Mollugin activates GLP-1R to improve cognitive dysfunction in type 2 diabetic mice.

AIMS: The incidence of diabetic cognitive dysfunction is increasing year by year, and it has gradually become a research hot spot. Studies have shown that glucagon-like peptide-1 receptor (GLP-1R) agonists can improve cognitive dysfunction in diabetic patients. This study focuses on whether small molecule GLP-1R agonists from traditional Chinese medicine (TCM) can improve the diabetic cognitive dysfunction. MATERIALS AND METHODS: The small molecules from TCM were screened by cell membrane chromatography (CMC) with GLP-1R-HEK293 cell membrane column. MTT assay, flow cytometry, immunofluorescence cytochemistry and other methods were used to determine the effects of mollugin on the apoptosis rate and reactive oxygen species (ROS) level of high glucose (HG)/hydrogen peroxide (H2O2) induced PC12 cells. Real-Time PCR was used to detect mRNA expression in mouse cerebral cortex. Water maze test was further used to confirm the effect of mollugin on cognitive dysfunction in T2DM mice. KEY FINDINGS: Mollugin bound to GLP-1R, promoted Ca2+ influx, increased insulin secretion and cAMP content in ß-TC-6 cells. Mollugin enhanced the cell viability, ameliorated apoptosis, reduced intracellular ROS levels in HG/H2O2-injured PC12 cells. Mollugin reduced the T2DM mice's escape latency, improved neuronal cell damage, decreased the expression of Pik3ca, Akt1 and Mapk1 mRNA in the cerebral cortex tissue. SIGNIFICANCE: The results suggest that mollugin could improve cognitive dysfunction in T2DM mice through activating GLP-1R/cAMP/PKA signal pathway.

Schisandrin B, a potential GLP-1R agonist, exerts anti-diabetic effects by stimulating insulin secretion.

Diabetes mellitus is a metabolic disease that is characterized by elevated blood sugar. Although glucagon-like peptide-1 receptor agonists (GLP-1RA) lower blood glucose in a glucose-dependent manner, most of them are macromolecule polypeptides. Macromolecular peptides are relatively expensive and inconvenient compared with small molecules. Therefore, this study sought to identify the small molecules binding to GLP-1R via cell membrane chromatography (CMC), confirm their agonistic activity, and further study its beneficial effects in a mouse model of type 2 diabetes mellitus (T2DM) induced by a combination of high-fat diet and streptozotocin. We used CMC, calcium imaging and molecular docking techniques to screen and identify the potential small molecule Schisandrin B (Sch B), which exhibits a strong binding effect to GLP-1R, from the small molecule library of traditional Chinese medicine. Through in-vitro experiments, we found that Sch B stimulated insulin secretion in ß-TC-6 cells, while GLP-1R antagonist Exendin9-39, adenylate cyclase inhibitor SQ22536, and protein kinase A (PKA) inhibitor H89 could significantly inhibit the insulin secretion induced by Sch B. In vivo, Sch B significantly improved fasting blood glucose levels, intraperitoneal glucose tolerance test damage, and the status of pancreatic tissue damage, and reduced serum insulin levels, total cholesterol, triglyceride and low density lipoprotein in T2DM mice. These results indicate that Sch B alleviates T2DM by promoting insulin release through the GLP-1R/cAMP/PKA signaling pathway, suggesting that Sch B may be a potential GLP-1RA, which is expected to provide a new therapeutic strategy for the prevention and treatment of T2DM.

Construction of graphene quantum dots-decorated EGFR cell membrane chromatography for screening active components from Peucedanum praeruptorum Dunn.

A novel stability-enhanced graphene quantum dot (GQD)-decorated epidermal growth factor receptor (EGFR) cell membrane chromatography was constructed to study the potential application of GQDs in bioaffinity chromatography, and to screen active components acting on EGFR from traditional Chinese medicine (TCM). The carboxyl groups on the surface of GQDs reacted with the amino groups of the amino-silica gel (SiO2-NH2) to form a covalent bond, thereby preparing the GQD-decorated silica gel (SiO2-GQDs). The EGFR cell membrane was further immobilized on the SiO2-GQDs through the same covalent binding method to obtain the GQD-decorated cell membrane stationary phase (SiO2-GQDs-CMSP). In this way, the cell membrane was firmly immobilized on the decorated silica carrier. The life span and stability of the GQD-decorated cell membrane chromatographic (SiO2-GQDs-CMC) column were both enhanced, and the optimal immobilization conditions of the EGFR cell membrane were also determined. This model was then verified by establishing a SiO2-GQDs-CMC online liquid chromatography-ion trap-time-of-flight (LC-IT-TOF) system to screen possible active components in Peucedanum praeruptorum Dunn. As a result, praeruptorin B (Pra-B) was screened out, and its inhibitory effect against EGFR cell growth was evaluated by the cell counting kit-8 (CCK-8) assay. Molecular docking assay was also conducted to further estimate the interaction between Pra-B and EGFR. Overall, this research indicated that GQDs may be a promising nanomaterial to be used in prolonging the life span of the CMC column, and Pra-B could be a potential EGFR inhibitor so as to treat cancer.

Hyaluronic Acid-Modified Porous Carbon-Coated Fe3O4 Nanoparticles for Magnetic Resonance Imaging-Guided Photothermal/Chemotherapy of Tumors.

Chemotherapy is an effective method for treating cancer, clinically. However, side effects of drug and multidrug resistance restrict its application. In recent years, the combined treatment of chemotherapy and photothermal therapy (PTT) is becoming a promising method for treating cancer. PTT utilizes nanomaterials absorbing near-infrared light and producing heat to acquire advanced hyperthermia strategy for cancer treatment. Carbon nanomaterials with good biocompatibility, high surface area, and excellent photothermal properties are an excellent nanoplatform for drug delivery and PTT. Herein, porous carbon-coated magnetite nanoparticles (PCCMNs) were successfully synthesized by a one-pot solvothermal method. Magnetite, a contrast agent, can be used for magnetic resonance imaging. Hyaluronic acid was used to modify the PCCMNs to achieve targeted therapy. The obtained nanohybrid with a good photothermal effect can realize combined PTT/chemotherapy and will be a promising nanoplatform for high efficacy theranostics.

Black Phosphorus Nanosheets as a Neuroprotective Nanomedicine for Neurodegenerative Disorder Therapy.

Transition-metal dyshomeostasis is recognized as a critical pathogenic factor at the onset and progression of neurodegenerative disorder (ND). Excess transition-metal ions such as Cu2+ can catalyze the generation of cytotoxic reactive oxygen species and thereafter induce neuronal cell apoptosis. Exploring new chelating agents, which are not only capable of capturing excess redox-active metal, but can also cross the blood-brain barrier (BBB), are highly desired for ND therapy. Herein, it is demonstrated that 2D black phosphorus (BP) nanosheets can capture Cu2+ efficiently and selectively to protect neuronal cells from Cu2+ -induced neurotoxicity. Moreover, both in vitro and in vivo studies show that the BBB permeability of BP nanosheets is significantly improved under near-infrared laser irradiation due to their strong photothermal effect, which overcomes the drawback of conventional chelating agents. Furthermore, the excellent biocompatibility and stability guarantee the biosafety of BP in future clinical applications. Therefore, these features make BP nanosheets have the great potential to work as an efficient neuroprotective nanodrug for ND therapy.

Surface plasmon resonance biosensors for simultaneous monitoring of amyloid-beta oligomers and fibrils and screening of select modulators.

Oligomeric amyloid-beta (Aß) peptides are considered as the most toxic species in Alzheimer's disease (AD). Monitoring of the Aß aggregation profiles is critical for elucidating the oligomer toxicity and may serve as a therapeutic target for AD. By immobilizing the capture antibodies of A11 and OC that are specific to the oligomers and fibrils, respectively, in separate fluidic channels, a novel surface plasmon resonance (SPR) biosensor was designed for monitoring the oligomeric and fibrillar species of Aß(1-42) simultaneously. The influence of curcumin, Cu(2+) and methylene blue on the amount of toxic oligomers and fibrils was evaluated. The half maximal inhibitory concentration (IC50) of curcumin and methylene blue was determined. The formation of Aß fibrils was also validated by the thioflavin T (ThT) fluorescence assay. The results demonstrate the utility of SPR as an analytical tool for rapid and comprehensive monitoring of Aß aggregation and screening of Aß modulators.

Amplified voltammetric characterization of cleavage of the biotinylated peptide by BACE1 and screening of BACE1 inhibitors.

Cleavage of amyloid precursor protein (APP) by the ß-site APP cleaving enzyme 1 (BACE1) is a key step in the formation of amyloid beta (Aß) peptide, the main component of amyloid plaques in Alzheimer's disease (AD). Suppression of BACE1 activity has thus become an efficient way for the treatment of AD. In this study, BACE1 in the absence or presence of BACE1 inhibitors was exposed to the biotinylated peptide substrate-modified electrode. This step was followed by the attachment of ferrocene (Fc)-capped gold nanoparticle/streptavidin conjugates. Due to the blockage of the BACE1 activity by select inhibitors, well-defined voltammetric peaks of high signal intensity were obtained. However, featureless voltammogram was obtained upon initiating the cleavage reaction. The proposed method is simple, sensitive, and suitable for monitoring of BACE1 activity and screening of BACE1 inhibitors.

Sensitive and continuous screening of inhibitors of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) at single SPR chips.

The development of new methods that meet the demand of high-throughput, high-fidelity screening of hit compounds is important to researching modalities of important diseases such as neurological disorders, HIV, and cancer. A surface plasmon resonance- (SPR-) based method capable of continuously screening enzyme inhibitors at a single chip with antibody-amplified signal enhancement has been developed. The proof of concept is demonstrated by monitoring the cleavage of chip-confined peptide substrates [a segment of the amyloid precursor protein (APP) with the Swiss mutation] by ß-site APP-cleaving enzyme 1 (BACE1). In the presence of a noninhibitor, BACE1 clips the peptide substrate at the cleavage site, detaching a fragment that is homologous to the N-terminus of the amyloid beta (Aß) peptide. Consequently, a subsequent injection of the Aß antibody does not lead to any molecular recognition or SPR signal change at the chip. In contrast, suppression of the BACE1 activity by a strong inhibitor leaves the peptide substrate intact, and the subsequent antibody attachment produces an easily detectable SPR signal. Compared to the widely used FRET (fluorescence resonance energy transfer) assay, the method reported here is more cost-effective, as unlabeled peptide is used as the BACE1 substrate. Furthermore, the assay is faster (each screening cycle lasts for ca. 1.5 h) and can be continuously carried out at a single, regenerable SPR chip for more than 30 h. Consequently, excellent reproducibility (RSD < 5%) and throughput can be attained. Two inhibitors were screened, and their half-maximal inhibitory concentrations (IC50) determined by the SPR method were in excellent agreement with values deduced from ELISA and mass spectrometry.