Biological properties of curcumin-cellular and molecular mechanisms of action

The Effect of Curcumin on Ethanol Induced Changes in Suprachiasmatic Nucleus (SCN) and Pineal

(1) Circadian clocks have been localized to discrete sites within the nervous system of several organisms and in mammals to the suprachiasmatic nucleus (SCN) in the anterior hypothalamus. The SCN controls and regulates the production and discharge of melatonin (hormonal message of darkness) from the pineal gland via a multisynaptic efferent pathway. The nocturnal rise in melatonin production from serotonin results due to an increased activity of serotonin N-acetyl transferase (NAT). (2) The complex interaction between alcohol and biological clock need to be understood as alcoholism results in various clock linked neuronal disorders especially loss of memory and amnesia like state of consciousness, sleep disorders, insomnia, dementia etc. (3) Serotonin, 5-Hydroxy-tryptamine (5-HT) plays an important role in mediating alcohol's effects on the brain. Understanding the impact of alcohol consumption on circadian system is a pre-requisite to help in treatment of alcohol induced neurological disorders. We, therefore, studied the effect of ethanol drinking and ethanol withdrawal on daily rhythms of serotonin and its metabolite, 5-hydroxy-indole acetic acid (5-HIAA) in SCN and Pineal of adult male Wistar rats maintained under light-dark (LD, 12:12) conditions. (4) Curcumin is well known for its protective properties such as antioxidant, anti-carcinogenic, anti-viral and anti-infectious etc. Hence, we studied the effect of curcumin on ethanol induced changes on 5-HT and 5-HIAA levels and rhythms in SCN and Pineal. (5) Ethanol withdrawal could not restore either rhythmicity or phases or levels of 5-HT and 5-HIAA. Curcumin administration resulted in partial restoration of daily 5-HT/5-HIAA ratio, with phase shifts in SCN and in Pineal. Understanding the impact of alcohol consumption on circadian system and the role of herbal medication on alcohol withdrawal will help in treatment of alcohol induced neurological disorders.

Regulation of heme oxygenase-1 expression by demethoxy curcuminoids through Nrf2 by a PI3-kinase/Akt-mediated pathway in mouse beta-cells

Curcumin (diferuloylmethane), a component of turmeric, has been shown to have therapeutic properties. Induction of phase 2 detoxifying enzymes is a potential mechanism through which some of the actions of curcumin could proceed. Heme oxygenase-1 (HO-1), an antioxidant phase 2 enzyme, has been reported to have cytoprotective effects in pancreatic beta-cells. Curcumin on further purification yields demethoxy curcumin (DMC) and bisdemethoxy curcumin (BDMC). The objective of the present study was to determine the mechanism by which these purified curcuminoids induce HO-1 in MIN6 cells, a mouse beta-cell line. Demethoxy curcuminoids induced HO-1 promoter linked to the luciferase reporter gene more effectively than curcumin. The induction was dependent on the presence of antioxidant response element (ARE) sites containing enhancer regions (E1 and E2) in HO-1 promoter and nuclear translocation of nuclear factor-E2-related factor (Nrf2), the transcription factor that binds to ARE. Curcuminoids stimulated multiple signaling pathways that are known to induce HO-1. Inhibition of specific signaling pathways with pharmacological inhibitors and cotransfection experiments suggested the involvement of phosphotidylinositol 3-kinase and Akt. Real-time quantitative RT-PCR analysis showed significant elevation in the mRNA levels of HO-1 and two other phase 2 enzymes, the regulatory subunit of glutamyl cysteine ligase, which is needed for the synthesis of glutathione, and NAD(P)H:quinone oxidoreductase, which detoxifies quinones. DMC and BDMC induced the expression of HO-1 and translocated Nrf2 to nucleus in beta-cells of mouse islets. Our observations suggest that demethoxy curcuminoids could be used to induce a cellular defense mechanism in beta-cells under conditions of stress as seen in diabetes.

Radioprotection and radiosensitization by curcumin

This chapter gives an overview of the radioprotective and radiosensitizing effect of curcumin. Ionizing radiations interact with biological molecules inducing radiolytic products like e(aq), *OH, *H, -OH, +H, O2, and peroxides. These free radicals damage important biomolecules and subsequently inflict deleterious effects in the organism. Whole-body exposure to ionizing radiations results in central nervous system, gastrointestinal tract, and bone marrow syndromes, whereas chronic irradiation causes cancer, birth anomalies, erythema, and dysfunctions to almost all organ of the body depending on the total dose and site of irradiation. Curcumin (diferuloyl methane), a yellow pigment present in the rhizomes of turmeric, has been used in Southeast Asia to give yellow color and flavor to curries. Turmeric has been used to treat various ailments in the Ayurvedic system of medicine in India. Recently, it has been evaluated for its radioprotective and radiosensitizing activities. Curcumin has been found to exert a dual mode of action after irradiation depending on its dose. It has been reported to protect various study systems against the deleterious effects induced by ionizing radiation and to enhance the effect of radiation. Therefore, curcumin can be very useful during radiotherapy of cancer. Administration of curcumin in patients will be able to kill the tumor cells effectively by enhancing the effect of radiation and, at the same time, protect normal cells against the harmful effects of radiation. The available information on curcumin suggests that the radioprotective effect might be mainly due to its ability to reduce oxidative stress and inhibit transcription of genes related to oxidative stress and inflammatory responses, whereas the radiosensitive activity might be due the upregulation of genes responsible for cell death.

Pharmacokinetics and pharmacodynamics of curcumin

Curcuma spp. contain turmerin, essential oils, and curcuminoids, including curcumin. Curcumin [1,7-bis-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione] is regarded as the most biologically active constituent of the spice turmeric and it comprises 2-8% of most turmeric preparations. Preclinical data from animal models and phase I clinical studies performed with human volunteers and patients with cancer have demonstrated low systemic bioavailability following oral dosing. Efficient first-pass metabolism and some degree of intestinal metabolism, particularly glucuronidation and sulfation of curcumin, might explain its poor systemic availability when administered via the oral route. A daily oral dose of 3.6 g of curcumin is compatible with detectable levels of the parent compound in colorectal tissue from patients with cancer. The levels demonstrated might be sufficient to exert pharmacological activity. There appears to be negligible distribution of the parent drug to hepatic tissue or other tissues beyond the gastrointestinal tract. Curcumin possesses wide-ranging anti-inflammatory and anticancer properties. Many of these biological activities can be attributed to its potent antioxidant capacity at neutral and acidic pH, its inhibition of cell signaling pathways at multiple levels, its diverse effects on cellular enzymes, and its effects on cell adhesion and angiogenesis. In particular, curcumin's ability to alter gene transcription and induce apoptosis in preclinical models advocates its potential utility in cancer chemoprevention and chemotherapy. With regard to considerable public and scientific interest in the use of phytochemicals derived from dietary components to combat or prevent human diseases, curcumin is currently a leading agent.

Clinical studies with curcumin

Curcumin has long been expected to be a therapeutic or preventive agent for several major human diseases because of its antioxidative, anti-inflammatory, and anticancerous effects. In phase I clinical studies, curcumin with doses up to 3600-8000 mg daily for 4 months did not result in discernible toxicities except mild nausea and diarrhea. The pharmacokinetic studies of curcumin indicated in general a low bioavailability of curcumin following oral application. Nevertheless, the pharmacologically active concentration of curcumin could be achieved in colorectal tissue in patients taking curcumin orally and might also be achievable in tissues such as skin and oral mucosa, which are directly exposed to the drugs applied locally or topically. The effect of curcumin was studied in patients with rheumatoid arthritis, inflammatory eye diseases, inflammatory bowel disease, chronic pancreatitis, psoriasis, hyperlipidemia, and cancers. Although the preliminary results did support the efficacy of curcumin in these diseases, the data to date are all preliminary and not conclusive. It is imperative that well-designed clinical trials, supported by better formulations of curcumin or novel routes of administration, be conducted in the near future.

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".

Viewpoint: mechanisms of action and therapeutic potential of neurohormetic phytochemicals

The nervous system is of fundamental importance in the adaptive (hormesis) responses of organisms to all types of stress, including environmental "toxins". Phytochemicals present in vegetables and fruits are believed to reduce the risk of several major diseases including cardiovascular disease, cancers and neurodegenerative disorders. Although antioxidant properties have been suggested as the basis of health benefits of phytochemicals, emerging findings suggest a quite different mechanism of action. Many phytochemicals normally function as toxins that protect the plants against insects and other damaging organisms. However, at the relatively low doses consumed by humans and other mammals these same "toxic" phytochemicals activate adaptive cellular stress response pathways that can protect the cells against a variety of adverse conditions. Recent findings have elucidated hormetic mechanisms of action of phytochemicals (e.g., resveratrol, curcumin, sulforaphanes and catechins) using cell culture and animal models of neurological disorders. Examples of hormesis pathways activated by phytochemicals include the transcription factor Nrf-2 which activates genes controlled by the antioxidant response element, and histone deacetylases of the sirtuin family and FOXO transcription factors. Such hormetic pathways stimulate the production of antioxidant enzymes, protein chaperones and neurotrophic factors. In several cases neurohormetic phytochemicals have been shown to suppress the disease process in animal models relevant to neurodegenerative disorders such as Alzheimer's and Parkinson's diseases, and can also improve outcome following a stroke. We are currently screening a panel of biopesticides in order to establish hormetic doses, neuroprotective efficacy, mechanisms of action and therapeutic potential as dietary supplements.

Glucuronidation of curcuminoids by human microsomal and recombinant UDP-glucuronosyltransferases

Glucuronidation is an important pathway in the metabolism of curcumin, but the isoforms of uridine-5'-diphosphoglucuronosyltransferase (UGT) involved are not known. Here, we report on the glucuronidation of the three natural curcuminoids and their major phase I metabolites with microsomes from human liver and intestine as well as with human recombinant UGTs. Microsomes from human liver generated predominantly the phenolic and small amounts of the alcoholic glucuronide of each curcuminoid, whereas intestinal microsomes formed only the phenolic conjugates but with higher activities. The phenolic glucuronidation of the curcuminoids was predominantly catalyzed by hepatic UGT1A1 and intestinal UGT1A8 and 1A10, whereas UGT1A9, 2B7, and 1A8 exhibited high activities for hexahydro-curcuminoids. UGT1A9 was able to form the alcoholic glucuronide of each curcuminoid in addition to the phenolic conjugate. These data suggest that the gastrointestinal tract contributes substantially to the glucuronidation of curcuminoids in humans, which may have important implications for their pharmacokinetic fate in vivo.

Effect of curcumin on hyperglycemia-induced vascular endothelial growth factor expression in streptozotocin-induced diabetic rat retina

Diabetic retinopathy is one of the most devastating microvascular complications of long standing type 1 and type 2 diabetes. Neovascularization stimulated by hyperglycemia-mediated induction of vascular endothelial growth factor (VEGF) has been implicated in the pathogenesis. Various small molecules have been investigated for their ability to inhibit angiogenesis. In this study, we evaluated whether curcumin and its dietary source turmeric can inhibit VEGF expression in strepotzotocin (STZ)-induced diabetic rat retina. Diabetes was induced in 3-month-old male WNIN rats by a single intraperitoneal injection of STZ. After induction, one group of diabetic rats were fed only the AIN-93 diet and the rest of the groups were fed with AIN-93 diet containing 0.002% or 0.01% curcumin or 0.5% turmeric for a period of 8 weeks. The control rats received sham injection and fed on the AIN-93 diet. At the end of 8 weeks animals were sacrificed and retina was dissected. The VEGF expression was analyzed by both real time PCR and immunoblotting. There was an increase in VEGF expression in diabetic retina as compared to control retina at both transcript and protein level. Notably, feeding of curcumin and turmeric to diabetic rats inhibited expression of VEGF. This study highlights the importance of biologically active compounds derived from dietary agents that could be explored further for the prevention and/or treatment of diabetic retinopathy.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

Influence of curcumin, capsaicin, and piperine on the rat liver drug-metabolizing enzyme system in vivo and in vitro

The effect of dietary supplementation of spice-active principles, curcumin (0.2%), capsaicin (0.015%), and piperine (0.02%) on the activities of the liver drug-metabolizing enzyme system was examined. All the 3 dietary spice principles significantly stimulated the activity of aryl hydroxylase. A synergistic action of dietary curcumin and capsaicin with respect to stimulating the activity of aryl hydroxylase was also evidenced when fed in combination. The activity of N-demethylase essentially remained unaffected by dietary curcumin, capsaicin, or their combination, but was significantly lowered as a result of piperine feeding. Uridine dinucleotide phosphate (UDP)-glucuronyl transferase activity was decreased by dietary piperine and the combination of curcumin and capsaicin. NADPH-cytochrome c reductase activity was significantly decreased by dietary piperine. The levels of hepatic microsomal cytochrome P450 and cytochrome b5 were not influenced by any of the dietary spice-active principles. These spice-active principles were also examined for their possible in vitro influence on the components of the hepatic drug-metabolizing enzyme system in rat liver microsomal preparation. Piperine significantly decreased the activity of liver microsomal aryl hydroxylase activity when included in the assay medium at 1 x 10(-6) mol/L, 1 x 10(-5) mol/L, and 1x 10(-4) mol/L level. Lowered activity of N-demethylase was observed in presence of capsaicin or piperine at 1 x 10(-6) mol/L in the assay medium. Hepatic microsomal glucuronyl transferase activity was significantly decreased in vitro by addition of capsaicin or piperine. Capsaicin and piperine brought about significant decrease in liver microsomal cytochrome P450 when included at 1 x 10(-6) mol/L and 1 x 10(-5) mol/L, the effect being much higher in the case of piperine. The results suggested that whereas the 3 spice principles have considerable similarity in structure, piperine is exceptional in its influence on the liver drug-metabolizing enzyme system. The study also indicated that a combination of curcumin and capsaicin does not produce any significant additive effect on the liver drug-metabolizing enzyme system.

Up-regulation of aldose reductase expression mediated by phosphatidylinositol 3-kinase/Akt and Nrf2 is involved in the protective effect of curcumin against oxidative damage

Up-regulation of aldose reductase (AR) by reactive oxygen species (ROS) and aldehyde derivatives has been observed in vascular smooth muscle cells. However, the pathophysiological consequences of the induction of AR in vascular tissues are not fully elucidated. Herein we report that an herb-derived polyphenolic compound, curcumin, elicited a dose- and time-dependent increase in AR expression. Inhibition of phosphatidylinositol 3-kinase (PI3K) and p38 mitogen-activated protein kinase (MAPK) significantly suppressed the curcumin-augmented mRNA levels and promoter activity of the AR gene. Luciferase reporter assays indicated that an osmotic response element in the promoter was essential for the responsiveness to curcumin. Curcumin accelerated the nuclear translocation of nuclear factor-erythroid 2-related factor 2 (Nrf2), and overexpression of Nrf2, but not the dominant negative Nrf2, enhanced the promoter activity of the AR gene. Cells preincubated with curcumin demonstrated resistance to ROS-induced apoptotic death. These effects were significantly attenuated in the presence of AR inhibitors or small interfering RNAs, indicating a protective role for AR against ROS-induced cell damage. Taken together, the activation of PI3K and p38 MAPK by curcumin augmented the expression of the AR gene via Nrf2, and increased AR activity may be an important cellular response against oxidative stress.

The interruption of the PDGF and EGF signaling pathways by curcumin stimulates gene expression of PPARgamma in rat activated hepatic stellate cell in vitro

Activation of hepatic stellate cells (HSC), the major effector in hepatic fibrogenesis, is coupled with sequential alterations in expression of genes, including the upregulation of platelet-derived growth factor-beta receptor (PDGF-betaR) and epidermal growth factor receptor (EGFR), as well as the down-regulation of the peroxisome proliferator-activated receptor-gamma (PPARgamma). However, the relationship among the alterations in expression of the genes and the activation of their signaling in activated HSC remains obscure. We recently showed that curcumin, the yellow pigment in curry, inhibited cell growth and induced gene expression of endogenous PPARgamma in activated HSC in vitro. The present study is to elucidate the underlying mechanisms, focusing on the impacts of PDGF and EGF signaling. It is hypothesized that the interruption of the PDGF and EGF signaling pathways by curcumin might stimulate gene expression of PPARgamma in activated HSC. Our results in this report indicate that the activation of PDGF or EGF signaling by exogenous PDGF or EGF inhibits PPARgamma gene expression in passaged HSC. Curcumin interrupts PDGF and EGF signaling demonstrated by inhibiting tyrosine phosphorylation of PDGF-betaR and EGFR and by reducing the levels of phosphorylated phosphatidylinositol-3 kinase (PI-3K/AKT), extracellular signal-regulated kinase (ERK) and the Jun N-terminal kinase (JNK). The blockade of PI-3K/AKT, ERK or JNK signaling negatively regulates PPARgamma gene expression in activated HSC, leading to the reduction in cell growth, including inducing cell arrest and apoptosis. Our results collectively demonstrate that the interruption of the PDGF and EGF signaling pathways by curcumin stimulates gene expression of PPARgamma in activated HSC. These results provide novel insights into the mechanisms of curcumin in the induction of PPARgamma gene expression in activated HSC.

Dietary curcumin does not protect kidney in glycerol-induced acute renal failure

Generation of reactive oxygen species significantly contribute to the pathogenesis of renal injury induced by myoglobin release. The present study was performed to investigate the effects of dietary curcumin, a natural antioxidant isolated from plant Curcuma longa, in an experimental model of myoglobinuric acute renal failure. Rats received curcumin at an oral dose of 100mg/kg/day for 30 days. Renal injury was induced with injection of hypertonic glycerol (10 ml/kg 50% solution) in hind limb muscle with blood urea of 57.8+/-7.2 vs. 7.72+/-1.03 mmol/l and serum creatinine of 444.4+/-61.3 vs. 51.8+/-10.6 micromol/l, in glycerol-induced acute renal failure (ARF) vs. control rats, respectively. After 48 h rats were sacrificed and thiobarbituric acid reactive substance (TBARS), glutathione, carbonyl content and kidney cortex brush border peptidase activities were determined in serum, kidney and liver. Rats that received curcumin in addition to glycerol had significantly lower TBARS in serum but not in kidney and liver. Carbonyl content in kidney and liver was significantly elevated in curcumin and glycerol treated rats and improved in animals treated with curcumin and glycerol together. The activities of kidney cortex enzymes, aminopeptidase N, angiotensinase A and dipeptidyl peptidase IV, were reduced in glycerol as well as in curcumin treated rats. The results obtained in this study provided additional evidence that despite its limited antioxidant activity curcumin did not protect kidney in myoglobinuric model of ARF.

Prevention of liver cirrhosis in rats by curcumin

BACKGROUND AND AIM

Curcumin, the major polyphenolic compound in turmeric, has been shown to attenuate hepatic damage in several animal models of liver injury. The aim of the present study was to examine the efficacy of curcumin in preventing thioacetamide-induced cirrhosis and to unravel the mechanism of curcumin's effect on hepatic fibrosis in rats.

METHODS

Liver cirrhosis was induced by thioacetamide (TAA; 200 mg/kg, i.p.) twice weekly for 12 weeks. One group of rats concomitantly received curcumin (300 mg/kg/day, by gavage for 12 weeks); the control group received the solvent at identical amounts and duration.

RESULTS

TAA administration induced liver cirrhosis, which was inhibited by curcumin. Liver histopathology, hydroxyproline levels and spleen weights were significantly lower in the rats treated with TAA+curcumin compared with TAA only (P<0.001). Immunohistochemical studies and in situ hybridization demonstrated inhibition of hepatic stellate cell (alpha smooth muscle actin-positive) activation and collagen alpha1 (I) gene expression in the livers of the TAA+curcumin-treated rats. Curcumin reduced oxidative stress as shown by the decreased hepatic nitrotyrosine staining in the curcumin+TAA-treated rats. Curcumin treatment had no effect on pre existing liver cirrhosis. As determined by in vitro studies using the rat HSC-T6 cell line, curcumin had no direct inhibitory effect on collagen alpha1 (I) messenger RNA expression. Further studies in these cells using reverse transcriptase-polymerase chain reaction demonstrated that curcumin had no effect on the expression of PDGF-induced TIMP-1 and TIMP-2, TGFbeta1, TGFbeta2 and MCP-1 but significantly inhibited tumor necrosis factor alpha expression. Curcumin had no effect on hepatic stellate cells proliferation. Zymography showed that curcumin had no effect on matrix metalloproteinase-2 activity.

CONCLUSIONS

Curcumin inhibited the development of TAA-induced liver cirrhosis mainly due to its anti-inflammatory activities and not by a direct anti-fibrotic effect. As curcumin ingestion is safe in humans, it may be reasonable to assess in clinical studies the beneficial effect of curcumin in slowing the development of liver cirrhosis.

Curcumin activates human glutathione S-transferase P1 expression through antioxidant response element

Curcumin is a plant-derived diferuloylmethane compound extracted from Curcuma longa, possessing antioxidative and anticarcinogenic properties. Antioxidants and oxidative stress are known to induce the expression of certain classes of detoxification enzymes. Since the upregulation of detoxifying enzymes affects the drug metabolism and cell defense system, it is important to understand the gene regulation by such agents. In this study, we demonstrated that curcumin could induce the expression of human glutathione S-transferase P1 (GSTP1). In HepG2 cells treated with 20muM curcumin, the level of GSTP1 mRNA was significantly increased. In luciferase reporter assays, curcumin augmented the promoter activity of a reporter construct carrying 336bp upstream of the 5'-flanking region of the GSTP1 gene. Mutation analyses revealed that the region including antioxidant response element (ARE), which overlaps AP1 in sequence, was essential to the response to curcumin. While the introduction of a wild-type Nrf2 expression construct augmented the promoter activity of the GSTP1 gene, co-expression of a dominant-negative Nrf2 abolished the responsiveness to curcumin. In addition, curcumin activated the expression of the luciferase gene from a reporter construct carrying multiple ARE consensus sequences but not one with multiple AP1 sites. In a gel mobility shift assay with an oligonucleotide with GSTP1 ARE, an increase in the amount of the binding complex was observed in the nuclear extracts of curcumin-treated HepG2 cells. These results suggested that ARE is the primary sequence for the curcumin-induced transactivation of the GSTP1 gene. The induction of GSTP1 may be one of the mechanisms underlying the multiple actions of curcumin.

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-induced degradation of ErbB2: A role for the E3 ubiquitin ligase CHIP and the Michael reaction acceptor activity of curcumin

We investigated the molecular mechanism underlying curcumin depletion of ErbB2 protein. Curcumin induced ErbB2 ubiquitination but pretreatment with proteasome inhibitors neither prevented curcumin depletion of ErbB2 protein nor further accumulated ubiquitinated ErbB2. Curcumin increased association of endogenous and ectopically expressed CHIP, a chaperone-dependent ubiquitin ligase, with ErbB2. In COS7 cells cotransfected with ErbB2 and various CHIP plasmids followed by curcumin treatment, CHIP-H260Q (a mutant lacking ubiquitin ligase activity) promoted less curcumin-induced ErbB2 ubiquitination than did wild type CHIP, and CHIP-K30A (a mutant incapable of binding Hsp90 and Hsp70) neither associated with ErbB2 nor promoted its ubiquitination. ErbB2 mutants lacking the kinase domain failed to associate with CHIP and were completely resistant to ubiquitination and depletion induced by curcumin. Finally, curcumin's Michael reaction acceptor functionality was required for both covalent association of curcumin with ErbB2 and curcumin-mediated ErbB2 depletion. These data suggest (1) that CHIP-dependent ErbB2 ubiquitination is implicated in curcumin-stimulated ErbB2 depletion, and (2) that covalent modification of ErbB2 by curcumin is the proximal signal which initiates this process.

Curcumin induces changes in expression of genes involved in cholesterol homeostasis

Curcuminoids, the yellow pigments of curcuma, exhibit anticarcinogenic, antioxidative and hypocholesterolemic activities. To understand the molecular basis for the hypocholesterolemic effects, we examined the effects of curcumin on hepatic gene expression, using the human hepatoma cell line HepG2 as a model system. Curcumin treatment caused an up to sevenfold, concentration-dependent increase in LDL-receptor mRNA, whereas mRNAs of the genes encoding the sterol biosynthetic enzymes HMG CoA reductase and farnesyl diphosphate synthase were only slightly increased at high curcumin concentrations where cell viability was reduced. Expression of the regulatory SREBP genes was moderately increased, whereas mRNAs of the PPARalpha target genes CD36/fatty acid translocase and fatty acid binding protein 1 were down-regulated. LXRalpha expression and accumulation of mRNA of the LXRalpha target gene ABCg1 were increased at low curcumin concentrations. Although curcumin strongly inhibited alkaline phosphatase activity, an activation of a retinoic acid response element reporter employing secreted alkaline phosphatase was observed. These changes in gene expression are consistent with the proposed hypocholesterolemic effect of curcumin.

Curcumin and Kolaviron Ameliorate Di-n-Butylphthalate-Induced Testicular Damage in Rats

The present study was carried out to evaluate the ameliorative effects of kolaviron (a biflavonoid from the seeds of Garcinia kola) and curcumin (from the rhizome, Curcuma longa L.) on the di-n-butylphthalate (DBP)-induced testicular damage in rats. Administration of DBP to rats at a dose of 2 g/kg for 9 days significantly decreased the relative testicular weights compared to the controls, while the weights of other organs remained unaffected. Curcumin or kolaviron did not affect all the organ weights of the animals. While only DBP treatment significantly increased the testicular malondialdehyde level and gamma-glutamyl transferase activity (gamma-GT), it markedly decreased glutathione level, the testicular catalase, glucose-6-phosphate dehydrogenase, superoxide dismutase, sperm gamma-GT activities and serum testosterone level compared to the control group. Data on cauda epididymal sperm count and live/dead ratio were not significantly affected in the DBP-treated rats. Alone, DBP treatment resulted in a 66% decrease in spermatozoa motility and a 77% increase in abnormal spermatozoa in comparison to control. DBP-treated rats showed marked degeneration of the seminiferous tubules with necrosis and defoliation of spermatocytes. The DBP-induced injuries in biochemical, spermatological parameters and histological structure of testis were recovered by treatment with kolaviron or curcumin. The pattern in the behaviour of these compounds might be correlated with their structural variations. Our results indicate that kolaviron and curcumin protect against testicular oxidative damage induced by DBP. The chemoprotective effects of these compounds may be due to their intrinsic antioxidant properties and as such may prove useful in combating phthalate-induced reproductive toxicity.

Experimental approaches for studying uptake and action of herbal medicines

In order to gain wider credibility, herbal medicines must go through the rigorous scientific scrutiny to which synthetic drugs are subjected, and this includes investigating their absorption, bioavailability and metabolism. This review describes approaches for determining how active compounds in herbal formulations enter the systemic circulation. To assess how bioactive molecules enter the target organs and cells, specific cell lines and organ culture models can be used, followed by in vitro models to show how they may regulate digestion, energy balance and metabolism. This could lead to a better understanding of how herbal medicines affect digestion and absorption; fundamental questions which should be answered in addition to their mechanism of action.

Modulation of protein kinase C by curcumin; inhibition and activation switched by calcium ions

BACKGROUND AND PURPOSE

Previous studies have identified the natural polyphenol curcumin as a protein kinase C (PKC) inhibitor. In contrast, we found significant stimulation of PKC activity following curcumin treatment. Thus, the mechanism of curcumin interaction with PKC was investigated.

EXPERIMENTAL APPROACH

We employed phosphorylation assays in the presence of soluble or membrane-bound PKC substrates, followed by SDS-PAGE, autoradiography and phosphorylation intensity measurements.

KEY RESULTS

Curcumin inhibited PKC in the absence of membranes whereas stimulation was observed in the presence of membranes. Further analysis indicated that curcumin decreased PKC activity by competition with Ca(2+) stimulation of the kinase, resulting in inhibition of activity at lower Ca(2+) concentrations and stimulation at higher Ca(2+) concentrations. The role of the membrane is likely to be facilitation of Ca(2+)-binding to the kinase, thus relieving the curcumin inhibition observed at limited Ca(2+) concentrations. Curcumin was found to mildly stimulate the catalytic subunit of PKC, which does not require Ca(2+) for activation. In addition, studies on Ca(2+)-independent PKC isoforms as well as another curcumin target (the sarcoplasmic reticulum Ca(2+)-ATPase) confirmed a correlation between Ca(2+) concentration and the curcumin effects.

CONCLUSIONS AND IMPLICATIONS

Curcumin competes with Ca(2+) for the regulatory domain of PKC, resulting in a Ca(2+)-dependent dual effect on the kinase. We propose that curcumin interacts with the Ca(2+)-binding domains in target proteins. To our knowledge, this is the first study that defines an interaction domain for curcumin, and provides a rationale for the broad specificity of this polyphenol as a chemopreventive drug.

Cytotoxic effect of curcumin on malaria parasite Plasmodium falciparum: inhibition of histone acetylation and generation of reactive oxygen species

The emergence of multidrug-resistant parasites is a major concern for malaria control, and development of novel drugs is a high priority. Curcumin, a natural polyphenolic compound, possesses diverse pharmacological properties. Among its antiprotozoan activities, curcumin was potent against both chloroquine-sensitive and -resistant Plasmodium falciparum strains. Consistent with findings in mammalian cell lines, curcumin's prooxidant activity promoted the production in P. falciparum of reactive oxygen species (ROS), whose cytotoxic effect could be antagonized by coincubation with antioxidants and ROS scavengers. Curcumin treatment also resulted in damage of both mitochondrial and nuclear DNA, probably due to the elevation of intracellular ROS. Furthermore, we have demonstrated that curcumin inhibited the histone acetyltransferase (HAT) activity of the recombinant P. falciparum general control nonderepressed 5 (PfGCN5) in vitro and reduced nuclear HAT activity of the parasite in culture. Curcumin-induced hypoacetylation of histone H3 at K9 and K14, but not H4 at K5, K8, K12, and K16, suggested that curcumin caused specific inhibition of the PfGCN5 HAT. Taken together, these results indicated that at least the generation of ROS and down-regulation of PfGCN5 HAT activity accounted for curcumin's cytotoxicity for malaria parasites.

The use of herbal and over-the-counter dietary supplements for the prevention of prostate cancer

Having a high probability of experiencing prostate cancer during their lifetime, men are increasingly seeking protection against this disease with the use of over-the-counter dietary supplements containing herbs, vitamins, or plant-derived biochemical agents. The use of these agents for prostate cancer prevention is driven by epidemiology supporting the idea that regional diets and consumption of specific dietary components (certain herbs, vitamins, isoflavones, and polyphenols) are associated with a lower risk for prostate cancer, in conjunction with basic research that is defining molecules within food substances that kill or suppress growth of cultured human prostate cancer cells. Moreover, there is a sense that these dietary agents lack side effects, although this assumption often is faulty. Unfortunately, at this time, there is insufficient clinical evidence to support the widespread use of these dietary supplements for chemoprevention of prostate cancer, although ongoing clinical trials of the most promising vitamins and minerals are approaching conclusion.

Effect of oral iron supplementation on unstimulated salivary flow rate: a randomized, double-blind, placebo-controlled trial

BACKGROUND

No treatment is known to permanently increase salivary flow in patients with hyposalivation. The objective of this study was to investigate the effect of iron supplementation on salivary flow rate.

METHODS

A double-blind, randomized, placebo-controlled trial was carried out on 50 individuals with a low unstimulated whole salivary flow rate and low serum ferritin. Half the individuals received 60 mg iron orally twice a day for 3 months, while the other half received placebo.

RESULTS

No statistically significant difference was found between the groups after treatment for the unstimulated flow rate and in the subjective assessments of oral dryness. The serum ferritin values increased significantly in the iron group but not in the placebo group.

CONCLUSION

Oral supplementation with iron for 3 months has no effect on salivary flow rate among individuals with hyposalivation and low serum ferritin values.

Neurohormetic phytochemicals: Low-dose toxins that induce adaptive neuronal stress responses

Diets rich in vegetables and fruits are associated with reduced risk of several major diseases, including neurodegenerative disorders. Although some beneficial phytochemicals might function solely as antioxidants, it is becoming clear that many of the beneficial chemicals in vegetables and fruits evolved as toxins (to dissuade insects and other predators) that, at subtoxic doses, activate adaptive cellular stress-response pathways in a variety of cells including neurons. Examples of such 'preconditioning' or 'neurohormesis' pathways include those involving cell-survival signaling kinases, the transcription factors NRF2 and CREB, and histone deacetylases of the sirtuin family. In these ways, neurohormetic phytochemicals such as resveratrol, sulforaphanes and curcumin might protect neurons against injury and disease by stimulating the production of antioxidant enzymes, neurotrophic factors, protein chaperones and other proteins that help cells to withstand stress. Thus, as we discuss in this review, highly conserved longevity and survival pathways in neurons are the targets of many phytochemicals.

Curcumin attenuates gentamicin-induced renal oxidative damage in rats

The present investigation reports the effect of curcumin, an antioxidant, on gentamicin-induced-renal oxidative damage in rats. Curcumin (200 mg/kg p.o.) was administered for 2 weeks before and 1 week simultaneously with gentamicin (100 mg/kg i.p.). Saline treated rats served as control. Serum creatinine, blood urea (BUN), urinary protein, glucose, urine gamma glutamyl transferase and urine volume increased in rats treated with gentamicin while creatinine clearance decreased compared to controls P<0.001. Renal histological examination revealed tubular necrosis. Curcumin significantly normalized the above parameters. Gentamicin decreased the activities of catalase (CAT), gutathione peroxidase (GSHPx) and the level of glutathione (GSH) but the activity of copper, zinc-superoxide dismutase (Cu, Zn-SOD) was unaltered compared to control. Curcumin attenuated the gentamicin-induced reduction in the activities of CAT, GSHPx and level of GSH by 31%, 55% and 74%, respectively. Curcumin attenuated the gentamicin-induced increases in both plasma malondialdehyde (MDA) and kidney MDA by 57% and 62%, respectively, as well as lipid hydroperoxide (LOOH) formation by 52% and 56% in rat plasma and kidney, respectively. However, Curcumin did not reduce gentamicin-induced formation of LOOH, both in the plasma and kidney, in the presence of exogenous oxidants (1 mM FeSO4, 1 mM ascorbate, 0.2 mM H2O2). Our data indicate that the natural antioxidant curcumin can be a potent protective agent against renal oxidative damage mediated by gentamicin.

Biosynthesis of curcuminoids and gingerols in turmeric (Curcuma longa) and ginger (Zingiber officinale): identification of curcuminoid synthase and hydroxycinnamoyl-CoA thioesterases

Members of the Zingiberaceae such as turmeric (Curcuma longa L.) and ginger (Zingiber officinale Rosc.) accumulate at high levels in their rhizomes important pharmacologically active metabolites that appear to be derived from the phenylpropanoid pathway. In ginger, these compounds are the gingerols; in turmeric these are the curcuminoids. Despite their importance, little is known about the biosynthesis of these compounds. This investigation describes the identification of enzymes in the biosynthetic pathway leading to the production of these bioactive natural products. Assays for enzymes in the phenylpropanoid pathway identified the corresponding enzyme activities in protein crude extracts from leaf, shoot and rhizome tissues from ginger and turmeric. These enzymes included phenylalanine ammonia lyase, polyketide synthases, p-coumaroyl shikimate transferase, p-coumaroyl quinate transferase, caffeic acid O-methyltransferase, and caffeoyl-CoA O-methyltransferase, which were evaluated because of their potential roles in controlling production of certain classes of gingerols and curcuminoids. All crude extracts possessed activity for all of these enzymes, with the exception of polyketide synthases. The results of polyketide synthase assays showed detectable curcuminoid synthase activity in the extracts from turmeric with the highest activity found in extracts from leaves. However, no gingerol synthase activity could be identified. This result was explained by the identification of thioesterase activities that cleaved phenylpropanoid pathway CoA esters, and which were found to be present at high levels in all tissues, especially in ginger tissues. These activities may shunt phenylpropanoid pathway intermediates away from the production of curcuminoids and gingerols, thereby potentially playing a regulatory role in the biosynthesis of these compounds.

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.

Differential effects of curcumin on vasoactive factors in the diabetic rat heart

Background

Increased oxidative stress has been associated with the pathogenesis of chronic diabetic complications, including cardiomyopathy. Recent studies indicate that curcumin, a potent antioxidant, may be beneficial in preventing diabetes-induced oxidative stress and subsequent secondary complications. We have investigated the effects of curcumin on the nitric oxide (NO) pathway in cardiac tissues and cultured cells.

Methods

Streptozotocin-induced diabetic rats were treated with curcumin for a period of one month. Heart tissues were then analyzed for endothelial NO synthase (eNOS) and inducible NO synthase (iNOS) mRNA expression. Oxidative protein and DNA damage were assessed by immunohistochemical analysis of nitrotyrosine and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Heart tissues were further subjected to endothelin-1 (ET-1) mRNA expression. In order to further characterize the effects of curcumin, we assayed microvascular endothelial cells (MVECs). Cultured MVECs, exposed either to glucose or glucose and varying concentrations of curcumin, were assessed for alterations of NOS expression and activation of nuclear factor-κB (NF-κB) and activating protein-1 (AP-1). Oxidative stress and ET-1 expression levels were also assayed.

Results

Our results indicate that one month of diabetes causes an upregulation of both eNOS and iNOS mRNA levels, and nitrotyrosine and 8-OHdG immunoreactivity in the heart. Treatment of diabetic rats with curcumin reduced eNOS and iNOS levels in association with reduced oxidative DNA and protein damage. Interestingly, curcumin further increased vasoconstrictor ET-1 in the heart. Exposure of MVECs to high glucose increased both eNOS and iNOS levels and oxidative stress. Curcumin prevented NOS alteration and oxidative stress in a dose-dependent manner which was mediated by nuclear factor-κB and activating protein-1. Exposure to curcumin also increased ET-1 levels in the MVECs.

Conclusion

Our studies indicate the differential effects of curcumin in vasoactive factor expression in the heart and indicate the importance of tissue microenvironment in the treatment of diabetic complications.

Curcumin-artemisinin combination therapy for malaria

Artemisinin and curcumin show an additive interaction in killing Plasmodium falciparum in culture. In vivo, 3 oral doses of curcumin following a single injection of alpha,beta-arteether to Plasmodium berghei-infected mice are able to prevent recrudescence due to alpha,beta-arteether monotherapy and ensure almost 100% survival of the animals.

Curcumin's Biphasic Hormetic Response on Proteasome Activity and Heat-Shock Protein Synthesis in Human Keratinocytes

Curcumin (diferuloylmethane), is a component of the yellow powder prepared from the roots of Curcuma longa (Zingiberaceae), also known as tumeric or turmeric. It is widely cultivated and used as a food ingredient in tropical areas of Asia and Central America. Treatment of mid-passage human epidermal keratinocytes with curcumin resulted in a biphasic hormetic dose-response with respect to proteasome activity. Curcumin treatment (up to 1 microM for 24 h) increased chymotrypsin-like activity by 46% compared to that in untreated keratinocytes. However, higher concentrations of curcumin were inhibitory, and at 10 microM the proteasome activity decreased to 46% of its initial value. Furthermore, the preincubation of human keratinocytes at 43 degrees C for 1 h, followed by 24-h treatment with 3 microM curcumin, led to an increase in heat-shock protein (hsp70 and hsp90) levels by 24% and 19%, respectively, and the effect was sustained at concentrations up to 10 microM. On the other hand, the level of the small hsp27 was unaffected by curcumin concentrations of 0.3-1 microM, while it decreased by 34% at 10 microM.

Attenuation of renal fibrosis by curcumin in rat obstructive nephropathy

OBJECTIVES

To test whether curcumin has a protective action against interstitial inflammation and the development of renal fibrosis in obstructive nephropathy. We also tested whether inhibition of nuclear factor kappa-B (NF-kappaB) and activator protein-1 (AP-1) by curcumin is involved in these mechanisms.

METHODS

Adult male rats underwent unilateral ureteral obstruction. The rats were treated with curcumin (200 mg/kg/day or 800 mg/kg/day), NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC; 200 mg/kg/day), or vehicle by gavage. Sham-operated rats served as controls. Seven days after unilateral ureteral obstruction, the activity of NF-kappaB and AP-1 was examined by electrophoretic mobility shift assay using nuclear protein extracts from the renal cortex. Gene expression of chemokines and pro-fibrotic molecules was determined by real-time reverse transcriptase-polymerase chain reaction. Macrophage infiltration and collagen III accumulation in the cortical interstitium was examined immunohistochemically.

RESULTS

Both curcumin and PDTC significantly attenuated interstitial macrophage influx and renal fibrosis. Ureteral occlusion activated both NF-kappaB and AP-1-DNA binding. Curcumin and PDTC significantly inhibited NF-kappaB activity, but not AP-1. Gene expression of chemokines and pro-fibrotic molecules was upregulated in unilateral ureteral obstruction that was attenuated by either curcumin or PDTC.

CONCLUSIONS

Curcumin protected against the renal interstitial inflammation and fibrosis elicited by ureteral occlusion. Inhibition of the NF-kappaB-dependent pathway is at least in part involved in the mechanisms, but AP-1 inhibition is unlikely to be involved in the beneficial effects of curcumin.

Use of liquid chromatography-electrospray ionization tandem mass spectrometry to identify diarylheptanoids in turmeric (Curcuma longa L.) rhizome

LC-ESI-MS/MS coupled to DAD analysis was used as an on-line tool for identification of diarylheptanoids in fresh turmeric rhizome extracts. Based on their mass spectra, from both negative and positive mode LC-ESI-MS/MS analysis, and supported by their DAD spectra, 19 diarylheptanoids were identified. Among these 19 compounds, curcumin, demethoxycurcumin, and bisdemethoxycurcumin were identified by comparing their chromatographic and spectral data with those of authentic standard compounds. The other diarylheptanoid compounds were identified or tentatively identified based on comparison to the three curcuminoids and each other. Twelve of the identified diarylheptanoids have not been previously reported from turmeric and six of these are new compounds.

Antioxidants and polyunsaturated fatty acids in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Oligodendrocyte damage and subsequent axonal demyelination is a hallmark of this disease. Different pathomechanisms, for example, immune-mediated inflammation, oxidative stress and excitotoxicity, are involved in the immunopathology of MS. The risk of developing MS is associated with increased dietary intake of saturated fatty acids. Polyunsaturated fatty acid (PUFA) and antioxidant deficiencies along with decreased cellular antioxidant defence mechanisms have been observed in MS patients. Furthermore, antioxidant and PUFA treatment in experimental allergic encephalomyelitis, an animal model of MS, decreased the clinical signs of disease. Low-molecular-weight antioxidants may support cellular antioxidant defences in various ways, including radical scavenging, interfering with gene transcription, protein expression, enzyme activity and by metal chelation. PUFAs may not only exert immunosuppressive actions through their incorporation in immune cells but also may affect cell function within the CNS. Both dietary antioxidants and PUFAs have the potential to diminish disease symptoms by targeting specific pathomechanisms and supporting recovery in MS.

Curcumin ameliorates acute thioacetamide-induced hepatotoxicity

BACKGROUND AND AIM

Increased production of reactive oxygen species and nitric oxide and activation of nuclear factor kappa B are implicated in the pathogenesis of various liver diseases, including fulminant hepatic failure. Curcumin is a naturally occurring anti-oxidant that reduces oxidative stress and inhibits nuclear factor kappa B and nitric oxide formation. The aim of the present study is to assess curcumin's therapeutic potential in acute thioacetamide hepatotoxicity, a rat model of fulminant hepatic failure.

METHODS

Fulminant hepatic failure was induced by two intraperitoneal (i.p.) injections of 300 mg/kg thioacetamide (TAA) at 24-h intervals. The experimental groups received a low-dose (200 mg/kg per day, i.p.) or a high-dose (400 mg/kg per day) of curcumin, initiated 48 h prior to the first TAA injection. A fourth group was administered neither TAA nor curcumin and served as a control.

RESULTS

The survival rate was higher in both curcumin-treated groups compared to the TAA only treated group. Biochemical parameters of liver injury, blood ammonia and hepatic necroinflammation were lower in the low-dose curcumin group compared to TAA controls, and were further reduced in the high-dose group (P < 0.05 and P < 0.01, respectively). Curcumin treatment also reduced the TAA-induced elevated hepatic levels of thiobarbituric acid-reactive substances (TBARS), and inhibited the nuclear binding of nuclear factor kappa B (NFkappaB) and inducible nitric oxide (iNOS) protein expression.

CONCLUSIONS

Curcumin improved survival and minimized oxidative stress, hepatocellular injury and hepatic necroinflammation, NFkappaB binding and iNOS expression in a rat model of FHF. These findings support the role of ROS, NFkappaB and iNOS in mediating liver insult due to TAA, and that of curcumin as a hepato-protectant.

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.

Chemoprevention of photocarcinogenesis by selected dietary botanicals

Epidemiological, clinical and laboratory studies have implicated solar ultraviolet (UV) radiation as a tumor initiator, tumor promoter and complete carcinogen, and their excessive exposure can lead to the development of various skin disorders including melanoma and nonmelanoma skin cancers. Sunscreens are useful, but their protection is not adequate to prevent the risk of UV-induced skin cancer. It may be because of inadequate use, incomplete spectral protection and toxicity. Therefore new chemopreventive methods are necessary to protect the skin from photodamaging effects of solar UV radiation. Chemoprevention refers to the use of agents that can inhibit, reverse or retard the process of skin carcinogenesis. In recent years, considerable interest has been focused on identifying naturally occurring botanicals, specifically dietary, for the prevention of photocarcinogenesis. A wide variety of botanicals, mostly dietary flavonoids or phenolic substances, have been reported to possess substantial anticarcinogenic and antimutagenic activities because of their antioxidant and antiinflammatory properties. This review summarizes chemopreventive effects of some selected botanicals, such as apigenin, curcumin, grape seed proanthocyanidins, resveratrol, silymarin, and green tea polyphenols, against photocarcinogenesis in in vitro and in vivo systems. Attention has also been focused on highlighting the mechanism of chemopreventive action of these dietary botanicals. We suggest that in addition to the use of these botanicals as dietary supplements for the protection of photocarcinogenesis, these botanicals may favorably supplement sunscreens protection and may provide additional antiphotocarcinogenic protection including the protection against other skin disorders caused by solar UV radiation.

Ethanolic Extracts from Curcuma longa Attenuates Behavioral, Immune, and Neuroendocrine Alterations in a Rat Chronic Mild Stress Model

The ethanolic extracts from the rhizome of Curcuma longa L. (turmeric), possesses a wide variety of biological activities related to the treatment and prevention of affective disorders. To study their antidepressant effects, the impacts of chronic mild stress (CMS) and of the subsequent administration of ethanolic extracts of C. longa were investigated. Male Sprague-Dawley rats subjected to the CMS procedure demonstrated increased serum interleukin-6 and tumor necrosis factor-alpha levels, as well as a reduction of natural killer cell activity in splenocytes. In addition, CMS-treated rats exhibited elevated corticotropin-releasing factor in serum and medulla oblongata and cortisol levels in serum, with no significant change in serum adrenocorticotropin hormone levels. The preferential behavior of reduction in sucrose intake was also observed. These findings indicate that the alterations in immune and hypothalamic-pituitary-adrenal (HPA) axis systems could participate in the behavioral response to the CMS procedure in animals. Administration of ethanolic extracts of C. longa largely reversed the above effects. These results demonstrate the antidepressant-like activity of ethanolic extracts of C. longa in the rat CMS model of depression, at least in part by improving the abnormalities in immune and the HPA axis functions.

Activation of NFkappaB is inhibited by curcumin and related enones

The transcription factor NFkappaB (NFkappaB) is up-regulated in many cancer cells where it contributes to development of the pro-survival, anti-apoptotic state. The natural product curcumin is a known inhibitor of activation of NFkappaB. Enone analogues of curcumin were compared with curcumin for their abilities to inhibit the TNFalpha-induced activation of NFkappaB, using the Panomics' NFkappaB Reporter Stable Cell Line. The enones tested included curcumin analogues that retained the 7-carbon spacer between the aromatic rings, analogues with a 5-carbon spacer, and analogues with a 3-carbon spacer. Inhibitors of NFkappaB activation were identified in all three series, a number of which were more active than curcumin. Enone analogues in the series with the 5-carbon spacer were especially active, including members that contained heterocyclic rings. 1,5-Bis(3-pyridyl)-1,4-pentadien-3-one was the most active analogue, IC50 = 3.4 +/- 0.2 microM. The most active analogues retain the enone functionality, although some analogues devoid of the enone functionality exhibited activity. The activity of the analogues as inhibitors of the activation of NFkappaB did not correlate with their anti-oxidant activity. The data suggest that the abilities of curcumin and analogues to prevent the stress-induced activation of NFkappaB result from the inhibition of specific targets rather than from activity as anti-oxidants.

Proapoptotic effect of curcumin on human neutrophils: activation of the p38 mitogen-activated protein kinase pathway

OBJECTIVE

Despite advances in the management of sepsis and acute respiratory distress syndrome, the mortality rate remains high. Delayed apoptosis of neutrophils is associated with multiple organ failure under those conditions. Thus, development of nontoxic neutrophil apoptosis regulating molecules may provide a novel therapeutic strategy. Curcumin is a promising dietary supplement for cancer prevention. However, the effect of curcumin on human neutrophil apoptosis remains unknown. We therefore hypothesized that curcumin would produce a proapoptotic effect on neutrophils.

DESIGN

Prospective, controlled, and randomized in vitro study.

SETTING

Research institute laboratory.

SUBJECTS

Human peripheral neutrophils obtained from normal subjects.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In the presence or absence of curcumin, both spontaneous neutrophil apoptosis and apoptosis of neutrophils following transmigration across a human lung endothelium-epithelium bilayer were studied by morphology and terminal dUTP nucleotide end labeling analyses, respectively. Myeloperoxidase activity and migration assays were performed to determine the impact of curcumin on neutrophil function. To elucidate the potential mechanism, the p38 mitogen-activated protein kinase pathway and caspase-3 activity were examined by Western blotting and enzymatic analyses. The data demonstrate that curcumin increased constitutive neutrophil apoptosis and abrogated the transbilayer migration-induced delay in neutrophil apoptosis. Neutrophil activation was reduced by curcumin treatment as evidenced by a decrease in migration and myeloperoxidase release. A marked increase in p38 phosphorylation and caspase-3 activity was observed following curcumin exposure. In addition, inhibition of p38 mitogen-activated protein kinase with SB203580 suppressed apoptosis and caspase-3 activation induced by curcumin. Thus, activation of p38 mitogen-activated protein kinase or an increase in caspase-3 activity appears to contribute to the proapoptotic effect of human neutrophil apoptosis by curcumin.

CONCLUSION

The characteristics of curcumin, including its proapoptotic effect and antidegranulation effect, make it a potential candidate for the therapy of neutrophil-induced lung injury and sepsis.

Synthesis of novel curcumin mimics with asymmetrical units and their anti-angiogenic activity

Novel curcumin mimics with asymmetrical units phenyl group with alkyl amide, chloro-substituted benzamide, or heteroaromatic amide moieties were synthesized and their anti-angiogenic activity was evaluated with the proliferation and tube formation inhibitory activity on the human umbilical vein endothelial cells. Compounds 5, 14, 17, and 18 showed potent growth inhibitory activity and tube formation inhibitory activity.

Curcumin induces human HT-29 colon adenocarcinoma cell apoptosis by activating p53 and regulating apoptosis-related protein expression

Curcumin, a major yellow pigment and active component of turmeric, has multiple anti-cancer properties. However, its molecular targets and mechanisms of action on human colon adenocarcinoma cells are unknown. In the present study, we examined the effects of curcumin on the proliferation of human colon adenocarcinoma HT-29 cells by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide method and confirmed the curcumin-induced apoptosis by morphology and DNA ladder formation. At the same time, p53, phospho-p53 (Ser15), and other apoptosis-related proteins such as Bax, Bcl-2, Bcl-xL, pro-caspase-3, and pro-caspase-9 were determined by Western blot analysis. The colon adenocarcinoma cells were treated with curcumin (0-75 microM) for 0-24 h. We observed that p53 was highly expressed in HT-29 cells and curcumin could up-regulate the serine phosphorylation of p53 in a time- and concentration-dependent manner. An increase in expression of the pro-apoptotic factor Bax and a decrease in expression of the anti-apoptotic factor Bcl-2 were also observed in a time-dependent manner after exposure of 50 microM curcumin, while the expression of the anti-apoptotic factor Bcl-xL was unchanged. Curcumin could also down-regulate the expression of pro-caspase-3 and pro-caspase-9 in a time-dependent manner. These data suggest a possible underlying molecular mechanism whereby curcumin could induce the apoptosis signaling pathway in human HT-29 colon adenocarcinoma cells by p53 activation and by the regulation of apoptosis-related proteins. This property of curcumin suggests that it could have a possible therapeutic potential in colon adenocarcinoma patients.

Prevention of kainic acid-induced changes in nitric oxide level and neuronal cell damage in the rat hippocampus by manganese complexes of curcumin and diacetylcurcumin

Curcumin is a natural antioxidant isolated from the medicinal plant Curcuma longa Linn. We previously reported that manganese complexes of curcumin (Cp-Mn) and diacetylcurcumin (DiAc-Cp-Mn) exhibited potent superoxide dismutase (SOD)-like activity in an in vitro assay. Nitric oxide (NO) is a free radial playing a multifaceted role in the brain and its excessive production is known to induce neurotoxicity. Here, we examined the in vivo effect of Cp-Mn and DiAc-Cp-Mn on NO levels enhanced by kainic acid (KA) and L-arginine (L-Arg) in the hippocampi of awake rats using a microdialysis technique. Injection of KA (10 mg/kg, i.p.) and L-Arg (1000 mg/kg, i.p.) significantly increased the concentration of NO and Cp-Mn and DiAc-Cp-Mn (50 mg/kg, i.p.) significantly reversed the effects of KA and L-Arg without affecting the basal NO concentration. Following KA-induced seizures, severe neuronal cell damage was observed in the CA1 and CA3 subfields of hippocampal 3 days after KA administration. Pretreatment with Cp-Mn and DiAc-Cp-Mn (50 mg/kg, i.p.) significantly attenuated KA-induced neuronal cell death in both CA1 and CA3 regions of rat hippocampus compared with vehicle control, and Cp-Mn and DiAc-Cp-Mn showed more potent neuroprotective effect than their parent compounds, curcumin and diacetylcurcumin. These results suggest that Cp-Mn and DiAc-Cp-Mn protect against KA-induced neuronal cell death by suppression of KA-induced increase in NO levels probably by their NO scavenging activity and antioxidative activity. Cp-Mn and DiAc-Cp-Mn have an advantage to be neuroprotective agents in the treatment of acute brain pathologies associated with NO-induced neurotoxicity and oxidative stress-induced neuronal damage such as epilepsy, stroke and traumatic brain injury.

Synthesis and characterization of dual function vanadyl, gallium and indium curcumin complexes for medicinal applications

Novel bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) complexes with the formula, ML(3), where M is Ga(III) or In(III), or of the formula, ML(2) where M is [VO](2+), have been synthesized and characterized by mass spectrometry, infrared and absorption spectroscopies, and elemental analysis. A new ligand, bis[4-acetyl-3-hydroxyphenyl]-1,6-heptadiene-3,5-dione (diacetylbisdemethoxycurcumin, DABC) was similarly characterized; an X-ray structure analysis was performed. Vanadyl complexes tested in an acute i.p. testing protocol in STZ-diabetic rats showed a lack of insulin enhancing potential. Vanadyl complexes were, however, more cytotoxic than were the ligands alone in standard MTT (3-[4,5-dimethylthiazole-2-yl]ate, -2,5-diphenyl-tetrazolium bromide) cytotoxicity testing, using mouse lymphoma cells. With the exception of DABC, that was not different from VO(DABC)(2), the complexes were not significantly different from one another, with IC(50) values in the 5-10 microM range. Gallium and indium curcumin complexes had IC(50) values in the same 5-10 microM range; whereas Ga(DAC)(3) and In(DAC)(3) (where DAC=diacetylcurcumin) were much less cytotoxic (IC(50)=20-30 microM). Antioxidant capacity was decreased in VO(DAC)(2), Ga(DAC)(3), and In(DAC)(3), compared to vanadyl, gallium and indium curcumin, corroborating the importance of curcumin's free phenolic OH groups for scavenging oxidants, and correlated with reduced cytotoxic potential.

Curcumin: The story so far

Curcumin is a polyphenol derived from the herbal remedy and dietary spice turmeric. It possesses diverse anti-inflammatory and anti-cancer properties following oral or topical administration. Apart from curcumin's potent antioxidant capacity at neutral and acidic pH, its mechanisms of action include inhibition of several cell signalling pathways at multiple levels, effects on cellular enzymes such as cyclooxygenase and glutathione S-transferases, immuno-modulation and effects on angiogenesis and cell-cell adhesion. Curcumin's ability to affect gene transcription and to induce apoptosis in preclinical models is likely to be of particular relevance to cancer chemoprevention and chemotherapy in patients. Although curcumin's low systemic bioavailability following oral dosing may limit access of sufficient concentrations for pharmacological effect in certain tissues, the attainment of biologically active levels in the gastrointestinal tract has been demonstrated in animals and humans. Sufficient data currently exist to advocate phase II clinical evaluation of oral curcumin in patients with invasive malignancy or pre-invasive lesions of the gastrointestinal tract, particularly the colon and rectum.

Curcumin modulation of Na,K-ATPase: phosphoenzyme accumulation, decreased K+ occlusion, and inhibition of hydrolytic activity

1 Curcumin, the major constitute of tumeric, is an important nutraceutical that has been shown to be useful in the treatment of many diseases. As an inhibitor of the sarcoplasmic reticulum Ca(2+)-ATPase, curcumin was shown to correct cystic fibrosis (CF) defects in some model systems, whereas others have reported no or little effects on CF after curcumin treatment, suggesting that curcumin effect is not due to simple inhibition of the Ca(2+)-ATPase. 2 We tested the hypothesis that curcumin may modulate other members of the P(2)-type ATPase superfamily by studying the effects of curcumin on the activity and kinetic properties of the Na,K-ATPase. 3 Curcumin treatment inhibited Na,K-ATPase activity in a dose-dependent manner (K(0.5) approximately 14.6 microM). Curcumin decreased the apparent affinity of Na,K-ATPase for K(+) and increased it for Na(+) and ATP. Kinetic analyses indicated that curcumin induces a three-fold reduction in the rate of E1P --> E2P transition, thereby increasing the steady-state phosphoenzyme level. Curcumin treatment significantly abrogated K(+) occlusion to the enzyme as evidenced from kinetic and proteolytic cleavage experiments. Curcumin also significantly decreased the vanadate sensitivity of the enzyme. 4 Thus, curcumin partially blocks the K(+) occlusion site, and induces a constitutive shift in the conformational equilibrium of the enzyme, towards the E1 conformation. 5 The physiological consequences of curcumin treatment previously reported in different epithelial model systems may, at least in part, be related to the direct effects of curcumin on Na,K-ATPase activity.