No abstract

The secretion of extracellular vesicles (EVs) in helminth parasites is a constitutive mechanism that promotes survival by improving their colonization and adaptation in the host tissue. In the present study, we analyzed the production of EVs from supernatants of cultures of Echinococcus granulosus protoscoleces and metacestodes and their interaction with dendritic cells, which have the ability to efficiently uptake and process microbial antigens, activating T lymphocytes. To experimentally increase the release of EVs, we used loperamide, a calcium channel blocker that increases the cytosolic calcium level in protoscoleces and EV secretion. An exosome-like enriched EV fraction isolated from the parasite culture medium was characterized by dynamic light scattering, transmission electron microscopy, proteomic analysis and immunoblot. This allowed identifying many proteins including: small EV markers such as TSG101, SDCBP, ALIX, tetraspanins and 14-3-3 proteins; proteins involved in vesicle-related transport; orthologs of mammalian proteins involved in the immune response, such as basigin, Bp29 and maspardin; and parasite antigens such as antigen 5, P29 and endophilin-1, which are of special interest due to their role in the parasite-host relationship. Finally, studies on the EVs-host cell interaction demonstrated that E. granulosus exosome-like vesicles were internalized by murine dendritic cells, inducing their maturation with increase of CD86 and with a slight down-regulation in the expression of MHCII molecules. These data suggest that E. granulosus EVs could interfere with the antigen presentation pathway of murine dendritic cells inducing immunoregulation in the host. Further studies are needed to better understand the role of these vesicles in parasite survival and as diagnostic markers and new vaccines.

No abstract

Cystic echinococcosis is a zoonotic infection caused by the larval stage of the cestodeEchinococcus granulosus. Chemotherapy currently employs benzimidazoles; however, 40% of cases do not respond favorably. With regard to these difficulties, novel therapeutic tools are needed to optimize treatment in humans. The aim of this work was to explore thein vitroandin vivoeffects of tamoxifen (TAM) againstE. granulosus. In addition, possible mechanisms for the susceptibility of TAM are discussed in relation to calcium homeostasis, P-glycoprotein inhibition, and antagonist effects on a putative steroid receptor. After 24 h of treatment, TAM, at a low micromolar concentration range (10 to 50 μM), inhibited the survival ofE. granulosusprotoscoleces and metacestodes. Moreover, we demonstrated the chemotherapeutic and chemopreventive pharmacological effects of the drug. At a dose rate of 20 mg/kg of body weight, TAM induced protection against the infection in mice. In the clinical efficacy studies, a reduction in cyst weight was observed after the administration of 20 mg/kg in mice with cysts developed during 3 or 6 months, compared to that of those collected from control mice. Since the collateral effects of high TAM doses have been largely documented in clinical trials, the use of low doses of this drug as a short-term therapy may be a novel alternative approach for human cystic echinococcosis treatment.

No abstract

Cystic echinococcosis (CE) is a worldwide distributed helminthic zoonosis caused by Echinococcus granulosus. Benzimidazole derivatives are currently the only drugs for chemotherapeutic treatment of CE. However, their low efficacy and the adverse effects encourage the search for new therapeutic targets. We evaluated the in vitro efficacy of Bortezomib (Bz), a proteasome inhibitor, in the larval stage of the parasite. After 96 h, Bz showed potent deleterious effects at a concentration of 5 μM and 0.5 μM in protoscoleces and metacestodes, respectively (P < 0.05). After 48 h of exposure to this drug, it was triggered a mRNA overexpression of chaperones (Eg-grp78 and Eg-calnexin) and of Eg-ire2/Eg-xbp1 (the conserved UPR pathway branch) in protoscoleces. No changes were detected in the transcriptional expression of chaperones in Bz-treated metacestodes, thus allowing ER stress to be evident and viability to highly decrease in comparison with protoscoleces. We also found that Bz treatment activated the autophagic process in both larval forms. These facts were evidenced by the increase in the amount of transcripts of the autophagy related genes (Eg-atg6, Eg-atg8, Eg-atg12, Eg-atg16) together with the increase in Eg-Atg8-II detected by western blot and by in toto immunofluorescence labeling. It was further confirmed by direct observation of autophagic structures by electronic microscopy. Finally, in order to determine the impact of autophagy induction on Echinococcus cell viability, we evaluated the efficacy of Bz in combination with rapamycin and a synergistic cytotoxic effect on protoscolex viability was observed when both drugs were used together. In conclusion, our findings demonstrated that Bz induced endoplasmic reticulum stress, autophagy and subsequent death allowing to identify unstudied parasite-host pathways that could provide a new insight for control of parasitic diseases.

No abstract

Cystic echinococcosis is a neglected parasitic disease caused by the larval stage of Echinococcus granulosus for which an effective treatment is not yet available. Since autophagy constitutes a homeostatic mechanism during stress, either inhibition or activation of its activity might be detrimental for survival of the parasite. Amongst the critical molecules that regulate autophagy, TOR, AMPK and sirtuins are the best characterized ones. Previously, we have identified the autophagic machinery, the occurrence of TORC1-controlled events, and the correlation between autophagy and the activation of the unfolded protein response in E. granulosus larval stage. In addition, we have demonstrated that the parasite is susceptible to metformin (Met), a drug that indirectly activates Eg-AMPK and induces energy stress. In this work, we demonstrate that Met induces autophagy in the E. granulosus larval stage. Electron microscopy analysis revealed the presence of autophagic structures in Met-treated protoscoleces. In accordance with these findings, the autophagic marker Eg-Atg8 as well as the transcriptional expression of Eg-atg6, Eg-atg8, Eg-atg12 and Eg-atg16 genes were significantly up-regulated in Met-treated parasites. The induction of the autophagic process was concomitant with Eg-foxO over-expression and its nuclear localization, which could be correlated with the transcriptional regulation of this pathway. On the other hand, the expression of Eg-AKT and Eg-Sirts suggests a possible participation of these conserved proteins in the regulation of Eg-FoxO. Therefore, through pharmacological activation of the AMPK-FoxO signaling pathway, Met could play a role in the death of the parasite contributing to the demonstrated anti-echinococcal effects of this drug. The understanding of the regulatory mechanisms of this pathway in E. granulosus represents a solid basis for choosing appropriate targets for new chemotherapeutic agents.