Immunohistochemical Study of Human Mitochondrial Ferritin in the Substantia Nigra Following Subarachnoid Hemorrhage.

Mitochondrial ferritin (FtMt) is a novel ferritin that sequesters iron and plays a protective role against oxidative stress. FtMt shares a high homology with H-ferritin but is expressed only in the brain, heart, and testis. In the midbrain, FtMt expression is observed in the substantia nigra. FtMt plays a neuroprotective role in the pathology of neurodegenerative diseases such as Parkinson's disease, where excessive iron induces oxidative stress, causing cell death. Herein, we investigated FtMt immunoreactivity in the brains of patients with subarachnoid hemorrhage (SAH). Double immunofluorescence labeling of tyrosine hydroxylase (TH) and FtMt showed high colocalization in the substantia nigra pars compacta (SNc) in control and SAH cases. However, in SAH cases, FtMt immunoreactivity was observed in some TH-negative neurons. Double immunofluorescence labeling of glial cell markers and FtMt showed no apparent colocalization. The number and ratio of FtMt-positive but TH-negative neurons significantly differed between the control and SAH groups. Prussian blue staining in SAH cases showed positive iron staining over a wide surface range and the substantia nigra. Thus, FtMt may be related to iron dynamics in the substantia nigra following subarachnoid hemorrhage.

Neuronal glutathione depletion elevates the Aß42/Aß40 ratio and tau aggregation in Alzheimer's disease mice.

Alzheimer's disease (AD) involves reduced glutathione levels, causing oxidative stress and contributing to neuronal cell death. Our prior research identified diminished glutamate-cysteine ligase catalytic subunit (GCLC) as linked to cell death. However, the effect of GCLC on AD features such as amyloid and tau pathology remained unclear. To address this, we investigated amyloid pathology and tau pathology in mice by combining neuron-specific conditional GCLC knockout mice with amyloid precursor protein (App) knockin (KI) or microtubule-associated protein tau (MAPT) KI mice. Intriguingly, GCLC knockout resulted in an increased Aß42/40 ratio. Additionally, GCLC deficiency in MAPT KI mice accelerated the oligomerization of tau through intermolecular disulfide bonds. These findings suggest that the decline in glutathione levels, due to aging or AD pathology, may contribute to the progression of AD.

Association of step counts with cognitive function in apparently healthy middle-aged and older Japanese men.

Background: Increasing physical activity may prevent cognitive decline. Previous studies primarily focused on older adults and used self-reported questionnaires to assess physical activity. We examined the relationship between step count, an objective measure of physical activity, and cognitive function in community-based middle-aged and older Japanese men. Methods: The Shiga Epidemiological Study of Subclinical Atherosclerosis randomly recruited community-dwelling healthy men aged 40-79 years from Shiga, Japan, and measured their step counts over 7 consecutive days using a pedometer at baseline (2006-2008). Among men who returned for follow-up (2009-2014), we assessed their cognitive function using the Cognitive Abilities Screening Instrument (CASI) score. We restricted our analyses to those with valid 7-day average step counts at baseline and those who remained free of stroke at follow-up (n = 676). Using analysis of covariance, we calculated the adjusted means of the CASI score according to the quartiles of the average step counts. Results: The mean (standard deviation) of age and unadjusted CASI score were 63.8 (9.1) years and 90.8 (5.8), respectively. The CASI score was elevated in higher quartiles of step counts (90.2, 90.4, 90.6, and 91.8 from the lowest to the highest quartile, respectively, [p for trend = 0.004]) in a model adjusted for age and education. Further adjustment for smoking, drinking, and other cardiovascular risk factors resulted in a similar pattern of association (p for trend = 0.005). Conclusion: In apparently healthy middle-aged and older Japanese men, a greater 7-day average step count at baseline was associated with significantly higher cognitive function score.

Fluorinated curcumin derivative (Shiga-Y6) modulates the level of thioredoxin-interacting protein (TXNIP) in a mouse model of diabetes.

Thioredoxin interacting protein (TXNIP) has emerged as a significant regulator of ß-cell mass and loss, rendering it an attractive target for treating diabetes. We previously showed that Shiga-Y6, a fluorinated curcumin derivative, inhibited TXNIP mRNA and protein expression in vitro, raising the question of whether the same effect could be translated in vivo. Herein, we examined the effect of Shiga-Y6 on TNXIP levels and explored its therapeutic potential in a mouse model of diabetes, Akita mice. We intraperitoneally injected Shiga-Y6 (SY6; 30 mg/kg of body weight) or vehicle into 8-week-old Akita mice for 28 consecutive days. On day 29, the mice were euthanized, following which the serum levels of glucose, insulin, and glucagon were measured using ELISA, the expression of TXNIP in pancreatic tissue lysates was determined using western blotting, and the level of ß-cell apoptosis was assessed using the TUNEL assay. TXNIP levels in the pancreatic tissue of Akita mice were significantly elevated compared with wild-type (WT) mice. Shiga-Y6 administration for 28 days significantly lowered those levels compared with Akita mice that received vehicle to a level comparable to WT mice. In immunohistochemical analysis, both α- to ß-cell ratio and the number of apoptotic ß-cells were significantly reduced in SY6-treated Akita mice, compared with vehicle-treated Akita mice. Findings from the present study suggest a potential of Shiga-Y6 as an antidiabetic agent through lowering TXNIP protein levels and ameliorating pancreatic ß-cells apoptosis.

Immunohistochemical Analysis of Mitochondrial Ferritin in the Midbrain of Patients with Parkinson's Disease.

Mitochondrial ferritin (FtMt) is an endogenous iron-storage protein localized in the mitochondria. FtMt is mainly observed in restricted tissues, such as those in the testis, islets of Langerhans, and brain. Further, it may protect cells from oxidative stress in neurodegenerative diseases, including Alzheimer's disease and progressive supranuclear palsy. However, the role of FtMt in Parkinson's disease (PD) remains unclear. Therefore, the current study investigated the localization and expression level of FtMt in the midbrain of patients with PD and healthy controls using immunohistochemical techniques. FtMt immunoreactivity was mainly detected in dopaminergic neurons in the substantia nigra pars compacta (SNc) in both healthy controls and patients with PD. In addition, FtMt-positive particles were observed outside the dopaminergic neurons in patients with PD. Based on a quantitative comparison, patients with PD had a significantly upregulated FtMt immunoreactivity in dopaminergic neurons than healthy controls. Our result might be helpful in future studies on the role of FtMt in PD.

Association of Arterial Stiffness and Atherosclerotic Burden With Brain Structural Changes Among Japanese Men.

Background Little is known regarding whether arterial stiffness and atherosclerotic burden are each independently associated with brain structural changes. Simultaneous assessments of both arterial stiffness and atherosclerotic burden in associations with brain could provide insights into the mechanisms of brain structural changes. Methods and Results Using data from the SESSA (Shiga Epidemiological Study of Subclinical Atherosclerosis), we analyzed data among 686 Japanese men (mean [SD] age, 67.9 [8.4] years; range, 46-83 years) free from history of stroke and myocardial infarction. Brachial-ankle pulse wave velocity and coronary artery calcification on computed tomography scans were measured between March 2010 and August 2014. Brain volumes (total brain volume, gray matter, Alzheimer disease signature and prefrontal) and brain vascular damage (white matter hyperintensities) were quantified using brain magnetic resonance imaging from January 2012 through February 2015. In multivariable adjustment models including mean arterial pressure, when brachial-ankle pulse wave velocity and coronary artery calcification were entered into the same models, the ß (95% CI) for Alzheimer disease signature volume for each 1-SD increase in brachial-ankle pulse wave velocity was -0.33 (-0.64 to -0.02), and the unstandardized ß (95% CI) for white matter hyperintensities for each 1-unit increase in coronary artery calcification was 0.68 (0.05-1.32). Brachial-ankle pulse wave velocity and coronary artery calcification were not statistically significantly associated with total brain and gray matter volumes. Conclusions Among Japanese men, higher arterial stiffness was associated with lower Alzheimer disease signature volumes, whereas higher atherosclerotic burden was associated with brain vascular damage. Arterial stiffness and atherosclerotic burden may be independently associated with brain structural changes via different pathways.

Identification of TEKTIN1-expressing multiciliated cells during spontaneous differentiation of non-human primate embryonic stem cells.

Tektins are a group of microtubule-stabilizing proteins necessary for cilia and flagella assembly. TEKTIN1 (TEKT1) is used as a sperm marker for monitoring germ cell differentiation in embryonic stem (ES) and induced pluripotent stem (iPS) cells. Although upregulation of TEKT1 has been reported during spontaneous differentiation of ES and iPS cells, it is unclear which cells express TEKT1. To identify TEKT1-expressing cells, we established an ES cell line derived from cynomolgus monkeys (Macaca fascicularis), which expresses Venus controlled by the TEKT1 promoter. Venus expression was detected at 5 weeks of differentiation on the surface of the embryoid body (EB), and it gradually increased with the concomitant formation of a leash-like structure at the EB periphery. Motile cilia were observed on the surface of the Venus-positive leash-like structure after 8 weeks of differentiation. The expression of cilia markers as well as TEKT1-5 and 9 + 2 microtubule structures, which are characteristic of motile cilia, were detected in Venus-positive cells. These results demonstrated that TEKT1-expressing cells are multiciliated epithelial-like cells that form a leash-like structure during the spontaneous differentiation of ES and iPS cells. These findings will provide a new research strategy for studying cilia biology, including ciliogenesis and ciliopathies.

Nonylphenol reduced the number of haploids in in vitro spermatogenesis of the endangered cyprinid Gnathopogon caerulescens.

Nonylphenol (NP), an endocrine disrupting chemical, is widely used in industrial and agricultural processes, causing NP influx into aquatic environments. NP induces hormonal imbalance, and male feminization, and reduces germ cell production during spermatogenesis; however, the mechanism by which it affects spermatogenesis remains unknown. Here, we investigated the effect of NP on spermatogenesis in honmoroko (Gnathopogon caerulescens), an endangered fish endemic to Lake Biwa, Japan, using an in vitro differentiation system. We collected spermatogonia from the testes of non-spawning G. caerulescens and subjected them to suspension culture. The spermatogonia differentiated into flagellated spermatozoa in 3 weeks, regardless of the presence of NP. NP concentrations as low as 1 nM caused a decrease in the number of germ cells in a dose-dependent manner, whereas the number of somatic cells decreased only at a high concentration of 1 µM. Flow cytometric analysis revealed that the decrease in germ cell number was attributed to haploids (spermatids and spermatozoa); the number of spermatogonia and spermatocytes was not affected by NP treatment. This result is consistent with the hypothesis that NP might repress the second meiosis or induce apoptosis in haploids. This study demonstrated that the combination of in vitro germ cell differentiation and flow cytometric analysis is useful for evaluating the direct effects of NP on germ cell differentiation in endangered endemic fish.

Optimization of 3D Immunofluorescence Analysis and Visualization Using IMARIS and MeshLab.

The precision of colocalization analysis is enhanced by 3D and is potentially more accurate than 2D. Even though 3D improves the visualization of colocalization analysis, rendering a colocalization model may generate a model with numerous polygons. We developed a 3D colocalization model of FtMt/LC3 followed by simplification. Double immunofluorescence staining of FtMt and LC3 was conducted, and stacked images were acquired. We used IMARIS to render the 3D colocalization model of FtMt/LC3 and further processed it with MeshLab to decimate and generate a less complex colocalization model. We examined the available simplification algorithm using MeshLab in detail and evaluated the feasibility of each procedure in generating a model with less complexity. The quality of the simplified model was subsequently assessed. MeshLab's available shaders were scrutinized to facilitate the spatial colocalization determination. Finally, we showed that QECD was the most effective method for reducing the polygonal complexity of the colocalization model without compromising its quality. In addition, we would recommend implementing the x-ray shader, which we found useful for visualizing colocalization. As 3D was found to be more accurate in quantifying colocalization, our study provides a novel and dependable method for rendering 3D models for colocalization analysis.

Visualization of Amyloid Oligomers in the Brain of Patients with Alzheimer's Disease.

In the pathogenesis of Alzheimer's disease (AD), highly neurotoxic amyloid-ß (Aß) oligomers appear early, they are thus considered to be deeply involved in the onset of Alzheimer's disease. However, Aß oligomer visualization is challenging in human tissues due to their multiple forms (e.g., low- and high-molecular-weight oligomers, including protofibrils) as well as their tendency to rapidly change forms and aggregate. In this review, we present two visualization approaches for Aß oligomers in tissues: an immunohistochemical (using the monoclonal antibody TxCo1 against toxic Aß oligomer conformers) and imaging mass spectrometry using the small chemical Shiga-Y51 that specifically binds Aß oligomers. TxCo1 immunohistochemistry revealed Aß oligomer distributions in postmortem human brains with AD. Using Shiga-Y51, imaging mass spectrometry revealed Aß oligomer distributions in the brain of a transgenic mouse model for AD. These two methods would potentially contribute to elucidating the pathological mechanisms underlying AD.

Optimization of the Linker Length in the Dimer Model of E22P-Aß40 Tethered at Position 38.

Since amyloid ß (Aß) oligomers are more cytotoxic than fibrils, various dimer models have been synthesized. We focused on the C-terminal region that could form a hydrophobic core in the aggregation process and identified a toxic conformer-restricted dimer model (E22P,G38DAP-Aß40 dimer) with an l,l-2,6-diaminopimelic acid linker (n = 3) at position 38, which exhibited moderate cytotoxicity. We synthesized four additional linkers (n = 2, 4, 5, 7) to determine the most appropriate distance between the two Aß40 monomers for a toxic dimer model. Each di-Fmoc-protected two-valent amino acid was synthesized from a corresponding dialdehyde or cycloalkene followed by ozonolysis, using a Horner-Wadsworth-Emmons reaction and asymmetric hydrogenation. Then, the corresponding Aß40 dimer models with these linkers at position 38 were synthesized using the solid-phase Fmoc strategy. Their cytotoxicity toward SH-SY5Y cells suggested that the shorter the linker length, the stronger the cytotoxicity. Particularly, the E22P,G38DAA-Aß40 dimer (n = 2) formed protofibrillar aggregates and exhibited the highest cytotoxicity, equivalent to E22P-Aß42, the most cytotoxic analogue of Aß42. Ion mobility-mass spectrometry (IM-MS) measurement indicated that all dimer models except the E22P,G38DAA-Aß40 dimer existed as stable oligomers (12-24-mer). NativePAGE analysis supported the IM-MS data, but larger oligomers (30-150-mer) were also detected after a 24 h incubation. Moreover, E22P,G38DAA-Aß40, E22P,G38DAP-Aß40, and E22P,G38DAZ-Aß40 (n = 5) dimers suppressed long-term potentiation (LTP). Overall, the ability to form fibrils with cross ß-sheet structures was key to achieving cytotoxicity, and forming stable oligomers less than 150-mer did not correlate with cytotoxicity and LTP suppression.

Synthesis and Characterization of Propeller- and Parallel-Type Full-Length Amyloid ß40 Trimer Models.

Oligomers of the amyloid ß (Aß) protein play a critical role in the pathogenesis of Alzheimer's disease. However, their heterogeneity and lability deter the identification of their tertiary structures and mechanisms of action. Aß trimers and Aß dimers may represent the smallest aggregation unit with cytotoxicity. Although propeller-type trimer models of E22P-Aß40 tethered by an aromatic linker have recently been synthesized, they unexpectedly exhibited little cytotoxicity. To increase the flexibility of trimeric propeller-type models, we designed and synthesized trimer models with an alkyl linker, tert-butyltris-l-alanine (tButA), at position 36 or 38. In addition, we synthesized two parallel-type trimer models tethered at position 38 using alkyl linkers of different lengths, α,α-di-l-norvalyl-l-glycine (di-nV-Gly) and α,α-di-l-homonorleucyl-l-glycine (di-hnL-Gly), based on the previously reported toxic dimer model. The propeller-type E22P,V36tButA-Aß40 trimer (4), which was designed to mimic the C-terminal anti-parallel ß-sheet structures proposed by the structural analysis of 150 kDa oligomers of Aß42, and the parallel-type E22P,G38di-nV-Gly-Aß40 trimer (6) showed significant cytotoxicity against SH-SY5Y cells and aggregative ability to form protofibrillar species. In contrast, the E22P,G38tButA-Aß40 trimer (5) and E22P,G38di-hnL-Gly-Aß40 trimer (7) exhibited weak cytotoxicity, though they formed quasi-stable oligomers observed by ion mobility-mass spectrometry and native polyacrylamide gel electrophoresis. These results suggest that 4 and 6 could have some phase of the structure of toxic Aß oligomers with a C-terminal hydrophobic core and that the conformation and/or aggregation process rather than the formation of stable oligomers contribute to the induction of cytotoxicity.

Pharmaceutical Potential of Casein-Derived Tripeptide Met-Lys-Pro: Improvement in Cognitive Impairments and Suppression of Inflammation in APP/PS1 Mice.

BACKGROUND: Tripeptide Met-Lys-Pro (MKP), a component of casein hydrolysates, has effective angiotensin-converting enzyme (ACE) inhibitory activity. Brain angiotensin II enzyme activates the NADPH oxidase complex via angiotensin II receptor type 1 (AT1) and enhances oxidative stress injury. ACE inhibitors improved cognitive function in Alzheimer's disease (AD) mouse models and previous clinical trials. Thus, although undetermined, MKP may be effective against pathological amyloid-ß (Aß) accumulation-induced cognitive impairment. OBJECTIVE: The current study aimed to investigate the potential of MKP as a pharmaceutical against AD by examining MKP's effect on cognitive function and molecular changes in the brain using double transgenic (APP/PS1) mice. METHODS: Experimental procedures were conducted in APP/PS1 mice (n = 38) with a C57BL/6 background. A novel object recognition test was used to evaluate recognition memory. ELISA was used to measure insoluble Aß40, Aß42, and TNF-α levels in brain tissue. Immunohistochemical analysis allowed the assessment of glial cell activation in MKP-treated APP/PS1 mice. RESULTS: The novel object recognition test revealed that MKP-treated APP/PS1 mice showed significant improvement in recognition memory. ELISA of brain tissue showed that MKP significantly reduced insoluble Aß40, Aß42, and TNF-α levels. Immunohistochemical analysis indicated the suppression of the marker for microglia and reactive astrocytes in MKP-treated APP/PS1 mice. CONCLUSION: Based on these results, we consider that MKP could ameliorate pathological Aß accumulation-induced cognitive impairment in APP/PS1 mice. Furthermore, our findings suggest that MKP potentially contributes to preventing cognitive decline in AD.

A Histochemical Analysis of Neurofibrillary Tangles in Olfactory Epithelium, a Study Based on an Autopsy Case of Juvenile Alzheimer's Disease.

The pathological changes of Alzheimer's disease (AD) begin 10-20 years before clinical onset, and it is therefore desirable to identify effective methods for early diagnosis. The nasal mucosa is a target tissue for measuring AD-related biomarkers because the olfactory nerve is the only cranial nerve that is exposed to the external environment. We describe an autopsy case of rapidly advanced juvenile AD (JAD), focusing on the olfactory system. The formation of senile plaques, neurofibrillary tangles (NFTs), and neuropil threads was examined in the temporal cortex, hippocampus, olfactory bulb, and olfactory and respiratory epithelia in the bilateral olfactory clefts. Neurodegenerative changes in the olfactory and respiratory epithelia and the pathological deposition of amyloid ß42 (Aß42) and phosphorylated tau were also examined. As a result, senile plaques, NFTs, and neuropil threads were found in the temporal cortex, hippocampus, and olfactory bulb. NFTs were also found in the olfactory epithelium. Degenerated olfactory cells and their axons stained positive for phosphorylated tau. Supporting cells in the degenerated olfactory epithelium stained positive for Aß42. In conclusion, pathological biomarkers of AD were expressed in the degenerated olfactory epithelium of this JAD patient. This observation suggests that nasal samples may be useful for the diagnosis of AD.

Nicotinic Acetylcholine Receptors and Microglia as Therapeutic and Imaging Targets in Alzheimer's Disease.

Amyloid-ß (Aß) accumulation and tauopathy are considered the pathological hallmarks of Alzheimer's disease (AD), but attenuation in choline signaling, including decreased nicotinic acetylcholine receptors (nAChRs), is evident in the early phase of AD. Currently, there are no drugs that can suppress the progression of AD due to a limited understanding of AD pathophysiology. For this, diagnostic methods that can assess disease progression non-invasively before the onset of AD symptoms are essential, and it would be valuable to incorporate the concept of neurotheranostics, which simultaneously enables diagnosis and treatment. The neuroprotective pathways activated by nAChRs are attractive targets as these receptors may regulate microglial-mediated neuroinflammation. Microglia exhibit both pro- and anti-inflammatory functions that could be modulated to mitigate AD pathogenesis. Currently, single-cell analysis is identifying microglial subpopulations that may have specific functions in different stages of AD pathologies. Thus, the ability to image nAChRs and microglia in AD according to the stage of the disease in the living brain may lead to the development of new diagnostic and therapeutic methods. In this review, we summarize and discuss the recent findings on the nAChRs and microglia, as well as their methods for live imaging in the context of diagnosis, prophylaxis, and therapy for AD.

Structure Optimization of the Toxic Conformation Model of Amyloid ß42 by Intramolecular Disulfide Bond Formation.

Amyloid ß (Aß) oligomers play a critical role in the pathology of Alzheimer's disease. Recently, we reported that a conformation-restricted Aß42 with an intramolecular disulfide bond through cysteine residues at positions 17/28 formed stable oligomers with potent cytotoxicity. To further optimize this compound as a toxic conformer model, we synthesized three analogues with a combination of cysteine and homocysteine at positions 17/28. The analogues with Cys-Cys, Cys-homoCys, or homoCys-Cys, but not the homoCys-homoCys analogue, exhibited potent cytotoxicity against SH-SY5Y and THP-1 cells even at 10 nM. In contrast, the cytotoxicity of conformation-restricted analogues at positions 16/29 or 18/27 was significantly weaker than that of wild-type Aß42. Furthermore, thioflavin-T assay, non-denaturing gel electrophoresis, and morphological studies suggested that the majority of these conformation-restricted analogues exists in an oligomeric state in cell culture medium, indicating that the toxic conformation of Aß42, rather than the oligomeric state, is essential to induce cytotoxicity.

LC3/FtMt Colocalization Patterns Reveal the Progression of FtMt Accumulation in Nigral Neurons of Patients with Progressive Supranuclear Palsy.

Mitochondrial ferritin (FtMt) is a mitochondrial iron storage protein associated with neurodegenerative diseases. In patients with progressive supranuclear palsy (PSP), FtMt was shown to accumulate in nigral neurons. Here, we investigated FtMt and LC3 in the post-mortem midbrain of PSP patients to reveal novel aspects of the pathology. Immunohistochemistry was used to assess the distribution and abnormal changes in FtMt and LC3 immunoreactivities. Colocalization analysis using double immunofluorescence was performed, and subcellular patterns were examined using 3D imaging and modeling. In the substantia nigra pars compacta (SNc), strong FtMt-IR and LC3-IR were observed in the neurons of PSP patients. In other midbrain regions, such as the superior colliculus, the FtMt-IR and LC3-IR remained unchanged. In the SNc, nigral neurons were categorized into four patterns based on subcellular LC3/FtMt immunofluorescence intensities, degree of colocalization, and subcellular overlapping. This categorization suggested that concomitant accumulation of LC3/FtMt is related to mitophagy processes. Using the LC3-IR to stage neuronal damage, we retraced LC3/FtMt patterns and revealed the progression of FtMt accumulation in nigral neurons. Informed by these findings, we proposed a hypothesis to explain the function of FtMt during PSP progression.

An insight into the neuroprotective and anti-neuroinflammatory effects and mechanisms of Moringa oleifera.

Neurodegenerative diseases (NDs) are sporadic maladies that affect patients' lives with progressive neurological disabilities and reduced quality of life. Neuroinflammation and oxidative reaction are among the pivotal factors for neurodegenerative conditions, contributing to the progression of NDs, such as Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS) and Huntington's disease (HD). Management of NDs is still less than optimum due to its wide range of causative factors and influences, such as lifestyle, genetic variants, and environmental aspects. The neuroprotective and anti-neuroinflammatory activities of Moringa oleifera have been documented in numerous studies due to its richness of phytochemicals with antioxidant and anti-inflammatory properties. This review highlights up-to-date research findings on the anti-neuroinflammatory and neuroprotective effects of M. oleifera, including mechanisms against NDs. The information was gathered from databases, which include Scopus, Science Direct, Ovid-MEDLINE, Springer, and Elsevier. Neuroprotective effects of M. oleifera were mainly assessed by using the crude extracts in vitro and in vivo experiments. Isolated compounds from M. oleifera such as moringin, astragalin, and isoquercitrin, and identified compounds of M. oleifera such as phenolic acids and flavonoids (chlorogenic acid, gallic acid, ferulic acid, caffeic acid, kaempferol, quercetin, myricetin, (-)-epicatechin, and isoquercitrin) have been reported to have neuropharmacological activities. Therefore, these compounds may potentially contribute to the neuroprotective and anti-neuroinflammatory effects. More in-depth studies using in vivo animal models of neurological-related disorders and extensive preclinical investigations, such as pharmacokinetics, toxicity, and bioavailability studies are necessary before clinical trials can be carried out to develop M. oleifera constituents into neuroprotective agents.

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.

A Fluorine-19 Magnetic Resonance Probe, Shiga-Y5, Downregulates Thioredoxin-Interacting Protein Expression in the Brain of a Mouse Model of Alzheimer's Disease.

Thioredoxin-interacting protein (TXNIP) is involved in multiple disease-associated functions related to oxidative stress, especially by inhibiting the anti-oxidant- and thiol-reducing activity of thioredoxin (TXN). Shiga-Y5 (SY5), a fluorine-19 magnetic resonance probe for detecting amyloid-ß deposition in the brain, previously showed therapeutic effects in a mouse model of Alzheimer's disease; however, the mechanism of action of SY5 remains unclear. SY5 passes the blood-brain barrier and then undergoes hydrolysis to produce a derivative, Shiga-Y6 (SY6), which is a TXNIP-negative regulator. Therefore, this study investigates the therapeutic role of SY5 as the prodrug of SY6 in the thioredoxin system in the brain of a mouse model of Alzheimer's disease. The intraperitoneal injection of SY5 significantly inhibited TXNIP mRNA (p = 0.0072) and protein expression (p = 0.0143) induced in the brain of APP/PS1 mice. In contrast, the levels of TXN mRNA (p = 0.0285) and protein (p = 0.0039) in the brain of APP/PS1 mice were increased after the injection of SY5. The ratio of TXN to TXNIP, which was decreased (p = 0.0131) in the brain of APP/PS1 mice, was significantly increased (p = 0.0072) after the injection of SY5. These results suggest that SY5 acts as a prodrug of SY6 in targeting the thioredoxin system and could be a potential therapeutic compound in oxidative stress-related diseases in the brain.