Cytotoxicity and microbiological effect of cationic peptide fragments isolated or combined for dental caries prevention

Author(s)

Paula Fernanda Kreling Domingues

• Document type: Doctoral Thesis
• Press: Araçatuba. 2016-10-31.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Odontologia. Araçatuba
• Defense date: 2016-09-05
• Advisor: Cristiane Duque; Célio Percinoto

Abstract

The immune system has several forms of defense against pathogenic microorganisms. The mucous membranes are a source of potent antimicrobial cationic peptides against a broad range of bacteria, fungi and enveloped viruses. The aim of study was evaluated the cytotoxicity and antimicrobial activity under planktonic and biofilm conditions of fragments derived from cationic peptides (CP): LL-37 (from hCAP-18), D6-17 and D1-23 (from β-defensin-3 derivative) against cariogenic bacteria. For cytotoxicity analysis, two lines of epithelial cells were exposed to serial dilutions of the CP fragments. MTT assays and DAPI staining were performed to evaluate cell metabolism and morphology, respectively. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined for the CP fragments and control (Chlorhexidine digluconate-CHX) against Streptococcus mutans (Sm), S. mitis, S. oralis, S. salivarius, S. sanguinis, Lactobacillus acidophilus, L. casei, L. rhamnosus, L. brevis, L. fermentum and Actinomyces israelii. Fractional inhibitory concentration (FIC) was obtained for the combinations of CP fragments on S. mutans. Biofilm assays were conducted with CHX and the best antimicrobial CP fragment against S. mutans strains. Confocal Laser Scanning Microscopy (CLSM) was used to analyze the Live/Dead cells and biofilm thickness. The results indicated that D6-17 did not affect the metabolism of either cell line. D1-23, LL-37 and CHX were not toxic for both cells, in concentrations below 0.2, 0.02 and 0.01mM, respectively. DAPI-staining cells demonstrated nuclei fragmentation for LL-37 group and cells with the aspect of apoptosis in the CHX group. Cells treated with D1-23 and D6-17 presented morphology similar to the control group (culture medium). D1-23 presented the best bactericidal activity against S. mutans, S. mitis and S. salivarius. LL-37 had a better effect against Lactobacillus and Actinomyces species. D6-17 showed bactericidal activity only against S. mutans, L. brevis and L. fermentum. Combinations of CP fragments did not show a synergic effect against S. mutans. D1-23 (10x MBC) presented a higher effect against S. mutans biofilm compared to CHX. CLSM analysis showed that D1-23 and CHX groups presented higher quantification of dead cells when compared to control (culture medium). The biofilm thickness were lower in the D1-23 group compared to CHX and control groups. We concluded that D1-23 showed a remarkable antimicrobial/anti-biofilm effect against cariogenic bacteria and low toxicity for epithelial cells. (AU)

• FAPESP's process: 13/12285-0 - Evaluation of the antimicrobial activity and cytotoxicity of cationic peptide fragments isolated or in combination in the prevention of dental caries.
• Grantee: Paula Fernanda Kreling Domingues
• Support Opportunities: Scholarships in Brazil - Doctorate