Cerebrovascular effects of endothelin-1 investigated using high-resolution magnetic resonance imaging in healthy volunteers

The Cells of the Vasculature: Advances in the Regulation of Vascular Tone in the Brain and Periphery

The vasculature is a complex tissue in which multiple cell types coordinate the regulation of tissue perfusion in response to hemodynamic and biochemical signals. Advances in this field are continuing to deepen our understanding of the relative importance of these cell types through the body. In the peripheral vasculature, tone is generated primarily by smooth muscle cells and regulated by endothelial cells, and neurons. In the brain parenchyma, unique cell types including pericytes, perivascular astrocytes and microglia, also contribute to the regulation of arterial and capillary tone. Here, we provide a cell-by-cell review of the regulation of vascular tone and highlight recent advances in the regulation of vascular tone in both the periphery and cerebral vasculature.

Endothelial-derived extracellular vesicles associated with electronic cigarette use impair cerebral microvascular cell function

The aim of this study was to determine the effect of circulating endothelial cell-derived microvesicles (EMVs) isolated from e-cigarette users on human cerebral microvascular endothelial cells (hCMECs) nitric oxide (NO) and endothelin (ET)-1 production and tissue-type plasminogen activator (t-PA) release. Circulating EMVs (CD144-PE) were isolated (flow cytometry) from 27 young adults (19-25 yr): 10 nonsmokers (6 M/4 F), 10 e-cigarette users (6 M/4 F), and 7 tobacco cigarette smokers (4 M/3 F). hCMECs were cultured and treated with isolated EMVs for 24 h. EMVs from e-cigarette users and cigarette smokers induced significantly higher expression of p-eNOS (Thr495; 28.4 ± 4.6 vs. 29.1 ± 2.8 vs. 22.9 ± 3.8 AU), Big ET-1 (138.8 ± 19.0 vs. 141.7 ± 19.1 vs. 90.3 ± 18.8 AU) and endothelin converting enzyme (107.6 ± 10.1 and 113.5 ± 11.8 vs. 86.5 ± 13.2 AU), and significantly lower expression of p-eNOS (Ser1177; 7.4 ± 1.7 vs. 6.5 ± 0.5 vs. 9.7 ± 1.6 AU) in hCMECs than EMVs from nonsmokers. NO production was significantly lower and ET-1 production was significantly higher in hCMECs treated with EMVs from e-cigarette (5.7 ± 0.8 µmol/L; 33.1 ± 2.9 pg/mL) and cigarette smokers (6.3 ± 0.7 µmol/L; 32.1 ± 3.9 pg/mL) than EMVs from nonsmokers (7.6 ± 1.2 µmol/L; 27.9 ± 3.1 pg/mL). t-PA release in response to thrombin was significantly lower in hCMECs treated with EMVs from e-cigarette users (from 38.8 ± 6.3 to 37.4 ± 8.3 pg/mL) and cigarette smokers (31.5 ± 5.5 to 34.6 ± 8.4 pg/mL) than EMVs from nonsmokers (38.9 ± 4.3 to 48.4 ± 7.9 pg/mL). There were no significant differences in NO, ET-1, or t-PA protein expression or production in hCMECs treated with EMVs from e-cigarette users and smokers. Circulating EMVs associated with e-cigarette use adversely affects brain microvascular endothelial cells and may contribute to reported cerebrovascular dysfunction with e-cigarette use.NEW & NOTEWORTHY In the present study, we determined the effect of circulating endothelial cell-derived microvesicles (EMVs) isolated from e-cigarette users on human cerebral microvascular endothelial cells (hCMECs) nitric oxide (NO) and endothelin (ET)-1 production and tissue-type plasminogen activator (t-PA) release. EMVs from e-cigarette users reduced brain microvascular endothelial cell NO production, enhanced ET-1 production, and impaired endothelial t-PA release. EMVs are a potential mediating factor in the increased risk of stroke associated with e-cigarette use.

Neuroendocrine regulation in stroke

The neuroendocrine system, a crosstalk between the central nervous system and endocrine glands, balances and controls hormone secretion and their functions. Neuroendocrine pathways and mechanisms often get dysregulated following stroke, leading to altered hormone secretion and aberrant receptor expression. Dysregulation of the hypothalamus-pituitary-thyroid (HPT) axis and hypothalamus-pituitary-adrenal (HPA) axis often led to severe stroke outcomes. Post-stroke complications such as cognitive impairment, depression, infection etc. are directly or indirectly influenced by the altered neuroendocrine activity that plays a crucial role in stroke vulnerability and susceptibility. Therefore, it is imperative to explore various neurohormonal inter-relationships in regulating stroke, its outcome, and prognosis. Here, we review the biology of different hormones associated with stroke and explore their regulation with a view towards prospective therapeutics.

Quercetin targets VCAM1 to prevent diabetic cerebrovascular endothelial cell injury

INTRODUCTION

Endothelial cells play important roles in neurodegenerative diseases caused by diabetes, therefore, we aimed at investigating the mechanisms through which endothelial cells are involved in diabetes development.

METHODS

Single cell analysis was performed to identify the major endothelial cell subtypes in cardiovascular tissues that are involved in diabetes development. A cell-cell communication approach was then used to identify ligand-receptor interaction pairs between these cell types. Differential expression analysis between the two experimental groups [standard chow diet group and diabetogenic diet with cholesterol (DDC) group] was used to identify diabetes-related differentially expressed genes (DEGs). The upregulated genes were used to identify candidate ligands or receptors, as well as the corresponding cell types. Cell trajectory inference was performed to identify the stage of cell development and changes in expression of candidate ligands or receptors during cell development. Gene set enrichment analysis (GSEA) was conducted to investigate the biological functions of genes of purpose. Finally, molecular dynamics simulations (MDSs) were used to predict potential drugs with the ability to target the proteins of purpose.

RESULTS

Seven cell types, including five endothelial cell subtypes (EC_1, EC_2, EC_3, EC_4, and EC_EndMT), were identified from endothelial cell-enriched single cell samples from the heart and aorta of mice. Cell-cell communication analysis revealed the potential ligand-receptor interactions between these cell types while five important ligand-receptor-associated genes, including Fn1, Vcam1, Fbn1, Col4a1, and Col4a2, were established by differential expression analysis. Among them, Vcam1 is mainly expressed in EC_EndMT and is involved in interactions between EC_EndMT and other cells. Cell trajectory extrapolation analysis revealed a shift from EC_2/EC_4 to EC_EndMT and a shift from EC_EndMT to EC_3/EC_1 during the progression of diabetes. GSEA analysis revealed that upregulation of VCAM1 may have inhibitory effects on cell growth and energy metabolism.

CONCLUSION

EC_EndMT subtypes have a complex role in neurodegenerative diseases caused by diabetes. Through mechanisms involved in cell-cell communication, Vcam1 may play an important role in dysregulation of biological functions of EC_ EndMT. Molecular docking results of the quercetin-VCAM1 complex suggest that quercetin may be an effective drug for targeting this protein.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Association of C-Terminal Pro-Endothelin-1 with Mortality in the Population-Based KORA F4 Study

Introduction

Endothelin-1 and its prohormone C-terminal pro-endothelin-1 (CT-proET-1) have been linked to metabolic alterations, inflammatory responses and cardiovascular events in selected study populations. We analyzed the association of CT-proET-1 with cardiovascular events and mortality, carotid intima-media-thickness as surrogate for early atherosclerotic lesions, biomarkers of subclinical inflammation and adipokines in a population-based study.

Methods

The cross-sectional and prospective analyses used data from the KORA F4 study with a median follow-up time of 9.1 (8.8–9.4) years. Data on CT-proET-1 and mortality were available for 1554 participants, data on the other outcomes in subgroups (n = 596–1554). The associations were estimated using multivariable linear regression and Cox proportional hazard models adjusted for sex, age, body mass index, estimated glomerular filtration rate, arterial hypertension, diabetes, low-density and high-density lipoprotein cholesterol, current and former smoking and physical activity. The Bonferroni method was used to correct for multiple testing.

Results

In the fully adjusted model, CT-proET-1 was associated with cardiovascular (hazard ratio (HR) per standard deviation increase: 1.66; 95% confidence interval (CI): 1.10–2.51; p = 0.017) and all-cause mortality (HR: 2.03; 95% CI 1.55–2.67; p < 0.001), but not with cardiovascular events, and was inversely associated with the intima-media thickness (β: −0.09 ± 0.03; p = 0.001). CT-proET-1 was positively associated with five out of ten biomarkers of subclinical inflammation and with two out of five adipokines after correction for multiple testing. After inclusion of biomarkers of subclinical inflammation in the Cox proportional hazard model, the association of CT-proET-1 with all-cause mortality persisted (p < 0.001).

Conclusion

These results emphasize the complexity of endothelin-1 actions and/or indicator functions of CT-proET-1. CT-proET-1 is a risk marker for all-cause mortality, which is likely independent of vascular endothelin-1 actions, cardiovascular disease and inflammation.

Migraine Aura, Transient Ischemic Attacks, Stroke, and Dying of the Brain Share the Same Key Pathophysiological Process in Neurons Driven by Gibbs–Donnan Forces, Namely Spreading Depolarization

Neuronal cytotoxic edema is the morphological correlate of the near-complete neuronal battery breakdown called spreading depolarization, or conversely, spreading depolarization is the electrophysiological correlate of the initial, still reversible phase of neuronal cytotoxic edema. Cytotoxic edema and spreading depolarization are thus different modalities of the same process, which represents a metastable universal reference state in the gray matter of the brain close to Gibbs–Donnan equilibrium. Different but merging sections of the spreading-depolarization continuum from short duration waves to intermediate duration waves to terminal waves occur in a plethora of clinical conditions, including migraine aura, ischemic stroke, traumatic brain injury, aneurysmal subarachnoid hemorrhage (aSAH) and delayed cerebral ischemia (DCI), spontaneous intracerebral hemorrhage, subdural hematoma, development of brain death, and the dying process during cardio circulatory arrest. Thus, spreading depolarization represents a prime and simultaneously the most neglected pathophysiological process in acute neurology. Aristides Leão postulated as early as the 1940s that the pathophysiological process in neurons underlying migraine aura is of the same nature as the pathophysiological process in neurons that occurs in response to cerebral circulatory arrest, because he assumed that spreading depolarization occurs in both conditions. With this in mind, it is not surprising that patients with migraine with aura have about a twofold increased risk of stroke, as some spreading depolarizations leading to the patient percept of migraine aura could be caused by cerebral ischemia. However, it is in the nature of spreading depolarization that it can have different etiologies and not all spreading depolarizations arise because of ischemia. Spreading depolarization is observed as a negative direct current (DC) shift and associated with different changes in spontaneous brain activity in the alternating current (AC) band of the electrocorticogram. These are non-spreading depression and spreading activity depression and epileptiform activity. The same spreading depolarization wave may be associated with different activity changes in adjacent brain regions. Here, we review the basal mechanism underlying spreading depolarization and the associated activity changes. Using original recordings in animals and patients, we illustrate that the associated changes in spontaneous activity are by no means trivial, but pose unsolved mechanistic puzzles and require proper scientific analysis.

Opening of BKCa channels causes migraine attacks: a new downstream target for the treatment of migraine

ABSTRACT

Migraine is a common and frequently disabling neurological disorder, but the initiating migraine mechanisms are still poorly understood. Potassium channel opening may cause migraine, and we therefore examined the migraine-inducing effect of MaxiPost, a large (big)-conductance calcium-activated potassium (BKCa) channel opener, on migraine induction and cephalic vasodilation in individuals with migraine. Twenty-six patients with migraine without aura were randomly allocated to receive an infusion of MaxiPost or placebo on 2 study days separated by at least 1 week. The primary endpoint was the difference in incidence of migraine attacks after MaxiPost compared with placebo. The secondary endpoints were the difference in incidence of headaches and the difference in area under the curve for headache intensity scores (0-12 hours), for middle cerebral artery blood flow velocity (VMCA) (0-2 hours), and for superficial temporal artery and radial artery diameter. Twenty-two patients completed the study. Twenty-one of 22 (95%) developed migraine attacks after MaxiPost compared with none after placebo (P < 0.0001); the difference of incidence is 95% (95% confidence interval 86%-100%). The incidence of headache over the 12-hour observation period was higher after MaxiPost day (n = 22) than after placebo (n = 7) (P < 0.0001). We found a significant increase of VMCA and superficial temporal and radial arteries' diameter. Because BKCa channel opening initiates migraine attacks, we suggest that BKCa channel blockers could be potential candidates for novel antimigraine drugs.

The Effect of K ATP Channel Blocker Glibenclamide on CGRP-Induced Headache and Hemodynamic in Healthy Volunteers

BACKGROUND

Calcitonin gene-related peptide (CGRP) dilates cranial arteries and triggers headache. The CGRP signaling pathway is partly dependent on activation of ATP-sensitive potassium (K ATP ) channels. Here, we investigated the effect of the K ATP channel blocker glibenclamide on CGRP-induced headache and vascular changes in healthy volunteers.

METHODS

In a randomized, double-blind, placebo-controlled, cross-over study, 20 healthy volunteers aged 18-27 years were randomly allocated to receive an intravenous infusion of 1.5 μg/min CGRP after oral pretreatment with glibenclamide (glibenclamide-CGRP day) or placebo (placebo-CGRP day). The primary endpoints were the difference in incidence of headache and the difference in area under the curve (AUC) for headache intensity scores (0-14 h) between glibenclamide and placebo. The secondary endpoints were the difference in AUC for middle cerebral artery blood flow velocity (V MCA ), superficial temporal artery (STA) and radial artery (RA) diameter, facial flushing, heart rate (HR) and mean arterial blood pressure (MAP) (0-4 h) between glibenclamide and placebo.

RESULTS

We found no significant difference in the incidence of headache between glibenclamide-CGRP day (14/20, 70%) and placebo-CGRP day (19/20, 95%) (P = 0.06). The AUC for headache intensity, V MCA , STA, RA, facial skin blood flow, HR, and MAP did not differ between glibenclamide-CGRP day compared to placebo-CGRP day (P > 0.05).

CONCLUSION

Pretreatment with a non-selective K ATP channel inhibitor glibenclamide did not attenuate CGRP-induced headache and hemodynamic changes in healthy volunteers. We suggest that CGRP-induced responses could be mediated via activation of specific isoforms of sulfonylurea receptor subunits of K ATP channel.

Cerebrovascular effects of glibenclamide investigated using high-resolution magnetic resonance imaging in healthy volunteers

Glibenclamide inhibits sulfonylurea receptor (SUR), which regulates several ion channels including SUR1-transient receptor potential melastatin 4 (SUR1-TRPM4) channel and ATP-sensitive potassium (K_ATP) channel. Stroke upregulates SURl-TRPM4 channel, which causes a rapid edema formation and brain swelling. Glibenclamide may antagonize the formation of cerebral edema during stroke. Preclinical studies showed that glibenclamide inhibits K_ATP channel-induced vasodilation without altering the basal vascular tone. The in vivo human cerebrovascular effects of glibenclamide have not previously been investigated.In a randomized, double-blind, placebo-controlled, three-way cross-over study, we used advanced 3 T MRI methods to investigate the effects of glibenclamide and K_ATP channel opener levcromakalim on mean global cerebral blood flow (CBF) and intra- and extracranial artery circumferences in 15 healthy volunteers. Glibenclamide administration did not alter the mean global CBF and the basal vascular tone. Following levcromakalim infusion, we observed a 14% increase of the mean global CBF and an 8% increase of middle cerebral artery (MCA) circumference, and glibenclamide did not attenuate levcromakalim-induced vascular changes. Collectively, the findings demonstrate the vital role of K_ATP channels in cerebrovascular hemodynamic and indicate that glibenclamide does not inhibit the protective effects of K_ATP channel activation during hypoxia and ischemia-induced brain injury.

Opening of ATP sensitive potassium channels causes migraine attacks with aura

Migraine afflicts more than one billion individuals worldwide and is a leading cause of years lived with disability. In about a third of individuals with migraine aura occur in relation to migraine headache. The common pathophysiological mechanisms underlying migraine headache and migraine aura are yet to be identified. Based on recent data, we hypothesized that levcromakalim, an ATP-sensitive potassium channel opener, would trigger migraine attacks with aura in migraine with aura patients.

Phase 1 study to access safety, tolerability, pharmacokinetics, and pharmacodynamics of kynurenine in healthy volunteers

The kynurenine pathway (KP) is the main path for tryptophan metabolism, and it represents a multitude of potential sites for drug discovery in neuroscience, including pain, stroke, and epilepsy. L‐kynurenine (LKYN), the first active metabolite in the pathway, emerges to be a prodrug targeting glutamate receptors. The safety, tolerability, pharmacokinetics, and pharmacodynamics of LKYN in humans have not been previously investigated. In an open‐label, single ascending dose study, six participants received an intravenous infusion of 50, 100, and 150 µg/kg LKYN and new six participants received an intravenous infusion of 0.3, 0.5, 1, and 5 mg/kg LKYN. To compare the pharmacological effects between species, we investigated in vivo the vascular effects of LKYN in rats. In humans, LKYN was safe and well‐tolerated at all dose levels examined. After infusion, LKYN plasma concentration increased significantly over time 3.23 ± 1.12 µg/mL (after 50 µg/kg), 4.04 ± 1.1 µg/mL (after 100 µg/kg), and 5.25 ± 1.01 µg/mL (after 150 µg/kg) (p ≤ 0.001). We observed no vascular changes after infusion compared with baseline. In rats, LKYN had no effect on HR and MAP and caused no dilation of dural and pial arteries. This first‐in‐human study of LKYN showed that LKYN was safe and well‐tolerated after intravenous infusion up to 5 mg/kg over 20 minutes. The lack of change in LKYN metabolites in plasma suggests a relatively slow metabolism of LKYN and no or little feed‐back effect of LKYN on its synthesis. The therapeutic potential of LKYN in stroke and epilepsy should be explored in future studies in humans.

White Matter Lesions in Migraine

Migraine, the third most common disease worldwide, is a well-known independent risk factor for subclinical focal deep white matter lesions (WMLs), even in young and otherwise healthy individuals with no cardiovascular risk factors. These WMLs are more commonly seen in migraine patients with transient neurologic symptoms preceding their headaches, the so-called aura, and those with a high attack frequency. The pathophysiology of migraine-related deep white matter hyperintensities remains poorly understood despite their prevalence. Characteristic differences in their distribution related to chronic small vessel ischemic disease compared with that of common periventricular WMLs in the elderly suggest a different underlying mechanism. Both ischemic and inflammatory mechanisms have been proposed, as there is increased cerebral vulnerability to ischemia in migraineurs, whereas there is also evidence of blood-brain barrier disruption with associated release of proinflammatory substances during migraine attacks. An enhanced susceptibility to spreading depolarization, the electrophysiological event underlying migraine, may be the mechanism that causes repetitive episodes of cerebral hypoperfusion and neuroinflammation during migraine attacks. WMLs can negatively affect both physical and cognitive function, underscoring the public health importance of migraine, and suggesting that migraine is an important contributor to neurologic deficits in the general population.

Nocebo response in human models of migraine: A systematic review and meta-analysis of randomized, double-blind, placebo-controlled, two-way crossover trials in migraine without aura and healthy volunteers

BACKGROUND

Human models of migraine have been used for the past 30 years to test putative 'trigger' molecules and ascertain whether they induce migraine attacks in humans. However, nocebo effects using this model have never been systematically explored.

OBJECTIVE

To assess the nocebo response rate in randomised clinical trials conducted at the Danish Headache Center, and in which human models of migraine were used.

METHODS

In this systematic review and meta-analysis, we searched PubMed for studies of human models of migraine with a randomised, double-blind, placebo-controlled, two-way crossover design that included data on the incidence of migraine attacks or headache after infusion of placebo. A total of 943 articles were screened by title and abstract. Of these, 27 studies met the inclusion criteria (published between 1994 and 2020) and were included in the qualitative and quantitative analysis. We performed a random effects meta-analysis for the incidence of migraine attacks or delayed headache after placebo infusion.

RESULTS

Twenty-seven studies were eligible for inclusion: 12 studies reported data for adults with migraine (n = 182), whereas 16 studies reported data on healthy volunteers (n = 210). For adults with migraine, the incidence of migraine attacks after placebo was 8.1% (95% CI = 2.5-15.5%, I² = 50.8%). The incidence of delayed headache was 25.9% (95% CI = 18.5-34.1%, I² = 18.9%). For healthy volunteers, the incidence of migraine attacks after placebo was 0.5% (95% CI = 0.0-3.6%, I² = 0.0%) while the incidence of delayed headache was 10.5% (95% CI = 4.8-17.6%, I² = 45.2%).

CONCLUSION

The nocebo response in randomised, placebo-controlled two-way crossover trials with intravenous infusions of placebo in migraine is negligible. Future studies using human models of migraine can be conducted by assuming a nocebo response rate of 15.5%.

Intravascular Endothelin-1 does not trigger or increase susceptibility to Spreading Depolarizations

Objectives

Spreading depolarizations (SD) likely manifest as aura in migraineurs. Triggers are unknown although vascular events have been implicated. Direct carotid puncture has been reported to trigger migraine with aura. The potent vasoconstrictor endothelin-1 (ET-1), which can be released from the endothelium under pathological conditions, may play a role. Here, we tested whether intracarotid ET-1 infusion triggers SD and whether systemic ET-1 infusion increases the susceptibility to SD.

Methods

Carotid infusions were performed in mice (C57BL/6, male) through a catheter placed at the carotid bifurcation via the external carotid artery. Intracarotid ET-1 (1.25 nmol/ml) was infused at various rates (2–16 μl/min) with or without heparin in the catheter and compared with vehicle infusion (PBS with 0.01% acetic acid) or sham-operated mice (n = 5). Systemic infusions ET-1 (1 nmol/kg, n = 7) or vehicle (n = 7) infusions were performed in rats (Sprague-Dawley, male) via the tail vein. Electrical SD threshold and KCl-induced SD frequency were measured after the infusion.

Results

Intracarotid infusion of saline (n = 19), vehicle (n = 7) or ET-1 (n = 12) all triggered SDs at various proportions (21%, 14% and 50%, respectively). These were often associated with severe hypoperfusion prior to SD onset. Heparinizing the infusion catheter completely prevented SD occurrence during the infusions (n = 8), implicating microembolization from carotid thrombi as the trigger. Sham-operated mice never developed SD. Systemic infusion of ET-1 did not affect the electrical SD threshold or KCl-induced SD frequency.

Conclusion

Intravascular ET-1 does not trigger or increase susceptibility to SD. Microembolization was the likely trigger for migraine auras in patients during carotid puncture.