Construction of Engineered EcN Bacteria Constitutively Highly Expressing RtSOD/RtSOD-CAT Fusion Protein and its...

Superoxide dismutase (SOD) is an antioxidant enzyme containing different metal ion, which can reduce oxidative stress and treat ulcerative colitis (UC). In addition, SOD's therapeutic effect can be enhanced when combined with other antioxidant enzymes, such as catalase (CAT). In this study, the probiotic Escherichia coli Nissle 1917 (EcN) was used as a chassis strain to develop two engineered variants, EcNc-RtSOD and EcNc-MLH. By using two cryptic plasmids, these strains were modified to constitutively express RtSOD and RtSOD-CAT (MLH), respectively. Furthermore, the engineered EcN strains were found to significantly reduce DSS-induced intestinal inflammation and promote intestinal mucosal healing in UC mice.Biochemical analyses revealed that the levels of superoxide dismutase (SOD) and catalase (CAT) in intestinal tissues were significantly elevated, while malondialdehyde (MDA) content was markedly reduced. Compared with the DSS group, the expression level of interleukin-6 (IL-6) in colon tissues of mice treated with RtSOD and MLH decreased by 24.04% and 37.68%, respectively. Similarly, the expression level of interleukin-1β (IL-1β) was reduced by 14.22% and 28.73%, respectively, in the RtSOD and MLH treatment groups compared to the DSS group. This study proposes a novel strategy for UC treatment that utilizes therapeutically engineered bacterial strains.