DNMT1 and Sp1 competitively regulate the expression of BACE1 in A2E-mediated photo-oxidative damage in RPE cells

Area of Science:

• Ophthalmology
• Neuroscience
• Molecular Biology

Background:

• Amyloid-beta (Aβ) plays a role in retinal damage, potentially contributing to age-related macular degeneration (AMD).
• The precise mechanisms of Aβ deposition in AMD remain unclear.
• Beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is crucial for Aβ production.

Purpose of the Study:

• To elucidate the regulatory mechanism of BACE1 in the context of Aβ deposition in retinal cells.
• To investigate potential therapeutic targets for AMD by studying BACE1 regulation.
• To utilize an A2E-mediated photo-oxidation model to mimic AMD-related cellular stress.

Main Methods:

• A2E-mediated photo-oxidation model to induce retinal stress and Aβ deposition.
• Analysis of BACE1 expression, Aβ levels, and DNA methylation patterns.
• Chromatin immunoprecipitation (ChIP) assay to assess Sp1 binding to the BACE1 promoter.
• Inhibition of Sp1 using mithramycin A (MTM) to evaluate its effects.

Main Results:

• Photo-oxidation increased Aβ levels and BACE1 expression, linked to BACE1 promoter hypomethylation and reduced DNMT1.
• DNMT1-mediated methylation normally suppresses Sp1 binding to the BACE1 promoter; reduced methylation enhances Sp1 binding and BACE1 transcription.
• Inhibition of Sp1 with MTM decreased BACE1 expression and improved retinal pigment epithelium (RPE) cell morphology and function.

Conclusions:

• BACE1 expression in retinal cells under photo-oxidative stress is competitively regulated by transcription factor Sp1 and DNMT1.
• Sp1 activation and DNMT1 inhibition contribute to increased BACE1 transcription and subsequent Aβ accumulation.
• Mithramycin A demonstrates a potential protective role against RPE damage by down-regulating BACE1, offering a novel therapeutic strategy for AMD.