Background: Heterophyiasis is one of the food-borne trematode infections, caused by the intestinal fluke
Heterophyes heterophyes. The exact role of nitric oxide (NO) in the immune response against the majority
of parasites remains controversial. It proved protective against a wide range of protozoan and helminthic
parasites. 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) and
neuronal 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) and
7-nitroindazole (7-NI) drugs, as selective inhibitors of iNOS and nNOS, respectively. Controls included
non-infected and infected untreated puppies. Intestinal tissue sections from all puppies were stained for
histopathological and immunohistochemical (IHC) assessments.
Results: Different intensities of iNOS and nNOS isoenzymes were observed in intestinal sections. The study
showed the highest concentration of iNOS isoenzyme in the infected-7-NI treated group. The control noninfected
puppies 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, improved
intestinal architecture, while inhibition of nNOS failed to eliminate experimental intestinal heterophyiasis.