Inhibition of lymphocyte mitogenesis by an arachidonic acid hydroperoxide

Incubation of murine spleen cells with the oxidation product of soybean lipoxidase-treated arachidonic acid results in profound inhibition of induction of proliferation and maturation of these cells. The active entity was shown to be the 15-hydroperoxide of arachidonic acid (15-HPAA). Inhibition of the enzymes of the cyclo-oxygenase pathway fails to disturb this effect, indicating that 15-HPAA is not a substrate for this series of enzymes. 15-HPAA produced in this manner interfered with RNA synthesis, DNA synthesis, and blastogenesis, while failing to exert cytotoxic effects on the cells themselves. A variety of lymphocyte subpopulations, distinguished by their responsiveness to a diverse group of mitogens, were all equally inhibited by the addition of 15-HPAA to culture. Addition of this agent even as late as 24 h after initiation of culture resulted in profound inhibition of the proliferative and differentiative responses of splenic B cells to bacterial lipopolysaccharide (LPS). Exposure of cells to 15-HPAA for 10–30 min was adequate to initiate inhibition, an event that exhibited marked temperature dependence. The effects of pre-incubation with 15-HPAA could not be reversed in its absence in recovery periods of up to 6 h prior to addition of LPS. The implications of these data with reference to cellular activation mechanisms are discussed.     

Biosynthesis of arachidonic acid by micromycetes (review)

Arachidonic acid (ARA, 5,8,1l,14-cis-eicosatetraenoic acid) is widely used in medicine, pharmaceutics, cosmetics, dietary nutrition, agriculture, and other fields. Microbiological production of ARA is of increased interest since the natural sources (pig liver, adrenal glands, and egg-yolk) cannot satisfy its growing requirements. Mechanisms for ARA biosynthesis as well as the regulation of enzymes involved in this process are considered. Review summarizes literature data concerning individual stages of microbiological ARA production, methods for screening of active strains-producers, physiological regulation of ARA synthesis in micromycetes (the effect of growth phase, medium composition, pH, temperature, and aeration), and effective technologies of fermentation and the product recovery. Information on the whole biotechnological process from strain selection to the ARA yield improvement and purification of the end product is presented.     

Biosynthesis,conjugation, catabolism and homeostasis of indole-3-acetic acid in Arabidopsis thaliana

Plant Molecular Biology -     

Biosynthesis,conjugation, catabolism and homeostasis of indole-3-acetic acid in Arabidopsis thaliana

Plant Molecular Biology -     

Biosynthesis of prostaglandins from arachidonic acid by the rat ovary

Biosynthesis of prostaglandins (PGs) from ¹⁴C-arachidonic acid was studied using homogenates of the ovaries from immature rats. In ascending order of metabolizing potency were, the ovaries from untreated rats, from rats treated with pregnant mare's serum gonadotropin (PMS), and from PMS-human chorionic gonadotropin (hCG) treated rats. Among the radioactive metabolites extracted, PGE₂ and 6-keto PGF_1∝ were purified and identified by silicic acid column-, thin layer-, reversed phase partition chromatographies, and radiogaschromatography. Production of PGE₂ and 6-keto PGF_1∝ was observed in homogenates of the ovaries of intact and PMS-hCG treated rats at conversion rates of 0.72; 0.43% and 7.62; 2.31%, but not by FMS treated rat ovaries. Treatment with PMS-hCG activated metabolism of arachidonic acid into radioactive metabolites including PGE2 and 6-keto PGF_1α to a large extent. Accordingly, it is concluded that luteinizing hormone and hCG play a significant role in the biosynthesis of PGs by the rat ovarian follicle.     

Effect of tert-butyl hydroperoxide on cyclooxygenase and lipoxygenase metabolism of arachidonic acid in rabbit platelets

The effect of tert-butyl hydroperoxide (t-BOOH) on the formation of thromboxane (TX) B2, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) from exogenous arachidonic acid (AA) in washed rabbit platelets was examined. t-BOOH enhanced TXB2 and HHT formation at concentrations of 8 microM and below, and at 50 microM it inhibited the formation, suggesting that platelet cyclooxygenase activity can be enhanced or inhibited by t-BOOH depending on the concentration. t-BOOH inhibited 12-HETE production in a dose-dependent manner. When the platelets were incubated with 12-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12-HPETE) instead of AA, t-BOOH failed to inhibit the conversion of 12-HPETE to 12-HETE, indicating that the inhibition of 12-HETE formation by t-BOOH occurs at the lipoxygenase step. Studies utilizing indomethacin (a selective cyclooxygenase inhibitor) and desferrioxamine (an iron-chelating agent) revealed that the inhibitory effect of t-BOOH on the lipoxygenase is not mediated through the activation of the cyclooxygenase and that this effect of t-BOOH is due to the hydroperoxy moiety. These results suggest that hydroperoxides play an important role in the control of platelet cyclooxygenase and lipoxygenase activities.     

植物叶绿素合成、分解代谢及信号调控

叶绿素(Chlorophyll, Chl)合成是决定植物光合效率的重要性状, 是决定作物产量的重要因素。参与植物Chl合成、分解代谢及信号调控的基因数目众多, 其中任何一个基因发生突变都有可能引起Chl含量的变化, 从而表现为各种叶色异常甚至导致植株死亡。自然或人工创造突变体, 对于Chl相关基因的功能分析非常必要。目前, Chl突变体己广泛应用于基础研究和生产实践。文章就该研究领域内的最新研究进展进行了概述。     

Biosynthesis and main biological properties of human gamma interferon

Conditions for and regularities of gamma-interferon production were elucidated. High interferon inducing activity of the known inductors such as concanavalin A, phytohemagglutinin and lentil lectin was asserted. It was shown that aqueous and alcoholic extracts of legumes seeds were also able to induce interferon synthesis in cultures of human peripheral blood leukocytes. By physicochemical properties such as stability to acids and liability to heating and by antigenic properties, interferon produced under such conditions was of type 2 (gamma). The maximum yield of interferon was observed in stationary and roller leukocyte cultures at a density of 2.10(6)-4.10(6) cells/ml on commercial rich media (IMDM and Eagle medium). Dynamics of gamma-interferon biosynthesis was determined. The peak of interferon production after the leukocyte induction with plant lectins was recorded in 72-96 hours.     

The regulation of formation of prostaglandins and arachidonoyl-CoA from arachidonic acid in rabbit kidney medulla microsomes by linoleic acid hydroperoxide

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). In the present study, we investigated the effects of linoleic acid (LA) and 13-hydroperoxyoctadecadienoic acid (13-HPODE) on the PG and AA-CoA formation from high and low concentrations of AA (60 and 5 microM) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 microM [(14)C]-AA in 0.1M Tris-HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl(2) and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. LA (10-50 microM) reduced only PG formation from both 60 and 5 microM AA. 13-HPODE (10-50 microM) also reduced PG formation from 60 and 5 microM AA, but the inhibitory potency was much stronger than that by LA. Furthermore, 13-HPODE had the potential to increase the AA-CoA formation with a decrease in the PG formation from 5 microM AA. These results suggest that 13-HPODE, but not LA, may shift AA away from COX pathway into ACS pathway under low substrate concentration (near physiological concentration of AA).     

Some biological properties of new quinoline-4-carboxylic acid and quinoline-4-carboxamide derivatives

The antimicrobial and morphogenetic effects of fourteen newly synthesized 2-substituted derivatives of quinoline-4-carboxylic acid and quinoline-4-carboxamide were studied using G⁺ and G⁻ bacteria, yeasts and filamentous fungi. The highest antimicrobial effects were found with substituted quinoline-4-carboxylic acid derivatives. Quinoline-4-carboxamides only weakly influenced the growth of the tested microorganisms. Some derivatives of quinoline-4-carboxylic acid elicited profound changes in the morphology of hyphal tips ofBotrytis cinerea, mainly their branching and the release of the cytoplasmic content. Quinoline derivatives, which elicited morphological changes, increased also the permeability of the plasmalemma of plant cells.     

Modulation of leukotriene synthesis and actions by synthetic derivatives of arachidonic acid

Seven analogs of arachidonic acid were tested for their coronary vasoactivity and their ability to inhibit LTC₄ and LTD₄ synthesis by lung tissue and to antagonize LTD₄ induced coronary constriction. None of the seven arachidonic acid analogs significantly altered peptide leukotriene production by minced cat lung. Two of the analogs (i.e., 7, 13-diethanoarachidonic acid and 7, 10, 13-triethanoarachidonic acid) exerted modest but significant coronary vasodilation in isolated cat coronary arteries, and significantly antagonized the coronary vasoconstrictor response to LTD₄. These analogs may be of interest in modulating leukotriene actions.     

Synthesis and biological properties of novel sphingosine derivatives

Sphingosine-1-phosphate (S-1P) derivatives such as threo-(2S,3S)-analogues, which are C-3 stereoisomers of natural erythro-(2S,3R)-S-1P, have been synthesized starting from l-serine or (1S,2S)-2-amino-1-aryl-1,3-propanediols (6). threo-(1S,2R)-2-Amino-1-aryl-3-bromopropanols (HBr salt) have also been prepared from 6. The threo-S-1Ps and the threo-amino-bromide derivatives have shown potent inhibitory activity against Ca(2+) ion mobilization in HL60 cells induced by erythro-S-1P, suggesting that these compounds would compete with cell surface EDG/S1P receptors.     

Syntheses and biological properties of cysteine-reactive epibatidine derivatives

The synthesis of epibatidine derivatives modified at the 2-position of the pyridine or pyrimidine rings by reactive functions are described for potential irreversible site-directed coupling reactions on cysteine mutants of neuronal nicotinic acetylcholine receptors. An improved synthesis of the 7-azabicyclo[2,2,1]hepta-2,5-diene key intermediate has been developed to allow reproducible syntheses of the epibatidine derivatives. Binding tests and electrophysiological experiments allowed to select the 2-substituted alpha-chloroacetamido 13 and the chloropyrimidine derivative 11 as potential site-directed probes for the epibatidine binding site.     

Transformation of an arachidonic acid hydroperoxide into epoxyhydroxy and trihydroxy fatty acids by liver microsomal cytochrome P-450

In the absence of NADPH, the addition of an arachidonic acid hydroperoxide, 15-hydroperoxyeicosa-5,8,11,13-tetraenoic acid, to liver microsomes, prepared from phenobarbital-treated rats, resulted in the formation of two major metabolites and several minor products, some of which have been purified by reverse-phase high-performance liquid chromatography. We propose the structures of the two major products to be 13-hydroxy-14,15-epoxyeicosa-5,8,11-trienoic acid and 11,14,15-trihydroxyeicosa-5,8,12-trienoic acid based on spectral characteristics and mass spectral analysis of derivatives of the compounds. A potential heterolytic cleavage product, 15-hydroxyeicosa-5,8,11,13-tetraenoic acid, was not a product of the reaction. Ferric cytochrome P-450 catalyzed the formation of these products as shown by the inability of boiled microsomes to support the reaction, the inhibition of epoxyhydroxy and trihydroxy fatty acid formation by imidazole derivatives which bind tightly to the ferric heme iron of cytochrome P-450, and the inability of carbon monoxide (which binds to ferrous P-450) and free iron chelators (EDTA and diethylenetriaminepentaacetic acid) to inhibit product formation. These results show that liver microsomal cytochrome P-450, in addition to its role in the NADPH-dependent metabolism of arachidonic acid, can utilize a hydroperoxide to produce an interesting series of potentially important arachidonic acid metabolites.     

Role of arachidonic acid derivatives in neutrophil aggregation: A hypothesis

Chemotactic substances stimulate neutrophils in suspension to aggregate. Arachidonic acid (but not several structurally related fatty acids) induces a similar neutrophil response. We now report that two blockers of arachidonic acid metabolism, indomethacin and 5,8,11,14-eicosatetraynoic acid, inhibit this arachidonic acid-mediated response. Moreover, both blockers also inhibit aggregation stimulated by a synthetic chemotactic tripeptide, formyl-methionyl-leucyl-phenylalanine, and their potency in doing so parallels their potency in inhibiting the response to arachidonic acid. These results suggest that metabolites of arachidonic acid may stimulate certain neutrophil functions and be involved in cellular responses to at least some chemotactic substances.     

Role of arachidonic acid derivatives in neutrophil aggregation: a hypothesis

Chemotactic substances stimulate neutrophils in suspension to aggregate. Arachidonic acid (but not several structurally related fatty acids) induces a similar neutrophil response. We now report that two blockers of arachidonic acid metabolism, indomethacin and 5,8,11,14-eicosatetraynoic acid, inhibit this arachidonic acid-mediated response. Moreover, both blockers also inhibit aggregation stimulated by a synthetic chemotactic tripeptide, formyl-methionyl-leucyl-phenylalanine, and their potency in doing so parallels their potency in inhibiting the response to arachidonic acid. These results suggest that metabolites of arachidonic acid may stimulate certain neutrophil functions and be involved in cellular responses to at least some chemotactic substances.