CRISPR-Cas9-producing probiotic bacteria for editing NOX2/gp91^phox and treating inflammatory bowel disease

The primary pathogenic mechanism of inflammatory bowel disease (IBD) involves elevated levels of reactive oxide species (ROS) in the gut, leading to oxidative stress and damage to the intestinal barrier function. We engineered a non-pathogenic bacterial strain, Escherichia coli Nissle 1917 (EcN), for oral CRISPR-Cas9 delivery to edit NOX2 (encoding the gp91^phox subunit of NADPH oxidase 2), thereby alleviating IBD symptoms by reducing ROS. EcN expressing the Cas9/sgRNA ribonucleoprotein (RNP) was encapsulated in a hydrogel (composed of hyaluronic acid, chitosan, and MgCl₂), which protected EcN-RNP from degradation and increased survival from 0.07% to 12%. EcN-RNP hydrogel reduced NOX2 expression by 47% and ROS by 88% in lipopolysaccharide-induced RAW264.7 cells. Moreover, oral delivery of EcN-RNP hydrogel mitigated inflammation in dextran sodium sulfate-induced colitis mouse models. Mechanistically, the hydrogel could activate the NRF2-HO1/GPX4 pathway by inhibiting NOX2 expression, enhancing oxidative defense, and promoting glutathione accumulation. Thus, the EcN-RNP hydrogel offers a promising therapeutic strategy for IBD.