Influência das citocinas IL-10, TGF-β1 e IFN-γ na susceptibilidade de células trofoblásticas humanas (linhagem BeWo) e células epiteliais uterinas humanas (linhagem HeLa) à infecção por Toxoplasma gondii: papel na expressão de ICAM-1, na adesão do parasito à célula hospedeira e vias de sinalização intracelulares ativadas

Abstract

Toxoplasma gondii is a parasite able to infect various cell types, including trophoblast cells. Studies demonstrated that interleukin (IL)-10, transforming growth factor (TGF)-β1 and interferon (IFN)-γ are cytokines involved in the susceptibility of BeWo trophoblast cells and cervical uterine cells (HeLa lineage) to T. gondii infection. Furthermore, T. gondii is able to adhere to the plasma membrane of host cells through intercellular adhesion molecule 1 (ICAM-1). The present study investigated two major aims: (i) the role of IL-10, TGF-β1 and IFN-γ in the expression of ICAM-1 in BeWo and HeLa cells and the adhesion of T. gondii to these cells under the influence of these cytokines; and (ii) the intracellular mechanisms triggered by IL-10, TGF-β1 and IFN-γ in BeWo and HeLa cells in the differential susceptibility of these cells to infection. In order to perform the first aim, BeWo and HeLa cells were infected or not by T. gondii (RH strain) and treated or not with rIL-10, rTGF-β1 or rIFN-γ. The cells were analyzed for the infection index, ICAM-1 expression, tumor necrosis factor (TNF)-α release, and for influence of ICAM-1 in the adhesion of the parasite to the host cells in the presence or absence of anti-ICAM-1 antibody. Additionally, to verify the second aim, BeWo and HeLa cells were treated or not with rIL-10, rTGF-β1 or rIFN-γ, infected or not by T. gondii (2F1 or RH strain), and analyzed for T. gondii proliferation index, cytokines production, phosphorylation of signal transducers and activators of transcription (STAT)-1, STAT-3, Smad2/3 and interferon regulatory factor (IRF)-1 expression, as well as the effect of the inhibition of these intracellular pathways in the proliferation of T. gondii. For the BeWo cells, rIL-10 and rTGF-β1 favored susceptibility to infection, but only rTGF-β1 and rIFN-γ promoted an increase of ICAM-1 expression, TNF-α release, the number of ICAM-1+ cells with membrane-adhered parasites and the total number of membrane adhered-parasites in ICAM-1+ cells. On the other hand, rTGF-β1 and rIFN-γ downregulated the expression of ICAM-1 triggered by T. gondii in HeLa cells, leading to control of the infection. In contrast to HeLa cells, T. gondii proliferation index was increased in BeWo cells treated with rIL-10 and rTGF-β1, while rIFN-γ was unable to control it. The parasite proliferation regulated by rIFN-γ and rIL-10 in BeWo and HeLa cells was associated with the high phosphorylation of STAT-1 and IRF-1 expression in HeLa cells and the activation of STAT-3 in BeWo cells. The influence of these intracellular pathways in the parasite proliferation was confirmed when STAT-1 or STAT-3 inhibitors were used to revert the effectors mechanisms of the parasite regulation induced by rIFN-γ and rIL-10. In relation to cytokine production, HeLa cells produced higher concentrations of MIF if compared to BeWo cells, while BeWo cells secreted higher concentrations of IL-6 when compared to HeLa cells. Taken together, these data conclude that IL-10, TGF-β1 or IFN-γ cytokines regulate the susceptibility of BeWo and HeLa cells to T. gondii infection when differentially modulate ICAM-1 expression and trigger distinct intracellular pathways, contributing to the understanding of this particular strategy used by T. gondii to adhere and invade trophoblast cells and the intracellular effects of some cytokines responsible to the higher susceptibility of trophoblast cells to infection.