Effects of cortisol and tetrahydrocortisol on the cloned fibroblast derived from rat carrageenin granuloma

Correlation in inflammatory fibroblasts between the number of glucocorticoid receptors and PGE2 release

The anti-inflammatory effects of glucocorticoids are mediated through steroid receptor occupancy and there is a significant correlation between the extent of receptor saturation and the extent of the biological effects. In a previously published study, we found that the number of these receptors was higher in inflammatory fibroblasts than in quiescent ones. PGE2 release, measured at the same time as the number of steroid receptors, was higher when the cells were from inflammatory tissue. Our aim, in the present study, was to determine whether the PGE2 released by cells during inflammatory processes could participate in increasing the number of steroid receptors. Fibroblasts obtained from rat quiescent subcutaneous connective tissue and granulomas were subcultured in monolayers. The specific binding of [3H]dexamethasone was assessed and analyzed by a method described by Kalimi et al. After a freeze-thaw cycle, we observed a decrease in the number of receptors in inflammatory fibroblasts. When the frozen and thawed fibroblasts were subcultured in the presence of PGE2 (10(-8) M), the number of receptors was enhanced in fibroblasts from inflammatory tissue. Cycloheximide (3 X 10(-7) M) prevented this increase. The release of PGE2 decreased after freezing and then increased simultaneously with the number of receptors in inflammatory cells. These findings suggest that PGE2 may play a role in regulating steroid effects on fibroblast function.

Glucocorticoid receptors in fibroblasts from synovial tissue. Changes during the inflammatory process. Preliminary results

There is known to be a significant correlation between the number of glucocorticoid receptors in tissues and their anti-inflammatory effect. In this work, the specific binding of glucocorticoids was studied in inflammatory fibroblasts. Human fibroblasts were obtained from the knee joint of a rheumatoid patient undergoing surgery; experimental fibroblasts were from rat granulomas. The same study was carried out in quiescent synovial fibroblasts from a healthy subject (post-traumatic amputation) and from rat subcutaneous conjunctive tissue. Fibroblasts were obtained by explant cultures and subcultures in monolayers. The stimulation state of cells was evaluated by the amounts of PGE2 and PGF2 alpha released into the culture media. Analysis of the proportions of steroid bound to whole cells showed evidence of specific glucocorticoid receptors in all fibroblasts. Their number was three times higher in cells from inflammatory tissues than from controls. This increased number of receptors in inflammatory cells could be the result of the action of one or more mediators that promote their biosynthesis.

Binding of soluble type I collagen to fibroblasts: effects of thermal activation of ligand, ligand concentration, pinocytosis, and cytoskeletal modifiers

Efficient binding of native, soluble 125I-labeled type I rat collagen to mouse 3T3 fibroblast monolayers requires prior warming of the ligand to 35-37 degrees C for 10-30 min. Decreased binding at high ligand concentrations is ascribed to ligand-ligand interactions rather than to negative cooperativity. Addition of bacterial collagenase to monolayers labeled with the 125I-ligand releases a constant fraction (80%) of the bound ligand over a 2-h interval at 37 degrees C, indicating that little of the ligand becomes inaccessible by pinocytosis. Colchicine (10(-7) M) and vinblastine (5 X 10(-8) M) do not inhibit binding by morphologically intact monolayers. Cytochalasins and concanavalin A show dose-related inhibition of binding by intact monolayers that is due to a reduction in the number of available binding sites rather than to a change in binding site affinity. The collagen binding site on the fibroblast surface is proposed as an organizing center for the assembly of periodic type I collagen fibrils.

Cortisol decreases the concentration of translatable type-I procollagen mRNA species in the developing chick-embryo calvaria

The calvarial mRNA species of chick embryos were translated in the rabbit reticulocyte-lysate cell-free translation system. The amount of procollagen type-I mRNA species was determined by digestion with bacterial collagenase and by fluorography of the cell-free translation products. Administration of cortisol resulted in a specific decrease in the cellular concentration of translatable procollagen type-I mRNA species in the calvaria of developing chick embryos. There was a lag period of up to 12 h before the response, which was dose-dependent. The data suggest that the decrease in amounts of procollagen mRNA species is the main reason for the lower amount of tissue collagen after topical or systemic administration of glucocorticoids, although other factors may contribute to the response.

Enhancement of prostaglandin synthesizing activity by the treatment with sodium n-butyrate on cloned mastocytoma cells and various other tissue cell lines

We have compared the effects of n-butyrate on the prostaglandin synthesizing activities of cloned mouse mastocytoma cells, and various other tissue culture cell lines. Cells were treated with 1 mM n-butyrate for 40 hrs before harvesting. Prostaglandin synthesizing activities of the treated and the control cells were examined in a cell-free assay system. The treatment of some of the cloned mastocytoma cells with n-butyrate brought about the synthesis of prostaglandin D2, E2 and F2 alpha that were not synthesized by the control cells. The treatment of epithelial liver cells (BC-90) also resulted in the formation of 6-keto-prostaglandin F1 alpha which was not formed by the control cells. However, n-butyrate caused relatively small changes in the prostaglandin synthesizing activities of other clones of mastocytoma cells, mouse hepatoma cells, HeLa cells, rat granuloma cells and human embryonic fibroblasts. These data suggest differential effects of n-butyrate on different types of cultured cells.

Characterization of the stimulatory effects of PGF2alpha on the release of arachidonic acid

Fibroblasts derived from a rat carrageenin granuloma were cultured in the presence of radioactive arachidonic acid, palmitic acid and linoleic acid. More than 90% of each labeled fatty acid was incorporated into a phospholipid fraction by the cells in 18 hrs. Arachidonic acid was evenly incorporated into phosphatidylcholine and phosphatidylethanolamine, while both palmitic acid and linoleic acid were almost entirely incorporated into phosphatidylcholine. The position of phosphatidylcholine where the fatty acids were incorporated was different for each fatty acid. The ratio of the amount of fatty acid incorporated into the 2-position to the amount incorporated into the 1-position of phosphatidylcholine for each fatty acid was greater than 90% for arachidonic acid, 2:1 for palmitic acid and 5:1 for linoleic acid. In the case of phosphatidylethanolamine, most arachidonic acid (greater than 90%) was incorporated into the 2-position. PGF2alpha caused the stimulation of arachidonic acid release but not of palmitic acid and linoleic acid from pre-labeled fibroblasts. The serum in the medium was completely replaceable by bovine serum albumin. The effect of PGF2Alpha increased with an increasing concentration of bovine serum albumin, suggesting that serum only acts as a "trap" for released arachidonic acid. The effect of PGF2Alpha was greater than bradykinin, and no synergistic effect was seen, although an additive effect was observed. The effect of PGF2Alpha depended on the concentration of calcium ions under magnesium-supplemented conditions.

Differential effects of hydrocortisone on both growth and collagen metabolism of human fibroblasts from normal and keloid tissue

Cultured fibroblasts isolated from normal and keloid tissue do not differ in their growth characteristics or in the rate of collagen synthesis under routine culture conditions. The addition of hydrocortisone to the culture media results in significant differences in both growth and collagen synthesis between these cell types. Collagen synthesis is inhibited 60% in normal cultures by hydrocortisone (0,5 micrograms/ml) and the population size at which density-dependent growth inhibition is achieved is increased. Keloid-derived fibroblasts grow to a lower maximum density in the presence of hydrocortisone, while their rate of collagen synthesis is not significantly reduced. The rate of non-collagen protein synthesis is increased significantly by hydrocortisone in both cell types. Comparison of normal and keloid-derived cultures obtained from a single individual suggests that the keloid phenotype with respect to both growth and collagen synthesis is restricted to the fibroblasts isolated from the keloid nodule.

Stimulatory effect of prostaglandins on the production of hexosamine-containing substances by cultured fibroblasts (4) adenosine 3':5'-cyclic monophosphate independent stimulation by prostaglandin F2alpha

The mechanism of the stimulatory effect of prostaglandin PG) F2alpha on the production of hexosamine-containing substances by cultured fibroblasts was studied with special reference to adenosine 3':5'-cyclic monophosphate (cAMP). At the stationary phase, the cells were exposed for 6 hrs to PGF2alpha, E1, cAMP or dibutyryl-cAMP in a wide range of concentrations. cAMP itself showed a slight stimulation on the production of hexosamine-containing substances, and the effect was enhanced by using the dibutyryl derivative. PGF2alpha had much a greater capacity than either the exogeneous cAMP or the dibutyryl-cAMP for enhancing the production of hexosamine-containing substances. To know whether cAMP is involved in the stimulatory effect of PGF2alpha, intracellular cAMP level was concomitantly measured in both PGF2alpha and PGE1 treated cultures. Although the cellular cAMP level in PGE1 treated cultures was much higher than that in the PGF2alpha treated cultures, the stimulatory effect on the production of hexosamine-containing substances in PGE1 treated cultures was always much smaller than that in the PGF2alpha treated cultures. Moreover, PGF2alpha had a significant stimulatory effect on the production of hexosamine-containing substances even at a low concentration as 100 pg/ml, which is small enough not to increase any cellular cAMP level. From these results, it was concluded that the stimulatory effect of PGF2alpha on the production of hexosamine-containing substances by cultured fibroblasts is not mediated by cAMP and is caused by a mechanism different from that caused by cAMP.

Inhibitory effects of glucocorticoids on collagen synthesis by mouse sponge granulomas and granuloma fibroblasts in culture

The basis for the glucocorticoid-mediated decrease in tissue collagen was studied in mouse granulomas and in primary granuloma fibroblast cultures. Injection of mice for 12 days with dexamethasone (0.35 mg/kg body weight) resulted in a 50--70% inhibition of collagen synthesis and accumulation in polyvinyl sponge-induced granulomas whereas total protein synthesis was inhibited by only about 25%. The decreased collagen content of the granuloma was accounted for by both a reduced fibroblast number and diminished synthesis per cell. Growth rates, total protein synthesis and collagen synthesis were the same in granuloma fibroblast cultures derived from control or steroid-treated mice. However, addition of 3.10(-7) M hydrocortisone to the culture medium caused a 30--50% inhibition of both collagen and non-collagen protein synthesis in firbroblasts from either source. These inhibitory effects were dose- and time-dependent with a lag time of 12--24 h. Prolyl hydroxylase activity was reduced both in sponge granulomas from glucocorticoid-treated mice and in hydrocortisone-treated fibroblast cultures. However, protein synthesis was inhibited to the same extent as the inhibition of prolyl hydroxylase activity and there was no effect on peptidyl prolyl hydroxylation. These results indicate that the glucocorticoid-induced reduction of collagen synthesis and accumulation observed in mouse granulomas and primary granuloma fibroblast cultures is not specific for this protein. Furthermore, glucocorticoid-induced inhibition of collagen synthesis cannot be attributed to underhydroxylation of collagen prolyl residues.

The effects of thromboxane B2 and 6-ketoprostaglandin F1alpha on cultured fibroblasts

The effects of thromboxane B2 and 6-ketoprostaglandin F1alpha on the synthesis of DNA, RNA and hexosamine-containing substances were studied. Thromboxane B2 (1 microgram/ml) added to cultures in the stationary phase caused the initiation of DNA synthesis and cell proliferation in a small proportion of cells. The same amount of thromboxane B2 also increased [3H]uridine incorporation into acid-insoluble fraction by 50% in 24 h, and stimulated the production of hexosamine-containing substances 2.5 fold over the control during the first 6 h. On the other hand, 6-ketoprostaglandin F1alpha was essentially inactive on these indexes except slight stimulation of DNA synthesis.

Stimulatory effect of prostaglandins on the production of hexosamine-containing substances by cultured fibroblasts (3) induction of hyaluronic acid synthetase by prostaglandin F2alpha

The mechanism of the stimulatory effect of prostaglandin(PG)F2alpha on the production of hexosamine-containing substances by cultured fibroblasts was studied. Treatment of the cells with 1 microgram/ml of PGF2alpha resulted in a doubled net synthesis of acidic glycosaminoglycans during 20 hrs measured with uronic acid as index, and also resulted in 300 per cent increase of 3H-glucosamine incorporation into hexosamine-containing substances during the first 6 hrs. Fractionation of the PGF2alpha-stimulated hexosamine-containing substances with double isotope technique revealed that hyaluronic acid was the most stimulated component. Prior to the increase of hyaluronic acid, hyaluronic acid synthetase activity was found to be augmented by PGF2alpha as high as 4 times over the control. The augmentation of hyaluronic acid synthetase activity by PGF2alpha did not take place if actinomycin D was simultaneously present in the culture medium, suggesting that PGF2alpha induced the enzyme.

Stimulative effect of prostaglandins on production of hexosamine-containing substances by cultured fibroblasts (2) early effect of various prostaglandins at various doses

Early effects of various prostaglandins on the production of hexosamine-containing substances by cultrued fibroblasts, which were derived from a rat carrageenin granuloma, were studied. At hte stationary phase, the cells were exposed for 6 h to one of the prostaglandin A1 (PGA1), A2, B1, B2, D2, F1 alpha, E1, E2 or arachidonic acid in various concentrations ranging from 0.01 to 10 microng/ml for all the stimuli and from 10 pg to 10 microng/ml for PGF2alpha. The activity of the cells in incorporating 3H-glucosamine into hexosamine-containing substances (acidic glycosaminoglycans and glycoproteins) during this period was compared with that of control cells. All the stimuli tested showed more or less stimulative effect on the synthesis of hexosamine-containing substances at their specific concentrations. PGF2alpha was found to be the most potent stimulant and its stimulative effect was found significant even at the low concentration of 100 pg/ml. PGD2, F1alpha and E2 were the next potent stimuli. Their optimum dose were aroung 1 microng/ml but they still had significant stimulation at the concentration of 0.01 microng/ml. Effect of PGE2 was rather mild. Stimulation by PGA1, A2, B1 and B2 or arachidonic acid was seen at high dose, and it seemed to be non-specific. The results suggested that these prostaglandins such as PGF2alpha, D2, F1alpha and E2 play some important role on regulating the production of intercellular ground substances.

Stimulation by prostaglandin F2alpha of acidic glycosaminoglycan production in cultured fibroblasts

The effect of PGF2alpha on the synthesis of hexosamine-containing substances (acidic glycosaminoglycans and glycoproteins) was studied in cultured fibroblasts derived from a rat carrageenin granuloma. Treatment with PGF2alpha ranging from 0.01 mug/ml to 20 mug/ml resulted in a significant increase of the production of these macromolecules by the cells. The stimulatory effect was found significant even at the low concentration of 10 ng/ml, and could be seen as early as 3h after exposure to PGF2alpha. The hexosamine-containing substances increased by PGF2alpha revealed that 80% of the increase was due to acidic glycosaminoglycans and the rest was due to glycoproteins.

Stimulatory effect of bleomycin on the synthesis of acidic glycosaminoglycans in cultured fibroblasts derived from rat carrageenin granuloma

Cultured fibroblasts derived from rat carrageenin granuloma were treated with bleomycin and the synthesis of hexosamine-containing substances was compared with that in control cells. Four day treatment with o.1 mug bleomycin/ml resulted in a significant increase of the production of these macromolecules by the cells, though DNA synthesis was remarkably inhibited at this dose of bleomycin. The stimulatory effect could be seen as early as the second day of bleomycin treatment, and was enhanced with increasing treatment time. Further fractionation of the hexosamine-containing substances revealed that synthesis of acidic glycosaminoglycans was more sensitive to bleomycin than that of glycoproteins, i.e., acidic glycosaminoglycans increased by 80% and glycoproteins by 53% after four day treatment with 0.1 mug bleomycin/ml. The increased components of acidic glycosaminoglycans included not only hyaluronic acid but also sulphated glycosaminoglycans. Collagen synthesis was increased by 23% by the same dose of bleomycin. N-Acetyl-beta-glucosaminidase, one of the degradation enzymes for acidic glycosaminoglycans released into the cultured medium, was decreased significantly by bleomycin.