Effect of vicanicin and protolichesterinic acid on human prostate cancer cells: Role of Hsp70 protein

Bioactive Lichen Secondary Metabolites and Their Presence in Species from Chile

Lichens are symbiotic organisms composed of at least one fungal and one algal species. They are found in different environments around the world, even in the poles and deserts. Some species can withstand extreme abiotic conditions, including radiation and the vacuum of space. Their chemistry is mainly due to the fungal metabolism and the production of several secondary metabolites with biological activity, which have been isolated due to an increasing interest from the pharmaceutical community. However, beyond the experimental data, little is known about their mechanisms of action and the potential pharmaceutical use of these kinds of molecules, especially the ones isolated from lesser-known species and/or lesser-studied countries. The main objective of this review is to analyze the bibliographical data of the biological activity of secondary metabolites from lichens, identifying the possible mechanisms of action and lichen species from Chile. We carried out a bibliographic revision of different scientific articles in order to collect all necessary information on the biological activity of the metabolites of these lichen species. For this, validated databases were used. We found the most recent reports where in vitro and in vivo studies have demonstrated the biological properties of these metabolites. The biological activity, namely anticancer, antioxidant, and anti-inflammatory activity, of 26 secondary metabolites are described, as well as their reported molecular mechanisms. The most notable metabolites found in this review were usnic acid, atranorin, protolichesterinic acid, and lobaric acid. Usnic acid was the most investigated metabolite, in addition to undergoing toxicological and pharmacological studies, where a hepatotoxicity effect was reported due to uncoupling oxidative phosphorylation. Additionally, no major studies have been made to validate the pharmacological application of these metabolites, and few advancements have been made in their artificial growth in bioreactors. Despite the described biological activities, there is little support to consider these metabolites in pharmaceutical formulations or to evaluate them in clinical trials. Nevertheless, it is important to carry out further studies regarding their possible human health effects. These lichen secondary metabolites present a promising research opportunity to find new pharmaceutical molecules due to their bioactive properties.

Lichen Depsides and Tridepsides: Progress in Pharmacological Approaches

Depsides and tridepsides are secondary metabolites found in lichens. In the last 10 years, there has been a growing interest in the pharmacological activity of these compounds. This review aims to discuss the research findings related to the biological effects and mechanisms of action of lichen depsides and tridepsides. The most studied compound is atranorin, followed by gyrophoric acid, diffractaic acid, and lecanoric acid. Antioxidant, cytotoxic, and antimicrobial activities are among the most investigated activities, mainly in in vitro studies, with occasional in silico and in vivo studies. Clinical trials have not been conducted using depsides and tridepsides. Therefore, future research should focus on conducting more in vivo work and clinical trials, as well as on evaluating the other activities. Moreover, despite the significant increase in research work on the pharmacology of depsides and tridepsides, there are many of these compounds which have yet to be investigated (e.g., hiascic acid, lassalic acid, ovoic acid, crustinic acid, and hypothamnolic acid).

Lichen Depsidones with Biological Interest

Depsidones are some of the most abundant secondary metabolites produced by lichens. These compounds have aroused great pharmacological interest due to their activities as antioxidants, antimicrobial, and cytotoxic agents. Hence, this paper aims to provide up-to-date knowledge including an overview of the potential biological interest of lichen depsidones. So far, the most studied depsidones are fumarprotocetraric acid, lobaric acid, norstictic acid, physodic acid, salazinic acid, and stictic acid. Their pharmacological activities have been mainly investigated in in vitro studies and, to a lesser extent, in in vivo studies. No clinical trials have been performed yet. Depsidones are promising cytotoxic agents that act against different cell lines of animal and human origin. Moreover, these compounds have shown antimicrobial activity against both Gram-positive and Gram-negative bacteria and fungi, mainly Candida spp. Furthermore, depsidones have antioxidant properties as revealed in oxidative stress in vitro and in vivo models. Future research should be focused on further investigating the mechanism of action of depsidones and in evaluating new potential actions as well as other depsidones that have not been studied yet from a pharmacological perspective. Likewise, more in vivo studies are prerequisite, and clinical trials for the most promising depsidones are encouraged.

Physodic acid sensitizes LNCaP prostate cancer cells to TRAIL-induced apoptosis

In spite of the extensive research for developing new therapies, prostate cancer is still one of the major human diseases with poor prognosis and high mortality. Therefore, with the aim of identifying novel agents with antigrowth and pro-apoptotic activity on prostate cancer cells, in the present study, we evaluated the effect of lichen secondary metabolite physodic acid on cell growth in human prostate cancer cells. In addition, we tested the apoptotic activity of physodic acid on TRAIL-resistant LNCaP cells in combination with TRAIL. The cell viability was measured using MTT assay. LDH release, a marker of membrane breakdown, was also measured. For the detection of apoptosis, the evaluation of DNA fragmentation and caspase-3 activity assay were employed. The expression of proteins was detected by Western blot analysis. It was observed that physodic acid showed a dose-response relationship in the range of 12.5-50 μM concentrations in LNCaP and DU-145 cells, activating an apoptotic process. In addition, physodic acid sensitizes LNCaP cells to TRAIL-induced apoptosis. The combination of physodic acid with other anti-prostate cancer therapies could be considered a promising strategy that warrants further investigations.

Schistosomicidal effect of divaricatic acid from Canoparmelia texana (Lichen): In vitro evaluation and ultrastructural analysis against adult worms of Schistosoma mansoni

In this study we evaluated the in vitro effect of divaricatic acid against coupled worms of Schistosoma mansoni. The schistosomicidal effect was evaluated through the bioassay of motility and mortality, cellular viability of the worms and ultrastructural analysis through Scanning Electron Microscopy. To evaluate the cytotoxicity of divaricatic acid, a cell viability assay was performed with human peripheral blood mononuclear cells. Divaricatic acid proved effect against S. mansoni after 3 hours of exposure. At the end of 24 h the concentrations of 100 - 200 μM presented lethality to the worms. Motility changes were observed at sublethal concentrations. The IC₅₀ obtained by the cell viability assay for S. mansoni was 100.6 μM (96.24 - 105.2 μM). Extensive damage to the worm's tegument was observed such as peeling, erosion, bubbles, edema, damage and loss of tubercles and spines, fissures and tissue ruptures. No cytotoxicity was observed in human peripheral blood mononuclear cells. This report provides data showing the schistosomicidal effect of divaricatic acid on S. mansoni, causing death, motile changes and ultrastructural damage to worms. In addition, divaricatic acid was shown to be non-toxic to human peripheral blood mononuclear cells at concentrations effective on S. mansoni.

Lichens as a repository of bioactive compounds: an open window for green therapy against diverse cancers

Lichens, algae and fungi-based symbiotic associations, are sources of many important secondary metabolites, such as antibiotics, anti-inflammatory, antioxidants, and anticancer agents. Wide range of experiments based on in vivo and in vitro studies revealed that lichens are a rich treasure of anti-cancer compounds. Lichen extracts and isolated lichen compounds can interact with all biological entities currently identified to be responsible for tumor development. The critical ways to control the cancer development include induction of cell cycle arrests, blocking communication of growth factors, activation of anti-tumor immunity, inhibition of tumor-friendly inflammation, inhibition of tumor metastasis, and suppressing chromosome dysfunction. Also, lichen-based compounds induce the killing of cells by the process of apoptosis, autophagy, and necrosis, that inturn positively modulates metabolic networks of cells against uncontrolled cell division. Many lichen-based compounds have proven to possess potential anti-cancer activity against a wide range of cancer cells, either alone or in conjunction with other anti-cancer compounds. This review primarily emphasizes on an updated account of the repository of secondary metabolites reported in lichens. Besides, we discuss the anti-cancer potential and possible mechanism of the most frequently reported secondary metabolites derived from lichens.

A New Depsidone from Teloschistes flavicans and the Antileukemic Activity

Lichens produce a variety of secondary metabolites that could be potential sources of pharmaceutically useful chemicals. However, only a limited number of lichen metabolites have been investigated for their biological significance. The objective of this study was to identify the potential compounds responsible for the antileukemic activity of lichen Teloschistes flavicans. Among three fractions (n-hexane, EtOAc, and MeOH-H₂O), the ethyl acetate (EtOAc) fraction of T. flavicans methanolic extract showed the strongest inhibition in the HL-60 cell line. Additionally, the EtOAc fraction was further purified to obtain a new depsidone, 2,7-dichloro-3,8-dimethoxy-1,6,9-trimethyl-11H-dibenzo[b,e][1,4]dioxepin-11-one, named as flavicansone, along with rhizonic acid, parietin, and vicanicin. Flavicansone demonstrated the most significant inhibitory action against cell proliferation among the four isolated compounds.

Anti-cancer Evaluation of Depsides Isolated from Indonesian Folious Lichens: Physcia millegrana, Parmelia dilatata and Parmelia aurulenta

Cancer is a serious health burden on global societies. The discovery and development of new anti-cancer therapies remains a challenging objective. Although it has been shown that lichen secondary metabolites may be potent sources for new anti-cancer agents, the Indonesian- grown folious lichens, Physcia millegrana,Parmelia dilatata and Parmeila aurulenta, have not yet been explored. In this study exhaustive preparative high-performance liquid chromatography was employed to isolate the lichen constituents with spectroscopic and spectrometric protocols identifying nine depsides 9–17, including the new methyl 4-formyl-2,3-dihydroxy-6-methylbenzoate 13. The cytotoxicity of the depsides towards cancer cells was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results indicated lowest toxicity of the depsides towards human A549 lung cancer cells. Importantly, the di-depsides (11, 12 and 17) showed greatest toxicity, indicating that these structures are biologically more active than the mono-depsides against the HepG2 liver cancer, A549 lung cancer and HL-60 leukemia cell lines.

Oxidative stress mediated by gyrophoric acid from the lichen Umbilicaria hirsuta affected apoptosis and stress/survival pathways in HeLa cells

Background

Lichens produce a huge diversity of bioactive compounds with several biological effects. Gyrophoric acid (GA) is found in high concentrations in the common lichen Umbilicaria hirsuta, however evidence for biological activity was limited to anti-proliferative activity described on several cancer cell lines.

Methods

We developed and validated a new protocol for GA isolation, resulting in a high yield of highly pure GA (validated by HPLC and NMR) in an easy and time saving manner. Anti-proliferative and pro-apoptotic activity, oxygen radicals formation and stress/survival proteins activity changes was study by flow cytometry.

Results

The highly purified GA showed anti-proliferative activity against HeLa (human cervix carcinoma) and other tumor cells. Moreover, GA threated cells showed a significant increase in caspase-3 activation followed by PARP cleavage, PS externalization and cell cycle changes mediated by oxidative stress. Production of oxygen radicals led to DNA damage and changes in stress/survival pathways activation.

Conclusions

GA treatment on HeLa cells clearly indicates ROS production and apoptosis as form of occurred cell death. Moreover, DNA damage and changing activity of stress/survival proteins as p38MAPK, Erk1/2 and Akt mediated by GA treatment confirm pro-apoptotic potential. The pharmacological potential of U. hirsuta derived GA is discussed.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2631-4) contains supplementary material, which is available to authorized users.

The Comprehensive Roles of ATRANORIN, A Secondary Metabolite from the Antarctic Lichen Stereocaulon caespitosum, in HCC Tumorigenesis

Hepatocellular carcinoma (HCC) is one of the most deadly genetic diseases, but surprisingly chemotherapeutic approaches against HCC are only limited to a few targets. In particular, considering the difficulty of a chemotherapeutic drug development in terms of cost and time enforces searching for surrogates to minimize effort and maximize efficiency in anti-cancer therapy. In spite of the report that approximately one thousand lichen-derived metabolites have been isolated, the knowledge about their functions and consequences in cancer development is relatively limited. Moreover, one of the major second metabolites from lichens, Atranorin has never been studied in HCC. Regarding this, we comprehensively analyze the effect of Atranorin by employing representative HCC cell lines and experimental approaches. Cell proliferation and cell cycle analysis using the compound consistently show the inhibitory effects of Atranorin. Moreover, cell death determination using Annexin-V and (Propidium Iodide) PI staining suggests that it induces cell death through necrosis. Lastly, the metastatic potential of HCC cell lines is significantly inhibited by the drug. Taken these together, we claim a novel functional finding that Atranorin comprehensively suppresses HCC tumorigenesis and metastatic potential, which could provide an important basis for anti-cancer therapeutics.

Potential of Borojoa patinoi Cuatrecasas water extract to inhibit nosocomial antibiotic resistant bacteria and cancer cell proliferation in vitro

Borojó (Borojoa patinoi Cuatrec.) is a fruit used in Colombian traditional medicine with supposed antihypertensive, antitumoral, diuretic, healing, immunological, anti-inflammatory and aphrodisiac effects. To explore the relative merits in terms of biological activities of borojó aqueous extract (BAE), we investigated in vitro its antimicrobial activity on nosocomial pathogenic and multidrug resistant (MDR) strains of Pseudomonas aeruginosa (6), Staphylococcus aureus (1) and Candida species (6), as well as its cytotoxicity on human conjunctive Wong-Kilbourne derivative (WKD) cells and Caco-2 cells from heterogeneous human epithelial colorectal adenocarcinoma. The bacteriostatic activity was observed overall on P. aeruginosa strains, as evidenced by the increase of the lag phase (43 hours) and reduction of the maximum growth rate detected using 187.5 mg BAE per mL. The bactericidal activity, instead, was observed at 375 mg BAE per mL. On the other hand, BAE showed an anti-proliferative effect against the Caco-2 cell line and was shown to be toxic on the WKD cell line at concentrations ranging from 0.05 to 187.5 μg mL-1. The analysis of the phenolic fraction of the fruit aqueous extract (BAE) using UHPLC-MS/MS showed the presence of 26 compounds, with vanillic, syringic and o-coumaric acids as the most abundant. Among these molecules, 7.81 ng mL-1 luteolin and myricetin, singly tested, were able to reduce bacterial growth. To the best of our knowledge, we are unaware of any previous studies demonstrating the anti-bacterial activity of borojó aqueous extract against antibiotic resistant strains of P. aeruginosa, and its anti-proliferative effect against WKD and Caco-2 cell lines. The latter result offers a potential base for new interest and investigations in relation to colon carcinoma models and borojó fruit consumption, since in Colombia this fruit is consumed also for its supposed antitumoral effects.

Laboratory assessment of divaricatic acid against Biomphalaria glabrata and Schistosoma mansoni cercariae

In this study, the molluscicidal and antiparasitic activities of divaricatic acid was evaluated, targeting the mollusc Biomphalaria glabrata and cercariae of the helminth Schistosoma mansoni. In addition, the environmental toxicity of divaricatic acid was assessed by bioassay using the microcrustacean Artemia salina. Divaricatic acid showed high toxicity against both adult snails (5μg/mL) and embryos (20μg/mL after 6h of exposure). Similar activity was observed in Schistosoma mansoni cercariae after only a short exposure time (10μg/mL after 30min of exposure). The divaricatic acid did not show toxicity in the acute test using Artemia salina at concentrations equal to or below 200μg/mL. The divaricatic acid proved to be a promising substance for the elimination of the snail Biomphalaria glabrata, an intermediate host of schistosomiasis, as well as the cercariae of the pathogen, while being non-toxic to the Artemia salina at the same concentrations. This is the first experimental observation of the molluscicidal and cercaricide activity of divaricatic acid.

Involvement of Bax and Bcl-2 in Induction of Apoptosis by Essential Oils of Three Lebanese Salvia Species in Human Prostate Cancer Cells

Prostate cancer is one of the most common forms of cancer in men, and research to find more effective and less toxic drugs has become necessary. In the frame of our ongoing program on traditionally used Salvia species from the Mediterranean Area, here we report the biological activities of Salvia aurea, S. judaica and S. viscosa essential oils against human prostate cancer cells (DU-145). The cell viability was measured by 3(4,5-dimethyl-thiazol-2-yl)2,5-diphenyl-tetrazolium bromide (MTT) test and lactate dehydrogenase (LDH) release was used to quantify necrosis cell death. Genomic DNA, caspase-3 activity, expression of cleaved caspase-9, B-cell lymphoma 2 (Bcl-2) and Bcl-2 associated X (Bax) proteins were analyzed in order to study the apoptotic process. The role of reactive oxygen species in cell death was also investigated. We found that the three essential oils, containing caryophyllene oxide as a main constituent, are capable of reducing the growth of human prostate cancer cells, activating an apoptotic process and increasing reactive oxygen species generation. These results suggest it could be profitable to further investigate the effects of these essential oils for their possible use as anticancer agents in prostate cancer, alone or in combination with chemotherapy agents.

An Antifungal Mechanism of Protolichesterinic Acid from the Lichen Usnea albopunctata Lies in the Accumulation of Intracellular ROS and Mitochondria-Mediated Cell Death Due to Apoptosis in Candida tropicalis

Candida species causes superficial and life-threatening systemic infections and are difficult to treat due to the resistance of these organism to various clinically used drugs. Protolichesterinic acid is a well-known lichen compound. Although the antibacterial activity of protolichesterinic acid has been reported earlier, the antifungal property and its mechanism of action are still largely unidentified. The goal of the present investigation is to explore the anticandidal activity and mechanism of action of protolichesterinic acid, especially against Candida tropicalis. The Minimum Inhibitory Concentration (MIC) value was established through microdilution techniques against four Candida species and out of four species tested, C. tropicalis showed a significant effect (MIC: 2 μg/ml). In the morphological interference assay, we observed the enhanced inhibition of hyphae when the cells were treated with protolichesterinic acid. Time-kill assay demonstrated that the maximum rate of killing was recorded between 2 and 6 h. C. tropicalis exposed to protolichesterinic acid exhibited an increased ROS production, which is one of the key factors of fungal death. The rise in ROS was due to the dysfunction of mitochondria caused by protolichesterinic acid. We confirmed that protolichesterinic acid-induced dysfunction of mitochondria in C. tropicalis. The damage of cell membrane due to protolichesterinic acid treatment was confirmed by the influx of propidium iodide and was further confirmed by the release of potassium ions. The treatment of protolichesterinic acid also triggered calcium ion signaling. Moreover, it commenced apoptosis which is clearly evidenced by Annexin V and propidium iodide staining. Interestingly protolichesterinic acid recorded excellent immunomodulatory property when tested against lymphocytes. Finally protolichesterinic acid showed low toxicity toward a normal human cell line Foreskin (FS) normal fibroblast. In in vivo test, protolichesterinic acid significantly enhanced the survival of C. tropicalis infected Caenorhabditis elegans. This investigation proposes that the protolichesterinic acid induces apoptosis in C. tropicalis via the enhanced accumulation of intracellular ROS and mitochondrial damage, which leads fungal cell death via apoptosis. Our work revealed a new key aspect of mechanisms of action of protolichesterinic acid in Candida species. This article is the first study on the antifungal and mechanism of action of protolichesterinic acid in Candida species.

Barbatic Acid Offers a New Possibility for Control of Biomphalaria Glabrata and Schistosomiasis

This study evaluated the biological activity of an ether extract and barbatic acid (BAR) from Cladia aggregata on embryos and adult mollusks of Biomphalaria glabrata, cercariae of Schistosoma mansoni and the microcrustacean Artemia salina. The ether extract and BAR were obtained by successive extractions with diethyl ether. The obtained extracts were analyzed using thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), proton nuclear magnetic resonance (¹H-NMR) and infrared (IR) spectroscopy. The results demonstrated that the ether extract exerted embryotoxic effects at 50 and 100 µg/mL and molluscicidal effects at 20 and 25 µg/mL. BAR exhibited no embryotoxicity, and its molluscicidal concentration was equal to that of the ether extract. However, after 60 min of exposure, 1 µg/mL BAR presented cercaricidal activity against the parasite S. mansoni at the second larval stage. Neither substance induced toxicity against A. salina. These results indicate the potential molluscicidal activities of the ether extract and BAR against B. glabrata and S. mansoni cercariae. In addition to these effects, there was a lack of toxicity against the aquatic environment and no damage to the biota, indicating the potential of these products for large-scale control and/or eradication of schistosomiasis.

Usnic acid and atranorin exert selective cytostatic and anti-invasive effects on human prostate and melanoma cancer cells

OBJECTIVES AND METHODS

Lichens are an interesting source of potential anti-tumor compounds, among which usnic acid and atranorin seem to be the most promising, but their impact on invasive potential of tumor cells has not yet been comprehensively addressed. The aim of the study was focused on the impact of the two lichen metabolites, on the viability (by Trypan blue test and fluoresceine diacetate and ethidium bromide assay), proliferation (cell counting in a Bürker's chamber), apoptosis (flow cytometry analysis and Western blot) and motile activity (cell movement recording and image analysis) and actin cytoskeleton organization (immunofluorescent staining) of melanoma HTB-140, prostate cancers DU-145 and PC-3, normal human skin fibroblasts and prostate epithelial PNT2 cells, with special emphasis to their selectivity and versatility.

RESULTS

Both compounds exerted strong inhibitory effects on cancer cell proliferation, migration and actin cytoskeleton organization, while their effect on apoptosis process was less relevant. The impact of usnic acid on the examined cancer cells was found more efficient in comparison to atranorin. Also, selective effect of both agents on tumor cells was observed.

SIGNIFICANCE

The ability of usnic acid and atranorin to inhibit cancer cells motility may have future implications for development of new therapeutic strategies targeted at the interference with the metastatic cascade.

Potential anticancer activity of lichen secondary metabolite physodic acid

Secondary metabolites present in lichens, which comprise aliphatic, cycloaliphatic, aromatic and terpenic compounds, are unique with respect to those of higher plants and show interesting biological and pharmacological activities. However, only a few of these compounds, have been assessed for their effectiveness against various in vitro cancer models. In the present study, we investigated the cytotoxicity of three lichen secondary metabolites (atranorin, gyrophoric acid and physodic acid) on A375 melanoma cancer cell line. The tested compounds arise from different lichen species collected in different areas of Continental and Antarctic Chile. The obtained results confirm the major efficiency of depsidones. In fact, depsides atranorin and gyrophoric acid, showed a lower activity inhibiting the melanoma cancer cells only at more high concentrations. Whereas the depsidone physodic acid, showed a dose-response relationship in the range of 6.25-50 μM concentrations in A375 cells, activating an apoptotic process, that probably involves the reduction of Hsp70 expression. Although the molecular mechanism, by which apoptosis is induced by physodic acid remains unclear, and of course further studies are needed, the results here reported confirm the promising biological properties of depsidone compounds, and may offer a further impulse to the development of analogues with more powerful efficiency against melanoma cells.

Mechanism of dihydroartemisinin-induced apoptosis in prostate cancer PC3 cells: An iTRAQ-based proteomic analysis

AIMS

Prostate cancer (PCa) is one of the most common cancers in men in the world. Advanced PCa, especially castration-resistant PCa (CRPC), is difficult to cure. There is an urgent need to develop novel agents for CPRC. Dihydroartemisinin (DHA) is a semisynthetic derivative of artemisinin and is a well-known antimalarial drug. DHA has been documented to be a potential anticancer agent for PCa. However, the mechanisms underlying the anticancer activity of DHA are still unknown.

MAIN METHODS

Proteomics analysis based on iTRAQ technology was performed to determine the protein profile changes in human prostate cancer PC3 cells treated by DHA, and apoptosis was detected by flow cytometry and transmission electron microscopy.

KEY FINDINGS

DHA induced obvious apoptosis in PC3 cells. Using iTRAQ technology, we found 86 differentially expressed proteins linked to the cytotoxicity of DHA in PC3 cells. Gene ontology analysis showed the differentially expressed proteins were mainly associated with the protein synthesis and translation. Protein interaction network analysis and KEGG pathway analysis revealed altered aminoacyl-tRNA biosynthesis and metabolic pathways. Moreover, one candidate protein, heat shock protein HSP70 (HSPA1A), was identified by western blot analysis.

SIGNIFICANCE

Our results indicate that multiple mechanisms involved in the anticancer activity of DHA in PC3 cells. Decreased HSP70 expression may have an important role in DHA-induced apoptosis in PC3 cells. Our data also provide novel insights into the anticancer mechanisms of DHA.

Secondary metabolites from cetrarioid lichens: Chemotaxonomy, biological activities and pharmaceutical potential

BACKGROUND

Lichens, as a symbiotic association of photobionts and mycobionts, display an unmatched environmental adaptability and a great chemical diversity. As an important morphological group, cetrarioid lichens are one of the most studied lichen taxa for their phylogeny, secondary chemistry, bioactivities and uses in folk medicines, especially the lichen Cetraria islandica. However, insufficient structure elucidation and discrepancy in bioactivity results could be found in a few studies.

PURPOSE

This review aimed to present a more detailed and updated overview of the knowledge of secondary metabolites from cetrarioid lichens in a critical manner, highlighting their potentials for pharmaceuticals as well as other applications. Here we also highlight the uses of molecular phylogenetics, metabolomics and ChemGPS-NP model for future bioprospecting, taxonomy and drug screening to accelerate applications of those lichen substances.

CHAPTERS

The paper starts with a short introduction in to the studies of lichen secondary metabolites, the biological classification of cetrarioid lichens and the aim. In light of ethnic uses of cetrarioid lichens for therapeutic purposes, molecular phylogeny is proposed as a tool for future bioprospecting of cetrarioid lichens, followed by a brief discussion of the taxonomic value of lichen substances. Then a delicate description of the bioactivities, patents, updated chemical structures and lichen sources is presented, where lichen substances are grouped by their chemical structures and discussed about their bioactivity in comparison with reference compounds. To accelerate the discovery of bioactivities and potential drug targets of lichen substances, the application of the ChemGPS NP model is highlighted. Finally the safety concerns of lichen substances (i.e. toxicity and immunogenicity) and future-prospects in the field are exhibited.

CONCLUSION

While the ethnic uses of cetrarioid lichens and the pharmaceutical potential of their secondary metabolites have been recognized, the knowledge of a large number of lichen substances with interesting structures is still limited to various in vitro assays with insufficient biological annotations, and this area still deserves more research in bioactivity, drug targets and screening. Attention should be paid on the accurate interpretation of their bioactivity for further applications avoiding over-interpretations from various in vitro bioassays.

Quercetin Suppresses the Migration and Invasion in Human Colon Cancer Caco-2 Cells Through Regulating Toll-like Receptor 4/Nuclear Factor-kappa B Pathway

Objective:

The migration and invasion features, which were associated with inflammatory response, acted as vital roles in the development of colon cancer. Quercetin, a bioflavonoid compound, was widely spread in vegetables and fruits. Although quercetin exerts antioxidant and anticancer activities, the molecular signaling pathways in human colon cancer cells remain unclear. Hence, the present study was conducted to investigate the suppression of quercetin on migratory and invasive activity of colon cancer and the underlying mechanism.

Materials and Methods:

The effect of quercetin on cell viability, migration, and invasion of Caco-2 cells was analyzed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, wound-healing assay, and transwell chambers assay, respectively. The protein expressions of toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB) p65, mitochondrial membrane potential-2 (MMP-2), and MMP-9 were detected by Western blot assay. The inflammatory factors, such as tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (Cox-2), and interleukin-6 (IL-6), in cell supernatant were detected by enzyme-linked immunosorbent assay.

Results:

The concentration of quercetin <20 μM was chosen for further experiments. Quercetin (5 μM) could remarkably suppress the migratory and invasive capacity of Caco-2 cells. The expressions of metastasis-related proteins of MMP-2, MMP-9 were decreased, whereas the expression of E-cadherin protein was increased by quercetin in a dose-dependent manner. Interestingly, the anti-TLR4 (2 μg) antibody or pyrrolidine dithiocarbamate (PDTC; 1 μM) could affect the inhibition of quercetin on cell migration and invasion, as well as the protein expressions of MMP-2, MMP-9, E-cadherin, TLR4, and NF-κB p65. In addition, quercetin could reduce the inflammation factors production of TNF-α, Cox-2, and IL-6.

Conclusion:

The findings suggested for the 1^st time that quercetin might exert its anticolon cancer activity via the TLR4- and/or NF-κB-mediated signaling pathway.

SUMMARY

Quercetin could remarkably suppress the migratory and invasive capacity of Caco-2 cells

The expressions of metastasis-related proteins of mitochondrial membrane potential-2 (MMP-2), MMP-9 were decreased, whereas the expression of E-cadherin protein was increased by quercetin in a dose-dependent manner

The anti-toll-like receptor 4 (TLR4) antibody or pyrrolidine dithiocarbamate affected the inhibition of quercetin on cell migration and invasion, as well as the protein expressions of MMP-2, MMP-9, E-cadherin, TLR4, and nuclear factor-kappa B p65

Quercetin could reduce the inflammation factors production of tumor necrosis factors-α, cyclooxygenase-2, and interleukin-6.

Abbreviations used: MTT: 3-(4,5-dimethylthiazol-2-yl)- 2,5-diphen yltetrazolium bromide, TLR4: Toll-like receptor 4, NF-κB: Nuclear factor-kappa B, MMP-2: Mitochondrial membrane potential-2, MMP-9: Mitochondrial membrane potential-9, TNF-α: Tumor necrosis factor-α, Cox-2: Cyclooxygenase-2, IL-6: Interleukin-6, ELISA: Enzyme-linked immunosorbent assay, PDTC: Pyrrolidine dithiocarbamate, ROS: Reactive oxygen species, DMSO: Dimethyl sulfoxide, FBS: Fetal bovine serum, DMEM: Dulbecco modified Eagle medium, OD: Optical density, IPP: Image Pro-plus, PBS: Phosphate buffered saline, SD: Standard deviation, ANOVA: One-way analysis of variance, SPSS: Statistical Package for the Social Sciences, ECM: Extracellular matrix, TLRs: Toll-like receptors, LPS: Lipopolysaccharide.

Murine breast carcinoma 4T1 cells are more sensitive to atranorin than normal epithelial NMuMG cells in vitro: Anticancer and hepatoprotective effects of atranorin in vivo

The aim of this study was to evaluate the anticancer effect of atranorin (ATR) on murine 4T1 breast carcinoma cells and compare its sensitivity with normal mammary epithelial NMuMG cells in vitro. Anti-tumor and hepatoprotective activity of ATR-therapy was examined on mouse model of 4T1-induced cancer disease. ATR significantly reduced clonogenic ability of carcinoma 4T1 cells at the concentration of 75 μM, but clonogenicity of normal NMuMG cells was not affected by any of ATR concentrations tested. Moreover, flow cytometric and BrdU incorporation analysis did not confirm the inhibited entry into S-phase of the cell cyle after ATR incubation, and on the contrary, it induced apoptosis associated with the activation of caspase-3 and PARP cleavage in 4T1 cells. Although ATR did not cause any significant changes in Bcl-xL protein expression in NMuMG cells, an apparent depletion of Bcl-xL protein in 4T1 cells after 48 h ATR therapy was confirmed. Based on this result as well as the result of the total cell number decline, we can conclude that 4T1 cells are more sensitive to ATR therapy than NMuMG cells. ATR administration resulted in significantly longer survival time of BALB/c mice inoculated with 4T1 cells, what was associated with reduced tumor size and the higher numbers of apoptotic 4T1 cells. No differences were recorded in the number of BrdU-positive tumor cells between ATR-treated group and controls. Results indicate that ATR has rather proapoptotic than antiproliferative effect on 4T1 cells in vitro and in vivo and normal NMuMG cells are less sensitive to ATR. Furthermore, our studies revealed protective effect of ATR against oxidative stress in the livers of the tumor-bearing mice.

Lichen secondary metabolites in Flavocetraria cucullata exhibit anti-cancer effects on human cancer cells through the induction of apoptosis and suppression of tumorigenic potentials

Lichens are symbiotic organisms which produce distinct secondary metabolic products. In the present study, we tested the cytotoxic activity of 17 lichen species against several human cancer cells and further investigated the molecular mechanisms underlying their anti-cancer activity. We found that among 17 lichens species, F. cucullata exhibited the most potent cytotoxicity in several human cancer cells. High performance liquid chromatography analysis revealed that the acetone extract of F. cucullata contains usnic acid, salazinic acid, Squamatic acid, Baeomycesic acid, d-protolichesterinic acid, and lichesterinic acid as subcomponents. MTT assay showed that cancer cell lines were more vulnerable to the cytotoxic effects of the extract than non-cancer cell lines. Furthermore, among the identified subcomponents, usnic acid treatment had a similar cytotoxic effect on cancer cell lines but with lower potency than the extract. At a lethal dose, treatment with the extract or with usnic acid greatly increased the apoptotic cell population and specifically activated the apoptotic signaling pathway; however, using sub-lethal doses, extract and usnic acid treatment decreased cancer cell motility and inhibited in vitro and in vivo tumorigenic potentials. In these cells, we observed significantly reduced levels of epithelial-mesenchymal transition (EMT) markers and phosphor-Akt, while phosphor-c-Jun and phosphor-ERK1/2 levels were only marginally affected. Overall, the anti-cancer activity of the extract is more potent than that of usnic acid alone. Taken together, F. cucullata and its subcomponent, usnic acid together with additional component, exert anti-cancer effects on human cancer cells through the induction of apoptosis and the inhibition of EMT.

Effects of anti-proliferative lichen metabolite, protolichesterinic acid on fatty acid synthase, cell signalling and drug response in breast cancer cells

BACKGROUND

The lichen compound (+)-protolichesterinic acid (+)-PA, isolated from Iceland moss, has anti-proliferative effects on several cancer cell lines. The chemical structure of (+)-PA is similar to a known fatty acid synthase (FASN) inhibitor C75.

AIMS

To test whether the anti-proliferative activity of (+)-PA is associated with effects on FASN and HER2 (human epidermal growth factor receptor 2) and major signalling pathways. Synergism between (+)-PA and lapatinib, a HER2 active drug, was also evaluated.

MATERIALS AND METHODS

Pure compound was isolated by preparative high-performance liquid chromatography (HPLC) and purity of (+)-PA analyzed by analytical HPLC. Cell viability was assessed using Crystal violet staining. FASN and HER2 expression was estimated by immunofluorescence. The Meso Scale Discovery (MSD)(®) assay was used to measure activation of ERK1/2 and AKT. Synergism was estimated by the CalcuSyn software.

RESULTS

Treatment with (+)-PA increased FASN expression in SK-BR-3 cells, which overexpress FASN and HER2, implying a compensatory response to inhibition of FASN activity. HER2 expression was decreased suggesting secondary downregulation. ERK1/2 and AKT signalling pathways were inhibited, probably due to reduced levels of HER2. No effects were observed in T-47D cells. Synergism between (+)-PA and lapatinib was observed in the SK-BR-3 cells.

CONCLUSION

Results suggest that the primary effect of (+)-PA is inhibition of FASN activity. Synergistic effects with lapatinib were seen only in SK-BR-3 cells, and not T-47D cells, further supporting the notion that (+)-PA acts by inhibiting FASN with secondary effects on HER2 expression and signalling. (+)-PA could therefore be a suitable agent for further testing, alone or in combination treatment against HER2-overexpressing breast cancer.

Protolichesterinic acid derivatives: α-methylene-γ-lactones as potent dual activators of PPARγ and Nrf2 transcriptional factors

PPARγ and Nrf2 are important transcriptional factors involved in many signaling pathways, especially in the anti-infectious response of macrophages. Compounds bearing a Michael acceptor moiety are well known to activate such transcriptional factors, we thus evaluated the potency of α,β-unsaturated lactones synthesized using fluorous phase organic synthesis. Compounds were first screened for their cytotoxicity in order to select lactones for PPARγ and Nrf2 activation evaluation. Among them, two α-methylene-γ-lactones were identified as potent dual activators of PPARγ and Nrf2 in macrophages.

Mini-review: Foldosome regulation of androgen receptor action in prostate cancer

Steroid hormone receptors play diverse roles in many aspects of human physiology including cell division, apoptosis and homeostasis, tissue differentiation, sexual development and response to stress. These ligand-activated transcription factors require the functional activity of numerous chaperone and chaperone-associated proteins, collectively termed the foldosome, at the crucial step of ligand recognition and binding. Since the initial isolation of foldosome components and pioneering research by Pratt, Toft and colleagues we understand much regarding cytosolic receptor function. The classical view, that the role of foldosome components is restricted to the cytosol, has been modified over recent years by research highlighting additional roles of chaperone proteins in nuclear translocation and target gene expression. Further, dysregulation of chaperone activity and expression has been implicated in various cancers, including breast and prostate cancer. Consequently, the foldosome provides an attractive therapeutic target in steroid hormone receptor-driven malignancies. This review summarises current knowledge of how the foldosome impacts upon androgen receptor signalling, which is the key therapeutic target on prostate cancer, and how foldosome components may be used as biomarkers or therapeutic targets in this disease.

Reactive oxygen species-mediated mitochondrial pathway is involved in Baohuoside I-induced apoptosis in human non-small cell lung cancer

Baohuoside I (also known as Icariside II) is a flavonoid isolated from Epimedium koreanum Nakai. Although Baohuoside I exhibits anti-inflammatory and anti-cancer activities, its molecular targets/pathways in human lung cancer cells are poorly understood. Therefore, in the present study, we investigated the usefulness of Baohuoside I as a potential apoptosis-inducing cytotoxic agent using human adenocarcinoma alveolar basal epithelial A549 cells as in vitro model. The apoptosis induced by Baohuoside I in A549 cells was confirmed by annexin V/propidium iodide double staining, cell cycle analysis and dUTP nick end labeling. Further research revealed that Baohuoside I accelerated apoptosis through the mitochondrial apoptotic pathway, involving the increment of BAX/Bcl-2 ratio, dissipation of mitochondrial membrane potential, transposition of cytochrome c, caspase 3 and caspase 9 activation, degradation of poly (ADP-ribose) polymerase and the over-production of reactive oxygen species (ROS). A pan-caspase inhibitor, Z-VAD-FMK, only partially prevented apoptosis induced by Baohuoside I, while NAC, a scavenger of ROS, diminished its effect more potently. In addition, the apoptotic effect of Baohuoside I was dependent on the activation of ROS downstream effectors, JNK and p38(MAPK), which could be almost abrogated by using inhibitors SB203580 (an inhibitor of p38(MAPK)) and SP600125 (an inhibitor of JNK). These findings suggested that Baohuoside I might exert its cytotoxic effect via the ROS/MAPK pathway.

Cytotoxic activity and antioxidant capacity of purified lichen metabolites: an in vitro study

The purpose of this study was to investigate the effects of six lichen metabolites (diffractaic acid, lobaric acid, usnic acid, vicanicin, variolaric acid, protolichesterinic acid) on proliferation, viability and reactive oxygen species (ROS) level towards three human cancer cell lines, MCF-7 (breast adenocarcinoma), HeLa (cervix adenocarcinoma) and HCT-116 (colon carcinoma). Cells were treated with different concentrations (2.5-100 μM) of these compounds for 48 h. In this comparative study, our lichen metabolites showed various cytotoxic effects in a concentration-dependent manner, and usnic acid was the most potent cytotoxic agent, while variolaric acid did not inhibit the proliferation of any of the three cell lines used. All tested lichen compounds did not exhibit free radical scavenging activity using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The lichen metabolites did not significantly increase the intracellular ROS level and did not prevent oxidative injury induced by t-butylhydroperoxide in HeLa cells. To better clarify the mechanism(s) of cytotoxic effect induced by protolichesterinic acid in HeLa cells, we investigated apoptotic markers such as condensation and fragmentation of nuclear chromatin and activation of caspase-3, 8 and 9. Our results revealed that the antiproliferative activity of 40 μM protolichesterinic acid in HeLa cells is related to its ability to induce programmed cell death involving caspase-3, 8 and 9 activation.