Uveitis remains a significant cause of vision loss worldwide, accounting for up to 15% of blindness in developed countries and even higher proportions elsewhere. While corticosteroids and immunosuppressants remain mainstays of treatment, their limitations – particularly in refractory disease – highlight the need for new therapeutic strategies. A recent Genes & Diseases study explores a promising molecular target: the cGAS–STING pathway.
The cyclic GMP–AMP synthase (cGAS)–stimulator of interferon genes (STING) axis is a key component of innate immunity, responsible for detecting cytosolic DNA and triggering inflammatory responses. While this pathway plays a protective role against infection, its dysregulation has been implicated in a range of inflammatory and autoimmune diseases. In the eye, emerging evidence suggests it may contribute to retinal inflammation – but its role in uveitis has remained unclear.
Using a well-established endotoxin-induced uveitis (EIU) mouse model, the China-based researchers investigated how this pathway influences ocular inflammation. EIU, induced via intravitreal lipopolysaccharide (LPS), closely mimics acute human uveitis, including cytokine upregulation, vascular leakage, and immune cell infiltration.
The team found that the cGAS–STING pathway is strongly activated in inflamed retinas. Transcriptomic analysis revealed enrichment of genes linked to cytosolic DNA sensing and interferon signaling, while protein studies confirmed increased expression of cGAS, STING, and downstream mediators such as TBK1 and IRF3. Notably, mitochondrial DNA (mtDNA) was found to accumulate in the cytoplasm following LPS exposure – acting as a trigger for cGAS activation and amplifying inflammation.
To probe causality, the researchers turned to Cgas knockout mice. The results were striking. Compared with wild-type animals, knockout mice exhibited markedly reduced ocular inflammation across multiple parameters. Fundus imaging and fluorescein angiography showed less vitreous haze and vascular leakage, while histological analysis revealed significantly fewer infiltrating inflammatory cells. Leukocyte adhesion to retinal vessels – a hallmark of inflammatory damage – was also substantially reduced.
At the cellular level, the absence of cGAS dampened activation of key immune players. Retinal macrophage recruitment and microglial activation were both suppressed, and there was a relative increase in regulatory T cells, suggesting a shift toward an anti-inflammatory environment.
Taken together, these findings position the cGAS–STING pathway as a central driver of inflammation in this uveitis model. Mechanistically, the study supports a model in which LPS-induced stress leads to mitochondrial dysfunction and mtDNA release, activating cGAS and downstream inflammatory cascades that culminate in retinal damage.
From a clinical perspective, the implications are compelling. Targeting cGAS – or components of its downstream signaling – could offer a novel approach for controlling intraocular inflammation, particularly in patients who do not respond adequately to current therapies. However, translation to the clinic will require further work, including validation in human tissues and clarification of whether STING-dependent mechanisms are solely responsible for the observed effects.
