title: Abrupt decreases in environmental humidity induce abnormalities in permeability barrier homeostasis.
abstract: Previous reports demonstrated that long-term exposure to extremes in humidity influence permeability barrier homeostasis. Here the effects of a sudden shift from a high humidity to a dry environment were studied. Mice were initially maintained in either a humid (> 80% relative humidity) or normal environment (relative humidity = 40-70%), and then transferred to a dry environment (< 10% relative humidity). Within 2 d of transfer from a humid to a dry environment a 6-7-fold increase in transepidermal water loss occurred that returned to normal within 7 d. No increase in transepidermal water loss occurred in response to a switch from a normal to a dry environment. At a time when barrier function was abnormal, both stratum corneum hydration and pH were normal, indicating that the mechanisms that regulate these functions differ. Following transfer from a humid to dry environment, electron microscopy revealed a marked decrease in: (i) lamellar bodies in the outermost stratum granulosum; (ii) deposition of lamellar body contents at the stratum granulosum-stratum corneum interface; and (iii) the quantity of intercellular lamellae in the stratum corneum, which together could account for the barrier abnormality. Transfer of mice from a normal to a dry environment rapidly stimulated epidermal proliferation, whereas animals switched from a humid to a dry environment displayed a delayed increase in proliferation that might also contribute to the barrier abnormality. The present study demonstrates that sudden changes from a high to a low humidity environment results in abnormal barrier function, which could adversely influence the incidence and/or severity of skin disorders.
authors.affiliation: Shiseido Research Center, Yokohama, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Sato
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Denda
authors.forename: Sandra
authors.initials: S
authors.lastname: Chang
authors.forename: Peter M
authors.initials: PM
authors.lastname: Elias
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Feingold
mesh_terms: D000818:Animals; D001834:Body Water / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004817:Epidermis / Q000648:ultrastructure; D006706:Homeostasis; D006813:Humidity; D008297:Male; D051379:Mice; D008812:Mice, Hairless; D008854:Microscopy, Electron; D010539:Permeability; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D012867:Skin / Q000378:metabolism*
chemical_list: D018809:Proliferating Cell Nuclear Antigen; D004247:DNA