Cardiac glycoside interconversions at the subcellular level in Convallaria majailis

Further evidence for the biosynthetic sequence periplorhamnoside → convallatoxol → convallatoxin, proposed after experiments in vivo, was obtained with subcellular fractions of Convallaria majalis leaves. A NADPH-dependent monooxygenase tentatively localized on mitochondrial membranes converted periplorhamnoside into convallatoxol. In contrast the enzyme transforming convallatoxol into convallatoxin could be detected only in the soluble fraction. The conversion required NAD as a cofactor, thus the specifity observed is that of an alcohol dehydrogenase.     

Subcellular localization of glucosyltransferases involved in cardiac glycoside glucosylation in leaves of Convallaria majalis

The glucosylation of convallatoxin and convallatoxol was investigated using homogenates and various subcellular fractions from leaves of Convallaria majalis. The enzyme activity reached a maximum about 5 weeks after the onset of flowering and was found distributed among the soluble and the light membrane fraction. Upon separation of the light membranes by sucrose density gradient centrifugation, glucosyltransferase activity was found solely in a fraction banding at a density of 1.07 g/cm³, which is thought to represent vacuole membranes.     

Zur biogenese von strophanthidin-glykosiden: Convallatoxol als vorstufe von convallatoxin in Convallaria majalis

Labelled convallatoxin was isolated from leaves of Convallaria majalis after administration of convallatoxol-19-³H and convallatoxol-U-¹⁴C, resp. Oxidation of-CH₂OH → -CHO at the glycoside level therefore is a possible step in the biogenesis of strophanthidin glycosides.     

Genetical and biochemical evidence that the hydroxylation pattern of the anthocyanin B-ring in Silene dioica is determined at the p-coumaroyl-coenzyme a stage

In petals of Silene dioica, gene P controls the 3′-hydroxylation of the anthocyanin B-ring and the hydroxylation pattern of the hydroxycinnamoyl acyl group bound to the 4″'-hydroxyl group of rhamnose of anthocyanidin 3-rhamnosyl(1→6)glucoside-5-glucoside. In this paper, experiments are presented which show that gene P is involved in the hydroxylation of p-coumaroyl-CoA to caffeoyl-CoA, which is then used both as a precursor in anthocyanin biosynthesis and as a substrate for the final acylation.     

6α-Hydroxylation of taurochenodeoxycholic acid and lithocholic acid by CYP3A4 in human liver microsomes

The aim of the present study was to identify the enzymes in human liver catalyzing hydroxylations of bile acids. Fourteen recombinant expressed cytochrome P450 (CYP) enzymes, human liver microsomes from different donors, and selective cytochrome P450 inhibitors were used to study the hydroxylation of taurochenodeoxycholic acid and lithocholic acid. Recombinant expressed CYP3A4 was the only enzyme that was active towards these bile acids and the enzyme catalyzed an efficient 6α-hydroxylation of both taurochenodeoxycholic acid and lithocholic acid. The V_max for 6α-hydroxylation of taurochenodeoxycholic acid by CYP3A4 was 18.2 nmol/nmol P450/min and the apparent K_m was 90 μM. Cytochrome b₅ was required for maximal activity. Human liver microsomes from 10 different donors, in which different P450 marker activities had been determined, were separately incubated with taurochenodeoxycholic acid and lithocholic acid. A strong correlation was found between 6α-hydroxylation of taurochenodeoxycholic acid, CYP3A levels (r²=0.97) and testosterone 6β-hydroxylation (r²=0.9). There was also a strong correlation between 6α-hydroxylation of lithocholic acid, CYP3A levels and testosterone 6β-hydroxylation (r²=0.7). Troleandomycin, a selective inhibitor of CYP3A enzymes, inhibited 6α-hydroxylation of taurochenodeoxycholic acid almost completely at a 10 μM concentration. Other inhibitors, such as α-naphthoflavone, sulfaphenazole and tranylcypromine had very little or no effect on the activity. The apparent K_m for 6α-hydroxylation of taurochenodeoxycholic by human liver microsomes was high (716 μM). This might give an explanation for the limited formation of 6α-hydroxylated bile acids in healthy humans. From the present results, it can be concluded that CYP3A4 is active in the 6α-hydroxylation of both taurochenodeoxycholic acid and lithocholic acid in human liver.     

Cytotoxic screening of medicinal and edible plants in Okinawa,Japan, and identification of the main toxic constituent of Rhodea japonica (Omoto)

The cytotoxic activity of ethanol extracts from 53 parts of 36 species of medicinal and edible plants cultivated in Okinawa was measured by using K562 human leukemia cells by a flow cytometric method. Two extracts from Rhodea japonica and Hypericum chinense were cytotoxic at a concentration of 10 microg/ml. The main cytotoxic constituent of Rhodea japonica was isolated and identified to be rhodexin A, which has been isolated as a cardetonic agent of the plant. The IC(50) value for rhodexin A against the growth of K562 cells was 19 nM, this activity being much stronger than that of ouabain (IC(50), 60 nM).     

Establishment of optimal regulatory network of colorectal cancer based on p42.3 protein

Objective: to establish regulatory network of colorectal cancer involving p42.3 protein and to provide theoretical evidence for deep functional exploration of p42.3 protein in the onset and development of colorectal cancer. Methods: with protein similarity algorithm, reference protein set of p42.3 cell apoptosis was built according to structural features of p42.3. GO and KEGG databases were used to establish regulatory network of tumor cell apoptosis involving p42.3; meanwhile, the largest possible working pathway that involves p42.3 protein was screened out based on Bayesian network theory. Besides, GO and KEGG were used to build regulatory network on early diagnosis gene markers for colorectal cancer including WWOX, K-ras, COX-2, p53, APC, DCC and PTEN, at the same time, a regulatory network of colorectal cancer cell apoptosis which involves p42.3 was established. Results: cell apoptotic regulatory network that p42.3 participates in primarily consists of Bcl-2 family genes and the largest possible pathway is p42.3 → FKBP → Bcl-2 centered as FKBP protein. Combined with colorectal cancer regulatory network that involves early diagnosis gene markers, it can be predicted that p42.3 is most likely to regulate the colorectal cancer cell apoptosis through FKBP → Bcl-2 → Bax → caspase-9 → caspase-3 pathway. Conclusion: the colorectal cancer apoptosis network based on p42.3 established in the study provides theoretical evidence for deep exploration of p42.3 regulatory mechanism and molecular targeting treatment of colorectal cancer.     

Genetic Association of rs1800780 (A→G) Polymorphism of the eNOS Gene with Susceptibility to Essential Hypertension in a Chinese Han Population

To investigate the association of eNOS gene polymorphism with essential hypertension in the Chinese Han population, we examined polymorphisms of the rs2070744 (T→C), rs1800780 (A→G), and rs3918181 (A→G) loci. The results demonstrated that the genotypic frequency at the rs1800780 (A→G) locus was significantly different between patients with essential hypertension and the control cohorts (P < 0.05); while genotypic frequencies and allelic frequencies at rs2070744 (T→C) and rs3918181 (A→G) loci had no statistical difference between the patient group and controls (P > 0.05). In addition, haplotype analysis found a statistically significant difference for haplotype TGA, with OR (95% CI) of 1.549 (1.116–2.150) (P < 0.05). These findings suggest that polymorphism of rs1800780 (A→G) in the eNOS gene may be one of the most important genetic factors associated with essential hypertension susceptibility, and those who have haplotype TGA may be at risk to develop essential hypertension.     

Convallatoxin promotes apoptosis and inhibits proliferation and angiogenesis through crosstalk between JAK2/STAT3 (T705) and mTOR/STAT3 (S727) signaling pathways in colorectal cancer

BackgroundAberrant activation of STAT3 is frequently encountered and promotes survival, cellular proliferation, migration, invasion and angiogenesis in tumor cell. Convallatoxin, triterpenoid ingredient, exhibits anticancer pharmacological properties.PurposeIn this work, we investigated the anticancer potential of convallatoxin and explored whether convallatoxin mediates its effect through interference with the STAT3 activation in colorectal cancer cells.MethodsIn vitro, the underlying mechanisms of convallatoxin at inhibiting STAT3 activation were investigated by homology modeling and molecular docking, luciferase reporter assay, MTT assay, RT-PCR, Western blotting and immunofluorescence assays. Changes in cellular proliferation, apoptosis, migration, invasion and angiogenesis were analyzed by EdU labeling assay, colony formation assay, flow cytometry assay, wound-healing assay, matrigel transwell invasion assay and tube formation assays. And in vivo, antitumor activity of convallatoxin was assessed in a murine xenograft model of HCT116 cells.ResultsConvallatoxin decreased the viability of colorectal cancer lines. Moreover, convallatoxin reduced the P-STAT3 (T705) via the JAK1, JAK2, and Src pathways and inhibited serine-727 phosphorylation of STAT3 via the PI3K-AKT-mTOR-STAT3 pathways in colorectal cancer cells. Interestingly, we discovered the crosstalk between mTOR and JAK2 in mTOR/STAT3 and JAK/STAT3 pathways, which collaboratively regulated STAT3 activation and convallatoxin play a role in it. Convallatoxin also downregulated the expression of target genes involved cell survival (e.g., Survivin, Bcl-xl, Bcl-2), proliferation (e.g., Cyclin D1), metastasis (e.g., MMP-9), and angiogenesis (e.g., VEGF). Indeed, we found that convallatoxin inhibited tube formation, migration, and invasion of endothelial cells, and inhibited the proliferation. Finally, in vivo observations were confirmed by showing antitumor activity of convallatoxin in a murine xenograft model.ConclusionThe result of the current study show that convallatoxin promotes apoptosis and inhibits proliferation and angiogenesis through crosstalk between JAK2/STAT3 (T705) and mTOR/STAT3 (S727) signaling pathways in colorectal cancer cells and indicate that convallatoxin could be a valuable candidate for the development of colorectal cancer therapeutic.     

Leucine incorporation in the ganglia of praying mantids during a learning process

Leucine incorporation into four ganglia (‘brain’. B; prothoracic ganglion, P; mesothoracic ganglion, M; and metathoracic ganglion, T) was studied in mantids (Stagmatoptera biocellata) trained not to attack a black star figure in movement. There were two experimental groups, i.e. LM and WH experimental groups, and one control group. The LM and WH groups differed in the experimental conditions of training in such a way that both had similar motor activity and sensorial stimulation but only one of them evinced learning (Maldonado and Tablante, 1975).After training, incorporation of |¹⁴C| leucine into P and B was greater in experimental than in control animals. This result is not necessarily related to learning because no difference was found between LM and WH experimental groups. The metabolic gradient of the four ganglia of the experimental animals was P→B→M→T, whereas that found for the control group was M→T→P→B. The authors interpret these findings as supporting a hypothesis previously set forth that correlates the metabolic gradient in the four ganglia with differences regarding control of motor activity and/or sensorial input.Experiments involving double labelling and electrophoresis indicated that the P and B changes after training involved all the proteins, and were not restricted to one or a few protein species.     

Evidence for geraniol as an obligatory precursor of isothujone

Isothujone (trans-thujan-3-one) was formed from MVA-[¹⁴C, ³H] in Tanacetum vulgare with retention of the pro-(4R) hydrogen of precursor, but with loss of the pro-(4S) hydrogen and of one hydrogen from C-5. Cell-free extracts could not sustain the formation of isothujone from MVA but yielded geraniol and nerol (3,7-dimethylocta-trans-2,6-dien-1-ol and its cis isomer) with retention of the pro-(4R) and loss of the pro-(4S) hydrogen in each case: no hydrogen was lost from C-5 of MVA in formation of geraniol, but one such atom was lost in the formation of nerol. These results support the sequence: geraniol → nerol → isothujone: in which the first two compounds (or their biogenetic equivalents) are interconverted by a redox process involving their derived aldehydes. They are not consistent with a direct pathway to nerol from C₅ intermediates or with routes involving cyclisation of linalol (3,7-dimethylocta-1,6-dien-3-ol) formed directly from the C₅ compounds or from geraniol. The cell-free preparations could not interconvert geraniol and nerol, their phosphates or pyrophosphates. This may be due to the inability of a prenyltransferase-isomerase multi-enzyme system to accept exogenously-supplied intermediates under these (in vitro) conditions.     

Highly sensitive high-performance liquid chromatographic assay for coumarin 7-hydroxylation and 7-ethoxycoumarin O-deethylation by human liver cytochrome P450 enzymes

A highly sensitive method for the determination of coumarin 7-hydroxylation and 7-ethoxycoumarin O-deethylation by human cytochrome P450 (P450 or CYP) enzymes was developed using high-performance liquid chromatography (HPLC). The newly developed HPLC method was found to be about 100-fold more sensitive than the previous spectrofluorimetric method in detecting the metabolite 7-hydroxycoumarin (umbelliferone). With this high sensitivity, the kinetics of coumarin 7-hydroxylation and 7-ethoxycoumarin O-deethylation catalyzed by human liver microsomal and recombinant P450 enzymes were determined more precisely. With 36 different substrate concentrations in these two reactions, coumarin 7-hydroxylation was found to be catalyzed mainly by a single enzyme CYP2A6 and 7-ethoxycoumarin was oxidized by at least two enzymes CYP2E1 and CYP1A2 in human liver microsomes.     

Progesterone transformations as a diagnostic feature in the generaAlternaria,Stemphylium andCladosporium

Various species of the generaAlternaria, Stemphylium andCladosporium were shown to display a specific reaction characteristic for the given genus. In theAlternaria genus this is a 1-2-dehydrogenation of the A ring of the steroid molecule, inStemphylium 14α-hydroxylation and inCladosporium 7β-hydroxylation. This chemotaxonomic feature may supplement morphological and functional criteria in the taxonomy of filamentous fungi (Hyphomycetes).     

Interaction of mannose-containing oligosaccharides with the fimbrial lectin of Escherichia coli

The sugar specificity of Escherichia coli 346 and of the type-1 fimbriae isolated from this organism has been studied by quantitative inhibition of the agglutination of mannan-containing yeast cells. The best inhibitors of the agglutination by the bacteria were the oligosaccharides Manα1→6[Manα1→3]Manα1→6[Manα1→2Manα1→3]ManαOMe, Manα1→6[Manα1→3]Manα1→6[Manα1→3]ManαOMe and Manα1→3Manβ1→4GlcNAc, and the aromatic glycoside p-nitrophenyl α-d-mannoside, all of which were 20–30 times more inhibitory than methyl α-d-mannoside. The disaccharides Manα1→3Man, Manα1→2Man and Manα1→6Man, the tetrasaccharide Manα1→2Manα1→3Manβ1→4GlcNAc and the pentasaccharide Manα1→2Manα1→2Manα1→3Manβ1→4GlcNAc, were all poor inhibitors. A very good correlation was found between the relative inhibitory activity of the different sugars tested with intact bacteria and with the isolated fimbriae. Our findings show that the combining site of the E. coli lectin is an extended one, corresponding to the size of a trisaccharide, that it contains a hydrophobic region, and that it is in the form of a pocket on the surface of the lectin. The combining site fits best the structures found in short oli gomannosidic chains present in N-glycosidically linked glycoproteins.     

Sequence analysis of lacZ- mutations induced by ion beam irradiation in double-stranded M13mp18DNA

While M13mp18 double-stranded DNA was irradiated with ion beam, and transfected intoE. coli JM103, a decrease of transfecting activity was discovered. The lacZ^- mutation frequency at 20% survival could reach (3.6–16.8) × 10⁴, about 2, 3–10 times that of unirradiated M13DNA. Altogether, 27 IacZ^-mutants were selected, 10 of which were used for sequencing. 7 of the sequenced mutants show base changes in 250-bp region examined (the remaining 3 mutants probably have base changes outside the regions sequenced). 5 of the base-changed mutants contain more than one mutational base sites (some of them even have 5–6 mutational base sites in 250-bp region examined); this dense distribution of base changes in polysites has seldom been seen in X-rays, Y-rays or UV induced DNA mutations. Our experiments also showed that the types of base changes include transitions(50%), transversions (45%) and deletion (5%); no addition or duplication was observed. The transitions were mainly C→T and A→G; the transversions were mainly C→A and C→G. The mutations involving cytosine residue (in the template strand) constitute about 60% of all the base changes observed. In comparison with the surrounding sequences of mutational base sites, the base located between TG and CT is found to be easily substituted.     

Structure of two antiviral triterpene saponins from anagallis arvensis

From Anagallis arvensistwo novel saponins were isolated. On the basis of the spectral analysis, the structure proposed for one of the saponins was the 3-O-glucose (1 → 3 or 4)[arbinose 1 → 4 or 3]-glucose(1→2)-xyloside of 23-hydroxy protoprimulagenin A. The other saponin contained an additional glucose.     

Metabolism of monoacylglycerol and diacylglycerol by enzyme preparations from spinach leaves

Acetone powders prepared from a 20,000g participate preparation from spinach leaf catalyzed several reactions involving monoacylglycerol and diacylglycerol. When these substrates were presented as Triton X-100-mixed micelles, diacylglycerol gave rise to free fatty acids, monoacylglycerol, triacylglycerols, and steryl esters, and in the presence of ethanol, small amounts of ethyl esters of fatty acid. Monoacylglycerol gave rise to free fatty acids and diacylglycerol, and in the presence of ethanol, large amounts of ethyl esters of fatty acid. In the presence of bovine serum albumin, the conversion of monoacylglycerol to free fatty acid was retarded. In the presence of bovine serum albumin, steryl ester was an important product from diacylglycerol. The system containing Triton X-100-mixed micelles and bovine serum albumin permitted analysis of reaction products which showed diacylglycerol to be an acyl donor in steryl ester biosynthesis. All reactions observed in the mixed micelle system were transacylation reactions involving various acceptors: dipalmitoylglycerol → monopalmitoylglycerol + palmitate; monopalmitoylglycerol → glycerol + palmitate; dipalmitoylglycerol + sterol → monopalmitoylglycerol + steryl palmitate; monopalmitoylglycerol + ethanol → ethyl palmitate + glycerol; monopalmitoylglycerol → dipalmitoylglycerol (+glycerol); dipalmitoylglycerol → tripalmitoylglycerol (+monopalmitoylglycerol).     

Molecular mechanisms of anti-oxidant and anti-aging effects induced by convallatoxin in Caenorhabditis elegans

Convallatoxin is widely used as a cardiac glycoside in acute and chronic congestive heart-failure and paroxysmal tachycardia, with many effects and underlying protective mechanisms on inflammation and cellular proliferation. However, convallatoxin has not been investigated in its antioxidant effects and lifespan extension in Caenorhabditis elegans. In this study, we found that convallatoxin (20?μM) could significantly prolong the lifespan of wild-type C. elegans up to 16.3% through daf-16, but not sir-2.1 signalling and increased thermotolerance and resistance to paraquat-induced oxidative stress. Convallatoxin also improved pharyngeal pumping, locomotion, reduced lipofuscin accumulation and reactive oxygen species levels in C. elegans, which were attributed to hormesis, free radical-scavenging effects in vivo, and up-regulation of stress resistance-related proteins, such as SOD-3 and HSP-16.1. Furthermore, aging-associated genes daf-16, sod-3, and ctl-2 also appeared to contribute to the stress-resistance effect of convallatoxin. In summary, this study demonstrates that convallatoxin can protect against heat and oxidative stress and extend the lifespan of C. elegans, pointing it as a potential novel drug for retarding the aging process in humans.