Thrombospondin-4 mediates TGF-ß-induced angiogenesis.

TGF-ß is a multifunctional cytokine affecting many cell types and implicated in tissue remodeling processes. Due to its many functions and cell-specific effects, the consequences of TGF-ß signaling are process-and stage-dependent, and it is not uncommon that TGF-ß exerts distinct and sometimes opposing effects on a disease progression depending on the stage and on the pathological changes associated with the stage. The mechanisms underlying cell- and process-specific effects of TGF-ß are poorly understood. We are describing a novel pathway that mediates induction of angiogenesis in response to TGF-ß1. We found that in endothelial cells (EC) thrombospondin-4 (TSP-4), a secreted extracellular matrix (ECM) protein, is upregulated in response to TGF-ß1 and mediates the effects of TGF-ß1 on angiogenesis. Upregulation of TSP-4 does not require the synthesis of new protein, is not caused by decreased secretion of TSP-4, and is mediated by activation of SMAD3. Using Thbs4-/- mice and TSP-4 shRNA, we found that TSP-4 mediated pro-angiogenic functions in cultured EC and angiogenesis in vivo in response to TGF-ß1. We observed~3-fold increases in tumor mass and levels of angiogenesis markers in animals injected with TGF-ß1, and these effects did not occur in Thbs4-/- animals. Injections of an inhibitor of TGF-ß1 signaling SB-431542 also decreased the weights of tumors and cancer angiogenesis. Our results from in vivo angiogenesis models and cultured EC document that TSP-4 mediates upregulation of angiogenesis by TGF-ß1. Upregulation of pro-angiogenic TSP-4 and selective effects of TSP-4 on EC may contribute to stimulation of tumor growth by TGF-ß despite the inhibition of cancer cell proliferation.

Role of T cell subsets in the modulation of Mycobacterium avium growth within human monocytes.

Mycobacterium avium frequently causes disseminated disease in patients with advanced AIDS with low CD4 counts. The effects of T lymphocyte on intracellular M. avium replication were examined. Plastic adherent monocytes and nonadherent lymphocytes were separated from peripheral blood mononuclear cells. After infection with M. avium, monocytes were cultured with or without autologous lymphocytes (1-10 cells/monocyte) for up to 7 days. Addition of lymphocytes to M. avium-infected monocytes significantly decreased intracellular M. avium growth after 7 days culture (n = 11, P < 0.01, paired t test) and increased IFN-gamma production compared to monocytes alone. Neutralizing IFN-gamma partially abrogated lymphocyte activity. CD4 depletion diminished anti-mycobactericidal effects and CD8(+) lymphocytes increased intracellular M. avium growth (P < 0.05, n = 5, t test). These data suggest that interactions between monocytes and nonadherent cell fractions such as CD4(+) T cells and NK cells are important in intracellular M. avium growth modulation in monocytes from healthy humans.

Enhancement by tumor necrosis factor-alpha of Fc alpha receptor expression and IgA-mediated superoxide generation and killing of Pseudomonas aeruginosa by polymorphonuclear leukocytes.

Polymorphonuclear leukocytes (PMNL) in bronchoalveolar lavage (BAL) fluid of cystic fibrosis patients express increased levels of receptor for the Fc portion of IgA (Fc alpha R), similar to those found on PMNL stimulated with FMLP in vitro. Since tumor necrosis factor-alpha (TNF alpha) is an activator of PMNL and is found at inflammatory sites, its effects on Fc alpha R expression and IgA-mediated PMNL functions were investigated. Exposure of PMNL to TNF alpha increased surface expression of Fc alpha R 2- to 3-fold, increased superoxide production in response to aggregated IgA 5-fold, and increased phagocytosis of IgA aggregates 3- to 4-fold. Interleukin-8 did not increase Fc alpha R expression and did not enhance IgA-mediated superoxide generation. IgA-dependent PMNL killing of Pseudomonas aeruginosa was enhanced when PMNL were pretreated with TNF alpha. Thus, interactions between phagocytic host defense mechanisms and mucosal IgA may be enhanced by TNF alpha in the inflammatory milieu of the cystic fibrosis lung.

Increased Fc alpha R expression and IgA-mediated function on neutrophils induced by chemoattractants.

The recent reports of receptors for IgA on blood and mucosal phagocytes suggest a more active role then previously thought for IgA in host defense. Using a mAb and flow cytometry we determined the expression of the Fc alpha R on resting and chemoattractant-stimulated blood neutrophils and compared them with mucosal neutrophils. Fc alpha R expression on blood neutrophils could be rapidly up-regulated in vitro, increasing three to fourfold within minutes of exposure to the chemoattractants FMLP (optimal at 10(-8) M) and zymosan activated serum (a source of C5a). The level of Fc alpha R expression found on neutrophils obtained from bronchoalveolar lavage of cystic fibrosis patients with chronic lung infection was almost identical to that found on blood neutrophils from the same patients maximally activated in vitro. The rise in Fc alpha R expression induced by 10(-8) M FMLP was rapid, with a plateau in 15 to 20 min, and was not inhibited by 10 mg/ml of cycloheximide or puromycin, suggesting that the mechanism of up-regulation involves translocation from intracellular storage pools. Ionomycin (2 mM) plus 1.2 mM CaCl2 also increased expression of Fc alpha R, and its effects were inhibited by EDTA. Trifluoperazine, an inhibitor of calmodulin and/or protein kinase C-dependent processes, blocked the increase in Fc alpha R expression induced by FMLP, but the effects of the chemoattractant were not blocked by EDTA, suggesting that intracellular stores of calcium are important in the physiologic regulation of Fc alpha R expression. Neutrophil superoxide production could be induced by aggregated IgA, and was increased if the neutrophils were pretreated with FMLP, correlating with the increase in Fc alpha R expression. The superoxide response to a suboptimal dose of aggregated IgG was unaffected by FMLP pretreatment, and antibodies to Fc gamma R failed to block the superoxide production induced by IgA. Thus, the increase in phagocyte surface expression of Fc alpha R induced by chemoattractants in vitro and on mucosal cells in vivo, and the concomitant increase in IgA-mediated function may greatly facilitate the defense of mucosal surfaces.

[Lipopolysaccharide changes in smooth-type avirulent Shigella in comparison with initial virulent strains]. / Izmeneniia lipopolisakharidov u avirulentnykh shigell gladkogo tipa po sravneniiu s iskhodnymi virulentnymi shtammami.

The comparative study of the lipopolysaccharides (LPS) of virulent and avirulent strains of S. sonnei, phase I (smooth colonies), has been made. Electrophoresis of LPS and subsequent densitometry of electrophoregrams have revealed the increase of the fraction of long 0-chains with a considerable number of recurring elements in 2 out of 3 LPS preparations obtained from avirulent shigellae. In mice immunized with these LPS preparations a considerably greater number of antibody-producing cells can be detected in Jerne's test on sheep red blood cells (SRBC) sensitized with the LPS of a virulent strain than on those sensitized with the above LPS preparations. Long 0-specific chains supposedly inhibit the fixation of individual complement components on the corresponding sensitized SRBC. The LPS of the third avirulent strain of S. sonnei, phase I, with transposon integrated into its genome, which has led to the formation of the avirulent variant of a previously virulent strain, seems to contain fine structural differences from the initial virulent strain. The immunogenicity of the LPS of this avirulent strain is greatly (3-4 times) decreased, which is manifested by the number of antibody-producing cells detected in Jerne's test on SRBC sensitized with LPS preparations obtained from these two strains.

[Quantitative characteristics of the transfer of the hematopoietic microenvironment]. / Kolichestvennye kharakteristiki perenosa gemopoéticheskogo mikrookruzheniia.

Heterotopic transplantation of marrow fragments results in the formation of new bone marrow organs. The amount of hemopoietic cells populating these organs is connected nonlinearly with the volume of the grafted tissue or with the number of transplanted marrow cells. Statistical analysis points out that the number of the populating cells depends on the radius of the initial bone marrow transplant. Thus, the previous data on the radiosensitivity of the microenvironmental transfering stromal cells and on their concentration obtained by measuring the size of the heterotopic bone marrow organs have turned out incorrect.