Biomedical subjects

V Mitolo

Publications and source records attributed to V Mitolo.

At least 37 records · Page 2Linked to original sources

PubMed1999

Inducible nitric oxide synthase and nitric oxide production in Leishmania infantum-infected human macrophages stimulated with interferon-gamma and bacterial lipopolysaccharide.

Nitric oxide produced by an inducible nitric oxide synthase constitutes one of the main microbicidal mechanisms of murine macrophages and its importance is now being recognized for human macrophages. In this study we evaluated inducible nitric oxide synthase expression, nitric oxide release, and parasitocidal ability of Leishmania infantum-infected monocyte-derived human macrophages. The inducible nitric oxide synthase was detected by immunofluorescence and western blotting and nitric oxide production was measured by the Griess reaction for nitrites. Parasite killing was microscopically evaluated by fluorescent dyes. Experiments were performed on macrophages with or without previous stimulation with recombinant human interferon-gamma and bacterial lipopolysaccharide. Inducible nitric oxide synthase expression and nitric oxide release were higher in Leishmania-infected stimulated macrophages than in uninfected cells or infected cells without previous stimulation. Nitric oxide production and parasitocidal activity against Leishmania infantum were reduced in macrophages treated with the nitric oxide synthase inhibitor L-N(G) monomethylarginine. These results suggest a microbicidal role for nitric oxide in human leishmaniasis, with the possible practical application of immunological or pharmacological regulation of nitric oxide synthesis in the treatment of this infection.

Animals↗

PubMed1999

Cellular responses to FMLP challenging: a mini-review.

FMLP (N-formyl-methionyl-leucyl-phenylalanine) and other N-formylpeptides are powerful "activators" of polymorphonuclear and mononuclear phagocytes, but they are also active on other cell types. Present knowledge about formylpeptide receptors and the relevant tools for their imaging and the study of their dynamics are briefly discussed. The main responses elicited by FMLP in granulocytes are cell polarisation, the generation of reactive oxygen species, the production of arachidonic acid metabolites, and the release of lysosomal enzymes. The transduction cascades involved and the agents able to modulate these responses are reviewed. Homologous desensitization and heterologous desensitization of the FMLP-receptor following ligation of other chemokine receptors are also outlined. Finally, the receptor expression and the pharmacological and toxic actions of FMLP upon other tissues and organs, and its actions on the developing embryo, are illustrated.

Animals↗

PubMed1998

Evaluation of nitric oxide production by Leishmania infantum-infected dog macrophages.

Protozoa of the genus Leishmania (L.) infect reticuloendothelial cells of several mammalian species, including dogs, in which they often give rise to a chronic, not self-healing visceral disease. Since the parasitocidal mechanism of macrophages towards Leishmania in dog has not yet been well investigated, in this work we have evaluated in Leishmania infantum-infected macrophage cultures from 10 healthy dogs, killing capacity and nitric oxide (NO) production, in terms of nitrite (NO2) levels. Parallel experiments were performed on macrophages stimulated with both Concanavalin A (ConA)-activated PBMC supernatants and Salmonella typhimurium lipopolysaccharide (LPS), and in the same conditions, but in the presence of the NO synthase inhibitor L-N monomethylarginine (L-NMMA). In L. infantum-infected macrophages, nitric oxide production was observed at a concentration significantly higher after stimulation with both Con A-activated PBMC supernatants and LPS than that observed in uninfected cells cultured in medium alone, or infected cells unstimulated or stimulated by PBMC supernatants or LPS alone, respectively. Moreover, NO production was abolished in the presence of the NO synthase inhibitor L-NMMA. Finally, killing of Leishmania by macrophages was significantly reduced in the presence of L-NMMA.

Animals↗

PubMed1998

Evaluation of killing, superoxide anion and nitric oxide production by Leishmania infantum-infected dog monocytes.

Protozoa of the genus Leishmania infect reticuloendothelial cells of several mammalian species, including dogs, in which they often give rise to a chronic, not self-healing visceral disease. The parasitocidal mechanism of peripheral blood monocytes towards Leishmania in the dog has not been investigated in detail. Consequently, Leishmania infantum-infected monocyte cultures of healthy dogs were evaluated using the following parameters: (1) phagocytosis and killing capacities; (2) oxidative burst, in terms of superoxide anion (O2-) release, and (3) nitric oxide (NO) activity, in terms of nitrite (NO2-) production in the presence or absence of the NO synthase inhibitor NG-monomethyl-L-arginine (NGMMLA). Parallel experiments were performed on monocytes stimulated with supernatants of concanavalin A-activated PBMC and on unstimulated monocytes. The amount of IFN-gamma in PBMC supernatants used for monocyte activation was determined by a biological assay on a canine Madin Darby cell line. Results demonstrated that phagocytosis, killing capacity and O2- production significantly increased in monocytes stimulated with supernatants, in comparison with unstimulated cells. A positive correlation was observed between the killing capacity, the O2- production and the amount of IFN-gamma in PBMC supernatants employed for monocyte activation. No significant differences were observed in NO production between unstimulated and stimulated cultures, or between the same cultures with and without NGMMLA. Finally, the killing percentage was similar in the presence or absence of NGMMLA, suggesting that in this experimental model peripheral blood dog monocytes lack NO-mediated killing.

Animals↗

PubMed1997

Polarizing response of human polymorphonuclear cells to Vibrio cholerae.

Leucocytes have the capacity to respond to chemotactic factors by becoming morphologically and functionally polarized and this method has been found to be suitable for measurement of chemotaxis. This work evaluates the effect of whole Vibrio cholerae biotype El Tor polarization of human polymorphonuclear (PMN) cells in comparison with strains of V. cholerae NAG, Vibrio alginolyticus and Salmonella typhi. V. cholerae O1 induced, at different cell/bacteria ratios, a significant increase in the percentage of polarized cells compared with PMN cells stimulated with formylmethionyl-leucyl-phenylalanine (FMLP) and the other bacteria tested. The capacity of V. cholerae O1 to induce PMN cell polarization may play a role on the inflammatory response recently described in diarrhoea caused by V. cholerae.

Adult↗

PubMed1996

Spontaneous binding of Vibrio cholerae to human leucocytes.

Various lymphocyte subpopulations have the capacity to bind different strains of Gram-negative bacteria. The capacity of a strain of Vibrio cholerae, biotype El Tor, isolated during an outbreak of cholera, to adhere to mononuclear cells isolated from peripheral blood was evaluated. V. cholerae binds to mononuclear cells in a dose-dependent manner. The binding was 76.1% at a cells/bacteria ratio of 1:200 and significantly decreased to 43.1% at a ratio of 1:1. The value of bound bacteria, a marker of the mean number of binding sites on the cell surface, decreased at lower cell/bacteria ratios. Studies on isolated cellular populations demonstrated that 51, 42 and 38%, respectively, of CD4+, CD8+ and B cells were bound by V. cholerae whereas monocytes exhibited a higher binding capacity. The data suggest that the percentage binding of V. cholerae to lymphocytes and monocytes was higher than the percentage found in previous studies with Gram-negative bacteria such as Yersinia enterocolitica, and Salmonella, but similar to Helicobacter pylori. The findings indicate that V. cholerae possesses multiple 'adhesins' such as fimbriae, flagella, haemagglutinins, lipopolysaccharides, and outer membrane proteins. The capacity to bind to blood lymphocytes may reflect the same capacity for the lymphocytes from the gastrointestinal associated lymphoid tissue. This cytoadherence may contribute to the uptake of V. cholerae from the gut and may contribute to activation of B cells and CD4+ lymphocytes.

Adult↗

PubMed1988