Fluorine-19 Magnetic Resonance Imaging for Detection of Amyloid ß Oligomers Using a Keto Form of Curcumin Derivative in a Mouse Model of Alzheimer's Disease.

Recent evidence suggests that the formation of soluble amyloid ß (Aß) aggregates with high toxicity, such as oligomers and protofibrils, is a key event that causes Alzheimer's disease (AD). However, understanding the pathophysiological role of such soluble Aß aggregates in the brain in vivo could be difficult due to the lack of a clinically available method to detect, visualize, and quantify soluble Aß aggregates in the brain. We had synthesized a novel fluorinated curcumin derivative with a fixed keto form, named as Shiga-Y51, which exhibited high selectivity to Aß oligomers in vitro. In this study, we investigated the in vivo detection of Aß oligomers by fluorine-19 (19F) magnetic resonance imaging (MRI) using Shiga-Y51 in an APP/PS1 double transgenic mouse model of AD. Significantly high levels of 19F signals were detected in the upper forebrain region of APP/PS1 mice compared with wild-type mice. Moreover, the highest levels of Aß oligomers were detected in the upper forebrain region of APP/PS1 mice in enzyme-linked immunosorbent assay. These findings suggested that 19F-MRI using Shiga-Y51 detected Aß oligomers in the in vivo brain. Therefore, 19F-MRI using Shiga-Y51 with a 7 T MR scanner could be a powerful tool for imaging Aß oligomers in the brain.

Fluorine-19 magnetic resonance imaging probe for the detection of tau pathology in female rTg4510 mice.

Aggregation of tau into neurofibrillary tangles (NFTs) is characteristic of tauopathies, including Alzheimer's disease. Recent advances in tau imaging have attracted much attention because of its potential contributions to early diagnosis and monitoring of disease progress. Fluorine-19 magnetic resonance imaging (19 F-MRI) may be extremely useful for tau imaging once a high-quality probe has been formulated. In this investigation, a novel fluorine-19-labeling compound has been developed as a probe for tau imaging using 19 F-MRI. This compound is a buta-1,3-diene derivative with a polyethylene glycol side chain bearing a CF3 group and is known as Shiga-X35. Female rTg4510 mice (a mouse model of tauopathy) and wild-type mice were intravenously injected with Shiga-X35, and magnetic resonance imaging of each mouse's head was conducted in a 7.0-T horizontal-bore magnetic resonance scanner. The 19 F-MRI in rTg4510 mice showed an intense signal in the forebrain region. Analysis of the signal intensity in the forebrain region revealed a significant accumulation of fluorine-19 magnetic resonance signal in the rTg4510 mice compared with the wild-type mice. Histological analysis showed fluorescent signals of Shiga-X35 binding to the NFTs in the brain sections of rTg4510 mice. Data collected as part of this investigation indicate that 19 F-MRI using Shiga-X35 could be a promising tool to evaluate tau pathology in the brain.

Age-related changes in the metabolic profiles of rat hippocampus, medial prefrontal cortex and striatum.

We have recently shown that age-dependent regional brain atrophy and lateral ventricle expansion may be linked with impaired cognitive and locomotor functions. However, metabolic profile transformation in different brain regions during aging is unknown. This study examined metabolic changes in the hippocampus, medial prefrontal cortex (mPFC) and striatum of middle- and late-aged Sprague-Dawley rats using ultrahigh performance liquid chromatography coupled with high-resolution accurate mass-orbitrap tandem mass spectrometry. Thirty-eight potential metabolites were altered in hippocampus, 29 in mPFC, and 14 in striatum. These alterations indicated that regional metabolic mechanisms in lated-aged rats are related to multiple pathways including glutathione, sphingolipid, tyrosine, and purine metabolism. Thus, our findings might be useful for understanding the complexity of metabolic mechanisms in aging and provide insight for aging and health span.

The effect of α-tocopherol, α- and γ-tocotrienols on amyloid-ß aggregation and disaggregation in vitro.

One of the neuropathological hallmarks of Alzheimer's disease (AD)-causing neurodegeneration and consequent memory deterioration, and eventually, cognitive decline-is amyloid-ß (Aß) aggregation forming amyloid plaques. Our previous study showed the potential of a tocotrienol-rich fraction-a mixture of naturally occurring of vitamin E analogs-to inhibit Aß aggregation and restore cognitive function in an AD mouse model. The current study examined the effect of three vitamin E analogs-α-tocopherol (α-TOC), α-tocotrienol (α-T3), and γ-tocotrienol (γ-T3)-on Aß aggregation, disaggregation, and oligomerization in vitro. Thioflavin T (ThT) assay showed α-T3 reduced Aß aggregation at 10 µM concentration. Furthermore, both α-T3 and γ-T3 demonstrated Aß disaggregation, as shown by the reduction of ThT fluorescence. However, α-TOC showed no significant effect. We confirmed the results for ThT assays with scanning electron microscopy imaging. Further investigation in photo-induced cross-linking of unmodified protein assay indicated a reduction in Aß oligomerization by γ-T3. The present study thus revealed the individual effect of each tocotrienol analog in reducing Aß aggregation and oligomerization as well as disaggregating preformed fibrils.

Modulation of Proteome Profile in AßPP/PS1 Mice Hippocampus, Medial Prefrontal Cortex, and Striatum by Palm Oil Derived Tocotrienol-Rich Fraction.

Tocotrienol-rich fraction (TRF) is a mixture of vitamin E analogs derived from palm oil. We previously demonstrated that supplementation with TRF improved cognitive function and modulated amyloid pathology in AßPP/PS1 mice brains. The current study was designed to examine proteomic profiles underlying the therapeutic effect of TRF in the brain. Proteomic analyses were performed on samples of hippocampus, medial prefrontal cortex (mPFC), and striatum using liquid chromatography coupled to Q Exactive HF Orbitrap mass spectrometry. From these analyses, we profiled a total of 5,847 proteins of which 155 proteins were differentially expressed between AßPP/PS1 and wild-type mice. TRF supplementation of these mice altered the expression of 255 proteins in the hippocampus, mPFC, and striatum. TRF also negatively modulated the expression of amyloid beta A4 protein and receptor-type tyrosine-protein phosphatase alpha protein in the hippocampus. The expression of proteins in metabolic pathways, oxidative phosphorylation, and those involved in Alzheimer's disease were altered in the brains of AßPP/PS1 mice that received TRF supplementation.

Proteome profiling in the hippocampus, medial prefrontal cortex, and striatum of aging rat.

Decrease in multiple functions occurs in the brain with aging, all of which can contribute to age-related cognitive and locomotor impairments. Brain atrophy specifically in hippocampus, medial prefrontal cortex (mPFC), and striatum, can contribute to this age-associated decline in function. Our recent metabolomics analysis showed age-related changes in these brain regions. To further understand the aging processes, analysis using a proteomics approach was carried out. This study was conducted to identify proteome profiles in the hippocampus, mPFC, and striatum of 14-, 18-, 23-, and 27-month-old rats. Proteomics analysis using ultrahigh performance liquid chromatography coupled with Q Exactive HF Orbitrap mass spectrometry identified 1074 proteins in the hippocampus, 871 proteins in the mPFC, and 241 proteins in the striatum. Of these proteins, 97 in the hippocampus, 25 in mPFC, and 5 in striatum were differentially expressed with age. The altered proteins were classified into three ontologies (cellular component, molecular function, and biological process) containing 44, 38, and 35 functional groups in the hippocampus, mPFC, and striatum, respectively. Most of these altered proteins participate in oxidative phosphorylation (e.g. cytochrome c oxidase and ATP synthase), glutathione metabolism (e.g. peroxiredoxins), or calcium signaling pathway (e.g. protein S100B and calmodulin). The most prominent changes were observed in the oldest animals. These results suggest that alterations in oxidative phosphorylation, glutathione metabolism, and calcium signaling pathway are involved in cognitive and locomotor impairments in aging.

Tocotrienol-Rich Fraction of Palm Oil Improves Behavioral Impairments and Regulates Metabolic Pathways in AßPP/PS1 Mice.

We have recently shown that the tocotrienol-rich fraction (TRF) of palm oil, a mixture of vitamin E analogs, improves amyloid pathology in vitro and in vivo. However, precise mechanisms remain unknown. In this study, we examined the effects of long-term (10 months) TRF treatment on behavioral impairments and brain metabolites in (15 months old) AßPP/PS1 double transgenic (Tg) Alzheimer's disease (AD) mice. The open field test, Morris water maze, and novel object recognition tasks revealed improved exploratory activity, spatial learning, and recognition memory, respectively, in TRF-treated Tg mice. Brain metabolite profiling of wild-type and Tg mice treated with and without TRF was performed using ultrahigh performance liquid chromatography (UHPLC) coupled to high-resolution accurate mass (HRAM)-orbitrap tandem mass spectrometry (MS/MS). Metabolic pathway analysis found perturbed metabolic pathways that linked to AD. TRF treatment partly ameliorated metabolic perturbations in Tg mouse hippocampus. The mechanism of this pre-emptive activity may occur via modulation of metabolic pathways dependent on Aß interaction or independent of Aß interaction.

Tocotrienol-Rich Fraction Modulates Amyloid Pathology and Improves Cognitive Function in AßPP/PS1 Mice.

Alzheimer's disease (AD) is the most common cause of dementia. The cardinal neuropathological characteristic of AD is the accumulation of amyloid-ß (Aß) into extracellular plaques that ultimately disrupt neuronal function and lead to neurodegeneration. One possible therapeutic strategy therefore is to prevent Aß aggregation. Previous studies have suggested that vitamin E analogs slow AD progression in humans. In the present study, we investigated the effects of the tocotrienol-rich fraction (TRF), a mixture of vitamin E analogs from palm oil, on amyloid pathology in vitro and in vivo. TRF treatment dose-dependently inhibited the formation of Aß fibrils and Aß oligomers in vitro. Moreover, daily TRF supplementation to AßPPswe/PS1dE9 double transgenic mice for 10 months attenuated Aß immunoreactive depositions and thioflavin-S-positive fibrillar type plaques in the brain, and eventually improved cognitive function in the novel object recognition test compared with control AßPPswe/PS1dE9 mice. The present result indicates that TRF reduced amyloid pathology and improved cognitive functions, and suggests that TRF is a potential therapeutic agent for AD.

Volumetric changes in the aging rat brain and its impact on cognitive and locomotor functions.

Impairments in cognitive and locomotor functions usually occur with advanced age, as do changes in brain volume. This study was conducted to assess changes in brain volume, cognitive and locomotor functions, and oxidative stress levels in middle- to late-aged rats. Forty-four male Sprague-Dawley rats were divided into four groups: 14, 18, 23, and 27months of age. 1H magnetic resonance imaging (MRI) was performed using a 7.0-Tesla MR scanner system. The volumes of the lateral ventricles, medial prefrontal cortex (mPFC), hippocampus, striatum, cerebellum, and whole brain were measured. Open field, object recognition, and Morris water maze tests were conducted to assess cognitive and locomotor functions. Blood was taken for measurements of malondialdehyde (MDA), protein carbonyl content, and antioxidant enzyme activity. The lateral ventricle volumes were larger, whereas the mPFC, hippocampus, and striatum volumes were smaller in 27-month-old rats than in 14-month-old rats. In behavioral tasks, the 27-month-old rats showed less exploratory activity and poorer spatial learning and memory than did the 14-month-old rats. Biochemical measurements likewise showed increased MDA and lower glutathione peroxidase (GPx) activity in the 27-month-old rats. In conclusion, age-related increases in oxidative stress, impairment in cognitive and locomotor functions, and changes in brain volume were observed, with the most marked impairments observed in later age.

Amyloid imaging using fluorine-19 magnetic resonance imaging ((19)F-MRI).

The formation of senile plaques followed by the deposition of amyloid-ß is the earliest pathological change in Alzheimer's disease. Thus, the detection of senile plaques remains the most important early diagnostic indicator of Alzheimer's disease. Amyloid imaging is a noninvasive technique for visualizing senile plaques in the brains of Alzheimer's patients using positron emission tomography (PET) or magnetic resonance imaging (MRI). Because fluorine-19 ((19)F) displays an intense nuclear magnetic resonance signal and is almost non-existent in the body, targets are detected with a higher signal-to-noise ratio using appropriate fluorinated contrast agents. The recent introduction of high-field MRI allows us to detect amyloid depositions in the brain of living mouse using (19)F-MRI. So far, at least three probes have been reported to detect amyloid deposition in the brain of transgenic mouse models of Alzheimer's disease; (E,E)-1-fluoro-2,5-bis-(3-hydroxycarbonyl-4-hydroxy)styrylbenzene (FSB), 1,7-bis(4'-hydroxy-3'-trifluoromethoxyphenyl)-4-methoxycarbonylethyl-1,6-heptadiene3,5-dione (FMeC1, Shiga-Y5) and 6-(3',6',9',15',18',21'-heptaoxa-23',23',23'-trifluorotricosanyloxy)-2-(4'-dimethylaminostyryl)benzoxazole (XP7, Shiga-X22). This review presents the recent advances in amyloid imaging using (19)F-MRI, including our own studies.

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 ß (Aß) in the brain is an initiating event in Alzheimer's disease (AD). Accordingly, modulating the abnormal Aß 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 Aß 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 Aß aggregates; however, only FMeC1 significantly attenuated the cell toxicity of Aß. These results indicate that FMeC1 may have potential for preventing AD.

Preferred features of a fluorine-19 MRI probe for amyloid detection in the brain.

Fluorine-19 magnetic resonance imaging (19F MRI) could be a promising approach for imaging amyloid deposition in the brain. However, the required features of a 19F MRI probe for amyloid detection remain unclear. In the present study, we investigated a series of compounds as potent 19F probes that could prevent the reduction in MR signal when bound to amyloid plaques in the brain. Each compound consists of styrylbenzoxazole as a core structure linked by a different length of polyethylene glycol (PEG) chain to one of three types of fluorine-labeled group: a trifluoroethoxy group, a hexafluoroisopropoxy group, or a 3',5'-bis(trifluoromethyl)benzylamino group. Among these compounds, 6-(3',6',9',15',18',21'-heptaoxa-23',23',23'-trifluoro tricosanyloxy)-2-(4'-dimethylaminostyryl)benzoxazole [compound 3b (m = 6)], which has a trifluoroethoxy group with seven ethylene glycol groups in the PEG chain, showed significant 19F MR signals in the brains of AßPPswe/PS1dE9 double-transgenic mice, but not wild-type mice. This suggested that compound 3b (m = 6) could be a useful 19F MRI probe for amyloid detection. Furthermore, this study identified the most effective length of PEG chain between the fluorine-labeled group and the core structure to ensure a strong MR signal when the probe is bound to amyloid plaques.