Ileal inducible nitric oxide synthase mRNA expression in response to stress is modified in Sprague-Dawley rats exposed to a previous intestinal inflammation

Abstract

The ability of stress to initiate or reactivate an inflammatory process seems to depend on an individual's susceptibility to stressful stimuli. The aim of this study was to establish whether previous inflammation alters the response to stress in Sprague-Dawley rats, a strain not especially susceptible to stressful stimuli. Stress exposure was performed in rats treated with indomethacin, to induce cyclic intestinal inflammation, during the inactive phase of inflammation. Both control and indomethacin-treated rats submitted to stress showed a decrease in body weight gain and blood leukocyte levels, as well as an increase in fecal pellet output. The increase in intestinal mucosal mast cell count induced by stress was similar in both groups of animals. Moreover, no differences were observed between control and indomethacin-treated rats in the degree of bacterial translocation and myeloperoxidase levels after stress exposure. Despite these similarities, differences between groups were observed in inducible nitric oxide synthase (iNOS) mRNA expression. Although ileal iNOS mRNA expression was inhibited in healthy rats submitted to stress, stress failed to modify this parameter in indomethacin-treated rats. As iNOS is another inflammatory marker, our results may allow the possibility that a previous intestinal inflammation could change the intestinal susceptibility to stress. Whether these differences in ileal iNOS expression can be indicative of a possible change in the predisposition to develop an intestinal inflammatory reaction in response to stress in Sprague-Dawley rats remains to be elucidated.

Keywords::

• Enteric bacteria
• bacterial translocation
• iNOS
• intestinal inflammation
• mast cells
• psychological stress

Acknowledgments

The authors are grateful to A. C. Hudson for the editorial revision of the manuscript, L. Abarca, for the help for the microbiological studies and A. Acosta for the care of the animals. This work was supported by FPU grant AP-2004-5574 from Ministerio de Ciencia e Innovación (financial support to E. Jorge), Grant BFU2007-62794 from Dirección General de Investigación, Ministerio de Ciencia e Innovación. CIBEREHD is funded by the Instituto de Salud Carlos III.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.