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Biomedical subjects

Y Koshihara

Publications and source records attributed to Y Koshihara.

At least 73 records · Page 4Linked to original sources
PubMed1988

Measurement of sulfidopeptide leukotrienes and their metabolism in human synovial fluid of patients with rheumatoid arthritis.

Leukotriene (LT)C4 in the synovial fluid of patients with osteoarthritis deformans (OA) and rheumatoid arthritis (RA) was measured by radioimmunoassay (RIA) after extraction with Sep-Pak C18 cartridge. The amounts of immunoreactive LTC4 (i-LTC4) in samples from patients with OA and RA were not significantly different, being 0.198 +/- 0.018 pmol/ml (n = 11) and 0.179 +/- 0.016 pmol/ml (n = 12), respectively. After separation by high performance liquid chromatography (HPLC) and measurement by RIA, the levels of other sulfidopeptide LTs, such as LTD4 and LTE4, in synovial fluid from patients with RA were found to be significantly higher than those in fluid from patients with OA. The leukocyte number in synovial fluids did not correlate with the i-LTC4 level. The metabolic activities of these synovial fluids were determined by incubating them with 3H-LTC4 and then separating sulfidopeptide LTs by HPLC. The conversion of LTC4 to LTD4 in synovial fluids of patients with OA and RA were similar, but the dipeptidase activity converting LTD4 to LTE4 was higher in fluid from patients with RA. It is suggested that a high level of LTE4 may contribute to exudation of synovial fluid, since LTE4 increases vascular permeability.

Arthritis, Rheumatoid↗
PubMed1987

In vitro calcification in human osteoblastic cell line derived from periosteum.

Human osteoblastic cell cultures were established from human periosteum, identified on the basis of high alkaline phosphatase activity in the confluent state. The cells in the growing state showed a fibroblastic morphology and grew to form multiple layers. The cells could spontaneously calcify, and the process was accelerated by alpha-glycerophosphate. Minerals deposited on the cells consisted exclusively of calcium and phosphorus, and matured into hydroxyapatite crystals. The calcification was stimulated by the treatment with 1 alpha,25-dihydroxy-vitamin D3. These results indicate that the osteoblastic cells have the capacity to differentiate into osteocytes and form calcified human bone tissue in vitro.

Adult↗
PubMed1987

In vitro effects of prostaglandins on human retinoblastoma cell line, Y-79 cells.

Prostaglandins (PGs) and their derivatives have been reported to modulate or inhibit a variety of tumor cells in vitro and in vivo. In the present study, an established retinoblastoma cell line, Y-79, was investigated for 1) its capacity to synthesize PGs and 2) its susceptibility to PGs and their derivative, 64E, exogenously given. The capacity of Y-79 cells to produce PGs was estimated by thin layer chromatography using [1-14C] arachidonic acid as a substrate, and it was found that no detectable amounts of PGD2, PGE2, PGF2 alpha, thromboxane B2, or 6-keto PGF1 alpha were produced by Y-79 cells. Furthermore, the effects of exogenously given PGs (PGA1, A2, D2, E1, E2, F2 alpha, and J2) and 64E on the cell proliferation of Y-79 cells in culture were examined. PGE1, E2, and F2 alpha showed no significant effects on the cell growth of Y-79 cells at all tested doses (1-20 micrograms/ml). On the other hand, PGA1, A2, D2, and J2, and 64E remarkably inhibited the cell growth of Y-79 cells. A dose-response study indicated that 64E was the most effective among these drugs, followed by PGJ2. PGD2, A1, and A2 were less effective than PGJ2. The present data demonstrate that Y-79 cells do not produce endogenous PGs, and that these cells are highly susceptible to exogenous PGs (PGJ2, D2, A1, and A2) as well as 64E.

Cell Division↗
PubMed1986

Contribution of lipoxygenase metabolites to IL-2 production in the early phase of lymphocyte activation.

Lipoxygenase inhibitors; eicosatetraynoic acid (ETYA), esculetin and caffeic acid, inhibited interleukin-2 (IL-2) production by Con A (concanavalin A)-stimulated murine spleen lymphocytes. They effectively inhibited IL-2 production without affecting cell viability when they were added to the cultures within around 6 hr after Con A stimulation. IL-1 production was also inhibited effectively when the inhibitors were added within 4 hr after stimulation. Therefore, immunosuppressive characteristics of these inhibitors can in part be explained by their inhibitory effects on production of lymphokines involved in the early phase of lymphocyte activation.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1986

Inhibitory effect of prostaglandin D2 on DNA synthesis in nuclei.

Prostaglandin (PG) D2 treatment inhibited DNA synthesis in isolated nuclei of mastocytoma P-815, 2-E-6 cells. On treatment with PGD2 (10 micrograms/ml), the inhibition was distinct by 8 hrs, and complete after 18 hrs. This effect of PGD2 on DNA synthesis in nuclei was not direct or mediated by cyclic AMP, but was a cell-mediated reaction. The cytoplasmic fractions of PGD2-treated and untreated cells both had stimulatory effects and their potencies were the same except for that of the cytoplasmic fraction of 8 hr-treated cells, which was less than that of the cytoplasmic fraction of untreated cells. On treatment with PGD2, inhibition of DNA synthesis in the nuclei began after 8 hrs, and this inhibition could not be reversed, even by adding the cytoplasmic fraction from untreated cells to the assay system. A nuclear salt extract prepared by adding 0.3 M NaCl to nuclei of cells that had been treated with PGD2 for 18 hrs had a much smaller stimulatory effect on DNA synthesis of salt-treated nuclei than an extract of nuclei from untreated cells. It is suggested that inhibition of cell growth by PGD2 is not mediated by intracellular cyclic AMP, but that PGD2 induces a factor(s) that inhibits nuclear DNA synthesis.

Adenylyl Cyclases↗
PubMed1985

Enhancement of endogenous production of 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid in aortic smooth muscle cells by platelet-derived growth factor.

Platelet-derived growth factor (PDGF) has a chemotactic effect on smooth muscle cells, which is inhibited by lipoxygenase inhibitor caffeic acid. In order to study the role of endogenous lipoxygenase products of arachidonic acid on the chemotactic action of PDGF, effects of PDGF on the lipoxygenase pathway in smooth muscle cells were examined. Lipoxygenase products were analyzed by high-performance liquid chromatography. 15-, 5- and 12-lipoxygenase activities, in order of magnitude, were found in smooth muscle cell homogenate. However, when the lipoxygenase products were analyzed using intact cells prelabelled with [14C]arachidonic acid, only 12-L-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE) was found to be produced endogenously. In addition, 12-HETE was not released into the medium. Treatment of the cells with PDGF increased the endogenous production of 12-HETE. The amounts of intracellular 12-HETE in PDGF-treated cells were 126, 132 and 146% at 1, 3, and 10 hr's after the initiation of PDGF treatment, respectively, when control value at each time point was considered as 100%. Caffeic acid (10(-4) M) completely inhibited the PDGF effect on 12-HETE production. However, PDGF treatment did not significantly alter the 12-lipoxygenase activity. These results suggest that the stimulatory effect of PDGF on 12-HETE production was not mediated by the activation of 12-lipoxygenase activity. Since 12-HETE itself is a potent chemoattractant for smooth muscle cells, the present dat strongly suggest that 12-HETE could be an important intracellular mediator of the chemotactic action of PDGF on aortic smooth muscle cells.

Animals↗
PubMed1985

Measurement of immunoreactive leukotriene C4 in blood of asthmatic children.

Peptide leukotriene (LT) such as LTC4, LTD4, LTE4 have been considered to be major mediators of immediate type hypersensitivity reaction such as asthma. We have developed a rapid and simple extraction method using a Sep-Pak C18 cartridge for the measurement of LTC4 by radioimmunoassay (i-LTC4). In this extraction method, 91% LTC4 was recovered in a final methanol fraction. The identity was confirmed by the recovery test and by the dilution method. The amount of i-LTC4 in plasma from asthmatic patients was determined by radioimmunoassay after the extraction. The order of the plasma level of i-LTC4 was; severe asthma greater than slight or moderate asthma greater than asthmatic patient without attack greater than healthy adult. The highest level of LTC4 was 0.27 +/- 0.11 pmol/ml in severe asthmatic plasma.

Adult↗
PubMed1985

New lipoxygenase inhibitors isolated from Chinese plants. Development of new anti-allergic drugs.

Some natural compounds isolated from Chinese plants were found to have strong inhibitory activity for 5-lipoxygenase and were thus able to inhibit leucotriene synthesis. Among these compounds, caffeic acid was selected for study; more than 100 of its derivatives were synthesized and tested for 5-lipoxygenase inhibitory activity. Two derivatives, TMK-919 and TMK-920, proved to be 100 times more potent than the parent compound and were able to inhibit the homologous PCA reaction significantly in rats at a dose of 10 mg/kg, i.v.

Animals↗
PubMed1984

Caffeic acid is a selective inhibitor for leukotriene biosynthesis.

.eukotrienes are significantly involved in immunoregulation and in a variety of diseases, including asthma, inflammation and various allergic conditions. They are initially biosynthesized by 5-lipoxygenase from arachidonic acid, which can also be metabolized to prostaglandin endoperoxide by cyclooxygenase. The specific inhibitors for 5-lipoxygenase would be useful not only as tools for investigating the regulation mechanism of leukotriene biosynthesis, but also as drugs for clinical use. Although recently a few selective inhibitors have been reported, most of them are difficult to obtain, since they are new compounds. We found that caffeic acid, which is one of the most common reagents, is a selective inhibitor for 5-lipoxygenase and therefore for leukotriene biosynthesis. The inhibitory effect of its methyl ester on 5-lipoxygenase (ID50 = 4.8 X 10(-7) M) was stronger than that of caffeic acid itself (ID50 = 3.7 X 10(-6) M). Caffeic acid inhibited 5-lipoxygenase in a non-competitive manner. Caffeic acid and its methyl ester did not inhibit prostaglandin synthase activity at all, at least up to 5 X 10(-4) M, but rather stimulate at higher doses. The biosynthesis of leukotriene C4 and D4 in mouse mast tumor cells was also inhibited completely with 10(-4) caffeic acid. Besides, caffeic acid had little effect on arachidonic acid metabolism in platelet at less than 1 X 10(-5) M, but at higher doses it showed a definite inhibitory effect, i.e., thromboxane B2, HHT (12(S)-hydroxy-5,8,10-heptadecatetraenoic acid) and 12-HETE (12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid) syntheses were inhibited 33, 40 and 80% at 1 X 10(-4) M, respectively. Platelet aggregation induced by arachidonic acid was also inhibited by caffeic acid at high dose, while platelet aggregation induced by ADP is not influenced by caffeic acid at all. The observations on caffeic acid and its derivatives may contribute to leukotriene research.

Animals↗
PubMed1984

Prostaglandin D2 lowers nuclear DNA polymerase activity in cultured mastocytoma cells.

Prostaglandin D2 strongly inhibited growth of cultured mastocytoma P-815, 2-E-6 cells, which were established and cloned from mouse mast tumor cells. The inhibition was dose-dependent (IC50=2.09 x 10-5 M). Prostaglandin D2 also inhibited the DNA synthesizing activity of the cells dose-dependently. We next measured the activities of endogenous DNA polymerases extracted from untreated and prostaglandin D2-treated cells. Prostaglandin D2-treated cells were the same suggesting there was no gross change in the size of the enzyme. Prostaglandin D2 pretreatment of the cells reduced endogenous DNA polymerase beta activity to 68% of the control value; the sedimentation coefficients of the enzymes from treated and untreated cells were both 3.5 S. Interestingly, prostaglandin D2 had no direct inhibitory effect on the activity of either DNA polymerase alpha or beta. Our results indicate that the activities of DNA polymerase alpha and beta are lower in prostaglandin D2-treated mastocytoma cells. This finding accounts for the lower level of DNA synthesis in these cells.

Animals↗
PubMed1983

Inhibitory effect of esculetin on 5-lipoxygenase and leukotriene biosynthesis.

Esculetin (6,7-dihydroxycoumarin) showed inhibitory effects on 5- and 12-lipoxygenases of cloned mastocytoma cells. The half-inhibition dose (ID50) for each enzyme was 4 X 10(-6) and 2.5 X 10(-6) M, respectively. No inhibition at all, but rather a stimulating effect on prostaglandin synthesis, was observed, especially at higher doses of esculetin. Leukotriene synthesis by mouse mast tumour cells was also reduced in the presence of esculetin in parallel with 5-lipoxygenase inhibition. From these results, esculetin may be useful as a tool for research on regulatory mechanisms or physiological functions of leukotrienes.

Animals↗