Inhibitory effects and mechanisms of proanthocyanidins against enterovirus 71 infection.

Proanthocyanidins (PC), a natural flavonoid compound, was reported to possess a variety of pharmacological activities such as anti-tumor and anti-viral effects. In this study, the anti-Enterovirus 71 (EV71) activities and mechanisms of PC were investigated both in vitro and in vivo. The results showed that PC possessed anti-EV71 activities in different cell lines with low toxicity. PC can block both the adsorption and entry processes of EV71 via directly binding to virus VP1 protein. PC may competitively interfere with the binding of VP1 to its receptor SCARB2. PC can also regulate three different MAPK signaling pathways to reduce EV71 infection and attenuate virus induced inflammatory responses. Importantly, intramuscular therapy of EV71-infected mice with PC markedly improved their survival and attenuated the severe clinical symptoms. Therefore, the natural compound PC has potential to be developed into a novel anti-EV71 agent targeting viral VP1 protein and MAPK pathways.

Ursolic acid alleviates tetrandrine-induced hepatotoxicity by competitively binding to the substrate-binding site of glutathione S-transferases.

BACKGROUND: Tetrandrine (TET), a bisbenzylisoquinoline alkaloid isolated from Stephania tetrandra S. Moore, is the only approved medicine in China for silicosis. However, TET-induced hepatotoxicity has raised safety concerns. The underlying toxic targets and mechanism induced by TET remain unclear; there are no targeted detoxification strategies developed for TET-induced hepatotoxicity. Ursolic acid (UA), a pentacyclic triterpene with liver protective effects, may have detoxification effects on TET-induced hepatotoxicity. PURPOSE: This study aims to explore toxic targets and mechanism of TET and present UA as a potential targeted therapy for alleviating TET-induced hepatotoxicity. METHODS: A TET-induced liver-injury model was established to evaluate TET toxicity and the potential UA detoxification effect. Alkenyl-modified TET and UA probes were designed to identify potential liver targets. Pharmacological and molecular biology methods were used to explore the underlying toxicity/detoxification mechanism. RESULTS: TET induced liver injury by covalently binding to the substrate-binding pocket (H-site) of glutathione S-transferases (GSTs) and inhibiting GST activity. The covalent binding led to toxic metabolite accumulation and caused redox imbalance and liver injury. UA protected the liver from TET-induced damage by competitively binding to the GST H-site. CONCLUSION: The mechanism of TET-induced hepatotoxicity is related to irreversible binding with the GST H-site and GST-activity inhibition. UA, a natural antidote, competed with TET on H-site binding and reversed the redox imbalance. This study revealed the hepatotoxic mechanism of TET and provided a targeted detoxifying agent, UA, to alleviate hepatotoxicity caused by GST inhibition.

Ursolic acid reduces hepatocellular apoptosis and alleviates alcohol-induced liver injury via irreversible inhibition of CASP3 in vivo.

Alcoholic liver disease (ALD) is one of the pathogenic factors of chronic liver disease with the highest clinical morbidity worldwide. Ursolic acid (UA), a pentacyclic terpenoid carboxylic acid, has shown many health benefits including antioxidative, anti-inflammatory, anticancer, and hepatoprotective activities. We previously found that UA was metabolized in vivo into epoxy-modified UA containing an epoxy electrophilic group and had the potential to react with nucleophilic groups. In this study we prepared an alkynyl-modified UA (AM-UA) probe for tracing and capturing the target protein of UA from liver in mice, then investigated the mode by which UA bound to its target in vivo. By conducting proteome identification and bioinformatics analysis, we identified caspase-3 (CASP3) as the primary target protein of UA associated with liver protection. Molecule docking analysis showed that the epoxy group of the UA metabolite reacted with Cys-163 of CASP3, forming a covalent bond with CASP3. The binding mode of the UA metabolites (UA, CM-UA, and EM-UA) was verified by biochemical evaluation, demonstrating that the epoxy group produced by metabolism played an important role in the inhibition of CASP3. In alcohol-treated HepG2 cells, pretreatment with the UA metabolite (10 µM) irreversibly inhibited CASP3 activities, and subsequently decreased the cleavage of PARP and cell apoptosis. Finally, pre-administration of UA (20-80 mg· kg-1 per day, ig, for 1 week) dose-dependently alleviated alcohol-induced liver injury in mice mainly via the inhibition of CASP3. In conclusion, this study demonstrates that UA is a valuable lead compound for the treatment of ALD.

Cinnamaldehyde changes the dynamic balance of glucose metabolism by targeting ENO1.

AIMS: Hepatic glucose metabolism involves a variety of catabolic and anabolic pathways, and the dynamic balance of glucose metabolism is regulated in response to environmental and nutritional changes. The molecular mechanism of glucose metabolism in liver is complex and has not been fully elucidated so far. In this study, we hope to elucidate the target and mechanism of cinnamaldehyde (CA) in regulating glucose metabolism. MATERIALS AND METHODS: Molecular image tracing and magnetic capture in combination with an alkynyl-CA probe (Al-CA) was used to show CA covalently binds to α-enolase (ENO1) in both mouse liver and HepG2 cells. Accurate metabolic flow assays subsequently demonstrated that the utilization of glycogenic amino acids and the biosynthesis of tricarboxylic acid (TCA) cycle intermediates were strengthened, which was detected using nontargeted and targeted metabolomics analyses. KEY FINDINGS: Our study shows that CA covalently bonds with ENO1, which affects the stability and activity of ENO1 and changes the dynamic balance of glucose metabolism. The interruption of gluconeogenic reflux by ENO1 enhanced TCA cycle, and eventually led to a decrease in blood glucose and the improvement of mitochondrial efficiency. SIGNIFICANCE: These results provide a detailed description of how CA maintains the dynamic balance of glucose utilization and improves energy metabolism.

Cinnamaldehyde Enhances Antimelanoma Activity through Covalently Binding ENO1 and Exhibits a Promoting Effect with Dacarbazine.

At present, melanoma is a common malignant tumor with the highest mortality rate of all types of skin cancer. Although the first option for treating melanoma is with chemicals, the effects are unsatisfactory and include poor medication response and high resistance. Therefore, developing new medicines or a novel combination approach would be a significant breakthrough. Here, we present cinnamaldehyde (CA) as a potential candidate, which exerted an antitumor effect in melanoma cell lines. Chemical biology methods of target fishing, molecular imaging, and live cell tracing by an alkynyl-CA probe revealed that the α-enolase (ENO1) protein was the target of CA. The covalent binding of CA with ENO1 changed the stability of the ENO1 protein and affected the glycolytic activity. Furthermore, our results demonstrated that dacarbazine (DTIC) showed a high promoting effect with CA for antimelanoma both in vivo and in vitro. The combination improved the DTIC cell cycle arrest in the S phase and markedly impacted melanoma growth. As a covalent inhibitor of ENO1, CA combined with DTIC may be beneficial in patients with drug resistance in antimelanoma therapy.

A natural AKT inhibitor swertiamarin targets AKT-PH domain, inhibits downstream signaling, and alleviates inflammation.

Swertiamarin (SW), a representative component in Flos Lonicerae Japonicae, has been reported to exert significant activity in preventing infections. In this research, we aim to clarify the details of SW and its target to explore SW's underlying anti-inflammatory mechanisms. An azide labeled SW probe was synthesized for protein target fishing, and the results demonstrated that AKT could be captured specifically. Immunofluorescence colocalization with AKT was implemented by a click reaction of the SW probe and alkynyl CY5. The result showed that AKT was one of the targets of SW. Then, a competitive combination experiment using a set of AKT inhibitors and a membrane translocation experiment confirmed that SW might target the pleckstrin homology (PH) domain of AKT. This specific binding directly deactivated the phosphorylation of AKT on both Ser473 and Thr308, which induced the dephosphorylation of IKK and NF-κB. Finally, proinflammatory cytokines (TNF-α, IL-6, and IL-8) were suppressed both in cells and in acute lung injury animal model by targeting AKT-PH domain. This study demonstrated that SW functions as a natural AKT inhibitor and presents significant anti-inflammatory activity by directly regulating the AKT-PH domain and inhibiting downstream inflammatory molecules.

Glycyrrhetinic acid binds to the conserved P-loop region and interferes with the interaction of RAS-effector proteins.

Members of the RAS proto-oncogene superfamily are indispensable molecular switches that play critical roles in cell proliferation, differentiation, and cell survival. Recent studies have attempted to prevent the interaction of RAS/GTP with RAS guanine nucleotide exchange factors (GEFs), impair RAS-effector interactions, and suppress RAS localization to prevent oncogenic signalling. The present study aimed to investigate the effect of the natural triterpenoic acid inhibitor glycyrrhetinic acid, which is isolated from the roots of Glycyrrhiza plant species, on RAS stability. We found that glycyrrhetinic acid may bind to the P-loop of RAS and alter its stability. Based on our biochemical tests and structural analysis results, glycyrrhetinic acid induced a conformational change in RAS. Meanwhile, glycyrrhetinic acid abolishes the function of RAS by interfering with the effector protein RAF kinase activation and RAS/MAPK signalling.

Quantitative Proteomics Combined with Affinity MS Revealed the Molecular Mechanism of Ginsenoside Antitumor Effects.

Ginsenosides have previously been demonstrated to effectively inhibit cancer cell growth and survival in both animal models and cell lines. However, the specific ginsenoside component that is the active ingredient for cancer treatment through interaction with a target protein remains unknown. By an integrated quantitative proteomics approach via affinity mass spectrum (MS) technology, we deciphered the core structure of the ginsenoside active ingredient derived from crude extracts of ginsenosides and progressed toward identifying the target protein that mediates its anticancer activity. The Tandem Mass Tag (TMT) labeling quantitative proteomics technique acquired 55620 MS/MS spectra that identified 5499 proteins and 3045 modified proteins. Of these identified proteins, 224 differentially expressed proteins and modified proteins were significantly altered in nonsmall cell lung cancer cell lines. Bioinformatics tools for comprehensive analysis revealed that the Ras protein played a general regulatory role in many functional pathways and was probably the direct target protein of a compound in ginsenosides. Then, affinity MS screening based on the Ras protein identified 20(s)-protopanaxadiol, 20(s)-Ginsenoside Rh2, and 20(s)-Ginsenoside Rg3 had affinity with Ras protein under different conditions. In particular, 20(s)-protopanaxadiol, whose derivatives are the reported antitumor compounds 20(s)-Ginsenoside Rh2 and 20(s)-Ginsenoside Rg3 that have a higher affinity for Ras via a low KD of 1.22 µM and the mutation sites of G12 and G60, was demonstrated to play a core role in those interactions. Moreover, the molecular mechanism and bioactivity assessment results confirmed the identity of the chemical ligand that was directly acting on the GTP binding pocket of Ras and shown to be effective in cancer cell bioactivity profiles.

The flavonoid baicalin improves glucose metabolism by targeting the PH domain of AKT and activating AKT/GSK3ß phosphorylation.

Baicalin is one of the main flavonoids of the dried root of Scutellaria baicalensis Georgi and is reported to exert beneficial effects on the regulation of glucose/lipid metabolism. However, understanding its specific target and unique mechanism for improving glucose utilization is a challenge. In this paper, target fishing with a baicalin probe reveals that baicalin interacts with AKT. An immunofluorescence assay further demonstrates the colocalization of baicalin with AKT in the cytoplasm. A competitive test and virtual docking show that baicalin might bind to the pleckstrin homology domain of AKT. This specific binding hampers AKT membrane translocation, activates the phosphorylation of AKT on Ser473, induces the downstream glycogen synthase kinase 3ß activation, and affects glycogen synthesis.

Ursolic Acid, a Natural Nutraceutical Agent, Targets Caspase3 and Alleviates Inflammation-Associated Downstream Signal Transduction.

SCOPE: Ursolic acid (UA) is a pentacyclicterpenoid carboxylic acid that is present in a wide variety of plant foods. There are many beneficial health effects that are attributed to the properties of UA. However, the specific cellular targets of UA and the mechanism underlying downstream signal transduction processes linked to the anti-inflammation pathway have not been thoroughly elucidated to date. METHODS AND RESULTS: Chemical biology strategies such as target fishing, click reaction synthesis of a UA probe and molecular imaging were used to identify potential target proteins of UA. Cysteinyl aspartate specific proteinase 3 (CASP3) and its downstream signaling pathway were verified as potential targets by molecular docking, intracellular enzyme activity evaluation and accurate pathway analysis. The results indicated that UA acted on CASP3, ERK1 and JNK2 targets, alleviated inflammation-associated downstream multiple signal transduction factors, including ERK1, NF-κB and STAT3, and exhibited anti-inflammation activities. CONCLUSION: As a natural dietary supplement, UA demonstrated anti-inflammation activity via inhibition of CASP3 and shows the potential to improve the therapy effect of several inflammation-associated diseases.

Mahuannin B an adenylate cyclase inhibitor attenuates hyperhidrosis via suppressing ß2-adrenoceptor/cAMP signaling pathway.

BACKGROUND: Based on the traditional application of traditional Chinese Medicines (TCMs), Ephedra Herba (EH) is used to cure cold fever by inducing sweating, whereas Ephedra Radix (ER) is used to treat hyperhidrosis. Although they come from the same plant, Ephedra sinica Stapf, but have play opposing roles in clinical applications. EH is known to contain ephedrine alkaloids, which is the driver of the physiological changes in sweating, heart rate and blood pressure. However, the active pharmacological ingredients (APIs) of ER and the mechanisms by which it restricts sweating remain unknown. PURPOSE: The current work aims to discover the hidroschesis APIs from ER, as well as to establish its action mechanism. METHODS: UPLC-Q/TOF-MS, PCA, and heat map were utilized for identifying the differences between EH and ER. HPLC integrated with a ß2-adrenoceptor (ß2-AR) activity luciferase reporter assay system was used to screen active inhibitors; molecular docking and a series of biological assays centered on ß2-AR-related signaling pathways were evaluated to understand the roles of APIs. RESULTS: The opposite effect on sweating of EH and ER can be attributed to the APIs of amphetamine-type alkaloids and flavonoid derivatives. Mahuannin B is an effective anti-hydrotic agent, inhibiting the production of cAMP via suppression of adenylate cyclase (AC) activity. CONCLUSION: The effects of EH and ER on sweat and ß2-AR-related signaling pathway are opposite due to different alkaloids and flavonoids of APIs in EH and ER. The present work not only sheds light on the hidroschesis action of mahuannin B, but also presents a potential target of AC in the treatment of hyperhidrosis.