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Multiple sclerosis (MS) is a complex human autoimmune-type disease with a predominantly unknown etiology. Immunologic destruction of myelin basic protein (MBP) throughout the nervous system is the major pathology of multiple sclerosis. This review will attempt to update new information about basic mechanisms and therapeutic management of the disease. The significance of the structure of MBP is discussed with respect to the contribution of such structures to the disease process. A number of MBP peptides that serve as the immunodominant antigens in MS patients have been identified. These peptides have been studied in animal models for their antigenic characteristics and ability to induce disease. Evidence for genetic contributions is reviewed with multigenerational twin studies providing the best evidence for susceptible haplotypes. The role of microorganisms/viruses and environmental agents are discussed as potential etiological factors but are now thought to be of minor importance to the primary causal development of the disease. Of major consideration are immunological mechanisms that contribute to the development of autoimmunity. In particular, antigen expression, cytokine and leukocyte interactions, and regulatory T-cells are discussed. Particular attention is given to regulatory T-cells (Treg), which help balance/modulate other T-cells such as Th1 and Th2 cells, and how such Treg regulate autoimmunity is addressed. The importance of the role of Tregs is exemplified by the demonstration that administration of oral antigens can induce specific Tregs that counteract experimental autoimmune encephalomyelitis in animal models. The significance of animal studies to human multiple sclerosis is discussed. A potential role for natural antibodies and innate immune mechanisms to help provide resistance to disease development is also reviewed. Finally, a variety of therapeutic agents that have been and continue to be utilized for multiple sclerosis is reviewed. Trials with oral antigens, such as glatirmer acetate (copolymer 1) especially in combination with interferon-β, have shown promise. Antibody therapy and bone marrow transplantation are also briefly discussed.

We determined the in vivo ability of infused human recombinant hemoglobin 1.1 (hr-Hb) and erythropoietin to rescue the hematopoietic activity from the suppressive effects of AZT in normal and in a murine model of AIDS (MAIDS) mice. Mice were fed with AZT for 8 weeks with or without treatment in the last 4 weeks by administering various concentrations of hr-Hb and/or erythropoietin (Epo). Blood parameters, body weight (BW) and erythroid burst-forming units (BFU-E) for all mice were determined. AZT-treated normal and MAIDS mice showed a significant decrease in hematocrit (64 and 78.1%), hemoglobin (27.2 and 45.5%), BW (17.5 and 35.5%), number of white (66.9 and 42.1%) and red blood cells (65.5 and 38%), and the number of BFU-E (73 and 59%), whereas the AZT-treated normal and MAIDS mice that received hr-Hb (5 mg/kg BW/day) and/or Epo (2 U/mouse/day) showed significant alleviation of AZT cytotoxicity. This was evident by the recovery in all blood indices examined, the number of BFU-E and the BW of mice treated. BFU-E recovery in MAIDS (97%) was greater than that in normal mice (63%) as compared to their controls. hr-Hb produced a similar response as the combination, however recovery was slightly better with the latter in some hematological parameters. Higher concentrations of hr-Hb (10-15 mg) did not result in a more significant increase in most blood indices. Our results indicate that infusion with hr-Hb can alleviate AZT toxicity in normal and in immunodeficient mice, and that hr-Hb may be clinically useful in preventing severe bone marrow depression brought about by various drugs or agents such as AZT.

A leukemoid reaction occurs after inoculation of L1210 leukemic cells into recipient mice and the degree of granulocytosis is correlated with tumor progression. It was found that the sera of leukemic mice contained elevated levels of colony stimulating activity (CSA) when compared with normal mouse sera. Media conditioned by L-1210 cells in vitro (L-1210-CM) contained CSA which stimulated normal bone marrow myeloid colony growth and an auto-stimulatory activity (ASA) which stimulated L-1210 cell proliferation. We studied the effects of trans -retinoic acid (RA) and 1,25 dihydroxyvitamin D3 (VD3) on the production of growth substances by L1210 cells. When L1210-CM was prepared in the presence of RA and VD3, the CSA and ASA were markedly inhibited. A combination of the two agents was more effective than either agent. Mice inoculated with 1 × 10 5 L1210 suspension culture cells treated with either agent or both combined survived significantly longer than controls. Mice inoculated with L1210 cells treated with the two agents combined survived longest. By using antibodies, preliminary analysis of growth substances generated in L1210-CM showed that it contains primarily GM-CSF and M-CSF-like activities which were distinct from ASA. Combination antibody titer assays revealed that ASA was not significantly inhibited with anti-GM-CSF and anti-M-CSF antibodies, while CSA was inhibited by between 61 and 84%. We conclude that RA and VD3 synergistically inhibit the release of growth-enhancing substances by L1210 cells which may reduce the growth advantage of leukemic cells and the resulting leukocytosis in lymphocytic leukemia.

We studied the toxic effects of azidothymidine (AZT) on the hemopoietic colony growth (CFU-E, BFU-E and CFU-GM) of bone marrow in a murine model of AIDS (MAIDS). A sparing effect by recombinant hemoglobin (r-Hb) on AZT suppression of MAIDS bone marrow was found when 10 microM of r-Hb was included in bone marrow cultures. The AZT toxicity dose response curve showed that at a concentration of 0.1 microM, AZT inhibited CFU-E by 66%, BFU-E by 55% and CFU-GM by 67%. The addition of r-Hb (10 microM) to AZT-treated cultures stimulated CFU-E, BFU-E and CFU-GM by 89, 125 and 160%, respectively, as compared with AZT-treated (control). The addition of r-Hb to non AZT-treated cultures showed further stimulation of CFU-E, BFU-E and CFU-GM to 100, 160 and 187% of the control, respectively. These results indicate that exogenous r-Hb reverses AZT-induced hemopoietic toxicity and may prove to be useful in ameliorating AZT toxicity in immunosuppressive diseases.

The ability of combination treatment with erythropoietin (Epo) and heme to rescue hematopoietic activity in mice from the suppressive effect of azidothymidine (AZT) was determined. Exposure of mice to AZT for 5 weeks produced marked anemia, thrombocytopenia, neutropenia, and weight loss, whereas mice that received Epo and heme for 3 subsequent weeks showed significant alleviation of AZT cytotoxicity. Treatment with Epo (10 U for 5 times/week) stimulated hematopoietic recovery in the AZT- treated animals and reduced the severe anemia and thrombocytopenia by 3 weeks. Administration of a lower Epo dose (1 U Epo) resulted in only a modest retardation of AZT-induced anemia, although, when combined with heme, there was a great improvement in recovery of erythropoiesis. The combination of heme with Epo (10 U) produced the optimum response, resulting in almost normal recovery of bone marrow cellularity as well as recovery of burst-forming units-erythroid (BFU-E) and splenic hematopoietic progenitor content (colony-forming unit-spleen [CFU-S]) by the end of 3 weeks of post-AZT treatment. Treatment with heme alone markedly enhanced the recovery of BFU-E and CFU-S, as well as body weight post-AZT; however, this recovery was not to the extent seen in combination with Epo (10 U). Long-term bone marrow cultures (LTBMCs) established from mice exposed to AZT for 8 weeks showed a marked reduction in cellularity and this was completely alleviated when mice received heme and Epo (10 U) for 3 weeks after 5 weeks of AZT administration. The additive effect of heme and Epo was seen in BFU-E production, as well as in CFU-S production, in LTBMCs. Thus, heme exerts a significant protective effect on hematopoietic progenitors in vivo and may be of potential clinical use in combination with Epo to promote effective erythropoiesis in the setting of AZT therapy.

Exposure of Hep3B cells to metalloporphyrins (tinprotoporphyrin and heme) or cobalt chloride resulted in the production of a significant number of heme oxygenase transcripts, erythropoietin transcripts or both, as indicated by in situ hybridization. Exposure to heme 10 μmol/L resulted in a 30-fold to 40-fold increase in cells expressing erythropoietin messenger RNA (erythropoietin-positive cells) by 6 hr; this increased level remained elevated for 24 hr. Tin-protoporphyrin (10 μmol/L) produced an eightfold to 10-fold increase in erythropoietin RNA within 40 min. This value then returned to control levels by 60 min. Exposure to cobalt chloride (100 μmol/L) resulted in a 20-fold to 30-fold increase in erythropoietin expression for 5 to 20 min, returning to control by 40 min. Additionally, nuclear runoff assays demonstrated that the increase in heme oxygenase or erythropoietin messenger RNA accumulation by cobalt chloride appeared to be a result of stimulated transcription of the heme oxygenase and erythropoietin genes. However, the pattern for heme oxygenase messenger RNA induction was different from that for erythropoietin expression. Heme produced an immediate expression of heme oxygenase RNA (50-fold within 5 min) and a second sustained response during the next 24 hr. Tin-protoporphyrin also produced an immediate response (40-fold within 5 min) and remained elevated (20-fold) for 6 hr. Cobalt chloride produced a 22-fold increase within 20 min and returned to the control value by 1 hr. Thus both erythropoietin and heme oxygenase genes appear to be expressed after treatment with tin-protoporphyrin, heme or cobalt chloride; however, the time and patterns of expression are different. The most significant feature of coexpression appears to be that induced by heme, where heme oxygenase is immediately expressed (5 min) with a second sustained expression during the next 10 to 24 hr, whereas erythropoietin sustained expression for 3 to 24 hr. (HEPATOLOGY 1993;17:861–868.)

Previous results have demonstrated links between cell-mediated immunity, interferon (IFN)-gamma and neopterin production with heme, porphyrins, and iron metabolism. In this study, we compared the effects of heme, several metalloporphyrins, protoporphyrin IX, and iron on the signal or IFN-gamma-mediated pathways, such as the expression of major histocompatibility complex class II antigens, neopterin formation, and the degradation of tryptophan. Using the human monocytic cell line, THP-1, we found that heme, Zn-mesoporphyrin, Zn-deuteroporphyrin, Co-protoporphyrin, and iron reduced the efficiency of the IFN-gamma signal. In addition, Zn-mesoporphyrin almost fully inhibited IFN-gamma-induced degradation of tryptophan by the heme protein, indoleamine 2,3-dioxygenase. In contrast, tin-protoporphyrin enhanced the IFN-gamma effects as seen by increased neopterin production, enhanced tryptophan degradation, and elevated HLA-DR antigen expression on cells. These effects are considered to be due to the action of heme, metalloporphyrins, iron, or heme byproducts on the IFN-gamma signal, rather than to direct effects on IFN-gamma-induced enzymatic pathways. Heme and metalloporphyrins were previously shown to affect heme oxygenase activity, T cell growth, and lipid peroxidation and to modulate interleukin 2 activity. These pathways are also known to be influenced by IFN-gamma, and our data suggest that heme and metalloporphyrins may directly modulate the efficiency of the IFN-gamma signal.

In this study we report on the establishment of novel conditions which permit efficient ret-rovirus-mediated gene transfer of human adenosine deaminase (ADA) into murine hematopoietic progenitors. Using Southern blot analysis and an ADA probe, we demonstrated that prestimulation of bone marrow cells over an in vitro culture of adherent stromal cell layers (ACLs) for two days provides favorable conditions for gene transfer in the absence of exogenous growth factors. In bone marrow transplant recipients reconstituted with retrovirally-marked cells, ADA was detected in spleen, thymus and bone marrow cells of the recipients eight months after transplantation. These observations were also seen in transplants of embryonal hematopoietic stem cells. By using different incubation protocols, it was found that the developmental fate of hematopoietic stem cells varied with the presence of exogenous growth factors or an ACL in the prestimulation phase. Poly-clonal hematopoiesis with multiple clones appearing simultaneously was revealed in mice reconstituted with growth factor-stimulated cells four months after transplantation. This was detected by multiple integration patterns of ADA integration into the genomes of individual colony forming units-spleen (CFU-S) in transplantation recipient mice. In contrast, two to five months after transplantation, polyclonal hematopoiesis was not observed in mice reconstituted with cells infected in the absence of growth factors. It appears that utilization of the bone marrow micro-environment through the use of an ACL results in a narrower spectrum of integration patterns, suggesting that a type of oligoclonal or monoclonal hematopoiesis is occurring. These studies demonstrate that an ACL provides novel conditions for successful gene transfer and stable integration of the vector into the genome. Use of an ACL may be advantageous for successful hcmatopoietic stem cell gene therapy.

In situ hybridization and Northern analysis of heme oxygenase (HO) mRNA was used to determine the induction and expression of HO by various environmental agents. Exposure of Hep3B cells to hemin (10 microM) for as little as 5 min resulted in significant production of HO transcripts and mRNA expression as seen by in situ hybridization. We followed the pattern of HO transcript accumulation by heme and results indicate that the peak of induction of HO by heme was reached between 10 and 20 minutes. Other metalloporphyrins were all effective in inducing HO mRNA after 1 h exposure. On the other hand, CoCl2 caused accumulation of HO mRNA at a later time than seen with the metalloporphyrins. However, lipopolysaccharide (LPS) gave a more immediate effect on HO induction which was somewhat similar to heme in its time course. Direct measurements of HO activity revealed that enzyme activity could be detected after about 20 min exposure to hemin, and this activity was inhibited by tin protoporphyrin (SnPP). The different pattern of HO mRNA induction by LPS as contrasted with CoCl2 suggests that LPS may act through a different translational factor, or stimulate free radical formation and the subsequent release of heme and induction of HO. These results indicate that heme causes accumulation of HO mRNA by a different mechanism than that of CoCl2. Finally, LPS shares a concomitant effect on induction of HO as an acute phase reactant type protein.

In the hematopoietic system the adherent stromal cells produce cytokines necessary for proliferation and differentiation of hematopoietic cells. In the present study, we showed the ability of adherent stromal cells to generate novel metabolites of arachidonic acid via the NADPH-cytochrome P450-dependent monooxygenase system. These metabolites were recovered in the incubation media, suggesting their release from cells. The formation of arachidonic acid metabolites was inhibited by 7-ethoxyresorufin and SKF-525A, but not by indomethacin or BW-755C. By using two-step high-pressure liquid chromatography (HPLC), bone marrow-adherent stromal cells and incubation media showed the presence of metabolites in a peak eluted at 19 to 20 minutes. The isolated HPLC peak was used to measure its effect on colony-forming unit-erythroid (CFU-E) growth and compare it with that of synthetic cytochrome P450 arachidonate metabolites, 19- and 20- hydroxyeicosatetraenoic (HETE) acid. These bone marrow cytochrome P450 arachidonic acid metabolites at picomolar concentration potentiated erythropoietin (Epo)-induced CFU-E growth by fourfold to sixfold. Addition of 19- and 20-HETE to the bone marrow culture resulted in a potentiating effect on CFU-E number in a dose-dependent manner. 20-HETE was much more potent in stimulating CFU-E growth than 19-HETE at a similar concentration of 10(-11) mol/L. The potentiating effect of 20- HETE resulted in a shifting to the left of the dose-response curve to Epo. To substantiate the finding of an active NADPH-dependent cytochrome P450-metabolizing system, we further examined the ability of adherent cells to metabolize exogenous pharmacologic compounds such as benzo(a)pyrene, a substrate for the heme-cytochrome P450 system, aryl hydrocarbon hydroxylase. The adherent stromal cytochrome P450 metabolizes benzo(a)pyrene at comparable levels to blood vessel endothelial cells. These novel observations underscore the importance of adherent stromal cytochrome P450 to metabolize endogenous substrates, including arachidonic acid, to compounds that may interact in a paracrine manner with Epodependent hematopoietic cells.

Heme (ferroprotoporphyrin IX) is a ubiquitous molecule that serves as the prosthetic group of a variety of important hemoproteins that are essential for hemopoietic processes. Heme is involved in oxygen transport as the prosthetic group of hemoglobin, in prostaglandin synthesis as the prosthetic group of cyclooxygenase, in the enzymatic decomposition of H2O2 as the prosthetic group of catalase and peroxidase, and in the inactivation of oxygen molecules, as the prosthetic group of mitochondrial and microsomal cytochrome P-450. The latter refers to a family of isozymes for which heme serves as the prosthetic group that oxidizes a wide variety of structurally unrelated compounds, inactivates leukotrienes (leukotriene B4), and metabolizes arachidonic acid (AA) to bioactive metabolites, some of which are involved in the signal transduction process for hematopoietic growth factors. However, the effect of heme on erythropoiesis appears to be distinct from its direct involvement as a prosthetic group.The expressi...

Anemia is a common characteristic of lymphoproliferative disorders (LPD) and the impairment of blood formation in these disorders is not fully understood. Heme synthesis and the heme degradative enzyme heme oxygenase are critical to hematopoietic differentiation and disturbances may contribute to anemic states. Tin protoporphyrin (SnPP) is a potent inhibitor of heme oxygenase, and has proven to be a useful clinical agent. Bone marrow cells from seven patients with LPD were studied for their in vitro hemopoietic response to growth factors and SnPP. Heme oxygenase mRNA levels were determined by Northern blot analysis of bone marrow samples. Quantitation of hematopoiesis in cultures with erythropoietin or GM-CSF revealed adequate CFU-E, BFU-E and CFU-GM growth by LPD bone marrow. Inclusion of 10 μM SnPP in cultures was found to significantly enhance CFU-E/BFU-E growth by LPD marrows, whereas Zinc protoporphyrin had a marked inhibitory effect. Little or no effect by SnPP was seen on CFU-GM. In contrast, normal bone marrow cultures failed to show an enhanced response to 10 μM SnPP. Analysis of heme oxygenase mRNA levels revealed that LPD marrows had elevated expression of heme oxygenase mRNA as contrasted with normals. Furthermore, measurements revealed that heme oxygenase activity was markedly suppressed by SnPP in the LPD bone marrow cultures. Results lend further support to the importance of heme oxygenase in the differentiation process. Although LPD bone marrow cells may respond to erythropoietin in vitro, in stressed conditions where heme oxygenase is elevated, suppression of heme oxygenase may potentiate the erythropoietic response in this disease.

The ability of peripheral-blood hematopoietic progenitor cells from AIDS patients and normal controls to respond to erythropoietin (Epo) was assessed for burst-forming units-erythroid (BFU-E). BFU-E colony formation from AIDS patients' peripheral blood responded to a wide range of Epo concentrations (0.5-4 U) in a similar manner as erythroid progenitors obtained from normal peripheral blood. The optimum dose response of BFU-E to Epo was 2 U which resulted in generation of 71 +/- 4 BFU-E in AIDS patients (n = 10), as compared to 77 +/- 5 BFU-E in normal donors (n = 3). The optimum concentration range of hemin enhancement of erythroid progenitor BFU-E was 10-50 microM. In all instances, Epo was essential for BFU-E growth. Inclusion of hemin at a concentration of 10 microM in AIDS patients' peripheral-blood erythroid progenitor cells resulted in enhancement of BFU-E by 136-215%. Similarly, inclusion of hemin (10-100 microM) in normal bone marrow erythroid progenitor cell cultures resulted in enhancement of BFU-E. Inclusion of an equivalent amount of iron or tin protoporphyrin to progenitors cells from AIDS patients' peripheral blood had no effect on the number of colonies observed. On the other hand, inclusion of another heme analogue, zinc protoporphyrin, in AIDS or normal cultures resulted in a 50% suppression of BFU-E colony formation. These results demonstrate that peripheral-blood mononuclear cells from AIDS patients retain the capacity to generate erythroid precursors such as BFU-E in the presence of Epo, and that hemin has a specific enhancement effect on growth of BFU-E colony formation obtained from peripheral blood or bone marrow cells.

The human monoblast cell line, U937, was employed to elucidate early events associated with differentiation induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) and 1,25-dihydroxy-Vitamin D3 (VD3). Exposure of cells to a combination of GM-CSF and VD3 resulted in an up-regulation of c-fos mRNA within 1 h and a marked down-regulation of c-myc mRNA by 24 h and this was associated with a shift of cell population from the S phase to the G0 + G1 phase of the cell cycle by 18%. This was followed by a marked enhancement of monocyte-associated cell surface antigens [OKM1 (CD11b), LeuM3 (CD14), M77.7], as determined by monoclonal antibodies and flow cytometry. Functional characteristics such as nitroblue-tetrazolium reduction, alpha-naphthyl butyrate esterase activity, and phagocytic capability occurred. Cells treated with GM-CSF or VD3 alone showed only minor changes. These results demonstrate a potent synergistic effect of GM-CSF and VD3 on induction of U937 differentiation. This differentiation was partially blocked by H7, a protein kinase C (PKC) inhibitor. Changes in c-myc and c-fos mRNA expressions and a shift in cell cycle were shown to be early events in this process.

We studied the effects of azidothymidine (AZT) on rat bone marrow heme metabolism and colony growth as determined by assays of granulocyte-macrophage (CFU-GM), erythroid (CFU-E), burst-forming erythroid (BFU-E), and alpha-aminolevulinic acid synthase (ALAS), the first enzyme in the heme pathway. In all cases, AZT (1-0.01 microM) was found to be toxic to bone marrow colony growth. When AZT was included in colony assays, 1 microM resulted in 98-100% inhibition, whereas lower concentrations (0.01 microM) inhibited growth by 58-76%. In addition, cultures from AZT-treated animals had a marked reduction in colony growth as compared with sham controls. In most cases, hemin (10(-5) M) was found to overcome some of the colony inhibitory effects of AZT. Analysis of heme metabolism indicated that ALAS activity was reduced by 71% in bone marrow cells from treated animals. ALAS activity for control was 204 +/- 33 pM ALA formed/4 X 10(6) cells/hr, whereas ALAS activity from AZT-treated animals was only 60 +/- 3 pM ALA formed/4 x 10(6) cells/hr. It is considered that AZT toxicity may be due to a depression in the pool of available heme, which is required for adequate hematopoiesis.

The cytokine network plays an important role in the growth and differentiation of normal and leukemic cells. Stimulation of this network, which has positive and negative regulators, results in the induction or inhibition of certain hematopoietic events. A cytokine can have multiple effects on various cell types, and combinations of cytokines with each other or with other exogenous substances produce more pronounced effects than any cytokine or agent individually. The mechanisms by which cytokines affect normal and leukemic cell growth and viability may vary depending on the target cell or the cytokine(s) in question. Diseases such as leukemia may result from abnormalities in the cytokine network or their receptors. Cytokines play a major role in leukemogenesis. Normally, hematopoietic cells require certain cytokines for their viability and growth. When the viability factors are withdrawn, apoptotic cell death naturally occurs. Prevention of programmed cell death by the abnormal production of a cytokine may release the cell from normal growth control leading to malignant transformation. Disregulation of genes for hematopoietic growth factors and their receptors may be one of the events that leads to leukemogenesis through an aberrant autocrine growth mechanism. However, cytokines have been used as therapeutic agents in various ways. Differentiation therapy has been widely investigated and proven effective in certain types of cancer. Gene therapy, where the cytokine cDNA is used to reduce tumorigenicity and/or increase immunogenicity is promising. Another kind of therapy using alkylated growth factors has been under focus. This review summarizes the actions and interactions of cytokines that are related to leukemic cell viability and growth. The use of cytokines as therapeutic agents is also discussed.

Gene transfer or gene therapy has advantages in the treatment of a variety of disorders due to its selective expression within specific mammalian cells. IFN-alpha has been used in the management of leukemia, and gene transfer of the IFN-alpha gene into hematopoietic progenitor cells may have great potential for the treatment of chronic myelogenous leukemia (CML). Therefore, we examined the ability of adenovirus (Ad)-IFN-alpha gene construct to transfect normal bone marrow hematopoietic CD34+ stem cells and the production of IFN-alpha protein by these cells. Ad-cytomegalovirus (CMV) promoter-driven IFN-alpha at multiple doses was assessed to transfect highly purified CD34+ cells in liquid culture. Optimal transduction of CD34+ cells with the AdCMV-IFN-alpha construct was achieved using 120 plaque forming units (pfu). Flow cytometric determinations revealed that there was no significant difference in CD34+ cell viability for the 8 or 12-h transfection periods. Immunoassay of IFN-alpha produced by CD34+ cells shows that IFN-alpha levels increased several fold in transfected cells and this was not seen in CD34+ cells transfected with the heme oxygenase gene (HO-1). These in vitro data suggest that adenovirus-mediated gene transfer of IFN-alpha into hematopoietic stem cells can be achieved and that the IFN-alpha protein is produced by viable CD34 progenitor cells.

Gene transfer or gene therapy has advantages in the treatment of a variety of disorders due to its selective expression within specific mammalian cells. Interferon-alpha (IFN-alpha) has been used in the management of leukemia but its diverse adverse activities with multiple potential side effects, possibly unrelated to therapeutic targets, may negatively influence the ability of IFN-alpha to treat this disorder. Therefore, we examined the ability of adenovirus (Ad)-IFN-alpha gene construct to transfect normal (CD34+ cells) and chronic myelogenous leukemia (CML) bone marrow mononuclear cells (BMMNC) and the transient overexpression of IFN-alpha in these cells. Ad-cytomegalovirus promoter driven IFN-alpha (AdCMV-IFN-alpha) at multiple doses was assessed to transfect highly purified CD34+ cells in liquid culture, and optimal transduction of CD34+ cells was achieved using 120 plaque forming units. Flow cytometric determinations revealed that there was no significant difference in cell viability for the 4 h or 24 h transfection periods. Immunoassay of IFN-alpha produced by CD34+ cells shows that IFN-alpha levels increased several fold in transfected cells. Transient expression of the IFN-alpha gene did not suppress proliferation of CD34+ progenitors as indicated by BFU-E or colony forming units-granulocyte-macrophage (CFU-GM) growth. Reverse transcriptase/polymerase chain reaction analysis of RNA from CD34+ harvested CFU-GM progenitor cells demonstrated transient IFN-alpha mRNA expression. Similarly, CML BMMNC were transfected with AdCMV-IFN-alpha under similar conditions as described for CD34+ cells. BMMNC cells exposed to adenovirus for 24 h and 48 h were found to express IFN-alpha at a substantial level. This in vitro data suggest that Ad-mediated gene transfer of IFN-alpha into hematopoietic stem cells can be achieved and that the IFN-alpha gene can be translated into its specific mRNA in CD34 progenitor cells.

The role of iron and heme was examined in bone marrow cells from iron-deficient and chronically iron-overloaded rats. Erythroid colony cultures (CFU-E) demonstrated that iron-overloaded bone marrow cells were poor hemin (iron carrier) and CFU-E responders in vitro, whereas iron-deficient marrows grew exuberant numbers of CFU-E and responded to hemin. Results support the concept that iron, or associated factors, plays an important role in the manipulation of HO activity which modulates the hemopoietic potential of the organism. Using cultures of erythroid (CFU-E, BFU-E) and myeloid (CFU-GM), results demonstrated that exogenous hemin (iron carrier) has a specific beneficial effect on human bone marrow progenitor cells, which is not seen with iron (10(-4)M) or other metalloporphyrins. Higher concentrations of iron (10(-3)M) and ZnPP were in fact inhibitory to bone marrow growth. This inhibition was not reversed with higher concentrations of Epo or GM-CSF. The beneficial effect of iron may be best realized in the bound form such as heme. In addition, the effect of bound and nonbound iron was tested for its effect on gene transfer. By using a murine adherent cell layer (ACL) in a prestimulation phase, followed by human gene transfer of ADA into mouse bone marrow cells and Southern blot analysis, successful gene transfer was accomplished. ADA integration patterns were detected in CFU-S from stem cells of mice 5-11 months after transfer. When 10 microM ferric chloride was included in the ACL prestimulation phase, there was a marked depression in ADA integration into stem cells as compared to heme or non-heme controls. Furthermore, heme-bound iron had no effect and deferoxamine included with iron was able to reverse the inhibitory effect of iron on the gene transfer process. Thus, iron must be non-bound to exert its suppressive effect, and chelation of excess iron under clinical conditions of iron overload may be essential for successive gene transfer.

The role of iron and heme was examined in bone marrow cells from iron-deficient and chronically iron-overloaded rats. Erythroid colony cultures (CFU-E) demonstrated that iron-overloaded bone marrow cells were poor hemin (iron carrier) and CFU-E responders in vitro, whereas iron-deficient marrows grew exuberant numbers of CFU-E and responded to hemin. Results support the concept that iron, or associated factors, plays an important role in the manipulation of HO activity which modulates the hemopoietic potential of the organism.

Results from this study show that a combination of heme and interleukin-1 (IL-1) treatment resulted in the most improved recovery of hematopoietic-stromal regeneration after sublethal irradiation. Less pronounced effects were obtained when heme or IL-1 were given singly. Sublethal irradiation of mice produced an initial (as early as day 1) intense depression of the hematopoietic system as evidenced by leukopenia. In vivo treatment of animals with heme in combination with IL-1, accelerated hematopoietic and stromal regeneration as determined by hematopoietic spleen colony forming unit assay (CFU-S), erythroid (BFU-E), myeloid (CFU-GM) clonal cultures, long-term bone marrow cultures (LTBMC), and the ability to regenerate hematopoiesis by ectopic (renal) stromal hemopoietic transplantation. Sixteen days after irradiation, leukocyte levels in heme and IL-1 treatment groups were higher than non-treated animals and were near normal values by 27 days. One day after irradiation, the capacity of stromal progenitors to form new bone and hematopoietic cells (ectopic foci) was severaly impaired, but recovered after 2–4 weeks. This recovery process was accelerated in heme and IL-1-treated animals. BFU-E, CFU-GM, and CFU-S capacity was also severely impaired in all animals 1–27 days after irradiation. CFU-S was only 0.15% of control by day 1 and 5% of control by day 16. Treatment with heme or IL-1 improved recovery by as much as 70% after 27 days of irradiation. A similar but enhanced recovery was seen for BFU-E and CFU-GM, with erythroid recovery the best. Total cellularity, adherent cell layer (ACL) formation, and donogenic capacity by LTBMCs (10 weeks) derived from irradiated animals was severely reduced, whereas the hematopoietic capacity by LTBMCs derived from heme- and IL-1-treated animals had recovery values similar to non-irradiated controls. These results suggest therapeutic use of heme and IL-1 after chemotherapy or bone marrow depression may be beneficial. © 1993 Wiley-Liss, Inc.

The strong and long-lasting hematotoxic effect after benzene exposure in vivo (300 ppm, 6 hours/day, 5 days/week for 2 weeks) was assessed in mice with bone marrow cells grown in long-term bone marrow culture (LTBMC). Bone marrow cultures initiated 1 day after the last benzene exposure did not produce adequate numbers of hematopoietic cells over 3 weeks and, in most cases, no erythroid or myeloid clonogenic cells could be recovered. The adherent cell layer of these cultures had a lower capacity for supporting in vitro hematopoiesis after the second seeding with normal bone marrow cells compared with control cultures. Two weeks after the last benzene exposure, body weight, hematocrit, bone marrow cellularity, and committed hematopoietic progenitor content (BFU-E and CFU-GM) were regenerated to normal or subnormal values, whereas hematopoiesis in LTBMC was very poor. Over 8 weeks, little or no significant committed progenitor production was observed. Treatment of mice exposed to benzene with hemin (three doses of 3 micrograms/gm body wt, iv, over 2-week for a total dose 9 micrograms/gm) partially overcame the toxic effect of benzene on the hematopoietic system as measured by the LTBMC method. Cultures from mice treated with hemin had modest recovery of BFU-E and CFU-GM clonogenic potential after 5 to 6 weeks in LTBMC. In contrast, little or no recovery was obtained for the adherent cell layer clonogenic capacity, even after hemin treatment. These results clearly indicate a strong, long-lasting toxic effect on the bone marrow stroma and a limited recovery of hematopoietic potential by clonogenic cells of the nonadherent population after in vivo hemin treatment.

The toxicity of azidothymidine (AZT) was studied on normal human bone marrow hemopoietic colony growth as determined by assays of CFU-E, BFU-E, and CFU-GM. The potential sparing effect of hemin and heme analogues on AZT-suppressed bone marrow was also investigated. AZT at a lower concentration (0.1 mumol/L) inhibited CFU-E by 68%, BFU-E by 84%, and CFU-GM by 59%. AZT at a higher concentration (1.0 mumol/L) inhibited CFU-E by 88%, BFU-E by 90%, and CFU-GM by 69%. Addition of hemin (10 mumol/L) to cultures containing AZT (0.1 mumol/L) increased CFU-E growth by 279%, BFU-E by 282%, and CFU-GM by 72%. A similar concentration of heme analogues did not have an enhancing effect; in contrast, zinc protoporphyrin (ZnPP) was inhibitory to bone marrow progenitors CFU-E, BFU-E, and CFU-GM. In addition, no enhancement of colony growth was obtained when progenitor cells were cultured in the presence of 10(-2)-10(-5) M iron. These results demonstrate that exogenous hemin has a specific beneficial effect on human bone marrow hematopoietic progenitor cells which is not seen with iron or other metalloporphyrins. Furthermore, this beneficial effect includes a reversal of the cytotoxic effect of AZT on bone marrow progenitors.

The effect of various concentrations of exogenous hemin on cellularity and hemopoietic clonal potential of cells maintained in murine long-term marrow cultures (LTBMC) was studied. Hemin, at concentrations of 1 and 10 microM, was added weekly to LTBMC and was found to produce a significant increase in cellularity for up to 8 weeks in culture. Lower concentrations of hemin (0.1 microM) were more effective for sustained cellularity in older cultures (10-12 weeks). Prior exposure of the adherent cell layer to high concentrations of hemin (10 microM) was found to have a beneficial effect on the support of newly seeded cultures; however, the effect of lower hemin concentrations (0.1-1 microM) on stromal cell layer formation was not significant. Supplementation of hemin for the first week in culture increased cumulative cell production as well as the number of granulocyte-macrophage colony-forming units (CFU-GM), and longevity of hemopoiesis in LTBMC was significantly increased with 0.1 microM hemin. In contrast with data obtained in short-term cultures, hemin in this system primarily affected the myeloid line of differentiation, whereas there was a less noticeable effect on the early erythroid progenitors (erythroid burst-forming units, BFU-E). Hemin, at 0.1 microM, increased spleen colony-forming units (CFU-S) to numbers several-fold higher than those of the control. Results suggest that hemin may produce mobilization of hemopoietic cells and committed precursors from adherent cells into suspension. Further, supplementation with hemin in LTBMC significantly increased the myeloid progenitor compartment and longevity of culture without altering the erythroid compartment.

Regulatory features of heme (ferroprotoporphyrin IX) on hematopoietic growth/differentiation and related processes are reviewed. It is emphasized that expressions of specific erythroid and nonerythroid heme biosynthetic and degradatory enzymes are required, and the regulatory processes whereby this occurs is considered. The specificity of heme, relationship to cellular events such as differentiation, response to growth factors, oncogene and receptor expression, and how heme counteracts toxic effects such as viral growth are all discussed. The significance of heme in the hemopoietic bone marrow microenvironment and growth factor network are considered. Finally, the third pathway for arachidonic acid metabolism via the heme-cytochrome P450 monooxygenase system, in addition to cyclooxygenase and lipoxygenase, by bone marrow adherent cells and its role in cellular differentiation is briefly reviewed.

Rats were treated with subcutaneous benzene, 440 mg/kg, for 3 and 14 days (acute and chronic exposure). Their hepatic cell heme and drug metabolizing enzymes as well as cell morphology by electron microscopy were examined. Electron micrographs of hepatocytes from the benzene-treated rats showed disruption of the mitochondrial membranes and mitochondrial structure. The activity of the rate-limiting enzyme of heme synthesis, δ-aminolevulinic acid synthase was increased 1.5–2-fold in both acutely and chronically exposed animals. In the acutely exposed animals, there was a 50% inhibition of the second enzyme of heme synthesis, δ-aminolevulinic acid dehydratase, while in the chronically exposed there was 70% inhibition. The rate-limiting enzyme of heme degradation, heme oxygenase, was increased more than twofold in both sets of animals. Cytochrome P-450 content was increased 77% in the acutely treated and 35% in the chronic. Associated with this increase in cytochrome P-450 content, there was a twofold increase in both arylhydrocarbon hydroxylase and aminopyrine-N-demethylase activities after acute exposure. During chronic exposure, however, there was a return to normal of the aminopyrine-N-demethylase activity and a decline in arylhydrocarbon hydroxylase induction to 1.25 times control. Results from this study indicate that benzene exposure produces adverse effects on mitochondria and heme metabolism. The precise relationships of these disturbances to benzene toxicity are not clear; however the possible role of heme oxygenase and degree of cytochrome P-450 induction are considered. Finally, the alterations of arylhydrocarbon hydroxylase and aminopyrine-N-demethylase activities point to a potential mechanism of differential toxicity from metabolites of benzene.

The effects of gold (Au), lead (Pb), and cadmium (Cd) on rat bone marrow in vitro erythropoiesis (CFUE) were studied. Au was found to be significantly toxic to CFUE growth at concentrations as low as 10(-9) M whereas Pb and Cd displayed toxicity at 10(-7) M. Addition of Pb plus Cd in combination had a greater toxic effect on CFUE growth than when the metals were added singly, and the toxic effect of Cd was reduced when Zinc (Zn) was added in combination to the cultures. When hemin (10(-6) M) was added to cultures containing 10(-6) M Au, Pb, or Cd, CFUE numbers were obtained that were equivalent to control cultures without hemin. Thus, hemin exerted a protective effect on erythropoiesis in the presence of otherwise toxic amounts of Au, Pb, and Cd. It is concluded that Au, Pb, and Cd have toxic effects on in vitro erythropoiesis and that this toxicity may be overcome in part by Zn or hemin. The possible involvement of the heme biosynthetic and degradative pathways is discussed with respect to these results.

Peripheral blood mononuclear cells from patients with polycythemia vera or myelofibrosis with myeloid metaplasia were studied for their erythroid colony growth characteristics in plasma clot cultures. In both diseases, erythroid colonies formed early in culture in the absence of added erythropoietin (endogenous colonies). In no instance did early, endogenous colony formation occur with peripheral blood cells from normals or patients with secondary polycythemia. A normal response to erythropoietin was observed with both control and patients' peripheral blood cells. Spleen mononuclear cells obtained from one patient with myelofibrosis also produced endogenous colonies and showed a response to erythropoietin. This study suggests that culture of peripheral blood mononuclear cells might serve as a useful tool in discriminating polycythemia vera from secondary polycythemia.

Bone marrow cells, peripheral blood lymphocytes, and sera from patients with sickle-cell anemia in hypoproliferative crisis were studied in the plasma clot culture system in the presence or absence of erythropoietin (Epo). Bone marrow cells from five patients demonstrated a marked ability to form erythroid colonies in the presence of Epo. These studies also suggested that bone marrow cells from some patients may have an increased sensitivity to Epo. The most outstanding observation in the present study was the marked erythroid colony inhibition by serum taken from one patient during crisis. Serum taken from the same patient two months after hypoproliferative crisis had no suppressive effect on erythroid colony formation. Lymphocytes taken from three patients in crisis had a stimulatory effect on erythroid colony formation when included in culture. The conclusion is that the defect of erythropoiesis in sickle-cell anemia during hypoproliferative crisis is not due to the absence of erythroid precursor cells or to the presence of suppressor lymphocytes, but may in some cases be associated with a circulating inhibitor of erythroid maturation.

Heme metabolism and in vitro erythropoietic growth (CFU-E, BFU-E) were examined in bone marrow cells taken from two siblings with apparent familial hypochromic microcytic anemia. Bone marrow cells from both patients grew adequate numbers of CFU-E and BFU-E colonies in culture in the presence of erythropoietin. In addition, small numbers of endogenous CFU-E were seen in 7-day cultures. Assays on bone marrow cells taken from both patients revealed that baseline delta-aminolevulinic synthase activity was considerably reduced, but increased six to seven fold (to normal levels) when patients' cells were exposed to pyridoxal phosphate (PLP). In both cases, ferrochelatase and delta-aminolevulinic acid dehydratase activities were normal. Bone marrow heme oxygenase showed no significant differences in activities between normals and patients values in the absence or presence of PLP. In contrast, heme synthesis by patients' bone marrow was less than that of normals. This study demonstrates that bone marrow cells from patients with this rare disorder have some disturbances in heme metabolism, whereas erythropoiesis appeared to be normal when cultured with adequate nutrients in vitro.

Azidothymidine (AZT) is a useful drug in management of AIDS. Nevertheless, its hematologic toxicity such as anemia and neutropenia present further complications to an already compromised hematopoietic state in patients. We studied the effects of AZT on human and murine bone marrow (BM) colony growth as determined by assays of CFU-E, BFU-E, CFU-GM, and fibroblastoid stromal (CFU-Fb) colonies. Cultures were grown in methylcellulose with growth factors and scored after three- to 14-day incubation. In general, murine marrow cultures were more sensitive to AZT as compared with human marrow. Furthermore, interindividual variation in toxicity to AZT was observed between marrow samples; 1 mumol/L AZT inhibited murine CFU-E, BFU-E, and CFU-GM by 98% to 100%, whereas human marrow was inhibited by 52%, 87%, and 65%, respectively. Lower concentrations of AZT (0.1 mumol/L) inhibited murine erythroid colony growth by 85% to 90%, whereas human growth was inhibited by only 39% to 52%. Myeloid colony inhibition was similar for human and murine systems. CFU-Fb growth was markedly suppressed (75%) by 1 mumol/L AZT. Hemin, at a concentration of 10 mumol/L, overcame some of the inhibitory effects of 1 to 0.1 mumol/L AZT without hindering antiviral activity. Inhibition of human CFU-E growth was completely overcome with hemin, whereas CFU-GM growth was recovered to 66% to 74% of control. A similar but less pronounced effect was observed for BFU-E. Furthermore, hemin does not decrease AZT's effects of HIV antigen content in vitro. We conclude that anemia and neutropenia, occurring as a result of AZT, may not be as pronounced in the presence of hemin. Furthermore, CFU-Fb was significantly reduced in the presence of low concentrations of AZT. This may indicate a major target site for BM toxicity since the stromal microenvironment may be responsible for maintaining short- and long-term hematopoiesis.

A case of dyskeratosis congenita (DC) with pancytopenia was studied in an attempt to elucidate the cause of the hypocellular bone marrow and pancytopenia. Levels of erythroid hemopoietic stem cells were estimated by clonal cell culture. Results showed a decrease in the number of precursor cells in both the bone marrow and the peripheral blood of this patient.

In vitro erythropoiesis by bone marrow and spleen cells was assessed in normal mice and during progression of Rauscher leukemia virus, variant-A (RLV-A) disease in mice. As RLV-A disease progressed from early through terminal stages, there was a marked increase in the numbers of in vitro splenic CFU-E and BFU-E. Conversely, bone marrow CFU-E and BFU-E demonstrated a concomitant decrease in numbers with disease progression. At no time were erythropoietin-independent (endogenous) erythroid colonies generated. The results suggest that compartmental alterations in erythroid precursors occur during progression of RLV-A.

This report demonstrates for the first time that human peripheral blood neutrophils and human bone marrow cells metabolize arachidonic acid (AA) by a cytochrome P450 dependent mechanism. The formation of the cytochrome P450 (P450) arachidonate metabolites is dependent on the addition of NADPH, prevented by SKF-525A (lOOμM), which is an inhibitor of cytochrome P450 enzymes, but not affected by the addition of BW-755C, a dual inhibitor of cyclooxygenase and lipoxygenase activities. Addition of the Ca++-ionophore A23187 to cell preparataions stimulated the release of both cyclooxygenase and lipoxygenase products but did not affect the formation of the P450 metabolites. Incubation of cell preparations with 14C-AA yielded a P450 dependent peak which eluted at 19 min. on reverse phase HPLC and was distinct from 5 and 15-hydroxyeicosatetraenoic acids (HETE's), prostaglandins and other leukotrienes. Recovery of the P450 dependent metabolite(s) was accomplished and preparations were tested in bone marrow clonal culture in order to determine if the substance(s) has/have any effect on the growth and differentiation of bone marrow cells. Results demonstrated that some of the material possessed powerful erythroid colony (CFU-E) enhancing activity at concentrations between 10-8-10-14M. These results demonstrate that human bone marrow and peripheral blood neutrophils possess a third pathway for AA metabolism which is P450 dependent, and that metabolite(s) of this pathway may have potent stimulatory effects on erythropoiesis.

Results from this study demonstrate that L1210 lymphocytic leukemia cells generate tumor cell colonies in plasma clot culture, and that the cells can be maintained in suspension cultures for 3 days without a loss in viability or clonogeneticy. Additions of 10 −5 –10 −8 M retinoic acid (RA) or 1,25-dihydroxyvitamin D 3 (1,25VD 3 ) to suspension cultures had no effect on cell viability. However, there was an increase in cellular adherence, nuclear chromatin condensation and a depression of clonogenic potential by 99–25%. Flow cytometry analysis of 3-day suspension cultures revealed that both RA or 1,25VD 3 promoted an accumulation of cells in G 1 -phase, with 1,25VD 3 being the most effective. For example, treatment with 10 −5 M 1,25VD 3 yielded a 76.7% G 1 -phase accumulation as contrasted with 36.3% for controls, and associated with this G 1 -shift was a 97% loss in clonogeneticy. Treatment with RA gave a slightly less G 1 -phase accumulation (64%), which was associated with a 74% loss in clonogeneticy. It is suggested that RA and 1,25VD 3 exert their cell cycle and anti-tumor effects by modulating cellular events or metabolism, or by promoting the accumulation of a quiescent cell population.

An inhibitor isolated from the serum-free culture medium of human myeloid leukemic HL-60 cells was able to suppress mitogen- and alloantigen-stimulated proliferative responses of normal lymphocytes in a dose-dependent manner. In vitro production, concentration, and purification by column chromatography and electrophoresis revealed that the inhibitor was produced constitutively, required RNA synthesis, and had a molecular weight in the range of 40,000-60,000. The inhibitor was also produced in vitro by myeloid leukemia cells isolated from patients with acute myelogenous leukemia. In a similar manner, the inhibitory material suppressed proliferative responses of allogeneic and autologous lymphocytes. Suppression was accompanied by drastically reduced production of interleukin 2 and lymphokines, which regulate differentiation of myeloid leukemia cells, and suppression was reversed by addition of exogenous interleukin 2. The inhibitor did not suppress clonogenic proliferation of normal granulocytes and macrophages suggesting that inhibition of production or interference with interleukin 2 activity as a possible mechanism. These interactions between leukemia cells and lymphocytes have shed new light on the immunosuppression and growth advantage of leukemia cells. Inhibitory activity of HL-60 cells was diminished after they were induced to differentiate, indicating that differentiation induced by lymphokines may be an effective means of controlling leukemia.

Bone marrow cells from three patients with idiopathic acquired sideroblastic anemia and one with X-linked sideroblastic anemia were simultaneously cultured in plasma clot and methylcellulose cultures in order to evaluate their erythroid colony (CFUE) cloning potential in these two systems. In contrast to normals, sideroblastic anemia bone marrow cells demonstrated a marked ability to form erythropoietin (Epo)-independent CFUE in methylcellulose culture, and were inhibited in their ability to generate CFUE in plasma clot culture even in the presence of Epo. Addition of citrated plasma to methylcellulose cultures inhibited Epo-independent CFUE growth, but not Epo-dependent growth, by both a normal and patients' bone marrow cells. These results demonstrate that bone marrow cells from some patients with sideroblastic anemia can undergo Epo-independent and Epo-dependent CFUE growth in vitro, and that there is a marked difference in CFUE growth depending on the type of clonal culture method used. It is suggested that the culture microenvironment, plasma, and sensitivity to Epo may be contributing factors which allow specific clones of sideroblastic anemia CFUE-forming cells to proliferate in vitro.

This report demonstrates for the first time that human peripheral blood neutrophils and human bone marrow cells metabolize arachidonic acid (AA) by a cytochrome P450 dependent mechanism. The formation of the cytochrome P450 (P450) arachidonate metabolites is dependent on the addition of NADPH, prevented by SKF-525A (100 microM), which is an inhibitor of cytochrome P450 enzymes, but not affected by the addition of BW-755C, a dual inhibitor of cyclooxygenase and lipoxygenase activities. Addition of the Ca+(+)-ionophore A23187 to cell preparations stimulated the release of both cyclooxygenase and lipoxygenase products but did not affect the formation of the P450 metabolites. Incubation of cell preparations with 14C-AA yielded a P450 dependent peak which eluted at 19 min. on reverse phase HPLC and was distinct from 5 and 15-hydroxyeicosatetraenoic acids (HETE's), prostaglandins and other leukotrienes. Recovery of the P450 dependent metabolite(s) was accomplished and preparations were tested in bone marrow clonal culture in order to determine if the substance(s) has/have any effect on the growth and differentiation of bone marrow cells. Results demonstrated that some of the material possessed powerful erythroid colony (CFU-E) enhancing activity at concentrations between 10(-8)-10(-14)M. These results demonstrate that human bone marrow and peripheral blood neutrophils possess a third pathway for AA metabolism which is P450 dependent, and that metabolite(s) of this pathway may have potent stimulatory effects on erythropoiesis.

We characterized the presence of the monooxygenase arylhydrocarbon-hydroxylase (AHH), in mouse bone marrow cells taken directly from animals and from bone marrow colony culture. Using a standard radio-isotopic assay it was found that AHH activity was present in mouse bone marrow cells and that there was demonstratable activity in preparations taken directly from differentiated erythroid and myeloid colony cultures. Murine colonies of erythroid (CFU-E) and granulocytes (CFU-GM) were grown and AHH activity determined in non-induced and 3-methylcholanthrene (3-MC) induced cultures. Addition of 3-MC to erythropoietin dependent CFU-E was found to induce AHH activity above controls in a dose dependent manner, with 75 micrograms generating a maximal effect. CFU-E taken from different incubation periods (1-4 days) revealed that AHH was maximal in 2 1/2 day cultures and thereafter declined. In contrast, maximal AHH activity was obtained from 6-7 day CFU-GM and 40 micrograms of 3-MC stimulated the activity by 88%. These results demonstrate that AHH is present in normal mouse bone marrow cells and developing hemopoietic colonies, and that induction of AHH may indicate an important role for these cytochrome P-450 monooxygenases in cell development and differentiation as well as in the metabolism of various drugs.

Bone marrow and peripheral blood cells from a patient with chronic myelogenous leukemia in erythroblastic transformation were studied by flow cytometry and for hemopoietic colony growth. Results demonstrated that this disorder had greatly expanded bone marrow erythroid colony (CFU-E) and myeloid colony (CFU-GM) progenitor compartments that were totally dependent upon erythropoietin and colony-stimulating factor. DNA, RNA and cell cycle analysis revealed that the bone marrow cells were diploid, had a high percentage of S phase cells (17%), and a unique bimodal RNA index of 5 and 13.8. Results are discussed and contrasted with other myeloproliferative disorders.

Interferons are known to have modulatory effects on hemopoiesis. Human bone marrow mononuclear cells were employed to test the effects of human recombinant beta-interferon on myeloid and erythroid hemopoietic stem cell growth. Results demonstrated that 1,000 U/ml of beta-interferon significantly inhibited myeloid growth [colony-forming unit (CFU)-granulocyte macrophage] by 40-50%, whereas a higher concentration (10,000 U/ml) abolished CFU-granulocyte macrophage growth by 80-100%. The inhibitory effects of beta-interferon were partially reversible by increasing the concentrations of colony stimulating activity in the culture and could not be abrogated by addition of toxic oxygen radical scavengers such as superoxide dismutase and catalase. The inhibitory effect of interferon was found to be partially dependent on the presence of accessory cells, since less inhibition was seen using T-cell and monocyte depleted bone marrow cells. Lower concentrations of beta-interferon (10-100 units/ml) were without effect. In contrast to myeloid cells, the human erythroid progenitors (CFU-erythroid, burst-forming unit-erythroid) appear to be more sensitive to the inhibitory effects of beta-interferon. In this regard it was found that 100 U/ml of beta-interferon suppressed erythroid growth by 40-50%. These results suggest that human recombinant beta-interferon is capable of suppressing hemopoietic colony growth.

L1210 leukemia is a murine leukemia which is associated with anemia and marked neutrophilia. In order to determine the significance of free radicals (FR) in this disorder, we determined the presence and localization of free radical scavengers (FRS) and scavenger-like systems in L1210 leukemia cells obtained in vivo and from in vitro cultures. FR are metabolized or detoxified by certain FRS such as glutathione (GSH and GSSG), superoxide dismutase (SOD) and enzymes such as epoxide hydrolase (EH). In all cases specific fractions of L1210 cells, bone marrow and liver were examined for FR/FRS levels. Reduced (GSH) and oxidized (GSSG) glutathione were measured fluorometrically using o-opthalaldehyde (OPT). SOD was determined colorimetrically utilizing pyrogallol by substrate autolysis inhibition, and EH was determined by utilizing [3H] styrene oxide as a substrate. Ratios of GSH/GSSG in fractions prepared from in vivo and in vitro L1210 cells showed a predominance of GSH-reductase with the highest activity in mitochondria (ratio = 15 vs. 10). Normal liver showed a similar pattern whereas, leukemic liver showed altered GSH/GSSG ratios in mitochrondria and microsomes. Leukemic bone marrow showed a predominance of GSH-reductase in all fractions. EH activity was highest in microsomal fractions obtained from L1210 cells grown in vitro and found to become increased in both the mitrochondrial (100%) and microsomal (200%) fractions when cells were exposed to retinoic acid (RA) in culture. SOD activity in the cytosolic (21.2 U SOD/mg) and mitochondrial (12 U SOD/mg) fractions whereas, leukemic liver showed a significant decrease in activity in all fractions compared to normals. SOD was determined in fractions taken from L1210 cells in vivo and in vitro. Results demonstrated detectable but reduced SOD activity in the L1210 cell fractions as contrasted with liver activity. Results from these studies indicate that certain FRS systems are functional in L1210 leukemic animals. Furthermore, variations in the ratios or levels may be of significance in the leukemic and hematological states.

Colony formation by erythroid precursors from human fetal liver, umbilical cord blood and adult peripheral blood has been studied in a plasma clot culture system. Fetal liver (FL) was obtained at post-mortem examination from 13-22 week abortuses. After mincing in Hanks' solution, cells in suspension were harvested by Ficoll-Hypaque centrifugation. Mononuclear cells were obtained by centrifugation of umbilical cord blood (CB) and normal adult peripheral blood (PB). All three types of preparations were incubated up to 14 d in 0.1 ml plasma clot cultures containing 0-4 u/ml erythropoietin (Epo) and 10(6) cells/ml. No colonies formed in the absence of Epo. Normal adult PB produced late-appearing colonies; there were no colonies at day 7 and up to 100 colonies/0.1 ml at day 14. CB produced early and late colonies with up to 200 colonies/0.1 ml at day 7 and 125 at day 14. Cells from FL produced many early colonies; over 1500 colonies/0.1 ml were sent at day 7 and there was a subsequent decline in colony count with longer incubation. In cultures of both CB and FL, colonies composed of either mature or immature cells were noted during both early and late stages of incubation suggesting that these cell sources contain a heterogeneous population of erythroid colony progenitors. Measurement of differential beta and gamma globin chain synthesis by erythroid colonies grown from fetal liver and umbilical cord blood gave results similar to those obtained by direct pulse-labelling of the original source of the cultured cells.

L1210 leukemia is a murine leukemia which is associated with anemia and marked neutrophilia. In order to determine the significance of free radicals (FR) in this disorder, we determined the presence and localization of free radical scavengers (FRS) and scavenger-like systems in L1210 leukemia cells obtained in vivo and from in vitro cultures. FR are metabolized or detoxified by certain FRS such as glutathione (GSH and GSSG), superoxide dismutase (SOD) and enzymes such as epoxide hydrolase (EH). In all cases specific fractions of L1210 cells, bone marrow and liver were examined for FR/FRS levels. Reduced (GSH) and oxidized (GSSG) glutathione were measured fluorometerically using o-opthalaldehyde (OPT). SOD was determined colorimetrically utilizing pyrogallol by substrate autolysis inhibition, and EH was determined by utilizing [3H] styrene oxide as a substrate. Ratios of GSH/GSSG in fractions prepared from in vivo and in vitro L1210 cells showed a predominance of GSH-reductase with the highest activity in mitochondria (ratio = 15 vs. 10). Normal liver showed a similar pattern whereas, leukemic liver showed altered GSH/GSSG ratios in mitochrondria and microsomes. Leukemic bone marrow showed a predominance of GSH-reductase in all fractions. EH activity was highest in microsomal fractions obtained from L1210 cells grown in vitro and found to become increased in both the mitrochondrial (100%) and microsomal (200%) fractions when cells were exposed to retinoic acid (RA) in culture. SOD activity in the cytosolic (21.2 U SOD/mg) and mitochondrial (12 U SOD/mg) fractions whereas, leukemic liver showed a significant decrease in activity in all fractions compared to normals. SOD was determined in fractions taken from L1210 cells in vivo and in vitro. Results demonstrated detectable but reduced SOD activity in the L1210 cell fractions as contrasted with liver activity. Results from these studies indicate that certain FRS systems are functional in L1210 leukemic animals. Furthermore, variations in the ratios or levels may be of significance in the leukemic and hematological states.

Heme metabolism was examined in developing in vitro erythroid colonies (CFUE) and in bone marrow samples taken directly from four normal donors and four patients with sideroblastic anemia. As previously reported, sideroblastic anemia bone marrow cells grew large numbers of CFUE in methylcellulose culture in the absence or presence of erythropoietin. Maximum activities of delta-aminolevulinic acid synthase (ALAS), ALA dehydratase (ALAD), and 14C-ALA incorporation into heme were achieved in normal marrow CFUE after 8 days of culture, whereas heme oxygenase progressively decreased to low levels of activity during the same period. Assays on nucleated bone marrow cells taken directly from patients revealed that ALAS activity was considerably reduced in idiopathic sideroblastic anemia (IASA) and X-linked sideroblastic anemia (X-SA) bone marrow specimens, whereas the activity increased more than twofold (normal levels) when cells were assayed from 8-day CFUE. In all cases, ALAD activity appeared to be within normal levels. Measurement of heme synthesis revealed that normal levels of 14C-ALA incorporation into heme were achieved in IASA cells but were reduced in X-SA cells. In marked contrast to levels in normal cells, heme oxygenase was found to be significantly elevated (two- to fourfold) in bone marrow cells taken directly from patients with IASA and X-SA. Results from this study demonstrate that IASA and X-SA bone marrow cells have disturbances in ALAS and heme metabolism, and that erythropoiesis (CFUE) can be restored to normal levels when cells are cultured in methylcellulose.

The activities of the heme biosynthetic enzymes ALA synthase (ALAS) and ALA dehydrase (ALAD) and the heme degradative enzyme heme oxygenase were analyzed from bone marrow cells obtained from young, middle-aged, and senescent rats. There was age-related reduced activity of bone marrow ALAS but no age-related difference in the activity of ALAD. In contrast, heme oxygenase activity was 50% greater in the senescent marrow cells. Incorporation of 14C-glycine into heme was 45% less in senescent rat marrow cells, whereas incorporation of 14C-delta-aminolevulinic acid was not related to age. Senescent bone marrow cells demonstrated a marked reduction in 14C-leucine and 3H-uridine incorporated into protein and nucleic acid synthesis, respectively. In vitro erythroid colony (CFUE) growth by senescent bone marrow cells was as much as 40% less compared with young bone marrow cells. The decreased ability to form CFUE by the senescent bone marrow cells may be related to reduced ALAS activity and increased heme oxygenase activity. Thus, part of the aging process appears to involve fluctuations in the enzyme activities and protein synthesis involved with metabolism of heme.