SIGLEC1 ubiquitination and degradation induced by MARCHF3 protects ARPE19 retinal cells from high glucose-induced oxidative stress, inflammation, and apoptosis.

BACKGROUND: During the onset of diabetic retinopathy (DR), hyperglycemia enhances oxidative stress, and excessive inflammation drives retinal disturbance. SIGLEC1 is a surface adhesion molecule that participates in immunoregulation and inflammation. This study investigated the functions and related mechanisms of SIGLEC1 in affecting high glucose (HG)-triggered retinal inflammation and oxidative stress.

METHODS: ARPE19 retinal cells were exposed to HG conditions. mRNA expression was analyzed by quantitative PCR, and protein analysis was performed by immunoblotting. Changes in cellular inflammation and oxidative stress were evaluated by measuring related markers. The MARCHF3/SIGLEC1 interaction and SIGLEC1 ubiquitination were detected by co-immunoprecipitation (Co-IP) assay. Treatment of cycloheximide (CHX) was used to analyze SIGLEC1 protein stability.

RESULTS: The GSE221521 dataset showed that SIGLEC1 was upregulated and MARCHF3 was downregulated in blood samples of DR patients. The consistent expression patterns were also found in HG-stimulated ARPE19 cells. Functionally, SIGLEC1 depletion attenuated HG-triggered inflammation, oxidative stress and apoptosis in ARPE19 cells. Conversely, MARCHF3 downregulation exacerbated HG-triggered inflammation and oxidative stress in ARPE19 cells. Mechanistically, MARCHF3 was confirmed as a key ubiquitin ligase regulating SIGLEC1 protein stability through ubiquitination and degradation. SIGLEC1 restoration partially abolished MARCHF3-caused anti-oxidative stress and anti-inflammation effects in HG-stimulated ARPE19 cells. Additionally, MARCHF3 inactivated HG-induced NF-κB activation via downregulation of SIGLEC1 in ARPE19 cells.

CONCLUSION: Our findings suggest that SIGLEC1 ubiquitination and degradation induced by MARCHF3 protects ARPE19 cells from HG-triggered inflammation and oxidative damage.