Inhibition of Abscisic Acid 8′-Hydroxylase Affects Dehydration Tolerance and Root Formation in Cuttings of Grapes (Vitis labrusca L. × Vitis vinifera L. cv. Kyoho) Under Drought Stress Conditions

The effects of an inhibitor (Abz-E3M) of abscisic acid (ABA) 8′-hydroxylase, which is a primary enzyme of ABA catabolism, on dehydration tolerance and root formation in grape cuttings under drought conditions were investigated. Cuttings of ‘Kyoho’ grape (Vitis labrusca L. × Vitis vinifera L.) were sprayed with 100 μM of Abz-E3M and subjected to water deficit conditions at the stage when their first leaves fully expanded. The physiological and morphological changes in the leaves and basal portions of the cuttings were determined. In Abz-E3M-treated leaves, lower ABA metabolite and higher ABA and indole-3-acetic acid (IAA) concentrations were observed. Compared to the untreated control leaves, higher water potential was significantly maintained in Abz-E3M-treated leaves. Abz-E3M applications resulted in lower proline accumulation and 2,2-diphenyl-2-picrylhydrazyl radical scavenging activity in the leaves and led to enhanced dehydration tolerance. In addition, the percentage of rooted cuttings was significantly increased by Abz-E3M application. In the basal portion of Abz-E3M-treated cuttings, endogenous IAA concentrations and the gene expressions of VvARF6 and VvARF8, which are positive regulators of adventitious root formation, were significantly increased. Moreover, the expression levels of the negative regulator, VvARF17, were significantly lower. These results suggested that the inhibition of ABA 8′-hydroxylase enhanced dehydration tolerance and adventitious rooting and may be an effective strategy for achieving drought stress tolerance in grape cuttings.

     

Encounter with unexpected collagenase-1 selective inhibitor: switchover of inhibitor binding pocket induced by fluorine atom

Phosphonamide-based inhibitors having trifluoromethyl moiety showed highly selective inhibition against MMP-1. A possible mechanism of the selectivity of MMP-1 inhibitors through the switchover of the binding pocket was speculated by computational calculations. As a consequence of the unexpected selectivity, the specific interaction of CF3 group of the inhibitor and Arg214 in the S1' pocket of MMP-1 conducted a low binding energy.     

A practical synthesis and biological evaluation of 9-halogenated PGF analogues

A series of 9-halo PGF analogues 1-2 and 5-13 were synthesized and biologically evaluated. Among the compounds, 2 was the best EP2-receptor agonist. A practical method of synthesizing 2 via the Julia olefination of an aldehyde 3 with an optically active sulfone 4, which was prepared by Sharpless asymmetric epoxidation of 15, was developed. Other 9-halogenated PGF analogues were synthesized essentially by the same procedure and evaluated. The absolute configuration of 16-OH of 2 was determined as S by the X-ray analysis of a salt consisting of a 1/1 molar ratio of 2 and L-lysine.     

Green tea flavonoids inhibit the LDL oxidation in osteogenic disordered rats fed a marginal ascorbic acid in diet

Osteogenic Disorder Shionogi (ODS) rats can not synthesize ascorbic acid (AA). We have examined the capacity of green tea flavonoids (GTF) to modify low-density lipoprotein (LDL) oxidation in ODS rats with dietary AA restriction. In the first experiment, ODS rats were fed diets containing 300 (AA300 diet) or 0 (AA0 diet) mg AA/kg diets for 20 d. In comparison with the AA300 diet, the AA0 diet significantly decreased the concentrations of plasma AA and alpha-tocopherol in LDL and significantly shortened the lag time of LDL oxidation in vitro. In the second experiment, ODS rats were fed one of the following three diets: the AA300 diet, the diet containing 25 mg AA (AA25, marginal AA)/kg diet (AA25 diet), or the diet containing 25 mg AA + 8 g GTF/kg diet (AA25 + GTF diet) for 20 d. Plasma AA concentration were significantly lower in rats fed AA25 compared with AA300 but not in those fed AA25 + GTF. LDL oxidation lag time was significantly longer in rats fed AA25 + GTF compared with the other two groups. Lag time for LDL oxidation was significantly and positively correlated with LDL alpha-tocopherol (r = 0.6885, P = 0.0191). These results suggest that dietary flavonoids suppress the LDL oxidation through the sparing effect on LDL alpha-tocopherol and/or plasma AA when AA intake is marginal in the ODS rats.     

NMR analysis of tautomerisms of active pinacidil-type potassium channel openers and a less active one

In order to clarify the structural difference between active pinacidil-type potassium channel openers and a less active one, the tautomerisms of pinacidil derivatives 1-3 were investigated by NMR spectrometries. The predominant tautomer of the less active compound 3 was different from those of the active compounds 1 and 2.     

UV-B protective effect of a polyacylated anthocyanin, HBA, in flower petals of the blue morning glory, Ipomoea tricolor cv. Heavenly Blue

The protective effects of polyacylated anthocyanin, heavenly blue anthocyanin (HBA), in blue flower petals of morning glory (Ipomoea tricolor cv. Heavenly Blue) against UV-B induced DNA damage were examined. We first clarified the concentration of HBA in epidermal vacuoles to be 12mM, and then constructed a UV-B irradiating apparatus resembling flower petal tissue to assess the screening effect of HBA. Monochromatic (280 and 310nm) or broad UV-B induced DNA lesions were reduced completely by the HBA filter to the same molecular numbers as those in living petal epidermis. However, diluted HBA solution and trisdeacyl HBA did not have the same reduction effect. HBA was more tolerant to solar radiation than trisdeacyl HBA. These data strongly suggest that polyacylated anthocyanins in flower petals can screen harmful UV-B efficiently. This action might be largely due to aromatic acyl residues.     

Pyrazole-O-glucosides as novel Na(+)-glucose cotransporter (SGLT) inhibitors

O-glucuronides and O-glucosides of a series of pyrazoles analogues were synthesized and evaluated for their SGLT inhibitory activity in brush border membrane vehicles (BBMVs) of rat kidney. O-glucosides of certain pyrazole analogues inhibited the transport of [(14)C]-glucose in BBMVs, and induced glucosuria in Wistar rats by intravenous injection.     

Design,synthesis and evaluation of novel azasugar-based MMP/ADAM inhibitors

In order to verify whether azasugar would be a useful scaffold for inhibitory activity against metalloproteinases, we synthesized some azasugar-based compounds. As a result, it is clarified that azasugar moiety could function as successful inhibitor of matrix metalloproteinase-1, -3 and -9 and TACE.     

Structural basis of the highly efficient trapping of the HIV Tat protein by an RNA aptamer

An RNA aptamer containing two binding sites exhibits extremely high affinity to the HIV Tat protein. We have determined the structure of the aptamer complexed with two argininamide molecules. Two adjacent U:A:U base triples were formed, which widens the major groove to make space for the two argininamide molecules. The argininamide molecules bind to the G bases through hydrogen bonds. The binding is stabilized through stacking interactions. The structure of the aptamer complexed with a Tat-derived arginine-rich peptide was also characterized. It was suggested that the aptamer structure is similar for both complexes and that the aptamer interacts with two different arginine residues of the peptide simultaneously at the two binding sites, which could explain the high affinity to Tat.     

Inhibition of checkpoint kinase 1 abrogates G2/M checkpoint activation and promotes apoptosis under heat stress

Hyperthermia induced by heat stress (HS) inhibits the proliferation of cancer cells and induces their apoptosis. However, the mechanism underlying HS-induced apoptosis remains elusive. Here, we demonstrated a novel evidence that checkpoint kinase 1 (Chk1) plays crucial roles in the apoptosis and regulation of cell cycle progression in cells under HS. In human leukemia Jurkat cells, interestingly, the ataxia telangiectasia and Rad-3 related (ATR)-Chk1 pathway was preferentially activated rather than the ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 (Chk2) pathway under HS. The selective inhibitors of ATR or Chk1 abrogated HS-induced apoptosis in human leukemia Jurkat cells whereas the inhibition of ATM or Chk2 caused only marginal effects. Inhibition of ATR and Chk1 also abrogated G2/M checkpoint activation by HS in Jurkat cells. The effects of small interfering RNA targeting Chk1 were similar to those of the selective inhibitor of Chk1. In addition, the efficiencies of Chk1 inhibition on G2/M checkpoint abrogation and apoptosis induction were confirmed in the adherent cancer cell lines HeLa, HSC3, and PC3, suggesting that the targeting of Chk1 can be effective in solid tumors cells. In conclusion, these findings indicate a novel molecular basis of G2/M checkpoint activation and apoptosis in cells exposed to HS.