Apigenin: a promising molecule for cancer prevention

Apigenin inhibits growth and induces apoptosis in human cholangiocarcinoma cells

A promising nutraceutical, apigenin, was recently revealed to exhibit biological activity in inhibiting several types of cancer. The effects of apigenin on the growth inhibition and apoptosis of the cholangiocarcinoma HuCCA-1 cell line were investigated. Protein alterations subsequent to apigenin treatment were studied using a proteomic approach. The values of 20, 50 and 90% inhibition of cell growth (IC₂₀, IC₅₀ and IC₉₀) were determined by MTT cell viability assay. Apoptotic cell death was detected using two different methods, a flow cytometric analysis (Muse Cell Analyzer) and DNA fragmentation assay. A number of conditions including attached and detached cells were selected to perform two-dimensional gel electrophoresis (2-DE) to study the alterations in the expression levels of treated and untreated proteins and identified by liquid chromatography (LC)/tandem mass spectrometry (MS/MS). The IC₂₀, IC₅₀ and IC₉₀ values of apigenin after 48 h treatment in HuCCA-1 cells were 25, 75 and 200 µM, respectively, indicating the cytotoxicity of this compound. Apigenin induced cell death in HuCCA-1 cells via apoptosis as detected by flow cytometric analysis and exhibited, as confirmed with DNA fragmentation, characteristics of apoptotic cells. A total of 67 proteins with altered expression were identified from the 2-DE analysis and LC/MS/MS. The cleavage of proteins involved in cytoskeletal, cytokeratin 8, 18 and 19, and high expression of S100-A6 and S100-A11 suggested that apoptosis was induced by apigenin via the caspase-dependent pathway. Notably, two proteins, heterogeneous nuclear ribonucleoprotein H and A2/B1, disappeared completely subsequent to treatment, suggesting the role of apigenin in inducing cell death. The present study indicated that apigenin demonstrates an induction of growth inhibition and apoptosis in cholangiocarcinoma cells and the apoptosis pathway was confirmed by proteomic analysis.

Pikuni-Blackfeet traditional medicine: Neuroprotective activities of medicinal plants used to treat Parkinson's disease-related symptoms

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder affecting 5% of the population over the age of 85 years. Current treatments primarily involve dopamine replacement therapy, which leads to temporary relief of motor symptoms but fails to slow the underlying neurodegeneration. Thus, there is a need for safe PD therapies with neuroprotective activity. In this study, we analyzed contemporary herbal medicinal practices used by members of the Pikuni-Blackfeet tribe from Western Montana to treat PD-related symptoms, in an effort to identify medicinal plants that are affordable to traditional communities and accessible to larger populations.

AIM OF THE STUDY

The aims of this study were to (i) identify medicinal plants used by the Pikuni-Blackfeet tribe to treat individuals with symptoms related to PD or other CNS disorders, and (ii) characterize a subset of the identified plants in terms of antioxidant and neuroprotective activities in cellular models of PD.

MATERIALS AND METHODS

Interviews of healers and local people were carried out on the Blackfeet Indian reservation. Plant samples were collected, and water extracts were produced for subsequent analysis. A subset of botanical extracts was tested for the ability to induce activation of the Nrf2-mediated transcriptional response and to protect against neurotoxicity elicited by the PD-related toxins rotenone and paraquat.

RESULTS

The ethnopharmacological interviews resulted in the documentation of 26 medicinal plants used to treat various ailments and diseases, including symptoms related to PD. Seven botanical extracts (out of a total of 10 extracts tested) showed activation of Nrf2-mediated transcriptional activity in primary cortical astrocytes. Extracts prepared from Allium sativum cloves, Trifolium pratense flowers, and Amelanchier arborea berries exhibited neuroprotective activity against toxicity elicited by rotenone, whereas only the extracts prepared from Allium sativum and Amelanchier arborea alleviated PQ-induced dopaminergic cell death.

CONCLUSIONS

Our findings highlight the potential clinical utility of plants used for medicinal purposes over generations by the Pikuni-Blackfeet people, and they shed light on mechanisms by which the plant extracts could slow neurodegeneration in PD.

Phytochemicals Targeting Estrogen Receptors: Beneficial Rather Than Adverse Effects?

In mammals, the effects of estrogen are mainly mediated by two different estrogen receptors, ERα and ERβ. These proteins are members of the nuclear receptor family, characterized by distinct structural and functional domains, and participate in the regulation of different biological processes, including cell growth, survival and differentiation. The two estrogen receptor (ER) subtypes are generated from two distinct genes and have partially distinct expression patterns. Their activities are modulated differently by a range of natural and synthetic ligands. Some of these ligands show agonistic or antagonistic effects depending on ER subtype and are described as selective ER modulators (SERMs). Accordingly, a few phytochemicals, called phytoestrogens, which are synthesized from plants and vegetables, show low estrogenic activity or anti-estrogenic activity with potentially anti-proliferative effects that offer nutraceutical or pharmacological advantages. These compounds may be used as hormonal substitutes or as complements in breast cancer treatments. In this review, we discuss and summarize the in vitro and in vivo effects of certain phytoestrogens and their potential roles in the interaction with estrogen receptors.

A systematic review on phenolic compounds in Passiflora plants: Exploring biodiversity for food, nutrition, and popular medicine

Passiflora plants are strategic in the context of biodiversity for food and nutrition. We applied the procedures of a systematic review protocol to study the state of the art on identification of phenolic compounds from Passiflora plants. An automated literature search was conducted using six databases and a combination of seven keywords. All the analytical, chromatographic, and spectroscopic methods were included. The studies were classified according to their method of identification, phenolic classes, and method of extraction. In total, 8,592 abstracts were found, from which 122 studies were selected for complete reading and 82 were selected for further analysis. Techniques of extraction, evaluated parts of the plant and methods of identification were systematized. Studies with leaves were most conspicuous (54.4%), 34 species of Passiflora were evaluated and orientin, isoorientin, vitexin, isovitexin were commonly found structures. A High Performance Liquid Chromatography-diode array detector was the technique most applied, with which the same structures were identified all through the studies, although other unknown structures were detected, but not elucidated. The use of Nuclear Magnetic Resonance and Mass Spectrometry, which are more sensitive techniques, needs to be intensified, to identify other unconventional compounds detected in Passiflora, to enhance the comprehension of the bioactive compounds in these plants.

Apigenin overcomes drug resistance by blocking the signal transducer and activator of transcription 3 signaling in breast cancer cells

Drug resistance in chemotherapy is a serious obstacle for the successful treatment of cancer. Drug resistance is caused by various factors, including the overexpression of P-glycoprotein (P-gp, MDR1). The development of new, useful compounds that overcome drug resistance is urgent. Apigenin, a dietary flavonoid, has been reported as an anticancer drug in vivo and in vitro. In the present study, we investigated whether apigenin is able to reverse drug resistance using adriamycin-resistant breast cancer cells (MCF-7/ADR). In our experiments, apigenin significantly decreased cell growth and colony formation in MCF-7/ADR cells and parental MCF-7 cells. This growth inhibition was related to the accumulation of cells in the sub-G₀/G₁ apoptotic population and an increase in the number of apoptotic cells. Apigenin reduced the mRNA expression of multidrug resistance 1 (MDR1) and multidrug resistance-associated proteins (MRPs) in MCF-7/ADR cells. Apigenin also downregulated the expression of P-gp. Apigenin reversed drug efflux from MCF-7/ADR cells, resulting in rhodamine 123 (Rho123) accumulation. Inhibition of drug resistance by apigenin is related to the suppression of the signal transducer and activator of transcription 3 (STAT3) signaling pathway. Apigenin decreased STAT3 activation (p-STAT3) and its nuclear translocation and inhibited the secretion of VEGF and MMP-9, which are STAT3 target genes. A STAT3 inhibitor, JAK inhibitor I and an HIF-1α inhibitor decreased cell growth in MCF-7 and MCF-7/ADR cells. Taken together, these results demonstrate that apigenin can overcome drug resistance.

In Vitro and In Vivo Anti-tumoral Effects of the Flavonoid Apigenin in Malignant Mesothelioma

Malignant mesothelioma (MM) is a tumor arising from mesothelium. MM patients’ survival is poor. The polyphenol 4′,5,7,-trihydroxyflavone Apigenin (API) is a “multifunctional drug”. Several studies have demonstrated API anti-tumoral effects. However, little is known on the in vitro and in vivo anti-tumoral effects of API in MM. Thus, we analyzed the in vitro effects of API on cell proliferation, cell cycle regulation, pro-survival signaling pathways, apoptosis, and autophagy of human and mouse MM cells. We evaluated the in vivo anti-tumor activities of API in mice transplanted with MM #40a cells forming ascites. API inhibited in vitro MM cells survival, increased reactive oxygen species intracellular production and induced DNA damage. API activated apoptosis but not autophagy. API-induced apoptosis was sustained by the increase of Bax/Bcl-2 ratio, increase of p53 expression, activation of both caspase 9 and caspase 8, cleavage of PARP-1, and increase of the percentage of cells in subG1 phase. API treatment affected the phosphorylation of ERK1/2, JNK and p38 MAPKs in a cell-type specific manner, inhibited AKT phosphorylation, decreased c-Jun expression and phosphorylation, and inhibited NF-κB nuclear translocation. Intraperitoneal administration of API increased the median survival of C57BL/6 mice intraperitoneally transplanted with #40a cells and reduced the risk of tumor growth. Our findings may have important implications for the design of MM treatment using API.

Assessing the anticancer effects associated with food products and/or nutraceuticals using in vitro and in vivo preclinical development-related pharmacological tests

This review is part of a special issue entitled "Role of dietary pattern, foods, nutrients and nutraceuticals in supporting cancer prevention and treatment" and describes a pharmacological strategy to determine the potential contribution of food-related components as anticancer agents against established cancer. Therefore, this review does not relate to chemoprevention, which is analysed in several other reviews in the current special issue, but rather focuses on the following: i) the biological events that currently represent barriers against the treatment of certain types of cancers, primarily metastatic cancers; ii) the in vitro and in vivo pharmacological pre-clinical tests that can be used to analyse the potential anticancer effects of food-related components; and iii) several examples of food-related components with anticancer effects. This review does not represent a catalogue-based listing of food-related components with more or less anticancer activity. By contrast, this review proposes an original pharmacological strategy that researchers can use to analyse the potential anticancer activity of any food-related component-e.g., by considering the crucial characteristics of cancer biological aggressiveness. This review also highlights that cancer patients undergoing chemotherapy should restrict the use of "food complements" without supervision by a medical nutritionist. By contrast, an equilibrated diet that includes the food-related components listed herein would be beneficial for cancer patients who are not undergoing chemotherapy.

Flavonoids as modulators of metabolic enzymes and drug transporters

Flavonoids, natural compounds found in plants and in plant-derived foods and beverages, have been extensively studied with regard to their capacity to modulate metabolic enzymes and drug transporters. In vitro, flavonoids predominantly inhibit the major phase I drug-metabolizing enzyme CYP450 3A4 and the enzymes responsible for the bioactivation of procarcinogens (CYP1 enzymes) and upregulate the enzymes involved in carcinogen detoxification (UDP-glucuronosyltransferases, glutathione S-transferases (GSTs)). Flavonoids have been reported to inhibit ATP-binding cassette (ABC) transporters (multidrug resistance (MDR)-associated proteins, breast cancer-resistance protein) that contribute to the development of MDR. P-glycoprotein, an ABC transporter that limits drug bioavailability and also induces MDR, was differently modulated by flavonoids. Flavonoids and their phase II metabolites (sulfates, glucuronides) inhibit organic anion transporters involved in the tubular uptake of nephrotoxic compounds. In vivo studies have partially confirmed in vitro findings, suggesting that the mechanisms underlying the modulatory effects of flavonoids are complex and difficult to predict in vivo. Data summarized in this review strongly support the view that flavonoids are promising candidates for the enhancement of oral drug bioavailability, chemoprevention, and reversal of MDR.

The Functional Characterization of a Site-Specific Apigenin 4'-O-methyltransferase Synthesized by the Liverwort Species Plagiochasma appendiculatum

Apigenin, a widely distributed flavone, exhibits excellent antioxidant, anti-inflammatory, and antitumor properties. In addition, the methylation of apigenin is generally considered to result in better absorption and greatly increased bioavailability. Here, four putative Class II methyltransferase genes were identified from the transcriptome sequences generated from the liverwort species Plagiochasma appendiculatum. Each was heterologously expressed as a His-fusion protein in Escherichia coli and their methylation activity against apigenin was tested. One of the four Class II OMT enzymes named 4'-O-methyltransferase (Pa4'OMT) was shown to react effectively with apigenin, catalyzing its conversion to acacetin. Besides the favorite substrate apigenin, the recombinant PaF4'OMT was shown to catalyze luteolin, naringenin, kaempferol, quercetin, genistein, scutellarein, and genkwanin to the corresponding 4'-methylation products. In vivo feeding experiments indicated that PaF4'OMT could convert apigenin to acacetin efficiently in E. coli and approximately 88.8 µM (25.2 mg/L) of product was synthesized when 100 µM of apigenin was supplemented. This is the first time that a Class II plant O-methyltransferase has been characterized in liverworts.

STAT3 targeting by polyphenols: Novel therapeutic strategy for melanoma

Melanoma or malignant melanocytes appear with the low incidence rate, but very high mortality rate worldwide. Epidemiological studies suggest that polyphenolic compounds contribute for prevention or treatment of several cancers particularly melanoma. Such findings motivate to dig out novel therapeutic strategies against melanoma, including research toward the development of new chemotherapeutic and biologic agents that can target the tumor cells by different mechanisms. Recently, it has been found that signal transducer and activator of transcription 3 (STAT3) is activated in many cancer cases surprisingly. Different evidences supply the aspect that STAT3 activation plays a vital role in the metastasis, including proliferation of cells, survival, invasion, migration, and angiogenesis. This significant feature plays a vital role in various cellular processes, such as cell proliferation and survival. Here, we reviewed the mechanisms of the STAT3 pathway regulation and their role in promoting melanoma. Also, we have evaluated the emerging data on polyphenols (PPs) specifically their contribution in melanoma therapies with an emphasis on their regulatory/inhibitory actions in relation to STAT3 pathway and current progress in the development of phytochemical therapeutic techniques. An understanding of targeting STAT3 by PPs brings an opportunity to melanoma therapy. © 2016 BioFactors, 43(3):347-370, 2017.

Development and evaluation of injectable nanosized drug delivery systems for apigenin

The purpose of this study was to develop different injectable nanosized drug delivery systems (NDDSs) i.e. liposome, lipid nanocapsule (LNC) and polymeric nanocapsule (PNC) encapsulating apigenin (AG) and compare their characteristics to identify the nanovector(s) that can deliver the largest quantity of AG while being biocompatible. Two liposomes with different surface characteristics (cationic and anionic), a LNC and a PNC were prepared. A novel tocopherol modified poly(ethylene glycol)-b-polyphosphate block-copolymer was used for the first time for the PNC preparation. The NDDSs were compared by their physicochemical characteristics, AG release, storage stability, stability in serum, complement consumption and toxicity against a human macrovascular endothelial cell line (EAhy926). The diameter and surface charge of the NDDSs were comparable with previously reported injectable nanocarriers. The NDDSs showed good encapsulation efficiency and drug loading. Moreover, the NDDSs were stable during storage and in fetal bovine serum for extended periods, showed low complement consumption and were non-toxic to EAhy926 cells up to high concentrations. Therefore, they can be considered as potential injectable nanocarriers of AG. Due to less pronounced burst effect and extended release characteristics, the nanocapsules could be favorable approaches for achieving prolonged pharmacological activity of AG using injectable NDDS.

Apigenin inhibits TNFα/IL-1α-induced CCL2 release through IKBK-epsilon signaling in MDA-MB-231 human breast cancer cells

Mortality associated with breast cancer is attributable to aggressive metastasis, to which TNFα plays a central orchestrating role. TNFα acts on breast tumor TNF receptors evoking the release of chemotactic proteins (e.g. MCP-1/CCL2). These proteins direct inward infiltration/migration of tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), myeloid-derived suppressor cells (MDSCs), T-regulatory cells (Tregs), T helper IL-17-producing cells (Th17s), metastasis-associated macrophages (MAMs) and cancer-associated fibroblasts (CAFs). Tumor embedded infiltrates collectively enable immune evasion, tumor growth, angiogenesis, and metastasis. In the current study, we investigate the potential of apigenin, a known anti-inflammatory constituent of parsley, to downregulate TNFα mediated release of chemokines from human triple-negative cells (MDA-MB-231 cells). The results show that TNFα stimulation leads to large rise of CCL2, granulocyte macrophage colony-stimulating factor (GMCSF), IL-1α and IL-6, all suppressed by apigenin. While many aspects of the transcriptome for NFkB signaling were evaluated, the data show signaling patterns associated with CCL2 were blocked by apigenin and mediated through suppressed mRNA and protein synthesis of IKBKe. Moreover, the data show that the attenuation of CCL2 by apigenin in the presence TNFα paralleled the suppression of phosphorylated extracellular signal-regulated kinase 1 (ERK 1/ 2). In summary, the obtained findings suggest that there exists a TNFα evoked release of CCL2 and other LSP recruiting cytokines from human breast cancer cells, which can be attenuated by apigenin.

Application of molecular imaging technology in evaluating the inhibiting effect of apigenin in vivo on subcutaneous hepatocellular carcinoma

The aim of this study was to evaluate the inhibiting effect of apigenin on liver cancer in vivo based on the optical molecular imaging method. Subcutaneous liver tumor models were established using respective 1 × 10⁶ firefly luciferase (fLuc) and green fluorescent protein (GFP) labeled human hepatocellular carcinoma cells (HepG2-fLuc and HepG2-GFP cells) in 20 BALB/c nude mice which were randomly divided into two groups, 10 in each group. After the tumor cells were implanted 15 days, apigenin was administered through intraperitoneal injection in group B, the other ten mice as control group A. Bioluminescence imaging (BLI) and fluorescence molecular imaging (FMI) were carried out for the follow-up of subcutaneous tumor model. As time goes on, intensity and distribution of bioluminescence and fluorescence of tumours increased gradually with the growth of tumours little by little. The whole process of observation was in accordance with known activities of HCC in the human liver. The tumor volume and tumor weight were significant lower in group B than in group A (p < 0.05), Subcutaneous tumours in the apigenin treatment group B based on BLI and FMI were significantly inhibited compared to the control group A (p < 0.05). Apigenin could be expected as a new drug to treat hepatocellular carcinoma. Optical molecular imaging technology enabled the non-invasive and reliable assessment of anti-tumor drug efficacy on liver cancer.

Apigenin suppresses the senescence-associated secretory phenotype and paracrine effects on breast cancer cells

Apigenin (4',5,7,-trihydroxyflavone) is a flavonoid found in certain herbs, fruits, and vegetables. Apigenin can attenuate inflammation, which is associated with many chronic diseases of aging. Senescent cells-stressed cells that accumulate with age in mammals-display a pro-inflammatory senescence-associated secretory phenotype (SASP) that can drive or exacerbate several age-related pathologies, including cancer. Flavonoids, including apigenin, were recently shown to reduce the SASP of a human fibroblast strain induced to senesce by bleomycin. Here, we confirm that apigenin suppresses the SASP in three human fibroblast strains induced to senesce by ionizing radiation, constitutive MAPK (mitogen-activated protein kinase) signaling, oncogenic RAS, or replicative exhaustion. Apigenin suppressed the SASP in part by suppressing IL-1α signaling through IRAK1 and IRAK4, p38-MAPK, and NF-κB. Apigenin was particularly potent at suppressing the expression and secretion of CXCL10 (IP10), a newly identified SASP factor. Further, apigenin-mediated suppression of the SASP substantially reduced the aggressive phenotype of human breast cancer cells, as determined by cell proliferation, extracellular matrix invasion, and epithelial-mesenchymal transition. Our results support the idea that apigenin is a promising natural product for reducing the impact of senescent cells on age-related diseases such as cancer.

The antiproliferative and apoptotic effects of apigenin on glioblastoma cells

OBJECTIVES

Glioblastoma (GBM) is highly proliferative, infiltrative, malignant and the most deadly form of brain tumour. The epidermal growth factor receptor (EGFR) is overexpressed, amplified and mutated in GBM and has been shown to play key and important roles in the proliferation, growth and survival of this tumour. The goal of our study was to investigate the antiproliferative, apoptotic and molecular effects of apigenin in GBM.

METHODS

Proliferation and viability tests were carried out using the trypan blue exclusion, MTT and lactate dehydrogenase (LDH) assays. Flow cytometry was used to examine the effects of apigenin on the cell cycle check-points. In addition, we determined the effects of apigenin on EGFR-mediated signalling pathways by Western blot analyses.

KEY FINDINGS

Our results showed that apigenin reduced cell viability and proliferation in a dose- and time-dependent manner while increasing cytotoxicity in GBM cells. Treatment with apigenin-induced is poly ADP-ribose polymerase (PARP) cleavage and caused cell cycle arrest at the G2M checkpoint. Furthermore, our data revealed that apigenin inhibited EGFR-mediated phosphorylation of mitogen-activated protein kinase (MAPK), AKT and mammalian target of rapamycin (mTOR) signalling pathways and attenuated the expression of Bcl-xL.

CONCLUSION

Our results demonstrated that apigenin has potent inhibitory effects on pathways involved in GBM proliferation and survival and could potentially be used as a therapeutic agent for GBM.

Apigenin-induced lysosomal degradation of β-catenin in Wnt/β-catenin signaling

The bioflavonoid apigenin has been shown to possess cancer-preventive and anti-cancer activities. In a drug screening, we found that apigenin can inhibit Wnt/β-catenin signaling, a pathway that participates in pivotal biological functions, which dis-regulation results in various human diseases including cancers. However, the underlying mechanism of apigenin in this pathway and its link to anti-cancer activities remain largely unknown. Here we showed that apigenin reduced the amount of total, cytoplasmic, and nuclear β-catenin, leading to the suppression in the β-catenin/TCF-mediated transcriptional activity, the expression of Wnt target genes, and cell proliferation of Wnt-stimulated P19 cells and Wnt-driven colorectal cancer cells. Western blotting and immunofluorescent staining analyses further revealed that apigenin could induce autophagy-mediated down-regulation of β-catenin in treated cells. Treatment with autophagy inhibitors wortmannin and chloroquine compromised this effect, substantiating the involvement of autophagy-lysosomal system on the degradation of β-catenin during Wnt signaling through inhibition of the AKT/mTOR signaling pathway. Our data not only pointed out a route for the inhibition of canonical Wnt signaling through the induction of autophagy-lysosomal degradation of key player β-catenin, but also suggested that apigenin or other treatments which can initiate this degradation event are potentially used for the therapy of Wnt-related diseases including cancers.

Potential Antitumor Activity and Apoptosis Induction of Glossostemon bruguieri Root Extract against Hepatocellular Carcinoma Cells

Glossostemon bruguieri (moghat) is used as a nutritive and demulcent drink. This study was performed to investigate the antiproliferative effects of moghat root extract (MRE) and its apoptotic mechanism in hepatocellular carcinoma (HCC) cells, HepG2 and Hep3B. MTT assay, morphological changes, apoptosis enzyme linked immunosorbent assay, caspase and apoptotic activation, flow cytometry, and immunoblot analysis were employed. The IC₅₀ of MRE for HepG2 (910 ± 6 μg/ml) and for Hep3B (1510 ± 5 μg/ml) induced significant growth-inhibitory effects against HCC cells, with no cytotoxic effect on normal hepatocytes. MRE treatment induced apoptotic effects to HepG2 cells in a caspase-dependent manner and via upregulating p53/p21 and PCNA. The upregulation of p21 was controlled by p53 expression in HepG2 but not in Hep3B despite upregulation of Bax protein in both cell lines. Interestingly, p21 may be a remarkable switch to G1 arrest in HepG2 cells, but not in Hep3B cells. In addition, Fas- and mitochondria-mediated pathways were found to be involved in MRE-induced apoptosis in Hep3B cells. The GC-MS analysis of MRE revealed two major constituents of pharmaceutical importance: the flavonoid apigenin (17.04%) and the terpenoid squalene (11.32%). The data presented in this paper introduces G. bruguieri as a promising nontoxic herb with therapeutic potential for HCC. To the authors' knowledge, the present study provides the first report on the anticancer activity of MRE on HCC cells.

Anti-oxidant and anti-inflammatory effects of apigenin in a rat model of sepsis: an immunological, biochemical, and histopathological study

OBJECTIVE

We hypothesize that apigenin may inhibit some cellular process of sepsis-induced spleen injury and simultaneously improve inflammation and oxidative stress. Therefore, the aim of this study was to investigate the potential protective effects of apigenin in a polymicrobial sepsis rat model of by cecal ligation and puncture.

MATERIALS AND METHODS

64 female Wistar albino rats were divided into 8 groups. The pro-inflammatory (tumor necrosis factor-alpha, interleukin-6, and interleukin-1-beta) and anti-inflammatory (tumor growth factor-beta and interleukin-10) cytokine levels were measured by enzyme-linked immunosorbent assay. CD3, CD68, and nuclear factor kappa B (NF-κB) positivity rates were detected by immunohistochemical methods. Oxidative stress parameters were measured by tissue biochemistry.

RESULTS

Sepsis caused a significant increase in TNF-alpha, IL-1-beta, IL-6, and TGF-beta levels whereas it reduced IL-10 level. Additionally, it led to an increase in CD3, CD68, and NF-κB positivity rates as well as oxidative stress parameters levels. However, apigenin inhibited the inflammation process, increased the IL-10 level and normalized the oxidative stress parameters.

DISCUSSION AND CONCLUSION

Pretreatment with apigenin results in a significant reduction in the amount of inflammatory cells. The beneficial effect of apigenin on spleen injury also involved inhibition of NF-κB pathway, suppression of proinflammatory cytokines, and induction of anti-inflammatory cytokine production. Additionally, it led to a decrease in oxidative stress in spleen tissue. Taking everything into account, apigenin may be an alternative therapeutic option for prevention of sepsis-induced organ.

Natural and Synthetic Flavonoids: Structure-Activity Relationship and Chemotherapeutic Potential for the Treatment of Leukemia

Flavonoids and their derivatives are polyphenolic secondary metabolites with an extensive spectrum of pharmacological activities, including antioxidants, antitumor, anti-inflammatory, and antiviral activities. These flavonoids can also act as chemopreventive agents by their interaction with different proteins and can play a vital role in chemotherapy, suggesting a positive correlation between a lower risk of cancer and a flavonoid-rich diet. These agents interfere with the main hallmarks of cancer by various individual mechanisms, such as inhibition of cell growth and proliferation by arresting the cell cycle, induction of apoptosis and differentiation, or a combination of these mechanisms. This review is an effort to highlight the therapeutic potential of natural and synthetic flavonoids as anticancer agents in leukemia treatment with respect to the structure-activity relationship (SAR) and their molecular mechanisms. Induction of cell death mechanisms, production of reactive oxygen species, and drug resistance mechanisms, including p-glycoprotein efflux, are among the best-described effects triggered by the flavonoid polyphenol family.

HLBT-100: a highly potent anti-cancer flavanone from Tillandsia recurvata (L.) L

BACKGROUND

The incidence and mortalities from cancers remain on the rise worldwide. Despite significant efforts to discover and develop novel anticancer agents, many cancers remain in the unmet need category. As such, efforts to discover and develop new and more effective and less toxic agents against cancer remain a top global priority. Our drug discovery approach is natural products based with a focus on plants. Tillandsia recurvata (L.) L. is one of the plants selected by our research team for further studies based on previous bioactivity findings on the anticancer activity of this plant.

METHODS

The plant biomass was extracted using supercritical fluid extraction technology with CO2 as the mobile phase. Bioactivity guided isolation was achieved by use of chromatographic technics combined with anti-proliferative assays to determine the active fraction and subsequently the pure compound. Following in house screening, the identified molecule was submitted to the US National Cancer Institute for screening on the NCI60 cell line panel using standard protocols. Effect of HLBT-100 on apoptosis, caspase 3/7, cell cycle and DNA fragmentation were assessed using standard protocols. Antiangiogenic activity was carried out using the ex vivo rat aortic ring assay.

RESULTS

A flavonoid of the flavanone class was isolated from T. recurvata (L.) L. with potent anticancer activity. The molecule was code named as HLBT-100 (also referred to as HLBT-001). The compound inhibited brain cancer (U87 MG), breast cancer (MDA-MB231), leukemia (MV4-11), melanoma (A375), and neuroblastoma (IMR-32) with IC50 concentrations of 0.054, 0.030, 0.024, 0.003 and 0.05 µM, respectively. The molecule also exhibited broad anticancer activity in the NCI60 panel inhibiting especially hematological, colon, CNS, melanoma, ovarian, breast and prostate cancers. Twenty-three of the NCI60 cell lines were inhibited with GI50 values <0.100 µM. In terms of potential mechanisms of action, the molecule demonstrated effect on the cell cycle as evidenced by the accumulation of cells with 

CONCLUSION

This paper describes for the first time the anticancer activity of HLBT-100 isolated from T. recurvate (L.) L. The broad and selective anticancer activity of HLBT-100 as evidenced by its potent activity against IMR-32, CNS cancer cell line while not active against neuro-2a, a normal CNS cell line. The activity demonstrated by HLBT-100 in these studies makes the molecule a potential candidate for further development targeting especially those cancers that remain in the unmet need category such as glioblastoma multiforme and acute myeloid leukemia in addition to other cancers.

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Key Words

• Angiogenesis
• Anticancer
• Ball Moss
• Flavanone
• Tillandsia recurvata

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Affiliation(s)

Henry I. C. Lowe Bio-Tech R&D Institute, University of the West Indies, 6 St. Johns Close, Mona, Jamaica Educational & Scientific LLC, 725 W Lombard St, Baltimore, MD 21201 USA Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA
Ngeh J. Toyang Educational & Scientific LLC, 725 W Lombard St, Baltimore, MD 21201 USA Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA
Charah T. Watson Bio-Tech R&D Institute, University of the West Indies, 6 St. Johns Close, Mona, Jamaica
Kenneth N. Ayeah Educational & Scientific LLC, 725 W Lombard St, Baltimore, MD 21201 USA Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA
Joseph Bryant Institute of Human Virology, University of Maryland School of Medicine, 725 W Lombard St, Baltimore, MD USA

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The estimation of the traditionally used yarrow (Achillea millefolium L. Asteraceae) oil extracts with anti-inflamatory potential in topical application

ETHNOPHARMACOLOGICAL RELEVANCE

Olive or sunflower oil yarrow extracts have been extensively used against inflammatory disorders and skin wound healing in traditional medicine.

AIM OF THE STUDY

To evaluate oil yarrow extracts traditional use in treatment of topical/dermatological skin impairments, sodium lauryl sulfate test was applied, and in vivo measuring of the biophysical parameters (erythema index, skin capacitance and the pH of the skin) in the artificially irritated skin was performed. As traditionally olive and sunflower oil have been used equally for extracts production, the experiment was carried out to investigate whether any of the oil extractants has the advantage over the other, and if the method of extraction might influence the desired activity. The observed activity has been connected to the chemical profile of the investigated extracts and their antioxidative properties.

MATERIALS AND METHODS

In vivo measurements were performed using the appropriate probes for measuring skin capacitance, pH of the skin and erythema index (EI). The designed experiment enabled the evaluation of the anti-inflammatory effects of a seven-day application of oil yarrow extracts known in traditional medicine, on artificially irritated skin of volunteers. The chemical profile for the investigated samples was achieved applying the HPLC and UHPLC-MS methods. Also, ferric reducing antioxidant power (FRAP) test was performed to assess the antioxidant properties of the investigated samples.

RESULTS

The application of tested oil extracts on artificially irritated skin in vivo demonstrated the ability to re-establish their optimal pH and hydration of skin to the values measured prior to the irritation. Considering the EI transition, the investigated samples succeeded in re-establishing the baseline values, with no significant difference after three- and seven-day application.

CONCLUSIONS

The data obtained in the study showed that the oil yarrow extracts had an evident anti-inflammatory property. Namely, the investigated extracts demonstrated significant anti-inflammatory effect in an in vivo double blind randomized study, using a sodium lauryl sulfate test. The skin parameters assessed in the study (skin capacitance, pH and EI) were restored to the basal values after three- and seven-day treatment with the tested extracts. The shown effects were attributed to yarrow oil extracts composition. The yarrow oil extracts might be used as promising base in the phytopreparations designed for dermatological application as anti-inflammatory agents with a positive impact on the skin pH and its moisture content.

Transcriptome-based repurposing of apigenin as a potential anti-fibrotic agent targeting hepatic stellate cells

We have used a computational approach to identify anti-fibrotic therapies by querying a transcriptome. A transcriptome signature of activated hepatic stellate cells (HSCs), the primary collagen-secreting cell in liver, and queried against a transcriptomic database that quantifies changes in gene expression in response to 1,309 FDA-approved drugs and bioactives (CMap). The flavonoid apigenin was among 9 top-ranked compounds predicted to have anti-fibrotic activity; indeed, apigenin dose-dependently reduced collagen I in the human HSC line, TWNT-4. To identify proteins mediating apigenin's effect, we next overlapped a 122-gene signature unique to HSCs with a list of 160 genes encoding proteins that are known to interact with apigenin, which identified C1QTNF2, encoding for Complement C1q tumor necrosis factor-related protein 2, a secreted adipocytokine with metabolic effects in liver. To validate its disease relevance, C1QTNF2 expression is reduced during hepatic stellate cell activation in culture and in a mouse model of alcoholic liver injury in vivo, and its expression correlates with better clinical outcomes in patients with hepatitis C cirrhosis (n = 216), suggesting it may have a protective role in cirrhosis progression.These findings reinforce the value of computational approaches to drug discovery for hepatic fibrosis, and identify C1QTNF2 as a potential mediator of apigenin's anti-fibrotic activity.

Patients on psychotropic medications and herbal supplement combinations: clinical considerations

Populations using herbs and herbal preparations are widespread and growing. As many herbal ingredients exert actions on psychotropic drug targets, psychiatrists should be well informed and aware of potential drug-drug interactions in clinical practice. Reliable and clinically useful information in this area, however, is fragmented, if not deficient. This paper reviewed the clinical aspects of herb-drug interactions, focusing in particular on the monoamine oxidase enzyme and P450 cytochrome enzyme-inhibitory properties of herbs and their potential interference with psychotropic drug actions and clinical judgement.

Apigenin inhibits proliferation and invasion, and induces apoptosis and cell cycle arrest in human melanoma cells

Malignant melanoma is the most invasive and fatal form of cutaneous cancer. Moreover it is extremely resistant to conventional chemotherapy and radiotherapy. Apigenin, a non-mutagenic flavonoid, has been found to exhibit chemopreventive and/or anticancerogenic properties in many different types of human cancer cells. Therefore, apigenin may have particular relevance for development as a chemotherapeutic agent for cancer treatment. In the present study, we investigated the effects of apigenin on the viability, migration and invasion potential, dendrite morphology, cell cycle distribution, apoptosis, phosphorylation of the extracellular signal-regulated protein kinase (ERK) and the AKT/mTOR signaling pathway in human melanoma A375 and C8161 cell lines in vitro. Apigenin effectively suppressed the proliferation of melanoma cells in vitro. Moreover, it inhibited cell migration and invasion, lengthened the dendrites, and induced G2/M phase arrest and apoptosis. Furthermore, apigenin promoted the activation of cleaved caspase-3 and cleaved PARP proteins and decreased the expression of phosphorylated (p)‑ERK1/2 proteins, p-AKT and p-mTOR. Consequently, apigenin is a novel therapeutic candidate for melanoma.

Apigenin alleviates STZ-induced diabetic cardiomyopathy

Apigenin is an important component of fruits and vegetables in human daily diets. Several cellular and animal models have been performed to demonstrate its anti-oxidant and anti-inflammatory bioactivities. However, the cardioprotective effects of apigenin in diabetic cardiomyopathy (DCM) remain unclear. In this study, we intended to explore the roles of apigenin in cardiac remodeling of DCM. Male C57BL/6 J mice were treated with streptozotocin (STZ, 50 mg/kg) for 5 consecutive days to induce DCM. The echocardiography and catheter-based measurements of hemodynamic parameters were performed to evaluate the cardiac function. Paraffin slices of harvested hearts were prepared for histological pathological analysis and TUNEL assay. Oxidative assay kits were used to detect Glutathione Peroxidase (GPx), Lipid Peroxidation Malondialdehyde (MDA), and Superoxide Dismutase (SOD). Western blot and real-time PCR were used for accessing the expressions of protein and mRNA. Diabetes mellitus exacerbated the cardiac dysfunction, fibrosis, and overaccumulation of 4-hydroxynonenal accompanying with down-regulation of Bcl2, GPx, and SOD, up-regulation of MDA, cleaved caspase3, and pro-apoptotic protein Bax, and contribution to the translocation of NF-κB. All these pathological changes could be effectively blunted by treatment of apigenin in vivo. Finally, H9c2 treated with high glucose or apigenin was used for further investigation of these effects in vitro; what is more, we also compared the effects between apigenin and Resveratrol in in vitro experiments. Our experiments have demonstrated that apigenin may be a potential drug for diabetic patients suffering from DCM.

Inhibition of MDA-MB-231 breast cancer cell proliferation and tumor growth by apigenin through induction of G2/M arrest and histone H3 acetylation-mediated p21WAF1/CIP1 expression

Apigenin (4',5,7-trihydroxyflavone), a flavonoid commonly found in fruits and vegetables, has anticancer properties in various malignant cancer cells. However, the molecular basis of the anticancer effect remains to be elucidated. In this study, we investigated the cellular mechanisms underlying the induction of cell cycle arrest by apigenin. Our results showed that apigenin at the nonapoptotic induction concentration inhibited cell proliferation and induced cell cycle arrest at the G2/M phase in the MDA-MB-231 breast cancer cell line. Immunoblot analysis indicated that apigenin suppressed the expression of cyclin A, cyclin B, and cyclin-dependent kinase-1 (CDK1), which control the G2-to-M phase transition in the cell cycle. In addition, apigenin upregulated p21^WAF1/CIP1 and increased the interaction of p21^WAF1/CIP1 with proliferating cell nuclear antigen (PCNA), which inhibits cell cycle progression. Furthermore, apigenin significantly inhibited histone deacetylase (HDAC) activity and induced histone H3 acetylation. The subsequent chromatin immunoprecipitation (ChIP) assay indicated that apigenin increased acetylation of histone H3 in the p21^WAF1/CIP1 promoter region, resulting in the increase of p21^WAF1/CIP1 transcription. In a tumor xenograft model, apigenin effectively delayed tumor growth. In these apigenin-treated tumors, we also observed reductions in the levels of cyclin A and cyclin B and increases in the levels of p21^WAF1/CIP1 and acetylated histone H3. These findings demonstrate for the first time that apigenin can be used in breast cancer prevention and treatment through epigenetic regulation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 434-444, 2017.

Integrated genomics-based mapping reveals the genetics underlying maize flavonoid biosynthesis

BACKGROUND

Flavonoids constitute a diverse class of secondary metabolites which exhibit potent bioactivities for human health and have been indicated to play an important role in plant development and defense. However, accumulation and variation of flavonoid content in diverse maize lines and the genes responsible for their biosynthesis in this important crop remain largely unknown. In this study, we combine genetic mapping, metabolite profiling and gene regulatory network analysis to further enhance understanding of the maize flavonoid pathway.

RESULTS

We repeatedly detected 25 QTL corresponding to 23 distinct flavonoids across different environments or populations. In addition, a total of 39 genes were revealed both by an expression based network analysis and genetic mapping. Finally, the function of three candidate genes, including two UDP-glycosyltransferases (UGT) and an oxygenase which belongs to the flavone synthase super family, was revealed via preliminary molecular functional characterization.

CONCLUSION

We explored the genetic influences on the flavonoid biosynthesis based on integrating the genomic, transcriptomic and metabolomic information which provided a rich source of potential candidate genes. The integrated genomics based genetic mapping strategy is highly efficient for defining the complexity of functional genetic variants and their respective regulatory networks as well as in helping to select candidate genes and allelic variance before embarking on laborious transgenic validations.

Anti-inflammatory effect of apigenin and hydroalcoholic extract of Dracocephalum kotschyi on acetic acid-induced colitis in rats

Colitis is an inflammatory disease of the intestine with unknown etiology involving multiple immune, genetic, and environmental factors. We were interested to examine the effect of total extract from Dracocephalum kotschyi (D. kotschyi) Boiss. on the experimental colitis. D. kotschyi hydroalcoholic extract (10, 20, and 40 mg/kg) or apigenin (5, 10, and 20 mg/kg) were administered orally 2 h prior to induction of colitis which was induced by intrarectal administration of acetic acid (4%) in rats. Prednisolone (4 m/kg) was used as the standard drug for comparison. Biochemical evaluation of inflamed colon was performed by measuring myeloperoxidase (MPO) activity. After 5 days treatment, mucosal ulceration was evaluated. Intrarectal instillation of acetic acid caused significant inflammatory reactions as indicated by macroscopic and microscopic changes. The activity of MPO increased in vehicle treated groups while recovered to normal level by pretreatment of animals with D. kotschyi extract, apigenin, or prednisolone. D. kotschyi and apigenin-treated groups showed significantly lower score values of macroscopic and microscopic characters when compared with the vehicle-treated negative control group. The beneficial effect of apigenin was comparable with that of prednisolone. This research has shown the anti-inflammatory potential of D. kotschyi extract and apigenin in experimentally induced colitis.

Enhanced chemotherapeutic efficacy of apigenin liposomes in colorectal cancer based on flavone-membrane interactions

Recent endeavors in exploiting vast array of natural phytochemicals to ameliorate colorectal cancer led us to investigate apigenin, a naturally occurring dietary flavone as a potential chemo-therapeutic agent. The present study focuses on establishing apigenin as a potential chemotherapeutic agent for alleviating colorectal cancer and reports the development of a stable liposomal nanocarrier with high encapsulation of the hydrophobic flavone apigenin for enhanced chemotherapeutic effects. The enhanced pharmacological activity of apigenin has been assigned to its ability to interact and subsequently influence membrane properties which also resulted in optimal yield of a stable, rigidified, non-leaky nano-carrier with ideal release kinetics. Extensive testing of drug and its liposomal counterpart for potential clinical chemotherapeutic applications yielded hemocompatibility and cytocompatibility with normal fibroblast cells while enhanced antineoplastic activity was observed in tumor xenograft model. The increased chemotherapeutic potential of liposomal apigenin highlights the clinical potential of apigenin-based vesicles.

Apigenin enhances the cisplatin cytotoxic effect through p53-modulated apoptosis

Epidemiological and experimental evidence suggests that dietary flavonoids, including apigenin, have anticancer roles. Apigenin has been reported to elevate p53, a critical molecule in the induction of apoptosis. The present study aimed to investigate whether apigenin, a dietary flavonoid, improves the cytotoxic effect of cisplatin in a cancer cell culture system, and to elucidate the mechanism of this effect. Multiple tumor cell types were treated with apigenin, cisplatin or both drugs. Cell viability was evaluated, and the cytotoxic effect was determined biochemically and microscopically. Treatment with apigenin increased cisplatin-induced DNA damage and the apoptosis of tumor cells in a p53-dependent manner. Apigenin, when used with cisplatin, inhibited cell proliferation and promoted mitogen-activated protein kinase activation and subsequent p53 phosphorylation, leading to p53 accumulation and upregulation of proapoptotic proteins. Cisplatin is one of the most commonly used chemotherapeutic drugs for malignant tumors, but resistance to this drug occurs. The current results therefore demonstrate that dietary flavonoids may diminish the resistance of cancers to cisplatin.

Formulation and characterization of an apigenin-phospholipid phytosome (APLC) for improved solubility, in vivo bioavailability, and antioxidant potential

The apigenin-phospholipid phytosome (APLC) was developed to improve the aqueous solubility, dissolution, in vivo bioavailability, and antioxidant activity of apigenin. The APLC synthesis was guided by a full factorial design strategy, incorporating specific formulation and process variables to deliver an optimized product. The design-optimized formulation was assayed for aqueous solubility, in vitro dissolution, pharmacokinetics, and antioxidant activity. The pharmacological evaluation was carried out by assessing its effects on carbon tetrachloride-induced elevation of liver function marker enzymes in a rat model. The antioxidant activity was assessed by studying its effects on the liver antioxidant marker enzymes. The developed model was validated using the design-optimized levels of formulation and process variables. The physical-chemical characterization confirmed the formation of phytosomes. The optimized formulation demonstrated over 36-fold higher aqueous solubility of apigenin, compared to that of pure apigenin. The formulation also exhibited a significantly higher rate and extent of apigenin release in dissolution studies. The pharmacokinetic analysis revealed a significant enhancement in the oral bioavailability of apigenin from the prepared formulation, compared to pure apigenin. The liver function tests indicated that the prepared phytosome showed a significantly improved restoration of all carbon tetrachloride-elevated rat liver function marker enzymes. The prepared formulation also exhibited antioxidant potential by significantly increasing the levels of glutathione, superoxide dismutase, catalase, and decreasing the levels of lipid peroxidase. The study shows that phospholipid-based phytosome is a promising and viable strategy for improving the delivery of apigenin and similar phytoconstituents with low aqueous solubility.

Inhibition of Human Monoamine Oxidase: Biological and Molecular Modeling Studies on Selected Natural Flavonoids

Naturally occurring flavonoids display a plethora of different biological activities, but emerging evidence suggests that this class of compounds may also act as antidepressant agents endowed with multiple mechanisms of action in the central nervous system, increasing central neurotransmission, limiting the reabsorption of bioamines by synaptosomes, and modulating the neuroendocrine and GABA_A systems. Due to their presence in foods, food-derived products, and nutraceuticals, we established their role and structure-activity relationships as reversible and competitive human monoamine oxidase (MAO) inhibitors. In addition, molecular modeling studies, which evaluated their modes of MAO inhibition, are presented. These findings could provide pivotal implications in the quest of novel drug-like compounds and for the establishment of harmful drug-dietary supplement interactions commonly reported in the therapy with antidepressant agents.

Fluorescence lifetime imaging with time-gated detection of hyaluronidase using a long lifetime azadioxatriangulenium (ADOTA) fluorophore

A fluorescence lifetime imaging probe with a long lifetime was used in combination with time-gating for the detection of hyaluronidase using hyaluronic acid as the probe template. This probe was developed by heavily labeling hyaluronic acid with long lifetime azadioxatriangulenium fluorophores (ADOTA). We used this probe to image hyaluronidase produced by DU-145 prostate cancer cells.

Natural products against cancer angiogenesis

The process of angiogenesis is quite well-known nowadays. Some medicines and extracts affecting this process are already used routinely in supporting the conventional treatment of many diseases that are considered angiogenic such as cancer. However, we must be aware that the area of currently used drugs of this type is much narrower than the theoretical possibilities existing in therapeutic angiogenesis. Plant substances are a large and diverse group of compounds that are found naturally in fruits, vegetables, spices, and medicinal plants. They also have different anticancer properties. The aim of this literature review article is to present the current state of knowledge concerning the molecular targets of tumor angiogenesis and the active substances (polyphenols, alkaloids, phytohormones, carbohydrates, and terpenes) derived from natural sources, whose activity against cancer angiogenesis has been confirmed.