Phosphorylation of αB-Crystallin Involves Interleukin-1β-Mediated Intracellular Retention in Retinal Müller Cells: A New Mechanism Underlying Fibrovascular Membrane Formation

Abstract

Purpose Chronic inflammation plays a pivotal role in the pathology of proliferative diabetic retinopathy (PDR), in which biological alterations of retinal glial cells are one of the key elements. The phosphorylation of αB-crystallin/ CRYAB modulates its molecular dynamics and chaperone activity, and attenuates αB-crystallin secretion via exosomes. In this study, we investigated the effect of phosphorylated αB-crystallin in retinal Müller cells on diabetic mimicking conditions, including interleukin (IL)-1β stimuli. Methods Human retinal Müller cells (MIO-M1) were used to examine gene and protein expressions with real-time quantitative PCR, enzyme linked immunosorbent assay (ELISA), and immunoblot analyses. Cell apoptosis was assessed by Caspase-3/7 assay and TdT-mediated dUTP nick-end labeling staining. Retinal tissues isolated from the Spontaneously Diabetic Torii (SDT) fatty rat, a type 2 diabetic animal model with obesity, and fibrovascular membranes from patients with PDR were examined by double-staining immunofluorescence. Results CRYAB mRNA was downregulated in MIO-M1 cells with the addition of 10 ng/mL IL-1β; however, intracellular αB-crystallin protein levels were maintained. The αB-crystallin serine 59 (Ser59) residue was phosphorylated with IL-1β application in MIO-M1 cells. Cell apoptosis in MIO-M1 cells was induced by CRYAB knockdown. Immunoreactivity for Ser59-phosphorylated αB-crystallin and glial fibrillary acidic protein was colocalized in glial cells of SDT fatty rats and fibrovascular membranes. Conclusions The Ser59 phosphorylation of αB-crystallin was modulated by IL-1β in Müller cells under diabetic mimicking inflammatory conditions, suggesting that αB-crystallin contributes to the pathogenesis of PDR through an anti-apoptotic effect.

Relationship between Biochemical Pathways and Non-Coding RNAs Involved in the Progression of Diabetic Retinopathy

“…Several pro-angiogenic cytokines-including vascular endothelial growth f (VEGF), insulin-like growth factor I (IGF-1), hepatocyte growth factor (HGF), fibroblast growth factor (b-FGF), platelet-derived growth factor (PDGF), inflammatory cytokines, such as IL-1β [48], Il-6 [49], IL-8, tumor necrosis factor-α (TN…”

“…Several pro-angiogenic cytokines—including vascular endothelial growth factor (VEGF), insulin-like growth factor I (IGF-1), hepatocyte growth factor (HGF), basic fibroblast growth factor (b-FGF), platelet-derived growth factor (PDGF), pro-inflammatory cytokines, such as IL-1β [ 48 ], Il-6 [ 49 ], IL-8, tumor necrosis factor-α (TNFα) [ 50 , 51 ], and angiopoietins [ 52 ]—are believed to be involved in the pathogenesis of PDR. Endothelial damage due to pericyte loss causes hypoperfusion, which leads to abnormalities in the structure and function of retinal blood vessels.…”

CRYAB suppresses ferroptosis and promotes osteogenic differentiation of human bone marrow stem cells via binding and stabilizing FTH1

“…The chaperone activity and molecular dynamics of CRYAB were regulated by its phosphorylation. In retinal muller cells, the stability of CRYAB was regulated by its phosphorylation at Ser59 [ 27 ]. Intriguingly, during BMSCs osteogenesis but not chondrogenesis and adipogenesis, CRYAB was elevated [ 28 , 29 ].…”

Relationship between Biochemical Pathways and Non-Coding RNAs Involved in the Progression of Diabetic Retinopathy

“…Several pro-angiogenic cytokines, including vascular endothelial growth factor (VEGF), insulinlike growth factor I (IGF-1), hepatocyte growth factor (HGF), basic fibroblast growth factor (b-FGF), platelet-derived growth factor (PDGF), pro-inflammatory cytokines such as IL-1β [48], Il-6 [49], IL-8, tumor necrosis factor-α (TNFα) [50,51] and angiopoietins [52] are believed to be involved in the pathogenesis of PDR. Endothelial failure due to pericyte loss induces hypoperfusion that conducts to abnormalities in the structure and function of retinal blood vessels.…”