Ebselen inhibits iron-induced tau phosphorylation by attenuating DMT1 up-regulation and cellular iron uptake

Dysregulation of iron homeostasis is involved in the pathological process of Alzheimer's disease (AD). We have recently reported that divalent metal transporter 1 (DMT1) is upregulated in an AD transgenic mouse brain, and that silencing of DMT1, which reduces cellular iron influx, results in inhibition of amyloidogenesis in vitro, suggesting a potential target of DMT1 for AD therapy. In the present study, we tested the hypothesis that inhibition of DMT1 with ebselen, a DMT1 transport inhibitor, could affect tau phosphorylation. Human neuroblastoma SH-SY5Y cells were pre-treated with ebselen and then treated with ferrous sulfate (dissolved in ascorbic acid), and the effects of ebselen on tau phosphorylation and the relative signaling pathways were examined. Our results showed that ebselen decreased iron influx, reduced iron-induced ROS production, inhibited the activities of cyclin-dependent kinase 5 and glycogen synthase kinase 3β, and ultimately attenuated the levels of tau phosphorylation at the sites of Thr205, Ser396 and Thr231. The present study indicates that the neuroprotective effect of ebselen on AD is not only related to its antioxidant activity as reported previously, but is also associated with a reduction in tau phosphorylation by inhibition of DMT1.     

Coumarin-3-carboxylic acid derivatives as potentiators and inhibitors of recombinant and native N-methyl-d-aspartate receptors

N-Methyl-d-aspartate receptors (NMDARs) are known to be involved in a range of neurological and neurodegenerative disorders and consequently the development of compounds that modulate the function of these receptors has been the subject of intense interest. We have recently reported that 6-bromocoumarin-3-carboxylic acid (UBP608) is a negative allosteric modulator with weak selectivity for GluN2A-containing NMDARs. In the present study, a series of commercially available and newly synthesized coumarin derivatives have been evaluated in a structure-activity relationship (SAR) study as modulators of recombinant NMDAR activity. The main conclusions from this SAR study were that substituents as large as iodo were accommodated at the 6-position and that 6,8-dibromo or 6,8-diiodo substitution of the coumarin ring enhanced the inhibitory activity at NMDARs. These coumarin derivatives are therefore excellent starting points for the development of more potent and GluN2 subunit selective inhibitors, which may have application in the treatment of a range of neurological disorders such as neuropathic pain, epilepsy and depression. Surprisingly, 4-methyl substitution of UBP608 to give UBP714, led to conversion of the inhibitory activity of UBP608 into potentiating activity at recombinant GluN1/GluN2 receptors. UBP714 also enhanced NMDAR mediated field EPSPs in the CA1 region of the hippocampus. UBP714 is therefore a novel template for the development of potent and subunit selective NMDAR potentiators that may have therapeutic applicability in the treatment of patients with cognitive deficits or schizophrenia.     

Effects of amphetamine on dopamine release in the rat nucleus accumbens shell region depend on cannabinoid CB1 receptor activation

The psychostimulant drug amphetamine is often prescribed to treat Attention-Deficit/Hyperactivity Disorder. The behavioral effects of the psychostimulant drug amphetamine depend on its ability to increase monoamine neurotransmission in brain regions such as the nucleus accumbens (NAC) and medial prefrontal cortex (mPFC). Recent behavioral data suggest that the endocannabinoid system also plays a role in this respect. Here we investigated the role of cannabinoid CB1 receptor activity in amphetamine-induced monoamine release in the NAC and/or mPFC of rats using in vivo microdialysis. Results show that systemic administration of a low, clinically relevant dose of amphetamine (0.5mg/kg) robustly increased dopamine and norepinephrine release (to ～175-350% of baseline values) in the NAC shell and core subregions as well as the ventral and dorsal parts of the mPFC, while moderately enhancing extracellular serotonin levels (to ～135% of baseline value) in the NAC core only. Although systemic administration of the CB1 receptor antagonist SR141716A (0-3mg/kg) alone did not affect monoamine release, it dose-dependently abolished amphetamine-induced dopamine release specifically in the NAC shell. SR141716A did not affect amphetamine-induced norepinephrine or serotonin release in any of the brain regions investigated. Thus, the effects of acute CB1 receptor blockade on amphetamine-induced monoamine transmission were restricted to dopamine, and more specifically to mesolimbic dopamine projections into the NAC shell. This brain region- and monoamine-selective role of CB1 receptors is suggested to subserve the behavioral effects of amphetamine.     

Immunopathological Changes in the Brain of Immunosuppressed Mice Experimentally Infected with Toxocara canis

Toxocariasis is a soil-transmitted helminthozoonosis due to infection of humans by larvae of Toxocara canis. The disease could produce cognitive and behavioral disturbances especially in children. Meanwhile, in our modern era, the incidence of immunosuppression has been progressively increasing due to increased incidence of malignancy as well as increased use of immunosuppressive agents. The present study aimed at comparing some of the pathological and immunological alterations in the brain of normal and immunosuppressed mice experimentally infected with T. canis. Therefore, 180 Swiss albino mice were divided into 4 groups including normal (control) group, immunocompetent T. canis-infected group, immunosuppressed group (control), and immunosuppressed infected group. Infected mice were subjected to larval counts in the brain, and the brains from all mice were assessed for histopathological changes, astrogliosis, and IL-5 mRNA expression levels in brain tissues. The results showed that under immunosuppression, there were significant increase in brain larval counts, significant enhancement of reactive gliosis, and significant reduction in IL-5 mRNA expression. All these changes were maximal in the chronic stage of infection. In conclusion, the immunopathological alterations in the brains of infected animals were progressive over time, and were exaggerated under the effect of immunosuppression as did the intensity of cerebral infection.     

COPS5 Protein Overexpression Increases Amyloid Plaque Burden,Decreases Spinophilin-immunoreactive Puncta,and Exacerbates Learning and Memory Deficits in the Mouse Brain

Brain accumulation of neurotoxic amyloid β (Aβ) peptide because of increased processing of amyloid precursor protein (APP), resulting in loss of synapses and neurodegeneration, is central to the pathogenesis of Alzheimer disease (AD). Therefore, the identification of molecules that regulate Aβ generation and those that cause synaptic damage is crucial for future therapeutic approaches for AD. We demonstrated previously that COPS5 regulates Aβ generation in neuronal cell lines in a RanBP9-dependent manner. Consistent with the data from cell lines, even by 6 months, COPS5 overexpression in APΔE9 mice (APΔE9/COPS5-Tg) significantly increased Aβ40 levels by 32% (p < 0.01) in the cortex and by 28% (p < 0.01) in the hippocampus, whereas the increases for Aβ42 were 37% (p < 0.05) and 34% (p < 0.05), respectively. By 12 months, the increase was even more robust. Aβ40 levels increased by 63% (p < 0.001) in the cortex and by 65% (p < 0.001) in the hippocampus. Similarly, Aβ42 levels were increased by 69% (p < 0.001) in the cortex and by 71% (p < 0.011) in the hippocampus. Increased Aβ levels were translated into an increased amyloid plaque burden both in the cortex (54%, p < 0.01) and hippocampus (64%, p < 0.01). Interestingly, COPS5 overexpression increased RanBP9 levels in the brain, which, in turn, led to increased amyloidogenic processing of APP, as reflected by increased levels of sAPPβ and decreased levels of sAPPα. Furthermore, COPS5 overexpression reduced spinophilin in both the cortex (19%, p < 0.05) and the hippocampus (20%, p < 0.05), leading to significant deficits in learning and memory skills. Therefore, like RanBP9, COPS5 also plays a pivotal role in amyloid pathology in vivo.     

Type 5 adenylyl cyclase disruption leads to enhanced exercise performance

The most important physiological mechanism mediating enhanced exercise performance is increased sympathetic, beta adrenergic receptor (β‐AR), and adenylyl cyclase (AC) activity. This is the first report of decreased AC activity mediating increased exercise performance. We demonstrated that AC5 disruption, that is, knock out (KO) mice, a longevity model, increases exercise performance. Importantly for its relation to longevity, exercise was also improved in old AC5 KO. The mechanism resided in skeletal muscle rather than in the heart, as confirmed by cardiac‐ and skeletal muscle‐specific AC5 KO's, where exercise performance was no longer improved by the cardiac‐specific AC5 KO, but was by the skeletal muscle‐specific AC5 KO, and there was no difference in cardiac output during exercise in AC5 KO vs. WT. Mitochondrial biogenesis was a major mechanism mediating the enhanced exercise. SIRT1, FoxO3a, MEK, and the anti‐oxidant, MnSOD were upregulated in AC5 KO mice. The improved exercise in the AC5 KO was blocked with either a SIRT1 inhibitor, MEK inhibitor, or by mating the AC5 KO with MnSOD hetero KO mice, confirming the role of SIRT1, MEK, and oxidative stress mechanisms. The Caenorhabditis elegans worm AC5 ortholog, acy‐3 by RNAi, also improved fitness, mitochondrial function, antioxidant defense, and lifespan, attesting to the evolutionary conservation of this pathway. Thus, decreasing sympathetic signaling through loss of AC5 is not only a mechanism to improve exercise performance, but is also a mechanism to improve healthful aging, as exercise also protects against diabetes, obesity, and cardiovascular disease, which all limit healthful aging.     

Dual inhibition of Kif15 by oxindole and quinazolinedione chemical probes

The mitotic spindle is a microtubule-based machine that segregates a replicated set of chromosomes during cell division. Many cancer drugs alter or disrupt the microtubules that form the mitotic spindle. Microtubule-dependent molecular motors that function during mitosis are logical alternative mitotic targets for drug development. Eg5 (Kinesin-5) and Kif15 (Kinesin-12), in particular, are an attractive pair of motor proteins, as they work in concert to drive centrosome separation and promote spindle bipolarity. Furthermore, we hypothesize that the clinical failure of Eg5 inhibitors may be (in part) due to compensation by Kif15. In order to test this idea, we screened a small library of kinase inhibitors and identified GW108X, an oxindole that inhibits Kif15 in vitro. We show that GW108X has a distinct mechanism of action compared with a commercially available Kif15 inhibitor, Kif15-IN-1 and may serve as a lead with which to further develop Kif15 inhibitors as clinically relevant agents.