FUNCTIONAL SITES OF CHEMICALLY-MODIFIED TETRACYCLINES - INHIBITION OFTHE OXIDATIVE ACTIVATION OF HUMAN NEUTROPHIL AND CHICKEN OSTEOCLAST PRO-MATRIX METALLOPROTEINASES

Objective. We studied the relative ability of 6 different chemically m odified non-antimicrobial analogs of tetracycline (CMT) to inhibit hum an and chicken matrix metalloproteinases (MMP) in vitro. The ability o f tetracycline and its analogs to inhibit MMP appears to depend on the Ca++/Zn++ binding site at C-11 (carbonyl oxygen) and C-12 (OH group) of the molecule, which is lacking in CMT-5, the pyrazole derivative of tetracycline. This significant property of CMT-5 was used to differen tiate between the effects of CMT on already active MMP versus the oxid ative activation of latent MMP (pro-MMP). Methods. Cultured chicken os teoclast conditioned medium and purified human neutrophil progelatinas e (MMP-9) and pro-collagenase (MMP-8) were assayed for proteinase acti vities using gelatin and collagen, respectively. The pro-MMP were acti vated either by preincubation with 1 mM aminophenylmercuric acetate (A PMA) or 100 mu M sodium hypochlorite (NaOCl). CMT were added either to the preincubation mixtures together with NaOCl or after activation of pro-MMP with NaOCl.Results. All CMT tested, except CMT-5, inhibited A PMA or NaOCl activated pro-MMP. However, CMT-5 (like the other CMT), i nhibited the oxidative activation of pro-MMP by NaOCl when added toget her by scavenging the reactive oxygen species. The degradation of type -I collagen by chicken osteoclast conditioned medium was probably due to MMP-2 and/or MMP-13. Conclusion. Oxidative activation of pro-MMP ma y be crucial during soft tissue/bone destruction in the inflammatory d iseases, including the arthritides. Our results indicate that the Ca+/Zn++ binding site of CMT is not essential for inhibition of the oxida tive activation of pro-MMP.