Leukaemia Inhibitory Factor Production Research Articles

Retinal blood vessel-origin yes-associated protein (YAP) governs astrocytic maturation via leukaemia inhibitory factor (LIF).

ObjectivesTo testify that endothelial cells (ECs) induce astrocyte maturation by leukaemia inhibitory factor (LIF) secretion.Materials and MethodsIn vivo experiments, mice bearing floxed alleles of YAP were crossed with mice expressing a Cre recombinase driven by the endothelial Tek promoter (Tek‐Cre) to finally obtain the following three genotypes: YAP f/f, Tek‐Cre; YAP f/w, Tek‐Cre; and YAP f/f. Retinal vascularization and astrocyte network were evaluated by whole‐mount fluorescence and Western blotting. In vitro, experiments were performed in an astrocyte and human microvascular endothelial cell (HMEC‐1) coculture model to analyse the mechanisms underlying the effect of endothelial YAP on astrocytes.ResultsIn vivo, YAPf/f;Tek‐Cre mice showed delayed angiogenesis, sparse vessels and decreased glial fibrillary acidic protein (GFAP)+ astrocytes but aberrant growth of endothelial networks and immature astrocytes (platelet‐derived growth factor A, PDGFRA+ astrocytes) overgrowth. In vitro, Yap deletion attenuated the LIF release that delayed the maturation of retinal astrocyte which was consistent with the results of HMEC‐1—astrocyte coculture. The effect of YAP overexpression on LIF‐LIFR axis in HMEC‐1 interferes the GFAP expression of astrocyte. In contrast, LIF protein rescues the astrocytic GFAP expression when EC YAP was inhibited by siRNAs.ConclusionsWe show that EC yes‐associated protein (YAP) is not only a critical coactivator of Hippo signalling in retinal vessel development but also plays an essential role in retinal astrocyte maturation by regulating LIF production.

Leukemia inhibitory factor: roles in embryo implantation and in nonhormonal contraception.

Leukaemia inhibitory factor (LIF) plays an indispensible role in embryo implantation. Aberrant LIF production is linked to implantation failure. LIF regulates multiple processes prior to and during implantation such as uterine transformation into a receptive state, decidualization, blastocyst growth and development, embryo-endometrial interaction, trophoblast invasion, and immune modulation. Due to its critical role, LIF has been a target for a nonhormonal contraception. In this review, we summarize up-to-date information on the role of LIF in implantation and its role in contraception.

Effects of IFN-β, leptin and simvastatin on LIF secretion by T lymphocytes of MS patients and healthy controls

In multiple sclerosis (MS), oligodendrocyte injury is believed to be caused by an aberrant immune response initiated by autoreactive T cells. Increasing evidence indicates that inflammatory responses in the central nervous system are not exclusively detrimental, but may also exert protective effects. Such protective effects are potentially mediated by the local secretion of neurotrophic factors by immune cells. We previously reported that T cells and monocytes in vitro and in inflammatory MS lesions produce leukaemia inhibitory factor (LIF), a member of the neuropoietic family of neurotrophins. In the present study, we report a reduced LIF production by CD4 + T cells of relapsing remitting MS patients as compared to healthy controls. Furthermore, immunomodulatory agents such as leptin, IFN-β and simvastatin were studied for their potential to alter LIF and secretion of other cytokines by T cells and monocytes of relapsing remitting MS patients and healthy controls. Low doses of simvastatin, but not IFN-β or leptin enhanced LIF secretion by CD4 + T cells of RR-MS patients. We further demonstrated that LIF did not influence viability, proliferation and cytokine secretion of T cells. Together these data provide new information on the regulation of LIF secretion by immune cells. Further insights into the complex regulation of neurotrophic factors such as LIF may prove useful for treatment of MS.

RENAL SYNTHESIS OF LEUKAEMIA INHIBITORY FACTOR (LIF), UNDER NORMAL AND INFLAMMATORY CONDITIONS

Leukaemia inhibitory factor (LIF) is a pleiotropic cytokine that is particularly involved in nephrogenesis and repair of the extracellular matrix. Transgenic mice overexpressing LIF have mesangial proliferative glomerulonephritis. Also, during local inflammatory reactions, such as kidney graft rejection or urinary tract infections, urinary LIF excretion is enhanced. The aim of the study therefore was to study LIF production by normal and inflammatory diseased kidneys (glomerulonephritis or graft rejection), maintained in short cultures. To determine the responsibility of the kidney itself in LIF synthesis, we measured LIF secretion into the culture supernatants of human mesangial or renal tubular epithelial cells. Fragments from diseased kidneys, whether grafts or not, released more LIF than normal human kidney fragments, mesangial or renal tubular epithelial cells. However, LIF production was delayed in renal transplants compared to glomerulonephritic samples taken from untreated patients. In every case, LIF production was enhanced by interleukin 1β (IL-1β) and inhibited by IL-4 or dexamethasone, except in two severe rejection episodes. So, LIF appeared to respond to pro- and anti-inflammatory stimuli, in vitro and in vivo. Considering its biological effects, LIF could play a role in inflammatory renal diseases.

Expression of nuclear factor kappa B in human endometrium; role in the control of interleukin 6 and leukaemia inhibitory factor production.

Expression of the rel-A component of nuclear factor kappa B (NFkappaB) by human endometrial cells was investigated by immunocytochemical analysis of cryostat sections cut from endometrial biopsy material and of cultured endometrial epithelial cells. In-vivo expression of rel-A was low in epithelial cells in endometrium obtained during the proliferative phase of the cycle, but increased in these cells during the secretory phase and was maximal at the time of implantation. In-vivo expression of rel-A by stromal cells did not vary greatly throughout the cycle, but showed a slight peak at the time of ovulation. In contrast similar expression of rel-A was seen in short-term cultures of epithelial cells prepared from both proliferative and secretory endometrium. Addition of the NFkappaB inhibitor SN50 (5 microg/ml) to confluent cultures of endometrial epithelial cells inhibited interleukin (IL)-1alpha (10 ng/ml) and tumour necrosis factor alpha (TNFalpha) (10 ng/ml) stimulated IL-6 (P < 0.001 and P < 0.01 respectively) and LIF (P < 0.01 and P < 0.05 respectively) production. The proteasome inhibitor MG132 (0.3 and 3 micromol/l) also caused a dose-dependent decrease in IL-1alpha and TNFalpha-stimulated IL-6 (P < 0.001 and P < 0.001 respectively) and leukaemia inhibitory factor (LIF) (P < 0. 001 and P < 0.001 respectively) production by endometrial epithelial cells. The results support the hypothesis that NFkappaB mediates signalling between IL-1 and TNFalpha receptors and the expression of LIF and IL-6 in endometrial epithelial cells.

LEUKAEMIA INHIBITORY FACTOR EXPRESSION IS INHIBITED BY GLUCOCORTICOIDS THROUGH POST-TRANSCRIPTIONAL MECHANISMS

Leukaemia inhibitory factor (LIF) is a pleiotropic cytokine which is involved in the regulation of the immune response and haematopoiesis. The authors investigated the regulation of the expression of LIF by glucocorticosteroids (GC). Endothelial cells (EC) constitutively produce LIF and this production is enhanced by interleukin 1 (IL-1). GC were found to inhibit the basal production of LIF by EC and to suppress its IL-1-induced augmentation. Whether corticosteroids suppress LIF production by blocking transcription of LIF mRNA, or by blocking LIF synthesis at a post-transcriptional level was examined. Northern blot hybridization analysis demonstrated that GC act mainly by decreasing the LIF mRNA level. In the presence of translation inhibitors a superinduction of LIF mRNA was observed. Dexamethasone (DEX) at a concentration of 1 μM was responsible for a rapid increase in the degradation rate of LIF mRNA which resulted in reducing its level by more than 50% within 2 h, whereas the transcription rate of LIF gene was not significantly altered in these conditions. These results demonstrated that GC inhibit LIF mRNA expression mainly by increasing the turnover rate of the LIF mRNA. The early LIF mRNA destabilizing activity of GC was translation dependent as shown by experiments with protein translation inhibitors. The results indicate that corticosteroids are inhibitors of LIF expression and that this inhibition mainly occurs through post-transcriptional mechanisms.

EFFECTS OF LIPID MEDIATORS ON THE SYNTHESIS OF LEUKAEMIA INHIBITORY FACTOR AND INTERLEUKIN 6 BY HUMAN BONE MARROW STROMAL CELLS

Human bone marrow stromal cells regulate haematopoiesis by releasing cytokines such as leukaemia inhibitory factor (LIF) and interleukin 6 (IL-6). We have investigated the effects of 5 lipid mediators (i.e. 12-HETE, 15-HETE, platelet-activating factor (PAF), LTB4and prostaglandin E2(PGE2)) on their LIF and IL-6 synthesis. 12-HETE, 15-HETE and LTB4(both at 1 μM) stimulate the LIF production by human bone marrow stromal cells grown in 10% fetal calf serum (FCS). In contrast, PAF and PGE2have no effect. 12-HETE (1 μM) enhances LIF synthesis in serum free medium 7.7-fold and stimulates IL-1 induced LIF production. 12-HETE, 15-HETE, PAF and LTB4have no effect on the spontaneous, serum- and cytokine-induced IL-6 synthesis by bone marrow stromal cells. In contrast PGE2significantly stimulates serum-induced IL-6 synthesis. This study reports for the first time that lipid mediators may act on human haematopoiesis by modulating LIF and IL-6 synthesis by bone marrow stromal cells. Particularly, 12-HETE enhances LIF but not IL-6 synthesis. The different regulation of IL-6 and LIF synthesis in response to lipid mediators highlights the complexity of the cytokine regulation into the human bone marrow.

Synthesis and regulation of leukaemia inhibitory factor in cultured bovine oviduct cells by hormones.

Leukaemia inhibitory factor (LIF) is an essential factor for embryo implantation. Factors generated by the oviduct cells (epithelial cells and fibroblasts) create the microenvironment for fertilization and first embryo stage development. Hence, it is feasible that the oviduct cells also synthesize LIF to promote and condition the embryo for implantation in the uterus. In the present study, we investigated whether cultured bovine oviduct epithelial cells and fibroblasts synthesize LIF. LIF production was measured in the conditioned medium of oviduct epithelial cells and fibroblasts, using LIF enzyme-linked immunosorbent assay. Moreover, expression of LIF mRNA was confirmed by LIF reverse transcriptase-polymerase chain reaction in extracts of RNA from oviduct epithelial/fibroblast cells. Quantitatively similar amounts of LIF were detected in the culture medium of epithelial cells and fibroblasts. In cells cultured for 1-7 days, the levels of LIF in the medium increased in a time-dependent manner. As compared to untreated cells, treatment of cells with 17beta-oestradiol (1-100 ng/ ml), but not progesterone (1-100 ng/ml) and insulin (20 ng/ml), increased the levels of LIF in a concentration-dependent manner (P < 0.05). Similarly, tumour necrosis factor-alpha (100 ng/ml) significantly induced the levels of LIF. The effects of 17beta-oestradiol (50 ng/ml) on LIF synthesis were enhanced and not blocked in the presence of tamoxifen (1 microg/ml), an oestrogen receptor antagonist, suggesting that the stimulatory effects of 17beta-oestradiol on LIF synthesis are not receptor-mediated. In conclusion 17beta-oestradiol, but not progesterone, induces LIF synthesis by bovine oviduct epithelial cells and fibroblasts and this may play an important role in the biology of early embryo development. However, the exact pathophysiological role of LIF within the oviduct needs to be further investigated.

SPONTANEOUS AND INDUCIBLE PRODUCTION OF LEUKAEMIA INHIBITORY FACTOR BY HUMAN BONE MARROW STROMAL CELLS

Leukaemia inhibitory factor (LIF) acts on the growth and differentiation of haematopoietic cells. By using a specific enzyme-linked immunosorbent assay for human LIF, we demonstrate that human bone marrow stromal cells produce LIF. LIF synthesis is enhanced in a dose-dependent manner after stimulation with lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (PMAS). LIF production in response to PMA is PKC-dependent since the two PKC inhibitors sphingosine and staurosporine markedly diminished it. Interleukin 1α (IL-1α), IL-1β, IL-3, IL-6, IL-8, tumour necrosis factor (TNF-α) and SCF (both at 10 ng/ml) stimulate LIF production. By contrast macrophage colony-stimulating factor (M-CSF), granulocyte (G)-CSF, GM-CSF, basic fibroblast growth factor (bFGF), platelet-activating factor (PAF), protaglandin E2(PGE2), leukotriene B4(LTB4), and leukotriene C4(LTC4) did not. These results suggest that bone marrow stromal cells might represent a major source for the cytokine-regulated local production of LIF inside human bone marrow.

The production of leukaemia inhibitory factor by human endometrium: presence in uterine flushings and production by cells in culture.

The concentration of leukaemia inhibitory factor (LIF) was measured in uterine flushings obtained from normal fertile women, from women with unexplained infertility and from women who suffered recurrent miscarriage. In normal fertile women, LIF was not detected in flushings obtained on days luteinizing hormone (LH)+0 to LH+6 of the cycle, but concentrations gradually increased from day LH+7 to a maximum at day LH+12. The amount of LIF in flushings obtained from women with unexplained infertility was significantly lower than in those from normal fertile women on day LH+10 (P < 0.05). The production of LIF by cultured human epithelial and stromal cells was also investigated. LIF was not detectable in the supernatants of cultured stromal cells. Basal LIF production by epithelial cells varied according to the stage in the cycle at which the biopsy was taken. Significantly more LIF was produced by epithelial cells from late proliferative and early secretory endometrium compared with amounts produced by cells from early proliferative (P < 0.001) and late secretory (P < 0.01) endometrium. High doses of progesterone and oestradiol caused a small decrease in epithelial cell LIF production: the combined effect of progesterone and oestradiol (P < 0.01) was greater than the effect of either steroid alone (P < 0.05). The results show, for the first time, the capability of human endometrium to produce LIF in vivo. The fact that maximum LIF concentrations are present at implantation and that decreased concentrations occur in women with unexplained infertility suggest the importance of this cytokine in embryo implantation.

LEUKAEMIA INHIBITORY FACTOR (LIF) PRODUCTION IN PLEURAL EFFUSIONS: Comparison with production of IL-4, IL-8, IL-10 and Macrophage-Colony Stimulating Factor (M-CSF)

Leukaemia inhibitory factor (LIF), a pleiotropic cytokine detected in various inflammatory body fluids, plays a poorly defined role in the pathogenesis of human disease. This study was conducted to correlate the LIF concentrations in pleural effusions with the type of pathology and to compare its levels with those of IL-4, IL-8, IL-10 and M-CSF for a given pathology. Pleural fluids from 97 patients were assayed for cytokines by specific ELISAs. The concentrations of all cytokines tested were higher in infectious pleural effusions than in other pathologies (malignant or transudative). The lowest levels were observed for transudates. Significant differences were noted between pathology groups for each cytokine. A good correlation was observed between LIF and IL-8 for malignant effusions [regression correlation coefficient (RC) = 0.480, P< 0.01], between LIF and IL-4 for infectious disorders (RC = 0.543, P< 0.05) between LIF and IL-10 for transudates (RC = 0.798, P< 0.001) and between M-CSF and IL-8 in all pathologies tested except for primitive neoplasia ( P< 0.05). The LIF concentration in pleural space seems to be strongly associated with the intensity of inflammatory reaction. The LIF production appears to have different regulatory patterns between aetiologic groups.

Leukaemia Inhibitory Factor derived from rat colon carcinoma cells increases host susceptibility to tumour growth

We have tested Leukaemia Inhibitory Factor (LIF) production by 12 rat colon tumour clones isolated from a single cell line that display various degrees of tumorigenicity. A highly significantly relationship was found between levels of soluble LIF produced by the clones and their in vivo tumorigenicity. Such results suggested a role for LIF as a tumour facilitating agent. To test this hypothesis, the highly tumorigenic and LIF producing PROb clone was transfected with the LIF cDNA in antisense orientation in order to decrease LIF production. Conversely, REGb, a low LIF producer that is rejected by syngeneic animals, as well as nude mice, was transfected with the LIF cDNA to increase its production. PROb cells transfected with antisense cDNA were shown to have decreased LIF production along with decreased tumorigenicity. LIF-transfected REGb cells expressing high LIF levels still regressed in syngeneic rats, but could form progressive tumours in nude mice. We did not detect LIF receptors on PROb or REGb cells and their in vitro proliferation was not modified by the addition of exogenous LIF. Therefore, LIF was not an autocrine growth regulator for PROb and REGb cells. Instead, LIF appears to facilitate in vivo tumour growth, without being an immunosuppressive factor sufficient on its own to allow growth of immunogenic cells in fully immunocompetent hosts.

Leukaemia inhibitory factor and the regulation of pre-implantation development of the mammalian embryo.

This paper reviews the evidence that certain growth factors, particularly leukaemia inhibitory factor (LIF), play a crucial role in regulating the development of the pre-implantation mammalian embryo. LIF was originally implicated in regulating the early development of the mouse embryo because it inhibited the differentiation of embryonic stem (ES) cells, pluripotential cells derived from the inner cell mass of the blastocyst. Subsequent studies on its role in vivo revealed, surprisingly, that it is essential for the growth rather than the differentiation of the blastocyst. In vivo, overtly normal blastocysts can be produced in a LIF-deficient environment that are capable of forming viable fertile adults. However, in the absence of LIF, they fail to implant and enter into a state resembling that exhibited by blastocysts undergoing delayed implantation, which is characterized by a cessation of cell proliferation. This failure to implant occurs because the principle sites of LIF production are the endometrial glands of the uterus. These synthesize and secrete LIF at implantation, with LIF synthesis essential for implantation. Preliminary evidence indicates that LIF synthesis is required both by the uterus for it to undergo decidualization and by the blastocyst for implantation. These data indicate that the maternal environment plays a crucial role in the development and growth of the pre-implantation embryo, by supplying factors that regulate these processes in the embryo.

Presence of leukaemia inhibitory factor and interleukin 6 in porcine uterine secretions prior to conceptus attachment

Leukaemia inhibitory factor (LIF) plays an important role in embryo development and implantation. We detected peak LIF activity in porcine uterine luminal fluids (ULF) at day 12 of gestation and during day 7 and 13 of the oestrous cycle. A radio-receptor competition assay showed the presence of a molecule in ULF specifically binding to human LIF receptor (LIF-R). LIF activity was partially neutralized by anti-human LIF antibody. Interleukin-6 (IL-6) activity was detected in ULF throughout the oestrous cycle and pre-implantation period. An anti-murine alpha chain (gp80) of IL-6 receptor (IL-6R) specifically neutralized this activity. LIF and IL-6 mRNA were only detected in day 11 endometrium. The presence of LIF or IL-6 in the uterine cavity has not been previously reported. Our results extend LIF production by endometrium during the oestrous cycle and pre-implantation period to another mammalian species other than mouse.