Design and synthesis of paclitaxel conjugated with an ErbB2-recognizing peptide, EC-1

The selective delivery of therapeutic agents to receptors overexpressed in cancer cells without harming the rest of the body is a major challenge in clinical oncology today. In this study, we report the design and synthesis of paclitaxel (PTX) conjugated with an erbB2-recognizing peptide (EC-1). The cyclic peptide EC-1 specifically binds to the extracellular domain of ErbB2 and selectively inhibits proliferation of breast cancer cells overexpressing ErbB2. PTX is a potent antitumor agent commonly used in the treatment of advanced metastatic breast cancer, yet patients have to suffer some side effects caused by its systemic toxicity. The aim of our conjugate is to specifically deliver antitumor agent PTX to breast cancer cells that overexpress oncogenic ErbB2 with the purpose to reduce toxicity and enhance selective killing of cancer cells. In this study, a concise and efficient synthetic route for the preparation of the PTX-EC-1 conjugate has been developed in 6% overall yield. This synthetic approach provides a general method for conjugating a highly functionalized and disulfide-bridge containing cyclopeptide to Taxol or other antitumor agents.     

All-atom contact potential approach to protein thermostability analysis

In this paper we use all-atom potential energy to define and analyze the inter-residue contacts in mesophilic and thermophilic proteins. Fifteen families of proteins are selected and each family has two representative proteins with greatly different preferred environmental temperatures. We find that both the number and energy of the contacts defined in this way show stronger correlations with the preferred temperatures of proteins than other factors used before. We also find that the charged-polar and charged-nonpolar residue contacts not only have larger contact numbers but also have lower single contact energies. Furthermore, the most important is that most of the thermophilic proteins have more charged-polar and charged-nonpolar residue contacts than their mesophilic counterparts. This suggests that they may play an important role in the thermostability of proteins, except usual charged-charged and nonpolar-nonpolar residue contacts. Charged residues may exert their profound influence by forming contacts not only with other charged residues but also with polar or nonpolar residues, thus further increasing the strength of contact network and then the thermostability of proteins.     

Study on glycosylated prodrugs of toxoflavins for antibody-directed enzyme tumor therapy

Eight novel toxoflavin glycosides, which are potential prodrugs in antibody directed enzyme prodrug therapy (ADEPT), were synthesized. The structures of all toxoflavin glycosides were characterized by (13)C NMR spectroscopy, elemental analysis, and MS. Their enzymatic hydrolysis activities were tested against beta-glucosidase (EC.3.2.1.21).     

Antidiabetic potential of oleanolic acid from Ligustrum lucidum Ait

Ligustrum lucidum Ait. has been used in traditional Chinese medicine for over 1000 years because of its anti-tumor, antimutagenic, antidiabetic, and hepatoprotective properties. The aim of this study was to determine whether oleanolic acid (OA) is the principal active compound of L. lucidum responsible for its antidiabetic properties, and to examine its effect on the expression of thyroid hormones and insulin secretion, thus revealing the mechanism by which L. lucidum modulates insulin levels in diabetes. When rats with streptozotocin-induced diabetes were treated with OA (100 and 200 mg/kg body mass per day, for 40 days), the changes in blood glucose levels and in oral glucose tolerance tests showed that hypoglycemia was more pronounced in OA-treated groups than in the diabetic control rats, and that the levels of triglyceride, total cholesterol, and low-density lipoportein cholesterol in OA-treated rats were lower than those in the diabetic control rats, whose high-density lipoprotein cholesterol increased. OA-treated rats also gained weight, and exhibited increased serum insulin levels. In contrast, OA treatment did not effect the levels of thyroid hormone or TSH in rats with streptozotocin-induced diabetes. These results indicate that OA has hypoglycemic and hypolipidemic effects. OA treatment might stimulate insulin release, and consequently, results in the modulation of glucose levels and regulation of lipid metabolism.     

An improved methodology for the quantification of uronic acid units in xylans and other polysaccharides

Uronic acids can be quantified either by a colorimetric determination after treatment with concentrated sulfuric acid and carbazole or by gas chromatography after methanolysis and subsequent acetylation. Both methods suffer from incomplete hydrolysis, an unavoidable degradation of the products to be analysed, and an inability to separate and quantify different types of uronic acids. In the present work, the fundamental chemistry involved in the two methods has been evaluated, and some modifications to increase their accuracy are suggested. By combining the two methods, a complete quantification of all individual types of uronic acids present in a sample can be achieved.     

Gene cloning and heterologous expression of a serine protease from Streptomyces fradiae var.k11

The gene sfp1, which encodes a predicted serine proteinase designated SFP1, was isolated by the screening of a gene library of the feather-degrading strain Streptomyces fradiae var.k11. The open reading frame of sfp1 encodes a protein of 454 amino acids with a calculated molecular mass of 46.19 kDa. Sequence analysis reveals that SFP1 possesses a typical pre-pro-mature organization that consists of a signal sequence, an N-terminal propeptide region, and a mature proteinase domain. The pre-enzyme of SFP1 was expressed in Escherichia coli and consequently purified. The 25.6 kDa fraction with protease activity separated by gel filtration chromatography indicated that the mature enzyme of SFP1 was formed by autolysis of the propeptide after its expression. The purified SFP1 is active under a broad range of pH and temperature. SFP1 has pH and temperature optima of pH 8.5 and 65 degrees C for its caseinolytic activity and pH 9 and 62 degrees C for its keratinolytic activity. SFP1 was sharply inhibited by the serine proteinase inhibitor phenylmethyl sulfonyl fluoride and exhibited a good stability to solvents, detergents, and salts. Comparison of the protease activity of SFP1 with other commercial proteases indicates that SFP1 has a considerable caseinolytic and keratinolytic activity as does proteinase K.     

Vaccinia virus infection induces dendritic cell maturation but inhibits antigen presentation by MHC class II

Vaccinia virus (VV) infection is known to inhibit dendritic cells (DC) functions in vitro. Paradoxically, VV is also highly immunogenic and thus has been used as a vaccine. In the present study, we investigated the effects of an in vivo VV infection on DC function by focusing on early innate immunity. Our data indicated that DC are activated upon in vivo VV infection of mice. Splenic DC from VV-infected mice expressed elevated levels of MHC class I and co-stimulatory molecules on their cell surface and exhibited the enhanced potential to produce cytokines upon LPS stimulation. DC from VV-infected mice also expressed a high level of interferon-beta. However, a VV infection resulted in the down-regulation of MHC class II expression and the impairment of antigen presentation to CD4 T cells by DC. Thus, during the early stage of a VV infection, although DC are impaired in some of the critical antigen presentation functions, they can promote innate immune defenses against viral infection.     

Human hepatocytes: isolation, cryopreservation and applications in drug development

The recent developments in the isolation, culturing, and cryopreservation of human hepatocytes, and the application of the cells in drug development are reviewed. Recent advances include the improvement of cryopreservation procedures to allow cell attachment, thereby extending the use of the cells to assays that requires prolong culturing such as enzyme induction studies. Applications of human hepatocytes in drug development include the evaluation of metabolic stability, metabolite profiling and identification, drug-drug interaction potential, and hepatotoxic potential. The use of intact human hepatocytes, because of the complete, undisrupted metabolic pathways and cofactors, allows the development of data more relevant to humans in vivo than tissue fractions such as human liver microsomes. Incorporation of key in vivo factors with the intact hepatocytes in vitro may help predictive human in vivo drug properties. For instance, evaluation of drug metabolism and drug-drug interactions with intact human hepatocytes in 100% human serum may eliminate the need to determine in vivo intracellular concentrations for the extrapolation of in vitro data to in vivo. Co-culturing of hepatocytes and nonhepatic primary cells from other organs in the integrated discrete multiple organ co-culture (IdMOC) may allow the evaluation of multiple organ interactions in drug metabolism and drug toxicity. In conclusion, human hepatocytes represent a critical experimental model for drug development, allowing early evaluation of human drug properties to guide the design and selection of drug candidates with a high probability of clinical success.