Anti-arrhythmic targeting of sympathetic stellate ganglion P2X3 receptors

Sympathetic hyperactivity associated with many primary cardiovascular diseases is pro-arrhythmic and a key contributor to sudden cardiac death. Surgically removing the sympathetic stellate ganglion has demonstrated therapeutic potential in minimising cardiac arrhythmia, but there are off-target risks prompting the need for more site-specific non-invasive approaches. Here we hypothesised that P2X3 purinergic receptors (P2X3R) may be a therapeutic target and play a role in the excessive sympathetic drive to the heart in cardiovascular disease. We investigated the role of P2X3R in the sympathetic stellate ganglion of Wistar and spontaneously hypertensive rats, and human-induced pluripotent stem cell (hiPSC)-derived sympathetic neurons, using a combination of immunohistochemistry, qRT-PCR, and in vitro calcium fluorescence imaging. Responses to ATP and P2X3R inhibition were investigated in intact stellate ganglion-heart preparations in situ. We confirm expression of P2X3R in sympathetic neurons of rat stellate ganglia at mRNA and protein levels. P2X3R mRNA was upregulated in SHR stellate ganglia compared to Wistar. Activation of P2X3R increased [Ca²⁺]_i in both isolated post-ganglionic sympathetic stellate neurons and hiPSC-derived sympathetic neurons, whereas microinjection of αβ-methylene ATP directly into right stellate ganglia induced tachycardia. Attenuation of these responses by a selective antagonist (AF353) indicated the tachycardia was P2X3R mediated. Inhibition of P2X3R rapidly restored the normal heart rhythm from sympathetic-induced cardiac arrhythmia. We show that stellate ganglion P2X3R contribute to sympathetically mediated cardiac chronotropic regulation. Our findings highlight the potential for inhibition of P2X3R located in the sympathetic stellate ganglion as a promising novel therapeutic for sympathetic nervous system-induced cardiac arrhythmias. KEY POINTS: Sympathetic nerve overactivity is pro-arrhythmic and a key contributor to left ventricular tachycardia and sudden cardiac death. P2X3 purinergic receptors are upregulated in stellate ganglia from prehypertensive rats. Stellate ganglion P2X3 receptors mediate increases in neuronal intracellular calcium and heart rate. Inhibiting P2X3 receptors rapidly and profoundly recovers normal heart rhythm from arrhythmia, highlighting the potential for inhibition of P2X3 receptors as a novel anti-arrhythmic.