title: The Neuroprotective Effect of Rapamycin as a Modulator of the mTOR-NF-κB Axis during Retinal Inflammation.
abstract: OBJECTIVE
  The determination of the molecular mechanism underlying retinal pathogenesis and visual dysfunction during innate inflammation, and the treatment effect of rapamycin thereon.
  
  
  METHODS
  The endotoxin-induced uveitis and retinitis mouse model was established by injecting lipopolysaccharide. The mice were subsequently treated with rapamycin, a mammalian target of rapamycin (mTOR) inhibitor. The rhodopsin mRNA and protein expression level in the retina and the photoreceptor outer segment (OS) length in immunohistochemical stainings were measured, and visual function was recorded by electroretinography. Inflammatory cytokines, their related molecules, mTOR, and LC3 levels were measured by real-time PCR and/or immunoblotting. Leukocyte adhesion during inflammation was analyzed using concanavalin A lectin.
  
  
  RESULTS
  The post-transcriptional reduction in the visual pigment of rod photoreceptor cells, rhodopsin, OS shortening, and rod photoreceptor cell dysfunction during inflammation were suppressed by rapamycin. Activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and induction of inflammatory cytokines, such as interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1), and the activation of the downstream signaling protein, signal transducer and activator of transcription 3 (STAT3), which reduces rhodopsin in the retina during inflammation, were attenuated by rapamycin. Increased leukocyte adhesion was also attenuated by rapamycin. Interestingly, although mTOR activation was observed after NF-κB activation, mTOR inhibition suppressed NF-κB activation at the early phase, indicating that the basal level of activated mTOR was sufficient to activate NF-κB in the retina. In addition, the inhibition of NF-κB suppressed mTOR activation, suggesting a positive feedback loop of mTOR and NF-κB during inflammation. The ratio of LC3II to LC3I, which reflects autophagy induction, was not changed by inflammation but was increased by rapamycin.
  
  
  CONCLUSIONS
  Our results propose the potential use of rapamycin as a neuroprotective therapy to suppress local activated mTOR levels, related inflammatory molecules, and the subsequent visual dysfunction during retinal inflammation.
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.|Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Okamoto
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.|Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ozawa
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.|Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Mamoru
authors.initials: M
authors.lastname: Kamoshita
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Osada
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Toda
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.|Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Toshihide
authors.initials: T
authors.lastname: Kurihara
authors.affiliation: Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.|Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Nagai
authors.affiliation: Department of Molecular Target Medicine Screening, Aichi Medical University School of Medicine, Nagakute, Aichi, 480-1195, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Umezawa
authors.affiliation: Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tsubota
mesh_terms: D000818:Animals; D007249:Inflammation / Q000188:drug therapy*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology / Q000627:therapeutic use; D012160:Retina / Q000187:drug effects* / Q000276:immunology*; D012173:Retinitis / Q000188:drug therapy* / Q000276:immunology; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology* / Q000627:therapeutic use*; D014605:Uveitis / Q000188:drug therapy / Q000276:immunology
chemical_list: D016328:NF-kappa B; D018696:Neuroprotective Agents; D020123:Sirolimus