verlukast and hydroquinone

Astrocytes may modulate the survival of motor neurons in amyotrophic lateral sclerosis (ALS). We have previously shown that fibroblast growth factor-1 (FGF-1) activates astrocytes to increase secretion of nerve growth factor (NGF). NGF in turn induces apoptosis in co-cultured motor neurons expressing the p75 neurotrophin receptor (p75NTR) by a mechanism involving nitric oxide (NO) and peroxynitrite formation. We show here that FGF-1 increased the expression of inducible nitric oxide synthase and NO production in astrocytes, making adjacent motor neurons vulnerable to NGF-induced apoptosis. Spinal cord astrocytes isolated from transgenic SOD1G93A rats displayed increased NO production and spontaneously induced apoptosis of co-cultured motor neurons. FGF-1 also activates the redox-sensitive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) in astrocytes. Because Nrf2 increases glutathione (GSH) biosynthesis, we investigated the role of GSH production by astrocytes on p75NTR-dependent motor neuron apoptosis. The combined treatment of astrocytes with FGF-1 and t-butylhydroquinone (tBHQ) increased GSH production and secretion, preventing motor neuron apoptosis. Moreover, Nrf2 activation in SOD1G93A astrocytes abolished their apoptotic activity. The protection exerted by increased Nrf2 activity was overcome by adding the NO donor DETA-NONOate to the co-cultures or by inhibiting GSH synthesis and release from astrocytes. These results suggest that activation of Nrf2 in astrocytes can reduce NO-dependent toxicity to motor neurons by increasing GSH biosynthesis.

Topics: Animals; Animals, Genetically Modified; Animals, Newborn; Antioxidants; Astrocytes; Blotting, Western; Cell Count; Cell Survival; Cells, Cultured; Coculture Techniques; Drug Interactions; Embryo, Mammalian; Enzyme Activation; Fibroblast Growth Factor 1; Glial Fibrillary Acidic Protein; Glutathione; Hydroquinones; Methionine; Motor Neurons; Nerve Growth Factor; NF-E2-Related Factor 2; Nitrates; Nitric Oxide Synthase Type II; Nitrites; Propionates; Pyrimidines; Quinolines; Rats; Rats, Sprague-Dawley; Receptor, Nerve Growth Factor; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Spinal Cord; Superoxide Dismutase; Transfection; Urea

Chronic exposure of humans to benzene (BZ), a Class I carcinogen, causes acute myelogenous leukemia, possibly via its bone marrow metabolite, hydroquinone (HQ). The ability to alter cytokine-dependent growth and differentiation in hematopoietic stem or progenitor cells appears to be a property of agents with leukemogenic potential. We have previously reported that BZ and HQ specifically stimulate granulopoiesis in mice and cause granulocytic differentiation in normal murine interleukin (IL)-3-dependent, granulocyte colony-stimulating factor (G-CSF)-inducible 32D myeloblasts. BZ induces granulocytic differentiation by upregulating the production of leukotriene D4 (LTD4), an essential intracellular mediator of G-CSF signaling. We report here that HQ (0.5-4.0 microM), as well as LTD4 (1 nM-10 microM), causes a concentration-dependent induction of granulocytic differentiation in 32D myeloblasts. Unlike LTD4, which induces terminal granulocytic differentiation, HQ undergoes a myeloperoxidase-dependent oxidation to bioreactive p-benzoquinone (BQ), which induces differentiation predominantly to the myelocyte stage. Studies with the highly specific LTD4 receptor antagonist, MK-571, suggest that BQ induces granulocytic differentiation in myeloblasts by activating the LTD4 receptor, thus obviating the requirement for LTD4. This was confirmed by the demonstration that HQ, in the presence of LTD4, shifts the stage-specific pattern of terminal differentiation induced by LTD4 to the incomplete (myelocyte) profile induced by HQ. The inability of HQ to induce a complete program of terminal granulocytic differentiation in myeloblasts, as well as its ability to compete with induction by LTD4, may have a bearing on the leukemogenic potential of BZ.

Topics: Animals; Benzene; Cell Differentiation; Cell Line; Granulocyte Colony-Stimulating Factor; Granulocytes; Hematopoiesis; Hematopoietic Stem Cells; Humans; Hydroquinones; Indomethacin; Leukemia, Myeloid, Acute; Leukotriene Antagonists; Leukotriene D4; Membrane Proteins; Mice; Peroxidase; Propionates; Quinolines; Receptors, Leukotriene; Signal Transduction