The multiple-step cleavage of amyloid precursor protein (APP) generates amyloid-β peptides (Aβ), highly toxic molecules causing Alzheimer's disease (AD). The nonspecific cleavage between the transmembrane region of APP (APPTM) and γ-secretase is the key step of Aβ generation. Reconstituting APPTM under physiologically-relevant conditions is crucial to investigate how it interacts with γ-secretase and for future AD drug discovery. Although producing recombinant APPTM was reported before, the large scale purification was hindered by the use of biological protease in the presence of membrane protein. Here, we expressed recombinant APPTM in Escherichia coli using the pMM-LR6 vector and recovered the fusion protein from inclusion bodies. By combining Ni-NTA chromatography, cyanogen bromide cleavage, and reverse phase high performance liquid chromatography (RP-HPLC), isotopically-labeled APPTM was obtained in high yield and high purity. The reconstitution of APPTM into dodecylphosphocholine (DPC) micelle generated mono dispersed 2D ¹⁵N-¹H HSQC spectra in high quality. We successfully established an efficient and reliable method for the expression, purification and reconstruction of APPTM, which may facilitate future investigation of APPTM and its complex in more native like membrane mimetics such as bicelle and nanodiscs.
Humans ; Amyloid beta-Protein Precursor/chemistry* ; Micelles ; Amyloid Precursor Protein Secretases/metabolism* ; Magnetic Resonance Spectroscopy ; Recombinant Proteins

Physalin B (PB), one of the major active steroidal constituents of Solanaceae Physalis plants, has a wide variety of biological activities. We found that PB significantly down-regulated β-amyloid (Aβ) secretion in N2a/APPsw cells. However, the underlying mechanisms are not well understood. In the current study, we investigated the changes in key enzymes involved in β-amyloid precursor protein (APP) metabolism and other APP metabolites by treating N2a/APPsw cells with PB at different concentrations. The results indicated that PB reduced Aβ secretion, which was caused by down-regulation of β-secretase (BACE1) expression, as indicated at both the protein and mRNA levels. Further research revealed that PB regulated BACE1 expression by inducing the activation of forkhead box O1 (FoxO1) and inhibiting the phosphorylation of signal transducer and activator of transcription 3 (STAT3). In addition, the effect of PB on BACE1 expression and Aβ secretion was reversed by treatment with FoxO1 siRNA and STAT3 antagonist S3I-201. In conclusion, these data demonstrated that PB can effectively down-regulate the expression of BACE1 to reduce Aβsecretion by activating the expression of FoxO1 and inhibiting the phosphorylation of STAT3.
Alzheimer Disease ; Amyloid Precursor Protein Secretases/metabolism* ; Amyloid beta-Peptides/metabolism* ; Aspartic Acid Endopeptidases/metabolism* ; Down-Regulation ; Forkhead Box Protein O1/genetics* ; Humans ; Phosphorylation ; STAT3 Transcription Factor/metabolism* ; Secosteroids

OBJECTIVETo observe the effects of Huannao Yicong Formula (, HYF) on learning and memory and it's regulating effect on γ-secretase related anterior pharynx defective 1 (APH-1), presenilin enhancer-2 (PEN-2) signaling pathway, so as to discuss and further clarify the mechanism of HYF on Alzheimer's disease.

METHODSSixty APP/PS1 transgenic mice, randomly allocated into 4 groups, the model group, the donepezil group (0.65 mg/kg), HYF low-dose group (HYF-L, 5.46 g/kg) and HYF high-dose group (HYF-H, 10.92 g/kg), 15 for each group. Another 15 C57BL/6J mice with the same age and same genetic background were allocated into the control group, proper dosage of drugs or distilled water were given by intragastric administration once daily for 12 weeks. After 12 weeks of administration, the learning and memory abilities of mice in each group was evaluated by the morris water maze test, amyloid precursor protein (APP), Aβand Aβlevels in hippocampus were detected by enzyme-linked immunosorbent assay, γ-secretase was detected by dual luciferase assaying, the levels of APH-1a, hypoxia-inducible factor 1α (HIF-1α), cAMP response element-binding protein (CREB) and PEN-2 and their mRNA expression was measured by Western blot and real-time polymerase chain reaction.

RESULTSHYF can ameliorate learning and memory deficits in APP/PS1 transgenic mice by decreasing the escape latency, improving the number of platform crossing and swimming speed (P<0.01, P<0.05). HYF can decrease the levels of APP, Aβ, Aβand the activity of γ-secretase in hippocampus of Alzheimer's disease model mice. HYF can down-regulate the levels of CREB and PEN-2 and the expression of their mRNA.

CONCLUSIONHYF can improve the learning and memory ability by inhibiting the activity of γ-secretase through the CREB/PEN-2 signaling pathway, and this may be one of the therapeutic mechanisms of HYF in Alzheimer's disease.

Amyloid Precursor Protein Secretases ; metabolism ; Amyloid beta-Protein Precursor ; metabolism ; Animals ; Cyclic AMP Response Element-Binding Protein ; genetics ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Endopeptidases ; genetics ; metabolism ; Enzyme-Linked Immunosorbent Assay ; Female ; Gene Expression Regulation ; drug effects ; Hippocampus ; drug effects ; metabolism ; pathology ; Hypoxia-Inducible Factor 1, alpha Subunit ; genetics ; metabolism ; Immunohistochemistry ; Learning ; drug effects ; Male ; Memory Disorders ; drug therapy ; genetics ; Mice, Inbred C57BL ; Mice, Transgenic ; Presenilin-1 ; metabolism ; Presenilin-2 ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Signal Transduction ; drug effects

OBJECTIVETo investigate the expression of miR-140-5p and ADAM10 in hypopharyngeal carcinoma tissues and their effects on the migration and invasion of FaDu cells and underlying mechanism.

METHODSThe miR-140-5p and ADAM10 mRNA levels in 33 cases of hypopharyngeal carcinoma tissues and adjacent normal tissues were measured by real-time quantitative polymerase chain reaction (RT-qPCR). Transwell migration assay and transwell invasion assay were used to test the metastasis ability of FaDu cells after upregulation or downregulation of miR-140-5p and downregulation of ADAM10. The protein expression levels of ADAM10 in hypopharyngeal carcinoma tissues and the FaDu cells after transfection were determined by Western blot assays.

RESULTSThe expression level of miR-140-5p was significantly downregulated in hypopharyngeal carcinoma tissues compared with adjacent tissues (t=-4.016, P<0.01), which was significantly correlated with tumor classification and lymph node metastasis (P<0.05). Conversely, mRNA and protein expressions of ADAM10 were significantly upregulated in tumor tissues (t=3.960, P<0.01; t=12.089, P<0.01), and were significantly downregulated in the FaDu cells after tranfected with si-ADAM10 (t=8.653, P<0.05; t=5.191, P<0.05). Transwell assay showed that compare with control group, the migration and invasive cells decreased significantly in hsa-mir-140-5p group (t=3.255, P<0.05; t=2.942, P<0.05), while increased significantly in anti-hsa-mir-140-5p group, (t=-13.521, P<0.05; t=-6.223, P<0.05). The migration and invasive cells in si-ADAM10 group were less than those in control group (t=4.759, P<0.05; t=3.663, P<0.05). The downregulation of ADAM10 attenuated the effect of anti-mir-140-5p in FaDu cells. Western blot assay showed that ADAM10 expression was apparently decreased in hsa-mir-140-5p group and increased in anti-mir-140-5p group compared with control group.

CONCLUSIONSThe expression of miR-140-5p was significantly downregulated in hypopharyngeal carcinoma tissues and correlated with tumor classification and lymph node metastasis. ADAM10 was upregulated in tumor tissues. MiR-140-5p suppresses the migration and invasion abilities of FaDu cells, possibly through downregulation of ADAM10.

ADAM Proteins ; metabolism ; ADAM10 Protein ; Amyloid Precursor Protein Secretases ; metabolism ; Cell Line, Tumor ; Cell Movement ; Down-Regulation ; Gene Expression Regulation, Neoplastic ; Humans ; Hypopharyngeal Neoplasms ; pathology ; Lymphatic Metastasis ; Membrane Proteins ; metabolism ; MicroRNAs ; metabolism ; RNA, Messenger ; metabolism ; Transfection

BACKGROUNDAmyloid β (Aβ) has been established as a key factor for the pathological changes in the brains of patients with Alzheimer's disease (AD), and cellular senescence is closely associated with aging and cognitive impairment. However, it remains blurred whether, in the AD brains, Aβ accelerates the neuronal senescence and whether this senescence, in turn, impairs the cognitive function. This study aimed to explore the expression of senescence-associated genes in the hippocampal tissue from young to aged 5XFAD mice and their age-matched wild type (WT) mice to determine whether senescent neurons are present in the transgenic AD mouse model.

METHODSThe 5XFAD mice and age-matched wild type mice, both raised from 1 to 18 months, were enrolled in the study. The senescence-associated genes in the hippocampus were analyzed and differentially expressed genes (DEGs) were screened by quantitative real-time polymerase chain reaction. Cognitive performance of the mice was evaluated by Y-maze and Morris water maze tests. Oligomeric Aβ (oAβ) (1-42) was applied to culture primary neurons to simulate the in vivo manifestation. Aging-related proteins were detected by Western blotting analysis and immunofluorescence.

RESULTSIn 5XFAD mice, of all the DEGs, the senescence-associated marker p16 was most significantly increased, even at the early age. It was mainly localized in neurons, with a marginal expression in astrocytes (labeled as glutamine synthetase), nil expression in activated microglia (labeled as Iba1), and negatively correlated with the spatial cognitive impairments of 5XFAD mice. oAβ (1-42) induced the production of senescence-related protein p16, but not p53 in vitro, which was in line with the in vivo manifestation.

CONCLUSIONSoAβ-accelerated neuronal senescence may be associated with the cognitive impairment in 5XFAD mice. Senescence-associated marker p16 can serve as an indicator to estimate the cognitive prognosis for AD population.

Alzheimer Disease ; metabolism ; physiopathology ; Amyloid Precursor Protein Secretases ; genetics ; metabolism ; Amyloid beta-Peptides ; metabolism ; Amyloid beta-Protein Precursor ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; genetics ; metabolism ; Brain ; metabolism ; physiopathology ; Cells, Cultured ; Cellular Senescence ; genetics ; physiology ; Cognition ; physiology ; Cognition Disorders ; metabolism ; physiopathology ; Disease Models, Animal ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; Neurons ; metabolism ; pathology ; Real-Time Polymerase Chain Reaction

OBJECTIVETo investigate the effect of γ-secretase inhibitor (N-[N-(3,5-difluorophenacetyl)-l -alanyl]-S-phenylglycine t-butyl ester, DAPT) on hyperoxia-induced brain white matter injury in mice.

MWTHODSThree-day-old C57BL/10J mouse pups were divided into air control (C) group, control+DAPT (10 mg/kg, injected intraperitoneally) group, hyperoxia group (exposed to 80% oxygen for 48 h), and hyperoxia+DAPT group. The brain and body weights of the mice were measured at postnatal days 3, 5, 12, and 28. Real-time PCR was used to detect Notch intracellular domain (NICD) mRNA expression in the brain after modeling, and the expressions of NG2 and myelin basic protein (MBP) were detected by double-labeled immunofluorescence assay to verify the oligdendrocycle type at postnatal day 12. The mice in each group were bred until postnatal day 28 for Morris water maze test.

RESULTSThe brain and body weights were significantly decreased in mice in hyperoxia group compared to the control mice, but increased significantly after DAPT treatment (P<0.05). Real-time PCR showed that a 48-hour hyperoxia exposure significantly increased NICD mRNA expression in the brain (P<0.05), which was decreased by co-treatment by DAPT (P<0.05). Hyperoxia also resulted in enhanced NG2 expression and lowered MBP expression in the brain (P<0.05). Compared with the control mice, the mice exposed to hyperoxia showed prolonged escape latency (P<0.05) and spent less time in the target quadrant with a lowered number of passing through the virtual platform (P<0.05). All these parameters were significantly improved by co-treatment with DAPT.

CONCLUSIONSpecific inhibition of Notch signaling pathway activation in the brain by the γ-secretase inhibitor DAPT can ameliorate white matter injury and learning and memory impairment in newborn mice with hyperoxia exposure.

Amyloid Precursor Protein Secretases ; antagonists & inhibitors ; Animals ; Body Weight ; Brain ; metabolism ; pathology ; Dipeptides ; pharmacology ; Hyperoxia ; physiopathology ; Mice ; Mice, Inbred C57BL ; Mice, Inbred Strains ; Organ Size ; Receptors, Notch ; metabolism ; Signal Transduction ; White Matter ; pathology

OBJECTIVETo investigate the effects of exogenous hydrogen sulfide (H2S) on β-site APP cleaving enzyme 1 (BACE-1) and β-amyloid peptide (Aβ) metabolism in primary culture of neurons under high-glucose condition.

METHODSThe cortical neurons in primary culture under normal and high glucose (60 mmol/L) conditions for 24 h were exposed to 25, 50 and 100 µmol/L NaHS. Aβ1-42 concentration in the cell culture was measured by ELISA, and BACE-1 mRNA and protein levels were detected by fluorescent quantitative real-time PCR and Western blotting, respectively.

RESULTSCompared with the neurons cultured in normal glucose, the neurons exposed to high glucose showed significantly increased Aβ1-42 concentration and BACE-1 mRNA and protein expressions (P<0.05). Exposure to 25, 50 and 100 µmol/L NaHS significantly decreased Aβ1-42 concentration and BACE-1 mRNA and protein expressions in the high-glucose cell culture (P<0.05).

CONCLUSIONNeurons exposed to high glucose exhibit increased Aβ1-42 levels and BACE-1 mRNA and protein expressions, which can be concentration-dependently decreased by NaHS.

Amyloid Precursor Protein Secretases ; metabolism ; Amyloid beta-Peptides ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; metabolism ; Cells, Cultured ; Culture Media ; chemistry ; Glucose ; chemistry ; Hydrogen Sulfide ; pharmacology ; Neurons ; drug effects ; metabolism ; Peptide Fragments ; metabolism ; Rats ; Rats, Sprague-Dawley

This study is to screen the Chinese herbal compounds which could inhibit the production of Abeta and investigate the underlying mechanism. Ten types of compounds which have potential value in the treatment of AD were selected as initial screening trial. The cell models which used could overexpress Abeta and beta-secretases or Abeta and gamma-secretases. Extracellular Abeta was determined by ELISA after the cell models treated with different concentrations of compounds (0.5-100 micromol x L(-1)), separately. Then the compounds were selected which could inhibit extracellular Abeta and their best concentration ranges were decided, too. Furthermore, the cell viability and apoptosis rate, the level of intracellular Abeta, beta and gamma-secretases were determined after the cell models treated with different concentrations of selected compounds. The results showed that 4 of the 10 compounds could reduce the level of extracellular Abeta; they were cryptotanshinone, astragalosides, gastrodin and paeoniflorin, and their best concentration ranges were 0.5-5.0, 0.5-5.0, 5.0-50, 1.0-25 micromol x L(-1), respectively. Further study indicated that the 4 selected compounds were nontoxic to the cellular models and lowering intracellular Abeta were more effective compared with extracellular; of which astragalosides and gastrodin showed dose-dependent inhibition to the activities of beta and gamma-secretases, with the maximum inhibiting rates of 78.2% and 80.3%, respectively. In conclusion, cryptotanshinone, astragalosides, gastrodin and paeoniflorin could inhibit the expression and secretion of Abeta, and the underlying inhibiting mechanism of astragalosides and gastrodin were related with the reduction of the beta and gamma-secretase activities, respectively.
Amyloid Precursor Protein Secretases ; metabolism ; Amyloid beta-Peptides ; antagonists & inhibitors ; Apoptosis ; Benzyl Alcohols ; pharmacology ; Cell Line ; Dose-Response Relationship, Drug ; Drug Evaluation, Preclinical ; Drugs, Chinese Herbal ; pharmacology ; Glucosides ; pharmacology ; Humans ; Monoterpenes ; pharmacology ; Phenanthrenes ; pharmacology ; Saponins ; pharmacology

BACKGROUNDBrain dysfunction is a frequent complication of sepsis, usually defined as sepsis-associated encephalopathy (SAE). Although the Notch signaling pathway has been proven to be involved in both ischemia and neuronal proliferation, its role in SAE is still unknown. Here, the effect of the Notch signaling pathway involved γ-secretase inhibitor DAPT on SAE in septic rats was investigated in a cecal ligation and puncture (CLP) model.

METHODSFifty-nine Sprague-Dawley rats were randomly divided into four groups, with the septic group receiving the CLP operation. Twenty-four hours after CLP or sham treatment, rats were sacrificed and their hippocampus was harvested for Western blot analysis. TNF-α expression was determined using an enzyme-linked immunosorbent assay (ELISA) kit. Neuronal apoptosis was assessed by TUNEL staining, and neuronal cell death was detected by H&E staining. Finally, a novel object recognition experiment was used to evaluate memory impairment.

RESULTSOur data showed that sepsis can increase the expression of hippocampal Notch receptor intracellular domain (NICD) and poly (adenosine diphosphate [ADP]-ribose) polymerase-1 (PARP-1), as well as the inflammatory response, neuronal apoptosis, neuronal death, and memory dysfunction in rats. The γ-secretase inhibitor N-[N-(3,5-difluorophenacetyl)-1-alanyl]-S-phenylglycine t-butyl ester (DAPT) can significantly decrease the level of NICD and PARP-1, reduce hippocampal neuronal apoptosis and death, attenuate TNF-α release and rescue cognitive impairment caused by CLP.

CONCLUSIONThe neuroprotective effect of DAPT on neuronal death and memory impairment in septic rats, which could be a new therapeutic approach for treating SAE in the future.

Amyloid Precursor Protein Secretases ; antagonists & inhibitors ; Animals ; Apoptosis ; drug effects ; Dipeptides ; therapeutic use ; Hippocampus ; drug effects ; metabolism ; Male ; Neurons ; cytology ; drug effects ; Neuroprotective Agents ; Poly (ADP-Ribose) Polymerase-1 ; Poly(ADP-ribose) Polymerases ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Notch ; metabolism ; Sepsis ; complications ; Sepsis-Associated Encephalopathy ; drug therapy ; enzymology ; Signal Transduction ; drug effects

To investigate the role and possible molecular mechanism of astrocytes in inflammation and amyloid β-protein (Aβ) formation, in this research, by using LPS to stimulate cultured rat astrocytes in vitro with or without anti-Toll-like receptor 4 (TLR4) antibody pretreatment, we first detected the TLR4, TNF-α, IL-1β, β-amyloid precursor protein (β-APP) and β-site APP clearing enzyme 1 (BACE1) mRNA with real-time PCR, and TLR4, NF-κB/P65 protein in cultured astrocytes by Western blot, and then further probed the translocation of NF-κB/P65 using immunofluorescence and the contents of TNF-α, IL-1β and Aβ in culture supernatant through ELISA. We found that all of these indexes increased at different degrees after LPS-stimulation. However, if pretreatment with anti- TLR4 antibody, such stimulating effects of LPS on the nuclear translocation of NF-κB/P65 and TNF-α, IL-1β, Aβ contents in astrocytic culture supernatant were reduced significantly or disappeared in comparison with the group with only LPS-administration. Our results suggest that TLR4 in astrocytes might play an important role in the inflammation and Aβ formation through the TLR4/NF-κB signaling pathway, thus providing new knowledge and understanding of the inflammatory hypothesis of AD pathogenesis.
Amyloid Precursor Protein Secretases ; metabolism ; Amyloid beta-Protein Precursor ; metabolism ; Animals ; Aspartic Acid Endopeptidases ; metabolism ; Astrocytes ; metabolism ; Cells, Cultured ; Cerebral Cortex ; cytology ; Inflammation ; metabolism ; Interleukin-1beta ; metabolism ; RNA, Messenger ; Rats ; Real-Time Polymerase Chain Reaction ; Signal Transduction ; Toll-Like Receptor 4 ; metabolism ; Transcription Factor RelA ; metabolism ; Tumor Necrosis Factor-alpha ; metabolism