Platelet-collagen adhesion: evidence for participation of antigenically distinct entities.

Univalent antibody fragments prepared from a rabbit antiserum raised against whole human platelets completely inhibited adhesion of platelets to immobilized trimeric collagen in a defined, Mg2+-dependent, adhesion assay. An octylglucoside extract of whole platelets completely neutralized this antibody, and all neutralizing activity bound to immobilized wheat germ agglutinin. Further fractionation on concanavalin A gave rise to subfractions that each neutralized only partially at saturation, when tested against antibody concentrations that inhibit 50% of platelet-collagen adhesion. When tested against higher antibody concentrations that completely inhibited adhesion, each subfraction had no detectable neutralizing effect, although the combined subfractions neutralized completely. This and other evidence suggests that more than one platelet entity participates in platelet-collagen adhesion. Although distinct, they appear to play interdependent roles in a single adhesion process

Localization of an endogenous lectin in chicken liver, intestine, and pancreas.

Extracts of adult chicken liver, pancreas, and intestine contain high levels of a lectin which appears to be identical to one previously purified from embryonic chick muscle. This lectin is virtually absent from adult muscle, but is highly concentrated in cells lining liver sinusoids, intestinal goblet cells, and the extracellular spaces surrounding pancreatic acini. These findings suggest that the lectin may play different roles in different tissues and at different times in the life of a chicken

Endogenous mammalian lectin localized extracellularly in lung elastic fibers.

An affinity-purified antibody preparation raised against a beta-galactoside-binding lectin from bovine lung was used to localize a similar lectin in rat lung by immunofluorescence and by electron microscopy after on-grid staining visualized with colloidal gold conjugated second antibody. The endogenous mammalian lectin was found in smooth muscle cells and squamous alveolar epithelial (type I) cells and was concentrated extracellularly in elastic fibers of pulmonary parenchyma and blood vessels. The extracellular localization of this lectin suggests that it, like others, functions by interaction with extracellular glycoconjugates

Valproic Acid Teratogenicity: A Toxicogenomics Approach

Embryonic development is a highly coordinated set of processes that depend on hierarchies of signaling and gene regulatory networks, and the disruption of such networks may underlie many cases of chemically induced birth defects. The antiepileptic drug valproic acid (VPA) is a potent inducer of neural tube defects (NTDs) in human and mouse embryos. As with many other developmental toxicants however, the mechanism of VPA teratogenicity is unknown. Using microarray analysis, we compared the global gene expression responses to VPA in mouse embryos during the critical stages of teratogen action in vivo with those in cultured P19 embryocarcinoma cells in vitro. Among the identified VPA-responsive genes, some have been associated previously with NTDs or VPA effects [vinculin, metallothioneins 1 and 2 (Mt1, Mt2), keratin 1-18 (Krt1-18)], whereas others provide novel putative VPA targets, some of which are associated with processes relevant to neural tube formation and closure [transgelin 2 (Tagln2), thyroid hormone receptor interacting protein 6, galectin-1 (Lgals1), inhibitor of DNA binding 1 (Idb1), fatty acid synthase (Fasn), annexins A5 and A11 (Anxa5, Anxa11)], or with VPA effects or known molecular actions of VPA (Lgals1, Mt1, Mt2, Id1, Fasn, Anxa5, Anxa11, Krt1-18). A subset of genes with a transcriptional response to VPA that is similar in embryos and the cell model can be evaluated as potential biomarkers for VPA-induced teratogenicity that could be exploited directly in P19 cell–based in vitro assays. As several of the identified genes may be activated or repressed through a pathway of histone deacetylase (HDAC) inhibition and specificity protein 1 activation, our data support a role of HDAC as an important molecular target of VPA action in vivo

Selective inhibition of T suppressor-cell function by a monosaccharide

Interactions between regulatory T lymphocytes and other cells are assumed to occur at the level of the cell surface. T cells which suppress the generation of specifically effector cells have been described as having antigenic, idiotypic, allotypic and I-region specificity1−4. Other T suppressor cells generated by in vitro cultivation with or without mitogenic stimulation5,6 have suppressive activity for T and B cells but no specificity can be assigned to them. These T suppressor cells (Ts) inhibit various lymphoid functions—this either reflects their polyclonal origin or indicates that the structures recognized by the Ts receptors must be common for many cell types. Carbohydrates on cell membrane-inserted glycoproteins or glycolipids might function as specific ligands for recognition by cellular receptors or soluble factors. Almost all cell-surface proteins of mammalian cells are glycosylated. There is evidence for lectin-like carbohydrate binding proteins not only in plants7 but also in toxins8, viruses9, prokaryotic cells10 and even mammalian cells, including T cells11. A functional role for these lectin-like proteins has been described for slime moulds and suggested for the selective association of embryonic cells12,13. We report here that addition of a monosaccharide can counteract the effect of T suppressor cells during the generation of alloreactive cytotoxic T cells (CTLs) in vitro

Serum galectin-9 levels are elevated in the patients with type 2 diabetes and chronic kidney disease

Background: Galectin-9 (Gal-9) induces apoptosis in activated T helper 1 (T(H)1) cells as a ligand for T cell immunoglobulin mucin-3 (Tim-3). Gal-9 also inhibits the G1 phase cell cycle arrest and hypertrophy in db/db mice, the hallmark of early diabetic nephropathy, by reversing the high glucose-induced up-regulation of cyclin dependent kinase inhibitors such as p27(Kip1) and p21(Cip1). Methods: We investigated the serum levels of Gal-9 in the patients with type 2 diabetes and various stages of chronic kidney disease (CKD) (n = 182). Results: Serum Gal-9 levels in the patients with type 2 diabetes were 131.9 +/- 105.4 pg/ml and Log(10)Gal-9 levels significantly and positively correlated with age (r = 0.227, p = 0.002), creatinine (r = 0.175, p = 0.018), urea nitrogen (r = 0.162, p = 0.028) and osmotic pressure (r = 0.187, p = 0.014) and negatively correlated with estimated glomerular filtration rate (eGFR) (r = -0.188, p = 0.011). Log(10)Gal-9 levels increased along with the progression of GFR categories of G1 to G4, and they were statistically significant by Jonckheere-Terpstra test (p = 0.012). Log(10)Gal-9 levels remained similar levels in albuminuria stages of A1 to A3. Conclusion: The elevation of serum Gal-9 in the patients with type 2 diabetes is closely linked to GFR and they may be related to the alteration of the immune response and inflammation of the patients with type 2 diabetes and CKD

Psoriasin, one of several new proteins identified in nasal lavage fluid from allergic and non-allergic individuals using 2-dimensional gel electrophoresis and mass spectrometry

BACKGROUND: Extravasation and luminal entry of plasma occurs continuously in the nose. This process is markedly facilitated in patients with symptomatic allergic rhinitis, resulting in an increased secretion of proteins. Identification of these proteins is an important step in the understanding of the pathological mechanisms in allergic diseases. DNA microarrays have recently made it possible to compare mRNA profiles of lavage fluids from healthy and diseased patients, whereas information on the protein level is still lacking. METHODS: Nasal lavage fluid was collected from 11 patients with symptomatic allergic rhinitis and 11 healthy volunteers. 2-dimensional gel electrophoresis was used to separate proteins in the lavage fluids. Protein spots were picked from the gels and identified using mass spectrometry and database search. Selected proteins were confirmed with western blot. RESULTS: 61 spots were identified, of which 21 were separate proteins. 6 of these proteins (psoriasin, galectin-3, alpha enolase, intersectin-2, Wnt-2B and hypothetical protein MGC33648) had not previously been described in nasal lavage fluids. The levels of psoriasin were markedly down-regulated in allergic individuals. Prolactin-inducible protein was also found to be down-regulated, whereas different fragments of albumin together with Ig gamma 2 chain c region, transthyretin and splice isoform 1 of Wnt-2B were up-regulated among the allergic patients. CONCLUSION: The identification of proteins in nasal lavage fluid with 2-dimensional gelelectrophoresis in combination with mass spectrometry is a novel tool to profile protein expression in allergic rhinitis and it might prove useful in the hunt for new therapeutic targets or diagnostic markers for allergic diseases. Psoriasin is a potent chemotactic factor and its down-regulation during inflammation might be of importance for the outcome of the disease

Structural Basis for Distinct Binding Properties of the Human Galectins to Thomsen-Friedenreich Antigen

The Thomsen-Friedenreich (TF or T) antigen, Galβ1-3GalNAcα1-O-Ser/Thr, is the core 1 structure of O-linked mucin type glycans appearing in tumor-associated glycosylation. The TF antigen occurs in about 90% of human cancer cells and is a potential ligand for the human endogenous galectins. It has been reported that human galectin-1 (Gal-1) and galectin-3 (Gal-3) can perform their cancer-related functions via specifically recognizing TF antigen. However, the detailed binding properties have not been clarified and structurally characterized. In this work, first we identified the distinct TF-binding abilities of Gal-1 and Gal-3. The affinity to TF antigen for Gal-3 is two orders of magnitude higher than that for Gal-1. The structures of Gal-3 carbohydrate recognition domain (CRD) complexed with TF antigen and derivatives, TFN and GM1, were then determined. These structures show a unique Glu-water-Arg-water motif-based mode as previously observed in the mushroom galectin AAL. The observation demonstrates that this recognition mode is commonly adopted by TF-binding galectins, either as endogenous or exogenous ones. The detailed structural comparisons between Gal-1 and Gal-3 CRD and mutagenesis experiments reveal that a pentad residue motif (51AHGDA55) at the loop (g1-L4) connecting β-strands 4 and 5 of Gal-1 produces a serious steric hindrance for TF binding. This motif is the main structural basis for Gal-1 with the low affinity to TF antigen. These findings provide the intrinsic structural elements for regulating the TF-binding activity of Gal-1 in some special conditions and also show certain target and approach for mediating some tumor-related bioactivities of human galectins