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Biomedical subjects

U H Lerner

Publications and source records attributed to U H Lerner.

At least 91 records · Page 5Linked to original sources
PubMed1991

Thrombin increases cytoplasmic Ca2+ and stimulates formation of prostaglandin E2 in the osteoblastic cell line MC3T3-El.

Using microfluorometric analysis in individual, fura-2 loaded cells, we found that thrombin (0.1-10 U/ml) caused a dose-dependent (EC50 approximately 0.5 U/ml), rapid (within seconds), transient increase in cytoplasmic Ca2+ in the osteoblastic cell line MC3T3-El. The thrombin induced rise in cytoplasmic Ca2+ was not dependent on extracellular Ca2+ and was unaffected by indomethacin. In MC3T3-El cells, thrombin (0.3-10 U/ml) caused a rapid and dose-dependent (EC50 approximately 0.5 U/ml) stimulation of PGE2 formation. The calcium ionophore A23187 (2 mumol/l) also rapidly stimulated an increase in cytoplasmic Ca2+ and the formation of PGE2 in MC3T3-El cells. These data indicate that thrombin mobilizes Ca2+ from intracellular stores and that Ca2+ may serve as a second messenger in thrombin induced stimulation of PGE2 biosynthesis in osteoblasts.

Animals↗
PubMed1991

Comparison of human interleukin-1 beta and its 163-171 peptide in bone resorption and the immune response.

Human interleukin-1 beta (IL-1 beta) caused a dose- and time-dependent enhancement of the release of 45Ca from prelabeled mouse calvaria in organ culture. In addition, IL-1 beta dose-dependently stimulated the formation of prostaglandin E2 (PGE2) and 6-keto-PGF1 alpha in the calvarial bones. However, IL-1 beta-induced 45Ca release was only partially inhibited by blocking the PGE2 response with indomethacin, suggesting that enhanced PGE2 formation in response to IL-1 beta is not necessary to obtain a bone resorptive effect, but that prostaglandins potentiate the action of IL-1 beta. The synthetic nonapeptide VQGEESNDK, corresponding to the fragment 163-171 of human IL-1 beta, administered simultaneously with antigen (SRBC) to C3H/HeN male mice, induced a dose-dependent enhancement of specific antibody-producing cells in the spleen (PFC). The degree of PFC stimulation was comparable to that caused by native human IL-1 beta. In mouse bone cultures, neither 45Ca release nor prostanoid formation was stimulated by fragment 163-171. These data indicate that (1) IL-1 beta-induced stimulation of bone resorption is dissociable from IL-1 beta-induced increase of prostanoid biosynthesis and (2) the epitope of the IL-1 beta molecule involved in the immunostimulatory effects may be different from that involved in the stimulatory effects on bone resorption.

Amino Acid Sequence↗
PubMed1991

On the role of polyamines in bone resorption induced by parathyroid hormone.

In order to elucidate the possible role of polyamines in the mobilization of mineral from long-term bone cultures stimulated with parathyroid hormone we have measured the activity of ornithine decarboxylase in osteoblasts, the levels of polyamines in calvarial bone and determined the effect of added polyamines and inhibitors of polyamine biosynthesis on calcium mobilization. Parathyroid hormone (10 nmol l-1) stimulated omithine decarboxylase activity by approximately 50% in both cultured bone cells of osteoblastic phenotype, UMR 106 and in mouse calvarial osteoblast-like cells. In mouse calvaria the levels of putrescine and spermidine were increased by parathyroid hormone after 24 hours. The levels of spermine were very low and were unchanged by parathyroid hormone. The two polyamine synthesis inhibitors alpha-difluoromethylornithine (DFMO; 2 mmol l-1) and methylglyoxal-bis-guanylhydrazone (MGBG; 50 mu mol l-1) did not significantly affect the mobilization of 45Ca from parathyroid hormone-stimulated bones. All three polyamines, putrescine, spermidine and spermine, inhibited the mobilization of 45Ca induced by parathyroid hormone in a dose-dependent manner. The inhibition induced by putrescine was reversible. In summary, we have shown that parathyroid hormone increases the accumulation of polyamines in bone, but the effect is small. Furthermore, inhibition of polyamine biosynthesis does not reduce parathyroid hormone-induced mineral mobilization and the addition of polyamines leads to a reduced rather than a stimulated mineral mobilization. Thus, polyamines do not seem to be critically involved in the changes in bone resorption induced by parathyroid hormone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Bradykinin stimulates prostaglandin E2 formation in isolated human osteoblast-like cells.

The effect of bradykinin on prostaglandin E2 formation in cells from human trabecular bone has been studied. The cells responded to parathyroid hormone with enhanced cyclic AMP formation and were growing as cuboidal-shaped, osteoblast-like cells. In these isolated human osteoblast-like cells, bradykinin (1 mumol/l) caused a rapid (5 min) stimulation of prostaglandin E2 formation. This finding indicates that human osteoblasts are equipped with receptors for bradykinin linked to an increase in prostaglandin formation.

Bradykinin↗
PubMed1990

Stimulation of bone resorption and cell proliferation in vitro by human gingival fibroblasts from patients with periodontal disease.

In the present communication we report that fibroblasts, isolated from human gingiva obtained from 13 different patients, secreted soluble product(s) which can promote bone resorption in vitro. Fibroblasts were isolated from explants of human gingiva, subcultured, grown to confluent monolayers, subsequently cultured in growth arrest media for 0-72 h and conditioned media harvested. Bone resorption was assessed in cultured mouse calvarial bone by quantifying the mobilization of minerals and the release of lysosomal enzymes. Human fibroblast-conditioned media (HFCM) dose-dependently stimulated the release of 45Ca from prelabelled bones and the mobilization of stable calcium and inorganic phosphate from unlabelled bones. In addition, HFCM increased the release of beta-glucuronidase and beta-N-acetylglucosaminidase from the calvaria. No effect of HFCM on the release of 45Ca from dead bones could be seen. HFCM caused a dose-dependent increased degradation of bone matrix proteins, as assessed by the release of 3H from [3H]proline-labelled calvaria. The stimulation of 45Ca release could already be seen after 3-12 h of treatment. Treatment of the bones with HFCM for 12 h was sufficient to obtain a prolonged stimulation of 45Ca release. Bones cultured in the presence of HFCM showed an increased number of osteoclasts. Calcitonin, but not indomethacin, inhibited 45Ca release stimulated by HFCM. Ultrafiltration of HFCM did not cause any loss of the 45Ca release response. The amount of bone-resorbing activity produced by the gingival cells was proportional to the number of cells. In addition, HFCM stimulated the proliferation of human fibroblasts and osteoblast-enriched mouse calvarial bone cells. It is concluded that human gingival fibroblasts secrete one or several factors that can stimulate osteoclastic bone resorption in vitro by a prostaglandin-independent pathway.

Adult↗
PubMed1990

Evidence for BK1 bradykinin-receptor-mediated prostaglandin formation in osteoblasts and subsequent enhancement of bone resorption.

1. The effects of the BK1 bradykinin (BK)-receptor agonist des-Arg9-BK on bone resorption and prostaglandin formation in osteoblasts have been studied. 2. Des-Arg9-BK (1 microM) stimulated the release of 45Ca from prelabelled neonatal mouse calvarial bones and the formation of prostaglandin E2 (PGE2) in calvarial bones. The stimulatory effect on bone resorption and PGE2 formation could be totally inhibited by indomethacin, flurbiprofen and hydrocortisone. 3. The BK1 receptor antagonist des-Arg9-Leu8-BK (10 microM) inhibited des-Arg9-BK (0.01-0.1 microM)-induced release of 45Ca from prelabelled neonatal mouse calvarial bones, while leaving BK (0.1-1 microM)-induced 45Ca release unaffected. 4. In isolated osteoblast-like cells from neonatal mouse calvarial bones, des-Arg9-BK (1 microM) induced a slowly developing increase in PGE2 formation that was significantly different from untreated controls after 24 h. Treatment with BK caused a rapid burst (within minutes) of PGE2 formation. 5. Des-Arg9-Leu8-BK (10 microM) selectively inhibited des-Arg9-BK (1 microM)-induced PGE2 and prostacyclin formation in isolated osteoblast-like cells incubated for 72 h. Des-Arg9-Leu8-BK did not affect BK and Lys-BK (1 microM)-induced PGE2 and prostacyclin formation in isolated osteoblast-like cells incubated for 72 h. 6. These data indicate that osteoblasts are equipped with BK1-receptors mediating enhanced prostaglandin formation and subsequent bone resorption.

Animals↗
PubMed1990

Bradykinin-2 receptor-mediated release of 3H-arachidonic acid and formation of prostaglandin E2 in human gingival fibroblasts.

Bradykinin stimulated production of prostaglandin E2 (PGE2) and the release of 3H-arachidonic acid by gingival fibroblasts in a time- and dose-dependent manner. The effect on PGE2 biosynthesis was seen already after 15 seconds and was maximal after 5 minutes. Several structurally unrelated inhibitors of arachidonic acid metabolism via the cyclooxygenase pathway totally abolished the PGE2 response to bradykinin. The stimulation of PGE2 formation was seen at and above 10 nmol/l of bradykinin. Des-Arg9-bradykinin was 100-fold less potent compared to bradykinin. Des-Arg9-Leu8-bradykinin did not antagonize bradykinin-induced PGE2 formation. Met-Lys-bradykinin and Lys-bradykinin also enhanced PGE2 formation in gingival fibroblasts. The stimulatory action of bradykinin on 3H-arachidonic acid release was observed after 30 s and progressively increased for at least 15 min. The stimulatory effect on 3H-arachidonic acid release by bradykinin was seen at and above 10 nmol/l, whereas des-Arg9-bradykinin was without effect up to a concentration of 1 mumol/l. Indomethacin did not affect bradykinin-induced 3H-arachidonic acid release. These data show that bradykinin, via a B2-receptor-mediated pathway, can stimulate arachidonic acid release and subsequent prostanoid formation in gingival fibroblasts. Consequently, gingival fibroblasts may contribute, by a bradykinin-regulated reaction, to the enhanced amounts of prostanoids found in gingival tissues and crevicular fluids in patients with periodontal diseases.

Analysis of Variance↗
PubMed1990

Calcitonin causes a sustained inhibition of protein kinase c-stimulated bone resorption in contrast to the transient inhibition of parathyroid hormone-induced bone resorption.

Calcitonin is a well known inhibitor of osteoclastic bone resorption, both in vivo and in vitro. However, it is also known that calcitonin has only a transient inhibitory effect on bone resorption. The mechanism for this so-called "escape from inhibition" phenomenon is not clear. In the present study, the inhibitory effect of calcitonin on phorbol ester-induced bone resorption was examined in cultured neonatal mouse calvaria. Bone resorption was assessed as the release of radioactivity from bones prelabelled in vivo with 45Ca. Two protein kinase C-activating phorbol esters, phorbol-12-myristate-13-acetate and phorbol-12,13-dibutyrate, both stimulated 45Ca release in 120-h cultures at a concentration of 10 nmol/l. Calcitonin (30 nmol/l) inhibited phorbol ester-stimulated bone resorption without any "escape from inhibition". This was in contrast to the transient inhibitory effect of calcitonin on bone resorption stimulated by parathyroid hormone (10 nmol/l), prostaglandin E2 (2 mumol/l), and bradykinin (1 mumol/l). Our results suggest that activation of protein kinase C produces a sustained inhibitory effect of calcitonin on bone resorption.

Animals↗
PubMed1990

The pathogenesis of loosening of total hip arthroplasties. The production of factors by periprosthetic tissues that stimulate in vitro bone resorption.

The production of factors capable of stimulating bone resorption in the newly formed periprosthetic capsule and in the bone-cement membrane obtained from patients reoperated due to aseptic loosening of cemented total hip prostheses was studied using organ culture techniques. Addition of culture media conditioned by membranes from six patients and bone-cement membranes from two patients to the mouse calvarial cultures resulted in a significantly increased release of calcium. The effect of capsule-conditioned media on calcium release was dose- and time-dependent and significantly reduced by the osteoclast inhibitor of calcitonin. Histologic analysis of bones at the end of the culture period showed that capsule-conditioned media enhanced the breakdown of mineralized bone and increased the number of osteoclasts. The observations showed that newly formed periprosthetic tissues from patients with loose total hip arthroplasties (THAs) can produce one or several factors that stimulate bone resorption in vitro by an osteoclast-mediated mechanism. Not only mechanical failure but also biologic reactions in the periprosthetic tissues eventually lead to osteoclast activation and may contribute to the loosening of THAs.

Adult↗
PubMed1989

Renal cell carcinoma in tissue culture secretes nondialyzable product that stimulates bone resorption in organ-cultured mouse calvaria.

The bone-resorbing capacity of human renal cell carcinomas in vitro has been examined. Bone resorption in cultures of mouse calvarial bones was assessed by the release of 45Ca from bones prelabeled in vivo and the mobilization of stable calcium and inorganic phosphate from nonlabeled bones. In addition, bone organic matrix degradation was determined either by the release of 3H from [3H]proline-labeled bones or by the loss of hydroxyproline from bone explants during culture. Tumor tissue-conditioned media (TCM) from 13 of 13 renal cell carcinomas stimulated bone resorption in a dose-dependent manner. From 5 of 13 kidneys with renal cell carcinoma, normal kidney cortex tissue was cultured and 4 of these 5 also produced bone-resorbing activity, but the amount was much less compared with the tumor tissue. The stimulatory effect of TCM on 45Ca release could be observed first after 12-24 h of culture. The effect could be inhibited by calcitonin but not by inhibitors of prostaglandin synthesis. The production of bone-resorbing activity by tumor cells could be inhibited by indomethacin and meclofenamic acid. In some tumors, the inhibition by indomethacin was total, whereas in other tumors only partial inhibition could be obtained. In 3 of 4, TCM bone-resorbing activity could be found in the retentate after dialysis. The results show that fresh human renal cell carcinoma tissue can elaborate prostanoid as well as nonprostanoid products that can stimulate bone resorption.

Animals↗
PubMed1989

Bradykinin stimulates production of prostaglandin E2 and prostacyclin in murine osteoblasts.

The effect of bradykinin on prostaglandin production in mouse calvarial bones and in isolated osteoblasts has been examined. Bradykinin (1 mumol/l) stimulated prostaglandin formation in neonatal mouse calvarial bones incubated for 30 min. In isolated osteoblast-like cells from neonatal mice calvarial bones and in a cloned mouse calvarial osteoblastic cell lineage (MC3T3-E1) bradykinin stimulated the production of prostaglandin E2 (PGE2) and 6-keto-prostaglandin F1 alpha (the stable breakdown product of prostacyclin). The stimulation of PGE2 production occurred rapidly (30 s) and reached its maximum after 5-10 min. The stimulatory effect of bradykinin on PGE2 production in isolated osteoblast-like cells and in MC3T3-E1 cells was dose dependent with apparent half maximal stimulation seen at 10 and 3 nmol/l, respectively. Bradykinin-induced prostaglandin production was totally reversible after withdrawal of the agonist. Pretreatment with bradykinin (1 mumol/l) resulted in desensitization to a subsequent challenge with bradykinin (1 mumol/l), while pretreatment with bradykinin had no effect upon arachidonic acid (30 mumol/l) induced prostaglandin formation. Bradykinin-induced production of PGE2 was abolished by several structurally unrelated, competitive and non-competitive inhibitors of arachidonic acid metabolism as well as by corticosteroids. The mouse calvarial osteoblast-like cells also showed a PGE2 and 6-keto-PGF1 alpha response to thrombin, but not to parathyroid hormone (PTH), calcitonin and 1 alpha(OH)D3. The formation of cyclic AMP in mouse calvarial osteoblasts was enhanced by PTH, bradykinin, thrombin and arachidonic acid but not by calcitonin and 1 alpha(OH)D3. The cyclic AMP response to bradykinin, thrombin and arachidonic acid, but not that to PTH, was abolished by indomethacin. The degree of confluency of the cell cultures greatly influenced the amount of prostaglandins being produced. At higher cell density the amount of prostanoids synthesized per cell was substantially decreased in untreated control cultures as well as in bradykinin- and arachidonic acid-treated cells. These data suggest that osteoblasts are equipped with receptors for bradykinin coupled to prostaglandin production.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Forskolin sensitizes parathyroid hormone-induced cyclic AMP response, but not the bone resorptive effect, in mouse calvarial bones.

The effect of forskolin on parathyroid hormone (PTH) stimulated bone resorption, as assessed in vitro by the release of 45Ca from prelabelled neonatal mouse calvarial bones, and cyclic AMP formation in mouse calvarial bones and osteoblast-like cells was investigated. Much higher concentrations (100-300-times) of PTH were required to stimulate cyclic AMP accumulation than to stimulate mineral mobilization in murine calvarial bones. PTH, in the absence of phosphodiesterase inhibitor, stimulated cyclic AMP formation in mouse calvarial bones at and above concentrations of 3-10 nmol/l with EC50 at 10-15 nmol/l. In the presence of forskolin (1 or 10 mumol/l) the minimal concentration required to obtain a cyclic AMP response to PTH was decreased by a factor of 30-100 and the EC50 value was decreased to 1-2 nmol/l. Similar results were seen in osteoblast-enriched cells. In addition, the magnitude of the PTH-induced cyclic AMP response was substantially potentiated by forskolin, both in calvarial bones and in isolated osteoblasts. Forskolin, in the absence of PTH, stimulated cyclic AMP levels in mouse calvaria at and above 1 mumol/l. In the presence of PTH, the response to forskolin was potentiated over the whole dose-response curve with apparent EC50 value at 1-2 mumol/l of forskolin. Forskolin (1 mumol/l) did not affect the magnitude of the 45Ca release response to PTH in 24 or 48 h cultures. In 96 h cultures, forskolin, in an additive manner, potentiated the effect of PTH on calcium mobilization. These results show that forskolin, in mouse calvarial bones and in isolated osteoblasts, in addition to directly stimulating cyclic AMP, can enhance receptor-mediated activation of adenylate cyclase. The finding that forskolin did not synergistically potentiate PTH-induced bone resorption suggests that there is no simple relationship between PTH-induced cyclic AMP formation and stimulation of bone resorption.

Animals↗
PubMed1989

Comparison between the effects of forskolin and calcitonin on bone resorption and osteoclast morphology in vitro.

The adenylate cyclase activator forskolin (1-10 mumol/L) inhibited 45Ca release from parathyroid hormone (PTH; 10 nmol/L) stimulated prelabeled neonatal mouse calvaria in short term culture (24 h). This effect of forskolin was potentiated by rolipram, Ro 20-1724, and isobutyl-methylxanthine, three structurally different inhibitors of cyclic AMP phosphodiesterase. Forskolin (10 mumol/L) and calcitonin (30 mU/mL) inhibited the mobilization of stable calcium and inorganic phosphate as well as the release of the lysomal enzymes beta-glucuronidase and beta-N-acetylglucosaminidase from PTH-stimulated unlabeled bones. Osteoclasts in PTH-stimulated calvaria showed active ruffled borders with numerous membrane infoldings. Treatment of PTH-stimulated bones with forskolin and calcitonin resulted in a rapid (2 h) loss of the active ruffled border. In addition, forskolin and calcitonin induced similar changes with respect to the number and size distribution of cytoplasmic vesicles in PTH-activated osteoclasts. After 24 h, all signs of osteoclast inactivation were still prominent, whereas after 48 h of treatment with forskolin or calcitonin, the reappearance of a ruffled border on a number of osteoclasts signaled an escape from the inhibitory action of both calcitonin or forskolin. These data indicate that forskolin inhibits bone resorption by a cyclic AMP dependent mechanism and that the effect of forskolin and calcitonin on bone resorption and osteoclast morphology are comparable. These observations lend further support to the view that cyclic AMP may be an intracellular mediator of the inhibitory action of calcitonin on multinucleated osteoclasts.

Acetylglucosaminidase↗
PubMed1989

Thrombin and bradykinin enhance prostaglandin production in human peripheral blood monocytes.

Thrombin and bradykinin stimulate production of prostaglandin E2 (PGE2), and 6-keto-prostaglandin F1 alpha (the stable breakdown product of prostacyclin) in isolated human peripheral blood monocytes in a dose- and time-dependent manner. Since PGE2 and prostacyclin can affect the activity of immunocompetent cells and bone resorbing osteoclasts, our finding indicates that thrombin and bradykinin, both of which are formed in inflammatory processes as a consequence of activation of the Hageman factor (coagulation factor XII), may have important roles in the modulation of the inflammatory response and the loss of alveolar bone in periodontitis.

Arachidonic Acids↗
PubMed1989

Parathyroid hormone stimulates prostanoid formation in mouse calvarial bones.

Bovine parathyroid hormone (bPTH 1-34) caused a time- and dose-dependent enhanced formation of the two prostanoids PGE2 and 6-keto-PGF1 alpha in cultured neonatal mouse calvarial bones, with threshold for action at 0.1 nmol/l. The PGE2 response to PTH was completely blocked by indomethacin, but insensitive to calcitonin. By contrast, indomethacin was without effect on 45Ca release induced by PTH. The PTH analogues (Nle 8, 18, Tyr 34)-bPTH (3-34) amide and (Tyr 34)-bPTH (7-34) amide, which are putative PTH antagonists, did not affect basal production of PGE2, nor did the analogues affect bPTH 1-34 induced PGE2 formation. The data show that PTH stimulates prostanoid formation in mouse bone cells and that this response is not directly linked to PTH-induced bone resorption.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Blood coagulation and bone metabolism: some characteristics of the bone resorptive effect of thrombin in mouse calvarial bones in vitro.

Chronic inflammatory processes are often associated with bone resorption. Stimulated by the current great interest in the role of coagulation factors in inflammation and immune injury, we have studied the effect of thrombin on mouse calvarial bones in vitro. Thrombin caused a dose-dependent (0.1-7 U/ml) stimulation of 45Ca release from neonatal mouse calvarial bones. Thrombin also stimulated the mobilization of stable calcium and inorganic phosphate, the release of 3H from [3H]proline-labelled calvaria, the production of lactate and the release of the lysosomal enzymes, beta-glucuronidase and beta-N-acetylglucosaminidase. Thrombin also enhanced 45Ca release from fetal rat long bones, although this bone resorption assay was less sensitive to thrombin than the mouse calvarial system. The bone resorption stimulatory activity of thrombin in mouse calvaria could be inhibited by calcitonin and an increased concentration of phosphate in the culture medium. Thrombin-induced 45Ca release in mouse calvaria was sensitive to inhibition by hydrocortisone and dexamethasone. By contrast, 45Ca release response to parathyroid hormone was insensitive to corticosteroids. The prostaglandin synthetase inhibitors indomethacin, meclofenamic acid and naproxen and 5,8,11,14-eicosatetraynoic acid reduced 45Ca release from thrombin-stimulated calvaria. However, significant stimulation by thrombin could be achieved also in bones treated with inhibitors of arachidonate metabolism. The results obtained suggest that thrombin can stimulate cell-mediated bone resorption by an osteoclast-dependent mechanism. The mechanism of action may involve both prostaglandin-dependent and prostaglandin-independent pathways. Our findings indicate that thrombin may contribute to the bone resorptive processes seen in periodontal disease and rheumatoid arthritis.

Adrenal Cortex Hormones↗