Constitutive Oxidative Stress by SEPHS1 Deficiency Induces Endothelial Cell Dysfunction.

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Selenophosphate synthetase (SEPHS) synthesizes selenophosphate, a key selenium donor for selenocysteine synthesis.
• Two SEPHS isoforms exist in eukaryotes: SEPHS1 and SEPHS2, with only SEPHS2 known to possess catalytic activity.

Purpose of the Study:

• To investigate the function of SEPHS1 in endothelial cells.
• To determine the effects of SEPHS1 deficiency on cellular processes, including oxidative stress, proliferation, and angiogenesis.

Main Methods:

• Targeted null mutations were introduced into the SEPHS1 gene (Sephs1) in cultured mouse 2H11 endothelial cells.
• Assessed cellular levels of superoxide, lipid peroxide, and nitric oxide.
• Evaluated cell proliferation, cell cycle progression (G2/M phase), DNA damage (gamma H2AX foci), and angiogenic tube formation.

Main Results:

• SEPHS1 deficiency led to increased superoxide and lipid peroxide accumulation, and decreased nitric oxide.
• Superoxide accumulation resulted from induced xanthine oxidase and NADPH oxidase activity, and reduced superoxide dismutase 1 (SOD1) and 3 (SOD3).
• SEPHS1-deficient cells exhibited inhibited proliferation, G2/M phase arrest, increased DNA damage, and impaired angiogenic tube formation.

Conclusions:

• SEPHS1 deficiency causes superoxide accumulation in endothelial cells, contributing to oxidative stress and cellular dysfunction.
• This dysfunction manifests as DNA damage, cell cycle arrest, and impaired angiogenesis, mediated by altered nitric oxide and reactive oxygen species (ROS) levels.
• This study highlights a novel role for SEPHS1 in maintaining endothelial cell function and preventing oxidative damage.