Michael Boubelik

Negative Regulation of Mast Cell Signaling and Function by the Adaptor LAB/NTAL

Engagement of the Fcɛ receptor I (FcɛRI) on mast cells and basophils initiates signaling pathways leading to degranulation. Early activation events include tyrosine phosphorylation of two transmembrane adaptor proteins, linker for activation of T cells (LAT) and non–T cell activation linker (NTAL; also called LAB; a product of Wbscr5 gene). Previous studies showed that the secretory response was partially inhibited in bone marrow–derived mast cells (BMMCs) from LAT-deficient mice. To clarify the role of NTAL in mast cell degranulation, we compared FcɛRI-mediated signaling events in BMMCs from NTAL-deficient and wild-type mice. Although NTAL is structurally similar to LAT, antigen-mediated degranulation responses were unexpectedly increased in NTAL-deficient mast cells. The earliest event affected was enhanced tyrosine phosphorylation of LAT in antigen-activated cells. This was accompanied by enhanced tyrosine phosphorylation and enzymatic activity of phospholipase C γ1 and phospholipase C γ2, resulting in elevated levels of inositol 1,4,5-trisphosphate and free intracellular Ca2+. NTAL-deficient BMMCs also exhibited an enhanced activity of phosphatidylinositol 3-OH kinase and Src homology 2 domain–containing protein tyrosine phosphatase-2. Although both LAT and NTAL are considered to be localized in membrane rafts, immunogold electron microscopy on isolated membrane sheets demonstrated their independent clustering. The combined data show that NTAL is functionally and topographically different from LAT.

Differential sensitivity to acute cholesterol lowering of activation mediated via the high-affinity IgE receptor and Thy-1 glycoprotein

Lateral cross‐linking of transmembrane high‐affinity IgE receptors (FcϵRI) or glycosylphosphatidylinositol‐anchored Thy‐1 glycoproteins on the surface of rat mast cells and rat basophilic leukemia (RBL) cells triggers the signaling pathways that lead to the release of allergy mediators. Although both of these pathways are initiated by an increased activity of Lyn kinase, the exact mechanism by which Lyn kinase interacts with aggregated FcϵRI and Thy‐1 is not completely understood. Here we demonstrate that pretreatment of RBL cells with methyl‐β‐cyclodextrin (MBCD) resulted in a dose‐ and time‐dependent decrease in cellular cholesterol, increased detergent solubilization of Thy‐1 and Lyn kinase, and a transient increase in tyrosine phosphorylation of several proteins. Acute lowering of cholesterol suppressed the activation through Thy‐1, as determined by tyrosine phosphorylation of Syk kinase and some other proteins, and modulation of free cytoplasmic calcium. In contrast, the FcϵRI‐mediated activation events were more resistant. Thy‐1 and FcϵRI in MBCD‐pretreated cells also differed in the extent of aggregation after cross‐linking: Thy‐1 formed large caps, whereas FcϵRI accumulated in small patches. MBCD treatment induced an increased release of secretory components in both Thy‐1‐ and FcϵRI‐activated cells. The combined data indicate that cholesterol depletion does not merely block receptor signaling but has more complex consequences.

Effects of p-nonylphenol and resveratrol on body and organ weight and in vivo fertility of outbred CD-1 mice

The aim of this study was to analyse the multigenerational effects of para-nonylphenol (NP) and resveratrol (RES) on the body weight, organ weight and reproductive fitness of outbred CD-1 mice. The data indicate that in male mice, NP had an effect on the weight of selected reproductive organs and the kidneys in the parental (P) generation males. Effects on selected reproductive organs, the liver and kidneys in the F1-generation males were also seen. In females, effects of NP on body weight and kidney weight were seen in the P generation, but no effects on any measured parameter were seen in the F1 generation. RES had no effect on body weight but did have some effect on selected male and female reproductive organs in the P generation. RES altered the spleen and liver weights of P-generation males and the kidney weight of F1-generation males. Acrosomal integrity (using a monoclonal antibody against intra-acrosomal sperm proteins) was assessed for both generations of NP- and RES-treated mice. A significant reduction in acrosomal integrity was seen in both generations of NP-treated, but not in RES-treated, mice. Fewer offspring were observed in the second litter of the F2 generation of mice treated with NP; no similar effect was seen in RES-treated mice. The litter sex ratio was not different from controls. Unlike RES, NP had a negative effect on spermatogenesis and sperm quality with a resultant impact on in vivo fertility.

Effect of an Endocrine Disruptor on Mammalian Fertility. Application of Monoclonal Antibodies against Sperm Proteins as Markers for Testing Sperm Damage

PROBLEM:  To determine the influence of an endocrine disruptor [bisphenol‐A (BPA)] on the integrated reproductive process as well as on individual reproductive organs and gametes in order to select suitable markers for testing sperm damage.

Development of a green fluorescent protein metastatic-cancer chick-embryo drug-screen model.

AbstractThe chick-embryo model has been an important tool to study tumor growth, metastasis, and angiogenesis. However, an imageable model with a genetic fluorescent tag in the growing and spreading cancer cells that is stable over time has not been developed. We report here the development of such an imageable fluorescent chick-embryo metastatic cancer model with the use of green fluorescent protein (GFP). Lewis lung carcinoma cells, stably expressing GFP, were injected on the 12th day of incubation in the chick embryo. GFP-Lewis lung carcinoma metastases were visualized by fluorescence, after seven days additional incubation, in the brain, heart, and sternum of the developing chick embryo, with the most frequent site being the brain. The combination of streptokinase and gemcitabine was evaluated in this GFP metastatic model. Twelve-day-old chick embryos were injected intravenously with GFP-Lewis lung cancer cells, along with these two agents either alone or in combination. The streptokinase-gemcitabine combination inhibited metastases at all sites. The effective dose of gemcitabine was found to be 10 mg/kg and streptokinase 2000 IU per embryo. The data in this report suggest that this new stably fluorescent imageable metastatic-cancer chick-embryo model will enable rapid screening of new antimetastatic agents. Abbreviation: GFP — green fluorescent protein

Soluble isoforms of CEACAM1 containing the A2 domain: increased serum levels in patients with obstructive jaundice and differences in 3-fucosyl-N-acetyl-lactosamine moiety

CEACAM1 (biliary glycoprotein or CD66a) is a member of the carcinoembryonic antigen (CEA) subgroup of the CEA family. Eleven RNA isoforms derived from the splicing of a single CEACAM1 gene have been described. Some of the CEACAM1 isoforms have been recognized by the CD66 antibodies in T and B lymphocytes, natural killer cells, granulocytes and epithelial cells in several human tissues. Although it is also present in soluble form in bile and serum, and elevated levels have been found in the serum of patients with liver diseases, it is not known which isoforms are primarily involved. In order to learn more about the distribution and properties of particular CEACAM1 isoforms, we have prepared a monoclonal antibody specific for the A2 domain of CEACAM1, designated TEC‐11. This antibody does not cross‐react with other members of the CEA family. Immunoblotting analysis revealed that the TEC‐11 epitope was present in all cell types expressing CEACAM1 containing the A2 domain [CEACAM1(A2)], including granulocytes (160 000 MW isoform) and sperm cells (140 000 MW isoform). A 115 000 MW isoform of CEACAM1(A2) was present in human serum, bile, saliva and seminal fluid. Human bile, saliva and seminal fluid also contained the 160 000 MW CEACAM1(A2) isoform. Significantly higher serum levels of the 115 000 MW CEACAM1(A2) isoform were detected in patients with obstructive jaundice. The 160 000 MW isoform of CEACAM1(A2) in bile, but not a 115 000 MW isoform in serum and bile, carried the 3‐fucosyl‐N‐acetyl‐lactosamine moiety. The combined data indicate that various isoforms of CEACAM1(A2) are present in different body fluids where they could take part in different CEACAM1‐mediated functions.

Tetraalkylammonium derivatives as real-time PCR enhancers and stabilizers of the qPCR mixtures containing SYBR Green I.

Tetraalkylammonium (TAA) derivatives have been reported to serve as stabilizers of asymmetrical cyanine dyes in aqueous solutions and to increase the yield and efficiency of polymerase chain reaction (PCR) detected by end-point analysis. In this study, we compared the ability of various TAA derivatives (with alkyl chain ranging from 1 to 5 carbons) and some other compounds to serve as enhancers of real-time PCR based on fluorescence detection from intercalating dye SYBR Green I (SGI). Our data indicate that TAA chlorides and some other TAA derivatives serve as potent enhancers of SGI-monitored real-time PCR. Optimal results were obtained with 10–16 mM tetrapropylammonium chloride. The effect of TAA compounds was dependent on the nature of counter ions present and composition of the reaction mixtures used. Based on measurements of SGI-generated fluorescence signal in the presence of PCR-amplified DNA fragments, oligonucleotide primers and/or various additives, we propose that TAA-derivatives reduce the binding of SGI to oligonucleotide primers and thus enhance primer–template interactions during annealing phase. Furthermore, these compounds serve as stabilizers of SGI-containing PCR mixtures. The combined data indicate that TAA derivatives might be a new class of additives contributing to robustness of real-time PCR monitored by asymmetrical cyanine dye SGI.

Exogenous Administration of Gangliosides Inhibits FcεRI-Mediated Mast Cell Degranulation by Decreasing the Activity of Phospholipase Cγ

Gangliosides released from tumor cells, as well as administered exogenously, suppress the immune responses by largely unknown mechanisms. We show here that a pretreatment of rat basophilic leukemia cells with isolated brain gangliosides inhibited the release of preformed secretory mediators from cells activated via FcεRI but not Thy-1 glycoprotein. Exogenously administered gangliosides also affected the cell-substrate adhesion and the levels of polymeric filamentous actin in Ag-activated cells. Although the production of phosphoinositides was also decreased, enzymatic activity of phosphatidylinositol 3-kinase was not inhibited. Gangliosides had no or only marginal effect on the association of aggregated FcεRI with glycosphingolipid-enriched membranes and on tyrosine phosphorylation of FcεRI and the linker for activation of T cells. Though pretreatment with gangliosides did not inhibit the association of linker for activation of T cells with phospholipase C (PLC)γ1 and PLCγ2, tyrosine phosphorylation of these enzymes, as well as their enzymatic activities and association with detergent-insoluble signaling assemblies were reduced. This resulted in a decreased production of inositol 1,4,5-trisphosphate and an inhibition of Ca2+ mobilization. The combined data support the concept that exogenously administered gangliosides interfere with those properties of glycosphingolipid-enriched membranes that are important for the formation of plasma membrane-associated signaling assemblies containing PLCγ but not for initial tyrosine phosphorylation of FcεRI subunits.

Syngeneic lymph-node-targeting model of green fluorescent protein-expressing Lewis lung carcinoma

The Lewis lung tumor has been extensively studied in both syngeneic and allogeneic mouse models. However, its metastatic potential and mechanism are poorly understood. The aim of the present study was to develop a highly metastatic lymph-node targeting, imageable model of the Lewis lung carcinoma in a syngeneic host. We report here a syngeneic model of the Lewis lung carcinoma in which the carcinoma cells are labeled with green fluorescent protein (GFP). The tumor cells were transplanted in the dorsal side of the ear of C57-B16 mice in order to give the tumor cells access to the lymphatic system. This model of the Lewis lung carcinoma extensively metastasized to numerous lymph nodes throughout the body of the animal as well as visceral organs, as visualized by fluorescence microscopy using the bright GFP signal. Twenty-one different metastatic sites, including lymph nodes throughout the body, were identified among the cohort of transplanted animals. The data demonstrate a predilection of the Lewis lung carcinoma for lymphatic pathways for metastasis throughout the animal body. The concomitant macrometastases to the visceral organs observed in this model may be remetastasis from the lymph nodes. This model of the Lewis lung carcinoma should be very useful in defining cellular trafficking and targeting mechanisms of metastasis, in particular those involving lymphatic pathways.

Wound healing gene therapy: cartilage regeneration induced by vascular endothelial growth factor plasmid

AIMS The identification of growth factors and cytokines with angiogenic activity has enabled new therapeutic treatments for a variety of diseases; this concept is called therapeutic angiogenesis. The vascular endothelial growth factor (VEGF) is the most critical regulator of vascular formation. In the present study, we were interested in the therapeutic angiogenesis effect using plasmid transfer of human complementary DNA VEGF(165) (phVEGF(165)) in experimental skin and cartilage trauma. METHODS Ten BALB/c mice were used for cartilage injury model. At 6 weeks of age, all mice were ear-punched, resulting in 2-mm-diameter puncture through the center of both pinnae. Each mouse got phVEGF(165) injection into the first ear and vector without insert or saline injection into the second one. The healing process was followed. The hollow diameter was measured on days 0, 14, and 42. Histological sections of experimental and control pinnae were taken from days 1, 3, 5, 7, 9, 11, 13, 15, 20, and 30 after experimental injury for hematoxylin and eosin and periodic acid Schiff staining and for human VEGF immunocytochemistry. The expression of human VEGF was also checked by real-time polymerase chain reaction in formalin-fixed, paraffin-embedded tissue sections. KEY FINDINGS In BALB/c mouse strain, a significant angiogenesis promotion and cartilage repair were observed after phVEGF(165) injection into the punched ear area. SIGNIFICANCE We suggest that administering phVEGF(165) leads to faster cartilage regeneration even if not only on the angiogenic basis.