title: High glucose induces Smad activation via the transcriptional coregulator p300 and contributes to cardiac fibrosis and hypertrophy.
abstract: BACKGROUND
  Despite advances in the treatment of heart failure, mortality remains high, particularly in individuals with diabetes. Activated transforming growth factor beta (TGF-β) contributes to the pathogenesis of the fibrotic interstitium observed in diabetic cardiomyopathy. We hypothesized that high glucose enhances the activity of the transcriptional co-activator p300, leading to the activation of TGF-β via acetylation of Smad2; and that by inhibiting p300, TGF-β activity will be reduced and heart failure prevented in a clinically relevant animal model of diabetic cardiomyopathy.
  
  
  METHODS
  p300 activity was assessed in H9c2 cardiomyoblasts under normal glucose (5.6 mmol/L-NG) and high glucose (25 mmol/L-HG) conditions. 3H-proline incorporation in cardiac fibroblasts was also assessed as a marker of collagen synthesis. The role of p300 activity in modifying TGF-β activity was investigated with a known p300 inhibitor, curcumin or p300 siRNA in vitro, and the functional effects of p300 inhibition were assessed using curcumin in a hemodynamically validated model of diabetic cardiomyopathy - the diabetic TG m(Ren-2)27 rat.
  
  
  RESULTS
  In vitro, H9c2 cells exposed to HG demonstrated increased p300 activity, Smad2 acetylation and increased TGF-β activity as assessed by Smad7 induction (all p < 0.05 c/w NG). Furthermore, HG induced 3H-proline incorporation as a marker of collagen synthesis (p < 0.05 c/w NG). p300 inhibition, using either siRNA or curcumin reduced p300 activity, Smad acetylation and TGF-β activity (all p < 0.05 c/w vehicle or scrambled siRNA). Furthermore, curcumin therapy reduced 3H-proline incorporation in HG and TGF-β stimulated fibroblasts (p < 0.05 c/w NG). To determine the functional significance of p300 inhibition, diabetic Ren-2 rats were randomized to receive curcumin or vehicle for 6 weeks. Curcumin treatment reduced cardiac hypertrophy, improved diastolic function and reduced extracellular matrix production, without affecting glycemic control, along with a reduction in TGF-β activity as assessed by Smad7 activation (all p < 0.05 c/w vehicle treated diabetic animals).
  
  
  CONCLUSIONS
  These findings suggest that high glucose increases the activity of the transcriptional co-regulator p300, which increases TGF-β activity via Smad2 acetylation. Modulation of p300 may be a novel strategy to treat diabetes induced heart failure.
authors.forename: Antoinette
authors.initials: A
authors.lastname: Bugyei-Twum
authors.forename: Andrew
authors.initials: A
authors.lastname: Advani
authors.forename: Suzanne L
authors.initials: SL
authors.lastname: Advani
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Kerri
authors.initials: K
authors.lastname: Thai
authors.forename: Darren J
authors.initials: DJ
authors.lastname: Kelly
authors.affiliation: Keenan Research Centre for Biomedical Science, St, Michael's Hospital, 209 Victoria Street, Toronto, ON M5B 1T8, Canada. connellyk@smh.ca.
authors.forename: Kim A
authors.initials: KA
authors.lastname: Connelly
mesh_terms: D000818:Animals; D006332:Cardiomegaly / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D002460:Cell Line; D050881:E1A-Associated p300 Protein / Q000378:metabolism*; D005355:Fibrosis; D005947:Glucose / Q000633:toxicity*; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D011897:Random Allocation; D051381:Rats; D055647:Rats, Transgenic; D051899:Smad2 Protein / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*
chemical_list: D051899:Smad2 Protein; C497784:Smad2 protein, rat; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat; D005947:Glucose