Effect of Globin Digests on Physical Fatigue in Mice.

Globin digest (GD) inhibits dietary hypertriglyceridemia; however, its effects on physical fatigue remain unknown. Therefore, this study aimed to investigate the potential anti-fatigue effects of GD. Repeated administration of GD and valine (Val)-Val-tyrosine (Tyr)-proline (Pro), a component of GD, for five days prevented the forced walking-induced decrease in locomotion. Furthermore, GD treatment reversed the forced walking-induced increase in blood lactate levels in mice and increased phosphorylated AMP-activated protein kinase (p-AMPK) in the soleus muscle, suggesting that the anti-fatigue effect of GD involves AMPK activation in the soleus muscle through reduced blood lactate.

Neuroglobin promotes the proliferation and suppresses the apoptosis of glioma cells by activating the PI3K/AKT pathway.

Our previous study demonstrated that neuroglobin (Ngb) functions as an independent predictive indicator of the prognosis of patients with glioma and promotes cancer cell growth by suppressing apoptosis. However, the understanding of the mechanisms underlying the survival­enhancing function of Ngb in glioma is limited. In the present study, KEGG PathwayFinder by gene correlation analysis was performed on the R2: Genomics Analysis and Visualization Platform, which revealed a high association between Ngb and the phosphatidylinositol 3­kinase (PI3K)/AKT pathway using glioma data (GSE4290) from the Gene Expression Omnibus database. Furthermore, western blotting experiments were performed in U251 and U87 glioma cells, and Ngb knockdown using short hairpin RNA reduced the protein levels of phosphorylated (p)­AKT, p­mammalian target of rapamycin (mTOR) and antiapoptotic factor Bcl­2, and increased the expression of the proapoptotic protein Bcl­2­associated X, in U251 cells. In addition, Ngb overexpression promoted the activation of the PI3K/AKT pathway in U87 cells. MK2206, a PI3K/AKT signaling inhibitor, reduced the expression of p­AKT and increased the levels of apoptosis­associated proteins, including cleaved poly(ADP­ribose) polymerase 1 and cleaved caspase­3/7/8, in Ngb­overexpressing U87 cells. Furthermore, MK2206 treatment reduced the proliferation and induced the apoptosis of Ngb­overexpressing U87 cells, as indicated by the results of MTT, colony formation and flow cytometry assays. In addition, insulin­like growth factor­1, a PI3K/AKT signaling activator, reversed Ngb knockdown­induced growth arrest and apoptosis in U251 cells. In conclusion, the results of the present study indicate that Ngb may facilitate a malignant phenotype of glioma cells by activating the PI3K/AKT pathway.

Protective effects of recombinant human cytoglobin against chronic alcohol-induced liver disease in vivo and in vitro.

Alcoholic liver disease (ALD) is an important worldwide public health issue with no satisfying treatment available since now. Here we explore the effects of recombinant human cytoglobin (rhCygb) on chronic alcohol-induced liver injury and the underlying mechanisms. In vivo studies showed that rhCygb was able to ameliorate alcohol-induced liver injury, significantly reversed increased serum index (ALT, AST, TG, TC and LDL-C) and decreased serum HDL-C. Histopathology observation of the liver of rats treated with rhCygb confirmed the biochemical data. Furthermore, rhCygb significantly inhibited Kupffer cells (KCs) proliferation and TNF-α expression in LPS-induced KCs. rhCygb also inhibited LPS-induced NADPH oxidase activity and ROS, NO and O2•- generation. These results collectively indicate that rhCygb exert the protective effect on chronic alcohol-induced liver injury through suppression of KC activation and oxidative stress. In view of its anti-oxidative stress and anti-inflammatory features, rhCygb might be a promising candidate for development as a therapeutic agent against ALD.

Self-fluorescent drug delivery vector based on genipin-crosslinked polyethylenimine conjugated globin nanoparticle.

A kind of self-fluorescent, biocompatible, and low-toxic Genipin crosslinked Globin-PEI nanoparticle (Gb-G-PEI NP) with high enzymolysis-stability and photo-stability was synthesized successfully. The properties of the Gb-G-PEI NP were characterized, including its particle size, surface zeta potential, morphology, paclitaxel (PTX) loading capacity and release. The Gb-G-PEI NPs as imaging probe were investigated by Confocal Laser Scanning Microscope (CLSM) in vitro and by fluorescence imaging system in vivo. Cell imaging results showed that the tumor cell line (HepG-2) had the faster cell uptake rate and metabolism rate than the normal cell line (L-O2), this difference showed its tumor selectivity. MTT assay revealed that the PTX-loaded Gb-G-PEI NPs showed almost the equal potence to tumor cell HepG-2 as the free PTX at the same PTX concentration, while a lower cytotoxicity to normal cell L-O2, suggesting its promising utilization as a drug delivery system. The imaging on mice demonstrated the possibility of the self-fluorescent Gb-G-PEI NPs as probe in vivo. So Gb-G-PEI NPs can be potentially utilized as both tracking marker and tumor cell selective drug delivery system in the biomaterial field.

Neuroglobin protects astroglial cells from hydrogen peroxide-induced oxidative stress and apoptotic cell death.

Oxidative stress, resulting from accumulation of reactive oxygen species, plays a critical role in astroglial cell death occurring in diverse neuropathological conditions. Numerous studies indicate that neuroglobin (Ngb) promotes neuron survival, but nothing is known regarding the action of Ngb in astroglial cell survival. Thus, the purpose of this study was to investigate the potential glioprotective effect of Ngb on hydrogen peroxide (H2 O2 )-induced oxidative stress and apoptosis in cultured mouse astrocytes. Incubation of cells with subnanomolar concentrations of Ngb (10-14 -10-10  M) was found to prevent both H2 O2 -evoked reduction in surviving cells number and accumulation of reactive oxygen species in a concentration-dependent manner. Furthermore, Ngb treatment abolishes H2 O2 -induced increase in mitochondrial oxygen consumption rates. Concomitantly, Ngb treatment rescues H2 O2 -associated reduced expression of endogenous antioxidant enzymes (superoxide dismutases and catalase) and prevents the stimulation of the expression of pro-inflammatory genes (inducible nitric oxide synthase, cyclooxygenase-2, and interleukin (IL) IL-6 and IL-33). Moreover, Ngb blocks the stimulation of Bax (pro-apoptotic) and the inhibition of Bcl-2 (anti-apoptotic) gene expression induced by H2 O2 , which in turn abolishes caspase 3 activation. The protective effect of Ngb upon H2 O2 induced activation of caspase 3 activity and cell death can be accounted for by activation of protein kinase A and mitogen-activated protein kinase transduction cascade. Finally, we demonstrate that Ngb increases Akt phosphorylation and prevents H2 O2 -provoked inhibition of ERK and Akt phosphorylation. Taken together, these data demonstrate for the first time that Ngb is a glioprotective agent that prevents H2 O2 -induced oxidative stress and apoptotic astroglial cell death. Protection of astrocytes from oxidative insult may thus contribute to the neuroprotective effect of Ngb.

The Effect of rhCygb on CCl4-Induced Hepatic Fibrogenesis in Rat.

This study aims to investigate whether the use of recombinant human cytoglobin (rhCygb) impact on hepatic fibrogenesis caused by CCl4. SD (n = 150) rats were randomly divided into three groups of normal, CCl4 model and rhCygb groups. After model establishment, rats in rhCygb groups were administered daily with rhCygb (2 mg/kg, s.c.). Histological lesions were staged according to metavir. Serum parameters including ALT, AST, HA, LN, Col III and Col IV were determined. The liver proteins were separated by 2-DE and identified. As a result, the stage of hepatic damage and liver fibrosis in rhCygb groups were significantly milder than that in CCl4 model groups. Meanwhile, rhCygb dramatically reversed serum levels of ALT and AST, and also markedly decreased the liver fibrosis markers levels of LN, HA, Col III and Col IV. In 2-DE, 33 proteins among three groups with the same changing tendency in normal and rhCygb treated groups compared with CCl4 model group were identified. GO analysis showed that several identified proteins involved in oxidative stress pathway. The study provides new insights and data for administration of rhCygb reversing CCl4-induced liver fibrosis suggesting that rhCygb might be used in the treatment of liver fibrosis.

Enhanced hepatic targeting, biodistribution and antifibrotic efficacy of tanshinone IIA loaded globin nanoparticles.

Tanshinone IIA (TA) has been recently used to treat liver diseases. However, the poor water solubility and fast metabolism obstruct TA in to be used for the treatment of liver diseases. To overcome this, TA was encapsulated into globin to form nanoparticles (TA-Gb-NPs) by our self-assembling method. We evaluated their biodistribution, pharmacokinetics, targeting ability to liver and antifibrotic effects. As a result, TA-Gb-NPs had a good hepatic targeting ability and achieved higher concentration and longer retention in liver than tanshinone IIA suspension (TA-S). Compared with TA-S, TA-Gb-NPs significantly improved serum biochemical parameters in thioacetamide (TAA) induced liver fibrosis mouse model. Furthermore, histological analysis of mouse liver slices revealed that TA-Gb-NPs could markedly reduce the fibrosis scores and attenuate the progression of the hepatic fibrosis. In conclusion, the TA-Gb-NPs may be a good candidate for the treatment of hepatic fibrosis.

Combination of mild hypothermia with neuroprotectants has greater neuroprotective effects during oxygen-glucose deprivation and reoxygenation-mediated neuronal injury.

Co-treatment of neuroprotective reagents may improve the therapeutic efficacy of hypothermia in protecting neurons during ischemic stroke. This study aimed to find promising drugs that enhance the neuroprotective effect of mild hypothermia (MH). 26 candidate drugs were selected based on different targets. Primary cultured cortical neurons were exposed to oxygen-glucose deprivation and reoxygenation (OGD/R) to induce neuronal damage, followed by either single treatment (a drug or MH) or a combination of a drug and MH. Results showed that, compared with single treatment, combination of MH with brain derived neurotrophic factor, glibenclamide, dizocilpine, human urinary kallidinogenase or neuroglobin displayed higher proportion of neuronal cell viability. The latter three drugs also caused less apoptosis rate in combined treatment. Furthermore, co-treatment of those three drugs and MH decreased the level of reactive oxygen species (ROS) and intracellular calcium accumulation, as well as stabilized mitochondrial membrane potential (MMP), indicating the combined neuroprotective effects are probably via inhibiting mitochondrial apoptosis pathway. Taken together, the study suggests that combined treatment with hypothermia and certain neuroprotective reagents provide a better protection against OGD/R-induced neuronal injury.

Ferric human neuroglobin scavenges superoxide to form oxy adduct.

Neuroglobin (Ngb) is the third member of the vertebrate globin family, and the structure was solved as a typical globin fold with a b-type heme. Although it has been proposed that Ngb could be involved in neuroprotection against oxidative stress, the protective mechanism has not been fully identified yet. In order to clarify functions under hypoxic condition, in this study, we focused on the scavenger activity of human Ngb (hNgb) against superoxide. The activity of hNgb for superoxide was evaluated to be 7.4 µM for IC50, the half maximal inhibitory concentration. The result indicates that hNgb can be an anti-oxidant, and the value was almost the same as that of ascorbic acid. In addition, we characterized oxidation states of a heme iron in superoxide-treated hNgb with spectroscopic measurements. Superoxide-treated hNgb in the ferric form was readily converted to the oxygenated ferrous form, and the result suggested that ferric hNgb could scavenge superoxide by change of an oxidation state in a heme iron. Moreover, mutational experiments were performed, and the each variant mutated at 46 and 55 positions suggested a disulfide bond between Cys46 and Cys55 could be essential to be sensors for oxidative stress with the direct binding of superoxide. As a consequence, we concluded that redox changes of the heme iron and the disulfide bond could regulate neuroprotective functions of hNgb, and it suggests that hNgb can afford protection against hypoxic and ischemic stress in the brain.

Neuroprotective effect of TAT PTD-Ngb fusion protein on primary cortical neurons against hypoxia-induced apoptosis.

Hypoxic-ischemic injury increases neuroglobin (Ngb) expression in the brain. In our previous study, we have generated a transactivator-of-transcription protein-transduction domain-neuroglobin fusion protein (TAT PTD-Ngb) that successfully mediated exogenous Ngb expression in the primary neurons. In this study, we further investigated the role of TAT PTD-Ngb in protecting neurons against hypoxia-induced apoptosis and explored the possible mechanism. The primary cultured neurons were divided into four groups: (1) the normal group (no hypoxic injury); (2) the vehicle group (vehicle treatment and hypoxia injury); (3) the TAT PTD-Ngb group (TAT PTD-Ngb treatment and hypoxia injury); and (4) the Ngb group (Ngb treatment and hypoxia injury). Translocation of TAT PTD-Ngb into neurons was detected using fluorescent immunostaining against His-tag as early as 30 min after incubation. MTT assay showed that the TAT PTD-Ngb group had significantly increased cell viability compared to the vehicle or Ngb group after hypoxia. The result of transmission electron microscopy (TEM) also displayed rescued ultrastructure in TAT PTD-Ngb neurons compared to that of apoptotic neurons. In addition, TAT PTD-Ngb neurons showed significantly increased expression of anti-apoptotic Bcl-2 protein and decreased activities of caspase-3 and caspase-9 in response to hypoxia. These results suggest that TAT PTD-Ngb fusion protein protects primary cortical neurons against hypoxia-induced injury possibly through suppressing mitochondria apoptotic pathway.

The effect of globin scaffold on osteoblast adhesion and phenotype expression in vitro.

PURPOSE: Different synthetic and natural biomaterials have been used in bone tissue regeneration. However, several limitations are associated with the use of synthetic as well as allogenous or xenogenous natural materials. This study evaluated, in an in vitro model, the behavior of rat osteoblastic cells cultured on a human globin scaffold. MATERIALS AND METHODS: Rat osteoblastic cells were isolated from the calvaria of 21-day-old fetal Sprague-Dawley rats. They were then grown in the presence of globin. Real-time polymerase chain reaction (RT-PCR) was performed to study the expression of cyclin D1, integrin Β1, Msx2, Dlx5, Runx2, and osteocalcin on days 1, 5, and 9. Moreover, alkaline phosphatase activity was measured on days 1, 3, 5, and 7. Alizarin red staining was performed on day 9 to observe calcium deposition. RESULTS: Cells were able to adhere, proliferate, and differentiate on globin scaffolds. Moreover, RT-PCR showed that globin may stimulate some key genes of osteoblastic differentiation (Runx2, osteocalcin, Dlx5). Globin had an inhibitory effect on alkaline phosphatase activity. Calcium deposits were seen after 9 days of culture. CONCLUSIONS: These results indicate that purified human globin might be a suitable scaffold for bone tissue regeneration.

Neuroglobin upregulation offers neuroprotection in traumatic brain injury.

OBJECTIVES: The aim of this study was to investigate rat neuroglobin (rNGB) expression level after traumatic brain injury (TBI) and further study its neuroprotective effects in TBI when it was overexpressed in adenoviral vector. METHODS: The Wistar rats (280-320 g) were divided into control, 12 and 36 hours after TBI groups (n = 3) and their TBI model was established. Subsequently, NGB expression level was examined by Western blot and immunohistochemical. Beyond that, adenoviral vectors pAdEasy-rNGB-GFP and pAdEasy-GFP were constructed and transfected into the rat brain respectively (pAdEasy-GFP was control), and the neuroprotective effects were examined by immunohistochemical. RESULTS: Immunohistochemical and Western blot results demonstrated that NGB expression level was increased at 12 and 36 hours after TBI injury compare with control. Meanwhile, the pAdEasy-rNGB-GFP transfected rats suffered less necrosis and apoptosis compare to control. CONCLUSIONS: NGB was upregulated in TBI and overexpressed rNGB had a significant neuroprotection in TBI. However, the mechanism remained unknown. This study suggested that rNGB overexpression may be a new strategy for treating of TBI.

Ligand binding, reactivity and biological activity of a distal pocket mutant of neuroglobin.

We have generated the Lys67Glu mutant form of neuroglobin. Experimental spectral studies are consistent with a six coordinate heme in which the distal histidine bond is stretched compared to the wild type protein. Carbon monoxide binding to the ferrous form of the mutant follows a hyperbolic concentration dependence limiting at the histidine dissociation rate of 0.7 s(-1). Further analysis indicates a significantly lowered histidine binding constant. Oxygen binding kinetic studies confirm the higher heme ligand dissociation level and indicate a p50 value for oxygen binding<1 mmHg. The ferrous form of the protein yields an oxygenated intermediate on reaction with oxygen. The rate of oxidation, by oxygen, follows a complex concentration dependence, consistent with the presence of two distinct oxidation mechanisms. A quantitative model for the two oxidation processes has been developed, which is consistent with a lowered distal histidine binding constant in the mutant form of the protein. These data suggest that the protein structure surrounding the heme site in neuroglobin limits access to external ligands and provides an energy barrier to the structural changes following ligand binding in this protein. However, the mutation does not appear to affect reactivity with cytochrome c and the anti-apoptotic activity of the mutant in human cells of neuronal origin is increased as compared to the wild type protein.

[A preliminary study of anti-aging and wound healing of recombination cytoglobin].

In this paper, the preliminary study on antioxidant, enhancement of antioxidant enzymes activity, reducing the content of oxygen free radicals, delaying skin aging of the recombination cytoglobin (rCygb) purified by our lab were investigated through human keratinocyte cell line (HaCAT) H2O2 oxidative stress model, mouse skin aging model caused by continuous subcutaneous injection D-gal, rat acute liver injury model induced by CCl4 and rat skin wound healing model. The results showed that rCygb improved the activities of total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px) and catalase (CAT), reduced the activities of lactate dehydrogenase (LDH) and alanine aminotransferase (ALT) as well as decreased the content of malondialdehyde (MDA). Skin biopsy showed that rCygb promoted angiogenesis, increased expression of collagen and improved the anti-inflammatory ability. All results displayed that rCygb improved the oxygen free radical scavenging ability, delayed skin aging and promoted wound healing.

Protection from intracellular oxidative stress by cytoglobin in normal and cancerous oesophageal cells.

Cytoglobin is an intracellular globin of unknown function that is expressed mostly in cells of a myofibroblast lineage. Possible functions of cytoglobin include buffering of intracellular oxygen and detoxification of reactive oxygen species. Previous work in our laboratory has demonstrated that cytoglobin affords protection from oxidant-induced DNA damage when over expressed in vitro, but the importance of this in more physiologically relevant models of disease is unknown. Cytoglobin is a candidate for the tylosis with oesophageal cancer gene, and its expression is strongly down-regulated in non-cancerous oesophageal biopsies from patients with TOC compared with normal biopsies. Therefore, oesophageal cells provide an ideal experimental model to test our hypothesis that downregulation of cytoglobin expression sensitises cells to the damaging effects of reactive oxygen species, particularly oxidative DNA damage, and that this could potentially contribute to the TOC phenotype. In the current study, we tested this hypothesis by manipulating cytoglobin expression in both normal and oesophageal cancer cell lines, which have normal physiological and no expression of cytoglobin respectively. Our results show that, in agreement with previous findings, over expression of cytoglobin in cancer cell lines afforded protection from chemically-induced oxidative stress but this was only observed at non-physiological concentrations of cytoglobin. In addition, down regulation of cytoglobin in normal oesophageal cells had no effect on their sensitivity to oxidative stress as assessed by a number of end points. We therefore conclude that normal physiological concentrations of cytoglobin do not offer cytoprotection from reactive oxygen species, at least in the current experimental model.

Neuroglobin attenuates Alzheimer-like tau hyperphosphorylation by activating Akt signaling.

Neuroglobin (Ngb) is a recently identified member of hemoglobin family, distributed mainly in central and peripheral nervous systems. Recent studies suggest that Ngb can protect neural cells from ß-amyloid-induced toxicity in Alzheimer disease (AD). Hyperphosphorylation of tau is another characterized pathological hallmark in the AD brains; however, it is not reported whether Ngb also affects tau phosphorylation. In this study, we found that the level of Ngb was significantly reduced in Tg2576 mice (a recognized mouse model of AD) and TgMAPt mice, and the level of Ngb was negatively correlated with tau phosphorylation. Over-expression of Ngb attenuates tau hyperphosphorylation at multiple AD-related sites induced by up-regulation of glycogen synthase kinase-3ß (GSK-3ß), a crucial tau kinase. While Ngb activates Akt and thus inhibits GSK-3ß, simultaneously inhibition of Akt abolishes the effects of Ngb on GSK-3ß inhibition and tau hyperphosphorylation. Our data indicate that Ngb may attenuate tau hyperphosphorylation through activating Akt signaling pathway, implying a therapeutic target for AD.

[Role of cytoglobin in protecting hepatic stellate cells against oxidation induced damage].

The aim of this study was to reveal the protection role and the related mechanism of cytoglobin on the oxidation induced hepatic stellate cell damage. We applied siRNA to interfere the endogenous cytoglobin gene, used recombinant cytoglobin protein to treat the completely activated human hepatic stellate cell line LX-2 and the incompletely activated primary rat hepatic stellate cells, or over-expressed cytoglobin protein in LX-2 cells. We used two different oxidative-stress related models, the hydrogen peroxide model and the iron-overload model in our experiments and investigated the proliferation status and the intracellular superoxide level of the cells. The results showed that endogenous cytoglobin exerted significant protective effects on hydrogen peroxide or iron-overload induced LX-2 cell damage, confirming that upregulation of cytoglobin was the protective response of activated hepatic stellate cells to oxidative stress. Recombinant cytoglobin protein could protect LX-2 cells from oxidation induced damage, and prevent primary rat hepatic stellate cells from excessive proliferation and injury. The cytoplasmic reactive oxygen species (ROS) scavenging capacity of the recombinant cytoglobin protein was not as good as its capacity in scavenging ROS outside the cells, likely owing to the lack of active transporting mechanisms. Intracellular over-expression of cytoglobin protein could exert significant protective effect on LX-2 cells treated with hydrogen peroxide or iron-overload. Our results would accelerate the exploitation of new anti-fibrotic targets.

Cytoglobin exhibits anti-fibrosis activity on liver in vivo and in vitro.

Cytoglobin, generated using genetic engineering method, is a kind of recombinant human stellate cell activation-associated protein. We speculate that it could influence the development of hepatic fibrosis like Sellate cell activation-associated protein which was discovered by Kawada et al. Therefore, we investigated its anti-fibrosis effect on liver both in vivo and in vitro. During our research, we found that cytoglobin showed obvious effect compared with the control group on Thioacetamide-induced liver fibrosis in SD rats, including significantly decrease in aspartate aminotransferase, Hyaluronic acid, laminin and collagen I(Col I) levels in serum and hydroxyproline in livers, which are the important indices reflecting the degree of hepatic fibrosis. Meanwhile, the viability of rat hepatic stellate cell line T6 (HSC-T6) cells was inhibited by cytoglobin and the apoptosis induced by cytoglobin in HSC-T6 cells was detected by Annexin V/PI double staining. Activation of the caspase cascade including caspase-3 for the intrinsic pathways was demonstrated. The results also showed that the expression of Bcl-2 protein decreased whereas that of Bax protein increased, leading to an increase of the Bax/Bcl-2 ratio. Our results demonstrated that cytoglobin exhibited anti-fibrosis activity on livers in vivo and in vitro, involving apoptosis induction.

Effect of globin digest on the liver injury and hepatic gene expression profile in galactosamine-induced liver injury in SD rats.

AIMS: We investigated the effect of globin digest (GD) on the liver injury and hepatic gene expression profile in galactosamine (GalN)-induced liver injury. MAIN METHODS: The effect of GD on the liver injury was examined by measuring the activities of serum transferases and hepatic antioxidant enzymes, histopathological analysis, gene expression profile, and proteins of the peroxisome proliferator-activated receptor alpha (PPARα) and met proto-oncogene (c-Met) in SD rats at 24 h after GalN administration. The effect of GD on the expression of PPARα and its target gene in AML-12 mouse hepatocytes was also examined. KEY FINDINGS: GD suppressed the elevated activities of serum transferases in GalN-induced liver injury in SD rats. The thiobarbituric acid reactive substance content in GalN-injured liver was a decreasing tendency by GD. GD suppressed the increased oxidized glutathione content, and increased the decreased protein, reduced glutathione contents, and catalase activity in GalN-injured liver. GD may improve the antioxidant defense system and protein synthesis in GalN-injured liver. GD suppressed the elevated expression of the genes related to the inflammation, and decreased the histopathological grade value of inflammatory cell infiltration in GalN-injured liver. GD increased the expression of PPARα protein in GalN-injured liver, and also increased the expression of PPARα and its target gene in AML-12 hepatocytes. The total and phosphorylated c-Met proteins in GalN-injured liver were the increasing tendencies by GD. SIGNIFICANCE: These findings indicate that GD has the hepatoprotective effect on GalN-induced liver injury in SD rats.

An antiapoptotic neuroprotective role for neuroglobin.

Cell death associated with mitochondrial dysfunction is common in acute neurological disorders and in neurodegenerative diseases. Neuronal apoptosis is regulated by multiple proteins, including neuroglobin, a small heme protein of ancient origin. Neuroglobin is found in high concentration in some neurons, and its high expression has been shown to promote survival of neurons in vitro and to protect brain from damage by both stroke and Alzheimer's disease in vivo. Early studies suggested this protective role might arise from the protein's capacity to bind oxygen or react with nitric oxide. Recent data, however, suggests that neither of these functions is likely to be of physiological significance. Other studies have shown that neuroglobin reacts very rapidly with cytochrome c released from mitochondria during cell death, thus interfering with the intrinsic pathway of apoptosis. Systems level computational modelling suggests that the physiological role of neuroglobin is to reset the trigger level for the post-mitochondrial execution of apoptosis. An understanding of the mechanism of action of neuroglobin might thus provide a rational basis for the design of new drug targets for inhibiting excessive neuronal cell death.