2-phenyl-4-4-5-5-tetramethylimidazoline-1-oxyl-3-oxide and 8-bromoguanosino-3--5--cyclic-monophosphorothioate

Topics: Animals; Arginine; Cattle; Cryopreservation; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Cyclic N-Oxides; Heparin; Imidazoles; Male; Nitric Oxide; Sperm Capacitation; Sperm Motility; Spermatozoa; Thionucleotides

Increased expression of glial fibrillary acidic protein (GFAP) represents astroglial activation and gliosis during neurodegeneration. However, the molecular mechanism behind increased expression of GFAP in astrocytes is poorly understood. The present study was undertaken to explore the role of nitric oxide (NO) in the expression of GFAP. Bacterial lipopolysachharides (LPSs) induced the production of NO and the expression of GFAP in mouse primary astrocytes. Either a scavenger of NO [2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO)] or an inhibitor of inducible nitric oxide synthase [l-N6-(I-iminoethyl)-lysine hydrochloride] blocked this induction of GFAP expression. Similarly, other inducers of NO production such as interferon-gamma, interleukin-1beta, human immunodeficiency virus type 1 gp120, fibrillar amyloid beta peptides, and double-stranded RNA (polyinosinic-polycytidilic acid) also induced the expression of GFAP through NO. The role of NO in the expression of GFAP was supported further by increased expression of GFAP by S-nitroso glutathione (GSNO), an NO donor. Interestingly, inhibition of nuclear factor kappaB (NF-kappaB) suppressed LPS- but not GSNO-induced expression of GFAP, suggesting that NO does not require NF-kappaB to induce GFAP and that NF-kappaB functions upstream of NO production. However, inhibition of LPS- and GSNO-induced expression of GFAP either by NS-2028 [a specific inhibitor of guanylate cyclase (GC)] or by KT5823 [a specific inhibitor of cGMP-activated protein kinase (PKG)], and induction of GFAP expression by either 8-Br cGMP (a cell-permeable cGMP analog) or MY-5445 (a specific inhibitor of cGMP phosphodiesterase) suggests that NO induces GFAP via GC-cGMP-PKG. This study illustrates a novel biological role of NO in regulating the expression of GFAP in astrocytes through the GC-cGMP-PKG pathway that may participate in the pathogenesis of neurodegenerative disorders.

Topics: Animals; Animals, Newborn; Astrocytes; Cell Survival; Cells, Cultured; Cerebral Cortex; Corpus Striatum; Cyclic GMP; Cyclic N-Oxides; Cytokines; Dose-Response Relationship, Drug; Drug Interactions; Electrophoretic Mobility Shift Assay; Enzyme Inhibitors; Fluorescent Antibody Technique; Free Radical Scavengers; Gene Expression; Glial Fibrillary Acidic Protein; HIV Envelope Protein gp120; Imidazoles; Lipopolysaccharides; Lysine; Male; Mice; Mice, Inbred C57BL; Nitric Oxide; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tetrazolium Salts; Thiazoles; Thionucleotides; Time Factors

Electrical stimulation of sensory neurons that innervate receptors on the tailfan of crayfish evokes a reflex response of motor neurons that produce movements of the blades of the tailfan, the uropods. We analyzed the modulatory effects of nitric oxide (NO) on the spike frequency of the reflex response. Bath application of L-arginine and SNAP, which elevate endogenous and exogenous NO levels, increased the frequency of the evoked response, whereas the application of L-NAME and PTIO, which reduce NO levels, decreased the frequency of the response. To determine through what pathway and target NO exerted these effects we bath applied ODQ, an inhibitor of soluble guanylyl cyclase (sGC), which decreased the frequency of response, and 8-br-cGMP, which increased the spike frequency of response. To provide further evidence that NO acts via sGC, we elevated NO levels with L-arginine while simultaneously inhibiting sGC with ODQ. This application reduced the response to control levels, indicating that NO in the terminal ganglion of crayfish acts via sGC to modulate cGMP levels, which in turn regulate the responses of the uropod motor neurons.

Topics: Analysis of Variance; Animals; Arginine; Astacoidea; Cyclic GMP; Cyclic N-Oxides; Drug Interactions; Electric Stimulation; Enzyme Inhibitors; Excitatory Postsynaptic Potentials; Female; Free Radical Scavengers; Imidazoles; In Vitro Techniques; Male; Muscles; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Donors; Oxadiazoles; Penicillamine; Picolines; Quinoxalines; Reflex; Thionucleotides