Toxoplasma gondii Infection Decreases Intestinal 5-Lipoxygenase Expression, while Exogenous LTB4 Controls Parasite Growth.

5-Lipoxygenase (5-LO) is an enzyme required for the production of leukotrienes and lipoxins and interferes with parasitic infections. In vitro, Toxoplasma gondii inhibits leukotriene B4 (LTB4) production, and mice deficient in 5-LO are highly susceptible to infection. The aim of this study was to investigate the effects of the pharmacological inhibition of the 5-LO pathway and exogenous LTB4 supplementation during experimental toxoplasmosis. For this purpose, susceptible C57BL/6 mice were orally infected with T. gondii and treated with LTB4 or MK886 (a selective leukotriene inhibitor through inhibition of 5-LO-activating protein [FLAP]). The parasitism, histology, and immunological parameters were analyzed. The infection decreased 5-LO expression in the small intestine, and treatment with MK886 reinforced this reduction during infection; in addition, MK886-treated infected mice presented higher intestinal parasitism, which was associated with lower local interleukin-6 (IL-6), interferon gamma (IFN-γ), and tumor necrosis factor (TNF) production. In contrast, treatment with LTB4 controlled parasite replication in the small intestine, liver, and lung and decreased pulmonary pathology. Interestingly, treatment with LTB4 also preserved the number of Paneth cells and increased α-defensins expression and IgA levels in the small intestine of infected mice. Altogether, these data demonstrated that T. gondii infection is associated with a decrease in 5-LO expression, and on the other hand, treatment with the 5-LO pathway product LTB4 resulted in better control of parasite growth in the organs, adding to the knowledge about the pathogenesis of T. gondii infection.