Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:APRD00369 (ROS)
 19,271 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Parathyroid hormone degradation is intimately connected with its action. By the action of the unique renal neutral cytosolic PTH ase, PTH is split into 1-34 and 35-84 fragments, and further into 35-70 and 71-84 fragments. Amino-terminal 1-34 peptide was found to participate in the autoregulation of PTH secretion, suppressing the intact PTH secretion both in vivo in humans and in vitro in the dispersed bovine parathyroid cells. C-terminal fragment 35-84 and N-terminal fragment 1-34 both suppress the alkaline phosphatase production by ROS 17/2.8 cells to a lesser extent than the intact PTH 1-84, and the sum of the effects of the two fragments approximately equaled that of the intact hormone. Fragments 35-70 and 71-84 were devoid of such activity. Intracellular free calcium of human vascular endothelial cells was raised by intact 1-84, lowered on the contrary by C-terminal 35-84 fragment, but fragments 1-34, 35-70 and 71-84 had no effect. Fragments generated by the actions, supporting the physiological significance of PTH degradation by its target cells.
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PMID:New actions of parathyroid hormone through its degradation. 130 Mar 29

In the present study the involvement of protein kinase-C (PKC) in the regulation of the vitamin D receptor (VDR) and interaction of PKC with cAMP-induced up-regulation of VDR in osteoblast-like cells were examined. Activation of PKC by incubation for 4 h with the phorbol ester phorbol 12-myristate 13-acetate (PMA) resulted in a comparable dose-dependent decrease in 1,25-dihydroxyvitamin D3 binding in the osteoblast-like cell lines UMR 106 and ROS 17/2.8, with a maximum inhibition at 100 nM and an IC50 at 5 nM PMA. Time-course studies revealed that in both UMR 106 and ROS 17/2.8 cells, 24-h incubation with PMA caused an increase in 1,25-dihydroxyvitamin D3 binding. This can be related to down-regulation of PKC. Scatchard analysis demonstrated that activation of PKC resulted not in a change in receptor affinity, but, rather, in an increase in VDR number. This is supported by Northern blot analysis, which shows at 2 h a decrease and at 24 h an increase in VDR mRNA. At 4 h, when activation of the cAMP pathway results in an increase in VDR, activation of PKC results in a decrease in VDR. Coincubation for 4 h with PMA caused a decrease in PTH- and forskolin-induced up-regulation of VDR. This inhibition is not due to a reduction in cAMP production, as PTH-stimulated cAMP production was potentiated by PMA. The effect of activation of PKC on VDR is not a general effect, as PMA does not affect basal ornithine decarboxylase activity and potentiates PTH-induced ornithine decarboxylase activity. The present study demonstrates that PKC is involved in the regulation of VDR in UMR 106 and ROS 17/2.8 and that PKC interacts with cAMP in the regulation of VDR. The current data point to a negative controlling role for PKC in the regulation of VDR. Moreover, two different cAMP-regulated actions in UMR 106 cells (VDR up-regulation and ornithine decarboxylase activity) are differently modulated by PKC. Although the precise mechanism by which PKC represses and stimulates gene expression is not yet clear, this study demonstrates the important regulatory role for PKC in two osteoblast-like sarcoma cell lines.
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PMID:Bidirectional regulation of the 1,25-dihydroxyvitamin D3 receptor by phorbol ester-activated protein kinase-C in osteoblast-like cells: interaction with adenosine 3',5'-monophosphate-induced up-regulation of the 1,25-dihydroxyvitamin D3 receptor. 131 52

The present study was designed to further understand the role of PTH on the secretion of the neutral metalloproteinases, collagenase and gelatinase, from the rat osteosarcoma clonal cell line, ROS 17/2.8. Semiconfluent cells were treated with bovine parathyroid hormone, b-PTH-(1-34) at 100 nM-0.01 nM for 24-96 hours and pooled, concentrated media were analyzed by functional assay for collagenase (3H-methyl collagen) and gelatinase (3H-methyl gelatin). Collagenase activity significantly decreased (P less than 0.01) in the PTH conditioned media in a dose-dependent manner before (98-64%) and after (91-39%) reduction and alkylation. SDS-PAGE and fluorography apparently showed the most degradation to alpha A chains in collagen with controls, whereas this substrate remained intact with PTH (100 nM). PTH (100 nM) media also showed neutral gelatinase activity approximately 2% compared to control before and after reduction and alkylation (P less than 0.01). Significant amounts of an inhibitor to collagenase and gelatinase might have been secreted at 1 nM and 0.01 nM PTH, since collagenase and gelatinase activities were greater after reduction and alkylation. Reduction and alkylation likely destroyed these significant amounts of inhibitor. Polymorphonuclear leukocyte collagenase activity was also inhibited 80% by PTH conditioned media, but not by control. However, upon reduction and alkylation which destroyed inhibitor, the PTH treated media showed only a 14% inhibition against polymorphonuclear leukocyte collagenase (P less than 0.01). PTH appeared to downregulate neutral metalloproteinase activities through its effects on an inhibitor. This downregulation may represent a specific phenotypic response to PTH in ROS 17/2.8 cells.
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PMID:Parathyroid hormone regulation of matrix degrading enzymes in rat osteoblastic osteosarcoma 17/2.8 cells. 132 16

The effects of the immunosuppressive drug cyclosporin A (CsA) were evaluated on ROS 17/2.8 cells in vitro. ROS cells were treated with CsA (0, 0.5, 1.0, 5.0 micrograms/ml) for 3 days with and without bovine parathyroid hormone (bPTH) (1-34) 10 nM. CsA at 0.5, 1.0, 5.0 micrograms/ml without PTH and at 5.0 micrograms/ml in the presence of PTH significantly inhibited proliferation, as determined by a tetrazolium colorimetric assay. In addition, ROS cell number was significantly reduced at 3 and 4 days with CsA (5.0 micrograms/ml) without affecting cell viability. Incorporation of [3H]-thymidine into DNA was significantly reduced by 3.0 and 5.0 micrograms/ml CsA after 12 and 24 hours exposure. Basal and 1,25-dihydroxyvitamin D3-stimulated alkaline phosphatase levels in confluent ROS cells were reduced (P less than 0.05) with CsA (1.0 and 3.0 microgramS/ml). Pretreatment of ROS 17/2.8 cells with CsA did not alter PTH-stimulated cAMP levels or [125I]-PTHrP binding to ROS cells. CsA treatment of ROS 17/2.8 cells induced a spindle-shaped appearance with loss of attachment in confluent cultures. When ROS cells were cultured in CsA-containing media, cellular attachment at 6 and 12 hours was reduced (P less than 0.05) compared with untreated ROS cells. These findings indicate that CsA was capable of inhibiting proliferation, cell number, mitogenesis, alkaline phosphatase levels, and cell attachment of ROS cells without affecting PTH binding or cAMP levels. This direct effect of CsA on osteoblasts may be important in changes of bone remodeling observed in CsA-treated humans and animals.
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PMID:Effects of cyclosporin A on rat osteoblasts (ROS 17/2.8 cells) in vitro. 133 Feb 39

PTH receptors on osteoblasts and calcitonin receptors on osteoclasts are coupled to adenylate cyclase. Despite similar transduction mechanisms, these hormones have opposing physiological actions. We investigated the consequences of persistent protein phosphorylation on bone resorption in neonatal mouse calvariae using okadaic acid (OA) and calyculin-A, two inhibitors of protein phosphatase-1 and -2A. These two inhibitors caused different responses in bone at picomolar and low nanomolar concentrations. OA inhibited, in a dose-dependent manner, bone resorption stimulated by PTH, 1,25-Dihydroxyvitamin D3, phorbol ester, and prostaglandin E2 (PGE2). OA did not inhibit the generation of the second messengers cAMP or PGs and did not have nonspecific toxic effects, as measured by protein and RNA synthesis. Thus, OA appeared to mimic the global inhibitory action of calcitonin on bone resorption. Unlike OA, calyculin-A elicited a biphasic dose response. At concentrations of 3.3 nM and greater, calyculin-A inhibited, in a dose-dependent manner, stimulated bone resorption. However, calyculin-A alone, at 0.625 and 2.5 nM, stimulated bone resorption via a PG-independent pathway. In calvariae, OA and calyculin-A increased phosphorylation of a 58- to 60-kilodalton protein. A protein of similar molecular mass was hyperphosphorylated in OA-treated ROS 17/2.8 osteoblast-like cells. We conclude that in addition to hormonal regulation of protein kinase activity, protein dephosphorylation plays a functionally important role in the modulation of bone resorption.
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PMID:Protein phosphatase inhibitors and bone resorption: inhibition by okadaic acid and biphasic actions of calyculin-A. 137 1

Local secretion of insulin-like growth factor binding proteins (IGFBPs) may modulate the effects of IGF-I and IGF-II on bone cell metabolism and proliferation. Several osteoblast-derived cell lines are currently used as interchangeable models to study IGFBP production, although it is unknown whether findings in one cell line can be extrapolated to another cell line or to normal human osteoblasts. In this study, we examined by Western ligand blotting both basal and regulated secretion of IGFBPs in vitro in 1) normal human osteoblast-like (hOB) cells cultured from explants of human trabecular bone; 2) an SV40-transformed hOB (HOBIT) cell line; and 3) several human (U-2, MG-63, TE-85) and rat (ROS 17/2.8 and UMR-106-01) osteosarcoma cell lines. Constitutively, hOB and HOBIT cells produced a similar pattern of IGFBPs, while all other cell lines produced their own unique pattern of IGFBPs. The two rat cell lines differed from the human cell lines as well as from each other. The response to hormonal stimulation also varied among the cell lines. Treatment of hOB and HOBIT cells with IGF-I resulted in a 2-fold increase in medium levels of IGFBP-3; IGF-I decreased levels of 24-kilodalton (kDa) IGFBP in hOB cell-conditioned medium. In addition, IGF-I markedly increased levels of the 29/32/34 kDa IGFBP triplet in U-2 cells, but had little or no effect in the other human and rat osteosarcoma cell lines. PTH increased a 29-kDa IGFBP apparent only in UMR 106-01 cell-conditioned medium, whereas GH had no direct effect on IGFBP secretion in any of the osteoblast-like cells tested. We conclude that basal and regulated secretion of IGFBPs from osteoblast-like cells is cell-line specific. Spontaneously transformed human or rat osteoblast-like cells provide unique model systems to study features of distinct IGFBPs and their regulation; however, hOB cells and their derivatives may be more appropriate models for understanding the regulation of IGFs in human bone.
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PMID:Basal and regulated secretion of insulin-like growth factor binding proteins in osteoblast-like cells is cell line specific. 137 4

Fibroblast-like rat marrow stromal cell (CFU-F) cultures have been characterized in terms of their responsiveness to calciotropic hormones, metal ions, the nonsteroidal antiinflammatory drug, and by their putative paracrine role in the maintenance of active populations of osteoblasts at the marrow-bone interface. These studies indicate that CFU-Fs lack a complete osteoblast signature. Subconfluent CFU-Fs grown in the presence or absence of 10(-7) M dexamethasone lack receptors for PTH and calcitonin, and fail to show enhanced cAMP or cGMP responses to 10(-7) M 1-34 PTH (rat), or any evidence of osteocalcin production [+/- 10(-9) M 1,25-(OH)2D3]. Low concentrations of fluoride [10(-12) and 10(-9) M] stimulated CFU-F grown in vitro in serum-free media, though higher levels (10(-7) and 10(-6) M), inhibited growth in vivo and in vitro. Aluminum (10(-12)-10(-7) M) and ibuprofen (10(-7) M) did not alter normal growth patterns, indicating an action on bone cells more differentiated than CFU-Fs. Serum-free conditioned medium (CM) from control and ovariectomized (OVX)/OVX+ dihydrotachysterol-Rx rat CFU-F cultures was mitogenic for neonatal rat calvarial osteoblasts in vitro, but not for ROS 17/2.8 cells. The studies affirm the mesenchymal-like character of CFU-Fs and project their significant role in sustaining functional endosteal osteogenic cell populations.
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PMID:Partial characterization of rat marrow stromal cells. 164 62

22-Oxacalcitriol (OCT), a synthetic vitamin D analog, can mimic the ability of 1,25-dihydroxyvitamin D3[1,25-(OH)2D3] to differentiate leukemia and skin cells, to enhance the immune response and to suppress PTH secretion, but has much less calcemic activity. The mechanism for this selective action is not understood. OCT has been shown to have a diminished ability to mobilize calcium from bone in vivo, but in vitro findings are contradictory. Little is known about the effect of OCT on bone forming cells. Therefore, the present studies were designed to investigate the actions of OCT at the molecular level in the osteoblast-like cell line, ROS 17/2.8. 3H-OCT was bound to the vitamin D receptor (VDR) in intact cells at the same rate as 3H-1,25-(OH)2D3. As previously found for 1,25-(OH)2D3, the time course of specific binding of OCT was biphasic, with an initial plateau at 1 h and a further increase from 2-8 h. Scatchard analysis demonstrated that exposure to 3H-1,25-(OH)2D3 increased VDR from 24 fmol/mg protein at 2 h to 85 fmol/mg protein at 8 h. Exposure to 3H-OCT increased VDR from 22 to 76 fmol/mg protein, indicating that OCT is also capable of up-regulating the VDR in ROS 17/2.8 cells. In contrast to the lower affinity of OCT for VDR reported for chick intestine and HL-60 cells, the Kd for OCT in intact ROS 17/2.8 cells was identical to that for 1,25-(OH)2D3. The effect of OCT on osteocalcin secretion and alkaline phosphatase (ALP) activity in ROS 17/2.8 cells was also determined. Pretreatment for 24 h with either 1,25-(OH)2D3 or OCT resulted in a dose-dependent enhancement of osteocalcin secretion. A 2-fold stimulation by both compounds was observed with 10(-7)M. ALP activity was measured after a 72-h incubation with 10(-7)M 1,25-(OH)2D3 or OCT. Both compounds increased ALP activity to the same extent. Stimulation by OCT of VDR levels, ALP activity, and osteocalcin secretion were inhibited by the addition of 5 microM cycloheximide, indicating that these actions of OCT require new protein synthesis. Thus, OCT, like 1,25-(OH)2D3, up-regulates the vitamin D receptor, stimulates osteocalcin secretion, and increases ALP activity in ROS 17/2.8 cells, suggesting that the analog may be as active as 1,25-(OH)2D3 in stimulating bone formation in vivo. The low activity of OCT in mobilizing calcium from bone in vivo does not appear to be due to an inability of this compound to act on osteoblasts.
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PMID:The activity of 22-oxacalcitriol in osteoblast-like (ROS 17/2.8) cells. 164 45

We have previously shown that 1,25-dihydroxyvitamin D [1,25-(OH)2D3] and glucocorticoid modulate adenylate cyclase activation by PTH in osteoblast-like cells. Here we examine whether steroid effects on PTH receptor density explain the modulation of PTH action. Receptor assays were performed on late logarithmicphase monolayers of ROS 17/2.8 cells using human PTH-like peptide (hPLP) as radioligand. Kd and receptor density were computed from competition of tracer amounts of [125I-Tyr36] hPLP-(1-36) with unlabeled hPLP-(1-36) (0.1-30 nM). Steroid treatment had little or no effect on affinity for ligand. Pretreating cells with 10 nM 1,25-(OH)2D3 for 48 h decreased PTH receptor number to 17% of control values. Treating cells with 10 nM of the glucocorticoid triamcinolone acetonide (TRM) increased receptor number 10-fold, but simultaneous treatment with 1,25-(OH)2D3 (10 nM) completely prevented this receptor increase. Steroid effects required 13-18 h of treatment. Dose-response relationships for steroid modulation, determined from binding at 0.17 nM radioligand, indicated an EC50 of 0.3 nM for glucocorticoid augmentation of PTH receptor number and 0.02 nM for 1,25-(OH)2D3 reduction of receptor number in the presence of absence of the maximum TRM effect. The initial rate of cAMP production by receptor-saturating concentrations of PTH was 11,500 molecules per receptor per minute in untreated cells, comparable to reported turnover numbers for mammalian adenylate cyclase. Control experiments were validated measuring cAMP in intact cells as an indicator of adenylate cyclase activity. Cyclic AMP production was reduced 63% by 1,25-(OH)2D3 (10 nM) treatment. Glucocorticoid (10 nM) enhanced cAMP production twofold but reduced cAMP generation per receptor by 80%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:1,25-dihydroxyvitamin D reduces parathyroid hormone receptor number in ROS 17/2.8 cells and prevents the glucocorticoid-induced increase in these receptors: relationship to adenylate cyclase activation. 165 16

PTH-related peptide (PTH-rP) has recently been discovered to exist in high concentrations in milk. The development of a commercial RIA for PTH-rP has allowed us to extend these studies. We measured the PTH-rP content of milk from 42 Jersey cows from a single farm in various stages of lactation. Colostrum (first milk) contained 56 +/- 12 ng/ml immunoreactive PTH-rP (iPTH-rP). The iPTH-rP contents of milk 1, 2, 3, 5, 7, and 9 months into lactation were 77 +/- 19, 59 +/- 14, 57 +/- 10, 106 +/- 11, 119 +/- 16, and 168 +/- 17 ng/ml, respectively. Plasma was obtained from 7 Jersey calves at birth and at intervals after the ingestion of colostrum. No iPTH-rP was detected in the plasma at birth. Two hours after the ingestion of colostrum, the iPTH-rP content of plasma was 81 +/- 25 pg/ml. The plasma iPTH-rP concentration continued to increase to 384 +/- 84 pg/ml at 7 h and peaked at 444 +/- 84 pg/ml 12 h after birth. Two calves were sampled through the 60th hour after birth, at which time plasma iPTH-rP was 483 +/- 36 pg/ml. The biological activity of the PTH-rP in milk and plasma was assessed by its ability to stimulate cAMP accumulation in ROS 17/2.8 cells. The specificity of this response was determined by the ability of antiserum to PTH-rP to block the activity. The biological activity of the milk samples was between 31-95% of the activity suggested by immunoassay. Biologically active PTH-rP could not be detected in any of the calf plasma samples. These results confirm the presence of biologically active PTH-rP in milk and suggest that the iPTH-rP is capable of being absorbed. However, our results indicate that the biological activity of the PTH-rP is nearly completely absent once in the systemic circulation.
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PMID:Parathyroid hormone-related peptide content of bovine milk and calf blood assessed by radioimmunoassay and bioassay. 165 14


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