Activity of the astrocytes' adenosine signaling system components in model of traumatic brain injury in vivo and in vitro

Glavno obeležje traumatske povrede mozga (TPM) je reaktivna astroglioza koja, između ostalog, uzrokuje i promene u signalizaciji purinima. Posebno važan aspekt purinske signalizacije u patološkim procesima centralnog nervnog sistema predstavlja dinamika promena vanćelijskih koncentracija neuroprotektora adenozina. Stoga je cilj ove doktorske teze bio ispitivanje ekspresije i funkcije komponenti adenozinskog signalnog sistema astrocita u in vivo i in vitro modelu moždane povrede, sa posebnim osvrtom na ulogu ekvilibrišućih nukleozidnih transportera (ENT). U in vivo studiji, izvedenoj na modelu ubodne lezije kore prednjeg mozga pacova, je pokazano da povreda dovodi do dinamičnih promena u ekspresiji ENT, ektonukleotidaza i adenozinskog A1 receptora. Sem toga, povreda uzrokuje i ćelijsku re-distribuciju ENT1/2 i ushodnu regulaciju transportera na reaktivnim astrocitima, što je posebno izraženo sedmog dana nakon ozlede. Uloga astrocita u orkestraciji adenozinskog signalnog sistema nakon povrede je detaljnije ispitana in vitro, nakon skarifikacije astrocitnog jednosloja. Rezultati su pokazali da skarifikacija povećava ekspresiju ENT1 i ENT2 tek u kasnijim vremenima. Bifazna promena u ekspresiji ekto-5`-nukleotidaze (e-5NT) je iskazana prvobitnim smanjenjem i potom povećanjem ekspresije u kasnijim vremenima nakon skarifikacije. Pored toga, skarifikacija astrocitnog jednosloja vodi promenama u koncentracijama adenozina i njegovih metabolita u ćelijskom medijumu. Naime, porast koncentracija adenozina u ranim vremenima nakon povrede, bio je praćen padom u kasnijim vremenima. Blokiranje ENT dipiridamolom (DPM) je dovelo do promena u koncentracijama adenozina nakon skarifikacije, ukazavši na ulogu ENT1/2 u kontroli vanćelijskih koncentracija ovog nukleozida...Reactive astrogliosis is a hallmark of traumatic brain injury (TBI), which, among the others alterations, causes changes in purinergic signaling. Due to its neuroprotective features, fluctuations of adenosine extracellular concentration are particularly important aspect of purinergic signaling in brain pathology. Hence, herein given thesis aimed to investigate expression and function of astrocytes’ adenosine signaling system components after brain injury in vitro and in vivo, with special regard to the role of equilibrative nucleoside transporters (ENT). In vivo study, performed on a model of cortical stub injury of rat forebrain, showed that injury caused dynamic changes in expression of ENTs, ectonucleotidases, and adenosine A1 receptor. Moreover, injury induced cell redistribution of ENT1/2 and upregulation of transporters on reactive astrocytes, which is especially pronounced seven day after the impact. The role of astrocytes in orchestration of adenosine signaling system after the injury was examined in more details in vitro, after scratch wound injury of astrocytic monolayer. Results have shown that scarification induced upregulation of ENT1 and ENT2 in later time points. Biphasic alteration in expression of e-5NT was shown in early downregulation followed by upregulation of the enzyme in later time points after the induction of scratch wound. Beside, scarification of astrocytic monolayer caused changes in concentration of adenosine and its metabolites in extracellular medium. The rise of adenosine concentration was noted early after the injury, which was followed by drop of the concentration in later time points examined. Blocking of ENT with dipyridamole (DPM) resulted in changes of observed adenosine concentration after the scarification, pointing out that ENT1/2 have significant role in controlling extracellular concentration of this nucleoside..

Real-time PCR and immunocytochemical study of chondroitin sulfate proteoglycans after scratch wounding in cultured astrocytes

Background: Various in vivo and in vitro models have been described in order to elucidate the pathobiology underlying the traumatic brain injury (TBI) and test potentially suitable treatments. Since TBI is a complex disease, models differ in regard to the aspect of TBI that is being investigated. One of the used in vitro models is the scratch wound assay, first established as a reproducible, low-cost assay for the analysis of cell migration in vitro. The aim of the present study was to further investigate the relevancy of this model as a counter­part of in vivo TBI models. Methods: We have examined the astrocytic response to a mechanical injury in terms of expression of chondroitin sulfate proteoglycans (CSPGs) - phosphacan, neurocan and brevican, using real-time PCR and immunocytochemistry. Results: Our results indicate that in vitro scratch wounding alters the expression profile of examined CSPGs. Four hours after the scratch injury of the astrocytic monolayer, real-time PCR analysis revealed upregulation of mRNA levels for phosphacan (3-fold) and neurocan (2-fold), whereas brevican mRNA was downregulated (2-fold). Immunofluorescent signal for phosphacan and neurocan was more intense in astrocytes close to the injury site, while brevican was scarcely present in cultured astrocytes. Conclusions: Obtained results indicate that CSPGs are differentially expressed by astrocytes after scratch wounding, demonstrating that the scratch wound model might be suitable for investigation of astrocyte-derived response to injury.Uvod: Brojni in vivo i in vitro modeli opisani su sa ciljem da se rasvetle patobiološki procesi koji su osnova traumatske povrede mozga (TPM) i testiraju potencijalni tretmani. Imajući u vidu da je TPM kompleksno oboljenje, ovi modeli se međusobno razlikuju shodno aspektu TPM koji se ispituje. Jedan od in vitro modela je i povreda ćelijskog jednosloja grebanjem (engl. 'scratch wound' assay), isprva ustanovljen kao ponovljiv, jeftin test za analizu celijske migracije in vitro. Cilj ove studije je da se bliže ispita relevantnost ovog modela u odnosu na in vivo modele TPM. Metode: Da bi se istražio odgovor astrocita na mehaničku povredu, praćena je ekspresija odabranih hondroitin-sulfatnih proteoglikana (CSPG) - fosfakana, neurokana i brevikana, korišćenjem PCR u realnom vremenu i imunocitohemije. Rezultati: Dobijeni rezultati su pokazali da in vitro povreda astrocitnog jednosloja menja profile ekspresije ispitivanih CSPG. Četiri sata nakon povrede, primena PCR u realnom vremenu analize pokazala je povećanje nivoa iRNK za fosfakan (trostruko) i neurokan (dvostruko), dok je iRNK za brevikan bila smanjena na polovinu kontrolne vrednosti. Imunofluorescentni signal poreklom od fosfakana i neurokana je bio intenzivniji u astrocitima bližim mestu povrede, dok je signal za brevikan bio slab kako u kontrolnoj, tako i u ozleđenoj grupi. Zaključak: Dobijeni rezultati pokazuju da povreda izazvana grebanjem različito utiče na ekspresiju ispitivanih CSPG u astrocitima, sto ukazuju da ovaj model može biti pogodan za ispitivanje odgovora astrocita na povredu.Projekat ministarstva br. III 4101

Brain cortical injury induces changes in peripheral lymphocyte ectonucleotidase activities

Injury and other pathological conditions induce a massive release of ATP and ADP that initiate an immune response. Extracellular nucleotides are degraded by ectonucleotidases: enzymes from E-NTPDase and E-NPP families sequentially hydrolyze ATP and ADP to AMP, which is further hydrolyzed by ecto-5'-nucleotidase to adenosine that exerts suppressive effects on immune cells. We investigated the ectonucleotidase activities of peripheral lymphocytes at different post-injury times after an unilateral brain injury in the rat. Significant and dynamic changes in the lymphocytic ectonucleotidase activities were obtained. ATP- and ADP-hydrolysis changes, together with their calculated ratios, indicate the major contribution of E-NTPDase 1 and its comparable upregulation between sham operation and injury. AMP hydrolysis changes were more brain-injury specific, with a longer-lasting lymphocytic response induced by cortical stab injury (CSI). In summary, CSI and sham operation induce the upregulation of the whole enzyme chain for adenine nucleotide hydrolysis in lymphocytes, suggesting an important roles of ectonucleotidases in the course of recovery after brain injury.Projekat ministarstva br. III4101

Real-time PCR and immunocytochemical study of chondroitin sulfate proteoglycans after scratch wounding in cultured astrocytes

Background: Various in vivo and in vitro models have been described in order to elucidate the pathobiology underlying the traumatic brain injury (TBI) and test potentially suitable treatments. Since TBI is a complex disease, models differ in regard to the aspect of TBI that is being investigated. One of the used in vitro models is the scratch wound assay, first established as a reproducible, low-cost assay for the analysis of cell migration in vitro. The aim of the present study was to further investigate the relevancy of this model as a counter­part of in vivo TBI models. Methods: We have examined the astrocytic response to a mechanical injury in terms of expression of chondroitin sulfate proteoglycans (CSPGs) - phosphacan, neurocan and brevican, using real-time PCR and immunocytochemistry. Results: Our results indicate that in vitro scratch wounding alters the expression profile of examined CSPGs. Four hours after the scratch injury of the astrocytic monolayer, real-time PCR analysis revealed upregulation of mRNA levels for phosphacan (3-fold) and neurocan (2-fold), whereas brevican mRNA was downregulated (2-fold). Immunofluorescent signal for phosphacan and neurocan was more intense in astrocytes close to the injury site, while brevican was scarcely present in cultured astrocytes. Conclusions: Obtained results indicate that CSPGs are differentially expressed by astrocytes after scratch wounding, demonstrating that the scratch wound model might be suitable for investigation of astrocyte-derived response to injury.Uvod: Brojni in vivo i in vitro modeli opisani su sa ciljem da se rasvetle patobiološki procesi koji su osnova traumatske povrede mozga (TPM) i testiraju potencijalni tretmani. Imajući u vidu da je TPM kompleksno oboljenje, ovi modeli se međusobno razlikuju shodno aspektu TPM koji se ispituje. Jedan od in vitro modela je i povreda ćelijskog jednosloja grebanjem (engl. 'scratch wound' assay), isprva ustanovljen kao ponovljiv, jeftin test za analizu celijske migracije in vitro. Cilj ove studije je da se bliže ispita relevantnost ovog modela u odnosu na in vivo modele TPM. Metode: Da bi se istražio odgovor astrocita na mehaničku povredu, praćena je ekspresija odabranih hondroitin-sulfatnih proteoglikana (CSPG) - fosfakana, neurokana i brevikana, korišćenjem PCR u realnom vremenu i imunocitohemije. Rezultati: Dobijeni rezultati su pokazali da in vitro povreda astrocitnog jednosloja menja profile ekspresije ispitivanih CSPG. Četiri sata nakon povrede, primena PCR u realnom vremenu analize pokazala je povećanje nivoa iRNK za fosfakan (trostruko) i neurokan (dvostruko), dok je iRNK za brevikan bila smanjena na polovinu kontrolne vrednosti. Imunofluorescentni signal poreklom od fosfakana i neurokana je bio intenzivniji u astrocitima bližim mestu povrede, dok je signal za brevikan bio slab kako u kontrolnoj, tako i u ozleđenoj grupi. Zaključak: Dobijeni rezultati pokazuju da povreda izazvana grebanjem različito utiče na ekspresiju ispitivanih CSPG u astrocitima, sto ukazuju da ovaj model može biti pogodan za ispitivanje odgovora astrocita na povredu.Projekat ministarstva br. III 4101

Volume Conduction Coupling of Whisker-Evoked Cortical LFP in the Mouse Olfactory Bulb

Summary: Local field potentials (LFPs) are an important measure of brain activity and have been used to address various mechanistic and behavioral questions. We revealed a prominent whisker-evoked LFP signal in the olfactory bulb and investigated its physiology. This signal, dependent on barrel cortex activation and highly correlated with its local activity, represented a pure volume conduction signal that was sourced back to the activity in the ventro-lateral orbitofrontal cortex, located a few millimeters away. Thus, we suggest that special care should be taken when acquiring and interpreting LFP data. : Local field potential (LFP) recordings are an important yet still obscure tool in neuroscience. In this issue, Parabucki and Lampl show volume conduction of LFP signals from cortex to olfactory bulb in mice, emphasizing that LFP can be misleading under certain circumstances. Keywords: LFP, local field potential, volume conduction, olfactory bulb, barrel cortex, current source densit

Brain cortical injury induces changes in peripheral lymphocyte ectonucleotidase activities

Injury and other pathological conditions induce a massive release of ATP and ADP that initiate an immune response. Extracellular nucleotides are degraded by ectonucleotidases: enzymes from E-NTPDase and E-NPP families sequentially hydrolyze ATP and ADP to AMP, which is further hydrolyzed by ecto-5’-nucleotidase to adenosine that exerts suppressive effects on immune cells. We investigated the ectonucleotidase activities of peripheral lymphocytes at different post-injury times after an unilateral brain injury in the rat. Significant and dynamic changes in the lymphocytic ectonucleotidase activities were obtained. ATP- and ADP-hydrolysis changes, together with their calculated ratios, indicate the major contribution of E-NTPDase 1 and its comparable upregulation between sham operation and injury. AMP hydrolysis changes were more brain-injury specific, with a longer-lasting lymphocytic response induced by cortical stab injury (CSI). In summary, CSI and sham operation induce the upregulation of the whole enzyme chain for adenine nucleotide hydrolysis in lymphocytes, suggesting an important roles of ectonucleotidases in the course of recovery after brain injury. [Projekat Ministarstva nauke Republike Srbije, br. III41014

Effect of stab injury in the rat cerebral cortex on temporal pattern of expression of neuronal cytoskeletal proteins: An immunohistochemical study

Compelling evidence now points to the critical role of the cytoskeleton in neurodegeneration. In the present study, using an immunohistochemical approach, we have shown that cortical stab injury (CSI) in adult Wistar rats significantly affects temporal pattern of expression of neurofilament proteins (NFs). a major cytoskeleton components of neurons, and microtubule-associated proteins (MAP2). At 3 days post-injury (dpi) most of the NFs immunoreactivity was found in pyknotic neurons and in fragmentized axonal processes in the perilesioned cortex. These cytoskeletal alterations became more pronounced by 10 dpi. At the subcellular level CSI also showed significant impact on NFs and MAP-2 expression. Thus, at 3 dpi most of the dendrites disappeared, while large neuronal somata appeared like open circles pointing to membrane disintegration. Conversely, at 10 dpi neuronal perikarya and a few new apical dendrites were strongly labeled. Since aberrant NF phosphorylation is a pathological hallmark of many human neurodegenerative disorders, as well as is found after stressor stimuli, the present results shed light into the expression of neurofilaments after the stab brain injury. (C) 2014 Elsevier GmbH. All rights reserved.Ministry of Education, Science and Technological Development of the Republic of Serbia {[}III41014

Expression of major ectonucleotidases after cortical stab brain injury in rats: A real-time PCR study

Ectonucleotidases are cell surface-located enzymes responsible for the extracellular degradation of nucleotides. They are comprised of several protein families: ectonucleoside triphosphate diphosphohydrolases (E-NTPDase), ectonucleotide pyrophosphatase/phosphodiesterases (E-NPPases) and ecto-5’-nucleotidase. Previously we showed that cortical stab injury alters ectonucleotidase activities in the rat brain, but that the specific enzymes responsible for these changes were not identified. In this study we investigated the gene expression of the specific ectonucleotidase enzymes, NTPDase1- 3, NPP1-3 and ecto-5’-nucleotidase, two and seven days after cortical stab injury in rats, using real-time PCR. Two days after the injury we observed only one significant change: the downregulation in NTPDase2 mRNA expression. Our results indicate that traumatic brain injury induces significant upregulation of NTPDase1, NTPDase2 and ecto-5’-nucleotidase transcripts, and the downregulation of NPP1, seven days after the injury. Thus, traumatic brain injury has diverse impacts on ectonucleotidases gene expression, which may be reflected in the enzyme activities and extracellular nucleotide concentrations in the perilesional tissue. [Projekat Ministarstva nauke Republike Srbije, br. III41014

Repetitive Hyperbaric Oxygenation Attenuates Reactive Astrogliosis and Suppresses Expression of Inflammatory Mediators in the Rat Model of Brain Injury

The exact mechanisms by which treatment with hyperbaric oxygen (HBOT) exerts its beneficial effects on recovery after brain injury are still unrevealed. Therefore, in this study we investigated the influence of repetitive HBOT on the reactive astrogliosis and expression of mediators of inflammation after cortical stab injury (CSI). CSI was performed on male Wistar rats, divided into control, sham, and lesioned groups with appropriate HBO. The HBOT protocol was as follows: 10 minutes of slow compression, 2.5 atmospheres absolute (ATA) for 60 minutes, and 10 minutes of slow decompression, once a day for 10 consecutive days. Data obtained using real-time polymerase chain reaction, Western blot, and immunohistochemical and immunofluorescence analyses revealed that repetitive HBOT applied after the CSI attenuates reactive astrogliosis and glial scarring, and reduces expression of GFAP (glial fibrillary acidic protein), vimentin, and ICAM-1 (intercellular adhesion molecule-1) both at gene and tissue levels. In addition, HBOT prevents expression of CD40 and its ligand CD40L on microglia, neutrophils, cortical neurons, and reactive astrocytes. Accordingly, repetitive HBOT, by prevention of glial scarring and limiting of expression of inflammatory mediators, supports formation of more permissive environment for repair and regeneration