DDIT4 S-Nitrosylation Aids p38-MAPK Signaling Complex Assembly to Promote Hepatic Reactive Oxygen Species Production

Area of Science:

• Hepatology
• Molecular Biology
• Cell Signaling

Background:

• Mitogen-activated protein kinase (MAPK) signaling is crucial for reactive oxygen species (ROS) production.
• Brahma-related gene 1 (BRG1), a chromatin remodeler, contributes to hepatic ROS accumulation in liver injury models.

Purpose of the Study:

• To investigate the role of BRG1 in regulating hepatic ROS production.
• To identify downstream targets of BRG1 involved in ROS generation.
• To explore therapeutic strategies targeting the BRG1-DDIT4 pathway.

Main Methods:

• Identification of DDIT4 as a direct transcriptional target of BRG1.
• In vitro and in vivo experiments assessing ROS production upon manipulation of BRG1 and DDIT4.
• Mechanistic studies on DDIT4's role in p38-MAPK signaling and S-nitrosylation.
• Molecular docking and confirmation of drug effects on DDIT4 and liver injury.
• Analysis of human liver biopsy specimens.

Main Results:

• DDIT4 overexpression restored ROS production in BRG1-deficient cells, while DDIT4 knockdown suppressed ROS.
• DDIT4 facilitates p38-MAPK complex assembly, driving ROS production via S-nitrosylation.
• Identified compounds (imatinib, nilotinib, nateglinide) attenuated ROS, p38-MAPK signaling, and liver injury by modulating DDIT4 S-nitrosylation.
• Positive correlation observed between ROS levels and BRG1/DDIT4/S-nitrosylated DDIT4 in human liver biopsies.

Conclusions:

• A novel transcription-based signaling cascade involving BRG1 and DDIT4 contributes to ROS production in liver injury.
• DDIT4 acts as a key mediator linking BRG1 to p38-MAPK signaling and ROS generation.
• Targeting DDIT4 S-nitrosylation presents a potential therapeutic avenue for liver diseases characterized by oxidative stress.