Trypanosoma cruzi infection modulates secreted phospholipase A2 expression in the salivary glands of Rhodnius prolixus.

Phospholipases A2 (PLA2) comprise a superfamily of enzymes that specifically catalyze hydrolysis of the ester bond at the sn-2 position of glycerophospholipids, generating lysophospholipids and fatty acids. In Rhodnius prolixus, one of the main vectors of the Chagas's disease etiologic agent Trypanosoma cruzi, it was previously shown that lysophosphatidylcholine, a bioactive lipid, found in the insect's saliva, contributes to the inhibition of platelet aggregation, and increases the production of nitric oxide, an important vasodilator. Due to its role in potentially generating LPC, here we studied the PLA2 present in the salivary glands of R. prolixus. PLA2 activity is approximately 100 times greater in the epithelium than in the contents of salivary glands. Our study reveals the role of the RpPLA2 XIIA gene in the insect feeding performance and in the fatty acids composition of phospholipids extracted from the salivary glands. Knockdown of RpPLA2 XIIA significantly altered the relative amounts of palmitic, palmitoleic, oleic and linoleic acids. A short-term decrease in the expression of RpPLA2 III and RpPLA2 XIIA in the salivary glands of R. prolixus was evident on the third day after infection by T. cruzi. Taken together, our results contribute to the understanding of the role of PLA2 in the salivary glands of hematophagous insects and show that the parasite is capable of modulating even tissues that are not colonized by it.

The Wnt/Beta-Catenin Pathway and Cytoskeletal Filaments Are Involved in the Positioning, Size, and Function of Lysosomes during Chick Myogenesis.

Lysosomes are highly dynamic organelles involved in the breakdown and recycling of macromolecules, cell cycle, cell differentiation, and cell death, among many other functions in eukaryotic cells. Recently, lysosomes have been identified as cellular hubs for the modulation of intracellular signaling pathways, such as the Wnt/beta-catenin pathway. Here we analyzed morphological and functional characteristics of lysosomes in muscle and non-muscle cells during chick myogenesis, as well as their modulation by the Wnt/beta-catenin pathway. Our results show that (i) muscle and non-muscle cells show differences in lysosomal size and its distribution, (ii) lysosomes are found in spherical structures in myoblasts and fibroblasts and tubular structures in myotubes, (iii) lysosomes are found close to the plasma membrane in fibroblasts and close to the nucleus in myoblasts and myotubes, (iv) lysosomal distribution and size are dependent on the integrity of microtubules and microfilaments in myogenic cells, (v) alterations in lysosomal function, in the expression of LAMP2, and in Wnt/beta-catenin pathway affect the distribution and size of lysosomes in myogenic cells, (vi) the effects of the knockdown of LAMP2 on myogenesis can be rescued by the activation of the Wnt/beta-catenin pathway, and (vii) the chloroquine Lys05 is a potent inhibitor of both the Wnt/beta-catenin pathway and lysosomal function. Our data highlight the involvement of the Wnt/beta-catenin pathway in the regulation of the positioning, size, and function of lysosomes during chick myogenesis.

Host cholesterol influences the activity of sterol biosynthesis inhibitors in Leishmania amazonensis.

A significant percentage of exogenous cholesterol was found in promastigotes and amastigotes of all studied species of Leishmania, suggesting a biological role for this molecule. Previous studies have shown that promastigotes of Leishmania uptake more low-density lipoprotein (LDL) particles under pharmacological pressure and are more susceptible to ergosterol inhibition in the absence of exogenous sources of cholesterol. This work shows that the host's LDL is available to intracellular amastigotes and that the absence of exogenous cholesterol enhances the potency of sterol biosynthesis inhibitors in infected macrophages. A complete understanding of cholesterol transport to the parasitophorous vacuole can guide the development of a new drug class to be used in combination with sterol biosynthesis inhibitors for the treatment of leishmaniases.

Bioactive lipids regulate Trypanosoma cruzi development.

Trypanosoma cruzi is the etiological agent of Chagas disease. These parasites undergo dramatic morphological and physiological changes during their life cycle. The human-infective metacyclic trypomastigotes differentiate from epimastigotes inside the midgut of the Triatominae insect vector. Our group has shown that the saliva and feces of Rhodnius prolixus contains a lysophospholipid, lysophosphatidylcholine (LPC), which modulates several aspects of T. cruzi infection in macrophages. LPC hydrolysis by a specific lysophospholipase D, autotaxin (ATX), generates lysophosphatidic acid (LPA). These bioactive lysophospholipids are multisignaling molecules and are found in human plasma ingested by the insect during blood feeding. Here, we show the role of LPC and LPA in T. cruzi proliferation and differentiation. Both lysophospholipids are able to induce parasite proliferation. We observed an increase in parasite growth with different fatty acyl chains, such as C18:0, C16:0, or C18:1 LPC. The dynamics of LPC and LPA effect on parasite proliferation was evaluated in vivo through a time- and space-dependent strategy in the vector gut. LPC but not LPA was also able to affect parasite metacyclogenesis. Finally, we determined LPA and LPC distribution in the parasite itself. Such bioactive lipids are associated with reservosomes of T. cruzi. To the best of our knowledge, this is the first study to suggest the role of surrounding bioactive lipids ingested during blood feeding in the control of parasite transmission.

Trypanosoma cruzi Epimastigotes Are Able to Manage Internal Cholesterol Levels under Nutritional Lipid Stress Conditions.

Trypanosoma cruzi epimastigotes store high amounts of cholesterol and cholesteryl esters in reservosomes. These unique organelles are responsible for cellular digestion by providing substrates for homeostasis and parasite differentiation. Here we demonstrate that under nutritional lipid stress, epimastigotes preferentially mobilized reservosome lipid stocks, instead of lipid bodies, leading to the consumption of parasite cholesterol reservoirs and production of ergosterol. Starved epimastigotes acquired more LDL-NBD-cholesterol by endocytosis and distributed the exogenous cholesterol to their membranes faster than control parasites. Moreover, the parasites were able to manage internal cholesterol levels, alternating between consumption and accumulation. With normal lipid availability, parasites esterified cholesterol exhibiting an ACAT-like activity that was sensitive to Avasimibe in a dose-dependent manner. This result also implies that exogenous cholesterol has a role in lipid reservoirs in epimastigotes.

Reservosomes: multipurpose organelles?

Reservosomes are endocytic organelles from Trypanosoma cruzi epimastigotes that store proteins and lipids for future use. The lack of molecular markers for the compartments of this parasite makes it difficult to clarify all reservosome functions, as they present characteristics of pre-lysosomes, lysosomes and recycling compartments.