T Mohanty1, P Alberius2, A Schmidtchen3, K Reiss4, J-M Schröder4, O E Sørensen1,5. 1. Division of Infection Medicine, Department of Clinical Sciences Lund, Lund University, Tornavägen 10, SE-221 84 Lund, Sweden. 2. Department of Plastic Surgery, Skåne University Hospital, Malmö, Sweden. 3. Division of Dermatology, Department of Clinical Sciences Lund, Lund University, Tornavägen 10, SE-221 84 Lund, Sweden. 4. Department of Dermatology, University of Kiel, Kiel, Germany. 5. Wound Healing Center, Copenhagen University Hospital, Bispebjerg Hospital, Copenhagen, Denmark.
Abstract
BACKGROUND: Wounds in the oral cavity, constantly exposed to both saliva and bacteria, heal quickly without infection. Furthermore, during licking of skin wounds, saliva promotes wound healing and plays a role in keeping the wound free of infection. OBJECTIVES: To investigate whether saliva induces expression of antimicrobial peptides (AMPs) in human epidermal keratinocytes and whether saliva promotes clearance of intracellular bacteria in these cells. METHODS: Expression of AMPs was investigated in the oral mucosa and ex vivo injured skin by immunohistochemistry. Human beta-defensin-3 expression was investigated in epidermal keratinocytes after saliva stimulation, using real-time polymerase chain reaction and immunofluorescence. RESULTS: We found higher expression of AMPs in the oral mucosa than in the epidermis. Saliva accelerated the injury-induced expression of AMPs in human skin ex vivo and was a potent inducer of the expression of AMPs in epidermal keratinocytes. The expression of AMPs was induced by metalloproteinase-dependent epidermal growth factor receptor (EGFR) transactivation mediated by a salivary lipid. Saliva increased the intracellular clearance of Staphylococcus aureus in keratinocytes through EGFR activation. CONCLUSIONS: These findings suggest a previously unreported role of saliva in innate immunity and demonstrate for the first time that saliva induces gene expression in epidermal keratinocytes.
BACKGROUND: Wounds in the oral cavity, constantly exposed to both saliva and bacteria, heal quickly without infection. Furthermore, during licking of skin wounds, saliva promotes wound healing and plays a role in keeping the wound free of infection. OBJECTIVES: To investigate whether saliva induces expression of antimicrobial peptides (AMPs) in human epidermal keratinocytes and whether saliva promotes clearance of intracellular bacteria in these cells. METHODS: Expression of AMPs was investigated in the oral mucosa and ex vivo injured skin by immunohistochemistry. Humanbeta-defensin-3 expression was investigated in epidermal keratinocytes after saliva stimulation, using real-time polymerase chain reaction and immunofluorescence. RESULTS: We found higher expression of AMPs in the oral mucosa than in the epidermis. Saliva accelerated the injury-induced expression of AMPs in human skin ex vivo and was a potent inducer of the expression of AMPs in epidermal keratinocytes. The expression of AMPs was induced by metalloproteinase-dependent epidermal growth factor receptor (EGFR) transactivation mediated by a salivary lipid. Saliva increased the intracellular clearance of Staphylococcus aureus in keratinocytes through EGFR activation. CONCLUSIONS: These findings suggest a previously unreported role of saliva in innate immunity and demonstrate for the first time that saliva induces gene expression in epidermal keratinocytes.