Ammonium acetate decreased in a concentration-dependent manner the phagocytic uptake of mannosylated latex microspheres and of yeast by immortalized human microglia (CHME-5) and astroglioma (GL-15) cells. In both cell lines ammonium acetate affected also the secretion of certain cytokines. The most conspicuous effects were the following: in both cell lines ammonium acetate enhanced greatly the secretion of tumor necrosis factor-alpha in the absence of any other stimulus. in the human microglia cells ammonia decreased the constitutive secretion of interleukin-6, but it enhanced the stimulated (interleukin-1 alpha, tumor necrosis factor-alpha, gamma-interferon and gamma-interferon + tumor necrosis factor-alpha) secretion of interleukin-8. In the astroglioma cell line, the stimulated release of tumor necrosis factor-alpha, interleukin-6 and interleukin-8 was diminished by ammonium acetate. The magnitude of the ammonia-effect depended on the stimulating agent (lipopolysaccharide, interleukin-1 alpha, tumor necrosis factor-alpha, gamma-interferon). The results are discussed with regard to their potential importance in the pathogenesis of human diseases with elevated blood and brain ammonia concentrations.

Acetates↗

PubMedDate not supplied

Learning of olfactory cues is not necessary for early lamb recognition by the mother.

Ewes identify their young through the use of different sensory modalities. Olfactory recognition, which mediates selective acceptance at the udder, is established at 4 h postpartum (pp). Visual and auditory cues are involved in recognition at a distance, which is evident at 12 h pp. This study investigates whether anosmic ewes are able (a) to develop visual and auditory recognition and (b) to restore selective acceptance of their lamb at the udder. Visual and auditory recognition was assessed in anosmic and intact ewes at 12 h and 24 h pp by a test of two choices: their own and an alien lamb. Selectivity at allowing suckling was tested by presenting successively an alien and the familiar lamb at 4 h, 3 days, and 1 month pp. In the two-choice recognition test, at both 12 h and 24 h pp, anosmic as well as intact ewes showed a preference for their familiar lamb. Although anosmic ewes showed no difference in their acceptance of alien and familiar lambs for suckling at 4 h and 3 days pp, they nursed the alien lamb less at 1 month pp and showed more rejection behaviors toward it. Thus, visual, auditory, or both those types of recognition can be rapidly established, independent of olfactory recognition. Moreover, differential behavior of anosmic ewes toward their own versus an alien lamb at the udder at 1 month suggests that vision and audition may compensate to some extent for the loss of olfaction.

Acoustic Stimulation↗

PubMedDate not supplied

Nitric oxide synthase inhibition by haem oxygenase decreases macrophage nitric-oxide-dependent cytotoxicity: a negative feedback mechanism for the regulation of nitric oxide production.

Nitric oxide (NO) production in macrophages by inducible nitric oxide synthase (NOS2) has multiple tissue damaging effects and is involved in the pathogenesis of inflammation and graft rejection. Haem oxygenase (HmOx) is the enzyme which degrades haem. Its inducible isoform, HmOx1, was recently shown to increase cellular resistance against oxidative stress and to decrease inflammation and graft rejection. Since haem is an essential cofactor for NOS2 activity, we investigated the effects of HmOx1-induction upon NO secretion in macrophages. We induced HmOx1 in BALB/c bone-marrow-derived macrophages by short-term exposure to haemin (20 micromol/l, 30 min); then we incubated them for 24 h to allow maximal expression of HmOx1 activity. Next, we activated the macrophages with lipopolysaccharide (LPS) and measured their NO production and their NO-dependent cytotoxicity against P815 cells. We found that HmOx induction 24 h before LPS activation in mouse macrophages suppresses their production of NO, while HmOx inhibition (with zinc protoporphyrin) increases NO secretion. NOS2 inhibition is reflected by the decrease of macrophage NO-dependent cytotoxicity against the P815 targets. We therefore propose that HmOx1 is a physiological inhibitor of NOS2 in activated macrophages because it decreases haem availability for NOS2 synthesis. NOS2 inhibition may explain the antinflammatory effects of HmOx induction which could also be used therapeutically in situations when NO hyperproduction leads to cytotoxic effects such as inflammation or transplant rejection.

Animals↗

PubMedDate not supplied

Quantification of neurotrophin mRNA expression in PMN mouse: modulation by xaliproden.

Compounds possessing neurotrophic properties may represent a possible treatment for neurodegenerative disorders such as amyotrophic lateral sclerosis. Xaliproden (SR57746A), an orally-active non-peptide compound, which has been found to exhibit neurotrophic effects in vitro and in vivo, increased the lifespan and delayed the progression of the motor neuron degeneration in PMN mice. We have used a quantitative reverse transcription/polymerase chain reaction amplification technique to study the regulation of neurotrophin mRNA and trk mRNA expression in PMN mice. NGF and NT-3 mRNA are downregulated in PMN mice. These deficiencies can be overcome by a treatment with xaliproden. Such an effect could contribute to neurotrophic effects of xaliproden in vivo and in vitro.

Animals↗

PubMedDate not supplied

MAPK activation via 5-hydroxytryptamine 1A receptor is involved in the neuroprotective effects of xaliproden.

Motoneurons require neurotrophic factors for their survival and their differentiation. Xaliproden (SR57746A) is a synthetic compound that exhibits in vivo and in vitro neurotrophic effects in several experimental studies. Here we demonstrate that neuroprotective effects of Xaliproden on motoneuron cultures are mediated by the activation of the mitogen activated protein kinase pathway. It is inhibited by PD98059, a selective and irreversible inhibitor of MEK1. The activation of this pathway seems to involve two different proteins, the protein kinase C and the Ras. Indeed, we show that Xaliproden is able to activate the MAP kinases ERK1/2 and PKC in motoneurons. In addition, the use of a 5-hydroxytryptamine 1A receptor antagonist, Pindobind and pertussis toxin, inhibits the effect of Xaliproden on motoneuron survival, suggesting the involvement of this G-protein coupled receptor. Morever, 8-OH-DPAT, an agonist of 5-hydroxytryptamine 1A receptor, increases the survival of mouse motoneurons but not by the same extent as BDNF or xaliproden. Since 8-OH-DPAT does not act synergistically with Xaliproden, it is likely that their neuroprotective properties involve a similar pathway. Taken together, these results indicate that neuroprotective effects of Xaliproden on mouse motoneurons are dependent on the mitogen-activated protein kinase activation via 5-hydroxytryptamine 1A receptor.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMedDate not supplied

Xaliproden (SR57746A) induces 5-HT1A receptor-mediated MAP kinase activation in PC12 cells.

Neurotrophic growth factors are involved in cell survival. However, natural growth factors have a very limited therapeutic use because of their short half-life. In the present study, we investigated the mechanism of action of a non-peptidic neurotrophic drug, Xaliproden, a potential molecule for the treatment of motoneuron diseases, since the transduction pathways of this synthetic 5-HT1A agonist are very poorly understood. Xaliproden does not activate the Trk receptor but causes a rapid increase in the activities of the ERK1 and ERK2 isoforms of MAP kinase, which then rapidly decrease to the basal level. We demonstrate that isoforms of the SHC adapter protein are phosphorylated independently of each other and are probably not the source of the Xaliproden-induced MAP kinases activation. The inhibitor of Ras farnesylation, FPT-1, and the protein kinase C inhibitors, GF 109203X and chelerythrine, inhibited the Xaliproden-induced MAP kinase activation, suggesting p21Ras and PKC involvement. Moreover, the observations that the 5-HT1A antagonist, pindobind, and pertussis toxin abolished the Xaliproden-induced ERK stimulation suggested that Xaliproden activates the MAP kinase pathways by stimulating the G protein-coupled receptor, 5-HT1A. These results demonstrate clearly that the non-peptidic compound, Xaliproden, exerts its neurotrophic effects through a mechanism of action differing from that of neurotrophins. These findings suggest that this compound does not involve MAPK activation by TrkA receptor stimulation but acts by MAP kinase pathway by a pertussis toxin-sensitive mechanism involving 5-HT1A receptors, p21 Ras and MEK-1 and by PKC and Akt pathways.

Adaptor Proteins, Signal Transducing↗

PubMedDate not supplied

The role of calcium and magnesium ions in uptake of beta-amyloid peptides by microglial cells.

Amyloid peptides 1-40 and 1-42 (Abeta 1-40 and Abeta 1-42) are major components of diffuse and neuritic senile plaques present in the brain of patients with Alzheimers disease. Their interaction with microglial cells was studied using a system partly mimicking these plaques, which consisted in heat-killed yeast particles coated with either Abeta 1-40 or Abeta 1-42. Using these particles, it has been shown in our laboratory that LRP is involved mainly in the elimination of Abeta 1-42-coated heat-killed yeast particles and partly in that of Abeta 1-40-coated heat-killed yeast particles by microglial cells in culture. We show here that in the presence of calcium and magnesium ions extracellular chelators, namely EDTA (for both ions) and EGTA (for calcium ions), the internalization of coated heat-killed particles was impaired. In the presence of BAPTA-AM, an intracellular chelator of calcium ions and thapsigargin, an inhibitor of the endoplasmic reticulum calcium pump, no effect was observed on the phagocytosis of Abeta 1-40-coated heat-killed yeast particles, whereas that of Abeta 1-42-coated heat-killed yeast particles was affected. These results suggest that different signaling mechanisms are involved after the internalization of Abeta 1-40 and Abeta 1-42.

Amyloid beta-Peptides↗

PubMedDate not supplied

Study of the dependence of human monocytes and macrophages antitumoral properties upon TNF-alpha expression or release.

This study compares the antitumoral properties of isolated circulating human blood monocytes (Mo) and of mature macrophages (MO) obtained by 7 days differentiation of Mo or isolated from alveolar washing. These cells were activated to cytotoxicity in the presence of recombinant human interferon-gamma (rHuIFN-gamma). This antitumoral effect was measured at a low (1/1) effector/target ratio without pretreatment of the tumor cells. Activated Mo released tumor necrosis factor-alpha (TNF-alpha) in the culture medium where their antitumoral activity could be totally neutralized by specific anti-rHuTNF-alpha antibodies. In contrast, blood monocytes derived macrophages differentiated and activated in vitro expressed TNF-alpha on their membrane where it could be labelled and partially neutralized by anti-rHuTNF-alpha antibodies. Direct effector/target contact was required for the activity of macrophages differentiated in culture or collected from the lung cavity of healthy subjects. When these macrophages were obtained from infected patients or subjected to LPS treatment, they directly released cytotoxic amounts of TNF in the extracellular fluid after activation with IFN-gamma. Monocytes act mainly by soluble mediators (TNF-alpha being a key factor), while differentiated macrophages in the absence of endotoxin act by close cell to cell contact involving the lytic action of membranous TNF-alpha as well as some release of soluble TNF-alpha. We also present evidences (based on the use of various protease inhibitors) that the role of proteases is much less crucial in the cytotoxic action of monocytes and macrophages.

Cytotoxicity, Immunologic↗

PubMedDate not supplied

Antitumoral effects of lipopolysaccharides, tumor necrosis factor, interferon and activated macrophages: synergism and tissue distribution.

Treatment of C57BL/6 mice bearing Lewis lung carcinoma or of BALB/c mice bearing EMT6 sarcoma with tumor necrosis factor (TNF), lipopolysaccharides (LPS) or interferon caused necrosis of the solid tumors and regression. Toxicity was observed in tumor-bearing animals when TNF or LPS were used at effective antitumoral doses. Similar antitumoral effects could be achieved using less than 1 million macrophages from C57BL/6, lung of from BALB/c peritoneal cavity expanded in vitro, and spontaneously fully activated to cytotoxicity during culture. This effect, observed after transfer twice a week by intravenous or peritumoral route, was not dependent on histocompatibility. Additive effects were observed after combined treatment with activated macrophages and a low dose of LPS or TNF. The biodistribution of labelled LPS and of labelled cytotoxic macrophages was studied in tumor-bearing mice. Although, as expected, LPS was concentrated essentially in the liver, a slow accumulation in the center of the tumor was observed. Macrophages injected intravenously accumulated in the lung and were then redistributed towards liver, kidney and the tumor periphery. Macrophages injected locally remained essentially in the tumor periphery with a slow redistribution in the body. The complementary localization of LPS and of cytotoxic macrophages respectively in the center and periphery of solid tumors might explain their synergism.

Animals↗

PubMedDate not supplied

Immunotherapy of murine sarcoma by adoptive transfer of resident peritoneal macrophages proliferating in culture.

Normal resident peritoneal macrophages from BALB/c mice were continuously grown and expanded in vitro as non tumorigenic cells on a confluent layer of mesothelial cells. These peritoneal macrophages expanded in vitro (EPM) were very cytotoxic against EMT6 sarcoma, Abelson myeloma, EL4, and L929S cells in culture. This tumoricidal effect was fully expressed without further activation with bacterial lipopolysaccharides (LPS). In vivo, adoptive transfer of one million EPM to BALB/c mice bearing subcutaneous EMT6 sarcoma caused regression of the solid tumor. In contrast, macrophages produced by 10 days' culture of bone marrow stem cells, or freshly isolated from the peritoneal cavity of BALB/c mice, were not cytotoxic in vitro or in vivo. Local injection in the vicinity of the tumor as well as intravenous transplantation of EPM effectively inhibited tumor growth. This antitumoral effect was further enhanced by intraperitoneal injection of 2 micrograms LPS to the tumor bearing mice.

Animals↗