Browsing by Author "González Ortiz, Marcelo Andrés"

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    D-Glucose increases the expression and activity of hCAT-1 and Spl binding to SLC7A1 promoter in human umbilical vein endothelium
    (2008) González Ortiz, Marcelo Andrés; Farías Jofré, Marcelo Enrique; Casanello Toledo, Paola Cecilia; Sobrevía Luarte, Luis Alberto
    L-Arginine is mainly transported by the human cationic amino acid transporter 1 (hCAT-1, protein codified by the gene SLC7A1) in human umbilical vein endothelial cells (HUVEC). hCAT-1 mediated L-arginine transport and nitric oxide (NO) synthesis are increased by 25 mM D-glucose in this cell type. Since Sp1 is a transcription factor activated by NO, we studied whether high D-glucose effect on transport was due to altered expression of hCAT-1 and abundance and activity of the transcription factor Sp1 in primary cultures of HUVEC. D-Glucose (25 mM, 24 hours) increased (~3.2 fold) the maximal velocity (Vmax), without altering the apparent Km, of L-arginine transport compared with cells in 5 mM D-glucose. High D-glucose also increased the hCAT-1 mRNA number of copies (~5-fold) and protein abundance (~2-fold), and Sp1 nuclear abundance and binding to SLC7A1 promoter region (−177 to −103 bp from ATG). Thus, the stimulatory effect of D-glucose on L-arginine transport could result from increased expression of hCAT-1 due to increased activity of Sp1 on the promoter of SLC7A1 in HUVEC.
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    Transforming growth factor beta 1 is involved in the inhibitory effect of high D-glucose on human equilibrative nucleosidie transporter 1 in human fetal endothelium
    (2008) Vega Pizarro, José Luis Eduardo; Farías Jofré, Marcelo Enrique; Puebla Aracena, Carlos Alberto; González Ortiz, Marcelo Andrés; Casanello Toledo, Paola Cecilia; Sobrevía Luarte, Luis Alberto
    Objectives: High D-glucose (25 mM) reduces adenosine transport via the human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelial cells (HUVEC). Interestingly, high D-glucose also increases the release of TGF-b1 from primary cultures of HUVEC leading to altered transport of L-arginine and synthesis of nitric oxide (NO), most likely due to activation of type II TGF-b1 receptors (TbRII). Since NO is involved in the repression of SLC29A1 gene expression in HUVEC, it is likely that D-glucose effect on hENT1 mediated adenosine transport involves TGF-b1 and activation of TbRII in this cell type. Therefore, we have studied whether TGF-b1 is involved in theinhibitory effect of high D-glucose on hENT1 in HUVEC. Methods: Cells were exposed to D-glucose (5-25 mM; 6-24 h) and/or TGF-b1 (0.1-10 ng/ml, 1-24 h) and [3H]adenosine transport (4 mCi/ml, 20 s, 22 C) was measured in absence or presence of nitrobenzylmercapto purine ribose (NBMPR, 1 mM, ENT1 inhibitor). These assays were performed in cells transduced with an adenovirus to induce expression of a truncated form of TbRII (Ad-tTbRII) or with a control adenovirus (Ad-control, empty vector). Results: In cells exposed to normal D-glucose (5 mM), TGF-b1 inhibited hENT1-mediated adenosine transport (~60%), an effect that was dose-dependent reaching a maximal inhibition at 2 ng/ml. The TGF-b1 effect was time-dependent with a significant inhibition of hENT1-mediated adenosine transport at 3 h of incubation, an effect that sustained for further 21 h. The effect of TGF-b1 was absent in cells transduced with Ad-tTbRII. In cells in high D-glucose (25 mM), hENT1-mediated adenosine transport was decreased compared with cells in normal D-glucose. This effect of high D-glucose was blocked in cells transduced with Ad-tTbRII, but it was unaltered in cells transduced with Adcontrol. Conclusion: These results suggest that TGF-b1 could mediate the inhibitory effect of high D-glucose on hENT1 activity by the activation of type II receptor for TGF-b1 in primary cultures of HUVEC.FONDECYT 1070865/1080534/7070249 (Chile), J.L. Vega, C. Puebla and M. González hold a CONICYT PhD fellowships. M. Farías holds CONICYT and PUC-School of Medicine PhD fellowships.