Experimental Preeclampsia Causes Long-Lasting Hippocampal Vascular Dysfunction and Memory Impairment

History of hypertensive disorders of pregnancy and risk of Alzheimer's disease and vascular dementia

The incidence of dementia, and specifically, Alzheimer's disease, is higher in women than men, even in middle age, making it possible to rule out lifespan differences between men and women as a contributing factor. Thus, it is plausible that pregnancy experience, which is unique to women, may play a contributing role. In this review, we discuss the different hypertensive disorders of pregnancy (HDP), Alzheimer's and vascular dementia, clinical, epidemiological, and preclinical studies that link a history of HDP with dementia. We also present potential mechanisms linking HDP, Alzheimer's, and vascular dementia. Several key symptoms that are shared among the disorders are presented as potential underlying mechanisms that link the adverse pregnancy disorder with the long-term postpartum neurological changes. Further, we present limitations of the existing literature, gaps, and opportunities for further research.

Aspirin Improves Uterine Artery Function in Hypercholesterolemic Preeclampsia

BACKGROUND

Excessive hypercholesterolemia in pregnancy increases the risk of preeclampsia (HC-PE), though the mechanisms remain unclear. We recently showed that uterine artery function is impaired in HC-PE pregnancies via activation of the TLR4 (toll-like receptor 4)/PGHS1 (prostaglandin H synthase 1) pathway. Low-dose aspirin lowers preeclampsia risk in high-risk pregnancies by inhibiting PGHS1, but its effects in HC-PE pregnancies are not known. Moreover, oxidized low-density lipoprotein (oxLDL) levels rise in HC-PE, potentially activating TLR4 and LOX-1 (lectin-like oxLDL receptor-1; scavenger receptor linked to vascular dysfunction in preeclampsia). However, whether this occurs in HC-PE is not known.

METHODS

Sprague Dawley rats received a control or high-cholesterol diet (to induce HC-PE) from gestational day 6 to 20, with placebo or low-dose aspirin (1.5 mg/kg daily) given from gestational day 10 to 20. On gestational day 20, pregnancy outcomes and uterine artery function were assessed.

RESULTS

Uterine artery blood flow velocity and placental weights were higher in HC-PE placebo-treated dams versus controls, but these were reduced by low-dose aspirin. Endothelium-dependent vasodilation was impaired in the uterine arteries of the HC-PE placebo group versus controls and was corrected by low-dose aspirin. Ex vivo inhibition of TLR4, PGHS1, or LOX-1 also normalized endothelium-dependent vasodilation in the HC-PE placebo-treated dams. Exposure to oxLDL in the bath (modeling a secondary hit) further impaired endothelium-dependent vasodilation in the uterine arteries of the HC-PE placebo group, partially via TLR4 and LOX-1, which was prevented by low-dose aspirin.

CONCLUSIONS

Low-dose aspirin improved uterine artery endothelial function in HC-PE pregnancies; likely by suppressing the TLR4/LOX-1/PGHS1 pathway.

Excessive Hypercholesterolemia in Pregnancy Impairs Later-Life Maternal Vascular Function in Rats

BACKGROUND

Preeclampsia is a risk factor for the development of later-life cardiovascular disease. However, the underlying mechanisms are poorly understood. Excessive hypercholesteremia in pregnancy induces a preeclampsia-like phenotype, but whether this also impacts maternal vascular function later in life has not been fully characterized.

METHODS AND RESULTS

Sprague Dawley rats received a control diet (CD) or a high-cholesterol (HCD) diet from gestational day 6 to 20, after which maternal vascular function was assessed 3 months postpartum. Exposure to an HCD in pregnancy reduced later-life endothelium-dependent vasodilation in carotid arteries (-15.24±3.27%), which was mediated via prostaglandin H synthase 2. There were no differences in vasodilation between CD and HCD postpartum rats in the mesenteric arteries, coronary arteries, or aortas. Vasoconstriction to phenylephrine increased in carotid arteries (61.02±21.48%) and reduced in aortas (-23.24±6.19%) of the HCD postpartum group versus CD dams, without differences in mesenteric and coronary arteries. The increased vasoconstriction in carotid arteries was due to lower nitric oxide modulation of constriction. Moreover, carotid artery myogenic response was reduced (-37.68±10.07%) and stiffness was increased (19.67±6.21%) in the HCD postpartum rats compared with CD along with decreased elastin density (-20.85±4.52%). The impact of the HCD on vascular function did not occur in age-matched never-pregnant female rats.

CONCLUSIONS

Excessive hypercholesterolemia in pregnancy impairs later-life maternal vascular function in rats with varying impacts across different vascular beds. Understanding mechanisms for pregnancy-specific excessive hypercholesterolemia provides avenues for targeted intervention strategies to reduce the burden of cardiovascular disease in women who had a complicated pregnancy.

Excessive hypercholesterolaemia during pregnancy as a risk factor for endothelial dysfunction in pre-eclampsia

Pregnancy induces significant changes in the maternal cardiovascular system, and insufficient vascular endothelial adaptations to pregnancy contribute to the development of pregnancy complications such as pre-eclampsia. Pre-eclampsia is not only a major cause of maternal morbidity and mortality, but also a significant risk factor for the development of later-life cardiovascular disease. However, the specific mechanisms underlying the pathophysiology of pre-eclampsia, as well as the mechanisms for an increased susceptibility to cardiovascular disease later in life, are not fully characterized. In this review, we discuss the concept that excessive pregnancy-specific dyslipidaemia, particularly hypercholesterolaemia, is a significant risk factor for the development of pre-eclampsia. We further outline novel potential mechanisms (i.e. oxidized low-density lipoprotein receptor 1 and toll-like receptor 4) underlying endothelial dysfunction induced by excessively high cholesterol levels during pregnancy (in the context of pre-eclampsia), in addition to discussing the overall implications of having had a pregnancy complicated by pre-eclampsia on later-life maternal vascular health. Determining the mechanisms by which excessive, pregnancy-specific dyslipidaemia/hypercholesterolaemia impact maternal endothelial health in pregnancy, and later in life, will create a window of opportunity to diagnose and develop targeted therapy for a susceptible population of women, aiming to ultimately reduce the societal burden of cardiovascular disease.

Pregnancy-related acute kidney injury leads to hypertension, reduced kidney function and cognitive impairment in postpartum rats

Introduction

Women with hypertensive disorders of pregnancy such as HELLP (hemolysis, elevated liver enzyme, low platelet) Syndrome are affected by acute kidney injury during pregnancy (PR-AKI) at higher rates than women without hypertension. Both hypertensive disorders of pregnancy and Acute Kidney Injury (AKI) outside the context of pregnancy have been associated with an increased risk of developing Chronic Kidney Disease (CKD) and cognitive impairment. In our current study, we set out to determine if PR-AKI led to the development of CKD and impaired cognition in the postpartum period and if HELLP syndrome exacerbates the impairments.

Methods

Using timed-pregnant Sprague Dawley rats, on gestational day (GD) 12, mini-osmotic pumps infusing anti-angiogenic factors were surgically placed in the intraperitoneal cavity to induce HELLP. On GD18, AKI was induced via bilateral renal reperfusion ischemia surgery. Mean arterial pressure and birth outcomes were used to assess the global effects of AKI, and liver enzymes were used to assess HELLP. CKD was assessed by measuring glomerular filtration rate (GFR), urinary output, and renal fibrosis. Anxiety-like behaviors, object recognition memory, spatial memory, and avoidance memory were assessed via behavioral experiments.

Results

HELLP + AKI rats demonstrated more evidence of renal injury, hypertension, and behavioral deficits compared to normal pregnant animals. In addition, AKI had a negative impact on birth outcomes and maternal survival.

Conclusion

HELLP + AKI together led to evidence of persistent hypertension, progressive renal dysfunction, and cognitive impairment, which were exacerbated compared to AKI or HELLP alone. These findings suggest that PR-AKI in the presence of a hypertensive disorder of pregnancy, such as HELLP, leads to the development of CKD, cognitive dysfunction, and hypertension.

Hypertensive disorders of pregnancy and the risk of maternal dementia: a systematic review and meta-analysis

OBJECTIVE

Hypertensive disorders of pregnancy, including preeclampsia, are associated with an increased risk for maternal cardiovascular disease, stroke, and chronic kidney disease. However, their association with subsequent maternal dementia or cognitive impairment is less well understood. This study aimed to review and synthesize the published literature on hypertensive disorders of pregnancy and the subsequent risk for maternal dementia or cognitive impairment.

DATA SOURCES

PubMed, Web of Science, Pyschinfo, and CINAHL were searched from database inception until July 31, 2022, for observational studies of hypertensive disorders of pregnancy and maternal dementia or cognitive impairment.

STUDY ELIGIBILITY CRITERIA

Selected studies included the following: a population of pregnant women, exposure to a hypertensive disorder of pregnancy of interest, and at least 1 primary outcome (dementia) or secondary outcome (cognitive impairment). Two reviewers were involved in study selection.

METHODS

We followed the Meta-analyses of Observational Studies in Epidemiology guidelines throughout. Random-effects meta-analyses were used to calculate the overall pooled estimates. Bias was assessed using an adapted version of the validated Newcastle-Ottawa Quality Assessment tool.

RESULTS

A total of 25 eligible studies were identified and included 2,501,673 women. Preeclampsia was associated with a significantly increased risk for vascular dementia (adjusted hazard ratio, 1.89; 95% confidence interval, 1.47-2.43), whereas no clear association was noted between preeclampsia and Alzheimer's disease (adjusted hazard ratio, 1.27; 95% confidence interval, 0.95-1.70), nor between preeclampsia and any (undifferentiated) dementia (adjusted hazard ratio, 1.18; 95% confidence interval, 0.95-1.47). However, in an analysis restricted to women aged 65 years and older, preeclampsia was associated with an increased risk for Alzheimer's disease (adjusted hazard ratio, 1.92; 95% confidence interval, 1.35-2.73) and any dementia (adjusted hazard ratio, 1.87; 95% confidence interval, 1.21-2.91).

CONCLUSION

Women whose pregnancies were complicated by preeclampsia seem to be at a substantially increased future risk for vascular dementia. The longer-term risks among these women with regards to Alzheimer's disease and other forms of dementia are less clear.

Guidelines for assessing maternal cardiovascular physiology during pregnancy and postpartum

Maternal mortality rates are at an all-time high across the world and are set to increase in subsequent years. Cardiovascular disease is the leading cause of death during pregnancy and postpartum, especially in the United States. Therefore, understanding the physiological changes in the cardiovascular system during normal pregnancy is necessary to understand disease-related pathology. Significant systemic and cardiovascular physiological changes occur during pregnancy that are essential for supporting the maternal-fetal dyad. The physiological impact of pregnancy on the cardiovascular system has been examined in both experimental animal models and in humans. However, there is a continued need in this field of study to provide increased rigor and reproducibility. Therefore, these guidelines aim to provide information regarding best practices and recommendations to accurately and rigorously measure cardiovascular physiology during normal and cardiovascular disease-complicated pregnancies in human and animal models.

Angiotensin II-mediated hippocampal hypoperfusion and vascular dysfunction contribute to vascular cognitive impairment in aged hypertensive rats

INTRODUCTION

Chronic hypertension increases the risk of vascular cognitive impairment (VCI) by ∼60%; however, how hypertension affects the vasculature of the hippocampus remains unclear but could contribute to VCI.

METHODS

Memory, hippocampal perfusion, and hippocampal arteriole (HA) function were investigated in male Wistar rats or spontaneously hypertensive rats (SHR) in early (4 to 5 months old), mid (8 to 9 months old), or late adulthood (14 to 15 months old). SHR in late adulthood were chronically treated with captopril (angiotensin converting enzyme inhibitor) or apocynin (antioxidant) to investigate the mechanisms by which hypertension contributes to VCI.

RESULTS

Impaired memory in SHR in late adulthood was associated with HA endothelial dysfunction, hyperconstriction, and ∼50% reduction in hippocampal blood flow. Captopril, but not apocynin, improved HA function, restored perfusion, and rescued memory function in aged SHR.

DISCUSSION

Hippocampal vascular dysfunction contributes to hypertension-induced memory decline through angiotensin II signaling, highlighting the therapeutic potential of HAs in protecting neurocognitive health later in life.

HIGHLIGHTS

Vascular dysfunction in the hippocampus contributes to vascular cognitive impairment. Memory declines with age during chronic hypertension. Angiotensin II causes endothelial dysfunction in the hippocampus in hypertension. Angiotensin II-mediated hippocampal arteriole dysfunction reduces blood flow. Vascular dysfunction in the hippocampus impairs perfusion and memory function.

Blood-Brain Barrier Dysfunction in Hypertensive Disorders of Pregnancy

PURPOSE OF REVIEW

The incidence of hypertensive disorders of pregnancy (HDP), especially preeclampsia has increased significantly over the last two decades. Patients with these disorders often report cerebral and visual symptoms, which are listed as potential diagnosis criteria for preeclampsia, if accompanied by new-onset hypertension. Recent studies indicate that cerebral complications in HDP patients are associated with a compromised blood-brain barrier (BBB). The purpose of this review is to highlight the recent literature focused on the BBB in HDP, identify gaps in knowledge, and discuss future directions in this research area.

RECENT FINDINGS

Majority of the studies addressing BBB changes in HDP are focused on preeclampsia. Recent studies show that hypertension induces increased association of perivascular macrophages/microglia to the cerebral vessels, increased circulating extracellular vesicles, and decreased autoregulation of cerebral blood flow. There is a critical need for more animal studies targeted to protecting the BBB and preventing cerebrovascular complications in the context of HDP. More clinical studies are needed that investigate both the short- and long-term interplay between each HDP subtype and BBB and cognitive function.

Cellular Immunotherapy in Mice Prevents Maternal Hypertension and Restores Anti-Inflammatory Cytokine Balance in Maternal and Fetal Tissues

Preeclampsia is the leading cause of maternal-fetal morbidity worldwide. The concept that persistent feto-placental intolerance is important in the pathogenesis of preeclampsia (PreE) has been demonstrated by our lab and others. Arginine vasopressin (AVP) infusion during pregnancy induces cardiovascular, renal, and T helper (TH) cell alterations in mice consistent with human PreE. In addition to their conventional immuno-stimulatory role, dendritic cells (DCs) also play a vital role in immune tolerance. In contrast to conventional DCs, regulatory DCs (DCregs) express low levels of co-stimulatory markers, produce anti-inflammatory cytokines, induce T regulatory (Treg) cells, and promote tolerance. In mice, DCregs prevent pro-inflammatory responses and induce antigen-specific tolerance. Given these known functions of DCregs, we hypothesize that DCregs will prevent the development of AVP-induced PreE in mice. C57BL/6J females were infused with AVP (24 ng/h) or saline throughout gestation via an osmotic minipump. Bone-marrow-derived DCregs were injected into AVP-infused dams at the time of the pump implantation or on gestational day (GD) 7. The blood pressure of the mice was taken throughout their pregnancy. The maternal urine proteins and TH-associated cytokines in maternal and fetal tissues were measured on GD 18. The treatment with DCregs effectively prevented the elevation of maternal blood pressure, proteinuria, and fetal growth restriction that were observed in AVP-infused dams. Furthermore, we noted a reduction in the pro-inflammatory TH-associated cytokines IFNγ and IL-17, while anti-inflammatory cytokines IL-4, IL-10, and TGFβ showed an increase following DCreg treatment. These outcomes provide strong evidence supporting the potential of DCregs as a valuable therapeutic approach in addressing PreE.

Preeclampsia history and postpartum risk of cerebrovascular disease and cognitive impairment: Potential mechanisms

Hypertensive disorders of pregnancy such as preeclampsia, eclampsia, superimposed preeclampsia, and gestational hypertension are major causes of fetal and maternal morbidity and mortality. Women with a history of hypertensive pregnancy disorders have increased risk of stroke and cognitive impairments later in life. Moreover, women with a history of preeclampsia have increased risk of mortality from diseases including stroke, Alzheimer's disease, and cardiovascular disease. The underlying pathophysiological mechanisms are currently not fully known. Here, we present clinical, epidemiological, and preclinical studies focused on evaluating the long-term cerebrovascular and cognitive dysfunction that affect women with a history of hypertensive pregnancy disorders and discuss potential underlying pathophysiological mechanisms.

Hippocampal Vascular Supply and Its Role in Vascular Cognitive Impairment

The incidence of age-related dementia is increasing as the world population ages and due to lack of effective treatments for dementia. Vascular contributions to cognitive impairment and dementia are increasing as the prevalence of pathologies associated with cerebrovascular disease rise, including chronic hypertension, diabetes, and ischemic stroke. The hippocampus is a bilateral deep brain structure that is central to learning, memory, and cognitive function and highly susceptible to hypoxic/ischemic injury. Compared with cortical brain regions such as the somatosensory cortex, less is known about the function of the hippocampal vasculature that is critical in maintaining neurocognitive health. This review focuses on the hippocampal vascular supply, presenting what is known about hippocampal hemodynamics and blood-brain barrier function during health and disease, and discusses evidence that supports its contribution to vascular cognitive impairment and dementia. Understanding vascular-mediated hippocampal injury that contributes to memory dysfunction during healthy aging and cerebrovascular disease is essential to develop effective treatments to slow cognitive decline. The hippocampus and its vasculature may represent one such therapeutic target to mitigate the dementia epidemic.