Granulocyte-macrophage colony-stimulating factor: more than a hemopoietin

The importance of lymphocytes in lung ischemia-reperfusion injury

In a murine model of lung ischemia-reperfusion injury (IRI), we previously demonstrated that lymphocytes increase in the alveolar space during the ischemic period. We hypothesized that these lymphocytes play an important role during ischemia in the development of lung IRI. In the present study, severe combined immunodeficiency (SCID) mice, lacking T cells, were used to further investigate our hypothesis. SCID and control mice underwent 90 minutes of left lung ischemia followed by 4 hours of reperfusion. A significant decrease in neutrophils, together with lower levels of interleukin-1beta, was found in SCID mice after reperfusion. We concluded that lymphocytes invading the lung during ischemia trigger an inflammatory response upon reperfusion. Antilymphocyte therapies in the donor should be further investigated as treatment strategies against IRI.

Granulocyte macrophage colony-stimulating factor regulates activity of the nervous system

OBJECTIVES

The peripheral administration of granulocyte macrophage colony-stimulating factor (GM-CSF), widely used for the treatment of cytopenias, is often associated with neurological effects [Lieschke et al., N Engl J Med 1992;327:28-34]. This cytokine has recently been reported to affect neurotransmitter metabolism in the nervous system [Bianchi, Neuroreport 1997;8:3587-3590]. To further investigate the neuromodulatory effect of GM-CSF we studied the influence of GM-CSF on the efferent electric activity in the splenic nerve and the integral neuronal activity in medullary gigantocellular reticular formation (MGRF) in rats.

METHODS

Anaesthetized (sodium thiopental 70 mg/kg, i.p.) Wistar rats were injected subcutaneously with 1 microg/kg of hr GM-CSF. Efferent electric activity in the splenic nerve and integral electric activity in MGRF were analyzed. The effectiveness of the applied dose of GM-CSF was verified by determining the elevation of the white blood cell count in peripheral blood 60 min after injection.

RESULTS

We found that GM-CSF increases efferent electric activity in the splenic nerve and decreases that of MGRF as is evident by the frequency of electric discharges. The latency of both effects was 5-15 min.

CONCLUSIONS

This data support the view that GM-CSF exerts a neuromodulatory effect and may provide a new link of neuroimmune communication.

Peripheral blood as a stem cell source for hematopoietic cell transplantation in children: is the effort in vein?

Since 1968 HSCT utilizing bone marrow as a stem cell source has become an accepted treatment modality for a variety of immunologic, hematologic and malignant disorders. However, with widespread use it became apparent that BM donation is inconvenient, uncomfortable and not without risk. These observations led to a search for a more easily and safely acquired hematopoietic stem cell source. Recent experience suggests that peripheral blood may serve as an alternative to marrow. Indeed if the current trend continues PBSC will soon replace BM in adults as the preferred stem cell source for both HLA-matched and unrelated HSCT. Furthermore adults who have experienced both seem to prefer PBSC to BM donation. Recently a number of small trials support the feasibility of PBSC harvest from HLA-matched minor sibling donors. With regard to the recipient, data indicate more rapid engraftment, an acceptable incidence of acute and chronic GVHD, decreased infection and an increased survival for patients with malignancies (suggesting an increased GVT/L effect) when PBSC are utilized. These observations based almost entirely on the adult experience are far from definitive when children are considered. The relatively lower risk and severity of acute and chronic GVHD, the more frequent use of HSCT for non-malignant disorders and the diminished role of GVT/L in the treatment of typical malignancies are factors particular to pediatric HSCT. In addition the sense that mobilization and harvest of PBSC may pose unique and significant risk for the young donor suggest to some that PBSC may not posses sufficient advantage to warrant their use in the pediatric transplant setting. Thus both the available adult-derived data and experience suggest clinical equipoise with regard to the choice of stem cell product, under certain circumstances, when children are considered. This circumstance strongly supports the need for a comprehensive study evaluating the safety and efficacy of PBSC vs. BM HSCT in children.

Modulation of TNF and GM-CSF release from dispersed human nasal polyp cells and human whole blood by inhibitors of different PDE isoenzymes and glucocorticoids

The aim of this study was to investigate the role of the inhibitors of different PDE isoenzymes (PDE 1-5) on the production of two pro-inflammatory cytokines - tumor necrosis factor alpha (TNF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Two in vitro models were used to compare the antiinflammatory properties of PDE inhibitors with that of glucocorticoids. The effect on TNF release from diluted human blood following lipopolysaccharide (LPS from Salmonella abortus equi) stimulation as well as the GM-CSF and TNF release from human nasal polyp cells following allergic stimulation were investigated. Both models proofed to be well suited for the characterisation of the antiinflammatory properties of new chemical entities. In diluted human blood and dispersed human nasal polyp cells the induced TNF release was most potently suppressed by selective PDE4 inhibitors. Amrinone and milrinone, selective PDE3 inhibitors, suppressed TNF secretion to a lesser extent. The effects of theophylline (unspecific PDE inhibitor), vinpocetine (PDE1 inhibitor), EHNA (PDE2 inhibitor) and the PDE5 inhibitors zaprinast and E 4021 were weak. In human blood, the tested glucocorticoids beclomethasone, dexamethasone and fluticasone inhibited the LPS induced TNF release potently in a concentration dependent manner, whereas in dispersed human nasal polyp cells, the effect of the glucocorticoids on allergically induced TNF release, with the exception of dexamethasone, was much less pronounced. Glucocorticoids were the most potent inhibitors of GM-CSF release and the effect correlates well with the affinity to the glucocorticoid receptor. The selective PDE 4 inhibitors, and to a certain extent the PDE3 inhibitors amrinone and milrinone, reduced the GM-CSF release in a concentration dependent manner. In all investigations selective PDE4 inhibitors reduced TNF release to a much higher degree (4-10 fold) than GM-CSF release.

Effects of granulocyte-macrophage colony stimulating factor (GM-CSF) in vivo on cytokine production and proliferation by spleen cells

GM-CSF is a potent stimulator of haematopoietic cells as well as some functions of granulocytes and macrophages. GM-CSF has many clinical uses; however, little is known about the effects of GM-CSF treatment in vivo on the responses of tissue lymphocytes in terms of secretion of Th-1 and Th-2 cytokines. We investigated this issue by measuring the responses of spleen cells from mice 24 h after treatment i.p. with saline or rmGM-CSF. GM-CSF at 16.7-50.0 microg/kg significantly increased (P < 0.01) spleen cellularity 2-2.5-fold and enhanced proliferative responses of non-stimulated (no mitogen) as well as concanavalin A (Con A)-stimulated spleen cells. Secretion of IFN-gamma by Con A (2.5 microg/ml)-stimulated spleen cells was significantly (P < 0.01) increased from 1.8 microg/ml by control spleen cells to 5.2 microg/ml by GM-CSF spleen cells. IL-10 production was greater (0.25 microg/ml, P < 0.05) by Con A-stimulated spleen cells from GM-CSF-treated mice compared to control spleen cells (0.06 microg/ml). By contrast, there were no significant differences in IL-4 production by Con A-stimulated spleen cells from the different groups. These results show that GM-CSF treatment increases spleen cellularity and primes lymphocytes for enhanced responses. The enhanced production of Th-1 cytokines by primed lymphocytes may partially explain the beneficial role of in vivo administration of GM-CSF in several clinical situations.

Immunobiology of hematopoietic colony-stimulating factors: potential application to disease prevention in the bovine

Colony-stimulating factors are a family of glycoproteins instrumental in regulation of hematopoiesis and inflammation. Clinical effects of various colony-stimulating factors have been reported in murine and human hosts. This review summarizes findings from some clinical trial evaluations of macrophage colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, granulocyte colony-stimulating factor, interleukin-1, interleukin-3, interleukin-4, interleukin-5, interleukin-6, and interleukin-7 administration to other species. These factors stimulate clonal expansion of progenitor cells in the bone marrow, induce differentiation of various cell lineages to a mature phenotype, and, in some cases, enhance the effector activities of immune cells. Each colony-stimulating factor has distinct lineages of bone marrow cells upon which they act, although there is some overlap in lineage activity and synergy between colony-stimulating factors. The close relationship in biological activity among different colony-stimulating factors is also reflected at the genomic level at which genes for some hematopoietic growth factors have been mapped to a region of human chromosome 5. Recently, colony-stimulating factor administration to cattle and its potential application to disease control in bovine preventive medicine programs has been investigated. Data from recent hematological, immunological, and intramammary bacterial (Staphylococcus aureus and Klebsiella pneumoniae) challenge studies in dairy cows are reviewed. These studies, with limited numbers of cows, found that rate of new infections, as well as duration and severity of infection, were reduced by pretreatment of cows with granulocyte-colony stimulating factor. The dose-dependent hematological and immunomodulatory effects of granulocyte colony-stimulating factor administration may explain reduced severity and incidence of mastitis in dairy cows given granulocyte colony-stimulating factor.

Cloning and sequencing of the cDNA for ovine granulocyte-macrophage colony-stimulating factor (GM-CSF)

Colony-stimulating factors (CSFs) are not only regulators of haemopoiesis but can also enhance the function of mature myeloid cells, and are therefore potential immune adjuvants. By use of the polymerase chain reaction (PCR) with primers based on the bovine granulocyte-macrophage CSF (GM-CSF) sequence, we have amplified the cDNA for ovine GM-CSF, produced from crude mRNA extracted from alveolar macrophages. The PCR product was cloned into pUC119, and electroporated into Escherichia coli. The complete nucleotide sequence of two clones, and the partial sequence of eight others, was determined. At the nucleotide and amino acid levels, the ovine and bovine GM-CSF sequences are 91% and 81% homologous, respectively.

Neurohormonal immunoregulation

The immune system may be divided into primary lymphoid organs (bone marrow, bursa of Fabricius, and thymus), which produce mature leukocytes and secondary organs (spleen, lymph nodes, tonsils, Peyer's patches, etc.), which are concerned with specific immune responses. In the primary organs, stem cells proliferate and differentiate into various subsets of polymorphonuclear and mononuclear cells. Evidence is increasing that cell proliferation in the primary lymphoid organs is dependent on pituitary growth hormone (GH) and prolactin (PRL), which control the expression of growth regulatory genes (protooncogenes) such as c-myc and also induce essential growth factors (insulinlike growth factor, thymic and bursal hormones, etc.) and, possibly, their receptors. The adrenocorticotropic hormone-adrenal axis serves as an inhibitory pathway, antagonizing the action of PRL and GH on primary lymphoid tissue. The effect of glucocorticoids is especially forceful on thymocytes through the activation of the genetically programmed suicide pathway. Sex hormones also regulate the primary lymphoid organs, but their mechanism of action remains to be clarified. Thymus-derived feedback signals toward the pituitary gland have already been described. The pituitary gland exerts a similar regulatory influence on mature lymphocytes during their antigen-driven differentiation. PRL or GH is required for primary immune reactions; however, the secondary immune response may be less dependent on these hormones. Once the immune system is primed, antigen itself becomes a primary regulator. Exposure of memory cells to antigen leads to the production of growth factors (interleukins) and to the expression of their receptors. Therefore, antigen appears to fulfill, at this stage, a role that is originally played by GH or PRL in the primary lymphoid organs and, to some extent, also during antigen-driven differentiation. During immune reactions, interleukin-1 and tumor necrosis factor activate the adrenocorticotropic hormoneadrenal axis, which plays an important role in setting upper limits to and terminating responses. Lymphocytes have receptors for and react to numerous hormones, neurotransmitters, and mediators derived from a number of organs and tissues. Therefore, ultimately the reaction of a lymphocyte will be the vector of all positive and negative signals received. A hierarchy and sequential system of signals exists. Primary regulatory signals (competence signals) represent the most powerful regulators (e.g., PRL, GH or antigen) of lymphoid cells. The delivery of a competence signal is the prerequisite for subsequent lymphoproliferation, which is regulated by growth factors that are specific for a certain developmental stage of the lymphoid cell and act sequentially. Hormonal factors that promote growth and differentiation deliver the second regulatory signals. Competence factors and growth and differentiation hormones regulate gene expression in lymphocytes. The third class of signals modulate the function of mature effector cells (e.g., locomotion, secretion, phagocytosis, cytotoxicity). Neuro-transmitters appear to function as secondary signal modulators and tertiary functional regulators.