Roles of calpain in the apoptosis of Eimeria tenella host cells at the middle and late developmental stages

This study investigated the role of calpain in Eimeria tenella –induced host cell apoptosis. Chick embryo cecal epithelial cell culture technology, flow cytometry, enzyme-linked immunosorbent assays, and fluorescence quantitative PCR were used to detect the E. tenella host cell apoptotic rate, Bax and Bid expression levels, and calpain activity. The results demonstrated that Bax, Bid, and calpain levels were upregulated and apoptosis was increased following E. tenella infection at 24–120 h. Calpain levels were reduced by pharmacological inhibition of calpain using SJA6017 or by blocking Ca 2+ entry into the cell using BAPTA/AM at 24–120 h. The mRNA and protein levels of Bax and Bid, the E. tenella infection rate, and the early apoptotic and late apoptotic (necrosis) rates were decreased by using SJA6017 at 24–120 h. These results indicated that E. tenella –promoted host cell apoptosis is regulated by calpain via Bid and Bax at 24–120 h. Thus, manipulation of calpain levels could be used to manage E. tenella infection in chickens in the middle and late developmental stages.