IVIVC Assessment of Two Mouse Brain Endothelial Cell Models for Drug Screening

Functional assessment of immortalized human brain microvascular endothelial cells with different passage numbers: A case study for a prospective proposal on variability management of in vitro blood-brain barrier models

In vitro blood-brain barrier (BBB) models, primarily consisting of brain microvascular endothelial cells (BMEC), are expected to play pivotal roles in evaluating drug permeability into the brain. However, these models often exhibit functional variability due to various factors, raising practical concerns that can hinder their use in drug development studies. By investigating cell passage numbers as one such factor, we aim to assess how BBB model functionality is affected and to propose a practical strategy for managing this variability. In transwell-BBB models - but not in spheroidal-BBB models - the intercellular barrier integrity was somewhat compromised when higher-passage human immortalized BMEC (HBMEC/ci18) were used. Nonetheless, a clear in vitro-in vivo correlation (IVIVC) curve could still be obtained with these transwell-BBB models, similar to those with lower passage number HBMEC/ci18, presumably allowing for reasonable estimation of in vivo drug permeability. Therefore, changes in functional levels of BBB models do not always significantly diminish their practical value in drug BBB permeability studies. Additionally, the IVIVC curve integrity may serve as an indicator for assessing acceptable BBB model functionality. These findings provide valuable insights for the future application of in vitro human BBB models in drug development studies.

Decreasing β-Catenin Leads to Altered Endothelial Morphology, Increased Barrier Permeability and Cognitive Impairment During Chronic Methamphetamine Exposure

Cognitive impairment induced by chronic methamphetamine (METH) exposure exhibits similarities to neurodegenerative disorders and is associated with blood-brain barrier (BBB) dysfunction. However, the potential involvement of β-catenin in maintaining BBB integrity during METH exposure remains unexplored. In this study, Y-maze and novel object recognition tests were conducted to assess cognitive impairment in mice exposed chronically to methamphetamine for 2 and 4 weeks. Gd-DTPA and Evans blue leakage tests revealed disruption of the BBB in the hippocampus, while chronic METH exposure for 2 and 4 weeks significantly decreased β-catenin levels along with its transcriptionally regulated protein, claudin5. Additionally, various neural injury-related proteins, such as APP, Aβ1-42, p-tau (Thr181) and p-tau (Ser396), as well as neuroinflammation-related proteins, such as IL-6, IL-1β, and TNF-α, exhibited increased levels following chronic METH exposure. Furthermore, plasma analysis indicated elevated levels of p-Tau (total), neurofilament light chain, and GFAP. In vitro experiments demonstrated that exposure to METH resulted in dose-dependent and time-dependent reductions in cellular activity and connectivity of bEnd.3 and hcmec/D3 cells. Furthermore, β-catenin exhibited decreased levels and altered subcellular localization, transitioning from the cell membrane to the cytoplasm and nucleus upon METH exposure. Overexpression of β-catenin was found to alleviate endothelial toxicity and attenuate junctional weakening induced by METH. The aforementioned findings underscore the crucial involvement of β-catenin in endothelial cells during chronic METH exposure-induced disruption of the BBB, thereby presenting a potential novel target for addressing METH-associated cerebrovascular dysfunction and cognitive impairment.

Brain targeted lactoferrin coated lipid nanocapsules for the combined effects of apocynin and lavender essential oil in PTZ induced seizures

Apocynin (APO) is a plant derived antioxidant exerting specific NADPH oxidase inhibitory action substantiating its neuroprotective effects in various CNS disorders, including epilepsy. Due to rapid elimination and poor bioavailability, treatment with APO is challenging. Correspondingly, novel APO-loaded lipid nanocapsules (APO-LNC) were formulated and coated with lactoferrin (LF-APO-LNC) to improve br ain targetability and prolong residence time. Lavender oil (LAV) was incorporated into LNC as a bioactive ingredient to act synergistically with APO in alleviating pentylenetetrazol (PTZ)-induced seizures. The optimized LF-APO-LAV/LNC showed a particle size 59.7 ± 4.5 nm with narrow distribution and 6.07 ± 1.6mV zeta potential) with high entrapment efficiency 92 ± 2.4% and sustained release (35% in 72 h). Following subcutaneous administration, LF-APO-LAV/LNC brought about ⁓twofold increase in plasma AUC and MRT compared to APO. A Log BB value of 0.2 ± 0.14 at 90 min reflects increased brain accumulation. In a PTZ-induced seizures rat model, LF-APO-LAV/LNC showed a Modified Racine score of 0.67 ± 0.47 with a significant increase in seizures latency and decrease in duration. Moreover, oxidant/antioxidant capacity and inflammatory markers levels in brain tissue were significantly improved. Histopathological and immunohistochemical assessment of brain tissue sections further supported these findings. The results suggest APO/LAV combination in LF-coated LNC as a promising approach to counteract seizures.

Patient-Derived Blood-Brain Barrier Model for Screening Copper Bis(thiosemicarbazone) Complexes as Potential Therapeutics in Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent cause of dementia characterized by a progressive cognitive decline. Addressing neuroinflammation represents a promising therapeutic avenue to treat AD; however, the development of effective antineuroinflammatory compounds is often hindered by their limited blood-brain barrier (BBB) permeability. Consequently, there is an urgent need for accurate, preclinical AD patient-specific BBB models to facilitate the early identification of immunomodulatory drugs capable of efficiently crossing the human AD BBB. This study presents a unique approach to BBB drug permeability screening as it utilizes the familial AD patient-derived induced brain endothelial-like cell (iBEC)-based model, which exhibits increased disease relevance and serves as an improved BBB drug permeability assessment tool when compared to traditionally employed in vitro models. To demonstrate its utility as a small molecule drug candidate screening platform, we investigated the effects of diacetylbis(N(4)-methylthiosemicarbazonato)copper(II) (CuII(atsm)) and a library of metal bis(thiosemicarbazone) complexes─a class of compounds exhibiting antineuroinflammatory therapeutic potential in neurodegenerative disorders. By evaluating the toxicity, cellular accumulation, and permeability of those compounds in the AD patient-derived iBEC, we have identified 3,4-hexanedione bis(N(4)-methylthiosemicarbazonato)copper(II) (CuII(dtsm)) as a candidate with good transport across the AD BBB. Furthermore, we have developed a multiplex approach where AD patient-derived iBEC were combined with immune modulators TNFα and IFNγ to establish an in vitro model representing the characteristic neuroinflammatory phenotype at the patient's BBB. Here, we observed that treatment with CuII(dtsm) not only reduced the expression of proinflammatory cytokine genes but also reversed the detrimental effects of TNFα and IFNγ on the integrity and function of the AD iBEC monolayer. This suggests a novel pathway through which copper bis(thiosemicarbazone) complexes may exert neurotherapeutic effects on AD by mitigating BBB neuroinflammation and related BBB integrity impairment. Together, the presented model provides an effective and easily scalable in vitro BBB platform for screening AD drug candidates. Its improved translational potential makes it a valuable tool for advancing the development of metal-based compounds aimed at modulating neuroinflammation in AD.

Recent advancements on in vitro blood-brain barrier model: A reliable and efficient screening approach for preclinical and clinical investigation

INTRODUCTION

The efficiency of brain therapeutics is greatly hindered by the blood-brain barrier (BBB). BBB's protective function, selective permeability, and dynamic functionality maintain the harmony between the brain and peripheral region. Thus, the design of any novel drug carrier system requires the complete study and investigation of BBB permeability, efflux transport, and the effect of associated cellular and non-vascular unit trafficking on BBB penetrability. The in vitro BBB models offer a most promising, and reliable mode of initial investigation of BBB permeability and associated factors as strong evidence for further preclinical and clinical investigation.

AREA COVERED

This review work covers the structure and functions of BBB components and different types of in vitro BBB models along with factors affecting BBB model development and model selection criteria.

EXPERT OPINION

In vivo models assume to reciprocate the physiological environment to the maximum extent. However, the interspecies variability, NVUs trafficking, dynamic behavior of BBB, etc., lead to non-reproducible results. The in vitro models are comparatively less complex, and flexible, as per the study design, could generate substantial evidence and help identify suitable in vivo animal model selection.

Simple and efficient protocol to isolate and culture brain microvascular endothelial cells from newborn mice

The neurovascular unit (NVU) is a multicellular structure comprising of neurons, glial cells, and non-neural cells, and it is supported by a specialized extracellular matrix, the basal lamina. Astrocytes, brain microvascular endothelial cells (BMECs), pericytes, and smooth muscle cells constitute the blood-brain barrier (BBB). BMECs have a mesodermal origin and invade the nervous system early in neural tube development, forming the BBB anatomical core. BMECs are connected by adherent junction complexes composed of integral membrane and cytoplasmic proteins. In vivo and in vitro studies have shown that, given the proximity and relationship with neural cells, BMECs acquire a unique gene expression profile, proteome, and specific mechanical and physical properties compared to endothelial cells from the general vasculature. BMECs are fundamental in maintaining brain homeostasis by regulating transcellular and paracellular transport of fluids, molecules, and cells. Therefore, it is essential to gain in-depth knowledge of the dynamic cellular structure of the cells in the NVU and their interactions with health and disease. Here we describe a significantly improved and simplified protocol using C57BL/6 newborn mice at postnatal day 1 (PND1) to isolate, purify, and culture BMECs monolayers in two different substrates (glass coverslips and transwell culture inserts). In vitro characterization and validation of the BMEC primary culture monolayers seeded on glass or insert included light microscopy, immunolabeling, and gene expression profile. Transendothelial electrical resistance (TEER) measurement and diffusion test were used as functional assays for adherent junction complexes and integrity and permeability of BMECs monolayers. The protocol presented here for the isolation and culture of BMECs is more straightforward than previously published protocols and yields a high number of purified cells. Finally, we tested BMECs function using the oxygen-glucose deprivation (OGD) model of hypoxia. This protocol may be suitable as a bioscaffold for secondary cell seeding allowing the study and better understanding of the NVU.

Evaluation of in vitro cornea models for quantifying destructive effects of chemicals

In vitro models are available as alternatives for the Draize eye irritation test. However, most of the alternative models are not quantitative nor designed to evaluate the effects of chemicals on the corneal barrier such as those encountered in pharmaceutical and cosmetic products. The objective of the present study was to investigate tissue electrical resistance to provide sensitive in vitro testing of tissue alteration caused by chemicals in pharmaceutical and cosmetic formulations as a potential eye irritation testing approach. The experimental protocols for effective tissue resistance measurements were examined using two in vitro eye models: porcine cornea and EpiCorneal. In these models, a test chemical was applied to the cornea or EpiCorneal tissue for 1 min, and tissue resistances/conductances were measured at 1-60 min after the application. The changes in conductance of the tissues after exposure to the chemicals were shown to provide quantitative evaluations to the influence of the chemicals. A correlation was found between the two in vitro models. The results suggest that these models can provide quantitative in vitro assessments of chemical formulations such as those prepared by eye-irritating chemicals.

In Vitro Modeling of the Blood–Brain Barrier for the Study of Physiological Conditions and Alzheimer’s Disease

The blood–brain barrier (BBB) is an essential structure for the maintenance of brain homeostasis. Alterations to the BBB are linked with a myriad of pathological conditions and play a significant role in the onset and evolution of neurodegenerative diseases, including Alzheimer’s disease. Thus, a deeper understanding of the BBB’s structure and function is mandatory for a better knowledge of neurodegenerative disorders and the development of effective therapies. Because studying the BBB in vivo imposes overwhelming difficulties, the in vitro approach remains the main possible way of research. With many in vitro BBB models having been developed over the last years, the main aim of this review is to systematically present the most relevant designs used in neurological research. In the first part of the article, the physiological and structural–functional parameters of the human BBB are detailed. Subsequently, available BBB models are presented in a comparative approach, highlighting their advantages and limitations. Finally, the new perspectives related to the study of Alzheimer’s disease with the help of novel devices that mimic the in vivo human BBB milieu gives the paper significant originality.

Bisdemethoxycurcumin (BDC)-Loaded H-Ferritin-Nanocages Mediate the Regulation of Inflammation in Alzheimer's Disease Patients

BACKGROUND

Bisdemethoxycurcumin (BDC) might be an inflammation inhibitor in Alzheimer's Disease (AD). However, BDC is almost insoluble in water, poorly absorbed by the organism, and degrades rapidly. We thus developed a new nanoformulation of BDC based on H-Ferritin nanocages (BDC-HFn).

METHODS

We tested the BDC-HFn solubility, stability, and ability to cross a blood-brain barrier (BBB) model. We tested the effect of BDC-HFn on AD and control (CTR) PBMCs to evaluate the transcriptomic profile by RNA-seq.

RESULTS

We developed a nanoformulation with a diameter of 12 nm to improve the solubility and stability. The comparison of the transcriptomics analyses between AD patients before and after BDC-HFn treatment showed a major number of DEG (2517). The pathway analysis showed that chemokines and macrophages activation differed between AD patients and controls after BDC-HFn treatment. BDC-HFn binds endothelial cells from the cerebral cortex and crosses through a BBB in vitro model.

CONCLUSIONS

Our data showed how BDC-Hfn could improve the stability of BDC. Significant differences in genes associated with inflammation between the same patients before and after BDC-Hfn treatment have been found. Inflammatory genes that are upregulated between AD and CTR after BDC-HFn treatment are converted and downregulated, suggesting a possible therapeutic approach.

Comparative studies between the murine immortalized brain endothelial cell line (bEnd.3) and induced pluripotent stem cell-derived human brain endothelial cells for paracellular transport

Brain microvascular endothelial cells, forming the anatomical site of the blood-brain barrier (BBB), are widely used as in vitro complements to in vivo BBB studies. Among the immortalized cells used as in vitro BBB models, the murine-derived bEnd.3 cells offer culturing consistency and low cost and are well characterized for functional and transport assays, but result in low transendothelial electrical resistance (TEER). Human-induced pluripotent stem cells differentiated into brain microvascular endothelial cells (ihBMECs) have superior barrier properties, but the process of differentiation is time-consuming and can result in mixed endothelial-epithelial gene expression. Here we performed a side-by-side comparison of the ihBMECs and bEnd.3 cells for key paracellular diffusional transport characteristics. The TEER across the ihBMECs was 45- to 68-fold higher than the bEnd.3 monolayer. The ihBMECs had significantly lower tracer permeability than the bEnd.3 cells. Both, however, could discriminate between the paracellular permeabilities of two tracers: sodium fluorescein (MW: 376 Da) and fluorescein isothiocyanate (FITC)-dextran (MW: 70 kDa). FITC-dextran permeability was a strong inverse-correlate of TEER in the bEnd.3 cells, whereas sodium fluorescein permeability was a strong inverse-correlate of TEER in the ihBMECs. Both bEnd.3 cells and ihBMECs showed the typical cobblestone morphology with robust uptake of acetylated LDL and strong immuno-positivity for vWF. Both models showed strong claudin-5 expression, albeit with differences in expression location. We further confirmed the vascular endothelial- (CD31 and tube-like formation) and erythrophagocytic-phenotypes and the response to inflammatory stimuli of ihBMECs. Overall, both bEnd.3 cells and ihBMECs express key brain endothelial phenotypic markers, and despite differential TEER measurements, these in vitro models can discriminate between the passage of different molecular weight tracers. Our results highlight the need to corroborate TEER measurements with different molecular weight tracers and that the bEnd.3 cells may be suitable for large molecule transport studies despite their low TEER.

Porphyromonas gingivalis Induces Proinflammatory Cytokine Expression Leading to Apoptotic Death through the Oxidative Stress/NF-κB Pathway in Brain Endothelial Cells

Porphyromonas gingivalis, a periodontal pathogen, has been proposed to cause blood vessel injury leading to cerebrovascular diseases such as stroke. Brain endothelial cells compose the blood-brain barrier that protects homeostasis of the central nervous system. However, whether P. gingivalis causes the death of endothelial cells and the underlying mechanisms remain unclear. This study aimed to investigate the impact and regulatory mechanisms of P. gingivalis infection in brain endothelial cells. We used bEnd.3 cells and primary mouse endothelial cells to assess the effects of P. gingivalis on endothelial cells. Our results showed that infection with live P. gingivalis, unlike heat-killed P. gingivalis, triggers brain endothelial cell death by inducing cell apoptosis. Moreover, P. gingivalis infection increased intracellular reactive oxygen species (ROS) production, activated NF-κB, and up-regulated the expression of IL-1β and TNF-α. Furthermore, N-acetyl-L-cysteine (NAC), a most frequently used antioxidant, treatment significantly reduced P. gingivalis-induced cell apoptosis and brain endothelial cell death. The enhancement of ROS production, NF-κB p65 activation, and proinflammatory cytokine expression was also attenuated by NAC treatment. The impact of P. gingivalis on brain endothelial cells was also confirmed using adult primary mouse brain endothelial cells (MBECs). In summary, our results showed that P. gingivalis up-regulates IL-1β and TNF-α protein expression, which consequently causes cell death of brain endothelial cells through the ROS/NF-κB pathway. Our results, together with the results of previous case-control studies and epidemiologic reports, strongly support the hypothesis that periodontal infection increases the risk of developing cerebrovascular disease.

Erythrocytes, a New Contributor to Age-Associated Loss of Blood-Brain Barrier Integrity

Blood exchanges between young and old partners demonstrate old blood has a detrimental effect on brain health of young animals. Previous studies primarily investigate soluble blood factors, such as transforming growth factor-beta, on the brain and the blood-brain barrier (BBB). However, the role of blood cellular components, particularly erythrocytes, has not been defined. Erythrocyte morphology and rigidity change as mammals age, altering their transport within the capillary bed. This impacts downstream biological events, such as the release of reactive oxygen species and hemoglobin, potentially compromising the BBB. Here, a micro electrical BBB (µE-BBB), with cocultured endothelial and astrocytic cells, and a built-in trans-endothelial electrical resistance (TEER) system is described to monitor the effect of capillary shear stress on erythrocytes derived from young and old mice and people and the subsequent effects of these cells on BBB integrity. This is monitored by the passage of fluorescein isothiocyanate-dextran and real-time profiling of TEER across the BBB after old and young erythrocyte exposure. Compared to young erythrocytes, old erythrocytes induce an increased permeability by 42% and diminished TEER by 2.9% of the µE-BBB. These results suggest that changes in circulating erythrocytes are a biomarker of aging in the context of BBB integrity.

Clofazimine functionalized polymeric nanoparticles for brain delivery in the tuberculosis treatment

Central nervous system tuberculosis (CNS-TB) is the most severe form of the disease especially due to the inability of therapeutics to cross the blood-brain barrier (BBB). Clofazimine (CFZ) stands out for presenting high in vitro activity against multi-drug resistant strains of Mycobacterium tuberculosis, however, CFZ physicochemical and pharmacokinetics properties limit drug penetration into the CNS and, consequently, its clinical use. The aim of this work was to develop polymeric nanoparticles (NPs) of poly(lactic-co-glycolic acid) (PLGA) and polyethylene glycol (PEG) loaded with CFZ and functionalized with a transferrin receptor (TfR)-binding peptide, aiming brain drug delivery for CNS-TB treatment by the intravenous route. The poor water solubility and high lipophilicity of CFZ was overcome through its entrapment into PLGA-PEG NPs manufactured by both conventional and microfluidic techniques using the nanoprecipitation principle. In vitro studies in brain endothelial hCMEC/D3 cells demonstrated that CFZ incorporation into the NPs was advantageous to reduce drug cytotoxicity. The TfR-binding peptide-functionalized NPs showed superior cell interaction and higher CFZ permeability across hCMEC/D3 cell monolayers compared to the non-functionalized NP control, thus indicating the efficacy of the functionalization strategy on providing CFZ transport through the BBB in vitro. The functionalized NPs demonstrate suitability for CFZ biological administration, suggested with low plasma protein binding, off-target biodistribution and precise delivery of CFZ towards the brain parenchyma.

4-Methoxybenzylalcohol protects brain microvascular endothelial cells against oxygen-glucose deprivation/reperfusion-induced injury via activation of the PI3K/AKT signaling pathway

Damage to the blood-brain barrier (BBB) during the process of cerebral ischemic injury is a key factor that affects the treatment of this condition. The present study aimed to assess the potential effects of 4-methoxybenzyl alcohol (4-MA) on brain microvascular endothelial cells (bEnd.3) against oxygen-glucose deprivation/reperfusion (OGD/Rep) using an in vitro model that mimics in vivo ischemia/reperfusion injury. In addition, the present study aimed to explore whether this underlying mechanism was associated with the inhibition of pro-inflammatory factors and the activation status of the PI3K/Akt signaling pathway. bEnd.3 cells were subjected to OGD/Rep-induced injury before being treated with 4-MA, following which cell viability, lactate dehydrogenase (LDH) release and levels of nitric oxidase (NO) were detected by colorimetry, pro-inflammatory factors including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6, were detected by ELISA. The expression levels of occluding and claudin-5were evaluated by immunofluorescence staining. The expression levels of AKT, phosphorylated (p)-Akt, endothelial nitric oxide synthase (eNOS) and p-eNOS were also measured by western blot analysis. After bEnd.3 cells were subjected to OGD/Rep-induced injury, cell viability and NO levels were significantly decreased, whilst LDH leakage and inflammatory factor (TNF-α, IL-1β and IL-6) levels were significantly increased. Treatment with 4-MA significantly ameliorated cell viability, LDH release and the levels of NO and pro-inflammatory factors TNF-α, IL-1β and IL-6 as a result of OGD/Rep. Furthermore, treatment with 4-MA upregulated the expression of occludin, claudin-5, Akt and eNOS, in addition to increasing eNOS and AKT phosphorylation in bEnd.3 cells. These results suggest that 4-MA can alleviate OGD/Rep-induced injury in bEnd.3 cells by inhibiting inflammation and by activating the PI3K/AKT signaling pathway as a possible mechanism. Therefore, 4-MA can serve as a potential candidate for treating OGD/Rep-induced injury.

Treatment of Alzheimer's Disease and Blood-Brain Barrier Drug Delivery

Despite the enormity of the societal and health burdens caused by Alzheimer's disease (AD), there have been no FDA approvals for new therapeutics for AD since 2003. This profound lack of progress in treatment of AD is due to dual problems, both related to the blood-brain barrier (BBB). First, 98% of small molecule drugs do not cross the BBB, and ~100% of biologic drugs do not cross the BBB, so BBB drug delivery technology is needed in AD drug development. Second, the pharmaceutical industry has not developed BBB drug delivery technology, which would enable industry to invent new therapeutics for AD that actually penetrate into brain parenchyma from blood. In 2020, less than 1% of all AD drug development projects use a BBB drug delivery technology. The pathogenesis of AD involves chronic neuro-inflammation, the progressive deposition of insoluble amyloid-beta or tau aggregates, and neural degeneration. New drugs that both attack these multiple sites in AD, and that have been coupled with BBB drug delivery technology, can lead to new and effective treatments of this serious disorder.

Modeling blood-brain barrier pathology in cerebrovascular disease in vitro: current and future paradigms

The complexity of the blood-brain barrier (BBB) and neurovascular unit (NVU) was and still is a challenge to bridge. A highly selective, restrictive and dynamic barrier, formed at the interface of blood and brain, the BBB is a "gatekeeper" and guardian of brain homeostasis and it also acts as a "sensor" of pathological events in blood and brain. The majority of brain and cerebrovascular pathologies are associated with BBB dysfunction, where changes at the BBB can lead to or support disease development. Thus, an ultimate goal of BBB research is to develop competent and highly translational models to understand mechanisms of BBB/NVU pathology and enable discovery and development of therapeutic strategies to improve vascular health and for the efficient delivery of drugs. This review article focuses on the progress being made to model BBB injury in cerebrovascular diseases in vitro.

Erratum: Puscas, I.; et al. IVIVC Assessment of Two Mouse Brain Endothelial Cell Models for Drug Screening. Pharmaceutics 2019, 11, 587

The authors wish to make the following corrections to this paper [...].