Involvement of intestinal inducible nitric oxide synthase (iNOS) in the early stages of murine salmonellosis

Local induction of inducible nitric oxide synthase (iNOS) and apoptosis was examined in the intestine of mice infected with virulent Salmonella enterica serovar Enteritidis 5694 (S. enteritidis) and its attenuated derivative mutant E/1/3. Both, intestinal iNOS mRNA expression and iNOS activity showed a peak at 4 h only in animals receiving the virulent S. enteritidis. Aminoguanidine treatment abrogated intestinal epithelial damage produced by virulent S. enteritidis and diminished apoptosis at the tips of the villi. Unlike the virulent strain, mutant E/1/3 induced massive iNOS expression in Peyer's patches, these findings may be related to its protective capacity. Our results suggest that intestinal iNOS participates in the early response to intestinal infection and that the final effect depends on the nature of the insult.