Bortezomib initiates endoplasmic reticulum stress, elicits autophagy and death in Echinococcus granulosus larval stage

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.

BaxΔ2 sensitizes colorectal cancer cells to proteasome inhibitor-induced cell death

“…4C ). Caspase 12 inhibitor also appeared to be effective, consistent with the fact that bortezomib mediates endoplasmic reticulum stress [ 29 , 30 ]. The results from the inhibition of caspase 6 could be explained by the fact that caspase 6 is known to be activated by caspase 3 [ 31 ].…”

“…One possible explanation for the formation of these vacuole is from the process of autophagy, but our results showed that neither LC3B nor BaxΔ2 were colocalized with the vacuoles. The results from many other studies regarding proteasome inhibitor-mediated autophagy have often been controversial and inconsistent [ 29 , 32 – 34 ], therefore the association between proteasome inhibitors and autophagy still remains to be further explored.…”

Interactions between hydatid cyst and regulated cell death may provide new therapeutic opportunities

“…Metacestodes from mice treated with Albendazole and Metformin showed complete tissue disruption with autophagosomes. [22,23,29] TOR is an effective in vitro anti-echinococcosis agent that induces autophagy. Bortezomib in the hydatid cyst can cause ER stress and provoke autophagy in protoscoleces.…”

Progress in the pharmacological treatment of human cystic and alveolar echinococcosis: Compounds and therapeutic targets

“…Genistein ( S1 Fig , compound 38) and derivatives, imatinib ( S1 Fig , compound 39), 5-fluorouracil ( S1 Fig , compound 40), paclitaxel ( S1 Fig , compound 41) and tamoxifen ( S1 Fig , compound 42) are scolicidal in vitro , all them after prolonged (˃ 24 hours) exposure time, and could be pre- and post-treatment candidate drugs to prevent recurrences in CE [ 25 , 173 – 175 ]. All those drugs, together with areneruthenium complexes ( S1 Fig , compound 43) [ 176 ] and bortezomib [ 177 , 178 ], showed also activity against CE or AE cysts in vitro ( Table 3 ), but only two–bortezomib and tamoxifen–were further tested in vivo [ 25 , 177 ]. Tamoxifen showed 100% activity against CE protoscoleces in vitro , although this rate was reduced to 40% (6 out of 10 treated mice developed cysts) when the treatment was given orally to mice at infection.…”