Yoshihisa Taniguchi

Redox control of resistance to cis-diamminedichloroplatinum (II) (CDDP): protective effect of human thioredoxin against CDDP-induced cytotoxicity.

Thioredoxin is a small ubiquitous protein with multiple biological functions, including cellular defense mechanisms against oxidative stress. In the present study, we investigated the role of human thioredoxin (hTRX) in the acquisition of cellular resistance to cis-diamminedichloroplatinum (II) (CDDP). The expression and activity of hTRX in Jurkat T cells was dose-dependently enhanced by exposure to CDDP, as determined by immunoblot analysis and insulin reducing assay. Furthermore, chloramphenicol acetyltransferase analysis using the hTRX promoter-reporter gene construct revealed that treatment of Jurkat cells with CDDP caused transcriptional activation of the hTRX gene, which might be mediated through increased generation of intracellular reactive oxygen intermediates. To examine the biological significance of hTRX induction, we established hTRX-overexpressing derivatives of L929 fibrosarcoma cells by stable transfection with the hTRX cDNA. The clones, which constitutively expressed the exogenous hTRX, displayed increased resistance to CDDP-induced cytotoxicity, compared with the control clones. After exposure to CDDP, the control cells showed a significant increase in the intracellular accumulation of peroxides, whereas the hTRX-transfected cells did not. Taken together, these results suggest that overexpressed hTRX is responsible for the development of cellular resistance to CDDP, possibly by scavenging intracellular toxic oxidants generated by this anticancer agent.

Transactivation of an inducible anti-oxidative stress protein, human thioredoxin by HTLV-I Tax.

Adult T-cell leukemia derived factor (ADF)/human thioredoxin (TRX), which has thiol reducing and radical scavenging activities, plays an essential role on cellular protection against oxidative stress and cell death. TRX itself is induced by various oxidative stress as well as the Human T-cell lymphotropic virus type I (HTLV-I) Tax protein. To investigate the mechanism of this induction, the promoter region of the TRX gene was analyzed. Chloramphenicol acetyltransferase (CAT) reporter constructs containing the TRX promoter sequences responded to the overexpression of the Tax protein, whereas various oxidative agents activated the TRX promoter through a newly identified oxidative responsive element. Moreover, TRX was translocated from the cytoplasm into the nucleus by ultraviolet irradiation, suggesting its possible role on sensing and transducing oxidative signals.

Activation of interleukin-2 receptor gene by Forskolin and cyclic AMP analogues

Forskolin (FK), a reversible activator of adenylate cyclase, markedly enhanced the expression of interleukin-2 receptor (IL-2-R) on a human natural killer (NK)-like cell line, YT. The FK-induced increase in IL-2-R on YT cells closely correlated with an increase in intracellular cyclic AMP (cAMP) level, and was mimicked by dibutyryl cyclic AMP (dbcAMP). FK induced both high and low affinity IL-2-R on the cells. Using a cDNA for the IL-2-R as a probe, the FK-induced IL-2-R expression was shown to be associated with an increase in IL-2-R mRNA. FK also enhanced the IL-2-R expression on a human T lymphotrophic virus I (HTLV-I) positive T-cell line (YTA-1H) and augmented the phorbol ester-induced expression of IL-2-R on HTLV-I negative T-cell lines (HSB-2 and HPB-ALL). These results suggest the possibility that the stimulation of adenylate cyclase may serve as a pathway leading to activation of the IL-2-R gene in certain types of lymphocytes.

Interleukin 1α mRNA in virus-transformed T and B cells

Summary IL-lα cDNA clone was isolated from a T cell line infected by the human T lymphocropic retrovirus type-I (HTLV-I/ATLV). We found significant amounts of mRNA hybridizing to IL-lα cDNA not only in HTLV-I-transformed T cells but also in Epstein-Barr Virus-transformed B cells. A part of IL-2 receptor inducing activity in Adult T cell leukemia (ATL) cell line seems to be due to IL-lα.

Transcription of IL-2 receptor gene is stimulated by ATL-derived factor produced by HTLV-I(+) T cell lines

In HTLV-I transformed T-cell lines established from the patients with adult T-cell leukemia (ATL), there is a constitutive activation of the normal IL-2 receptor (IL-2-R) gene. These cell lines continuously produce an ATL-derived factor (ADF), an IL-2-R inducing factor without IL-2 activity. ADF enhances the expression of the IL-2-R through the augmentation of the IL-2-R mRNA in the HTLV-I(+) T-cell line (ED) as well as the NK cell line cells (YT). In YT cells, the transcriptional initiation of the promoter of the IL-2-R gene was enhanced by ADF but not by IL-2. Production of ADF by HTLV-I(+) T-cell lines may be involved in the abnormal expression of IL-2-Rs on these cells.

Structure of the mouse thioredoxin-encoding gene and its processed pseudogene

Thioredoxins (TXN) are small proteins with various biological functions, such as redox regulation, found in many species including bacteria, plants and animals. We previously reported the isolation of the TXN-encoding cDNAs from human and mouse. In order to elucidate the functions of the mammalian TXN system, we planned to generate Txn knockout mice, and cloned the genomic DNA fragments using the Txn cDNA as a probe. The Txn gene extends over 12 kb and consists of five exons separated by four introns. Detailed Southern analyses revealed that the mouse genome contains only one active Txn gene and one processed pseudogene (Txn-ps1), in contrast to some species which have families of active TXN-encoding genes. These findings should help to understand Txn itself, and provide a basis for transgenic experiments by gene targeting.

IL-2 Receptor Gene Activation by ATL-Derived Factor (ADF)

The interaction of Interleukin 2 (IL-2) and its specific receptor, Interleukin 2 receptor (IL-2R) (1), plays an important role for the growth and activation of lymphoid cells. One of the unique features of lymphocytes in immune system is the selective proliferation of the clones specific for variety of the antigens. In mature T lymphocytes (T-cells) which express antigen-specific T-cell receptors, the cell growth driven by IL-2/IL-2-R interaction appears to be strictly regulated by the initiative signals elicited by the interaction between T-cell receptors and the corresponding antigens.

Interleukin-2 receptor-inducing factor(s) in adult T cell leukemia.

The expression of the interleukin-2 receptor (IL-2-R) is regulated by transcriptional and post-transcriptional mechanisms. IL-2-R gene expression is induced by pharmacological agents including calcium ions, phorbol esters such as phorbol myristate acetate (PMA) and forskolin (FK), a direct activator of adenylate cyclase. HTLV-I(+) leukemic T cells and T cell lines from patients with adult T cell leukemia (ATL) continuously expressed IL-2-R without production of IL-2. However, there was no abnormality of the structural gene for IL-2-R in these cell lines as well as in fresh leukemic cells of ATL. We have detected that many HTLV-I(+) T4(+) T cell lines constitutively produce a non-IL-2 lymphokine named ATL-derived factor (ADF), which induced the expression of the high-affinity IL-2-R on a variety of cells including HTLV-I(+) T cells, myeloid leukemia cells and YT cells. IL-2-R-inducing agents such as ADF and FK were shown to induce elevation of the mRNA levels for IL-2-R through transcriptional enhancement of the IL-2-R gene. The possible involvement of IL-2-R-inducing cytokines in the physiological lymphocyte activation and the leukemogenesis in ATL and other T cell leukemias is discussed.

ADF (adult T-cell leukemia-derived factor) /human thioredoxin gene; Activation by HTLV-I Tax

HTLV-I/II INFECTION AMONG POPULATION SUBJECTED TO LOW DOSIS OF RADIATION AS A RESULT OF CHERNOBYL ACCIDENT. N, Senyuta, I. Osechensky, L, Mescheryakova, V, Gurtsevitch Since increased incidence of infectious and noninfectious diseases was registered in population exposed to radiation, the study of H T L V I / I I prevalence in above population seems to be of importance. Present investigation was carried out among inhabitants of Bryansk province contaminated by the radioactive emmissions ([57Cs) from the ~hernobyl accident in dosis of about 15 Ci/km~ Individual radiation dose assessment revealed that the accumulated dosis for 95% of above population was not over lO cSv (centisivert) while only for 5% of them accumulated dosis was equal to 40 cSv and more, Serum samples were collected from 1676 volonteers over 16 years old ~16-60). For detection of HTLV-I/II antibodies 2 screening test-systems <Serodia HTLV-I, Japan and EIA HTLV-I Abbott, USA) were used. Repeatedly reactive <RR) samples were further analysed by Western blot (W.b.) assay with both cellular lysats of HTLV-I produced cell lines MT-2 or Cgl/PL. The results obtained were as follows: 2 and 3 serum samples of 1676 tested were found to be RR in Serodia and Abbott assays, respectively. However, no one of them revealed HTLV-specific antibodies in W.b. assay and hence these samples were estimated as a negative. These data probably indicate either the absent or low level of HTLVI/II infection in inhabitants of Bryansk province. To come to the final conclusion about the role of radiation in HTLV-I/II activation and spread another population groups from regions affected by Chernobyl accident should be studied,