Synthesis, biological evaluation and structural determination of beta-aminoacyl-containing cyclic hydrazine derivatives as dipeptidyl peptidase IV (DPP-IV) inhibitors

Inhibitors of dipeptidyl peptidase IV (DPP-IV) have been shown to be effective treatments for type 2 diabetes. A series of beta-aminoacyl-containing cyclic hydrazine derivatives were synthesized and evaluated as DPP-IV inhibitors. One member of this series, (R)-3-amino-1-(2-benzoyl-1,2-diazepan-1-yl)-4-(2,4,5-trifluorophenyl)butan-1-one (10f), showed potent in vitro activity, good selectivity and in vivo efficacy in mouse models. Also, the binding mode of compound 10f was determined by X-ray crystallography.     

Characterization of the centromere and peri-centromere retrotransposons in Brassica rapa and their distribution in related Brassica species

We report the identification and characterization of the major repeats in the centromeric and peri-centromeric heterochromatin of Brassica rapa. The analysis involved the characterization of 88 629 bacterial artificial chromosomes (BAC) end sequences and the complete sequences of two BAC clones. We identified centromere-specific retrotransposons of Brassica (CRB) and various peri-centromere-specific retrotransposons (PCRBr). Three copies of the CRB were identified in one BAC clone as nested insertions within a tandem array of 24 copies of a 176 bp centromeric repeat, CentBr. A complex mosaic structure consisting of nine PCRBr elements and large blocks of 238 bp degenerate tandem repeats (TR238) were found in or near a derivative of 5S-25S rDNA sequences. The chromosomal positions of selected repeats were determined using in situ hybridization. These revealed that CRB is a major component of all centromeres in three diploid Brassica species and their allotetraploid relatives. However, CentBr was not detected in the most distantly related of the diploid species analyzed, B. nigra. PCRBr and TR238 were found to be major components in the peri-centromeric heterochromatin blocks of four chromosomes of B. rapa. These repetitive elements were not identified in B. oleracea or B. nigra, indicating that they are A-genome-specific. GenBank accession numbers: KBrH001P13 (AC 166739); KBrH015B20 (AC 166740); end sequences of KBrH BAC library (CW 978640 - CW 988843); end sequences of KBrS BAC library (DU 826965 - DU 835595); end sequences of KBrB BAC library (DX 010661 - DX 083363).     

<Emphasis Type="Italic">ATHB23</Emphasis>, an <Emphasis Type="Italic">Arabidopsis</Emphasis> class I homeodomain-leucine zipper gene,is expressed in the adaxial region of young leaves

Homeobox genes are essential regulators of plant development. ATHB23, a class I homeodomain leucine zipper gene of Arabidopsis, was found to be induced by treatment with the phytohormone gibberellin (GA). In order to clarify its role in development, we performed a histochemical analysis of transgenic plants containing a construct with a GUS::GFP reporter under the control of the 1.5 kb upstream region of ATHB23. The construct was mainly expressed in young leaves and the styles of flowers but not in mature leaves. Microscopic examination of young leaves revealed that it was expressed in the adaxial domain of leaf primordia and the rib meristem. Expression of ATHB23, like that of GA5 encoding GA 20-oxidase, was reduced in mutants related to adaxial-abaxial leaf polarity (phb-1d, se-2, and kan1 kan2). Reduced expression of the GUS::GFP reporter gene was also observed in an se-2 background. These results indicate that ATHB23 is under the control of GA and other activators such as PHB, and is involved in establishing polarity during leaf development.     

Hydrotropic polymeric micelles for enhanced paclitaxel solubility: in vitro and in vivo characterization

The purpose of this investigation was to characterize the in vitro stability and in vivo disposition of paclitaxel in rats after solubilization of paclitaxel into hydrotropic polymeric micelles. The amphiphilic block copolymers consisted of a micellar shell-forming poly(ethylene glycol) (PEG) block and a core-forming poly(2-(4-vinylbenzyloxy)-N,N-diethylnicotinamide) (P(VBODENA)) block. N,N-Diethylnicotinamide (DENA) in the micellar inner core resulted in effective paclitaxel solubilization and stabilization. Solubilization of paclitaxel using polymeric micelles of poly(ethylene glycol)-b-P(D,L-lactide) (PEG-b-PLA) served as a control for the stability study. Up to 37.4 wt % paclitaxel could be loaded in PEG-b-P(VBODENA) micelles, whereas the maximum loading amount for PEG-b-PLA micelles was 27.6 wt %. Thermal analysis showed that paclitaxel in the polymeric micelles existed in the molecularly dispersed amorphous state even at loadings over 30 wt %. Paclitaxel-loaded hydrotropic polymeric micelles retained their stability in water for weeks, whereas paclitaxel-loaded PEG-b-PLA micelles precipitated in a few days. Hydrotropic polymer micelles were more effective than PEG-PLA micelle formulations in inhibiting the proliferation of human cancer cells. Paclitaxel in hydrotropic polymer micelles was administered orally (3.8 mg/kg), intravenously (2.5 mg/kg), or via the portal vein (2.5 mg/kg) to rats. The oral bioavailability was 12.4% of the intravenous administration. Our data suggest that polymeric micelles with a hydrotropic structure are superior as a carrier of paclitaxel due to a high solubilizing capacity combined with long-term stability, which has not been accomplished by other existing polymeric micelle systems.     

The biological significance of methionine sulfoxide stereochemistry

Methionine can be oxidized by reactive oxygen species to a mixture of two diastereomers, methionine-S-sulfoxide and methionine-R-sulfoxide. Both free amino acid and protein-based forms of methionine-S-sulfoxide are stereospecifically reduced by MsrA, whereas the reduction of methionine-R-sulfoxide requires two enzymes, MsrB and fRMsr, which act on its protein-based and free amino acid forms, respectively. However, mammals lack fRMsr and are characterized by deficiency in the reduction of free methionine-R-sulfoxide. The biological significance of such biased reduction of methionine sulfoxide has not been fully explored. MsrA and MsrB activities decrease during aging, leading to accumulation of protein-based and free amino acid forms of methionine sulfoxide. Since methionine is an indispensible amino acid in human nutrition and a key metabolite in sulfur, methylation, and transsulfuration pathways, the consequences of accumulation of its oxidized forms require further studies. Finally, in addition to methionine, methylsulfinyl groups are present in various drugs and natural compounds, and their differential reduction by Msrs may have important therapeutic implications.