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Biomedical subjects

B B Aggarwal

Publications and source records attributed to B B Aggarwal.

At least 55 records · Page 3Linked to original sources
PubMed1999

Human immunodeficiency virus-1-tat induces matrix metalloproteinase-9 in monocytes through protein tyrosine phosphatase-mediated activation of nuclear transcription factor NF-kappaB.

We have previously shown that human immunodeficiency virus (HIV)-1-tat induces the production of matrix metalloproteinase-9 (MMP-9) in human monocytes by a mechanism that is not understood. In the present report, we demonstrate that HIV-tat-induced expression of MMP-9 is blocked by inhibitors of protein tyrosine phosphatases (PTPases). PTPase inhibitors also blocked HIV-tat-induced nuclear transcription factor NF-kappaB activation and IkappaBalpha degradation required for MMP-9 induction. These results suggest that HIV-tat induces MMP-9 in human monocytes through activation of PTPase and NF-kappaB.

DNA-Binding Proteins↗
PubMed1999

VEGI, a new member of the TNF family activates nuclear factor-kappa B and c-Jun N-terminal kinase and modulates cell growth.

Recently a new member of the human tumor necrosis factor (TNF) family named as VEGI was reported. However, very little is known about the biological activities displayed by this cytokine. In this report, we show that in myeloid cells VEGI activated the transcription factor kappa B (NF-kappa B) as determined by the electrophoretic mobility shift assay, induced degradation of I kappa B alpha, and nuclear translocation of p65 subunit of NF-kappa B. VEGI also activated NF-kappa B-dependent reporter gene expression. In addition, VEGI activated c-Jun N-terminal kinase. When examined for growth modulatory effects, VEGI inhibited the proliferation of breast carcinoma (MCF-7), epithelial (HeLa), and myeloid (U-937 and ML-1a) tumor cells; and activated caspase-3 leading to PARP cleavage. VEGI-induced cytotoxicity was potentiated by inhibitors of protein synthesis. VEGI also induced proliferation of normal human foreskin fibroblast cells. The activity of VEGI could neither be neutralized by antibodies against TNF, nor could it compete with TNF binding, indicating that the activity of VEGI is not due to TNF and it binds to a distinct receptor. These results suggest that VEGI, a new member of the TNF family, has a signaling pathway similar to TNF and is most likely a multifunctional cytokine.

Base Sequence↗
PubMed1999

Phenylarsine oxide blocks interleukin-1beta-induced activation of the nuclear transcription factor NF-kappaB, inhibits proliferation, and induces apoptosis of acute myelogenous leukemia cells.

Arsenic compounds have recently been shown to induce high rates of complete remission in patients with acute promyelocytic leukemia (APL). One of these compounds, As(2)O(3), induces apoptosis in APL cells via a mechanism independent of the retinoic acid pathway. To test the hypothesis that arsenic compounds may be effective against other forms of acute myelogenous leukemia (AML), we studied the membrane-permeable arsenic compound phenylarsine oxide (PAO). Because interleukin-1beta (IL-1beta) plays a key role in AML cell proliferation, we first tested the effect of PAO on OCIM2 and OCI/AML3 AML cell lines, both of which produce IL-1beta and proliferate in response to it. We found that PAO inhibited the proliferation of both OCIM2 and OCI/AML3 cells in a dose-dependent fashion (0.01 to 0.1 micromol/L) and that IL-1beta partially reversed this inhibitory effect. We then measured IL-1beta levels in these cells by using an enzyme-linked immunosorbent assay and Western immunoblotting and found that PAO almost completely abolished the production of IL-1beta in these AML cells, whereas it did not affect the production of IL-1 receptor antagonist. Because PAO inhibits activation of the transcription factor NF-kappaB and because NF-kappaB modulates an array of signals controlling cellular survival, proliferation, and cytokine production, we also studied the effect of PAO on NF-kappaB activation in AML cells and found that PAO suppressed the IL-1beta-induced activation of NF-kappaB. Because inhibition of NF-kappaB may result in cellular apoptosis, we also tested whether PAO may induce apoptotic cell death in AML cells. We found that PAO induced apoptosis in OCIM2 cells through activation of the cystein protease caspase 3 and subsequent cleavage of its substrate, the DNA repair enzyme poly (ADP-ribose) polymerase. The PAO-induced apoptosis was caspase dependent, because it was completely blocked by the caspase inhibitor Z-DEVD-FMK. Finally, we tested the effect of PAO on fresh AML marrow cells from 7 patients with newly diagnosed AML and found that PAO suppressed AML colony-forming cell proliferation in a dose-dependent fashion. Taken together, our data showing that PAO is an effective in vitro inhibitor of AML cells suggest that this compound may have a role in future therapies for AML.

Acute Disease↗
PubMed1999

Overexpression of gamma-glutamylcysteine synthetase suppresses tumor necrosis factor-induced apoptosis and activation of nuclear transcription factor-kappa B and activator protein-1.

Tumor necrosis factor (TNF) is a highly pleiotropic cytokine whose activity is at least partially regulated by the redox status of the cell. The cellular redox status is controlled primarily by glutathione, a major cellular antioxidant, whose synthesis is regulated by the rate-limiting enzyme gamma-glutamylcysteine synthetase (gamma-GCS). In the present report we investigated the effect of gamma-GCS overexpression on the TNF-induced activation of nuclear transcription factors NF-kappa B and AP-1, stress-activated protein kinase/c-Jun amino-terminal kinase (JNK) and apoptosis. Transfection of cells with gamma-GCS cDNA blocked TNF-induced NF-kappa B activation, cytoplasmic I kappa B alpha degradation, nuclear translocation of p65, and NF-kappa B-dependent gene transcription. gamma-GCS overexpression also completely suppressed NF-kappa B activation induced by phorbol ester and okadaic acid, whereas that induced by H2O2, ceramide, and lipopolysaccharide was minimally affected. gamma-GCS also abolished the activation of AP-1 induced by TNF and inhibited TNF-induced activation of JNK and mitogen-activated protein kinase kinase. TNF-mediated cytotoxicity and activation of caspase-3 were both abrogated in gamma-GCS-overexpressing cells. Overall, our results indicate that most of the pleiotropic actions of TNF are regulated by the glutathione-controlled redox status of the cell.

Animals↗
PubMed1999

Identification and characterization of a novel cytokine, THANK, a TNF homologue that activates apoptosis, nuclear factor-kappaB, and c-Jun NH2-terminal kinase.

By using the amino acid sequence motif of tumor necrosis factor (TNF), we searched the expressed sequence tag data base and identified a novel full-length cDNA encoding 285 amino acid residues and named it THANK. THANK is a type II transmembrane protein with 15-20% overall amino acid sequence homology to TNF, LT-alpha, FasL, and LIGHT, all members of the TNF family. The mRNA for THANK was expressed at high levels by peripheral blood leukocytes, lymph node, spleen, and thymus and at low levels by small intestine, pancreas, placenta, and lungs. THANK was also prominently expressed in hematopoietic cell lines. The recombinant purified protein expressed in the baculovirus system had an approximate molecular size 20 kDa with amino-terminal sequence of AVQGP. Treatment of human myeloid U937 cells with purified THANK activated nuclear transcription factor-kappaB (NF-kappaB) consisting of p50 and p65. Activation was time- and dose-dependent, beginning with as little as a 1 pM amount of the cytokines and as early as 15 min. Under the same conditions, THANK also activated c-jun NH2-terminal kinase (JNK) in U937 cells. THANK also strongly suppressed the growth of tumor cell lines and activated caspase-3. Although THANK had all the activities and potency of TNF, it did not bind to the TNF receptors. Thus our results indicate that THANK is a novel cytokine that belongs to the TNF family and activates apoptosis, NF-kappaB, and JNK through a distinct receptor.

Amino Acid Sequence↗
PubMed1999

Suppression of tumor necrosis factor-activated nuclear transcription factor-kappaB, activator protein-1, c-Jun N-terminal kinase, and apoptosis by beta-lapachone.

Beta-lapachone, the product of a tree from South America, is known to exhibit various pharmacologic properties, the mechanisms of which are poorly understood. In the present report, we examined the effect of beta-lapachone on the tumor necrosis factor (TNF)-induced activation of the nuclear transcription factors NF-kappaB and activator protein-1 (AP-1) in human myeloid U937 cells. TNF-induced NF-kappaB activation, p65 translocation, IkappaBalpha degradation, and NF-kappaB-dependent reporter gene expression were inhibited in cells pretreated with beta-lapachone. Direct treatment of the p50-p65 heterodimer of NF-kappaB with beta-lapachone had no effect on its ability to bind to the DNA. Besides myeloid cells, beta-lapachone was also inhibitory in T-cells and epithelial cells. Beta-lapachone also suppressed the activation of NF-kappaB by lipopolysaccharide, okadaic acid, and ceramide but had no significant effect on activation by H2O2 or phorbol myristate acetate, indicating that its action is selective. Beta-lapachone also abolished TNF-induced activation of AP-1, c-Jun N-terminal kinase, and mitogen-activated protein kinase kinase (MAPKK or MEK). TNF-induced cytotoxicity and activation of caspase-3 were also abolished by beta-lapachone. Because reducing agents (dithiothreitol and N-acetylcysteine) reversed the effect of beta-lapachone, it suggests the role of a critical sulfhydryl group. Overall, our results identify NF-kappaB, AP-1, and apoptosis as novel targets for beta-lapachone, and this may explain some of its pharmacologic effects.

Acetylcysteine↗
PubMed1999

Activation of NF-kappaB by RANK requires tumor necrosis factor receptor-associated factor (TRAF) 6 and NF-kappaB-inducing kinase. Identification of a novel TRAF6 interaction motif.

Various members of the tumor necrosis factor (TNF) receptor superfamily activate nuclear factor kappaB (NF-kappaB) and the c-Jun N-terminal kinase (JNK) pathways through their interaction with TNF receptor-associated factors (TRAFs) and NF-kappaB-inducing kinase (NIK). We have previously shown that the cytoplasmic domain of receptor activator of NF-kappaB (RANK) interacts with TRAF2, TRAF5, and TRAF6 and that its overexpression activates NF-kappaB and JNK pathways. Through a detailed mutational analysis of the cytoplasmic domain of RANK, we demonstrate that TRAF2 and TRAF5 bind to consensus TRAF binding motifs located in the C terminus at positions 565-568 and 606-611, respectively. In contrast, TRAF6 interacts with a novel motif located between residues 340 and 358 of RANK. Furthermore, transfection experiments with RANK and its deletion mutants in human embryonic 293 cells revealed that the TRAF6-binding region (340-358), but not the TRAF2 or TRAF5-binding region, is necessary and sufficient for RANK-induced NF-kappaB activation. Moreover, a kinase mutant of NIK (NIK-KM) inhibited RANK-induced NF-kappaB activation. However, RANK-mediated JNK activation required a distal portion (427-603) of RANK containing the TRAF2-binding domain. Thus, our results indicate that RANK interacts with various TRAFs through distinct motifs and activates NF-kappaB via a novel TRAF6 interaction motif, which then activates NIK, thus leading to NF-kappaB activation, whereas RANK most likely activates JNK through a TRAF2-interacting region in RANK.

Amino Acid Sequence↗
PubMed1999

Lead activates nuclear transcription factor-kappaB, activator protein-1, and amino-terminal c-Jun kinase in pheochromocytoma cells.

Lead (Pb) is a ubiquitous environmental contaminant that produces variety of effects on the central and peripheral nervous system, induces inflammatory response, and modulates immune functions. Though increase in lipid peroxidation and reactive oxygen intermediates (ROI) have been observed in Pb-induced toxicity, the molecular mechanism underlying these effects is largely unknown. Since nuclear factor kappa B (NF-kappaB) and activator protein (AP-1) are known to be activated by oxidative stress, we hypothesized that Pb-induced effects may be modulated via these transcription factors. The effects of Pb on NF-kappaB, AP-1, and related kinases were studied in pheochromocytoma cells (PC-12). Our results showed that treatment of murine PC-12 cells with Pb resulted in activation of NF-kappaB and degradation of IkappaBalpha (the inhibitory subunit of NF-kappaB). Pb-induced NF-kappaB dependent gene expression was also enhanced. The binding of Pb-induced NF-kappaB to DNA was blocked by antibodies for p65 and p50 but not by c-Rel or nonspecific antibodies such as cyclin D-1 and preimmune serum, suggesting that NF-kappaB consisted of p65 and p50 subunits. Similar to its effects on NF-kappaB, Pb also activated AP-1 in a time- and dose-dependent manner. Besides activating these transcription factors, Pb was also found to upregulate the related kinases such as mitogen activated protein kinase kinase (MEK) and c-Jun N-terminal kinase (JNK) (also known as stress-activated protein kinase) in a dose- and time-dependent manner. Thus, these results suggest that NF-kappaB, AP-1, MEK, and JNK may be important mediators of Pb-induced signaling in gene expression mediating inflammatory response and immunomodulation.

Animals↗
PubMed1999

Immunosuppressive leflunomide metabolite (A77 1726) blocks TNF-dependent nuclear factor-kappa B activation and gene expression.

Leflunomide is a novel immunosuppressive and antiinflammatory agent currently being tested for treatment of autoimmune diseases and transplant rejection. NF-kappa B is a transcription factor activated in response to a wide variety of inflammatory stimuli, including TNF, but whether leflunomide blocks NF-kappa B activation is not known. In the present report we demonstrate that treatment of a human T cell line (Jurkat) with leflunomide blocks TNF-mediated NF-kappa B activation in a dose- and time-dependent manner, with maximum inhibition at 5-10 microM. Inhibition was not restricted to TNF-induced activation, because leflunomide also inhibited NF-kappa B activation induced by other inflammatory agents, including phorbol ester, LPS, H2O2, okadaic acid, and ceramide. Leflunomide blocked the degradation of I kappa B alpha and subsequent nuclear translocation of the p65 subunit, steps essential for NF-kappa B activation. This correlated with inhibition of dual specificity-mitogen-activated protein kinase kinase as well as an Src protein tyrosine kinase, p56lck, by leflunomide. Reducing agents did not reverse the effect of leflunomide. Leflunomide also suppressed the TNF-activated NF-kappa B-dependent reporter gene expression. Our results thus indicate that leflunomide is a potent inhibitor of NF-kappa B activation induced by a wide variety of inflammatory stimuli, and this provides the molecular basis for its anti-inflammatory and immunosuppressive effects.

Aniline Compounds↗
PubMed1999

Photo-oxidative stress down-modulates the activity of nuclear factor-kappaB via involvement of caspase-1, leading to apoptosis of photoreceptor cells.

The mechanisms of photoreceptor cell death via apoptosis, in retinal dystrophies, are largely not understood. In the present report we show that visible light exposure of mouse cultured 661W photoreceptor cells at 4.5 milliwatt/cm2 caused a significant increase in oxidative damage of 661W cells, leading to apoptosis of these cells. These cells show constitutive expression of nuclear factor-kappaB (NF-kappaB), and light exposure of photoreceptor cells results in lowering of NF-kappaB levels in both the nuclear and cytosolic fractions in a time-dependent manner. Immunoblot analysis of IkappaBalpha and p50, and p65 (RelA) subunits of NF-kappaB, suggested that photo-oxidative stress results in their depletion. Immunocytochemical studies using antibody to RelA subunit of NF-kappaB further revealed the presence of this subunit constitutively both in the nucleus and cytoplasm of the 661W cells. Upon exposure to photo-oxidative stress, a depletion of the cytoplasmic and nuclear RelA subunit was observed. The depletion of NF-kappaB appears to be mediated through involvement of caspase-1. Furthermore, transfection of these cells with a dominant negative mutant IkappaBalpha greatly enhanced the kinetics of down modulation of NF-kappaB, resulting in a faster photo-oxidative stress-induced apoptosis. Taken together, these studies show that the presence of NF-kappaB RelA subunit in the nucleus is essential for protection of photoreceptor cells against apoptosis mediated by an oxidative pathway.

Animals↗
PubMed1999

Lipopolysaccharide inhibits TNF-induced apoptosis: role of nuclear factor-kappaB activation and reactive oxygen intermediates.

LPS, a component of the cell wall in Gram-negative bacteria, induces inflammation and septic shock syndrome by stimulating various inflammatory cytokines including TNF. How LPS affects the TNF-mediated cellular responses, however, is not understood. In this study, the effect of LPS on TNF-mediated apoptosis in human histiocytic lymphoma U-937 cells was investigated. We found that treatment of cells with LPS completely abolished TNF-mediated cytotoxicity and activation of caspase-3. LPS-chelating antibiotic, polymyxin B, suppressed the antiapoptotic activity, indicating the specificity of the effect. Within minutes, LPS through CD14 induced the activation of NF-kappaB, degradation of IkappaBalpha (inhibitory subunit of NF-kappaB) and IkappaBbeta, and nuclear translocation of p65. An antioxidant, pyrrolidine dithiocarbamate, which blocked LPS-induced NF-kappaB activation, also abolished the antiapoptotic effects of LPS at the same time. Besides TNF, the apoptosis induced by taxol and okadaic acid was also sensitive to LPS-induced NF-kappaB activation, whereas that induced by H2O2, doxorubicin, daunomycin, vincristine, and vinblastine was NF-kappaB insensitive. Tumor cells that constitutively expressed NF-kappaB also showed resistance to the apoptotic effects of TNF, taxol, and okadaic acid, but sensitivity to all other agents, indicating the critical role of NF-kappaB in blocking apoptosis induced by certain agents. Overall, these results indicate that LPS induces resistance to the apoptotic effects of TNF and other agents, and that NF-kappaB activation, whether induced or constitutive, inhibits this apoptosis.

Apoptosis↗
PubMed1999

TNF-induced signaling in apoptosis.

Out of the almost 17 members of the TNF superfamily, TNF is probably the most potent inducer of apoptosis. TNF activates both cell-survival and cell-death mechanisms simultaneously. Activation of NF-kB-dependent genes regulates the survival and proliferative effects pf TNF, whereas activation of caspases regulates the apoptotic effects. TNF-induced apoptosis is mediated primarily through the activation of type I receptors, the death domain of which recruits more than a dozen different signaling proteins, which together are considered part of an apoptotic cascade. This cascade does not, however, account for the role of reactive oxygen intermediates, ceramide, phospholipases, and serine proteases which are also implicated in TNF-induced apoptosis. This cascade also does not explain how type II TNF receptors which lack the death domain, induce apoptosis. Nevertheless, this review of apoptosis signaling will be limited to those proteins that makeup the cascade.

Animals↗
PubMed1999

Cellular resistance to vincristine suppresses NF-kappa B activation and apoptosis but enhances c-Jun-NH2-terminal protein kinase activation by tumor necrosis.

Tumor necrosis factor (TNF) is a pleiotropic cytokine that potentiates the cytotoxic effects of chemotherapeutic drugs. Although emergence of resistance to chemotherapeutic drugs is a major problem in cancer therapy, its mechanism is incompletely understood. Recently, activation of a nuclear transcription factor NF-kappa B has been reported to be a signal for anti-apoptosis. In this report, we investigated the effect of TNF on activation of NF-kappa B, c-Jun N-terminal kinase (JNK), and apoptosis in vincristine-resistant human histiocytic lymphoma U937-VR cells. Unlike the parent clone (U937-VS), no activation of caspase-3, known to be required for apoptosism was found in vincristine-resistant cells on exposure to vincristine. These cells were also more resistant than U-937-VS cells to doxorubicin, daunomycin, and taxol. TNF-induced NF-kappa B activation, I kappa B alpha degradation, and nuclear translocation of p65 were all found to be highly suppressed in the U-937-VR cells. NF-kappa B activation by LPS, H2O2, and okadaic acid was also suppressed. However, vincristine resistance enhanced TNF-induced JNK activation. When examined for apoptosis, vincristine resistance suppressed the cytotoxic effects and caspase-3 activation by TNF. The resistant phenotype in U937-VR cells was independent of the expression of the apoptosis-suppressor, Bcl-2. Thus, overall these results indicate that vincristine resistance correlates with suppression of NF-kappa B activation, cytotoxicity, and caspase-3 activation but enhancement of JNK activation by TNF.

Journal Article↗
PubMed1999

Antioxidants differentially regulate activation of nuclear factor-kappa B, activator protein-1, c-jun amino-terminal kinases, and apoptosis induced by tumor necrosis factor: evidence that JNK and NF-kappa B activation are not linked to apoptosis.

Tumor necrosis factor (TNF) is known to mediate its signaling through generation of reactive oxygen species (ROS), but the type of TNF signal regulated by ROS and the nature of the ROS species involved are not fully understood. In this report, we investigated the effect of various superoxide radical quenchers--pyrrolidine dithiocarbamate (PDTC), N-acetyl-L-cysteine (NAC), and glutathione (GSH)--an hydroxyl radical quencher (mannitol), and lipid peroxide quenchers--butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA)--on TNF-induced activation of nuclear transcription factors-kappa B (NF-kappa B) and activator protein-1 (AP-1), c-jun amino-terminal kinase (JNK), and apoptosis in human monocytic U937 cells. TNF-induced NF-kappa B activation was inhibited by both superoxide and lipid peroxide quenchers but potentiated by an hydroxyl radical quencher. In contrast, none of the radical quenchers had any significant effect on TNF-induced AP-1 activation. TNF-induced JNK activation, similar to NF-kappa B, was inhibited by both superoxide and lipid peroxide quenchers but potentiated by hydroxyl radical quencher. TNF-induced activation of caspase activity was blocked by all three types of quenchers. TNF cytotoxicity, however, was potentiated by superoxide radical quenchers and suppressed by hydroxyl radical and lipid peroxide quenchers. Overall, these results suggest that hydroxyl radicals mediate TNF-induced apoptosis but not activation of NF-kappa B, AP-1, and JNK; superoxide radicals mediate NF-kappa B and JNK activation but potentiate apoptosis; and lipid peroxides are required for all the signals induced by TNF.

Acetylcysteine↗
PubMed1999

VEGI, a novel cytokine of the tumor necrosis factor family, is an angiogenesis inhibitor that suppresses the growth of colon carcinomas in vivo.

A novel member of the tumor necrosis factor (TNF) family has been identified from the human umbilical vein endothelial cell cDNA library, named vascular endothelial growth inhibitor (VEGI). The VEGI gene was mapped to human chromosome 9q32. The cDNA for VEGI encodes a protein of 174 amino acid residues with the characteristics of a type II transmembrane protein. Its amino acid sequence is 20-30% identical to other members of the TNF family. Unlike other members of the TNF family, VEGI is expressed predominantly in endothelial cells. Local production of a secreted form of VEGI via gene transfer caused complete suppression of the growth of MC-38 murine colon cancers in syngeneic C57BL/6 mice. Histological examination showed marked reduction of vascularization in MC-38 tumors that expressed soluble but not membrane-bound VEGI or were transfected with control vector. The conditioned media from soluble VEGI-expressing cells showed marked inhibitory effect on in vitro proliferation of adult bovine aortic endothelial cells. Our data suggest that VEGI is a novel angiogenesis inhibitor of the TNF family and functions in part by directly inhibiting endothelial cell proliferation. The results further suggest that VEGI maybe highly valuable toward angiogenesis-based cancer therapy.

Amino Acid Sequence↗
PubMed1999

Altered actin cytoskeleton and inhibition of matrix metalloproteinase expression by vanadate and phenylarsine oxide, inhibitors of phosphotyrosine phosphatases: modulation of migration and invasion of human malignant glioma cells.

Cell-matrix interactions exert a profound influence on cell function and behavior. Our earlier observations suggested that disruption of the actin cytoskeleton results in the inhibition of phorbol ester-induced matrix metalloproteinase (MMP)-9 expression. In this study, to understand the role of protein tyrosine phosphatases in matrix metalloproteinase-9 expression, we treated glioblastoma cells with vanadate and phenylarsine oxide (PAO), which are inhibitors of protein tyrosine phosphatases. Vanadate and PAO inhibited expression of phorbol ester-induced MMP-9 as well as constitutive expression of matrix metalloproteinase-2 in a dose- and time-dependent fashion. An assay of the activity of phosphotyrosine phosphatase (PTPase) indicated that vanadate-treated cells had reduced PTPase activity compared with that of untreated controls. Vanadate and PAO also inhibited actin polymerization, cell spreading, migration, and invasion of glioma cells. Furthermore, elevated levels of protein tyrosine phosphorylation were observed in vanadate- and PAO-treated cells in both a concentration- and time-dependent fashion and were seen to have an inverse correlation with focal adhesion kinase protein expression. These results suggest that vanadate and PAO inhibited migration and invasion of glioma cells by their effect on the cytoskeleton and inhibition of MMP expression.

Actins↗