Ethanolic extracts of Lamiaceae species inhibit the bacterial infection of human lung fibroblasts and stimulate cell migration

Abstract

BACKGROUND The increasing bacterial resistance to antibiotics poses a serious global threat. For that reason, the research into plant-derived antibacterial agents has become progressively more interesting, particularly in regard to their capacity to prevent the delay or inability of wound closure and healing. OBJECTIVES The aim of this study was to evaluate i) the antibacterial potential of ethanolic extracts (70% ethanol) of 18 Lamiaceae species against four Gram-negative and three Gram-positive bacterial strains; ii) the effect of these extracts on Pseudomonas aeruginosa PAO1 infection of human lung fibroblasts (MRC-5), and iii) the effect on MRC-5 cell migration. METHODS The antibacterial activity was tested by minimal inhibitory concentration (MIC) assay. The effect on bacterial infection of MRC-5 cells was determined using the invasion assay, while the cell migration was assessed with Scratch assay. RESULTS The tested Gram-positive bacteria, especially Bacillus subtilis, are more sensitive to the effects of ethanolic extracts than the Gram-negative bacteria. Moreover, the tested extracts significantly inhibited the invasion of Pseudomonas aeruginosa PAO1 during MRC-5 infection, and most of them also displayed promising stimulating potential on MRC-5 migration in a disrupted cell monolayer. Finally, the results of IBR (integrated biomarker response) analysis highlighted Salvia officinalis ethanolic extract as the most active one, which is in accordance with the existing data suggesting that this plant represents an effective antibacterial and wound-healing agent commonly used in traditional medicine. Altogether, these results are expected to foster further studies that will focus on combating bacterial resistance to antibiotics using natural products.