The Myofilament Ca 2 Sensitizer Levosimendan Preserves Systolic

The Myofilament Ca 2+ Sensitizer Levosimendan Preserves Systolic Function in Rats with Volume Overload Heart Failure Kristin Lewis, DVM Pathology Resident/Graduate Research Associate The Ohio State University, Columbus, OH The Research Institute, Nationwide Children’s Hospital, Columbus, OH

2 types of hemodynamic overload HF Volume Overload Pressure Overload © © Increased afterload Concentric hypertrophy Fibrosis Examples: • Hypertension • Aortic stenosis © © Increased preload Eccentric hypertrophy ECM degradation Examples: • • Aortic/Mitral regurgitation Myocardial infarct Ventricular septal defect Arterio-venous fistulae

Progression of Volume Overload (VO) to Heart Failure Reversible Mitral regurgitation Arterio-venous Fistulae Irreversible Systolic Dysfunction Volume Overload LV Remodeling HF Death Diastolic Dysfunction LV Dysfunction Time (months to years) Overt HF Time (months)

MR treatment options • Surgical repair/replacement – Optimal timing for patients with symptoms or decreased function is defined – Optimal timing for asymptomatic patients is controversial • Intervene early or “watch and wait”? – Post-operative dysfunction • Pharmacologic therapy – Can these agents delay surgery or improve function postoperatively? – Optimal agents?

VO-induced HF with aortocaval fistula (ACF) in the rat 18 g Aorta

ACF progressive increase in LVEDd, LVEDs Chest wall “Anterior” Sham LVEDd LVEDs 4 wk ACF “Posterior” Time 8 wk ACF 15 wk ACF

VO is accompanied by functional deterioration % Fractional Shortening * * LVEDd LVEDs *= P < 0. 05 vs. Sham

ACF Altered Ca 2+ responsiveness and handling 8 wk ACF Sham ACF SERCA 2 a PLB p. PLB *** p<0. 001 vs. Sham

Hypothesis Therapeutic strategies targeting myofilament Ca 2+ sensitivity will preserve/improve LV function in valvular heart disease

Myofilament Ca 2+ sensitizer: Levosimendan ECHO (q 2 w) Hemodymanics Myocyte isolation Tissue collection SHA M ACF (n=22) ACF (n=23) (n=28) Levo, 1 mg/kg 0 wk Adapted from Papp Z, et al. Int J Cardiol. 2011 Jul 23. 8 wk

Levo may attenuate the increase in LVEDD Sham LVEDd **** p<0. 0001 vs Sham-Veh; ^ p<0. 05, ^^ p<0. 01 vs ACF-Veh LVEDs ACF-Veh ACF-Levo

Levo improved LV systolic function * p<0. 05, ** p<0. 01, *** p<0. 001, **** p<0. 0001 vs Sham-Veh ^ p<0. 05, ^^^^ p<0. 0001 vs ACF-Veh

Levo ↑myofilament Ca 2+ sensitivity & ↑ maximal force without ↑ Ca 2+ transient * p<0. 05, ** p<0. 01 vs Sham-Veh ^ p<0. 05, ^^^ p<0. 001, ^^^^ p<0. 0001 vs ACF-Veh

Levo does not result in vasodilation

Levo improved LV diastolic function **** p<0. 0001 vs Sham-Veh ^ p<0. 05, ^^^ p<0. 001 vs ACF-Veh

c. My. BP-C and c. Tn. I • Cardiac Myosin Binding Protein-C (c. My. BP-C) – Thick filament associated protein – Phosphorylation ↑ contraction and relaxation & ↓Ca 2+ sensitivity • Cardiac Troponin I (c. Tn. I) – Thin filament associated protein – Phosphorylation ↓Ca 2+ sensitivity earlier onset of relaxation Adapted from Landstrom AP, et al. Circulation. 2010 Dec 7; 122(23): 2441 -9 Colson BA et al. J Mol Cell Cardiol. 2012 Nov; 53(5): 609 -16 Michalek AJ et al. Biophys J. 2013 Jan 22; 104(2): 442 -52.

Phosphorylation at c. My. BP-C Ser 273, Ser 302 and c. Tn. I Ser 23/24 may drive functional improvement Sham ACF+L Sham p. Ser 273 p. Ser 302 p. Ser 23/24 Total c. My. BP-C Total c. Tn. I ACF+L

Summary § Myofilament Ca 2+ sensitizer therapy improved systolic and diastolic function § Improved systolic function is due to increased myofilament Ca 2+ sensitivity § Improved diastolic function may be due to c. My. BP-C and/or c. Tn. I phosphorylation § Myofilament Ca 2+ sensitizer therapy mildly attenuated increase in LVEDD § Therapeutic strategies targeting myofilament Ca 2+ sensitivity may improve function prior to load reduction surgery

Acknowledgements Nationwide Children’s Hospital • Lucchesi lab – – – – Pam Lucchesi Aaron Trask Aaron West Jean Zhang Anu Guggilam Kirk Hutchinson Mary Cismowski • Vivarium – Natalie Snyder – Brenna Barbour – Erin Grove The Ohio State University • Veterinary Biosciences Funding Sources • ACVP/STP Coalition Fellowship & Genentech • NIH R 01 -HL 056046 • Nationwide Children’s