Active loading of verteporfin into cationic liposome for neovasculature- and tumor-targeted photodynamic therapy / 药学学报

To target neovasculature and tumor cells, a novel cationic liposome with verteporfin (BPD) active-loaded in lumen (CLL) was designed and its basic in vitro and in vivo behaviors were evaluated in this study. Calcium acetate gradient loading method was applied to encapsulate BPD actively and cationic lipid (2,3-dioleoy-loxy-propyl)-trimethylammonium (DOTAP) was added by post-insertion for the positive charge of CLL. Results of characterization showed that the diameter and zeta-potential of CLL were around 100 nm and 28 mV, respectively. Compared with passive loading liposomes, CLL significantly enhanced the stability of BPD loading. What's more, the loaded BPD in lumen could switch off the fluorescence and photosensitization during blood circulation by homo-fluorescence resonance energy transfer (homo-FRET) effect, leading to the diminished phototoxicity to normal tissues. In vitro cellular uptake and cytotoxicity assay exhibited that positive charge dramatically enhanced the uptake of CLL both in vascular endothelial cells and tumor cells leading to superior therapeutic efficacy. In vivo study further showed that CLL reduced the clearance rate and increased tumor accumulation compared with passive loading group. Quantitative results of exvivo organ indicated that negligible CLL distributed in normal organs contributing to low phototoxicity. Animal experiments were conducted according to the Guidelines of the Experimental Animal Ethics Committee of Peking University Health Science Center and International Animal Experiments. In conclusion, we successfully designed a novel cationic targeting liposome that overcame the limitations of passive loading and significantly enhanced the efficacy of photodynamic therapy.

Impacts of particle shape on cellular uptake and tumor imaging application of ultra-pH sensitive micelles / 药学学报

This study was designed to investigate the impacts of particle shape of micelles on cell uptake and tumor imaging applications. We designed and synthesized an ultra-pH sensitive PEG-iPDPA diblock polymer, and prepared it into wormlike micelles and spherical micelles by thin-film dispersion method and modified solvent evaporation method, respectively. Firstly, the pH responsiveness of two kinds of micelles was investigated in vitro. Both forms of micelles responded to pH sensitively, and each of them could reach 100 times of ON/OFF fold after conjugated with BDP fluorescent probe. Moreover, the cellular uptake of two forms of micelles depended on the concentration and incubation time. However, the amount of cellular uptake of spherical micelles was much higher than that of the wormlike micelles, which proved that the shape of nanoparticles had a great influence on the cellular uptake. The results of in vivo imaging revealed that the spherical micelles had a better tumor accumulation as well as tumor imaging outcomes. Finally, the biosafety of micelles was tested by MTT assay and H&E staining, which indicated that none of the two kinds of micelles had obvious toxicity. Collectively, these results suggest that the spherical micelles could be a better carrier compared with wormlike micelles in terms of cellular uptake, tumor accumulation and tumor detection.

Identification of tetracenomycin X from a marine-derived Saccharothrix sp. guided by genes sequence analysis / 药学学报

The crude extracts of the fermentation broth from a marine sediment-derived actinomycete strain, Saccharothrix sp. 10-10, showed significant antibacterial activities against drug-resistant pathogens. A genome-mining PCR-based experiment targeting the genes encoding key enzymes involved in the biosynthesis of secondary metabolites indicated that the strain 10-10 showed the potential to produce tetracenomycin-like compounds. Further chemical investigation of the cultures of this strain led to the identification of two antibiotics, including a tetracenomycin (Tcm) analogs, Tcm X (1), and a tomaymycin derivative, oxotomaymycin (2). Their structures were identified by spectroscopic data analysis, including UV, 1D-NMR, 2D-NMR and MS spectra. Tcm X (1) showed moderate antibacterial activities against a number of drug-resistant pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) pathogens, with the MIC values in the range of 32-64 microg x mL(-1). In addition, 1 also displayed significant cytotoxic activities against human cancer cell lines, including HL60 (leukemia), HepG2 (liver), and MCF-7 (breast) with the IC 50 values of 5.1, 9.7 and 18.0 micromol x L(-1), respectively. Guided by the PCR-based gene sequence analysis, Tcm X (1) and oxotomaymycin (2) were identified from the genus of Saccharothrix and their 13C NMR data were correctly assigned on the basis of 2D NMR spectroscopic data analysis for the first time.

Halogenated natural products from the marine-derived actinobacteria and their halogenation mechanism / 药学学报

In the last decade, along with the development of taxonomy research in marine-derived actinobacteria, more and more halogenated natural products were discovered from marine actinobacteria. Most of them showed good biological activity and unique structure compared to those from land. The special halogenation mechanism in some compounds' biosynthesis has drawn great attention. So in this review, we focus on the halogenated natural products from marine actinobacteria and their halogenation mechanisms.

Effects of rapamycin-loaded poly(lactic-co-glycolic) acid nanoparticles on distribution of cell cycle, expression of p27 protein, and proliferation of human umbilical arterial vascular smooth muscle cell in vitro / 中国医学科学院学报

<p><b>OBJECTIVE</b>To evaluate the effects of rapamycin (RPM)-loaded poly (lactic-co- glycolic) acid (PLGA) nanoparticles (NPs) on the proliferation, distribution of cell cycle, and expression of p27 protein in human umbilical arterial vascular smooth muscle cell (HUASMC) in vitro.</p><p><b>METHODS</b>The primarily culture model of HUASMC was successfully established by explant-attached method in vitro. The cells were administrated with different doses of RPM, and RPM-PLGA NPs were observed as treat groups compared with PLGA NPs and M231-SMGs medium cultured group. The effect of RPM-PLGA NPs on proliferation of HUASMC was assessed using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetry method. The influences of RPM-PLGA NPs on the cell cycle and cellular growth kinetics of HUASMCs were tested by flow cytometry. The effect of RPM-PLGA NPs on the expression of p27 protein of HUASMCs was assessed through an immunohistochemical method.</p><p><b>RESULTS</b>Compared with the control group, the proliferation of HUASMCs was inhibited by 50 microg/L and higher concentration of RPM-PLGA NPs in a dose-dependent manner (P < 0.05). The numbers of cells entering cell cycle of S/G2/M phases were significantly lower in RPM-PLGA NPs and RPM treated groups. Histologically, the expression of p27 were up-regulated in 500 microg/L RPM-PLGA NPs and 100 microg/L RPM treated group (all P < 0.01 ) when compared with the control group.</p><p><b>CONCLUSIONS</b>RPM-PLGA NPs has a similar effects as RPM in inhibiting the growth of in vitro cultured HUASMC. It can remarkably suppress the expression of in vitro cultured HUASMC p27 protein, arrest its cell cycle at G1/S phase, and inhibit its proliferation.</p>

Deletion of spiramycin 3-O-acyltransferase gene from Streptomyces spiramyceticus F21 resulting in the production of spiramycin I as major component / 生物工程学报

Spiramycin (SP) belongs to the 16-member macrolide antibiotics. It contains three components,namely SP I, SP II and SP III, which differ structurally in the acylation moieties on the C3 of the lactone. The SP I component contains a hydroxyl group at C3. SP II, and SP III are formed by further acetylation or propionylation of the C3 of SP I, by the same 3-O-acyltransferase (3-O-AT) . The study focused on simplifying spiramycin components. Theoretically, disruption/deletion of the 3-O-AT gene will reduce/stop the acylation of SP I to SP II and SP III. In this study, degenerated primers were designed according to the conserved regions of 3-O-acyltransferase, MdmB and AcyA in the medicamycin and carbomycin producers of S. mycarofaciens and S. thermotolerans, respectively, and an 878bp DNA fragment was amplified from the spiramycin-producer of S. spiramyceticus F21. Blast analysis of the 878bp DNA fragment suggested that it encoded the 3-O-acyltransferase (3-0-AT, sspA) gene for spiramycin biosynthesis. The flanking regions of this 878bp DNA fragment were then amplified by single-oligonucleotide-nested PCR, and a total of 4.3 kb DNA was obtained (3457nt among the 4.3kb fragment was sequenced, and deposited in GenBank DQ642742),covering the whole putative 3-O-acyltransferase gene, sspA. The sspA was then deleted from the S. spiramyceticus F21 genome by double cross-over homologous recombination, mediated by temperature-sensitive plasmid pKC1139. A comparison was done of the components of spiramycins produced by the sspA-deleted mutant strain with that of the parent strain by HPLC analysis, which showed that sspA-deleted mutant produced SP I (72%), SP II (18%), and SP III (9.6%), whereas parent strain produced SP I (7.8%), SP II (67%), and SP III (25%), respectively, demonstrating the role of ssp A in the acylation of SP I into SP II and SP III. The ssp A-deleted mutant strain obtained in this study may be used for the production of SP I, or may serve as a good starter for the construction of spiramycin derivatives.

Cloning and analysis of geldanamycin partial biosynthetic gene cluster of Streptomyces hygroscopicus 17997 / 生物工程学报

A geldanamycin (GDM) producing strain, Streptomyces hygroscopicus 17997, was isolated from Yunnan China soil by our institute researchers. GDM is an ansamycin antibiotic, which has the ability to bind with Hsp90 (Heat Shock Protein 90) and alter its function. Hsp90 is a chaperone protein involved in the regulation of the cell cycle, cell growth, cell survival, apoptosis, and oncogenesis. So it plays a key role in regulating the physiology of cells exposed to environmental stress and in maintaining the malignant phenotype of tumor cells. As an inhibitor of Hsp90, GDM possesses potent antitumor and antivirus bioactivity, but the hypato-toxicity and poor solubility in water limits its clinical use. Two GDM derivatives, 17-(Allylamino)-17-demethoxygeldanamycin (17-AAG) and 17-dimethylamino-ethylamino-17-demethoxygeldanamycin (17-DMAG), both showing lesser hepato-toxicity, are now in Phase II and Phase I clinic trials. In order to accomplish the structure modification of GDM by genetic means, an attempt to obtain the biosynthetic gene cluster of GDM from S. hygroscopicus 17997 was made. In this study, a pair of primers was designed according to a conserved sequence of one of possible post-PKS (polyketides synthase) modification genes, the carbamoyltransferase (CT) gene (gdmN) in GDM biosynthesis. The 732 bp PCR product was obtained from the S. hygroscopicus 17997 genomic DNA. Through the colony-PCR Binary Search Method, using the CT gene primers, six positive cosmid clones, CT1-6, were identified from the S. hygroscopicus 17997 cosmid genomic library. The CT gene containing fragments were verified and localized by Southern blot. The CT-4 positive cosmid was then sub-cloned and sequenced. Approximately 28.356kb of foreign gene sequence from CT-4 cosmid and by further PCR extension reaction was obtained. Based on BLAST analysis, this sequence contains 13 possible ORFs and their deduced functions are believed to be involved in GDM production. The ORF1 encoding products show homology (87%) with incomplete sixth module and complete seventh module of PKS, gdmA3, in S. hygroscopicus NRRL 3602. The ORF2-13 gene products are similar to gdmF(9 5%), gdmM(8 8%), gdmN (92%), gdmH (92%), I (93%), J (90%), K (93%), G (96%), gdmO (91%), gdmP (93%) and two transcription regulation genes gdmRI (83%) and gdmRII (90%). The obtained possible GDM biosynthetic gene cluster in S. hygroscopicus 17997 will facilitate the further functional analysis of the genes and to modify the structure of GDM through combinatorial biosynthesis.

Expression of a human myofibrillogenesis regulator 1 gene in E. coli and its immunogenicity / 中国医学科学院学报

<p><b>OBJECTIVE</b>To study the expression of human myofibrillogenesis regulator 1 (MR-1) gene in E. coli and obtain the MR-1 protein and its antibody for further investigation of its biological function.</p><p><b>METHODS</b>Expression vectors pGEX-5X-1, pET30a (+), and pET24a (+), as well as host strain E. coli BL21 (DE3) and BL21-CodonPlus (DE3) -RIL were used for expression of MR-1. MR-1 N-terminal with GST or T7-tag or C-terminal with His-tag, separately, or N terminal with T7-tag and C terminal with His-tag, simultaneously, were fused in plasmids pGEX-5X-1, pET30a (+) , and pET24a (+). The expressed MR-1-T protein, separated and purified by preparative SDS-PAGE, was applied to immunize the rabbits. The titer of the antibody was assayed by ELISA and its immunogenicity was tested by Western blot with pcDNA3/MR-1 transfected human breast cancer cell MCF7.</p><p><b>RESULTS</b>The MR-1 protein was successfully expressed as inclusion body by fusing its N-terminal with T7-tag in E. coli BL21-CodonPlus (DE3) -RIL. MR-1 protein was purified by electro-elution from SDS-PAGE gel. Using this purified protein, polyclonal antibody in rabbit against MR-1 was essentially generated. ELISA and Western blot showed the titer of this antibody was about 1:10(5) with high immunogenicity.</p><p><b>CONCLUSIONS</b>The N-terminal fusion tag is the most important mechanism for MR-1 expression. The polyclonal antibody of the generated MR-1 protein in E. coli may be applied for its further biological function studies.</p>

Cloning of mMR-1 gene and expression in Pichia pastoris systems / 生物工程学报

hMR-1 (Homo Myofibrillogenesis Regulator 1, AF417001) is a novel homo gene, which was firstly cloned in our laboratory. The former studies revealed that hMR-1 is a transmembrane protein which shows protein interaction with sarcomeric proteins like myomesin I, myosin regulatory light chain, alpha-enolase and some cell regulator proteins such as eukaryotic translation initiation factor3 subunit 5 (eIF3S5) and etc. In this work, we focused on cloning the homologous gene of hMR-1 from mouse C57BL/6J and exploring its expression using Pichia pastoris yeast system. Two pairs of primers were synthesized according to the hMR-1 gene homologous sequence on mouse genome chromosome 1. The mouse MR-1 gene (mMR-1) was cloned by PCR following the first round RT-PCR from mouse C57BL/6J spleen total RNA. Sequence analysis verified that mMR-1 gene and amino acids sequence showed 90.4% and 90.1% identity with hMR-1, respectively. The prediction of hydrophobic transmembrane structure of mMR-1 suggested it is also a transmembrane protein. The mMR-1 Pichia pastoris expression vector pPIC9-mMR-1 was constructed by fusion of the flanking mMR-1 ORF in the pPIC9 plasmid. After linearization of pPIC9-mMR-1 with Sal I, the 8.5kb DNA fragment was transformed into Pichia pastoris GS115 strain by electroporation. GS115/Mut+ pPIC9-mMR-1 transformants were selected on minimal methanol medium. Integration of mMR-1 gene into the yeast genome in the recombinants was verified by PCR from the transformants total DNA. The mMR-1 protein was expressed by induction under the concentration of 0.5 % methanol. The specific induced protein of 25 kD molecular mass in SDS-PAGE was confirmed to be the mMR-1 protein by Western blot rsing hMR-1 polyclonal antibody. The expression level of this recombinant mMR-1 protein was about 50 mg/L. The successful expression of mMR-1 in the Pichia pastoris GS115 will facilitate the further functional analysis of the novel gene MR-1 in animal model.

Establishment of gene transduction system in geldanamycin producer - Streptomyces hygroscopicus 17997 and its application for gene disruption experiment / 生物工程学报

Streptomyces hygroscopicus 17997 produces the antiviral and antitumor ansamycin antibiotic, geldanamycin. Studies on geldanamycin biosynthetic pathway will provide good tools for genetic manipulation of the antibiotic-producing strain to improve the productivity or to facilitate making novel geldanamycin analogs. The structural similarities between geldanamycin and ansamycins such as rifamycin or ansatrienin suggest that both geldanamycin and ansamycins has a closely related pathways of biosynthesis and that biosynthetic system for geldanamycin is similar to the one of type I polyketide synthase (PKS) enzyme system. To explore the possible PKS genes involved in geldanamycin biosynthesis, the degenerate primers were designed according to the conserved sequence of KS-AT region from erythromycin and oleandomycin type I PKS genes. Cosmids containing multiple PKS genes (pCGBK2,4,6,10,11,18) were obtained by hybridization with the PCR products, which were amplified from S. hygroscopisus 17997 genomic DNA. The designed primers above were used for PCR. Development of a Streptomyces temperate phage phiC31-derivative KC515( tsrR) transduction system was carried out for identification of cosmids containing the PKS gene related to biosynthesis of geldanamycin. Several factors, mainly the Ca2+ and Mg + concentrations in different culture media affecting the frequency of gene transfection, were optimized .Transfection efficiency could reach up to 10(3) /microg DNA on YMG medium supplemented with 10mmol/L MgSO4. Reversely, the transfection efficiency decreased when YMG medium was supplemented with 30mmol/L MgSO4. Gene transfection system based on the integration-defective phage KC515 had been established for S. hygroscopicus17997. Recombinant phages (ph111, 258, 287, 116, 105) were constructed by insertion of the homologous to PKS gene fragments into the KC515 phage vector. Gene disruption experiments were performed by transduction of recombinant phages into S. hygroscopicus 17997 genome, and disruption of geldanamycin production was observed as a result of homologous recombination between the cloned insert in recombinant phage and the S. hygroscopicus 17997 genome by integration. Thiostrepton resistant transductants were selected and integration event was analyzed by Southern hybridization. The fermentation broth extracts from five resistant transductants were analyzed by TLC and HPLC. The results showed that only G16 mutant failed to produce geldanamycin. This result showed that the integration of the insert DNA fragment in recombinant phage phl6 into the chromosome of S. hygroscopicus disrupted the expression of the geldanamycin biosynthetic genes. The original cosmid pCGBK10 containing this cloned insert was predicted to encode PKS genes in the geldanamycin biosynthesis. This study laid the foundation for cloning the PKS genes involved in geldanamycin biosynthetic gene cluster from S. hygroscopicus 17997.

Study on relationship between length of homologous sequences and chromosomic recombination rate in Saccharopolyspora erythraea / 生物工程学报

In order to study the relationship between lengths of homologous fragments and chromsomic recombination rate in Saccharopolyspora erythraea, three homologous sequences, with mutant loci and different flanking sequences, (26bp + 27bp), (500bp + 576bp) and (1908bp + 1749bp), were synthesized by chemical reaction or PCR amplification, and cloned into pWHM3 to construct homologous recombination plasmids, pWHM1113, pWHM1116 and pWHM1119. When the plasmids were transformed into protoplast of Saccharopolyspora erythraea A226 under PEG mediated, on an average 30, 69 and 170 transformants grew on each plate for the three plasmids respectively, but chromosomic integration frequency were 0, 2% and 19% among corresponding transformants. Both pWHM1116 and pWHM1119 could take double crossover recombination, and exchange the mutant loci in the chromosome. It was concluded that when the flanking sequences were equal or more than (500bp + 576bp), they could take effective single and double recombination with Saccharopolyspora erythraea chromosome.

Construction of Saccharopolyspora erythraea M synthesizing a novel ketolide 3-deoxy-3-oxo-erythronolide B / 生物工程学报

Genetic engineering on macrolide antibiotics was a new field in recent years and more than 100 novel polyketides had been produced until then. Using genomic DNA of S. erythraea A226 as a template, about 3.2 kb DNA fragment without KR6 domain was amplified by overlapping PCR technique and cloned into pWHM3 carrier, which resulted in the construction of homologous recombinant plasmid pWHM2201. Plasmid pWHM2201 was introduced into protoplasts of S. erythraea A226 by PEG-mediated transformation and integrated into the gene locus for erythromycin biosynthesis. After integrants grew for two generations on R3M media without Tsr, they were protoplasted and grown on R3M plates. By PCR identification, 8 mutants without KR6 domain were selected out and named S. erythraea M(1-8). With the identification of mass spectrometry, it was proved that S. erythraea M1 synthesized a novel ketolide compound 3-deoxy-3-oxo-erythronolide B.