Some properties of prostaglandin E2 receptors in rabbit alveolar bone cell membranes

The influence of prostaglandins on steroid conversions by human gingival fibroblasts

The aim of this investigation was to study the effects of prostaglandins E1 and E2 (PGE1 and PGE2) on the accumulation, release and metabolism of C19 steroids by human gingival fibroblasts (HGF) and gingivae, due to their anabolic potential in inflammatory repair. For the accumulation studies, HGF were incubated with 14C-testosterone at timed intervals and the cell-digests analysed for label uptake. The release of 5 alpha-dihydrotestosterone (DHT) by HGF was studied by preincubating the cells with 14C-DHT and reincubating with cold steroid to quantify its release at timed intervals. For the metabolic studies, HGF/gingival tissue were incubated with 14C-testosterone and serial concentrations of PGE1 and PGE2 to study their effects on the synthesis of DHT. The incubations were terminated at 24 h and extracted metabolites were analysed and quantified. The accumulation of 14C-testosterone by human gingival fibroblasts was elevated 3-fold at 24 h by PGE1 (n = 3, p < 0.001; 1-way ANOVA). The release of 14C-DHT was enhanced nearly 2-fold by PGE1 (n = 3, p < 0.001), compared with controls. Both PGE1 and PGE2 caused 2-fold increases in DHT synthesis by HGF and 3-fold increases in 4-androstenedione formation (n = 4, p < 0.001). With the tissue incubations PGE1/PGE2 caused 3-4 fold increases in DHT synthesis (n = 5, p < 0.005; Wilcoxon signed rank statistic for paired observations). Direct stimulation of the accumulation/release and metabolism of these steroids by prostaglandins in gingivae may contribute to the anabolic potential of androgens in inflammatory periodontal disease.

Effects of cytokines on prostaglandin E and cAMP levels in human periodontal ligament fibroblasts in vitro

The stimulation of PGE synthesis and cAMP production by cytokines have important physiological effects in many target tissues. The effects of interleukin-1 alpha and -1 beta, tumour necrosis factor-alpha and interferon-gamma on PGE and cAMP production by periodontal ligament fibroblasts were studied. Fibroblasts in the 4th-6th passage, grown and maintained in DMEM supplemented with 10% equine serum, were incubated with graded doses of the various cytokines for 0.25, 0.5, 1.2, 4, 24, 48 or 72 h. At the end of each incubation, PGE in the medium and the cellular content of cAMP were evaluated by a combined immunohistochemical microphotometric procedure, and conventional radiometric assays. The fibroblasts responded to all the cytokines with a dose- and time-related increase in the levels of PGE and cAMP. Such increases were inhibited by the inclusion of indomethacin in the medium. The addition of exogenous PGE reversed that inhibition in respect of cAMP production. Immunohistochemical localization showed PGE predominantly in the cytoplasm and cAMP in the nucleus. These findings indicate that: (1) human periodontal ligament fibroblasts respond to these cytokines by increased synthesis of PGE and the production of cAMP; and (2) the cAMP production is secondary to the PGE synthesis. They suggest that these cytokines may regulate the function of these fibroblasts in physiological remodelling of the periodontium, as well as in inflammatory reactions.

Immunohistochemical assessment of the effect of chemical and mechanical stimuli on cAMP and prostaglandin E levels in human gingival fibroblasts in vitro

These were evaluated by: (1) a combined immunohistochemical-microphotometric procedure (IH) and (2) conventional radiometric assays. Human gingival fibroblasts were in the sixth passage, grown and maintained in Dulbecco minimal essential medium (DMEM) supplemented with 10 per cent horse serum. For chemical and hormonal stimuli, cells (2 x 10(4] were seeded on tissue-culture chamber/slides, and incubated with graded doses of either parathyroid hormone (PTH) or prostaglandin E2 (PGE2) for assessment of their adenosine-3',5'-monophosphate (cAMP) levels, and with indomethacin or colchicine for their effect on PGE levels. For mechanical stimuli, cells (1 x 10(6] were seeded on culture dishes with a flexible plastic membrane and stretched for 5, 30, 60 or 120 min by placing the membrane over a convex surface and weighting the dish cover. After freeze drying, cells were stained by an immunoperoxidase technique for either cAMP or PGE, using monoclonal antibodies. The staining intensity of fibroblasts was determined at 600 nm wavelength. Per cent light absorbance of 15 cells in each slide was measured and the results tested by analysis of variance. The gingival fibroblasts responded to the drugs and hormones in a dose- and time-related fashion. Stretching significantly increased their synthesis of PGE with concomitant increase in cAMP. The IH results were compared with the radiometric assays to confirm the validity of this technique; both assays were valid for describing the quantitative responses of these cells to the stimuli. In particular, the IH method could localize those intracellular sites which demonstrated chances in relative cAMP and PGE concentrations in response to hormonal stimuli.

Identification of prostaglandin E2 receptor sites in the embryonic murine palate

This study reports the existence and characteristics of prostaglandin E2 (PGE2) receptor sites during development of the murine embryonic palate. A radioligand binding technique utilizing [3H]-PGE2 was employed in the identification and characterization of binding sites. On day 13 of gestation, palatal PGE2 receptor sites were saturable (at 3.5 nM [3H]-PGE2) with high affinity (KD 1.6 nM) and low capacity (0.018 fmole/mg protein). Specific [3H]-PGE2 binding was completely reversible by 30 min. The rank order of prostanoid binding affinity at specific PGE2 binding sites was: E2 greater than F2 alpha greater than A2 greater than E1 = D2. The ability of embryonic palate mesenchymal cells to respond to PGE2 with dose-dependent accumulations of intracellular cAMP demonstrated the functional nature of these binding sites. Analysis of palatal PGE2 receptor characteristics during the period of palatal development also indicated significant temporal alterations in both receptor affinity and density.

Effect of sixth component of complement on the prostaglandin E1 stimulated adenyl cyclase activity in rat calvaria

Human serum enhanced the PGE1 stimulated adenyl cyclase activity in membrane rich fraction of rat calvaria, but heated serum did not. Human C6 enhanced the PGE1 stimulated adenyl cyclase activity. C6 did not enhance the PTH stimulated adenyl cyclase activity. The enhancement of the PGE1 stimulated adenyl cyclase activity with C6 was due to increasing Vmax. The enhancement of the enzyme activity with C6 was significantly inhibited with anti-C6 antibody. Adenyl cyclase was not activated with C6 alone.