Targeting BKCa Channels to Treat Maternal Vascular Dysfunction in Pre-Eclampsia

Abstract

Pre-eclampsia (PE) is a hypertensive disorder of pregnancy, contributing to 70,000 maternal deaths and 500,000 stillbirths worldwide each year. Preterm iatrogenic delivery is often necessary, which can have serious consequences for offspring. There is a clear clinical need for the development of novel treatments to control maternal hypertension and safely prolong gestation. Microvascular dysfunction is a hallmark of PE; past research has focused on endothelial dysfunction in PE, whilst dysfunction specific to the vascular smooth muscle (VSM) has not been widely studied. Control of VSM relaxation is largely mediated by large conductance calcium-activated potassium (BKCa) channels on the VSM cell membrane, which are activated by ryanodine receptor-mediated localised calcium ion (Ca2+) release events (Ca2+ sparks) from the sarcoplasmic reticulum. There is evidence in ovine models of PE that vasorelaxatory Ca2+ spark - mediated BKCa channel activity is reduced. This thesis sought to test the hypothesis that the Ca2+ spark - BKCa channel regulatory axis is impaired in PE, and that experimental agents that target the BKCa channel to induce relaxation might present a novel therapeutic approach in PE. Omental resistance arteries from normotensive pregnant women (NP) and women with PE were pressurised to 80 mmHg and imaged by high-speed spinning-disk laser confocal microscopy to measure Ca2+ spark release. Ca2+ spark frequency was significantly decreased in the PE group compared to NP. To explore the potential of bypassing this reduction in Ca2+ sparks and directly activating BKCa channel activity, a novel BKCa agonist Human Beta Defensin 2 (HBD2) was assessed using wire myography. HBD2 (0.01-10 nmol/L) induced significant vasorelaxation in submaximally constricted omental arteries from NP and PE pregnancies; this effect was blocked by 15 µmol/L paxilline, indicating BKCa channel involvement. A pilot study aiming to validate the Storkhead-Box Protein 1 (STOX1) mouse model of PE did not confirm a PE-like phenotype, and so we were unable to progress in vivo treatment studies further in this project. The data presented in this thesis have identified a striking impairment in Ca2+-mediated VSM regulation in PE. It may be possible to bypass these impairments to induce vasorelaxation via direct targeting of the BKCa channel. Subsequent investigation is now needed to further characterise VSM vasorelaxatory impairments in PE and to establish whether we can target specific components of the Ca2+ spark - BKCa channel regulatory axis to improve vascular function. Ultimately, this research aims to develop effective interventions that will alleviate the maternal clinical features of PE, reducing maternal and neonatal morbidity.

Date of Award	1 Aug 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Stephanie Worton (Supervisor), Adam Greenstein (Supervisor) & Elizabeth Cottrell (Supervisor)