Anti-genotoxic activity of Vitis coignetiae Pulliat towards heterocyclic amines and isolation and identification of caftaric acid as an antimutagenic component from the juice

Our study demonstrated that the formation of DNA adducts in liver, lungs, colon and kidneys of mice given a carcinogenic heterocyclic amine, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), in the diet significantly decreased following the administration of the juice of Vitis coignetiae, purple berries from a vine tree. The juice of V. coignetiae significantly inhibited the clastogenicity and mutagenicity of heterocyclic amines in the micronucleus assay and the Ames test, and was an effective inhibitor of the activities of phase I enzymes (cytochrome P450 1A1 and cytochrome P450 1A2) and enhancer of the activities of phase II enzymes (uridine 5'-diphospho-glucuronosyltransferase and glutathione S-transferase). We investigated the purification and isolation of an active compound in the juice of V. coignetiae using antimutagenicity as a separation marker. Caftaric acid, a polyphenolic compound, was identified as a component responsible for antimutagenicity in the juice of V. coignetiae towards the carcinogenic heterocyclic amine 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). This is the first report of antimutagenicity of caftaric acid. Caftaric acid was reported as an inhibitor of the protein-protein interactions mediated by the Src-family kinases. The impact of the juice of V. coignetiae and its constituents on tumor initiation and promotion thus warrants further study.     

iTRAQ analysis reveals mechanisms of growth defects due to excess zinc in Arabidopsis

The micronutrient zinc is essential for all living organisms, but it is toxic at high concentrations. Here, to understand the effects of excess zinc on plant cells, we performed an iTRAQ (for isobaric tags for relative and absolute quantification)-based quantitative proteomics approach to analyze microsomal proteins from Arabidopsis (Arabidopsis thaliana) roots. Our approach was sensitive enough to identify 521 proteins, including several membrane proteins. Among them, IRT1, an iron and zinc transporter, and FRO2, a ferric-chelate reductase, increased greatly in response to excess zinc. The expression of these two genes has been previously reported to increase under iron-deficient conditions. Indeed, the concentration of iron was significantly decreased in roots and shoots under excess zinc. Also, seven subunits of the vacuolar H(+)-ATPase (V-ATPase), a proton pump on the tonoplast and endosome, were identified, and three of them decreased significantly in response to excess zinc. In addition, excess zinc in the wild type decreased V-ATPase activity and length of roots and cells to levels comparable to those of the untreated de-etiolated3-1 mutant, which bears a mutation in V-ATPase subunit C. Interestingly, excess zinc led to the formation of branched and abnormally shaped root hairs, a phenotype that correlates with decreased levels of proteins of several root hair-defective mutants. Our results point out mechanisms of growth defects caused by excess zinc in which cross talk between iron and zinc homeostasis and V-ATPase activity might play a central role.     

Functional evaluation of a nitrogenase-like protochlorophyllide reductase encoded by the chloroplast DNA of Physcomitrella patens in the cyanobacterium Leptolyngbya boryana

Dark-operative protochlorophyllide (Pchlide) oxidoreductase (DPOR) is a nitrogenase-like enzyme consisting of the two components, L-protein (a ChlL dimer) and NB-protein (a ChlN-ChlB heterotetramer), to catalyze Pchlide reduction in Chl biosynthesis. While nitrogenase is distributed only among certain prokaryotes, the probable structural genes for DPOR are encoded by chloroplast DNA in lower plants. Here we show functional evaluation of DPOR encoded by chloroplast DNA in a moss Physcomitrella patens by the complementation analysis of the cyanobacterium Leptolyngbya boryana and the heterologous reconstitution of the moss L-protein and the cyanobacterial NB-protein. Two shuttle vectors to overexpress chlL and chlN-chlB from P. patens were introduced into the cyanobacterial chlL- and chlB-lacking mutants, respectively. Both transformants restored the ability to perform Chl biosynthesis in the dark, indicating that the chloroplast-encoded DPOR components form an active complex with the cyanobacterial components. The L-protein of P. patens was purified from the cyanobacterial transformant, and DPOR activity was reconstituted in a heterologous combination with the cyanobacterial NB-protein. The specific activity of the L-protein from P. patens was determined to be 118 nmol min(-1) mg (-1), which is even higher than that of the cyanobacterial L-protein (76 nmol min(-1) mg (-1)). Upon exposure to air, the activity of the L-protein from P. patens decayed with a half-life of 30 s, which was eight times faster than that of the cyanobacterial L-protein (240 s). These results suggested that the chloroplast-encoded L-protein functions as efficiently as the cyanobacterial L-protein but is more oxygen labile than the cyanobacterial L-protein.     

Structural evidence of α-aminoacylated lipoproteins of Staphylococcus aureus

Bacterial lipoproteins are known to be diacylated or triacylated and activate mammalian immune cells via Toll-like receptor 2/6 or 2/1 heterodimer. Because the genomes of low G+C content gram-positive bacteria, such as Staphylococcus aureus, do not contain Escherichia coli-type apolipoprotein N-acyltransferase, an enzyme converting diacylated lipoproteins into triacylated forms, it has been widely believed that native lipoproteins of S. aureus are diacylated. However, we recently demonstrated that one lipoprotein SitC purified from S. aureus RN4220 strain was triacylated. Almost simultaneously, another group reported that another lipoprotein SA2202 purified from S. aureus SA113 strain was diacylated. The determination of exact lipidated structures of S. aureus lipoproteins is thus crucial for elucidating the molecular basis of host-microorganism interactions. Toward this purpose, we intensively used MS-based analyses. Here, we demonstrate that SitC lipoprotein of S. aureus RN4220 strain has two lipoprotein lipase-labile O-esterified fatty acids and one lipoprotein lipase-resistant fatty acid. Further MS/MS analysis of the lipoprotein lipase digest revealed that the lipoprotein lipase-resistant fatty acid was acylated to α-amino group of the N-terminal cysteine residue of SitC. Triacylated forms of SitC with various length fatty acids were also confirmed in cell lysate of the RN4220 and Triton X-114 phase in three other S. aureus strains, including SA113 strain and one Staphylococcus epidermidis strain. Moreover, four other major lipoproteins including SA2202 in S. aureus strains were identified as N-acylated. These results strongly suggest that lipoproteins of S. aureus are mainly in the N-acylated triacyl form.     

Cilostazol activates function of bone marrow-derived endothelial progenitor cell for re-endothelialization in a carotid balloon injury model

Background

Cilostazol(CLZ) has been used as a vasodilating anti-platelet drug clinically and demonstrated to inhibit proliferation of smooth muscle cells and effect on endothelial cells. However, the effect of CLZ on re-endothelialization including bone marrow (BM)-derived endothelial progenitor cell (EPC) contribution is unclear. We have investigated the hypothesis that CLZ might accelerate re-endothelialization with EPCs.

Methodology/Principal Findings

Balloon carotid denudation was performed in male Sprague-Dawley rats. CLZ group was given CLZ mixed feed from 2weeks before carotid injury. Control group was fed normal diet. CLZ accelerated re-endothelialization at 2 weeks after surgery and resulted in a significant reduction of neointima formation 4 weeks after surgery compared with that in control group. CLZ also increased the number of circulating EPCs throughout the time course. We examined the contribution of BM-derived EPCs to re-endothelialization by BM transplantation from Tie2/lacZ mice to nude rats. The number of Tie2-regulated X-gal positive cells on injured arterial luminal surface was increased at 2 weeks after surgery in CLZ group compared with that in control group. In vitro, CLZ enhanced proliferation, adhesion and migration activity, and differentiation with mRNA upregulation of adhesion molecule integrin αvβ3, chemokine receptor CXCR4 and growth factor VEGF assessed by real-time RT-PCR in rat BM-derived cultured EPCs. In addition, CLZ markedly increased the expression of SDF-1α that is a ligand of CXCR4 receptor in EPCs, in the media following vascular injury.

Conclusions/Significance

CLZ promotes EPC mobilization from BM and EPC recruitment to sites of arterial injury, and thereby inhibited neointima formation with acceleration of re-endothelialization with EPCs as well as pre-existing endothelial cells in a rat carotid balloon injury model. CLZ could be not only an anti-platelet agent but also a promising tool for endothelial regeneration, which is a key event for preventing atherosclerosis or restenosis after vascular intervention.     

Octaarginine-modified liposomes enhance the anti-oxidant effect of Lecithinized superoxide dismutase by increasing its cellular uptake

The anti-oxidant enzyme superoxide dismutase (SOD) has the potential for use as a therapeutic agent in the treatment of various diseases caused by reactive oxygen species. However, achieving this would be difficult without a suitable delivery system for SOD. We previously reported that PC-SOD, in which four molecules of a phosphatidylcholine (PC) derivative were covalently bound to each dimer of recombinant human CuZnSOD, was a high affinity for the cell membrane [14]. Here, we show that an octaarginine (R8) modified liposome equipped with PC-SOD (R8-LP (PC-SOD)) enhances its anti-oxidant effect. High-density R8-modified liposomes can stimulate macropinocytosis and are taken up efficiently by cells as demonstrated in a previous study [21]. Flow cytometry analyses showed that R8-LP (PC-SOD) was taken up by cells more efficiently than PC-SOD. Moreover, R8-LP (PC-SOD) liposomes were found to scavenge superoxide anions (O₂⁻) very efficiently. These results suggest that the efficient cytosolic delivery of PC-SOD by R8-modified liposomes would enhance the anti-oxidant effects of PC-SOD.     

Highly specific unnatural base pair systems as a third base pair for PCR amplification

Toward the expansion of the genetic alphabet of DNA, we present highly efficient unnatural base pair systems as an artificial third base pair for PCR. Hydrophobic unnatural base pair systems between 7-(2-thienyl)imidazo[4,5-b]pyridine (Ds) and 2-nitro-4-propynylpyrrole (Px) were fine-tuned for efficient PCR, by assessing the amplification efficiency and fidelity using different polymerases and template sequence contexts and modified Px bases. Then, we found that some modifications of the Px base reduced the misincorporation rate of the unnatural base substrates opposite the natural bases in templates without reducing the Ds-Px pairing selectivity. Under optimized conditions using Deep Vent DNA polymerase, the misincorporation rate was extremely low (0.005%/bp/replication), which is close to that of the natural base mispairings by the polymerase. DNA fragments with different sequence contexts were amplified ～10(10)-fold by 40 cycles of PCR, and the selectivity of the Ds-Px pairing was >99.9%/replication, except for 99.77%/replication for unfavorable purine-Ds-purine motifs. Furthermore, >97% of the Ds-Px pair in DNA survived in the 10(28)-fold amplified products after 100-cycle PCR (10 cycles repeated 10 times). This highly specific Ds-Px pair system provides a framework for new biotechnology.