SGLT2i Canagliflozin Exerts Neuroprotection in Diabetic Retinopathy by Inhibiting Microglial Proinflammatory Cytokine Release by Downregulating the TLR4/NF-κB/NLRP3 Pathway.
TL;DR
These findings identify CANA as a promising therapeutic candidate for DR, acting through TLR4/NF-κB/NLRP3-dependent modulation of microglial activation and inhibited the TLR4/NF-κB/NLRP3 pathway.
Abstract
Purpose
Diabetic retinopathy (DR) is the leading cause of preventable blindness among working-age adults. Sodium-glucose cotransporter 2 inhibitors (SGLT2is), first-line treatments for diabetes mellitus (DM), have demonstrated efficacy in decelerating DR progression. However, the mechanisms remain unclear. This study investigates how canagliflozin (CANA), an SGLT2 inhibitor, exerts neuroprotective effects in DR by suppressing microglial proinflammatory cytokine release.
Materials And Methods
Using high-fat diet (HFD) and streptozotocin (STZ)-induced diabetic mice and BV-2 microglial cells under high glucose (HG) conditions, we elucidate the mechanistic link between CANA and neuroinflammation suppression in DR. Retinal structure and function were assessed using optical coherence tomography and electroretinography. Protein was evaluated via Western blotting, immunostaining, and enzyme-linked immunosorbent assay. Cell viability was measured using the Cell Counting Kit-8 assay.
Results
CANA demonstrated significant neuroprotective effects in diabetic retinopathy (DR) by attenuating microglia-mediated neuroinflammation. In HFD and STZ-induced diabetic mice, the ganglion cell complex thickness and a-wave and b-wave amplitudes decreased (p < 0.05). CANA upregulated the ganglion cell complex thickness (p < 0.05) and TSPO expression (p < 0.05), and tended to increase a-wave and b-wave amplitudes (p > 0.05) in retinas in DM mice. In BV-2 cells, HG activated BV-2 cells, downregulated TSPO expression, and promoted proinflammatory cytokine release, toll-like receptor 4 (TLR4) and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) expression, and nuclear translocation of p65 and phosphorylated p65 (p < 0.05). CANA reduced BV-2 cell viability, upregulated TSPO, while suppressing proinflammatory cytokine release, TLR4 and NLRP3 expression, and nuclear translocation of p65 and phosphorylated p65 (p < 0.05). Notably, CANA inhibited the TLR4/NF-κB/NLRP3 pathway, evidenced by reduced TLR4/NLRP3 protein levels and diminished nuclear translocation of p65 and phosphorylated p65 in microglia.
Conclusions
These findings identify CANA as a promising therapeutic candidate for DR, acting through TLR4/NF-κB/NLRP3-dependent modulation of microglial activation.