leukotriene-b4 and Cell-Transformation--Neoplastic

In mammalian cells, reactive oxygen species (ROS) are produced via a variety of cellular oxidative processes, including the activity of NADPH oxidases (NOX), the activity of xanthine oxidases, the metabolism of arachidonic acid (AA) by lipoxygenases (LOX) and cyclooxygenases (COX), and the mitochondrial respiratory chain. Although NOX-generated ROS are the best characterized examples of ROS in mammalian cells, ROS are also generated by the oxidative metabolism (e.g., via LOX and COX) of AA that is released from the membrane phospholipids via the activity of cytosolic phospholipase A(2) (cPLA(2)). Recently, growing evidence suggests that LOX- and COX-generated AA metabolites can induce ROS generation by stimulating NOX and that a potential signaling connection exits between the LOX/COX metabolites and NOX. In this review, we discuss the results of recent studies that report the generation of ROS by LOX metabolites, especially 5-LOX metabolites, via NOX stimulation. In particular, we have focused on the contribution of leukotriene B(4) (LTB(4)), a potent bioactive eicosanoid that is derived from 5-LOX, and its receptors, BLT1 and BLT2, to NOX stimulation through a signaling mechanism that leads to ROS generation.

Topics: Aging; Animals; Apoptosis; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Cell Transformation, Neoplastic; Cytosol; Humans; Leukotriene B4; Mice; Mitochondria; NADPH Oxidases; Oxidation-Reduction; Phospholipases A; Prostaglandin-Endoperoxide Synthases; Reactive Oxygen Species; Signal Transduction; Xanthine Oxidase

Mutations in adenomatous polyposis coli (APC) gene are found in more than 80% of colorectal cancer (CRC) patients. The nuclear transcription factor Nrf2 plays a central role in the regulation of oxidative stress and inflammation. Previously, we have shown that chronic inflammation in Nrf2(-/-) (Nrf2 knockout; KO) mice resulted in higher expression of inflammatory markers and cytokines, coupled with higher inflammatory damage to the colonic crypt cells, as compared to the Nrf2(+/+) (wild type; WT) mice. Induction of mutation in the colon by administration of carcinogen, AOM prior to DSS-induced inflammation resulted in higher tumor incidence and numbers in Nrf2KO mice. These results indicate that Nrf2-dependent inhibition of inflammation appears to be critical in inhibiting mutation-initiated colorectal carcinogenesis. In this study, we aim to investigate if loss of Nrf2 would dose-dependently promote intestinal tumorigenesis in Apc(min/+) mice. To demonstrate the in vivo mechanisms, we constructed both Apc mutated and Nrf2 deficient strain Apc(min/+) mice with C57BL/6 Nrf2KO mice to obtain F1, Apc(min/+) ;Nrf2(+/-) and F2, Apc(min/+) ;Nrf2(-/-) mice. Nrf2KO decreased the protein expression of antioxidant enzyme NQO1 in Apc(min/+) . In contrast, Nrf2KO enhanced the expression of inflammatory markers such as COX-2, cPLA, LTB4 in Apc(min/+) . Finally, Nrf2KO resulted in higher level of PCNA and c-Myc expression in intestinal tissue, indicating the deficiency of Nrf2 promotes proliferation of intestinal crypt cells in Apc(min/+) . Taken together, our results suggest that Nrf2KO attenuates anti-oxidative stress pathway, induces inflammation, and increases proliferative potential in the intestinal crypts leading to enhanced intestinal carcinogenesis and adenomas in Apc(min/+) .

Topics: Adenomatous Polyposis Coli Protein; Animals; Cell Proliferation; Cell Transformation, Neoplastic; Colorectal Neoplasms; Gene Knockout Techniques; Inflammation; Intestinal Mucosa; Intestinal Polyps; Intestines; Leukotriene B4; Male; Mice; Mice, Knockout; NAD(P)H Dehydrogenase (Quinone); NF-E2-Related Factor 2; Oxidative Stress; Signal Transduction

Ras signaling pathways are well-recognized for their involvement in cancer cell proliferation; however, considerably less is known regarding their contribution to invasion and metastasis. Here, we demonstrate that a novel BLT2, a low-affinity leukotriene B(4) receptor-linked signaling cascade involving the generation of reactive oxygen species (ROS) via Nox1, NF-kappaB stimulation and subsequent upregulation of matrix metalloproteinase-9 (MMP-9) is a potential mechanism by which Ras promotes invasion and metastasis. We found that inhibition of BLT2 signaling markedly suppressed Ras-evoked metastasis and reduced the associated mortality in mice. Consistent with the proposed role of BLT2 as a key downstream mediator of Ras signaling to metastasis, BLT2 expression alone resulted in the formation of numerous metastatic lung nodules and the nodules formation was significantly attenuated by the inhibition of MMP-9, a downstream component of BLT2. Together, our results reveal the previously unsuspected function of BLT2-linked cascade in driving oncogenic Ras-induced metastasis and would provide a valuable insight into invasion and metastasis.

Topics: Animals; Cell Transformation, Neoplastic; Genes, ras; Humans; Leukotriene B4; Matrix Metalloproteinase 9; Mice; Neoplasm Invasiveness; Neoplasm Metastasis; Neoplasms; Neovascularization, Pathologic; ras Proteins; Rats; Reactive Oxygen Species; Receptors, Leukotriene B4; Tumor Cells, Cultured; Up-Regulation

Human B lymphocytes can produce leukotriene B4 but the biological function of the 5-lipoxygenase (5-LO) pathway in B cells is unclear. In order to better understand and define the role of 5-LO in B cells, we investigated the expression of 5-LO mRNA and protein in subsets of B cells from human tonsils and different types of B cell lymphoma.. Based on RT-PCR and western blot/immunohistochemical staining, with a polyclonal antibody raised against 5-LO, high expression of 5-LO was found in mantle zone B cells from tonsils. By contrast, only a weak expression of 5-LO was detected in germinal centre cells and no expression in plasma cells from tonsils. This pattern of 5-LO expression was preserved in malignant lymphoma with high expression in mantle B cell lymphoma (MCL) and weak or no expression in follicular lymphoma. Primary leukemized MCL, so called B-prolymphocytic leukaemia cells, and MCL cell lines also expressed 5-LO and readily produced LTB4 after activation.. The present report demonstrates the expression of 5-LO mainly in normal and malignant mantle zone B cells while the expression is low or absent in germinal centre B cells and plasma cells, indicating a role of the 5-LO pathway in B cells before the cells finally differentiate to plasma cells.

Topics: Arachidonate 5-Lipoxygenase; B-Lymphocyte Subsets; B-Lymphocytes; Blotting, Western; Cell Differentiation; Cell Line; Cell Transformation, Neoplastic; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Leukemic; Humans; Immunity, Cellular; Immunologic Memory; Immunophenotyping; Leukemia, Prolymphocytic, B-Cell; Leukotriene B4; Lymphocyte Activation; Lymphoma, Follicular; Lymphoma, Mantle-Cell; Microscopy, Fluorescence; Palatine Tonsil; Polymerase Chain Reaction; Signal Transduction

We investigated the effects of a gamma-tocopherol-rich mixture of tocopherols (gamma-TmT, containing 57% gamma-T, 24% delta-T, and 13% alpha-T) on colon carcinogenesis in azoxymethane (AOM)/dextran sulfate sodium (DSS)-treated mice. In experiment 1, 6-week-old male CF-1 mice were given a dose of AOM (10 mg/kg body weight, i.p.), and 1 week later, 1.5% DSS in drinking water for 1 week. The mice were maintained on either a gamma-TmT (0.3%)-enriched or a standard AIN93M diet, starting 1 week before the AOM injection, until the termination of experiment. In the AOM/DSS-treated mice, dietary gamma-TmT treatment resulted in a significantly lower colon inflammation index (52% of the control) on day 7 and number of colon adenomas (9% of the control) on week 7. gamma-TmT treatment also resulted in higher apoptotic index in adenomas, lower prostaglandin E2, leukotriene B4, and nitrotyrosine levels in the colon, and lower prostaglandin E2, leukotriene B4, and 8-isoprostane levels in the plasma on week 7. Some of the decreases were observed even on day 7. In experiment 2 with AOM/DSS- treated mice sacrificed on week 21, dietary 0.17% or 0.3% gamma-TmT treatment, starting 1 week before the AOM injection, significantly inhibited adenocarcinoma and adenoma formation in the colon (to 17-33% of the control). Dietary 0.3% gamma-TmT that was initiated after DSS treatment also exhibited a similar inhibitory activity. The present study showed that gamma-TmT effectively inhibited colon carcinogenesis in AOM/DSS-treated mice, and the inhibition may be due to the apoptosis-inducing, anti-inflammatory, antioxidative, and reactive nitrogen species-trapping activities of tocopherols.

Topics: Adenocarcinoma; Adenoma; Animals; Antioxidants; Apoptosis; Azoxymethane; Carcinogens; Cell Transformation, Neoplastic; Cocarcinogenesis; Colon; Colonic Neoplasms; Dextran Sulfate; Dinoprost; Dinoprostone; Dose-Response Relationship, Drug; gamma-Tocopherol; Inflammation; Leukotriene B4; Male; Mice; Tyrosine

EBV specific cellular memory is not transferred from mother to child. By addition of the immunomodulators PSK and Trx80, that act on monocytes we could generate EBV-specific T cell response in cord-blood derived mononuclear cultures infected with the virus. In such cultures EBV infected B lymphocytes activated T and NK cells, and the immunostimulators activated the monocytes. Lymphokines produced by the monocytes induced the T and NK cells to progress into a functional activation state and they inhibited the EBV induced proliferation of B lymphocytes. Leukotrienes have been well studied in allergic and inflammatory responses, but less is known about their contribution to cellular immunity. In these experiments leukotriene LTB, produced by the activated monocytes was involved in the activation of effector cells. LTB4 was detected in the culture supernatants and addition of LTB4 biosynthesis inhibitors abolished the activation. These experiments showed thus that endogenously produced LTB4 can induce effector cell responses. Addition of LTB4 to the infected culture or readdition of LTB4 treated monocytes to the culture of infected monocyte depleted cell population induced also T cell activation and led to inhibition of B cell proliferation. These results demonstrated thus that LTB4 can contribute to the activation of innate immunity.

Topics: B-Lymphocytes; Cell Transformation, Neoplastic; Cells, Cultured; Fetal Blood; Herpesvirus 4, Human; Humans; Immunity, Innate; Leukotriene B4; T-Lymphocytes, Cytotoxic

Exposure of a human leukemic cell line HL-60 to 1% dimethylsulfoxide (DMSO) for 4 days induced myeloid differentiation. DMSO-differentiated HL-60 cells displayed high and low-affinity binding sites for leukotriene B4 (LTB4). The pretreatment of myeloid differentiated HL-60 cells with 1-10 nM LTB4 enhanced superoxide production evoked by 100 nM formyl-methionyl-leucylphenylalanine (fMLP) to 127-137% of the controls stimulated by fMLP alone. A concentration eliciting a half maximal increase (EC50) of LTB4 for the enhancing effect on superoxide production evoked by fMLP was 0.32 nM. This was roughly similar to the dissociation constant (Kd) of high affinity receptors for LTB4 (0.23 nM). These results suggest that high affinity receptors transduce the enhancing effect of LTB4 on fMLP-induced superoxide production. Although it seems possible that enhancement of fMLP-induced superoxide production is associated with a substantial increase and/or an affinity alteration in receptors for fMLP, LTB4-pretreated cells failed to show significant changes in fMLP binding compared to non-pretreated ones. It seems likely that Ca2+ influx transduces enhancement of fMLP-induced superoxide production, because extracellular Ca2+ is necessary for an enhancing effect of fMLP-induced superoxide production. Also, EC50 of LTB4 for Ca2+ influx (0.78 nM) was similar to that of the enhancing effect of superoxide generation evoked by fMLP. Although pretreatment of LTB4 failed to enhance the maximal level of fMLP-induced intracellular Ca2+ rise, transient overshoot in intracellular Ca2+ evoked by fMLP declined more rqpidly after LTB4 pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Calcium; Cell Line; Cell Transformation, Neoplastic; Dimethyl Sulfoxide; Drug Synergism; Humans; Leukemia, Myeloid, Acute; Leukotriene B4; N-Formylmethionine Leucyl-Phenylalanine; Receptors, Immunologic; Receptors, Leukotriene B4; Superoxides

We used chicken myelomonocytic cells transformed by a temperature-sensitive mutant of the myb/ets oncogene-containing avian leukemia virus E26 to study the regulation of leukotriene (LT) synthesis during macrophage differentiation. Cells exposed to arachidonic acid and the Ca2+ ionophore 23187 produced up to 180 times more LTs at the nonpermissive temperature (42 degrees C) than at the permissive temperature (37 degrees C). Induction of LT synthesis was detectable within 2 hr after temperature shift, whereas conventional macrophage markers became evident after 2-3 days. N-Formylmethionylleucylphenylalanine, opsonized zymosan, and complement factor C5a induced LT synthesis in temperature-sensitive mutant-transformed cells only when the cells were maintained at 42 degrees C, and this effect was blocked by pertussis toxin. When cells were kept at 42 degrees C for 48 hr and then shifted back to 37 degrees C to induce retrodifferentiation, LT synthesis rates declined within 8 hr and reached near control values within 36 hr. Retrodifferentiation also led to decreased LT synthesis in response to N-formylmethionylleucylphenylalanine, opsonized zymosan, and C5a. These results indicate that activation of the 5-lipoxygenase pathway is a very early event in the macrophage differentiation pathway that is directly or indirectly controlled by the temperature-sensitive v-myb protein.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Avian Leukosis Virus; Cell Line; Cell Transformation, Neoplastic; Cells, Cultured; Chickens; Cycloheximide; Dactinomycin; Kinetics; Leukotriene B4; Macrophages; Mutation; N-Formylmethionine Leucyl-Phenylalanine; Oncogenes; SRS-A

In vitro fibroblast chemotaxis was studied in the presence of synthetic leukotriene B4 (LTB4) and of supernatants from ionophore-stimulated lymphocytes, monocytes, and basophils (LMB-S). LTB4 and LMB-S induced a dose-related, directed migration of human and rat embryonic fibroblasts. By checkerboard analysis, this response was chemotactic and not chemokinetic. Optimal migration toward LTB4 occurred at 10(-8) M concentrations, while higher concentrations were inhibitory. The LMB-S contained two types of fibroblast chemotactic factors, one that corresponded to LTB4 and one additional, heat labile, non-dialyzable substance of greater than 10 kilodaltons. LTB4 and LMB-S were inactive against transformed human connective tissue cells (HT 1080, McCoy) while these cells moved well in response to conditioned medium derived from confluent fibroblast monolayer cultures. These results suggest that LTB4 is a specific chemoattractant for fibroblasts and that it acts in concert with other chemotactic factors derived from inflammatory leukocytes to regulate the influx of fibroblasts to tissue sites.

Topics: Animals; Basophils; Cell Line; Cell Transformation, Neoplastic; Chemotaxis; Embryo, Mammalian; Fibroblasts; Humans; Leukotriene B4; Lymphocytes; Monocytes; Sarcoma; Synovial Fluid

Isolated dog mastocytoma cells sensitized with dog anti-ragweed IgE and challenged with ragweed antigen or incubated with ionophore A23187 or the carboxy-terminal dodecapeptide of platelet factor 4, PF4(59-70), release histamine and concurrently generate leukotrienes B4, C4, and D4. In contrast, the exposure of mastocytoma cells to 0.1-3 micrograms/ml of 15-hydroxyeicosatetraenoic acid (15-HETE) stimulates selectively the generation of leukotrienes, in the absence of histamine release, while 0.1-1 micrograms/ml of compound 48/80 releases histamine without enhancing the generation of leukotrienes. That natural stimuli are capable of selectively activating one synthetic or secretory compartment of mast cells suggests that separate subsets of receptors as well as different biochemical events may serve to mobilize each class of mediators.

Topics: Allergens; Animals; Arachidonic Acids; Calcimycin; Cell Transformation, Neoplastic; Dogs; Histamine Release; Hydroxyeicosatetraenoic Acids; Kinetics; Leukotriene B4; Mast-Cell Sarcoma; p-Methoxy-N-methylphenethylamine; Platelet Factor 4; SRS-A