Stress increases susceptibility to oxidative/nitrosative mucosal damage in an experimental model of colitis in rats

Inflammatory bowel diseases (IBDs) are multifactorial processes. Clinical and animal studies indicate that emotional stress may contribute to the onset and progress of these diseases. On the other hand, enhanced free radical production in mucosal cells has been also implicated in the pathogenesis of IBD. Using an experimental model of colitis induced by intrarectal instillation of 2,4,6-trinitrobenzene sulfonic acid (TNBS) plus ethanol (vehicle), we sought to determine whether prior exposure to immobilization stress modifies the susceptibility to oxidative damage in colonic mucosa. Several groups of Wistar rats were used: control (C) and stressed (by immobilization of 6 hr every day during 10 days; S) groups and rats receiving a colitis-inducing dose of TNBS on day 5 (30 mg; TNBS30) and a noninflammatory dose of TNBS on day 5 (5 mg; TNBS5) with or without stress (prior exposure, days 0-5, and after, days 5-10). At the 10th day, colonic tissue was dissected and processed for biochemical studies. TNBS30 led to body weight loss, macroscopic colonic ulceration, and inflammation (determined by histological parameters and myeloperoxidase [MPO] activity) and to an increase in inducible nitric oxide synthase (NOS-2) activity and expression. TNBS5-instilled animals' body weight and biochemical inflammatory parameters were not significantly different from those in control animals. Interestingly, while stress did not modify body weight, macroscopic aspect of the mucosa, or NOS activity in animals receiving TNBS30, immobilization increased body weight loss, MPO levels, and malondialdehyde (MDA; an indicator of lipid peroxidation) levels after TNBS5. On the other hand, stress increased NOS-2 activity and immunohistochemical expression after instillation of TNBS5. Moreover, constitutive, Ca2+-dependent NOS activity decreased in stressed animals instilled with TNBS5 compared with nonstressed animals receiving TNBS5 (-28.5 +/- 6.6%; P < 0.05). These findings indicate that previous exposure to stressful stimuli is a factor in susceptibility to oxidative damage in experimental colitis and support a possible protective effect of treatment of stress before and during the development of inflammation in the colon.