Neuroprotective effects of exogenous activin A on oxygen-glucose deprivation in PC12 cells

Delayed administration of interleukin-4 coacervate alleviates the neurotoxic phenotype of astrocytes and promotes functional recovery after a contusion spinal cord injury

Objective. Macrophages and astrocytes play a crucial role in the aftermath of a traumatic spinal cord injury (SCI). Infiltrating macrophages adopt a pro-inflammatory phenotype while resident astrocytes adopt a neurotoxic phenotype at the injury site, both of which contribute to neuronal death and inhibit axonal regeneration. The cytokine interleukin-4 (IL-4) has shown significant promise in preclinical models of SCI by alleviating the macrophage-mediated inflammation and promoting functional recovery. However, its effect on neurotoxic reactive astrocytes remains to be elucidated, which we explored in this study. We also studied the beneficial effects of a sustained release of IL-4 from an injectable biomaterial compared to bolus administration of IL-4.Approach. We fabricated a heparin-based coacervate capable of anchoring and releasing bioactive IL-4 and tested its efficacyin vitroandin vivo. Main results. We show that IL-4 coacervate is biocompatible and drives a robust anti-inflammatory macrophage phenotype in culture. We also show that IL-4 and IL-4 coacervate can alleviate the reactive neurotoxic phenotype of astrocytes in culture. Finally, using a murine model of contusion SCI, we show that IL-4 and IL-4 coacervate, injected intraspinally 2 d post-injury, can reduce macrophage-mediated inflammation, and alleviate neurotoxic astrocyte phenotype, acutely and chronically, while also promoting neuroprotection with significant improvements in hindlimb locomotor recovery. We observed that IL-4 coacervate can promote a more robust regenerative macrophage phenotypein vitro, as well as match its efficacyin vivo,compared to bolus IL-4.Significance. Our work shows the promise of coacervate as a great choice for local and prolonged delivery of cytokines like IL-4. We support this by showing that the coacervate can release bioactive IL-4, which acts on macrophages and astrocytes to promote a pro-regenerative environment following a SCI leading to robust neuroprotective and functional outcomes.

Neuroprotective Effects of Activin A against Cerebral Ischemia/Reperfusion Injury in Mice by Enhancing Nrf2 Expression to Attenuate Neuronal Ferroptosis

Activin A (Act A) is a member of the transforming growth factor-β (TGF-β) superfamily and can protect against ischemic cerebral injury. Ferroptosis, a newly discovered type of programmed cell death, contributes to the pathogenesis of cerebral ischemia-reperfusion injury (CIRI). However, little is known on whether Act A can modulate neuronal ferroptosis to protect against CIRI in a mouse model of middle cerebral artery occlusion (MCAO) and an HT22 cell model of oxygen-glucose deprivation/reoxygenation (OGD/R). The results indicated that Act A treatment relieved CIRI by improving neurological deficits and reducing the infarct volume in mice. MCAO stimulated iron accumulation and malondialdehyde formation and upregulated ACSL4 expression but downregulated GPX4 expression, a hallmark of ferroptosis in the brain of mice. Treatment with Act A significantly mitigated MCAO-triggered ferroptosis in the brain of mice. Furthermore, Act A treatment enhanced the MCAO-upregulated nuclear factor erythroid-2-related factor 2 (Nrf2) expression in the brains of mice. Similar results were observed in HT22 cells following OGD/R and pretreatment with Act A. The neuronal protective effect of Act A in HT22 cells was attenuated by treatment with ML385, an Nrf2 inhibitor. To conclude, Act A attenuated CIRI by enhancing Nrf2 expression and inhibiting neuronal ferroptosis.

Brain Damage in Preterm and Full-Term Neonates: Serum Biomarkers for the Early Diagnosis and Intervention

The Brain is vulnerable to numerous insults that can act in the pre-, peri-, and post-natal period. There is growing evidence that demonstrate how oxidative stress (OS) could represent the final common pathway of all these insults. Fetuses and newborns are particularly vulnerable to OS due to their inability to active the antioxidant defenses. Specific molecules involved in OS could be measured in biologic fluids as early biomarkers of neonatal brain injury with an essential role in neuroprotection. Although S-100B seems to be the most studied biomarker, its use in clinical practice is limited by the complexity of brain damage etiopathogenesis and the time of blood sampling in relation to the brain injury. Reliable early specific serum markers are currently lacking in clinical practice. It is essential to determine if there are specific biomarkers that can help caregivers to monitor the progression of the disease in order to active an early neuroprotective strategy. We aimed to describe, in an educational review, the actual evidence on serum biomarkers for the early identification of newborns at a high risk of neurological diseases. To move the biomarkers from the bench to the bedside, the assays must be not only be of a high sensitivity but suitable for the very rapid processing and return of the results for the clinical practice to act on. For the best prognosis, more studies should focus on the association of these biomarkers to the type and severity of perinatal brain damage.

Xenon Nanobubbles for the Image-Guided Preemptive Treatment of Acute Ischemic Stroke via Neuroprotection and Microcirculatory Restoration

Early lesion site diagnosis and neuroprotection are crucial to the theranostics of acute ischemic stroke. Xenon (Xe), as a nontoxic gaseous neuroprotectant, holds great promise for ischemic stroke therapy. In this study, Xe-encapsulated lipid nanobubbles (Xe-NBs) have been prepared for the real-time ultrasound image-guided preemptive treatment of the early stroke. The lipids are self-assembled at the interface of free Xe bubbles, and the mean diameter of Xe-NBs is 225 ± 11 nm with a Xe content of 73 ± 2 μL/mL. The in vitro results show that Xe-NBs can protect oxygen/glucose-deprived PC12 cells against apoptosis and oxidative stress. Based on the ischemic stroke mice model, the biodistribution, timely ultrasound imaging, and the therapeutic effects of Xe-NBs for stroke lesions were investigated in vivo. The accumulation of Xe-NBs to the ischemic lesion endows ultrasound contrast imaging with the lesion area. The cerebral blood flow measurement indicates that the administration of Xe-NBs can improve microcirculatory restoration, resulting in reduced acute microvascular injury in the lesion area. Furthermore, local delivery of therapeutic Xe can significantly reduce the volume of cerebral infarction and restore the neurological function with reduced neuron injury against apoptosis. Therefore, Xe-NBs provide a novel nanosystem for the safe and rapid theranostics of acute ischemic stroke, which is promising to translate into the clinical management of stroke.

Activin A and Acvr2b mRNA from Umbilical Cord Blood Are Not Reliable Markers of Mild or Moderate Neonatal Hypoxic-Ischemic Encephalopathy

BACKGROUND

Activin A protein and its receptor ACVR2B have been considered viable biomarkers for the diagnosis of hypoxic-ischemic encephalopathy (HIE). This study aimed to assess umbilical cord blood (UCB) levels of Activin A and Acvr2b messenger RNA (mRNA) as early biomarkers of mild and moderate HIE and long-term neurodevelopmental outcome.

METHODS

One-hundred and twenty-six infants were included in the analyses from the BiHiVE2 cohort, a multi-center study, recruited in Ireland and Sweden (2013 to 2015). UCB serum Activin A and whole blood Acvr2b mRNA were measured using enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, respectively.

RESULTS

Activin A analysis included 101 infants (controls, n = 50, perinatal asphyxia, n = 28, HIE, n = 23). No differences were detected across groups (p = 0.69). No differences were detected across HIE grades (p = 0.12). Acvr2b mRNA analysis included 67 infants (controls, n = 22, perinatal asphyxia, n = 23, and HIE, n = 22), and no differences were observed across groups (p = 0.75). No differences were detected across HIE grades (p = 0.58). No differences were detected in neurodevelopmental outcome in infants followed up to 18 to 36 months in serum Activin A or in whole blood Acvr2b mRNA (p = 0.55 and p = 0.90, respectively).

CONCLUSION

UCB Activin A and Acvr2b mRNA are not valid biomarkers of infants with mild or moderate HIE; they are unable to distinguish infants with HIE or infants with poor neurodevelopmental outcomes.

Smurf2 exerts neuroprotective effects on cerebral ischemic injury

The present study aimed to explore specific mechanisms involved in mediating the neuroprotective effects of Smad ubiquitination regulatory factor 2 (Smurf2) in cerebral ischemic injury. A middle cerebral artery occlusion (MCAO) mouse model and an oxygen–glucose deprivation (OGD)–treated neuron model were developed. The expression of Smurf2, Yin Yang 1 (YY1), hypoxia-inducible factor-1 alpha (HIF1α), and DNA damage–inducible transcript 4 gene (DDIT4) was analyzed. Thereafter, the expression of Smurf2, YY1, HIF1α, and DDIT4 was altered in the MCAO mice and OGD-treated neurons. Apoptosis in tissues and cerebral infarction were assessed. In neurons, the expression of apoptosis-related proteins, viability, and apoptosis were assessed, followed by evaluation of lactate dehydrogenase leakage rate. The interaction between Smurf2 and YY1 was analyzed by coimmunoprecipitation assay and that between YY1 ubiquitination by in vivo ubiquitination experiment. The results showed downregulation of Smurf2 and upregulation of YY1, HIF1α, and DDIT4 in both MCAO mice and OGD-treated neurons. Smurf2 elevated YY1 ubiquitination and degradation, and YY1 increased HIF1α expression to promote DDIT4 in neurons. Overexpressed Smurf2 or downregulated YY1, HIF1α, or DDIT4 reduced the volume of cerebral infarction and apoptosis in MCAO mice, while enhancing cell viability and reducing apoptosis and lactate dehydrogenase leakage in OGD-treated neurons. In summary, our findings elucidated a neuroprotective role of Smurf2 in cerebral ischemic injury via inactivation of the YY1/HIF1α/DDIT4 axis.

Activin A improves the neurological outcome after ischemic stroke in mice by promoting oligodendroglial ACVR1B-mediated white matter remyelination

Activin A plays important roles in ischemic injury and white matter remyelination, but its mechanisms are unclear. In this study, the adult male C57BL/6 J mice were used to establish the model of 1 h middle cerebral artery occlusion/reperfusion (MCAO/R) 1 d to 28 d-induced ischemic stroke in vivo. We found that the neurological outcome was positively correlated with the levels of myelin associated proteins (include MAG, CNPase, MOG and MBP, n = 6 per group) both in corpus callosum and internal capsule of mice with ischemic stroke. The dynamic changes of Luxol fast blue (LFB) staining intensity, oligodendrocyte (CC1⁺) and proliferated oligodendrocyte precursor (Ki67⁺/PDGFRα⁺) cell numbers indicated demyelination and spontaneous remyelination occurred in the corpus callosum of mice after 1 h MCAO/R 1 d-28 d (n = 6 per group). Activin receptor type I (ACVR1) inhibitor SB431542 aggregated neurological deficits, and reduced MAG, MOG and MBP protein levels of mice with ischemic stroke (n = 6 per group). Meanwhile, recombinant mouse (rm) Activin A enhanced the neurological function recovery, MAG, MOG and MBP protein levels of mice with 1 h MCAO/R 28 d. In addition, the injection of AAV-based ACVR1B shRNA with Olig2 promoter could reverse rmActivin A-induced the increases of CC1⁺ cell number, LFB intensity, MAG, MOG and MBP protein levels in the corpus callosum (n = 6 per group), and neurological function recovery (n = 10 per group) of mice with 1 h MCAO/R 28 d. These results suggested that Activin A improves the neurological outcome through promoting oligodendroglial ACVR1B-mediated white matter remyelination of mice with ischemic stroke, which may provide a potential therapeutic strategy for ischemic stroke.

Activin A in Mammalian Physiology

Activins are dimeric glycoproteins belonging to the transforming growth factor beta superfamily and resulting from the assembly of two beta subunits, which may also be combined with alpha subunits to form inhibins. Activins were discovered in 1986 following the isolation of inhibins from porcine follicular fluid, and were characterized as ovarian hormones that stimulate follicle stimulating hormone (FSH) release by the pituitary gland. In particular, activin A was shown to be the isoform of greater physiological importance in humans. The current understanding of activin A surpasses the reproductive system and allows its classification as a hormone, a growth factor, and a cytokine. In more than 30 yr of intense research, activin A was localized in female and male reproductive organs but also in other organs and systems as diverse as the brain, liver, lung, bone, and gut. Moreover, its roles include embryonic differentiation, trophoblast invasion of the uterine wall in early pregnancy, and fetal/neonate brain protection in hypoxic conditions. It is now recognized that activin A overexpression may be either cytostatic or mitogenic, depending on the cell type, with important implications for tumor biology. Activin A also regulates bone formation and regeneration, enhances joint inflammation in rheumatoid arthritis, and triggers pathogenic mechanisms in the respiratory system. In this 30-yr review, we analyze the evidence for physiological roles of activin A and the potential use of activin agonists and antagonists as therapeutic agents.

Research Progress on the Role and Mechanism of Action of Activin A in Brain Injury

Activin A belongs to the transforming growth factor superfamily and has a variety of biological functions. Studies have revealed that activin A can regulate the body's immune and inflammatory responses and participate in the regulation of cell death. In addition, activin A also has neurotrophic function and plays an important role in the repair of brain damage. This article summarizes recent advances in understanding the role and mechanism of action of activin A in brain injury and provides new hints into the application of activin A in the treatment of brain injury.

Local Immunomodulation with Anti-inflammatory Cytokine-Encoding Lentivirus Enhances Functional Recovery after Spinal Cord Injury

Trauma to the spinal cord and associated secondary inflammation can lead to permanent loss of sensory and motor function below the injury level, with the resulting environment serving as a barrier that limits regeneration. In this study, we investigate the localized expression of anti-inflammatory cytokines IL-10 and IL-4 via lentiviral transduction in multichannel bridges. Porous multichannel bridges provide physical guidance for axonal outgrowth with the cytokines hypothesized to modulate the neuroinflammatory microenvironment and enhance axonal regeneration. Gene expression analyses indicated that induced IL-10 and IL-4 expression decreased expression of pro-inflammatory genes and increased pro-regenerative genes relative to control. Moreover, these factors led to increased numbers of axons and myelination, with approximately 45% of axons myelinated and the number of oligodendrocyte myelinated axons significantly increased by 3- to 4-fold. Furthermore, the combination of a bridge with IL-10 and IL-4 expression improved locomotor function after injury to an average score of 6 relative to an average score of 3 for injury alone. Collectively, these studies highlight the potential for localized immunomodulation to decrease secondary inflammation and enhance regeneration that may have numerous applications.

Activin receptors regulate the oligodendrocyte lineage in health and disease

The most prevalent neurological disorders of myelin include perinatal brain injury leading to cerebral palsy in infants and multiple sclerosis in adults. Although these disorders have distinct etiologies, they share a common neuropathological feature of failed progenitor differentiation into myelin-producing oligodendrocytes and lack of myelin, for which there is an unmet clinical need. Here, we reveal that a molecular pathology common to both disorders is dysregulation of activin receptors and that activin receptor signaling is required for the majority of myelin generation in development and following injury. Using a constitutive conditional knockout of all activin receptor signaling in oligodendrocyte lineage cells, we discovered this signaling to be required for myelination via regulation of oligodendrocyte differentiation and myelin compaction. These processes were found to be dependent on the activin receptor subtype Acvr2a, which is expressed during oligodendrocyte differentiation and axonal ensheathment in development and following myelin injury. During efficient myelin regeneration, Acvr2a upregulation was seen to coincide with downregulation of Acvr2b, a receptor subtype with relatively higher ligand affinity; Acvr2b was shown to be dispensable for activin receptor-driven oligodendrocyte differentiation and its overexpression was sufficient to impair the abovementioned ligand-driven responses. In actively myelinating or remyelinating areas of human perinatal brain injury and multiple sclerosis tissue, respectively, oligodendrocyte lineage cells expressing Acvr2a outnumbered those expressing Acvr2b, whereas in non-repairing lesions Acvr2b+ cells were increased. Thus, we propose that following human white matter injury, this increase in Acvr2b expression would sequester ligand and consequently impair Acvr2a-driven oligodendrocyte differentiation and myelin formation. Our results demonstrate dysregulated activin receptor signaling in common myelin disorders and reveal Acvr2a as a novel therapeutic target for myelin generation following injury across the lifespan.

Neuroprotective Effects of Bioactive Compounds and MAPK Pathway Modulation in "Ischemia"-Stressed PC12 Pheochromocytoma Cells

This review surveys the efforts taken to investigate in vitro neuroprotective features of synthetic compounds and cell-released growth factors on PC12 clonal cell line temporarily deprived of oxygen and glucose followed by reoxygenation (OGD/R). These cells have been used previously to mimic some of the properties of in vivo brain ischemia-reperfusion-injury (IRI) and have been instrumental in identifying common mechanisms such as calcium overload, redox potential, lipid peroxidation and MAPKs modulation. In addition, they were useful for establishing the role of certain membrane penetrable cocktails of antioxidants as well as potential growth factors which may act in neuroprotection. Pharmacological mechanisms of neuroprotection addressing modulation of the MAPK cascade and increased redox potential by natural products, drugs and growth factors secreted by stem cells, in either undifferentiated or nerve growth factor-differentiated PC12 cells exposed to ischemic conditions are discussed for future prospects in neuroprotection studies.

Extract of Spatholobus suberctus Dunn ameliorates ischemia-induced injury by targeting miR-494

Cerebral stroke is a leading cause of death and permanent disability. The current therapeutic outcome of ischemic stroke (>85% of all strokes) is very poor, thus novel therapeutic drug is urgently needed. In vitro cell model of ischemia was established by oxygen-glucose deprivation (OGD) and in vivo animal model of ischemia was established by middle cerebral artery occlusion (MCAO). The effects of Spatholobus suberctus Dunn extract (SSCE) on OGD-induced cell injury, MCAO-induced neural injury and miR-494 level were all evaluated. The possible target genes were virtually screened utilizing bioinformatics and verified by luciferase assay. Subsequently, the effects of abnormally expressed miR-494 on OGD-induced cell injury and target gene expression were determined. Additionally, whether SSCE affected target gene expression through modulation of miR-494 was studied. Finally, the effects of aberrantly expressed Sox8 on OGD-induced injury and signaling pathways were estimated. SSCE reduced OGD-induced cell injury and ameliorated MCAO-induced neuronal injury, along with down-regulation of miR-494. Then, OGD-induced cell injury was increased by miR-494 overexpression but decreased by miR-494 silence. Sox8 was a target gene of miR-494, and SSCE could up-regulate Sox8 expression via down-regulating miR-494. Afterwards, OGD-induced cell injury was proved to be increased by Sox8 inhibition but reduced by Sox8 overexpression. Finally, OGD-induced inhibition of PI3K/AKT/mTOR and MAPK pathways was further inhibited by Sox8 silence but activated by Sox8 overexpression. SSCE ameliorates ischemia-induced injury both in vitro and in vivo by miR-494-mediated modulation of Sox8, involving activations of PI3K/AKT/mTOR and MAPK pathways.

Neuroprotective effects of Activin A on endoplasmic reticulum stress-mediated apoptotic and autophagic PC12 cell death

Activin A, a member of the transforming growth factor-beta superfamily, plays a neuroprotective role in multiple neurological diseases. Endoplasmic reticulum (ER) stress-mediated apoptotic and autophagic cell death is implicated in a wide range of diseases, including cerebral ischemia and neurodegenerative diseases. Thapsigargin was used to induce PC12 cell death, and Activin A was used for intervention. Our results showed that Activin A significantly inhibited morphological changes in thapsigargin-induced apoptotic cells, and the expression of apoptosis-associated proteins [cleaved-caspase-12, C/EBP homologous protein (CHOP) and cleaved-caspase-3] and biomarkers of autophagy (Beclin-1 and light chain 3), and downregulated the expression of thapsigargin-induced ER stress-associated proteins [inositol requiring enzyme-1 (IRE1), tumor necrosis factor receptor-associated factor 2 (TRAF2), apoptosis signal-regulating kinase 1 (ASK1), c-Jun N-terminal kinase (JNK) and p38]. The inhibition of thapsigargin-induced cell death was concentration-dependent. These findings suggest that administration of Activin A protects PC12 cells against ER stress-mediated apoptotic and autophagic cell death by inhibiting the activation of the IRE1-TRAF2-ASK1-JNK/p38 cascade.

Effects of activin A and its downstream ERK1/2 in oxygen and glucose deprivation after isoflurane-induced postconditioning

BACKGROUND

Isoflurane postconditioning (ISPOC) plays a neuroprotection role in the brain. Previous studies confirmed that isoflurane postconditioning can provide better protection than preconditioning in acute hypoxic-ischemic brain damage, such as acute craniocerebral trauma and ischemic stroke. Numerous studies have reported that activin A can protect rat's brain from cell injury. However, whether activin A and its downstream ERK1/2 were involved in isoflurane postconditioning-induced neuroprotection is unknown.

METHODS

A total of 80 healthy Sprague-Dawley rats weighing 50-70g were randomly divided into 10 groups of 8: normal control, oxygen and glucose deprivation (OGD), 1.5% ISPOC, 3.0% ISPOC, 4.5% ISPOC, blocker of activin A (SB431542), blocker of ERK1/2 (U0126), 3.0% ISPOC+SB431542, 3.0% ISPOC+U0126, and vehicle (dimethyl sulfoxide(DMSO)) group. Blockers (SB431542 and U0126) were used in each concentration of isoflurane before OGD. Hematoxylin-eosin staining, 2,3,5-triphenyl tetrazolium chloride staining, and propidium iodide (PI) staining were conducted to assess the reliability in the brain slices. Immunofluorescence, Western blot, and quantitative real-time PCR(Q-PCR) were performed to validate the protein expression levels of activin A, Smad2/3, P-Smad2/3, ERK1/2, and phosphorylation ERK1/2 (P-ERK1/2).

RESULTS

The number of damaged neurons and mean fluorescence intensity(MFI) of PI staining increased, but formazan generation, expression levels of activin A and P-ERK1/2 protein, and mRNA synthesis level of activin A decreased in the OGD group compared with the normal control group (p<0.05). The number of damaged neurons and MFI of PI staining decreased, but formazan production, expression levels of activin A, P-Smad2/3, and P-ERK1/2, and mRNA synthesis level of activin A increased significantly in the 1.5% ISPOC and 3.0% ISPOC groups (p<0.05) compared with the OGD group. The result in the 4.5% ISPOC group, was completely opposite to the 1.5% ISPOC and 3.0% ISPOC groups. The number of damage neuron and MFI of PI staining increased, but formazan production, expression levels of activin A, P-Smad2/3, and P-ERK1/2, and mRNA synthesis level of activin A decreased in the 4.5% ISPOC group. However, the expression levels of activin A, P-Smad2/3, and P-ERK1/2, and mRNA synthesis level of activin A in the 4.5% ISPOC group were higher than the OGD group (p<0.05). The other results were compared between the SB431542 group/the U0126 group and 3.0% ISPOC group. The MFI of PI staining increased, but the expression levels of activin A, P-Smad2/3, and P-ERK1/2 decreased (p<0.05). The expression level of ERK1/2 protein in all groups exhibited no change (p>0.05).

CONCLUSION

Results of this study showed that 3.0% concentration of isoflurane postconditioning provided better neuroprotection than 1.5% and 4.5% concentrations of isoflurane. Activin A/Smad 2/3 and activin A/ERK1/2 signaling pathway may be involved in ISPOC-induced neuroprotection.

rLj-RGD3, a Novel Three-RGD-Motif-Containing Recombinant Protein from Lampetra japonica, Protects PC12 Cells from Injury Induced by Oxygen-Glucose Deprivation and Reperfusion

rLj-RGD3 is a 14.5 kDa recombinant protein with 3 RGD (Arg-Gly-Asp) motifs from the salivary gland secretions of Lampetra japonica, which is a histidine-rich and arginine-rich protein. Previous reports indicated that rLj-RGD3 has typical functions of RGD-toxin protein, such as platelet aggregation suppression tumour metastasis and angiogenesis inhibition. Because histidine and arginine have cerebral ischemia-reperfusion and neuroprotective functions, we investigated whether rLj-RGD3 has such activities and studied the mechanism. The effects of rLj-RGD3 on neuroprotection and antiapoptosis were determined. The expression level of focal adhesion kinase (FAK), p-FAK, Caspase-3, and Bcl-2 after oxygen-glucose deprivation and reperfusion (OGD-R) was examined. The viability of PC12 cells incubated with rLj-RGD3 at high concentrations (16 μmol/L) increased significantly due to its ability to protect the cells from apoptosis after OGD-R-induced injury. Furthermore, rLj-RGD3 attenuated the damage due to OGD-R. Most of the PC12 cells were apoptotic after OGD-R. In contrast, the number of apoptotic PC12 cells was significantly decreased in the group treated with a high-dose of rLj-RGD3. In addition, rLj-RGD3 activated FAK and p-FAK protein. rLj-RGD3 inhibited Caspase-3 and upregulated Bcl-2 protein expression in PC12 cells after OGD-R. The study provides the first evidence for neuroprotective effects of rLj-RGD3 in ischemic injury that may be partly mediated through inhibition of Caspase-3 and upregulation of Bcl-2, FAK, and p-FAK protein expression.

Protective effects of aloin on oxygen and glucose deprivation-induced injury in PC12 cells

The present study aims to determine whether aloin could protect cells from ischemic and reperfusion injury in vitro and to elucidate the related mechanisms. Oxygen and glucose deprivation model in PC12 cells was used in the present study. 2-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH) assay and Hoechst 33342 nuclear staining were used to evaluate the protective effects of aloin, at concentrations of 10, 20, or 40 μg/mL in PC12 cells. PCR was applied to detect fluorescence caspase-3, Bax and Bcl-2 mRNA expression in PC12 cells. The contents of malondialdehyde (MDA), superoxide dismutase (SOD) activity were evaluated by biochemical method. The concentration of intracellular-free calcium [Ca(2+)]i, mitochondrial membrane potential (MMP) were determined to estimate the degree of neuronal damage. It was shown that aloin (10, 20, and 40 μg/mL) significantly attenuated PC12 cells damage with characteristics of an increased injured cells absorbance of MTT and releases of LDH, decreasing cell apoptosis, and antagonizing decreases in SOD activity and increase in MDA level induced by OGD-reoxygenation. Meanwhile pretreatment with aloin significantly reduced injury-induced intracellular ROS, increased MMP (P<0.01), but it inhibited [Ca(2+)]i (P<0.01) elevation in a dose-dependent manner. Furthermore, pre-treatment with aloin significantly up-regulated Bcl-2 mRNA expression, down-regulated Bax mRNA expression and consequently activated caspase-3 mRNA expression in a dose-dependent manner. The results indicated that the protection of aloin on OGD-induced apoptosis in PC12 cells is associated with its suppression on OGD-induced oxidative stress and protection on mitochondrial function and inhibition of caspase activity. Alion could be a promising candidate in the development of a novel class of anti-ischemic agent.

Mesenchymal stem cells suppress neuronal apoptosis and decrease IL-10 release via the TLR2/NFκB pathway in rats with hypoxic-ischemic brain damage

BACKGROUND

Hypoxic-ischemic brain damage (HIBD) is a major cause of infant mortality and neurological disability in children. Many studies have demonstrated that mesenchymal stem cell (MSC) transplantation facilitates the restoration of the biological function of injured tissue following HIBD via immunomodulation. This study aimed to elucidate the mechanisms by which MSCs mediate immunomodulation via the key effectors Toll-like receptor 2 (TLR2) and interleukin-10 (IL-10).

RESULTS

We showed that TLR2 expression in the brain of HIBD rats was upregulated following HIBD and that MSC transplantation suppressed the expression of TLR2 and the release of IL-10, thereby alleviating the learning-memory deficits of HIBD rats. Following treatment with the specific TLR2 agonist Pam3CSK4 to activate TLR2, learning-memory function became further impaired, and the levels of nuclear factor kappa B (NFκB) and Bax expression and IL-10 release were significantly increased compared with those in HIBD rats that did not receive Pam3CSK4. In vitro, we found that MSC co-culture downregulated TLR2/NFκB signaling and repressed Bax expression and IL-10 secretion in oxygen and glucose deprivation (OGD)-injured adrenal pheochromocytoma (PC12) cells. Furthermore, NFκB and Bax expression and IL-10 release were enhanced following Pam3CSK4 treatment and were decreased following siTLR2 treatment in OGD-injured PC12 cells in the presence or absence of MSCs.

CONCLUSIONS

Our data indicate that TLR2 is involved in HIBD and that MSCs decrease apoptosis and improve learning-memory function in HIBD rats by suppressing the TLR2/NFκB signaling pathway via a feedback mechanism that reduces IL-10 release. These findings strongly suggest that MSC transplantation improves HIBD via the inhibition of the TLR2/NFκB pathway.

Neonatal hypoxic ischemic encephalopathy-related biomarkers in serum and cerebrospinal fluid

Neonatal hypoxic ischemic encephalopathy (HIE) is a common disease caused by perinatal asphyxia, a major cause of neonatal death, neurological behavior, and long-term disability. Currently, the diagnosis and prognosis of neonatal HIE are based on nervous system clinical manifestations, imaging and electrophysiological examination. These take time and late diagnosis allows brain injury to occur in newborns, so that infants of many brain injury missed the best treatment time, left with varying degrees of neurological sequelae. The use of biomarkers to monitor brain injury and evaluate neuroprotective effects might allow the early intervention and treatment of neonatal HIE to reduce mortality rates. This study reviewed the mechanism of neonatal hypoxic ischemic encephalopathy in relation to numerous brain-related biomarkers including NSE, S-100β, GFAP, UCH-L1, Tau protein, miRNA, LDH, and CK-BB. In early diagnosis of neonatal HIE, S-100β and activin A seems to be better biomarkers. Biomarkers with the greatest potential to predict long-term neurologic handicap of neonates with HIE are GFAP and UCH-L1 and when combined with other markers or brain imaging can increase the detection rate of HIE. Tau protein is a unique biological component of nervous tissues, and might have value for neonatal HIE diagnosis. Combination of more than two biological markers should be a future research direction.

Survival response of hippocampal neurons under low oxygen conditions induced by Hippophae rhamnoides is associated with JAK/STAT signaling

Janus activated kinase/signal transducers and activators of transcription (JAK/STATs) pathway are associated with various neuronal functions including cell survival and inflammation. In the present study, it is hypothesized that protective action of aqueous extract of Hippophae rhamnoides in hippocampal neurons against hypoxia is mediated via JAK/STATs. Neuronal cells exposed to hypoxia (0.5% O2) display higher reactive oxygen species with compromised antioxidant status compared to unexposed control cells. Further, these cells had elevated levels of pro-inflammatory cytokines; tumor necrosis factor α and interleukin 6 and nuclear factor κappa B. Moreover, the expression of JAK1 was found to be highly expressed with phosphorylation of STAT3 and STAT5. Cells treated with JAK1, STAT3 and STAT5 specific inhibitors resulted in more cell death compared to hypoxic cells. Treatment of cells with extract prevented oxidative stress and inflammatory response associated with hypoxia. The extract treated cells had more cell survival than hypoxic cells with induction of JAK1 and STAT5b. Cells treated with extract having suppressed JAK1 or STAT3 or STAT5 expression showed reduced cell viability than the cell treated with extract alone. Overall, the findings from these studies indicate that the aqueous extract of Hippophae rhamnoides treatment inhibited hypoxia induced oxidative stress by altering cellular JAK1, STAT3 and STAT5 levels thereby enhancing cellular survival response to hypoxia and provide a basis for possible use of aqueous extract of Hippophae rhamnoides in facilitating tolerance to hypoxia.

Endogenous protection derived from activin A/Smads transduction loop stimulated via ischemic injury in PC12 cells

Activin A (ActA), a member of transforming growth factor-beta (TGF-b) super- family, affects many cellular processes, including ischemic stroke. Though the neuroprotective effects of exogenous ActA on oxygen-glucose deprivation (OGD) injury have already been reported by us, the endogenous role of ActA remains poorly understood. To further define the role and mechanism of endogenous ActA and its signaling in response to acute ischemic damage, we used an OGD model in PC12 cells to simulate ischemic injury on neurons in vitro. Cells were pre-treated by monoclonal antibody against activin receptor type IIA (ActRII-Ab). We found that ActRII-Ab augments ischemic injury in PC12 cells. Further, the extracellular secretion of ActA as well as phosphorylation of smad3 in PC12 cells was also up-regulated by OGD, but suppressed by ActRII-Ab. Taken together, our results show that ActRII-Ab may augment ischemic injury via blocking of transmembrane signal transduction of ActA, which confirmed the existence of endogenous neuroprotective effects derived from the ActA/Smads pathway. ActRIIA plays an important role in transferring neuronal protective signals inside. It is highly possible that ActA transmembrance signaling is a part of the positive feed-back loop for extracellular ActA secretion.

M2 microglia and macrophages drive oligodendrocyte differentiation during CNS remyelination

The lack of therapies for progressive multiple sclerosis highlights the need to understand the regenerative process of remyelination that can follow CNS demyelination. This involves an innate immune response consisting of microglia and macrophages, which can be polarized to distinct functional phenotypes: pro-inflammatory (M1) and anti-inflammatory or immunoregulatory (M2). We found that a switch from an M1- to an M2-dominant response occurred in microglia and peripherally derived macrophages as remyelination started. Oligodendrocyte differentiation was enhanced in vitro with M2 cell conditioned media and impaired in vivo following intra-lesional M2 cell depletion. M2 cell densities were increased in lesions of aged mice in which remyelination was enhanced by parabiotic coupling to a younger mouse and in multiple sclerosis lesions that normally show remyelination. Blocking M2 cell-derived activin-A inhibited oligodendrocyte differentiation during remyelination in cerebellar slice cultures. Thus, our results indicate that M2 cell polarization is essential for efficient remyelination and identify activin-A as a therapeutic target for CNS regeneration.

M2 microglia and macrophages drive oligodendrocyte differentiation during CNS remyelination

The lack of therapies for progressive multiple sclerosis highlights the need to understand the regenerative process of remyelination that can follow CNS demyelination. This involves an innate immune response consisting of microglia and macrophages, which can be polarized to distinct functional phenotypes: pro-inflammatory (M1) and anti-inflammatory or immunoregulatory (M2). We found that a switch from an M1- to an M2-dominant response occurred in microglia and peripherally derived macrophages as remyelination started. Oligodendrocyte differentiation was enhanced in vitro with M2 cell conditioned media and impaired in vivo following intra-lesional M2 cell depletion. M2 cell densities were increased in lesions of aged mice in which remyelination was enhanced by parabiotic coupling to a younger mouse and in multiple sclerosis lesions that normally show remyelination. Blocking M2 cell-derived activin-A inhibited oligodendrocyte differentiation during remyelination in cerebellar slice cultures. Thus, our results indicate that M2 cell polarization is essential for efficient remyelination and identify activin-A as a therapeutic target for CNS regeneration.

Effects of SARA on oxygen-glucose deprivation in PC12 cell line

Ischemic stroke is a major composition of cerebrovascular disease, seriously threatening to human health in the world. Activin A (ActA), belonging to transforming growth factor-beta (TGF-β) super family, plays an important role in the hypoxic-ischemic brain injury through ActA/Smads pathway. While as an essential phosphorylation assistor in TGF-β signaling, the functions and mechanisms of smad anchor for receptor activation (SARA) in ischemic brain injury remain poorly understood. To solve this problem and explore the pathological processes of ischemic stroke, we used an Oxygen-Glucose deprivation (OGD) model in nerve growth factor-induced differentiated rattus PC12 pheochromocytoma cells and down regulated the expressions of SARA by RNA interference technology. Our results showed that the repression of SARA before OGD exposure reduced the expressions of Smad2, 3, 4 mRNA and the phosphorylation rate of Smad2 protein, but it did not affect the mRNA expressions of Smad7. After OGD treatment, ActA/Smads pathway was activated and the expression of SARA in the SARA pre-repression group was significantly up-regulated. The pre-repression of SARA increased the sensitivities of nerve-like cells to OGD damage. Moreover, the mRNA expression of Smad7 which was supposed to participate in the negative feedback of ActA/Smads pathway was also elevated due to OGD injury. Taken together, these results suggest a positive role of SARA in assisting the phosphorylation of Smad2 and maintaining the neuron protective effect of ActA/Smads pathway.

Biomarkers of brain injury in the premature infant

The term “encephalopathy of prematurity” encompasses not only the acute brain injury [such as intraventricular hemorrhage (IVH)] but also complex disturbance on the infant’s subsequent brain development. In premature infants, the most frequent recognized source of brain injury is IVH and periventricular leukomalacia (PVL). Furthermore 20–25% infants with birth weigh less than 1,500 g will have IVH and that proportion increases to 45% if the birth weight is less than 500–750 g. In addition, nearly 60% of very low birth weight newborns will have hypoxic-ischemic injury. Therefore permanent lifetime neurodevelopmental disabilities are frequent in premature infants. Innovative approach to prevent or decrease brain injury in preterm infants requires discovery of biomarkers able to discriminate infants at risk for injury, monitor the progression of the injury, and assess efficacy of neuroprotective clinical trials. In this article, we will review biomarkers studied in premature infants with IVH, Post-hemorrhagic ventricular dilation (PHVD), and PVL including: S100b, Activin A, erythropoietin, chemokine CCL 18, GFAP, and NFL will also be examined. Some of the most promising biomarkers for IVH are S100β and Activin. The concentrations of TGF-β1, MMP-9, and PAI-1 in cerebrospinal fluid could be used to discriminate patients that will require shunt after PHVD. Neonatal brain injury is frequent in premature infants admitted to the neonatal intensive care and we hope to contribute to the awareness and interest in clinical validation of established as well as novel neonatal brain injury biomarkers.