Blood-brain Barrier Transport Research Articles

Regional distribution of unbound eletriptan and sumatriptan in the CNS and PNS in rats: implications for a potential central action

BackgroundTriptans are potent 5-HT1B/1D/1F receptor agonists used in migraine therapy, thought to act through peripheral mechanisms. It remains unclear whether triptans cross the blood-brain barrier (BBB) sufficiently to stimulate central 5-HT1B/1D/1F receptors. This study investigates the disposition of eletriptan and sumatriptan in central nervous system (CNS) and peripheral nervous system (PNS) regions and predicts regional 5-HT1B/1D/1F receptor occupancies at clinically relevant concentrations.MethodsUsing the Combinatory Mapping Approach (CMA) for regions of interest (ROI), we assessed the unbound tissue-to-plasma concentration ratio (Kp, uu, ROI) in rats at steady state across CNS (hypothalamus, brain stem, cerebellum, frontal cortex, parietal cortex, striatum, hippocampus, whole brain, and spinal cord) and PNS (trigeminal ganglion and sciatic nerve) regions. We used Kp, uu, ROI values to estimate unbound target-site concentrations and 5-HT1B/1D/1F receptor occupancies in humans.ResultsWe observed heterogenous triptan transport across CNS and PNS regions with the highest extent of unbound drug transport across the blood-nerve barrier in the trigeminal ganglion (Kp, uu, TG: eletriptan: 0.519, and sumatriptan: 0.923). Both drugs displayed restricted entry across the BBB (Kp, uu, whole brain: eletriptan: 0.058, and sumatriptan: 0.045) combined with high inter-regional variability. We estimated near-complete receptor occupancy in the trigeminal ganglion, while lower occupancies were observed in the whole brain, irrespective of the drug or receptor subtype. For instance, eletriptan was predicted to achieve 84% 5-HT1B receptor occupancy in the trigeminal ganglion and 37% in the whole brain at clinically relevant concentrations.ConclusionsThis study suggests that despite low BBB transport, both eletriptan and sumatriptan achieve unbound concentrations sufficient to stimulate 5-HT1B, 5-HT1D, and 5-HT1F receptors not only in the trigeminal ganglion, but also in the CNS. Further research is needed to determine whether central mechanisms contribute to triptan’s antimigraine effect and/or side effects.Graphical

Conformational Plasticity Enhances the Brain Penetration of a Metabolically Stable, Dual-Functional Opioid-Peptide CycloAnt

CycloAnt is an opioid peptide that produces potent and efficacious antinociception with significantly reduced side effects upon systemic administration in mice. To verify its CNS-mediated antinociception, we determined its binding affinity at the opioid receptors, its proteolytic stability in mouse serum, metabolic stability in mouse liver microsomes, and pharmacokinetics in mice. CycloAnt exhibited stability toward proteolytic degradation in serum and resistance against metabolism mediated by cytochrome P450 enzymes (CYP450s) and UDP-glucuronosyl transferases (UGTs) in mouse liver microsomes. A pharmacokinetic study of CycloAnt in mice confirmed that CycloAnt crossed the blood–brain barrier (BBB) with a brain-to-plasma ratio of 11.5%, a high extent of BBB transport for a peptide. To elucidate the structural basis underlying its BBB penetration, we investigated its conformation in water and DMSO using 1H NMR spectroscopy. The results show that CycloAnt displays an extended conformation in water with most amide NHs being exposed, while in less polar DMSO, it adopts a compact conformation with all amide NHs locked in intramolecular hydrogen bonds. The chameleonic property helps CycloAnt permeate the BBB.

Involvement of Proton-Coupled Organic Cation Antiporter in Human Blood-Brain Barrier Transport of Mesoridazine and Metoclopramide.

Mesoridazine and metoclopramide are cationic drugs that are distributed in the human brain despite being substrates of multidrug resistance protein 1 (MDR1), an efflux transporter expressed at the blood-brain barrier (BBB). We investigated their transport mechanisms at the BBB using hCMEC/D3, a human cerebral microvascular endothelial cell line often used as an in vitro BBB model. The cells exhibited time- and concentration-dependent uptake of mesoridazine and metoclopramide, with Km values of 34 and 277 µM, respectively. The uptake of both drugs significantly decreased in the presence of typical inhibitors and/or substrates of the H+-coupled organic cation (H+/OC) antiporter but not in the presence of inhibitors or substrates of organic cation transporters (OCTs), OCTN2, OATPs, SLC35F2, or the plasma membrane monoamine transporter (PMAT). Furthermore, metoclopramide uptake by hCMEC/D3 cells was pH- and energy-dependent, whereas mesoridazine uptake was unaffected by intracellular acidification and treatment with metabolic inhibitors. These results suggest that the H+/OC antiporter is involved in the influx of mesoridazine and metoclopramide into the brain across the BBB.

A biocompatible polydopamine platform for targeted delivery of nicotinamide mononucleotide and boosting NAD+ levels in the brain.

Nicotinamide mononucleotide (NMN), a precursor of the coenzyme nicotinamide adenine dinucleotide (NAD+), has gained wide attention as an anti-aging agent, which plays a significant role in intracellular redox reactions. However, its effectiveness is limited by easy metabolism in the liver and subsequent excretion as nicotinamide, resulting in low bioavailability, particularly in the brain. Additionally, the blood-brain barrier (BBB) further hinders NMN supply to the brain, compromising its potential anti-aging effects. Herein, we developed a biocompatible polydopamine (PDA) platform to deliver NMN for boosting NAD+ levels in the brain for the first time. The lactoferrin (Lf) ligand was covalently attached to the PDA spheres to improve BBB transport efficiency. The resultant PDA-based system, referred to as PDA-Lf-NMN, not only exhibited superior BBB penetration ability but also improved the utilization rate of brain NMN in elevating NAD+ levels compared to NMN alone for both young (3 months) and old (21 months) mice. Moreover, after the old mice were treated with low-dose PDA-Lf-NMN (8 mg kg-1 day-1), they exhibited improved spatial cognition. Importantly, these nanomedicines did not induce any cellular necrosis or apoptosis. It provides a promising avenue for delivering NMN specifically to the brain, boosting NAD+ levels for promoting longevity and treating brain aging-related diseases.

Placental extracellular vesicles: their unique characteristics of the blood-brain barrier transport

Placental extracellular vesicles: their unique characteristics of the blood-brain barrier transport

Exploring Kp,uu,BBB values smaller than unity in remoxipride: A physiologically-based CNS model approach highlighting brain metabolism in drugs with passive blood-brain barrier transport

(Aim)Kp,uu,BBB values are crucial indicators of drug distribution into the brain, representing the steady-state relationship between unbound concentrations in plasma and in brain extracellular fluid (brainECF). Kp,uu,BBB values < 1 are often interpreted as indicators of dominant active efflux transport processes at the blood-brain barrier (BBB). However, the potential impact of brain metabolism on this value is typically not addressed. In this study, we investigated the brain distribution of remoxipride, as a paradigm compound for passive BBB transport with yet unexplained brain elimination that was hypothesized to represent brain metabolism. (Methods)The physiologically-based LeiCNS pharmacokinetic predictor (LeiCNS-PK model) was used to compare brain distribution of remoxipride with and without Michaelis-Menten kinetics at the BBB and/or brain cell organelle levels. To that end, multiple in-house (IV 0.7, 3.5, 4, 5.2, 7, 8, 14 and 16 mg kg-1) and external (IV 4 and 8 mg kg-1) rat microdialysis studies plasma and brainECF data were analysed. (Results)The incorporation of active elimination through presumed brain metabolism of remoxipride in the LeiCNS-PK model significantly improved the prediction accuracy of experimentally observed brainECF profiles of this drug. The model integrated with brain metabolism in both barriers and organelles levels is named LeiCNS-PK3.5. (Conclusion)For drugs with Kp,uu,BBB values < 1, not only the current interpretation of dominant BBB efflux transport, but also potential brain metabolism needs to be considered, especially because these may be concentration dependent. This will improve the mechanistic understanding of the processes that determine brain PK profiles.

Angiopep-2 conjugated biomimetic nano-delivery system loaded with resveratrol for the treatment of methamphetamine addiction

Methamphetamine (METH) addiction can damage the central nervous system, resulting in cognitive impairment and memory deficits. Low target effects have limited the utility of anti-addiction drugs because the presence of the blood–brain barrier hinders the effective delivery of drugs to the brain. Angiopep-2 can recognize and target low-density lipoprotein receptor-associated protein 1 (LRP-1) on the surface of cerebral capillary endothelial cells, causing cross-cell phagocytosis, and thus has high blood–brain barrier transport capacity. Resveratrol (RSV) has been found to be a neuroprotective agent in many nervous system diseases. In our study, we modified Angiopep-2 on the surface of the erythrocyte membrane to obtain a modified erythrocyte membrane (Ang-RBCm) and coated RSV-loaded poly(ε-caprolactone)–poly(ethylene glycol) (PCL-PEG) nanoparticles with Ang-RBCm (Ang-RBCm@RSVNPs) to treat METH addiction. Our results showed that Ang-RBCm@RSVNPs can penetrate the blood–brain barrier and accumulate in the brain better than free RSV. Besides, mice treatetd with Ang-RBCm@RSVNPs showed less preference to METH-paired chamber and no noticeable tissue toxicity or abnormality was found in H&E staining images. Electrophysiological experiments demonstrated Ang-RBCm@RSVNPs could elevate synaptic plasticity impaired by METH. These indicated that Ang-RBCm@RSVNPs has better anti-addiction and neuroprotective effects. Therefore, Ang-RBCm@RSVNPs has great potential in the treatment of METH addiction.

Circulating low-molecular-weight (poly)phenol metabolites in the brain: unveiling in vitro and in vivo blood-brain barrier transport.

Circulating metabolites resulting from colonic metabolism of dietary (poly)phenols are highly abundant in the bloodstream, though still marginally explored, particularly concerning their brain accessibility. Our goal is to disclose (poly)phenol metabolites' blood-brain barrier (BBB) transport, in vivo and in vitro, as well as their role at BBB level. For three selected metabolites, benzene-1,2-diol-3-sulfate/benzene-1,3-diol-2-sulfate (pyrogallol-sulfate - Pyr-sulf), benzene-1,3-diol-6-sulfate (phloroglucinol-sulfate - Phlo-sulf), and phenol-3-sulfate (resorcinol-sulfate - Res-sulf), BBB transport was assessed in human brain microvascular endothelial cells (HBMEC). Their potential in modulating in vitro BBB properties at circulating concentrations was also studied. Metabolites' fate towards the brain, liver, kidney, urine, and blood was disclosed in Wistar rats upon injection. Transport kinetics in HBMEC highlighted different BBB permeability rates, where Pyr-sulf emerged as the most in vitro BBB permeable metabolite. Pyr-sulf was also the most potent regarding BBB properties improvement, namely increased beta(β)-catenin membrane expression and reduction of zonula occludens-1 membrane gaps. Whereas no differences were observed for transferrin, increased expression of caveolin-1 upon Pyr-sulf and Res-sulf treatments was found. Pyr-sulf was also capable of modulating gene and protein expression of some solute carrier transporters. Notably, each of the injected metabolites exhibited a unique tissue distribution in vivo, with the remarkable ability to almost immediately reach the brain.

Quantitative PET imaging and modeling of molecular blood-brain barrier permeability.

Blood-brain barrier (BBB) disruption is involved in the pathogenesis and progression of many neurological and systemic diseases. Non-invasive assessment of BBB permeability in humans has mainly been performed with dynamic contrast-enhanced magnetic resonance imaging, evaluating the BBB as a structural barrier. Here, we developed a novel non-invasive positron emission tomography (PET) method in humans to measure the BBB permeability of molecular radiotracers that cross the BBB through different transport mechanisms. Our method uses high-temporal resolution dynamic imaging and kinetic modeling to jointly estimate cerebral blood flow and tracer-specific BBB transport rate from a single dynamic PET scan and measure the molecular permeability-surface area (PS) product of the radiotracer. We show our method can resolve BBB PS across three PET radiotracers with greatly differing permeabilities, measure reductions in BBB PS of 18F-fluorodeoxyglucose (FDG) in healthy aging, and demonstrate a possible brain-body association between decreased FDG BBB PS in patients with metabolic dysfunction-associated steatotic liver inflammation. Our method opens new directions to efficiently study the molecular permeability of the human BBB in vivo using the large catalogue of available molecular PET tracers.

Iron Reduces the Trafficking of Fatty Acids from Human Immortalised Brain Microvascular Endothelial Cells Through Modulation of Fatty Acid Transport Protein 1 (FATP1/SLC27A1)

PurposeAlzheimer’s disease (AD) is associated with brain accumulation of amyloid-beta (Aβ) and neurofibrillary tangle formation, in addition to reduced brain docosahexaenoic acid (DHA) and increased brain iron levels. DHA requires access across the blood–brain barrier (BBB) to enter the brain, and iron has been shown to affect the expression and function of a number of BBB transporters. Therefore, this study aimed to assess the effect of iron on the expression and function of fatty acid binding protein 5 (FABP5) and fatty acid transport protein 1 (FATP1), both which mediate brain endothelial cell trafficking of DHA.MethodsThe mRNA and protein levels of FABP5 and FATP1 in human cerebral microvascular endothelial (hCMEC/D3) cells was assessed by RT-qPCR and Western blot, respectively following ferric ammonium citrate (FAC) treatment (up to 750 µM, 72 h). The function of FABP5 and FATP1 was assessed via uptake and efflux of radiolabelled 3H-oleic acid and 14C-DHA.ResultsFAC (500 µM, 72 h) had no impact on the expression of FABP5 at the protein and mRNA level in hCMEC/D3 cells, which was associated with a lack of effect on the uptake of 14C-DHA. FAC led to a 19.7% reduction in FATP1 protein abundance in hCMEC/D3 cells with no impact on mRNA levels, and this was associated with up to a 32.6% reduction in efflux of 14C-DHA.ConclusionsThese studies demonstrate a role of iron in down-regulating FATP1 protein abundance and function at the BBB, which may have implications on fatty acid access to the brain.Graphical

Neutrophil-based Trojan horse containing polymer nano-therapeutics for sono-activatable ferroptosis-immunotherapy of orthotopic glioma

The blood-brain barrier (BBB) and tumor microenvironment of glioma limit the efficacies of various therapies, and thus glioma treatment is challenging. We herein report semiconducting polymer nano-therapeutics (SPCFe/siP) that can achieve efficient delivery into orthotopic glioma sites via neutrophil-mediated BBB transport for sono-activatable ferroptosis-immunotherapy. Such SPCFe/siP contain a semiconducting polymer, programmed death-ligand 1 (PD-L1) siRNA and iron oxide (Fe3O4) nanoparticles loaded into a singlet oxygen (1O2)-cleavable nanocarrier with surface conjugation of a neutrophil targeting ligand, sialic acid. SPCFe/siP effectively bind to neutrophils via sialic acid-based targeting pathway, and neutrophils containing SPCFe/siP serve as Trojan horses to migrate across BBB for improved delivery efficacy into orthotopic glioma sites. Upon irradiation by ultrasound (US), the semiconducting polymers produce 1O2 to destroy 1O2-cleavable nanocarriers for precise on-demand releases of Fe3O4 nanoparticles and PD-L1 siRNA, in which, Fe3O4 nanoparticles induce ferroptosis and subsequent immunogenic cell death (ICD), and PD-L1 siRNA downregulated the expression of PD-L1 for tumor cells, allowing for sono-activatable ferroptosis-immunotherapy. A strong immunological effect is formed, leading to noteworthy restriction of orthotopic glioma tumor growth and improvement of mouse survival. This study provides a neutrophil-targeting nanosystem with efficient brain delivery and activatable therapeutic action for treatment of orthotopic glioma.

Neuroinflammation-on-a-chip for multiple sclerosis research: a narrative review.

Multiple sclerosis (MS) is a chronic inflammatory condition that impacts the central nervous system. It is distinguished by processes like demyelination, gliosis, neuro-axonal harm, and inflammation. The prevailing theory suggests that MS originates from an immune response directed against the body's own antigens within the central nervous system. The main aim of this research paper "Neuroinflammation-on-a-Chip" for studying multiple sclerosis is to enhance our comprehension of MS development, demonstrate the application of cutting-edge technology, and potentially provide valuable insights for therapeutic approaches. The available literature for this Narrative Review was searched on various bibliographic databases, PubMed, NCBI, and many other medical references using an individually verified, prespecified approach. Studies regarding the significance of MS and its neuroinflammatory pathogenesis in addition to the development and optimization of neuroinflammatory-on-a-chip and the advancement in innovations in this field have been reviewed in this research for a better understanding of "Neuroinflammation-on-a-chip for multiple sclerosis". The level of evidence of the included studies was considered as per the Centre for Evidence-Based Medicine recommendations. Several studies have indicated that the brain-chip model closely mimics cortical brain tissue compared to commonly used conventional cell culture methods like the Transwell culture system. Additionally, these studies have clearly demonstrated that further research using brain chips has the potential to enhance our understanding of the molecular mechanisms and roles of blood-brain barrier (BBB) transporters in both normal and disease conditions. Understanding neuroinflammation processes remains essential to establish new MS treatments approaches. The utilization of brain chips promises to advance our understanding of the molecular processes involving BBB transporters, both in normal and diseased states. Further research needs to be addressed in order to enhance the performance and understanding of neuroinflammation on a chip, hence aiming to provide more effective treatments for all CNS diseases.

Safety, pharmacokinetics, and potential neurological interactions of ivermectin, tafenoquine, and chloroquine in Rhesus macaques.

Ivermectin (IVM) could be used for malaria control as treated individuals are lethal to blood-feeding Anopheles, resulting in reduced transmission. Tafenoquine (TQ) is used to clear the liver reservoir of Plasmodium vivax and as a prophylactic treatment in high-risk populations. It has been suggested to use ivermectin and tafenoquine in combination, but the safety of these drugs in combination has not been evaluated. Early derivatives of 8-aminoquinolones (8-AQ) were neurotoxic, and ivermectin is an inhibitor of the P-glycoprotein (P-gp) blood brain barrier (BBB) transporter. Thus, there is concern that co-administration of these drugs could be neurotoxic. This study aimed to evaluate the safety and pharmacokinetic interaction of tafenoquine, ivermectin, and chloroquine (CQ) in Rhesus macaques. No clinical, biochemistry, or hematological outcomes of concern were observed. The Cambridge Neuropsychological Test Automated Battery (CANTAB) was employed to assess potential neurological deficits following drug administration. Some impairment was observed with tafenoquine alone and in the same monkeys with subsequent co-administrations. Co-administration of chloroquine and tafenoquine resulted in increased plasma exposure to tafenoquine. Urine concentrations of the 5,6 orthoquinone TQ metabolite were increased with co-administration of tafenoquine and ivermectin. There was an increase in ivermectin plasma exposure when co-administered with chloroquine. No interaction of tafenoquine on ivermectin was observed in vitro. Chloroquine and trace levels of ivermectin, but not tafenoquine, were observed in the cerebrospinal fluid. The 3''-O-demethyl ivermectin metabolite was observed in macaque plasma but not in urine or cerebrospinal fluid. Overall, the combination of ivermectin, tafenoquine, and chloroquine did not have clinical, neurological, or pharmacological interactions of concern in macaques; therefore, this combination could be considered for evaluation in human trials.

The putative proton-coupled organic cation antiporter is involved in uptake of triptans into human brain capillary endothelial cells

BackgroundTriptans are anti-migraine drugs with a potential central site of action. However, it is not known to what extent triptans cross the blood–brain barrier (BBB). The aim of this study was therefore to determine if triptans pass the brain capillary endothelium and investigate the possible underlying mechanisms with focus on the involvement of the putative proton-coupled organic cation (H+/OC) antiporter. Additionally, we evaluated whether triptans interacted with the efflux transporter, P-glycoprotein (P-gp).MethodsWe investigated the cellular uptake characteristics of the prototypical H+/OC antiporter substrates, pyrilamine and oxycodone, and seven different triptans in the human brain microvascular endothelial cell line, hCMEC/D3. Triptan interactions with P-gp were studied using the IPEC-J2 MDR1 cell line. Lastly, in vivo neuropharmacokinetic assessment of the unbound brain-to-plasma disposition of eletriptan was conducted in wild type and mdr1a/1b knockout mice.ResultsWe demonstrated that most triptans were able to inhibit uptake of the H+/OC antiporter substrate, pyrilamine, with eletriptan emerging as the strongest inhibitor. Eletriptan, almotriptan, and sumatriptan exhibited a pH-dependent uptake into hCMEC/D3 cells. Eletriptan demonstrated saturable uptake kinetics with an apparent Km of 89 ± 38 µM and a Jmax of 2.2 ± 0.7 nmol·min−1·mg protein−1 (n = 3). Bidirectional transport experiments across IPEC-J2 MDR1 monolayers showed that eletriptan is transported by P-gp, thus indicating that eletriptan is both a substrate of the H+/OC antiporter and P-gp. This was further confirmed in vivo, where the unbound brain-to-unbound plasma concentration ratio (Kp,uu) was 0.04 in wild type mice while the ratio rose to 1.32 in mdr1a/1b knockout mice.ConclusionsWe have demonstrated that the triptan family of compounds possesses affinity for the H+/OC antiporter proposing that the putative H+/OC antiporter plays a role in the BBB transport of triptans, particularly eletriptan. Our in vivo studies indicate that eletriptan is subjected to simultaneous brain uptake and efflux, possibly facilitated by the putative H+/OC antiporter and P-gp, respectively. Our findings offer novel insights into the potential central site of action involved in migraine treatment with triptans and highlight the significance of potential transporter related drug-drug interactions.Graphical

Non-linear blood-brain barrier transport and dosing strategies influence receptor occupancy ratios of morphine and its metabolites in pain matrix.

Morphine is important for treatment of acute and chronic pain. However, there is high interpatient variability and often inadequate pain relief and adverse effects. To better understand variability in the dose-effect relationships of morphine, we investigated the effects of its non-linear blood-brain barrier (BBB) transport on μ-receptor occupancy in different CNS locations, in conjunction with its main metabolites that bind to the same receptor. CNS exposure profiles for morphine, M3G and M6G for clinically relevant dosing regimens based on intravenous, oral immediate- and extended-release formulations were generated using a physiology-based pharmacokinetic model of the CNS, with non-linear BBB transport of morphine. The simulated CNS exposure profiles were then used to derive corresponding μ-receptor occupancies at multiple CNS pain matrix locations. Simulated CNS exposure profiles for morphine, M3G and M6G, associated with non-linear BBB transport of morphine resulted in varying μ-receptor occupancies between different dose regimens, formulations and CNS locations. At lower doses, the μ-receptor occupancy of morphine was relatively higher than at higher doses of morphine, due to the relative contribution of M3G and M6G. At such higher doses, M6G showed higher occupancy than morphine, whereas M3G occupancy was low throughout the dose ranges. Non-linear BBB transport of morphine affects the μ-receptor occupancy ratios of morphine with its metabolites, depending on dose and route of administration, and CNS location. These predictions need validation in animal or clinical experiments, to understand the clinical implications.

Optimal timing for drug delivery into the hippocampus by focused ultrasound: A comparison of hydrophilic and lipophilic compounds

AimsPrevious studies have reported that focused ultrasound (FUS) helps modulate the blood-brain barrier (BBB). These studies have generally used the paracellular pathway owing to tight junction proteins (TJPs) regulation. However, BBB transport pathways also include diffusion and transcytosis. Few studies have examined transcellular transport across endothelial cells. We supposed that increased BBB permeability caused by FUS may affect transcytosis. We investigated drug delivery through transcytosis and paracellular transport to the brain after BBB modulation using FUS. Main methodsFUS and microbubbles were applied to the hippocampus of rats, and were euthanized at 1, 4, 24, and 48 h after sonication. To investigate paracellular transport, we analyzed TJPs, including zona occludens-1 (ZO-1) and occludin. We also investigated caveola-mediated transcytosis by analyzing caveola formation and major facilitator superfamily domain-containing 2a (Mfsd2a) levels, which inhibit caveola vesicle formation. Key findingsOne hour after FUS, ZO-1 and occludin expression was the lowest and gradually increased over time, returning to baseline 24 h after FUS treatment. Compared with that of TJPs, caveola formation started to increase 1 h after FUS treatment and peaked at 4 h after FUS treatment before returning to baseline by 48 h after FUS treatment. Decreased Mfsd2a levels were observed at 1 h and 4 h after FUS treatment, indicating increased caveola formation. SignificanceFUS induces BBB permeability changes and regulates both paracellular transport and caveola-mediated transcytosis. However, a time difference was observed between these two mechanisms. Hence, when delivering drugs into the brain after FUS, the optimal drug administration timing should be determined by the mechanism by which each drug passes through the BBB.

Advances in nanomedicines: a promising therapeutic strategy for ischemic cerebral stroke treatment.

Ischemic stroke, prevalent among the elderly, necessitates attention to reperfusion injury post treatment. Limited drug access to the brain, owing to the blood-brain barrier, restricts clinical applications. Identifying efficient drug carriers capable of penetrating this barrier is crucial. Blood-brain barrier transporters play a vital role in nutrient transport to the brain. Recently, nanoparticles emerged as drug carriers, enhancing drug permeability via surface-modified ligands. This article introduces the blood-brain barrier structure, elucidates reperfusion injury pathogenesis, compiles ischemic stroke treatment drugs, explores nanomaterials for drug encapsulation and emphasizes their advantages over conventional drugs. Utilizing nanoparticles as drug-delivery systems offers targeting and efficiency benefits absent in traditional drugs. The prospects for nanomedicine in stroke treatment are promising.

Silica Nanoparticles Decrease Glutamate Uptake in Blood–Brain Barrier Components

Glutamate is the major excitatory amino acid in the vertebrate brain, playing an important role in most brain functions. It exerts its activity through plasma membrane receptors and transporters, expressed both in neurons and glia cells. Overstimulation of neuronal glutamate receptors is linked to cell death in a process known as excitotoxicity, that is prevented by the efficient removal of the neurotransmitter through glutamate transporters enriched in the glia plasma membrane and in the components of the blood–brain barrier (BBB). Silica nanoparticles (SiO2-NPs) have been widely used in biomedical applications and directed to enter the circulatory system; however, little is known about the potential adverse effects of SiO2-NPs exposure on the BBB transport systems that support the critical isolation function between the central nervous system (CNS) and the peripheral circulation. In this contribution, we investigated the plausible SiO2-NPs-mediated disruption of the glutamate transport system expressed by BBB cell components. First, we evaluated the cytotoxic effect of SiO2-NPs on human brain endothelial (HBEC) and Uppsala 87 Malignant glioma (U-87MG) cell lines. Transport kinetics were evaluated, and the exposure effect of SiO2-NPs on glutamate transport activity was determined in both cell lines. Exposure of the cells to different SiO2-NP concentrations (0.4, 4.8, 10, and 20 µg/ml) and time periods (3 and 6 h) did not affect cell viability. We found that the radio-labeled D-aspartate ([3H]-D-Asp) uptake is mostly sodium-dependent, and downregulated by its own substrate (glutamate). Furthermore, SiO2-NPs exposure on endothelial and astrocytes decreases [3H]-D-Asp uptake in a dose-dependent manner. Interestingly, a decrease in the transporter catalytic efficiency, probably linked to a diminution in the affinity of the transporter, was detected upon SiO2-NPs. These results favor the notion that exposure to SiO2-NPs could disrupt BBB function and by these means shed some light into our understanding of the deleterious effects of air pollution on the CNS.

The proteome of the blood–brain barrier in rat and mouse: highly specific identification of proteins on the luminal surface of brain microvessels by in vivo glycocapture

BackgroundThe active transport of molecules into the brain from blood is regulated by receptors, transporters, and other cell surface proteins that are present on the luminal surface of endothelial cells at the blood–brain barrier (BBB). However, proteomic profiling of proteins present on the luminal endothelial cell surface of the BBB has proven challenging due to difficulty in labelling these proteins in a way that allows efficient purification of these relatively low abundance cell surface proteins.MethodsHere we describe a novel perfusion-based labelling workflow: in vivo glycocapture. This workflow relies on the oxidation of glycans present on the luminal vessel surface via perfusion of a mild oxidizing agent, followed by subsequent isolation of glycoproteins by covalent linkage of their oxidized glycans to hydrazide beads. Mass spectrometry-based identification of the isolated proteins enables high-confidence identification of endothelial cell surface proteins in rats and mice.ResultsUsing the developed workflow, 347 proteins were identified from the BBB in rat and 224 proteins in mouse, for a total of 395 proteins in both species combined. These proteins included many proteins with transporter activity (73 proteins), cell adhesion proteins (47 proteins), and transmembrane signal receptors (31 proteins). To identify proteins that are enriched in vessels relative to the entire brain, we established a vessel-enrichment score and showed that proteins with a high vessel-enrichment score are involved in vascular development functions, binding to integrins, and cell adhesion. Using publicly-available single-cell RNAseq data, we show that the proteins identified by in vivo glycocapture were more likely to be detected by scRNAseq in endothelial cells than in any other cell type. Furthermore, nearly 50% of the genes encoding cell-surface proteins that were detected by scRNAseq in endothelial cells were also identified by in vivo glycocapture.ConclusionsThe proteins identified by in vivo glycocapture in this work represent the most complete and specific profiling of proteins on the luminal BBB surface to date. The identified proteins reflect possible targets for the development of antibodies to improve the crossing of therapeutic proteins into the brain and will contribute to our further understanding of BBB transport mechanisms.

The Active Glucuronide Metabolite of the Brain Protectant IMM-H004 with Poor Blood-Brain Barrier Permeability Demonstrates a High Partition in the Rat Brain via Multiple Mechanisms.

Glucuronidation is an essential metabolic pathway for a variety of drugs. IMM-H004 is a novel neuroprotective agent against ischemic stroke, and its glucuronide metabolite IMM-H004G exhibits similar pharmacological activity. Despite possessing a higher molecular weight and polarity, brain exposure of IMM-H004G is much higher than that of IMM-H004. This study aimed to investigate the brain metabolism and transport mechanisms of IMM-H004 and IMM-H004G. First, the possibility of IMM-H004 glucuronidation in the brain was evaluated in several human brain cell lines and rat homogenate. Subsequently, the blood-brain barrier carrier-mediated transport mechanism of IMM-H004 and IMM-H004G was studied using overexpression cell models. In addition, intracerebroventricular injection, in situ brain perfusion model, and microdialysis/microinjection techniques were performed to study the distribution profiles of IMM-H004 and IMM-H004G. IMM-H004 could be metabolized to IMM-H004G in both rat brain and HEB cells mediated by UGT1A7. However, IMM-H004G could not be hydrolyzed back into IMM-H004. Furthermore, the entry and efflux of IMM-H004 in the brain were mediated by the pyrilamine-sensitive H+/OC antiporter and P-gp, respectively, while the transport of IMM-H004G from the blood to the brain was facilitated by OATP1A2 and OATP2B1. Ultimately, stronger concentration gradients and OATP-mediated uptake played a critical role in promoting greater brain exposure of IMM-H004G. The active glucuronide metabolite of the brain protectant IMM-H004 with poor blood-brain barrier permeability demonstrates a high partition in the rat brain via multiple mechanisms, and our findings deepen the understanding of the mechanisms underlying the blood-brain barrier metabolism and transport of active glucuronide conjugates.