Comparative study of in vitro inhibition of activation of the classical and alternative pathways of human complement by the magnesium and sodium salts of the anti-inflammatory peptide N-acetyl-aspartyl-glutamic acid (NAAGA).

The inhibitory activity of the sodium salt of the anti-inflammatory peptide N-acetyl-aspartyl-glutamic acid (NAAGA) on activation of the classical and alternative pathways of human complement was compared with that of the clinically used magnesium salt of NAAGA (NAAGA-Mg). Sodium salt of NAAGA (NAAGA-Na) inhibited both pathways of activation in a dose-dependent manner at concentration ranging from 1 to 10 mM by acting on formation and/or function of the C3 convertases as shown by the inhibitory capacity of the peptide on the release of the C3 cleavage fragment C3b and C3a. NAAGA-Na was as effective as NAAGA-Mg in inhibiting classical pathway activation at concentration above 10 mM. NAAGA-Na was more effective than NAAGA-Mg in inhibiting the alternative pathway since the sodium salt did not interfere with Mg-dependent formation of the alternative pathway C3 convertase.