title: Association of the TLR4 signaling pathway in the retina of streptozotocin-induced diabetic rats.
abstract: BACKGROUND
  Diabetic retinopathy is severe damage to the retina caused by complications of diabetes, and is the prevailing cause of blindness. Accumulating evidence from both animal models and humans suggests that the inflammatory process plays a key role in the development of diabetic retinopathy and is facilitated by innate immune response. The aim of this study was to examine whether the TLR4 signaling pathway was involved in the streptozotocin-induced diabetic rat retina.
  
  
  METHODS
  Diabetes was induced by a single intraperitoneal injection of streptozotocin, and rat diabetic retinopathy was examined at 4 weeks of diabetes duration. Then the accumulated leukocytes were counted in vivo by acridine orange leukocyte fluorography, and the retinal vascular permeability was measured by the Evans blue assay. The expressions of TLR4 and its downstream signaling molecules were measured by RT-PCR or Western blot respectively. To evaluate the effect of blocking TLR4 on diabetic retinopathy, TAK-242, a selective TLR4 antagonist, was administered by intraperitoneal injection.
  
  
  RESULTS
  Our results showed that the retina of diabetic rats demonstrated accumulated leukocytes and retinal vascular permeability. The mRNA and protein expressions of TLR4 were upregulated in streptozotocin-treated diabetic rat retina. Furthermore, the protein levels of TLR4 downstream signaling molecules were significantly increased in streptozotocin-treated animals. In addition, the protein levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and interferon (IFN)-β, three downstream proinflammatory cytokines of TLR4 signal transduction pathway, were also markedly increased in diabetic rats. Administration of TAK-242 attenuated leukocytes accumulated and retinal vascular permeability, and decreased TLR4 downstream signaling molecules and proinflammatory cytokines in streptozotocin-induced animals.
  
  
  CONCLUSIONS
  Together, these data have demonstrated that TLR4 has a critical role in streptozotocin-induced diabetic retinopathy at the level of inflammatory cytokine induction, in both the MyD88-dependent and MyD88-independent pathways. TLR4 may become a new potential pharmacological target for treating diabetic retinopathy.
authors.affiliation: Department of Ophthalmology, Beijing Capital Medical University Affiliated Beijing Friendship Hospital, Beijing, 100050, People's Republic of China.
authors.forename: Yan-Ling
authors.initials: YL
authors.lastname: Wang
authors.forename: Kang
authors.initials: K
authors.lastname: Wang
authors.forename: Shu-Jing
authors.initials: SJ
authors.lastname: Yu
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.forename: Peng-Yao
authors.initials: PY
authors.lastname: Lin
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: Li
authors.forename: Jian-You
authors.initials: JY
authors.lastname: Guo
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001813:Blood-Retinal Barrier; D015153:Blotting, Western; D002199:Capillary Permeability; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D003930:Diabetic Retinopathy / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D007274:Injections, Intraperitoneal; D016899:Interferon-beta / Q000235:genetics / Q000378:metabolism; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism; D007958:Leukocyte Count; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D060888:Real-Time Polymerase Chain Reaction; D012160:Retina / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D053583:Interleukin-1beta; D013449:Sulfonamides; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; C507035:ethyl 6-(N-(2-chloro-4-fluorophenyl)sulfamoyl)cyclohex-1-ene-1-carboxylate; D016899:Interferon-beta