Interleukin-1β Increases Prostaglandin E 2-Stimulated Adenosine 3′,5′-cyclic Monophosphate Production in Rabbit Pigmented Ciliary Epithelium

Abstract

This study was designed to determine the effects of interleukin-1 on basal and prostaglandin E 2-stimulated adenosine 3′,5′-cyclic monophosphate production by primary and first passage cultures of non-transformed rabbit pigmented and non-pigmented ciliary epithelial cells. Confluent cultures of rabbit pigmented and non-pigmented ciliary epithelial cells were incubated for varying periods of time in serum-free medium with or without interleukin-1β, tumor necrosis factor-α, bacterial lipopolysaccharide, transforming growth factor-β2, cycloheximide, indomethacin and combinations of these agents. Cells were then preincubated for 10min with serum-free medium plus the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine and then stimulated for 10min with serum-free medium plus 3-isobutyl-1-methylxanthine (for basal adenosine 3′,5′-cyclic monophosphate production) or serum-free medium containing several concentrations of prostaglandin E 2and 3-isobutyl-1-methylxanthine. In certain experiments isoproterenol, vasoactive intestinal peptide, or forskolin was substituted for prostaglandin E 2. Adenosine 3′,5′-cyclic monophosphate was then extracted into ice-cold absolute ethanol and measured by radioimmunoassay. Prostaglandin E 2stimulated adenosine 3′,5′-cyclic monophosphate production in pigmented and non-pigmented ciliary epithelial cells in a dose-dependent manner. Incubation with interleukin-1β (150Uml -1) increased prostaglandin E 2-stimulated, but not basal adenosine 3′,5′-cyclic monophosphate production in pigmented ciliary epithelial cells. This interleukin-1β-induced enhancement of prostaglandin E 2-stimulated adenosine 3′,5′-cyclic monophosphate production, called the interleukin-1 effect, was not seen with non-pigmented ciliary epithelial cells. The interleukin-1 effect was dependent upon interleukin-1β concentration, time and de novo protein synthesis. The interleukin 1 effect could not be reproduced by replacing interleukin-1β with tumor necrosis factor-α or bacterial lipopolysaccharide and was specific for prostaglandin E 2, since interleukin-1β did not enhance isoproterenol-, vasoactive intestinal peptide-, or forskolin-induced adenosine 3′,5′-cyclic monophosphate production. Chronic exposure to prostaglandin E 2(during the 3hr incubation period), with or without interleukin-1β in the incubation medium, reduced subsequent prostaglandin E 2-stimulated adenosine 3′,5′-cyclic monophosphate production. Inhibition of de novo prostaglandin synthesis with indomethacin increased the interleukin-1 effect. The interleukin-1 effect was inhibited by the immunosuppressive cytokine, transforming growth factor-β2, in a dose-dependent manner. This is the first report of prostaglandin E 2-induced stimulation of adenosine 3′,5′-cyclic monophosphate production by pigmented ciliary epithelial cells and of the unique ability of interleukin-1 to increase this effect. The results are consistent with interleukin-1-induced upregulation of prostaglandin E receptors. Since transforming growth factor-β2 inhibited this interleukin-1 effect, this immunosuppressive cytokine may exert negative feedback and thus regulate the physiological consequences of the interleukin-1 effect.