Iridoid glucosides against Staphylococcus aureus infection and inhibit inflammation on bovine mammary epithelial cells

Abstract

Staphylococcus aureus can cause diseases in humans and livestock, destroy the body barrier, exacerbate inflammation, and seriously threaten human health and animal husbandry development. Iridoid glucosides isolated from Rehmannia glutinosa is an important Chinese traditional medicine widely used in various diseases. The aim of this study was to investigate whether the iridoid glucosides were effective against S. aureus infection and inhibit inflammation of bovine mammary epithelial cells. The antibacterial potential was determined using the in vitro broth microdilution assay against S. aureus. Then, the antibiofilm activity was tested using a BCA protein assay, an electric conductivity assay, and scanning electron microscopy. Finally, the anti-inflammatory activities were investigated by measuring nitric oxide (NO), tumor necrosis factor- α (TNF-α), interleukin 6 (IL-6), and interleukin 1β (IL-1β) production in S. aureus-stimulated MAC-T cells, respectively. Biofilm results indicated that both 1MIC and 3MIC S. aureus groups showed a significant increase in a dose-dependent manner after two hours of iridoid glucosides treatment. This indicated that iridoid glucosides treatment caused the leakage of intracellular electrolytes. NO、ELISA and RT- PCR results showed the iridoid glucosides inhibit the NO, TNF-α, IL-6, and IL-1β production in S. aureus-stimulated MAC-T in a concentration-dependent manner. In summary, iridoid glucosides had antibacterial, antibiofilm, and anti-inflammatory activity against S. aureus, and they might have application value and development potential in therapy for bovine mastitis.