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Updated: Apr 18, 2026
Author Spotlight: Unraveling the Pathogenesis of Age-Related Macular Degeneration and Discovering Potential Therapies
Published on: July 28, 2023
Apolipoprotein E promotes subretinal mononuclear phagocyte survival and chronic inflammation in age-related macular
Olivier Levy1, Bertrand Calippe1, Sophie Lavalette1
1INSERM, Paris, France UPMC Univ Paris 06 UMR_S 968 Institut de la Vision, Paris, France Centre Hospitalier National d'Ophtalmologie des Quinze-Vingts INSERM-DHOS CIC 503, Paris, France.
Abstract:
Physiologically, the retinal pigment epithelium (RPE) expresses immunosuppressive signals such as FAS ligand (FASL), which prevents the accumulation of leukocytes in the subretinal space. Age-related macular degeneration (AMD) is associated with a breakdown of the subretinal immunosuppressive environment and chronic accumulation of mononuclear phagocytes (MPs). We show that subretinal MPs in AMD patients accumulate on the RPE and express high levels of APOE. MPs of Cx3cr1(-/-) mice that develop MP accumulation on the RPE, photoreceptor degeneration, and increased choroidal neovascularization similarly express high levels of APOE. ApoE deletion in Cx3cr1(-/-) mice prevents pathogenic age- and stress-induced subretinal MP accumulation. We demonstrate that increased APOE levels induce IL-6 in MPs via the activation of the TLR2-CD14-dependent innate immunity receptor cluster. IL-6 in turn represses RPE FasL expression and prolongs subretinal MP survival. This mechanism may account, in part, for the MP accumulation observed in Cx3cr1(-/-) mice. Our results underline the inflammatory role of APOE in sterile inflammation in the immunosuppressive subretinal space. They provide rationale for the implication of IL-6 in AMD and open avenues toward therapies inhibiting pathogenic chronic inflammation in late AMD.
Insights
In age-related macular degeneration (AMD), apolipoprotein E (APOE) drives inflammation by increasing IL-6, which represses immunosuppressive signals and promotes mononuclear phagocyte accumulation in the eye. Deleting APOE prevents this pathogenic buildup, suggesting new therapeutic targets for AMD.
Area of Science:
- Ophthalmology
- Immunology
- Genetics
Background:
- The retinal pigment epithelium (RPE) normally maintains an immunosuppressive subretinal environment via FAS ligand (FASL).
- Age-related macular degeneration (AMD) involves a breakdown of this environment, leading to chronic mononuclear phagocyte (MP) accumulation.
- Subretinal MPs in AMD patients and Cx3cr1(-/-) mice express high levels of apolipoprotein E (APOE).
Purpose of the Study:
- To investigate the role of APOE in subretinal MP accumulation and its contribution to AMD pathogenesis.
- To elucidate the molecular mechanisms by which APOE influences the subretinal immune environment.
Main Methods:
- Analysis of subretinal MPs from AMD patients and Cx3cr1(-/-) mice.
- Genetic deletion of ApoE in Cx3cr1(-/-) mice to assess its impact on MP accumulation.
- In vitro studies to determine the signaling pathways involved in APOE-mediated inflammation (TLR2-CD14, IL-6).
Main Results:
- Subretinal MPs in AMD and Cx3cr1(-/-) mice express high APOE levels.
- ApoE deletion in Cx3cr1(-/-) mice prevented pathogenic subretinal MP accumulation.
- Increased APOE induced IL-6 production in MPs via TLR2-CD14 activation.
- IL-6 repressed RPE FasL expression and prolonged MP survival, contributing to MP accumulation.
Conclusions:
- APOE plays a critical inflammatory role in sterile inflammation within the subretinal space.
- The APOE-IL-6-FasL axis contributes to MP accumulation in AMD.
- Targeting APOE or IL-6 may offer novel therapeutic strategies for late-stage AMD by inhibiting chronic inflammation.
