Toll-like receptor-4 knockout mice are more resistant to optic nerve crush damage than wild-type mice

• Published in: Clinical & experimental ophthalmology 2015-09, Vol.43 (7), p.655-665
• Main Authors: Morzaev, Dana, Nicholson, James D, Caspi, Tomm, Weiss, Shirel, Hochhauser, Edith, Goldenberg-Cohen, Nitza
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Disease Models, Animal; Glial Fibrillary Acidic Protein; Homeodomain Proteins - metabolism; ischemic retina; Leukocyte Common Antigens - genetics; Leukocyte Common Antigens - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; Nerve Crush; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; neuroprotection; Optic nerve; optic nerve crush model; Optic Nerve Injuries - genetics; Optic Nerve Injuries - metabolism; Optic Nerve Injuries - pathology; Real-Time Polymerase Chain Reaction; Retinal Ganglion Cells - metabolism; Retinal Ganglion Cells - pathology; RNA, Messenger - genetics; Rodents; Thy-1 Antigens - metabolism; TLR-4 knockout mouse; Toll-Like Receptor 4 - physiology; Transcription Factor Brn-3B - metabolism; Tumor Necrosis Factor-alpha - genetics; Tumor Necrosis Factor-alpha - metabolism
• ISSN: 1442-6404; 1442-9071
• DOI: 10.1111/ceo.12521

Background This study aims to investigate the role of the inflammatory response following optic nerve crush (ONC) in knockout mice for the toll‐like receptor‐4 gene (TLR4−/−) compared to wild‐type (WT) mice. Methods ONC was induced in TLR4−/− and C57BL6 WT mice. Histological sections of the retina and optic nerve were analysed on days 1, 3 or 21 after injury. Molecular analysis with real‐time quantitative polymerase chain reaction was used to study the expression of CD45, tumour necrosis‐alpha (TNF‐α) and glial fibrillary acidic protein, as well as retinal ganglion cell (RGC) markers THY‐1 and Brn3b. Results There was a 25.5% and 38% loss in the RGC layer of the ONC‐injured eyes of the TLR4−/− and the WT mice, respectively (with 27% and 9% of the remaining cells positive for Brn3a, respectively). Mean levels of Thy‐1 and Brn3b were higher in the TLR4−/− mice. CD45 and Iba1 staining revealed infiltration of inflammatory cells into the injured nerve and retina in both groups. Molecular analysis of the optic nerve on day 1 showed increased TNF‐α expression and reduced CD45 and GFAP expression; on day 3, CD45 reverted to baseline but GFAP remained low; on day 21, all 3 markers were at baseline in the TLR4−/− group and decreased in the WT group. Conclusion Inflammation plays a major role in the response to ONC injury. Reduced levels of inflammation are associated with improved RGC preservation. The increase in TNF‐α and reduction in CD45 in both TLR4−/− and WT mice may indicate the presence of an alternative pathway for induction of RGC death.