Vampire bat salivary plasminogen activator (desmoteplase) inhibits tissue-type plasminogen activator-induced potentiation of excitotoxic injury

Background and Purpose - In contrast to tissue-type plasminogen activator (tPA), vampire bat ( Desmodus rotundus) salivary plasminogen activator ( desmoteplase [ DSPA]) does not promote excitotoxic injury when injected directly into the brain. We have compared the excitotoxic effects of intravenously delivered tPA and DSPA and determined whether DSPA can antagonize the neurotoxic and calcium enhancing effects of tPA. Methods - The brain striatal region of wild-type c57 Black 6 mice was stereotaxically injected with N-methyl-D-Aspartate ( NMDA); 24 hour later, mice received an intravenous injection of tPA or DSPA ( 10 mg/kg) and lesion size was assessed after 24 hours. Cell death and calcium mobilization studies were performed using cultures of primary murine cortical neurons. Results - NMDA-mediated injury was increased after intravenous administration of tPA, whereas no additional toxicity was seen after administration of DSPA. Unlike DSPA, tPA enhanced NMDA-induced cell death and the NMDA-mediated increase in intracellular calcium levels in vitro. Moreover, the enhancing effects of tPA were blocked by DSPA. Conclusions - Intravenous administration of tPA promotes excitotoxic injury, raising the possibility that leakage of tPA from the vasculature into the parenchyma contributes to brain damage. The lack of such toxicity by DSPA further encourages its use as a thrombolytic agent in the treatment of ischemic stroke

Effects of lipopolysaccharide on glial phenotype and activity of glutamate transporters: Evidence for delayed up-regulation and redistribution of GLT-1

Excitatory amino acid transporters (EAATs) are responsible for homeostasis of extracellular l-glutamate, and the glial transporters are functionally dominant. EAAT expression or function is altered in acute and chronic neurological conditions, but little is known about the regulation of EAATs in reactive astroglia found in such neuropathologies. These studies examined the effects of the bacterial endotoxin lipopolysaccharide (LPS) on glial EAATs in vitro. The effects of LPS (1 ?g/ml, 24-72 h) on EAAT activity and expression were examined in primary cultures of mouse astrocytes. [3H]d-aspartate uptake increased to 129% of control by 72 h treatment with LPS. Saturation analysis revealed that apparent Km was unchanged whilst Vmax was significantly increased to 172% of control by 72 h LPS treatment. Biotinylation and Western blotting indicated that cell-surface expression of GLT-1 was significantly elevated (146% control) by LPS treatment whereas GLAST expression was unchanged. Confocal analyses revealed that LPS treatment resulted in cytoskeletal changes and stellation of astrocytes, with rearrangement of F-actin (as shown by phalloidin labelling). Immunocytochemistry revealed clustering of GLAST, and increased expression and redistribution of GLT-1 to the cell-surface following treatment with LPS. Similar experiments were conducted in microglia, where LPS (50 ng/ml) was found to up-regulate expression of GLT-1 at 24 and 72 h in concert with cytoskeletal changes accompanying activation. These findings suggest an association of cytoskeletal changes in glia with EAAT activity, with the predominant adaptation involving up-regulation and redistribution of GLT-

Treatment Of Segmental Bone Defects In Rats By The Stimulation Of Bone Marrow Osteo-Progenitor Cells With Prostaglandin E-2

An alternative to bone grafting is engineered osteo-conductive material that carries osteo-progenitor cells with osteo-stimulant factors impregnated on a malleable osteo-conductive material. We used bone marrow stem cells as the source of osteo-progenitor cells and stimulated them with prostaglandin E-2 using demineralised bone matrix as a carrier. We treated 35 skeletally mature male Wistar albino rats with segmentary radial bone defects using five different treatment groups. Group I received no treatment; the remaining four groups all received a mixture of bone marrow and demineralised bone matrix. In group III, a copolymer was added. In group IV, prostaglandin E-2 and in group V prostaglandin E-2 within a copolymer was added to the mixture. Eight weeks after the surgical procedure, the rats were sacrificed. Radiological and histological evaluation of the radial bone showed that while there was no significant healing in groups I, II and III, there was a significant healing response in groups IV and V.Wo

Novel Neuroinflammatory Targets in the Chronically Injured Spinal Cord

Injury to the spinal cord is known to result in inflammation. To date, the preponderance of research has focused on the acute neuroinflammatory response, which begins immediately and is believed to terminate within hours to (at most) days after the injury. However, recent studies have demonstrated that postinjury inflammation is not restricted to the first few hours or days after injury, but can last for months to years after a spinal cord injury (SCI). These chronic studies have revealed that increased numbers of inflammatory cells, such as microglia and macrophages, and inflammatory factors, including cytokines, chemokines, and enzyme products are found at markedly delayed times after injury. Here we review experimental work on a selection of the novel inflammatory factors observed chronically after SCI, including the nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase enzyme and galectin-3. We will discuss the role of these proteins in inflammation with regard to both detrimental and beneficial effects of neuroinflammation after injury. Finally, the potential of these proteins to serve as therapeutic targets will be considered, and a novel therapeutic approach (i.e., the agonist for metabotropic glutamate receptor 5 [mGluR5], [RS]-2-Chloro-5-hydroxyphenylglycine [CHPG]) will be discussed. This review will demonstrate the expression and activity profiles, roles in potentiation of injury, and therapy studies of these inflammatory factors suggest that not only are these chronically expressed factors viable targets for SCI treatment, but that the therapeutic window is broader than has previously been thought