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Biomedical subjects

K Waku

Publications and source records attributed to K Waku.

At least 73 records · Page 4Linked to original sources
PubMed1991

Transient activation of 1-O-alkyl-sn-glycero-3-phosphocholine: acetyl-CoA acetyltransferase during the incubation of macrophages.

The activity of the platelet-activating factor (PAF)-synthesizing enzyme, 1-O-alkyl-sn-glycero-3-phosphocholine (lysoPAF):acetyl-CoA acetyltransferase (EC 2.3.1.67) in alveolar macrophage lysate was found to be elevated after warming the cells to 37 degrees C. Such an increase in enzyme activity was detectable only when intact cells were warmed. The stimulation was transient, reaching a peak at 2 min, and then gradually decreased to the control level. We could not find increased PAF formation in warmed cells which had increased acetyltransferase activity, even though substantial amounts of lysoPAF were shown to be present within cells. In contrast, considerable amounts of PAF were formed after treatment of the cells with exogenous lysoPAF. These results suggest that the activation of acetyltransferase is not sufficient to induce PAF formation and that the increased availability of substrates, especially lysoPAF, in the cells is indispensable for triggering PAF biosynthesis in this type of cells.

Acetyl Coenzyme A↗
PubMed1991

Regulation of the biosynthesis of platelet-activating factor in alveolar macrophages.

Activities of enzymes which metabolize lysoplatelet-activating factor (lysoPAF) and platelet-activating factor (PAF) were studied in rabbit alveolar macrophage lysates. Substantial acetyltransferase activity was noted in the presence of 100 microM acetyl-coenzyme A (CoA), and this activity was increased in A23187-stimulated cell lysate. On the other hand, in the absence of exogenous acetyl-CoA, lysoPAF was mainly acylated through a transacylation pathway rather than by acetyltransferase in both control and A23187-stimulated cell lysates. We confirmed that the intracellular concentration of acetyl-CoA is relatively low. The observations suggest that the transacylation system may play an equally important role in the regulation of the availability of lysoPAF in intact cells. Intracellular lysoPAF was also maintained at relatively low levels. Interestingly, large amounts of PAF were produced even in unstimulated cells upon addition of an excess of exogenous lysoPAF, suggesting that generation of an adequate amount of lysoPAF within cells may be sufficient to trigger PAF synthesis in this type of cells.

Acetyl Coenzyme A↗
PubMed1991

Production of platelet-activating factor by human normodense and hypodense eosinophils.

Normodense eosinophils and neutrophils from normal donors produced considerable amounts of platelet-activating factor (PAF) when stimulated with ionophore A23187. PAF produced by eosinophils appeared to be degraded more rapidly than PAF formed by neutrophils, suggesting a higher activity of PAF-degrading enzyme in eosinophils. Substantial proportions of PAF newly formed by both eosinophils and neutrophils were shown to be cell-associated. By comparison, hypodense eosinophils obtained from a patient with idiopathic hypereosinophilic syndrome produced an extremely large amount of PAF and released much of it into the incubation medium. The accelerated formation of PAF in hypodense eosinophils may be related to various cardiovascular complications associated with hypereosinophilic syndrome.

Eosinophilia↗
PubMed1991

Prevention by zinc of cadmium inhibition of stearoyl-CoA desaturase in rat liver.

Rats were fed a fat-free diet that contained zinc (50 ppm; ZA rats) or a fat-free diet without zinc (less than 2 ppm; ZD rats) for 16 days. Some rats in these two groups were injected subcutaneously with cadmium (Cd) at a dose of 0.01 mmol/kg body weight 48 h before they were killed. The treatment of ZD rats with Cd reduced the activity of liver microsomal stearoyl-CoA desaturase by 90% without any changes in the activity of NADH-cytochrome b5 reductase or in the microsomal level of cytochrome b5 whereas the activity of stearoyl-CoA desaturase was reduced by only 35% by the treatment of ZA rats with Cd. Exposure of ZD rats to Cd decreased the proportions of 18:1 (n-9) and 20:3 (n-9) in the major phospholipids of the liver, whereas the ZA rats showed few changes in fatty acid composition when they were treated with Cd. Although the changes in fatty acid composition were most marked in phosphatidylcholine among the various phospholipids, the activity of microsomal l-acylglycerophosphocholine (1-acyl GPC) acyltransferase was not affected by treatment with Cd. These results suggest that zinc is essential for the protection of hepatic stearoyl-CoA desaturase from challenges by Cd and that delta 9 desaturase plays a crucial role in the control of the acyl composition of hepatic phospholipids.

Animals↗
PubMed1991

Suppression of ethanolamine-containing glycerophospholipid synthesis in HL-60 cells during retinoic acid-induced differentiation.

Synthesis and degradation of glycerophospholipids in HL-60 cells and retinoic acid (RA)-treated HL-60 cells were examined. The synthesis of each subclass of ethanolamine-containing glycerophospholipids was extremely suppressed in RA-treated HL-60 cells, while that of other glycerophospholipids was not seriously affected. A pulse-chase experiment revealed that about 88% of 1,2-diacyl and 28% of 1-alkenyl-2-acyl glycerophosphoethanolamine were degraded during 4 days in RA-treated HL-60 cells. These characteristics of metabolism observed in RA-treated HL-60 cells might be responsible for the change of subclass composition of ethanolamine-containing glycerophospholipids in HL-60 cells during differentiation to granulocytes.

Cell Differentiation↗
PubMed1991

Production of platelet-activating factor in slugs.

The land slug, Incilaria bilineata, was shown to contain a large amount of 1-O-alkyl-2-acyl (long chain)-sn-glycero-3-phosphocholine, which accounts for as much as 47% of the choline glycerophospholipid fraction. Since this unique either phospholipid has been regarded as a stored precursor form of platelet-activating factor (PAF) in mammalian inflammatory cells, we examined the possibility of the presence of PAF in this animal. We obtained the evidence for the occurrence of significant amounts of PAF in two species of slugs, Incilaria bilineta and Incilaria fruhstorferi. Gas chromatography-mass spectrometry analysis revealed that the alkyl fatty chain of PAF principally consists of 16:0. We confirmed the presence of both enzyme activities catalyzing the formation of PAF, one for the remodeling pathway and the other for the de novo pathway. We also found the occurrence of other enzyme activities involved in PAF metabolism: acetylhydrolase activity which inactivates PAF and phospholipase A2 activity toward alkylacylglycerophosphocholine. However, we failed to detect cofactor-independent transacylation activity in this animal. The amounts of PAF in slugs were markedly increased when slugs were administered several treatments which are considered to induce shock, such as the injection of dimethyl sulfoxide or injuries. These results suggest that PAF is produced and may have certain physiological and pathological roles in the land slug, as in the case of mammals.

Acetyltransferases↗
PubMed1990

Ether lysophospholipid-induced production of platelet-activating factor in human polymorphonuclear leukocytes.

Human polymorphonuclear leukocytes (PMN) produced considerable amounts of platelet-activating factor (PAF) when exposed to various concentrations of lyso-PAF, especially in the absence of albumin. The amount of produced PAF in the presence of 5 microM lyso-PAF (without albumin) was 1.1 pmol/10 min per 2.5 X 10(6) cells, which was close to the level in the case of opsonized zymosan stimulation. We found that the activity of neither acetyltransferase nor acetylhydrolase was affected markedly by the treatment of cells with lyso-PAF, suggesting that the increased availability of lyso-PAF could be responsible for the induction of PAF synthesis. We also found that PAF synthesis was induced not only by lyso-PAF but also by ether-containing ethanolamine lysophospholipids, 1-alkenyl(alkyl)-sn-glycero-3-phosphoethanolamine (GPE). The addition of 1-alkenyl(alkyl)-GPE caused the degradation of pre-existing 1-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine (GPC) and an increased level of lyso-PAF, followed by the formation of PAF. By contrast, 1-acyl-GPC and 1-acyl-GPE failed to induce PAF production. These results suggest a possible key role of the availability of lyso-PAF in triggering the biosynthesis of PAF in human PMN.

Acetates↗
PubMed1990

Effects of zinc deficiency on the fatty acid composition and metabolism in rats fed a fat-free diet.

The effects of dietary zinc deficiency (ZD) on the composition and metabolism of the fatty acyl chains of phospholipids in rat liver were investigated with a fat-free diet. The levels of (n - 9) fatty acids such as 18:1 and 20: 3(n - 9) in liver phospholipids (PL) were significantly lower in ZD-rats (19.4% and 5.4%, respectively) than in PF-rats (25.2 and 8.3%). On the other hand, the levels of (n - 6) acids such as 18:2 and 20:4 were higher in ZD-rats (3.3 and 19.1%, respectively) than in PF-rats (2.1 and 14.9%). In order to study the metabolism of fatty acids in vivo, 14C-18:0 or 14C-18:2 was intravenously injected, and then the conversion to the respective metabolite was examined. After the injection of 14C-18:0, the radioactivity was found in 18:0 (49.3% of the total), 18:1 (33.2%), and 20:3 (n - 9) (9.1%) in liver PL in PF-rats at 24 h. In ZD-rats, the radioactivity was dramatically lower in 18:1 (23.5%) and 20:3 (n - 9) (3.6%), suggesting that the conversion of 18:0 to 18:1 and 20:3 (n - 9) was strongly inhibited in ZD-rats. When 14C-18:2 was injected, the radioactivity was mainly found in 18:2, 20:3 (n - 6), and 20:4. The radioactivity in 20:4 in ZD-rats was slightly higher than that in control rats. These results indicate that zinc deficiency affects the fatty acid metabolism in liver, in particular, it causes a reduction in delta 9 desaturase activity, when rats are fed a fat-free diet.

Animals↗
PubMed1990

The effect of cadmium on the composition and metabolism of hepatic fatty acids in zinc-adequate and zinc-deficient rats.

Exposure to cadmium (Cd) caused changes in the fatty acid composition of phospholipids, such as increases in levels of saturated and (n-6) fatty acids and decreases in levels of (n-9) fatty acids, in the liver phospholipids of rats fed a fat-free diet. These changes were similar to those caused by dietary zinc deficiency. The changes in fatty acid composition after administration of Cd were greater in zinc-deficient (ZD) rats than zinc-adequate (ZA) rats. When [14C]18:0 was injected intravenously in order to examine the metabolism of (n-9) fatty acids, a decrease in the rate of conversion of [14C]18:0 to [14C]18:1 was observed in liver phospholipids after treatment of ZD rats with Cd. These results suggested that Cd can affect the metabolism of fatty acids in relation to zinc status and, in particular, causes a reduction in the activity of delta 9-desaturase which converts 18:0 to 18:1.

Animals↗
PubMed1989

Augmented production of platelet-activating factor in human polymorphonuclear leukocytes by ketone bodies.

The production of platelet-activating factor (PAF) in A23187-stimulated human polymorphonuclear leukocytes was markedly increased in the presence of 5 mM acetoacetate and beta-hydroxybutyrate. Such an augmentation was observed even at 500 microM but not at 50 microM. The augmented production of PAF by acetoacetate was also observed in the presence of autologous serum and was most prominent in the case of opsonized zymosan-stimulation rather than A23187-stimulation. These observations suggest that increased levels of acetoacetate and beta-hydroxybutyrate in blood may lead to the augmented production of PAF, which would amplify the various PAF-mediated biological reactions.

3-Hydroxybutyric Acid↗
PubMed1989

Selective acyl transfer in the reacylation of brain glycerophospholipids. Comparison of three acylation systems for 1-alk-1'-enylglycero-3-phosphoethanolamine, 1-acylglycero-3-phosphoethanolamine and 1-acylglycero-3-phosphocholine in rat brain microsomes.

The activities of three acylation systems for 1-alkenylglycerophosphoethanolamine (1-alkenyl-GPE), 1-acyl-GPE and 1-acylglycerophosphocholine (1-acyl-GPC) were compared in rat brain microsomes and the acyl selectivity of each system was clarified. The rate of CoA-independent transacylation of 1-[3H]alkenyl-GPE (approx. 4.5 nmol/10 min per mg protein) was about twice as high as in the case of 1-[3H]acyl-GPE and 1-[14C]acyl-GPC. On the other hand, the rates of CoA-dependent transacylation and CoA + ATP-dependent acylation (acylation of free fatty acids by acyl-CoA synthetase and acyl-CoA acyltransferase) of lysophospholipids were in the order 1-acyl-GPC greater than 1-acyl-GPE much greater than 1-alkenyl-GPE. HPLC analysis of newly synthesized molecular species revealed that the CoA-independent transacylation system exclusively esterified docosahexaenoate and arachidonate, regardless of the lysophospholipid class. The CoA-dependent transacylation and CoA + ATP-dependent acylation systems were almost the same with respect to the selectivities for unsaturated fatty acids when the same acceptor lysophospholipid was used, but some distinctive acyl selectivities were observed with different acceptor lysophospholipids. 1-Alkenyl-GPE selectively acquired only oleate in these two systems. 1-Acyl-GPE and 1-acyl-GPC showed selectivities for both arachidonate and oleate. In addition, an appreciable amount of palmitate was transferred to 1-acyl-GPC, not to 1-acyl-GPE, in CoA- or CoA + ATP-dependent manner. The acylation of exogenously added acyl-CoA revealed that the acyl selectivities of the CoA-dependent transacylation and CoA + ATP-dependent acylation systems may be mainly governed through the selective action of acyl-CoA acyltransferase. The preferential utilization of oleoyl-CoA by all acceptors and the different utilization of arachidonoyl-CoA between alkenyl and acyllysophospholipids indicated that there might be two distinct acyl-CoA:lysophospholipid acyltransferases that discriminate between oleoyl-CoA and arachidonoyl-CoA, respectively. Our present results clearly show that all three microsomal acylation systems can be active in the reacylation of three major brain glycerophospholipids and that the higher contribution of the CoA-independent system in the reacylation of ethanolamine glycerophospholipids, especially alkenylacyl-GPE, may tend to enrich docosahexaenoate in these phospholipids, as compared with in the case of diacyl-GPC.

Acyltransferases↗
PubMed1989

Separation of the molecular species of diacyl and alkenylacyl subclasses of the methyl ester of dinitrophenylethanolamine glycerophospholipid by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) procedure for the separation of the molecular species of alkenylacyl and diacyl subclasses after the derivatization of ethanolamine glycero-phospholipids (EGP) to the methyl ester of the dinitrophenylated lipids is described. Methyl esters of dinitrophenylethanolamine glycerophospholipids were first separated into alkenylacyl, alkylacyl and diacyl subclasses by thin-layer chromatography, then each subclass was separated into individual molecular species by reversed-phase HPLC. By converting the EGP into UV-absorbing derivatives, it proved possible to utilize the specificity of spectrophotometric detection for the determination of the individual molecular species. Alkenylacyl and diacyl derivatives were resolved into fifteen to twenty different species in a single HPLC run. The method should facilitate studies on the metabolism of the polar head group of both molecular species of alkenylacyl and diacyl glycerophosphoethanolamine in a variety of tissues using radioactive precursors.

Animals↗
PubMed1989

The de novo synthesis of molecular species of phosphatidylinositol from endogenously labeled CDP diacylglycerol in alveolar macrophage microsomes.

The de novo synthesis of molecular species of phosphatidylinositol (PI) from endogenously labeled CDP diacylglycerol (CDP-DG) and phosphatidic acid (PA), with [14C]-glycerol 3-phosphate, in microsomes of macrophages was studied using a recently developed HPLC technique. Endogenously labeled PA, CDP-DG, and PI were sequentially formed from labeled glycerol 3-phosphate through the addition of CoA, CTP, and then inositol into microsomes. The rate of formation of CDP-DG from endogenously labeled PA was low as compared with those of PA and PI. The low rate of CDP-DG synthesis suggests that it may be the rate-limiting step in the de novo synthesis of PI. Analysis of newly synthesized molecular species of PI by HPLC revealed that large proportions of radioactivity were associated with the 16:0-18:1, 16:0-18:2, 18:1-18:2, and 18:2-18:2 species, and a small amount, 2-3%, of radioactivity was associated with the 18:0-20:4 species. The profiles of newly synthesized PA and CDP-DG species were quite similar to those of PI species. This suggests that the enzymes involved in the formation of PI species from glycerol 3-phosphate show little specificity toward different molecular species of substrates. The results of the present study also suggest that free fatty acid composition in microsomes greatly affect the composition of the molecular species of PI synthesized through the de novo pathway, since the proportion of fatty acids utilized for the de novo synthesis of PI species was similar to that of free fatty acids in the microsomal membrane.

Adenosine Triphosphate↗
PubMed1988

Coenzyme A-dependent transacylation system in rabbit liver microsomes.

The activities of cofactor-independent and CoA-dependent transacylation were examined for various rabbit tissues. Liver microsomes were found to exhibit relatively high CoA-dependent transacylation activity, while the cofactor-independent transacylation activity was low. The apparent Km values for CoA were 1.4 microM (acceptor, 1-acyl-sn-glycero-3-phosphocholine (1-acyl-GPC] and 3.8 microM (acceptor, 1-acyl-sn-glycero-3-phosphoethanolamine (1-acyl-GPE], respectively. The apparent Vmax values were 2.6 nmol/min/mg (1-acyl-GPC) and 1.2 nmol/min/mg (1-acyl-GPE), respectively. The CoA-dependent transacylation reaction shows a distinct fatty acid specificity. [14C]18:2 and [14C]20:4 at the 2-positions and [14C]18:0 at the 1-positions of donor phospholipids were transferred to lysophospholipids in the presence of CoA. We observed the formation of considerable amounts of acyl-CoA from these fatty acids during the reaction, without the participation of ATP. The transfer of other fatty acids between phospholipids was shown to be almost nil. The very low transfer of 18:1 was in marked contrast to the effective utilization of 18:1-CoA by acyl-CoA:1-acyl-GPC acyltransferase. The effects of several compounds and heat treatment on these two acylation reactions were also examined. The CoA-dependent transacylation reaction may be important for the selective acylation of certain lysophospholipids, such as 1-acyl-GPE, in living cells with the cooperation of acyl-CoA:lysophospholipid acyltransferase, which generates CoA for the former reaction.

Acylation↗
PubMed1988

Selective inhibition of free arachidonic acid production in activated alveolar macrophages by calmodulin antagonists.

The effect of calmodulin antagonists on the amounts of free fatty acids produced by rabbit alveolar macrophages was determined by fluorometric high-performance liquid chromatography. Opsonized zymosan-induced arachidonic acid production was dramatically suppressed in the presence of W-7 and trifluoperazine without an effect on the production of other fatty acids. Calmodulin antagonists inhibited phospholipase A and abolished the release of arachidonic acid from phospholipids. The present results suggest that a zymosan-sensitive pool of 20:4, which is different from that of other fatty acids, is present in macrophages and that calmodulin antagonists selectively inhibit phospholipase A, which preferentially degrades phospholipids with 20:4.

Acetophenones↗
PubMed1988

Species pattern of phosphatidylinositol from lung surfactant and a comparison of the species pattern of phosphatidylinositol and phosphatidylglycerol synthesized de novo in lung microsomal fractions.

1. Phosphatidylinositol (PI) is a minor component of lung surfactant which may be able to replace the functionally important phosphatidylglycerol (PG) [Beppu, Clements & Goerke (1983) J. Appl. Physiol. 55, 496-502] without disturbing lung function. The dipalmitoyl species is one of the main species for both PI (14.4%) and PG (16.9%). Besides the C16:0--C16:0 species, the C16:0--C18:0, C16:0--C18:1, C16:0--C18:2 and C18:0--C18:1 species showed comparable proportions in the PG and PI fractions. These similarities of the species patterns and the acidic character of both phospholipids could explain why surfactant PG may be replaced by PI. 2. PI and PG were radiolabelled by incubation of microsomal fractions with [14C]glycerol 3-phosphate (Gro3P). For 11 out of 14 molecular species of PI and PG we measured comparable proportions of radioactivity. The radioactivity of these 11 species accounted together for more than 80% of the total. The addition of inositol to the incubation system decreased the incorporation in vitro of Gro3P into PG and CDP-DG (diacylglycerol) of lung microsomes (microsomal fractions), but did not change the distribution of radioactivity among the molecular species of PG. These results supported the idea that both acidic surfactant phospholipids may be synthesized de novo from a common CDP-DG pool in lung microsomes.

Acylation↗