Ellagic acid checks lymphoma promotion via regulation of PKC signaling pathway

Potential of Plant-Derived Compounds in Preventing and Reversing Organ Fibrosis and the Underlying Mechanisms

Increased production of extracellular matrix is a necessary response to tissue damage and stress. In a normal healing process, the increase in extracellular matrix is transient. In some instances; however, the increase in extracellular matrix can persist as fibrosis, leading to deleterious alterations in organ structure, biomechanical properties, and function. Indeed, fibrosis is now appreciated to be an important cause of mortality and morbidity. Extensive research has illustrated that fibrosis can be slowed, arrested or even reversed; however, few drugs have been approved specifically for anti-fibrotic treatment. This is in part due to the complex pathways responsible for fibrogenesis and the undesirable side effects of drugs targeting these pathways. Natural products have been utilized for thousands of years as a major component of traditional medicine and currently account for almost one-third of drugs used clinically worldwide. A variety of plant-derived compounds have been demonstrated to have preventative or even reversal effects on fibrosis. This review will discuss the effects and the underlying mechanisms of some of the major plant-derived compounds that have been identified to impact fibrosis.

Ellagic Acid and Cancer Hallmarks: Insights from Experimental Evidence

Cancer is a complex and multifaceted disease with a high global incidence and mortality rate. Although cancer therapy has evolved significantly over the years, numerous challenges persist on the path to effectively combating this multifaceted disease. Natural compounds derived from plants, fungi, or marine organisms have garnered considerable attention as potential therapeutic agents in the field of cancer research. Ellagic acid (EA), a natural polyphenolic compound found in various fruits and nuts, has emerged as a potential cancer prevention and treatment agent. This review summarizes the experimental evidence supporting the role of EA in targeting key hallmarks of cancer, including proliferation, angiogenesis, apoptosis evasion, immune evasion, inflammation, genomic instability, and more. We discuss the molecular mechanisms by which EA modulates signaling pathways and molecular targets involved in these cancer hallmarks, based on in vitro and in vivo studies. The multifaceted actions of EA make it a promising candidate for cancer prevention and therapy. Understanding its impact on cancer biology can pave the way for developing novel strategies to combat this complex disease.

The effect of ellagic acid on the metabolic syndrome: A review article

Objective

(s): Metabolic syndrome is a collection of metabolic abnormalities that includes hyperglycemia, dyslipidemia, hypertension, and obesity. Ellagic acid is found in various fruits and vegetables. It has been reported to have several pharmacological properties, such as antibacterial, antifungal, antiviral, anti-inflammatory, hepatoprotective, cardioprotective, chemopreventive, neuroprotective, gastroprotective, and antidiabetic. Our current study aims to shed light on the probable efficiency of ellagic acid in managing metabolic syndrome and its complications.

Materials and methods

To prepare the present review, the databases or search engines utilized included Scopus, PubMed, Science Direct, and Google Scholar, and relevant articles have been gathered with no time limit until March 2023.

Results

Several investigations indicated that ellagic acid could be a potent compound for the treatment of many disorders such as diabetes, hypertension, and hyperlipidemia by various mechanisms, including increasing insulin secretion, insulin receptor substrate protein 1 expression, regulating glucose transporter 4, triglyceride, total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), attenuating tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), reactive oxygen species (ROS), malondialdehyde (MDA), and oxidative stress in related tissues. Furthermore, ellagic acid ameliorates mitochondrial function, upregulates uncoupling protein 1 (found in brown and white adipose tissues), and regulates blood levels of nitrate/nitrite and vascular relaxations in response to acetylcholine and sodium nitroprusside.

Conclusion

Ellagic acid can treat or manage metabolic syndrome and associated complications, according to earlier studies. To validate the beneficial effects of ellagic acid on metabolic syndrome, additional preclinical and clinical research is necessary.

The multifaceted mechanisms of ellagic acid in the treatment of tumors: State-of-the-art

Ellagic acid (EA) is a kind of polyphenol compound extracted from a variety of herbs, such as paeoniae paeoniae, raspberry, Chebule, walnut kernel, myrrh, loquat leaf, pomegranate bark, quisquite, and fairy herb. It has anti-tumor, anti-oxidation, anti-inflammatory, anti-mutation, anti-bacterial, anti-allergic and multiple pharmacological properties. Studies have shown its anti-tumor effect in gastric cancer, liver cancer, pancreatic cancer, breast cancer, colorectal cancer, lung cancer and other malignant tumors, mainly through inducing tumor cell apoptosis, inhibiting tumor cell proliferation, inhibiting tumor cell metastasis and invasion, inducing autophagy, affecting tumor metabolic reprogramming and other forms of anti-tumor efficacy. Its molecular mechanism is mainly reflected in inhibiting the proliferation of tumor cells through VEGFR-2 signaling pathway, Notch signaling pathway, PKC signaling pathway and COX-2 signaling pathway. PI3K/Akt signaling pathway, JNK (cJun) signaling pathway, mitochondrial pathway, Bcl-2 / Bax signaling pathway, TGF-β/Smad3 signaling pathway induced apoptosis of tumor cells and blocked EMT process and MMP SDF1α/CXCR4 signaling pathway inhibits the metastasis and invasion of tumor cells, induces autophagy and affects tumor metabolic reprogramming to produce anti-tumor effects. At present, the analysis of the anti-tumor mechanism of ellagic acid is slightly lacking, so this study comprehensively searched the literature on the anti-tumor mechanism of ellagic acid in various databases, reviewed the research progress of the anti-tumor effect and mechanism of ellagic acid, in order to provide reference and theoretical basis for the further development and application of ellagic acid.

Synergism of ellagic acid in combination with radiotherapy and chemotherapy for cancer treatment

BACKGROUND

Ellagic acid (EA) is a polyphenol compound abundant in berries, walnuts, pecans, pomegranate, cranberries, and other plant foods and exerts a wide array of biological properties. In particular, EA has received considerable research attention in anti-cancer therapy. EA administered alone has been shown to exert effects against human cancers through multiple pathways. In addition, EA may increase tumor sensitivity to chemotherapy and radiotherapy. Namely, EA combination with a relatively low dosage of therapeutic drugs or optimized radiation dose could improve the treatment outcome. More importantly, EA could counteract chemotherapy-related adverse reactions.

PURPOSE

This review aims to summarize the in vitro and in vivo experimental evidence of synergism of EA in radiotherapy/chemotherapy for the treatment of cancers. In addition, the preventive effect of EA to counteract chemotherapy-induced toxicity is also discussed.

METHODS

The searches were performed in the PubMed, Web of Science and Google scholar and introduced the information about the role of EA in cancer treatment.

RESULTS

EA exhibits synergistic effects in radiotherapy/chemotherapy for the treatment of cancers and exerts a great potential in reducing the side effects of chemotherapy and radiotherapy due to its biological activities, such as antioxidant and anti-inflammatory activities.

CONCLUSION

EA could be a promising drug adjuvant for cancer treatment. In the near future, novel strategies for EA delivery systems that overcome the low EA solubility and bioavailability should be studied further to fully exploit the therapeutic potential of EA.

Current insights into epigenetics, noncoding RNA interactome and clinical pharmacokinetics of dietary polyphenols in cancer chemoprevention

Several studies have reported the health-beneficial effects of dietary phytochemicals, namely polyphenols, to prevent various diseases, including cancer. Polyphenols, like (-)-epigallocatechin-3-gallate (EGCG) from green tea, curcumin from turmeric, and ellagic acid from pomegranate are known to act by modulating antioxidant, anti-inflammatory and apoptotic signal transduction pathways in the tumor milieu. The evolving literature underscores the role of epigenetic regulation of genes associated with cancer by these polyphenols, primarily via non-coding RNAs (ncRNAs), such as microRNAs (miRNA) and long noncoding RNA (lncRNA). However, there is little clarity on the exact role(s) played by these ncRNAs and their interactions with other ncRNAs, or with their protein targets, in response to modulation by these dietary polyphenols. Here, we review ncRNA interactions and functional networks of the complex ncRNA interactome with their targets in preclinical studies along with the role of epigenetics as well as key aspects of pharmacokinetics and phytochemistry of dietary polyphenols. We also summarize the current state of clinical trials with these dietary polyphenols. Taken together, this synthetic review provides insights into the molecular aspects underlying the anticancer chemopreventive effects of dietary polyphenols as well as summarizes data on novel biomarkers modulated by these polyphenols for preventive or therapeutic purposes in various types of cancer.

Putative role of natural products as Protein Kinase C modulator in different disease conditions

INTRODUCTION

Protein kinase C (PKC) is a promising drug target for various therapeutic areas. Natural products derived from plants, animals, microorganisms, and marine organisms have been used by humans as medicine from prehistoric times. Recently, several compounds derived from plants have been found to modulate PKC activities through competitive binding with ATP binding site, and other allosteric regions of PKC. As a result fresh race has been started in academia and pharmaceutical companies to develop an effective naturally derived small-molecule inhibitor to target PKC activities. Herein, in this review, we have discussed several natural products and their derivatives, which are reported to have an impact on PKC signaling cascade.

METHODS

All information presented in this review article regarding the regulation of PKC by natural products has been acquired by a systematic search of various electronic databases, including ScienceDirect, Scopus, Google Scholar, Web of science, ResearchGate, and PubMed. The keywords PKC, natural products, curcumin, rottlerin, quercetin, ellagic acid, epigallocatechin-3 gallate, ingenol 3 angelate, resveratrol, protocatechuic acid, tannic acid, PKC modulators from marine organism, bryostatin, staurosporine, midostaurin, sangivamycin, and other relevant key words were explored.

RESULTS

The natural products and their derivatives including curcumin, rottlerin, quercetin, ellagic acid, epigallocatechin-3 gallate, ingenol 3 angelate, resveratrol, bryostatin, staurosporine, and midostaurin play a major role in the management of PKC activity during various disease progression.

CONCLUSION

Based on the comprehensive literature survey, it could be concluded that various natural products can regulate PKC activity during disease progression. However, extensive research is needed to circumvent the challenge of isoform specific regulation of PKC by natural products.

Achyranthes aspera L. leaf extract induced anticancer effects on Dalton's Lymphoma via regulation of PKCα signaling pathway and mitochondrial apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Epidemiological studies promote the inclusion of natural-products in diet due to their inhibitory effects on various types of cancer. Among them, Achyranthes aspera L. (Family Amaranthaceae) is a medicinal plant in Ayurvedic pharmacopeia, found in India, Southeast Asia, America, and Sub-Saharan Africa. It is endowed with anti-inflammatory, anti-oxidant, and anti-cancer activities. However, its potential effect on Non-Hodgkin lymphomas (NHLs), has not yet been clarified.

AIM OF THE STUDY

In the present study, we aimed to investigate the effect of Achyranthes aspera L. leaf extracts on highly aggressive murine NHL called Dalton's Lymphoma (DL) in vitro and in vivo.

MATERIAL AND METHODS

GC-HRMS analysis was carried out for the identification of compounds present in A. aspera leaf extract. The cytotoxicity of various A. aspera leaf extracts was evaluated on DL cells by MTT assay. Chromatin condensation, nuclear fragmentation, and morphological changes were observed by microscopy technique. Flow cytometry was used to measure the changes in mitochondrial membrane potential (ΔΨm) and apoptosis. In addition, the expressions of apoptosis-related proteins were detected by western blotting. Meanwhile, the in vivo anti-tumor effect of leaf extract was tested in DL induced Balb/c mice.

RESULT

GC-HRMS analysis of A. aspera methanolic leaf extract (AAML) revealed the presence of ten pharmacologically active compounds. The results showed that AAML suppressed cell proliferation, decreased mitochondrial membrane potential, changed the morphological structure, and induced apoptosis. Moreover, AAML could promote the release of cytochrome c by regulating Bcl-2 family proteins and then activated caspase-9/ -3 to triggered cell apoptosis. At the same time in DL cells treated with AAML, the protein kinase Cα (PKCα) pathway was inhibited in a concentration-dependent manner. Remarkably, in vivo, AAML mediated suppression of DL growth in Balb/c mice was accompanied by attenuation of the PKCα pathway and induction of apoptosis. Our result suggested that AAML promotes mitochondrial apoptotic cascade in DL cells by suppressing the PKCα signaling pathway.

CONCLUSION

The study suggests that AAML could potently suppress DL progression by promoting apoptosis via mitochondrial-cascade and attenuation of the PKCα signaling pathway.

Transcriptome analysis of signaling pathways targeted by Ellagic acid in hepatocellular carcinoma cells

BACKGROUND

Ellagic acid (EA) possesses prominent inhibitory activities against various cancers, including hepatocellular carcinoma (HCC). Our recent study demonstrated EA's activities in reducing HCC cell proliferation and tumor formation. However, the mechanisms of EA to exert its anticancer activities and its primary targets in cancer cells have not been systematically explored.

METHODS

Cell proliferation assay and flow cytometric analysis were used to examine the effects of EA treatment on viability and apoptosis, respectively, of HepG2 cells. RNA-seq studies and associated pathway analyses by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were employed to determine EA's primary targets. Differentially expressed genes (DEG) in EA-treated HepG2 cells were verified by RT-qPCR and Western blot. Integrative analyses of the RNA-seq dataset with a TCGA dataset derived from HCC patients were conducted to verify EA-targeted genes and signaling pathways. Interaction network analysis of the DEGs, shRNA-mediated knockdown, cell viability assay, and colony formation assay were used to validate EA's primary targets.

RESULTS

EA reduced cell viability, caused DNA damage, and induced cell cycle arrest at G1 phase of HepG2 cells. We identified 5765 DEGs encoding proteins with over 2.0-fold changes in EA-treated HepG2 cells by DESeq2. These DEGs showed significant enrichment in the pathways regulating DNA replication and cell cycle progression. As primary targets, p21 was significantly upregulated, while MCM2-7 were uniformly downregulated in response to EA treatment. Consistently, p21 knockdown desensitized liver cells to EA in cell viability and colony formation assays.

CONCLUSION

EA induced G1 phase arrest and promoted apoptosis of HCC cells through activating the p21 gene and downregulating the MCM2-7 genes, respectively.

GENERAL SIGNIFICANCE

The discoveries in this study provide helpful insights into developing novel strategies in the therapeutic treatment of HCC patients.

Role of ellagic acid for the prevention and treatment of liver diseases

Globally, one of the alarming problems is the prevalence and burden of liver diseases, which accounts for 2 million cases per year. Chronic liver aetiologies such as hepatitis infections, alcoholic or non-alcoholic liver disease, environmental agents, and drug-induced toxicity are invariably responsible for liver fibrosis progression to finally hepatocellular carcinoma. Current treatment options are unable to overwhelm and cure liver diseases. Emerging findings suggest researchers' interest in using evidence-based complementary medicine such as ellagic acid with extensive pharmacological properties. They include antioxidant, anti-inflammatory, anti-hyperlipidaemic, anti-viral, anti-angiogenic, and anticancer activity. The molecular functions elicited by ellagic acid include scavenging of free radicals, regulation of lipid metabolism, the prohibition of fibrogenesis response-mediating proteins, inhibits hepatic stellate cells and myofibroblasts, restrains hepatic viral replication, facilitates suppression of growth factors, regulates transcription factors, proinflammatory cytokines, augments the liver immune response, fosters apoptosis and inhibits cell proliferation in tumorigenic cells. This review will most notably focus on preclinical and clinical information based on currently available evidence to warrant ellagic acid's prospective role in preventing liver diseases.

Ellagic acid and human cancers: a systems pharmacology and docking study to identify principal hub genes and main mechanisms of action

Research on anticancer properties of natural compounds, as effective materials that are available while causing minimal side effects, is growing. Ellagic acid (EA) is a well-known polyphenolic compound, which has been found in both free and complex modes in several medicinal plants such as pomegranate, walnut, and berries. Although many articles have reported anticancer properties for this compound, its mechanism of action has not been fully elucidated. In this study, we used several online and offline bioinformatics tools and databases to identify the mechanism of action of EA on various types of human malignancies including bladder, blood, breast, cervical, colorectal, liver, pancreas, and prostate cancers. In this context, after identifying and extracting EA-affected human genes/proteins that have been reported in various references, we built the related gene networks and determined functional hub genes. In addition, docking was performed to recognize target proteins that react directly with EA and are in fact most affected by this compound. Our findings revealed that EA exerts its anticancer effects by influencing specific hub genes in various types of cancers. Moreover, different cellular signaling pathways are affected by this natural compound. Generally, it turned out that EA probably exerts most of its anticancer activities, through induction of apoptosis, as well as P53 and WNT signaling pathways, and also by affecting the expression of several hub genes such as CDKN1A, CDK4, CDK2, CDK6, TP53, JUN, CCNA2, MAPK14, CDK1, and CCNB1 and especially interactions with some related proteins including P53, CDK6, and MAPK14.

Ellagic acid in suppressing in vivo and in vitro oxidative stresses

Oxidative stress is a biological condition produced by a variety of factors, causing several chronic diseases. Oxidative stress was, therefore, treated with natural antioxidants, such as ellagic acid (EA). EA has a major role in protecting against different diseases associated with oxidative stress. This review critically discussed the antioxidant role of EA in biological systems. The in vitro and in vivo studies have confirmed the protective role of EA in suppressing oxidative stress. The review also discussed the mechanism of EA in suppressing of oxidative stress, which showed that EA activates specific endogenous antioxidant enzymes and suppresses specific genes responsible for inflammation, diseases, or disturbance of biochemical systems. The amount of EA used and duration, which plays a significant role in the treatment of oxidative stress has been discussed. In conclusion, EA is a strong natural antioxidant, which possesses the suppressing power of oxidative stress in biological systems.

Lipopolysaccharide stimulates endogenous β-glucuronidase via PKC/NF-κB/c-myc signaling cascade: a possible factor in hepatolithiasis formation

Hepatolithiasis is commonly encountered in Southeastern and Eastern Asian countries, but the pathogenesis mechanism of stone formation is still not well understood. Now, the role of endogenous β-glucuronidase in pigment stones formation is being gradually recognized. In this study, the mechanism of increased expression and secretion of endogenous β-glucuronidase during hepatolithiasis formation was investigated. We assessed the endogenous β-glucuronidase, c-myc, p-p65, and p-PKC expression in liver specimens with hepatolithiasis by immunohistochemical staining, and found that compared with that in normal liver samples, the expression of endogenous β-glucuronidase, c-myc, p-p65, and p-PKC in liver specimens with hepatolithiasis significantly increased, and their expressions were positively correlated with each other. Lipopolysaccharide (LPS) induced increased expression of endogenous β-glucuronidase and c-myc in hepatocytes and intrahepatic biliary epithelial cells in a dose- and time-dependent manner, and endogenous β-glucuronidase secretion increased, correspondingly. C-myc siRNA transfection effectively inhibited the LPS-induced expression of endogenous β-glucuronidase. Furthermore, NF-κB inhibitor pyrrolidine dithiocarbamate or PKC inhibitor chelerythrine could effectively inhibit the LPS-induced expression of c-myc and endogenous β-glucuronidase, and the expression of p-p65 was also partly inhibited by chelerythrine. Our clinical observations and experimental data indicate that LPS could induce the increased expression and secretion of endogenous β-glucuronidase via a signaling cascade of PKC/NF-κB/c-myc in hepatocytes and intrahepatic biliary epithelial cells, and endogenous β-glucuronidase might play a possible role in the formation of hepatolithiasis.

High glucose/lysophosphatidylcholine levels stimulate extracellular matrix deposition in diabetic nephropathy via platelet‑activating factor receptor

Platelet-activating factor (PAF), protein kinase C (PKC)βI, transforming growth factor (TGF)-β1 and aberrant extracellular matrix (ECM) deposition have been associated with diabetic nephropathy (DN). However, the mechanistic basis underlying this association remains to be elucidated. The present study investigated the association among the aforementioned factors in a DN model consisting of human mesangial cells (HMCs) exposed to high glucose (HG) and lysophosphatidylcholine (LPC) treatments. HMCs were divided into the following treatment groups: Control; PAF; PAF+PKCβI inhibitor LY333531; HG + LPC; PAF + HG + LPC; and PAF + HG + LPC + LY333531. Cells were cultured for 24 h, and PKCβI and TGF-β1 expression was determined using the reverse transcription-quantitative polymerase chain reaction and western blotting. The expression levels of the ECM-associated molecules collagen IV and fibronectin in the supernatant were detected using ELISA analysis. Subcellular localization of PKCβI was assessed using immunocytochemistry. PKCβI and TGF-β1 expression was increased in the PAF + HG + LPC group compared with the other groups (P<0.05); however, this effect was abolished in the presence of LY333531 (P<0.05). Supernatant fibronectin and collagen IV levels were increased in the PAF + HG + LPC group compared with the others (P<0.05); this was reversed by treatment with LY333531 (P<0.05). In cells treated with PAF, HG and LPC, PKCβI was translocated from the cytosol to the nucleus, an effect which was blocked when PKCβI expression was inhibited (P<0.05). The findings of the present study demonstrated that PAF stimulated ECM deposition in HMCs via activation of the PKC-TGF-β1 axis in a DN model.

Multiple effects of ellagic acid on human colorectal carcinoma cells identified by gene expression profile analysis

Colorectal carcinoma (CRC) is the third most commonly diagnosed cancer in the world. Phytochemicals have become a research hotspot in recent years as cancer prevention and treatment agents due to their low toxicity and limited side-effects. Ellagic acid (EA), a natural phenolic constituent, displays various biological activities, including anticancer effects. However, the detailed anticancer mechanisms of EA remain unclear. In the present study, we found that EA inhibited the growth of HCT-116 colon cancer cells. Moreover, we identified differentially expressed genes (DEGs) by microarray profiling of HCT-116 cells treated with EA. A total of 857 DEGs (363 upregulated and 494 downregulated) were identified with a >1.5-fold change in expression after treatment with EA for 72 h. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that a large number of cellular functions were modified by EA including proliferation, apoptosis, cell cycle and angiogenesis. Interaction network analysis using DEGs provided details of their interactions and predicted the key target pathways of EA. To verify the result of cDNA microarray, 10 selected DEGs related to proliferation, apoptosis or cell cycle were further confirmed by real-time RT-PCR. Based on microarray data, we identified several crucial functions of EA. These results provide important new data for EA in anti-CRC research.

The NF-κB pathway participates in the response to sulfide stress in Urechis unicinctus

The NF-κB pathway is known to be involved in regulating apoptosis, inflammation and immunity in organisms. In this study, we first identified full-length cDNA sequences of two key molecules in the NF-κB pathway, namely, NEMO and p65, and characterized their responses in the hindgut of Urechis unicinctus (Echiura, Urechidae) exposed to sulfide. The full-length of cDNA was 2491 bp for U. unicinctus NEMO (UuNEMO) and 1971 bp for U. unicinctus p65 (Uup65), and both polyclonal antibodies were prepared using UuNEMO or Uup65 expressed prokaryotically with the sequence of their whole open reading frame. Immunoprecipitation and Western blotting showed that the NF-κB pathway was activated in U. unicinctus exposed to sulfide, in which the content of UuNEMO ubiquitination and nuclear Uup65 increased significantly (p < 0.05) in hindgut tissue of U. unicinctus exposed to sulfide. Furthermore, the mRNA level of UuBcl-xL, a downstream anti-apoptosis gene of the NF-κB pathway, increased significantly (p < 0.05) from 48 h to 72 h and the mRNA level of UuBax, a Bcl-xL antagonist gene, decreased significantly (p < 0.05) at 48 h in the hindgut of U. unicinctus exposed to 50 μM sulfide. During the 150 μM sulfide exposure, the level of UuBcl-xL showed no obvious change, whereas the UuBax mRNA level increased significantly (p < 0.05) at 72 h post-exposure to 150 μM sulfide. We suggested that the activated NF-κB pathway up-regulates UuBcl-xL expression, and evokes an anti-apoptotic response to resist sulfide damage at 50 μM in U. unicinctus. Meanwhile, a Bax-mediated pro-apoptotic response occurs when U. unicinctus is exposed to 150 μM sulfide.

Polyphenol compounds and PKC signaling

BACKGROUND

Naturally occurring polyphenols found in food sources provide huge health benefits. Several polyphenolic compounds are implicated in the prevention of disease states, such as cancer. One of the mechanisms by which polyphenols exert their biological actions is by interfering in the protein kinase C (PKC) signaling pathways. PKC belongs to a superfamily of serine-threonine kinase and are primarily involved in phosphorylation of target proteins controlling activation and inhibition of many cellular processes directly or indirectly.

SCOPE OF REVIEW

Despite the availability of substantial literature data on polyphenols' regulation of PKC, no comprehensive review article is currently available on this subject. This article reviews PKC-polyphenol interactions and its relevance to various disease states. In particular, salient features of polyphenols, PKC, interactions of naturally occurring polyphenols with PKC, and future perspective of research on this subject are discussed.

MAJOR CONCLUSIONS

Some polyphenols exert their antioxidant properties by regulating the transcription of the antioxidant enzyme genes through PKC signaling. Regulation of PKC by polyphenols is isoform dependent. The activation or inhibition of PKC by polyphenols has been found to be dependent on the presence of membrane, Ca(2+) ion, cofactors, cell and tissue types etc. Two polyphenols, curcumin and resveratrol are in clinical trials for the treatment of colon cancer.

GENERAL SIGNIFICANCE

The fact that 74% of the cancer drugs are derived from natural sources, naturally occurring polyphenols or its simple analogs with improved bioavailability may have the potential to be cancer drugs in the future.

Role of ellagic acid in regulation of apoptosis by modulating novel and atypical PKC in lymphoma bearing mice

Background

Protein kinase C regulates various cellular processes including cell proliferation, cell adhesion, apoptosis, angiogenesis, invasion, and metastasis. Activation of different PKC isozymes results in distinct cellular responses. Novel PKCs are mainly involved in apoptotic process. Atypical PKC subfamily plays a critical role in cell proliferation and apoptosis, cell differentiation and motility. However, Atypical PKCs show contradictory regulation in different tissues or cancer cells. The mechanism of diversified effects is not well explored. Antioxidant ellagic acid shows hepatoprotective, anti-carcinogenic and anti-mutagenic properties. Present study is focused to analyze the effect of ellagic acid on novel and atypical isozymes of PKC in regulation of PKC-mediated apoptosis in liver of lymphoma bearing mice. Implication of ellagic acid treatment to DL mice was analyzed on caspase-3 mediated apoptosis via PKCδ induced activation; and on maintenance of adequate supply of energy during cancer growth.

Methods

15–20 weeks old adult DL mice were divided into four groups (n = 6). Group 2, 3, 4 were treated with different doses of ellagic acid (40 mg/kg, 60 mg/kg and 80 mg/kg bw). The mice were sacrificed after 19 days of treatment and liver was used for study. The effect of ellagic acid was determined on expression of novel and atypical PKC isozymes. Apoptotic potentiality of ellagic acid was checked on activities of caspase-3 and PKCδ in terms of their catalytic fragments. Aerobic glycolysis was monitored by LDH activity, especially activity of LDH A.

Results

Ellagic acid treatment caused up regulation of expression of almost all novel and atypical PKC isozymes. Activities of PKCδ and caspase-3 were enhanced by ellagic acid, however activities of total LDH and LDH-A were inhibited.

Conclusion

The results show that ellagic acid promotes apoptosis in lymphoma bearing mice via novel and atypical PKCs which involves PKCδ induced caspase-3 activation; and inhibition of glycolytic pathway.

Ellagic Acid, a Dietary Polyphenol, Inhibits Tautomerase Activity of Human Macrophage Migration Inhibitory Factor and Its Pro-inflammatory Responses in Human Peripheral Blood Mononuclear Cells

Ellagic acid (EA), a phenolic lactone, inhibited tautomerase activity of human macrophage migration inhibitory factor (MIF) noncompetitively (Ki = 1.97 ± 0.7 μM). The binding of EA to MIF was determined by following the quenching of tryptophan fluorescence. We synthesized several EA derivatives, and their structure-activity relationship studies indicated that the planar conjugated lactone moiety of EA was essential for MIF inhibition. MIF induces nuclear translocation of NF-κB and chemotaxis of peripheral blood mononuclear cells (PBMCs) to promote inflammation. We were interested in evaluating the effect of EA on nuclear translocation of NF-κB and chemotactic activity in human PBMCs in the presence of MIF. The results showed that EA inhibited MIF-induced NF-κB nuclear translocation in PBMCs, as evident from confocal immunofluorescence microscopic data. EA also inhibited MIF-mediated chemotaxis of PBMCs. Thus, we report MIF-inhibitory activity of EA and inhibition of MIF-mediated proinflammatory responses in PBMCs by EA.

Research progress on the anticarcinogenic actions and mechanisms of ellagic acid

Cancer is a leading cause of death worldwide. Cancer treatments by chemotherapeutic agents, surgery, and radiation have not been highly effective in reducing the incidence of cancers and increasing the survival rate of cancer patients. In recent years, plant-derived compounds have attracted considerable attention as alternative cancer remedies for enhancing cancer prevention and treatment because of their low toxicities, low costs, and low side effects. Ellagic acid (EA) is a natural phenolic constituent. Recent in vitro and in vivo experiments have revealed that EA elicits anticarcinogenic effects by inhibiting tumor cell proliferation, inducing apoptosis, breaking DNA binding to carcinogens, blocking virus infection, and disturbing inflammation, angiogenesis, and drug-resistance processes required for tumor growth and metastasis. This review enumerates the anticarcinogenic actions and mechanisms of EA. It also discusses future directions on the applications of EA.

Ellagic acid inhibits PKC signaling by improving antioxidant defense system in murine T cell lymphoma

Antioxidants protect the cells from the damaging effects of reactive oxygen species (ROS). Production of ROS during cellular metabolism is balanced by their removal by antioxidants. Any condition leading to increased levels of ROS results in oxidative stress, which participates in multistage carcinogenesis by causing oxidative DNA damage, mutations in the proto-oncogenes and tumor suppressor genes. Antioxidant defense system is required to overcome the process of carcinogenesis generated by ROS. Antioxidant enzymes are major contributors to endogenous antioxidant defense system. Protein kinase C (PKC) is generally involved in cell proliferation and its over expression leads to abnormal tumor growth. Out of three classes of PKC, classical PKC is mainly involved in cell proliferation and tumor growth. Classical PKC initiates signaling pathway and leads to activation of a number of downstream protein via activation of NF-κB. Therefore any agent which can promotes the endogenous antioxidant defense system should be able to down regulate PKC and NF-κB activation and thus may be useful in reducing cancer progression. To investigate this hypothesis we have tested the effect of antioxidant ellagic acid on antioxidant enzymes and PKC signaling in Dalton's lymphoma bearing (DL) mice. DL mice were treated with three different doses of ellagic acid. The treatment significantly increases the activity and expression of antioxidant enzymes and down regulates the expression of classical isozymes of PKC as well as the activation of NF-κB, indicating that ellagic acid improves antioxidant defense system and PKC signaling via NF-κB which may contribute to its cancer preventive role.

Ellagic Acid Reduces Adipogenesis through Inhibition of Differentiation-Prevention of the Induction of Rb Phosphorylation in 3T3-L1 Adipocytes

Ellagic acid (EA) present in many fruits and nuts serves as antiproliferation, anti-inflammatory, and antitumorigenic properties. However, the effect of EA on preadipocytes adipogenesis and its mechanism(s) have not been elucidated. The present study was designed to examine the effect of EA on adipogenesis in 3T3-L1 preadipocytes and underlying mechanism(s) of action involved. Data show that EA administration decreased the accumulation of lipid droplets. The inhibition was diminished when the addition of EA was delayed to days 2–4 of differentiation. Clonal expansion was reduced in the presence of EA. FACS analysis showed that EA blocked the cell cycle at the G1/S transition. EdU incorporation also confirmed that EA refrained cell from entering S phase. Our data also revealed that the differentiation-induced protein expression of Cyclin A and phosphorylation of the retinoblastoma protein (Rb) were impaired by EA. Differentiation-dependent expression and DNA-binding ability of C/EBPα were also inhibited by EA. Alterations in cell cycle-associated proteins may be important with respect to the antiadipogenic action of EA. In conclusion, EA is capable of inhibiting adipogenesis in 3T3-L1 adipocytes possibly through reduction of Cyclin A protein expression and Rb phosphorylation. With the blocking of G1/S phase transition, EA suppresses terminal differentiation and lipid accumulation in 3T3-L1 adipocytes.