Inibidores de ciclooxigenase (COX)-2 reduzem a infecção por Toxoplasma gondii (cepa RH) e modulam a resposta imune e a formação de corpos lipídicos em células trofoblásticas humanas vilosas (BeWo) e extravilosas (HTR-8/SVneo)

Abstract

Toxoplasma gondii is an obligate intracellular parasite that causes congenital toxoplasmosis, causing severe sequelae like miscarriage. Many intracellular pathogens have devoloped mechanisms of evasion of the host immune response. One of these mechanisms is the induction of the production of inflammatory mediators, such as cyclooxygenase (COX) -2 and prostaglandin E2 (PGE2), favoring the growth of pathogens. Many studies have shown that COX-2 and PGE2 are key mediators for the spread and persistence of Trypanosoma cruzi infection in the host organism. These mediators are produced and stored in lipid droplets (LDs), lipid-rich organelles important for the maintenance of pathogens. It was seen that LDs are increased during T. gondii infection in macrophages and skeletal muscle cells, but no relationship has been established between COX-2, immune response, LD and parasitic load during Toxoplasma infection in human trophoblast cells. Thus, the objective of the present study was to evaluate the role of COX-2 and LDs during T. gondii infection in human villous trophoblasts cells (BeWo), and extravillous (HTR-8/SVneo). BeWo and HTR-8/SVneo cells were treated with different concentrations of COX inhibitors, Meloxicam, COX-1 and COX-2 inhibitor, and Celecoxib, a COX-2 specific inhibitor, in order to evaluate the cell viability by the MTT. Then, BeWo and HTR-8/SVneo cells were infected with T. gondii and treated with Meloxicam or Celecoxib for another 24 hours. After this, the proliferation rate of T. gondii was performed on the cells by the β-galactosidase assay, and the cell culture supernatant was used to evaluate the cytokine profile by the ELISA assay. Subsequently, BeWo and HTR-8/SVneo cells were infected or not with T. gondii in the presence or absence of fetal bovine serum (FBS) for 24 hours. After this time, staining of lipid bodies with Oil Red O was performed. Then, BeWo and HTR-8/SVneo cells were infected with T. gondii and treated with Meloxicam or Celexocibe for 24 hours. After that time, staining of lipid bodies with Oil Red O was performed. Our results demonstrate that COX-2 inhibitors have not decreased the viability of BeWo and HTR-8 / SVneo cells. In addition, treatment with COX-2 inhibitors was able to decrease the intracellular proliferation of T. gondii in the two human trophoblast cell lineages. Later, we observed that inhibition of COX-2 induced secretion of pro-inflammatory cytokines in BeWo and HTR-8/SVneo cells, such as IL-6 and MIF, and decreased the production of anti-inflammatory cytokines in BeWo cells, IL-4 and IL-10, and in HTR-8/SVneo cells, IL-4 and TGF-β1. Next, we saw that T. gondii infection induced the production of LDs in both cell lineages, and that this production was increased with the addition of FBS. Subsequently, we observed that BeWo and HTR-8/SVneo cells, infected and treated with COX-2 inhibitors, decreased production of LDs. Thus, we conclude that the success of T. gondii infection in human trophoblastic cells is dependent on COX-2, since its inhibition induces a pro-inflammatory immune response capable of controlling parasitism and, at the same time, decreasing the availability of LD in both cell lineages.