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D Bayley

Publications and source records attributed to D Bayley.

8 recordsLinked to original sources
PubMed1992

Differential metabolism of 25-hydroxyvitamin D3 by cultured synovial fluid macrophages and fibroblast-like cells from patients with arthritis.

Differential metabolism of 25-hydroxyvitamin D3 (25(OH)D3) has been shown for macrophages and fibroblast-like cells (possibly synoviocytes) cultured for two to 50 days after isolation from the synovial fluid of 12 patients with various forms of inflammatory arthritis. Macrophages synthesised the active metabolite of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), the synthesis of which was increased by bacterial lipopolysaccharide, a known macrophage activating factor. In contrast, fibroblast-like cells formed 24, 25-dihydroxyvitamin D3 (24,25(OH)2D3), synthesis of which was stimulated by 1,25(OH)2D3 and inhibited by lipopolysaccharide. The synthesis of 1,25(OH)2D3 and 24,25(OH)2D3 by macrophages and fibroblast-like cells respectively was inhibited by ketoconazole, indicating that both hydroxylases are dependent on cytochrome P-450. Mean (SEM) synovial fluid and serum 25(OH)D3 concentrations were 16.7 (1.7) and 22.2 (2.6) ng/ml and those of 1,25(OH)2D3 were 29.4 (4.8) and 43.3 (4.0) pg/ml respectively. In most cases concentrations were lower in synovial fluid than in paired serum samples, but in two patients 1,25(OH)2D3 concentrations were greater in synovial fluid than in serum, suggesting local synthesis within the affected joints.

24,25-Dihydroxyvitamin D 3↗
PubMed1992

Inhibition by prostaglandin E1 and E2 of 1,25-dihydroxyvitamin D3 synthesis by synovial fluid macrophages from arthritic joints.

Previous work has shown that renal metabolism of 25-dihydroxyvitamin D3 (25(OH)D3) to the active metabolite, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is stimulated by prostaglandin E2 and inhibited by acetylsalicylate (aspirin). As prostaglandins are primary inflammatory mediators and synovial fluid macrophages are known to synthesise 1,25(OH)2D3 in vitro, the effects of prostaglandin E1, prostaglandin E2, and aspirin on the metabolism of 25(OH)D3 by cells cultured from synovial fluid of patients with inflammatory arthritis were investigated. Most cultures contained non-proliferating macrophages which formed 1,25(OH)2D3; however, two of 13 cultures contained colonies of rapidly proliferating fibroblast-like cells which formed 24,25(OH)2D3 (24,25(OH)2D3). Prostaglandin E1 and prostaglandin E2 (0.01-10 mumol/l) induced marked inhibition of 1,25(OH)2D3 synthesis (up to 94%) in a dose dependent manner after preincubations of 24 hours but not over straightforward six hour incubations. Exposure of macrophages to aspirin (1 mumol/l-1 mmol/l) for 24 hours did not affect 1,25(OH)2D3 synthesis unless the cells had been pretreated with lipopolysaccharides, in which instance 1 mM aspirin increased 1,25(OH)2D3 synthesis. Lipopolysaccharide is a macrophage activating factor which stimulates macrophages to form 1,25(OH)2D3, and it also induces prostaglandin synthesis which would be inhibited by aspirin. Taken together these results suggest that prostaglandin E1 and prostaglandin E2 synthesised by macrophages may act in an autocrine manner to attenuate the ability of macrophage activating factors, such as lipopolysaccharide, to stimulate 1,25(OH)2D3 synthesis. Prostaglandins synthesised by other inflammatory cells may also inhibit 1,25(OH)2D3 synthesis in a paracrine manner. In contrast, prostaglandin E2 and aspirin had limited effects on fibroblast 24,25(OH)2D3 synthesis. This study shows that the effects of prostaglandin E1, prostaglandin E2, and aspirin in macrophages contrast with those previously reported for the renal 25(OH)D3-1alpha-hydroxylase, where prostaglandin E2 stimulated and aspirin inhibited enzyme activity. These results further emphasise that synthesis of 1,25(OH)2D3 in non-renal sites is independently regulated, which is consistent with it having an immunological role at a local level rather than playing a part in systemic calcium homeostasis.

Alprostadil↗
PubMed1991

Metabolism of 25-hydroxyvitamin D3 to 24,25-dihydroxyvitamin D3 by blood derived macrophages from a patient with alveolar rhabdomyosarcoma during short-term culture and 1 alpha,25-dihydroxyvitamin D3 after long-term culture.

We have examined the ability of blood-derived monocytes and macrophages isolated from a patient with alveolar rhabdomyosarcoma and hypercalcaemia, to form 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) or 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) from 25-hydroxyvitamin D3 (25(OH)D3). Adherent monocyte-macrophage cells incubated with 25(OH)D3 over the initial 2 days in culture synthesized 1.9 pmol 24,25(OH)2D3/h/incubation (representing 0.63 pmol/h/10(6) cells), whereas macrophages synthesized 1.03 and 1.15 pmol 1 alpha,25(OH)2D3/h/incubation after 1 and 4 weeks in culture respectively. In a further experiment synthesis of 1 alpha,25(OH)2D3 by long-term cultured macrophages fell from 2.25 to 0.04 pmol/h/incubation following exposure to 10 nM 1 alpha,25(OH)2D3 for 7 days, whereas 24,25(OH)2D3 synthesis was induced (0.46 pmol/h/incubation). The vitamin D3 metabolites were identified by co-chromatography with authentic 24,25(OH)2D3 or 1 alpha,25(OH)2D3 in three different high-performance liquid chromatography systems. Serum 1 alpha,25(OH)2D3 in the patient was markedly suppressed at 5 pg/ml (normal 20-50 pg/ml) indicating that raised 1 alpha,25(OH)2D3 was not the cause of the hypercalcaemia, but rather, that raised calcium may have suppressed renal 1 alpha,25(OH)2D3 synthesis. Administration of APD (3-amino-1-hydroxypropylidine-1,1-bisphosphonate) corrected the hypercalcaemia in the patient suggesting that increased bone resorption was responsible for the raised calcium. The results of this study show for the first time that immature blood derived monocyte-macrophage cells can synthesize 24,25(OH)2D3 before they mature into macrophages able to synthesize 1 alpha,25(OH)2D3.

24,25-Dihydroxyvitamin D 3↗
PubMed1991

Studies on an adherent variant of the human promyelomonocytic HL60 leukaemia cell line that constitutively expresses 25-hydroxyvitamin D3-24-hydroxylase activity which is inhibited by 1 alpha,25-dihydroxyvitamin D3.

The constitutive expression of 25-hydroxyvitamin D3-24-hydroxylase (25-(OH)D3-24-hydroxylase) activity has been studied in an adherent variant (Ad-HL60) of the human promyelomonocytic leukaemia cell line HL60. The Ad-HL60 cells have a more differentiated phenotype than the non-adherent cells from which they were derived, and synthesized 1.88 +/- 0.07 (+/- S.E.M.) pmol 24,25-(OH)2D3/h per 10(6) cells following culture in RPMI-1640 medium containing less than 0.02 nM 1 alpha,25-(OH)2D3. They also synthesized 1.66 +/- 0.05 pmol 24,25-(OH)2D3/h per 10(6) cells following culture in 1 alpha,25(OH)2D3-free medium supplemented with 1 g bovine serum albumin/l instead of 10% serum. In contrast, non-adherent HL60 cells required exposure to 10-100 nM 1 alpha,25-(OH)2D3 to induce equivalent 24,25-(OH)2D3 synthesis. The 25-(OH)D3-24-hydroxylase expressed by Ad-HL60 cells had an apparent Michaelis constant of 1 microM and maximal rate of 20 pmol/h per 10(6) cells with substrate concentrations from 0.012 to 1.2 microM/incubation (5-500 ng/ml). Furthermore, 24,25-(OH)2D3 synthesis was inhibited in a dose-dependent manner by ketoconazole (0.01-10 microM), suggesting that the enzyme is cytochrome P-450 dependent. Ad-HL60 cells expressed approximately 3500 specific receptors for 1 alpha,25-(OH)2D3/cell with a dissociation constant of 40 pM. Following exposure to 0.1-100 nM 1 alpha,25-(OH)2D3, Ad-HL60 cell proliferation was significantly inhibited compared with controls grown in medium containing less than 0.02 nM 1 alpha,25-(OH)2D3 for 96 h. Expression of 25-(OH)D3-24-hydroxylase was also inhibited in a dose- and time-dependent manner; however, expression of nonspecific esterase was not induced. Both of these findings are contrary to those previously demonstrated for non-adherent HL60 cells, whereas the dose-dependent inhibition of cell proliferation by 1 alpha,25-(OH)2D3 occurs in both adherent and non-adherent phenotypes. These observations on Ad-HL60 cells represent the first description of a cell type in which 1 alpha,25-(OH)2D3 appears to inhibit 25-(OH)D3-24-hydroxylase activity. The Ad-HL60 cells also constitutively metabolized 1 alpha,25-(OH)2D3 in a manner consistent with formation of 1 alpha,25-(OH)2D3 without previous exposure to 1 alpha,25-(OH)2D3. In contrast, many other cell types, including non-adherent HL60 cells, require exposure to 1 alpha,25-(OH)2D3 to induce metabolism of 1 alpha,25-(OH)2D3 to 1 alpha,24,25-(OH)3D3, a reaction that represents the initial step for catabolism of 1 alpha,25-(OH)2D3 to calcitroic acid.

Calcitriol↗
PubMed1990

Synthesis of 1,25-dihydroxyvitamin D3 by spleen cells isolated from two patients with myelofibrosis and a normal subject.

The ability to synthesise [3H]1,25(OH)2D3 was studied in spleen cells incubated in short-term primary culture with [3H]25(OH)D3 which were isolated from two patients with idiopathic myelofibrosis and from one normal subject. Formation of a metabolite co-chromatographing with authentic 1,25(OH)2D3 on three different high-performance liquid chromatography systems was observed for cells from all three patients. [3H]1,25(OH)2D3 synthesis was 0.37 and 1.6 fmol/10(6) cells/incubation for cells with a density below that of lymphocyte separating media (1.077 g/ml) for the two myelofibrotic patients respectively and 0.15 fmol/10(6) cells/incubation for the normal subject. The most likely cell type capable of this synthesis were those of the monocyte-macrophage lineage which would have been present in abnormally high numbers in the patients with myelofibrosis. However, the exact identity of the cell-type responsible could not be determined because of the heterogeneity of cell types present. The observation that spleen cells from two patients with myelofibrosis and from a normal accident victim could metabolise [3H]25(OH)D3 to its active form [3H]1,25(OH)2D3 suggests a possible role for this metabolite in spleen haematopoiesis.

Calcitriol↗
PubMed1989

Metabolism of 25-hydroxyvitamin D3 to 24,25-dihydroxyvitamin D3 and its sensitivity to ketoconazole in 1 alpha,25-dihydroxyvitamin D3-differentiated HL60 cells.

Regulation of the metabolism of [3H]25-hydroxyvitamin D3 ([ 3H]25-(OH)D3) in vitro to material with the characteristics of [3H]24,25-dihydroxyvitamin D3 ([3H]24,25-(OH)2D3) has been studied in the human promyelocytic cell line HL60. Synthesis of 24,25-(OH)2D3 was induced in a dose-dependent manner in cells pretreated with 0.1-100 nM 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3) for 4 days. This treatment also inhibited cell proliferation and stimulated differentiation to a macrophage phenotype that was characterized by staining for non-specific esterase (NSE) activity. The ability to synthesize [3H]24,25-(OH)2D3 from [3H]25-(OH)D3 and the expression of NSE activity both responded to changes in concentration of 1 alpha,25-(OH)2D3 in the culture medium in a parallel manner. Synthesis of [3H]24,25-(OH)2D3 was linear when the incubation time was between 1 and 8 h and the cell number between 1 and 12 x 10(6) cells/incubation. The optimum substrate concentration for its synthesis was 125 nM, giving an apparent Michaelis constant of 360 nM. The identity of the [3H]24,25-(OH)2D3 synthesized by these cells was confirmed by co-chromatography with authentic 24,25-(OH)2D3 on normal-phase and reverse-phase high-performance liquid chromatography systems and by its reaction to sodium-m-periodate. Cells that had been exposed to 100 nM 1 alpha,25-(OH)2D3 for 4 days synthesized 2.17 +/- 0.07 (S.E.M.) pmol 24,25-(OH)2D3/10(6) cells per h.(ABSTRACT TRUNCATED AT 250 WORDS)

24,25-Dihydroxyvitamin D 3↗
PubMed1985

Paget's disease and the temporal bone--a clinical and histopathological review of six temporal bones.

Paget's disease of bone occurs more commonly in the elderly and has been reported to involve the temporal bone in 30% of those afflicted. The clinical and histopathological features of six temporal bones from three patients with this disease are reported and the relevant literature reviewed. The effect of Paget's disease on the middle ear structures was more variable than its extension into the otic capsule. Pagetic involvement of the otic capsule was observed in five temporal bones. One patient had bilateral asymptomatic neurofibromas in the eighth cranial nerve. the potential mechanisms responsible for the conductive deafness, the sensorineural deafness and vestibular dysfunction associated with Paget's disease are discussed.

Age Factors↗