Circulating xanthine oxidase in human ischemia reperfusion

Area of Science:

• Biochemistry
• Physiology
• Pathology

Background:

• Reactive oxygen species (ROS) contribute to ischemia-induced injury.
• Xanthine oxidase (XO) is a primary source of ROS.
• The role of XO and xanthine dehydrogenase (XDH) release during ischemia-reperfusion is not fully understood.

Purpose of the Study:

• To investigate the release of XO and XDH into circulation during ischemia-reperfusion of the human liver and intestine.
• To quantify the enzymatic activity of XO and XDH in plasma following aortic cross-clamp procedures.

Main Methods:

• Blood samples were collected from a patient before and after aortic cross-clamp.
• Plasma was incubated with xanthine to measure XDH+XO and XO activity.
• Urate formation was quantified using high-performance liquid chromatography (HPLC).

Main Results:

• XDH+XO and XO activities significantly increased after reperfusion of the superior mesenteric, celiac, and right renal arteries.
• Enzymatic activities rose from baseline levels (1.88 and 1.66 microU/mg protein) to post-reperfusion levels (3.77 and 3.11 microU/mg protein) within 7 minutes.
• A significant release of ROS-generating enzymes into circulation was observed.

Conclusions:

• Ischemia-reperfusion leads to the release of XO and XDH into the bloodstream.
• This enzyme release represents a significant source of ROS.
• The findings suggest a mechanism for observed lung or heart damage after liver and intestinal ischemia.