Microglial IFN-β promotes an ISG15+ Müller glial subtype that compromises antioxidant defense and promotes early barrier injury in diabetic retinopathy.
Key Findings
Results
A spatially clustered ISG15+ Müller glial subtype is expanded in streptozotocin-induced diabetic mice.
The ISG15+ Müller glial subtype was identified using spatial transcriptomics or spatial clustering approaches in a streptozotocin (STZ)-induced diabetic mouse model.
This subtype represents a distinct Müller glial program linked to interferon signaling.
The expansion of this subtype was associated with early diabetic retinopathy pathology.
Results
High glucose alone did not increase free ISG15 or ISGylation in primary Müller glia, but conditioned medium from high glucose-exposed microglia induced both.
Direct high glucose treatment of primary Müller glia was insufficient to increase basal free ISG15 protein or detectable ISGylation (ISG15-dependent protein modification).
Conditioned medium collected from high glucose-exposed microglia successfully induced free ISG15 and ISGylation in Müller glia.
The effect of conditioned medium was recapitulated by exogenous IFN-β treatment.
Type I interferon receptor 1 (IFNAR1) inhibition attenuated both free ISG15 and ISGylation induced by microglial conditioned medium.
Results
Retinal Ifnb1 expression increased in diabetic retinas and was associated with microglia in vivo.
In vivo RNAscope (single-molecule fluorescent in situ hybridization) signals for Ifnb1 were spatially associated with microglia in the retina.
Retinal Ifnb1 expression was elevated in diabetic retinas compared to controls.
Microglial depletion reduced Ifnb1 expression in the retina.
Microglial depletion also limited the expansion of the ISG15+ Müller glial subtype, establishing a microglial-to-Müller glial signaling axis.
Results
Müller glia-specific Isg15 deletion preserved blood-retinal barrier integrity and reduced vascular pathology in diabetic retinopathy.
Loss of ISG15 in Müller glia reduced markers of oxidative stress in the diabetic retina.
Lipid peroxidation, an indicator of oxidative membrane damage, was reduced in Müller glia-specific Isg15 knockout animals.
Glutathione redox imbalance was mitigated, suggesting improved antioxidant defense capacity.
These oxidative stress outcomes were downstream of ISG15 and ISGylation activity in Müller glia.
Results
Loss of ISG15 or disruption of ISGylation blunted interferon-driven oxidative stress in Müller glia and reduced Müller glia-conditioned medium-dependent endothelial migration and tube formation.
Genetic loss of ISG15 or pharmacological disruption of ISGylation attenuated IFN-β-driven oxidative stress responses in Müller glia.
Conditioned medium from ISG15-deficient or ISGylation-disrupted Müller glia showed reduced ability to promote endothelial cell migration.
Tube formation by endothelial cells, a measure of angiogenic or pathological vascular remodeling capacity, was also reduced.
These results indicate ISG15 in Müller glia mediates paracrine signals that affect endothelial behavior.
Results
IFN-β promoted ISGylation and proteasome-dependent degradation of peroxiredoxin 6 (PRDX6) without altering Prdx6 transcripts.
IFN-β treatment induced ISGylation of PRDX6, a peroxidase involved in antioxidant defense and lipid metabolism.
ISGylated PRDX6 underwent proteasome-dependent degradation, reducing PRDX6 protein levels.
Prdx6 mRNA levels were not altered, indicating post-translational rather than transcriptional regulation.
This mechanism—ISGylation targeting PRDX6 for degradation—provides a molecular explanation for how ISG15 activity compromises antioxidant defense in Müller glia.
What This Means
This research investigates why the retina becomes damaged early in diabetes, focusing on a specific type of support cell called Müller glia. The study found that when blood sugar is high, immune cells in the retina called microglia release a signaling protein called IFN-β (interferon-beta). This signal activates a particular subgroup of Müller glia that produce high levels of a molecule called ISG15, which chemically modifies other proteins in a process called ISGylation. Crucially, the high glucose environment alone was not enough to trigger this process in Müller glia—the signal had to come from the activated microglia, revealing an important chain of communication between immune and support cells in the diabetic retina.
The study found that ISG15 activity in Müller glia causes the degradation of a key antioxidant protein called PRDX6 (peroxiredoxin 6). When ISG15 tags PRDX6, the cell's protein disposal system breaks it down, leaving the retina more vulnerable to oxidative damage—a type of cellular injury caused by reactive molecules. When the researchers deleted Isg15 specifically in Müller glia of diabetic mice, the retinal blood vessel barrier stayed more intact, fewer blood vessels became non-functional, and oxidative damage was reduced. The secretions from these ISG15-active Müller glia also promoted abnormal behaviors in blood vessel cells, suggesting these glial cells actively worsen vascular disease.
This research suggests that the chain of events—microglial IFN-β signaling → ISG15+ Müller glia activation → PRDX6 degradation → oxidative stress and blood-retinal barrier breakdown—represents a key early mechanism in diabetic retinopathy. Understanding this pathway could point toward new therapeutic targets, such as blocking IFNAR1 or ISGylation, to prevent early retinal damage in people with diabetes before vision loss occurs.
Niu T, Jiang Y, Xing X, Zhu Q, Liu X, Lv K, et al.. (2026). ISG15+ Müller glial subtype contributes to early blood-retinal barrier breakdown in diabetic retinopathy.. The Journal of clinical investigation. https://doi.org/10.1172/JCI205800