Efeitos da sinalização purinérgica nas infecções por Leishmania amazonensis

Abstract

Leishmania is the protozoan that causes leishmaniasis, a tropical disease that is still neglected. The infection process causes the release of ATP (adenosine triphosphate) into the extracellular environment. ATP signals through P2-type purinergic receptors, present in different cells, and this signaling results in an increase in pro-inflammatory cytokines, such as TNF-α, IL-1 and IL-12. The inflammatory response is regulated by the hydrolysis of ATP into AMP (adenosine monophosphate), by the action of the enzyme CD39 (nucleoside triphosphate diphosphohydrolase 1), which in turn is converted into adenosine by the action of the enzyme CD73 (5'- ectonucleotidase). Adenosine has anti-inflammatory effects by binding to P1 family receptors, especially A2A and A2B receptors. This study evaluated the role of purinergic signaling in the immune response of human macrophages infected with Leishmania amazonensis (MOI 5:1) expressing the fluorescent protein GFP. Infection of human macrophages, derived from THP-1 cells, with L. amazonensis increases the expression of A2A and A2B receptors, assessed by quantitativereal-time PCR. Treatment of human macrophages with selective antagonists of the A2A receptor (ZM241385) and the A2B receptor (PSB-603) reduces the parasitism of macrophages infected with L. amazonensis, as assessed by flow cytometry. In addition, inhibition of the A2A and A2B adenosine receptors increases the production of reactive oxygen intermediates (ROS), highly toxic molecules for the parasite, as assessed by the CM-H2DCFDA fluorescent probe, and increases the production of TNF, IL-1β and IL-6, inflammatory cytokines that play a role in controlling the infection, as assessed by CBA (Cytometric Bead Array), when compared to untreated macrophages, in cells infected with L. amazonensis. These data suggest that the A2A adenosine receptors, and more significantly the A2B receptors, are essential for L. amazonensis to avoid a pro-inflammatory immune response, inferring an ease of replication during the infection process.