Efeito da inibição seletiva das ciclooxigenases 1 e 2 na integridade epitelial cólica em modelo de colite crônica induzida por TNBS em ratos

Abstract

Crohn's disease (CD) is a transmural inflammatory disease of the mucosa that can affect any region of the gastrointestinal tract (GIT). Patients with CD usually present conditions associated with this disease where the use of anti-inflammatory cyclooxygenase inhibitors (COX) is necessary. However, there are contradictions regarding the beneficial use of these drugs in the epithelial integrity of patients with CD. In the attempt to elucidate this divergence, the present study evaluated the effect of COX-1 and 2 on the colonic tissue integrity of rats induced by colitis using 2,4,6-Trinitrobenzene sulphonic acid (TNBS). It was possible to observe the degree of inflammation of the colonic tissue of these animals after 7 (colitis 7th day), 14 (colitis 14th day) and 28 (colitis 28th day) days of induction. Data were expressed as mean ± standard error of the mean and were considered statistically different when p <0.05. The histopathological evaluation showed that the Colitis group 7th day presented the greatest alterations when compared to the Sham group, in contrast to the Colitis group 14th day, which showed fewer changes of microscopic scores than the Colitis group 7th day when compared to the Sham group and the group Colitis 28th day had no morphological changes when compared to the Sham group. In addition to the microscopic score criteria, the macroscopic, wet weight and myeloperoxidase (MPO) scores of these groups were also evaluated, and the Colitis group 7th day was the only group that demonstrated these increased analysis criteria in relation to the Sham group. The colonic mucosa of the animals of the Colitis group 7th presented a lower transient electrical resistance (TEER) at baseline (32.0 ± 1.9 Ω/cm²) when compared to the Sham group (36.4 ± 1.6 Ω/cm²) differently from those observed in the groups Colitis 14th day and Colitis 28th day, which showed no difference for the Sham group. We chose the Colitis group 7th day for demonstrating the most expressive inflammation results to test the effect of COX-1 and COX-2 inhibitors on the colonic mucosa integrity of these animals. After being exposed in an ex-vivo chamber model of Üssing to acetylsalicylic acid (ASA), the colonic mucosa of the animals of the Colitis group 7th day showed a decrease of TEER when compared to those of the Sham group also exposed to ASA (76.85 ± 4.66% and 91.21 ± 2.79%, *p <0.05, respectively). Another difference observed was the increase in the permeability to fluorescein in the Colitis 7th day AAS group, compared to the Sham AAS group (397.6 ± 75.62 and 198.4 ± 49.43, *p <0.05, respectively). When evaluating the action of specific inhibitors of COX-1 (SC-560) and COX-2 (Celecoxib), it was possible to observe that there was a decrease in the TEER of the Colitis group 7th day exposed to SC-560 when compared to the Colitis group 7th day (73.6 ± 3.5% and 94.1 ± 4.16%, *p <0.05, respectively), however, there was no difference in TEER when the 7th day colitis groups exposed to celecoxib and Colitis 7th day (92.81 ± 5.03 and 94.1 ± 4.16%, * p <0.05, respectively). Another data obtained was the decrease in the TEER of the Colitis 7th day SC-560 (73.6 ± 3.5%) when compared to the Sham SC-560 group (90.9 ± 3.02%), in agreement with the results of fluorescein permeability, where the Colitis 7th day SC-560 (294.8 ± 41.97) had a higher fluorescein flux than the Sham SC-560 group (116.8 ± 34.51). Differently from the results observed with the COX-1 inhibitor, the colitis group 7th day Celecoxib did not show a statistical difference in the fall in TEER when compared to the Sham celecoxib group (92.81 ± 5.03 and 93.19 ± 3.12% respectively), in agreement with the fluorescein permeability results, where the Colite group 7th day Celecoxib, when compared to the Sham Celecoxib group, did not present a difference in the passage of fluorescein (228.8 ± 51.71 and 258.3 ± 87.41, respectively). These data together reveal the deleterious effects of COX-1 inhibitors on the integrity of colonic tissue in animals with colitis.