Dual Keap1-Dependent actions of pubescenoside A against ulcerative colitis: Promoting DDX5 ubiquitination degradation and Nrf2 nuclear translocation to suppress inflammation

Ulcerative colitis (UC) is a chronic inflammatory disorder of the colon, characterized by a complex clinical syndrome. Pubescenoside A (PBA), a phenylpropanoid derived from Ilex pubescens, exhibits significant anti-inflammatory effects; however, the impact and underlying mechanism of PBA on UC remain unclear. Therefore, the aim of this study is to investigate the potential mechanism of PBA against UC using in vivo and in vitro experiments. Pubescenoside A effectively enhances weight loss in UC mice, decreases the disease activity index (DAI). Regarding colonic morphology, PBA ameliorates colorectal stenosis and shortening, reduces intestinal mucosal ulceration, diminishes inflammatory cell infiltration, and tends to normalize glandular arrangement. Furthermore, PBA effectively suppresses pro-inflammatory factors. Mechanism studies have shown that PBA can directly target Kelch-like ECH associated protein 1 (Keap1), subsequently promoting the interaction between Keap1 and DEAD-box RNA helicase 5 (DDX5) to enhance ubiquitination and degradation of DDX5, leading to a down-regulation of C-C motif chemokine ligand 3 (CCL3) expression. Additionally, PBA disrupts the Keap1/Nrf2 complex, facilitating Nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear entry to inhibit the Nuclear factor-κB (NF-κB) pathway. Importantly, in Gpt-lgr5-creERT2 Keap1^flox/flox mice, the anti-UC effect of PBA was attenuated. Our results indicated that PBA mitigated UC by targeting Keap1, thereby promoting the ubiquitination degradation of DDX5 and facilitating the nuclear entry of Nrf2.