The effect of the mitochondrial permeability transition pore on apoptosis in Eimeria tenella host cells.

Although the mitochondrial permeability transition pore (MPTP) is associated with cellular apoptosis and necrosis, its effect in host response to Eimeria infections is not well understood. In an effort to better understand the effect of MPTP on apoptosis in Eimeria tenella host cells, an MPTP inhibitor (cyclosporin A) was used to inhibit MPTP opening in vitro. Cecal epithelial cells from chick embryos, which were either treated or non-treated with cyclosporin A, were used as Eimeria tenella host cells. In addition, primary chick embryo cecum epithelial cell culture techniques and flow cytometry were used to detect the dynamic changes in MPTP opening, mitochondrial transmembrane potential, and cell apoptosis rate of Eimeria tenella host cells. Compared with the control group, cytometric techniques showed that untreated host cells exhibited a significantly higher (P < 0.01) degree of MPTP opening but lower (P < 0.01 or P < 0.05) mitochondrial transmembrane potential. Moreover, untreated group cells had less apoptosis (P < 0.01) at 4 h and more apoptosis (P < 0.05 or P < 0.01) at 24 to 120 h as compared with control group cells. After the application of cyclosporin A, the degree of MPTP opening in the treated group was significantly lower (P < 0.01) at 4 to 120 h compared to the untreated group, whereas the treated group had higher (P < 0.05 or P < 0.01) mitochondrial transmembrane potentials at 24 to 120 h. Flow cytometry assays also showed that there was less (P < 0.05 or P < 0.01) apoptosis after 24 h in the treated group than in the untreated group. Taken together, these observations indicate that MPTP is a key node that plays a predominant role in the mitochondrial apoptosis pathway in the host cell induced by Eimeria tenella.

Calcium homeostasis in mitochondrion-mediated apoptosis of chick embryo cecal epithelial cells induced by Eimeria tenella infection.

In this study, the process of Eimeria tenella-induced apoptosis and the effect of calcium homeostasis were investigated in chick embryo cecal epithelial cells. In particular, we examined cytochrome c release into the cytoplasm, mitochondrial permeability transition pore (MPTP) opening, and changes in [Ca(2+)]c and apoptosis in host cells. Apoptosis, MPTP opening, cytochrome c release, and [Ca(2+)]c in host cells increased following infection. This trend was reversed by blocking the increase in [Ca(2+)]c using BAPTA/AM and EGTA (intra- and extracellular chelators of Ca(2+), respectively) and by applying heparin sodium and ryanodine (blockers of the inositol triphosphate and ryanodine receptors of the endoplasmic reticulum, respectively). These results indicate that [Ca(2+)]c plays a significant role in host cell mitochondrial apoptosis, which is induced via modulation of extracellular Ca(2+) levels and endoplasmic reticulum Ca(2+) channels. Thus, agents that restore Ca(2+) homeostasis may be useful for managing E. tenella infection in chickens.

Relationship between Eimeria tenella development and host cell apoptosis in chickens.

Coccidiosis causes considerable economic losses in the poultry industry. At present, the pathology of coccidiosis is preventable with anticoccidials and vaccination, although at considerable cost to the international poultry industry. The purpose of the present study was to elucidate the relationship between Eimeria tenella development and host cell apoptosis in chickens, which provides a theoretical basis for further study of the injury mechanism of E. tenella and the prevention and treatment of coccidiosis. Cecal epithelial cells from chick embryo were used as host cells in vitro. In addition, flow cytometry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling, and histopathological assays were used to detect the dynamic changes in E. tenella infection rates, DNA injury rates, and apoptosis rates in groups treated with and without the caspase-9 inhibitor Z-LEHD-FMK. Following E. tenella infection, we demonstrated that untreated cells had less apoptosis at 4 h and, inversely, more apoptosis at 24 to 120 h compared with control cells. Furthermore, after the application of Z-LEHD-FMK, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays, and translation of phosphatidyl serines to the host cell plasma membrane surface, the treated group chick embryo cecal epithelial cells exhibited decreased apoptosis and DNA injuries (P<0.01) at 24 to 120 h. However, light microscopy showed that E. tenella infection rates of treated cells were higher (P<0.01) than untreated cells during the whole experimental period. Together, these observations suggest that E. tenella can protect host cells from apoptosis at early stages of development but can promote apoptosis during the middle to late stages. In addition, the inhibition of host cell apoptosis can be beneficial to the intracellular growth and development of E. tenella.