Inhibiting HMGB1-RAGE axis prevents pro-inflammatory macrophages/microglia polarization and affords neuroprotection after spinal cord injury.

BACKGROUND: Spinal cord injury (SCI) favors a persistent pro-inflammatory macrophages/microglia-mediated response with only a transient appearance of anti-inflammatory phenotype of immune cells. However, the mechanisms controlling this special sterile inflammation after SCI are still not fully elucidated. It is known that damage-associated molecular patterns (DAMPs) released from necrotic cells after injury can trigger severe inflammation. High mobility group box 1(HMGB1), a ubiquitously expressed DNA binding protein, is an identified DAMP, and our previous study demonstrated that reactive astrocytes could undergo necroptosis and release HMGB1 after SCI in mice. The present study aimed to explore the effects and the possible mechanism of HMGB1on macrophages/microglia polarization, as well as the neuroprotective effects by HMGB1 inhibition after SCI. METHODS: In this study, the expression and the concentration of HMGB1 was determined by qRT-PCR, ELISA, and immunohistochemistry. Glycyrrhizin was applied to inhibit HMGB1, while FPS-ZM1 to suppress receptor for advanced glycation end products (RAGE). The polarization of macrophages/microglia in vitro and in vivo was detected by qRT-PCR, immunostaining, and western blot. The lesion area was detected by GFAP staining, while neuronal survival was examined by Nissl staining. Luxol fast blue (LFB) staining, DAB staining, and western blot were adopted to evaluate the myelin loss. Basso-Beattie-Bresnahan (BBB) scoring and rump-height Index (RHI) assay was applied to evaluate locomotor functional recovery. RESULTS: Our data showed that HMGB1 can be elevated and released from necroptotic astrocytes and HMGB1 could induce pro-inflammatory microglia through the RAGE-nuclear factor-kappa B (NF-κB) pathway. We further demonstrated that inhibiting HMGB1 or RAGE effectively decreased the numbers of detrimental pro-inflammatory macrophages/microglia while increased anti-inflammatory cells after SCI. Furthermore, our data showed that inhibiting HMGB1 or RAGE significantly decreased neuronal loss and demyelination, and improved functional recovery after SCI. CONCLUSIONS: The data implicated that HMGB1-RAGE axis contributed to the dominant pro-inflammatory macrophages/microglia-mediated pro-inflammatory response, and inhibiting this pathway afforded neuroprotection for SCI. Thus, therapies designed to modulate immune microenvironment based on this cascade might be a prospective treatment for SCI.

Inhibition of SNK-SPAR signaling pathway promotes the restoration of motor function in a rat model of ischemic stroke.

This study aimed to investigate the effects of SPAR signaling pathway on the restoration of motor function in ischemic stroke (IS). Sprague-Dawley male rats were separated into the control and sham groups, as well as the group for middle cerebral artery occlusion (MCAO) model establishment. Successfully established rat ischemic models were randomly divided into model, SNKMCAO-del and pcDNA3.1-SNK groups. The evaluation of motor function among the rats in each group was assessed using a balance beam, a screen test and the Garcia scoring method. CatWalk gait analysis was employed to evaluate the effect of the SNK signaling pathway on rat motor function. Triphenyltetrazolium chloride (TTC) and TUNEL staining were techniques were utilized for cerebral infarction (CI) area as well for hippocampal neuron apoptosis. The quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting methods were performed to detect mRNA and protein expressions of SNK and SPAR. When compared with the model group, the SNKMCAO-del group displayed decreased motor function score and CI area, while contrasting results were observed in the pcDNA3.1-SNK group. According to the results obtained from the CatWalk gait analysis, the SNKMCAO-del group showed a clear improvement compared to the model group whereas the pcDNA3.1-SNK group exhibited poorer results than the model group in the objective parameters of the study, such as movement, speed, running duration, print area, maximal contact area, maximal, mean intensity, and stride length. These findings suggested that SNK gene silencing promotes motor function by inhibiting the SNK-SPAR signaling pathway in rats with ischemic stroke.

Bilateral Medial Medullary Infarction with Nondominant Vertebral Artery Occlusion.

Bilateral medial medullary infarction (MMI) is a rare stroke subtype. Here, we report a case with bilateral MMI caused by nondominant vertebral artery occlusion confirmed by brain digital subtraction angiography and magnetic resonance imaging basi-parallel-anatomical-scanning. We highlight that anterior spinal arteries could originate from a unilateral vertebral artery (VA). Radiologists and neurologists should pay attention to the nondominant VA as bilateral MMI may be induced by occlusion of nondominant VA that supplies the bilateral anteromedial territories of the medulla.

[The effect of edaravone on MAPKs signal pathway associated with Abeta(25-35) treatment in PC12 cells].

OBJECTIVE: To explore whether edaravone protects cells damage via mitogen-activated protein kinases (MAPKs) signal pathway, and which procedure of p38 be affected so as to add theories for AD pathogenesis and treatments. METHODS: According to different drugs treated, PC12 cells in vitro were divided into four groups. Negative control group: cells were treated with media alone. AD model group: cells were treated with 30 pmol/L Abeta(25-35). Inhibitor control group: cells were treated with 10 micromol/L SB203580 Cp38 mitogen-activated protein kinase (p38) inhibitor], 10 micromol/L SP600125 [c-Jun NH2 terminal kinase (JNK) inhibitor], or 10 micromol/L PD98059 extracelular signal regulated kinase (ERK) inhibitor]. Low-dose, middle-dose and high-dose edaravone group: cells plated for 24 hours treated with 30 micromol/L Abeta(25-35) and co-treated with 20, 40, 80 micromol/L edaravone 3 hours, respectively. The morphology of the treated cells were observed, the p-p38, p-JNK and p-ERK proteins in each group were tested by the Western blot. The p38 mRNA were tested in each group above (only add SB203580 10 micromol/L in third group) by the real time PCR. RESULTS: (1) The p-p38 protein was significantly increased in model control group compared with that in negative control group (P<0.05). The p-p38 protein in the inhibitor group and edaravone groups was decreased significantly (P<0.05) when compared with that in model control group. The p-p38 proteins were significantly increased in the three edaravone groups compared with that in inhibiter control group (P<0.05). The p-p38 protein in middle-dose edaravone group was decreased compared with that in low-dose edaravone group (P<0.05). There was no relationship in dose-dependent manner about edaravone. Compared with three edaravone groups, the p-p38 protein was lower than it in high-dose edaravone & inhibiter group (P<0.05). (2) The p-JNK protein was significantly increased in model control group compared with that in negative control group (P<0.05). The p-JNK protein in the inhibitor group was decreased compared with that in model control group (P<0.05). (3) No significantly difference of p-ERK protein concentration was observed in other groups when compared with that in negative control group (P>0.05 each). (4) Compared with negative control group, the p38 mRNA in model control group was significantly increased, and it was significantly decreased in inhibitor control group (P<0.05 each). In 40 micromol/L and 80 micromol/L edaravone groups, the p38 mRNA was significantly decreased compared with that in model control group, and it still was decreased compared with that in inhibitor control group (P<0.05). The p38 mRNA in 40 micromol/L edaravone group was the lowest among three edaravone groups, and it was obviously different from that in 20 micromol/L and 80 micromol/L edaravone groups (P<0.05). CONCLUSION: Abeta(25-35) could increase the p-p38 and p-JNK protein expression in cultured PC12 cells, but there was no obviously expression of p-ERK protein. These indicated that Abeta(25-35) might activate MAPKs signal pathway, especially p38 and JNK, and lead to PC12 cell damage. Edaravone could decrease p38 mRNA induced-Abeta(25-35), which indicated edaravone could protect PC12 cell damage via blocking p38 signal pathway in mRNA stage and protein stage simultaneously. Hence, it is promising that edaravone would be a new medicine for AD.

[Characteristic of microglial activation of hippocampus in experimental epileptic rats].

OBJECTIVE: To investigate the characteristics of microglial activation of hippocampus in experimental epileptic rats. METHODS: Morphological changes and proliferation of OX-42 positive cells were compared at different time points after status of epilepticus (SE) in lithium-pilocarpine induced epileptic rats. RESULTS: OX-42 positive cells were activated after SE, which increased to a peak at 3-7 d and in a relatively stable state at 7-14 d; then gradually decreased after 14d and returned to slightly higher level than previously at 21 d. CONCLUSION: Inflammatory injury, microglial activation and cell proliferation are closely related after seizures, microglial activation may be an important mechanism in the inflammatory injury of epilepsy.

[Effect of Helicobacter pylori infection on platelet activation and coagulation function in patients with acute cerebral infarction].

OBJECTIVE: To investigate the effect of Helicobacter pylori (Hp) on platelet activation and coagulation function in patients with acute cerebral infarction. METHODS: Sixty-six patients with acute cerebral infarction and 50 health individuals were enrolled in the study. Hp antibody,expression of CD62p on platelets and clotting indexes were measured and compared between two groups. RESULTS: The positive rate of Hp-IgG and Hp-CagA in cerebral infarction patients were higher than that in controls (P<0.05). The positive rate of CD62p in patients with positive Hp-IgG and Hp-CagA was significantly higher than that in negative patients and also controls (P<0.05). The APTT and TT were lower and FIB was higher in patients with positive Hp antibody than those in patients with negative Hp antibody (P<0.05),but there was no difference in PT,PTR and INR (P>0.05). CONCLUSION: Hp infection can activate platelets and affect coagulation function,which may be involved in the development of cerebral infarction.

[The anti-aging effect of EPO and the preliminary probe into its mechanisms].

OBJECTIVE: To study whether erythropoietin ( EPO) has the anti-aging effect and the mechanisms of how it effects. METHODS: 5% D-galactose hypodermic injection for 6 weeks to establish the aging model. Divided rats into 5 groups randomly: the normal control (group A), the aging model (group B), the low dosage (1 000 U/ (kg x d)) of recombinant human erythropoietin (rhEPO) intervene (group C), the middle dosage (3 000 U/(kg x d)) of rhEPO intervene (group D) and the high dosage (5 000 U/(kg x d)) of rhEPO intervene (group E), 10 rats in each group. Morris water maze was used to comparing the behavioral indexes. After decapitating the rats, the malonaldehyde (MDA), Na(+)-K+ ATPase, total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) of brain tissue were tested. One rat from each group was selected randomly to observe the hippocampal ultramicrostructure. RESULTS: (1) Compared with group A, the learning and memory ability of group B reduced, the level of MDA, the Na(+)-K+ ATPase, T-AOC and the SOD activities of brain tissue decreased (P < 0.05), besides, a series of aging changes were observed in the hippocampal ultramicro-structure in group B. (2) Compared with group B, an improved learning and memory ability of group D, a reduced MDA content and an increased activity of Na(+)-K+ ATPase, T-AOC and the SOD activities of brain tissue in group D were also observed with a improved hippocampal ultramicro-structure. (3) The low dosage of rhEPO intervention could against the decrease of the activities of brain Na(+)-K+ ATPase, SOD of aging rat (P < 0.05), but had no significant effects on the rest of the indicators. The high dosage of rhEPO intervention had no significant improvements on various indicators of aging rats in high dosage of rhEPO intervention group was noticed (P > 0.05). CONCLUSION: The middle dosage of EPO has the anti-aging effect, and its mechanisms may be related to enhancing the antioxidant enzymes activity and increasing the antioxidant capacity.

Necroptotic astrocytes induced neuronal apoptosis partially through EVs-derived pro-BDNF.

Our previous study showed that neuronal apoptosis was significantly increased upon treatment of conditioned medium (CM) from necroptotic astrocytes (NAS), leaving the underlying mechanism unclear. Considering the nutritive and supportive roles of astrocytes, we first examined the neurotrophic phenotype of necroptotic astrocytes with focus on glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), two important neurotrophic factors, and it was unexpectedly found that the expression of GDNF and BDNF were up-regulated in necroptotic astrocytes in vitro. A question was raised as to whether the functional secreted forms of neurotrophic factors were increased. Considering that extracellular vesicles (EVs) were carriers of secreted substances and their roles in cellular interaction, we isolated EVs from astrocytes and found EVs from normal and necroptotic astrocytes (EVs-NAS) had characteristics of exosomes. We then examined GDNF and BDNF in EVs-NAS, and BDNF was interestingly found as an immature form of pro-BDNF. The expression of pro-BDNF was found to be increased in EVs-NAS, and EVs-NAS had a negative effect on neuronal survival. To verify that whether pro-BDNF was involved in the detrimental effect of EVs-NAS, anti-pro-BDNF antibody was applied, and we found that neuronal apoptosis-induced by EVs-NAS could be significantly attenuated by blocking pro-BDNF, which suggested that necroptotic astrocytes induced neuronal apoptosis partially through EVs-derived pro-BDNF. The data expand our understanding in neurotrophic phenotype of necroptotic astrocytes, and may provide us new strategies targeting on EVs-NAS in treatment of neurological diseases.

[Expression of vascular endothelial growth factor and microvessel density in hippocampus of rats with aging].

OBJECTIVE: To investigate the expression of vascular endothelial growth factor (VEGF) and microvessel density (MVD) in hippocampus of rats with aging. METHODS: Paraffin sections of brain tissue of rats at the age of 3, 18, 24, 30 months were stained by immunohistochemistry, the expression of VEGF and MVD was quantitatively analyzed. RESULTS: Innunohistochemical staining showed that the VEGF-positive cells were mainly pyramidal neuron in hippocampus; the intensity of VEGF-positivity in neuron cells was decreased with the aging (P<0.05). The MVD in hippocampus was also decreased with the aging of rats (P<0.05). CONCLUSION: Increasing VEGF contents and improving blood circulation in brain tissue may prevent or treat vascular dementia and cerebrovascular diseases.

[Expression of GLUT 3 in different brain regions of aged rats].

OBJECTIVE: To examine the distribution of glucose transport 3 (GLUT 3) in different brain regions of aged rats and to investigate its role in ageing process of the nervous system. METHODS: The GLUT 3 expression in different brain regions was examined with immunohistochemical method in rats aged 3, 18 and 30 months, respectively. RESULTS: The number of GLUT 3-positive cells varied in the different brain regions in rats of all age groups (P<0.01); the CA1 region contained the greatest number of positive cells,and fewer in the motor cortex and cerebellum. The number of GLUT 3-positive cells was reduced in the brain of aged rats (P<0.01); and the neural cells in 4 different brain regions presented with large cell body and loose alignment. CONCLUSION: The expression of GLUT 3 decreased in aged rats, which suggests that GLUT 3 may be involved in the ageing process of nervous system.

[Hypoxia inducible factor-1alpha expression trends in hippocampus of rat of different ages].

OBJECTIVE: To reveal the expression trends of HIF-1alpha in hippocampus of different age rats, investigate the role of HIF-1alpha in the aging process of nervous system. METHODS: The cerebral tissues was collectd from rats of different age, including 3, 18, 24, 36 months old. There were 6 rats in each age group. The expressions of nissl body and HIF-1alpha in different part of hippocampus were observed by nissl staining and immunohistochemical technique. RESULTS: (1) With the increase of rat age, nerve cells appeared to be bigger and to arrange sparsely, while the nissl body decreased; (2) The positive HIF-1alpha staining cells in CA1, CA3 region of hippocampus increased along with the increase of rat age. The difference between any two age groups showed statistical significance (P < 0.05). CONCLUSION: The function of protein synthesis weakened in nerve cells but the expression of HIF-1alpha increased with the age increasing, which may play an important role in aging of nervous system.

[Expression of p38MAPK in the olfactory bulb of rats with Alzheimer's disease].

OBJECTIVE: To identify the changes of expression of p38MAPK in the olfactory bulb (OB) of rats with Alzheimer's Disease (AD) and to explore the functional mechanism of p38MAPK in the pathological changes of AD. METHODS: AD animal model was established by injecting amyloid-beta peptide 25-35 into the lateral cerebral ventricle of rats. The learning and memory abilities of rats were measured by Y-maze experiment. The expressions of p38MAPK in the OBs of rats in the AD group, saline control group, p38MAPK inhibitor group and inhibitor control (con-inhibitor) group were examined by immunohistochemistry. RESULTS: (1) The capabilities of learning and memory of the rats were impaired significantly at day 7 and day 14 after the induction of AD. Significant learning and memory differences were found (P < 0.05) between the AD group and the other groups. (2) The expression of p38MAPK in the OBs of rats was found at day 4 after the induction of AD. The expression increased with time. The AD rats had more positive p38MAPK cells than those in the saline controls (P < 0.05). The expression of phospho-p38MAPK in the rats with AD increased significantly (P < 0.01) compared with those in the saline group. The AD rats treated with p38MAPK inhibitor had less expression of phospho-p38MAPK than those in the AD group and the inhibitor control (P < 0.01). CONCLUSIONS; Abeta25-35 can activate p38MAPK signal transduction pathway. p38MAPK may play a role in the formation of dysosmia in AD. SB203580, a p38MAPK inhibitor, can reduce the neurotoxicity evoked by p38MAPK.

[Expression of Ref-1 in hippocampus CA1 area of rats with Alzheimer's disease].

OBJECTIVE: To investigate the expression of Redox factor-1(Ref-1) in rats with Alzheimer's disease (AD). METHODS: AD rat model was established by a single injection of beta-amyloid peptide (Abeta25-35) into the lateral cerebral ventricle of rats. Y-shape maze task was conducted to check the ethology. At 4th, 7th and 14th day after injection, Ref-1 expression in hippocampus CA1 area was detected by immunohistochemistry. RESULT: The numbers of repeated learning and error and the total reaction time in AD group were significantly higher than those in control group at 7th and 14th day after injection of Abeta25-35 (P<0.05). At 4th day after injection of Abeta25-35, the Ref-1 expression was increased with time prolongation in AD group(P<0.01). CONCLUSION: Injection of Abeta25-35 in lateral cerebral ventricle can decrease the learning and memory abilities of rats, and results also indicate that Ref-1 expression in hippocampus may be involved in the development of AD.

Calculations of spin-polarized Goos-Hänchen displacement in magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit couplings.

We theoretically investigate Goos-Hänchen (GH) displacement by modelling the spin transport in an archetypal device structure-a magnetically confined GaAs/Al x Ga1-x As nanostructure modulated by spin-orbit coupling (SOC). Both Rashba and Dresselhaus SOCs are taken into account. The degree of spin-polarized GH displacement can be tuned by Rashba or Dresselhaus SOC, i.e. interfacial confining electric field or strain engineering. Based on such a semiconductor nanostructure, a controllable spatial spin splitter can be proposed for spintronics applications.

Puerarin Up-regulates Methyl-CpG Binding Protein 2 Phosphorylation in Hippocampus of Vascular Dementia Rats.

OBJECTIVE: To observe the effect of puerarin on methyl-CpG binding protein 2 (MeCP2) phosphorylation (pMeCP2) in the hippocampus of a rat model of vascular dementia (VD). METHODS: Thirty-six healthy Sprague-Dawley rats were randomly assigned to the sham-operated group, dementia group and puerarintreated group using a random number table (n=12 per group). The modifified permanent bilateral common carotid artery occlusion method was used to establish the VD model. The sham-operated and dementia groups were given 2 mL/d of saline, while the puerarin-treated group was given 100 mg/(kg•d) of puerarin for 17 days. The learning and memory abilities were evaluated by the Morris water maze test. Hematoxylin-eosin staining, immunohistochemical (IHC) staining and Western blot analysis were carried out to observe changes in neuron morphology and in level of pMeCP2 in the hippocampus, respectively. RESULTS: The morphologies of rat hippocampal neurons in the puerarintreated group were markedly improved compared with the dementia group. The escape latency of the dementia group was significantly longer than the sham-operated group (P<0.05), while the puerarin-treated group was obviously shorter than the dementia group (P<0.05). Cross-platform times of the dementia group were signifificantly decreased compared with the sham-operated group (P<0.05), while the puerarin-treated group was obviously increased compared with the dementia group (P<0.05). IHC staining showed no significant difference in the number of MeCP2 positive cells among 3 groups (P>0.05). The number of pMeCP2 positive cells in the CA1 region of hippocampus in the dementia group was signifificantly increased compared with the sham-operated group, and the puerarin-treated group was signifificantly increased compared with the dementia group (both P<0.05). Western blot analysis showed no signifificant difference of MeCP2 expression among 3 groups (P>0.05). The expression of pMeCP2 in the dementia group was signifificantly increased compared with the sham-operated group, while it in the puerarin-treated group was signifificantly increased compared with the dementia group (P<0.05). CONCLUSION: Puerarin could play a role in the protection of nerve cells through up-regulating pMeCP2 in the hippocampus, improving neuron morphologies, and enhancing learning and memory ablities in a rat model of VD.

[A study on expression of HIF-1alpha and EPO in the hippocampus of rats with vascular dementia].

OBJECTIVE: To observe the expression rule of hypoxia inducible factor-1 (HIF-1alpha) and erythropoietion (EPO) in the formation of vascular dementia (VD) and investigate the possible pathogenesis of VD. METHODS: Rats of experimental group were treated with a permanent bilateral common carotid arteries (CCA) occlusion (2-VO) for establishing vascular dementia model. Rats were evaluated on learning-memory ability by Y-type water maze test. The dynamic expression of HIF-1alpha and EPO in hippocampal CA1 region were measured by immunohistochemical assay method. RESULTS: (1) The learning-memory ability of rats in VD groups was progressively decreased as the ischemic duration prolonged (P < 0.05); (2) In VD group, the expression of HIF-1alpha and EPO in hippocampal CA1 region were most obvious at 1 w, and then declined progressively but still above the normal level (P < 0.01); (3) In VD group, the expression of HIF-1alpha and EPO at each ischemic point and their corresponding learning-memory ability were in significant correlation at the 0.01 level. CONCLUSION: Both HIF-1alpha and EPO contribute to the formation of VD, and HIF-1/EPO anoxic signal transduction may play a protecting role in this process.

[Effects of recombinant human erythropoietin on brain-derived neurotrophic factor expression in different brain regions of aging rats].

OBJECTIVE: To explore the effect of recombinant human erythropoietin (rhEPO) on expression of brain-derived neurotrophic factor (BDNF) in different brain regions of aging rats. METHODS: Forty male SD rats were randomized equally into negative control group, D-galactose group, EPO treatment group, and positive control group. Rat models of subacute aging were established by continuous subcutaneous injection of 5% D-galactose. Immunohistochemical staining was used to analyze the variation of BDNF expressions in different brain regions of the aging rats with different treatments. RESULTS: Significant brain region-specific differences in BDNF expression were found among the rats in different groups. Compared with those in the negative control group, the numbers of BDNF-positive cells in the hippocampal CA1 region, CA3 region, dentate gyrus (DG) and frontal cortex were all decreased obviously in D-galactose group (P<0.05) but increased in both EPO group and the positive control group (P<0.05) without significant differences between the latter two groups. In the rats in the same group, the number of BDNF-positive cells varied markedly in different brain regions (P<0.05), and the expression level of BDNF was the highest in the frontal cortex followed by the hippocampal CA3 region and the dentate gyrus, and was the lowest in the hippocampal CA1 region. CONCLUSION: Treatment with rhEPO enhances the expression of BDNF in rat neural cells, suggesting that rhEPO may protect the nervous system from aging by regulating the BDNF pathway.

Immature dendritic cell exosomes suppress experimental autoimmune myasthenia gravis.

Immature dendritic cell-derived exosomes (iMDEX) display a certain degree of immunosuppressive activity in autoimmune diseases. However, the role of iMDEX in experimental autoimmune myasthenia gravis (EAMG) is still unclear. Therefore, we tested the effects of mouse bone marrow (BM)-derived iMDEX on tolerance induction in a mouse model of EAMG. In this study, we found that the CELLine culture system produced more exosomes, the morphology and phenotype of these exosomes were found to be identical when compared with traditional cell culture. And, iMDEX(1000) ameliorated the progression of EAMG by reducing AChR-reactive lymphocyte proliferation, AChR antibody levels and pro-inflammatory cytokine levels.

Voltage-controllable spin beam splitter based on realistic magnetic-barrier nanostructure.

We report a theoretical investigation on the Goos-Hänchen (GH) effect of spin electron beams in realistic magnetic-barrier (MB) nanostructures under an applied voltage, which can be experimentally created by lithographic patterning of ferromagnetic (FM) or superconducting films. GH shifts of spin electron beams are calculated numerically for the InAs material system, with the help of the stationary phase method. It is shown that a significant spin polarization effect can be induced by such MB nanostructures with symmetric magnetic field profiles. It also is shown that both magnitude and sign of the spin polarization is closely relative to the electric barrier (EB) produced by a constant voltage applied to the metallic FM stripe of system. These interesting properties may provide an alternative way to spin injection into the semiconductor, and such nanostructures can serve as voltage-tunable spin beam splitters.