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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55000200000
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600000
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1000000Normal
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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8,000
10,000 2D RV?
HF HF +
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1,000,000 3D LV?
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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