Remote ischemic preconditioning differentially affects NADPH oxidase isoforms during hepatic ischemia-reperfusion

Area of Science:

• Hepatology and critical care medicine
• Molecular biology and enzyme function
• Surgical research

Background:

• Hepatic ischemia-reperfusion (IR) injury is a significant clinical challenge.
• Superoxide-generating enzymes, particularly NADPH oxidases (NOX), play a role in IR pathophysiology.
• Remote ischemic preconditioning (IPC) is a potential protective strategy.

Purpose of the Study:

• To investigate the role of major superoxide-generating enzymes in hepatic IR.
• To assess the specific involvement of NADPH oxidase (NOX) isoforms NOX2 and NOX4 in remote IPC's protective mechanism.

Main Methods:

• Induction of 60-minute partial liver ischemia in rats with or without remote IPC (limb IR).
• Assessment of hepatic microcirculation using intravital microscopy and spectrophotometry.
• Biochemical assays for inflammatory markers (MPO, XOR, TNF-α, HMGB-1), liver damage enzymes (AST, ALT, LDH), and NOX2/NOX4 protein expression via Western blot.

Main Results:

• Remote IPC significantly reduced IR-induced NOX2 expression, while NOX4 expression remained unchanged.
• IPC provided significant but incomplete protection against leukocyte-endothelial interactions and microcirculatory flow impairment.
• Hepatocellular damage, inflammatory markers (cytokines, MPO, XOR), and necroenzymes (AST, ALT, LDH) were diminished by IPC.

Conclusions:

• Remote IPC mitigates IR-induced microcirculatory dysfunction and associated damage.
• The protective effect of IPC is not uniform across all NOX homologs, as NOX4 activity was unaffected.
• Unchanged NOX4 activity may contribute to the residual liver damage and inflammation observed after IPC.