Rifamycins as inhibitors of collagenase activity: Their possible pharmacological role in collagen degradative diseases

The interaction of commercial rifamycin SV, rifamycin B, rifampicin and some other semi-synthetic analogous with collagenase in vitro was studied by using the fluorogenic substrate Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2. Increased fluorescence, due to the removal of the NH2-terminal dinitrophenyl group, after cleavage of the probe by collagenase was monitored and related to the enzyme activity. The peptide was an efficient substrate for collagenase with a K(m) of 0.83 μM at 20°C in the presence of 10 μM Ca2+, pH = 7.5. In the same conditions, in the presence of rifamycin SV, rifampicin and rifamycin B or their semi-synthetic analogues AM41, MC11 and MC30, a marked inhibition of the enzyme activity was observed and an IC50 ranging from 13.1 to 20.7 μM was calculated. The inhibitory effect was reversible as demonstrated by restoration of enzyme activity by dialysis. These results may support the hypothesis that drugs based upon inhibitors of collagenase activity will provide a therapeutical tool for the underlying pathological destruction of extracellular matrix observed for instance in rheumatoid arthritis as reported by several authors.