Nicotine Exacerbates Arrhythmogenesis in Rabbit Right Ventricular Outflow Tract Triggered by Chronic Obstructive Pulmonary Disease

Abstract

Cigarette smoke includes nicotine that increases ventricular tachycardia (VT) risk. Chronic obstructive pulmonary disease (COPD) and right ventricular outflow tract (RVOT) constitute the primary risk factor and origin of VT, respectively. To investigate the arrhythmogenesis of nicotine in COPD, we employed tachypacing with or without H89, KN93 and KB-R7943 treatment, along with patch clamp experiments and Masson's trichrome staining in control rabbits and rabbits with human leukocyte elastase (0.3 unit/kg)-induced COPD. Following 20-Hz tachypacing and isoproterenol treatment, COPD RVOTs had a higher VT incidence than control RVOTs. Nicotine-treated COPD RVOTs had higher ventricular arrhythmogenesis than non-treated COPD RVOTs. VTs induced in COPD and nicotine-treated COPD RVOTs were suppressed by H89, KN93, or KB-R7943. COPD RVOT myocytes exhibited shorter action potentials than control RVOT myocytes; nicotine-treated COPD RVOT myocytes exhibited longer action potentials than COPD RVOT myocytes. Both COPD and nicotine-treated COPD myocytes had smaller L-type Ca²⁺ currents and larger NCX currents than control RVOT myocytes. Nicotine-treated COPD RVOT myocytes had larger late Na⁺ currents than control and COPD RVOT myocytes. COPD and nicotine-treated COPD RVOTs exhibited more fibrosis. Nicotine-treated COPD RVOTs had the highest level of fibrosis. COPD intensifies RVOT VT through electrical and structural remodelling and Ca²⁺ dysregulation through the activation of PKA, CaMKII and NCX signalling pathways. Nicotine further exacerbates VTs in the rabbit RVOT triggered by COPD.

Keywords: chronic obstructive pulmonary disease; nicotine; right ventricular outflow tract; ventricular tachycardia.

FIGURE 1

Rapid ventricular pacing (RVP) effects on right ventricular outflow tracts (RVOTs) in control, chronic obstructive pulmonary disease (COPD) and nicotine‐treated COPD groups. (A) The upper panel highlights that RVP (20 Hz) induced no ventricular tachycardia (VT) in control RVOTs. The middle panel illustrates nonsustained VT in COPD RVOTs. The lower panel displays RVP‐induced nonsustained VT in nicotine‐treated COPD RVOTs. (B) Sustained VT is evident in the tracing of nicotine‐treated COPD RVOTs. * indicates nonsustained or sustained VT in panels A and B. (C) The upper and lower panels show the incidence of nonsustained and sustained VT, respectively, induced in control RVOTs (n = 12), COPD RVOTs (n = 12), and nicotine‐treated COPD RVOTs (n = 9). *p < 0.05 and ***p < 0.005.

FIGURE 2

Effect of combined rapid ventricular pacing (RVP, 20 Hz) and isoproterenol (ISO, 1 μM) administration on ventricular tachycardia (VT) occurrence in control, chronic obstructive pulmonary disease (COPD) and nicotine‐treated COPD groups. (A) The upper panels illustrate nonsustained VT induced by RVP and isoproterenol infusion in all three groups. * indicates nonsustained VT. The lower panels illustrate incidence, duration and rate of nonsustained VT induced by RVP and isoproterenol infusion in control RVOTs (n = 12), COPD RVOTs (n = 12) and nicotine‐treated COPD RVOTs (n = 9). (B) The upper panels present sustained VT induced by RVP and isoproterenol infusion in all three groups. * indicates sustained VT. The lower panels display incidence, duration and rate of sustained VT induced by RVP and isoproterenol infusion in different groups. *p < 0.05 and **p < 0.01.

FIGURE 3

Effects of H89 (10 μM), KN93 (1 μM) and KB‐R7943 (10 μM) treatment on ventricular tachycardia (VT) in right ventricular outflow tract (RVOTs) from chronic obstructive pulmonary disease (COPD) and nicotine‐treated COPD rabbits. The upper panels depict the suppression of nonsustained VTs induced by rapid ventricular pacing (RVP, 20 Hz) and isoproterenol (ISO, 1 μM) infusion upon cotreatment with H89 (panel A), KN93 (panel B) and KB‐R7943 (panel C) in both the COPD and nicotine‐treated COPD groups. * indicates nonsustained or sustained VT. The lower panels illustrate the incidence of nonsustained and sustained VT induced by RVP and isoproterenol infusion, before and after treatment with H89 (Panel A) in both the COPD (n = 9) and nicotine‐treated COPD (n = 8) groups; KN93 (Panel B) in both the COPD (n = 8) and nicotine‐treated COPD (n = 8) groups; and KB‐R7943 (Panel C) in both the COPD (n = 8) and nicotine‐treated COPD (n = 8) groups. **p < 0.01 and ***p < 0.005.

FIGURE 4

Effects of chronic obstructive pulmonary disease (COPD) and nicotine treatment on action potentials in isolated RVOT myocytes. The upper panel illustrates representative action potential traces from control right ventricular outflow tract (RVOT) myocytes (n = 12), COPD RVOT myocytes (n = 15) and nicotine‐treated COPD RVOT myocytes (n = 16). The lower panels present average data of the action potential parameters in the different groups. APA = action potential amplitude; RMP = resting membrane potential; APD₉₀, APD₅₀ and APD₂₀ = action potential duration at 90%, 50% and 20% repolarisation, respectively. *p < 0.05, **p < 0.01 and ***p < 0.005.

FIGURE 5

L‐type Ca²⁺ current (I_Ca‐L) and Na⁺–Ca²⁺ exchanger current (I_NCX) in right ventricular outflow tract (RVOT) myocytes from control, chronic obstructive pulmonary disease (COPD) and nicotine‐treated COPD rabbits. The left panel, upper part presents the recorded I_Ca‐L tracings in control RVOT (n = 13), COPD RVOT (n = 12) and nicotine‐treated COPD RVOT (n = 13) myocytes. The left panel, lower part displays the current–voltage relationship of I_Ca‐L within these three groups. *p < 0.05 for when the COPD RVOT myocytes were compared with the control RVOT myocytes; ^† p < 0.05, ^†† p < 0.01 and ^††† p < 0.005 for when the nicotine‐treated COPD RVOT myocytes were compared with the control RVOT myocytes; and ^# p < 0.05 and ^## p < 0.01 for when nicotine‐treated COPD RVOT myocytes were compared with the COPD RVOT myocytes. The right panel, upper part depicts the recorded I_NCX tracings in control RVOT (n = 9), COPD RVOT (n = 11) and nicotine‐treated COPD RVOT (n = 9) myocytes. The lower part presents the current–voltage relationship of I_NCX within these three groups. *p < 0.05 for when comparing the COPD RVOT myocytes to the control RVOT myocytes; ^† p < 0.05 for when the nicotine‐treated COPD RVOT myocytes were compared with the control RVOT myocytes; and ^# p < 0.05 for when nicotine‐treated COPD RVOT myocytes were compared with the COPD RVOT myocytes.

FIGURE 6

Transient outward K⁺ current (I_to) and Late Na⁺ current (I_Na‐Late) in right ventricular outflow tract (RVOT) myocytes from control, chronic obstructive pulmonary disease (COPD) and nicotine‐treated COPD rabbits. (A) The upper panels present the recorded I_to tracings in control RVOT (n = 16), COPD RVOT (n = 9) and nicotine‐treated COPD RVOT myocytes (n = 10). The lower panel displays the current–voltage relationship of I_to within these three groups. Insets in the current traces indicate the clamp protocols employed. (B) The upper panels present the recorded I_Na‐Late tracings in control RVOT (n = 9), COPD RVOT (n = 9) and nicotine‐treated COPD RVOT (n = 15) myocytes. The lower panels display the current–voltage relationship of I_Na‐Late in these three groups. ***p < 0.005.

FIGURE 7

Histopathology of the right ventricular outflow tract (RVOT) from control, chronic obstructive pulmonary disease (COPD) and nicotine‐treated COPD rabbits. The upper panel displays representative Masson‘s trichrome stains. The lower panel presents the average data for the control (n = 6), COPD (n = 6) and nicotine‐treated COPD (n = 6) RVOT myocytes. *p < 0.05 and ***p < 0.005.