Cytokine-mediated inhibition of fibrillar amyloid-beta peptide degradation by human mononuclear phagocytes

Vaccination therapy of AD animal models and patients strongly suggests an active role of brain mononuclear phagocytes in immune-mediated clearance of amyloid-beta peptides (Abeta) in brain. Although Abeta uptake by macrophages can be regulated by pro- and anti-inflammatory cytokines, their effects on macrophage-mediated Abeta degradation are poorly understood. To better understand this mechanism of degradation, we examined whether pro- and anti-inflammatory cytokines affect the degradation of Abeta using primary cultured human monocyte-derived macrophages (MDM) and microglia using pulse-chase analysis of fibrillar and oligomer (125)I-Abeta40 and Abeta42. Initial uptake of fibrillar Abeta40 and Abeta42 was 40% and its degradation was saturated by 120 h in both MDM and microglia, compared with an initial uptake of oligomeric Abeta less than 0.5% and saturation of degradation within 24 h. IFN-gamma increased the intracellular retention of fibrillar Abeta40 and Abeta42 by inhibiting degradation, whereas IL-4, IL-10, and TGF-beta1, but not IL-13 and IL-27, enhanced degradation. Fibrillar Abeta degradation in MDM is sensitive to lysosomal and insulin degrading enzyme inhibitors but insensitive to proteasomal and neprilysin inhibitors. IFN-gamma and TNF-alpha directly reduced the expression of insulin degrading enzyme and chaperone molecules (heat shock protein 70 and heat shock cognate protein 70), which are involved in refolding of aggregated proteins. Coculture of MDM with activated, but not naive T cells, suppressed Abeta degradation in MDM, which was partially blocked by a combination of neutralizing Abs against proinflammatory cytokines. These data suggest that proinflammatory cytokines suppress Abeta degradation in MDM, whereas select anti-inflammatory and regulatory cytokines antagonize these effects.

Unsatisfying functions and multiobjective fuzzy satisfaction design using genetic algorithms

This paper describes a new fuzzy satisfaction method using genetic algorithms (GA) for multiobjective problems. First, an unsatisfying function, which has a one-to-one correspondence with the membership function, is introduced for expressing "fuzziness". Next, the multiobjective design problem is transformed into a satisfaction problem of constraints by introducing an aspiration level for each objective. Here, in order to handle the fuzziness involved in aspiration levels and constraints, the unsatisfying function is used, and the problem is formulated as a multiobjective minimization problem of unsatisfaction ratings. Then, a GA is employed to solve the problem, and a new strategy is proposed to obtain a group of Pareto-optimal solutions in which the decision maker (DM) is interested. The DM can then seek a satisfaction solution by modifying parameters interactively according to preferences.

The POU homeobox protein Oct-1 regulates radial glia formation downstream of Notch signaling

Radial glia cells function as guide cells for neuronal migration and a source of neural progenitor cells, and play a crucial role for the development of the central nervous system. To date, several signals have been demonstrated to promote the formation of radial glia cells and Notch signaling is one such signal. However, the mechanism of the signaling hierarchy of radial glia developmental cascade promoted by Notch signaling still remains incomplete. Here we show that Notch signaling promotes Xenopus radial glia formation and that the Notch activation is sufficient for radial glia formation prior to neural tube closure. Moreover, we have identified Oct-1 (POU2f1), a POU transcription factor, as a downstream target of Notch signaling by microarray based screen. We demonstrate that the expression of Oct-1 in the brain is regulated by Notch signaling and that Oct-1 is sufficient and necessary for radial glia formation. Together, Oct-1 is a downstream effector of Notch signaling during radial glia formation.

Phosphorylation of claudin-5 and occludin by rho kinase in brain endothelial cells

Critical to the proper maintenance of blood-brain-barrier (BBB) integrity are the endothelial tight junctions (TJs). Posttranslational modifications of essential endothelial TJ proteins, occludin and claudin-5, contribute and possibly disrupt BBB integrity. Our previous work has shown that Rho kinase (RhoK) activation mediates occludin and claudin-5 phosphorylation resulting in diminished barrier tightness and enhanced monocyte migration across BBB in the setting of human immunodeficiency virus-1 encephalitis (HIVE). To determine whether RhoK can directly phosphorylate TJ proteins, we examined phosphorylation of cytoplasmic domains of recombinant claudin-5 and occludin by RhoK. We found that RhoK predominately phosphorylated two sites on occludin (T382 and S507) and one site on claudin-5 (T207). Specific anti-phosphopeptide antibodies were developed for these sites, allowing the detection of phosphorylated occludin at T382 and S507, and claudin-5 at T207 from full-length recombinant occludin and claudin-5 transiently expressed in COS-7 cells and mouse brain microvascular endothelial cells. Finally, these phosphospecific antibodies demonstrated enhanced staining of brain endothelial cells in the mouse model for HIVE and human HIVE brains featuring mononuclear cell infiltration across disrupted BBB. Our results demonstrated the direct phosphorylation of occludin and claudin-5 by RhoK at specific sites, which was increased in encephalitic brain tissue. These antibodies could be useful reagents for monitoring BBB dysfunction in vivo.

Polyfluorinated Bis-styrylbenzene β-Amyloid Plaque Binding Ligands

beta-Amyloid (Abeta) binding affinities and specificities for six bis-styrylbenzenes with multiple magnetically equivalent fluorine atoms in the form of a tetrafluorophenyl core or symmetrical trifluoromethyl and trifluoromethoxy groups were determined by means of fluorescence titrations with amyloid peptide Abeta1-40 and a novel in vitro fluorescence-based assay using APP/PS1 transgenic mouse brain sections. Bis-styrylbenzenes with a tetrafluorophenyl core had increased Abeta binding affinities compared to their monofluorophenyl or phenyl counterparts. Bis-styrylbenzenes with carboxylic acid functional groups had lower Abeta binding affinities than their neutral counterparts. Selected bis-styrylbenzenes were demonstrated to have good blood-brain barrier penetration capabilities. These data extend the SAR of bis-styrylbenzene Abeta binding and provide direction for the development of a noninvasive probe for early detection of Alzheimer's disease using 19F MRI.

Interferon-gamma and tumor necrosis factor-alpha regulate amyloid-beta plaque deposition and beta-secretase expression in Swedish mutant APP transgenic mice

Reactive astrocytes and microglia in Alzheimer's disease surround amyloid plaques and secrete proinflammatory cytokines that affect neuronal function. Relationship between cytokine signaling and amyloid-beta peptide (Abeta) accumulation is poorly understood. Thus, we generated a novel Swedish beta-amyloid precursor protein mutant (APP) transgenic mouse in which the interferon (IFN)-gamma receptor type I was knocked out (APP/GRKO). IFN-gamma signaling loss in the APP/GRKO mice reduced gliosis and amyloid plaques at 14 months of age. Aggregated Abeta induced IFN-gamma production from co-culture of astrocytes and microglia, and IFN-gamma elicited tumor necrosis factor (TNF)-alpha secretion in wild type (WT) but not GRKO microglia co-cultured with astrocytes. Both IFN-gamma and TNF-alpha enhanced Abeta production from APP-expressing astrocytes and cortical neurons. TNF-alpha directly stimulated beta-site APP-cleaving enzyme (BACE1) expression and enhanced beta-processing of APP in astrocytes. The numbers of reactive astrocytes expressing BACE1 were increased in APP compared with APP/GRKO mice in both cortex and hippocampus. IFN-gamma and TNF-alpha activation of WT microglia suppressed Abeta degradation, whereas GRKO microglia had no changes. These results support the idea that glial IFN-gamma and TNF-alpha enhance Abeta deposition through BACE1 expression and suppression of Abeta clearance. Taken together, these observations suggest that proinflammatory cytokines are directly linked to Alzheimer's disease pathogenesis.

Kinetic analysis of aggregated amyloid-beta peptide clearance in adult bone-marrow-derived macrophages from APP and CCL2 transgenic mice

Accumulating evidence suggests that bone-marrow (BM)-derived mononuclear phagocytes have an important role in the clearance of soluble and aggregated amyloid-beta peptides (Abeta) in Alzheimer's disease (AD) brains. However, the exact kinetics of Abeta clearance in mononuclear phagocytes derived from transgenic animal models of AD expressing beta-amyloid precursor protein (APP) mutants have been poorly characterized. We have examined whether CCL2 and APP expression affects the clearance of Abeta in conjunction with our control, acetylated low-density lipoprotein (AcLDL), using primary cultured BM-derived macrophages derived from adult APP, CCL2, APP/CCL2, and control littermates. Pulse-chase analysis demonstrated three distinct destinations for Abeta40 and AcLDL: intracellular retention, degradation, and secretion. As predicted, 50% of Abeta remained intracellularly contained even 5 days after pulse, while 40% of degraded and 14% of nondegraded Abeta were secreted. APP/CCL2 macrophages show reduced intracellular Abeta retention, along with enhanced secretion of both degraded and nondegraded Abeta. Abeta accumulation in aggresome is also partially reduced in APP/CCL2 macrophages as compared to other APP, CCL2, or control groups, suggesting impaired sorting of aggregated Abeta in aggresomes. The degradation of intracranially injected (125)I-Abeta40 aggregates was also enhanced in adult APP/CCL2 mice as compared to APP littermates in vivo. These data suggest that APP and CCL2 synergistically enhance BM-derived macrophage-mediated clearance of Abeta. In contrast, the clearance of AcLDL by BM-derived macrophages was not significantly enhanced by the presence of either APP or CCL2.

Drug evolution concept in drug design: 2. Chimera method

The drug evolution method represents a novel approach towards efficient rational drug design by implementing the drug evolution concept to the creation and development of general chemical libraries with the purpose of allowing the identification of drug candidates with improved odds and lesser costs than the traditional drug design strategies. As another example of successful translation of the biological evolution into chemical evolution, the chimera method comprises the grafting of selected building blocks, identified through a basic search within a drug library, onto the same substitution sites on a rationally chosen scaffold. The method allows the creation of a library containing both drugs and prospective drug candidates without any priorly required knowledge on the pursued disease or molecular target. Two libraries having scaffolds derived from para-aminobenzoic acid and salicylic acid have exemplified the application of the chimera method. The validation of the method has been achieved through the high number of recognized drugs within the library, which exhibit in the same time a wide variety of therapeutic activities and interact with a broad spectrum of molecular targets. The drug-enriched chimera libraries are expected to provide a highly efficient access to novel drug candidates whose unspecified therapeutic effects should be further revealed through high-throughput screening.

The intracellular domain of X-Serrate-1 is cleaved and suppresses primary neurogenesis in Xenopus laevis

The Notch ligands, Delta/Serrate/Lag-2 (DSL) proteins, mediate the Notch signaling pathway in a numerous developmental processes in multicellular organisms. Although the ligands induce the activation of the Notch receptor, the intracellular domain-deleted forms of the ligands cause dominant-negative phenotypes, implying that the intracellular domain is necessary for the Notch signal transduction. Here we examined the role of the intracellular domain of Xenopus Serrate (XSICD) in Xenopus embryos. X-Serrate-1 has the putative nuclear localization sequence (NLS) in downstream of the transmembrane domain. Biochemical analysis revealed that XSICD fragments are cleaved from the C-terminus side of X-Serrate-1. Fluorescence microscopic analysis showed that the nuclear localization of XSICD occurs in the neuroectoderm of the embryo injected with the full-length X-Serrate-1/GFP. Overexpression of XSICD showed the inhibitory effect on primary neurogenesis. However, a point mutation in the NLSs of XSICD inhibited the nuclear localization of XSICD, which caused the induction of a neurogenic phenotype. The animal cap assay revealed that X-Serrate-1 suppresses primary neurogenesis in neuralized animal cap, but X-Delta-1 does not. Moreover, XSICD could not activate the expression of the canonical Notch target gene, XESR-1 in contrast to the case of full-length X-Serrate-1. These results suggest that the combination of XSICD-mediated intracellular signaling and the extracellular domain of Notch ligands-mediated activation of Notch receptor is involved in the primary neurogenesis. Moreover, we propose a bi-directional signaling pathway mediated by X-Serrate-1 in Notch signaling.

Cysteine-rich region of X-Serrate-1 is required for activation of Notch signaling in Xenopus primary neurogenesis

The Notch family genes encode single-pass transmembrane proteins which function in a variety of cell fate specifications in invertebrates and vertebrates. In Xenopus primary neurogenesis, the Notch ligands, X-Delta-1 and X-Serrate-1, mediate Notch signaling and regulate cell differentiation. In the present study, we examined the role of the Serrate-specific cysteine-rich (CR) region in the primary neurogenesis of Xenopus embryos. The ligand constructs containing the DSL (Delta/Serrate/Lag-2) domain in the extracellular region caused a reduction in primary neurons, whereas the DSL-deleted form of X-Delta-1 resulted in the overproduction of primary neurons. However, the DSL-deleted form of X-Serrate-1 or the construct containing only the CR region in the extracellular domain (SerCR) reduced the number of primary neurons. In contrast, the CR-deleted form of X-Serrate-1 (SerACR) lost activity as a Notch ligand, regardless of the presence of the DSL domain within the extracellular domain. Overexpression of X-Delta-1 and X-Serrate-1 strongly induced the expression of Xenopus ESR-1 (XESR-1), a gene related to Drosophila Enhancer of split. SerCR alone also moderately induced the expression of XESR-1, but the SerACR form did not induce this expression. Co-injection of X-Notch-1deltaICD, which deletes the intracellular domain (ICD), with SerCR suppressed a neurogenic phenotype, although co-injection of X-Su(H)1DBM with SerCR did not, indicating that SerCR affects primary neurogenesis through the Notch/Su(H) pathway. These results suggestthatthe CR region of Xenopus Serrate is required for the activation of Notch signaling and cell fate specification in primary neurogenesis.

Study on the packing geometry, stoichiometry, and membrane interaction of three analogs related to a pore-forming small globular protein

A de novo designed pore-forming small globular protein (SGP) with antitumor activity consists of four helices: 3 basic amphipathic helices composed of Leu and Lys surrounding a central hydrophobic helix composed of oligoalanine. These helices are connected by a beta-turn-forming sequence and two beta-turn-unfavorable ones (S. Lee, T. Kiyota, T. Kunitake, E. Matsumoto, S. Yamashita, K. Anzai, and G. Sugihara Biochemistry 1997, Vol. 36, pp. 3782-3791). In the present work, we designed and synthesized three new SGP analogs in order to study the stoichiometric packing geometry and stability of SGP. The replacement of alanines in the central helix of SGP with leucines (SGP-L), which make the helix much larger in size and more hydrophobic, resulted in an equilibrium of monomeric-trimeric structure. The replacement of some Lys residues by Glu residues in the hydrophilic regions of the amphipathic helices (SGP-E) led to a decrease in helical content and the formation of an equilibrium of monomeric-trimeric structure. The alteration of beta-turn regions with Gly residues, which makes these regions flexible (SGP-G), established an equilibrium of monomeric-dimeric states in buffer. The hydrophobic alpha-helix of SGP-L penetrated into the lipid bilayers in a manner that stabilized model membranes and biomembranes, whereas the central helices of SGP-G and -E destabilized them by forming channels. SGP and its analogs may be a useful model to study the role of the hydrophobic and hydrophilic regions in the formation of monomer-oligomer of proteins and to better understand the insertion of membrane targeting proteins into biomembranes.

Taxines from the needles of Taxus wallichiana

A taxine, 5 alpha O-(3'-dimethylamino-3'-phenylpropionyl) taxinine M (1) together with two known compounds 7-O-acetyltaxine A (2) and 2 alpha-acetoxy-2' beta-deacetylaustrospicatine (3) were isolated from the needles of the Himalayan yew, Taxus wallichiana Zucc. Their structures were elucidated on the basis of the NMR spectral data, ESI-MS/MS analysis and chemical methods. Compounds 1 and 3 showed moderate cytotoxic activity against the lung cancer cell line A549 in vitro.

De novo-designed peptide transforms Golgi-specific lipids into Golgi-like nanotubules

Cellular organelles, such as the Golgi apparatus and the endoplasmic reticulum, adopt characteristic structures depending on their function. While the tubular shapes of these structures result from complex protein-lipid interactions that are not fully understood, some fundamental machinery must be required. We show here that a de novo-designed 18-mer amphipathic alpha-helical peptide, Hel 13-5, transforms spherical liposomes made from a Golgi-specific phospholipid mixture into nanotubules on the scale of and resembling the shape of the nanotubules that form the Golgi apparatus. Furthermore, we show that that the size and the shape of such nanotubules depend on lipid composition and peptide properties such as length and the ratio of hydrophobic to hydrophilic amino acids. Although the question of precisely how nature engineers organellar membranes remains unknown, our simple novel system provides a basic set of tools to begin addressing this question.

X-Serrate-1 is involved in primary neurogenesis in Xenopus laevis in a complementary manner with X-Delta-1

Notch, Delta and Serrate encode transmembrane proteins that function in cell fate specification in the Drosophila melanogaster embryo. Here we report gene expression patterns and functional characterization of a Xenopus Serrate homolog, X-Serrate-1. The isolated cDNA encoded a transmembrane protein with a Delta/Serrate/LAG-2 domain, 16 epidermal growth factor-like repeats and a cysteine-rich region. Expression of X-Serrate-1 was observed ubiquitously from unfertilized egg to tadpole, but an upregulation occurred in the tailbud stage embryo. Adult expression was found in eye, brain, kidney, heart, spleen and ovary. Whole-mount in situ hybridization revealed that the organ-related expression in eye, brain, heart and kidney occurred from an early stage of rudiment formation. Overexpression of X-Serrate-1 led to a reduction of primary neurons, whereas an intracellularly deleted form of X-Serrate-1 increased the number of primary neurons. Although the function of X-Serrate-1 in primary neurogenesis was quite similar to that of X-Delta-1, expression of X-Serrate-1 and X-Delta-1 did not affect each other. Co-injection experiments showed that wild-type X-Serrate-1 and X-Delta-1 suppressed overproduction of primary neurons induced by dominant-negative forms of X-Delta-1 and X-Serrate-1, respectively. These results suggest that X-Serrate-1 regulates the patterning of primary neurons in a complementary manner with X-Delta-1-mediated Notch signaling.

Comparative effect of amrinone, aminophylline and diltiazem on rat airway smooth muscle

We investigated the effect of amrinone, a phosphodiesterase III inhibitor, on rat airway smooth muscle, and thereafter, compared its activity with aminophylline and diltiazem. Amrinone produced relaxation of the acetylcholine-induced airway contraction in a dose-related manner. This bronchodilatory activity of amrinone was similar to that of aminophylline, but smaller than that of diltiazem. The 50% relaxant effect (ED50) of amrinone, aminophylline and diltiazem were 3.6 x 10(-4) M, 1.4 x 10(-4) M and 1.4 x 10(-5) M, respectively. Diltiazem was the most potent airway relaxant, and amrinone was less potent in these experiments. Taken together in its positive inotropic and chronotropic effects and anti-inflammatory activity, however, amrinone could be beneficial for treatment of patients suffering from asthma or heart failure with cardiac asthma.

Morphological behavior of acidic and neutral liposomes induced by basic amphiphilic alpha-helical peptides with systematically varied hydrophobic-hydrophilic balance

Lipid-peptide interaction has been investigated using cationic amphiphilic alpha-helical peptides and systematically varying their hydrophobic-hydrophilic balance (HHB). The influence of the peptides on neutral and acidic liposomes was examined by 1) Trp fluorescence quenched by brominated phospholipid, 2) membrane-clearing ability, 3) size determination of liposomes by dynamic light scattering, 4) morphological observation by electron microscopy, and 5) ability to form planar lipid bilayers from channels. The peptides examined consist of hydrophobic Leu and hydrophilic Lys residues with ratios 13:5, 11:7, 9:9, 7:11, and 5:13 (abbreviated as Hels 13-5, 11-7, 9-9, 7-11, and 5-13, respectively; Kiyota, T., S. Lee, and G. Sugihara. 1996. Biochemistry. 35:13196-13204). The most hydrophobic peptide (Hel 13-5) induced a twisted ribbon-like fibril structure for egg PC liposomes. In a 3/1 (egg PC/egg PG) lipid mixture, Hel 13-5 addition caused fusion of the liposomes. Hel 13-5 formed ion channels in neutral lipid bilayer (egg PE/egg PC = 7/3) at low peptide concentrations, but not in an acidic bilayer (egg PE/brain PS = 7/3). The peptides with hydrophobicity less than Hel 13-5 (Hels 11-7 and Hel 9-9) were able to partially immerse their hydrophobic part of the amphiphilic helix in lipid bilayers and fragment liposome to small bicelles or micelles, and then the bicelles aggregated to form a larger assembly. Peptides Hel 11-7 and Hel 9-9 each formed strong ion channels. Peptides (Hel 7-11 and Hel 5-13) with a more hydrophilic HHB interacted with an acidic lipid bilayer by charge interaction, in which the former immerses the hydrophobic part in lipid bilayer, and the latter did not immerse, and formed large assemblies by aggregation of original liposomes. The present study clearly showed that hydrophobic-hydrophilic balance of a peptide is a crucial factor in understanding lipid-peptide interactions.

Importance of hydrophobic region in amphiphilic structures of alpha-helical peptides for their gene transfer-ability into cells

It has been showned that cationic alpha-helical peptides can be useful as nucleic acid-carrier molecules for gene transfer into cells. In order to investigate the significancemake sure of importance of the hydrophobic region in amphiphilic peptides in relation to their transfection ability, we have employed five kinds of peptides with a systematically varied hydrophobic-hydrophilic balance in the amphiphilic structures, and have evaluated the relationship between the structure and the gene transfer ability of the peptides into COS-7 cells. The peptides with a large hydrophobic region took alpha-helical structures, formed large aggregates and showed high transfection efficiency. Their high efficiency can be explained on the basis of their ability to form stable aggregates which can be internalized by endocytosis and remain resistant to digestion in lysosomal vesicles. Furthermore, it was suggested that the hydrophobic region of peptides plays an important role in the disruption of the endosomal membrane, which ca prevent the degradation of DNA in lysosomal vesicles. When peptides do not have so strong membrane-disruptive activity, but form aggregates which can be incorporated by endocytosis, the transfection efficiency can be recovered by the addition of an endosome-disruptive peptide.

The antithrombotic effects of recombinant human soluble thrombomodulin (rhsTM) on tissue factor-induced disseminated intravascular coagulation in crab-eating monkeys (Macaca fascicularis)

We evaluated the antithrombotic effects of recombinant human soluble thrombomodulin (rhsTM) in plasma and in a monkey model. rhsTM dose-dependently prolonged activated partial thromboplastin time (APTT) in the following order: humans > monkeys > rats >> rabbits. The prolongation of APTT by rhsTM was also observed in protein C-deficient plasma. rhsTM activated protein C and inactivated factor Va in human and monkey plasma, but not in rat plasma. These findings suggest that the antithrombotic activities of rhsTM are fully expressed in human and monkey. Therefore, to evaluate the whole activity of rhsTM in a clinical model, tissue factor (TF) was intravenously infused into crab-eating monkeys to induce disseminated intravascular coagulation (DIC). Pretreatment with rhsTM reduced fall in fibrinogen with a biphasic and moderate dose-dependency curve, and reduced thrombin-antithrombin III (TAT) levels with a flat linear dose-dependency, while heparin prevented fall in fibrinogen with a steep linear dose-dependency curve without reducing TAT levels. Further evidence suggesting that rhsTM activates protein C in vivo was also obtained. Taken together, the data indicate that rhsTM fully expresses its antithrombotic activities in human and monkey but not in rat and rabbit, and rhsTM prevents TF-induced DIC in monkeys by suppressing thrombin generation.

De novo design, synthesis, and characterization of a pore-forming small globular protein and its insertion into lipid bilayers

The question of how to design a water-soluble globular protein remains. We report here the synthesis of a native-like and pore-forming small globular protein (SGP, 69 amino acid residues). The protein was designed to have four helices: a Trp-containing short hydrophobic helix in the middle surrounded by three Tyr-containing long basic amphiphilic helices. Size-exclusion chromatography and CD measurements indicated that in buffer solution SGP is monomeric with a 50% helical structure. SGP did not completely denature even at high temperature (90 degrees C) and at relatively high Gu x HCl concentration so that the denaturant concentration at the midpoint of the transition is 5 M. Dye binding studies and fluorescence energy transfer experiments showed that SGP possesses a hydrophobic binding site and its Trp of the central helix is present at a relatively hydrophobic region and accepts the energy from Tyr(s) in other amphiphilic helices, indicating that SGP takes a stable globular-like structure in aqueous solution. From the depth-dependent fluorescent studies using egg PC liposomes containing n-doxyl fatty acids and brominated phospholipid as quenchers, it was found that the hydrophobic central alpha-helix is able to enter spontaneously into the lipid bilayers and the Trp in the central alpha-helix is located at about the middle of the alkyl chain in the outer layer of the phospholipid bilayer. The peptide is also able to increase the membrane permeability with two modes of current (basal current and single ion channel) in planar phospholipid bilayers, indicating the spontaneous insertion of the protein into the lipid bilayer (basal current) and then the formation of a uniform size of channel pore (14 pS). SGP is useful as a basic and starting model to find good amino acid sequences that fold to a desired protein structure and to search translocation mechanisms from aqueous solution into lipid bilayers.

Design and synthesis of amphiphilic alpha-helical model peptides with systematically varied hydrophobic-hydrophilic balance and their interaction with lipid- and bio-membranes

Five amphiphilic alpha-helical peptides of 18 residues containing a hydrophobic Trp residue as a fluorescence probe were designed. The peptides were made up of hydrophobic Leu and hydrophilic Lys residues of a ratio of 13:5, 11:7, 9:9, 7:11, and 5:13 (abbreviated as Hels 13-5, 11-7, 9-9, 7-11, and 5-13, respectively). These peptides generate ideal amphiphilic alpha-helical structures, which have systematically varied hydrophobic-hydrophilic balance (relative amphiphilic potential) as a result of different hydrophobicities and almost the same hydrophobic moments. Their hydrophobic-hydrophilic balance was estimated both theoretically from the calculated hydrophobicity values (or the magnitude of hydrophobic faces) and experimentally from the retention times in reverse phase high-performance liquid chromatography (RP-HPLC). Circular dichroism, liposome-lytic, and Trp-fluorescent studies in buffer and in the presence of acidic and neutral liposomes clearly showed that the increasing hydrophobic face area not only increases the affinity for lipid but also increases the trend of self-association. The structure-activity relationship estimated by means of leakage ability and hemolytic activity demonstrated that the model- and bio-membrane perturbation ability is completely parallel to the magnitude of the hydrophobic face area. The lipid-binding study in guanidine hydrochloride solution showed that the peptides with a hydrophobic face larger than the hydrophilic face (Hels 13-5 and 11-7) immerse their hydrophobic regions in lipid bilayers and that the inverse ones (Hels 7-11 and 5-13) interact only between the anionic lipid head groups and cationic peptide residues on liposome surfaces. The peptide Hel 9-9, which has exactly the same hydrophobic and hydrophilic regions, was found to be at a critical boundary among these peptides in terms of (1) behavior of peptide self-aggregation in buffer solution and membrane perturbation ability, (2) transfer from bulk solution to neutral lipid bilayers, and (3) necessity of charge interaction in lipid-peptide binding.

Multicenter evaluation of a colorimetric microplate antimycobacterial susceptibility test: comparative study with the NCCLS M24-P

A colorimetric test method using the microplate culture technique for the determination of susceptibility of Mycobacterium tuberculosis against antimycobacterial agents was developed and evaluated by the multicenter study. The test method utilizes an oxidation-reduction dye, 2,3-diphenyl-5-thienyl-(2)-tetrazolium chloride (STC), as an indicator of mycobacterial growth. When compared to the presently available test method, some modifications were also included; lower inoculum density (10-fold dilution), inclusion of an inoculum diluted 1:100 as a growth control, and the preparation of inoculum preincubated in Middlebrook 7H9 broth and spectrophotometrically adjusted to McFarland #1 turbidity. The test method evaluated was highly precise and reliable to detect antimycobacterial resistances when the ATCC reference strains were tested. Also, the interpretations of the test result were highly comparable to those determined by the method of NCCLS M24-P, the % agreements ranging from 76.1% (ethambutol) to 91.3% (streptomycin). The test results were also comparable to those determined by Ogawa media; > 90% agreed with susceptible, intermediate, or resistant. The appearance of mycobacterial colonies on the test media was easily read, and the test results were more comparable to those of NCCLS M24-P. With these results, it can be concluded that the colorimetric microplate susceptibility test method described will be more suitable for clinical mycobacteriology laboratories.

[Antitumor effects of Behenoyl-ara-C (BH-AC) in combination with Idarubicin (IDA) in P 388 leukemic cell bearing mice]

The antitumor effects of Behenoyl-ara-C (BH-AC) in combination with Idarubicin (IDA) on leukemia were studied. First, a combination of IDA with Ara-C, which is the main metabolite of BH-AC, was evaluated with regard to its in vitro cytotoxic activity on mouse P 388 leukemic cells. The effect of this combination proved to be additive according to isobologram analysis. Secondly, the antitumor activity of an intravenous bolus-administration of a combination of BH-AC and IDA was evaluated by the life span of P 388 bearing mice, and compared with the activity of the Ara-C and IDA combination. The antitumor activity of Ara-C administered alone was clearly dependent on the administration schedule and was most intense when Ara-C was administered with the most frequent injections (3 bolus injections/day x 3 days), whereas antitumor activity of BH-AC was less dependent on the schedule. IDA administered alone showed dose-dependency in its antitumor activity up to 3 mg/kg. The maximum effects of IDA were observed with amounts of 3 - 4 mg/kg. In the same leukemia model, the combination of frequent injections of BH-AC and a single injection of IDA (increased life span: ILS>300%; cure ratio: CR = 3/5) conferred a more potent effect compared to the results of BH-AC (ILS = 133%, CR = 0/5) or IDA (ILS = 67%, CR = 2/5) alone. The effect of BH-AC and IDA combination was comparable or superior to that of the Ara-C and IDA (ILS = 233%, CR = 2/5) combination. These results indicated the possibility of clinical usefulness with a combination therapy of BH-AC and IDA against leukemia.

Antithrombotic effects of recombinant human soluble thrombomodulin (rhs-TM) on arteriovenous shunt thrombosis in rats

We examined the antithrombotic effect of recombinant human soluble thrombomodulin (rhs-TM) using an arteriovenous shunt thrombosis model and its influence on hemostasis in rats. Intravenous administration of rhs-TM (0.5-4 mg/kg) significantly inhibited thrombus formation and prolonged ex vivo activated partial thromboplastin time (APTT) in a dose-dependent manner. Thrombus formation was inhibited to the same extent in animals treated with heparin (25-200 U/kg) and in those treated with rhs-TM (0.5-4 mg/kg), but heparin had a much stronger effect on prolonging APTT. In the hemorrhagic study using the rat template bleeding time method, rhs-TM exhibited the prolongation of the bleeding time only at the highest effective dose (rhs-TM; 4 mg/kg) of the thrombosis experiments. Thus, rhs-TM exhibits the inhibitory effect on thrombus formation with less APTT prolongation in comparison with heparin and without significant pertubation of hemostasis.

Intravenous extended infusion of recombinant human soluble thrombomodulin prevented tissue factor-induced disseminated intravascular coagulation in rats

This study demonstrated that intravenous infusion of recombinant human soluble thrombomodulin (rhs-TM) could inhibit disseminated intravascular coagulation (DIC) caused by 4 hr infusion of tissue factor (TF) in rats. Extended infusion of TF reduced fibrinogen and platelet counts and elevated serum FDP level. Pretreatment and coinfusion of rhs-TM could block changes of these DIC-parameters without prolongation of APTT. Heparin, which is a potent anti-DIC drug, could also inhibit these changes with extra prolongation of APTT and PT. Thus, these results suggest thrombomodulin prevent DIC less bleeding tendency than heparin.