Novel Biotransformations of 7-Ethoxycoumarin by Streptomyces griseus

Biotransformation of 7-ethoxycoumarin by Streptomyces griseus resulted in the accumulation of two metabolites which were isolated and identified as 7-hydroxycoumarin and 7-hydroxy-6-methoxycoumarin. A novel series of biotransformation reactions is implicated in the conversion of the ethoxycoumarin substrate to these products, including O-deethylation, 6-hydroxylation to form a 6,7-dihydroxycoumarin catechol, and subsequent O-methylation. Either 7-hydroxycoumarin or 6,7-dihydroxycoumarin was biotransformed to 7-hydroxy-6-methoxycoumarin by S. griseus. Trace amounts of the isomeric 6-hydroxy-7-methoxycoumarin were detected when 6,7-dihydroxycoumarin was used as the substrate. Efforts to obtain a cell-free catechol-O-methyltransferase enzyme system from S. griseus were unsuccessful. However, [methyl-¹⁴C]methionine was used with cultures of S. griseus to form 7-hydroxy-6-[¹⁴C]methoxycoumarin.     

Depolarization activates ERK and proline-rich tyrosine kinase 2 (PYK2) independently in different cellular compartments in hippocampal slices

In the hippocampus, extracellular signal-regulated kinase (ERK) and the non-receptor protein proline-rich tyrosine kinase 2 (PYK2) are activated by depolarization and involved in synaptic plasticity. Both are also activated under pathological conditions following ischemia, convulsions, or electroconvulsive shock. Although in non-neuronal cells PYK2 activates ERK through the recruitment of Src-family kinases (SFKs), the link between these pathways in the hippocampus is not known. We addressed this question using K(+)-depolarized rat hippocampal slices. Depolarization increased the phosphorylation of PYK2, SFKs, and ERK. These effects resulted from Ca(2+) influx through voltage-gated Ca(2+) channels and were diminished by GF109203X, a protein kinase C inhibitor. Inhibition of SFKs with PP2 decreased PYK2 tyrosine phosphorylation dramatically, but not its autophosphorylation on Tyr-402. Moreover, PYK2 autophosphorylation and total tyrosine phosphorylation were profoundly altered in fyn-/- mice, revealing an important functional relationship between Fyn and PYK2 in the hippocampus. In contrast, ERK activation was unaltered by PP2, Fyn knock-out, or LY294002, a phosphatidyl-inositol-3-kinase inhibitor. ERK activation was prevented by MEK inhibitors that had no effect on PYK2. Immunofluorescence of hippocampal slices showed that PYK2 and ERK were activated in distinct cellular compartments in somatodendritic regions and nerve terminals, respectively, with virtually no overlap. Activation of ERK was critical for the rephosphorylation of a synaptic vesicle protein, synapsin I, following depolarization, underlining its functional importance in nerve terminals. Thus, in hippocampal slices, in contrast to cell lines, depolarization-induced activation of non-receptor tyrosine kinases and ERK occurs independently in distinct cellular compartments in which they appear to have different functional roles.     

The hyperlipemic hamster - a model for testing the anti-atherogenic effect of amlodipine

Male Golden Syrian hamsters were subjected to a hyperlipemic diet. At intervals ranging from 2 to 14 weeks, the animals were examined for changes in serum constituents and structural modifications of lesion-prone areas: the cardiac valves, coronary arteries and aortic arch. Serum was characterized by a gradual increase in cholesterol, triglycerides and a decrease in total peroxyl-radical trapping potential. The sequence of modifications of the endothelial cells, smooth muscle cells, and migrating plasma monocytes as well as of the extracellular matrix were established. Amlodipine treatment of hyperlipemic hamster was assessed. Amlodipine exhibited an athero-protective effect, acting as antioxidant, reducing the LDL uptake by the vessel wall and consequently, limiting the size and extent of lesioned areas. The hyperlipemic hamster is a reliable model to unravel the cellular alterations leading to atheroma formation, and for testing the effect of drugs in this process.     

TNF-α Acts as an Immunoregulator in the Mouse Brain by Reducing the Incidence of Severe Disease Following Japanese Encephalitis Virus Infection

Japanese encephalitis virus (JEV) causes acute central nervous system (CNS) disease in humans, in whom the clinical symptoms vary from febrile illness to meningitis and encephalitis. However, the mechanism of severe encephalitis has not been fully elucidated. In this study, using a mouse model, we investigated the pathogenetic mechanisms that correlate with fatal JEV infection. Following extraneural infection with the JaOArS982 strain of JEV, infected mice exhibited clinical signs ranging from mild to fatal outcome. Comparison of the pathogenetic response between severe and mild cases of JaOArS982-infected mice revealed increased levels of TNF-α in the brains of severe cases. However, unexpectedly, the mortality rate of TNF-α KO mice was significantly increased compared with that of WT mice, indicating that TNF-α plays a protective role against fatal infection. Interestingly, there were no significant differences of viral load in the CNS between WT and TNF-α KO mice. However, exaggerated inflammatory responses were observed in the CNS of TNF-α KO mice. Although these observations were also obtained in IL-10 KO mice, the mortality and enhanced inflammatory responses were more pronounced in TNF-α KO mice. Our findings therefore provide the first evidence that TNF-α has an immunoregulatory effect on pro-inflammatory cytokines in the CNS during JEV infection and consequently protects the animals from fatal disease. Thus, we propose that the increased level of TNF-α in severe cases was the result of severe disease, and secondly that immunopathological effects contribute to severe neuronal degeneration resulting in fatal disease. In future, further elucidation of the immunoregulatory mechanism of TNF-α will be an important priority to enable the development of effective treatment strategies for Japanese encephalitis.     

VAMP-Associated Protein B (VAPB) Promotes Breast Tumor Growth by Modulation of Akt Activity

VAPB (VAMP- associated protein B) is an ER protein that regulates multiple biological functions. Although aberrant expression of VAPB is associated with breast cancer, its function in tumor cells is poorly understood. In this report, we provide evidence that VAPB regulates breast tumor cell proliferation and AKT activation. VAPB protein expression is elevated in primary and metastatic tumor specimens, and VAPB mRNA expression levels correlated negatively with patient survival in two large breast tumor datasets. Overexpression of VAPB in mammary epithelial cells increased cell growth, whereas VAPB knockdown in tumor cells inhibited cell proliferation in vitro and suppressed tumor growth in orthotopic mammary gland allografts. The growth regulation of mammary tumor cells controlled by VAPB appears to be mediated, at least in part, by modulation of AKT activity. Overexpression of VAPB in MCF10A-HER2 cells enhances phosphorylation of AKT. In contrast, knockdown of VAPB in MMTV-Neu tumor cells inhibited pAKT levels. Pharmacological inhibition of AKT significantly reduced three-dimensional spheroid growth induced by VAPB. Collectively, the genetic, functional and mechanistic analyses suggest a role of VAPB in tumor promotion in human breast cancer.     

Production of tyrosine from sucrose or glucose achieved by rapid genetic changes to phenylalanine-producing <Emphasis Type="Italic">Escherichia coli</Emphasis> strains

Escherichia coli K12 strains producing l-phenylalanine were converted to l-tyrosine-producing strains using a novel genetic method for gene replacement. We deleted a region of the E. coli K12 chromosome including the pheA gene encoding chorismate mutase/prephenate dehydratase, its leader peptide (pheL), and its promoter using a new polymerase chain reaction-based method that does not leave a chromosomal scar. For high level expression of tyrA, encoding chorismate mutase/prephenate dehydrogenase, its native promoter was replaced with the strong trc promoter. The linked ΔpheLA and Ptrc-tyrA::Kan^R genetic modifications were moved into l-phenylalanine producing strains by generalized transduction to convert l-phenylalanine-producing strains to l-tyrosine-producing strains. Moreover, introduction of a plasmid carrying genes responsible for sucrose degradation into these strains enabled l-tyrosine-production from sucrose.     

Expression of GLP-1R protein and its clinical role in intrahepatic cholangiocarcinoma tissues

The study investigates the expression and clinical role of GLP-1R in intrahepatic cholangiocarcinoma (ICC) tissues. ICC tissue, tissue around tumour and normal liver tissue samples from 176 ICC patients were investigated for GLP-1R expression by immunohistochemistry and western blots. Expression levels were correlated to clinical variables and to the postoperative outcome. High GLP-1R expression levels were detected in tumor tissue samples. Kaplan–Meier method was used for survival analysis of patients follow-up data. Results showed that median survival time of patients with high GLP-1R positive expression in ICC tissue were 22 months. Median survival time of patients with low GLP-1R positive expression in ICC tissue were 19.8 months. There wasn’t statistical difference (p = 0.332) between two groups. Immunohistochemistry semi-quantitative analysis showed that tissue differentiation is not prognostic risk factors. In patients with GLP-1R positive expression in ICC tissue, lymph node metastasis was important prognostic factors (p = 0.001). Although statistical analysis showed that GLP-1R can not be judged as a risk prognostic factors, GLP-1 might become a new target for therapy of ICC.