Neuroglobin-overexpressing transgenic mice are resistant to cerebral and myocardial ischemia

Role of orphan G-protein coupled receptors in tissue ischemia: A comprehensive review

Ischemic events lead to many diseases and deaths worldwide. Ischemia/reperfusion (I/R) occurs due to reduced blood circulation in tissues followed by blood reflow. Reoxygenation of ischemic tissues is characterized by oxidative stress, inflammation, energy distress, and endoplasmic reticulum stress. There are still no adequate clinical protocols or pharmacological approaches to address the consequences of I/R damage. G protein-coupled receptors (GPCRs) are important therapeutic targets. They compose a large family of seven transmembrane-spanning proteins that are involved in many biological functions. Orphan GPCRs are a large subgroup of these receptors expressed in different organs. In the present review, we summarized the literature regarding the role of orphan GPCRs in I/R in different organs. We focused on the effect of these receptors on modulating cellular and molecular processes underlying ischemia including apoptosis, inflammation, and autophagy. The study showed that GPR3, GPR4, GPR17, GPR30, GPR31, GPR35, GPR37, GPR39, GPR55, GPR65, GPR68, GPR75, GPR81, and GPR91 are involved in ischemic events, mainly in the brain and heart. These receptors offer new possibilities for treating I/R injuries in the body.

Controlled oxygen delivery to power tissue regeneration

Oxygen plays a crucial role in human embryogenesis, homeostasis, and tissue regeneration. Emerging engineered regenerative solutions call for novel oxygen delivery systems. To become a reality, these systems must consider physiological processes, oxygen release mechanisms and the target application. In this review, we explore the biological relevance of oxygen at both a cellular and tissue level, and the importance of its controlled delivery via engineered biomaterials and devices. Recent advances and upcoming trends in the field are also discussed with a focus on tissue-engineered constructs that could meet metabolic demands to facilitate regeneration.

Redox and spectroscopic properties of mammalian nitrite reductase-like hemoproteins

Besides the canonical pathway of L-arginine oxidation to produce nitric oxide (NO) in vivo, the nitrate-nitrite-NO pathway has been widely accepted as another source for circulating NO in mammals, especially under hypoxia. To date, there have been at least ten heme-containing nitrite reductase-like proteins discovered in mammals with activities mainly identified in vitro, including four globins (hemoglobin, myoglobin, neuroglobin (Ngb), cytoglobin (Cygb)), three mitochondrial respiratory chain enzymes (cytochrome c oxidase, cytochrome bc₁, cytochrome c), and three other heme proteins (endothelial nitric oxide synthase, cytochrome P450 and indoleamine 2,3-dioxygenase 1 (IDO1)). The pathophysiological functions of these proteins are closely related to their redox and spectroscopic properties, as well as their protein structure, although the physiological roles of Ngb, Cygb and IDO1 remain unclear. So far, comprehensive summaries of the redox and spectroscopic properties of these nitrite reductase-like hemoproteins are still lacking. In this review, we have mainly summarized the published data on the application of ultraviolet-visible, electron paramagnetic resonance, circular dichroism and resonance Raman spectroscopies, and X-ray crystallography in studying nitrite reductase-like activity of these 10 proteins, in order to sort out the relationships among enzymatic function, structure and spectroscopic characterization, which might help in understanding their roles in redox biology and medicine.

Distribution of Neuroglobin in Pericytes is Associated with Blood-Brain Barrier Leakage against Cerebral Ischemia in Mice

With emerging data on the various functions of neuroglobin (Ngb), such as neuroprotection and neurogenesis, we investigated the role of Ngb in the neurovascular unit (NVU) of the brain. To study the distribution and function of Ngb after cerebral ischemia, transient middle cerebral artery occlusion (tMCAO) was performed in mice. Brain immunostaining and fluorescence-activated cell sorting were used to analyze the role of Ngb according to the location and cell type. In normal brain tissue, it was observed that Ngb was distributed not only in neurons but also around the brain’s blood vessels. Interestingly, Ngb was largely expressed in platelet-derived growth factor receptor β (PDGFRβ)-positive pericytes in the NVU. After tMCAO, Ngb levels were significantly decreased in the core of the infarct, and Ngb and PDGFRβ-positive pericytes were detached from the vasculature. In contrast, in the penumbra of the infarct, PDGFRβ-positive pericytes expressing Ngb were increased compared with that in the core of the infarct. Moreover, the cerebral blood vessels, which have Ngb-positive PDGFRβ pericytes, showed reduced blood-brain barrier (BBB) leakage after tMCAO. It showed that Ngb-positive PDGFRβ pericytes stayed around the endothelial cells and reduced the BBB leakage in the NVU. Our results indicate that Ngb may play a role in attenuating BBB leakage in part by its association with PDGFRβ. In this study, the distribution and function of Ngb in the pericytes of the cerebrovascular system have been elucidated, which contributes to the treatment of stroke through a new function of Ngb.

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.

Neuroglobin Is Involved in the Hypoxic Stress Response in the Brain

Neuroglobin is an oxygen-binding heme protein expressed predominantly in the brain. Despite many years of research, the exact distribution and expression of neuroglobin in the neocortical development and under mild hypoxia stress still remain unclear. Therefore, we aim to explore the expression of neuroglobin during neocortex expansion and under mild hypoxia stress in vivo. We used Kunming mice to examine the expression of Ngb protein during neocortex expansion. In addition, we analyzed the density of Ngb-positive neural stem cells using the Image-Pro PLUS (v.6) computer software program (Media Cybernetics, Inc.). Our data indicated that the density of the neuroglobin-positive neurons in mice cerebral cortex displayed a downward trend after birth compared with high expression of neuroglobin in a prenatal period. Similarly, we identified that neurons were capable of ascending neuroglobin levels in response to mild hypoxic stress compared with the no intervention group. These findings suggest that neuroglobin behaves as a compensatory protein regulating oxygen provision in the process of neocortical development or under physiological hypoxia, further contributing to the discovery of novel therapeutic methods for neurological disorders, which is clinically important.

Human Galectin-7 Gene LGALS7 Promoter Sequence Polymorphisms and Risk of Spontaneous Intracerebral Hemorrhage: A Prospective Study

Background and purpose

Despite evidence for the role of genetic factors in stroke, only a small proportion of strokes have been clearly attributed to monogenic factors, due to phenotypic heterogeneity. The goal of this study was to determine whether a significant relationship exists between human galectin-7 gene LGALS7 promoter region polymorphisms and the risk of stroke due to non-traumatic intracerebral hemorrhage (ICH).

Methods

This two-stage genetic association study included an initial exploratory stage followed by a discovery stage. During the exploratory stage, transgenic galectin-7 mice or transgenic mice with the scrambled sequence of the hairpin structure –silenced down gene LGALS7—were generated and then expressed differentially expressed proteins and galectin-7-interacting proteins were identified through proteomic analysis. During the discovery stage, a single-nucleotide polymorphism (SNP) genotyping approach was used to determine associations between 2 LGALS7 SNPs and ICH stroke risk for a cohort of 24 patients with stroke of the Chinese Han population and 70 controls.

Results

During the exploratory phase, LGALS7 expression was found to be decreased in TGLGALS–DOWN mice as compared to its expression in TGLGALS mice. During the discovery phase, analysis of LGALS7 sequences of 24 non-traumatic ICH cases and 70 controls led to the identification of 2 ICH susceptibility loci: a genomic region on 19q13.2 containing two LGALS7 SNPs, rs567785577 and rs138945880, whereby the A allele of rs567785577 and the T allele of rs138945880 were associated with greater risk of contracting ICH [for T and A vs. C and G, unadjusted odds ratio (OR) = 13.5; 95% CI = 2.249–146.5; p = 0.002]. This is the first study to genotype the galectin-7 promoter in patients with hemorrhagic stroke. Genotype and allele association tests and preliminary analysis of patients with stroke revealed that a single locus may be a genetic risk factor for hemorrhagic stroke.

Conclusion

A and T alleles of two novel SNP loci of 19q13.2, rs567785577 and rs138945880, respectively, were evaluated for associations with susceptibility to ICH. Further studies with expanded case numbers that include subjects of other ethnic populations are needed to elucidate mechanisms underlying associations between these SNPs and ICH risk.

Biological Implications of a Stroke Therapy Based in Neuroglobin Hyaluronate Nanoparticles. Neuroprotective Role and Molecular Bases

Exogenous neuroprotective protein neuroglobin (Ngb) cannot cross the blood-brain barrier. To overcome this difficulty, we synthesized hyaluronate nanoparticles (NPs), able to deliver Ngb into the brain in an animal model of stroke (MCAO). These NPs effectively reached neurons, and were microscopically identified after 24 h of reperfusion. Compared to MCAO non-treated animals, those treated with Ngb-NPs showed survival rates up to 50% higher, and better neurological scores. Tissue damage improved with the treatment, but no changes in the infarct volume or in the oxidative/nitrosative values were detected. A proteomics approach (p-value < 0.02; fold change = 0.05) in the infarcted areas showed a total of 219 proteins that significantly changed their expression after stroke and treatment with Ngb-NPs. Of special interest, are proteins such as FBXO7 and NTRK2, which were downexpressed in stroke, but overexpressed after treatment with Ngb-NPs; and ATX2L, which was overexpressed only under the effect of Ngb. Interestingly, the proteins affected by the treatment with Ngb were involved in mitochondrial function and cell death, endocytosis, protein metabolism, cytoskeletal remodeling, or synaptic function, and in regenerative processes, such as dendritogenesis, neuritogenesis, or sinaptogenesis. Consequently, our pharmaceutical preparation may open new therapeutic scopes for stroke and possibly for other neurodegenerative pathologies.

The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity

Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.

Overexpression of Neuroglobin Promotes Energy Metabolism and Autophagy Induction in Human Neuroblastoma SH-SY5Y Cells

Neuroglobin (NGB) is an O₂-binding globin mainly expressed in the central and peripheral nervous systems and cerebrospinal fluid. Previously, it was demonstrated that NGB overexpression protects cells from hypoxia-induced death. To investigate processes promoted by NGB overexpression, we used a cellular model of neuroblastoma stably overexpressing an NGB-FLAG construct. We used a proteomic approach to identify the specific profile following NGB overexpression. To evaluate the role of NGB overexpression in increasing energetic metabolism, we measured oxygen consumption rate (OCR) and the extracellular acidification rate through Seahorse XF technology. The effect on autophagy induction was evaluated by analyzing SQSTM1/p62 and LC3-II expression. Proteomic analysis revealed several differentially regulated proteins, involved in oxidative phosphorylation and integral mitochondrial proteins linked to energy metabolism. The analysis of mitochondrial metabolism demonstrated that NGB overexpression increases mitochondrial ATP production. Indeed, NGB overexpression enhances bioenergetic metabolism, increasing OCR and oxygen consumption. Analysis of autophagy induction revealed an increase of LC3-II together with a significant decrease of SQSTM1/p62, and NGB-LC3-II association during autophagosome formation. These results highlight the active participation of NGB in several cellular processes that can be upregulated in response to NGB overexpression, playing a role in the adaptive response to stress in neuroblastoma cells.

Structural and (Pseudo-)Enzymatic Properties of Neuroglobin: Its Possible Role in Neuroprotection

Neuroglobin (Ngb), the third member of the globin family, was discovered in human and murine brains in 2000. This monomeric globin is structurally similar to myoglobin (Mb) and hemoglobin (Hb) α and β subunits, but it hosts a bis-histidyl six-coordinated heme-Fe atom. Therefore, the heme-based reactivity of Ngb is modulated by the dissociation of the distal HisE7-heme-Fe bond, which reflects in turn the redox state of the cell. The high Ngb levels (~100–200 μM) present in the retinal ganglion cell layer and in the optic nerve facilitate the O₂ buffer and delivery. In contrast, the very low levels of Ngb (~1 μM) in most tissues and organs support (pseudo-)enzymatic properties including NO/O₂ metabolism, peroxynitrite and free radical scavenging, nitrite, hydroxylamine, hydrogen sulfide reduction, and the nitration of aromatic compounds. Here, structural and (pseudo-)enzymatic properties of Ngb, which are at the root of tissue and organ protection, are reviewed, envisaging a possible role in the protection from neuronal degeneration of the retina and the optic nerve.

Carbon Monoxide-Neuroglobin Axis Targeting Metabolism Against Inflammation in BV-2 Microglial Cells

Microglia are the immune competent cell of the central nervous system (CNS), promoting brain homeostasis and regulating inflammatory response against infection and injury. Chronic or exacerbated neuroinflammation is a cause of damage in several brain pathologies. Endogenous carbon monoxide (CO), produced from the degradation of heme, is described as anti-apoptotic and anti-inflammatory in several contexts, including in the CNS. Neuroglobin (Ngb) is a haemoglobin-homologous protein, which upregulation triggers antioxidant defence and prevents neuronal apoptosis. Thus, we hypothesised a crosstalk between CO and Ngb, in particular, that the anti-neuroinflammatory role of CO in microglia depends on Ngb. A novel CO-releasing molecule (ALF826) based on molybdenum was used for delivering CO in microglial culture.BV-2 mouse microglial cell line was challenged with lipopolysaccharide (LPS) for triggering inflammation, and after 6 h ALF826 was added. CO exposure limited inflammation by decreasing inducible nitric oxide synthase (iNOS) expression and the production of nitric oxide (NO) and tumour necrosis factor-α (TNF-α), and by increasing interleukine-10 (IL-10) release. CO-induced Ngb upregulation correlated in time with CO's anti-inflammatory effect. Moreover, knocking down Ngb reversed the anti-inflammatory effect of CO, suggesting that dependents on Ngb expression. CO-induced Ngb upregulation was independent on ROS signalling, but partially dependent on the transcriptional factor SP1. Finally, microglial cell metabolism is also involved in the inflammatory response. In fact, LPS treatment decreased oxygen consumption in microglia, indicating a switch to glycolysis, which is associated with a proinflammatory. While CO treatment increased oxygen consumption, reverting LPS effect and indicating a metabolic shift into a more oxidative metabolism. Moreover, in the absence of Ngb, this phenotype was no longer observed, indicating Ngb is needed for CO's modulation of microglial metabolism. Finally, the metabolic shift induced by CO did not depend on alteration of mitochondrial population. In conclusion, neuroglobin emerges for the first time as a key player for CO signalling against exacerbated inflammation in microglia.

Neuroglobin in Retinal Neurodegeneration: A Potential Target in Therapeutic Approaches

Retinal neurodegeneration affects an increasing number of people worldwide causing vision impairments and blindness, reducing quality of life, and generating a great economic challenge. Due to the complexity of the tissue, and the diversity of retinal neurodegenerative diseases in terms of etiology and clinical presentation, so far, there are no cures and only a few early pathological markers have been identified. Increasing efforts have been made to identify and potentiate endogenous protective mechanisms or to abolish detrimental stress responses to preserve retinal structure and function. The discovering of the intracellular monomeric globin neuroglobin (NGB), found at high concentration in the retina, has opened new possibilities for the treatment of retinal disease. Indeed, the NGB capability to reversibly bind oxygen and its neuroprotective function against several types of insults including oxidative stress, ischemia, and neurodegenerative conditions have raised the interest in the possible role of the globin as oxygen supplier in the retina and as a target for retinal neurodegeneration. Here, we provide the undercurrent knowledge on NGB distribution in retinal layers and the evidence about the connection between NGB level modulation and the functional outcome in terms of retinal neuroprotection to provide a novel therapeutic/preventive target for visual pathway degenerative disease.

Regulatory role of microRNA-320 during off-pump coronary artery bypass grafting with dexmedetomidine adjunct anesthesia

The present study investigated the effects of dexmedetomidine on the expression level of microRNA-320 (miR-320) and neuroglobin (NGB) in patients undergoing off-pump coronary artery bypass grafting (OPCABG). A total of 40 patients undergoing OPCABG were recruited and randomly divided into the dexmedetomidine and normal saline groups (treated before anesthesia), respectively. The NGB levels in the blood samples before and after surgery were analyzed and compared. The CATH.a cells were cultured and induced with dexmedetomidine, and the NGB expression level was detected. CATH.a cells were treated with NGB and lipopolysaccharide (LPS), and the cell survival rate was determined. The miR-320 expression levels in the blood samples and dexmedetomidine-induced cells were detected. Dual-luciferase reporter assay was performed. Compared with control subjects, patients in the dexmedetomidine group had higher NGB levels in the blood. In the CATH.a cells, the dexmedetomidine treatment upregulated the NGB levels. Moreover, upon pre-incubation with NGB and LPS stimulation, dexmedetomidine elevated cell viability. Furthermore, miR-320 expression levels were significantly downregulated in the blood of patients in the dexmedetomidine group, as well as in the dexmedetomidine-induced cells. Dual-luciferase reporter assay confirmed that miRNA-320a directly targeted on NGB, and upregulated miRNA-320a in CATH.a cells decreased cell proliferation activity. Pre-administration of dexmedetomidine can decrease miR-320 expression level in the blood of patients undergoing OPCABG, stimulating the high expression of NGB and increasing the proliferation activity of neuronal cells, which may decrease the postoperative cognitive impairment.

The role of globins in cardiovascular physiology

Globin proteins exist in every cell type of the vasculature, from erythrocytes to endothelial cells, vascular smooth muscle cells, and peripheral nerve cells. Many globin subtypes are also expressed in muscle tissues (including cardiac and skeletal muscle), in other organ-specific cell types, and in cells of the central nervous system. The ability of each of these globins to interact with molecular oxygen (O₂) and nitric oxide (NO) is preserved across these contexts. Endothelial α-globin is an example of extra-erythrocytic globin expression. Other globins, including myoglobin, cytoglobin, and neuroglobin are observed in other vascular tissues. Myoglobin is observed primarily in skeletal muscle and smooth muscle cells surrounding the aorta or other large arteries. Cytoglobin is found in vascular smooth muscle but can also be expressed in non-vascular cell types, especially in oxidative stress conditions after ischemic insult. Neuroglobin was first observed in neuronal cells, and its expression appears to be restricted mainly to the central and peripheral nervous systems. Brain and central nervous system neurons expressing neuroglobin are positioned close to many arteries within the brain parenchyma and can control smooth muscle contraction and, thus, tissue perfusion and vascular reactivity. Overall, reactions between NO and globin heme-iron contribute to vascular homeostasis by regulating vasodilatory NO signals and scaveging reactive species in cells of the mammalian vascular system. Here, we discuss how globin proteins affect vascular physiology with a focus on NO biology, and offer perspectives for future study of these functions.

Neuroglobin: A New Possible Marker of Estrogen-Responsive Breast Cancer

The expression of the α-subtype of Estrogen Receptor (ERα) characterizes most breast cancers (more than 75%), for which endocrine therapy is the mainstay for their treatment. However, a high percentage of ERα+ breast cancers are de novo or acquired resistance to endocrine therapy, and the definition of new targets for improving therapeutic interventions and the prediction of treatment response is demanding. Our previous data identified the ERα/AKT/neuroglobin (NGB) pathway as a common pro-survival process activated in different ERα breast cancer cell lines. However, no in vivo association between the globin and the malignity of breast cancer has yet been done. Here, we evaluated the levels and localization of NGB in ERα+ breast ductal carcinoma tissue of different grades derived from pre-and post-menopausal patients. The results indicate a strong association between NGB accumulation, ERα, AKT activation, and the G3 grade, while no association with the menopausal state has been evidenced. Analyses of the data set (e.g., GOBO) strengthen the idea that NGB accumulation could be linked to tumor cell aggressiveness (high grade) and resistance to treatment. These data support the view that NGB accumulation, mainly related to ER expression and tumor grade, represents a compensatory process, which allows cancer cells to survive in an unfavorable environment.

RNA-Seq analysis of knocking out the neuroprotective proton-sensitive GPR68 on basal and acute ischemia-induced transcriptome changes and signaling in mouse brain

Brain acid signaling plays important roles in both physiological and disease conditions. One key neuronal metabotropic proton receptor in the brain is GPR68, which contributes to hippocampal long-term potentiation (LTP) and mediates neuroprotection in acidotic and ischemic conditions. Here, to gain greater understanding of GPR68 function in the brain, we performed mRNA-Seq analysis in mice. First, we studied sham-operated animals to determine baseline expression. Compared to wild type (WT), GPR68-/- (KO) brain downregulated genes that are enriched in Gene Ontology (GO) terms of misfolding protein binding, response to organic cyclic compounds, and endoplasmic reticulum chaperone complex. Next, we examined the expression profile following transient middle cerebral artery occlusion (tMCAO). tMCAO-upregulated genes cluster to cytokine/chemokine-related functions and immune responses, while tMCAO-downregulated genes cluster to channel activities and synaptic signaling. For proton-sensitive receptors, tMCAO downregulated ASIC1a and upregulated GPR4 and GPR65, but had no effect on ASIC2, PAC, or GPR68. GPR68 deletion did not alter the expression of these proton receptors, either at baseline or after ischemia. Lastly, we performed GeneVenn analysis of differential genes at baseline and post-tMCAO. Ischemia upregulated the expression of three hemoglobin genes, along with H2-Aa, Ppbp, Siglece, and Tagln, in WT but not in KO. Immunostaining showed that tMCAO-induced hemoglobin localized to neurons. Western blot analysis further showed that hemoglobin induction is GPR68-dependent. Together, these data suggest that GPR68 deletion at baseline disrupts chaperone functions and cellular signaling responses and imply a contribution of hemoglobin-mediated antioxidant mechanism to GPR68-dependent neuroprotection in ischemia.

Neuroglobin and mitochondria: The impact on neurodegenerative diseases

Dysfunctional mitochondria have severe consequences on cell functions including Reactive Oxygen Specie (ROS) generation, alteration of mitochondrial signaling, Ca²⁺ buffering, and activation of apoptotic pathway. These dysfunctions are closely linked with degenerative diseases including neurodegeneration. The discovery of neuroglobin (NGB) as an endogenous neuroprotective protein, which effects seem to depend on its mitochondrial localization, could drive new therapeutic strategies against aged-related neurodegenerative diseases. Indeed, high levels of NGB are active against several brain injuries, including neurodegeneration, hypoxia, ischemia, toxicity, and nutrient deprivation opening a new scenario in the comprehension of the relationship between neural pathologies and mitochondrial homeostasis. In this review, we provide the current understanding of the role of mitochondria in neurodegeneration and discuss structural and functional connection between NGB and mitochondria with the purpose of defining a novel mitochondrial-based neuroprotective mechanism(s).

The potential of mitochondrial modulation by neuroglobin in treatment of neurological disorders

Neuroglobin is the third member of the globin family to be identified in 2000 in neurons of both human and mouse nervous systems. Neuroglobin is an oxygen-binding globin found in neurons within the central nervous system as well as in peripheral neurons, that produces a protective effect against hypoxic/ischemic damage induced by promoting oxygen availability within the mitochondria. Numerous investigations have demonstrated that impaired neuroglobin functioning is implicated in the pathogenesis of multiple neurodegenerative disorders. Several in vitro and animal studies have reported the potential of neuroglobin upregulation in improving the neuroprotection through modulation of mitochondrial functions, such as ATP production, clearing reactive oxygen species (ROS), promoting the dynamics of mitochondria, and controlling apoptosis. Neuroglobin acts as a stress-inducible globin, which has been associated hypoxic/ischemic insults where it acts to protect the heart and brain, providing a wide range of applicability in the treatment of human disorders. This review article discusses normal physiological functions of neuroglobin in mitochondria-associated pathways, as well as outlining how dysregulation of neuroglobin is associated with the pathogenesis of neurodegenerative disorders.

Neuroprotective effect of intermittent hypobaric hypoxia preconditioning on cerebral ischemia/reperfusion in rats

BACKGROUND

Ischemic tolerance is an endogenous protective mechanism in organs or tissues undergoing one or more short-term sublethal ischemias. Intermittent hypobaric hypoxia preconditioning (IHHP) can induce tolerance and thus protect brain tissues from cerebral ischemic injury (CIR). The current study evaluated the neuroprotective effect of IHHP.

METHODS

The established xenograft model was divided into the ischemia/reperfusion (I/R), IHHP, IHHP+I/R, and sham groups. Transmission electron microscopy was used to observe alterations in neuron ultrastructure. Neuron damage was detected using Nissl staining. Western blot and qRT-PCR were used to evaluate the relative expression of genes and proteins related to apoptosis. Immunohistochemistry was used to determine the expression of proteins involved in the processes of neuroprotection and repair.

RESULTS

Our results indicated that the damage to the neurons, organelles, and axons was significantly less following ischemia/reperfusion and intermittent hypobaric hypoxia reconditioning treatment than that in the ischemia/reperfusion group. Compared to the ischemia/reperfusion group, significant downregulation of pro-apoptotic gene/protein expressions along with upregulation of anti-apoptotic and nerve regeneration gene/protein expressions in the IHHP+I/R group were observed.

CONCLUSION

IHHP can significantly reduce ischemia/reperfusion injury in rat brain nerves and promote nerve repair.

Dexmedetomidine Mediates Neuroglobin Up-Regulation and Alleviates the Hypoxia/Reoxygenation Injury by Inhibiting Neuronal Apoptosis in Developing Rats

Background

Exploring the effective therapy for neonatal hypoxic-ischemic brain injury is an important goal. This study was designed to investigate how dexmedetomidine (DEX) contribute to hypoxic brain injury.

Methods

Developing Sprague-Dawley rat models of hypoxia/reoxygenation (H/R) injury were constructed to simulate neonatal hypoxic brain injury for DEX treatment. Immunohistochemistry and western blot were performed to measure neuroglobin (Ngb) protein expression in hippocampal tissues. Hippocampal neuron injury and apoptosis were detected by Nissl staining and TUNEL assay, respectively. A Morris water maze (MWM) test was performed to evaluate the long-term learning and memory function.

Results

The expression of Ngb was increased following H/R model establishment and up-regulated by medium and high doses of DEX, but not up-regulated by low doses of DEX. Medium and high doses of DEX alleviated the H/R injury as well as induced the reduction of Nissl bodies and apoptosis. Besides, medium and high doses of DEX down-regulated cytosolic Cyt-c, Apaf-1, and caspase-3 in H/R injury model. MWM test showed that medium and high doses of DEX significantly shortened the escape latency and enhanced the number of platform crossings. However, low doses of DEX have no effect on Nissl bodies, mitochondrial apoptosis, expression of apoptosis-related proteins and long-term learning functions.

Conclusions

DEX induced Ngb expression in H/R rat models. The neuroprotection of DEX-mediated Ngb up-regulation may be achieved by inhibiting neuronal apoptosis through the mitochondrial pathway. Findings indicated that DEX may be useful as an effective therapy for neonatal hypoxic brain injury.

Lessons from the post-genomic era: Globin diversity beyond oxygen binding and transport

Vertebrate hemoglobin (Hb) and myoglobin (Mb) were among the first proteins whose structures and sequences were determined over 50 years ago. In the subsequent pregenomic period, numerous related proteins came to light in plants, invertebrates and bacteria, that shared the myoglobin fold, a signature sequence motif characteristic of a 3-on-3 α-helical sandwich. Concomitantly, eukaryote and bacterial globins with a truncated 2-on-2 α-helical fold were discovered. Genomic information over the last 20 years has dramatically expanded the list of known globins, demonstrating their existence in a limited number of archaeal genomes, a majority of bacterial genomes and an overwhelming majority of eukaryote genomes. In vertebrates, 6 additional globin types were identified, namely neuroglobin (Ngb), cytoglobin (Cygb), globin E (GbE), globin X (GbX), globin Y (GbY) and androglobin (Adgb). Furthermore, functions beyond the familiar oxygen transport and storage have been discovered within the vertebrate globin family, including NO metabolism, peroxidase activity, scavenging of free radicals, and signaling functions. The extension of the knowledge on globin functions suggests that the original roles of bacterial globins must have been enzymatic, involved in defense against NO toxicity, and perhaps also as sensors of O₂, regulating taxis away or towards high O₂ concentrations. In this review, we aimed to discuss the evolution and remarkable functional diversity of vertebrate globins with particular focus on the variety of non-canonical expression sites of mammalian globins and their according impressive variability of atypical functions.

Insight into the molecular sex dimorphism of ischaemic stroke in rat cerebral cortex: Focus on neuroglobin, sex steroids and autophagy

Including sex is of paramount importance in preclinical and clinical stroke researches, and molecular studies dealing in depth with sex differences in stroke pathophysiology are needed. To gain insight into the molecular sex dimorphism of ischaemic stroke in rat cerebral cortex, male and female adult rats were subjected to transient middle cerebral artery occlusion. The expression of neuroglobin (Ngb) and other functionally related molecules involved in sex steroid signalling (oestrogen and androgen receptors), steroidogenesis (StAR, TSPO and aromatase) and autophagic activity (LC3B-II/LC3B-I ratio, UCP2 and HIF-1α) was assessed in the ipsilateral ischaemic and contralateral non-ischaemic hemispheres. An increased expression of Ngb was detected in the injured female cerebral cortex. In contrast, increased expression of oestrogen receptor α, GPER, StAR, TSPO and UCP2, and decreased androgen receptor expression were detected in the injured male cortex. In both sexes, the ischaemic insult induced an upregulation of LC3B-II/-I ratio, indicative of increased autophagy. Therefore, the cerebral cortex activates both sex-specific and common molecular responses with neuroprotective potential after ischaemia-reperfusion, which globally results in similar stroke outcome in both sexes. Nonetheless, these different potential molecular targets should be taken into account when neuroprotective drugs aiming to reduce brain damage in ischaemic stroke are investigated.

Negative surface charges in neuroglobin modulate the interaction with cytochrome c

Neuroglobin is a heme protein present in the nervous system cells of mammals and other organisms. Although cytoprotective effects of neuroglobin on neuronal damage have been reported, the physiological mechanisms of neuroglobin function remain unknown. In recent years, a role for neuroglobin as a reductant for extramitochondrial cytochrome c has been proposed. According to this hypothesis, cytoplasmic neuroglobin can interact with cytochrome c released from the mitochondria and reduce its heme group to the ferrous state, thus preventing cytochrome c-dependent assembly of the apoptosome. The interaction of neuroglobin and cytochrome c has been studied by surface plasmon resonance techniques and molecular dynamics, however the empirical evidence on the specific residues of neuroglobin and cytochrome c involved in the interaction is scarce and indirect. This study analyzes the role of five negatively charged residues in the neuroglobin surface putatively involved in the interaction with cytochrome c - Glu60, Asp63, Asp73, Glu 87 and Glu151 - by site-directed mutagenesis. Characterization of the electron transfer between neuroglobin mutants and cytochrome c indicates that Asp73 is critical for the interaction, and Glu60, Asp63 and Glu87 also contribute to the neuroglobin-cytochrome c interaction. Based on the results, structures and binding surfaces for the neuroglobin-cytochrome c complex compatible with the experimental observations are proposed. These data can guide further studies on neuroglobin function and its involvement in cytochrome c signaling cascades.

Mn-TAT PTD-Ngb attenuates oxidative injury by an enhanced ROS scavenging ability and the regulation of redox signaling pathway

Neurological diseases have a close relationship to excessive reactive oxygen species (ROS). Neuroglobin (Ngb), an intrinsic protective factor, protected cells from hypoxic/ischemic injury. In the present, we reported a novel neuroprotective manganese porphyrin reconstituted metal protein, Mn-TAT PTD-Ngb, consisting of a HIV Tat protein transduction domain sequence (TAT PTD) attached to the N-terminal of apo-Ngb. Mn-TAT PTD-Ngb had a stronger ROS scavenging ability than that of TAT PTD-Ngb, and reduced intracellular ROS production and restored the function of the mitochondria and inhibited the mitochondria-dependent apoptosis. Besides, Mn-TAT PTD-Ngb activated the phosphoinositide-3 kinase (PI3K)/Akt signaling pathway, which up-regulated the expression of nuclear factor E2-related factor 2 (Nrf2), Heme oxygenase-1 (HO-1), superoxide dismutase (SOD), catalase (CAT). The results showed that the redox chemistry of Mn-TAT PTD-Ngb and redox regulation of multiple signaling pathways attenuated the oxidative injury.

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.

Neuroglobin: A Novel Player in the Oxidative Stress Response of Cancer Cells

Reactive oxygen species (ROS) result from intracellular aerobic metabolism and/or extracellular stimuli. Although endogenous antioxidant systems exquisitely balance ROS production, an excess of ROS production, commonly found in diverse human degenerative pathologies including cancer, gives rise to the oxidative stress. Increased oxidative stress in cancer is related to the sustained proliferation and metabolism of cancer cells. However, cancer cells show an intrinsic higher antioxidant capacity with respect to the normal counterpart as well as an ability to cope with oxidative stress-induced cell death by establishing mechanisms of adaptation, which define a selective advantage against the adverse oxidative stress environment. The identification of survival factors and adaptive pathways, set up by cancer cells against oxidative stress, provides multiple targets for the therapeutic intervention against cancer. Neuroglobin (NGB), a globin primarily described in neurons as an oxidative stress sensor and cytoprotective factor against redox imbalance, has been recently recognized as a novel tumor-associated protein. In this review, the involvement of NGB in the cancer cell adaptation and resistance to oxidative stress will be discussed highlighting the globin role in the regulation of both the stress-induced apoptotic pathway and antioxidant systems activated by cancer cells.

Neuroglobin Expression Models as a Tool to Study Its Function

Neuroglobin (Ngb) is an evolutionary conserved member of the globin family with a primary expression in neurons of which the exact functions remain elusive. A plethora of in vivo and in vitro model systems has been generated to this day to determine the functional biological roles of Ngb. Here, we provide a comprehensive overview and discussion of the different Ngb models, covering animal and cellular models of both overexpression and knockout strategies. Intriguingly, an in-depth literature search of available Ngb expression models revealed crucial discrepancies in the outcomes observed in different models. Not only does the level of Ngb expression—either physiologically, overexpressed, or downregulated—alter its functional properties, the experimental setup, being in vitro or in vivo, does impact the functional outcome as well and, hence, whether or not a physiological and/or therapeutic role is ascribed to Ngb. These differences could highlight either technical or biological adaptations and should be considered until elucidation of the Ngb biology.

Evaluation of neuroglobin and cytoglobin expression in adult rats exposed to silver nanoparticles during prepubescence

Silver nanoparticles (AgNPs) are clusters of silver atoms with diameters that range from 1 to 100 nm. Due to the various shapes and large surface areas, AgNPs have been employed in the food and textile industries and medical fields. Therefore, because of the widespread use of these compounds, the aim of this study was to evaluate the effect of AgNP exposure on the gene and protein expression levels of Neuroglobin (Ngb) and Cytoglobin (Cygb), in the rat cortex, hippocampus and cerebellum. Post-natal day (PND) 21 male Wistar rats were randomly divided into three groups. One group received 15 μg/kg body weight of AgNP by gavage another group received 30 μg/kg and the control group that received saline, from PND23 to PND58. On PND102 the animals were euthanized and the cortex, hippocampus and cerebellum were isolated and evaluated for gene and protein expression levels of Nbg and Cygb. The results demonstrated that the 30 μg/kg AgNP group displayed increased gene and protein expression of Cygb in the cortex. In the Hippocampus, AgNP exposure did not modulate gene or protein expression levels of Ngb and Cygb. In cerebellum the Ngb gene and protein expression was increased with both doses of AgNP. AgNP exposure during prepubescence can modulate the gene and protein expression levels of Ngb and Cygb in adulthood. Furthermore, the observed modulation was specific to the cerebellum, and cortex, and was dose dependent.

Regulatory effect of neuroglobin in the recovery of spinal cord injury

OBJECTIVE

The present study was aimed to investigate the therapeutic potential of neuroglobin in the recovery of spinal cord injury.

METHODS

The male albino Wistar strain rats were used as an experimental model, and adeno associated virus (AAV) was administered in the T12 section of spinal cord ten days prior to the injury. Basso Beattie Bresnahan (BBB) locomotor rating scale was used to determine the recovery of the hind limb during four weeks post-operation. Malondialdehyde (MDA), catalase and superoxide dismutase (SOD) were determined in the spinal cord tissues. Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) assay was carried out to determine the presence of apoptotic cells. Immunofluorescence analysis was carried out to determine the neuroglobin expression. Western blot analysis was carried out to determine the protein expressions of caspase-3, cytochrome c, bax and bcl-2 in the spinal cord tissues.

RESULTS

Experimental results showed that rats were recovered from the spinal cord injury due to increased neuroglobin expression. Lipid peroxidation was reduced, whereas catalase and SOD activity were increased in the spinal cord tissues. Apoptosis and lesions were significantly reduced in the spinal cord tissues. Caspase-3, cytochrome c and bax levels were significantly reduced, whereas bcl-2 expression was reduced in the spinal cord tissues.

CONCLUSION

Taking all these data together, it is suggested that the increased neuroglobin expression could improve the locomotor function.

Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation

Nitric oxide (NO) is a small free radical with critical signaling roles in physiology and pathophysiology. The generation of sufficient NO levels to regulate the resistance of the blood vessels and hence the maintenance of adequate blood flow is critical to the healthy performance of the vasculature. A novel paradigm indicates that classical NO synthesis by dedicated NO synthases is supplemented by nitrite reduction pathways under hypoxia. At the same time, reactive oxygen species (ROS), which include superoxide and hydrogen peroxide, are produced in the vascular system for signaling purposes, as effectors of the immune response, or as byproducts of cellular metabolism. NO and ROS can be generated by distinct enzymes or by the same enzyme through alternate reduction and oxidation processes. The latter oxidoreductase systems include NO synthases, molybdopterin enzymes, and hemoglobins, which can form superoxide by reduction of molecular oxygen or NO by reduction of inorganic nitrite. Enzymatic uncoupling, changes in oxygen tension, and the concentration of coenzymes and reductants can modulate the NO/ROS production from these oxidoreductases and determine the redox balance in health and disease. The dysregulation of the mechanisms involved in the generation of NO and ROS is an important cause of cardiovascular disease and target for therapy. In this review we will present the biology of NO and ROS in the cardiovascular system, with special emphasis on their routes of formation and regulation, as well as the therapeutic challenges and opportunities for the management of NO and ROS in cardiovascular disease.

Cognitive Deficits Are Attenuated in Neuroglobin Overexpressing Mice Exposed to a Model of Obstructive Sleep Apnea

Background: Obstructive sleep apnea (OSA) is a highly prevalent disease manifesting as intermittent hypoxia during sleep (IH) and is increasingly recognized as being independently associated with neurobehavioral deficits. These deficits may be due to increased apoptosis in the hippocampus and cerebral cortex, as well as increased oxidative stress and inflammation. It has been reported that neuroglobin (Ngb) is upregulated in response to hypoxia-ischemia insults and exhibits a protective role in ischemia-reperfusion brain injury. We hypothesized that transgenic overexpression of Ngb would attenuate spatial learning deficits in a murine model of OSA.

Methods:Wild-type mice and Ngb overexpressing male mice (Ngb-TG) were randomly assigned to either IH or room air (RA) exposures. The effects of IH during the light period on performance in a water maze spatial task were assessed, as well as anxiety and depressive-like behaviors using elevated plus maze (EPM) and forced swim tests. Cortical tissues from all the mice were extracted for biochemical studies for lipid peroxidation.

Results:Ngb TG mice exhibited increased Ngb immunoreactivity in brain tissues and IH did not elicit significant changes in Ngb expression in either Ngb-TG mice or WT mice. On a standard place training task in the water maze, Ngb-TG mice displayed preserved spatial learning, and were protected from the reduced spatial learning performances observed in WT mice exposed to IH. Furthermore, anxiety and depression levels were enhanced in WT mice exposed to IH as compared to RA controls, while alterations emerged in Ngb-TG mice exposed to IH. Furthermore, WT mice, but not Ngb-TG mice had significantly elevated levels of malondialdehyde in cortical lysates following IH exposures.

Conclusions:In a murine model of OSA, oxidative stress responses and neurocognitive and behavioral impairments induced by IH during sleep are attenuated by the neuroprotective effects of Ngb.

Neuroglobin as a Novel Biomarker for Predicting Poor Outcomes in Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

Neuroglobin (Ngb) has a high affinity for oxygen and helps prevent hypoxic-ischemic brain damage. In this study we analyzed the relationship between Ngb levels and clinical outcomes of aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

Serum Ngb levels were measured in 58 patients with aSAH and 27 control individuals using the enzyme-linked immunosorbent assay. To continuously assess aSAH, we measured serum Ngb levels on days 1, 2, 3, 5, and 7 after aSAH. Clinical data were collected using the Hunt and Hess Scale, the Glasgow Coma Scale (GCS), the World Federation of Neurological Surgeons (WFNS) Scale, and the modified Fisher Scale. Clinical outcomes included 6-month mortality and 6-month unfavorable outcomes (modified Rankin Scale (mRS) score of 3-6).

RESULTS

Serum Ngb levels increased after aSAH, peaked on day 2, and then gradually decreased. Serum Ngb levels on admission were higher in the patient group than in the control group (7.67 ± 2.56 ng/mL vs. 6.45 ± 0.88 ng/mL, P < 0.05). Multivariate logistic regression analysis indicated that serum Ngb levels on day 2 after aSAH were independently related to 6-month mortality (odds ratio [OR] = 0.265, 95% confidence interval [CI] = 0.094-0.747, P < 0.05) and 6-month unfavorable outcomes (OR = 1.919, 95% CI = 1.158-3.180, P < 0.05), and receiver operating characteristic curve analysis showed that serum Ngb levels on day 2 predicted 6-month mortality and 6-month unfavorable outcomes, with areas under the curve of 0.893 (P < 0.05; 95% CI, 0.812-0.974) and 0.818 (P < 0.05; 95% CI, 0.691-0.954), respectively, based on the best thresholds.

CONCLUSIONS

Serum Ngb levels on day 2 after aSAH were strongly associated with poor outcomes in aSAH, suggesting that Ngb may be a novel biomarker for predicting poor outcomes in aSAH.

Compensatory role of Neuroglobin in nervous and non-nervous cancer cells in response to the nutrient deprivation

Environmental factors or adverse growth conditions that may reduce cell function or viability are considered stress. The cell ability to sense and respond to environmental stresses determine its function and survival destiny. We recently defined Neuroglobin (NGB), a heme-protein, as a compensatory protein in the 17β-Estradiol (E2) anti-apoptotic activity and as a sensor of oxidative stress in both neurons and breast cancer cells. Here, the possibility that NGB levels could represent a pivotal regulator of integrated response of cancer cells to stress has been evaluated. Data obtained in neuroblastoma and in breast cancer cell lines evidence that nutrient deprivation significantly up-regulated NGB levels at different time points. However, the analysis of autophagy activation led to exclude any possible role of stress- or E2-induced NGB in the upstream regulation of general autophagy. However, the over-expression of Flag-NGB in ERα stable transfected HEK-293 cells completely affects nutrient deprivation-induced decrease in cell number. In addition, reported results indicate that modulation of the anti-apoptotic Bcl-2 level may play a key role in the protective NGB function against energetic stress. Overall, these data define a role of NGB as compensatory protein in the cell machinery activated in response to stress and as general stress adaptation marker of cancer cells susceptible to oxidative stress, oxygen and, as demonstrated here for the first time, even to nutrient willingness. Despite the lacking of any direct NGB role on autophagic flux activated by energetic stress, NGB upregulation appears functional in delaying stress-related cell death allowing an appropriate cell response and adaptation to the changing extracellular conditions.

Cytoprotective effects of transgenic neuroglobin overexpression in an acute and chronic mouse model of ischemic heart disease

Neuroglobin (NGB) is an oxygen-binding protein that is mainly expressed in nervous tissues where it is considered to be neuroprotective during ischemic brain injury. Interestingly, transgenic mice overexpressing NGB reveal cytoprotective effects on tissues lacking endogenous NGB, which might indicate a therapeutic role for NGB in a broad range of ischemic conditions. In the present study, we investigated the effect of NGB overexpression on survival as well as on the size and occurrence of myocardial infarctions (MI) in a mouse model of acute MI (AMI) and a model of advanced atherosclerosis (ApoE ^-/- Fbn1 ^C1039G+/- mice), in which coronary plaques and MI develop in mice being fed a Western-type diet. Overexpression of NGB significantly enhanced post-AMI survival and reduced MI size by 14% 1 week after AMI. Gene expression analysis of the infarction border showed reduction of tissue hypoxia and attenuation of hypoxia-induced inflammatory pathways, which might be responsible for these beneficial effects. In contrast, NGB overexpression did not affect survival or occurrence of MI in the atherosclerotic mice although the incidence of coronary plaques was significantly reduced. In conclusion, NGB proved to act cytoprotectively during MI in the acute setting while this effect was less pronounced in the atherosclerosis model.

Chimeric ZHHH neuroglobin acts as a cell membrane-penetrating inducer of neurite outgrowth

Neuroglobin (Ngb) is a heme protein expressed in the vertebrate brain. We previously engineered a chimeric Ngb protein, in which module M1 of human Ngb is replaced by that of zebrafish Ngb, and showed that the chimeric ZHHH Ngb has a cell membrane-penetrating activity similar to that of zebrafish Ngb and also rescues cells from death caused by hypoxia/reoxygenation as does human Ngb. Recently, it was reported that overexpression of mammalian Ngb in neuronal cells induces neurite outgrowth. In this study, we performed neurite outgrowth assays of chimeric Ngb using rat pheochromocytoma PC12 cells. Addition of chimeric Ngb, but not human or zebrafish Ngb, exogenously to the cell medium induces neurite outgrowth. On the other hand, the K7A/K9Q chimeric Ngb double mutant, which cannot translocate into cells, did not induce neurite outgrowth, suggesting that the cell membrane-penetrating activity of the chimeric Ngb is crucial for its neurite outgrowth-promoting activity. We also prepared several site-directed chimeric Ngb mutants and demonstrated that residues crucial for neurite outgrowth-inducing activity of the chimeric Ngb are not exactly the same as those for its neuroprotective activity.

Evaluation of globins expression in brain, heart, and lung in rats exposed to side stream cigarette smoke

The side stream cigarette smoke (SSCS) is a contributing factor in the pathogenesis of cigarette smoking-induced toxicity. Hemoglobin (Hb), myoglobin (Mb), neuroglobin (Ngb), and cytoglobin (Cygb) are globins with different distributions and functions in the tissues and have similar actions by providing O₂ (oxygen) for respiratory chain, detoxification of ROS and nitric oxide (NO), and protect tissues against irreversible lesions. We aimed to investigate the effects of SSCS exposure on gene and protein expression of Ngb, Cygb, and Mb in different tissue. The Ngb and Cygb gene and protein expression in the cerebral cortex increased after 1 week of rat exposure to SSCS. In hippocampus, the Ngb gene and protein expression increased after 1 week or more of exposure and no change was observed in Cygb gene and protein expression. In myocardium, Mb and Cygb gene expression increased at 1 and 4 weeks of exposure, while protein expression of both increased at 1, 2, 3, and 4 weeks. In lung, observed an increase in Cygb gene and protein expression after 2, 3, and 4 weeks of exposure. The findings suggest that SSCS modulates Ngb, Cygb, and Mb in central and peripheral tissue © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1252-1261, 2017.

Clinical significance of changes in serum neuroglobin and HIF-1α concentrations during the early-phase of acute ischemic stroke

BACKGROUND

Neuroglobin (NGB) has been described as a neuroprotective agent in cerebral ischemia, hypoxia inducible factor (HIF) has shown an important role in modulating hypoxic and ischemic injury, and therefore they have the potential to impact outcomes after acute ischemic stroke (AIS). Thus, we investigated early changes in the concentrations of serum NGB and HIF-1α after AIS and evaluated the relations of both NGB and HIF-1α to stroke severity and prognosis.

METHODS

We prospectively measured the serum concentrations of NGB and HIF-1α in 40 patients with AIS at 24, 48, 72, and 96h after stroke. Correlation combined with infarct size and National Institutes of Health Stroke Scale (NIHSS) score of the patients was analyzed. Receiver operating characteristic (ROC) curve was used to appraise their value in predicting the 90-day outcome after AIS.

RESULTS

Serum NGB concentrations increased and peaked at 72h after AIS, whereas serum concentrations of HIF-1α increased for 48h. Peak serum NGB concentration correlated significantly with both infarct size (R²=0.484, p<0.001) and admission NIHSS score (R²=0.578, p<0.001), while serum HIF-1α concentration was only correlated to a patient's infarct size (R²=0.394, p<0.001). ROC curve analysis suggested that the serum NGB concentration had a significantly better predictive power for poor outcome.

CONCLUSIONS

NGB level increased in serum after AIS accompanied by increases in serum HIF-1α, and was suggested as a predictor of stroke severity and poor prognosis.

Neuroglobin, a Factor Playing for Nerve Cell Survival

Cell death represents the final outcome of several pathological conditions of the central nervous system and available evidence suggests that in both acute injuries and neurodegenerative diseases it is often associated with mitochondrial dysfunction. Thus, the possibility to prevent mitochondrial events involved in cell death might represent efficient tools to limit neuronal damage. In recent years, increased attention has been paid to the endogenous protein neuroglobin, since accumulating evidence showed that its high expression was associated with preserved mitochondrial function and to an increased survival of nerve cells in vitro and in vivo in a variety of experimental models of cell insult. The biological and structural features of neuroglobin and the mitochondria-related mechanisms of neuroglobin-induced neuroprotection will be here briefly discussed. In this respect, the inhibition of the intrinsic pathway of apoptosis emerges as a key neuroprotective effect induced by the protein. These findings could open the possibility to develop efficient neuroglobin-mediated therapeutic strategies aimed at minimizing the neuronal cell death occurring in impacting neurological pathologies like stroke and neurodegenerative diseases.

Brain globins in physiology and pathology

Globins are globular proteins for either transport or storage of oxygen which are critical for cellular metabolism. Four globins have been identified in rodent and human brains. Among them, neuroglobin, cytoglobin and hemoglobin chains are constitutively expressed in normal brain, while myoglobin is only expressed in some neurological disorders. Studies on the molecular structure, expression and functional features of these brain globins indicated that they may play crucial roles in maintenance of neural cell survival and activity, including neurons and astrocytes. Their regulation in neurological disorders may help thoroughly understand initiation and progression of ischemia, Alzheimer's disease and glioma, etc. Elucidation of the brain globin functions might remarkably improve medical strategies that sustain neurological homeostasis and treat neurological diseases. Here the expression pattern and functions of brain globins and their involvement in neurological disorders are reviewed.

Limb remote ischemic per-conditioning in combination with post-conditioning reduces brain damage and promotes neuroglobin expression in the rat brain after ischemic stroke

Purpose: Limb remote ischemic per-conditioning or post-conditioning has been shown to be neuroprotective after cerebral ischemic stroke. However, the effect of combining remote per-conditioning with post-conditioning on ischemic/reperfusion injury as well as the underlying mechanisms are largely unexplored.

Methods: Here, adult male Sprague Dawley rats were subjected to middle cerebral artery occlusion (MCAO). The limb ischemic stimulus was immediately applied after onset of focal ischemia (per-conditioning), followed by repeated short episodes of remote ischemia 24 hr after reperfusion (post-conditioning). The infarct volume, motor function, and the expression of neuroglobin (Ngb) were measured at different durations after reperfusion.

Results: We found that a single episode of limb remote per-conditioning afforded short-term protection, but combining repeated remote post-conditioning during the 14 days after reperfusion significantly ameliorated cerebral ischemia/reperfusion injury. Interestingly, we also found that ischemic per- and post-conditioning significantly increased expression of Ngb, an oxygen-binding globin protein that has been demonstrated to be neuroprotective against stroke, at peri-infarct regions from day 1 to day 14 following ischemia/reperfusion.

Conclusion: Our results suggest that the conventional per-conditioning combined with post-conditioning may be used as a novel neuroprotective strategy against ischemia-reperfusion injury, and Ngb seems to be one of the important players in limb remote ischemia-mediated neuroprotection.

Rutin-encapsulated chitosan nanoparticles targeted to the brain in the treatment of Cerebral Ischemia

OBJECTIVE

Rutin, a potent antioxidant, has been reported to reduce the risk of ischemic disease. Our study aims to prepare rutin-encapsulated-chitosan nanoparticles (RUT-CS-NPs) via ionic gelation method and determine its results, based on different parameters i.e. surface morphology characterization, in-vitro or ex-vivo release, dynamic light scattering and differential scanning calorimetry (DSC), for treating cerebral ischemia.

METHODS

UPLC-ESI-Q-TOF-MS/MS was used to evaluate the optimized RT-CS-NPs1 for brain-drug uptake as well as to follow-up the pharmacokinetics, bio-distrbution, brain-targeting efficiency and potential after intranasal administration (i.n.).

KEY FINDINGS

A particle size of <100nm for the formulation, significantly affected by drug:CS ratio, and entrapment efficiency and loading capacity of 84.98%±4.18% and 39.48%±3.16%, respectively were observed for RUT. Pharmacokinetics, bio-distribution, brain-targeting efficiency (1443.48±39.39%) and brain drug-targeting potential (93.00±5.69%) showed enhanced bioavailability for RUT in brain as compared to intravenous administration. In addition; improved neurobehavioral activity, histopathology and reduced infarction volume effects were observed in middle cerebral artery occlusion (MCAO) induced cerebral ischemic rats model after i.n. administration of RUT-CS-NPs.

CONCLUSION

A significant role of mucoadhesive-RT-CS-NPs1 as observed after high targeting potential and efficiency of the formulation prove; RUT-CS-NPs are more effectively accessed and target easily the brain.

Identification of residues crucial for the interaction between human neuroglobin and the α-subunit of heterotrimeric Gi protein

Mammalian neuroglobin (Ngb) protects neuronal cells under conditions of oxidative stress. We previously showed that human Ngb acts as a guanine nucleotide dissociation inhibitor (GDI) for the α-subunits of heterotrimeric Gi/o proteins and inhibits the decrease in cAMP concentration, leading to protection against cell death. In the present study, we used an eukaryotic expression vector driving high-level expression of human wild-type Ngb or Ngb mutants that either exhibit or lack GDI activities in human cells. We demonstrate that the GDI activity of human Ngb is tightly correlated with its neuroprotective activity. We further demonstrate that Glu53, Glu60, and Glu118 of human Ngb are crucial for both the neuroprotective activity and interaction with Gαi1. Moreover, we show that Lys46, Lys70, Arg208, Lys209, and Lys210 residues of Gαi1 are important for binding to human Ngb. We propose a molecular docking model of the complex between human Ngb and Gαi1.