title: Attenuated development of cardiac fibrosis in left ventricular pressure overload by SM16, an orally active inhibitor of ALK5.
abstract: Pressure overload-induced TGF-β signaling activates cardiac fibroblasts (CFB) and leads to increased extracellular matrix (ECM) protein synthesis including fibrosis. Excessive ECM accumulation may in turn affect cardiac function contributing to development of heart failure. The aim of this study was to examine the effects of SM16, an orally active small molecular inhibitor of ALK5, on pressure overload-induced cardiac fibrosis. One week after aortic banding (AB), C57Bl/6J mice were randomized to standard chow or chow with SM16. Sham operated animals served as controls. Following 4 weeks AB, mice were characterized by echocardiography and cardiovascular magnetic resonance before sacrifice. SM16 abolished phosphorylation of SMAD2 induced by AB in vivo and by TGF-β in CFB in vitro. Interestingly, Masson Trichrome and Picrosirius Red stained myocardial left ventricular tissue revealed reduced development of fibrosis and collagen cross-linking following AB in the SM16 treated group, which was confirmed by reduced hydroxyproline incorporation. Furthermore, treatment with SM16 attenuated mRNA expression following induction of AB in vivo and stimulation with TGF-β in CFB in vitro of Col1a2, the cross-linking enzyme LOX, and the pro-fibrotic glycoproteins SPARC and osteopontin. Reduced ECM synthesis by CFB and a reduction in myocardial stiffness due to attenuated development of fibrosis and collagen cross-linking might have contributed to the improved diastolic function and cardiac output seen in vivo, in combination with reduced lung weight and ANP expression by treatment with SM16. Despite these beneficial effects on cardiac function and development of heart failure, mice treated with SM16 exhibited increased mortality, increased LV dilatation and inflammatory heart valve lesions that may limit the use of SM16 and possibly also other small molecular inhibitors of ALK5, as future therapeutic drugs.
authors.affiliation: Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway; Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Kristin V T
authors.initials: KV
authors.lastname: Engebretsen
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Kristine
authors.initials: K
authors.lastname: Skårdal
authors.affiliation: Department of Pathology, Oslo University Hospital Ullevål and University of Oslo, Oslo, Norway.
authors.forename: Sigrid
authors.initials: S
authors.lastname: Bjørnstad
authors.affiliation: Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway; Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Henriette S
authors.initials: HS
authors.lastname: Marstein
authors.affiliation: Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway; Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Biljana
authors.initials: B
authors.lastname: Skrbic
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Ivar
authors.initials: I
authors.lastname: Sjaastad
authors.affiliation: Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Christensen
authors.affiliation: Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway; Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway.
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Bjørnstad
authors.affiliation: Department of Cardiothoracic Surgery, Oslo University Hospital Ullevål, Oslo, Norway; Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway; KG Jebsen Cardiac Research Center and Center for Heart Failure Research, University of Oslo, Oslo, Norway. Electronic address: theis.tonnessen@medisin.uio.no.
authors.forename: Theis
authors.initials: T
authors.lastname: Tønnessen
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001024:Aortic Valve Stenosis / Q000378:metabolism / Q000503:physiopathology; D053961:Azabicyclo Compounds / Q000008:administration & dosage*; D002316:Cardiotonic Agents / Q000008:administration & dosage*; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D005109:Extracellular Matrix / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005355:Fibrosis; D057809:HEK293 Cells; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000378:metabolism* / Q000503:physiopathology; D008810:Mice, Inbred C57BL; D009206:Myocardium / Q000473:pathology*; D061251:Primary Cell Culture; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors*; D015398:Signal Transduction; D051899:Smad2 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000502:physiology; D017725:Ventricular Pressure
chemical_list: D053961:Azabicyclo Compounds; D002316:Cardiotonic Agents; D018125:Receptors, Transforming Growth Factor beta; C528106:SM16 compound; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D016212:Transforming Growth Factor beta; D003094:Collagen; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse
keywords: Cardiac fibroblasts; Cardiac fibrosis; Glycoproteins; Heart failure; Pressure overload