Mode of action on deacetylation of acetylated methyl glycoside by cellulose acetate esterase from Neisseria sicca SB

The regioselective deacetylation of purified cellulose acetate esterase from Neisseria sicca SB was investigated on methyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside and 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside. The substrates were used as model compounds of cellulose acetate in order to estimate the mechanism for deacetylation of cellulose acetate by the enzyme. The enzyme rapidly deacetylated at position C-3 of methyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside to accumulate 2,4,6-triacetate as the main initial reaction product in about 70% yield. Deacetylation was followed at position C-2, and generated 4,6-diacetate in 50% yield. The enzyme deacetylated the product at positions C-4 and C-6 at slower rates, and generated 4- and 6-monoacetates at a later reaction stage. Finally, it gave a completely deacetylated product. For 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranoside, CA esterase deacetylated at positions C-3 and C-6 to give 2,4,6- and 2,3,4-triacetate. Deacetylation proceeded sequentially at positions C-3 and C-6 to accumulate 2,4-diacetate in 55% yield. The enzyme exhibited regioselectivity for the deacetylation of the acetylglycoside.     

Hypoxic stress enhances osteoclast differentiation via increasing IGF2 production by non-osteoclastic cells

Development of bone depends on a continuous supply of bone-degrading osteoclasts. Although several factors such as cytokines and integrins have been shown to be important for osteoclast recruitment, their mechanism of action is poorly understood. In this study, we demonstrated the enhancement of osteoclast formation by hypoxia and investigated the molecular mechanisms involved. Primary mouse bone marrow cells were cultured in normoxic and hypoxic conditions, and RNA was prepared from each group of cells. Total RNAs were applied to a DNA microarray analysis and then RT-PCR was performed to confirm the microarray data. The most interesting finding of our microarray analysis was upregulation of insulin-like growth factor 2 (IGF2) and stromal cell-derived factor 1 (SDF1) under hypoxic conditions. RT-PCR analysis revealed that IGF2 expression was markedly upregulated in the non-osteoclastic cells. The addition of exogenous IGF2 increased the number of osteoclastic TRAP-positive multinuclear cells formed under normoxic conditions, whereas the addition of exogenous SDF1 did not change osteoclast formation. These results suggest that the upregulation of IGF2 derived from non-osteoclastic cells might be a crucial factor for osteoclast differentiation.     

Sphingosine 1-phosphate inhibits migration and RANTES production in human bronchial smooth muscle cells

Sphingosine 1-phosphate (S1P), a bioactive lipid mediator, has been shown to be increased in bronchoalveolar lavage fluid after allergen challenge in asthmatic patients. Here, we examined S1P actions and their intracellular signalings in cultured human bronchial smooth muscle cells (BSMCs). Expression of mRNAs of three subtypes of S1P receptors, including S1P(1), S1P(2), and S1P(3), was detected in BSMCs, and exposure of the cells to S1P inhibited platelet-derived growth factor (PDGF)-induced migration and tumor necrosis factor-alpha-induced RANTES production. S1P also inhibited PDGF-induced Rac1 activation, and dominant negative Rac1 inhibited PDGF-induced migration. On the other hand, dominant negative Galpha(q) attenuated the S1P-induced inhibition of RANTES production. Finally, an S1P(2)-selective antagonist, JTE-013, suppressed the S1P-induced inhibition of migration response and RANTES production. These results suggest that S1P attenuates cell migration by inhibiting a Rac1-dependent signaling pathway and decreases RANTES production by stimulating a Galpha(q)-dependent mechanism both possibly through the S1P(2) receptors.     

Antinociceptive effect of 7-hydroxymitragynine in mice: Discovery of an orally active opioid analgesic from the Thai medicinal herb Mitragyna speciosa

Mitragynine is an indole alkaloid isolated from the Thai medicinal plant Mitragyna speciosa. We previously reported the morphine-like action of mitragynine and its related compounds in the in vitro assays. In the present study, we investigated the opioid effects of 7-hydroxymitragynine, which is isolated as its novel constituent, on contraction of isolated ileum, binding of the specific ligands to opioid receptors and nociceptive stimuli in mice. In guinea-pig ileum, 7-hydroxymitragynine inhibited electrically induced contraction through the opioid receptors. Receptor-binding assays revealed that 7-hydroxymitragynine has a higher affinity for micro-opioid receptors relative to the other opioid receptors. Administration of 7-hydroxymitragynine (2.5-10 mg/kg, s.c.) induced dose-dependent antinociceptive effects in tail-flick and hot-plate tests in mice. Its effect was more potent than that of morphine in both tests. When orally administered, 7-hydroxymitragynine (5-10 mg/kg) showed potent antinociceptive activities in tail-flick and hot-plate tests. In contrast, only weak antinociception was observed in the case of oral administration of morphine at a dose of 20 mg/kg. It was found that 7-hydroxymitragynine is a novel opioid agonist that is structurally different from the other opioid agonists, and has potent analgesic activity when orally administered.     

Different In Vivo Effects of HIV-1 Immunodominant Epitope-Specific Cytotoxic T Lymphocytes on Selection of Escape Mutant Viruses

HIV-1 escape mutants are well known to be selected by immune pressure via HIV-1-specific cytotoxic T lymphocytes (CTLs) and neutralizing antibodies. The ability of the CTLs to suppress HIV-1 replication is assumed to be associated with the selection of escape mutants from the CTLs. Therefore, we first investigated the correlation between the ability of HLA-A*1101-restricted CTLs recognizing immunodominant epitopes in vitro and the selection of escape mutants. The result showed that there was no correlation between the ability of these CTLs to suppress HIV-1 replication in vitro and the appearance of escape mutants. The CTLs that had a strong ability to suppress HIV-1 replication in vitro but failed to select escape mutants expressed a higher level of PD-1 in vivo, whereas those that had a strong ability to suppress HIV-1 replication in vitro and selected escape mutants expressed a low level of PD-1. Ex vivo analysis of these CTLs revealed that the latter CTLs had a significantly stronger ability to recognize the epitope than the former ones. These results suggest that escape mutations are selected by HIV-1-specific CTLs that have a stronger ability to recognize HIV-1 in vivo but not in vitro.HIV-1-specific cytotoxic T lymphocytes (CTLs) have an important role in the control of HIV-1 replication during acute and chronic phases of an HIV-1 infection (5, 28, 33). On the other hand, HIV-1 can escape from the host immune system by various mechanisms. These may include the appearance of HIV-1 carrying escape mutations in its immunodominant CTL epitopes as well as Nef-mediated downregulation of HLA class I molecules. There is a growing body of evidence for the former mechanism, i.e., that CTLs targeting immunodominant HIV-1 epitopes select escape mutants in chronically HIV-1-infected individuals (18, 20, 36), whereas the latter mechanism was proved by demonstrating that HIV-1-specific CTLs fail to kill Nef-positive-HIV-1-infected CD4⁺ T cells but effectively kill Nef-defective-HIV-1-infected ones or that they suppress the replication of Nef-defective HIV-1 much more than that of Nef-positive HIV-1 (12, 13, 42, 45).It is speculated that HIV-1 immunodominant epitope-specific CTLs have the ability to suppress HIV-1 replication and effectively select escape mutants. However, the correlation between this ability of the CTLs and the appearance of escape mutants is still unclear, because it is not easy to evaluate the ability of HIV-1-specific CTLs to exert a strong immune pressure in vivo. To examine this ability, most previous studies measured the number of HIV-1-specific CTLs or CD8⁺ T cells and the CTL activity against target cells prepulsed with the epitope peptide or those infected with HIV-1 recombinant vaccinia virus (6, 7, 23, 46). However, the results obtained from such experiments do not reflect the ability of the CTLs to exert immune pressure in vivo. We and other groups previously utilized an assay to directly evaluate the ability of the CTLs to suppress HIV-1 replication in vitro (1, 17, 18, 42, 43). This assay may be better for evaluation of immune pressure by HIV-1-specific CTLs than other assays, because the ability of the CTLs to suppress HIV-1 replication is directly measured in cultures of HIV-1-infected CD4⁺ T cells incubated with HIV-1-specific CTL clones. But it still remains unknown whether this assay reflects immune pressure in vivo.In the present study, we investigated whether HIV-1-specific CTLs having a strong ability to suppress HIV-1 replication could positively select escape mutants. Since HLA-A*1101 is known to be an HLA allele relatively associated with a slow progression to AIDS (32), it is speculated that some HLA-A*1101-restricted CTLs would have a strong ability to suppress HIV-1 replication in vitro. Therefore, we first focused on 4 well-known HLA-A*1101-restricted CTL epitopes in the present study. We investigated the frequency of CTLs specific for these epitopes in chronically HIV-1-infected individuals, the ability of these CTLs to suppress HIV-1 replication in vitro, and whether the escape mutants were selected by the CTLs. Furthermore, we analyzed the expression of Programmed Death-1 (PD-1) on these CTLs ex vivo and antigen recognition of them.     

Chirality of camphor derivatives by density functional theory

Infrared (IR) and vibrational circular dichroism (VCD) spectra of chiral camphor, camphorquinone and camphor-10-sulfonic acid (CSA), known as standard compounds for electronic circular dichroism (ECD) spectroscopy, are measured and their vibrational frequencies, infrared intensities, and rotational strengths are calculated using density functional theory (DFT). The observed IR and VCD spectra of chiral camphor and camphorquinone in carbon tetrachloride solution are reproduced by the DFT calculations, but those of CSA are not. DFT calculations of hydration models, where an anionic CSA specifically binds a few water molecules, are carried out. The average of the simulated VCD spectra in the hydration models is more consistent with the observed spectra. In addition, the wavelengths and dipole and rotational strengths for chiral camphor, camphorquinone, anionic CSA, and the hydration models were calculated by time-dependent DFT. In the region of 280-300 nm, the calculated wavelengths of the ECD bands for chiral camphor and camphorquinone coincide with the observed wavelengths that have been reported, and the calculated wavelengths for the hydration models are closer to the observed wavelengths reported than are those calculated for chiral anionic CSA. Consequently, the analysis combined with VCD and ECD spectroscopy using DFT calculations can elucidate the chirality of optically active molecules, even in an aqueous solution.     

Ordered assembly of Sld3, GINS and Cdc45 is distinctly regulated by DDK and CDK for activation of replication origins

Initiation of chromosome DNA replication in eukaryotes is tightly regulated through assembly of replication factors at replication origins. Here, we investigated dependence of the assembly of the initiation complex on particular factors using temperature-sensitive fission yeast mutants. The psf3-1 mutant, a GINS component mutant, arrested with unreplicated DNA at the restrictive temperature and the DNA content gradually increased, suggesting a defect in DNA replication. The mutation impaired GINS complex formation, as shown by pull-down experiments. Chromatin immunoprecipitation assays indicated that GINS integrity was required for origin loading of Psf2, Cut5 and Cdc45, but not Sld3. In contrast, loading of Psf2 onto origins depended on Sld3 and Cut5 but not on Cdc45. These results suggest that Sld3 functions furthest upstream in initiation complex assembly, followed by GINS and Cut5, then Cdc45. Consistent with this conclusion, Cdc7-Dbf4 kinase (DDK) but not cyclin-dependent kinase (CDK) was required for Sld3 loading, whereas recruitment of the other factors depended on both kinases. These results suggest that DDK and CDK regulate distinct steps in activation of replication origins in fission yeast.     

Capacity of dental pulp differentiation after tooth transplantation

Under pathological conditions, dental pulp elaborates both bone and dentin matrix in which the contribution of periodontal tissue cannot be excluded. This study has aimed to clarify the capability of dental pulp to deposit bone matrix in an auto-graft experiment by using (1) immunohistochemistry for 5-bromo-2′-deoxyuridine (BrdU) and nestin and (2) histochemistry for tartrate-resistant acid phosphatase (TRAP). Following the extraction of the molars of 3-week-old mice, the roots and pulp floor were resected and immediately transplanted into the sublingual region. On Days 5–7, tubular dentin formation commenced next to the pre-existing dentin at the pulp horn in which nestin-positive odontoblast-like cells were arranged. Up until Day 14, bone-like tissue formation occurred in the pulp chamber in which intense TRAP-positive cells appeared. These results suggest that odontoblast- and osteoblast-lineage cells reside in the dental pulp. Overall, specific dental pulp regeneration should provide fundamental knowledge for the realization of human tooth regeneration in the near future.This work was supported in part by a grant from MEXT to promote the 2001-multidisciplinary research project (in 2001–2005), KAKENHI (B) (no. 16390523 to H.O.) from MEXT, and the Japan-Korea Joint Research Project from JSPS and KOSEF (no. F01-2005-000-10212-0).     

Profile of rhythmic gene expression in the livers of obese diabetic KK-A(y) mice

Although a number of genes expressed in most tissues, including the liver, exhibit circadian regulation, gene expression profiles are usually examined only at one scheduled time each day. In this study, we investigated the effects of obese diabetes on the hepatic mRNA levels of various genes at 6-h intervals over a single 24-h period. Microarray analysis revealed that many genes are expressed rhythmically, not only in control KK mice but also in obese diabetic KK-A(y) mice. Real-time quantitative PCR verified that 19 of 23 putative circadianly expressed genes showed significant 24-h rhythmicity in both strains. However, obese diabetes attenuated these expression rhythms in 10 of 19 genes. More importantly, the effects of obese diabetes were observed throughout the day in only two genes. These results suggest that observation time influences the results of gene expression analyses of genes expressed circadianly.