Cellular calcium signaling in cardiac arrhythmias

Crystal M. Ripplinger, Ph.D.

Assistant Professor

Department of Pharmacology, UC Davis

• Leading cause of death in the industrialized world• Due to many different underlying causes

Sudden Cardiac Death - Ventricular Arrhythmia

IschemicCoronary artery disease

Non-IschemicValvular disease

Hypertension

GeneticCardiomyopathy / Channelopathy

Multi-Scale Approaches

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Arrhythmia Research at UC Davis

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Whole Organism:Chiamvimonvat,Chen, Ripplinger

Whole Heart:Ripplinger

Cellular/Sub-cellular:Bers, Bossuyt,

Chen-Izu, Xiang,Chiamvimonvat

Protein:Sack, Yarov-Yarovoy

Computational:Clancy, Grandi,

Izu, Sato

Arrhythmia Research at UC Davis

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Whole Organism:Chiamvimonvat,Chen, Ripplinger

Whole Heart:Ripplinger

Cellular/Sub-cellular:Bers, Bossuyt,

Chen-Izu, Xiang,Chiamvimonvat

Protein:Sack, Yarov-Yarovoy

Computational:Clancy, Grandi,

Izu, Sato

Excitation-Contraction Coupling:Cellular Level

Bers DM (2010) Nature.

Excitation-Contraction Coupling: Whole HeartDual Optical Imaging of Vm and Ca2+

Excitation-Contraction

Uncoupler:

Blebbistatin (~10 μM)

082010

Vm

Fluorescence

Ca2+

Fluorescence

ECG

- Vm

- Ca2+

Dual Optical Imaging of Vm and Ca2+

Dual Optical Imaging of Vm and Ca2+

Cardiac Sympathetic Nerves

Batulevicius et al.,Auton Neurosci, 2008

Saburkina et al.,Heart Rhythm, 2010

Altered Sympathetic Activity and Arrhythmia

Li, AJP 2003

Hyper/De-nervationfollowing MI

Hyperinnervationwith high cholesterol

CON

HC

Liu, CircRes 2003

Altered sympathetic activity in patients with

ICD shocks

Boogers, JACC 2010

Chen, CV Res 2001

How does sympathetic activity trigger

arrhythmia?Isolated cardiac

myocyte

Isolated Cell

IntactHeart

?Pogwizd and Bers, Circ Res 2001

Norepinephrine

So Little Source, So Much Sink: Requirements for

Afterdepolarizations to Propagate in TissueYuanfang Xie, Daisuke Sato, Alan Garfinkel, Zhilin Qu, James N. Weiss,

Biophys J. 2010

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Cellular HF

Cellular HF + uncoupling

1D 2D 3D

~5000 cells

Protocol: Apply controlled local sympathetic stimulation to the intact heart

Normal Rabbit HeartVarying doses ofNorepinephrine (NE)Low Dose: 30 – 120 μMHigh Dose: 125 – 250 μMControl: Normal Tyrode’s

LV

RV

Can localized β-AR stimulation produce spatio-

temporal synchronization of SR Ca2+ release to

produce propagating PVCs in the intact heart?

NE–induced PVCs

Myles et al, Circ Res, 2012.

NE–induced PVCs

Vm

Fluorescence

PVCs

Mechanism of PVCs: SR Ca2+ release

Myles et al, Circ Res, 2012. Vm Vm

Ca2+

Quantify Area of Exposure to NE

Right Ventricle requires less area of NE

exposure to trigger SR Ca2+ release

~2D vs. 3D Tissue Geometry

Myles et al, Circ Res, 2012.

How many Myocytes are in short Vm- Ca2+ delay zone

(and may trigger PVC)?

Quasi-2D/RV

Epi

Endo

Epi

Endo

Area of

source-sink

Interaction

12,200 cells 2 x 106 cells

3D/LV

Experimental

How many Myocytes are in short Vm- Ca2+ delay zone

(and may trigger PVC)?

Quasi-2D/RV

Epi

Endo

Epi

Endo

Area of

source-sink

Interaction

12,200 cells 2 x 106 cells

3D/LV

Experimental

Theoretical (Xie, Sato, Garfinkel, Zu & Weiss, 2010)

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817,280 cells7,854 cells

Summary

Integrative approach – building on cellular-level and computational datasets to understand how pathological calcium handling leads to arrhythmia at the whole-heart level

Whole-heart data, in turn, validates and confirms cellular and computational findings

Ongoing studies:

Determine the impact of HF remodeling on localized β-AR-induced PVCs

UC Davis Rabbit Model of Non-Ischemic Heart Failure – currently used by ~8 labs, ~30 different experiments/animal

People:

• Rachel Myles, MD, PhD

• Lianguo Wang, MD

• Chaoyi Kang

• Nicole De Jesus

• Shannon Murphy, PhD

Collaborators: Dr. Don Bers,

Dr. Daisuke Sato

Acknowledgements:Funding:

• NIH: R01 HL111600

• AHA : SDG 9010015

• NIH: P30 HL101280

• UC Davis CTSC