Carbonyl reductase and nitrofenil esterase activity in Fasciola hepatica recovered from triclabendazole treated sheep

HUGO SOLANA G; PEDRO ORTIZ O; PAULA ALZOLA B. . ; SILVANA SCARCELLA O.

Congreso; XXII Congreso Panamericano de Ciencias Veterinarias; 2010

Fasciolasis is a zoonotic parasitic disease caused by Fasciola hepatica.  Its control is mainly based on the use of triclabendazole (TCBZ), a halogenated benzimidazole thiol derivative which shows excellent efficacy against both juvenile (immature) and adult stages. TCBZ is metabolised into its anthelmintically active sulphoxide metabolite (TCBZSO) by the host liver but also by the parasite’s subcellular fractions. It has also been reported that F. hepatica had significantly higher sulphoxidative activity compared to nematode and cestode parasites. Parasite resistance to different anthelmintics is growing worldwide, including the resistance of F. hepatica to TCBZ. The helminth parasites possess different biochemical mechanisms for detoxification. Overall, parasites may evade drug antiparasitic effects by: i) mutation of target receptors, ii) overexpression of efflux transport pumps and/or iii) overexpression of metabolic enzymatic systems. Hence, the knowledge of detoxification mechanisms in F. hepatica is needed. This preliminary work was aimed to assess the enzymatic activity of Carbonyl Reductase and Nitrofenil Esterase in susceptible adult F. hepatica specimens recovered from TCBZ treated sheep. Four untreated sheep were inoculated with 200 metacercaries of F. hepatica susceptible to TCBZ. The infection was confirmed 16 weeks later by the presence of eggs in faeces and indirect estimation of liver damage after determination of high levels of serum glutamate dehydrogenase and gamma glutamyl transferase activities. The animals were treated with TCBZ (10 mg/kg.) and sacrificed at 3, 24, 48 and 60 h post-treatment. Adult fluke specimens were collected from bile ducts. Parasites were homogenised and the cytosolic fraction was obtained following by recovery the supernatant of the ultracentrifugation at 100.000g/1h.  The highest activities for both enzymes, Carbonyl Reductase and Nitrofenil Esterase, were observed at 24 and 48 h post-TCBZ administration. This values resulted higher compared to that measured in the cytosolic fraction obtained at 3 and 60 h and from control flukes which were not exposed to the drug. The activity for both enzymes returned to levels similar to those measured in non-exposed flukes, 60 h after TCBZ treatment. TCBZ action may induce secondary oxidative stress in F. hepatica, which may explain the observed increment in activities of both enzymes as a defensive mechanism. In fact, the highest activity was observed at the time (24 h) when the peak TCBZSO concentration was measured within the flukes recovered from treated sheep. These preliminary results may be useful to further understand the mechanisms underlying the drug metabolism/disposition and activity in target helminth parasites.