Serum inhibitors for human mast cell growth: possible role of retinol

BACKGROUND

In vitro culture systems have been used to study the physiological and pathological characteristics of human mast cells. However, there are some differences in proliferation and maturation of mast cells between fetal bovine serum (FBS)-containing and serum-deprived cultures. Accordingly, we attempted to identify circulating factor(s) affecting the development of human mast cells.

METHODS

We measured the serum levels of retinol and several cytokines. To elucidate the antiproliferative effects of the serum, a retinoic acid receptor (RARalpha) antagonist and neutralizing antibodies against cytokines were used.

RESULTS

Similar to FBS, human serum dose-dependently suppressed the growth of tryptase+ cells from CD34+ cord blood cells or 20-week cultured mast cells under stimulation with stem cell factor (SCF). The serum-mediated inhibition might be based on a decline in proliferation rate. Among inhibitors for mast cell growth, retinol and transforming growth factor (TGF)-beta1 were present at high levels in human serum. In contrast with anti-TGF-beta1 antibody, an RARalpha antagonist counteracted the serum-induced suppression of human mast cell proliferation.

CONCLUSIONS

Our results suggest that retinol and its derivatives act as a circulating regulator for human mast cell growth. The RARalpha antagonist may be a useful tool to obtain higher numbers of mast cells in FBS-containing cultures.

Radical anion of isolable dialkylsilylene

By the reduction of an isolable dialkylsilylene, 2,2,5,5-[tetrakis(trimethylsilyl)]-1-silacyclopentane-1,1-diyl (1), with cesium, rubidium, potassium, sodium, and lithium 4,4'-di(tert-butyl)biphenylide in DME at low temperatures, the corresponding silylene radical anion 2 was generated as the first persistent silylene radical anion in solution and characterized by ESR spectroscopy. Radical anion 2 is rather stable at -70 degrees C in DME but decomposes rapidly at room temperature with a half-life time of ca. 20 min. The g-factor and 29Si hyperfine splitting constants (hfs's) of 2 are almost independent of the countercations, indicating that 2 exists as a free ion or a solvent-separated ion pair in a polar DME solution. A very small hfs due to the 29Si nucleus of the divalent silicon (3.0 mT) as well as a very large g-factor (2.0077) indicates that an unpaired electron is accommodated in the vacant 3ppi orbital of silylene 1.

Non-synonymous single nucleotide alterations in the microsomal epoxide hydrolase gene and their functional effects

1. By sequencing genomic DNA from 72 established cell lines derived from Japanese individuals, we detected 25 single nucleotide alterations in the microsomal epoxide hydrolase (EPHX1) gene. Of them, five were exonic alterations resulting in amino acid alterations (77C>G, T26S; 128G>C, R43T; 337T>C, Y113H; 416A>G, H139R; 823A>G, T275A). The T26S, R43T, Y113H and H139R substitutions were found at relatively high frequencies and seemed to be polymorphic, and T26S and T275A were novel. 2. To examine the effects of these amino acid alterations on EPHX1 function, EPHX1 cDNA constructs of wild-type and five variants were transfected into COS-1 cells, and their hydrolytic activities for cis-stilbene oxide were determined in vitro. Although all of the transfectants expressed EPHX1 mRNA and protein at similar levels, the variant H139R protein was expressed at a significantly higher level (128% of the wild-type). K(m) values were not significantly different between the wild-type and variants. 3. Increase (140%) in the enzymatic activity (V(max)) of the variant H139R was accompanied by the increased EPHX1 protein level without any significant change in the intrinsic EPHX1 activity. On the other hand, the variant R43T showed increased values for V(max) and clearance (V(max)/K(m)) (around 130%) both on a microsomal protein basis and on a EPHX1 protein basis. 4. These results suggest that R43T as well as H139R increase epoxide hydrolase activity.

A stable silicon-based allene analogue with a formally sp-hybridized silicon atom

Carbon chemistry exhibits a rich variety in bonding patterns, with homo- or heteronuclear multiple bonds involving sp-hybridized carbon atoms as found in molecules such as acetylenes, nitriles, allenes and carbon dioxide. Carbon's heavier homologues in group 14 of the periodic table--including silicon, germanium and tin--were long thought incapable of forming multiple bonds because of the less effective p(pi)-p(pi) orbital overlap involved in the multiple bonds. However, bulky substituents can protect unsaturated bonds and stabilize compounds with formally sp-hybridized heavy group-14 atoms: stable germanium, tin and lead analogues of acetylene derivatives and a marginally stable tristannaallene have now been reported. However, no stable silicon compounds with formal sp-silicon atoms have been isolated. Evidence for the existence of a persistent disilaacetylene and trapping of transient 2-silaallenes and other X = Si = X' type compounds (X, X' = O, CR2, NR, and so on) are also known, but stable silicon compounds with formally sp-hybridized silicon atoms have not yet been isolated. Here we report the synthesis of a thermally stable, crystalline trisilaallene derivative containing a formally sp-hybridized silicon atom. We find that, in contrast to linear carbon allenes, the trisilaallene is significantly bent. The central silicon in the molecule is dynamically disordered, which we ascribe to ready rotation of the central silicon atom around the molecular axis.

Gene expression profiling of Ca2+-atpase inhibitor DTBHQ and antigen-stimulated RBL-2H3 mast cells

OBJECTIVE AND DESIGN

Ca2+ signaling is critical for mast cell activation by antigen stimulation, and we previously described that the signaling can be mimicked by Ca2+-ATPase inhibitors. We therefore investigated the effect of the Ca2+-ATPase inhibitor and antigen stimulation on the gene expression profiles of RBL-2H3 mast cells.

MATERIAL

A Ca2+-ATPase inhibitor, 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ), an antigen (dinitrophenylated BSA), a high-density oligonucleotide microarray (Affymetrix GeneChip) technique, and a well-characterized rat mast cell line RBL-2H3 were used.

TREATMENT

RBL-2H3 cells were activated for 3 h with 10 microM DTBHQ, which increases cytosolic Ca2+ concentration, or 10 microg/ml antigen, which cross-links IgE receptors, and the mRNA expression profiles (8,799 genes) were analyzed with GeneChip arrays (n = 3).

METHODS

Expression levels were measured by GeneChip, and the differences were tested by Welch's t-test and P-values less than 0.05 were considered statistically significant. Values are expressed as means +/- SEM.

RESULTS

The genes, including MCP-1, GADD45, Relaxin H1, CSF-1, c-jun-oncogene, Pyk-2, NKR-P2 and CREM, were significantly up-regulated by both DTBHQ and antigen stimuli, whereas the genes including interleukin (IL)-3, IL-4, IL-9, IL-13, GADD153, butyrate response factor, and Fas ligand, were up-regulated by DTBHQ alone. On the other hand, the expression of several genes, including GATA-1, were down-regulated by DTBHQ stimulation.

CONCLUSIONS

These results suggest 1) that DTBHQ seems to induce proinflammatory responses by stimulating the production of several cytokines through the expression of several transcription factors, 2) that the changes in gene expression profile induced by DTBHQ and by IgE receptor cross-linking in mast cells were almost the same, but many more stress-inducible genes like GADD 153 were up-regulated by the former.

Microcirculation in the macular area of eyes with an idiopathic epiretinal membrane

PURPOSE

To measure the microcirculation in the macula area of eyes before and after the removal of an idiopathic epiretinal membrane (ERM) by vitreous surgery.

METHODS

Tissue blood flow in the macula was examined with the Heidelberg retina flowmeter in 12 eyes with an ERM before and 3, 6, and 12 months after vitrectomy. Blood flow measurements were performed in a 10 x 5 degree area in the macula that was divided into superior and inferior areas. At least three measurements were obtained, and the mean blood flow (MBF) was calculated by scanning laser Doppler flowmetry. The ratio of the MBF in the affected eye to that in the fellow eye was used for statistical analysis.

RESULTS

The ratios of the MBF in the affected to the fellow eye in the superior area before and 1, 3, 6, and 12 months after surgery were 0.73, 0.51, 0.77, 0.88, and 1.01, respectively. The ratios of the MBF in the inferior area for the same periods were 0.70, 0.52, 0.75, 0.83, and 0.98, respectively.

CONCLUSIONS

Eyes with an ERM showed abnormal hemodynamics in the macula that gradually improved after vitrectomy to a status comparable with the MBF of the normal fellow eye.

Non-synonymous single nucleotide alterations found in the CYP2C8 gene result in reduced in vitro paclitaxel metabolism

By sequencing genomic DNA from 73 established cell lines derived from Japanese individuals, we detected 9 single nucleotide polymorphisms (SNPs) in the CYP2C8 gene. Of them, 3 exonic SNPs resulted in amino acid alterations (g416a, R139K; a1196g, K399R; c1210g, P404A). The first two alterations were detected concurrently in one cell line and thought to be the same as CYP2C8*3. To examine the effects of these amino acid alterations on CYP2C8 function, wild-type and four types of variant CYP2C8 cDNA constructs (R139K, K399R, R139K/K399R and P404A) were transfected into Hep G2 cells and their paclitaxel 6a-hydroxylase activities were determined in vitro. Km values were not significantly different from that of the wild-type in any of the variants studied. The variant R139K/K399R showed reduced values for Vmax and clearance (Vmax/Km) similar to those of its single variant, R139K. The variant P404A also showed a significantly lowered clearance due to reduced level of protein expression. These results suggest that not only the double variant (R139K/K399R, CYP2C8*3) but also our novel variant P404A in the CYP2C8 gene are less efficient in paclitaxel metabolism.

14-3-3 proteins regulate intracellular localization of the bZIP transcriptional activator RSG

Gibberellins (GAs) are essential regulators of many aspects of plant development, including stem elongation, seed germination, and flowering. RSG is a transcriptional activator with a basic leucine zipper domain that regulates endogenous amounts of GAs through the control of a GA biosynthetic enzyme. The ubiquitous expression of RSG in plant organs suggests an involvement of post-transcriptional and/or post-translational modifications of the transcription factor. Here, we identify the 14-3-3 signaling proteins as RSG binding partners. The mutant version of RSG that could not bind to 14-3-3 proteins exhibited a higher transcriptional activity than did wild-type RSG. Consistent with this observation, the mutant RSG that could not bind to 14-3-3 proteins was localized predominantly in the nucleus, whereas wild-type RSG was distributed throughout the cell. Using the nuclear export inhibitor leptomycin B, we also showed that RSG, apparently statically localized in the cytoplasm, is capable of shuttling in and out of the nucleus. These results suggest that 14-3-3 proteins negatively modulate RSG, which is involved in the regulation of endogenous amounts of GAs, by controlling its intracellular localization.

14-3-3 proteins regulate intracellular localization of the bZIP transcriptional activator RSG

Gibberellins (GAs) are essential regulators of many aspects of plant development, including stem elongation, seed germination, and flowering. RSG is a transcriptional activator with a basic leucine zipper domain that regulates endogenous amounts of GAs through the control of a GA biosynthetic enzyme. The ubiquitous expression of RSG in plant organs suggests an involvement of post-transcriptional and/or post-translational modifications of the transcription factor. Here, we identify the 14-3-3 signaling proteins as RSG binding partners. The mutant version of RSG that could not bind to 14-3-3 proteins exhibited a higher transcriptional activity than did wild-type RSG. Consistent with this observation, the mutant RSG that could not bind to 14-3-3 proteins was localized predominantly in the nucleus, whereas wild-type RSG was distributed throughout the cell. Using the nuclear export inhibitor leptomycin B, we also showed that RSG, apparently statically localized in the cytoplasm, is capable of shuttling in and out of the nucleus. These results suggest that 14-3-3 proteins negatively modulate RSG, which is involved in the regulation of endogenous amounts of GAs, by controlling its intracellular localization.

Release from or through a wax matrix system. I. Basic release properties of the wax matrix system

Release properties from a wax matrix tablet was examined. To obtain basic release properties, the wax matrix tablet was prepared from a physical mixture of drug and wax powder (hydrogenated caster oil) at a fixed mixing ratio. Properties of release from the single flat-faced surface or curved side surface of the wax matrix tablet were examined. The applicability of the square-root time law and of Higuchi equations was confirmed. The release rate constant obtained as g/min(1/2) changed with the release direction. However, the release rate constant obtained as g/cm2 x min(1/2) was almost the same. Hence it was suggested that the release property was almost the same and the wax matrix structure was uniform independent of release surface or direction at a fixed mixing ratio. However, these equations could not explain the entire release process. The applicability of a semilogarithmic equation was not as good compared with the square-root time law or Higuchi equation. However, it was revealed that the semilogarithmic equation was available to simulate the entire release process, even though the fit was somewhat poor. Hence it was suggested that the semilogarithmic equation was sufficient to describe the release process. The release rate constant was varied with release direction. However, these release rate constants were expressed by a function of the effective surface area and initial amount, independent of the release direction.

The effect of propafenone on premature ventricular contractions (PVC): an analysis based on heart rate dependency of PVCs

The effect of 450 mg/day propafenone for two weeks on premature ventricular contractions (PVCs) was studied in combination with an assessment of heart rate (HR) dependency of PVCs using Holter ECG monitoring in patients with more than 720 PVCs per day. The PVC-HR correlation was classified into positive (P), bidirectional (B), and flat and negative (FN) correlation groups. The positive group included only patients in whom PVC frequency increased with a heart rate increase, while the bidirectional group included patients with PVCs whose frequency increased at low heart rates and decreased at high heart rates. The FN group contained both flat (PVC frequency was almost fixed regardless of heart rate changes) and negative (PVC frequency decreased as heart rate increased) correlations. The effectiveness of propafenone was 70% in the positive group and 50% in the nonpositive group which included both bidirectional (67%) and FN (0%) groups, using a > 70% PVC reduction as a criterion of efficacy. From this, we concluded that propafenone is effective in patients showing either positive or bidirectional PVC-HR correlation. The coupling interval (CI) of PVCs was also prolonged by propafenone as a whole. The present study suggests that there are differences in the mechanism of PVC development in patients with flat or negative correlation and those with a positive or bidirectional correlation. Thus, this type of analysis contributes to an understanding of the action of antiarrhythmic agents, and may allow the prediction of their efficacy on PVCs.