Benzodiazepines that bind at peripheral sites inhibit cell proliferation.

[3H]Ro5-4864 binds to mouse thymoma cells in a specific, saturable, and reversible manner. Scatchard analysis shows a single class of binding sites with a Kd of 4.4 nM and a Bmax of 477 fmol per 10(6) cells. This benzodiazepine binding site is of the peripheral type, based on the relative potencies of Ro5-4864 and clonazepam in competing for [3H]diazepam binding. Fifteen benzodiazepines that bind to this site with affinities ranging from 6 nM to 1 microM also reversibly inhibit the proliferation of thymoma cells in culture at the micromolar dose range. There is a strong positive correlation (r = 0.85) between the binding constants of these compounds for the peripheral-type sites and their ED50 in inhibiting the uptake of [3H]thymidine into the cells. These sites may be involved in the regulation of thymoma cell proliferation.     

Follicular dendritic cells inhibit human B-lymphocyte proliferation.

In germinal centers, B lymphocytes are intimately associated with follicular dendritic cells (FDCs). It has been hypothesized that FDCs are involved in the regulation of B-cell growth and differentiation through cell-cell interactions. In this study, highly enriched preparations of FDCs were isolated by cell sorting using the FDC restricted monoclonal antibody DRC-1. When irradiated FDCs were cultured with mitogen stimulated B cells, B cell 3H-TdR uptake was inhibited by up to 80%. This inhibitory effect was not seen when paraformaldehyde fixed FDCs were added to B-cell cultures, suggesting that the FDCs needed to be metabolically active. Moreover, supernatants from cultured FDCs were similarly able to inhibit B-cell proliferation. These results demonstrate that FDCs may downregulate the clonal expansion of B cells that occurs within lymphoid follicles as part of the normal physiologic immune response. Potentially, the loss of the inhibitory role of FDCs in vivo may be of importance in certain infectious and neoplastic processes in which germinal centers are affected.     

Leukotriene B4 activates T cells that inhibit B-cell proliferation in EBV-infected cord blood-derived mononuclear cell cultures

Epstein-Barr virus (EBV)-specific cellular memory is not transferred from mother to child. Therefore, EBV-induced B-cell proliferation in in vitro-infected cord blood mononuclear cell cultures is not inhibited. However, by addition of immunomodulators, polysaccharide K (PSK) or truncated thioredoxin (Trx80) that activate monocytes, EBV-specific T-cell response could be generated in such cultures. Presently, we demonstrate that leukotriene B(4) (LTB(4)) is involved in the effect of the immunomodulators. LTB(4) was detected in the medium, and T-cell activation was compromised by addition of leukotriene biosynthesis inhibitors. Moreover, we found that LTB(4) added to infected cultures, which did not receive the immunomodulators, induced functional activation of the T cells. LTB(4) activated the monocytes and acted directly on the T cells. In consequence, addition of LTB(4) inhibited the EBV-induced proliferation of B lymphocytes. Specific cytotoxicity could be generated by restimulation of the T cells. The experiments showed successive stages of T-cell activation in acquisition of their immunologic effector function. This is orchestrated by complex cellular interactions, and autocrine loops mediated by soluble factors-here interferon (IFN)-gamma, interleukin (IL)-15, IL-12, and LTB(4). Importantly, the results indicate that endogenous LTB(4) can induce T-cell activation that inhibits the EBV-induced proliferation of B lymphocytes.     

Prepubertal rat Sertoli cells secrete a mitogenic factor(s) that stimulates germ and somatic cell proliferation

Sertoli cells were isolated from prepubertal 6- and 12-day-old rats. The Sertoli cell-conditioned media (SCCM-6 and SCCM-12) can markedly stimulate the proliferation of somatic cells and quiescent rat prespermatogonia in a dose-dependent and an age-related manner. SCCM-12 stimulated cell proliferation of BALB/c 3T3 fibroblasts up to 7-fold over control values, but did not stimulate to the same degree the germ cell mitotic activity. SCCM-6 stimulated proliferation of prespermatogonia up to 5-10-fold over controls. The mitogenic factor(s) in SCCM-6 appears to be more specific to prespermatogonia than to somatic cells which is consistent with the in vivo stimulation of mitosis in germ cells 5-6 days after birth and with the action of 'mitosis inducing substance'. The mitogenic factor(s) appears to be protein with a molecular weight over 8000 and sensitive to heat and trypsin treatment. These results suggest that the different mitogenicity of prepubertal rat SCCM on germ and somatic cells may be due to secretion of multiple mitogens by Sertoli cells in an age-dependent manner.     

F-box protein FBXL2 targets cyclin D2 for ubiquitination and degradation to inhibit leukemic cell proliferation

Hematologic maligancies exhibit a growth advantage by up-regulation of components within the molecular apparatus involved in cell-cycle progression. The SCF (Skip-Cullin1-F-box protein) E3 ligase family provides homeostatic feedback control of cell division by mediating ubiquitination and degradation of cell-cycle proteins. By screening several previously undescribed E3 ligase components, we describe the behavior of a relatively new SCF subunit, termed FBXL2, that ubiquitinates and destabilizes cyclin D2 protein leading to G(0) phase arrest and apoptosis in leukemic and B-lymphoblastoid cell lines. FBXL2 expression was strongly suppressed, and yet cyclin D2 protein levels were robustly expressed in acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) patient samples. Depletion of endogenous FBXL2 stabilized cyclin D2 levels, whereas ectopically expressed FBXL2 decreased cyclin D2 lifespan. FBXL2 did not bind a phosphodegron within its substrate, which is typical of other F-box proteins, but uniquely targeted a calmodulin-binding signature within cyclin D2 to facilitate its polyubiquitination. Calmodulin competes with the F-box protein for access to this motif where it bound and protected cyclin D2 from FBXL2. Calmodulin reversed FBXL2-induced G(0) phase arrest and attenuated FBXL2-induced apoptosis of lymphoblastoid cells. These results suggest an antiproliferative effect of SCF(FBXL2) in lymphoproliferative malignancies.     

Human endothelial cells are stimulated and vascular smooth muscle cells are inhibited in their proliferation and migration by heparins.

The actions of two natural heparins and a semi synthetic low molecular weight heparin with low anticoagulant activity have been studied on the migration and proliferation of human vascular endothelial and vascular smooth muscle cells in vitro. In a migration assay non irradiated confluent cultures of endothelial cells and smooth muscle cells were "wounded" with a sharp razor blade in such a way, that the migration of individual cells from the wound edge into a region void of cells could be measured. The maximum distance migrated (perpendicularly to the wound edge) three days after wounding, was taken as an index for migratory activity. All tested heparins reduced migration of vascular smooth muscle cells and enhanced migration of vascular endothelial cells in a concentration dependent manner. Cell proliferation was studied in clone culture. All heparins tested were found to inhibit smooth muscle cell growth. The number of clones, as well as the size of single clones, were smaller with increasing concentrations of natural and low molecular weight heparin. The endothelial cells, however, exhibited contrary responses; with increasing concentrations of heparin, the cloning efficiency and the cell number of individual endothelial cell clones increased. This opposite effects of natural heparins and low molecular weight heparin could be of importance in preventing secondary stenosing intimal proliferations after angioplasty, bypass operation and embolectomy or even atherogenesis. Since the low molecular weight heparin has only a low anticoagulatory activity, it may be more appropriate than natural heparins for long term therapy to prevent artery stenoses caused by intimal SMC proliferation.     

Mesenchymal stem cell-natural killer cell interactions: evidence that activated NK cells are capable of killing MSCs, whereas MSCs can inhibit IL-2-induced NK-cell proliferation

In recent years, mesenchymal stem cells (MSCs) have been shown to inhibit T-lymphocyte proliferation induced by alloantigens or mitogens. However, no substantial information is available regarding their effect on natural killer (NK) cells. Here we show that MSCs sharply inhibit IL-2-induced proliferation of resting NK cells, whereas they only partially affect the proliferation of activated NK cells. In addition, we show that IL-2-activated NK cells (but not freshly isolated NK cells) efficiently lyse autologous and allogeneic MSCs. The activating NK receptors NKp30, NKG2D, and DNAM-1 represented the major receptors responsible for the induction of NK-mediated cytotoxicity against MSCs. Accordingly, MSCs expressed the known ligands for these activating NK receptors-ULBPs, PVR, and Nectin-2. Moreover, NK-mediated lysis was inhibited when IFN-gamma-exposed MSCs were used as target cells as a consequence of the up-regulation of HLA class I molecules at the MSC surface. The interaction between NK cells and MSCs resulted not only in the lysis of MSCs but also in cytokine production by NK cells. These results should be taken into account when evaluating the possible use of MSCs in novel therapeutic strategies designed to improve engraftment or to suppress graft-versus-host disease (GVHD) in bone marrow transplantation.     

Nodal signaling regulates the entry into meiosis in fetal germ cells

The mechanisms regulating the entry into meiosis in mammalian germ cells remain incompletely understood. We investigated the involvement of the TGF-β family members in fetal germ cell meiosis initiation. Nodal, a member of the TGF-β family, and its target genes are precociously expressed in embryonic gonads and show sexual dimorphism in favor of the developing testis. Nodal receptor genes, Acvr2a and Acvr2b, Alk4, and Tdgf1/Cripto, were identified in male germ cells. Nodal itself, Tdgf1, and Lefty1 and Lefty2 are targets of Nodal signaling and were all found specifically expressed in male germ cells. To elucidate the role of this signaling pathway, activin-like kinases that mediate TGF-β/Nodal/activin signaling were inhibited in 11.5 d postconception testis in organotypic culture. Activin-like kinases inhibition disrupted normal male germ cell development and induced germ cell entry into meiosis such as that observed in female germ cells at the equivalent stage. Interestingly Stra8, the gatekeeper of the mitotic/meiotic switch, was induced independently of any change of either Cyp26b1 or Fgf9 expression, the two genes currently identified as testicular meiotic inhibitors. On the other hand, recombinant Nodal significantly dampened Stra8 expression and germ cell meiosis in cultured 11.5 d postconception ovaries. Our results allowed us to propose for the first time an autocrine role of Nodal during the development of germ cells and indicate that members of the TGB-β family may reinforce the male fate and prevent meiosis in embryonic germ cells.     

Pituitary hormones inhibit the function and differentiation of fetal Sertoli cells

Although the role of pituitary hormones in fetal Sertoli cell proliferation is well understood, their involvement in fetal Sertoli cell differentiation is poorly documented. In this study, we evaluated rat fetal Sertoli cell function by measuring basal transferrin secretion ex vivo and transferrin and anti-Müllerian hormone (AMH) mRNA levels in vivo. The differentiation state of the Sertoli cells was estimated from the amount of transferrin secreted ex vivo after acute stimulation with FSH. Surprisingly, we found that the amount of transferrin secreted by each Sertoli cell in basal condition and after acute FSH stimulation decreased between 18.5 and 21.5 day post coitum (dpc), which corresponds to the onset of pituitary hormone secretion. All of the Sertoli cell parameters measured (basal and FSH-stimulated transferrin secretion ex vivo, transferrin and AMH mRNA levels in vivo) were higher in 21.5-dpc fetuses that had been decapitated on 16.5 dpc than in control littermates. Furthermore, immunostaining for AMH was strongly increased after decapitation. Taken together, these results suggest that pituitary hormones in the fetus and in the immature or adult rat differently regulate Sertoli cells, which suggests that fetal Sertoli cells have their own particular physiology.     

Effects of agents that inhibit cellular iron incorporation on bladder cancer cell proliferation

Agents that interfere with cellular iron (Fe) incorporation inhibit tumor cell proliferation, including metals that bind to transferrin (Tf) such as gallium (Ga) or indium (In) and Fe chelators such as desferrioxamine (DFO). Ga nitrate is effective in the treatment of metastatic bladder cancer and these patients exhibit evidence for interference with Fe metabolism. We show here that bladder cancer cell proliferation in vitro is dependent on Tf-Fe. Concentrations of DFO that can be readily achieved in vivo inhibit cellular proliferation even in the presence of physiologic concentrations of Tf-Fe. Inhibition of proliferation by Tf-Ga is associated with decreased cellular Fe incorporation. However, when a physiologic concentration of Tf-Fe is added to an equimolar concentration of Tf-Ga, significant Fe incorporation is evident despite inhibition of proliferation. Thus, besides interference with Fe incorporation, Ga may also interfere with intracellular Fe distribution and/or directly inhibit an Fe- (or non-Fe- ) requiring process necessary for cellular proliferation. DFO followed sequentially by Tf-Ga results in marked potentiation of inhibition of proliferation. The effects of this combination appear to be related to both interference with Fe metabolism and increased Ga uptake. This sequential combination may be useful in the treatment of bladder cancer.     

lin-Sca-1+ cells and age-dependent changes of their proliferation potential are reliant on mesenchymal stromal cells and are leukemia inhibitory factor dependent

Aging as a process is paralleled by a variety of hematological alterations. Characteristic features are a diminished homeostatic control of blood cell production and a decline in immune functions. It is generally accepted that stromal cells play a basal role in hematopoiesis by providing survival and differentiation signals, by secreting cytokines, or through direct contact with hematopoietic stem cells, thereby supporting the generation and replenishment of hematopoi- etic progenitor cells (HPC). Here we demonstrated that HPC-related colony formation is positively influenced by mesenchymal stromal cells (MSCs) when grown in co-culture, in particular regarding the number of primary granulocyte/macrophage colony-forming units as well as with respect to the average size of the formed colonies. These effects were more pronounced when the MSCs originated from young donors than from old ones. Because leukemia inhibitory factor (LIF) plays an important role during hematopoiesis, properties of lin- Sca-1+ cells and MSCs derived from LIF-deficient mice (LIF-/-) were determined both ex vivo and in vitro. LIF-/- animals contain a significantly reduced number of lin- Sca-1+ cells, nevertheless the replating capacity of LIF-/- HPCs was found to be generally unchanged when compared to those from LIF+/+ animals. However, when cocultured with MSCs, LIF-/- lin- Sca-1+ cells exhibited comparable characteristics to HPCs derived from old wild-type animals.     

花姜酮通过抗氧化应激抑制人气道平滑肌细胞的增殖

目的 探讨花姜酮对转化生长因子β (transforming growth factor-β,TGF-β)诱导人气道平滑肌细胞(human airway smooth muscle cells,HASMCs)增殖的抑制作用及其机制.方法 用CCK-8的方法检测细胞增殖;用荧光显微镜观察2,7-二氯荧光乙酰乙酸(DCFH-DA)染色后细胞内的活性氧(reactive oxygen species,ROS);用流式细胞术检测细胞内ROS水平.结果 TGF-β1(1μg/L)作用72 h后可以明显促进HASMCs的增殖(P＜0.05);花姜酮可以呈浓度依赖性的抑制HASMCs的增殖(P＜0 05),抑制细胞内ROS的水平,以花姜酮组(30 mmol/L)的抑制作用最明显(P＜0.01).结论 花姜酮可以抑制HASMCs的增殖,其机制可能是通过抑制细胞内的ROS产生.     

Hematopoietic stem cells are not direct cytotoxic targets of natural killer cells

Bone marrow (BM) transplants from one individual to an irradiated histoincompatible individual of the same species are rejected. In mice, the primary host barrier cells that recognize bone marrow grafts bearing hematopoietic histocompatibility antigens bear surface markers of natural killer (NK) lymphocytes. Because of the innate ability of NK cells to kill susceptible targets, it has been proposed that the cytotoxic bone marrow graft rejection. To test this hypothesis, we purified hematopoietic stem cells from mice and incubated them with purified populations of actively cytotoxic allogeneic and semisyngeneic NK cells, followed by analysis of the ability of the treated hematopoietic stem cells (HSCs) to rescue lethally irradiated syngeneic animals. Such rescue was unimpaired. Also, HSC allografts were transplanted into transgenic mice deficient in NK and killer T-cell cytotoxicity generated by expressing diphtheria toxin A chain under the control of granzyme A promoter. Allogeneic HSCs were susceptible to allogeneic restriction in these mice, implying that the effector functions of NK marker-positive cells do not require NK cell cytotoxicity.     

树突状细胞诱导的抗肿瘤免疫诱导移植瘤细胞凋亡并抑制其增殖

目的研究树突状细胞(DC)体外诱导的细胞免疫能否抑制裸鼠移植瘤生长及其机制.方法联合应用粒/巨噬细胞集落刺激因子(GM-CSF)及白介素-4(IL-4)直接从肝癌患者外周血中培养出DC,以源于人肝癌细胞系HepG2肿瘤细胞的肿瘤抗原粗提物刺激DC,DC激活同源的T淋巴细胞产生细胞毒性T淋巴细胞(CTL),建立裸鼠人肝癌细胞系HepG2移植瘤模型.以CTL治疗裸鼠HepG2移植瘤并观察治疗效果,检测移植瘤标本肿瘤细胞凋亡情况.结果DC诱导的CTL通过诱导肿瘤细胞凋亡并抑制其增殖而抑制移植瘤生长.结论经肿瘤抗原激发的DC有可能在肿瘤的治疗中发挥重要作用.