Influência de células trofoblásticas BeWo e infecção por Toxoplasma gondii na modulação dos mecanismos de morte celular em células THP-1

Abstract

During pregnancy, maternal organism is submitted to immunological alterations, which are necessary to fetus maintenance. This fetal tolerance depends on the cell interactions that occur at maternal-fetal interface. Therefore, trophoblast cells interact with immune cells, as monocytes, and it is determinant for gestational success. However, in consequence of this immunomodulation process, the maternal organism becomes more susceptible to infections by pathogens, such as Toxoplasma gondii, which interfere directly in the crosstalk between trophoblast cells and monocytes, causing pregnancy complications. Mechanisms of cell death that occurs in cell populations present at maternal-fetal interface are involved in the gestational development and, in this way, this study aimed to evaluate the influence o trophoblast cell (BeWo line) and T. gondii infection in the modulation of death mechanisms in monocytes (THP-1 line). For this, THP-1 cells were stimulated or not with supernatants of BeWo cells (infected or uninfected with T. gondii) and then infected with T. gondii. In THP-1 cells were analyzed: the index of cell death and apoptosis, the expression of death receptor (Fas/CD95) and intracellular proteins associated to death in these cells (survivin, phosphorylated ERK1/2, p38, JNK, active caspase 3), human Fas ligand (FasL) secretion and the influence of soluble factors secreted with BeWo cells, which have the capacity to interfere in these mechanisms of THP-1 cell death. The results showed that supernatants of BeWo cells induced the increase of the index of cell death in uninfected THP-1 cells, but only supernatant of infected BeWo cells altered this index in infected THP-1 cells, reducing it. Moreover, infected THP-1 cells presented cell death index higher than uninfected THP-1 cells. Both supernatants of BeWo cells induced increased in the expression of phosphatidylserine in uninfected THP-1 cells and infected THP-1 cells expressed less phosphatidylserine than uninfected THP-1 cells. Macrophage 13 migration inhibitory factor (MIF) and transforming growth factor beta 1 (TGF-pi), both secreted by BeWo cells, actuated in the induction of cell death in uninfected THP-1 cells, but only TGF-pi, interfered in the cell death of infected THP-1 cells, inhibiting it. Furthermore, both of these soluble factors were able to decrease the expression of phosphatidylserine in uninfected THP-1 cells, but only TGF-pi altered this expression in infected THP-1 cells. The expression of Fas/CD95 was higher in infected THP-1 cells than uninfected THP-1 cells. In uninfected THP-1 cells, Fas/CD95 expression was higher when these cells were stimulated with supernatants of BeWo cells and in infected THP-1 cells, this phenomenon was repeated in those that were stimulated with supernatant of infected BeWo cells. The secretion of FasL was higher in infected THP-1 cells, but in BeWo cells, the infection did not altered the secretion of this ligand. Both intracellular proteins analyzed, phophorylated ERK1/2 and active caspase 3 were less expressed in infected THP-1 cells and both supernatants of BeWo cells, induced decreased of active caspase 3 expression in uninfected and infected THP-1 cells. These results showed that BeWo trophoblast cells modulate mechanisms of cell death in THP- 1 cells and these alterations can be associated with the maintenance and success of pregnancy. Furthermore, T. gondii infection also interferes in these cell interactions which occur in the maternal-fetal interface.