Daijiro Yanagisawa

Relationship between the tautomeric structures of curcumin derivatives and their Aβ-binding activities in the context of therapies for Alzheimer's disease

Curcumin, which can exist in an equilibrium between keto and enol tautomers, binds to beta-amyloid (Abeta) fibrils/aggregates. The aim of this study was to assess the relationship between the tautomeric structures of curcumin derivatives and their Abeta-binding activities. Curcumin derivatives with keto-enol tautomerism showed high levels of binding to Abeta aggregates but not to Abeta monomers. The binding activity of the keto form analogue of curcumin to Abeta aggregates was found to be much weaker than that of curcumin derivatives with keto-enol tautomerism. The color of a curcumin derivative with keto-enol tautomerism, which was substituted at the C-4 position, changed from yellow to orange within 30 min of being combined with Abeta aggregates in physiological buffer. This resulted from a remarkable increase in the enol form with extended conjugation of double bonds upon binding. These findings suggest that curcumin derivatives exist predominantly in the enol form during binding to Abeta aggregates, and that the enolization of curcumin derivatives is crucial for binding to Abeta aggregates. The keto-enol tautomerism of curcumin derivatives may be a novel target for the design of amyloid-binding agents that can be used both for therapy and for amyloid detection in Alzheimers disease.

Microglial transplantation increases amyloid-β clearance in Alzheimer model rats

Immunization with amyloid‐β (Aβ) peptides, a therapeutic approach in Alzheimers disease (AD), reduces brain Aβ, and microglial Aβ phagocytosis has been proposed as an Aβ‐lowering mechanism. We transplanted rat microglia into the rat lateral ventricle just after intra‐hippocampal Aβ injection, and then investigated the contribution of exogenous microglia to Aβ clearance. Migration of exogenous microglia from the lateral ventricle to Aβ plaque was detected by magnetic resonance imaging and histochemical analysis, and the clearance of Aβ was increased by transplantation. These results suggest the possible usefulness of exogenous microglia to the therapeutic approach in AD.

DJ-1 protects against neurodegeneration caused by focal cerebral ischemia and reperfusion in rats

Reactive oxygen species (ROS) is massively produced in the brain after cerebral ischemia and reperfusion. It reacts strongly with cellular components, which has detrimental effects and leads to neuronal cell death. DJ-1, which was found to be the causative gene of familial Parkinsons disease PARK7, is a multifunction protein, which plays a key role in transcriptional regulation, and a molecular chaperone. In this study, we investigated the neuroprotective effect of DJ-1 against neurodegeneration caused by ischemia/reperfusion injury. Cerebral ischemia was induced in rats by 120 mins of middle cerebral artery occlusion (MCAO) using an intraluminal introduction method. The intrastriatal injection of recombinant glutathione S-transferase-tagged human DJ-1 (GST-DJ-1) markedly reduced infarct size in 2,3,5-triphenyltetrazolium chloride staining at 3 days after MCAO. In addition, we performed a noninvasive evaluation of ischemic size using magnetic resonance imaging and found a significant reduction of infarct size with the administration of GST-DJ-1. In GST-DJ-1-treated rats, behavioral dysfunction and nitrotyrosine formation were significantly inhibited. Furthermore, GST-DJ-1 markedly inhibited H2O2-mediated ROS production in SH-SY5Y cells. These results indicate that GST-DJ-1 exerts a neuroprotective effect by reducing ROS-mediated neuronal injury, suggesting that DJ-1 may be a useful therapeutic target for ischemic neurodegeneration.

In vivo detection of amyloid β deposition using 19F magnetic resonance imaging with a 19F-containing curcumin derivative in a mouse model of Alzheimer's disease

Amyloid β (Aβ) deposition in the brain is considered the initiating event in the progression of Alzheimers disease (AD). Amyloid imaging is widely studied in diagnosing AD and evaluating the disease stage, with considerable advances achieved in recent years. We have developed a novel ¹⁹F-containing curcumin derivative (named FMeC1) as a potential imaging agent. This compound can exist in equilibrium between keto and enol tautomers, with the enol form able to bind Aβ aggregates while the keto form cannot. This study investigated whether FMeC1 is suitable as a ¹⁹F magnetic resonance imaging (MRI) probe to detect Aβ deposition in the Tg2576 mouse, a model of AD. In ¹⁹F nuclear magnetic resonance (NMR) spectra obtained from the whole head, a delayed decreased rate of F ¹⁹F signal was observed in Tg2576 mice that were peripherally injected with FMeC1 in comparison to wild-type mice. Furthermore, ¹⁹F MRI displayed remarkable levels of ¹⁹F signal in the brain of Tg2576 mice after the injection of FMeC1. Histological analysis of FMeC1-injected mouse brain showed penetration of the compound across the blood-brain barrier and binding to Aβ plaques in peripherally injected Tg2576 mice. Moreover, the distribution of Aβ deposits in Tg2576 mice was in accordance with the region of the brain in which the ¹⁹F signal was imaged. FMeC1 also exhibited an affinity for senile plaques in human brain sections. These findings suggest the usefulness of FMeC1 as a ¹⁹F MRI probe for the detection of amyloid deposition in the brain. Furthermore, the properties of FMeC1 could form the basis for further novel amyloid imaging probes.

Improvement of focal ischemia-induced rat dopaminergic dysfunction by striatal transplantation of mouse embryonic stem cells.

Middle cerebral artery occlusion (MCAO) caused behavioral dysfunction with massive neuronal loss. Cell transplantation may recover this deficit by replacing damaged brain cells. In this study, we examined the effects of transplantation of mouse embryonic stem (ES) cells or ES cell-derived neuron-like (ES-N) cells on behavioral function in ischemic rats. Seven days after MCAO, ES or ES-N cells were transplanted into ipsilateral striata (but not the substantia nigra) of ischemic rats. Transplanted rats exhibited a gradual reduction in the number of rotations induced by methamphetamine compared to vehicle-injected rats. These rats also showed a significant improvement in rota-rod performance. At 15 weeks after transplantation, immunoreactivities for tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the striatum were significantly recovered in rats grafted with ES or ES-N cells compared to vehicle-injected rats. These results suggest that intrastriatal-transplantation of ES or ES-N cells improved the dopaminergic function and subsequently recover behavioral dysfunction in focal ischemic rats.

Mitochondrial ferritin in neurodegenerative diseases

Mitochondrial ferritin (FtMt) is a novel protein encoded by an intronless gene mapped to chromosome 5q23.1. Ferritin is ubiquitously expressed; however, FtMt expression is restricted to specific tissues such as the testis and the brain. The distribution pattern of FtMt suggests a functional role for this protein in the brain; however, data concerning the roles of FtMt in neurodegenerative diseases remain scarce. In the human cerebral cortex, FtMt expression was increased in Alzheimers disease patients compared to control cases. Cultured neuroblastoma cells showed low-level expression of FtMt, which was increased by H2O2 treatment. FtMt overexpression showed a neuroprotective effect against H2O2-induced oxidative stress and Aβ-induced neurotoxicity in neuroblastoma cells. FtMt expression was also detected in dopaminergic neurons in the substantia nigra and was increased in patients with restless legs syndrome, while FtMt had a protective effect against cell death in a neuroblastoma cell line model of Parkinsons disease. FtMt is involved in other neurodegenerative diseases such as age-related macular degeneration (AMD), with an FtMt gene mutation identified in AMD patients, and Friedreichs ataxia, which is caused by a deficiency in frataxin. FtMt overexpression in frataxin-deficient cells increased cell resistance to H2O2 damage. These results implicate a neuroprotective role of FtMt in neurodegenerative diseases.

Curcuminoid binds to amyloid-β1-42 oligomer and fibril.

Studies of Alzheimers disease (AD) strongly support the hypothesis that amyloid-β (Aβ) deposition in the brain is the initiating event in the progression of AD. Aβ peptides easily form long insoluble amyloid fibrils, which accumulate in deposits known as senile plaques. On the other hand, recent work indicated that soluble Aβ oligomers, rather than monomers or insoluble Aβ fibrils, might be responsible for neuronal and synaptic dysfunction in AD. Curcumin, a low molecular weight yellow-orange pigment derived from the turmeric plant, has shown therapeutic effects in transgenic mouse models of AD. However, it remains unclear whether curcumin interacts directly with the Aβ oligomers. This study investigated any interaction between curcumin and Aβ oligomers such as globulomer and Aβ-derived diffusible ligand (ADDL). Globulomer was observed as a cluster of spherical structures by electron microscopic analysis, and ADDL was also detected as small spherical structures. Fluorescence analysis revealed a significant increase in the fluorescence of curcumin when reacted with both oligomers. Furthermore quartz crystal microbalance analysis showed significant frequency decreases in oligomer-immobilized electrodes following the addition of curcumin. These results strongly suggested that curcumin binds to Aβ oligomers and to Aβ fibrils. The association of curcumin with Aβ oligomers may contribute to the therapeutic effect on AD. Based on these findings, curcumin could provide the basis of a novel concept in AD therapies targeting Aβ oligomers.

Serofendic acid prevents 6-hydroxydopamine-induced nigral neurodegeneration and drug-induced rotational asymmetry in hemi-parkinsonian rats.

Serofendic acid was recently identified as a neuroprotective factor from fetal calf serum. This study was designed to evaluate the neuroprotective effects of an intranigral microinjection of serofendic acid based on behavioral, neurochemical and histochemical studies in hemi‐parkinsonian rats using 6‐hydroxydopamine (6‐OHDA). Rats were injected with 6‐OHDA in the presence or absence of serofendic acid, or were treated with serofendic acid on the same lateral side, at 12, 24 or 72 h after 6‐OHDA lesion. Intranigral injection of 6‐OHDA alone induced a massive loss of tyrosine hydroxylase (TH)‐immunopositive neurons in the substantia nigra pars compacta (SNpc). Either simultaneous or 12 h post‐administration of serofendic acid significantly prevented both dopaminergic neurodegeneration and drug‐induced rotational asymmetry. Immunoreactivities for oxidative stress markers, such as 3‐nitrotyrosine (3‐NT) and 4‐hydroxy‐2‐nonenal (4‐HNE), were markedly detected in the SNpc of rats injected with 6‐OHDA alone. These immunoreactivities were markedly suppressed by the co‐administration of serofendic acid, similar to the results in vehicle‐treated control rats. In addition, serofendic acid inhibited 6‐OHDA‐induced α‐synuclein expression and glial activation in the SNpc. These results suggest that serofendic acid protects against 6‐OHDA‐induced SNpc dopaminergic neurodegeneration in a rat model of Parkinsons disease.

Inhalable Curcumin: Offering the Potential for Translation to Imaging and Treatment of Alzheimer's Disease

Curcumin is a promising compound that can be used as a theranostic agent to aid research in Alzheimers disease. Beyond its ability to bind to amyloid plaques, the compound can also cross the blood-brain barrier. Presently, curcumin can be applied only to animal models, as the formulation needed for iv injection renders it unfit for human use. Here, we describe a novel technique to aerosolize a curcumin derivative, FMeC1, and facilitate its safe delivery to the brain. Aside from the translational applicability of this approach, a study in the 5XFAD mouse model suggested that inhalation exposure to an aerosolized FMeC1 modestly improved the distribution of the compound in the brain. Additionally, immunohistochemistry data confirms that following aerosol delivery, FMeC1 binds amyloid plaques expressed in the hippocampal areas and cortex.

Curcumin derivative with the substitution at C-4 position, but not curcumin, is effective against amyloid pathology in APP/PS1 mice

Recent evidence supports the amyloid cascade hypothesis that a pathological change of amyloid β (Aβ) in the brain is an initiating event in Alzheimers disease (AD). Accordingly, modulating the abnormal Aβ aggregation is considered a potential therapeutic target in AD. Curcumin, a low-molecular-weight polyphenol derived from the well-known curry spice turmeric, has shown favorable effects on preventing or treating AD pathology. The present study investigated the effects of curcumin and 2 novel curcumin derivatives, FMeC1 and FMeC2, on AD pathology in APPswe/PS1dE9 double transgenic mice. Mice fed a chow diet that contained FMeC1 for 6 months showed a reduction in insoluble Aβ deposits and glial cell activity together with reduced cognitive deficits, compared to animals receiving a control diet or with curcumin or FMeC2 in their diet. Both curcumin and FMeC1 modulated the formation of Aβ aggregates; however, only FMeC1 significantly attenuated the cell toxicity of Aβ. These results indicate that FMeC1 may have potential for preventing AD.