Analysis of the susceptibility of reducing disaccharides composed of d-glucose to glycation using the Maillard reaction and a novel sensitive method that measures the percentage of the open-ring form.

The susceptibility to glycation of all d-glucose-containing reducing disaccharides (kojibiose, sophorose, nigerose, laminaribiose, maltose, cellobiose, isomaltose, and gentiobiose) was evaluated by Maillard browning and the percentages of their acyclic forms estimated using a novel method to evaluate reactivity toward oxime formation were compared for the first time. This new method is facile and applicable to non-labeled carbohydrates, and it is extremely sensitive, more so than any other previously reported methods. The disaccharides linked by 1-6 bonds displayed both high browning intensity and oxime formation reactivity, and they had the greatest amount of the acyclic form. On the other hand, the proportion of acyclic form was generally very low when glucoses were linked by 1-2, 1-3 and 1-4 bonds. The stability of the 1-3 linkage was drastically reduced when basicity was increased due to ß-elimination and the production of a highly reactive dehydrated hexose. The 1-4-linked structures, involved in the formation of amylose and cellulose, respectively, were found to be advantageous due to their relatively low susceptibility to glycation.

Synthesis and evaluation of anti-tubercular activity of new dithiocarbamate sugar derivatives.

The present study was undertaken to optimize the anti-tubercular activity of 2-acetamido-2-deoxy-ß-D-glucopyranosyl N,N-dimethyldithiocarbamate (OCT313, Glc-NAc-DMDC), a lead compound previously reported by us. Structural modifications of OCT313 included the replacements of the DMDC group at C-1 by pyrrolidine dithiocarbamate (PDTC) and the acetyl group at C-2 by either propyl, butyl, benzyl or oleic acid groups. The antimycobacterial activities of these derivatives were evaluated against Mycobacterium tuberculosis (MTB). Glc-NAc-pyrrolidine dithiocarbamate (OCT313HK, Glc-NAc-PDTC) exhibited the most potent anti-tubercular activity with the minimal inhibitory concentration (MIC) of 6.25-12.5 µg/ml. The antibacterial activity of OCT313HK was highly specific to MTB and Mycobacterium bovis BCG, but not against Mycobacterium avium, Mycobacterium smegmatis, Staphylococcus aureus or Escherichia coli. Importantly, OCT313HK was also effective against MTB clinical isolates, including multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains. Interestingly, OCT313HK was exerted the primary bactericidal activity, and it was also exhibited the bacteriolytic activity at high concentrations. We next investigated whether the mycobacterial monooxygenase EthA, a common activator of thiocarbamide-containing anti-tubercular drugs, also activated OCT313HK. Contrary to our expectations, the anti-tubercular activity of dithiocarbamate sugar derivatives and dithiocarbamates were not dependent on ethA expression, in contrast to thiocarbamide-containing drugs. Overall, this study presents OCT313HK as a novel and potent compound against MTB, particularly promising to overcome drug resistance.

Synthesis of new sugar derivatives and evaluation of their antibacterial activities against Mycobacterium tuberculosis.

A series of sugar derivatives (1-13) were synthesized and evaluated for antibacterial activity against Mycobacteriumtuberculosis (MTB), especially multi-drug resistant (MDR) MTB, and the structure-activity relationships of these compounds were studied. The results showed that the compound OCT313 (2-acetamido-2deoxy-beta-D-glucopyranosyl N,N-dimethyldithiocarbamate) (4) exhibited significant in vitro bactericidal activity, and that the dithiocarbamate group at C-1 position of the glucopyranoside ring was requisite for the antibacterial activity.

Comparable studies of immunostimulating activities in vitro among Mycobacterium bovis bacillus Calmette-Guérin (BCG) substrains.

During the serial passage of Mycobacterium bovis bacillus Calmette-Guérin (BCG) in different countries after initial seed distribution from the Pasteur Institute, specific insertions and deletions in the genome among BCG substrains were observed and speculated to result in differences in immunological activities. 'Early-shared strains' of BCG (Russia, Moreau, Japan, Sweden, Birkhaug), distributed by the Pasteur Institute, which conserve three types of mycolate (alpha, methoxy, keto) in cell wall, exhibited stronger activities of induction of nitric oxide, interleukin-1beta (IL-1beta), IL-6, IL-8, IL-12 and tumor necrosis factor (TNF)-alpha, from human epithelial cell line A549, human myelomonocytic cell line THP-1 and mouse bone marrow cells in the presence of interferon-gamma (IFN-gamma) than did 'late-shared strains' of BCG (Danish, Glaxo, Mexico, Tice, Connaught, Montreal, Phipps, Australia, Pasteur). The stronger induction of IL-12 and TNF-alpha in the presence of IFN-gamma was also observed by trehalose 6,6'-dimycolate (TDM) extracted from BCG-Japan than by TDM from BCG-Connaught, which lacks the methoxymycolate residue. These results suggest that 'early-shared strains' are more potent immunostimulating agents than 'late-shared strains', which could be attributed partially to methoxymycolate. Our study provides the basic information for immunological characterization of various BCG strains and may contribute to a re-evaluation of them as a reference strain for vaccination against tuberculosis.

Synthesis of new sugar derivatives from Stachys sieboldi Miq and antibacterial evaluation against Mycobacterium tuberculosis, Mycobacterium avium, and Staphylococcus aureus.

A series of sugar derivatives (7-14) were synthesized from stachyose, a sugar compound of Stachys sieboldi Miq, and evaluated for antibacterial activity against Mycobacterium tuberculosis, Mycobacterium avium, and Staphylococcus aureus, and their structure-activity relationships were studied. The results showed that the compound OCT359 (allyl O-(2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl)-(1-->6)-O-(2,3,4-tri-O-acetyl-alpha-D-galactopyranosyl)-(1-->6)-O-2,3,4-tri-O-acetyl-beta-D-glucopyranoside) (12) exhibited in vitro antibacterial activity. The allyl group at C-1 and the acetoxy groups of the manninotrioside were requisite for the antibacterial activity.

N-acetylneuraminic acid coupled human recombinant TNFalpha exhibits enhanced anti-tumor activity against Meth-A fibrosarcoma and reduced toxicity.

In order to study the effect of glycosylation on its biological activities and to develop tumor necrosis factor alpha (TNFalpha) with less deleterious effects, N-acetylneuraminic acid (NeuAc) with a C9 spacer was chemically coupled to human recombinant TNFalpha. NeuAc-coupled TNFalpha (NeuAc-TNFalpha) exhibited reduced activities in vitro by about threefold compared to native TNFalpha. In this study, we examined a variety of TNFalpha activities in vivo. NeuAc-TNFalpha reduced activities in the up-regulation of serum levels of IL-6 and NOx, but comparable activity as native TNFalpha in the down-regulation of the serum level of glucose. However, NeuAc-TNFalpha was more potent than TNFalpha in the up-regulation of the serum level of serum amyloid A (SAA). NeuAc-TNFalpha was less toxic to mice. In addition, NeuAc-TNFalpha exhibited an augmented anti-tumor activity against Meth-A fibrosarcoma without hemorrhagic necrosis. These results indicate that coupling with NeuAc enabled us to develop neoglycoTNFalpha with selective activities in vivo, including enhanced anti-tumor activity but reduced toxicity.

Synthesis of glycosylated human tumor necrosis factor alpha coupled with N-acetylneuraminic acid.

In order to study the effect of glycosylation on its biological activities, and to develop TNFalpha with less deleterious effects, recombinant human TNFalpha was chemically coupled with N-acetylneuraminic acid (NeuAc). NeuAc with C9 spacer was coupled to TNFalpha by acyl azide method. Two glycosylated TNFalphas, designated L NeuAc-TNFalpha and H NeuAc-TNFalpha, were purified by anion-exchange chromatography. NeuAc coupling to TNFalpha was confirmed by lectin blotting. Average number of carbohydrate molecules introduced per molecule of L NeuAc-TNFalpha and H NeuAc-TNFalpha were estimated to be 1.0 and 1.5, respectively. We examined a variety of TNFalpha activities in vitro, including antiproliferative or cytotoxic activities to tumor cells, proliferative effect on fibroblast cells, stimulatory effects on IL-6 production by melanoma cells and NF-kappaB activation in hepatoma cells. L NeuAc-TNFalpha and H NeuAc-TNFalpha exhibited reduced activities about 1/3 and 1/10 as compared to native TNFalpha in all the activities performed in vitro.

Protective effects of EGCg or GCg, a green tea catechin epimer, against postischemic myocardial dysfunction in guinea-pig hearts.

The protective effects of (-)-epigallocatechin-3-gallate (EGCg) or the C-2 epimer, (-)-gallocatechin-3-gallate (GCg), afforded by their antioxidative activity among green tea catechins were investigated in perfused guinea-pig Langendorff hearts subjected to ischemia and reperfusion. The recovery (%) of the left ventricular developed pressure from ischemia by reperfusion was 34.4% in the control, while in the presence of EGCg (3x10(-5) M) or GCg (3x10(-6) M, a more diluted concentration than that of EGCg), it led to a maximal increase of 78.4% or 76.2%, consistent with a significant preservative effect on the tissue level of ATP at the end of ischemia or reperfusion. In the perfused preparation of mitochondria, EGCg (10(-5) M) inhibited mitochondrial Ca(2+) elevation by changes in the Ca(2+) content or the acidification of perfusate, similarly to findings with cyclosporin A, a well known inhibitor of the mitochondrial permeability transition pore. By in vitro electron paramagnetic resonance (EPR), EGCg or GCg was found to directly quench the activity of active oxygen radicals, with the strongest activity in tea catechins. EGCg or GCg decreased the caspase-3 activity induced apoptosis. Therefore, it is concluded that the beneficial effects of EGCg or GCg play an important role in ischemia-reperfusion hearts in close relation with nitric oxide (NO), active oxygen radicals and biological redox systems in mitochondria.

Decline in glucokinase activity in the arcuate nucleus of streptozotocin-induced diabetic rats.

Glucokinase (GK) is known to be the critical glucose sensor of pancreatic B-cells. However, the localization and functional role of GK in the brain remains to be elucidated. In this study, we measured both the activity and mRNA level of GK in the hypothalamic nuclei and the cortex of rats injected intraperitoneally with streptozotocin or vehicle. GK activity was measured by a fluorometric assay; and the GK mRNA level, by use of the real-time reverse transcription polymerase chain reaction. GK activity in vehicle-treated rats was high in the arcuate nucleus, moderate or low in the ventromedial nucleus, lateral hypothalamic area, and paraventricular nucleus, and very low in the cortex. The order of GK mRNA level was almost the same as that of GK activity. GK activity and GK mRNA level only in the arcuate nucleus of streptozotocin-treated rats at 7 d, but not at 2 d, after treatment were lower than those of vehicle-treated rats. The results suggest that prolonged hyperglycemia induced by diabetes decreased the activity of GK in the arcuate nucleus.

Synthesis and biological activities in vitro and in vivo of glycosylated human interleukin-1alpha, neoglyco IL-1alpha, coupled with N -acetylneuraminyl-galactose.

In order to study the effect of glycosylation on its biological activities, and to develop IL-1alpha with less deleterious effects, recombinant human IL-1alpha was chemically coupled with N -acetylneuraminic acid (alpha1-6) galactose (Neu5Ac-Gal). Glycosylated IL-1alpha (Neu5Ac-Gal-IL-1alpha) was purified by anion-exchange chromatography and average number of carbohydrate molecules introduced per molecule of IL-1alpha was 2.5. Neu5Ac-Gal-IL-1alpha exhibited reduced activities about 1/15-fold compared to IL-1alpha in all the activities performed in vitro. Binding affinities of Neu5Ac-Gal-IL-1alpha to Type I and Type II IL-1 receptors were decreased to 1/15 and 1/10, respectively. Neu5Ac-Gal-IL-1alpha exhibited reduction in activities in vivo, including induction of serum amyloid A and NOx, and down-regulation of serum glucose. However, Neu5Ac-Gal-IL-1alpha exhibited comparable activity to IL-1alpha in improvement of the recovery of peripheral white blood cells from myelosuppression in 5-fluorouracil-treated mice. In addition, tissue level of Neu5Ac-Gal-IL-1alpha was relatively high compared to IL-1alpha. These results indicate that coupling with Neu5Ac-Gal enabled us to develop neoIL-1alpha with selective activities in vivo.

Multiple mechanisms involved in the inhibition of proinflammatory cytokine production from human monocytes by N-(p-coumaroyl)serotonin and its derivatives.

We have reported that N-(p-coumaroyl)serotonin(CS) isolated from safflower oil cake (Carthamus tinctorius L.) inhibits the production of proinflammatory cytokines by endotoxin (LPS)- stimulated human monocytes. In this study, the effects of CS and its three derivatives, N-(trans-cinnamoyl)serotonin (Cin.S), N-(trans-cinnamoyl)tryptamine (Cin.T), and N-(p-coumaroyl)tryptamine (CT) on the production of proinflammatory cytokines were compared. Cin.S possessed radical scavenging activity at a comparable level to CS, while CT and Cin.T exhibited lower activity, suggesting that hydroxyl group in serotonin is essential for the antioxidative activity. CS and CT strongly inhibited the production of proinflammatory cytokines (IL-1alpha, IL-1beta, IL-6, IL-8, and TNF-alpha) from LPS-stimulated human monocytes. However, Cin.S inhibited the production of only IL-1alpha and IL-1beta, and Cin.T inhibited none of these cytokines production. CS and CT markedly inhibited the protein synthesis in monocytes, the inhibitory effect of Cin.S was moderate, and that of Cin.T was quite weak. These results indicate that CS and its derivatives inhibit the production of proinflammatory cytokines through multiple mechanisms.

Simple fibroblast-based assay for screening of new antimicrobial drugs against Mycobacterium tuberculosis.

In this study, we propose a simple and reproducible host-cell-based assay for the screening of antimycobacterial drugs that is suitable for drug discovery. The method evaluates both antimycobacterial activity of the drugs and their cytotoxicity to host cells. The basis of this simple fibroblast-based assay (SFA) is that cells of human lung fibroblast cell line MRC-5, which are highly sensitive to mycobacterial cytotoxicity, are killed by virulent Mycobacterium tuberculosis strain H(37)Rv bacilli in response to the viability of bacilli. Clinically used antimycobacterial drugs inhibited the mycobacterial cytotoxicity to MRC-5 cells in a dose-dependent manner. MICs of isoniazid, streptomycin, rifampin, and ethambutol determined by this SFA (0.428, 1.816, 0.013, and 3.465 microg/ml, respectively) were within 1 log of MICs determined by the broth dilution test (BDT) using Middlebrook 7H9 medium. The MIC of pyrazinamide, which exhibits bactericidal activity only at a high dose by BDT (1,231 microg/ml at pH 6.6 and 492 microg/ml at pH 5.8), was 3.847 microg/ml in the modified method of SFA. On the other hand, sodium azide, a toxic agent for both mammalian cells and bacteria, exhibited cytotoxicity to fibroblasts at a dose lower than that required to inhibit mycobacterial growth. Thus, this fibroblast-based method enabled us to evaluate both antibacterial activity of drugs and their cytotoxicity to human cells within a short period of time.