Ionic lanthanum passage across cerebral endothelium exposed to hyperosmotic arabinose

Hyperosmotic media infused into the cerebral circulation open the blood-brain barrier to protein and colloid. The mechanism whereby such substances cross the affected vessels is still disputed. We describe here the transendothelial route taken by ionic lanthanum (La 3+ ), a small electron-dense tracer which, unlike colloidal lanthanum, can be administered to the living animal. In adult rats, 2.9 ml of hyperosmotic (1.4 M) arabinose was infused into the internal carotid artery as a 30-s bolus, followed by 5 mM LaCl 3 . To find the extravasated La 3+ , which is invisible by light microscopy, horseradish peroxidase (HRP) was injected simultaneously into the femoral vein. The hyperosmotic treatment resulted in exudation of both HRP and La 3+ primarily around cerebral arterioles. The La 3+ crossed arterioles through successive tight junctions between endothelial cells. Although the tight junctions were not discernibly opened, they must have become permeable because the extracellular pools between successive tight junctions were penetrated by the La 3+ . These pools are normally inaccessible to La 3+ . Luminal and abluminal pits and cytoplasmic vesicles, some of them containing La 3+ , formed intraendothelial clusters. Their role, if any, in the transfer of ion remains remains uncertain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47227/1/401_2004_Article_BF00685347.pd

A Murine Model of Polymyositis Induced by Coxsackievirus B1 (Tucson Strain)

A murine model of polymyositis induced by coxsackievirus B1, Tucson strain (CVB T ) is described. Intraperitoneal CVB T inoculation of CD 1 Swiss mice less than 48 hours old resulted in proximal hindquarter weakness that was first apparent 7 days after viral challenge and persisted for more than 10 weeks. Electromyographic and histologic evidence of a continuing myositis was present during this entire period of time. However, virus was not detectable later than 2 weeks post infection, despite clinical progression of disease. The finding of electromyographic and histologic abnormalities in CVB T -infected mice, long after virus had cleared and neutralizing antibody production evoked, suggests that persistent myositis may be immunologically mediated, triggered by the initial acute viral infection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37767/1/1780270411_ftp.pd

Abnormal neuromuscular transmission in an infantile myasthenic syndrome

A term infant required intubation for respiratory depression. Examination revealed hypotonia and areflexia with intact extraocular movements. Electrodiagnostic studies demonstrated defective neuromuscular transmission characterized by borderline low motor evoked amplitudes, profound decremental responses at all stimulation rates, and moderate facilitation (50 to 740%) 15 seconds after 5 seconds of 50 Hz stimulation. Repetitive muscle action potential responses were not recorded following stimulation of nerves by single shocks. Sensory evoked responses and needle electromyographic findings were normal, as were acetylcholine receptor antibody levels. Results of muscle histochemical analyses, including acetylcholinesterase stains, were normal. End-plate histometric analyses demonstrated only a slight reduction in mean synaptic vesicle diameter compared with that in an adult control subject. In vitro muscle contractile properties, stimulating the muscle directly, were normal. Anticholinesterase medications were ineffective. Guanidine produced clinical deterioration. The amplitude of motor evoked responses progressively declined, whereas the percentage of decrement and amount of post-tetanic facilitation increased. Although the nature of the transmission defect was not identified, the data are consistent with abnormal acetylcholine resynthesis, mobilization, or storage without abnormality of release or receptors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50308/1/410160107_ftp.pd

The Neuropathology of Fatal Cerebral Malaria in Malawian Children

We examined the brains of 50 Malawian children who satisfied the clinical definition of cerebral malaria (CM) during life; 37 children had sequestration of infected red blood cells (iRBCs) and no other cause of death, and 13 had a nonmalarial cause of death with no cerebral sequestration. For comparison, 18 patients with coma and no parasitemia were included. We subdivided the 37 CM cases into two groups based on the cerebral microvasculature pathology: iRBC sequestration only (CM1) or sequestration with intravascular and perivascular pathology (CM2). We characterized and quantified the axonal and myelin damage, blood-brain barrier (BBB) disruption, and cellular immune responses and correlated these changes with iRBC sequestration and microvascular pathology. Axonal and myelin damage was associated with ring hemorrhages and vascular thrombosis in the cerebral and cerebellar white matter and brainstem of the CM2 cases. Diffuse axonal and myelin damage were present in CM1 and CM2 cases in areas of prominent iRBC sequestration. Disruption of the BBB was associated with ring hemorrhages and vascular thrombosis in CM2 cases and with sequestration in both CM1 and CM2 groups. Monocytes with phagocytosed hemozoin accumulated within microvessels containing iRBCs in CM2 cases but were not present in the adjacent neuropil. These findings are consistent with a link between iRBC sequestration and intravascular and perivascular pathology in fatal pediatric CM, resulting in myelin damage, axonal injury, and breakdown of the BBB

Regulation of CCL2 and CCL3 expression in human brain endothelial cells by cytokines and lipopolysaccharide

Background. Chemokines are emerging as important mediators of CNS inflammation capable of activating leukocyte integrins and directing the migration of leukocyte subsets to sites of antigenic challenge. In this study we investigated the expression, release and binding of CCL2 (MCP-1) and CCL3 (MIP-1α) in an in vitro model of the human blood-brain barrier. Methods The kinetics of expression and cytokine upregulation and release of the β-chemokines CCL2 and CCL3 were studied by immunocytochemistry and enzyme-linked immunosorbent assay in primary cultures of human brain microvessel endothelial cells (HBMEC). In addition, the differential binding of these chemokines to the basal and apical endothelial cell surfaces was assessed by immunoelectron microscopy. Results Untreated HBMEC synthesize and release low levels of CCL2. CCL3 is minimally expressed, but not released by resting HBMEC. Treatment with TNF-α, IL-1β, LPS and a combination of TNF-α and IFN-γ, but not IFN-γ alone, significantly upregulated the expression and release of both chemokines in a time-dependent manner. The released CCL2 and CCL3 bound to the apical and basal endothelial surfaces, respectively. This distribution was reversed in cytokine-activated HBMEC resulting in a predominantly basal localization of CCL2 and apical distribution of CCL3. Conclusions Since cerebral endothelial cells are the first resident CNS cells to contact circulating leukocytes, expression, release and presentation of CCL2 and CCL3 on cerebral endothelium suggests an important role for these chemokines in regulating the trafficking of inflammatory cells across the BBB in CNS inflammation.Medicine, Faculty ofPathology and Laboratory Medicine, Department ofNon UBCReviewedFacult

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-g. 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.Medicine, Faculty ofPathology and Laboratory Medicine, Department ofReviewedFacult

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 pathogenesi

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