Investigating the expression of P2 purinergic receptors in sympathetic ganglia and perivascular nerves of arteries

Eldaly, Dalyan (2022) Investigating the expression of P2 purinergic receptors in sympathetic ganglia and perivascular nerves of arteries. Doctoral thesis, University of East Anglia.

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Hypertension, also known as high blood pressure, is a serious medical condition that can increase the risk of several diseases including heart failure, stroke, and chronic kidney disease. It is a major cause of premature death worldwide, affecting up to one in every four men and one in every five women. One of the factors that play a role in hypertension progression is blood vessel innervation via perivascular sympathetic nerves. The importance of ATP released from sympathetic nerves as an extracellular signalling molecule is now well known and evidence is accumulating that ATP, and other nucleotides (ADP, UTP and UDP) play key roles in cardiovascular physiology and pathology via P2X (ion channel) and P2Y (G protein-coupled) receptors. Pre-junctional nerve terminals are equipped with a number of auto- and/or heteroreceptors, including ionotropic P2X and metabotropic P2Y receptors. Pre-junctional purinergic receptors serve as modulation sites of neurotransmitter release via ATP and other nucleotides released by neuronal activity and pathological signals. However, very little is currently known about the expression of P2 receptors in sympathetic post-ganglionic nerves that innervate blood tissues, where they have a potential pre-junctional role in regulating neurotransmission. This project aimed to characterise the P2 receptor profiles in mouse superior cervical ganglion and perivascular nerve terminals of the superior mesenteric artery and carotid artery. In addition, we aimed to investigate the expression and function of P2 receptors in human SH-SY5Y cells and in vitro differentiated SH-SY5Y cells as a model of adrenergic sympathetic neurons. RT-PCR revealed the presence of mRNA in all P2 receptors was expressed in superior cervical ganglion. However, some receptors (P2X2, P2X3, P2X5, P2X6, P2Y1, P2Y4 and P2Y12) were expressed in the superior cervical ganglion, but not expressed in the superior mesenteric artery and carotid artery. We suggest that receptor subtypes detected in sympathetic ganglia but not arteries could be expressed by sympathetic post-ganglionic nerves that innervate arteries and could serve as auto- and/or heteroreceptors to modulate neurotransmitters release. We confirmed the expression of all P2X (with the exception of P2X5 and P2X6) and P2Y1 at the protein level by immunohistochemistry, and we found these receptors colocalised with the general marker of neurons (PGP9.5), the adrenergic sympathetic marker tyrosine hydroxylase in superior cervical ganglion and perivascular nerves within the adventitia of the arteries. Moreover, it was determined in this project that the P2X agonist (BzATP) promoted intracellular calcium responses in differentiated SH-SY5Y cells are principally mediated by P2X7 receptors. The data outlined that P2X7 receptors are functionally active in differentiated SH-SY5Y cells and may be a novel and interesting drug target for modulating neurotransmission and thus may have potential therapeutic applications in vascular diseases including hypertension. Further research is required to fully investigate the physiological roles of all of the P2 receptor subtypes expressed in sympathetic ganglia and pre-junctional sympathetic nerve terminals of arteries.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Nicola Veasy
Date Deposited: 23 Mar 2023 10:43
Last Modified: 23 Mar 2023 10:43


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