Biomedical subjects

J Louahed

Publications and source records attributed to J Louahed.

10 recordsLinked to original sources

PubMed1998

Intraepithelial infiltration by mast cells with both connective tissue-type and mucosal-type characteristics in gut, trachea, and kidneys of IL-9 transgenic mice.

IL-9 transgenic mice were analyzed for the presence of mast cells in different tissues. In these mice, increased mast cell infiltration was found in the gastric and intestinal epithelium as well as in the upper airways and kidney epithelium, but not in other organs, such as skin. IL-9 transgenic mast cells do not show signs of massive degranulation such as that found in IL-4 transgenic mice and are not involved in spontaneous pathologic changes. Gastric mast cells showed a phenotype related to connective-type mast cells, since they were stained by safranin, and strong expression of mouse mast cell protease-4 and -5 was found in this organ. However, they also expressed proteases related to the mucosal cell type, such as mouse mast cell protease-1 and -2. In vitro, although IL-9 by itself did not induce mast cell development from bone marrow progenitors, it strongly synergized with stem cell factor for the growth and differentiation of mast cells expressing the same protease pattern as that observed in IL-9 transgenic mice. Since constitutive stem cell factor expression was observed in vivo, and anti-c-Kit Abs inhibited IL-9 transgenic mastocytosis in the gut, this synergistic combination of factors is likely to be responsible for the mastocytosis observed in IL-9 transgenic mice. Taken together, these data demonstrate that IL-9 induces the in vivo amplification of a nonclassical mast cell subset with a mucosal localization but expressing proteases characteristic of both connective tissue-type and mucosal mast cells.

Animals↗

PubMed1998

Murine adseverin (D5), a novel member of the gelsolin family, and murine adseverin are induced by interleukin-9 in T-helper lymphocytes.

We identified a number of upregulated genes by differential screening of interleukin-9-stimulated T-helper lymphocytes. Interestingly, two of these messengers encode proteins that are similar to proteins of the gelsolin family. The first displays a typical structure of six homologous domains and shows a high level of identity (90%) with bovine adseverin (or scinderin) and may therefore be considered the murine adseverin homolog. The second encodes a protein with only five segments. Sequence comparison shows that most of the fifth segment and a short amino-terminal part of the sixth segment (amino acids 528 to 628 of adseverin) are missing, and thus, this form may represent an alternatively spliced product derived from the same gene. The corresponding protein is called mouse adseverin (D5). We expressed both proteins in Escherichia coli and show that mouse adseverin displays the typical characteristics of all members of the gelsolin family with respect to actin binding (capping, severing, and nucleation) and its regulation by Ca2+. In contrast, mouse adseverin (D5) fails to nucleate actin polymerization, although like mouse adseverin and gelsolin, it severs and caps actin filaments in a Ca2+-dependent manner. Adseverin is present in all of the tissues and most of the cell lines tested, although at low concentrations. Mouse adseverin (D5) was found only in blood cells and in cell lines derived from T-helper lymphocytes and mast cells, where it is weakly expressed. In a gel filtration experiment, we demonstrated that mouse adseverin forms a 1:2 complex with G actin which is stable only in the presence of Ca2+, while no stable complex was observed for mouse adseverin (D5).

Actins↗

PubMed1998

Role of interleukin-10 in the lung response to silica in mice.

There is evidence that, following exposure to crystalline silica, the release of several proinflammatory cytokines contributes to the induction of unbalanced inflammatory reaction leading to lung fibrosis. We have examined the potential contribution of interleukin-10 (IL-10), an anti-inflammatory cytokine, in the development of silicosis. In a mouse model of inflammatory lung reaction induced by intratracheal instillation of silica (0.5 mg and 5 mg DQ12/mouse), the levels of IL-10 protein (determined by ELISA) both in cells obtained after bronchoalveolar lavage (BAL) and in lung tissue homogenates were significantly increased when compared with controls. After in vitro lipopolysaccharide (LPS) stimulation (1 microg/ml), BAL cells obtained from silica-treated animals produced significantly more IL-10 protein and mRNA than cells obtained from control animals. To examine the role of IL-10 in the lung reaction induced by silica, IL-10-deficient animals were instilled with 5 mg of silica. Twenty-four hours after treatment, the amplitude of the inflammatory response (lactate dehydrogenase [LDH], protein and number of inflammatory cells in BAL) was significantly greater in IL-10-deficient animals than in the wild type. In contrast, the fibrotic response, evaluated by measuring lung hydroxyproline content and by histopathologic analysis 30 days after silica, was significantly less important in IL-10-deficient than in wild-type mice. Together, these data suggest that increased IL-10 synthesis induced by silica can limit the amplitude of the inflammatory reaction, but also contributes to amplify the lung fibrotic response.

Animals↗

PubMed1997

Cocaine induces apoptosis in cortical neurons of fetal mice.

Exposure of fetal mouse brain cocultures to cocaine results selectively in the loss of neurites followed by neuronal death. By using enriched neuronal cultures, we here demonstrate that disappearance of neurons, when cultured with cocaine, is caused by apoptosis, based on (1) characteristic morphology of apoptotic nuclei at the level of neurons but not of glial cells by optic microscopy, and on total cell pellets by electron microscopy; (2) fragmentation of total DNA with a typical "ladder" pattern on agarose gels; (3) extensive in situ DNA fragmentation labeling (TUNEL method); and (4) prevention of cell loss by cycloheximide. The major metabolites of cocaine have no detectable effects on neurons, indicating that apoptosis is due to cocaine itself. Inappropriate neuronal apoptosis in cocaine-exposed fetal brain could perturb the neurodevelopmental program and contribute to the quantitative neuronal defects that are too frequently reported in the offspring of cocaine-abusing pregnant women.

Animals↗

PubMed1996

Differential activity of dexamethasone on IL-2-, IL-4-, or IL-9-induced proliferation of murine factor-dependent T cell lines.

Mouse helper T cell lines were developed that proliferate permanently without Ag and APCs in response to either IL-2, IL-4, or IL-9, three cytokines whose receptors interact with the IL-2R gamma-chain for signal transduction. Depending on the growth factor, a marked difference was observed regarding the ability of dexamethasone (DEX) to inhibit cell proliferation. In three different cell lines, proliferation induced by IL-2 was completely arrested, while that supported by IL-9 was hardly affected. With IL-4, proliferation was also maintained but less markedly than with IL-9. Although DEX was able to induce apoptosis in these cells, the inhibition of IL-2-induced proliferation was not the result of apoptosis, as this process was equally antagonized by all three factors. Moreover, addition of IL-4 or IL-9 to cultures previously incubated with IL-2 and DEX for several days restored cell proliferation. Finally, autonomous cell variants derived from the factor-dependent cell lines were still protected by IL-4 and IL-9 against growth inhibition by DEX. Together, these results indicate that growth stimulation in the presence of glucocorticoids and inhibition of apoptosis involve distinct aspects of cytokine activities.

Animals↗

PubMed1995

IL-9 induces expression of granzymes and high-affinity IgE receptor in murine T helper clones.

Interleukin 9 (IL-9) is a TH2 cytokine that has been shown to promote the antigen-independent growth of some mouse T helper clones. To characterize the specificity of IL-9-mediated T cell activation, we used a murine T cell clone that could grow with either IL-9 or IL-2. After differential hybridization of a cDNA library, we isolated three genes that were expressed preferentially in the presence of IL-9. Two of them correspond respectively to granzyme A and granzyme B, two proteases expressed by activated T cells. By Northern blot hybridization and functional assays, we found that IL-9 induced the expression of granzyme B in several T cell clones as well as in mast cell lines. In addition, other proteases such as the mouse mast cell proteases were also found to be expressed by IL-9-activated T cell clones. The third IL-9-induced cDNA corresponds to the alpha-chain of the high-affinity receptor for IgE. Several T cell clones expressed this IgE receptor mRNA and were able to bind IgE with high affinity. Taken together, our results indicate that IL-9 induces a mast cell-like phenotype in T cell clones.

Animals↗

PubMed1995

Interleukin-9 is a major anti-apoptotic factor for thymic lymphomas.

We have recently shown that interleukin-9 (IL-9) strongly stimulates the proliferation of mouse thymic lymphomas in vitro. Here we report that this factor is also one of the most potent inhibitors of apoptosis induced by dexamethasone (DEX) in such cell lines, even if they do not depend on exogenous factors for growth. For the murine thymic lymphoma BW5147, protection against apoptosis was also obtained with IL-4 and less strongly with IL-6, whereas IL-2, IL-7, and IL-10 were inactive. Moreover, IL-4 and IL-9 maintained proliferation of these cells in the presence of DEX. Analysis of eight other factor-independent thymic lymphoma lines showed significant protection in seven and six cell lines with IL-9 and IL-4, respectively, whereas only three were protected by IL-7 and only two by IL-2. Comparison of the responses to IL-2 and IL-9 in a factor-dependent cell line that responds to both cytokines showed that IL-2 is a stronger inducer of proliferation, while IL-9 is more efficient in protecting the cells against apoptosis. Taken together, our observations suggest that, for thymic lymphomas, proliferation and apoptosis involve distinct regulatory mechanisms and can be differentially regulated by cytokines.

Alkaloids↗

PubMed1995

Interleukin-9 and its receptor: involvement in mast cell differentiation and T cell oncogenesis.

Interleukin-9 (IL-9) is a multifunctional cytokine produced by activated TH2 clones in vitro and during TH2-like T cell responses in vivo. The IL-9 receptor is a member of the hemopoietin receptor superfamily and interacts with the gamma chain of the IL-2 receptor for signal transduction. Various observations indicate that IL-9 is actively involved in mast cell responses by inducing the proliferation and differentiation of these cells. The role of IL-9 in T cell responses is less clear. Although freshly isolated normal T cells do not respond to IL-9, this cytokine induces the proliferation of murine T cell lymphomas in vitro and in vivo overexpression of IL-9 results in the development of thymic lymphomas. In the human, the existence of an IL-9-mediated autocrine loop has been suggested for some malignancies such as Hodgkin's disease. Other potential biological targets for IL-9 include B lymphocytes, hematopoietic progenitors, and immature neuronal cell lines.

Amino Acid Sequence↗

PubMed1993

Interleukin-9.

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Amino Acid Sequence↗

PubMed1990

Rat (and mouse) monoclonal antibodies. VIII. ELISA measurement of Ig production in mouse hybridoma culture supernatants.

We describe a rat monoclonal antibody (MAb)-based solid-phase immunoenzymometric assay for the quantification of mouse hybridoma culture supernatant immunoglobulins (Igs). This assay involves the use of two rat MAbs, LO-MK-1 and LO-MK-2, which bind distinct mouse kappa light chain epitopes expressed by all murine kappa Igs. The assay permits reliable measurement of all murine kappa IgG subclasses in the 2-120 ng/ml range and murine kappa IgM class in the 2-30 ng/ml range. The intra- and interassay coefficients of variation in the measurement of Ig in mouse hybridoma culture supernatants averaged 7.5% and 5% respectively. The assay is simple, reproducible, rapid and does not require specific equipment. It is of potential value to all laboratories engaged in hybridoma technology.

Animals↗