The RyR2-R2474S mutation in a CPVT mouse model significantly increased sympathetic neuron innervation density in ventricular tissue compared to wild type (3.8±0.5 vs 1.8±0.4 µm²; p<0.01).
The RyR2-R2474S mutation in CPVT mice causes sympathetic hyperinnervation and altered neurotransmitter levels, highlighting a neuronal mechanism for pro-arrhythmia.
Absolute Event Rate: 3.8% vs 1.8%
p-value: p=<0.01
Abstract Background Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome caused by mutations in RYR2 (encoding ryanodine receptor 2, RyR2). Investigation into the pro-arrhythmic effects of these mutations have focused exclusively on cardiomyocytes. However, RyR2 is also present in neuronal tissue. Moreover, patients often present with clinical signs of autonomic nervous system (ANS) dysfunction, and treatment strategies frequently target the ANS. Purpose To assess whether RyR2 mutations affect the neurons that modulate cardiac function, impact on cardiac innervation, and modulate cardiac neurotransmitter levels in an established CPVT mouse model (RyR2-R2474S). Methods RNA sequencing, immunocytochemistry, live-cell fluorescence imaging, immunohistochemistry and liquid chromatography–mass spectrometry. Results Analysis of published RNA sequencing datasets 1,2 revealed that RyR2 is abundantly expressed in mouse stellate ganglia (SG; crucial autonomic modulators of cardiac function). Using immunocytochemistry, we confirm the presence of RyR2 protein in these peripheral, cardiac-modulating neurons. Functional investigation revealed a reduction of caffeine-induced calcium release in isolated CPVT SG neurons (Fura Red AM F/F0 CPVT 0.53±0.01 vs wild type (WT) 0.45±0.01; p0.01), indicating the occurrence of intracellular calcium leakage. Moreover, cultured CPVT SG neurons showed increased neurite outgrowth (βIII tubulin/DAPI-positive area CPVT 6.9±0.6 vs WT 4.1±0.6 µm²; p0.01). Immunohistochemical staining of mouse heart cryosections with tyrosine hydroxylase (TH) demonstrated a significant increase in the density of sympathetic neuron innervation in ventricular tissue of CPVT mice (TH-positive area CPVT 3.8±0.5 vs WT 1.8±0.4 µm²; p0.01), and increased innervation heterogeneity (CPVT 5.4±1.3 vs WT 2.3±0.5 Δ µm²; p0.05). Neurotransmitter quantification in ventricular tissue revealed reduced levels of epinephrine in CPVT hearts (CPVT 0.023±0.002 vs WT 0.041±0.005 nmol/g; p0.01), elevated levels of the norepinephrine (NE) metabolite normetanephrine (NMN), and a consequent increase in the NMN/NE ratio, which is an index of NE turnover (CPVT 0.26±0.02 vs WT 0.16±0.01 nmol/g; p0.05). Quantification of blood plasma neurotransmitter metabolites revealed an increase in the dopamine metabolite 3-MT (CPVT 2.4±0.3 vs WT 1.3±0.2 nmol/g; p0.05). Conclusions Stellate ganglia neurons that modulate cardiac function abundantly express RyR2. The RyR2-R2474S mutation leads to increased stellate ganglia neurite outgrowth, sympathetic hyperinnervation and increased innervation heterogeneity in the ventricular myocardium, potentially contributing to pro-arrhythmia. In addition, the observed alterations of cardiac neurotransmitters and their metabolites may provide a novel blood biomarker for improved risk stratification in CPVT patients.
O’Reilly et al. (Sat,) conducted a other in Catecholaminergic polymorphic ventricular tachycardia (CPVT). RyR2-R2474S mutation (CPVT mouse model) vs. Wild type (WT) was evaluated on Sympathetic neuron innervation density in ventricular tissue (TH-positive area, µm²) (p=<0.01). The RyR2-R2474S mutation in a CPVT mouse model significantly increased sympathetic neuron innervation density in ventricular tissue compared to wild type (3.8±0.5 vs 1.8±0.4 µm²; p<0.01).