title: Etanercept restores normal insulin signal transduction in β2-adrenergic receptor knockout mice.
abstract: BACKGROUND
  Inhibition of TNFα protects the retina against diabetic-like changes in rodent models. The mechanism by which TNFα induces deleterious retinal changes is not known. Previously, we have shown that TNFα can inhibit normal insulin signal transduction, leading to increased apoptosis in both retinal endothelial cells (REC) and Müller cells. Additionally, β2-adrenergic receptor knockout mice (β2KO) have increased TNFα levels and decreased insulin receptor activity. In this study, we hypothesized that inhibition of TNFα in β2KO mice would increase normal insulin signaling, leading to improved retinal function.
  
  
  METHODS
  C57BL6 or β2KO mice were left untreated or treated with etanercept (0.3 mg/kg subcutaneously, 3× a week) for 2 months. Electroretinogram analyses were done before treatment was initiated and after two months of treatment with etanercept on all mice. Western blot or ELISA analyses were done on whole retinal lysates from all four groups of mice for TNFα, suppressor of cytokine signaling 3 (SOCS3), insulin receptor, and apoptotic proteins.
  
  
  RESULTS
  Etanercept significantly reduced TNFα levels in β2KO mice, leading to increased insulin receptor phosphorylation on tyrosine 1150/1151. SOCS3 levels were increased in β2KO mice, which were reduced after etanercept treatment. Pro-apoptotic proteins were reduced in etanercept-treated β2KO mice. Etanercept improved ERG amplitudes in β2KO mice.
  
  
  CONCLUSIONS
  Inhibition of TNFα by etanercept protects the retina likely through reduced TNFα-mediated insulin resistance, leading to reduced apoptosis.
authors.forename: Youde
authors.initials: Y
authors.lastname: Jiang
authors.forename: Qiuhua
authors.initials: Q
authors.lastname: Zhang
authors.forename: Eun-Ah
authors.initials: EA
authors.lastname: Ye
authors.affiliation: Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN, USA. jsteinl1@uthsc.edu.
authors.forename: Jena J
authors.initials: JJ
authors.lastname: Steinle
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D004596:Electroretinography; D004797:Enzyme-Linked Immunosorbent Assay; D000068800:Etanercept; D007074:Immunoglobulin G / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation / Q000187:drug effects; D018343:Receptors, Adrenergic, beta-2 / Q000172:deficiency* / Q000235:genetics; D018124:Receptors, Tumor Necrosis Factor; D012160:Retina / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D007074:Immunoglobulin G; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; D018343:Receptors, Adrenergic, beta-2; D018124:Receptors, Tumor Necrosis Factor; C491411:Socs3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014409:Tumor Necrosis Factor-alpha; D053148:Caspase 3; D000068800:Etanercept