Expression of sarcolectin in the human pituitary gland and amniotic fluid.

Sarcolectin (SCL) is a 55 kDa protein cross-reacting with a cytokeratin 7 monomer found in placental blood, sarcomas and various tissues. It blocks the synthesis of interferon-dependent secondary proteins, induces cell DNA activation and sensitizes cells to viral infection. SCL is a potent promoter of tissue growth. In the present report, we demonstrate that SCL is expressed in the human pituitary gland at the mRNA and protein levels. We show also its presence in human amniotic fluid in high titres while interferon titres is weak. These results allow to postulate a potential role of SCL as a growth factor participating in human foetal development.

Early days in interferon research.

I describe in this article the early days of interferon research in France. In 1957, when Isaacs and Lindenmann published their results in the same time we worked on a para-influenza 3 virus inhibitor. Thereafter we confirmed this important discovery and initiated research studies about anti-tumor action of interferon.

Acute and selective inhibition of adipocyte glyceroneogenesis and cytosolic phosphoenolpyruvate carboxykinase by interferon gamma.

Interferon gamma (IFN-gamma) was previously shown to promote fatty acid (FA) release from adipose tissue (AT). Net lipolysis is an equilibrium between triglyceride breakdown and FA re-esterification. The latter requires activated glyceroneogenesis for glycerol-3-phosphate synthesis and increased cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C), the key enzyme in this pathway. We wondered whether glyceroneogenesis and PEPCK-C would be IFN-gamma targets. We injected mice with IFN-gamma, and exposed either AT explants and isolated adipocytes from humans and mice or 3T3-F442A adipocytes to IFN-gamma before monitoring expression of genes involved in lipid metabolism and the metabolic consequences. We show that IFN-gamma induces a large increase in FA release without affecting glycerol output and decreases [1-(14)C]-pyruvate incorporation into lipids, thus demonstrating that FA re-esterification is reduced due to diminished glyceroneogenesis. A series of mRNA encoding proteins involved in FA metabolism remained unaffected by IFN-gamma, while that of PEPCK-C was rapidly and drastically lowered. IFN-gamma effect opposed that of the beta-agonist isoproterenol and of 8-Br-cAMP. In IFN-gamma-treated mice, PEPCK-C gene expression was decreased in AT, but not in liver or kidney. Thus, IFN-gamma exerts a tissue-specific action in rodents and humans, having glyceroneogenesis and the PEPCK-C gene as selective targets to intensify FA release from adipocytes.

Differentiation-dependent expression of interferon gamma and toll-like receptor 9 in 3T3-F442A adipocytes.

3T3-F442A and BFC-1 cells are widely used for studying adipocyte differentiation and metabolism. Macrophage markers were previously reported in these cell lines. We examined whether 3T3-F442A and BFC-1 would produce interferon-gamma (IFN-gamma), the expression of which is a matter of debate in cells other than T-lymphocytes and natural killer cells, like macrophages or dendritic. IFN-gamma was absent from preadipocytes. However 3T3-F442A, but not BFC-1, presented a differentiation-dependent induction of IFN-gamma mRNA and protein. Immunofluorescence studies showed that IFN-gamma was located in mature adipocytes. IFN-gamma was retrieved in the culture medium. Then, we examined the expression of other markers of T-lymphocytes or macrophages, like the CD3/T-cell receptor complex or Toll-like receptors (TLR) -2 and -9, in these cells. Transcripts for the three subunits of CD3 were undetectable whatever the differentiation stage. In contrast, TLR-2 and -9 genes were expressed differentially during the differentiation process. TLR-2 mRNA was induced early then decreased while TLR9 transcript appeared at later days and increased in parallel to IFN-gamma. In contrast to what was expected from 3T3-F442A cells, IFN-gamma was absent from adipocytes isolated either from subcutaneous or periepidydimal mouse adipose tissue. However, TLR-2 and -9 mRNAs were present in both adipose depots although at various levels. Hence, we detect the presence of two markers of innate immunity, TLR-2 and -9, in in vivo-derived adipocytes and we demonstrate that differentiated 3T3-F442A cells selectively express IFN-gamma and TLR-9 in a manner that resembles what is occurring for natural killer dendritic cells.

Effects of sarcolectin (SCL) on human peripheral blood mononuclear cells.

Sarcolectin (SCL) is a tissue growth factor found in various human or animal tissues, functioning in balance with interferons (IFNs) that can inhibit growth and affect cell differentiation. Like somatotropin, SCL is found in the pituitary gland. In humans, the SCL gene is located on chromosome 12 (q12-q13) and expressed as a 55 kDa protein consisting of 469 amino-acids. After a single activation of peripheral blood mononuclear cells (PBMC) obtained from more than 30 individuals, highly significant cell proliferation was found to peak after 7 days in culture. The presence of adherent cells was necessary for cell proliferation. SCL induced over-expression of alpha-IL-2 receptor (CD25) leading to proliferation of CD3+/CD4+/CD45RO+ T cells. Thus in PBMC, SCL induced CD4+ T cell growth and expression of inflammatory cytokine genes, including TNF-alpha, IL-1beta, IL-6 and IL-8. IFNs are also produced following activation as a feedback response which is maintained for about 20 days.

Expression of macrophage-selective markers in human and rodent adipocytes.

CD14, CD68 and/or mouse F4/80 or human epidermal growth factor module-containing mucin-like receptor 1 (EMR1) are widely used as macrophage-specific markers. Since macrophages infiltrate several tissues during inflammatory processes, CD14, CD68 and EMR1-F4/80 have been employed to discriminate between tissue-containing macrophages, like adipose tissue (AT), and other cells. Using real-time PCR experiments, we show that isolated adipocytes from humans and mice AT express high levels of CD14 and CD68 mRNA, whereas EMR1-F4/80 is mainly present in the macrophage-containing stroma-vascular fraction. Furthermore, fibroblasts-like cells (adipoblasts), preadipocytes and adipocytes from the murine cell lines, 3T3-F442A and BFC-1, express CD14 and CD68 mRNA and protein as determined by fluorescence-activated cell sorter, but not F4/80 which, as expected, is strongly expressed in the macrophage cell line RAW264.7. These results reinforce the view that EMR1-F4/80 is the best macrophage marker to date and show that CD14 and CD68 are not macrophage-specific proteins.

The interferon antagonist sarcolectin in the progress of HIV-1 infection and in AIDS.

Sarcolectin (SCL) is a nonspecific stimulator of cellular DNA synthesis that was found in all animal sera tested to date. It inhibits the established interferon (IFN)-dependent antiviral state, restoring cells to their normal status. In this study, we examined the excretion/secretion of the IFN antagonist SCL in sera from healthy donors and in sera collected during different periods of human immunodeficiency virus type 1 (HIV-1) infection. We followed HIV-1-infected patients during all stages of development (seroconversion, initial and advanced phases of AIDS) and found a significant increase in SCL in sera of HIV-infected patients compared with seronegative subjects used as controls. This increase was established during seroconversion, and then the titers leveled off. In the final stage of the disease, the SCL titer increased again very significantly. We attribute this rapid rise to the virus-dependent destruction of T cells that can no longer be repaired. The high SCL level observed at this final stage, which is most predictive of the disease's progression, suggests that the action, rather than the production, of IFN is impaired.