Chitosan oligosaccharides alleviate macrophage pyroptosis and protect sepsis mice via activating the Nrf2/GPX4 pathway

In the process of sepsis, excessive occurrence of pyroptosis, a form of programmed cell death acting as a defense mechanism against pathogens, can disrupt immune responses, thus leading to tissue damage and organ dysfunction. Chitosan oligosaccharide (COS), derived from chitosan degradation, has demonstrated diverse beneficial effects. However, its impact on sepsis-induced pyroptosis remains unexplored. In the present study, ATP/LPS was utilized to induce canonical-pyroptosis in THP-1 cells, while bacterial outer membrane vesicles (OMV) were employed to trigger non-canonical pyroptosis in RAW264.7 cells. Our results revealed a dose-dependent effect of COS on both types of pyroptosis. This was evidenced by a reduction in the expression of pro-inflammatory cytokines, as well as crucial regulatory proteins involved in pyroptosis. In addition, COS inhibited the cleavage of caspase-1 and GSDMD, and reduced ASC oligomerization. The underlying mechanism revealed that COS acts an antioxidant, reducing the release of pyroptosis-induced ROS and malondialdehyde (MDA) by upregulation the expression and promoting the nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2), which led to an elevation of glutathione peroxidase 4 (GPX4) and superoxide dismutase (SOD). Notably, the actions of COS were completely reversed by the Nrf2 inhibitor. Consequently, COS intervention increased the survival rate of sepsis.