Activation of NFkappaB is inhibited by curcumin and related enones

Potential applications of curcumin and its novel synthetic analogs and nanotechnology-based formulations in cancer prevention and therapy

Curcumin has attracted great attention in the therapeutic arsenal in clinical oncology due to its chemopreventive, antitumoral, radiosensibilizing and chemosensibilizing activities against various types of aggressive and recurrent cancers. These malignancies include leukemias, lymphomas, multiple myeloma, brain cancer, melanoma and skin, lung, prostate, breast, ovarian, liver, gastrointestinal, pancreatic and colorectal epithelial cancers. Curcumin mediates its anti-proliferative, anti-invasive and apoptotic effects on cancer cells, including cancer stem/progenitor cells and their progenies, through multiple molecular mechanisms. The oncogenic pathways inhibited by curcumin encompass the members of epidermal growth factor receptors (EGFR and erbB2), sonic hedgehog (SHH)/GLIs and Wnt/β-catenin and downstream signaling elements such as Akt, nuclear factor-kappa B (NF-κB) and signal transducers and activators of transcription (STATs). In counterbalance, the high metabolic instability and poor systemic bioavailability of curcumin limit its therapeutic efficacy in human. Of great therapeutic interest, the selective delivery of synthetic analogs or nanotechnology-based formulations of curcumin to tumors, alone or in combination with other anticancer drugs, may improve their chemopreventive and chemotherapeutic efficacies against cancer progression and relapse. Novel curcumin formulations may also be used to reverse drug resistance, eradicate the total cancer cell mass and improve the anticarcinogenic efficacy of the current anti-hormonal and chemotherapeutic treatments for patients with various aggressive and lethal cancers.

Curcumin: an anti-inflammatory molecule from a curry spice on the path to cancer treatment

Oxidative damage and inflammation have been pointed out in preclinical studies as the root cause of cancer and other chronic diseases such as diabetes, hypertension, Alzheimer's disease, etc. Epidemiological and clinical studies have suggested that cancer could be prevented or significantly reduced by treatment with anti-oxidant and anti-inflammatory drugs, therefore, curcumin, a principal component of turmeric (a curry spice) showing strong anti-oxidant and anti-inflammatory activities, might be a potential candidate for the prevention and/or treatment of cancer and other chronic diseases. However, curcumin, a highly pleiotropic molecule with an excellent safety profile targeting multiple diseases with strong evidence on the molecular level, could not achieve its optimum therapeutic outcome in past clinical trials, largely due to its low solubility and poor bioavailability. Curcumin can be developed as a therapeutic drug through improvement in formulation properties or delivery systems, enabling its enhanced absorption and cellular uptake. This review mainly focuses on the anti-inflammatory potential of curcumin and recent developments in dosage form and nanoparticulate delivery systems with the possibilities of therapeutic application of curcumin for the prevention and/or treatment of cancer.

Catalytic asymmetric Michael addition with curcumin derivative

Catalytic asymmetric Michael additions with curcumin derivatives were achieved by a new series of tertiary amine-thiourea organocatalysts to afford the Michael adducts in high yields and excellent enantioselectivities.

Curcumin and its analogues: potential anticancer agents

This review chronicles the exploration of the curcumin in terms of development of analogues for the anticancer activity over the last century. Curcumin is a natural phytochemical obtained from dried root and rhizome of Turmeric (Curcuma Longa). It has been shown to interfere with multiple cell signaling pathways, including apoptosis (activation of caspases and downregulation of antiapoptotic gene products), proliferation (HER-2, EGFR, and AP-1), angiogenesis (VEGF), and inflammation (NF-kappaB, TNF, IL-6, IL-1, COX-2, and 5-LOX). In the last decade it has been much explored and various synthetic analogues have been prepared and evaluated for various pharmacological activities. Most of the analogues have shown very good anticancer activity in various models and various cell lines. However, some analogues have also shown antioxidant, anti-HIV, antimutagenic, antiangiogenic, antimalarial, antitubercular, antiandrogenic, COX inhibitory activities. Few analogues have shown very potent results and may be considered as clinical candidates for the development of future anticancer agent. This review contains 728 curcumin analogues and covers the literature from 1815 to mid 2009 and 93 references are cited.

Synthesis and identification of new 4-arylidene curcumin analogues as potential anticancer agents targeting nuclear factor-κB signaling pathway

A series of curcumin analogues including new 4-arylidene curcumin analogues (4-arylidene-1,7-bisarylhepta-1,6-diene-3,5-diones) were synthesized. Cell growth inhibition assays revealed that most 4-arylidene curcumin analogues can effectively decrease the growth of a panel of lung cancer cells at submicromolar and low micromolar concentrations. High content analysis technology coupled with biochemical studies showed that this new class of 4-arylidene curcumin analogues exhibits significantly improved NF-κB inhibition activity over the parent compound curcumin, at least in part by inhibiting IκB phosphorylation and degradation via IKK blockage; selected 4-arylidene curcumin analogues also reduced the tumorigenic potential of cancer cells in a clonogenic assay.

The effect of curcumin on insulin release in rat-isolated pancreatic islets

Curcumin exerts a hypoglycemic action and induces heme-oxygenase-1 (HO-1). We evaluated the effect of curcumin on isolated islets of Langerhans and studied whether its action on insulin secretion is mediated by inducible HO-1. Islets were isolated from rats and divided into control islets, islets incubated in different curcumin concentrations, islets incubated in hemin, islets incubated in curcumin and HO inhibitor, stannous mesoporphyrin (SnMP), islets incubated in hemin and SnMP, islets incubated in SnMP only, and islets incubated in 16.7 mmol/L glucose. Heme-oxygenase activity, HO-1 expression, and insulin estimation was assessed. Insulin secretion, HO-1 gene expression and HO activity were significantly increased in islets incubated in curcumin, hemin, and glucose compared with controls. This increase in insulin secretion was significantly decreased by incubation of islets in SnMP. The action of curcumin on insulin secretion from the isolated islets may be, in part, mediated through increased HO-1 gene expression.

Curcumin reverses attenuated carbachol-induced contraction of the colon in a rat model of colitis

BACKGROUND

Curcumin ameliorates colitis whether it reverses colitis-induced reduction in colonic contractility remains to be investigated.

OBJECTIVES

To investigate the effect of curcumin on colitis-induced reduction of carbachol-induced contraction in colon segments from rats treated with trinitrobenzenesulphonic acid.

METHODS

Colitis was induced in rats by intra rectal administration of trinitrobenzenesulphonic acid and followed for 5 days. A group of animals which received trinitobenzene sulphonic acids was treated with curcumin (100 mg/Kg and 200 mg/kg body weight) 2 hrs prior to induction of colitis. The controls received phosphate buffered saline in a similar fashion. Markers of inflammation and contractility of colon were assayed using standard procedures.

RESULTS

Induction of colitis was associated with increased myeloperoxidase activity and malondialdehyde levels, gross histological changes characterized by infiltration of inflammatory cells. All these changes were prevented by treatment with curcumin (100 mg/kg). Treatment with curcumin also reduced the histological scores from 3.34+/-0.40 to 1.75+/-0.30 confirming an anti-inflammatory effect of curcumin in this experimental model of colitis. Colonic reactivity to carbachol was decreased in colitis affecting the maximum response but not sensitivity. Treatment with curcumin had no effect on sensitivity of the colon to carbachol in any of the preparations. Curcumin however reversed the decrease in carbachol-induced contraction associated with trinitrobenzenesulphonic acid treatment. The same dose of curcumin had no effect on either the potency of or the maximum response to carbachol in control rats. Tissue expression of NF-kB was increased in colon segments from trinitrobenzenesulphonic acid -treated rats and this was inhibited in rats treated with curcumin.

CONCLUSIONS

Based on these findings it is concluded that curcumin prevented the reduction in carbachol-induced contraction in trinitrobenzenesulphonic acid -treated rats by modulating NF-kB signaling pathway.

The functional assessment of Alpinia pricei on metabolic syndrome induced by sucrose-containing drinking water in mice

This study was designed to test whether Alpinia pricei (AP), a member of the ginger family indigenous to Taiwan, reduced metabolic syndrome induced by sucrose-containing drinking water in C57BL/6J mice. Mice given a chow diet were divided into a control group (C) or a test group given 30% sucrose water (SW) to drink ad libitum. After 22 weeks, mice in the SW group were subdivided into SW and SW + AP groups, the latter receiving a chow diet with an ethanol extract of AP (1500 mg/kg dosage). Four weeks later, bio-indexes associated with metabolic syndrome were measured. Compared with the C group, the SW group had significantly higher body weight, visceral fat weights, serum and tissue lipid, serum insulin level and the area under the curve for blood glucose of the insulin tolerance test (p < 0.05). These indicators in the SW + AP group were lower than in the SW group except for serum lipid, although slightly higher than the C group. The SW + AP group also showed significantly lower serum levels of leptin and tumor necrosis factor-alpha and a significantly higher level of adiponectin than the SW group. These results indicated that visceral adiposity and insulin resistance induced by sucrose water drinking might be alleviated by AP supplementation.

Curcumin in cancer management: recent results of analogue design and clinical studies and desirable future research

The ability of the curry constituent curcumin to delay the onset of cancer has been the topic of extensive research for many years. Abundant literature is devoted to mechanisms by which curcumin may mediate this activity. These insights have prompted investigations in which curcumin as lead molecule serves as a scaffold for synthetic chemical attempts to optimize pharmacological potency. Among the published analogues with notable efficacy are dimethylcurcumin, 1,5-bis(3-pyridyl)-1,4-pentadien-3-one and 3,5-bis-(2-fluorobenzylidene)-piperidinium-4-one acetate. Results of a small number of clinical pilot studies conducted with curcumin at doses of up to 12 g suggest tentatively that it is safe in humans. Prevention of adenoma recurrence constitutes a clinical paradigm worthy of further investigation for curcumin. Future clinical study should include measurement of mechanism-based pharmacodynamic parameters.

Structure-activity relationship studies of curcumin analogues

Two series of curcumin analogues, a total of twenty-four compounds, were synthesized and evaluated. The most potent compound, compound 23, showed potent growth inhibitory activities on both prostate and breast cancer lines with IC(50) values in sub-micromolar range, fifty times more potent than curcumin. Curcumin analogues might be potential anti-tumor agents for breast and prostate cancers.

Interaction between curcumin and opioid system in the formalin test of rats

In this study, the effect of curcumin on the formalin-induced pain was investigated in rats. Interaction between curcumin and opioid system using morphine and naloxone was also examined. A biphasic pain response was induced after intraplantar injection of formalin (50 microL, 1%). Curcumin, morphin and naloxone had no effect on the early phase of pain. Late phase of pain was suppressed by curcumin at the doses of 100 and 200 mg kg(-1) body weigh. Morphine (1 mg kg(-1) BW) reduced, whereas naloxone (1 mg kg(-1) BW) did not affect the late phase of pain. Currcumin did not influence the morphine-induced antinociception, but reversed the effect of naloxone on pain. Present findings indicate that curcumin may produce antinociception by activation of both opioid and non opioid mechanisms of pain.

Curcumin reduces the toxic effects of iron loading in rat liver epithelial cells

BACKGROUND/AIMS

Iron overload can cause liver toxicity and increase the risk of liver failure or hepatocellular carcinoma in humans. Curcumin (diferuloylmethane), a component of the food spice turmeric, has antioxidant, iron binding and hepatoprotective properties. The aim of this study was to quantify its effects on iron overload and the resulting downstream toxic effects in cultured T51B rat liver epithelial cells.

METHODS

T51B cells were loaded with ferric ammonium citrate (FAC) with or without the iron delivery agent 8-hydroxyquinoline. Cytotoxicity was measured by methylthiazolyldiphenyl-tetrazolium bromide assay. Iron uptake and iron bioavailability were documented by chemical assay, quench of calcein fluorescence and ferritin induction. Reactive oxygen species (ROS) were measured by a fluorescence assay using 2',7'-dichlorodihydrofluorescein diacetate. Oxidative stress signalling to jnk, c-jun and p38 was measured by a Western blot with phospho-specific antibodies.

RESULTS

Curcumin bound iron, but did not block iron uptake or bioavailability in T51B cells given FAC. However, it reduced cytotoxicity, blocked the generation of ROS and eliminated signalling to cellular stress pathways caused by iron. Inhibition was observed over a wide range of FAC concentrations (50-500 microM), with an apparent IC(50) in all cases between 5 and 10 microM curcumin. In contrast, desferoxamine blocked both iron uptake and toxic effects of iron at concentrations that depended on the FAC concentration. The effects of curcumin also differed from those of alpha-tocopherol, which did not bind iron and was less effective at blocking iron-stimulated ROS generation.

CONCLUSIONS

Curcumin reduced iron-dependent oxidative stress and iron toxicity in T51B cells without blocking iron uptake.

1,5-diaryl-3-oxo-1,4-pentadienes: a case for antineoplastics with multiple targets

A number of organic molecules which contain the 1,5-diaryl-3-oxo-1,4-pentadienyl group, referred to hereafter as the dienone moiety, have antineoplastic properties. Emphasis is made on the attachment of this structural moiety to several molecular scaffolds, namely piperidines, N-acylpiperidines, cycloalkanes and 3,4-dihydro-1H-napthalenes. Many of these compounds are potent cytotoxins having micromolar and nanomolar IC(50) values towards a wide range of neoplastic and transformed cells. On occasions, greater toxicity towards neoplasms than normal cells has been demonstrated. A number of these compounds have in vivo anticancer properties and in general excellent tolerability in rodents is demonstrated. The way in which a number of physicochemical properties such as redox potentials, torsion angles, atomic charges and logP values govern cytotoxic potencies are presented. The importance of the shapes of different compounds as determined by molecular modeling in contributing to antineoplastic properties is outlined. Arguments are presented in favour of designing antineoplastics which have multiple sites of action in contrast to those bioactive molecules which have only one molecular target. A number of compounds which possess the dienone group have different modes of action some of which are chronicled in this review, such as inducing apoptosis, affecting respiration in mitochondria, inhibiting macromolecular biosynthesis and both inhibiting and stimulating certain enzymes. Other important properties of these compounds are discussed including their anti-angiogenic, MDR-revertant and antioxidant properties. It is hoped that this eulogy of the importance of the dienone group will encourage researchers to consider incorporating this structural unit into candidate cytotoxins in the future.

Exploration and synthesis of curcumin analogues with improved structural stability both in vitro and in vivo as cytotoxic agents

Curcumin has a surprisingly wide range of chemo-preventive and chemo-therapeutic activities and is under investigation for the treatment of various human cancers. However, the clinical application of curcumin has been significantly limited by its instability and poor metabolic property. Although a number of synthetic modifications of curcumin have been studied intensively in order to develop a molecule with enhanced bioactivities, few synthetic studies were done for the improvement of pharmacokinetic profiles. In the present study, a series of mono-carbonyl analogues of curcumin were designed and synthesized by deleting the reactive beta-diketone moiety, which was considered to be responsible for the pharmacokinetic limitation of curcumin. The results of the in vitro stability studies and in vivo pharmacokinetic studies indicated that the stability of these mono-carbonyl analogues was greatly enhanced in vitro and their pharmacokinetic profiles were also significantly improved in vivo. Furthermore, the cytotoxic activities of mono-carbonyl analogues were evaluated in seven different tumor cell lines by MTT assay and the structure-activity relation (SAR) was discussed and concluded. The results suggest that the five-carbon linker-containing analogues of curcumin may be favorable for the curcumin-based drug development both pharmacokinetically and pharmacologically.

Curcumin prevents human dendritic cell response to immune stimulants

Curcumin, a compound found in the Indian spice turmeric, has anti-inflammatory and immunomodulatory properties, though the mechanism remains unclear. Dendritic cells (DCs) are important to generating an immune response and the effect of curcumin on human DCs has not been explored. The role curcumin in the DC response to bacterial and viral infection was investigated in vitro using LPS and Poly I:C as models of infection. CD14(+) monocytes, isolated from human peripheral blood, were cultured in GM-CSF- and IL-4-supplemented medium to generate immature DCs. Cultures were incubated with curcumin, stimulated with LPS or Poly I:C and functional assays were performed. Curcumin prevents DCs from responding to immunostimulants and inducing CD4(+) T cell proliferation by blocking maturation marker, cytokine and chemokine expression and reducing both migration and endocytosis. These data suggest a therapeutic role for curcumin as an immune suppressant.

Role of Oxidative Stress and NFkB in Hypoxia-Induced Pulmonary Edema

Hypoxia is well known to increase the free radical generation in the body, leading to oxidative stress. In the present study, we have determined whether the increased oxidative stress further upregulates the nuclear transcription factor (NFkB) in the development of pulmonary edema. The rats were exposed to hypobaric hypoxia at 7620 m (280 mm Hg) for different durations, that is, 3 hrs, 6 hrs, 12 hrs, and 24 hrs at 25 ± 1°C. The results revealed that exposure of animals to hypobaric hypoxia led to a significant increase in vascular leakage, with time up to 6 hrs (256.38 ± 61 rfu/g) as compared with control (143.63 ± 60.1 rfu/g). There was a significant increase in reactive oxygen species, lipid peroxidation, and superoxide dismutase levels, with a concurrent decrease in lung glutathione peroxidase activity. There was 13-fold increase in the expression of NFkB level in nuclear fraction of lung homogenates of hypoxic animals over control rats. The DNA binding activity of NFkB was found to be increased significantly ( P < 0.001) in the lungs of rats exposed to hypoxia as compared with control. Further, we observed a significant increase in proinflammatory cytokines such as IL-1, IL-6, and TNF-α with concomitant upregulation of cell adhesion molecules such as ICAM-I, VCAM-I, and P-selectin in the lung of rats exposed to hypoxia as compared with control. Interestingly, pretreatment of animals with curcumin (NFkB blocker) attenuated hypoxia-induced vascular leakage in lungs with concomitant reduction of NFkB levels. The present study therefore reveals the possible involvement of NFkB in the development of pulmonary edema.

Biological activities of curcumin and its analogues (Congeners) made by man and Mother Nature

Curcumin, a yellow pigment present in the Indian spice turmeric (associated with curry powder), has been linked with suppression of inflammation; angiogenesis; tumorigenesis; diabetes; diseases of the cardiovascular, pulmonary, and neurological systems, of skin, and of liver; loss of bone and muscle; depression; chronic fatigue; and neuropathic pain. The utility of curcumin is limited by its color, lack of water solubility, and relatively low in vivo bioavailability. Because of the multiple therapeutic activities attributed to curcumin, however, there is an intense search for a "super curcumin" without these problems. Multiple approaches are being sought to overcome these limitations. These include discovery of natural curcumin analogues from turmeric; discovery of natural curcumin analogues made by Mother Nature; synthesis of "man-made" curcumin analogues; reformulation of curcumin with various oils and with inhibitors of metabolism (e.g., piperine); development of liposomal and nanoparticle formulations of curcumin; conjugation of curcumin prodrugs; and linking curcumin with polyethylene glycol. Curcumin is a homodimer of feruloylmethane containing a methoxy group and a hydroxyl group, a heptadiene with two Michael acceptors, and an alpha,beta-diketone. Structural homologues involving modification of all these groups are being considered. This review focuses on the status of all these approaches in generating a "super curcumin.".

Novel role of curcumin in the prevention of cytokine-induced islet death in vitro and diabetogenesis in vivo

BACKGROUND AND PURPOSE

Oxidative stress caused by cytokine exposure is a major cause of pancreatic islet death in vitro and of diabetogenesis. Antioxidant compounds may prevent cytokine-induced damage to islet cells. Hence, we studied the potential of curcumin, an antioxidant and anti-inflammatory compound, in vitro to protect islets against pro-inflammatory cytokines and in vivo to prevent the progression of diabetes induced by multiple low doses of streptozotocin (MLD-STZ).

EXPERIMENTAL APPROACH

Pancreatic islets from C57/BL6J mice were pretreated with curcumin (10 microM) and then exposed to a combination of cytokines. Islet viability, reactive oxygen species (ROS), NO, inducible NO synthase and NF-kappaB translocation were studied. Curcumin pretreated (7.5 mg kg(-1) day(-1)) C57/BL6J mice were given MLD-STZ (40 mg kg(-1)), and various parameters of diabetes induction and progression were monitored.

KEY RESULTS

Curcumin protected islets from cytokine-induced islet death in vitro by scavenging ROS and normalized cytokine-induced NF-kappaB translocation by inhibiting phosphorylation of inhibitor of kappa B alpha (IkappaBalpha). In vivo, curcumin also prevented MLD-STZ, as revealed by sustained normoglycaemia, normal glucose clearance and maintained pancreatic GLUT2 levels. Pro-inflammatory cytokine concentrations in the serum and pancreas were raised in STZ-treated animals, but not in animals pretreated with curcumin before STZ.

CONCLUSIONS AND IMPLICATIONS

Here, we have demonstrated for the first time that curcumin in vitro protects pancreatic islets against cytokine-induced death and dysfunction and in vivo prevents STZ-induced diabetes.

Curcumin and resveratrol inhibit nuclear factor-kappaB-mediated cytokine expression in adipocytes

BACKGROUND

Adipocytes express inflammatory mediators that contribute to the low-level, chronic inflammation found in obese subjects and have been linked to the onset of cardiovascular disorders and insulin resistance associated with type 2 diabetes mellitus. A reduction in inflammatory gene expression in adipocytes would be expected to reverse this low-level, inflammatory state and improve cardiovascular function and insulin sensitivity. The natural products, curcumin and resveratrol, are established anti-inflammatory compounds that mediate their effects by inhibiting activation of NF-kappaB signaling. In the present study, we examined if these natural products can inhibit NF-kappaB activation in adipocytes and in doing so reduce cytokine expression.

METHODS

Cytokine (TNF-alpha, IL-1beta, IL-6) and COX-2 gene expression in 3T3-L1-derived adipocytes was measured by quantitative real-time PCR (qRT-PCR) with or without TNFalpha-stimulation. Cytokine protein and prostaglandin E2 (PGE2) expression were measured by ELISA. Effects of curcumin and resveratrol were evaluated by treating TNFalpha-stimulated adipocytes with each compound and 1) assessing the activation state of the NF-kappaB signaling pathway and 2) measuring inflammatory gene expression by qRT-PCR and ELISA.

RESULTS

Both preadipocytes and differentiated adipocytes express the genes for TNF-alpha, IL-6, and COX-2, key mediators of the inflammatory response. Preadipocytes were also found to express IL-1beta; however, IL-1beta expression was absent in differentiated adipocytes. TNF-alpha treatment activated NF-kappaB signaling in differentiated adipocytes by inducing IkappaB degradation and NF-kappaB translocation to the nucleus, and as a result increased IL-6 (6-fold) and COX-2 (2.5-fold) mRNA levels. TNF-alpha also activated IL-1beta gene expression in differentiated adipocytes, but had no effect on endogenous TNF-alpha mRNA levels. No detectable TNFalpha or IL-1beta was secreted by adipocytes. Curcumin and resveratrol treatment inhibited NF-kappaB activation and resulted in a reduction of TNF-alpha, IL-1beta, IL-6, and COX-2 gene expression (IC50 = 2 muM) and a reduction of secreted IL-6 and PGE2 (IC50 ~ 20 muM).

CONCLUSION

Curcumin and resveratrol are able to inhibit TNFalpha-activated NF-kappaB signaling in adipocytes and as a result significantly reduce cytokine expression. These data suggest that curcumin and resveratrol may provide a novel and safe approach to reduce or inhibit the chronic inflammatory properties of adipose tissue.

Synthesis and anti-inflammatory activities of mono-carbonyl analogues of curcumin

Curcumin has been extensively studied for its anti-inflammatory activities. However, its potential beneficial effects on various disease preventions and treatments are limited by its unstable structure. The beta-diketone moiety renders curcumin to be rapidly metabolized by aldo-keto reductase in liver. In the present study, a series of curcumin analogues with more stable chemical structures were synthesized and several compounds showed an enhanced ability to inhibit lipopolysaccharide (LPS)-induced TNF-alpha and IL-6 synthesis in macrophages.

Synthesis, crystal structure and anti-inflammatory properties of curcumin analogues

Curcuminoids have been reported to possess multifunctional bioactivities, especially the ability to inhibit proinflammatory induction. Since it has been suggested that the seven-carbon beta-diketone linker in curcumin is responsible for its instability, nine mono-carbonyl five-carbon linker containing analogues were designed and synthesized. Their bioactivity against lipopolysaccharide-induced TNF-alpha amd IL-6 secretion was evaluated by using mouse J774.1 macrophages. The results showed that the 3'-methoxyl plays an important role in bioactivity and cyclohexanone containing analogues exhibited stronger inflammatory inhibition than acetone and cyclopentanone analogues. Subsequently the most active analogue 3c was determined using single-crystal X-ray diffraction. X-ray analysis and comparison with curcumin reveals that the presence of cyclohexanone in 3c, which remotely resembles the 6-membered ring in the enol tautomer in curcumin, may play an important role in the bioactivity. It is suggested that five-carbon linker analogues containing a cyclohexane ring which are synthetically assessable may be pharmacologically important.

Curcumin prevents streptozotocin-induced islet damage by scavenging free radicals: a prophylactic and protective role

Pancreatic islet cell death is the cause of deficient insulin production in diabetes mellitus. Approaches towards prevention of cell death are of prophylactic importance in control and management of hyperglycemia. Generation of oxidative stress is implicated in streptozotocin, a beta cell specific toxin-induced islet cell death. In this context, antioxidants raise an interest for therapeutic purposes. Curcumin, a common dietary spice is a well known antioxidant and hence we investigated its effect on streptozotocin-induced islet damage in vitro. Isolated islets from C57/BL6J mice were incubated with curcumin for 24 h and later exposed to streptozotocin for 8 h. The effect of streptozotocin exposure to islets was determined with respect to islet viability and functionality, cellular reactive oxygen species concentrations and levels of activated poly (ADP-ribose) polymerase-1. Cellular antioxidant potential (Cu/Zn superoxide dismutase) and advanced glycation end-product related damage was assessed to determine the metabolic status of treated and untreated islets. Islet viability and secreted insulin in curcumin pretreated islets were significantly higher than islets exposed to streptozotocin alone. Curcumin retarded generation of islet reactive oxygen species along with inhibition of Poly ADP-ribose polymerase-1 activation. Although curcumin did not cause overexpression of Cu/Zn superoxide dismutase, it prevented reduction in levels of cellular free radical scavenging enzymes. Our data shows that curcumin protects islets against streptozotocin-induced oxidative stress by scavenging free radicals. We show here for the first time, that prophylactic use of curcumin may effectively rescue islets from damage without affecting the normal function of these cellular structures.

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".

Synthesis of novel curcumin analogues and their evaluation as selective cyclooxygenase-1 (COX-1) inhibitors

Curcumin, a major yellow pigment and active component of turmeric, has been shown to possess anti-inflammatory and anti-cancer activities. Recent studies have indicated that cyclooxygenase-1 (COX-1) plays an important role in inflammation and carcinogenesis. In order to find more selective COX-1 inhibitors a series of novel curcumin derivatives was synthesized and evaluated for their ability to inhibit this enzyme using in vitro inhibition assays for COX-1 and COX-2 by measuring PGE(2) production. All curcumin analogues showed a higher rate of COX-1 inhibition. The most potent curcumin compounds were (1E,6E)-1,7-di-(2,3,4-trimethoxyphenyl)-1,6-heptadien-3,5-dione (4) (COX-1: IC(50) = 0.06 microM, COX-2: IC(50) > 100 microM, selectivity index>1666) and (1E,6E)-methyl 4-[7-(4-methoxycarbonyl)phenyl]-3,5-dioxo-1,6-heptadienyl]benzoate (6) (COX-1: IC(50) = 0.05 microM, COX-2: IC(50) > 100 microM, selectivity index > 2000). Curcumin analogues therefore represent a novel class of highly selective COX-1 inhibitors and promising candidates for in vivo studies.

Curcumin down regulates smokeless tobacco-induced NF-κB activation and COX-2 expression in human oral premalignant and cancer cells

Smokeless tobacco (ST) consumption is a major cause of oral cancer in South East Asia including India. Recently, we showed that exposure to smokeless tobacco extract (STE) (khaini) results in increased expression and activation of nuclear factor-kappaB (NF-kappaB) and its downstream target cyclooxygenase-2 (COX-2) in human oral cell systems in vitro. The present study was designed to test the hypothesis that curcumin may inhibit the activation of NF-kappaB in ST exposed oral premalignant and cancer cells. Exposure of oral premalignant and cancer cells to curcumin resulted in significant decrease in cell viability and induced apoptosis. STE-induced nuclear translocation and DNA-binding activity of NF-kappaB were inhibited in curcumin pretreated oral premalignant and cancer cells in vitro. Curcumin treatment led to decreased expression of NF-kappaB and COX-2. The tobacco specific nitrosamine, 4-(methylnitrosamino-)-1-(3-pyridyl)-1-butanone (NNK), is one of the carcinogenic components of STE (khaini). We demonstrate that curcumin pretreatment abrogated NNK-induced activation of NF-kappaB and COX-2 expression, suggesting that NNK is one of the factors in STE (khaini) modulated by curcumin. In conclusion, our findings demonstrate for the first time that curcumin downregulates STE (khaini) or NNK-induced NF-kappaB and COX-2 in oral premalignant and cancer cells in vitro.

TPA-induced up-regulation of activator protein-1 can be inhibited or enhanced by analogs of the natural product curcumin

The activator protein-1 (AP-1) family of transcription factors, including the most common member c-Jun-c-Fos, participates in regulation of expression of numerous genes involved in proliferation, apoptosis, and tumorigenesis in response to a wide array of stimuli including pro-inflammatory cytokines, growth factors, stress, and tumor promoters. A number of plant polyphenols including curcumin, a yellow compound in the spice turmeric, have been shown to inhibit the activation of AP-1. Curcumin is a polyphenolic dienone that is potentially reactive as a Michael acceptor and also is a strong anti-oxidant. Multiple activities reported for curcumin, including inhibition of the stress-induced activation of AP-1, have been suggested to involve the anti-oxidant properties of curcumin. In the present study, a library of analogs of curcumin was screened for activity against the TPA-induced activation of AP-1 using the Panomics AP-1 Reporter 293 stable cell line which is designed for screening potential inhibitors. Numerous analogs were identified that were more active than curcumin, including analogs that were not anti-oxidants and analogs that were not Michael acceptors. Clearly, anti-oxidant activity or reactivity as a Michael acceptor is not an essential feature of active compounds. In addition, a number of analogs were identified that enhanced the TPA-induced activation of AP-1. The results from screening were confirmed using BV-2 microglial cells where curcumin and analogs were shown to inhibit LPS-induced COX-2 expression; analogs identified as more potent than curcumin in the screening assay were also more potent than curcumin in preventing COX-2 expression.

Toll-like receptor-4 mediates cigarette smoke-induced cytokine production by human macrophages

BACKGROUND

The major risk factor for the development of COPD is cigarette smoking. Smoking causes activation of resident cells and the recruitment of inflammatory cells into the lungs, which leads to release of pro-inflammatory cytokines, chemotactic factors, oxygen radicals and proteases. In the present study evidence is found for a new cellular mechanism that refers to a link between smoking and inflammation in lungs.

METHODS

Employing human monocyte-derived macrophages, different techniques including FACS analysis, Cytometric Bead Array Assay and ELISA were achieved to evaluate the effects of CS on pro-inflammatory cytokine secretion including IL-8. Then, Toll-like receptor neutralization was performed to study the involvement of Toll-like receptor-4 in IL-8 production. Finally, signaling pathways in macrophages after exposure to CS medium were investigated performing ELISA and Western analysis.

RESULTS

We demonstrate that especially human monocytes are sensitive to produce IL-8 upon cigarette smoke stimulation compared to lymphocytes or neutrophils. Moreover, monocyte-derived macrophages produce high amounts of the cytokine. The IL-8 production is dependent on Toll-like receptor 4 stimulation and LPS is not involved. Further research resolved the cellular mechanism by which cigarette smoke induces cytokine production in monocyte-derived macrophages. Cigarette smoke causes subsequently a concentration-dependent phosphorylation of IRAK and degradation of TRAF6. Moreover, IkappaBalpha was phosphorylated which suggests involvement of NF-kappaB. In addition, NFkappaB-inhibitor blocked cigarette smoke-induced IL-8 production.

CONCLUSION

These findings link cigarette smoke to inflammation and lead to new insights/therapeutic strategies in the pathogenesis of lung emphysema.