Escherichia coli K1 RS218 Interacts with Human Brain Microvascular Endothelial Cells via Type 1 Fimbria Bacteria in the Fimbriated State

Escherichia coli K1 is a major gram-negative organism causing neonatal meningitis. E. coli K1 binding to and invasion of human brain microvascular endothelial cells (HBMEC) are a prerequisite for E. coli penetration into the central nervous system in vivo. In the present study, we showed using DNA microarray analysis that E. coli K1 associated with HBMEC expressed significantly higher levels of the fim genes compared to nonassociated bacteria. We also showed that E. coli K1 binding to and invasion of HBMEC were significantly decreased with its fimH deletion mutant and type 1 fimbria locked-off mutant, while they were significantly increased with its type 1 fimbria locked-on mutant. E. coli K1 strains associated with HBMEC were predominantly type 1 fimbria phase-on (i.e., fimbriated) bacteria. Taken together, we showed for the first time that type 1 fimbriae play an important role in E. coli K1 binding to and invasion of HBMEC and that type 1 fimbria phase-on E. coli is the major population interacting with HBMEC

Evaluation of soluble junctional adhesion molecule-A as a biomarker of human brain endothelial barrier breakdown

Background: An inducible release of soluble junctional adhesion molecule-A (sJAM-A) under pro-inflammatory conditions was described in cultured non-CNS endothelial cells (EC) and increased sJAM-A serum levels were found to indicate inflammation in non-CNS vascular beds. Here we studied the regulation of JAM-A expression in cultured brain EC and evaluated sJAM-A as a serum biomarker of blood-brain barrier (BBB) function. Methodology/Principal Findings: As previously reported in non-CNS EC types, pro-inflammatory stimulation of primary or immortalized (hCMEC/D3) human brain microvascular EC (HBMEC) induced a redistribution of cell-bound JAM-A on the cell surface away from tight junctions, along with a dissociation from the cytoskeleton. This was paralleled by reduced immunocytochemical staining of occludin and zonula occludens-1 as well as by increased paracellular permeability for dextran 3000. Both a self-developed ELISA test and Western blot analysis detected a constitutive sJAM-A release by HBMEC into culture supernatants, which importantly was unaffected by pro-inflammatory or hypoxia/reoxygenation challenge. Accordingly, serum levels of sJAM-A were unaltered in 14 patients with clinically active multiple sclerosis compared to 45 stable patients and remained unchanged in 13 patients with acute ischemic non-small vessel stroke over time. Conclusion: Soluble JAM-A was not suited as a biomarker of BBB breakdown in our hands. The unexpected non-inducibility of sJAM-A release at the human BBB might contribute to a particular resistance of brain EC to inflammatory stimuli, protecting the CNS compartment

PECAM-1 engagement counteracts ICAM-1-induced signaling in brain vascular endothelial cells

Interactions between leukocytes and vascular endothelial cells are mediated by a complex set of membrane adhesion molecules which transduce bi-directional signals in both cell types. Endothelium of the cerebral blood vessels, which constitute the blood–brain barrier, strictly controls adhesion and trafficking of leukocytes into the brain. Investigating signaling pathways triggered by the engagement of adhesion molecules expressed on brain endothelial cells, we previously documented the role of ICAM-1 in activation of the tyrosine phosphorylation of several actin-binding proteins and subsequent rearrangements of the actin cytoskeleton. In the present study, we show that, whereas PECAM-1 is known to control positively the trans-endothelial migration of leukocytes via homophilic interactions between leukocytes and endothelial cells, PECAM-1 engagement on brain endothelial surface unexpectedly counteracts the ICAM-1-induced tyrosine phosphorylation of cortactin and rearrangements of the actin cytoskeleton. We present evidence that the PECAM-1-associated tyrosine phosphatase SHP-2 is required for ICAM-1 signaling, suggesting that its activity might crucially contribute to the regulation of ICAM-1 signaling by PECAM-1. Our findings reveal a novel activity for PECAM-1 which, by counteracting ICAM-1-induced activation, could directly contribute to limit activation and maintain integrity of brain vascular endothelium

Acanthamoeba induces cell-cycle arrest in host cells

Acanthamoeba can cause fatal granulomatous amoebic encephalitis (GAE) and eye keratitis. However, the pathogenesis and pathophysiology of these emerging diseases remain unclear. In this study, the effects of Acanthamoeba on the host cell cycle using human brain microvascular endothelial cells (HBMEC) and human corneal epithelial cells (HCEC) were determined. Two isolates of Acanthamoeba belonging to the T1 genotype (GAE isolate) and T4 genotype (keratitis isolate) were used, which showed severe cytotoxicity on HBMEC and HCEC, respectively. No tissue specificity was observed in their ability to exhibit binding to the host cells. To determine the effects of Acanthamoeba on the host cell cycle, a cell-cycle-specific gene array was used. This screened for 96 genes specific for host cell-cycle regulation. It was observed that Acanthamoeba inhibited expression of genes encoding cyclins F and G1 and cyclin-dependent kinase 6, which are proteins important for cell-cycle progression. Moreover, upregulation was observed of the expression of genes such as GADD45A and p130 Rb, associated with cell-cycle arrest, indicating cell-cycle inhibition. Next, the effect of Acanthamoeba on retinoblastoma protein (pRb) phosphorylation was determined. pRb is a potent inhibitor of G1-to-S cell-cycle progression; however, its function is inhibited upon phosphorylation, allowing progression into S phase. Western blotting revealed that Acanthamoeba abolished pRb phosphorylation leading to cell-cycle arrest at the G1-to-S transition. Taken together, these studies demonstrated for the first time that Acanthamoeba inhibits the host cell cycle at the transcriptional level, as well as by modulating pRb phosphorylation using host cell-signalling mechanisms. A complete understanding of Acanthamoeba–host cell interactions may help in developing novel strategies to treat Acanthamoeba infections

Talin1 Promotes Prostate Cancer Invasion and Metastasis via AKT Signaling and Anoikis Resistance

Talin1 is an integrin regulatory protein that mediates integrin interactions with the extracellular matrix (ECM). This study investigated the significance of talin1 in prostate cancer progression to metastasis in vitro and in vivo. Talin1 overexpression enhanced prostate cancer cell adhesion, migration and invasion by activating survival signals and anoikis resistance. ShRNA-mediated talin1 loss led to a significant suppression of prostate cancer cell migration and transendothelial invasion in vitro and a significant inhibition of prostate cancer metastasis in vivo. Talin1 regulates cell survival signals via phosphorylation of focal adhesion kinase (FAK) and AKT. Targeting AKT activation led to a significant reduction of talin1-mediated prostate cancer cell invasion. Furthermore, talin1 expression was determined by immunostaining in prostate tissue from the TRAMP mouse model and in human prostate cancer specimens. Talin1 levels directly correlated with prostate tumor progression to metastasis in TRAMP mice. Talin1 profiling in human prostate specimens revealed a significantly higher expression of cytoplasmic talin1 in metastatic tissue compared to primary prostate tumors and benign prostate tissue (P<0.0001). This evidence suggests a potential value for talin1 as a marker of prostate cancer metastasis and implies that disrupting talin1 mediated signaling may have therapeutic significance in the treatment of metastatic disease

Post-mortem culture of Balamuthia mandrillaris from the brain and cerebrospinal fluid of a case of granulomatous amoebic meningoencephalitis, using human brain microvascular endothelial cells

The first isolation in the UK of Balamuthia mandrillaris amoebae from a fatal case of granulomatous amoebic meningoencephalitis is reported. Using primary cultures of human brain microvascular endothelial cells (HBMECs), amoebae were isolated from the brain and cerebrospinal fluid (CSF). The cultures showed a cytopathic effect at 20–28 days, but morphologically identifiable B. mandrillaris amoebae were seen in cleared plaques in subcultures at 45 days. The identification of the organism was later confirmed using PCR on Chelex-treated extracts. Serum taken while the patient was still alive reacted strongly with slide antigen prepared from cultures of the post-mortem isolate, and also with those from a baboon B. mandrillaris strain at 1 : 10 000 in indirect immunofluorescence, but with Acanthamoeba castellanii (Neff) at 1 : 160, supporting B. mandrillaris to be the causative agent. If the presence of amoebae in the post-mortem CSF reflects the condition in life, PCR studies on CSF and on biopsies of cutaneous lesions may also be a valuable tool. The role of HBMECs in understanding the interactions of B. mandrillaris with the blood–brain barrier is discussed

Acanthamoeba castellanii induces host cell death via a phosphatidylinositol 3-kinase-dependent mechanism

Granulomatous amoebic encephalitis due to Acanthamoeba castellanii is a serious human infection with fatal consequences, but it is not clear how the circulating amoebae interact with the blood-brain barrier and transmigrate into the central nervous system. We studied the effects of an Acanthamoeba encephalitis isolate belonging to the T1 genotype on human brain microvascular endothelial cells, which constitute the blood-brain barrier. Using an apoptosis-specific enzyme-linked immunosorbent assay, we showed that Acanthamoeba induces programmed cell death in brain microvascular endothelial cells. Next, we observed that Acanthamoeba specifically activates phosphatidylinositol 3-kinase. Acanthamoeba-mediated brain endothelial cell death was abolished using LY294002, a phosphatidylinositol 3-kinase inhibitor. These results were further confirmed using brain microvascular endothelial cells expressing dominant negative forms of phosphatidylinositol 3-kinase. This is the first demonstration that Acanthamoeba-mediated brain microvascular endothelial cell death is dependent on phosphatidylinositol 3-kinase

Experimental Validation of the Predicted Binding Site of Escherichia coli K1 Outer Membrane Protein A to Human Brain Microvascular Endothelial Cells: Identification of Critical Mutations That Prevent E. coli Meningitis

Escherichia coli K1, the most common cause of meningitis in neonates, has been shown to interact with GlcNAc1–4GlcNAc epitopes of Ecgp96 on human brain microvascular endothelial cells (HBMECs) via OmpA (outer membrane protein A). However, the precise domains of extracellular loops of OmpA interacting with the chitobiose epitopes have not been elucidated. We report the loop-barrel model of these OmpA interactions with the carbohydrate moieties of Ecgp96 predicted from molecular modeling. To test this model experimentally, we generated E. coli K1 strains expressing OmpA with mutations of residues predicted to be critical for interaction with the HBMEC and tested E. coli invasion efficiency. For these same mutations, we predicted the interaction free energies (including explicit calculation of the entropy) from molecular dynamics (MD), finding excellent correlation (R^2 = 90%) with experimental invasion efficiency. Particularly important is that mutating specific residues in loops 1, 2, and 4 to alanines resulted in significant inhibition of E. coli K1 invasion in HBMECs, which is consistent with the complete lack of binding found in the MD simulations for these two cases. These studies suggest that inhibition of the interactions of these residues of Loop 1, 2, and 4 with Ecgp96 could provide a therapeutic strategy to prevent neonatal meningitis due to E. coli K1

Phylogenetic Analysis of Cell Types using Histone Modifications

In cell differentiation, a cell of a less specialized type becomes one of a more specialized type, even though all cells have the same genome. Transcription factors and epigenetic marks like histone modifications can play a significant role in the differentiation process. In this paper, we present a simple analysis of cell types and differentiation paths using phylogenetic inference based on ChIP-Seq histone modification data. We propose new data representation techniques and new distance measures for ChIP-Seq data and use these together with standard phylogenetic inference methods to build biologically meaningful trees that indicate how diverse types of cells are related. We demonstrate our approach on H3K4me3 and H3K27me3 data for 37 and 13 types of cells respectively, using the dataset to explore various issues surrounding replicate data, variability between cells of the same type, and robustness. The promising results we obtain point the way to a new approach to the study of cell differentiation.Comment: Peer-reviewed and presented as part of the 13th Workshop on Algorithms in Bioinformatics (WABI2013

Comparative study of four immortalised human brain capillary endothelial cell lines, hCMEC/D3, hBMED, TY10, and BB19, and optimization of culture conditions, for an in vitro blood-brain barrier model for drug permeability studies

BACKGROUND: Reliable human in vitro blood–brain barrier (BBB) models suitable for high-throughput screening are urgently needed in early drug discovery and development for assessing the ability of promising bioactive compounds to overcome the BBB. To establish an improved human in vitro BBB model, we compared four currently available and well characterized immortalized human brain capillary endothelial cell lines, hCMEC/D3, hBMEC, TY10, and BB19, with respect to barrier tightness and paracellular permeability. Co-culture systems using immortalized human astrocytes (SVG-A cell line) and immortalized human pericytes (HBPCT cell line) were designed with the aim of positively influencing barrier tightness. METHODS: Tight junction (TJ) formation was assessed by transendothelial electrical resistance (TEER) measurements using a conventional epithelial voltohmmeter (EVOM) and an automated CellZscope system which records TEER and cell layer capacitance (C(CL)) in real-time. Paracellular permeability was assessed using two fluorescent marker compounds with low BBB penetration (sodium fluorescein (Na-F) and lucifer yellow (LY)). Conditions were optimized for each endothelial cell line by screening a series of 24-well tissue culture inserts from different providers. For hBMEC cells, further optimization was carried out by varying coating material, coating procedure, cell seeding density, and growth media composition. Biochemical characterization of cell type-specific transmembrane adherens junction protein VE-cadherin and of TJ proteins ZO-1 and claudin-5 were carried out for each endothelial cell line. In addition, immunostaining for ZO-1 in hBMEC cell line was performed. RESULTS: The four cell lines all expressed the endothelial cell type-specific adherens junction protein VE-cadherin. The TJ protein ZO-1 was expressed in hCMEC/D3 and in hBMEC cells. ZO-1 expression could be confirmed in hBMEC cells by immunocytochemical staining. Claudin-5 expression was detected in hCMEC/D3, TY10, and at a very low level in hBMEC cells. Highest TEER values and lowest paracellular permeability for Na-F and LY were obtained with mono-cultures of hBMEC cell line when cultivated on 24-well tissue culture inserts from Greiner Bio-one® (transparent PET membrane, 3.0 μm pore size). In co-culture models with SVG-A and HBPCT cells, no increase of TEER could be observed, suggesting that none of the investigated endothelial cell lines responded positively to stimuli from immortalized astrocytic or pericytic cells. CONCLUSIONS: Under the conditions examined in our experiments, hBMEC proved to be the most suitable human cell line for an in vitro BBB model concerning barrier tightness in a 24-well mono-culture system intended for higher throughput. This BBB model is being validated with several compounds (known to cross or not to cross the BBB), and will potentially be selected for the assessment of BBB permeation of bioactive natural products