Correlation of hemorrhage, axonal damage, and blood-tissue barrier disruption in brain and retina of Malawian children with fatal cerebral malaria

Background: The retinal and brain histopathological findings in children who died from cerebral malaria (CM) have been recently described. Similar changes occur in both structures, but the findings have not been directly compared in the same patients. In this study, we compared clinical retinal findings and retinal and cerebral histopathological changes in a series of patients in Blantyre, Malawi, who died of CM.

Methods: The features systematically compared in the same patient were: (1) clinical, gross and microscopic retinal hemorrhages with microscopic cerebral hemorrhages, (2) retinal and cerebral hemorrhage-associated and -unassociated axonal damage, and fibrinogen leakage, and (3) differences in the above features between the pathological categories of CM without microvascular pathology (CM1) and CM with microvascular pathology (CM2) in retina and brain.

Results: Forty-seven patients were included: seven CM1, 28 CM2, and 12 controls. In the 35 malaria cases retinal and cerebral pathology correlated in all features except for non-hemorrhage associated fibrinogen leakage. Regarding CM1 and CM2 cases, the only differences were in the proportion of patients with hemorrhage-associated cerebral pathology, and this was expected, based on the definitions of CM1 and CM2. The retina did not show this difference. Non-hemorrhage associated pathology was similar for the two groups.

Comment: As postulated, histopathological features of hemorrhages, axonal damage and non-hemorrhage associated fibrinogen leakage correlated in the retina and brain of individual patients, although the difference in hemorrhages between the CM1 and CM2 groups was not consistently observed in the retina. These results help to underpin the utility of ophthalmoscopic examination and fundus findings to help in diagnosis and assessment of cerebral malaria patients, but may not help in distinguishing between CM1 and CM2 patients during life.

Midline Cerebellar Medulloblastoma in a Seventy-One-Year-Old Patient

BACKGROUND

Medulloblastoma is the most common malignant central nervous system tumour in children but, in contrast, quite rare in adults. Hemispheric, rather than midline, cerebellar medulloblastomas are more common in older children and adults. We present the unusual case of a 71-year-old man who presented with a fourth ventricular mass that proved to be a medulloblastoma.

METHODS

A 71-year-old man presented with progressive balance problems, slurred speech and double vision. A CT scan of the brain revealed a hyperattenuating, partially calcified, avidly enhancing mass within the fourth ventricle. Diffusion weighted MRI showed restricted diffusion within the mass. The patient underwent a midline suboccipital craniotomy and a subtotal resection was achieved.

RESULTS

Histological examination showed a densely cellular neoplasm composed of small cells with a tendency towards neuroblastic rosette formation. Most cells were strongly positive for neuron-specific enolase and synaptophysin. Ultrastructurally, tumour cells showed evidence of neuronal differentiation. These findings were consistent with a classical medulloblastoma.

CONCLUSION

Adult medulloblastoma should be considered in the differential diagnosis of a partially calcified hyperattenuating mass within the fourth ventricle.

Differential regulation of CD4+ T cell adhesion to cerebral microvascular endothelium by the β-chemokines CCL2 and CCL3

In Multiple sclerosis (MS), circulating lymphocytes cross the blood–brain barrier (BBB) and accumulate at sites of antigenic challenge. This process depends on specific interactions between lymphocytes and cerebral microvascular endothelium that involve endothelial activation by cytokines and the presence of chemokines. Chemokines play a key role in the orchestration of immune responses, acting both as chemoattractants and activators of leukocyte subsets. In the present study, we investigated the effects of the β-chemokines, CCL2 and CCL3, on the adhesion of CD4+ T cell subsets to human brain microvessel endothelial cells (HBMEC). Chemokines added to the lower compartment of a two-chamber chemotaxis system under confluent resting or cytokine-activated HBMEC, diffused through the culture substrate and bound to the basal surface of HBMEC. The low rate of adhesion of naïve, resting and memory CD4+ T cells to resting HBMEC was significantly upregulated following treatment of HBMEC with TNF-α and IFN-γ. Recently activated CD4+ T cells readily adhered to resting monolayers. Concentration gradients of CCL2 upregulated the adhesion of activated CD4+ T cells to cytokine treated but not resting HBMEC. The presence of CCL3 in the lower chamber increased the adhesion of memory T cells to both unstimulated and cytokine-treated HBMEC. These findings emphasize the importance of brain endothelial cell activation and the role of CCL2 and CCL3 in regulating the adhesion of CD4+ T cell subsets to BBB endothelium, thus contributing to the specificity of immune responses in MS.

Epstein-Barr virus infection of human brain microvessel endothelial cells: a novel role in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurological disease that is widely regarded as the outcome of complex interactions between a genetic predisposition and an environmental trigger. Epstein-Barr virus (EBV) has recently been associated with the onset of MS, yet understanding how it elicits autoimmunity remains elusive. Neuroinflammation, including the entry of autoreactive T cells, likely follows a breach of the blood-brain barrier (BBB) leading to CNS lesions in MS. We show that EBV can infect human BBB cells leading to increased production of pro-inflammatory mediators that result in immune cell adherence thus modeling a key step in MS pathogenesis.

Regulation of CXCL12 and CXCR4 expression by human brain endothelial cells and their role in CD4+ and CD8+ T cell adhesion and transendothelial migration

Chemokines have emerged as important mediators of leukocyte recruitment to the CNS across the normally restrictive blood-brain barrier (BBB). In the present study we investigated the regulation of CXCL12 and its receptor, CXCR4, expression in human brain microvessel endothelial cells (HBMEC) and the effects of CXCL12 on the adhesion and migration of CD4+ and CD8+ T lymphocytes across HBMEC monolayers. Resting HBMEC constitutively expressed CXCL12 and CXCR4. Treatment with TNF-alpha, IFN-gamma, IL-1beta and LPS downregulated CXCL12 and CXCR4 expression and CXCL12 ligation induced internalization of CXCR4. The minimal adhesion and migration of CD4+ and CD8+ T lymphocytes across resting HBMEC were increased following cytokine treatment of HBMEC. CXCL12 gradients further enhanced adhesion of both T cell subsets to activated HBMEC and migration across resting monolayers. A greater number of CD8+ T lymphocytes adhered and migrated across activated HBMEC compared to CD4+ T cells. These studies provide insight into the regulation of CXCL12 and CXCR4 expression in cerebral EC and indicate an important role for CXCL12 in T cell subset recruitment across the BBB in CNS inflammation.

Differentiation of blood monocytes to dendritic cells following reverse transmigration across the blood-brain barrier (94.6)

Dendritic cells (DC) are absent in the normal human central nervous system (CNS) but their presence has been documented in neuroinflammation. The origin of CNS DC is still controversial. The objective of this study was to determine whether monocytes that cross the blood-brain barrier (BBB) differentiate into DC. Primary human brain microvessel endothelial cells (HBMEC) were cultured on collagen gels. Purified human CD14+ monocytes were incubated with confluent HBMEC for 48h and the reverse transmigrated (RT) cells were characterized by FACS analysis. Approximately 50% of the monocytes reverse transmigrated across HBMEC monolayers and 70% of the RT cells expressed DC-SIGN. Monocytes incubated on gels in the absence of HBMEC retained their phenotype. The percentage of RT cells expressing CD83 increased from 25% to 70% when human CNS myelin was incorporated into the gels, and there was significant increase in CCR7 expression. Analysis of culture supernatants showed high levels of IL-6, TNF-α, PGE2 and IL-1β when HBMEC were cultured on myelin gels suggesting that these cytokines may contribute to the differentiation of monocytes to mature DC. There was an associated increase of MIP-3β, MCP-1, MIP-1α, and MIP-1β in the supernatants. Mixed lymphocyte reactions by co-culturing CFSE-labeled T cells and RT cells showed that RT cells were capable of stimulating allogeneic T cell proliferation. In conclusion, the results suggest that monocytes which reverse-transmigrate across HBMEC differentiate into mostly mature DC capable of inducing T cell proliferative responses. (Supported by MSS, Canada)

Adhesion and migration of polymorphonuclear leukocytes across human brain microvessel endothelial cells are differentially regulated by endothelial cell adhesion molecules and modulate monolayer permeability☆

The mechanisms by which polymorphonuclear leukocytes (PMN) cross the human blood-brain barrier have not been fully elucidated. Using a well characterized in vitro model of the human BBB, we examined the role of endothelial cell adhesion molecules on the adhesion and transendothelial migration of PMN across primary cultures of human brain microvessel endothelial cells (HBMEC). A small number of PMN (0.06%) adhered to unstimulated HBMEC, and the basal adhesion was not affected by anti-adhesion molecule antibodies. Treatment of HBMEC with tumor necrosis factor (TNF)-alpha resulted in increased PMN adhesion that was significantly inhibited by blocking antibodies to E-selectin and ICAM-1, but not VCAM-1 or PECAM-1. A very small number of adherent PMN migrated across unstimulated HBMEC monolayers. Migration increased 2 to 20 fold following stimulation of HBMEC with TNF-alpha. Monoclonal antibody blocking studies showed that PMN used ICAM-1, but not VCAM-1, E-selectin or PECAM-1 to move across activated monolayers. Anti-adhesion molecule antibodies did not diminish the basal PMN migration. Ultrastructurally, PMN often aggregated on top and between adjacent endothelial cells and adhered by first extending pseudopodia along the apical endothelial surface. They then flattened and inserted themselves between endothelial cells in order to migrate across the monolayers. At the end of the migration period, the cultures resumed their continuity with no evidence of disruption. Transendothelial migration of PMN decreased the transendothelial electrical resistance and increased the permeability to horseradish peroxidase, which penetrated alongside the migrating leukocytes. A blocking antibody to ICAM-1 that greatly decreased migration, had no effect on the permeability changes. These studies provide insights into the mechanisms that regulate the entry of PMN into the brain and the increased permeability of the BBB in CNS inflammation.

Nitric oxide reduces T lymphocyte adhesion to human brain microvessel endothelial cells via a cGMP-dependent pathway

The entry of lymphocytes into the brain is normally limited by the blood-brain barrier, however, during inflammation prominent lymphocytic infiltration occurs. In this study, we investigated the effects of nitric oxide (NO) on the adhesion of T cells to cultured human brain microvessel endothelial cells. T cell adhesion to unstimulated or tumor necrosis factor-alpha (TNF-alpha)-treated cells was quantified by counting the number of lymphocytes bound to the monolayer by light microscopy. TNF-alpha increased T cell adhesion in a time-dependent manner. Incubation of monolayers with NO donors decreased adhesion. This effect was blocked by a guanylyl cyclase inhibitor and mimicked by a cGMP agonist, and was thus dependent on the generation of cGMP. NO did not modulate adhesion molecule expression in the endothelial cells, suggesting an action on the T cells. Pre-treatment of T cells with NO or a cGMP agonist decreased binding to recombinant endothelial adhesion molecules. These findings suggest that NO can modulate the adhesion of T cells to human brain microvessel endothelial cells via a cGMP-dependent mechanism, and may thus regulate lymphocyte traffic during central nervous system inflammation.

Severe vascular disturbance in a case of familial brain calcinosis

Here we present the first neuropathological study of a case of autosomal dominant brain calcinosis in a family followed through five generations. The 71-year-old female who came to autopsy had unusually severe and extensive bilateral brain calcifications. The process appeared to start with deposition of minute calcium-positive spheroids of less than 1 mum in diameter in capillaries that otherwise appeared normal. These could be observed extending to areas distant from the main pathology. In more advanced stages, larger spheroids completely covered some capillaries while sparing others. In heavily affected regions, ghost capillaries were observed where only calcium spheroids remained after endothelial cells and basement membranes had disappeared. Vessels of all sizes were affected, and large accretions were observed in the basal ganglia, thalamus and cerebellum. Combined scanning electron microscopy and X-ray spectrometry of these large deposits revealed a dominant presence of calcium and phosphorous, plus carbon and oxygen indicative of organic material, and small amounts of sodium, potassium, sulfur, and magnesium. Reactive astrocytes and reactive microglia accumulated around the calcified deposits, indicating a mild ongoing inflammatory process. The results suggest that severe vascular impairment and mild inflammation contribute to the slow but inexorable progression of hereditary brain calcinosis.

Cytokines, nitric oxide, and cGMP modulate the permeability of an in vitro model of the human blood-brain barrier

The endothelial cells (EC) of the microvasculature in the brain form the anatomical basis of the blood-brain barrier (BBB). In the present study, the effects of agents that modify the permeability of a well-established in vitro model of the human BBB were studied. The monolayers formed by confluent human brain microvessel endothelial cell (HBMEC) cultures are impermeable to the macromolecule tracer horseradish peroxidase (HRP) and have high electrical resistance. Exposure of HBMEC to various cytokines including TNF-alpha, IL-1beta, interferon gamma (IFN-gamma), or lipopolysaccharide (LPS) decreased transendothelial electrical resistance (TEER) mainly by increasing the permeability of the tight junctions. Primary cultures of HBMEC express endothelial nitric oxide synthase (eNOS) and produce low levels of NO. Treatment with the NO donors sodium nitroprusside (SNP) and DETA NONOate or the cGMP agonist 8-Br-cGMP significantly increased monolayer resistance. Conversely, inhibition of soluble guanylyl cyclase with ODQ rapidly decreased the resistance, and pretreatment of HBMEC with Rp-8-CPT-cGMPS, an inhibitor of cGMP-dependent protein kinase, partially prevented the 8-Br-cGMP-induced increase in resistance. Furthermore, NO donors and 8-Br-cGMP could also reverse the increased permeability of the monolayers induced by IL-1beta, IFN-gamma, and LPS. These results indicate that NO can decrease the permeability of the human BBB through a mechanism at least partly dependent on cGMP production and cGMP-dependent protein kinase activation.

Nitric oxide regulates interactions of PMN with human brain microvessel endothelial cells

The hypothesis that the NO/cGMP pathway modulates PMN adhesion to human brain microvessel endothelial cells (HBMEC) was examined. Human PMN were incubated with resting or TNF-alpha-treated endothelial monolayers, and adhesion was quantified by light microscopy. TNF-alpha upregulated PMN adhesion in a time-dependent manner. Treatment of HBMEC with the NO donors SNP and DETA NONOate for 4 or 24 h decreased PMN adhesion. This was completely reversed by the guanylyl cyclase inhibitor ODQ, while addition of a cGMP agonist (8-Br-cGMP) decreased PMN adhesion. NO donors did not affect the levels of E-selectin or ICAM-1 in HBMEC. However, pre-treatment of PMN with NO donors or 8-Br-cGMP decreased their adhesion to recombinant E-selectin and ICAM-1, suggesting an effect of NO on PMN. These findings indicate that NO modulates PMN-HBMEC interactions through cGMP and decreases the binding of PMN to the adhesion molecules E-selectin and ICAM-1.

The beta chemokines CCL4 and CCL5 enhance adhesion of specific CD4+ T cell subsets to human brain endothelial cells

Chemokines are key mediators of inflammation, acting as subset-specific chemoattractants and activators of leukocytes. In the present study we investigated the effects of chemokine concentration gradients on CD4+ T cell (TC4) adhesion to human brain microvessel endothelial cells (HBMECs) in vitro. CCL4 or CCL5 were placed in a double chamber chemotaxis system beneath confluent resting HBMEC monolayers or cultures co-incubated with TNF-alpha and IFN-gamma to mimic an inflammatory milieu. Chemokines readily diffused across activated HBMEC monolayers while binding to the sub-endothelial regions, establishing a chemotactic and haptotactic gradient. Naïve or resting TC4 adhered poorly to resting HBMECs compared to memory or recently activated TC4, but all subsets adhered more readily to cytokine-treated HBMECs. Chemokine gradients (10-100 ng/ml) of both CCL4 and CCL5 significantly enhanced the adhesion of memory and recently activated TC4 to cytokine-treated HBMECs, as much as doubling adhesion in a manner that correlated with chemokine receptor expression. Neither chemokine influenced adhesion to resting HBMEC monolayers nor the adhesion of resting or naïve TC4. These findings emphasize the role and importance of CNS-derived beta-chemokines in regulating the traffic of recently activated TC subsets (those previously localized to the CNS in vivo) across cytokine-activated cerebral endothelium in inflammatory diseases.

Notch activation results in phenotypic and functional changes consistent with endothelial-to-mesenchymal transformation

Various studies have identified a critical role for Notch signaling in cardiovascular development. In this and other systems, Notch receptors and ligands are expressed in regions that undergo epithelial-to-mesenchymal transformation. However, there is no direct evidence that Notch activation can induce mesenchymal transdifferentiation. In this study we show that Notch activation in endothelial cells results in morphological, phenotypic, and functional changes consistent with mesenchymal transformation. These changes include downregulation of endothelial markers (vascular endothelial [VE]-cadherin, Tie1, Tie2, platelet-endothelial cell adhesion molecule-1, and endothelial NO synthase), upregulation of mesenchymal markers (alpha-smooth muscle actin, fibronectin, and platelet-derived growth factor receptors), and migration toward platelet-derived growth factor-BB. Notch-induced endothelial-to-mesenchymal transformation does not seem to require external regulation and is restricted to cells expressing activated Notch. Jagged1 stimulation of endothelial cells induces a similar mesenchymal transformation, and Jagged1, Notch1, and Notch4 are expressed in the ventricular outflow tract during stages of endocardial cushion formation. This is the first evidence that Jagged1-Notch interactions induce endothelial-to-mesenchymal transformation, and our findings suggest that Notch signaling may be required for proper endocardial cushion differentiation and/or vascular smooth muscle cell development.

Induction of β-chemokine secretion by human brain microvessel endothelial cells via CD40/CD40L interactions

beta-chemokines play an important role during the course of central nervous system (CNS) inflammation. Using primary cultures of human cerebral microvascular endothelial cells, we detected increased monocyte chemoattractant protein-1 (MCP-1) and regulated upon activation normal T cell expressed and secreted (RANTES) production following incubation with soluble CD40L. These results suggest a potential mechanism by which activated CD40L positive T cells may enhance beta-chemokine expression and thus influence the recruitment of mononuclear cells across the human blood-brain barrier.

CD40 expressed by human brain endothelial cells regulates CD4+ T cell adhesion to endothelium

Recent evidence suggests that interactions between CD40 on antigen presenting cells (APC) and CD40L on T cells generate signals that result in the activation of APC. In this study, the expression and function of CD40 was investigated in primary cultures of human brain microvessel endothelial cells (HBMEC). Results revealed constitutive expression of CD40 on untreated HBMEC. Stimulation with TNF-alpha, IFN-gamma, LPS or combination of TNF-alpha and IFN-gamma significantly upregulated CD40. The majority of CD40 molecules were localized on the apical surface of EC. Incubation of HBMEC with soluble CD40L resulted in increased expression of the adhesion molecules E-selectin, VCAM-1 and ICAM-1. Consequently, the adhesion of both resting and anti-CD3 activated CD4+ T lymphocytes to CD40L treated HBMEC was significantly increased compared to unstimulated EC. The expression of CD40 by cerebral endothelium, and endothelial cell activation following binding of CD40 to its ligand, CD40L, suggest a potential mechanism by which activated CD40L expressing T cells could enhance adhesion and migration of inflammatory cells across the blood-brain barrier (BBB) to sites of inflammation in the human central nervous system (CNS).

The kinetics, function, and regulation of P-selectin expressed by human brain microvessel endothelial cells in primary culture

P-selectin is an endothelial cell adhesion glycoprotein expressed on the cell surface early in inflammation where it binds to blood leukocytes. This study examines the expression, function, and regulation of P-selectin in primary cultures of human brain microvessel endothelial cells (HBMEC). Surface expression of P-selectin was minimal in unstimulated HBMEC; however, it was significantly augmented upon stimulation with histamine (10(-7)-10(-3) M) and thrombin (0.01-1 U/ml). Expression increased rapidly at 10 min and remained elevated at 60 min. Immunogold electron microscopy showed that histamine (10(-7) M) increased surface expression preferentially on the apical surface of subconfluent monolayers. A cell binding assay showed that the adhesion of polymorphonuclear leukocytes (PMNs) to confluent monolayers was augmented after histamine treatment. Histamine-induced surface expression of P-selectin was blocked by the histamine H2 receptor antagonist cimetidine. The H1 receptor antagonist mepyramine had no effect. Expression was reduced by the extracellular calcium chelator EDTA and blocked by the cyclic AMP phosphodiesterase inhibitor rolipram. Thus histamine and thrombin both increase P-selectin expression in HBMEC. Histamine mediates expression through the H2, but not the H1, receptor and calcium, whereas expression is reduced by cyclic AMP. The histamine-induced expression increases PMN binding to the HBMEC. These data suggest that P-selectin plays a role in the recruitment of acute inflammatory cells to the CNS.

Expression and function of the costimulatory molecules B7-1 (CD80) and B7-2 (CD86) in an in vitro model of the human blood--brain barrier

The interaction of B7 molecules with their ligand provides important accessory signals for optimal T cell activation and proliferation. In this study the in vitro expression of B7-1 and B7-2 by human brain microvessel endothelial cells (HBMEC) was investigated by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and immunocytochemistry. In addition, the contribution of B7 molecules to T cell proliferation on cerebral endothelial cells was studied by coincubating purified CD4+ T cells with resting or cytokine activated HBMEC. Untreated cultures constitutively expressed B7-2 RNA and surface protein, but lacked B7-1 expression. Treatment with TNF-alpha and IFN-gamma upregulated B7-2 and induced de novo expression of B7-1. Monoclonal blocking antibodies to B7-1 or B7-2 and human CTLA-4Ig chimeric protein significantly reduced the ability of HBMEC to support alpha-CD3-induced proliferation of CD4+ T lymphocytes. Expression of B7 glycoproteins and the ability to provide secondary signals for T cell proliferation suggest a potential role of the human cerebral endothelium in T cell activation during the early stages of central nervous system inflammation.

Characterization of ABCB9, an ATP binding cassette protein associated with lysosomes

We have cloned full-length human and mouse cDNAs of ABCB9, which encodes a predicted multiple-spanning transmembrane domain and a nucleotide-binding domain with Walker motifs. It is therefore designated as a "half" ATP binding cassette (ABC) transporter. Northern analysis shows that the ABCB9 mRNA is expressed at a high level in testes and moderate levels in brain and spinal cord. A splice variant mRNA deleted in the last pair of predicted transmembrane segments was shown to be expressed in human tissues. Phylogenetic analysis indicates that ABCB9 is closely related to TAP1 and TAP2, two "half" ABC proteins found in endoplasmic reticulum. ABCB9 protein colocalized with the lysosomal markers, LAMP1 and LAMP2, in transfected cells. ABCB9 protein appears to be most highly expressed in the Sertoli cells of the seminiferous tubules in mouse and rat testes. These cells have high levels of phagocytosis and secretory activities. These findings pave the way for further investigation into the potential novel function of ABCB9 in lysosomes.

Expression of complement messenger RNAs by human endothelial cells

This study evaluated complement mRNA expression in human brain microvessel endothelial cells (HBMEC), human umbilical vein endothelial cells (HUVEC), and cells of the human derived ECV304 line. Cerebral endothelial cells and HUVEC expressed detectable levels of complement gene mRNAs for the C1q B-chain, C1r, C1s, C2, C3, C4, C5, C7, C8 gamma-subunit and C9. In addition to C6 mRNA, C1q and C9 were not detected in ECV304 cells. These results indicate that endothelial cells may be a source of complement proteins in brain and other organs of the body.

A1 functions at the mitochondria to delay endothelial apoptosis in response to tumor necrosis factor

Tumor necrosis factor (TNF) does not cause endothelial apoptosis unless the expression of cytoprotective genes is blocked. We have previously demonstrated that one of the TNF-inducible cytoprotective genes is the Bcl-2 family member, A1. A1 is induced by the action of the transcription factor, NFkappaB, in response to inflammatory mediators. In this report we demonstrate that, as with other cell types, inhibition of NFkappaB initiates microvascular endothelial apoptosis in response to TNF. A1 is able to inhibit this apoptosis over 24 h. We demonstrate that A1 is localized to and functions at the mitochondria. Whereas A1 is able to inhibit mitochondrial depolarization, loss of cytochrome c, cleavage of caspase 9, BID, and poly(ADP-ribose) polymerase, it does not block caspase 8 or caspase 3 cleavage. In contrast, A1 is not able to prevent endothelial apoptosis by TNF over 72 h, when NFkappaB signaling is blocked. On the other hand, the caspase inhibitor, benzyloxycarbonyl-VAD-formylmethyl ketone, completely blocks TNF-induced endothelial apoptosis over 72 h. Our findings indicate that A1 is able to maintain temporary survival of endothelial cells in response to TNF by maintaining mitochondrial viability and function. However, a mitochondria-independent caspase pathway eventually results in endothelial death despite mitochondrial protection by A1.

Expression of the beta-chemokines RANTES and MIP-1 beta by human brain microvessel endothelial cells in primary culture

The mechanisms that regulate inflammatory cell recruitment across the blood-brain barrier (BBB) during CNS inflammation have not been fully characterized. Likely players in this process include the chemokines, small secondary messengers of inflammation capable of subset-specific leukocyte activation and chemoattraction. Primary cultures of human brain microvessel endothelial cells (HBMEC) were examined for their in vitro expression of the beta chemokines RANTES and MIP-1beta. Untreated HBMEC expressed low levels of RANTES and MIP-1beta RNA that were significantly upregulated following cytokine treatment. Parallel studies performed on human umbilical vein endothelial cells (HUVEC) showed induction of RANTES but not MIP-1beta RNA. Following stimulation with LPS, TNF-alpha, IFN-gamma, and IL-1beta alone or in combination, HBMEC released significant amounts of RANTES and MIP-1beta into the culture supernatants. RANTES secretion by HUVEC could be induced only with TNF-alpha/IFN-gamma. Both RANTES and MIP-1beta were detected by immunocytochemistry on the apical and basal surfaces of HBMEC, as well as bound to basal lamina-like material under the basal cell surface. Cytokine stimulation induced significant increase of RANTES and MIP-1beta molecules associated with the EC surface and subendothelial matrix. The expression of RANTES and MIP-1beta by HBMEC suggests that these chemokines may play an important role in mediating inflammatory responses and leukocyte trafficking across the BBB.

Blood mononuclear cells in patients with HTLV-I-associated myelopathy: lymphocytes are highly activated and adhesion to endothelial cells is increased

We have investigated lymphocyte subpopulations and blood mononuclear cell (MNC) adhesion to activated endothelial monolayers in patients with human T lymphotropic virus type I (HTLV-I) associated myelopathy (HAM), in HTLV-I asymptomatic carriers (carriers), and in seronegative controls. HAM patients and carriers had higher levels of CD4(+)CD29(+) "memory cells" than controls (P < 0.05). The percentage of CD3(+)CD27(-) "primed T cell" was elevated in patients with HAM (P < 0.05), but not in carriers. HAM patients had higher levels of CD8(+)CD57(+) "cytotoxic cells" (P < 0.05) than controls and carriers. The percentages of CD4(+) cells coexpressing activation markers HLA-DR and CD25, and of CD8(+) cells expressing HLA-DR, were significantly higher in HAM patients and carriers than in controls. Functional experiments indicated that MNC from HAM patients adhered more to activated endothelial monolayers than MNC from carriers or controls. Blocking studies demonstrated that the adhesion molecules VLA-4 and ICAM-1 and also L-selectin all contributed to increased binding. Analysis of expression of molecules involved in adhesion indicated that in HAM patients, L-selectin (CD62L) expression on CD4(+) and CD8(+) subsets was lower than in controls. Interestingly, HAM patients had a lower percentage of CD4(+) subsets expressing L-selectin than carriers (P < 0.05). In contrast, the percentage of CD4(+) and CD8(+) cells expressing VLA-4 (CD49d) was found to be higher in both HAM patients and carriers compared with controls. After 2 days in culture without mitogen, the percentage of T cells expressing ICAM-1 (CD54) increased in culture in carriers and more profoundly in HAM, but not in controls (P < 0. 05). After culture, T cells expressing the early activation antigen CD69 were also increased in HAM and carriers (P < 0.05) but not in controls. Interestingly, the levels of CD8(+) cells coexpressing activation antigen HLA-DR and CD38 were higher in HAM patients compared with both carriers and controls (P < 0.05) after culture. These findings are consistent with the observations that HTLV-I produces chronic lymphocyte activation with increased adhesion. This may be sufficient to initiate events leading to central nervous system inflammation and ultimately to HAM.

Agonist-stimulated calcium entry in primary cultures of human cerebral microvascular endothelial cells

Primary cultures of human cerebral microvascular endothelial cells (HCMEC) were loaded with fura-2. The intracellular free Ca2+ concentration ([Ca2+]i) was measured by digital imaging microscopy. Agonists ATP (100 micro), thrombin (10 units/ml), and histamine (25 microM) induced a transient [Ca2+]i increase. Histamine (100 microM) induced a biphasic [Ca2+]i increase with an initial [Ca2+]i peak followed by a [Ca2+]i plateau. The [Ca2+]i plateau was blocked by the receptor-operated Ca2+ channel (ROC) blockers SK&F 96365 and NCDC, indicating a contribution by Ca2+ influx through ROC to the [Ca2+]i plateau. However, this [Ca2+]i plateau was not blocked by the voltage-gated Ca2+ channel (VGC) blocker diltiazem (DTZ). Depolarization with 80K+ or application of the VGC agonist BAY K 8644 did not alter the resting [Ca2+]i; but 80K+ reduced the histamine (100 microM) induced [Ca2+]i plateau. These results show that HCMEC are devoid of functional VGC. Thus the membrane potential (Em) regulates Ca2+ entry mainly by enhancing the electrochemical Ca2+ gradient, such that hyperpolarization increases while depolarization decreases [Ca2+]i. Blockade of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) by CPA increased [Ca2+]i. This effect was dependent on extracellular Ca2+ and reduced by iberiotoxin (IBTX) blockade of Ca2+-activated K+ channels (Kca), suggesting a role for Kca in regulating Ca2+ influx. Ca2+ is the principal activator of endothelial nitric oxide synthase (eNOS), which stimulates cyclic GMP production. The final result that the eNOS inhibitor L-NAME enhanced the histamine (100 microM) induced [Ca2+]i plateau suggests a negative feedback loop (via cGMP) of endothelial NO on its own synthesis in the regulation of endothelial [Ca2+]i signal.

Expression and function of lymphocyte function associated antigen-3 (LFA-3) at the blood-brain barrier

Lymphocyte function associated antigen-3 (LFA-3) is a cell surface glycoprotein involved in antigen independent T-cell activation and proliferation. The expression and function of LFA-3 at the blood-brain barrier were studied in an in vitro model consisting of primary cultures of human brain microvessel endothelial cells (HBMEC). Surface expression of LFA-3 was detected by immunogold silver staining and the presence of RNA by reverse transcriptase-polymerase chain reaction (RT-PCR). Unstimulated HBMEC in primary culture constitutively express LFA-3 on their surface. Expression is only marginally upregulated following stimulation with tumor necrosis factor-alpha (TNF-alpha) or interferon-gamma (IFN-gamma). Similarly, LFA-3 RNA is present constitutively in unstimulated HBMEC with minimal increase after co-incubation with TNF-alpha and IFN-gamma. The function of LFA-3 as a costimulatory molecule on HBMEC was investigated by incubating purified CD4+ T-lymphocytes with resting or IFN-gamma treated HBMEC monolayers. Proliferation of alpha-CD3 activated CD4+ T-cells was significantly increased upon incubation with resting or activated endothelial cells. Monoclonal antibodies to LFA-3 consistently blocked the proliferative response by 64-76%. The ability of the cerebral endothelium to express LFA-3 and provide secondary signals for T-cell proliferation suggests that cerebral EC may be important in the initiation of inflammatory responses in the human central nervous system.

In vitro adhesion and migration of T lymphocytes across monolayers of human brain microvessel endothelial cells: regulation by ICAM-1, VCAM-1, E-selectin and PECAM-1

Increased lymphocyte traffic across an altered blood-brain barrier (BBB) is a prominent and early event in inflammatory and immune-mediated CNS diseases. The factors that control the entry of lymphocytes into the brain have not been fully elucidated. In this study, primary cultures of human brain microvessel endothelial cells (HBMEC) were used to investigate the role of endothelial cell (EC) adhesion molecules in the adhesion and migration of peripheral blood T lymphocytes across TNF-alpha treated and untreated monolayers. Adhesion of T cells to unstimulated HBMEC was minimal and few of the adherent cells migrated across the monolayers. Treatment of HBMEC with TNF-alpha augmented adhesion by 5-fold. The binding to activated EC was significantly, but not completely, inhibited by monoclonal antibodies (mAbs) to ICAM-1 and VCAM-1, whereas adhesion to unstimulated EC was blocked by mAb to ICAM-1 but not VCAM-1. Transendothelial migration of lymphocytes increased by up to 30-fold following treatment of HBMEC with TNF-alpha. Migration across activated monolayers, but not across untreated EC, was almost completely blocked by Ab to ICAM-1 and significantly inhibited by Abs to PECAM-1 and E-selectin. VCAM-1 was not utilized during transendothelial migration. Ultrastructurally, pseudopodia from lymphocytes contacted finger-like cytoplasmic projections on EC and eventually penetrated the EC cytoplasm at focal points along the apical surface. Migrating lymphocytes moved either through the EC cytoplasm or between adjacent EC across intercellular contacts. The overlying monolayers showed no evidence of disruption and intercellular junctions appeared intact over the migrated T cells. These studies indicate that adhesion and migration of T lymphocytes across the cerebral endothelial barrier are distinct processes that depend upon the activation state of EC and are controlled by diverse receptor-ligand interactions.

Glomeruloid vascular structures in glioblastoma multiforme: an immunohistochemical and ultrastructural study

Microvascular proliferation and glomeruloid vascular structures are important histopathological features of glioblastoma multiforme (GBM). The nature of cells participating in the formation of these structures remains unclear and is the subject of this study. To define these cells better, immunohistochemical markers directed against Factor VIII-related antigen (FVIIIR:Ag), alpha smooth-muscle actin (alpha-SMA), and the lectin Ulex europaeus agglutinin type I (UEA-I) were used. Cells lining the vascular channels and a large number of proliferating abluminal cells participating in glomeruloid vascular structure formation showed positive cytoplasmic staining for FVIIIR:Ag and UEA-I. Abluminal and luminal cells were variably labeled for alpha-SMA. Ultrastructurally, complex aggregates of focally anastomosing capillaries with narrow lumina composed the glomeruloid vascular structure. Endothelial cells were hyperplastic, varied in size and shape, overlapped focally, and contained numerous cytoplasmic filaments. Tight junctions bound together adjacent and overlapping endothelial cells. Weibel-Palade bodies, usually absent from brain microvessels, were present in increased numbers in the newly formed capillaries. Each capillary loop was surrounded by basal lamina encompassing a discontinuous layer of pericytes. This study indicates that glomeruloid vascular structures in GBM are complex aggregates of newly formed microchannels lined with hyperplastic endothelial cells that have an altered morphological phenotype and that these microchannels are supported by basal lamina and pericytes and are devoid of astrocytic end-feet.

Plasmodium falciparum: involvement of additional receptors in the cytoadherence of infected erythrocytes to microvascular endothelial cells

The involvement of additional ligands in the cytoadhesion of PRBC to endothelial cells was studied by the use of human microvascular endothelial cells (HMEC-1), brain microvascular endothelial cells (HBEC-51), umbilical vein endothelial (HUVEC), and C32 melanoma cells as well as soluble CD36, ICAM-1, and thrombospondin in the adhesion assays. Immunostaining showed that ICAM-1 and thrombospondin were expressed by all cell lines, whereas CD36 and VCAM-1 were expressed constitutively only by C32 melanoma cells and HBEC-51, respectively; none of these cells had basal expression of E-selectin. Bindings of the parental HB3 parasite strain to HMEC-1 and HUVEC were higher than that to HBEC-51 and C32 melanoma cells. Selections by panning the parental HB3 through HMEC-1 (HB3EC-6 line) or C32 melanoma cells (HB3C32-6 to HMEC-1 was higher than that to C32 melanoma cells. Antibody or peptide blockade against CD36, ICAM-1, and thrombospondin or preincubation of target cells with TNF-alpha and IFN-gamma did not significantly alter the binding intensity of HB3EC-6 to HMEC-1 and HB3C32-6 to C32 melanoma cells. Preincubation of HMEC-1 with IL-4, however, reduced its binding with HB3EC-6. In vitro selection did not enhance the binding of PRBC to plate-bound CD36 or thrombospondin; binding to ICAM-1 was negligible. The binding of both selected lines was inhibited by dextran sulfate and sulfatides, but not by chondroitin sulfate A. These results suggested that in addition to CD36 and thrombospondin, sulfated glycoconjugates were probably concurrently utilized by these PRBC as receptors. Experiments with freshly isolated Kenyan parasites indicated that they also exhibited a similar mechanism of binding to endothelial cells.

Platelet/endothelial cell adhesion molecule-1 (PECAM-1) expression by human brain microvessel endothelial cells in primary culture

PECAM-1 expression was investigated in primary cultures of human brain microvessel endothelial cells (HBMEC). HBMEC constitutively express PECAM-1 along their apical cell surface, advancing processes and on the basal surface at points of contact with the extracellular matrix. Surface expression is not altered by cytokine or lipopolysaccharide treatment. This distribution may mediate cell-cell contract and migration during angiogenesis and HBMEC-leukocyte interactions in CNS inflammation.

Regualtion by cytokines and lipopolysaccharide of E-selectin expression by human brain microvessel endothelial cells in primary culture

E-selectin is an adhesion molecule expressed on endothelial cells after treatment with inflammatory agents in vitro and in inflammatory diseases in vivo. Interactions between leukocytes and endothelial cells are mediated partly through this adhesion molecule. In this study, the kinetic expression of E-selectin by human cerebral endothelium was studied under standard conditions and following treatment of primary cultures with bacterial lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and interferon-gamma (IFN-gamma). Surface expression of E-selectin was detected by immunocytochemistry, ELISA and immunoelectron microscopy. Untreated human cerebral endothelial cells constitutively expressed low levels of E-selectin. Treatment with LPS, TNF-alpha and IL-beta increased the mean level of E-selectin expression per cell and the percentage of cells expressing E-selectin, in a time and concentration-dependent manner. E-selectin expression was maximal by 4 h post-stimulation and returned unstimulated levels by 48 h. LPS and TNF-alpha were most effective followed by IL-1beta, while the IFN-gamma had no effect on E-selectin expression. Immunoelectron microscopy demonstrated that E-selectin was preferentially expressed on the apical surface of unstimulated and TNF-alpha treated cells. Cytokine stimulation induced a several-fold increase of E-selectin expression on the apical and to a lesser extent on the basal cell surface. Modulation of E-selectin expression on cerebral endothelium by inflammatory cytokines suggests a potentially important role of this adhesion molecule in the recruitment of leukocytes in central nervous (CNS) inflammation.

Tenascin-C expression by angiogenic vessels in human astrocytomas and by human brain endothelial cells in vitro

The expression of the extracellular matrix glycoprotein tenascin-C (TN) is enhanced in human astrocytomas and correlates with angiogenesis. To determine whether vascular cells are able to synthesize TN, we investigated the expression of TN protein and mRNA in nine astrocytomas. Immunogold electron microscopy in two glioblastomas multiforme detected the presence of TN in an extracellular perivascular location and to a lesser extent among tumor cells, confirming light microscopy immunohistochemical findings. In situ hybridization of astrocytomas using a digoxigenin-labeled antisense riboprobe detected strong staining for TN mRNA in vascular cells, especially in hyperplastic vessels, including those at the invasive edge of the tumors but not in vessels of normal brains. We observed weaker staining in tumor cells indicating a higher level of TN mRNA in vascular than in tumor cells. No staining was detected with the sense probe. Moreover, we investigated the ability of human brain microvessel endothelial cells (HBMECs) in primary culture to synthesize TN in vitro. Western blot analysis of the culture supernatants from HBMECs detected large amounts of TN. Immunogold silver staining demonstrated the presence of TN on the surface of HBMECs and in the subendothelial matrix. The distribution of TN mRNA in vascular cells of astrocytomas and the ability of HBMECs to synthesize TN in vitro demonstrate that vascular cells, including endothelial cells, are a major source of TN associated with angiogenesis. Furthermore, our results suggest that TN expression may be associated with endothelial cell activation and may play an important role in angiogenesis.

Interferon-beta downregulates interferon-gamma-induced class II MHC molecule expression and morphological changes in primary cultures of human brain microvessel endothelial cells

Regulation of class II MHC (Ia) antigen expression by interferons beta and gamma was studied in an in vitro model of the blood-brain barrier. Primary cultures of human brain microvessel endothelial cells were incubated with IFN-beta, gamma or a combination of the two cytokines and surface expression of class II MHC molecules was investigated with the immunogold silver staining technique and enzyme-linked immunosorbent assay. Treatment of monolayers with IFN-beta (100-6000 U/ml) failed to induce Class II MHC molecules. Co-incubation with IFN-gamma (100 U/ml), with or without pretreatment with IFN-beta, significantly inhibited the IFN-gamma-induced de novo expression in a concentration-dependent manner. Downregulation was less significant when incubation with both cytokines was preceded by 2-day treatment with IFN-gamma and was not observed in cultures incubated for an additional 4 days with IFN-gamma. Endothelial cells treated with IFN-gamma exhibited prominent morphological changes and frequent overlapping. These changes were not observed in the presence of either IFN-beta or both cytokines in the media. IFN-beta alone, or in combination with IFN-gamma, significantly inhibited the growth of endothelial cells, while only slight inhibition was observed with IFN-gamma. The results of these studies suggest that IFN-beta may function in modulating IFN-gamma-mediated immune responses in the human central nervous system at the level of the blood-brain barrier and this negative regulatory mechanism may be, at least in part, responsible for the recently reported beneficial effect of IFN-beta in relapsing-remitting multiple sclerosis.

Expression of vascular cell adhesion molecule-1 (VCAM-1) by human brain microvessel endothelial cells in primary culture

Vascular cell adhesion molecule-1 (VCAM-1) is an endothelial cell membrane glycoprotein that has been implicated in leukocyte/endothelial cell interactions in inflammation. In this study, we report the expression of VCAM-1 in primary cultures of human brain microvessel endothelial cells (HBMEC) under standard conditions and following bacterial lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), or interferon-gamma (IFN-gamma) treatment. Surface expression was detected and quantitated by light and immunogold electron microscopy and ELISA. Unstimulated cerebral endothelial cells (EC) constitutively expressed low levels of VCAM-1. LPS, TNF-alpha, or IL-1 beta increased the overall intensity of surface staining and the percentage of cells expressing VCAM-1 in a time- and concentration-dependent manner. LPS had the most potent effect, followed by TNF-alpha and then IL-1 beta. IFN-gamma did not upregulate VCAM-1. The level of VCAM-1 expression increased by 12-24 hr and returned to unstimulated levels by 48 hr. Immunoelectron microscopy demonstrated that VCAM-1 was preferentially localized on the apical as compared to the basal surface in both unstimulated and cytokine-treated cells. In addition, the intensity of immunostaining was significantly greater in stimulated versus unstimulated EC. The polarization and significant upregulation of VCAM-1 after cytokine treatment suggest a possible role of this adhesion molecule in inflammatory and autoimmune processes within the central nervous system.

In vitro interaction of coronaviruses with primate and human brain microvascular endothelial cells

Primary human and primate brain microvascular endothelial cells were tested for permissiveness to coronaviruses JHM and 229E. While sub-genomic viral RNAs could be detected up to 72 hours post-infection, primate cells were abortively infected and neither virus caused cytopathology. Human cells were non-permissive for JHM but permissive for 229E replication; peak production of progeny 229E and observable cytopathic effects occurred approximately 22 and 32 hour post-infection, respectively. Using the criterion of cytopathology induction in infected endothelial cells, 229E was compared to other human RNA and DNA viruses. In addition, virus induced modulation of intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1) and HLA I was monitored by immunostaining of infected cells.

Additive effect of allopurinol and deferoxamine in the prevention of spinal cord injury caused by aortic crossclamping

Fourteen domestic swine were divided into two groups. Group A (n = 7) was the control group, in which no pharmacologic intervention was applied. In group B (n = 7), the ischemic-reperfused spinal cord was treated with the combination of allopurinol (50 mg/kg/day for 3 days before the day of operation) and deferoxamine (Desferal, 50 mg/kg administered intravenously over 3 to 4 hours). The administration of deferoxamine was completed 1 hour before crossclamping. The crossclamp was placed on the descending aorta just distal to the left subclavian artery for 30 minutes. Proximal hypertension was controlled with sodium nitroprusside and volume depletion. Methods of assessment included an evaluation of the neurologic status of the animals by quantitative Tarlov criteria, blood flow by radiolabeled microspheres, and histologic examination of the spinal cord. All animals in the control group, group A, were completely paraplegic with 0% recovery by Tarlov criteria at 24 hours after the removal of the crossclamp. In contrast, all animals in group B, in which the combination of allopurinol and deferoxamine was used, completely recovered (100% recovery by Tarlov criteria), and at 24 hours after the ischemic episode they were able to walk with no difficulty and had intact sensation. Functional parameters of these animals fully correlated with the morphologic findings. Widespread acute neuronal injury and vacuolation of neuropil were observed in the control group of animals. In contrast, animals in group B showed much less pronounced morphologic changes after the same period of ischemia. In summary, the combined use of these agents significantly (p < 0.001) reduced the incidence of paraplegia induced by aortic crossclamping with 82% additivity.

Hippocampal synaptic pathology in patients with temporal lobe epilepsy

Immunostaining of synaptic terminals was studied in the hippocampus of 26 patients who had surgical resections for intractable temporal lobe epilepsy. Two monoclonal antibodies (EP10 and SP12) reactive with distinct synaptic antigens were used on paraffin-embedded tissues. The results indicated qualitative reductions on synaptic terminals in CA4 and other regions where cell loss is reported. The inner molecular layer of the dentate gyrus was observed to have increased synaptic immunostaining. Synaptic terminal loss in CA4 and redistribution in the molecular layer were most frequent in cases with hippocampal sclerosis. However, both forms of synaptic pathology were also noted in most cases where the pathological findings were classified as indefinite, and in some cases associated with mass lesions of the temporal lobe. These results support the importance of neuronal loss and synaptic reorganization as possible mechanisms of illness in epilepsy. They also indicate that synaptic immunostaining may be a useful adjunct to routine neuropathological diagnostic techniques.

Effects of interferon-gamma on primary cultures of human brain microvessel endothelial cells

Primary cultures of human brain microvessel endothelial cells were used to study the effects of human recombinant interferon-gamma (IFN-gamma) on cerebral endothelium in vitro. Incubation of monolayers with various concentrations of IFN-gamma (10 to 200 U/ml) for 12 to 96 hours induced surface expression of class II major histocompatibility complex (Ia) antigen in a time- and concentration-dependent manner. In immunogold-stained cultures, labeling was observed as early as 12 hours, was maximal after 48 hours, and persisted at plateau levels in the continuous presence of the cytokine. Expression was blocked by coincubation with anti-IFN-gamma antibody and was reversed 4 days following removal of IFN-gamma from the culture media. Endothelial cells treated with IFN-gamma for 3 to 4 days became spindle-shaped, extensively overlapped, and frequently formed cellular whorls. These changes did not occur in the presence of anti-IFN-gamma antibody and reversed upon removal of IFN-gamma from the media. The morphological alterations were associated with increased permeability of confluent monolayers to macromolecules as compared with untreated cultures. The results of these studies indicate that human brain microvessel endothelial cells respond to in vitro cytokine stimulation by undergoing profound morphological, functional, and permeability changes. We conclude that cerebral endothelium may play an important role in the initiation and regulation of lymphocyte traffic across the blood-brain barrier in inflammatory disorders of the human central nervous system.

Upregulation of intercellular adhesion molecule-1 (ICAM-1) expression in primary cultures of human brain microvessel endothelial cells by cytokines and lipopolysaccharide

The expression of intercellular adhesion molecule-1 (ICAM-1) by human cerebral endothelium was studied in primary cultures of human brain microvessel endothelial cells following treatment with bacterial lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and interferon-gamma (IFN-gamma). Surface expression of ICAM-1 was examined with the immunogold silver staining technique. Intact cerebral endothelial cells constitutively express low levels of ICAM-1. Stimulation with LPS and cytokines induces upregulation of ICAM-1 which is minimal with IFN-gamma and maximal with LPS or a combination of IFN-gamma and TNF-alpha. Upregulation of ICAM-1 expression is concentration- and time-dependent, is observed as early as 4 h following incubation and persists for up to 72 h in the continuous presence of LPS or cytokines. The ICAM-1 expression is not reversed by 3 days after removal of the LPS or cytokines. These findings may be relevant to the interactions between leukocytes and brain microvessel endothelial cells in inflammatory and demyelinating diseases of the CNS.

Ultrastructural localization of factor VIII-related antigen in cultured human brain microvessel endothelial cells

Immunogold staining of primary cultures of human brain microvessel endothelial cells demonstrated the presence of Factor VIII-related antigen within cytoplasmic vesicles in close association with the rough endoplasmic reticulum and Golgi apparatus. Immunoperoxidase staining, at the light microscopic level, revealed a similar granular, perinuclear staining. The morphology and location of these vesicular profiles indicate that they are part of the trans-Golgi region where terminal processing and short-term storage of Factor VIII-related antigen takes place. Weibel-Palade bodies, specific storage organelles for von Willebrand factor in large vessel endothelium, were not observed in cerebral microvessel endothelium. The release of Factor VIII-related antigen from the cytoplasmic vesicles was influenced by some of the factors known to stimulate or inhibit the regulated pathway of secretion from Weibel-Palade bodies. Thus, stimulation of endothelial cells with calcium ionophore A23187 resulted in almost complete loss of staining, while addition of EGTA to the culture medium led to slight increase of intracellular pools of Factor VIII-related antigen. Pre-incubation of monolayers with interferon-gamma was associated with significant increase in the number of labeled vesicles, suggesting an additional role of this cytokine in the localized immune reaction within the central nervous system.

Haemophilus influenzae lipopolysaccharide disrupts confluent monolayers of bovine brain endothelial cells via a serum-dependent cytotoxic pathway

An in vitro blood-brain barrier (BBB) model consisting of primary cultures of bovine brain microvascular endothelial cells was used to examine the effect of Haemophilus influenzae type b (Hib) on the BBB. Whole bacteria and purified lipopolysaccharide (LPS; greater than 10 ng/ml) caused marked cytotoxicity on the bovine brain endothelial cells. This effect could be completely blocked by polymyxin B. Similar cytotoxic effects were observed with a cultured bovine pulmonary endothelial cell line. Serum was essential for the LPS-mediated cytotoxic effect, and human, horse, bovine, or fetal calf serum all had similar effects. The serum factor was not a complement component. A monoclonal antibody against CD14, a receptor involved in mediating the effect of LPS in monocytes, completely blocked the cytotoxic effect in both brain and pulmonary endothelial cells. These results suggest that Hib LPS disrupts an in vitro BBB model via a serum- and CD14-dependent pathway and that LPS has cytotoxic effects on bovine endothelial cells without the involvement of monocytic cells, an effect that may be important in gram-negative meningitis and in endotoxic shock.

Adhesion and migration of human polymorphonuclear leukocytes across cultured bovine brain microvessel endothelial cells

Adhesion and migration of human polymorphonuclear leukocytes (PMN) across cerebral endothelium were studied in an in vitro model consisting of monolayers of bovine brain microvessel endothelial cells (BBMEC) grown on amniotic stroma or collagen membranes. Polymorphonuclear leukocytes were stimulated to adhere to and migrate across confluent BBMEC monolayers in response to chemotactic gradients produced by formyl-methionyl-leucyl phenylalanine (fMLP), leukotriene B4 (LTB4) or acetyl-glyceryl-ether-phosphorylcholine (AGEPC) placed below the cultures. Under these conditions, PMN adherence to endothelium was 2-10-fold greater than that observed in the absence of chemoattractants or in the presence of equal concentrations of chemoattractants below and above the cultures. Transendothelial migration of PMN occurred rapidly and at focal points across the monolayers. Scanning and electron microscopic studies revealed that stimulated PMN migrated across the monolayers by first adhering to the apical surface of the endothelium and then moving between adjacent endothelial cells. Following their migration, PMN accumulated beneath the endothelium. The overlying endothelial monolayers showed no evidence of disruption and the interendothelial junctions appeared intact at the end of the migration period. We conclude that this in vitro system reproduces the endothelial cell-leukocyte interactions occurring during acute inflammation in vivo and should provide a useful in vitro model for studying the molecular mechanisms underlying these interactions in inflammatory diseases of the central nervous system.

Neurologic complications in allogeneic bone marrow transplant patients receiving cyclosporin

Regimens using cyclosporin (CSP) and either methylprednisolone (MP) or methotrexate (MTX) have been useful in the prophylaxis of acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT). However, CSP produces a number of side effects, including neurologic toxicity. A retrospective review of recipients of 239 BMTs given CSP-based prophylactic regimens revealed that 10 patients (4.2%, 95% confidence interval 0% to 10.4%) experienced a syndrome characterized by hypertension, severe visual disturbances, seizures and occipital lobe density changes on brain computed tomography (nine patients) or nuclear magnetic resonance imaging (one patient). Neurologic findings were reversible in all cases, usually after temporary discontinuation of CSP. Univariate analysis identified the following risk factors for neurotoxicity: use of unrelated or HLA-mismatched related donors, administration of etoposide (VP-16) or total body irradiation as part of conditioning, use of corticosteroids for prophylaxis or treatment of acute GVHD, or development of either acute GVHD or clinically significant microangiopathic hemolytic anemia (MAHA) post-BMT. In multivariate analysis, the most important predictors were the use of VP-16 (p = 0.008), the use of a continuous infusion CSP plus MP prophylactic regimen for GVHD (p = 0.003) and the development of MAHA after BMT (p less than 0.001). The strong association with MAHA suggests that endothelial damage is related to the development of this complication.

Extensive replacement of spinal cord and brainstem by hemangioblastoma in a case of von Hippel-Lindau disease

We report an extremely unusual case of von Hippel-Lindau disease, characterized by almost total replacement of the spinal cord and most of the medulla by capillary hemangioblastoma (CHB). A 34-year-old female presented 20 years earlier with signs of lower limb weakness. She developed progressive quadriplegia despite multiple surgical attempts to remove separate CHBs from the midthoracic and cervical spinal cord. Spinal cord lesions continued to develop as did multiple cerebellar CHBs. She eventually became respirator-dependent and died following severe upper gastrointestinal hemorrhage. At autopsy there was extensive replacement of spinal cord and medulla by CHB as well as multiple solid and cystic cerebellar tumors. Both kidneys were enlarged and largely replaced by renal cell carcinomas and simple cysts. Additionally she had small pancreatic cysts and microscopic pulmonary hamartomas were observed. There was no evidence of retinal lesions clinically or at autopsy. Light microscopic and immunohistochemical studies of the lesions are presented. The early onset of this disease in a female, with such extensive spinal cord involvement, in addition to other CNS and visceral manifestations of von Hippel-Lindau disease, is unusual and has not been previously reported.

Culture and characterization of microvascular endothelial cells derived from human brain

Primary cultures of human cerebral endothelial cells were established from microvessels isolated from cortical fragments removed at surgery for seizure disorder and from brains at autopsy. A uniform population of cells growing in close association to each other formed confluent monolayers by 7 to 10 days in culture. They contained factor VIII/Von Willebrand antigen, the most specific marker for cells of endothelial origin, and showed lectin-binding sites for Ulex europaeus agglutinin characteristic of human endothelium. Cultured cells formed thin, continuous monolayers, contained few pinocytotic vesicles, and were joined together by tight junctional complexes. More than 99% of the intercellular junctions restricted the transendothelial passage of horseradish peroxidase. Monolayers of human brain microvessel endothelial cells thus resemble cerebral endothelium in vivo and should provide a useful in vitro model for studies of the biology of these cells and their role in the pathogenesis of certain human central nervous system diseases associated with abnormal blood-brain barrier function.

Innervation of the zona fasciculata of the adult human adrenal cortex: a light and electron microscopic study

Autonomic innervation of the adrenal cortex has been demonstrated in several species. Detailed ultrastructural studies on the innervation of the zona fasciculata of the normal human adrenal cortex are lacking. We report herein our observations on the pattern of innervation of the cells of the zona fasciculata of the normal adult human cortex at both the light and electron microscope levels. Postganglionic unmyelinated fibers were observed to descend from a dense capsular meshwork and to be distributed as delicate branches among the columns of endocrine cells. Immunoperoxidase staining confirmed the presence of nerve fibers in the zona fasciculata in a distribution similar to that observed after staining with silver impregnation methods. Ultrastructural findings lent further support to these observations by the demonstration of bundles of unmyelinated fibers with focal enlargements containing terminal boutons with both clear and dense core vesicles in close approximation with the endocrine cells.

Severe cerebral damage in ornithine transcarbamylase deficiency

Two patients are described with hyperammonemia due to ornithine transcarbamylase (OTC) deficiency who suffered severe shrinkage and collapse of the brain. The cerebral cortex was spongy and cavitated, containing only a few residual neurons, and was markedly gliosed. In one patient the basal ganglia were affected and harbored Alzheimer type II astrocytes. These lesions resemble those of acquired hepatocerebral degeneration and occur especially in female children with the milder form of the disease, who have a potential to survive. Strict observance of dietary restrictions is mandatory to avoid catastrophic damage to the brain.