Cyclooxygenase-1 mediates neuroinflammation and neurotoxicity in a mouse model of retinitis pigmentosa

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Cyclooxygenase-1 mediates neuroinflammation and neurotoxicity in a mouse model of retinitis pigmentosa Wei Yang1†, Guoyin Xiong2† and Bin Lin1*

Abstract Background: Retinitis pigmentosa (RP) is a group of inherited eye disorders with progressive degeneration of photoreceptors in the retina, ultimately leading to partial or complete blindness. The mechanisms underlying photoreceptor degeneration are not yet completely understood. Neuroinflammation is reported to play a pathological role in RP. However, the mechanisms that trigger neuroinflammation remain largely unknown. To address this question, we investigated the role of cyclooxygenase-1 (COX-1), a key enzyme in the conversion of arachidonic acid to proinflammatory prostaglandins, in the rd10 mouse model of RP. Methods: We backcrossed COX-1 knockout mice (COX-1−/−) onto the rd10 mouse model of RP and investigated the impact of COX-1 deletion on neuroinflammation in the resulting COX-1−/−/rd10 mouse line, using a combination of immunocytochemistry, flow cytometry, qPCR, ELISA, and a series of simple visual tests. Results: We found that genetic ablation or pharmacological inhibition of COX-1 alleviated neuroinflammation and subsequently preserved retinal photoreceptor and function and visual performance in rd10 mice. Moreover, we observed that the pharmacological inhibition of the prostaglandin E2 (PGE2) EP2 receptors largely replicated the beneficial effects of COX-1 deletion, suggesting that EP2 receptor was a critical downstream effector of COX-1mediated neurotoxicity in rd10 mice. Conclusion: Our data suggest that the COX-1/PGE2/EP2 signaling pathway was partly responsible for significantly increased neuroinflammation and disease progression in rd10 mice, and that EP2 receptor could be targeted therapeutically to block the pathological activity of COX-1 without inducing any potential side effects in treating RP patients. Keywords: rd10 mice, Photoreceptors, Neuroinflammation, COX-1, EP2 receptor

* Correspondence: [email protected] † Wei Yang and Guoyin Xiong contributed equally to this work. 1 School of Optometry, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a c