Transthyretin Upregulates Long Non-Coding RNA MEG3 by Affecting PABPC1 in Diabetic Retinopathy

Abstract

The aim of the study was to demonstrate how transthyretin (TTR) could affect long non-coding RNA (lncRNA) of maternally expressed gene 3 (MEG3) and play important roles in diabetic retinopathy (DR). A DR model in C57BL/6 mice was established after intraperitoneal injection of streptozotocin (STZ). After intravitreal injection with TTR pAAV vector, MEG3 short hairpin RNA (shRNA), scrambled shRNA, or MEG3, retinal imaging, retinal trypsin digestion, and fundus vascular permeability tests were performed. Cell counting kit-8 (CCK8), transwell, and Matrigel assays were employed to detect the proliferation and migration of human retinal microvascular endothelial cells (hRECs). The binding between long non-coding RNA of maternally expressed gene 3 (lncRNA-MEG3) and microRNA-223-3p (miR-223-3p) was observed by using luciferase reporter assays, while co-immunoprecipitation (co-IP) was employed to confirm the interaction between TTR and the target. In the DR mice model, retinal vascular leakage and angiogenesis were repressed by overexpressing TTR. In vitro, the added TTR promoted the level of lncRNA-MEG3 by interacting with poly (A) binding protein cytoplasmic 1 (PABPC1), and then repressed proliferation and angiogenesis of hRECs. In vivo, silencing or overexpressing lncRNA-MEG3 significantly affected retinal vascular phenotypes. Additionally, the interaction between lncRNA-MEG3 and miR-223-3p was confirmed, and silencing of miR-223-3p revealed similar effects on hRECs as overexpression of lncRNA-MEG3. In summary, in the DR environment, TTR might affect the lncRNA MEG3/miR-223-3p axis by the direct binding with PABPC1, and finally repress retinal vessel proliferation.Keywords: diabetic retinopathy (DR); transthyretin (TTR); long non-coding RNA (lncRNA); maternally expressed gene 3 (MEG3); polyadenylate-binding protein cytoplasmic 1 (PABPC1) Int.In the eyes, transthyretin (TTR) is mainly expressed in human retinal pigment epithelial cells (hRPECs) and the choroid [7], and it usually works as the carrier of thyroxine (T4) and retinol [8,9]. As previously reported, TTR should be correlated with diabetes-associated diseases, e.g., type I diabetes patients showed lower serum TTR levels [10]. In clinical investigations, myopia was revealed to protect diabetic patients from suffering DR [11,12]. Our previous work has demonstrated that higher vitreous TTR content of high myopia patient [13] might help to prevent the progression of DR [14]. The serum and vitreous TTR levels in DR patients were associated with DR progression [15]; TTR suppressed angiogenesis by affecting the angiopoietin-Tie signaling pathway in hyperglycemia [16], and enhanced the apoptosis of hRECs through a hypoxia-associated 78-kDa glucose-regulated protein (GRP78)-dependent pathway [17]. Still, the regulatory mechanisms involving TTR in DR are not entirely clear.Long non-coding RNAs (lncRNAs) regulate targeted mRNA expression via the microRNA (miRNA) response element known as competing endogenous RNA (ceRNA) [18,19]. LncRNAs are known to play vital roles in oc...

Transthyretin Amyloidosis: Update on the Clinical Spectrum, Pathogenesis, and Disease-Modifying Therapies

“…In vitro studies suggested that both wild-type TTR and variant TTR regulate endothelial cell functions [61,62]. Studies of microangiopathy associated with diabetes mellitus have also provided evidence regarding the regulation of endothelial cell functions by TTR [63,64]. A study of sural nerve biopsy specimens from patients with ATTRv amyloidosis demonstrated that abnormalities of endoneurial microvessels, including the disruption of blood-nerve barriers, occurred before the initiation of amyloid deposition [51].…”

Transthyretin: From Structural Stability to Osteoarticular and Cardiovascular Diseases

“…Under hyperglycemic conditions, TTR represses angiogenesis by inhibiting the proliferation of hRECs through the tyrosine protein kinase receptor 2 (Tie 2) signaling pathway [ 240 ]. TTR also suppresses the proliferation of hRECs by long noncoding RNA (lncRNA) MEG3 in the miR-223-3p/FBXW7/Notch1 signaling pathway [ 225 , 241 ]. Therefore, TTR regulates lncRNAs to repress vascular leakage in the retina [ 226 , 241 ].…”

“…TTR also suppresses the proliferation of hRECs by long noncoding RNA (lncRNA) MEG3 in the miR-223-3p/FBXW7/Notch1 signaling pathway [ 225 , 241 ]. Therefore, TTR regulates lncRNAs to repress vascular leakage in the retina [ 226 , 241 ]. TTR is also able to regulate and interact with vascular endothelial growth factor [ 240 , 242 ].…”

LncRNA NEAT1 regulated diabetic retinal epithelial-mesenchymal transition through regulating miR-204/SOX4 axis

“…ShRNA were administrated with previous study (Fan et al, 2019), mice in DM+sh-NEAT1 group were injected with 1 µL of shRNA targeting NEAT1 in the vitreous cavity, and mice in DM+sh-NC group were injected with the same amount of non-targeting shRNA. Mice were injected every three weeks.…”

“…Many genetic variants found by genome-wide association studies (GWAS) increased the possibility of type 2 diabetes (Flannick & Florez, 2016), such as sex-determining region Y-related (SRY) high-mobility group box 4 (SOX4), which was discovered as a diabetes susceptibility gene and a new-called master regulator of EMT (Ragvin et al, 2010). It was reported that inhibition of SOX4 could decrease the expression of EMT-related mRNA expression and protein levels in human peritoneal mesothelial cells (HPMCs) induced with TGF-β1 (Xiao et al, 2015).…”