Curcumin induces stress response, neurite outgrowth and prevent NF-kappaB activation by inhibiting the proteasome function.
TL;DR: It is shown that curcumin disrupts UPS function by directly inhibiting the enzyme activity of the proteasome’s 20S core catalytic component, which causes an increase in half-life of IκB-α that ultimately leads to the down-regulation of NF-κB activation.
Abstract: Curcumin, a natural polyphenolic compound, has long been known as an anti-tumour and anti-inflammatory compound; although, the common mechanism through which it exhibits such properties are remains unclear. Recently, we reported that the curcumin-induced apoptosis is mediated through the impairment of ubiquitin proteasome system (UPS). Here, we show that curcumin disrupts UPS function by directly inhibiting the enzyme activity of the proteasome's 20S core catalytic component. Like other proteasome inhibitors, curcumin exposure induces neurite outgrowth and the stress response, as evident from the induction of various cytosolic and endoplasmic reticulum chaperones as well as induction of transcription factor CHOP/GADD153. The direct inhibition of proteasome activity also causes an increase in half-life of IkappaB-alpha that ultimately leads to the down-regulation of NF-kappaB activation. These results suggest that curcumin-induced proteasomal malfunction might be linked with both anti-proliferative and anti-inflammatory activities.
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TL;DR: Curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway, cell survival pathway, and protein kinase pathway.
Abstract: Cancer is a hyperproliferative disorder that is usually treated by chemotherapeutic agents that are toxic not only to tumor cells but also to normal cells, so these agents produce major side effects. In addition, these agents are highly expensive and thus not affordable for most. Moreover, such agents cannot be used for cancer prevention. Traditional medicines are generally free of the deleterious side effects and usually inexpensive. Curcumin, a component of turmeric (Curcuma longa), is one such agent that is safe, affordable, and efficacious. How curcumin kills tumor cells is the focus of this review. We show that curcumin modulates growth of tumor cells through regulation of multiple cell signaling pathways including cell proliferation pathway (cyclin D1, c-myc), cell survival pathway (Bcl-2, Bcl-xL, cFLIP, XIAP, c-IAP1), caspase activation pathway (caspase-8, 3, 9), tumor suppressor pathway (p53, p21) death receptor pathway (DR4, DR5), mitochondrial pathways, and protein kinase pathway (JNK, Akt, and AMPK). How curcumin selectively kills tumor cells, and not normal cells, is also described in detail.
700 citations
Cites background from "Curcumin induces stress response, n..."
...The direct inhibition of proteasome activity also causes an increase in half-life of IκBα that ultimately leads to the down-regulation of NF-κB activation (169), thus activating the apoptotic pathway....
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...Studies have shown that curcumin mediates its apoptotic and antiinflammatory activities through modulation of the redox status of the cell (42,149,169)....
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TL;DR: This paper reviews the latest reports on the potential therapy of skin disorders through treatment with phenolic compounds, considering mostly a single specific compound or a combination of compounds in a plant extract.
Abstract: Phenolic compounds constitute a group of secondary metabolites which have important functions in plants. Besides the beneficial effects on the plant host, phenolic metabolites (polyphenols) exhibit a series of biological properties that influence the human in a health-promoting manner. Evidence suggests that people can benefit from plant phenolics obtained either by the diet or through skin application, because they can alleviate symptoms and inhibit the development of various skin disorders. Due to their natural origin and low toxicity, phenolic compounds are a promising tool in eliminating the causes and effects of skin aging, skin diseases, and skin damage, including wounds and burns. Polyphenols also act protectively and help prevent or attenuate the progression of certain skin disorders, both embarrassing minor problems (e.g., wrinkles, acne) or serious, potentially life-threatening diseases such as cancer. This paper reviews the latest reports on the potential therapy of skin disorders through treatment with phenolic compounds, considering mostly a single specific compound or a combination of compounds in a plant extract.
447 citations
Cites background from "Curcumin induces stress response, n..."
...Other phenolic compounds with similar activity, a negative effect on cancer cells’ proteasome, are catechin-3-gallate and epigallocatechin gallate [223,224], gallic acid [225] apigenin, quercetin and myricetin [226], curcumin [227], and genistein [228]....
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TL;DR: Curcumin has been shown to have protective and therapeutic effects against cancers of the blood, skin, oral cavity, lung, pancreas, and intestinal tract, and to suppress angiogenesis and metastasis in rodents.
387 citations
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...The curcumin-induced proteasomal malfunction might e linked with both antiproliferative and antiinflammatory activities.(80) NF- B plays important roles in inflammation, cell proliferation, apotosis, and oncogenesis....
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TL;DR: The current review focuses on the diverse molecular targets modulated by curcumin that contribute to its efficacy against various human cancers.
Abstract: Despite significant advances in treatment modalities over the last decade, neither the incidence of the disease nor the mortality due to cancer has altered in the last thirty years. Available anti-cancer drugs exhibit limited efficacy, associated with severe side effects, and are also expensive. Thus identification of pharmacological agents that do not have these disadvantages is required. Curcumin, a polyphenolic compound derived from turmeric (Curcumin longa), is one such agent that has been extensively studied over the last three to four decades for its potential anti-inflammatory and/or anti-cancer effects. Curcumin has been found to suppress initiation, progression, and metastasis of a variety of tumors. These anti-cancer effects are predominantly mediated through its negative regulation of various transcription factors, growth factors, inflammatory cytokines, protein kinases, and other oncogenic molecules. It also abrogates proliferation of cancer cells by arresting them at different phases of the cell cycle and/or by inducing their apoptosis. The current review focuses on the diverse molecular targets modulated by curcumin that contribute to its efficacy against various human cancers.
374 citations
Cites background from "Curcumin induces stress response, n..."
...Curcumin inhibits the Notch signaling pathway in pancreatic cancer cells [69], and has been shown to be a potent proteasomal inhibitor [70], inhibiting the 20S proteasome and inducing degradation of IκBα in colon cancers [71]....
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TL;DR: 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.
Abstract: 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.
213 citations
Cites background from "Curcumin induces stress response, n..."
...In their follow-up studies, these authors demonstrated that curcumin disrupts UPS function by directly inhibiting the enzyme activity of the proteasome's 20S core catalytic component [136, 137]....
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...The direct inhibition of proteasome activity also caused an increase in the half-life of IjB-alpha that ultimately led to the down-regulation of NF-jB activation [136]....
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References
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TL;DR: The impaired proteasomal function plays an important role in polyglutamine protein-induced cell death and is associated with disrupted mitochondrial membrane potential, released cytochrome c from mitochondria into the cytosol and activated caspase-9- and caspases-3-like proteases.
Abstract: Expansion of CAG repeats within the coding region of target genes is the cause of several autosomal dominant neurodegenerative diseases including Huntington's disease (HD). A hallmark of HD is the proteolytic production of N-terminal fragments of huntingtin containing polyglutamine repeats that form ubiquitinated aggregates in the nucleus and cytoplasm of the affected neurons. In this study, we used an ecdysone-inducible stable mouse neuro2a cell line that expresses truncated N-terminal huntingtin (tNhtt) with different polyglutamine length, along with mice transgenic for HD exon 1, to demonstrate that the ubiquitin-proteasome pathway is involved in the pathogenesis of HD. Proteasomal 20S core catalytic component was redistributed to the polyglutamine aggregates in both the cellular and transgenic mouse models. Proteasome inhibitor dramatically increased the rate of aggregate formation caused by tNhtt protein with 60 glutamine (60Q) repeats, but had very little influence on aggregate formation by tNhtt protein with 150Q repeats. Both normal and polyglutamine-expanded tNhtt proteins were degraded by proteasome, but the rate of degradation was inversely proportional to the repeat length. The shift of the proteasomal components from the total cellular environment to the aggregates, as well as the comparatively slower degradation of tNhtt with longer polyglutamine, decreased the proteasome's availability for degrading other key target proteins, such as p53. This altered proteasomal function was associated with disrupted mitochondrial membrane potential, released cytochrome c from mitochondria into the cytosol and activated caspase-9- and caspase-3-like proteases. These results suggest that the impaired proteasomal function plays an important role in polyglutamine protein-induced cell death.
466 citations
TL;DR: The current knowledge of NF-κB, the possible mechanisms of its activation, its potential role in cancer, and various strategies being employed to target the NF-σB signaling pathway for cancer drug development are reviewed.
Abstract: Nuclear factor kappa B (NF-κB) is a family of inducible transcription factors found virtually ubiquitously in all cells. Since its discovery by Sen and Baltimore in 1986, much has been discovered about its mechanisms of activation, its target genes, and its function in a variety of human diseases including those related to inflammation, asthma, atherosclerosis, AIDS, septic shock, arthritis, and cancer. Due to its role in a wide variety of diseases, NF-κB has become one of the major targets for drug development. Here, we review our current knowledge of NF-κB, the possible mechanisms of its activation, its potential role in cancer, and various strategies being employed to target the NF-κB signaling pathway for cancer drug development.
425 citations
TL;DR: The data indicate that curcumin can cause cell damage by inactivating the Akt-related cell survival pathway and release of cytochrome c, providing a new mechanism forCurcumin-induced cytotoxicity.
Abstract: Curcumin, a natural, biologically active compound extracted from rhizomes of Curcuma species, has been shown to possess potent anti-inflammatory, anti-tumor and anti-oxidative properties. The mechanism by which curcumin initiates apoptosis remains poorly understood. In the present report we investigated the effect of curcumin on the activation of the apoptotic pathway in human renal Caki cells. Treatment of Caki cells with 50 microM curcumin resulted in the activation of caspase 3, cleavage of phospholipase C-gamma1 and DNA fragmentation. Curcumin-induced apoptosis is mediated through the activation of caspase, which is specifically inhibited by the caspase inhibitor, benzyloxycarbony-Val-Ala-Asp-fluoromethyl ketone. Curcumin causes dose-dependent apoptosis and DNA fragmentation of Caki cells, which is preceded by the sequential dephosphorylation of Akt, down-regulation of the anti-apoptotic Bcl-2, Bcl-XL and IAP proteins, release of cytochrome c and activation of caspase 3. Cyclosporin A, as well as caspase inhibitor, specifically inhibit curcumin-induced apoptosis in Caki cells. Pre-treatment with N-acetyl-cysteine, markedly prevented dephosphorylation of Akt, and cytochrome c release, and cell death, suggesting a role for reactive oxygen species in this process. The data indicate that curcumin can cause cell damage by inactivating the Akt-related cell survival pathway and release of cytochrome c, providing a new mechanism for curcumin-induced cytotoxicity.
417 citations
TL;DR: The inhibition of the MEKK1-JNK pathway reveals a possible mechanism of suppression of AP-1 and NF-κB signaling by curcumin, and may explain the potent anti-inflammatory and anti-carcinogenic effects of this chemical.
Abstract: Curcumin, a dietary pigment in curry, suppresses tumor initiation and tumor promotion. Curcumin is also a potent inhibitor for AP-1 and NF-kappaB activation. In this report, we show that curcumin inhibits JNK activation by various agonists including PMA plus ionomycin, anisomycin, UV-C, gamma radiation, TNF-alpha, and sodium orthovanadate. Although both JNK and ERK activation by phorbol 12-myristate 13-acetate (PMA) plus ionomycin were suppressed by curcumin, the JNK pathway was more sensitive. The IC50 (50% inhibition concentration) of curcumin was between 5-10 microM for JNK activation and was 20 microM for ERK activation. In transfection assays, curcumin moderately suppressed MEKK1-induced JNK activation; however, it effectively blocked JNK activation caused by co-transfection of TAK1, GCK, or HPK1. Curcumin did not directly inhibit JNK, SEK1, MEKK1 or HPK1 activity. Although curcumin suppressed TAK1 and GCK activities at high concentrations, this inhibition cannot fully account for the JNK inhibition by curcumin in vivo. Our data suggest that curcumin may affect the JNK pathway by interfering with the signaling molecule(s) at the same level or proximally upstream of the MAPKKK level. Taken together, the inhibition of the MEKK1-JNK pathway reveals a possible mechanism of suppression of AP-1 and NF-kappaB signaling by curcumin, and may explain the potent anti-inflammatory and anti-carcinogenic effects of this chemical.
403 citations
TL;DR: These findings show that the effect of curcumin on phorbol 12-myristate 13-acetate-induced inflammation/tumor promotion could be studied at the molecular level.
Abstract: Curcumin, a dietary pigment responsible for the yellow color of curry, is a potent inhibitor of tumor promotion by phorbol esters. Functional activation of transcriptional factor c-Jun/AP-1 is believed to play an important role in signal transduction of phorbol 12-myristate 13-acetate-induced tumor promotion. Suppression of the c-Jun/AP-1 activation by curcumin is observed in mouse fibroblast cells. In vitro experiments indicate that inhibition of c-Jun/AP-1 binding to its cognate motif by curcumin may be responsible for the inhibition of c-Jun/AP-1-mediated gene expression. These findings show that the effect of curcumin on phorbol 12-myristate 13-acetate-induced inflammation/tumor promotion could be studied at the molecular level.
391 citations