Anne Bousseau

Modulation of interleukin-1 and tumor necrosis factor expression by β-adrenergic agonists in mouse ameboid microglial cells

SummaryBrain macrophages (ameboid microglial cells) purified to homogeneity and cultured in vitro synthesize and release IL-1 and TNF upon stimulation with lipo-polysaccharide (LPS). This induction can be measured at the levels of transcription and translation. In the present study we have analysed whether certain compounds normally present in the nervous tissue could regulate cytokine production by brain macrophages. We demonstrate that the β-adrenergic agonist isoproterenol, at a concentration of 10-7 M; inhibits the LPS-induced transcription and release of TNFα. At the same concentration, isoproterenol increases the accumulation of IL-1α and IL-1β mRNAs. In spite of its strong effect on IL-1 mRNA accumulation, the adrenergic agonist did not enhance IL-1 activity produced by microglial cells. On the contrary, as is the case for TNF, the LPS-induced production of IL-1 was inhibited by isoproterenol. The effects of isoproterenol on cytokine production specifically involve the β2 and not the β1 adrenergic receptor. It thus appears (i) that the accumulation of mRNAs coding for TNFα on one hand and IL-1α and β on the other is regulated in two opposite ways by the stimulation of the β2-adrenergic receptor and (ii) that mRNA accumulation and cytokine production and secretion are not necessarily coupled.

Amoeboid Microglial Cells and not Astrocytes Synthesize TNF-α in Swiss Mouse Brain Cell Cultures

The role of tumour necrosis factor (TNF‐α) in brain physiology and pathology has been the focus of several studies. However, the source of this lymphokine in the central nervous system and the regulation of its synthesis is still poorly understood. We have therefore used purified astrocytes and brain macrophages in culture to compare the abilities of these two cell types to synthesize TNF‐α and its mRNA. We find that, in the Swiss mouse, no significant TNF activity or TNF‐α mRNA are produced by astrocytes, even following activation with lipopolysaccharides (LPS). On the other hand, purified microglial cells express a cytotoxic activity able to kill TNF‐sensitive LM cells. Part of this activity is released into the culture medium and part remains bound to the membrane after mild paraformaldehyde treatment, demonstrating the existence in the culture of the soluble and membrane‐bound forms of TNF activity. The fact that amoeboid microglial cells, and not astrocytes, are the actual source of TNF in brain cultures was further demonstrated by Northern blot analysis and in situ hybridization using a TNF‐α specific oligonucleotide probe. The definition of the cell type which, in the CNS, is responsible for TNF synthesis will allow the regulation of this lymphokine to be analysed and opens the way for a better understanding of the interactions between amoeboid microglial cells and the other cell types which make up the nervous system.

RP 54745, a potential antirheumatic compound. I. Inhibitor of macrophage stimulation and interleukin-1 production

RP 54745 is an amino-dithiole-one compound found to be active at micromolar concentration on the metabolism of stimulated macrophages, for example, the hexose monophosphate pathway (HMP) and the exocytosis of lysosomal enzymes. LPS-induced interleukin-1 (IL-1) production by murine peritoneal macrophages was also diminished by this compoundin vitro as well asin vivo. This effect was confirmed at the mRNA level; at the concentration of 3×10−6M, the IL-1α and β mRNA signals were inhibited, whereas the TNFα mRNA signal was only slightly lessened. These observations were confirmedin vivo, with a dose of RP 54745 of 25 mg kg−1. These results led us to consider that RP 54745 might influence certain cells and cytokines implicated in the regulation of the immune system, the disfunctioning of which can lead to inflammatory disorders or autoimmune pathologies.

ANTI-HIV ACTIVITY OF N-(2,3-DIHALOGENOPROPYL)- AND N-ALLYL-GLYCINE CONTAINING PENTAPEPTIDES

Abstract A series of peptides containing N -(2,3-dihalopropyl)-glycine or alanine residues has been prepared as potential suicide substrates of the HIV pol -protease or as enzyme-activated prodrugs. Halogenation of unsaturated N -allyl peptide precursors in dichloromethane occurs with participation of a neighboring amide group and leads to halohydrins instead of the expected dihalides. Use of X 2 / LiX/HOAc conditions gives the desired dihalogenated derivatives. These functionalized substrate analogs are not inhibitors of the enzyme. However, Boc-Ala-Phe- N -(2,3-dihalogenopropyl)-Gly-Ile-Val-OMe (halogen= Br and Cl) inhibit the cytopathic effect induced by HIV-1 in CEM cell cultures and the reverse transcriptase activity in cell culture supernatants. The corresponding unsaturated N -allyl precursor also displays an antiviral effect.

RP 54745, a potential antirheumatic compound. II.In vivo properties in different animal models

The results obtained with RP 54745, an amino-dithiole-one compound, on stimulated macrophages, revealing inhibition of the hexose monophosphate pathway (HMP), of the exocytosis of lysosomal enzymes and of the production of interleukin-1 (IL-1), by the compoundin vitro as well asin vivo, suggested that RP 54745 might influence cells and cytokines implicated in the regulation of the immune system, the disfunctioning of which can lead to inflammatory disorders or autoimmune pathologies. RP 54745 was effective at moderate oral doses (around 5 mg kg−1) in different mouse models of induced arthritis and in the MRL/lpr mice, genetically predisposed to develop an autoimmune pathology including arthritic disorders. The clinical status of the MRL mice, and several of their disturbed biochemical and immunological parameters, improved after a 3-month treatment with RP 54745. This activity of RP 54745 makes it a very attractive antirheumatic compound and a potentially effective treatment in pathologies where IL-1 production is exacerbated.