title: Papain Degrades Tight Junction Proteins of Human Keratinocytes In Vitro and Sensitizes C57BL/6 Mice via the Skin Independent of its Enzymatic Activity or TLR4 Activation.
abstract: Papain is commonly used in food, pharmaceutical, textile, and cosmetic industries and is known to induce occupational allergic asthma. We have previously shown that the papain-like cysteine protease Dermatophagoides pteronyssinus 1 from house dust mite exhibits percutaneous sensitization potential. We aimed here to investigate the potential of papain itself in epicutaneous sensitization. The effects of papain on tight junction (TJ) proteins were tested in vitro in human primary keratinocytes. Using C57BL/6 wild-type and Toll-like receptor 4 (TLR4)-deficient mice, we analyzed the sensitization potential of papain, its effects on the skin barrier, and immune cell recruitment. Our results show that papain affects the skin barrier by increasing transepidermal water loss, degrading TJ proteins and inducing vasodilation. When topically applied, papain exhibited a high epicutaneous inflammatory potential by recruiting neutrophils, mast cells, and CD3-positive cells and by induction of a TH2-biased antibody response. However, its high potency for specific sensitization via the skin was TLR4 independent and, in spite of its capacity to degrade epidermal TJ proteins, does not rely on its enzymatic function. From our data, we conclude that papain has all features to act as a strong allergen via the skin.
authors.affiliation: Department of Pathophysiology and Allergy Research, Comparative Immunology and Oncology, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.|Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University of Vienna and University Vienna, Vienna, Austria.
authors.forename: Caroline
authors.initials: C
authors.lastname: Stremnitzer
authors.affiliation: Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University of Vienna and University Vienna, Vienna, Austria.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Manzano-Szalai
authors.affiliation: Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University of Vienna and University Vienna, Vienna, Austria.
authors.forename: Anna
authors.initials: A
authors.lastname: Willensdorfer
authors.affiliation: Department of Pathophysiology and Allergy Research, Comparative Immunology and Oncology, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.
authors.forename: Philipp
authors.initials: P
authors.lastname: Starkl
authors.affiliation: Institute of Anatomy, University of Lübeck, Lübeck, Germany and Airway Research Center North, Member of the German Center for Lung Research (DZL), Germany.
authors.forename: Mario
authors.initials: M
authors.lastname: Pieper
authors.affiliation: Institute of Anatomy, University of Lübeck, Lübeck, Germany and Airway Research Center North, Member of the German Center for Lung Research (DZL), Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: König
authors.affiliation: Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Mildner
authors.affiliation: Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: Erwin
authors.initials: E
authors.lastname: Tschachler
authors.affiliation: Institute of Animal Breeding and Genetics and Biomodels Austria, University of Veterinary Medicine Vienna, Vienna, Austria.
authors.forename: Ursula
authors.initials: U
authors.lastname: Reichart
authors.affiliation: Department of Pathophysiology and Allergy Research, Comparative Immunology and Oncology, Center of Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria.|Comparative Medicine, Messerli Research Institute of the University of Veterinary Medicine Vienna, Medical University of Vienna and University Vienna, Vienna, Austria.
authors.forename: Erika
authors.initials: E
authors.lastname: Jensen-Jarolim
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005455:Fluorescent Antibody Technique; D007114:Immunization / Q000379:methods*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D015603:Keratinocytes / Q000187:drug effects / Q000276:immunology*; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism; D010206:Papain / Q000494:pharmacology*; D011897:Random Allocation; D012867:Skin / Q000187:drug effects / Q000276:immunology; D062725:Tight Junction Proteins / Q000187:drug effects* / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D062725:Tight Junction Proteins; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D010206:Papain