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In JoVE (1)
Other Publications (18)
- Journal of Colloid and Interface Science
- Molecular Pharmaceutics
- Cancer Letters
- Cancer Letters
- Planta Medica
- Pharmaceutical Research
- Biochemical Pharmacology
- Molecular Cancer Therapeutics
- Cancer Research
- Molecular Cancer Therapeutics
- International Journal of Cancer. Journal International Du Cancer
- Blood
- Biochemical Pharmacology
- International Journal of Cancer. Journal International Du Cancer
- Neoplasia (New York, N.Y.)
- Biochemical Pharmacology
- Proceedings of the National Academy of Sciences of the United States of America
- Nature Communications
Articles by Preetha Anand in JoVE
JoVE General
Isolation and Purification of Kinesin from Drosophila Embryos
This is a protocol to isolate active full length Kinesin from Drosophila embryos for single-molecule biophysical studies. We show how to collect embryos, make the embryo lysate, and then polymerize microtubules (MTs). Kinesin is purified by immobilizing it on the MTs, spinning down the Kinesin-MT complexes, and then releasing the kinesin from the MTs via ATP addition.
Other articles by Preetha Anand on PubMed
Interfacial Properties As Predictors of Radioresistance in Cervical Cancer
The prediction of radioresistance of tumours, early in the course of radiotherapy, may help clinicians in deciding the optimal treatment strategy for each case. This study was carried out to investigate an in vitro technique to predict radiosensitivity, after a single radiation dose of 2 Gy in cervical cancer. Langmuir films of tissue homogenates of biopsy samples from 20 cervical cancer patients treated with radiotherapy alone and 15 normal controls were evaluated. The tensiometric profiles before and after giving 2 Gy of radiation, were compared with that of controls and were correlated with the clinical radioresponsiveness evaluated on completion of the radiotherapy course of 70-78 Gy over a period of 50-55 days. The tensiometric profiles measured after a single dose of radiation can be used to fingerprint the clinical radioresponsiveness of the cervical cancer tissues. The hysteresis of the monolayers of completely radioresponsive post-radiotherapy tissue homogenates was 5.8 times greater than that of partially radioresponsive post-radiotherapy tissue homogenates and was statistically significant using Mann-Whitney test (p<0.05). From our results, the following tensiometric criteria for prediction of radioresistance emerge. After first dose of radiation, if the minimum surface tension of tissue homogenate is greater than 50 mN/m and hysteresis area is less than 20 microJ those tissues will be in the partially radioresponsive and for completely radioresponsive tissue homogenates, the minimum surface tension will be less than 47 mN/m and the hysteresis area will be greater than 33 microJ. The cholesterol and phospholipid content of radioresponsive cervical cancerous tissues after radiotherapy was found to be 1.2 and 2.2 times lower than that of the untreated tissues and due to lower lipid content organic phase surface activity of radioresponsive cancerous tissues after radiotherapy was less than that of the untreated tissue organic phase. The radiation induced tensiometric profile changes of radioresponsive cervical cancerous tissues can be correlated to the radiation induced lipid profile changes. This technique, due to its simplicity and high precision, can serve as a predictive tool for radioresponsiveness and is easily translatable to the clinical setting. Randomized large sample trials are necessary to validate this technique further and help in the translation from bench to clinics.
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.
Curcumin and Cancer: an "old-age" Disease with an "age-old" Solution
Cancer is primarily a disease of old age, and that life style plays a major role in the development of most cancers is now well recognized. While plant-based formulations have been used to treat cancer for centuries, current treatments usually involve poisonous mustard gas, chemotherapy, radiation, and targeted therapies. While traditional plant-derived medicines are safe, what are the active principles in them and how do they mediate their effects against cancer is perhaps best illustrated by curcumin, a derivative of turmeric used for centuries to treat a wide variety of inflammatory conditions. Curcumin is a diferuloylmethane derived from the Indian spice, turmeric (popularly called "curry powder") that has been shown to interfere with multiple cell signaling pathways, including cell cycle (cyclin D1 and cyclin E), apoptosis (activation of caspases and down-regulation of antiapoptotic gene products), proliferation (HER-2, EGFR, and AP-1), survival (PI3K/AKT pathway), invasion (MMP-9 and adhesion molecules), angiogenesis (VEGF), metastasis (CXCR-4) and inflammation (NF-kappaB, TNF, IL-6, IL-1, COX-2, and 5-LOX). The activity of curcumin reported against leukemia and lymphoma, gastrointestinal cancers, genitourinary cancers, breast cancer, ovarian cancer, head and neck squamous cell carcinoma, lung cancer, melanoma, neurological cancers, and sarcoma reflects its ability to affect multiple targets. Thus an "old-age" disease such as cancer requires an "age-old" treatment.
Curcumin Inhibits Proliferation, Invasion, Angiogenesis and Metastasis of Different Cancers Through Interaction with Multiple Cell Signaling Proteins
Because most cancers are caused by dysregulation of as many as 500 different genes, agents that target multiple gene products are needed for prevention and treatment of cancer. Curcumin, a yellow coloring agent in turmeric, has been shown to interact with a wide variety of proteins and modify their expression and activity. These include inflammatory cytokines and enzymes, transcription factors, and gene products linked with cell survival, proliferation, invasion, and angiogenesis. Curcumin has been found to inhibit the proliferation of various tumor cells in culture, prevents carcinogen-induced cancers in rodents, and inhibits the growth of human tumors in xenotransplant or orthotransplant animal models either alone or in combination with chemotherapeutic agents or radiation. Several phase I and phase II clinical trials indicate that curcumin is quite safe and may exhibit therapeutic efficacy. These aspects of curcumin are discussed further in detail in this review.
Potential of Spice-derived Phytochemicals for Cancer Prevention
Although spices have been used for thousands of years and are known for their flavor, taste and color in the food, they are not usually recognized for their medicinal value. Extensive research within the last two decades from our laboratory and others has indicated that there are phytochemicals present in spices that may prevent various chronic illnesses including cancerous, diabetic, cardiovascular, pulmonary, neurological and autoimmune diseases. For instance, the potential of turmeric (curcumin), red chilli (capsaicin), cloves (eugenol), ginger (zerumbone), fennel (anethole), kokum (gambogic acid), fenugreek (diosgenin), and black cumin (thymoquinone) in cancer prevention has been established. Additionally, the mechanism by which these agents mediate anticancer effects is also becoming increasingly evident. The current review describes the active components of some of the major spices, their mechanisms of action and their potential in cancer prevention.
Cancer is a Preventable Disease That Requires Major Lifestyle Changes
This year, more than 1 million Americans and more than 10 million people worldwide are expected to be diagnosed with cancer, a disease commonly believed to be preventable. Only 5-10% of all cancer cases can be attributed to genetic defects, whereas the remaining 90-95% have their roots in the environment and lifestyle. The lifestyle factors include cigarette smoking, diet (fried foods, red meat), alcohol, sun exposure, environmental pollutants, infections, stress, obesity, and physical inactivity. The evidence indicates that of all cancer-related deaths, almost 25-30% are due to tobacco, as many as 30-35% are linked to diet, about 15-20% are due to infections, and the remaining percentage are due to other factors like radiation, stress, physical activity, environmental pollutants etc. Therefore, cancer prevention requires smoking cessation, increased ingestion of fruits and vegetables, moderate use of alcohol, caloric restriction, exercise, avoidance of direct exposure to sunlight, minimal meat consumption, use of whole grains, use of vaccinations, and regular check-ups. In this review, we present evidence that inflammation is the link between the agents/factors that cause cancer and the agents that prevent it. In addition, we provide evidence that cancer is a preventable disease that requires major lifestyle changes.
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.".
Coronarin D, a Labdane Diterpene, Inhibits Both Constitutive and Inducible Nuclear Factor-kappa B Pathway Activation, Leading to Potentiation of Apoptosis, Inhibition of Invasion, and Suppression of Osteoclastogenesis
Compounds isolated from members of the Zingiberaceae family are traditionally used as a medicine against inflammatory diseases, but little is known about the mechanism. Here, we report the isolation and structural identification of coronarin D [E-labda-8(17),12-diene-15-ol], a labdane-type diterpene, from Hedychium coronarium and delineate its mechanism of action. Because the transcription factor nuclear factor-kappaB (NF-kappaB) is a key mediator of inflammation, apoptosis, invasion, and osteoclastogenesis, we investigated the effect of coronarin D on NF-kappaB activation pathway, NF-kappaB-regulated gene products, and NF-kappaB-regulated cellular responses. The coronarin D inhibited NF-kappaB activation induced by different inflammatory stimuli and carcinogens. This labdane also suppressed constitutive NF-kappaB activity in different cell lines and inhibited IkappaBalpha kinase activation, thus leading to the suppression of IkappaBalpha phosphorylation, degradation, p65 nuclear translocation, and reporter gene transcription. Coronarin D also inhibited the NF-kappaB-regulated gene products involved in cell survival (inhibitor of apoptosis protein 1, Bcl-2, survivin, and tumor necrosis factor receptor-associated factor-2), proliferation (c-myc, cyclin D1, and cyclooxygenase-2), invasion (matrix metalloproteinase-9), and angiogenesis (vascular endothelial growth factor). Suppression of these gene products by the diterpene enhanced apoptosis induced by TNF and chemotherapeutic agents, suppressed TNF-induced cellular invasion, and abrogated receptor activator of NF-kappaB ligand-induced osteoclastogenesis. Coronarin D was found to be more potent than its analogue coronarin D acid. Overall, our results show that coronarin D inhibited NF-kappaB activation pathway, which leads to inhibition of inflammation, invasion, and osteoclastogenesis, as well as potentiation of apoptosis.
Modification of Cysteine Residue in P65 Subunit of Nuclear Factor-kappaB (NF-kappaB) by Picroliv Suppresses NF-kappaB-regulated Gene Products and Potentiates Apoptosis
Picroliv, an iridoid glycoside derived from the plant Picrorhiza kurroa, is used traditionally to treat fever, asthma, hepatitis, and other inflammatory conditions. However, the exact mechanism of its therapeutic action is still unknown. Because nuclear factor-kappaB (NF-kappaB) activation plays a major role in inflammation and carcinogenesis, we postulated that picroliv must interfere with this pathway by inhibiting the activation of NF-kappaB-mediated signal cascade. Electrophoretic mobility shift assay showed that pretreatment with picroliv abrogated tumor necrosis factor (TNF)-induced activation of NF-kappaB. The glycoside also inhibited NF-kappaB activated by carcinogenic and inflammatory agents, such as cigarette smoke condensate, phorbol 12-myristate 13-acetate, okadaic acid, hydrogen peroxide, lipopolysaccharide, and epidermal growth factor. When examined for the mechanism of action, we found that picroliv inhibited activation of IkappaBalpha kinase, leading to inhibition of phosphorylation and degradation of IkappaBalpha. It also inhibited phosphorylation and nuclear translocation of p65. Further studies revealed that picroliv directly inhibits the binding of p65 to DNA, which was reversed by the treatment with reducing agents, suggesting a role for a cysteine residue in interaction with picroliv. Mutation of Cys(38) in p65 to serine abolished this effect of picroliv. NF-kappaB inhibition by picroliv leads to suppression of NF-kappaB-regulated proteins, including those linked with cell survival (inhibitor of apoptosis protein 1, Bcl-2, Bcl-xL, survivin, and TNF receptor-associated factor 2), proliferation (cyclin D1 and cyclooxygenase-2), angiogenesis (vascular endothelial growth factor), and invasion (intercellular adhesion molecule-1 and matrix metalloproteinase-9). Suppression of these proteins enhanced apoptosis induced by TNF. Overall, our results show that picroliv inhibits the NF-kappaB activation pathway, which may explain its anti-inflammatory and anticarcinogenic effects.
Curcumin Circumvents Chemoresistance in Vitro and Potentiates the Effect of Thalidomide and Bortezomib Against Human Multiple Myeloma in Nude Mice Model
Curcumin (diferuloylmethane), a yellow pigment in turmeric, has been shown to inhibit the activation of nuclear factor-kappaB (NF-kappaB), a transcription factor closely linked to chemoresistance in multiple myeloma cells. Whether curcumin can overcome chemoresistance and enhance the activity of thalidomide and bortezomib, used to treat patients with multiple myeloma, was investigated in vitro and in xenograft model in nude mice. Our results show that curcumin inhibited the proliferation of human multiple myeloma cells regardless of their sensitivity to dexamethasone, doxorubicin, or melphalan. Curcumin also potentiated the apoptotic effects of thalidomide and bortezomib by down-regulating the constitutive activation of NF-kappaB and Akt, and this correlated with the suppression of NF-kappaB-regulated gene products, including cyclin D1, Bcl-xL, Bcl-2, TRAF1, cIAP-1, XIAP, survivin, and vascular endothelial growth factor. Furthermore, in a nude mice model, we found that curcumin potentiated the antitumor effects of bortezomib (P<0.001, vehicle versus bortezomib+curcumin; P<0.001, bortezomib versus bortezomib+curcumin), and this correlated with suppression of Ki-67 (P<0.001 versus control), CD31 (P<0.001 versus vehicle), and vascular endothelial growth factor (P<0.001 versus vehicle) expression. Collectively, our results suggest that curcumin overcomes chemoresistance and sensitizes multiple myeloma cells to thalidomide and bortezomib by down-regulating NF-kappaB and NF-kappaB-regulated gene products.
Curcumin Sensitizes Human Colorectal Cancer to Capecitabine by Modulation of Cyclin D1, COX-2, MMP-9, VEGF and CXCR4 Expression in an Orthotopic Mouse Model
Because of the poor prognosis and the development of resistance against chemotherapeutic drugs, the current treatment for advanced metastatic colorectal cancer (CRC) is ineffective. Whether curcumin (a component of turmeric) can potentiate the effect of capecitabine against growth and metastasis of CRC was investigated. The effect of curcumin on proliferation of CRC cell lines was examined by mitochondrial dye-uptake assay, apoptosis by esterase staining, nuclear factor-kappaB (NF-kappaB) by electrophoretic mobility shift assay and gene expression by Western blot analysis. The effect of curcumin on the growth and metastasis of CRC was also examined in orthotopically implanted tumors in nude mice. In vitro, curcumin inhibited the proliferation of human CRC cell lines, potentiated capecitabine-induced apoptosis, inhibited NF-kappaB activation and suppressed NF-kappaB-regulated gene products. In nude mice, the combination of curcumin and capecitabine was found to be more effective than either agent alone in reducing tumor volume (p = 0.001 vs. control; p = 0.031 vs. capecitabine alone), Ki-67 proliferation index (p = 0.001 vs. control) and microvessel density marker CD31. The combination treatment was also highly effective in suppressing ascites and distant metastasis to the liver, intestines, lungs, rectum and spleen. This effect was accompanied by suppressed expression of activated NF-kappaB and NF-kappaB-regulated gene products (cyclin D1,c-myc, bcl-2, bcl-xL, cIAP-1, COX-2, ICAM-1, MMP-9, CXCR4 and VEGF). Overall, our results suggest that curcumin sensitizes CRC to the antitumor and antimetastatic effects of capecitabine by suppressing NF-kappaB cell signaling pathway.
Modification of the Cysteine Residues in IkappaBalpha Kinase and NF-kappaB (p65) by Xanthohumol Leads to Suppression of NF-kappaB-regulated Gene Products and Potentiation of Apoptosis in Leukemia Cells
Xanthohumol (XN), a prenylated chalcone isolated from hop plant, exhibits anti-inflammatory, antiproliferative, and antiangiogenic properties through an undefined mechanism. Whether examined by intracellular esterase activity, phosphatidylserine externalization, DNA strand breaks, or caspase activation, we found that XN potentiated tumor necrosis factor-induced apoptosis in leukemia and myeloma cells. This enhancement of apoptosis correlated with down-regulation of nuclear factor-kappaB (NF-kappaB) survivin, bcl-xL, XIAP, cIAP1, cIAP2, cylin D1, and c-myc. XN down-regulated both constitutive and inducible NF-kappaB activation, inhibition of phosphorylation and degradation of IkappaBalpha, suppression of p65 nuclear translocation, and NF-kappaB-dependent reporter gene transcription. XN directly inhibited tumor necrosis factor-induced IkappaBalpha kinase (IKK) activation and a reducing agent abolished this inhibition, indicating the role of cysteine residue. XN had no effect on the IKK activity when cysteine residue 179 of IKK was mutated to alanine. XN also directly inhibited binding of p65 to DNA, a reducing agent reversed this effect, and mutation of cysteine residue 38 to serine of p65 abolished this effect. Thus, our results show that modification of cysteine residues of IKK and p65 by XN leads to inhibition of the NF-kappaB activation pathway, suppression of antiapoptotic gene products, and potentiation of apoptosis in leukemia cells.
Design of Curcumin-loaded PLGA Nanoparticles Formulation with Enhanced Cellular Uptake, and Increased Bioactivity in Vitro and Superior Bioavailability in Vivo
Curcumin, a yellow pigment present in the spice turmeric (Curcuma longa), has been linked with antioxidant, anti-inflammatory, antiproliferative, anticancer, antidiabetic, antirheumatic, and antiviral effects, but its optimum potential is limited by its lack of solubility in aqueous solvents and poor oral bioavailability. We employed a polymer-based nanoparticle approach to improve bioavailability. Curcumin was encapsulated with 97.5% efficiency in biodegradable nanoparticulate formulation based on poly (lactide-co-glycolide) (PLGA) and a stabilizer polyethylene glycol (PEG)-5000. Dynamic laser light scattering and transmission electron microscopy indicated a particle diameter of 80.9 nm. This curcumin, renamed from hereon "as curcumin (NP)", was characterized for its biological activity. In vitro curcumin (NP) exhibited very rapid and more efficient cellular uptake than curcumin. Estrase staining revealed that curcumin (NP) was at least as potent as or more potent than curcumin in inducing apoptosis of leukemic cells and in suppressing proliferation of various tumor cell lines. When examined by electrophoretic gel shift mobility assay, curcumin (NP) was more active than curcumin in inhibiting TNF-induced NF-kappaB activation and in suppression of NF-kappaB-regulated proteins involved in cell proliferation (cyclin D1), invasion (MMP-9), and angiogenesis (VEGF). In mice, curcumin (NP) was more bioavailable and had a longer half-life than curcumin. Overall we demonstrate that curcumin-loaded PLGA nanoparticles formulation has enhanced cellular uptake, and increased bioactivity in vitro and superior bioavailability in vivo over curcumin.
Resveratrol, a Multitargeted Agent, Can Enhance Antitumor Activity of Gemcitabine in Vitro and in Orthotopic Mouse Model of Human Pancreatic Cancer
Gemcitabine, while a standard treatment of advanced pancreatic cancer (PaCa), alone is not very effective. New agents that are safe and effective are highly needed. Resveratrol is one such agent which is safe and multitargeted; and has been linked with suppression of survival, proliferation, invasion and angiogenesis of cancer. Whether resveratrol can sensitize PaCa to gemcitabine in vitro and in vivo was investigated. We established PaCa xenografts in nude mice, randomized into 4 groups, and treated with vehicle, gemcitabine, resveratrol and with combination. Modulation of NF-kappaB and markers of proliferation, angiogenesis and invasion were ascertained using electrophoretic mobility shift assay (EMSA), immunohistochemistry and western blot analysis. Resveratrol inhibited the proliferation of 4 different human PaCa cell lines, synergized the apoptotic effects of gemcitabine, inhibited the constitutive activation of NF-kappaB and expression of bcl-2, bcl-xL, COX-2, cyclin D1 MMP-9 and VEGF. In an orthotopic model of human PaCa, we found that resveratrol significantly suppressed the growth of the tumor (p < 0.001) and this effect was further enhanced by gemcitabine (p < 0.001). Both the markers of proliferation index Ki-67 and the micro vessel density CD31 were significantly downregulated in tumor tissue by the combination of gemcitabine and resveratrol (p < 0.001 vs. control; p < 0.01 vs. gemcitabine). As compared to vehicle control, resveratrol also suppressed the NF-kappaB activation and expression of cyclin D1, COX-2, ICAM-1, MMP-9 and survivin. Overall our results demonstrate that resveratrol can potentiate the effects of gemcitabine through suppression of markers of proliferation, invasion, angiogenesis and metastasis.
Characterization and Mechanistic Studies of a Novel Melanoma-targeting Construct Containing IκBa for Specific Inhibition of Nuclear Factor-κB Activity
The transcription factor nuclear factor-κB (NF-κB) is a central mediator of growth and homeostasis for both normal and neoplastic cells. IκBα is the natural intracellular inhibitor of NF-κB and can effectively complex with and thereby inhibit the biologic activity and translocation of NF-κB to the nucleus. We designed a fusion protein designated IκBα/scFvMEL composing of human IκBα and the single-chain antibody scFvMEL, targets melanoma gp240 antigen. Cells treated with IκBα/scFvMEL before irradiation showed specifically inhibition of both constitutive and radiation-induced NF-κB activity on gp240 antigen-positive A375M cells. Pretreatment of A375M cells with IκBα/scFvMEL significantly sensitized melanoma cells to ionizing radiation assessed using a clonogenic survival assay. Mechanistic studies showed that IκBα/scFvMEL, when exogenously added to A375M cells, could be coimmunoprecipitated with the p65 subunit of NF-κB. IκBα/scFvMEL inhibited in a time and/or dose-dependent manner of tumor necrosis factor α- or radiation-induced NF-κB activity in vitro. IκBα/scFvMEL was also shown to specifically inhibit the translocation of the NF-κB p65 subunit to the cell nucleus and NF-κB-mediated gene transcription. Further, initial studies showed that mice bearing well-established A375M xenografts were treated (intravenously) with IκBα/scFvMEL and showed a significant suppression of tumor growth. We also observed a decrease in levels of Bcl-2 and Bcl-XL signaling events downstream of NF-κB in the tumor model. These studies demonstrate for the first time that tumor cell-targeted delivery of IκBα may be beneficial for the treatment of melanoma when combined with standard anticancer therapies such as radiation.
Suppression of Pro-inflammatory and Proliferative Pathways by Diferuloylmethane (curcumin) and Its Analogues Dibenzoylmethane, Dibenzoylpropane, and Dibenzylideneacetone: Role of Michael Acceptors and Michael Donors
Curcumin, a diferuloylmethane, has been shown to exhibit anti-inflammatory and anti-proliferative activities. Whereas curcumin has both a Michael acceptor and a Michael donor units, its analogues dibenzoylmethane (DBM, a component of licorice) and dibenzoylpropane (DBP) have a Michael donor but not a Michael acceptor unit, and the analogue dibenzylideneacetone (DBA) has a Michael acceptor unit. In the current report, we investigated the potency of DBM, DBP, and DBA in relation to curcumin for their ability to suppress TNF-induced NF-κB activation, NF-κB-regulated gene products, and cell proliferation. We found that all four agents were active in suppressing NF-κB activation; curcumin was most active and DBM was least active. When examined for its ability to inhibit the direct DNA binding activity of p65, a subunit of NF-κB, only DBP inhibited the binding. For inhibition of TNF-induced IKK activation, DBA was most active. For suppression of TNF-induced expression of NF-κB-regulated gene products such as COX-2 (inflammation marker), cyclin D1 (proliferation marker), and VEGF (angiogenesis marker), DBA and curcumin were more active than DBM. Similarly for suppression of proliferation of leukemia (KBM-5), T cell leukemia (Jurkat), prostate (DU145), and breast (MDA-MB-231) cancer cells, curcumin and DBA were most active and DBP was least active. Overall, our results indicate that although curcumin and its analogues exhibit activities to suppress inflammatory pathways and cellular proliferation, a lack of Michael acceptor units in DBM and DBP can reduce their activities.
Mechanical Stochastic Tug-of-war Models Cannot Explain Bidirectional Lipid-droplet Transport
Intracellular transport via the microtubule motors kinesin and dynein plays an important role in maintaining cell structure and function. Often, multiple kinesin or dynein motors move the same cargo. Their collective function depends critically on the single motors' detachment kinetics under load, which we experimentally measure here. This experimental constraint--combined with other experimentally determined parameters--is then incorporated into theoretical stochastic and mean-field models. Comparison of modeling results and in vitro data shows good agreement for the stochastic, but not mean-field, model. Many cargos in vivo move bidirectionally, frequently reversing course. Because both kinesin and dynein are present on the cargos, one popular hypothesis explaining the frequent reversals is that the opposite-polarity motors engage in unregulated stochastic tugs-of-war. Then, the cargos' motion can be explained entirely by the outcome of these opposite-motor competitions. Here, we use fully calibrated stochastic and mean-field models to test the tug-of-war hypothesis. Neither model agrees well with our in vivo data, suggesting that, in addition to inevitable tugs-of-war between opposite motors, there is an additional level of regulation not included in the models.
Casein Kinase 2 Reverses Tail-independent Inactivation of Kinesin-1
Kinesin-1 is a plus-end microtubule-based motor, and defects in kinesin-based transport are linked to diseases including neurodegeneration. Kinesin can auto-inhibit via a head-tail interaction, but is believed to be active otherwise. Here we report a tail-independent inactivation of kinesin, reversible by the disease-relevant signalling protein, casein kinase 2 (CK2). The majority of initially active kinesin (native or tail-less) loses its ability to interact with microtubules in vitro, and CK2 reverses this inactivation (approximately fourfold) without altering kinesin's single motor properties. This activation pathway does not require motor phosphorylation, and is independent of head-tail auto-inhibition. In cultured mammalian cells, reducing CK2 expression, but not its kinase activity, decreases the force required to stall lipid droplet transport, consistent with a decreased number of active kinesin motors. Our results provide the first direct evidence of a protein kinase upregulating kinesin-based transport, and suggest a novel pathway for regulating the activity of cargo-bound kinesin.
