Curcumin activates Wnt/β-catenin signaling pathway through inhibiting the activity of GSK-3β in APPswe transfected SY5Y cells

Curcumin eluting nanofibers augment osteogenesis toward phytochemical based bone tissue engineering

Curcumin is a phenolic compound isolated from Curcuma longa that is known to exhibit wide ranging biological activity including potential benefits for bone growth. The aim of this work was to engineer curcumin eluting tissue scaffolds and investigate their potential use in bone tissue regeneration. We prepared curcumin loaded poly(ε-caprolactone) (PCL) nanofibers by electrospinning. Morphological characterization of the nanofibers revealed that the average diameter of neat fibers and that of fibers with 1 wt% and 5 wt% curcumin is 840  ±  130 nm, 827  ±  129 nm and 680  ±  110 nm, respectively. Fourier transformation infrared spectroscopy and ¹H nuclear magnetic resonance confirmed the successful loading of the drug in fibers. In aqueous medium, the fibers released  ≈18% of the encapsulated drug in 3 d and  ≈60% in 9 d. The cell response to the curcumin loaded nanofibers was assessed using MC3T3-E1 pre-osteoblasts. Cell proliferation was moderated with increased loading of curcumin and was 50% lower on the fibers containing 5% curcumin at day 10 than the control fibers. Osteogenesis was confirmed by assaying the expression of alkaline phosphatase and staining of mineral deposits by Alizarin red stain, which were both markedly higher for 1% curcumin compared to neat polymer but lower for 5% curcumin. Mineral deposition was also confirmed chemically by Fourier transform infrared spectroscopy. These results were corroborated by increased gene and protein expression of known osteogenic markers in 1% curcumin. Thus, controlled release of curcumin from polymer scaffolds is a promising strategy for bone tissue regeneration.

Curcumin Rescues Diabetic Renal Fibrosis by Targeting Superoxide-Mediated Wnt Signaling Pathways

The purposes of this study were to investigate whether curcumin can weaken diabetic nephropathy by modulating both oxidative stress and renal injury from Wnt signaling mediation. Wnt5a/β-catenin depression and induction of superoxide synthesis are associated with high glucose (HG) induced transforming growth factor (TGF)-β1 and fibronectin expression in mesangial cells. Curcumin resumes HG depression of Wnt/β-catenin signaling and alleviates HG induction of superoxide, TGF-β1 and fibronectin expression in renal mesangial cell. Exogenous curcumin alleviated urinary total proteinuria and serum superoxide level in diabetic rats. Based on laser-captured microdissection for quantitative real-time polymerase chain reaction, it was found that diabetes significantly increased TGF-β1 and fibronectin expression in line with depressed Wnt5a expression. Curcumin treatment reduced the TGF-β1 and fibronectin activation and the inhibiting effect of diabetes on Wnt5a/β-catenin expression in renal glomeruli. Immunohistochemistry showed that curcumin treatment significantly reduced 8-hydroxy-2'-deoxyguanosine, TGF-β1 and fibronectin, and was in line with the restoration of the suppressed Wnt5a expression immunoreactivities in glomeruli of diabetic rats. Curcumin alleviated extracellular matrix accumulation in diabetic nephropathy by not only preventing the diabetes-mediated superoxide synthesis but also resuming downregulation of Wnt/β-catenin signaling. These findings suggest that regulation of Wnt activity by curcumin is a feasible alternative strategy to rescue diabetic renal injury.

Neuroprotective Effect of Osthole on Neuron Synapses in an Alzheimer's Disease Cell Model via Upregulation of MicroRNA-9

Accumulation of β-amyloid peptide (Aβ) in the brain plays an important role in the pathogenesis of Alzheimer's disease (AD). It has been reported that osthole exerts its neuroprotective effect on neuronal synapses, but its exact mechanism is obscure. Recently, microRNAs have been demonstrated to play a crucial role in inducing synaptotoxicity by Aβ, implying that targeting microRNAs could be a therapeutic approach of AD. In the present study, we investigated the neuroprotective effects of osthole on a cell model of AD by transducing APP695 Swedish mutant (APP695swe, APP) into mouse cortical neurons and human SH-SY5Y cells. In this study, the cell counting kit CCK-8, apoptosis assay, immunofluorescence analysis, enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction, and Western blot assay were used. We found that osthole could enhance cell viability, prevent cell death, and reverse the reduction of synaptic proteins (synapsin-1, synaptophysin, and postsynaptic density-95) in APP-overexpressed cells, which was attributed to increases in microRNA-9 (miR-9) expression and subsequent decreases in CAMKK2 and p-AMPKα expressions. These results demonstrated that osthole plays a neuroprotective activity role in part through upregulating miR-9 in AD.

The role of the Wnt canonical signaling in neurodegenerative diseases

The Wnt/β-catenin or Wnt canonical pathway controls multiple biological processes throughout development and adult life. Growing evidences have suggested that deregulation of the Wnt canonical pathway could be involved in the pathogenesis of neurodegenerative diseases. The Wnt canonical signaling is a pathway tightly regulated, which activation results in the inhibition of the Glycogen Synthase Kinase 3β (GSK-3β) function and in increased β-catenin activity, that migrates into the nucleus, activating the transcription of the Wnt target genes. Conversely, when the Wnt canonical pathway is turned off, increased levels of GSK-3β promote β-catenin degradation. Hence, GSK-3β could be considered as a key regulator of the Wnt canonical pathway. Of note, GSK-3β has also been involved in the modulation of inflammation and apoptosis, determining the delicate balance between immune tolerance/inflammation and neuronal survival/neurodegeneration. In this review, we have summarized the current acknowledgements about the role of the Wnt canonical pathway in the pathogenesis of some neurodegenerative diseases including Alzheimer's disease, cerebral ischemia, Parkinson's disease, Huntington's disease, multiple sclerosis and amyotrophic lateral sclerosis, with particular regard to the main in vitro and in vivo studies in this field, by reviewing 85 research articles about.

An ornamental plant targets epigenetic signaling to block cancer stem cell-driven colon carcinogenesis

Phytochemicals modulate key cellular signaling pathways and have proven anticancer effects. Alcea rosea(AR; Hollyhock) is an ornamental plant with known anti-inflammatory properties. This study explored its role as an anticancer agent. The AR seed extract (AR extract) inhibited proliferation and colony formation in a dose- and time-dependent manner and promoted apoptosis as was evidenced by cleavage of PARP and increased expression of Bax accompanying reduced levels of BCL-xl protein in HCT116 and SW480 cells, respectively. In addition, AR extract-arrested cells at Go/G1 phase of cell cycle and exhibited decreases in Cyclin D1. AR extract-treated cells exhibited reduced number and size of colonospheres in a dose-dependent manner concomitant with decreases in cancer stem cell (CSC) markers ALDH1A1 and Dclk1. Relative levels of β-catenin, Notch-ICD, Hes1 and EZH2 were also attenuated by AR extract. TOP-flash reporter activity, a measure of Wnt signaling, decreased significantly in response to treatment while overexpression of wild type but not mutant EZH2, reversed the inhibitory effects. Moreover, WIF1 (a Wnt antagonist) promoter activity increased dramatically following treatment with AR extract which phenocopied increases in WIF1 reporter activity following EZH2 knockdown.In vivo, AR extract attenuated tumor growth due probably to reduced levels of EZH2, β-catenin, CyclinD1 and Ki-67 along with reduced levels of CSC markers. Since partial purification via HPLC yielded a prominent peak, efforts are underway to identify the active ingredient(s). Taken together, the results clearly suggest that AR extract/active component(s) can be an effective preventative/therapeutic agent to target colon cancer.

Examining the potential clinical value of curcumin in the prevention and diagnosis of Alzheimer’s disease

Curcumin derived from turmeric is well documented for its anti-carcinogenic, antioxidant and anti-inflammatory properties. Recent studies show that curcumin also possesses neuroprotective and cognitive-enhancing properties that may help delay or prevent neurodegenerative diseases, including Alzheimer’s disease (AD). Currently, clinical diagnosis of AD is onerous, and it is primarily based on the exclusion of other causes of dementia. In addition, phase III clinical trials of potential treatments have mostly failed, leaving disease-modifying interventions elusive. AD can be characterised neuropathologically by the deposition of extracellular β amyloid (Aβ) plaques and intracellular accumulation of tau-containing neurofibrillary tangles. Disruptions in Aβ metabolism/clearance contribute to AD pathogenesis. In vitro studies have shown that Aβ metabolism is altered by curcumin, and animal studies report that curcumin may influence brain function and the development of dementia, because of its antioxidant and anti-inflammatory properties, as well as its ability to influence Aβ metabolism. However, clinical studies of curcumin have revealed limited effects to date, most likely because of curcumin’s relatively low solubility and bioavailability, and because of selection of cohorts with diagnosed AD, in whom there is already major neuropathology. However, the fresh approach of targeting early AD pathology (by treating healthy, pre-clinical and mild cognitive impairment-stage cohorts) combined with new curcumin formulations that increase bioavailability is renewing optimism concerning curcumin-based therapy. The aim of this paper is to review the current evidence supporting an association between curcumin and modulation of AD pathology, including in vitro and in vivo studies. We also review the use of curcumin in emerging retinal imaging technology, as a fluorochrome for AD diagnostics.

Sustained proliferation in cancer: Mechanisms and novel therapeutic targets

Proliferation is an important part of cancer development and progression. This is manifest by altered expression and/or activity of cell cycle related proteins. Constitutive activation of many signal transduction pathways also stimulates cell growth. Early steps in tumor development are associated with a fibrogenic response and the development of a hypoxic environment which favors the survival and proliferation of cancer stem cells. Part of the survival strategy of cancer stem cells may manifested by alterations in cell metabolism. Once tumors appear, growth and metastasis may be supported by overproduction of appropriate hormones (in hormonally dependent cancers), by promoting angiogenesis, by undergoing epithelial to mesenchymal transition, by triggering autophagy, and by taking cues from surrounding stromal cells. A number of natural compounds (e.g., curcumin, resveratrol, indole-3-carbinol, brassinin, sulforaphane, epigallocatechin-3-gallate, genistein, ellagitannins, lycopene and quercetin) have been found to inhibit one or more pathways that contribute to proliferation (e.g., hypoxia inducible factor 1, nuclear factor kappa B, phosphoinositide 3 kinase/Akt, insulin-like growth factor receptor 1, Wnt, cell cycle associated proteins, as well as androgen and estrogen receptor signaling). These data, in combination with bioinformatics analyses, will be very important for identifying signaling pathways and molecular targets that may provide early diagnostic markers and/or critical targets for the development of new drugs or drug combinations that block tumor formation and progression.

Neuroglobin Attenuates Beta Amyloid-Induced Apoptosis Through Inhibiting Caspases Activity by Activating PI3K/Akt Signaling Pathway

Excessive accumulation and deposition of amyloid-beta (Aβ) has been considered as a pivotal event in the pathogenesis of Alzheimer's disease (AD). Neuronal apoptosis is one of the characteristics of AD, which is a possible mechanism underlying Aβ-induced neuronal neurotoxicity. Neuroglobin (Ngb) is a newly discovered vertebrate heme protein that exhibits neuroprotective functions against cell death associated with hypoxic and amyloid insult. However, until now, the exact mechanism of neuroglobin's protective action has not been determined. To investigate the potential neuroprotective roles and mechanisms of Ngb, transgenic AD mice (APPswe/PSEN1dE9) and SH-SY5Y cells transfected with pAPPswe were enrolled into the study. In vivo, overexpression of Ngb via intracerebroventricular injection with pNgb attenuated memory, cognitive impairment, and plaque generations. In pAPPswe transfected SH-SY5Y cells, Ngb not only decreased the generation of Aβ42, but also attenuated mitochondrial dysfunction and apoptosis through suppressing the activation of caspase-3, caspase-9 by Akt activating phosphorylation, which were restrained by phosphatidylinositol 3-kinase inhibitor (LY294002). Our data indicate the anti-apoptotic property of Ngb may play a neuroprotective role against AD.

Treatment with curcumin alleviates sublesional bone loss following spinal cord injury in rats

This work aimed to investigate the therapeutic effect of curcumin on sublesional bone loss induced by spinal cord injury (SCI) in rats. SCI model in this work was generated in rats by surgical transaction of the cord at the T10-12 level. After the surgery, animals were treated with curcumin (110 mg/kg body mass/day, via oral gavages) for 2 weeks. Treatment of SCI rats with curcumin prevented the reduction of bone mass in tibiae and femurs, preserved bone microstructure including trabecular bone volume fraction, trabecular number, and trabecular thickness in proximal tibiae, and preserved mechanical properties of femoral midshaft. Treatment of SCI rats with curcumin increased osteoblast surface and reduced osteoclast surface in proximal tibiae. Treatment of SCI rats with curcumin increased osteocalcin mRNA expression and reduced mRNA levels of tartrate-resistant acid phosphatase and mRNA ratio of receptor activator of NF-κB ligand/osteoprotegerin in distal femurs. Treatment of SCI rats with curcumin reduced serum and femoral levels of thiobarbituric acid reactive substances. Treatment of SCI rats with curcumin had no significant effect on serum 25(OH)D, but enhanced mRNA and protein expression of vitamin D receptor (VDR) in distal femurs. Treatment of SCI rats with curcumin enhanced mRNA levels of Wnt3a, Lrp5, and ctnnb1 and upregulated protein expression of β-catenin in distal femurs. In conclusions, treatment with curcumin abated oxidative stress, activated VDR, and enhanced Wnt/β-catenin pathway, which might explain its beneficial effect against sublesional bone loss following SCI in rats, at least in part.

Dietary phytochemicals alter epigenetic events and signaling pathways for inhibition of metastasis cascade: phytoblockers of metastasis cascade

Cancer metastasis is a multistep process in which a cancer cell spreads from the site of the primary lesion, passes through the circulatory system, and establishes a secondary tumor at a new nonadjacent organ or part. Inhibition of cancer progression by dietary phytochemicals (DPs) offers significant promise for reducing the incidence and mortality of cancer. Consumption of DPs in the diet has been linked to a decrease in the rate of metastatic cancer in a number of preclinical animal models and human epidemiological studies. DPs have been reported to modulate the numerous biological events including epigenetic events (noncoding micro-RNAs, histone modification, and DNA methylation) and multiple signaling transduction pathways (Wnt/β-catenin, Notch, Sonic hedgehog, COX-2, EGFR, MAPK-ERK, JAK-STAT, Akt/PI3K/mTOR, NF-κB, AP-1, etc.), which can play a key role in regulation of metastasis cascade. Extensive studies have also been performed to determine the molecular mechanisms underlying antimetastatic activity of DPs, with results indicating that these DPs have significant inhibitory activity at nearly every step of the metastatic cascade. DPs have anticancer effects by inducing apoptosis and by inhibiting cell growth, migration, invasion, and angiogenesis. Growing evidence has also shown that these natural agents potentiate the efficacy of chemotherapy and radiotherapy through the regulation of multiple signaling pathways. In this review, we discuss the variety of molecular mechanisms by which DPs regulate metastatic cascade and highlight the potentials of these DPs as promising therapeutic inhibitors of cancer.

Low dose nicotine attenuates Aβ neurotoxicity through activation early growth response gene 1 pathway

Epidemiological studies indicate that smoking is negatively correlated with the incidence and development of Alzheimer's disease (AD). Nicotine was reported to be the active factor. However, the detailed mechanisms still remain to be fully elucidated. Early growth response gene 1 (EGR-1) plays important roles in several important biological processes such as promoting cell growth, differentiation, anti oxidative stress, and apoptosis, but few in the pathogenesis of AD. In the present study, we show that nicotine can activate the MAPK/ERK/EGR-1 signaling pathway partially through α7 nAChR. In addition, the up-regulation of EGR-1 by nicotine can also increase the phosphorylation of CyclinD1 which contributes to the attenuation of amyloid-β (Aβ(25-35)) -induced neurotoxicity. Although nicotine and Aβ(25-35) can activate EGR-1, the expression of EGR-1 is down-regulated following treatment with nicotine and Aβ(25-35). This study demonstrates that low dose nicotine attenuates Aβ(25-35)-induced neurotoxicity in vitro and in vivo through activating EGR-1 pathway.

Antioxidative effects of ethyl 2-(3-(benzo[d]thiazol-2-yl)ureido)acetate against amyloid β-induced oxidative cell death via NF-κB, GSK-3β and β-catenin signaling pathways in cultured cortical neurons

We have previously shown that 2-(3-(benzo[d]thiazol-2-yl)ureido)acetate (KHG21834) attenuates amyloid beta(Aβ)25-35-induced apoptotic death and shows anti-inflammatory activity against Aβ25-35-induced microglial activation. However, antioxidative effects of KHG21834 against Aβ-induced oxidative stress have not yet been reported. In the present study, we investigated the antioxidative function of KHG21834 in primary cultured cortical neurons, to expand the potential therapeutic efficacy of KHG21834. Pretreatment with KHG21834 protected against Aβ-induced neuronal cell death and mitochondrial damage, and significantly restored GSH levels and the activities of catalase, superoxide dismutase, and glutathione peroxidase, and also suppressed the production of reactive oxygen species and protein oxidation. These results imply that KHG21834 may play a role in cellular defense mechanisms against Aβ-induced oxidative stress in cultured cortical neurons. Furthermore, KHG21834 significantly attenuated the effects of Aβ treatment on levels of NF-κB, β-catenin, and GSK-3β proteins in cortical neurons. Taken together, our results suggest that the antioxidant effects of KHG21834 may result at least in part from its ability to regulate the NF-κB, β-catenin, and GSK-3β signaling pathways. To our knowledge, this is the first report showing that KHG21834 significantly attenuates Aβ25-35-induced oxidative stress in primary cortical neurons, and provides novel insights into KHG21834 as a possible therapeutic agent for the treatment of Aβ-mediated neurotoxicity involving oxidative stress.

Rescue of an in vitro neuron phenotype identified in Niemann-Pick disease, type C1 induced pluripotent stem cell-derived neurons by modulating the WNT pathway and calcium signaling

Niemann-Pick disease, type C1 (NPC1) is a familial disorder that has devastating consequences on postnatal development with multisystem effects, including neurodegeneration. There is no Food and Drug Administration-approved treatment option for NPC1; however, several potentially therapeutic compounds have been identified in assays using yeast, rodent models, and NPC1 human fibroblasts. Although these discoveries were made in fibroblasts from NPC1 subjects and were in some instances validated in animal models of the disease, testing these drugs on a cell type more relevant for NPC1 neurological disease would greatly facilitate both study of the disease and identification of more relevant therapeutic compounds. Toward this goal, we have generated an induced pluripotent stem cell line from a subject homozygous for the most frequent NPC1 mutation (p.I1061T) and subsequently created a stable line of neural stem cells (NSCs). These NSCs were then used to create neurons as an appropriate disease model. NPC1 neurons display a premature cell death phenotype, and gene expression analysis of these cells suggests dysfunction of important signaling pathways, including calcium and WNT. The clear readout from these cells makes them ideal candidates for high-throughput screening and will be a valuable tool to better understand the development of NPC1 in neural cells, as well as to develop better therapeutic options for NPC1.

Melatonin-mediated β-catenin activation protects neuron cells against prion protein-induced neurotoxicity

Activation of β-catenin in neurons regulates mitochondrial function and protects against protein misfolding disorders, including Alzheimer's disease and Huntington's disease. Melatonin, a natural secretory product of the pineal gland, exerts neuroprotective effects through the activation of β-catenin. In this study, melatonin increased β-catenin protein expression and activation in human neuroblastoma cell lines SH-SY5Y cells. Melatonin also inhibited PrP (106-126)-induced neurotoxicity and the inhibition attenuated by treatment of β-catenin inhibitor ICG-001. Activation of β-catenin blocked PrP (106-126)-mediated downregulation of anti-apoptotic protein survivin and Bcl-2. Reduction of mitochondrial membrane potential, translocation of Bax, and cytochrome c release which induced by PrP (106-126) treatment were inhibited by β-catenin activation, which contributed to prevented PrP (106-126)-induced neuronal cell death. In conclusion, β-catenin activation by melatonin prevented PrP (106-126)-induced neuronal cell death through regulating anti-apoptotic proteins and mitochondrial pathways. These results also suggest the therapeutic value of Wnt/β-catenin signaling in prion-related disorders as influenced by melatonin.

2-Cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride protects against beta-amyloid-induced activation of the apoptotic cascade in cultured cortical neurons

Aggregated β-amyloid, implicated in the pathogenesis of Alzheimer's disease (AD), induces neurotoxicity by evoking a cascade of oxidative damage-dependent apoptosis in neurons. We investigated the molecular mechanisms underlying the protective effect of 2-cyclopropylimino-3-methyl-1,3-thiazoline hydrochloride (KHG26377) against the beta-amyloid (Aβ25-35)-induced primary cortical neuronal cell neurotoxicity. Treatment with KHG26377 attenuated the Aβ25-35-induced apoptosis by decreasing the Bax/Bcl-2 ratio and suppressing the activation of caspase-3. A marked increase in calcium influx and in the level of reactive oxygen species together with a decrease in glutathione levels was found after Aβ25-35 exposure; however, KHG26377 treatment reversed these changes in a concentration-dependent manner. In addition, KHG26377 significantly suppressed Aβ25-35-induced toxicity concomitant with a reduction in the activation of extracellular signal-regulated kinases 1 and 2 and nuclear factor kappa B. The KHG26377-induced protection of neuronal cells against Aβ toxicity was also mediated by suppressing the expression of glycogen synthase kinase-3β, increasing the levels of β-catenin, and reducing the levels of phosphorylated tau. Our findings suggest that KHG26377 may modulate the neurotoxic effects of β-amyloid and provide a rationale for treatment of AD.

TL-2 attenuates β-amyloid induced neuronal apoptosis through the AKT/GSK-3β/β-catenin pathway

β-amyloid (Aβ)-mediated neuronal apoptosis contributes to the progression of Alzheimer's disease (AD), although the exact mechanism remains unclear. This study aimed to investigate whether Dalesconol B (TL-2), a potent immunosuppressive agent with an unusual carbon skeleton, could inhibit Aβ-induced apoptosis in vitro and in vivo and to explore the underlying mechanisms. Aβ(1-42) was injected to bilateral hippocampus of mice to make the AD models in vivo. TL-2 was able to cross the blood-brain barrier and attenuate memory deficits in the AD mice. TL-2 also inhibited Aβ(1-42)-induced neuronal apoptosis in vitro and in vivo. In addition, TL-2 could activate the AKT/GSK-3β pathway, and inhibition of AKT and activation of GSK-3β partially eliminated the neuroprotective effects of TL-2. Furthermore, TL-2 induced the nuclear translocation of β-catenin and enhanced its transcriptional activity through the AKT/GSK-3β pathway to promote neuronal survival. These results suggest that TL-2 might be a potential drug for AD treatment.

Curcumin Stimulates Proliferation of Spinal Cord Neural Progenitor Cells via a Mitogen-Activated Protein Kinase Signaling Pathway

Objective

The aims of our study are to evaluate the effect of curcumin on spinal cord neural progenitor cell (SC-NPC) proliferation and to clarify the mechanisms of mitogen-activated protein (MAP) kinase signaling pathways in SC-NPCs.

Methods

We established cultures of SC-NPCs, extracted from the spinal cord of Sprague-Dawley rats weighing 250 g to 350 g. We measured proliferation rates of SC-NPCs after curcumin treatment at different dosage. The immuno-blotting method was used to evaluate the MAP kinase signaling protein that contains extracellular signal-regulated kinases (ERKs), p38, c-Jun NH₂-terminal kinases (JNKs) and β-actin as the control group.

Results

Curcumin has a biphasic effect on SC-NPC proliferation. Lower dosage (0.1, 0.5, 1 µM) of curcumin increased SC-NPC proliferation. However, higher dosage decreased SC-NPC proliferation. Also, curcumin stimulates proliferation of SC-NPCs via the MAP kinase signaling pathway, especially involving the p-ERK and p-38 protein. The p-ERK protein and p38 protein levels varied depending on curcumin dosage (0.5 and 1 µM, p<0.05).

Conclusion

Curcumin can stimulate proliferation of SC-NPCs via ERKs and the p38 signaling pathway in low concentrations.

Downregulation of PI3K/Akt/mTOR signaling pathway in curcumin-induced autophagy in APP/PS1 double transgenic mice

Autophagy is a lysosomal degradation pathway, which is essential for cell survival, proliferation, differentiation and homeostasis. It is well known that beta-amyloid (Aβ) aggregation is one of key characteristics for Alzheimer's disease (AD), which triggers a complex pathological cascade, leading to neurodegeneration. Recent studies have shown that Aβ peptide is generated from amyloid β precursor protein (APP) during autophagic turnover of APP-rich organelles by autophagy. Aβ generation during normal autophagy is subsequently degraded by lysosomes. Curcumin, a nature plant extraction, has been reported to inhibit the generation and deposition of Aβ; however, the underlying mechanisms are not fully understood yet. In the present study, we reported that curcumin treatment not only attenuated cognitive impairment detected by Morris water maze test, but also inhibited the generation of Aβ investigated by immunohistochemistry in APP/PS1 double transgenic AD mice. Moreover, curcumin induced autophagy in the mice, evidenced by LC3 immunofluorescence analysis and western blot assays on LC3. Furthermore, we found that curcumin significantly decreased the expression of Phosphatidylinositol 3-Kinase (PI3K), phosphorylated Akt and rapamycin (mTOR) at protein levels, respectively. Taken together, our data suggests that curcumin inhibits Aβ generation and induces of autophagy by downregulating PI3K/Akt/mTOR signaling pathway, and further shows a neuroprotective effect. Meanwhile curcumin might be a candidate neuroprotective agent for AD patients treatment by inducing autophagy.

Curcumin affects β-catenin pathway in hepatic stellate cell in vitro and in vivo

OBJECTIVES

Emerging evidence indicates that Wnt/β-catenin pathway is linked to the fibrosis of different organs including liver fibrosis. β-Catenin promotes hepatic stellate cells (HSCs) activation, a key event in the development of liver fibrosis, and has emerged as a novel mediator of fibrosis. Curcumin, a natural active ingredient derived from turmeric, possesses an inhibitory effect on liver fibrosis. This study is aimed to examine whether curcumin affects β-catenin expression/activity in HSCs and explores the underlying mechanisms.

METHODS

The researchers used Western blot, real-time PCR, transfection assay and electrophoretic mobility shift assay and employed cultured HSCs and rat model of liver injury.

KEY FINDINGS

Results showed that curcumin could reduce β-catenin protein level in HSCs in vitro and in vivo. Both β-catenin transactivation activity and DNA-binding activity were suppressed by curcumin. Moreover, nuclear β-catenin protein level was decreased by curcumin treatment. Further experiments suggested that delta-like homologue 1 contributed to curcumin inhibition of β-catenin transactivation activity in cultured HSCs.

CONCLUSIONS

Curcumin affects β-catenin pathway in HSCs and might suggest a possible new explanation for the effects of curcumin on HSC activation and liver fibrosis.

The role of Wnt signaling in the development of Alzheimer's disease: a potential therapeutic target?

Accumulating evidence supports a key role for Wnt signaling in the development of the central nervous system (CNS) during embryonic development and in the regulation of the structure and function of the adult brain. Alzheimer's disease (AD) is the most common form of senile dementia, which is characterized by β -amyloid (A β ) deposition in specific brain regions. However, the molecular mechanism underlying AD pathology remains elusive. Dysfunctional Wnt signaling is associated with several diseases such as epilepsy, cancer, metabolic disease, and AD. Increasing evidence suggests that downregulation of Wnt signaling, induced by A β , is associated with disease progression of AD. More importantly, persistent activation of Wnt signaling through Wnt ligands, or inhibition of negative regulators of Wnt signaling, such as Dickkopf-1 (DKK-1) and glycogen synthase kinase-3 β (GSK-3 β ) that are hyperactive in the disease state, is able to protect against A β toxicity and ameliorate cognitive performance in AD. Together, these data suggest that Wnt signaling might be a potential therapeutic target of AD. Here, we review recent studies related to the progression of AD where Wnt signaling might be relevant and participate in the development of the disease. Then, we focus on the potential relevance of manipulating the Wnt signaling pathway for the treatment of AD.

Reverse engineering of Alzheimer's disease based on biomarker pathways analysis

Alzheimer's disease (AD) poses an increasingly profound problem to society, yet progress toward a genuine understanding of the disease remains worryingly slow. Perhaps, the most outstanding problem with the biology of AD is the question of its mechanistic origins, that is, it remains unclear wherein the molecular failures occur that underlie the disease. We demonstrate how molecular biomarkers could help define the nature of AD in terms of the early biochemical events that correlate with disease progression. We use a novel panel of biomolecules that appears in cerebrospinal fluid of AD patients. As changes in the relative abundance of these molecular markers are associated with progression to AD from mild cognitive impairment, we make the assumption that by tracking their origins we can identify the biochemical conditions that predispose their presence and consequently cause the onset of AD. We couple these protein markers with an analysis of a series of genetic factors and together this hypothesis essentially allows us to redefine AD in terms of the molecular pathways that underlie the disease.

Amyloid beta: multiple mechanisms of toxicity and only some protective effects?

Amyloid beta (Aβ) is a peptide of 39–43 amino acids found in large amounts and forming deposits in the brain tissue of patients with Alzheimer's disease (AD). For this reason, it has been implicated in the pathophysiology of damage observed in this type of dementia. However, the role of Aβ in the pathophysiology of AD is not yet precisely understood. Aβ has been experimentally shown to have a wide range of toxic mechanisms in vivo and in vitro, such as excitotoxicity, mitochondrial alterations, synaptic dysfunction, altered calcium homeostasis, oxidative stress, and so forth. In contrast, Aβ has also shown some interesting neuroprotective and physiological properties under certain experimental conditions, suggesting that both physiological and pathological roles of Aβ may depend on several factors. In this paper, we reviewed both toxic and protective mechanisms of Aβ to further explore what their potential roles could be in the pathophysiology of AD. The complete understanding of such apparently opposed effects will also be an important guide for the therapeutic efforts coming in the future.

Curcumin-loaded nanoparticles potently induce adult neurogenesis and reverse cognitive deficits in Alzheimer's disease model via canonical Wnt/β-catenin pathway

Neurogenesis, a process of generation of new neurons, is reported to be reduced in several neurodegenerative disorders including Alzheimer's disease (AD). Induction of neurogenesis by targeting endogenous neural stem cells (NSC) could be a promising therapeutic approach to such diseases by influencing the brain self-regenerative capacity. Curcumin, a neuroprotective agent, has poor brain bioavailability. Herein, we report that curcumin-encapsulated PLGA nanoparticles (Cur-PLGA-NPs) potently induce NSC proliferation and neuronal differentiation in vitro and in the hippocampus and subventricular zone of adult rats, as compared to uncoated bulk curcumin. Cur-PLGA-NPs induce neurogenesis by internalization into the hippocampal NSC. Cur-PLGA-NPs significantly increase expression of genes involved in cell proliferation (reelin, nestin, and Pax6) and neuronal differentiation (neurogenin, neuroD1, neuregulin, neuroligin, and Stat3). Curcumin nanoparticles increase neuronal differentiation by activating the Wnt/β-catenin pathway, involved in regulation of neurogenesis. These nanoparticles caused enhanced nuclear translocation of β-catenin, decreased GSK-3β levels, and increased promoter activity of the TCF/LEF and cyclin-D1. Pharmacological and siRNA-mediated genetic inhibition of the Wnt pathway blocked neurogenesis-stimulating effects of curcumin. These nanoparticles reverse learning and memory impairments in an amyloid beta induced rat model of AD-like phenotypes, by inducing neurogenesis. In silico molecular docking studies suggest that curcumin interacts with Wif-1, Dkk, and GSK-3β. These results suggest that curcumin nanoparticles induce adult neurogenesis through activation of the canonical Wnt/β-catenin pathway and may offer a therapeutic approach to treating neurodegenerative diseases such as AD, by enhancing a brain self-repair mechanism.

Natural products as promising drug candidates for the treatment of Alzheimer's disease: molecular mechanism aspect

Alzheimer’s disease (AD) is the most common neurodegenerative disorder to date, with no curative or preventive therapy. Histopathological hallmarks of AD include deposition of β-amyloid plaques and formation of neurofibrillary tangles. Extent studies on pathology of the disease have made important discoveries regarding mechanism of disease and potential therapeutic targets. Many cellular changes including oxidative stress, disruption of Ca2+ homeostasis, inflammation, metabolic disturbances, and accumulation of unfolded/misfolded proteins can lead to programmed cell death in AD. Despite intensive research, only five approved drugs are available for the management of AD. Hence, there is a need to look at alternative therapies. Use of natural products and culinary herbs in medicine has gained popularity in recent years. Several natural substances with neuroprotective effects have been widely studied. Most of these compounds have remarkable antioxidant properties and act mainly by scavenging free radical species. Some of them increase cell survival and improve cognition by directly affecting amyloidogenesis and programmed cell death pathways. Further studies on these natural products and their mechanism of action, parallel with the use of novel pharmaceutical drug design and delivery techniques, enable us to offer an addition to conventional medicine. This review discussed some natural products with potential neuroprotective properties against Aβ with respect to their mechanism of action.

Free and nanoencapsulated curcumin suppress β-amyloid-induced cognitive impairments in rats: involvement of BDNF and Akt/GSK-3β signaling pathway

Alzheimer's disease (AD), a neurodegenerative disorder exhibiting progressive loss of memory and cognitive functions, is characterized by the presence of neuritic plaques composed of neurofibrillary tangles and β-amyloid (Aβ) peptide. Drug delivery to the brain still remains highly challenging for the treatment of AD. Several studies have been shown that curcumin is associated with anti-amyloidogenic properties, but therapeutic application of its beneficial effects is limited. Here we investigated possible mechanisms involved in curcumin protection against Aβ(1-42)-induced cognitive impairment and, due to its poor bioavailability, we developed curcumin-loaded lipid-core nanocapsules in an attempt to improve the neuroprotective effect of this polyphenol. Animals received a single intracerebroventricular injection of Aβ(1-42) and they were administered either free curcumin or curcumin-loaded lipid-core nanocapsules (Cur-LNC) intraperitoneally for 10days. Aβ(1-42)-infused animals showed a significant impairment on learning-memory ability, which was paralleled by a significant decrease in hippocampal synaptophysin levels. Furthermore, animals exhibited activated astrocytes and microglial cells, as well as disturbance in BDNF expression and Akt/GSK-3β signaling pathway, beyond tau hyperphosphorylation. Our findings demonstrate that administration of curcumin was effective in preventing behavioral impairments, neuroinflammation, tau hyperphosphorylation as well as cell signaling disturbances triggered by Aβ in vivo. Of high interest, Cur-LNC in a dose 20-fold lower presented similar neuroprotective results compared to the effective dose of free curcumin. Considered overall, the data suggest that curcumin is a potential therapeutic agent for neurocognition and nanoencapsulation of curcumin in LNC might constitute a promising therapeutic alternative in the treatment of neurodegenerative diseases such as AD.

Curcumin: a natural substance with potential efficacy in Alzheimer's disease

Curcumin is a component of turmeric, a spice used in many types of cooking. Epidemiological evidence suggesting that populations that eat food with a substantial amount of curcumin were at lower risk of Alzheimer’s disease (AD) led to the idea that this compound might have a neuroprotective effect. Curcumin has substantial antioxidant and anti-inflammatory effects, and is being used as a potential preventative agent or treatment for many types of cancer. There is evidence to suggest that the addition of curcumin to cultured neuronal cells decreases brain inflammation and protects against β-amyloid-induced neurotoxicity. Curcumin also protects against toxicity when β-amyloid is administered to produce animal models of AD. Curcumin decreases β-amyloid formation from amyloid precursor protein, and also inhibits aggregation of β-amyloid into pleated sheets. Studies in transgenic mice with overproduction of β-amyloid demonstrate a neuroprotective effect of curcumin as well. Cognitive function was also improved in these animal models. Clinical trials of curcumin in AD have not been very promising. It is possible that this is due to poor oral bioavailability of curcumin in humans, and thus several approaches are being developed to improve delivery systems or to create analogs that will mimic the neuroprotective effects and easily reach the brain. The lack of efficacy of curcumin in humans with AD may also result from treating for too short a time or starting treatment too late in the course of the disease, where substantial neuronal death has already occurred and cannot be reversed. Curcumin may be beneficial in protecting against development or progression of AD if taken over the long term and started before symptoms of AD become apparent.

Inhibition of Wnt/β-catenin signaling mediates ursolic acid-induced apoptosis in PC-3 prostate cancer cells

BACKGROUND

Ursolic acid, a pentacyclic triterpenoid, is known to exert antitumor activity in breast, lung, liver and colon cancers. Nonetheless, the underlying mechanism of ursolic acid in prostate cancer cells still remains unclear. To investigate the antitumor mechanism, the apoptotic mechanism of ursolic acid via Wnt/β-catenin signaling was examined in PC-3 prostate cancer cells.

METHODS

Cytotoxicity assay, flow cytometry, immunofluorescence assay and western blotting were performed.

RESULTS

Ursolic acid showed cytotoxicity against PC-3, LNCaP and DU145 prostate cancer cells with IC50 of 35 μM, 47 μM and 80 μM, respectively. Also, ursolic acid significantly increased the number of ethidium homodimer stained cells and apoptotic bodies, and dose-dependently enhanced the sub-G1 apoptotic accumulation in PC-3 cells. Consistently, western blotting revealed that ursolic acid effectively cleaved poly (ADP-ribose) polymerase (PARP), activated caspase-9 and -3, suppressed the expression of survival proteins such as Bcl-XL, Bcl-2 and Mcl-1, and upregulated the expression of Bax in PC-3 cells. Interestingly, ursolic acid suppressed the expression of Wnt5α/β and β-catenin, and enhanced the phosphorylation of glycogen synthase kinase 3 β (GSK3β). Furthermore, the GSK3β inhibitor SB216763 or Wnt3a-conditioned medium (Wnt3a-CM) reversed the cleavages of caspase-3 and PARP induced by ursolic acid in PC-3 cells.

CONCLUSIONS

Our findings suggest that ursolic acid induces apoptosis via inhibition of the Wnt5/β-catenin pathway and activation of caspase in PC-3 prostate cancer cells. These results support scientific evidence that medicinal plants containing ursolic acid can be applied to cancer prevention and treatment as a complement and alternative medicine (CAM) agent.

Curcumin prevents formation of polyglutamine aggregates by inhibiting Vps36, a component of the ESCRT-II complex

Small molecules with antioxidative properties have been implicated in amyloid disorders. Curcumin is the active ingredient present in turmeric and known for several biological and medicinal effects. Adequate evidence substantiates the importance of curcumin in Alzheimer's disease and recent evidence suggests its role in Prion and Parkinson's disease. However, contradictory effects have been suggested for Huntington's disease. This difference provided a compelling reason to investigate the effect of curcumin on glutamine-rich (Q-rich) and non-glutamine-rich (non Q-rich) amyloid aggregates in the well established yeast model system. Curcumin significantly inhibited the formation of htt72Q-GFP (a Q-rich) and Het-s-GFP (a non Q-rich) aggregates in yeast. We show that curcumin prevents htt72Q-GFP aggregation by down regulating Vps36, a component of the ESCRT-II (Endosomal sorting complex required for transport). Moreover, curcumin disrupted the htt72Q-GFP aggregates that were pre-formed in yeast and cured the yeast prion, [PSI(+)].

Protective effects of curcumin on amyloid-β-induced neuronal oxidative damage

To investigate the protective effects of curcumin against amyloid-β (Aβ)-induced neuronal damage. Primary rat cortical neurons were cultured with different treatments of Aβ and curcumin. Neuronal morphologies, viability and damage were assessed. Neuronal oxidative stress was assessed, including extracellular hydrogen peroxide and intracellular reactive oxygen species. The abilities of curcumin to scavenge free radicals and to inhibit Aβ aggregation and β-sheeted formation are further assessed and discussed. Curcumin preserves cell viability, which is decreased by Aβ. The results of changed morphology, released Lactate dehydrogenases and cell viability assays indicate that curcumin protects Aβ-induced neuronal damage. Curcumin depresses Aβ-induced up-regulation of neuronal oxidative stress. The treatment sequence impacts the protective effect of curcumin on Aβ-induced neuronal damage. Curcumin shows a more protective effect on neuronal oxidative damage when curcumin was added into cultured neurons not later than Aβ, especially prior to Aβ. The abilities of curcumin to scavenge free radicals and to inhibit the formation of β-sheeted aggregation are both beneficial to depress Aβ-induced oxidative damage. Curcumin prevents neurons from Aβ-induced oxidative damage, implying the therapeutic usage for the treatment of Alzheimer's disease patients.