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Biomedical subjects

A Santoni

Publications and source records attributed to A Santoni.

At least 91 records · Page 5Linked to original sources
PubMed1994

In vivo phenotypic characteristics of AKR T-cell lymphomas with different leukemic potential: possible role of alpha 4 beta 7 integrin in the progression towards the leukemic phenotype.

The present study was undertaken in order to determine whether the expression of specific surface molecules which mediate immune recognition as well as cell-cell and cell-matrix interactions is associated with the leukemic evolution of T-cell lymphomas. To this end, we have investigated the in vivo phenotypic characteristics and the in vitro natural-killer(NK)-cell susceptibility of a group of MCF-247-induced AKR/J T-cell lymphomas with different leukemic potential. We found that in the AKR/J model, the biological aggressiveness of leukemic cells is not dependent upon an escape from host immune surveillance as a consequence of an in vivo down-regulation of H2-Kk determinants or a resistance to NK lysis. Moreover, NK susceptibility of AKR/J lymphomas does not seem to correlate with the level of H2-antigen expression. No obvious correlation was found between the leukemic phenotype and the amount of MEL-14, LFA-1, ICAM-1, Pgp-1/CD44 and THAM/CD26 antigen expression. An in vivo coordinated up-regulation of alpha 4 and beta 7 integrin chains, with the highest levels of expression detected in secondary sites of leukemic infiltration, was observed in the highly leukemic lymphoma NQ22 and, albeit to a lesser extent, in lymphomas with moderate leukemic potential. Conversely, non-leukemic lymphomas were repeatedly alpha 4- and beta 7-negative. These findings suggest that in the AKR/J system the expression of alpha 4 beta 7 integrin may contribute to leukemic spreading of T-cell lymphomas.

Animals↗
PubMed1994

Interferon-alpha, beta and tumor necrosis factor-alpha enhance the frequency of miniature end-plate potentials at rat neuromuscular junction.

The effects of the two cytokines, rat interferon-alpha, beta and human tumor necrosis factor-alpha, were studied at the rat neuromuscular junction by using classical electrophysiological techniques. Both cytokines in a similar way at concentrations of 2,000 and 35,000 U/ml, respectively, increased transiently and with a relatively long delay (15 to 25 min) the frequency of miniature endplate potentials. The observed effects may be related to complex second messenger mechanisms and contribute to modulation and plasticity of neurotransmission.

Animals↗
PubMed1994

Long term activation of natural killer cells results in modulation of beta 1-integrin expression and function.

Integrin expression and function is largely modulated by cell activation. Here we provide evidence that long term activation of human NK cells results in a marked modulation of beta 1-integrin expression and adhesive functions. By flow cytometry and immunochemical analysis we have detected induction of alpha 1 beta 1 and alpha 2 beta 1, increased expression of alpha 4 beta 1 and alpha 5 beta 1, and decline of alpha 6 beta 1 on CD3-CD56+ NK cells generated from 10-day coculture of nonadherent PBMC with irradiated RPMI 8866 EBV+ lymphoblastoid B cell line. Adhesion assays performed on extracellular matrix-coated plates showed that, unlike fresh NK cells, long term-activated NK cells bind to native collagen I via alpha 2 beta 1 and to heat-denatured collagen I in an RGD-dependent manner, although they lose the ability to bind to laminin. In regard to the adhesion to FN, no major quantitative changes are observed after long term NK cell activation. However, whereas alpha 4 beta 1 and alpha 5 beta 1 completely mediate the adhesion of fresh NK cells to fibronectin, binding of activated NK cells is only partially beta 1-dependent and seems to involve also non-beta 1-integrin(s) recognizing and RGD sequence. The modulation of beta 1-integrin expression and the acquisition of new adhesive properties on long term-activated NK cells may be relevant for their traffic and tissue localization during inflammation and immune response.

Amino Acid Sequence↗
PubMed1994

Involvement of p21ras activation in T cell CD69 expression.

The involvement of p21ras in the induction of the early activation antigen CD69 was investigated in T cells. Expression of a v-Ha-ras coding for a constitutively active ras protein in Jurkat cells resulted in CD69 induction on the cell surface. Transfected ras was shown to be constitutively activated and functionally efficient, since it could be immunoprecipitated in the guanosine triphosphate (GTP)-bound form and it induced transactivation of an AP-1 consensus-chloramphenicol acetyltransferase reporter gene. The requirement for ras activation in T cell receptor (TcR) CD3-mediated CD69 induction was also investigated. The expression of a dominant negative c-Ha-ras-N17 mutant markedly reduced the amount of GTP that could be immunoprecipitated from ras proteins after TcR/CD3 triggering in Jurkat cells, and concomitantly decreased TcR/CD3-mediated CD69 induction. These results suggest a central role for ras in TcR/CD3-mediated CD69 expression in T cells.

Antigens, CD↗
PubMed1994

Induction of the nitric oxide-synthesizing pathway in fresh and interleukin 2-cultured rat natural killer cells.

Several lines of evidence suggest that nitric oxide (NO), generated through nitric oxide synthase (NOS) by cleavage of terminal guanidino nitrogen from L-arginine, mediates tumor cell killing by mononuclear phagocytes. Natural killer (NK) cells are cytotoxic effector cells that lyse a variety of tumor and virus-infected cells in a MHC-unrestricted manner. NK cells cultured with interleukin 2 proliferate and acquire the ability to lyse a wide range of targets, including NK-resistant tumor cells (LAK activity). The present study was designed to investigate whether a NOS pathway exists in fresh or IL-2-activated NK cells and to assess the importance of NO synthesis in their activation and cytotoxic functions. NKR-P1 triggering, which is known to induce NK cell activation and mediate reverse ADCC, was able to induce arginine metabolism with consequent increase of nitrite and citrulline levels. Moreover, stimulated NO synthesis leads to guanylate cyclase activity with consequent cGMP generation. We also report that cytotoxic activities of fresh or IL-2-activated NK cells appear to be dependent on arginine levels in medium. Tumoricidal activity of both these effector cells, assessed against YAC-1 and P815 target cells, respectively, was indeed significantly reduced when cytotoxic assays were performed in arginine-free medium or in the presence of the L-arginine analog L-N-monomethyl-arginine, which inhibits nitroxide formation from L-arginine. Normal levels of cytotoxic activities could be restored by addition of exogenous L-arginine. NO generation by NK and LAK cells, determined as nitrite, citrulline, and cGMP synthesis, correlated well with their cytotoxic activities. Moreover, NOS activity gradually increased during the LAK generation and correlated well with the increasing capability of IL-2-activated NK cells to lyse NK-resistant targets, such as P815.

Amino Acid Oxidoreductases↗
PubMed1994

In vitro and in vivo impact of a new glycosphingolipid on neutrophils.

A new water-soluble, orally absorbable de-N-acetyl-lysoganglioside (WILD20), breakdown product of the monosialoganglioside GM1, was found to influence some parameters of neutrophil response to inflammation stimuli. Superoxide anion production appears inhibited, along with neutrophil killing properties. A block of both pathways of arachidonic acid cascade and PAF was also found, as well as neutrophil ICAM-1-mediated adhesion to endothelial cells. Of particular interest was the significant reduction of neutrophils observed at the site of inflammation, whichever agonist was used. The effects on neutrophil physiology found in normal or in pathological conditions, are in favour of a WILD20-related inhibitory effect on neutrophil contribution to inflammation.

Animals↗
PubMed1994

The CD69 receptor: a multipurpose cell-surface trigger for hematopoietic cells.

CD69 was initially described as being restricted to recently activated lymphoid cells, but is now known to be expressed on the surface of all hematopoietically derived leukocytes. Crosslinking of CD69 generates intracellular signals in all cell lineages studied, both mouse and human, and results in a variety of cellular end responses. Since a specific ligand has not yet been identified, a definite functional identity for CD69 is still missing. However, as discussed here by Roberto Testi and colleagues, the broad expression of CD69 and its conserved ability to generate intracellular signals suggests a general role for the CD69 receptor in the biology of hematopoietic cells.

Animals↗
PubMed1994

A phase II study of advanced colorectal cancer patients treated with combination 5-fluorouracil plus leucovorin and subcutaneous interleukin-2 plus alpha interferon.

Twenty-one patients with advanced, pretreated colorectal cancer in disease progression were entered in a phase II study to investigate the use of 5-fluorouracil (5FU) + leucovorin with subcutaneous Interleukin-2 + alpha interferon (alpha-IFN). Eighteen of these patients were evaluable for response to treatment: 1 partial response (PR) (duration 8 months), 9 stable disease (SD) (median duration of 6.5 months, range 2-15) and 8 progressive disease (PD). The PR patient survived for 15 months, the SD patients for a median of 11 months and 8 months for PD patients. Toxicity evaluated in the 21 patients reached grade 4 for mucositis in two cases. Grade 3 toxicity was observed more frequently for fever (52.3%) and diarrhea (33.3%) and was most probably the result of the combined side-effect of chemotherapy and the biological response modifiers (BRMs). Treatment was, for the most part, carried out on an out-patient basis as originally planned. In 15 patients tests were carried out to verify whether any immuno-activation had taken place. Significant increases were found during the course of therapy regarding cluster of differentiation activation (HLA-DR, CD71, CS25). Different curves were observed during the course of treatment with respect to the CD8 value, which proved higher in SD patients than in PD patients. Our study would seem to suggest that the addition of BRMs to 5FU + leucovorin could increase survival. The next step, however, must be to determine lower doses of IL-2 for subcutaneous administration in order to reduce toxicity but maintain the same immunostimulation.

Adult↗
PubMed1994

Follicle-stimulating hormone-induced phospholipase A2 activity and eicosanoid generation in rat Sertoli cells.

The possibility that FSH stimulates the phospholipase A2 (PLA2) pathway was studied in cultured immature Sertoli cells. FSH induced [3H]-arachidonic acid (AA) release from prelabeled cells in a time- and concentration-dependent fashion (ED50 = 21.8 +/- 1.9 ng/ml). This response could be fully prevented by pretreatment of cells with the PLA2 inhibitor, mepacrine. That PLA2 was the main enzyme responsible for cleavage of AA from membrane phospholipids was directly shown by PLA2 activity assay using vesicles of radiolabeled phosphatidylcholine (PC) as substrate. Furthermore, FSH stimulated eicosanoid generation in a time-dependent manner through the cyclooxygenase but not the lipoxygenase pathway. In fact, higher levels of prostaglandin (PG) E2, F2 alpha, and the stable products of PGI2 and thromboxane A2 (6-keto PGF1 alpha and thromboxane B2, respectively) were generated by the gonadotropin-treated cells as compared to control cells. The effect was inhibited by mepacrine, further supporting the pivotal role of PLA2 in the release of the eicosanoid precursor, AA. Finally, the effect of the main product of FSH-induced AA metabolism, i.e., PGE2, was studied. Intracellular cAMP accumulation in Sertoli cells was stimulated by the prostanoid in a dose-dependent manner (ED50 = 2.3 +/- 0.37 nM). PGE2 also significantly stimulated aromatase activity, a specific marker of Sertoli cell functions, measured as 17 beta-estradiol production (ED50 = 4.7 +/- 0.8 nM). Similar results were obtained with PGF2 alpha. Our findings show that FSH, through the activation of PLA2, leads to AA release with consequent metabolism by the cyclooxygenase pathway.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Candida albicans expresses a fibronectin receptor antigenically related to alpha 5 beta 1 integrin.

Cell adhesion molecules, by regulating host-micro-organism interaction, play a major role in the pathogenesis of infectious diseases. The present study was undertaken to investigate the expression of the fibronectin (FN) receptor prototype, alpha 5 beta 1 integrin, on Candida albicans and its involvement in the adhesion to FN. By immunofluorescence and fluorescence activated cell sorter (FACS) analysis, several monoclonal antibodies (mAbs) directed against human alpha 5 or beta 1 integrin subunits, or two different antisera to FN receptor positively stained C. albicans yeast and germ tube phases, this immunoreactivity increasing upon germ tube transition. Twenty-five to thirty per cent of [3H]glucose-labelled Candida yeasts specifically adhered to FN and this adhesion was increased upon germ tube transition. C. albicans yeast and germ tube forms bound to an RGD-containing 120 kDa tryptic fragment of FN and adhesion to FN was markedly inhibited by GRGDSP, but not GRGESP peptides. Moreover, binding of both C. albicans phases to FN was strongly inhibited by anti-alpha 5 SAM-1 mAb, or both anti-fibronectin receptor (FNr) antisera. Overall these results indicate that C. albicans yeast and germ tube phases express a receptor antigenically related to alpha 5 beta 1 integrin which mediates their adhesion to FN. The alpha 5 beta 1 integrin-like receptor expression on C. albicans could be relevant for fungus-host interaction and in the dissemination process of Candida infection.

Antigens, Fungal↗
PubMed1994

Reduction of spontaneous autoimmune diabetes in diabetes-prone BB rats with the novel immunosuppressant fusidic acid. Effect on T-cell proliferation and production of interferon-gamma.

Diabetes-prone (DP) BB rats spontaneously develop a hyperglycaemic condition which closely resembles human insulin-dependent diabetes mellitus (IDDM), both in terms of clinical and histological features. The incidence of IDDM was significantly reduced when these animals were treated with 2 or 4 mg fusidic acid (FA)/day i.m. from day 30 to day 120 of age. In addition, the mean insulitis score was significantly diminished in the animals treated with FA compared to both vehicle-treated and untreated controls. Finally, 2 mg/day of FA i.m. prevented cell proliferation and interferon-gamma secretion from peripheral blood mononuclear cells upon ex vivo stimulation with concanavalin A. The capacity of FA to substantially reduce the incidence of autoimmune diabetes in a well-known animal model of human IDDM supports previous observations regarding the immunosuppressive properties of FA and its potential use in the treatment of human autoimmune diabetes.

Age Factors↗
PubMed1993

Transcriptional regulation of interleukin-2 gene expression by CD69-generated signals.

The 5' flanking region of the human interleukin (IL)-2 gene was investigated for enhancer activity in response to CD69-generated signals, using a chloramphenicol acetyltransferase (CAT)-driven transient expression system in Jurkat cells. The region extending from -317 to +47 relative to the initiation site of IL-2 gene transcription was shown to contain sequences able to respond to CD69 cross-linking, by enhancing by about 100% a phorbol 12-myristate 13-acetate (PMA)-plus-ionomycin stimulation of CAT activity. A similar increase in CAT activity produced by PMA-plus-anti-CD3 mAb was induced by CD69 cross-linking, while a 200% increase over that obtained by PMA-plus-anti-CD28 mAb stimulation was seen. Analysis of enhancer deletion mutants revealed that proximal AP-1, OCT-1/octamer-associated protein and nuclear factor of activated T cells (NFAT) binding regions were all necessary to allow CD69-mediated enhancement of CAT activity. By gel mobility shift analysis, cyclosporin A-sensitive NFAT-binding induction and enhancement of AP-1 binding activity could be detected in nuclear extracts of both Jurkat and peripheral blood T cells after simultaneous CD69 and protein kinase C stimulation. Finally, CD69-mediated signals could increase NFAT and AP-1 binding activity following PMA and ionomycin stimulation in peripheral blood T cells. Collectively, these data suggest that CD69-generated signals participate in the control of the IL-2 gene expression at the transcriptional level, likely acting through NFAT and AP-1 transcription factor complexes.

Antigens, CD↗
PubMed1993

Continuous in vivo activation and transient hyporesponsiveness to TcR/CD3 triggering of human gut lamina propria lymphocytes.

Three-color immunofluorescence and flow cytometric analysis showed that the vast majority of normal human T-lamina propria lymphocytes (LPL) expressed high levels of the early activation antigen CD69, together with CD45R0, irrespective of their CD4, CD8 or gamma/delta-TcR phenotype, indicating that they are continuously stimulated in vivo. Importantly, measurement of cytoplasmic [Ca2+]i showed that T-LPL had significantly higher basal [Ca2+]i levels, compared to autologous peripheral blood lymphocytes (PBL). Both cytoplasmic [Ca2+]i elevation and inositol (1,4,5) trisphosphate generation following CD3 cross-linking by monoclonal antibodies in vitro were essentially abolished in T-LPL, as compared to autologous T-PBL. Moreover, freshly isolated LPL could be induced to proliferate by CD2- or CD28-mediated signals, but not by CD3-mediated signals. Surprisingly however, impairment in TcR/CD3-mediated early signaling and proliferation in T-LPL could be completely reversed by 24 h incubation of the cells at 37 degrees C in culture medium, a condition which allowed basal intracellular [Ca2+]i to return to levels comparable to peripheral T cells. Our data suggest that selective hyporesponsiveness to TcR/CD3-mediated signaling may represent a transient event during continuous in vivo activation of mucosal lymphocytes.

Calcium↗
PubMed1993

Involvement of phospholipase A2 activation and arachidonic acid metabolism in the cytotoxic functions of rat NK cells.

Arachidonic acid (AA) release via phospholipase A2 (PLA2) activation and generation of eicosanoids have been implicated as playing signaling roles in a variety of cell types. Here we show evidence that interaction of fresh NK cells with membranes from sensitive or antibody (Ab)-coated targets generates eicosanoids through both cyclooxygenase (CO) and lipoxygenase (LO) pathways. Eicosanoid generation is attributable to PLA2 activation since pretreatment with PLA2 irreversible inhibitors, such as mepacrine or para-bromophenacylbromide (pBPB), completely blocks AA metabolite generation. The involvement of PLA2 or AA metabolites in the cytotoxic functions of rat NK cells has also been investigated. Treatment of effector cells with mepacrine or pBPB resulted in complete, irreversible, dose-dependent inhibition of both NK and ADCC activities, which were completely reversed by the addition of exogenous PLA2 or its hydrolysis products, AA and lysophosphatidylcholine (lysoPC). Among the metabolites of AA released by NK cells, the 5-LO product leukotriene B4 (LTB4) seems to play an important role in cytolytic activities of NK cells. Indeed, the LO inhibitor, nordihydroguaiaretic acid (NDGA), totally abrogated both NK and ADCC activities, which were restored by the addition of exogenous LTB4. However, the failure of LTB4 to reverse mepacrine or pBPB-induced inhibition of NK and ADCC suggests that its effects could be mediated by PLA2. The results are consistent with a crucial role for the target-stimulated AA release as a fundamental step in the signal transduction pathway in NK cell. Moreover, LTB4 generation seems to be responsible for further PLA2 activation in a second step leading to the amplification of response.

Animals↗
PubMed1993

Tissue distribution of very late activation antigens-1/6 and very late activation antigen ligands in the normal thymus and in thymoma.

The expression of very late activation antigens (VLAs)-1/6 was correlated with that of the VLA ligands fibronectin, laminin, collagen, and vascular cell adhesion molecule-1 in sections of normal thymus, in thymocyte suspensions, and in 10 cases of thymoma. Capsular epithelial cells are VLA-2+, VLA-3+, and VLA-6+ and face the thymic basement membrane, which is rich in fibronectin, laminin, and collagen type IV. Cortical epithelial cells are VLA-2+ and are embedded in a reticular meshwork of nonorganized extracellular matrix (ECM) that is rich in fibronectin. Cortical thymocytes, identified as CD3dim cells by using immunofluorescence in suspension, are highly positive for VLA-4, a fibronectin ligand. Most cortical macrophages are positive for vascular cell adhesion molecule-1, a molecule recognized by VLA-4. Medullary epithelial cells are VLA-2+/VLA-3+ and are codistributed with fibrous strands of organized ECM that are positive for fibronectin, collagen, and laminin. Medullary thymocytes, identified as CD3bright cells, are positive for VLA-4 and VLA-6, a ligand for laminin. Our findings suggest that intrathymic thymocyte maturation is associated with changes in expression of VLA molecules, which are apparently correlated with the presence of VLA ligands in the tissue microenvironment. Thymomas were classified as cortical (three), common (five), or medullary (two) type. Expression of VLA molecules and distribution of ECM in the three histological subtypes were reminiscent of those observed in the respective regions of the normal thymus. All cases of thymoma were characterized by overexpression of VLA molecules on neoplastic cells, which was associated with increased deposition of organized ECM rich in fibronectin, laminin, and collagen.

Antigen-Presenting Cells↗
PubMed1992

Tumor necrosis factor alters synaptic transmission in rat hippocampal slices.

The effects of human recombinant tumor necrosis factor (TNF-alpha) on the synaptic transmission were studied in rat hippocampal slices by using extracellular field potential recordings. Population spikes and/or excitatory postsynaptic potentials were extracellularly recorded in hippocampus CA1 region from stratum pyramidale and stratum radiatum, respectively, and synaptic transmission was examined in the Schaffer collateral/commissural-CA1 pathway. Basal neurotransmission slightly and promptly increased in slices acutely exposed to TNF-alpha (1-100 nM). Examination of the long-term potentiation (LTP) revealed that a brief treatment with the cytokine did not influence LTP, while a long-lasting application of TNF-alpha (50 min or more) inhibited LTP in a dose-dependent way in the range of 1-100 nM. A role for TNF-alpha as a peptide of immunological significance belonging to the family of brain neuromodulators is discussed.

Animals↗