
chemical_list: D011347:Procollagen; D012333:RNA, Messenger; D053818:Chymases
keywords: Autophagy; Cardiac fibroblast; Chymase; Intracellular procollagen; Volume overload