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Factors affecting antimicrobial activity of MUC7 12-mer, a human salivary mucin-derived peptide.

Wei GX, Campagna AN, Bobek LA - Ann. Clin. Microbiol. Antimicrob. (2007)

Bottom Line: To examine the effect of salts or EDTA, a checkerboard microdilution technique was used.The peptide exhibited higher inhibitory activity against C. albicans at pH 7, 8, and 9 than at pH 5 and 6, and temperature up to 60 degrees C did not affect the activity.MUC7 12-mer peptide is effective anticandidal agent at physiological concentrations of variety of ions in the oral cavity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oral Biology, School of Dental Medicine, University at Buffalo, SUNY, 3435 Main Street, Buffalo, USA, NY 14214. gwei@buffalo.edu.

ABSTRACT

Background: MUC7 12-mer (RKSYKCLHKRCR), a cationic antimicrobial peptide derived from the human low-molecular-weight salivary mucin MUC7, possesses potent antimicrobial activity in vitro. In order to evaluate the potential therapeutic application of the MUC7 12-mer, we examined the effects of mono- and divalent cations, EDTA, pH, and temperature on its antimicrobial activity.

Methods: Minimal Inhibitory Concentrations (MICs) were determined using a liquid growth inhibition assay in 96-well microtiter plates. MUC7 12-mer was added at concentrations of 1.56-50 microM. MICs were determined at three endpoints: MIC-0, MIC-1, and MIC-2 (the lowest drug concentration showing 10%, 25% and 50% of growth, respectively). To examine the effect of salts or EDTA, a checkerboard microdilution technique was used. Fractional inhibitory concentration index (FICi) was calculated on the basis of MIC-0. The viability of microbial cells treated with MUC7 12-mer in the presence of sodium or potassium was also determined by killing assay or flow cytometry.

Results: The MICs of MUC7 12-mer against organisms tested ranged from 6.25-50 microM. For C. albicans, antagonism (FICi 4.5) was observed for the combination of MUC7 12-mer and calcium; however, there was synergism (FICi 0.22) between MUC7 12-mer and EDTA, and the synergism was retained in the presence of calcium at its physiological concentration (1-2 mM). No antagonism but additivity or indifference (FICi 0.55-2.5) was observed for the combination of MUC7 12-mer and each K+, Na+, Mg2+, or Zn2+. MUC7 12-mer peptide (at 25 microM) also exerted killing activity in the presence of NaCl, (up to 25 mM for C. albicans and up to 150 mM for E. coli, a physiological concentration of sodium in the oral cavity and serum, respectively) and retained candidacidal activity in the presence of KCl (up to 40 mM). The peptide exhibited higher inhibitory activity against C. albicans at pH 7, 8, and 9 than at pH 5 and 6, and temperature up to 60 degrees C did not affect the activity.

Conclusion: MUC7 12-mer peptide is effective anticandidal agent at physiological concentrations of variety of ions in the oral cavity. These results suggest that, especially in combination with EDTA, it could potentially be applied as an alternative therapeutic agent for the treatment of human oral candidiasis.

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Effect of pH on MIC of MUC7 12-mer against C. albicans. MIC-0, MIC-1 and MIC-2 indicate the lowest agent concentration showing no more than 10%, 25% and 50% growth respectively, in comparison to that of the agent-free control. The bars indicate the geometric means of two independent experiments, each performed in duplicate. The error bars show the 95% confidence intervals for the means.
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Figure 4: Effect of pH on MIC of MUC7 12-mer against C. albicans. MIC-0, MIC-1 and MIC-2 indicate the lowest agent concentration showing no more than 10%, 25% and 50% growth respectively, in comparison to that of the agent-free control. The bars indicate the geometric means of two independent experiments, each performed in duplicate. The error bars show the 95% confidence intervals for the means.

Mentions: The effect of pH on the activity of the peptide was established by determining the MIC of MUC7 12-mer against C. albicans DIS at pH values varying from 5 to 9 (Figure 4). There are no significant differences among the MIC-0, MIC-1, and MIC-2 (95% confidence intervals overlap). However, MICs of MUC7 12-mer were higher in acidic conditions than in neutral and basic conditions, and its antimicrobial activity was optimum at pH 8 (95% confidence intervals do not overlap).


Factors affecting antimicrobial activity of MUC7 12-mer, a human salivary mucin-derived peptide.

Wei GX, Campagna AN, Bobek LA - Ann. Clin. Microbiol. Antimicrob. (2007)

Effect of pH on MIC of MUC7 12-mer against C. albicans. MIC-0, MIC-1 and MIC-2 indicate the lowest agent concentration showing no more than 10%, 25% and 50% growth respectively, in comparison to that of the agent-free control. The bars indicate the geometric means of two independent experiments, each performed in duplicate. The error bars show the 95% confidence intervals for the means.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211505&req=5

Figure 4: Effect of pH on MIC of MUC7 12-mer against C. albicans. MIC-0, MIC-1 and MIC-2 indicate the lowest agent concentration showing no more than 10%, 25% and 50% growth respectively, in comparison to that of the agent-free control. The bars indicate the geometric means of two independent experiments, each performed in duplicate. The error bars show the 95% confidence intervals for the means.
Mentions: The effect of pH on the activity of the peptide was established by determining the MIC of MUC7 12-mer against C. albicans DIS at pH values varying from 5 to 9 (Figure 4). There are no significant differences among the MIC-0, MIC-1, and MIC-2 (95% confidence intervals overlap). However, MICs of MUC7 12-mer were higher in acidic conditions than in neutral and basic conditions, and its antimicrobial activity was optimum at pH 8 (95% confidence intervals do not overlap).

Bottom Line: To examine the effect of salts or EDTA, a checkerboard microdilution technique was used.The peptide exhibited higher inhibitory activity against C. albicans at pH 7, 8, and 9 than at pH 5 and 6, and temperature up to 60 degrees C did not affect the activity.MUC7 12-mer peptide is effective anticandidal agent at physiological concentrations of variety of ions in the oral cavity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oral Biology, School of Dental Medicine, University at Buffalo, SUNY, 3435 Main Street, Buffalo, USA, NY 14214. gwei@buffalo.edu.

ABSTRACT

Background: MUC7 12-mer (RKSYKCLHKRCR), a cationic antimicrobial peptide derived from the human low-molecular-weight salivary mucin MUC7, possesses potent antimicrobial activity in vitro. In order to evaluate the potential therapeutic application of the MUC7 12-mer, we examined the effects of mono- and divalent cations, EDTA, pH, and temperature on its antimicrobial activity.

Methods: Minimal Inhibitory Concentrations (MICs) were determined using a liquid growth inhibition assay in 96-well microtiter plates. MUC7 12-mer was added at concentrations of 1.56-50 microM. MICs were determined at three endpoints: MIC-0, MIC-1, and MIC-2 (the lowest drug concentration showing 10%, 25% and 50% of growth, respectively). To examine the effect of salts or EDTA, a checkerboard microdilution technique was used. Fractional inhibitory concentration index (FICi) was calculated on the basis of MIC-0. The viability of microbial cells treated with MUC7 12-mer in the presence of sodium or potassium was also determined by killing assay or flow cytometry.

Results: The MICs of MUC7 12-mer against organisms tested ranged from 6.25-50 microM. For C. albicans, antagonism (FICi 4.5) was observed for the combination of MUC7 12-mer and calcium; however, there was synergism (FICi 0.22) between MUC7 12-mer and EDTA, and the synergism was retained in the presence of calcium at its physiological concentration (1-2 mM). No antagonism but additivity or indifference (FICi 0.55-2.5) was observed for the combination of MUC7 12-mer and each K+, Na+, Mg2+, or Zn2+. MUC7 12-mer peptide (at 25 microM) also exerted killing activity in the presence of NaCl, (up to 25 mM for C. albicans and up to 150 mM for E. coli, a physiological concentration of sodium in the oral cavity and serum, respectively) and retained candidacidal activity in the presence of KCl (up to 40 mM). The peptide exhibited higher inhibitory activity against C. albicans at pH 7, 8, and 9 than at pH 5 and 6, and temperature up to 60 degrees C did not affect the activity.

Conclusion: MUC7 12-mer peptide is effective anticandidal agent at physiological concentrations of variety of ions in the oral cavity. These results suggest that, especially in combination with EDTA, it could potentially be applied as an alternative therapeutic agent for the treatment of human oral candidiasis.

Show MeSH
Related in: MedlinePlus