			Home About us Contact

Normal Lymphocytes (normal + lymphocyte)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Telomere uncapping during in vitro T-lymphocyte senescence

AGING CELL, Issue 1 2009
Amel Chebel
Summary Normal lymphocytes represent examples of somatic cells that are able to induce telomerase activity when stimulated. As previously reported, we showed that, during lymphocyte long-term culture and repeated stimulations, the appearance of senescent cells is associated with telomere shortening and a progressive drop in telomerase activity. We further showed that this shortening preferentially occured at long telomeres and was interrupted at each stimulation by a transitory increase in telomere length. In agreement with the fact that telomere uncapping triggers lymphocyte senescence, we observed an increase in ,-H2AX and 53BP1 foci as well as in the percentage of cells exhibiting DNA damage foci in telomeres. Such a DNA damage response may be related to the continuous increase of p16ink4a upon cell stimulation and cell aging. Remarkably, at each stimulation, the expression of shelterin genes, such as hTRF1, hTANK1, hTIN2, hPOT1 and hRAP1, was decreased. We propose that telomere dysfunction during lymphocyte senescence caused by iterative stimulations does not only result from an excessive telomere shortening, but also from a decrease in shelterin content. These observations may be relevant for T-cell biology and aging. [source]

Identification of different isoforms of eEF1A in the nuclear fraction of human T-lymphoblastic cancer cell line specifically binding to aptameric cytotoxic GT oligomers

FEBS JOURNAL, Issue 15 2003
Barbara Dapas
GT oligomers, showing a dose-dependent cytotoxic effect on a variety of human cancer cell lines, but not on normal human lymphocytes, recognize and form complexes with nuclear proteins. By working with human T-lymphoblastic CCRF-CEM cells and by using MS and SouthWestern blotting, we identified eukaryotic elongation factor 1 alpha (eEF1A) as the main nuclear protein that specifically recognizes these oligonucleotides. Western blotting and supershift assays confirmed the nature of this protein and its involvement in forming a cytotoxicity-related complex (CRC). On the contrary, normal human lymphocytes did not show nuclear proteins able to produce CRC in a SouthWestern blot. Comparative bidimensional PAGE and Western-blotting analysis for eEF1A revealed the presence of a specific cluster of spots, focusing at more basic pH, in nuclear extracts of cancer cells but absent in those of normal lymphocytes. Moreover, a bidimensional PAGE SouthWestern blot demonstrated that cytotoxic GT oligomers selectively recognized the more basic eEF1A isoform expressed only in cancer cells. These results suggest the involvement of eEF1A, associated with the nuclear-enriched fraction, in the growth and maintenance of tumour cells, possibly modulated by post-translational processing of the polypeptide chain. [source]

Intrinsic genetic instability of normal human lymphocytes and its implication for loss of heterozygosity

GENES, CHROMOSOMES AND CANCER, Issue 4 2001
Arnolda G. de Nooij-van Dalen
A combination of flow cytometry and microsatellite analysis was used to investigate loss of expression of HLA-A and/or HLA-B alleles and concurrent LOH at polymorphic chromosome 6 loci both in freshly isolated lymphocytes (in vivo mutations) and in lymphocytes cultured ex vivo. The fraction of in vivo mutants that showed LOH at 6p appeared to vary from 0%,49% for various donors. During culturing ex vivo, HLA-A, cells arose at a high rate and showed simultaneous loss of expression at the linked HLA-B locus. Up to 90% of the ex vivo arisen HLA-A2, cell population showed LOH of multiple 6p markers, and 50% had lost heterozygosity at 6q. This ex vivo spectrum resembles that found in HLA-A2 mutants obtained from lymphoblastoid cells. The HLA-A2 mutants present in vivo may reflect only a small fraction of the mutants that can be detected ex vivo. In normal lymphocytes, in vivo only mitotic recombination appears to be sustained, indicating the importance of this mechanism for tumor initiation in normal cells. Although mutations resulting in LOH at both chromosome 6 arms were shown to result in nonviable cells in normal lymphocytes, they have been shown to result in viable mutants in lymphoblastoid cells. We hypothesize that these types of mutations also occur in vivo but only survive in cells that already harbor a mutated genetic background. In light of the high rate at which these types of mutations occur, they may contribute to cancer progression. © 2001 Wiley-Liss, Inc. [source]

Effect of Bupleuri Radix Extracts on the Toxicity of 5-Fluorouracil in HepG2 Hepatoma Cells and Normal Human Lymphocytes

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 4 2008
Su Jin Kang
We sought to assess whether Bupleuri Radix extract enhances 5-fluorouracil-induced cytotoxicity in HepG2 hepatoma cells, while protecting normal blood lymphocytes. Bupleuri Radix, used for treatment of liver disease in oriental medicine, possesses antitumour properties; it induces apoptosis through cell arrest in tumour cells, but does not affect normal lymphocytes. In this study, we evaluated the protective and enhancing effects of Bupleuri Radix on 5-fluorouracil-induced cytotoxicity in HepG2 cells and normal lymphocytes. Treatment with Bupleuri Radix increased the micronuclei frequency and DNA damage, resulting from 5-fluorouracil treatment. However, when human lymphocytes were cotreated with Bupleuri Radix and 5-fluorouracil, the frequency of 5-fluorouracil-induced micronuclei decreased. Although the extent of 5-fluorouracil-induced DNA damage, determined by single-cell gel electrophoresis, increased after treating HepG2 cells with Bupleuri Radix, it decreased in normal lymphocytes. When cells were treated with 20 µM 5-fluorouracil and 200 µg/ml Bupleuri Radix simultaneously, Bax protein increased in HepG2 cells at 24 hr; however, p21 and p53 proteins were up-regulated in normal human lymphocytes. Cotreatment with 200 µg/ml Bupleuri Radix and 20 µM 5-fluorouracil resulted in cell arrest at the late G1/early S phase in HepG2 cells (55.80 ± 0.19%) and normal lymphocytes (97.19 ± 0.27%). In addition, Bupleuri Radix and 5-fluorouracil treatment increased mitochondria membrane potential collapse only in HepG2 cells (19.02%), while it was not changed in lymphocytes. In conclusion, our findings suggest that Bupleuri Radix may be effective as a therapeutic agent to treat hepatomas. [source]