Theissenolactone C exhibited ocular protection in endotoxin-induced uveitis by attenuating ocular inflammatory responses and glial activation

[Speaker] Fan-Li Lin:1
[Co-author] Jau-Der Ho:2, Yu-Wen Cheng:3, George C. Y. Chiou:4, Jing-Lun Yen:1, Hung-Ming Chang:5, Tzong-Huei Lee:6, George Hsiao:1,7
1:Graduate Institute of Medical Sciences and Department of Pharmacology, School of Medicine, College of Medicine, Taipei Medical University, Taiwan, 2:Department of Ophthalmology, Taipei Medical University Hospital, Taiwan, 3:School of Pharmacy, College of Pharmacy, Taipei Medical University, Taiwan, 4:Department of Neuroscience and Experimental Therapeutics and Institute of Ocular Pharmacology, College of Medicine, Texas A&M Health Science Center, College Statio, USA, 5:Department of Anatomy, School of Medicine, College of Medicine, Taipei Medical University, Taiwan, 6:Institute of Fisheries Science, National Taiwan University, Taiwan, 7:Ph. D. Program for the Clinical Drug Discovery from Botanical Herbs, College of Pharmacy, Taipei Medical University, Taiwan

Background: Uveitis, an ocular inflammatory emergency, is one of the most common causes of severe visual loss. A fungal ingredient, theissenolactone C (LC53), has been shown to suppress lipopolysaccharide (LPS)-induced inflammation in monocytes. In this study, we investigated the ocular protective effects of LC53 on experimental endotoxin-induced uveitis (EIU) and related mechanisms involved.

Methods: EIU was induced in Sprague-Dawley (SD) rat by subcutaneous injection of LPS (1 mg/kg) into a single footpad. For the LC53 treatment group, the rat was intraperitoneally injected with LC53 (20 mg/kg) before LPS injection. Ophthalmic scoring and scotopic electroretinographic (ERG) analyses were evaluated for anterior inflammatory reactivity and retinal function, respectively. The eye tissue and aqueous humor were harvested and evaluated by immunofluorescence, Western blot, zymography, Oxyblot, and enzyme-linked immunosorbent assay (ELISA). In addition, Western blot, ELISA, and reactive oxygen species (ROS) assay were carried out in LPS-stimulated BV-2 microglial cells to clarify the effects and mechanisms of LC53.

Results: The administration of LC53 suppressed the EIU-induced hyperemia in the iris and restored the clinical scoring. Additionally, the retina functional deficiency of EIU was protected by LC53. LC53 significantly reduced tumor necrosis factor (TNF)-a, monocyte chemoattractant protein-1 (MCP-1), activation of matrix metalloproteinase (MMP)-2 and MMP-9, the protein leakage, and oxidative stress in EIU. The neuroinflammatory reactivity of GFAP and accumulation of monocytes/macrophages were also down-regulated by LC53 during EIU. In EIU eye, LC53 decreased the phosphorylation of p65, expression of HSP90, Bax, and cleaved-caspase-3. Moreover, LC53 induced Bcl-2 expression after EIU induction. According to the microglia studies, LC53 significantly inhibited the release of TNF-a, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, as well as ROS production in LPS-stimulated microglial BV2 cells. The microglial activation of IKKb and p65 phosphorylation was concentration-dependently attenuated by LC53.

Conclusion: Our findings indicated that LC53 exerted the ocular-protective effect through its inhibition on neuroinflammation, glial activation, and apoptosis in EIU, suggesting a therapeutic potential with down-regulation of the NF-kB signaling for uveitis and retinal inflammatory diseases.

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