Anti-gastric adenocarcinoma activity of 2-Methoxy-1,4-naphthoquinone, an anti-Helicobacter pylori compound from Impatiens balsamina L

Revealing the mechanism of ethyl acetate extracts of Semen Impatientis against prostate cancer based on network pharmacology and transcriptomics

ETHNOPHARMACOLOGICAL RELEVANCE

Prostate cancer (PCa) is the most common malignancy of the male genitourinary system and currently lacks effective treatment. Semen Impatientis, the dried ripe seed of Impatiens balsamina L., is described by the Chinese Pharmacopoeia as a traditional Chinese medicine (TCM) and is used in clinical practice to treat tumors, abdominal masses, etc. In our previous study, the ethyl acetate extracts of Semen Impatientis (EAESI) was demonstrated to be the most effective extract against PCa among various extracts. However, the biological effects of EAESI against PCa in vivo and the specific antitumor mechanisms involved remain unknown.

AIM OF THE STUDY

In this study, we aimed to investigate the antitumor effect of EAESI on PCa in vitro and in vivo by performing network pharmacology analysis, transcriptomic analysis, and experiments to explore and verify the underlying mechanisms involved.

MATERIALS AND METHODS

The antitumor effect of EAESI on PCa in vitro and in vivo was investigated via CCK-8, EdU, flow cytometry, and wound healing assays and xenograft tumor models. Network pharmacology analysis and transcriptomic analysis were employed to explore the underlying mechanism of EAESI against PCa. Activating transcription factor 3 (ATF3) and androgen receptor (AR) were confirmed to be the targets of EAESI against PCa by RT‒qPCR, western blotting, and rescue assays. In addition, the interaction between ATF3 and AR was assessed by coimmunoprecipitation, immunofluorescence, and nuclear-cytoplasmic separation assays.

RESULTS

EAESI decreased cell viability, inhibited cell proliferation and migration, and induced apoptosis in AR+ and AR- PCa cells. Moreover, EAESI suppressed the growth of xenograft tumors in vivo. Network pharmacology analysis revealed that the hub targets of EAESI against PCa included AR, AKT1, TP53, and CCND1. Transcriptomic analysis indicated that activating transcription factor 3 (ATF3) was the most likely critical target of EAESI. EAESI downregulated AR expression and decreased the transcriptional activity of AR through ATF3 in AR+ PCa cells; and EAESI promoted the expression of ATF3 and exerted its antitumor effect via ATF3 in AR+ and AR- PCa cells.

CONCLUSIONS

EAESI exerts good antitumor effects on PCa both in vitro and in vivo, and ATF3 and AR are the critical targets through which EAESI exerts antitumor effects on AR+ and AR- PCa cells.

De-novo whole genome assembly of the orange jewelweed, Impatiens capensis Meerb. (Balsaminaceae) using nanopore long-read sequencing

The plant family Balsaminaceae comprises only two genera, and they are a study in contrasts. While Impatiens is an impressively prolific genus, with over 1,000 species and more being discovered each year, its sister genus, Hydrocera, has one solitary species, H. triflora. The two genera also differ in geographic distribution and habitat type (Impatiens species are widely distributed in much of the Old World and N. America, while H. triflora is confined to wetlands specific to S. India, Sri Lanka, and SE Asia). Other contrasting features include plant habit, habitat, floral architecture, mode of seed dispersal, and a host of other traits. The family Balsaminaceae is therefore an excellent model for studying speciation and character evolution as well as understanding the proximal and evolutionary forces that have driven the two genera to adopt such contrasting evolutionary paths. Various species of the Impatiens genus are also commercially important in the ornamental flower industry and as sources of phytochemicals that are of medicinal and other commercial value. As a preliminary step towards studying the genomic basis of the contrasting features of the two genera, we have sequenced and assembled, de novo, the genome of an iconic Impatiens species from N. America, namely I. capensis, and report our findings here.

Impatiens balsamina: An updated review on the ethnobotanical uses, phytochemistry, and pharmacological activity

ETHNOPHARMACOLOGICAL RELEVANCE

Impatiens balsamina is an annual herb of the Balsaminaceae family, which is cultivated extensively in Asia as an ornamental plant. Notably, as a folk medicine, I. balsamina has been long prescribed for the treatment of rheumatism, isthmus, generalized pain, fractures, inflammation of the nails, scurvy, carbuncles, dysentery, bruises, foot diseases, etc. AIM OF THE STUDY: The paper overviews comprehensive information on ethnobotanical uses, phytochemistry, pharmacological activity, and toxicity of I. balsamina, aiming at laying a sturdy foundation for further development of I. balsamina.

MATERIALS AND METHODS

Research information was acquired through electronic databases such as Web of Science, PubMed, SciFinder, ScienceDirect, Google Scholar, and CNKI with the keyword "Impatiens balsamina ".

RESULTS

Briefly, more than 307 natural compounds have been separated and identified from various medicinal parts of I. balsamina, which are classified into diverse groups, like flavonoids, naphthoquinones, coumarins, terpenoids, sterols, phenols, fatty acids and their ester, naphthalene derivatives, nitrogen-containing compounds, polysaccharides, and other compounds. In particular, 2-methoxy-1,4-naphthoquinone, one of the naphthoquinones, is the predominant and most representative component. Moreover, I. balsamina furnishes numerous and complicated pharmacological activities, including antimicrobial, antiallergic, antipruritic, antitumor, antioxidant, anti-inflammatory, immunomodulatory, anti-hepatic fibrosis, insecticidal, and anthelmintic as well as enzyme-inhibiting activities, etc. Toxicological studies have shown that the hexane extract of the stems and leaves was less toxic, and the hydroalcoholic extract of stems was more toxic.

CONCLUSIONS

The paper contributes to updating the ethnobotanical uses, phytochemistry, pharmacological activity, and toxicity of I. balsamina, which offer abundant information for future investigations and applications of I. balsamina.

2-Methoxy-1,4-naphthoquinone regulated molecular alternation of Fusarium proliferatum revealed by high-dimensional biological data

Fungi Fusarium proliferatum and the toxins it produces are hazardous to agricultural plants, animals, and human health. However, there is a lack of more effective and environment-friendly natural anti-F. proliferatum agents. In the search for natural anti-fungal agents, we found that naturally originated 2-methoxy-1,4-naphthoquinone (MNQ) with a minimal inhibitory dose of 8.0 mg L^-1 possessed a potential inhibitory effect on F. proliferatum. The results of transcriptomic, proteomic, and metabolomic reveal a total of 1314 differential expression genes (DEGs, 873 up-regulated and 441 down-regulated), 259 differential expression proteins (DEPs, 104 up-regulated and 155 down-regulated), and 86 differential accumulation metabolites (DAMs, 49 up-regulated and 37 down-regulated) in MNQ-induced F. proliferatum. Further, the correlation analysis of transcriptomic, proteomic, and metabolomic indicated that these DEGs, DEPs, and DAMs were co-mapped in the pathways of glyoxylate and dicarboxylate metabolism, glycine, serine, and threonine metabolism, and pyruvate metabolism that linked to the TCA cycle. Furthermore, the key DEGs of the significantly co-mapped pathways were verified with qPCR analysis, which was related to the permeability of the cell membrane of F. proliferatum. Thus, these findings will provide fundamental scientific data on the molecular shifts of MNQ-induced F. proliferatum.

Quality consistency evaluation of commercial Impatiens Caulis by integrating UPLC-QTOF-MS/MS chemical profiling and UPLC-DAD multi-components quantification approaches

In this study, ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS/MS) and ultra-high performance liquid chromatography coupled with photo-diode array spectrometry (UPLC-DAD) were firstly integrated to qualitatively characterize the chemical profiles and quantitatively determine the major components in Impatiens Caulis (IC), a Chinese medicinal herb derived from the dried stem of Impatiens balsamina. The qualitative analysis revealed that there was no difference in chemical profiles of twenty commercial IC samples. A total of 45 components were characterized, there in 5 naphthoquinones, 3 coumarins, 5 phenolic acids, 12 flavonoids and 3 other compounds were identified definitely. However, the quantitative results showed a significant difference in these IC samples. In particular, the highest content of total quantified compounds was even 9.49 times of the lowest one. Furthermore, the average contents of these quantified compounds in twenty commercial IC samples had high values of relative standard deviation (RSD) ranged from 15.64% to 98.76%, suggesting a poor quality consistency in these commercial IC samples. Therefore, efficacy related chemical markers as well as the cultivation region, harvest time and/or post-harvest handling of IC should be further investigated for ensuring its quality and efficacy consistency.

Study on the Potential Application of Impatiens balsamina L. Flowers Extract as a Natural Colouring Ingredient in a Pastry Product

Flowers of the genus Impatiens are classified as edible; however, their inclusion in the human diet is not yet a common practice. Its attractive colours have stirred great interest by the food industry. In this sense, rose (BP) and orange (BO) I. balsamina flowers were nutritionally studied, followed by an in-depth chemical study profile. The non-anthocyanin and anthocyanin profiles of extracts of both flower varieties were also determined by high-performance liquid chromatography coupled to a diode array and mass spectrometry detector (HPLC-DAD-ESI/MS). The results demonstrated that both varieties presented significant amounts of phenolic compounds, having identified nine non-anthocyanin compounds and 14 anthocyanin compounds. BP extract stood out in its bioactive properties (antioxidant and antimicrobial potential) and was selected for incorporation in "bombocas" filling. Its performance as a colouring ingredient was compared with the control formulations (white filling) and with E163 (anthocyanins) colorant. The incorporation of the natural ingredient did not cause changes in the chemical and nutritional composition of the product; and although the colour conferred was lighter than presented by the formulation with E163 (suggesting a more natural aspect), the higher antioxidant activity could meet the expectations of the current high-demand consumer.

Comparative transcriptome analysis to identify candidate genes involved in 2-methoxy-1,4-naphthoquinone (MNQ) biosynthesis in Impatiens balsamina L

Impatiens balsamina L. is a tropical ornamental and traditional medicinal herb rich in natural compounds, especially 2-methoxy-1,4-naphthoquinone (MNQ) which is a bioactive compound with tested anticancer activities. Characterization of key genes involved in the shikimate and 1,4-dihydroxy-2-naphthoate (DHNA) pathways responsible for MNQ biosynthesis and their expression profiles in I. balsamina will facilitate adoption of genetic/metabolic engineering or synthetic biology approaches to further increase production for pre-commercialization. In this study, HPLC analysis showed that MNQ was present in significantly higher quantities in the capsule pericarps throughout three developmental stages (early-, mature- and postbreaker stages) whilst its immediate precursor, 2-hydroxy-1,4-naphthoquinone (lawsone) was mainly detected in mature leaves. Transcriptomes of I. balsamina derived from leaf, flower, and three capsule developmental stages were generated, totalling 59.643 Gb of raw reads that were assembled into 94,659 unigenes (595,828 transcripts). A total of 73.96% of unigenes were functionally annotated against seven public databases and 50,786 differentially expressed genes (DEGs) were identified. Expression profiles of 20 selected genes from four major secondary metabolism pathways were studied and validated using qRT-PCR method. Majority of the DHNA pathway genes were found to be significantly upregulated in early stage capsule compared to flower and leaf, suggesting tissue-specific synthesis of MNQ. Correlation analysis identified 11 candidate unigenes related to three enzymes (NADH-quinone oxidoreductase, UDP-glycosyltransferases and S-adenosylmethionine-dependent O-methyltransferase) important in the final steps of MNQ biosynthesis based on genes expression profiles consistent with MNQ content. This study provides the first molecular insight into the dynamics of MNQ biosynthesis and accumulation across different tissues of I. balsamina and serves as a valuable resource to facilitate further manipulation to increase production of MNQ.

2-Methoxy-1,4-naphthoquinone Induces Metabolic Shifts in Penicillium Digitatum Revealed by High-Dimensional Biological Data

Penicillium digitatum is the primary pathogen causing the green mold of citrus. The need for the development of higher effective and lower toxic natural antifungal agents is urgent, owing to the lack of antifungal agents that can successfully combat P. digitatum. Herein, the effects and mechanisms of 2-methoxy-1,4-naphthoquinone (MNQ) as a potential inhibitor of P. digitatumwere studied. First, MNQ showed a significant anti-P. digitatum effect with a minimum inhibitory concentration value of 5.0 μg/mL. Then, transcriptome, proteome, and metabolome profiling were performed on the MNQ-treated P. digitatum. A total of 910 genes, 297 proteins, and 174 metabolites changed significantly. The omics analysis indicated that it could be seen that MNQ mainly inhibits the growth of P. digitatum by affecting the synthesis of branched-chain amino acids and cell walls. These findings will be a great contribution to the further understanding of the possible molecular action of MNQ.

Naphthoquinone Derivatives Isolated from Plants: Recent Advances in Biological Activity

Naturally occurring naphthoquinones (NQs) comprising highly reactive small molecules are the subject of increasing attention due to their promising biological activities such as antioxidant, antimicrobial, apoptosis-inducing activities, and especially anticancer activity. Lapachol, lapachone, and napabucasin belong to the NQs and are in phase II clinical trials for the treatment of many cancers. This review aims to provide a comprehensive and updated overview on the biological activities of several new NQs isolated from different species of plants reported from January 2013 to January 2020, their potential therapeutic applications and their clinical significance.

Label-Free Proteomic Analysis of Molecular Effects of 2-Methoxy-1,4-naphthoquinone on Penicillium italicum

Penicillium italicum is the principal pathogen causing blue mold of citrus. Searching for novel antifungal agents is an important aspect of the post-harvest citrus industry because of the lack of higher effective and low toxic antifungal agents. Herein, the effects of 2-methoxy-1,4-naphthoquinone (MNQ) on P. italicum and its mechanism were carried out by a series of methods. MNQ had a significant anti-P. italicum effect with an MIC value of 5.0 µg/mL. The label-free protein profiling under different MNQ conditions identified a total of 3037 proteins in the control group and the treatment group. Among them, there were 129 differentially expressed proteins (DEPs, up-regulated > 2.0-fold or down-regulated < 0.5-fold, p < 0.05), 19 up-regulated proteins, 26 down-regulated proteins, and 67 proteins that were specific for the treatment group and another 17 proteins that were specific for the control group. Of these, 83 proteins were sub-categorized into 23 hierarchically-structured GO classifications. Most of the identified DEPs were involved in molecular function (47%), meanwhile 27% DEPs were involved in the cellular component and 26% DEPs were involved in the biological process. Twenty-eight proteins identified for differential metabolic pathways by KEGG were sub-categorized into 60 classifications. Functional characterization by GO and KEGG enrichment results suggests that the DEPs are mainly related to energy generation (mitochondrial carrier protein, glycoside hydrolase, acyl-CoA dehydrogenase, and ribulose-phosphate 3-epimerase), NADPH supply (enolase, pyruvate carboxylase), oxidative stress (catalase, glutathione synthetase), and pentose phosphate pathway (ribulose-phosphate 3-epimerase and xylulose 5-phosphate). Three of the down-regulated proteins selected randomly the nitro-reductase family protein, mono-oxygenase, and cytochrome P450 were verified using parallel reaction monitoring. These findings illustrated that MNQ may inhibit P. italicum by disrupting the metabolic processes, especially in energy metabolism and stimulus response that are both critical for the growth of the fungus. In conclusion, based on the molecular mechanisms, MNQ can be developed as a potential anti-fungi agent against P. italicum.

In Vitro Inhibition of Helicobacter pylori Growth by Redox Cycling Phenylaminojuglones

Infection by Helicobacter pylori increases 10 times the risk of developing gastric cancer. Juglone, a natural occurring 1,4-naphthoquinone, prevents H. pylori growth by interfering with some of its critical metabolic pathways. Here, we report the design, synthesis, and in vitro evaluation of a series of juglone derivatives, namely, 2/3-phenylaminojuglones, as potential H. pylori growth inhibitors. Results show that 5 out of 12 phenylaminojuglones (at 1.5 μg/mL) were 1.5-2.2-fold more active than juglone. Interestingly, most of the phenylaminojuglones (10 out of 12) were 1.1-2.8 fold more active than metronidazole, a known H. pylori growth inhibitor. The most active compound, namely, 2-((3,4,5-trimethoxyphenyl)amino)-5-hydroxynaphthalene-1,4-dione 7, showed significant higher halo of growth inhibitions (HGI = 32.25 mm) to that of juglone and metronidazole (HGI = 14.50 and 11.67 mm). Structural activity relationships of the series suggest that the nature and location of the nitrogen substituents in the juglone scaffold, likely due in part to their redox potential, may influence the antibacterial activity of the series.

Ethyl Acetate Extracts of Semen Impatientis Inhibit Proliferation and Induce Apoptosis of Human Prostate Cancer Cell Lines through AKT/ERK Pathways

Objective. To investigate the inhibitory effect of ethyl acetate extracts of Impatiens balsamina L. on prostate cancer cells. Methods. Impatiens balsamina L. was extracted to get water, ethanol, oil ether, ethyl acetate, and butanol extracts. CCK-8 assay was used to detect the inhibitory effect. Apoptosis rates and cell cycle distribution were detected by flow cytometry. Transwell assay was performed to test the ability of migration. The expressions of Bcl-2, Bax, cleaved-caspase-3, p-ERK, ERK, p-AKT, AKT, cyclin D1, cyclin E, and MMP2 were detected by Western blot. Results. Ethyl acetate extracts had the strongest inhibitory effect. After being treated with different concentrations of ethyl acetate extracts, the percentage of G0/G1 phase increased significantly, cyclin D1 and cyclin E expression decreased, apoptosis rate was significantly higher, and the ability of migration of PC-3 and RV1 was inhibited significantly. Western blot showed that the expressions of Bcl-2, p-ERK, and p-AKT were significantly decreased, but the expressions of Bax and caspase-3 cleavage were increased. Conclusions. Impatiens balsamina L. inhibited the proliferation of human prostate cancer cells; ethyl acetate extracts have the strongest effect. It could inhibit cell proliferation and migration, cause G1 phase arrest, and induce apoptosis probably through inhibition of the AKT and ERK pathways.

Adverse Effects of Hydroalcoholic Extracts and the Major Components in the Stems of Impatiens balsamina L. on Caenorhabditis elegans

Impatiens balsamina L. (Balsaminaceae), an annual herb found throughout China, has been extensively used in traditional Chinese medicine (TCM). However, our knowledge regarding the adverse effects of I. balsamina in vivo is very limited. In this present study, the nematode Caenorhabditis elegans model was employed to fully assess the adverse effects of hydroalcoholic (EtOH 55%) extracts of I. balsamina stems (HAEIBS) in vivo. After exposure to 10 mg/mL HAEIBS, the major organism-level endpoints of C. elegans of percent survival, frequency of head thrash and body bends, and reproduction had decreased by 24%, 30%, and 25%, respectively. The lifespan of C. elegans was also greatly reduced after HAEIBS exposure compared to the controls. The active compounds in HAEIBS were separated using high speed countercurrent chromatograph (HSCCC) and characterized by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR). Two compounds, lawsone and 2-methoxy-1,4-naphthoquinone (MNQ), and their adverse effects were then more thoroughly detailed in this study. It was found that lawsone is the major toxin in HAEIBS with a higher toxicity than MNQ in terms of negative impact on C. elegans mortality, locomotion, reproduction, and lifespan. Our data also suggests that the C. elegans model may be useful for assessing the possible toxicity of other Chinese medicines, plant extracts, and/or compounds.

Ethnopharmacological analysis of medicinal plants used against non-communicable diseases in Rodrigues Island, Indian Ocean

ETHNOPHARMACOLOGICAL RELEVANCE

Rodrigues is an autonomous outer island that form part of the Republic of Mauritius and one of three islands that constitute the Mascarene archipelago in the Indian Ocean. Though herbal medicine is in common use in Rodrigues, there has been no ethnopharmacological study to document quantitatively such traditional practise particularly against non-communicable diseases (NCD) which is currently a growing major health issue on the island. The aim of the present study was to collect, analyse and document traditionally used medicinal plants (MP) from key informants and traditional medicine practitioners (TMP) in the tropical island of Rodrigues to treat and/or manage common NCD.

MATERIALS AND METHODS

Data was collected via face-to-face interviews with MP users (n=113) and TMP (n=9). Seven quantitative ethnopharmacological indices, namely family use value (FUV), use value (UV), informant agreement ratio (IAR), relative frequency of citation (RFC), fidelity level (FL), relative importance (RI) and ethnobotanicity index (EI) were calculated.

RESULTS

Hundred and three plants belonging to 55 families were recorded for the treatment and/or management of 27 different NCD. Three of the MP (Terminalia bentzoë (L.) L.F, Sarcostemma cf. adontolepis Balf.f. and Clerodendrum laciniatum Balf.f.) recorded are endemic to Rodrigues and 2 (Carissa xylopicron Thouars., Phyllanthus casticum Willemet f.) endemic to the Mascarene Islands. The most solicited MP family was Asteraceae with a total of 8 species. Citrus aurantifolia (Christm.) Swingle scored the highest RFC (RFC=1.02) value. Ten plants were found to score 100% FL and the highest IAR (0.98) was observed for the disease category of certain conditions originating in the perinatal period. Arecaceae scored the highest FUV value and Ayapana triplinervis (Vahl) R.M. King et H.Rob highest UV (UV= 2.72).

CONCLUSION

Given the dearth of updated information on traditional medicine of Rodrigues, this study can provide an opportunity to establish valuable primary information on the different MP used by the local people and hence can open new perspectives for further pharmacological research.

Depside derivatives with anti-hepatic fibrosis and anti-diabetic activities from Impatiens balsamina L. flowers

Eighteen compounds (1-18), seven new (3-9) and eleven previously reported (1, 2, and 10-18), were isolated from the flowers of Impatiens balsamina (Linn). The structures of the isolated compounds were elucidated using different spectroscopic methods, including NMR (1D and 2D), UV, IR, and HR-ESI-MS. Analysis of the bioassay results showed the compounds had notable anti-hepatic fibrosis activity against murine Hepatic Stellate Cells (t-HSC/Cl-6) and anti-diabetics activity against α-glucosidase. Specifically, new compounds 7, 8, 9 showed significant inhibitory activity on t-HSC/Cl-6 cells with IC50 values of 42.12, 109.2, and 34.04 μg/mL respectively, while the IC50 values of positive control Silymarin and Fufang Biejia Ruangan Pian were 202.34 and 231.56 μg/mL, respectively. In addition, compounds 2, 4, 7, 8, 10, 11, 17, and 18 exhibited excellent α-glucosidase inhibitory activity. Among these compounds, 7 exhibited the highest activity with an IC50 value of 0.72 μg/mL, while the IC50 value of the positive control acarbose was 3.36 μg/mL. This is the first study evaluating the anti-hepatic fibrosis and anti-diabetic activities of compounds isolated from the flowers of I. balsamina.

Differential proteomic analysis on the effects of 2-methoxy-1,4-naphthoquinone towards MDA-MB-231 cell line

BACKGROUND

We have previously reported the anti-metastatic effects of 2-methoxy-1,4-naphthoquinone (MNQ) against MDA-MB-231 cell line.

PURPOSE

To investigate the molecular mechanism underlying the anti-metastatic effects of MNQ towards MDA-MB-231 cell line via the comparative proteomic approach.

STUDY DESIGN/METHODS

Differentially expressed proteins in MNQ-treated MDA-MB-231 cells were identified by using two-dimensional gel electrophoresis coupled with tandem mass spectrometry. Proteins and signalling pathways associated with the identified MNQ-altered proteins were studied by using Western blotting.

RESULTS

Significant modulation of MDA-MB-231 cell proteome was observed upon treatment with MNQ in which the expressions of 19 proteins were found to be downregulated whereas another eight were upregulated (>1.5 fold, p < 0.05). The altered proteins were mainly related to cytoskeletal functions and regulations, mRNA processing, protein modifications and oxidative stress response. Notably, two of the downregulated proteins, protein S100-A4 (S100A4) and laminin-binding protein (RPSA) are known to play key roles in driving metastasis and were verified using Western blotting. Further investigation using Western blotting also revealed that MNQ decreased the activations of pro-metastatic ERK1/2 and NF-κB signalling pathways. Moreover, MNQ was shown to stimulate the expression of the metastatic suppressor, E-cadherin.

CONCLUSION

This study reports a proposed mechanism by which MNQ exerts its anti-metastatic effects against MDA-MB-231 cell line. The findings from this study offer new insights on the potential of MNQ to be developed as a novel anti-metastatic agent.

AMPK-activated protein kinase activation by Impatiens balsamina L. is related to apoptosis in HSC-2 human oral cancer cells

Objective:

In the present study, we investigated the efficacy of a methanol extract from Impatiens balsamina L. (MEIB) against HSC-2 human oral cancer cells.

Materials and Methods:

The anti-cancer efficacies of MEIB were performed by methanethiosulfonate assay, phospho-kinase array, Western blot, 4’-6-diamidino-2-phenylindole staining, trypan blue exclusion assay and 5,5’,6,6’-tetrachloro-1,1’,3,3’-tetraethylbenzimidazolylcarbocyanine iodide assay.

Results:

MEIB decreased the cell viability of HSC-2 cells. According to phospho-kinase arrays, MEIB markedly activated AMP-activated protein kinase (AMPK) signaling, but inactivated mammalian target of rapamycin signaling. MEIB induced apoptosis as evidenced by activation of caspase-3, poly (ADP-ribose) polymerase cleavage and nuclear condensation. In addition, AMPK activation by two known activators (5-aminoimidazole-4-carboxamide-1-β-ribofuranoside and metformin) decreased cell viability and induced apoptosis. Moreover, MEIB increased the expression levels of mitochondria-related proteins (t-Bid, Bak and Bad), which contributed to the disruption of mitochondrial membrane potential, cytochrome C release and activation of caspase-9. Metformin also increased t-Bid expression and the subsequent release of cytochrome C into the cytosol.

Conclusion:

These results suggest that MEIB may be of therapeutic value for treating oral cancer and that its mechanism of action occurs through AMPK and t-Bid.