Molecular properties of the putative autolysin Atl(WM) encoded by Staphylococcus warneri M: mutational and biochemical analyses of the amidase and glucosaminidase domains

The putative autolysin Atl_WM of Staphylococcus warneri M is a modular protein exhibiting two enzyme activities, an N-terminal side amidase (ami_atlwm-R1-R2) and a C-terminal side glucosaminidase (R3-glu_atlwm). Zymographic analysis of the protein overproduced in Escherichia coli showed that both enzymes were active toward 17 Gram-positive bacteria, including staphylococci, lactobacilli, lactococci, enterococci, and micrococci. The purified enzyme core ami_atlwm (or glu_atlwm) had the pH and temperature optima of about 7.0 (5.5) and 41 (50) °C, respectively. ami_atlwm was inactivated by EDTA, and was stimulated by such salts as CoCl₂, MnCl₂, CaCl₂, or ZnCl₂. Six mutations within ami_atlwm, (H362A, E421A, H467A, H479, D481A, and Y491D) drastically reduced cell-lytic activity. Comparative analysis with other related amidases suggested that the three residues H362, H467, and D481 likely act as ligands (and/or active sites). The lytic activity of glu_atlwm markedly declined in four mutants (E1238A, E1238Q, T1239A, and Y1332A). For determination of the putative cell-recognition regions, four domains (R1-R2, R1, R2, and R3) were purified; all the proteins substantially bound to S. warneri M cells from exponential to stationary growth phases, and R1-R2 aggregated the cells. Protein sequencing and immunoblot analysis suggested that the extacellular Atl_WM might be primarily processed at two specific sites (one between pro and ami_atlwm, and the other between R2 and R3) to yield the mature amidase and glucosaminidase.     

Attenuation of acute and chronic liver injury in rats by iron-deficient diet

Oxidative stress due to iron deposition in hepatocytes or Kupffer cells contributes to the initiation and perpetuation of liver injury. The aim of this study was to clarify the association between dietary iron and liver injuries in rats. Liver injury was initiated by the administration of thioacetamide or ligation of the common bile duct in rats fed a control diet (CD) or iron-deficient diet (ID). In the acute liver injury model induced by thioacetamide, serum levels of aspartate aminotransferase and alanine aminotransferase, as well as hepatic levels of lipid peroxide and 4-hydroxynonenal, were significantly decreased in the ID group. The expression of 8-hydroxydeoxyguanosine and terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling positivity showed a similar tendency. The expression of interleukin-1beta and monocyte chemotactic protein-1 mRNA was suppressed in the ID group. In liver fibrosis induced by an 8-wk thioacetamide administration, ID suppressed collagen deposition and smooth muscle alpha-actin expression. The expressions of collagen 1A2, transforming growth factor beta, and platelet-derived growth factor receptor beta mRNA were all significantly decreased in the ID group. Liver fibrosis was additionally suppressed in the bile-duct ligation model by ID. In culture experiments, deferoxamine attenuated the activation process of rat hepatic stellate cells, a dominant producer of collagen in the liver. In conclusion, reduced dietary iron is considered to be beneficial in improving acute and chronic liver injuries by reducing oxidative stress. The results obtained in this study support the clinical usefulness of an iron-reduced diet for the improvement of liver disorders induced by chronic hepatitis C and alcoholic/nonalcoholic steatohepatitis.     

Liver injury due to 3-amino-1-methyl-5h-pyrido [4,3-b] indole (Trp-P-2) and its prevention by miso

Trp-P-2(3-amino-1-methyl-5H-pyrido [4,3-b] indole) ingestion for 42 d by C3H/HeJJcl mice caused elevation of serum alanine transaminase (ALT) activity and several signs of liver injury. These alterations were not observed in mice fed the diet supplemented with 10% miso. This suggests a preventive effect of miso as to Trp-P-2 induced liver injury.     

Metabolic profiling of flavonoids in Lotus japonicus using liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry

Flavonoids detected from a model legume plant, Lotus japonicus accessions Miyakojima MG-20 and Gifu B-129, were profiled using liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR/MS). Five flavonols and two anthocyanidins were detected as aglycones. LC-FTICR/MS facilitated simultaneous detection of 61 flavonoids including compounds that have not been reported previously. Chemical information of the peaks such as retention time, lambdamax, m/z value of the quasi-molecular ion, m/z value of MS/MS fragment ions, and relative intensity of MS/MS fragments was obtained, along with the molecular formulas and conjugate structures. Fourteen were completely identified by comparison with authentic compounds. The high accuracy of m/z values, being 0.081 ppm between observed and theoretical values, allowed prediction of molecular formulas of unknown compounds with the help of isotope peak information for determination of chemical composition. Based on a predicted elemental composition, the presence of a novel nitrogen-containing flavonoid was proposed. A comparison of flavonoid profiles in flowers, stems, and leaves demonstrated that the flowers yielded the most complex profile, containing 30 flower-specific flavonoids including gossypetin glycosides and isorhamnetin glycosides. A comparison of flavonoid profiles between MG-20 and B-129 grown under the same conditions revealed that the accumulation of anthocyanins was higher in B-129 than MG-20, particularly in the stem. Developmental changes in the flavonoid profiles demonstrated that kaempferol glycosides increased promptly after germination. In contrast, quercetin glycosides, predominant flavonoids in the seeds, were not detectable in growing leaves.     

The bacterial stringent response, conserved in chloroplasts, controls plant fertilization

The chloroplast, an essential organelle for plants, performs a wide variety of metabolic processes for host cells, which include photosynthesis as well as amino acid and fatty acid biosynthesis. The organelle conserves many bacterial systems in its functions, implicating its origin from symbiosis of a photosynthetic bacterium. In bacterial cells, the stringent response acts as a global regulatory system for gene expression mediated by a small nucleotide, guanosine 5'-diphosphate 3'-diphosphate (ppGpp), that is necessary for cell adaptation to diverse environmental stimuli such as amino acid starvation. Recent studies indicated that proteins similar to the bacterial ppGpp synthase/hydrolyase are conserved in plants, although their precise roles are not known. Here we show that the stringent response in chloroplasts is crucial for normal plant fertilization. Specifically, one of the Arabidopsis ppGpp synthase homologs, CRSH (Ca(2+)-activated RelA/SpoT homolog), exhibits calcium-dependent ppGpp synthesis activity in vitro, and is localized in chloroplasts in vivo. A knockdown mutation of CRSH in Arabidopsis results in a significant reduction in silique size and seed production, indicating that plant reproduction is under the control of chloroplast function through a ppGpp-mediated stringent response.     

Efficient and high-throughput vector construction and Agrobacterium-mediated transformation of Arabidopsis thaliana suspension-cultured cells for functional genomics

We established a large-scale, high-throughput protocol to construct Arabidopsis thaliana suspension-cultured cell lines, each of which carries a single transgene, using Agrobacterium-mediated transformation. We took advantage of RIKEN Arabidopsis full-length (RAFL) cDNA clones and the Gateway cloning system for high-throughput preparation of binary vectors carrying individual full-length cDNA sequences. Throughout all cloning steps, multiple-well plates were used to treat 96 samples simultaneously in a high-throughput manner. The optimal conditions for Agrobacterium-mediated transformation of 96 independent binary vector constructs were established to obtain transgenic cell lines efficiently. We evaluated the protocol by generating transgenic Arabidopsis T87 cell lines carrying individual 96 metabolism-related RAFL cDNA fragments, and showed that the protocol was useful for high-throughput and large-scale production of gain-of-function lines for functional genomics.     

The influence of gender on cardiac fibrosis induced by sympathetic stimulation

We examined the influence of sex steroids on cardiac effects of sympathetic agents in mice. The mice were divided into four groups: males, neutered males (N-males), females, and neutered females (N-females). Dobutamine (DOB; 2.5, 5.0, 10 microg/kg/min) or isoproterenol (ISO; 0.01, 0.02, 0.04 microg/kg/min) were given intravenously to compare the fractional shortening (FS). These mice received isoproterenol twice daily at a dose of 7.5 microg/g/day for 3 weeks. The rate of cardiac fibrosis was evaluated pathologically with Azan stain after 3 weeks of ISO. DOB and ISO significantly increased the FS in the male group, compared with other groups. There was no significant difference in FS between the female and N-female groups. Cardiac fibrosis significantly increased in the male group, compared with the N-male group. The female and N-female groups had increased cardiac fibrosis, compared with the male and N-male groups. These findings suggest that testosterone is one of the factors of modulation of the response to the sympathetic nervous system. Further study is needed to clarify the relationships between female sex steroids and cardiac fibrosis.     

Severe hypercholesterolemia, hypertriglyceridemia, and atherosclerosis in mice lacking both leptin and the low density lipoprotein receptor.

Leptin-deficient mice (ob/ob) are an excellent murine model for obesity, insulin resistance, and diabetes, all of which are components of a multiple risk factor syndrome that, along with hypercholesterolemia, precipitates a potential high risk for atherosclerosis. In the current study, we show an unexpectedly severe hyperlipidemia in ob/ob mice on a background of low density lipoprotein receptor (LDLR) deficiency (-/-). Doubly mutant mice (LDLR-/-;ob/ob) exhibited striking elevations in both total plasma cholesterol (TC) and triglyceride (TG) levels (1715 +/- 87 and 1016 +/- 172 mg/dl, respectively), at age 3-4 months, resulting in extensive atherosclerotic lesions throughout the aorta by 6 months. Lipoprotein analyses revealed the elevated TC and TG levels to be due to a large increase in an apoB-containing broad-beta remnant lipoprotein fraction. While fasting, diet restriction, and low level leptin treatment significantly lowered TG levels, they caused only slight changes in TC levels. Hepatic cholesterol and triglyceride contents as well as mRNA levels of cholesterologenic and lipogenic enzymes suggest that leptin deficiency increased hepatic triglyceride production but did not change cholesterol production in ob/ob mice regardless of their LDLR genotype. These data provide evidence that the hypertriglyceridemia and hypercholesterolemia in the doubly mutant mice are caused by distinct mechanisms and point to the possibility that leptin might have some impact on plasma cholesterol metabolism, possibly through an LDLR-independent pathway. This model will be an excellent tool for future studies on the relationship between impaired fuel metabolism, increased plasma remnant lipoproteins, diabetes, and atherosclerosis.     

Thrombin promotes fibroblast proliferation during the early stages of experimental radiation pneumonitis.

Huang, L., Ogushi, F., Tani, K., Ogawa, H., Kawano, T., Endo, T., Izumi, K., Ueno, J., Nishitani, H. and Sone, S. Thrombin Promotes Fibroblast Proliferation during the Early Stages of Experimental Radiation Pneumonitis. Radiat. Res. 156, 45-52 (2001).To clarify the role of thrombin in the pathogenesis of radiation-induced pneumonitis, we measured the thrombin activity and fibroblast growth-inducing activity in bronchoalveolar lavage fluid obtained from the irradiated lungs of rats at 1, 2, 4, 8 and 18 weeks after irradiation. Thrombin activity was not detected in the bronchoalveolar lavage fluid from unirradiated rats, but the bronchoalveolar lavage fluid from irradiated rats showed significantly increased thrombin activity which reached a maximum at 4 weeks after treatment. Higher fibroblast growth-inducing activity was detected in the bronchoalveolar lavage fluid from irradiated rats at 4 and 18 weeks than in fluid from unirradiated rats. Bronchoalveolar lavage fluid from irradiated rats that were pretreated with the thrombin inhibitors antithrombin III and argatroban showed significantly inhibited fibroblast growth-inducing activity and thrombin activity at 4 weeks. However, these thrombin inhibitors did not inhibit fibroblast growth-inducing activity in bronchoalveolar lavage fluid from irradiated rats at 18 weeks. Purified rat thrombin similarly induced proliferation of fibroblasts derived from irradiated and unirradiated rats. These findings suggest that thrombin may play an important role as a fibroblast growth-inducing factor during the early stages of radiation pneumonitis.