Differential effects of acute, chronic and combined stress paradigms on small intestinal and colonic permeability in rats.

Adriana Lauffer, Tim Vanuytsel, Fernando Fornari, Ricard Farré.

Resultados parciais da minha tese de doutorado apresentando no congresso mundial de gastroenterologia, o DDW (Digestive Disease Weeck) em Chicago, Estados Unidos, em maio de 2014.

BACKGROUND: Psychological stress increases intestinal permeability (IP), which may be involved in the pathogenesis of functional gastrointestinal disorders, such as irritable bowel syndrome (IBS) and functional dyspepsia. Most animal models use acute or chronic stress paradigms. However, in clinical practice, many patients are often subjected to chronic psychological stress with superimposed acute episodes. The differential effects of acute and chronic stress and the combination of both on intestinal barrier function have not been characterized. AIM: To assess the effect of acute and chronic stress, isolated or combined, on IP. METHODS: Thirty-two Wistar rats were randomized to a sham group (n=8), acute stress (AS, n=8), chronic stress (CS, n=8) or acute plus chronic stress (ACS, n=8). CS and ACS rats were submitted to crowding stress (8 rats per cage, Vicario et al. 2012) for 15 days, while sham and AS rats were housed with 2 rats per cage. After this period, the AS and ACS group were put in a small metabolic cage for 24 hours until sacrifice. Jejunal and distal colonic IP was analyzed using transepithelial electrical resistance (TEER). Moreover, RT-PCR for several tight junction proteins as Occludin (Occl), Claudin 1 and 2 (Cln 1,2) and zonula occludens-1 (ZO-1) was performed. The different groups were compared with a one-way ANOVA followed by a Bonferroni post hoc test. RESULTS: Animals subjected to chronic stress (CS and ACS) gained less weight over time compared to the sham group (at 14 days 27.9± 2.5 g vs. 50.5± 2.4 g, P<0.0001), confirming adequate stress induction. Corticosterone levels were significantly elevated in AS and ACS, but not in CS alone. TEER of jejunal tissues was significantly reduced after acute, chronic and combined stress (table 1) and a significant negative correlation between corticosterone plasma levels and TEER was observed (r=-0.55, P=0.004). Gene-expression of Occl, ZO-1 and Cln1 were up-regulated in the AS rats only and negatively correlated with TEER (r=-0.40, P<0.05; r=-0.49, P

TEER jejunum (Ωxcm2) TEER colon (Ωxcm2) Corticosterone (ng/mL)
Sham 51.6±1.6 45.4±2.1 51.8±16.7
AS 37.4±1.5*** 48.8±0.9 195.1±41.6 *
CS 42.6±2.3** 44.3±1.9 76.9±12.4
ACS 36.6±1.0*** 38.1±2.2* 328.9±35.5 ***
Table 1. Summary of the main results. vs Sham: P<0.05*, P<0.01**, P<0.001***