TDP-43 pathology in subacute sclerosing panencephalitis.

Subacute sclerosing panencephalitis (SSPE) is a fatal, slowly progressive brain disorder caused by a mutated measles virus. Both subacute inflammatory and neurodegenerative mechanisms appear to play significant roles in the pathogenesis. TAR DNA-binding protein 43 (TDP-43) inclusions are a common co-pathology in several neurodegenerative disorders with diverse pathogenesis. In the present study, we examined brains of 16 autopsied SSPE patients for the presence of TDP-43 pathology and possible associations with tau pathology. Immunohistochemical staining identified TDP-43 inclusions in 31% of SSPE cases. TDP-43 pathology was widely distributed in the brains, most severely in the atrophied cerebral cortex (temporal and parietal), and most frequently as tangle- and thread-like neuronal cytoplasmic inclusions. It was associated with longer disease duration (>4 years) and tau pathology (all TDP-43-positive cases had tau-positive neurofibrillary tangles). This study demonstrates for the first time an association between TDP-43 pathology and SSPE. The co-occurrence of TDP-43 and tau aggregates and correlation with the disease duration suggest that both pathological proteins are involved in the neurodegenerative process induced by viral inflammation.

Dexras1 Induces Dysdifferentiation of Oligodendrocytes and Myelin Injury by Inhibiting the cAMP-CREB Pathway after Subarachnoid Hemorrhage.

White matter damage (WMD), one of the research hotspots of subarachnoid hemorrhage (SAH), mainly manifests itself as myelin injury and oligodendrocyte differentiation disorder after SAH, although the specific mechanism remains unclear. Dexamethasone-induced Ras-related protein 1(Dexras1) has been reported to be involved in nervous system damage in autoimmune encephalitis and multiple sclerosis. However, whether Dexras1 participates in dysdifferentiation of oligodendrocytes and myelin injury after SAH has yet to be examined, which is the reason for creating the research content of this article. Here, intracerebroventricular lentiviral administration was used to modulate Dexras1 levels in order to determine its functional influence on neurological injury after SAH. Immunofluorescence, transmission electron microscopy, and Western blotting methods, were used to investigate the effects of Dexras1 on demyelination, glial cell activation, and differentiation of oligodendrocyte progenitor cells (OPCs) after SAH. Primary rat brain neurons were treated with oxyhemoglobin to verify the association between Dexras1 and cAMP-CREB. The results showed that Dexras1 levels were significantly increased upon in vivo SAH model, accompanied by OPC differentiation disturbances and myelin injury. Dexras1 overexpression significantly worsened OPC dysdifferentiation and myelin injury after SAH. In contrast, Dexras1 knockdown ameliorated myelin injury, OPC dysdifferentiation, and glial cell activation. Further research of the underlying mechanism discovered that the cAMP-CREB pathway was inhibited after Dexras1 overexpression in the in vitro model of SAH. This study is the first to confirm that Dexras1 induced oligodendrocyte dysdifferentiation and myelin injury after SAH by inhibiting the cAMP-CREB pathway. This present research may reveal novel therapeutic targets for the amelioration of brain injury and neurological dysfunction after SAH.

Proteasome and Neuroprotective Effect of Hyperbaric Oxygen Preconditioning in Experimental Global Cerebral Ischemia in Rats.

OBJECTIVES: We investigated the involvement of the proteasome in the mechanism of preconditioning with hyperbaric oxygen (HBO-PC). METHODS: The experiments were performed on male Wistar rats subjected to a transient global cerebral ischemia of 5 min duration (2-vessel occlusion model) and preconditioned or not with HBO for 5 preceding days (1 h HBO at 2.5 atmosphere absolute [ATA] daily). In subgroups of preconditioned rats, the proteasome inhibitor MG132 was administered 30 min prior to each preconditioning session. Twenty-four hours and 7 days post-ischemia, after neurobehavioral assessment, the brains were collected and evaluated for morphological changes and quantitative immunohistochemistry of cell markers and apoptosis-related proteins. RESULTS: We observed reduced damage of CA1 pyramidal cells in the HBO preconditioned group only at 7 days post-ischemia. However, both at early (24 h) and later (7 days) time points, HBO-PC enhanced the tissue expression of 20S core particle of the proteasome and of the nestin, diminished astroglial reactivity, and reduced p53, rabbit anti-p53 upregulated modulator of apoptosis (PUMA), and rabbit anti-B cell lymphoma-2 interacting mediator of cell death (Bim) expressions in the hippocampus and cerebral cortex. HBO-PC also improved T-maze performance at 7 days. Proteasome inhibitor abolished the beneficial effects of HBO-PC on post-ischemic neuronal injury and functional impairment and reduced the ischemic alterations in the expression of investigated proteins. SIGNIFICANCE: Preconditioning with hyperbaric oxygen-induced brain protection against severe ischemic brain insult appears to involve the proteasome, which can be linked to a depletion of apoptotic proteins and improved regenerative potential.

Inhibiting CK2 among Promising Therapeutic Strategies for Gliomas and Several Other Neoplasms.

In gliomas, casein kinase 2 (CK2) plays a dominant role in cell survival and tumour invasiveness and is upregulated in many brain tumours. Among CK2 inhibitors, benzimidazole and isothiourea derivatives hold a dominant position. While targeting glioma tumour cells, they show limited toxicity towards normal cells. Research in recent years has shown that these compounds can be suitable as components of combined therapies with hyperbaric oxygenation. Such a combination increases the susceptibility of glioma tumour cells to cell death via apoptosis. Moreover, researchers planning on using any other antiglioma investigational pharmaceutics may want to consider using these agents in combination with CK2 inhibitors. However, different compounds are not equally effective when in such combination. More research is needed to elucidate the mechanism of treatment and optimize the treatment regimen. In addition, the role of CK2 in gliomagenesis and maintenance seems to have been challenged recently, as some compounds structurally similar to CK2 inhibitors do not inhibit CK2 while still being effective at reducing glioma viability and invasion. Furthermore, some newly developed inhibitors specific for CK2 do not appear to have strong anticancer properties. Further experimental and clinical studies of these inhibitors and combined therapies are warranted.

Harnessing oxidative stress for anti-glioma therapy.

Glioma cells use intermediate levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) for growth and invasion, and suppressing these reactive molecules thus may compromise processes that are vital for glioma survival. Increased oxidative stress has been identified in glioma cells, in particular in glioma stem-like cells. Studies have shown that these cells harbor potent antioxidant defenses, although endogenous protection against nitrosative stress remains understudied. The enhancement of oxidative or nitrosative stress offers a potential target for triggering glioma cell death, but whether oxidative and nitrosative stresses can be combined for therapeutic effects requires further research. The optimal approach of harnessing oxidative stress for anti-glioma therapy should include the induction of free radical-induced oxidative damage and the suppression of antioxidant defense mechanisms selectively in glioma cells. However, selective induction of oxidative/nitrosative stress in glioma cells remains a therapeutic challenge, and research into selective drug delivery systems is ongoing. Because of multifactorial mechanisms of glioma growth, progression, and invasion, prospective oncological therapies may include not only therapeutic oxidative/nitrosative stress but also inhibition of oncogenic kinases, antioxidant molecules, and programmed cell death mediators.

Effect of Lubricant Type on the Friction Behaviours and Surface Topography in Metal Forming of Ti-6Al-4V Titanium Alloy Sheets.

The aim of the research described in this paper is to analyse the synergistic effect of types of synthetic oil and their density on the value of the coefficient of friction (COF) of Ti-6Al-4V titanium alloy sheets. Lubrication performance of commercial synthetic oils (machine, gear, engine and hydraulic) was tested in a strip draw friction test. The friction tests consisted of pulling a strip specimen between two cylindrical fixed countersamples. The countersamples were placed in the simulator base mounted on a uniaxial tensile test machine. Due to the complex synergistic effect of different strip drawing test parameters on the COF, artificial neural networks were used to find this relationship. In the case of both dry and lubricated conditions, a clear trend was found of a reduction of the coefficient of friction with nominal pressure. Engine oil 10W-40 was found to be the least favourable lubricant in reducing the coefficient of friction of Grade 5 titanium sheets. The two main tribological mechanisms, i.e., galling and ploughing, played the most important role in the friction process on the test sheets. In the range of nominal pressures considered, and with the synthetic oils tested, the most favourable lubrication conditions can be obtained by using a type of oil with a low viscosity index and a high kinematic viscosity.

Central Composite Design Optimisation in Single Point Incremental Forming of Truncated Cones from Commercially Pure Titanium Grade 2 Sheet Metals.

Single point incremental forming (SPIF) is an emerging process that is well-known to be suited for fabrication in small series production. The aim of this paper was to determine the optimal input parameters of the process in order to minimise the maximum of both the axial and the in-plane components of the forming force achieved during SPIF and the surface roughness of the internal surface of truncated-cone drawpieces. Grade 2 pure titanium sheets with a thickness of 0.4 mm were used as the test material. The central composite design and response surface method was used to determine the number of experiments required to study the responses through building a second-order quadratic model. Two directions of rotation of the forming tool were also considered. The input parameters were spindle speed, tool feed rate, and step size. The mathematical relations were defined using the response surfaces to predict the surface roughness of the drawpieces and the components of the forming force. It was found that feed rate has an insignificant role in both axial and in-plane forming forces, but step size is a major factor affecting axial and radial forming forces. However, step size directly affects the surface roughness on the inner surfaces of the drawpieces. Overall, the spindle speed -579 rpm (clockwise direction), tool feed 2000 mm/min, and step size 0.5 mm assure a minimisation of both force components and the surface roughness of drawpieces.

Hepcidin Promoted Ferroptosis through Iron Metabolism which Is Associated with DMT1 Signaling Activation in Early Brain Injury following Subarachnoid Hemorrhage.

Iron metabolism disturbances play an important role in early brain injury (EBI) after subarachnoid hemorrhage (SAH), and hepcidin largely influences iron metabolism. Importantly, iron metabolism may be associated with ferroptosis, recently a nonapoptotic iron-dependent form of cell death that may have a great impact on brain injury after SAH. We investigated hepcidin on iron metabolism and ferroptosis involving divalent metal transporter 1 (DMT1), and ferroportin-1 (FPN1) in a rat model of SAH. Male Sprague-Dawley rats were subjected to the endovascular perforation to induce SAH, and treated with heparin (inhibitor of hepcidin), or oncostatin M (OSM, inducer of hepcidin), or ebselen (inhibitor of DMT1) by intracerebroventricular injections. Hepcidin, DMT1, FPN1 and glutathione peroxidase 4 (GPX4), were detected by western blot and immunofluorescence. Iron metabolism was detected through Perl's iron staining and iron content assay. Ferroptosis, the ROS production, lipid peroxidation (LPO) was evaluated by monitoring methane dicarboxylic aldehyde (MDA), glutathione (GSH), glutathione peroxidase 4 (GPX4) activity, and transmission electron microscopy. Neurological deficit scores, Evans blue staining and brain water content were also determined to detect EBI 72 h after SAH. Our results showed that inhibition of DMT1 by ebselen could suppress iron accumulation and lipid peroxidation, and thereby alleviate ferroptosis and EBI in SAH rats. Heparin downregulated the expression of hepcidin and DMT1, increased FPN1, and exerted protective effects that were equivalent to those of ebselen on ferroptosis and EBI. In addition, OSM increased the expression of hepcidin and DMT1, decreased FPN1, and aggravated ferroptosis and EBI, while the effect on ferroptosis was reversed by ebselen. Therefore, the study revealed that hepcidin could regulate iron metabolism and contribute to ferroptosis via DMT1 signaling activation in rats with EBI after SAH.

Targeting protein kinases for anti-glioma treatment.

The genetic alterations related to many kinases are responsible for the formation of glial tumours. In addition it is the cell kinases that keep the cancerous signalling machinery in motion, thus enabling tumour cell growth, motility and invasion. Kinase inhibitors may have a potential to surpass the classical oncolytic treatment for gliomas. However, overcoming drug resistance mechanisms and limited blood-brain barrier (BBB) permeability are the remaining daunting issues. Latest research explores novel kinase inhibitors, yielding several promising results, including those from CK2 inhibition studies, as well as the possibility of relabelling the inhibitors previously approved for tumours other than glial tumours.

The insights into molecular pathways of hypoxia-inducible factor in the brain.

The objectives of this present work were to review recent developments on the role of hypoxia-inducible factor (HIF) in the survival of cells under normoxic versus hypoxic and inflammatory brain conditions. The dual nature of HIF effects appears well established, based on the accumulated evidence of HIF playing both the role of adaptive factor and mediator of cell demise. Cellular HIF responses depend on pathophysiological conditions, developmental phase, comorbidities, and administered medications. In addition, HIF-1α and HIF-2α actions may vary in the same tissues. The multiple roles of HIF in stem cells are emerging. HIF not only regulates expression of target genes and thereby influences resultant protein levels but also contributes to epigenetic changes that may reciprocally provide feedback regulations loops. These HIF-dependent alterations in neurological diseases and its responses to treatments in vivo need to be examined alongside with a functional status of subjects involved in such studies. The knowledge of HIF pathways might be helpful in devising HIF-mimetics and modulating drugs, acting on the molecular level to improve clinical outcomes, as exemplified here by clinical and experimental data of selected brain diseases, occasionally corroborated by the data from disorders of other organs. Because of complex role of HIF in brain injuries, prospective therapeutic interventions need to differentially target HIF responses depending on their roles in the molecular mechanisms of neurologic diseases.

Novel small molecule protein kinase CK2 inhibitors exert potent antitumor effects on T98G and SEGA cells in vitro.

Tumours of astroglial origin, both malignant glioblastoma (GBM) and benign subependymal giant cell astrocytoma (SEGA), pose a serious medical problem. Casein kinase 2 (CK2), a member of the serine/threonine kinase family, has antiapoptotic properties and plays a vital role in glial tumour cell survival. It contributes to invasive cell growth and is often upregulated in malignant neoplastic cells; however, its role in benign tumours of astrocytic origin is less understood. In the present study we investigated the effects of small molecule CK2 inhibitors on proliferation and viability of glioma cells in vitro. The experiments were conducted on commercial T98G malignant glioma cell line and the SEGA cell line, derived from a paediatric case of tuberous sclerosis complex (TSC). Cell cultures were incubated with selected CK2 inhibitors: 4,5,6,7-tetrabromo-1H-benzimidazole (TBI), 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole (DMAT) and 4,5,6,7-tetrabromo-1H-benzotriazole (TBB) at 0.1, 1, 10, 25, 50, 75 and 100 µM concentrations for 24 and 48 hours. Cell proliferation was assessed using a cell counter and cell viability was evaluated by MTT assay. TBB at 75 µM and 100 µM, and TBI starting from 25 µM, both reduced T98G cell proliferation after 24 hours, while DMAT was ineffective. All tested small molecule CK2 inhibitors appear to reduce T98G cell growth and viability after 48 hours, although TBI appeared to be the most effective and reduced cell growth in the 50-100 µM dose range. TBI also showed potential efficacy in reducing the number and viability of SEGA cells after 48 hours. Proliferation and viability of SEGA cells have proven resistant to TBB treatment. DMAT only reduced the viability of SEGA cells at 24 (at 100 µM) and 48 hours (10-100 µM). Importantly, normal human astrocyte cells were found to be moderately resistant to TBB, while their viability was mildly reduced at higher doses of DMAT and TBI. In conclusion, CK2 appears to play a role not only in malignant glioma cells but it can also sustain the viability and proliferation of benign astrocytoma cells. The obtained antitumor effects of CK2 inhibitors significantly exceeded their mild or no effect on normal astrocytes in control, which supports the therapeutic potential of these compounds against gliomas.

Hyperbaric oxygen increases glioma cell sensitivity to antitumor treatment with a novel isothiourea derivative in vitro.

Glioblastoma (GBM) is the most common primary brain tumor. Tumor hypoxia is a pivotal factor responsible for the progression of this malignant glioma, and its resistance to radiation and chemotherapy. Thus, improved tumor tissue oxygenation may promote greater sensitivity to anticancer treatment. Protein kinase D1 (PKD1) protects cells from oxidative stress, and its abnormal activity serves an important role in multiple malignancies. The present study examined the effects of various oxygen conditions on the cytotoxic potential of the novel isothiourea derivate N,N'­dimethyl­S­(2,3,4,5,6­pentabromobenzyl)­â€‹isothiouronium bromide (ZKK­3) against the T98G GBM cell line. ZKK­3 was applied at concentrations of 10, 25 and 50 µM, and cells were maintained under conditions of normoxia, anoxia, hypoxia, hyperbaric oxygen (HBO), hypoxia/hypoxia and hypoxia/HBO. The proliferation and viability of neoplastic cells, and protein expression levels of hypoxia­inducible factor 1α (HIF­1α), PKD1, phosphorylated (p)PKD1 (Ser 916) and pPKD1 (Ser 744/748) kinases were evaluated. Oxygen deficiency, particularly regarding hypoxia, could diminish the cytotoxic effect of ZKK­3 at 25 and 50 µM and improve T98G cell survival compared with normoxia. HBO significantly reduced cell proliferation and increased T98G cell sensitivity to ZKK­3 when compared with normoxia. HIF­1α expression levels were increased under hypoxia compared with normoxia and decreased under HBO compared with hypoxia/hypoxia at 0, 10 and 50 µM ZKK­3, suggesting that HBO improved oxygenation of the cells. ZKK­3 exhibited inhibitory activity against pPKD1 (Ser 916) kinase; however, the examined oxygen conditions did not appear to significantly influence the expression of this phosphorylated form in cells treated with the tested compound. Regarding pPKD1 (Ser 744/748), a significant difference in expression was observed only for cells treated with 10 µM ZKK­3 and hypoxia/hypoxia compared with normoxia. However, there were significant differences in the expression levels of both phosphorylated forms of PKD1 under different oxygen conditions in the controls. In conclusion, the combination of isothiourea derivatives and hyperbaric oxygenation appears to be a promising therapeutic approach for malignant glioma treatment.

Potent Antitumour Effects of Novel Pentabromobenzylisothioureas Studied on Human Glial-derived Tumour Cell Lines.

BACKGROUND/AIM: Tumours of astroglial origin are the most common primary brain malignancy characterized by infiltrative growth and resistance to standard antitumour therapy. Glioma progression is thought to be related to various intracellular signal transduction pathways that involve the activation of protein kinases. Protein kinases play important roles in cell differentiation, proliferation, and survival. Recently, novel, specific inhibitors of constitutively active serine/threonine kinases and structurally similar isothiourea derivatives were suggested to induce apoptosis and inhibit proliferation in several types of human cancer cells. MATERIALS AND METHODS: In this study, we examined the cytotoxic and proapoptotic activities of selected modified pentabromobenzyl isothioureas (ZKKs) in an adult human glioblastoma (T98G) and a subependymal giant cell astrocytoma cell (SEGA) line. We evaluated cell proliferation, viability, and apoptosis. RESULTS: Two pentabromobenzyl isothiourea bromide derivatives, ZKK-13 and N,N,N'-trimethyl-ZKK1 (TRIM), exhibited the most potent cytotoxic and proapoptotic efficacies against human glioma-derived cells, even at a very low concentration (1 µM). ZKK-13 (25-50 µM) inhibited cell growth by approximately 80-90% in 24 and 48 h of treatment. We showed that selected ZKKs exerted antiproliferative activity against astroglial neoplastic cells of both low- and high-grade tumour malignancy classes. No synergistic effects were detected when ZKKs were combined with serine/threonine kinase inhibitors. CONCLUSION: Our findings indicated that modified ZKKs show promise for the treatment of glioma-derived brain tumours.

The efficacy of hyperbaric oxygen in hemorrhagic stroke: experimental and clinical implications.

Hemorrhagic stroke, accounting for 10-30% of stroke cases, carries high rates of morbidity and mortality. This review presents the current knowledge on the efficacy of hyperbaric oxygen (HBO)-based modalities in the preclinical research on hemorrhagic stroke. Both preconditioning and post-treatment with HBO are considered as prospective therapeutic options. High efficacy of HBO therapy (HBOT) for brain hemorrhage has been noted. We found that moderate hyperbaric pressures appear optimal for therapeutic effect, while the therapeutic window of opportunity is short. HBO preconditioning offers more modest neuroprotective benefit as compared to HBO post-treatment for experimental intracerebral hemorrhage. We advocate for mandatory calculations of percent changes in the experimentally investigated indexes of HBO effectiveness and stress the need to design new clinical trials on HBO for hemorrhagic stroke.

Hyperbaric oxygen modalities are differentially effective in distinct brain ischemia models.

The effectiveness and efficacy of hyperbaric oxygen (HBO) preconditioning and post-treatment modalities have been demonstrated in experimental models of ischemic cerebrovascular diseases, including global brain ischemia, transient focal and permanent focal cerebral ischemia, and experimental neonatal hypoxia-ischemia encephalopathy. In general, early and repetitive post-treatment of HBO appears to create enhanced protection against brain ischemia whereas delayed HBO treatment after transient focal ischemia may even aggravate brain injury. This review advocates the level of injury reduction upon HBO as an important component for translational evaluation of HBO based treatment modalities. The combined preconditioning and HBO post-treatment that would provide synergistic effects is also worth considering.

Hyperbaric oxygen as an adjunctive therapy in treatment of malignancies, including brain tumours.

Hyperbaric oxygen (HBO) therapy is widely used as an adjunctive treatment for various pathological states, predominantly related to hypoxic and/or ischaemic conditions. It also holds promise as an approach to overcoming the problem of oxygen deficiency in the poorly oxygenated regions of the neoplastic tissue. Occurrence of local hypoxia within the central areas of solid tumours is one of the major issues contributing to ineffective medical treatment. However, in anti-cancer therapy, HBO alone gives a limited curative effect and is typically not applied by itself. More often, HBO is used as an adjuvant treatment along with other therapeutic modalities, such as radio- and chemotherapy. This review outlines the existing data regarding the medical use of HBO in cancer treatment, with a particular focus on the use of HBO in the treatment of brain tumours. We conclude that the administration of HBO can provide many clinical benefits in the treatment of tumours, including management of highly malignant gliomas. Applied immediately before irradiation, it is safe and well tolerated by patients, causing rare and limited side effects. The results obtained with a combination of HBO/radiotherapy protocol proved to be especially favourable compared to radiation treatment alone. HBO can also increase the cytostatic effect of certain drugs, which may render standard chemotherapy more effective. The currently available data support the legitimacy of conducting further research on the use of HBO in the treatment of malignancies.

Isoflurane on brain inflammation.

Brain inflammation may play an important role in the pathophysiology of early brain injury after subarachnoid hemorrhage (SAH). Our aim was to demonstrate brain inflammation development and to determine whether isoflurane, a clinically available volatile anesthetic agent, prevents brain inflammation after SAH. This study used 162 8-week-old male CD-1 mice. We induced SAH with endovascular perforation in mice and randomly assigned animals to sham-operated (n=21), SAH+vehicle-air (n=35) and SAH+2% isoflurane (n=31). In addition to the evaluation of brain injury (neurological scores, brain edema and Evans blue dye extravasation), brain inflammation was evaluated by means of expression changes in markers of inflammatory cells (ionized calcium binding adaptor molecule-1, myeloperoxidase), cytokines (tumor necrosis factor [TNF]-α, interleukin-1ß), adhesion molecules (intercellular adhesion molecule [ICAM]-1, P-selectin), inducers of inflammation (cyclooxygenase-2, phosphorylated c-Jun N-terminal kinase [p-JNK]) and endothelial cell activation (von Willebrand factor) at 24h post-SAH. Sphingosine kinase inhibitor (N, N-dimethylsphingosine [DMS]) and sphingosine-1-phosphate receptor-1/3 antagonist (VPC23019) were used to block isoflurane's effects (n=22, each). SAH caused early brain injury, which was associated with inflammation so that all evaluated markers of inflammation were increased. Isoflurane significantly inhibited both brain injury (P<0.001, respectively) and inflammation (myeloperoxidase, P=0.022; interleukin-1ß, P=0.002; TNF-α, P=0.015; P-selectin, P=0.010; ICAM-1, P=0.016; p-JNK, P<0.001; cyclooxygenase-2, P=0.003, respectively). This beneficial effect of isoflurane was abolished with DMS and VPC23019. Isoflurane may suppress post-SAH brain inflammation possibly via the sphingosine-related pathway.

Erythropoietin inhibits HIF-1α expression via upregulation of PHD-2 transcription and translation in an in vitro model of hypoxia-ischemia.

Hypoxia inducible factor (HIF)-1α is the central transcriptional factor for the regulation of oxygen-associated genes in response to hypoxia. Erythropoietin (EPO), a hematopoietic growth factor, increases oxygen availability during hypoxia/ischemia and is associated with neuroprotection following hypoxia-ischemia in laboratory models of stroke. However, EPO has failed to translate in a clinical setting. Thus, it is critical to elucidate the key players in EPO-induced neuroprotection. Our preliminary studies have shown that EPO, as a downstream gene of HIF, inhibits HIF-1α in a dose-dependent manner in an in vitro model of hypoxia-ischemia. This study is designed to elucidate the primary mediator of EPO-induced HIF-1α inhibition and subsequent cell survival/neuroprotection. Oxygen and glucose deprivation (OGD) of nerve growth factor-differentiated rat pheochromocytoma (PC-12) cells were used to model hypoxia-ischemia in an in vitro environment. The profile of HIF-1α, HIF-2α and prolyl hydroxylase domain 2 (PHD-2) expression; HIF-1α and prolyl hydroxylase (PHD-2) mRNA levels; matrix metalloproteinase (MMP)-9; and cell death was evaluated in the presence and absence of either EPO or PHD-2 inhibitor during OGD. Our findings showed that EPO treatment resulted in an increase in PHD-2 transcription and translation, inhibition of HIF-1α expression, reactive oxygen species formation, and MMP-9 activity, resulting in increased cell survival after OGD. We also observed that EPO-induced cell survival/neuroprotection was reversed by siRNA silencing of PHD-2. This led to the conclusion that PHD-2 is a key mediator of EPO-induced HIF-1α inhibition and subsequent neuroprotection in an in vitro model of hypoxia-ischemia.