Chemical and Cellular Formation of Reactive Oxygen Species from Secondary Organic Aerosols in Epithelial Lining Fluid

INTRODUCTION

Oxidative stress mediated by reactive oxygen species (ROS) is a key process for adverse aerosol health effects. Secondary organic aerosols (SOA) account for a major fraction of particulate matter with aerodynamic diameter ≤2.5 µm (PM2.5). PM2.5 inhalation and deposition into the respiratory tract causes the formation of ROS by chemical reactions and phagocytosis of macrophages in the epithelial lining fluid (ELF), but their relative contributions are not well quantified and their link to oxidative stress remains uncertain. The specific aims of this project were (1) elucidating the chemical mechanism and quantifying the formation kinetics of ROS in the ELF by SOA; (2) quantifying the relative importance of ROS formation by chemical reactions and macrophages in the ELF.

METHODS

SOA particles were generated using reaction chambers from oxidation of various precursors including isoprene, terpenes, and aromatic compounds with or without nitrogen oxides (NOx). We collected size-segregated PM at two highway sites in Anaheim, CA, and Long Beach, CA, and at an urban site in Irvine, CA, during two wildfire events. The collected particles were extracted into water or surrogate ELF that contained lung antioxidants. ROS generation was quantified using electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique. PM oxidative potential (OP) was also quantified using the dithiothreitol assay. In addition, kinetic modeling was applied for analysis and interpretation of experimental data. Finally, we quantified cellular superoxide release by RAW264.7 macrophage cells upon exposure to quinones and isoprene SOA using a chemiluminescence assay as calibrated with an EPR spin-probing technique. We also applied cellular imaging techniques to study the cellular mechanism of superoxide release and oxidative damage on cell membranes.

RESULTS

Superoxide radicals (·O2-) were formed from aqueous reactions of biogenic SOA generated by hydroxy radical (·OH) photooxidation of isoprene, β-pinene, α-terpineol, and d-limonene. The temporal evolution of ·OH and ·O2- formation was elucidated by kinetic modeling with a cascade of aqueous reactions, including the decomposition of organic hydroperoxides (ROOH), ·OH oxidation of primary or secondary alcohols, and unimolecular decomposition of α-hydroxyperoxyl radicals. Relative yields of various types of ROS reflected the relative abundance of ROOH and alcohols contained in SOA, which generated under high NOx conditions, exhibited lower ROS yields. ROS formation by SOA was also affected by pH. Isoprene SOA had higher ·OH and organic radical yields at neutral than at acidic pH. At low pH ·O2- was the dominant species generated by all types of SOA. At neutral pH, α-terpineol SOA exhibited a substantial yield of carbon-centered organic radicals (R·), while no radical formation was observed by aromatic SOA.

Organic radicals in the ELF were formed by mixtures of Fe2+ and SOA generated from photooxidation of isoprene, α-terpineol, and toluene. The molar yields of organic radicals by SOA were 5-10 times higher in ELF than in water. Fe2+ enhanced organic radical yields by a factor of 20-80. Ascorbate mediated redox cycling of iron ions and sustained organic peroxide decomposition, as supported by kinetic modeling reproducing time- and concentration-dependence of organic radical formation, as well as by additional experiments observing the formation of Fe2+ and ascorbate radicals in mixtures of ascorbate and Fe3+. ·OH and superoxide were found to be efficiently scavenged by antioxidants.

Wildfire PM mainly generated ·OH and R· with minor contributions from superoxide and oxygen-centered organic radicals (RO·). PM OP was high in wildfire PM, exhibiting very weak correlation with radical forms of ROS. These results were in stark contrast with PM collected at highway and urban sites, which generated much higher amounts of radicals dominated by ·OH radicals that correlated well with OP. By combining field measurements of size-segregated chemical composition, a human respiratory tract model, and kinetic modeling, we quantified production rates and concentrations of different types of ROS in different regions of the ELF by considering particle-size-dependent respiratory deposition. While hydrogen peroxide (H2O2) and ·O2- production were governed by Fe and Cu ions, ·OH radicals were mainly generated by organic compounds and Fenton-like reactions of metal ions. We obtained mixed results for correlations between PM OP and ROS formation, providing rationale and limitations of the use of oxidative potential as an indicator for PM toxicity in epidemiological and toxicological studies.

Quinones and isoprene SOA activated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in macrophages, releasing massive amounts of superoxide via respiratory burst and overwhelming the superoxide formation by aqueous chemical reactions in the ELF. The threshold dose for macrophage activation was much smaller for quinones compared with isoprene SOA. The released ROS caused lipid peroxidation to increase cell membrane fluidity, inducing oxidative damage and stress. Further increases of doses led to the activation of antioxidant response elements, reducing the net cellular superoxide production. At very high doses and long exposure times, chemical production became comparably important or dominant if the escalation of oxidative stress led to cell death.

CONCLUSIONS

The mechanistic understandings and quantitative information on ROS generation by SOA particles provided a basis for further elucidation of adverse aerosol health effects and oxidative stress by PM2.5. For a comprehensive assessment of PM toxicity and health effects via oxidative stress, it is important to consider both chemical reactions and cellular processes for the formation of ROS in the ELF. Chemical composition of PM strongly influences ROS formation; further investigations are required to study ROS formation from various PM sources. Such research will provide critical information to environmental agencies and policymakers for the development of air quality policy and regulation.

Coproduction of lipids and carotenoids by the novel green alga Coelastrella sp. depending on cultivation conditions

A novel green alga Coelastrella sp. D3-1 was isolated, and its unique and significant lipid and carotenoid coproduction capability was characterised depending on cultivation conditions. The main component of produced lipids was triacylglycerol under nutrient depletion conditions, in which fatty-methyl-esters made up 20-44% of the dry cell weight (DCW) and consisted of abundant C16:0 and C18:1 fatty acids. The red (orange)-stage cells also produced a large portion of carotenoids (38.5% of the DCW) involving echinenone, canthaxanthin, and astaxanthin as major components accumulated over only 5-6 days under optimal conditions. Stress tests revealed resistance of the cells to pH 2-11, high temperatures (40-60 °C), ultraviolet irradiation, drought, and H₂O₂ treatment, thereby showing a robust nature. Both green- and red (orange)-stage cell extracts also showed antioxidant and anti-inflammatory abilities, implying that they have significant functions as useful biorefinery materials.

Understanding interactions of organic nitrates with the surface and bulk of organic films: implications for particle growth in the atmosphere

Understanding impacts of secondary organic aerosol (SOA) in air requires a molecular-level understanding of particle growth via interactions between gases and particle surfaces. The interactions of three gaseous organic nitrates with selected organic substrates were measured at 296 K using attenuated total reflection Fourier transform infrared spectroscopy. The organic substrates included a long chain alkane (triacontane, TC), a keto-acid (pinonic acid, PA), an amorphous ester oligomer (poly(ethylene adipate) di-hydroxy terminated, PEA), and laboratory-generated SOA from α-pinene ozonolysis. There was no uptake of the organic nitrates on the non-polar TC substrate, but significant uptake occurred on PEA, PA, and α-pinene SOA. Net uptake coefficients (γ) at the shortest reaction times accessible in these experiments ranged from 3 × 10-4 to 9 × 10-6 and partition coefficients (K) from 1 × 107 to 9 × 104. Trends in γ did not quantitatively follow trends in K, suggesting that the intermolecular forces involved in gas-surface interactions are not the same as those in the bulk, which is supported by theoretical calculations. Kinetic modeling showed that nitrates diffused throughout the organic films over several minutes, and that the bulk diffusion coefficients evolved as uptake/desorption occurred. A plasticizing effect occurred upon incorporation of the organic nitrates, whereas desorption caused decreases in diffusion coefficients in the upper layers, suggesting a crusting effect. Accurate predictions of particle growth in the atmosphere will require knowledge of uptake coefficients, which are likely to be several orders of magnitude less than one, and of the intermolecular interactions of gases with particle surfaces as well as with the particle bulk.

Chemical kinetics of multiphase reactions between ozone and human skin lipids: Implications for indoor air quality and health effects

Ozone reacts with skin lipids such as squalene, generating an array of organic compounds, some of which can act as respiratory or skin irritants. Thus, it is important to quantify and predict the formation of these products under different conditions in indoor environments. We developed the kinetic multilayer model that explicitly resolves mass transport and chemical reactions at the skin and in the gas phase (KM-SUB-Skin). It can reproduce the concentrations of ozone and organic compounds in previous measurements and new experiments. This enabled the spatial and temporal concentration profiles in the skin oil and underlying skin layers to be resolved. Upon exposure to ~30 ppb ozone, the concentrations of squalene ozonolysis products in the gas phase and in the skin reach up to several ppb and on the order of ~10 mmol m^-3 . Depending on various factors including the number of people, room size, and air exchange rates, concentrations of ozone can decrease substantially due to reactions with skin lipids. Ozone and dicarbonyls quickly react away in the upper layers of the skin, preventing them from penetrating deeply into the skin and hence reaching the blood.

Direct imaging of changes in aerosol particle viscosity upon hydration and chemical aging

We report quantitative, real-time, online observations of microscopic viscosity changes in aerosol particles of atmospherically relevant composition, using fluorescence lifetime imaging (FLIM) of viscosity.

Organic aerosol particles (OA) play major roles in atmospheric chemistry, climate, and public health. Aerosol particle viscosity is highly important since it can determine the ability of chemical species such as oxidants, organics or water to diffuse into the particle bulk. Recent measurements indicate that OA may be present in highly viscous states, however, diffusion rates of small molecules such as water are not limited by these high viscosities. Direct observational evidence of kinetic barriers caused by high viscosity and low diffusivity in aerosol particles were not available until recently; and techniques that are able to dynamically quantify and track viscosity changes during atmospherically relevant processes are still unavailable for atmospheric aerosols. Here we report quantitative, real-time, online observations of microscopic viscosity changes in aerosol particles of atmospherically relevant composition, using fluorescence lifetime imaging (FLIM) of viscosity. We show that microviscosity in ozonated oleic acid droplets and secondary organic aerosol (SOA) particles formed by ozonolysis of myrcene increases substantially with decreasing humidity and atmospheric oxidative aging processes. Furthermore, we found unexpected heterogeneities of microviscosity inside individual aerosol particles. The results of this study enhance our understanding of organic aerosol processes on microscopic scales and may have important implications for the modeling of atmospheric aerosol growth, composition and interactions with trace gases and clouds.

Molecular characterization of a novel soybean gene encoding a neutral PR-5 protein induced by high-salt stress

In this study, we characterized a novel soybean gene encoding a neutral PR-5 protein and compared it to two acidic isoforms of soybean PR-5 protein. This gene, designated as Glycine max osmotin-like protein, b isoform (GmOLPb, accession no. AB370233), encoded a putative protein having the greatest similarity to chickpea PR-5b (89% identity). Unlike the two acidic PR-5, GmOLPa and P21, the protein had a C-terminal elongation responsible for possible vacuolar targeting and after maturation showed a calculated molecular mass of 21.9kDa with pI 6.0. The 3D models, predicted by the homology modeling, contained four alpha-helixes and 16 beta-strands and formed three characteristic domains. The two acidic PR-5 proteins also showed a 3D structure very similar to GmOLPb, although the electrostatic potential on molecular surface of each PR-5 was significantly different. In the study of the gene expression under conditions of high-salt stress, GmOLPb was highly induced in the leaves of the soybean, particularly in the lower part of a leaf. The expression started at 2h after initiation of the stress and was highly induced between 18-72h. Gene expression of P21e (protein homologous to P21) was transiently induced by high-salt stress, but took place earlier than the gene expressions of GmOLPa and GmOLPb. Such differential expression was observed also under investigation with methyl jasmonate and salicylic acid. These results suggested that each soybean PR-5 might play a distinctive role in the defensive system protecting the soybean plant against high-salt stress, particularly in the leaves of the soybean.

Crucial Roles of MZF1 and Sp1 in the Transcriptional Regulation of the Peptidylarginine Deiminase Type I Gene (PADI1) in Human Keratinocytes

Peptidylarginine deiminases (PADs) catalyze the conversion of protein-bound arginine residues into citrulline residues in a calcium-dependent manner. The PAD1 gene (PADI1) is expressed in a few tissues, including the epidermis, where the protein is detected with a higher level in the more differentiated keratinocytes. Using quantitative reverse transcription-PCR experiments, we show that PADI1 mRNAs are more abundant in keratinocytes cultured with 1.2 than 0.15 mM calcium. We cloned and characterized the promoter region using human keratinocytes transfected with variously deleted fragments of the 5'-upstream region of PADI1 coupled to the luciferase gene. We found that as few as 195 bp upstream from the transcription initiation site were sufficient to direct transcription of the reporter gene. Mutations of MZF1- or Sp1-binding sites markedly reduced PADI1 promoter activity. Chromatin immunoprecipitation assays revealed that MZF1 and Sp1/Sp3 bind to this region in vivo. Furthermore, MZF1 or Sp1 small interfering RNAs (siRNAs) effectively diminished PADI1 expression in keratinocytes cultured in both low- and high-calcium-containing medium. In addition, the expression of MZF1 and PAD1 increased in parallel when normal human epidermal keratinocytes underwent differentiation. These data indicate that MZF1 and Sp1/Sp3 binding to the promoter region drive the PADI1 expression.

Molecular characterization of a novel salt-inducible gene for an OSBP (oxysterol-binding protein)-homologue from soybean

Oxysterol-binding protein (OSBP) and its homologues constitute a protein family in many eukaryotes from yeast to humans, which are involved in cellular lipid metabolism, vesicle transport and signal transduction. In this study, we characterized a novel salt-inducible gene for an OSBP-homologue from soybean (Glycine max [L.] Merr.). The soybean OSBP-homologous gene, denoted as G. max OSBP (GmOSBP), encoded a 789 aa putative protein with two characteristic domains; the pleckstrin homology (PH) domain and the ligand-binding (LB) domain, in the N- and C-terminus, respectively. The GmOSBP-PH domain showed localization into/around the nucleus in a transient subcellular localization assay. The phylogenetic relationship of the GmOSBP-LB domain to those in other OSBP-homologues suggested that GmOSBP might bind a lipid molecule(s) different from the ligand-candidates found for the human/yeast OSBP-homologues. The GmOSBP gene was constitutively transcribed in all of the soybean organs examined--root, stem and trifoliate leaf--at low levels and was highly induced in all these organs by high-salt stress (300 mM NaCl). Interestingly, gene expression of GmOSBP was also markedly induced in the senesced soybean cotyledon, which contains high levels of a variety of cellular lipids utilized for energy for germination and as membrane components. Therefore, we suggest that GmOSBP may be involved in some physiological reactions for stress-response and cotyledon senescence in the soybean.

Purification and characterization of three neutral extracellular isoperoxidases from rye leaves

Rye (Secale cereale L.) seedlings; contain two major flavone glucuronides, luteolin 7-O-diglucuronyl-4'-O-glucuronide (L3GlcUA) (1) and luteolin 7-O-diglucuronide (L2GlcUA) (2) in abundance in the apoplast of primary leaves; express a large number of peroxidase isoenzymes; and release H(2)O(2) into the apoplast during primary leaf development. We purified and characterized three neutral extracellular peroxidase isoenzymes (rPOXs N1, N2, and N3) that can oxidize L2GlcUA as a natural substrate. The isoelectric points and molecular weights of rPOXs N1, N2, and N3 were 6.1, 7.2, and 6.3, and 42, 37, and 51 kDa, respectively. The optimum pH of the rPOXs N1, N2, and N3 were 5.5, 5.5, and 8.5, respectively, and their optimum temperatures ranged from 45 to 50 degrees C for all isoenzymes. rPOXs N1, N2, and N3 recognized flavonoids with 3', 4'-OH groups as potential substrates, but not flavonoids with a glycosylated 4'-OH group or those without a 3'-OH group. The activities on phenol-type substrates were high in the order of guaiacol>catechol>o-cresol for all isoenzymes. rPOXs N1, N2, and N3 exhibited broad reactivity with endogenous hydrogen donors including luteolin glucuronides derived from the apoplast of rye primary leaves.

Molecular cloning and characterization of a novel salt-inducible gene encoding an acidic isoform of PR-5 protein in soybean (Glycine max [L.] Merr.)

We identified a novel salt-inducible soybean gene encoding an acidic-isoform of pathogenesis-related protein group 5 (PR-5 protein). The soybean PR-5-homologous gene, designated as Glycine max osmotin-like protein, acidic isoform (GmOLPa)), encodes a putative polypeptide having an N-terminal signal peptide. The mature GmOLPa protein without the signal peptide has a calculated molecular mass of 21.5 kDa and a pI value of 4.4, and was distinguishable from a known PR-5-homologous gene of soybean (namely P21 protein) through examination of the structural features. A comparison with two intracellular salt-inducible PR-5 proteins, tobacco osmotin and tomato NP24, revealed that GmOLPa did not have a C-terminal extension sequence functioning as a vacuole-targeting motif. The GmOLPa gene was transcribed constitutively in the soybean root and was induced almost exclusively in the root during 24 h of high-salt stress (300 mM NaCl). Interestingly, GmOLPa gene expression in the stem and leaf, not observed until 24 h, was markedly induced at 48 and 72 h after commencement of the high-salt stress. Abscisic acid (ABA) and dehydration also induced expression of the GmOLPa gene in the root; additionally, dehydration slightly induced expression in the stem and leaf. In fact, the 5'-upstream sequence of the GmOLPa gene contained several putative cis-elements known to be involved in responsiveness to ABA and dehydration, e.g. ABA-responsive element (ABRE), MYB/MYC, and low temperature-responsive element (LTRE). These results suggested that GmOLPa may function as a protective PR-5 protein in the extracellular space of the soybean root in response to high-salt stress and dehydration.

NF-Y and Sp1/Sp3 are involved in the transcriptional regulation of the peptidylarginine deiminase type III gene (PADI3) in human keratinocytes

Human peptidylarginine deiminase type III gene (PADI3) encodes a crucial post-translational modification enzyme that converts protein-bound arginine residues into citrulline residues. Its expression is restricted to a few cell types, including keratinocytes in the granular layer of the epidermis and in the inner root sheath of hair follicles. In these cells, the enzyme is involved in terminal processing of intermediate filament-binding proteins such as filaggrin and trichohyalin. To study the molecular mechanisms that control the expression of PADI3 in human keratinocytes at the transcriptional level, we characterized its promoter region using human keratinocytes transfected with variously deleted fragments of the 5'-upstream region of PADI3 coupled to the luciferase gene. We found that as few as 129 bp upstream from the transcription initiation site were sufficient to direct transcription of the reporter gene. Electrophoretic mobility-shift and chromatin immunoprecipitation assays revealed that NF-Y (nuclear factor Y) and Sp1/Sp3 (specificity protein 1/3) bind to this region in vitro and in vivo. Moreover, mutation of the Sp1- or NF-Y-binding motif markedly reduced PADI3 promoter activity. Furthermore, Sp1 or NF-YA (NF-Y subunit) small interfering RNAs effectively diminished PADI3 expression in keratinocytes cultured in both low- and high-calcium medium. These data indicate that PADI3 expression is driven by Sp1/Sp3 and NF-Y binding to the promoter region.

Molecular cloning and characterization of a novel soybean gene encoding a leucine-zipper-like protein induced to salt stress

To understand molecular responses to salt stress in soybean (Glycine max [L.] Merr.), we identified 106 salt-inducible soybean genes that expressed differentially at 72 h after 100 mM NaCl treatment using the cDNA-amplified fragment length polymorphism (AFLP) method. The genes were designated as G. max Transcript-Derived Fragments (GmTDFs). Among these genes, we characterized a soybean gene GmTDF-5 that encoded an unknown protein of 367 amino acids. The GmTDF-5 protein was a putative cytosolic protein with two leucine-zipper motifs at the N-terminal and was calculated as 40.7 kDa. Southern blot analysis indicated that GmTDF-5 presents as an intron-less single gene on soybean genome and possibly distributes narrowly throughout the higher plants. By 100 mM NaCl treatment, the gene expression of GmTDF-5 was induced in the stem and lower-expanded leaf, and the amount of mRNA increased 5.1- and 2.0-fold up to 72 h, respectively. Interestingly, GmTDF-5 expression in the upper-leaf appeared dramatically with 10.0-fold increase at 72 h after the salt stress, but not until 48 h. Hyperosmotic pressure (mannitol treatment) and dehydration also caused the increases similar to NaCl treatment in the levels of GmTDF-5 expression. These results suggest that GmTDF-5 might be a novel cytosolic leucine-zipper-like protein functioning in mature organs of soybean shoot against water-potential changes.

Regulation of the expression of peptidylarginine deiminase type II gene (PADI2) in human keratinocytes involves Sp1 and Sp3 transcription factors

Peptidylarginine deiminases (PAD) convert protein-bound arginine residues into citrulline residues in a Ca(2+) ion-dependent manner. Among the five isoforms (PAD1, 2, 3, 4, and 6) existing in rodents and humans, PAD2 is the most widely expressed in both species, tissues, and organs. In order to study the mechanisms regulating the expression of the human PAD2 gene, PADI2, we characterized its promoter region using transfected human keratinocytes. A series of reporter gene constructions derived from the 2 kb region upstream of the transcription initiation site defined a minimal promoter sequence from nucleotides -132 to -41. This PADI2 region is GC-rich and lacks canonical TATA and CAAT boxes. Investigation of cis-acting elements in the region, further deletion analyses and electrophoretic mobility shift assays using specific antibodies revealed four Sp1-binding sites and identified Sp1 and Sp3 as binding factors important for the promoter activity. These results suggest that Sp1/Sp3 cooperation may provide a mechanism to control the transcription of PADI2.

Cloning of two cysteine proteinase genes, CysP1 and CysP2, from soybean cotyledons by cDNA representational difference analysis

By cDNA representational difference analysis (cDNA RDA) and rapid amplification of cDNA ends (RACE), we isolated two cDNAs, CysP1 and CysP2, from the cotyledons of growing soybean (Glycine max (L.) Merr.) seedlings. CysP1 cDNA is 1265 bp in size with a 1089-bp open reading frame (ORF), and CysP2 cDNA is 1270 bp in size with a 1089-bp ORF. Either CysP1 or CysP2 encodes a cysteine proteinase (CPR) with a C-terminal KDEL motif. The similarities between CysP1 and CysP2 are 93.5% in nucleotide sequences and 93.6% in deduced amino acid sequences. Furthermore, we determined the nucleotide sequences of CysP1 genomic DNA (1846 bp) and CysP2 genomic DNA (1831 bp). Both consisted of four exons and three introns. RNA-blot analysis revealed that both CysP1 and CysP2 were expressed from 6 days after germination (DAG) to 13 or 14 DAG in the cotyledons of growing seedlings and did so in a short period (9-12 DAG) in rejuvenated cotyledons. The transcripts of CysP1 and CysP2 were also detected in the root, flower and pod of soybean plants. Their physiological roles in the cotyledons of growing seedlings are discussed.

UDP-glucuronic acid:soyasapogenol glucuronosyltransferase involved in saponin biosynthesis in germinating soybean seeds

We detected UDP-glucuronic acid:soyasapogenol glucuronosyltransferase (UGASGT) activity in the microsomal fraction from germinating soybean (Glycine max [L.] Merr.) seed. A microsomal fraction was isolated from germinating soybean seed and treated with various detergents to solubilize the enzyme. UGASGT activity was monitored throughout purification using UDP-[U-(14)C]glucuronic acid and soyasapogenol B as substrates. Purification of UGASGT was achieved by HiTrap Q, Superdex 200, and HiTrap Blue chromatography procedures. This resulted in >205-fold enrichment relative to the starting homogenate. UGASGT was found to require divalent cations for activity. Studies on the substrate specificity of UGASGT demonstrated that the specificity for the sugar residue transferred was very high, as activity was scarcely found when UDP-glucuronic acid was replaced by other UDP sugars: UDP-glucose and UDP-galactose. Soyasapogenols, which are the aglycons of soybean saponin, are usable acceptors, but glycyrrhetinic acid, sophoradiol, beta-amyrin, and flavonoids are not. These findings suggest that this UGASGT was a specific enzyme for UDP-glucuronic acid as a donor and soyasapogenols as acceptors, and that it was related to the biosynthesis of the sugar chain in soybean saponin. This study provides a basis for the molecular characterization of a key enzyme in saponin biosynthesis in soybean. The isolation of the gene may enable its use in the elucidation of the biosynthesis and physiological role of saponins in soybean.

Human peptidylarginine deiminase type III: molecular cloning and nucleotide sequence of the cDNA, properties of the recombinant enzyme, and immunohistochemical localization in human skin

Peptidylarginine deiminase catalyzes the post-translational modification of proteins through the conversion of arginine to citrulline in the presence of calcium ions. In rodents, peptidylarginine deiminase has been classified into four isoforms, types I, II, III, and IV, which are distinct in their molecular weights, substrate specificities, and tissue localization. Of these isoforms, only type III was detected in epidermis and hair follicles. Although the role of this enzyme in these tissues is not yet clear, indirect data have shown that several structural proteins such as filaggrin, trichohyalin, and keratin are substrates for peptidylarginine deiminase. In this study, we cloned the full-length cDNA of human peptidylarginine deiminase type III (3142 bp) from cultured human keratinocytes by reverse transcription-polymerase chain reaction and by rapid amplification of cDNA ends methods. This cDNA contained a 1995 bp open reading frame encoding 664 amino acids (Mr = 74 770). To explore the physicochemical and enzymatic properties of human peptidylarginine deiminase type III, we constructed a plasmid for producing a recombinant human peptidylarginine deiminase type III in bacteria. The enzymatic characteristics of the recombinant enzyme were very similar to those of the rodent peptidylarginine deiminase type III. The recombinant enzyme showed the catalytic activities toward structural proteins of epidermis and hair follicle, filaggrin and trichohyalin, in which the deiminations maxima of about 60% and 13% arginine residues were observed in filaggrin and trichohyalin, respectively. An immunohistochemical study of human scalp skin with a monospecific anti-peptidyl-arginine deiminase type III antibody revealed that the type III enzyme was localized to the inner root sheath and outer root sheath of hair follicles. Peptidylarginine deiminase type III in the inner root sheath was notable between supramatrix and keratogenous zone and was scarcely detected in cornified hair zone. The enzyme was also expressed in the cuticle layer of hair. On the other hand, expression of the enzyme in the epidermis was very low. These data imply that human peptidylarginine deiminase type III is the predominant isoform in hair follicles and may function as a modulator of hair structural proteins, including trichohyalin during hair and hair follicle formation.

Inflammatory pseudotumor of the spleen: a case report

We report on an inflammatory pseudotumor of the spleen. A 72-year-old woman visited our hospital complaining of nausea. Physical examination and laboratory investigations were unremarkable. Ultrasonography, computed tomography, magnetic resonance imaging and angiography showed a hypovascular splenic mass measuring about 5 cm in diameter with a calcification in the center of the lesion. Splenectomy was performed. The removed spleen, weighing 145 g, contained a tan-white, circumscribed mass, measuring 6.2 x 5.5 x 5.3 cm. Histologically, the splenic mass was composed of an admixture of inflammatory cellular elements, predominantly plasma cells and lymphocytes with hyalinization, fibrosis, lymph follicles and multinuclear giant cells, suggestive of a inflammatory pseudotumor. The patient is currently alive and asymptomatic, 24 months after surgery. Inflammatory pseudotumors of the spleen are extremely rare and only 39 cases have been reported in the medical literature.

Cervical carcinoma: efficacy of thin-section oblique axial T2-weighted images for evaluating parametrial invasion

BACKGROUND

To investigate the efficacy of thin-section oblique axial T2-weighted images in the assessment of parametrial invasion by cervical carcinoma.

METHODS

One hundred parametria of 50 patients with cervical carcinoma were evaluated with pathologic correlation. We compared the sensitivity, specificity, and diagnostic accuracy in the assessment of parametrial invasion by cervical carcinoma between axial T2-weighted images and thin-section oblique axial T2-weighted images.

RESULTS

Thin-section oblique axial T2-weighted images provided accurate cross sections of the cervix with excellent detail and detected parametrial invasion more accurately than did axial T2-weighted images showing cross sections of the trunk. Although the sensitivity, specificity, and accuracy for parametrial invasion were 46.4%, 91.7%, and 79.0%, respectively, on axial T2-weighted images, the corresponding values were 67.9%, 97. 2%, and 89.0%, respectively, on thin-section oblique axial T2-weighted images. There were statistically significant differences in the sensitivity (p = 0.014), specificity (p = 0.046), and accuracy (p = 0.002) in detecting parametrial invasion between these two types of images.

CONCLUSIONS

Thin-section oblique axial T2-weighted images are useful for the assessment of parametrial invasion by cervical carcinoma.

Endometrial carcinoma: efficacy of thin-section oblique axial MR images for evaluating cervical invasion

BACKGROUND

To investigate the efficacy of thin-section oblique axial magnetic resonance (MR) images in evaluating cervical invasion by endometrial carcinoma.

METHODS

Sixty-seven patients with endometrial carcinoma were evaluated with pathologic correlation. We compared the accuracy in the assessment of cervical invasion by endometrial carcinoma between parasagittal MR images and thin-section oblique axial MR images by using T2-weighted and contrast-enhanced T1-weighted pulse sequences.

RESULTS

Cervical invasion by endometrial carcinoma was confirmed by pathologic examination. Cervical invasion was seen in 16 patients. The accuracy rates of parasagittal T2-weighted images, thin-section oblique axial T2-weighted images, parasagittal contrast-enhanced T1-weighted images, and thin-section oblique axial contrast-enhanced T1-weighted images were 74.7%, 89.5%, 82.0%, and 95.5%, respectively. Statistically significant differences were seen between parasagittal T2-weighted images and thin-section oblique axial T2-weighted images (p = 0.002) and between parasagittal contrast-enhanced T1-weighted images and thin-section oblique axial contrast-enhanced T1-weighted images (p = 0.003).

CONCLUSION

Thin-section oblique axial MR images are considered to be useful for the assessment of cervical invasion by endometrial carcinoma.

Endometrial carcinoma: multisection dynamic MR imaging using a three-dimensional FLASH technique during breath holding

PURPOSE

Our aim was to investigate the usefulness of multisection dynamic MR imaging using a 3D FLASH technique during breath holding in assessing myometrial invasion by endometrial carcinoma.

MATERIALS AND METHODS

Twenty-eight endometrial carcinomas were evaluated with pathologic correlation. Dynamic MR imaging was performed using the 3D FLASH technique during breath holding. We compared accuracy in the assessment of myometrial invasion by endometrial carcinoma between T2-weighted images, contrast-enhanced T1-weighted images, and dynamic MR images.

RESULTS

The accuracy rates in estimating myometrial invasion with T2-weighted images, contrast-enhanced T1-weighted images, and dynamic MR images were 64.3%, 67.8%, and 85.7%, respectively. Statistically significant differences were seen between dynamic MR images and both T2-weighted images and contrast-enhanced T1-weighted images.

CONCLUSION

Multisection dynamic MR imaging using the 3D FLASH technique during breath holding is useful for the evaluation of myometrial invasion by endometrial carcinoma with polypoid growth or an unclear junctional zone on T2-weighted images.

Molecular cloning of cDNAs of mouse peptidylarginine deiminase type I, type III and type IV, and the expression pattern of type I in mouse

Peptidylarginine deiminases (PADs), a group of post-translational enzymes, catalyze the conversion of protein-bound arginine residues to citrulline residues in a calcium ion-dependent manner and are widely distributed in various organs of vertebrates. Although the existence of four isoforms of PAD (types I, II, III, and IV) is reported in rodents, the relative functions of the isoforms with respect to their colocation in the tissues have yet to be explored. In this study, we cloned the full-length cDNA encoding mouse PAD type I by screening a uterine cDNA library and using the RACE method. This cDNA consists of an open reading frame of 1989 bases encoding 662 amino acids (73,823 Da), a 5'-untranslated region of 127 bases and a 3'-untranslated region of 1639 bases. Comparative reverse transcription-PCR and Northern-blot analyses detected PAD type I mRNA only in the epidermis and uterus. Administration of estrogen to adult ovariectomized mice increased the content of PAD type I mRNA in the uterus, providing evidence that its expression is under the control of the sex steroid hormone. We also cloned the full-length cDNAs of mouse PAD type III and type IV by the reverse transcription-PCR and RACE methods. The primary structure of PAD type III contains 664 amino acids (75,098 Da) deduced from the coding region of 1995 bases, and the primary structure of PAD type IV consists of 666 amino acids (74,475 Da) deduced from the coding region of 2001 bases. Comparison of the deduced amino acid sequences of all four isoforms of PAD showed about 50% identity with each other, the 3' regions being highly homologous compared with the 5' regions.

Cloning of cDNA encoding a novel isoform (type IV) of peptidylarginine deiminase from rat epidermis

We isolated a new clone that showed structural similarities with the rat peptidylarginine deiminase (PAD) types II and III. The full-length cDNA sequence of this novel PAD comprised 1998 bp encoding a sequence for 666 amino acid residues (Mr 74467), a 3'-non-coding region of 115 bp and a 5'-non-coding region of 16 bp. The derived amino acid sequence of the PAD showed 51.1 and 54.0% identities with the sequences of types II and III, respectively. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) assays of mRNAs from several tissues of rat indicated that the PAD message is highly expressed in the pancreas, spleen, and ovary and, less strongly expressed in the liver, lung, stomach, kidney, uterus, and dermis, and weakly expressed in the brain, heart and epidermis. Since this expression pattern was quite different from those of the previously reported PAD types I, II, and III, we designated this novel PAD as type IV.

MR appearance of endometrial carcinoma and mucinous cystadenoma in a postmenopausal patient treated with tamoxifen for breast cancer

We present a case of endometrial carcinoma accompanied with mucinous cystadenoma in a 70-year-old postmenopausal woman treated with tamoxifen for breast cancer demonstrated by MR imaging. Tamoxifen therapy (20 mg/day) had been carried out for more than 11 years since the surgical procedure for the primary tumor. MR images showed a markedly enlarged uterus containing endometrial carcinoma, cystic atrophy of the endometrium, and a right adnexal mass with multicystic components of various signal intensities.

Studies on agents with vasodilator and beta-blocking activities. V. Synthesis and pharmacological activity of the optical isomers of TZC-5665

Synthesis of the four optical isomers of TZC-5665 (1), a candidate for the treatment of congestive heart failure, was achieved by the reaction of chiral diaminopyridazinone (2) with chiral glycidyl ether. (3). The hypotensive and beta-blocking activities of 1 and its optical isomers were examined when given intravenously into anesthetized rats. Furthermore these compounds were evaluated for inhibitory activity on cAMP phosphodiesterase III. Among the four optical isomers, Ra,Sb-one (1c) possessed the essential activities of TZC-5665 (1).

Stimulation of human keratinocyte growth by alginate oligosaccharides, a possible co-factor for epidermal growth factor in cell culture

Oligosaccharides, involved in regulation of plant developmental and defensive processes, were tested to determine their ability to enhance proliferation of human keratinocytes. A mixture of alginate oligosaccharides remarkably stimulated keratinocyte growth and [3H]thymidine uptake in the presence of epidermal growth factor (EGF). The activity was comparable to bovine pituitary extract, a common complement in keratinocyte culture, and additive on BPE-induced stimulation. The most effective oligosaccharide in the mixture was identified and its chemical structure was determined. These findings demonstrate a novel activity of alginate oligosaccharide(s) in keratinocyte growth and suggest a possible co-factor for EGF-dependent stimulation in medium for keratinocytes.

Isolation and molecular cloning of epidermal- and hair follicle-specific peptidylarginine deiminase (type III) from rat

Peptidylarginine deiminase (PAD) is a post-translational modification enzyme that catalyzes deimination of arginine residues of proteins in the presence of calcium ions. There are three types of PAD in rodent tissues: PAD types I, II, and III [Terakawa et al. (1991) J. Biochem. 110, 661-666]. Type III enzyme was detected only in the epidermis and in hair follicles. In this study, we have purified PAD type III from 2-day-old rat epidermis by a four-step procedure that included soybean trypsin inhibitor-affinity chromatography. The enzyme was purified about 600-fold from the crude extract and the recovery was 23%. The final preparation of the enzyme gave only a single protein band on SDS-PAGE and showed an apparent molecular weight of 76,000. Subsequently, we cloned and sequenced the full-length cDNA encoding rat PAD type III by reverse transcription-polymerase chain reaction (RT-PCR) using degenerate oligonucleotide primers designed from the internal amino acid sequences and by the rapid amplification of the cDNA ends method. The composite cDNA sequence contained a 5' untranslated region of 42 bp, an open reading frame of 1,995 bases that encoded 664 amino acids (Mr=75,036), a 3' untranslated region of 1,063 bp, and part of a poly(A)+ tail. The entire reading frame sequence of rat PAD type III showed 51% homology with that of rat PAD type II, and the C-terminal region is highly conserved between the two types. The cloned gene was expressed in Escherichia coli cells to produce PAD type III, which had not only enzymatic activity, but also immunoreactivity against specific antibodies toward PAD type II. Furthermore, the specific expression of the enzyme in the epidermis and hair follicles was confirmed by RT-PCR assays of mRNAs from several tissues.

Mouse uterus peptidylarginine deiminase is expressed in decidual cells during pregnancy

Peptidylarginine deiminase is localized in the cytosol of the luminal and glandular epithelia of the nonpregnant murine uterus and its expression is regulated by sex hormones [Takahara et al., [1989]: J Biol Chem 264, 13361-13368; Takahara et al. [1992]: J Biol Chem 267,520-525]. Here, we demonstrate that changes occur in the enzyme level in the mouse uterus during pregnancy and parturition. After a rapid decrease in enzymatic activity from day 1 to day 5 of pregnancy, the activity sharply increased during the middle stage of pregnancy (day 8 to day 10) and then gradually decreased during late pregnancy. Expression of the enzyme occurred only in the decidual cells that had differentiated from endometrial stroma cells surrounding the implantation site. The immunochemical properties of the enzyme expressed in the decidualized cells was indistinguishable from those in the uterine epithelia. These results suggest that peptidylarginine deiminase has important roles in decidual cells and not just in the epithelia of the nonpregnant uterus. Moreover, the level of enzyme activity increased slightly just before parturition (day 17), and then decreased during the 12 h period after parturition. The tissue localization of the enzyme expressed around the time of parturition changed from decidua to the luminal and glandular epithelia. Semiquantitative analyses of the enzyme mRNA content in the pregnant uteri showed a remarkable increase from day 7 leading to the onset of the enzyme synthesis in the decidual cells. After reaching the maximal level at day 12, small peaks in the mRNA level were observed at two times during late pregnancy. Since these serial changes in the mRNA level did not correlate with changes in sex hormones, the expression of decidual peptidylarginine deiminase seemed to be controlled by factors other than sex hormones.

Aggregated form of dextransucrases from Leuconostoc mesenteroides NRRL B-512F and its constitutive mutant

Purified dextransucrases [EC 2.4.1.5], DSW-D and DSW-G, from Leuconostoc mesenteroides B-512F were obtained from affinity chromatography with DEAE-Sephadex A-50 by elution with clinical dextran and guanidine-HCl, respectively. DSM-G was purified from the B-512F mutant strain SH 3002, which produces dextransucrase constitutively. Although the sugar contents of the purified enzymes were different, their molecular masses by SDS-PAGE were all 170 kDa. DSW-D and DSW-G were highly aggregated and the all the activities were eluted at the void volume (V0) on Sepharose 6B, while the DSM-G was eluted at 1.2 x V0 volume. On rechromatography, DSM-G was separated into three peaks corresponding to the aggregated form, monomeric form, and partially digested form, respectively. The aggregation of Leuconostoc dextransucrase was looser than that of streptococcal glucosyltransferases, but the structures of these enzymes had high homology with each other.

Existence and differential changes of peptidylarginine deiminase type II in mouse yolk-sac erythroid cells

Peptidylarginine deiminase (PAD) catalyzes the conversion of arginyl residues in proteins to citrullyl residues in the presence of Ca2+. Recently, we obtained a monoclonal antibody, EH7, which reacted only with mouse PAD type II. Here, we describe immunohistochemical findings on the cellular localization of PAD type II in mouse fetus by using the monoclonal antibody. PAD type II is expressed in yolk-sac erythroid cells and the level of the enzyme in these cells decreases as the cells differentiate.

Expression of mouse uterine peptidylarginine deiminase in Escherichia coli: construction of expression plasmid and properties of the recombinant enzyme

To study the structure/function relationships of peptidylarginine deiminase (PAD), we constructed an Escherichia coli expression plasmid for mouse uterine PAD. First, segments of a cDNA encoding murine PAD were subcloned into a single plasmid, and the resulting plasmid, pKSPAD1, was inserted into an expression vector, pKK223-3, at the EcoRI and HindIII restriction sites. Since no detectable amount or activity of the PAD was produced by E. coli carrying that plasmid, the 5'-untranslated sequence of the cDNA was replaced with several synthetic DNAs. One of the constructed plasmids, pKKPAD4, which had a unique DNA linker containing a pair of Shine-Dalgarno sequences and a short preceding cistron inserted into the adjacent 5'-region of the coding region, produced a large quantity of mouse PAD as an unfused protein in E. coli. The purified recombinant PAD was indistinguishable from the native enzyme with respect to some structural properties, such as molecular mass, amino- and carboxyl-terminal sequences, and circular dichroism spectra. However, the alpha-amino group of the amino-terminal methionine residue of the recombinant PAD was not acetylated as was that of the native enzyme. Comparison of the recombinant PAD with the natural enzyme did not indicate significant differences in their sensitivity to activation by Ca2+ and in their substrate specificity toward arginine derivatives. The rates of modification of soybean trypsin inhibitor (Kunitz) were also similar for the recombinant and native PADs. These results indicate that the recombinant PAD has biological activities identical to those of the native enzyme and that the N alpha-acetyl group in the native PAD does not appear to have any particular role in the enzyme's catalytic function.

Production and epitope specificity of monoclonal antibody against mouse peptidylarginine deiminase type II

Peptidylarginine deiminase catalyzes the conversion of arginyl residues in proteins to citrullyl residues in the presence of Ca2+. We described the preparation of monoclonal antibody (subclass type IgG1) specific to mouse peptidylarginine deiminase type II. The antibody had no effect on the enzyme activity and its specific epitope was localized in the eight-residue segment at the amino-terminal portion of the enzyme.

An active-site peptide containing the second essential carboxyl group of dextransucrase from Leuconostoc mesenteroides by chemical modifications

The treatment of Leuconostoc mesenteroides B-512F dextransucrase with 10 mM 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and glycine ethyl ester (GEE) inactivated the enzyme almost completely within 24 min where the modification of one carboxyl group/mol of the enzyme by EDC was attained. Though 30 mM diethyl pyrocarbonate (DEP) also inactivated the enzyme, about 35% of the activity remained during a 36-min incubation. When 10 mol of imidazole residues/mol of the enzyme was modified by DEP, 50% of the activity was still retained. The addition of the substrate sucrose greatly retarded the enzyme inactivation by EDC. However, the addition of dextran slightly protected the inactivation of the glucosyl-transferring activity and accelerated the inactivation of the sucrose-cleaving activity. In the case of DEP, the addition of sucrose or dextran gave no influence on the inactivation of the enzyme. Therefore, the carboxyl group seemed to play a more important role in the substrate binding and in the catalytic activity of the dextransucrase than the imidazolium group. Differential labeling of Leuconostoc dextransucrase by EDC was conducted in the presence of a sucrose analog, sucrose monocaprate. The fluorescent probe N-(1-naphthyl)ethylenediamine (EDAN) was used as the nucleophile instead of GEE. A fluorescent labeled peptide was isolated from a trypsin digest of the EDC-EDAN modified enzyme. The amino acid sequence of the isolated peptide was Leu-Gln-Glu-Asp-Asn-Ser-Asn-Val-Val-Val-Glu-Ala.(ABSTRACT TRUNCATED AT 250 WORDS)

Composition and structure of "group B saponin" in soybean seed

The composition of "group B saponin" in soybean seed was analyzed by HPLC, and six kinds of "group B saponin," named Ba, Bb, Bb', Bc, Bd and Be according to elution order from HPLC, were detected. Of these saponins, Ba, Bb, Bb' and Bc were identified with soyasaponin V, I, III and II, respectively. Bd and Be were novel saponins possessing soyasapogenol E as the aglycone and the same sugar chain as Ba and Bb, respectively. These saponins were very unstable in the isolated state and had a tendency to form Ba and Bb, respectively. From these results, Bd and Be are presumed to be the precursors of Ba and Bb in soybean seed.