The transfer of maternal antigen-specific IgG regulates the development of allergic airway inflammation early in life in an FcRn-dependent manner

Asthma is a chronic inflammatory airway disease characterized by airway hyperreactivity, increased mucus production, and reversible airway contraction. Asthma is a complex genetic trait caused by environmental factors in genetically predisposed individuals. The transportation of maternal antigen-specific IgG via amniotic fluid, placenta and breast milk plays an important role in passive immunity. First, to examine whether maternal passive immunity by the transportation of antigen-specific IgG via FcRn regulates allergic airway inflammation, ovalbumin-immunized FcRn^+/− female mice were bred with FcRn^−/− male mice to evaluate the degree of ovalbumin-induced allergic airway inflammation of FcRn^−/− offspring. Maternal passive immunity regulated allergic airway inflammation in an FcRn-dependent manner. Second, to examine the role of maternal antigen-specific IgG1 injection into mothers, we intravenously injected ovalbumin-specific IgG1 into wild-type or FcRn^+/− mice immediately after they gave birth. The offspring were sensitized and challenged with ovalbumin. Antigen-specific IgG1 administered to lactating mice reduced allergic airway inflammation in their offspring in an FcRn-dependent manner. Last, to exclude the factor of maternal passive immunity other than ovalbumin-specific IgG1, we administered ovalbumin-specific IgG1 orally to offspring after birth. Oral administration of ovalbumin-specific IgG1 to offspring during the lactating period prevented the development of allergic airway inflammation in an FcRn-dependent manner. These data show that the transfer of maternal antigen-specific IgG regulates the development of allergic airway inflammation early in life in an FcRn-dependent manner.     

Genetic analysis of abdominal fat distribution in SM/J and A/J mice

Each abdominal fat depot, such as mesenteric or epididymal, differently contributes to the development of insulin resistance. The aim of this study was to identify the genetic regions that contribute to fat accumulation in epididymal/mesenteric fat and to examine whether or not the genetic regions that affect glucose metabolism and body fat distribution are coincident. We previously mapped a major quantitative trait locus (QTL) (T2dm2sa) for impaired glucose tolerance on chromosome 2 and revealed that SM.A-T2dm2sa congenic mice showed not only glucose tolerance but also fat accumulation. In the present study, to identify the loci/genes that control the accumulation of abdominal fat, we perfomed QTL analyses of epididymal/mesenteric fat weight by using (A/J×SM.A-T2dm2sa)F2 mice in which the effect of T2dm2sa was excluded. As a result, two highly significant QTLs for mesenteric fat, as well as three significant QTLs for epididymal/mesenteric fat, were mapped on the different chromosomal regions. This suggests that the fat accumulations in individual fat depots are controlled by distinct genomic regions. Our comparison of these QTLs for abdominal fat distribution with those for glucose metabolism revealed that the major genetic factors affecting body fat distribution do not coincide with genetic factors affecting glucose metabolism in (A/J×SM.A-T2dm2sa)F2.     

Effect of glucosamine and related compounds on the degranulation of mast cells and ear swelling induced by dinitrofluorobenzene in mice

AimsGlucosamine has been used safely to relieve osteoarthritis in humans, but the precise mechanism underlying its efficacy is still unclear. In this study, we investigated the direct effects of glucosamine and related compounds on mast cell mediated inflammation using cultured mast cells and an animal model.Main methodsDinitrophenyl (DNP)-IgE-sensitized rat basophilic leukemia RBL-2H3 cells were treated with glucosamine-HCl (GlcN-HCl), N-acetylglucosamine (GlcNAc), chitin oligomer or chitosan oligomer. Cells were stimulated by DNP-BSA to induce degranulation and released β-hexosaminedase was determined colorimetrically to measure the degree of degranulation. Dinitrofluorobenzene (DNFB) sensitized BALB/c mice were administrated orally with 1 or 0.1 mg GlcN-HCl or GlcNAc for 6 days. One hour after the final administration, mice were challenged by DNFB to induce ear swelling.Key findingsGlcN-HCl significantly inhibited the antigen-induced degranulation of RBL-2H3 cells at higher than 0.01 mg/mL for 24 h-treatment while GlcNAc, a chitin oligomer and a chitosan oligomer had no effect. GlcN-HCl also suppressed intracellular calcium mobilization. GlcN-HCl and GlcNAc significantly suppressed the antigen-induced up-regulation of TNF-α and IL-6 mRNA. Ear swelling and histamine levels of plasma and ear in DNFB-treated mice were significantly suppressed by oral administration of GlcN-HCl or GlcNAc (0.1 and 1 mg) for 6 days.SignificanceOur results strongly suggest that GlcN-HCl and GlcNAc have anti-inflammatory effects in vivo by suppressing the activation of mast cells.     

PYR/PYL/RCAR family members are major in‐vivo ABI1 protein phosphatase 2C‐interacting proteins in Arabidopsis

Abscisic acid (ABA) mediates resistance to abiotic stress and controls developmental processes in plants. The group‐A PP2Cs, of which ABI1 is the prototypical member, are protein phosphatases that play critical roles as negative regulators very early in ABA signal transduction. Because redundancy is thought to limit the genetic dissection of early ABA signalling, to identify redundant and early ABA signalling proteins, we pursued a proteomics approach. We generated YFP‐tagged ABI1 Arabidopsis expression lines and identified in vivo ABI1‐interacting proteins by mass‐spectrometric analyses of ABI1 complexes. Known ABA signalling components were isolated including SnRK2 protein kinases. We confirm previous studies in yeast and now show that ABI1 interacts with the ABA‐signalling kinases OST1, SnRK2.2 and SnRK2.3 in plants. Interestingly, the most robust in planta ABI1‐interacting proteins in all LC‐MS/MS experiments were nine of the 14 PYR/PYL/RCAR proteins, which were recently reported as ABA‐binding signal transduction proteins, providing evidence for in vivo PYR/PYL/RCAR interactions with ABI1 in Arabidopsis. ABI1–PYR1 interaction was stimulated within 5 min of ABA treatment in Arabidopsis. Interestingly, in contrast, PYR1 and SnRK2.3 co‐immunoprecipitated equally well in the presence and absence of ABA. To investigate the biological relevance of the PYR/PYLs, we analysed pyr1/pyl1/pyl2/pyl4 quadruple mutant plants and found strong insensitivities in ABA‐induced stomatal closure and ABA‐inhibition of stomatal opening. These findings demonstrate that ABI1 can interact with several PYR/PYL/RCAR family members in Arabidopsis, that PYR1–ABI1 interaction is rapidly stimulated by ABA in Arabidopsis and indicate new SnRK2 kinase‐PYR/PYL/RCAR interactions in an emerging model for PYR/PYL/RCAR‐mediated ABA signalling.     

Metabolic activation of N-thiazol-2-yl benzamide as glucokinase activators: Impacts of glutathione trapping on covalent binding

Glucokinase activators (GKAs) are currently under investigation as potential antidiabetic agents by many pharmaceutical companies. Most of GKAs reported previously possess N-aminothiazol-2-yl amide moiety in their structures because the aminothiazole moiety interacts with glucokinase (GK) and shows strong GK activation. During the development of N-aminothiazol-2-yl amide derivatives, we identified a bioactivation and metabolic liability of 2-aminothizole substructure of GKA 3 by assessing covalent binding, metabolites in liver microsomes and glutathione (GSH) trap assay.     

Essential in Vivo Roles of the C-type Lectin Receptor CLEC-2: EMBRYONIC/NEONATAL LETHALITY OF CLEC-2-DEFICIENT MICE BY BLOOD/LYMPHATIC MISCONNECTIONS AND IMPAIRED THROMBUS FORMATION OF CLEC-2-DEFICIENT PLATELETS*?

CLEC-2 has been described recently as playing crucial roles in thrombosis/hemostasis, tumor metastasis, and lymphangiogenesis. The snake venom rhodocytin is known as a strong platelet activator, and we have shown that this effect is mediated by CLEC-2 (Suzuki-Inoue, K., Fuller, G. L., García, A., Eble, J. A., Pöhlmann, S., Inoue, O., Gartner, T. K., Hughan, S. C., Pearce, A. C., Laing, G. D., Theakston, R. D., Schweighoffer, E., Zitzmann, N., Morita, T., Tybulewicz, V. L., Ozaki, Y., and Watson, S. P. (2006) Blood 107, 542–549). Podoplanin, which is expressed on the surface of tumor cells, is an endogenous ligand for CLEC-2 and facilitates tumor metastasis by inducing platelet aggregation. Mice deficient in podoplanin, which is also expressed on the surface of lymphatic endothelial cells, show abnormal patterns of lymphatic vessel formation. In this study, we report on the generation and phenotype of CLEC-2-deficient mice. These mice are lethal at the embryonic/neonatal stages associated with disorganized and blood-filled lymphatic vessels and severe edema. Moreover, by transplantation of fetal liver cells from Clec-2^−/− or Clec-2^+/+ embryos, we were able to demonstrate that CLEC-2 is involved in thrombus stabilization in vitro and in vivo, possibly through homophilic interactions without apparent increase in bleeding tendency. We propose that CLEC-2 could be an ideal novel target protein for an anti-platelet drug, which inhibits pathological thrombus formation but not physiological hemostasis.