Neuroprotective effect of novel cognitive enhancer noopept on AD-related cellular model involves the attenuation of apoptosis and tau hyperphosphorylation

Background

Noopept (N-phenyl-acetyl-L-prolylglycine ethyl ester) was constructed as a dipeptide analog of the standard cognition enhancer, piracetam. Our previous experiments have demonstrated the cognition restoring effect of noopept in several animal models of Alzheimer disease (AD). Noopept was also shown to prevent ionic disbalance, excitotoxicity, free radicals and pro-inflammatory cytokines accumulation, and neurotrophine deficit typical for different kinds of brain damages, including AD. In this study, we investigated the neuroprotective action of noopept on cellular model of AD, Aβ_25–35-induced toxicity in PC12 cells and revealed the underlying mechanisms.

Results

The neuroprotective effect of noopept (added to the medium at 10 μM concentration, 72 hours before Аβ_25–35) was studied on Аβ_25–35-induced injury (5 μM for 24 h) in PC12 cells. The ability of drug to protect the impairments of cell viability, calcium homeostasis, ROS level, mitochondrial function, tau phosphorylation and neurite outgrowth caused by Аβ_25–35 were evaluated.Following the exposure of PC12 cells to Аβ_25–35 an increase of the level of ROS, intracellular calcium, and tau phosphorylation at Ser396 were observed; these changes were accompanied by a decrease in cell viability and an increase of apoptosis. Noopept treatment before the amyloid-beta exposure improved PC12 cells viability, reduced the number of early and late apoptotic cells, the levels of intracellular reactive oxygen species and calcium and enhanced the mitochondrial membrane potential. In addition, pretreatment of PC12 cell with noopept significantly attenuated tau hyperphosphorylation at Ser396 and ameliorated the alterations of neurite outgrowth evoked by Аβ_25–35.

Conclusions

Taken together, these data provide evidence that novel cognitive enhancer noopept protects PC12 cell against deleterious actions of Aβ through inhibiting the oxidative damage and calcium overload as well as suppressing the mitochondrial apoptotic pathway. Moreover, neuroprotective properties of noopept likely include its ability to decrease tau phosphorylation and to restore the altered morphology of PC12 cells. Therefore, this nootropic dipeptide is able to positively affect not only common pathogenic pathways but also disease-specific mechanisms underlying Aβ-related pathology.     

Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta25–35 via the Autophagy Pathway

Evidence shows that an abnormal deposition of amyloid beta-peptide_25–35 (Aβ_25–35) was the primary cause of the pathogenesis of Alzheimer’s disease (AD). And the elimination of Aβ_25–35 is considered an important target for the treatment of AD. Triptolide (TP), isolated from Tripterygium wilfordii Hook.f. (TWHF), has been shown to possess a broad spectrum of biological profiles, including neurotrophic and neuroprotective effects. In our study investigating the effect and potential mechanism of triptolide on cytotoxicity of differentiated rat pheochromocytoma cell line (the PC12 cell line is often used as a neuronal developmental model) induced by Amyloid-Beta_25–35 (Aβ_25–35), we used 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) assay, flow cytometry, Western blot, and acridine orange staining to detect whether triptolide could inhibit Aβ_25–35–induced cell apoptosis. We focused on the potential role of the autophagy pathway in Aβ_25–35-treated differentiated PC12 cells. Our experiments show that cell viability is significantly decreased, and the apoptosis increased in Aβ_25–35-treated differentiated PC12 cells. Meanwhile, Aβ_25–35 treatment increased the expression of microtubule-associated protein light chain 3 II (LC3 II), which indicates an activation of autophagy. However, triptolide could protect differentiated PC12 cells against Aβ_25–35-induced cytotoxicity and attenuate Aβ_25–35-induced differentiated PC12 cell apoptosis. Triptolide could also suppress the level of autophagy. In order to assess the effect of autophagy on the protective effects of triptolide in differentiated PC12 cells treated with Aβ_25–35, we used 3-Methyladenine (3-MA, an autophagy inhibitor) and rapamycin (an autophagy activator). MTT assay showed that 3-MA elevated cell viability compared with the Aβ_25–35-treated group and rapamycin inhibits the protection of triptolide. These results suggest that triptolide will repair the neurological damage in AD caused by deposition of Aβ_25–35 via the autophagy pathway, all of which may provide an exciting view of the potential application of triptolide or TWHF as a future research for AD.     

The Role of Heat Shock Protein 70 in the Protective Effect of YC-1 on β-Amyloid-Induced Toxicity in Differentiated PC12 Cells

Neurodegenerative brain disorders such as Alzheimer’s disease (AD) have been well investigated. However, significant methods for the treatment of the progression of AD are unavailable currently. Heat shock protein 70 (Hsp70) plays important roles in neural protection from stress by assisting cellular protein folding. In this study, we investigated the effect and the molecular mechanism of YC-1, an activator of guanylyl cyclase (GC), on Aβ_25–35-induced cytotoxicity in differentiated PC12 cells. The results of this study showed that Aβ_25–35 (10 µM) significantly increased p25 protein production in a pattern that was consistent with the increase in μ-calpain expression. Moreover, Aβ_25–35 significantly increased tau hyperphosphorylation and induced differentiated PC12 cell death. YC-1 (0.5–10 µM) prevented the cell death induced by Aβ_25–35. In addition, YC-1 (1, 10 µM) significantly blocked Aβ_25–35-induced μ-calpain expression and decreased the formation of p25 and tau hyperphosphorylation. Moreover, YC-1 (5–20 µM) alone or combined with Aβ_25–35 (10 µM) significantly increased the expression of Hsp70 in differentiated PC12 cells. The neuroprotective effect of YC-1 was significantly attenuated by an Hsp70 inhibitor (quercetin, 50 µM) or in PC12 cells transfected with an Hsp70 small interfering RNA. However, pretreatment of cells with the GC inhibitor ODQ (10 µM) did not affect the neuroprotective effect of YC-1 against Aβ_25–35 in differentiated PC12 cells. These results suggest that the neuroprotective effect of YC-1 against Aβ_25–35-induced toxicity is mainly mediated by the induction of Hsp70. Thus, YC-1 is a potential agent against AD.     

Keratin 19 interacts with GSK3β to regulate its nuclear accumulation and degradation of cyclin D3

Cyclin D3 regulates the G1/S transition and is frequently overexpressed in several cancer types including breast cancer, where it promotes tumor progression. Here we show that a cytoskeletal protein keratin 19 (K19) physically interacts with a serine/threonine kinase GSK3β and prevents GSK3β-dependent degradation of cyclin D3. The absence of K19 allowed active GSK3β to accumulate in the nucleus and degrade cyclin D3. Specifically, the head (H) domain of K19 was required to sustain inhibitory phosphorylation of GSK3β Ser9, prevent nuclear accumulation of GSK3β, and maintain cyclin D3 levels and cell proliferation. K19 was found to interact with GSK3β and K19–GSK3β interaction was mapped out to require Ser10 and Ser35 residues on the H domain of K19. Unlike wildtype K19, S10A and S35A mutants failed to maintain total and nuclear cyclin D3 levels and induce cell proliferation. Finally, we show that the K19–GSK3β-cyclin D3 pathway affected sensitivity of cells toward inhibitors to cyclin-dependent kinase 4 and 6 (CDK4/6). Overall, these findings establish a role for K19 in the regulation of GSK3β-cyclin D3 pathway and demonstrate a potential strategy for overcoming resistance to CDK4/6 inhibitors.     

Resveratrol Inhibits β-Amyloid-Induced Neuronal Apoptosis through Regulation of SIRT1-ROCK1 Signaling Pathway

Alzheimer’s disease (AD) is characterized by the accumulation of β-amyloid peptide (Aβ) and loss of neurons. Recently, a growing body of evidences have indicated that as a herbal compound naturally derived from grapes, resveratrol modulates the pathophysiology of AD, however, with a largely unclear mechanism. Therefore, we aimed to investigate the protection of resveratrol against the neurotoxicity of β-amyloid peptide 25–35 (Aβ_25–35) and further explore its underlying mechanism in the present study. PC12 cells were injuried by Aβ_25–35, and resveratrol at different concentrations was added into the culture medium. We observed that resveratrol increased cell viability through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) colorimetric assays. Flow cytometry indicated the reduction of cell apoptosis by resveratrol. Moreover, resveratrol also stabilized the intercellular Ca²⁺ homeostasis and attenuated Aβ_25–35 neurotoxicity. Additionally, Aβ_25–35-suppressed silent information regulator 1 (SIRT1) activity was significantly reversed by resveratrol, resulting in the downregulation of Rho-associated kinase 1 (ROCK1). Our results clearly revealed that resveratrol significantly protected PC12 cells and inhibited the β-amyloid-induced cell apoptosis through the upregulation of SIRT1. Moreover, as a downstream signal molecule, ROCK1 was negatively regulated by SIRT1. Taken together, our study demonstrated that SIRT1-ROCK1 pathway played a critical role in the pathomechanism of AD.     

miRNA let-7e Modulates the Wnt Pathway and Early Nephrogenic Markers in Mouse Embryonic Stem Cell Differentiation

This study indicates that embryonic stem cells [ESCs] cultured with retinoic acid and activin A significantly upregulate the miRNA let-7e. This specific miRNA modulates the Wnt pathway and the expression of early nephrogenic markers under these differentiation conditions. The differentiation markers WT1, Pax2 and Wnt4 were downregulated when miRNA let-7e was silenced, thus indicating the role of miRNA let-7e in the differentiation process. PKCβ, GSK3β phosphorylation (GSK3β^P) and β-catenin expression was reduced in differentiated cells and reversed by miRNA let-7e silencing. Addition of a PKCβ inhibitor to the miRNA let-7e silenced cells abolished let-7e-derived effects in differentiation markers, and reversed the increase in GSK3β^P and β-catenin, thus indicating that miRNA let-7e is involved in differentiation via the modulation of GSK3β phosphorylation and β-catenin production.     

First Administration of the Fc-Attenuated Anti-β Amyloid Antibody GSK933776 to Patients with Mild Alzheimer’s Disease: A Randomized,Placebo-Controlled Study

Objective

To assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of the Fc-inactivated anti-β amyloid (Aβ) monoclonal antibody (mAb) GSK933776 in patients with mild Alzheimer’s disease (AD) or mild cognitive impairment (MCI).

Methods

This was a two-part, single blind, placebo-controlled, first-time-in-human (FTIH) study of single (n = 18) and repeat dose (n = 32) intravenous GSK933776 0.001–6 mg/kg (ClinicalTrials.gov: NCT00459550). Additional safety data from an open-label, uncontrolled, single dose study of intravenous GSK933776 1–6 mg/kg (n = 18) are included (ClinicalTrials.gov: NCT01424436).

Results

There were no cases of amyloid-related imaging abnormalities-edema (ARIA-E) or –hemorrhage (ARIA-H) after GSK933776 administration in both studies. Three patients across the two studies developed anti-GSK933776 antibodies. Plasma GSK933776 half-life (t_1/2) was 10–15 days after repeat dosing. After each of three administrations of GSK933776, plasma levels of total Aβ42 and Aβ increased whereas plasma levels of free Aβ decreased dose dependently; no changes were observed for placebo. For total Aβ42 the peak:trough ratio was ≤2 at doses ≥3 mg/kg; for total Aβ the ratio was ≤2 at 6 mg/kg. CSF concentrations of Aβ showed increases from baseline to week 12 for Aβ X–38 (week 12:baseline ratio: 1.65; 95%CI: 1.38, 1.93) and Aβ X–42 (week 12:baseline ratio: 1.18; 95%CI: 1.06, 1.30) for values pooled across doses.

Conclusion

In this FTIH study the Fc-inactivated anti-Aβ mAb GSK933776 engaged its target in plasma and CSF without causing brain ARIA-E/H in patients with mild AD or MCI.

Trial Registration

ClinicalTrials.gov NCT00459550     

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.     

Glycogen synthase kinase 3β promotes osteosarcoma invasion and migration via regulating PTEN and phosphorylation of focal adhesion kinase

Aim: Typical features of human osteosarcoma are highly invasive and migratory capacities. Our study aimed to investigate the roles of glycogen synthase kinase 3β (GSK3β) in human osteosarcoma metastasis.Methods: GSK3β expressions in clinical osteosarcoma tissues with or without metastasis were examined by immunohistochemical staining. The expressions of GSK3β, p-GSK3β^Ser9, and p-GSK3β^Tyr216 in human osteoblast cells (hFOB1.19) and human osteosarcoma cells (MG63, SaOS-2, and U2-OS) were detected by Western blotting. The GSK3β activity was measured by non-radio isotopic in vitro kinase assay. Migration and invasion abilities of MG-63 cells treated with small-molecular GSK3β inhibitors were respectively examined by monolayer-based wound-healing assay and transwell assay. The mRNA expressions of GSK3β, matrix metalloproteinase-2 (MMP-2), MMP-9, phosphatase with tensin homology (PTEN), and focal adhesion kinase (FAK) were detected after siRNA transfection for 72 h. Meanwhile, protein expressions of GSK3β, FAK, p-FAK^Y397, PTEN, MMP-2, and MMP-9 were measured by Western blotting.Results: Clinical osteosarcoma tissues with metastasis showed higher GSK3β expressions. MG63 and U2-OS cells that were easy to occur metastasis showed significantly higher expressions and activities of GSK3β than SaOS-2 cells. Inhibition of GSK3β with small-molecular GSK3β inhibitors in MG63 cells significantly attenuated cell migration and invasion. These effects were associated with reduced expressions of MMP-2 and MMP-9. Moreover, increased PTEN and decreased p-FAK^Y397 expressions were observed following GSK3β knockdown by siRNA transfection. Conclusion: GSK3β might promote osteosarcoma invasion and migration via pathways associated with PTEN and phosphorylation of FAK.     

Protein Kinase A Opposes the Phosphorylation-dependent Recruitment of Glycogen Synthase Kinase 3β to A-kinase Anchoring Protein 220

The proximity of an enzyme to its substrate can influence rate and magnitude of catalysis. A-kinase anchoring protein 220 (AKAP220) is a multivalent anchoring protein that can sequester a variety of signal transduction enzymes. These include protein kinase A (PKA) and glycogen synthase kinase 3β (GSK3β). Using a combination of molecular and cellular approaches we show that GSK3β phosphorylation of Thr-1132 on AKAP220 initiates recruitment of this kinase into the enzyme scaffold. We also find that AKAP220 anchors GSK3β and its substrate β-catenin in membrane ruffles. Interestingly, GSK3β can be released from the multienzyme complex in response to PKA phosphorylation on serine 9, which suppresses GSK3β activity. The signaling scaffold may enhance this regulatory mechanism, as AKAP220 has the capacity to anchor two PKA holoenzymes. Site 1 on AKAP220 (residues 610–623) preferentially interacts with RII, whereas site 2 (residues 1633–1646) exhibits a dual specificity for RI and RII. In vitro affinity measurements revealed that site 2 on AKAP220 binds RII with ∼10-fold higher affinity than site 1. Occupancy of both R subunit binding sites on AKAP220 could provide a mechanism to amplify local cAMP responses and enable cross-talk between PKA and GSK3β.     

Light and Electron Microscopy Study of Glycogen Synthase Kinase-3β in the Mouse Brain

Glycogen synthase kinase-3β (GSK3β) is highly abundant in the brain. Various biochemical analyses have indicated that GSK3β is localized to different intracellular compartments within brain cells. However, ultrastructural visualization of this kinase in various brain regions and in different brain cell types has not been reported. The goal of the present study was to examine GSK3β distribution and subcellular localization in the brain using immunohistochemistry combined with light and electron microscopy. Initial examination by light microscopy revealed that GSK3β is expressed in brain neurons and their dendrites throughout all the rostrocaudal extent of the adult mouse brain, and abundant GSK3β staining was found in the cortex, hippocampus, basal ganglia, the cerebellum, and some brainstem nuclei. Examination by transmission electron microscopy revealed highly specific subcellular localization of GSK3β in neurons and astrocytes. At the subcellular level, GSK3β was present in the rough endoplasmic reticulum, free ribosomes, and mitochondria of neurons and astrocytes. In addition GSK3β was also present in dendrites and dendritic spines, with some postsynaptic densities clearly labeled for GSK3β. Phosphorylation at serine-9 of GSK3β (pSer9GSK3β) reduces kinase activity. pSer9GSK3β labeling was present in all brain regions, but the pattern of staining was clearly different, with an abundance of labeling in microglia cells in all regions analyzed and much less neuronal staining in the subcortical regions. At the subcellular level pSer9GSK3β labeling was located in the endoplasmic reticulum, free ribosomes and in some of the nuclei. Overall, in normal brains constitutively active GSK3β is predominantly present in neurons while pSer9GSK3β is more evident in resting microglia cells. This visual assessment of GSK3β localization within the subcellular structures of various brain cells may help in understanding the diverse role of GSK3β signaling in the brain.     

Pharmacological Inhibition of Glycogen Synthase Kinase 3 Regulates T Cell Development In Vitro

The development of functional T cells requires receptor-mediated transition through multiple checkpoints in the thymus. Double negative 3 (DN3) thymocytes are selected for the presence of a rearranged TCR beta chain in a process termed β-selection which requires signalling via the pre-TCR, Notch1 and CXCL12. Signal integration by these receptors converges on core pathways including the Phosphatidylinositol–3-kinase (PI3K) pathway. Glycogen Synthase Kinase 3 (GSK3) is generally thought to be negatively regulated by the PI3K pathway but its role in β-selection has not been characterised. Here we show that developmental progression of DN3 thymocytes is promoted following inhibition of GSK3 by the synthetic compound CHIR99021. CHIR99021 allows differentiation in the absence of pre-TCR-, Notch1- or CXCL12-mediated signalling. It antagonizes IL-7-mediated inhibition of DP thymocyte differentiation and increases IL-7-promoted cell recovery. These data indicate a potentially important role for inactivation of GSK3 during β-selection. They might help to establish an in vitro stromal cell-free culture system of thymocyte development and offer a new platform for screening regulators of proliferation, differentiation and apoptosis.     

Systemic Administration of Substance P Recovers Beta Amyloid-Induced Cognitive Deficits in Rat: Involvement of Kv Potassium Channels

Reduced levels of Substance P (SP), an endogenous neuropeptide endowed with neuroprotective and anti-apoptotic properties, have been found in brain and spinal fluid of Alzheimer''s disease (AD) patients. Potassium (K⁺) channel dysfunction is implicated in AD development and the amyloid-β (Aβ)-induced up-regulation of voltage-gated potassium channel subunits could be considered a significant step in Aβ brain toxicity. The aim of this study was to evaluate whether SP could reduce, in vivo, Aβ-induced overexpression of Kv subunits. Rats were intracerebroventricularly infused with amyloid-β 25–35 (Aβ_25–35, 20 µg) peptide. SP (50 µg/Kg, i.p.) was daily administered, for 7 days starting from the day of the surgery. Here we demonstrate that the Aβ infused rats showed impairment in cognitive performances in the Morris water maze task 4 weeks after Aβ_25–35 infusion and that this impairing effect was prevented by SP administration.Kv1.4, Kv2.1 and Kv4.2 subunit levels were quantified in hippocampus and in cerebral cortex by Western blot analysis and immunofluorescence. Interestingly, SP reduced Kv1.4 levels overexpressed by Aβ, both in hippocampus and cerebral cortex.Our findings provide in vivo evidence for a neuroprotective activity of systemic administration of SP in a rat model of AD and suggest a possible mechanism underlying this effect.     

The Chlamydia pneumoniae Inclusion Membrane Protein Cpn1027 Interacts with Host Cell Wnt Signaling Pathway Regulator Cytoplasmic Activation/Proliferation-Associated Protein 2 (Caprin2)

We previously identified hypothetical protein Cpn1027 as a novel inclusion membrane protein that is unique to Chlamydia pneumoniae. In the current study, using a yeast-two hybrid screen assay, we identified host cell cytoplasmic activation/proliferation-associated protein 2 (Caprin2) as an interacting partner of Cpn1027. The interaction was confirmed and mapped to the C-termini of both Cpn1027 and Caprin2 using co-immunoprecipitation and GST pull-down assays. A RFP-Caprin2 fusion protein was recruited to the chlamydial inclusion and so was the endogenous GSK3β, a critical component of the β-catenin destruction complex in the Wnt signaling pathway. Cpn1027 also co-precipitated GSK3β. Caprin2 is a key regulator of the Wnt signaling pathway by promoting the recruitment of the β-catenin destruction complex to the cytoplasmic membrane in the presence of Wnt signaling while GSK3β is required for priming β-catenin for degradation in the absence of Wnt signaling. The Cpn1027 interactions with Caprin2 and GSK3β may allow C. pneumoniae to actively sequester the β-catenin destruction complex so that β-catenin is maintained even in the absence of extracellular Wnt activation signals. The maintained β-catenin can trans-activate Wnt target genes including Bcl-2, which may contribute to the chlamydial antiapoptotic activity. We found that the C. pneumoniae-infected cells were more resistant to apoptosis induction and the anti-apoptotic activity was dependent on β-catenin. Thus, the current study suggests that the chlamydial inclusion protein Cpn1027 may be able to manipulate host Wnt signaling pathway for enhancing the chlamydial anti-apoptotic activity.     

GSK3β phosphorylation modulates CLASP–microtubule association and lamella microtubule attachment

Polarity of the microtubule (MT) cytoskeleton is essential for many cell functions. Cytoplasmic linker–associated proteins (CLASPs) are MT-associated proteins thought to organize intracellular MTs and display a unique spatiotemporal regulation. In migrating epithelial cells, CLASPs track MT plus ends in the cell body but bind along MTs in the lamella. In this study, we demonstrate that glycogen synthase kinase 3β (GSK3β) directly phosphorylates CLASPs at multiple sites in the domain required for MT plus end tracking. Although complete phosphorylation disrupts both plus end tracking and association along lamella MTs, we show that partial phosphorylation of the identified GSK3β motifs determines whether CLASPs track plus ends or associate along MTs. In addition, we find that expression of constitutively active GSK3β destabilizes lamella MTs by disrupting lateral MT interactions with the cell cortex. GSK3β-induced lamella MT destabilization was partially rescued by expression of CLASP2 with mutated phosphorylation sites. This indicates that CLASP-mediated stabilization of peripheral MTs, which likely occurs in the vicinity of focal adhesions, may be regulated by local GSK3β inactivation.     

Ginsenoside Rg1 Decreases Aβ1–42 Level by Upregulating PPARγ and IDE Expression in the Hippocampus of a Rat Model of Alzheimer's Disease

Background and Purpose

The present study was designed to examine the effects of ginsenoside Rg1 on expression of peroxisome proliferator-activated receptor γ (PPARγ) and insulin-degrading enzyme (IDE) in the hippocampus of rat model of Alzheimer''s disease (AD) to determine how ginsenoside Rg1 (Rg1) decreases Aβ levels in AD.

Experimental Approach

Experimental AD was induced in rats by a bilateral injection of 10 µg soluble beta-amyloid peptide 1–42 (Aβ_1–42) into the CA1 region of the hippocampus, and the rats were treated with Rg1 (10 mg·kg⁻¹, intraperitoneally) for 28 days. The Morris water maze was used to test spatial learning and memory performance. Hematoxylin-eosin staining was performed to analyze the hippocampal histopathological damage. Immunohistochemistry, western blotting, and real-time PCR were used to detect Aβ_1–42, PPARγ, and insulin-degrading enzyme (IDE) expression in the hippocampus.

Key Results

Injection of soluble Aβ_1–42 into the hippocampus led to significant dysfunction of learning and memory, hippocampal histopathological abnormalities and increased Aβ_1–42 levels in the hippocampus. Rg1 treatment significantly improved learning and memory function, attenuated hippocampal histopathological abnormalities, reduced Aβ_1–42 levels and increased PPARγ and IDE expression in the hippocampus; these effects of Rg1 could be effectively inhibited by GW9662, a PPARγ antagonist.

Conclusions and Implications

Given that PPARγ can upregulate IDE expression and IDE can degrade Aβ_1–42, these results indicate that Rg1 can increase IDE expression in the hippocampus by upregulating PPARγ, leading to decreased Aβ levels, attenuated hippocampal histopathological abnormalities and improved learning and memory in a rat model of AD.     

Methyllycaconitine Alleviates Amyloid-β Peptides-Induced Cytotoxicity in SH-SY5Y Cells

Alzheimer''s disease (AD) is a chronic progressive neurodegenerative disorder. As the most common form of dementia, it affects more than 35 million people worldwide and is increasing. Excessive extracellular deposition of amyloid-β peptide (Aβ) is a pathologic feature of AD. Accumulating evidence indicates that macroautophagy is involved in the pathogenesis of AD, but its exact role is still unclear. Although major findings on the molecular mechanisms have been reported, there are still no effective treatments to prevent, halt, or reverse Alzheimer''s disease. In this study, we investigated whether Aβ_25–35 could trigger an autophagy process and inhibit the growth of SH-SY5Y cells. Furthermore, we examined the effect of methyllycaconitine (MLA) on the cytotoxity of Aβ_25–35. MLA had a protective effect against cytotoxity of Aβ, which may be related to its inhibition of Aβ-induced autophagy and the involvement of the mammalian target of rapamycin pathway. Moreover, MLA had a good safety profile. MLA treatment may be a promising therapeutic tool for AD.     

Diaminothiazoles Modify Tau Phosphorylation and Improve the Tauopathy in Mouse Models

Although Tau accumulation is a feature of several neurodegenerative conditions, treatment options for these conditions are nonexistent. Targeting Tau kinases represents a potential therapeutic approach. Small molecules in the diaminothiazole class are potent Tau kinase inhibitors that target CDK5 and GSK3β. Lead compounds from the series have IC₅₀ values toward CDK5/p25 and GSK3β in the low nanomolar range and no observed toxicity in the therapeutic dose range. Neuronal protective effects and decreased PHF-1 immunoreactivity were observed in two animal models, 3×Tg-AD and CK-p25. Treatment nearly eliminated Sarkosyl-insoluble Tau with the most prominent effect on the phosphorylation at Ser-404. Treatment also induced the recovery of memory in a fear conditioning assay. Given the contribution of both CDK5/p25 and GSK3β to Tau phosphorylation, effective treatment of tauopathies may require dual kinase targeting.