The Inhibitory Effects of Low-Dose Ionizing Radiation in IgE-Mediated Allergic Responses

Ionizing radiation has different biological effects according to dose and dose rate. In particular, the biological effect of low-dose radiation is unclear. Low-dose whole-body gamma irradiation activates immune responses in several ways. However, the effects and mechanism of low-dose radiation on allergic responses remain poorly understood. Previously, we reported that low-dose ionizing radiation inhibits mediator release in IgE-mediated RBL-2H3 mast cell activation. In this study, to have any physiological relevance, we investigated whether low-dose radiation inhibits allergic responses in activated human mast cells (HMC-1(5C6) and LAD2 cells), mouse models of passive cutaneous anaphylaxis and the late-phase cutaneous response. High-dose radiation induced cell death, but low-dose ionizing radiation of <0.5 Gy did not induce mast cell death. Low-dose ionizing radiation that did not induce cell death significantly suppressed mediator release from human mast cells (HMC-1(5C6) and LAD2 cells) that were activated by antigen-antibody reaction. To determine the inhibitory mechanism of mediator released by low-dose ionizing radiation, we examined the phosphorylation of intracellular signaling molecules such as Lyn, Syk, phospholipase Cγ, and protein kinase C, as well as the intracellular free Ca²⁺ concentration ([Ca²⁺]_i). The phosphorylation of signaling molecules and [Ca²⁺]_i following stimulation of FcεRI receptors was inhibited by low dose ionizing radiation. In agreement with its in vitro effect, ionizing radiation also significantly inhibited inflammatory cells infiltration, cytokine mRNA expression (TNF-α, IL-4, IL-13), and symptoms of passive cutaneous anaphylaxis reaction and the late-phase cutaneous response in anti-dinitrophenyl IgE-sensitized mice. These results indicate that ionizing radiation inhibits both mast cell-mediated immediate- and delayed-type allergic reactions in vivo and in vitro.     

X-ray crystallographic studies of HemK from Thermotoga maritima, an N5-glutamine methyltransferase

The enzyme HemK (or PrmC) is one of the first identified methyltransferases that modify glutamine. It methylates the highly conserved GGQ motif in class I release factors (RF1 and RF2) in Escherichia coli. HemK from Thermotoga maritima was over-expressed and crystallized in the presence of S-adenosylmethionine at 296 K using ammonium sulfate as the precipitant. X-ray diffraction data were collected to 2.5 A resolution from a native crystal. The crystal is orthorhombic, belonging to the space group I222 (or I2(1)2(1)2(1)), with unit-cell parameters of a = 104.24, b = 118.73, and c = 146.62 A. Two (or three) monomers of recombinant HemK are likely to be present in the crystallographic asymmetric unit, giving a V(M) of 3.62 A3 Da(-1) (or 2.41 A3 Da(-1)), with a solvent content of 62.7% (or 44.0%).     

A newly synthesized,potent tyrosinase inhibitor: 5-(6-Hydroxy-2-naphthyl)-1,2,3-benzenetriol

In searching for new agents with a depigmenting effect, we synthesized a derivative of resveratrol, 5-(6-hydroxy-2-naphthyl)-1,2,3-benzenetriol (5HNB) with a potent tyrosinase inhibitory activity. 5HNB inhibited mushroom tyrosinase with an IC₅₀ value of 2.95 μM, which is more potent than the well-known anti-tyrosinase activity of kojic acid (IC₅₀ = 38.24). The results of the enzymatic inhibition kinetics by Lineweaver–Burk analysis indicated 5HNB inhibits tyrosinase non-competitively when l-tyrosine was used as the substrate. Based on the strong inhibitory action of 5HNB, it is expected that 5HNB can suppress melanin production in which tyrosinase plays the essential role. Our expectation was confirmed by the experimentations with B16 melanoma cells in which 5HNB inhibited melanin production. We propose that 5HNB might have skin-whitening effects as well as therapeutic potential for treating skin pigmentation disorders.     

Persistence of circadian variation in arterial blood pressure in beta1/beta2-adrenergic receptor-deficient mice

The beta-adrenergic pathway has been considered one important effector of circadian variation in arterial pressure. Experiments were performed in beta1/beta2-adrenergic receptor-deficient mice (beta1/beta2ADR-/-) to assess whether this pathway is required for circadian variation in mean arterial pressure (MAP) and to determine the impact of its loss on the response to changes in dietary salt. Twenty-four-hour recordings of MAP, heart rate (HR), and locomotor activity were made in conscious 16- to 17-wk-old mice [wild-type, (WT), n = 7; beta1/beta2ADR-/-, n = 10] by telemetry. Both WT and beta1/beta2ADR-/- mice demonstrated robust circadian variation in MAP and HR, although 24-h mean MAP was 10% lower (102.02 +/- 1.81 vs. 92.11 +/- 2.62 mmHg) in beta1/beta2ADR-/- than WT, HR was 16% lower and day-night differences reduced. Both WT and beta1/beta2ADR-/- mice adapted to changed salt intake without changed MAP. However, the beta1/beta2ADR-/- mice demonstrated a striking reduction in locomotor activity in light and dark phases of the day. In WT mice, MAP was markedly affected by locomotor activity, resulting in bimodal distributions in both light and dark. When MAP was analyzed using only intervals without locomotor activity, bimodality and circadian differences were reduced, and there was no significant difference between the two genotypes. The results indicate that there is no direct effect or role for the beta-adrenergic system in circadian variation of arterial pressure in mice, aside from the indirect consequences of altered locomotor activity. Our results also confirm that locomotor activity contributes strongly to circadian variation in blood pressure in mice.     

紫羊茅重金属抗性和敏感品种中类金属硫蛋白基因的鉴定及表达初探

重金属对生命机体的作用具有双重性。一方面,作为多数辅酶的辅助因子对细胞的正常代谢必不可少;另一方面,当重金属超过一定的浓度时对细胞有较大的毒性。在长期的进化过程中,生物可能形成一种调节细胞内重金属浓度的机制。这种机制在动物和真菌中被认为同金属硫蛋白(metallothionein,MT)的作用密切相关。植物中也存在类似的与重金属结合的低分子量蛋白(heavy metal binding pep-tide)。最近对拟南芥菜和水稻中类金属硫蛋白(MT-like)基因的研究证实其作用与动物MT相似。紫羊茅品种“Merlin”是一种从锌铅矿区的重金属污染地采集的单子叶草种,对镉和铜的抗性都较高,分别达到50mg/L和30mg/L,而5mg/L Cd~(2 )或2mg/L Cu~(2 )便可抑制敏感品种“S59”的正常生长。目前     

Evaluation of Antimicrobial Properties of Lichen Substances against Plant Pathogens

Plant pathogens pose major threats on agriculture and horticulture, causing significant economic loss worldwide. Due to the continuous and excessive use of synthetic pesticides, emergence of pesticide resistant pathogens has become more frequent. Thus, there is a growing needs for environmentally-friendly and selective antimicrobial agents with a novel mode of action, which may be used in combination with conventional pesticides to delay development of pesticide resistance. In this study, we evaluated the potentials of lichen substances as novel biopesticides against eight bacterial and twelve fungal plant pathogens that have historically caused significant phytopathological problems in South Korea. Eight lichen substances of diverse chemical origins were extracted from axenic culture or dried specimen, and further purified for comparative analysis of their antimicrobial properties. Usnic acid and vulpinic acid exhibited strong antibacterial activities against Clavibacter michiganensis subsp. michiganensis. In addition, usnic acid and vulpinic acid were highly effective in the growth inhibition of fungal pathogens, such as Diaporthe eres, D. actinidiae, and Sclerotinia sclerotiorum. Intriguingly, the growth of Rhizoctonia solani was specifically inhibited by lecanoric acid, indicating that lichen substances exhibit some degrees of selectivity to plant pathogens. These results suggested that lichen substance can be used as a selective biopesticide for controlling plant disease of agricultural and horticultural significance, minimizing possible emergence of pesticide resistant pathogens in fields.     

Characterization of germin-like protein with polyphenol oxidase activity from Satsuma mandarine

Polyphenol oxidases (PPOs) catalyzing the oxygen dependent oxidation of phenols to quinones are ubiquitously distributed in plants and are assumed to be involved in plant defense against pests and pathogens. A protein with high PPO activity was identified in Satsuma mandarine, extracted with Tris–HCl buffer, purified by salt precipitation and column chromatography, and characterized by mass spectrometry as germin-like protein (GLP), which belongs to pathogenesis related protein (PR) family. In the present study, the structure and enzymatic properties of GLP were characterized using spectroscopy methods. Based on native PAGE analysis, the molecular weight of GLP was estimated to be 108 kDa and GLP was identified as a pentamer containing five subunits of 22 kDa. The optimum pH and temperature for PPO catalyzing activity of GLP was 6.5 and 65 °C, respectively. Kinetic constants were 0.0365 M and 0.0196 M with the substrates catechol and pyrogallol, respectively. The structural characterization of GLP provided better insights into the regions responsible for its PPO activity.     

Cryopreservation of somatic embryos of the herbaceous peony (Paeonia lactiflora Pall.) by air drying

This study was carried out to establish a suitable method for the cryopreservation of somatic embryos of the herbaceous peony. The somatic embryos were obtained from cotyledon and anther cultures on a MS medium supplemented with abscisic acid (ABA) and phenylacetic acid (PAA), respectively. The frequency of somatic embryo formation was the greatest (61%) from the cotyledons cultured on a MS medium supplemented with 1.0 mg l(-1) of ABA. Embryos were also obtained directly from anthers cultured on a MS medium with or without 2.0 mg l(-1) of PAA. For the cryopreservation of peony somatic embryos, the embryos were dried under a stream of sterile air and frozen by immersion in liquid nitrogen. Thawed embryos were germinated into plantlets after placing on a medium containing 0.3 mg l(-1) of gibberellic acid (GA(3)). The frequency of the post-thaw regrowth of cryopreserved somatic embryos was related to their size and desiccation time, the latter ranging from 0 to 2 h. When the somatic embryos were desiccated for 1 h, the frequency of post-thaw regrowth was greater than 66%. The frequency of post-thaw regrowth of the cryopreserved somatic embryos from anthers and cotyledon tissues was generally high when they were 2-3 mm in size. Desiccation may be a suitable method for the cryopreservation of somatic embryos of the herbaceous peony.     

Peroxisomal proteomics, a new tool for risk assessment of peroxisome proliferating pollutants in the marine environment

In an attempt to improve the detection of peroxisome proliferation as a biomarker in environmental pollution assessment, we have applied a novel approach based on peroxisomal proteomics. Peroxisomal proteins from digestive glands of mussels Mytilus galloprovincialis were analyzed using 2-DE and MS. We have generated a reference 2-DE map from samples obtained in a well-studied reference area and compared this with peroxisomal proteomes from other sequenced genomes. In addition, by comparing 2-DE maps from control samples with samples obtained in a polluted area, we have characterized the peroxisome proliferation expression pattern associated with exposure to a polluted environment. Over 100 spots were reproducibly resolved per 2-DE map; 55 differentially expressed spots were quantitatively detected and analyzed, and 14 of these showed an increase in protein expression of more than fourfold. Epoxide hydrolase, peroxisomal antioxidant enzyme, and sarcosine oxidase (SOX) have been identified by ESI MS/MS, and acyl-CoA oxidase, multifunctional protein, and Cu,Zn-superoxide dismutase were immunolocalized by Western blotting. Our results indicate that a peroxisomal protein pattern associated to marine pollutant exposure can be generated, and this approach may have a greater potential as biomarker than traditional, single-protein markers.