Effects of Propofol Treatment in Neural Progenitors Derived from Human-Induced Pluripotent Stem Cells

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.

Anaesthesia and brain development: a review of propofol-induced neurotoxicity in pediatric populations

With the advancement of medical technology, there are increasing opportunities for new-borns, infants, and pregnant women to be exposed to general anaesthesia. Propofol is commonly used for the induction of anaesthesia, maintenance of general intravenous anaesthesia and sedation of intensive-care children. Many previous studies have found that propofol has organ-protective effects, but growing evidence suggests that propofol interferes with brain development, affecting learning and cognitive function. The purpose of this review is to summarize the latest progress in understanding the neurotoxicity of propofol. Evidence from case studies and clinical studies suggests that propofol has neurotoxicity on the developing brain. We classify the findings on propofol-induced neurotoxicity based on its damage mechanism. We end by summarizing the current protective strategies against propofol neurotoxicity. Fully understanding the neurotoxic mechanisms of propofol can help us use it at a reasonable dosage, reduce its side effects, and increase patient safety.

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

Background

Recently, the safety of repeated and lengthy anesthesia administration has been called into question, a subset of these animal studies demonstrated that anesthetics induced blood-brain barrier (BBB) dysfunction. The BBB is critical in protecting the brain parenchyma from the surrounding micro-vasculature. BBB breakdown and dysfunction has been observed in several neurodegenerative diseases and may contribute to both the initiation and the progression of the disease. In this study we utilize a human induced pluripotent stem cell (iPSC) derived-BBB model, exhibiting near in vivo properties, to evaluate the effects of anesthetics on critical barrier properties.

Methods

iPSC-derived brain microvascular endothelial cells (BMECs) expressed near in vivo barrier tightness assessed by trans-endothelial electrical resistance and para-cellular permeability. Efflux transporter activity was determined by substrate transport in the presence of specific inhibitors. Trans-cellular transport was measured utilizing large fluorescently tagged dextran. Tight junction localization in BMECs was evaluated with fluorescent microscopy. The anesthetic, propofol was exposed to BMECs at varying durations and concentrations and BBB properties were monitored post-exposure.

Results

Following propofol exposure, BMECs displayed reduced resistance and increased permeability indicative of a leaky barrier. Reduced barrier tightness and the dysregulation of occludin, a tight junction protein, were partly the result of an elevation in matrix metalloproteinase (MMP) levels. Efflux transporter activity and trans-cellular transport were unaffected by propofol exposure. Propofol induced barrier dysfunction was partially restored following matrix metalloproteinase inhibition.

Conclusion

For the first time, we have demonstrated that propofol alters BBB integrity utilizing a human in vitro BBB model that displays key in vivo characteristics. A leaky BBB enables otherwise impermeable molecules such as pathogens and toxins the ability to reach vulnerable cell types of the brain parenchyma. A robust human in vitro BBB model will allow for the evaluation of several anesthetics at fluctuating clinical scenarios and to elucidate mechanisms with the goal of ultimately improving anesthesia safety.

Combination of IKVAV, LRE, and GPQGIWGQ Bioactive Signaling Peptides Increases Human Induced Pluripotent Stem Cell Derived Neural Stem Cells Extracellular Matrix Remodeling and Neurite Extension

Extracellular matrix (ECM) remodeling is emerging as a modulator of neural maturation and axon extension. Most studies have used rodent cells to develop matrices capable of manipulating extracellular matrix remodeling for regenerative applications. However, clinically relevant human induced pluripotent stem cell derived neural stem cells (hNSC) do not always behave in a similar manner as rodent cells. In this study, hNSC response to a hyaluronic acid matrix with laminin derived IKVAV and LRE peptide signaling that has previously shown to promote ECM remodeling and neurite extension by mouse embryonic stem cells is examined. The addition of enzymatically degradable cross linker GPQGIWGQ to the IKVAV and LRE containing hyaluronic acid matrix is necessary to promote neurite extension, hyaluronic acid degradation, and gelatinase expression over hyaluronic acid matrices containing GPQGIWGQ, IKVAV and LRE, or no peptides. Changes in peptide content alters a number of matrix properties that can contribute to the cellular response, but increases in mesh size are not observed with cross linker cleavage in this study. Overall, these data imply a complex interaction between IKVAV, LRE, and GPQGIWGQ to modulate hNSC behavior.

Effect of Laminin Derived Peptides IKVAV and LRE Tethered to Hyaluronic Acid on hiPSC Derived Neural Stem Cell Morphology, Attachment and Neurite Extension

Low neural tissue extracellular matrix (ECM) content has led to the understudy of its effects on neural cells and tissue. Hyaluronic acid (HA) and laminin are major neural ECM components, but direct comparisons of their cellular effects could not be located in the literature. The current study uses human-induced pluripotent stem-cell-derived neural stem cells to assess the effects of HA, laminin, and HA with laminin-derived peptides IKVAV and LRE on cellular morphology, attachment, neurite extension and ECM remodeling. Increased attachment was observed on HA with and without IKVAV and LRE compared to laminin. Cellular morphology and neurite extension were similar on all surfaces. Using a direct binding inhibitor of Cav2.2 voltage gated calcium channel activity, a known binding partner of LRE, reduced attachment on HA with and without IKVAV and LRE and altered cellular morphology on surfaces with laminin or IKVAV and LRE. HA with IKVAV and LRE reduced the fluorescent intensity of fibronectin staining, but did not alter the localization of ECM remodeling enzymes matrix metalloprotease 2 and 9 staining compared to HA. Overall, the data indicate HA, IKVAV and LRE have complementary effects on human-induced pluripotent stem-cell-derived neural stem cell behavior.

Alzheimer's Disease Presenilin-1 Mutation Sensitizes Neurons to Impaired Autophagy Flux and Propofol Neurotoxicity: Role of Calcium Dysregulation

BACKGROUND

Disruption of intracellular Ca2+ homeostasis and associated autophagy dysfunction contribute to neuropathology in Alzheimer's disease (AD).

OBJECTIVE

To study the effects of propofol on cell viability via its effects on intracellular Ca2+ homeostasis, and the impact of autophagy, in a neuronal model of presenilin-mutated familial AD (FAD).

METHODS

We treated PC12 cells, stably transfected with either mutated presenilin-1 (L286V) or wild type (WT) controls, with propofol at different doses and durations, in the presence or absence of extracellular Ca2+, antagonists of inositol trisphosphate receptors (InsP3R, xestospongin C) and/or ryanodine receptors (RYR, dantrolene), or an inhibitor of autophagy flux (Bafilomycin). We determined cell viability, cytosolic Ca2+ concentrations ([Ca2+]c), vATPase protein expression, and lysosomal acidification.

RESULTS

The propofol dose- and time-dependently decreased cell viability significantly more in L286V than WT cells, especially at the pharmacological dose (>50μM), and together with bafilomycin (40 nM). Clinically used concentrations of propofol (<20μM) tended to increase cell viability. Propofol significantly increased [Ca2+]c more in L286V than in WT cells, which was associated with decrease of vATPase expression and localization to the lysosome. Both toxicity and increased Ca2+ levels were ameliorated by inhibiting InsP3R/RYR. However, the combined inhibition of both receptors paradoxically increased [Ca2+]c, by inducing Ca2+ influx from the extracellular space, causing greater cytotoxicity.

CONCLUSION

Impairment in autophagy function acts to deteriorate cell death induced by propofol in FAD neuronal cells. Cell death is ameliorated by either RYR or InsP3R antagonists on their own, but not when both are co-administered.

Propofol inhibits biological functions of leukaemia stem and differentiated cells through suppressing Wnt/β-catenin and Akt/mTOR

The biological roles of intravenous anaesthetic propofol in cancer have been shown by various studies using cancer cell lines that represent differentiated cancer cells. However, the activities of propofol in cancer stem cells have not been elucidated. In this work, we examined the effects and mechanisms of propofol on acute myeloid leukaemia (AML) differentiated and CD34⁺ CD38^- stem cells. We found that propofol inhibited growth, differentiation and self-renewal capabilities of AML stem cells regardless of cellular origin and genetic profiling. In addition, propofol inhibited the growth of AML differentiated cells. Propofol significantly induced apoptosis of AML differentiated but not CD34⁺ CD38^- stem cells. We further found that propofol significantly augmented the efficacy of AML standard therapeutic drugs. Consistent with the previous findings, we showed that propofol suppressed the Akt/mTOR pathway in AML cells. We also found that propofol inhibited pathways important for stem cell maintenance and self-renewal, such as Wnt/β-catenin. Overexpression of constitutively active Akt partially reversed the inhibitory effects of propofol in AML differentiated cells. Stabilization of β-catenin using genetic and pharmacological approaches also partially rescued the inhibitory effects of propofol in AML differentiated and stem cells. Our work shows that propofol targets leukaemia cells at all stages of development, in a cell type-specific manner. Inhibition of both Akt/mTOR and Wnt/β-catenin is required for the action of propofol in AML. Our findings also highlight the activities of propofol on cancer stem cells.

Studying Human Neurological Disorders Using Induced Pluripotent Stem Cells: From 2D Monolayer to 3D Organoid and Blood Brain Barrier Models

Neurological disorders have emerged as a predominant healthcare concern in recent years due to their severe consequences on quality of life and prevalence throughout the world. Understanding the underlying mechanisms of these diseases and the interactions between different brain cell types is essential for the development of new therapeutics. Induced pluripotent stem cells (iPSCs) are invaluable tools for neurological disease modeling, as they have unlimited self-renewal and differentiation capacity. Mounting evidence shows: (i) various brain cells can be generated from iPSCs in two-dimensional (2D) monolayer cultures; and (ii) further advances in 3D culture systems have led to the differentiation of iPSCs into organoids with multiple brain cell types and specific brain regions. These 3D organoids have gained widespread attention as in vitro tools to recapitulate complex features of the brain, and (iii) complex interactions between iPSC-derived brain cell types can recapitulate physiological and pathological conditions of blood-brain barrier (BBB). As iPSCs can be generated from diverse patient populations, researchers have effectively applied 2D, 3D, and BBB models to recapitulate genetically complex neurological disorders and reveal novel insights into molecular and genetic mechanisms of neurological disorders. In this review, we describe recent progress in the generation of 2D, 3D, and BBB models from iPSCs and further discuss their limitations, advantages, and future ventures. This review also covers the current status of applications of 2D, 3D, and BBB models in drug screening, precision medicine, and modeling a wide range of neurological diseases (e.g., neurodegenerative diseases, neurodevelopmental disorders, brain injury, and neuropsychiatric disorders). © 2019 American Physiological Society. Compr Physiol 9:565-611, 2019.