Effects of Sivelestat on DNA damage, oxidative stress and inflammatory response in a chronic colitis model in mice

In this thesis study, the pathogenesis, inflammatory processes, oxidative stress, and DNA damage mechanisms of ulcerative colitis were investigated through an experimental colitis model induced by AOM/DSS. The aim of the study was to investigate the relationship between ulcerative colitis and the development of colorectal cancer, as well as the effects of Sivelestat administration on the aforementioned processes. In the study, a total of 24 BALB/c mice, aged 10±2 weeks, were divided into three groups: control, colitis, and colitis + Sivelestat. In the experimental model, 12 mg/kg AOM was administered intraperitoneally on days zero and four to the colitis and colitis + Sivelestat groups. Then, 5 kDa DSS was added to the drinking water at a concentration of 3% and given ad libitum for 7 days. This process was repeated four times to create a chronic inflammatory model. After the final DSS period, 50 mg/kg Sivelestat was administered intraperitoneally to the Sivelestat group for 5 days. All mice were euthanized by exsanguination at the end of the experiment; histopathological, immunohistochemical, and biochemical analyses were performed. Histopathological analyses revealed that DSS administration caused significant tissue damage, including inflammatory cell infiltration, epithelial hyperplasia, crypt loss, and ulceration. In the colitis group, lesions were more severe in the distal colon, while milder lesions were found in the mid-colon and proximal colon. Following Sivelestat administration, it was determined that the inflammatory response and histopathological damage decreased, although this decrease was not statistically significant. In immunohistochemical evaluations, the expression levels of 4-HNE, NRF-2, PARP1, ELA2, Ly6G, H2AX, γH2AX, 8-OHdG, COX-2, and TNF-α proteins were significantly increased in the colitis group compared to the control group. After Sivelestat treatment, a significant decrease was observed in γH2AX, 4-HNE, ELA2, Ly6G, COX-2, and TNF-α expression levels compared to the colitis group. However, no significant decrease was observed in NRF-2 and 8-OHdG expression levels, while PARP1 expression remained high in both groups, with no significant difference. H2AX expression was higher in the Sivelestat group than in the colitis group. Biochemical analyses also supported the histopathological and immunohistochemical findings. It was determined that Sivelestat administration decreased MDA levels, an indicator of oxidative stress, and increased GSH levels, an indicator of antioxidant capacity. No difference was observed in SOD levels. In conclusion, this study demonstrates that Sivelestat has the potential to suppress inflammation, DNA damage, and oxidative stress markers as a neutrophil elastase inhibitor. The findings suggest that neutrophil elastase inhibitors may be evaluated as potential therapeutic agents in the management of ulcerative colitis and its complications.