The Effects of Propofol on a Human in vitro Blood-Brain Barrier Model

Alcohol diminishes barrier integrity in human stem cell-derived brain microvascular endothelial cells: Role of reactive oxygen species

The World Health Organization has linked alcohol consumption to over 200 diseases including neurodegenerative diseases. A dysfunctional blood-brain barrier (BBB) has been found to be influential in a number of brain disorders. The BBB is critical in maintaining homeostasis between the brain vasculature and parenchyma and a loss in barrier integrity would enable otherwise impermeable immune cells, molecules, and inflammatory mediators to reach the brain parenchyma. A subset of studies demonstrated that alcohol could diminish BBB integrity, but it is unclear if this effect translates clinically. In this study, we utilize a human stem cell-derived BBB model with near in vivo properties to investigate the effects of alcohol on critical barrier properties. Barrier forming brain-like microvascular endothelial cells (BMECs) were derived from human induced pluripotent stem cells (iPSCs) and exposed to several alcohol concentrations. Alcohol decreased barrier integrity observed by a loss in trans-endothelial electrical resistance and an increase in sodium fluorescein permeability. Alcohol decreased expression and junctional localization of tight junction proteins, a critical component to barrier integrity. Additionally, alcohol did not affect efflux transporter activity or cell viability in BMECs. The detrimental effects of alcohol on BBB properties were due to in part elevated reactive oxygen species (ROS); as scavenging ROS improved barrier properties, including the restoration of tight junction expression and localization. These data suggest that excessive alcohol consumption could diminish the BBB and contribute to the development or exacerbation of brain disorders. CLINICAL TRIAL NUMBER AND REGISTRY URL: Not applicable.

A Comparative Study of Common Anesthetics Propofol, Sevoflurane, Isoflurane and Ketamine on Lipid Membrane Fluidity

The membrane fluidity increases induced by popular anesthetic agents (propofol, isoflurane, sevoflurane, and ketamine/xylazine) were measured at the clinical and supra-clinical concentrations in red blood cell (RBC) membrane as well as four model membranes. Membrane fluidity changes were monitored using the excimer/monomer (E/M) ratio of dipyrene-PC and fluorescence anisotropies of DPH-PC and TMA-DPH. Propofol, sevoflurane and isoflurane increased membrane fluidity instantaneously. The largest increase occurs in membranes made of saturated lipids. RBCs were labeled with TMA-DPH, and the increase in membrane fluidity at clinical concentrations of isoflurane and sevoflurane was more than that induced by ten times the legal limit of alcohol in human blood. However, membrane fluidity was essentially unchanged by ketamine/xylazine up to 210 µM. These results strongly correlate with our recent in vivo experiments and reveal a clear connection between increasing membrane fluidity in model membranes, increasing the blood-brain barrier (BBB) permeability in mice, and inducing effective anesthesia in animals. Interestingly, at the most commonly used clinical concentrations, the membrane fluidity increases induced by propofol, sevoflurane, and isoflurane were very similar, despite the fact that different categories of anesthetics were used and their chemical concentrations were different by 100 times. This indicates that at clinical concentrations of these anesthetics, a similar level of membrane disruption at the BBB is achieved. Thus, our results strongly support the lipid hypothesis of the mechanism of general anesthetics.

ICU patient-on-a-chip emulating orchestration of mast cells and cerebral organoids in neuroinflammation

Propofol and midazolam are the current standard of care for prolonged sedation in Intensive Care Units (ICUs). However, the effects and mechanism of these sedatives in brain tissue are unclear. Herein, the development of an ICU patient-on-a-chip platform to elucidate those effects is reported. The humanized neural tissue compartment combines mast cells differentiated from human induced pluripotent stem cells (hiPSCs) with cerebral organoids in a three-dimensional (3D) matrix, which is covered with a membrane populated with human cerebral microvascular endothelial cells (hCMEC/D3) that separates the tissue chamber from the vascular lumen, where sedatives were infused for four days to evaluate neurotoxicity and cell-mediated immune responses. Subsequent to propofol administration, gene expressions of CD40 and TNF-α in mast cells, AIF1 in microglia and GFAP/S100B/OLIG2/MBP in macroglia were elevated, as well as NOS2, CD80, CD40, CD68, IL6 and TNF-α mediated proinflammation is noted in cerebral organoids, which resulted in higher expressions of GJB1, GABA-A and NMDAR1 in the tissue construct of the platform. Besides, midazolam administration stimulated expression of CD40 and CD203c+ reactivated mast cell proliferation and compromised BBB permeability and decreased TEER values with higher barrier disruption, whereas increased populations of CD11b+ microglia, higher expressions of GFAP/DLG4/GJB1 and GABA-A-/NMDAR1- identities, as well as glutamate related neurotoxicity and IL1B, IFNG, IFNA1, IL6 genes mediated proinflammation, resulting in increased apoptotic zones are observed in cerebral organoids. These results suggest that different sedatives cause variations in cell type activation that modulate different pathways related to neuroinflammation and neurotoxicity in the ICU patient-on-chip platform.

Anesthetic technique and incidence of delirium after total knee or hip arthroplasty: a nationwide cohort study

BACKGROUND

The optimal type of anesthesia for reducing postoperative delirium remains undetermined. This study aimed to assess the relationship between type of anesthesia and postoperative delirium.

METHODS

This retrospective national cohort study used data collected between 2016 and 2021 from the National Health Insurance Service of South Korea. Adult patients who underwent primary total hip or total knee arthroplasty under general or regional anesthesia were included. Patients with postoperative delirium were identified after arthroplasty according to the International Classification of Diseases 10th revision code for delirium (F05). The patients were divided into two groups: regional anesthesia (RA group) and general anesthesia (GA group). The primary endpoint was the incidence of postoperative delirium during hospitalization after total hip or knee arthroplasty.

RESULTS

Our study sample consisted of 664,598 patients: 474,932 in the RA group and 189,666 in the GA group. After propensity score (PS) matching, 276,582 patients (138,291 in each group) were included in the final analysis. In the PS-matched cohort, the incidence of delirium following total knee or total hip arthroplasty was 2.8% (3,842/138,291) in the GA group and 2.3% (3,147/138,291) in the RA group. In logistic regression, the RA group was associated with 18% (odds ratio: 0.82, 95% confidence interval: 0.78, 0.86; P < 0.001) lower postoperative incidence than the GA group.

CONCLUSION

Compared to general anesthesia, regional anesthesia was associated with a decreased incidence of postoperative delirium in patients who underwent total hip or total knee arthroplasty. Our findings indicate that avoiding general anesthesia may prevent delirium after lower limb surgery.

Exploring dysfunctional barrier phenotypes associated with glaucoma using a human pluripotent stem cell-based model of the neurovascular unit

Glaucoma is a neurodegenerative disease that results in the degeneration of retinal ganglion cells (RGCs) and subsequent loss of vision. While RGCs are the primary cell type affected in glaucoma, neighboring cell types selectively modulate RGCs to maintain overall homeostasis. Among these neighboring cell types, astrocytes, microvascular endothelial cells (MVECs), and pericytes coordinate with neurons to form the neurovascular unit that provides a physical barrier to limit the passage of toxic materials from the blood into neural tissue. Previous studies have demonstrated that these barrier properties may be compromised in the progression of glaucoma, yet mechanisms by which this happens have remained incompletely understood. Thus, the goals of this study were to adapt a human pluripotent stem cell (hPSC)-based model of the neurovascular unit to the study of barrier integrity relevant to glaucoma. To achieve this, hPSCs were differentiated into the cell types that contribute to this barrier, including RGCs, astrocytes, and MVECs, then assembled into an established Transwell®-insert model. The ability of these cell types to contribute to an in vitro barrier model was tested for their ability to recapitulate characteristic barrier properties. Results revealed that barrier properties of MVECs were enhanced when cultured in the presence of RGCs and astrocytes compared to MVECs cultured alone. Conversely, the versatility of this system to model aspects of barrier dysfunction relevant to glaucoma was tested using an hPSC line with a glaucoma-specific Optineurin (E50K) mutation as well as a paired isogenic control, where MVECs then exhibited reduced barrier integrity. To identify factors that could result in barrier dysfunction, results revealed an increased expression of TGFβ2 in glaucoma-associated OPTN(E50K) astrocytes, indicating a potential role for TGFβ2 in disease manifestation. To test this hypothesis, we explored the ability to modulate exogenous TGFβ2 in both isogenic control and OPTN(E50K) experimental conditions. Collectively, the results of this study indicated that the repurposing of this in vitro barrier model for glaucoma reliably mimicked some aspects of barrier dysfunction, and may serve as a platform for drug discovery, as well as a powerful in vitro model to test the consequences of barrier dysfunction upon RGCs in glaucoma.

The Acute Impact of Propofol on Blood-Brain Barrier Integrity in Mice

PURPOSE

We investigated whether short term infusion of propofol, a highly lipophilic agonist at GABAA receptors, which is in widespread clinical use as anesthetic and sedative, affects passive blood-brain barrier (BBB) permeability in vivo.

METHODS

Mice were anesthetized with an intraperitoneal injection of ketamine/xylazine followed by a continuous IV infusion of propofol in lipid emulsion through a tail vein catheter. Control groups received ketamine/xylazine anesthesia and an infusion of Intralipid, or ketamine/xylazine anesthesia only. [13C12]sucrose as a permeability marker was injected as IV bolus 15 min after start of the infusions. Brain uptake clearance, Kin, of sucrose was calculated from the brain concentrations at 30 min and the area under the plasma-concentration time curve. We also measured the plasma and brain concentration of propofol at the terminal time point.

RESULTS

The Kin value for propofol-infused mice was significantly higher, by a factor of 1.55 and 1.87, compared to the Intralipid infusion and the ketamine/xylazine groups, respectively, while the control groups were not significantly different. No difference was seen in the expression levels of tight junction proteins in brain across all groups. The propofol plasma concentration at the end of infusion (10.7 µM) matched the clinically relevant range of blood concentrations reported in humans, while concentration in brain was 2.5-fold higher than plasma.

CONCLUSIONS

Propofol at clinical plasma concentrations acutely increases BBB permeability, extending our previous results with volatile anesthetics to a lipophilic injectable agent. This prompts further exploration, potentially refining clinical practices and ensuring safety, especially during extended propofol infusion schemes.

FUS-mediated blood-brain barrier disruption for delivering anti-Aβ antibodies in 5XFAD Alzheimer's disease mice

PURPOSE

Amyloid-β (Aβ) peptides, the main component of amyloid plaques found in the Alzheimer's disease (AD) brain, are implicated in its pathogenesis, and are considered a key target in AD therapeutics. We herein propose a reliable strategy for non-invasively delivering a specific anti-Aβ antibody in a mouse model of AD by microbubbles-enhanced Focused Ultrasound (FUS)-mediated Blood-brain barrier disruption (BBBD), using a simple single stage MR-compatible positioning device.

METHODS

The initial experimental work involved wild-type mice and was devoted to selecting the sonication protocol for efficient and safe BBBD. Pulsed FUS was applied using a single-element FUS transducer of 1 MHz (80 mm radius of curvature and 50 mm diameter). The success and extent of BBBD were assessed by Evans Blue extravasation and brain damage by hematoxylin and eosin staining. 5XFAD mice were divided into different subgroups; control (n = 1), FUS + MBs alone (n = 5), antibody alone (n = 5), and FUS + antibody combined (n = 10). The changes in antibody deposition among groups were determined by immunohistochemistry.

RESULTS

It was confirmed that the antibody could not normally enter the brain parenchyma. A single treatment with MBs-enhanced pulsed FUS using the optimized protocol (1 MHz, 0.5 MPa in-situ pressure, 10 ms bursts, 1% duty factor, 100 s duration) transiently disrupted the BBB allowing for non-invasive antibody delivery to amyloid plaques within the sonicated brain regions. This was consistently reproduced in ten mice.

CONCLUSION

These preliminary findings should be confirmed by longer-term studies examining the antibody effects on plaque clearance and cognitive benefit to hold promise for developing disease-modifying anti-Aβ therapeutics for clinical use.

Propofol-induced hippocampal Neurotoxicity: A mitochondrial perspective

Propofol is a frequently used anesthetic. It can induce neurodegeneration and inhibit neurogenesis in the hippocampus. This effect may be temporary. It can, however, become permanent in vulnerable populations, such as the elderly, who are more susceptible to Alzheimer's disease, and neonates and children, whose brains are still developing and require neurogenesis. Current clinical practice strategies have failed to provide an effective solution to this problem. In addition, the molecular mechanism of this toxicity is not fully understood. Recent advances in molecular research have revealed that apoptosis, in close association with mitochondria, is a crucial mechanism through which propofol contributes to hippocampal toxicity. Preventing the toxicity of propofol on the hippocampus has shown promise in in-vivo, in-vitro, and to a lesser extent human studies. This study seeks to provide a comprehensive literature review of the effects of propofol toxicity on the hippocampus via mitochondria and to suggest translational suggestions based on these molecular results.

A human pluripotent stem cell-derived in vitro model of the blood-brain barrier in cerebral malaria

BACKGROUND

Blood-brain barrier (BBB) disruption is a central feature of cerebral malaria (CM), a severe complication of Plasmodium falciparum (Pf) infections. In CM, sequestration of Pf-infected red blood cells (Pf-iRBCs) to brain endothelial cells combined with inflammation, hemolysis, microvasculature obstruction and endothelial dysfunction mediates BBB disruption, resulting in severe neurologic symptoms including coma and seizures, potentially leading to death or long-term sequelae. In vitro models have advanced our knowledge of CM-mediated BBB disruption, but their physiological relevance remains uncertain. Using human induced pluripotent stem cell-derived brain microvascular endothelial cells (hiPSC-BMECs), we aimed to develop a novel in vitro model of the BBB in CM, exhibiting enhanced barrier properties.

METHODS

hiPSC-BMECs were co-cultured with HB3var03 strain Pf-iRBCs up to 9 h. Barrier integrity was measured using transendothelial electrical resistance (TEER) and sodium fluorescein permeability assays. Localization and expression of tight junction (TJ) proteins (occludin, zonula occludens-1, claudin-5), cellular adhesion molecules (ICAM-1, VCAM-1), and endothelial surface markers (EPCR) were determined using immunofluorescence imaging (IF) and western blotting (WB). Expression of angiogenic and cell stress markers were measured using multiplex proteome profiler arrays.

RESULTS

After 6-h of co-culture with Pf-iRBCs, hiPSC-BMECs showed reduced TEER and increased sodium fluorescein permeability compared to co-culture with uninfected RBCs, indicative of a leaky barrier. We observed disruptions in localization of occludin, zonula occludens-1, and claudin-5 by IF, but no change in protein expression by WB in Pf-iRBC co-cultures. Expression of ICAM-1 and VCAM-1 but not EPCR was elevated in hiPSC-BMECs with Pf-iRBC co-culture compared to uninfected RBC co-culture. In addition, there was an increase in expression of angiogenin, platelet factor-4, and phospho-heat shock protein-27 in the Pf-iRBCs co-culture compared to uninfected RBC co-culture.

CONCLUSION

These findings demonstrate the validity of our hiPSC-BMECs based model of the BBB, that displays enhanced barrier integrity and appropriate TJ protein localization. In the hiPSC-BMEC co-culture with Pf-iRBCs, reduced TEER, increased paracellular permeability, changes in TJ protein localization, increase in expression of adhesion molecules, and markers of angiogenesis and cellular stress all point towards a novel model with enhanced barrier properties, suitable for investigating pathogenic mechanisms underlying BBB disruption in CM.

Studying the Effects of Dissolved Noble Gases and High Hydrostatic Pressure on the Spherical DOPC Bilayer Using Molecular Dynamic Simulations

Fine-grained molecular dynamics simulations have been conducted to depict lipid objects enclosed in water and interacting with a series of noble gases dissolved in the medium. The simple point-charge (SPC) water system, featuring a boundary composed of 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) molecules, maintained stability throughout the simulation under standard conditions. This allowed for the accurate modeling of the effects of hydrostatic pressure at an ambient pressure of 25 bar. The chosen pressure references the 240 m depth of seawater: the horizon frequently used by commercial divers, who comprise the primary patient population of the neurological complication of inert gas narcosis and the consequences of high-pressure neurological syndrome. To quantify and validate the neurological effects of noble gases and discriminate them from high hydrostatic pressure, we reduced the dissolved gas molar concentration to 1.5%, three times smaller than what we previously tested for the planar bilayer (3.5%). The nucleation and growth of xenon, argon and neon nanobubbles proved consistent with the data from the planar bilayer simulations. On the other hand, hyperbaric helium induces only a residual distorting effect on the liposome, with no significant condensed gas fraction observed within the hydrophobic core. The bubbles were distributed over a large volume-both in the bulk solvent and in the lipid phase-thereby causing substantial membrane distortion. This finding serves as evidence of the validity of the multisite distortion hypothesis for the neurological effect of inert gases at high pressure.

Benefits of remimazolam as an anesthetic sedative for older patients: A review

Owing to the decreased levels of receptors in the peripheral and central nervous systems, the functions of various organ systems decline in older patients. When administering anesthesia to older patients, it is necessary to consider the effects of medication on the homeostatic balance. Remimazolam, a new benzodiazepine, was recently developed as an anesthetic drug that has shown promise in clinical anesthesia application owing to its molecular structure, targets, pharmacodynamics, and pharmacokinetic characteristics. Remimazolam exhibits a rapid onset and metabolism, with minor effects on liver and kidney functions. Moreover, the drug has a specific antagonist, flumazenil. It is safer to use in older patients than other anesthetic sedatives and has been widely used since its introduction. Comparisons of the pharmacokinetics, metabolic pathways, effects on target organs, and hemodynamics of different drugs with those of commonly used anesthetic sedative drugs are useful to inform clinical practice. This article elaborates on the benefits of remimazolam compared with those of other anesthetic sedatives for sedation in older patients to demonstrate how it offers a new option for anesthetics in older patients. In cases involving older patients with increased clinical complexities or very old patients requiring anesthesia, remimazolam can be selected as the preferred anesthetic sedative, as outlined in this review.

Inhalational Anesthesia Reduced Transient Neurological Events After Revascularization Surgery for Moyamoya Disease

BACKGROUND AND OBJECTIVES

The choice between inhalational and total intravenous anesthesia (TIVA) in revascularization surgery for Moyamoya disease (MMD) remains a topic of debate. Anesthesia methods have changed with the advent of new anesthetics. This study investigated whether modern anesthesia methods affected the development of neurological symptoms after revascularization surgery for MMD.

METHODS

This single-center retrospective study included 63 adult patients (82 hemispheres) with MMD treated with direct and indirect bypass surgeries at our hospital between 2013 and 2022. Patients were divided into inhalational anesthesia (IA) and TIVA groups based on the anesthesia maintenance method. Baseline patient characteristics; postoperative neurological symptoms, including hyperperfusion syndrome, cerebral infarction, and transient neurological events (TNEs); and cortical hyperintensity belt (CHB) sign scores (5-point scale from 0 to 4) on postoperative magnetic resonance imaging were compared between the two groups. The operation methods, anesthetics, and intraoperative hemodynamic and ventilatory parameters were compared between patients with and without TNEs.

RESULTS

The IA and TIVA groups comprised 39 and 43 hemispheres, respectively. The frequency of postoperative hyperperfusion syndrome and cerebral infarction did not differ between the groups, but the number of TNEs in the IA group (5/39; 13%) was significantly lower than that in the TIVA group (16/43; 37%). Multivariate logistic regression analysis revealed that TNEs were associated with TIVA (odds ratio, 3.91; 95% CI, 1.24-12.35; P = .02). The median [IQR] postoperative CHB sign score in the IA group (2 [1-3]) was significantly lower than that in the TIVA group (4 [3-4]).

CONCLUSION

The IA group had fewer postoperative TNEs and lower CHB sign scores than the TIVA group. Although further studies are needed, this study provides insights into the prevention of TNEs with IA and reconsideration of the optimal anesthesia for MMD.

Machine Learning Technology for EEG-Forecast of the Blood-Brain Barrier Leakage and the Activation of the Brain's Drainage System during Isoflurane Anesthesia

Anesthesia enables the painless performance of complex surgical procedures. However, the effects of anesthesia on the brain may not be limited only by its duration. Also, anesthetic agents may cause long-lasting changes in the brain. There is growing evidence that anesthesia can disrupt the integrity of the blood-brain barrier (BBB), leading to neuroinflammation and neurotoxicity. However, there are no widely used methods for real-time BBB monitoring during surgery. The development of technologies for an express diagnosis of the opening of the BBB (OBBB) is a challenge for reducing post-surgical/anesthesia consequences. In this study on male rats, we demonstrate a successful application of machine learning technology, such as artificial neural networks (ANNs), to recognize the OBBB induced by isoflurane, which is widely used in surgery. The ANNs were trained on our previously presented data obtained on the sound-induced OBBB with an 85% testing accuracy. Using an optical and nonlinear analysis of the OBBB, we found that 1% isoflurane does not induce any changes in the BBB, while 4% isoflurane caused significant BBB leakage in all tested rats. Both 1% and 4% isoflurane stimulate the brain's drainage system (BDS) in a dose-related manner. We show that ANNs can recognize the OBBB induced by 4% isoflurane in 57% of rats and BDS activation induced by 1% isoflurane in 81% of rats. These results open new perspectives for the development of clinically significant bedside technologies for EEG-monitoring of OBBB and BDS.

Research progress on perioperative blood-brain barrier damage and its potential mechanism

The blood-brain barrier (BBB) is an important barrier separating the central nervous system from the periphery. The composition includes endothelial cells, pericytes, astrocytes, synapses and tight junction proteins. During the perioperative period, anesthesia and surgical operations are also a kind of stress to the body, which may be accompanied by blood-brain barrier damage and brain metabolism dysfunction. Perioperative blood-brain barrier destruction is closely associated with cognitive impairment and may increase the risk of postoperative mortality, which is not conducive to enhanced recovery after surgery. However, the potential pathophysiological process and specific mechanism of blood-brain barrier damage during the perioperative period have not been fully elucidated. Changes in blood-brain barrier permeability, inflammation and neuroinflammation, oxidative stress, ferroptosis, and intestinal dysbiosis may be involved in blood-brain barrier damage. We aim to review the research progress of perioperative blood-brain barrier damage and its potential adverse effects and potential molecular mechanisms, and provide ideas for the study of homeostasis maintenance of brain function and precision anesthesia.

The Crosstalk between the Blood–Brain Barrier Dysfunction and Neuroinflammation after General Anaesthesia

As we know, with continuous medical progress, the treatment of many diseases can be conducted via surgery, which often relies on general anaesthesia for its satisfactory performance. With the widespread use of general anaesthetics, people are beginning to question the safety of general anaesthesia and there is a growing interest in central nervous system (CNS) complications associated with anaesthetics. Recently, abundant evidence has suggested that both blood–brain barrier (BBB) dysfunction and neuroinflammation play roles in the development of CNS complications after anaesthesia. Whether there is a crosstalk between BBB dysfunction and neuroinflammation after general anaesthesia, and whether this possible crosstalk could be a therapeutic target for CNS complications after general anaesthesia needs to be clarified by further studies.