Molecular Mechanism Study of Dietary Fiber Lignin Intervention in Ulcerative Colitis through GPR37

Lignin is dietary fiber from plant cell walls with multiple biological antioxidant and anti-inflammatory activities. However, whether lignin protects from ulcerative colitis (UC) and underlying mechanisms is unclear. Herein, UC mouse modeling was established with dextran sulfate sodium (DSS) and treatment with lignin for 1 week. Results showed that lignin inhibited the disease activity index (DAI), histological damage, and cell death in UC mice. We also found that lignin reversed the alterations of ferroptotic features in DSS-induced mice and ferroptotic cells, as evidenced by increased expression of GPX4 and 4-HNE and decreased transferrin expression, ameliorating the phenomenon of iron overload, GSH depletion, and ROS and MDA production. Furthermore, the increased expression of NRF2 was observed in IECs under lignin treatment. Also, the upstream regulatory molecule ERK of NRF2 was activated. Further research revealed that lignin can bind GPR37. Meanwhile, lignin was able to alleviate colitis by improving the composition of the intestinal flora in DSS mice and its effect was similar to that of 5-ASA. Taken together, these findings suggest that lignin protects against ferroptosis in UC by combining GPR37 and activating the ERK-NRF2-GPX4 signaling axis, which provides new ideas for clinical intervention in the treatment of UC.