Objective: Ethanol is a common solvent for many MMP inhibitors. Control studies revealed that ethanol, alone, partially inhibited MMPs. The purpose of this study was to compare the MMP-inhibiting activity of a series of alcohols. Methods: Two MMP models were used. Soluble rhMMP-9, and insoluble matrix-bound endogenous MMPs in demineralized dentin beams. Increasing concentrations of methanol, ethanol, propanols, butanols, pentanols, and hydroxyethyl methacrylate (HEMA) were compared for their ability to inhibit rhMMP-9 using the Sensolyte Generic MMP kit from AnaSpec. Those alcohols that inhibited rhMMP-9 more than 50% were then incubated with demineralized dentin beams for 30 d to determine if they inhibit loss of dry mass and solubilization of hydroxyproline as indices of degradation of collagen, compared to alcohol-free controls. Results: Inhibition of rhMMP-9 increased with aliphatic chain length up to pentanol, with HEMA being the most inhibitory of the mono-alcohols, with 22 wt% HEMA causing 99% inhibition. The alcohols that inhibited rhMMP-9 more than 50% included 1-propanol, 2-butanol, tert-butanol, HEMA and 1,2-propandiol. They all inhibited the loss of dry mass of dentin beams between 79-85% compared to alcohol-free controls (p<0.05) and inhibited solubilization of collagen peptides (i.e. hydroxyproline release) between 78-99% (p<0.05).
Inhibition of proteases by alcohols | |||||
Protease activity | Ethanol | 1-propanol | 2-butanol | tert-butanol | HEMA |
rhMMP-9 | 14.3±4.6%a | 79.7±0.4%b | 78.7±2.1%b | 91.1±0.4%c | 99.4±0.6%c |
HYP release from matrix | 88.1 ± 4.2%c | 78.2±6%b | 82.9±5%b | 85.8±9%c | 85.6±4%c |
Groups identified by different superscript letters are significantly different (p<0.05). All alcohols were used at a concentration of 4.28 moles/L.
Conclusion: The results indicate that alcohols with 4-6 methylene groups inhibit MMPs more effectively than methanol or ethanol. MMP inhibition was directly related to the Hoy's solubility parameter for dispersive forces (i.e. to their hydrophobicity). Supported, in part, by R01 DE015306-06 from the NIDCR to DP (PI).