[Show abstract][Hide abstract] ABSTRACT: Identifying agents that inhibit amyloid beta peptide (Aβ) aggregation is the ultimate goal for slowing Alzheimer's disease (AD) progression. This study investigated whether the glycoside asiaticoside inhibits Aβ1-42 fibrillation in vitro.
Fluorescence correlation spectroscopy (FCS), evaluating the Brownian diffusion times of moving particles in a small confocal volume at the single-molecule level, was used. If asiaticoside inhibits early Aβ1-42 fibrillation steps, more Aβs would remain free and rapidly diffuse in the confocal volume. In contrast, "weaker or no inhibition" permits a greater number of Aβs to polymerize into oligomers, leading to fibers and gives rise to slow diffusion times in the solution. Trace amounts of 5-carboxytetramethylrhodamine (TAMRA)-labeled Aβ1-42 in the presence of excess unlabeled Aβ1-42 (10 μM) was used as a fluorescent probe. Steady-state and kinetic-Thioflavin T (ThT) fluorospectroscopy, laser-scanning fluorescence microscopy (LSM), and transmission electron microscopy (TEM) were also used to monitor fibrillation. Binding of asiaticoside with Aβ1-42 at the atomic level was computationally examined using the Molegro Virtual Docker and PatchDock.
With 1 h of incubation time for aggregation, FCS data analysis revealed that the diffusion time of TAMRA-Aβ1-42 was 208 ± 4 μs, which decreased to 164 ± 8.0 μs in the presence of asiaticoside, clearly indicating that asiaticoside inhibited the early stages Aβ1-42 of fibrillation, leaving more free Aβs in the solution and permitting their rapid diffusion in the confocal volume. The inhibitory effects were also evidenced by reduced fiber formation as assessed by steady-state and kinetic ThT fluorospectroscopy, LSM, and TEM. Asiaticoside elongated the lag phase of Aβ1-42 fibrillation, indicating the formation of smaller amyloid species were impaired in the presence of asiaticoside. Molecular docking revealed that asiaticoside binds with amyloid intra- and inter-molecular amino acid residues, which are responsible for β-sheet formation and longitudinal extension of fibrils.
Finally, asiaticoside prevents amyloidogenesis that precedes neurodegeneration in patients with Alzheimer's disease.
BMC Complementary and Alternative Medicine 04/2016; 15(118). DOI:10.1186/s12906-015-0620-9 · 2.02 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The accumulation of amyloid β peptide 1-42 (Aβ 1-42) in the brain of Alzheimer's disease (AD) patients is known to be associated with neurodegeneration and memory impairment. More recently, we reported that madecassoside, an active component of Centella asiatica, improved memory impairment in an Aβ 1-42 infusion rat model of AD, ameliorated neurotoxicity in SH-SY5Y cells, and inhibited in vitro Aβ 1-42 fibril formation. In the present study, we investigated the utility of in silico analyses in corroborating observed in vivo and in vitro effects of madecassoside in AD to further assess the therapeutic benefits of madecassoside. The 3D structure of Aβ 1-42 was downloaded from the Research Collaboratory for Structural Bioinformatics (RCSB) Protein Data Bank (PDB). The binding of madecassoside to Aβ 1-42 was assessed by molecular docking. The chemical structure of madecassoside was modeled and converted to the PDB format. Madecassoside was found to successfully dock with Aβ 1-42. Computational demonstration of the binding of madecassoside to Aβ 1-42 further corroborated the inhibitory effect of madecassoside on Aβ 1-42 fibrillogenesis which was demonstrated in our previous study. These data showed the potential utility of madecassoside as a preventive medication in Aβ 1-42-induced neurodegenerative diseases such as AD.
Advances in Alzheimer's Disease 07/2015; 4(02):37-44. DOI:10.4236/aad.2015.42005
[Show abstract][Hide abstract] ABSTRACT: The present study investigated the impact of a single oral ingestion of ginger on thermoregulatory function and fat oxidation in humans. Morning and afternoon oral intake of 1.0 g dried ginger root powder did not alter rectal temperature, skin blood flow, O2 consumption, CO2 production, and thermal sensation and comfort, or induce sweating at an ambient temperature of 28 °C. Ginger ingestion had no effect on threshold temperatures for skin blood flow or thermal sweating. Serum levels of free fatty acids were significantly elevated at 120 min after ginger ingestion in both the morning and afternoon. Morning ginger intake significantly reduced respiratory exchange ratios and elevated fat oxidation by 13.5 % at 120 min after ingestion. This was not the case in the afternoon. These results suggest that the effect of a single oral ginger administration on the peripheral and central thermoregulatory function is miniscule, but does facilitate fat utilization although the timing of the administration may be relevant.
International Journal of Biometeorology 01/2015; DOI:10.1007/s00484-015-0957-2 · 3.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated age-dependent changes in heat exposure-induced hypothalamic neurogenesis and acquired heat tolerance in rats. We previously reported that neuronal progenitor cell proliferation and neural differentiation are enhanced in the hypothalamus of long-term heat-acclimated (HA) rats. Male Wistar rats, 5 weeks (Young), 10–11 months (Adult), or 22–25 months (Old) old, were subjected to an ambient temperature of 32°C for 40–50 days (HA rats). Rats underwent a heat tolerance test. In HA rats, increases in abdominal temperature (Tab) in the Young, Adult, and Old groups were significantly smaller than those in their respective controls (CNs). However, increase in Tab of HA rats became greater with advancing age. The number of hypothalamic bromodeoxyuridine (BrdU)-immunopositive cells double stained with a mature neuron marker, neuronal nuclei (NeuN), of HA rats was significantly higher in the Young group than that in the CN group. In Young HA, BrdU/NeuN-immunopositive cells of the preoptic area/anterior hypothalamus appeared to be the highest among regions examined. A large number of newborn neuron was also located in the ventromedial and dorsomedial nuclei, and posterior hypothalamic area, whereas heat exposure did not increase this in the Adult and Old groups. Aging may interfere with heat exposure-induced hypothalamic neurogenesis and acquired heat tolerance in rats. This article is protected by copyright. All rights reserved.
The Journal of Comparative Neurology 12/2014; 523(8). DOI:10.1002/cne.23732 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Arachidonic acid (20:4n-6, ARA) is a major component of the cell membrane, whereas ARA-derived eicosanoids are formed when cells are damaged. Aging is associated with an accretion of oxidative stress in skeletal muscles. In this study, we examined the effects of chronic administration (13 weeks) of ARA (240 mg/kg/day) on fatty acid composition, antioxidative status, and morphology of slow (soleus muscles) and fast (extensor digitorum longus muscles; EDL)-twitch muscles in aged rats (21 months old). The level of reactive oxygen species was higher in the EDL of ARA-administered rats than in that of control rats. ARA administration decreased the muscle cell volumes and increased the number of slow myosin heavy chain (MHC)-positive cells in the EDL. The relative content of MHC2X was increased whereas the relative content of MHC2B was decreased in the EDL of ARA-administered rats. These results suggest that ARA deposition in the fast-twitch muscle of aged rats reduced cell volume with an increase in oxidative stress.
[Show abstract][Hide abstract] ABSTRACT: We investigated whether a highly purified eicosapentaenoic acid (EPA) and a concentrated n-
3 fatty acid formulation (prescription TAK-085) containing EPA and docosahexaenoic acid (DHA) ethyl
ester improve the learning ability of aged rats and whether this specific outcome has any relation with
the brain levels of EPA-derived eicosanoids and DHA-derived docosanoids. The rats were tested for
reference memory errors (RMEs) and working memory errors (WMEs) in an eight-arm radial maze.
Fatty acid compositions were analyzed by GC, whereas brain eicosanoid/docosanoids were measured
by LC-ESI-MS-MS-based analysis. The levels of lipid peroxides (LPOs) were measured by thiobarbituric
acid reactive substances. Compared with the control rats, the administration of TAK-085 at 300
mg*kg−1day−1 for 17 weeks reduced the number of RMEs in aged rats. Both TAK-085 and EPA
administration increased plasma EPA and DHA levels in aged rats, with concurrent increases in DHA
and decreases in arachidonic acid in the corticohippocampal brain tissues. TAK-085 administration
significantly increased the formation of EPA-derived 5-HETE and DHA-derived 7-, 10-, and 17-HDoHE,
PD1, RvD1, and RvD2. ARA-derived PGE2, PGD2, and PGF2α significantly decreased in TAK-085-
treated rats. DHA-derived mediators demonstrated a significantly negative correlation with the
number of RMEs, whereas EPA-derived mediators did not exhibit any relationship. Furthermore,
compared with the control rats, the levels of LPO in the plasma, cerebral cortex, and hippocampus
were significantly reduced in TAK-085-treated rats. The findings of the present study suggest that
long-term EPA+DHA administration may be a possible preventative strategy against age-related
Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 10/2014; 1851(2):In press. DOI:10.1016/j.bbalip.2014.10.009 · 5.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Alzheimer’s disease (AD) is characterized by brain deposition of amyloid β (Aβ) fibers, leading to neurodegeneration and impairments of memory. Effective medication for AD is still an elusive. Here, we investigated the effects of madecassoside (MD), an active triterpenoid in Centella asiatica, on in vitro Aβ1-42 fibrillation and Aβ1-42-induced toxicity in SH-SY5Y cells and memory impairment in Aβ1-42-infused Alzheimer’s disease (AD) model rats in vivo. MD significantly inhibited the Aβ1-42 fibril formation, as indicated by thioflavin-T fluorometry, laser scanning microscopy and transmission electron microscopy. Co-treatment with MD significantly attenuated Aβ1-42-induced apoptosis in SH-SY5Y cells. The AD rat model displayed a significant loss of spatial memory, which was significantly improved with oral preadministration of MD. MD also decreased the brain Aβ1-42 burden, oxidative stress, TNF and cathepsin D levels, with concomitant increases in BDNF and PSD-95 levels in the hippocampus. Our data indicate that MD may provide therapeutic benefits in AD.
[Show abstract][Hide abstract] ABSTRACT: Long-term continuous exposure to high ambient temperatures induces complete heat acclimation in humans and animals. However, to date, the effects of long-term exposure to heat stress on cells have not been fully evaluated. In this study, we investigated an adaptive physiological process induced in culture cells by continuous exposure to mild heat stress for 60 days. The results of this investigation provide evidence that after long-term heat acclimation in cells, (1) heat shock protein levels are increased, (2) hypoxia inducible factor-1α (HIF-1α) expression is upregulated, and (3) heat shock-induced and hypoxia-induced apoptoses are attenuated. These results suggest that the hypoxia response pathway is an intrinsic part of the heat acclimation repertoire and that the HIF-1 pathway following long-term heat acclimation induces cells with cross tolerance against hypoxia.
[Show abstract][Hide abstract] ABSTRACT: The omega-3 polyunsaturated fatty acids (ω-3 PUFAs) docosahexaenoic acid (DHA) and/or eicosapentaenoic acid (EPA) protect against diabetic nephropathy by inhibiting inflammation. The aim of this study was to assess the effects of highly purified DHA and EPA or EPA only administration on renal function and renal eicosanoid and docosanoid levels in an animal model of metabolic syndrome, SHR.Cg-Leprcp/NDmcr (SHRcp) rats. Male SHRcp rats were divided into 3 groups. Control (5% arabic gum), TAK-085 (300 mg/kg/day, containing 467 mg/g EPA and 365 mg/g DHA), or EPA (300 mg/kg/day) was orally administered for 20 weeks. The urinary albumin to creatinine ratio in the TAK-085-administered group was significantly lower than that in other groups. The glomerular sclerosis score in the TAK-085-administered group was significantly lower than that in the other groups. Although DHA levels were increased in total kidney fatty acids, the levels of nonesterified DHA were not significantly different among the 3 groups, whereas the levels of protectin D1, resolvin D1, and resolvin D2 were significantly increased in the TAK-085-administered group. The results show that the use of combination therapy with DHA and EPA in SHRcp rats improved or prevented renal failure associate with metabolic syndrome with decreasing triglyceride levels and increasing ω-3 PUFA lipid mediators.
[Show abstract][Hide abstract] ABSTRACT: Metabolic syndrome is implicated in the decline of cognitive ability. We investigated whether the prescription n-3 fatty acid administration improves cognitive learning ability in SHR.Cg-Lepr (cp) /NDmcr (SHR-cp) rats, a metabolic syndrome model, in comparison with administration of eicosapentaenoic acid (EPA, C20:5, n-3) alone. Administration of TAK-085 [highly purified and concentrated n-3 fatty acid formulation containing EPA ethyl ester and docosahexaenoic acid (DHA, C22:6, n-3) ethyl ester] at 300 mg/kg body weight per day for 13 weeks reduced the number of reference memory-related errors in SHR-cp rats, but EPA alone had no effect, suggesting that long-term TAK-085 administration improves cognitive learning ability in a rat model of metabolic syndrome. However, the working memory-related errors were not affected in either of the rat groups. TAK-085 and EPA administration increased plasma EPA and DHA levels of SHR-cp rats, associating with an increase in EPA and DHA in the cerebral cortex. The TAK-085 administration decreased the lipid peroxide levels and reactive oxygen species in the cerebral cortex and hippocampus of SHR-cp rats, suggesting that TAK-085 increases antioxidative defenses. Its administration also increased the brain-derived neurotrophic factor levels in the cortical and hippocampal tissues of TAK-085-administered rats. The present study suggests that long-term TAK-085 administration is a possible therapeutic strategy for protecting against metabolic syndrome-induced learning decline.
Neurochemical Research 08/2013; 38(10). DOI:10.1007/s11064-013-1121-1 · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It is known that aquaporin (AQP) 5 expression in the apical membrane of acinar cells in salivary glands is important for the secretion of saliva in rodents and humans. Although heat acclimation enhances saliva secretion in rodents, the molecular mechanism of how heat induces saliva secretion has not been determined. Here, we found that heat acclimation enhanced the expression of AQP5 and AQP1 in rat submandibular glands concomitant with the promotion of the HIF-1α pathway, leading to VEGF induction and CD31-positive angiogenesis. The apical membrane distribution of AQP5 in serous acinar cells enhanced after heat acclimation, while AQP1 expression was restricted to the endothelial cells in the submandibular glands. A network of AQPs may be involved in heat-acclimated regulation in saliva secretion. Because AQPs probably plays a crucial role in saliva secretion in humans, these findings may lead to a novel strategy for treating saliva hyposecretion.
[Show abstract][Hide abstract] ABSTRACT: Natural killer (NK) cells have many functional activities, including cytotoxicity and the capacity to produce cytokines and chemokines. NK cell activity is regulated partly by eicosanoids, which are produced from arachidonic acid (ARA) and eicosapentaenoic (EPA) acid. In this study, we investigated the effects of long-term therapy with ARA or docosahexaenoic acid (DHA) on the cytotoxic effects of the NK cells of young rats, which were fed on a nonfish oil diet for two generations. Control oil, ARA (240 mg/kg BW/day) or DHA (240 mg/kg BW/day) were orally administrated to the rats for 13 weeks before determining the cytotoxic activity of NK cells from the spleen against YAC-1 mouse lymphoma cell line, as well as the plasma levels of docosanoids or eicosanoids and inflammatory cytokines. Long-term ARA administration significantly suppressed the cytotoxic activity of NK cells. Moreover, ARA administration significantly increased the plasma levels of ARA, prostaglandin (PG) E2, and PGD2. However, DHA administration did not produce any different effects compared with those in the control rats. Furthermore, the inflammatory cytokine levels were not affected by the administration of ARA or DHA. These results suggest that long-term ARA administration has an inhibitory effect on the tumor cytotoxicity of NK cells in rat spleen lymphocytes owing to the enhanced synthesis of PGE2 and PGD2 from ARA because of the elevated plasma ARA levels in young rats.