title: Colonization of epidermal tissue by Staphylococcus aureus produces localized hypoxia and stimulates secretion of antioxidant and caspase-14 proteins.
abstract: A partial-thickness epidermal explant model was colonized with green fluorescent protein (GFP)-expressing Staphylococcus aureus, and the pattern of S. aureus biofilm growth was characterized using electron and confocal laser scanning microscopy. The oxygen concentration in explants was quantified using microelectrodes. The relative effective diffusivity and porosity of the epidermis were determined using magnetic resonance imaging, while hydrogen peroxide (H2O2) concentration in explant media was measured by using microelectrodes. Secreted proteins were identified and quantified using elevated-energy mass spectrometry (MS(E)). S. aureus biofilm grows predominantly in lipid-rich areas around hair follicles and associated skin folds. Dissolved oxygen was selectively depleted (2- to 3-fold) in these locations, but the relative effective diffusivity and porosity did not change between colonized and control epidermis. Histological analysis revealed keratinocyte damage across all the layers of colonized epidermis after 4 days of culture. The colonized explants released significantly (P < 0.01) more antioxidant proteins of both epidermal and S. aureus origin, consistent with elevated H2O2 concentrations found in the media from the colonized explants (P< 0.001). Caspase-14 was also elevated significantly in the media from the colonized explants. While H2O2 induces primary keratinocyte differentiation, caspase-14 is required for terminal keratinocyte differentiation and desquamation. These results are consistent with a localized biological impact from S. aureus in response to colonization of the skin surface.
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA.
authors.forename: Abdul G
authors.initials: AG
authors.lastname: Lone
authors.affiliation: School of Chemical Engineering & Bioengineering, Washington State University, Pullman, Washington, USA.
authors.forename: Erhan
authors.initials: E
authors.lastname: Atci
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Renslow
authors.affiliation: School of Chemical Engineering & Bioengineering, Washington State University, Pullman, Washington, USA.
authors.forename: Haluk
authors.initials: H
authors.lastname: Beyenal
authors.affiliation: Animal Disease Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Pullman, Washington, USA Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Noh
authors.affiliation: Department of Veterinary Clinical Sciences, Washington State University, Pullman, Washington, USA.
authors.forename: Boel
authors.initials: B
authors.lastname: Fransson
authors.affiliation: School of Chemical Engineering & Bioengineering, Washington State University, Pullman, Washington, USA.
authors.forename: Nehal
authors.initials: N
authors.lastname: Abu-Lail
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA.
authors.forename: Jeong-Jin
authors.initials: JJ
authors.lastname: Park
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman, Washington, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Gang
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, Washington, USA Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington, USA drcall@wsu.edu.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Call
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D018441:Biofilms; D053456:Caspase 14 / Q000378:metabolism*; D004817:Epidermis / Q000201:enzymology* / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D021381:Protein Transport; D012867:Skin / Q000201:enzymology / Q000378:metabolism / Q000382:microbiology; D013203:Staphylococcal Infections / Q000201:enzymology* / Q000378:metabolism / Q000382:microbiology; D013211:Staphylococcus aureus / Q000254:growth & development* / Q000502:physiology; D013552:Swine
chemical_list: D000975:Antioxidants; D053456:Caspase 14; D010100:Oxygen