Abstract:

Objective To explore the apoptosis induced by dexamethasone and adenosine triphosphate （ATP） in protoscolex of Echinococcus granulosus. Methods Protoscoleces were cultured in vitro and used for the experiment in 4 groups： dexamethasone （5 mmol/L） group, ATP （1.6 mmol/L） group, dexamethasone （5 mmol/L）＋ATP （1.6 mmol/L） group, and RPMI 1640 medium as control group. The morphology of protoscolex was observed by light microscopy. After drug treatment for 8 h, the group with significant morphological changes in protoscolex was selected to observe the ultra-structure of protoscolex by transmission electron microscopy. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay （TUNEL） was employed to observe the apoptosis. Caspase-3 activity was detected with a kit, and DNA frag-ments were seperated by agarose gel electrophoresis. Results After induced for 8 h, the protoscoleces shrank in dexamethasone group and dexamethasone＋ATP group, the rosellum was invaginated. Compared with the control, the calcareous corpuscles in the protoscolex significantly reduced and blurred in the two groups. The morphological changes in protoscolex of dexamethasone＋ATP group was more obvious than that of dexamethasone group. Electron microscopy showed that dexame-thasone＋ATP-treated protoscoleces possessed typical morphological features of apoptosis, including the cell volume reduction with densified cytoplasm, cell membrane blebbing, and nuclear heterochromatin peripheral aggregation below the nuclear membrane. A few apoptotic cells were found in protoscolex of dexamethasone＋ATP group by TUNEL, while none in the control. Caspase-3 activity significantly increased 12-fold compared to the control. About 150 bp DNA fragment exhibited the typical DNA ladder formation characteristic for apoptosis in dexamethasone＋ATP group. Conclusion Apoptosis in the protoscolex of E. granulosus may be induced by dexamethasone and ATP in vitro.

Key words: Echinococcus granulosus, Protoscolex, Dexamethasone, Adenosine triphosphate, Apoptosis