Crotoxin Elicits Differential Increases in Macrophage Lipid Droplet Formation In Vitro Modulated during Leishmania (Leishmania) amazonensis Infection.

Leishmania spp. is an obligate intracellular parasite that primarily infects macrophages. During infection, leukocytes are activated, culminating in the formation of lipid droplets (LDs), which are sites for the synthesis of eicosanoids that modulate the immune response. Crotoxin (CTX), the major toxin derived from Crotalus durissus terrificus (Cdt) snake venom, exhibits pro-inflammatory properties by promoting LD formation and further eicosanoid production. The aim of the present study was to analyze the effects of CTX on the formation of LDs in uninfected and Leishmania (Leishmania) amazonensis-infected macrophages. Cells were treated with CTX (2.4 and 4.8 μg/mL) and infected or not with parasites, before analyzing LD formation. The kinetic effect of CTX in uninfected macrophages demonstrated a time-dependent and progressive formation of LDs. CTX inhibited the accumulation of LDs during the first 12 h of infection and reduced the parasite load. Ultrastructural analysis revealed different electron densities and sizes of LDs in or near the parasitophore vacuole, indicating that LDs are used by the parasite. Increased levels of prostaglandin E2 (PGE2) also indicated the utilization of LDs by infected macrophages after CTX treatment. CTX stimulated the production of lipid-derived proinflammatory molecules by macrophages, thereby killing the parasite.