title: Doxycycline Attenuates Endotoxin-Induced Uveitis by Prostaglandin E2-EP4 Signaling.
abstract: OBJECTIVE
  We explored the anti-inflammatory effects of doxycycline in experimental uveitis and the underlying mechanisms.
  
  
  METHODS
  Rats with endotoxin-induced uveitis (EIU) received doxycycline (1.5 mg/kg) or the control vehicle via intraperitoneal injection. Clinical scores were graded under a slit lamp. Rat peritoneal macrophages were used in vitro to further explore the anti-inflammatory mechanisms of doxycycline. The levels of nitric oxide (NO), TNF-α, IL-1β, prostaglandin E2 (PGE2), cyclooxygenase (COX)-2, I kappa B-α (IκB-α), inducible nitric oxide synthase (iNOS), Akt, caspase-3, and nuclear factor-kappa B (NF-κB) were analyzed.
  
  
  RESULTS
  Treatment with doxycycline dramatically reduced the clinical scores of EIU (P < 0.001), with significant decreases in inflammatory cell infiltration, protein concentrations, and the production of NO, TNF-α, and IL-1β in the aqueous humor (AqH). In vitro, doxycycline significantly inhibited the production of NO, IL-1β, and TNF-α in peritoneal macrophages by modulating the PI3K/Akt/IκB-α/NF-κB pathway. Importantly, we found that doxycycline significantly enhanced COX2 expression and PGE2 production both in vivo and in vitro. More importantly, blockade of the EP4 receptor of PGE2 significantly reversed the doxycycline-mediated inhibition of macrophages and the PI3K/Akt pathway in vitro. Furthermore, simultaneous injection of an EP4 antagonist and doxycycline significantly blocked the doxycycline-mediated attenuation of EIU.
  
  
  CONCLUSIONS
  Doxycycline can ameliorate EIU, and PGE2-EP4 signaling is essential for the anti-inflammatory effects of doxycycline in vitro and in vivo.
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China 2Department of Ophthalmology, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Wenru
authors.initials: W
authors.lastname: Su
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Xiaokang
authors.initials: X
authors.lastname: Cheng
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Dai
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Longhui
authors.initials: L
authors.lastname: Han
authors.affiliation: State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Liang
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use*; D001082:Aqueous Humor / Q000737:chemistry; D053148:Caspase 3 / Q000032:analysis; D051546:Cyclooxygenase 2 / Q000032:analysis; D015232:Dinoprostone / Q000032:analysis / Q000502:physiology*; D004318:Doxycycline / Q000627:therapeutic use*; D004731:Endotoxins / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000032:analysis; D008264:Macrophages / Q000187:drug effects; D008297:Male; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000032:analysis; D019001:Nitric Oxide Synthase / Q000032:analysis; D052247:Nitric Oxide Synthase Type II / Q000032:analysis; D005996:Nitroglycerin / Q000032:analysis; D051057:Proto-Oncogene Proteins c-akt / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D058309:Receptors, Prostaglandin E, EP4 Subtype / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D066167:Slit Lamp; D014605:Uveitis / Q000139:chemically induced / Q000188:drug therapy*
chemical_list: D000893:Anti-Inflammatory Agents; D004731:Endotoxins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606206:Nfkbia protein, rat; D058309:Receptors, Prostaglandin E, EP4 Subtype; D000072000:NF-KappaB Inhibitor alpha; C044101:endotoxin, Escherichia coli; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; D005996:Nitroglycerin; D015232:Dinoprostone; D004318:Doxycycline