A susceptibilidade à infecção pelas cepas ME49 e RH de Toxoplasma gondii é dependente de ciclooxigenases em modelo experimental Calomys callosus

Abstract

Toxoplasma gondii is an obligate intracellular protozoan parasite that infects a wide range of warm-blooded vertebrates, including humans. Many studies show that the ciclooxygenase-2 (COX-2) is a potent modulator of immune response in multiple types of infection. However, the role of cyclooxygenase during an infection by T. gondii is still not clear. Therefore, the aim of this study was to investigate the functional role of COX-2 in Calomys callosus rodents infected with T. gondii, an excellent in vivo experimental model traditionally used for studying toxoplasmosis. For this purpose, C. callosus females were infected with fifty cysts of T. gondii (ME49 strain), treated with ciclooxygenase inhibitors as Meloxicam, COX-1 and COX-2 inhibitor, and Celecoxib, COX-2 selective inhibitor, and evaluated every 48 hours to check the body weight change and morbidity for 40 consecutive days. As a control, the animals were infected and not treated with ciclooxygenase inhibitors. After 40 days of infection was performed collection and processing of the brains for immunohistochemistry or real-time PCR for the detection of T. gondii, while evaluating the serum of animals for the detection of cytokines by ELISA. Furthermore, the peritoneal macrophages of C. callosus, uninfected or infected with T. gondii RH strain, were treated with Meloxicam or Celecoxib in order to evaluate the parasite intracellular proliferation by beta-galactosidase assay, and the supernatant was collected for cytokine detection by ELISA and production of nitrite by Griess method, after 24h of infection. The results showed that the morbidity of the animals changed after infection by T. gondii, regardless of both treatments. Regarding the change in body weight, animals treated with Celecoxib had a smaller loss of weight when compared to their respective control. Immunohistochemistry and real-time PCR performed on brain tissue showed a significant reduction of tissue cysts in animals treated with both inhibitors when compared to infected and untreated animals. Besides, it was observed that both treatments with the inhibitors were able to control the T. gondii intracellular proliferation in peritoneal macrophages. On the serum of C. callosus, the ELISA data shows that animals treated with Meloxicam showed a tendency to increase the MIF production when compared to the PBS control. In the supernatant of peritoneal macrophages, there was an increase in TNF-α production and IL-6 reduction, and Griess assay showed that both treatments induced a high production of nitrite. All these results indicate that cyclooxygenases are capable of favoring infection by T. gondii, since inhibition of these mediators induced significant control of infection. In conclusion, our results show that COX-1 and COX-2 are important to facilitate the T. gondii infection in the brain and peritoneal macrophages of C. callosus.