Interleukin-1 beta independently stimulates production of prostaglandin E2 and cyclic AMP from human decidual cells.

Interleukin-1 beta (IL-1 beta) increased the production of cyclic AMP and prostaglandin E2 (PGE2) by cultured human decidual cells during 24 h of stimulation, but not over short incubation times (< 6 h). At concentrations of IL-1 beta ranging from 1 to 100 pg/ml, there were parallel changes in cyclic AMP and PGE2 levels, but 1000 pg of IL-1 beta/ml inhibited cyclic AMP production while still stimulating PGE2 synthesis. The possible link between cyclic AMP and PGE2 was therefore studied further. Inhibition of IL-1 beta-stimulated PGE2 synthesis by indomethacin and direct addition of PGE2 had no effect on cyclic AMP levels, indicating that PGE2 did not increase cyclic AMP production by human decidual cells and confirming the independent synthesis of cyclic AMP and PGE2. The increase in cyclic AMP production induced by IL-1 beta is dependent on protein synthesis, but it is not known which component of the adenylate cyclase is increased. A phosphodiesterase inhibitor potentiated the effects of IL-1 beta on cyclic AMP synthesis, indicating that the cytokine may increase cyclic AMP metabolism. We suggest that high concentrations of IL-1 beta activate phosphodiesterase activity more than adenylate cyclase, which gives rise to the low levels of cyclic AMP noted above. IL-1 beta also decreased forskolin-stimulated cyclic AMP production, which again indicates increased cyclic AMP metabolism. Since most concentrations of IL-1 beta alone increased cyclic AMP levels, this stimulation must out-weigh the increase in metabolism apparent in the presence of forskolin, phosphodiesterase inhibitor or high levels of interleukin. It is clear that IL-1 beta increased decidual PGE2 production independently of cyclic AMP, and that other second messenger must mediate the action of this cytokine.

Decidual adenylate cyclase and prostaglandin production in vitro.

Human decidua contains an active adenylate cyclase, and a number of studies indicate that adenylate cyclase is functionally linked to increased in vitro prostaglandin synthesis. Increased decidual prostaglandin synthesis is associated with parturition, and therefore activation of adenylate cyclase may be involved in the control of human parturition. In this study, third trimester human decidual cells were preincubated for no more than 24 h prior to stimulation with a number of reagents which increase cellular cyclic AMP levels. Forskolin rapidly increased intracellular and extracellular cyclic AMP levels, but there was no increase in prostaglandin E2 biosynthesis during incubations ranging from 5 min up to 24 h. Dibutyryl cyclic AMP or 8-bromo-cyclic AMP were also without effect on PGE2 production, which suggests that the adenylate cyclase was not linked to the mechanisms regulating prostaglandin production. Cholera toxin increased basal cyclic AMP and PGE2 synthesis, and was without effect on IL-1 beta-stimulated PGE2 levels. PGE2 synthesis was increased by 24 h culture with IL-1 beta in all the cell preparations, indicating that the cells were biologically active, and that the lack of effect of changes in cyclic AMP synthesis on PGE2 levels could not be attributed to a defect in the prostaglandin synthetic pathway. Our findings did not agree with earlier work which showed that changes in cyclic AMP were correlated with changes in PGE2 production by human decidual cells. It is clear that in the previous studies the decidual cells were preincubated for 4-7 days prior to stimulation, in contrast with 24 h in our investigation.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 beta-stimulated prostaglandin synthesis by human decidual cells is independent of protein kinase C.

Basal prostaglandin E2 (PGE2) synthesis by human decidual cells was stimulated by phorbol myristate acetate (PMA) which activates protein kinase C. Staurosporine, which is an inhibitor of protein kinase C in most systems, also increased basal PGE2 synthesis. Further work is needed to explain this finding, as another inhibitor of protein kinase C, H7, inhibited PGE2 production under similar culture conditions. Interleukin-1 beta (IL-1 beta)-stimulated PGE2 synthesis was potentiated by coincubation with PMA or staurosporine, indicating that IL-1 beta and protein kinase C increase decidual PGE2 synthesis through different mechanisms. Desensitization of the decidual cells for 24 h with PMA did not affect IL-1 beta-stimulated PGE2 synthesis. The complex roles of protein kinase C in regulating decidual prostaglandin synthesis require further investigation, but it is clear that the effects of IL-1 beta are not mediated by protein kinase C.

The "interleukin 1 receptor antagonist" is a partial agonist of prostaglandin synthesis by human decidual cells.

In many systems the interleukin-1 receptor antagonist opposes the effects of interleukin-1 beta. We considered that it might block interleukin-1 beta-stimulated prostaglandin production from human decidual cells. Very high levels of interleukin-1 receptor antagonist (> 1000 pg/ml) had limited inhibitory effects on IL-1 beta-stimulated PGE2 synthesis, and lower levels of antagonist (< 1000 pg/ml) increased the effects of IL-1 beta. Low concentrations of the antagonist alone (1-100 pg/ml) increased basal PGE2 production, whereas higher levels (10-100 ng/ml) had less effect. It seems, therefore, that in human decidua the "antagonist" is more accurately described as a partial agonist. It has been suggested that the IL-1 receptor antagonist could be used to inhibit decidual prostaglandin synthesis and thereby prevent preterm labor, but this report shows that caution should be exercised before using the receptor antagonist.

Prostanoid production by rat aortic endothelial cells by bradykinin and histamine.

The present studies demonstrate that rat aortic endothelial cells, when stimulated with either bradykinin or histamine, caused the release of both PGI2 and PGE2. The method has also been used to characterize the histamine receptor involved which is H1-subtype. The findings suggest that prostanoid production by bradykinin and histamine constitutes an alternative mechanism to endothelium-derived relaxing factor in mediating vasodilatation.

Human leukocyte cathepsin G and elastase specifically suppress thrombin-induced prostacyclin production in human endothelial cells.

Polymorphonuclear leukocytes (PMN) when activated release products that can potentially injure endothelial cells or alter endothelial function. Exposure of cultured human umbilical vein endothelial cells to cathepsin G and elastase isolated from human PMN at concentrations reached in vivo (100 ng/mL to 10 micrograms/mL) selectively inhibited thrombin-induced prostacyclin production and the thrombin-induced rise in cytosolic free calcium ([Ca++]i) concentration. These proteases also blocked thrombin-induced release of arachidonic acid from prelabeled endothelial cells (EC). In contrast, induction of prostacyclin (PGI2) production by arachidonate, histamine, or the calcium ionophore A23187 was not altered by treatment of EC with these proteases. The effects of the proteases were concentration-dependent, were blocked by serum or serum protease inhibitors, and were reversed when the endothelial cells were further cultured for 24 hours in the absence of the proteases. Elastase, but not cathepsin G, also produced detachment of endothelial cells. Thus, the major leukocyte proteases selectively suppress thrombin-induced prostacyclin production by human vascular endothelial cells and may alter the hemostatic balance at sites of PMN activation.

Isolation, characterisation, growth and culture of endothelial cells from the rat aorta.

Rat aortic endothelial cells have been isolated by the explantation technique and grown in culture. They have been identified morphologically using standard staining techniques, biochemically by identification of angiotensin convertase and have been positively stained for Factor VIII-related antigen by immunofluorescence using both anti-human and anti-rat Factor VIII antibodies. The explantation technique is a successful alternative to enzyme digestion which is not applicable to rat aortic endothelial cells because of the nature of their attachment to the subendothelial layer.

Release of eicosanoids from cultured rat aortic endothelial cells; studies with arachidonic acid and calcium ionophore A23187.

The release of prostanoids from the three different vascular cell types derived from rat aortic explants has been studied in vitro. Under resting conditions and when incubated with exogenous arachidonic acid (AA, 10 microM), the endothelial cells (EC) produced the highest concentration of prostacyclin (PGI2 PGE2 PGF2 alpha TxA2). In contrast, PGE2 was the major prostanoid produced by the smooth muscle cells and fibroblasts. Pretreatment of EC with aspirin (10 microM) or indomethacin (10 microM) effectively inhibited the production of prostanoids by these cells. Incubation with the calcium ionophore A23187 (10 microM) did not stimulate production of PGI2 or leukotriene B4 (LTB4) by EC. However, treatment of EC with a combination of A23187 and AA led to production of amounts of both PGI2 and LTB4 which were greater than the summed values for the different drug treatments. These findings indicate that the concentration of substrate, AA, is a limiting factor in prostanoid formation by these cultured vascular cells but that rat EC are relatively poor in the enzymes required for leukotriene formation.

A pharmacological analysis of the responses of the gastrointestinal smooth muscle of the bat to transmural and periarterial nerve stimulation.

A comparative study of the responses of the gastrointestinal tract of the guinea-pig and of the fruit-eating bat Eidolon helvum to transmural nerve stimulation (TNS) was made. The stomach and rectum of the guinea-pig, the bat and the guinea-pig ileum contracted in response to TNS. These contractions were cholinergic in nature because atropine blocked and physostigmine potentiated them. Tetrodotoxin reversibly abolished these contractions suggesting that they were nerve-mediated. The bat isolated ileum usually responded to TNS with mixed motor and inhibitory components. In some cases, there were only motor or inhibitory components. The motor component was abolished by atropine and potentiated by physostigmine. However, the inhibitory component was non-adrenergic and non-cholinergic (NANC). Tetrodotoxin abolished the motor component without influencing the inhibitory components. Periarterial nerve stimulation of the bat ileum produced a relaxation that was blocked by bretylium, propranolol, phentolamine, reserpine and tetrodotoxin. It is concluded that the bat gastrointestinal smooth muscle, like the guinea-pig, has cholinergic excitatory innervation; however, the bat ileum has both a cholinergic excitatory innervation and a nonadrenergic and non-cholinergic inhibitory component.