Abstract
Purpose :
The phosphorylation of αB-crystallin/CRYAB, one of small heat shock proteins also known as HSPB5, modulates its molecular dynamics and chaperone activity. Hyperglycemia and chronic inflammation play pivotal roles in the pathology of diabetic retinopathy, in which biological alterations of retinal glial cells are one of the key elements. However, αB-crystallin expression changes remain elusive in retinal glia cells under various diabetic stimuli. Here, we show interleukin (IL)-1β, an inflammatory cytokine upregulated in diabetic retinopathy, regulates the phosphorylation and mRNA expression of αB-crystallin in Müller cells.
Methods :
Human Müller cells (MIO-M1) were used to evaluate changes in gene and protein expression with real-time quantitative PCR, enzyme linked immunosorbent assay (ELISA) and immunoblot analyses. Retinal tissues, isolated from the Spontaneously Diabetic Torii (SDT) fatty rat, a type 2 diabetic animal model with obesity, were examined by double-staining immunofluorescence.
Results :
Real-time PCR and ELISA showed that CRYAB mRNA and αB-crystallin protein expression decreased in 50mM high glucose medium compared with 50mM mannitol. CRYAB transcripts expression was downregulated with 10ng/ml IL-1β (fold change; 24 hours = 0.33, 48h = 0.38, p < 0.01). AlphaB-crystallin serine 59 residue was phosphorylated with IL-1β application, which was inhibited following CRYAB siRNA induction in MIO-M1 cells. There was co-localization of glial fibrillary acidic protein (GFAP) with αB-crystallin and phosphorylated αB-crystallin at serine 59 in Müller cells in retinal specimens of SDT fatty rats.
Conclusions :
CRYAB mRNA expression and the phosphorylation of αB-crystallin serine 59 residue were modulated by IL-1β in Müller cells under diabetic conditions, suggesting that αB-crystallin contributes to the pathogenesis of diabetic retinopathy.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.