Siglecs are sialic acid binding Ig-like lectins, subset of the immunoglobulin superfamily. They are characterized by a homologous N-terminal V-set Ig-like domain and C2 set Ig-like domains. N-terminal domains have sialic acid binding activity. In humans, 11 Siglecs have been described sialoadhesin(Siglec-1), CD22(Siglec-2), CD33(Siglec-3), MAG(Siglec-4), more recently described CD33-related Siglecs(Siglec 5-11). Siglecs express most signal via immunoreceptor tyrosine-based inhibition motif(ITIM) cytoplasmic domains. The cytoplasmic tails of all Siglecs except sialoadhesin have one or more tyrosine residues within potential signaling motifs. Inhibitory function of other Siglecs such as Siglec-7 or Siglec-9 was shown in RBL-2H3 cells. Co-crosslinking of Siglec-7 or Siglec-9 and Fc epsilon R1 substantially reduced the serotonin release of RBL-7 and RBL-9 cells. Siglec-8 is expressed on human eosinophils, mast cells and basophils. Siglec-8 has two tyrosine motifs, a proximal motif and a distal motif. They have some inhibitory functions in immune system. We have observed that Siglec-8 is able to inhibit the IgE receptor-mediated beta-hexosaminidase release of RBL-2H3 cells following co-crosslinking. Co-crosslinking of Siglec-8 and Fc epsilon R1 reduced the hexosaminidase release of RBL-2H3 cells. These results show that Siglec-8 is as potent as Siglec-7 and Siglec-9 in delivering inhibitory signals to RBL-2H3 cells. Siglec-8 should be a new member of the inhibitory receptor superfamily and the membrane-proximal ITIM is essential for the inhibitory function of Siglec-8 molecules. Although these molecules present specific marker for the allergic cell types, more work is needed to understand the signaling mechanism and the role in various disease processes.
Basophils ; beta-N-Acetylhexosaminidases ; Cytoplasm ; Eosinophils ; Hexosaminidases ; Humans ; Immune System ; Immunoglobulin E ; Immunoglobulins ; Inflammation* ; Lectins ; Mast Cells ; N-Acetylneuraminic Acid ; Serotonin ; Sialic Acid Binding Ig-like Lectin 1 ; Sialic Acid Binding Immunoglobulin-like Lectins* ; Tyrosine

Sialoadhesin (Sn) expression has been demonstrated on murine and rat macrophages in lymphatic organs and is recognized by the monoclonal antibody (mAb) ED3 in the rat. Sialoadhesin (Siglec-1), the ED3 antigen in the rat, is a subtype of sialic acid -binding Ig-like lectins (Siglecs) that bind specifically to sialic acid-containing structures such as selectins and was originally identified as the sheep erythrocyte receptor (SER) responsible for sialic acid-dependent binding of native sheep erythrocytes (SE) to resident murine bone marrow macrophages in rosetting assays. The aim of the present study was to investigate the expression and potential function of sialoadhesin in the stratified squamous epithelium of the rat tongue, esophagus and skin. The expression of sialoadhesin was demonstrated by immunohistochemical analysis with the mAb ED3. This study demonstrated not only the presence of sialoadhesin on the basal epithelial cells of the stratified epithelium in normal rat tongue, esophagus and skin but also its upregulated expression on these cells in CY-treated rats. The results of the present study shed some light on the potential function of sialoadhesin in the basal epithelial cells of the stratified epithelium. Further studies may provide more insight into the role of sialoadhesin in the epithelial stem cells.
Animals ; Bone Marrow ; Cyclophosphamide* ; Epithelial Cells* ; Epithelium* ; Erythrocytes ; Esophagus ; Lectins ; Macrophages ; N-Acetylneuraminic Acid ; Rats* ; Selectins ; Sheep ; Sialic Acid Binding Ig-like Lectin 1 ; Skin ; Stem Cells ; Tongue ; Up-Regulation*

This study is to investigate the effect of downregulation histone deacetylases 1 (HDAC1) gene by the technology of RNA interference on the differentiation of HL-60 cells line. The optimal segment targeting HDAC1 gene was designed and transfected into HL-60 cells by Lipofectamine 2000. The HDAC1 mRNA and protein level were detected by RT-PCR and Western blotting. The morphologic change of HL-60 cells was detected by an optical microscope with Wright-Giemsa. Cell differentiation was tested by NBT reduction assay. Expression of CD13, CD33 and CD14 was measured by flow cytometry. The results indicated that HDAC1 mRNA and protein were markedly suppressed by the siRNA targeting HDAC1 in a concentration-dependent manner. HDAC1 siRNA promoted cell differentiation. HL-60 cells became more mature in morphology after transfected to HDAC1 siRNA at a concentration of 30-60 nmol x L(-1) for 24 h. NBT reduction ability of HDAC1 siRNA with 30 nmol x L(-1) was 0.31 +/- 0.09, compared with negative control (0.20 +/- 0.02) (t = -3.1, P < 0.01), and with 60 nmol x L(-1) was 0.25 +/- 0.02 in comparison with negative control (0.21 +/- 0.04) (t = -2.12, P < 0.05). But it has no change in HDAC1 siRNA > or = 120 nmol x L(-1). After transfection with 60 nmol x L(-1) HDAC1 siRNA to HL-60 cells, the expression of CD13 was (96.50 +/- 0.70)% in compared to siRNA-NC (3.39 +/- 0.68) % (t = 164.9, P < 0.000 5), CD33 was (66.73 +/- 0.50) % in compared to siRNA-NC (96.80 +/- 1.70) % (t = 43.4, P < 0.000 5). CD14 was (0.53 +/- 0.00) % by comparison with siRNA-NC (0.49 +/- 0.02) % (t = -0.97, P > 0.1). HDAC1 siRNA promoted cell differentiation in indicated concentration. HDAC1 might be one of the targets of gene therapy for leukemia.
CD13 Antigens ; metabolism ; Cell Differentiation ; Down-Regulation ; HL-60 Cells ; Histone Deacetylase 1 ; genetics ; metabolism ; Humans ; Lipopolysaccharide Receptors ; metabolism ; RNA Interference ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; genetics ; Sialic Acid Binding Ig-like Lectin 3 ; metabolism ; Transfection

OBJECTIVE12-0-tetradecanoylphorbol-13 acetate (TPA) plays an important role in precipitating cell differentiation for various tumor cells, especially leukemic cells. Changes of many genes may be involved in this process. The purpose of this study was to observe the relationship between the EGR1mRNA expression and cell differentiation during TPA-induced K562 cell differentiation.

METHODSIncubation of human K562 cells in vitro was applied to cultivate K562 cells. The cells were treated in two different ways. K562 cells of experiment group were treated with TPA and those of control group were treated without TPA. Using morphology (Wright's staining and NSE staining) and flow cytometry (FCM), the investigators observed the differentiation characteristics of K562 cells, cell-cycle and the differentiation antigen expressions of CD33 and CD14 on cell membranes. RT-PCR was carried out to assay EGR1 mRNA expression.

RESULTSAfter treated with TPA for 7 d, the morphology of K562 cells obviously tended to mature differentiation, like monocytes. The differentiation rate of induced K562 cells was up to 95% in experiment group and 4.5% in control group, respectively. Using SPSS software, the above result showed statistical significance (P < 0.01). Using NSE staining, K562 cells showed positive reaction. Some of them were densely stained. The positive rate was up to 86%. More than half of the positive cells could be inhibited by NaF. The inhibiting rate of NaF was up to 58.72%, showing statistical difference when compared with that of control group. FCM analysis showed that most of K562 cells stimulated by TPA underwent G1/S phase cell-cycle arrest. The composing rate of cell-cycle in TPA-treated group showed that (53.7 +/- 1.25)% of cells were at G0 + G1 phase and (44.3 +/- 1.32)% were at S phase (P < 0.05). The level of CD33 expression on cell membranes was mildly decreased from 0.997% to 0.893% (P > 0.05). However, the level of CD14 expression was significantly increased from 0.049% to 0.387% (P < 0.05).

CONCLUSIONK562 cells could express EGR1mRNA during TPA-induced differentiation, which suggested that EGR1mRNA might participate in the process of K562 cells differentiating into monocyte/macrophages, and might play an important role in precipitating and maintaining cell differentiation for leukemic cells.

Antigens, CD ; metabolism ; Antigens, Differentiation, Myelomonocytic ; metabolism ; Carcinogens ; pharmacology ; Cell Cycle ; drug effects ; genetics ; Cell Differentiation ; drug effects ; genetics ; Cell Division ; drug effects ; genetics ; Cell Membrane ; chemistry ; drug effects ; DNA-Binding Proteins ; genetics ; Early Growth Response Protein 1 ; Flow Cytometry ; Gene Expression Regulation, Neoplastic ; drug effects ; Humans ; Immediate-Early Proteins ; genetics ; K562 Cells ; Lipopolysaccharide Receptors ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Sialic Acid Binding Ig-like Lectin 3 ; Tetradecanoylphorbol Acetate ; pharmacology ; Transcription Factors ; genetics

OBJECTIVETo explore the synergic effect of heparan sulfate (HS) and cytokines on the growth of human umbilical cord blood (UCB) hematopoietic cells.

METHODSHematopoietic cells from human UCB were cultured with (1) cytokines (rhIL-3, rhIL-1beta, rhIL-6 and SCF) or (2) SN (supernatant from cultured human marrow stromal cells) and cytokines, or (3) SN, or (4) HS and cytokines. Cellular proliferation, CFU-GM yields and changes of cell immunophenotype were observed.

RESULTSHematopoietic cell proliferation reached peak at the 14th day. The number of total nucleated cells increased 134.5-, 171.3-, 81.5- and 167.2-fold in (1), (2), (3) and (4) groups, respectively, at the 21th day, the (3) group significantly decreased. CD(34)(+) cells increased at the 7th day and reached peak, at the 14th day with a percentage of 68.4%, 82.5%, 69.8% and 79.3%, and at the 21th day 56.2%, 71.7.%, 12.3% and 73.3%, respectively. CD(33)(+) cells reached peak at the 14th day and increased by 80.2%, 68.6%, 81.6% and 70.3%, respectively, and remained these levels at the 21th day. CD(38)(+) cells increased by 66.6%, 73.8%, 70.4% and 71.9% at the 7th day and remained this level at the 14th and the 21th day. From the first week of culture, the percentage of CFU-GM increased in all of the four groups, at the second week of culture, it increased by 250%, 279%, 217% and 273%, and at the third week still increased by 151%, 240%, 145% and 231%, respectively.

CONCLUSIONThe combination of SN and cytokines have a synergic effect in promoting proliferation of hematopoietic cell from human UCB. The synergic effect remained the same when SN was replaced by heparan sulfate.

ADP-ribosyl Cyclase ; analysis ; ADP-ribosyl Cyclase 1 ; Antigens, CD ; analysis ; Antigens, CD34 ; analysis ; Antigens, Differentiation, Myelomonocytic ; analysis ; Cell Division ; drug effects ; Cells, Cultured ; Cytokines ; pharmacology ; Drug Synergism ; Fetal Blood ; cytology ; drug effects ; immunology ; Heparitin Sulfate ; pharmacology ; Humans ; Infant, Newborn ; Interleukin-1 ; pharmacology ; Interleukin-3 ; pharmacology ; Leukocytes, Mononuclear ; cytology ; drug effects ; immunology ; Membrane Glycoproteins ; Recombinant Proteins ; pharmacology ; Sialic Acid Binding Ig-like Lectin 3 ; Time Factors