Specialized digestive mechanism for an insect-bacterium gut symbiosis

In Burkholderia-Riptortus symbiosis, the host bean bug Riptortus pedestris harbors Burkholderia symbionts in its symbiotic organ, M4 midgut, for use as a nutrient source. After occupying M4, excess Burkholderia symbionts are moved to the M4B region, wherein they are effectively digested and absorbed. Previous studies have shown that M4B has strong symbiont-specific antibacterial activity, which is not because of the expression of antimicrobial peptides but rather because of the expression of digestive enzymes, mainly cathepsin L protease. However, in this study, inhibition of cathepsin L activity did not reduce the bactericidal activity of M4B, indicating that there is an unknown digestive mechanism that renders specifically potent bactericidal activity against Burkholderia symbionts. Transmission electron microscopy revealed that the lumen of symbiotic M4B was filled with a fibrillar matter in contrast to the empty lumen of aposymbiotic M4B. Using chromatographic and electrophoretic analyses, we found that the bactericidal substances in M4B existed as high-molecular-weight (HMW) complexes that were resistant to protease degradation. The bactericidal HMW complexes were visualized on non-denaturing gels using protein- and polysaccharide-staining reagents, thereby indicating that the HMW complexes are composed of proteins and polysaccharides. Strongly stained M4B lumen with Periodic acid-Schiff (PAS) reagent in M4B paraffin sections confirmed HMW complexes with polysaccharide components. Furthermore, M4B smears stained with Periodic acid-Schiff revealed the presence of polysaccharide fibers. Therefore, we propose a key digestive mechanism of M4B: bacteriolytic fibers, polysaccharide fibers associated with digestive enzymes such as cathepsin L, specialized for Burkholderia symbionts in Riptortus gut symbiosis.

Disseminated Rasamsonia argillacea infection in a dog

CASE HISTORY

A 4-year-old, male neutered Borzoi presented for unlocalised pain and frequent episodes of vocalisation.

CLINICAL FINDINGS

Pain was localised to the lumbar spine and radiographs revealed a L3-L4 lesion consistent with discospondylitis. The dog was treated for presumptive bacterial discospondylitis with surgical debridement, spinal stabilisation, and cephalexin. Samples collected from the affected intervertebral disc at the time of surgery revealed lymphoplasmacytic inflammation with no causative agent identified on histopathology or bacterial culture. After an initial period of improvement, signs recurred despite an 8-week antibiotic course, with the development of inappetence, weight loss, polydipsia, and polyuria. Repeat radiographs revealed a new cervical intervertebral lesion, and concurrent pyelonephritis was diagnosed based on blood and urine results. Fungal culture of urine resulted in growth of Rasamsonia argillacea species complex and disseminated fungal disease was clinically diagnosed. Antifungal treatment was commenced, however the dog deteriorated, and euthanasia was performed.

PATHOLOGICAL FINDINGS

Multifocal white plaques were grossly visualised in the spleen, mesenteric lymph nodes, cervical vertebrae, and kidneys. Periodic acid-Schiff-positive, fine, parallel-walled, occasionally branching, septate hyphae 5-10 μm in diameter, and conidia 5-7 μm in diameter were found on sectioning all organs. R. argillacea species complex was identified by fungal culture of urine and was considered the species of fungal organism seen histologically. The isolate was subsequently confirmed as R. argillacea by DNA sequencing.

DIAGNOSIS

Disseminated Rasamsonia argillacea infection.

CLINICAL RELEVANCE

Rasamsonia argillacea species complex is a recognised invasive mycosis in veterinary medicine, with disseminated disease causing significant clinical complications and death. This is believed to be the first report of infection caused by R. argillacea in a dog in Australasia and highlights the importance of awareness of a potential fungal aetiology in dogs with discospondylitis.Abbreviations: CLSI: Clinical and Laboratory Standards Institute; CRI: Constant rate infusion; MEC: Minimum effective concentration; MIC: Minimum inhibitory concentration; PAS: Periodic acid-Schiff.

Danshen injection induces autophagy in podocytes to alleviate nephrotic syndrome via the PI3K/AKT/mTOR pathway

BACKGROUND

Danshen injection (DSI) is an agent extracted from the Salvia miltiorrhiza Bunge, a natural drug commonly used to alleviate kidney diseases. However, the material basis and therapeutic effects of DSI on nephrotic syndrome (NS) remain unclear.

PURPOSE

To investigate the material basis of DSI and the therapeutic effects and underlying mechanisms of NS.

METHODS

NS models were established using adriamycin-induced BALB/c mice and lipopolysaccharide-induced mouse podocytes (MPC-5). Following DSI and prednisone administration, kidney coefficients, 24 h urine protein, blood urea nitrogen, and serum creatinine levels were tested. Histomorphology was observed by periodic acid-Schiff staining and hematoxylin and eosin staining of the kidney sections. The glomerular basement membrane and autophagosomes of the kidneys were observed using transmission electron microscopy. Nephrin and desmin levels in the glomeruli were tested using immunohistochemistry. The viability of MPC-5 cells was tested using cell counting kit-8 after chloroquine and rapamycin administration in combination with DSI. The in vivo and in vitro protein levels of phosphatidylinositol 3-kinase (PI3K), AKT, phosphorylated AKT (Ser473), mammalian target of rapamycin (mTOR), microtubule-associated protein light chain 3 (LC3), beclin1, cleaved caspase-3, and caspase-3 were detected using western blotting.

RESULTS

Our results showed that DSI contained nine main components: caffeic acid, danshensu, lithospermic acid, rosmarinic acid, salvianolic acid A, salvianolic acid B, salvianolic acid C, salvianolic acid D, and 3, 4-Dihydroxybenzaldehyde. In in vivo studies, the NS mice showed renal function and pathological impairment. Podocytes were damaged, with decreased levels of autophagy and apoptosis, accompanied by inhibition of the PI3K/AKT/mTOR signaling. DSI administration resulted in improved renal function and pathology in NS mice, with the activation of autophagy and PI3K/AKT/mTOR signaling in the kidneys. Additionally, podocytes were less damaged and intracellular autophagosomes were markedly increased. In vitro studies have shown that DSI activated MPC-5 autophagy and reduced apoptosis via the PI3K/AKT/mTOR pathway.

CONCLUSION

Collectively, this study demonstrated that DSI activated podocyte autophagy and reduced apoptosis via the PI3K/AKT/mTOR signaling, ultimately attenuating NS. Our study clarified the main components of DSI and elucidated its therapeutic effects and potential mechanisms for NS, providing new targets and agents for the clinical treatment of NS.

Estrogen deficiency aggravates fluoride-induced small intestinal mucosa damage and junctional complexes proteins expression disorder in rats

To investigate the effect of estrogen deficiency on the small intestinal mucosal barrier induced by fluoride (F), F exposure models of ovariectomy (OVX) rats (surgically removed ovaries) and non-OVX rats (normal condition) were established by adding sodium fluoride (NaF) (0, 25, 50, and 100 mg/L, calculated by F ion) in drinking water for 90 days. The intestinal mucosal histomorphology, mucosal barrier function, and protein expression levels of tight junctions (TJs), adhesion junctions (AJs), and desmosomes were evaluated in the duodenum, jejunum, and ileum. Hematoxylin-eosin (HE) staining and 5-Bromo-2-deoxyUridine (BrdU) measurement showed that excessive F-induced damage to intestinal epithelial cells and inhibited the proliferation of intestinal epithelial cells, eventually decreasing the number of goblet cells and decreasing glycoprotein secretion, as indicated by Alcian blue and periodic acid-Schiff (AB-PAS) and periodic acid-Schiff (PAS) staining. Further immunofluorescence analysis demonstrated that excessive F decreased the protein expression levels of occludin, zonula occludens-1 (ZO-1), E-cadherin, and desmoplakin (P < 0.05, P < 0.01) and enhanced the expression of claudin-2 (P < 0.01), suggesting that cell-to-cell junctions were disrupted. Collectively, F exposure impaired the small intestinal mucosal barrier by inducing damage to intestinal epithelial cells and inhibiting intestinal epithelial cell proliferation. Disorders in the junctional complex protein expression blocked the synergy between intercellular communication and aggravated mucosal injury. In particular, estrogen deficiency exacerbated F-induced enterotoxicity, which provides new explanations for the development and severity of intestinal disease in postmenopausal women with high-F areas.

Oxysophocarpine inhibits airway inflammation and mucus hypersecretion through JNK/AP-1 pathway in vivo and in vitro

Asthma is a high-incidence disease in the world. Oxysophocarpine (OSC), a quinolizidine alkaloid displays various pharmacological functions including anti-inflammation, neuroprotective, anti-virus and antioxidant. Here, we established mice and cell asthmatic model to explore the effects of OSC for asthma treatment. Mice were sensitized and challenged with ovalbumin (OVA) and treated with OSC before challenge. Enzyme-linked immuno sorbent assay (ELISA), hematoxylin and eosin (H&E), periodic acid-schiff (PAS), tolonium chloride staining and immunohistochemical assay were performed. OSC treatment inhibited inflammatory cell infiltration and mucus secretion in the airway, reduced IgE level in mouse serum and decreased IL-4, IL-5 production in bronchoalveolar lavage fluid (BALF). OSC also reduced the spleen index to regulate immune function. Meanwhile, NCI-H292 cells were induced by lipopolysaccharide (LPS) to simulate airway epithelial injury. OSC pretreatment decreased the IL-6 and IL-8 cytokine levels, mucin 5 AC expression, and mucin 5 AC mRNA level in the cell model. Further, OSC suppressed the phosphorylation of c-Jun N-terminal kinase (JNK), and activator protein 1 (AP-1, Fos and Jun). These findings revealed that OSC alleviated bronchial asthma associated with JNK/AP-1 signaling pathway.

Porcine Deltacoronavirus Utilizes Sialic Acid as an Attachment Receptor and Trypsin Can Influence the Binding Activity

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that causes diarrhea in nursing piglets. Studies showed that PDCoV uses porcine aminopeptidase N (pAPN) as an entry receptor, but the infection of pAPN-knockout cells or pigs with PDCoV revealed that pAPN might be not a critical functional receptor, implying there exists an unidentified receptor involved in PDCoV infection. Herein, we report that sialic acid (SA) can act as an attachment receptor for PDCoV invasion and facilitate its infection. We first demonstrated that the carbohydrates destroyed on the cell membrane using NaIO₄ can alleviate the susceptibility of cells to PDCoV. Further study showed that the removal of SA, a typical cell-surface carbohydrate, could influence the PDCoV infectivity to the cells significantly, suggesting that SA was involved in the infection. The results of plaque assay and Western blotting revealed that SA promoted PDCoV infection by increasing the number of viruses binding to SA on the cell surface during the adsorption phase, which was also confirmed by atomic force microscopy at the microscopic level. In in vivo experiments, we found that the distribution levels of PDCoV and SA were closely relevant in the swine intestine, which contains huge amount of trypsin. We further confirmed that SA-binding capacity to PDCoV is related to the pre-treatment of PDCoV with trypsin. In conclusion, SA is a novel attachment receptor for PDCoV infection to enhance its attachment to cells, which is dependent on the pre-treatment of trypsin on PDCoV. This study paves the way for dissecting the mechanisms of PDCoV–host interactions and provides new strategies to control PDCoV infection.

Superhydrophilic Polyurethane/Polydopamine Nanofibrous Materials Enhancing Cell Adhesion for Application in Tissue Engineering

The use of nanofibrous materials in the field of tissue engineering requires a fast, efficient, scalable production method and excellent wettability of the obtained materials, leading to enhanced cell adhesion. We proposed the production method of superhydrophilic nanofibrous materials in a two-step process. The process is designed to increase the wettability of resulting scaffolds and to enhance the rate of fibroblast cell adhesion. Polyurethane (PU) nanofibrous material was produced in the solution blow spinning process. Then the PU fibers surface was modified by dopamine polymerization in water solution. Two variants of the modification were examined: dopamine polymerization under atmospheric oxygen (V-I) and using sodium periodate as an oxidative agent (V-II). Hydrophobic PU materials after the treatment became highly hydrophilic, regardless of the modification variant. This effect originates from polydopamine (PDA) coating properties and nanoscale surface structures. The modification improved the mechanical properties of the materials. Materials obtained in the V-II process exhibit superior properties over those from the V-I, and require shorter modification time (less than 30 min). Modifications significantly improved fibroblasts adhesion. The cells spread after 2 h on both PDA-modified PU nanofibrous materials, which was not observed for unmodified PU. Proposed technology could be beneficial in applications like scaffolds for tissue engineering.

Characterization of Biofilm Formation in [Pasteurella] pneumotropica and [Actinobacillus] muris Isolates of Mouse Origin

[Pasteurella] pneumotropica biotypes Jawetz and Heyl and [Actinobacillus] muris are the most prevalent Pasteurellaceae species isolated from laboratory mouse. However, mechanisms contributing to their high prevalence such as the ability to form biofilms have not been studied yet. In the present investigation we analyze if these bacterial species can produce biofilms in vitro and investigate whether proteins, extracellular DNA and polysaccharides are involved in the biofilm formation and structure by inhibition and dispersal assays using proteinase K, DNase I and sodium periodate. Finally, the capacity of the biofilms to confer resistance to antibiotics is examined. We demonstrate that both [P.] pneumotropica biotypes but not [A.] muris are able to form robust biofilms in vitro, a phenotype which is widely spread among the field isolates. The biofilm inhibition and dispersal assays by proteinase and DNase lead to a strong inhibition in biofilm formation when added at the initiation of the biofilm formation and dispersed pre-formed [P.] pneumotropica biofilms, revealing thus that proteins and extracellular DNA are essential in biofilm formation and structure. Sodium periodate inhibited the bacterial growth when added at the beginning of the biofilm formation assay, making difficult the assessment of the role of β-1,6-linked polysaccharides in the biofilm formation, and had a biofilm stimulating effect when added on pre-established mature biofilms of [P.] pneumotropica biotype Heyl and a majority of [P.] pneumotropica biotype Jawetz strains, suggesting that the presence of β-1,6-linked polysaccharides on the bacterial surface might attenuate the biofilm production. Conversely, no effect or a decrease in the biofilm quantity was observed by biofilm dispersal using sodium periodate on further biotype Jawetz isolates, suggesting that polysaccharides might be incorporated in the biofilm structure. We additionally show that [P.] pneumotropica cells enclosed in biofilms were less sensitive to treatment with amoxicillin and enrofloxacin than planktonic bacteria. Taken together, these findings provide a first step in understanding of the biofilm mechanisms in [P.] pneumotropica, which might contribute to elucidation of colonization and pathogenesis mechanisms for these obligate inhabitants of the mouse mucosa.

Adhesion of smooth and rough phenotypes of Flavobacterium psychrophilum to polystyrene surfaces

Phenotypic smooth cells of the fish pathogenic bacterium Flavobacterium psychrophilum have previously been reported to be more adhesive to polystyrene surfaces than corresponding rough cells. In this study, the adhesion ability of smooth and rough cells of F. psychrophilum to polystyrene surfaces was investigated in detail with a crystal violet staining method. By treating both polystyrene surfaces with fish mucus and carbohydrates and the bacterial cells with carbohydrates, the involvement of lectins in the adhesion process was investigated. Smooth cells showed significantly higher adhesion ability to untreated polystyrene surfaces compared with corresponding rough cells and increasing water hardness had an inhibitory effect on the adhesion. Treatment of polystyrene surfaces with D-glucose, D-galactose and fish mucus increased the adhesion ability of smooth cells to polystyrene. Furthermore, treatment of the smooth cells with D-glucose, D-galactose and sialic acid decreased the adhesion ability of the cells, indicating that the adhesion is likely mediated by complementary lectins on the surface of the cells. Sodium (meta)periodate treatment of smooth cells also decreased the adhesion ability to polystyrene, suggesting that the lectins, such as the dominating sialic acid-binding lectin, are probably localized in the extracellular polysaccharides surrounding the cells.

Development of a hypersensitive periodate-cleavable amino acid that is methionine- and disulfide-compatible and its application in MHC exchange reagents for T cell characterisation

Incorporation of cleavable linkers into peptides and proteins is of particular value in the study of biological processes. Here we describe the synthesis of a cleavable linker that is hypersensitive to oxidative cleavage as the result of the periodate reactivity of a vicinal amino alcohol moiety. Two strategies directed towards the synthesis of a building block suitable for solid-phase peptide synthesis were developed: a chemoenzymatic route, involving L-threonine aldolase, and an enantioselective chemical route; these led to α,γ-diamino-β-hydroxybutanoic acids in diastereoisomerically mixed and enantiopure forms, respectively. Incorporation of the 1,2-amino alcohol linker into the backbone of a peptide generated a conditional peptide that was rapidly cleaved at very low concentrations of sodium periodate. This cleavable peptide ligand was applied in the generation of MHC exchange reagents for the detection of antigen-specific T cells in peripheral blood cells. The extremely low concentration of periodate required to trigger MHC peptide exchange allowed the co-oxidation of methionine and disulfide residues to be avoided. Conditional MHC reagents hypersensitive to periodate can now be applied without limitations when UV irradiation is undesired or less practical.

Study of the formation of a biofilm by clinical strains of Staphylococcus aureus

A study on biofilm formation was carried out using five methicillin-sensitive [MSSA] and five methicillin-resistant [MRSA] strains of S. aureus. In each group, there were four strains isolated from patients from Kinshasa (Democratic Republic of Congo, DRC) and one reference strain. All of the strains were hydrophobic. The adherence of the bacteria to an abiotic surface was studied with the Biofilm Ring Test (BFRT®) and the crystal violet staining method (CVSM). Both techniques showed that eight of the strains formed biofilms within 2-3 h. The extent of the biofilm formed by one strain could only be observed with the CVSM. Periodate prevented the formation of biofilms and, in separate experiments, destroyed the biofilm pre-formed by the MSSA reference, but not those pre-formed by the clinical strains. Proteinase K destroyed all pre-formed biofilms. Six of the strains were icaA+; the clinical MSSA strains were not. The results also indicated different mechanisms of biofilm development between MSSA and MRSA clinical strains. The BFRT® and the CVSM are complementary techniques to study the adhesion of bacteria and the development of biofilms.

Alanine racemase mutants of Burkholderia pseudomallei and Burkholderia mallei and use of alanine racemase as a non-antibiotic-based selectable marker

Burkholderia pseudomallei and Burkholderia mallei are category B select agents and must be studied under BSL3 containment in the United States. They are typically resistant to multiple antibiotics, and the antibiotics used to treat B. pseudomallei or B. mallei infections may not be used as selective agents with the corresponding Burkholderia species. Here, we investigated alanine racemase deficient mutants of B. pseudomallei and B. mallei for development of non-antibiotic-based genetic selection methods and for attenuation of virulence. The genome of B. pseudomallei K96243 has two annotated alanine racemase genes (bpsl2179 and bpss0711), and B. mallei ATCC 23344 has one (bma1575). Each of these genes encodes a functional enzyme that can complement the alanine racemase deficiency of Escherichia coli strain ALA1. Herein, we show that B. pseudomallei with in-frame deletions in both bpsl2179 and bpss0711, or B. mallei with an in-frame deletion in bma1575, requires exogenous D-alanine for growth. Introduction of bpsl2179 on a multicopy plasmid into alanine racemase deficient variants of either Burkholderia species eliminated the requirement for D-alanine. During log phase growth without D-alanine, the viable counts of alanine racemase deficient mutants of B. pseudomallei and B. mallei decreased within 2 hours by about 1000-fold and 10-fold, respectively, and no viable bacteria were present at 24 hours. We constructed several genetic tools with bpsl2179 as a selectable genetic marker, and we used them without any antibiotic selection to construct an in-frame ΔflgK mutant in the alanine racemase deficient variant of B. pseudomallei K96243. In murine peritoneal macrophages, wild type B. mallei ATCC 23344 was killed much more rapidly than wild type B. pseudomallei K96243. In addition, the alanine racemase deficient mutant of B. pseudomallei K96243 exhibited attenuation versus its isogenic parental strain with respect to growth and survival in murine peritoneal macrophages.

In vitro markers for virulence in Yersinia ruckeri

In this study, different traits that have been associated with bacterial virulence were studied in Yersinia ruckeri. Two isolates that had been shown to cause disease and mortality in experimentally infected rainbow trout were compared with five avirulent isolates. Both virulent isolates showed high adhesion to gill and intestinal mucus of rainbow trout, whereas the majority of non-virulent strains demonstrated significantly lower adhesion. A decrease in adherence capability following bacterial treatment with sodium metaperiodate and proteolytic enzymes suggested the involvement of carbohydrates and proteins. All strains were able to adhere to and invade chinook salmon embryo cell line (CHSE-214), fathead minnow epithelial cell line (FHM) and rainbow trout liver cell line (R1). One non-virulent strain was highly adhesive and invasive in the three cell lines, whereas the virulent strains showed moderate adhesive and invasive capacity. The internalization of several isolates was inhibited by colchicine and cytochalasin-D, suggesting that microtubules and microfilaments play a role. For all strains, intracellular survival assays showed a decrease of viable bacteria in the cells 6 h after inoculation, suggesting that Y. ruckeri is not able to multiply or survive inside cultured cells. Analysis of the susceptibility to the bactericidal effect of rainbow trout serum demonstrated that virulent Y. ruckeri strains were serum resistant, whereas non-virulent strains were generally serum sensitive.

Mistletoe lectin binds to multidrug resistance-associated protein MRP5

BACKGROUND

Mistletoe lectins (MLs) are the active components of aqueous mistletoe extracts widely used in complementary cancer therapy, however, it is not clear if they bind to carbohydrate residues only or whether they interact with proteins as well. Protein-protein interactions do not seem unlikely as MLs act at very low molar concentrations usually observed with peptide-peptide interactions only and not seen with lectin-sugar interactions.

MATERIALS AND METHODS

In order to detect protein-protein interactions a random peptide library was screened for the ability to bind to MLs.

RESULTS

MLs bound to peptides showing homologies to multidrug resistance-associated protein 5 (MRP5). However, the MLs only slightly modified the MRP5 efflux pump, while periodate treatment to inhibit cell membrane binding via glycan completely abolished the ML-I binding sites in MRP5 overexpressing cells.

CONCLUSION

The protein sequence is not important for ML-I binding, indicating that the biological activity of MLs can most likely be attributed to the sugar chains.

Design of anti- and pro-aggregation variants to assess the effects of methionine oxidation in human prion protein

Prion disease is characterized by the alpha-->beta structural conversion of the cellular prion protein (PrP(C)) into the misfolded and aggregated "scrapie" (PrP(Sc)) isoform. It has been speculated that methionine (Met) oxidation in PrP(C) may have a special role in this process, but has not been detailed and assigned individually to the 9 Met residues of full-length, recombinant human PrP(C) [rhPrP(C)(23-231)]. To better understand this oxidative event in PrP aggregation, the extent of periodate-induced Met oxidation was monitored by electrospray ionization-MS and correlated with aggregation propensity. Also, the Met residues were replaced with isosteric and chemically stable, nonoxidizable analogs, i.e., with the more hydrophobic norleucine (Nle) and the highly hydrophilic methoxinine (Mox). The Nle-rhPrP(C) variant is an alpha-helix rich protein (like Met-rhPrP(C)) resistant to oxidation that lacks the in vitro aggregation properties of the parent protein. Conversely, the Mox-rhPrP(C) variant is a beta-sheet rich protein that features strong proaggregation behavior. In contrast to the parent Met-rhPrP(C), the Nle/Mox-containing variants are not sensitive to periodate-induced in vitro aggregation. The experimental results fully support a direct correlation of the alpha-->beta secondary structure conversion in rhPrP(C) with the conformational preferences of Met/Nle/Mox residues. Accordingly, sporadic prion and other neurodegenerative diseases, as well as various aging processes, might also be caused by oxidative stress leading to Met oxidation.

The inactivation of the bovine J blood group substance by the periodate ion

1. Treatment of J-positive (Jcs) bovine erythrocytes with periodate (0.25 mmol/l final concentration, 1 hour, room temperature) has no effect on the J activity. Higher periodate concentrations cause spontaneous haemolyses. 2. Treatment of the lipids extracted from (and containing all J activity of) Jcs erythrocytes with periodate leads to a decrease of J activity even with lower periodate concentrations. 3. Treatment of the stroma prepared from Jcs erythrocytes with periodate demonstrated the relative stability of the J antigen up to 0.25 mmol/l periodate. At the same time the sialic acid concentration of stroma is reduced to about 13% of the initial concentration. 4. Desialylation of Jcs erythrocytes or Jcs stroma with sialidase does not affect the J activity thus confirming previous findings. On the other hand, the J activity of desialylated Jcs stroma is much more susceptible to periodate. 5. It is concluded that membrane-bound sialic acid shields the membrane-bound J antigen from being attacked by periodate.

Migration inhibition produced by sodium periodate oxidation of the macrophage membrane, and reversal by sodium borohydride

Guinea pig peritoneal exudate cells were harvested 3 to 4 days after the intraperitoneal injection of Marcol oil. The washed cells were exposed to various concentrations of sodium periodate in phosphate-buffered saline (PBS) at pH 7.4 for 10 min at +4 degrees C. The cells were then used in the in vitro migration assay, and migration was consistently inhibited at concentrations from 10(-3) to 10(-5) M. The viability of the macrophages was not affected by this treatment. Sodium borohydride (10(-3) to 10(-5) M) in PBS for 10 min at pH 7.4 reversed the periodate effect. Experiments with purified macrophages showed that sodium periodate has a direct effect on macrophage function rather than an indirect effect via the potentiation of migration inhibition factor. In support of this, the in vitro spreading of macrophages on glass substrate for 1 h has been shown to be inhibited. This spreading inhibition can also be reversed by treatment with sodium borohydride. These results provide a new approach to understanding the biological significance and role of macrophage migration inhibition.

Contribution of the mannan backbone of cryptococcal glucuronoxylomannan and a glycolytic enzyme of Staphylococcus aureus to contact-mediated killing of Cryptococcus neoformans

The fungal pathogen Cryptococcus neoformans is killed by the bacterium Staphylococcus aureus, and the killing is inhibited by soluble capsular polysaccharides. To investigate the mechanism of killing, cells in coculture were examined by scanning and transmission electron microscopy. S. aureus attached to the capsule of C. neoformans, and the ultrastructure of the attached C. neoformans cells was characteristic of dead cells. To identify the molecules that contributed to the fungal-bacterial interaction, we treated each with NaIO(4) or protease. Treatment of C. neoformans with NaIO(4) promoted adherence. It was inferred that cleavage of xylose and glucuronic acid side chains of glucuronoxylomannan (GXM) allowed S. aureus to recognize mannose residues in the backbone, which resisted periodate oxidation. On the other hand, treatment of S. aureus with protease decreased adherence, suggesting that protein contributed to attachment in S. aureus. In confirmation, side chain-cleaved polysaccharide or defined alpha-(1-->3)-mannan inhibited the killing at lower concentrations than native GXM did. Also, these polysaccharides reduced the adherence of the two species and induced clumping of pure S. aureus cells. alpha-(1-->3)-Mannooligosaccharides with a degree of polymerization (DP) of >/=3 induced cluster formation of S. aureus in a dose-dependent manner. Surface plasmon resonance analyses showed interaction of GXM and surface protein from S. aureus; the interaction was inhibited by oligosaccharides with a DP of > or =3. Conformations of alpha-(1-->3) oligosaccharides were predicted. The three-dimensional structures of mannooligosaccharides larger than triose appeared curved and could be imagined to be recognized by a hypothetical staphylococcal lectin. Native polyacrylamide gel electrophoresis of staphylococcal protein followed by electroblotting, enzyme-linked immunolectin assay, protein staining, and N-terminal amino acid sequencing suggested that the candidate protein was triosephosphate isomerase (TPI). The enzymatic activities were confirmed by using whole cells of S. aureus. TPI point mutants of S. aureus decreased the ability to interact with C. neoformans. Thus, TPI on S. aureus adheres to the capsule of C. neoformans by recognizing the structure of mannotriose units in the backbone of GXM; we suggest that this contact is required for killing of C. neoformans.

Susceptibility of staphylococcal biofilms to enzymatic treatments depends on their chemical composition

Bacterial infections are serious complications after orthopaedic implant surgery. Staphylococci, with Staphylococcus epidermidis as a leading species, are the prevalent and most important species involved in orthopaedic implant-related infections. The biofilm mode of growth of these bacteria on an implant surface protects the organisms from the host's immune system and from antibiotic therapy. Therapeutic agents that disintegrate the biofilm matrix would release planktonic cells into the environment and therefore allow antibiotics to eliminate the bacteria. An addition of a biofilm-degrading agent to a solution used for washing-draining procedures of infected orthopaedic implants would greatly improve the efficiency of the procedure and thus help to avoid the removal of the implant. We have previously shown that the extracellular staphylococcal matrix consists of a poly-N-acetylglucosamine (PNAG), extracellular teichoic acids (TAs) and protein components. In this study, we accessed the sensitivity of pre-formed biofilms of five clinical staphylococcal strains associated with orthopaedic prosthesis infections and with known compositions of the biofilm matrix to periodate, Pectinex Ultra SP, proteinase K, trypsin, pancreatin and dispersin B, an enzyme with a PNAG-hydrolysing activity. We also tested the effect of these agents on the purified carbohydrate components of staphylococcal biofilms, PNAG and TA. We found that the enzymatic detachment of staphylococcal biofilms depends on the nature of their constituents and varies between the clinical isolates. We suggest that a treatment with dispersin B followed by a protease (proteinase K or trypsin) could be capable to eradicate biofilms of a variety of staphylococcal strains on inert surfaces.

Analysis of protein-linked glycosylation in a sperm-somatic cell adhesion system

Murine sperm initiate fertilization by binding to the specialized extracellular matrix of their complementary eggs, known as the zona pellucida. On the basis of data reported in this study, mouse sperm also bind to rabbit erythrocytes with higher affinity than they do to murine eggs. This unusual interaction between a germ cell and a somatic cell ("sperm-somatic cell adhesion system") is also carbohydrate dependent based on its sensitivity to mild periodate oxidation. To determine what types of carbohydrate sequences could be involved in this interaction, the protein-linked oligosaccharides of rabbit erythrocytes were sequenced using novel matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry methods that enabled the analysis of individual components up to m/z 9000. The N-glycans are primarily complex biantennary and triantennary types terminated with Galalpha1-3Gal sequences. The majority of these oligosaccharides also possess one antenna consisting of a highly branched polylactosamine-type sequence that is also associated with many glycosphingolipids that coat rabbit erythrocytes. These erythrocytes also express Core 1 and Core 2 O-glycans terminated primarily with Galalpha1-3Gal sequences and to a lesser extent sialic acid. These results confirm that rabbit erythrocytes and mouse eggs present very different types of carbohydrate sequences on their surfaces. However, oligosaccharides terminated with beta1-6-linked N-acetyllactosamine or its alpha1-3 galactosylated analog are expressed on both the mouse zona pellucida and this somatic cell type. The far more abundant presentation of such sequences on rabbit erythrocytes compared with murine eggs could explain why mouse sperm display such exceptional affinity for this somatic cell type.

Protein methylation is required to maintain optimal HIV-1 infectivity

Background:

Protein methylation is recognized as a major protein modification pathway regulating diverse cellular events such as protein trafficking, transcription, and signal transduction. More recently, protein arginine methyltransferase activity has been shown to regulate HIV-1 transcription via Tat. In this study, adenosine periodate (AdOx) was used to globally inhibit protein methyltransferase activity so that the effect of protein methylation on HIV-1 infectivity could be assessed.

Results:

Two cell culture models were used: HIV-1-infected CEM T-cells and HEK293T cells transfected with a proviral DNA plasmid. In both models, AdOx treatment of cells increased the levels of virion in culture supernatant. However, these viruses had increased levels of unprocessed or partially processed Gag-Pol, significantly increased diameter, and displayed reduced infectivity in a MAGI X4 assay. AdOx reduced infectivity equally in both dividing and non-dividing cells. However, infectivity was further reduced if Vpr was deleted suggesting virion proteins, other than Vpr, were affected by protein methylation. Endogenous reverse transcription was not inhibited in AdOx-treated HIV-1, and infectivity could be restored by pseudotyping HIV with VSV-G envelope protein. These experiments suggest that AdOx affects an early event between receptor binding and uncoating, but not reverse transcription.

Conclusion:

Overall, we have shown for the first time that protein methylation contributes towards maximal virus infectivity. Furthermore, our results also indicate that protein methylation regulates HIV-1 infectivity in a complex manner most likely involving the methylation of multiple viral or cellular proteins and/or multiple steps of replication.

[Interaction of chaotropically modified immunoglobulins with protein and glicolipid antigens]

The features of interaction of native and chaotropically modified immunoglobulins with proteins (ovalbumin) and glicolipids (lipopolysaccharides, LPS) enterobacteria Escherichia coli K235, Salmonella minnesota and Salmonella enteritidis have been investigated. It has been established, that after processing of native antibodies with 3.5 M KSCN their ability to contact to the specified antigenes repeatedly grows. Besides the intensity of interaction of modified immunoglobulins with the mentioned above antigenes was various, that is determined by the presence of structural distinctions between antigen determinants of proteins and glycolipid antigens, and also between O-polysaccharide chains of LPS in different species of enterobacteria.

The interaction between the amoebaBalamuthia mandrillarisand extracellular matrix glycoproteinsin vitro

Balamuthia mandrillaris, a soil amoeba, is the causative agent ofBalamuthiagranulomatous amoebic encephalitis, a life-threatening brain infection. This amoeba is acquired from contaminated soil and may enter the host through cutaneous lesions or through nasal passages, migrating to the lungs or brain. During invasion,B. mandrillarishas access to components of the extracellular matrix (ECM) of the host. Therefore, we investigated the interaction ofB. mandrillariswith 3 ECM glycoproteins (collagen-I, fibronectin and laminin-1) that are encountered in host connective tissues and at the basal lamina. Using optical microscopy, amoeba association on ECM-coated surfaces was examined. Binding of amoebae on laminin was greater than that on collagen or fibronectin. Laminin-adheredB. mandrillarisexhibited elongated and spread forms, distinctive from those observed for amoebae on a plastic surface. Collagen and fibronectin-adheredB. mandrillarispresented elongated shapes with cellular expansions. Binding to collagen, fibronectin, or laminin was inhibited when amoebae were pre-treated with sialic acid. Treatment with galactose resulted in diminished binding of amoebae on laminin, while mannose increased binding in all coating conditions tested. Dependence of divalent cations on amoeba binding was demonstrated for laminin-amoeba interaction. Collectively, the results indicate thatB. mandrillarisrecognizes specific glycoproteins of the mammalian extracellular matrix.

Indirect spectrophotometric determination of arbutin, whitening agent through oxidation by periodate and complexation with ferric chloride

A simple and accurate spectrophotometric method for the determination of arbutin (glycosylated hydroquinone) is described. It is based on the oxidation of arbutin by periodate in presence of iodate. Excess periodate causes liberation of iodine at pH 8.0. The unreacted periodate is determined by measurement of the liberated iodine spectrophotometrically in the wavelength range (300-500 nm). A calibration curve was constructed for more accurate results and the correlation coefficient of linear regression analysis was -0.9778. The precision of this method was better than 6.17% R.S.D. (n=3). Regression analysis of Bear-Lambert plot shows good correlation in the concentration range 25-125 ug/ml. The identification limit was determined to be 25 ug/ml a detailed study of the reaction conditions was carried out, including effect of changing pH, time, temperature and volume of periodate. Analyzing pure and authentic samples containing arbutin tested the validity of the proposed method which has an average percent recovery of 100.86%. An alternative method is also proposed which involves a complexation reaction between arbutin and ferric chloride solution. The produced complex which is yellowish-green in color was determined spectophotometrically.

A distinct small RNA pathway silences selfish genetic elements in the germline

In the Drosophila germline, repeat-associated small interfering RNAs (rasiRNAs) ensure genomic stability by silencing endogenous selfish genetic elements such as retrotransposons and repetitive sequences. Whereas small interfering RNAs (siRNAs) derive from both the sense and antisense strands of their double-stranded RNA precursors, rasiRNAs arise mainly from the antisense strand. rasiRNA production appears not to require Dicer-1, which makes microRNAs (miRNAs), or Dicer-2, which makes siRNAs, and rasiRNAs lack the 2',3' hydroxy termini characteristic of animal siRNA and miRNA. Unlike siRNAs and miRNAs, rasiRNAs function through the Piwi, rather than the Ago, Argonaute protein subfamily. Our data suggest that rasiRNAs protect the fly germline through a silencing mechanism distinct from both the miRNA and RNA interference pathways.

Expression of putative Escherichia coli heat-labile enterotoxin (LT) receptors on intestinal brush borders from pigs of different ages

Many strains of enterotoxigenic Escherichia coli (ETEC) that cause diarrhoea in young piglets secrete a heat-labile enterotoxin (LTp) that binds to specific glycoconjugates on porcine intestinal epithelial cells. Binding of LTp to an appropriate glycoconjugate facilitates the uptake and trafficking of the toxin into the cell, where it stimulates intracellular changes that promote fluid secretion and diarrhoea. The objective of the current study was to identify the LTp-binding glycoconjugates on porcine intestinal epithelial cells, the natural target cells for LTp. We found that LTp binds, in an age-correlated manner, to an acidic glycosphingolipid (GSL) that co-migrated with GM1 on thin-layer chromatography (TLC), a small acidic GSL that appears to be a sulphatide, a neutral GSL that co-migrated with neolactotetraglycosylceramide (nLc4) on TLC, and two glycoproteins (36 and 205 kDa). Of these potential LTp receptors, the GM1-co-migrating GSL was detected most intensely in young animals, while the other four LTp-binding glycoconjugates were detected most intensely in older pigs (> or= 4 weeks). Since ETEC primarily cause disease in young piglets, the GM1-co-migrating GSL is the most likely candidate for a functional LTp receptor.

Glycosylation of beet western yellows virus proteins is implicated in the aphid transmission of the virus

Beet western yellows virus relies on the aphid M. persicae for its transmission in a persistent and circulative mode. To be transmitted, the virus must cross the midgut and the accessory salivary gland epithelial barriers by a transcytosis mechanism where vector receptors interact with virions. The aphid and the peptidic viral determinants implicated in this interaction mechanism have been studied. In this paper, we report that the coat and the readthrough proteins that constitute the capsid of this virus are glycosylated. Modification of the glucidic core of these structural viral proteins by oxidation with sodium metaperiodate or deglycosylation with N-glycosidase F or alpha-D-galactosidase abrogates the aphid transmission of the virus. Aphid transmission could also be inhibited by lectins directed against alpha-D-galactose when aphids were allowed to acquire virus on artificial membranes. These results suggest that the glucidic cores of the capsid proteins of beet western yellows virus contain alpha-D-galactose residues that are implicated in virus-aphid interaction and promote aphid transmission of the virus.

Disinfection of microorganisms by use of electrochemically regenerated periodate

A new method for disinfection of microorganisms by electrochemically regenerated periodate was developed. Oxidation of iodate to periodate was observed at 1.25 V versus a silver/silver chloride electrode in a cyclic voltammogram of potassium iodate. When 1.25 V was applied in 1.0 mM potassium iodate, approximately 4-log inactivation of Escherichia coli was observed in 30 min.

In vitro differentiation of mouse embryonic stem cells: enrichment of endodermal cells in the embryoid body

Embryonic stem (ES) cells have the potential to differentiate into all three germ layers, providing new perspectives not only for embryonic development but also for the application in cell replacement therapies. Even though the formation of an embryoid body (EB) in a suspension culture has been the most popular method to differentiate ES cells into a wide range of cells, not much is known about the characteristics of EB cells. To this end, we investigated the process of EB formation in the suspension culture of ES cells at weekly intervals for up to 6 weeks. We observed that the central apoptotic area is most active in the first week of EB formation and that the cell adhesion molecules, except beta-catenin, are highly expressed throughout the examination period. The sequential expression of endodermal genes in EBs during the 6-week culture correlated closely with that of normal embryo development. The outer surface of EBs stained positive for alpha-fetoprotein and GATA-4. When isolated from the 2-week-old EB by trypsin treatment, these endodermal lineage cells matured in vitro into hepatocytes upon stimulation with various hepatotrophic factors. In conclusion, our results demonstrate that endodermal cells can be retrieved from EBs and matured into specific cell types, opening new therapeutic usage of these in vitro differentiated cells in the cell replacement therapy of various diseases.

Oral and vaginal epithelial cell anti-Candida activity is acid labile and does not require live epithelial cells

BACKGROUND

Candida albicans is the causative agent of oral and vaginal candidiasis. Innate host defenses against C. albicans are important against each infection. Among these are oral and vaginal epithelial cells that have anti-Candida activity. The mechanism of action includes a requirement for cell contact with no role for soluble factors, and a putative role for carbohydrates based on the sensitivity of the activity to periodic acid.

METHODS

Periodic acid treatment of epithelial cells as well as the property of partial resistance of antifungal activity to fixation was used to further dissect the mechanism of action.

RESULTS

The results herein effectively now challenge a role for carbohydrates alone. Firstly, the putative carbohydrate(s) released into supernatants of periodic acid-treated epithelial cells could not compete with fresh epithelial cells for activity, and equivalent abrogation of activity was observed by periodic acid-treated cells irrespective of the amount of carbohydrate released. Instead, the similar abrogation of activity following treatment with other acids or when cocultured under acidic conditions suggests that the activity is acid-labile. Finally, while activity requires intact epithelial cells, it does not require live cells; activity was minimally affected by fixing epithelial cells prior to coculture where the majority of cells remained impermeable to Trypan blue but were defined as non-viable by positive nuclear staining with propidium iodide.

CONCLUSION

These results suggest that antifungal activity is dependent on contact by intact, but not necessarily live, epithelial cells through an acid-labile mechanism.

The effect of inflammation on the generation of plasma DNA from dead and dying cells in the peritoneum

To assess the effects of inflammation on the generation of circulating DNA from dead and dying cells, plasma DNA levels were determined in BALB/c mice, administered apoptotic or necrotic Jurkat cells following induction of peritonitis by treatment with thioglycollate (TG), peptone (PT), or sodium periodate (NaIO(4)). In mice receiving TG or NaIO(4), plasma DNA levels following intraperitoneal administration of Jurkat cells were significantly reduced compared with controls, whereas they were not affected in mice receiving PT. To determine the basis of these differences, the cellular composition of peritoneal fluids prior to the administration of the dead cells was analyzed. Among agents tested, TG administration led to the largest increase in cells, both neutrophils and monocytes. As shown by flow cytometry, the exudates contained apoptotic neutrophils and macrophages, with the highest levels in the TG-induced exudates. Analysis of DNA and caspase 3 in the fluids also showed differences. TG exudates showed increases in DNA and caspase 3, while NaIO(4)-induced exudates had an increase only in DNA. Fluid from PT-treated mice did not have increases in DNA or caspase 3. Together, these results indicate that prior inflammation can affect the generation of blood DNA from apoptotic or necrotic cells, although this effect may vary depending on the composition of the exudates with respect to cells as well as DNA.

In vitro characterization of a tRNA editing activity in the mitochondria of Spizellomyces punctatus, a Chytridiomycete fungus

In the chytridiomycete fungus, Spizellomyces punctatus, all eight of the mitochondrially encoded tRNAs are predicted to have one or more base pair mismatches at the first three positions of their aminoacyl acceptor stems. These tRNAs are edited post-transcriptionally by replacement of the 5'-nucleotide in each mismatched pair with a nucleotide that can form a standard Watson-Crick base pair with its counterpart in the 3'-half of the stem. The type of mitochondrial tRNA editing found in S. punctatus also occurs in Acanthamoeba castellanii, a distantly related amoeboid protist. Using an S. punctatus mitochondrial extract, we have developed an in vitro assay of tRNA editing in which nucleotides are incorporated into various tRNA substrates. Experiments employing synthetic transcripts revealed that the S. punctatus tRNA editing activity incorporates nucleotides on the 5'-side of substrate tRNAs, uses the 3'-sequence as a template for incorporation, and adds nucleotides in a 3'-to-5' direction. This activity can add nucleotides to a triphosphorylated 5'-end in the absence of ATP but requires ATP to add nucleotides to a monophosphorylated 5'-end; moreover, it functions independently of the state of tRNA 3' processing. These data parallel results obtained in a previous in vitro study of A. castellanii tRNA editing, suggesting that remarkably similar activities function in the mitochondria of these two organisms. The evolutionary origins of these activities are discussed.

Requirement of PPARα in maintaining phospholipid and triacylglycerol homeostasis during energy deprivation

The peroxisome proliferator-activated receptor alpha (PPARalpha) has been implicated as a key control of fatty acid catabolism during the cellular fasting. However, little is known regarding changes of individual fatty acids in hepatic triacylglycerol (TG) and phospholipid (PL) as a result of starvation. In the present work, the effects of 72 h fasting on hepatic TG and PL fatty acid profiles in PPARalpha-null (KO) mice and their wild-type (WT) counterparts were investigated. Our results indicated that mice deficient in PPARalpha displayed hepatomegaly and hypoketonemia following 72 h starvation. Histochemical analyses revealed that severe fatty infiltration was observed in the livers of KO mice under fasted conditions. Furthermore, 72 h fasting resulted in a 2.8-fold higher accumulation of hepatic TG in KO mice than in WT mice fasted for the same length of time. Surprisingly, the total hepatic PL contents in fasted KO mice decreased by 45%, but no significant change in hepatic PL content was observed in WT mice following starvation. Gas chromatographic analysis indicated that KO mice were deprived of arachidonic (20:4n-6) and docosahexaenoic (22:6n-3) acids during fasting. Taken together, these results show that PPARalpha plays an important role in regulation of fatty acid metabolism as well as phospholipid homeostasis during energy deprivation.

Glycopeptide derived from hen egg ovomucin has the ability to bind enterohemorrhagic Escherichia coli O157:H7

Ovomucin glycopeptide (OGP) was prepared by size exclusion chromatography after Pronase digestion of hen egg ovomucin, and the binding of OGP to foodborne pathogens (Bacillus cereus,Clostridium perfringens, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enteritidis, Salmonella typhimurium, and Staphylococcus aureus) was investigaed. Binding assays with biotinylated bacteria as probes in microtiter plates showed that OGP bound to only E. coli O157:H7 among these foodborne pathogens. Periodate treatment markedly reduced the binding ability, indicating that E. coli O157:H7 bound to carbohydrate moieties of OGP. Lectin blot analysis with Maackia amurensis (MAA) and Sambucus nigra (SNA), which are specific for oligosaccharides containing sialic acid, revealed their binding sites in OGP were similar to the E. coli O157:H7 binding sites that were probed with biotinylated E. coli O157:H7 after Western blotting of OGP. Sialydase treatment of OGP abolished its ability to bind E. coli O157:H7, demonstrating that sialic acid played an important role in the binding. These results suggest that OGP has E. coli O157:H7-specific binding sites that consist of sialic acid. On the basis of these properties, OGP has the potential to be an ingredient with a protective effect against E. coli O157:H7 infection and to be a novel probe for the detection of E. coli O157:H7 in the food hygiene field.

Sialic acid acts as a receptor for equine rhinitis A virus binding and infection

Equine rhinitis A virus (ERAV) is a member of the genus Aphthovirus, family Picornaviridae, and causes respiratory disease in horses worldwide. To characterize the putative receptor molecule(s) of the ERAV isolate 393/76 (ERAV.393/76) on the surface of Vero and other cells, an assay was developed to measure the binding of purified biotinylated ERAV.393/76 virions to cells by flow cytometry. Using this assay, the level of binding to different cell types correlated with the relative infectivity of ERAV in each cell type. In particular, equine fetal kidney cells, mouse fibroblast cells, rabbit kidney-13 and Crandell feline kidney cells bound virus at high levels and produced high virus yields (⩾107 TCID50 ml−1). Madin–Darby bovine kidney and baby hamster kidney cells showed little or no binding of virus, producing yields of ⩽101·8 TCID50 ml−1. Treatment of Vero and other cells with sodium periodate and the metabolic inhibitors tunicamycin, benzyl N-acetyl-α-d-galactosamide, d,l-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol and proteases indicated that part of the receptor-binding and entry complex for ERAV.393/76 is on N-linked carbohydrates and that the carbohydrate is likely to be present on a protein rather than a lipid backbone. The effect of carbohydrate-specific lectins and neuraminidases on ERAV.393/76 binding and infection of Vero and other cell types implicated α2,3-linked sialic acid residues on the carbohydrate complex in the binding and infection of ERAV.

Effects of periodate and chondroitin 4-sulfate on proteoglycan stabilization of ostrich pericardium. Inhibition of calcification in subcutaneous implants in rats

Chemical modification of biological materials used in the manufacture of cardiac valves tends to reduce the relatively high degree of biodegradation and calcification of the implanted bioprostheses. The most widely used treatment to reduce biodegradability of the valves is glutaraldehyde fixation. However, this treatment is potentially toxic and induces tissue calcification. In order to minimize these undesirable effects, we have analyzed the effect of a pre-fixation of endogenous proteoglycans and exogenous glycosaminoglycans, as well as the borohydride reduction influence on the different modified ostrich pericardium implants after subcutaneous implantation in rats. The presence of calcific deposits was detected in all implanted GA-fixed samples; however, calcification was highly reduced in both groups of periodate-prefixed materials, which showed also a very low Ca/P molar ratio. Borohydride post-treatment of these biomaterials resulted in a significant increase in calcium phosphate precipitation, with the appearance of calcium deposits mainly in an amorphous form even though X-ray diffraction allowed the detection of brushite- and apatite-like crystals. Regarding tissue stability, no significant differences were found among the borohydride-untreated implants but higher levels of matrix metalloproteinases were observed by gelatin zymography in the periodate pre-fixed materials. This increase was partially reduced by pre-fixation of exogenous chondroitin 4-sulfate. On the other hand, borohydride post-treatment not only increased calcification, but also reduced tissue stability and increased the presence of matrix-degrading activities.

A minimalist glutamyl-tRNA synthetase dedicated to aminoacylation of the tRNAAsp QUC anticodon

Escherichia coli encodes YadB, a protein displaying 34% identity with the catalytic core of glutamyl-tRNA synthetase but lacking the anticodon-binding domain. We show that YadB is a tRNA modifying enzyme that evidently glutamylates the queuosine residue, a modified nucleoside at the wobble position of the tRNA(Asp) QUC anticodon. This conclusion is supported by a variety of biochemical data and by the inability of the enzyme to glutamylate tRNA(Asp) isolated from an E.coli tRNA-guanosine transglycosylase minus strain deprived of the capacity to exchange guanosine 34 with queuosine. Structural mimicry between the tRNA(Asp) anticodon stem and the tRNA(Glu) amino acid acceptor stem in prokaryotes encoding YadB proteins indicates that the function of these tRNA modifying enzymes, which we rename glutamyl-Q tRNA(Asp) synthetases, is conserved among prokaryotes.

In vitro adhesion and invasion inhibition of Shigella dysenteriae, Shigella flexneri and Shigella sonnei clinical strains by human milk proteins

BACKGROUND

Shigella is the etiological agent of shigellosis, a disease responsible for more than 500,000 deaths of children per year, in developing countries. These pathogens colonize the intestinal colon, invade, spreading to the other enterocytes. Breastfeeding plays a very important role in protecting infants from intestinal infections. Amongst milk compounds, glycosylated proteins prevent the adhesion of many enteropathogens in vitro. The aim of this work was to determine the effect of human milk proteins on the colonization potential of Shigella dysenteriae, S. flexneri and S. sonnei. To fulfill this purpose, pooled milk samples from five donors, were fractionated by gel filtration and affinity chromatography. Using tissue culture, the milk fractions obtained were tested in Shigella adhesion and invasion assays.

RESULTS

Our revealed showed that both adhesion and invasion of Shigella species were inhibited by low concentration of secretory immunoglobulin A, lactoferrin and free secretory component. This work also showed that, these proteins bind to superficial and whole-cell Shigella proteins.

CONCLUSIONS

Our findings suggest that human milk may act inhibiting adhesion and, consequently, invasion of Shigella, thereafter preventing shigellosis in infants.

Inhibition of experimental lung metastases of Lewis lung carcinoma cells by chemically modified heparin with reduced anticoagulant activity

Heparin, a widely used anticoagulant, is known to have anti-metastatic activity, although the mechanism is not fully understood. In the present study, we investigated the mechanism of this anti-metastatic activity using periodate-oxidized and borohydride-reduced heparin with low anticoagulant activity (LAC heparin). The anticoagulant activity of LAC heparin is markedly reduced to almost the control level in terms of prothrombin time in vitro, and no hemorrhagic complication was observed with injection of LAC heparin into mice in vivo. LAC heparin injected intravenously with Lewis lung carcinoma cells or 10 min before tumor cell injection significantly inhibited, to the same extent as intact heparin and in a dose- and time-dependent manner, the lung colonization that develops after intravenous injection (i.v.) of tumor cells. Flow cytometric analysis revealed that Lewis lung carcinoma cells strongly express heparan sulfate on their surface. Both the LAC heparin and intact heparin inhibited the adhesion and invasion of tumor cells to Matrigel-coated dishes in vitro without significant effect on the tumor cell growth. LAC heparin also significantly diminished tumor cell retention in the lung after i.v. of LacZ gene-tagged Lewis lung carcinoma cells. These results suggest that LAC heparin may prevent tumor cells from attachment to the subendothelial matrix of lung capillaries by competitively inhibiting cell surface heparan sulfate functions and suppress lung colonization.

Covalently-Bound Heparin Makes Collagen Thromboresistant

Objective— Blood compatibility of artificial surfaces depends on their immunogenic and thrombogenic properties. Collagen’s weak antigenicity makes it an attractive candidate for stent coatings or fabrication of vascular grafts. However, the thrombogenic nature of collagen limits its application. We examined whether heparinization can make collagen more thromboresistant.

Methods and Results— Collagen was heparinized by crosslinking collagen with extensively periodate oxidized heparin and/or by covalently bonding of mildly periodate oxidized heparin. Both ways of heparinization have no effect on platelet adhesion and could not abolish induction of platelet procoagulant activity. However, thrombin generation was completely prevented under static and flow conditions. The functionality of immobilized heparin was confirmed by specific uptake of antithrombin, 13.5±4.7 pmol/cm 2 and 1.95±0.21 pmol/cm 2 for mildly and heavily periodated heparin, respectively.

Conclusions— These results indicate that immobilization of heparin on collagen, even as a crosslinker, is a very effective way to prevent surface thrombus formation. These data encourage the application of heparinized collagen as stent-graft material in animal and eventually human studies.

Molecular Basis of the Dynamic Strength of the Sialyl Lewis X—Selectin Interaction

The selectins are Ca(2+)-dependent cell adhesion molecules that facilitate the initial attachment of leukocytes to the vascular endothelium by binding to a carbohydrate moiety as exemplified by the tetrasaccharide, sialyl Lewis X (sLeX). An important property of the selectin-sLeX interaction is its ability to withstand the hydrodynamic force of the blood flow. Herein, we used single-molecule dynamic force spectroscopy (DFS) to identify the molecular determinants within sLeX that give rise to the dynamic properties of the selectin/sLeX interaction. Our atomic force microscopy (AFM) measurements revealed that the unbinding of the selectin/sLeX complexes involves overcoming at least two activation barriers. The inner barrier, which determines the dynamic response of the complex at high forces, is governed by the interaction between the Fuc residue of sLeX and a Ca2+ ion chelated to the lectin domain of the selectin molecule, whereas the outer activation barrier can be attributed to interactions involving the sialic acid residue of sLeX. Due to their steep inner activation barriers, the selectin-sLeX complexes are less sensitive to high pulling forces. Hence, besides its contribution to the bond energy, the Ca2+ ion also grants the selectin-sLeX complexes a tensile strength that is crucial for the selectin-mediated rolling of leukocytes.

Oligosaccharide receptor mimics inhibit Legionella pneumophila attachment to human respiratory epithelial cells

Legionnaire's disease is caused by the intracellular pathogen Legionella pneumophila, presenting as an acute pneumonia. Attachment is the key step during infection, often relying on an interaction between host cell oligosaccharides and bacterial adhesins. Inhibition of this interaction by receptor mimics offers possible novel therapeutic treatments. L. pneumophila attachment to the A549 cell line was significantly reduced by treatment with tunicamycin (73.6%) and sodium metaperiodate (63.7%). This indicates the importance of cell surface oligosaccharide chains in adhesion. A number of putative anti-adhesion compounds inhibited attachment to the A549 and U937 cell lines. The most inhibitory compounds were polymeric saccharides, GalNAcbeta1-4Gal, Galbeta1-4GlcNAc and para-nitrophenol. These compounds inhibited adhesion to a range of human respiratory cell lines, including nasal epithelial, bronchial epithelial and alveolar epithelial cell lines and the human monocytic cell line, U937. Some eukaryotic receptors for L. pneumophila were determined to be the glycolipids, asialo-GM1 and asialo-GM2 that contain the inhibitory saccharide moiety, GalNAcbeta1-4Gal. The identified compounds have the potential to be used as novel treatments for Legionnaire's disease.

Intergeneric coaggregations among Oligotropha carboxidovorans and Acinetobacter species present in activated sludge

The coaggregation traits of two pairs of sewage sludge bacteria were tested and characterized. Oligotropha carboxidovorans S23 coaggregated with two strains of the genus Acinetobacter viz. Acinetobacter junii S33 (56%) and Acinetobacter johnsonii S35 (99%). Coaggregates of O. carboxidovorans S23 and A. junii S33 were small (20-40 microm), weak and susceptible to EDTA and a commercial protease (Actinase E). Actinase/periodate pretreatment of the partners prior to coaggregation revealed that interaction in this case was mediated by protein surface components. Coaggregates of O. carboxidovorans S23 and A. johnsonii S35 were large (above 100 microm), strong and not deflocculated by EDTA or Actinase E. Only periodate pretreatment of A. johnsonii S35 prevented this coaggregation indicating a role for a carbohydrate-containing moiety without the involvement of protein components. The potential mechanisms and strength of bacterial coaggregations seem to be pair dependent.

MG2 and lactoferrin form a heterotypic complex in salivary secretions

Protein-protein interactions are necessary for homeostasis to be maintained and for biological systems to be integrated. Heterotypic complexes occur in saliva, and a complex between MG2 and SIgA has been suggested to promote microbial clearance from the oral cavity. In this study, we used a peptide display library to investigate previously unrecognized heterotypic complexes involving MG2 and other proteins. The library was panned with MG2 12 times, and analyses of clones identified the sequence Ala-Leu-Leu-Cys-, which occurs in salivary lactoferrin. Blotting experiments confirmed that MG2 and lactoferrin form a heterotypic complex in vitro and in vivo. Periodate treatment of MG2 did not affect the interaction. A synthetic lactoferrin peptide containing the motif Ala-Leu-Leu-Cys-blocked the interaction between MG2 and lactoferrin, confirming the specificity of the interaction identified by panning. This complex may enhance the properties of these salivary components in the oral environment.

Binding of extracellular matrix molecules by enterococci

The bacterial surfaces of enterococci are not uniform. This fact is confirmed by several studies and by our results when great differences between individual strains with regard to their cell surface hydrophobicity, binding of eight ECM (extracellular matrix) molecules immobilized on latex beads and four selected ECM molecules in microtiter plates were observed. The strains expressing high binding of ECM molecules (e.g., HJ 18, HJ 23, HJ 24, HJ 26, HJ 28, HJ 36, etc.) were found among Enterococcus faecalis and E. faecium by PAA (particle agglutination assay). On the other hand, weak ECM binders (e.g., HJ 21, HJ 32, HJ 34, HJ 38, HJ 39, HJ 42, HJ 43) were also found. A direct correlation was found between porcine mucin and fetuin binding ability of eight selected strains tested in microtiter plates and by PAA. Moreover, the influence of tunicamycin treatment was different because significant (P < 0.001) blocking effect of tunicamycin was observed with two selected strains (HJ 26 and HJ 36), whereas two strains (HJ 18 and HJ 22) were not significantly affected in their fetuin binding. The treatment of six enterococcal strains with proteolytic enzymes, pronase P, and trypsin, and with sodium metaperiodate also significantly (P < 0.001) decreased their fetuin binding. This suggests that both protein and carbohydrate moieties are involved in the binding of immobilized fetuin. However, the influence of these chemicals on the fetuin binding by individual strains was different.

Pair-dependent co-aggregation behavior of non-flocculating sludge bacteria

Two strains of non-flocculating sewage sludge bacteria (Xanthomonas sp. S53 and Microbacterium esteraromaticum S51) showed 91% and 77% co-aggregation, respectively, with Acinetobacter johnsonii S35 using a spectrophometric assay. The co-aggregates in case of Xanthomonas sp. S53 and A. johnsonii S35 were above 100 microm and stable against EDTA (2 mM) and a commercial protease (0.2 mg ml(-1)). Protease/periodate pretreatment of the partners did not affect this co-aggregation. On the other hand, co-aggregates of M. esteraromaticum S51 and A. johnsonii S35 (50-70 microm) were deflocculated by EDTA or protease. Protease pretreatment of M. esteraromaticum S51 and periodate pretreatment of A. johnsonii S35 prevented their co-aggregation with respective untreated partners. The potential co-aggregation mechanisms of A. johnsonii S35 varied depending upon the other partner involved.

Evidence that binding of cucumber necrosis virus to vector zoospores involves recognition of oligosaccharides

Despite the importance of vectors in natural dissemination of plant viruses, relatively little is known about the molecular features of viruses and vectors that permit their interaction in nature. Cucumber necrosis virus (CNV) is a small spherical virus whose transmission in nature is facilitated by zoospores of the fungus Olpidium bornovanus. Previous studies have shown that specific regions of the CNV capsid are involved in transmission and that transmission defects in several CNV transmission mutants are due to inefficient attachment of virions to the zoospore surface. In this study, we have undertaken to determine if zoospores contain specific receptors for CNV. We show that in vitro binding of CNV to zoospores is saturable and that vector zoospores bind CNV more efficiently than nonvector zoospores. Further studies show that treatment of zoospores with periodate and trypsin reduces CNV binding, suggesting the involvement of glycoproteins in zoospore attachment. In virus overlay assays, CNV binds to several proteins, whereas CNV transmission mutants either fail to bind or bind at significantly reduced levels. The possible involvement of specific sugars in attachment was investigated by incubating CNV with zoospores in the presence of various sugars. Two mannose derivatives (methyl alpha-D-mannopyranoside and D-mannosamine), as well as three mannose-containing oligosaccharides (mannotriose, alpha3,alpha6-mannopentaose, and yeast mannan) and L-(-)-fucose, all inhibited CNV binding at relatively low concentrations. Taken together, our studies suggest that binding of CNV to zoospores is mediated by specific mannose and/or fucose-containing oligosaccharides. This is the first time sugars have been implicated in transmission of a plant virus.

Surface engineering of living myoblasts via selective periodate oxidation

Cell surface molecules are vital for normal cell activity. To study the functions of these molecules or manipulate cell behavior, the ability to decorate cell surfaces with bioactive molecules of our choosing is a potentially powerful technique. Here, we describe the molecular engineering of living L6 myoblast monolayers via selective periodate oxidation of sialic acid residues and the application of this surface modification in the artificial aggregation of cells. The aldehyde groups generated by this reaction were used to selectively ligate a model molecule, biotin hydrazide, to the cell surfaces. Flow cytometry analysis after staining with fluorescently conjugated avidin revealed a concentration-dependent increase in fluorescence compared to untreated cells with a maximal shift of 345.1 +/- 27.4-fold and an EC(50) of 17.4 +/- 1.1 microM. This mild oxidation reaction did not affect cell number, viability, or morphology. We then compared this chemical technique with the metabolic incorporation of reactive cell surface ketone groups using N-levulinoylmannosamine (ManLev). In this cell line, only a 22.3-fold fluorescence shift was observed compared to untreated cells when myoblasts were incubated with a high concentration of ManLev for 48 hours. Periodate oxidation was then used to modify myoblast surfaces to induce cell aggregation. Crosslinking biotinylated myoblasts, which do not spontaneously aggregate in culture, with avidin resulted in the rapid formation of millimeter-sized, multicellular structures. These data indicate that sodium periodate treatment is an effective, noncytotoxic method for the in vitro molecular engineering of living cell surfaces with the potential for cell biology and tissue engineering applications.