Role of Complement and Histones in Sepsis

Area of Science:

• Immunology
• Pathophysiology
• Pharmacology

Background:

• Sepsis remains a leading cause of mortality with no specific FDA-approved treatments despite numerous clinical trials.
• The mouse model of polymicrobial sepsis is crucial for understanding human sepsis pathophysiology.
• Adverse effects of sepsis involve complement activation products, particularly C5a anaphylatoxin and its receptors.

Purpose of the Study:

• To investigate the role of complement activation products, specifically C5a, in sepsis-induced organ dysfunction.
• To elucidate the relationship between C5a, extracellular histones, and sepsis progression.
• To evaluate therapeutic strategies targeting C5a for sepsis treatment.

Main Methods:

• Utilized a mouse model of polymicrobial sepsis.
• Monitored complement activation products (C5a) and extracellular histones in plasma.
• Assessed the impact of C5a and its receptors (C5aR1, C5aR2) on cell injury and organ dysfunction.
• Investigated the effects of C5a neutralization via antibody and C5aR1 absence on sepsis outcomes.
• Evaluated survival rates in septic mice.

Main Results:

• C5a appearance in sepsis correlates with extracellular histone presence in plasma.
• Extracellular histones exhibit potent pro-inflammatory and pro-thrombotic activities, causing cell injury and multiorgan dysfunction.
• Sepsis-induced cardiomyopathy is dependent on C5a, its receptors, and histones.
• Neutralization of C5a or absence of C5aR1 prevents extracellular histone appearance and mitigates cell and organ failure.
• Blockade of C5a with antibodies significantly improves survival rates in septic mice.

Conclusions:

• C5a plays a critical role in sepsis pathogenesis by promoting the release and activity of extracellular histones.
• Targeting C5a represents a promising therapeutic strategy to prevent organ damage and improve survival in sepsis.
• Further research into C5a-histone interactions may reveal novel therapeutic interventions for sepsis.