Acute toxic effects of diclofenac exposure on freshwater crayfish (Procambarus clarkii): Insights from hepatopancreatic pathology, molecular regulation and intestinal microbiota

In this study, we exposed adult male crayfish (Procambarus clarkii) to different concentrations of diclofenac (DCF) for 96 h. In the meantime, we investigated the alternations of hepatopancreatic pathology, molecular regulation and intestinal microbiota of P. clarkii exposed to DCF. The results demonstrated DCF led to histological changes including epithelium vacuolization and tubule lumen dilatation in the hepatopancreas. Transcriptome sequencing analysis showed that 642 and 586 genes were differentially expressed in the hepatopancreas of P. clarkii exposed to 1 and 10 mg/L DCF, respectively. DCF could affect the functions of antioxidation, immunity and metabolism of hepatopancreas by inducing the abnormal expressions of immune- and redox-related genes. GO enrichment results demonstrated that 10 mg/L DCF exposure could modulate the processes of molting, amino sugar metabolism, protein hydrolysis and intracellular protein translocation of P. clarkii. Additionally, the abundances of bacterial families including Shewanellaceae, Bacteroidaceae, Vibrionaceae, Erysipelotrichaceae, Aeromonadaceae, Moraxellaceae, etc. in the intestine were significantly changed after DCF exposure, and the disruption of intestinal flora might further cause abnormal intestinal metabolism in P. clarkii. This study provides novel mechanistic insights into the toxic effects of anti-inflammatory drugs on aquatic crustaceans.

Targeting 3CLpro and SARS-CoV-2 RdRp by Amphimedon sp. Metabolites: A Computational Study

Since December 2019, novel coronavirus disease 2019 (COVID-19) pandemic has caused tremendous economic loss and serious health problems worldwide. In this study, we investigated 14 natural compounds isolated from Amphimedon sp. via a molecular docking study, to examine their ability to act as anti-COVID-19 agents. Moreover, the pharmacokinetic properties of the most promising compounds were studied. The docking study showed that virtually screened compounds were effective against the new coronavirus via dual inhibition of SARS-CoV-2 RdRp and the 3CL main protease. In particular, nakinadine B (1), 20-hepacosenoic acid (11) and amphimedoside C (12) were the most promising compounds, as they demonstrated good interactions with the pockets of both enzymes. Based on the analysis of the molecular docking results, compounds 1 and 12 were selected for molecular dynamics simulation studies. Our results showed Amphimedon sp. to be a rich source for anti-COVID-19 metabolites.

Lacto-N-fucopentaose-III ameliorates acute and persisting hippocampal synaptic plasticity and transmission deficits in a Gulf War Illness mouse model

AIMS

The present study investigated if treatment with the immunotherapeutic, lacto-N-fucopentaose-III (LNFPIII), resulted in amelioration of acute and persisting deficits in synaptic plasticity and transmission as well as trophic factor expression along the hippocampal dorsoventral axis in a mouse model of Gulf War Illness (GWI).

MAIN METHODS

Mice received either coadministered or delayed LNFPIII treatment throughout or following, respectively, exposure to a 15-day GWI induction paradigm. Subsets of animals were subsequently sacrificed 48 h, seven months, or 11 months post GWI-related (GWIR) exposure for hippocampal qPCR or in vitro electrophysiology experiments.

KEY FINDINGS

Progressively worsened impairments in hippocampal synaptic plasticity, as well as a biphasic effect on hippocampal synaptic transmission, were detected in GWIR-exposed animals. Dorsoventral-specific impairments in hippocampal synaptic responses became more pronounced over time, particularly in the dorsal hippocampus. Notably, delayed LNFPIII treatment ameliorated GWI-related aberrations in hippocampal synaptic plasticity and transmission seven and 11 months post-exposure, an effect that was consistent with enhanced hippocampal trophic factor expression and absence of increased interleukin 6 (IL-6) in animals treated with LNFPIII.

SIGNIFICANCE

Approximately a third of Gulf War Veterans have GWI; however, GWI therapeutics are presently limited to targeted and symptomatic treatments. As increasing evidence underscores the substantial role of persisting neuroimmune dysfunction in GWI, efficacious neuroactive immunotherapeutics hold substantial promise in yielding GWI remission. The findings in the present report indicate that LNFPIII may be an efficacious candidate for ameliorating persisting neurological abnormalities presented in GWI.

A Comparison of Two Structurally Related Human Milk Oligosaccharide Conjugates in a Model of Diet-Induced Obesity

Obesity is the largest risk factor for the development of chronic diseases in industrialized countries. Excessive fat accumulation triggers a state of chronic low-grade inflammation to the detriment of numerous organs. To address this problem, our lab has been examining the anti-inflammatory mechanisms of two human milk oligosaccharides (HMOs), lacto-N-fucopentaose III (LNFPIII) and lacto-N-neotetraose (LNnT). LNFPIII and LNnT are HMOs that differ in structure via presence/absence of an α1,3-linked fucose. We utilize LNFPIII and LNnT in conjugate form, where 10-12 molecules of LNFPIII or LNnT are conjugated to a 40 kDa dextran carrier (P3DEX/NTDEX). Previous studies from our lab have shown that LNFPIII conjugates are anti-inflammatory, act on multiple cell types, and are therapeutic in a wide range of murine inflammatory disease models. The α1,3-linked fucose residue on LNFPIII makes it difficult and more expensive to synthesize. Therefore, we asked if LNnT conjugates induced similar therapeutic effects to LNFPIII. Herein, we compare the therapeutic effects of P3DEX and NTDEX in a model of diet-induced obesity (DIO). Male C57BL/6 mice were placed on a high-fat diet for six weeks and then injected twice per week for eight weeks with 25µg of 40 kDa dextran (DEX; vehicle control), P3DEX, or NTDEX. We found that treatment with P3DEX, but not NTDEX, led to reductions in body weight, adipose tissue (AT) weights, and fasting blood glucose levels. Mice treated with P3DEX also demonstrated improvements in glucose homeostasis and insulin tolerance. Treatment with P3DEX or NTDEX also induced different profiles of serum chemokines, cytokines, adipokines, and incretin hormones, with P3DEX notably reducing circulating levels of leptin and resistin. P3DEX also reduced WAT inflammation and hepatic lipid accumulation, whereas NTDEX seemed to worsen these parameters. These results suggest that the small structural difference between P3DEX and NTDEX has significant effects on the conjugates' therapeutic abilities. Future work will focus on identifying the receptors for these conjugates and delineating the mechanisms by which P3DEX and NTDEX exert their effects.

Galectin-3 mediates cardiac remodeling caused by impaired glucose and lipid metabolism through inhibiting two pathways of activating Akt

Pathological cardiac remodeling is a leading cause of mortality in patients with diabetes. Given the glucose and lipid metabolism disorders (GLDs) in patients with diabetes, it is urgent to conduct a comprehensive study of the myocardial damage under GLDs and find key mechanisms. Apolipoprotein E knockout (ApoE-/-) mice, low-density lipoprotein receptor heterozygote (Ldlr+/-) Syrian golden hamsters, or H9C2 cells were used to construct GLDs models. GLDs significantly promoted cardiomyocyte fibrosis, apoptosis, and hypertrophy in vivo and in vitro, but inhibition of galectin-3 (Gal-3) could significantly reverse this process. Then, the signal transmission pathways were determined. It was found that GLDs considerably inhibited the phosphorylation of Akt at Thr308/Ser473, whereas the silencing of Gal-3 could reverse the inhibition of Akt activity through phosphoinositide 3-kinase-AktThr308 (PI3K-AktThr308) and AMP-activated protein kinase-mammalian target of rapamycin complex 2-AktSer473 (AMPK-mTOR2-AktSer473) pathways. Finally, the PI3K, mTOR, AMPK inhibitor, and Akt activator were used to investigate the role of pathways in regulating cardiac remodeling. Phospho-AktThr308 could mediate myocardial fibrosis, whereas myocardial apoptosis and hypertrophy were regulated by both phospho-AktThr308 and phospho-AktSer473. In conclusion, Gal-3 was an important regulatory factor in GLDs-induced cardiac remodeling, and Gal-3 could suppress the phosphorylation of Akt at different sites in mediating cardiomyocyte fibrosis, apoptosis, and hypertrophy.NEW & NOTEWORTHY Studies on the pathogenesis of diabetic cardiac remodeling are highly desired. Glucose and lipid metabolism are both disordered in diabetes. Glucose and lipid metabolism disturbances promote myocardial fibrosis, apoptosis, and hypertrophy through galectin-3. Galectin-3 promotes cardiac remodeling by inhibiting phosphorylation of AktThr308 or AktSer473. The present study finds that glucose and lipid metabolism disorders are important causes for myocardial damage and provides novel ideas for the prevention and treatment of diabetic cardiac remodeling.

Selective Toll-Like Receptor 4 Antagonists Prevent Acute Blood-Brain Barrier Disruption After Subarachnoid Hemorrhage in Mice

There are no direct evidences showing the linkage between Toll-like receptor 4 (TLR4) and blood-brain barrier (BBB) disruption after subarachnoid hemorrhage (SAH). The purpose of this study was to examine if selective blockage of TLR4 prevents BBB disruption after SAH in mice and if the TLR4 signaling involves mitogen-activated protein kinases (MAPKs). One hundred and fifty-one C57BL/6 male mice underwent sham or endovascular perforation SAH operation, randomly followed by an intracerebroventricular infusion of vehicle or two dosages (117 or 585 ng) of a selective TLR4 antagonist IAXO-102 at 30 min post-operation. The effects were evaluated by survival rates, neurological scores, and brain water content at 24-72 h and immunoglobulin G immunostaining and Western blotting at 24 h post-SAH. IAXO-102 significantly prevented post-SAH neurological impairments, brain edema, and BBB disruption, resulting in improved survival rates. IAXO-102 also significantly suppressed post-SAH activation of a major isoform of MAPK p46 c-Jun N-terminal kinase (JNK) and matrix metalloproteinase-9 as well as periostin induction and preserved tight junction protein zona occludens-1. Another selective TLR4 antagonist TAK-242, which has a different binding site from IAXO-102, also showed similar effects to IAXO-102. This study first provided the evidence that TLR4 signaling is involved in post-SAH acute BBB disruption and that the signaling is mediated at least partly by JNK activation. TLR4-targeted therapy may be promising to reduce post-SAH morbidities and mortalities.

Importance of prumycin produced by Bacillus amyloliquefaciens SD-32 in biocontrol against cucumber powdery mildew disease

BACKGROUND

Powdery mildew disease of cucurbits is caused mainly by Podosphaera fusca, which is one of the most important limiting factors in cucurbit production worldwide. Previously we reported that Bacillus amyloliquefaciens biocontrol strain SD-32 produces C₁₇ bacillomycin D and [Ile 2002]surfactin, and that these metabolites play important roles in SD-32's biocontrol over cucumber gray mold disease. Our further investigation demonstrated that the culture broth and its supernatant suppressed cucumber powdery mildew disease in greenhouse experiments. However, the active principle(s) remained unknown.

RESULTS

The active compound was isolated from the culture supernatant after anti-powdery mildew disease activity-guided purification and identified as prumycin. Prumycin significantly suppressed the disease, whereas bacillomycin D and [Ile 2002]surfactin did not. Prumycin did not induce the expression of plant defense genes (PR1a and VSP1), suggesting that it does not act via plant defense response. Light microscopic observations of prumycin-treated cucumber cotyledon suggested that prumycin inhibits the conidial germination of P. fusca.

CONCLUSION

This study demonstrates that prumycin is a major factor in SD-32's suppression of cucumber powdery mildew disease. Our findings shed light for the first time on prumycin's role in biocontrol by Bacillus against this disease. © 2017 Society of Chemical Industry.

Structural modification of LPS in colistin-resistant, KPC-producing Klebsiella pneumoniae

BACKGROUND

Colistin resistance in Klebsiella pneumoniae typically involves inactivation or mutations of chromosomal genes mgrB, pmrAB or phoPQ, but data regarding consequent modifications of LPS are limited.

OBJECTIVES

To examine the sequences of chromosomal loci implicated in colistin resistance and the respective LPS-derived lipid A profiles using 11 pairs of colistin-susceptible and -resistant KPC-producing K. pneumoniae clinical strains.

METHODS

The strains were subjected to high-throughput sequencing with Illumina HiSeq. The mgrB gene was amplified by PCR and sequenced. Lipid profiles were determined using MALDI-TOF MS.

RESULTS

All patients were treated with colistimethate prior to the isolation of colistin-resistant strains (MIC >2 mg/L). Seven of 11 colistin-resistant strains had deletion or insertional inactivation of mgrB. Three strains, including one with an mgrB deletion, had non-synonymous pmrB mutations associated with colistin resistance. When analysed by MALDI-TOF MS, all colistin-resistant strains generated mass spectra containing ions at m/z 1955 and 1971, consistent with addition of 4-amino-4-deoxy-l-arabinose (Ara4N) to lipid A, whereas only one of the susceptible strains displayed this lipid A phenotype.

CONCLUSIONS

The pathway to colistin resistance in K. pneumoniae primarily involves lipid A modification with Ara4N in clinical settings.

Linker dependent intercalation of bisbenzimidazole-aminosugars in an RNA duplex; selectivity in RNA vs. DNA binding

Neomycin and Hoechst 33258 are two well-known nucleic acid binders that interact with RNA and DNA duplexes with high affinities respectively. In this manuscript, we report that covalent attachment of bisbenzimidazole unit derived from Hoechst 33258 to neomycin leads to intercalative binding of the bisbenzimidazole unit (oriented at 64-74° with respected to the RNA helical axis) in a linker length dependent manner. The dual binding and intercalation of conjugates were supported by thermal denaturation, CD, LD and UV-Vis absorption experiments. These studies highlight the importance of linker length in dual recognition by conjugates, for effective RNA recognition, which can lead to novel ways of recognizing RNA structures. Additionally, the ligand library screens also identify DNA and RNA selective compounds, with compound 9, containing a long linker, showing a 20.3°C change in RNA duplex Tm with only a 13.0°C change in Tm for the corresponding DNA duplex. Significantly, the shorter linker in compound 3 shows almost the reverse trend, a 23.8°C change in DNA Tm, with only a 9.1°C change in Tm for the corresponding RNA duplex.

[Helminth derived Immunomodulatory Glycan LNFP3 Impairs Pathogenesis of Peripheral Neuropathic Pain and Spinal Glial Activation]

OBJECTIVES

To investigate the effect of helminth-derived immunomodulatory glycan lacto-N-fucopentaose3(LNFP3) on the pathogenesis of neuropathic pain and spinal glial activation in the corresponding time windows after adult rat tibial nerve permanent transection (modified spared nerve injury, mSNI).

METHODS

Ten weeks old male adult Sprague-Dawley (SD) rats weighing 250-300 g were randomly grouped into four groups: sham-operated group (n =6), mSNI group (n =6), mSNI plus bovine serum albumin (BSA) group (n =12) and mSNI plus LNFP3 group (n=12). Rats were subjected to surgical operation or sham operation on the right tibial nerves and were intraperitoneal injected BSA or LNEP3-BSA conjugates by the group design. Animals from each group (n=6 per group) were subjected to the plantar test,von Frey hairs test, pinprick test and acetone test for critical evaluation of region-specific pain responses on the plantar sural and saphenous skin territories of ipsilateral and contralateral hindpaws after injuries. Transverse frozen sections of L3-4 spinal cords from the remaining animals of mSNI plus BSA group and mSNI plus LNFP3 group 7 and 14 d after injury (n=3 for each time point per group)were prepared and subjected to immunofluorescent staining of microglia/macrophage marker [cluster of differentiation molecule 11b (CD11b)] and astrocyte marker [glial fibrillary acidic protein (GFAP)], for analysis of spinal glial activation.

RESULTS

After adult rat mSNI, early systematic administration of LNFP3 significantly but not completely attenuated region-specific pathological pain evoked by mechanical and thermal stimuli on the sural and saphenous skin territories of rat hindpaw plantar surfaces in acute (4/5 d after injuries) and subacute (7/8 d and 14/15 d after injuries) phases. Meanwhile, in the ipsilateral spinal cord dorsal horns, this early systematic treatment inhibited microglia/macrophage activation 7 d after injury and astrocyte activation 7 and 14 d after injury.

CONCLUSIONS

Early systematic administration of LNFP3 impairs the pathogenesis (acute induction and chronic transition) of neuropathic pain and spinal glial activation in the corresponding time windows after adult rat mSNI.

A platform for the discovery of new macrolide antibiotics

The chemical modification of structurally complex fermentation products, a process known as semisynthesis, has been an important tool in the discovery and manufacture of antibiotics for the treatment of various infectious diseases. However, many of the therapeutics obtained in this way are no longer effective, because bacterial resistance to these compounds has developed. Here we present a practical, fully synthetic route to macrolide antibiotics by the convergent assembly of simple chemical building blocks, enabling the synthesis of diverse structures not accessible by traditional semisynthetic approaches. More than 300 new macrolide antibiotic candidates, as well as the clinical candidate solithromycin, have been synthesized using our convergent approach. Evaluation of these compounds against a panel of pathogenic bacteria revealed that the majority of these structures had antibiotic activity, some efficacious against strains resistant to macrolides in current use. The chemistry we describe here provides a platform for the discovery of new macrolide antibiotics and may also serve as the basis for their manufacture.

A Neoglycoconjugate Containing the Human Milk Sugar LNFPIII Drives Anti-Inflammatory Activation of Antigen Presenting Cells in a CD14 Dependent Pathway

The milk pentasaccharide LNFPIII has therapeutic action for metabolic and autoimmune diseases and prolongs transplant survival in mice when presented as a neoglycoconjugate. Within LNFPIII is the Lewis^x trisaccharide, expressed by many helminth parasites. In humans, LNFPIII is found in human milk and also known as stage-specific embryonic antigen-1. LNFPIII-NGC drives alternative activation of macrophages and dendritic cells via NFκB activation in a TLR4 dependent mechanism. However, the connection between LNFPIII-NGC activation of APCs, TLR4 signaling and subsequent MAP kinase signaling leading to anti-inflammatory activation of APCs remains unknown. In this study we determined that the innate receptor CD14 was essential for LNFPIII-NGC induction of both ERK and NFkB activation in APCs. Induction of ERK activation by LNFPIII-NGC was completely dependent on CD14/TLR4-Ras-Raf1/TPL2-MEK axis in bone marrow derived dendritic cells (BMDCs). In addition, LNFPIII-NGC preferentially induced the production of Th2 “favoring” chemokines CCL22 and matrix metalloprotease protein-9 in a CD14 dependent manner in BMDCs. In contrast, LNFPIII-NGC induces significantly lower levels of Th1 “favoring” chemokines, MIP1α, MIP1β and MIP-2 compared to levels in LPS stimulated cells. Interestingly, NGC of the identical human milk sugar LNnT, minus the alpha 1–3 linked fucose, failed to activate APCs via TLR4/MD2/CD14 receptor complex, suggesting that the alpha 1–3 linked fucose in LNFPIII and not on LNnT, is required for this process. Using specific chemical inhibitors of the MAPK pathway, we found that LNFPIII-NGC induction of CCL22, MMP9 and IL-10 production was dependent on ERK activation. Over all, this study suggests that LNFPIII-NGC utilizes CD14/TLR4-MAPK (ERK) axis in modulating APC activation to produce anti-inflammatory chemokines and cytokines in a manner distinct from that seen for the pro-inflammatory PAMP LPS. These pathways may explain the in vivo therapeutic effect of LNFPIII-NGC treatment for inflammation based diseases.

Pharmacological and behavioral characterization of D-473, an orally active triple reuptake inhibitor targeting dopamine, serotonin and norepinephrine transporters

Major depressive disorder (MDD) is a debilitating disease affecting a wide cross section of people around the world. The current therapy for depression is less than adequate and there is a considerable unmet need for more efficacious treatment. Dopamine has been shown to play a significant role in depression including production of anhedonia which has been one of the untreated symptoms in MDD. It has been hypothesized that drugs acting at all three monoamine transporters including dopamine transporter should provide more efficacious antidepressants activity. This has led to the development of triple reuptake inhibitor D-473 which is a novel pyran based molecule and interacts with all three monoamine transporters. The monoamine uptake inhibition activity in the cloned human transporters expressed in HEK-293 cells (70.4, 9.18 and 39.7 for DAT, SERT and NET, respectively) indicates a serotonin preferring triple reuptake inhibition profile for this drug. The drug D-473 exhibited good brain penetration and produced efficacious activity in rat forced swim test under oral administration. The optimal efficacy dose did not produce any locomotor activation. Microdialysis experiment demonstrated that systemic administration of D-473 elevated extracellular level of the three monoamines DA, 5-HT, and NE efficaciously in the dorsal lateral striatum (DLS) and the medial prefrontal cortex (mPFC) area, indicating in vivo blockade of all three monoamine transporters by D-473. Thus, the current biological data from D-473 indicate potent antidepressant activity of the molecule.

Glucose Trimming ofN-Glycan in Endoplasmic Reticulum Is Indispensable for the Growth ofRaphanus sativusSeedling (kaiware radish)

Recently I found that glycosidase inhibitors such as castanospermine, deoxynojirimycin, swainsonine, 2-acetamindo 2,3-dideoxynojirimycin, and deoxymannojirimycin change the N-glycan structure of root glycoproteins, and that the glucosidase inhibitors castanospermine and deoxynojirimycin suppress the growth of Raphanus sativus seedlings (Mega, T., J. Biochem., 2004). The present study undertook to see whether the growth suppression is due to the inhibition of glucose trimming in endoplasmic reticulum (ER). The study, using three glucosidase inhibitors, castanospermine, N-methyl deoxynojirimycin, and deoxynojirimycin, upon the growth of R. sativus foliage leaf, made clear that glucose trimming is indispensable for plant growth, because the inhibition of glucose trimming correlated with leaf growth. On the other hand, processing inhibition in the Golgi apparatus by other glycosidase inhibitors had little effect on plant growth, although N-glycan processing was disrupted depending on inhibitor specificity. These results suggest that N-glycan processing after glucosidase processing is dispensable for plant growth and cell differentiation.

Saquayamycins G-K, cytotoxic angucyclines from Streptomyces sp. Including two analogues bearing the aminosugar rednose

Streptomyces sp. KY40-1, a strain isolated from the Kentucky Appalachian foothills, is the producer of moromycins A (18) and B (19). Further investigations of this strain led to the isolation and structure elucidation of the five new saquayamycins G-K (1-5), along with known compounds. Two of the new compounds bear the unusual aminosugar rednose, which was found here for the first time in angucyclines. The different attachment positions of this aminosugar in these two compounds indicate a high acceptor substrate flexibility of the responsible glycosyl transferase or alternatively the involvement of multiple glycosyl transferases. The cytotoxic activity of the isolated compounds was determined using human prostate cancer (PC-3) and non-small-cell lung cancer (H460) cell lines. Cell viability assays showed that saquayamycins J (4), K (5), A (7), and B (8) were most active in PC3 cells, with saquayamycin B (8) showing the highest activity (GI(50) = 0.0075 μM). The aminosugar-containing saquayamycins H (2) and saquayamycin B (8) showed the highest activity against H460 cells, with a GI(50) of 3.3 and 3.9 μM, respectively. The results presented here provide more insights into the structure-activity relationship of saquayamycins with respect to the nature, number, and linkage of sugar residues.

[Novel biologically active compounds isolated from unexploited organisms, cellular sime molds]

Cellular slime molds are thought to be excellent model organisms for the study of cell and developmental biology because of their simple pattern of development. However, there have been few reports on secondary metabolites of them. We have focused on the utility of cellular slime molds as novel resources for natural product chemistry, and have studied the diversity of secondary metabolites produced by them as well as their physiological and pharmacological activities. We have recently isolated many novel compounds from the fruiting bodies of various species of Dictyostelium cellular slime molds. Total syntheses and biological evaluation of these compounds have been carried out. It was shown that dictyopyrones and dictyomedins may regulate Dictyostelium development. Amino sugar derivatives such as furanodictines and dictyoglucosamines induced neuronal differentiation of rat PC-12 cells. In addition, brefelamide inhibited the cellular proliferation of 1321N1 human astrocytoma cells. These results show that cellular slime molds are promising sources in natural product chemistry.

Inhibition of glycosaminoglycan synthesis and protein glycosylation with WAS-406 and azaserine result in reduced islet amyloid formation in vitro

Deposition of islet amyloid polypeptide (IAPP) as amyloid in the pancreatic islet occurs in approximately 90% of individuals with Type 2 diabetes and is associated with decreased islet beta-cell mass and function. Human IAPP (hIAPP), but not rodent IAPP, is amyloidogenic and toxic to islet beta-cells. In addition to IAPP, islet amyloid deposits contain other components, including heparan sulfate proteoglycans (HSPGs). The small molecule 2-acetamido-1,3,6-tri-O-acetyl-2,4-dideoxy-alpha-D-xylo-hexopyranose (WAS-406) inhibits HSPG synthesis in hepatocytes and blocks systemic amyloid A deposition in vivo. To determine whether WAS-406 inhibits localized amyloid formation in the islet, we incubated hIAPP transgenic mouse islets for up to 7 days in 16.7 mM glucose (conditions that result in amyloid deposition) plus increasing concentrations of the inhibitor. WAS-406 at doses of 0, 10, 100, and 1,000 microM resulted in a dose-dependent decrease in amyloid deposition (% islet area occupied by amyloid: 0.66 +/- 0.14%, 0.10 +/- 0.06%, 0.09 +/- 0.07%, and 0.004 +/- 0.003%, P < 0.001) and an increase in beta-cell area in hIAPP transgenic islets (55.0 +/- 2.6 vs. 60.6 +/- 2.2% islet area for 0 vs. 100 microM inhibitor, P = 0.05). Glycosaminoglycan, including heparan sulfate, synthesis was inhibited in both hIAPP transgenic and nontransgenic islets (the latter is a control that does not develop amyloid), while O-linked protein glycosylation was also decreased, and WAS-406 treatment tended to decrease islet viability in nontransgenic islets. Azaserine, an inhibitor of the rate-limiting step of the hexosamine biosynthesis pathway, replicated the effects of WAS-406, resulting in reduction of O-linked protein glycosylation and glycosaminoglycan synthesis and inhibition of islet amyloid formation. In summary, interventions that decrease both glycosaminoglycan synthesis and O-linked protein glycosylation are effective in reducing islet amyloid formation, but their utility as pharmacological agents may be limited due to adverse effects on the islet.

[Isolation and characterization of lectin from the surface of Grifola frondosa (FR.) S.F. Gray mycelium]

For the first time, from the surface of the dikaryotic mycelium of the xylotrophic basidiomycete Grifola frondosa 0917 a lectin has been isolated with a molecular mass of 68 +/- 1 kDa, consisting of two subunits of 33-34 kDa each. The lectin is a hydrophilic glycoprotein with the protein : glycan ratio of 3 : 1. It exhibits high affinity to native rabbit erythrocytes and to human erythrocytes of the 0 blood group, but not to trypsin-treated ones. The hemagglutination (HA) caused by lectin was not blocked by any of the 25 tested mono-, di-, and amino sugars; it was also not blocked by some of glyco derivatives. Only 13.9 microg/ml of the homogeneous preparation of a polysaccharide, a linear D-rhamnan with the structure of the repetitive component --> 2)-beta-D-Rhap-(1 --> 3)-alpha-D-Rhap-(1 --> 3)-alpha-D-Rhap-(1 --> 2)-alpha-D-Rhap-(1 --> 2)-alpha-D-Rhap-(1 --> blocked hemagglutination completely. The analysis of the amino acid composition of the lectin showed the greatest percentage of amino acids with positively charged R groups, arginine, lysine, and histidine, as well as the complete absence of sulfur-containing amino acids, cysteine, and methionine. D-glucose and D-glucosamine were detected in the carbohydrate part.

Anomer-selective glycosidase inhibition by 2-N-alkylated 1-azafagomines

Alkylation of 1-azafagomine at the 2-N position was achieved by reductive amination of 1-N-acetyl-3,4,6-tri-O-benzyl-1-azafagomine by using aldehydes, palladium hydroxide, and hydrogen in EtOAc/water/acetic acid followed by deprotection. The 2-N-butyl, hexyl, heptyl, nonyl, decyl, and 3-phenylpropyl derivatives were made in this manner, and were tested for inhibition of alpha-glucosidase from yeast, and of beta-glucosidase from almonds. The new compounds were stronger beta-glucosidase inhibitors than 1-azafagomine, but weaker alpha-glucosidase inhibitors.

Synthesis and evaluation of amino-threoses in d- and l-series: Are five membered ring amino-sugars more potent glycosidase inhibitors than the six membered ones?

Cyclic D- and L-4-aminothreose were synthesised from ethyl D- and L-tartrate, respectively. D-aminothreose was a potent inhibitor of alpha-glucosidase and of alpha-mannosidase. From the glycosidase inhibition potencies of the four 4-amino-4-deoxy-tetroses, the contribution of binding of each functionality of the 5 and 6 membered ring amino-sugars towards the various glycosidases is discussed.

Amino sugars: new inhibitors of zeaxanthin epoxidase, a violaxanthin cycle enzyme

The effect of three sugars and their amino derivatives on violaxanthin cycle enzymes activity was investigated in duckweed (Lemna trisulca), a model water-plant. No effect of sugars and amino sugars on violaxanthin de-epoxidase was observed independent of incubation time; however, epoxidation of zeaxanthin to violaxanthin was inhibited. The minimum amino sugar concentrations causing maximum inhibition of zeaxanthin epoxidation have been estimated. Amino sugars but not sugars caused more than a 50% inhibition of zeaxanthin epoxidation in duckweed after a 24h incubation when applied at a concentration of 0.5%. Incubation with amino sugars under a 6d photoperiod enhanced the inhibitory effect. Zeaxanthin epoxidation was completely inhibited under such conditions, whereas only a minor inhibitory effect was observed in sugar treated plants. The strong amino sugar inhibition of zeaxanthin epoxidase activity represents additional evidence for the creation of an unstable carotenoid carbocation in the molecular mechanism of epoxidation.

Chemoenzymatic synthesis of artificial glycopolypeptides containing multivalent sialyloligosaccharides with a γ-polyglutamic acid backbone and their effect on inhibition of infection by influenza viruses

Highly water-soluble, artificial glycopolypeptides with a gamma-polyglutamic acid (gamma-PGA) backbone derived from Bacillus subtilis sp. and multivalent sialyloligosaccharide units have been chemoenzymatically synthesized as potential polymeric inhibitors of infection by bird and human influenza viruses. 5-Trifluoroacetamidopentyl beta-N-acetyllactosaminide and 5-trifluoroacetamidopentyl beta-lactoside were enzymatically synthesized from LacNAc and lactose, respectively, by cellulase-mediated condensation with 5-trifluoroacetamido-1-pentanol. After deacetylation, the resulting 5-aminopentyl beta-LacNAc and beta-lactoside glycosides were coupled to the alpha-carboxyl groups of the gamma-PGA side chains. The artificial glycopolypeptides carrying LacNAc and lactose were further converted to Neu5Acalpha2-(3/6)Galbeta1-4Glcbeta and Neu5Acalpha2-(3/6)Galbeta1-4GlcNAcbeta sialyloligosaccharide units by alpha2,3- and alpha2,6-sialyltransferase, respectively. The interaction of these glycopolypeptides with various influenza virus strains has been investigated by three different methods. Glycopolypeptides carrying Neu5Acalpha2,6LacNAc inhibited hemagglutination mediated by influenza A and B viruses, and their relative binding affinities for hemagglutinin were 10(2)- to 10(4)-fold higher than that of the naturally occurring fetuin control. A glycopolypeptide carrying Neu5Acalpha2,6LacNAc inhibited infection by A/Memphis/1/71 (H3N2) 93 times more strongly than fetuin, as assessed by cytopathic effects on virus-infected MDCK cells. The avian virus [A/duck/Hong kong/4/78 (H5N3)] bound strongly to Neu5Acalpha2,3LacNAc/Lac-carrying glycopolypeptides, whereas the human virus [A/Memphis/1/71 (H3N2)] bound to Neu5Acalpha2,6LacNAc in preference to Neu5Acalpha2,6Lac. Taken together, these results indicate that the binding of viruses to terminal sialic acids is markedly affected by the structure of the asialo portion, in this case either LacNAc or lactose, in the sugar chain of glycopolypeptides.

N-acetyllactosamine conjugated to gold nanoparticles inhibits enteropathogenic Escherichia coli colonization of the epithelium in human intestinal biopsy specimens

We previously reported that the bundle-forming pilus-mediated localized adherence of enteropathogenic Escherichia coli to HEp-2, T84, and Caco-2 cells is inhibited by N-acetyllactosamine neoglycoconjugates. The results presented here extend this observation to the epithelium of biopsy specimens obtained from the human adult duodenum, terminal ileum, and colon.

Prevention of psoriasis-like lesions development in fsn/fsn mice by helminth glycans

The helminth glycan LNFPIII is an immunomodulatory molecule, driving CD4(+) Th2-type biasing as well as immune suppression. Psoriasis is an autoimmune disease where the immune mechanisms as well as the antigens responsible for development of immune autoreactivity are still not known. In the absence of defined immunological mechanisms, we asked whether LNFPIII would function as novel therapy for psoriasis. We tested the therapeutic efficacy of LNFPIII using the flaky skin (fsn)/fsn mutant mouse model of psoriasis-like lesion development. We found that treatment of mice with LNFPIII prevented the appearance of psoriatic skin lesions on fsn/fsn mice. Examination of the skin 2 weeks after treatment demonstrated that prevention of skin lesions was associated with maintenance of normal epidermis thickness in LNFPIII-treated mice as compared with a significantly thickened epidermis in control treated and diseased mice. In addition, cells from skin of LNFPIII-treated mice produced lower amounts of interferon-gamma as compared with cells from skin of control treated diseased mice. Examination of macrophages and T cells from peripheral lymph nodes of control and LNFPIII-treated fsn/fsn mice showed that glycan treatment reduced the numbers of Gr1(+)F4/80(+) macrophages and the numbers of CD8(+) T cells, restoring the numbers of these two cell populations as well as the CD4 : CD8 ratio to near normal levels. Overall, the results from this study suggest that the helminth immunomodulatory glycan LNFPIII functions to prevent development of psoriatic-like skin lesions in fsn/fsn mice.

Basis for N-acetyllactosamine-mediated inhibition of enteropathogenic Escherichia coli localized adherence

In a previous article, the authors reported that exposing wild-type enteropathogenic Escherichia coli (EPEC) to chemically synthesized N-acetyllactosamine glycosides covalently coupled to BSA (LacNAc-BSA) inhibited localized adherence (LA) by these organisms and also caused them to lose their bundle-forming pili (BFP), the filamentous surface appendages responsible for their LA phenotype. This effect has now been further investigated by screening a panel of LacNAc-BSA-related glycosides for their ability to inhibit EPEC LA, which revealed that LacNAc-BSA retained its status as the most effective inhibitor of EPEC LA. It was also shown that LacNAc-BSA did not cause the loss of BFP in an EPEC strain containing a non-polar mutation in the bfpF gene and, as a consequence, unable to retract its BFP. LacNAc-BSA also effectively inhibited LA of the bfpF mutant EPEC. Taken together, these observations suggest that, as well as triggering BfpF-mediated BFP retraction, LacNAc-BSA likely functions as a competitive inhibitor of EPEC binding to LacNAc-related receptors on host cells. Moreover, transmission electron microscopy revealed that LacNAc conjugated to gold nanoparticles bound specifically to BFP. This observation indicated that either the major BFP structural subunit (BfpA) itself or, possibly, an accessory protein co-assembled with BfpA into the BFP filaments, contains a LacNAc-specific EPEC adhesin. The results suggest a mechanism whereby the initial binding of EPEC to LacNAc-like receptors on host cells triggers BfpF-mediated BFP retraction. This could then expedite the intimate adherence phase of the multi-step EPEC colonization process by drawing the organisms closer to the host-cell plasma membrane.

Synthesis, glycosidase activity and X-ray crystallography of 3-amino-sugars

The cleavage of two sugar epoxides, methyl 2,3-anhydro-alpha-D-mannopyranoside and 2,3-anhydro-alpha-D-allopyranoside, with amines is presented as a method for preparing a library of 3-amino-sugars (methyl 3-amino-3-deoxy-alpha-D-altropyranosides and methyl 3-amino-3-deoxy-alpha-D-glucopyranosides) as potential glycosidase inhibitors. Several of the altropyranosides were micromolar inhibitors of bovine liver beta-galactosidase and almond beta-glucosidase. X-ray crystal structures were determined for one of the methyl 3-amino-3-deoxy-alpha-D-altropyranosides, 4t, and one of the methyl 3-amino-3-deoxy-alpha-D-glucopyranosides, 6d.

LNFPIII/LeX-stimulated macrophages activate natural killer cells via CD40-CD40L interaction

Lacto-N-fucopentaose III (LNFPIII) is a human milk sugar containing the biologically active Lewis X (LeX) trisaccharide. LNFPIII/LeX is also expressed by immunosuppressive helminth parasites, by bacteria, and on a number of tumor/cancer cells. In this report, we first demonstrate that LNFPIII activates macrophages in vitro as indicated by upregulation of Gr-1 expression on F4/80(+) cells. Further, we investigated the effect of LNFPIII-activated macrophages on NK cell activity. We found that LNFPIII-stimulated F4/80(+) cells were able to activate NK cells, inducing upregulation of CD69 expression and gamma interferon (IFN-gamma) production. The experiments show that NK cell activation is macrophage dependent, since NK cells alone did not secrete IFN-gamma in response to LNFPIII. Furthermore, we found that activation of NK cells by glycan-stimulated macrophages required cell-cell contact. As part of the cell-cell contact mechanism, we determined that CD40-CD40L interaction was critical for IFN-gamma secretion by NK cells, as the addition of anti-CD40L antibodies to the coculture blocked IFN-gamma production. We also demonstrated that LNFPIII-stimulated macrophages secrete prostaglandin E(2), interleukin-10 (IL-10), and tumor necrosis factor alpha (TNF-alpha) but a very low level of IL-12. Interestingly, addition of anti-TNF-alpha, anti-IL-10, or anti-IL-12 monoclonal antibodies did not significantly alter NK cell activity. Our data show that these soluble mediators are not critical for LNFPIII-stimulated macrophage activation of NK cells and provide further evidence for the importance of cell-cell contact and CD40-CD40L interactions between macrophages and NK cells.

Thioureido N-acetyllactosamine derivatives as potent galectin-7 and 9N inhibitors

Derivatives of N-acetyllactosamine carrying structurally diverse thioureido groups at galactose C3 were prepared from a C3'-azido N-acetyllactosamine derivative in a three-step reaction sequence involving azide reduction and isothiocyanate formation by thiophosgene treatment of the C3-amine, followed by reaction of the isothiocyanate with a panel of amines. Evaluation of the N-acetyllactosamine thioureas as inhibitors against galectins-1, 3, 7, 8N (N-terminal domain), and 9N (N-terminal domain) revealed thiourea-mediated affinity enhancements for galectins-1, 3, 7, and 9N. In particular, good inhibitors were discovered against galectin-7 and 9N (K(d) 23 and 47 microM, respectively, for a 3-pyridylmethylthiourea derivative), which represents more than an order of magnitude affinity enhancement over the parent natural N-acetyllactosamine.

Iminosugar-producing Thai medicinal plants

Alpha-1-C-hydroxymethylfagomine (7), 3-O-beta-D-glucopyranosyl-DMDP (12), and 2,5-dideoxy-2,5-imino-D-glucitol (13) were isolated from the Thai traditional crude drug "Non tai yak" (Stemona tuberosa), which also contains a high concentration level of alpha-homonojirimycin (0.1% dry weight). "Thopthaep" (Connarus ferrugineus) and "Cha em thai" (Albizia myriophylla) contained 1-deoxymannojirimycin (DMJ) (10) at levels of 0.083% (dry weight) and 0.17% (dry weight), respectively. 2-O-alpha-D-Galactopyranosyl-DMJ (20), 3-O-beta-D-glucopyranosyl-DMJ (21), 1,4-dideoxymannojirimycin (17), 1,4-dideoxyallonojirimycin (18), and 1,4-dideoxyaltronojirimycin (19) from C. ferrugineus and 2-O-beta-D-glucopyranosyl-DMJ (22) and 4-O-beta-D-glucopyranosyl-DMJ (23) from A. myriophylla were isolated as new compounds.

Crystal structure and mechanism of the Escherichia coli ArnA (PmrI) transformylase domain. An enzyme for lipid A modification with 4-amino-4-deoxy-L-arabinose and polymyxin resistance

Gram-negative bacteria have evolved mechanisms to resist the bactericidal action of cationic antimicrobial peptides of the innate immune system and antibiotics such as polymyxin. The strategy involves the addition of the positively charged sugar 4-amino-4-deoxy-l-arabinose (Ara4N) to lipid A in their outer membrane. ArnA is a key enzyme in the Ara4N-lipid A modification pathway. It is a bifunctional enzyme catalyzing (1) the oxidative decarboxylation of UDP-glucuronic acid (UDP-GlcA) to the UDP-4' '-ketopentose [UDP-beta-(l-threo-pentapyranosyl-4' '-ulose] and (2) the N-10-formyltetrahydrofolate-dependent formylation of UDP-Ara4N. Here we demonstrate that the transformylase activity of the Escherichia coli ArnA is contained in its 300 N-terminal residues. We designate it the ArnA transformylase domain and describe its crystal structure solved to 1.7 A resolution. The enzyme adopts a bilobal structure with an N-terminal Rossmann fold domain containing the N-10-formyltetrahydrofolate binding site and a C-terminal subdomain resembling an OB fold. Sequence and structure conservation around the active site of ArnA transformylase and other N-10-formyltetrahydrofolate-utilizing enzymes suggests that the HxSLLPxxxG motif can be used to identify enzymes that belong to this family. Binding of an N-10-formyltetrahydrofolate analogue was modeled into the structure of ArnA based on its similarity with glycinamide ribonucleotide formyltransferase. We also propose a mechanism for the transformylation reaction catalyzed by ArnA involving residues N(102), H(104), and D(140). Supporting this hypothesis, point mutation of any of these residues abolishes activity.

A Madagascar Sponge Batzella sp. as a source of alkylated iminosugars

Three new C-alkylated iminosugars, batzellasides A (3), B (4), and C (5), along with the known halitoxin (2) polymer were isolated from a Batzella sp. sponge, collected off the west coast of Madagascar. Although this class of azasugars is well known from terrestrial sources, our report represents the first examples of iminosugars from a marine organism. Comparison with the properties of known natural and synthetic iminosugars assisted in the structure determinations. Compounds 3-5 inhibited the growth of Staphylococcus epidermidis with MICs of < or =6.3 microg/mL.

Cellular effects of deoxynojirimycin analogues: inhibition of N-linked oligosaccharide processing and generation of free glucosylated oligosaccharides

In the accompanying paper [Mellor, Neville, Harvey, Platt, Dwek and Butters (2004) Biochem. J. 381, 861-866] we treated HL60 cells with N-alk(en)yl-deoxynojirimycin (DNJ) compounds to inhibit glucosphingolipid (GSL) biosynthesis and identified a number of non-GSL-derived, small, free oligosaccharides (FOS) most likely produced due to inhibition of the oligosaccharide-processing enzymes a-glucosidases I and II. When HL60 cells were treated with concentrations of N-alk(en)ylated DNJ analogues that inhibited GSL biosynthesis completely, N-butyl- and N-nonyl-DNJ inhibited endoplasmic reticulum (ER) glucosidases I and II, but octadecyl-DNJ did not, probably due to the lack of ER lumen access for this novel, long-chain derivative. Glucosidase inhibition resulted in the appearance of free Glc1-3Man structures, which is evidence of Golgi glycoprotein endomannosidase processing of oligosaccharides with retained glucose residues. Additional large FOS was also detected in cells following a 16 h treatment with N-butyl- and N-nonyl-DNJ. When these FOS structures (>30, including >20 species not present in control cells) were characterized by enzyme digests and MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS, all were found to be polymannose-type oligosaccharides, of which the majority were glucosylated and had only one reducing terminal GlcNAc (N-acetylglucosamine) residue (FOS-GlcNAc1), demonstrating a cytosolic location. These results support the proposal that the increase in glucosylated FOS results from enzyme-mediated cytosolic cleavage of oligosaccharides from glycoproteins exported from the ER because of misfolding or excessive retention. Importantly, the present study characterizes the cellular properties of DNJs further and demonstrates that side-chain modifications allow selective inhibition of protein and lipid glycosylation pathways. This represents the most detailed characterization of the FOS structures arising from ER a-glucosidase inhibition to date.

Anti-tuberculosis activity of some N-pentopyranosylamines

With the advent of multidrug-resistant Mycobacterium tuberculosis, new effective drugs are rapidly needed. Thirty-two derivatives of some N-pentopyranosylamines were prepared and tested under the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) program. This communication is presenting their antituberculosis activity in the primary screen.

Glycosyltransferase activity can be selectively modulated by chemical modifications of acceptor substrates

A range of N-acetyllactosamine derivatives, which are modified by a wide range of functionalities at C-2(') and C-6, have been synthesised and the kinetic parameters of transfer catalysed by recombinant alpha-2,6-sialyltransferase and alpha-1,3-fucoyltransferase VI determined. Several of the chemical modifications led to selective modulate the activity the enzymes and offer promising lead compounds for the development of oligosaccharide primers for selective metabolic inhibition of oligosaccharide biosynthesis.

Two potent competitive inhibitors discriminating α-glucosidase family I from family II

The inhibition kinetics for isoacarbose (a pseudotetrasaccharide, IsoAca) and acarviosine-glucose (pseudotrisaccharide, AcvGlc), both of which are derivatives of acarbose, were investigated with various types of alpha-glucosidases obtained from microorganisms, plants, and insects. IsoAca and AcvGlc, competitive inhibitors, allowed classification of alpha-glucosidases into two groups. Enzymes of the first group were strongly inhibited by AcvGlc and weakly by IsoAca, in which the K(i) values of AcvGlc (0.35-3.0 microM) were 21- to 440-fold smaller than those of IsoAca. However, the second group of enzymes showed similar K(i) values, ranging from 1.6 to 8.0 microM for both compounds. This classification for alpha-glucosidases is in total agreement with that based on the similarity of their amino acid sequences (family I and family II). This indicated that the alpha-glucosidase families I and II could be clearly distinguished based on their inhibition kinetic data for IsoAca and AcvGlc. The two groups of alpha-glucosidases seemed to recognize distinctively the extra reducing-terminal glucose unit in IsoAca.

The design and synthesis of a selective inhibitor of fucosyltransferase VI

Inversion of configuration of the C-2[prime or minute] hydroxyl of methyl N-acetyllactosamine was accomplished by a two-step procedure involving oxidation to a ketone followed by reduction with NaBH(4). After deprotection, the resulting derivative was examined as a substrate for [small alpha]-(2,6)- and [small alpha]-(2,3)-sialyltransferase and fucosyltransferase III, IV, V and VI. It was found that none of these enzymes could glycosylate. However, it showed exquisite selectivity for inhibition of fucosyltransferase VI. The kinetic data support an unusual mechanism in which the inhibitor can bind to the GDP-fucose complex as well as another enzyme form.

RNA polymerase mutation activates the production of a dormant antibiotic 3,3'-neotrehalosadiamine via an autoinduction mechanism in Bacillus subtilis

Bacillus and Streptomyces species possess the ability to produce a variety of commercially important metabolites and extracellular enzymes. We previously demonstrated that antibiotic production in Streptomyces coeli-color A3(2) and Streptomyces lividans can be enhanced by RNA polymerase (RNAP) mutations selected for the rifampicin-resistant (Rif(r)) phenotype. Here, we have shown that the introduction of a certain Rif(r) rpoB mutation into a B. subtilis strain resulted in cells that overproduce an aminosugar antibiotic 3,3'-neotrehalosadiamine (NTD), the production of which is dormant in the wild-type strain. Mutational and recombinant gene expression analyses have revealed a polycistronic gene ntdABC (formally yhjLKJ) and a monocistronic gene ntdR (formally yhjM) as the NTD biosynthesis operon and a positive regulator for ntdABC, respectively. Analysis of transcriptional fusions to a lacZ reporter revealed that NTD acts as an autoinducer for its own biosynthesis genes via NtdR protein. Our results also showed that the Rif(r) rpoB mutation causes an increase in the activity of sigma(A)-dependent promoters including ntdABC promoter. Therefore, we propose that unlike the wild-type RNAP, the mutant RNAP efficiently recognized the sigma(A)-dependent promoters, resulting in the dramatic activation of the NTD biosynthesis pathway by an autoinduction mechanism.

Synthesis of N-acetyllactosamine derivatives with variation in the aglycon moiety for the study of inhibition of sialyl Lewis x expression

Herein we describe an inhibition study of the sialyl Lewis x (sLe(x)) expression on a human monocytic cell line (U937), using a series of peracetylated N-Acetyllactosamine (LacNAc) analogues with variation at the aglycon moiety. It was found that the extent of inhibition was related to the hydrophobicity and structure of the aglycon. In general, peracetylated LacNAc analogues with a naphthyl or biphenyl aglycon (3, 4, 6, and 7) were better in suppression of sLe(x) expression than a benzyl derivative (2). Steady-state kinetic experiments with human alpha-1,3-fucosyltransferases IV and VI (FucT IV and VI, EC 2.4.1.65) revealed that the deacetylated LacNAc-aglycons with naphthyl (18, 19, and 20) or biphenyl (17) moieties exhibited higher affinity to the fucosyltransferases than aglycon moieties with smaller hydrophobic groups (14, 15, and 16). These results are in agreement with the findings of the U937 cell-based experiments, and suggest that the higher enzyme affinity LacNAc-aglycons make better acceptor decoys and, hence, the observed differences in LacNAc-aglycon inhihitory effects on sLe(x) expression.

Development of carbohydrate-based scaffolds for restricted presentation of recognition groups. Extension to divalent ligands and implications for the structure of dimerized receptors

The solution structure of glycosyl amides has been studied by using NMR. A strong preference is displayed by tertiary aromatic glycosyl amides for E-anti structures in contrast with secondary aromatic glycosyl amides where Z-anti structures predominate. The structural diversity displayed by these classes of molecules would seem to be important as the directional properties of the aromatic ring, or groups attached to the aromatic ring, would be determined by choosing to have either a secondary or tertiary amide at the anomeric center and could be considered when designing bioactive molecules with carbohydrate scaffolds. The structural analysis was also carried out for related divalent secondary and tertiary glycosyl amides and these compounds display preferences similar to that of the monovalent compounds. The constrained divalent compounds have potential for promoting formation of clusters that will have restricted structure and thus have potential for novel studies of mechanisms of action of multivalent ligands. Possible applications of such compounds would be as scaffolds for the design and synthesis of ligands that will facilitate protein-protein or other receptor-receptor interactions. The affinity of restricted divalent (or higher order) ligands, designed to bind to proteins that recognize carbohydrates which would facilitate clustering and concomitantly promote protein-protein interactions, may be significantly higher than monovalent counterparts or multivalent ligands without these properties. This may be useful as a new approach in the development of therapeutics based on carbohydrates.

Acarviosine-simmondsin, a novel compound obtained from acarviosine-glucose and simmondsin by Thermus maltogenic amylase and its in vivo effect on food intake and hyperglycemia

Simmondsin was modified with acarviosine-glucose using the transglycosylation activity of Thermus maltogenic amylase to synthesize a novel compound with both antiobesity and hypoglycemic activity. The LC/MS and 13C NMR analyses confirmed that the structure of the major transglycosylation product was acarviosine-simmondsin (Acv-simmondsin), in which acarviosine was attached to the glucose moiety of simmondsin by an alpha-(1,6)-glycosidic linkage. It was found that Acv-simmondsin was a potent competitive inhibitor of alpha-glucosidase with the Ki value of 0.69 microM and a mixed type inhibitor of alpha-amylase with the Ki and KI of 20.78 microM and 26.31 microM, respectively. The administration of Acv-simmondsin (0.1 g/100 g diet/day) to mice for 5 days significantly reduced food intake by 35%, compared to 25% with simmondsin in control obese mice. Acv-simmondsin (50 mg/kg BW) suppressed the postprandial blood glucose response to sucrose (1 g/kg BW) by 74%, compared to 71% with acarbose, in normal rats.

Synthesis and potential antimetastatic activity of monovalent and divalent beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-D-glucopyranosides

Anomers of monovalent and divalent beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-D-gluco-pyranosides were synthesized under different glycosylation conditions, and evaluated for in vitro antimetastatic activity. Three compounds showed promising inhibitory effects on cancer cell attachment, spreading, migration, and invasion.

Baylis-Hillman reaction: convenient ascending syntheses and biological evaluation of acyclic deoxy monosaccharides as potential antimycobacterial agents

A series of acyclic deoxy carbohydrate derivatives from easily available carbohydrate enals 1, 2, 3 or 5 were prepared involving the Baylis-Hillman reaction. These newly formed carbohydrate based Baylis-Hillman adducts and their amino derivatives were evaluated for their antimycobacterial activity against Mycobacterium tuberculosis H(37)R(v). Among the compounds evaluated for their antimycobacterial activity, compound (10) showed the desired activity in the range of 3.125 microg/mL.

Low micromolar inhibitors of galectin-3 based on 3'-derivatization of N-acetyllactosamine

A strategy for generating potential galectin inhibitors was devised based on derivatization at the C-3' atom in 3'-amino-N-acetyllactosamine by using structural knowledge of the galectin carbohydrate recognition site. A collection of 12 compounds was prepared by N-acylations or N-sulfonylations. Hydrophobic tagging of the O-3 atom in the N-acetylglucosamine residue with a stearic ester allowed rapid and simple product purification. The compounds were screened in a galectin-3 binding assay and three compounds with significantly higher inhibitory activities compared to the parent N-acetyllactosaminide were found. These three best inhibitors all carried an aromatic amide at the C-3' position of the galactose moiety, which indicates that favorable interactions were formed between the aromatic group and galectin-3. The best inhibitor had an IC50 value (4.4 microM) about 50 times better than the parent N-acetyllactosaminide, which implies that it has potential as a valuable tool for studying galectin-3 biological functions and also as a lead compound for the development of galectin-3-blocking pharmaceuticals.

Lipid A modifications in polymyxin-resistant Salmonella typhimurium: PMRA-dependent 4-amino-4-deoxy-L-arabinose, and phosphoethanolamine incorporation

Lipid A of Salmonella typhimurium can be resolved into multiple molecular species. Many of these substances are more polar than the predominant hexa-acylated lipid A 1,4'-bisphosphate of Escherichia coli K-12. By using new isolation methods, we have purified six lipid A subtypes (St1 to St6) from wild type S. typhimurium. We demonstrate that these lipid A variants are covalently modified with one or two 4-amino-4-deoxy-l-arabinose (l-Ara4N) moieties. Each lipid A species with a defined set of polar modifications can be further derivatized with a palmitoyl moiety and/or a 2-hydroxymyristoyl residue in place of the secondary myristoyl chain at position 3'. The unexpected finding that St5 and St6 contain two l-Ara4N residues accounts for the anomalous structures of lipid A precursors seen in S. typhimurium mutants defective in 3-deoxy-d-manno-octulosonic acid biosynthesis in which only the 1-phosphate group is modified with the l-Ara4N moiety (Strain, S. M., Armitage, I. M., Anderson, L., Takayama, K., Quershi, N., and Raetz, C. R. H. (1985) J. Biol. Chem. 260, 16089-16098). Phosphoethanolamine (pEtN)-modified lipid A species are much less abundant than l-Ara4N containing forms in wild type S. typhimurium grown in broth but accumulate to high levels when l-Ara4N synthesis is blocked in pmrA(C)pmrE(-) and pmrA(C)pmrF(-) mutants. Purification and analysis of selected compounds demonstrate that one or two pEtN moieties may be present. Our findings show that S. typhimurium contains versatile enzymes capable of modifying both the 1- and 4'-phosphates of lipid A with l-Ara4N and/or pEtN groups. PmrA null mutants of S. typhimurium produce lipid A species without any pEtN or l-Ara4N substituents. However, PmrA is not needed for the incorporation of 2-hydroxymyristate or palmitate.

Accumulation of a polyisoprene-linked amino sugar in polymyxin-resistant Salmonella typhimurium and Escherichia coli: structural characterization and transfer to lipid A in the periplasm

Polymyxin-resistant mutants of Escherichia coli and Salmonella typhimurium accumulate a novel minor lipid that can donate 4-amino-4-deoxy-l-arabinose units (l-Ara4N) to lipid A. We now report the purification of this lipid from a pss(-) pmrA(C) mutant of E. coli and assign its structure as undecaprenyl phosphate-alpha-l-Ara4N. Approximately 0.2 mg of homogeneous material was isolated from an 8-liter culture by solvent extraction, followed by chromatography on DEAE-cellulose, C18 reverse phase resin, and silicic acid. Matrix-assisted laser desorption ionization/time of flight mass spectrometry in the negative mode yielded a single species [M - H](-) at m/z 977.5, consistent with undecaprenyl phosphate-alpha-l-Ara4N (M(r) = 978.41). (31)P NMR spectroscopy showed a single phosphorus atom at -0.44 ppm characteristic of a phosphodiester linkage. Selective inverse decoupling difference spectroscopy demonstrated that the undecaprenyl phosphate group is attached to the anomeric carbon of the l-Ara4N unit. One- and two-dimensional (1)H NMR studies confirmed the presence of a polyisoprene chain and a sugar moiety with chemical shifts and coupling constants expected for an equatorially substituted arabinopyranoside. Heteronuclear multiple-quantum coherence spectroscopy analysis demonstrated that a nitrogen atom is attached to C-4 of the sugar residue. The purified donor supports in vitro conversion of lipid IV(A) to lipid II(A), which is substituted with a single l-Ara4N moiety. The identification of undecaprenyl phosphate-alpha-l-Ara4N implies that l-Ara4N transfer to lipid A occurs in the periplasm of polymyxin-resistant strains, and establishes a new enzymatic pathway by which Gram-negative bacteria acquire antibiotic resistance.

An inner membrane enzyme in Salmonella and Escherichia coli that transfers 4-amino-4-deoxy-L-arabinose to lipid A: induction on polymyxin-resistant mutants and role of a novel lipid-linked donor

Attachment of the cationic sugar 4-amino-4-deoxy-l-arabinose (l-Ara4N) to lipid A is required for the maintenance of polymyxin resistance in Escherichia coli and Salmonella typhimurium. The enzymes that synthesize l-Ara4N and transfer it to lipid A have not been identified. We now report an inner membrane enzyme, expressed in polymyxin-resistant mutants, that adds one or two l-Ara4N moieties to lipid A or its immediate precursors. No soluble factors are required. A gene located near minute 51 on the S. typhimurium and E. coli chromosomes (previously termed orf5, pmrK, or yfbI) encodes the l-Ara4N transferase. The enzyme, renamed ArnT, consists of 548 amino acid residues in S. typhimurium with 12 possible membrane-spanning regions. ArnT displays distant similarity to yeast protein mannosyltransferases. ArnT adds two l-Ara4N units to lipid A precursors containing a Kdo disaccharide. However, as shown by mass spectrometry and NMR spectroscopy, it transfers only a single l-Ara4N residue to the 1-phosphate moiety of lipid IV(A), a precursor lacking Kdo. Proteins with full-length sequence similarity to ArnT are present in genomes of other bacteria thought to synthesize l-Ara4N-modified lipid A, including Pseudomonas aeruginosa and Yersinia pestis. As shown in the following article (Trent, M. S., Ribeiro, A. A., Doerrler, W. T., Lin, S., Cotter, R. J., and Raetz, C. R. H. (2001) J. Biol. Chem. 276, 43132-43144), ArnT utilizes the novel lipid undecaprenyl phosphate-alpha-l-Ara4N as its sugar donor, suggesting that l-Ara4N transfer to lipid A occurs on the periplasmic side of the inner membrane.

Combinatorial library of five-membered iminocyclitol and the inhibitory activities against glyco-enzymes

BACKGROUND

Oligosaccharide processing enzymes are important classes of catalysts involved in synthesizing specific oligosaccharide structures on proteins and sphingolipids. Development of specific inhibitors of such enzymes is of current interest as these inhibitors may be used to control cellular functions. Five-membered iminocyclitols have been shown to be potent inhibitors of such enzymes. Since a rational design and synthesis of inhibitors is often extremely difficult due to the limited information regarding the structure of the active site, we carried out a combinatorial library approach.

RESULTS

To create diversity, we decided to use an aldehyde group of a protected iminocyclitol for reductive amination and the Strecker reaction. After transformation of the nitrile group introduced by the Strecker reaction into an amine and amide and complete deprotection, a small library of five-membered iminocyclitols consisting of 27 compounds was synthesized. A series of compounds obtained by reductive amination was first screened as potential inhibitors of glycosidases and glycosyltransferases. Among them, compounds carrying a C(10)-alkyl group showed marked enhancement of inhibitory activity against alpha-mannosidase at 10 microM concentration when compared with its parent compound and deoxymannojirimycin. Furthermore, compounds having the phenylethyl group showed an extremely strong inhibitory effect against alpha-galactosaminidase at a K(i) value of 29.4 nM. Compounds with an aminomethyl and amide group at the C-1' position of these two molecules showed a decrease in inhibitory activities.

CONCLUSIONS

A combinatorial approach based on five-membered iminocyclitols with a galacto-configuration was exploited. The potential usefulness of the library as a source of inhibitors of glycoenzymes is clearly shown in this study.