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Biomedical subjects

M Guenounou

Publications and source records attributed to M Guenounou.

At least 37 records · Page 2Linked to original sources
PubMed1996

Role of interferon-gamma against invasion by Toxoplasma gondii in a human monocytic cell line (THP1): involvement of the parasite's secretory phospholipase A2.

We examined the role of IFN gamma in protection against Toxoplasma gondii in the monocytoid cell line THP1. The addition of IFN gamma to cultured infected THP1 cells reduced the number of parasitized cells without altering intracellular multiplication during the first 24 hr. This reduction was potentiated by bacterial lipopolysaccharide (LPS). We also examined the role of an enzyme important for T. gondii cellular invasion, secretory phospholipase-A2 (sPLA2) and its relation with IFN gamma-induced protection. Treatment of cells or parasites with a specific inhibitor of sPLA2 significantly reduced the number of infected cells at 6 hr. The addition of exogenous sPLA2 from Naja naja venom did not interfere with the protective effect of IFN gamma and conferred protection when used alone. PLA2 activity was measured in supernatants of parasites maintained in the presence of IFN gamma, and the results suggested that IFN gamma opposes cell invasion by T. gondii by suppressing parasite production of PLA2.

Animals↗
PubMed1996

Differential regulation of TNF alpha, IL-1 beta, IL-6, IL-8, TNF beta, and IL-10 by pentoxifylline.

Pentoxifylline (PTX) is a methylxanthine drug known to inhibit the production of tumor necrosis factor-alpha (TNF alpha), which plays a key role in inflammation. Recent studies also revealed that other cytokines may be inhibited by PTX. We investigated PTX effects on production and mRNA expression of TNF alpha, IL-1 beta, IL-6, IL-8, TNF beta and IL-10. Cytokine release was studied in 1/10 diluted whole blood culture (WB) and in peripheral blood mononuclear cell (PBMC) culture. Cytokine production was triggered in both culture systems by endotoxin (LPS) or by phorbol ester (PMA) plus phytohemagglutinin (PHA). Our results showed that expression and production of TNF alpha and TNF beta were inhibited by PTX in a dose-dependent manner. Moreover, we observed that depending on the way of activating cells, PTX induced an up- or a down-regulation (in PMA + PHA or LPS stimulated cells, respectively) for IL-1 and IL-6 release. We also noted that the effects of PTX on IL-6, IL-8 and IL-10 production were different in WB and in PBMC culture. In conclusion PTX acts on cytokine in a complex manner depending on cellular environment and on the method of activation.

Anti-Inflammatory Agents↗
PubMed1996

Differential spontaneous expression of mRNA for IL-4, IL-10, IL-13, IL-2 and interferon-gamma (IFN-gamma) in peripheral blood mononuclear cells (PBMC) from atopic patients.

Distinct cytokine-producing T cell subsets are well known to play a major role in IgE production and to be differentially regulated in allergic patients, although the characterization of the type 1/type 2 cytokine pattern in PBMC during allergic responses remains to be clearly defined. The aim of this study was to determine whether different cytokine profiles are observed directly in PBMC of atopic donors. We attempted to study several cytokines (IL-2, IFN-gamma, IL-4, IL-10 and IL-13) using not only ELISA but also polymerase chain reaction (PCR) techniques, because the frequency of cytokine-producing cells in peripheral blood is very low. All the patients were selected during their acute symptomatologic phase. Data showed a significantly higher production of IL-4 (P = 0.05) and IL-10 (P < 0.005) as determined by ELISA in phytohaemagglutinin (PHA)/phorbol myristate acetate (PMA)-stimulated mononuclear cells of atopic donors compared with controls, although spontaneous IL-4 production without stimulation was never detected within either atopic or control groups. The reverse-transcriptase (RT)-PCR technique appeared to be advantageous in that it allowed the detection of the spontaneous expression of cytokine mRNA in cells without stimulation. We found a clear expression of IL-4 mRNA spontaneously in all atopic patients, whereas normal donors in most cases did not show specific signals (P < 0.0001). Less differences between atopic subjects and controls were found in IL-10 mRNA expression. Although the technique of RT-PCR amplification used in this study is semiquantitative, a reproducible and significant (P < 0.001) enhancement of IL-10 mRNA expression was observed in atopic donors. A heterogeneous expression of IL-13 mRNA was observed in individuals from the two groups studied, although mean levels in atopic donors were slightly enhanced compared with controls (P = 0.02). Furthermore, we did not observe any alteration in the expression of the type 1-derived cytokines such as IFN-gamma and IL-2. In addition, we showed a lack of correlation between the expression of serum IgE (total or specific) and spontaneous IL-4 mRNA expression. This study showed a tendency of PBMC from atopic donors to express a type 2-like cytokine pattern, with IL-4 as the most discriminatory cytokine. Additionally, as the level of serum IgE has a low predictive value in allergic disease, and as the elevated expression of IL-4 that we found was not correlated with serum IgE, we could strongly suggest that the measurement of IL-4 in blood mononuclear cells may be of great value in the analysis of allergic responses in atopic donors.

Adolescent↗
PubMed1996

Spontaneous CD30 mRNA expression in peripheral blood mononuclear cells from atopic patients with high IgE serum levels.

CD30 is a surface molecule which can be expressed by normal B and T lymphocytes. Our study focused on the CD30 expression and release compared with IL-4 expression as well as CD23-alpha/beta in peripheral blood mononuclear cells (PBMC) from atopic subjects and controls. Data showed a lack of CD30 mRNA expression in the PBMC of control subjects, while it was significantly expressed in those of 6/11 atopic patients. No substantial amounts of spontaneous soluble CD30 (sCD30) could be detected by ELISA in both atopic and control groups. Interestingly, CD30 mRNA expression in PBMC of allergic patients was positively correlated with IgE serum levels (r = 0.79, P = 0.003). Studies on purified B cells showed that CD30 was expressed mainly in CD19+B cells of allergic patients. These data suggest highly a potential functional significance of the CD30 molecule in IgE response during allergic diseases.

Adolescent↗
PubMed1996

Expression and production of cytokines by heterohybrids and their parental B cells in CLL.

Three hybrids derived from CD5+ B cell chronic lymphocytic leukemia (B-CLL) and their parental B cells were studied for phenotypic evolution, immunoglobulin (Ig), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) secretion. When phenotypic evolution was examined, hybrids showed the loss of classical B cell markers, indicating that they follow the same pattern of phenotypic differentiation as normal B cells. Hybrids displayed spontaneous high Ig secretion, which did not appear to be modified through stimulation by phorbol 12-myristate 13-acetate (PMA), recombinant interferon-gamma (rIFN-gamma) and Staphylococcus aureus Cowan I (SAC). Parental cells secreted minimal amounts of Ig spontaneously or through IFN-gamma and SAC stimulation, whereas PMA succeeded in increasing this secretion. An opposite pattern was observed when TNF-alpha and IL-6 secretion an expression at the mRNA level were assessed in hybrids and parental cells. TNF-alpha and IL-6 were spontaneously secreted by parental cells and this secretion was increased after PMA and SAC stimulation, both cytokine secretion and expression at the mRNA level were negative in hybrid cells. The absence of expression of these cytokines could be explained either by chromosomal loss or by down regulation. These results indicate that when parental CLL cells are induced to differentiate in the heterohybrid model, they acquire high spontaneous secretion of Ig, lose the classical B cell phenotypic markers and down regulate the expression of the cytokines studied.

B-Lymphocytes↗
PubMed1995

Regulatory effects of pentoxifylline on T-helper cell-derived cytokine production in human blood cells.

Pentoxifylline (PTX), a methyl xanthine derivative, was examined for its regulatory effect on Th1-and Th2-cell-derived cytokines in human whole blood and peripheral blood mononuclear cells stimulated with phytohemagglutinin (PHA) and phorbol myristate acetate (PMA). Cytokine production was analyzed by enzyme-linked immunosorbent assay and cytokine mRNA expression was examined by the polymerase chain reaction (PCR) after reverse transcription (RT). The results showed that PTX at 5 x 10(-4) M concentration selectively suppressed Th-1 cytokines [interleukin-2 (IL-2) and interferon-gamma (IFN-gamma)] but not IL-4, as observed by the measurement of protein secretion. Using sensitive RT-PCR assays, data show that at this same PTX concentration (5 x 10(-4) M), these cells also exhibited inhibition in the expression of IL-4 and IL-10 mRNA, together with inhibition of IL-2 and IFN-gamma mRNA expression. At 1 x 10(-4) M, no apparent change in IL-4 and IL-10 mRNA expression was observed, whereas IL-2 mRNA was still inhibited. It was noted that PTX at 1 x 10(-3) M induced a generalized inhibition of all cytokines. Our findings showed that PTX at the appropriate concentrations could induce selective suppression of IL-2 and IFN-gamma, whereas at high concentrations this drug could act as a suppressive agent of both Th1- and Th2-derived cytokines. Moreover, these data provide further evidence that the induction of IL-2 gene transcription is highly sensitive to an elevation of cAMP, whereas IL-4 gene transcription appeared to be less affected.

Adult↗
PubMed1995

[Respiratory burst of neutrophils and cytokine profile in the non-insulin-dependent diabetic].

Many clinical and experimental data are in favour of a participation of leukocytes in vascular disease. Diabetes, a risk factor, is associated with a dysfunction of neutrophils. If chemotaxis and phagocytosis are deficient, it is not clearly established whether superoxide generation is conserved in these patients. We have measured this function in 35 noninsulin dependent diabetic patients, compared with a control population. We have assessed, in parallel, a profile of the cytokines involved in vascular phenomenons including TNF alpha, IL-1 beta et IL-6. Our results indicate that the generation of free radicals is normal in diabetics, with a significant elevation of TNF alpha. These results suggest a possible participation of this cytokine in the modulation of granulocyte reactivity.

Adult↗
PubMed1994

Cuprophane but not synthetic membrane induces increases in serum tumor necrosis factor-alpha levels during hemodialysis.

Cytokine synthesis and secretion by blood mononuclear cells is a well-documented phenomenon in hemodialyzed patients. The present study was conducted in 17 chronically hemodialyzed patients to test the relative effect of uremic toxicity, membrane biocompatibility, dialysate composition, and the risk of endotoxinemia on the serum level of tumor necrosis factor-alpha (TNF-alpha). The only significant parameter that influenced circulating TNF-alpha was the chemical characteristics of the dialyzer membrane. Tumor necrosis factor-alpha levels significantly increased during the session with cuprophane, whereas they decreased with AN69. The TNF-alpha increase was documented whatever the dialysate buffer and the presence or absence (negative Limulus amoebocyte lysate test) of endotoxin in the dialysate. In the subgroup of patients treated with a contaminated dialysate and AN69, none had clinical symptoms and the central body temperature remained constant throughout the session. In these patients, serum TNF-alpha levels did not change after priming the dialyzer with sterile saline. In conclusion, the serum TNF-alpha level during hemodialysis appears to be modulated by biocompatibility, permeability, and binding properties of dialysis membrane rather than dialysate composition. Endotoxin in the dialysate did not result in positive TNF-alpha balance no matter what its possible priming effect on mononucleated blood cells.

Acrylic Resins↗
PubMed1994

Interaction of virulent and non-virulent Rhodococcus equi human isolates with phagocytes, fibroblast- and epithelial-derived cells.

Rhodococcus equi is a facultative, intracellular, Gram-positive coccobacillus, increasingly reported in pneumonia of AIDS-infected patients. We investigated killing resistance properties of human R. equi virulent and avirulent human strains. Avirulent beta-lactam-susceptible strains had lower intracellular colony forming units after 45 min incubation in murine macrophages J774 and human monocyte-macrophage TPH-1 than those of virulent strains. Only virulent beta-lactam-resistant strains persisted within macrophages for at least 18 min only. A beta-lactam-resistant mutant was obtained from a beta-lactam-susceptible strain after selection in a penicillin G-containing culture medium. This mutant strain, like the natural virulent strains, persisted within macrophages, harboured cell-associated appendages, produced phage-like particles and induced, after its intravenous inoculation, a chronic infection in BALB/c nude mice. Supernatant culture of virulent strains transferred partial macrophage-killing resistance properties to avirulent strains. The same supernatant was toxic for L-929, HeLa and Vero cell cultures. These supernatant effects were heat-inactivated, trypsin-inactivated and did not seem to be linked to phage-like particle presence. These data argue that virulence, beta-lactam-resistance, and macrophage-killing resistance are associated in human R. equi isolates. Moreover, only virulent strains produced uncharacterized toxic factors.

Animals↗
PubMed1994

Alveolar type II epithelial cells produce interleukin-6 in vitro and in vivo. Regulation by alveolar macrophage secretory products.

The aims of this study were (a) to determine if rat alveolar type II (ATII) cells and human pulmonary epithelial-derived cells (A549 cell line) could generate IL-6 in vitro, (b) to characterize the cytokine regulation of IL-6 gene and protein expression in these cells, and (c) to detect the in vivo expression of immunoreactive IL-6 by human ATII cells. Rat ATII cells in primary culture secreted bioactive IL-6 and immunostained with an anti-IL-6 antiserum. Spontaneous IL-6 secretion by rat ATII cells amounted to 5,690 +/- 770 pg/ml/10(6) cells (n = 12) and was fivefold higher than spontaneous rat alveolar macrophages IL-6 secretion (1,052 +/- 286 pg/ml/10(6) cells, n = 8, P = 0.001). Rat alveolar macrophage conditioned media (CM) increased IL-6 secretion by rat ATII cells through the effect of IL-1 and TNF. IL-6 gene expression and IL-6 secretion by A549 cells was induced by IL-1 beta, TNF alpha, and by human alveolar macrophages and THP1 cells CM. Induction was abolished when CM were preincubated with anti-IL-1 beta and anti-TNF alpha antibody. The combination of IFN gamma and LPS induced the expression of IL-6 mRNA by A549 cells whereas LPS alone had no effect. Immunohistochemical staining evidenced the expression of immunoreactive IL-6 by hyperplastic ATII cells in fibrotic human lung, a condition in which alveolar macrophages are known to be activated. ATII cells in normal human lung did not express immunoreactive IL-6. Our findings demonstrate that ATII cells may be an important source of IL-6 in the alveolar space thereby participating to the regulation of the intra-alveolar immune response.

Animals↗
PubMed1993

Antisense oligonucleotides to interleukin-4 regulate IgE and IgG2a production by spleen cells from Nippostrongylus brasiliensis-infected rats.

Interleukin-4 (IL-4) plays a key role in the regulation of immunoglobulin production. In the present study, we examined the role of IL-4 in the production of IgE and IgG2a by spleen cells from Nippostrongylus brasiliensis-infected rats using the antisense oligonucleotide strategy. Three antisense oligonucleotides (15 and 20 nucleotides) were selected near the ATG initiation codon of the murine IL-4 gene. Significant and reproducible inhibitions of IgE and IgG2a production were observed with the addition of two different oligonucleotides, the most inhibitory being specific for 15 nucleotides corresponding to the downstream AUG sequence oligodeoxynucleotide (ODN-1), while the corresponding sense sequence had no effect. The inhibition was directly related to the ODN-1 concentration on IgE response, and IgG2a production was more sensitive to the inhibitory effect of ODN-1 than the IgE response. Our results suggest that the ODN-1 effect is rather specific for the IL-4 gene since the production of other cytokines was not modified and the exogenous addition of IL-4 reversed the ODN-1 effect. In contrast to IgE and IgG2a, ODN-1 induced a significant enhancement of IgM synthesis. The use of a phosphorothioate ODN of the same sequence as ODN-1 resulted in a greater inhibitory effect on IgE and IgG2a production. These data indicate that IL-4 contributes to the spontaneous production of IgE and IgG2a, and argue that antisense strategy constitutes a useful tool for the regulation of antibody response.

Animals↗
PubMed1993

Effect of cytokine-specific antisense oligonucleotides on the immunoglobulin production by rat spleen cells in vitro.

We examined in this study the regulation of immunoglobulin (IgM, IgG, IgE) production by spleen cells from N brasiliensis infected rats following addition of antisense oligodeoxynucleotides (ODNs). The ODNs were selected near the AUG initiation codon of mRNA specific for interleukin 4 (IL-4) or interleukin 2 (IL-2). Results show that addition of antisense to IL-4 inhibited IgE production, while the production of IgG and IgM increased. The use of sense IL-4 sequence did not affect immunoglobulin production. In contrast, the use of antisense IL-2 ODN induced an enhancement of IgE as well as of IgM and IgG responses. Both the Ig secretion in culture supernatants and the number of Ig secreting cells, as detected by an Elispot assay, were influenced by the presence of antisense IL-4 ODNs. These results clearly show the involvement of IL-2 and IL-4 in the regulation of isotype selection during antibody synthesis and that IL-2 and IL-4 do operate differently on IgE production. They also argue that antisense strategy represents a useful tool for the antibody regulation.

Animals↗
PubMed1993

Involvement of interferon-gamma and tumor necrosis factor-alpha in host defense against Rhodococcus equi.

Rhodococcus equi is a facultative, intracellular, gram-positive coccobacillus increasingly reported as an opportunistic pathogen in AIDS patients. In vitro, splenic cells of noninfected euthymic mice produced tumor necrosis factor-alpha (TNF alpha) in greater amounts when incubated with live R. equi rather than with killed bacteria. In vivo, interferon-gamma (IFN-gamma) and TNF alpha serum levels of infected euthymic mice remained below the level of detectability. Treatment of infected nude mice, which developed chronic infection, with discontinuous injections of IFN-gamma, TNF alpha, or both did not decrease bacterial colony-forming units in liver, spleen, or lungs. However, treatment of infected euthymic mice, which cured a R. equi inoculum within 3 weeks, with anti-IFN-gamma or anti-TNF alpha antibodies (or both) significantly increased tissue colony counts. These data argue that, in this murine model, endogenous IFN-gamma and TNF alpha are involved in the cell-mediated immunologic response against R. equi infection.

Actinomycetales Infections↗
PubMed1993

Involvement of tumor necrosis factor alpha in intracellular multiplication of Legionella pneumophila in human monocytes.

We investigated the role of tumor necrosis factor alpha (TNF-alpha) in human peripheral monocytes infected with Legionella pneumophila in vitro. Exogenous TNF-alpha significantly inhibited the intracellular multiplication of the bacterium. This effect was concentration and time dependent and was abrogated by anti-TNF antibodies. TNF-alpha levels in the culture supernatants were low but were enhanced by the addition of gamma interferon. When monocytes were cultured and infected in the presence of pentoxyphilline, a potent inhibitor of TNF-alpha synthesis, the intracellular bacterial growth was enhanced. The effect of pentoxyphilline was concentration and time dependent and was due to the inhibition of TNF-alpha production, as shown by Northern (RNA) blot hybridization of total RNA. In addition, the pentoxyphilline partially abolished the inhibitory effect of gamma interferon on bacterial intracellular multiplication. These results suggest that gamma interferon inhibits, at least partially, the intracellular multiplication of L. pneumophila by enhancing TNF-alpha synthesis.

Humans↗
PubMed1992

Inhibition of production of tumor necrosis factor by monoclonal antibodies to lipopolysaccharides.

Murine monoclonal antibodies to lipopolysaccharides (LPS) from rough J5 mutant of Escherichia coli O111:B4 protected D-galactosamine-treated mice against lethal effects of LPS and provided protection in an experimental infection model with live E. coli. Three previously prepared anti-LPS antibodies were evaluated for ability to inhibit LPS-induced tumor necrosis factor (TNF) secretion. In vivo, TNF production was induced in mice treated with D-galactosamine and challenged with LPS. Two antibodies (D6B3 and D6B4) decreased serum TNF levels and prevented lethal effects of LPS. Nonprotective anti-LPS antibody (D9A2) and an unrelated antibody to neomycin did not reduce circulating TNF levels after LPS challenge. Pretreatment of mice with D6B3 and D6B4 protected mice from infection with E. coli and prevented serum TNF increases induced by E. coli infection. In nonprotected animals, high levels of TNF were detected in serum 3-6 h after infection; animals died within 24 h. In vitro, addition of protective antibodies to macrophage cultures at initiation of LPS stimulation inhibited TNF production. Nonprotective antibody D9A2 failed to block LPS-induced TNF production.

Animals↗
PubMed1992

Tumour necrosis factor, IL-1 and IL-6 in bronchoalveolar washings and their in vitro production during Nippostrongylus brasiliensis infection.

Bronchoalveolar washings (BAW) were obtained from rats primarily infected with N. brasiliensis during the early infection stage that coincides with the lung passage of the parasite and the recruitment of inflammatory cells. BAW were tested for IL-1, IL-6 and tumour necrosis factor (TNF) activities. We found that IL-1 production occurred only on day 1 post infection and ceased thereafter. IL-6 activity was present as from day 1 with a maximum on day 3 post infection and then returned to its normal levels on day 5 post infection. TNF activity was not recovered in BAW at any time of the early infection. Results obtained from the in vitro culture of BAW-adherent cells demonstrated that on day 1 post infection IL-1, but also large amounts of TNF were produced spontaneously, whereas IL-6 was continuously released. Bacterial lipopolysaccharide (LPS) stimulation of the cell culture resulted in an amplification of the cytokine production. Our results suggest that pulmonary cytokines detected in BAW were at least in part produced by alveolar macrophages. Furthermore, the kinetics of IL-1, TNF and IL-6 production show that these monokines are induced at different times during the course of infection, suggesting that cytokine production may follow different regulation patterns during the early phase of N. brasiliensis infection.

Animals↗
PubMed1992

Study of pentoxifylline induced modulation of TNF alpha and interleukin-6 secretion in healthy and septic patients by the use of an ex-vivo model on whole blood.

The aim of this work is to reinvestigate the pentoxifylline (PTX) action on TNF alpha and IL-6 production using a whole blood ex-vivo model. 5 healthy controls, 2 septic patients (4 samples) and 3 patients in septic shock (7 samples) have been studied. Our data confirm the inhibitory action of PTX on TNF alpha production in healthy controls. This inhibition is nearly complete for a PTX concentration of 10(-3) M. More surprisingly a suppressive activity of PTX on IL-6 secretion has been found both in controls and septic patients. On the 7 samples of the 3 patients with septic shock no TNF alpha production has been detected. Taken altogether, these observations suggest a potential role for PTX as a modulator of the major cytokines involved in the pathogenesis of septic shock.

Blood↗