The blood-brain barrier (BBB) is a selective barrier and a functional gatekeeper for the central nervous system (CNS), essential for maintaining brain homeostasis. The BBB is composed of specialized ...brain endothelial cells (BECs) lining the brain capillaries. The tight junctions formed by BECs regulate paracellular transport, whereas transcellular transport is regulated by specialized transporters, pumps and receptors. Cytokine-induced neuroinflammation, such as the tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), appear to play a role in BBB dysfunction and contribute to the progression of Alzheimer’s disease (AD) by contributing to amyloid-β (Aβ) peptide accumulation. Here, we investigated whether TNF-α and IL-1β modulate the permeability of the BBB and alter Aβ peptide transport across BECs. We used a human BBB in vitro model based on the use of brain-like endothelial cells (BLECs) obtained from endothelial cells derived from CD34+ stem cells cocultivated with brain pericytes. We demonstrated that TNF-α and IL-1β differentially induced changes in BLECs’ permeability by inducing alterations in the organization of junctional complexes as well as in transcelluar trafficking. Further, TNF-α and IL-1β act directly on BLECs by decreasing LRP1 and BCRP protein expression as well as the specific efflux of Aβ peptide. These results provide mechanisms by which CNS inflammation might modulate BBB permeability and promote Aβ peptide accumulation. A future therapeutic intervention targeting vascular inflammation at the BBB may have the therapeutic potential to slow down the progression of AD.
Cardiovascular diseases, like atherosclerosis, and neurodegenerative diseases affecting the central nervous system (CNS) are closely linked to alterations of cholesterol metabolism. Therefore, ...innovative pharmacological approaches aiming at counteracting cholesterol imbalance display promising therapeutic potential. However, these approaches need to take into account the existence of biological barriers such as intestinal and blood-brain barriers which participate in the organ homeostasis and are major defense systems against xenobiotics. Interest in cyclodextrins (CDs) as medicinal agents has increased continuously based on their ability to actively extract lipids from cell membranes and to provide suitable carrier system for drug delivery. Many novel CD derivatives are constantly generated with the objective to improve CD bioavailability, biocompatibility and therapeutic outcomes. Newly designed drug formulation complexes incorporating CDs as drug carriers have demonstrated better efficiency in treating cardiovascular and neurodegenerative diseases. CD-based therapies as cholesterol-sequestrating agent have recently demonstrated promising advances with KLEPTOSE
CRYSMEB in atherosclerosis as well as with the 2-hydroxypropyl-β-cyclodextrin (HPβCD) in clinical trials for Niemann-Pick type C disease. Based on this success, many investigations evaluating the therapeutical beneficial of CDs in Alzheimer's, Parkinson's and Huntington's diseases are currently on-going.
Bearing grafts based on fatty esters derivatives, lipidyl-cyclodextrins (L-CDs) are compounds able to form water-soluble nano-objects. In this context, bicatenary biobased lipidic-cyclodextrins of ...low DS were easily synthesized from a fatty ester epoxide by means of alternative methods (ball-milling conditions, use of enzymes). The ring opening reaction of methyl oleate epoxide needs ball-milling and is highly specific of cyclodextrins in solventless conditions. L-CDs are thus composed of complex mixtures that were deciphered by an extensive structural analysis using mainly mass spectrometry and NMR spectroscopy. In addition, as part of their potential use as vectors of active drugs, these products were submitted to an integrity study on in vitro model of the blood-brain-barrier (BBB) and the intestinal epithelium. No toxicity has been observed, suggesting that applications for the vectorization of active ingredients can be expected.
Abstract Brain is the most cholesterol rich organ of the whole body and recent studies suggest a role for the blood–brain barrier (BBB) in cerebral cholesterol homeostasis. Low density lipoprotein ...receptor (LDLR)-related receptors and ATP-binding Cassette (ABC) transporters play an important role in peripheral sterol homeostasis. The purpose of this study was to determine the mRNA expression profiles of ABC transporters (ABCA1, 2, 3, 7 and ABCG1) and low density lipoprotein receptor (LDLR)-related receptors (LDLR, vLDLR, LRP1, LRP2 and LRP8) in BBB endothelium using an in vitro co-culture model of bovine brain capillary endothelial cells (BCECs) and rat glial cells. All transcripts tested are expressed by BCECs and in capillary extract, except vLDLR. Glial cells influence ABCG1, A1, 2, 7 and LRP1 transcription, suggesting a role in cerebral lipid supply/elimination through the modulation of the expression of these transporters and receptors by these cells. Altogether, these results highlight the importance of glial input in the BBB transport phenotype for sterol homeostasis in the central nervous system, and confirm the importance of the BBB in this process.
That promising neuroprotectants failed to demonstrate benefit against stroke highlights the great difficulties to translate preclinical pharmacological effects in clinical outcomes. Part of this ...hurdle implies the complex response to injury of the neurovascular unit increasing the cerebrovascular permeability at the level of the blood-brain barrier (BBB). Previous studies reported neuroprotection in animal models upon activation of the nuclear receptor PPARalpha(peroxisome proliferator-activated receptor)alpha, but the cellular targets at the BBB level remain largely unexplored. Here, to study whether PPAR-alpha activation acts on BBB permeability, we adapted a mouse BBB cell model to ischaemic conditions at the stage of occlusion defined in vitro as oxygen-glucose deprivation (OGD). This model consists of a co-culture of brain capillary endothelial cells (ECs) on a filter insert placed upon a rat glial cell culture. The EC monolayer permeability increase induced by 4 h of OGD was significantly restricted after treatment with the PPAR-alpha agonist fenofibric acid (FA) 24 h before or at the onset of OGD. Treatments of separated ECs or glial cells showed that this protective effect was conferred by BBB ECs but not glial cells. Furthermore, co-cultures with ECs from PPAR-alpha-deficient mice revealed that FA had no effect on OGD-induced hyperpermeability. No transcriptional modulation of classical PPAR-alpha target genes such as SOD, ICAM-1, VCAM-1, ACO, CPT-1, PDK-4 or ET-1 was observed in wild type mouse ECs. In conclusion, these results suggest that part of the preventive PPAR-alpha-mediated protection may occur via BBB ECs by limiting hyperpermeability.
Abstract NXY-059, a polar compound with limited transport across the blood-brain barrier, has demonstrated neuroprotection in several animal models of acute ischemic stroke but failed to confirm ...clinical benefit in the second phase III trial (SAINT-II). To improve the understanding of the mechanisms responsible for its neuroprotective action in preclinical models a series of experiments was carried out in an in vitro blood-brain barrier (BBB) model. A clinically attainable concentration of 250 μmol/L of NXY-059 administered at the onset or up to 4 h after oxygen glucose deprivation (OGD) produced a significant reduction in the increased BBB permeability caused by OGD. Furthermore, OGD produced a huge influx of tissue plasminogen activator across the BBB, which was substantially reduced by NXY-059. This study suggests that the neuroprotective effects of NXY-059 preclinically, may at least in part be attributed to its ability to restore functionality of the brain endothelium.
Although an immense knowledge has accumulated concerning regulation of cholesterol homeostasis in the body, this does not include the brain, where details are just emerging. Using an in vitro ...blood-brain barrier model, the authors have demonstrated that low-density lipoprotein (LDL) underwent transcytosis through the endothelial cells (ECs) by a receptor-mediated process, bypassing the lysosomal compartment. Moreover, caveolae might be involved in these blood-borne molecule transports from the blood to the brain. Although several ligands are known to be internalized through cell surface caveolae, the subsequent intracellular pathways have remained elusive. By cell fractionation experiment and Western blot, the authors have demonstrated that the LDL receptor is located in the caveolae membrane fraction. Then, LDLs internalized were detected by electron microscopy in multivesicular bodies. The authors identified in brain capillary ECs a novel endosomal compartment, mildly acidic, positive for marker Lamp-1 but devoid of any degradative capability. From the point of view of pH, cellular location, and caveolae-derived formation, the multivesicular organelles described here can be related to the caveosome structure. These results could provide clues to physiological functions of caveolae-caveosome transcellular pathway in brain capillary ECs and may help in the rational design of more effective therapeutic drugs to the brain.
Atherosclerosis is an inflammatory disease that leads to an aberrant accumulation of cholesterol in vessel walls forming atherosclerotic plaques. During this process, the mechanism regulating complex ...cellular cholesterol pools defined as the reverse cholesterol transport (RCT) is altered as well as expression and functionality of transporters involved in this process, namely ABCA1, ABCG1, and SR-BI. Macrophages, arterial endothelial and smooth muscle cells (SMCs) have been involved in the atherosclerotic plaque formation. As macrophages are widely described as the major cell type forming the foam cells by accumulating intracellular cholesterol, RCT alterations have been poorly studied at the arterial endothelial cell and SMC levels. Amongst the therapeutics tested to actively counteract cellular cholesterol accumulation, the methylated β-cyclodextrin, KLEPTOSE® CRYSMEβ, has recently shown promising effects on decreasing the atherosclerotic plaque size in atherosclerotic mouse models. Therefore we investigated in vitro the RCT process occurring in SMCs and in arterial endothelial cells (ABAE) as well as the ability of some modified β-CDs with different methylation degree to modify RCT in these cells. To this aim, cells were incubated in the presence of different methylated β-CDs, including KLEPTOSE® CRYSMEβ. Both cell types were shown to express basal levels of ABCA1 and SR-BI whereas ABCG1 was solely found in ABAE. Upon CD treatments, the percentage of membrane-extracted cholesterol correlated to the methylation degree of the CDs independently of the lipid composition of the cell membranes. Decreasing the cellular cholesterol content with CDs led to reduce the expression levels of ABCA1 and ABCG1. In addition, the cholesterol efflux to ApoA-I and HDL particles was significantly decreased suggesting that cells forming the blood vessel wall are able to counteract the CD-induced loss of cholesterol. Taken together, our observations suggest that methylated β-CDs can significantly reduce the cellular cholesterol content of cells forming atherosclerotic lesions and can subsequently modulate the expression of ABC transporters involved in RCT. The use of methylated β-CDs would represent a valuable and efficient tool to interfere with atherosclerosis pathogenesis in patients, nonetheless their mode of action still needs further investigations to be fully understood and finely controlled at the cellular level.
Cyclodextrins (CDs) can be envisaged to cure some diseases related to the brain, but the behavior of these compounds toward the blood-brain barrier (BBB) remains largely unexplored to envisage such ...clinical applications. To fulfill this gap, the toxicity and endothelial permeability for native, methylated, and hydroxypropylated alpha-, beta-, and gamma-CDs have been studied on an in vitro model of BBB. As shown by the endothelial permeability for sucrose and immunofluorescence stainings, the native CDs are the most toxic CDs (alpha- > beta- > gamma-CD). Whereas the chemical modification of beta-CD did not affect the toxicity of this CD, differences are observed for the alpha- and gamma-CD. To determine the origin of toxicity, lipid effluxes on the brain capillary endothelial cells were performed in the presence of native CDs. It was found that alpha-CD removed phospholipids and that beta-CD extracted phospholipids and cholesterol. gamma-CD was less lipid-selective than the other CDs. Finally, the endothelial permeability of each CD has been determined. Surprisingly, no structure/permeability relationship has been observed according to the nature and chemical modifications of CDs.
Methylated β-cyclodextrins (CDs) are used to increase the brain delivery of doxorubicin (DOX) by modifying the P-gp activity.
Co-incubations of various β-cyclodextrins and doxorubicin have been ...evaluated on an in vitro model of blood–brain barrier in order to increase the delivery of this P-gp substrate to the brain. Among these cyclodextrins used, the Rame-β-cyclodextrin and Crysme-β-cyclodextrin increased the transport by a factor of 2 and 3.7, respectively. This increase was attributed to the cholesterol extraction property of these cyclodextrins from brain capillary endothelial cells leading to a modulation of the P-gp activity.
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