ERK5 Regulates Glucose-Induced Increased Fibronectin Production in the Endothelial Cells and in the Retina in Diabetes
ABSTRACT PURPOSE: Fibronectin (FN) production and deposition in the tissue is a characteristic feature of diabetic retinopathy. ERK5 is a recent member of MAPK family which plays a critical role in cardiovascular development and maintaining endothelial cell integrity. The aim of the study is to investigate the role of ERK5 signaling in glucose-induced FN overproduction. METHOD: Dermal-derived human microvascular endothelial cells (HMVECs) and human retinal microvascular endothelial cells (HRMECs) were used in this study. FN mRNA levels and secreted FN protein levels were measured using real-time PCR and ELISA respectively. Constitutively active MEK5 (CAMEK5) adenovirus was used to upregulate ERK5. Dominant negative MEK5 (DNMEK5) and ERK5 siRNA (siERK5) were used to downregulate ERK5. In parallel retinal tissues of diabetic rats were examined. Results: A significant decrease of FN was observed at both protein and mRNA levels following CAMEK5 transduction in basal as well as in high glucose. Dominant negative MEK5 (DNMEK5) transduction led to further enhancement of glucose-induced increased FN expression. ERK5 siRNA (siERK5) treatment led to an increase of FN synthesis. Retinal tissues of diabetic rats showed FN upregulation and ERK5 downregulation. TGFβ1 mRNA and phosphorylated Smad2 were markedly suppressed by CAMEK5 transduction with and without glucose treatment. On the other hand siERK5 transfection enhanced TGFβ1 mRNA expression. Exogenous NGF supplementation resulted in elevated phosphorylated and total ERK5 with and without glucose treatment. CONCLUSION: our experiments demonstrated a novel mechanism of glucose-induced increased FN production which is mediated through decreased ERK5 signaling.
SourceAvailable from: Subrata Chakrabarti[Show abstract] [Hide abstract]
ABSTRACT: Diabetic retinopathy is the lead among causes of blindness in North America. Glucose-induced endothelial injury is the most important cause of diabetic retinopathy and other vascular complications. Extracellular signal-regulated kinase 5 (ERK5), also known as big mitogen-activated protein kinase 1 (BMK1), is a member of mitogen-activated protein kinases (MAPK) family. Physiologically, it is critical for cardiovascular development and maintenance of the endothelial cell integrity. Extracellular signal-regulated kinase 5 is protective for endothelial cells under stimulation and stress. Decreased activation of ERK5 results in increased endothelial cell death. Extracellular signal-regulated kinase 5 signaling may be subject to alteration by hyperglycemia, while signaling pathway including ERK5 may be subject to alteration during pathogenesis of diabetic complications. In this review, the role of ERK5 in diabetic macro- and microvascular complications with a focus on diabetic retinopathy are summarized and discussed.01/2015; 4(1):17-26.
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ABSTRACT: The vascular basement membrane (BM) contains extracellular matrix (ECM) proteins that assemble in a highly organized manner to form a supportive substratum for cell attachment facilitating myriad functions that are vital to cell survival and overall retinal homeostasis. The BM provides a microenvironment in which bidirectional signaling through integrins regulates cell attachment, turnover, and functionality. In diabetic retinopathy, the BM undergoes profound structural and functional changes, and recent studies have brought to light the implications of such changes. Thickened vascular BM in the retinal capillaries actively participate in the development and progression of characteristic changes associated with diabetic retinopathy. High glucose (HG)-induced compromised cell-cell communication via gap junctions (GJ) in retinal vascular cells may disrupt homeostasis in the retinal microenvironment. In this review, the role of altered ECM synthesis, compromised GJ activity, and disturbed retinal homeostasis in the development of retinal vascular lesions in diabetic retinopathy are discussed. Copyright © 2014. Published by Elsevier Ltd.Experimental Eye Research 04/2015; 133. DOI:10.1016/j.exer.2014.08.011 · 3.02 Impact Factor
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ABSTRACT: Background Lithospermic acid B (LAB), an active component isolated from Salvia miltiorrhiza radix, has been reported to have antioxidant effects. We examined the effects of LAB on the prevention of diabetic retinopathy in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model of type 2 diabetes. Methods and Findings LAB (10 or 20 mg/kg) or normal saline were given orally once daily to 24-week-old male OLETF rats for 52 weeks. At the end of treatment, fundoscopic findings, vascular endothelial growth factor (VEGF) expression in the eyeball, VEGF levels in the ocular fluid, and any structural abnormalities in the retina were assessed. Glucose metabolism, serum levels of high-sensitivity C-reactive protein (hsCRP), monocyte chemotactic protein-1 (MCP1), and tumor necrosis factor-alpha (TNFα) and urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels were also measured. Treatment with LAB prevented vascular leakage and basement membrane thickening in retinal capillaries in a dose-dependent manner. Insulin resistance and glucose intolerance were significantly improved by LAB treatment. The levels of serum hsCRP, MCP1, TNFα, and urinary 8-OHdG were lower in the LAB-treated OLETF rats than in the controls. Conclusions Treatment with LAB had a preventive effect on the development of diabetic retinopathy in this animal model, probably because of its antioxidative effects and anti-inflammatory effects.PLoS ONE 06/2014; 9(6):e98232. DOI:10.1371/journal.pone.0098232 · 3.53 Impact Factor