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Am J Physiol Cell Physiol 291: C327-C336, 2006. First published February 22, 2006; doi:10.1152/ajpcell.00316.2005
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VASCULAR BIOLOGY

Thyroid hormones increase inducible nitric oxide synthase gene expression downstream from PKC-{zeta} in murine tumor T lymphocytes

María Laura Barreiro Arcos,1 Gabriela Gorelik,1 Alicia Klecha,2 Ana María Genaro,1,2 and Graciela A. Cremaschi1,2

1Laboratorio de Inmunofarmacología, Centro de Estudios Farmacológicos y Botánicos, Consejo Nacional de Investigaciones Científicas y Técnicas; and 2Laboratorio de Radioisótopos, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina

Submitted 30 June 2005 ; accepted in final form 15 February 2006

Regulation of cell proliferation by thyroid hormone (TH) has been demonstrated, but the effect of THs and the mechanisms involved in lymphocyte activity have not been elucidated. Differential expression of PKC isoenzymes and high nitric oxide synthase (NOS) activity have been described in tumor T lymphocytes. We have analyzed the direct actions of TH on normal T lymphocytes and BW5147 T lymphoma cells in relation to PKC and NOS activities. THs increased tumor and mitogen-induced normal T lymphocyte proliferation. PKC isoenzyme-selective blockers impaired these effects in both cell types, indicating the participation of Ca2+-dependent and -independent isoenzymes in normal and tumor cells, respectively. TH actions were blunted by extra- and intracellular Ca2+ blockers only in normal T lymphocytes, whereas NOS blockers impaired TH-induced proliferation in T lymphoma cells. Incubation for 24 h with TH induced a rise in total and membrane-associated PKC activities in both cell types and led to a rapid and transient effect only in tumor cells. THs increased atypical PKC-{zeta} expression in BW5147 cells and classical PKC isoenzymes in mitogen-stimulated normal T cells. TH augmented NOS activity and inducible NOS protein and gene expression only in tumor cells. Blockade of PKC and the atypical PKC-{zeta} isoform inhibited TH-mediated stimulation of inducible NOS and cell proliferation. These results show, for the first time, that differential intracellular signals are involved in TH modulation of lymphocyte physiology and pathophysiology.

3,5,3'-l-triiodothyronine; thyroxine; T lymphoma; protein kinase C isoenzymes


Address for reprint requests and other correspondence: G. A. Cremaschi, CEFYBO-CONICET, Paraguay 2155 (1121), Buenos Aires, Argentina (e-mail: grace{at}ffyb.uba.ar)






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