Sphingolipids drive Akt-mediated Dendritic cell (DC) functioning induced by triiodothyronine (T3)

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

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

We reported that mice DCs express thyroid hormone receptor b1and that physiological levels of T3 promote their maturation andability to direct Th1 adaptive and T cytotoxic responses which wereexploited in an antitumor vaccination protocol. T3 effects involvednon-classical Akt activation. Besides, sphingolipids are key elementsin signal transduction cascades. The major bioactive sphingolipidsinclude: sphingosine, sphingosine-1-phosphate (S1P),ceramide and ceramide-1-phosphate and they are involved in Aktactivation. Our aim was to assess the participation of this pathway inT3-induced effects on DC functioning. Murine bone marrow derivedDCs were treated with T3 (5 nM) for different times and chemicalinhibitors of the sphingolipids (GW4869: neutral sphingomyelinase-nSMAse-, SKI: Sphingosine kinases -SphK-, Imipramine: acidsphingomyelinase -aSMAse- and NVP: ceramide kinase -CK-).Intracellular and secreted IL-12 production (sensitive marker of T3action on DCs) were assayed by flow cytometry and ELISA, respectively.The expression of mRNAs coding the enzymes nSMAse,aSMAse, SphK and CK was evaluated by RT-PCR, while changesin the levels of mRNAs coding SphK1, SphK2 and CK mRNAs inducedby T3 through RT-qPCR. The involvement of sphingolipids inT3-promoted Akt activation was evaluated by Western Blot. Resultsshowed that DCs express mRNA for all evaluated enzymes and thatT3 regulates the expression of SphK1, SphK2 and CK. Furthermore,exposure of DCs to T3 and all inhibitors significantly suppressedtheir 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 ofT3-induced Akt phosphorylation. These findings revealed sphingolipidsparticipation in T3 effects at DC level and suggest C1P andS1P involvement in T3-dependent Akt activation. Considering thetherapeutic impact of T3-treated DCs, these results provide initialmolecular tools to manipulate the immunogenic potential of DCs.Keywords: dendritic cells, triiodothyronine, sphingolipids, Akt.