Isolation and structural identification of glycopolymers of Bifidobacterium bifidum BIM B-733D as putative players in pathogenesis of autoimmune thyroid diseases

Bifidobacterium bifidum 791 (commercially available as B. bifidum BIM B-733D) cell-surface biopolymers (BPs) interact selectively with human serum thyroid peroxidase (TPO) and thyroglobulin (Tg) autoantibodies (anti TPO and anti Tg, respectively). BPanti-TPO and BPanti-Tg were isolated from the soluble fraction of B. bifidum BIM B-733D by affinity chromatography with anti-TPO or anti-Tg, respectively. Homogeneity of affinity eluates (AEanti-TPO and AEanti-Tg) was tested by size exclusion chromatography. For each AE, the elution profiles generated on the basis of absorbance at 280 nm do not conform to ELISA data for functional activity characteristic of BPs. Moreover, high functional activity was detected in chromatographic fractions that had significantly different molecular weights and no absorbance at 280 nm, which suggests a non-protein (carbohydrate) nature of BPanti-TPO and BPanti-Tg. The semi-preparative size exclusion chromatography of AEanti-TPO and AEanti-Tg with detection by refractometer gave 5,000-7,000 Da fractions containing substances that interact selectively with either anti TPO (BPanti-TPO) or anti-Tg (BPanti-Tg) according to ELISA data. Analysis by two-dimensional NMR spectroscopy including a 1H, 13C-heteronuclear single-quantum coherence experiment indicated that both substances are linear α-1,6-glucans. For the first time, an immunological similarity (molecular mimicry) of glycopolymers of B. bifidum BIM B-733D and human thyroid proteins, TPO and Tg, was shown. On the whole, our data point to a possible role of bifidobacteria in the pathogenesis of autoimmune thyroid diseases (ATD). The main requirements for triggering/acceleration or prevention/abrogation of ATD by bifidobacteria through molecular mimicry mechanism are hypothesised to be (1) genetic predisposition to ATD and (2) intestinal epithelium penetration by α-1,6-glucan.

[Effect of sutent and celecoxib on the properties of endothelial cells in vitro]

We studied the anti-angiogenic properties of sutent (SU11248) and celecoxib in human endothelial cell line EA. hy 926 in vitro. Sutent 0.05-0.5 microg/ml suppressed their proliferation and migration depending on dose while celecoxib did the same at 5.0 microg/ml. We were the first to demonstrate that endothelial cell incubation was followed by increase in 5'-nucleotidase activity in the presence of sutent while celecoxib did not produce such effect. It may be suggested that elevated 5'-nucleotidase concentration at the membranes of endothelial cells might in turn contribute to the pool of extracellular adenosine to stimulate antiinflammatory effect. Our data also contribute to the knowledge about the anti-angiogenic properties of sutent and celecoxib.

Effect of lactate on functional activity of macrophages under normal conditions and during tumor growth

Lactate modulated functional activity of macrophages from intact mice and animals with transplantable syngeneic hepatoma 22a. Sodium lactate in a concentration of 6.5 mM in vitro increased functional activity of resident peritoneal macrophages from intact mice. The growth of transplantable syngeneic hepatoma 22a was associated with the absence of correlation between nitrite synthesis by peritoneal macrophages and serum lactate concentration. Therefore, this agent cannot be considered as a systemic activator of macrophages.

[Characteristics of immunoaffinity chromatography and a new method for isolation of human thyroid peroxidase from subcellular fractions of thyroid gland]

A system for quantitative determinations of human thyroid peroxidase (TPO) in biological fluids has been obtained, based on the use of enzyme-linked immunosorbent assay. Immunochemical properties of TPO were studied under variable conditions, and a new method for isolating the protein from microsomes, mitochondria, and cytosol of thyroid glands of patients with diverse thyroid diseases was developed. The procedure involves solubilization of subcellular fractions with detergents, their sonication, two sequential runs of chromatography (on sorbents with immolbilized monoclonal antibodies against TPO and goat anti-human immunoglobulin antibodies), treatment with ribonuclease, and dialysis. Highly purified preparations of intact TPO and a product of its limited trypsinolysis are expected to be used as research tools and components of high-sensitivity immunoassays.

[Characteristics of monoclonal antibodies against human thyroid peroxidase for use in immunoaffinity chromatography and immunoassays]

Two types of monoclonal antibodies (MABs) against human thyroid peroxidase (TPO) have been obtained, which interact with spatially separated conformational epitopes of the antigen (Ka values are in the range 10(8)-10(9) M(-1)). The binding site of MAB F8 is in the immunodominant region of the TPO molecule, in the vicinity of the autoantigenic determinants, whereas the epitope specific for MAB A1 lies outside this location. Both MABs retain the ability to form immune complexes after solid-phase immobilization and chemical modification with a biotin derivative. The above properties suggest that MABs A1 and F8 may be used in immunoaffinity chromatography (isolation and purification of TPO from natural sources) and immunoassays for determinations of TPO (in biological fluids) and TPO autoantibodies (in human blood serum).

Effect of VEGF on Mouse Thymocyte Proliferation and Apoptosis In Vitro

Vascular endothelial growth factor is not only angiogenic, but also immunoregulatory factor. For evaluation of the possibility of its direct interaction with mouse thymocytes we studied the effect of vascular endothelial growth factor on proliferation and apoptosis of thymocytes and expression of genes for the corresponding receptor on these cells. Vascular endothelial growth factor modulated mitogen-induced proliferation of thymocytes and stimulated spontaneous apoptosis in intact thymus cells. Thymocytes express mRNA of type 2, but not type 1 vascular endothelial growth factor receptors.

Effect of hyperlipoproteinemia on functional activity of peritoneal macrophages during tumor growth

The role of hypercholesterolemia as a factor modulating functional activity of macrophages during the growth of syngeneic transplanted 22a hepatoma in mice was studied. Starting from day 21 after inoculation of tumor cells we observed the development of hyperlipoproteinemia paralleled by an increase in macrophage activity parameters. The total serum cholesterol content and production of nitroxide anions by macrophages were in positive correlation on days 14-35 of tumor growth. We hypothesized that the development of hypercholesterolemia at the late stages of some tumor growth is a factor stimulating production of nitrites and 5'-nucleotidase activity.

Effect of metabolic factors on apoptosis in thymocytes during tumor growth

Intensive apoptotic death of thymocytes is a possible mechanism of thymus involution during tumor growth. We studied the role of hypercholesterolemia and lactate acidosis in the induction of increased sensitivity of thymocytes to apoptosis during growth of transplanted hepatoma 22a in mice. Spontaneous apoptosis in thymocytes during tumor growth in mice was studied in vitro by acridine orange/ethidium bromide staining and diphenylamine test. Plasma levels of lactate, total cholesterol, alpha-cholesterol, and triglycerides were measured. A positive correlation was found between intensification of apoptosis (diphenylamine test) and increased concentration of total plasma cholesterol on days 21 and 28 after inoculation of tumor cells. Plasma lactate content did not increase at this term. We hypothesize that hypercholesterolemia accompanying tumor growth acts as a factor increasing thymocyte sensitivity to apoptosis.

Effect of hyperlipidemia on functional activity of peritoneal macrophages in CBA and C57Bl/6 mice

The effect of experimental hyperlipidemia on functional activity of macrophages was studied in CBA and C57Bl/6 mice resistant and sensitive to the formation of aorta lesions, respectively. Two-month atherogenic diet increased the content of cholesterol in the serum and cells of peritoneal exudate in mice of both strains. In parallel, production of nitrites and 5'-nucleotidase activity in peritoneal macrophages increased, while parameters of phagocytosis, pinocytosis, and NBT test remained unchanged. Changes in the state of macrophages can be explained by increased cholesterol content. The absence of differences in functional activity of macrophages in CBA and C57Bl/6 mice indicates that the observed shifts are insignificant for the development of fatty streaks in the aorta.

[Autoantibodies to human thyroid peroxidase in immunoassay and immunoaffinity chromatography]

A biochemical system of radioimmunoassay of human thyroid peroxidase (TPO) with the use of specific autoantibodies was developed for the first time. This system includes lyophilized preparations of human autoantibodies to TPO, radioiodinated TPO, standards prepared from pure TPO, and the solid-phase protein A as a precipitating agent. An analytical system was used to study the TPO distribution in fractions of thyroid tissue homogenate. Differences in TPO concentrations in mitochondria, microsomes, and supernatant fluid depending on thyroid pathology and tissue storage conditions were found. The behavior of immobilized anti-TPO-autoantibodies in immunoaffinity chromatography of this microsomal antigen was studied.

[Inactivation of the human thyroid peroxidase by ultrasound cavitation]

The inactivation kinetics of a human thyroid peroxidase protein fraction upon sonication (ultrasound frequency 27 kHz, power 60 W/cm2) of the enzyme solution in 15 mM phosphate buffer, pH 7.5, was studied. To quantitatively characterize the dependence of the slowest stage of the human thyroid peroxidase inactivation on temperature (36.0-50.4) degrees C, an effective constant of ultrasound inactivation rate Kin(US) was used. From the temperature dependence of Kin(US) at temperatures below 43 degrees C, the activation energy was estimated to be 8.11 kcal/mol. It was shown that the rate of human thyroid peroxidase inactivation strongly depends on the concentration of total protein in solution: the kin(US) value decreases more than sixfold in the protein concentration range from 0.2 to 0.8 mg/ml. It was also shown that poly(2-aminodisulfide-4-nitrophenol), its complexes with human serum albumin as well as the complexes human serum albumin--poly(gallic acid disulfide) substantially inhibit the ultrasound-induced inactivation of the enzyme and can be its effective stabilizers in the ultrasound cavitation field. This confirms the suggestion that active free radicals HO., O2.- and HO2. play a key role in the inactivation of human thyroid peroxidase. A general scheme of the inactivation of human thyroid peroxidase is proposed, which represents a chain of successive and parallel reversible and irreversible elementary steps.

Effect of hyperlipidemia on thymocyte sensitivity to apoptosis in CBA and C57Bl/6 mice

Effects of experimental hyperlipidemia on apoptosis and proliferation of thymocytes in response to mitogens were studied in CBA and C57Bl/6 mice. The concentrations of cholesterol in the serum and thymocyte membranes increased in both mouse strains. Spontaneous and dexamethasone-induced apoptosis in vitro and the proliferative response to phytohemagglutinin and concanavalin A were enhanced in thymocytes from C57Bl/6 mice and suppressed in cells from CBA mice. These data suggest opposite reactions of thymocyte to increased serum cholesterol concentration in these two strains, associated with stimulation and suppression of cell activity.

[Autoimmune disorders in liqvidators 11 years after the Chernobyl accident]

We studied long-lasting consequences of the low-doses irradiation on the immune system of 71 clean-up workers who participated in the emergency work after the Chernobyl Plant accident in 1986 and 25 healthy donors from Belarus. In sera of the workers the level of autoantibodies to thyroid gland antigens (thyroglobulin and microsomal fraction of thyroid gland) was increased in 48% of cases, the level of autoantibodies to lens oculis antigen was increased in 44% of cases; the level of circulating immune complexes was elevated in 55%, and the serum level of thyroglobulin in 60% of people. Immunological disorders were found without any definite clinical evidences of diseases and this allows us to consider the examined contingent as a group of risk for the development of autoimmune pathology in the future.

[The role of apoptosis in the thymic involution during growth of the syngeneic transplanted tumor in mice]

Thymic involution accompanies the growth of many human and animals tumors but the precise mechanism of this phenomenon is unknown. We tried to elucidate the role of apoptosis as a possible mechanism of thymic involution during tumor growth. The mice were inoculated subcutaneously with syngeneic hepatoma 22a cells. Starting from the 3rd week after tumor inoculation, progressive thymic involution was observed. Histological studies revealed distinct delymphatization of the thymic cortex, reduced numbers of big lymphocytes in the subcapsular zone and of mitoses in the cortex, and an increased amount of mast cells. This was followed by decreased DNA synthesis in vitro as measured from 3H-thymidine incorporation. The number of pycnoses in the cortex was two to three times that in the thymus of control animals. DNA gel electrophoresis did not reveal any signs of apoptosis in the thymocytes without preincubation. Within 2 h of in vitro incubation of the thymocytes taken on the 7th day after the tumor inoculation, spontaneous apoptosis was more expressed than in the thymocytes from intact mice. This may reflect different induction mechanisms of apoptosis in the thymocytes from the tumor bearing and control mice. We propose that the mechanism of thymic involution during tumor growth is related to inhibition of thymocytes' proliferation, impaired differentiation and enhanced intrathymic death caused by cytokine release from the nonlymphoid thymic population.

[Interaction of transcortin with human syncytiotrophoblast]

Interactions of transcortin (corticosteroid-binding globulin, CBG) variants, nCBG and rCBG, present in the blood of pregnant women, and microvesicular fraction of the brush border membrane of human placental syncytiotrophoblast at 23 +/- 2 degrees C were studied. Interaction of nCBG in complex with a steroid with each of the two types for specific binding was found associated with transmembranous transfer of glycoprotein. Interaction of rCBG with binding sites of both types did not involve subsequent glycoprotein transfer through the membrane. Possibility of penetration of only one CBG variant through syncytiotrophoblast membrane suggests the presence of different mechanisms of these glycoproteins' participation in the hormonal effects of steroids associated with them.

[The effect of steroids on binding of transcortin with human syncytiotrophoblasts]

The effects of steroids on specific binding of transcortin (corticosteroid-binding globulin, CBG) variants (nCBG and vCBG) from pregnant women sera to the microvesicular membrane fraction derived from placental syncytiotrophoblast brush border have been studied. It was shown that native CBG variants stripped of steroids lose their ability to interact with specific membrane sites. Specific binding of CBG variants was found to increase in parallel with an increasing per cent content of glycoproteins associated with cortisol, reaching a maximum at cortisol concentrations of 5.10(-8)-5.10(-7) M which is saturating for the complex formation. Specific binding sites in the syncytiotrophoblast membrane do not differentiate between the nCBG complexed to cortisol, corticosterone, progesterone or testosterone but show a selectivity towards the vCBG-cortisol complex.

[Splenocyte functional activity in mice growing the syngeneic transplantable hepatoma 22a]

The growth of syngeneic transplantable hepatoma 22a is not accompanied by alteration of functional activity of T-lymphocytes in the spleens of tumor-bearing hosts as evidenced by means of PHA-blasttransformation test. The contents of T-lymphocytes in the spleens of tumor-bearers was non changed. The cytotoxic activity of the splenocytes towards hepatoma 22a cells was increased either in vivo (Winn-test) or in vitro (cytotoxic test) as compared with splenocytes of intact mice. By means of the test of inhibition of peritoneal macrophage adherence, the increased level of sensibilization of splenocytes towards tissue antigens was shown in mice hearing hepatoma 22a.