Activation of Phosphatidylinositol 3-Kinase/Akt and Impairment of Nuclear Factor-κB Molecular Mechanisms Behind the Arrested Maturation/Activation State of Leishmania infantum-Infected Dendritic Cells

Understanding the complex interactions between Leishmania and dendritic cells (DCs) is central to the modulation of the outcome of this infection given that an effective immune response against Leishmania is dependent on the successful activation and maturation of DCs We report here that Leishmania infantum promastigotes successfully infect mouse bone marrow derived DCs without triggering maturation as shown by a failure in the up regulation of CD40 and CD86 expression and that parasites strongly counteract the lipopolysaccharide triggered maturation of DCs A small increase in interleukin (IL) 12 and IL 10 transcription and secretion and a decrease in IL 6 were observed in infected cells This arrested DC maturation state is actively promoted by parasites because heat killed or fixed parasites increased cytokine and costimulatory molecule expression At a molecular level L infantum rapidly induced activation of phosphatidylinositol 3 kinase/Akt and extra cellular signal regulated kinase 1/2 whereas no effect was observed in the c Jun N terminal kinase and p38 mitogen activated protein kinase proinflammatory pathways Moreover parasites actively promoted cleavage of the nuclear factor kappa B p65(RelA) subunit causing its impairment The blockade of phosphatidylinositol 3 kinase/Akt by either treatment of bone marrow derived DCs with wortmannin or transfection with an Akt dominant negative mutant resulted in a strong decrease in infection rates revealing for the first time a crucial role of this pathway on Leishmania engulfment by DCs Overall our data indicate that activation of Akt and impairment of nuclear factor kappa B are responsible for immunogenicity sub version of L infantum infected DCs (Am J Pathol 2010 177 2898-2911 DOI 10 2353/ajpath 2010.100367)