参考文献

TLRs are involved in innate cell activation by conserved structures expressed by microorganisms. Human T cells express the mRNA encoding most of TLRs. Therefore,we tested whether some TLR ligands may modulate the function of highly purified human CD4+ T lymphocytes. We report that,in the absence of APCs,flagellin (a TLR5 ligand) and R-848 (a TLR7/8 ligand) synergized with suboptimal concentrations of TCR-dependent (anti-CD3 mAb) or -independent stimuli (anti-CD2 mAbs or IL-2) to up-regulate proliferation and IFN-gamma,IL-8,and IL-10 but not IL-4 production by human CD4+ T cells. No effect of poly(I:C) and LPS,ligands for TLR3 and TLR4,respectively,was detected. We also observed that CD4+CD45RO+ memory T cell responses to TLR ligands were more potent than those observed with CD4+CD45RA+ naive T cells. Moreover,among the memory T cells,CCR7- effector cells were more sensitive to TLR ligands than CCR7+ central memory cells. These data demonstrate for the first time a direct effect of TLR5 and TLR7/8 ligands on human T cells,and highlight an innate arm in T cell functions. They also suggest that some components from invading microorganisms may directly stimulate effector memory T cells located in tissues by up-regulating cytokine and chemokine production. View Publication

The dedifferentiation agent reversine" [2-(4-morpholinoanilino)-N(6)-cyclohexyladenine 2] was found to be a moderately potent antagonist for the human A(3) adenosine receptor (AR) with a K(i) value of 0.66 microM. This result prompted an exploration of the structure-activity relationship of related derivatives� View Publication

The identification of neural stem cells (NSCs) in situ has been prevented by the inability to identify a marker consistently expressed in all adult NSCs and is thus generally accomplished using the in vitro neurosphere-forming assay. The high-mobility group transcription factor Sox2 is expressed in embryonic neural epithelial stem cells; because these cells are thought to give rise to the adult NSC population,we hypothesized that Sox2 may continue to be expressed in adult NSCs. Using Sox2:EGFP transgenic mice,we show that Sox2 is expressed in neurogenic regions along the rostral-caudal axis of the central nervous system throughout life. Furthermore,all neurospheres derived from these neurogenic regions express Sox2,suggesting that Sox2 is indeed expressed in adult NSCs. We demonstrate that NSCs are heterogeneous within the adult brain,with differing capacities for cell production. In vitro,all neurospheres express Sox2,but the expression of markers common to early progenitor cells within individual neurospheres varies; this heterogeneity of NSCs is mirrored in vivo. For example,both glial fibrillary acidic protein and NG2 are expressed within individual neurospheres,but their expression is mutually exclusive; likewise,these two markers show distinct staining patterns within the Sox2+ regions of the brain's neurogenic regions. Thus,we propose that the expression of Sox2 is a unifying characteristic of NSCs in the adult brain,but that not all NSCs maintain the ability to form all neural cell types in vivo. View Publication

Activation of the transcription factor,nuclear factor-kappaB (NF-kappaB),results in up-regulation of not only antiapoptotic genes but also proapoptotic genes,including death receptor 4 (DR4) and death receptor 5 (DR5). Therefore,NF-kappaB activation either suppresses or promotes apoptosis depending on the type of stimulus or cell context. We showed previously that the synthetic retinoid,6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437),effectively induces apoptosis particularly in androgen-independent prostate carcinoma cells. This effect was associated with the ability of CD437 to induce the expression of DR4 and DR5. In the present study,we examined the hypothesis that NF-kappaB activation plays a role in CD437-induced death receptor expression and apoptosis. Treatment of DU145 cells with CD437 resulted in a rapid decrease (textgreater or = 3 hours) of IkappaBalpha,which was accompanied by increased translocation of the NF-kappaB subunit p65 from the cytoplasm to the nucleus and increased NF-kappaB DNA-binding activity (textgreater or = 4 hours). The NF-kappaB inhibitor,helenalin,inhibited CD437-induced IkappaBalpha reduction and p65 nuclear translocation. Accordingly,it also abrogated CD437-induced up-regulation of DR4,activation of caspase-8 and caspase-3,and increased DNA fragmentation. Overexpression of an IkappaBalpha dominant-negative mutant blocked not only CD437-induced p65 nuclear translocation but also DR4 up-regulation,caspase activation,and DNA fragmentation. CD437 was unable to decrease IkappaBalpha protein levels and up-regulate DR4 expression in CD437-resistant DU145 cells. Moreover,knockdown of Fas-associated death domain,caspase-8,and DR4,respectively,suppressed CD437-induced apoptosis. Collectively,these results indicate that CD437 activates NF-kappaB via decreasing IkappaBalpha protein and thereby induces DR4 expression and subsequent apoptosis in DU145 cells. View Publication

DNA methylation regulates gene expression in normal and malignant cells. The possibility to reactivate epigenetically silenced genes has generated considerable interest in the development of DNA methyltransferase inhibitors. Here,we provide a detailed characterization of RG108,a novel small molecule that effectively blocked DNA methyltransferases in vitro and did not cause covalent enzyme trapping in human cell lines. Incubation of cells with low micromolar concentrations of the compound resulted in significant demethylation of genomic DNA without any detectable toxicity. Intriguingly,RG108 caused demethylation and reactivation of tumor suppressor genes,but it did not affect the methylation of centromeric satellite sequences. These results establish RG108 as a DNA methyltransferase inhibitor with fundamentally novel characteristics that will be particularly useful for the experimental modulation of epigenetic gene regulation. View Publication

The hematopoietic stem cell (HSC) gives rise to all mature,terminally differentiated cells of the blood. Here we show that calmodulin-dependent protein kinase IV (CaMKIV) is present in c-Kit+ ScaI+ Lin(-/low) hematopoietic progenitor cells (KLS cells) and that its absence results in hematopoietic failure,characterized by a diminished KLS cell population and by an inability of these cells to reconstitute blood cells upon serial transplantation. KLS cell failure in the absence of CaMKIV is correlated with increased apoptosis and proliferation of these cells in vivo and in vitro. In turn,these cell biological defects are correlated with decreases in CREB-serine 133 phosphorylation as well as in CREB-binding protein (CBP) and Bcl-2 levels. Re-expression of CaMKIV in Camk4-/- KLS cells results in the rescue of the proliferation defects in vitro as well as in the restoration of CBP and Bcl-2 to wild type levels. These studies show that CaMKIV is a regulator of HSC homeostasis and suggest that its effects may be in part mediated via regulation of CBP and Bcl-2. View Publication

A series of 30 N10-substituted phenoxazines were synthesized and screened as potential inhibitors of Akt. In cellular assays at 5 mum,17 compounds inhibited insulin-like growth factor 1 (IGF-I)-stimulated phosphorylation of Akt (Ser-473) by at least 50% but did not inhibit IGF-I-stimulated phosphorylation of Erk-1/2 (Thr-202/Tyr-204). Substitutions at the 2-position (Cl or CF3) did not alter inhibitory activity,whereas N10-substitutions with derivatives having acetyl (20B) or morpholino (12B) side chain lost activity compared with propyl or butyl substituents (7B and 14B). Inhibition of Akt phosphorylation was associated with the inhibition of IGF-I stimulation of the mammalian target of rapamycin phosphorylation (Ser-2448 and Ser-2481),phosphorylation of p70 S6 kinase (Thr-389),and ribosomal protein S6 (Ser-235/236) in Rh1,Rh18,and Rh30 cell lines. The two most potent compounds 10-[4'-(N-diethylamino)butyl]-2-chlorophenoxazine (10B) and 10-[4'-[(beta-hydroxyethyl)piperazino]butyl]-2-chlorophenoxazine (15B) (in vitro,IC50 approximately 1-2 microM) were studied further. Inhibition of Akt phosphorylation correlated with inhibition of its kinase activity as determined in vitro after immunoprecipitation. Akt inhibitory phenoxazines did not inhibit the activity of recombinant phosphatidylinositol 3'-kinase,PDK1,or SGK1 but potently inhibited the kinase activity of recombinant Akt and Akt deltaPH,a mutant lacking the pleckstrin homology domain. Akt inhibitory phenoxazines blocked IGF-I-stimulated nuclear translocation of Akt in Rh1 cells and suppressed growth of Rh1,Rh18,and Rh30 cells (IC50 2-5 microM),whereas inactive" derivatives were textgreater or = 10-fold less potent inhibitors of cell growth. In contrast to rapamycin analogs� View Publication

BACKGROUND/AIMS The Rho-ROCK signaling pathways play an important role in the activation of hepatic stellate cells (HSCs). We investigated the effects of fasudil hydrochloride hydrate (fasudil),a Rho-kinase (ROCK) inhibitor,on cell growth,collagen production,and collagenase activity in HSCs. METHODS Rat HSCs and human HSC-derived TWNT-4 cells were cultured for studies on stress fiber formation and alpha-smooth muscle actin (alpha-SMA) expression. Proliferation was measured by BrdU incorporation,and apoptosis by TUNEL assay. The phosphorylation states of the MAP kinases (MAPKs),extra cellular signal -regulated kinase 1/2 (ERK1/2),c-jun kinase (JNK),and p38 were evaluated by western blot analysis. Type I collagen,matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) production and gene expression were evaluated by ELISA and real-time PCR,respectively. Collagenase activity (active MMP-1) was also evaluated. RESULTS Fasudil (100 microM) inhibited cell spreading,the formation of stress fibers,and expression of alpha-SMA with concomitant suppression of cell growth,although it did not induce apoptosis. Fasudil inhibited phosphorylation of ERK1/2,JNK,and p38. Treatment with fasudil suppressed the production and transcription of collagen and TIMP,stimulated the production and transcription of MMP-1,and enhanced collagenase activity. CONCLUSION These findings demonstrated that fasudil not only suppresses proliferation and collagen production but also increases collagenase activity. View Publication

Purmorphamine is a novel small molecule with osteogenesis-inducing activity in multipotent mesenchymal progenitor cells,but there has been no evaluation of its effect on human cells to date. The aim of this study was to investigate the induction of osteogenic activity by purmorphamine in human osteoblasts differentiated from bone marrow mesenchymal cells. Cells were cultured in 24-well plates at a density of 2x10(4)/well in medium containing 1,2 or 3 microM purmorphamine,or vehicle. At 7,14 and 21 days,cell proliferation,viability,and alkaline phosphatase (ALP) activity were evaluated. Bone-like nodule formation was evaluated at 21 days. Purmorphamine did not affect cell proliferation or viability,but increased ALP activity and bone-like nodule formation. These results indicate that events related to osteoblast differentiation,including increased ALP activity and bone-like nodule formation,are enhanced by purmorphamine. View Publication

Although significant advances have been made over the last decade with respect to our understanding of stem cell biology,progress has been limited in the development of successful techniques for clinically significant ex vivo expansion of hematopoietic stem and progenitor cells. We here describe the effect of Notch ligand density on induction of Notch signaling and subsequent cell fate of human CD34+CD38- cord blood progenitors. Lower densities of Delta1(ext-IgG) enhanced the generation of CD34+ cells as well as CD14+ and CD7+ cells,consistent with early myeloid and lymphoid differentiation,respectively. However,culture with increased amounts of Delta1(ext-IgG) induced apoptosis of CD34+ precursors resulting in decreased cell numbers,without affecting generation of CD7+ cells. RNA interference studies revealed that the promotion of lymphoid differentiation was primarily mediated by Delta1 activation of Notch1. Furthermore,enhanced generation of NOD/SCID repopulating cells was seen following culture with lower but not higher densities of ligand. These studies indicate critical,quantitative aspects of Notch signaling in affecting hematopoietic precursor cell-fate outcomes and suggest that density of Notch ligands in different organ systems may be an important determinant in regulating cell-fate outcomes. Moreover,these findings contribute to the development of methodology for manipulation of hematopoietic precursors for therapeutic purposes. View Publication