verlukast and Neuroblastoma

Oxidative stress has been implicated in a variety of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. Astrocytes play a significant role in maintaining survival of neurons by supplying antioxidants such as glutathione (GSH) to neurons. Recently, we found that noradrenaline increased the intracellular GSH concentration in astrocytes via β

Topics: Adrenergic beta-3 Receptor Agonists; Adrenergic beta-3 Receptor Antagonists; Animals; Astrocytes; Astrocytoma; Brain; Buthionine Sulfoximine; Cell Line, Tumor; Coculture Techniques; Dioxoles; Glutathione; Humans; Hydrogen Peroxide; Mice; Mice, Inbred C57BL; Neuroblastoma; Neurons; Neuroprotective Agents; Norepinephrine; Oxidative Stress; Propanolamines; Propionates; Quinolines; Receptors, Adrenergic, beta-3

The effects of LY-171883, an orally active leukotriene antagonist, on membrane currents were examined in pituitary GH(3) and in neuroblastoma IMR-32 cells. In GH(3) cells, LY-171883 (1-300 microM) reversibly increased the amplitude of Ca(2+)-activated K(+) current in a concentration-dependent manner with an EC(50) value of 15 microM. In excised inside-out patches recorded from GH(3) cells, the application of LY-171883 into cytosolic face did not modify single channel conductance of large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels; however, it did increase the channel activity. The LY-171883-stimulated activity of BK(Ca) channels is dependent on membrane potential, and results mainly from an increase in mean open time and a decrease in mean closed time. However, REV-5901 (30 microM) suppressed the activity of BK(Ca) channels and MK-571 (30 microM) did not have any effect on it. Under the current-clamp condition, LY-171883 (30 microM) caused membrane hyperpolarization as well as decreased the firing rate of action potentials in GH(3) cells. In neuroblastoma IMR-32 cells, the application of LY-171883 (30 microM) also stimulated BK(Ca) channel activity in a voltage-dependent manner. However, neither clofibrate (30 microM) nor leukotriene D(4) (10 microM) affected the channel activity in IMR-32 cells. Troglitazone (30 microM) decreased the channel activity, but ciglitazone (30 microM) enhanced it. This study clearly demonstrates that LY-171883 stimulates the activity of BK(Ca) channels in a manner unlikely to be linked to its blockade of leukotriene receptors or stimulation of peroxisome proliferator-activated receptors. The stimulatory effects on these channels may, at least in part, contribute to the underlying cellular mechanisms by which LY-171883 affects neuronal or neuroendocrine function.

Topics: Acetophenones; Action Potentials; Animals; Cell Membrane; Electrophysiology; Humans; Large-Conductance Calcium-Activated Potassium Channels; Leukotriene Antagonists; Leukotriene D4; Membrane Potentials; Neuroblastoma; Patch-Clamp Techniques; Pituitary Neoplasms; Potassium Channels, Calcium-Activated; Propionates; Quinolines; Rats; Tetrazoles; Trypsin; Tumor Cells, Cultured

Recent studies suggest that bone marrow (BM)-derived chemotactic mediators such as chemokines play key roles in hematopoietic stem cell trafficking. Lipid mediators, particularly leukotrienes, are involved in leukocyte chemotaxis during inflammation but have also been detected in the normal BM. Therefore, the effects of leukotrienes on hematopoietic progenitor cells were analyzed. Cysteinyl leukotrienes, particularly leukotriene D4 (LTD4), induced strong intracellular calcium fluxes and actin polymerization in mobilized and BM CD34(+) progenitors. Chemotaxis and in vitro transendothelial migration of CD34(+) and more primitive CD34(+)/CD38(-) cells were 2-fold increased by LTD4 at an optimum concentration of 25 to 50 nM. Accordingly, CD34(+) cells expressed the 7-transmembrane LTD4 receptor CysLT1 by reverse transcriptase-polymerase chain reaction and Western blot. Effects of LTD4 were suppressed by the CysLT1 receptor antagonist MK-571 and reduced by pertussis toxin. In contrast, LTB4 induced strong responses only in mature granulocytes. LTD4-induced calcium fluxes were also observed in granulocytes but were not reduced by MK-571, suggesting that these effects were mediated by other receptors (eg, CysLT2) rather than by CysLT1. In addition, expression of 5-lipoxygenase, the key enzyme of leukotriene biosynthesis, was detected in both hematopoietic progenitor cells and mature leukocytes. The study concludes that the functionally active LTD4 receptor CysLT1 is preferentially expressed in immature hematopoietic progenitor cells. LTD4 released in the BM might regulate progenitor cell trafficking and could also act as an autocrine mediator of hematopoiesis. This would be a first physiologic effect of cysteinyl leukotrienes apart from the many known pathophysiologic actions related to allergy and inflammation. (Blood. 2001;97:3433-3440)

Topics: Antigens, CD34; Arachidonate 5-Lipoxygenase; Blotting, Western; Bone Marrow Cells; Calcium; Chemotaxis; Endothelium; Gene Expression; Granulocytes; Hematopoietic Stem Cells; HL-60 Cells; Humans; Leukotriene Antagonists; Leukotriene D4; Membrane Proteins; Neuroblastoma; Pertussis Toxin; Propionates; Quinolines; Receptors, Leukotriene; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stromal Cells; Tumor Cells, Cultured; Virulence Factors, Bordetella