Complement Factor D protects mice from ethanol-induced inflammation and liver injury

Area of Science:

• Immunology
• Hepatology
• Innate Immune System

Background:

• Complement activation is crucial for host defense and clearing apoptotic cells.
• Emerging evidence implicates complement in alcoholic liver disease (ALD).
• The role of the alternative complement pathway in ethanol-induced liver injury remains unclear.

Purpose of the Study:

• To investigate the role of the alternative complement pathway, specifically complement factor D (FD), in ethanol-induced liver injury.
• To determine if FD-dependent complement activation is protective or detrimental in ALD.

Main Methods:

• Utilized various knockout mouse models (C1qa-/-, C4-/-, FD-/-) fed an ethanol-containing diet.
• Assessed liver injury, steatosis, and proinflammatory cytokine expression.
• Measured hepatic complement activation via C1q and C3 cleavage products.
• Evaluated apoptotic cell accumulation and fibrogenic responses.

Main Results:

• Chronic ethanol exposure increased liver injury, steatosis, and inflammation in wild-type mice.
• FD-deficient mice exhibited exacerbated liver injury, steatosis, and inflammation compared to wild-type mice.
• FD deficiency impaired complement activation (C3 cleavage) during chronic ethanol exposure, leading to increased apoptotic cells and fibrosis.

Conclusions:

• Complement factor D (FD) plays a protective role in ALD by amplifying complement activation.
• FD-dependent complement amplification is an adaptive response promoting hepatic healing and recovery.
• These findings reveal a dual role for complement in ALD, with FD mediating protective mechanisms against ethanol-induced damage.