Paquinimod attenuates retinal injuries by suppressing the S100A9/TLR4 signaling in an experimental model of diabetic retinopathy

Diabetic retinopathy (DR), the most common ocular complication of diabetes mellitus (DM), has exhibited an increase in incidence over the past decade. S100 calcium-binding protein A9 (S100A9) plays a significant role in inflammation and cancer. Toll-like receptor 4 (TLR4), a transmembrane receptor, initiates signaling cascades upon ligand binding. S100A9 activates TLR4, and their involvement in various diseases is well-established. We found elevated S100A9/TLR4 pathway proteins in the vitreous of DR patients. Bioinformatics analysis revealed differential gene expression related to this pathway. These proteins were also detected in diabetic rat retinas and induced structural damage. Paquinimod, an S100A9 inhibitor, decreased pathway protein expression and reduced retinal damage. Our study validates the S100A9/TLR4 pathway in diabetic retinas and suggests its potential as a therapeutic target for DR. Targeting S100A9 could offer a novel approach to prevention and treatment. •S100A9 and TLR4 proteins are highly expressed in diabetic retinopathy.•Activation of the S100A9/TLR4 pathway causes retinal tissue damage in diabetic retinopathy rats.•Paquinimod reduces S100A9/TLR4 pathway protein expression and alleviates retinal damage.