Cardiac contractility I. Cardiomyocyte contractility, Ca 2+ - PowerPoint PPT Presentation

Cardiac contractility I. Cardiomyocyte contractility, Ca 2+ availability vs. Ca 2+ sensitivity ZOLTÁN PAPP Muscle Biophysics PhD Summer School Thursday, 30 August, 2018, Budapest 8:30 – 9:30 Division of Clinical Physiology, Department of Cardiology University of Debrecen Hungary

Cardiac contractility I. Cardiomyocyte contractility, Ca 2+ availability vs. Ca 2+ sensitivity ZOLTÁN PAPP Muscle Biophysics PhD Summer School Thursday, 30 August, 2018, Budapest 8:30 – 9:30 Division of Clinical Physiology, Department of Cardiology University of Debrecen Hungary

Cardiac contractions and relaxations form the basis of cardiac function

Cardiac contractility depends on cardiomyocytes

What makes a cardiomyocyte work? cardiomyocyte

Sarcomeric structure in the heart is similar to that of skeletal myofibres sarcomere

Force generation depends on actin and myosin Fatty acids Fatty acids Glucose Glucose FA-CoA FA-CoA Pyruvate Pyruvate CPT1/2 CPT1/2 PDH PDH Acetyl-CoA Acetyl-CoA Krebs Krebs Ca 2+ Ca 2+  -Oxi-  -Oxi- + + Cycle Cycle dation dation NADH NADH + + ETC ETC Fe 3+ Fe 3+ + + ROS ROS ATP ATP Ca 2+ Ca 2+ Contraction/ Contraction/ Relaxation Relaxation

The actin and myosin cross-bridge cycle deGoma et al., J Am Coll Cardiol 2006;48:2397 – 409

Frank-Starling mechanism: ventricular end-diastolic volume regulates force of contraction Ernest Henry Starling 1866-1927

The Frank-Starling-mechanism and the length-tension relationship

The Frank-Starling-mechanism and the length-tension relationship 100 Force (%) Cardiac muscle 3,0 Sarcomere- 1 1,4 1,8 2,2 2,6 length (  m)

The Frank-Starling-mechanism and the length-tension relationship 100 Skeletal muscle Force (%) Cardiac muscle 3,0 Sarcomere- 1 1,4 1,8 2,2 2,6 length (  m)

What makes a cardiomyocyte work? Answer 1: myofilaments Cardiomyocyte

Excitation-contraction coupling and Ca 2+ transport Sarcolemma Ca 2+ ATPase NCX [Ca 2+ ] i AP T-tubule Contraction SR 200 ms Ca 2+ Channel RyR PLB SERCA NCX Myofilaments Adapted from Sjaastad et al., 2003

Ca 2+ transients regulate cardiac contractile force K + Na + Na + Ca 2+ [Ca 2+ ] i  I Ca-L Cardiomyocyte

Positive staircase

Positive staircase in human heart Tension Ca 2+

Ca 2+ movements are frequency dependent

What makes a cardiomyocyte work? Answer 2: Ca 2+ K + Na + Na + Ca 2+ [Ca 2+ ] i  I Ca-L cardiomyocyte

 - adrenergic regulation of contractility

 - adrenergic regulation of contractility out  -AR in PKA G s ATP AC cAMP RyR2 Sarcoplasmic Reticulum Ca 2+ Ca 2+ LTCC Serca2 PLB PKA PKA Ca 2+ T-tubule PKA myofilaments CREB nucleus Cardiac  contractility Fischmeister et al.,

Cyclic nucleotide mycrodomains in cardiomyocytes out  1 -AR in G s AC cAMP RyR2 Sarcoplasmic PDE4B Reticulum Ca 2+ PDE3 Ca 2+ LTCC Serca2 PDE2 PLB  2 -AR AKAP18 δ G s Ca 2+ G i T-tubule myofilaments nucleus Fischmeister et al.,

Cycic nucleotide mycrodomains in cardiomyocytes out  1 -AR pGC PI3K γ in PDE3B cGMP AKAP79 PDE5 G s PDE2 cGMP PDE8 AC cAMP AKAP15 sGC RyR2 Sarcoplasmic PDE4B Reticulum Ca 2+ PDE3 Ca 2+ LTCC Serca2 CST2 PP2A PP1 PDE2 mAKAP PLB  2 -AR AKAP18 δ G s PDE4D3 arrestin Ca 2+ AKAP79 PDE4D5 G i myomegalin PDE4D3 T-tubule cAMP PDE3A PKA myofilaments PDE3A CREB ICER PDE3A PDE1 AKAP-lbc mAKAP PKC nucleus Epac1 PKD ERK5 PDE4D3 Fischmeister et al.,

What makes a cardiomyocyte work? Answer 3: signaling mechanisms K + Na + Na + Ca 2+ [Ca 2+ ] i  I Ca-L PDE PKA 5’ -AMP cAMP  ATP cardiomyocyte β 1 R G s AC

Myocardial contractility = Ca 2+ -availibility + Ca 2+ -sensitivity K + Na + Na + Ca 2+ [Ca 2+ ] i  I Ca-L ATP + preignition cardiomyocyte - preignition

Ca 2+ -sensitivity and contractile force under steady-state conditions contraction Ca 2+ -sensitivity Force Force systole diastole [Ca 2+ ] time

Ca 2+ -sensitivity and contractile force under steady-state conditions contraction Ca 2+ -sensitivity Force Force systole diastole [Ca 2+ ] time

Ca 2+ -sensitivity is increased in chronic heart failure 1.0 0.8 Relative force 0.6 Donor pCa 50 Heart = 0.26 0.4 failure 0.2 0.0 6.0 5.5 5.0 4.5 pCa van der Velden J, et al. Cardiovasc Res 57,37-47, 2003

Phosphorylation deficit in chronic heart failure 1. 1.0 protein P 0.8 0.8 proteinkinase A Relative force 0.6 0.6 Donor pCa 50 Heart = 0,26 0.4 0.4 failure Donor PKA pCa 50 0.2 0.2 Heart = 0,01 faiure PKA 0.0 0.0 6.0 5.5 5.0 4.5 6.0 5.5 5.0 4.5 pCa van der Velden J, et al. Cardiovasc Res 57,37-47, 2003

The  - adrenergic system during chronic heart failure

Metabolic changes impair contractile performance during acute heart failure (e.g. ischaemia)

Intracellular acidosis decreases Ca 2+ -sensitivity of force production pH: 7.0 cTnC cTnI pH: 6.2 Robertson…Sykes, Arch Biochem Biophys. 2013 Dec 12. doi: 10.1016/j.abb.2013.12.003. Metzger et al., Journal of Physiology (1996), 492.1, pp. 163-172

Inorganic phosphate (P i ) decreases contractile force in permeabilized cardiac trabeculae of the rat P i Kentish J. J Physiol.1986;370,585-604.

Force measurements in isolated cardiomyocytes width Force transducer Motor 70 µm height Measured parameters: Force (F) turnover rate of the actin-myosin cycle (k tr ) 70 µm

Ca 2+ - contracture in a single cardiomyocyte Length Force 2 25 kN/m active force passive force 4,82 pCa 9 20 sec

Determination of the Ca 2+ -sensitivity of force production Maximal Ca 2+ -activated force (F o ) Force (rel.) n Hill Ca 2+ -sensitivity (pCa 50 )

Measuring the turnover rate of actin-myosin cycle in cardiomyocytes Length P 2 25 kN/m Force 4.75 passive pCa 10 20 sec

Measuring the turnover rate of actin-myosin cycle in cardiomyocytes Length P 2 25 kN/m Force 4.75 passive pCa 10 20 sec Length Hossz k tr 25 kN/m 2 Force Erő 1 sec

Isometric force and k tr are both Ca 2+ -dependent A A B pCa: 1 4.82 Force (relative) 0.5 P 0 (relative unit) 5.4 0 6 5 pCa C 5.6 1 5.8 k tr (1/sec) 6.0 6.2 0 6.5 10 6 5 pCa 1 sec

Frank-Starling mechanism and Ca 2+ -sensitivity of force production ventricular volume contractile force time time

Frank-Starling mechanism and Ca 2+ -sensitivity of force production ventricular volume contractile force sarcomere length 1,9 µm time 2,3 µm time

Frank-Starling mechanism and Ca 2+ -sensitivity of force production Ca 2+ -sensitivity ventricular volume contractile force sarcomere length 1,9 µm [Ca 2+ ] time 2,3 µm [Ca 2+ ] time

Ca 2+ -sensitivity and sarcomere length Ca 2+ -sensitivity sarcomere length (SL) (pCa 50 ) ? ? crossbridge kinetics (k tr ) myosin heavy chain

Length dependent Ca 2+ -sensitisation is conservative in mammalians  pCa 50 : ~0,1 Sertés Human Humán Mouse Pig Egér 1 1 1 Normalized force Normalizált erő SL: 2.3  m SL: 1.9  m 0 0 0 7 6 5 7 6 5 7 6 5 pCa pCa pCa Édes IF.,…Papp Z. Am. J. Physiol. 293: R20-R29, 2007

k tr is species dependent, but does not depend on sarcomere length 9 9 9 Egér Sertés Humán Human Mouse Pig 6 6 6 k tr (s -1 )  m S L : 2 .3 3 3 3  m S L : 1 .9 0 0 0 7 6 5 7 6 5 7 6 5 pCa pCa pCa Édes IF.,…Papp Z. Am. J. Physiol. 293: R20-R29, 2007

Length dependent Ca 2+ -sensitisation does not depend on k tr

Length dependent Ca 2+ -sensitisation does not depend on k tr k tr = f app + g app

Length dependent Ca 2+ -sensitisation is compatible with SL dependent cross-bridge recruitment Myosin head Tropomyosin Actin Blocked state Closed state Open state

Summary 1. Cardiomyocyte contractions and relaxations are controlled by interactions between myoplasmic Ca 2+ and myofilament proteins. 2. The Frank-Starling mechanism is the function of sarcomere length. The force-frequency relationship is governed by cardiomyocyte Ca 2+ 3. homeostasis. Cardiomyocyte signaling mechanisms affect Ca 2+ -availability and Ca 2+ - 4. sensitivity of force production. The Frank-Starling mechanism involves changes in Ca 2+ -sensitivity of force 5. production.

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