Heme Oxygenase-1 Deletion Affects Stress Erythropoiesis

BACKGROUND:Homeostatic erythropoiesis leads to the formation of mature red blood cells under non-stress conditions, and the production of new erythrocytes occurs as the need arises. In response to environmental stimuli, such as bone marrow transplantation, myelosuppression, or anemia, erythroid progenitors proliferate rapidly in a process referred to as stress erythropoiesis. We have previously demonstrated that heme oxygenase-1 (HO-1) deficiency leads to disrupted stress hematopoiesis. Here, we describe the specific effects of HO-1 deficiency on stress erythropoiesis. METHODOLOGY/PRINCIPAL FINDINGS:We used a transplant model to induce stress conditions. In irradiated recipients that received hmox(+/-) or hmox(+/+) bone marrow cells, we evaluated (i) the erythrocyte parameters in the peripheral blood; (ii) the staining intensity of CD71-, Ter119-, and CD49d-specific surface markers during erythroblast differentiation; (iii) the patterns of histological iron staining; and (iv) the number of Mac-1(+)-cells expressing TNF-α. In the spleens of mice that received hmox(+/-) cells, we show (i) decreases in the proerythroblast, basophilic, and polychromatophilic erythroblast populations; (ii) increases in the insoluble iron levels and decreases in the soluble iron levels; (iii) increased numbers of Mac-1(+)-cells expressing TNF-α; and (iv) decreased levels of CD49d expression in the basophilic and polychromatophilic erythroblast populations. CONCLUSIONS/SIGNIFICANCE:As reflected by effects on secreted and cell surface proteins, HO-1 deletion likely affects stress erythropoiesis through the retention of erythroblasts in the erythroblastic islands of the spleen. Thus, HO-1 may serve as a therapeutic target for controlling erythropoiesis, and the dysregulation of HO-1 may be a predisposing condition for hematologic diseases

Development of B Cells and Erythrocytes Is Specifically Impaired by the Drug Celastrol in Mice

Background: Celastrol, an active compound extracted from the root of the Chinese medicine ‘‘Thunder of God Vine’’ (Tripterygium wilfordii), exhibits anticancer, antioxidant and anti-inflammatory activities, and interest in the therapeutic potential of celastrol is increasing. However, described side effects following treatment are significant and require investigation prior to initiating clinical trials. Here, we investigated the effects of celastrol on the adult murine hematopoietic system. Methodology/Principal Findings: Animals were treated daily with celastrol over a four-day period and peripheral blood, bone marrow, spleen, and peritoneal cavity were harvested for cell phenotyping. Treated mice showed specific impairment of the development of B cells and erythrocytes in all tested organs. In bone marrow, these alterations were accompanied by decreases in populations of common lymphoid progenitors (CLP), common myeloid progenitors (CMP) and megakaryocyte-erythrocyte progenitors (MEP). Conclusions/Significance: These results indicate that celastrol acts through regulators of adult hematopoiesis and could be used as a modulator of the hematopoietic system. These observations provide valuable information for further assessmen

NKX3.1 is a direct TAL1 target gene that mediates proliferation of TAL1-expressing human T cell acute lymphoblastic leukemia

TAL1 (also known as SCL) is expressed in >40% of human T cell acute lymphoblastic leukemias (T-ALLs). TAL1 encodes a basic helix-loop-helix transcription factor that can interfere with the transcriptional activity of E2A and HEB during T cell leukemogenesis; however, the oncogenic pathways directly activated by TAL1 are not characterized. In this study, we show that, in human TAL1–expressing T-ALL cell lines, TAL1 directly activates NKX3.1, a tumor suppressor gene required for prostate stem cell maintenance. In human T-ALL cell lines, NKX3.1 gene activation is mediated by a TAL1–LMO–Ldb1 complex that is recruited by GATA-3 bound to an NKX3.1 gene promoter regulatory sequence. TAL1-induced NKX3.1 activation is associated with suppression of HP1-α (heterochromatin protein 1 α) binding and opening of chromatin on the NKX3.1 gene promoter. NKX3.1 is necessary for T-ALL proliferation, can partially restore proliferation in TAL1 knockdown cells, and directly regulates miR-17-92. In primary human TAL1-expressing leukemic cells, the NKX3.1 gene is expressed independently of the Notch pathway, and its inactivation impairs proliferation. Finally, TAL1 or NKX3.1 knockdown abrogates the ability of human T-ALL cells to efficiently induce leukemia development in mice. These results suggest that tumor suppressor or oncogenic activity of NKX3.1 depends on tissue expression

Régulation de l'expression et fonction anti-tumorale de la sémaphorine SEMA3F

Notre groupe a cloné en 3p21.3 un gène codant pour la sémaphorine SEMA3F. C'est une protéine sécrétée impliquée initialement dans la migration cellulaire. Nos objectifs étaient d'étudier la régulation de l'expression de SEMA3F et de vérifier son rôle anti-tumoral chez l'animal. Nous avons établi la carte du promoteur de SEMA3F, identifié de multiples sites d'initiation de la transcription dans un îlot CpG et isolé une région nécessaire à l'expression. La méthylation de SEMA3F et le remodelage de la chromatine interviennent dans cette régulation. Nous avons aussi déterminé le profil d'expression et les propriétés biologiques des 2 formes épissées de SEMA3F durant la maturation du système nerveux murin. Malgré des fonctions redondantes, ces isoformes subissent une régulation temporelle et régionale. Enfin, nous avons décrit l'activité anti-tumorale de SEMA3F dans le poumon de rats immunodéficients. La neuropiline 2, les intégrines et les MAPKinases semblent impliquées dans ce phénomène.Our group cloned the SEMA3F gene in the 3p21.3 chromosomic region. It is a secreted protein initially implicated in the cellular migration. Our aims were to study the regulation of SEMA3F expression and to verify its anti-tumoral rule in the animal. We have mapped the promoter of SEMA3F, localized the transcriptional initiation sites within the CpG-island and defined the region necessary for transcriptional activation. The methylation of SEMA3F and the chromatin remodeling are implicated in this regulation. We also have studied the expression and the biological properties of the two spliced forms of SEMA3F during the maturation of the mouse brain. Although functionally redundant, these forms are characterized by a temporal and regional specific regulation. Finally, we have described the anti-tumoral activity of SEMA3F into the lungs of nude rats. The neuropilin 2, integrins and MAPKinases seem to be implicated in this effect.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Comment un suppresseur de tumeur se prend au jeu de la prolifération leucémique chez l’homme

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Redundant functions but temporal and regional regulation of two alternatively spliced isoforms of semaphorin 3F in the nervous system.

SEMA3F is a secreted semaphorin that affects axon and cell guidance in the developing nervous system, and is also thought to have anti-tumor activity. Two spliced forms of SEMA3F have been identified that differ by the insertion of 31 amino acids in the sema domain. Here, we investigated the bioactivity of these isoforms and show, using coculture and binding assays, that they share common axonal chemorepulsive properties and binding to neuropilin receptors. SEMA3F isoforms were also found to regulate endothelial cell morphology by remodeling lamellipodial protrusions. Although Sema3F expression globally decreased during mouse development, we noted an enrichment of the longest isoform at postnatal stages in some territories such as the brainstem and spinal cord. These results indicate that although functionally redundant in cell culture assays, Sema3F spliced forms are characterized in vivo by a temporal and regional specific regulation during maturation of the nervous system

Semaphorin SEMA3F Has a Repulsing Activity on Breast Cancer Cells and Inhibits E-Cadherin-Mediated Cell Adhesion

Previously, we demonstrated that loss of SEMA3F, a secreted semaphorin encoded in 3p21.3, is associated with higher stages in lung cancer and primary tumor cells studied with anti-vascular endothelial growth factor (VEGF) and SEMA3F antibodies. In vitro, SEMA3F inhibits cell spreading; this activity is opposed by VEGF. These results suggest that VEGF and SEMA3F compete for binding to their common neuropilin receptor. In the present report, we investigated the attractive/repulsive effects of SEMA3F on cell migration when cells were grown in a three-dimensional system and exposed to a SEMA3F gradient. In addition, we adapted the neurobiologic stripe assay to analyze the migration of tumor cells in response to SEMA3F. In the motile breast cancer cell line C100, which expresses both neuropilin-1 (NRP1) and neuropilin-2 (NRP2) receptors, SEMA3F had a repulsive effect, which was blocked by anti-NRP2 antibody. In less motile MCF7 cells, which express only NRP1, SEMA3F inhibited cell contacts with loss of membrane-associated E-cadherin and β-catenin without motility induction. Cell spreading and proliferation were reduced. These results support the concept that in a first step during tumorigenesis, normal tissues expressing SEMA3F would try to prevent tumor cells from spreading and attaching to the stroma for further implantation