CONICET | Buscador de Institutos y Recursos Humanos

Background: Thyroid hormones (THs) exert a broad range of actions on development, growth and cell differentiation including immune cell regulation. These actions involved both genomic and non genomic mechanisms. We demonstrated that THs induce BW 5147 T lymphoma cell division, through the activation of atypical PKC z and the inducible isoform of NOS (iNOS). Objetives: To analyze the intracellular signals involved, elucidating the contribution of both genomic and non genomic effects. Methods: Proliferation was evaluated through [3H]-thymidine incorporation; PKC activity in cytosolic and membrane fractions was determined by specific substrate phosphorylation; NOS activity was measured by [14C]-citrulline formation; protein and mRNA levels were determined by western blot and RT-PCR respectively; NF-kB nuclear translocation was measured by EMSA. Results: Selective blockers of acidic and neutral sphingomyelinases, imipramine and GW 4869 respectively, inhibited TH effects on proliferation as well as on PKC z activity. TH as well as their cell-impermeable analogs, T3 and T4 coupled to agarose (ag), were able to activate NF-kB. Both T3-ag and T4-ag increase cell proliferation , but to a lesser extent than uncoupled hormones, leading to a rapid translocation of PKC to cell membranes and to ERK phosphorylation. Pre-treatment of cell with a PKC z pseudosubstrate inhibited all these effects. However, HT-ag were unable to induced iNOS expression at both the protein and mRNA levels. Conclusions: These results indicate that THs actions on T lymphoma cell proliferation involved the non genomic activation of PKC, NF-kB and ERK, but the genomic consequent iNOS induction and activation are also necessary for a full effect.