title: Inhibition of gelatinase B (matrix metalloproteinase-9) by dihydrolipoic acid.
abstract: Alpha-lipoic acid (LA) is a disulphide-containing fatty acid that is absorbed from the diet and transported to tissues. Once it has been taken up by mammalian cells, LA is reduced to dihydrolipoic acid (DHLA), a vicinal dithiol, and rapidly effluxed into the extracellular milieu. We hypothesized that DHLA may be an effective inhibitor of human gelatinase B (GelB). Purified human GelB was incubated with 0 to 200 micromol/L DHLA, and residual enzyme activity was measured by HPLC using a fluorogenic substrate (matrix metalloproteinase substrate III). DHLA inhibited GelB in a dose-dependent fashion with an IC50 of 20 micromol/L. Oxidation of DHLA resulted in a loss of DHLA's capacity to inhibit GelB. The DHLA-mediated inhibition of GelB was independent of the zinc concentration in the reaction buffer. DHLA had no inhibitory effect on gelatinase A. Zymographs of activated neutrophil lysates demonstrated that higher concentrations of DHLA also prevent the activation of GelB proenzyme. Bronchoalveolar lavage fluid from mice fed a diet enriched with LA showed significantly increased GelB inhibitory capacity (p = 0.0002 vs. regular diet). We conclude that DHLA can modulate neutrophil-derived GelB activity through direct inhibition of enzyme activity and by preventing the activation of GelB proenzyme.
authors.affiliation: Pulmonary Division, Faculty of Medicine, University of Sherbrooke, Canada. Andre.Cantin@USherbrooke.ca
authors.forename: André M
authors.initials: AM
authors.lastname: Cantin
authors.forename: Marc
authors.initials: M
authors.lastname: Martel
authors.forename: Geneviève
authors.initials: G
authors.lastname: Drouin
authors.forename: Benoit
authors.initials: B
authors.lastname: Paquette
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000187:drug effects; D018093:Gelatinases / Q000187:drug effects; D006801:Humans; D061965:Matrix Metalloproteinase Inhibitors; D008666:Metalloendopeptidases / Q000187:drug effects; D051379:Mice; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D011658:Pulmonary Fibrosis / Q000097:blood / Q000378:metabolism; D008063:Thioctic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D061965:Matrix Metalloproteinase Inhibitors; D008063:Thioctic Acid; C015144:dihydrolipoic acid; D018093:Gelatinases; D008666:Metalloendopeptidases; C069860:progelatinase