Depletion of the Receptor-Interacting Protein Kinase 3 (RIP3) Decreases Photoreceptor Cell Death During the Early Stages of Ocular Murine Cytomegalovirus Infection

作者：Xu Jinxian; Mo Juan; Liu Xinglou; Marshall Brendan; Atherton Sally S; Dong Zheng; Smith Sylvia; Zhang Ming^*

来源：Investigative Ophthalmology & Visual Science, 2018, 59(6): 2445-2458.

DOI：10.1167/iovs.18-24086

• apoptosis
• murine cytomegalovirus
• innate immune response
• retinitis

PURPOSE. The purpose of this study was to determine if the receptor-interacting protein kinase 3 (RIP3) plays a significant role in innate immune responses and death of bystander retinal neurons during murine cytomegalovirus (MCMV) retinal infection, by comparing the innate immune response and cell death in RIP3-depleted mice (Rip3(-/-)) and Rip3(+/+) control mice.
METHODS. Rip3(-/-) and Rip3(+/+) mice were immunosuppressed (IS) and inoculated with MCMV via the supraciliary route. Virus-injected and mock-injected control eyes were removed at days 4, 7, and 10 post infection (p. i.) and markers of innate immunity and cell death were analyzed.
RESULTS. Compared to Rip3(+/+) mice, significantly more MCMV was recovered and more MCMV-infected RPE cells were observed in injected eyes of Rip3(-/-) mice at days 4 and 7 p. i. In contrast, fewer TUNEL-stained photoreceptors were observed in Rip3(-/-) eyes than in Rip3(+/+) eyes at these times. Electron microscopy showed that significantly more apoptotic photoreceptor cells were present in Rip3(+/+) mice than in Rip3(-/-) mice. Immunohistochemistry showed that the majority of TUNEL-stained photoreceptors died via mitochondrial flavoprotein apoptosis-inducing factor (AIF)-mediated, caspase 3-independent apoptosis. The majority of RIP3-expressing cells in infected eyes were RPE cells, microglia/macrophages, and glia, whereas retinal neurons contained much lower amounts of RIP3. Western blots showed significantly higher levels of activated nuclear factor-kappa B and caspase 1 were present in Rip3(+/+) eyes compared to Rip3(-/-) eyes.
CONCLUSIONS. Our results suggest that RIP3 enhances innate immune responses against ocular MCMV infection via activation of the inflammasome and nuclear factor-kappa B, which also leads to inflammation and death of bystander cells by multiple pathways including apoptosis and necroptosis.

• 出版日期2018-5