Biomedical subjects

Y Ikeda

Publications and source records attributed to Y Ikeda.

At least 127 records · Page 7Linked to original sources

PubMed2001

Activation of the p21(CIP1/WAF1) promoter by bone morphogenetic protein-2 in mouse B lineage cells.

BMPs exert a negative growth effect on various types of cells. We have previously reported that BMP-2 inhibited the growth of HS-72 mouse hybridoma cells by inducing p21(CIP1/WAF1) expression. In the present study, we demonstrated that BMP-2 activated the mouse p21(CIP1/WAF1) promoter in HS-72 cells, and that a 29-base pair (b) region of the promoter (-1928/-1900 relative to the TATA box), conserved between mice and humans, was responsive to BMP-2 as well as expression of Smad1, Smad4, and constitutively active mutants of BMP type I receptors. Furthermore, an oligonucleotide containing the 29-b region was found to be associated with Smad4 and phosphorylated Smad1 in the nuclear extract of BMP-2-stimulated HS-72 cells. These results suggested that BMP-2 might activate p21(CIP1/WAF1) transcription by inducing a binding of Smad4 and Smad1 to the 29-b region in HS-72 cells.

Animals↗

PubMed2001

Major roles of prostanoid receptors IP and EP(3) in endotoxin-induced enhancement of pain perception.

To know the roles of prostaglandin I (IP) and prostaglandin E (EP) receptors in pain perception, we compared the acetic acid-induced writhing response in mice deficient in prostaglandin receptors, i.e. IP, EP(1,) EP(2,) EP(3,) or EP(4,) with or without lipopolysaccharide (LPS) pretreatment. Without LPS pretreatment, IP-receptor deficient mice showed a significantly smaller number of responses, as previously reported, whereas mice deficient in any of the EP-receptor subtypes showed a number of writhings similar to those of wild-type mice. When mice were pretreated with LPS for 24 hr to induce cyclooxygenase-2 expression, the wild-type as well as EP(1)-, EP(2)-, or EP(4)-receptor-deficient mice showed a similar enhanced writhing response, whereas IP- and EP(3)-receptor-deficient mice had a significantly less enhanced number of writhings. These results indicate that IP and EP(3) are the major prostaglandin receptors mediating the enhanced acetic acid-induced writhing response in mice pre-exposed to LPS, i.e. in endotoxin-enhanced inflammatory nociception.

Animals↗

PubMed2001

Down-regulation of the alpha-Gal epitope expression in N-glycans of swine endothelial cells by transfection with the N-acetylglucosaminyltransferase III gene. Modulation of the biosynthesis of terminal structures by a bisecting GlcNAc.

The down-regulation of the alpha-Gal epitope (Galalpha1,3Galbeta-R) in swine tissues would be highly desirable, in terms of preventing hyperacute rejection in pig-to-human xenotransplantation. In an earlier study, we reported that the introduction of the beta1,4-N-acetylglucosaminyltransferase (GnT) III gene into swine endothelial cells resulted in a substantial reduction in the expression of the alpha-Gal epitope. In this study, we report on the mechanism for this down-regulation of the alpha-Gal epitope by means of structural and kinetic analyses. The structural analyses revealed that the amount of N-linked oligosaccharides bearing the alpha-Gal epitopes in the GnT-III-transfected cells was less than 10% that in parental cells, due to the alteration of the terminal structures as well as a decrease in branch formation. In addition, it appeared that the addition of a bisecting GlcNAc, which is catalyzed by GnT-III, leads to a more efficient sialylation rather than alpha-galactosylation. In vitro kinetic analyses showed that the bisecting GlcNAc has an inhibitory effect on alpha-galactosylation, but does not significantly affect the sialylation. These results suggest that the bisecting GlcNAc in the core is capable of modifying the biosynthesis of the terminal structures via its differential effects on the capping glycosyltransferase reactions. The findings may contribute to the development of a novel strategy to eliminate carbohydrate xenoantigens.

Acetylglucosamine↗

PubMed2001

Transcriptional regulation of the murine acetyl-CoA synthetase 1 gene through multiple clustered binding sites for sterol regulatory element-binding proteins and a single neighboring site for Sp1.

Cytosolic acetyl-CoA synthetase (AceCS1) activates acetate to supply the cells with acetyl-CoA for lipid synthesis. The cDNA for the mammalian AceCS1 has been isolated recently, and the mRNA was shown to be negatively regulated by sterols in cultured cells. In the current study, we describe the molecular mechanisms directing the sterol-regulated expression of murine AceCS1 by cloning and functional studies of the 5'-flanking region of the AceCS1 gene. An AceCS1 promoter-reporter gene (approximately 2.1 kilobase pairs) was negatively regulated when sterols were added to the medium of cultured cells, and the promoter was markedly induced by co-transfection of a plasmid that expresses the transcriptionally active nuclear form of either sterol regulatory element-binding protein (SREBP)-1a or -2 in HepG2 cells. Sequence analysis suggested that the AceCS1 promoter contains an E-box, two putative CCAAT-boxes, eight sterol regulatory element (SRE) motifs, and six GC-boxes. Gel shift assays demonstrated that all eight SRE motifs bound purified SREBP-1a in vitro with similar affinity. Luciferase reporter gene assays revealed that sterol regulation was critically dependent on three closely spaced SRE motifs and an adjacent GC-box. However, mutation of two putative upstream CCAAT-boxes did not affect SREBP dependent activation. Electrophoretic mobility "supershift" analyses confirmed that both Sp1 and Sp3 bound to the critical GC-box. In addition, transfection studies in Drosophila SL2 cells demonstrated that SREBP synergistically activated the AceCS1 promoter along with Sp1 or Sp3 but not with nuclear factor-Y.

Acetate-CoA Ligase↗

PubMed2001

Immunodominant epitopes on glycoprotein IIb-IIIa recognized by autoreactive T cells in patients with immune thrombocytopenic purpura.

It was recently reported that autoreactive CD4(+) T cells to glycoprotein IIb-IIIa (GPIIb-IIIa) mediate antiplatelet autoantibody production in patients with immune thrombocytopenic purpura (ITP). To further examine the antigenic specificity of the GPIIb-IIIa-reactive T cells, 6 recombinant fragments encoding different portions of GPIIbalpha or GPIIIa were generated and tested for their ability to stimulate antigen-specific T-cell proliferation and anti-GPIIb-IIIa antibody production in vitro. T cells from the peripheral blood of 25 patients with ITP and 10 healthy donors proliferated in response to recombinant GPIIb-IIIa fragments in various combinations. The amino-terminal portions of both GPIIbalpha and GPIIIa (IIbalpha18-259 and IIIa22-262) were frequently recognized (60% and 64%, respectively) compared with other fragments (4%-28%) in patients with ITP, but this tendency was not detected in healthy donors. In subsequent analyses in patients with ITP, T-cell reactivities to IIbalpha18-259 and IIIa22-262 were consistently detected, whereas those to other fragments were sometimes lost. In vitro antigenic stimulation of peripheral blood mononuclear cells with IIbalpha18-259 or IIIa22-262 promoted the synthesis of anti-GPIIb-IIIa antibodies in patients with ITP, but not in healthy donors. Of 15 CD4(+) T-cell lines specific for platelet-derived GPIIb-IIIa generated from 5 patients with ITP, 13 lines recognized IIbalpha18-259, IIIa22-262, or both. T-cell lines reactive to IIbalpha18-259 or IIIa22-262 promoted the production of anti-GPIIb-IIIa antibodies that were capable of binding to normal platelet surfaces. These results indicate that the immunodominant epitopes recognized by pathogenic CD4(+) T cells in patients with ITP are located within the amino-terminal portions of both GPIIbalpha and GPIIIa.

Adult↗

PubMed2001

Generation of definitive hematopoietic stem cells from murine early yolk sac and paraaortic splanchnopleures by aorta-gonad-mesonephros region-derived stromal cells.

There is controversy as to whether murine definitive hematopoiesis originates from yolk sac (YS) or the intraembryonic region. This study reports the generation of definitive hematopoietic stem cells (HSCs) from both early YS and intraembryonic paraaortic splanchnopleures (P-Sp) on AGM-S3 stromal cells derived from the aorta-gonad-mesonephros (AGM) region at 10.5 days post coitum (dpc). YS and P-Sp cells at 8.5 dpc generated no definitive hematopoiesis-derived colony-forming cells in cocultures with AGM-S3 cells, but spleen colony-forming cells and HSCs capable of reconstituting definitive hematopoiesis in adult mice simultaneously appeared on day 4 of coculture. Precursors for definitive HSCs were present in YS and P-Sp at 8.0 dpc, a time when YS and embryo were not connected by blood vessels. It is proposed that precursors with the potential to generate definitive HSCs appear independently in YS and intraembryonic P-Sp and that the P-Sp or AGM region affords the microenvironment that facilitates generation of definitive hematopoiesis from precursors.

Animals↗

PubMed2001

Prostate carcinomas developing in transgenic rats with SV40 T antigen expression under probasin promoter control are strictly androgen dependent.

We have generated a transgenic rat with the SV40 T antigen under probasin promoter control, allowing prostate-specific gene expression. Males demonstrate atypical epithelial cell proliferation in the prostate from 4 weeks of age and develop prostate carcinomas at 100% incidence before they are 15 weeks old. Castration at 5 weeks of age was found to inhibit the prostate tumor formation completely, whereas testosterone propionate administration induced marked cell proliferation as well as microinvasion in prostate carcinomas. Castration at 20 weeks of age, after tumor development, even with testosterone propionate treatment, induced complete tumor involution within 5 weeks. To investigate the underling processes, sequential histological changes were monitored 1, 2, 3, 7, 14, and 21 days after castration. At days 1-3, many apoptotic bodies and inflammatory cells, including foam cells, were observed, and clear glandular structures were no longer evident in the tumors. Seven days after castration, most glands were involved, and nuclei of the cells did not show atypia. After 14 and 21 days, only atrophic glands were observed. During this process, expression of caspase 3, caspase 6, BAX, bcl-x, TRPM-2, and MMP7 genes was apparently increased. Comparison of the gene expression profile between a prostate carcinoma in a transgenic animal and a normal prostate of a wild-type rat by a cDNA array technique was also conducted. The results suggested that our model is suitable to investigate mechanisms of carcinogenesis, including androgen dependence, involution, and apoptosis.

Androgen-Binding Protein↗

PubMed2001

Differential localization and colocalization of two neuron-types of sodium-dependent inorganic phosphate cotransporters in rat forebrain.

We studied by immunohistochemistry the distribution of differentiation-associated sodium-dependent inorganic phosphate (Pi) cotransporter (DNPI) in the rat forebrain, in comparison with brain-specific cotransporter (BNPI). DNPI-staining was principally seen in axonal synaptic terminals which showed a widespread but discrete pattern of distribution different from that of the BNPI-staining. In the diencephalon, marked DNPI-staining was seen in the dorsal lateral geniculate, medial geniculate, ventral posterolateral, ventral posteromedial, anterior, and reticular thalamic nuclei without the colocalization with BNPI-staining. DNPI-staining showed a strong mosaical pattern and overlapped well the BNPI-staining in the medial habenular nucleus. DNPI-staining was moderate over the hypothalamus and notably localized in neurosecretory terminals containing corticotropin-releasing hormone in the median eminence. In contrast, the BNPI-staining was region-related and strong in the ventromedial and mammillary nuclei. In the telencephalon, laminar DNPI-staining was seen over the neocortex, corresponding to the thalamocortical termination, and also found in the retrosplenial cortex and the striatum, with the highest intensity in the accumbens nucleus shell. The present results suggest that DNPI serves as a dominant Pi transport system in synaptic terminals of diencephalic neurons including thalamocortical and thalamostriatal pathways as well as the hypothalamic neuroendocrine system in the rat forebrain.

Animals↗

PubMed2001

Human ABCA1 contains a large amino-terminal extracellular domain homologous to an epitope of Sjögren's Syndrome.

ABCA1 has been suggested to play a key role in cellular lipid release from peripheral cells. In order to study structure-function relationship of this protein, the protein product of a full-length human ABCA1 cDNA was examined for its functions and topological orientation. The electrophoretic mobilities of human ABCA1 expressed in transfected cells increased when treated with N-glycosidase F, suggesting that ABCA1 is highly glycosylated. The ABCA1 was photoaffinity-labeled with ATP and mediated the apoA-I-dependent-release of cholesterol and phospholipid. The influenza hemagglutinin (HA) epitope was introduced into the amino-terminus (N-HA) or between the residues 207 and 208 (207-HA) of the protein. While an antibody against the C-terminus peptide of ABCA1 detected both fusion proteins, an anti-HA antibody did not react with the N-HA fusion protein. Confocal microscopy demonstrated strong cell surface signal with the anti-HA antibody of nonpermeabilized HEK293 cells expressing the 207-HA fusion protein. The results suggested that the signal peptide in the amino-terminal region is cleaved off in its mature form and that the following large hydrophilic region is exposed to outside of cells unlike previously proposed models. We found that this amino-terminal extracellular domain contains a segment homologous to the autoantigen SS-N, an epitope of Sjögren's syndrome, and further identified that ABCA7 codes for the autoantigen SS-N.

ATP Binding Cassette Transporter 1↗

PubMed2001

Cerebral hemorrhage due to heparin limits its neuroprotective effects: studies in a rabbit model of photothrombotic middle cerebral artery occlusion.

We investigated the efficacy of heparin on cerebral ischemic damage in a rabbit model of middle cerebral artery (MCA) photothrombosis and in the same model, cerebral hemorrhage induced by heparin as its side effect was also investigated. Using a photothrombosis model in rabbits, 38 animals were divided into four groups, heparin low-dose I and II, heparin high-dose and vehicle. In heparin low-dose I (n=10) or II (n=7), heparin was administered for 23.5 or 22 h, respectively, starting 30 or 120 min after the start of photo-irradiation to induce thrombosis. In high-dose (n=7), heparin was administered 30 min after the start of photo-irradiation for 23.5 h. In the vehicle treated group (control), 14 animals were infused continuously with saline for 23.5 h. Heparin at low and high doses prolonged Activated partial thromboplastin time (aPTT) by about 3 and 10 times compared with control group. The results show that cerebral hemorrhage was present in all animals, gross hemorrhage was observed in one animal each of the heparin low-dose I and high-dose groups, and in three animals of the heparin low-dose II group, while no gross hemorrhage was observed in control group. In heparin low-dose I, the size of cerebral infarction was significantly (P<0.01) reduced and neurological deficits were significantly (P<0.01) improved. In contrast, in heparin high-dose, the infarct size significantly increased, especially in the cortex (P<0.0001), and neurological deficits were significantly (P<0.01) worsened. In heparin low-dose II, the size of cerebral hemorrhage significantly (P<0.001) increased compared with the control group. In conclusion, using a photothrombotic model in the rabbit MCA, we have investigated the antithrombotic benefits and hemorrhagic risks associated with heparin. Of unique feature of our model is the fact that in a single animal model, we could evaluate doses of heparin which reduce cerebral infarction and doses which can promote cerebral hemorrhage. This model can be extended to determine both benefits and risks of antithrombotic agents.

Animals↗

PubMed2001

Reorganization of the uncrossed visual pathways as revealed by Fos-like immunoreactivity in rats with neonatal monocular enucleation.

To elucidate the neuronal characteristics of the functional expansion in the uncrossed visual pathways (UXVPs), resulting from early monocular enucleation in rats, the feasibility of stimulus-dependent induction of the immediate early gene c-fos was examined immunohistochemically. In the UXVPs of rats with monocular enucleation at birth, patterned visual stimuli induced Fos-like immunoreactive (FLI) neurons much more densely in wide areas of the superficial layer throughout the superior colliculus (SC), and in the striate and extrastriate areas of the visual cortex (VC). In the UXVPs of rats monocularly enucleated after maturity, however, only a few stimulus-dependent FLI neurons were scattered in the restricted portions of the SC and the VC.

Animals↗

PubMed2001

Renal tubule-specific transcription and chromosomal localization of rat thiazide-sensitive Na-Cl cotransporter gene.

The molecular mechanism underlying the renal expression localization of the thiazide-sensitive Na-Cl cotransporter (TSC) gene was studied. The TSC gene was localized to chromosome 19p12-14. In cultured cells, tissue-specific transcription activity of the 5'-flanking region of the rat rTSC gene (5'FL/rTSC) was demonstrated, and the major promoter region was located between position -580 and -141. To further examine the tissue-specific transcription, transgenic rats harboring the 5'FL/rTSC fused upstream of the LacZ gene were generated. Immunohistochemical analysis clearly showed that LacZ gene expression was co-localized to distal convoluted tubules (DCT) with TSC, indicating that the 5'FL/rTSC regulates the renal tubule-specific TSC expression. Because a transcription factor, HFH-3 (hepatocyte nuclear factor-3/folk head homologue-3), had also been localized to DCT, a possible role of the putative cis-acting element (HFH-3/rTSC, -400/-387 position) for HFH-3 binding in the tissue-specific transcription was examined. Deletion and mutation analyses suggested that transcription of the HFH-3/rTSC was actually responsive to HFH-3, and electrophoretic mobility shift assay showed a direct binding of in vitro synthesized HFH-3 to the HFH-3/rTSC. In conclusion, the rTSC gene is localized to rat chromosome 19p12--24. The transcription regulatory region of the TSC gene confers DCT-specific gene expression. DCT-specific transcription factor HFH-3 may be involved in the renal tubule-specific transcription of TSC gene.

Animals↗

PubMed2001

Thromboxane A(2) synthase inhibitor enhanced antithrombotic efficacy of GPIIb-IIIa receptor antagonist without increasing bleeding.

The advantage of platelet integrin GPIIb-IIIa receptor antagonists in the prevention of thrombotic occlusion was clearly proven in patients who underwent interventional treatment of the coronary artery, but its value in cerebral ischemia is still under investigation. The expectation of intracranial hemorrhage on strong inhibition of platelet function restricts its application in cerebral ischemia. To minimize bleeding while keeping antithrombotic activity, we have tried to find an appropriate approach using a combination of platelet integrin GPIIb-IIIa receptor antagonist and some other antithrombotic agents. The time to thrombotic occlusion was measured using a photothrombotic occlusion model of guinea pig middle cerebral artery. A platelet integrin GPIIb-IIIa receptor antagonist, ME3277 (sodium hydrogen [4-[(4,5,6,7-tetrahydrothieno [3,2-c] pyridin-2-yl) carbonylamino] acetyl-o-phenylene] dioxydiacetate), delayed occlusion time from 7.3 min in vehicle to 15.0, 20.6 and 25.9 min (P<0.05) at 0.1, 0.3 and 1 mg/kg, respectively. ME3277 profoundly inhibited ex vivo platelet aggregation and the highest dose of ME3277 prolonged (3.5 folds, P<0.01) the bleeding time measured in the hind paw. A thromboxane A(2) synthase inhibitor, sodium ozagrel, significantly delayed occlusion time to 19.5 min at 30 mg/kg (P<0.05) while it did not affect bleeding time or platelet aggregation. ME3277 (0.1 mg/kg) in combination with 10 mg/kg sodium ozagrel synergistically delayed occlusion time (sodium ozagrel alone; 7.9 min, combination; 26.1 min, P<0.05 vs. ME3277 alone). Sodium ozagrel did not affect ex vivo platelet aggregation or bleeding time when combined with 0.1 mg/kg of ME3277. This synergy was cancelled by combination with 30 mg/kg aspirin (14.7 min). A thromboxane A(2) receptor antagonist, vapiprost (0.1 mg/kg), did not enhance the antithrombotic efficacy of ME3277. These results imply that local prostacyclin production enhances the in vivo antithrombotic effect of the platelet integrin GPIIb-IIIa receptor antagonist. Therefore, the thromboxane A(2) synthase inhibitor allowed a reduction in the dose level of the platelet integrin GPIIb-IIIa receptor antagonist for cerebral thrombosis, which resulted in a reduced risk of bleeding.

Amides↗

PubMed2001

Laparoscopic partial or cortical-sparing adrenalectomy by dividing the adrenal central vein.

BACKGROUND: We perform laparoscopic partial adrenalectomy without sectioning the adrenal central vein has been described because it is important to preserve this vein in the remnant adrenal gland in order to maintain its function. In this article, we describe our technique for laparoscopic partial or cortical-sparing adrenalectomy by dividing the adrenal central vein. METHODS: The procedures were performed in four patients with aldosterone-producing adenomas (APA) and two patients with pheochromocytomas. RESULTS: There were no postoperative complications. At follow-up, adrenal 131I-adosterol scintigrams showed that remnant adrenal function had been preserved in all cases. CONCLUSION: Since the vascular bed adjacent to the remnant adrenal gland is integral to the preservation of its function, it is important to perform procedures that do not separate the remnant adrenal gland from the retroperitonium space. Because the operative field is clearly visualized on the high-magnification video monitor, this delicate procedure can be performed with a high degree of accuracy via the laparoscopic approach. We consider this operative technique to be useful for selected cases.

Adrenal Cortex↗

PubMed2001

Evidence for bradykinin mediation of carrageenin-induced inflammatory pain: a study using kininogen-deficient Brown Norway Katholiek rats.

Inflammatory pain was induced following an intradermal injection of carrageenin into rat paws, and the hyperalgesia was measured in terms of withdrawal time following thermal pain stimulation of the inflamed paw. This hyperalgesia was significantly less in kininogen-deficient Brown Norway (B/N)-Katholiek rats, which also showed less swelling in carrageenin-induced paw edema, than in normal B/N-Kitasato rats at 1 approximately 4 hr after the carrageenin injection (at the early phase). However, 24 hr after the injection, hyperalgesia and the swelling volume of the kininogen-deficient rats were almost the same as those in normal rats. The bradykinin B2 receptor antagonist FR173657, (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2,4-dichloro-3-[(2-methyl-8-quinolinyl)oxymethyl]phenyl]-N-methylaminocarbonylmethyl]acrylamide, attenuated the carrageenin-induced swelling and hyperalgesia of the normal rats at the early phase to almost the levels of the B/N-Katholiek rats. Pretreatment with indomethacin, a cyclooxygenase inhibitor, also inhibited the carrageenin-induced responses significantly in normal rats. These results indicate that bradykinin, acting on the B2 receptor, is the main mediator at the early phase of inflammatory pain of carrageenin edema and that prostaglandins, produced by cyclooxygenase, potentiate the effects of bradykinin.

Animals↗

PubMed2001

Genes highly expressed in the early phase of murine graft-versus-host reaction.

Graft-versus-host reaction (GVHR) is a complex process initiated upon allorecognition. For detection of early molecular events in GVHR, we first assessed time courses with respect to symptoms and serum interferon (IFN)-gamma levels and then used the differential display method to compare gene transcript patterns during the early phase between acute lethal GVHR mice and syngeneic controls. In the GVHR mice, high expression levels of seven genes encoding the following molecules were detected: TGTP/Mg21 (an IFN-gamma-related signaling molecule), vitronectin, Nedd5 (a mammalian septin), manganese superoxide dismutase, activin betaC subunit, PRCC (a papillary renal cell carcinoma-associated molecule), and an uncharacterized gene corresponding to a mouse expressed sequence tag (EST). The expression levels of most genes peaked before the symptomatological onset and the peak of IFN-gamma levels. Thus, gene expression monitoring may characterize the inductive process of GVHR and aid in the development of gene-based diagnostics and therapies.

Animals↗

PubMed2001

Induction of hyporesponsiveness to fully allogeneic cardiac grafts by intratracheal delivery of alloantigen.

BACKGROUND: Soluble protein delivered through the mucosal surface can induce immunological unresponsiveness. The purpose of this study was to determine if prior exposure to alloantigen via the trachea could modulate the immune response to subsequent cardiac allografts. METHODS: Hearts from C57BL/10(H2b) mice were transplanted into CBA(H2k) recipients. Recipient mice were given donor 1x10(7) splenocytes into the trachea with or without antibody specific for mouse CD80 (1G10) and/or CD86 (GL1) (100 microg each) 7 days before transplantation. RESULTS: All grafts survived in recipients treated with intratracheal delivery of alloantigen for over 35 days (mean survival time [MST], 56 days), whereas naive control mice and mice treated with syngeneic antigen rejected grafts acutely (MST, 8 and 7 days, respectively). Interestingly, when 1G10, GL1, or both of them were combined with the protocol, the majority of grafts were rejected within 21 days after grafting (MST, 7, 15, and 17 days, respectively). CONCLUSION: Intratracheal delivery of alloantigen induced significantly prolonged survival of fully mismatched cardiac allografts and the effect was abrogated by the blockade CD80 and/or CD86 pathway.

Animals↗

PubMed2001

Mcl-1, an early-induction molecule, modulates activin A-induced apoptosis and differentiation of CML cells.

Activin A, one member of the transforming growth factor (TGF)-beta superfamily, is known to be a commitment factor for cell death and differentiation. In the present study, we demonstrate that human chronic myeloid leukemia (CML) cell lines, KU812 and K562 cells, either induced apoptosis or differentiation, respectively, by treatment with activin A. During these cell fate decisive events caused by activin A, rapid and transient up-regulation of Mcl-1 was observed in both cell lines. In activin A-induced apoptosis of KU812 cells, continuous up-regulation of Bax was observed. After the decrease in Mcl-1 expression had occurred, activation of caspase-9 and caspase-3 and cleavage of DFF45 were shown to take place in KU812 cells, resulting in the fragmentation of the genomic DNA of the cells. In contrast, the down-regulation of Mcl-1 without up-regulation of Bax caused accumulation of hemoglobin (Hb) contents in activin A-treated K562 cells. Interestingly, erythropoietin (EPO) prevented activin A-induced apoptosis with continuous expression of Mcl-1 and caused KU812 cells to undergo erythroid differentiation. To address the role of Mcl-1 in activin A-treated CML cells, KU812 and K562 cells were stably transfected with cDNA encoding Mcl-1 (designated as KU812/mcl and K562/mcl cells). As in combined effect of activin A and EPO on the parental KU812 cells, activin A induced differentiation, but not apoptosis, of KU812/mcl cells without modulating Bax levels. Activin A-treated K562/mcl cells, as well as parental cells, were only differentiated to erythroid cells. These results suggest that Mcl-1 is an early inducible gene activated by the activin A signaling pathway for both cellular differentiation and apoptosis, and continuous expression of Mcl-1 may be contributed to differentiation signals to the erythroid lineage in CML cells.

Activins↗