The inhibitory effect of rosmarinic acid on complement involves the C5 convertase

Area of Science:

• Immunology
• Pharmacology

Background:

• Rosmarinic acid (RA), a natural compound from Melissa officinalis, exhibits anti-inflammatory properties.
• RA has shown potential in modulating complement-dependent inflammatory processes.

Purpose of the Study:

• To elucidate the precise mechanism by which Rosmarinic acid inhibits complement activation.
• To investigate the effects of RA on both classical and alternative complement pathways in vitro.

Main Methods:

• In vitro assays were used to assess RA's impact on complement-mediated lysis, C1q binding, and convertase activity.
• The study examined RA's effect on classical and alternative pathway convertases, membrane attack complex formation, and C3/C5 fragment generation.

Main Results:

• Rosmarinic acid demonstrated dose-dependent inhibition of classical pathway lysis, with maximal effect at 2.6 mM.
• RA showed significant inhibition of lysis and C5a generation when targeting the C5 convertase.
• Little impact was observed on C1q binding or the classical and alternative pathway convertases themselves.

Conclusions:

• The primary inhibitory mechanism of Rosmarinic acid involves the C5 convertase.
• RA's ability to inhibit the terminal complement pathway suggests potential therapeutic applications in complement-mediated diseases.