Investigation of Acute and Chronic Effects of Statins on Vascular Function in Hypertensive Disorders of Pregnancy, with a Major Focus on Pre-eclampsia.

Abstract

Pre-eclampsia (PE), which affects 3-5% of pregnancies, is defined as new-onset hypertension and proteinuria post-20 weeks of gestation. There are no effective therapies for PE, which remains a leading cause of maternal and fetal morbidity and mortality. Chronic hypertension (CHT) is a risk factor for PE and shares similar pathological similarities such as endothelial dysfunction with women with CHT often going on to develop superimposed PE. Statins have been proposed as a candidate therapy for PE due to their pleiotropic effects such as being anti-inflammatory, antioxidants and increasing NO bioavailability. However, statins are currently contraindicated in pregnancy and studies have shown them to have detrimental effects in 1st trimester placental explants. Investigations into statins’ ability to ameliorate the observed endothelial dysfunction in PE but also side effects on vascular function is lacking. With pravastatin already being assessed in clinical trials for the treatment and prevention of PE, it is important to also investigate whether other statins are safe and efficacious for use in PE. In particular pitavastatin, a novel statin which has not be investigated in pregnancy studies and has potent pleiotropic effects. This study hypothesized that acute statin exposure would be able to improve vascular function without detrimental effects on fetal vessels in hypertensive pregnancies relative to normotensive ones. Similarly, the endothelial nitric oxide synthase knockout mouse (eNOS-/-), a model of CHT and FGR, and wildtype (WT) mice were used to assess both acute (ex-vivo) and chronic (in-vivo) statin exposure. Human chorionic plate arteries (CPAs) from normal and PE pregnancies and omental arteries (OAs) from normal, PE, chronic hypertensive and superimposed PE pregnancies were mounted on a wire myograph. Contraction was assessed with KPSS and thromboxane-mimetic U46619. Arteries were incubated for 2h with 1µM or 10µM of a statin; time-controls in parallel. U46619 dose–response curves were repeated or dose-response curves with NO-donor SNP or endothelium-dependent bradykinin (BK; humans only) or acetylcholine (ACh; mice only) performed following U46619 pre-constriction. Uterine and umbilical arteries from eNOS-/- and WT mice were collected at embryonic day (E)18.5 and their function assessed as above. In a separate study, pitavastatin (6µg/ml) was administered, via drinking water, to eNOS-/- and WT dams from E10.5-E18.5. Uterine, mesenteric and umbilical arteries were harvested at E18.5, ex-vivo vascular function was assessed using wire myography while maternal body, hysterectomized and organ weight were recorded, as well as fetal/placental /biometric measurements. Key findings:- • CPAs from normal and PE pregnancies showed similar responses following exposure to the vasoconstrictive agent U46619 and the relaxatory agent SNP. Short-term exposure to pravastatin, simvastatin and pitavastatin did not cause detrimental effects on CPA reactivity. • Acute exposure of OAs from hypertensive pregnancies to pitavastatin (1 µM) does not reduce U46619-mediated contraction or enhance BK-mediated relaxation of vessels. Although endothelial function of OAs from hypertensive pregnancies showed no difference to those from normotensive pregnancies. • Endothelial dysfunction was evident in the eNOS-/- mice relative to WT mice. Short-term exposure to pitavastatin at a suprapharmacological dose had no beneficial effect on vascular function in eNOS-/- mice and a potentially harmful effect in uterine and umbilical arteries from WT mice. Chronic pitavastatin exposure resulted in an enhanced relaxation to ACh in uterine arteries from eNOS-/- treated mice. This all occurred without pitavastatin having any obvious detrimental effects on the fetus as evidenced by normal fetal/placental weight and litter size. In conclusion, the work within this thesis has demonstrated that acute treatment with statins does not

Date of Award	1 Aug 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Jenny Myers (Supervisor) & Mark Dilworth (Supervisor)