The Anti-Tumor Agent Sodium Selenate Decreases Methylated PP2A, Increases GSK3βY216 Phosphorylation, Including Tau Disease Epitopes and Reduces Neuronal Excitability in SHSY-5Y Neurons

Combination of berberine and low glucose inhibits gastric cancer through the PP2A/GSK3β/MCL-1 signaling pathway

Intermittent fasting as an adjuvant therapy in clinical practice is an emerging treatment modality to target tumor growth by reducing glucose utilization. Berberine, an alkaloid extracted from the traditional Chinese medicine Coptidis Rhizoma, has been shown to be a safe and effective antitumor agent in several cancers. Hence, the purpose of the present study was to investigate the effects of the combination of berberine and low glucose on gastric cancer. Our results showed that the combination of berberine and low glucose effectively inhibited cell viability, promoted apoptosis, and reduced the migration ability of MGC803 cells. In addition, the combination was shown to activate the PP2A/GSK3β signaling axis, leading to the downregulation of the downstream pro-survival protein MCL-1, which leads to the death of gastric cancer cells. In addition, the inhibitor of GSK3β partially reversed the effect of this combination on MGC803 cells. In vivo experiments demonstrated that berberine effectively impaired the growth of xenograft tumors, when administered during intermittent fasting (hypoglycemic conditions), and was well tolerated by nude mice without the occurrence of any adverse effects. Based on these results, we conclude that the berberine/low-glucose combination can inhibit the growth of gastric cancer through the PP2A/GSK3β/MCL-1 signaling pathway. Accordingly, this combination of drugs and lifestyle may become a new type of safe and effective anti-cancer therapy.

Lapatinib ditosylate rescues memory impairment in D-galactose/ovariectomized rats: Potential repositioning of an anti-cancer drug for the treatment of Alzheimer's disease

Epidermal growth factor receptor (EGFR) signaling plays a substantial role in learning and memory. The upregulation of EGFR has been embroiled in the pathophysiology of Alzheimer's disease (AD). Nevertheless, most of EGFR-tyrosine kinase inhibitors (EGFR-TKIs) have been extensively studied for non-CNS diseases such as cancer and rheumatoid arthritis. TKIs targeting-based research in neurodegenerative disorders sounds to be lagging behind those of other diseases. Hence, this study aims to explore the molecular signaling pathways and the efficacy of treatment with lapatinib ditosylate (LAP), as one of EGFR-TKIs that has not yet been investigated in AD, on cognitive decline induced by ovariectomy (OVX) with chronic administration of D-galactose (D-gal) in female Wistar albino rats. OVX rats were injected with 150 mg/kg/day D-gal ip for 8 weeks to induce AD. Administration of 100 mg/kg/day LAP p.o. for 3 weeks starting after the 8^th week of D-gal administration improved memory and debilitated histopathological alterations. LAP decreased the expression of GFAP, p-tau, and Aβ 1-42. Besides, it reduced EGFR, HER-2, TNF-α, NOX-1, GluR-II, p38 MAPK, and p-mTOR. LAP increased nitrite, and neuronal pro-survival transduction proteins; p-PI3K, p-AKT, and p-GSK-3β levels. Taken together, these findings suggest the role of LAP in ameliorating D-gal-induced AD in OVX rats via activating the pro-survival pathway; PI3K-Akt-GSK-3β, while inhibiting p-mTOR, NOX-1, and p38 MAPK pathways. Moreover, this research offered a significant opportunity to advance awareness of the repositioning of TKI anti-cancer drugs for the treatment of AD.

DHCR24 Knockdown Lead to Hyperphosphorylation of Tau at Thr181, Thr231, Ser262, Ser396, and Ser422 Sites by Membrane Lipid-Raft Dependent PP2A Signaling in SH-SY5Y Cells

Accumulating data suggest that the downregulation of DHCR24 is linked to the pathological risk factors of AD, denoting a potential role of DHCR24 in AD pathogenesis. However, it remains unclear whether the downregulation of DHCR24 affects the abnormal heper-phosphorylation of tau protein, which is involved in tauopathy. In present papers, immunofluorescence and Filipin III fluorescence results showed that DHCR24 knockdown significantly lowered the level of plasma membrane cholesterol and expression level of membrane lipid-raft structural protein caveolin-1; and overexpression of DHCR24 could increase the plasma membrane cholesterol levels and facilitating caveolae structure through increase the expression of caveolin-1. PP2A is the key phosphatase involving in tau phosphorylation, which is localized in cholesterol-dependent caveola/raft lipid domains. Here, the PP2A activity was detected by western blot assay. Interestingly, the level of p-PP2Ac at Y307 (inactive) and p-GSK3β at Y216 (active) in the downstream of the PP2A signal pathway were both significantly increased in silencing DHCR24 SH-SY5Y cells, which denoted an inhibition of the PP2A and activation of GSK3β signaling. Conversely, overexpression of DHCR24 blunted the inhibition effect of PP2A and activation of GSK3β. Besides, in the SH-SY5Y cell lines we demonstrated that DHCR24 knockdown obviously induced hyperphosphorylation of tau at Thr181, Thr231, Ser262, Ser396, and Ser422 Sites. In contrast, DHCR24 overexpression protects neuronal SH-SY5Y cells against the hyperphosphorylation of tau at Thr181, Thr231, Ser262, Ser396, and Ser422 Sites. Furthermore, PP2A activator D-erythro-Sphingosine (DES) also obviously inhibited the hyperphosphorylation of tau induced by DHCR24 knockdown. Collectively, our findings firstly confirmed that DHCR24 knockdown obviously induced abnormal hyperphosphorylation of tau by a novel lipid raft-dependent PP2A signaling. We propose that DHCR24 downregulation led to altered cholesterol synthesis as a potential mechanism in the progression of tau hyperphosphorylation involving in AD and other tauopathies.

The Function of Selenium in Central Nervous System: Lessons from MsrB1 Knockout Mouse Models

MsrB1 used to be named selenoprotein R, for it was first identified as a selenocysteine containing protein by searching for the selenocysteine insert sequence (SECIS) in the human genome. Later, it was found that MsrB1 is homologous to PilB in Neisseria gonorrhoeae, which is a methionine sulfoxide reductase (Msr), specifically reducing L-methionine sulfoxide (L-Met-O) in proteins. In humans and mice, four members constitute the Msr family, which are MsrA, MsrB1, MsrB2, and MsrB3. MsrA can reduce free or protein-containing L-Met-O (S), whereas MsrBs can only function on the L-Met-O (R) epimer in proteins. Though there are isomerases existent that could transfer L-Met-O (S) to L-Met-O (R) and vice-versa, the loss of Msr individually results in different phenotypes in mice models. These observations indicate that the function of one Msr cannot be totally complemented by another. Among the mammalian Msrs, MsrB1 is the only selenocysteine-containing protein, and we recently found that loss of MsrB1 perturbs the synaptic plasticity in mice, along with the astrogliosis in their brains. In this review, we summarized the effects resulting from Msr deficiency and the bioactivity of selenium in the central nervous system, especially those that we learned from the MsrB1 knockout mouse model. We hope it will be helpful in better understanding how the trace element selenium participates in the reduction of L-Met-O and becomes involved in neurobiology.

BAY 73-6691 Alters Neuron Plasticity and Phosphorylation of Tau Through Regulation of Cyclic Guanosine Monophosphate/Protein Kinase G/Cyclic Adenosine Monophosphate Response Element-Binding Protein Pathway

Alzheimer’s disease (AD) is one of neurodegenerative diseases characterized by cognitive and memory decline, accompanying with neurofibrillary tangles (NFTs) made of hyperphosphorylated tau protein and senile plaques (SP) accumulated by β-amyloid protein (Aβ). BAY 73-6691, an inhibitor of phosphodiesterase-9 (PDE-9), can improve learning and memory of elderly rats. However, the effects of BAY 73-6691 on neuroapoptotic and neuroinflammatory events, as well as synaptic plasticity of differentiated PC12 cells are remain unclear. In this work, we screened apoptotic cells induced by Aβ25-35 via flow cytometry. TNF-α, IL-1β, IL-6 secreted by PC12 cells were estimated by ELISA kits. The levels of cGMP, PKG and CREB mediated by BAY 73-6691 were assessed. Moreover, we conducted western blots analysis to evaluate the phosphorylation of tau and synaptic related proteins. Results showed that BAY 73-6691 could reduce Aβ25-35-triggered neuroapoptosis and neuroinflammation. Phosphorylation of tau was inhibited by BAY 73-6691, whereas sildenafil citrate (SC, an inhibitor of cGMP) partially weakened the effect of BAY 73-6691. Additionally, synaptic plasticity restored by BAY 73-6691 was also suppressed via SC. Taken together, BAY 73-6691 exhibited neuro protective effects, and altered tau phosphorylation as well as synaptic related proteins through cGMP/PKG/CREB pathway.

Protective effects of chondroitin sulphate nano-selenium on a mouse model of Alzheimer's disease

In this study, the effect of chondroitin sulphate nano-selenium (CS@Se) on Alzheimer's disease (AD) in mice was investigated. CS@Se alleviated anxiety and improved the spatial learning and memory impairment in AD mice. CS@Se significantly reduced cell oedema and pyknosis, protected the mitochondria, and improved abnormal changes in the ultrastructure of hippocampal neuron synapses of AD mice. Moreover, CS@Se significantly increased the levels of superoxide dismutase(SOD), glutathione peroxidase (GSH-Px), Na⁺/K⁺-ATPase assay (Na⁺/K⁺-ATPase) and acetyltransferase (ChAT), and decreased the levels of malondialdehyde (MDA) and acetylcholinesterase (ChAE) in AD mice. Western blot results showed that CS@Se can attenuate excessive phosphorylation of tau (Ser396/Ser404) by regulating the expression of glycogen synthase kinase-3 beta (GSK-3β). In addition, CS@Se can activate the extracellular signal-regulated kinase 1/2 (ERK 1/2) and p38 mitogen-activated protein kinase (p38 MAPK) signalling pathways to inhibit nuclear transcription factor kappa B (NF-κB) nuclear translocation, thereby regulating the expression of pro-inflammatory cytokines. In summary, CS@Se can reduce oxidative stress damage, inhibit excessive tau phosphorylation, reduce inflammation to delay AD development, and increase the learning and memory capacities of AD mice.

Berberine mitigates cognitive decline in an Alzheimer's Disease Mouse Model by targeting both tau hyperphosphorylation and autophagic clearance

Berberine is a natural isoquinoline alkaloid isolated from the Rhizoma coptidis. Recent advances in research throw more lights of its beneficial role towards Alzheimer's disease (AD), including promoting β-amyloid (Aβ) clearance, as well as inhibiting Aβ production in the triple-transgenic mouse model of Alzheimer's disease (3×Tg AD). However, it remains unclarified if berberine has an effect on tau pathology. According to our study, berberine did not only significantly improve 3×Tg AD mice's spatial learning capacity and memory retentions, but also attenuated the hyperphosphorylation of tau. via modulating the activity of Akt/glycogen synthase kinase-3β and protein phosphatase 2A. Moreover, berberine reduced the level of tau through an autophagy-based route. It promoted autophagic clearance of tau by enhancing the activity of autophagy via the class III PI3K/beclin-1 pathway. Thus, our results suggest that berberine could mitigate cognitive decline by simultaneously targeting the hyperphosphorylation of tau and the autophagic clearance of tau in AD mice. These findings strongly support berberine as a potential drug candidate for AD.

The correlation between the methylation of PTEN gene and the apoptosis of osteosarcoma cells mediated by SeHA nanoparticles

The invasive spreading of residual osteosarcoma cells becomes a serious threat to human health, urgently needing new bone regenerative biomaterials for orthopedic therapy. Thus, in this work, selenite-substituted hydroxyapatite (SeHA) nanoparticles were prepared for both inhibiting the recurrence of the tumor and accelerating the regenerative repair of bone defect. Physicochemical characterization showed these synthetic nanoparticles were spherical poly-crystals with the shape of snowflakes. Such structure benefited them to inhibit the cellular viability of osteosarcoma cells by about (58.90 ± 14.37)% during 24 h co-culturing. The expression level of cell growth-related genes such as PTEN, MMP-9, Cyclin D1, Cyclin A2, Annexin A2 and CDC2 decreased. Bisulfite Sequence PCR of PTEN gene exhibited about (22.40 ± 5.39)%, (45.91 ± 6.36)% and (25.90 ± 5.36)% promoter methylation in control, HA and SeHA group. Animal experiment also proved the similar effects. Almost no recurrence were observed in SeHA group. Oppositely, the slowly recurrent growth of the remnant tumor appeared in purely surgical group. The overall survival and toxicity analysis showed that, in the usage dose of 0-0.1 g, the SeHA-0.01 exhibited higher inhibitory recurrence and metastasis potentials, lower renal toxicity and better anti-inflammation function. Immunohistochemistry stain showed the reduced expression of PTEN, MMP-9, Ki-67 and Annexin A2, but slightly increased expression of DNMT1 and BMP-2. Compared the methylation status of PTEN gene in each group, it was confirming that SeHA nanoparticles hardly possessed the de-methylation effect, but the pure HA strikingly increased the methylation level of such gene. It seemed the dopant selenite ions possessed de-methylation effect onto PTEN gene. Therefore, from the viewpoint of inhibiting metastatic potentials, the SeHA-0.01 might be a feasible biomaterial to inhibit the relapse of the tumor post-surgery.