Glycyrrhetinic acid-triggered cytoprotective autophagy via inositolrequiring enzyme 1α-c-Jun N-terminal kinase cascade in non-small cell lung cancer cells

OBJECTIVE Glycyrrhetinic acid(GA),one of the main bioactive constituents of the famous Chinese medicinal herb Glycyrrhizauralensis Fisch,presents potent cytotoxicity to various cancer cells both in vitro and in vivo.Herein,we′d like to determine whether GA triggers autophagy in non-small cell lung cancer cells and the mechanisms involved.METHODS Cell proliferation was determined by MTT assay and colony formation.AnnexinⅤ/PI staining,Hoechst33342 staining,and Western blotting were used to detect GA-induced apoptosis.GA-induced autophagy was measured by expression of the lipid modification of light chain-3(LC3)and transfected with GFP-LC3 or GFP-RFP-LC3 plasmid.Pharmacological regulators,siRNA,and plasmid transfection were used to study the mechanisms of GA-triggered autophagy.RESULTS GA inhibited cell proliferation and induced apoptosis in a concentrationdependent manner in non-small cell lung cancer A549 cells.GA induced autophagyas evidenced by up-regulation of LC3-Ⅱexpression when combined treatment with chloroquine and induction of the red punta after GFP-RFP-LC3 plasmid transfection.Knockdown of autophagy related proteins(ATG)7,ATG 5,or beclin 1by siRNA,the expression of LC3-Ⅱand GFP-LC3 punt atriggered by GA were decreased.Furthermore,the c-Jun N-terminal kinase(JNK)pathways were activated after treatment with GA,and pretreatment with JNK inhibitor SP600125 or silence of JNK pathway by siRNA of JNK or c-jun obviously reduced GA-induced LC3-Ⅱexpression and GFP-LC3 punta formation.GA also stimulate dendoplasmic reticulum stress response by triggering inositol-requiring enzyme 1α(IRE1α)pathway,and knockdown of IRE1αinhibited the activation of JNK pathway and autophagy induced by GA.In addition,GA-induced cell proliferative inhibition and apoptosis were both enhanced when silence of autophagy as well as JNK pathway.CONCLUSION Our study demonstrated,for the first time,that GA induced a cytoprotective autophagy in non-small cell lung cancer cells by activating the IRE1α-JNK pathway,which might decreased the anti-cancer effects of GA.

Pharmacophore modeling for the identification of small-molecule inhibitors of TACE

OBJECTIVE To employ pharmacophore modeling to identify a TACE inhibitor from an inhouse database of 66 organic compounds.METHODS To identify the common features required for TACE inhibition,we generated a pharmacophore model from a set of TACE-selective inhibitor using the Common Feature Pharmacophore Model protocol implemented in Discovery Studio 3.1.1.A fluorimetric assay was used to investigate the potential ability of compounds to inhibit TACE enzymatic activity.The ability of compound 1 to inhibit TACE activity in a human monocyte THP-1 cell line was evaluated by ELISA.RESULTS In this study,apharmacophore model constructed from a training set of TACE inhibitors was used to screen an in-house database of organic compounds,from which compound 1 emerged as a top candidate.In a cell-free assay,compound 1inhibited TACE enzymatic activity in a dose-dependent manner.Moreover,compound 1 inhibited the production of soluble TNF-αin human acute monocytic leukemia THP-1 cells without impacting nitric oxide production,and exhibited anti-proliferative activity against THP-1cells.CONCLUSION Compound 1 was found to inhibit TACE enzymatic activity in a cell-free system and LPS-induced TNF-αsecretion in cellulo.We envisage that compound 1 may be employed as a useful scaffold for the development of more potent TACE inhibitors.

Identification of a natural product-like STAT3 dimerization inhibitor by structure-based virtual screening

OBJECTIVE To apply molecular docking techniques to identify STAT3 inhibitors from a database of over 90 000 natural product and natural product-like compounds.METHODS Molecular docking was used for the virtual screening campaign and hit validation of STAT3 inhibitor.To further evaluate the potency of candidates at inhibiting STAT3-DNA binding activity,a STAT3 and STAT1transcription factor ELISA was performed.A dual-luciferase reporter assay,co-immunoprecipitation assay and Western blotting were carried out for the investigation of effect of compound 1 on STAT3-driven transcription,STAT3 dimerization and STAT3 phosphorylation.Finally,the cell toxicity of compound 1 was assessed by using MTT assay on different cell lines.RESULTS The virtual screening campaign furnished fourteen hit compounds,from which compound 1 emerged as a top candidate.Compound 1inhibited STAT3DNA-binding activity in vitro and attenuated STAT3-directed transcription in cellulo with selectivity over STAT1 and comparable potency to the wellknown STAT3 inhibitor S3I-201.Furthermore,compound 1 inhibited STAT3 dimerization and decreased STAT3 phosphorylation in cells without affecting STAT1 dimerization and phosphorylation.Compound 1 also exhibited selective anti-proliferative activity against cancer cells over normal cells in vitro.CONCLUSION The benzofuran derivative 1 was identified as a potential inhibitor of STAT3 dimerization using in silico screening.Molecular docking analysis suggested that compound 1 might putatively function as an inhibitor of STAT3 dimerization by binding to the SH2 domain.To the best of our knowledge,compound 1 has not been reported as a STAT3 inhibitor and no biological activity of compound 1 has been presented in the literature.

Virtual screening and optimization of typeⅡ inhibitors of JAK2 from a natural product library

OBJECTIVE To utilize a structure-based lead optimization approach to generate novel natural product-like typeⅡ inhibitors of JAK2 using the DOLPHIN protocol.METHODS Initially,the DOLHPIN computational protocol was employed to convert an active(DFG-in)conformation of JAK2 into a typeⅡ-compatible conformation,which was used as a model for the structure-based virtual screening of 150 000 natural product-like compounds in silico.The novel biflavonoid analogues were designed and synthesized based on the structure of lead compound and then tested for JAK2 and STAT3 inhibitory activity,cytotoxicity and HCV antiviral activity.RESULTS The top eleven highest-scoring compounds were generated from the initial high-throughput virtual screening.Amentoflavone 1a,a biflavonoid from the Chinese plant Gingko biloba,emerged as a promising candidate for further biological evaluation.In dose-response experiments,amentoflavone 1ainhibited JAK2 activity in a concentration dependent fashion with an IC50 value of 5μmol·L-1.As a proof-of-concept,we designed nine analogues 1b-1j with the addition of one or more aliphatic side chains to the biflavonoid scaffold of 1a.The octyl(C8)analogue 1bdisplayed superior potency against JAK2 activity and HCV activity compared to the parent compound 1a,validating the structure-based lead optimization approach used in this study.Moreover,kinetic analysis indicated that analogue 1bexhibited a non-competitive mode of inhibition,suggesting that this compound may be a putative typeⅡ inhibitor of JAK2.CONCLUSION Amentoflavone 1ahas been identified as a JAK2 inhibitor by structure-based virtual screening of a natural product library.In silico optimization using the DOLPHIN model yielded analogues with enhanced potency against JAK2 activity and HCV activity in cellulo.Molecular modeling and kinetic experiments suggested that the analogues may function as typeⅡ inhibitors of JAK2.