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S Murota

Publications and source records attributed to S Murota.

At least 145 records · Page 8Linked to original sources
PubMed1990

The control of vascular endothelial cell injury.

The mechanism by which MCI-186 showed a potent cytoprotective effect on the in vitro endothelial cell injury due to 15-HPETE was studied. Stimulation of human leukocytes with various chemical mediators such as TPA, f-Met-Leu-Phe, LTB4, etc. elicited the production of active oxygens, which could be detected by luminol-dependent chemiluminescence. Among the chemical mediators tested, TPA elicited the chemiluminescence the most, and f-Met-Leu-Phe and LTB4 came next. When the leukocytes were directly placed on a monolayer of cultured endothelial cells, followed by stimulating the leukocytes with TPA, severe endothelial cell injury was observed. The effect of TPA was dose dependent. There was good correlation between the active oxygen releasing activity and the cytotoxic activity. When the leukocytes were placed on a filter which was set apart from the monolayer of endothelial cell in a culture dish, and stimulated the leukocytes with TPA, no cytotoxicity was observed. These data strongly suggest that the substance responsible for the cytotoxicity must be a very labile and short-lived substance, presumably active oxygens. On the other hand, MCI-186 was found to have a complete quenching activity to the chemiluminescence due to active oxygens in the TPA-leukocyte system. Taken together, these factors indicate that the potent cytoprotective effect of MCI-186 may be due to its specific radical scavenging activity.

Animals↗
PubMed1990

Prostaglandin E2 evokes intracellular calcium rise in mouse osteoblastic cell line, MC3T3E-1.

The effect of prostaglandin (PG) E2 on the intracellular free calcium concentration ([Ca2+]i) in mouse osteoblastic clone, MC3T3E-1 cells, was investigated with the fluorescent probe fura-2. In the growing phase of MC3T3E-1, PGE2 evoked a transient rise of [Ca2+]i in a dose-dependent manner in the range from 0.28 microM to 5.6 microM of PGE2. The elevation of [Ca2+]i induced by PGE2 was not affected by the presence of EGTA. Moreover, PGE2 (5.6 microM) evoked an acute accumulation of intracellular inositol-1,4,5-trisphosphate (InsP3). The absolute content of InsP3 increased from 5.8 pmole/10(6) cells to 19.2 pmole/10(6) cells within 30 sec after the PGE2 treatment. The degree of [Ca2+]i elevation induced by PGE2 was dependent on the day after subculturing. At day 3, the response to PGE2 was the most pronounced during the 8-day experimental periods. These data suggest that PGE2 evoked a [Ca2+]i rise via a phospholipase C-InsP3 pathway in osteoblasts, particularly in the growing phase.

Animals↗
PubMed1989

Arachidonic acid metabolism in cultured astrocytes from rat embryo and in C6 glioma cells.

Arachidonic acid metabolism in primary cultures of astroglial cells prepared from cerebra of rat embryos was examined. Arachidonic acid was mainly metabolized through the lipoxygenase pathway and the major metabolites formed were 12-hydroxyeicosatetraenoic acid (12-HETE), 11-HETE and 15-HETE. By contrast, in C6 cells, which are considered to be of astroglial origin, arachidonic acid was mainly metabolized through the cyclooxygenase pathway and the major metabolites formed were prostaglandin (PG)E2, PGF2 alpha and thromboxane B2.

Animals↗
PubMed1989

Cadmium stimulates prostaglandin E2 synthesis in osteoblast-like cells, MC3T3-E1.

The effect of Cd on prostaglandin E2 production in osteoblasts was studied using cloned osteoblast-like cells, MC3T3-E1, which were established from new-born mouse calvaria. Treatment of the cells with Cd caused a dose- (0-10 microM) and time- (0-24 h) dependent increase in the release of prostaglandin E2 from the cells into the culture medium. A lag time of 4 h was required for the onset of the phenomenon. The release of [14C]arachidonic acid from prelabeled cell membrane was little influenced by the Cd treatment, while conversion of [14C]arachidonic acid to prostaglandin E2 by the homogenate of the cells treated with Cd was enhanced as compared to that by untreated cells. The stimulatory effect of Cd on prostaglandin E2 production was abolished in the presence of cycloheximide (100 ng/ml). By Western blot analysis with polyclonal rabbit anti-cyclooxygenase antibody, it was revealed that Cd treatment augmented the amount of immunoreactive cyclooxygenase in the cells. These results strongly suggest that Cd stimulates prostaglandin E2 production through the induction of cyclooxygenase in MC3T3-E1 cells. This effect of Cd may be involved in the mechanisms of Cd-induced bone injury.

Animals↗
PubMed1989

Leukotriene C4 stimulates angiogenesis in bovine carotid artery endothelial cells in vitro.

In order to investigate the mechanism of angiogenesis involved in inflammatory processes, the effects of leukotrienes and prostaglandin E2 on in vitro tube formation of cultured vascular endothelial cells were examined. Endothelial cells from bovine carotid artery were cultured for 4 days between two layers of collagen gel and the lengths of organized tubes were quantitatively estimated with an image analyzer. Treatment with 10(-8)-10(-6)M of prostaglandin E2 increased the tubular lengths, and leukotriene C4 stimulated tube formation at far lower concentrations (10(-15)-10(-9)M) but leukotriene B4 and D4 were not effective on the tube formation. It was also found that endothelial cell migration was stimulated by almost the same concentrations of leukotriene C4 as those stimulating tube formation. These data suggest that leukotriene C4 is, at least, one of the important factors involved in angiogenesis during inflammatory processes.

Animals↗
PubMed1989

Cadmium stimulates prostaglandin E2 production and bone resorption in cultured fetal mouse calvaria.

The effect of cadmium on bone resorption was studied using isolated fetal mouse calvaria. Cadmium stimulated bone resorption and PGE2 production in a dose-dependent manner. The minimal concentration of cadmium which stimulated bone resorption was the same as that stimulated prostaglandin E2 production. The stimulatory effects of cadmium (0.5 microM) on bone resorption and prostaglandin E2 production were completely inhibited by indomethacin. Exogenously added PGE2 (100ng/ml) abolished the inhibitory effect of indomethacin on bone resorption stimulated by cadmium. These results strongly indicate that cadmium stimulates bone resorption via prostaglandin E2 mediated mechanism.

Animals↗
PubMed1989

Prostaglandins promote osteoclastlike cell formation by a mechanism involving cyclic adenosine 3',5'-monophosphate in mouse bone marrow cell cultures.

We have developed a mouse bone marrow culture system in which multinucleated osteoclast (OC)-like cells are formed within 8 days. Using this culture system, we examined the effect of prostaglandins (PGs), potent bone-resorbing agents, on OC-like cell formation. Four PGs (PGE1 and PGE2 at 10(-8)-10(-5) M, 6-keto-PGF1 alpha at 10(-5) M, and PGF2 alpha at 10(-6)-10(-5) M) significantly stimulated the formation of OC-like cells. The potency of the PGs in inducing OC-like cell formation was the highest in PGE1 and PGE2, followed by PGF2 alpha and 6-keto-PGF1 alpha in that order, and the order was highly correlated with the order of the potency in increasing the production of cyclic adenosine 3',5'-monophosphate (cAMP) in bone marrow cells. Addition of dibutyryl-cAMP also induced OC-like cell formation. Moreover, isobutylmethylxanthine (IBMX), a potent inhibitor of phosphodiesterase, potentiated the OC-like cell formation induced by PGE2, whereas salmon calcitonin greatly inhibited it. Calcitonin induced cAMP production in cultures treated with PGE2, but not in cultures with vehicle. When bone marrow mononuclear cells were cultured on dentine slices in the presence of PGE2, multinucleated OC-like cells were similarly formed and they resorbed calcified dentine, resulting in so-called Howship's lacunae. These results suggest that PGs stimulate resorption of calcified tissues by promoting osteoclast formation. The activity of PGs in inducing OC-like cell formation is considered mediated mainly by a mechanism involving cAMP.

Animals↗
PubMed1989

The detection of platelet-activating factor in inflamed human gingival tissue.

Platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; PAF) is a biologically active lipid, like the prostaglandins, which mediates allergic and inflammatory reactions. Aggregation of washed rabbit platelets was induced by a lipid prepared from inflamed gingiva. The mobility of the active lipid was coincident with that of authentic PAF on thin-layer chromatography. The aggregation was dose-dependent and inhibited by pretreatment with a specific PAF antagonist, ONO 6240, but not by indomethacin or creatine phosphate/creatine phosphokinase, which inhibit the platelet aggregation due to arachidonic acid or ADP, respectively. Thus the active lipid was identified as PAF; the amount of PAF detected was 118.1 +/- 79.7 pg/50 mg tissue (n = 6, mean +/- SD), the amount in normal tissue being 13.0 +/- 11.3 pg/50 mg tissue (n = 6). There was therefore a significant difference between the tissues. Lyso PAF, the metabolite of PAF with acetylhydrolase, was not detectable in either gingival tissue. Thus PAF was produced more in inflamed gingival tissue than in normal tissue; PAF may be involved in the occurrence and maintenance of periodontal disease.

Adult↗
PubMed1989

Involvement of arachidonic acid metabolites in increases in vascular permeability in experimental dental pulpal inflammation in the rat.

Pulp was experimentally inflamed by applying bacterial lipopolysaccharide (LPS). Changes in arachidonic acid (AA) metabolites were determined by measuring the conversion of exogenously added AA in pulp homogenates. The inflamed pulp produced 12-hydroxy-eicosatetraenoic acid (12-HETE), 6-keto-prostaglandin (PG) F1 alpha greater than PGE2, thromboxane B2 and 11-HETE, which was further identified with high-performance liquid chromatography. The LPS treatment caused a 2.0-fold increase in 12-HETE production at 1 h, a 3.8-fold increase in 6-keto-PGF1 alpha production at 12 h and increases in PGE2 and 11-HETE production of 8.8- and 5.5-fold, respectively, at 24 h. Vascular permeability in the inflamed pulp was measured by quantifying the amount of an extravasated dye; it increased markedly from 6 h and reached a peak at 12 h after the LPS application. When indomethacin (0.3-30 mg/kg, s.c.) was given before LPS, both the production of 6-keto-PGF1 alpha and PGE2 and the increase in vascular permeability were inhibited dose dependently. Exogenously applied PGE2 and PGI2 methyl ester reduced the inhibition of the increase in vascular permeability caused by indomethacin. Thus PGE2 and PGI2 may be involved in increases in vascular permeability in pulpal inflammation.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1989

Preventive effects of zinc on cadmium-induced inhibition of alkaline phosphatase activity and mineralization activity in osteoblast-like cells, MC3T3-E1.

In order to determine the specific action of cadmium on bone metabolism, the effect of cadmium on alkaline phosphatase activity, a marker enzyme of osteoblasts, was compared with that of other divalent heavy metal ions, i.e., zinc, manganese, lead, copper, nickel and mercury (10 microM each), using cloned osteoblast-like cells, MC3T3-E1. Cadmium had the strongest inhibitory effect on alkaline phosphatase activity of the cells among the metals tested. At the same dose, however, cadmium failed to inhibit cellular glucose-6-phosphatase and lactate dehydrogenase activities, suggesting that the inhibitory effect of cadmium on alkaline phosphatase was specific and was not dependent on cell injury. Cadmium treatment caused a significant decrease in cellular zinc level, but mercury treatment had no such effect at the dose inhibiting alkaline phosphatase activity. There was a good correlation between decrease of cellular zinc level and inhibition of alkaline phosphatase activity in cadmium-treated cells. Concomitant treatment of the cells with zinc prevented the cadmium-induced inhibition of alkaline phosphatase activity. However, this was not the case in the mercury-induced inhibition. Cadmium also inhibited the mineralization of osteoblasts. When 10 or 20 microM zinc was concomitantly added to the cultures, the inhibition of mineralization was prevented. These data suggest that the inhibitory effect of cadmium in osteoblasts may be closely related to its influence on the cellular zinc metabolism.

Alkaline Phosphatase↗
PubMed1988

Comparison of arachidonic acid metabolism between myofibroblasts and fibroblasts isolated from rat palatal mucoperiosteum.

Myofibroblasts were cultured successfully from experimental wound tissue in rat palatal mucoperiosteum. Arachidonic acid metabolizing activity in cultured myofibroblasts was compared with that in fibroblasts cultured from normal mucoperiosteum. Prostaglandins biosynthesized from [14C]arachidonic acid in cell-free homogenates of both myofibroblasts and fibroblasts were prostaglandins D2, E2 and F2 alpha, and the activity producing each prostaglandin was not significantly different between the myofibroblasts and the fibroblasts, whereas smooth muscle cells, which are histologically similar to myofibroblasts, produced mainly 6-ketoprostaglandin F1 alpha, and relatively small amounts of prostaglandin E2. The release of arachidonic acid from cells prelabeled with [14C]arachidonic acid was compared among three types of cell. The calcium ionophore A23187 strongly enhanced arachidonic acid release in all three cell types. Bradykinin, 5-hydroxytryptamine and prostaglandin F2 alpha affected the stimulation of arachidonic acid release in the fibroblasts but were less or not effective in the myofibroblasts and smooth muscle cells. In addition, prostaglandin E2 biosynthesized in response to several stimuli was measured by radioimmunoassay. The content of prostaglandin E2 correlated closely with arachidonic acid release. In this study, we showed homogeneity between the myofibroblasts and fibroblasts in prostaglandin synthesizing activity and similarity in response to various stimuli between the myofibroblasts and smooth muscle cells, from the standpoint of arachidonic acid metabolism.

Animals↗
PubMed1988

A new in vitro method using fura-2 for the quantification of endothelial cell injury.

Endothelial cell injury was determined by a new method based on measuring a specific release of fura-2, a fluorescent calcium indicator. We examined the cytotoxicity of 15-hydroperoxyeicosatetraenoic acid (15-HPETE) on cultured endothelial cells using the fura-2 assay. The new assay was compared to traditional assays for cytolysis such as measuring the release of 51Chromium (51Cr) or lactate dehydrogenase (LDH). The fura-2 method were able to detect minor and early phase membrane damage in endothelial cells due to the hydroperoxide. Significant release of fura-2 was detected by 5, 10, 25 and 50 mu/ml of 15-HPETE (5, 10 and 25 micrograms/ml p less than 0.01; 50 micrograms/ml, p less than 0.001) as early as 1 hour after the start of the 15-HPETE treatment. The fura-2 assay was so sensitive to the endothelial cell injury that the damage of the cells due to 15-HPETE at the dose of as low as 5 mu/ml could be detected in as early as 30 min. On the other hand, in the traditional 51Cr or LDH release assay, only the cell damage caused by high dose (50 mu/ml) of 15-HPETE could be detected in as late as 6 hours after the start of 15-HPETE exposure. The new method may be useful for the approach to searching injurious substances or their antagonists to several kinds of cells.

Benzofurans↗
PubMed1988

Preventive effect of MCI-186 on 15-HPETE induced vascular endothelial cell injury in vitro.

Using cultured bovine aortic endothelial cells, the effects of MCI-186, a radical scavenger, were studied on arachidonic acid metabolism and on the cell injury caused by 15-HPETE. MCI-186 at 3 X 10(-5) M enhanced prostacyclin production in the intact endothelial cells without affecting phospholipase A2. When endothelial cell homogenates were used as an enzyme source, it was found that MCI-186 stimulated the conversion of arachidonic acid to prostacyclin like phenol, perhaps by trapping OH radicals produced in the process of the conversion of PGG2 to PGH2. On the other hand, MCI-186 was found to inhibit lipoxygenase metabolism of arachidonic acid in cell free homogenates of rat basophilic leukemia cells. The lipoxygenase inhibition caused by 3 X 10(-5) M MCI-186 was almost equivalent to that caused by 3 X 10(-6) M BW 755C. MCI-186 remarkably protected against endothelial cell damage caused by 15-HPETE. 3 X 10(-5) M of 15-HPETE caused endothelial cell death in about 60% of the population: however, pretreatment of the cells with 10(-5) M of MCI-186 or concomitant addition of 10(-5) M of MCI-186 with 15-HPETE to the cultures prevented the cell death completely. These results suggest that MCI-186 may become an unique anti-ischemic drug.

Animals↗
PubMed1988

Impaired polymorphonuclear leukocyte 15-lipoxygenase activity in juvenile and rapidly progressive periodontitis.

15-lipoxygenase activity was investigated in sonicated polymorphonuclear leukocytes (PMNLs) from patients with juvenile and rapidly progressive periodontitis and adult periodontitis. The group with juvenile and rapidly progressive periodontitis had 17 patients (6 male, 11 female, mean age 27.4 years), and the age matched control group had 18 normal individuals (11 male, 7 female, mean age 26.3 years). The group with adult periodontitis had 14 patients with 9 male, 5 female, mean age 45.2 years and the age-matched control group had 6 normal subjects with 5 male, 1 female, mean age 43.7 years. 15-hydroxyeicosa-tetraenoic acid (15-HETE) synthesized in the group with juvenile and rapidly progressive periodontitis was 0.219 +/- 0.102 ng/mg protein (mean +/- S.D.), while it was 0.410 +/- 0.138 ng/mg protein in the age-matched control group. There was a significant difference between the two groups. The group with adult periodontitis produced 0.358 +/- 0.124 ng/mg protein and the age matched control group produced 0.448 +/- 0.176 ng/mg protein (no significant difference). These results are relevant to reports that PMNLs of patients with juvenile and rapidly progressive periodontitis have abnormal functions, while those of patients with adult periodontitis are normal.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1987

Arachidonic-acid metabolism in normal and experimentally-inflamed rat dental pulp.

Pulp homogenates were incubated with [14C]-arachidonic acid and the metabolites separated by thin-layer chromatography. The main products of normal pulp were 6-keto-prostaglandin (PG) F1 alpha and 12-hydroxy-eicosatetraenoic acid (12-HETE), further identified by high performance-liquid chromatography. Thromboxane (TX) B2, and PGD2, E2 and F2 alpha were also detected at less than 30 per cent of 6-keto-PGF1 alpha. When the pulp was inflamed by applying bacterial lipopolysaccharide, production of all these metabolites increased; in particular, PGE2 was increased 9.3-fold compared with normal, and 6-keto-PGF1 alpha and HETE 3.8- and 2.0-fold, respectively. An unidentified product, slightly more polar than 12-HETE, was also markedly produced by the inflamed pulp. Thus arachidonic-acid metabolites including lipoxygenase products may be involved in the development of pulpal inflammation.

6-Ketoprostaglandin F1 alpha↗