Understanding the main route of drug entry in adult Fasciola hepatica : Further insights into closantel pharmacological activity

CEBALLOS, L.; CANTON, C.; CADENAZZI, G.; LARSEN, K.; VIRKEL, G.; MORENO, L.; FAIRWEATHER, I.; LANUSSE, C.; ALVAREZ, L.

EXPERIMENTAL PARASITOLOGY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Año: 2017

0014-4894

Closantel (CLS) is highly effective against adult liver flukes after its oral or subcutaneous(sc) administration in ruminants. Trans-tegumental diffusion and oral ingestion are the twopotential routes available for the entry of drugs into Fasciola hepatica. The work reportedhere contributes to improve the understanding of CLS pharmacology. The main goals ofwere: I) to determine the pattern of in vivo CLS accumulation into adult F. hepatica andrelevant tissues in CLS-treated sheep; II) to investigate the influence of thephysicochemical composition of the incubation medium on the CLS diffusion process intoadult F. hepatica; III) to assess the ovicidal activity of CLS against F. hepatica eggs; andIV) to investigate the in vivo effect of CLS treatment on glutathione S-transferases activityin adult liver flukes exposed to CLS. Fourteen healthy sheep were each orally infected with75 F. hepatica metacercariae. Sixteen (16) weeks after infection, animals were treatedwith CLS by oral (n= 6, 10 mg/kg) or sub-cutaneous (sc) (n= 6, 5 mg/kg) route. At 12, 24and 36 h post-treatment, animals were sacrificed (n= 2) and samples of blood, bile andadult F. hepatica were collected. In addition, flukes recovered from non-treated sheep (n=2) were ex vivo incubated (60 min) in the presence of CLS in either RPMI or bile asincubation medium. CLS concentration was measured by HPLC. The ovicidal activity ofCLS was investigated using eggs obtained from the bile of untreated sheep. Finally,glutathione S-transferase activity in F. hepatica recovered from untreated and CLS-treatedsheep was assessed. In the in vivo studies, the highest CLS concentrations weremeasured in plasma and adult liver flukes. A positive correlation was observed betweenCLS concentration in plasma and in F. hepatica. Results obtained in the current workindicate that the in vivo accumulation of CLS into adult liver flukes occurs mainly by the oral route. After ex vivo incubation, the uptake of CLS by the parasite was markedlydiminished in the presence of bile compared with that observed in the presence of RPMIas incubation medium. CLS lacks ovicidal activity at therapeutically relevantconcentrations. Lastly, CLS significantly increased glutathione S-transferase activity influkes recovered at 12 h (oral treatment) and 24 h (sc treatment), compared to the controlliver flukes.