Aug 2026· Journal of cell communication and signaling· Vol 20· 0 citations· 33 references
Medicine
TL;DR
The FOXO6–SMURF2–NR4A1–NR4A1 axis critically regulates ferroptosis in RPE cells during DR, and this interaction critically regulates ferroptosis in RPE cells during DR.
Abstract
Abstract Diabetic retinopathy (DR) is the main cause of vision loss, with retinal pigment epithelial (RPE) cell dysfunction as a key contributor. Ferroptosis is implicated in RPE injury under hyperglycemia; however, its upstream regulatory mechanisms remain unclear. High glucose (HG)‐induced human RPE ARPE‐19 cells and a diabetic mouse model were used. Ferroptosis was assessed through biochemical assays, Western blot, fluorescence probes, and histological staining. Protein interactions and transcriptional regulation were examined using Co‐IP, glutathione S‐transferase pull‐down, ChIP, and luciferase reporter assays. Immunofluorescence staining was used as key indicator expression in retinal tissues. Nuclear receptor 4A1 (NR4A1) expression was upregulated under HG‐induced ARPE‐19 cells. NR4A1 knockdown alleviated HG‐induced iron accumulation, lipid peroxidation, and ferroptosis marker changes. Mechanistically, SMAD‐specific E3 ubiquitin protein ligase 2 (SMURF2) interacted with NR4A1 and promoted its ubiquitination and degradation. Forkhead box O6 (FOXO6) was upregulated by HG and repressed SMURF2 transcription. SMURF2 overexpression mitigated HG‐induced ARPE‐19 ferroptosis and retinal injury in DR mice, an effect reversed by NR4A1 co‐overexpression. SMURF2 knockdown reversed the effect of FOXO6 knockdown on HG‐induced ferroptosis in ARPE‐19 cells and retinal injury in DR mice. The FOXO6–SMURF2–NR4A1 axis critically regulates ferroptosis in RPE cells during DR.
A posttranscriptional regulation of FTH1 by RSL1D1 is unveiled and the implication of RSL1D1/FTH1 in cellular senescence and ferroptosis in diabetic retinopathy in DR is uncovered.
Leilei Qin, Yanli Guo, Yi Zhang et al.· Biochimica et biophysica act...· 0 citations
The cKIAA1462/miR-183-5p/HMGB1 axis plays a critical role in diabetic RPE injury by dual regulation of autophagy and pyroptosis by targeting this pathway may offer a novel therapeutic strategy for early diabetic retinopathy.
Lufei Wang, Jia’nan Xie, Longfei Yang et al.· Journal of Translational Med...· 0 citations
Diabetic retinopathy (DR) is characterized by progressive retinal microvascular injury, with oxidative stress and ferroptosis increasingly recognized as key pathogenic contributors. This study investigated whether ubiquitin C-terminal hydrolase L1 (UCHL1) regulates retinal endothelial ferroptosis through stabilization of nuclear factor erythroid 2-related factor 2 (NRF2). Analysis of the GSE102485 dataset identified UCHL1 as a downregulated deubiquitinating enzyme in DR. Streptozotocin-induced type 1 diabetic mice and high glucose (HG)-induced human retinal capillary endothelial cells (HRCECs) were used, together with UCHL1 inhibition/knockdown, AAV-mediated UCHL1 overexpression, and NRF2 knockdown. UCHL1 expression was reduced in diabetic retinas and HG-induced HRCECs, accompanied by ferroptosis activation, mitochondrial injury, and endothelial dysfunction. Pharmacological inhibition or siRNA-mediated depletion of UCHL1 intensified oxidative stress, Fe2⁺ accumulation, lipid peroxidation, mitochondrial fragmentation, and cristae disruption, while impairing endothelial barrier integrity, migration, and tube formation. In vivo, LDN57444 aggravated retinal vascular leakage and fundus vascular abnormalities, whereas AAV-UCHL1 preserved retinal architecture and reduced vascular permeability. Mechanistically, co-immunoprecipitation and ubiquitination assays demonstrated that UCHL1 interacted with NRF2 and stabilized NRF2 by removing K48-linked polyubiquitin chains. Nuclear-cytoplasmic fractionation further showed that UCHL1 overexpression restored NRF2 abundance and increased nuclear NRF2 accumulation under HG conditions. Ferrostatin-1 rescued UCHL1 depletion-induced ferroptotic injury, whereas NRF2 knockdown abolished the protection conferred by UCHL1 overexpression. These findings highlight the UCHL1/NRF2 axis may represent a therapeutic target in DR.
Sanhua Xu, Jun Huang, Yi-Cang Wang et al.· Biochemical Pharmacology· 0 citations
Tumor necrosis factor receptor-associated factor 4 (TRAF4) is a RING-type E3 ubiquitin ligase linked to vascular inflammation, but whether it drives endothelial ferroptosis in atherosclerosis (AS) remains unclear. TRAF4 expression was assessed in GEO dataset GSE166780, ApoE-/- mice fed a high-fat diet for 4 months, and oxidized low-density lipoprotein (ox-LDL)-treated human coronary artery endothelial cells (HCAECs; 50 μg/mL, 24 h). In vivo, mice received tail-vein delivery of shTRAF4 vector. Plaque burden, endothelial injury, inflammatory responses, and ferroptosis were evaluated by histology, qRT-PCR, western blotting, immunofluorescence, reactive oxygen species (ROS) staining, and biochemical assays. TRAF4-PRMT5 and PRMT5-GPX4 interactions were examined by co-immunoprecipitation and GST pull-down. PRMT5 ubiquitination and protein stability were analyzed using MG132 and cycloheximide assays, and rescue experiments were performed by co-silencing TRAF4 and PRMT5. Our results showed that TRAF4 was upregulated in atherosclerotic tissues, the public dataset, and ox-LDL-treated HCAECs. TRAF4 knockdown reduced plaque burden, VCAM-1 expression, serum lipids and inflammatory cytokines, and attenuated ROS accumulation, ferrous iron (Fe2+) overload, lipid peroxidation, and Glutathione peroxidase 4 (GPX4) loss in vivo. In HCAECs, TRAF4 silencing improved viability, nitric oxide production, and mitochondrial function while reducing apoptosis, monocyte adhesion, inflammatory cytokine release, and ferroptosis. Mechanistically, TRAF4 directly bound PRMT5 and promoted its K48-linked ubiquitin-dependent degradation. CD31/TRAF4 co-staining confirmed endothelial TRAF4 enrichment in atherosclerotic tissue. PRMT5 bound GPX4, enhanced GPX4 methylation, and stabilized GPX4 protein. PRMT5 knockdown partially reversed the anti-ferroptotic effects of TRAF4 deficiency. Overall, TRAF4 promotes endothelial ferroptosis and AS progression by driving PRMT5 ubiquitination and destabilizing GPX4. The TRAF4-PRMT5-GPX4 axis may represent a therapeutic target in AS.
Abstract Background NOP2/Sun RNA methyltransferase family member 4 (NSUN4)‐mediated 5‐methylcytosine (m5C) modification has been implicated in diabetes‐related diseases. However, its role and molecular mechanism in diabetic nephropathy (DN) remain unclear. Methods DN mouse model was constructed by injecting with streptozotocin (STZ). High glucose (HG)‐induced HK‐2 cells were used to establish a cellular model of DN. The levels of NSUN4, SMAD ubiquitination regulatory factor 1 (SMURF1), calcium/calmodulin‐dependent protein kinase 1 (CAMK1), and mitochondrial‐related proteins were analyzed using qRT‐PCR, western blot, or immunohistochemical staining. Renal injury in mice was evaluated using relevant kits and histological staining. Cell apoptosis, ROS production and proliferation were examined by TUNEL, dihydroethidium, MitoSOX Red and EdU staining. The interaction between SMURF1 and Aly/REF export factor (ALYREF) or CAMK1 was confirmed by RNA immunoprecipitation, Co‐IP and ubiquitination assay. Results Upregulation of NSUN4 increased the m5C level in DN. Knockout of NSUN4 alleviated STZ‐induced renal injury in mice by repressing renal tubule cell mitochondrial fission and promoting mitochondrial fusion. NSUN4 downregulation reduced mitochondrial fission and promoted mitochondrial fusion to relieve HG‐induced HK‐2 cell apoptosis. NSUN4‐mediated m5C modification promoted SMURF1 mRNA stability by regulating ALYREF. SMURF1 overexpression rescued the suppressive effect of NSUN4 knockdown on cell mitochondrial fission and apoptosis. Besides, SMURF1 facilitated the ubiquitination and degradation of CAMK1. Furthermore, sh‐CAMK1 abolished the inhibitory effect of sh‐SMURF1 on cell mitochondrial fission and apoptosis. Meanwhile, downregulation of NSUN4 relieved STZ‐induced renal injury in DN mice by reducing mitochondrial fission via the SMURF1/CAMK1 axis. Conclusion NSUN4‐mediated upregulation of SMURF1 promoted mitochondrial fission to accelerate DN progression via increasing CAMK1 ubiquitination. The discovery of the NSUN4/SMURF1/CAMK1 axis provides new insights into DN pathogenesis.
Danyi Yang, Yin-Yin Chen, Hao Li et al.· Clinical and Translational M...· 0 citations
Inhibition of FZD7 restores endogenous anti-ferroptotic mechanisms and confers retinal protection, establishing FZD7 as a previously unrecognized therapeutic target for diabetic retinopathy.
Jiaojiao Jiang, Liu Zheng, Lu Wang et al.· Journal of Pharmacological S...· 0 citations
