Star power: harnessing the reactive astrocyte response to promote remyelination in multiple sclerosis

Astrocytes are indispensable for central nervous system development and homeostasis. In response to injury and disease, astrocytes are integral to the immunological- and the, albeit limited, repair response. In this review, we will examine some of the functions reactive astrocytes play in the context of multiple sclerosis and related animal models. We will consider the heterogeneity or plasticity of astrocytes and the mechanisms by which they promote or mitigate demyelination. Finally, we will discuss a set of biomedical strategies that can stimulate astrocytes in their promyelinating response.

Integrating single-cell and spatially resolved transcriptomic strategies to survey the astrocyte response to stroke in male mice

Astrocytes, a type of glial cell in the central nervous system (CNS), adopt diverse states in response to injury that are influenced by their location relative to the insult. Here, we describe a platform for spatially resolved, single-cell transcriptomics and proteomics, called tDISCO (tissue-digital microfluidic isolation of single cells for -Omics). We use tDISCO alongside two high-throughput platforms for spatial (Visium) and single-cell transcriptomics (10X Chromium) to examine the heterogeneity of the astrocyte response to a cortical ischemic stroke in male mice. We show that integration of Visium and 10X Chromium datasets infers two astrocyte populations, proximal or distal to the injury site, while tDISCO determines the spatial boundaries and molecular profiles that define these populations. We find that proximal astrocytes show differences in lipid shuttling, with enriched expression of Apoe and Fabp5. Our datasets provide a resource for understanding the roles of astrocytes in stroke and showcase the utility of tDISCO for hypothesis-driven, spatially resolved single-cell experiments.

Digital Microfluidics for Microproteomic Analysis of Minute Mammalian Tissue Samples Enabled by a Photocleavable Surfactant

Proteome profiles of precious tissue samples have great clinical potential for accelerating disease biomarker discovery and promoting novel strategies for early diagnosis and treatment. However, tiny clinical tissue samples are often difficult to handle and analyze with conventional proteomic methods. Automated digital microfluidic (DMF) workflows facilitate the manipulation of size-limited tissue samples. Here, we report the assessment of a DMF microproteomics workflow enabled by a photocleavable surfactant for proteomic analysis of minute tissue samples. The surfactant 4-hexylphenylazosulfonate (Azo) was found to facilitate fast droplet movement on DMF and enhance the proteomics analysis. Comparisons of Azo and n-Dodecyl β-d-maltoside (DDM) using small samples of HeLa digest standards and MCF-7 cell digests revealed distinct differences at the peptide level despite similar results at the protein level. The DMF microproteomics workflow was applied for the sample preparation of ∼3 μg biopsies from murine brain tissue. A total of 1969 proteins were identified in three samples, including established neural biomarkers and proteins related to synaptic signaling. Going forward, we propose that the Azo-enabled DMF workflow has the potential to advance the practical clinical application of DMF for the analysis of size-limited tissue samples.

Morphological, cytogenetic and molecular characterisation of FLT3 mutations in Pakistani patients with de novo acute myeloid leukaemia: A single centre experience

INTRODUCTION

Mutations in FLT3 are the most commonly reported genetic changes in AML patients. These mutations are normally identified in approximately one third of newly diagnosed patients and are reported to have prognostic significance.

MATERIALS AND METHODS

Peripheral blood samples was collected from 63 AML patients to study their morphological, cytogenetic and molecular features. PCR was used to determine the prevalence of FLT3 mutations; internal tandem duplication (ITD) and tyrosine kinase domain (TKD) in AML patients.

RESULTS

Among 63 AML patients, 42 were males and 21 were females with male to female ratio 2:1 with median age of 32 years. AML-M2 was the predominant French-American-British (FAB) subtype (42%) followed by M4 (27%), M3 (8%), M1 (8%), M0 (8%) and M5 (7%) respectively. Cytogenetic analysis of 60 patients showed 58% as cytogenetically normal (CN) whereas 42% had aberrant karyotype.The most frequent aberrations were trisomy8, t(8;21), t(15;17) (8.3%) each, inversion16 (5%), and different deletions (12%) respectively. FAB-M4 subtype showed most of the chromosomal anomalies. Among 63 AML patients, 22% showed FLT3/ITD while 6.4% had D835 mutation after molecular analysis. FLT3 mutations were found in most of the FAB subtypes and cytogenetic groups. FLT3/ITD mutations were more common in patients with normal karyotype (26%) and usually present with hyperleukocytosis but association between two was not significant.

CONCLUSION

The cytogenetic data of adult AML from Pakistan showed presence of favourable prognostic karyotype with comparable prevalence as reported in international data. Moreover, FLT3/ITD mutations are commonly found in our patients as determined by molecular analysis. Therefore, inclusion of this unfavourable prognostic marker should be routine in molecular diagnostic testing of AML.

Oral probiotic therapy improves motor function in a rodent model of sensorimotor stroke

Ischemic stroke is a debilitating neurological disease with few effective therapeutics. Previous work has shown that oral probiotic treatment prior to stroke can attenuate cerebral infarction and neuroinflammation, highlighting the gut-microbiota-brain axis as a novel therapeutic target. Whether a more clinically relevant, post-stroke, administration of probiotics can improve stroke outcomes is unknown. In this study, we examined the effect of post-stroke oral probiotic therapy on motor behavior in the pre-clinical mouse endothelin-1 (ET-1) model of sensorimotor stroke. We found that post-stroke oral probiotic therapy with Cerebiome^® (Lallemand, Montreal, Canada), containing B. longum R0175 and L. helveticus R0052, improved functional recovery and changed the composition of the post-stroke gut microbiota. Interestingly, oral Cerebiome^® administration did not result in alterations of lesion volume or the number of CD8+/Iba1+ cells in the injured tissue. Overall, these findings suggest that probiotic treatment following injury can improve sensorimotor function.

Ascl1 phospho-site mutations enhance neuronal conversion of adult cortical astrocytes in vivo

Direct neuronal reprogramming, the process whereby a terminally differentiated cell is converted into an induced neuron without traversing a pluripotent state, has tremendous therapeutic potential for a host of neurodegenerative diseases. While there is strong evidence for astrocyte-to-neuron conversion in vitro, in vivo studies in the adult brain are less supportive or controversial. Here, we set out to enhance the efficacy of neuronal conversion of adult astrocytes in vivo by optimizing the neurogenic capacity of a driver transcription factor encoded by the proneural gene Ascl1. Specifically, we mutated six serine phospho-acceptor sites in Ascl1 to alanines (Ascl1SA6) to prevent phosphorylation by proline-directed serine/threonine kinases. Native Ascl1 or Ascl1SA6 were expressed in adult, murine cortical astrocytes under the control of a glial fibrillary acidic protein (GFAP) promoter using adeno-associated viruses (AAVs). When targeted to the cerebral cortex in vivo, mCherry+ cells transduced with AAV8-GFAP-Ascl1SA6-mCherry or AAV8-GFAP-Ascl1-mCherry expressed neuronal markers within 14 days post-transduction, with Ascl1SA6 promoting the formation of more mature dendritic arbors compared to Ascl1. However, mCherry expression disappeared by 2-months post-transduction of the AAV8-GFAP-mCherry control-vector. To circumvent reporter issues, AAV-GFAP-iCre (control) and AAV-GFAP-Ascl1 (or Ascl1SA6)-iCre constructs were generated and injected into the cerebral cortex of Rosa reporter mice. In all comparisons of AAV capsids (AAV5 and AAV8), GFAP promoters (long and short), and reporter mice (Rosa-zsGreen and Rosa-tdtomato), Ascl1SA6 transduced cells more frequently expressed early- (Dcx) and late- (NeuN) neuronal markers. Furthermore, Ascl1SA6 repressed the expression of astrocytic markers Sox9 and GFAP more efficiently than Ascl1. Finally, we co-transduced an AAV expressing ChR2-(H134R)-YFP, an optogenetic actuator. After channelrhodopsin photostimulation, we found that Ascl1SA6 co-transduced astrocytes exhibited a significantly faster decay of evoked potentials to baseline, a neuronal feature, when compared to iCre control cells. Taken together, our findings support an enhanced neuronal conversion efficiency of Ascl1SA6 vs. Ascl1, and position Ascl1SA6 as a critical transcription factor for future studies aimed at converting adult brain astrocytes to mature neurons to treat disease.

Traditional Uses of Animals in the Himalayan Region of Azad Jammu and Kashmir

Background: The use of animals and animal-derived products in ethnopharmacological applications is an ancient human practice that continues in many regions today. The local people of the Himalayan region harbor rich traditional knowledge used to treat a variety of human ailments. The present study was intended with the aim of examining animal-based traditional medicine utilized by the population of the Himalayan region of Azad Jammu and Kashmir.

Methods: Data were collected from 2017 to 2019 through individual and group interviews. Data on traditional uses of animal products were analyzed, utilizing following indices such as the frequency of citation, use value, relative importance, similarity index, principal component analysis, and cluster analysis to find the highly preferred species in the area.

Results: Ethnomedicinal uses of 62 species of vertebrates and invertebrates were documented. Flesh, fat, bone, whole body, milk, skin, egg, head, feathers, bile, blood, and honey were all used in these applications. The uses of 25 animals are reported here for the first time from the study area (mainly insects and birds, including iconic species like the kalij pheasant, Lophura leucomelanos; Himalayan monal, L. impejanus; and western tragopon, Tragopan melanocephalus). The diversity and range of animal-based medicines utilized in these communities are indications of their strong connections with local ecosystems.

Conclusion: Our results provide baseline data valuable for the conservation of vertebrate and invertebrate diversity in the region of Himalayan of Azad Jammu and Kashmir. It is possible that screening this fauna for medicinally active chemicals could contribute to the development of new animal-based drugs.

Signal requirement for cortical potential of transplantable human neuroepithelial stem cells

The cerebral cortex develops from dorsal forebrain neuroepithelial progenitor cells. Following the initial expansion of the progenitor cell pool, these cells generate neurons of all the cortical layers and then astrocytes and oligodendrocytes. Yet, the regulatory pathways that control the expansion and maintenance of the progenitor cell pool are currently unknown. Here we define six basic pathway components that regulate proliferation of cortically specified human neuroepithelial stem cells (cNESCs) in vitro without the loss of cerebral cortex developmental potential. We show that activation of FGF and inhibition of BMP and ACTIVIN A signalling are required for long-term cNESC proliferation. We also demonstrate that cNESCs preserve dorsal telencephalon-specific potential when GSK3, AKT and nuclear CATENIN-β1 activity are low. Remarkably, regulation of these six pathway components supports the clonal expansion of cNESCs. Moreover, cNESCs differentiate into lower- and upper-layer cortical neurons in vitro and in vivo. The identification of mechanisms that drive the neuroepithelial stem cell self-renewal and differentiation and preserve this potential in vitro is key to developing regenerative and cell-based therapeutic approaches to treat neurological conditions.

Prevalence and molecular detection of contagious bovine pleuropneumonia in large ruminants in Punjab, Pakistan

Contagious bovine pleuropneumonia (CBPP) is a highly contagious disease of cattle caused by Mycoplasma mycoides subsp. mycoides. It is characterized by anorexia, fever, dyspnea, polypnea, cough, and nasal discharges. Gross lesions in the lung such as marbling, sequestra, thickening of interlobular septa, and consolidation are evident. Serological tests including complement fixation test and competitive enzyme-linked immunosorbent assay and molecular tests such as polymerase chain reactions are used for diagnostic purposes. In this study, lung samples of suspected large ruminants (cattle n=560, buffalo n=293) were collected from abattoirs of three districts of Punjab namely Lahore, Kasur and Jhang. PCR was performed with specific primers, targeting the 16S ribosomal RNA gene to detect the positive cases. The results indicated that 49 samples (8.75%) of cattle were positive, with maximum prevalence was observed in Jhang with 16 positive samples (10.06%), but CBPP was not detected in any buffalo sample. High prevalence of disease was seen in cattle of more than seven years of age, in female cattle, and in cross-bred cattle. Age and gender were found significantly associated (P<0.05) with the prevalence of the disease. Gene sequencing of identified 5 isolates of Mycoplasma mycoides subsp. mycoides had more than 99% similarities with the strains isolated from China, Italy, Australia and Tanzania and were categorized into a monophyletic group but strain isolated from Portugal had more than 55% variable regions, hence clustered separately. This study confirms the presence of contagious bovine pleuropneumonia in the country which can be a threat to the livestock export market and warrants the implementation of control measures to mitigate the economic losses associated with the disease.

Spatial and Temporal distribution of Aedes (Diptera: Culicidae) mosquitoes in Shah Alam

Surveys are conducted at central zone of Shah Alam in determining the distribution of dengue vector mosquito population. A minimum of 100 houses was randomly searched for breeding at every 24 localities in central zone of Shah Alam. Number of buildings at central zone of Shah Alam was obtained from the local authorities in order to calculate the sample size. The positive and wet containers in each locality were recorded and the types of container for positive containers were categorized accordingly. The numbers of larvae in each container were collected. The pupal index (PI), house index (HI), container index (CI), and the Breteau index were calculated for each locality. Plastic containers (CID 1) showed the highest number of positive, while Seksyen 1 and Seksyen 14 showed the highest percentage of BI with 70% and 80% respectively. This study would provide the information regarding Aedes mosquito infestation and , highlighted the central region as the dengue fever was fluctuating in these area. It can also help to create strategy to reduce the mosquito menace in our country with more cost-effective mosquito larval control.

Adult Neural Stem Cells from the Subventricular Zone Give Rise to Reactive Astrocytes in the Cortex after Stroke

Reactive astrocytes (RAs) have been reported to convert to multipotent neural stem cells (NSCs) capable of neurosphere (NS) formation and multilineage differentiation in vitro. Using genetic tagging, we determined that subventricular zone (SVZ) NSCs give rise to NSs derived from the stroke-injured cortex. We demonstrate that these cells can be isolated from the cortex in two different models of stroke and from different stroke-lesioned cortical regions. Interestingly, SVZ NSCs give rise to a subpopulation of RAs in the cortex that contribute to astrogliosis and scar formation. Last, we show that these SVZ derived RAs can be converted to neurons in vivo by forced expression of Ascl1. Identifying the contribution of cells originating from the SVZ to injury repair has implications for neural regeneration strategies.

Induced Pluripotent Stem Cells and Disorders of the Nervous System: Progress, Problems, and Prospects

Advances in cellular reprograming have shown that the delivery of specific transcription factors can result in the shift of one cell type to another. Brief forced expression of the four Yamanaka reprogramming factors (Klf4, Sox2, c-Myc, and Oct4) is able to convert many cell types into induced pluripotent stem cells, whereas some lineage specific transcription factors can convert cells from one type directly to another. Numerous strategies have already been developed for deriving neural cell types, with the hopes of better understanding/alleviating neurodegenerative disease. These cells facilitate drug discovery and constitute an autologous source of cells for brain repair, thus, avoiding rejection issues faced by allografts derived from embryonic stem cells. However, proper characterization of the various types of reprogrammed cells and an understanding of how these cells acquire neural fate is necessary before their translation into the clinic. Here, we review the progress, problems, and prospects with reprogrammed cell types with regards to neurodegenerative disease.

Astrocytes negatively regulate neurogenesis through the Jagged1-mediated Notch pathway

Adult neurogenesis is regulated by a number of cellular players within the neurogenic niche. Astrocytes participate actively in brain development, regulation of the mature central nervous system (CNS), and brain plasticity. They are important regulators of the local environment in adult neurogenic niches through the secretion of diffusible morphogenic factors, such as Wnts. Astrocytes control the neurogenic niche also through membrane-associated factors, however, the identity of these factors and the mechanisms involved are largely unknown. In this study, we sought to determine the mechanisms underlying our earlier finding of increased neuronal differentiation of neural progenitor cells when cocultured with astrocytes lacking glial fibrillary acidic protein (GFAP) and vimentin (GFAP(-/-) Vim(-/-) ). We used primary astrocyte and neurosphere cocultures to demonstrate that astrocytes inhibit neuronal differentiation through a cell-cell contact. GFAP(-/-) Vim(-/-) astrocytes showed reduced endocytosis of Notch ligand Jagged1, reduced Notch signaling, and increased neuronal differentiation of neurosphere cultures. This effect of GFAP(-/-) Vim(-/-) astrocytes was abrogated in the presence of immobilized Jagged1 in a manner dependent on the activity of γ-secretase. Finally, we used GFAP(-/-) Vim(-/-) mice to show that in the absence of GFAP and vimentin, hippocampal neurogenesis under basal conditions as well as after injury is increased. We conclude that astrocytes negatively regulate neurogenesis through the Notch pathway, and endocytosis of Notch ligand Jagged1 in astrocytes and Notch signaling from astrocytes to neural stem/progenitor cells depends on the intermediate filament proteins GFAP and vimentin.

IFN-γ-induced increase in the mobility of MHC class II compartments in astrocytes depends on intermediate filaments

Background

In immune-mediated diseases of the central nervous system, astrocytes exposed to interferon-γ (IFN-γ) can express major histocompatibility complex (MHC) class II molecules and antigens on their surface. MHC class II molecules are thought to be delivered to the cell surface by membrane-bound vesicles. However, the characteristics and dynamics of this vesicular traffic are unclear, particularly in reactive astrocytes, which overexpress intermediate filament (IF) proteins that may affect trafficking. The aim of this study was to determine the mobility of MHC class II vesicles in wild-type (WT) astrocytes and in astrocytes devoid of IFs.

Methods

The identity of MHC class II compartments in WT and IF-deficient astrocytes 48 h after IFN-γ activation was determined immunocytochemically by using confocal microscopy. Time-lapse confocal imaging and Alexa Fluor⁵⁴⁶-dextran labeling of late endosomes/lysosomes in IFN-γ treated cells was used to characterize the motion of MHC class II vesicles. The mobility of vesicles was analyzed using ParticleTR software.

Results

Confocal imaging of primary cultures of WT and IF-deficient astrocytes revealed IFN-γ induced MHC class II expression in late endosomes/lysosomes, which were specifically labeled with Alexa Fluor⁵⁴⁶-conjugated dextran. Live imaging revealed faster movement of dextran-positive vesicles in IFN-γ-treated than in untreated astrocytes. Vesicle mobility was lower in IFN-γ-treated IF-deficient astrocytes than in WT astrocytes. Thus, the IFN-γ-induced increase in the mobility of MHC class II compartments is IF-dependent.

Conclusions

Since reactivity of astrocytes is a hallmark of many CNS pathologies, it is likely that the up-regulation of IFs under such conditions allows a faster and therefore a more efficient delivery of MHC class II molecules to the cell surface. In vivo, such regulatory mechanisms may enable antigen-presenting reactive astrocytes to respond rapidly and in a controlled manner to CNS inflammation.

Defining cell populations with single-cell gene expression profiling: correlations and identification of astrocyte subpopulations

Single-cell gene expression levels show substantial variations among cells in seemingly homogenous populations. Astrocytes perform many control and regulatory functions in the central nervous system. In contrast to neurons, we have limited knowledge about functional diversity of astrocytes and its molecular basis. To study astrocyte heterogeneity and stem/progenitor cell properties of astrocytes, we used single-cell gene expression profiling in primary mouse astrocytes and dissociated mouse neurosphere cells. The transcript number variability for astrocytes showed lognormal features and revealed that cells in primary cultures to a large extent co-express markers of astrocytes and neural stem/progenitor cells. We show how subpopulations of cells can be identified at single-cell level using unsupervised algorithms and that gene correlations can be used to identify differences in activity of important transcriptional pathways. We identified two subpopulations of astrocytes with distinct gene expression profiles. One had an expression profile very similar to that of neurosphere cells, whereas the other showed characteristics of activated astrocytes in vivo.

Characterization and anti-microbial susceptibility of gram-negative bacteria isolated from bloodstream infections of cancer patients on chemotherapy in Pakistan

PURPOSE

Bloodstream infection remains a major cause of morbidity and mortality in patients undergoing treatment for cancer. Severe infections due to Gram-negative bacilli & staphylococci are common in cancer patients. Altered gut flora because of frequent antibiotic administration and damage of epithelial surfaces contribute to the development of infection. To access the use of new potent antibiotics against bloodstream infection in cancer patients and to determine the cross resistance of Gram-negative bacterial strains.

MATERIALS AND METHODS

We studied the bacterial spectrum & antimicrobial susceptibility pattern of cephalosporins, fluoroquinolones, carbapenems and aminoglycosides against Gram-negative bacterial strains in cancer patients. The susceptibility was determined by broth dilution method according to National Committee for Clinical Laboratory Standards (NCCLS) now called Clinical Laboratory Standards Institute (CLSI) during study period (July 2006 to Jan 2007).

RESULTS

A total of 60 Gram-negative bacterial blood cultures were examined. Among these, Pseudomonas aeruginosa was the most common (38%). The Minimum Inhibitory Concentration at which 50% (MIC 50 ) and 90% (MIC 90 ) of Enterobacteriaceae and P. aeruginosa inhibited were found. Resistance in P.aeruginosa against cefepime, meropenem, ciprofloxacin, ceftriaxone, tobramycin, cefoperazone and imipenem was 60%, 13%, 80%, 67%, 40%, 90% and 10% respectively while for Enterobacteriaceae 80%, 20%, 88%, 72%, 20%, 90% and four per cent resistance was observed. Meropenem was found to be the most effective antimicrobial against Gram-negative bacteria.

CONCLUSION

High resistance observed in this study warrants the needs of surveillance of resistant pattern of antimicrobial agents. Due to increased level of drug resistance, carbapenem would be a prudent choice in high- risk cases.

Antimicrobial susceptibility patterns and characterization of clinical isolates of Staphylococcus aureus in immunocompromised cancer patients undergoing chemotherapy in Pakistan

Cancer patients undergoing chemotherapy are highly prone to infections because of suppression of their immune system. in the present study, the activity of fluoroquinolones, cephalosporins, glycopeptides and oxazolidinones was evaluated in Staphylococcus aureus strains by broth dilution method according to Clinical and laboratory Standards institute (ClSi), USA guidelines. the frequency of methicillin-resistant S. aureus (mRSA) and methicillin-sensitive S. aureus (mSSA) strains was 67% and 33% respectively. The MIC(50 )and MIC(90 )of isolates were ciprofloxacin 8 and 32 microg/ml for mRSA, 8 and 16 microg/ml for mSSA, levofloxacin 8 and 16 microg/ml for mRSA and mSSA, gatifloxacin 4 and 16 microg/ml for mRSA and 4 and 8 microg/ml for mSSA. MIC(50 )and MIC(90 )of vancomycin and linzolid were 1 and 2 microg/ml, 2 and 4 microg/ml for both mRSA and mSSA strains respectively. this study shows a high prevalence of and resistance in mRSA. However, vancomycin and linezolid were highly active and could be used for treating mRSA infections.

Ultra-fast Microwave Synthesis of ZnO Nanowires and their Dynamic Response Toward Hydrogen Gas

Ultra-fast and large-quantity (grams) synthesis of one-dimensional ZnO nanowires has been carried out by a novel microwave-assisted method. High purity Zinc (Zn) metal was used as source material and placed on microwave absorber. The evaporation/oxidation process occurs under exposure to microwave in less than 100 s. Field effect scanning electron microscopy analysis reveals the formation of high aspect-ratio and high density ZnO nanowires with diameter ranging from 70 to 80 nm. Comprehensive structural analysis showed that these ZnO nanowires are single crystal in nature with excellent crystal quality. The gas sensor made of these ZnO nanowires exhibited excellent sensitivity, fast response, and good reproducibility. Furthermore, the method can be extended for the synthesis of other oxide nanowires that will be the building block of future nanoscale devices.

Substantial migration of SVZ cells to the cortex results in the generation of new neurons in the excitotoxically damaged immature rat brain

Mammalian SVZ progenitors continuously generate new neurons in the olfactory bulb. After injury, changes in SVZ cell number suggest injury-induced migration. Studies that trace the migration of SVZ precursors into neurodegenerating areas are lacking. Previously, we showed a decrease in BrdU+SVZ cells following excitotoxic damage to the immature rat cortex. Here, we demonstrate that NMDA-induced injury forces endogenous Cell Tracker Green (CTG) labeled VZ/SVZ precursors out of the SVZ into the neurodegenerating cortex. CTG+/Nestin+/Filamin A+ precursors are closely associated with vimentin+/GFAP+/GLAST+ filaments and express both chemokine receptor CXCR4 and Robo1. In the cortex, SVZ-derived progenitors show a progressive expression of developing, migrating and mature neurons and glial markers. CTG+/GFAP+ astrocytes greatly outnumber CTG+/MAP2+/NeuN+ neurons. SVZ-derived progenitors differentiate into both tbr1+ cortical glutamatergic neurons and calretinin+ interneurons. But, there is little integration of these neurons into the existing circuitry, as seen by Fluorogold retrograde tracing from the internal capsule.

Distinct spatial and temporal activation of caspase pathways in neurons and glial cells after excitotoxic damage to the immature rat brain

Although cleaved caspase-3 is known to be involved in apoptotic cell death mechanisms in neurons, it can also be involved in a nonapoptotic role in astrocytes after postnatal excitotoxic injury. Here we evaluate participation of upstream pathways activating caspase-3 in neurons and glial cells, by studying the intrinsic pathway via caspase-9, the extrinsic pathway via caspase-8, and activation of the p53-dependent pathway. N-methyl-D-aspartate (NMDA) was injected intracortically in 9-day-old postnatal rats, which were sacrificed at several survival times between 4 hr postlesion (pl) and 7 days pl. We analyzed temporal and spatial expression of caspase-8, caspase-9, and p53 and correlation with neuronal and glial markers and caspase-3 activation. Caspase-9 was significantly activated at 10 hpl, strongly correlating with caspase-3. It was present mainly in damaged cortical and hippocampal neurons but was also seen in astrocytes and oligodendrocytes in layer VI and corpus callosum (cc). Caspase-8 showed a diminished correlation with caspase-3. It was present in cortical neurons at 10-72 hpl, showing layer specificity, and also in astroglial and microglial nuclei, mainly in layer VI and cc. p53 Expression increased at 10-72 hpl but did not correlate with caspase-3. p53 Was seen in neurons of the degenerating cortex and in some astrocytes and microglial cells of layer VI and cc. In conclusion, after neonatal excitotoxicity, mainly the mitochondrial intrinsic pathway mediates neuronal caspase-3 and cell death. In astrocytes, caspase-3 is not widely correlated with caspase-8, caspase-9, or p53, except in layer VI-cc astrocytes, where activation of upstream cascades occurs.

Survivin and heat shock protein 25/27 colocalize with cleaved caspase-3 in surviving reactive astrocytes following excitotoxicity to the immature brain

Following immature excitotoxic brain damage, distinct patterns of caspase activation have been described in neurons and glial cells. Neuronal cells show activation of the mitochondrial apoptosis pathway, caspase-3 cleavage and apoptotic cell death, while reactive astrocytes show caspase-3 cleavage that is not always correlated with enzymatic protease activity and does not generally terminate in cell death. Accordingly, the aim of the present study was to evaluate the astrocytic colocalization of cleaved caspase-3 and several anti-apoptotic proteins of the inhibitor of apoptosis proteins family (IAPs), such as survivin and cellular inhibitor of apoptosis-2 (cIAP-2), and the heat shock proteins (HSPs) family, Hsp25/27 and Hsc70/Hsp70, which can all prevent caspases from cleaving their substrates. At several survival times ranging from 4 h to 14 days after cortical excitotoxic damage induced by N-methyl-d-aspartate (NMDA) injection at postnatal day 9 in rat pups, single and double immunohistochemical techniques were performed in free floating cryostat sections and sections were analyzed by confocal microscopy. Our results show that survivin and Hsp25/27 are primarily expressed in reactive astrocytes of the damaged cortex and the adjacent white matter. In addition, both molecules strongly colocalize with cleaved caspase-3. Survivin is primarily located in the nucleus, like cleaved caspase-3; while Hsp25/27 is cytoplasmic but very frequently found in cells showing nuclear caspase-3. cIAP-2 was mostly found in damaged neurons but also in some glial scar reactive astrocytes and showed fewer correlation with caspase-3. Hsc70/Hsp70 was only expressed in injured neurons and did not correlate with caspase-3. Thus, we conclude that primarily survivin and Hsp25/27 may participate in the inhibition of cleaved caspase-3 in reactive astrocytes and may be involved in protecting astrocytes after injury.

Caspase-3 activation in astrocytes following postnatal excitotoxic damage correlates with cytoskeletal remodeling but not with cell death or proliferation

Caspase-3 has classically been defined as the main executioner of programmed cell death. However, recent data supports the participation of this protease in non-apoptotic cellular events including cell proliferation, cell cycle regulation, and cellular differentiation. In this study, astroglial cleavage of caspase-3 was analyzed following excitotoxic damage in postnatal rats to determine if its presence is associated with apoptotic cell death, cell proliferation, or cytoskeletal remodeling. A well-characterized in vivo model of excitotoxicity was studied, where damage was induced by intracortical injection of N-methyl-D-asparate (NMDA) in postnatal day 9 rats. Our results demonstrate that cleaved caspase-3 was mainly observed in the nucleus of activated astrocytes in the lesioned hemisphere as early as 4 h postlesion and persisted until the glial scar was formed at 7-14 days, and it was not associated with TUNEL labeling. Caspase-3 enzymatic activity was detected at 10 h and 1 day postlesion in astrocytes, and co-localized with caspase-cleaved fragments of glial fibrillary acidic protein (CCP-GFAP). However, at longer survival times, when astroglial hypertrophy was observed, astroglial caspase-3 did not generally correlate with GFAP cleavage, but instead was associated with de novo expression of vimentin. Moreover, astroglial caspase-3 cleavage was not associated with BrdU incorporation. These results provide further evidence for a nontraditional role of caspases in cellular function that is independent of cell death and suggest that caspase activation is important for astroglial cytoskeleton remodeling following cellular injury.

Antioxidant Cu/Zn SOD: Expression in postnatal brain progenitor cells

Precursor cells have been shown to be affected by oxidative stress, in vivo and vitro, but little is known about the expression of antioxidant mechanisms in neuronal/glial differentiation. We have characterized the expression of Cu/Zn superoxide dismutase (Cu/Zn SOD), one of the main antioxidant proteins involved in the breakdown of superoxide, in the immature rat dorsolateral subventricular zone (SVZ), rostral migratory stream (RMS) and hippocampal subgranular zone (SGZ). Progenitor cells were identified immunohistochemically on cryostat sections by 5'Bromodeoxyuridine (BrdU) incorporation and expressing cells were further characterized using double labeling for progenitor markers. In the SVZ, only a subpopulation of BrdU+ cells, mostly found in the medial SVZ, expressed Cu/Zn SOD. These cells were mostly nestin+ and some were also vimentin+. In contrast, in the lateral SVZ few Cu/Zn SOD+/BrdU+ cells were found. These were primarily nestin+, vimentin-, showed some PSA-NCAM expression, but only a few were NG2+. In the RMS and SGZ virtually all BrdU+ progenitors were Cu/Zn SOD+ and expressed nestin and vimentin. Some RMS cells were also PSA-NCAM+. These findings show a heterogeneous expression of Cu/Zn SOD in restricted cell types in the germinative zones and suggest a role for antioxidant Cu/Zn SOD in progenitor cells of the immature rat brain.

Cu/Zn superoxide dismutase expression in the postnatal rat brain following an excitotoxic injury

Background

In the nervous system, as in other organs, Cu/Zn superoxide dismutase (Cu/Zn SOD) is a key antioxidant enzyme involved in superoxide detoxification in normal cellular metabolism and after cell injury. Although it has been suggested that immature brain has a different susceptibility to oxidative damage than adult brain, the distribution and cell-specific expression of this enzyme in immature brain and after postnatal brain damage has not been documented.

Methods

In this study, we used immunohistochemistry and western blot to analyze the expression of Cu/Zn SOD in intact immature rat brain and in immature rat brain after an NMDA-induced excitotoxic cortical injury performed at postnatal day 9. Double immunofluorescence labelling was used to identify Cu/Zn SOD-expressing cell populations.

Results

In intact immature brain, Cu/Zn SOD enzyme was widely expressed at high levels in neurons mainly located in cortical layers II, III and V, in the sub-plate, in the pyriform cortex, in the hippocampus, and in the hypothalamus. Glial fibrillary acidic protein-positive cells only showed Cu/Zn SOD expression in the glia limitans and in scattered cells of the ventricle walls. No expression was detected in interfascicular oligodendroglia, microglia or endothelial cells. Following excitotoxic damage, neuronal Cu/Zn SOD was rapidly downregulated (over 2–4 hours) at the injection site before neurodegeneration signals and TUNEL staining were observed. Later, from 1 day post-lesion onward, an upregulation of Cu/Zn SOD was found due to increased expression in astroglia. A further increase was observed at 3, 5 and 7 days that corresponded to extensive induction of Cu/Zn SOD in highly reactive astrocytes and in the astroglial scar.

Conclusion

We show here that, in the intact immature brain, the expression of Cu/Zn SOD was mainly found in neurons. When damage occurs, a strong and very rapid downregulation of this enzyme precedes neuronal degeneration, and is followed by an upregulation of Cu/Zn SOD in astroglial cells.

Proliferation dynamics of germinative zone cells in the intact and excitotoxically lesioned postnatal rat brain

BACKGROUND

The forebrain subventricular zone (SVZ)-olfactory bulb pathway and hippocampal subgranular zone (SGZ) generate neurons into adulthood in the mammalian brain. Neurogenesis increases after injury to the adult brain, but few studies examine the effect of injury on neural and glial precursors in the postnatal brain. To characterize the spatio-temporal dynamics of cell proliferation in the germinative zones, this study utilized a model of postnatal damage induced by NMDA injection in the right sensorimotor cortex at postnatal day 9. Dividing cell populations were labeled with 5-Bromodeoxyuridine (BrdU) in the intact and damaged postnatal brain. Identity of proliferating cells was determined by double immunolabeling with nestin, GFAP, NeuN and tomato lectin (TL).

RESULTS

In the control brain, grouped BrdU+ cells were observed in the Rostral Migratory Stream (RMS), SVZ and SGZ. Maximal proliferation was seen at P12, persisted until P23 and diminished by P49. After injury, a striking reduction in the number of BrdU+ cells was observed in the ipsilateral SVZ from 10 hours (58% decrease) until 14 days post-lesion (88% decrease). In contrast, an increase in grouped BrdU+ cells was seen in the striatum adjacent to the depleted SVZ. Significantly reduced numbers of BrdU+ cells were also seen in the RMS until 3 days post-lesion. No changes were noted in the SGZ. Both in controls and lesioned hemispheres, BrdU+ cells located in the germinal zones were mostly nestin positive and negative for GFAP, NeuN, and TL. In the SVZ area lining the ventricle, BrdU+/nestin+ cells were mainly located between TL+ ependyma and parenchymal GFAP+ astrocytes. After excitotoxicity, a decrease in the number and orientation of GFAP/nestin+ prolongations leaving the SVZ to the cortex, corpus callosum and striatum was noted until 5 days post-lesion.

CONCLUSION

Postnatal excitotoxic injury differentially affects proliferating cells in the germinative zones: no change is observed in the dentate gyrus whereas excitotoxicity causes a significant decrease in proliferating cells in the SVZ and RMS. Depletion of BrdU+ cells in the postnatal SVZ and RMS differs from previous studies after adult brain injury and may affect the SVZ-RMS migration and is suggestive of progenitor recruitment to injured areas.

Analysis of trichloroacetic acid in the urine of workers occupationally exposed to trichloroethylene by capillary gas chromatography

A gas chromatographic procedure is described for the determination of trichloroacetic acid in urine, the major metabolite of trichloroethylene exposure. Trichloroacetic acid was derivatised to its methyl ester with BF3/methanol reagent and then extracted into toluene and analysed by capillary gas chromatography using electron-capture detection. The response was linear in the range 0.4-100 mg/l of trichloroacetic acid in urine and showed a relative recovery of 99.6%. The procedure is suitable for monitoring occupational exposure to trichloroethylene.

Does catheter traction reduce post-transurethral resection of the prostate blood loss?

OBJECTIVE

To determine if traction on a catheter after transurethral resection of the prostate (TURP) reduces post-operative bleeding.

PATIENTS AND METHODS

This prospective trial included 115 consecutive patients undergoing TURP. After resection patients were randomly selected to have either traction (57) or no traction (58) on the catheter for 30 min. Blood loss was measured during and for 2 h after the operation. A simple method for applying constant traction is described.

RESULTS

Catheter traction reduced post-operative bleeding while applied, but had no further effect after the removal of traction.

CONCLUSION

Catheter traction is a useful technique to aid the control of post-TURP bleeding.