Insights into the effects of inducible and neuronal nitric oxide synthase isoenzymes in experimental intestinal heterophyiasis

Abstract

Background: Heterophyiasis is one of the food-borne trematode infections, caused by the intestinal flukeHeterophyes heterophyes. The exact role of nitric oxide (NO) in the immune response against the majorityof parasites remains controversial. It proved protective against a wide range of protozoan and helminthicparasites. Nevertheless, its role in intestinal heterophyiasis is yet to be explored.Objectives: The study aims to explore the possible roles of inducible nitric oxide synthase (iNOS) andneuronal nitric oxide synthase (nNOS) in experimental intestinal heterophyiasis.Material and Methods: The experimental study design included infection of male puppies with H.heterophyes encysted metacercariae (EMC), followed by treatment with aminoguanidine (AG) and7-nitroindazole (7-NI) drugs, as selective inhibitors of iNOS and nNOS, respectively. Controls includednon-infected and infected untreated puppies. Intestinal tissue sections from all puppies were stained forhistopathological and immunohistochemical (IHC) assessments.Results: Different intensities of iNOS and nNOS isoenzymes were observed in intestinal sections. The studyshowed the highest concentration of iNOS isoenzyme in the infected-7-NI treated group. The control noninfectedpuppies exhibited the highest levels of nNOS expression, with statistical significance (P<0.05).The study also showed that AG significantly reduced the degree of inflammatory cellular infiltrations.Additionally, the over-production of NO worsened the degree of intestinal apoptotic changes.Conclusion: Results obtained in the study suggested that inhibition of iNOS, to some extent, improvedintestinal architecture, while inhibition of nNOS failed to eliminate experimental intestinal heterophyiasis.