Critical role of leukocyte function-associated antigen-1 in liver accumulation of CD4+NKT cells

In contrast to peripheral lymphoid organs, a high percentage of T cells in the liver are CD4+NKT cells. We asked whether adhesion molecules play any role in the accumulation of CD4+NKT cells in the liver. Liver CD4+NKT cells expressed ICAM-1 and high levels of LFA-1. In the livers of LFA-1-deficient mice, the number of CD4+NKT cells was markedly decreased. This reduction was restricted to the liver, and no reduction was found in the other organs analyzed. In contrast, the number of liver CD4+NKT cells in ICAM-1-deficient mice was only marginally reduced. In a reciprocal radiation thymocyte reconstitution system with LFA-1-deficient and wild-type mice, LFA-1 expressed on liver cells other than CD4+NKT cells was required for an accumulation of CD4+NKT cells in the liver. These results demonstrate a crucial role for LFA-1 in the accumulation of CD4+NKT cells in the liver.     

Large-scale analysis of the genes involved in fin regeneration and blastema formation in the medaka, Oryzias latipes

Medaka is an attractive model to study epimorphic regeneration. The fins have remarkable regenerative capacity and are replaced about 14 days after amputation. The formation of blastema, a mass of undifferentiated cells, is essential for regeneration; however, the molecular mechanisms are incompletely defined. To identify the genes required for fin regeneration, especially for blastema formation, we constructed cDNA libraries from fin regenerates at 3 days postamputation and 10 days postamputation. A total of 16,866 expression sequence tags (ESTs) were sequenced and subjected to BLASTX analysis. The result revealed that about 60% of them showed strong matches to previously identified proteins, and major signaling molecules related to development, including FGF, BMP, Wnt, Notch/Delta, and Ephrin/Eph signaling pathways were isolated. To identify novel genes that showed specific expression during fin regeneration, cDNA microarray was generated based on 2900 independent ESTs from each library which had no sequence similarity to known proteins. We obtained 6 candidate genes associated with blastema formation by gene expression pattern screening in competitive hybridization analyses and in situ hybridization. Olrfe16d23 and olrfe14k04 were expressed only in early regenerating stages when blastema formation was induced. The expression of olrf5n23, which encodes a novel signal peptide, was detected in wound epidermis throughout regeneration. Olrfe23l22, olrfe20n22, and olrfe24i02 were expressed notably in the blastema region. Our study has thus identified the gene expression profiles and some novel candidate genes to facilitate elucidation of the molecular mechanisms of fin regeneration.     

Neutrophilia in LFA-1-deficient mice confers resistance to listeriosis: possible contribution of granulocyte-colony-stimulating factor and IL-17

LFA-1 (CD11a/CD18) plays a crucial role in various inflammatory responses. In this study, we show that LFA-1(-/-) mice are far more resistant to Listeria monocytogenes infection than LFA-1(+/-) mice. Consistent with this, we found the following: 1) the numbers of granulocytes infiltrating the liver were markedly higher in LFA-1(-/-) mice than in LFA-1(+/-) mice, 2) increased antilisterial resistance in LFA-1(-/-) mice was abrogated by depletion of granulocytes, and 3) the numbers of granulocytes in peripheral blood, and the serum levels of both G-CSF and IL-17 were higher in LFA-1(-/-) mice than in LFA-1(+/-) mice. Neither spontaneous apoptosis nor survival of granulocytes from LFA-1(-/-) mice were affected by physiological concentrations of G-CSF. Our data suggest regulatory effects of LFA-1 on G-CSF and IL-17 secretion, and as a corollary on neutrophilia. Consequently, we conclude that increased resistance of LFA-1(-/-) mice to listeriosis is due to neutrophilia facilitating liver infiltration by granulocytes promptly after L. monocytogenes infection, although it is LFA-1 independent.     

Highly biased type 1 immune responses in mice deficient in LFA-1 in Listeria monocytogenes infection are caused by elevated IL-12 production by granulocytes

LFA-1 (CD11a/CD18) plays a key role in various inflammatory responses. Here we show that the acquired immune response to Listeria monocytogenes is highly biased toward type 1 in the absence of LFA-1. At the early stage of listeriosis, numbers of IFN-gamma producers in the liver and spleen of LFA-1(-/-) mice were markedly increased compared with heterozygous littermates and Valpha14(+)NKT cell-deficient mice, and NK cells were major IFN-gamma producers. Numbers of IL-12 producers were also markedly elevated in LFA-1(-/-) mice compared with heterozygous littermates, and endogenous IL-12 neutralization impaired IFN-gamma production by NK cells. Granulocyte depletion diminished numbers of IL-12 producers and IFN-gamma-secreting NK cells in the liver of LFA-1(-/-) mice. Granulocytes from the liver of L. monocytogenes-infected LFA-1(-/-) mice were potent IL-12 producers. Thus, in the absence of LFA-1, granulocytes are a major source of IL-12 at the early stage of listeriosis. We assume that highly biased type 1 immune responses in LFA-1(-/-) mice are caused by increased levels of IL-12 from granulocytes and that granulocytes play a major role in IFN-gamma secretion by NK cells. In conclusion, LFA-1 regulates type 1 immune responses by controlling prompt infiltration of IL-12-producing granulocytes into sites of inflammation.     

Are there two forms of beta 2-N-acetylglucosaminyltransferase I in rat testicular and epididymal fluids?

The activity of alpha 3-D-mannoside-beta-1,2-N-acetylglucosaminyltransferase I (GnT I; EC 2.4.1.101), which catalyzes the first step in the conversion of oligomannose to complex or hybrid N-glycans of glycoproteins, was detected in rat testicular and cauda epididymal fluids. The GnT I activity of testicular fluid had a pH optimum of 6.0, whereas that of the cauda epididymal fluid was optimal at pH 7.0. The enzyme in testicular fluid had an absolute requirement for either Co2+, or Mn2+, Mg2+ and Ca2+, the activity being stimulated by these cations in the above order, whereas that of cauda epididymal fluid had an absolute requirement for Mn2+ or Ca2+, with Co2+ and Mg2+ being ineffective. The specific activity of GnT I in cauda epididymal fluid was somewhat higher than in testicular fluid. The apparent Km value for alpha 1-3 alpha 1-6mannopentaose of GnT I in the testicular and epididymal fluids was 0.57 and 0.38 mM, respectively. The substrate specificity for both GnT I activities decreased in the following order: alpha1-3 alpha 1-6mannopentaose>alpha1-3 alpha 1-6mannotriose>alpha 1-3mannobiose>alpha 1-6mannobiose. These data suggest that two forms of GnT I exist in the testicular and epididymal fluids.     

ecNOS gene polymorphism is associated with endothelium-dependent vasodilation in Type 2 diabetes

The association between endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphism and vascular endothelial function has not been clarified. We investigated the impact of ecNOS gene polymorphism on endothelial function in 95 patients with Type 2 diabetes (ecNOS genotype: 4b/b, n = 62; 4b/a, n = 30; 4a/a, n = 3). Flow-mediated (endothelium dependent, FMD) and nitroglycerin-induced (endothelium independent, NTG) vasodilations of the right brachial artery were studied using a phase-locked echotracking system. There were no significant differences in clinical characteristics among the ecNOS genotypes. The FMD was significantly lower in the patients with ecNOS4a allele than in those without ecNOS4a allele (P < 0.05). Multiple regression analysis showed that ecNOS4a allele and mean blood pressure were significant independent determinants for reduced FMD in all patients (R(2) = 0.122, P = 0.0025). The ecNOS4a allele was an independent determinant for reduced FMD in smokers but not in nonsmokers. These results suggest that ecNOS4a allele is a genetic risk factor for endothelial dysfunction in diabetic patients, especially in smokers.     

EST analysis of gene expression in testis of the ascidian Ciona intestinalis

To explore the gene expression underlying spermatogenesis, a large-scale analysis has been done on the cDNAs from testis of the ascidian, Ciona intestinalis. A set of 5,461 expressed sequence tags was analyzed and grouped into 2,806 independent clusters. Approximately 30% of the clusters showed significant sequence matches to the proteins reported in DDBJ/GenBank/EMBL database including a set of proteins closely related to the gene regulation during spermatogenesis, functional and morphological changes of spermatogenic cells during spermiogenesis, and physiological functions of sperm, as well as those with housekeeping functions commonly expressed in other cells. Some clones show similarities to the proteins present in vertebrate lymphocytes, suggesting a primitive immune system in ascidians. We have also found some genes that are known to participate in hormonal regulation of spermatogenesis in vertebrates. The large majority of the genes expressed in Ciona testis show no significant matches to known proteins and the further analysis of these genes may shed new light on the molecular mechanism of spermatogenesis and sperm functions.     

Molecular isolation and characterization of novel four subisoforms of ECE-2

Although the four polypeptides of blasticidin S (BS) deaminase (BSD) are packed rather tightly coordinated to the "structural and catalytic" zinc atom of each subunit, the C-terminal region of the enzyme was suggested to be somewhat molten and flexible [M. Kimura, S. Sekido, Y. Isogai, and I. Yamaguchi (2000) J. Biochem. 127, 955-963]. To understand roles of this flexible region, we constructed five C-terminal deletion variants of BSD (each successively deleted from the C-terminal end up to five residues) and analyzed their biochemical properties focusing on the structure and activity of the enzyme. BSD and all of the deletion mutants showed the unique rigid conformation (e.g., characterized by their stabilities in SDS solution) and high levels of resistance against protease digestions. Furthermore, both the wild-type and deletion apoenzymes exhibited similar physical properties in thermodynamic refolding into the stable tetramer conformation. However, these small C-terminal deletions exerted deleterious effects on the catalytic efficiency of the enzyme as indicated by their strongly reduced k(cat)/K(m) value. Judging from the altered kinetic parameters and unaltered structural properties of the deletion variants, these C-terminal residues appear to be directly involved in enzyme-substrate interaction. In this short flexible region, Tyr-126, Trp-128, and Gly-130 were the key residues. Most notably, removal of Gly-130 markedly increased K(m) for BS without affecting its k(cat) value. These results indicate that the flexible C-terminal region is important for catalytic function and that a single Gly residue at the C-terminal end of BSD contributes significantly in facilitating access of a substrate to the active site.     

Possible role of cell surface H+ -ATP synthase in the extracellular ATP synthesis and proliferation of human umbilical vein endothelial cells

Extracellular ATP synthesis on human umbilical vein endothelial cells (HUVECs) was examined, and it was found that HUVECs possess high ATP synthesis activity on the cell surface. Extracellular ATP generation was detected within 5 s after addition of ADP and inorganic phosphate and reached a maximal level at 15 s. This type of ATP synthesis was almost completely inhibited by mitochondrial H(+)-ATP synthase inhibitors (e.g., efrapeptins, resveratrol, and piceatannol), which target the F(1) catalytic domain. Oligomycin and carbonyl cyanide m-chlorophenylhydrazone, but not potassium cyanide, also inhibited extracellular ATP synthesis on HUVECs, suggesting that cell surface ATP synthase employs the transmembrane electrochemical potential difference of protons to synthesize ATP as well as mitochondrial H(+)-ATP synthase. The F(1)-targeting H(+)-ATP synthase inhibitors markedly inhibited the proliferation of HUVECs, but intracellular ATP levels in HUVECs treated with these inhibitors were only slightly affected, as shown by comparison with the control cells. Interestingly, piceatannol inhibited only partially the activation of Syk (a nonreceptor tyrosine kinase), which has been shown to play a role in a number of endothelial cell functions, including cell growth and migration. These findings suggest that H(+)-ATP synthase-like molecules on the surface of HUVECs play an important role not only in extracellular ATP synthesis but also in the proliferation of HUVECs. The present results demonstrate that the use of small molecular H(+)-ATP synthase inhibitors targeting the F(1) catalytic domain may lead to significant advances in potential antiangiogenic cancer therapies.