BackgroundLysophosphatidylcholine (LPC) is the main phospholipid component of oxidized low-density lipoprotein (oxLDL) and is usually noted as a marker of several human diseases, such as atherosclerosis, cancer and diabetes. Some studies suggest that oxLDL modulates Toll-like receptor (TLR) signaling. However, effector molecules that are present in oxLDL particles and can trigger TLR signaling are not yet clear. LPC was previously described as an attenuator of sepsis and as an immune suppressor. In the present study, we have evaluated the role of LPC as a dual modulator of the TLR-mediated signaling pathway.Methodology/Principal FindingsHEK 293A cells were transfected with TLR expression constructs and stimulated with LPC molecules with different fatty acid chain lengths and saturation levels. All LPC molecules activated both TLR4 and TLR2-1 signaling, as evaluated by NF-қB activation and IL-8 production. These data were confirmed by Western blot analysis of NF-қB translocation in isolated nuclei of peritoneal murine macrophages. However, LPC counteracted the TLR4 signaling induced by LPS. In this case, NF-қB translocation, nitric oxide (NO) synthesis and the expression of inducible nitric oxide synthase (iNOS) were blocked. Moreover, LPC activated the MAP Kinases p38 and JNK, but not ERK, in murine macrophages. Interestingly, LPC blocked LPS-induced ERK activation in peritoneal macrophages but not in TLR-transfected cells.Conclusions/SignificanceThe above results indicate that LPC is a dual-activity ligand molecule. It is able to trigger a classical proinflammatory phenotype by activating TLR4- and TLR2-1-mediated signaling. However, in the presence of classical TLR ligands, LPC counteracts some of the TLR-mediated intracellular responses, ultimately inducing an anti-inflammatory phenotype; LPC may thus play a role in the regulation of cell immune responses and disease progression.

Most eukaryotic cells contain varying amounts of cytosolic lipidic inclusions termed lipid bodies (LBs) or lipid droplets (LDs). In mammalian cells, such as macrophages, these lipid-rich organelles are formed in response to host-pathogen interaction during infectious diseases and are sites for biosynthesis of arachidonic acid (AA)-derived inflammatory mediators (eicosanoids). Less clear are the functions of LBs in pathogenic lower eukaryotes. In this study, we demonstrated that LBs, visualized by light microscopy with different probes and transmission electron microscopy (TEM), are produced in trypomastigote forms of the parasite Trypanosoma cruzi, the causal agent of Chagas’ disease, after both host interaction and exogenous AA stimulation. Quantitative TEM revealed that LBs from amastigotes, the intracellular forms of the parasite, growing in vivo have increased size and electron-density compared to LBs from amastigotes living in vitro. AA-stimulated trypomastigotes released high amounts of prostaglandin E2 (PGE2) and showed PGE2 synthase expression. Raman spectroscopy demonstrated increased unsaturated lipid content and AA incorporation in stimulated parasites. Moreover, both Raman and MALDI mass spectroscopy revealed increased AA content in LBs purified from AA-stimulated parasites compared to LBs from unstimulated group. By using a specific technique for eicosanoid detection, we immunolocalized PGE2 within LBs from AA-stimulated trypomastigotes. Altogether, our findings demonstrate that LBs from the parasite Trypanosoma cruzi are not just lipid storage inclusions but dynamic organelles, able to respond to host interaction and inflammatory events and involved in the AA metabolism. Acting as sources of PGE2, a potent immunomodulatory lipid mediator that inhibits many aspects of innate and adaptive immunity, newly-formed parasite LBs may be implicated with the pathogen survival in its host.

Cardiovascular diseases and thrombotic events became major clinical problems in the combined antiretroviral therapy (cART) era. Although the precise mechanisms behind these clinical problems have not been fully elucidated, a persistent pro-inflammatory state plays a central role. As platelets play important roles on both, thrombus formation and inflammatory/immune response, we aimed at investigating platelet function in HIV-infected subjects virologically controlled through cART. We evaluate parameters of activation, mitochondrial function and activation of apoptosis pathways in platelets from 30 HIV-infected individuals under stable cART and 36 healthy volunteers. Despite viral control achieved through cART, HIV-infected individuals exhibited increased platelet activation as indicated by P-selectin expression and platelet spreading when adhered on fibrinogen-coated surfaces. Platelets from HIV-infected subjects also exhibited mitochondrial dysfunction and activation of apoptosis pathways. Finally, thrombin stimuli induced lower levels of P-selectin translocation and RANTES secretion, but not TXA2 synthesis, in platelets from HIV-infected individuals compared to control; and labeling of platelet alpha granules showed reduced granule content in platelets from HIV-infected individuals when compared to healthy subjects. In summary, platelets derived from HIV-infected individuals under stable cART exhibit a phenotype of increased activation, activation of the intrinsic pathway of apoptosis and undermined granule secretion in response to thrombin.

Trypanosoma cruzi, the etiological agent of Chagas disease, is transmitted by bug feces deposited on human skin during a blood meal. However, parasite infection occurs through the wound produced by insect mouthparts. Saliva of the Triatominae bug Rhodnius prolixus is a source of lysophosphatidylcholine (LPC). Here, we tested the role of both triatomine saliva and LPC on parasite transmission. We show that vector saliva is a powerful inducer of cell chemotaxis. A massive number of inflammatory cells were found at the sites where LPC or saliva was inoculated into the skin of mice. LPC is a known chemoattractant for monocytes, but neutrophil recruitment induced by saliva is LPC independent. The preincubation of peritoneal macrophages with saliva or LPC increased fivefold the association of T. cruzi with these cells. Moreover, saliva and LPC block nitric oxide production by T. cruzi-exposed macrophages. The injection of saliva or LPC into mouse skin in the presence of the parasite induces an up-to-sixfold increase in blood parasitemia. Together, our data suggest that saliva of the Triatominae enhances T. cruzi transmission and that some of its biological effects are attributed to LPC. This is a demonstration that a vector-derived lysophospholipid may act as an enhancing factor of Chagas disease.