title: Tetrahydrobiopterin improves diastolic dysfunction by reversing changes in myofilament properties.
abstract: Despite the increasing prevalence of heart failure with preserved left ventricular function, there are no specific treatments, partially because the mechanism of impaired relaxation is incompletely understood. Evidence indicates that cardiac relaxation may depend on nitric oxide (NO), generated by NO synthase (NOS) requiring the co-factor tetrahydrobiopterin (BH(4)). Recently, we reported that hypertension-induced diastolic dysfunction was accompanied by cardiac BH(4) depletion, NOS uncoupling, a depression in myofilament cross-bridge kinetics, and S-glutathionylation of myosin binding protein C (MyBP-C). We hypothesized that the mechanism by which BH(4) ameliorates diastolic dysfunction is by preventing glutathionylation of MyBP-C and thus reversing changes of myofilament properties that occur during diastolic dysfunction. We used the deoxycorticosterone acetate (DOCA)-salt mouse model, which demonstrates mild hypertension, myocardial oxidative stress, and diastolic dysfunction. Mice were divided into two groups that received control diet and two groups that received BH(4) supplement for 7days after developing diastolic dysfunction at post-operative day 11. Mice were assessed by echocardiography. Left ventricular papillary detergent-extracted fiber bundles were isolated for simultaneous determination of force and ATPase activity. Sarcomeric protein glutathionylation was assessed by immunoblotting. DOCA-salt mice exhibited diastolic dysfunction that was reversed after BH(4) treatment. Diastolic sarcomere length (DOCA-salt 1.70±0.01 vs. DOCA-salt+BH(4) 1.77±0.01μm, P<0.001) and relengthening (relaxation constant, τ, DOCA-salt 0.28±0.02 vs. DOCA-salt+BH(4) 0.08±0.01, P<0.001) were also restored to control by BH(4) treatment. pCa(50) for tension increased in DOCA-salt compared to sham but reverted to sham levels after BH(4) treatment. Maximum ATPase rate and tension cost (ΔATPase/ΔTension) decreased in DOCA-salt compared to sham, but increased after BH(4) treatment. Cardiac MyBP-C glutathionylation increased in DOCA-salt compared to sham, but decreased with BH(4) treatment. MyBP-C glutathionylation correlated with the presence of diastolic dysfunction. Our results suggest that by depressing S-glutathionylation of MyBP-C, BH(4) ameliorates diastolic dysfunction by reversing a decrease in cross-bridge turnover kinetics. These data provide evidence for modulation of cardiac relaxation by post-translational modification of myofilament proteins.
authors.affiliation: Department of Medicine, Section of Cardiology, College of Medicine, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Euy-Myoung
authors.initials: EM
authors.lastname: Jeong
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Monasky
authors.forename: Lianzhi
authors.initials: L
authors.lastname: Gu
authors.forename: Domenico M
authors.initials: DM
authors.lastname: Taglieri
authors.forename: Bindiya G
authors.initials: BG
authors.lastname: Patel
authors.forename: Hong
authors.initials: H
authors.lastname: Liu
authors.forename: Qiongying
authors.initials: Q
authors.lastname: Wang
authors.forename: Ian
authors.initials: I
authors.lastname: Greener
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Dudley
authors.forename: R John
authors.initials: RJ
authors.lastname: Solaro
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000284:Administration, Oral; D000818:Animals; D001708:Biopterins / Q000008:administration & dosage / Q000031:analogs & derivatives*; D002317:Cardiovascular Agents / Q000008:administration & dosage*; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D003900:Desoxycorticosterone / Q000494:pharmacology; D003971:Diastole / Q000187:drug effects; D019587:Dietary Supplements; D005978:Glutathione / Q000378:metabolism; D054144:Heart Failure, Diastolic / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000503:physiopathology; D051379:Mice; D009210:Myofibrils / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D018384:Oxidative Stress; D011499:Protein Processing, Post-Translational; D013318:Stroke Volume / Q000187:drug effects; D014463:Ultrasonography; D000099163:Myosin Binding Protein C
chemical_list: D000251:Adenosine Triphosphatases; D001708:Biopterins; D002317:Cardiovascular Agents; D002352:Carrier Proteins; D003900:Desoxycorticosterone; D005978:Glutathione; D000099163:Myosin Binding Protein C; C003402:sapropterin