vasoactive-intestinal-peptide and Trichinellosis

We investigated the effects of an enteric infection with the parasitic nematode, Trichinella spiralis, on peptidergic and cholinergic neural pathways of the guinea pig jejunum. The content of the enteric neuropeptides, substance P (SP) and vasoactive intestinal peptide (VIP), and the activities of the key cholinergic enzymes, acetylcholinesterase (AChE) and choline acetyltransferase (ChAT), were measured and compared in extracts of jejunal muscularis externa (ME) obtained from uninfected jejunum and T. spiralis-inflamed jejunum. Significant decreases were detected in both SP immunoreactivity and AChE activity on days 6 and 10 postinfection (PI) in nematode-infected guinea pig jejunum compared to uninfected controls. The maximum changes observed for SP and AChE both occurred on day 10 PI and were evident as decreases of 37% and 48%, respectively, from the mean uninfected control values for SP and AChE. In contrast, VIP immunoreactivity and ChAT activity showed no significant changes during the enteric phase of T. spiralis infection. Nematode-evoked histopathological changes in jejunal tissues from infected animals were associated with significant increases in myeloperoxidase (MPO) activity, an index of inflammation intensity, which occurred on day 6 PI (885% of mean control) and day 10 PI (469% of mean control) coinciding temporally with the significant decrease in SP content and AChE activity during infection. Thus, intestinal motor disturbances observed in mammalian hosts during enteric nematode infections involve inflammation-generated changes in the neurohumoral control of smooth muscle function.

Topics: Acetylcholinesterase; Animals; Choline O-Acetyltransferase; Enteritis; Guinea Pigs; Intestinal Diseases, Parasitic; Jejunal Diseases; Jejunum; Male; Neuropeptides; Peroxidase; Substance P; Trichinella spiralis; Trichinellosis; Vasoactive Intestinal Peptide

Our aim was to characterize and quantitate changes in two key neuropeptides, substance P (SP) and vasoactive intestinal peptide (VIP), that are involved in governing neurally-mediated gastrointestinal (GI) reflex activity during enteric inflammation in the ferret. Neuropeptide content was determined by radioimmunoassay of extracts of jejunal, ileal and colonic muscularis externa from uninfected ferrets and ferrets infected with enteric stages of the parasitic nematode, Trichinella spiralis. Increased myeloperoxidase activity (MPO), an enzymatic marker of inflammation, occurred in all three gut regions. Histopathological changes were present only in the small intestine. Significant reductions were detected in both SP (72% decrease) and VIP (62% decrease) in the inflamed jejunum. Ileal concentrations of both SP (77% decrease) and VIP (46% decrease) were also decreased during T. spiralis infection compared to uninfected ferrets. Only SP (58% decrease) concentration showed a significant change in colonic tissues from infected ferrets; colonic VIP was unaltered. Parasite-induced inflammation caused significant changes in peptide-containing enteric neural pathways and might contribute to functional GI motor disturbances that occur during nematode infections in mammalian hosts.

Topics: Animals; Colon; Ferrets; Ileum; Inflammation; Intestinal Mucosa; Jejunum; Male; Peroxidase; Radioimmunoassay; Substance P; Trichinella spiralis; Trichinellosis; Vasoactive Intestinal Peptide