Ex vivo model of epilepsy in organotypic slices-a new tool for drug screening

BACKGROUND

Epilepsy is a prevalent neurological disorder worldwide. It is characterized by an enduring predisposition to generate seizures and its development is accompanied by alterations in many cellular processes. Organotypic slice cultures represent a multicellular environment with the potential to assess biological mechanisms, and they are used as a starting point for refining molecules for in vivo studies. Here, we investigated organotypic slice cultures as a model of epilepsy.

METHODS

We assessed, by electrophysiological recordings, the spontaneous activity of organotypic slices maintained under different culture protocols. Moreover, we evaluated, through molecular-based approaches, neurogenesis, neuronal death, gliosis, expression of proinflammatory cytokines, and activation of NLRP3 inflammasome (nucleotide-binding, leucine-rich repeat, pyrin domain) as biomarkers of neuroinflammation.

RESULTS

We demonstrated that organotypic slices, maintained under a serum deprivation culture protocol, develop epileptic-like activity. Furthermore, throughout a comparative study with slices that do not depict any epileptiform activity, slices with epileptiform activity were found to display significant differences in terms of inflammation-related features, such as (1) increased neuronal death, with higher incidence in CA1 pyramidal neurons of the hippocampus; (2) activation of astrocytes and microglia, assessed through western blot and immunohistochemistry; (3) upregulation of proinflammatory cytokines, specifically interleukin-1β (IL-1β), interleukin-6, and tumor necrosis factor α, revealed by qPCR; and (4) enhanced expression of NLRP3, assessed by western blot, together with increased NLRP3 activation, showed by IL-1β quantification.

CONCLUSIONS

Thus, organotypic slice cultures gradually deprived of serum mimic the epileptic-like activity, as well as the inflammatory events associated with in vivo epilepsy. This system can be considered a new tool to explore the interplay between neuroinflammation and epilepsy and to screen potential drug candidates, within the inflammatory cascades, to reduce/halt epileptogenesis.

Neuroprotective activity of 2-amino-1,3,4-thiadiazole derivative 4BrABT--an in vitro study

4BrABT (2-(4-Bromophenylamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole) is a compound known for its interesting in vitro anticancer profile. 4BrABT inhibited proliferation and motility of several cancer cell lines in concentrations which were not toxic to normal cells. A major problem associated with cancer chemotherapy, but also caused by environmental factors such as pesticides, is neurotoxicity. Therefore, the aim of the presented study was an in vitro evaluation of the neuroprotective activity of this compound. 4BrABT activity (1-100 μM) was tested in cultures of mouse neurons, rat astrocytes and rat oligodendrocytes. A possible protective action of the compound in different neurodegenerative models, as serum deprivation (SD), excitotoxicity (presence of 500 μM glutamate in culture medium), as well as cisplatin toxicity (astroglia--50 μM and oligodendroglia--100 μM) was investigated. Cell viability in the tested cultures was assessed with the use of LDH and MTT methods. Moreover, 4BrABT ability to prevent the cisplatin-induced apoptosis in astrocyte and oligodendrocyte cultures was analysed after Hoechst 33342 fluorostaining. The obtained results indicate that 4BrABT was not toxic to neurons, astrocytes and oligodendrocytes. Moreover, a decrease in the neuronal LDH level was observed, which may suggest the ability of 4BrABT to act as a trophic agent. Furthermore, the protective action of the studied compound was shown in neuronal cultures exposed to neurotoxic conditions (presence of glutamate and trophic stress) and in cisplatin-treated astrocytes and oligodendrocytes. The expression of anticancer and neuroprotective activity raises hopes for the potential use of 4BrABT as a safe anticancer drug, or neuroprotective agent in chemotherapy-associated neurotoxicity.

Sphingosine kinase 1 localized to the plasma membrane lipid raft microdomain overcomes serum deprivation induced growth inhibition

Several studies have demonstrated that sphingosine kinase 1 (SphK1) translocates to the plasma membrane (PM) upon its activation and further suggested the plasma membrane lipid raft microdomain (PMLRM) as a target for SphK1 relocalization. To date, however, direct evidence of SphK1 localization to the PMLRM has been lacking. In this report, using multiple biochemical and subcellular fractionation techniques we demonstrate that endogenous SphK1 protein and its substrate, D-erythro-sphingosine, are present within the PMLRM. Additionally, we demonstrate that the PMA stimulation of SphK1 localized to the PMLRM results in production of sphingosine-1-phosphate as well as induction of cell growth under serum deprivation conditions. We further report that Ser225Ala and Thr54Cys mutations, reported to abrogate phosphatidylserine binding, block SphK1 targeting to the PMLRM and SphK1 induced cell growth. Together these findings provide direct evidence that the PMLRM is the major site of action for SphK1 to overcome serum-deprived cell growth inhibition.

The neuroprotective effect of Activin A and B: implication for neurodegenerative diseases

Activin is a member of the transforming growth factor-beta superfamily which comprises a growing list of multifunctional proteins that function as modulators of cell proliferation, differentiation, hormone secretion and neuronal survival. This study examined the neuroprotective effect of both Activin A and B in serum withdrawal and oxidative stress apoptotic cellular models and investigated the expression of pro- and anti-apoptotic proteins, which may account for the mechanism of Activin-induced neuroprotection. Here, we report that recombinant Activin A and B are neuroprotective against serum deprivation- and toxin- [either the parkinsonism-inducing neurotoxin, 6-hydroxydopamine (6-OHDA) or the peroxynitrite donor, 3-(4-morpholinyl) sydnonimine hydrochloride (SIN-1)] induced neuronal death in human SH-SY5Y neuroblastoma cells. Furthermore, we demonstrate for the first time that transient transfection with Activin betaA or betaB significantly protect SH-SY5Y and rat pheochromocytoma PC12 cells against serum withdrawal-induced apoptosis. This survival effect is mediated by the Bcl-2 family members and involves inhibition of caspase-3 activation; reduction of cleaved poly-ADP ribose polymerase and phosphorylated H2A.X protein levels and elevation of tyrosine hydroxylase expression. These results indicate that both Activin-A and -B share the potential to induce neuroprotective activity and thus may have positive impact on aging and neurodegenerative diseases to retard the accelerated rate of neuronal degeneration.

Cesium chloride protects cerebellar granule neurons from apoptosis induced by low potassium

Neuronal apoptosis plays a critical role in the pathogenesis of neurodegenerative disorders, and neuroprotective agents targeting apoptotic signaling could have therapeutic use. Here we report that cesium chloride, an alternative medicine in treating radiological poison and cancer, has neuroprotective actions. Serum and potassium deprivation induced cerebellar granule neurons to undergo apoptosis, which correlated with the activation of caspase-3. Cesium prevented both the activation of caspase-3 and neuronal apoptosis in a dose-dependent manner. Cesium at 8 mM increased the survival of neurons from 45 +/- 3% to 91 +/- 5% of control. Cesium's neuroprotection was not mediated by PI3/Akt or MAPK signaling pathways, since it was unable to activate either Akt or MAPK by phosphorylation. In addition, specific inhibitors of PI3 kinase and MAP kinase did not block cesium's neuroprotective effects. On the other hand, cesium inactivated GSK3beta by phosphorylation of serine-9 and GSK3beta-specific inhibitor SB415286 prevented neuronal apoptosis. These data indicate that cesium's neuroprotection is likely via inactivating GSK3beta. Furthermore, cesium also prevented H(2)O(2)-induced neuronal death (increased the survival of neurons from 72 +/- 4% to 89 +/- 3% of control). Given its relative safety and good penetration of the brain blood barrier, our findings support the potential therapeutic use of cesium in neurodegenerative diseases.

Efficacy and safety of voriconazole as an additive in Optisol GS: a preservation medium for corneal donor tissue

PURPOSE

To assess the endothelial toxicity and the microbiological efficacy of voriconazole (100 microg/mL) as an antimicrobial additive to Optisol GS.

METHODS

A total of 533 donor rims were studied. One half of each donor rim was placed in standard Optisol GS and the other half rim in Optisol GS fortified with voriconazole (100 microg/mL). All rims were refrigerated for 24 hours at 3 degrees C and placed in thioglycolate broth and incubated at 37 degrees C for 7 days. A pair of donor buttons not used in transplantation was stored for 2 days in each solution and examined for endothelial changes with electron microscopy (EM). A second pair of cornea buttons was examined for toxicity by endothelial staining with 0.3% trypan blue and 0.2% alizarin red.

RESULTS

Seven of 533 corneal rim cultures were positive for fungal organisms in the Optisol GS group. No rims were positive for fungal growth in the voriconazole-fortified Optisol GS medium. The difference was statistically significant (P = 0.015; Fisher exact test). There was no difference in the cellular morphology of the button stored in voriconazole fortified Optisol GS compared with Optisol GS using EM. In the bioassay, the percentage of nonviable cells in the voriconazole-fortified medium compared with the control medium was nonsignificant (P < 0.05, Student t test).

CONCLUSIONS

Voriconazole seems to be safe as a fortifying agent for cornea storage medium. It significantly reduces the rate of positive fungal rim cultures and shows no signs of endothelial cytotoxicity as viewed by EM and by a bioassay of trypan blue and alizarin red.

Hydrogen peroxide attenuates insulin-like growth factor-1 neuroprotective effect, prevented by minocycline

Oxidative stress-induced neuronal death due to hydrogen peroxide overload plays a critical role in the pathogenesis of numerous neurological diseases. Insulin-like growth factor-1 (IGF-1) is important in maintaining neuronal survival, proliferation, and differentiation in the central nervous system. We now report that sublethal doses of hydrogen peroxide attenuated IGF-1 neuroprotective activity on cultured cerebellar granule neurons under potassium and serum deprivation. Interestingly, this attenuation can be prevented by minocycline, an antibiotic that has been shown to have neuroprotective activity in animal models of neuronal injury. Furthermore, hydrogen peroxide also blocked IGF-1's neuroprotection for cortical neurons deprived of neurotrophic factors (B27), which was prevented by minocycline. Our data suggest that inhibition of IGF-1 signaling by hydrogen peroxide may constitute an additional pathway contributing to its neurotoxicity. More importantly, combining minocycline and IGF-1 could be an effective treatment in neurological diseases associated with both oxidative stress and deficiency of IGF-1.

Deep anterior lamellar keratoplasty for keratoconus

PURPOSE

To investigate surgical outcomes after deep anterior lamellar keratoplasty (DALKP) in eyes with keratoconus.

METHODS

Retrospective review of 127 eyes of 118 keratoconus patients who underwent DALKP at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia between January 1, 1998 and November 30, 2001. The mean age of all patients was 25.9 years (range 11-70 years). The mean follow-up for all patients was 10.9 months (range 4-61 months). Baring of Descemet's membrane (DM) during DALKP was achieved in 47 (37%) eyes; some stroma was left during operation in the remaining 80 (63%) eyes. Snellen visual acuity, intraoperative complications, and postoperative graft status were assessed.

RESULTS

At the last follow-up visit, 74% of all eyes were able to achieve a best-corrected visual acuity of 20/50 or better. This level of improvement was more statistically significant with baring of DM (P = 0.005). Intraoperative perforation of DM occurred in 16 (13%) cases and was statistically significant in eyes with deep corneal scars (P = 0.012). However, this perforation did not seem to have an impact on the final visual acuity (P = 0.48). Main graft-related complications included graft-host vascularization (7/127), stromal graft rejection (4/127), graft infection (1/127), and persistent epithelial defect (1/127).

CONCLUSIONS

Deep lamellar keratoplasty provides a safer and successful alternative to penetrating keratoplasty for keratoconus patients but remains a challenging procedure. Endothelial graft rejection is absent after DALKP. However, stromal graft rejection, although very rare, does occur.

Neuroprotective effects of minocycline against in vitro and in vivo retinal ganglion cell damage

The purpose of this study was to determine whether minocycline, a semi-synthetic tetracycline derivative, reduces (a) the in vitro neuronal damage occurring after serum deprivation in cultured retinal ganglion cells (RGC-5, a rat ganglion cell line transformed using E1A virus) and/or (b) the in vivo retinal damage induced by N-methyl-D-aspartate (NMDA) intravitreal injection in mice. In addition, we examined minocycline's putative mechanisms of action against oxidative stress and endoplasmic reticulum (ER) stress. In vitro, retinal damage was induced by 24-h serum deprivation, and cell viability was measured by Hoechst 33342 staining or resazurin reduction assay. In cultures of RGC-5 cells maintained in serum-free medium for up to 24 h, the number of cells undergoing cell death was reduced by minocycline (0.2-20 microM). Serum deprivation resulted in increased oxidative stress, as revealed by an increase in the fluorescence intensity for 5-(and-6)-chloromethyl-2', 7'-dichlorodihydrofluorescein diacetate (CM-H2DCFDA), a reactive oxygen species (ROS) indicator. Minocycline at 2 and 20 microM inhibited this ROS production. However, even at 20 microM minocycline did not inhibit the retinal damage induced by tunicamycin (an ER stress inducer). Furthermore, in mice in vivo minocycline at 90 mg/kg intraperitoneally administered 60 min before an NMDA intravitreal injection reduced the NMDA-induced retinal damage. These findings indicate that minocycline has neuroprotective effects against in vitro and in vivo retinal damage, and that an inhibitory effect on ROS production may contribute to the underlying mechanisms.

Overexpression of torsinA in PC12 cells protects against toxicity

Childhood-onset dystonia is an autosomal dominant movement disorder associated with a three base pair (GAG) deletion mutation in the DYT1 gene. This gene encodes a novel ATP-binding protein called torsinA, which in the central nervous system is expressed exclusively in neurons. Neither the function of torsinA nor its role in the pathophysiology of DYT1 dystonia is known. In order to better understand the cellular functions of torsinA, we established PC12 cell lines overexpressing wild-type or mutant torsinA and subjected them to various conditions deleterious to cell survival. Treatment of control PC12 cells with an inhibitor of proteasomal activity, an oxidizing agent, or trophic withdrawal, resulted in cell death, whereas PC12 cells that overexpressed torsinA were significantly protected against each of these treatments. Overexpression of mutant torsinA failed to protect cells against trophic withdrawal. These results suggest that torsinA may play a protective role in neurons against a variety of cellular insults.

Humanin inhibits cell death of serum-deprived PC12h cells

Humanin (HN) and S14G HN (HNG) are recently discovered polypeptides that rescue cells from death induced by multiple different types of familial Alzheimer's disease genes and by amyloid-beta. However, the cytoprotective activity of these peptides against other cell death-inducing stimuli remains unclear. In this study, we demonstrated, using three different methods (MTS assay, caspase-3 assay, and detection of DNA fragmentation), that both HN and HNG protect PC12 cells from death elicited by serum deprivation. This implies the potential of the peptides to rescue cells from a broad spectrum, if not all, of cell death-inducing factors. Further investigations on HN may lead the possible application of this peptide as therapeutic agent for the treatment of other neurodegenerative diseases.

Evaluation of neuronal cell death by laser scanning cytometry

We developed a method in which laser scanning cytometry (LSC) is applied to evaluate cell viability. Neuronal cell death induced by glutamic acid, serum potassium deprivation and 3-nitropropionic acid was studied in cerebellar granule cells by neutral red assay (NR) and LSC, using propidium iodide (PI) as fluorescent dye. PI labeled the nuclei of dead neurons and increased fluorescence was measured using a laser scanning cytometer. Similar levels of damage for each injury were detected by NR or LSC. The protocol presented here, provides a fast and sensitive assay for the analysis of neuronal viability using LSC, and can be used to study new neuroprotective drugs in neuronal cell cultures.

CD43 expression in a B cell lymphoma, WEHI 231, reduces susceptibility to G1 arrest and extends survival in culture upon serum depletion

CD43 is a major surface sialoprotein on hemopoietic cells, whose extracellular domain is heavily O-glycosylated. The functional role of CD43 in the hemopoietic system is not fully understood; however, it has been suggested that CD43 may have a role in cell-cell repulsion and in modifying T cell proliferation and activation. CD43 is expressed in immature B cells in the bone marrow, but not by peripheral B cells, except for B-1 B cells and plasma cells. To analyze the biological effect of CD43 in B-lineage cells, we transfected mouse CD43 cDNA into a CD43- B cell lymphoma, WEHI 231, and the growth and survival in culture were compared to those of a parental cell line, human CD8 transfectants, and CD43- revertants established from CD43+ clones. We observed that CD43 expression supported cell growth in culture upon serum reduction, whereas growth of CD43- cell lines was barely detected under this condition. CD43- cell lines accumulated in G1 phase of the cell cycle, and the numbers of viable cells were greatly reduced during culture upon serum depletion, whereas expression of CD43 reduced the susceptibility to G1 arrest and temporarily retarded the apoptotic process, which, in turn, resulted in an increase and maintenance of the number of viable cells in culture. The results suggest that CD43 may have some role in the survival and expansion of B-lineage cells. The biological effect of CD43 was initiated without stimulation by cross-linking and was significantly impaired by replacement of the extracellular domain by the human CD8 extracellular domain. The basis of these regulatory processes is discussed.