Thioredoxin-1 Attenuates Early Graft Loss after Intraportal Islet Transplantation in Mice

Aims

Recent studies suggest that decreasing oxidative stress is crucial to achieve successful islet transplantation. Thioredoxin-1 (TRX), which is a multifunctional redox-active protein, has been reported to suppress oxidative stress. Furthermore, it also has anti-inflammatory and anti-apoptotic effects. In this study, we investigated the effects of TRX on early graft loss after islet transplantation.

Methods

Intraportal islet transplantation was performed for two groups of streptozotocin-induced diabetic mice: a control and a TRX group. In addition, TRX-transgenic (Tg) mice were alternately used as islet donors or recipients.

Results

The changes in blood glucose levels were significantly lower in the TRX group compared with the TRX-Tg donor and control groups (p<0.01). Glucose tolerance and the residual graft mass were considerably better in the TRX group. TRX significantly suppressed the serum levels of interleukin-1β (p<0.05), although neither anti-apoptotic nor anti-chemotactic effects were observed. Notably, no increase in the 8-hydroxy-2′-deoxyguanosine level was observed after islet infusion, irrespective of TRX administration.

Conclusions

The present study demonstrates that overexpression of TRX on the islet grafts is not sufficient to improve engraftment. In contrast, TRX administration to the recipients exerts protective effects on transplanted islet grafts by suppressing the serum levels of interleukin-1β. However, TRX alone appears to be insufficient to completely prevent early graft loss after islet transplantation. We therefore propose that a combination of TRX and other anti-inflammatory treatments represents a promising regimen for improving the efficacy of islet transplantation.     

A Convenient and Stereoselective Synthesis of 2′-Deoxy-β-L-Ribonucleosides

Abstract

2′-Deoxy-β-L-ribonucleosides containing usual bases which are useful as synthons for modified oligodeoxyribonucleotides, were conveniently synthesized by a stereoselective glycosylation procedure. The method is suitable for large-scale preparations.     

An exo-alpha-sialidase from bifidobacteria involved in the degradation of sialyloligosaccharides in human milk and intestinal glycoconjugates

Bifidobacteria are health-promoting enteric commensals that are assumed to proliferate predominantly in the intestines of breast-fed infants by assimilating human milk oligosaccharides (HMOs) that are frequently fucosylated and/or sialylated. We previously identified two different α-l-fucosidases in Bifidobacterium bifidum and showed that the strain furnishes an extracellular degradation pathway for fucosylated HMOs. However, the catabolism of sialylated HMOs by bifidobacteria has remained unresolved. Here we describe the identification and characterization of an exo-α-sialidase in bifidobacteria. By expression cloning, we isolated a novel exo-α-sialidase gene (siabb2) from B. bifidum JCM1254, which encodes a protein (SiaBb2) consisting of 835-amino-acid residues with a predicted molecular mass of 87 kDa. SiaBb2 possesses an N-terminal signal sequence, a sialidase catalytic domain classified into the glycoside hydrolase family 33 (GH33) and a C-terminal transmembrane region, indicating that the mature SiaBb2 is an extracellular membrane-anchored enzyme. The recombinant enzyme expressed in Escherichia coli showed the highest activity in an acidic pH range from 4.0 to 5.0, and at 50 °C. Notably, 80% activity remained after 30 min incubation at 80 °C, indicating that the enzyme is highly thermostable. SiaBb2 liberated sialic acids from sialyloligosaccharides, gangliosides, glycoproteins and colominic acid; however, the linkage preference of the enzyme was remarkably biased toward the α2,3-linkage rather than α2,6- and α2,8-linkages. Expression of siabb2 in B. longum 105-A, which has no endogenous exo-α-sialidase, enabled this strain to degrade sialyloligosaccharides present in human milk. Our results suggest that SiaBb2 plays a crucial role in bifidobacterial catabolism of sialylated HMOs.     

Urinary stone analysis in a patient with hyperuricemia to determine the mechanism of stone formation

In order to determine the mechanism of urinary stone formation in patients with hyperuricemia, we analyzed the crystal components and matrix proteins in a urinary stone from such a patient. Micro-area X-ray spectrometry and infrared (IR) spectroscopy suggested that the outside of the stone was composed of calcium oxalate monohydrate (COM) and the inside of uric acid (UA). Proteomic analysis identified 37 and 14 proteins from the inside and outside of the stone, respectively, as matrix proteins. The proteins that were identified in an ethylenediaminetetraacetic acid (EDTA) fraction were able to bind calcium ions. Thus, calcium-binding proteins may play a significant role in the formation of urinary stones in patients with hyperuricemia.     

Efficacy of benzbromarone in hyperuricemic patients associated with chronic kidney disease

We have retrospectively evaluated the uric acid control status and renal function changes over a period of up to 7 years in 35 patients with renal impairment who had stage 3 or higher chronic kidney disease (CKD; stage 3 in 32 patients, stage 4 in 2 patients, and stage 5 in 1 patient) associated with hyperuricemia and were receiving monotherapy with benzbromarone as an antihyperuricemic drug. Serum uric acid levels significantly decreased from 8.5 ± 0.9 to 6.1 ± 0.8 mg/dL at 6 months and were subsequently controlled at less than 7.0 mg/dL in most patients. Most patients received benzbromarone at a dose of 25-50 mg/day, whereas 150-200 mg/day was used in some patients with stage 4 or 5 CKD. No significant changes in estimated glomerular filtration rate (eGFR) from the baseline value of 46.2 ± 11.5 mL/minute/1.73 m(2) were found after benzbromarone therapy. Although the renal function impairment did not improve by reducing the serum uric acid levels with benzbromarone, the renal function did not deteriorate further on the therapy. These results suggest that benzbromarone is applicable to the management of hyperuricemia associated with renal impairment.     

Rapid assay for detecting gyrA and parC mutations associated with fluoroquinolone resistance in Enterobacteriaceae

We developed a PCR-RFLP assay to detect mutations in the quinolone-resistance determining regions of gyrA and parC associated with fluoroquinolone resistance in Enterobacteriaceae. The assay detected mutations associated with reduced susceptibility to fluoroquinolones and may therefore serve as a specific, rapid, inexpensive, and simple testing alternative.     

Isolation of R-(−)-3-Hydroxy-β-ionone from Burley Tobacco

The tritium-hydrogen exchange method was used to determine the total racemization of amino acid residues of four proteins (ribonuclease A, lysozyme, soybean protein and casein) during their exposure to an alkali. Tritium was incorporated with first order kinetics into these proteins during their incubation in 0.2 n NaOH at 40°C. The tritium-hydrogen exchange increased as the temperature and the alkali concentration increased. In contrast, pepsin digestibility decreased extensively in the initial stage of the treatment. This phenomenon was verified by the subsite theory of protease, that only minor racemization renders the extended range of the peptide chain around the racemized amino acids non-susceptible to pepsin. General precautions against the racemization of food protein treated with alkalis are discussed briefly in terms of the deterioration of nutrients.     

Growth and β-Glucan 10C3K Production by a Mutant of Alcaligenes faecalis var. myxogenes in Defined Medium

A defined medium was developed in which Alcaligenes faecalis var. myxogenes 10C3 mutant K produced a large quantity of β-glucan 10C3K. The medium contained 4% glucose together with 0.1% citrate, succinate or fumarate as the carbon source, 0.15% (NH₄)₂HPO₄ as the nitrogen source and mineral salts. When NaNH₄HPO₄, KNO₃ or urea was used at a concentration of 0.03% nitrogen as the sole nitrogen source, salts of organic acid were not needed in addition to glucose.

In culture medium containing phosphate buffer (M/15, pH 6.5~8.0) large amounts of polysaccharide were formed and its yield from the 4% glucose added was about 50%. Thus, it was shown that polysaccharide production is enhanced greatly if a suitable pH for polysaccharide production is maintained during incubation.