C3 activation by monosodium urate monohydrate and other crystalline material

Area of Science:

• Immunology
• Biochemistry
• Crystallography

Background:

• Monosodium urate monohydrate (MSUM) crystals are implicated in gouty arthritis pathogenesis.
• The complement system plays a critical role in innate immunity and inflammation.

Purpose of the Study:

• To investigate the capacity of MSUM crystals to activate the complement system.
• To elucidate the mechanisms and dependencies of MSUM-induced complement activation.

Main Methods:

• Electrophoretic analysis of complement component C3 conversion (beta1C to beta1A).
• Assays conducted in human serum with varying concentrations of MSUM.
• Calcium dependency assessed using chelators like EDTA and EGTA.
• Effect of heat treatment on MSUM's activation potential.

Main Results:

• MSUM is a potent activator of the complement system, specifically C3, in a time- and dose-dependent manner.
• Complement activation by MSUM is calcium-dependent, indicating a role for the classic pathway.
• Excess calcium or magnesium inhibited MSUM-induced C3 activation.
• Zymosan was more potent than MSUM; calcium pyrophosphate dihydrate and hydroxyapatite also activated C3.

Conclusions:

• MSUM crystals are potent activators of the complement system via the classic pathway.
• The calcium-dependent nature of MSUM-induced complement activation highlights its inflammatory potential.
• MSUM's ability to activate complement is comparable to other known activators like zymosan.