Neuroglobin boosts axon regeneration during ischemic reperfusion via p38 binding and activation depending on oxygen signal

Xiaoxuming decoction enhanced neuroprotection after cerebral ischemia/reperfusion via the JAK2/STAT3 signaling pathway based on UPLC/HRMS, network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Xiao-xu-ming decoction (XXMD), a prominent traditional Chinese medicinal formula historically revered for stroke treatment, demonstrates pronounced efficacy in ameliorating ischemic stroke injury.

AIM OF THE STUDY

This study aims to investigate the effects and mechanisms of XXMD on neuroprotection subsequent to cerebral ischemia/reperfusion in vivo and in vitro.

MATERIALS AND METHODS

Neurobehavioral test, TTC staining, HE staining and nissl staining were used to examine the neuroprotective effect of XXMD on cerebral ischemia-reperfusion injury induced by middle cerebral artery occlusion (MCAO) in rats. Additionally, we assessed cell viability and injury with CCK8 and lactate dehydrogenase (LDH) assays. The changes in neuronal ultra-structure were observed after oxygen-glucose deprivation and reoxygenation (OGD/R) by transmission electron microscopy (TEM). Network analysis combined with ultrahighperformance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) predicted the mechanism of XXMD on ischemic stroke injury. Furthermore, the expression of neuroplasticity-related proteins neurofilament 200 (NF200), microtubule-associated protein 2 (MAP2), postsynaptic density protein 95 (PSD95), synaptophysin (SYN), phosphorylated Janus kinase2 (p-JAK2), and phosphorylated signal transduction and activator of transcription 3 (p-STAT3) was evaluated by immunofluorescence staining and Western blot analyses.

RESULTS

XXMD significantly improved Ethology, infarct area and pathological changes after MCAO and reperfusion, reducing morphological and ultrastructural alterations and decreased cell viability in HT22 cells induced by OGD/R. Network pharmacology showed that 1153 compounds of XXMD were matched. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that XXMD treated ischemia stroke mainly regulating inflammation reaction-related signaling pathways, atherosclerosish-related signaling pathways. Molecular docking results showed that TP53, AKT1, STAT3, and IL6 are closely bound to the corresponding active ingredients. XXMD treatment significantly reversed the above alternations. XXMD or AG490 up-regulated the expression of neuroplasticity-associated proteins, and reduced phosphorylation of JAK2, STAT3 expression following OGD/R.

CONCLUSION

XXMD exerts neuroprotective effects by promoting neural plasticity via regulating the JAK2/STAT3 pathway, indicating a promising alternative therapeutic strategy for ischemic stroke.

Neuroglobin protects dopaminergic neurons in a Parkinson's cell model by interacting with mitochondrial complex NDUFA10

The study aimed to validate the protective effect of neuroglobin (Ngb) in a cell model of Parkinson's disease (PD) and explore its therapeutic potential. Lentivirus-Ngb (LvNgb) and siRNA-Ngb (siNgb) were used to achieve Ngb overexpression and knockdown, respectively, in a sporadic PD cell model. Apoptosis was evaluated by flow cytometry-based Annexin V/propidium iodide assays. Activation of the pro-apoptotic factor, Caspase-9, was detected by immunoblotting, and Complex I activities were detected by using enzyme-linked immunosorbent assay (ELISA). Mitochondrial dysfunction was examined by measuring the mitochondrial membrane potential (MMP), NAD+/NADH ratios, and reactive oxygen species (ROS) levels. Additionally, coimmunoprecipitation (Co-IP) assays were conducted in mouse neuroblastoma cell line 9D (MN9D) cells to determine the interactions of Ngb with the Complex I subunit NDUFA10. The results showed that Ngb overexpression reduced the percentages of apoptotic cells, total caspase-9 levels and restored Complex I activities in the PD cell model. Conversely, knockdown of Ngb resulted in an increase in apoptotic cells, higher total caspase-9 levels, and decreased Complex I activities. Furthermore, Ngb overexpression restored MMP and NAD+/NADH ratios and alleviated ROS-mediated oxidative stress in MN9D cells. Finally, Co-IP confirmed the interaction between Ngb and NDUFA10 in MN9D cells. In conclusion, Ngb protects MN9D cells against apoptosis by interacting with Complex I subunit NDUFA10, rescuing its activity and inhibiting the mitochondrial pathway of apoptosis in the MPP+-mediated PD model.

Zwitterionic Conductive Hydrogel-Based Nerve Guidance Conduit Promotes Peripheral Nerve Regeneration in Rats

In recent years, conductive biomaterials have been widely used to enhance peripheral nerve regeneration. However, most biomaterials use electronic conductors to increase the conductivity of materials. As information carriers, electronic conductors always transmit discontinuous electrical signals, while biological systems essentially transmit continuous signals through ions. Herein, an ion-based conductive hydrogel was fabricated by simple copolymerization of the zwitterionic monomer sulfobetin methacrylate and hydroxyethyl methacrylate. Benefiting from the excellent mechanical stability, suitable electrical conductivity, and good cytocompatibility of the zwitterionic hydrogel, the Schwann cells cultured on the hydrogel could grow and proliferate better, and dorsal root ganglian had an increased neurite length. The zwitterionic hydrogel-based nerve guidance conduits were then implanted into a 10 mm sciatic nerve defect model in rats. Morphological analysis and electrophysiological data showed that the grafts achieved a regeneration effect close to that of the autologous nerve. Overall, our developed zwitterionic hydrogel facilitates efficient and efficacious peripheral nerve regeneration by mimicking the electrical and mechanical properties of the extracellular matrix and creating a suitable regeneration microenvironment, providing a new material reserve for the repair of peripheral nerve injury.

The effects of protein-rich extract from Rhizoma Gastrodiae against cerebral ischemia/reperfusion injury via regulating MAPK and PI3K/AKT signaling pathway

BACKGROUND

Rhizoma Gastrodiae is a highly valuable traditional Chinese medicine and functional health food that has been used in China to treat neurological disorders for thousands of years. Rhizoma Gastrodiae contains various of biological activities, such as antioxidative, neuroprotective, learning improvement, anxiolytic, and antidepressant effects. However, no studies have been conducted to explore the effects of the protein components in Rhizoma Gastrodiae (GEPS) and its potential protective effects against ischemic stroke.Our main goal was to investigate the effects of GEPS on ischemia/reperfusion (I/R) injury and its possible mechanisms.

METHODS

A middle cerebral artery occlusion (MCAO) induced focal cerebral ischemia mouse model and an oxygen-glucose deprivation (OGD/R) injury model in HT22 cells were established. A neurobehavioral test was performed 24 h after MCAO, and brain infarction was measured. A Morris water maze experiment was conducted on Day 14 after reperfusion in mice. Hematoxylin and eosin (HE) and TUNEL staining were performed to assess apoptotic neuronal death. Immunohistochemical analysis was used to detect BDNF and GAP43 expression. The content of SOD, MDA, GSH-PX and ROS were detected. The protein expression was analyzed using Western blotting. Cell viability was determined by MTT assay. Cell apoptosis was examined by flow cytometry.

RESULTS

GEPS reduced apoptosis, decreased cerebral infarction, improved neurological defects, and ameliorated oxidative stress in the ischemic penumbra. In addition, GEPS increased the expression of BDNF and GA43 in the penumbra. Mechanistically, GEPS counteracted MCAO-induced PI3K/AKT inhibition and activation of MAPK signaling pathways.

CONCLUSION

GEPS has a clear neuroprotective effect on I/R injury, and its mechanism may be linked to the PI3K/AKT and MAPK signaling pathways.

Neuroglobin Facilitates Neuronal Oxygenation through Tropic Migration under Hypoxia or Anemia in Rat: How Does the Brain Breathe?

The discovery of neuroglobin (Ngb), a brain- or neuron-specific member of the hemoglobin family, has revolutionized our understanding of brain oxygen metabolism. Currently, how Ngb plays such a role remains far from clear. Here, we report a novel mechanism by which Ngb might facilitate neuronal oxygenation upon hypoxia or anemia. We found that Ngb was present in, co-localized to, and co-migrated with mitochondria in the cell body and neurites of neurons. Hypoxia induced a sudden and prominent migration of Ngb towards the cytoplasmic membrane (CM) or cell surface in living neurons, and this was accompanied by the mitochondria. In vivo, hypotonic and anemic hypoxia induced a reversible Ngb migration toward the CM in cerebral cortical neurons in rat brains but did not alter the expression level of Ngb or its cytoplasm/mitochondria ratio. Knock-down of Ngb by RNA interference significantly diminished respiratory succinate dehydrogenase (SDH) and ATPase activity in neuronal N2a cells. Over-expression of Ngb enhanced SDH activity in N2a cells upon hypoxia. Mutation of Ngb at its oxygen-binding site (His64) significantly increased SDH activity and reduced ATPase activity in N2a cells. Taken together, Ngb was physically and functionally linked to mitochondria. In response to an insufficient oxygen supply, Ngb migrated towards the source of oxygen to facilitate neuronal oxygenation. This novel mechanism of neuronal respiration provides new insights into the understanding and treatment of neurological diseases such as stroke and Alzheimer's disease and diseases that cause hypoxia in the brain such as anemia.

Isoquercitrin Played a Neuroprotective Role in Rats After Cerebral Ischemia/Reperfusion Through Up-Regulating Neuroglobin and Anti-Oxidative Stress

BACKGROUND

This study aims to investigate whether isoquercitrin (Iso) exerts a neuroprotective role effect after cerebral ischemia-reperfusion (CIR) via up-regulating neuroglobin (Ngb) or reducing oxidative stress.

METHODS

The middle cerebral artery occlusion/reperfusion (MCAO/R) model was constructed using Sprague Dawley rats. First, we divided 40 mice into 5 groups (n = 8): sham, MCAO/R, Low-dosed Iso (5 mg/kg Iso), Mid-dosed Iso (10 mg/kg Iso), and High-dosed Iso (20 mg/kg Iso). Then, 48 rats were separated into 6 groups (n = 8): sham, MCAO/R, Iso, artificial cerebrospinal fluid, Ngb antisense oligodeoxynucleotides (AS-ODNs), and AS-ODNs ± Iso. The effects of Iso on brain tissue injury and oxidative stress were evaluated using hematoxylin-eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, immunofluorescence, western blotting, and real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and reactive oxygen species (ROS) detection.

RESULTS

The neurologic score, infarct volume, histopathology, apoptosis rate, and ROS production were reduced in Iso dose-dependent. The Ngb expression enhanced in Iso dose-dependent. The oxidative stress-related factors SOD, GSH, CAT, Nrf2, HO-1, and HIF-1α levels also increased in Iso dose-dependent, whereas the MDA levels decreased. However, related regulation of Iso on brain tissue damage and oxidative stress were reversed after low expression of Ngb.

CONCLUSION

Isoquercitrin played a neuroprotective role after CIR through up-regulating of Ngb and anti-oxidative stress.

SnRNA-seq reveals the heterogeneity of spinal ventral horn and mechanism of motor neuron axon regeneration

Spinal motor neurons, the distinctive neurons of the central nervous system, extend into the peripheral nervous system and have outstanding ability of axon regeneration after injury. Here, we explored the heterogeneity of spinal ventral horn cells after rat sciatic nerve crush via single-nuclei RNA sequencing. Interestingly, regeneration mainly occurred in a Sncg⁺ and Anxa2⁺ motor neuron subtype (MN2) surrounded by a newly emerged microglia subtype (Mg6) after injury. Subsequently, microglia depletion slowed down the regeneration of sciatic nerve. OPCs were also involved into the regeneration process. Knockdown of Cacna2d2 in vitro and systemic blocking of Cacna2d2 in vivo improved the axon growth ability, hinting us the importance of Ca²⁺. Ultimately, we proposed three possible phases of motor neuron axon regeneration: preparation stage, early regeneration stage, and regeneration stage. Taken together, our study provided a resource for deciphering the underlying mechanism of motor neuron axon regeneration in a single cell dimension.

Estrogens as a Possible Therapeutic Strategy for the Management of Neuroinflammation and Neuroprotection in COVID-19

The Coronavirus disease 2019 (COVID-19) affects several tissues, including the central and peripheral nervous system. It has also been related to signs and symptoms that suggest neuroinflammation with possible effects in the short, medium, and long term. Estrogens could have a positive impact on the management of the disease, not only due to its already known immunomodulator effect, but also activating other pathways that may be important in the pathophysiology of COVID-19, such as the regulation of the virus receptor and its metabolites. In addition, they can have a positive effect on neuroinflammation secondary to pathologies other than COVID-19. The aim of this study is to analyze the molecular mechanisms that link estrogens with their possible therapeutic effect for neuroinflammation related to COVID-19. Advanced searches were performed in scientific databases as Pub- Med, ProQuest, EBSCO, the Science Citation index, and clinical trials. Estrogens have been shown to participate in the immune modulation of the response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In addition to this mechanism, we propose that estrogens can regulate the expression and activity of the Angiotensin-converting enzyme 2 (ACE2), reestablishing its cytoprotective function, which may be limited by its interaction with SARS-CoV-2. In this proposal, estrogens and estrogenic compounds could increase the synthesis of Angiotensin-(1-7) (Ang-(1-7)) that acts through the Mas receptor (MasR) in cells that are being attacked by the virus. Estrogens can be a promising, accessible, and low-cost treatment for neuroprotection and neuroinflammation in patients with COVID-19, due to its direct immunomodulatory capacity in decreasing cytokine storm and increasing cytoprotective capacity of the axis ACE2/Ang (1-7)/MasR.

New Strategies for Stroke Therapy: Nanoencapsulated Neuroglobin

Stroke is a global health and socio-economic problem. However, no efficient preventive and/or palliative treatments have yet been found. Neuroglobin (Ngb) is an endogen neuroprotective protein, but it only exerts its beneficial action against stroke after increasing its basal levels. Therefore, its systemic administration appears to be an efficient therapy applicable to stroke and other neurodegenerative pathologies. Unfortunately, Ngb cannot cross the blood-brain barrier (BBB), making its direct pharmacological use unfeasible. Thus, the association of Ngb with a drug delivery system (DDS), such as nanoparticles (NPs), appears to be a good strategy for overcoming this handicap. NPs are a type of DDS which efficiently transport Ngb and increase its bioavailability in the infarcted area. Hence, we previously built hyaluronate NPS linked to Ngb (Ngb-NPs) as a therapeutic tool against stroke. This nanoformulation induced an improvement of the cerebral infarct prognosis. However, this innovative therapy is still in development, and a more in-depth study focusing on its long-lasting neuroprotectant and neuroregenerative capabilities is needed. In short, this review aims to update the state-of-the-art of stroke therapies based on Ngb, paying special attention to the use of nanotechnological drug-delivering tools.

Oleanolic Acid Inhibits Neuronal Pyroptosis in Ischaemic Stroke by Inhibiting miR-186-5p Expression

Ischaemic stroke is a common condition leading to human disability and death. Previous studies have shown that oleanolic acid (OA) ameliorates oxidative injury and cerebral ischaemic damage, and miR-186-5p is verified to be elevated in serum from ischaemic stroke patients. Herein, we investigated whether OA regulates miR-186-5p expression to control neuroglobin (Ngb) levels, thereby inhibiting neuronal pyroptosis in ischaemic stroke. Three concentrations of OA (0.5, 2, or 8 μM) were added to primary hippocampal neurons subjected to oxygen–glucose deprivation/reperfusion (OGD/R), a cell model of ischaemic stroke. We found that OA treatment markedly inhibited pyroptosis. qRT–PCR and western blot revealed that OA suppressed the expression of pyroptosis-associated genes. Furthermore, OA inhibited LDH and proinflammatory cytokine release. In addition, miR-186-5p was downregulated while Ngb was upregulated in OA-treated OGD/R neurons. MiR-186-5p knockdown repressed OGD/R-induced pyroptosis and suppressed LDH and inflammatory cytokine release. In addition, a dual luciferase reporter assay confirmed that miR-186-5p directly targeted Ngb. OA reduced miR-186-5p to regulate Ngb levels, thereby inhibiting pyroptosis in both OGD/R-treated neurons and MCAO mice. In conclusion, OA alleviates pyroptosis in vivo and in vitro by downregulating miR-186-5p and upregulating Ngb expression, which provides a novel theoretical basis illustrating that OA can be considered a drug for ischaemic stroke.

Neuroglobin, clues to function and mechanism

Neuroglobin is expressed in vertebrate brain and belongs to a branch of the globin family that diverged early in evolution. Sequence conservation and presence in nervous cells of several taxa suggests a relevant role in the nervous system, with tight structural restraints. Twenty years after its discovery, a rich scientific literature provides convincing evidence of the involvement of neuroglobin in sustaining neuron viability in physiological and pathological conditions however, a full and conclusive picture of its specific function, or set of functions is still lacking. The difficulty of unambiguously assigning a precise mechanism and biochemical role to neuroglobin might arise from the participation to one or more cell mechanism that redundantly guarantee the functioning of the highly specialized and metabolically demanding central nervous system of vertebrates. Here we collect findings and hypotheses arising from recent biochemical, biophysical, structural, in cell and in vivo experimental work on neuroglobin, aiming at providing an overview of the most recent literature. Proteins are said to have jobs and hobbies, it is possible that, in the case of neuroglobin, evolution has selected for it more than one job, and support to cover for its occasional failings. Disentangling the mechanisms and roles of neuroglobin is thus a challenging task that might be achieved by considering data from different disciplines and experimental approaches.

Melatonin attenuates reactive astrogliosis and glial scar formation following cerebral ischemia and reperfusion injury mediated by GSK-3β and RIP1K

Even though astrocytes have been widely reported to support several brain functions, studies have emerged that they exert deleterious effects on the brain after ischemia and reperfusion (I/R) injury. The present study investigated the neuroprotective effects of melatonin on the processes of reactive astrogliosis and glial scar formation, as well as axonal regeneration after transient middle cerebral artery occlusion. Male Wistar rats were randomly divided into four groups: sham-operated, I/R, I/R treated with melatonin, and I/R treated with edaravone. All drugs were administered via intraperitoneal injection at the onset of reperfusion and were continued until the rats were sacrificed on Day 7 or 14 after the surgery. Melatonin presented long-term benefits on cerebral damage after I/R injury, as demonstrated by a decreased infarct volume, histopathological changes, and reduced neuronal cell death. We also found that melatonin attenuated reactive astrogliosis and glial scar formation and, consequently, enhanced axonal regeneration and promoted neurobehavioral recovery. Furthermore, glycogen synthase kinase-3 beta (GSK-3β) and receptor-interacting serine/threonine-protein 1 kinase (RIP1K), which had previously been revealed as proteins involved in astrocyte responses, were significantly reduced after melatonin administration. Taken together, melatonin effectively counteracted the deleterious effects due to astrocyte responses and improved axonal regeneration to promote functional recovery during the chronic phase of cerebral I/R injury by inhibiting GSK-3β and RIP1K activities.

Sinensetin attenuates oxygen-glucose deprivation/reperfusion-induced neurotoxicity by MAPK pathway in human cerebral microvascular endothelial cells

Sinensetin is a polymethoxylated flavone with anti-inflammatory and anti-oxidative activities. This work aimed to explore the function and mechanism of sinensetin in oxygen and glucose deprivation/reperfusion (OGD/R)-induced neurotoxicity. The overlapping target genes of cerebral stroke and sinensetin were determined according to GeneCards and ParmMapper tools and were subjected to Gene Ontology (GO) annotations and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Human cerebral microvascular endothelial cells (HCMECs) were stimulated with OGD/R. Neurotoxicity was investigated by Cell Counting Kit-8, lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) level, qRT-PCR, and TUNEL analysis. The proteins (p38, JNK, and ERK) in mitogen-activated protein kinase (MAPK) signaling were measured using Western blotting. Total of 50 overlapping target genes of cerebral stroke and sinensetin were predicted. Pathway analysis showed they might be involved in the MAPK pathway. Sinensetin attenuated OGD/R-induced neurotoxicity by mitigating viability reduction, LDH release, ROS generation, inflammatory response, and apoptosis in HCMECs. Sinensetin weakened OGD/R-induced activation of the MAPK pathway via decreasing the phosphorylation of p38, JNK, and ERK. The pathway inhibitors mitigated the activation of the MAPK signaling, and sinensetin exacerbated this effect. The inhibitors reversed OGD/R-induced neurotoxicity in HCMECs, and sinensetin contributed to this role. Overall, sinensetin prevents OGD/R-induced neurotoxicity through decreasing the activation of MAPK pathway.

Macrophage-specific RhoA knockout delays Wallerian degeneration after peripheral nerve injury in mice

Background

Plenty of macrophages are recruited to the injured nerve to play key roles in the immunoreaction and engulf the debris of degenerated axons and myelin during Wallerian degeneration, thus creating a conducive microenvironment for nerve regeneration. Recently, drugs targeting the RhoA pathway have been widely used to promote peripheral axonal regeneration. However, the role of RhoA in macrophage during Wallerian degeneration and nerve regeneration after peripheral nerve injury is still unknown. Herein, we come up with the hypothesis that RhoA might influence Wallerian degeneration and nerve regeneration by affecting the migration and phagocytosis of macrophages after peripheral nerve injury.

Methods

Immunohistochemistry, Western blotting, H&E staining, and electrophysiology were performed to access the Wallerian degeneration and axonal regeneration after sciatic nerve transection and crush injury in the Lyz^Cre+/−; RhoA^flox/flox (cKO) mice or Lyz2^Cre+/− (Cre) mice, regardless of sex. Macrophages’ migration and phagocytosis were detected in the injured nerves and the cultured macrophages. Moreover, the expression and potential roles of ROCK and MLCK were also evaluated in the cultured macrophages.

Results

1. RhoA was specifically knocked out in macrophages of the cKO mice; 2. The segmentation of axons and myelin, the axonal regeneration, and nerve conduction in the injured nerve were significantly impeded while the myoatrophy was more severe in the cKO mice compared with those in Cre mice; 3. RhoA knockout attenuated the migration and phagocytosis of macrophages in vivo and in vitro; 4. ROCK and MLCK were downregulated in the cKO macrophages while inhibition of ROCK and MLCK could weaken the migration and phagocytosis of macrophages.

Conclusions

Our findings suggest that RhoA depletion in macrophages exerts a detrimental effect on Wallerian degeneration and nerve regeneration, which is most likely due to the impaired migration and phagocytosis of macrophages resulted from disrupted RhoA/ROCK/MLCK pathway. Since previous research has proved RhoA inhibition in neurons was favoring for axonal regeneration, the present study reminds us of that the cellular specificity of RhoA-targeted drugs is needed to be considered in the future application for treating peripheral nerve injury.

The p38 MAPK/NF-κB pathway mediates GLT-1 up-regulation during cerebral ischemic preconditioning-induced brain ischemic tolerance in rats

Our previous finding suggests that p38 MAPK contributes to the GLT-1 upregulation during induction of brain ischemic tolerance by cerebral ischemic preconditioning (CIP), however, the underlying mechanism is still unclear. Here, we investigated the molecular mechanisms underlying the CIP-induced GLT-1 upregulation by using Western blotting, Co-immunoprecipitation (Co-IP), electrophoretic mobility shift assay (EMSA) and thionin staining in rat hippocampus CA1 subset. We found that application of BAY11-7082 (an inhibitor of NF-κB), or dihydrokainate (an inhibitor of GLT-1), or SB203580 (an inhibitor of p38 MAPK) could attenuate the CIP-induced neuronal protection in hippocampus CA1 region of rats. Moreover, CIP caused rapid activation of NF-κB, as evidenced by nuclear translocation of NF-κB p50 protein, which led to active p50/p65 dimer formation and increased DNA binding activity. GLT-1 was also increased after CIP. Pretreatment with BAY11-7082 blocked the CIP-induced GLT-1 upregulation. The above results suggest that NF-κB participates in GLT-1 up-regulation during the induction of brain ischemic tolerance by CIP. We also found that pretreatment with SB203580 caused significant reduction of NF-κB p50 protein in nucleus, NF-κB p50/p65 dimer nuclear translocation and DNA binding activity of NF-κB. Together, we conclude that p38 MAPK/NF-κB pathway participates in the mediation of GLT-1 up-regulation during the induction of brain ischemic tolerance induced by CIP.

Role of Neuroglobin in the Neuroprotective Actions of Estradiol and Estrogenic Compounds

Estradiol exerts neuroprotective actions that are mediated by the regulation of a variety of signaling pathways and homeostatic molecules. Among these is neuroglobin, which is upregulated by estradiol and translocated to the mitochondria to sustain neuronal and glial cell adaptation to injury. In this paper, we will discuss the role of neuroglobin in the neuroprotective mechanisms elicited by estradiol acting on neurons, astrocytes and microglia. We will also consider the role of neuroglobin in the neuroprotective actions of clinically relevant synthetic steroids, such as tibolone. Finally, the possible contribution of the estrogenic regulation of neuroglobin to the generation of sex differences in brain pathology and the potential application of neuroglobin as therapy against neurological diseases will be examined.

Neuroglobin alleviates arsenic-induced neuronal damage

People who drink water contaminated with arsenic for a long time develop neuritis, cerebellar symptoms, and deficits in memory and intellectual function. Arsenic induces oxidative stress and promotes apoptosis through multiple signalling pathways in nerve cells. Neuroglobin (Ngb), as a key mediator, is considered to be protective against oxidative stress. In this study, we aimed to study the effects of Ngb knockdown in arsenite-treated rat neurons on levels of apoptosis markers and reactive oxygen species and serum Ngb levels of subjects from arsenic-endemic regions in China. We discovered that arsenic-induced apoptosis and reactive oxygen species production were enhanced in Ngb-knocked-down rat neurons. Silencing of Ngb aggravated the arsenic-induced decrease in the rate of Bcl-2/Bax and the levels of Bcl-2 protein following arsenite treatment. The results also showed that serum Ngb levels were independently negatively correlated with arsenic concentration in drinking water. Furthermore, the serum Ngb levels of four groups (245 individuals) according to different degree exposure to arsenic were 815.18 ± 89.52, 1247.97 ± 117.18, 774.79 ± 91.55, and 482.72 ± 49.30 pg/mL, respectively. Taken together, it can be deduced that Ngb has protective effects against arsenic-induced apoptosis by eliminating reactive oxygen species.

The KATP channel opener, nicorandil, ameliorates brain damage by modulating synaptogenesis after ischemic stroke

With population growth and aging, more and more patients with cerebral infarction have varying degrees of disability. ATP-sensitive potassium (KATP) channels regulate many cellular functions by coupling metabolic status with cell membrane electrical activity. Nicorandil (N-(2-hydroxyethyl)-nicotinamide nitrate) is the first KATP channel opener approved for clinical use. It has been reported that it might exert protective effects on the cerebral infarction by increasing cerebral blood flow and reducing inflammation. However, only a few studies explored its role in synaptogenesis. We made the rat model of middle cerebral artery occlusion (MCAO). Nicorandil was administered to rats via oral administration immediately after the surgery at a dose of 7.5 mg/kg and then daily for the next days. Infarct volume, cerebral edema, neurological deficits, cognitive impairment, and the level of Synaptophysin (SYP)、Growth associated protein-43 (GAP43) and neuronal nuclear antigen (NeuN) levels were measured to evaluate the effect of nicorandil. Our data showed that nicorandil treatment could decrease brain damage, improve learning and memory, and increase SYP、GAP43 and NeuN level. Taken together, we propose that nicorandil, as an opener of the KATP channel, provides a neuroprotective role in MCAO by promoting synaptic connections.

Tanshinone IIA Promotes Axonal Regeneration in Rats with Focal Cerebral Ischemia Through the Inhibition of Nogo-A/NgR1/RhoA/ROCKII/MLC Signaling

Purpose

The aim of this study was to evaluate the neuroprotective effect of tanshinone IIA (TSA) on focal cerebral ischemia in rats and to investigate whether it was associated with Nogo-A/NgR1/RhoA/Rho-associated protein kinase 2 (ROCKII)/myosin light chain (MLC) signaling.

Methods

In this study, focal cerebral ischemia animal model was used. Neurological deficit scores and infarction volume were investigated to evaluate the neuroprotection of TSA. Hematoxylin-eosin staining, Nissl staining, and immunofluorescence staining were conducted to detect ischemic changes in brain tissue and changes in neurofilament protein 200 (NF200) and growth-associated protein-43 (GAP-43) expression, respectively. Western blotting and qRT-PCR analyses were used to detect the expression levels of NF200, GAP-43 and Nogo-A/NgR1/RhoA/ROCKII/MLC pathway-related signaling molecules.

Results

TSA treatment can improve the survival rate of rats, reduce the neurological score and infarct volume, and reduce neuron damage. In addition, TSA also increased axon length and enhanced expression of NF200 and GAP-43. Importantly, TSA significantly attenuated the expression of Nogo-A, NgR1, RhoA, ROCKII, and p-MLC, and thus inhibiting the activation of this signaling pathway.

Conclusion

TSA promoted axonal regeneration by inhibiting the Nogo-A/NgR1/RhoA/ROCKII/MLC signaling pathway, thereby exerting neuroprotective effects in cerebral ischemia rats, which provided support for the clinical application of TSA in stroke treatment.

Hyaluronate Nanoparticles as a Delivery System to Carry Neuroglobin to the Brain after Stroke

Therapies against stroke can restore the blood supply but cannot prevent the ischemic damage nor stimulate the recovery of the infarcted zone. The neuroglobin protein plays an important role in the neuro-regeneration process after stroke; however, the method for its effective systemic application has not been identified yet, as neuroglobin is unable to pass through the blood-brain barrier. Previously, we developed different types of sodium hyaluronate nanoparticles, which successfully cross the blood-brain barrier after stroke. In this work, these nanoparticles have been used to carry neuroglobin through the bloodstream to the nerve cells in rats submitted to stroke. We have biosynthesized rat-recombinant neuroglobin and determined the formulation of sodium hyaluronate nanoparticles loaded with neuroglobin, as well as its size and ζ-potential, encapsulation efficiently, in vitro release, and its kinetic of liberation. The results show that the formulation achieved is highly compatible with pharmaceutical use and may act as a delivery system to transport neuroglobin within the blood. We have found that this formulation injected intravenously immediately after stroke reached the damaged cerebral parenchyma at early stages (2 h). Neuroglobin colocalizes with its nanocarriers inside the nerve cells and remains after 24 h of reperfusion. In conclusion, the systemic administration of neuroglobin linked to nanoparticles is a potential neuroprotective drug-delivery strategy after stroke episodes.

2,3,7,8-Tetrachlorodibenzo-p-dioxin and up-regulation of neurofilament expression in neuronal cells: Evaluation of AhR and MAPK pathways

Dioxin exposure is reported to affect nervous system development and increase the risk of neurodegenerative diseases. Generally, dioxin exerts its neurotoxicity via aryl hydrocarbon receptor (AhR). Neurofilament (NF) light (NFL) protein is a biomarker for both neuronal differentiation and neurodegeneration and its expression is controlled by the mitogen-activated protein kinase (MAPK) pathway. However, the effects of dioxin on NFL expression and involved mechanisms are incompletely understood. We aimed to investigate the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on NFL expression and elucidate the underlining signaling pathways and their potential crosstalk, specifically between MAPK and AhR pathway. We employed primary cultured rat cortical neurons to evaluate the effect of TCDD exposure on NFL expression. We also used nerve growth factor (NGF)-treated PC12 cells with specific inhibitors to investigate the involvement of and potential crosstalk between the MAPK pathway and the AhR pathway in mediating the effects of TCDD on NFL expression. After TCDD exposure, NFL mRNA and protein levels were upregulated in cultured neurons. NFL protein was preferentially found in the cell body compared with neurites of the cultured neurons. In PC12 cells, TCDD enhanced both NGF-induced NFL expression and phosphorylation of ERK1/2 and p38. The addition of MAPK-pathway inhibitors (PD98059 and SB230580) partially blocked the TCDD-induced NFL upregulation. CH223191, an AhR antagonist, reversed the upregulation of NFL and phosphorylation of ERK1/2 and p38 induced by TCDD. This study demonstrated TCDD-induced upregulation of NFL in cultured neurons, with protein retained in the cell body. TCDD action was dependent on activation of AhR and MAPK, while crosstalk was found between these two signaling pathways.

Cell Chromatography-Based Screening of the Active Components in Buyang Huanwu Decoction Promoting Axonal Regeneration

Buyang Huanwu decoction (BHD), a popular formulation prescribed in traditional Chinese medicine (TCM) for the treatment of ischemic stroke, has been reported to have a potential role in promoting axonal regeneration. The purpose of the study was to screen and identify bioactive compounds from BHD using live PC12 cells coupled with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Using this approach, we successfully identified six bioactive components from BHD. These components have protective effects on oxygen-glucose deprivation/reperfusion (OGD/R) injury to PC12 cells. Furthermore, calycosin-7-d-glucoside (CG) and formononetin-7-O-β-d-glucoside (FG) could upregulate the protein expression of growth-associated protein 43 (GAP-43) and brain-derived neurotrophic factor (BDNF). This study suggests that living cells combined with HPLC-MS/MS can be used for the screening of active ingredients in TCMs.

Nobiletin alleviates cerebral ischemic-reperfusion injury via MAPK signaling pathway

BACKGROUND

Nobiletin (NOB), isolated from Citrus nobilis, has been reported to inhibit cerebral ischemia/reperfusion (I/R) induced cell apoptosis in the brain. The mechanisms and the protective ability of NOB on cerebral I/R rats are unclear.

METHODS

A middle cerebral artery occlusion (MCAO) rat model was established and treated with different doses of NOB. The neurological deficits, brain water content and brain index were explored after reperfusion, and TTC staining was applied to assess the infarct area. The production of reactive oxygen species (ROS) related enzymes in the ischemic cortex samples from each group was measured. TUNEL staining was performed to evaluate neuronal cell apoptosis in brain tissues. The expression of cell apoptosis related proteins, p-p38 and MAPKAP-2 and the levels of inflammatory factors were examined by western blotting assay and ELISA.

RESULTS

NOB treatment notably improved the neurological deficits, brain water content and brain index in an MCAO model, accompanied by decreased infarct area in the brain tissue. Apoptosis induced by cerebral I/R was also decreased by NOB administration via upregulating Bcl-2 and downregulating Bax and caspase3. The levels of pro-inflammatory mediators TNF-α, IL-6 were reduced and anti-inflammatory cytokine IL-10 was increased by NOB treatment in MCAO rats. Further, we found that the expression of p-p38 and MAPKAP-2 was reduced by NOB treatment in MCAO rats.

CONCLUSION

The present results suggest that NOB serves a protective role in I/R-induced cerebral-neuron injury. The mechanisms underlying these effects may be associated with the MAPK signaling pathway.

Elevated Neuroglobin Lessens Neuroinflammation and Alleviates Neurobehavioral Deficits Induced by Acute Inhalation of Combustion Smoke in the Mouse

Acute inhalation of combustion smoke produces long-term neurologic deficits in survivors. To study the mechanisms that contribute to the development of neurologic deficits and identify targets for prevention, we developed a mouse model of acute inhalation of combustion smoke, which supports longitudinal investigation of mechanisms that underlie the smoke induced inimical sequelae in the brain. Using a transgenic mouse engineered to overexpress neuroglobin, a neuroprotective oxygen-binding globin protein, we previously demonstrated that elevated neuroglobin preserves mitochondrial respiration and attenuates formation of oxidative DNA damage in the mouse brain after smoke exposure. In the current study, we show that elevated neuronal neuroglobin attenuates the persistent inflammatory changes induced by smoke exposure in the mouse brain and mitigates concordant smoke-induced long-term neurobehavioral deficits. Specifically, we found that increases in hippocampal density of GFAP and Iba-1 positive cells that are detected post-smoke in wild-type mice are absent in the neuroglobin overexpressing transgenic (Ngb-tg) mice. Similarly, the smoke induced hippocampal myelin depletion is not observed in the Ngb-tg mice. Importantly, elevated neuroglobin alleviates behavioral and memory deficits that develop after acute smoke inhalation in the wild-type mice. Taken together, our findings suggest that the protective effects exerted by neuroglobin in the brains of smoke exposed mice afford protection from long-term neurologic sequelae of acute inhalation of combustion smoke. Our transgenic mouse provides a tool for assessing the potential of elevated neuroglobin as possible strategy for management of smoke inhalation injury.

Dexmedetomidine protects hippocampal neurons against hypoxia/reoxygenation-induced apoptosis through activation HIF-1α/p53 signaling

PURPOSE

To observe the effect of dexmedetomidine (DEX) on mitochondrial apoptosis of hippocampal neurons in hypoxia/reoxygenation (H/R) brain injury in developing rats, and to investigate its regulatory mechanism on HIF-1α/p53 signaling pathway.

METHODS

Hypoxia/reoxygenation model was used in this study. TUNEL assay was performed to detect cell apoptosis. Immunohistochemical analysis and Western-blotting analysis were conducted to detect Cytochrome-C (Cyt-c), APAF-1, Caspase-3, Neuroglobin (Ngb), HIF-1α and p53 expression. After 28 days, Morris water maze (MWM) was performed.

RESULTS

50 μg/kg DEX improved H/R-induced brain injury and inhibited mitochondrial apoptosis in rats. Western-blotting and Immunohistochemical results demonstrated that DEX could up-regulate Ngb through α₂ receptor to inhibit H/R-induced mitochondrial apoptosis. In addition, by adding inhibitors yohimbine and 2-methoxyestradiol (2ME2), we found that DEX could activate HIF-1α/p53 signaling pathway. MWM test showed that DEX could enhance long-term learning and memory of H/R brain injury rats.

CONCLUSION

DEX alleviates H/R-induced brain injury and mitochondrial apoptosis in developing rats through α₂ receptor, which may be related to activation of HIF-1α/p53 signaling pathway to up-regulate the expression of Ngb.

The Neuroprotective Effect of Hemin and the Related Mechanism in Sevoflurane Exposed Neonatal Rats

Background

Many studies have reported that sevoflurane can increase neuronal apoptosis and result in cognitive deficits in rodents. Although neurotoxicity may be associated with mitochondrial dysfunction and oxidative stress, the exact mechanism remains unclear. In order to evaluate potential treatment therapies, we studied the effects of hemin on neurotoxicity of neonatal rat sevoflurane exposure.

Methods

Postnatal day (P) seven rats were assigned randomly to four groups; (1) group C: non-anesthesia, (2) group H: intraperitoneal hemin (50 mg kg^-1) treatment on days 5 and 6, (3) group S: 3% sevoflurane exposure for 4 h, and (4) group SH: hemin treatment + sevoflurane exposure. The expression of neuroglobin in neonatal hippocampus was determined by western blot and immunohistochemistry. Neuroglobin was localized by immunofluorescence. Western blot for the expression of cleaved caspase-3 and TUNEL were used to detect neonatal hippocampal apoptosis, and cytochrome c was used to evaluate mitochondrial function. Drp-1 and Mfn-2 immunoblotting were used to assess mitochondrial dynamics. The Morris water maze test was performed to detect cognitive function in the rats on P30.

Results

Exposure to sevoflurane increased the expression of cleaved caspase-3, cytochrome c, and Drp1 in the neonatal hippocampus and resulted in cognitive deficiency but decreased expression of Mfn2. Hemin reduced apoptosis, improved mitochondrial dynamics and ameliorated the cognitive impairment caused by sevoflurane exposure.

Conclusion

Hemin reduced neuronal apoptosis, improved mitochondrial dynamics and protected against cognitive deficits induced by sevoflurane in neonatal rats. This neuroprotective effect may be achieved by increasing the expression of neuroglobin.

Vitexin protects against ischemia/reperfusion-induced brain endothelial permeability

Brain endothelial permeability plays a crucial role in blood-brain barrier (BBB), but the permeability enhancement in cerebral ischemia reperfusion (I/R). Vitexin has certain neuroprotective effects, but the effect brain endothelial permeability in I/R injury was unknown. In this study, the effects of Vitexin on endothelial permeability and the underlying mechanisms in human brain microvascular endothelial cells (HBMEc) I/R injury model were investigated. Cell viability, lactate dehydrogenase (LDH), inflammation and apoptosis were detected. The effects of Vitexin on BBB integrity tight junction, matrix metalloproteinases (MMP) were also investigated. The mechanism was confirmed by PI3K inhibitor and NOS inhibitor in normal or eNOS siRNA transfection HBMEc. Vitexin significantly reduced LDH, Caspase 3 level, alleviated inflammation, also could maintain BBB integrity, increased tight junction proteins expression and inhibited MMP. The mechanism is related to reduction of intracellular NO and ONOO^-, regulated eNOS, iNOS activity. Vitexin significantly preserved eNOS phosphorylation in response to the activated Akt. Moreover, combined with PI3K inhibitor or low dosage of NOS inhibitor, totally abolished Vitexin-induced eNOS phosphorylation, the protected effect was also attenuated, but still significantly between model cells. However, combined with high dosage NOS inhibitor which both inhibited the eNOS phosphorylation and iNOS, the protected effect of Vitexin was abrogated. In addition, eNOS silencing cells were used to further clarify the regulatory role of Vitexin on iNOS. Our findings showed that Vitexin could play a protective role in I/R-induced brain endothelial permeability by simultaneously increase eNOS phosphorylation and inhibit iNOS.

Fucosterol exerts protection against amyloid β-induced neurotoxicity, reduces intracellular levels of amyloid β and enhances the mRNA expression of neuroglobin in amyloid β-induced SH-SY5Y cells

Alzheimer's disease (AD) is a neurodegenerative disease that leads to progressive loss of neurons which often results in deterioration of memory and cognitive function. The development of AD is highly associated with the formation of senile plaques and neurofibrillary tangles. Amyloid β (Aβ) induces neurotoxicity and contributes to the development of AD. Recent evidences also highlighted the importance of neuroglobin (Ngb) in ameliorating AD. This study assessed the ability of fucosterol, a phytosterol found in brown alga, in protecting SH-SY5Y cells against Aβ-induced neurotoxicity. Its effects on the mRNA levels of APP and Ngb as well as the intracellular Aβ levels were also determined in Aβ-induced SH-SY5Y cells. SH-SY5Y cells were exposed to fucosterol prior to Aβ treatment. The effect on apoptosis was determined using Annexin V FITC staining and mRNA expression was studied using RT-PCR. Flow cytometry confirmed the protective effects of fucosterol on SH-SY5Y cells against Aβ-induced apoptosis. Pretreatment with fucosterol increased the Ngb mRNA levels but reduced the levels of APP mRNA and intracellular Aβ in Aβ-induced SH-SY5Y cells. These observations demonstrated the protective properties of fucosterol against Aβ-induced neurotoxicity in neuronal cells.

Neuroglobin Regulates Wnt/β-Catenin and NFκB Signaling Pathway through Dvl1

Neuroglobin is an endogenous neuroprotective protein, but the underlying neuroprotective mechanisms remain to be elucidated. Our previous yeast two-hybrid screening study identified that Dishevelled-1, a key hub protein of Wnt/β-Catenin signaling, is an interaction partner of Neuroglobin. In this study, we further examined the role of Neuroglobin in regulating Dishevelled-1 and the downstream Wnt/β-Catenin and NFκB signaling pathway. We found that Neuroglobin directly interacts with Dishevelled-1 by co-immunoprecipitation, and the two proteins are co-localized in both cytoplasma and nucleus of SK-N-SH cells. Moreover, the ectopic expression of Neuroglobin promotes the degradation of exogenous and endogenous Dishevelled-1 through the proteasomal degradation pathway. Furthermore, our results showed that Neuroglobin significantly inhibits the luciferase activity of Topflash reporter and the expression of β-Catenin mediated by Dishevelled-1 in SK-N-SH cells. In addition, we also documented that Neuroglobin enhances TNF-α-induced NFκB activation via down-regulating Dishevelled-1. Finally, 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) assays showed that Neuroglobin is an important neuroprotectant that protects SK-N-SH cells from TNF-α-induced decrease in cell viability. Taken together, these findings demonstrated that Neuroglobin functions as an important modulator of the Wnt/β-Catenin and NFκB signaling pathway through regulating Dishevelled-1.