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Title: Induction of guanosine triphosphate-cyclohydrolase by follicle- stimulating hormone enhances interleukin-1β-stimulated nitric oxide synthase activity in granulosa cells
Authors: Tabraue, Carlos 
Diaz Peñate, Raquel
Gallardo, German 
Hernandez Gonzalez, Inmaculada 
Quintana, José 
López Blanco, Felix 
González Reyes, Juan
Fanjul, Luisa F. 
Ruiz De Galarreta, Carlos M.
UNESCO Clasification: 2403 Bioquímica
320502 Endocrinología
2415 Biología molecular
32 Ciencias médicas
Keywords: Vascular Smooth-Muscle
Rat Ovary
Receptor Antagonist
Cytokines, et al
Issue Date: 1997
Journal: Endocrinology (Philadelphia) 
Abstract: In cultured granulosa cells, interleukin-1β(IL-1β) induced a time- dependent (16-72 h) and dose-related (0.3-30 ng/ml) stimulation of nitric oxide (NO) synthase (NOS) activity, as determined by the catalytic conversion of [3H]arginine to [3H]citrulline and NO2 accumulation in the culture medium. Although FSH alone failed to stimulate NOS activity, concomitant treatment with the gonadotropin (200 ng/ml) or the cell-permeant cAMP analog (Bu)2cAMP (0.5 mM) markedly enhanced IL-1β-induced NO generation in cultured granulosa cells. The effect of IL-1β on citrulline biosynthesis and NO2 accumulation was abrogated by the NOS inhibitor N(G)-methyl-L-arginine or the IL-1-receptor antagonist protein. In contrast bacterial endotoxin (lipopolysaccharide), interferon-γ or tumor necrosis factor-α, which are well known inducers of inducible NOS (iNOS) in a variety of immunocompetent and nonimmunocompetent cell types, failed to increase [3H]citrulline formation or NO2 accumulation in untreated or FSH-stimulated cells. As demonstrated by reverse transcriptase-PCR analysis, IL-1β-stimulated NO generation was accompanied by a time-dependent increase in messenger RNA levels for iNOS and GTP-cyclohydrolase (GTPCH), the rate-limiting step for de novo tetrahydrobiopterin (BH4) biosynthesis. Treatment with FSH augmented only GTPCH messenger RNA expression, and a more than additive GTPCH signal was observed when cells were simultaneously challenged with IL-1β and FSH. Treatment with the GTPCH inhibitor 2,4-diamino-6-hydroxypyrimidine prevented IL-1β-induced NOS activity in untreated or FSH-stimulated cells, and this inhibition was completely reversed by sepiapterin, a substrate for BH4 biosynthesis, via an alternative pterin salvage pathway present in many cell types. As BH4 is an essential cofactor for NOS catalytic activity, these observations strongly suggest that FSH-induced biosynthesis of endogenous BH4 is essential for full iNOS biosynthetic capacity in IL-1β-stimulated granulosa cells.
ISSN: 0013-7227
DOI: 10.1210/endo.138.1.4854
Source: Endocrinology [ISSN 0013-7227],v. 138 (1), p. 162-168
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