Claudin-5: gatekeeper of neurological function

The canine blood-brain barrier in health and disease: focus on brain protection

This review examines the role of the canine blood-brain barrier (BBB) in health and disease, focusing on the impact of the multidrug resistance (MDR) transporter P-glycoprotein (P-gp) encoded by the ABCB1/MDR1 gene. The BBB is critical in maintaining central nervous system homeostasis and brain protection against xenobiotics and environmental drugs that may be circulating in the blood stream. We revise key anatomical, histological and functional aspects of the canine BBB and examine the role of the ABCB1/MDR1 gene mutation in specific dog breeds that exhibit reduced P-gp activity and disrupted drug brain pharmacokinetics. The review also covers factors that may disrupt the canine BBB, including the actions of aging, canine cognitive dysfunction, epilepsy, inflammation, infection, traumatic brain injury, among others. We highlight the critical importance of this barrier in maintaining central nervous system homeostasis and protecting against xenobiotics and conclude that a number of neurological-related diseases may increase vulnerability of the BBB in the canine species and discuss its profound impacts on canine health.

Insights into 2D and 3D cell culture models for nanoparticle-based drug delivery to glioblastoma

Glioblastoma (GBM) remains a formidable challenge due to its aggressive nature, protected location within the brain, and resistance to conventional treatments. Its complex tumor microenvironment (TME), coupled with the blood-brain barrier (BBB), hinders drug delivery leading to poor treatment outcomes. Nanoparticles (NPs) offer a promising solution, as they can improve the pharmacokinetic properties of anticancer agents. By functionalizing NPs with targeting molecules, researchers aim to enhance drug concentration in the brain. However, developing effective NP-based therapies requires robust in vitro models that accurately capture the complexities of GBM. Two-dimensional (2D) and three-dimensional (3D) cell culture models provide a versatile platform for studying NP-cell interactions. By customizing cell types, incorporating TME components, and adjusting flow conditions, researchers can tailor these models to specific research questions. While 2D models offer a simpler starting point, 3D models, such as multicellular spheroids and organoids, can more accurately replicate the complex TME, including the BBB and tumor heterogeneity. These models enable a more comprehensive evaluation of NP efficacy and safety, ultimately accelerating drug development and reducing reliance on animal testing.

Restoration of blood brain barrier integrity post neurosurgical resection in drug resistant epilepsy

Surgery for temporal lobe epilepsy (TLE) is a well-recognised therapy for drug resistant seizures which occur in more than 50 % of patients with TLE. Blood-brain barrier (BBB) dysfunction is commonly observed in resected brain tissue from patients with treatment resistant epilepsy however, no studies have documented the recovery of BBB function following surgery. We firstly prospectively performed dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on seven patients scheduled for temporal lobe resections before and after resection. DCE-MRI revealed BBB dysfunction in frontal and temporal brain regions. At 6-24 months post-resection, there was a reduction in the percentage of brain volume with BBB dysfunction in 5/7 patients. We then retrospectively characterised resected brain tissue from 6 further TLE cases (total n = 13) by q-RT-PCR and immunohistochemistry which revealed region-specific changes in markers of BBB integrity and inflammation with changes in CLDN12 and TJP1/2 in the hippocampus and CSF1R pathway genes in cortical and hippocampal tissue. BBB dysfunction is a key component of the molecular disruption caused by seizures and in longstanding early onset chronic epilepsy that is refractory to treatment. Here, we demonstrate for the first time the rescue of BBB dysfunction by controlling seizures after surgery.

Liposomes as versatile agents for the management of traumatic and nontraumatic central nervous system disorders: drug stability, targeting efficiency, and safety

Various nanoparticle-based drug delivery systems for the treatment of neurological disorders have been widely studied. However, their inability to cross the blood-brain barrier hampers the clinical translation of these therapeutic strategies. Liposomes are nanoparticles composed of lipid bilayers, which can effectively encapsulate drugs and improve drug delivery across the blood-brain barrier and into brain tissue through their targeting and permeability. Therefore, they can potentially treat traumatic and nontraumatic central nervous system diseases. In this review, we outlined the common properties and preparation methods of liposomes, including thin-film hydration, reverse-phase evaporation, solvent injection techniques, detergent removal methods, and microfluidics techniques. Afterwards, we comprehensively discussed the current applications of liposomes in central nervous system diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, traumatic brain injury, spinal cord injury, and brain tumors. Most studies related to liposomes are still in the laboratory stage and have not yet entered clinical trials. Additionally, their application as drug delivery systems in clinical practice faces challenges such as drug stability, targeting efficiency, and safety. Therefore, we proposed development strategies related to liposomes to further promote their development in neurological disease research.

Blood-Brain and Blood-Gill Barrier Disruption in Coho Salmon Exposed to Roadway Runoff and 6PPD-Quinone

The tire-derived chemical N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone) causes acute mortality in coho salmon (Oncorhynchus kisutch), yet its mechanisms of toxicity remain poorly understood. We exposed juvenile coho salmon to roadway runoff or 6PPD-quinone to investigate whether disruption of the blood-brain barrier (BBB) and blood-gill barrier cause behavioral symptoms of urban runoff mortality syndrome in this sensitive species. BBB disruption was present in one-third of presymptomatic fish and in all symptomatic individuals, supporting its role in toxicity. Co-occurring brain and gill barrier disruptions at the onset of sustained surface swimming suggest a systemic vascular response rather than localized brain injury. Histological analysis of coho brains revealed red blood cell congestion within intact endothelia, consistent with circulatory collapse and plasma leakage, likely impairing oxygen delivery and disrupting neuronal signaling. Behavioral symptoms also coincided with altered expression of BBB junctional proteins genes (ocln, cld5α, and vecad). In Chinook salmon (Oncorhynchus tshawytscha), exposure to a high but environmentally relevant concentration of 6PPD-quinone reduced expression of the scaffolding protein zo-1, suggesting potential sublethal effects. These findings identify BBB disruption as a key event in 6PPD-quinone toxicity and link vascular injury to behavioral symptoms in coho salmon. Ongoing work in this model will further clarify mechanisms of action and support assessments of environmental and human health risks from tire-derived chemicals.

Aged human serum induces vascular changes in an isogenic co-culture venule model

Vascular aging and dysfunction are significant contributors to age-related cardiovascular and neurodegenerative diseases. In particular, aging impacts small vessels, damaging vascular integrity leading to leakage events and inflammation, which can be further exacerbated by environmental factors. Here, we generate and evaluate an isogenic endothelial cell and pericyte venule-like co-culture model of microvasculature under perfusion with male aged human serum over 4 days. Using this model in comparison to male young human serum perfusion controls, we define the molecular and functional changes induced by aging-related circulatory cues, including functional loss of paracellular barrier integrity and modulation of transport of low-density lipoprotein. Additionally, in comparison with endothelial monoculture, we identify critical changes to basement membrane composition and aged-serum-mediated cell cycle shifts with pericyte co-culture. This modular approach reveals key impacts to further our understanding of vascular aging and to leverage in designing therapeutic and preventative approaches.

Multiple sclerosis: etiology in the context of neurovascular unit and immune system involvement and advancements with in vitro blood-brain barrier models

Multiple sclerosis affects a significant portion of the world's adult population and is the most common nontraumatic neuroimmunology disorder. Although the specific etiology of multiple sclerosis remains unknown, it has been associated with autoimmune components. While current treatment options relieve some symptoms in MS patients, most are immunosuppressive and only delay the progression of the disease without conferring definitive curative measures. Hence, a thorough understanding of disease pathobiology, the contribution of the neurovascular unit (NVU), and biological body-on-a-chip systems that replicate the blood-brain barrier may open new horizons for the discovery of potential therapeutics for MS.

Biophysical basis of tight junction barrier modulation by a pan-claudin-binding molecule

Claudins are a 27-member family of membrane proteins that form and fortify specialized cell contacts in endothelium and epithelium called tight junctions. Tight junctions restrict paracellular transport through tissues by forming molecular barriers between cells. Claudin-binding molecules thus hold promise for modulating tight junction permeability to deliver drugs or as therapeutics to treat tight junction-linked disease. The development of claudin-binding molecules, however, is hindered by their physicochemical intractability and small targetable surfaces. Here, we determine that a synthetic antibody fragment (sFab) that we developed binds with nanomolar affinity directly to 10 claudin subtypes and other distantly related claudin family members but not to other tight junction-localized membrane proteins. It does so by targeting the extracellular surfaces of claudins, which we verify by applying this sFab to a model intestinal epithelium and observe that it opens paracellular barriers comparable to a known, but application limited, tight junction modulating protein. This pan-claudin-binding molecule holds potential for both basic and translational applications as it is a probe of claudin and tight junction structure in vitro and in vivo and a tool to modulate the permeability of tight junctions broadly across tissue barriers.

The Role of TDP-43 in SARS-CoV-2-Related Neurodegenerative Changes

The coronavirus disease 2019 (COVID-19) pandemic has been linked to long-term neurological effects with multifaceted complications of neurodegenerative diseases. Several studies have found that pathological changes in transactive response DNA-binding protein of 43 kDa (TDP-43) are involved in these cases. This review explores the causal interactions between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and TDP-43 from multiple perspectives. Some viral proteins of SARS-CoV-2 have been shown to induce pathological changes in TDP-43 through its cleavage, aggregation, and mislocalization. SARS-CoV-2 infection can cause liquid-liquid phase separation and stress granule formation, which accelerate the condensation of TDP-43, resulting in host RNA metabolism disruption. TDP-43 has been proposed to interact with SARS-CoV-2 RNA, though its role in viral replication remains to be fully elucidated. This interaction potentially facilitates viral replication, while viral-induced oxidative stress and protease activity accelerate TDP-43 pathology. Evidence from both clinical and experimental studies indicates that SARS-CoV-2 infection may contribute to long-term neurological sequelae, including amyotrophic lateral sclerosis-like and frontotemporal dementia-like features, as well as increased phosphorylated TDP-43 deposition in the central nervous system. Biomarker studies further support the link between TDP-43 dysregulation and neurological complications of long-term effects of COVID-19 (long COVID). In this review, we presented a novel integrative framework of TDP-43 pathology, bridging a gap between SARS-CoV-2 infection and mechanisms of neurodegeneration. These findings underscore the need for further research to clarify the TDP-43-related neurodegeneration underlying SARS-CoV-2 infection and to develop therapeutic strategies aimed at mitigating long-term neurological effects in patients with long COVID.

Nicotinamide derivatives protect the blood-brain barrier against oxidative stress

Nicotinamides play a crucial role in energy metabolism and maintenance of the redox homeostasis counteracting oxidative stress and elevated reactive oxidative species (ROS) in human cells. The levels of nicotinamides decline with age and are associated with various pathologies, including ones linked with the blood-brain barrier disorder. Therefore, the investigation of the bioactivity of synthetic nicotinamide derivates (NAs) and evaluation of their potential to protect the blood-brain barrier (BBB) from oxidative stress is emerging as an important new strategy. In the current study, we tested different NAs as potential exogenous substitutes for such biological processes. All tested derivatives were non-toxic and attenuated elevation of ROS production in brain endothelial cells induced by tert-butyl hydroperoxide (tBHP), but one specifically was protective on the cell-cultured model of the BBB. The most promising NA was a derivative containing methoxy moiety (NA-4OCH3), which not only increased cell impedance, but had a protective effect on brain endothelial cells barrier against tBHP-induced oxidative stress on several levels: reducing the ROS level and restoring the activity of glutathione, mitochondrial membrane potential, superoxide dismutase enzymes activity to the basal level. In addition, NA-4OCH3 increased the integrity of both human and rat cell-based BBB model after tBHP-treatment seen by the elevated transendothelial electrical resistance, tight junction protein claudin-5 level as well as the decreased permeability of markers across the barrier. This study highlights novel approach to protect the BBB from oxidative stress-induced dysfunction, positioning NA-4OCH3 as potential neuroprotective agent for ROS-mediated disease interventions, with implications for neurodegeneration and BBB.

Blood-Brain Barrier (BBB) Dysfunction in CNS Diseases: Paying Attention to Pericytes

BACKGROUND

Dysfunction of the blood-brain barrier (BBB) is an important pathological mechanism in central nervous system (CNS) diseases and can trigger a series of pathological reactions, such as neuroinflammatory responses, oxidative stress, immune infiltration, etc., thereby worsening brain damage. However, pericytes are often overlooked by researchers, and no review research has yet summarized the mechanism by which pericytes contribute to BBB dysfunction in CNS diseases.

RESULTS

Therefore, this review explores the pathophysiology of BBB dysfunction in CNS diseases and provides a detailed account of the biological characteristics of pericytes, especially the controversy over their biomarkers. Subsequently, we review the role of pericytes in CNS diseases such as Alzheimer's disease, vascular dementia, multiple sclerosis, ischemic stroke, and hemorrhagic stroke, with a particular focus on the role of pericytes in BBB dysfunction. In addition, we also discuss treatments based on pericytes, such as regenerative medicine that induces pericyte differentiation and Pericyte-Extracellular Vesicles.

CONCLUSIONS

This review aims to provide a more comprehensive understanding and guidance on the role of pericytes in BBB dysfunction in CNS diseases and serve clinical treatment.

Biomarkers in Aneurysmatic and Spontaneous Subarachnoid Haemorrhage: A Clinical Prospective Multicentre Biomarker Panel Study of S100B, Claudin-5, Interleukin-10, TREM-1, TREM-2 and Neurofilament Light Chain As Well As Immunoglobulin G and M

Following aneurysmatic subarachnoid haemorrhage (SAH), complex pathophysiological processes take place which result in ischaemia, dysfunction of the blood-brain barrier and the clinical development of vasospasms and delayed cerebral ischaemia (DCI). The aim of this study was to present a biomarker panel that can be used for temporal assignment in the pathophysiological process after haemorrhage, a prediction of vasospasm, DCI or outcome. In a prospective multicentre approach, complex laboratory chemistry tests were used to determine the value of the biomarkers S100B, Claudin-5, Interleukin (IL) -10, Triggering receptor expresses on myeloid cells (TREM)-1 and TREM-2, and neurofilament light chain (NfL) as well as IgG and IgM in plasma and Cerebro-spinal-fluid (CSF) in SAH patients. The predictive power of mentioned biomarkers with regard to the occurrence of vasospasms, DCI and the outcome (Glasgow Outcome Scale) were defined by using sophisticated statistical methods with the level of significance at p ≤ 0.05. Mean age of the 12 patients included was 56 (SD:14) years with 67% female patients and that of the 11 control subjects was 74 (SD:3) years with 55% female subjects. S100B showed higher concentrations compared to the control patients on the first four days (p ≤ 0.0141). For IL-10, the CSF concentrations showed a continuous increase: day 2 (p = 0.0074), day 4 (p = 0.0012), and day 5 (p < 0.0001). Regarding the TREM1 and TREM2 balance, CSF concentrations of TREM1 increased until day eight (p ≤ 0.0055). TREM-2 plasma concentrations decreased below the levels of control patients and appeared unchanged for the further course. The greatest difference in the CSF concentration of NfL between the patients and the control group was seen on day 8 (p = 0.0104). The differentiation between patients with and without DCI showed different concentration curves of the TREM1 CSF-plasma index with increasing concentrations for patients with DCI. The TREM 2 CSF-plasma index showed higher concentrations for patients with DCI. Patients without DCI showed a decreasing concentration of the NfL CSF-plasma index compared to an increase when vasospasm was detected. NfL, TREM-1 and TREM-2 have the potential to be relevant biomarkers for SAH in the intermediate and delayed injury phase.

Brain microvascular endothelial cells differentiated from a Friedreich's Ataxia patient iPSC are deficient in tight junction protein expression and paracellularly permeable

Friedreich's Ataxia (FA) is a rare, inherited ataxia resulting from GAA triplet expansions in the first intron of the Frataxin (FXN) gene, which encodes a mitochondrial protein involved in the incorporation of iron into iron-sulfur clusters. We previously identified decreased levels of F-actin and tight junction (TJ) proteins, which coincided with paracellular permeability in an FXN shRNA-mediated knockdown immortalized human brain microvascular endothelial cell (BMVEC) model. This premise is underexplored in the FA literature, prompting us to confirm these findings using a patient-derived iPSC model. One line each of FA patient iPSCs and age- and sex-matched apparently healthy iPSCs were differentiated into BMVEC-like cells. We quantified actin glutathionylation, F-actin abundance, TJ expression and organization, and barrier integrity. In the absence of dysregulated F-actin organization, FA iBMVEC exhibited a loss of 50% ZO-1, 63% Occludin, and 19% Claudin-5 protein expression, along with a disruption in the bi-cellular organization of the latter two proteins. Functionally, this correlated with barrier hyperpermeability, delayed barrier maturation, and increased flux of the fluorescent tracer Lucifer Yellow. These data indicate that decreased barrier integrity is a pathophysiological phenotype of FA brain microvascular endothelial cells. Clinically, this may represent a targetable pathway to reduce brain iron accumulation, neuroinflammation, and neurodegeneration profiles in FA. Additionally, an investigation into other barrier systems, such as the blood-nerve barrier, blood-CSF barrier, or cardiac vasculature, may provide insights into the extra-neural symptoms experienced by FA patients.

Review: The potential role of placental extracellular vesicles in blood-brain barrier disruption and neuroinflammation in preeclampsia

Preeclampsia is a complex pregnancy disorder characterized by hypertension and multisystem organ damage, notably affecting the liver, kidneys, and brain. Eclampsia, a severe form of preeclampsia, is marked by the sudden onset of generalized tonic-clonic seizures. Brain complications, including eclampsia, are responsible for 60-70 % of preeclampsia-related maternal deaths, particularly in low-income regions. Despite the significant impact of brain complications in preeclampsia, their underlying pathophysiology remains unclear. Evidence suggests that brain edema in preeclampsia and eclampsia results from disruption of the blood-brain barrier (BBB). Although direct analysis of the BBB is challenging, in vitro studies indicate that plasma from women with preeclampsia can compromise the BBB, with the specific circulating factors involved still unidentified. Among the potential culprits, recent findings highlight placental-derived small extracellular vesicles (PDsEVs) as key players in BBB disruption observed in preeclampsia. This review examines the role of PDsEVs in the pathophysiology of brain edema associated with preeclampsia, emphasizing areas for future research, including neuroinflammation and neuron dysfunction. Additionally, we discuss the protective role of magnesium sulfate in these processes.

Breaking the Barrier: The Role of Proinflammatory Cytokines in BBB Dysfunction

The BBB is created by a special system of brain microvascular endothelial cells (BMECs), pericytes (PCs), the capillary basement membrane, and the terminal branches ("end-feet") of astrocytes (ACs). The key function of the BBB is to protect the central nervous system (CNS) from potentially harmful/toxic substances in the bloodstream by selectively controlling the entry of cells and molecules, including nutrients and components of the immune system. The loss of BBB integrity in response to neuroinflammation, as manifested by an increase in permeability, depends predominantly on the activity of proinflammatory cytokines. However, the pathomechanism of structural and functional changes in the BBB under the influence of individual cytokines is still poorly understood. This review summarizes the current state of knowledge on this topic, which is important from both pathophysiological and therapeutic points of view. The structures and functions of all components of the BBB are reviewed, with emphasis given to differences between this and other locations of the circulatory system. The protein composition of the interendothelial tight junctions in the context of regulating BBB permeability is presented, as is the role of pericyte-BMEC interactions in the exchange of metabolites, ions, and nucleic acids. Finally, the documented actions of proinflammatory cytokines within the BBB are discussed.

Modulation of brain immune microenvironment and cellular dynamics in systemic inflammation

Background: Sepsis-associated encephalopathy (SAE) is a severe complication of sepsis, affecting approximately 70% of patients, leading to increased mortality and long-term cognitive impairments among survivors. However, there is a lack of comprehensive studies on the development of SAE, especially related to the cellular communication networks in the brain microenvironment. Methods: We evaluated the impact of myeloid cells on the brain's immune microenvironment through glial cell alterations using bulk and single-cell transcriptomics data from human and mouse models and validated this with correlative experiments. We also developed the DeconvCellLink R package to study neuroinflammation-associated cellular interaction networks. A dynamic brain immune microenvironment map showing temporal alterations in brain cellular network during systemic inflammatory reactions was constructed using time-series data. Results: While brain cellular alterations differed between human and animal models, a highly conserved set of sepsis-associated genes regulating immune microenvironment signalling was identified. The dynamic alterations in cellular interaction networks and cytokines revealed brain immune cells' temporal response to systemic inflammation. We also found that valproic acid could mitigate sepsis-induced neuroinflammation by regulating glial cell balance and modulating the neuroimmune microenvironment. Conclusion: Through dynamic cellular communication networks, the study revealed that, immune dysregulation in the inflamed brain in SAE involves overactivation of innate immunity, with neutrophils playing a crucial role, providing a scientific framework for developing novel therapeutic strategies and offering new insights into the mechanisms underlying sepsis-induced brain dysfunction.

Alpha‑Asarone Ameliorates Neuronal Injury After Ischemic Stroke and Hemorrhagic Transformation by Attenuating Blood-Brain Barrier Destruction, Promoting Neurogenesis, and Inhibiting Neuroinflammation

Recombinant tissue-type plasminogen activator (rt-PA), the primary drug for acute ischemic stroke (IS), has a narrow therapeutic window and carries a potential risk of hemorrhagic transformation (HT). Without rt-PA administration, patients may suffer permanent cerebral ischemia. Alpha-asarone (ASA), a natural compound derived from Acorus tatarinowii Schott, exhibits diverse neuropharmacological effects. This study aims to investigate whether ASA could improve outcomes in IS and be used to mitigate HT induced by rt-PA. We employed models of permanent middle cerebral artery occlusion (pMCAO) and photothrombotic cortical injury (PCI) to investigate both the therapeutic efficacy and underlying mechanisms of ASA during the acute and recovery periods following IS, respectively. Additionally, Sprague-Dawley rats were subjected to rt-PA treatment at 6-h post-PCI to mimic HT (rt-PA-HT). Our results revealed three key findings: (1) ASA demonstrated therapeutic effects in the acute phase of pMCAO rats by alleviating blood-brain barrier damage through inhibition of glial cell-mediated neuroinflammation; (2) administration of ASA 24 h after stroke ameliorated the neurological damage during the recovery phase in PCI mice by promoting neurogenesis via activation of the BDNF/ERK/CREB signaling pathway; (3) ASA attenuated rt-PA-HT injury by modulating the NLRP3/Caspase1/IL-1β and IL-18 pathways. Overall, our findings suggest that ASA mitigates neuronal injury following IS and HT, positioning it as a promising candidate for treating these conditions.

Exercise Training Alters the Hippocampal Expression of Blood-Brain Barrier Components and Behavior of Western Diet-Fed Female Rats

Overeating highly palatable foods typical of a Western diet (WD) has been linked to cognitive impairments in animal models and humans. Exercise training was proposed as an important behavioral intervention with beneficial effects, including improving peripheral insulin sensitivity, improving central functions such as learning and memory, and restoring a dysregulated blood-brain barrier (BBB). The purpose of the present study was to characterize the effect of exercise training in rats fed with the WD with special emphasis on BBB. Adult female Long Evans rats were subjected to 12 weeks of WD feeding (WD group), or simultaneous WD feeding and wheel-running training (WD/EX group), or were fed a WD for 6 weeks without training and then subjected to diet and training for an additional 6 weeks (WD_WD/EX group). A sedentary (untrained) group of lean rats was fed a standard rodent chow (CTR group). In all experimental groups, we measured behavioral and physiological parameters, and the hippocampal levels of proteins structurally and functionally related to BBB, including proinflammatory cytokines and products of elevated lipid peroxidation. Exercise training in combination with a WD decreased locomotor and exploratory activities and induced short-term memory impairments. The behavioral changes were accompanied by reduced levels of occludin, claudin-5, and ZO-1 proteins in the hippocampus, suggesting changes in the integrity and increased permeability of BBB. In the WD_WD/EX rats, we found increased hippocampal levels of malondialdehyde (MDA) and neurotrophins (Bdnf, Vegfa) suggesting that increased energy expenditure by obese rats stimulates endogenous protective processes. The training introduced after 6 weeks of WD feeding in rats showing an obese phenotype may suggest that the sequence and moment of presumably protective intervention (exercise training) could alleviate or, on the contrary, exacerbate the level of stress and its consequences.

Dimethyloxalylglycine improves functional recovery through inhibiting cell apoptosis and enhancing blood-spinal cord barrier repair after spinal cord injury

PURPOSE

The secondary damage of spinal cord injury (SCI) starts from the collapse of the blood spinal cord barrier (BSCB) to chronic and devastating neurological deficits. Thereby, the retention of the integrity and permeability of BSCB is well-recognized as one of the major therapies to promote functional recovery after SCI. Previous studies have demonstrated activation of hypoxia inducible factor-1α (HIF-1α) provides anti-apoptosis and neuroprotection in SCI. Endogenous HIF-1α, rapidly degraded by prolylhydroxylase, is insufficient for promoting functional recovery. Dimethyloxalylglycine (DMOG), a highly selective inhibitor of prolylhydroxylase, has been reported to have a positive effect on axon regeneration. However, the roles and underlying mechanisms of DMOG in BSCB restoration remain unclear. Herein, we aim to investigate pathological changes of BSCB restoration in rats with SCI treated by DOMG and evaluate the therapeutic effects of DMOG.

METHODS

The work was performed from 2022 to 2023. In this study, Allen's impact model and human umbilical vein endothelial cells were employed to explore the mechanism of DMOG. In the phenotypic validation experiment, the rats were randomly divided into 3 groups: sham group, SCI group, and SCI + DMOG group (10 rats for each). Histological analysis via Nissl staining, Basso-Beattie-Bresnahan scale, and footprint analysis was to evaluate the functional recovery after SCI. Western blotting, TUNEL assay, and immunofluorescence staining were employed to exhibit levels of tight junction and adhesion junction of BSCB, HIF-1α, cell apoptosis, and endoplasmic reticulum (ER) stress. The one-way ANOVA test was used for statistical analysis. The difference was considered statistically significant at p < 0.05.

RESULTS

In this study, we observed the expression of HIF-1α reduced in the SCI model. DMOG treatment remarkably augmented HIF-1α level, alleviated endothelial cells apoptosis and disruption of BSCB, and enhanced functional recovery post-SCI. Besides, the administration of DMOG offset the activation of ER stress induced by SCI, but this phenomenon was blocked by tunicamycin (an ER stress activator). Finally, we disclosed that DMOG maintained the integrity and permeability of BSCB by inhibiting ER stress, and inhibition of HIF-1α erased the protection from DMOG.

CONCLUSIONS

Our findings illustrate that the administration of DMOG alleviates the devastation of BSCB and HIF-1α-induced inhibition of ER stress.

Oroxylin A Attenuates Homocysteine-Induced Blood-Brain Barrier (BBB) Dysfunction by Reducing Endothelial Permeability and Activating the CREB/Claudin-5 Signaling Pathway

Recent reports have indicated that elevated levels of homocysteine (Hcy) are closely linked to blood-brain barrier (BBB) dysfunction in neurological disorders. Oroxylin A (OA) is a key bioactive flavonoid that has been reported to regulate brain functions. However, the role of OA in Hcy-related BBB dysfunction is less reported. In this study, we aimed to elucidate the role and molecular mechanism of OA in Hcy-mediated BBB dysfunction using both in vivo and in vitro investigations. Our findings indicate that the expression of the tight junction (TJ) protein Claudin-5 declined, and the diffusion of sodium fluorescein elevated in brains of Hcy-challenged mice. These effects were notably rescued by administration of OA. In Hcy-challenged bEnd.3 brain microvascular endothelial cells, increased endothelial permeability, reduced trans-endothelial electrical resistance (TEER), and downregulated Claudin-5 were observed. These effects were significantly reversed by 25 and 50 μM OA. Interestingly, OA treatment restored the dephosphorylation of CREB at Ser133 induced by Hcy. However, the addition of the protein kinase A/cAMP-response element binding protein (PKA/CREB) inhibitor H89 counteracted the protective effects of OA on inhibiting endothelial permeability and promoting Claudin-5 expression. Together, we demonstrate that OA protects against Hcy-induced BBB dysfunction by maintaining the integrity of endothelial barriers. This protective effect is achieved through the activation of the CREB/Claudin-5 signaling pathway, highlighting the potential therapeutic value of OA in addressing BBB-related neurological disorders.

Endothelial cells as key players in cerebral small vessel disease

Cerebral small vessel disease (SVD) is a vascular disorder that increases the risk of stroke and dementia and is diagnosed through brain MRI. Current primary prevention and secondary treatment of SVD are focused on lifestyle interventions and vascular risk factor control, including blood pressure reduction. However, these interventions have limited effects, a proportion of individuals with sporadic SVD do not have hypertension, and SVD shows strong familial and genetic underpinnings. Here, we describe the increasing evidence that cerebral endothelial cell dysfunction is a key mechanism of SVD. Dysfunctional endothelial cells can cause cerebral blood vessel dysfunction, alter blood-brain barrier integrity and interfere with cell-cell interactions in the neuro-glial-vascular unit, thereby causing damage to adjacent brain tissue. Endothelial cells in SVD may become dysfunctional through intrinsic mechanisms via genetic vulnerability to SVD and/or via extrinsic factors such as hypertension, smoking and diabetes. Drugs that act on endothelial pathways are already looking promising in clinical trials, and understanding their action on endothelial cells and the surrounding brain may lead to the development of other therapies to limit disease progression and improve outcomes for individuals with SVD.

Claudin-1 impairs blood-brain barrier by downregulating endothelial junctional proteins in traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of death and disability in patients. Brain microvasculature endothelial cells form the blood-brain barrier (BBB) which functions to maintain a protective barrier for the brain from the passive entry of systemic solutes. As a result of the cellular disruption caused by TBI, the BBB is compromised. Tight junction disruption in the endothelium of the BBB has been implicated in this response, but the underlying mechanisms remain unresolved. We utilized various in vivo models of severe to mild TBI as well as in vitro exposure of brain endothelial cells (bEND.3) to analyze conditions encountered following TBI to gain mechanistic insight into alterations observed at the BBB. We found that claudin-1 (CLDN1), was significantly increased in the brain endothelium both in vivo and in vitro. The observed increase of CLDN1 expression correlated with down-regulation of claudin-5 (CLDN5), occludin (OCLN), and zonula occludens (ZO-1), thereby altering BBB integrity by decreasing TEER and increasing permeability. Knockdown of CLDN1 in these pathogenic conditions showed stability of the endothelial junctional proteins. A decline in the epigenetic regulator silent information regulator family protein 1 (SIRT1), a member of the NAD+ dependent protein deacetylases, coincided with this upregulation of CLDN1. Indeed, the quenching of oxidative stress through NAC treatment was able to reduce injury-induced upregulation of CLDN1 in vitro. Mechanistically, an SRC-dependent tyrosine phosphorylation of OCLN and ZO-1 in CLDN1-modulated conditions was observed. Our findings will provide new insights into BBB deregulation and new possible treatment opportunities for TBI.

Tissue origin of endothelial cells determines immune system modulation and regulation of HIF-1α-, TGF-β-, and VEGF signaling

Tight junctions of vascular endothelial cells in the central nervous system form the blood-brain and inner blood-retinal barriers, the integrity of which are further influenced by neighboring cells such as pericytes, astrocytes/Müller glial processes, and immune cells. In addition, the retina is shielded from the fenestrated endothelium of the choriocapillaris by the epithelial barrier of the retinal pigment epithelium. Dysfunction of the blood retinal barriers and/or proliferation of retinal and choroidal endothelial cells are caused by late stages of diabetic retinopathy (DR) and neovascular age-related macular degeneration (nAMD), the main causes of blindness in western countries. To elucidate endothelial-derived pathomechanisms in DR and nAMD, we established immortalized mouse cell lines of retinal and choroidal endothelial cells and immortalized brain endothelial cells as CNS-derived controls. We then used immunofluorescence staining, state-of-the-art long-range RNA sequencing and monolayer permeability assays to compare the functional state of these cells depending on their tissue origin. We furthermore demonstrate that activation of the wingless-type MMTV integration site (Wnt)/β-catenin signaling pathway restored blood brain/retinal barrier properties in brain and retinal endothelial cells, but unexpectedly increased permeability of choroidal endothelial cells. Transcriptome profiling showed that depending on the tissue origin of endothelial cells, regulation of the immune system was altered and pathways such as hypoxia-inducible factor (HIF)-1/2α, transforming growth factor (TGF)-β, and vascular endothelial growth factor (VEGF) were differentially regulated, strongly indicating their contribution in the molecular pathogenesis of DR and nAMD. These findings significantly increase the understanding of the vascular biology of endothelial cells, highlighting the fact that depending on their tissue origin, their contribution to vascular pathologies varies.

Glioblastoma induced blood-brain barrier dysfunction via a paracrine mechanism that increases claudin-1 expression

Blood-brain barrier (BBB) disruption is a well-known phenomenon in glioblastoma (GBM). However, the mechanism driving BBB dysfunction in previously established vasculature at the invasive edge of GBM is still unknown. In this study, we aimed to determine if GBM paracrine signaling is sufficient to induce BBB dysfunction and identify changes in the tight junctions of the BBB. An in vivo U-87 MG xenograft model and an in vitro primary brain endothelial cell BBB model were established for barrier dysfunction monitoring. Immunofluorescent staining revealed significantly higher claudin-1 expression and significantly lower claudin-5 expression in the tumor vs. normal brain tissue of our in vivo model (p < 0.01). Additionally, claudin-1 expression co-localized with brain cell type markers for endothelium, pericytes, and microglia. In vitro exposure of brain microvascular endothelial cells to GBM conditioned media resulted in a significant decrease in transendothelial electrical resistance as well as delocalization of claudin-5 from the tight junctions. These results suggest GBM cells secrete factors capable of inducing changes in the tight junction proteins of the BBB and decreasing barrier integrity. Future studies will aim to identify the mechanism in which these changes occur.

Innate immune sensors and regulators at the blood brain barrier: focus on toll-like receptors and inflammasomes as mediators of neuro-immune crosstalk and inflammation

Cerebral endothelial cells (CEC) that form the brain capillaries are the principal constituents of the blood brain barrier (BBB), the main active interface between the blood and the brain which plays a protective role by restricting the infiltration of pathogens, harmful substances and immune cells into the brain while allowing the entry of essential nutrients. Aberrant CEC function often leads to increased permeability of the BBB altering the bidirectional communication between the brain and the bloodstream and facilitating the extravasation of immune cells into the brain. In addition to their role as essential gatekeepers of the BBB, CEC exhibit immune cell properties as they can receive and transmit signals between the blood and the brain partly via release of inflammatory effectors in pathological conditions. Cerebral endothelial cells express innate immune receptors, including toll like receptors (TLRs) and inflammasomes which are the first sensors of exogenous or endogenous dangers and initiators of immune and inflammatory responses which drive neural dysfunction and degeneration. Accumulating evidence indicates that activation of TLRs and inflammasomes in CEC compromises BBB integrity, promotes aberrant neuroimmune interactions and modulates both systemic and neuroinflammation, common pathological features of neurodegenerative and psychiatric diseases and central nervous system (CNS) infections and injuries. The goal of the present review is to provide an overview of the pivotal roles played by TLRs and inflammasomes in CEC function and discuss the molecular and cellular mechanisms by which they contribute to BBB disruption and neuroinflammation especially in the context of traumatic and ischemic brain injuries and brain infections. We will especially focus on the most recent advances and literature reports in the field to highlight the knowledge gaps. We will discuss future research directions that can advance our understanding of the central contribution of innate immune receptors to CEC and BBB dysfunction and the potential of innate immune receptors at the BBB as promising therapeutic targets in a wide variety of pathological conditions of the brain.

Progression of experimental autoimmune encephalomyelitis in mice and neutrophil-mediated blood-brain barrier dysfunction requires non-muscle myosin light chain kinase

Blood-brain barrier (BBB) dysfunction occurs in numerous central nervous system disorders. Unfortunately, a limited understanding of the mechanisms governing barrier function hinders the identification and assessment of BBB-targeted therapies. Previously, we found that non-muscle myosin light chain kinase (nmMLCK) negatively regulates the tight junction protein claudin-5 in brain microvascular endothelial cells (BMVECs) under inflammatory conditions. Here, we used complementary animal and primary cell co-culture models to further investigate nmMLCK and claudin-5 during neuroinflammation. We found that nmMLCK-knockout mice resisted experimental autoimmune encephalomyelitis (EAE), including paralysis, demyelination, neutrophil infiltration, and BBB dysfunction. However, transiently silencing claudin-5 culminated in a fulminant disease course. In parallel, we found that neutrophil-secreted factors triggered a biphasic loss in the barrier quality of wild-type BMVEC monolayers, plus pronounced neutrophil migration during the second phase. Conversely, nmMLCK-knockout monolayers resisted barrier dysfunction and neutrophil migration. Lastly, we found an inverse relationship between claudin-5 expression in BMVECs and neutrophil migration. Overall, our findings support a pathogenic role for nmMLCK in BMVECs during EAE that includes BBB dysfunction and neutrophil infiltration, reveal that claudin-5 contributes to the immune barrier properties of BMVECs, and underscore the harmful effects of claudin-5 loss during neuroinflammation.

Harmine-induced disruption of the blood-brain barrier via excessive mitophagy in zebrafish

Stroke is a serious condition with sudden onset, high severity, and significant rates of mortality and disability, ranking as the second leading cause of death globally at 11.6%. Hemorrhagic stroke, characterized by non-traumatic rupture of cerebral vessels, can cause secondary brain injury such as neurotoxicity, inflammation, reactive oxygen species, and blood-brain barrier (BBB) damage. The integrity of the BBB plays a crucial role in stroke outcomes, as its disruption can exacerbate injury. Harmine, a natural β-carboline alkaloid, has been studied for various pharmacological effects, including its potential benefits in protecting cardiac and cognitive functions. However, its impact on cerebrovascular conditions, particularly in the context of stroke, remains underexplored. This study investigates harmine's effects on BBB integrity and its role in inducing cerebral hemorrhage in zebrafish. We found that harmine disrupts BBB permeability, leading to cerebral hemorrhage through modulation of tight junction protein Claudin-5 and cytoskeletal protein F-actin expression. Furthermore, harmine altered mitochondrial morphology, causing structural imbalance, excessive mitophagy, and cell death. Together, these data indicate that harmine can induce BBB damage and intracerebral hemorrhage in zebrafish, and provide a possible mechanism and explanation for this effect.

Extracellular Vesicles From Preeclampsia Disrupt the Blood-Brain Barrier by Reducing CLDN5

BACKGROUND

The physiopathology of life-threatening cerebrovascular complications in preeclampsia is unknown. We investigated whether disruption of the blood-brain barrier, generated using circulating small extracellular vesicles (sEVs) from women with preeclampsia or placentae cultured under hypoxic conditions, impairs the expression of tight junction proteins, such as CLDN5 (claudin-5), mediated by VEGF (vascular endothelial growth factor), and activation of KDR (VEGFR2 [VEGF receptor 2]).

METHODS

We perform a preclinical mechanistic study using sEVs isolated from plasma of pregnant women with normal pregnancy (sEVs-NP; n=9), sEVs isolated from plasma of women with preeclampsia (sEVs-PE; n=9), or sEVs isolated from placentas cultured in normoxia (sEVs-Nor; n=10) or sEVs isolated from placentas cultured in hypoxia (sEVs-Hyp; n=10). The integrity of the blood-brain barrier was evaluated using in vitro (human [hCMEC/D3] and mouse [BEND/3 (brain endothelial cell 3)] brain endothelial cell lines) and in vivo (nonpregnant C57BL/6J mice [4-5 months old; n=13] injected with sEVs-Hyp) models.

RESULTS

sEVs-PE and sEVs-Hyp reduced total and membrane-associated protein CLDN5 levels (P<0.05). These results were negated with sEVs-PE sonication. sEVs-Hyp injected into nonpregnant mice generated neurological deficits and blood-brain barrier disruption, specifically in the posterior area of the brain, associated with brain endothelial cell uptake of sEVs, sEVs-Hyp high extravasation, and reduction in CLDN5 levels in the brain cortex. Furthermore, sEVs-PE and sEVs-sHyp had higher VEGF levels than sEVs-NP and sEVs-Nor. Human brain endothelial cells exposed to sEVs-PE exhibited a reduction in the activation of KDR. Reduction in CLDN5 observed in cells treated with sEVs-Hyp was further enhanced in cells treated with KDR selective inhibitor.

CONCLUSIONS

sEVs-PE disrupts the blood-brain barrier, an effect replicated with sEVs-Hyp, and involves reduced CLDN5 and elevated VEGF contained within these vesicles. However, our results do not support the participation of KDR activation in the downregulation of CLDN5 observed with sEVs-Hyp. These findings will improve our understanding of the pathophysiology of cerebrovascular alterations in women with preeclampsia.

Ferric Ammonium Citrate Reduces Claudin-5 Abundance and Function in Primary Mouse Brain Endothelial Cells

BACKGROUND

Iron overload is implicated in many neurodegenerative diseases, where there is also blood-brain barrier (BBB) dysfunction. As there is a growing interest in the role of iron in modulating key BBB proteins, this study assessed the effect of iron on the expression and function of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and claudin-5 in primary mouse brain endothelial cells (MBECs) and their abundance in mouse brain microvessel-enriched membrane fractions (MVEFs).

METHODS

Following a 48 h treatment with ferric ammonium citrate (FAC, 250 µM), MBEC protein abundance (P-gp, BCRP and claudin-5) and mRNA (abcb1a, abcg2, and cldn5) were assessed by western blotting and RT-qPCR, respectively. Protein function was evaluated by assessing transport of substrates 3H-digoxin (P-gp), 3H-prazosin (BCRP) and 14C-sucrose (paracellular permeability). C57BL/6 mice received iron dextran (100 mg/kg, intraperitoneally) over 4 weeks, and MVEF protein abundance and iron levels (in MVEFs and plasma) were quantified via western blotting and inductively coupled plasma-mass spectrometry (ICP-MS), respectively.

RESULTS

FAC treatment reduced P-gp protein by 50% and abcb1a mRNA by 43%, without affecting 3H-digoxin transport. FAC did not alter BCRP protein or function, but decreased abcg2 mRNA by 59%. FAC reduced claudin-5 protein and cldn5 mRNA by 65% and 70%, respectively, resulting in a 200% increase in 14C-sucrose permeability. In vivo, iron dextran treatment significantly elevated plasma iron levels (2.2-fold) but did not affect brain MVEF iron content or alter P-gp, BCRP or claudin-5 protein abundance.

CONCLUSIONS

Iron overload modulates BBB transporters and junction proteins in vitro, highlighting potential implications for CNS drug delivery in neurodegenerative diseases.

Safety, Tolerability and Pharmacokinetic-Pharmacodynamic Relationship of NX210c Peptide in Healthy Elderly Volunteers: Randomized, Placebo-Controlled, Double-Blind, Multiple Ascending Dose Study

INTRODUCTION

Blood-brain barrier (BBB) integrity is fundamental to brain homeostasis, enabling control of substance exchange and safeguarding neurons against harmful toxins, pathogens, and immune cells that lead to dysregulation and inflammation involved in ageing and neurodegenerative diseases (NDD). The cyclized peptide NX210c is a thrombospondin type 1 repeat analogue derived from subcommissural organ-spondin. It exerts beneficial effects in animal models of NDD owing to its effects on neurons and endothelial cells. NX210c demonstrated a good safety profile in a single ascending dose phase 1a clinical study. The present multiple ascending dose phase 1b study was performed to evaluate the tolerability and pharmacological effects of repeated doses of NX210c in healthy elderly (age: > 55 years) volunteers.

METHODS

This was a randomized, placebo-controlled, double-blind study (EudraCT No. 2022-002868-76), investigating safety/tolerability, pharmacokinetics, and pharmacodynamics (including blood and cerebrospinal fluid biomarkers). Participants received 5 or 10 mg/kg NX210c or placebo (10-min infusion) thrice weekly for 4 weeks in an ascending dose fashion. Follow-up was conducted 2 weeks after last dosing.

RESULTS

The investigation included 29 participants. No serious adverse events were recorded and all adverse events were mild. Dedicated central nervous system testing did not reveal neurotoxicity. Biomarker evaluation showed a statistically significant reduction in blood claudin-5 and a trend toward reduction of blood homocysteine. In silico data modelling revealed salient pharmacokinetic-pharmacodynamic relationships, including reduction of claudin-5, neurofilament light chain, and SPARC-like protein 1 release, and degradation of homocysteine.

CONCLUSION

Multiple doses of NX210c exhibited a good safety profile, showed non-cumulative pharmacokinetics, and exerted pharmacodynamic effects on biomarkers linked to BBB integrity. The effects of NX210c on claudin-5 and biomarkers influencing BBB integrity-and the overarching brain protection it offers-provide a novel therapeutic strategy targeting an underlying driver of neurodegenerative conditions for which disease-modifying treatments are limited or not available.

Cell-specific transcriptional signatures of vascular cells in Alzheimer's disease: perspectives, pathways, and therapeutic directions

Alzheimer's disease (AD) is a debilitating neurodegenerative disease that is marked by profound neurovascular dysfunction and significant cell-specific alterations in the brain vasculature. Recent advances in high throughput single-cell transcriptomics technology have enabled the study of the human brain vasculature at an unprecedented depth. Additionally, the understudied niche of cerebrovascular cells, such as endothelial and mural cells, and their subtypes have been scrutinized for understanding cellular and transcriptional heterogeneity in AD. Here, we provide an overview of rich transcriptional signatures derived from recent single-cell and single-nucleus transcriptomic studies of human brain vascular cells and their implications for targeted therapy for AD. We conducted an in-depth literature search using Medline and Covidence to identify pertinent AD studies that utilized single-cell technologies in human post-mortem brain tissue by focusing on understanding the transcriptional differences in cerebrovascular cell types and subtypes in AD and cognitively normal older adults. We also discuss impaired cellular crosstalk between vascular cells and neuroglial units, as well as astrocytes in AD. Additionally, we contextualize the findings from single-cell studies of distinct endothelial cells, smooth muscle cells, fibroblasts, and pericytes in the human AD brain and highlight pathways for potential therapeutic interventions as a concerted multi-omic effort with spatial transcriptomics technology, neuroimaging, and neuropathology. Overall, we provide a detailed account of the vascular cell-specific transcriptional signatures in AD and their crucial cellular crosstalk with the neuroglial unit.

Deciphering the Blood-Brain Barrier Paradox in Brain Metastasis Development and Therapy

Gatekeeper or accomplice? That is the paradoxical role of the blood-brain barrier (BBB) in developing brain metastasis (BM). BM occurs when cancerous cells from primary cancer elsewhere in the body gain the ability to metastasize and invade the brain parenchyma despite the formidable defense of the BBB. These metastatic cells manipulate the BBB's components, changing them from gatekeepers of the brain to accomplices that aid in their progression into the brain tissue. This dual role of the BBB-as both a protective system and a potential facilitator of metastatic cells-highlights its complexity. Even with metastasis therapy such as chemotherapy, BM usually recurs due to the BBB limiting the crossing of drugs via the efflux transporters; therefore, treatment efficacy is limited. The pathophysiology is also complex, and our understanding of the paradoxical interplay between the BBB components and metastatic cells still needs to be improved. However, advancements in clinical research are helping to bridge the knowledge gap, which is essential for developing effective metastasis therapy. By targeting the BBB neurovascular unit components such as the polarization of microglia, astrocytes, and pericytes, or by utilizing technological tools like focused ultrasound to transiently disrupt the BBB and therapeutic nanoparticles to improve drug delivery efficiency to BM tissue, we can better address this pathology. This narrative review delves into the latest literature to analyze the paradoxical role of the BBB components in the manifestation of BM and explores potential therapeutic avenues targeting the BBB-tumor cell interaction.

The Crucial Role of the Blood-Brain Barrier in Neurodegenerative Diseases: Mechanisms of Disruption and Therapeutic Implications

The blood-brain barrier (BBB) is a crucial structure that maintains brain homeostasis by regulating the entry of molecules and cells from the bloodstream into the central nervous system (CNS). Neurodegenerative diseases such as Alzheimer's and Parkinson's disease, as well as ischemic stroke, compromise the integrity of the BBB. This leads to increased permeability and the infiltration of harmful substances, thereby accelerating neurodegeneration. In this review, we explore the mechanisms underlying BBB disruption, including oxidative stress, neuroinflammation, vascular dysfunction, and the loss of tight junction integrity, in patients with neurodegenerative diseases. We discuss how BBB breakdown contributes to neuroinflammation, neurotoxicity, and the abnormal accumulation of pathological proteins, all of which exacerbate neuronal damage and facilitate disease progression. Furthermore, we discuss potential therapeutic strategies aimed at preserving or restoring BBB function, such as anti-inflammatory treatments, antioxidant therapies, and approaches to enhance tight junction integrity. Given the central role of the BBB in neurodegeneration, maintaining its integrity represents a promising therapeutic approach to slow or prevent the progression of neurodegenerative diseases.

Prophylactic use of probiotics as an adjunctive treatment for ischemic stroke via the gut-spleen-brain axis

A growing body of research has focused on the role of spleen in orchestrating brain injury through the peripheral immune system following stroke, highlighting the brain-spleen axis as a potential target for mitigating neuronal damage during stroke. The gut microbiota plays a pivotal role in the bidirectional communication between the gut and the brain. Several studies have suggested that probiotic supplements hold promise as a strategic approach to maintaining a balanced intestinal microecology, reducing the apoptosis of intestinal epithelial cells, protecting the intestinal mucosal and blood-brain barrier (BBB), enhancing both intestinal and systemic immune functions, and thereby potentially affecting the pathogenesis and progression of ischemic stroke. In this study, we aimed to clarify the neuroprotective effects of supplementation with Lactobacillus, specifically Limosilactobacillus reuteri GMNL-89 (G89) and Lacticaseibacillus paracasei GMNL-133 (G133) on ischemic stroke and investigate how G89 and G133 modulate the communication mechanisms between the gut, brain, and spleen following ischemic stroke. We explored the neuroprotection and the underlying mechanisms of Lactobacillus supplementation in C57BL/6 mice subjected to permanent middle cerebral artery occlusion. Our results revealed that oral treatment with G89 or G133 alone, as well as oral administration combining G89 and G133, significantly decreased the infarct volume and improved the neurological function in mice with ischemic stroke. Moreover, G89 treatment alone preserved the tight junction integrity of gut barrier, while G133 alone and the combined treatment of G89 and G133 would significantly decreased the BBB permeability, and thereby significantly attenuated stroke-induced local and systemic inflammatory responses. Both G89 and G133 regulated cytotoxic T cells, and the balance between T helper 1 cells and T helper 2 cells in the spleen following ischemic stroke. Additionally, the combined administration of G89 and G133 improved the gut dysbiosis and significantly increased the concentration of short-chain fatty acids. In conclusion, our findings suggest that G89 and G133 may be used as nutrient supplements, holding promise as a prospective approach to combat ischemic stroke by modulating the gut-spleen-brain axis.

Claudin-5 and occludin levels in patients with psychiatric disorders - A systematic review

BACKGROUND

Recent research has underscored the critical role of blood-brain barrier (BBB) integrity in psychiatric disorders, highlighting disruptions in tight junction (TJ) proteins, specifically claudin-5 and occludin. These proteins are pivotal in maintaining the BBB's selective permeability, which is essential forbrain homeostasis. Altered levels of the TJ proteins have been observed in various psychiatric conditions, suggesting potential as biomarkers for the pathophysiology of these disorders. This systematic review synthesizes existing research on the alterations of claudin-5 and occludin levels in the serum of individuals with psychiatric disorders, evaluating their correlation with BBB dysfunction and psychiatric pathophysiology.

METHODS

In adherence to the PRISMA guidelines, a comprehensive search strategy was employed, utilizing databases such as PubMed, Google Scholar, Web of Science, and Scopus. The review encompassed studies published between 2000 and 2024 that measured serum claudin-5 and occludin levels of psychiatric patients. Thorough data extraction and synthesis were conducted.

RESULTS

Seventeen studies met the inclusion criteria. Key findings include indications for increased claudin-5 levels in Schizophrenia, Bipolar Disorder, Depression, and Specific learning disorder, and increased occludin levels in ADHD and Autism Spectrum Disorder patients. No significant differences were found in studies of patients with Alcohol Use and Insomnia Disorder.

CONCLUSIONS

The review underscores the potential association between altered serum levels of claudin-5 and occludin and psychiatric disorders, supporting their utility as biomarkers for BBB integrity and psychiatric pathophysiology. Further research is essential to elucidate the mechanisms linking TJ protein alterations with pathophysiology and, potentially, neuroprogression in psychiatric disorders, which could lead to novel diagnostic and therapeutic strategies.

Unveiling the Mysteries of the Blood-brain Barrier: The Problem of the Brain/spinal Pharmacotherapy

The most critical issue impeding the development of innovative cerebrospinal medications is the blood-brain barrier (BBB). The BBB limits the ability of most medications to penetrate the brain to the CNS. The BBB structure and functions are summarized, with the physical barrier generated by endothelial tight junctions and the transport barrier formed by transporters within the membrane and vesicular processes. The functions of connected cells, particularly the end feet of astrocytic glial cells, microglia, and pericytes, are described. The drugs that cross the blood brain barrier are explained below along with their mechanisms. Some of the associated conditions and problems are given.

Resveratrol and ceftriaxone encapsulated in hybrid nanoparticles to prevent dopaminergic neurons from degeneration for Parkinson's disease treatment

The purpose of this study is to evaluate the influence of phospholipid-polymer nanoparticles (PNPs) on mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling of dopaminergic neurons in degenerated brain. Resveratrol (RES)- and ceftriaxone (CEF)-entrapped PNPs with surface leptin (Lep) and transferrin (Tf) were fabricated to rescue both 1-methyl-4-phenylpyridinium (MPP+)-insulted SH-SY5Y cells and Wistar rats. Based on PNPs, anti-apoptosis of RES and CEF, and targeting of Lep and Tf were investigated. Experimental results revealed that 20-30 % alginic acid (Alg) yielded the maximal particle size, physical stability and entrapment efficiency of CEF, and the minimal release percentage of CEF. Increasing Alg content in PNPs decreased the entrapment efficiency of RES, and facilitated the release of RES. Optimized PNP composition was about 40 % Alg, 15 % phosphatidylserine and 45 % poly-ε-caprolactone. Lep-Tf-PNPs ameliorated brain permeability of RES and CEF without jeopardizing the blood-brain barrier, and promoted the viability of MPP+-insulted SH-SY5Y cells. Immunofluorescence images and western blots of MPP+-insulted SH-SY5Y cells showed that Lep-Tf-RES-CEF-PNPs upregulated dopamine transporter, tyrosine hydroxylase, B-cell lymphoma 2 (Bcl-2), cyclic AMP response element-binding protein and ERK5 expressions, and downregulated Bcl-2-associated X protein (Bax), α-synuclein (α-syn), phosphorylated tau protein (p-tau), c-Jun N-terminal kinase and ERK1/2 expressions. Lep-Tf-RES-CEF-PNPs unveiled a strong capacity to recover Bcl-2, Bax, α-syn and p-tau levels from MPP+ injury in the substantia nigra of rats. Hence, Lep-Tf-RES-CEF-PNPs can retard α-syn fibril formation, prevent tau protein from phosphorylation, and moderate MAPK/ERK and phosphatidylinositol 3-kinase/protein kinase B, and are promising for brain- and neuron-targeted pharmacotherapy to manage Parkinson's disease.

Blood-brain barrier dysfunction in multiple system atrophy: A human postmortem study

Multiple system atrophy (MSA) is a rare neurodegenerative disease characterized by an accumulation of phosphorylated α-synuclein (p-αsyn) in oligodendrocytes in the form of glial cytoplasmic inclusions (GCIs). In MSA, not only mature oligodendrocytes but also oligodendrocyte precursor cells (OPCs) are affected. The latter play an important role in remyelination by differentiating into mature oligodendrocytes, as well as maintaining the blood-brain barrier (BBB) by promoting the expression of tight junction proteins. We have hypothesized that in MSA, the BBB is impaired as a result of aberrant interactions between affected OPCs and the cerebral vasculature. To verify this hypothesis, we conducted a neuropathological examination of postmortem brains from MSA patients and control subjects, focusing on the primary motor area, one of the main regions affected in MSA. Using double immunofluorescence, we quantified the expression of tight junction protein claudin-5 in capillary endothelial cells and found that it was significantly lower in MSA than in controls in both the gray matter and white matter. Furthermore, a significantly higher amount of fibrinogen was extravasated into the brain parenchyma in MSA patients than in controls. In addition, leakage of IgG was detected almost specifically in MSA brain parenchyma, as visualized in three dimensions by combining techniques of chemical tissue clearing and light sheet microscopy. Finally, we confirmed accumulation of p-αsyn-positive GCIs along the cerebral vasculature within OPCs. These results suggest that BBB dysfunction and associated fibrinogen extravasation are constant findings in MSA, presumably triggered by the deposition of p-αsyn in perivascular OPCs.

Single-cell transcriptomic and neuropathologic analysis reveals dysregulation of the integrated stress response in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a sporadic neurodegenerative tauopathy variably affecting brainstem and cortical structures, and characterized by tau inclusions in neurons and glia. The precise mechanism whereby these protein aggregates lead to cell death remains unclear. To investigate the contribution of these different cellular abnormalities to PSP pathogenesis, we performed single-nucleus RNA sequencing (snRNA-seq) and analyzed 50,708 high quality nuclei targeting the diencephalon, including the subthalamic nucleus and adjacent structures, from human post-mortem PSP brains with varying degrees of pathology compared to controls. Cell-type-specific differential expression and pathway analysis identified both common and discrete changes in numerous pathways previously implicated in PSP and other neurodegenerative disorders. This included EIF2 signaling, an adaptive pathway activated in response to diverse stressors, which was activated in multiple vulnerable cell types and validated in independent snRNA-seq and bulk RNA-seq datasets. Using immunohistochemistry, we found that activated eIF2α was positively correlated with tau pathology burden in vulnerable brain regions. Multiplex immunofluorescence localized activated eIF2α positivity to hyperphosphorylated tau (p-tau) positive neurons and ALDH1L1-positive astrocytes, supporting the increased transcriptomic EIF2 activation observed in these vulnerable cell types. In conclusion, these data provide insights into cell-type-specific pathological changes in PSP and support the hypothesis that failure of adaptive stress pathways play a mechanistic role in the pathogenesis and progression of PSP.

Rescue of cochlear vascular pathology prevents sensory hair cell loss in Norrie disease

Variants in the gene NDP cause Norrie disease, a severe dual-sensory disorder characterized by congenital blindness due to disrupted retinal vascular development and progressive hearing loss accompanied by sensory hair cell death. NDP encodes the secreted signaling molecule norrin. The role of norrin in the cochlea is incompletely understood. We investigated whether the Norrie disease cochlear pathology can be ameliorated in an Ndp-knockout (Ndp-KO) mouse model by conditional activation of stabilized β-catenin in vascular endothelial cells. We hypothesized that in the cochlea microvasculature, β-catenin is the primary downstream intracellular effector of norrin binding to endothelial cell surface receptors and that restoration of this signaling pathway is sufficient to prevent sensory hair cell death and hearing loss. We show that tamoxifen induction of Cdh5CreERT2;Ctnnb1flex3/+;Ndp-KO mice stabilizing β-catenin in vascular endothelial cells alone rescued defects in cochlear vascular barrier function, restored dysregulated expression of endothelial cell disease biomarkers (Cldn5, Abcb1a, Slc7a1, and Slc7a5), and prevented progressive outer hair cell death and hearing loss. Single-cell transcriptome profiling of human cochleas showed NDP expression by fibrocytes and glial cells while receptor gene expression (FZD4, TSPAN12, LRP5, and LRP6) coincided in vascular endothelial cells. Our findings support the conclusion that vascular endothelial cells are a primary target of norrin signaling in the cochlea of mice and humans and restoration of β-catenin regulation of target gene expression within cochlear endothelial cells is sufficient to maintain a cochlear microenvironment critical for hair cell survival.

Sturge-Weber syndrome: updates in translational neurology

Sturge-Weber syndrome (SWS) is a rare congenital neurovascular disorder that initially presents with a facial port-wine birthmark (PWB) and most commonly associated with a R183Q somatic mosaic mutation in the gene GNAQ. This mutation is enriched in endothelial cells. Contrast-enhanced magnetic resonance imaging (MRI) diagnoses brain abnormalities including leptomeningeal vascular malformation, an enlarged choroid plexus, and abnormal cortical and subcortical blood vessels. Mouse SWS models identify dysregulated proteins important for abnormal vasculogenesis and blood brain barrier permeability. Recent clinical research has focused on early diagnosis, biomarker development, presymptomatic treatment, and development of novel treatment strategies. Prospective pilot clinical drug trials with cannabidiol (Epidiolex) or with sirolimus, an mTOR inhibitor, indicate possible reductions in seizure frequency and improved cognitive outcome. This review connects the most recent molecular research in SWS cell culture and animal models to developing new treatment methods and identifies future areas of research.

Engineering extracellular vesicles to transiently permeabilize the blood-brain barrier

BACKGROUND

Drug delivery to the brain is challenging due to the restrict permeability of the blood brain barrier (BBB). Recent studies indicate that BBB permeability increases over time during physiological aging likely due to factors (including extracellular vesicles (EVs)) that exist in the bloodstream. Therefore, inspiration can be taken from aging to develop new strategies for the transient opening of the BBB for drug delivery to the brain.

RESULTS

Here, we evaluated the impact of small EVs (sEVs) enriched with microRNAs (miRNAs) overexpressed during aging, with the capacity to interfere transiently with the BBB. Initially, we investigated whether the miRNAs were overexpressed in sEVs collected from plasma of aged individuals. Next, we evaluated the opening properties of the miRNA-enriched sEVs in a static or dynamic (under flow) human in vitro BBB model. Our results showed that miR-383-3p-enriched sEVs significantly increased BBB permeability in a reversible manner by decreasing the expression of claudin 5, an important tight junction protein of brain endothelial cells (BECs) of the BBB, mediated in part by the knockdown of activating transcription factor 4 (ATF4).

CONCLUSIONS

Our findings suggest that engineered sEVs have potential as a strategy for the temporary BBB opening, making it easier for drugs to reach the brain when injected into the bloodstream.

Unraveling the Role of the Blood-Brain Barrier in the Pathophysiology of Depression: Recent Advances and Future Perspectives

Depression is a highly prevalent psychological disorder characterized by persistent dysphoria, psychomotor retardation, insomnia, anhedonia, suicidal ideation, and a remarkable decrease in overall well-being. Despite the prevalence of accessible antidepressant therapies, many individuals do not achieve substantial improvement. Understanding the multifactorial pathophysiology and the heterogeneous nature of the disorder could lead the way toward better outcomes. Recent findings have elucidated the substantial impact of compromised blood-brain barrier (BBB) integrity on the manifestation of depression. BBB functions as an indispensable defense mechanism, tightly overseeing the transport of molecules from the periphery to preserve the integrity of the brain parenchyma. The dysfunction of the BBB has been implicated in a multitude of neurological disorders, and its disruption and consequent brain alterations could potentially serve as important factors in the pathogenesis and progression of depression. In this review, we extensively examine the pathophysiological relevance of the BBB and delve into the specific modifications of its components that underlie the complexities of depression. A particular focus has been placed on examining the effects of peripheral inflammation on the BBB in depression and elucidating the intricate interactions between the gut, BBB, and brain. Furthermore, this review encompasses significant updates on the assessment of BBB integrity and permeability, providing a comprehensive overview of the topic. Finally, we outline the therapeutic relevance and strategies based on BBB in depression, including COVID-19-associated BBB disruption and neuropsychiatric implications. Understanding the comprehensive pathogenic cascade of depression is crucial for shaping the trajectory of future research endeavors.

Is there a link between peripheral inflammation and blood brain barrier integrity in children with attention-deficit/hyperactivity disorder? A case-control study

BACKGROUND

Claudin-5 is a vital constituent of tight junctions, which are critical elements of the blood-brain barrier. In people with neuropsychiatric disorders, peripheral inflammation is often found, although it is less common in healthy populations. The objective of this study was to examine the relationship between Claudin-5, peripheral immune cells, and the severity of symptoms in children with attention deficit hyperactivity disorder (ADHD).

METHODS

The study included a cohort of 33 children diagnosed with ADHD and 29 control subjects, all aged between 5 and 12 years. The intensity of ADHD symptoms was evaluated using Conner's questionnaire, which the parents completed. Each kid had serum level measurements of Claudin-5 and a complete blood count in order to establish a correlation with symptoms of ADHD.

RESULTS

Serum Claudin-5 levels are lower in the ADHD group compared to the control group; median (IQR) = 30.94 (4-137) and 44.12 (4-223.3) respectively (p = 0.69). The levels of neutrophils and neutrophil/lymphocyte ratio are significantly higher in ADHD than in controls (p = 0.011 and 0.015, respectively). Lymphocytes have a significant positive correlation with ADHD symptoms severity, namely, total Conner's scale and inattention (p = 0.021 and 0.004 respectively), while NLR has a significant negative correlation with total Conner's score and impulsivity (p = 0.046, p = 0.038), also a negative correlation yet not significant between serum Claudin-5 level and total Conner's score, hyperactivity, impulsivity, and inattention. Neutrophils were found to have a significant positive linear regression with Claudin-5 (p = 0.023).

CONCLUSION

These results revealed that BBB integrity is affected in ADHD children, as claudin-5 levels were found to be lower in children with ADHD, lymphocytes were found to be associated with increased ADHD symptoms severity, and NLR was associated with decreased symptoms severity, which may be via the positive effects of increased neutrophils on Claudin-5 levels.

Circadian control of polycyclic aromatic hydrocarbon-induced dysregulation of endothelial tight junctions and mitochondrial bioenergetics

The study evaluates the impact of environmental toxicants, such as polycyclic aromatic hydrocarbons (PAHs), on circadian regulations and functions of brain endothelial cells, which form the main structural element of the blood-brain barrier (BBB). PAH are lipophilic and highly toxic environmental pollutants that accumulate in human and animal tissues. Environmental factors related to climate change, such as an increase in frequency and intensity of wildfires or enhanced strength of hurricanes or tropical cyclones, may lead to redistribution of these toxicants and enhanced human exposure. These natural disasters are also associated with disruption of circadian rhythms in affected populations, linking increased exposure to environmental toxicants to alterations of circadian rhythm pathways. Several vital physiological processes are coordinated by circadian rhythms, and disruption of the circadian clock can contribute to the development of several diseases. The blood-brain barrier (BBB) is crucial for protecting the brain from blood-borne harmful substances, and its integrity is influenced by circadian rhythms. Exposure of brain endothelial cells to a human and environmentally-relevant PAH mixture resulted in dose-dependent alterations of expression of critical circadian modulators, such as Clock, Bmal1, Cry1/2, and Per1/2. Moreover, silencing of the circadian Clock gene potentiated the impact of PAHs on the expression of the main tight junction genes and proteins (namely, claudin-5, occludin, JAM-2, and ZO-2), as well as mitochondrial bioenergetics. Findings from this study contribute to a better understanding of pathological influence of PAH-induced health effects, especially those related to circadian rhythm disruption.

Nanotechnological approaches for efficient N2B delivery: from small-molecule drugs to biopharmaceuticals

Central nervous system diseases negatively affect patients and society. Providing successful noninvasive treatments for these diseases is challenging because of the presence of the blood-brain barrier. While protecting the brain's homeostasis, the barrier limits the passage of almost all large-molecule drugs and most small-molecule drugs. A noninvasive method, nose-to-brain delivery (N2B delivery) has been proposed to overcome this challenge. By exploiting the direct anatomical interaction between the nose and the brain, the drugs can reach the target, the brain. Moreover, the drugs can be encapsulated into various drug delivery systems to enhance physicochemical characteristics and targeting success. Many preclinical data show that this strategy can effectively deliver biopharmaceuticals to the brain. Therefore, this review focuses on N2B delivery while giving examples of different drug delivery systems suitable for the applications. In addition, we emphasize the importance of the effective delivery of monoclonal antibodies and RNA and stress the recent literature tackling this challenge. While giving examples of nanotechnological approaches for the effective delivery of small or large molecules from the current literature, we highlight the preclinical studies and their results to prove the strategies' success and limitations.

Biophysical Basis of Paracellular Barrier Modulation by a Pan-Claudin-Binding Molecule

Claudins are a 27-member protein family that form and fortify specialized cell contacts in endothelium and epithelium called tight junctions. Tight junctions restrict paracellular transport across tissues by forming molecular barriers between cells. Claudin-binding molecules thus hold promise for modulating tight junction permeability to deliver drugs or as therapeutics to treat tight junction-linked disease. The development of claudin-binding molecules, however, is hindered by their intractability and small targetable surfaces. Here, we determine that a synthetic antibody fragment (sFab) we developed binds directly to 10 claudin subtypes with nanomolar affinity by targeting claudin's paracellular-exposed surface. Application of this sFab to cells that model intestinal epithelium show that it opens the paracellular barrier comparable to a known, but application limited, tight junction modulator. This novel pan-claudin-binding molecule can probe claudin or tight junction structure and holds potential as a broad modulator of tight junction permeability for basic or translational applications.

The Link Between Paraquat and Demyelination: A Review of Current Evidence

Paraquat (1,1'-dimethyl-4,4'-bipyridilium dichloride), a widely used bipyridinium herbicide, is known for inducing oxidative stress, leading to extensive cellular toxicity, particularly in the lungs, liver, kidneys, and central nervous system (CNS), and is implicated in fatal poisonings. Due to its biochemical similarities with the neurotoxin 1-methyl-4-phenylpyridinium (MPP+), paraquat has been used as a Parkinson's disease model, although its broader neurotoxic effects suggest the participation of multiple mechanisms. Demyelinating diseases are conditions characterized by damage to the myelin sheath of neurons. They affect the CNS and peripheral nervous system (PNS), resulting in diverse clinical manifestations. In recent years, growing concerns have emerged about the impact of chronic, low-level exposure to herbicides on human health, particularly due to agricultural runoff contaminating drinking water sources and their presence in food. Studies indicate that paraquat may significantly impact myelinating cells, myelin-related gene expression, myelin structure, and cause neuroinflammation, potentially contributing to demyelination. Therefore, demyelination may represent another mechanism of neurotoxicity associated with paraquat, which requires further investigation. This manuscript reviews the potential association between paraquat and demyelination. Understanding this link is crucial for enhancing strategies to minimize exposure and preserve public health.

Diblock Copolymers of Poly(ethylene oxide)-b-poly(propylene oxide) Stabilize a Blood-Brain Barrier Model under Oxidative Stress

The blood-brain barrier (BBB) is a highly restrictive barrier at the interface between the brain and the vascular system. Even under BBB dysfunction, it is extremely difficult to deliver therapies across the barrier, limiting the options for treatment of neurological injuries and disorders. To circumvent these challenges, there is interest in developing therapies that directly engage with the damaged BBB to restore its function. Previous studies revealed that poloxamer 188 (P188), a water-soluble triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), partially mitigated BBB dysfunction in vivo. In the context of stabilization of the damaged BBB, the mechanism of action of PEO-PPO block copolymers is unknown, and there has been minimal exploration of polymers beyond P188. In this study, a human-based in vitro BBB model under oxidative stress was used to investigate polymer-BBB interactions since oxidative stress is closely linked with BBB dysfunction in many neurological injuries and disorders. PEO-PPO block copolymers of varied numbers of chemically distinct blocks, PEO block length, and functionality of the end group of the PPO block were assessed for their efficacy in improving key physiological readouts associated with BBB dysfunction. While treatment with P188 did not mitigate damage in the in vitro BBB model, treatment with three diblock copolymers improved barrier integrity under oxidative stress to a similar extent. Of the considered variations in the block copolymer design, the reduction in the number of chemically distinct blocks had the strongest influence on therapeutic function. The demonstrated efficacy of three alternative PEO-PPO diblock copolymers in this work reveals the potential of these polymers as a class of therapeutics that directly treat the damaged BBB, expanding the options for treatment of neurological injuries and disorders.

Blood-brain barrier disruption following brain injury: Implications for clinical practice

The blood-brain barrier (BBB) plays a critical role in regulating the exchange of substances between peripheral blood and the central nervous system and in maintaining the stability of the neurovascular unit in neurological diseases. To guide clinical treatment and basic research on BBB protection following brain injury, this manuscript reviews how BBB disruption develops and influences neural recovery after stroke and traumatic brain injury (TBI). By summarizing the pathological mechanisms of BBB damage, we underscore the critical role of promoting BBB repair in managing brain injury. We also emphasize the potential for personalized and precise therapeutic strategies and the need for continued research and innovation. From this, broadening insights into the mechanisms of BBB disruption and repair could pave the way for breakthroughs in the treatment of brain injury-related diseases.