ELAVL1-stabilized USP22 promotes diabetic nephropathy progression via mediating podocyte injury and death by triggering ACSL4 deubiquitination

Background

Diabetic nephropathy (DN) represents approximately 50 % of all chronic kidney disease cases. Given the established involvement of USP22 in DN progression, this study investigated its underlying regulatory mechanisms.

Methods

Mouse podocytes were treated with high glucose (HG), and a diabetic mouse model was established. Podocyte viability and apoptosis were assessed by CCK-8 and TUNEL/flow cytometry, respectively. Ferroptosis markers (Fe²⁺, ROS, MDA, and GSH) and inflammatory cytokines were quantified using ELISA and commercial kits per manufacturers' protocols. The interaction of USP22 with ACSL4 was demonstrated through protein stability and co-immunoprecipitation (Co-IP) assays. Additionally, RNA immunoprecipitation (RIP) and mRNA stability assays were employed to elucidate the ELAVL1/USP22 interaction.

Results

In HG-treated podocytes, USP22 silencing enhanced cell viability (P = 0.0018), repressed apoptosis (P = 0.0019), and reduced the release of inflammatory cytokines (IL-1β: P = 0.0002; TNF-α: P < 0.0001) and ferroptosis markers (Fe²⁺: P = 0.0002; ROS: P = 0.0005; MDA: P = 0.0017; GSH: P = 0.0086). Conversely, USP22 overexpression in HG-treated podocytes exhibited the opposite effects (P < 0.05). USP22 increased ACSL4 expression (P = 0.0012) in a deubiquitination-dependent manner. Notably, ACSL4 overexpression rescued USP22 depletion-mediated alterations on cell viability, apoptosis, inflammation, and ferroptosis (P < 0.05). Moreover, ELAVL1 stabilized USP22 mRNA through interaction (P = 0.0075). USP22 silencing alleviated DN progression and reduced inflammation cytokine secretion in a diabetic mouse model (P < 0.05).

Conclusion

ELAVL1-stabilized USP22 promotes DN progression by exacerbating podocyte injury and enhancing inflammatory responses and cell death through ACSL4 deubiquitination-dependent mechanisms.