Dysregulation of metabolic pathways in a mouse model of allergic asthma.

BACKGROUND: Asthma is a complex lung disease resulting from the interplay of genetic and environmental factors. To understand the molecular changes that occur during the development of allergic asthma without genetic and environmental confounders, an experimental model of allergic asthma in mice was used. Our goals were to (1) identify changes at the small molecule level due to allergen exposure, (2) determine perturbed pathways due to disease, and (3) determine whether small molecule changes correlate with lung function. METHODS: In this experimental model of allergic asthma, matched bronchoalveolar lavage (BAL) fluid and plasma were collected from three groups of C57BL6 mice (control vs sensitized and/or challenged with ovalbumin, n=3-5/group) 6 hour, 24 hour, and 48 hour after the last challenge. Samples were analyzed using liquid chromatography-mass spectrometry-based metabolomics. Airway hyper-responsiveness (AHR) measurements and differential cell counts were performed. RESULTS: In total, 398 and 368 dysregulated metabolites in the BAL fluid and plasma of sensitized and challenged mice were identified, respectively. These belonged to four, interconnected pathways relevant to asthma pathogenesis: sphingolipid metabolism (P=6.6×10-5 ), arginine and proline metabolism (P=1.12×10-7 ), glycerophospholipid metabolism (P=1.3×10-10 ), and the neurotrophin signaling pathway (P=7.0×10-6 ). Furthermore, within the arginine and proline metabolism pathway, a positive correlation between urea-1-carboxylate and AHR was observed in plasma metabolites, while ornithine revealed a reciprocal effect. In addition, agmatine positively correlated with lung eosinophilia. CONCLUSION: These findings point to potential targets and pathways that may be central to asthma pathogenesis and can serve as novel therapeutic targets.

Childhood asthma is associated with mutations and gene expression differences of ORMDL genes that can interact.

BACKGROUND: Genomewide association studies identified ORMDL3 as a plausible asthma candidate gene. ORMDL proteins regulate sphingolipid metabolism and ceramide homeostasis and participate in lymphocyte activation and eosinophil recruitment. Strong sequence homology between the three ORMDL genes and ORMDL protein conservation among different species suggest that they may have shared functions. We hypothesized that if single nucleotide polymorphisms (SNPs) in ORMDL3 alter its gene expression and play a role in asthma, variants in ORMDL1 and ORMDL2 might also be associated with asthma. METHODS: Asthma associations of 44 genotyped SNPs were determined in at least 1303 subjects (651 asthmatics). ORMDL expression was evaluated in peripheral blood mononuclear cells (PBMC) from 55 subjects (eight asthmatics) before and after allergen stimulation, and in blood (n = 60, 5 asthmatics). Allele-specific cis-effects on ORMDL expression were assessed. Interactions between human ORMDL proteins were determined in living cells. RESULTS: Sixteen SNPs in all three ORMDLs were associated with asthma (14 in ORMDL3). Baseline expression of ORMDL1 (P = 1.7 × 10(-6) ) and ORMDL2 (P = 4.9 × 10(-5) ) was significantly higher in PBMC from asthmatics, while induction of ORMDLs upon stimulation was stronger in nonasthmatics. Disease-associated alleles (rs8079416, rs4795405, rs3902920) alter ORMDL3 expression. ORMDL proteins formed homo- and heterooligomers and displayed similar patterns of interaction with SERCA2 and SPT1. CONCLUSIONS: Polymorphisms in ORMDL genes are associated with asthma. Asthmatics exhibit increased ORMDL levels, suggesting that ORMDLs contribute to asthma. Formation of heterooligomers and similar interaction patterns with proteins involved in calcium homeostasis and sphingolipid metabolism could indicate shared biological roles of ORMDLs, influencing airway remodeling and hyperresponsiveness.

Fine-mapping of IgE-associated loci 1q23, 5q31, and 12q13 using 1000 Genomes Project data.

BACKGROUND: Genome-wide association studies (GWAS) repeatedly identified 1q23 (FCER1A), 5q31 (RAD50-IL13 and IL4), and 12q13 (STAT6) as major susceptibility loci influencing the regulation of total serum IgE levels. As GWAS may be insufficient to capture causal variants, we performed fine-mapping and re-genotyping of the three loci using 1000 Genomes Project datasets. METHODS: Linkage disequilibrium tagging polymorphisms and polymorphisms of putative functional relevance were genotyped by chip technology (24 polymorphisms) or MALDI-TOF-MS (40 polymorphisms) in at least 1303 German children (651 asthmatics). The effect of polymorphisms on total serum IgE, IgE percentiles, and atopic diseases was assessed, and a risk score model was applied for gene-by-gene interaction analyses. Functional effects of putative causal variants from these three loci were studied in silico. RESULTS: Associations from GWAS were confirmed and extended. For 1q23 and 5q31, the majority of associations were found with mild to moderately elevated IgE levels, while in the 12q13 locus, single-nucleotide polymorphisms (SNPs) were associated with strongly elevated IgE levels. Gene-by-gene interaction analyses suggested that the presence of mutations in all three loci increases the risk for elevated IgE up to fourfold. CONCLUSION: This fine-mapping study confirmed previous associations and identified novel associations of SNPs in 1q23, 5q31, and 12q13 with different levels of serum IgE and their concomitant contribution to IgE regulation.

STAT6 polymorphisms are associated with neonatal regulatory T cells and cytokines and atopic diseases at 3 years.

BACKGROUND: The transcription factor STAT6 is crucial for activation of the interleukin (IL)-4/IL-13 pathway and has been linked to regulatory T cells (Tregs). Associations of STAT6 polymorphisms with IgE levels were described; however, their impact on neonatal immune responses and early disease development is unknown. METHODS: STAT6 polymorphisms were genotyped in cord blood mononuclear cells by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Gene expression was assessed by real-time polymerase chain reaction (PCR) and cytokines by Multiplex. At age 3 years, atopic diseases were assessed by questionnaires. RESULTS: STAT6 rs324011 but not rs1059513 polymorphism was associated with significant or borderline significant decreased mRNA expression of Treg-associated genes (FOXP3, GITR, LAG3). Heterozygotes and minor allele homozygotes of rs324011 had low levels of tumor necrosis factor alpha (TNF-α) and increased interferon gamma (IFN-γ) (P ≤ 0.04), while heterozygotes and minor allele homozygotes of rs1059513 had increased TNF-α and Granulocyte-macrophage colony-stimulating factor (GM-CSF) (P ≤ 0.05). In minor allele homozygotes of rs324011, expression of Treg-associated genes was strongly inverse correlated with IFN-γ (unstimulated, r = -0.7, P = 0.111; LpA stimulation, r = -0.8, P = 0.011), but not in heterozygotes or major allele homozygotes. Heterozygotes and minor allele homozygotes of rs324011 presented a lower risk of atopic dermatitis and obstructive bronchitis until age 3 years. CONCLUSIONS: Two STAT6 polymorphisms were associated with altered immune responses already at birth. STAT6 rs324011 was associated with lower neonatal Treg and increased Th1 response. Those neonates had a lower risk of atopic dermatitis and obstructive bronchitis until 3 years. Our data suggest a role for STAT6 polymorphisms in early immune regulation and implications on early atopic disease development.

Purification of Thiobacillus denitrificans siroheme sulfite reductase and investigation of some molecular and catalytic properties.

A siroheme-containing sulfite reductase was isolated from Thiobacillus denitrificans, purified to an electrophoretically homogenous state, and investigated with regard to some of its molecular and catalytic properties. The enzyme was a tetramer with a molecular weight of 160 000, consisting of two types of subunits arranged to an alpha 2 beta 2-structure. The molecular weight of the alpha-subunit was 38 000, that of the beta-subunit 43 000. As prosthetic groups siroheme and Fe/S groupings could be detected. The absorption spectrum showed maxima at 273 nm, 393 nm, and 594 nm; the molar extinction coefficient at these wavelengths were 280, 181, and 60 . 10(3) cm2 . mmol-1, respectively. With reduced viologen dyes the enzyme reduced sulfite to sulfide, thiosulfate and trithionate. In many properties T. denitrificans sulfite reductase closely resembled desulfoviridin, the dissimilatory sulfite reductase of Dssulfovibrio species. It is proposed that the physiological function of this enzyme is not to reduce but rather to form sulfite from reduced sulfur compounds in the course of dissimilatory sulfur oxidation in T. denitrificans.

Association of a STAT 6 haplotype with elevated serum IgE levels in a population based cohort of white adults.

BACKGROUND: Several studies have shown linkage of chromosome 12q 13-24 with atopy related phenotypes. Among candidate genes in this region is STAT6 (signal transducer and activator of transcription), which is essential for Th2 cell differentiation, recruitment, and effector function. METHODS: We evaluated six polymorphisms of STAT6 for evidence of associations with serum IgE levels and atopic diseases in a population based cross sectional cohort of 1407 German adults. Genotyping was performed using the matrix assisted laser desorption ionisation-time of flight mass spectrometry method. Haplotypes were estimated using the SAS/Genetics module, and population-derived IgE percentiles (50% IgE>53 kU/l, 66% IgE>99 kU/l and 90% IgE>307 kU/l) were modelled as outcome variables in haplotype trend regression analysis. RESULTS: All polymorphisms were genotyped successfully. Haplotype reconstruction revealed 8/64 possible haplotypes, reaching estimated frequencies of 1% or more. One polymorphism in intron 2 (rs324011) showed a significant association with total serum IgE (p = 0.015). A STAT6 risk haplotype for elevated IgE showing odds ratios of 1.7 (p = 0.015) for IgE cut-off 100 kU/l, and 1.54 (p = 0.032), 1.6 (p = 0.025), and 2.54 (p = 0.007) for IgE percentiles 50%, 66%, and 90%, respectively was detected. The increased risk of this haplotype was confirmed by linear haplotype trend regression on log transformed IgE values (p = 0.007). Analysis further revealed a risk haplotype for specific sensitisation and a risk haplotype for asthma. CONCLUSION: The data indicate that genetic variants within STAT6 contribute significantly to IgE regulation and manifestation of atopic diseases.

Sulfur metabolism in Thiobacillus denitrificans evidence for the presence of a sulfite reducatase activity.

The relatively high specific sulfite reductase activity of 25 mU/mg protein was found in extracts from Thiobacillus dentrificans. The absorption spectrum of the partially pruified enzyme was similar to the siroheme containing sulfite reductases from other sources. It is suggested that the T. denitrificans sulfite reductase may function during the oxidation of reduced sulfur compounds.

Regulation of C3-enzymes in facultative phototrophic bacteria: the cold-labile pyruvate kinase of Rhodopseudomonas sphaeroides.

Pyruvate kinase (EC2.7.1.40) from Rhodopseudomonas sphaeroides was purified 40-fold be precipitation with protamine sulfate and ammonium sulfate followed by gel-filtration. The preparations obtained from cells grown with different carbon sources or cultural conditions differ with respect to specific activity but not with respect to molecular weight (250000 dalton) or regulatory properties. The phosphoenolpyruvate (PEP)-saturation cruve of the enzyme is sigmoidal with Hill coefficients varying from nH equals 1.8 (pH 9.2) to 2.7 (pH 6.0). The enzyme is activated by adenosinemonophosphate (AMP) and the sugarmonophosphates ribose-5-phosphate (R-5-P), glucose-6-phosphate (G-6-P), and-to a lesser extent-fructose-6-phosphate (F-6-P). Fructose-1.6-bisphosphate (FDP) has no measurable effect. Inhibitors of the enzyme are adenosinetriphosphate (ATP), inorganic phosphate (Pi) and the dicarboxylic acids succinate and fumarate. Kinetic analysis reveals that the sugar-phosphates and the dicarboxylic acids act as true allosteric ligands, whereas the effects of AMP, ATP, and Pi cannot be interpreted soley in terms of allosteric interactions. Cold-treatment of the enzymes lead to a rapid loss of activity, but does not change the regulatory properties of the enzyme. Analysis of the kinetics of cold-inactivation and its reversal at 30 percent C, together with studies on the gelfiltration behaviour of the native and the cold-treated enzyme make it likely that the cold-induced loss of activity is due to a dissociation of the enzyme.

Novel microbial inhibitors of ACE. Isolation and characterization.

Two novel microbial ACE-inhibitors BAY o 6997 and BAY q 1313 were detected in the fermentation broths of streptomyces spec. WS 464 and spec. WS 1065, respectively. Both were isolated and purified by ion exchange chromatography as initial steps, and final purification was achieved by HPLC or additional chromatography of the Cu-chelate (BAY q 1313). Both inhibitors are reversibly inactivated on chelation with Cu2+ or Zn2+. Irreversible inactivation occurs on standing in aqueous and acidic solution or in ammonium hydroxide at room temperature and more rapidly on heating. In 4 M sodium hydroxide solutions BAY o 6997 is completely stable, and BAY q 1313 still remarkably stable even on longer heating to 80 degrees C. Thus, BAY o 6997 was alternatively and advantageously isolated after heating of its solution in 4 M sodium hydroxide to 37 degrees C for 2 days and subsequent fractional precipitation with ethanol in a relatively pure state. Total hydrolysis yielded His, 2-methylamino-4-amino-butyric acid and alpha-keto butyric acid (BAY o 6997) and pyruvic acid (BAY q 1313) respectively. The unusual stability of both inhibitors in sodium hydroxide solution on the one hand and their instability on heating and storage in aqueous or acidic solutions on the other hand clearly prove that the constituents are not linked by amide bonds.

Structures of BAY o 6997 and BAY q 1313 microbial ACE inhibitors.

BAY o 6997 and BAY q 1313 are two novel ACE inhibitors produced by Streptomyces WS 464 and Streptomyces WS 1065, respectively. Their structures were elucidated by NMR and MS analysis of the inhibitors and a substance which formed on decomposition of BAY o 6997 on heating in 4 M acetic acid. Both inhibitors are composed of the same amino acids, namely His and 2-methylamino-4-aminobutyric acid. The 2-amino group of His and the 4-amino group of the 2-methylamino-4-aminobutyric acid are bridged by differently substituted ethylene moieties. As determined by gas chromatography on a chiral phase, both amino acids isolated from the total hydrolysate after derivatisation, at least in BAY o 6997, possess the L-configuration.