Curcumin: Getting Back to the Roots

Highly active anticancer curcumin analogues

Curcumin, a compound in the human food supply, represents a near-perfect starting point for drug discovery. Consequently, a number of research groups have taken the natural product as a starting point to prepare and biologically evaluate a wide variety of curcumin analogues. One widely used structural modification truncates the central conjugated beta-diketone in curcumin to the monocarbonyl dienone. A diverse array of the latter compounds exhibit cytotoxicities against an equally diverse set of cancer-related cell lines. Importantly, these compounds still retain toxicity profiles in rodents comparable to the parent natural product, whereas some analogues (e.g., EF-24, 41) exhibit good oral bioavailability and good pharmacokinetics in mice. Thiol conjugates of EF-24 analogues have been prepared that address stability and solubility issues while demonstrating cellular activities similar to the unmodified dienones. In parallel experiments, the factor VIIa-tissue factor complex (fVIIa-TF) has been exploited to develop a targeting strategy for the analogues. In particular, the EF24-FFRck-fVIIa protein conjugate is not only somewhat more effective relative to the drug alone against breast cancer and melanocyte cells. Both simple curcumin analogues and the protein conjugate evidence antiangiogenic activity in cell culture. The implication is that the fVIIa-TF targeting process, like the dienone drugs, permits a double-pronged attack with the potential to destroy a tumor directly by apoptosis.

CURCUMIN: THE INDIAN SOLID GOLD

Turmeric, derived from the plant Curcuma longa, is a gold-colored spice commonly used in the Indian subcontinent, not only for health care but also for the preservation of food and as a yellow dye for textiles. Curcumin, which gives the yellow color to turmeric, was first isolated almost two centuries ago, and its structure as diferuloylmethane was determined in 1910. Since the time of Ayurveda (1900 Bc) numerous therapeutic activities have been assigned to turmeric for a wide variety of diseases and conditions, including those of the skin, pulmonary, and gastrointestinal systems, aches, pains, wounds, sprains, and liver disorders. Extensive research within the last half century has proven that most of these activities, once associated with turmeric, are due to curcumin. Curcumin has been shown to exhibit antioxidant, anti-inflammatory, antiviral, antibacterial, antifungal, and anticancer activities and thus has a potential against various malignant diseases, diabetes, allergies, arthritis, Alzheimer's disease, and other chronic illnesses. These effects are mediated through the regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other enzymes. Curcumin exhibits activities similar to recently discovered tumor necrosis factor blockers (e.g., HUMIRA, REMICADE, and ENBREL), a vascular endothelial cell growth factor blocker (e.g., AVASTIN), human epidermal growth factor receptor blockers (e.g., ERBITUX, ERLOTINIB, and GEFTINIB), and a HER2 blocker (e.g., HERCEPTIN). Considering the recent scientific bandwagon that multitargeted therapy is better than monotargeted therapy for most diseases, curcumin can be considered an ideal "Spice for Life".

Metabolism and anticancer activity of the curcumin analogue, dimethoxycurcumin

PURPOSE

The plant-derived compound curcumin has shown promising abilities as a cancer chemoprevention and chemotherapy agent in vitro and in vivo but exhibits poor bioavailability. Therefore, there is a need to investigate modified curcumin congeners for improved anticancer activity and pharmacokinetic properties.

EXPERIMENTAL DESIGN

The synthetic curcumin analogue dimethoxycurcumin was compared with curcumin for ability to inhibit proliferation and apoptosis of human HCT116 colon cancer cells in vitro by estimating the GI(50) and LC(50) values and detecting the extent of apoptosis by flow cytometry analysis of the cell cycle. Metabolic stability and/or identification of metabolites were evaluated by recently developed mass spectrometric approaches after incubation with mouse and human liver microsomes and cancer cells in vitro. Additionally, circulating levels of dimethoxycurcumin and curcumin were determined in mice following i.p. administration.

RESULTS

Dimethoxycurcumin is significantly more potent than curcumin in inhibiting proliferation and inducing apoptosis in HCT116 cells treated for 48 h. Nearly 100% of curcumin but <30% of dimethoxycurcumin was degraded in cells treated for 48 h, and incubation with liver microsomes confirmed the limited metabolism of dimethoxycurcumin. Both compounds were rapidly degraded in vivo but dimethoxycurcumin was more stable.

CONCLUSIONS

Compared with curcumin, dimethoxycurcumin is (a) more stable in cultured cells, (b) more potent in the ability to kill cancer cells by apoptosis, (c) less extensively metabolized in microsomal systems, and (d) more stable in vivo. It is likely that the differential extent of apoptosis induced by curcumin and dimethoxycurcumin in vitro is associated with the metabolite profiling and/or the extent of stability.

Protection from acute and chronic lung diseases by curcumin

The aim of this review has been to describe the current state of the therapeutic potential of curcumin in acute and chronic lung injuries. Occupational and environmental exposures to mineral dusts, airborne pollutants, cigarette smoke, chemotherapy, and radiotherapy injure the lungs, resulting in acute and chronic inflammatory lung diseases. Despite major advances in treating lung diseases, until now disease-modifying efficacy has not been demonstrated for any of the existing drugs. Current medical therapy offers only marginal benefit; therefore, there is an essential need to develop new drugs that might be of effective benefit in clinical settings. Over the years, there has been increasing evidence that curcumin, a phytochemical present in turmeric (Curcuma longa), has a wide spectrum of therapeutic properties and a remarkable range of protective effects in various diseases. Several experimental animal models have tested curcumin on lung fibrosis and these studies demonstrate that curcumin attenuates lung injury and fibrosis caused by radiation, chemotherapeutic drugs, and toxicants. The growing amount of data from pharmacological and animal studies also supports the notion that curcumin plays a protective role in chronic obstructive pulmonary disease, acute lung injury, acute respiratory distress syndrome, and allergic asthma, its therapeutic action being on the prevention or modulation of inflammation and oxidative stress. These findings give substance to the possibility of testing curcumin in patients with lung diseases.

Modulation of transcription factors by curcumin

Curcumin is the active ingredient of turmeric that has been consumed as a dietary spice for ages. Turmeric is widely used in traditional Indian medicine to cure biliary disorders, anorexia, cough, diabetic wounds, hepatic disorders, rheumatism, and sinusitis. Extensive investigation over the last five decades has indicated that curcumin reduces blood cholesterol, prevents low-density lipoprotein oxidation, inhibits platelet aggregation, suppresses thrombosis and myocardial infarction, suppresses symptoms associated with type II diabetes, rheumatoid arthritis, multiple sclerosis, and Alzheimer's disease, inhibits HIV replication, enhances wound healing, protects from liver injury, increases bile secretion, protects from cataract formation, and protects from pulmonary toxicity and fibrosis. Evidence indicates that the divergent effects of curcumin are dependent on its pleiotropic molecular effects. These include the regulation of signal transduction pathways and direct modulation of several enzymatic activities. Most of these signaling cascades lead to the activation of transcription factors. Curcumin has been found to modulate the activity of several key transcription factors and, in turn, the cellular expression profiles. Curcumin has been shown to elicit vital cellular responses such as cell cycle arrest, apoptosis, and differentiation by activating a cascade of molecular events. In this chapter, we briefly review the effects of curcumin on transcription factors NF-KB, AP-1, Egr-1, STATs, PPAR-gamma, beta-catenin, nrf2, EpRE, p53, CBP, and androgen receptor (AR) and AR-related cofactors giving major emphasis to the molecular mechanisms of its action.

Comparison of oxaliplatin- and curcumin-mediated antiproliferative effects in colorectal cell lines

Colorectal cancer remains a leading cause of cancer death worldwide, despite markedly improved response rates to current systemic therapies. Oxaliplatin either alone or incorporated into 5-fluorouracil/leucovorin regimes has resulted in increased survival rates, particularly with regards to metastatic colorectal carcinoma. The chemopreventive polyphenol curcumin, which is currently in clinical trial, has been advocated for use in colorectal cancer either singly or in combination with chemotherapeutic drugs. In this study, the antiproliferative capacity of both compounds was compared in HCEC (normal-derived), HT29 (p53 mutant adenocarcinoma) and HCT116 (p53wt adenocarcinoma) colorectal cell lines to determine whether effects were cell-type specific at pharmacologically achievable doses, and whether the combination resulted in enhanced efficacy. Both oxaliplatin and curcumin displayed marked antiproliferative capacity at therapeutic concentrations in the two tumor cell lines. Order of sensitivity to oxaliplatin was HCT116>HT29>HCEC, whereas order of sensitivity to curcumin was HT29>HCT116>HCEC. HCT116 cells underwent induction of G2/M arrest in response to both oxaliplatin (irreversible) and curcumin (reversible). Apoptosis was induced by both agents, and up to 16-fold induction of p53 protein was observed in response to the combination. Antiproliferative effects in HT29 cells were largely cell cycle independent, and were mediated by induction of apoptosis. Effects were greatly enhanced in both cell lines when agents were combined. This study provides further evidence that curcumin may be of use in therapeutic regimes directed against colorectal cancer, and suggests that in combination with oxaliplatin it may enhance efficacy of the latter in both p53wt and p53 mutant colorectal tumors.

SAHA induces apoptosis in hepatoma cells and synergistically interacts with the proteasome inhibitor Bortezomib

Histone deacetylase (HDAC) inhibitors represent a promising group of anticancer agents. This paper shows that the HDAC inhibitor suberoylanilide hydroxamic acid (SAHA) stimulated at 5-10 microM apoptosis in human hepatoma HepG2 and Huh6 cells, but was ineffective in primary human hepatocytes (PHH). In HepG2 cells SAHA induced the extrinsic apoptotic pathway, increasing the expression of both FasL and FasL receptor and causing the activation of caspase-8. Moreover, SAHA enhanced the level of Bim proteins, stimulated alternative splicing of the Bcl-X transcript with the expression of the proapoptotic Bcl-Xs isoform, induced degradation of Bid into the apoptotic factor t-Bid and dephosphorylation and inactivation of the anti-apoptotic factor Akt. Consequently, SAHA caused loss of mitochondrial transmembrane potential, release of cytochrome c from mitochondria, activation of caspase-3 and degradation of PARP. Interestingly, a combination of suboptimal doses of SAHA (1 microM) and bortezomib (5-10 nM), a potent inhibitor of 26S proteasome, synergistically induced apoptosis in both HepG2 and Huh6 cells, but was ineffective in PHH. Combined treatment increased with synergistic effects the expression levels of c-Jun, phospho-c-Jun and FasL and the production of Bcl-Xs. These effects were accompanied by activation of Bid, caspase-8 and 3. In conclusion, SAHA stimulated apoptosis in hepatoma cells and exerted a synergistic apoptotic effect when combined with bortezomib. In contrast, these treatments were quite ineffective in inducing apoptosis in PHH. Thus, our results suggest the potential application of the SAHA/bortezomib combination in clinical trials for liver cancer.

Evolution of medical treatment for endometriosis: back to the roots?

Experimental evidence is accumulating to suggest that medicinal botanicals have anti-inflammatory and pain-alleviating properties and hold promise for treatment of endometriosis. Herein, we present a systematic review of clinical and experimental data on the use of medicinal herbs in the treatment of endometriosis. Although there is a general lack of evidence from clinical studies on the potential efficacy of medicinal herbs for the treatment of endometriosis-associated symptoms, our review highlights the anti-inflammatory and pain-alleviating mechanisms of action of herbal remedies. Medicinal herbs and their active components exhibit cytokine-suppressive, COX-2-inhibiting, antioxidant, sedative and pain-alleviating properties. Each of these mechanisms of action would be predicted to have salutary effects in endometriosis. Better understanding of the mechanisms of action, toxicity and herb-herb and herb-drug interactions permits the optimization of design and execution of complementary alternative medicine trials for endometriosis-associated pain. A potential benefit of herbal therapy is the likelihood of synergistic interactions within individual or combinations of plants. In this sense, phytotherapies may be analogous to nutraceuticals or whole food nutrition. We encourage the development of herbal analogues and establishment of special, simplified registration procedures for certain medicinal products, particularly herbal derivates with a long tradition of safe use.

Systematic review: the application of molecular pathogenesis to prevention and treatment of oesophageal adenocarcinoma

BACKGROUND

Oesophageal adenocarcinoma is an increasingly common cancer with a poor prognosis. It develops in a stepwise progression from Barrett's metaplasia to dysplasia, and then adenocarcinoma followed by metastasis.

AIM

To outline the key molecular changes in oesophageal adenocarcinoma and to summarize the chemopreventative and therapeutic strategies proposed.

METHODS

A literature search was performed to identify appropriate research papers in the field. Search terms included: Barrett's (o)esophagus, intestinal metaplasia, (o)esophageal adenocarcinoma, molecular changes, genetic changes, pathogenesis, chemoprevention, therapeutic strategies and treatment. The search was restricted to English language articles.

RESULTS

A large number of molecular changes have been identified in the progression from Barrett's oesophagus to oesophageal adenocarcinoma although there does not appear to be an obligate order of events. Potential chemoprevention strategies include acid suppression, anti-inflammatory agents and antioxidants. In established adenocarcinoma, targeted treatments under evaluation include receptor tyrosine kinase inhibitors of EGFR and cyclin-dependent kinase inhibitors, which may benefit a subgroup of patients.

CONCLUSIONS

Advances in molecular methodology have led to a greater understanding of the oesophageal adenocarcinoma pathways, which provides opportunities for chemoprevention and therapeutic strategies with a mechanistic basis. More work is required to assess both the safety and efficacy of these new treatments.

Effect of curcumin and curcumin copper complex (1:1) on radiation-induced changes of anti-oxidant enzymes levels in the livers of Swiss albino mice

The effect of mononuclear copper (II) complex of curcumin in 1:1 stoichiometry (hereafter referred to as complex) administered 30 min before gamma-irradiation (4.5 Gy) on alterations in antioxidant and Thiobarbituric acid reactive substances (TBARS) levels in livers was studied in comparison to curcumin at a dose of 50 mg/kg. The different antioxidants like GSH, GST, catalase, SOD, TBARS and total thiols were estimated in the liver homogenates excised at different time intervals (1, 2 and 4 h) post irradiation using colorimetric methods. There was a radiation-induced decrease in the levels of all the studied enzymes at 1 h post irradiation, while an increase was observed at later time points. Both curcumin and complex treatment in sham-irradiated mice decreased the levels of GSH and total thiols, whereas there was an increase in the levels of catalase, GST and SOD compared to normal control. Under the influence of irradiation, both curcumin and complex treatment protected the decline in the levels of GSH, GST, SOD, catalase and total thiols, and inhibited radiation-induced lipid peroxidation. Further, the complex was found to be more effective in protecting the enzymes at 1 h post irradiation compared to curcumin treated group. This may be due to the higher rate constants of the complex compared to curcumin for their reactions with various free radicals.

Curcumin reverses breast tumor exosomes mediated immune suppression of NK cell tumor cytotoxicity

An important characteristic of tumors is that they at some point in their development overcome the surveillance of the immune system. Tumors secrete exosomes, multivesicular bodies containing a distinct set of proteins that can fuse with cells of the circulating immune system. Purified exosomes from TS/A breast cancer cells, but not non-exosomal fractions, inhibit (at concentrations of nanograms per ml protein) IL-2-induced natural killer (NK) cell cytotoxicity. The dietary polyphenol, curcumin (diferuloylmethane), partially reverses tumor exosome-mediated inhibition of natural killer cell activation, which is mediated through the impairment of the ubiquitin-proteasome system. Exposure of mouse breast tumor cells to curcumin causes a dose-dependent increase in ubiquitinated exosomal proteins compared to those in untreated TS/A breast tumor cells. Furthermore, exosomes isolated from tumor cells pretreated with curcumin have a much attenuated inhibition of IL-2 stimulated NK cell activation. Jak3-mediated activation of Stat5 is required for tumor cytotoxicity of IL-2 stimulated NK cells. TS/A tumor exosomes strongly inhibit activation of Stat5, whereas the tumor exosomes isolated from curcumin-pretreated tumor cells have a lowered potency for inhibition of IL-2 stimulated NK cell cytotoxicity. These data suggest that partial reversal of tumor exosome-mediated inhibition of NK cell tumor cytotoxicity may account for the anti-cancer properties of curcumin.

Polymeric nanoparticle-encapsulated curcumin ("nanocurcumin"): a novel strategy for human cancer therapy

Background

Curcumin, a yellow polyphenol extracted from the rhizome of turmeric (Curcuma longa), has potent anti-cancer properties as demonstrated in a plethora of human cancer cell line and animal carcinogenesis models. Nevertheless, widespread clinical application of this relatively efficacious agent in cancer and other diseases has been limited due to poor aqueous solubility, and consequently, minimal systemic bioavailability. Nanoparticle-based drug delivery approaches have the potential for rendering hydrophobic agents like curcumin dispersible in aqueous media, thus circumventing the pitfalls of poor solubility.

Results

We have synthesized polymeric nanoparticle encapsulated formulation of curcumin – nanocurcumin – utilizing the micellar aggregates of cross-linked and random copolymers of N-isopropylacrylamide (NIPAAM), with N-vinyl-2-pyrrolidone (VP) and poly(ethyleneglycol)monoacrylate (PEG-A). Physico-chemical characterization of the polymeric nanoparticles by dynamic laser light scattering and transmission electron microscopy confirms a narrow size distribution in the 50 nm range. Nanocurcumin, unlike free curcumin, is readily dispersed in aqueous media. Nanocurcumin demonstrates comparable in vitro therapeutic efficacy to free curcumin against a panel of human pancreatic cancer cell lines, as assessed by cell viability and clonogenicity assays in soft agar. Further, nanocurcumin's mechanisms of action on pancreatic cancer cells mirror that of free curcumin, including induction of cellular apoptosis, blockade of nuclear factor kappa B (NFκB) activation, and downregulation of steady state levels of multiple pro-inflammatory cytokines (IL-6, IL-8, and TNFα).

Conclusion

Nanocurcumin provides an opportunity to expand the clinical repertoire of this efficacious agent by enabling ready aqueous dispersion. Future studies utilizing nanocurcumin are warranted in pre-clinical in vivo models of cancer and other diseases that might benefit from the effects of curcumin.

Neuroprotective effect of curcumin on focal cerebral ischemic rats by preventing blood–brain barrier damage

Curcumin, a member of the curcuminoid family of compounds, is a yellow colored phenolic pigment obtained from powdered rhizome of C. longa Linn. Recent studies have demonstrated that curcumin has protective effects against cerebral ischemia/reperfusion injury. However, little is known about its mechanism. Disruption of the blood-brain barrier occurs after stroke. Protection of the blood-brain barrier has become an important target of stroke interventions in experimental therapeutic. The objective of the present study was to determine whether curcumin prevents cerebral ischemia/reperfusion injury by protecting blood-brain barrier integrity. We report that a single injection of curcumin (1 and 2 mg/kg, i.v.) 30 min after focal cerebral ischemia/reperfusion in rats significantly diminished infarct volume, improved neurological deficit, decreased mortality, reduced the water content of the brain and the extravasation of Evans blue dye in ipsilateral hemisphere in a dose-dependent manner. In cultured astrocytes, curcumin significantly inhibited inducible nitric oxide synthase (iNOS) expression and NO(x) (Nitrites/nitrates contents) production induced by lipopolysaccharide (LPS)/tumor necrosis factor alpha (TNF(alpha)). Furthermore, curcumin prevented ONOO(-) donor SIN-1-induced cerebral capillaries endothelial cells damage. We concluded that curcumin ameliorates cerebral ischemia/reperfusion injury by preventing ONOO(-) mediated blood-brain barrier damage.

Keratinocyte proliferation, differentiation, and apoptosis--differential mechanisms of regulation by curcumin, EGCG and apigenin

We have proposed that it is important to examine the impact of chemopreventive agents on the function of normal human epidermal keratinocytes since these cells comprise the barrier that protects the body from a range of environmental insults. In this context, it is widely appreciated that cancer may be retarded by consumption or topical application of naturally occurring food-derived chemopreventive agents. Our studies show that (-)-epigallocatechin-3-gallate (EGCG), a green tea-derived polyphenol, acts to enhance the differentiation of normal human keratinocytes as evidenced by its ability to increase involucrin (hINV), transglutaminase type 1 (TG1) and caspase-14 gene expression. EGCG also stimulates keratinocyte morphological differentiation. These actions of EGCG are mediated via activation of a nPKC, Ras, MEKK1, MEK3, p38delta-ERK1/2 signaling cascade which leads to increased activator protein 1 (AP1) and CAATT enhancer binding protein (C/EBP) transcription factor expression, increased binding of these factors to DNA, and increased gene transcription. In contrast, apigenin, a dietary flavonoid derived from plants and vegetables, and curcumin, an agent derived from turmeric, inhibit differentiation by suppressing MAPK signal transduction and reducing API transcription factor level. Curcumin also acts to enhance apoptosis, although EGCG and apigenin do not stimulate apoptosis. In addition, all of these agents inhibit keratinocyte proliferation. These findings indicate that each of these diet-derived chemopreventive agents has a profound impact on normal human keratinocyte function and that they operate via distinct and sometimes opposing mechanisms. However, all are expected to act as chemopreventive agents.

Evidence that curcumin suppresses the growth of malignant gliomas in vitro and in vivo through induction of autophagy: role of Akt and extracellular signal-regulated kinase signaling pathways

Autophagy is a response of cancer cells to various anticancer therapies. It is designated as programmed cell death type II and characterized by the formation of autophagic vacuoles in the cytoplasm. The Akt/mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (p70S6K) and the extracellular signal-regulated kinases 1/2 (ERK1/2) pathways are two major pathways that regulate autophagy induced by nutrient starvation. These pathways are also frequently associated with oncogenesis in a variety of cancer cell types, including malignant gliomas. However, few studies have examined both of these signal pathways in the context of anticancer therapy-induced autophagy in cancer cells, and the effect of autophagy on cell death remains unclear. Here, we examined the anticancer efficacy and mechanisms of curcumin, a natural compound with low toxicity in normal cells, in U87-MG and U373-MG malignant glioma cells. Curcumin induced G(2)/M arrest and nonapoptotic autophagic cell death in both cell types. It inhibited the Akt/mTOR/p70S6K pathway and activated the ERK1/2 pathway, resulting in induction of autophagy. It is interesting that activation of the Akt pathway inhibited curcumin-induced autophagy and cytotoxicity, whereas inhibition of the ERK1/2 pathway inhibited curcumin-induced autophagy and induced apoptosis, thus resulting in enhanced cytotoxicity. These results imply that the effect of autophagy on cell death may be pathway-specific. In the subcutaneous xenograft model of U87-MG cells, curcumin inhibited tumor growth significantly (P < 0.05) and induced autophagy. These results suggest that curcumin has high anticancer efficacy in vitro and in vivo by inducing autophagy and warrant further investigation toward possible clinical application in patients with malignant glioma.

Spleen tyrosine kinase (Syk), a novel target of curcumin, is required for B lymphoma growth

Curcumin (diferuloylmethane), a component of dietary spice turmeric (Curcuma longa), has been shown in recent studies to have therapeutic potential in the treatment of cancer, diabetes, arthritis, and osteoporosis. We investigated the ability of curcumin to modulate the growth of B lymphomas. Curcumin inhibited the growth of both murine and human B lymphoma in vitro and murine B lymphoma in vivo. We also demonstrate that curcumin-mediated growth inhibition of B lymphoma is through inhibition of the survival kinase Akt and its key target Bad. However, in vitro kinase assays show that Akt is not a direct target of curcumin. We identified a novel target for curcumin in B lymphoma viz spleen tyrosine kinase (Syk). Syk is constitutively activated in primary tumors and B lymphoma cell lines and curcumin down-modulates Syk activity accompanied by down-regulation of Akt activation. Moreover, we show that overexpression of Akt, a target of Syk, or Bcl-x(L), a target of Akt can overcome curcumin-induced apoptosis of B lymphoma cells. These observations suggest a novel growth promoting role for Syk in lymphoma cells.

Analysis of thein vitro metabolites of diferuloylmethane (curcumin) by liquid chromatography — tandem mass spectrometry on a hybrid quadrupole linear ion trap system: newly identified metabolites

In this study, we have described a novel approach for determining the metabolic scheme of diferuloylmethane (curcumin) in mouse and human liver microsomal preparations using a hybrid quadrupole linear ion trap mass spectrometer coupled with liquid chromatography for the detection of new metabolites. Application of various acquisition modes allowed targeted searches for metabolites with high sensitivity and selectivity using information of the mass spectral fragmentation properties of curcumin. Structural assignments for metabolites previously reported in the literature were made with confidence using the described approach. In addition, we identified curcumin metabolites that had not previously been reported, such as curcumin bisglucuronide and O-demethylated derivatives. The major pathways of curcumin metabolism in vitro have been summarized. Finally, very similar metabolic pathways of curcumin were observed in human and mouse microsomes.

The redox chemistry of the Alzheimer's disease amyloid beta peptide

There is a growing body of evidence to support a role for oxidative stress in Alzheimer's disease (AD), with increased levels of lipid peroxidation, DNA and protein oxidation products (HNE, 8-HO-guanidine and protein carbonyls respectively) in AD brains. The brain is a highly oxidative organ consuming 20% of the body's oxygen despite accounting for only 2% of the total body weight. With normal ageing the brain accumulates metals ions such iron (Fe), zinc (Zn) and copper (Cu). Consequently the brain is abundant in antioxidants to control and prevent the detrimental formation of reactive oxygen species (ROS) generated via Fenton chemistry involving redox active metal ion reduction and activation of molecular oxygen. In AD there is an over accumulation of the Amyloid beta peptide (Abeta), this is the result of either an elevated generation from amyloid precursor protein (APP) or inefficient clearance of Abeta from the brain. Abeta can efficiently generate reactive oxygen species in the presence of the transition metals copper and iron in vitro. Under oxidative conditions Abeta will form stable dityrosine cross-linked dimers which are generated from free radical attack on the tyrosine residue at position 10. There are elevated levels of urea and SDS resistant stable linked Abeta oligomers as well as dityrosine cross-linked peptides and proteins in AD brain. Since soluble Abeta levels correlate best with the degree of degeneration [C.A. McLean, R.A. Cherny, F.W. Fraser, S.J. Fuller, M.J. Smith, K. Beyreuther, A.I. Bush, C.L. Masters, Soluble pool of Abeta amyloid as a determinant of severity of neurodegeneration in Alzheimer's disease, Ann. Neurol. 46 (1999) 860-866] we suggest that the toxic Abeta species corresponds to a soluble dityrosine cross-linked oligomer. Current therapeutic strategies using metal chelators such as clioquinol and desferrioxamine have had some success in altering the progression of AD symptoms. Similarly, natural antioxidants curcumin and ginkgo extract have modest but positive effects in slowing AD development. Therefore, drugs that target the oxidative pathways in AD could have genuine therapeutic efficacy.

Curcumin content of turmeric and curry powders

Curcumin, derived from the rhizome curcuma longa, is one of the primary ingredients in turmeric and curry powders that are used as spices in Middle Eastern and Asian countries, especially on the Indian subcontinent. More recently, laboratory studies have demonstrated that dietary curcumin exhibits various biological activities and significantly inhibits colon tumorigenesis and tumor size in animals. Curcumin displays both anti-inflammatory and antioxidant properties, giving it the potential to be considered in the development of cancer preventive strategies and applications in clinical research. Experimental studies have shown the biological activities of the compound, but much more information on pharmacokinetics, bioavailability, and food content are needed. Whether the amount of curcumin in turmeric and curry powders is sufficient to suggest effects on biological activities and cancer risk is unknown. To determine and compare the quantitative amounts of curcumin that are present in several brands of turmeric and curry powders, a high performance liquid chromatography technique was used to analyze 28 spice products described as turmeric or curry powders and two negative controls. Pure turmeric powder had the highest curcumin concentration, averaging 3.14% by weight. The curry powder samples, with one exception, had relatively small amounts of curcumin present, and the variability in content was great. The curcumin content of these seasoning products that are consumed as a component of the diet should be considered in evaluating baseline tissue concentration and response to curcumin supplementation, which is under study in chemoprevention trials.

Dimethylfumarate induces immunosuppression via glutathione depletion and subsequent induction of heme oxygenase 1

A mixture of different fumaric acid esters (FAE) is established for systemic therapy of psoriasis, a frequent inflammatory skin disease. The main active compound of FAE, however, has not been identified so far, and the mechanisms of activity are only partially understood. We analyzed the impact of FAE on in vitro immune function and aimed to gain knowledge about the mode of action. Dimethylfumarate (DMF) and diethylfumarate (DEF), but not fumaric acid, methylhydrogenfumarate and ethylhydrogenfumarate, exhibited potent depression of inflammatory cytokine secretion (e.g., tumor necrosis factoralpha, IL-12, and IFNgamma) in activated human peripheral blood mononuclear cells. Moreover, solely DMF and DEF inhibited alloreactive T-cell proliferation in mixed leukocyte reaction. Interestingly, these immunosuppressive effects were accompanied by the strong induction of the anti-inflammatory stress protein heme oxygenase 1 (HO-1). Supplementation with exogenous glutathione (GSH), which is known to bind DMF, prevented both HO-1 induction as well as the anti-inflammatory effects of DMF. Moreover, inhibition of HO-1 activity restored the diminished IL-12 and IFNgamma production after FAE treatment. These results suggest that DMF acts as active compound within the FAE mixture and at least partially mediates its immunomodulatory activity by the induction of the anti-inflammatory stress protein HO-1 ascribed to the functional depletion of reduced GSH.

Effect of Curcumin Treatment on Protein Phosphorylation in K562 Cells

Deregulation of signaling pathways is a common feature observed in human cancers and other diseases. Therefore, there is a strong need for compounds that are able to modulate or inactivate upregulated signaling events. Natural compounds extracted from plants have long been used and still present a dynamic domain in the research of new therapeutic tools. Among those molecules, curcumin was already described for its antioxidative, anti-inflammatory, and antiseptic properties. Many actions of curcumin target proteins and kinases implicated in the signaling pathways. However, the effects described depend on the treatment conditions used, as well as the cell line studied, and these features vary strongly from one study to the other. During this work, we evaluated the effect of one curcumin treatment (20 muM, 48 h) on the phosphorylation of a number of proteins and kinases in the human chronic myelogenous leukemia cell line K562. These results allow to compare the results obtained in one condition on various proteins.

Natural products as alternative treatments for metabolic bone disorders and for maintenance of bone health

Bone metabolism involves a complex balance between the deposition of matrix and mineralization and resorption. There is now good evidence that dietary components and herbal products can influence these processes, particularly by inhibiting bone resorption, thus having beneficial effects on the skeleton. For example, it has been reported that a number of common vegetables, including onion, garlic and parsley, can inhibit bone resorption in ovariectomized rats. Essential oils derived from sage, rosemary, thyme and other herbs inhibit osteoclast activity in vitro and in vitro and leading to an increase in bone mineral density. Soya, a rich source of isoflavones, has shown promising results and epidemiological evidence to support a use in maintaining bone health, and various traditional herbal formulae in Chinese and Ayurvedic medicine also have demonstrable effects in pharmacological models of osteoporosis. Recently, cannabinoids have been described as having positive effects on osteoblast differentiation, and the presence of cannabinoid receptors in bone tissue indicates a more complex role in bone metabolism than previously thought. The first part of this review briefly discusses normal bone metabolism and disorders caused by its disruption, with particular reference to osteoporosis and current pharmacological treatments. The effects of natural products on bone and connective tissue are then discussed, to include items of diet, herbal extracts and food supplements, with evidence for their efficacy outlined.

High-performance liquid chromatography analysis of curcumin in rat plasma: application to pharmacokinetics of polymeric micellar formulation of curcumin

A simple, rapid and reliable high-performance liquid chromatographic (HPLC) method was developed and validated for the determination of curcumin in rat plasma. Plasma was precipitated with acetonitrile after addition of the internal standard (IS), 4-hydroxybenzophenone. Separation was achieved on a Waters muBondapak C(18) column (3.9 x 300 mm, 5 microm) using acetonitrile (55%) and citric buffer, pH 3.0 (45%) as the mobile phase (flow rate = 1.0 mL/min). The UV detection wavelength was 300 and 428 nm for IS and curcumin, respectively. The extraction efficiencies were 97.08, 95.69 and 94.90% for 50, 200 and 1000 ng/mL of curcumin in rat plasma, respectively. The calibration curve was linear over the range 0.02-1 microg/mL with a correlation coefficient of r(2) > 0.999. The intra- and inter-day coefficients of variation were less than 13%, and mean intra- and inter-day errors were less than +/-6% at 50, 200 and 1000 ng/mL of curcumin. This assay was successfully applied to the pharmacokinetic studies of both solubilized curcumin and its polymeric micellar formulation in rats. It was found that polymeric micelles increased the half-life of curcumin 162-fold that of solubilized curcumin and increased the volume of distribution (Vd(ss)) by 70-fold.

Curcumin Affects Development of Zebrafish Embryo

Embryotoxic and teratogenic effects of curcumin on the development of zebrafish embryo were investi-gated in this study. The LD(50) values of curcumin (24-h incubation) were estimated at 7.5 microM and 5 microM for embryos and larvae, respectively. The developmental defects caused by curcumin treatments include bent or hook-like tails, spinal column curving, edema in pericardial sac, retarded yolk sac resorption, and shorter body length. In curcumin-treated larvae, fluorescence signals of curcumin were found in edamae sac and some skin cells. Together, these results indicate that zebrafish are suitable model organisms to study the toxic effects of curcumin.

Nuclear factor-kappaB (NF-kappaB) is frequently expressed in lung cancer and preneoplastic lesions

BACKGROUND

Nuclear factor-kappaB (NF-kappaB), a key transcription factor thought to play a major role in carcinogenesis, regulates many important signaling pathways involved in tumor promotion. Although NF-kappaB can be activated in lung cancer cell lines by tobacco exposure, there have been no studies of the expression of NF-kappaB in lung cancer pathogenesis.

METHODS

The immunohistochemical expression of NF-kappaB p65 was investigated in 394 lung cancers (370 nonsmall cell lung carcinomas [NSCLC]; and 24 small cell lung carcinomas [SCLC]) and 269 lung normal epithelium and preneoplastic lesions, including hyperplasias, squamous metaplasias, dysplasias, and atypical adenomatous hyperplasias.

RESULTS

High levels of nuclear immunohistochemical expression of NF-kappaB p65 were detected in the lung cancers, with significantly higher levels in SCLCs compared with NSCLCs (P<.0001). In adenocarcinomas the NF-kappaB p65 expression level was significantly higher in advanced TNM stages (III-IV) than in earlier stages (I-II) (P<.0001), and when NF-kappaB p65 is dichotomized using 50% as the cutoff point (high vs low), a higher NF-kappaB p65 expression level was detected in tumors having either K-RAS (P = .02) or EGFR (P = .009) mutations compared with wildtype tumors. A relatively high level of nuclear NF-kappaB p65 expression was detected in normal and mildly abnormal epithelium, and a progression with increasing histology severity was detected in preneoplastic lesions.

CONCLUSIONS

NF-kappaB p65 nuclear expression is an early and frequent phenomenon in the pathogenesis of lung cancer. The findings indicate that NF-kappaB activation plays an important role in lung cancer pathogenesis and is a suitable target for the development of new lung cancer therapies and chemoprevention strategies.

Curcumin suppresses AP1 transcription factor-dependent differentiation and activates apoptosis in human epidermal keratinocytes

The diet-derived cancer preventive agent, curcumin, inhibits skin cancer cell proliferation and tumor formation. However, its effect on normal human keratinocyte differentiation, proliferation, and apoptosis has not been adequately studied. Involucrin (hINV) is a marker of keratinocyte differentiation and a useful model for the study of chemopreventive agent action. We show that curcumin suppresses the differentiation agent-dependent activation of hINV gene expression and that an AP1 transcription factor DNA binding site in the hINV gene is required for this regulation. A protein kinase C, Ras, MEKK1, MEK3 signaling cascade controls hINV expression by regulating AP1 factor level. Curcumin treatment inhibits the novel protein kinase C-, Ras-, and MEKK1-dependent activation of hINV promoter activity and reduces the differentiation agent-dependent increase in AP1 factor level and DNA binding. This reduction requires proteasome function. In addition, curcumin treatment reduces cell number, which is associated with a reduced cyclin and cdk1 levels. Curcumin treatment also suppresses the Bcl-xL level, leading to reduced mitochondrial membrane potential and increased cleavage of procaspases and poly(ADP-ribose) polymerase. These studies provide important insights regarding the mechanism whereby curcumin acts as a chemopreventive agent in normal human epidermis.

Oxidative stress in Alzheimer's disease

Oxidative damage is a major feature in the pathophysiology of Alzheimer's disease (AD). In this review, we discuss free radical-mediated damage to the biochemical components involved in the pathology and clinical symptoms of AD. We explain how amyloid beta-protein (Abeta), microtubule-associated protein tau, presenilins, apolipoprotein E, mitochondria and proteases play a role in increasing oxidative stress in AD. Abeta not only can induce oxidative stress, but its generation is also increased as a result of oxidative stress. Finally, a hypothetical model linking oxidative stress with beta-amyloid and neurofibrillary tangle pathology in AD is proposed.

Synthetic curcuminoids modulate the arachidonic acid metabolism of human platelet 12-lipoxygenase and reduce sprout formation of human endothelial cells

Platelet 12-lipoxygenase (P-12-LOX) is overexpressed in different types of cancers, including prostate cancer, and the level of expression is correlated with the grade of this cancer. Arachidonic acid is metabolized by 12-LOX to 12(S)-hydroxyeicosatetraenoic acid [12(S)-HETE], and this biologically active metabolite is involved in prostate cancer progression by modulating cell proliferation in multiple cancer-related pathways inducing angiogenesis and metastasis. Thus, inhibition of P-12-LOX can reduce these two processes. Several lipoxygenase inhibitors are known, including plant and mammalian lipoxygenases, but only a few of them are known inhibitors of P-12-LOX. Curcumin is one of these lipoxygenase inhibitors. Using a homology model of the three-dimensional structure of human P-12-LOX, we did computational docking of synthetic curcuminoids (curcumin derivatives) to identify inhibitors superior to curcumin. Docking of the known inhibitors curcumin and NDGA to P-12-LOX was used to optimize the docking protocol for the system in study. Over 75% of the compounds of interest were successfully docked into the active site of P-12-LOX, many of them sharing similar binding modes. Curcuminoids that did not dock into the active site did not inhibit P-12-LOX. From a set of the curcuminoids that were successfully docked and selected for testing, two were found to inhibit human lipoxygenase better than curcumin. False-positive curcuminoids showed high LogP (theoretical) values, indicating poor water solubility, a possible reason for lack of inhibitory activity or/and nonrealistic binding. Additionally, the curcuminoids inhibiting P-12-LOX were tested for their ability to reduce sprout formation of endothelial cells (in vitro model of angiogenesis). We found that only curcuminoids inhibiting human P-12-LOX and the known inhibitor NDGA reduced sprout formation. Only limited inhibition of sprout formation at approximately IC(50) concentrations has been seen. At IC(50), a substantial amount of 12-HETE can be produced by lipoxygenase, providing a stimulus for angiogenic sprouting of endothelial cells. Increasing the concentration of lipoxygenase inhibitors above IC(50), thus decreasing the concentration of 12(S)-HETE produced, greatly reduced sprout formation for all inhibitors tested. This universal event for all tested lipoxygenase inhibitors suggests that the inhibition of sprout formation was most likely due to the inhibition of human P-12-LOX but not other cancer-related pathways.

Molecular targets of dietary agents for prevention and therapy of cancer

While fruits and vegetables are recommended for prevention of cancer and other diseases, their active ingredients (at the molecular level) and their mechanisms of action less well understood. Extensive research during the last half century has identified various molecular targets that can potentially be used not only for the prevention of cancer but also for treatment. However, lack of success with targeted monotherapy resulting from bypass mechanisms has forced researchers to employ either combination therapy or agents that interfere with multiple cell-signaling pathways. In this review, we present evidence that numerous agents identified from fruits and vegetables can interfere with several cell-signaling pathways. The agents include curcumin (turmeric), resveratrol (red grapes, peanuts and berries), genistein (soybean), diallyl sulfide (allium), S-allyl cysteine (allium), allicin (garlic), lycopene (tomato), capsaicin (red chilli), diosgenin (fenugreek), 6-gingerol (ginger), ellagic acid (pomegranate), ursolic acid (apple, pears, prunes), silymarin (milk thistle), anethol (anise, camphor, and fennel), catechins (green tea), eugenol (cloves), indole-3-carbinol (cruciferous vegetables), limonene (citrus fruits), beta carotene (carrots), and dietary fiber. For instance, the cell-signaling pathways inhibited by curcumin alone include NF-kappaB, AP-1, STAT3, Akt, Bcl-2, Bcl-X(L), caspases, PARP, IKK, EGFR, HER2, JNK, MAPK, COX2, and 5-LOX. The active principle identified in fruit and vegetables and the molecular targets modulated may be the basis for how these dietary agents not only prevent but also treat cancer and other diseases. This work reaffirms what Hippocrates said 25 centuries ago, let food be thy medicine and medicine be thy food.

Turmeric and Curcumin Modulate the Conjugation of 1-Naphthol in Caco-2 Cells

Turmeric, the powdered dry rhizome of the Curcuma longa plant, and curcumin, the major anti-oxidant constituent of turmeric, have been shown to possess chemopreventive activity. To elucidate the possible interaction of turmeric and curcumin with conjugation reactions, which in many cases are involved in the activation of procarcinogens, we measured their effects in the conjugation of 1-naphthol in Caco-2 cells, a human colon carcinoma cell line, within a 24 h period. Turmeric exhibits inhibitory activity toward both sulfo- and glucuronosyl conjugations of 1-naphthol at approximately the same levels (IC(50)=0.24 and 0.29 mg/ml, respectively). Curcumin inhibits sulfo-conjugation at lower concentrations (IC(50)=9.7 microg/ml), but only showed weak inhibition toward glucuronosyl conjugation of 1-naphthol in Caco-2 cells. In addition, turmeric was found to strongly inhibit in vitro phenol sulfotransferase (SULT) activity and demonstrate moderate inhibitory properties against UDP-glucuronosyl transferase (UGT) activity in Caco-2 cells (IC(50)=0.17 mg/ml and 0.62 mg/ml, respectively). Curcumin also strongly inhibits in vitro phenol sulfotransferase activity with an IC(50) of 2.4 microg/ml. Moreover, and in contrast to the moderate inhibition of UGT activity by turmeric and curcumin, both induce the expression of the UGT1A1 and UGT1A6 genes, revealed by real-time PCR analysis. These findings are indicative of a possible interaction of both turmeric and curcumin with conjugation reactions in the human intestinal tract and colon. This in turn may affect the bioavailability of therapeutic drugs and toxicity levels of environmental chemicals, particularly procarcinogens.