Grapefruit Flavonoid Naringenin Sex-Dependently Modulates Action Potential in an In Silico Human Ventricular Cardiomyocyte Model

Abstract

Recent in vitro studies showed that grapefruit (Citrus × paradisi) flavonoid naringenin alters the function of cardiac ion channels. Here, we explored the effect of naringenin on cardiomyocyte action potentials (APs) using a detailed in silico model of ventricular electrophysiology. Concentration-dependent effects of naringenin on seven major cardiac ion channels were incorporated into the Tomek-Rodriguez modification of O'Hara-Rudy (ToR-ORd) human ventricular endocardium model. To investigate the sex-dependent effect of naringenin, previously reported sex-specific ionic modifications were implemented into the model. Next, populations of 1000 models accommodating intercellular variability were generated. The results show, naringenin at various concentrations prolonged AP duration (APD) in male and female cardiomyocytes. Pacing cells at higher frequencies abbreviated APD differently in males versus females; for example, at 3 Hz, 50 μM naringenin induced AP and calcium alternans only in the female cardiomyocyte. Finally, a population modeling approach corroborated that naringenin significantly prolonged APD in a concentration-dependent manner, with a larger effect in females than in males. In conclusion, our study demonstrates that the APD-prolonging effect of naringenin was larger in females, and that pacing at faster rates induces AP alternation earlier in females, suggesting a potentially higher proarrhythmic risk of naringenin in females than in males.

Keywords: antioxidant; cardiac arrhythmia; cardiovascular risk; citrus fruit; computational modeling; flavonoid; grapefruit juice; ion channel electrophysiology; naringenin.

Figure 1

Sex-specific ionic modifications implemented in the human ventricular cardiomyocyte model and concentration-dependent inhibitions of cardiac ion channels by naringenin. (A) Ten Tomek–Rodriguez adaptations of O’Hara–Rudy (ToR-ORd) model parameters were modified to obtain sex-specific human ventricular endocardium electrophysiology. The scaling factors were obtained from Peirlinck, Sahli Costabal, and Kuhl [14]. (B) The concentration–response curves displaying the concentration-dependent inhibition of seven major cardiac ion channels together with the associated 50% inhibitory concentrations (IC₅₀) and Hill factors [12].

Figure 2

Sex-dependent effect of naringenin on the action potential of ventricular cardiomyocytes. (A) The comparison of male and female action potentials of ventricular endocardium. (B–D) The concentration-dependent effect of naringenin on male and female ventricular action potentials. The baseline/no-compound conditions (M0 and F0) were used to calculate the absolute (Abs) difference in (D). All simulations were performed in 1 Hz pacing frequency. (APA = action potential amplitude; APD = action potential duration; CL = cycle length; F0 = Female 0 μM; F10 = Female 10 μM; F30 = Female 30 μM; F100 = Female 100 μM; M0 = Male 0 μM; M10 = Male 10 μM; M30 = Male 30 μM; M100 = Male 100 μM; RMP = resting membrane potential).

Figure 3

The rate-dependent effect of naringenin on human ventricular action potentials. (A–C) The rate-dependent effects of 50 μM naringenin on male and female action potentials. At 3 Hz pacing frequency (C), both calcium and action potential (AP) alternans were documented in the female AP, but not in the male AP. (D) The frequency–APD curve displaying the relationship between pacing rate and changes in AP duration at 90% repolarization (APD₉₀) in response to the administration of 50 μM naringenin. (E) The effect of 100 μM naringenin at 3 Hz pacing frequency. (F) The frequency–APD curve displaying the relationship between pacing rate and changes in APD₉₀ in response to the administration of other concentrations of naringenin.

Figure 4

Populations of models depicting the effect of naringenin on ventricular action potentials. One thousand model variations of the ToR-ORd model were made by altering the maximum conductance of nine major cardiac ion channels to represent biological variations (e.g., intercellular variability) in ventricular cardiomyocytes. In this figure, ‘only’ 100 AP variations were shown to maintain visibility. Naringenin was administered in three different concentrations: 10 (B,F), 30 (C,G), and 100 μM (D,H). Male = blue APs (A–D); Female = magenta APs (E–H).

Figure 5

The comparison of action potential durations (APDs; APD₃₀ (A), APD₅₀ (B), APD₇₀ (C) and APD₉₀ (D)) for various concentrations of naringenin. The data were extracted from the population of models consisting 1000 model variations shown in Figure 4. Statistical analyses were performed using one-way analysis of variance (ANOVA) with Tukey’s multiple comparison test between concentrations in males and females, and in the same concentrations across sex (i.e., M0 vs. M10, M0 vs. M30, M0 vs. M100, M10 vs. M30, M10 vs. M100, M30 vs. M100, F0 vs. F10, F0 vs. F30, F0 vs. F100, F10 vs. F30, F10 vs. F100, F30 vs. F100, M0 vs. F0, M10 vs. F10, M30 vs. F30, and M100 vs. F100). Statistical significance is reached if p < 0.05.

Figure 6

The comparison of other action potential properties (i.e., APA (A), dV/dt_max (B) and RMP (C)) in various concentrations of naringenin. The data were extracted from the population of models consisting 1000 model variations shown in Figure 4. Statistical analyses were performed using one-way analysis of variance (ANOVA) with Tukey’s multiple comparison test between concentrations in males and females, and in the same concentrations across sex (i.e., M0 vs. M10, M0 vs. M30, M0 vs. M100, M10 vs. M30, M10 vs. M100, M30 vs. M100, F0 vs. F10, F0 vs. F30, F0 vs. F100, F10 vs. F30, F10 vs. F100, F30 vs. F100, M0 vs. F0, M10 vs. F10, M30 vs. F30, and M100 vs. F100). Statistical significance is reached if p < 0.05. (APA = action potential amplitude; NS = not significant; RMP = resting membrane potential).