Expression Dynamics of HSP Genes in Hydatid Germinal Cells Exposed to Hydrogen Peroxide

Abstract

Cystic echinococcosis, caused by the larval stage of Echinococcus granulosus, is a chronic parasitic disease in which parasite tolerance to oxidative stress may facilitate long-term survival within the host. Heat shock proteins (HSPs) are conserved molecular chaperones that maintain proteostasis under adverse conditions. This study investigated the presence, sequence conservation, and oxidative-stress responsiveness of HSP60, HSP70-5 and HSP90-5 in E. granulosus G1, alongside the cytotoxic effect of H₂O₂ on G1 germinal cells. Target genes and germinal cells were obtained from hydatid cysts collected from naturally infected sheep livers. HSP genes were amplified by conventional PCR, sequenced, and compared with G1 reference sequences. Germinal cells were exposed to H₂O₂, and cytotoxicity and gene expression were assessed using MTT assay and RT-qPCR, respectively. All three HSP genes were detected in 100% of cyst samples and showed 100% nucleotide identity with corresponding G1 references. H₂O₂ induced concentration-dependent cytotoxicity in G1 germinal cells (IC₅₀ = 350 µM). H₂O₂ exposure significantly upregulated all investigated genes; HSP70-5 showed the strongest induction (187.56-fold at 200 µM; 238.92-fold at 350 µM), whereas HSP60 increased to 2.51- and 3.08-fold, and HSP90-5 to 3.21- and 3.92-fold, respectively. These findings indicate that HSP60, HSP70-5 and HSP90-5 are highly conserved in E. granulosus G1 and support their potential utility as diagnostic markers for this strain. Despite lacking major enzymatic antioxidant defenses, G1 germinal cells exhibited substantial oxidative-stress tolerance, underpinned by marked upregulation of HSP genes, particularly HSP70-5. Coordinated HSP-mediated responses may thus represent a key molecular basis for the prolonged persistence of E. granulosus G1 within the intermediate host.