Mitochondrial pathways are involved in Eimeria tenella-induced apoptosis of chick embryo cecal epithelial cells

Drp1 regulated PINK1-dependent mitophagy protected duck follicular granulosa cells from acute heat stress injury

The mitochondrial quality control system is crucial in maintaining cellular homeostasis during environmental stress. Granulosa cells are the main cells secreting steroid hormones, and mitochondria are the key organelles for steroid hormone synthesis. The impact of the mitochondrial quality control system on granulosa cells' steroid hormone synthesis and survival under heat stress is still unclear. Here, we showed that acute heat stress induces mitochondrial damage and significantly increases the number of mitophagy-like vesicles in the cytoplasm of duck ovary granulosa cells at the ultra-structural level. Meanwhile, we also found heat stress significantly increased mitochondrial fission and mitophagy-related protein expression levels both in vivo and in vitro. Furthermore, by confocal fluorescence analysis, we discovered that LC3 was distributed spot-like manner near the nucleus in the heat treatment group, and the LC3 spots and lysosomes were colocalized with Mito-Tracker in the heat treatment group. We further detected the mitophagy-related protein in the cytoplasm and mitochondria, respectively. Results showed that the PINK1 protein was significantly increased both in cytoplasm and mitochondria, while the LC3-Ⅱ/LC3-Ⅰ ratio increase only occurred in mitochondrial. In addition, the autophagy protein induced by acute heat treatment was effectively inhibited by the mitophagy inhibitor CysA. Finally, we demonstrated that the alteration of cellular mitophagy by siRNA interference with Drp1 and PINK1 inhibited the steroid synthesis of granulosa cells and increased cell apoptosis. Study provides strong evidence that the Drp1 regulated PINK1-dependent mitophagy pathway protects follicular granulosa cells from acute heat stress-induced injury.

The Immunoprotective Effect of ROP27 Protein of Eimeria tenella

Eimeria tenella rhoptry protein has the properties of a protective antigen. EtROP27 is a pathogenic gene that is detected via a transcriptome, but its expression pattern, immunogenicity, and potency are unknown. Therefore, a gene segment of EtROP27 was amplified and transplanted into the pET28a prokaryotic vector for the expression of the recombinant protein, and it subsequently purified for the generation of a polyclonal antibody. Then, RT-PCR and Western blotting were performed to understand the expression pattern of EtROP27. Subsequently, animal experiments were conducted to evaluate the immunoprotective effect of the recombinant protein with different immunizing doses (50, 100, and 150 μg). The results showed that the expression of EtROP27 gradually increased with the prolongation of infection time, reaching the highest level at 96 h and then decreasing. Additionally, EtROP27 is a natural antigen of coccidia that can stimulate the body to produce high levels of IgY. As with recombinant protein vaccines, the results of immune protection evaluation tests showed that the average weight gain rates of the immune challenge groups were significantly higher than that of the challenged control group, and their average lesion scores were significantly lower than that of the challenged control group. Furthermore, the oocyst excretion decreased by 81.25%, 86.21%, and 80.01%, and the anticoccidial index was 159.45, 171.47, and 166.75, respectively, for these groups. EtROP27 is a promising antigen gene candidate for the development of a coccidiosis vaccine.

The role of Ca2+ in the injury of host cells during the schizogenic stage of E. tenella

Cecal epithelial cell damage is a key factor in host injure during the development of E. tenella. The intracellular free Ca²⁺ of the host cell is closely related to the invasion, development and proliferation of intracellular parasites, and cell damage. To determine the relationship between Ca²⁺ and host cell damage in the schizogenic stage of E. tenella, we established a chick embryo cecal epithelial cells model of E. tenella infection. Fluorescence staining, flow cytometry, transmission electron microscopy, inhibition and blocking experiments were used to detect the damage effect and mechanism of host cells during the schizogenic stage of E. tenella. The results showed that the host cells cytoskeletal remodeling, cell and organelle structure was destroyed, and apoptosis and necrosis were increased during the schizont stage of E. tenella. Furthermore, the above-mentioned effects of the schizogenic stage of E. tenella on cells can be alleviated by reducing the intracellular Ca²⁺ concentration in the host cells. These observations indicate that the effect of host cell injury was closely related to Ca²⁺ during schizont stage of E. tenella.

The interaction between free Ca2+ in host cells and invasion of E. tenella

Eimeria tenella is the most pathogenic and common coccidia that causes chicken coccidiosis. The intracellular free Ca²⁺ of the host cell is closely related to the invasion, development, and proliferation of intracellular parasites. To determine the dynamic changes of intracellular free Ca²⁺ and its function in the process of E. tenella invading host cells, we established a chick embryo cecal epithelial cells model of E. tenella infection. Chick embryo cecal epithelial cells were treated with different Ca²⁺ signal inhibitor, respectively, and then infected with E. tenella. The results showed that extracellular Ca²⁺, Ca²⁺ channels on the cell membrane, IP3R ion channels on the endoplasmic reticulum membrane, and RyR ion channels regulated the free Ca²⁺ in cecal epithelial cells. Through fluorescence labeling and invasion rate detection, we found that the intracellular Ca²⁺ did not change significantly during the invasion of E. tenella, but its stability was critical to the invasion of parasites.

Fecal metabolomic analysis of rabbits infected with Eimeria intestinalis and Eimeria magna based on LC-MS/MS technique

Rabbit coccidiosis is a common parasitic disease leading to economic losses in the rabbit industry. The intestinal flora plays a key role in pathogenesis of coccidiosis, and fecal metabolome mediates host-microbiome interactions as a functional readout of the gut microbiome. In this study, the E. intestinalis-infected and E. magna-infected rabbit models were established to investigate metabolic alterations and metabolic pathways based on LC-MS/MS technique for the first time. Multivariate OPLS-DA analysis was performed to explore differential metabolites. In total, 288 metabolites were detected from infected and uninfected rabbits. The level of 33 metabolites increased and 4 decreased in rabbits infected with E. intestinalis. Eight pathways were significantly perturbed during E. intestinalis infection including biosynthesis of unsaturated fatty acids, fatty acid biosynthesis, etc. After rabbits infected with E. magna, 13 metabolites were altered and 7 metabolic pathways were dysregulated. These metabolites and metabolic pathways were mainly involved in tuberculosis, parathyroid hormone synthesis, etc. Besides, 25 metabolites differed in abundance between E. intestinalis infection group and E. magna infection group, the major perturbed metabolic pathways were lipid metabolism and endocrine system, respectively. In general, it is confirmed that E. intestinalis and E. magna infection destroyed the intestinal flora, which caused corresponding changes in metabolites, and provide novel insights into the molecular mechanisms of rabbit-parasite interactions.

Coccidia-Microbiota Interactions and Their Effects on the Host

As a common parasitic disease in animals, coccidiosis substantially affects the health of the host, even in the absence of clinical symptoms and intestinal tract colonization. Gut microbiota is an important part of organisms and is closely related to the parasite and host. Parasitic infections often have adverse effects on the host, and their pathogenic effects are related to the parasite species, parasitic site and host-parasite interactions. Coccidia-microbiota-host interactions represent a complex network in which changes in one link may affect the other two factors. Furthermore, coccidia-microbiota interactions are not well understood and require further research. Here, we discuss the mechanisms by which coccidia interact directly or indirectly with the gut microbiota and the effects on the host. Understanding the mechanisms underlying coccidia-microbiota-host interactions is important to identify new probiotic strategies for the prevention and control of coccidiosis.

Eimeria acervulina Microneme Protein 3 Inhibits Apoptosis of the Chicken Duodenal Epithelial Cell by Targeting the Casitas B-Lineage Lymphoma Protein

Eimeria acervulina (E. acervulina) causes coccidiosis in poultry which persists as economic pain worldwide. Most damage to the intestinal mucosa results from apoptosis of the infected intestinal epithelial cells. The Microneme protein 3 (MIC3) protein is a key virulence factor in some parasites involved in host cell apoptosis inhibition. Here, we studied whether and how MIC3 affects the apoptosis in E. acervulina infected chicken duodenal epithelial cells. Through flow cytometry (FCM), we found that the presence of merozoites and the overexpression of MIC3 significantly decreased apoptosis and the activity of caspase-3 in chicken duodenal epithelial cells at 4, 6, and 8 h post merozoite infection (P < 0.01). Silencing the Casitas B-lineage lymphoma (CBL) protein, a host receptor for MIC3 with shRNA was shown to promote apoptosis in the chicken duodenal epithelial cells. The early apoptotic rate of host cells in the lentiviral-MIC3 group was significantly lower than that in the lentiviral-MIC3 + shRNA CBL group at 4 h after MIC3 expression (P < 0.01), and it was moderately decreased in the lentiviral-MIC3 + shRNA CBL group compared with that in the shRNA CBL group. Our data indicated that MIC3 inhibited early apoptosis of E. acervulina infected chicken duodenal epithelial cells by targeting host receptor-CBL protein. These findings unveiled one of the mechanisms of how intracellular parasites affect the apoptosis of infected host cells, which provided a deeper understanding of their pathogenesis.