Alcohol Intoxication, Arrhythmias and Inward Rectifiers 4 th Global Summit on Toxicology,...

Alcohol Intoxication, Arrhythmias and Inward Rectifiers

4th Global Summit on Toxicology, Philadelphia (USA), 26. 8. 2015

Markéta BébarováDepartment of Physiology, Faculty of Medicine, Masaryk University,

Brno, Czech Republic

Proarrhythmogenic Effect of Alcohol Consumption

• supraventricular arrhythmias - atrial fibrillation (holiday heart sy)

http://chilternhillsheartclinic.com/content-images/image-chhc-IWpyt.jpg

• ventricular arrhythmias- ventricular extrasystoles - ventricular arrhythmias - torsades de pointes

http://img.medscape.com/pi/emed/ckb/emergency_medicine/756148-756734-760963-1575961.jpg

• prolongation of P wave, QRS complex, PR and QTc intervals

• direct effects on ionic channels and transporters

• indirect effects on the cardiac electrophysiology(e.g. changes of membrane phospholipids under ethanol, catecholamine release caused by ethanol and acetaldehyde, electrolyte dysbalance, pH changes)

Proarrhythmogenic Effect of Alcohol ConsumptionMechanisms

Ethanol

• depolarizing: INa and ICa (e.g. Habuchi et al. 1995, Bébarová et al. 2010)

• repolarizing: IKr (O´Leary 2002, Himmel 2007) and Ito (Bébarová et al. 2010)

inhibition of Na+/K+-ATPase (McCall and Ryan 1987)

ICa

IKr

inhibition of ionic currents:

Acetaldehyde ICa activation (Chen et al. 1999 and 2012)

• direct effects on ionic channels and transporters

• indirect effects on the cardiac electrophysiology(e.g. changes of membrane phospholipids under ethanol, catecholamine release caused by ethanol and acetaldehyde, electrolyte dysbalance, pH changes)


Ethanol

• depolarizing: INa and ICa (e.g. Habuchi et al. 1995, Bébarová et al. 2010)

• repolarizing: IKr (O´Leary 2002, Himmel 2007) and Ito (Bébarová et al. 2010)

inhibition of Na+/K+-ATPase (McCall and Ryan 1987)

ICa

IKr

inhibition of ionic currents:

Acetaldehyde ICa activation (Chen et al. 1999 and 2012)

http://tmedweb.tulane.edu/tmedwiki/doku.php/intro_to_the_heart_cardiac_electrophysiology

IK(Ach)


Cardiac inward rectifiers (both IK1 and IK(Ach)) are known to play an important role in arrhythmogenesis!(e.g. Dhamoon and Jalife 2005, Piao et al. 2007, Schimpf et al. 2008, Sekar et al. 2009, Wakili et al. 2011)

• IK1: Lazslo et al. (2009) statistically insignificant activation (by 25%)

• Kir2.1: Yakamura et al. (2001), Aryal et al. (2009) inhibition

• Kir3.1/3.4: Kobayashi et al. (2009), Yakamura et al. (2001), Aryal et al. (2009) significant activation

• IK(Ach): ?

Ethanol

Bébarová et al., J Physiol Pharmacol 2014;65(4):497-509



Ethanol• IK1

rat ventricles


Acetaldehyde• IK1: Chen et al. (1999) no effect on the inward component at 1 mM• IK(Ach): ?



Acetaldehyde


• IK1

rat ventricles

Bébarová et al., Physiol Res 2015 (in press)


• Atrial fibrillation is the most often arrhythmia related to alcohol consumption.


Aim of the study

Analysis of ethanol and acetaldehyde effects on atrial inward rectifiers, IK1 and IK(Ach)

• Data on atrial inward rectifiers are insufficient.

Methods

voltage clamp mode

Im

Um

Whole cell patch clamp technique

rat atrial cell CHO cells

Im

Um

current clamp mode

Results Ethanol & IK1

Concentration Dependence

0.1 1 10 100

80

100

120

140

160

Changes induced by 80 mM ethanol

Results Ethanol & Constitutively Active IK(Ach)



Results Ethanol & Action Potential WaveformChanges induced by 20 mM ethanol in rat atrial cells

Rat Atrial Cell Modelling

Results Ethanol & Acetylcholine-induced IK(Ach)


activation inhibition

activation inhibition



Results Ethanol & Acetylcholine-induced IK(Ach)

ConclusionsEthanol at clinically relevant concentrations caused:

1) minor, likely not relevant changes of the atrial IK1

2) significant increase of the atrial constitutively active component of IK(Ach)

- no interspecies differences including human channels

- may cause pro-arrhythmic heterogeneity of repolarization within the atrial tissue

- responsible for significant shortening of action potential, thus, of the refractory period (re-entry)

3) significant dual changes of the atrial acetylcholine-induced component of IK(Ach)

Thank you for your attention!

Supported by the grant project NT14301-3/2013 provided by the Ministery of Health of the Czech Republic.

Peter Matejovič

Zuzana Hořáková

Michal Pásek

Milena Šimurdová

Jiří Šimurda

Department of Physiology, Faculty of Medicine, Masaryk University, Brno, Czech Republic

Jan Hošek Department of Molecular Biology and Pharmaceutical Biotechnology, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences Brno, Czech Republic


Heijman et al. (Circ Res 2014;114:1483-1499)

http://tmedweb.tulane.edu/tmedwiki/doku.php/intro_to_the_heart_cardiac_electrophysiology

IK(Ach)

Results Ethanol & IK1


Effect on human Kir2.3 channels


Cardiac inward rectifiers (both IK1 and IK(Ach)) are known to play an important role in arrhythmogenesis!

Ethanol• IK1

rat atria

020 mV

control 300 nM tertiapin-Q

20 ms

0

5

10

15

20

25

20 mM eth

APD

un

de

r te

rtia

pin

-Q (

%)

APD50

APD90

con

**

0

20 mM ethanol 20 mM ethanol

+ 300 nM tertiapin-Q

-75

-60

-45

-30

-15

020 mM eth

APD90

un

de

r a

cety

lch

olin

e (

%)

smaller APD90

under eth

bigger APD90

under eth

con

20 ms

control 3 M acetylcholine

0 20 mV 0

20 mM ethanol 20 mM ethanol

+ 3 M acetylcholine

Results Acetaldehyde & Ventricular IK1

Results Acetaldehyde & Ventricular IK1

Voltage Dependence Action Potential Waveform

• Ethanol i acetaldehyd vykazují v klinicky relevantních koncentracích reverzibilní vliv na proud IK1 v komorách.

Bébarová et al. (Acta Physiol 2010)

Závěry I – komorové srdeční buňky

• Ethanol – dvojí efekt na IK1, v nižších koncentracích než které ovlivňují jiné proudy

0,92‰

Ethanol & IK1 – model lidské komorové buňky

Alcohol Intoxication, Arrhythmias and Inward Rectifiers 4 th Global Summit on Toxicology,...

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