Biomedical subjects

Bharat B Aggarwal

Publications and source records attributed to Bharat B Aggarwal.

At least 91 records · Page 5Linked to original sources

PubMed2004

Expression of constitutively active nuclear-kappa B RelA transcription factor in blasts of acute myeloid leukemia.

The nuclear transcription factor NF-kappa B regulates cell survival, proliferation, and differentiation. Little is known about NF-kappa B in myeloid malignancies. In this report, we assessed NF-kappa B in a group of myeloid neoplasms by using an electrophoretic mobility shift assay (EMSA) and immunofluorescence methods in freshly isolated leukemia cells. We analyzed 30 cases of acute myeloid leukemia (AML), 5 cases of myelodysplastic syndrome (MDS), 3 cases of chronic myelomonocytic leukemia (CMML), 15 cases of chronic myeloid leukemia in chronic phase (CML-CP), and 2 cases of chronic myeloid leukemia in blast crisis (CML-BC). Unstimulated cells (bone marrow and peripheral blood) from 17 normal donors and apheresis samples from 6 peripheral blood stem cell donors treated with granulocyte colony-stimulating factor (G-CSF) were used as controls. When EMSA was used, NF-kappa B was elevated in 14 of 30 (47%) cases of AML, in both cases of CML-BC, and in all reference donors treated with G-CSF, but it was at basal levels in all cases of MDS and CML-CP and in normal donors (P = <.01). Immunofluorescence analysis confirmed strong nuclear RelA/NF-kappa B immunoreactivity in AML blasts but not in normal bone marrow. Bcl-2, a downstream molecule, was expressed in cases with elevated NF-kappa B, but not in cases with basal levels of NF-kappa B, suggesting that NF-kappa B is active and provides the cells with survival advantages in vivo. These results suggest that suppression of NF-kappa B may be a useful therapeutic strategy for a subset of patients with AML.

Adolescent↗

PubMed2004

Regulation of TRAIL-induced apoptosis by ectopic expression of antiapoptotic factors.

The discovery of an agent that selectively kills tumor cells and not normal cells is the dream of every cancer researcher. Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), first discovered in 1995, was heralded as a selective killer of tumor cells, and its potential is still thought to be high. Almost immediately, broad efforts were made to understand its activity at the molecular level. TRAIL has been shown to interact with the cell surface through five distinct receptors, named death receptor (DR) 4, DR5, decoy receptor (Dc)R1, DcR2, and osteoprotegrin. It activates nuclear factor (NF)-kappaB, c-Jun N-terminal kinases, and apoptosis. The apoptotic signals are mediated through Fas-associated death domain protein (FADD)-mediated recruitment of caspase-8 and caspase-3. Additionally, caspase-8 can cleave Bcl-2 homology domain 3 (BH3)-interfering domain death agonist (Bid), and the cleaved Bid then causes the release of mitochondrial cytochrome c, leading to the activation of pro-caspase-9, which can then activate pro-caspase-3. TRAIL-induced apoptosis is negatively regulated by numerous cellular factors including decoy receptors, cellular FADD-like interleukin 1 beta-converting enzyme (FLICE) interacting protein (cFLIP), cellular inhibitor of apoptosis protein (cIAP), X-linked IAP (XIAP), survivin, and NF-kappaB. Second mitochondria-derived activator of caspases (Smac)?direct IAP binding protein with low pI (DIABLO) mediates proapoptotic signals through inaction of IAP. How the TRAIL-induced apoptosis is downregulated by these factors is discussed in detail in this review. Whether TRAIL selectively kills tumor cells without harming normal cells is also discussed.

Animals↗

PubMed2004

Suppression of the nuclear factor-kappaB activation pathway by spice-derived phytochemicals: reasoning for seasoning.

The activation of nuclear transcription factor kappaB has now been linked with a variety of inflammatory diseases, including cancer, atherosclerosis, myocardial infarction, diabetes, allergy, asthma, arthritis, Crohn's disease, multiple sclerosis, Alzheimer's disease, osteoporosis, psoriasis, septic shock, and AIDS. Extensive research in the last few years has shown that the pathway that activates this transcription factor can be interrupted by phytochemicals derived from spices such as turmeric (curcumin), red pepper (capsaicin), cloves (eugenol), ginger (gingerol), cumin, anise, and fennel (anethol), basil and rosemary (ursolic acid), garlic (diallyl sulfide, S-allylmercaptocysteine, ajoene), and pomegranate (ellagic acid). For the first time, therefore, research provides "reasoning for seasoning."

Biological Factors↗

PubMed2004

From chemoprevention to chemotherapy: common targets and common goals.

Three decades of research have revealed that cancer is easier to prevent than to treat and that consumption of certain fruits and vegetables can reduce the risk of cancer. Whereas chemotherapy is designed to destroy cancer after it appears, chemoprevention involves the abrogation or delay in the onset of cancer. Regardless of whether a chemopreventive or chemotherapeutic approach is taken, cancer is a multifactorial disease that requires modulation of multiple pathways and multiple targets. Various molecular targets of chemoprevention are also relevant to the therapy of cancer. These targets include the activation of apoptosis; suppression of growth factor expression or signalling; downregulation of antiapoptotic proteins; suppression of phosphatidylinositol-3'-kinase/Akt, NF-kappaB, Janus kinase-signal transducer and activator of transcription and activator protein-1 signalling pathways; and downregulation of angiogenesis through inhibition of vascular endothelial growth factor expression, cyclooxygenase-2, matrix metalloproteinase-9, urokinase-type plasminogen activator, adhesion molecules and cyclin D1. Pharmacologically safe phytochemicals that have been identified from plants or their variant forms can modulate these molecular targets. These phytochemicals include genistein, resveratrol, dially sulfide, S-ally cysteine, allicin, lycopene, capsaicin, curcumin, 6-gingerol, ellagic acid, ursolic acid, betulinic acid, flavopiridol, silymarin, anethol, catechins and eugenol. Recent work has shown that these phytochemicals also can reverse chemoresistance and radioresistance. Because of their pharmacological safety, these agents can be used alone to prevent cancer and in combination with chemotherapy to treat cancer.

Chemoprevention↗

PubMed2004

Nuclear transcription factor NF-kappa B: role in biology and medicine.

The inducible transcription factor nuclear factor-kappa B (NF-kappaB) plays a central role in regulation of many immune, inflammatory and carcinogenic responses. While normal activation of NF-kappaB is required for cell survival and immunity, aberrant regulation of NF-kappaB leads to development of many pathological states especially those involved in acute inflammation. Recent advances in our knowledge of the signaling mechanisms those control the activation of NF-kappaB highlights the intriguing aspect of NF-kappaB regulation, namely the ability of many different signal transduction pathways originating from a wide variety of inducing mechanisms to converge on a single target, the NF-kappaB/IkappaB complex. In this review we summarize our current understanding of the NF-kappaB signaling pathways, their role in various cellular responses and the potential of using NF-kappaB as a therapeutic target in modern medicine.

Animals↗

PubMed2003

Nuclear factor-kappaB and STAT3 are constitutively active in CD138+ cells derived from multiple myeloma patients, and suppression of these transcription factors leads to apoptosis.

Chemoresistance is a major problem in the treatment of patients with multiple myeloma (MM). Because of the central role of the nuclear transcription factors nuclear factor-kappaB (NF-kappaB) and signal transducer and activator of transcription 3 (STAT3) in chemoresistance, cell survival, and proliferation, we investigated whether MM cells derived from patients express activated NF-kappaB and STAT3 and if their suppression induces apoptosis. We assayed CD138+ cells from the bone marrow of 22 MM patients and checked for the activated forms of NF-kappaB and STAT3 by immunocytochemistry. We found that MM cells from all the patients expressed the activated forms of NF-kappaB and STAT3 but to a variable degree (NF-kappaB: low, 3 of 22; moderate, 5 of 22; or high, 14 of 22; STAT3: none, 1 of 22; low, 3 of 22; moderate, 5 of 22; or high, 14 of 22). Constitutive activation of NF-kappaB was in some cases also independently confirmed by electrophoretic mobility gel shift assay. In contrast to MM patients, activated forms of NF-kappaB and STAT3 were absent in cells from healthy individuals. Suppression of NF-kappaB and STAT3 activation in MM cells by ex vivo treatment with curcumin (diferuloylmethane) resulted in a decrease in adhesion to bone marrow stromal cells, cytokine secretion, and in the viability of cells. When compared with curcumin, dexamethasone was less effective in suppression of NF-kappaB activation and induction of apoptosis in myeloma cells. Overall, our results indicate that fresh cells from MM patients express constitutively active NF-kappaB and STAT3, and suppression of these transcription factors inhibits the survival of the cells.

Adult↗

PubMed2003

Mechanisms for lysophosphatidic acid-induced cytokine production in ovarian cancer cells.

A potential role for lysophosphatidic acid (LPA) in human oncogenesis was first suggested by the observation that LPA is present at elevated levels in ascites of ovarian cancer patients. In the current study, we demonstrated that LPA is a potent inducer of interleukin-6 (IL-6) and interleukin-8 (IL-8) production in ovarian cancer cells. Both IL-6 and IL-8 have been implicated in ovarian cancer progression. We characterized the IL-8 gene promoter to ascertain the transcriptional mechanism underlying LPA -induced expression of these cytokines. LPA stimulated the transcriptional activity of the IL-8 gene with little effect on IL-8 mRNA stability. The optimal response of the IL-8 gene promoter to LPA relied on binding sites for NF-kappaB and AP-1, two transcription factors that were strongly activated by LPA in ovarian cancer cell lines. Positive regulators of the NF-kappaB and AP-1 pathways synergistically activated the IL-8 gene promoter. Further, the effect of LPA on IL-6 and IL-8 generation is mediated by the Edg LPA receptors as enforced expression of LPA receptors restored LPA-induced IL-6 and IL-8 production in non-responsive cells and enhanced the sensitivity to LPA in responsive cell lines. The LPA(2) receptor was identified to be the most efficient in linking LPA to IL-6 and IL-8 production although LPA(1) and LPA(3) were also capable of increasing the response to a certain degree. These studies elucidate the transcriptional mechanism and the Edg LPA receptors involved in LPA-induced IL-6 and IL-8 production and suggest potential strategies to restrain the expression of these cytokines in ovarian cancer.

Cell Line, Tumor↗

PubMed2003

Evidence that receptor activator of nuclear factor (NF)-kappaB ligand can suppress cell proliferation and induce apoptosis through activation of a NF-kappaB-independent and TRAF6-dependent mechanism.

The receptor activator of NF-kappaB ligand (RANKL), a recently identified member of the tumor necrosis factor (TNF) superfamily, has been shown to induce osteoclastogenesis and dendritic cell survival. Most members of the TNF superfamily suppress cell proliferation and induce apoptosis, but whether RANKL does so is not known. We demonstrate that treatment of monocyte RAW 264.7 cells with RANKL induces dose-dependent growth inhibition (IC50 = 10 ng/ml) as determined by dye uptake and [3H]thymidine incorporation methods. Suppression of RANKL-induced NF-kappaB activation by dominant-negative IkappaBalpha or by the NEMO-peptide had no effect on RANKL-induced cell growth inhibition. Inhibition of RANKL-induced JNK activation, however, abolished the RANKL-induced apoptosis. Suppression of interaction of RANK with TRAF6 by TRAF6-binding peptide abrogated the anti-proliferative effects of RANKL, suggesting the critical role of TRAF6. Flow cytometric analysis of cells treated with RANKL showed accumulation of cells in G0/G1 phase of the cell cycle, and this accumulation correlated with a decline in the levels of cyclin D1, cyclin D3, and cyclin E and an increase in cyclin-dependent kinase inhibitor p27 (Kip). Flow cytometric analysis showed the presence of annexin V-positive cells in cultures treated with RANKL. RANKL-induced apoptosis was further confirmed using calcein AM/ethidium homodimer-1 dye and cleavage of poly(ADP-ribose) polymerase (PARP), procaspase 3, and procaspase 9; benzyloxycarbonyl-VAD, the pancaspase inhibitor, suppressed the PARP cleavage. Thus, overall, our studies indicate that RANKL can inhibit cell proliferation and induce apoptosis through a TRAF-6-dependent but NF-kappaB-independent mechanism.

Animals↗

PubMed2003

Flavopiridol inhibits NF-kappaB activation induced by various carcinogens and inflammatory agents through inhibition of IkappaBalpha kinase and p65 phosphorylation: abrogation of cyclin D1, cyclooxygenase-2, and matrix metalloprotease-9.

Flavopiridol, a synthetic flavone closely related to a compound originally isolated from the stem bark of the native Indian plant Dysoxylum binectariferum, has been found to inhibit cyclin-dependent kinases, induce apoptosis, suppress inflammation, and modulate the immune response. Because several genes in which expression is altered by flavopiridol are regulated by NF-kappaB, we propose that this flavone must affect the activation of NF-kappaB. For this report, we investigated the effect of flavopiridol on NF-kappaB activation by various carcinogens and inflammatory agents. Flavopiridol suppressed tumor necrosis factor (TNF)-activation of NF-kappaB in a dose- and time-dependent manner in several cell types, with optimum inhibition occurring upon treatment of cells with 100 nm flavopiridol for 6 h. This effect was mediated through inhibition of IkappaBalpha kinase, phosphorylation, ubiquitination, and degradation of IkappaBalpha (an inhibitor of NF-kappaB), and suppression of phosphorylation, acylation, and nuclear translocation of the p65 subunit of NF-kappaB. Besides TNF, flavopiridol also suppressed NF-kappaB activated by a carcinogen (cigarette smoke condensate), tumor promoters (phorbol myristate acetate and okadaic acid), and an inflammatory agent (H2O2). TNF-induced NF-kappaB-dependent reporter gene transcription was also suppressed by this flavone. NF-kappaB reporter activity induced by TNF receptor 1, TNF receptor-associated death domain, TNF receptor-associated factor-2, NF-kappaB-inducing kinase, and IkappaBalpha kinase, were all blocked by flavopiridol but not that activated by p65. Furthermore, flavopiridol suppressed TNF-induced activation of Akt. Flavopiridol also inhibited the expression of the TNF-induced NF-kappaB-regulated gene products cyclin D1, cyclooxygenase-2, and matrix metalloproteinase-9. Overall, our results indicated that flavopiridol inhibits activation of NF-kappaB and NF-kappaB-regulated gene expression, which may explain the ability of flavopiridol to suppress inflammation, modulate the immune response, and regulate cell growth.

Carcinogens↗

PubMed2003

Regulation of proliferation, survival and apoptosis by members of the TNF superfamily.

Tumor necrosis factor (TNF) was first identified in 1984 as a cytokine with anti-tumor effects in vitro and in vivo. Extensive research since then has shown that there are at least 18 distinct members of the TNF super family and they exhibit 15-25% amino acid sequence homology with each other. These family members bind to distinct receptors, which are homologous in their extracellular domain. These cytokines have been implicated in a wide variety of diseases including tumorigenesis, septic shock, viral replication, bone resorption, rheumatoid arthritis, diabetes, and other inflammatory diseases. TNF blockers have been approved for human use in treating some of these conditions in the United States and other countries. Various members of the TNF super family mediate either proliferation, survival, or apoptosis of cells. Although distinct receptors, all members share a common cell signaling pathway that mediates the activation of nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein kinases (e.g. c-jun N-terminal kinase). Regulation of cell growth and activation of NF-kappaB and of c-jun N-terminal kinase by the TNF super family is mediated through sequential activation/association of a set of cell signaling proteins named TNF receptor-associated factors, Fas-associated death domain and FADD-like ICE, caspases, receptor-interacting protein, NF-kappaB-inducing kinases, and IkappaBalpha kinases. Both apoptotic and antiapoptotic signals are activated simultaneously by the same cytokine in the same cell. Together these cytokines regulate cell growth/survival/apoptosis in a complex dance of changing partners and overlapping steps.

Animals↗

PubMed2003

Curcumin (diferuloylmethane) inhibits constitutive and IL-6-inducible STAT3 phosphorylation in human multiple myeloma cells.

Numerous reports suggest that IL-6 promotes survival and proliferation of multiple myeloma (MM) cells through the phosphorylation of a cell signaling protein, STAT3. Thus, agents that suppress STAT3 phosphorylation have potential for the treatment of MM. In the present report, we demonstrate that curcumin (diferuloylmethane), a pharmacologically safe agent in humans, inhibited IL-6-induced STAT3 phosphorylation and consequent STAT3 nuclear translocation. Curcumin had no effect on STAT5 phosphorylation, but inhibited the IFN-alpha-induced STAT1 phosphorylation. The constitutive phosphorylation of STAT3 found in certain MM cells was also abrogated by treatment with curcumin. Curcumin-induced inhibition of STAT3 phosphorylation was reversible. Compared with AG490, a well-characterized Janus kinase 2 inhibitor, curcumin was a more rapid (30 min vs 8 h) and more potent (10 micro M vs 100 micro M) inhibitor of STAT3 phosphorylation. In a similar manner, the dose of curcumin completely suppressed proliferation of MM cells; the same dose of AG490 had no effect. In contrast, a cell-permeable STAT3 inhibitor peptide that can inhibit the STAT3 phosphorylation mediated by Src blocked the constitutive phosphorylation of STAT3 and also suppressed the growth of myeloma cells. TNF-alpha and lymphotoxin also induced the proliferation of MM cells, but through a mechanism independent of STAT3 phosphorylation. In addition, dexamethasone-resistant MM cells were found to be sensitive to curcumin. Overall, our results demonstrated that curcumin was a potent inhibitor of STAT3 phosphorylation, and this plays a role in the suppression of MM proliferation.

Active Transport, Cell Nucleus↗

PubMed2003

Betulinic acid suppresses carcinogen-induced NF-kappa B activation through inhibition of I kappa B alpha kinase and p65 phosphorylation: abrogation of cyclooxygenase-2 and matrix metalloprotease-9.

Betulinic acid (BA), a pentacyclic triterpene isolated from the bark of the white birch tree, has been reported to be a selective inducer of apoptosis in tumor cells. It also exhibits anti-inflammatory and immunomodulatory properties. How BA mediates these effects is not known. Because of the critical role of the transcription factor NF-kappaB in growth modulatory, inflammatory, and immune responses, we postulated that BA modulates the activity of this factor. In this study we investigated the effect of BA on NF-kappaB and NF-kappaB-regulated gene expression activated by a variety of inflammatory and carcinogenic agents. BA suppressed NF-kappaB activation induced by TNF, PMA, cigarette smoke, okadaic acid, IL-1, and H(2)O(2). The suppression of NF-kappaB activation was not cell-type specific. BA suppressed the activation of IkappaBalpha kinase, thus abrogating the phosphorylation and degradation of IkappaBalpha. We found that BA inhibited NF-kappaB activated by TNFR 1, TNFR-associated death domain, TNFR-associated factor 2, NF-kappaB-inducing kinase, and IkappaBalpha kinase. Treatment of cells with this triterpinoid also suppressed NF-kappaB-dependent reporter gene expression and the production of NF-kappaB-regulated gene products such as cyclooxygenase-2 and matrix metaloproteinase-9 induced by inflammatory stimuli. Furthermore, BA enhanced TNF-induced apoptosis. Overall, our results indicated that BA inhibits activation of NF-kappaB and NF-kappaB-regulated gene expression induced by carcinogens and inflammatory stimuli. This may provide a molecular basis for the ability of BA to mediate apoptosis, suppress inflammation, and modulate the immune response.

Active Transport, Cell Nucleus↗

PubMed2003

Ursolic acid inhibits nuclear factor-kappaB activation induced by carcinogenic agents through suppression of IkappaBalpha kinase and p65 phosphorylation: correlation with down-regulation of cyclooxygenase 2, matrix metalloproteinase 9, and cyclin D1.

The process of tumorigenesis requires cellular transformation, hyperproliferation, invasion, angiogenesis, and metastasis. Several genes that mediate these processes are regulated by the transcription factor nuclear factor-kappaB (NF-kappaB). The latter is activated by various carcinogens, inflammatory agents, and tumor promoters. Thus, agents that can suppress NF-kappaB activation have the potential to suppress carcinogenesis. Ursolic acid, a pentacyclic triterpene acid, has been shown to suppress the expression of several genes associated with tumorigenesis, but whether ursolic acid mediates its effects through suppression of NF-kappaB is not understood. In the study described in the present report, we found that ursolic acid suppressed NF-kappaB activation induced by various carcinogens including tumor necrosis factor (TNF), phorbol ester, okadaic acid, H(2)O(2), and cigarette smoke. These effects were not cell type specific. Ursolic acid inhibited DNA binding of NF-kappaB consisting of p50 and p65. Ursolic acid inhibited IkappaBalpha degradation, IkappaBalpha phosphorylation, IkappaBalpha kinase activation, p65 phosphorylation, p65 nuclear translocation, and NF-kappaB-dependent reporter gene expression. Ursolic acid also inhibited NF-kappaB-dependent reporter gene expression activated by TNF receptor, TNF receptor-associated death domain, TNF receptor-associated factor, NF-kappaB-inducing kinase, IkappaBalpha kinase, and p65. The inhibition of NF-kappaB activation correlated with suppression of NF-kappaB-dependent cyclin D1, cyclooxygenase 2, and matrix metalloproteinase 9 expression. Thus, overall, our results indicate that ursolic acid inhibits IkappaBalpha kinase and p65 phosphorylation, leading to the suppression of NF-kappaB activation induced by various carcinogens. These actions of ursolic acid may mediate its antitumorigenic and chemosensitizing effects.

Anticarcinogenic Agents↗

PubMed2003

Curcumin (diferuloylmethane) down-regulates cigarette smoke-induced NF-kappaB activation through inhibition of IkappaBalpha kinase in human lung epithelial cells: correlation with suppression of COX-2, MMP-9 and cyclin D1.

Cigarette smoke (CS) is a major cause of a variety of malignancies including cancers of the larynx, oral cavity and pharynx, esophagus, pancreas, kidney, bladder and lung. The signal transduction pathway that mediates the effects of CS is not well understood but nuclear factor-kappa B (NF-kappaB) is probably involved. The gas phase of CS contains free radicals such as superoxide radicals, hydroxyl radicals and hydrogen peroxide, which potentially can activate NF-kappaB. Benzo[a]pyrene, another potent carcinogen of CS, can also activate NF-kappaB, but by an as yet unknown mechanism. Various other agents that activate NF-kappaB are either tumor initiators or tumor promoters, and NF-kappaB activation can block apoptosis, promote proliferation and mediate tumorigenesis. Therefore, NF-kappaB is an ideal target for preventing CS-induced lung carcinogenesis. Thus, agents that abrogate NF-kappaB activation have the potential to suppress lung carcinogenesis. Because curcumin, a diferuloylmethane, is anticarcinogenic, we investigated the effect of this phytochemical on CS-induced NF-kappaB activation and NF-kappaB-regulated gene expression in human non-small cell lung carcinoma cells. Exposure of cells to CS induced persistent activation of NF-kappaB, and pre-treatment with curcumin abolished the CS-induced DNA-binding of NF-kappaB, IkappaBalpha kinase activation, IkBalpha phosphorylation and degradation, p65 nuclear translocation and CS-induced NF-kappaB-dependent reporter gene expression. The inhibition of NF-kappaB activation correlated with suppression of CS-induced NF-kappaB-dependent cyclin D1, cyclooxygenase-2 and matrix metalloproteinase-9 expression. Overall our results indicate that CS-induced NF-kappaB activation and NF-kappaB-regulated gene expression in human non-small cell lung carcinoma cells is suppressed by curcumin through suppression of IkappaBalpha kinase.

Antineoplastic Agents↗

PubMed2003

Hydrogen peroxide activates NF-kappa B through tyrosine phosphorylation of I kappa B alpha and serine phosphorylation of p65: evidence for the involvement of I kappa B alpha kinase and Syk protein-tyrosine kinase.

Although it is well established that reactive oxygen intermediates mediate the NF-kappaB activation induced by most agents, how H2O2 activates this transcription factor is not well understood. We found that treatment of human myeloid KBM-5 cells with H2O2 activated NF-kappaB in a dose- and time-dependent manner much as tumor necrosis factor (TNF) did but unlike TNF, H2O2 had no effect on IkappaBalpha degradation. Unexpectedly, however, like TNF-induced activation, H2O2-induced NF-kappaB activation was blocked by the calpain inhibitor N-Ac-Leu-Leu-norleucinal, suggesting that a proteosomal pathway was involved. Although H2O2 activated IkappaBalpha kinase, it did not induce the serine phosphorylation of IkappaBalpha. Like TNF, H2O2 induced the serine phosphorylation of the p65 subunit of NF-kappaB, leading to its nuclear translocation. We found that H2O2 induced the tyrosine phosphorylation of IkappaBalpha, which is needed for NF-kappaB activation. We present several lines of evidence to suggest that the Syk protein-tyrosine kinase is involved in H2O2-induced NF-kappaB activation. First, H2O2 activated Syk in KBM-5 cells; second, H2O2 failed to activate NF-kappaB in cells that do not express Syk protein; third, overexpression of Syk increased H2O2-induced NF-kappaB activation; and fourth, reduction of Syk transcription using small interfering RNA inhibited H2O2-induced NF-kappaB activation. We also showed that Syk induced the tyrosine phosphorylation of IkappaBalpha, which caused the dissociation, phosphorylation, and nuclear translocation of p65. Thus, overall, our results demonstrate that H2O2 induces NF-kappaB activation, not through serine phosphorylation or degradation of IkappaBalpha, but through Syk-mediated tyrosine phosphorylation of IkappaBalpha

Active Transport, Cell Nucleus↗

PubMed2003

Genetic deletion of the tumor necrosis factor receptor p60 or p80 sensitizes macrophages to lipopolysaccharide-induced nuclear factor-kappa B, mitogen-activated protein kinases, and apoptosis.

Whether deletion of tumor necrosis factor (TNF) receptor 1 or 2 affects lipopolysaccharide (LPS)-mediated signaling is not understood. In this report, we used macrophages derived from wild type (wt) mice and from mice null for the type 1 receptor (p60-/-), the type 2 receptor (p80-/-), or both (p60-/- p80-/-) to investigate the effect of these receptors on LPS-mediated activation of NF-kappaB, mitogen-activated protein kinases, and apoptosis. LPS activated NF-kappaB by 3-4-fold in wt cells but by 9-10-fold in p60-/-, p80-/-, and p60-/- p80-/- macrophages. These results correlated with the IkappaBalpha kinase activation, which is needed for NF-kappaB activation. LPS-induced cyclooxygenase-2 and inducible NO synthase proteins and NO production were maximum in p60-/- p80-/- macrophages and minimum in wt cells. LPS activated C-Jun N-terminal kinase, p38MAPK, and extracellular signal-regulated kinase in wt cells, but the levels were much higher in p60-/-, p80-/-, and p60-/- p80-/- cells. LPS-induced cytotoxicity, poly(ADP-ribose) polymerase cleavage, and annexin V staining were also highest in p60-/- p80-/- cells and lowest in wt cells. The difference in LPS signaling was unrelated to the expression of LPS receptors, CD14, or toll-like receptor 4. Overall, our studies indicate that deletion of either of the TNF receptors sensitizes the macrophages to LPS and provide evidence for cross-talk between TNF and LPS signaling.

Animals↗

PubMed2003

Resveratrol blocks interleukin-1beta-induced activation of the nuclear transcription factor NF-kappaB, inhibits proliferation, causes S-phase arrest, and induces apoptosis of acute myeloid leukemia cells.

Resveratrol, an edible polyphenolic stilbene, has been reported to possess substantial antileukemic activities in different leukemia cell lines. We investigated whether resveratrol is active against fresh acute myeloid leukemia (AML) cells and its mechanism of action. Because interleukin 1beta(IL-1beta) plays a key role in proliferation of AML cells, we first tested the effect of resveratrol on the AML cell lines OCIM2 and OCI/AML3, both of which produce IL-1beta and proliferate in response to it. Resveratrol inhibited proliferation of both cell lines in a dose-dependent fashion (5-75 microM) by arresting the cells at S phase, thus preventing their progression through the cell cycle; IL-1beta partially reversed this inhibitory effect. Resveratrol significantly reduced production of IL-1beta in OCIM2 cells. It also suppressed the IL-1beta-induced activation of transcription factor nuclear factor kappaB (NF-kappaB), which modulates an array of signals controlling cellular survival, proliferation, and cytokine production. Indeed, incubation of OCIM2 cells with resveratrol resulted in apoptotic cell death. Because caspase inhibitors Ac-DEVD-CHO or z-DEVD-FMK partially reversed the antiproliferative effect of resveratrol, we tested its effect on the caspase pathway and found that resveratrol induced the activation of the cysteine protease caspase 3 and subsequent cleavage of the DNA repair enzyme poly (adenosine diphosphate [ADP]-ribose) polymerase. Finally, resveratrol suppressed colony-forming cell proliferation of fresh AML marrow cells from 5 patients with newly diagnosed AML in a dose-dependent fashion. Taken together, our data showing that resveratrol is an effective in vitro inhibitor of AML cells suggest that this compound may have a role in future therapies for AML.

Acute Disease↗

PubMed2003

Adenosine suppresses activation of nuclear factor-kappaB selectively induced by tumor necrosis factor in different cell types.

Adenosine is an endogenous immunomodulator that has been shown to exhibit anti-inflammatory and immunosuppressive properties through a mechanism that is not fully established. Owing to the pivotal role of nuclear factor (NF)-kappaB in these responses, we tested the hypothesis that adenosine mediates its effects through suppression of NF-kappaB activation. We investigated the effects of adenosine on NF-kappaB activation induced by various inflammatory agents in human myeloid KBM-5 cells. The treatment of these cells with adenosine suppressed TNF-induced NF-kappaB activation, but had no effect on activation of another redox-sensitive transcription factor, AP-1. These effects were not restricted to myeloid cells, as NF-kappaB activation in other lymphocytic and epithelial cell types was also inhibited. The effect on TNF-induced NF-kappaB activation was selective as adenosine had minimal effect on NF-kappaB activation induced by H(2)O(2), PMA, LPS, okadaic acid, or ceramide, suggesting differences in the pathway leading to NF-kappaB activation by different agents. Adenosine also suppressed NF-kappaB-dependent reporter gene expression activated by TNF or by overexpression of TNFR1, TRAF 2, NIK, and p65 subunit of NF-kappaB. The suppression of TNF-induced NF-kappaB activation by adenosine was found not to be because of inhibition of TNF-induced IkappaBalpha phosphorylation and degradation or IkappaBalpha kinase activation. The suppression of TNF-induced NF-kappaB activation was unique to adenosine, as neither its metabolites (inosine, AMP, and ATP) nor pyrimidines (thymidine and uridine) had any effect. Overall, our results clearly demonstrate that adenosine selectively suppresses TNF-induced NF-kappaB activation, which may contribute to its role in suppression of inflammation and of the immune system.

Adenosine↗