Targeting NOTCH1-KEAP1 axis retards chronic liver injury and liver cancer progression via regulating stabilization of NRF2.

[BACKGROUND] Chronic liver injury is a key factor in diseases like hepatocellular carcinoma (HCC), steatohepatitis (NASH), and viral hepatitis type B and C (HBV, HCV). Understanding its molecular mechanisms is crucial for effective treatment. The NOTCH1 signaling pathway, though not fully understood, is implicated in liver injury and may be a potential therapeutic target.

[METHODS] Clinical HCC, HBV, HCV and NASH samples and additional in vitro and in vivo performances were subjected to confirm the role of NOTCH1 and its downstream targets via a series of biochemical assays, molecular analysis approaches and targeted signaling pathway assay, etc. RESULTS: The present study first verified the abnormal elevation of NOTCH1 in hepatocytes from patients with steatohepatitis, HCC, HBV, HCV, and mouse models. Crucially, we discovered that hepatocyte-specific NOTCH1 knockout reduces hepatocellular damage in chronic liver inflammation and HCC mouse models, whereas adeno-associated virus serotype 8 (AAV8)-mediated NOTCH1 overexpression in hepatocytes exacerbates liver injury-related phenotype on-setting. Mechanistically, we showed that NOTCH1 has a new role in controlling ferroptosis and oxidative damage in hepatocytes. It interacts with Kelch-like ECH-associated protein 1 (KEAP1) and is directly recruited through its intracellular domain (NICD1). Additionally, the KEAP1 recruited by NOTCH1 impeded the binding stability of KEAP1-NFE2 like BZIP transcription factor 2 (Nrf2), promote the separation of KEAP1 and Nrf2, thereby reducing the stability of Nrf2 and hindering the ubiquitination-related proteasome degradation of Nrf2. Crucially, we also discovered that NOTCH1's ANK domain is essential for NICD1-KEAP1 contacts and signaling activation. The inability of NOTCH1 with ANK domain mutants (ΔANK) to connect with KEAP1 and increase its expression emphasizes the importance of the ANK domain in KEAP1-NRF2 signaling. By reversing the downregulation of KEAP1 and the overexpression of NRF2, ANK function is linked to ferroptosis and ROS buildup. ANK domain targeting may slow the course of HCC and liver damage.

[CONCLUSIONS] Targeting the NOTCH1-KEAP1-NRF2 axis as a possible chronic hepatic injury therapy is supported by these findings, which identify NOTCH1-KEAP1 as an NRF2 suppressor that accelerates the progression of liver injury.