Helicobacter pylori infection potentiates aspirin induced gastric mucosal injury in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection and non-steroidal anti-inflammatory drugs are two major causes of gastric ulceration but interactions between H pylori and these drugs in gastric mucosal injury are unclear.

AIMS

We studied the influence of experimental H pylori infection on gastric mucosal injury induced by aspirin.

SUBJECTS

Male Mongolian gerbils free of specific pathogens were used.

METHODS

H pylori ATCC43504 culture broth was administered by oral gavage at seven weeks of age. After three weeks, acidified aspirin (400 mg/kg) was administered orally, and three hours later the total area of gastric erosions, myeloperoxidase (MPO) activity (an index of neutrophil accumulation), thiobarbituric acid reactive substances (TBARS, an index of lipid peroxidation), and KC/GRO (a chemoattractive cytokine in rodents) were measured in gastric mucosa. To determine the role of neutrophils in these circumstances, antigerbil neutrophil rabbit serum (ANS) was administered to some animals 18 hours before aspirin.

RESULTS

Aspirin caused more extensive haemorrhagic erosions (33.1 (12.3) mm2) associated with greater MPO activity (1887.7 (598.5) microU/mg protein) and TBARS (0.33 (0.14) nmol/mg protein) and KC/GRO concentrations (28.3 (9.5) pg/mg protein) in infected than in uninfected gerbils (13.7 (2.3); 204.0 (68.9); 0.12 (0.06); 3.1 (0.8), respectively) Pretreatment with ANS inhibited the increases in gastric erosions, MPO activity, and TBARS but not KC/GRO concentration. The reduction in aspirin induced mucosal injury by administration of ANS was much greater in H pylori infected animals (65%) than in uninfected animals (31%).

CONCLUSIONS

H pylori infection potentiates aspirin induced gastric mucosal injury by mechanisms that include accumulation of activated neutrophils.

Phagocytosis in vitro of polyethylene glycol-modified liposome-encapsulated hemoglobin by human peripheral blood monocytes plus macrophages through scavenger receptors

Liposome-encapsulated hemoglobin (LEH), a candidate for red blood cell substitute, is cleared from circulation primarily by the phagocytic system, most likely after opsonization of the vesicles by immunoproteins, particularly complement components. Although modification of LEH by polyethylene glycol (PEG) derivatives prolongs its half-life by blocking the opsonization, the half-life is still short as compared with that of red blood cell components. Therefore, this study was performed to elucidate the opsonin-independent mechanisms that regulate phagocytosis of Neo Red Cell (NRC), a PEG-modified LEH, in culture. PKH67 was used as a fluorescence marker, allowing the quantitation of the phagocytosis of NRC by peripheral blood monocytes plus macrophages. The phagocytosis of PKH67-labeled NRC was inhibited by the addition of an excess of unlabeled NRC, indicating that the phagocytosis of PKH67-labeled NRC is specific to NRC, but not to PKH67. The phagocytosis of NRC was blocked about 70% by anti-CD14, 60% by anti-CD36 and 30% by anti-CD51/61 (vitronectin receptor, alpha(v)beta3). These results provided evidence of an opsonin-independent pathway for the phagocytosis of PEG-modified LEH.

Effect of peracylation of beta-cyclodextrin on the molecular structure and on the formation of inclusion complexes: an X-ray study

The molecular structures of peracylated beta-cyclodextrins (CDs)--heptakis(2,3,6-tri-O-acetyl)-beta-CD (TA), heptakis(2,3,6-tri-O-propanoyl)-beta-CD (TP), and heptakis(2,3,6-tri-O-butanoyl)-beta-CD (TB)--have been determined by single crystal X-ray structure analysis. Due to the lack of O2...O3' hydrogen bonds between adjacent glucose units of the peracylated CDs, the macrocycles are elliptically distorted into nonplanar boat-shaped structures. The glucose units are tilted with respect to the O4 plane to relieve steric hindrance between adjacent acyl chains. In TB, all glucose units adopt the common (4)C(1)-chair conformation and one butanoyl chain intramolecularly penetrates the cavity, whereas, in TA and TP, one glucose unit each occurs in (O)S(2)-skew-boat conformation and one acyl chain closes the O6 side like a lid. In each of the three homologous molecules the intramolecular self-inclusion and lidlike orientation of acyl chains forces the associated O5-C5-C6-O6 torsion angle into a trans-conformation never observed before for unsubstituted CD; the inclusion behavior of TA, TP, and TB in solution has been studied by circular dichroism spectroscopy with the drug molsidomine and several organic compounds. No inclusion complexes are formed, which is attributed to the intramolecular closure of the molecular cavity by one of the acyl chains.

Prednisolone-appended alpha-cyclodextrin: alleviation of systemic adverse effect of prednisolone after intracolonic administration in 2,4,6-trinitrobenzenesulfonic acid-induced colitis rats

The titled compound is a cyclodextrin derivative in which prednisolone 21-succinate (PDsuc) is covalently bound to one of the secondary hydroxyl groups of alpha-cyclodextrin (alpha-CyD) via an ester linkage. In this study, the PDsuc-appended alpha-CyD ester conjugate (PDsuc/alpha-CyD conjugate) was intracolonically administered to rats with 2,4,6-trinitrobenzensulfonic acid-induced colitis, and its antiinflammatory and systemic adverse effects were compared with those of prednisolone (PD) alone and the PD/2-hydroxypropyl-beta-CyD complex (PD/HP-beta-CyD complex), which is a noncovalent inclusion complex. Colonic damage score, ratio of distal colon wet weight to body weight, and myeloperoxidase activity were evaluated as measures of the therapeutic effect of PD, whereas the ratio of thymus wet weight to body weight was evaluated as a measure of the side effect of PD. The local antiinflammatory activity increased in the order of PD alone approximately PDsuc/alpha-CyD conjugate < PD/HP-beta-CyD complex. As to systemic adverse effect, the PD/HP-beta-CyD complex and PD alone caused thymolysis at doses of 5-10 mg/kg. In contrast, the PDsuc/alpha-CyD conjugate showed no clear systemic adverse effect at the same doses. The low adverse effect of the conjugate may be ascribed to the slow release of PD in the colon, which keeps the local concentration in the colon at a low but constant level. The results suggest that the PDsuc/alpha-CyD conjugate can alleviate the systemic adverse effect of PD while maintaining the therapeutic activity of PD. This kind of knowledge will be useful in the rational design of steroid prodrugs for the colon-specific drug delivery system.

RHC/c genotyping based on polymorphism in the promoter region of the RHCE gene

Designing of PCR tests for the RHC allele is difficult because of the high DNA sequence homology between RHC and RHD genes, which differ by only a one-nucleotide substitution at position 48 in exon 1 of the RHCE gene. We sequenced the promoter region of the RHCE gene, and compared our results with the reported sequence. Genomic DNA was prepared from blood samples collected from 656 Japanese donors. The DNA segment encompassing the promoter region and exon 1 of the RHCE gene from 30 donors was amplified by PCR and analyzed by DNA sequencing. Four nucleotide differences between RHC/c and RHD were found at positions -468, -304, -58, and -46. On the basis of the nucleotide differences at positions -468 (RHCE vs. RHD) and -292 (RHC vs. RHc), we then developed a novel polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for RHC/c genotyping. Analysis of the genomic DNA from the 656 donors revealed that this method could discriminate RHC from RHc, irrespective of the RHD genotype, with only a few exceptions. The combination of our system and the intron 2-based PCR-RFLP method previously reported may prove to be more accurate than either of the methods alone, and therefore, useful and valuable for RHC/c genotyping.

Stabilizing and solubilizing effects of sulfobutyl ether beta-cyclodextrin on prostaglandin E1 analogue

PURPOSE

Parent cyclodextrins are known to accelerate the degradations such as dehydration and isomerization of E-type prostaglandins in neutral and alkaline solutions. The objective of this study was to attempt the stabilization and solubilization of E1-type prostaglandin analogue in aqueous solution by biocompatible cyclodextrin derivatives.

METHODS

The interaction of an E1-type prostaglandin, methyl 7-[(1R,2R,3R)-3-hydroxy-2-[(E)-(3S)-3-hydroxy-4-(m-methoxymethylphenyl)1-butenyl]-5-oxocyclopentyl]-5-thiaheptanoate (MEester) with cyclodextrins (CyDs) was studied by spectroscopies and the solubility method. The degradation of MEester was monitored by high-performance liquid chromatography.

RESULTS

1H-nuclear magnetic resonance spectroscopic studies indicated that MEester forms 1:1 inclusion complexes with alpha-, beta-, and gamma-CyDs in solutions, where alpha-CyD interacts with the a-side chain containing methyl ester moiety of the drug, whereas beta- and gamma-CyDs preferentially include around the five-membered ring and both side chains of the drug. Parent alpha-CyD and hydrophilic derivatives, such as 2-hydoxypropyl-alpha- and -beta-CyDs, sulfobutyl ether beta-CyD (SBE-beta-CyD) and maltosyl beta-CyD showed higher solubilizing abilities against MEester over parent beta- and gamma-CyDs. SBE-beta-CyD and 2,6-dimethyl-beta-CyD (DM-beta-CyD) significantly decelerated the degradation of MEester, particularly the base-catalyzed dehydration, in neutral and alkaline solutions, whereas other CyDs accelerated the degradation. The acid-catalyzed degradation of MEester (pH < 3) was decelerated by the addition of CyDs, especially alpha-CyD.

CONCLUSIONS

SBE-beta-CyD with low hemolytic activity and low toxicity is useful as a pharmaceutical carrier for the preparation of injectable MEester, because of its higher stabilizing and solubilizing effects on MEester. Furthermore, SBE-beta-CyD can be useful as a stabilizing agent for drugs, that are subject to base-catalyzed degradations, probably because of the electric repulsion between anionic charges of the sulfobutyl moiety and catalytic anionic species such as hydroxide ion.

Improvement of some pharmaceutical properties of DY-9760e by sulfobutyl ether beta-cyclodextrin

The interaction of DY-9760e, a novel cytoprotective agent, with sulfobutyl ether beta-cyclodextrin (SBE-beta-CyD) in phosphate buffered saline (PBS) at various pH and ionic-strengths was studied by spectroscopic methods and the solubility method, and the results were compared with that of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD). The circular dichroism (CD) spectroscopic studies suggested that both beta-CyDs form the inclusion complexes with DY-9760e in a molar ratio of 1:1, and the interaction of DY-9760e with SBE-beta-CyD is much stronger than that with HP-beta-CyD at any pH studied, in terms of a synergetic effect of hydrophobic and electrostatic interactions. The different intermolecular interaction between the SBE-and HP-beta-CyD complexes was clearly reflected in the stability constant (K'), e.g. the different dependence of K' value on pH and ionic strength of solutions. 1H- and 13C-NMR studies suggested that HP-beta-CyD interacts preferably with the benzene ring of DY-9760e, whereas SBE-beta-CyD interacts not only with the benzene ring via hydrophobic interaction but also with the piperazine ring of the drug via electrostatic interaction. The solubilizing ability of SBE-beta-CyD against DY-9760e was much greater than that of HP-beta-CyD at any pH studied. Furthermore, SBE-beta-CyD markedly suppressed the photo-degradation of DY-9760e in aqueous solution and reduced the adsorption of DY-9760e from PBS to polyvinyl chloride (PVC) tubes after incubation. The results suggest that SBE-beta-CyD is useful in preparing parenteral solutions of poorly water-soluble drugs with positive charge such as DY-9760e.

Liposome-encapsulated superoxide dismutase suppresses liposome-mediated augmentation of TNF-alpha production from peripheral blood leucocytes

Liposome-encapsulated hemoglobin (LEH), a candidate for a red cell substitute, has been reported to be cleared from circulation primarily by the phagocytic system and modulate the production of inflammatory cytokines, such as TNF-alpha and IL-6, both in vivo and in vitro. In this study, we investigated the effects of liposome vesicles on the LPS-induced TNF-alpha production using a whole blood culture system. We also studied the effects of superoxide dismutase (SOD) encapsulated in liposome on the cytokine production. The pre-treatment of whole blood with liposome vesicles potentiated the LPS-induced TNF-alpha production. The encapsulation of SOD in the liposome vesicles suppressed the liposome-mediated augmentation of TNF-alpha production in a dose-dependent manner. These results suggest that encapsulation of SOD in LEH decreases the production of inflammatory cytokines from the phagocytic system which may be caused or augmented by LEH infusion in vivo.

Inhibitory effects of novel hydrophilic cyclodextrin derivatives on nitric oxide production in macrophages stimulated with lipopolysaccharide

PURPOSE

The objective of this study is to examine the effects of cyclodextrins (CyDs) on nitric oxide (NO) production in macrophages stimulated with lipopolysaccharide (LPS).

METHODS

RAW264.7 cells, a mouse macrophage-like cell, were used. Cytotoxicity of CyDs was evaluated by WST-1 method. Nitrite, iNOS, and iNOS mRNA were determined by Griess method, Western blotting, and reverse transcription-polymerase chain reaction (RT-PCR) analysis, respectively. The interaction of LPS with CyDs was evaluated by utilizing a competitive inclusion phenomenon. The binding of FITC-labeled LPS to the surface of RAW264.7 cells was measured by a flow cytometry.

RESULTS

Of 15 CyDs, 2,6-di-O-methyl-alpha-CyD (DM-alpha-CyD), and 2,6-di-O-methyl-3-O-acetyl-beta-cyclodextrin (DMA-beta-CyD) had greater inhibitory activity than did the other CyDs against NO production in RAW264.7 cells stimulated with LPS, without showing any cytotoxicity. DM-alpha-CyD and DMA-beta-CyD specifically inhibited the increase in iNOS and iNOS mRNA levels elicited by stimulation with LPS in RAW264.7 cells. DM-alpha-CyD and DMA-beta-CyD suppressed the binding of FITC-labeled LPS to the surface of cells, probably resulting in inhibitory effects on iNOS expression and NO production. DM-alpha-CyD had a greater interaction with RAW264.7 cells than did DMA-beta-CyD. The pretreatment of RAW264.7 cells with DM-alpha-CyD, not DMA-beta-CyD, decreased the LPS binding to the cell surface. The results suggested that the inhibitory mechanism of the LPS binding to the cell surface is different between DM-alpha-CyD and DMA-beta-CyD.

CONCLUSIONS

The present results suggest that DM-alpha-CyD and DMAbeta-CyD attenuates NO production by inhibiting iNOS gene expression in RAW264.7 cells stimulated with LPS, probably due to the suppression of LPS binding to LPS receptors on the cells in the different way.

Comparative studies of the enhancing effects of cyclodextrins on the solubility and oral bioavailability of tacrolimus in rats

The enhancing effects of cyclodextrins (CyDs) on the solubility, the dissolution rate, and the bioavailability of tacrolimus after oral administration to rats were examined and compared with those after administration of a PROGRAF capsule containing the solid dispersion formulation of tacrolimus. Here we used natural CyDs and the hydrophilic beta-CyD derivatives; that is, randomly methylated-beta-cyclodextrin (RM-beta-CyD), heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD), 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD), and sulfobutyl ether beta-cyclodextrins (SBE-beta-CyDs). Of the natural CyDs, the solubility of tacrolimus increased in the addition of beta-CyD, indicating that the cavity of beta-CyD comfortably fits the drug. Of the beta-CyD derivatives, DM-beta-CyD had the greatest solubilizing activity and gave the A(p) type phase solubility curve as defined by Higuchi and Connors, suggesting the formation of higher-order complexes. The result of van't Hoff plot suggests that the enthalpy is dominant for the complexation of tacrolimus with DM-beta-CyD. The dissolution rate of tacrolimus was markedly augmented by the complexation with DM-beta-CyD, reflecting its solubilizing activity. An in vivo study revealed that DM-beta-CyD increased the bioavailability of tacrolimus with low variability in the absorption after oral administration of the tacrolimus suspension to rats. The present results suggest that DM-beta-CyD is particularly useful in designing oral preparations of tacrolimus with an enhanced bioavailability and a reduced variability in absorption.

Enhancement of gene expression by polyamidoamine dendrimer conjugates with alpha-, beta-, and gamma-cyclodextrins

To improve the transfection efficiency of nonviral vector, we synthesized the starburst polyamidoamine dendrimer conjugates with alpha-, beta-, and gamma-cyclodextrins (CDE conjugates), expecting the synergistic effect of dendrimer and cyclodextrins (CyDs). The (1)H NMR spectroscopic data indicated that alpha-, beta-, and gamma-CyDs are covalently bound to dendrimer in a molar ratio of 1:1. The agarose gel electrophoretic studies revealed that CDE conjugates formed the complexes with plasmid DNA (pDNA) and protected the degradation of pDNA by DNase I in the same manner as dendrimer. CDE conjugates showed a potent luciferase gene expression, especially in the dendrimer conjugate with alpha-CyD (alpha-CDE conjugate) which provided the greatest transfection activity (approximately 100 times higher than those of dendrimer alone and of the physical mixture of dendrimer and alpha-CyD) in NIH3T3 and RAW264.7 cells. In addition, the gene transfer activity of alpha-CDE conjugate was superior to that of Lipofectin. The enhancing gene transfer effect of alpha-CDE conjugate may be attributable to not only increasing the cellular association, but also changing the intracellular trafficking of pDNA. These findings suggest that alpha-CDE conjugate could be a new preferable nonviral vector of pDNA.

Preparation of prednisolone-appended alpha-, beta- and gamma-cyclodextrins: substitution at secondary hydroxyl groups and in vitro hydrolysis behavior

The carboxyl group of prednisolone 21-hemisuccinate was conjugated to one of the hydroxyl groups of alpha-, beta-, and gamma-cyclodextrins using a coupling agent, carbonyldiimidazole. The direct coupling produced prednisolone-appended cyclodextrin conjugates in which the drug is selectively introduced at one of the secondary hydroxyl groups of cyclodextrins through an ester linkage. The aqueous solubility (> 50% w/v at 25 degrees C) of these conjugates was much higher than those of prednisolone and its 21-hemisuccinate. Prednisolone was slowly released from the conjugate: the percents of prednisolone and its hemisuccinates released from the alpha-, beta-, and gamma-cyclodextrin conjugates were 49, 57, and 85%, respectively, for 24-h. The release pathway is proposed to be via two fast acyl migrations between the 2- and 3-hydroxyl groups of cyclodextrins and between the 21- and 17-hydroxyl groups of prednisolone. The slow release of prednisolone from the ester conjugates was in sharp contrast to the fast release of the prednisolone amide conjugate reported previously. Because of relatively slow and/or site-specific release properties, the present prednisolone-appended cyclodextrin conjugates may be of value as an orally administered delayed-release and/or colon-specific prodrug.

Contribution of P-glycoprotein to the enhancing effects of dimethyl-beta-cyclodextrin on oral bioavailability of tacrolimus

We recently reported that of all hydrophilic cyclodextrin (CyD) derivatives examined, 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-CyD) most significantly increased the aqueous solubility and the dissolution rate, resulting in the improvement of oral bioavailability of the immunosuppressive drug tacrolimus in rats. In the present study, we showed that DM-beta-CyD increased the dissolution rate and oral bioavailability of tacrolimus in rats with increases in the molar ratio of the complexes (DM-beta-CyD:tacrolimus). However, nonlinear pharmacokinetic behavior of tacrolimus after oral administration in rats was observed. Thus, an additional mechanism of the solubilizing effect of DM-beta-CyD on oral bioavailability of tacrolimus was postulated. To gain insight into this additional mechanism of action of DM-beta-CyD, its effects on the efflux of tacrolimus and rhodamine 123, a P-glycoprotein (P-gp) substrate, were examined using both Caco-2 and vinblastine-resistant Caco-2 (Caco-2R) cell monolayers. Pretreatment of the apical membranes of the monolayers with DM-beta-CyD decreased the efflux of tacrolimus and rhodamine 123 without an associated cytotoxicity. DM-beta-CyD decreased the P-gp level in the apical membranes of both Caco-2 and Caco-2R cell monolayers, probably by allowing release of P-gp from the apical membrane into the transport buffer. DM-beta-CyD, however, did not decrease the MDR1 gene expression in Caco-2 or Caco-2R cells. These results suggested that the enhancing effect of DM-beta-CyD on the oral bioavailability of tacrolimus is due not only to its solubilizing effect but also, at least in part, to its inhibitory effect on the P-gp-mediated efflux of tacrolimus from intestinal epithelial cells.

Preparation of prednisolone-appended alpha-, beta- and gamma-cyclodextrins: substitution at secondary hydroxyl groups and in vitro hydrolysis behavior

The carboxyl group of prednisolone 21-hemisuccinate was conjugated to one of the hydroxyl groups of alpha-, beta-, and gamma-cyclodextrins using a coupling agent, carbonyldiimidazole. The direct coupling produced prednisolone-appended cyclodextrin conjugates in which the drug is selectively introduced at one of the secondary hydroxyl groups of cyclodextrins through an ester linkage. The aqueous solubility (> 50% w/v at 25 degrees C) of these conjugates was much higher than those of prednisolone and its 21-hemisuccinate. Prednisolone was slowly released from the conjugate: the percents of prednisolone and its hemisuccinates released from the alpha-, beta-, and gamma-cyclodextrin conjugates were 49, 57, and 85%, respectively, for 24-h. The release pathway is proposed to be via two fast acyl migrations between the 2- and 3-hydroxyl groups of cyclodextrins and between the 21- and 17-hydroxyl groups of prednisolone. The slow release of prednisolone from the ester conjugates was in sharp contrast to the fast release of the prednisolone amide conjugate reported previously. Because of relatively slow and/or site-specific release properties, the present prednisolone-appended cyclodextrin conjugates may be of value as an orally administered delayed-release and/or colon-specific prodrug.

A moderate interaction of maltosyl-alpha-cyclodextrin with Caco-2 cells in comparison with the parent cyclodextrin

The cytotoxicity of maltosyl-alpha-cyclodextrin (G2-alpha-CyD) and maltosyl-beta-cyclodextrin (G2-beta-CyD) toward Caco-2 cells was compared with that of natural alpha-cyclodextrin (alpha-CyD), beta-cyclodextrin (beta-CyD) and gamma-cyclodextrin (gamma-CyD). The degree of increase in cytotoxicity was dependent on the CyD's type and the concentration: the cytotoxicity of CyDs at the same concentration increased in the order of gamma-CyD<G2-beta-CyD<G2-alpha-CyD<<alpha-CyD, although beta-CyD could not be compared to other CyDs because of low solubility in water. Alpha-CyD decreased transepithelial electrical resistance (TEER) and increased the apical-to-basolateral (AP-to-BL) transport of [3H]mannitol, a paracellular transport marker, in a concentration-dependent manner, suggesting that alpha-CyD decreased the integrity of Caco-2 cell monolayers. In addition, alpha-CyD increased the AP-to-BL transport of rhodamine 123, a transcellular transport marker, under the experimental conditions being independent of P-glycoprotein. In contrast, G2-alpha-CyD, G2-betaCyD and gamma-CyD had slight effect on both TEER and the transport of mannitol and rhodamine 123 even at relatively high concentrations up to 150 mM. The inability of G2-alpha-CyD and G2-beta-CyD to effect TEER and the transport of mannitol and rhodamine 123 could be explained by the findings that these maltosylated CyDs released only a small amount of membrane constituents from Caco-2 cell monolayers and interacted only weakly with monolayers composed of L-alpha-dipalmitoylphosphatidylcholine (DPPC) formed on water. These results indicate that G2-alpha-CyD has less cytotoxicity and less disturbing ability toward Caco-2 cell monolayers than alpha-CyD, and G2-beta-CyD has, at least, comparable cytotoxicity to beta-CyD toward them. Thus, from the safety point of view, highly water-soluble G2-alpha-CyD and G2-beta-CyD may be particularly useful in various pharmaceutical formulations.

Improvement of solubility and oral bioavailability of rutin by complexation with 2-hydroxypropyl-beta-cyclodextrin

The object of this study was to enhance the solubility, dissolution rate, and oral bioavailability of rutin by complexation with 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD). The interaction of rutin with cyclodextrins (CyDs) was evaluated by the solubility, and ultraviolet (UV) and circular dichroism (CD) spectrophotometries. The chemical and enzymatic stability of rutin was examined in an alkaline buffer solution and in rat small intestinal homogenates, respectively. Dissolution rates of rutin and its CyD complexes were measured by the dispersed amount method. In vivo absorption studies of rutin after oral administration via conventional tablet containing rutin alone or its beta-CyD complexes was performed on beagle dogs. The stability constants calculated from the phase solubility method increased in the order of HP-gamma-CyD < G2-beta-CyD < beta-CyD < HP-beta-CyD. Spectroscopic studies also revealed that HP-beta-CyD and beta-CyD formed a relatively more stable inclusion complex with rutin. The dissolution rates of rutin increased by the complexation with CyDs in the order of rutin alone < HP-beta-CyD < or = beta-CyD. HP-beta-CyD inhibited the hydrolysis of rutin in the alkaline buffer solution and the small intestinal homogenates of rats, suggesting that HP-beta-CyD may stabilize rutin in a gastrointestinal tract after oral administration. When the tablet containing rutin or its beta-CyD complexes was administered to beagle dogs, the plasma levels of homovanillic acid (HVA) (a major stable metabolite of rutin) after oral administration of HP-beta-CyD complex were much higher than in either that of rutin alone or in its beta-CyD complex. The in vivo absorption study suggests that HP-beta-CyD increased the oral bioavailability of rutin from the gastrointestinal tracts of beagle dogs because of the increase in solubility, faster dissolution rate, and gastrointestinal stability. HP-beta-CyD has a significant advantage with respect to providing high aqueous solubility while maintaining a lack of toxicity in oral pharmaceutical preparations of rutin.

Serum-free coculture system for ex vivo expansion of human cord blood primitive progenitors and SCID mouse-reconstituting cells using human bone marrow primary stromal cells

OBJECTIVE

In an attempt to maintain and expand human stem cells, many investigators have used xenogeneic, especially murine, stromal cells and fetal calf serum. Because of the possible transmission of infectious diseases, however, the safety of the delivery of grafts expanded in culture using xenogeneic cells and serum has been debated. Using primary human marrow stromal cells, we established a novel serum-free culture system to expand human primitive progenitors and transplantable stem cells.

MATERIALS AND METHODS

Cord blood CD34(+) cells were cultured on a monolayer of human primary marrow stromal cells in the presence of thrombopoietin (TPO), flt3/flk2 ligand (FL), and/or stem cell factor (SCF) under serum-free conditions. After 2 or 4 weeks of culture, cells were examined for clonogenic progenitors and severe combined immunodeficient disorder (SCID) mouse-reconstituting cells (SRC).

RESULTS

In the presence of TPO, FL, and SCF, marrow stromal cells supported more than a 100- and 1,000-fold expansion of CD34(+) cells and colony-forming units in culture after 2 and 4 weeks of incubation, respectively. In addition, cobblestone area-forming cells were expanded more than 18- and 60-fold after 2 and 4 weeks of culture, respectively. Furthermore, SRC assay demonstrated augmented engraftment by cultured cells.

CONCLUSION

This ex vivo expansion system should prove valuable in clinical settings in which stromal cells are available from recipients or stem cell donors.

Analysis of the phase solubility diagram of a phenacetin/competitor/beta-cyclodextrin ternary system, involving competitive inclusion complexation

The competitive inclusion complexations in the ternary phenacetin/competitors/beta-cyclodextrin (beta-CyD) systems were investigated by the solubility method, where m-bromobenzoic acid (m-BBA) and o-toluic acid (o-TA) were used as competitors. The solubility changes of the drug and competitors as a function of beta-CyD concentration in the ternary systems were formulated using their stability constants and intrinsic solubilities. The decrease in solubility of phenacetin by the addition of competitors could be quantitatively simulated by the formulation, when both drug and competitor give A(L) type solubility diagrams. On the other hand, when one of the guests gives a B(S) type solubility diagram, its solubility change was clearly reflected in that of the another guest, i.e., phenacetin gave an A(L) type solubility diagram in the binary phenacetin/beta-CyD system and o-TA gave a B(S) type diagram in the binary o-TA/beta-CyD system, but in the ternary phenacetin/o-TA/beta-CyD system, a new plateau region appeared in the original A(L) type diagram of phenacetin. This was explained by the solubilization theory of Higuchi and Connors. The solubility analysis of the ternary drug/competitor/CyD systems may be particularly useful for determination of the stability constant of a drug whose physicochemical and spectroscopic analyses are difficult, because they can be calculated by monitoring the solubility change of a competitor, without monitoring that of a drug. Furthermore, the present results suggest that attention should be paid to the type of the phase solubility diagram, as well as the magnitude of the stability constant and the solubility of the complex, for a rational formulation design of CyD complexes.

Release characteristics of a short-chain fatty acid, n-butyric acid, from its beta-cyclodextrin ester conjugate in rat biological media

6(A)-O-(n-Butanoyl)-beta-cyclodextrin was prepared and its hydrolysis behavior in aqueous solutions and in rat intestinal fluids was investigated. Furthermore, the enzymatic hydrolyses of the n-butyric acid-beta-cyclodextrin conjugate using alpha-amylase and esterase were studied to gain insight into the release behavior of n-butyric acid from the conjugate. The hydrolysis of the conjugate proceeded according to a first-order kinetics in aqueous solution, and gave a V-shaped pH profile, indicating a specific acid-base-catalyzed hydrolysis at acidic and neutral-alkaline regions, respectively. The half-lives (t(1/2)) of the conjugate at pH 4.4, 6.8, and 7.4 at 37 degrees C were approximately 580, 43, and 6 days, respectively, indicating that the conjugate is stable in aqueous solution. No appreciable release of n-butyric acid from the conjugate was observed in the stomach and small intestinal contents of rats, or in the small and large intestinal homogenates of rats. On the other hand, a fast disappearance of the conjugate and an appearance of n-butyric acid were observed in the cecal and colonic contents of rats. The t(1/2) values of the disappearance were approximately 4, 1, and 6 h in 10 and 15% cecal contents and 10% colonic contents, respectively, and the appearance of n-butyric acid after 6 h was approximately 10% in the 15% cecal contents. Aspergillus oryzae alpha-amylase hydrolyzed the conjugate to small saccharide conjugates, such as the triose and maltose conjugates, but there was no appreciable release of n-butyric acid. The conjugate was less susceptible to carboxylic esterase (from porcine live), thus releasing no appreciable amounts of n-butyric acid. On the other hand, a fast release of n-butyric acid was observed when the esterase was employed after amylase hydrolysis, suggesting that two types of enzymes, sugar-degrading and ester-hydrolyzing enzymes, are necessary for the release of n-butyric acid from the conjugate in large intestinal contents.

[New anticoagulants]

The quest to develop new antithrombotic agents has been stimulated by clinical needs and by advances in biotechnology that have made it possible to produce drugs that target specific steps in thrombogenesis. Established anticoagulants such as unfractionated heparin and the coumarins are effective, but have two major limitations: narrow therapeutic windows and highly unpredictable dose-response relationships. Consequently, these drugs often cause complications such as serious bleeding that require close monitoring of their use by laboratory tests to balance safety and effect. These limitations provided the impetus for the development of new anticoagulants that inactivate thrombin, factor Xa, factor IXa or the factor VIIa/tissue factor complex. Similarly, agents that enhance the protein C anticoagulant pathway have also been developed. Of these, direct thrombin inhibitors, soluble thrombomodulin, protein C, and activated protein C have been evaluated clinically for parenteral administration. However, there is enormous interest in the development of safer and more effective oral anticoagulants. In the future, such orally active direct inhibitors of thrombin and factor Xa, if they can be given safely without the need for laboratory monitoring, may replace the coumarins for the long-term treatment of thromboembolic disorders. To achieve these goals, these compounds need high, consistent oral bioavailability.

Comparison of sensitivity to ultraviolet B irradiation between human lymphocytes and hematopoietic stem cells

To investigate the clinical applicability of prophylaxis of post-transplant graft-versus-host disease by UV-B irradiation of stem cell preparations, the UV-B sensitivities of human lymphocytes and primitive hematopoietic progenitors were compared. The mononuclear cell fractions (MNC) derived from human cord blood and granulocyte-colony-stimulating factor-mobilized peripheral blood were used. After UV-B irradiation, lymphocyte proliferation ability, hematopoietic colony-forming cells, and apoptotic cells were analyzed. At a dose of 33 J/m(2), significant differences were observed in the residual percentages of hematopoietic progenitors and lymphocyte functions [ANOVA, F (5,46) = 19.4; P <.0001], and the difference between CFU-C (85.2% + 24.0%; n = 8) and MLR (12.7% + 12. 6%; n = 10) was significant (P <.0001). There were no significant differences in the residual percentages of CFU-C, HPP-CFC, and LTC-IC. Percentages of annexin V-positive cells in the total MNC and the CD34(+) cell population in MNC after UV-B irradiation were 69.8% and 18.7%, respectively. In conclusion, there was a range of UV-B doses over which T lymphocytes were inactivated but hematopoietic progenitors, including HPP-CFC and LTC-IC, were preserved.

Stromal cell-dependent ex vivo expansion of human cord blood progenitors and augmentation of transplantable stem cell activity

In vitro maintenance and expansion of human hematopoietic stem cells is crucial for many clinical applications. Thrombopoietin (TPO) and flt3/flk2 ligand (FL) have been suggested to support the proliferation of primitive hematopoietic progenitors and the expansion of transplantable stem cells in culture. In this study, we examined the synergistic effects of the murine stromal cell line MS-5 and a combination of the two cytokines, TPO and FL, on the ex vivo expansion of human cord blood primitive progenitors and transplantable stem cells. A monolayer of MS-5 cells with TPO/FL synergistically supported a more than 600-fold expansion of human cord blood CD34+ cells and CD34+CD38- cells in 2 weeks of culture. Colony-forming unit in culture (CFU-C) and 5-week and 8-week cobblestone area-forming cells (CAFC) were also expanded approximately 300-, 4- and 13-fold, respectively. When MS-5 cells were physically separated from progenitors by a Transwell filter, the synergy was reduced to a quarter of the control, suggesting that direct cell-cell contact between MS-5 cells and progenitors is required for maximum expansion. The severe-combined immunodeficient (scid) mouse-reconstituting cell (SRC) assay demonstrated the slight augmentation of transplantable stem cell activity in culture. These results indicated that MS-5 cells provide a milieu that stimulates the proliferation of primitive progenitors including transplantable stem cells.

Inclusion complex of 3,9-bis(N,N-dimethylcarbamoyloxy)-5H-benzofuro[3,2-c]quinoline-6-one (KCA-098) with heptakis(2,6-di-O-methyl)-beta-cyclodextrin: interaction and dissolution properties

Interactions of KCA-098 with heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD) in solution and in the solid state were studied by the solubility method, UV and fluorescence spectroscopy, powder X-ray diffractometry, and thermal analysis. The KCA-098/DM-beta-CyD system showed an A(L) type solubility diagram with stability constants of 5870 and 2220 M(-1) in aqueous and 10% methanol solutions, respectively. Following the addition of DM-beta-CyD, the maximum UV wavelength of KCA-098 was shifted to a longer wavelength and the fluorescence intensity was decreased. A similar spectral change was observed when KCA-098 was dissolved in less polar solvents, especially in proton-acceptor solvents, such as acetone and dimethylsulfoxide, suggesting that KCA-098 interacts with DM-beta-CyD through not only a hydrophobic interaction but also hydrogen bonding. The solid complex of KCA-098 with DM-beta-CyD in a molar ratio of 1:1 was prepared by the kneading method and the solvent evaporation method, using organic solvents. Powder X-ray diffractometric and differential scanning calorimetric studies indicated that KCA-098 was dispersed as microparticles on the DM-beta-CyD complex in the solid state prepared by the solvent evaporation method although it dispersed as crystals in the sample prepared by the kneading method. The dissolution of KCA-098 from the solid complex prepared by the former method was markedly faster than that prepared by the latter method, although it slowed down with the passage of time. The reduced dissolution of KCA-098 was explained by crystallization to the hydrate form in the medium. These data indicate that poorly water-soluble KCA-098 interacts with DM-beta-CyD in water and in the solid state and that a fast-dissolving form of KCA-098 can be obtained by evaporating with DM-beta-CyD using organic solvents.

Hydrolysis behavior of prednisolone 21-hemisuccinate/beta-cyclodextrin amide conjugate: involvement of intramolecular catalysis of amide group in drug release

Prednisolone 21-hemisuccinate/beta-cyclodextrin (beta-CyD) amide conjugate was prepared by binding prednisolone 21-hemisuccinate covalently to the amino group of mono(6-deoxy-6-amino)-beta-CyD through amide linkage. Prednisolone 21-hemisuccinate was intramolecularly transformed to prednisolone 17-hemisuccinate, and the parent drug, prednisolone, was slowly released from the 21-hemisuccinate with a half life of 69 h in pH 7.0 at 37 degrees C; the drug release at 25 degrees C was less than 10% for 48 h. In sharp contrast, the hydrolysis of prednisolone 21-hemisuccinate/beta-CyD amide conjugate was significantly faster (half life of 6.50 min at 25 degrees C) and gave prednisolone and mono(6-deoxy-6-succimino)-beta-CyD as products. The hydrolysis of the beta-CyD amide conjugate was subject to a specific-base catalysis in the alkaline region. The rapid hydrolysis of the conjugate can be ascribed to the involvement of an intramolecular nucleophilic catalysis of the amide group in the reaction. The succinic acid, bound to a drug through ester linkage at one carboxylic group and bound to a pro-moiety through amide linkage at another carboxylic group, may be useful as a spacer for construction of the immediate release type prodrugs of CyDs.