Control of granulocytes and macrophages: molecular, cellular, and clinical aspects

Pretreatment with granulocyte colony-stimulating factor attenuated renal ischaemia and reperfusion injury via activation of PI3/Akt signal pathway

AIM

Granulocyte colony-stimulating factor (G-CSF) has been shown to exert protective effects in various tissues and experimental models of ischaemia-induced injury. However, the mechanism of renoprotective action in ischaemia/reperfusion (I/R) renal injury of G-CSF was unknown.

METHODS

Male C57BL/6J mice, subjected to renal ischaemia for 45 min, 48 h and 7 days reperfusion, were administered either saline, wortmannin, G-CSF, and G-CSF plus wortmannin 3 days prior to I/R. Saline-treated group served as the control. At 48 h and 7 days of reperfusion, the mice were killed.

RESULTS

Significantly, renal dysfunction and morphological injury were identified at 48 h and 7 days after I/R. Wortmannin pretreatment worsened the renal injury significantly. However, G-CSF pretreatment significantly attenuated renal injury, reduced the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive ratio of renal tubular epithelial cells and inflammation cytokine expression in the kidney. Moreover, G-CSF pretreatment inhibited the expression of Bax and increased the expression of bcl-2 and p-Akt in the kidney. Wortmannin blunted the beneficial effects of G-CSF.

CONCLUSION

The cytoprotective action of G-CSF against I/R injury seems to be associated with its anti-apoptotic action mediated by upregulation of p-Akt signal pathway.

Humoral responses to Plasmodium falciparum blood-stage antigens and association with incidence of clinical malaria in children living in an area of seasonal malaria transmission in Burkina Faso, West Africa

There is longstanding evidence that immunoglobulin G (IgG) has a role in protection against clinical malaria, and human antibodies of the cytophilic subclasses are thought to be particularly critical in this respect. In this cohort study, 286 Burkinabè children 6 months to 15 years old were kept under malaria surveillance in order to assess the protective role of antibody responses against four antigens which are currently being evaluated as vaccine candidates: apical membrane antigen 1 (AMA1), merozoite surface protein 1-19 (MSP1-19), MSP3, and glutamate-rich protein (GLURP). Total IgG, IgM, and IgG subclass responses were measured just before the malaria transmission season. The incidence of malaria was 2.4 episodes per child year of risk. After adjusting for the confounding effects of age, the level of total IgG to GLURP was strongly associated with reduced malaria incidence (incidence rate ratio associated with a doubling of total IgG, 0.79; 95% confidence interval, 0.66 to 0.94; P = 0.009.); there was a borderline statistically significant association between the level of total IgG to MSP3 and malaria incidence and no evidence of an association for total IgG to AMA1 and to MSP1-19. Of the IgG subclass responses studied, only IgG3 and IgG4 against GLURP and IgG1 against AMA1 were associated with reduced risk of clinical malaria. There was no evidence of an interaction between responses to AMA1 and baseline parasitemia in their effects on malaria incidence. Currently included in malaria vaccine formulations for clinical trials in humans, these blood-stage antigens, AMA1 and GLURP, offer good prospects for malaria vaccine development.

Granulocyte-Macrophage Colony-Stimulating Factor (CSF) and Macrophage CSF-Dependent Macrophage Phenotypes Display Differences in Cytokine Profiles and Transcription Factor Activities: Implications for CSF Blockade in Inflammation

GM-CSF and M-CSF (CSF-1) can enhance macrophage lineage numbers as well as modulate their differentiation and function. Of recent potential significance for the therapy of inflammatory/autoimmune diseases, their blockade in relevant animal models leads to a reduction in disease activity. What the critical actions are of these CSFs on macrophages during inflammatory reactions are unknown. To address this issue, adherent macrophages (GM-BMM and BMM) were first derived from murine bone marrow precursors by GM-CSF and M-CSF, respectively, and stimulated in vitro with LPS to measure secreted cytokine production, as well as NF-kappaB and AP-1 activities. GM-BMM preferentially produced TNF-alpha, IL-6, IL-12p70, and IL-23 whereas, conversely, BMM generated more IL-10 and CCL2; strikingly the latter population could not produce detectable IL-12p70 and IL-23. Following LPS stimulation, GM-BMM displayed rapid IkappaBalpha degradation, RelA nuclear translocation, and NF-kappaB DNA binding relative to BMM, as well as a faster and enhanced AP-1 activation. Each macrophage population was also pretreated with the other CSF before LPS stimulation and found to adopt the phenotype of the other population to some extent as judged by cytokine production and NF-kappaB activity. Thus, GM-CSF and M-CSF demonstrate, at the level of macrophage cytokine production, different and even competing responses with implications for their respective roles in inflammation, including a possible dampening or suppressive role for M-CSF in certain circumstances.

Effects of low dose GM-CSF on microglial inflammatory profiles to diverse pathogen-associated molecular patterns (PAMPs)

BACKGROUND

It is well appreciated that obtaining sufficient numbers of primary microglia for in vitro experiments has always been a challenge for scientists studying the biological properties of these cells. Supplementing culture medium with granulocyte-macrophage colony-stimulating factor (GM-CSF) partially alleviates this problem by increasing microglial yield. However, GM-CSF has also been reported to transition microglia into a dendritic cell (DC)-like phenotype and consequently, affect their immune properties.

METHODS

Although the concentration of GM-CSF used in our protocol for mouse microglial expansion (0.5 ng/ml) is at least 10-fold less compared to doses reported to affect microglial maturation and function (>/= 5 ng/ml), in this study we compared the responses of microglia derived from mixed glial cultures propagated in the presence/absence of low dose GM-CSF to establish whether this growth factor significantly altered the immune properties of microglia to diverse bacterial stimuli. These stimuli included the gram-positive pathogen Staphylococcus aureus (S. aureus) and its cell wall product peptidoglycan (PGN), a Toll-like receptor 2 (TLR2) agonist; the TLR3 ligand polyinosine-polycytidylic acid (polyI:C), a synthetic mimic of viral double-stranded RNA; lipopolysaccharide (LPS) a TLR4 agonist; and the TLR9 ligand CpG oligonucleotide (CpG-ODN), a synthetic form of bacteria/viral DNA.

RESULTS

Interestingly, the relative numbers of microglia recovered from mixed glial cultures following the initial harvest were not influenced by GM-CSF. However, following the second and third collections of the same mixed cultures, the yield of microglia from GM-CSF-supplemented flasks was increased two-fold. Despite the ability of GM-CSF to expand microglial numbers, cells propagated in the presence/absence of GM-CSF demonstrated roughly equivalent responses following S. aureus and PGN stimulation. Specifically, the induction of tumor necrosis factor-alpha (TNF-alpha), macrophage inflammatory protein-2 (MIP-2/CXCL2), and major histocompatibility complex (MHC) class II, CD80, CD86 expression by microglia in response to S. aureus were similar regardless of whether cells had been exposed to GM-CSF during the mixed culture period. In addition, microglial phagocytosis of intact bacteria was unaffected by GM-CSF. In contrast, upon S. aureus stimulation, CD40 expression was induced more prominently in microglia expanded in GM-CSF. Analysis of microglial responses to additional pathogen-associate molecular patterns (PAMPs) revealed that low dose GM-CSF did not significantly alter TNF-alpha or MIP-2 production in response to the TLR3 and TLR4 agonists polyI:C or LPS, respectively; however, cells expanded in the presence of GM-CSF produced lower levels of both mediators following CpG-ODN stimulation.

CONCLUSION

We demonstrate that low levels of GM-CSF are sufficient to expand microglial numbers without significantly affecting their immunological responses following activation of TLR2, TLR4 or TLR3 signaling. Therefore, low dose GM-CSF can be considered as a reliable method to achieve higher microglial yields without introducing dramatic activation artifacts.

Biologically active human GM-CSF produced in the seeds of transgenic rice plants

Rice flour is a well-known and characterized source of pharmaceutical ingredients, which are gluten-free and incorporated in many drug delivery applications such as excipient starch. To further exploit this uniqueness, the synthetic capacity of rice endosperm tissue, the basis of rice flour, was extended by genetic transformation. Recombinant human GM-CSF, a cytokine used in treating neutropenia and with other potential clinical applications, has been expressed in transgenic rice seeds using a rice glutelin promoter. Rice seeds accumulated human GM-CSF to a level of 1.3% of total soluble protein. The rice seed-produced human GM-CSF was found to be biologically active when tested using a human cell line TF-1. Use of rice as a host plant offers not only attractive features of safe production in seeds but also self-containment of foreign genes, as rice is primarily a self-pollinated crop plant.

The presence of N-terminal secretion signal sequences leads to strong stimulation of the total expression levels of three tested medically important proteins during high-cell-density cultivations of Escherichia coli

Genetic optimizations to achieve high-level production of three different proteins of medical importance for humans, granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon alpha 2b (IFN-alpha2b), and single-chain antibody variable fragment (scFv-phOx), were investigated during high-cell-density cultivations of Escherichia coli. All three proteins were poorly expressed when put under control of the strong Pm/xylS promoter/regulator system, but high volumetric yields of GM-CSF and scFv-phOx (up to 1.7 and 2.3 g/liter, respectively) were achieved when the respective genes were fused to a translocation signal sequence. The choice of signal sequence, pelB, ompA, or synthetic signal sequence CSP, displayed a high and specific impact on the total expression levels for these two proteins. Data obtained by quantitative PCR confirmed relatively high in vivo transcript levels without using a fused signal sequence, suggesting that the signal sequences mainly stimulate translation. IFN-alpha2b expression remained poor even when fused to a signal sequence, and an alternative IFN-alpha2b coding sequence that was optimized for effective expression in Escherichia coli was therefore synthesized. The total expression level of this optimized gene remained low, while high-level production (0.6 g/liter) was achieved when the gene was fused to a signal sequence. Together, our results demonstrate a critical role of signal sequences for achieving industrial level expression of three human proteins in E. coli under the conditions tested, and this effect has to our knowledge not previously been systematically investigated.

Efficient transient expression of human GM-CSF protein in Nicotiana benthamiana using potato virus X vector

The human granulocyte macrophage colony-stimulating factor (GM-CSF) is a glycoprotein with important clinical applications for the treatment of neutropenia and aplastic anemia and reducing infections associated with bone marrow transplants. We evaluated the potential for using a potato virus X (PVX) viral vector system for efficient expression of the biologically functional GM-CSF protein in Nicotiana benthamiana leaves. The GM-CSF gene was cloned into PVX viral expression vector, driven with the CaMV 35S promoter. Gene transfer was accomplished by inoculating N. benthamiana leaves with the plasmid DNA of PVX vector containing the GM-CSF gene. The expression level of the recombinant GM-CSF protein was determined with ELISA and its size was confirmed by Western blot analysis. The results showed that: (1) leaf age significantly affects GM-CSF protein concentration with younger leaves accumulating 19.8 mg g(-1) soluble protein which is 2.6 times the concentration in older leaves, (2) recombinant protein accumulation within a given leaf declined slightly over time but was not significantly different between 7 and 11 days post-inoculation (dpi), and (3) the two leaves immediately above the inoculated leaves play an important role for GM-CSF accumulation in the younger leaves. Protein extracts of infected N. benthamiana leaves contained recombinant human GM-CSF protein in concentrations of up to 2% of total soluble protein, but only when the pair of leaves immediately above the inoculated leaves remained intact. The recombinant protein actively stimulated the growth of human TF-1 cells suggesting that the recombinant human GM-CSF expressed via PVX viral vector was biologically active.

C/EBPβ is required for 'emergency' granulopoiesis

During 'emergency' situations such as infections, host defense requires rapid mobilization of bone marrow granulocyte progenitors. 'Steady-state' granulopoiesis is absolutely dependent on the C/EBPalpha transcription factor, but the transcriptional mechanisms underlying emergency granulopoiesis remain unclear. Here we show that large numbers of granulocytes were generated from C/EBPalpha-deficient progenitors after cytokine stimulation in vivo. Cytokine treatment or fungal infection induced upregulation of C/EBPbeta but not C/EBPalpha or C/EBPepsilon transcripts in granulocyte progenitors, and C/EBPbeta-deficient progenitors showed decreased emergency-induced granulopoiesis in vitro and in vivo. C/EBPbeta inhibited proliferation less severely than did C/EBPalpha. These data suggest a critical function for C/EBPbeta in emergency granulopoiesis, which demands both differentiation and proliferation of granulocyte precursors.

Treatment with granulocyte colony-stimulating factor ameliorates chronic heart failure

Chronic heart failure remains a leading cause of mortality. Although granulocyte colony-stimulating factor (G-CSF) is reported to have a beneficial affect on postinfarction cardiac remodeling and dysfunction when administered before the onset of or at the acute stage of myocardial infarction (MI), its effect on established heart failure is unknown. We show here that subcutaneous administration of G-CSF greatly improves the function of murine hearts failing due to a large, healed MI. G-CSF changed the geometry of the infarct scar from elongated and thin to short and thick, induced hypertrophy among surviving cardiomyocytes, and reduced myocardial fibrosis. Expression of G-CSF receptor was confirmed in failing hearts and was upregulated by G-CSF treatment. G-CSF treatment also led to activation of signal transducer and activator of transcription-3 and induction of GATA-4 and various sarcomeric proteins such as myosin heavy chain, troponin I and desmin. Expression of metalloproteinase-2 and -9 was also increased in G-CSF-treated hearts, while that of tumor necrosis factor-alpha, angiotensin II type 1 receptor (AT1) and transforming growth factor-beta1 was reduced. Although activation of Akt was noted in G-CSF-treated hearts, vessel density was unchanged, and apoptosis was too rare to exert a meaningful effect. No bone marrow-derived cardiomyocytes or vascular cells were detected in the failing hearts of green fluorescent protein chimeric mice. Finally, beneficial effects of G-CSF on cardiac function were found persisting long after discontinuing the treatment (2 weeks). Collectively, these findings suggest G-CSF administration could be an effective approach to treating chronic heart failure following a large MI.

Heparin-binding Sites in Granulocyte-Macrophage Colony-stimulating Factor

The biological activity of granulocyte-macrophage colony-stimulating factor (GM-CSF) is modulated by the sulfated glycosaminoglycans (GAGs) heparan sulfate and heparin. However, the molecular mechanisms involved in such interactions are still not completely understood. We have proposed previously that helix C, one of the four alpha-helices of human GM-CSF (hGM-CSF), contains a GAG-binding site in which positively charged residues are spatially positioned for interaction with the sulfate moieties of the GAGs (Wettreich, A., Sebollela, A., Carvalho, M. A., Azevedo, S. P., Borojevic, R., Ferreira, S. T., and Coelho-Sampaio, T. (1999) J. Biol. Chem. 274, 31468-31475). Protonation of two histidine residues (His83 and His87) in helix C of hGM-CSF appears to act as a pH-dependent molecular switch to control the interaction with GAGs. Based on these findings, we have now generated a triple mutant form of murine GM-CSF (mGM-CSF) in which three noncharged residues in helix C of the murine factor (Tyr83, Gln85, and Tyr87) were replaced by the corresponding basic residues present in hGM-CSF (His83, Lys85, and His87). Binding assays on heparin-Sepharose showed that, at acidic pH, the triple mutant mGM-CSF binds to immobilized heparin with significantly higher affinity than wild type (WT) mGM-CSF and that neither protein binds to the column at neutral pH. The fact that even WT mGM-CSF binds to heparin at acidic pH indicates the existence of a distinct, lower affinity heparin-binding site in the protein. Chemical modification of the single histidine residue (His15) located in helix A of WT mGM-CSF with diethyl pyrocarbonate totally abolished binding to immobilized heparin. Moreover, replacement of His15 for an alanine residue significantly reduced the affinity of mGM-CSF for heparin at pH 5.0 and completely blocked heparin binding to a synthetic peptide corresponding to helix A of GM-CSF. These results indicate a major role of histidine residues in the regulation of the binding of GM-CSF to GAGs, supporting the notion that an acidic microenvironment is required for GM-CSF-dependent regulation of target cells. In addition, our results provide insight into the molecular basis of the strict species specificity of the biological activity of GM-CSF.

Production of biologically active GM-CSF in sugarcane: a secure biofactory

Over 300 transgenic sugarcane plants representing approx. 200 independent lines producing the human cytokine granulocyte macrophage colony stimulating factor (GM-CSF) were analyzed for recombinant protein accumulation and activity levels. Expression constructs differed in use of the maize polyubiquitin 1, Mubi-1, or the sugarcane polyubiquitin 9, SCubi9, promoters; presence or absence of a C-terminal HDEL tag for ER retention; and presence or absence of a 6X Histidine tag for metal ion affinity purification. Accumulation of GM-CSF protein ranged from undetectable to 0.02% of total soluble protein. No significant difference was observed between the two promoters; however, the ER retention tag was required for higher accumulation levels. Human bone marrow cells (TF-1), which require GM-CSF for cell division, proliferated when growth media was supplemented with transgenic sugarcane extracts. Comparison to purified commercially produced GM-CSF indicated the sugarcane-produced protein had essentially identical activity levels. In a 14-month field trial, accumulation levels remained stable. This is the first report of field production of GM-CSF. During the field trial, no flowering of the trial plants occurred; no pollen or seed was produced. Drying, burning, and burial of the test plants effectively blocked possible routes for the transgenic sugarcane to enter the environment or food supply. Sugarcane may provide a highly secure system for biofactory production of pharmaceutical proteins.

Immunophenotypic changes induced on human HL60 leukaemia cells by 1alpha,25-dihydroxyvitamin D3 and 12-O-tetradecanoyl phorbol-13-acetate

1alpha,25-Dihydroxyvitamin D3 (1,25D3) induces HL60 cells to acquire a monocyte-like phenotype, while cells treated with 12-O-tetradecanoyl phorbol-13-acetate (TPA) resemble macrophages. Using a microarray of 82 CD antibodies, 24 cluster of differentiation (CD) antigens were detected on HL60 cells. 1,25D3 induced the following antigens in decreasing order of the change: CD14, CD11c, CD11b, CD54, CD86, CD38 and CD66c, with repression of CD117, CD71, CD95, CD45 and CD64. TPA induced the following antigens in decreasing order of the change: CD11c, CD9, CD11b, CD54, CD38, CD45RO and CD66c, with repression of CD4, CD117, CD95, CD71 and CD64. The results presented provide a basis for monitoring differentiation therapy of myeloid leukaemias in patients.

Overexpression of protein kinase C-{epsilon} in the mouse epidermis leads to a spontaneous myeloproliferative-like disease

Protein kinase C (PKC)-epsilon, a Ca(2+)-independent, phospholipid-dependent serine/threonine kinase, is among the PKC isoforms expressed in mouse epidermis. We reported that FVB/N transgenic mouse lines that overexpress (8- or 18-fold) PKC-epsilon protein in basal epidermal cells and cells of the hair follicle develop papilloma-independent squamous cell carcinoma (SCC) elicited by 7,12-dimethylbenz(a)anthracene initiation and 12-O-tetradecanoylphorbol-13-acetate-promotion or by repeated ultraviolet radiation exposures. The susceptibility to the development of SCC was proportional to the level of expression of the PKC-epsilon transgene. We now report that PKC-epsilon FVB/N transgenic mice (line 215) that overexpress in epidermis approximately 18-fold PKC-epsilon protein more than their wild-type littermates spontaneously develop a myeloproliferative-like disease (MPD) in 100% of PKC-epsilon transgenic mice. The MPD was characterized by an excess of neutrophils and eosinophils, resulting in invasion of almost all vital organs of the mouse by 6 months of age. On gross examination these mice present with splenomegaly, hepatomegaly, and severe lymphadenopathy. Examination of the bone marrow revealed almost complete effacement by neutrophils, eosinophils, and their precursors. Furthermore, the spleen and lymph nodes were enlarged and exhibited marked extramedullary hematopoiesis. Complete pathological analysis of the second PKC-epsilon transgenic mouse (line 224) that expresses approximately eightfold PKC-epsilon protein more than their wild-type littermates revealed no remarkable findings in any of the affected organs as seen in line 215. However, peripheral blood analyses of PKC-epsilon transgenic mice indicated significant increases of neutrophils in the circulating blood in both PKC-epsilon transgenic lines. To determine whether there was an imbalance of cytokines in PKC-epsilon transgenic mice (line 215), resulting in aberrant myelopoiesis, we analyzed 17 cytokines in the peripheral blood. This analysis indicated that interleukin-5, interleukin-6, and granulocyte-colony stimulating factor were up-regulated as a function of age. The transgene PKC-epsilon was not detected in any of the affected organs (bone marrow, liver, spleen, lung) We suggest that overexpression of PKC-epsilon in the epidermis may lead to the induction of specific cytokines that may, in a paracrine mechanism, perturb normal hematopoiesis in bone marrow resulting in a granulocytic skew toward that of neutrophils and eosinophils. The susceptibility of PKC-epsilon transgenic mice to the induction of SCC and the spontaneous development of MPD are unrelated.

p53 is a regulator of macrophage differentiation

While it is well accepted that p53 plays a role in apoptosis, less is known as to its involvement in cell differentiation. Here we show that wild-type p53 facilitates IL-6-dependent macrophage differentiation. Treatment of M1/2 cells expressing the temperature-sensitive p53 143 (Val to Ala) mutant, at the wild-type conformation, facilitated the appearance of mature macrophages that exhibited phagocytic activity. Enhancement of differentiation by the p53 143 (Val to Ala) in the wild-type conformation was coupled with the inhibition of apoptosis induction by this protein. In agreement with previous studies, we found that p53 levels were reduced during p53-dependent macrophage differentiation. This occurred when p53 levels before IL-6 stimuli were high. Interestingly, the p53 143 (Val to Ala) protein, at the mutant conformation, enhanced macrophage differentiation, as did the wild-type conformation, whereas the p53 273 (Arg to His) core mutant exerted an inhibitory effect on this pathway. The transcription-deficient p53 molecules, p53 (22-23) and p53 22,23,143, could not induce p53-dependent differentiation. Moreover, the p53 (22-23) protein inhibited the p53-independent differentiation pathway. Interestingly, the p53 (22-23) protein not only blocked IL-6-mediated differentiation, but also induced significant apoptotic cell death, upon IL-6 stimulation. Taken together, our data show that wild-type p53 enhances macrophage differentiation, while various p53 mutant types exert different effects on this differentiation pathway.

DNA microarray screening of differential gene expression in bone marrow samples from AML, non-AML patients and AML cell lines

This study used cDNA microarray technology to compare gene expression profiles in acute myeloblastic leukaemia (AML) with cDNA dot-blot and real time PCR analysis of cDNA transcripts to confirm array data. Patient AML marrow samples and AML cell lines were compared with normal/non-AML samples. Screening revealed five particular genes to be significantly differentially expressed across the sample groups. The migration-inhibitory factor-related-proteins 8 and 14 (MRP-8 and MRP-14) genes, the products of which inhibit cell migration and differentiation were the most highly expressed in non-malignant cells. The high-mobility-group-protein gene (HMG-1) was up regulated in leukaemic samples and cell lines, which may be associated with aggressive disease. Also upregulated in malignant samples were genes encoding c-myc and glutathione-S-transferase pi (GSTP), the latter implicated in chemotherapy resistance. Faulty expression of such genes may contribute to the pathogenesis of AML and resistance to treatment.

Bioimmunotherapy of rodent malaria: co-treatment with recombinant mouse granulocyte-macrophage colony-stimulating factor and an enkephalin fragment peptide Tyr-Gly-Gly

We have earlier shown that recombinant mouse granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and methionine-enkephalin co-treatment can protect mice from malaria. We now report the bioimmunotherapeutic effect of rmGM-CSF and a synthetic enkephalin fragment peptide Tyr-Gly-Gly (TGG) co-treatment on blood-induced Plasmodium berghei infection in Swiss mice. Mice were completely aparasitimic following co-treatment with rmGM-CSF (10.0 microg/kg) and TGG (2.0 mg/kg x 3 per day, intraperitoneally (i.p.)) starting from day -1 to day +4; however, in monotherapy, neither of these agents showed any detectable bioimmunotherapeutic effect. Curiously, similar co-treatment with rmGM-CSF (10.0 microg/kg) and higher doses of TGG (10.0 mg/kg) did not protect the mice. The combined bioimmunotherapeutic effect of these agents was abrogated by the separate administration each of rabbit neutralizing anti-rmGM-CSF antibody, non-selective opioid receptor antagonist naltrexone (10.0 mg/kg x 6 per day, i.p.), and silica (3.0 mg per mouse, intravenously (i.v.)). The peritoneal and splenic macrophages from the protected mice showed a significant (P<0.05) increase in their pool-size and the phagocytic activity, ex vivo. Furthermore, the protected mice, as compared to the unprotected ones, showed a significant (P<0.05) maximum increase in their serum nitrate and nitrite, interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) levels in their splenic homogenates, on the day before the beginning of the resolution of parasitaemia. Selective inhibitors of both inducible (aminoguanidine) and all forms (L-N(G)-monomethyl arginine) of nitric oxide (NO) synthase, significantly (P<0.05) augmented the mortality of co-treated mice, suggesting the role of NO in protection. These data show that, in P. berghei-infected mice, co-treatment with rmGM-CSF and conditional doses of TGG can impart protection, apparently through partly NO-dependent and macrophage-mediated mechanism(s).

Respirable antisense oligonucleotides: a new, third drug class targeting respiratory disease

PURPOSE OF REVIEW

To describe the potential of a new class of respiratory drugs, respirable antisense oligonucleotides.

RECENT FINDINGS

The first respirable antisense oligonucleotide, EPI-2010, has now reached clinical trials. It has shown intriguing initial indications of efficacy and the potential to be the first once-per-week asthma preventative. Respirable antisense oligonucleotides are capable of addressing targets that have proven to be intractable to traditional 'small molecule' approaches, and against which newer monoclonal antibody strategies may also not be optimal. Respirable antisense oligonucleotides functionally, but not genetically, ablate gene expression by blocking the template function of target respiratory messenger RNAs by as yet incompletely defined mechanisms. They do so with an avidity and specificity which can be several orders of magnitude greater than those shown by small molecule antagonists for their protein targets. The target properties of respiratory messenger RNAs are strikingly different from those of respiratory proteins, enabling respirable antisense oligonucleotides to offer the potential of longer duration of effect, increased specificity of effect, and lack of systemic side effects compared with either traditional small molecule protein antagonists or monoclonal antibodies.

SUMMARY

Respirable antisense oligonucleotides represent a new, third class of respiratory drugs with the potential to extend the range of therapeutic responses to otherwise intractable respiratory targets, and to address precedented targets with the possibility of improving on such features as safety and durability of response.

Granulocyte colony-stimulating factor and its receptor in normal hematopoietic cell development and myeloid disease

Hematopoiesis, the process of blood cell formation, is orchestrated by cytokines and growth factors that stimulate the expansion of different progenitor cell subsets and regulate their survival and differentiation into mature blood cells. Granulocyte colony-stimulating factor (G-CSF) is the major hematopoietic growth factor involved in the control of neutrophil development. G-CSF is now applied on a routine basis in the clinic for treatment of congenital and acquired neutropenias. G-CSF activates a receptor of the hematopoietin receptor superfamily, the G-CSF receptor (G-CSF-R), which subsequently triggers multiple signaling mechanisms. Here we review how these mechanisms contribute to the specific responses of hematopoietic cells to G-CSF and how perturbations in the function of the G-CSF-R are implicated in various types of myeloid disease.

NOD/SCID mice engineered to express human IL-3, GM-CSF and Steel factor constitutively mobilize engrafted human progenitors and compromise human stem cell regeneration

Transplantation of immunodeficient mice with human hematopoietic cells has greatly facilitated studies of the earliest stages of human hematopoiesis. These include demonstration of the ability of injected 'human-specific' hematopoietic growth factors to enhance the production of human cells at multiple levels of differentiation. In contrast, the effects of continuous exposure to such molecules have not been well investigated. Here, we show that nonobese diabetic severe combined immunodeficiency mice genetically engineered to produce ng/ml serum levels of human interleukin-3 (IL-3), granulocyte/macrophage-stimulating factor (GM-CSF) and Steel factor (SF) display a complex phenotype when transplanted with primitive human bone marrow (BM) or fetal liver cells. This phenotype is characterized by an enhancement of terminal human myelopoiesis and a matched suppression of terminal human erythropoiesis, with a slight reduction in human B-lymphopoiesis in the BM of the engrafted mice. Human clonogenic progenitors are more prevalent in the blood of the transplanted growth factor-producing mice and this is accompanied by a very marked reduction of more primitive human cells in the BM. Our findings suggest that long-term exposure of primitive human hematopoietic cells to elevated levels of human IL-3, GM-CSF and SF in vivo may deleteriously affect the stem cell compartment, while expanding terminal myelopoiesis.

Reprogramming of human postmitotic neutrophils into macrophages by growth factors

It is generally recognized that postmitotic neutrophils give rise to polymorphonuclear neutrophils alone. We obtained evidence for a lineage switch of human postmitotic neutrophils into macrophages in culture. When the CD15+CD14- cell population, which predominantly consists of band neutrophils, was cultured with granulocyte macrophage-colony-stimulating factor, tumor necrosis factor-alpha, interferon-gamma, and interleukin-4, and subsequently with macrophage colony-stimulating factor alone, the resultant cells had morphologic, cytochemical, and phenotypic features of macrophages. In contrast to the starting population, they were negative for myeloperoxidase, specific esterase, and lactoferrin, and they up-regulated nonspecific esterase activity and the expression of macrophage colony-stimulating factor receptor, mannose receptor, and HLA-DR. CD15+CD14- cells proceeded to macrophages through the CD15-CD14- cell population. Microarray analysis of gene expression also disclosed the lineage conversion from neutrophils to macrophages. Macrophages derived from CD15+CD14- neutrophils had phagocytic function. Data obtained using 3 different techniques, including Ki-67 staining, bromodeoxyuridine incorporation, and cytoplasmic dye labeling, together with the yield of cells, indicated that the generation of macrophages from CD15+CD14- neutrophils did not result from a contamination of progenitors for macrophages. Our data show that in response to cytokines, postmitotic neutrophils can become macrophages. This may represent another differentiation pathway toward macrophages in human postnatal hematopoiesis.

Granulocyte colony-stimulating factor-induced terminal maturation of human myeloid cells is specifically associated with up-regulation of receptor-mediated function and CD10 expression

The acute promyelocytic leukemia cell line NB4 was differentiated by all-trans retinoic acid (ATRA), which enhanced the superoxide-producing capacity stimulated by the chemotactic peptide and phorbol ester in this cell line. Granulocyte colony-stimulating factor (G-CSF) by itself had no effect on NB4 cells but exerted additional enhancing effects on the respiratory burst activity in the presence of ATRA. This finding was not due to the induction of G-CSF receptor by ATRA, because NB4 cells expressed abundant G-CSF receptor with or without ATRA. Unlike ATRA, G-CSF enhanced superoxide release stimulated by the chemotactic peptide but not by phorbol ester. In addition, G-CSF but not ATRA attenuated cell death and enhanced survival during differentiation. Cell surface expression of the chemotactic peptide receptors CD33 and CD10 but not of CD11b and CD11c was up-regulated by ATRA plus G-CSF far more profoundly than by ATRA alone. Fundamentally identical but slightly different phenomena for the cell surface expression of CD33 and CD10 were observed in the normal human bone marrow mononuclear cells; G-CSF induced CD10 even in the absence of ATRA and down-regulated CD33 in normal cells. The present results indicate that G-CSF-induced terminal maturation of human myeloid cells is associated with up-regulation of receptor-mediated function and CD10 expression.

Dysregulation of transcriptions in primary granule constituents during myeloid proliferation and differentiation in patients with severe congenital neutropenia

We examined the expression of granule constituent genes in myeloid progenitor cells during proliferation and differentiation in patients with severe congenital neutropenia (SCN). The heterozygous mutation of the neutrophil elastase gene was identified in two of four patients. The CD34+/granulocyte-colony stimulating factor receptor (G-CSFR)+ cells of SCN patients showed defective responsiveness to G-CSF in serum-deprived culture. The CD34+/G-CSFR+ cells expressed low levels of the granule constituent mRNAs. The transcription levels of primary granule enzyme genes in CD34+/G-CSFR+ cells were gradually enhanced and then decreased when cells were induced toward myeloid lineage with G-CSF in normal subjects. However, the primary up-regulation and the following down-regulation of these enzyme transcriptions were not clearly observed in SCN patients. No differences in expressions of the lactoferrin gene were seen between normal subjects and patients with SCN. We hypothesize that the abnormal regulation of the transcription in primary granule constituents might involve the defective proliferation and differentiation of myeloid cells in patients with SCN.

Lipid Droplet Formation in Human Myeloid NB4 Cells Stimulated by All Trans Retinoic Acid and Granulocyte Colony-Stimulating Factor: Possible Involvement of Peroxisome Proliferator-Activated Receptor .GAMMA

All trans retinoic acid (ATRA), a differentiation inducer for human myeloid NB4 cells, induced accumulation of lipid droplet as determined by positivity of Nile Red and Oil Red O in this cell line. Granulocyte colony-stimulating factor (G-CSF), although not having detectable effect by itself, exerted the additive effects on lipid droplet formation in NB4 cells when combined with ATRA. mRNA analysis for peroxisome proliferator-activated receptors (PPARs) revealed the initial transient downregulation followed by upregulation of the transcript for PPARgamma2, a master molecule for adipogenesis, and upregulation of PPARalpha. BADGE, a synthetic antagonist for PPARgamma, potently inhibited lipid droplet formation in NB4 cells stimulated by ATRA and/or G-CSF, but not the functional differentiation of the cells by ATRA and/or G-CSF. These results suggest that ATRA and G-CSF induce lipid droplet formation via certain PPARgamma-mediated specific mechanisms in human myeloid NB4 cells during functional differentiation.

Biological activity of human granulocyte-macrophage colony stimulating factor is maintained in a fusion with seed glutelin peptide

Human granulocyte-macrophage colony stimulating factor (GM-CSF), a cytokine with many applications in clinical medicine, was produced specifically in the seeds of transgenic tobacco plants. Two rice endosperm-specific glutelin promoters of different size and sequence, Gt1 and Gt3, were used to direct expression. Also in the Gt3 construct, the GM-CSF coding region was in fusion with the first 24 nucleotides of the mature rice glutelin sequence at its 5' end. With the Gt1 construct plants, seed extracts contained the recombinant human GM-CSF protein up to a level of 0.03% of total soluble protein. Transgenic seed extracts actively stimulated the growth of human TF-1 cells suggesting that the seed-produced GM-CSF alone and in fusion with the rice glutelin peptide was stable and biologically active. Furthermore, native tobacco seed extracts inhibited the activity of E. coli-derived GM-CSF in this cytokine-dependent cell line. The seeds of F1 generation plants retained the biological activity of human GM-CSF protein indicating that the human coding sequence was stably inherited. The feasibility of oral delivery of such stable seed-produced cytokines is discussed.

Evaluation of role of G-CSF in the production, survival, and release of neutrophils from bone marrow into circulation

In steady-state hematopoiesis, G-CSF (granulocyte-colony stimulating factor) regulates the level of neutrophils in the bone marrow and blood. In this study, we have exploited the availability of G-CSF-deficient mice to evaluate the role of G-CSF in steady-state granulopoiesis and the release of granulocytes from marrow into circulation. The thymidine analogue bromodeoxyuridine (BrdU) was used to label dividing bone marrow cells, allowing us to follow the release of granulocytes into circulation. Interestingly, the labeling index and the amount of BrdU incorporated by blast cells in bone marrow was greater in G-CSF-deficient mice than in wild-type mice. In blood, 2 different populations of BrdU-positive granulocytes, BrdU(bright) and BrdU(dim), could be detected. The kinetics of release of the BrdU(bright) granulocytes from bone marrow into blood was similar in wild-type and G-CSF-deficient mice; however, BrdU(dim) granulocytes peaked earlier in G-CSF-deficient mice. Our findings suggest that the mean transit time of granulocytes through the postmitotic pool is similar in G-CSF-deficient and control mice, although the transit time through the mitotic pool is reduced in G-CSF-deficient mice. Moreover, the reduced numbers of granulocytes that characterize G-CSF-deficient mice is primarily due to increased apoptosis in cells within the granulocytic lineage. Collectively, our data suggest that at steady state, G-CSF is critical for the survival of granulocytic cells; however, it is dispensable for trafficking of granulocytes from bone marrow into circulation.

Increased production of human granulocyte-macrophage colony stimulating factor (hGM-CSF) by the addition of stabilizing polymer in plant suspension cultures

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a glycoprotein that stimulates the production of granulocytes, macrophages, and white blood cells. Secretion of human GM-CSF from cell suspension cultures of genetically modified tobacco has been facilitated using natural mammalian leader sequences. At the mid-exponential growth phase (day 4 after the initiation of cell suspension culture), GM-CSF was detected in the medium at a maximum concentration of 180 microg l(-1). However, the secreted GM-CSF was unstable in the medium, and rapidly degraded after day 5. In order to stabilize the secreted GM-CSF, three stabilizing polymers were tested, polyethylene glycol, polyvinylpyrrolidone and gelatin. Gelatin was the most effective in stabilizing the secreted GM-CSF. Following the addition of 5% (w/v) gelatin, the maximum GM-CSF concentration reached 783 microg l(-1), a 4.6-fold increase over control.

Candida albicans infection enhances immunosuppression induced by cyclophosphamide by selective priming of suppressive myeloid progenitors for NO production

Systemic infections caused by fungi after cytoreductive therapies are especially difficult to deal with in spite of currently available antimicrobials. However, little is known about the effects of fungi on the immune system of immunosuppressed hosts. We have addressed this by studying the in vitro T cell responses after systemic infection with Candida albicans in cyclophosphamide-treated mice. After cyclophosphamide treatment, a massive splenic colonization of the spleens, but not lymph nodes, by immature myeloid progenitor (Ly-6G(+)CD11b(+))cells is observed. These cells are able to suppress proliferation of T lymphocytes via a nitric oxide (NO)-dependent mechanism. Systemic infection with a sublethal dose of C. albicans did not cause immunosuppression per se but strongly increased NO-dependent suppression in cyclophosphamide-treated mice, by selective priming of suppressive myeloid progenitors (Ly-6G(+)CD11b(+)CD31(+)CD40(+)WGA(+)CD117(low/-)CD34(low/-)) for iNOS protein expression. The results indicate that systemic C. albicans infection can augment the effects of immunosuppressive therapies by promoting functional changes in immunosuppressive cells.

The proto-oncogene c-myc in hematopoietic development and leukemogenesis

The proto-oncogene c-myc has been shown to play a pivotal role in cell cycle regulation, metabolism, apoptosis, differentiation, cell adhesion, and tumorigenesis, and participates in regulating hematopoietic homeostasis. It is a transcription regulator that is part of an extensive network of interacting factors. Most probably, different biological responses are elicited by different overlapping subsets of c-Myc target genes, both induced and suppressed. Results obtained from studies employing mouse models are consistent with the need for at least one, and possibly two, mutations in addition to deregulated c-myc for malignant tumor formation. Repression of c-myc is required for terminal differentiation of many cell types, including hematopoietic cells. It has been shown that deregulated expression of c-myc in both M1 myeloid leukemic cells and normal myeloid cells derived from murine bone marrow, not only blocked terminal differentiation and its associated growth arrest, but also induced apoptosis, which is dependent on the Fas/CD95 pathway. There is evidence to suggest that the CD95/Fas death receptor pathway is an integral part of the apoptotic response associated with the end of the normal terminal myeloid differentiation program, and that deregulated c-myc expression can activate this signaling pathway prematurely. The ability of egr-1 to promote terminal myeloid differentiation when co-expressed with c-myc, and of c-fos to partially abrogate the block imparted by deregulated c-myc on myeloid differentiation, make these two genes candidate tumor suppressors. Several different transcription factors have been implicated in the down-regulation of c-myc expression during differentiation, including C/EBPalpha, CTCF, BLIMP-1, and RFX1. Alterations in the expression and/or function of these transcription factors, or of the c-Myc and Max interacting proteins, such as MM-1 and Mxi1, can influence the neoplastic process. Understanding how c-Myc controls cellular phenotypes, including the leukemic phenotype, should provide novel tools for designing drugs to promote differentiation and/or apoptosis of leukemic cells.

Accumulation of c-Cbl and rapid termination of colony-stimulating factor 1 receptor signaling in interferon consensus sequence binding protein-deficient bone marrow-derived macrophages

Mice deficient for the transcription factor interferon consensus sequence binding protein (ICSBP) are immunodeficient and develop granulocytic leukemia. Further analyses indicated that ICSBP is a molecular switch factor directing the differentiation of bipotential myeloid precursors to the monocytic lineage. To reveal the molecular mechanisms responsible for the deregulation of myelopoiesis, we examined the signaling of the colony-stimulating factor 1 receptor (CSF-1R) in bone marrow-derived macrophages (BMMs) from ICSBP(-/-) mice. We found that in the absence of ICSBP, CSF-1R signaling is attenuated as seen from an accelerated termination of Erk phosphorylation and reduced cell growth. This finding coincides with an increased CSF-1R ubiquitination and an enhanced accumulation of c-Cbl. c-Cbl is an ubiquitin-ligase known to down-regulate activated CSF-1R by targeting it to the endocytic pathway. Our results indicate that upon CSF-1R activation, c-Cbl itself is partly proteolytically degraded in ICSBP(+/+) but not in ICSBP(-/-) BMMs. Congruently, the expression of a major endosomal/lysosomal protease, cathepsin B, is strongly reduced in ICSBP(-/-) BMMs.

Elucidating critical mechanisms of deregulated stem cell turnover in the chronic phase of chronic myeloid leukemia

Chronic myeloid leukemia (CML) has been studied intensively for many years; yet its treatment remains problematic and its biology remains elusive. In chronic phase, the leukemic clone appears to be maintained by a small number of BCR-ABL-positive hematopoietic stem cells that differentiate normally and amplify slowly. In contrast, as these cells enter the intermediate stages of lineage restriction, their progeny are selectively expanded and generate an enlarged pool of neoplastic progenitors. Recent analyses of purified subsets of primitive CML cells have provided a coherent explanation for this dichotomous behavior of BCR-ABL-positive stem and progenitor cells based on the discovery of an unusual autocrine IL-3/G-CSF mechanism activated in them. This only partially counteracts in vivosignals that maintain normal stem cells in a quiescent state but, when active in CML stem cells, promotes their differentiation in favor of their self-renewal. In more differentiated CML progenitors, the same mechanism has a more potent mitogenic effect which is then extinguished when the cells enter the terminal stages of differentiation. Thus, further expansion of the clone is limited until inevitably additional mutations are acquired that further distort or override the regulatory mechanisms still operative in the chronic phase.

Inhibition of antigen-induced eosinophilia and airway hyperresponsiveness by antisense oligonucleotides directed against the common beta chain of IL-3, IL-5, GM-CSF receptors in a rat model of allergic asthma

Airway obstruction, hyperresponsiveness, and the accumulation and persistence within the airways of inflammatory cells characterize asthma. Interleukin (IL)-3, granulocyte macrophage colony- stimulating factor (GM-CSF), and IL-5 are among several cytokines that have been shown to be increased in asthma and to contribute to atopic inflammation. They mediate their effect via receptors that have a common beta subunit (beta(c)). We hypothesized that blocking of this common beta(c) would impair the airway response to antigen. We report that an antisense (AS) phosphorothioate oligodeoxynucleotide (ODN) found to specifically inhibit transcription of the beta(c) in rat bone marrow cells also caused inhibition of beta(c) mRNA expression and of immunoreactive cells within the lungs of Brown Norway (BN) rats when injected intratracheally (p < 0.01). Inhibition of beta(c) significantly reduced (p < 0.01) experimentally induced eosinophilia in vivo in ovalbumin (OVA)-sensitized BN rats after antigen challenge. Furthermore, when compared with mismatch-treated rats, beta(c) AS-ODN caused inhibition of antigen-induced airway hyperresponsiveness to leukotriene D4. Taken together, our findings demonstrate that the common beta(c) of IL-3, IL-5, and GM-CSF receptors is involved in the eosinophil influx and airway hyperresponsiveness that follow OVA challenge and underscore the potential utility of a topical antisense approach targeting beta(c) for the treatment of asthma.

Activated Fes protein tyrosine kinase induces terminal macrophage differentiation of myeloid progenitors (U937 cells) and activation of the transcription factor PU.1

The c-fps/fes proto-oncogene encodes a 92-kDa protein tyrosine kinase that is preferentially expressed in myeloid and endothelial cells. Fes is believed to play a role in vascular development and myelopoiesis and in the inflammatory responses of granulocytes and macrophages. To help define the biological role of this kinase and identify its downstream targets, we have developed a gain-of-function allele of Fes that has potent biological activity in myeloid cell progenitors. Introduction of constitutively active Fes into bipotential U937 cells induced the appearance of fully differentiated macrophages within 6 to 12 days. The Fes-expressing differentiated cells became adherent, had distinctive macrophage morphology, and exhibited increased expression of myelomonocytic differentiation markers, including CD11b, CD11c, CD18, CD14, and the macrophage colony-stimulating factor receptor. These cells acquired phagocytic properties and exhibited NADPH oxidase and nonspecific esterase activities, confirming that they were functionally active macrophages. Concomitantly, there was downregulation of the granulocytic marker granulocyte colony-stimulating factor receptor, indicating that the biological activity of Fes was coordinated in a lineage-specific manner. A constitutively active Src did not induce macrophage morphology or upregulation of myelomonocytic markers in U937 cells, suggesting that the biological activity we observed was not a general consequence of expression of an activated nonreceptor tyrosine kinase. Analysis of possible downstream targets of Fes revealed that this kinase activated the ets family transcription factor PU.1, which is essential for macrophage development. Our results strongly implicate Fes as a key regulator of terminal macrophage differentiation and identify PU.1 as a transcription factor that may mediate some of its biological activities in myeloid cells.

Deregulated c-Myc prematurely recruits both Type I and II CD95/Fas apoptotic pathways associated with terminal myeloid differentiation

Previously we have reported that deregulated expression of c-myc in normal and leukemic myeloid cells blocked differentiation and, concomitantly, induced p53-independent apoptosis. Here, we show that this morbidity was due to premature recruitment of the Fas/CD95 cell death pathway which normally operates to induce apoptosis at the end of the terminal myeloid differentiation program. Analysis of the regulated components of this pathway revealed that IL6-mediated induction of differentiation resulted in rapid cell surface expression of CD95 receptor. Deregulated c-myc prevented the downregulation of CD95 ligand by maintaining its transcription, but caused premature downregulation of c-FLIP. First, the Type II (mitochondria-dependent, bcl-2-sensitive) and, then, the Type I (mitochondria-independent, bcl-2-insensitive) pathway were activated. Stable exogenous c-FLIP expression completely rescued the apoptotic phenotype. Furthermore, when the deregulated c-myc transgene was stably transduced into bone marrow cells from Fas(lpr/lpr) (CD95 receptor mutant) and FasL(gld/gld) (CD95 ligand mutant) mice, cell death was significantly suppressed relative to c-myc-transduced wild type bone marrow cells upon induction of differentiation. These data indicate that c-myc-mediated apoptosis associated with blocks in myeloid differentiation is dependent on the Fas/CD95 pathway. Our findings offer important new insights into understanding how deregulated c-myc alters normal blood cell homeostasis, and how additional mutations might promote leukemogenesis.

Forced expression of murine IL-17E induces growth retardation, jaundice, a Th2-biased response, and multiorgan inflammation in mice

IL-17 is a proinflammatory cytokine, and its in vivo expression induces neutrophilia in mice. IL-17E is a recently described member of an emerging family of IL-17-related cytokines. IL-17E has been shown to bind IL-17Rh1, a protein distantly related to the IL-17R, suggesting that IL-17E probably possesses unique biological functions. In this study, we have identified the murine ortholog of IL-17E and developed transgenic mice to characterize its actions in vivo. Biological consequences of overexpression of murine (m)IL-17E, both unique to IL-17E and similar to IL-17, were revealed. Exposure to mIL-17E resulted in a Th2-biased response, characterized by eosinophilia, increased serum IgE and IgG1, and a Th2 cytokine profile including elevated serum levels of IL-13 and IL-5 and elevated gene expression of IL-4, IL-5, IL-10, and IL-13 was observed in many tissues. Increased gene expression of IFN-gamma in several tissues and elevated serum TNF-alpha were also noted. In addition, IL-17E induces G-CSF production in vitro and mIL-17E-transgenic mice had increased serum G-CSF and exhibit neutrophilia, a property shared by IL-17. Moreover, exposure to mIL-17E elicited pathological changes in multiple tissues, particularly liver, heart, and lungs, characterized by mixed inflammatory cell infiltration, epithelial hyperplasia, and hypertrophy. Taken together, these findings suggest that IL-17E is a unique pleiotropic cytokine and may be an important mediator of inflammatory and immune responses.

Inhibition of GM-CSF/IL-3/IL-5 signaling by antisense oligodeoxynucleotides targeting the common beta chain of their receptors

Granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and IL-5 play a key role in allergic inflammation. They mediate their effect via receptors that consist of two distinct subunits, a cytokine-specific alpha subunit and a common beta subunit (betac) that transduces cell signaling. We sought to down-regulate the biologic activities of GM-CSF, IL-3, and IL-5 simultaneously by inhibiting betac mRNA expression with antisense technology. Experiments were performed with TF-1 cells (a human erythroleukemia cell line expressing GM-CSF, IL-3, and IL-5 receptors, which proliferates in response to these cytokines), monocytic U937 cells, which require these cytokines for differentiation, and purified human eosinophils. Cells were treated with antisense phosphorothioate oligodeoxynucleotides (ODN) targeting betac mRNA. In contrast to nontreated cells and cells treated by sense or mismatched ODN, antisense ODN inhibited betac mRNA expression and significantly decreased the level of cell surface betac protein expression on TF-1 and U937 cells. Receptor function was also affected. Antisense ODN were able to inhibit TF-1 cell proliferation in vitro in the presence of GM-CSF, IL-3, or IL-5 in the culture medium and eosinophil survival. We suggest that antisense ODN against betac may provide a new therapeutic alternative for the treatment of neoplastic or allergic diseases associated with eosinophilic inflammation.

Differentiation, apoptosis, and function of human immature and mature myeloid cells: intracellular signaling mechanism

Human myeloid cells include hematopoietic cells at various stages of differentiation, from immature myeloid cells to mature phagocytes. Normal immature myeloid cells undergo differentiation concomitantly with proliferation in response to hematopoietic growth factors, and terminally differentiated cells, ie, mature phagocytes, exert their effector functions and then die a natural death via apoptosis. However, leukemic myeloid cells are induced to differentiate with growth suppression by several inducers, such as retinoic acid. This review describes differentiation, apoptosis, and functionality of human myeloid cells. mainly focusing on the intracellular signaling mechanism. The signal transduction system for these biological events of the life cycle of myeloid cells has recently been studied, and several characteristics have been elucidated. First, the signaling pathway for myeloid differentiation is mainly focused in the mitogen-activated protein kinases, such as extracellular signal-regulated kinase and p38, and transcriptional factors such as the signal transducers and activators of transcription PU.1 and CCAAT enhancer binding protein. Second, the signaling mechanism for myeloid cell apoptosis is fundamentally identical to that found in other cells. Caspases, caspase-activated DNase, and mitochondrial molecules such as apoptosis-inducing factor have been reported to be important, and mitogen-activated protein kinases such as p38 appear to be less important. Finally, p38 and phosphatidylinositol 3-kinase play critical roles in the signaling cascade for functional activation of mature phagocytes. The reasons why the same signaling molecules play distinct roles according to the differentiation stage and biological event await future clarification.

Administration of post-autologous PBSCT rhG-CSF is associated with long-term low concentrations of bone marrow hematopoietic progenitor cells

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) has been widely used after autologous peripheral blood stem cell transplant (APBSCT) in an attempt to reduce the duration of neutropenia, but whether this treatment has any influence on long-term engraftment remains unknown. We have retrospectively analyzed data from breast cancer patients to compare post-APBSCT rhG-CSF administration in terms of the short-term benefit and myeloid marrow regeneration after 1 year. Group A included 10 patients not treated with post-APBSCT rhG-CSF, while groups B and C comprised 15 and 13 patients treated with this drug from days +1 and +6, respectively. No differences among the three groups were found in age, diagnosis, previous chemo-radiotherapy, CD34+/CD71- cell concentration in pre-transplant bone marrow (BM), mobilization schedule, CD34+ cell yield, conditioning regimen and post-transplant radiotherapy. Post-APBSCT rhG-CSF was shown to accelerate neutrophil recovery, but there were no significant differences in platelet recovery, transfusion requirements, days of fever, antibiotic administration or inhospital stay. With regard to BM hematopoietic precursors 1 year after APBSCT, significantly lower concentrations of total CD34+ cells, committed CD34+/CD33+ subsets, and more immature CD34+/CD71- cells were found in both groups B and C compared with patients not having received the cytokine (group A). Thus, post-APBSCT rhG-CSF administration does not appear to beneficially affect procedure outcome, and might even impair long-term marrow hematopoiesis.

Cold shock domain factors activate the granulocyte-macrophage colony-stimulating factor promoter in stimulated Jurkat T cells

Cold shock domain (CSD) family members have been shown to play roles in either transcriptional activation or repression of many genes in various cell types. We have previously shown that CSD proteins dbpAv and dbpB (also known as YB-1) act to repress granulocyte-macrophage colony-stimulating factor transcription in human embryonic lung (HEL) fibroblasts via binding to single-stranded DNA regions across the promoter. Here we show that the same CSD factors are involved in granulocyte-macrophage colony-stimulating factor transcriptional activation in Jurkat T cells. Unlike the mechanisms of CSD repression in HEL fibroblasts, CSD-mediated activation in Jurkat T cells is not mediated through DNA binding but presumably through protein-protein interactions via the C terminus of the CSD protein with transcription factors such as RelA/NF-kappaB p65. We demonstrate that Jurkat T cells lack truncated CSD factor subtypes present in HEL fibroblasts, which raises the possibility that the cellular content of CSD proteins may determine their final role as activators or repressors of transcription.

Differences in proliferation of the hematopoietic cell line TF-1 and cytokine production by peripheral blood leukocytes induced by 2 naturally occurring forms of human IL-3

BACKGROUND

A naturally occurring polymorphism in the coding region of the human IL3 gene leads to a change in amino acid residue 8 from proline to serine.

OBJECTIVE

We sought to determine whether the 2 different forms of IL-3 varied in function. These different forms are available as recombinant proteins (recombinant human IL-3/proline 8 [rhIL-3/P8] and recombinant human IL-3/serine 8 [rhIL-3/S8]).

METHODS

The erythroleukemic cell line TF-1 was incubated with varying concentrations of rhIL-3/P8 or rhIL-3/S8 to determine the capacity of each type of IL-3 to induce proliferation. Human leukocytes were primed with rhIL-3/P8 or rhIL-3/S8 for up to 24 hours and then stimulated with anti-IgE and assessed for leukotrienes (LTs), IL-4, and TNF-alpha.

RESULTS

Proliferation of TF-1 cells was induced by both forms of IL-3 at 48 and 72 hours but to a greater degree by rhIL-3/P8. In contrast, the mean fold increase over control values of LT and IL-4 production was higher after priming the cells with rhIL-3/S8 versus rhIL-3/P8. Additionally, TNF-alpha production was greater (and reached significance only) for rhIL-3/S8. This activity was independent of IgE and thus directly stimulated by IL-3. Studies with basophil-enriched and basophil-depleted cell preparations revealed that LT production was evident only from the former and TNF-alpha only from the latter.

CONCLUSION

We conclude that the 2 naturally occurring forms of human IL-3 have similar spectra of activities on cells with IL-3 receptors, but the 2 forms have reversed relative efficacies for promoting proliferation (rhIL-3/P8 > rhIL-3/S8) compared with priming or inducing mediator secretion (rhIL-3/S8 > rhIL-3/P8).

Abnormalities of primitive myeloid progenitor cells expressing granulocyte colony-stimulating factor receptor in patients with severe congenital neutropenia

To define the basis for faulty granulopoiesis in patients with severe congenital neutropenia (SCN), the expression of granulocyte colony-stimulating factor receptor (G-CSFR) in primitive myeloid progenitor cells and their responsiveness to hematopoietic factors were studied. Flow cytometric analysis of bone marrow cells based on the expression of CD34, Kit receptor, and G-CSFR demonstrated a reduced frequency of CD34+/Kit+/ G-CSFR+cells in patients with SCN. The granulocyte-macrophage colony formation of CD34+/Kit+/G-CSFR+ cells in patients was markedly decreased in response to G-CSF alone and to the combination of stem cell factor, the ligand for flk2/flt3, and IL-3 with or without G-CSF in serum-deprived semisolid culture. In contrast, no difference in the responsiveness of CD34+/Kit+/G-CSFR− cells was noted between patients with SCN and subjects without SCN. These results demonstrate that the presence of qualitative and quantitative abnormalities of primitive myeloid progenitor cells expressing G-CSFR may play an important role in the impairment of granulopoiesis in patients with SCN.

Abnormalities of primitive myeloid progenitor cells expressing granulocyte colony-stimulating factor receptor in patients with severe congenital neutropenia

To define the basis for faulty granulopoiesis in patients with severe congenital neutropenia (SCN), the expression of granulocyte colony-stimulating factor receptor (G-CSFR) in primitive myeloid progenitor cells and their responsiveness to hematopoietic factors were studied. Flow cytometric analysis of bone marrow cells based on the expression of CD34, Kit receptor, and G-CSFR demonstrated a reduced frequency of CD34+/Kit+/ G-CSFR+cells in patients with SCN. The granulocyte-macrophage colony formation of CD34+/Kit+/G-CSFR+ cells in patients was markedly decreased in response to G-CSF alone and to the combination of stem cell factor, the ligand for flk2/flt3, and IL-3 with or without G-CSF in serum-deprived semisolid culture. In contrast, no difference in the responsiveness of CD34+/Kit+/G-CSFR− cells was noted between patients with SCN and subjects without SCN. These results demonstrate that the presence of qualitative and quantitative abnormalities of primitive myeloid progenitor cells expressing G-CSFR may play an important role in the impairment of granulopoiesis in patients with SCN.

Recombinant murine granulocyte-macrophage colony-stimulating factor modulates the course of pulmonary histoplasmosis in immunocompetent and immunodeficient mice

Several endogenous cytokines, including granulocyte-macrophage colony-stimulating factor (GM-CSF), are necessary for eliminating Histoplasma capsulatum from tissues. In this study, we explored the efficacy of recombinant murine GM-CSF in the treatment of pulmonary histoplasmosis. This cytokine significantly reduced fungal burden in a dose-dependent manner. Pretreatment did not consistently produce a better result than treatment started after infection. The biological effectiveness of GM-CSF was not associated with modulation of lung cytokine production or alteration in lung inflammation, but it directly activated a nonadherent lung cell population to exert anti-Histoplasma activity. GM-CSF improved survival of T-cell-depleted mice exposed to H. capsulatum. When combined with a suboptimal amount of amphotericin B, GM-CSF enhanced survival of normal or T-cell-depleted mice given a lethal challenge. These results suggest that this cytokine may be useful as an adjunctive treatment for histoplasmosis.