Antiproliferation and apoptosis induced by curcumin in human ovarian cancer cells

Curcumin, an active ingredient from the rhizome of the plant, Curcuma longa, has antioxidant, anti-inflammatory and anti-cancer activities. It has recently been demonstrated that the chemopreventive activities of curcumin might be due to its ability to inhibit cell growth and induce apoptosis. In the present study, we have investigated the effects of curcumin on growth and apoptosis in the human ovarian cancer cell line Ho-8910 by MTT assay, fluorescence microscopy, flow cytometry and Western blotting. Our data revealed that curcumin could significantly inhibit the growth and induce apoptosis in Ho-8910 cells. A decrease in expression of Bcl-2, Bcl-X(L) and pro-caspase-3 was observed after exposure to 40 microM curcumin, while the levels of p53 and Bax were increased in the curcumin-treated cells. These activities may contribute to the anticarcinogenic action of curcumin.     

Proteomics screening of molecular targets of curcumin in mouse brain

Aims

Curcumin is one of the most important constituent of Curcuma longa L. with antioxidant, anti-inflammatory and anticancer effects. In this study, we investigated potential intracellular targets of curcumin by affinity chromatography based on target deconvolution. Identification of curcumin interacting proteins may help in evaluating biological and side effects of this natural compound.

Main methods

Curcumin was immobilized through a linker to sepharose beads as solid matrix. Pull down assay was performed by passing tissue lysate of mouse brain through the column to enrich and purify curcumin interacting proteins. Then proteins were separated using two-dimensional gel electrophoresis and identified using MALDI/TOF/TOF mass spectrometry.

Key findings

Our results show that curcumin physically binds to a wide range of cellular proteins including structural proteins, metabolic enzymes and proteins involved in apoptosis pathway.

Significance

Finding curcumin interacting proteins may help in understanding a part of curcumin pharmacological effects.     

Chemopreventive potential of curcumin in prostate cancer

The long latency and high incidence of prostate carcinogenesis provides the opportunity to intervene with chemoprevention in order to prevent or eradicate prostate malignancies. We present here an overview of the chemopreventive potential of curcumin (diferuloylmethane), a well-known natural compound that exhibits therapeutic promise for prostate cancer. In fact, it interferes with prostate cancer proliferation and metastasis development through the down-regulation of androgen receptor and epidermal growth factor receptor, but also through the induction of cell cycle arrest. It regulates the inflammatory response through the inhibition of pro-inflammatory mediators and the NF-κB signaling pathway. These results are consistent with this compound’s ability to up-induce pro-apoptotic proteins and to down-regulate the anti-apoptotic counterparts. Alone or in combination with TRAIL-mediated immunotherapy or radiotherapy, curcumin is also reported to be a good inducer of prostate cancer cell death by apoptosis. Curcumin appears thus as a non-toxic alternative for prostate cancer prevention, treatment or co-treatment.     

Microbial transformation of curcumin by Rhizopus chinensis

Abstract

Curcumin (1) is a potent antioxidant and antitumor natural product. In spite of its efficacy and safety, its clinical use is hindered mainly by poor water solubility and bioavailability. Structural modification to introduce hydrophilic functions is a promising approach to resolve this problem. In the present study we first found that curcumin could be efficiently converted into glucosides by filamentous fungi including Rhizopus chinensis IFFI 03043, Absidia coerulea AS 3.3389 and Cunninghamella elegans AS 3.1207. Curcumin 4′-O-β-d-glucoside (2), together with hexahydrocurcumin (3), was isolated from a preparative-scale biotransformation with R. chinensis IFFI 03043 and characterized fully by NMR and MS. A time-course study revealed that curcumin could be efficiently converted into curcumin 4′-O-β-d-glucoside within 8 h when administered at 0.05 mmol L^?1 and the productivity was 57%. Additionally, the biotransformation products of curcumin by different fungal strains were analyzed by LC/MS. At least 15 metabolites were detected, and the predominant biotransformation reaction was glucosylation. This study provides a simple, efficient and less expensive approach for the preparation of curcumin glucosides. The introduction of the glucosyl function might be able to enhance the bioavailability of curcumin.     

Binding and stabilization of transthyretin by curcumin

Biophysical evidences suggest that transthyretin (TTR) tetramer dissociation to the monomeric intermediate and subsequent polymerization leads to amyloid fibril formation, which is implicated in the pathogenesis of familial amyloid polyneuropathy (FAP) and senile systemic amyloidosis (SSA). Hence, inhibition of fibril formation is considered a potential therapeutic strategy. Here in we demonstrate that curcumin, a phenolic constituent of curry spice turmeric, binds to the active site of TTR through fluorescence quenching and ANS displacement studies. Binding of curcumin appears to inhibit the denaturant induced tertiary and quaternary structural changes in TTR as monitored by intrinsic emission fluorescence and glutaraldehyde cross-linking studies. However, curcumin did not bind to TTR at acidic pH. Protonation/ isomerization of the side chain oxygen atoms of curcumin at low pH might hamper the binding. These results suggest that curcumin binds to and stabilizes TTR thereby highlight the importance of the side chain conformations of the ligand in binding to TTR.     

Molecular docking analysis of lupeol with different cancer targets

Lupeol is one of the secondary metabolite (triterpenoid) present in many medicinally effective plants. It has numerous biological and pharmacological actions. Lupeol is found to have effective herbs and has immense biological activity against several diseases including its cytotoxic effect on cancer cells. In recent drug designing, molecular study of analysis is usually used for understanding the target and the ligand interaction. Therefore, it is of interest to document the molecular docking analysis data of lupeol with different cancer targets such as Caspase- 3, BCL-2, Topoisomerase, PTK, mTOR, H-Ras, PI3K, and AKT. These molecular docking studies were carried out by using AutoDock tools 4.2 version software. Molecular docking analyses of lupeol with target protein were found to have good dock score and minimum inhibition constant. BCL-2, Topoisomerase, PTK, mTOR and PI3Kdocking studies showed the best binding energy inhibition constant and ligand efficiency. The in-silico molecular docking analysis showed that the lupeol having relatively good docking energy, affinity and efficiency towards the active macromolecule, thus it may be considered as good inhibitor of proliferating cancer cells. By this knowledge of docking results, the lupeol can be used as promising drug for anticancer activity.     

Acceleration of oxidative protein folding by curcumin through novel non-redox chemistry

Curcumin, the major constituent of turmeric is a known antioxidant. We have examined the oxidative folding of the model four-disulfide-bond-containing protein bovine pancreatic ribonuclease A (RNase A) in its presence; results indicate that RNase A regeneration rate increases in a curcumin-dependent manner. Examination of the native tendency of the fully-reduced polypeptide and the stability of key folding intermediates suggests that the increased oxidative folding rate can be attributed to native-like elements induced within the fully-reduced polypeptide and the stabilization of native-like species by this non-redox-active natural product. Our results provide a template for the design of curcuminoid-based synthetic small-molecule fold catalysts that accelerate the folding of ER-processed proteins; this assumes significance given that nitrosative stress and dysfunction of the ER-resident oxidoreductase protein disulfide isomerise due to S-nitrosylation are factors associated with the pathogenesis of Alzheimer’s and Parkinson’s diseases.     

Molecular pathogenesis and therapeutic targets in epithelial ovarian cancer

Ovarian cancer, the most aggressive gynecologic cancer, is the foremost cause of death from gynecologic malignancies in the developed world. Two primary reasons explain its aggressive behavior: most patients present with advanced disease at diagnosis, and die of recurrences from disease that has become resistant to conventional chemotherapies. In this paper on epithelial ovarian cancer (EOC), we will review molecular alterations associated with the few precursor lesions identified to date, followed by the more commonly recognized processes of de novo carcinogenesis, metastasis, and the development of chemoresistance. We will propose a unifying model of ovarian epithelial tumorigenesis that takes into account various hypotheses. We will also review novel approaches to overcome the major problem of chemoresistance in ovarian cancer. Finally, we will discuss advances and new challenges in the development of mouse model systems to investigate EOC precursor lesions, progression, metastasis, and chemoresistance.     

Impact of curcumin treatment on diabetic albino rats

The current study was aimed to study the effect of curcumin on the expression levels of brain glucose transporter 1 protein (GLUT1) and femoral muscle glucose transporter 4 protein (GLUT4), in addition to study its possible therapeutic role in ameliorating insulin resistance and the metabolic disturbance in the obese and type 2 diabetic male albino Wistar rat model. Diabetes was induced by a high-fat (HF) diet with low dose streptozotocin (STZ). Curcumin was administered intragastrically for 8 weeks (80 mg/kg BW/day). The HF-diet group developed obesity, hyperglycemia, hyperinsulinemia, reduced liver glycogen content with significant dyslipidemia. In the diabetic control group, hyperglycemia and insulin resistance high calculated homeostasis model assessment (HOMA-IR-index score) were pronounced, with reductions in liver and muscle glycogen contents, concomitant with dyslipidemia and significantly elevated malondialdehyde levels in liver and pancreas. GLUT1 and GLUT4 were down-regulated in the obese and the diabetic control groups, respectively. Curcumin, showed glucose-lowering effect and decreased insulin resistance, dyslipidemia and malondialdehyde levels in both tissues, it increased liver & muscle glycogen contents, compared to the diabetic control. Curcumin significantly up-regulated GLUT4 gene expression, compared to the diabetic control group. In conclusions, these results indicate a therapeutic role of curcumin in improving the diabetic status, obesity and enhancing the expression of GLUT4 gene.     

Exploring pyrimidine-substituted curcumin analogues: Design,synthesis and effects on EGFR signaling

Epidermal growth factor receptor (EGFR) is an effective molecular target of anti-cancer therapies. Curcumin inhibits cancer cell growth in vitro by suppressing gene expression of EGFR and reduces tumor growth in various animal models. To overcome instable and insoluble properties of curcumin as therapeutics, we designed and synthesized six novel pyrimidine-substituted curcumin analogues with or without a hydroxyl group originally present in curcumin. The cell viability tests indicated that IC₅₀ of the analogues containing hydroxyl group were 3 to 8-fold lower than those of the analogues without hydroxyl group in two colon cancer cell lines tested. Western blot analysis indicates the analogues containing hydroxyl group inhibited expression and tyrosine phosphorylation of EGFR. Further protein analyses showed that the analogues had anti-cellular proliferation, pro-apoptosis, and cell cycle arrest properties associated with suppressed EGFR expression. These results indicate that the hydroxyl groups in curcumin and the analogues were critical for observed biological activities.     

Epigenetic changes induced by curcumin and other natural compounds

Epigenetic regulation, which includes changes in DNA methylation, histone modifications, and alteration in microRNA (miRNA) expression without any change in the DNA sequence, constitutes an important mechanism by which dietary components can selectively activate or inactivate gene expression. Curcumin (diferuloylmethane), a component of the golden spice Curcuma longa, commonly known as turmeric, has recently been determined to induce epigenetic changes. This review summarizes current knowledge about the effect of curcumin on the regulation of histone deacetylases, histone acetyltransferases, DNA methyltransferase I, and miRNAs. How these changes lead to modulation of gene expression is also discussed. We also discuss other nutraceuticals which exhibit similar properties. The development of curcumin for clinical use as a regulator of epigenetic changes, however, needs further investigation to determine novel and effective chemopreventive strategies, either alone or in combination with other anticancer agents, for improving cancer treatment.     

Enhancement of pancreatic lipase inhibitory activity of curcumin by radiolytic transformation

The naturally occurring yellow dietary diarylheptanoid curcumin (1) was converted by γ-ray to two new γ-lactones, curculactones A (2) and B (3), as well as four known transformates, erythro-1-(3-methoxy-4-hydroxy-phenyl)-propan-1,2-diol (4), threo-1-(3-methoxy-4-hydroxy-phenyl)-propan-1,2-diol (5), vanillic acid (6), and vanillin (7). The structures of the two new γ-lactone derivatives were elucidated on the basis of spectroscopic methods. The steroisomeric phenylpropanoids 4 and 5 exhibited significantly enhanced inhibitory activity against pancreatic lipase when compared to parent curcumin.     

Synergistic effect of curcumin on epigallocatechin gallate-induced anticancer action in PC3 prostate cancer cells

Epigallocatechin gallate (EGCG) and curcumin are well known to naturally-occurring anticancer agents. The aim of this study was to verify the combined beneficial anticancer effects of curcumin and EGCG on PC3 prostate cancer cells, which are resistant to chemotherapy drugs and apoptosis inducers. EGCG showed weaker inhibitory effect on PC3 cell proliferation than two other prostate cancer cell lines, LNCaP and DU145. Co-treatment of curcumin improved antiproliferative effect of EGCG on PC3 cells. The protein expressions of p21 were significantly increased by the co-treatment of EGCG and curcumin, whereas it was not changed by the treatment with each individual compound. Moreover, treatments of EGCG and curcumin arrested both S and G2/M phases of PC3 cells. These results suggest that the enhanced inhibitory effect of EGCG on PC3 cell proliferation by curcumin was mediated by the synergic up-regulation of p21-induced growth arrest and followed cell growth arrest. [BMB Reports 2015; 48(8): 461-466]     

Synthesis and preliminary evaluation of curcumin analogues as cytotoxic agents

A series of curcumin analogues with different substituents at the 4-position of the phenyl group were synthesized and screened for in vitro cytotoxicity against a panel of human cancer cell lines. Several novel curcumin analogues, especially 32 and 34, exhibited selective and potent cytotoxic activity against human epidermoid carcinoma cell line A-431 and human glioblastoma cell line U-251, implying their specific potential in the chemoprevention and chemotherapy of skin cancer and glioma. The preliminary SAR information extracted from the results suggested that introduction of appropriate substituents to the 4′-positions could be a promising approach for the development of new cytotoxic curcumin analogues with special selectivity for A-431 and U-251 cell lines.     

Apigenin shows synergistic anticancer activity with curcumin by binding at different sites of tubulin

Apigenin, a natural flavone, present in many plants sources, induced apoptosis and cell death in lung epithelium cancer (A549) cells with an IC₅₀ value of 93.7 ± 3.7 μM for 48 h treatment. Target identification investigations using A549 cells and also in cell-free system demonstrated that apigenin depolymerized microtubules and inhibited reassembly of cold depolymerized microtubules of A549 cells. Again apigenin inhibited polymerization of purified tubulin with an IC₅₀ value of 79.8 ± 2.4 μM. It bounds to tubulin in cell-free system and quenched the intrinsic fluorescence of tubulin in a concentration- and time-dependent manner. The interaction was temperature-dependent and kinetics of binding was biphasic in nature with binding rate constants of 11.5 × 10⁻⁷ M⁻¹ s⁻¹ and 4.0 × 10⁻⁹ M⁻¹ s⁻¹ for fast and slow phases at 37 °C, respectively. The stoichiometry of tubulin–apigenin binding was 1:1 and binding the binding constant (K_d) was 6.08 ± 0.096 μM. Interestingly, apigenin showed synergistic anti-cancer effect with another natural anti-tubulin agent curcumin. Apigenin and curcumin synergistically induced cell death and apoptosis and also blocked cell cycle progression at G₂/M phase of A549 cells. The synergistic activity of apigenin and curcumin was also apparent from their strong depolymerizing effects on interphase microtubules and inhibitory effect of reassembly of cold depolymerized microtubules when used in combinations, indicating that these ligands bind to tubulin at different sites. In silico modeling suggested apigenin bounds at the interphase of α–β-subunit of tubulin. The binding site is 19 Å in distance from the previously predicted curcumin binding site. Binding studies with purified protein also showed both apigenin and curcumin can simultaneously bind to purified tubulin. Understanding the mechanism of synergistic effect of apigenin and curcumin could be helped to develop anti-cancer combination drugs from cheap and readily available nutraceuticals.     

Photokilling of bacteria by the natural dye curcumin

Curcumin is a yellow-orange compound derived from the root of Curcuma longa (Zingiberaceae family), that has been used as a medicine, spice and coloring agent. Curcumin has proved nontoxic in a number of cell culture and whole animal studies. Curcumin has, however, been reported to have bactericidal effects at very high concentrations. When illuminated, curcumin exerted potent phototoxic effects in micromolar amounts. Gram-negative bacteria displayed greater resistance to curcumin phototoxicity relative to Gram-positive bacteria. Oxygen was required for curcumin phototoxicity. Curcumin binding to cells was not required for photokilling; the reactive intermediate therefore must be relatively long-lived. The mechanism(s) of curcumin phototoxicity may involve hydrogen peroxide production. Singlet excited oxygen was not detected.Publication no 35 of the Center for Photochemical Sciences     

Proteomics: a strategy to understand the novel targets in protein misfolding and cancer therapy

Proteins carry out important functions as they fold themselves. Protein misfolding occurs during different biochemical processes and may lead to the development of diseases such as cancer, which is characterized by genetic instability. The cancer microenvironment exposes malignant cells to a variety of stressful conditions that may further promote protein misfolding. Tumor development and progression often arises from mutations that interfere with the appropriate function of tumor-suppressor proteins and oncogenes. These may be due to alteration of catalytic activity of the protein, loss of binding sites for effector proteins or alterations of the native folded protein conformation. Src family kinases, p53, mTOR and C-terminus of HSC70 interacting protein (CHIPs) are some examples associated with protein misfolding and tumorigenesis. Molecular chaperones, such as heat-shock protein (HSP)70 and HSP90, assist protein folding and recognize target misfolded proteins for degradation. It is likely that this misfolding in cancer is linked by common principles, and may, therefore, present an exciting possibility to identify common targets for therapeutic intervention. Here we aim to review a number of examples that show how alterations in the folding of tumor-suppressor proteins or oncogenes lead to tumorigenesis. The possibility of targeting the targets to repair or degrade protein misfolding in cancer therapy is discussed.     

SIRT1 activation by curcumin pretreatment attenuates mitochondrial oxidative damage induced by myocardial ischemia reperfusion injury

Ischemia reperfusion (IR) injury (IRI) is harmful to the cardiovascular system and causes mitochondrial oxidative stress. Silent information regulator 1 (SIRT1), a type of histone deacetylase, contributes to IRI. Curcumin (Cur) is a strong natural antioxidant and is the active component in Curcuma longa; Cur has protective effects against IRI and may regulate the activity of SIRT1. This study was designed to investigate the protective effect of Cur pretreatment on myocardial IRI and to elucidate this potential mechanism. Isolated and in vivo rat hearts and cultured neonatal rat cardiomyocytes were subjected to IR. Prior to this procedure, the hearts or cardiomyocytes were exposed to Cur in the absence or presence of the SIRT1 inhibitor sirtinol or SIRT1 siRNA. Cur conferred a cardioprotective effect, as shown by improved postischemic cardiac function, decreased myocardial infarct size, decreased myocardial apoptotic index, and several biochemical parameters, including the up-regulation of the antiapoptotic protein Bcl2 and the down-regulation of the proapoptotic protein Bax. Sirtinol and SIRT1 siRNA each blocked the Cur-mediated cardioprotection by inhibiting SIRT1 signaling. Cur also resulted in a well-preserved mitochondrial redox potential, significantly elevated mitochondrial superoxide dismutase activity, and decreased formation of mitochondrial hydrogen peroxide and malondialdehyde. These observations indicated that the IR-induced mitochondrial oxidative damage was remarkably attenuated. However, this Cur-elevated mitochondrial function was reversed by sirtinol or SIRT1 siRNA treatment. In summary, our results demonstrate that Cur pretreatment attenuates IRI by reducing IR-induced mitochondrial oxidative damage through the activation of SIRT1 signaling.