NUPR1 Inhibition Prevents Mitotic Catastrophe: A Novel Therapeutic Strategy for Podocyte Injury in Diabetic Kidney Disease

As terminally differentiated cells, podocytes exhibit a very limited capacity for self-repair and regeneration. Under pathological conditions, abnormal re-entry of podocytes into the mitotic cycle can induce mitotic catastrophe (MC), resulting in podocyte loss and glomerular structural injury, thereby accelerating the progression of diabetic kidney disease (DKD). This study aimed to elucidate the precise role of NUPR1 in podocyte injury under DKD conditions, investigate its molecular mechanisms in modulating mitotic catastrophe, and assess the potential of NUPR1 as a therapeutic target for treating DKD.

Through the analysis of single-cell sequencing data from DKD mouse model, we identified NUPR1 as a potentially key gene. Its expression and distribution in renal tissues of DKD patients were further examined via immunofluorescence. To investigate the role of NUPR1 in renal injury, we established a DKD mouse model with NUPR1 overexpression and assessed its impact on podocyte damage. In vitro, a high glucose-induced podocyte injury model was used to explore the function of NUPR1 through knockdown and overexpression experiments. Transcriptome sequencing was employed to preliminarily identify biological processes associated with NUPR1, followed by validation using Western blot and cell cycle analysis. To elucidate the underlying mechanism, we performed bioinformatic analysis, co-immunoprecipitation (Co-IP), chromatin immunoprecipitation (ChIP), dual-luciferase reporter assays, and ChIP-re-ChIP experiments, which revealed the direct regulatory role of NUPR1 on its downstream target genes. Finally, we administered the NUPR1 small molecule inhibitor ZZW-115 intraperitoneally to DKD model mice and comprehensively evaluated its therapeutic potential both in vivo and in vitro.

Through single-cell RNA sequencing analysis, we identified that NUPR1 is predominantly and specifically expressed in podocytes and is markedly upregulated in renal biopsies from DKD patients. Notably, the protein level of NUPR1 showed a positive correlation with the degree of albuminuria in DKD patients. Overexpression of NUPR1 in DKD mice exacerbated podocyte injury and increased albuminuria. Functional analyses revealed that NUPR1 promotes aberrant podocyte entry into the G2/M phase, thereby triggering MC and aggravating renal injury. Mechanistically, NUPR1 recruits BRD2 to the Cyclin B2 promoter, forming a transcriptional complex that enhances Cyclin B2 expression. Genetic or pharmacological disruption of this NUPR1-BRD2 interaction suppressed Cyclin B2 expression, prevented MC, and preserved podocyte numbers. Therapeutically, pharmacological inhibition of NUPR1 using ZZW-115 significantly alleviated albuminuria, reduced mesangial matrix expansion, and mitigated podocyte injury in DKD mice, without impacting systemic glucose levels. 

This study reveals the critical role of NUPR1 in podocyte injury in DKD. We found that NUPR1 exacerbates renal damage by driving aberrant podocyte entry into the G2/M phase and subsequent mitotic catastrophe. This effect is mediated through a functional NUPR1/BRD2 transcriptional complex that directly upregulates Cyclin B2. Therapeutically, pharmacological inhibition of NUPR1 with ZZW-115 alleviated podocyte injury and delayed DKD, establishing NUPR1 as a potential therapeutic target.