Permeability of the Blood–Brain Barrier (BBB) to Nanoparticles, Bacteria and Phages Studied in BBB Organoids Under Normoxic and Hypoxic Conditions In Vitro

Hypoxia modulates gene expression and affects multiple aspects of endothelial cell biology. Fibulin-5 (FBLN5) is an extracellular matrix protein essential for elastic fiber assembly and vasculogenesis that participates in vascular remodeling and controls endothelial cell adhesion, motility, and proliferation. In this context, we aimed to analyze FBLN5 regulation by hypoxia in endothelial cells. Hypoxia (1% O(2)) increased FBLN5 mRNA levels in endothelial cells in a time-dependent manner. Maximal induction (∼2.5-fold) was achieved after 24 h of hypoxia. This effect paralleled an increase in both intracellular and extracellular FBLN5 protein levels. The increase in FBLN5 mRNA levels observed in hypoxic cells was blocked by inhibitors of the PI3K/Akt/mTOR pathway (LY294002 and rapamycin) and mimicked by dimethyl oxal glycine, which prevents proline hydroxylase-mediated degradation of HIF-1α. Silencing of HIF-1α completely prevented hypoxia-induced FBLN5 up-regulation. Accordingly, both hypoxia and HIF-1α overexpression increased FBLN5 transcriptional activity. Serial promoter deletion and mutagenesis studies revealed the involvement of a putative hypoxia response element (HRE) located at -78 bp. In fact, EMSA and ChIP assays demonstrated increased HIF-1 binding to this site in hypoxic cells. Interestingly, the rate of endothelial cells undergoing apoptosis in cultures exposed to hypoxia increased in FBLN5 knockdown cells, suggesting that hypoxia-induced FBLN5 expression contributes to preserve cell survival. These results provide evidence that HIF-1 signaling underlies the increase of FBLN5 expression elicited by hypoxia in endothelial cells and suggest that FBLN5 induction could be involved in the adaptive survival response of endothelial cells to hypoxia.

Although p53-inactivating mutations have been described in the majority of human cancers, their role in prostate cancer is controversial as mutations are uncommon, particularly in early lesions. p53 is activated by hypoxia and other stressors and is primarily regulated by the Mdm2 protein. Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the conversion of arachidonic acid to prostaglandins and other eicosanoids, is also induced by hypoxia. COX-2 and resultant prostaglandins increase tumor cell proliferation, resistance to apoptosis, and angiogenesis. Previous reports indicate a complex, reciprocal relationship between p53 and COX-2. To elucidate the effects of COX-2 on p53 in response to hypoxia, we transfected the COX-2 gene into the p53-positive, COX-2-negative MDA-PCa-2b human prostate cancer cell line. The expression of functional p53 and Mdm2 was compared in COX-2+ versus COX-2- cells under normoxic and hypoxic conditions. Our results demonstrated that hypoxia increases both COX-2 protein levels and p53 transcriptional activity in these cells. Forced expression of COX-2 increased tumor cell viability and decreased apoptosis in response to hypoxia. COX-2+ cells had increased Mdm2 phosphorylation in either normoxic or hypoxic conditions. Overexpression of COX-2 abrogated hypoxia-induced p53 phosphorylation and promoted the binding of p53 to Mdm2 protein in hypoxic cells. In addition, COX-2-expressing cells exhibited decreased hypoxia-induced nuclear accumulation of p53 protein. Finally, forced expression of COX-2 suppressed both basal and hypoxia-induced p53 transcriptional activity, and this effect was mimicked by the addition of PGE2 to wild-type cells. These results demonstrated a role for COX-2 in the suppression of hypoxia-induced p53 activity via both direct effects and indirect modulation of Mdm2 activity. These data imply that COX-2-positive prostate cancer cells can have impaired p53 function even in the presence of wild-type p53 and that p53 activity can be restored in these cells via inhibition of COX-2 activity.

The blood brain barrier (BBB) has evolved unique characteristics such as dense coverage of the endothelial cells by pericytes and interactions with astrocytes through perivascular endfeet. We study BBB formation in a 3-dimensional multicellular spheroid system of human primary brain endothelial cells (hpBECs), primary pericytes (hpPs) and primary astrocytes (hpAs). We show for the first time that hpBECs, hpPs and hpAs spontaneously self-organize into a defined multicellular structure which recapitulates the complex arrangement of the individual cell types in the BBB structure. Pericytes play a crucial role mediating the interaction between hpBECs and hpAs. This process is not dependent on a scaffold support demonstrating that formation and cellular architecture of the BBB is intrinsically programmed within each specific cell type. In a matrigel setup the hpBECs, hpPs and hpAs also undergo self-arrangement to form endothelial tube-like structures tightly covered by hpPs and loosely attached hpAs mainly at the junctions.

Testing of a hypothesis for osmotic opening of the blood-brain barrier.

Hypoxia-inducible factor 1 alpha (HIF1alpha) and its related factor, HLF, activate expression of a group of genes such as erythropoietin in response to low oxygen. Transfection analysis using fusion genes of GAL4DBD with various fragments of the two factors delineated two transcription activation domains which are inducible in response to hypoxia and are localized in the C-terminal half. Their sequences are conserved between HLF and HIF1alpha. One is designated NAD (N-terminal activation domain), while the other is CAD (C-terminal activation domain). Immunoblot analysis revealed that NADs, which were rarely detectable at normoxia, became stabilized and accumulated at hypoxia, whereas CADs were constitutively expressed. In the mammalian two-hybrid system, CAD and NAD baits enhanced the luciferase expression from a reporter gene by co-transfection with CREB-binding protein (CBP) prey, whereas CAD, but not NAD, enhanced beta-galactosidase expression in yeast by CBP co-expression, suggesting that NAD and CAD interact with CBP/p300 by a different mechanism. Co-transfection experiments revealed that expression of Ref-1 and thioredoxin further enhanced the luciferase activity expressed by CAD, but not by NAD. Amino acid replacement in the sequences of CADs revealed a specific cysteine to be essential for their hypoxia-inducible interaction with CBP. Nuclear translocation of thioredoxin from cytoplasm was observed upon reducing O2 concentrations.

Cell-type specific differences in antiretroviral penetration and the effects of HIV-1 Tat and morphine among primary human brain endothelial cells, astrocytes, pericytes, and microglia

Construction of a novel blood brain barrier-glioma microfluidic chip model: Applications in the evaluation of permeability and anti-glioma activity of traditional Chinese medicine components

Blood brain barrier (BBB) cells play key roles in the physiology and pathology of the central nervous system (CNS). BBB dysfunction is implicated in many neurodegenerative diseases, including Alzheimer’s disease (AD). The BBB consists of capillary endothelial cells, pericytes encircling the endothelium and surrounding astrocytes extending their processes towards it. Although there have been many attempts to develop in vitro BBB models, the complex interaction between these cell types makes it extremely difficult to determine their individual contribution to neurotoxicity in vivo. Thus, we developed and optimised an in vitro multicellular co-culture model within the Kirkstall Quasi Vivo System. The main aim was to determine the optimal environment to culture human brain primary endothelial cells, pericytes and astrocytes whilst maintaining cellular communication without formation of a barrier in order to assess the contribution of each cell type to the overall response. As a proof of concept for the present system, the effects of amyloid-beta 25-35 peptide (Aβ25-35), a hallmark of AD, were explored. This multicellular system will be a valuable tool for future studies on the specific roles of individual BBB cell type (while making connection with each other through medium) in CNS disorders as well as in cytotoxicity tests.

Constructing areliable in vitro blood-brain barrier (BBB) model using human primary cells has been considered a major challenge during the past decades. These systems could provide valuable information regarding the effect of therapeutic compounds on different BBB cell types (endothelial cells, astrocytes, pericytes) and their ability to cross the barrier in order to reach the brain. Several attempts have been made to develop in vitro BBB models, but these studies mainly used rat, bovine, and porcine cells rather than human primary cells. Genetically modified cell lines have also been used, but they do not appear to maintain physiological properties of the BBB. Here, we describe a detailed protocol for co-culturing and maintaining human brain primary endothelial cells, pericytes, and astrocytes under flow to create an in vitro human BBB model, which can be used for toxicity testing and for studying cross-interaction among different cell types involved in the BBB formation.

Objective To investigate the effect of chimeric promoter composed of hypoxia response element (HRE) and tumor specific cell proliferation-associated nuclear antigen (Ki-67) promoter on the replication ability of oncolytic adenovirus and its cytotoxic activity under hypoxic conditions. Methods The HRE sequence, as an enhancer, was inserted upstream of the Ki-67 promoter and, at the same time carried the reporter gene enhanced green fluorescent protein (EGFP) to construct oncolytic adenovirus Ad-HRE-Ki-67-EGFP, and the titer of adenoviruses was measured by the tissue culture infective dose (TCID50). Normal renal epithelial cells HK-2 and renal cancer cells OSRC-2 and ACHN were infected with two kinds of viruses under normoxic (21% O2) or hypoxic (1% O2) conditions respectively for 24 h, and the virus tumor-targeting was detected by fluorescence microscopy and flow cytometry. Western blotting was performed to detect the expression of hypoxia-related protein hypoxia-inducible factor-1 alpha (HIF-1α), vascular endothelial growth factor (VEGF) and the expression of E1A protein. Cell counting kit-8 (CCK-8) assay was used to detect the cytotoxity of virus on cells. Results The recombinant oncolytic virus Ad-HRE-Ki67-EGFP was successfully constructed. Under normoxic conditions, the efficiency of ACHN and OSRC-2 infection by chimeric HRE oncolytic adenovirus in renal cancer cells was (47.5±2.6)% and (35.2±3.4)%, while that in hypoxic conditions was (86.4±3.4)% and (73.5±2.3)%, indicating that the infection efficiency was higher under hypoxic conditions (ACHN: t=15.760; OSRC-2: t=16.190; P<0.01); Normal renal tubular epithelial cells HK-2 were infected with Ad-Ki-67-EGFP or Ad-HRE-Ki-67-EGFP under normoxic conditions. The infection efficiency was (22.4±3.1)% and (22.9±2.2)% respectively, compared with that of ACHN and OSRC-2 cells [ACHN: (68.4±3.3)% and (72.1±2.9)%; OSRC-2: (56.1±3.1)% and (61.4±2.3)%], the difference was statistically significant (Ad-Ki-67-EGFP: t=17.650, 13.390; Ad-HRE-Ki-67-EGFP: t=23.680, 21.430, P<0.01), indicating that the two adenoviruses have a targeting effect on renal cancer cells. Western blotting data showed that the expression of HIF-1α, VEGF and p53 protein were increased under hypoxic conditions and was time-dependent, indicating that hypoxia can regulate the transcription and translation of HIF-1α, VEGF and p53 proteins. Under hypoxic conditions, the expression level of E1A protein in OSRC-2 and ACHN infected with Ad-HRE-Ki67-EGFP was significantly higher than that after Ad-Ki67-EGFP infection. It indicated that HRE can enhance the replication ability of virus under hypoxic conditions. CCK-8 results showed that when the multiple infection (MOI) values were 20, 100, the survival rate of the Ad-HRE-Ki-67-EGFP-normoxia virus group in ACHN and OSRC-2 cells was (73.4±2.0)%, (56.4±1.5)% and (79.9±1.8)%, (61.3±2.7)%, the Ad-HRE-Ki-67-EGFP-hypoxia virus group was (63.1±2.0)%, (31.6±2.1)% and (68.1±2.6)%, (35.8±3.1)%, the Ad-HRE-Ki-67-EGFP-hypoxia virus group showed a stronger proliferation inhibitory effect [MOI (20): t=6.328, 6.441; MOI (100): t=16.410, 10.790, P<0.01]. Conclusion Under hypoxic conditions, chimeric HRE sequence recombinant oncolytic adenovirus has stronger replication ability and cell killing effect in renal carcinoma cells. Key words: Renal cell carcinoma; Oncolytic adenovirus; Hypoxia response element; Hypoxia

Streptococcus pyogenes expresses the LPXTG motif-containing cell envelope serine protease SpyCep (also called ScpC, PrtS) that degrades and inactivates the major chemoattractant interleukin 8 (IL-8), thereby impairing host neutrophil recruitment. In this study, we identified a novel function of SpyCep: the ability to mediate uptake into primary human endothelial cells. SpyCep triggered its uptake into endothelial cells but not into human epithelial cells originating from pharynx or lung, indicating an endothelial cell-specific uptake mechanism. SpyCep mediated cellular invasion by an endosomal/lysosomal pathway distinct from the caveolae-mediated invasion pathway of S. pyogenes. Recombinant expression and purification of proteolytically active SpyCep and a series of subfragments allowed functional dissection of the domains responsible for endothelial cell invasion and IL-8 degradation. The N-terminal PR domain was sufficient to mediate endothelial cell invasion, whereas for IL-8-degrading activity, the protease domain and the flanking A domain were required. A polyclonal rabbit serum raised against the recombinant protease efficiently blocked the invasion-mediating activity of SpyCep but not its proteolytic function, further indicating that SpyCep-mediated internalization is independent from its enzymatic activity. SpyCep may thus specifically mediate its own uptake as secreted protein into human endothelial cells.

Stroke is one of the leading causes of adult disability throughout the world and, even though neural mechanisms of loss of function have been extensively studied, many aspects of poststroke cerebral responses remain poorly understood. Of particular interest is the mounting evidence of the capacity of the adult brain to reorganize after injury, which is believed to contribute to limitation of the extent of neural dysfunction and to restoration of affected neural functions. Processes such as neuronal plasticity, glial proliferation, and neovascularization may be essential for preservation or recovery of function after stroke and may conceivably go hand-in-hand at nearby and remote sites of active tissue reorganization.1,2 Specifically, the acute initiation of neurovascular remodeling, stimulating the proliferation and growth of existing arteries/arterioles (ie, arteriogenesis) or new capillaries (ie, angiogenesis), may be critical to facilitate the survival and restructuring of neural tissue, which ultimately may contribute to functional recovery at later stages.3 A variety of vascular imaging strategies is available for in vivo detection, characterization, and quantification of these processes, which can significantly aid in elucidation of the role of neurovascular remodeling after stroke, as discussed in this review. Because most of the described imaging modalities are present in experimental and clinical settings, this raises significant opportunities for translational studies. Growth and remodeling of existing and nascent vascular networks in health and disease involve a number of critical steps that have been comprehensively described by Risau4 and Carmeliet.5 Arteriogenesis involves adaptive growth and proliferation of preexisting (collateral) arteries and arterioles in response to increase in intravascular shear forces. The increased shear stress leads to upregulation of cell adhesion molecules, followed by accumulation of monocytes and other leukocytes that release cytokines and growth factors around the proliferating and maturating arteries.6 Although arteriogenic growth of collateral …

In vitro blood–brain barrier permeability and cerebral endothelial cell uptake of the neuroprotective nitrone compound NXY-059 in normoxic, hypoxic and ischemic conditions

2023 TERMIS – AMERICAS Conference &amp; Exhibition Boston Marriott Copley Place April 11–14, 2023

Photoinduced Carbene for Effective Photodynamic Therapy Against Hypoxic Cancer Cells