Curcumin, a dietary spice from turmeric, is known to be anti-inflammatory, anticarcinogenic, and antithrombotic. Here, we studied the mechanism of the antiplatelet action of curcumin. We show that curcumin inhibited platelet aggregation mediated by the platelet agonists epinephrine (200 microM), ADP (4 microM), platelet-activating factor (PAF; 800 nM), collagen (20 microg/mL), and arachidonic acid (AA: 0.75 mM). Curcumin preferentially inhibited PAF- and AA-induced aggregation (IC50; 25-20 microM), whereas much higher concentrations of curcumin were required to inhibit aggregation induced by other platelet agonists. Pretreatment of platelets with curcumin resulted in inhibition of platelet aggregation induced by calcium ionophore A-23187 (IC50; 100 microM), but curcumin up to 250 microM had no inhibitory effect on aggregation induced by the protein kinase C (PKC) activator phorbol myrsitate acetate (1 microM). Curcumin (100 microM) inhibited the A-23187-induced mobilization of intracellular Ca2+ as determined by using fura-2 acetoxymethyl ester. Curcumin also inhibited the formation of thromboxane A2 (TXA2) by platelets (IC50; 70 microM). These results suggest that the curcumin-mediated preferential inhibition of PAF- and AA-induced platelet aggregation involves inhibitory effects on TXA2 synthesis and Ca2+ signaling, but without the involvement of PKC.
The effects of curcumin, the yellow pigment of the spice, turmeric (Curcuma longa) on the mutagenicity of several environmental mutagens were investigated in the Salmonella/microsome test with or without Aroclor 1254-induced rat-liver homogenate (S-9 mix). With Salmonella typhimurium strain TA98 in the presence of S-9 mix, curcumin inhibited the mutagenicity of bidi and cigarette smoke condensates, tobacco and masheri extracts, benzo[a]pyrne and dimethyl benzo[a]anthracene in a dose-dependent manner. Curcumin did not influence the mutagenicity without S-9 mix of sodium azide, monoacetylhydrazine and streptozocin in strain TA100 nor of 4-nitrophenylenediamine in strain TA98. Our observations indicate that curcumin may alter the metabolic activation and detoxification of mutagens.
Studies in vitro and in animal models of colorectal and hepatocellular cancers suggest that curcumin is an effective chemopreventive agent. In this pilot trial, we investigated whether oral administration of curcumin results in concentrations of the agent in normal and malignant human liver tissue, which are sufficient to elicit pharmacological activity. In total, 12 patients with hepatic metastases from colorectal cancer received 450-3600 mg of curcumin daily, for 1 week prior to surgery. Levels of curcumin and its metabolites were measured by HPLC in portal and peripheral blood, bile and liver tissue. Curcumin was poorly available, following oral administration, with low nanomolar levels of the parent compound and its glucuronide and sulphate conjugates found in the peripheral or portal circulation. While curcumin was not found in liver tissue, trace levels of products of its metabolic reduction were detected. In patients who had received curcumin, levels of malondialdehyde-DNA (M(1)G) adduct, which reflect oxidative DNA changes, were not decreased in post-treatment normal and malignant liver tissue when compared to pretreatment samples. The results suggest that doses of curcumin required to furnish hepatic levels sufficient to exert pharmacological activity are probably not feasible in humans.
Nitric oxide (NO) is involved in different stages of malignancies. Increased levels of NO have been reported in different leukemias. Imatinib is the preferred drug for the treatment of chronic myeloid leukemia (CML). Turmeric powder contains curcumin which has anti-leukemic property and also decreases NO synthesis. This study was conducted on fifty patients of CML divided into two groups, group A receiving imatinib alone and group B receiving turmeric powder along with imatinib for six weeks. Nitric oxide levels were estimated in these patients before and after receiving therapy and were analyzed statistically. Nitric oxide levels were found to be significantly decreased in both the groups, but more significantly in group B after receiving the respective treatments. Thus, curcumin acts as an adjuvant to imatinib in decreasing the NO levels and may help in the treatment of CML patients.
The effects of turmeric extract and its pure yellow pigments curcumin I, II and III were tested on the nitrosation of methylurea by sodium nitrite at pH 3.6 and 30 degrees C. The nitrosomethylurea formed was monitored by checking the mutagenicity in S. typhimurium strains TA1535 and TA100 without metabolic activation. Turmeric extract as well as curcumins exhibit dose-dependent decreases of nitrosation. Curcumin III was the most effective nitrosation inhibitor among the compounds tested. The simultaneous treatment of inhibitor with nitrosation precursors was essential and pre- or post-treatment of inhibitor had no effect on the mutagenicity of nitrosomethylurea. The binding of nitrite with the inhibitors was studied at pH 3.6 and 30 degrees C. Curcumin I shows a dose-dependent depletion of nitrite ions thus making nitrite non-available for nitrosation. Curcumin I and III when tested also showed a time-dependent depletion of nitrite ions at pH 3.6 and 30 degrees C. Curcumin III has a higher affinity for nitrite ions than curcumin I.
Studies in vitro and in animal models of colorectal and hepatocellular cancers suggest that curcumin is an effective chemopreventive agent. In this pilot trial, we investigated whether oral administration of curcumin results in concentrations of the agent in normal and malignant human liver tissue, which are sufficient to elicit pharmacological activity. In total, 12 patients with hepatic metastases from colorectal cancer received 450-3600 mg of curcumin daily, for 1 week prior to surgery. Levels of curcumin and its metabolites were measured by HPLC in portal and peripheral blood, bile and liver tissue. Curcumin was poorly available, following oral administration, with low nanomolar levels of the parent compound and its glucuronide and sulphate conjugates found in the peripheral or portal circulation. While curcumin was not found in liver tissue, trace levels of products of its metabolic reduction were detected. In patients who had received curcumin, levels of malondialdehyde-DNA (M(1)G) adduct, which reflect oxidative DNA changes, were not decreased in post-treatment normal and malignant liver tissue when compared to pretreatment samples. The results suggest that doses of curcumin required to furnish hepatic levels sufficient to exert pharmacological activity are probably not feasible in humans.
Bcr/Abl is a chimeric oncogene that can cause both acute and chronic human leukemias. Bcr/Abl-encoded proteins exhibit elevated kinase activity compared to c-Abl, but the mechanisms of transformation are largely unknown. Some of the biological effects of Bcr/Abl overlap with those of hematopoietic cytokines, particularly interleukin 3 (IL-3). Such effects include mitogenesis, enhanced survival, and enhanced basophilic differentiation. Therefore, it has been suggested that p210Bcr/Abl and the IL-3 receptor may activate some common signal transduction pathways. An important pathway for IL-3 signaling involves activation of the Janus family kinases (JAKs) and subsequent tyrosyl phosphorylation of STAT proteins (signal transducers and activators of transcription). This pathway directly links growth factor receptors to gene transcription. We analyzed JAK activation, STAT protein phosphorylation, and the formation of specific DNA-binding complexes containing STAT proteins, in a series of leukemia cell lines transformed by Bcr/Abl or other oncogenes. We also examined these events in cell lines transformed by a temperature sensitive (ts) mutant of Bcr/Abl, where the kinase activity of Abl could be regulated. STAT1 and STAT5 were found to be constitutively phosphorylated in 32D, Ba/F3, and TF-1 cells transformed by Bcr/Abl, but not in the untransformed parental cell lines in the absence of IL-3. Phosphorylation of STAT1 and STAT5 was also observed in the human leukemia cell lines K562 and BV173, which express the Bcr/Abl oncogene, but not in several Bcr/Abl-negative leukemia cell lines. Phosphorylation of STAT1 and STAT5 was directly due to the tyrosine kinase activity of Bcr/Abl since it could be activated or deactivated by temperature shifting of cells expressing the Bcr/Abl ts mutant. DNA-STAT complexes were detected in all Bcr/Abl-transformed cell lines and they were supershifted by antibodies against STAT1 and STAT5. DNA-STAT complexes in 32Dp210Bcr/Abl cells were similar, but not identical, to those formed after IL-3 stimulation. It is interesting to note that JAK kinases (JAK1, JAK2, JAK3, and Tyk2) were not consistently activated in Bcr/Abl-positive cells. These data suggest that STATs can be activated directly by Bcr/Abl, possibly bypassing JAK family kinase activation. Overall, our results suggest a novel mechanism that could contribute to some of the major biological effects of Bcr/Abl transformation.
Many environmental chemicals and pesticides have been found to be estrogenic and have been shown to stimulate the growth of estrogen receptor-positive (ER-positive) human breast cancer cells. Since it is difficult to avoid human exposure to environmental estrogens, a potentially important area of research is the development of dietary strategies to prevent the stimulated growth of breast tumors by environmental estrogens. In this context, the inhibitory action of curcumin and a combination of curcumin and isoflavonoids were studied in ER-positive human breast cancer cells (MCF-7 and T47D) and ER-negative MDA-MB-231 cells induced by the pesticide o,p'-DDT and the environmental pollutants 4-nonylphenol and 4-octylphenol. The median inhibitory concentration (IC50) for curcumin in T47D cells was 10 microM when measured at either a 48-hr or a 6-day incubation time. The IC50 value for curcumin was within the 8-10 microM range for inhibiting the growth of T47D cells induced by a 10- microM concentration each of 4-nonylphenol, 4-octylphenol, and o, p'-DDT. The IC50 for curcumin in MCF-7 cells induced by 10 microM of either o,p'-DDT, 4-octylphenol, or 4-nonylphenol were 9, 39, and >50 microM, respectively. A combination of curcumin and isoflavonoids was able to inhibit the induced growth of ER-positive cells up to 95%. For MDA-MB-231 cells, the IC50 for curcumin was 17 microM, which was reduced to 11 microM in the presence of 25 microM genistein. Curcumin and genistein induce drastic changes in the morphological shape of both ER-positive and ER-negative cells. Data presented here indicate that a mixture of curcumin and isoflavonoids is the most potent inhibitor against the growth of human breast tumor cells. These data suggest that combinations of natural plant compounds may have preventive and therapeutic applications against the growth of breast tumors induced by environmental estrogens.
Background:
Curcumin, the yellow pigment in turmeric, has been shown to prevent tumor progression in a variety of tissues in rodents. The authors investigated the effect of curcumin on human carcinoma cell lines to determine whether constitutive interleukin-8 (IL-8) production of tumor cells was correlated with nuclear factor kappaB (NF-kappaB) activation and cell growth activity.Methods:
A human pancreatic carcinoma cell line, SUIT-2, was incubated with various concentrations of curcumin for 2 hours. Biologic features, including IL-8 production, DNA binding activity, transactivation of NF-kappaB, cell growth activity, cell viability, and the expression of IL-8 receptors (CXCR1 and CXCR2) were analyzed.Results:
The constitutive production of IL-8 was inhibited by curcumin at concentrations of 10-100 microM in a dose dependent manner. NF-kappaB activity was reduced significantly by curcumin treatment. Pretreatment with curcumin inhibited the growth rate of carcinoma cells significantly. Such cell growth inhibition by curcumin was not recovered by exogenous recombinant IL-8. The investigation of expression in IL-8 receptors, CXCR1 and CXCR2, revealed that the expression of both receptors was enhanced remarkably by curcumin. Exogenous IL-8 could not recover this enhancement of IL-8 receptors. These results suggest that curcumin inhibits IL-8-induced receptor internalization.Cconclusions:
The authors concluded that curcumin contributed not only to the inhibition of IL-8 production but also to signal transduction through IL-8 receptors. These data suggest that curcumin reduces numerous IL-8 bioactivities that contribute to tumor growth and carcinoma cell viability. From this point of view, curcumin is a potent anticancer agent that inhibits the production of proinflammatory cytokines, including IL-8, by tumor cells.
Curcumin (diferuloyl methane), belonging to 1,3-diketone group and isolated from the rhizomes of Cwrcwna longa Linn, possesses potent antiinflammatory and anti-rheumatic properties (1, 2). It also inhibits collagen and adrenaline-induced aggregation of platelets & vL?ko as well as &x vivo but does not affect prostacyclin (PGI2) synthesis by rat thoracic aorta (3). Collagen-induced platelet aggregation is known to be associated to an increase in the thromboxane A (TXA2) level (4). xi; It is, therefore, likely that curcumin may have anti-T 2 activity. Aggregation of platelets plays a vital role in initiation of thrombosis. It was, therefore, planned to studv the effect of curcumin in an .& vivo model of.thrombosis-and compare it with aspirin. The effect of curcumin has also been studied on platelet thromboxane 82 (TXB2) and malonaldehyde (MDA) production. M
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In Trinidad, those of African descent are more likely to contract human immunodeficiency virus (HIV) than the Indian population despite similar risks and behavior patterns. Two food additives that are components of curry may be one of the factors accounting for the difference in infection rates between these two groups. Curcumin is one of these food additives and has been studied by the Harvard Medical School for its antiviral properties. There is also anecdotal evidence that curcumin may be an effective agent against HIV-1. It was determined that curcumin inhibits transcription through inhibition of the long terminal repeat region of the genetic material of HIV. One individual with an elevated P24 ingested 2.5 g of curcumin a day. His P24 was repeated 7 days later. In this short period of time, there was a substantial drop in the P24 antigen (a measure of viral activity). Curcumin also has been studied by AIDS Research Alliance, a community-based clinical trials group in Los Angeles. Preliminary data from patients who have access to curcumin suggest a strong anti-HIV activity. These data lay the ground work for new studies.
In traditional medicine, Ayurveda, several spices and herbs are held to possess medicinal properties. Earlier we have reported that extracts from several spices, including turmeric, inhibit platelet aggregation and modulate eicosanoid biosynthesis. Due to their eicosanoid-modulating property, it was suggested that the spices may serve to provide clues to drugs directed to arachidonic acid (AA) pathway enzymes as pharmacological targets. Curcumin, a major component of turmeric, inhibited platelet aggregation induced by arachidonate, adrenaline and collagen. This compound inhibited thromboxane B2 (TXB2) production from exogenous [14C] arachidonate in washed platelets with a concomitant increase in the formation of 12-lipoxygenase products. Moreover, curcumin inhibited the incorporation of [14C]AA into platelet phospholipids and inhibited the deacylation of AA-labelled phospholipids (liberation of free AA) on stimulation with calcium ionophore A23187. Curcumin's anti-inflammatory property may, in part, be explained by its effects on eicosanoid biosynthesis.
Curcumin, a relatively non-toxic natural product isolated from Curcuma longa, is a modest inhibitor of the HIV-1 (IC50 = 100 microM) and HIV-2 (IC50 = 250 microM) proteases. Simple modifications of the curcumin structure raise the IC50 value but complexes of the central dihydroxy groups of curcumin with boron lower the IC50 to a value as low as 6 microM. The boron complexes are also time-dependent inactivators of the HIV proteases. The increased affinity of the boron complexes may reflect binding of the orthogonal domains of the inhibitor in interesecting sites within the substrate-binding cavity of the enzyme, while activation of the alpha, beta-unsaturated carbonyl group of curcumin by chelation to boron probably accounts for time-dependent inhibition of the enzyme.