Kosuke Kajitani

MTH1, an oxidized purine nucleoside triphosphatase, protects the dopamine neurons from oxidative damage in nucleic acids caused by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

We previously reported that 8-oxoguanine (8-oxoG) accumulates in the cytoplasm of dopamine neurons in the substantia nigra of patients with Parkinson’s disease and the expression of MTH1 carrying an oxidized purine nucleoside triphosphatase activity increases in these neurons, thus suggesting that oxidative damage in nucleic acids is involved in dopamine neuron loss. In the present study, we found that levels of 8-oxoG in cellular DNA and RNA increased in the mouse nigrostriatal system during the tyrosine hydroxylase (TH)-positive dopamine neuron loss induced by the administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MTH1-null mice exhibited a greater accumulation of 8-oxoG in mitochondrial DNA accompanied by a more significant decrease in TH and dopamine transporter immunoreactivities in the striatum after MPTP administration, than in wild-type mice. We thus demonstrated that MTH1 protects the dopamine neurons from oxidative damage in the nucleic acids, especially in the mitochondrial DNA of striatal nerve terminals of dopamine neurons.

MTH1, an oxidized purine nucleoside triphosphatase, suppresses the accumulation of oxidative damage of nucleic acids in the hippocampal microglia during kainate-induced excitotoxicity

Enhanced oxidative stress has been implicated in the excitotoxicity of the CNS, and 8-oxo-7,8-dihydro-guanine (8-oxoG), a major type of oxidative damage in nucleic acids, was reported to be accumulated in the rat hippocampus after kainate administration. We herein showed that the 8-oxoG levels in mitochondrial DNA and cellular RNA increased significantly in the CA3 subregion of the mouse hippocampus 6–12 h after kainate administration but returned to basal levels within a few days. Laser-scanning confocal microscopy revealed the 8-oxoG accumulation in mitochondrial DNA to be remarkable in CA3 microglia, whereas that in nuclear DNA or cellular RNA was also detected in the CA3 pyramidal cells and astrocytes. 8-oxoG accumulation in cellular DNA or RNA should be suppressed by MutT homolog 1 (MTH1) with 8-oxo-dGTPase (8-oxo-7,8-dihydro-2′-deoxyguanosine triphosphatase) activity and 8-oxoG-DNA glycosylase 1 (OGG1) with 8-oxoG DNA glycosylase activity. We thus examined the expression level of MTH1 and OGG1 in the mouse hippocampus after kainate administration. The Mth1 mRNA level decreased soon after kainate administration and then quickly recovered beyond the basal level, and a continuously increased MTH1 protein level was observed, whereas the Ogg1 mRNA level remained constant. MTH1-null and wild-type mice exhibited a similar degree of CA3 neuron loss after kainate administration; however, the 8-oxoG levels that accumulated in mitochondrial DNA and cellular RNA in the CA3 microglia significantly increased in the MTH1-null mice in comparison with wild-type mice, thus demonstrating that MTH1 efficiently suppresses the accumulation of 8-oxoG in both cellular DNA and RNA in the hippocampus, especially in microglia, caused by excitotoxicity.

Galectin-1 promotes basal and kainate-induced proliferation of neural progenitors in the dentate gyrus of adult mouse hippocampus

We examined the expression of galectin-1, an endogenous lectin with one carbohydrate-binding domain, in the adult mouse hippocampus after systemic kainate administration. We found that the expression of galectin-1 was remarkably increased in activated astrocytes of the CA3 subregion and dentate gyrus of the hippocampus, and in nestin-positive neural progenitors in the dentate gyrus. Quantitative reverse transcription PCR (RT-PCR) analysis revealed that the galectin-1 mRNA level in hippocampus began to increase 1 day after kainate administration and that a 13-fold increase was attained within 3 days. Western blotting analysis confirmed that the level of galectin-1 protein increased to more than three-fold a week after the exposure. We showed that isolated astrocytes express and secrete galectin-1. To clarify the significance of the increased expression of galectin-1 in hippocampus, we compared the levels of hippocampal cell proliferation in galectin-1 knockout and wild-type mice after saline or kainate administration. The number of 5-bromo-2′-deoxyuridine (BrdU)-positive cells detected in the subgranular zone (SGZ) of galectin-1 knockout mice decreased to 62% with saline, and to 52% with kainate, as compared with the number seen in the wild-type mice. Most of the BrdU-positive cells in SGZ expressed doublecortin and neuron-specific nuclear protein, indicating that they are immature neurons. We therefore concluded that galectin-1 promotes basal and kainate-induced proliferation of neural progenitors in the hippocampus.

fosB-Null Mice Display Impaired Adult Hippocampal Neurogenesis and Spontaneous Epilepsy with Depressive Behavior

Patients with epilepsy are at high risk for major depression relative to the general population, and both disorders are associated with changes in adult hippocampal neurogenesis, although the mechanisms underlying disease onset remain unknown. The expression of fosB, an immediate early gene encoding FosB and ΔFosB/Δ2ΔFosB by alternative splicing and translation initiation, is known to be induced in neural progenitor cells within the subventricular zone of the lateral ventricles and subgranular zone of the hippocampus, following transient forebrain ischemia in the rat brain. Moreover, adenovirus-mediated expression of fosB gene products can promote neural stem cell proliferation. We recently found that fosB-null mice show increased depressive behavior, suggesting impaired neurogenesis in fosB-null mice. In the current study, we analyzed neurogenesis in the hippocampal dentate gyrus of fosB-null and fosBd/d mice that express ΔFosB/Δ2ΔFosB but not FosB, in comparison with wild-type mice, alongside neuropathology, behaviors, and gene expression profiles. fosB-null but not fosBd/d mice displayed impaired neurogenesis in the adult hippocampus and spontaneous epilepsy. Microarray analysis revealed that genes related to neurogenesis, depression, and epilepsy were altered in the hippocampus of fosB-null mice. Thus, we conclude that the fosB-null mouse is the first animal model to provide a genetic and molecular basis for the comorbidity between depression and epilepsy with abnormal neurogenesis, all of which are caused by loss of a single gene, fosB.

Fosb gene products contribute to excitotoxic microglial activation by regulating the expression of complement C5a receptors in microglia.

The Fosb gene encodes subunits of the activator protein‐1 transcription factor complex. Two mature mRNAs, Fosb and ΔFosb, encoding full‐length FOSB and ΔFOSB proteins respectively, are formed by alternative splicing of Fosb mRNA. Fosb products are expressed in several brain regions. Moreover, Fosb‐null mice exhibit depressive‐like behaviors and adult‐onset spontaneous epilepsy, demonstrating important roles in neurological and psychiatric disorders. Study of Fosb products has focused almost exclusively on neurons; their function in glial cells remains to be explored. In this study, we found that microglia express equivalent levels of Fosb and ΔFosb mRNAs to hippocampal neurons and, using microarray analysis, we identified six microglial genes whose expression is dependent on Fosb products. Of these genes, we focused on C5ar1 and C5ar2, which encode receptors for complement C5a. In isolated Fosb‐null microglia, chemotactic responsiveness toward the truncated form of C5a was significantly lower than that in wild‐type cells. Fosb‐null mice were significantly resistant to kainate‐induced seizures compared with wild‐type mice. C5ar1 mRNA levels and C5aR1 immunoreactivity were increased in wild‐type hippocampus 24 hours after kainate administration; however, such induction was significantly reduced in Fosb‐null hippocampus. Furthermore, microglial activation after kainate administration was significantly diminished in Fosb‐null hippocampus, as shown by significant reductions in CD68 immunoreactivity, morphological change and reduced levels of Il6 and Tnf mRNAs, although no change in the number of Iba‐1‐positive cells was observed. These findings demonstrate that, under excitotoxicity, Fosb products contribute to a neuroinflammatory response in the hippocampus through regulation of microglial C5ar1 and C5ar2 expression. GLIA 2014;62:1284–1298

Nitric Oxide Synthase Mediates the Ability of Darbepoetin Alfa to Improve the Cognitive Performance of STOP Null Mice

STOP (stable tubule only polypeptide) null mice display neurochemical and behavioral abnormalities that resemble several well-recognized features of schizophrenia. Recent evidence suggests that the hematopoietic growth factor erythropoietin improves the cognitive performance of schizophrenics. The mechanism, however, by which erythropoietin is able to improve the cognition of schizophrenics is unclear. To address this question, we first determined whether acute administration of the erythropoietin analog known as darbepoetin alfa (D. alfa) improved performance deficits of STOP null mice in the novel objective recognition task (NORT). NORT performance of STOP null mice, but not wild-type littermates, was enhanced 3 h after a single injection of D. alfa (25 μg/kg, i.p.). Improved NORT performance was accompanied by elevated NADPH diaphorase staining in the ventral hippocampus as well as medial and cortical aspects of the amygdala, indicative of increased nitric oxide synthase (NOS) activity in these structures. NOS generates the intracellular messenger nitric oxide (NO) implicated in learning and memory. In keeping with this hypothesis, D. alfa significantly increased NO metabolite levels (nitrate and nitrite, NOx) in the hippocampus of both wild-type and STOP null mice. The NOS inhibitor, N (G)-nitro-L- arginine methyl ester (L-NAME; 25 mg/kg, i.p.), completely reversed the increase in hippocampal NOx levels produced by D. alfa. Moreover, L-NAME also inhibited the ability of D. alfa to improve the NORT performance of STOP null mice. Taken together, these observations suggest D. alfa enhances the NORT performance of STOP null mice by increasing production of NO.

Nitric Oxide Synthase Mediates the Ability of Darbepoetin alfa to Attenuate Pre-existing Spatial Working Memory Deficits in Rats Subjected to Transient Global Ischemia

Erythropoietin has been reported to improve the behavioral performance of healthy mice in tests thought to depend on synaptic plasticity in the CA1 region of the hippocampus. We show here for the first time that a single injection of the erythropoietin analog darbepoetin alfa reverses pre-existing cognitive deficits in adult rats that had been subjected to transient global ischemia produced by four-vessel occlusion (4-VO). Quantification of neuronal density demonstrated that 12 min of 4-VO selectively killed more than 90% of CA1 neurons in the dorsal hippocampus. Rats that had sustained a bilateral loss of hippocampal CA1 neurons in this range (4-VO rats) displayed more errors and longer escape latencies in the Barnes maze compared with sham-operated controls. A single injection of darbepoetin alfa (5000 U/kg i.p.) 4 h before behavioral testing decreased deficits in escape latency for 4-VO rats but not sham-operated controls. This improvement in spatial working memory performance was correlated with increased levels of nitric-oxide metabolites in the ventral hippocampus. Systemic administration of the nitric-oxide synthase inhibitor N(G)-nitro-l-nitro-arginine methyl ester reversed the increase in nitric-oxide metabolites and improvements in spatial working memory produced by darbepoetin alfa (5000 U/kg, i.p.) at a dose (10 mg/kg, i.p.) that did not impair the spatial working memory performance of intact rats. Taken together, these findings suggest that darbepoetin alfa reverses pre-existing spatial working memory deficits resulting from transient global ischemia by increasing the activity of nitric-oxide synthase, an enzyme implicated in synaptic plasticity.

Characterization of galectin-1-positive cells in the mouse hippocampus.

Galectin-1 (gal-1) is one of several well-studied proteins from the galectin families. It is a 14.5 kDa glycoprotein with a single carbohydrate-binding domain. To examine the distribution and properties of gal-1 in the mouse hippocampus, we performed immunohistochemistry using an anti-gal-1 antibody. We found that most gal-1-positive cells showed both NeuN and &bgr;-tubulin III (Tuj-1) immunoreactivity (NeuN: 93%, &bgr;-tubulin III: 88%). Furthermore, we clarified that 77% of gal-1-positive cells expressed somatostatin, 79% of gal-1-positive cells expressed GAD67, 34% of gal-1-positive cells expressed parvalbumin, 5% of gal-1-positive cells expressed calretinin, 2% of gal-1-positive cells expressed calbindin, and 31% of gal-1-positive cells expressed neuropeptide Y in the mouse hippocampus. These results indicate that gal-1 is expressed in interneurons that also express &bgr;-tubulin III and gal-1 may be a novel marker for interneuron subpopulations in the hippocampus.

Successful treatment of poststroke emotional incontinence with Yokukansan, an Asian herbal medicine: Report of two cases

peripheral arterial disease, venous insufficiency, and leg ulcers. Regarding local complications, there are reports in the literature of erythema, ecchymosis, pain, and a sensation of crepitation resulting from CO2 therapy. Danger of gas emboli with CO2 injections has not been reported. The treatment is especially beneficial for elderly adults with pressure ulcers due to immobility because they may have injections at home, avoiding hospitalization. The technique can improve tissue oxygenation, contributing to ulcer healing.

Galectin-1 deficiency improves axonal swelling of motor neurones in SOD1G93A transgenic mice

Galectin‐1, a member of the β‐galactoside‐binding lectin family, accumulates in neurofilamentous lesions in the spinal cords of both sporadic and familial amyotrophic lateral sclerosis (ALS) patients with a superoxide dismutase 1 gene (SOD1) mutation (A4V). The aim of this study was to evaluate the roles of endogenous galectin‐1 in the pathogenesis of ALS.