Quantitative phosphoproteomic analysis of chicken DF-1 cells infected with Eimeria tenella, using tandem mass tag (TMT) and parallel reaction monitoring (PRM) mass spectrometry.

Eimeria tenella is an obligate intracellular parasite which causes great harm to the poultry breeding industry. Protein phosphorylation plays a vital role in host cell-E. tenella interactions. However, no comprehensive phosphoproteomic analyses of host cells at various phases of E. tenella infection have been published. In this study, quantitative phosphoproteomic analysis of chicken embryo DF-1 fibroblasts that were uninfected (UI) or infected with E. tenella for 6 h (PI6, the early invasion phase) or 36 h (PI36, the trophozoite development phase) was conducted. A total of 10,122 phosphopeptides matched to 3,398 host cell phosphoproteins were identified and 13,437 phosphorylation sites were identified. Of these, 491, 1,253, and 275 differentially expressed phosphorylated proteins were identified in the PI6/UI, PI36/UI, and PI36/PI6 comparisons, respectively. KEGG pathway enrichment analysis showed that E. tenella modulated host cell processes through phosphorylation, including focal adhesion, regulation of the actin cytoskeleton, and FoxO signaling to support its early invasion phase, and modulating adherens junctions and the ErbB signaling pathway to favor its trophozoite development. These results enrich the data on the interaction between E. tenella and host cells and facilitate a better understanding of the molecular mechanisms underlying host-parasite relationships.

Title: Analyse phosphoprotéomique quantitative de cellules DF-1 de poulet infectées par Eimeria tenella, par spectrométrie de masse avec marqueur de masse en tandem (TMT) et surveillance des réactions parallèles (PRM). Abstract: Eimeria tenella est un parasite intracellulaire obligatoire qui cause de graves dommages à l'industrie de l'élevage de volailles. La phosphorylation des protéines joue un rôle essentiel dans les interactions entre la cellule hôte et E. tenella. Cependant, aucune analyse phosphoprotéomique complète des cellules hôtes à différentes phases de l'infection par E. tenella n'a été publiée. Dans cette étude, une analyse phosphoprotéomique quantitative de fibroblastes DF-1 d'embryon de poulet non infectés (NI) ou infectés par E. tenella pendant 6 h (PI6, la phase d'invasion précoce) ou 36 h (PI36, la phase de développement des trophozoïtes) a été réalisée. Un total de 10 122 phosphopeptides correspondant à 3 398 phosphoprotéines de cellules hôtes ont été identifiés et 13 437 sites de phosphorylation ont été identifiés. Parmi celles-ci, 491, 1 253 et 275 protéines différentiellement phosphorylées exprimées ont été identifiées respectivement dans les comparaisons PI6/NI, PI36/NI et PI36/PI6. L'analyse d'enrichissement de la voie KEGG a montré qu'E. tenella modulait les processus de la cellule hôte par phosphorylation, y compris l'adhésion focale, la régulation du cytosquelette d'actine et la signalisation FoxO, pour aider sa phase d'invasion précoce, et la modulation des jonctions adhérentes et de la voie de signalisation ErbB pour favoriser le développement de son trophozoïte. Ces résultats enrichissent les données sur l'interaction entre E. tenella et les cellules hôtes et facilitent une meilleure compréhension des mécanismes moléculaires sous-jacents aux relations hôtes­parasites.

Drp1/Mff signaling pathway is involved in fluoride-induced abnormal fission of hepatocyte mitochondria in mice.

Fluoride, a toxic substance, is widely distributed in the environment and causes serious damage to the body. This study was performed to investigate the effects of fluoride on mitochondrial fission in mouse hepatocytes. A total of 48 mice were equally divided into four groups and admisnistered with NaF in drinking water at fluorine ion concentrations of 0, 25, 50 and 100 mg/L for 70 days. The pathomorphology and ultrastructurre of hepatocytes were then observed. The mitochondrial lesion parameters (number, length, width and vacuolization area) are evaluated. The expression of Drp1, Mff, Fis1, MiD49, MiD51 and Dyn2, which are associated with mitochondrial fission, was determined by quantitative real-time PCR and Western blot analysis. Apoptosis was detected by using TUNEL assay. Results showed that fluoride causes notable changes in the pathological morphology of liver tissues and severely damages the ultrastructure of hepatocytes. Damage manifested as nuclear condensation, nuclear membrane breakdown, mitochondrial vacuolation, increased fragmentation, and mitochondrial fission. Moreover, mRNA and protein expression levels were significantly upregulated in the Drp1/Mff signaling pathway. The mRNA expression levels of Cyt c, caspase 9 and 3 markedly increased in the fluoride treated groups in a dose-dependent manner. The percentage of TUNEL-positive nuclei in the liver remarkably increased after fluoride treatment. Overall, the results indicate that excessive fluoride exposure can increase mitochondrial fission via the Drp1/Mff signaling pathway, severely damage the mitochondrial structure, and lead to apoptosis of hepatocytes.

Effects of Eimeria tenella infection on the barrier damage and microbiota diversity of chicken cecum.

The symbiosis of host and intestinal microbiota constitutes a microecosystem and plays an important role in maintaining intestinal homeostasis and regulating the host's immune system. Eimeria tenella, an obligate intracellular apicomplexan parasite, can cause coccidiosis, a serious intestinal disease. In this study, the effects of E. tenella infection on development parameters (villus height, crypt depth, mucosa thickness, muscularis thickness, and serosa thickness) and microbiota in chicken cecum were investigated. Fourteen-day-old male Hy-Line Variety Brown layer chickens were inoculated with sporulated oocysts of E. tenella. Cecal tissues were collected 7 d after inoculation. Relative density of goblet cells and glycoproteins were determined by Alcian blue periodic acid-Schiff staining and periodic acid-Schiff staining, respectively. Intestinal development parameters were also evaluated. Cecal contents were extracted, and the composition of cecal microflora was examined by Illumine sequencing in the V3-V4 region of the 16S rRNA gene. Results indicated that E. tenella infection destroyed the structure of cecal tissue and reduced the relative density of goblet cells and glycoproteins. Sequencing analysis indicated that E. tenella infection altered the diversity and composition of cecal microbiota. The populations of Proteobacteria, Enterococcus, Incertae, and Escherichia-Shigella decreased, and those of Bacteroidales and Rikenella significantly increased in the infected group compared with those in the control group. Hence, the pathological damage caused by E. tenella infection is associated with cecal microbiota dysbiosis, and this finding may be used to develop an alternative measure for alleviating the effect of coccidiosis on the poultry industry.

Eukaryotic elongation factor 2 is involved in the anticoccidial action of diclazuril in the second-generation merozoites of Eimeria tenella.

Eimeria tenella, an obligate intracellular parasite, can actively invade the cecal epithelial cells of chickens and cause severe enteric disease. Eukaryotic elongation factor 2 (eEF2) plays a major role in protein synthesis and cell survival. This study aims to explore the exact mechanisms underlying diclazuril inhibition in second-generation merozoites of E. tenella. The eEF2 cDNA of the second-generation merozoites of E. tenella (EtEF2) was cloned by reverse transcriptase polymerase chain reaction and rapid amplification of cDNA ends. Diclazuril-induced expression profiles of EtEF2 were also analyzed. The cloned full-length cDNA (2893 bp) of the EtEF2 nucleotide sequence encompassed a 2499 bp open reading frame (ORF) that encoded a polypeptide of 832 residues with an estimated molecular mass of 93.12 kDa and a theoretical isoelectric point of 5.99. The EtEF2 nucleotide sequence was submitted to the GenBank database with the accession number KF188423. The EtEF2 protein sequence shared 99 % homology with the eEF2 sequence of Toxoplasma gondii (GenBank XP_002367778.1). The GTPase activity domain and ADP-ribosylation domain were conserved signature sequences of the eEF2 gene family. The changes in the transcriptional and translational levels of EtEF2 were detected through quantitative real-time PCR and Western blot analyses. The mRNA expression level of EtEF2 was 2.706 fold increases and the protein level of EtEF2 was increased 67.31 % under diclazuril treatment. In addition, the localization of EtEF2 was investigated through immunofluorescence assay. Experimental results demonstrated that EtEF2 was distributed primarily in the cytoplasm of second-generation merozoites, and its fluorescence intensity was enhanced after diclazuril treatment. These findings indicated that EtEF2 may have an important role in understanding the signaling mechanism underlying the anticoccidial action of diclazuril and could be a promising target for novel drug exploration.

Mitochondrial respiratory chain dysfunction mediated by ROS is a primary point of fluoride-induced damage in Hepa1-6 cells.

To evaluate the mechanism of fluoride (F) mitochondrial toxicity, we cultured Hepa1-6 cells with different F concentrations (0, 1 and 2 mmoL/L) and determined cell pathological morphology, mitochondrial respiratory chain damage and cell cycle change. Results showed that the activities and mRNA expression levels of antioxidant enzymes considerably decreased, whereas the contents of reactive oxygen species (ROS), malondialdehyde (MDA) and nitric oxide (NO) markedly increased. Breakage of mitochondrial cristae and substantial vacuolated mitochondria were observed by transmission electron microscopy. These results indicate the F-induced oxidative damage in Hepa1-6 cells. The enzyme activities of mitochondrial complexes I, II, III and IV were disordered in Hepa1-6 cells treated by excessive F, thereby indicating a remarkable down-regulation. Further research showed that complex subunits also demonstrated the development of disorder, in which the protein expressions levels of NDUFV2 and SDHA were substantially down-regulated, whereas those of CYC1 and COX Ⅳ were markedly up-regulated. Reductions in ATP and mitochondrial membrane potential were detected with the dysfunction of the mitochondrial respiratory chain. The G2/M phase arrest of the cell cycle in Hepa1-6 cells was measured via flow cytometry, and the up-regulated protein expressions of Cyt c, caspase 9, caspase 3 and substantial apoptotic cells were determined. In summary, this study demonstrated that ROS-mediated mitochondrial respiratory chain dysfunction causes F-induced Hepa1-6 cell damage.

Mitochondria-Mediated Pathway Regulates C2C12 Cell Apoptosis Induced by Fluoride.

This study was designed to investigate the mechanisms of excessive fluoride-induced apoptosis via mitochondria-mediated pathway in skeletal muscle cells (C2C12 cells). C2C12 cells were cultured with the fluoride concentrations (0, 1, and 2.5 mmol/L) for 48 h. The morphology and ultrastructural changes of C2C12 cells were observed using a light microscope and transmission electron microscope (TEM). The protein expression levels of apoptosis factors, including Bax, Bcl-2, cytochrome c (Cyt c), caspase-3, and caspase-9, were measured using real-time polymerase chain reaction (real-time PCR) and immunocytofluorescence. The morphology and ultrastructure of C2C12 cells were seriously damaged by fluoride at 1 and 2.5 mmol/L doses, including swollen mitochondria, vacuolization, ridge breakage, and disappearance of the nuclear membrane. Simultaneously, compared with the control group, the expression levels of Bax, Bcl-2, Cyt c, caspase-3, and caspase-9 were up-regulated after fluoride treatment. Excessive fluoride damages the ultrastructure in mitochondria, leading to the release of Cyt c from the mitochondria to cytoplasm in C2C12 cells; thereby, activated caspases cascade apoptosis process through a mitochondria-mediated pathway.

PI3K/AKT signaling pathway involvement in fluoride-induced apoptosis in C2C12 cells.

To investigate the mechanisms of fluoride-induced apoptosis, a fluoride-induced C2C12 skeletal muscle cell (C2C12 cell) model was established in this study, and the viability of the C2C12 cells was measured using an MTT assay. Cell morphological changes were observed via haematoxylin and eosin staining and transmission electron microscopy. Apoptosis was monitored through Hoechst staining. The mRNA and protein expression of PI3K, PDK1, AKT1, BAD, Bcl-2, Bax and caspase-9 were detected through real-time PCR and western blotting, respectively. The results showed that the survival rates of C2C12 cells decreased gradually with an increasing fluoride doses. The C2C12 cell structure was seriously damaged by fluoride, presenting with pyknosis, mitochondrial ridge disruption and swollen endoplasmic reticulum. Furthermore, the expression of mRNA in PI3K, BAD, Bcl-2, Bax and caspase-9 were significantly increased in the fluoride group (P < 0.01), while the expression of PDK1 was markedly decreased (P < 0.01). The expression of protein in BAD, Bcl-2 and Bax were significantly increased in the fluoride group (P < 0.01), while the expression of PDK1 and P-AKT1 was markedly decreased (P < 0.01). In conclusion, fluoride-induced apoptosis in C2C12 cells is related to the PI3K/AKT signaling pathway.