Combined Oxygen-glucose Deprivation Research Articles

Overexpression of Transcripts Coding for Renin-b but Not for Renin-a Reduce Oxidative Stress and Increase Cardiomyoblast Survival under Starvation Conditions.

A stimulated renin-angiotensin system is known to promote oxidative stress, apoptosis, necrosis and fibrosis. Renin transcripts (renin-b; renin-c) encoding a cytosolic renin isoform have been discovered that may in contrast to the commonly known secretory renin (renin-a) exert protective effects Here, we analyzed the effect of renin-a and renin-b overexpression in H9c2 cardiomyoblasts on apoptosis and necrosis as well as on potential mechanisms involved in cell death processes. To mimic ischemic conditions, cells were exposed to glucose starvation, anoxia or combined oxygen–glucose deprivation (OGD) for 24 h. Under OGD, control cells exhibited markedly increased necrotic and apoptotic cell death accompanied by enhanced ROS accumulation, loss of mitochondrial membrane potential and decreased ATP levels. The effects of OGD on necrosis were exaggerated in renin-a cells, but markedly diminished in renin-b cells. However, with respect to apoptosis, the effects of OGD were almost completely abolished in renin-b cells but interestingly also moderately diminished in renin-a cells. Under glucose depletion we found opposing responses between renin-a and renin-b cells; while the rate of necrosis and apoptosis was aggravated in renin-a cells, it was attenuated in renin-b cells. Based on our results, strategies targeting the regulation of cytosolic renin-b as well as the identification of pathways involved in the protective effects of renin-b may be helpful to improve the treatment of ischemia-relevant diseases.

Non-secretory renin reduces oxidative stress and increases cardiomyoblast survival during glucose and oxygen deprivation

Although the renin-angiotensin system usually promotes oxidative stress and cell death, renin transcripts have been discovered, whose transcription product may be cardioprotective. These transcripts encode a non-secretory renin isoform that is localized in the cytosol and within mitochondria. Here we tested the hypotheses that cytosolic renin [ren(2-9)] expression promotes cell survival under hypoxia and glucose depletion by preserving the mitochondrial membrane potential (∆Ψm) and mitigating the accumulation of ROS. To simulate ischemic insults, we exposed H9c2 cells to glucose deprivation, anoxia or to combined oxygen-glucose deprivation (OGD) for 24 hours and determined renin expression. Furthermore, H9c2 cells transfected with the empty pIRES vector (pIRES cells) or ren(2-9) cDNA-containing vector [ren(2-9) cells] were analyzed for cell death, ∆Ψm, ATP levels, accumulation of ROS, and cytosolic Ca2+ content. In pIRES cells, expression of ren(1A-9) was stimulated under all three ischemia-related conditions. After OGD, the cells lost their ∆Ψm and exhibited enhanced ROS accumulation, increased cytosolic Ca2+ levels, decreased ATP levels as well as increased cell death. In contrast, ren(2-9) cells were markedly protected from these effects. Ren(2-9) appears to represent a protective response to OGD by reducing ROS generation and preserving mitochondrial functions. Therefore, it is a promising new target for the prevention of ischemia-induced myocardial damage.

Stem Cell-Derived Exosomes Protect Astrocyte Cultures From in vitro Ischemia and Decrease Injury as Post-stroke Intravenous Therapy.

In the present study, we assessed efficacy of exosomes harvested from human and mouse stem cell cultures in protection of mouse primary astrocyte and neuronal cell cultures following in vitro ischemia, and against ischemic stroke in vivo. Cell media was collected from primary mouse neural stem cell (NSC) cultures or from human induced pluripotent stem cell-derived cardiomyocyte (iCM) cultures. Exosomes were extracted and purified by polyethylene glycol complexing and centrifugation, and exosome size and concentration were determined with a NanoSiteTM particle analyzer. Exosomes were applied to primary mouse cortical astrocyte or neuronal cultures prior to, and/or during, combined oxygen-glucose deprivation (OGD) injury. Cell death was assessed via lactate dehydrogenase (LHD) and propidium iodide staining 24 h after injury. NSC-derived exosomes afforded marked protection to astrocytes following OGD. A more modest (but significant) level of protection was observed with human iCM-derived exosomes applied to astrocytes, and with NSC-derived exosomes applied to primary neuronal cultures. In subsequent experiments, NSC-derived exosomes were injected intravenously into adult male mice 2 h after transient (1 h) middle cerebral artery occlusion (MCAO). Gross motor function was assessed 1 day after reperfusion and infarct volume was assessed 4 days after reperfusion. Mice treated post-stroke with intravenous NSC-derived exosomes exhibited significantly reduced infarct volumes. Together, these results suggest that exosomes isolated from mouse NSCs provide neuroprotection against experimental stroke possibly via preservation of astrocyte function. Intravenous NSC-derived exosome treatment may therefore provide a novel clinical adjuvant for stroke in the immediate post-injury period.

Corrigendum to "Immunosuppressant cytoprotection correlates with HMGB1 suppression in primary astrocyte cultures exposed to combined oxygen-glucose deprivation" [Pharmacol. Rep. 63 (2011) 392-402

Corrigendum to "Immunosuppressant cytoprotection correlates with HMGB1 suppression in primary astrocyte cultures exposed to combined oxygen-glucose deprivation" [Pharmacol. Rep. 63 (2011) 392-402

Time-Dependent Changes in Apoptosis Upon Autophagy Inhibition in Astrocytes Exposed to Oxygen and Glucose Deprivation.

Recent studies have implicated the role of autophagy in brain ischemia pathophysiology. However, it remains unclear whether autophagy activation is protective or detrimental to astrocytes undergoing ischemic stress. This study evaluated the influence of ischemia-induced autophagy on cell death and the course of intrinsic and extrinsic apoptosis in primary cultures of rat cortical astrocytes exposed to combined oxygen-glucose deprivation (OGD). The role of autophagy was assessed by pharmacological inhibition with 3-methyladenine (3-MA). Cell viability was evaluated by measuring LDH release and through the use of the alamarBlue Assay. Apoptosis and necrosis were determined by fluorescence microscopy after Hoechst 33,342 and propidium iodide staining, respectively. The levels of apoptosis-related proteinswere analyzed by immunoblotting. The downregulation of autophagy during OGD resulted in decreased cell viability and time-dependent changes in levels of apoptosis and necrosis. After short-term OGD (1, 4h), cells treated with 3-MA showed higher level of cleaved caspase3 compared with control cells. This result was consistent with an evaluation of apoptotic cell number by fluorescence microscopy. However, after prolonged exposure to OGD (8, 24h), thenumber ofapoptotic astrocytes (microscopically evaluated)did not differ or was even lower (as marked by caspase 3) in the presence of the autophagy inhibitorin comparison tothe control. A higher level of necrosis was observed in 3-MA-treated cells compared to non-treated cells after 24h OGD. The downregulation of autophagy caused time-dependent changes in both extrinsic (cleaved caspase 8, TNFα) and intrinsic (cleaved caspase 9) apoptotic pathways. Our results strongly indicate that the activation of autophagy in astrocytes undergoing ischemic stress is an adaptive mechanism, which allows for longer cell survival by delaying the initiation of apoptosis and necrosis.

Pro-apoptotic function of GABA-related transcripts following stroke

Following cerebral injuries such as stroke, a structural and functional reorganization of the impaired tissue occurs, which is often accompanied by a re-expression of developmental genes. During brain development, embryonic splice variants of the GABA-synthesizing GAD67 gene (collectively termed EGAD) participate in cell proliferation, migration, and neuronal differentiation. We thus hypothesized an involvement of EGAD in post-ischemic plasticity. EGAD transcripts were up-regulated at early reperfusion times in the injured area following transient middle cerebral artery occlusion (with a peak expression of 4.5-fold at 6h in C57BL/6 mice). Cell-specific analysis by a combination of radioactive in situ hybridization and immunolabeling revealed EGAD up-regulation in TUNEL-positive neurons. This unexpected cell death-associated expression of EGAD was confirmed in cell culture models of ischemia (combined oxygen–glucose deprivation) and apoptosis (staurosporine). Staurosporine-mediated cell death led to cleaved Caspase-3 activation, a key regulator of apoptosis following stroke. Blocking of staurosporine-associated EGAD expression via antisense RNA treatment reduced cleaved Caspase-3 activation by ~30%. In addition to the involvement of EGAD in proliferative processes during brain development, we found here that EGAD participates in cell death under pathophysiological conditions in the adult brain. Re-expression of EGAD in neurons following stroke may play a role in aberrant cell cycle activation, consequently being pro-apoptotic. Our observation of a new GABA related pro-apoptotic mechanism and its successful modification might be of significant clinical relevance.

AMP-activated protein kinase is involved in induction of protective autophagy in astrocytes exposed to oxygen-glucose deprivation.

AMP-activated kinase (AMPK) acts as the intracellular ATP depletion sensor, which detects and limits increases in the AMP/ATP ratio. AMPK may be significantly activated under stress conditions that deplete cellular ATP levels such as ischemia/hypoxia or glucose deprivation. Recent studies strongly suggest that AMPK participates in autophagy regulation, but it is not known whether AMPK activated by ischemia regulates autophagy in astrocytes and the consequence of autophagy activation in ischemic astrocytes are unclear. We have investigated the contribution of AMPK to autophagy activation in rat primary astrocyte cultures subjected to ischemia-simulating conditions (combined oxygen glucose deprivation, OGD) and its potential effects on astrocyte damage induced by OGD (1-12 h). The evidence supports the conclusion that AMPK activation at early stages of OGD is involved in induction of protective autophagy in astrocytes. Inhibition of AMPK, either by siAMPKα1 or by compound C, significantly attenuated the expression of autophagy-related proteins and decrease of astrocyte viability following OGD. The findings provide additional data about the role of AMPK in ischemic astrocytes and downstream responses that may be involved in OGD-induced protective autophagy.

Oxygen-glucose deprivation promotes gliogenesis and microglia activation in organotypic hippocampal slice culture: involvement of metalloproteinases.

Organotypic hippocampal cultures are used as an alternative model for studying molecular mechanism(s) of neurogenesis after combined oxygen-glucose deprivation (OGD) mimicking ischemic conditions. The aim of the present work was to investigate the effect of OGD on stem/progenitor cells proliferation and/or differentiation in the hippocampus. Our attention was primarily focused on the relationship between neurogenesis-associated processes and activity of matrix metalloproteinases (MMPs). Cell proliferation was detected by using BrdU incorporation. Newly generated BrdU (+) cells were identified by labeling with specific cell markers. In order to check the activity and localization of MMPs we conducted in situ zymography in conjunction with immunohistochemistry. In our experimental conditions OGD-insult followed by 24 h of recovery caused the damage of neuronal cells in CA1. At 1 week cell death appears all over the hippocampus. We found that expected stimulation of endogenous neurogenesis fails as a source of compensation for the lost neurons in OGD-treated cultures. The modulation of culture microenvironment after ischemia favors the dominant proliferation of glial cells expressed by the enhancement of newly-generated oligodendrocyte progenitors. In addition, during our study we also detected some BrdU labeled nuclei encapsulated by GFAP positive processes. However, the majority of BrdU positive cells expressed microglial specific stain, particularly pronounced in CA1area. The OGD-promoted responses involved activation of metalloproteinases, which matches the progression of gliogenesis. On the other hand, the high activity of MMPs associated with microglial cells implicate their involvement in the mechanism participating in OGD-induced cell damage.

A dietary polyphenol resveratrol acts to provide neuroprotection in recurrent stroke models by regulating AMPK and SIRT1 signaling, thereby reducing energy requirements during ischemia

Polyphenol resveratrol (RSV) has been associated with Silent Information Regulator T1 (SIRT1) and AMP-activated protein kinase (AMPK) metabolic stress sensors and probably responds to the intracellular energy status. Our aim here was to investigate the neuroprotective effects of RSV and its association with SIRT1 and AMPK signaling in recurrent ischemia models. In this study, elderly male Wistar rats received a combination of two mild transient middle cerebral artery occlusions (tMCAOs) as an in vivo recurrent ischemic model. Primary cultured cortical neuronal cells subjected to combined oxygen-glucose deprivation (OGD) were used as an in vitro recurrent ischemic model. RSV administration significantly reduced infarct volumes, improved behavioral deficits and protected neuronal cells from cell death in recurrent ischemic stroke models in vivo and in vitro. RSV treatments significantly increased the intracellular NAD(+) /NADH ratio, AMPK and SIRT1 activities, decreased energy assumption and restored cell energy ATP level. SIRT1 and AMPK inhibitors and specific small interfering RNA (siRNA) for SIRT1 and AMPK significantly abrogated the neuroprotection induced by RSV. AMPK-siRNA and inhibitor decreased SIRT1 activities; however, SIRT1-siRNA and inhibitor had no impact on phospho-AMPK (p-AMPK) levels. These results indicated that the neuroprotective effects of RSV increased the intracellular NAD(+) /NADH ratio as well as AMPK and SIRT1 activities, thereby reducing energy ATP requirements during ischemia. SIRT1 is a downstream target of p-AMPK signaling induced by RSV in the recurrent ischemic stroke model.

Adenosine and inosine exert cytoprotective effects in an in vitro model of liver ischemia-reperfusion injury

Liver ischemia represents a common clinical problem. In the present study, using an in vitro model of hepatic ischemia-reperfusion injury, we evaluated the potential cytoprotective effect of the purine metabolites, such as adenosine and inosine, and studied the mode of their pharmacological actions. The human hepatocellular carcinoma-derived cell line HepG2 was subjected to combined oxygen-glucose deprivation (COGD; 0-14-24 h), followed by re-oxygenation (0-4-24 h). Adenosine or inosine (300–1,000 μM) were applied in pretreatment. Cell viability and cytotoxicity were measured by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide and lactate dehydrogenase methods, respectively. The results showed that both adenosine and inosine exerted cytoprotective effects, and these effects were not related to receptor-mediated actions, since they were not prevented by selective adenosine receptor antagonists. On the other hand, the adenosine deaminase inhibitor erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (EHNA, 10 μM) markedly and almost fully reversed the protective effect of adenosine during COGD, while it did not influence the cytoprotective effect of inosine in the same assay conditions. These results suggest that the cytoprotective effects are related to intracellular actions, and, in the case of adenosine also involve intracellular conversion to inosine. The likely interpretation of these findings is that inosine serves as an alternative source of energy to produce ATP during hypoxic conditions. The protective effects are also partially dependent on adenosine kinase, as the inhibitor 4-amino-5-(3-bromophenyl)-7-(6-morpholino-pyridin-3-yl)pyrido[2,3-d]pyrimidine, 2HCl (ABT 702, 30 μM) significantly reversed the protective effect of both adenosine and inosine during hypoxia and re-oxygenation. Collectively, the current results support the view that during hypoxia, adenosine and inosine exert cytoprotective effects via receptor-independent, intracellular modes of action, which, in part, depend on the restoration of cellular bioenergetics. The present study supports the view that testing of inosine for protection against various forms of warm and cold liver ischemia is relevant.

Metabolic Modulation of Cytokine‐Induced Brain Endothelial Adhesion Molecule Expression

Cytokines contribute to cerebro-vascular inflammatory and immune responses by inducing ECAMs' expression. Ischemic insults can be separated into aglycemic and hypoxic components. However, whether aglycemia, hypoxia or OGD plays a major role in dysregulating BBB or promotes immune cell infiltration via ECAMs' expression is not clear. We investigated how expression of ICAM-1, VCAM-1, MAdCAM-1, PECAM-1, E- and P-selectin in response to TNF-α, IL-1β and IFN-γ was altered by aglycemia (A), hypoxia (H) or combined oxygen glucose deprivation (OGD). A cell surface enzyme linked immunoabsorbent assay (cell surface ELISA) was used to analyze ECAM expression. We observed that ICAM-1 and PECAM-1 expressions were insensitive to hypoxia, aglycemia or OGD. Conversely, VCAM-1 and E-selectin were increased by hypoxia, but not by aglycemia. MAdCAM-1 and P-selectin were induced by hypoxia, and decreased by aglycemia. Patterns of cytokine-regulated ECAMs' expression were also modified by metabolic conditions. Our results indicate that patterns of inflammation-associated ECAMs represent cumulative influences from metabolic stressors, as well as cytokine activation. The expression of ECAMs following tissue injury reflects mechanistic interactions between metabolic disturbances, and alterations in tissue cytokines. Normalization of tissue metabolism, as well as cytokine profiles, may provide important targets for therapeutic treatment of inflammation.

Immunosuppressant cytoprotection correlates with HMGB1 suppression in primary astrocyte cultures exposed to combined oxygen-glucose deprivation

The protective potential of immunosuppressants has been reported in many experimental models of ischemia both in vivo and in vitro, suggesting a novel therapeutic application of these drugs. Because high-mobility group box 1 (HMGB1) protein has recently been reported to be involved in ischemic brain injury, the purpose of the present study was to determine whether treatment with immunosuppressants could decrease the expression and release of HMGB1 in astrocytes exposed to simulated ischemic conditions (combined oxygen-glucose deprivation, OGD). We also investigated whether immunosuppressive drugs could attenuate necrosis in astrocyte cultures exposed to OGD. Finally, we studied the influence of immunosuppressants on the expression of NFκB, inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2). Cells were treated with cyclosporine A, FK506 and rapamycin (all drugs at concentrations of 0.1, 1 and 10µM). Our study provides evidence that immunosuppressants decrease the expression and release of HMGB1 in ischemic astrocytes. Our data suggest that HMGB1 release may be partly an active process triggered by oxidative stress because the antioxidant N-acetylcysteine (NAC) clearly attenuated HMGB1 expression and release. Furthermore, we show that the immunosuppressants, at the same concentrations that significantly suppressed HMGB1 expression and release, were also able to prevent the necrosis of ischemic astrocytes and inhibit the expression of inflammatory mediators (NFκB, iNOS and COX-2). These results provide further information about the cytoprotective mechanisms of immunosuppressants on ischemic astrocytes, especially in relation to the pathophysiology of ischemic brain injury. It appears that the protective effects of immunosuppressants can be mediated in part by the suppressing the expression and release of HMGB1 in astrocytes, which leads to the attenuation of ischemia-induced necrosis and neuroinflammation.

Fas/CD95 Regulatory Protein Faim2 Is Neuroprotective after Transient Brain Ischemia

Death receptor (DR) signaling has a major impact on the outcome of numerous neurological diseases, including ischemic stroke. DRs mediate not only cell death signals, but also proinflammatory responses and cell proliferation. Identification of regulatory proteins that control the switch between apoptotic and alternative DR signaling opens new therapeutic opportunities. Fas apoptotic inhibitory molecule 2 (Faim2) is an evolutionary conserved, neuron-specific inhibitor of Fas/CD95-mediated apoptosis. To investigate its role during development and in disease models, we generated Faim2-deficient mice. The ubiquitous null mutation displayed a viable and fertile phenotype without overt deficiencies. However, lack of Faim2 caused an increase in susceptibility to combined oxygen-glucose deprivation in primary neurons in vitro as well as in caspase-associated cell death, stroke volume, and neurological impairment after cerebral ischemia in vivo. These processes were rescued by lentiviral Faim2 gene transfer. In summary, we provide evidence that Faim2 is a novel neuroprotective molecule in the context of cerebral ischemia.

Effects of propofol on mitochondrial membrane permeability during hypoxia/reoxygenation in rat hippocampal neurons

Objective To investigate the effects of propofol on mitochondrial membrane permeability during hypoxia/reoxygenation （H/R） in rat hippocampal neurons. Methods Primary cultured hippocampal neurons of fetal rats obtained from Wistar （17-18 days of gestation） were randomly divided into 3 groups： Ⅰ control group （group C）, Ⅱ H/R group and Ⅲ propofol ＋ H/R group. Neurons were cultured in the culture medium with combined oxygen glucose deprivation for 2 h followed by reoxygenation in group Ⅱ and Ⅲ. In group Ⅲ propofol was added to the culture medium with the final concentration of 20 μ mol/L before combined oxygen glucose deprivation.Neuronal viability was detected by MTT assay and mitochondrial membrane potential （MMP） with flow cytometry at 0, 4, 8, 12 and 24 h after reoxygenation （T1-5） and the permeability of cell membrane and mitochondrial membrane was monitored at T5 using laser confocal scanning microscope. Results The neuronal viability and MMP were significantly decreased （P 〈 0.05）, while the permeability of cell membrane and mitochondrial membrane was increased at T5 in group Ⅱ as compared to group Ⅰ . The neuronal viability at T1-4 and MMP at T1-5 were significantly increased （P 〈 0.05）, while the permeability of cell membrane and mitochondrial membrane was decreased at T5 in group Ⅲ compared to group Ⅱ . Conclusion Propofol can protect rat hippocampal neurons against H/R injury through increasing MMP, improving the cell and mitochondrial membrane permeability, and increasing the neuronal viability. Key words: Propofol; Cell hypoxia; Oxygen; Mitochondrial membranes; Permeability; Hippocampus; Neurons

Cytosolic phospholipase A2 inhibition is involved in the protective effect of nortriptyline in primary astrocyte cultures exposed to combined oxygen-glucose deprivation

The protective potential of nortriptyline has been reported in a few experimental models of brain ischemia, both in vivo and in vitro. However, the detailed molecular mechanisms of the protective action of the drug are still unresolved. The aim of the present study was to determine whether treatment with low or medium concentrations of nortriptyline (0.1–10µM) might have an effect on cPLA2 protein and/or mRNA expression in ischemic astrocytes, and whether this influence might be related to its potential positive influence on cell viability. On the 21st day in vitro, primary cultures of rat cortical astrocytes were subjected to ischemia-simulating conditions (combined oxygen glucose deprivation, OGD) for 24h and exposed to nortriptyline. The drug at concentrations of 0.1 and 1µM attenuated the expression of cPLA2 (both the phosphorylated and unphosphorylated forms) together with a significant decrease in the cPLA2 mRNA level in ischemic astrocytes. We have demonstrated that nortriptyline influences a decrease in cPLA2-mediated arachidonic acid (AA) release through a mechanism that appears to involve the attenuation of both PKC and Erk1/2 kinase expression. Nortriptyline also significantly prevented mitochondrial depolarization in ischemic astrocytes. Moreover, the antidepressant protected glial cells against OGD-induced apoptosis and necrosis. Our findings document a role for cPLA2 expression attenuation and AA release inhibition in the protective effect of nortriptyline in ischemic astrocytes.

Inhibition of cytosolic phospholipase A2 is involved in the protective effect of nortriptyline on astrocytes exposed to combined oxygen-glucose deprivation

Inhibition of cytosolic phospholipase A2 is involved in the protective effect of nortriptyline on astrocytes exposed to combined oxygen-glucose deprivation

Effects of naloxone on the expression of stem cell factor and C-kit receptor in combined oxygen-glucose deprivation of primary cultured human embryonic neuron in vitro

To explore the effects of naloxone on the expression of c-kit receptor (c-kit R) and its ligand stem cell factor (SCF) in human embryo neuronal hypoxic injury. Serum-free cerebral cortical cultures prepared from embryonic human brains were deprived of both oxygen and glucose which would set up an environment more likely with that of in vivo ischemic injury. Neurons in 24-well culture plates were randomly divided into four groups: control group, hypoxia group, naloxone 0.5 microg/ml group and naloxone 10 microg/ml group. MTT assay and biological analysis were performed to study the cell death and the changes of extracellular concentrations of lactate dehydrogenase (LDH) after combined oxygen-glucose deprivation. Neurons in 25 ml culture flasks were also randomly allocated into four groups as previously described. Intracellular total RNA were extracted at different time points: pre-hypoxia, immediately after hypoxia, and 3, 6, 12, and 24 hours after reoxygenation. The changes of SCF/c-kit R mRNA expression in hypoxic neurons treated with different concentrations of naloxone pre and post oxygen-glucose deprivation were determined with RT-PCR. The cell vitality detected by MTT assay decreased significantly in hypoxia group and naloxone 0.5 microg/ml group when compared with control group (P<0.01), while no significant difference was found between naloxone 0.5 microg/ml group and hypoxia group or between naloxone 10 microg/ml group and control group. Extracellular concentration of LDH significantly increased in hypoxia group (P<0.05), while no difference was found between naloxone 0.5 microg/ml group and control group, between naloxone 0.5 microg/ml and hypoxia group, or between naloxone 10 microg/ml and control group (all P>0.05). Immediately after oxygen-glucose deprivation, the expression of SCF/c-kit R mRNA increased significantly (P<0.01). Among those the expression of SCF presented a distribution of double-peak value within 24 hours. After treated with different concentrations of naloxone, the peak value of each group were delayed to appear and went down with the increasing of naloxone concentration. The peak values in all treated groups were significantly different from that in control group (P<0.01). The expression of SCF/c-kit R mRNA increases at the early stage after combined oxygen-glucose deprivation. Naloxone 0.5 microg/ml can attenuate cell injuries and regulate the expression of SCF/c-kit R. Naloxone may protect neurons by modulating the expressions of some cytokines.

Cytosolic phospholipase A2 inhibition is involved in the protective effect of nortriptyline in primary astrocyte cultures exposed to combined oxygen-glucose deprivation

Cytosolic phospholipase A2 inhibition is involved in the protective effect of nortriptyline in primary astrocyte cultures exposed to combined oxygen-glucose deprivation

Cytoprotective effects of adenosine and inosine in an in vitro model of acute tubular necrosis

We have established an in vitro model of acute tubular necrosis in rat kidney tubular cells, using combined oxygen-glucose deprivation (COGD) and screened a library of 1280 pharmacologically active compounds for cytoprotective effects. We used in vitro cell-based, high throughput, screening, with cells subjected to COGD using hypoxia chambers, followed by re-oxygenation. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and the Alamar Blue assay measured mitochondrial respiration and the lactate dehydrogenase assay was used to indicate cell death. ATP levels were measured using a luminometric assay. Adenosine markedly reduced cellular injury, with maximal cytoprotective effect at 100 microM and an EC(50) value of 14 microM. Inosine was also found to be cytoprotective. The selective A(3) adenosine receptor antagonist MRS 1523 attenuated the protective effects of adenosine and inosine, while an A(3) adenosine receptor agonist provided a partial protective effect. Adenosine deaminase inhibition attenuated the cytoprotective effect of adenosine but not of inosine during COGD. Inhibition of adenosine kinase reduced the protective effects of both adenosine and inosine during COGD. Pretreatment of the cells with adenosine or inosine markedly protected against the fall in cellular ATP content in the cells subjected to COGD. The cytoprotection elicited by adenosine and inosine in a model of renal ischaemia involved both interactions with cell surface adenosine receptors on renal tubular epithelial cells and intracellular metabolism and conversion of adenosine to ATP.

Effect of FK506 and cyclosporine A on the expression of BDNF, tyrosine kinase B and p75 neurotrophin receptors in astrocytes exposed to simulated ischemia in vitro

We investigated whether the immunosuppressive drugs, FK506 and cyclosporine A, increase BDNF protein and/or mRNA expression in ischemic astrocytes and if an increase could be related to changes in the nuclear expression of p-CREB, p-Erk1/2 and p-Akt. The influence of these immunosuppressants on protein and mRNA levels of TrkB and p75(NTR) receptors was also examined. On day 21, cultures of rat astrocytes were subjected to ischemic conditions simulated in vitro (combined oxygen glucose deprivation, OGD) for 8h and exposed to FK506 (10-1000nM) and cyclosporine A (0.25-10microM). FK506 and cyclosporine A (at 1000nM and 0.25microM, respectively) stimulated the expression and release of BDNF in cultured rat cerebral cortical astrocytes exposed to OGD. The immunosuppressants at these doses simultaneously increased p-CREB and p-Erk1/2 expression in the nuclear fraction of astrocytes. The results RT-PCR and Western blot analysis provided further evidence of a modulating influence of the drugs on the expression of trkB and p75(NTR) genes and their protein products in ischemic astrocytes.