Titanium and zinc fluorides inhibit salivary matrix metalloproteinases at low concentrations

To evaluate the inhibition of the activity of salivary matrix metalloproteinases (MMPs) (MMP-2 and MMP-9) by solutions of titanium tetrafluoride (TiF₄), zinc fluoride (ZnF₂), stannous fluoride (SnF₂), and sodium fluoride (NaF). Saliva was collected from eight healthy individuals. Pooled saliva was centrifuged; the supernatants were incubated for 2 h (26°C) and subjected to gelatin zymography. TiF₄, ZnF₂, SnF₂, and NaF, were added into the incubation buffer in clinically relevant concentrations (0.01-2 wt%). The electrophoretic bands were scanned, and the transmittance values were analyzed with imagej software. Four bands were detected in the control group, two bands less clear, close to the molecular weight of 70 kDa and two more evident bands, close to 90 kDa. These enzymes were characterized as MMPs, as their activities were inhibited by ethylenediaminetetraacetic acid and not inhibited by N-ethylmaleimide. All tested fluorides were able to inhibit at least partially the activity of salivary MMPs. TiF₄ and ZnF₂ had an inhibitory effect at all tested concentrations, whereas at 0.01% and 0.05% NaF and SnF₂ suppressed only partially MMPs activity. In conclusion, TiF₄ and ZnF₂ were able to completely inhibit MMPs expression even at very low concentrations, whereas the effect of NaF and SnF₂ was dose dependent.