Sphingolipids drive Akt-mediated dendritic cell (DC) functioning induced by triiodotyronine (T3)

GIUSIANO L; FOZZATTI L; SOLER MF; ALAMINO VA; BARREIRO ARCOS ML; CREMASCHI GA; MONTESINOS MM; PELLIZAS CG

Buenos Aires

Congreso; Biosciences Annual Meeting; 2017

Sociedad Argentina de Inmunología (SAI)

We reported that mice DCs express thyroid hormone receptor b1 and that physiological levels of T3 promote their maturation and ability to direct Th1 adaptive and T cytotoxic responses which were exploited in an antitumor vaccination protocol. T3 effects involved non-classical Akt activation. Besides, sphingolipids are key ele-ments in signal transduction cascades. The major bioactive sphin-golipids include: sphingosine, sphingosine-1-phosphate (S1P), ceramide and ceramide-1-phosphate and they are involved in Akt activation. Our aim was to assess the participation of this pathway in T3-induced effects on DC functioning. Murine bone marrow derived DCs were treated with T3 (5 nM) for different times and chemical inhibitors of the sphingolipids (GW4869: neutral sphingomyelinase -nSMAse-, SKI: Sphingosine kinases -SphK-, Imipramine: acid sphingomyelinase -aSMAse- and NVP: ceramide kinase -CK-). Intracellular and secreted IL-12 production (sensitive marker of T3 action on DCs) were assayed by fow cytometry and ELISA, respec-tively. The expression of mRNAs coding the enzymes nSMAse, aSMAse, SphK and CK was evaluated by RT-PCR, while changes in the levels of mRNAs coding SphK1, SphK2 and CK mRNAs in-duced by T3 through RT-qPCR. The involvement of sphingolipids in T3-promoted Akt activation was evaluated by Western Blot. Results showed that DCs express mRNA for all evaluated enzymes and that T3 regulates the expression of SphK1, SphK2 and CK. Furthermore, exposure of DCs to T3 and all inhibitors signifcantly suppressed their ability to produce IL-12 in response to T3 (p≤0.05). Besides, GW4869 (p≤0.05) and Imipramine (p≤0.05) decreased the level of T3-induced Akt phosphorylation. These fndings revealed sphingo-lipids participation in T3 effects at DC level and suggest C1P and S1P involvement in T3-dependent Akt activation. Considering the therapeutic impact of T3-treated DCs, these results provide initial molecular tools to manipulate the immunogenic potential of DCs.Keywords: dendritic cells, triiodothyronine, sphingolipids, Akt.