Auxin increases phospholipase A2 activity within 2min (Paul, R., Holk, A. and Scherer, G.F.E. (1998) Fatty acids and lysophospholipids as potential second messengers in auxin action. Rapid activation ...of phospholipase A2 activity by auxin in suspension-cultured parsley and soybean cells. Plant J. 16, 601–611) and the phospholipase A inhibitors, ETYA and HELSS, inhibit elongation growth of etiolated Arabidopsis hypoctyls (Holk, A., Rietz, S., Zahn, M., Quader, H. and Scherer, G.F.E. (2002) Molecular identification of cytosolic, patatin-related phospholipases A from Arabidopsis with potential functions in plant signal transduction. Plant Physiol. 130, 90–101). To identify the mode of action, rapid auxin-regulated gene expression was tested for sensitivity to these PLA2 inhibitors using seedlings expressing β-glucuronidase (GUS) under the control of the synthetic auxin-responsive promoter DR5. ETYA and HELSS inhibited the auxin-induced increases in GUS activity, the steady-state level of the corresponding GUS mRNA and the mRNAs encoded by four other auxin-induced genes, IAA1, IAA5, IAA19 and ARF19. Factors that bind to the auxin response elements of the DR5 promoter and thereby regulate gene expression are regulated by a set of proteins such as Aux/IAA1 whose abundances are, in part, under control of E3 ubiquitin ligase SCF complexes. To investigate this mechanism further, the effect of ETYA on Aux/IAA1 degradation rate was examined using seedlings expressing Aux/IAA1:luciferase fusion proteins. In the presence of cycloheximide and excluding synthesis of IAA1:luciferase, ETYA had no apparent effect on degradation rates of IAA1, either with or without exogenous auxin. Therefore, the E3 ubiquitin ligase SCFTIR1 complex is an unlikely direct target of the PLA inhibitor. When cycloheximide was omitted, however, the inhibitors ETYA and HELSS blocked a sustained auxin-induced decrease in its steady-state level, indicating an unknown target capable to regulate Aux/IAA protein levels and, hence, transcription.
An innovative and efficient synthesis of highly congested 2-amino-3-aminomethyl-5-methylsulfanyl/
sec-aminobiphenyl-4-carbonitriles
4 has been delineated through base catalyzed ring transformation of ...6-aryl-4-methylsulfanyl/
sec-amino-2
H-pyran-2-one-3-carbonitriles
1 with Boc-protected 1,3-diamino-2-propanone
2, followed by TFA catalyzed hydrolysis of the intermediate 3-
tert-butoxycarbonylaminomethyl-4-cyano-5-methylsulfanyl/
sec-aminobiphenyl-2-ylcarbamic acid
tert-butyl ester
3 in moderate yields as the TFA salts.
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An innovative route for the synthesis of substituted dibenzofurans has been delineated through a ring transformation reaction of suitably functionalized
2H-pyran-2-ones by reaction ...with 7-methoxybenzofuran-3-one, in high yield. The novelty of the procedure lies in the creation of an aromatic ring from a 2
H-pyran-2-one involving the –COCH
2-moiety of the substrate.
Benzo
bthiophene and its benzannulated derivatives are important classes of compounds due to their unique chemical properties and biosteric relationship with indole. In this letter, we report a ...convenient route for the synthesis of substituted naphtho
bthiophenes through a ring transformation reaction of suitably functionalized 2
H-pyran-2-ones with 6,7-dihydro-5
H-benzothiophene-4-one, in good yields.
Aspergillus luchuensis is widely used as a starter of saccharification in the koji industry, but no secondary metabolites have been reported from this fungus. Herein, we report the isolation and ...identification of four new diketopiperazine derivatives (1–4), one new methyl 4-(3-acetyl-2, 6-dihydroxyphenyl)-2-methoxybutanoate (5), and six known compounds (6–11) from the rice koji of A. luchuensis. The structures of 1–5 were determined by extensive spectral analysis including 1D and 2D NMR, HRESIMS, and CD, and ECD calculation. In antioxidant assays, compound 10 displayed moderate DPPH scavenging activity with an EC50 value of 60.8μM; compounds 1–4, 10 and 11 showed reducing ability with EC50 values ranging from 8.73 to 176.39μM. Compounds 1–11 showed no cytotoxicity against cell lines A549, K562, ASPC, and H460 at 200μM. Our current reports support the safety of A. luchuensis in food chemistry and confirm this fungus to be a new source of natural antioxidants.
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Thrombin and tryptase stimulation of human bladder microvascular endothelial cells (Cambrex Bioscience, Walkersville, Maryland) results in the production of multiple membrane phospholipid derived ...inflammatory mediators via the activation of a calcium independent phospholipase A2 that may have important implications in bladder inflammatory conditions, such as interstitial cystitis. We examined the effect of multiple phospholipase A2 and cyclooxygenase inhibitors on the immediate release of prostacyclin from human bladder microvascular endothelial cells.
We stimulated confluent human bladder microvascular endothelial cell monolayers with thrombin or tryptase and measured the immediate release of prostacyclin. Human bladder microvascular endothelial cells were pretreated with several selective phospholipase A2 and cyclooxygenase inhibitors before thrombin or tryptase stimulation to determine which combination of phospholipase A2/cyclooxygenase isoforms was involved in this process. Phospholipase A2 activity was measured using (16:0, 3H18:1) plasmenylcholine substrate in the absence of calcium. 3H arachidonic acid release was measured in the surrounding medium from prelabeled human bladder microvascular endothelial cell monolayers. Prostacyclin release into the surrounding medium was measured using a commercially available immunoassay kit.
The immediate increase in prostacyclin release from thrombin or tryptase stimulated human bladder microvascular endothelial cells depended on the activation of membrane associated calcium independent phospholipase A2, resulting in an increase in arachidonic acid production. Constitutively active cyclooxygenase-1 was then responsible for further metabolism of free arachidonic acid to prostacyclin.
These results show that the search for a suitable anti-inflammatory agent that selectively target specific phospholipase A2 isoforms requires rigorous testing in several cell types in response to various stimuli.
