Changes in the choroid plexuses and brain barriers associated with high blood pressure and ageing

Hypertension, blood-brain barrier disruption and changes in intracranial pressure

Intracranial pressure (ICP) is pressure within the cranium, between 5 and 15 mmHg in a normal brain, and is influenced by the dynamic balance between brain tissue, cerebrospinal fluid (CSF) and cerebral blood volume. ICP is vital for cerebral health, impacting outcomes in various neurological conditions. Disruptions, such as cerebral haemorrhage, hydrocephalus and malignant hypertension, can lead to elevated ICP, a dangerous condition known as intracranial hypertension (IH). Systemic hypertension significantly impacts cerebral health by causing microvascular damage, dysfunction of the blood-brain barrier (BBB) and impairment of intracranial compliance (ICC). This increases the risk of IH), cerebral ischaemia, neuroinflammation and lacunar infarction, further worsening neurological dysfunction. This review describes the complex relationship between hypertension and ICP regulation, focusing on the mechanisms underlying ICP and ICC adjustments in hypertensive conditions and emphasizing the role of BBB integrity and cerebral blood flow (CBF) dynamics. It discusses how the sympathetic output might change the regulation of CBF and the maintenance of ICP, highlighting how hypertensive conditions can impair this mechanism, increasing the risk of cerebral ischaemia. The neurovascular unit, including astrocytes and microglia, plays a significant role in this process, contributing to IH in hypertensive patients. Understanding the effects of hypertension on ICP and ICC could lead to therapies aimed at preserving BBB integrity, reducing inflammation and improving cerebral compliance, potentially preventing brain dysfunction and reducing stroke risk in hypertensive patients. This review underscores the need for early detection and intervention to mitigate the severe consequences of uncontrolled hypertension on cerebral health.

Retinal Thickness Correlates with Cerebral Hemodynamic Changes in Patients with Carotid Artery Stenosis

Background: We aimed to assess the retinal structural and choroidal changes in carotid artery stenosis (CAS) patients and their association with cerebral hemodynamic changes. Asymptomatic and symptomatic patients with unilateral CAS were enrolled in our study. Material and methods: Swept-source optical coherence tomography (SS-OCT) was used to image the retinal nerve fiber layer (RNFL), ganglion cell-inner plexiform layer (GCIPL), while SS-OCT angiography (SS-OCTA) was used to image and measure the choroidal vascular volume (CVV) and choroidal vascular index (CVI). Computed Tomography Perfusion (CTP) was used to assess the cerebral perfusion parameters; relative perfusion (r) was calculated as the ratio of the value on the contralateral side to that on the ipsilateral side. Results: Compared with contralateral eyes, ipsilateral eyes showed significantly thinner RNFL (p < 0.001), GCIPL (p = 0.013) and CVV (p = 0.001). Relative cerebral blood volume (rCBV) showed a significant correlation with RNFL (p < 0.001), GCIPL (p < 0.001) and CVI (p = 0.027), while the relative permeability surface (rPS) correlated with RNFL (p < 0.001) and GCIPL (p < 0.001). Conclusions: Our report suggests that retinal and choroidal changes have the potential to detect hemodynamic changes in CAS patients and could predict the risk of stroke.

Delayed Minocycline Treatment Ameliorates Hydrocephalus Development and Choroid Plexus Inflammation in Spontaneously Hypertensive Rats

Hydrocephalus is a complicated disorder that affects both adult and pediatric populations. The mechanism of hydrocephalus development, especially when there is no mass lesion present causing an obstructive, is poorly understood. Prior studies have demonstrated that spontaneously hypertensive rats (SHRs) develop hydrocephalus by week 7, which was attenuated with minocycline. The aim of this study was to determine sex differences in hydrocephalus development and to examine the effect of minocycline administration after hydrocephalus onset. Male and female Wistar-Kyoto rats (WKYs) and SHRs underwent magnetic resonance imaging at weeks 7 and 9 to determine ventricular volume. Choroid plexus epiplexus cell activation, cognitive deficits, white matter atrophy, and hippocampal neuronal loss were examined at week 9. In the second phase of the experiment, male SHRs (7 weeks old) were treated with either saline or minocycline (20 mg/kg) for 14 days, and similar radiologic, histologic, and behavior tests were performed. Hydrocephalus was present at week 7 and increased at week 9 in both male and female SHRs, which was associated with greater epiplexus cell activation than WKYs. Male SHRs had greater ventricular volume and epiplexus cell activation compared to female SHRs. Minocycline administration improved cognitive function, white matter atrophy, and hippocampal neuronal cell loss. In conclusion, while both male and female SHRs developed hydrocephalus and epiplexus cell activation by week 9, it was more severe in males. Delayed minocycline treatment alleviated hydrocephalus, epiplexus macrophage activation, brain pathology, and cognitive impairment in male SHRs.

Choroid Plexus in Alzheimer's Disease-The Current State of Knowledge

The choroid plexus (CP), located in each of the four ventricles of the brain, is formed by a monolayer of epithelial cells that surrounds a highly vascularized connective tissue with permeable capillaries. These cells are joined by tight junctions forming the blood-cerebrospinal fluid barrier (BCSFB), which strictly regulates the exchange of substances between the blood and cerebrospinal fluid (CSF). The primary purpose of the CP is to secrete CSF, but it also plays a role in the immune surveillance of the central nervous system (CNS) and in the removal of neurotoxic compounds from the CSF. According to recent findings, the CP is also involved in the modulation of the circadian cycle and neurogenesis. In diseases such as Alzheimer's disease (AD), the function of the CP is impaired, resulting in an altered secretory, barrier, transport, and immune function. This review describes the current state of knowledge concerning the roles of the CP and BCSFB in the pathophysiology of AD and summarizes recently proposed therapies that aim to restore CP and BCSFB functions.