Genomic and non-genomic intracelular pathways envolved in thyroid hormone mediated T lymphoma cell proliferation

CREMASCHI GA; FARÍAS RN; KLECHA AJ; STERLE HA; GENARO AM; BARREIRO ARCOS ML

Creta

Workshop; 5 th International Leukocyte Signal Transduction Workshop; 2009

Thyroid hormones (THs) exert a broad range of actions on development, growth and cell differentiation by both genomic and non-genomic mechanisms. We have previously shown that THs induce BW5147 T lymphoma (BW) cell division, through the activation of the atypical protein kinase ζ (PKC ζ) and the inducible isoform of nitric oxide synthase (iNOS). The aim of this work was to analyze the contribution of both genomic and non-genomic effects in these intracellular signals. For this purpose the action of non-cell permeable THs coupled to agarose (TH-ag) was analyzed. Both T3-ag and T4-ag induced BW cell proliferation, although to a lesser extent than free hormones. THs as well as TH-ag induced the rapid translocation of PKC to cell membranes, extracellular , extracellular signal-regulated kinase ½ (ERK1/2) phosphorylation and the activation of NF-κB. THs but not TH-ag lead to NOS activation and to an increase in iNOS expression both at the protein and mRNA levels. Selective blockers of acidic and neutral sphingomielinases, imipramine and GW4869 respectively, inhibited THs and TH-ag effects on proliferation and on PKCζ  avtivity. Also pretreatment of T lymphoma cells with the myristoylated PKCζ pseudosubstrate inhibited the same actions, NF-κB and the TH-mediated activation of NOS activity as well. These results indicate that THs trigger a non-genomic signaling cascade that involves sphingomielinases-mediated activation of PKCζ. As a consequence of this ERK1/2 and NF-κB are activated down-stream PKCζ leading in this way to the genomic increase of iNOS and to cell proliferation.