A1 adenosine receptor attenuates intracerebral hemorrhage-induced secondary brain injury in rats by activating the P38-MAPKAP2-Hsp27 pathway

Adenosine receptor A1 enhanced mitochondrial biogenesis and exerted neuroprotection after cerebral ischemia through PGC-1α

Ischemic stroke is a common cause of morbidity and mortality worldwide. The current treatment fails to achieve satisfactory results, because interventional therapy as first-line treatment management has a strict time window. In recent years, a large number of studies have confirmed that adenosine, as an inhibitory neurotransmitter, has a protective effect on cerebral ischemic injury. Nevertheless, direct administration of adenosine has many side effects. Previous studies showed that adenosine exerted neuroprotective effects mainly through adenosine receptor A1 (A1 receptor). Therefore, further study on the mechanism of A 1 receptor induced neuroprotection may find new targets for stroke treament. Mitochondrial biogenesis (MB) is a therapeutic target for ischemic stroke, and the nuclear-encoded peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) is a major regulator of MB. However, the influence of A1 receptor on MB and PGC-1α is unclear. In this study, using the middle cerebral artery occlusion (MCAO) model of mice, we evaluated the temporal and spatial effects of A1 receptor after ischemic stroke and verified the neuroprotection of A1 receptor. Neurological scores were used to assess functional changes in mice. At the same time, we observed the effect of activating A1 receptor on MB and PGC-1α, and the effect of knockdown PGC-1α on A1 receptor induced MB in vitro. WB and immunofluorescence were used to detect relevant indicators of MB. In addition, we downregulated PGC-1α in vivo to observe the effects on A1 receptor induced MB and neuroprotection. The findings indicated that A1 receptor was increased and mainly expressed on neurons in the penumbra, further activated A1 receptor after stroke had neuroprotection. In vitro, activation of A1 promotes MB and increases the expression level of PGC-1α, while downregulation of PGC-1α partially reverses the effect of A1 receptor after OGD/R. Down regulation of PGC-1α in the penumbra neurons can reverse the effects of activation of A1 receptor on MB and neuroprotection. Taken together, these findings indicated that A1receptor promotes MB and improves neurological function after ischemic stroke via PGC-1α.

Neuroprotection by Trans-Resveratrol in Rats With Intracerebral Hemorrhage: Insights into the Role of Adenosine A1 Receptors

Given the neuroprotective effects of trans-resveratrol (RV), this study aimed to investigate the involvement of the adenosine A1 receptor (A1R) in RV-mediated neuroprotection in a rat intracerebral hemorrhage (ICH) model induced by intrastriatal injection of collagenase. Rats were divided into 5 groups: (1) control, (2) sham-operated, (3) ICH pretreated with vehicle, (4) ICH pretreated with RV, and (5) ICH pretreated with RV and the A1R antagonist DPCPX. At 48 hours after ICH, the rats were subjected to neurological testing. Brain tissues were assessed for neuronal density and morphological features using routine and immunohistochemical staining. Expression of tumor necrosis factor-α (TNF-α), caspase-3, and RIPK3 proteins was examined using ELISA. A1R, MAPK P38, Hsp90, TrkB, and BDNF genes were examined using RT-qPCR. RV protected against neurological deficits and neuronal depletion, restored the expression of TNF-α, CASP3, RIPK3, A1R, and Hsp90, and increased BDNF/TrkB. DPCPX abolished the effects of RV on neurological outcomes, neuronal density, CASP3, RIPK3, A1R, Hsp90, and BDNF. These data indicate that the neuroprotection by RV involves A1R and inhibits CASP3-dependent apoptosis and RIPK3-dependent necroptosis in the perihematoma region; this is likely to be mediated by crosstalk between A1R and the BDNF/TrkB pathway.

Hypoxia- and Inflammation-Related Transcription Factor SP3 May Be Involved in Platelet Activation and Inflammation in Intracranial Hemorrhage

The purpose of this study was to identify the biomarkers implicated in the development of intracranial hemorrhage (ICH) and potential regulatory pathways. In the transcriptomic data for patients with ICH, we identified DEmiRNAs and DEmRNAs related to hypoxia, inflammation, and their transcription factors (TFs). An ICH-based miRNA-TF-mRNA regulatory network was thus constructed, and four biomarkers (TIMP1, PLAUR, DDIT3, and CD40) were screened for their association with inflammation or hypoxia by machine learning. Following this, SP3 was found to be a transcription factor involved in hypoxia and inflammation, which regulates TIMP1 and PLAUR. From the constructed miRNA-TF-mRNA regulatory network, we identified three axes, hsa-miR-940/RUNX1/TIMP1, hsa-miR-571/SP3/TIMP1, and hsa-miR-571/SP3/PLAUR, which may be involved in the development of ICH. Upregulated TIMP1 and PLAUR were validated in an independent clinical cohort 3 days after ICH onset. According to Gene Set Enrichment Analysis (GSEA), SP3 was discovered to be important in interleukin signaling and platelet activation for hemostasis. Transcription factor SP3 associated with hypoxia or inflammation plays an important role in development of ICH. This study provides potential targets for monitoring the severity of inflammation and hypoxia in patients with ICH.

Adenosine A1 Receptor Agonist (R-PIA) before Pilocarpine Modulates Pro- and Anti-Apoptotic Factors in an Animal Model of Epilepsy

We aimed to characterize the mechanisms involved in neuroprotection by R-PIA administered before pilocarpine-induced seizures. Caspase-1 and caspase-3 activities were assayed using fluorimetry, and cathepsin D, HSP-70, and AKT expression levels were assayed using Western Blot of hippocampal samples. R-PIA was injected before pilocarpine (PILO), and four groups were studied at 1 h 30 min and 7 days following initiation of status epilepticus (SE): PILO, R-PIA+PILO, SALINE, and R-PIA+SALINE. At 1 h 30 min, significantly higher activities of caspase-1 and -3 were observed in the PILO group than in the SALINE group. Caspase-1 and -3 activities were higher in the R-PIA+PILO group than in the PILO group. At 7 days following SE, caspase-1 and -3 activities were higher than in the initial post-seizure phase compared to the SALINE group. The pretreatment of rats receiving PILO significantly reduced caspase activities compared to the PILO group. Expression of HSP-70, AKT, and cathepsin D was significantly higher in the PILO group than in the SALINE. In the R-PIA+PILO group, the expression of AKT and HSP-70 was greater than in rats receiving only PILO, while cathepsin D presented decreased expression. Pretreatment with R-PIA in PILO-injected rats strongly inhibited caspase-1 and caspase-3 activities and cathepsin D expression. It also increased expression levels of the neuroprotective proteins HSP-70 and AKT, suggesting an important role in modulating the cellular survival cascade.

Phosphorylation at S548 as a Functional Switch of Sterile Alpha and TIR Motif-Containing 1 in Cerebral Ischemia/Reperfusion Injury in Rats

Sterile alpha and Toll/interleukin-1 receptor motif-containing 1 (SARM1) is a pro-degenerative molecule in Wallerian degeneration, which is mainly expressed in brain/neurons and colocalized with mitochondria and microtubules. The aim of this study was to determine the role of SARM1 in cerebral ischemia/reperfusion (I/R) injury and the underlying mechanisms. In vivo, a middle cerebral artery occlusion/reperfusion (MCAO/R) model in adult male Sprague Dawley rats (250-300 g) was established, and in vitro, cultured primary neurons were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to imitate I/R injury. Overexpression lentiviruses encoding wild-type SARM1 and SARM1 with serine 548 alanine mutation (S548A) were constructed and administered to rats by intra-penumbral injection. First, the potential role of SARM1 in cerebral I/R injury was confirmed by the increased protein levels of SARM1 within penumbra tissue, especially in neurons. Second, there was an increase in the phosphorylation ratio of p-SARM1(S548)/SARM1 at 2 h after MCAO/R. Third, on the basis of site-specific mutagenesis, we identified S548 as a key site for SARM1 phosphorylation in I/R conditions. Fourth, SARM1 (S548A) overexpression reduced infarct size, neuronal death, and neurobehavioral dysfunction, while wild-type SARM1 overexpression had the opposite effects. Finally, we found that SARM1 phosphorylation at the S548 site switched SARM1 function from promoting mitochondrial transport to inhibiting mitochondrial transport along axons after I/R injury. Restriction of SARM1 phosphorylation at S548 may be a promising intervention target for I/R injury; thus, exogenous administration of SARM1 (S548A) may be a novel strategy for improving neurological outcomes.

iTRAQ-based proteomic profiling reveals protein alterations after traumatic brain injury and supports thyroxine as a potential treatment

Traumatic brain injury (TBI) is a primary cause of disability and death across the world. Previously, RNA analysis was widely used to study the pathophysiological mechanisms underlying TBI; however, the relatively low correlation between the transcriptome and proteome revealed that RNA transcription abundance does not reliably predict protein abundance, which led to the emergence of proteomic research. In this study, an iTRAQ proteomics approach was applied to detect protein alterations after TBI on a large scale. A total of 3937 proteins were identified, and 146 proteins were significantly changed after TBI. Moreover, 23 upregulated proteins were verified by parallel reaction monitoring (PRM), and fold changes in 16 proteins were consistent with iTRAQ outcomes. Transthyretin (Ttr) upregulation has been demonstrated at the transcriptional level, and this study further confirmed this at the protein level. After treatment with thyroxine (T4), which is transported by Ttr, the effects of T4 on neuronal histopathology and behavioral performance were determined in vivo (TBI + T4 group). Brain edema was alleviated, and the integrity of the blood brain barrier (BBB) improved. Escape latency in the Morris water maze (MWM) declined significantly compared with the group without T4 treatment. Modified neurological severity scores (mNSS) of the TBI + T4 group decreased from day 1 to day 7 post-TBI compared with the TBI + saline group. These results indicate that T4 treatment has potential to alleviate pathologic and behavioral abnormalities post-TBI. Protein alterations after T4 treatment were also detected by iTRAQ proteomics. Upregulation of proteins like Lgals3, Gfap and Apoe after TBI were reversed by T4 treatment. GO enrichment showed T4 mainly affected intermediate filament organization, cholesterol transportation and axonal regeneration. In summary, iTRAQ proteomics provides information about the impact of TBI on protein alterations and yields insight into underlying mechanisms and pathways involved in TBI and T4 treatment. Finally, Ttr and other proteins identified by iTRAQ may become potential novel treatment targets post-TBI.

Adenosine Receptors in Modulation of Central Nervous System Disorders

The ubiquitous signaling nucleoside molecule, adenosine is found in different cells of the human body to provide its numerous pharmacological role. The associated actions of endogenous adenosine are largely dependent on conformational change of the widely expressed heterodimeric G-protein-coupled A1, A2A, A2B, and A3 adenosine receptors (ARs). These receptors are well conserved on the surface of specific cells, where potent neuromodulatory properties of this bioactive molecule reflected by its easy passage through the rigid blood-brainbarrier, to simultaneously act on the central nervous system (CNS). The minimal concentration of adenosine in body fluids (30-300 nM) is adequate to exert its neuromodulatory action in the CNS, whereas the modulatory effect of adenosine on ARs is the consequence of several neurodegenerative diseases. Modulatory action concerning the activation of such receptors in the CNS could be facilitated towards neuroprotective action against such CNS disorders. Our aim herein is to discuss briefly pathophysiological roles of adenosine on ARs in the modulation of different CNS disorders, which could be focused towards the identification of potential drug targets in recovering accompanying CNS disorders. Researches with active components with AR modulatory action have been extended and already reached to the bedside of the patients through clinical research in the improvement of CNS disorders. Therefore, this review consist of recent findings in literatures concerning the impact of ARs on diverse CNS disease pathways with the possible relevance to neurodegeneration.

Neuroprotection by trans-resveratrol against collagenase-induced neurological and neurobehavioural deficits in rats involves adenosine A1 receptors

Objective: Trans-resveratrol has been shown to have neuroprotective effects and could be a promising therapeutic agent in the treatment of intracerebral haemorrhage (ICH). This study aimed to investigate the involvement of the adenosine A1 receptor (A1R) in trans-resveratrol-induced neuroprotection in rats with collagenase-induced ICH.Methods: Sixty male Sprague-Dawley rats weighing 330-380 g were randomly divided into five groups (n = 12): (i) control, (ii) sham-operated rats, (iii) ICH rats pretreated with vehicle (0.1% DMSO saline, i.c.v.), (iv) ICH rats pretreated with trans-resveratrol (0.9 µg, i.c.v.) and (v) ICH rats pretreated with trans-resveratrol (0.9 µg) and the A1R antagonist, DPCPX (2.5 µg, i.c.v.). Thirty minutes after pretreatment, ICH was induced by intrastriatal injection of collagenase (0.04 U). Forty-eight hours after ICH, the rats were assessed using a variety of neurobehavioural tests. Subsequently, rats were sacrificed and brains were subjected to gross morphological examination of the haematoma area and histological examination of the damaged area.Results: Severe neurobehavioural deficits and haematoma with diffuse oedema were observed after intrastriatal collagenase injection. Pretreatment with trans-resveratrol partially restored general locomotor activity, muscle strength and coordination, which was accompanied with reduction of haematoma volume by 73.22% (P < 0.05) and damaged area by 60.77% (P < 0.05) in comparison to the vehicle-pretreated ICH group. The trans-resveratrol-induced improvement in neurobehavioural outcomes and morphological features of brain tissues was inhibited by DPCPX pretreatment.Conclusion: This study demonstrates that the A1R activation is possibly the mechanism underlying the trans-resveratrol-induced neurological and neurobehavioural protection in rats with ICH.

The PERK Pathway Plays a Neuroprotective Role During the Early Phase of Secondary Brain Injury Induced by Experimental Intracerebral Hemorrhage

The protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathway, which is a branch of the unfolded protein response, participates in a range of pathophysiological processes of neurological diseases. However, few studies have investigated the role of the PERK in intracerebral hemorrhage (ICH). The present study evaluated the role of the PERK pathway during the early phase of ICH-induced secondary brain injury (SBI) and its potential mechanisms. An autologous whole blood ICH model was established in rats, and cultured primary cortical neurons were treated with oxyhemoglobin to mimic ICH in vitro. We found that levels of phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2α) and activating transcription factor 4 (ATF4) increased significantly and peaked at 12 h during the early phase of the ICH. To further elucidate the role of the PERK pathway, we assessed the effects of the PERK inhibitor, GSK2606414, and the eIF2α dephosphorylation antagonist, salubrinal, at 12 h after ICH both in vivo and in vitro. Inhibition of PERK with GSK2606414 suppressed the protein levels of p-eIF2α and ATF4, resulting in increase of transcriptional activator CCAAT/enhancer-binding protein homologous protein (CHOP) and caspase-12, which promoted apoptosis and reduced neuronal survival. Treatment with salubrinal yielded opposite results, which suggested that activation of the PERK pathway could promote neuronal survival and reduce apoptosis. In conclusion, the present study has demonstrated the neuroprotective effects of the PERK pathway during the early phase of ICH-induced SBI. These findings highlight the potential value of PERK pathway as a therapeutic target for ICH.

GATA-4 regulates neuronal apoptosis after intracerebral hemorrhage via the NF-κB/Bax/Caspase-3 pathway both in vivo and in vitro

GATA-binding protein 4 (GATA-4)，a member of the GATA family of transcription factors, is expressed in the normal brain and participates in the neural inflammatory response and senescence. However, few studies have investigated whether GATA-4 is involved in the brain damage induced by intracerebral hemorrhage (ICH). The aim of this study was to investigate in vivo and in vitro the role of GATA-4 in ICH-induced secondary brain injury (SBI) and its potential underlying mechanisms. A rat model of ICH was established by autologous blood injection in vivo. In vitro, oxidized hemoglobin was applied to mimic the effects of ICH in neuronal culture. The function of GATA-4 and its mechanism of action after ICH were investigated using siRNA-mediated knockdown and plasmid-mediated overexpression techniques combined with immunofluorescence, western blot, and other molecular methods. It was found that the expression of GATA-4 was increased in the brain of rats after ICH, and its phosphorylation also increased correspondingly. Furthermore, knocking down the expression of GATA-4 led to a significant decrease in neurobehavioral scores and neuronal apoptosis, indicating that secondary brain damage was improved. Conversely, the overexpression of GATA-4 aggravated brain damage. Blockade of a critical phosphorylation site on the GATA-4 overexpression plasmid alleviated the exacerbated damage in vitro and in vivo. Moreover, GATA-4 promoted the activation of NF-κB, and increased the expression of Bax, and cysteine aspartate-specific protease 3 (caspase-3) in its cleaved form, causing neuronal apoptosis. In conclusion, the expression of GATA-4 was increased in the brain of rats after ICH. GATA-4 phosphorylation mediates the function of the protein in ICH-induced SBI. Neuronal apoptosis after ICH was mainly induced by NF-κB activation, which was promoted by GATA-4.

The Role of Heat Shock Proteins in Regulating Receptor Signal Transduction

Heat shock proteins (Hsp) are a class of stress-inducible proteins that mainly act as molecular protein chaperones. This chaperone activity is diverse, including assisting in nascent protein folding and regulating client protein location and translocation within the cell. The main proteins within the Hsp family, particularly Hsp70 and Hsp90, also have a highly diverse and numerous set of protein clients, which when combined with the high expression levels of Hsp proteins (2%-6% of total protein content) establishes these molecules as "central regulators" of cell protein physiology. Among the client proteins, Hsps regulate numerous signal-transduction and receptor-regulatory kinases, and indeed directly regulate some receptors themselves. This also makes the Hsps, particularly Hsp90, central regulators of signal-transduction machinery, with important impacts on endogenous and drug ligand responses. Among these roles, Hsp90 in particular acts to maintain mature signaling kinases in a metastable conformation permissive for signaling activation. In this review, we will focus on the roles of the Hsps, with a special focus on Hsp90, in regulating receptor signaling and subsequent physiologic responses. We will also explore potential means to manipulate Hsp function to improve receptor-targeted therapies. Overall, Hsps are important regulators of receptor signaling that are receiving increasing interest and exploration, particularly as Hsp90 inhibitors progress toward clinical approval for the treatment of cancer. Understanding the complex interplay of Hsp regulation of receptor signaling may provide important avenues to improve patient treatment.

Inhibition of EPAC2 Attenuates Intracerebral Hemorrhage-Induced Secondary Brain Injury via the p38/BIM/Caspase-3 Pathway

Exchange proteins directly activated by cAMP (EPACs) are critical cAMP-dependent signaling pathway intermediaries that have been implicated in the pathogenesis of several human diseases, particularly neurological disorders. However, their pathogenic role in secondary brain injury (SBI) induced by intracranial hemorrhage (ICH) is unknown. The aim of this study was to examine the effects of EPAC2 on ICH-induced SBI and its underlying mechanisms. An in vivo ICH model was established in Sprague-Dawley rats by autologous blood injection. In addition, rat primary cortical neuronal cultures were exposed to oxyhemoglobin to simulate ICH in vitro. The function of EPAC2 in SBI induced by ICH was studied using the EPAC2-specific inhibitor ESI-05. In this study, we found that EPAC2 protein expression was significantly increased in the ICH models in vitro and in vivo. Furthermore, EPAC2 activation was inhibited by ESI-05 under ICH conditions. Inhibition of EPAC2 decreased the apoptosis rate of nerve cells in the cortex accompanied by a corresponding decrease in the protein expression of phosphorylated p38, Bcl-2-like protein 11 (BIM), and caspase-3. In summary, this study showed that inhibition of EPAC2 activation by ESI-05 suppressed SBI induced by ICH via the p38/BIM/caspase-3 signaling pathway.

GCN2 reduces inflammation by p-eIF2α/ATF4 pathway after intracerebral hemorrhage in mice

Intracerebral hemorrhage (ICH) is a common and severe neurological disorder, which is associated with high rates of mortality and morbidity. This study aimed to evaluate whether general control non-derepressible-2 (GCN2) stimulation ameliorated neuroinflammation after ICH. Male CD-1 mice were subjected to experimental ICH by infusion of bacterial collagenase. Post-ictus assessment included neurobehavioral tests, brain edema measurement, quantification of neutrophil infiltration and microglia activation, and measurement of TNF-α and IL-1β expression at 24h after ICH. Furthermore, we tested the long-term neurological improvement by GCN2 at 21 days after ICH. Our results showed that GCN2 improved neurological function and reduced brain edema at 24 and 72 h following experimental ICH in CD-1 mice in contrast to the vehicle administration alone. GCN2 was also found to decrease levels of IL-1β and TNF-α, and inhibit neutrophil infiltration activation. In addititon, GCN2 also alleviated long-term neurological impairment after ICH. However, inhibition of eIF2α or ATF4 abolished the protective effects of GCN2, indicating eIF2α/ATF4 signaling pathway as the downstream mediator of GCN2.

Cab45s inhibits neuronal apoptosis following intracerebral hemorrhage in adult rats

Recent studies have shown that Cab45s, belonging to the CREC family, can fight against apoptosis in the cancer cell lines. Here, we report that Cab45s may involve in neuronal apoptosis at the early stage of intracerebral hemorrhage (ICH) in pathophysiology. We found that expression of Cab45s was enhanced in areas contiguous to hematoma following ICH in adult rats, and that so were the expressions of Glucose-regulated protein 78 (GRP78), pro-apoptotic Bcl-2-associated X protein (Bax) and active caspase-3. In vitro, coimmunoprecipitation analysis indicated the interaction between Cab45s and GRP78. Depletion of Cab45s attenuated the expression of GRP78, but increased the expressions of Bax and caspase-3 in PC12 cells treated with hemin, which finally promoted apoptosis. Together, these results reveal that Cab45s might exert its anti-apoptotic function against neuronal apoptosis. Thus, the study may provide evidences for regulating Cab45s as a potentially reliable treatment for the secondary damage following ICH.

Dynamic protein expression of NF-κB following rat intracerebral hemorrhage and its association with apoptosis

The aim of the present study was to evaluate the dynamic protein expression of nuclear factor (NF)-κB and apoptosis in the cerebral tissue surrounding hematoma following intracerebral hemorrhage (ICH) in rats. A total of 80 healthy male Wistar rats were divided into a sham-surgery group and an ICH group. The ICH model was established by injecting autogenous non-heparin anticoagulant arterial blood into the caudate putamen. NF-κB levels were assessed by immunohistochemistry at different time points subsequent to surgery, and apoptosis condition was investigated by terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling. Different levels of NF-κB were expressed in the cerebral tissue around the ICH at each time point in the ICH group. NF-κB protein expression was detected at 3 h following hemorrhage, mainly in the cytoplasm. Following 6 h, NF-κB was identified in the nucleus. Its expression peaked at 72 h following hemorrhage, and persisted for 5 days. Apoptosis was observed 6 h following hemorrhage, and had increased significantly by 12 h. The rate of apoptosis continued to rise from 72-120 h following hemorrhage. Correlation analysis revealed a significant positive correlation between NF-κB expression and apoptosis (r=0.753; P<0.01). The enhancement of NF-κB expression and apoptosis around ICH, and the significant positive correlation between NF-κB expression and apoptosis, indicates that NF-κB activation may enhance cerebral apoptosis in rats following ICH.

Adenosine decreases oxidative stress and protects H2O2-treated neural stem cells against apoptosis through decreasing Mst1 expression

Overproduction of free radicals during oxidative stress induces damage to key biomolecules and activates programed cell death pathways. Neuronal cell death in the nervous system leads to a number of neurodegenerative diseases. The aim of the present study was to evaluate the neuroprotective effect of adenosine on inhibition of apoptosis induced by hydrogen peroxide (H₂O₂) in bone marrow-derived neural stem cells (B-dNSCs), with focus on its regulatory effect on the expression of mammalian sterile 20-like kinase 1 (Mst1), as a novel proapoptotic kinase. B-dNSCs were exposed to adenosine at different doses (2, 4, 6, 8 and 10 µM) for 48 h followed by 125 µM H₂O₂ for 30 min. Using MTT, terminal deoxynucleotidyl transferase dUTP nick-end labeling and real-time reverse transcription polymerase chain reaction assays, the effects of adenosine on cell survival, apoptosis and Mst1, nuclear factor (erythroid-derived 2)-like 2 and B-cell lymphoma 2 and adenosine A1 receptor expression were evaluated in pretreated B-dNSCs compared with controls (cells treated with H₂O₂ only). Firstly, results of the MTT assay indicated 6 µM adenosine to be the most protective dose in terms of promotion of cell viability. Subsequent assays using this dosage indicated that apoptosis rate and Mst1 expression in B-dNSCs pretreated with 6 µM adenosine were significantly decreased compared with the control group. These findings suggest that adenosine protects B-dNSCs against oxidative stress-induced cell death, and therefore, that it may be used to promote the survival rate of B-dNSCs and as a candidate for the treatment of oxidative stress-mediated neurological diseases.

TAR DNA Binding Protein-43 Loss of Function Induced by Phosphorylation at S409/410 Blocks Autophagic Flux and Participates in Secondary Brain Injury After Intracerebral Hemorrhage

This study aimed to determine the role of TAR DNA binding protein-43 (TDP-43) in intracerebral hemorrhage (ICH)-induced secondary brain injury (SBI) and its underlying mechanisms. After ICH, expression of TDP-43 in the nucleus was significantly decreased, and its expression in the cytoplasm increased both in vivo and in vitro, which indicates that TDP-43 translocates from the nucleus to the cytoplasm during SBI after ICH. In addition, mutations at S409/410 of TDP-43 could inhibit its phosphorylation, attenuate nuclear loss, and abolish the increase in neuronal apoptosis in the subcortex. Inhibition of TDP-43 phosphorylation attenuated ICH-induced downregulation of mTOR activity and dynactin1 expression, which may relieve blocking of autophagosome-lysosome fusion and the increase of autophagosomal and lysosomal biogenesis induced by ICH. However, knockdown of TDP-43 could worsen ICH-induced SBI. Furthermore, TDP-43 could be dephosphorylated by calcineurin (CN), and CN activity was increased by OxyHb treatment. In conclusion, this study demonstrated that TDP-43 loss-of-function by phosphorylation at S409/410 may block autophagosome-lysosome fusion and induce elevation of LC3II and p62 levels by inhibiting the activity of mTOR and expression of dynactin1. This mechanism may play an important role in ICH-induced SBI, and TDP-43 may be a potential therapeutic target.

PERK Pathway Activation Promotes Intracerebral Hemorrhage Induced Secondary Brain Injury by Inducing Neuronal Apoptosis Both in Vivo and in Vitro

The protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK) signaling pathway was reported to exert an important role in neuronal apoptosis. The present study was designed to investigate the roles of the PERK signaling pathway in the secondary brain injury (SBI) induced by intracerebral hemorrhage (ICH) and its potential mechanisms. Sprague-Dawley rats were used to establish ICH models by injecting autologous blood (100 μl), and cultured primary rat cortical neurons were exposed to oxyhemoglobin (10 μM) to mimic ICH in vitro. The PERK antagonist, GSK2606414, and inhibitor of eukaryotic translation initiation factor 2 subunit α (eIF2α) dephosphorylation, salubrinal, were used to study the roles of PERK signaling pathway in ICH-induced SBI. Our results showed that the protein levels of p-eIF2α and ATF4 were upregulated following ICH, peaking at 48 h. Application of GSK2606414 reversed this increase in vivo and in vitro, thereby preventing ICH-induced neuronal apoptosis. On the contrary, salubrinal inhibited the dephosphorylation of eIF2α, resulting in the elevation of p-eIF2α, which could activate downstream of PERK signaling and induce neuronal apoptosis and necrosis following ICH in vitro and in vivo. Thus, PERK signaling pathway plays an important role in ICH-induced apoptosis and blocking its activation has neuroprotective effects that alleviates SBI, suggesting that targeting this pathway could be a promising therapeutic strategy for improving patient outcome after ICH.

Neuroprotection Exerted by Netrin-1 and Kinesin Motor KIF1A in Secondary Brain Injury following Experimental Intracerebral Hemorrhage in Rats

Binding of extracellular netrin-1 to its receptors, deleted in colorectal cancer (DCC) and uncoordinated gene 5H2 (UNC5H2), inhibits apoptosis mediated by these receptors. A neuron-specific kinesin motor protein, KIF1A, has been shown to participate in netrin-1 secretion. This study aimed to identify the roles of netrin-1 and KIF1A in secondary brain injury after intracerebral hemorrhage (ICH) and the potential mechanisms. An autologous blood ICH model was established in adult male Sprague-Dawley rats, and cultured neurons were exposed to OxyHb to mimic ICH conditions in vitro. Mouse recombinant netrin-1, expression vectors encoding KIF1A, and KIF1A-specific siRNAs were administered intracerebroventricularly. After ICH, protein levels of netrin-1, DCC, and UNC5H2 increased, while protein levels of KIF1A decreased. Levels of UNC5H2 and DCC bound to netrin-1 increased after ICH but were significantly lower than the increase in total amount of protein. Administration of recombinant netrin-1 attenuated neuronal apoptosis and degeneration in ICH rats. Moreover, KIF1A overexpression increased concentrations of netrin-1 in cerebrospinal fluid and cell culture supernatant and exerted neuroprotective effects via netrin-1 and its receptor pathways. KIF1A plays a critical role in netrin-1 secretion by neurons. An increase in protein levels of netrin-1 may be a neuroprotective strategy after ICH. However, this process is almost completely abolished by ICH-induced loss of KIF1A. An exogenous increase of KIF1A may be a potential strategy for neuroprotection via the netrin-1 pathway.

Phosphorylation at S153 as a Functional Switch of Phosphatidylethanolamine Binding Protein 1 in Cerebral Ischemia-Reperfusion Injury in Rats

This study aimed to estimate the role of phosphatidylethanolamine binding protein 1 (PEBP1) in cerebral ischemia-reperfusion (I/R) injury and the underlying mechanisms. Middle cerebral artery occlusion/reperfusion (MCAO/R) model in adult male Sprague Dawley rats (250-280 g) were established and cultured neurons were exposed to oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic I/R injury in vitro. Expression vectors encoding wild-type PEBP1 and PEBP1 with Ser153Ala mutation (S153A), PEBP1 specific siRNAs, and human recombinant PEBP1 (rhPEBP1) were administered intracerebroventricularly. Endogenous PEBP1 level and its phosphorylation at Ser153 were increased within penumbra tissue and cultured neurons after I/R, accompanied by decreased interaction between PEBP1 and Raf-1. There was a trend toward increased Raf-1/MEK/ERK/NF-κB signaling pathway and phosphatidylcholine-phospholipase C (PC-PLC) activity after I/R, which was enhanced by wild-type PEBP1overexpression and rhPEBP1 treatment and inhibited by PEBP1 (S153A) overexpression. And PEBP1 (S153A) overexpression increased its interaction with Raf-1, reduced infarct size, neuronal death and inflammation, and improved neurological function after I/R, while wild-type PEBP1overexpression exerted opposite effects, suggesting that phosphorylation at Ser153 may exert as a functional switch of PEBP1 by switching PEBP1 from Raf-1 inhibition to PC-PLC activation following I/R. Compared with PEBP1 knockdown, PEBP1 (S153A) overexpression exerted a better rescue effect on I/R injury, which further proved that PEBP1 may be a good protein gone bad with phosphorylation at S153 as a functional switch following I/R. Collectively, our findings suggest that PEBP1 contributed to neuronal death and inflammation after I/R. Selective inhibition of PEBP1 phosphorylation may be a novel approach to ameliorate I/R injury.

Oleuropein protects intracerebral hemorrhage-induced disruption of blood-brain barrier through alleviation of oxidative stress

BACKGROUND

Intracerebral haemorrhage (ICH) as a devastating form of stroke has remained a public health threat due to lack of FDA-approved therapy. Oxidative stress originated from blood cell degradation products plays a crucial role in the ICH pathogenesis. In this study we evaluated oleuropein, a potent natural antioxidant from olive, in a well-established rat ICH model from overall symptoms to detailed molecular mechanism.

METHODS

ICH model was established by collagenase injection to the brain of rats, which were randomly divided into groups with vehicle mock treatment, followed by treatment with different doses of oleuropein via daily intraperitoneal injection post-ICH for 3days. The overall neurological deficit, brain edema level and blood-brain barrier (BBB) integrity were then measured in different treatment groups. To understand the protection mechanism of oleuropein in ICH, BBB structural components ZO-1 and occludin, oxidative stress and MAPK signalling pathways were also examined.

RESULTS

Oleuropein treatment showed overall alleviation of ICH-associated neurological deficit and brain edema in a dose dependent manner. Consistently, it could preserve the BBB structure and attenuate oxidative stress as well as ICH-induced MAPK activation in brain tissue.

CONCLUSION

Our study suggests oleuropein could be used as a promising therapeutic agent for ICH.

Role for RIP1 in mediating necroptosis in experimental intracerebral hemorrhage model both in vivo and in vitro

Cell death is a hallmark of second brain injury after intracerebral hemorrhage (ICH); however, the mechanism still has not been fully illustrated. In this study, we explored whether necroptosis, a type of regulated necrosis, has an essential role in brain injury after ICH. We found that inhibiting receptor-interacting protein 1 (RIP1) – a core element of the necroptotic pathway – by a specific chemical inhibitor or genetic knockdown attenuated brain injury in a rat model of ICH. Furthermore, necroptosis of cultured neurons could be induced by conditioned medium from microglia stimulated with oxygen hemoglobin, and this effect could be inhibited by TNF-α inhibitor, indicating that TNF-α secreted from activated microglia is an important factor in inducing necroptosis of neurons. Undoubtedly, overexpression of RIP1 increased conditioned medium-induced necroptosis in vitro, but this effect was partially diminished in mutation of serine kinase phosphorylation site of RIP1, showing that phosphorylation of RIP1 is the essential molecular mechanism of necroptosis, which was activated in the in vitro model of ICH. Collectively, our investigation identified that necroptosis is an important mechanism of cell death in brain injury after ICH, and inhibition of necroptosis may be a potential therapeutic intervention of ICH.