Effects of rare earth compounds on growth and apoptosis of leukemic cell lines

To explore a new agent for inhibiting leukemic cells, we investigated the effects of rare earth compounds (lanthanum chloride and cerium chloride) on the growth and apoptosis of HL-60 and NB4 cells. The growth of HL-60 and NB4 cells was tested by 3-(4,5-dimethylthiazole-2-yl)-2,5-biphenyl tetrazolium bromide (MTT) colorimetric assay. The apoptosis was measured by light microscopy, flow cytometry, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) method. The effect of LaCl(3) on normal bone marrow hematopoietic progenitor cells was evaluated by colony-forming unit-granulocyte-macrophage (CFU-GM) assay. Under our experimental conditions, MTT assay showed that 48-h treatment with 1, 2, and 3 mM LaCl(3) or 48- and 72-h treatments with 1 mM LaCl(3) could significantly inhibit the growth of HL-60 cells. Treatment with 2 and 4 mM CeCl(3) for 72 h could significantly inhibit the growth of NB4 cells. Apoptosis could be detected on treatment with 2 mM LaCl(3) for 24 h in HL-60 cells by light microscopic morphology examination, flow cytometric analysis, and TUNEL method. Apoptosis could be also detected on treatment with 2 mM CeCl(3) for 72 h in NB4 cells. Treatment with 1 mM LaCl(3) could arrest the transitions from G0/G1 to S phase. The granulocyte-macrophage colony formation of normal bone marrow cells was not significantly inhibited at lower concentrations of LaCl(3) (0.5 to 2 mM). Our results indicate that at certain concentrations, the rare earth compounds may inhibit the growth of leukemic cells, induce them to apoptosis, and have no significant inhibitory effects on normal bone marrow hematopoietic progenitor cells (CFU-GM). The mechanism needs to be further investigated.     

Lanthanum chloride bidirectionally influences calcification in bovine vascular smooth muscle cells

Vascular calcification (VC) is frequent prevalence in patients with chronic kidney disease (CKD) and atherosclerosis. Lanthanum carbonate is used as an orally administered phosphate-binding agent to reduce the gastrointestinal absorption of phosphate and ameliorate VC in advanced CKD. In this study, we used bovine vascular smooth muscle cells as a model VC in vitro and studied the effects of lanthanum chloride on calcium deposition. Exposure of cells to LaCl(3) at the concentration of 0.1 μM suppressed the β-glycerophosphate-induced alkaline phosphatase activity and calcium deposition. Furthermore, LaCl(3) upregulated the β-glycerophosphate-suppressed expression of calcium-sensing receptor. In contrast to the inhibitory effect of LaCl(3) on calcium deposition, higher level lanthanum (50 μM) was found to promote immediately precipitation of calcium phosphate in cell culture medium. At this concentration, LaCl(3) was found to induce cell apoptosis which involves caspases-9 and -3. These data indicate that the promotory effect of LaCl(3) on calcium deposition is likely mediated by induction of apoptosis. Our in vitro findings do suggest that, in the context of raised lanthanum, greater attention should be paid to potential toxic effects associated to the use of lanthanide-based drugs.     

鸡端粒酶RNA基因的克隆

本研究采用扩增条件优化的PCR扩增技术,以MDCC-MSBl细胞基因组DNA为模板扩增出鸡端粒酶RNA(chicken telomerase RNA,chTR)全长基因,克隆到pMD18-T载体中,经酶切鉴定和PCR鉴定后测定序列.序列分析表明所克隆的鸡端粒酶RNA基因全长465 bp,其中模板区的11个核苷(5'-CUAACCCUAAU-3')合成端粒亚单位(TTAGGG)n.chTR基因的克隆为进一步研究chTR在马立克氏病发病过程中的作用以及马立克氏病的发病机制提供可能的序列基础.     

Lanthanum inhibits steady-state turnover of the sarcoplasmic reticulum calcium ATPase by replacing magnesium as the catalytic ion

LaATP is shown to be an effective inhibitor of the calcium ATPase of sarcoplasmic reticulum because the binding of LaATP to cE.Ca2 results in the formation of lanthanum phosphoenzyme, which decays slowly. Steady-state activity of the calcium ATPase in leaky sarcoplasmic reticulum vesicles is inhibited 50% by 0.16 microM LaCl3 (15 nM free La3+, 21 nM LaATP) in the presence of 25 microM Ca2+ and 49 microM MgATP (5 mM MgSO4, 100 mM KCl, 40 mM 4-morpholinepropanesulfonic acid, pH 7.0, 25 degrees C). However, 50% inhibition of the uptake of 45Ca and phosphorylation by [gamma-32P]ATP in a single turnover experiment requires 100 microM LaCl3 (28 microM free La3+) in the presence of 25 microM Ca2+; this inhibition is reversed by calcium but inhibition of steady-state turnover is not. Therefore, binding of La3+ to the cytoplasmic calcium transport site is not responsible for the inhibition of steady-state ATPase activity. The addition of 6.7 microM LaCl3 (1.1 microM free La3+) has no effect on the rate of dephosphorylation of phosphoenzyme formed from MgATP and enzyme in leaky vesicles, while 6.7 mM CaCl2 slows the rate of phosphoenzyme hydrolysis as expected; 6.7 microM LaCl3 and 6.7 mM CaCl2 cause 95 and 98% inhibition of steady-state ATPase activity, respectively. This shows that inhibition of ATPase activity in the steady state is not caused by binding of La3+ to the intravesicular calcium transport site of the phosphoenzyme. Inhibition of ATPase activity by 2 microM LaCl3 (0.16 microM free La3+, 0.31 microM LaATP) requires greater than 5 s, which corresponds to approximately 50 turnovers, to reach a steady-state level of greater than or equal to 80% inhibition. Inhibition by La3+ is fully reversed by the addition of 0.55 mM CaCl2 and 0.50 mM EGTA; this reactivation is slow with t1/2 approximately 9 s. Two forms of phosphoenzyme are present in reactions that are partially inhibited by La3+: phosphoenzyme with Mg2+ at the catalytic site and phosphoenzyme with La3+ at the catalytic site, which undergo hydrolysis with observed rate constants of greater than 4 and 0.05 s-1, respectively. We conclude, therefore, that La3+ inhibits steady-state ATPase activity under these conditions by replacing Mg2+ as the catalytic ion for phosphoryl transfer. The slow development of inhibition corresponds to the accumulation of lanthanum phosphoenzyme. Initially, most of the enzyme catalyzes MgATP hydrolysis, but the fraction of enzyme with La3+ bound to the catalytic site gradually increases because lanthanum phosphoenzyme undergoes hydrolysis much more slowly than does magnesium phosphoenzyme.(ABSTRACT TRUNCATED AT 400 WORDS)     

The combination of lanthanum chloride and the calcimimetic calindol delays the progression of vascular smooth muscle cells calcification

Phosphate (Pi)-binders are commonly used in dialysis patients to control high Pi levels, that associated with vascular calcification (VC). The aim of this study was to investigate the effects of lanthanum chloride (LaCl(3)) on the progression of high Pi-induced VC, in rat vascular smooth muscle cells (VSMCs). Pi-induced Ca deposition was inhibited by LaCl(3), with a maximal effect at 100μM (59.0±2.5% inhibition). Furthermore, we studied the effects on VC of calcium sensing receptor (CaSR) agonists. Gadolinium chloride, neomycin, spermine, and the calcimimetic calindol significantly inhibited Pi-induced VC (55.9±2.2%, 37.3±4.7%, 30.2±5.7%, and 63.8±5.7%, respectively). To investigate the hypothesis that LaCl(3) reduces the progression of VC by interacting with the CaSR, we performed a concentration-response curve of LaCl(3) in presence of a sub-effective concentration of calindol (10nM). Interestingly, this curve was shifted to the left (IC(50) 9.6±2.6μM), compared to the curve in the presence of LaCl(3) alone (IC(50) 19.0±4.8μM). In conclusion, we demonstrated that lanthanum chloride effectively reduces the progression of high phosphate-induced vascular calcification. In addition, LaCl(3) cooperates with the calcimimetic calindol in decreasing Ca deposition in this in vitro model. These results suggest the potential role of lanthanum in the treatment of VC induced by high Pi.     

Hydroxyl radical-induced apoptosis in human tumor cells is associated with telomere shortening but not telomerase inhibition and caspase activation

Reactive oxygen species (ROS) have been found to trigger apoptosis in tumor cells. At the same time, telomerase is found to be associated with malignancy and reduced apoptosis. However little is known about the linkage between ROS such as *OH and telomerase/telomere. To address the interrelations between *OH and telomerase/telomere in tumor cell killing, HeLa, 293 and MW451 cells were induced to undergo apoptosis with *OH radicals generated via Fe(2+)-mediated Fenton reactions (0.1 mM FeSO(4) plus 0.3-0.9 mM H2O2) and telomerase activity, telomere length were measured during apoptosis. We found that during *OH-induced apoptosis, telomere shortening took place while no changes in telomerase activity were observed. Our results suggest that *OH-induced telomere shortening is not through telomerase inhibition but possibly a direct effect of *OH on telomeres themselves indicating that telomere shortening but not telomerase inhibition is the primary event during *OH-induced apoptosis. Strikingly, we also found that *OH-induced apoptosis in HeLa cells is caspase-3-independent but is associated with reduction of mitochondrial transmembrane potential. Our results indicate that *OH triggers apoptotic tumor cell death through a telomere-related, caspase-independent pathway.     

Effects of lanthanum on calcium-dependent phenomena in human red cells.

Lanthanum (0.25 mM) does not penetrate into fresh or Mg2+-depleted cells, whereas it does into ATP-depleted or ATP + 2,3-diphosphoglycerate-depleted cells, into cells containing more than 3 mM calcium, or cells stored for more than 4 weeks in acid/citrate/dextrose solution. In fresh cells loaded with calcium, extracellular lanthanum blocks the active Ca2+-efflux completely and inhibits (Ca2+ + Mg2+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) activity to about 50%. In Mg2+-depleted cells Ca2+-Ca2+ exchange is inhibited by lanthanum. Ca2+-leak is unaffected by lanthanum up to 0.25 mM concentration; higher lanthanum concentrations reduce leak rate. In NaCl medium Ca2+-leak +/ S.D. amounts to 0.28 +/ 0.08 mumol/1 of cells per min, whereas in KC1 medium to 0.15 +/ 0.04 mumol/1 of cells per min at 2.5 mM [Ca2+]e and 0.25 mM [La3+]e pH 7.1. Lanthanum inhibits Ca2+-dependent rapid K+ transport in ATP-depleted and propranolol-treated red cells, i.e. whenever intracellular calcium is below a critical level. The inhibition of the rapid K+ transport can be attributed to protein-lanthanum interactions on the cell surface, since lanthanum is effectively detached from the membrane lipids by propranolol. Lanthanum at 0.2--0.25 mM concentration has no direct effect on the morphology of red cells. The shape regeneration of Ca2+-loaded cells, however, is blocked by lanthanum owing to Ca2+-pump inhibition. Using lanthanum the transition in cell shape can be quantitatively correlated to intracellular Ca2+ concentrations.     

Induction of apoptosis by fungal culture materials containing cyclopiazonic acid and T-2 toxin in primary lymphoid organs of broiler chickens

Thirty-six, twenty-eight-day-old broiler chicks were randomly distributed into three groups of 12 birds each. Two groups were fed diets containing 10 ppm cyclopiazonic acid (CPA) and 1ppm T-2 toxin, respectively, to determine the mechanism of cell death in spleen and thymus at 6, 12, 24, and 36 h of post-treatment. The other group served as control. T-2 toxin treated group showed significant (P < 0.01) induction of apoptosis in thymus with peak induction at 24 h post-treatment where as, no significant differences were observed between the control and CPA groups. The CPA toxin treated group showed significant (P < 0.01) induction of apoptosis in spleen with peak induction at 24 h post-treatment. No significant differences were observed between the control and T-2 toxin group even though the latter showed a slight increase in the quantity of apoptotic cells at 36 h post-treatment in spleen. The semi-thin sections stained with toluidine blue from the spleen of CPA treated group exhibited crescent margination of chromatin against the nuclear envelope and shrinkage of lymphoid cells without any surrounding inflammation, the characteristics of apoptosis. The apoptotic thymocytes from T-2 fed birds appeared shrunken with condensed nucleus and showed crescent margination of chromatin against the nuclear envelope without any surrounding inflammation when compared with well-defined nuclei with dispersed chromatin in normal thymocytes. Ultrastructurally, splenocytes of the CPA treated group and thymocytes of the T-2 toxin treated birds showed apoptotic bodies characterized by crescent margination of the chromatin against the nuclear envelope. The study indicates that one route of the CPA and T-2 toxin induced cell death in lymphoid organs of broiler chicken is by apoptosis.Forms part of M.V.Sc. thesis of the first author approved by the Tamil Nadu Veterinary and Animal Sciences University, Chennai 600 051, India.     

Protection from acute cellular injury using Sleeping Beauty mediated telomerase gene transfer

We developed a Sleeping Beauty (SB) transposon mediated hTERT gene delivery system for in vitro use. We have constructed telomerase or luciferase gene expressing SB-transposons with a SV40 enhancer (pT3.hTERT.Con and pT3.Con, respectively) or without an enhancer (pT3.Pro). Using the SB transposon system in vitro hTERT gene overexpression has protective effects from acute cellular injury by tert-butyl hydroperoxide (t-BH), carbon tetrachloride (CCl(4)), and d-galactosamine (d-GalN) in normal human cells IMR-90. pT3.hTERT.Con vector and helper plasmid co-transfection resulted in a approximately 3-fold increase in telomerase activity which was maintained for 14 days. Trypan blue and Cell Death Detection Assays showed the protective effects of the telomerase gene against toxic agents. Fourteen days after co-transfection with pT3.hTERT.Con vector and helper plasmid, IMR-90 cells were incubated with 1.2mM t-BH for 50 min, 5mM CCl(4) for 1.5h or 30 mM d-GalN for 24h. Cell viability of SB-mediated telomerase overexpressing cells significantly increased by 48% (t-BH), 43% (CCl(4)), and 25% (d-GalN) in comparison to mock treated cells. Cell Death Detection ELISA showed a decrease in the rate of apoptosis by 47%. In summary, SB transposon mediated telomerase gene transfer may have a protective effect against t-BH, CCl(4), or d-GalN induced acute cellular injury, and this results suggested SB-mediated telomerase therapy for tissue engineering.     

Propagation and infectivity titration of the Gifu-1 strain of chicken anemia agent in a cell line (MDCC-MSB1) derived from Marek's disease lymphoma

Chicken anemia agent (CAA) propagated in an established cell line derived from Marek's disease (MD) lymphoma (MDCC-MSB1). When passaged 19 times in MDCC-MSB1 cell cultures, it produced anemia of the same severity in chicks as it did before passage. Titration of the infectivity of CAA was performed successfully with subcultures of MDCC-MSB1 cell cultures which had been inoculated with serial tenfold dilutions of infected material. In it, no infected cultures could be subcultured. The propagation of CAA was also proved in the MD cell line, MDCC-JP2, and the avian lymphoid leukosis (LL) cell line, LSCC-1104B1, but not in the two MD cell lines, MDCC-RP1 and MDCC-BP1, or in the two LL cell lines, LSCC-1104X5 and LSCC-TLT. No CAA propagated in cell cultures prepared from skin and muscle, liver, or brain of chick embryos, or kidney, thymus, bursa of Fabricius, bone marrow, or white blood cells of chickens.     

Lanthanide ion enhancement of interferon binding to cells

Pretreatment of purified [125I]-labeled human and mouse beta interferons (IFN) with lanthanum chloride (LaCl3) enhanced 20-30 fold the binding of the [125I]-IFNs to human A549 and mouse L cells at 0 degree C and also enhanced antiviral activity in homologous cells. Although lanthanides enhanced cross-species binding of both human and mouse [125I]-IFNs, there was no increase in cross-species antiviral activity. Unlabeled IFN not treated with LaCl3 did not compete with [125I]-IFN treated with LaCl3 for cellular receptors. However, unlabeled IFN treated with LaCl3 did compete with LaCl3-treated [125I]-IFN. These results suggest that lanthanide treated IFNs do not bind to the same receptors as native IFNs.     

5-Fluorouracil (5-FU) induced apoptosis in gastric cancer cell lines: role of the p53 gene

We examined chemosensitivity to 5-fluorouracil (5-FU) in four human gastric cancer cell lines, by analyzing the expression of p53 and its related genes. Treatment with 1mM 5-FU induced variable degrees of apoptosis in the cultured cells. The apoptotic indices 72 h after treatment were approximately 14% in MKN-74 (wild-type p53 gene), 12% in MKN-45 (wild-type), 3% in MKN-28 (mutated) and 0.5% in KATO-III cells (deleted), respectively. On the other hand, 50 M 5-FU had little effect on the induction of apoptosis in MKN-74 cells, the value being approximately 2% after 72 h. Induction of P53 expression was noted 3 h after initiating the treatment, followed by the induction of P21/Waf1 after 6 h in both MKN-74 and MKN-45 cells. The same expression mode was noted in MKN-74 treated with 50 M 5-FU. Conversely, the level of P53 expression was constant in MKN-28 cells and absent in KATO-III cells, in which P21/Waf1 had never been induced. The Bax/Bcl-2 expression ratio was gradually elevated for up to 72 h in MKN-74 and MKN-45 cells treated with 1mM 5-FU; in contrast, it was unchanged in MKN-28 and KATO-III cells, and MKN-74 treated with 50 M 5-FU. These results might indicate that (1) 1mM 5-FU induces apoptosis in cultured gastric cancer cells carrying the wild-type p53 gene, but not those carrying the mutated type or a gene deletion, and (2) the elevated Bax/Bcl-2 expression ratio plays a more crucial role than the higher expression of P21/Waf1 in the induction of p53- gene dependent apoptosis.     

Nerve growth factor withdrawal-mediated apoptosis in naive and differentiated PC12 cells through p53/caspase-3-dependent and -independent pathways

Programmed cell death is regulated in response to a variety of stimuli, including the tumor suppressor protein p53, that can mediate cell cycle arrest through p21/Waf1 and apoptosis through the Bcl-2/Bax equilibrium and caspases. Neuronal cell apoptosis has been reported to require p53, whereas other data suggest that neuronal cell death may be independent of p53. Comparison of wild type PC12 to a temperature-sensitive PC12 cell line that depresses the normal function of p53 has permitted investigation of the importance of p53 in a variety of cell functions. This study examined the role of p53 in trophic factor withdrawal-mediated apoptosis in both na?ve and differentiated PC12 cells. Our data show that as PC12 cells differentiate they are more poised to undergo apoptosis than their undifferentiated counterparts. Survival assays with XTT (sodium 3'-1-(phenylaminocarbonyl)-3,4-tetrazolium-bis(4-methoxy-6-nitro)benzene sulfonic acid) and TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) demonstrated that lack of p53 is initially protective against apoptosis. The window of protection is about 20 h for na?ve and 36 h for differentiated cells. Apoptosis involved caspases 3, 6, and 9. However, caspase 3 activation was absent in cells lacking p53, concomitant with the delayed apoptosis. When the expression of caspase 3 was silenced with interference RNA, wild type PC12 cells revealed a morphology and biochemistry similar to PC12[p53ts] cells, indicating that caspase 3 accounts for the observed delay in apoptosis in p53 dysfunction. These results suggest that p53 is important, but not essential, in factor withdrawal-mediated apoptosis. Parallel pathways of caspase-mediated apoptosis are activated later in the absence of functional p53.     

Effect of high phosphate concentration on osteoclast differentiation as well as bone-resorbing activity

Although high inorganic phosphate (Pi) concentration in culture media directly inhibits generation of new osteoclasts and also inhibits bone resorption by mature osteoclasts, its precise mechanism and the physiological role have not been elucidated. The present study was performed to investigate these issues. Increase in extracellular Pi concentration ([Pi](e)) (2.5-4 mM) concentration dependently inhibited 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] or parathyroid hormone (PTH)-(1-34)-induced osteoclast-like cell formation from unfractionated bone cells in the presence of stromal cells. Increase in [Pi](e) (2.5-4 mM) concentration dependently inhibited 1,25(OH)(2)D(3)-, PTH-(1-34)-, or receptor activator of NF-kappaB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF)-induced osteoclast-like cell formation from hemopoietic blast cells in the absence of stromal cells. Increase in [Pi](e) (2.5-4 mM) dose dependently stimulated the expression of osteoprotegerin (OPG) mRNA and increased the expression of OPG mRNA suppressed by PTH-(1-34) or 1,25(OH)(2)D(3) in unfractionated bone cells, while it did not affect RANKL mRNA. Increase in [Pi](e) (2.5-4 mM) concentration dependently inhibited the bone-resorbing activity of isolated rabbit osteoclasts. Increase in [Pi](e) (4 mM) induced the apoptosis of isolated rabbit osteoclasts while it did not affect the apoptosis of osteoclast precursor cells and mouse macrophage-like cell line C7 cells that can differentiate into osteoclasts in the presence of RANKL and M-CSF. These results indicate that increase in [Pi](e) inhibits osteoclast differentiation both by up-regulating OPG expression and by direct action on osteoclast precursor cells. It is also indicated that increase in [Pi](e) inhibits osteoclastic activity at least in part by the direct induction of apoptosis of osteoclasts.     

Inhibition of K+-sensitive p-nitrophenylphosphatase activity on Rhesus-positive red cells after incubation with IgG-anti-Rhesus-D.

The incubation of ghosts derived from human Rhesus-positive red cells with IgG-anti-Rhesus-D inhibited the K+-sensitive p-nitrophenylphosphatase activity. This enzyme has a partial function in the (Na+ + K+)-ATPase system related to the phosphorylation step, which is important for active potassium transport through the red cell membrane. The specificity of the impairment by the antigen-antibody reaction in the Rhesus-D system was proved by the following controls. Ghosts obtained from Rhesus-negative red cells incubated by IgG-anti-Rhesus-D and those of Rhesus-positive red cells treated with non-immune serum did not show any reduction of the K+-p-nitrophenylphosphatase activity. The ghost preparation with lanthanum carried out after hypotonic hemolysis of the washed red cells in 2 mM LaCl3 at pH 6 was the most suitable procedure to explore this topic in comparison to other techniques for preparing ghosts of red cells.