Does usnic acid affect microtubules in human cancer cells?

A New Rare Halogenated Depside from Lichen and Study of its Anti-Proliferative Activity

Lichens are a symbiotic association of algae and fungus, belonging to the family Parmeliaceae. Some lichen species are edible and used as an active ingredient for preparation of exotic spices as well as folklore medicine to cure different kinds of ailments. A specimen of lichen was collected from Munner in the Kerala State of South India for chemical profiling. Chemical analyses of the diethyl ether extract of the defatted lichen led to the isolation of six phenols 1-6 with variation of relative abundance. Amongst them, the relative abundance of compound 3 was the greatest (1 % of crude extract) and it was identified as atranorin. The structures of known compounds were confirmed by comparison of their 1H-NMR, 13C NMR, and mass data with published values available in the literature. In vitro bioassay for anti-proliferative activity of these compounds has been conducted against various human cancer cell lines in comparison with paclitaxel as control using SRB assay. Interestingly, a new compound 5 was found along with previously reported compounds from this lichen. This new compound was designated as fluoroatranorin 5 which was reported for the first time herein. The structural characterization of a new depside was determined by spectral methods such as 1H-NMR, 13C NMR, 19F NMR, IR, LC-HRESI-MS, and LC-MS/MS study. Its structure was confirmed by single crystal X-ray diffraction study. This new compound was designated as fluoroatranorin 5 which was reported first time herein. Anti-proliferative activity of all these compounds was evaluated against six different cancer cell lines. The inhibitory activity, IC50 value of compounds 1-3 and 5 exhibited at 99.64, 102.04, 109.20, 53.0 and 2.4 μM on cancer cell lines HT-29 (colon), Hela (cervical), HT-29, HPAC (pancreas) and A2780 (ovarian cancer cell line) respectively in comparison with paclitaxel as control. The new compound 5 exhibited significant activity with IC50 value 2.4 μM on A2780 ovarian cancer cell line.

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.

Usnic acid inhibits hypertrophic scarring in a rabbit ear model by suppressing scar tissue angiogenesis

Hypertrophic scarring is a common condition in the Chinese population; however, there are currently no satisfactory drugs to treat the disorder. Previous studies showed that angiogenesis plays an important role in the early phase of hypertrophic scarring and inhibition of angiogenesis has been reported as an effective strategy for anti-hypertrophic scar therapy. A recent study showed that usnic acid (UA), an active compound found mainly in lichens, inhibited tumor angiogenesis both in vivo and in vitro. To investigate the therapeutic effects of UA on hypertrophic scarring and to explore the possible mechanism involved, a rabbit ear hypertrophic scar model was established. Scars were treated once a week for four weeks with UA, DMSO or triamcinolone acetonide acetate. Histological evaluation of hematoxylin and eosin staining indicated that UA significantly inhibited hypertrophic scar formation, with obvious reductions in scar height and coloration. The scar elevation index (SEI) was also evidently reduced. Masson's trichrome staining showed that UA significantly ameliorated accumulation of collagen tissue. Immunohistochemical analysis of CD31 expression showed that UA significantly inhibited scar angiogenesis. In vitro, UA inhibited endothelial cell migration and tube formation as well as the proliferation of both human umbilical vein endothelial cells and scar fibroblast cells. These results provide the first evidence of the therapeutic effectiveness of UA in hypertrophic scar formation in an animal model via a mechanism that involves suppression of scar angiogenesis.

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.

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.

Usnic acid inhibits growth and induces cell cycle arrest and apoptosis in human lung carcinoma A549 cells

Usnic acid (UA) is a secondary metabolite abundantly found in lichens. Some studies have shown the anticancer potential of UA; however, its efficacy and associated mechanisms are yet to be fully explored. Herein, we assessed the anticancer potency and associated molecular alterations by UA in human lung carcinoma A549 cells. UA treatment (25-100 μM) for 24 and 48 h decreased total cell number by 39-67% (P < 0.01) and 68-89% (P < 0.001), respectively, and enhanced cell death by up to twofold and eightfold (P < 0.001), respectively. UA (1-10 μM) also significantly (P < 0.001) suppressed colony formation of A549 cells. The cell growth inhibition was associated with cell cycle arrest at G0/ G1 phase. UA decreased the expression of cyclin-dependent kinase (CDK)4, CDK6, and cyclin D1 and increased the expression of CDK inhibitor (CDKI) p21/cip1 protein. While examining the cell death associated molecular changes, we observed that UA induces mitochondrial membrane depolarization and led to more than twofold increase (P < 0.01) in apoptotic cells. The apoptotic effect of UA was accompanied by enhanced poly(ADP-ribose) polymerase cleavage. This study shows that UA inhibits cell growth involving G0/G1 phase cell cycle arrest and induces cell death via mitochondrial membrane depolarization and induction of apoptosis in human lung carcinoma cells.

The synthesis, characterization, antimicrobial and antimutagenic activities of hydroxyphenylimino ligands and their metal complexes of usnic acid isolated from Usnea longissima

Novel Schiff base ligands of usnic acid isolated from Usnea longissima and their metal complexes were synthesized and characterized. Investigated their antimicrobial and antimutagenic activities.

Usnic acid inhibits breast tumor angiogenesis and growth by suppressing VEGFR2-mediated AKT and ERK1/2 signaling pathways

Tumor growth depends on angiogenesis and inducing angiogenesis is one of the most important hallmarks in the cancer development. Treatment with small molecules that inhibit angiogenesis has been an effective strategy for anti-cancer therapy. Some anti-angiogenic factors are derived from traditional Chinese herbs. Usnic acid (UA), an active compound mainly found in lichens, has shown some biological and physiological activities. However, the role and mechanism of UA in tumor angiogenesis are still unknown. The aim of this study was to assess the effects of UA on tumor angiogenesis. In this study, we demonstrated that UA strongly inhibited in vivo angiogenesis in a chick embryo chorioallantoic membrane assay and vascular endothelial growth factor-induced mouse corneal angiogenesis model. In a mouse xenograft tumor model, UA suppressed Bcap-37 breast tumor growth and angiogenesis without affecting mice body weight. In an in vitro assay, UA not only significantly inhibited endothelial cell proliferation, migration and tube formation, but also induced morphological changes and apoptosis in endothelial cells. In addition, UA inhibited Bcap-37 tumor cell proliferation. Moreover, western blot analysis of cell signaling molecules indicated that UA blocked vascular endothelial growth factor receptor (VEGFR) 2 mediated Extracellular signal-regulated protein kinases 1 and 2(ERK1/2) and AKT/P70S6K signaling pathways in endothelial cells. These results provided the first evidence of the biological function and molecular mechanism of UA in tumor angiogenesis.