Lipoxygenase interactions with natural flavonoid, quercetin, reveal a complex with protocatechuic acid in its X-ray structure at 2.1 A resolution

PUFA metabolites have a profound effect on inflammatory diseases and cancer progression. Blocking their production by inhibiting PUFA metabolizing enzymes (dioxygenases: cyclooxygenases and LOXs) might be a successful way to control and relieve such problems, if we learn to better understand their actions at a molecular level. Compounds with strong antioxidative and free radical scavenging properties, such as polyphenols, could be effective in blocking PUFA activities, and natural flavonoids possess such qualities. Quercetin belongs to the group of natural catecholic compounds and is known as a potent, competitive inhibitor of LOX. Structural analysis reveals that quercetin entrapped within LOX undergoes degradation, and the resulting compound has been identified by X-ray analysis as protocatechuic acid (3,4-dihydroxybenzoic acid) positioned near the iron site. Its C3-OH group points toward His523, C4-OH forms a hydrogen bond with O=C from the enzyme's C-terminus, and the carboxylic group is incorporated into the hydrogen bonding network of the active-site neighborhood via Gln514. This unexpected result, together with our previous observations concerning other polyphenols, yields new evidence about the metabolism of natural flavonoids. These compounds might be vulnerable to the co-oxidase activity of LOX, leading to enzyme-stimulated oxidative degradation, which results in an inhibitor of a lower molecular weight.     

The structural genomics experimental pipeline: insights from global target lists

Structural genomics (SG) initiatives are currently attempting to achieve the high-throughput determination of protein structures on a genome-wide scale. Here we analyze the SG target data that have been publicly released over a period of 16 months to assess the potential of the SG initiatives. We use statistical techniques most commonly applied in epidemiology to describe the dynamics of targets through the experimental SG pipeline. There is no clear bottleneck among the key stages of cloning, expression, purification and crystallization. An SG target will progress through each of these steps with a probability of approximately 45%. Around 80% of targets with diffraction data will yield a crystal structure, and 20% of targets with HSQC spectra will yield an NMR structure. We also find the overlaps among SG targets: 61% of SG protein sequences share at least 30% sequence identity with one or more other SG targets. There is no significant difference in average structure quality among SG structures and other structures in the PDB determined by "traditional" methods, but on average SG structures are deposited to the PDB twice as quickly after X-ray data collection.     

Down-regulation by nuclear factor kappaB of human 25-hydroxyvitamin D3 1alpha-hydroxylase promoter

1,25-(OH)(2) vitamin D(3) is important for calcium homeostasis and cell differentiation. The key enzyme for the activation of liver-derived 25(OH) vitamin D(3) is 25-hydroxyvitamin D(3) 1alpha-hydroxylase. It is expressed mainly in the kidney but also in peripheral tissues. A 1413-bp fragment of the 1alpha-hydroxylase promoter was cloned into luciferase vectors pGL2basic and pGL3basic. Sequence analyses revealed four base exchanges and three base deletions compared with the published sequence which were identically found in five control persons. In silico promoter analyses revealed 17 putative nuclear factor (NF)kappaB sites, 10 of which were found to bind NFkappaB in EMSA experiments. Cotransfection of NFkappaB p50 and p65 subunits resulted in dramatic reduction of the promoter activity of the full-length construct as well as a series of 5'-deletion constructs. Deletion of the farmost 3'-situated NFkappaB-responsive element almost abolished NFkappaB responsiveness. Treatment of human embryonic kidney 293 cells with sulfasalazine, a NFkappaB inhibitor, resulted in enhanced 1alpha-hydroxylase mRNA production. Down-regulation of 1alpha-hydroxylase promoter through NFkappaB signaling may contribute to the pathogenesis of inflammation-associated osteopenia/osteoporosis.     

Effect of restricted feed intake and addition of vitamins B2 and B6 and folic acid on the liver concentration of zinc and copper in rats

The aim of the present study was to investigate the influence of nutritional deficiency and dietary addition of vitamins (B₂, B₆, and folate) on hepatic concentration of zinc and copper in rats. The experiment was performed on 260 growing male Wistar rats divided into 13 groups. Animals of 11 groups were fed isocaloric diets (14.7 MJ/kg) in which the 20% of energy was derived from protein. Another two groups of rats were offered diets with 9% or 4.5% of energy originating from protein. Animals of both mentioned groups and of the control group (20% of energy from protein) were offered diets ad libitum. The other 10 groups were offered 50% and 30% of the amount consumed in the control group. Eight groups, from those 10 restricted ones, were differentiated by dietary addition of vitamins B₂ and B₆ and folate (300% addition). Restricted feed intake did not affect the liver zinc concentration but significantly increased the copper concentration. The addition of vitamin B₆ decreased the liver Zn concentration. The highest liver Cu concentration was noted in rats offered restricted diets to only 30% of intake in the control group and high in vitamin B₂ and in rats supplemented with all of studied vitamins together. It suggests that vitamin B₂ had the strongest impact on liver Cu concentration in rats fed restricted diets.     

Localization of human chorionic gonadotropin beta subunit transcripts in ovarian cancer tissue

Recent studies demonstrated that besides placenta and malignant trophoblastic tumors, hCG and especially its beta-subunit is secreted by a varieties of tumors of different origin. The aim of the present investigation was to determine the expression pattern of human chorionic gonadotropin gene in ovarian cancer tissue. The study included 8 patients with epithelial ovarian carcinoma. The expression and distribution of hCGbeta mRNA was assessed by in situ RT-PCR method. The semi-quantitative assessment was performed using computer image analysis. Transformation of the images into the pseudocolour scale showed a clear difference in fluorescence intensity among individual cancer cells. The intensity of ISRT-PCR products corresponding with expression level of hCGbeta demonstrated that its production by individual cancer cells is different. In all studied specimens of the ovarian carcinoma tissue, cancer cells characterized by the presence of active hCGbeta gene were found, whereas noncancerous tissue demonstrated lack of the gene expression. Thus, the study clearly shows that the expression of hCGbeta is the feature of ovarian cancer tissue.     

Effects of cellulose, carboxymethylcellulose and inulin fed to rats as single supplements or in combinations on their caecal parameters

We compared the effect of diets containing different nondigestible carbohydrates: cellulose (C), inulin (IN) and carboxymethylcellulose (CMC) as single supplements or in dietary combination on caecal physiology of rats. Sixty male Wistar rats (Rattus norvegicus) were divided into five groups and for 4 weeks were fed a casein diet with the compared carbohydrates (4% of diet) or a combination of IN+C or IN+CMC (both 4+4%). Diet intake and FCR index remained unaffected by the treatments, whereas IN improved the body weight gain of rats compared to CMC. Compared to C group, all diets containing IN and CMC decreased the caecal pH as well as enlarged the caecum, thus increasing the weights of contents and tissue, especially upon CMC treatment. Rats given carboxymethylcellulose (CMC and IN+CMC groups) had watery caecal digesta, and some of them suffered from diarrhoea. In the case of CMC, the caecal enlargement was due to tissue hypertrophy and digesta accumulation mostly in response to an increased bulk of contents. Unlike C+IN, the dietary combination of CMC- and inulin-enhanced fermentation in the caecum of rats, however the proportion of acetate, propionate and butyrate was less beneficial. Compared to CMC, inulin gave a higher concentration of SCFA, especially of butyrate and propionate. The action of inulin in the caecum of rats could be pronounced by dietary treatment combined with CMC.     

Changes of GABA(A)receptor activation kinetics in hippocampal neurons cultured for different periods of time

Cell culture is a convenient model for pharmacokinetic studies, but during the culture period, GABA(A)receptors are likely to undergo different modulatory processes. In this study, the current responses to ultrafast GABA applications were recorded from patches excised from neurons cultured for either up to two days (short-term culture) or for more than two weeks (long-term culture). The dose-dependencies of the current rising phases revealed significant differences between the two groups. In the short-term cultures, the responses to both saturating and non-saturating GABA concentrations were slower than in the case of the long-term cultures. We conclude that the GABA(A)receptors in cultured neurons undergo profound kinetic changes involving the modulation of the binding reaction and transitions between bound states.     

Protective effect of vaccination with DNA of the H. Pylori genomic library in experimentally infected mice

Immunologically mediated protection against H. pylori infection is an attractive alternative to antibiotic treatment. We compared the efficacy of conventional protein vaccination with that of genetic vaccination against experimental infection with H. pylori in mice. For oral immunization, we used the recombinant peptide of an antigenic fragment of UreB (rUreB) or H. pylori-whole cell lysate antigens, and for genetic immunization, we used recombinant pcDNA and pSec plasmids inserted with the fragment of ureB or DNA of the H. pylori genomic library. Mice were challenged with the mouse stomach-adapted H. pylori Sidney Strain. The detection of gastric bacterial colonization was performed by real-time PCR of a 26-kDa Helicobacter-specific gene, and the presence of serum H. pylori-specific antibodies was determined using direct ELISA assay. The most effective treatment appeared to be oral vaccination with rUreB and either intramuscular or intradermal vaccination with DNA of the H. pylori genomic library. Intradermal genetic vaccination with genomic library DNA significantly increased the IgG antibody response. Our study revealed acceptable efficacies of genetic vaccination with DNA of the H. pylori genomic library.     

Prevalence of agglutinating antibodies against<Emphasis Type="Italic"> Listeria monocytogenes</Emphasis> in chicks of the white stork (<Emphasis Type="Italic">Ciconia ciconia</Emphasis> Linnaeus, 1758) in Poland

In 2002 and 2003, blood samples from white stork (Ciconia ciconia) chicks were examined for the presence of antibodies against Listeria monocytogenes. Listeria antibodies were detected in 121 (59%) of 205 chick samples. The probability of Listeria antibodies being present increased with chick age; chicks detected with Listeria antibodies were in better condition than those without the bacterium.