CURCUMIN: THE INDIAN SOLID GOLD

Advances in research on the signaling pathways involved in activation and phenotypic transformation of hepatic stellate cells and their inhibitors

Liver fibrosis is a progressive pathologic process that involves deposition of excess extracellular matrix leading to distorted architecture and culminating in cirrhosis. It is believed that activation and phenotypic transformation of hepatic stellate cells (HSCs) play a central role in the development and resolution of liver fibrosis. Many cytokines and related signaling pathways are involved in the phenotypic transformation and proliferation of HSCs. In recent years, great advances have been made in the study of these signaling pathways and their specific inhibitors, thereby providing a new avenue for clinical therapy of liver fibrosis. However, as the mechanisms underlying the roles of these signaling pathways are very complicated, further intensive studies are still essential. In this article, we will review the advances in research on the signaling pathways involved in activation and phenotypic transformation of hepatic stellate cells and their inhibitors.

Curcumin inhibits ACTH- and angiotensin II-stimulated cortisol secretion and Ca(v)3.2 current

Adrenocorticotropic hormone and angiotensin II stimulate cortisol secretion from bovine adrenal zona fasciculata cells by the activation of adenylate cyclase and phospholipase C-coupled receptors. Curcumin (1- 20 muM), a compound found in the spice turmeric, inhibited cortisol secretion stimulated by ACTH, AngII, and 8CPT-cAMP. Curcumin also suppressed ACTH-stimulated increases in mRNAs coding for steroid acute regulatory protein and CYP11a1 steroid hydroxylase. In whole cell patch clamp recordings from AZF cells, curcumin at slightly higher concentrations also inhibited Ca(v)3.2 current. These results identify curcumin as an effective inhibitor of ACTH- and AngII-stimulated cortisol secretion. The inhibition of Ca(v)3.2 current by curcumin may contribute to its suppression of secretion.

The role of MD-2 in the opsonophagocytosis of Gram-negative bacteria

PURPOSE OF REVIEW

The identification of human Toll-like receptors has drastically changed our understanding of host-pathogen interactions. This review presents recent data on myeloid differentiation factor 2 (MD-2), a membrane-bound and soluble receptor for Gram-negative lipopolysaccharide, and its central role in the recognition of Gram-negative bacteria, phagocytosis, and Toll-like receptor 4 signalling.

RECENT FINDINGS

Phagocytosis is a complex mechanism involving a variety of receptors and opsonins. The heterogeneity of phagocytic mechanisms allows the optimization of bacteria recognition, phagocytosis, and killing. Notably, Toll-like receptors were known to play a role in phagocytosis, both by modulating opsonins and phagocytosis receptors' expression and activity, and by contributing to bacterial recognition and presentation to host cells. Recent data provide additional insight into the function of Toll-like receptors and associated proteins. In addition to bacterial recognition and activation of inflammatory cascades, MD-2 has been recently shown to be an opsonin for Gram-negative bacteria and an acute-phase protein. These newly described characteristics directly link Gram-negative bacteria recognition, transduction of Toll-like receptor 4 inflammatory signalling, phagocytosis and bacterial clearance.

SUMMARY

Recent progress in the understanding of Gram-negative bacteria recognition by host cells as well as physiologic functionality of MD-2 suggests that MD-2 is a critical compound in host response to pathogens and plays a central role in physiologic adaptation to various insults.

Combinatorial biosynthesis of non-bacterial and unnatural flavonoids, stilbenoids and curcuminoids by microorganisms

One of the approaches of combinatorial biosynthesis is combining genes from different organisms and designing a new set of gene clusters to produce bioactive compounds, leading to diversification of both chemical and natural product libraries. This makes efficient use of the potential of the host organisms, especially when microorganisms are used. An Escherichia coli system, in which artificial biosynthetic pathways for production of plant-specific medicinal polyketides, such as flavonoids, stilbenoids, isoflavonoids, and curcuminoids, are assembled, has been designed and expressed. Starting with amino acids tyrosine and phenylalanine as substrates, this system yields naringenin, resveratrol, genistein, and curcumin, for example, all of which are beneficial to human health because of their wide variety of biological activities. Supplementation of unnatural carboxylic acids to the recombinant E. coli cells carrying the artificial pathways by precursor-directed biosynthesis results in production of unnatural compounds. Addition of decorating or modification enzymes to the artificial pathway leads to production of natural and unnatural flavonols, flavones, and methylated resveratrols. This microbial system is promising for construction of larger libraries by employing other polyketide synthases and decorating enzymes of various origins. In addition, the concept of building and expressing artificial biosynthetic pathways for production of non-bacterial and unnatural compounds in microorganisms should be successfully applied to production of not only plant-specific polyketides but also many other useful compound classes.

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

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

New difluoro Knoevenagel condensates of curcumin, their Schiff bases and copper complexes as proteasome inhibitors and apoptosis inducers in cancer cells

PURPOSE

Emerging evidence clearly suggests the potential chemopreventive and anti-tumor activity of a well known "natural agent" curcumin. However, studies have shown that curcumin is not readily bioavailable, and thus the tissue bioavailability of curcumin is also poor except for gastrointestinal track. Because of the potential biological activity of curcumin, many studies have attempted for making a better analog of curcumin that is equally effective or better with increased bioavailability, which was the purpose of our current study.

METHODS

We have designed and synthesized new difluoro Knoevenagel condensates of curcumin and Schiff bases along with their copper (II) complexes and evaluated their biological activities with respect to the inhibitory effects on purified rabbit 26S proteasome, and growth inhibition and induction of apoptosis in colon and pancreatic cancer cell lines.

RESULTS

All copper complexes possess distorted square planar geometries with 1:1 metal to ligand stoichiometry with reversible copper redox couple. The difluoro compound CDF exhibited inhibitory effects on purified rabbit 20S proteasome or cellular 26S proteasome, and caused both growth inhibition of cancer cell lines and induced apoptotic cell death in our preliminary assessment.

CONCLUSION

Our results suggest that our newly synthesized classes of curcumin analogs could be useful as chemopreventive and/or therapeutic agents against cancers.

Curcumin inhibits prosurvival pathways in chronic lymphocytic leukemia B cells and may overcome their stromal protection in combination with EGCG

PURPOSE

Chronic lymphocytic leukemia (CLL) is incurable with current chemotherapy treatments. Curcumin (diferuloylmethane), an active ingredient in the spice turmeric, inhibits tumor metastasis, invasion, and angiogenesis in tumor cell lines. We evaluated the effects of curcumin on the viability of primary CLL B cells and its ability to overcome stromal mediated protection.

EXPERIMENTAL DESIGN

The in vitro effect of curcumin on primary CLL B cells was evaluated using fluorescence activated cell sorter analysis and Western blotting. For some experiments, CLL B cells were cocultured with human stromal cells to evaluate the effects of curcumin on leukemia cells cultured in their microenvironment. Finally, the effect of curcumin in combination with the green tea extract epigallocatechin-3 gallate (EGCG) was evaluated.

RESULTS

Curcumin induced apoptosis in CLL B cells in a dose-dependent (5-20 micromol/L) manner and inhibited constitutively active prosurvival pathways, including signal transducers and activators of transcription 3 (STAT3), AKT, and nuclear factor kappaB. Moreover, curcumin suppressed expression of the anti-apoptotic proteins Mcl-1 and X-linked inhibitor of apoptosis protein (XIAP), and up-regulated the pro-apoptotic protein BIM. Coculture of CLL B cells with stromal cells resulted in elevated levels of STAT3, increased expression of Mcl-1 and XIAP, and decreased sensitivity to curcumin. When curcumin was administered simultaneously with EGCG, antagonism was observed for most patient samples. In contrast, sequential administration of these agents led to substantial increases in CLL B-cell death and could overcome stromal protection.

CONCLUSIONS

Curcumin treatment was able to overcome stromal protection of CLL B cells on in vitro testing and to synergize with EGCG when administered in a sequential fashion. Additional evaluation of curcumin as a potential therapeutic agent for treatment of CLL seems warranted.

Combinatorial biosynthesis of plant medicinal polyketides by microorganisms

Combinatorial biosynthesis includes an approach in which genes from different organisms are assembled to design and construct an artificial gene cluster for production of bioactive compounds. An Escherichia coli system carrying artificial biosynthetic pathways for production of plant-specific medicinal polyketides, such as flavonoids, stilbenoids, isoflavonoids, and curcuminoids, was designed and expressed. Starting with amino acids tyrosine and phenylalanine as substrates, this system yielded, for example, naringenin, resveratrol, genistein, and curcumin. Supplementation of unnatural carboxylic acids as precursors to the E. coli cells led to production of unnatural compounds. Addition of modification enzymes to the artificial pathways led to production of natural and unnatural flavonols, flavones, and methylated resveratrols. This microbial system is promising not only for construction of larger libraries by employing other polyketide synthases and modification enzymes of various origins as members of the artificial pathway but also for efficient use of the potential of the host microorganisms.

Neuroprotective and antiinflammatory properties of a novel demethylated curcuminoid

A demethylated derivative of curcumin (DC; 67.8% bisdemethylcurcumin, 20.7% demethylmonodemethoxycurcumin, 5.86% bisdemethoxycurcumin, 2.58% demethylcurcumin) was prepared by using a 95% extract of curcumin (C(95); 72.2% curcumin, 18.8% monodemethoxycurcumin, 4.5% bisdemethoxycurcumin). DC increased glutathione and reduced reactive oxygen species (ROS) in HT4 neuronal cells. In a model of glutamate-induced death of HT4, DC was more effective than C(95) in neuroprotection. The protective effects of DC were retained even when DC was withdrawn from culture media after pretreatment. DC treatment, unlike an equal dose of C(95), completely spared glutamate-induced loss of cellular GSH. Both DC and C(95) prevented glutamate-induced elevation of cellular ROS but failed to attenuate glutamate-induced elevation of intracellular calcium. In human microvascular endothelial cells (HMECs) challenged with TNF-alpha, GeneChip analysis revealed that only a subcluster of 23 TNF-alpha-inducible genes were uniquely sensitive to C(95). In sharp contrast, 1,065 TNF-alpha-inducible genes were sensitive to DC but not to C(95), suggesting that DC was more effective in antagonizing the effects of TNF-alpha on HMECs. Functional analysis identified that the genes uniquely sensitive to DC belonged in four functional categories: cytokine-receptor interaction, focal adhesion, cell adhesion, and apoptosis. Real-time PCR as well as ELISA studies demonstrated that TNF-alpha-inducible CXCL10 and CXCL11 expression was sensitive to DC but not to C(95). Flow-cytometry studies recognized ICAM-1 and VCAM-1 as TNF-alpha-inducible adhesion molecules that were uniquely sensitive to DC. Taken together, DC exhibited promising neuroprotective and antiinflammatory properties that must be characterized in vivo.

Multi-targeted therapy by curcumin: how spicy is it?

Although traditional medicines have been used for thousands of years, for most such medicines neither the active component nor their molecular targets have been very well identified. Curcumin, a yellow component of turmeric or curry powder, however, is an exception. Although inhibitors of cyclooxygenase-2, HER2, tumor necrosis factor, EGFR, Bcr-abl, proteosome, and vascular endothelial cell growth factor have been approved for human use by the United States Food and Drug Administration (FDA), curcumin as a single agent can down-regulate all these targets. Curcumin can also activate apoptosis, down-regulate cell survival gene products, and up-regulate p53, p21, and p27. Although curcumin is poorly absorbed after ingestion, multiple studies have suggested that even low levels of physiologically achievable concentrations of curcumin may be sufficient for its chemopreventive and chemotherapeutic activity. Thus, curcumin regulates multiple targets (multitargeted therapy), which is needed for treatment of most diseases, and it is inexpensive and has been found to be safe in human clinical trials. The present article reviews the key molecular mechanisms of curcumin action and compares this to some of the single-targeted therapies currently available for human cancer.

Curcumin supplementation lowers TNF-alpha, IL-6, IL-8, and MCP-1 secretion in high glucose-treated cultured monocytes and blood levels of TNF-alpha, IL-6, MCP-1, glucose, and glycosylated hemoglobin in diabetic rats

This study examined the hypothesis that curcumin supplementation decreases blood levels of IL-6, MCP-1, TNF-alpha, hyperglycemia, and oxidative stress by using a cell-culture model and a diabetic rat model. U937 monocytes were cultured with control (7 mM) and high glucose (35 mM) in the absence or presence of curcumin (0.01-1 microM) at 37 degrees C for 24 h. Diabetes was induced in Sprague-Dawley rats by injection of streptozotocin (STZ) (i.p., 65 mg/kg BW). Control buffer, olive oil, or curcumin (100 mg/kg BW) supplementation was administered by gavage daily for 7 weeks. Blood was collected by heart puncture with light anesthesia. Results show that the effect of high glucose on lipid peroxidation, IL-6, IL-8, MCP-1, and TNF-alpha secretion was inhibited by curcumin in cultured monocytes. In the rat model, diabetes caused a significant increase in blood levels of IL-6, MCP-1, TNF-alpha, glucose, HbA(1), and oxidative stress, which was significantly decreased in curcumin-supplemented rats. Thus, curcumin can decrease markers of vascular inflammation and oxidative stress levels in both a cell-culture model and in the blood of diabetic rats. This suggests that curcumin supplementation can reduce glycemia and the risk of vascular inflammation in diabetes.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Synthesis and evaluation of electron-rich curcumin analogues

The natural product curcumin has long been recognized for its medicinal properties and is utilized for the treatment of many diseases. However, it remains unknown whether this activity is based on its presumably promiscuous scaffold, or if it results from the Michael acceptor properties of the alpha,beta-unsaturated 1,3-diketone moiety central to its structure. To probe this issue, electron-rich pyrazole and isoxazole analogues were prepared and evaluated against two breast cancer cell lines, which resulted in the identification of several compounds that exhibit low micromolar to mid nanomolar anti-proliferative activity. A conjugate addition study was also performed to compare the relative electrophilicity of the diketone, pyrazole and isoxazole analogues.

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.

Pharmacological basis for the role of curcumin in chronic diseases: an age-old spice with modern targets

Curcumin (diferuloylmethane), a yellow pigment in the spice turmeric (also called curry powder), has been used for centuries as a treatment for inflammatory diseases. Extensive research within the past two decades has shown that curcumin mediates its anti-inflammatory effects through the downregulation of inflammatory transcription factors (such as nuclear factor kappaB), enzymes (such as cyclooxygenase 2 and 5 lipoxygenase) and cytokines (such as tumor necrosis factor, interleukin 1 and interleukin 6). Because of the crucial role of inflammation in most chronic diseases, the potential of curcumin has been examined in neoplastic, neurological, cardiovascular, pulmonary and metabolic diseases. The pharmacodynamics and pharmacokinetics of curcumin have been examined in animals and in humans. Various pharmacological aspects of curcumin in vitro and in vivo are discussed in detail here.

Ultraviolet radiation-induced transcription is associated with gene-specific histone acetylation

UVR is an important environmental carcinogen and a powerful modulator of the cutaneous immune system. Exposure to UVR activates many signaling pathways leading to changes in the expression of several hundred genes. While the covalent modification of histones has been shown to play a central role in regulating gene expression, the impact of UVR on histone modifications and the contribution of histone acetyltransferases (HATs) and histone deacetylases (HDACs) to the UVR-induced transcriptional response have not been completely characterized. In this report, we have examined the impact of UVR on histone H3 K9/14 acetylation. The potential role of UVR-induced histone acetylation in the UVR transcriptional response was also explored using the HAT inhibitor curcumin and HDAC inhibitor trichostatin A (TSA). We found that UVR caused an increase in histone H3 acetylation within the promoter regions of ATF3, COX2, IL-8, MKP1 and MnSOD. In most of the regions examined, histone H3 acetylation peaked 24 h after UVR and then returned to baseline levels by 72 h. The induction of ATF3, COX2 and MKP1 was blocked in the presence of curcumin at doses that decrease in vivo histone H3 acetylation but not at lower doses that do not affect acetylation levels. We also provide evidence that for ATF3, a transcriptional superinduction occurs after repeat exposures to UVR that can be recapitulated when the second UVR exposure is replaced with TSA treatment. Thus, UVR can alter histone acetylation within human keratinocytes and these changes may contribute to the UVR-transcriptional response.

Curcumin and muscle wasting: a new role for an old drug?

Sepsis, severe injury, and cancer are associated with loss of muscle mass. Muscle wasting in these conditions is mainly caused by increased proteolysis, at least in part regulated by nuclear factor-kappaB. Despite recent progress in the understanding of mediators and mechanisms involved in muscle wasting, effective and universally accepted treatments by which muscle atrophy can be prevented or reversed are still lacking. We review recent evidence suggesting that curcumin (diferuloylmethane), a component of the spice turmeric, may prevent loss of muscle mass during sepsis and endotoxemia and may stimulate muscle regeneration after traumatic injury. Curcumin has been part of the traditional Asian medicine for centuries, mainly because of its anti-inflammatory properties. Studies suggest that inhibition of nuclear factor-kappaB is one of the mechanisms by which curcumin exerts its ant-inflammatory effects. Curcumin is easily accessible, inexpensive, and non-toxic even at high doses, and may therefore offer an important treatment modality in muscle wasting and injury. It should be noted, however, that the muscle-sparing effects of curcumin are not universally accepted, and more studies are therefore needed to further test the role of curcumin in the prevention and treatment of muscle wasting.

Curcumin prevents and reverses cirrhosis induced by bile duct obstruction or CCl4 in rats: role of TGF-beta modulation and oxidative stress

Curcumin is a phytophenolic compound, which is highly efficacious for treating several inflammatory diseases. The aim of this study was to evaluate the efficacy of curcumin in preventing or reversing liver cirrhosis. A 4-week bile duct ligation (BDL) rat model was used to test the ability of curcumin (100 mg/kg, p.o., daily) to prevent cirrhosis. To reverse cirrhosis, CCl(4) was administered chronically for 3 months, and then it was withdrawn and curcumin administered for 2 months. Alanine aminotransferase, gamma-glutamyl transpeptidase, liver histopathology, bilirubin, glycogen, reduced and oxidized glutathione, and TGF-beta (mRNA and protein) levels were assessed. Curcumin preserved normal values of markers of liver damage in BDL rats. Fibrosis, assessed by measuring hydroxyproline levels and histopathology, increased nearly fivefold after BDL and this effect was partially but significantly prevented by curcumin. BDL increased transforming growth factor-beta (TGF-beta) levels (mRNA and proteins), while curcumin partially suppressed this mediator of fibrosis. Curcumin also partially reversed the fibrosis induced by CCl(4). Curcumin was effective in preventing and reversing cirrhosis, probably by its ability of reducing TGF-beta expression. These data suggest that curcumin might be an effective antifibrotic and fibrolitic drug in the treatment of chronic hepatic diseases.

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.

NF-kappaB mediates the survival of human bronchial epithelial cells exposed to cigarette smoke extract

BACKGROUND

We have previously reported that low concentrations of cigarette smoke extract induce DNA damage without leading to apoptosis or necrosis in human bronchial epithelial cells (HBECs), and that IL-6/STAT3 signaling contributes to the cell survival. Since NF-kappaB is also involved in regulating apoptosis and cell survival, the current study was designed to investigate the role of NF-kappaB in mediating cell survival in response to cigarette smoke exposure in HBECs.

METHODS

Both the pharmacologic inhibitor of NF-kappaB, curcumin, and RNA interference targeting p65 were used to block NF-kappaB signaling in HBECs. Apoptosis and cell survival were then assessed by various methods including COMET assay, LIVE/DEAD Cytotoxicity/Viability assay and colony formation assay.

RESULTS

Cigarette smoke extract (CSE) caused DNA damage and cell cycle arrest in S phase without leading to apoptosis in HBECs as evidenced by TUNEL assay, COMET assay and DNA content assay. CSE stimulated NF-kappaB -DNA binding activity and up-regulated Bcl-XL protein in HBECs. Inhibition of NF-kappaB by the pharmacologic inhibitor curcumin (20 microM) or suppression of p65 by siRNA resulted in a significant increase in cell death in response to cigarette smoke exposure. Furthermore, cells lacking p65 were incapable of forming cellular colonies when these cells were exposed to CSE, while they behaved normally in the regular culture medium.

CONCLUSION

The current study demonstrates that CSE activates NF-kappaB and up-regulates Bcl-XL through NF-kB activation in HBECs, and that CSE induces cell death in cells lacking p65. These results suggest that activation of NF-kappaB regulates cell survival following DNA damage by cigarette smoke in human bronchial epithelial cells.

Synthesis, structure, and bioevaluation of 2,5-bis(arylmethenyl)cyclopentanones

Curcumin is an excellent lead compound with a variety of bioactivity. Recent articles reported that curcumin's instability and low bioavailability in vivo are mainly due to its easily decomposable beta-diketone moiety. With the aim of bioactive curcumin analogs with better pharmacokinetic property, we present here 11 bis(arylmethenyl)cyclopentanones similar to curcumin and without beta-diketone moiety by reacting relevant arylaldehydes and cyclopentanones. The analogs were structurally determined by 1HNMR and MS spectra, and the crystal structure of 6 was analyzed by X-ray diffraction. Their antibacterial activities in vitro against seven Gram-positive and Gram-negative bacteria were tested, and their inhibition of TNF-alpha and IL-6 secretion in LPS-induced mouse macrophages was investigated using enzyme-linked immunosorbent assay. It was observed that several derivatives displayed higher activity when compared with curcumin, and most of the analogs exhibited activities against the ampicillin-resistant Gram-negative Enterobacter cloacae.

Coupling endoplasmic reticulum stress to the cell death program in mouse melanoma cells: effect of curcumin

The microenvironment of cancerous cells includes endoplasmic reticulum (ER) stress the resistance to which is required for the survival and growth of tumors. Acute ER stress triggers the induction of a family of ER stress proteins that promotes survival and/or growth of the cancer cells, and also confers resistance to radiation and chemotherapy. Prolonged or severe ER stress, however, may ultimately overwhelm the cellular protective mechanisms, triggering cell death through specific programmed cell death (pcd) pathways. Thus, downregulation of the protective stress proteins may offer a new therapeutic approach to cancer treatment. In this regard, recent reports have demonstrated the roles of the phytochemical curcumin in the inhibition of proteasomal activity and triggering the accumulation of cytosolic Ca(2+) by inhibiting the Ca(2+)-ATPase pump, both of which enhance ER stress. Using a mouse melanoma cell line, we investigated the possibility that curcumin may trigger ER stress leading to programmed cell death. Our studies demonstrate that curcumin triggers ER stress and the activation of specific cell death pathways that feature caspase cleavage and activation, p23 cleavage, and downregulation of the anti-apoptotic Mcl-1 protein.

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.".

Emerging amyloid beta (Ab) peptide modulators for the treatment of Alzheimer's disease (AD)

BACKGROUND

According to the 'amyloid cascade hypothesis' of Alzheimer's disease (AD), abnormal processing of beta-amyloid precursor protein (betaAPP) into toxic amyloid beta (Abeta)-peptides is central to the etiopathology of this uniquely human brain disorder.

OBJECTIVE

To review current AD drugs, pharmacological approaches and strategies aimed at modulating Abeta-peptide generation and/or aggregation in the treatment of AD.

METHODS

Data searches at various websites: Alzheimer Research Forum; individual drug company databases; Medline; Pharmaprojects database; unpublished research; inter-University research communications.

RESULTS/CONCLUSION

Considerable research effort has focused on secretase-mediated mechanisms of betaAPP processing, and the latest pharmacological strategies have used selective Abeta-peptide-lowering agents (SALA) to provide therapeutic benefit against Abeta-initiated neurodegenerative pathology. Currently, dedicated anticholinesterase, glutamatergic agonist and Abeta-peptide immunization have had little impact in the clinical treatment of AD. One unexpected benefit of statins (HMG-CoA inhibitors), besides their cholesterol lowering abilities, has been their ancillary effects in potentiating the enzymatic mechanisms that generate Abeta-peptides. The long-term benefits or complications of statin-based therapies for use in the clinical management of AD are not known.

Curcumin: from ancient medicine to current clinical trials

Curcumin is the active ingredient in the traditional herbal remedy and dietary spice turmeric (Curcuma longa). Curcumin has a surprisingly wide range of beneficial properties, including anti-inflammatory, antioxidant, chemopreventive and chemotherapeutic activity. The pleiotropic activities of curcumin derive from its complex chemistry as well as its ability to influence multiple signaling pathways, including survival pathways such as those regulated by NF-kappaB, Akt, and growth factors; cytoprotective pathways dependent on Nrf2; and metastatic and angiogenic pathways. Curcumin is a free radical scavenger and hydrogen donor, and exhibits both pro- and antioxidant activity. It also binds metals, particularly iron and copper, and can function as an iron chelator. Curcumin is remarkably non-toxic and exhibits limited bioavailability. Curcumin exhibits great promise as a therapeutic agent, and is currently in human clinical trials for a variety of conditions, including multiple myeloma, pancreatic cancer, myelodysplastic syndromes, colon cancer, psoriasis and Alzheimer's disease.

Different curcuminoids inhibit T-lymphocyte proliferation independently of their radical scavenging activities

PURPOSE

We investigated the inhibitory effects of curcumin, curcumin derivatives and degradation products on OKT3-induced human peripheral blood mononuclear cell (PBMC) proliferation and the role of their radical scavenging activity.

METHODS

OKT3-induced human PBMC proliferation was determined by measuring 3H-thymidine incorporation. Radical scavenging activity was evaluated by using an in vitro DPPH assay.

RESULTS

OKT3-induced PBMC proliferation was inhibited by curcumin, isocurcumin, bisdesmethoxy-, diacetyl-, tetrahydro-, hexahydro-, and octahydrocurcumin as well as by vanillin, ferulic acid, and dihydroferulic acid with IC50-values of 2.8, 2.8, 6.4, 1.0, 25, 38, 82, 729, 457, and >1,000 microM, respectively. The investigated substances with the strongest effect on radical scavenging were tetrahydro-, hexahydro-, and octahydrocurcumin with IC50 values of 10.0, 11.7, and 12.3 microM, respectively. IC50-values of dihydroferulic acid, ferulic acid, and curcumin were 19.5, 37, and 40 microM. The substances with the lowest radical scavenging activities were vanillin, isocurcumin, diacetylcurcumin, and bisdesmethoxycurcumin with IC50 values higher than 100 microM each.

CONCLUSIONS

Curcuminoid-induced inhibition of OKT3-induced PBMC proliferation depends on the number of carbon atoms and double bonds of the 1,6-heptadiene-3,5-dione structure as well as on the phenolic ring substitutes of the curcuminoids but is not correlated to their respective radical scavenging activity.

Curcumin structure-function, bioavailability, and efficacy in models of neuroinflammation and Alzheimer's disease

Curcumin can reduce inflammation and neurodegeneration, but its chemical instability and metabolism raise concerns, including whether the more stable metabolite tetrahydrocurcumin (TC) may mediate efficacy. We examined the antioxidant, anti-inflammatory, or anti-amyloidogenic effects of dietary curcumin and TC, either administered chronically to aged Tg2576 APPsw mice or acutely to lipopolysaccharide (LPS)-injected wild-type mice. Despite dramatically higher drug plasma levels after TC compared with curcumin gavage, resulting brain levels of parent compounds were similar, correlating with reduction in LPS-stimulated inducible nitric-oxide synthase, nitrotyrosine, F2 isoprostanes, and carbonyls. In both the acute (LPS) and chronic inflammation (Tg2576), TC and curcumin similarly reduced interleukin-1beta. Despite these similarities, only curcumin was effective in reducing amyloid plaque burden, insoluble beta-amyloid peptide (Abeta), and carbonyls. TC had no impact on plaques or insoluble Abeta, but both reduced Tris-buffered saline-soluble Abeta and phospho-c-Jun NH(2)-terminal kinase (JNK). Curcumin but not TC prevented Abeta aggregation. The TC metabolite was detected in brain and plasma from mice chronically fed the parent compound. These data indicate that the dienone bridge present in curcumin, but not in TC, is necessary to reduce plaque deposition and protein oxidation in an Alzheimer's model. Nevertheless, TC did reduce neuroinflammation and soluble Abeta, effects that may be attributable to limiting JNK-mediated transcription. Because of its favorable safety profile and the involvement of misfolded proteins, oxidative damage, and inflammation in multiple chronic degenerative diseases, these data relating curcumin dosing to the blood and tissue levels required for efficacy should help translation efforts from multiple successful preclinical models.

Inhibition of Nod2 signaling and target gene expression by curcumin

Nod2 is an intracellular pattern recognition receptor that detects a conserved moiety of bacterial peptidoglycan and subsequently activates proinflammatory signaling pathways. Mutations in Nod2 have been implicated to be linked to inflammatory granulomatous disorders, such as Crohn's disease and Blau syndrome. Many phytochemicals possess anti-inflammatory properties. However, it is not known whether any of these phytochemicals might modulate Nod2-mediated immune responses and thus might be of therapeutic value for the intervention of these inflammatory diseases. In this report, we demonstrate that curcumin, a polyphenol found in the plant Curcuma longa, and parthenolide, a sesquiterpene lactone, suppress both ligand-induced and lauric acid-induced Nod2 signaling, leading to the suppression of nuclear factor-kappaB activation and target gene interleukin-8 expression. We provide molecular and biochemical evidence that the suppression is mediated through the inhibition of Nod2 oligomerization and subsequent inhibition of downstream signaling. These results demonstrate for the first time that curcumin and parthenolide can directly inhibit Nod2-mediated signaling pathways at the receptor level and suggest that Nod2-mediated inflammatory responses can be modulated by these phytochemicals. It remains to be determined whether these phytochemicals possess protective or therapeutic efficacy against Nod2-mediated inflammatory disorders.

Curcumin inhibits bTREK-1 K+ channels and stimulates cortisol secretion from adrenocortical cells

Bovine adrenal zona fasciculata (AZF) cells express bTREK-1 K(+) channels that set the resting membrane potential. Inhibition of these channels by adrenocorticotropic hormone (ACTH) is coupled to membrane depolarization and cortisol secretion. Curcumin, a phytochemical with medicinal properties extracted from the spice turmeric, was found to modulate both bTREK-1 K(+) currents and cortisol secretion from AZF cells. In whole-cell patch clamp experiments, curcumin inhibited bTREK-1 with an IC(50) of 0.93muM by a mechanism that was voltage-independent. bTREK-1 inhibition by curcumin occurred through interaction with an external binding site and was independent of ATP hydrolysis. Curcumin produced a concentration-dependent increase in cortisol secretion that persisted for up to 24h. At a maximally effective concentration of 50muM, curcumin increased secretion as much as 10-fold. These results demonstrate that curcumin potently inhibits bTREK-1 K(+) channels and stimulates cortisol secretion from bovine AZF cells. The inhibition of bTREK-1 by curcumin may be linked to cortisol secretion through membrane depolarization. Since TREK-1 is widely expressed in a variety of cells, it is likely that some of the biological actions of curcumin, including its therapeutic effects, may be mediated through inhibition of these K(+) channels.

Curcumin, a known phenolic from Curcuma longa, attenuates the virulence of Pseudomonas aeruginosa PAO1 in whole plant and animal pathogenicity models

The effect of curcumin on the virulence of Pseudomonas aeruginosa (PAO1) using whole plant and animal pathogenicity models was investigated. The effect of curcumin on PAO1 virulence was studied by employing in vitro assays for virulence factor production, Arabidopsis thaliana/Caenorhabditis elegans pathogenicity models, and whole genome microarray analysis. It is shown that the curcumin inhibits PAO1 virulence factors such as biofilm formation, pyocyanin biosynthesis, elastase/protease activity, and acyl homoserine lactone (HSL) production. As a consequence of this, curcumin treatment resulted in the reduced pathogenicity of P. aeruginosa-C. elegans and P. aeruginosa-A. thaliana infection models. In addition, transcriptome analysis of curcumin-treated PAO1 revealed down-regulation of 31 quorum sensing (QS) genes, of which many have already been reported for virulence. The supplementation of HSLs along with the curcumin treatment resulted in increased pathogencity and recovery of higher bacterial titers in a plant pathogenecity model. These data reveal the involvement of curcumin in QS interruption to reduce pathogenicity. Curcumin attenuates PAO1 virulence by down-regulation of virulence factors, QS, and biofilm initiation genes. The effect of curcumin on multiple targets such as virulence, QS, and biofilm initiation makes curcumin a potential supplemental molecule for the treatment of P. aeruginosa infections.

Utilization of Ayurveda in health care: an approach for prevention, health promotion, and treatment of disease. Part 1--Ayurveda, the science of life

Ayurveda is a natural health care system that originated in India more than 5000 years ago. Its main objective is to achieve optimal health and well-being through a comprehensive approach that addresses mind, body, behavior, and environment. Ayurveda emphasizes prevention and health promotion, and provides treatment for disease. It considers the development of consciousness to be essential for optimal health and meditation as the main technique for achieving this. Treatment of disease is highly individualized and depends on the psychophysiologic constitution of the patient. There are different dietary and lifestyle recommendations for each season of the year. Common spices are utilized in treatment, as well as herbs and herbal mixtures, and special preparations known as Rasayanas are used for rejuvenation, promotion of longevity, and slowing of the aging process. A group of purification procedures known as Panchakarma removes toxins from the physiology. Whereas Western allopathic medicine is excellent in handling acute medical crises, Ayurveda demonstrates an ability to manage chronic disorders that Western medicine has been unable to. It may be projected from Ayurveda's comprehensive approach, emphasis on prevention, and ability to manage chronic disorders that its widespread use would improve the health status of the world's population.

Curcumin treatment alleviates the effects of glutathione depletion in vitro and in vivo: therapeutic implications for Parkinson's disease explained via in silico studies

Oxidative stress has been implicated in the degeneration of dopaminergic neurons in the substantia nigra (SN) of Parkinson's disease (PD) patients. An important biochemical feature of presymptomatic PD is a significant depletion of the thiol antioxidant glutathione (GSH) in these neurons resulting in oxidative stress, mitochondrial dysfunction, and ultimately cell death. We have earlier demonstrated that curcumin, a natural polyphenol obtained from turmeric, protects against peroxynitrite-mediated mitochondrial dysfunction both in vitro and in vivo. Here we report that treatment of dopaminergic neuronal cells and mice with curcumin restores depletion of GSH levels, protects against protein oxidation, and preserves mitochondrial complex I activity which normally is impaired due to GSH loss. Using systems biology and dynamic modeling we have explained the mechanism of curcumin action in a model of mitochondrial dysfunction linked to GSH metabolism that corroborates the major findings of our experimental work. These data suggest that curcumin has potential therapeutic value for neurodegenerative diseases involving GSH depletion-mediated oxidative stress.

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.

Excited-State pKa Values of Curcumin

Curcumin is one of the most extensively studied natural pigments. The significant phototoxicity of curcumin against a variety of bacteria and viruses has made the pigment a potential photodynamic drug. To explore whether the phototoxic mechanisms of curcumin involve light-induced acidification, the excited-state p Ka values of the pigment were determined by the Förster cycle. It was found that the excited-state p Ka values of curcumin [ i.e., 7.56 (7.72), 8.72 (8.14) and 10.17 (10.35)] are rather higher than those of counterpart phenolic photosensitizers, which implies that light-induced acidification is unlikely to be responsible for the phototoxicity of curcumin.

Multipotent natural agents to combat Alzheimer's disease. Functional spectrum and structural features

With the accelerated aging of human society, Alzheimeros disease (AD) is becoming one of the biggest threats to human health. Since multiple pathogenetic factors are implicated in the disease, the current hitting-one-target therapeutic strategy has proved inefficient to AD. As a result, finding multipotent agents that aim at multiple targets is attracting more and more attention. Although multifunctional anti-AD agents can be created by incorporating two or more pharmacophores in one scaffold, naturally occurring multipotent agents also attracted much attention. In this review, we first describe the functions of some typical naturally originated multipotent anti-AD compounds, then summarize their structural features and reveal that phenolics with certain flexibility predominate in these agents, which are of significance to find novel multipotent drugs to combat AD and other neurodegenerative diseases as well.

Curcumin sensitizes TRAIL-resistant xenografts: molecular mechanisms of apoptosis, metastasis and angiogenesis

BACKGROUND

We have recently shown that curcumin (a diferuloylmethane, the yellow pigment in turmeric) enhances apoptosis-inducing potential of TRAIL in prostate cancer PC-3 cells, and sensitizes TRAIL-resistant LNCaP cells in vitro through multiple mechanisms. The objectives of this study were to investigate the molecular mechanisms by which curcumin sensitized TRAIL-resistant LNCaP xenografts in vivo.

METHODS

Prostate cancer TRAIL-resistant LNCaP cells were implanted in Balb c nude mice to examine the effects of curcumin and/or TRAIL on tumor growth and genes related to apoptosis, metastasis and angiogenesis.

RESULTS

Curcumin inhibited growth of LNCaP xenografts in nude mice by inducing apoptosis (TUNEL staining) and inhibiting proliferation (PCNA and Ki67 staining), and sensitized these tumors to undergo apoptosis by TRAIL. In xenogrfated tumors, curcumin upregulated the expression of TRAIL-R1/DR4, TRAIL-R2/DR5, Bax, Bak, p21/WAF1, and p27/KIP1, and inhibited the activation of NFkappaB and its gene products such as cyclin D1, VEGF, uPA, MMP-2, MMP-9, Bcl-2 and Bcl-XL. The regulation of death receptors and members of Bcl-2 family, and inactivation of NFkappaB may sensitize TRAIL-resistant LNCaP xenografts. Curcumin also inhibited number of blood vessels in tumors, and circulating endothelial growth factor receptor 2-positive endothelial cells in mice.

CONCLUSION

The ability of curcumin to inhibit tumor growth, metastasis and angiogenesis, and enhance the therapeutic potential of TRAIL suggests that curcumin alone or in combination with TRAIL can be used for prostate cancer prevention and/or therapy.

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.

Curcumin: potential for hepatic fibrosis therapy?

The beneficial antioxidative, anti-inflammatory and antitumorigenic effects of curcumin have been well documented in relation to cancer and other chronic diseases. Recent evidence suggests that it may be of therapeutic interest in chronic liver disease. Hepatic fibrosis (scarring) occurs in advanced liver disease, where normal hepatic tissue is replaced with collagen-rich extracellular matrix and, if left untreated, results in cirrhosis. Curcumin inhibits liver cirrhosis in a rodent model and exerts multiple biological effects in hepatic stellate cells (HSCs), which play a central role in the pathogenesis of hepatic fibrosis. In response to liver injury, these cells proliferate producing pro-inflammatory mediators and extracellular matrix. Curcumin induces apoptosis and suppresses proliferation in HSCs. In addition, it inhibits extracellular matrix formation by enhancing HSC matrix metalloproteinase expression via PPARgamma and suppressing connective tissue growth factor (CTGF) expression. In this issue, Chen and co-workers propose that curcumin suppresses CTGF expression in HSC by inhibiting ERK and NF-kappaB activation. These studies suggest that curcumin modulates several intracellular signalling pathways in HSC and may be of future interest in hepatic fibrosis therapy.

Bioavailability of curcumin: problems and promises

Curcumin, a polyphenolic compound derived from dietary spice turmeric, possesses diverse pharmacologic effects including anti-inflammatory, antioxidant, antiproliferative and antiangiogenic activities. Phase I clinical trials have shown that curcumin is safe even at high doses (12 g/day) in humans but exhibit poor bioavailability. Major reasons contributing to the low plasma and tissue levels of curcumin appear to be due to poor absorption, rapid metabolism, and rapid systemic elimination. To improve the bioavailability of curcumin, numerous approaches have been undertaken. These approaches involve, first, the use of adjuvant like piperine that interferes with glucuronidation; second, the use of liposomal curcumin; third, curcumin nanoparticles; fourth, the use of curcumin phospholipid complex; and fifth, the use of structural analogues of curcumin (e.g., EF-24). The latter has been reported to have a rapid absorption with a peak plasma half-life. Despite the lower bioavailability, therapeutic efficacy of curcumin against various human diseases, including cancer, cardiovascular diseases, diabetes, arthritis, neurological diseases and Crohn's disease, has been documented. Enhanced bioavailability of curcumin in the near future is likely to bring this promising natural product to the forefront of therapeutic agents for treatment of human disease.