Metabolism of curcumin and induction of mitotic catastrophe in human cancer cells

Utility of Intravenous Curcumin Nanodelivery Systems for Improving In Vivo Pharmacokinetics and Anticancer Pharmacodynamics

Curcumin nanoformulations for intravenous injection have been developed to offset poor absorption, biotransformation, degradation, and excessive clearance associated with parenteral delivery. This review investigates (1) whether intravenous nanoformulations improve curcumin pharmacokinetics (PK) and (2) whether improved PK yields greater therapeutic efficacy. Standard PK parameters (measured maximum concentration [C_max], area under the curve [AUC], distribution volume [V_d], and clearance [CL]) of intravenously administered free curcumin in mice and rats were sourced from literature and compared to curcumin formulated in nanoparticles, micelles, and liposomes. The studies that also featured analysis of pharmacodynamics (PD) in murine cancer models were used to determine whether improved PK of nanoencapsulated curcumin resulted in improved PD. The distribution and clearance of free and nanoformulated curcumin were very fast, typically accounting for >80% curcumin elimination from plasma within 60 min. Case-matched analysis demonstrated that curcumin nanoencapsulation generally improved curcumin PK in terms of measured C_max (n = 27) and AUC (n = 33), and to a lesser extent V_d and CL. However, when the data were unpaired and clustered for comparative analysis, only 5 out of the 12 analyzed nanoformulations maintained a higher relative curcumin concentration in plasma over time compared to free curcumin. Quantitative analysis of the mean plasma concentration of free curcumin versus nanoformulated curcumin did not reveal an overall marked improvement in curcumin PK. No correlation was found between PK and PD, suggesting that augmentation of the systemic presence of curcumin does not necessarily lead to greater therapeutic efficacy.

Design of New Improved Curcumin Derivatives to Multi-targets of Cancer and Inflammation

BACKGROUND

Curcumin is a major active principle of Curcuma longa. There are more than 1700 citations in the Medline, reflecting various biological effects of curcumin. Most of these biological activities are associated with the antioxidant, anti-inflammatory and antitumor activity of the molecule. Several reports suggest various targets of natural curcumin that include growth factors, growth factor receptor, cytokines, enzymes and gene regulators of apoptosis. This review focuses on the improved curcumin derivatives that target the cancer and inflammation.

METHODOLOGY

In this present review, we explored the anticancer drugs with curcumin-based drugs under pre-clinical and clinical studies with critical examination. Based on the strong scientific reports of patentable and non-patented literature survey, we have investigated the mode of the interactions of curcumin-based molecules with the target molecules.

RESULTS

Advanced studies have added new dimensions of the molecular response of cancer cells to curcumin at the genomic level. However, poor bioavailability of the molecule seems to be the major limitation of the curcumin. Several researchers have been involved to improve the curcumin derivatives to overcome this limitation. Sufficient data of clinical trials to various cancers that include multiple myeloma, pancreatic cancer and colon cancer, have also been discussed.

CONCLUSION

The detailed analysis of the structure-activity relationship (SAR) and common synthesis of curcumin-based derivatives have been discussed in the review. Utilising the predictions of in silico coupled with validation reports of in vitro and in vivo studies have concluded many targets for curcumin. Among them, cancer-related inflammation genes regulating curcumin-based molecules are a very promising target to overcome hurdles in the multimodality therapy of cancer.

Reductive metabolites of curcumin and their therapeutic effects

Curcumin, a secondary metabolite from the turmeric plant is one of the most promising natural products, which has been studied extensively for decades. It has demonstrated several pharmacological activities in vitro and in vivo. Various studies have indicated that the pharmacological activity of curcumin is contributed by its metabolites. The aim of this review is to present an overview of metabolic products of curcumin produced upon its reduction like di, tetra, hexa and octa-hydrocurcumin. In addition, this paper has systematically analyzed the current information regarding medicinal use of reduced metabolites of curcumin and identified the limitations which have hindered its widespread usage in the medical world. Several diverse therapeutic effects have shown to be exhibited by reduced metabolites of curcumin such as antioxidant, anti-cancerous, anti-inflammatory and immunoregulatory activities. The potential underlying molecular mechanisms of the biological activities of reduced metabolites of curcumin have also been highlighted, which may provide insight into the principle of effectiveness of curcumin.

The differential cellular uptake of curcuminoids in vitro depends dominantly on albumin interaction

BACKGROUND

Curcuminoids, mainly present in the plant rhizomes of turmeric (Curcuma longa), consist of mainly three forms (curcumin (CUR), bisdemethoxycurcumin (BDMC) and demethoxycurcumin (DMC)). It has been reported that different forms of curcuminoids possess different biological activities. However, the mechanisms associated with these differences are not well-understood. Recently, our laboratory found differences in the cellular uptake of these curcuminoids. Therefore, it has been inferred that these differences contribute to the different biological activities.

PURPOSE

In this study, we investigated the mechanisms of differential cellular uptake of these curcuminoids.

METHOD

Based on our previous study, we hypothesized the differential cellular uptake is caused by (I) polarity, (II) transporters, (III) metabolism rate of curcuminoids and (IV) medium components. These four hypotheses were each investigated by (I) neutralizing the polarities of curcuminoids by encapsulation into poly(lactic-co-glycolic) acid nanoparticles (PLGA-NPs), (II) inhibition of polyphenol-related absorption transporters, (III) analysis of the cellular curcuminoids and their metabolites by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and (IV) use of different mediums in cell study.

RESULTS

The differential cellular uptake was not affected by (I-III). However, when investigating (IV), not only CUR but also BDMC and DMC were incorporated into cells when serum free media was used. Furthermore, when we used the serum free medium containing bovine serum albumin (BSA), only CUR was taken up but BDMC and DMC were not. Therefore, we identified that the differential cellular uptake of curcuminoids is caused by the medium components, especially BSA. Also, the fluorescence quenching study suggested that differential cellular uptake is due to the different interaction between BSA and each curcuminoid.

CONCLUSION

The differential cellular uptake of curcuminoids was caused by the different interaction between curcuminoids and BSA. The results from this study might give clues on the mechanisms by which curcuminoids exhibit different physiological activities.

Bioactivity, Health Benefits, and Related Molecular Mechanisms of Curcumin: Current Progress, Challenges, and Perspectives

Curcumin is a principal curcuminoid of turmeric (Curcuma longa), which is commonly used as a spice in cooking and a yellow pigment in the food processing industry. Recent studies have demonstrated that curcumin has a variety of biological activities and pharmacological performances, providing protection and promotion of human health. In addition to presenting an overview of the gut metabolism of curcumin, this paper reviews the current research progress on its versatile bioactivity, such as antioxidant, anti-inflammatory, and immune-regulatory activities, and also intensively discusses its health benefits, including the protective or preventive effects on cancers and diabetes, as well as the liver, nervous system, and cardiovascular systems, highlighting the potential molecular mechanisms. Besides, the beneficial effects of curcumin on human are further stated based on clinical trials. Considering that there is still a debate on the beneficial effects of curcumin, we also discuss related challenges and prospects. Overall, curcumin is a promising ingredient of novel functional foods, with protective efficacy in preventing certain diseases. We hope this comprehensive and updated review will be helpful for promoting human-based studies to facilitate its use in human health and diseases in the future.

A novel bioavailable hydrogenated curcuminoids formulation (CuroWhite™) improves symptoms and diagnostic indicators in rheumatoid arthritis patients - A randomized, double blind and placebo controlled study

Rheumatoid arthritis (RA) is an inflammatory disease that cause chronic pain, disability and joint destruction. The present placebo controlled randomized study aimed to evaluate the efficacy of a novel hydrogenated curcuminoid formulation-CuroWhite™, in rheumatoid arthritis (RA) patients. Twenty four RA patients were randomized in 1:1:1 ratio to receive 250 mg, 500 mg CuroWhite or placebo as one capsule a day, over a period of three months. Improvement in the ACR response, changes in disease activity assessed using the DAS 28 score, change in physical function assessed on change in ESR, CRP, RF values were evaluated before and after the study. Results suggested that patients who received CuroWhite both low and high doses reported statistically significant changes in their clinical symptoms towards end of the study when compared with placebo. There were significant changes in DAS28 (50–64%) VAS (63–72%) ESR (88–89%), CRP (31–45%) RF (80–84%) values and ACR response for CuroWhite groups in comparison with placebo. Thus, CuroWhite acts as the analgesic and anti-inflammatory product for management of RA by the reduction of the inflammatory action which was confirmed by improvement in ESR, CRP, VAS, RF, DAS-28 and ACR responses. CuroWhite was significantly effective against RA with highly safe without serious side effects and well tolerated.

A Toxicological Evaluation of a Standardized Hydrogenated Extract of Curcumin (CuroWhite™)

A series of toxicological investigations were conducted in order to evaluate the genotoxic potential and repeated-dose oral toxicity of CuroWhite, a proprietary extract of curcumin that has been hydrogenated and standardized to not less than 25% hydrogenated curcuminoid content. All tests were conducted in general accordance with internationally accepted standards. The test item was not mutagenic in the bacterial reverse mutation test or in vitro mammalian chromosomal aberration test, and no in vivo genotoxic activity was observed in rat bone marrow in the micronucleus test. A 90-day repeated-dose study was conducted in male and female Sprague-Dawley rats. Two mortalities occurred in the main and satellite high-dose groups and were determined due to gavage error. No organ specific or other toxic effects of the test item were observed up to the maximum dose of 800 mg/kg bw/day, administered by gavage. NOAEL was, therefore, estimated as 800 mg/kg bw/day.

Acute and subchronic oral toxicity studies of hydrogenated curcuminoid formulation 'CuroWhite' in rats

Hydrogenated curcuminoids are the major metabolites of the curcumin and ‘CuroWhite’ is a unique blend of hydrogenated curcuminoids encapsulated with β-cyclodextrin. There is no particular scientific evidence for the toxicology regarding the hydrogenated curcuminoids, so the present work reports the results of the studies investigating the acute (single dose) and subchronic (repeatedly 90 days) oral toxicity of the CuroWhite in Sprague Dawley rats. For acute oral toxicity testing a sighting study was conducted on female rats in a sequential manner to allow selection of the appropriate starting dose for the main study. In acute toxicity, the dosage was 2000 mg/kg body weight for four female rats. In the sub-chronic study, rats of both sexes divided into three groups and each group were orally treated with CuroWhite daily at 200, 400 and 800 mg/kg for 90 days consecutively. No evidence of treatment related toxicity was detected during the study. Thus, data analysis of mortality, body weight gain, feed consumption, clinical observations, hematology, organ weights and histopathological findings did not show significant differences between control and treated groups. It is concluded that CuroWhite orally administered to rats was safe and no drug-related toxicity was detected even at the highest doses investigated in both acute (2000 mg/kg) and subchronic toxicity (200, 400 and 800 mg/kg) studies. Based on the study, the no-observed-adverse-effect level (NOAEL) value could be considered as 800 mg/kg per day in both the sexes. These results indicate that CuroWhite can be generally regarded as safe for use as a food additive.

Metabolic fate of poly-(lactic-co-glycolic acid)-based curcumin nanoparticles following oral administration

Purpose

Curcumin (CUR), the main polyphenol in turmeric, is poorly absorbed and rapidly metabolized following oral administration, which severely curtails its bioavailability. Poly-(lactic-co-glycolic acid)-based CUR nanoparticles (CUR-NP) have recently been suggested to improve CUR bioavailability, but this has not been fully verified. Specifically, no data are available about curcumin glucuronide (CURG), the major metabolite of CUR found in the plasma following oral administration of CUR-NP. Herein, we investigated the absorption and metabolism of CUR-NP and evaluated whether CUR-NP improves CUR bioavailability.

Methods

Following oral administration of CUR-NP in rats, we analyzed the plasma and organ distribution of CUR and its metabolites using high-performance liquid chromatography-tandem mass spectrometry. To elucidate the mechanism of increased intestinal absorption of CUR-NP, we prepared mixed micelles comprised of phosphatidylcholine and bile salts and examined the micellar solubility of CUR-NP. Additionally, we investigated the cellular incorporation of the resultant micelles into differentiated Caco-2 human intestinal cells.

Results

Following in vivo administration of CUR-NP, CUR was effectively absorbed and present mainly as CURG in the plasma which contained significant amounts of the metabolite compared with other organs. Thus, CUR-NP increased intestinal absorption of CUR rather than decreasing metabolic degradation and conversion to other metabolites. In vitro, CUR encapsulated in CUR-NP was solubilized in mixed micelles; however, whether the micelles contained CUR or CUR-NP had little influence on cellular uptake efficiency. Therefore, we suggest that the high solubilization capacity of CUR-NP in mixed micelles, rather than cellular uptake efficiency, explains the high intestinal absorption of CUR-NP in vivo.

Conclusion

These findings provide a better understanding of the bioavailability of CUR and CUR-NP following oral administration. To improve the bioavailability of CUR, future studies should focus on enhancing the resistance to metabolic degradation and conversion of CUR to other metabolites, which may lead to novel discoveries regarding food function and disease prevention.

Stable isotope labeling strategy for curcumin metabolite study in human liver microsomes by liquid chromatography-tandem mass spectrometry

The identification of drug metabolites is very important in drug development. Nowadays, the most widely used methods are isotopes and mass spectrometry. However, the commercial isotopic labeled reagents are usually very expensive, and the rapid and convenient identification of metabolites is still difficult. In this paper, an (18)O isotope labeling strategy was developed and the isotopes were used as a tool to identify drug metabolites using mass spectrometry. Curcumin was selected as a model drug to evaluate the established method, and the (18)O labeled curcumin was successfully synthesized. The non-labeled and (18)O labeled curcumin were simultaneously metabolized in human liver microsomes (HLMs) and analyzed by liquid chromatography/mass spectrometry (LC-MS). The two groups of chromatograms obtained from metabolic reaction mixture with and without cofactors were compared and analyzed using Metabolynx software (Waters Corp., Milford, MA, USA). The mass spectra of the newly appearing chromatographic peaks in the experimental sample were further analyzed to find the metabolite candidates. Their chemical structures were confirmed by tandem mass spectrometry. Three metabolites, including two reduction products and a glucuronide conjugate, were successfully detected under their specific HLMs metabolic conditions, which were in accordance with the literature reported results. The results demonstrated that the developed isotope labeling method, together with post-acquisition data processing using Metabolynx software, could be used for fast identification of new drug metabolites.

Application of ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry to identify curcumin metabolites produced by human intestinal bacteria

Curcumin, a yellow pigment derived from the rhizomes of Curcuma longa Linn, is a natural antioxidant that exhibits a variety of pharmacological activities and therapeutic properties. However, as curcumin is generally conjugated when absorbed through the intestine, free curcumin is present at extremely low levels in the body. Thus, curcumin metabolites are presumed to be responsible for curcumin bioactivity. In this study, we describe a strategy using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF MS) with automated data analysis software (MetaboLynx(XS)) for rapid analysis of the metabolic profile of curcumin in human intestinal flora. The results show that curcumin undergoes extensive phase I and phase II metabolism. A total of 23 curcumin metabolites were detected and identified in vitro. Furthermore, we identified a number of novel metabolic pathways of curcumin in the human intestinal microflora system.

Celecoxib prevents curcumin-induced apoptosis in a hematopoietic cancer cell model

Molecules targeting pro-inflammatory pathways have demonstrated beneficial effects in cancer treatment. More recently, combination of natural and synthetic anti-inflammatory drugs was suggested as an appealing strategy to inhibit tumor growth. Herein, we show that curcumin, a polyphenol from Curcuma longa and celecoxib induce apoptosis in hematopoietic cancer cell lines (Hel, Jurkat, K562, Raji, and U937). Further investigations on the most sensitive cell line, U937, indicated that these effects were tightly associated with an accumulation of the cells in S and G2/M for curcumin and in G0/G1 phase of cell cycle for celecoxib, respectively. The effect of celecoxib on cell cycle is associated with an induction of p27 and the down-regulation of cyclin D1. However, in the case of combination experiments, the pretreatment of U937 cells with celecoxib at non-apoptogenic concentrations counteracted curcumin-induced apoptosis. We found that this effect correlated with the prevention of the accumulation in S and G2/M phase of cell cycle induced by curcumin. Similar results have been obtained when celecoxib and curcumin were co-administrated at the same time. Overall our data suggest that this natural and synthetic drug combination is detrimental for cell death induction.

Differential cellular uptake and metabolism of curcuminoids in monocytes/macrophages: regulatory effects on lipid accumulation

We have previously shown that curcumin (CUR) may increase lipid accumulation in cultured human acute monocytic leukaemia cell line THP-1 monocytes/macrophages, but that tetrahydrocurcumin (THC), an in vivo metabolite of CUR, has no such effect. In the present study, we hypothesised that the different cellular uptake and/or metabolism of CUR and THC might be a possible explanation for the previously observed differences in their effects on lipid accumulation in THP-1 monocytes/macrophages. Chromatography with tandem MS revealed that CUR was readily taken up by THP-1 monocytes/macrophages and slowly metabolised to hexahydrocurcumin sulphate. By contrast, the uptake of THC was low. In parallel with CUR uptake, increased lipid uptake was observed in THP-1 macrophages but not with the uptake of THC or another CUR metabolite and structurally related compounds. From these results, it is possible to deduce that CUR and THC are taken up and metabolised differently in THP-1 cells, which determine their biological activity. The remarkable differential cellular uptake of CUR, relative to THC and other similar molecules, may imply that the CUR uptake into cells may occur via a transporter.

Curcumin glucuronides: assessing the proliferative activity against human cell lines

A gram scale synthesis of the glucuronide metabolites of curcumin were completed in four steps. The newly synthesized curcumin glucuronide compounds 2 and 3 along with curcumin 1 were tested and their anti-proliferative effects against KBM-5, Jurkat cell, U266, and A549 cell lines were reported. Biological data revealed that as much as 1 μM curcumin 1 exhibited anticancer activity and almost 100% cell kill was noted at 10 μM on two out of four cell lines; while curcumin mono-glucuronide 2 as well as di-glucuronide 3 displayed no suppression of cell proliferation.

The molecular basis for the pharmacokinetics and pharmacodynamics of curcumin and its metabolites in relation to cancer

This review addresses the oncopharmacological properties of curcumin at the molecular level. First, the interactions between curcumin and its molecular targets are addressed on the basis of curcumin's distinct chemical properties, which include H-bond donating and accepting capacity of the β-dicarbonyl moiety and the phenylic hydroxyl groups, H-bond accepting capacity of the methoxy ethers, multivalent metal and nonmetal cation binding properties, high partition coefficient, rotamerization around multiple C-C bonds, and the ability to act as a Michael acceptor. Next, the in vitro chemical stability of curcumin is elaborated in the context of its susceptibility to photochemical and chemical modification and degradation (e.g., alkaline hydrolysis). Specific modification and degradatory pathways are provided, which mainly entail radical-based intermediates, and the in vitro catabolites are identified. The implications of curcumin's (photo)chemical instability are addressed in light of pharmaceutical curcumin preparations, the use of curcumin analogues, and implementation of nanoparticulate drug delivery systems. Furthermore, the pharmacokinetics of curcumin and its most important degradation products are detailed in light of curcumin's poor bioavailability. Particular emphasis is placed on xenobiotic phase I and II metabolism as well as excretion of curcumin in the intestines (first pass), the liver (second pass), and other organs in addition to the pharmacokinetics of curcumin metabolites and their systemic clearance. Lastly, a summary is provided of the clinical pharmacodynamics of curcumin followed by a detailed account of curcumin's direct molecular targets, whereby the phenotypical/biological changes induced in cancer cells upon completion of the curcumin-triggered signaling cascade(s) are addressed in the framework of the hallmarks of cancer. The direct molecular targets include the ErbB family of receptors, protein kinase C, enzymes involved in prostaglandin synthesis, vitamin D receptor, and DNA.

Comparison of the effects of curcumin and curcumin glucuronide in human hepatocellular carcinoma HepG2 cells

Curcumin is a yellow pigment found in turmeric (Curcuma Longa L.), and is reported, in recent studies, to have several pharmacological effects, including anti-oxidant, anti-inflammatory, anti-tumour and lipid-lowering properties. However, as most curcumin is conjugated when absorbed through the intestine, free curcumin is present at extremely low levels inside the body. Therefore, curcumin metabolites have been presumed to be responsible for the curcumin bioactivity. In this study, we first confirmed that curcumin glucuronide is the major metabolite of curcumin found in the plasma after oral administration of curcumin in rats. Next, we synthesised curcumin glucuronide and compared the effects of curcumin and curcumin glucuronide on gene expression in a human hepatoma cell line (HepG2). We found that the effects of curcumin glucuronide are weaker than those of curcumin and that this difference is related to relative absorption rates of curcumin and curcumin glucuronide into HepG2 cells.

Bioactivity of turmeric-derived curcuminoids and related metabolites in breast cancer

While the chemotherapeutic effect of curcumin, one of three major curcuminoids derived from turmeric, has been reported, largely unexplored are the effects of complex turmeric extracts more analogous to traditional medicinal preparations, as well as the relative importance of the three curcuminoids and their metabolites as anti-cancer agents. These studies document the pharmacodynamic effects of chemically-complex turmeric extracts relative to curcuminoids on human breast cancer cell growth and tumor cell secretion of parathyroid hormone-related protein (PTHrP), an important driver of cancer bone metastasis. Finally, relative effects of structurallyrelated metabolites of curcuminoids were assessed on the same endpoints. We report that 3 curcuminoid-containing turmeric extracts differing with respect to the inclusion of additional naturally occurring chemicals (essential oils and/or polar compounds) were equipotent in inhibiting human breast cancer MDA-MB-231 cell growth (IC50=10-16µg/mL) and secretion of osteolytic PTHrP (IC50=2-3µg/mL) when concentrations were normalized to curcuminoid content. Moreover, these effects were curcuminoid-specific, as botanically-related gingerol containing extracts had no effect. While curcumin and bis-demethoxycurcumin were equipotent to each other and to the naturally occurring curcuminoid mixture (IC50=58µM), demethoxycurcumin did not have any effect on cell growth. However, each of the individual curcuminoids inhibited PTHrP secretion (IC50=22-31µM) to the same degree as the curcuminoid mixture (IC50=16µM). Degradative curcuminoid metabolites (vanillin and ferulic acid) did not inhibit cell growth or PTHrP, while reduced metabolites (tetrahydrocurcuminoids) had inhibitory effects on cell growth and PTHrP secretion but only at concentrations ≥10-fold higher than the curcuminoids. These studies emphasize the structural and biological importance of curcuminoids in the anti-breast cancer effects of turmeric and contradict recent assertions that certain of the curcuminoid metabolites studied here mediate these anti-cancer effects.

Metabolism and permeability of curcumin in cultured Caco-2 cells

SCOPE

Curcumin (CUR) and its major metabolite hexahydro-CUR were studied in Caco-2 cells and in the Caco-2 Millicell® system in vitro to simulate their in vivo intestinal metabolism and absorption in humans.

METHODS AND RESULTS

Analysis of the incubation medium and cell lysate showed that Caco-2 cells reduce CUR to hexahydro-CUR and octahydro-CUR, and conjugate CUR and its reductive metabolites with glucuronic acid and sulfate. Using the Caco-2 Millicell® system, an efficient transfer of the conjugates into the basolateral, but not the apical, compartment was observed after apical administration. Likewise, hexahydro-CUR was reduced to octahydro-CUR, and glucuronide and sulfate conjugates almost exclusively permeated to the basolateral side. The apparent permeability coefficients (Papp values) of CUR, hexahydro-CUR and their metabolites were determined and found to be extremely low for unchanged CUR, but somewhat higher for hexahydro-CUR and the conjugated metabolites.

CONCLUSION

The results of this study clearly show that the systemic bioavailability of CUR from the intestine after oral intake must be expected to be virtually zero. Reductive and conjugated metabolites, formed from CUR in the intestine, exhibit moderate absorption. Thus, any biological effects elicited by CUR in tissues other than the gastrointestinal tract are likely due to CUR metabolites.

Curcuminoid binding to embryonal carcinoma cells: reductive metabolism, induction of apoptosis, senescence, and inhibition of cell proliferation

Curcumin preparations typically contain a mixture of polyphenols, collectively referred to as curcuminoids. In addition to the primary component curcumin, they also contain smaller amounts of the co-extracted derivatives demethoxycurcumin and bisdemethoxycurcumin. Curcuminoids can be differentially solubilized in serum, which allows for the systematic analysis of concentration-dependent cellular binding, biological effects, and metabolism. Technical grade curcumin was solubilized in fetal calf serum by two alternative methods yielding saturated preparations containing either predominantly curcumin (60%) or bisdemethoxycurcumin (55%). Continual exposure of NT2/D1 cells for 4–6 days to either preparation in cell culture media reduced cell division (1–5 µM), induced senescence (6–7 µM) or comprehensive cell death (8–10 µM) in a concentration-dependent manner. Some of these effects could also be elicited in cells transiently exposed to higher concentrations of curcuminoids (47 µM) for 0.5–4 h. Curcuminoids induced apoptosis by generalized activation of caspases but without nucleosomal fragmentation. The equilibrium binding of serum-solubilized curcuminoids to NT2/D1 cells incubated with increasing amounts of curcuminoid-saturated serum occurred with apparent overall dissociation constants in the 6–10 µM range. However, the presence of excess free serum decreased cellular binding in a hyperbolic manner. Cellular binding was overwhelmingly associated with membrane fractions and bound curcuminoids were metabolized in NT2/D1 cells via a previously unidentified reduction pathway. Both the binding affinities for curcuminoids and their reductive metabolic pathways varied in other cell lines. These results suggest that curcuminoids interact with cellular binding sites, thereby activating signal transduction pathways that initiate a variety of biological responses. The dose-dependent effects of these responses further imply that distinct cellular pathways are sequentially activated and that this activation is dependent on the affinity of curcuminoids for the respective binding sites. Defined serum-solubilized curcuminoids used in cell culture media are thus suitable for further investigating the differential activation of signal transduction pathways.

Demethoxycurcumin Retards Cell Growth and Induces Apoptosis in Human Brain Malignant Glioma GBM 8401 Cells

Demethoxycurcumin (DMC; a curcumin-related demethoxy compound) has been recently shown to display antioxidant and antitumor activities. It has also produced a potent chemopreventive action against cancer. In the present study, the antiproliferation (using the MTT assay, DMC was found to have cytotoxic activities against GBM 8401 cell with IC₅₀ values at 22.71 μM) and induced apoptosis effects of DMC have been investigated in human brain malignant glioma GBM 8401 cells. We have studied the mitochondrial membrane potential (MMP), DNA fragmentation, caspase activation, and NF-κB transcriptional factor activity. By these approaches, our results indicated that DMC has produced an inhibition of cell proliferation as well as the activation of apoptosis in GBM 8401 cells. Both effects were observed to increase in proportion with the dosage of DMC treatment, and the apoptosis was induced by DMC in human brain malignant glioma GBM 8401 cells via mitochondria- and caspase-dependent pathways.

Enhancement of curcumin oral absorption and pharmacokinetics of curcuminoids and curcumin metabolites in mice

PURPOSE

Curcumin has shown a variety of biological activity for various human diseases including cancer in preclinical setting. Its poor oral bioavailability poses significant pharmacological barriers to its clinical application. Here, we established a practical nano-emulsion curcumin (NEC) containing up to 20% curcumin (w/w) and conducted the pharmacokinetics of curcuminoids and curcumin metabolites in mice.

METHODS

This high loading NEC was formulated based on the high solubility of curcumin in polyethylene glycols (PEGs) and the synergistic enhancement of curcumin absorption by PEGs and Cremophor EL. The pharmacokinetics of curcuminoids and curcumin metabolites was characterized in mice using a LC-MS/MS method, and the pharmacokinetic parameters were determined using WinNonlin computer software.

RESULTS

A tenfold increase in the AUC (0→24h) and more than 40-fold increase in the C (max) in mice were observed after an oral dose of NEC compared with suspension curcumin in 1% methylcellulose. The plasma pharmacokinetics of its two natural congeners, demethoxycurcumin and bisdemethoxycurcumin, and three metabolites, tetrahydrocurcumin (THC), curcumin-O-glucuronide, and curcumin-O-sulfate, was characterized for the first time in mice after an oral dose of NEC.

CONCLUSION

This oral absorption enhanced NEC may provide a practical formulation to conduct the correlative study of the PK of curcuminoids and their pharmacodynamics, e.g., hypomethylation activity in vivo.

Phase IIa clinical trial of curcumin for the prevention of colorectal neoplasia

Curcumin is derived from the spice tumeric and has antiinflammatory and antineoplastic effects in vitro and in animal models, including preventing aberrant crypt foci (ACF) and adenomas in murine models of colorectal carcinogenesis. Inhibiting the production of the procarcinogenic eicosanoids prostaglandin E₂ (PGE₂) and 5-hydroxyeicosatetraenoic acid (5-HETE) can suppress carcinogenesis in rodents. Curcumin reduces mucosal concentrations of PGE₂ (via inhibition of cyclooxygenases 1 and 2) and 5-HETE (via inhibition of 5-lipoxygenase) in rats. Although preclinical data support curcumin activity in many sites, the poor bioavailability reported for this agent supports its use in the colorectum. We assessed the effects of oral curcumin (2 g or 4 g per day for 30 days) on PGE₂ within ACF (primary endpoint), 5-HETE, ACF number, and proliferation in a nonrandomized, open-label clinical trial in 44 eligible smokers with eight or more ACF on screening colonoscopy. We assessed pre- and posttreatment concentrations of PGE₂ and 5-HETE by liquid chromatography tandem mass spectroscopy in ACF and normal-tissue biopsies; ACF number via rectal endoscopy; proliferation by Ki-67 immunohistochemistry; and curcumin concentrations by high-performance liquid chromatography in serum and rectal mucosal samples. Forty-one subjects completed the study. Neither dose of curcumin reduced PGE₂ or 5-HETE within ACF or normal mucosa or reduced Ki-67 in normal mucosa. A significant 40% reduction in ACF number occurred with the 4-g dose (P < 0.005), whereas ACF were not reduced in the 2-g group. The ACF reduction in the 4-g group was associated with a significant, five-fold increase in posttreatment plasma curcumin/conjugate levels (versus pretreatment; P = 0.009). Curcumin was well tolerated at both 2 g and 4 g. Our data suggest that curcumin can decrease ACF number, and this is potentially mediated by curcumin conjugates delivered systemically.

Metabolism as a key to histone deacetylase inhibition

There is growing interest in the epigenetic mechanisms that are dysregulated in cancer and other human pathologies. Under this broad umbrella, modulators of histone deacetylase (HDAC) activity have gained interest as both cancer chemopreventive and therapeutic agents. Of the first generation, FDA-approved HDAC inhibitors to have progressed to clinical trials, vorinostat represents a "direct acting" compound with structural features suitable for docking into the HDAC pocket, whereas romidepsin can be considered a prodrug that undergoes reductive metabolism to generate the active intermediate (a zinc-binding thiol). It is now evident that other agents, including those in the human diet, can be converted by metabolism to intermediates that affect HDAC activity. Examples are cited of short-chain fatty acids, seleno-α-keto acids, small molecule thiols, mercapturic acid metabolites, indoles, and polyphenols. The findings are discussed in the context of putative endogenous HDAC inhibitors generated by intermediary metabolism (e.g. pyruvate), the yin-yang of HDAC inhibition versus HDAC activation, and the screening assays that might be most appropriate for discovery of novel HDAC inhibitors in the future.

Autoxidative and cyclooxygenase-2 catalyzed transformation of the dietary chemopreventive agent curcumin

The efficacy of the diphenol curcumin as a cancer chemopreventive agent is limited by its chemical and metabolic instability. Non-enzymatic degradation has been described to yield vanillin, ferulic acid, and feruloylmethane through cleavage of the heptadienone chain connecting the phenolic rings. Here we provide evidence for an alternative mechanism, resulting in autoxidative cyclization of the heptadienone moiety as a major pathway of degradation. Autoxidative transformation of curcumin was pH-dependent with the highest rate at pH 8 (2.2 μM/min) and associated with stoichiometric uptake of O(2). Oxidation was also catalyzed by recombinant cyclooxygenase-2 (COX-2) (50 nm; 7.5 μM/min), and the rate was increased ≈10-fold by the addition of 300 μM H(2)O(2). The COX-2 catalyzed transformation was inhibited by acetaminophen but not indomethacin, suggesting catalysis occurred by the peroxidase activity. We propose a mechanism of enzymatic or autoxidative hydrogen abstraction from a phenolic hydroxyl to give a quinone methide and a delocalized radical in the heptadienone chain that undergoes 5-exo cyclization and oxygenation. Hydration of the quinone methide (measured by the incorporation of O-18 from H(2)(18)O) and rearrangement under loss of water gives the final dioxygenated bicyclopentadione product. When curcumin was added to RAW264.7 cells, the bicyclopentadione was increased 1.8-fold in cells activated by LPS; vanillin and other putative cleavage products were negligible. Oxidation to a reactive quinone methide is the mechanistic basis of many phenolic anti-cancer drugs. It is possible, therefore, that oxidative transformation of curcumin, a prominent but previously unrecognized reaction, contributes to its cancer chemopreventive activity.

Curcuminoids suppress the growth and induce apoptosis through caspase-3-dependent pathways in glioblastoma multiforme (GBM) 8401 cells

Curcuminoids, natural plant components, have been recently shown to display antioxidant and anti-inflammatory activities. They also produce potent chemo-preventive action against several types of cancer. In the present study, the anti-proliferative and induced apoptosis effects of curcuminoids have been investigated in human brain glioblastoma multiforme (GBM) 8401 cells. Results indicated that curcuminoids have produced an inhibition of cell proliferation in a dose-dependent manner as dosage increased from 12.5 to 100 μM (n = 6) via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay as well as activation of apoptosis in GBM 8401 cells. Both effects were observed to increase in proportion with the dose of curcuminoids. We have studied the mitochondrial membrane potential (ΔΨm), DNA fragmentation, caspase-3, caspase-8, and caspase-9 activation, and nuclear factor κB (NF-κB) transcriptional factor activity to analyze apoptosis in GBM 8401 cells. From these approaches, apoptosis was induced by curcuminoids in human brain GBM 8401 cells via mitochondria and a caspase-dependent pathway. The results observed with proliferation inhibition (y = 94.694e(-0.025x), R(2) = 0.9901, and n = 6) and apoptosis (y = 0.9789e(-0.0102x), R(2) = 0.99854, and n = 3) depend upon the amount of curcuminoid treatment in the cancer cells.

Curcumin suppresses the dynamic instability of microtubules, activates the mitotic checkpoint and induces apoptosis in MCF-7 cells

In this study, curcumin, a potential anticancer agent, was found to dampen the dynamic instability of individual microtubules in living MCF-7 cells. It strongly reduced the rate and extent of shortening states, and modestly reduced the rate and extent of growing states. In addition, curcumin decreased the fraction of time microtubules spent in the growing state and strongly increased the time microtubules spent in the pause state. Brief treatment with curcumin depolymerized mitotic microtubules, perturbed microtubule-kinetochore attachment and disturbed the mitotic spindle structure. Curcumin also perturbed the localization of the kinesin protein Eg5 and induced monopolar spindle formation. Further, curcumin increased the accumulation of Mad2 and BubR1 at the kinetochores, indicating that it activated the mitotic checkpoint. In addition, curcumin treatment increased the metaphase/anaphase ratio, indicating that it can delay mitotic progression from the metaphase to anaphase. We provide evidence suggesting that the affected cells underwent apoptosis via the p53-dependent apoptotic pathway. The results support the idea that kinetic stabilization of microtubule dynamics assists in the nuclear translocation of p53. Curcumin exerted additive effects when combined with vinblastine, a microtubule depolymerizing drug, whereas the combination of curcumin with paclitaxel, a microtubule-stabilizing drug, produced an antagonistic effect on the inhibition of MCF-7 cell proliferation. The results together suggested that curcumin inhibited MCF-7 cell proliferation by inhibiting the assembly dynamics of microtubules.

Curcumin-the paradigm of a multi-target natural compound with applications in cancer prevention and treatment

As cancer is a multifactor disease, it may require treatment with compounds able to target multiple intracellular components. We summarize here how curcumin is able to modulate many components of intracellular signaling pathways implicated in inflammation, cell proliferation and invasion and to induce genetic modulations eventually leading to tumor cell death. Clinical applications of this natural compound were initially limited by its low solubility and bioavailability in both plasma and tissues but combination with adjuvant and delivery vehicles was reported to largely improve bio-availability of curcumin. Moreover, curcumin was reported to act in synergism with several natural compounds or synthetic agents commonly used in chemotherapy. Based on this, curcumin could thus be considered as a good candidate for cancer prevention and treatment when used alone or in combination with other conventional treatments.

A potential role for Helicobacter pylori heat shock protein 60 in gastric tumorigenesis

Helicobacter pylori has been found to promote the malignant process leading to gastric cancer. Heat shock protein 60 of H. pylori (HpHSP60) was previously been identified as a potent immunogene. This study investigates the role of HpHSP60 in gastric cancer carcinogenesis. The effect of HpHSP60 on cell proliferation, anti-death activity, angiogenesis and cell migration were explored. The results showed that HpHSP60 enhanced migration by gastric cancer cells and promoted tube formation by umbilical vein endothelial cells (HUVECs); however, HpHSP60 did not increase cell proliferation nor was this protein able to rescue gastric cancer cells from death. Moreover, the results also indicated HpHSP60 had different effects on AGS gastric cancer cells or THP-1 monocytic cells in terms of their expression of pro-inflammatory cytokines, which are known to be important to cancer development. We propose that HpHSP60 may trigger the initiation of carcinogenesis by inducing pro-inflammatory cytokine release and by promoting angiogenesis and metastasis. Thus, this extracellular pathogen-derived HSP60 is potentially a vigorous virulence factor that can act as a carcinogen during gastric tumorigenesis.

Curcumin and cancer cells: how many ways can curry kill tumor cells selectively?

Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.

Curcuminoids suppress the growth of pharynx and nasopharyngeal carcinoma cells through induced apoptosis

Nasopharyngeal carcinoma (NPC) is one of the common malignant cancers in China, and radiotherapy or chemotherapy is the main therapy method for NPC. Curcuminoids (or curcumin), natural antioxidants, have been recently shown to produce a potent chemopreventive action against several types of cancer. They have also displayed antioxidant and anti-inflammatory activities. In the present study, the antiproliferation and induced apoptosis effects of curcuminoids have been investigated in Detroit 562 cells (human pharynx carcinoma) and HONE-1 (human nasopharyngeal carcinoma) cells. Results indicated that curcuminoids have produced an inhibition of cell proliferation as well as the activation of apoptosis in these cancer cells. Both effects were observed to increase in proportion with the dose of curcuminoids. The DNA fragmentation, caspase-3 activation,and NF-kappaB transcriptional factor activity have been studied. By these approaches, apoptosis was induced by curcuminoids in the pharynx and nasopharyngeal cancer cells via caspase-3-dependent pathway. However, a different dependency has been observed, whereas proliferation inhibition and apoptosis depend upon the amount of curcuminoid treatment in the cancer cells.