Apoptotic mechanisms in the control of erythropoiesis

The MAPK ERK1 is a negative regulator of the adult steady-state splenic erythropoiesis

The mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase 1 (ERK1) and ERK2 are among the main signal transduction molecules, but little is known about their isoform-specific functions in vivo. We have examined the role of ERK1 in adult hematopoiesis with ERK1(-/-) mice. Loss of ERK1 resulted in an enhanced splenic erythropoiesis, characterized by an accumulation of erythroid progenitors in the spleen, without any effect on the other lineages or on bone marrow erythropoiesis. This result suggests that the ablation of ERK1 induces a splenic stress erythropoiesis phenotype. However, the mice display no anemia. Deletion of ERK1 did not affect erythropoietin (EPO) serum levels or EPO/EPO receptor signaling and was not compensated by ERK2. Splenic stress erythropoiesis response has been shown to require bone morphogenetic protein 4 (BMP4)-dependent signaling in vivo and to rely on the expansion of a resident specialized population of erythroid progenitors, termed stress erythroid burst-forming units (BFU-Es). A great expansion of stress BFU-Es and increased levels of BMP4 mRNA were found in ERK1(-/-) spleens. The ERK1(-/-) phenotype can be transferred by bone marrow cells. These findings show that ERK1 controls a BMP4-dependent step, regulating the steady state of splenic erythropoiesis.

A multi-scale model of erythropoiesis

In this paper, a multi-scale mathematical model of erythropoiesis is proposed in which erythroid progenitors are supposed to be able to self-renew. Three cellular processes control erythropoiesis: self-renewal, differentiation and apoptosis. We describe these processes and regulatory networks that govern them. Two proteins (ERK and Fas) are considered as the basic proteins participating in this regulation. All erythroid progenitors are divided into several sub-populations depending on their maturity level. Feedback regulations by erythropoietin, glucocorticoids and Fas ligand (FasL) are introduced in the model. The model consists of a system of ordinary differential equations describing intracellular protein concentration evolution and cell population dynamics. We study steady states and their stability. We carry out computer simulations of an anaemia situation and analyse the results.

Rac1 and Rac2 GTPases are necessary for early erythropoietic expansion in the bone marrow but not in the spleen

BACKGROUND

The small Rho GTPases Rac1 and Rac2 have both overlapping and distinct roles in actin organization, cell survival, and proliferation in various hematopoietic cell lineages. The role of these Rac GTPases in erythropoiesis has not yet been fully elucidated.

DESIGN AND METHODS

Cre-recombinase-induced deletion of Rac1 genomic sequence was accomplished on a Rac2-null genetic background, in mouse hematopoietic cells in vivo. The erythroid progenitors and precursors in the bone marrow and spleen of these genetically engineered animals were evaluated by colony assays and flow cytometry. Apoptosis and proliferation of the different stages of erythroid progenitors and precursors were evaluated by flow cytometry.

RESULTS

Erythropoiesis in Rac1(-/-);Rac2(-/-) mice is characterized by abnormal burst-forming unit-erythroid colony morphology and decreased numbers of megakaryocyte-erythrocyte progenitors, erythroid colony-forming units, and erythroblasts in the bone marrow. In contrast, splenic erythropoiesis is increased. Combined Rac1 and Rac2 deficiency compromises proliferation of the megakaryocyte-erythrocyte progenitor population in the bone marrow, while it allows increased survival and proliferation of megakaryocyte-erythrocyte progenitors in the spleen. Conclusions These data suggest that Rac1 and Rac2 GTPases are essential for normal bone marrow erythropoiesis but that they are dispensable for erythropoiesis in the spleen, implying different signaling pathways for homeostatic and stress erythropoiesis.

Hemozoin (malarial pigment) directly promotes apoptosis of erythroid precursors

Severe malarial anemia is the most common syndrome of severe malaria in endemic areas. The pathophysiology of chronic malaria is characterised by a striking degree of abnormal development of erythroid precursors (dyserythropoiesis) and an inadequate erythropoietic response in spite of elevated levels of erythropoietin. The cause of dyserythropoiesis is unclear although it has been suggested that bone-marrow macrophages release cytokines, chemokines or lipo-peroxides after exposure to hemozoin, a crystalloid form of undigested heme moieties from malarial infected erythrocytes, and so inhibit erythropoiesis. However, we have previously shown that hemozoin may directly inhibit erythroid development in vitro and the levels of hemozoin in plasma from patients with malarial anemia and hemozoin within the bone marrow was associated with reduced reticulocyte response. We hypothesized that macrophages may reduce, not enhance, the inhibitory effect of hemozoin on erythropoiesis. In an in vitro model of erythropoiesis, we now show that inhibition of erythroid cell development by hemozoin isolated from P. falciparum is characterised by delayed expression of the erythroid markers and increased apoptosis of progenitor cells. Crucially, macrophages appear to protect erythroid cells from hemozoin, consistent with a direct contribution of hemozoin to the depression of reticulocyte output from the bone marrow in children with malarial anemia. Moreover, hemozoin isolated from P. falciparum in vitro inhibits erythroid development independently of inflammatory mediators by inducing apoptotic pathways that not only involve activation of caspase 8 and cleavage of caspase 3 but also loss of mitochondrial potential. Taken together these data are consistent with a direct effect of hemozoin in inducing apoptosis in developing erythroid cells in malarial anemia. Accumulation of hemozoin in the bone marrow could therefore result in inadequate reticulocytosis in children that have adequate levels of circulating erythropoietin.

Heme oxygenase: the key to renal function regulation

Heme oxygenase (HO) plays a critical role in attenuating the production of reactive oxygen species through its ability to degrade heme in an enzymatic process that leads to the production of equimolar amounts of carbon monoxide and biliverdin/bilirubin and the release of free iron. The present review examines the beneficial role of HO-1 (inducible form of HO) that is achieved by increased expression of this enzyme in renal tissue. The influence of the HO system on renal physiology, obesity, vascular dysfunction, and blood pressure regulation is reviewed, and the clinical potential of increased levels of HO-1 protein, HO activity, and HO-derived end products of heme degradation is discussed relative to renal disease. The use of pharmacological and genetic approaches to investigate the role of the HO system in the kidney is key to the development of therapeutic approaches to prevent the adverse effects that accrue due to an impairment in renal function.

The potential of human peripheral blood derived CD34+ cells for ex vivo red blood cell production

The potential of peripheral blood derived CD34+ cells for ex vivo erythropoiesis was investigated in a stroma-free culture system using a novel strategy of daily passaging. By expanding PB-derived CD34+ cells up to 1.5 x 10(6)-fold this method achieved expansion factors previously only reported for CD34+ cells derived from more potent stem cell sources such as cord blood, bone marrow and mobilized peripheral blood. Analysis of cell surface markers showed differentiation of immature CD34+ cells to populations with 80% CD71-/GpA+ cells and up to 45% enucleated cells, indicating a significant amount of terminal maturation. Cell crowdedness was found to have decisive effects on in vitro erythropoiesis. Cell density per surface area rather than cell concentration per media volume determined cell expansion during exponential growth where more crowded cells showed reduced overall expansion. In late stage erythropoiesis, however, when cells no longer proliferating, increased cell density was seen to enhance cell viability. These results indicate that peripheral blood derived haematopoietic stem cells can be an alternative to cells sourced from bone marrow, cord blood or leukapheresis in terms of expansion potential. This provides distinct advantages in terms of availability for studies of conditions for scale-up and maturation, and may have particular clinical applications in the future.

Gab1 transduces PI3K-mediated erythropoietin signals to the Erk pathway and regulates erythropoietin-dependent proliferation and survival of erythroid cells

In this study, we examined the biological functions of Gab1 in erythropoietin receptor (EPOR)-mediated signaling in vivo. Knockdown of Gab1 by the introduction of the Gab1 siRNA expression vector into F-36P human erythroleukemia (F-36P-Gab1-siRNA) cells resulted in a reduction of cell proliferation and survival in response to EPO. EPO-induced activation of Erk1/2 but not of Akt was significantly suppressed in F-36P-Gab1-siRNA cells compared with mock-transfected F-36P cells. The co-immunoprecipitation experiments revealed an EPO-enhanced association of Gab1 with the Grb2-SOS1 complex and SHP-2 in F-36P cells. A selective inhibitor of phosphatidylinositol 3-kinase (PI3K) LY294002 and short interfering RNA (siRNA) duplexes targeting the p85 regulatory subunit of PI3K (p85-siRNA) independently suppressed tyrosine phosphorylation of Gab1; its association with Grb2, SHP-2 and p85; and the activation of Erk in EPO-treated F-36P cells. LY294002 inhibited EPO-induced tyrosine phosphorylation of Gab1 and its association with Grb2 in human primary EPO-sensitive erythroid cells. The co-immunoprecipitation experiments using the Jak inhibitor AG490 or siRNA duplexes targeting Jak2 and in vitro binding experiments demonstrated that Jak2 regulated Gab1-mediated Erk activation through tyrosine phosphorylation of Gab1. Taken together, these results suggest that Gab1 couples PI3K-mediated EPO signals with the Ras/Erk pathway and that Gab1 plays an important role in EPOR-mediated signal transduction involved in the proliferation and survival of erythroid cells.

Identification of gene networks associated with erythroid differentiation

Erythropoiesis is a multistep process involving a large number of genes, which balance between proliferation, differentiation and survival of the erythroid cells. To understand the molecular mechanisms of erythropoiesis and related pathological aberrations, we analyzed three stages of in vitro differentiating human erythroid cells by expression profiling. We identified distinct clusters of genes, each with a unique expression pattern during differentiation. As JAK2 was shown to play a central role in myeloproliferative disorders, we focused on one cluster which includes JAK2 and other genes with high correlation to JAK2 expression. These genes had a low expression at the early erythroblast which increased in the intermediate stage and further slightly increased in the last stage of differentiation. Our results indicate that gene networks may associate with JAK2 expression in erythroid differentiation. It is intriguing to determine whether the pathogenesis of polycythemia vera (PV), harboring a common or uncommon JAK2 mutation, involves alterations in independent gene pathways that underlie the normal erythropoietic process.

Hematopoietic defects in the Ts1Cje mouse model of Down syndrome

Down syndrome (DS) persons are born with various hematopoietic abnormalities, ranging from relatively benign, such as neutrophilia and macrocytosis, to a more severe transient myeloproliferative disorder (TMD). In most cases, these abnormalities resolve in the first few months to years of life. However, sometimes the TMD represents a premalignant disease that develops into acute megakaryocytic leukemia (AMKL), usually in association with acquired GATA1 mutations. To gain insight into the mechanisms responsible for these abnormalities, we analyzed the hematopoietic development of the Ts1Cje mouse model of DS. Our analyses identified defects in mature blood cells, including macrocytosis and anemia, as well as abnormalities in fetal liver and bone marrow stem and progenitor cell function. Despite these defects, the Ts1Cje mice do not develop disease resembling either TMD or AMKL, and this was not altered by a loss of function allele of Gata1. Thus, loss of Gata1 and partial trisomy of chromosome 21 orthologs, when combined, do not appear to be sufficient to induce TMD or AMKL-like phenotypes in mice.

Bone marrow aspirate and biopsy: a pathologist's perspective. II. interpretation of the bone marrow aspirate and biopsy

Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Classification of cell death: recommendations of the Nomenclature Committee on Cell Death 2009

Different types of cell death are often defined by morphological criteria, without a clear reference to precise biochemical mechanisms. The Nomenclature Committee on Cell Death (NCCD) proposes unified criteria for the definition of cell death and of its different morphologies, while formulating several caveats against the misuse of words and concepts that slow down progress in the area of cell death research. Authors, reviewers and editors of scientific periodicals are invited to abandon expressions like 'percentage apoptosis' and to replace them with more accurate descriptions of the biochemical and cellular parameters that are actually measured. Moreover, at the present stage, it should be accepted that caspase-independent mechanisms can cooperate with (or substitute for) caspases in the execution of lethal signaling pathways and that 'autophagic cell death' is a type of cell death occurring together with (but not necessarily by) autophagic vacuolization. This study details the 2009 recommendations of the NCCD on the use of cell death-related terminology including 'entosis', 'mitotic catastrophe', 'necrosis', 'necroptosis' and 'pyroptosis'.

Lead exposure induces pycnosis and enucleation of peripheral erythrocytes in the domestic fowl

Lead (Pb) shot were administered orally to young chickens to determine the effects on red blood cells (RBCs). The concentrations of Pb in the blood of young chickens rose rapidly after Pb administration and were maintained at high levels for several days. The number of RBCs with pycnotic nuclei, reticulocytes and enucleated RBCs increased concurrently. Pycnotic nuclei were surrounded by enlarged nucleolemmal cisternae, which sometimes opened to the extracellular space. Gel electrophoresis showed that the presence of pycnotic nuclei was not associated with DNA fragmentation typical of apoptosis. It was concluded that exposure to lead shot changes nuclear morphology in the peripheral blood of domestic fowl.

Myelodysplasia and anemia of chronic disease in human tumor necrosis factor-alpha transgenic mice

TNF-alpha is a pleitropic cytokine that expresses both pro- and anti-inflammatory activity and transgenic mice expressing human tumor necrosis factor-alpha (TNF-alpha) exhibit a progressive polyarthritis that models rheumatoid arthritis (RA). One of the common comorbidities of RA is anemia of chronic disease (ACD). The purpose of these experiments was to study the changes in the bone marrow and peripheral blood that accompany polyarthritis in TNF-alpha transgenic mice in an effort to better understand the pathogenesis of myelodysplasia and ACD. Polychromatic cytometry, hematology and serum cytokine analysis were used to study the pathogenesis of ACD in human TNF-alpha transgenic mice. Our hematological evaluation revealed a mild, compensated, microcytic hypochromic anemia, and monocytosis. In the bone marrow, we observed alterations in cell kinetics, decreased relative expression of transferrin receptor and increased apoptosis and cell death in several late precursor cell populations. Although significant levels of human TNF-alpha were found in the serum, neither change in serum murine erythropoietin nor any significant difference observed in serum levels of murine IL-beta, IL-5, IL-6, IL-10, IL-12(p70), IL-17, TNF-alpha, IFNgamma, GM-CSF, MIP-1alphaJE, MCP-5 was observed. Tg197 mice develop a compensated, microcytic, hypochromic anemia, and a functional iron deficiency by 9 weeks of age. Changes in peripheral blood are reflected in alterations in cell kinetics, transferrin receptor expression and markedly increased apoptosis and cell death in the bone marrow indicating that TNF-alpha may contribute to myelodysplasia in ACD. Moreover, since human TNF-alpha can interact only with murine TNFR1, our data suggest that TNFR1 may play an important role in the development of ACD.

Impaired erythropoiesis after haemorrhagic shock in mice is associated with erythroid progenitor apoptosis in vivo

OBJECTIVE

Multiply traumatised patients often suffer from blood loss and from subsequent therapy-resistant anaemia, possibly mediated by apoptosis, necrosis, or humoral factors. Therefore, the underlying mechanisms were investigated in bone marrow (BM) and peripheral blood in a murine resuscitated haemorrhagic shock (HS) model.

METHODS

In healthy male mice, pressure-controlled HS was induced for 60 min. The BM was analysed for Annexin-V, 7-amino-actinomycin D, apoptotic enzymes (caspases-3/7, -8, and -9), expression of death receptors (CD120a, CD95), mitochondrial proteins (Bax, Bcl-2, Bcl-x), as well as erythropoietin (EPO) receptor (EPO-R). Blood cell count, peripheral EPO, and tumour necrosis factor-alpha response were additionally monitored.

RESULTS

Twenty-four and 72 h after HS, EPO and EPO-R were strongly up-regulated in peripheral blood and BM, respectively. Decreasing numbers of erythroid progenitors in BM after HS correlated with significant apoptotic changes confirmed by increased caspases-3/7, -8, -9 activity in total BM, death receptor CD95 and CD120a expression on erythroid progenitors, and down-regulated mitochondrial Bcl-2 expression in total BM. Erythroid progenitors in peripheral blood were found to be increased after 72 h.

CONCLUSION

Despite the massive EPO response and up-regulation of EPO-R, BM erythroblasts (EBs) decreased. This could be due to deficient maturation of erythroid progenitors. Furthermore, the increased intrinsic and extrinsic apoptosis activation suggests programmed death of erythroid progenitors. We propose that both apoptosis and negatively regulated erythropoiesis contribute to BM dysfunction, while erythroid progenitor egress plays an additional role.

Supportive care and use of hematopoietic growth factors in myelodysplastic syndromes

Supportive care constitutes the basis of the management of patients with myelodysplastic syndromes (MDS). Appropriate treatment of cytopenia, as well as of other related complications, not only improves quality of life but also may positively affect the overall survival of patients. Anemia is the most common cytopenia in MDS, and the requirement for regular transfusions is a major clinical problem for patients with low-risk MDS. An important therapeutic goal in this patient group is to maintain acceptable hemoglobin levels without transfusions. Today, this goal can be achieved by treatment with erythropoietin (Epo) +/- granulocyte colony-stimulating factor (G-CSF), or by more targeted treatment such as antithymocyte globulin or lenalidomide in around 50% of patients. For the remaining patients, and for those who lose their therapeutic response, chronic transfusion therapy, with or without the addition of chelating agents, is the only option and it is important that this treatment is scheduled to meet the needs of the individual patient. Severe thrombocytopenia has recently been reported to respond to thrombopoietic agents, such as AMG 531.

Regulated expression of microRNAs in normal and polycythemia vera erythropoiesis

OBJECTIVE

Polycythemia vera (PV) is a myeloproliferative disorder, arising from the acquired mutation(s) of a hematopoietic stem cell. The JAK2 V617F somatic mutation is found in most PV patients; however, it is not the disease-initiating mutation. Because microRNAs (miRNAs) play a regulatory role in hematopoiesis, we studied miRNA expressions in PV and normal erythropoiesis.

METHODS

Peripheral blood mononuclear cells were cultured in a three-phase liquid system resulting in synchronized expansion of erythroid progenitors. Using gene-expression profiling by CombiMatrix MicroRNArray, we searched for PV-specific changes at days 1, 14, and 21. Twelve miRNA candidates were then reevaluated by quantitative real-time polymerase chain reaction in a larger number of samples obtained from progenitors at the same stage of differentiation.

RESULTS

A significant difference in miR-150 expression was found in PV. In normal erythropoiesis, three expression patterns of miRNAs were observed: progressive downregulation of miR-150, miR-155, miR-221, miR-222; upregulation of miR-451, miR-16 at late stages of erythropoiesis; and biphasic regulation of miR-339, miR-378. The miR-451 appears to be erythroid-specific.

CONCLUSIONS

We identified the miRNAs with regulated expression in erythropoiesis; one appeared to be PV-specific. Their miRNA expression levels define early, intermediate, and late stages of erythroid differentiation. The validity of our findings was confirmed in nonexpanded peripheral blood cells.

Variable Bax antigenicity is linked to keratinocyte position within epidermal strata and UV-induced apoptosis

Pro- and anti-apoptotic members of the Bcl-2 family are fundamental in the control of apoptosis. Among them, Bax plays a key role in apoptosis induction by mediating the release of apoptogenic factors from mitochondria to the cytosol. In this report, we investigated, by immunohistofluorescence, the in vivo distribution of Bax in normal human epidermis before and 24 h after exposure to solar-simulated radiation. Bax expression was evaluated with three different, Western blot pretested, anti-Bax antibodies (Ab) and correlated with markers of keratinocyte differentiation and apoptosis using anti-beta(1) integrin and anti-active caspase-3 Abs respectively. Using anti-Bax N20 and A-3533 polyclonal Ab, we found that, whereas undifferentiated keratinocytes of the basal proliferative compartment contained Bax in the cytosol, the differentiated suprabasal cells had Bax mainly in the nucleus. This immunoreactivity pattern was not modified by skin irradiation. Interestingly, the well known apoptosis-related Bax redistribution to mitochondria in response to a cell death signal, could be detected only with yet another, the 2D2 monoclonal Ab. This relocalization occurred specifically in apoptotic, active caspase-3 positive cells of irradiated epidermis. Our data highlight the differentiation- and apoptosis-associated changes in the pattern of Bax subcellular and cellular distribution as uncovered by different anti-Bax Abs and suggest that Bax undergoes successive activation that progresses in parallel with keratinocyte differentiation and apoptosis.

CNTO 530: molecular pharmacology in human UT-7EPO cells and pharmacokinetics and pharmacodynamics in mice

CNTO 530 is a 58 kD antibody Fc domain fusion protein, created using Centocor's MIMETIBODY platform, that contains two EMP1 sequences as a pharmacophore. CNTO 530 has no sequence homology with EPO but acts as a novel erythropoietin receptor agonist. In UT-7(EPO) cells, CNTO 530 caused protein phosporylation of the erythropoietin receptor associated signaling pathway (Jak2, STAT5, AKT and ERK1/2). CNTO 530 also rescued these cells from apoptosis and mediated proliferation. In mice, pharmacokinetic analysis showed that CNTO 530 was slowly cleared from circulation with a t(1/2) approximately 40 h. Pharmacodynamic analysis in mice showed that a single sc dose of CNTO 530 caused a long-lived stimulation of erythropoiesis that translated into increases in red blood cell counts and hemoglobin values that were maintained for at least 28 d. In conclusion, CNTO 530 is a long-lived EPO-R agonist that stimulates erythropoiesis in a manner similar to epoetin-alpha. These data suggest that CNTO 530 may be an effective treatment of anemia in humans.

Polyclonal immunoglobulin E levels are correlated with hemoglobin values and overall survival in patients with multiple myeloma

PURPOSE

Polyclonal IgG, IgA, and IgM immunoglobulins are often decreased in sera of patients with multiple myeloma (MM), whereas very few data are available on polyclonal IgE levels. We have determined IgE levels in a large series of MM patients at diagnosis and subjects with monoclonal gammopathy of undetermined significance (MGUS) and correlated IgE levels with survival and prognostic factors in MM.

EXPERIMENTAL DESIGN

IgE were determined with a commercially available ELISA kit in 201 MM patients at diagnosis, 144 subjects with MGUS, and 77 age-matched controls.

RESULTS

IgE levels progressively decreased from controls to MGUS and from MGUS to MM (P = 0.001). MM patients with IgE levels of >11.5 IU/mL (median) had a better survival than patients with IgE of <11.5 IU/mL (P = 0.048). The difference was even more significant when MM patients were divided according to clinical cutoff values. Patients with elevated IgE levels (>100 IU/mL) had from 2 to 3 years longer survival than those with low (<10 IU/mL) or intermediate values (10-100 IU/mL; P < 0.01). IgE levels were positively and negatively correlated with hemoglobin (P = 0.006) and beta2-microglobulin levels (P = 0.007), respectively. Univariate and multivariate analyses confirmed that high IgE levels are positive predictors of overall survival (P = 0.03 and 0.08, respectively) and strongly correlated with hemoglobin values.

CONCLUSIONS

Because IgE levels are dependent on Th(2) responses, these data open new perspectives in the interpretation of antitumor immune responses and pathogenesis of anemia in MM.

Expression of Fas and Fas-ligand in donor hematopoietic stem and progenitor cells is dissociated from the sensitivity to apoptosis

OBJECTIVE

The interaction between the Fas receptor and its cognate ligand (FasL) has been implicated in the mutual suppression of donor and host hematopoietic cells after transplantation. Following the observation of deficient early engraftment of Fas and FasL-defective donor cells and recipients, we determined the role of the Fas-FasL interaction.

METHODS

Donor cells were recovered after syngeneic (CD45.1-->CD45.2) transplants from various organs and assessed for expression of Fas/FasL in reference to lineage markers, carboxyfluorescein succinimidyl ester dilution, Sca-1 and c-kit expression. Naïve and bone marrow-homed cells were challenged for apoptosis ex vivo.

RESULTS

The Fas receptor and ligand were markedly upregulated to 40% to 60% (p < 0.001 vs 5-10% in naïve cells) within 2 days after syngeneic transplantation, while residual host cells displayed modest and delayed upregulation of these molecules ( approximately 10%). All lin(-)Sca(+)c-kit(+) cells were Fas(+)FasL(+), including 95% of Sca-1(+) and 30% of c-kit(+) cells. Fas and FasL expression varied in donor cells that homed to bone marrow, spleen, liver and lung, and was induced by interaction with the stroma, irradiation, cell cycling, and differentiation. Bone marrow-homed donor cells challenged with supralethal doses of FasL were insensitive to apoptosis (3.2% +/- 1% vs 38% +/- 5% in naïve bone marrow cells), and engraftment was not affected by pretransplantation exposure of donor cells to an apoptotic challenge with FasL.

CONCLUSION

There was no evidence of Fas-mediated suppression of donor and host cell activity after transplantation. Resistance to Fas-mediated apoptosis evolves as a functional characteristic of hematopoietic reconstituting stem and progenitor cells, providing them competitive engraftment advantage over committed progenitors.

Reduced erythroid cell and erythropoietin production in response to acute anemia in prion protein-deficient (Prnp-/-) mice

Cellular prion protein (PrPc) participates in the pathogenesis of prion diseases but its normal function remains unclear. PrPc is expressed on hematopoietic cells, including erythroid precursors. We investigated the role of PrPc in erythropoiesis in vivo with phenylhydrazine-induced acute anemia. Induction of equivalent anemia in wild-type (WT) and Prnp-/- mice resulted in a higher number of circulating reticulocytes, hematocrits and spleen weights in WT mice than in Prnp-/- mice on Days 5 and 7. Examination of bone marrow erythroid precursor cells (Ter119+) on Day 5 revealed no significant differences in the number of these cells between the two types of animals. However, a higher percentage of Ter119+ cells were going through apoptosis in Prnp-/- mice than in WT mice. Plasma erythropoietin (Epo) levels and Epo mRNA in kidneys peaked on Day 3 in response to anemia for both types of animals but rose less in Prnp-/- (5500 pg/ml ) than in WT (18,000 pg/ml) animals. Administration of recombinant human Epo to mice produced an equivalent reticulocyte response in both types of animals suggesting that the potential for erythroid generation is intact in Prnp-/- animals. These observations indicate that PrPc may modulate tissue hypoxia-sensing mechanisms or effect hypoxia target gene expression.

Ribosomal protein S19 deficiency leads to reduced proliferation and increased apoptosis but does not affect terminal erythroid differentiation in a cell line model of Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) is a congenital red-cell aplasia in which 25% of the patients have a mutation in the ribosomal protein (RP) S19 gene. It is not known how the RPS19 deficiency impairs erythropoiesis and proliferation of hematopoietic progenitors. To elucidate molecular mechanisms in RPS19-deficient DBA, we analyzed the effects of RPS19 deficiency on erythropoietin (EPO)-induced signal transduction, cell cycle, and apoptosis in RPS19-deficient TF-1 cells. We did not find any abnormality in EPO-induced signal transduction. However, RPS19-deficient TF-1 cells showed G0/G1 arrest (82% vs. 58%; p < .05) together with accumulation of p21 and p27. The fraction of apoptotic cells detected by Annexin V analysis also increased compared with control cells (13% vs. 3.1%; p < .05). Western blot analysis of apoptosis-related proteins showed that the level of bcl-2 and Bad was decreased and Bax was increased in RPS19-deficient TF-1 cells. Moreover, primary CD34-positive cells from DBA patients detected by Annexin V analysis also generated a higher number of apoptotic cells compared with normal CD34-positive cells during in vitro culture (38% vs. 8.9%; n = 5; p < .001). Finally, we show that although RPS19 silencing reduces EPO-induced development of erythroid progenitors expressing glycophorin A (GPA), RPS19 silencing in cells already expressing GPA does not affect GPA expression. These findings indicate that RPS19 deficiency causes apoptosis and accelerated loss of erythroid progenitors in RPS19-deficient DBA.

Modification of sialidase levels and sialoglycoconjugate pattern during erythroid and erytroleukemic cell differentiation

Glycosphingolipids and glycoproteins play pivotal roles in the complex series of events governing cell adhesion and signal transduction. Aberrant glycosilation, typical of tumor cells, represents a key event in the induction of invasion and metastasis. Sialidases remove sialic acid residues from sialoconjugates and, in mammals, these enzymes have been proved to be involved in several cellular phenomena, including cell proliferation and differentiation, membrane function, and malignant transformation. Herein we show that only the lysosomal sialidase Neu1 and the plasma membrane-associated sialidase Neu3 are expressed in CFU-E erythroid precursors and K562 erythroleukemic cells. Tumour cells show much higher expression levels than CFU-E cells and, during differentiation, the content of the two enzymes progressively decreases. The sialoglycoconjugate pattern is different in the two cell types. In fact, the differentiating erythroid precursors show an increase of the typical erythrocyte sphingolipids, whereas K562 cells treated with butyrate show a marked increase of GD1a, GM2, PE, and ceramide. Finally, during differentiation the sialoglycoprotein content of erythroid cells shows a marked increase, and in K562 cells the process induces the synthesis of some sialoglycoprotein typical of the erythroid membrane. Overall, these results point out the great differences in sialoglycoconjugate and sialidase patterns exhibited by normal and tumour cells.

Nouveaux critères d’évaluation de la viabilité des hématies destinées à la transfusion

In light of recent results on the mechanism of programmed cell death of human red blood cells (RBC), the aim of the present study was to solve the enigma of the rapid clearance of transfused RBCs.

MATERIALS AND METHODS

We describe new criteria of RBC viability founded on the use of flow cytometry. They were applied, in association with the classical ones: ATP and hemolysis measurements, to RBCs stored in SAGM medium for 42 days.

RESULTS AND CONCLUSIONS

Application of an original method of flow cytometric quantitation of in vitro erythrophagocytosis showed that an important proportion of stored RBCs were phagocytized although the following classical signals for phagocytosis were absent, i.e.: desialylation, phosphatidylserine exposure in the outer leaflet of the RBC membrane, loss of CD47 receptor, an antiphagocytosis signal. In addition, ATP was still present and hemolysis was very low. This enigma was solved by the use of scanning electron microscopy, which showed the disappearance of discocytes and the presence of an important proportion of spheroechinocytes, which are the phagocytable forms of RBCs. The mechanism of this dramatic morphological transformation remains to be elucidated.

Fas transduces dual apoptotic and trophic signals in hematopoietic progenitors

Stem cells and progenitors are often required to realize their differentiation potential in hostile microenvironments. The Fas/Fas ligand (FasL) interaction is a major effector pathway of apoptosis, which negatively regulates the expansion of differentiated hematopoietic cells. The involvement of this molecular interaction in the function of hematopoietic stem and progenitor cells is not well understood. In the murine syngeneic transplant setting, both Fas and FasL are acutely upregulated in bone marrow-homed donor cells; however, the Fas(+) cells are largely insensitive to FasL-induced apoptosis. In heterogeneous populations of lineage-negative (lin(-)) bone marrow cells and progenitors isolated by counterflow centrifugal elutriation, trimerization of the Fas receptor enhanced the clonogenic activity. Inhibition of caspases 3 and 8 did not affect the trophic signals mediated by Fas, yet it efficiently blocked the apoptotic pathways. Fas-mediated tropism appears to be of physiological significance, as pre-exposure of donor cells to FasL improved the radioprotective qualities of hematopoietic progenitors, resulting in superior survival of myeloablated hosts. Under these conditions, the activity of long-term reconstituting cells was not affected, as determined in sequential secondary and tertiary transplants. Dual caspase-independent tropic and caspase-dependent apoptotic signaling place the Fas receptor at an important junction of activation and death. This regulatory mechanism of hematopoietic homeostasis activates progenitors to promote the recovery from aplasia and converts into a negative regulator in distal stages of cell differentiation. Disclosure of potential conflicts of interest is found at the end of this article.

Pharmacodynamics of Recombinant Human Erythropoietin in Murine Bone Marrow

PURPOSE

Originally approved for three times/week dosing, recombinant human erythropoietin (rhEPO) is now often used at weekly intervals. We have studied rhEPO in mice to better understand why the extended dosing interval retains efficacy.

METHODS

C57Bl/6 mice received a single sc. dose of rhEPO (3,000 IU/kg). Bone marrow and blood were collected at 8 h and 1, 2, 5 and 7 days. Staining for TER-119 and CD71, pulse labeling with bromodeoxyuridine, annexin-V binding and vital staining with 7-aminoactinomycin D: were used cell cycle and apoptosis in erythroblasts by four color flow cytometry.

RESULTS

A wave of proliferation and/or maturation progressed through all erythroblasts, resulting in the emigration of immature reticulocytes into the periphery. An increase in the fraction of erythroblasts in S and G2M was found, but suppression of apoptosis was not.

CONCLUSIONS

Most of the effects of rhEPO occurred 48 h after dosing, when the concentration of rhEPO was less than 1% of Cmax, suggesting that the processes set in motion by rhEPO can continue after rhEPO concentrations fall. Our observation of apoptosis in erythroblasts even when rhEPO concentrations were high suggests that regulatory mechanisms which down-regulate erythropoiesis are also engaged.

Stable transcriptional status in the apoptotic erythroid genome

When a cell is destined for apoptosis, will its genome reprogram its transcriptional machinery to overcome the life-threatening challenge? To address this issue, we performed a genome-wide transcriptome analysis in EPO (erythropoietin) deprivation-induced apoptotic erythroid cells using the SAGE method. The results show that the transcript contents for the majority of the genes remain unchanged in the apoptotic cells, including the apoptotic genes and the heat shock genes. Of the small number of genes with an altered expression, they are mainly associated with cellular structure. Our study reveals that there is no genetic reprogramming for the transcriptional machinery in the apoptotic genome. Apoptosis, as defined by programmed cell death, is not a crisis but a peaceful physiological process.

Hematopoietic stem-cell behavior in nonhuman primates

Little is known about the behavior of hematopoietic stem cells (HSCs) in primates because direct observations and competitive-repopulation assays are not feasible. Therefore, we used 2 different and independent experimental strategies, the tracking of transgene expression after retroviral-mediated gene transfer (N = 11 baboons; N = 7 rhesus macaques) and quantitation of the average telomere length of granulocytes (N = 132 baboons; N = 14 macaques), together with stochastic methods, to study HSC kinetics in vivo. The average replication rate for baboon HSCs is once per 36 weeks according to gene-marking analyses and once per 23 weeks according to telomere-shortening analyses. Comparable results were derived from the macaque data. These rates are substantially slower than the average replication rates previously reported for HSCs in mice (once per 2.5 weeks) and cats (once per 8.3 weeks). Because baboons and macaques live for 25 to 45 years, much longer than mice ( approximately 2 years) and cats (12-18 years), we can compute that HSCs undergo a relatively constant number ( approximately 80-200) of lifetime replications. Thus, our data suggest that the self-renewal capacity of mammalian stem cells in vivo is defined and evolutionarily conserved.

A jekyll and hyde role of cyclin E in the genotoxic stress response: switching from cell cycle control to apoptosis regulation

Cyclin E protein levels and associated kinase activity rise in late G(1) phase, reach a peak at the G(1)/S transition, and quickly decline during S phase. The cyclin E/Cdk2 complex has a well-established function in regulating two fundamental biological processes: cell cycle progression and DNA replication. However, cyclin E expression is deregulated in a wide range of tumors. Our recent reports have uncovered a critical role for cyclin E, independent of Cdk2, in the cell death of hematopoietic tumor cells exposed to genotoxic stress. An 18-kD C-terminal fragment of cyclin E, p18-cyclin E, which is generated by caspase-mediated cleavage in hematopoietic cells during genotoxic stress-induced apoptosis has a critical role in the amplification of the intrinsic apoptotic pathway. By interacting with Ku70, p18-cyclin E liberates Bax, which participates in the amplification of apoptosis by sustaining a positive feedback loop targeting mitochondria. This process is independent of p53 function and new RNA or protein synthesis. Therefore, cyclin E emerges as an arbiter of the genotoxic stress response by regulating a finite physiological balance between cell proliferation and death in hematopoietic cells.

Cancer Chemotherapy-Related Symptoms: Evidence to Suggest a Role for Proinflammatory Cytokines

PURPOSE/OBJECTIVES

To provide an overview of the evidence that supports a role for the proinflammatory cytokines interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) in the etiology of cancer chemotherapy-related symptoms.

DATA SOURCES

Electronic nursing, psychology, and medicine databases; online meeting abstracts; and personal experimental observations.

DATA SYNTHESIS

Substantial evidence implicates the proinflammatory cytokines IL-1beta, TNF-alpha, and IL-6 in the etiology of chemotherapy-related anorexia, cachexia, anemia, pain, sleep disturbance, fatigue, and depression.

CONCLUSIONS

Further investigation into the role of these cytokines in the genesis of chemotherapy-related symptoms is warranted. The development of appropriate animal models likely will be key to understanding the relationship among cancer chemotherapy, proinflammatory cytokines, and symptoms.

IMPLICATIONS FOR NURSING

Nurses traditionally have been leaders in symptom management. The symptoms experienced by patients undergoing chemotherapy have a profound negative impact on quality of life and patients' ability to receive prescribed treatments. An understanding of potential mechanisms underlying the physiologic and behavioral consequences of chemotherapy administration will aid nurses in the development of interventions to effectively manage chemotherapy-related symptoms.

A statistical pattern recognition approach for determining cellular viability and lineage phenotype in cultured cells and murine bone marrow

BACKGROUND

Cellular binding of annexin V and membrane permeability to 7-aminoactinomycin D (7AAD) are important tools for studying apoptosis and cell death by flow cytometry. Combining viability markers with cell surface marker expression is routinely used to study various cell lineages. Current classification methods using strict thresholds, or "gates," on the fluorescent intensity of these markers are subjective in nature and may not fully describe the phenotypes of interest. We have developed objective criteria for phenotypic boundary recognition through the application of statistical pattern recognition. This task was achieved using artificial neural networks (ANNs) that were trained to recognize subsets of cells with known phenotypes, and then used to determine decision boundaries based on statistical measures of similarity. This approach was then used to test the hypothesis that erythropoietin (EPO) inhibits apoptosis and cell death in erythroid precursor cells in murine bone marrow.

METHODS

Our method was developed for classification of viability using an in vitro cell system and then applied to an ex vivo analysis of murine late-stage erythroid progenitors. To induce apoptosis and cell death in vitro, an EPO-dependent human leukemic cell line, UT-7(EPO) cells were incubated without recombinant human erythropoietin (rhEPO) for 72 h. Five different ANNs were trained to recognize live, apoptotic, and dead cells using a "known" subset of the data for training, and a K-fold cross validation procedure for error estimation. The ANNs developed with the in vitro system were then applied to classify cells from an ex vivo study of rhEPO treated mice. Tg197 (human tumor necrosis-alpha transgenic mice, a model of anemia of chronic disease) received a single s.c. dose of 10,000 U/kg rhEPO and femoral bone marrow was collected 1, 2, 4, and 8 days after dosing. Femoral bone marrow cells were stained with TER-119 PE, CD71 APC enable identification of erythroid precursors, and annexin V FITC and 7AAD to identify the apoptotic and dead cells. During classification forward and side angle light scatter were also input to all pattern recognition systems.

RESULTS

Similar decision boundaries between live, apoptotic, and dead cells were consistently identified by the neural networks. The best performing network was a radial basis function multi-perceptron that produced an estimated average error rate of 4.5% +/- 0.9%. Using these boundaries, the following results were reached: depriving UT-7(EPO) cells of rhEPO induced apoptosis and cell death while the addition of rhEPO rescued the cells in a dose-dependent manner. In vivo, treatment with rhEPO resulted in an increase of live erythroid cells in the bone marrow to 119.8% +/- 9.8% of control at the 8 day time point. However, a statistically significant transient increase in TER-119(+) CD71(+) 7AAD(+) dead erythroid precursors was observed at the 1 and 2 day time points with a corresponding decrease in TER-119(+) CD71(+) 7AAD(-) Annexin V(-) live erythroid precursors, and no change in the number of TER-119(+) CD71(+) annexin V(+) 7AAD(-) apoptotic erythroid precursors in the bone marrow.

CONCLUSIONS

A statistical pattern recognition approach to viability classification provides an objective rationale for setting decision boundaries between "positive" and "negative" intensity measures in cytometric data. Using this approach we have confirmed that rhEPO inhibits apoptosis and cell death in an EPO dependent cell line in vitro, but failed to do so in vivo, suggesting EPO may not act as a simple antiapoptotic agent in the bone marrow. Rather, homeostatic mechanisms may regulate the pharmacodynamic response to rhEPO.

The chromatin of differentiating erythroblasts is cleaved into large size fragments independent of caspase activated DNase and apoptosis inducing factor

Erythroblast cell differentiation involves self-controlled and limited nuclear proteolysis prior nucleus loss. Early evidence suggests that apoptotic-like pathways are activated during this process. The chromatin of developing erythroblasts becomes fragmented in vivo, however, the exact mechanisms and molecules involved remain elusive. In this study, erythroblasts were differentiated in culture from CD34-enriched umbilical cord blood progenitor cells and the characteristics of DNA fragmentation were examined. This analysis shows that the chromatin of differentiating erythroblasts is cleaved into discrete fragments of 50-200 kb. This process most likely involves one or several endonucleases as we detect in vivo double strand DNA cleavage. However, major players of the apoptotic DNA degradation, caspase activated DNase and apoptosis inducing factor, are not activated in these cells. Therefore, our data suggests that erythroblast chromatin degradation may involve enzymes distinct form those active in apoptotic cells.

Erythropoiesis in multiply injured patients

Posttraumatic anemia in multiply injured patients is caused by hemorrhage, reduced red blood cell survival, and impaired erythropoiesis. Trauma-induced hyperinflammation causes impaired bone-marrow function by means of blunted erythropoietin (EPO) response, reduced iron availability, suppression and egress of erythroid progenitor cells. To treat posttraumatic anemia in severely injured patients, symptomatic therapy by blood transfusion is not sufficient. Furthermore, EPO, iron, and the use of red cell substitutes should be considered. The posttraumatic systemic inflammatory response syndrome (SIRS) induces posttraumatic anemia. Thus, a worsening of SIRS by a "second-hit" through blood transfusion ought to be avoided.

Heat shock protein 70 inhibits the nuclear import of apoptosis-inducing factor to avoid DNA fragmentation in TF-1 cells during erythropoiesis

Loss of mitochondrial membrane potential (DeltaPsi(m)) and release of AIF (apoptosis-inducing factor) from mitochondria are key steps in apoptosis. In TF-1 model, DeltaPsi(m) was depolarized with AIF release during erythroid development. Yet, no DNA fragmentation was observed. When DeltaPsi(m) depolarization had been blocked, erythropoiesis was suppressed. Interestingly, heat shock protein 70 (Hsp70) was found transiently upregulated during depolarization and it retained AIF in the cytosol to avoid DNA damages. When Hsp inhibitor was added, DNA fragmentation occurred. We show this mechanism for the first time in erythropoiesis how cells with DeltaPsi(m) depolarization and AIF release escape apoptosis.

Biochemistry, physiology, and complications of blood doping: facts and speculation

Competition is a natural part of human nature. Techniques and substances employed to enhance athletic performance and to achieve unfair success in sport have a long history, and there has been little knowledge or acceptance of potential harmful effects. Among doping practices, blood doping has become an integral part of endurance sport disciplines over the past decade. The definition of blood doping includes methods or substances administered for non-medical reasons to healthy athletes for improving aerobic performance. It includes all means aimed at producing an increased or more efficient mechanism of oxygen transport and delivery to peripheral tissues and muscles. The aim of this review is to discuss the biochemistry, physiology, and complications of blood doping and to provide an update on current antidoping policies.

Mitochondria in hematopoiesis and hematological diseases

Mitochondria are involved in hematopoietic cell homeostasis through multiple ways such as oxidative phosphorylation, various metabolic processes and the release of cytochrome c in the cytosol to trigger caspase activation and cell death. In erythroid cells, the mitochondrial steps in heme synthesis, iron (Fe) metabolism and Fe-sulfur (Fe-S) cluster biogenesis are of particular importance. Mutations in the specific delta-aminolevulinic acid synthase (ALAS) 2 isoform that catalyses the first and rate-limiting step in heme synthesis pathway in the mitochondrial matrix, lead to ineffective erythropoiesis that characterizes X-linked sideroblastic anemia (XLSA), the most common inherited sideroblastic anemia. Mutations in the adenosine triphosphate-binding cassette protein ABCB7, identified in XLSA with ataxia (XLSA-A), disrupt the maturation of cytosolic (Fe-S) clusters, leading to mitochondrial Fe accumulation. In addition, large deletions in mitochondrial DNA, whose integrity depends on a specific DNA polymerase, are the hallmark of Pearson's syndrome, a rare congenital disorder with sideroblastic anemia. In acquired myelodysplastic syndromes at early stage, exacerbation of physiological pathways involving caspases and the mitochondria in erythroid differentiation leads to abnormal activation of a mitochondria-mediated apoptotic cell death pathway. In contrast, oncogenesis-associated changes at the mitochondrial level can alter the apoptotic response of transformed hematopoietic cells to chemotherapeutic agents. Recent findings in mitochondria metabolism and functions open new perspectives in treating hematopoietic cell diseases, for example various compounds currently developed to trigger tumor cell death by directly targeting the mitochondria could prove efficient as either cytotoxic drugs or chemosensitizing agents in treating hematological malignancies.

Pleiotropic role of histone deacetylases in the regulation of human adult erythropoiesis

Histone acetylation and deacetylation play fundamental roles in transcriptional regulation. We investigated the role of histone deacetylases (HDACs) in human adult haematopoiesis, using the structurally distinct HDAC inhibitors FK228 (depsipeptide) and Trichostatin A. When CD34+ cells were cultured with interleukin (IL)-3 or stem cell factor (SCF) + IL-3, FK228 (0.5 ng/ml) specifically enhanced the generation of immature erythroid cells with a CD36+ glycophorin A (GPA)low phenotype. In semisolid cultures, FK228 promoted the formation of erythroid colonies by CD34+ cells with IL-3 and SCF + IL-3. Furthermore, upon exposure to FK228, CD34+ cell-derived CD36+ GPA- cells were induced to form erythroid colonies with IL-3 alone. Conversely, FK228 inhibited the generation of CD36+ GPAhigh relatively mature erythroid cells from CD34+ cells in the presence of erythropoietin (EPO) and SCF + EPO. FK228 suppressed the EPO-mediated survival of CD36+ GPAlow/- and CD36+ GPAhigh cells and induced their apoptosis. Similar effects were observed for trichostatin A in the generation of erythroid cells in IL-3- and EPO-containing cultures. These data suggest that HDACs negatively regulate the IL-3-mediated growth of early erythroid precursors by suppressing their responsiveness to IL-3, while playing an important role in EPO-mediated differentiation and survival of erythroid precursors. Our data revealed that HDACs have diverse functions in human adult erythropoiesis.

A Role for Heme Oxygenase-1 in the Antioxidant and Antiapoptotic Effects of Erythropoietin: The Start of a Good News/Bad News Story?

Erythropoietin (EPO) is the major regulator of erythropoiesis. EPO's actions have been shown to be antiapoptotic and dependent on JAK2 signaling and Akt phosphorylation. These effects serve as link between EPO and heme oxygenase-1 (HO-1). HO-1 is an inducible enzyme with potent antioxidant and antiapoptotic activities which are regulated by Akt signaling. EPO's ability to alter cellular systems that involve apoptosis and oxidants suggests that EPO treatments are likely to have multiple and different effects which may start a good news/bad news story. Recombinant human EPO is the recognized treatment of choice to address anemia and to stimulate erythropoiesis in chronic renal failure patients, through its antiapoptotic action which likely involves HO-1. On the other hand, EPO treatment to address anemia in cancer patients, while providing significant improvements in cancer patients' quality of life, its effects on survival are equivocal, likely due to its linkage with HO-1. Two clinical trials of EPO in patients with solid tumors have, in fact, shown specific negative effects on survival. However, EPO's effect on tumor growth and survival is not uniformily pro growth and pro survival, as EPO may act synergistically with chemotherapy to induce apoptosis. Finally, compounds have been synthesized that do not trigger EPO receptor and thus may allow experimental distinction and, therefore, at least potentially affect at the clinical level the tissue-protective effects of EPO (e.g., antiapoptosis) without provoking its other potentially detrimental effects.

Immunohistochemical detection of CD 95 (Fas) & Fas ligand (Fas-L) in plasma cells of multiple myeloma and its correlation with survival

Multiple myeloma (MM) is a malignant disease resulting from an uncontrolled proliferation of a neoplastic plasma cell clone in the bone marrow, which might also be induced by the loss of control on apoptosis. Fas ligand (Fas-L), a member of the tumor necrosis factor family, induces apoptosis mediated via its transmembrane death receptor Fas (Apo-1/CD95) antigen. In the present study, immunostaining was performed on the initial diagnostic bone marrow biopsies of 36 MM patients (1 stage I, 5 stage II, 30 stage III), to evaluate the distribution of Fas receptor and Fas-L on malignant plasma cells. Both Fas and Fas-L were positive in 13 cases and negative in 3, whereas 10 cases were Fas-negative, Fas-L-positive and 10 were Fas-positive, Fas-L-negative. Although no association was found between the expression of Fas receptor or Fas-L and overall survival, Fas-L positivity was significantly associated with a shorter event-free survival (p = 0.0335). In this study, it has been shown that the expression of Fas-L, in malignant plasma cells of myeloma patients significantly shortens the event-free survival, indicating that the defect in apoptosis might be associated with disease progression in MM.

Differential expression changes in K562 cells during the hemin-induced erythroid differentiation and the phorbol myristate acetate (PMA)-induced megakaryocytic differentiation

K562 cell line has been used as a model of common progenitor of erythroblasts and magakaryocytes and can be differentiated into erythroid and megakaryocytic lineages by hemin and phorbol myristate acetate (PMA) respectively. We analyzed mRNA expression in un-induced, hemin-induced and PMA-induced K562 cells by differential display reverse transcription polymerase chain reaction (DDRT-PCR) method. 314 differential expression sequence tags (ESTs) were obtained. Among them, 201 ESTs displayed up-regulation and 85 ESTs down-regulation after hemin induction, 186 ESTs showed up-regulation and 72 ESTs down-regulation after PMA induction. The differentially expressed genes included those encoding transcription factors, signaling factors, apoptosis-associated factors and others. 45 of these ESTs stand for genes whose open reading frames were found but whose functions remain unknown. 4 ESTs represent possibly new genes. Furthermore we compared differences of gene expression during hemin-induced erythroid differentiation and PMA-induced megakaryocytic differentiation and found that the expressional changes of some transcription factors and metabolism proteins are the common but the expressional changes of some signal pathways in these two differentiation processes are different. These results suggested that erythroid differentiation and megakaryocytic differentiation are associated in activation and repression of different signal pathways.

New insights into the pathophysiology of cobalamin deficiency

Cobalamin-deficient (Cbl-D) central neuropathy in the rat is associated with a locally increased expression of neurotoxic tumour necrosis factor-alpha (TNF-alpha) and a locally decreased expression of neurotrophic epidermal growth factor (EGF). These recent findings suggest that cobalamin oppositely regulates the expression of TNF-alpha and EGF, and raise the possibility that these effects might be independent of its coenzyme function. Furthermore, adult Cbl-D patients have high levels of TNF-alpha and low levels of EGF in the serum and cerebrospinal fluid. Serum levels of TNF-alpha and EGF of cobalamin-treated patients normalize concomitantly with haematological disease remission. These observations suggest that cobalamin deficiency induces an imbalance in TNF-alpha and EGF levels in biological fluids that might have a role in the pathogenesis of the damage caused by pernicious anaemia.

h-Goliath, paralog of GRAIL, is a new E3 ligase protein, expressed in human leukocytes

In Drosophila, the RING finger protein d-Goliath was originally identified as a transcription factor involved in the embryo mesoderm formation [Bouchard, M.L., Cote, S., 1993. The Drosophila melanogaster developmental gene g1 encodes a variant zinc-finger-motif protein. Gene 125, 205-209]. In mouse, the m-Goliath mRNA level was shown to be increased in growth factor withdrawal-induced apoptosis of myeloid cells [Baker, S.J., Reddy, E.P., 2000. Cloning of murine G1RP, a novel gene related to Drosophila melanogaster g1. Gene 248, 33-40]. Due to its putative function of transcription factor in apoptosis, we cloned the human cDNA for h-Goliath and characterized the expression of the protein in blood and bone marrow cells. The human protein of 419 aa (44 kDa) contains a protease-associated domain, a transmembrane domain and a RING-H2 motif. This structure classifies h-Goliath as a new member of a human family of ubiquitin ligases with GRAIL (gene related to anergy in lymphocytes) as founder. This E3 ligase controls the development of T cell clonal anergy by ubiquitination [Anandasabapathy, N., Ford, G.S., Bloom, D., Holness, C., Paragas, V., Seroogy, C., Skrenta, H., Hollenhorst, M., Fathman, C.G., Soares, L., 2003. GRAIL: an E3 ubiquitin ligase that inhibits cytokine gene transcription is expressed in anergic CD4+ T cells. Immunity 18, 535-547]. In vitro ubiquitination studies support the E3 ubiquitin ligase activity of h-Goliath. In human, the protein is expressed under 3 isoforms, a major one at 28 kDa and two others at 46 and 55 kDa. These proteins come from a common precursor (44 kDa) as we observed using in vitro transcription-translation. Using immunohistochemistry on blood or bone marrow smears, of healthy or leukemia samples, we found that the protein expression was restricted to the cytoplasm of progenitors and fully differentiated leukocyte populations. We did not observe any modification of h-Goliath expression or localization in leukemia. In these cells, this new E3 ubiquitin ligase protein does not seem associated with a differentiation state of the cell or with apoptosis.

A balance between Raf-1 and Fas expression sets the pace of erythroid differentiation

Normal erythropoiesis critically depends on the balance between the renewal of precursor cells and their differentiation. If the renewal phase is shortened, the decrease in the precursor pool results in anemia; conversely, impaired differentiation increases the number of proliferating progenitors and the potential risk of leukemic transformation. Using gene ablation, we have discovered 2 self-sustaining signal transduction loops that antagonize each other and regulate erythroid progenitor proliferation and differentiation, respectively. We identify Raf-1 as the main activator of the MEK/ERK cascade and as the key molecule in maintaining progenitor proliferation. Differentiation, in contrast, is mediated by Fas via the activation of both the ASK1/JNK/p38 module and the caspase cascade. The point of convergence between the 2 cascades is activated ERK, which positively feeds back on the proliferation pathway by maintaining the expression of Raf-1, while inhibiting the expression of Fas and therefore differentiation. In turn, Fas, once expressed, antagonizes proliferation by exerting a negative feedback on ERK activation and Raf-1 expression. Simultaneously, Fas-mediated caspase activation precipitates differentiation. These results identify Raf-1 and Fas as the key molecules whose expression finely tunes erythropoiesis and the extent of ERK activation as the switch that tips the balance between them.

Erythropoietin activates caspase-3 and downregulates CAD during erythroid differentiation in TF-1 cells - A protection mechanism against DNA fragmentation

The involvement of caspase-3 and its failure in the induction of DNA fragmentation during erythropoiesis were investigated with TF-1 cells. During erythroid differentiation, caspase-3 activation and cleavage of caspase-3 substrates such as ICAD (inhibitor of caspase-activated DNase) were detected without concomitant phosphatidyl-serine (PS) externalization and DNA fragmentation. These observations are in contrast to our understanding that DNA is degraded by CAD (caspase-activated DNase) when ICAD is cleaved by caspase-3. Our study demonstrates that CAD is downregulated at the mRNA and protein level during the erythroid differentiation in TF-1 cells. This provides a mechanism for the first time how cells avoid DNA fragmentation with activated caspase-3.