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T Nakadate

Publications and source records attributed to T Nakadate.

At least 73 records · Page 4Linked to original sources

Inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced tumor promotion and epidermal ornithine decarboxylase activity in mouse skin by palmitoylcarnitine.

Palmitoylcarnitine, which has been reported to be an inhibitor of calcium-activated, phospholipid-dependent protein kinase (protein kinase C), inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced epidermal ornithine decarboxylase in mouse skin in a dose-dependent manner. Neither acetylcarnitine nor palmitic acid inhibited TPA-caused ornithine decarboxylase induction. In addition, palmitoylcarnitine markedly inhibited skin tumor promotion induced by TPA. Palmitoylcarnitine inhibited epidermal protein kinase C activity which was stimulated by Ca2+ in the presence of phosphatidylserine but failed to inhibit the enzyme activity which was stimulated by TPA in the presence of either phosphatidylserine or Ca2+ plus phosphatidylserine. Therefore, it seems unlikely that the potent anti-tumor-promoting action of palmitoylcarnitine, which is shown in the present study, is explained solely by its effect on protein kinase C.

Animals↗

[Factors controlling tumor promotion induced by TPA].

Phospholipase A2 inhibitors and lipoxygenase inhibitors markedly suppressed mouse skin ODC (ornithine decarboxylase) induction and promotion of papilloma by TPA. The inhibitory potency was related to the inhibition of epidermal 12-lipoxygenase. Lipoxygenase inhibitors, such as AA 861 and tetrahydrochalcone were lacking in the inhibitory action on protein kinase C. Moreover, palmitoylcarnitin, a protein kinase C inhibitor, inhibited TPA-induced differention of HL 60 cells and TPA-induced epidermal ODC induction and tumor promotion in mouse skin. Intraperitoneal injection of TPA also induced ODC in liver, kidney and spleen, but not in the skin of mice. In isolated mouse epidermal cells, TPA and diacylglycerol induced ODC. The induction of ODC was inhibited by phospholipase A2 inhibitors, lipoxygenase inhibitors, anticalmodulines, Ca++ entry blockers and Ca++ antagonists. These results indicate that intracellular Ca++ is involved in TPA induction of ODC.

Animals↗

Effects of chalcone derivatives on lipoxygenase and cyclooxygenase activities of mouse epidermis.

The effects of chalcone derivatives on 12-lipoxygenase and cyclooxygenase of mouse epidermis were investigated. The chalcone derivatives which have 3,4-dihydroxycinnamoyl structure in the molecule, such as 3,4-dihydroxychalcone, 3,4,2'-trihydroxychalcone, 3,4,4'-trihydroxychalcone and 3,4,2'4'-tetrahydroxychalcone, potently inhibited epidermal 12-lipoxygenase activity. Although some of them also inhibited cyclooxygenase activity at relatively high concentrations, the inhibitory effects of these chalcone derivatives on 12-lipoxygenase were 10 times or more potent than their effects on cyclooxygenase. The chalcone derivatives which have cinnamoyl or 4-hydroxycinnamoyl structure, instead of 3,4-dihydroxycinnamoyl structure, in the molecule, showed little or no inhibitory effects on either 12-lipoxygenase or cyclooxygenase activities. The inhibitory effects of chalcone derivatives on 12-lipoxygenase and cyclooxygenase of mouse epidermis are dependent on the particular structure, i.e. 3,4-dihydroxycinnamoyl structure, of the chalcone derivatives.

Animals↗

Inhibition of mouse epidermal 12-lipoxygenase by 2,3,4-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinon e (AA861).

2,3,5-Trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone (AA861) strongly inhibited epidermal lipoxygenase activity which was determined by the formation of [14C]12-hydroxy-5,8,10,14-eicosatetraenoic acid by incubating [14C]arachidonic acid with cytosol fraction of epidermal homogenate of CD-1 mice. AA861 failed to inhibit epidermal cyclooxygenase activity. The present results indicate that AA861 is a potent inhibitor of 12-lipoxygenase in mouse epidermis (IC50 1.9 microM).

Animals↗

Inhibition of teleocidin-caused epidermal ornithine decarboxylase induction by phospholipase A2-, cyclooxygenase- and lipoxygenase-inhibitors.

Teleocidin (5 micrograms/mouse), a potent tumor promoting indole alkaloid from Streptomyces, induced epidermal ornithine decarboxylase (ODC) in CD-1 mice. Teleocidin-caused ODC induction was inhibited by the treatment of indomethacin (2 mumol/mouse), a selective cyclooxygenase inhibitor, and p-bromophenacyl bromide (BPB) (30 mumol/mouse), a phospholipase A2 inhibitor. Teleocidin-caused ODC induction inhibited by indomethacin was completely restored by concurrent application of prostaglandin E2 (PGE2) (140 nmol/mouse). On the other hand, teleocidin-caused ODC induction inhibited by BPB was not restored by the treatment of mice with PGE2, but partially restored by the treatment with arachidonic acid (1 mumol/mouse). Treatment of mice with lipoxygenase inhibitors such as BW755C (30 mumol/mouse), nordihydroguaiaretic acid (NDGA) (30 mumol/mouse), quercetin (10 mumol/mouse), and 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone (AA861) (10 mumol/mouse) clearly suppressed ODC induction by teleocidin. Moreover, both NDGA (30 mumol/mouse) and quercetin (10 mumol/mouse) inhibited the restoring effect of PGE2. Therefore, our present results suggest that arachidonate metabolites, i.e., not only cyclooxygenase product(s) but also lipoxygenase product(s), are involved in the mechanism of ODC induction by teleocidin.

Animals↗

Inhibition of 12-O-tetradecanoylphorbol-13-acetate-induced increase in vascular permeability in mouse skin by lipoxygenase inhibitors.

The painting of mouse dorsal skin with 12-O-tetradecanoylphorbol-13-acetate (TPA) (0.2-2.5 nmol/mouse) induced a dose-related increase in vascular permeability, which was determined by pontamine sky blue exudation into the skin 5 hr after the TPA treatment. Marked infiltration of neutrophils in the dermal interstitium was also observed 5 hr after TPA treatment. Treatment of mice with nordihydroguaiaretic acid (NDGA) (10 mumol/mouse). 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone (AA861) (10 mumol/mouse) and quercetin (3 mumol/mouse) significantly inhibited the TPA-induced dye exudation. However, indomethacin (250-1000 nmol/mouse) tended to inhibit the TPA-induced dye exudation, but the inhibition was not statistically significant. Treatment with AA861 (10 mumol/mouse) also caused a marked inhibition of TPA-induced neutrophil infiltration. Quercetin, NDGA and AA861 inhibited epidermal lipoxygenase activity, but indomethacin failed to inhibit it. On the other hand, indomethacin inhibited epidermal cyclooxygenase, but quercetin, NDGA and AA861 failed to inhibit it. The present study suggests involvement of a lipoxygenase product(s) in the mechanism of the TPA-induced increase in vascular permeability in the dorsal skin of mice.

Animals↗

Lipoxygenase inhibitors and cyclic AMP-mediated insulin secretion caused by forskolin, theophylline and dibutyryl cyclic AMP.

Forskolin caused a marked and a concentration-dependent elevation of cyclic AMP content in isolated pancreatic islets (EC50, 10 microM). Cyclic AMP level reached a plateau within 30 min after the addition of 10 microM forskolin. In a low glucose (3.3 mM) medium, forskolin induced slight but significant insulin secretion in a concentration-dependent manner (EC50, 0.3 microM). When the glucose concentration was increased to 5.5 mM, marked enhancement of insulin secretion was observed with forskolin (EC50, 0.5 microM). Lipoxygenase inhibitors, such as nordihydroguaiaretic acid, 3-amino-1-(trifluoromethylphenyl)-2-pyrazoline and 1-phenyl-3-pyrazolidinone failed to affect the forskolin-stimulated cyclic AMP generation. The selective cyclooxygenase inhibitor indomethacin also had no influence on forskolin-stimulated cyclic AMP generation. Insulinotropic effects of forskolin, however, were suppressed by these lipoxygenase inhibitors but not by indomethacin. Both nordihydroguaiaretic acid and 1-phenyl-3-pyrazolidinone also prevented the insulinotropic effects of theophylline and dibutyryl cyclic AMP, whereas indomethacin failed to inhibit them. It seems conceivable that a lipoxygenase product(s) is involved in the insulin secretory process distal to cyclic AMP generation, or that alternatively a lipoxygenase product(s) is permissively involved in the insulin secretory process independently from the cyclic AMP-mediated process.

4,5-Dihydro-1-(3-(trifluoromethyl)phenyl)-1H-pyraz↗

Potent antitumor promoting activity of N-6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, a calmodulin antagonist, in mouse skin tumor formation induced by 7,12-dimethylbenz[a]anthracene plus teleocidin.

A calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) markedly inhibited the promoting activity of teleocidin on formation of skin tumors in mice initiated by 7,12-dimethylbenz[a]anthracene. This result strongly indicates that the critical action of the Ca2+-calmodulin system is responsible for tumor promotion in mouse skin.

9,10-Dimethyl-1,2-benzanthracene↗

Inhibition by palmitoylcarnitine of adhesion and morphological changes in HL-60 cells induced by 12-O-tetradecanoylphorbol-13-acetate.

Effects of DL-palmitoylcarnitine (PC), an inhibitor of calciumactivated, phospholipid-dependent protein kinase (protein kinase C), on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced cell differentiation were investigated in human promyelocytic leukemia cells (HL-60). TPA caused HL-60 cell adhesion concomitant with morphological changes, and an increase in acid phosphatase activity. The median effective concentration was 1 nM, which corresponded well to the dissociation constant of [3H]TPA binding to the cell extract. [3H]TPA binding to the cell extract was saturable and reversible. The maximal number of [3H]TPA-binding sites was 1.5 pmol/mg protein and a Hill coefficient was unity, indicating noncooperative interactions. PC, but neither palmitic acid nor DL-carnitine, inhibited the TPA-induced cell adhesion and morphological changes with the median inhibitory concentration of 1 microM, whereas a TPA-induced increase in acid phosphatase activity was not affected by 3 microM PC. Addition of PC 1 or 2 days after the addition of TPA was also effective in inhibiting the cell adhesion. Among various acylcarnitines, PC had the largest effect. [3H]TPA binding to the cell extract was not inhibited by PC at the concentration which was effective in inhibiting the TPA-induced cell adhesion. These results indicate that protein kinase C possibly mediates HL-60 cell differentiation induced by TPA.

Caenorhabditis elegans Proteins↗

Effects of flavonoids and antioxidants on 12-O-tetradecanoyl-phorbol-13-acetate-caused epidermal ornithine decarboxylase induction and tumor promotion in relation to lipoxygenase inhibition by these compounds.

The effects of flavonoids, antioxidants and related compounds on 12-O-tetradecanoylphorbol-13-acetate (TPA)-caused epidermal ornithine decarboxylase (ODC) induction, DNA synthesis and skin tumor promotion, and on epidermal lipoxygenase activity, were investigated using CD-1 mice. Morin, fisetin , kaempferol and n-propyl gallate potently inhibited epidermal lipoxygenase activity, and esculetin , butylated hydroxyanisole (BHA), alpha-naphthol and 2,3- dihydroxynaphthalene (2,3- DHNA ) moderately inhibited it. alpha-Tocopherol, (+)catechin, (-) epicatechin and butylated hydroxytoluene (BHT) were inactive. Similarly, morin, fisetin , kaempferol and n-propyl gallate markedly inhibited TPA-caused ODC induction. Esculetin , BHA, alpha-naphthol, 2,3- DHNA and alpha-tocopherol inhibited it less potently, but significantly. (+)Catechin, (-) epicatechin and BHT failed to inhibit or only slightly inhibited TPA-caused ODC induction. TPA-caused DNA synthesis was not inhibited by morin, esculetin , (+)-catechin or alpha-tocopherol. The TPA-induced skin tumor promotion was markedly inhibited by morin and slightly suppressed by esculetin and alpha-tocopherol, but (+)-catechin was inactive. Thus, the inhibitory effects of flavonoids and antioxidants on the TPA-caused ODC induction and tumor promotion were roughly parallel with their activities of lipoxygenase inhibition. These results further support our hypothesis that a lipoxygenase product(s) is involved in the mechanism of TPA-caused ODC induction and tumor promotion.

Animals↗

[Intrapulmonary reactions of workers exposed to dust and ozone].

Forty-one dust-and-ozone-exposed and 37 nonexposed workers, belonging to the Research and Development Division of a photo-copier manufacturing industry, were examined to assess the effect of the exposure to carbon, iron and resin dust and ozone in the air of the work environment by means of questionnaires on their physical condition, smoking habits and exposure history by interview, chest X-rays, testing of ventilatory functions, transcutaneous PO2 (tcPO2) test and H2O2-induced hemolysis test. The following results were obtained. Respirable dust concentrations in the air of the work place were 0.1-1.0 mg/m3, total dust concentrations 0.2-2.0 mg/m3, and ozone concentrations 0.004-0.06 ppm (0.008-0.12 mg/m3). According to the Japanese Classification of Radiographs of Pneumoconioses, the exposed workers showed a higher rate of profusion 0/1 and over, and category 1 and over (1/0 and over) than the nonexposed workers. Ventilatory function testing revealed no difference between exposed workers and nonexposed workers, but small airway narrowing was suspected in smoking workers in comparison with nonsmoking workers. Transcutaneous PO2 showed no difference between exposed and nonexposed workers, between smoking and nonsmoking workers, and between any of the paired six combinations out of the four groups of workers, i.e., nonsmoking and nonexposed, nonsmoking and exposed, smoking and nonexposed, and smoking and exposed. It was estimated by H2O2-induced hemolysis test that smoking and/or dust exposure, especially long-term exposure, gave rise to aggravation of fragility of the erythrocyte membrane by lipid peroxidation with ozone or active oxygen produced by the reaction of dust and alveolar macrophages. The questionnaire was considered indispensable to ascertain the workers' exposure history. No worker in this work environment showed clinical signs indicating a need for medical care or home response. There results may indicate that in resolving the pathogenesis of pneumoconiosis further studies will be required on the prevalence rate of profusion 0/1 and over (or category 1 and over) under low concentrations of dust exposure and on the intrapulmonary reactions induced by low doses of dust exposure.

Adult↗

Insulinotropic effect of the tumor promoter teleocidin in isolated pancreatic islets.

A tumor promoter teleocidin induced insulin secretion from isolated pancreatic islets in a concentration-dependent manner. The teleocidin-induced secretion was inhibited by p-bromophenacyl bromide, nordihydroguaiaretic acid, 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline and 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone, but not by indomethacin. Insulinotropic concentrations of teleocidin stimulated 6-keto-prostaglandin F1 alpha release from pancreatic islets. These results suggest that phospholipase A2 activation and lipoxygenase product(s) are involved in the mechanism of teleocidin-induced insulin secretion.

Alkaloids↗

Developmental changes in the effect of morphine, epinephrine and carbachol on plasma cyclic nucleotide level in rats.

The developmental changes in the effects of morphine, FK 33-824, a synthetic opioid peptide, epinephrine and carbachol on the plasma cyclic AMP and GMP level were investigated in rats ranging in age from 1 to 49 days. The effect of morphine in elevating plasma cyclic AMP and GMP level increased with age with a peak at day 21. The effect of FK 33-824 followed a similar developmental course of that of morphine except at day 49. Epinephrine and carbachol increased the plasma cyclic AMP level even in one-day old rats. The increase in plasma cyclic GMP induced by carbachol increased with age, peaked at day 14, then declined until day 49. These results suggest that the delay in advent of the effect of opioids on plasma cyclic nucleotides in the early neonatal period is mainly due to the slow development of opioid receptors in the brain.

Aging↗

Modulation of insulin secretion by lipoxygenase products of arachidonic acid. Relation to lipoxygenase activity of pancreatic islets.

Glucose (16.7 mM)-induced insulin secretion from isolated pancreatic islets of rats was inhibited by nordihydroguaiaretic acid (NDGA), 1-phenyl-3-pyrazolidinone (phenidone), 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline (BW755C), 2,3,5-trimethyl-6-(12-hydroxy-5,10-dodecadiynyl)-1,4-benzoquinone (AA861), and 2,6-di-tert-butyl-4-methylphenol (BHT). Indomethacin and aspirin, however, failed to inhibit the glucose-induced insulin secretion but rather tended to enhance it. The glucose-induced insulin secretion was inhibited by 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE) (50 microM), 15-hydroperoxy-5,8,11,13-eicosatetraenoic acid (15-HPETE) (100 microM), and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) (100 microM), but not by 5-hydroxy-6,8,11,14-eicosatetraenoic acid (5-HETE) (100 microM). Exogenous 5-HETE (10 microM) induced significant insulin secretion in a low glucose (3.3 mM) medium. Racemic 5-HETE also showed insulinotropic effect in a concentration-dependent manner with the concentrations 20 microM or above, whereas 12-HETE, 15-HETE, 15-HPETE, 5,12-dihydroxy-6,8,10,14-eicosatetraenoic acid, 5-hydroxy-6-glutathionyl-7,9,11,14-eicosatetraenoic acid, 5-hydroxy-6-cysteinylglycinyl-7,9,11,14-eicosatetraenoic acid, prostaglandin E2, and prostaglandin F2 alpha failed to induce insulin secretion. Although significant insulin release was observed with arachidonic acid (greater than or equal to 100 microM), reduce cell viability was evident at 200 microM. When the 10,000 X g supernatant of isolated pancreatic islet homogenate was incubated with [3H]arachidonic acid at 37 degrees C in the presence of GSH and Ca2+, and the labeled metabolites then extracted with ethyl acetate and subjected to reverse phase high pressure liquid chromatography, several radioactive peaks, coeluted with authentic 15-, 12-, and 5-HETE, were observed. The radioactive peaks were completely suppressed by the addition of either NDGA, BW755C, or phenidone into the medium. The results support our contention i.e. the involvement of lipoxygenase product(s) in the secretory mechanism of insulin, and further suggest that 5-lipoxygenase system may play a role.

Animals↗

Stimulation of 6-keto-prostaglandin F1 alpha release from isolated pancreatic islets by an insulinotropic concentration of glucose.

In a glucose-free medium, the release of 6-keto-prostaglandin F1 alpha from isolated pancreatic islets was 1.67 pg/islet/60 min. The release was not altered by increasing the glucose concentration to 3.3 mM, whereas the release was significantly increased to 3.79 pg/islet/60 min by 16.7 mM glucose. Indomethacin (10 microM) and mepacrine (100 microM) markedly suppressed the 6-keto-prostaglandin F1 alpha release. The results indicate that the insulinotropic concentration of glucose enhances the enzymatic formation of 6-keto-prostaglandin F1 alpha in pancreatic islets. It seems highly possible that glucose enhances 6-keto-prostaglandin F1 alpha formation by stimulating phospholipase A2 in pancreatic islets.

6-Ketoprostaglandin F1 alpha↗

Protection against alloxan-induced diabetes in mice by stimulation of alpha 2-adrenergic receptors.

A single intravenous injection of alloxan in mice induced hyperglycemia in a dose dependent fashion. This diabetogenic action of alloxan was prevented by a single intraperitoneal injection of the alpha 2-adrenergic agonists, i.e. oxymetazoline, clonidine or epinephrine 40 min prior to the injection of alloxan. The alpha 1-adrenergic agonists, i.e. methoxamine and phenylephrine, and a beta-adrenergic agonist, isoproterenol, failed to prevent the diabetogenic action of alloxan. The inhibitory effect of clonidine on alloxan-induced diabetes was antagonized by yohimbine or phentolamine, but not by prazosin. Although alpha 2-adrenergic agonists caused a transient hyperglycemia at the time of alloxan administration (40 min after the administration of alpha 2-adrenergic agonists), the plasma glucose level at the time of alloxan injection did not correlate with the anti-diabetogenic effect of alpha 2-adrenergic agents. These results clearly demonstrate that the alpha 2-adrenergic mechanism which inhibits insulin release from pancreatic B cells prevented the diabetogenic action of alloxan in mice.

Adrenergic alpha-Agonists↗

Inhibition of dibutyryl cyclic AMP-induced insulin release by alpha-2 adrenergic stimulation.

Effects of alpha adrenergic agonists and antagonists on dibutyryl cAMP (Bt2cAMP)-induced insulin release were investigated with isolated rat pancreatic islets. Bt2cAMP (4 mM) produced 2-fold stimulation of insulin release in all the concentrations of glucose examined (3.3-16.7 mM). Clonidine but not phenylephrine inhibited the Bt2cAMP-stimulated insulin release in a concentration-dependent manner with approximate EC50 of nanomolar range. Yohimbine but not prazosin antagonized the inhibitory effect of clonidine on the Bt2-cAMP-induced insulin release. These results suggest that alpha-2 adrenergic mechanisms are involved in a step distal to cAMP generation.

Adrenergic alpha-Agonists↗