Myelosuppressive Cytokines and Peptides

Simulated microgravity affects stroma-dependent ex vivo myelopoiesis

Microgravity is known negatively affect physiology of living beings, including hematopoiesis. Dysregulation of hematopoietic cells and supporting stroma relationships in bone marrow niche may be in charge. We compared the efficacy of ex vivo expansion of hematopoietic stem and progenitor cells (HSPCs) in presence of native or osteocommitted MSCs under simulated microgravity (Smg) using Random Positioning Machine (RPM). In comparison with 1 g, a decrease of MSC-associated HSPCs and an increase of floating HSPCs was observed after 7 days of Smg exposure. Among floating HSPCs, primitive progenitors were presented by late CD34⁺/133^-. Total CFUs as well as erythroid (BFU-E) and granulocytic (CFU-G) numbers were lower. MSC-associated primitive HSPCs demonstrated increased proportion of late CD34⁺/133^- in expense of early CD34^-/133⁺. Osteo-MSCs preferentially supported late primitive CD34⁺ and more committed HSPCs as followed from increase of CFUs, and CD235a⁺ erythroid progenitors. Under Smg, an increased VEGF, eotaxin, and GRO-a levels, and a decrease in RANTES were found in the osteo-MSC-HSPC co-cultures. IL-6,-8, -13, G-CSF, GRO-a, MCP-3, MIP-1b, VEGF increased in co-culture with osteo-MSCs vs intact MSCs. Based on the findings, the misbalance between primitive/committed HSPCs and a decrease in hematopoiesis-supportive activity of osteocommitted cells are supposed to underline hematopoietic disorders during space flights.

Immunomodulatory Activity of the Marine Sponge, Haliclona (Soestella) sp. (Haplosclerida: Chalinidae), from Sri Lanka in Wistar Albino Rats: Immunosuppression and Th1-Skewed Cytokine Response

Natural secondary metabolites of sponges of the genus Haliclona are associated with an array of biological activity with therapeutic usage. We investigated the immunopharmacological properties of a presumably novel marine sponge species from Sri Lanka, Haliclona (Soestella) sp. Sponge material was collected from southern Sri Lanka by scuba diving. Sponge identification was based on spicule and skeleton morphology using light microscopy. Selected in vivo and ex vivo tests investigated nonfunctional and functional immunomodulatory activity of the Haliclona (Soestella) sp. crude extract (HSCE) in the Wistar rat model. Compared to the controls, rats orally gavaged daily for 14 consecutive days with 15 mg/kg dose of the HSCE manifested a significant reduction of immune cell counts of total WBCs (by 17%; p < 0.01), lymphocytes (38%), platelets (52%), splenocytes (20%), and bone marrow cells (BMC; 60%) (p < 0.001), with a concurrent increase in the neutrophil : lymphocyte ratio (p < 0.05); RBC counts abated by 53% (p < 0.001). A significant reduction of the splenosomatic index was evident with the 10 and 15 mg/kg doses (p < 0.001). Rat plasma TNF-α cytokine level was augmented by tenfold (p < 0.001), IL-6 level by twofold (p < 0.01) with the 15 mg/kg HSCE treatment, while IL-10 was detectable in rat plasma only with this treatment; the corresponding Th₁ : Th₂ cytokine ratio (TNF-α : IL-10) was indicative of an unequivocal Th1-skewed cytokine response (p < 0.01). Ex vivo bone marrow cell and splenocyte proliferation were significantly and dose dependently impaired by HSCE (IC₅₀ 0.719 and 0.931 μg/mL, respectively; p < 0.05). Subacute toxicity testing established that HSCE was devoid of general toxic, hepatotoxic, and nephrotoxic effects. In conclusion, HSCE was orally active, nontoxic, and effectively suppressed nonfunctional and functional immunological parameters of Wistar rats, suggestive of the potential use of the HSCE as an immunosuppressant drug lead.

Class II transactivator-mediated regulation of major histocompatibility complex class II antigen expression is important for hematopoietic progenitor cell suppression by chemokines and iron-binding proteins

OBJECTIVE

Iron-binding proteins H-ferritin (HF) and lactoferrin (LF), as well as chemokines, tumor necrosis factor (TNF)-alpha, and interferon (IFN)-gamma suppress hematopoietic progenitor cell (HPC) proliferation. Major histocompatibility complex (MHC) class II antigens have been associated with suppressive effects of HF and LF. Because the transcription factor class II transactivator (CIITA) regulates expression of MHC class II antigens, we evaluated influences of CIITA and MHC class II antigens on suppression of colony formation by murine bone marrow HPC in response to HF, LF, CC, and CXC chemokines, TNF-alpha, and IFN-gamma. We also evaluated hematopoiesis in mice deficient in both CIITA and MHC class II antigens (CIITA -/-), in mice deficient in MHC class II antigens but not in CIITA (MHC class II -/-), and in mice deficient in CIITA but not in MHC class II antigens (CIITA-IE).

MATERIALS AND METHODS

HF, LF, CCL3/MIP-1alpha, CXCL5/ENA-78, CXCL8/IL-8, CCL5/RANTES, TNF-alpha, and IFN-gamma were assessed for effects on colony formation by bone marrow HPC (colony-forming unit granulocyte-macrophage, burst-forming unit erythroid, and colony-forming unit multipotential) stimulated in vitro by combinations of growth factors including erythropoietin, stem cell factor, pokeweed mitogen mouse spleen cell conditioned medium, and hemin. Bone marrow cells were from CIITA -/-, MHC class II antigen -/-, CIITA-IE, and littermate control mice. We also evaluated cycling status (percent cells in S-phase) and absolute numbers of marrow and spleen HPC in these mice.

RESULTS

Multiple growth factor-stimulated colony formation by control bone marrow HPC was significantly suppressed by HF, LF, CCL3, CXCL5, CXCL8, TNF-alpha, and IFN-gamma, but not by CCL5. However, HPC from CIITA -/- and MHC class II antigen -/- mouse marrow was insensitive to inhibition by HF, LF, CCL3, CXCL5, CXCL8, and CCL5; these HPC were inhibited by TNF-alpha and IFN-gamma. Restoration of MHC class II expression in CIITA -/- (CIITA-IE) mice restored responsiveness of HPC to inhibition by HF, LF, CCL3, CXCL5, and CXCL8. Increased cycling of splenic HPC in CIITA -/- and MHC class II antigen -/-, compared to control and CIITA-IE, mice was noted.

CONCLUSIONS

Myelosuppressive effects of iron-binding proteins HF and LF and chemokines CCL3, CXCL5, and CXCL8 on mouse bone marrow HPC require expression of MHC class II antigens, and CIITA is involved in this responsiveness through its regulation of expression of MHC class II antigens.

Transforming growth factor-beta 1 induces apoptosis independently of p53 and selectively reduces expression of Bcl-2 in multipotent hematopoietic cells

Transforming growth factor-beta1 (TGF-beta1) can inhibit cell proliferation or induce apoptosis in multipotent hematopoietic cells. To study the mechanisms of TGF-beta1 action on primitive hematopoietic cells, we used the interleukin-3 (IL-3)-dependent, multipotent FDCP-Mix cell line. TGF-beta1-mediated growth inhibition was observed in high concentrations of IL-3, while at lower IL-3 concentrations TGF-beta1 induced apoptosis. The proapoptotic effects of TGF-beta1 occur via a p53-independent pathway, since p53(null) FDCP-Mix demonstrated the same responses to TGF-beta1. IL-3 has been suggested to enhance survival via an increase in (antiapoptotic) Bcl-x(L) expression. In FDCP-Mix cells, neither IL-3 nor TGF-beta1 induced any change in Bcl-x(L) protein levels or the proapoptotic proteins Bad or Bax. However, TGF-beta1 had a major effect on Bcl-2 levels, reducing them in the presence of high and low concentrations of IL-3. Overexpression of Bcl-2 in FDCP-Mix cells rescued them from TGF-beta1-induced apoptosis but was incapable of inhibiting TGF-beta1-mediated growth arrest. We conclude that TGF-beta1-induced cell death is independent of p53 and inhibited by Bcl-2, with no effect on Bcl-x(L). The significance of these results for stem cell survival in bone marrow are discussed.

Abnormal chemokine-induced responses of immature and mature hematopoietic cells from motheaten mice implicate the protein tyrosine phosphatase SHP-1 in chemokine responses

Chemokines regulate a number of biological processes, including trafficking of diverse leukocytes and proliferation of myeloid progenitor cells. SHP-1 (Src homology 2 domain tyrosine phosphatase 1), a phosphotyrosine phosphatase, is considered an important regulator of signaling for a number of cytokine receptors. Since specific tyrosine phosphorylation of proteins is important for biological activities induced by chemokines, we examined the role of SHP-1 in functions of chemokines using viable motheaten (me(v)/me(v)) mice that were deficient in SHP-1. Chemotactic responses to stromal call-derived factor 1 (SDF-1), a CXC chemokine, were enhanced with bone marrow myeloid progenitor cells as well as macrophages, T cells, and B cells from me(v)/me(v) versus wild-type (+/+) mice. SDF-1-dependent actin polymerization and activation of mitogen-activated protein kinases were also greater in me(v)/me(v) versus +/+ cells. In contrast, immature subsets of me(v)/me(v) bone marrow myeloid progenitors were resistant to effects of a number of chemokines that suppressed proliferation of +/+ progenitors. These altered chemokine responses did not appear to be due to enhanced expression of CXCR4 or lack of chemokine receptor expression. However, expression of some chemokine receptors (CCR1, CCR2, CCR3, and CXCR2) was significantly enhanced in me(v)/me(v) T cells. Our results implicate SHP-1 involvement in a number of different chemokine-induced biological activities.

Enhanced Myeloid Progenitor Cell Cycling and Apoptosis in Mice Lacking the Chemokine Receptor, CCR2

Chemokines regulate hematopoiesis in part by influencing the proliferative status of myeloid progenitor cells (MPC). Human MCP-1/murine JE, a myelosuppressive chemokine, specifically binds C-C chemokine receptor 2 (CCR2). Transgenic mice containing a targeted disruption in CCR2 that prevents expression of CCR2 mRNA and protein and have MPC that are insensitive to inhibition by MCP-1 and JE in vitro were assessed for potential abnormalities in growth of bone marrow (BM) and spleen MPC. MPC in both unseparated and c-kit+lin− populations of BM from CCR2-deficient (−/−) mice were in a greatly increased proliferation state compared with CCR2 littermate control (+/+) mice, an effect not apparent with progenitors from spleens of CCR2 (−/−) mice. Increased cycling status of CCR2 (−/−) BM MPC did not result in increased numbers of nucleated cells or MPC in BM or spleens of CCR2 (−/−) mice. Possible reasons for this apparent discrepancy were highlighted by flow cytometric analysis of c-kit+lin− BM cells and colony formation by MPC subjected to delayed addition of growth factors. The c-kit+lin− population of BM cells from CCR2 (−/−) mice had a significantly higher percentage of apoptotic cells than those from CCR2 (+/+) BM. However, elevated apoptosis was not associated with decreased numbers of c-kit+lin− cells. The increased percentage of apoptotic c-kit+lin− cells was due to elevated apoptosis within the c-kitdimlin−, but not the c-kitbrightlin−, subpopulations of cells. Consistent with enhanced apoptosis of phenotypically defined cells, MPC from CCR2 (−/−) BM and purified c-kit+lin− cells demonstrated decreased cell survival in vitro upon delayed addition of growth factors. The data suggest that signals received by CCR2 limit proliferation of progenitor cells in the BM, but also enhance survival of these cells.

Enhanced Myeloid Progenitor Cell Cycling and Apoptosis in Mice Lacking the Chemokine Receptor, CCR2

Chemokines regulate hematopoiesis in part by influencing the proliferative status of myeloid progenitor cells (MPC). Human MCP-1/murine JE, a myelosuppressive chemokine, specifically binds C-C chemokine receptor 2 (CCR2). Transgenic mice containing a targeted disruption in CCR2 that prevents expression of CCR2 mRNA and protein and have MPC that are insensitive to inhibition by MCP-1 and JE in vitro were assessed for potential abnormalities in growth of bone marrow (BM) and spleen MPC. MPC in both unseparated and c-kit+lin− populations of BM from CCR2-deficient (−/−) mice were in a greatly increased proliferation state compared with CCR2 littermate control (+/+) mice, an effect not apparent with progenitors from spleens of CCR2 (−/−) mice. Increased cycling status of CCR2 (−/−) BM MPC did not result in increased numbers of nucleated cells or MPC in BM or spleens of CCR2 (−/−) mice. Possible reasons for this apparent discrepancy were highlighted by flow cytometric analysis of c-kit+lin− BM cells and colony formation by MPC subjected to delayed addition of growth factors. The c-kit+lin− population of BM cells from CCR2 (−/−) mice had a significantly higher percentage of apoptotic cells than those from CCR2 (+/+) BM. However, elevated apoptosis was not associated with decreased numbers of c-kit+lin− cells. The increased percentage of apoptotic c-kit+lin− cells was due to elevated apoptosis within the c-kitdimlin−, but not the c-kitbrightlin−, subpopulations of cells. Consistent with enhanced apoptosis of phenotypically defined cells, MPC from CCR2 (−/−) BM and purified c-kit+lin− cells demonstrated decreased cell survival in vitro upon delayed addition of growth factors. The data suggest that signals received by CCR2 limit proliferation of progenitor cells in the BM, but also enhance survival of these cells.

Myeloid progenitor cell proliferation and mobilization effects of BB10010, a genetically engineered variant of human macrophage inflammatory protein-1alpha, in a phase I clinical trial in patients with relapsed/refractory breast cancer

Macrophage Inflammatory Protein (MIP)-1alpha is myelosuppressive in vitro and in vivo for hematopoietic stem and immature subsets of myeloid progenitor cells, demonstrates some myeloprotective effects in mice treated with Ara-C and hydroxyurea, and has stem/progenitor cell mobilizing activity in mice. Based on these observations, BB10010, a genetic variant of MIP-1alpha, was assessed for effects on marrow and blood myeloid progenitor cells in patients with relapsed/refractory breast cancer. MIP-1alpha readily polymerizes, whereas BB10010 has a reduced tendency to form large polymers at physiological pH and ionic strength and retains biological activity. Patients were injected with 5, 10, 30 or 100 microg/kg BB10010 s.c. daily for 3 days. BB10010 significantly reduced the cycling status of marrow myeloid progenitors from pretreatment levels of 39-58% to 0 - 11% one day after the third and last injection of BB10010. This was associated with significant decreases in frequency of marrow progenitors (number of colonies formed per number of cells plated) and percent biopsied marrow CD34+ cells. The suppressive effects were reversible in patients and the rapidity of this reversal demonstrated in mouse studies. BB10010 had no effect on nucleated cellularity or on the proliferation of nucleated cells as assessed in marrow biopsies from the patients. These latter effects may in part reflect the noted decreased apoptosis of nucleated cells by BB10010. BB10010 also demonstrated significant but modest myeloid progenitor cell mobilizing capacity. Blood progenitors were in a slow or non-cycling state prior to treatment and this did not change after administration of BB10010. The above effects of BB10010 were similar at the four different dosage levels assessed. These results demonstrate in humans the suppressive and mobilizing effects of MIP-1alpha and BB10010 previously noted in vivo in mice.

Biology and mechanisms of action of synergistically stimulated myeloid progenitor cell proliferation and suppression by chemokines

A number of cytokines can act together to stimulate/enhance the proliferation of hematopoietic stem and progenitor cells in a greater than additive fashion. An example of this is the combination of a colony-stimulating factor with a potent costimulating molecule such as steel factor. Certain members of the chemokine family of cytokines can suppress this synergistically enhanced proliferation. This review focuses on cytokines involved in these stimulating/enhancing/suppressing effects with regard to biological activity and what is beginning to be learned about the intracellular signal transduction events that may be mediating these effects. Examples of intracellular mediators involved include, but are not limited to, the Raf-1/ MAP kinase pathway and cyclin-dependent kinase inhibitors p21cip-1 and p27kip-1 for cell proliferation, and eukaryotic initiation factor-4E and 4E binding protein 1 for protein synthesis.