The effect of nitric oxide on cytokine‐induced release of PGE₂ by human cultured astroglial cells

Abstract

1 The role of the L-arginine-nitric oxide (NO) pathway on the formation of prostaglandin E 2 (PGE 2 ) by human cultured astroglial cells incubated with interleukin-1b (IL-1b) and tumour necrosis factor-a (TNF-a) was investigated. 2 Incubation of T 67 astroglial cell line with IL-b (10 ng ml 71 ) and TNF-a (500 u ml 71 ) produced a signi®cant (P50.05) increase of both nitrite (the breakdown product of NO), cyclic GMP and PGE 2 levels in cell supernatants. N o -nitro-L-arginine methyl ester (L-NAME; 20 ± 300 mM), an inhibitor of NO synthase (NOS), inhibited the increase of cyclic GMP and nitrite levels found in supernatants of cytokine-treated astroglial cells and reduced the release of PGE 2 . The latter e ect showed that the enhanced arachidonic acid (AA) metabolism subsequent to stimulation of astroglial cells with IL-1b and TNF-a was, at least in part, induced by NO. This occurred also when sodium nitroprusside (SNP; 120 mM), an NO donor, was incubated with astroglial cells, an e ect antagonized by oxyhaemoglobin (OxyHb; 10 mM). 3 The inhibition elicited by L-NAME on PGE 2 -release by cytokine-treated astroglial cells was reversed by adding AA (40 mM), showing that the e ect of NO on cytokine-dependent PGE 2 release occurred at the cyclo-oxygenase (COX) level. Furthermore, the release of PGE 2 in cytokine-treated astroglial cells was inhibited by indomethacin (10 mM), a COX inhibitor as well as by preincubating cells with dexamethasone (20 mM), an inhibitor of inducible enzymes, showing that the inducible isoform of COX (COX-2) was involved. 4 On the other hand, pretreating astroglial cells with methylene blue (MB; 10 mM), an inhibitor of NO biological activity acting at the guanylate cyclase level, failed to a ect PGE 2 release in cytokine-treated astroglial cells, leading to the conclusion that cyclic GMP changes related to NO formation are not involved in the generation of AA metabolites. 5 The present experiments demonstrated that the release of PGE 2 by astroglial cells pretreated with IL1b and TNF-a is due to enhanced COX-2 activity via activation of the L-arginine-NO pathway, and this may be relevant to the understanding of the pathophysiological mechanisms underlying neuroimmune disorders.

Intrathecal HIV-1 Envelope Glycoprotein gp120 Induces Enhanced Pain States Mediated by Spinal Cord Proinflammatory Cytokines

“…First, gp120 increases extracellular excitatory amino acids (Lipton et al, 1994). These are agonists at dorsal horn NMDA receptors that, when activated, increase intracellular calcium in neurons (Dawson et al, 1993), microglia (Giulian et al, 1990), and astrocytes (Mollace et al, 1998). Second, the present studies show that gp120 rapidly releases IL-1.…”

“…Only two prerequisites are required for NO production by cNOS: (1) intracellular L-arginine, the substrate for cNOS (Dreyer et al, 1999), and (2) elevation of intracellular calcium, which activates cNOS (Murphy and Grzybicki, 1996). gp120 (Corasaniti et al, 1995), IL-1 (Mollace et al, 1998), and TNF (Mollace et al, 1998) each activate the L-arginine transporter, thereby increasing intracellular L-arginine. Increased intracellular calcium can also occur rapidly after intrathecal gp120.…”

Nitric oxide (NO) modulation of PAF‐induced cardiopulmonary action: interaction between NO synthase and cyclo‐oxygenase‐2 pathways

“…To ascribe the reduced enhancement of PAF-induced pulmonary hypertension by L-NNA in the presence of NS 398 to an eect of NOS on COX activity may also be a matter of speculation. Anyway, our data from HLPs provide evidence that PAF-stimulated COX and NOS activities interact with each other, as reported for dierent stimulating agents in vitro (Tsai et al, 1994;Mollace et al, 1998;Watkins et al, 1997) and in vivo (Sautebin et al, 1995).…”

Cross‐talk between group IIA‐phospholipase A2 and inducible NO‐synthase in rat renal mesangial cells

“…NO is hypothesized to interact with the iron-haem centre of the active site of the COX enzymes thereby modulating enzyme activity (Salvemini et al, 1993). In addition, NO stimulates prostaglandin formation in animal models of in¯ammation (Salvemini et al, 1994;Salvemini, 1997;Sautebin et al, 1995) and in several cell systems such as airway epithelial cells (Watkins et al, 1997), osteoblasts (Kanematsu et al, 1997) and astroglial cells (Mollace et al, 1998). Furthermore, in Cells were treated for 24 h with 8-bromo-cGMP (500 mM) in absence or presence of IL-1b (2 nM) as indicated.…”