Ascorbate inhibits NADPH oxidase subunit p47phox expression in microvascular endothelial cells

Area of Science:

• Biochemistry
• Cell Biology
• Pharmacology

Background:

• Endothelial dysfunction in sepsis is driven by reactive oxygen species (ROS) production.
• NADPH oxidases in endothelial cells are key sources of ROS and potential therapeutic targets.
• Ascorbate (vitamin C) is an antioxidant that improves outcomes in experimental sepsis.

Purpose of the Study:

• To investigate the hypothesis that ascorbate regulates NADPH oxidases in microvascular endothelial cells during septic insult.

Main Methods:

• Mouse microvascular endothelial cells were exposed to Escherichia coli lipopolysaccharide (LPS) and interferon-gamma (IFNgamma).
• NADPH oxidase activity and p47phox subunit expression were measured.
• Cells were pretreated with ascorbate, catalase, or Jak2 inhibitors; exogenous hydrogen peroxide was also used.

Main Results:

• LPS+IFNgamma increased NADPH oxidase activity and p47phox expression, which ascorbate pretreatment prevented.
• Ascorbate inhibited the LPS+IFNgamma-induced activation of the Jak2/Stat1/IRF1 signaling pathway.
• Exogenous hydrogen peroxide-induced p47phox expression was also blocked by ascorbate.

Conclusions:

• Ascorbate inhibits septic insult-stimulated redox-sensitive Jak2/Stat1/IRF1 signaling, p47phox expression, and NADPH oxidase activity in microvascular endothelial cells.
• Inhibition of endothelial NADPH oxidases by ascorbate presents a potential new therapeutic approach for sepsis.