Browsing by Author "Iruretagoyena, M"

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    Role of Nrf2 in the regulation of the Mrp2 (ABCC2) gene
    (2006) Vollrath, V; Wielandt, AM; Iruretagoyena, M; Chianale, J
    The Nrf2 (nuclear factor-erythroid 2 p45-related factor 2) transcription factor regulates gene expression of the GCLC (glutamate-cysteine ligase catalytic subunit), which is a key enzyme in glutathione synthesis, and GSTs (glutathione S-transferases) via the ARE (antioxidant-response element). The Mrp2 (multidrug-resistance protein 2) pump mediates the excretion of GSH and GSSG excretion as well as endo- and xeno-biotics that are conjugated with GSH, glucuronate or sulphate. Considering that Mrp2 acts synergistically with these enzymes, we hypothesized that the regulation of Mrp2 gene expression is also dependent on Nrf`2. Using BHA (butylated hydroxyanisole), which is a classical activator of the ARE-Nrf2 pathway, we observed an increase in the transcriptional activity of Mrp2, GCLC and Gstal/Gsta2 genes in the mouse liver. A similar pattern of co-induction of Mrp2 and GCLC genes was also observed in mouse (Hepa 1-6) and human (HepG2) hepatoma cells treated with BHA, beta-NF (beta-naphthoflavone), 2,4,5-T (trichlorophenoxyacetic acid) or 2AAF (2-acetylaminofluorene), suggesting that these genes share common mechanism(s) of transcriptional activation in response to exposure to xenobiotics. To define the mechanism of Mrp2 gene induction, the 5'-flanking region of the mouse Mrp2 gene (2.0 kb) was isolated, and two ARE-like sequences were found: ARE-2 (-1391 to -1381) and ARE-1 (-95 to -85). Deletion analyses demonstrated that the proximal region (-185 to +99) contains the elements for the basal expression and xenobiotic-mediated induction of the Mrp2 gene. Gel-shift and supershift assays indicated that Nrf2-protein complexes bind ARE sequences of the Mrp2 promoter, preferentially to the ARE-1 sequence. Overexpression of Nrf2 increased ARE-1-mediated CAT (chloramphenicol acetyltransferase) gene activity, while overexpression of mutant Nrf2 protein repressed the activity. Thus Nrf2 appears to regulate Mrp2 gene expression via an ARE element located at the proximal region of its promoter in response to exposure to xenobiotics.
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    Selective depletion of Vβ2+CD8+ T cells in peripheral blood from rheumatic heart disease patients
    (2003) Carrión, F; Fernandez, M; Iruretagoyena, M; Andrade, LEC; Odete-Hilário, M; Figueroa, F
    Acute rheumatic fever (ARF) and its chronic valvular sequelae are the delayed consequence of a pharyngeal infection with group A Streptococcus (GAS). Several GAS proteins have been shown to be superantigens, raising the possibility that the expansion or deletion of T cells expressing specific Vbeta regions might play a role in the pathogenesis of ARF or chronic rheumatic heart disease (RHD). We therefore analyzed by four-color flow cytometry, the V repertoire on CD3, CD4 and CD8 T cells from four ARF patients, 10 RHD patients and also nine healthy controls. A selective depletion of Vbeta2+ T cells was found only in the CD8 subset of chronic RHD patients. This is of interest since a number of GAS superantigens exert their effects on Vbeta2+ cells and because only CD8+ T cells from ARF and RHD patients undergo anergy in response to GAS superantigens. Our results suggests that an ongoing immune process is present in RHD patients and that CD8+ T cells may have an important immunoregulatory role in the pathogenesis of the disease. (C) 2003 Elsevier Science Ltd. All rights reserved.