Triphenyltin enhances the neutrophilic differentiation of promyelocytic HL-60 cells

Triphenyltin (TPT) is an environmental endocrine disruptor and toxic substance, but little information is available on its immunological effects. To assess the effect of TPT on leukocyte differentiation, we investigated its effect on the neutrophilic differentiation of HL-60 cells induced by dimethyl sulfoxide and granulocyte colony-stimulating factor (G-CSF) for 6 days. At a low concentration, 10(-7)M, TPT increased superoxide production by differentiated HL-60 cells stimulated with opsonized zymosan (OZ) by about 45% and increased expression of CD18, a component of the OZ-receptor, by about 90%. Real-time PCR analysis revealed that TPT augmented the expression not only of CD18 but also of components of superoxide-generating NADPH-oxidase, p47phox, 2.7-fold, and p67phox, 2.0-fold, and of granulocyte colony-stimulating factor receptor (G-CSFR), 3.0-fold, whereas various other endocrine disruptors, including parathion, vinclozolin, and bisphenol A, had no such enhancing effects. The results of a DNA macroarray analysis showed that TPT enhanced the expression of G-CSFR and certain other neutrophil functional proteins, including CD14 and myeloid leukemia cell differentiation protein (MCL-1), and that TPT induced a decrease in expression of LC-PTP, leukocyte protein-tyrosine phosphatase, to about half the control level. The TPT-dependent suppression of LC-PTP was confirmed by real-time PCR analysis, and the results of immunoblotting indicated that TPT enhances the expression of myeloid specific tyrosine kinase hck by about 30% at the protein level, and this together with the reduction of LC-PTP may enhance tyrosine phosphorylation, in turn resulting in enhancement of superoxide production. These findings suggest that TPT may have an enhancing effect on the neutrophilic maturation of leukocytes.     

Crystal structure of chartreusin derivative A132

The crystal structure of chartreusin derivative A132 (benzilidene chartreusin) has been determined by single-crystal X-ray diffraction. The space group is C2 with unit cell dimensions, a=18.482(4), b=8.749(3), c=43.906(2) A, beta=94.87(2) degrees, and the structure was refined to R-factors of 0.2365 (6585 all unique reflections) and 0.087 (2914 reflections with F(o)>4 sigma(F(o))) by a full-matrix least-squares method. There are two molecules in an asymmetric unit. Both molecules have similar structures, which are favorable to bind with DNA in the minor groove. A modeling study of the A132-DNA complex based on the X-ray structures suggests that the sugar moiety of A132 may play an important role in recognizing the sequence of DNA base pairs.     

PI3K is a key molecule in the Nrf2-mediated regulation of antioxidative proteins by hemin in human neuroblastoma cells

Oxidative stress and ferrous metabolism are important in the pathogenesis in Parkinson's disease. In dopaminergic neurons, several stress proteins are upregulated under oxidative stress. To clarify this mechanism, we investigated hemin-related signal transduction and the induction of oxidative stress-related proteins in SH-SY5Y cells. We identified phosphatidylinositol 3-kinase (PI3K) and Nrf2 as important molecules in the induction of heme oxygenase-1, thioredoxin, and peroxiredoxin-I. PI3K-related signal controlled Nrf2 activation, and consequently, PI3K inhibitors blocked the nuclear translocation of Nrf2 and induction of stress proteins. These observations suggest that PI3K and Nrf2 are key molecules in maintaining suitable conditions under oxidative stress and ferrous metabolism.     

Strictly polyphosphate-dependent glucokinase in a polyphosphate-accumulating bacterium,Microlunatus phosphovorus

ATP-dependent glucokinase is suggested to have evolved from a hypothetical polyphosphate (polyP)-dependent glucokinase (polyP-GK) via a bifunctional polyP/ATP glucokinase (polyP/ATP-GK). Here we showed that polyP-GK is present in a polyP-accumulating bacterium, Microlunatus phosphovorus. The polyP-GK produced glucose-6-P(i) from glucose and polyP, but it could not phosphorylate glucose with ATP. The polyP-GK was most closely related to the polyP/ATP-GK of Mycobacterium tuberculosis.     

Possible involvement of optimally phosphorylated L-plastin in activation of superoxide-generating NADPH oxidase

The involvement of protein phosphatases in the activation of superoxide (O2-)- generating enzyme in human neutrophils was examined using calyculin A, an inhibitor of protein phosphatase type 1 and 2A. Calyculin A inhibited the phorbol myristate acetate (PMA)- and opsonized zymosan (OZ)-activated O2- generation by human neutrophils. This inhibitory effect of calyculin A on PMA-activated O2- generation was reversed by the addition of KT5926, a specific inhibitor of myosin light chain kinase and Ca2+/calmodulin-dependent protein kinase II. These results suggest that the addition of calyculin A may cause hyperphosphorylation of some protein(s) that plays a crucial role in the PMA-dependent activation of O2- generating enzyme, and that this protein hyperphosphorylation may be evoked by a KT5926-sensitive kinase or its downstream kinase. Whereas two-dimensional analysis involving 32P revealed that calyculin A caused the hyperphosphorylation of many proteins, KT5926 mainly reduced the calyculin A-induced hyperphosphorylation of a 67 kDa protein in activated neutrophils, suggesting that the hyperphosphorylation of the 67 kDa protein might inhibit the PMA-dependent activation of NADPH oxidase. The 67 kDa cytosolic protein was moderately phosphorylated on the addition of PMA. On the other hand, in the absence of calyculin A, KT5926 inhibited both PMA-induced O2- generation and phosphorylation of the 67 kDa protein. Amino acid sequence analysis of peptides derived from the 67 kDa protein revealed that the 67 kDa protein was identical to L-plastin, an actin-bundling protein. We conclude that optimally phosphorylated L-plastin may play some crucial role in the activation of NADPH oxidase.     

Monitoring of Bacillus thermodenitrificans OHT-1 in compost by whole cell hybridization

Thermophilic aerobic composting is a widely practiced method for the disposal of exhaust materials. We isolated a thermophilic bacteria strain from a compost sample under aerobic conditions at 60 degrees C. On the basis of its 16S rRNA sequence and physiological characteristics, this strain was identified as Bacillus thermodenitrificans OHT-1. An 18-subunit oligonucleotide probe for 16S rRNA, labeled with fluorescein isothiocyanate, was developed for the detection of B. thermodenitrificans. Spores and vegetative cells of B. thermodenitrificans OHT-1 were detected in liquid culture and laboratory compost by whole cell hybridization using this oligonucleotide probe. The results obtained by whole cell hybridization were evaluated in growth experiments of B. thermodenitrificans OHT-1 in laboratory compost and were used to enumerate spores and vegetative cells.     

Amyloid fibril formation of the mouse V(L) domain at acidic pH

The recombinant V(L) domain that represents the variable part of the light chain (type kappa) of mouse monoclonal antibody F11 directed against human spleen ferritin was found to form amyloid fibrils at acidic pH as evidenced by electron microscopy, thioflavin T binding, and apple-green birefringence after Congo red staining. This is the first demonstration of amyloid fibril formation of the mouse V(L) domain. To understand the mechanism of acidic pH-induced amyloid fibril formation, conformational changes of the V(L) domain were studied by one-dimensional NMR, differential scanning calorimetry, analytical ultracentrifugation, hydrophobic dye binding, far-UV circular dichroism, and tryptophan fluorescence. The results indicated accumulation of two intermediate states during acid unfolding, which might be responsible for amyloid fibril formation. The more structured intermediate that exhibited maximal accumulation at pH 3 retained the nativelike secondary structure and a hydrophobic core, but exposed hydrophobic surfaces that bind 8-anilino-1-naphthalenesulfonate. Below pH 2, a more disordered intermediate with dequenched tryptophan fluorescence but still retaining the beta-sheet structure accumulated. The optimal pH of amyloid fibril formation (i.e., pH 4) was close to the optimal pH of the accumulation of the nativelike intermediate, suggesting that the amyloid fibrils might be formed through this intermediate.