Defensin γ-thionin from Capsicum chinense has immunomodulatory effects on bovine mammary epithelial cells during Staphylococcus aureus internalization

beta-Defensins are members of the antimicrobial peptide superfamily that are produced in various species from different kingdoms, including plants. Plant defensins exhibit primarily antifungal activities, unlike those from animals that exhibit a broad-spectrum antimicrobial action. Recently, immunomodulatory roles of mammal beta-defensins have been observed to regulate inflammation and activate the immune system. Similar roles for plant beta-defensins remain unknown. In addition, the regulation of the immune system by mammalian beta-defensins has been studied in humans and mice models, particularly in immune cells, but few studies have investigated these peptides in epithelial cells, which are in intimate contact with pathogens. The aim of this work was to evaluate the effect of the chemically synthesized beta-defensin gamma-thionin from Capsicum chinense on the innate immune response of bovine mammary epithelial cells (bMECs) infected with Staphylococcus aureus, the primary pathogen responsible for bovine mastitis, which is capable of living within bMECs. Our results indicate that gamma-thionin at 0.1 mu g/ml was able to reduce the internalization of S. aureus into bMECs (similar to 50%), and it also modulates the innate immune response of these cells by inducing the mRNA expression (similar to 5-fold) and membrane abundance (similar to 3-fold) of Toll-like receptor 2 (TLR2), as well as by inducing genes coding for the pro-inflammatory cytokines TNF-alpha and IL-1 beta (similar to 14 and 8-fold, respectively) before and after the bacterial infection. gamma-Thionin also induces the expression of the mRNA of anti-inflammatory cytokine IL-10 (similar to 12-fold). Interestingly, the reduction in bacterial internalization coincides with the production of other antimicrobial products by bMECs, such as NO before infection, and the secretion into the medium of the endogenous antimicrobial peptide DEFB1 after infection. The results from this work support the potential use of beta-defensins from plants as immunomodulators of the mammalian innate immune response. (C) 2016 Elsevier Inc. All rights reserved.