The effects of nitric oxide donors on the sporulation of Eimeria tenella oocysts

Evaluation of optimum conditions for decoquinate nanoliposomes and their anticoccidial efficacy against diclazuril-resistant Eimeria tenella infections in broilers

Decoquinate (DQ) is used for prophylaxis against coccidian infections within the digestive tract of chickens, but DQ is extremely insoluble in water. Hence, improving the water solubility of DQ is extremely important. First, decoquinate nanoliposomes (DQNLs) were prepared by the thin-film dispersion-ultrasonic method. The preparation conditions of DQNLs were optimized using the orthogonal test. The optimal preparation conditions of DQNLs were: a ratio of egg-yolk lecithin:drug (w/w) of 10:1, ratio of egg-yolk lecithin:cholesterol (w/w) of 5:1, rotary-evaporation temperature of 50 ℃, and ultrasound duration of 15 min. The encapsulation efficiency of DQNLs prepared under these conditions reached 99.24 % and drug loading was 5.67 %. The characterization of optimized DQNLs was also done. Transmission electron microscopy of DQNLs showed that they had the characteristic structure of liposomes. The mean particle size was 115.6 nm. The polydispersity index was 0.175. The zeta potential was -39.1 mV. The stability of DQNLs was high upon storage at 4 ℃. In vivo studies demonstrated that the lower dose (5 mg/L) of DQNLs in drinking water obtained the similar anticoccidial efficacy to that of 40 mg/kg DQ in feed against diclazuril-resistance Eimeria tenella isolate. The in vitro inhibitory effect of DQNLs on the sporulation of Eimeria tenella oocysts was dose-dependent. Therefore, the anticoccidial efficacy of DQ was enhanced significantly after being encapsulated into nanoliposomes.

Inhibitory effect of S-nitroso-glutathione on Eimeria tenella oocysts was mainly limited to the early stages of sporogony

The objective of this study was to evaluate the action of S-nitroso-glutathione (GSNO) on the sporogony and the mRNA expression for EtCRK2 (a cyclin-dependent kinase related protein-2 in Eimeria tenella) during oocyst sporulation. Meanwhile, the effects of GSNO on the sporozoite excystability and infectivity to chickens were also investigated. The results showed that within 10 h after the initial sporulation, the sporulation process could be interrupted by GSNO treatment, and most of the oocysts failed to continue to sporulate. However, if the sporulation lasted more than 12 h, the sporogony process could not be blocked by GSNO. RT-PCR assay suggested that in the early stage of sporulation, the mRNA expression of EtCRK2 was completely inhibited by GSNO. For the infective oocysts or sporocysts treated by GSNO, the proportion of sporozoite excystation decreased significantly by about 20% and 40%, respectively. However, clinical coccidiosis could be observed in all experimental broilers inoculated with the oocysts or sporocysts treated by GSNO or not. The animal test showed that GSNO treatment reduced the infectivity of sporocysts, whereas it did not alleviate that of oocysts to broilers. Taken together, the data indicated that the viability of sporulated E. tenella oocysts could not be inactivated in vitro by GSNO. The inhibiting action of GSNO on oocysts was mainly limited to the early stages of sporulation, and this may partially associate with the inhibition of EtCRK2 mRNA expression.

The effects of S-nitroso-glutathione on the activities of some isoenzymes in Eimeria tenella oocysts

A preliminary study showed that the sporogony process of Eimeria tenella oocysts could be irreversibly inhibited by the S-nitrosothiols, such as S-nitroso-glutathione (GSNO), S-nitroso-N-acetyl-penicillamine. However, the mechanism is unclear at present. In this study the polyacrylamide gel electrophoresis (PAGE) and nitroblue tetrazolium (NBT) photoreduction methods were used to analyze the effects of GSNO on the activities of lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase (G6PD), aconitase and superoxide dismutase (SOD). Methods of specific substrate staining were employed to display the enzymes after PAGE. The results showed that the activities of LDH, G6PD, aconitase and SOD in fresh unsporulated and sporulated oocysts could be distinctly detected after treatment by GSNO or without treatment. However, there were no obvious alterations of the tested enzymes' activities in all oocysts treated by GSNO or not. This indicated that the inhibitory effects of GSNO on the sporulation of E. tenella oocysts did not work through inactivating the activities of LDH, G6PD, aconitase and SOD, and the activities of these enzymes in sporulated oocysts were also not inactivated by GSNO.